The Role of Bovine Kappa-Casein Glycomacropeptide in Modulating the Microbiome and Inflammatory Responses of Irritable Bowel Syndrome

Abstract

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder marked by chronic abdominal pain, bloating, and irregular bowel habits. Effective treatments are still actively sought. Kappa-casein glycomacropeptide (GMP), a milk-derived peptide, holds promise because it can modulate the gut microbiome, immune responses, gut motility, and barrier functions, as well as binding toxins. These properties align with the recognized pathophysiological aspects of IBS, including gut microbiota imbalances, immune system dysregulation, and altered gut barrier functions. This review delves into GMP’s role in regulating the gut microbiome, accentuating its influence on bacterial populations and its potential to promote beneficial bacteria while inhibiting pathogenic varieties. It further investigates the gut microbial shifts observed in IBS patients and contemplates GMP’s potential for restoring microbial equilibrium and overall gut health. The anti-inflammatory attributes of GMP, especially its impact on vital inflammatory markers and capacity to temper the low-grade inflammation present in IBS are also discussed. In addition, this review delves into current research on GMP’s effects on gut motility and barrier integrity and examines the changes in gut motility and barrier function observed in IBS sufferers. The overarching goal is to assess the potential clinical utility of GMP in IBS management.

Full text

Citation: Qu, Y.; Park, S.H.; Dallas,
D.C. The Role of Bovine Kappa-
Casein Glycomacropeptide in
Modulating the Microbiome and
Inflammatory Responses of Irritable
Bowel Syndrome. Nutrients 2023,15,
3991. https://doi.org/10.3390/
nu15183991
Academic Editor: Esben
Skipper Sørensen
Received: 30 August 2023
Revised: 10 September 2023
Accepted: 12 September 2023
Published: 15 September 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
nutrients
Review
The Role of Bovine Kappa-Casein Glycomacropeptide in
Modulating the Microbiome and Inflammatory Responses of
Irritable Bowel Syndrome
Yunyao Qu 1,2, Si Hong Park 1and David C. Dallas 1,2, *
1Department of Food Science & Technology, Oregon State University, Corvallis, OR 97331, USA;
yunyao.qu@oregonstate.edu (Y.Q.); sihong.park@oregonstate.edu (S.H.P.)
2Nutrition Program, College of Health, Oregon State University, Corvallis, OR 97331, USA
*Correspondence: dave.dallas@oregonstate.edu
Abstract:
Irritable bowel syndrome (IBS) is a common gastrointestinal disorder marked by chronic
abdominal pain, bloating, and irregular bowel habits. Effective treatments are still actively sought.
Kappa-casein glycomacropeptide (GMP), a milk-derived peptide, holds promise because it can mod-
ulate the gut microbiome, immune responses, gut motility, and barrier functions, as well as binding
toxins. These properties align with the recognized pathophysiological aspects of IBS, including gut
microbiota imbalances, immune system dysregulation, and altered gut barrier functions. This review
delves into GMP’s role in regulating the gut microbiome, accentuating its influence on bacterial
populations and its potential to promote beneficial bacteria while inhibiting pathogenic varieties.
It further investigates the gut microbial shifts observed in IBS patients and contemplates GMP’s
potential for restoring microbial equilibrium and overall gut health. The anti-inflammatory attributes
of GMP, especially its impact on vital inflammatory markers and capacity to temper the low-grade
inflammation present in IBS are also discussed. In addition, this review delves into current research
on GMP’s effects on gut motility and barrier integrity and examines the changes in gut motility and
barrier function observed in IBS sufferers. The overarching goal is to assess the potential clinical
utility of GMP in IBS management.
Keywords:
irritable bowel syndrome (IBS); kappa-casein glycomacropeptide (GMP); gut microbiome;
gut motility; gut barrier function; inflammation; therapeutic benefits
1. Introduction
1.1. Background on Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a complex, chronic functional bowel disorder charac-
terized by altered bowel habits and abdominal discomfort or pain [
1
]. Common symptoms
include abdominal pain or discomfort, bloating, gas, diarrhea, and constipation; the disor-
der can severely impact an individual’s quality of life [
2
]. In some cases, IBS can also cause
nausea, fatigue, and changes in appetite [
3
]. IBS is diagnosed based on a combination of
symptoms and no single test can definitively diagnose the disorder.
Affecting 10–15% of the population in North America, 6–19% in Europe, and 3–20%
in Asia [
3
–
5
], IBS has significantly impacted healthcare utilization and costs [
6
]. IBS has a
higher prevalence among individuals assigned female at birth compared to males, with a
female-to-male ratio of approximately 2:1 [7].
The exact cause of IBS remains unknown. However, it is thought to result from a
combination of genetic, psychological, and environmental factors affecting the functioning
of the digestive system [3,8].
Nutrients 2023,15, 3991. https://doi.org/10.3390/nu15183991 https://www.mdpi.com/journal/nutrients

Nutrients 2023,15, 3991 2 of 22
1.2. Current Treatment Modalities for IBS
Current treatment strategies for IBS primarily focus on alleviating IBS symptoms [
9
].
Pharmacological approaches are varied, including the use of bulking agents, which have
shown mixed results in alleviating constipation [
10
,
11
]. Antidiarrheal agents such as
loperamide are effective at modulating stool consistency, though they do not address
abdominal pain [
12
,
13
]. Antispasmodics aim to alleviate IBS pain by inhibiting mus-
cle wall contractile pathways. However, their effectiveness remains unclear due to in-
consistent clinical trial results and potential side effects such as exacerbating constipa-
tion [
14
,
15
]. The use of prokinetics, agents known to stimulate gastrointestinal motility,
has been largely discouraged in treating IBS with constipation due to their proven ineffec-
tiveness and associated cardiac toxicity, with some even being withdrawn from several
countries [
16
–
18
]. Low doses of antidepressants have demonstrated potential for alleviating
chronic abdominal pain, a prevalent symptom in IBS patients, by influencing the brain–gut
axis [
19
,
19
,
20
]. Serotoninergic agents, such as cilansetron, are currently undergoing trials
for their potential to reduce abdominal pain in IBS characterized by diarrhea (IBS-D), albeit
with concerns about potential ischemic colitis [
21
]. Neurotrophins are also being examined
for their ability to accelerate intestinal transit, though their precise role and safety profile
in IBS management remains unclear [
22
]. Additionally, exploring tachykinin receptor
antagonists is in its infancy, with preliminary studies indicating potential for alleviating
various IBS symptoms. However, comprehensive clinical trials are needed to ascertain their
efficacy and safety [
23
–
25
]. Somatostatin analogs may offer potential benefits in managing
pain and severe diarrhea in IBS patients by modulating various brain centers involved in
pain perception. However, their clinical application is hindered by the lack of practical
administration methods and comprehensive clinical trials [
26
]. Adrenergic modulators are
also under investigation, with some potentially improving abdominal discomfort and stool
consistency. However, further studies are essential to determine their safety, especially
considering the severe cardiac toxicity associated with some agents in this category [
27
,
28
].
Non-pharmacological interventions have also been applied to IBS management. For
example, elimination diets can identify foods associated with symptoms for future avoid-
ance [
29
]. The use of probiotics in IBS management is also being explored, but clinical
evidence remains inconclusive [
30
]. Psychotherapy can address psychological factors in-
tricately linked to IBS; for instance, stress management and cognitive behavioral therapy
have shown promise for alleviating IBS symptoms [31].
Herein, we highlight the role of the gut microbiome and inflammation in the patho-
genesis of IBS, and the potential to therapeutically target these underlying factors.
1.3. Importance of the Gut Microbiome and Inflammation in IBS Pathogenesis
Recent research has recognized the importance of the gut microbiome and low-grade
inflammation in the pathogenesis of IBS [
32
–
34
]. Dysbiosis, or an imbalance in the gut
microbiota composition, has been observed in IBS patients and may contribute to the onset
and maintenance of IBS symptoms [
35
]. Studies indicate that ~73% of people with IBS
have dysbiosis compared with 16% of otherwise healthy individuals [
36
–
39
]. Altered gut
microbiota can lead to increased gut permeability, allowing for the translocation of bacterial
components such as lipopolysaccharide (LPS) and the triggering of immune activation [
40
].
This immune activation can lead to low-grade chronic inflammation [
32
], which may
further aggravate IBS symptoms. Thus, targeting the gut microbiota and inflammation has
emerged as a promising therapeutic strategy for IBS [41].
1.4. Bovine Kappa-Casein Glycomacropeptide: A Potential Nutritional Intervention in IBS
Management
Since IBS pathogenesis has been linked to altered gut microbiota composition and
increased inflammation in the gut, nutritional interventions could potentially alleviate and
positively influence symptoms. One nutritional supplement that can potentially improve
the dysregulated physiology in IBS is glycomacropeptide (GMP).

Nutrients 2023,15, 3991 3 of 22
GMP, a 64-amino acid fragment derived from bovine
κ
-casein during cheesemaking,
constitutes 20–25% of whey protein and exists in various forms with distinct genetic vari-
ants and post-translational modifications, including glycosylation (Figure 1) [
42
–
45
]. It
undergoes glycosylation with 11 different O-linked glycan structures attached primarily to
the threonine and serine residues in the peptide [
46
]. Commercial extraction from sweet
whey involves processes such as ultrafiltration and ion exchange chromatography [
47
]. Due
to its deficiency in certain aromatic amino acids, GMP is a significant dietary source for indi-
viduals with phenylketonuria (PKU), a disorder impairing phenylalanine metabolism [
48
].
Present in dairy products including milk and yogurt, albeit in lower concentrations than
isolated sweet whey protein, GMP is also released in the consumer’s gut from
κ
-casein by
gastric pepsin [49,50].
Nutrients 2023, 15, x FOR PEER REVIEW 3 of 23
1.4. Bovine Kappa-Casein Glycomacropeptide: A Potential Nutritional Intervention in
IBS Management
Since IBS pathogenesis has been linked to altered gut microbiota composition and
increased inflammation in the gut, nutritional interventions could potentially alleviate
and positively influence symptoms. One nutritional supplement that can potentially im-
prove the dysregulated physiology in IBS is glycomacropeptide (GMP).
GMP, a 64-amino acid fragment derived from bovine κ-casein during cheesemaking,
constitutes 20–25% of whey protein and exists in various forms with distinct genetic vari-
ants and post-translational modifications, including glycosylation (Figure 1) [42–45]. It
undergoes glycosylation with 11 different O-linked glycan structures aached primarily
to the threonine and serine residues in the peptide [46]. Commercial extraction from sweet
whey involves processes such as ultrafiltration and ion exchange chromatography [47].
Due to its deficiency in certain aromatic amino acids, GMP is a significant dietary source
for individuals with phenylketonuria (PKU), a disorder impairing phenylalanine metab-
olism [48]. Present in dairy products including milk and yogurt, albeit in lower concen-
trations than isolated sweet whey protein, GMP is also released in the consumer’s gut
from κ-casein by gastric pepsin [49,50].
Figure 1. Structural representation of bovine κ-casein glycomacropeptide (GMP) highlighting its
amino acid sequence and predominant O-linked glycans. Glycan symbols: yellow square, N-acetyl
galactosamine; yellow circle, galactose; and purple diamond, N-acetyl neuraminic acid.
In vitro and animal studies have aributed several health-promoting bioactivities to
GMP, including antimicrobial and prebiotic activities, immunomodulatory properties,
and toxin-binding capabilities, highlighting its potential for mitigating gastrointestinal
symptoms prevalent in conditions similar to IBS [51–57]. GMP’s potential role remains
largely unexplored in the evolving landscape of IBS treatment research. In this review, we
aim to critically evaluate GMP’s influence on the gut microbiome, immune responses, gut
motility, barrier functions, and toxin-binding, assessing its potential to address the altered
microbiome, immune regulation, and gut function in IBS patients (Figure 2).
Figure 1.
Structural representation of bovine
κ
-casein glycomacropeptide (GMP) highlighting its
amino acid sequence and predominant O-linked glycans. Glycan symbols: yellow square, N-acetyl
galactosamine; yellow circle, galactose; and purple diamond, N-acetyl neuraminic acid.
In vitro
and animal studies have attributed several health-promoting bioactivities
to GMP, including antimicrobial and prebiotic activities, immunomodulatory properties,
and toxin-binding capabilities, highlighting its potential for mitigating gastrointestinal
symptoms prevalent in conditions similar to IBS [
51
–
57
]. GMP’s potential role remains
largely unexplored in the evolving landscape of IBS treatment research. In this review, we
aim to critically evaluate GMP’s influence on the gut microbiome, immune responses, gut
motility, barrier functions, and toxin-binding, assessing its potential to address the altered
microbiome, immune regulation, and gut function in IBS patients (Figure 2).

Nutrients 2023,15, 3991 4 of 22
Nutrients 2023, 15, x FOR PEER REVIEW 4 of 23
Figure 2. GMP’s diverse bioactivities and their potential relevance in targeting the pathophysiolog-
ical aspects of IBS.
2. GMP and the Microbiome in IBS
2.1. Gut Microbiome in IBS
The gut microbiome plays a crucial role in developing and maintaining human
health.
Studies on microbiota diversity in IBS patients have yielded variable results. The mi-
crobiomes of those with IBS often exhibit lower diversity than those who are healthy, in-
dicating a reduced number of different bacterial species, a condition referred to as dysbio-
sis [3,8,36,58–63]. However, other studies have found no significant difference in diversity
between IBS patients and healthy individuals [64–67]. These inconsistent findings high-
light the complexity of the relationship between microbial diversity and IBS. A beer un-
derstanding of the factors affecting microbial diversity among individuals with IBS and
their implications for its development and management is needed.
Some studies indicate that individuals with IBS have specific family-, genus- or spe-
cies-level differences in their microbiota compared with healthy individuals, although the
specific differences identified have varied between studies. Piayanon et al. recently re-
viewed these microbial differences in people with IBS and found a set of common differ-
ences across studies, including increased family Enterobacteriaceae (belonging to the phy-
lum Proteobacteria), family Lactobacillaceae and genus Bacteroides, decreased unculturable
Clostridiales I, and genus Faecalibacterium (including Faecalibacterium prausnii and genus
Bifidobacterium) [68].
Changes in the gut bacterial composition of patients with IBS may be partially re-
sponsible for their observed symptoms. For example, in patients with an IBS type charac-
terized by constipation (IBS-C), the abundance of methane-producing bacteria Methano-
bacteriales is higher than in healthy individuals [60]. This association may be due to me-
thane’s ability to decrease intestinal peristalsis and increase transit time [69]. Conversely,
in patients with IBS-D, the abundance of Methanobacteriales is lower than in healthy con-
trols [60,69], which could lower gut methane production and decrease transit time [69].
Furthermore, IBS-D patients were observed to have higher abundances of hydrogen sul-
fide-producing bacteria [70]. The higher hydrogen sulfide production may be partially
responsible for symptoms observed in IBS-D, as previous studies have associated breath
hydrogen sulfide levels with diarrhea [71]. Furthermore, rat studies indicate that hydro-
gen sulfide relaxes smooth muscles [72]. Investigations by Parkes et al. revealed that indi-
viduals with IBS exhibit increased rectal mucosa production, which correlates with higher
levels of bacteria such as Bacteroides and Clostridia. These bacteria have a strong affinity for
Figure 2.
GMP’s diverse bioactivities and their potential relevance in targeting the pathophysiological
aspects of IBS.
2. GMP and the Microbiome in IBS
2.1. Gut Microbiome in IBS
The gut microbiome plays a crucial role in developing and maintaining human health.
Studies on microbiota diversity in IBS patients have yielded variable results. The
microbiomes of those with IBS often exhibit lower diversity than those who are healthy,
indicating a reduced number of different bacterial species, a condition referred to as
dysbiosis [
3
,
8
,
36
,
58
–
63
]. However, other studies have found no significant difference in
diversity between IBS patients and healthy individuals [
64
–
67
]. These inconsistent findings
highlight the complexity of the relationship between microbial diversity and IBS. A better
understanding of the factors affecting microbial diversity among individuals with IBS and
their implications for its development and management is needed.
Some studies indicate that individuals with IBS have specific family-, genus- or species-
level differences in their microbiota compared with healthy individuals, although the spe-
cific differences identified have varied between studies. Pittayanon et al. recently reviewed
these microbial differences in people with IBS and found a set of common differences across
studies, including increased family Enterobacteriaceae (belonging to the phylum Proteobacte-
ria), family Lactobacillaceae and genus Bacteroides, decreased unculturable Clostridiales I, and
genus Faecalibacterium (including Faecalibacterium prausnitzi and genus Bifidobacterium) [
68
].
Changes in the gut bacterial composition of patients with IBS may be partially respon-
sible for their observed symptoms. For example, in patients with an IBS type characterized
by constipation (IBS-C), the abundance of methane-producing bacteria Methanobacteriales is
higher than in healthy individuals [
60
]. This association may be due to methane’s ability
to decrease intestinal peristalsis and increase transit time [
69
]. Conversely, in patients
with IBS-D, the abundance of Methanobacteriales is lower than in healthy controls [
60
,
69
],
which could lower gut methane production and decrease transit time [
69
]. Furthermore,
IBS-D patients were observed to have higher abundances of hydrogen sulfide-producing
bacteria [
70
]. The higher hydrogen sulfide production may be partially responsible for
symptoms observed in IBS-D, as previous studies have associated breath hydrogen sulfide
levels with diarrhea [
71
]. Furthermore, rat studies indicate that hydrogen sulfide relaxes
smooth muscles [
72
]. Investigations by Parkes et al. revealed that individuals with IBS
exhibit increased rectal mucosa production, which correlates with higher levels of bacteria
such as Bacteroides and Clostridia. These bacteria have a strong affinity for mucin and
their proliferation in this environment may have implications for the pathophysiology of
IBS [73].
Fecal microbiota transplants have emerged as a valuable tool in this field, providing
evidence of the microbial contribution to IBS. El-Salhy et al. conducted a study in which

Nutrients 2023,15, 3991 5 of 22
fecal transplants from healthy donors resulted in notable improvements in IBS symptoms
and overall quality of life [
74
]. Similarly, Crouzet et al. demonstrated that transferring stool
from IBS-D patients to germ-free rats increased intestinal motility, intestinal permeability,
and visceral organ pain sensitivity, all of which are commonly observed in individuals with
IBS-D [75].
Some studies have found beneficial effects for managing IBS symptoms from con-
suming probiotics. For example, studies have indicated the beneficial effects of probiotic
strains such as Bifidobacterium infantis (B. infantis) and Lactobacillus in improving symp-
toms and overall management of IBS [
76
,
77
]. A randomized controlled trial conducted by
Enck et al. found that a mixture of Escherichia coli (E. coli) (DSM 17252) and Enterococcus
faecalis (DSM 16440) led to improved symptoms in people with IBS [
78
]. Additionally,
O’Mahony et al. found that supplementing IBS patients with the probiotic strain B. infantis
35624 for eight weeks reduced symptom scores for abdominal pain/discomfort, bloat-
ing/distention, and bowel movement difficulty. Compared to the placebo group, it also
normalized the abnormal ratio of the anti-inflammatory cytokine IL-10 to the proinflam-
matory cytokine IL-12 in IBS patients [
77
]. These results suggest that B. infantis 35624 can
alleviate symptoms and modulate the immune response in individuals with IBS. However,
other studies have shown no improvement [
79
–
81
]. For example, several trials have inves-
tigated the effects of specific Lactobacillus strains on IBS symptoms but found no significant
benefits. These trials include those examining the impact of Lactobacillus casei (L. casei)GG,
Lactobacillus plantarum (L. plantarum)DSM 9843, and Lactobacillus salivarius (L. salivarius)
UCC43 [
79
–
81
]. Despite initial expectations, these studies did not demonstrate a notable
improvement in symptoms, suggesting that probiotics’ efficacy in managing IBS may vary
depending on the specific strains used.
In addition to highlighting differences in microbial composition between healthy
individuals and IBS patients, considering the intricate interaction between the gut micro-
biota and the host’s immune system is also important. The gut microbiota plays a critical
role in maintaining immunological homeostasis, and alterations in microbial populations
associated with IBS may be consequential to immune function. Further exploration of
the gut microbiome and its impact on the immune system will be discussed later in this
review, providing a comprehensive understanding of the gut microbiome and its potential
modulation in managing IBS.
2.2. GMP as an Antimicrobial Agent
GMP reportedly exhibits antimicrobial properties, contributing to its potential thera-
peutic effects (Table 1) [
57
,
82
–
86
]. GMP’s antimicrobial effects do not involve direct killing
of the bacteria but rather inhibit the adhesion of bacterial pathogens to intestinal cells [
57
].
For example, GMP can decrease the attachment of specific strains of enteropathogenic E. coli
(EPEC) O125:H32, EPEC O111:H2, and enterohemorrhagic E. coli (EHEC) 12900 O157:H7 as
well as Salmonella enteritidis to HT29 and Caco-2 intestinal cell lines [
84
,
85
,
87
]. However,
reduced adhesion is highly species-specific, with GMP not inhibiting the adhesion of other
E. coli strains [
87
] or Desulfovibrio desulfuricans [
85
], a micro-organism often associated with
IBS [
88
] and inactive inflammatory bowel disease (IBD) [
89
,
90
]. Similarly, GMP reduces
pathogenic E. coli (verotoxigenic E. coli and EPEC) strains’ adhesion to human HT29 tissue
cell cultures [
85
]. GMP’s ability to prevent bacterial adhesion is typically attributed to
its glycosylation [
87
]. For example, Nakajima et al. found that GMP’s binding ability to
enterohemorrhagic E. coli O157:H7 was significantly reduced after removing the sialic acid
present in GMP (a process known as desialylation) [84].

Nutrients 2023,15, 3991 6 of 22
Table 1. Studies on the effects of GMP on the microbiome.
Study Type References GMP Product Study Model Effects on Microbiome 1
Clinical Trial
Brück et al., 2006 [86]α-lactalbumin and GMP-enriched
infant formulae Healthy term infants (n= 85) (n) gut microbiota
Wernlund et al., 2021 [91] GMP Healthy adults
(n= 25) (n) gut microbiota
Montanari et al., 2022 [92] GMP People with PKU
(n= 9)
(+) Agathobacter spp.; (+) Subdoligranulum;(n) for
gut microbiota diversity; (n) Short-chain fatty
acids (SCFA)
Yu et al., 2022 [93] scGOS/lcFOS (9:1) and GMP Very preterm infants
(n= 72) (+) Bifidobacterium
Hansen et al., 2023 [94] GMP Obese postmenopausal women (n= 13) (−)Streptococcus; (−)αdiversity
Animal Study
Sawin et al., 2015 [95] GMP Wild-type and PKU mice—fed GMP (−)Proteobacteria; (−)Desulfovibrio; (+) SCFA
Jiménez et al., 2016
[96]GMP Rats—fed
(+) Lactobacillus; (+) Bifidobacterium; (+) Bacteroides
Ntemiri et al., 2019 [97] GMP Mice with humanized fecal microbiota—fed (n) gut microbiota
Yuan et al., 2020 [98] GHP C57BL/6J mice with induced type 2
diabetes—fed
(+) Diversity of gut microbiota; (−)
Firmicutes:Bacteroidetes ratio; (+)
Bacteroidales_S24-7; (+) Ruminiclostridium; (+)
Blautia; (+) Allobaculum; (−)Helicobacteraceae
Chen et al., 2012 [99] GMP BALB/c mice—fed (+) Lactobacillus; (+) Bifidobacteria; (−)
Enterobacteriaceae; (−) coliforms; (n) Enterococcus
Gustavo Hermes et al., 2013 [82] GMP Piglets—fed
(−)E. coli attachment to intestinal mucosa; (+)
Lactobacillus; (−)Enterobacteria; (−) villi with E.
coli adherence
Rong et al., 2015 [83] GMP Piglets—fed
(−) Intestinal barrier permeability damage
caused by E. coli K88 infection; (−) Acute
inflammatory response induced by E. coli K88
infection
Wu et al., 2020 [100] GMP Sow and piglet model—fed
(+) Prevotella; (+) Fusobacterium; (+)
unclassified_f__Prevotellaceae; (+)
norank_f__Ruminococcaceae; (+)
Christensenellaceae_R-7_group; (+)
Ruminococcaceae_UCG-005; (+)
Ruminococcaceae_UCG-010

Nutrients 2023,15, 3991 7 of 22
Table 1. Cont.
Study Type References GMP Product Study Model Effects on Microbiome 1
Cell study
Nakajima et al., 2005 [84] GMP Caco-2 cells (−) Adhesion of Salmonella enteritidis and
enterohemorrhagic E. coli O157:H7 to Caco-2 cells
Rhoades et al., 2005 [85] GMP HT29 cells
(−) Adhesion of pathogenic E. coli (VTEC and
EPEC) strains to human HT29 tissue cell cultures;
(−) Adhesion of Lactobacillus pentosus (L.
pentosus), Lactobacillus acidophilus (L. acidophilus),
and L. casei strains; (n) Adhesion of Desulfovibrio
desulfuricans or Lactobacillus gasseri (L. gasseri)
Brück et al., 2006 [57]α-lactalbumin and GMP Caco-2 cells
(
−
) Adhesion of Enteropathogenic E. coli (EPEC),
Salmonella typhimurium and Shigella flexneri
Feeney et al., 2017 [87] GMP HT29 and Caco-2 cells
(−) Epithelial cell barrier dysfunction; (−)
pathogen adhesion of Enterohemorrhagic E. coli
(EHEC) and Enteropathogenic E. coli (EPEC)
Culture and
medium study
Azuma et al., 1984 [101] GMP Bacterial culture of B. infantisS12 (+) B. infantisS12
Brück et al., 2003 [56] GMP and α-lactalbumin Bacterial culture (+) Bifidobacteria; (+) Lactobacilli; (−)Bacteroides;
(−)Clostridia; (−)E. coli
Robitaille et al., 2013 [53] GMP Bacterial culture (+) Lactobacillus rhamnosus (L. rhamnosus); (+)
Bifidobacterium thermophilum (B. thermophilum)
Tian et al., 2015 [102] GHP Yogurt
(+) Bifidobacterium animalis spp. Lactis BB12
(BB-12); (+) Streptococcus thermophilus; (n)
Lactobacillus bulgaricus
Ntemiri et al., 2017 [103] GMP Artificial colon model (+) Coprococcus; (+) Clostridium cluster XIVb; (+)
Fecal microbiota diversity
O’Riordan et al., 2018 [104] GMP Bacterial culture (+) Bifidobacterium longum ssp. infantis
Morozumi et al., 2023 [105] GMP GMP containing medium (+) Bifidobacterium bifidum; (+) Bifidobacterium
breve
1
(+) Indicates an observed positive change in the microbiome, such as an increase in abundance or effect; (
−
) Indicates an observed negative change in the microbiome, such as a
decrease in abundance or effect; (n) No significant change. Abbreviations used in the table: GMP: Glycomacropeptide; GHP: Hydrolyzed Glycomacropeptide; PKU: Phenylketonuria;
SCFA: Short-chain fatty acids; scGOS/lcFOS: short-chain galactooligosaccharides/long-chain fructooligosaccharides; EPEC: Enteropathogenic E. coli; EHEC: Enterohemorrhagic E. coli;
VTEC: Verotoxigenic E. coli; BB-12: Bifidobacterium animalis spp. Lactis BB12.

Nutrients 2023,15, 3991 8 of 22
Although GMP can be effective in preventing pathogen adhesion to intestinal cells, it
can also inhibit the binding of certain probiotic organisms. For example, GMP has been
shown to reduce the adhesion of various probiotic Lactobacillus strains, such as L. pentosus,
L. casei, and L. acidophilus, but not of L. gasseri to HT29 cells [85].
GMP contributes to the enhancement of mucus barrier function by binding to bac-
teria or mucin proteins directly. The intestinal epithelium is covered with a mucus layer
comprising highly glycosylated proteins called mucins, which contribute to gut barrier
function [
106
]. Pathogens such as Helicobacter pylori can bind to mucins as a first step in
infection [
106
]. GMP contains multiple sialic acid residues that are similar to glycans on
mucins, which are selectively targeted by bacterial lectins. When GMP is present, its glycans
compete with the natural mucin glycans in the gut for binding sites on bacterial lectins.
This competition can inhibit the adhesion of bacteria to the gut lining. For instance, GMP
has been shown to prevent the binding of enterotoxigenic E. coli K88 fimbriae to mucins [
82
].
Thus, GMP’s prevention of bacterial adherence can improve barrier function and prevent
infection. Supplementing BALB/c mice diets with GMP reduced the abundance of fecal
Enterobacteriaceae and coliforms [
99
]. However, there was no significant effect observed on
Enterococcus. In piglets, oral GMP reduced the percentage of villi with E. coli adherence
but did not reduce diarrhea [
82
]. Rong et al. found that supplementing weaning piglets’
diets with 1% GMP mitigated the negative effects of E. coli K88 infection, including reduced
growth, increased intestinal tissue pathogenic bacteria count, and damage to the intestinal
barrier [
83
]. Additionally, GMP lowered the acute inflammatory response induced by the
infection. These findings suggest that GMP has potential beneficial effects on improving gut
health and reducing the impact of bacterial infections in piglets. However, GMP’s specific
effects on diarrhea symptoms may vary. Further research is needed to fully understand its
mechanisms of action and potential applications in human subjects with conditions such
as IBS.
2.3. GMP as a Prebiotic
In vitro
and animal studies indicate that GMP’s prebiotic properties can enhance pop-
ulations of beneficial bacteria, i.e., Bifidobacteria and Lactobacillus [
53
,
56
,
96
,
99
,
101
] (Table 1).
Studies indicate that GMP’s glycan and peptide moiety may be responsible for its
growth-promoting abilities. The glycosylation of GMP is often considered the basis for its
prebiotic activity. For example, O’Riordan et al. found that GMP’s bifidogenic effect and
transcriptional response were significantly reduced upon removing glycans via periodate
oxidation [
104
]. However, some studies indicate that the peptide moiety has prebiotic
effects. For example, Robitaille et al. found that glycosylated, unglycosylated, and mixed
GMP were equally effective at fostering the growth of the probiotics L. rhamnosus RW-
9595-M and B. thermophilum RBL67 in culture media compared to the control [
53
]. GMP
appears to retain its prebiotic actions even after partial digestion. For example, Tian et al.
found that GMP digested by trypsin had higher growth-promoting effects on BB12 than
intact GMP [
102
]. After a 4-week intervention, Yu et al. found that the formula was
enriched with short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides
(scGOS/lcFOS). GMP also promoted an increased abundance of Bifidobacterium in the gut
microbiota of preterm infants [
93
], but the probiotic effect observed may not only derive
from the GMP component.
Therefore, GMP may help support beneficial bacteria growth, which can help crowd
out pathogens. This function is important because a balanced microbiota is crucial for
overall gut health.
2.4. GMP’s Influence on the Gut Microbiome
GMP has the potential to ameliorate dysbiosis (Table 1). For example, GMP supple-
mentation increased the microbial diversity in an ex vivo fecal culture model of elderly
subjects with lower microbial diversity than the lactose control [
103
]. Similarly, GMP
hydrolysate supplementation helped restore microbial diversity in mice with type 2 dia-

Nutrients 2023,15, 3991 9 of 22
betes [
98
]. Specifically, GMP hydrolysate supplementation lowered Helicobacteraceae levels;
increased Ruminococcaceae, the Bacteroidales_S24-7_group,Ruminiclostridium,Blautia, and
Allobaculum and decreased the Firmicutes:Bacteroidetes ratio. This finding is relevant to IBS,
as patients with IBS had a 1.2–3.5-fold higher ratio of Firmicutes:Bacteroidetes compared to
healthy controls [
38
,
67
,
107
–
109
]. Sawin et al. demonstrated that providing a GMP-based
diet to weaned PKU and wild-type C57BL/6 mice reduced Proteobacteria, specifically the
genera Desulfovibrio, associated with IBD [
110
], compared to casein- or amino acid-based
diets [
95
]. Sawin et al. also found that the GMP diet increased the cecal concentrations
of SCFAs, including acetate, propionate, and butyrate, in both mouse types compared to
the casein and amino acid diets. These increases in SCFA levels may lead to improved
intestinal barrier function [
111
] and reduced systemic inflammation [
112
]. However, in a
murine model “humanized” with human fecal microbiota, GMP derived from bovine milk
did not exhibit prebiotic activity on fecal microbiota [97].
GMP’s influence on the human gut microbiome has been explored in multiple con-
texts, yet the outcomes vary and are often contingent upon the study demographics and
specifics of the supplementation. In a study with healthy-term infants randomized to
different infant formulas, including those enriched in alpha-lactalbumin with varying
GMP levels, no significant shifts in bacterial counts were observed across six months [
86
].
Hansen et al. showed that obese postmenopausal women’s consumption of GMP supple-
ments reduced Streptococcus bacteria when taken twice daily and an overall decrease in
microbial diversity when taken thrice daily [
94
]. However, after replacing dietary proteins
with GMP in humans with PKU for six months, Montanari et al. found no changes in
overall gut microbiome diversity (albeit, with some increases in a few beneficial species) or
short-chain fatty acid levels compared to the baseline [
92
]. Similarly, Wernlund et al. found
no significant changes in fecal microbiota composition or SCFA content when comparing
healthy adults before and after GMP supplementation (25 g/day) for four weeks and com-
pared to skim milk-supplemented controls [
91
]. These results suggest that GMP may not
substantially influence humans’ gut microbiome. However, the supplementation duration
and the specific supplement and dose used could have affected these findings. Further
research is necessary to explore GMP’s impact on the gut microbiome in humans.
2.5. Potential Implications of GMP-Induced Microbiota Modulation in IBS
Cell and animal studies suggest that GMP can positively influence gut microbiota
composition, indicating its value for IBS patients. Since dysbiosis is a common feature of
IBS, GMP’s ability to inhibit the adhesion of pathogenic bacteria and promote beneficial
bacteria growth could contribute to restoring a healthy gut microbiota balance in these
individuals if taken as a supplement. However, these findings suggest that GMP’s ability to
inhibit the binding of certain beneficial Lactobacillus strains to intestinal cells may counteract
these beneficial effects. Moreover, current studies of GMP supplementation in humans
provide scarce evidence that GMP can positively modulate the human microbiome. More
research is needed to determine the effects of GMP supplementation on the microbiome of
IBS patients. Since GMP is known to be digested partially within the human gut [
113
–
115
],
encapsulation and other delivery strategies may be needed to enhance its effectiveness.
3. GMP and Inflammation in IBS
3.1. Inflammation in IBS
Although the precise etiology of IBS remains unknown, inflammation may be a
contributing factor [
32
]. In some studies, low-grade inflammation and immune activation
were found in IBS patients [
116
–
118
]. This inflammation may be instigated by infections,
alterations in the gut microbiota, or increased intestinal permeability, potentially causing
symptoms such as abdominal pain or altered bowel habits [
32
]. Moreover, the involvement
of the brain–gut axis, which affects neuroendocrine pathways and glucocorticoid receptor
genes, could foster a pro-inflammatory state, contributing to the manifestation of IBS
symptoms [32].

Nutrients 2023,15, 3991 10 of 22
Some studies have identified cytokine differences between IBS patients and healthy
controls [
54
,
119
–
122
]. More specifically, people with IBS often have decreased levels of anti-
inflammatory cytokines such as IL-10 compared to healthy individuals [
119
,
120
,
123
,
124
]. IL-
10 normally regulates and dampens inflammation by inhibiting pro-inflammatory cytokine
production and promoting regulatory immune cell activity [
124
]. However, when IL-10
production is suppressed, the inflammatory process may become prolonged or exaggerated,
resulting in chronic or recurrent symptoms and the development of certain conditions,
such as IBS. However, not all studies found decreased IL-10 in IBS patients; for example,
Vara et al. found that IL-10 levels were higher in people with IBS compared to healthy
controls [54].
Studies have indicated that compared to healthy individuals, IBS patients have higher
levels of pro-inflammatory cytokines in their plasma. In past studies, cytokines that
have appeared at higher levels in IBS patients include (IL)-1, IL-3, IL-4, IL-5, IL-6, IL-8,
IL-12, IL-13, IL-16, IL-17, IL-18, tumor necrosis factor-alpha (TNF-
α
), and interferon-
γ
(IFN-
γ
) [
32
,
54
,
122
,
125
,
126
]. Higher pro-inflammatory cytokine levels may indicate chronic
inflammation in people with IBS [
116
]. These findings suggest that IBS patients have
atypical immune regulation, and more research is needed to understand how the immune
system is activated in IBS patients.
Fecal calprotectin (FC) is a calcium- and magnesium-binding protein primarily pro-
duced in neutrophils. When found in the intestine or feces, it indicates the presence of
neutrophil migration to the inflamed intestinal mucosa [
127
]. FC is a biomarker of intestinal
inflammation. Some studies have reported higher FC levels in a subset of IBS patients, even
exceeding those observed in individuals with inflammatory bowel disease (IBD) [
128
]. Choi
and Jeong found higher FC levels in children with IBS than in healthy controls, indicating a
potential association between FC and IBS in this population [
129
]. However, some studies
did not find significant differences in FC between IBS patients and controls [
130
,
131
]. More
research is needed to determine the factors contributing to elevated FC levels in some IBS
patients and clarify its role in the pathophysiology of the condition. Understanding the
relationship between FC, inflammation, and symptom generation in IBS could provide
valuable insights into the underlying mechanisms and potential therapeutic strategies for
managing this complex disorder.
Severe viral or bacterial infections can cause inflammation of the gastrointestinal tract
(acute gastroenteritis) and induce IBS symptoms that persist even after the pathogen is
eliminated from the body (post-infectious IBS) [
34
]. Post-infectious IBS is characterized by
increased T-lymphocytes, mast cells, and cytokines, which can alter gastrointestinal func-
tions, increase intestinal permeability, and potentially cause chronic IBS symptoms [
129
].
A meta-analysis showed that the risk of developing IBS increased six-fold after a gas-
trointestinal infection and remained elevated for 2–3 years after the initial infection was
resolved [132].
3.2. GMP as an Anti-Inflammatory Agent
GMP has anti-inflammatory properties in many cell and animal studies (Table 2).
However, some studies indicate that GMP has pro-inflammatory effects in cell and animal
studies. Human studies with GMP supplementation indicate a more limited capacity to
modulate inflammation (Table 2).

Nutrients 2023,15, 3991 11 of 22
Table 2. Studies on the effects of GMP on inflammation.
Study Type References GMP Product Study Model Effects on Inflammation 1
Clinical Trial
Hvas et al., 2016 [133] GMP People with ulcerative
colitis (n= 24)
(n) Cytokine levels
(−) endoscopic colonic
inflammation
Wernlund et al., 2021 [91] GMP Healthy adults (n= 24) (n) No significant change
Hansen et al., 2023 [94] GMP Obese postmenopausal
women (n= 13) (n) No significant change
Animal Study
Daddaoua et al., 2005 [134] GMP
Rats with
trinitrobenzenesulfonic
acid-induced colitis—fed
(−) IL-1
Requena et al., 2008 [135] GMP Rats with induced
ileitis—fed
(−) IL-1β; (−) TNF-α; (−) IL-17;
(n) IFN-γ; (−) IL-2; (−) IL-1Ra
Requena et al., 2010 [136] GMP Rat splenocytes and
Wistar rats—fed (+) IL-10; (−) IFN-γ; (−) TNF-α
López-Posadas et al., 2010 [137] GMP Rats—fed (−) IL-1β; (−) IL-17; (−) IL-23;
(−) IL-6; (−) TGF-β; (−) IL-10
Ortega-González et al.,
2014 [138]GMP C57BL/6 mice—fed (+) IL-6; (+) IL-10; (+) TNF-α; (+)
IFN-γ
Sawin et al., 2015 [139] GMP
PKU (Pah(enu2)) and
wild-type (WT) C57Bl/6
mice—fed
(+) Acetate; (+) propionate; (+)
butyrate; (−) IFN-γ; (−) TNF-α;
(−) IL-1β; (−) IL-2; (−) IL-10
Muñoz et al., 2017 [140] GMP C57BL/6 wild-type and
Rag−/−mice—fed
(−) IL-4; (−) IL-5; (−) IL-13; (+)
IL-10
Cervantes-García et al.,
2020 [141]GMP Rats—fed (−) IL-1β
Reyes-Pavón et al., 2020 [142] GMP Rats—fed (−) IL-1β; (−) TNF-α; (−) IL-5;
(−) IL-13
Cell study
Mikkelsen et al., 2005 [143] GMP
Murine spleen cells and
dendritic cells challenged
with LPS, Concanavalin-A,
and PHA
(−) IL-1β; (−) TNF-α; (−) IL-6
Requena et al., 2010 [136] GMP THP-1 cells (+) IL-8; (+) IL-1β
Cheng et al., 2015 [144] GHP Macrophages (−) TNF-α; (−) IL-1β; (−) IL-6
Li et al., 2017 [145] GHP
LPS-stimulated RAW264.7
macrophages (−) TNF-α; (−) IL-1β; (−) IL-6
Foisy-Sauvéet al., 2020 [146] GMP Caco-2/15 Cells
(−) Oxidative stress; (−)
malondialdehyde; (+)
superoxide dismutase 2; (+)
glutathione peroxidase
Arbizu et al., 2020 [147] GMP HT29-MTX and Caco-2
cells
(+) Intestinal barrier function;
(−) LPS-induced inflammation;
(+) Tight junction proteins
Lu et al., 2022 [148] GMP
LPS-stimulated RAW264.7
macrophages (+) IL-1α; (+) TNF-α; (+) IL-10
1
(+) Indicates an observed positive change in the microbiome, such as an increase in abundance or effect; (
−
) Indi-
cates an observed negative change in the microbiome, such as a decrease in abundance or effect; (n) No significant
change. Abbreviations used in the table: GMP: Glycomacropeptide; GHP: Hydrolyzed Glycomacropeptide; PHA:
Phytohemagglutinin; IL: Interleukin; IL-1Ra: Interleukin-1 receptor antagonist; TNF-
α
: Tumor Necrosis Factor
alpha; IFN-
γ
: Interferon gamma; TGF-
β
: Transforming Growth Factor beta; PKU: Phenylketonuria; Pah (enu2):
Phenylalanine hydroxylase enzyme mutation in a PKU mouse model; WT: Wild type; LPS: Lipopolysaccharides;
Rag
−
/
−
: Recombination activating gene knockout mice, which lack mature T and B lymphocytes; THP-1 cells: A
human monocyte cell line.
Many studies conducted on different cell lines have indicated GMP’s anti-inflammatory
properties. For instance, when murine spleen cells and dendritic cells were challenged with
inflammatory agents such as LPS, Concanavalin-A, and Phytohemagglutinin, GMP was
found to reduce levels of IL-1
β
, TNF-
α
, and IL-6 [
143
]. Macrophage studies, especially

Nutrients 2023,15, 3991 12 of 22
regarding inflammation, have often examined TNF-
α
, IL-1
β
, and IL-6 levels as indicators.
For example, one study indicated that hydrolyzed GMP (GHP) reduced these cytokines
in LPS-stimulated macrophages [
144
]. Similarly, GHP reduced TNF-
α
, IL-1
β
, and IL-6
levels in LPS-stimulated RAW264.7 macrophages [
145
]. The anti-inflammatory response of
GMP was further evident in a study of HT29-MTX and Caco-2 cells. Here, GMP reduced
LPS-induced inflammation, which may have been partially responsible for the increase in
tight junction proteins and improved intestinal barrier function [147].
GMP has demonstrated anti-inflammatory effects across various animal models. In
rats subjected to trinitrobenzenesulfonic acid-induced colitis, GMP administration resulted
in decreased IL-1 levels [
134
]. Similarly, in rats with experimental ileitis, GMP’s reduction
in inflammatory markers (IL-1
β
, TNF-
α
, IL-17, IL-2, and IL-1Ra) was comparable to the
therapeutic effects of the standard drug, 5-aminosalicylic acid [
135
]. A study on rat spleno-
cytes and Wistar rats also supports GMP’s anti-inflammatory capabilities, wherein GMP
decreased levels of IFN-
γ
and TNF-
α
[
136
]. Rats in another investigation showed dimin-
ished expression of a host of inflammatory cytokines, including IL-1
β
, IL-17, IL-23, IL-6,
TGF-
β
, and IL-10, when their diet incorporated GMP [
137
]. A study with PKU (Pah(enu2))
and wild-type (WT) C57BL/6 mice indicated an anti-inflammatory response to GMP, with
decreases in IFN-
γ
, TNF-
α
, IL-1
β
, IL-2, and IL-10 [
139
]. Similarly, C57BL/6 wild-type and
Rag
−
/
−
mice showed lowered IL-4, IL-5, and IL-13 levels when fed with GMP [
140
]. In
more recent rat studies, GMP’s effect remained consistent: one highlighted a decline in
IL-1
β
levels following GMP supplementation [
141
], while another documented reduced
levels of IL-1β, TNF-α, IL-5, and IL-13 with GMP in the diet [142].
Though most animal and cell studies have revealed GMP’s anti-inflammatory effects,
some show pro-inflammatory effects. For example, in THP-1 cells, GMP treatment elevated
levels of IL-8 and IL-1
β
[
136
]. Furthermore, GMP exposure in LPS-stimulated RAW264.7
macrophages upregulated IL-1
α
and TNF-
α
[
148
]. Similarly, in C57BL/6 mice, GMP
supplementation increased levels of IL-6, TNF-
α
, and IFN-
γ
[
138
]. These findings indicate
that while GMP has predominantly shown anti-inflammatory effects, there are instances
and conditions where it exhibits pro-inflammatory effects [136,138,148].
Human studies on the immunomodulatory activity of GMP have provided varied
findings. GMP supplementation decreased endoscopically observed colonic inflamma-
tion when added to standard therapy for individuals with ulcerative colitis. However,
despite this localized improvement, the subjects’ plasma cytokine levels were not signif-
icantly altered [
133
]. Extending the research to the broader population, a study with 24
healthy adults indicated that a four-week regimen of GMP supplementation did not lead
to any marked immunomodulatory effects compared to skim milk [
91
]. Similarly, in a
targeted study on obese postmenopausal women, GMP supplementation did not induce
any prominent changes in immune responses [94].
3.3. Potential Implications of GMP-Induced Anti-Inflammatory Modulation in IBS
Since most cell and animal studies indicate that GMP has anti-inflammatory prop-
erties (suppressing the production of pro-inflammatory cytokines, such as TNF-
α
and
IL-6 [
134
–
137
,
139
,
141
–
145
,
147
,
148
] and promoting the production of anti-inflammatory cy-
tokines, such as IL-10 [
136
,
138
,
140
,
148
]), GMP supplementation may help treat individuals
with chronic inflammation, including people with IBS. This modulation of inflammatory
mediators may alleviate symptoms. Since inflammation plays a significant role in IBS
pathogenesis, addressing inflammation is essential for symptom management.
Further research is needed to identify the mechanisms underlying GMP’s anti-
inflammatory effects in IBS. Rigorous clinical trials are necessary to evaluate the efficacy,
optimal dosages, and long-term effects of GMP supplementation in IBS patients.

Nutrients 2023,15, 3991 13 of 22
4. GMP’s Toxin Binding, Gut Motility-Decreasing, and Barrier Function-Enhancing
Properties in IBS
GMP has toxin binding, gut motility-decreasing, and barrier function-enhancing
properties (Table 3) that may help manage IBS symptoms.
Table 3. Studies on the effects of GMP on other functions.
Study Type References GMP Product Study Model Effects 1
Animal Study
Vasilevskaia et al.,
1977 [149]GMP Dogs—ntravenous
injection
(−) Gastric juice
secretion
Stan and Chernikov,
1979 [150]GMP Dogs—intravenous
injection (−) Gastric secretion
Stan et al., 1983 [151] GMP Dogs—intravenous
injection
(
−
) Food motility of the
stomach fundus; (−)
Cyclic-repetitive
vomiting; (−) Gastric
secretion; (−) Gastric
motility
Rong et al., 2015 [83] GMP Piglets—fed
(+) Protection against E.
coli K88-induced barrier
permeability damage
Wu et al., 2020 [100] GOS and GMP Sow and piglet
model—fed
(+) Tight junctions and
mucins to enhance
intestinal barrier
functions
Cell study
Kawasaki et al.,
1992 [55]GMP CHO-K1 cells
(−) Cholera toxin
binding; (−)
morphological changes
Arbizu et al., 2020 [
147
]
GMP HT29-MTX and Caco-2
cells
(+) Intestinal barrier
function; (−)
LPS-induced
inflammation; (+) Tight
junction proteins
1
(+) Indicates an observed positive change in the microbiome, such as an increase in abundance or effect; (
−
)
Indicates an observed negative change in the microbiome, such as a decrease in abundance or effect; (n) No
significant change. Abbreviations used in the table: GMP: Glycomacropeptide; GOS: Galactooligosaccharides;
LPS: Lipopolysaccharides.
4.1. Binding Toxin
Some gut bacteria (i.e., Campylobacter,Shigella,E. coli, and Salmonella) can produce
toxins, including endotoxins and exotoxins. These toxins can stimulate the immune system
and cause inflammation, disrupting gut motility and permeability. These toxins and their
effects may contribute to the symptoms and pathology of post-infectious irritable bowel
syndrome (PI-IBS) [152], including visceral hypersensitivity [153].
LPS is one of the most concerning endotoxins produced by certain Gram-negative
bacteria (i.e., Bacteroidales). High levels of LPS can increase the permeability of the gut
barrier [
154
]. This increased permeability allows LPS and other toxins to enter the blood-
stream, causing systemic inflammation. The presence of LPS in the gut may contribute to
the development and maintenance of IBS symptoms. Studies have shown that patients with
diarrhea-predominant IBS (IBS-D) exhibit significantly higher serum levels of LPS [
155
].
Binding and neutralizing these toxins could help manage IBS symptoms by decreasing gut
permeability and inflammation.
In vitro
studies have demonstrated that GMP can bind to bacterial toxins (Table 3),
such as LPS [
147
] and Vibrio cholerae-produced cholera toxin (CT) [
55
]. GMP and host cells
compete for the same binding sites on bacterial toxins. When GMP binds to these harmful
toxins, it prevents them from interacting with host cells. GMP can inhibit the binding of CT

Nutrients 2023,15, 3991 14 of 22
to Chinese hamster ovary (CHO-K1) cells and ganglioside GM1, which serve as the binding
site for CT, and reduce CT-induced morphological changes in the cells [
55
]. Feeding mice 1
mg of GMP per day protected almost all mice from diarrhea caused by CT. These findings
emphasize GMP’s potential as a preventive measure against toxin-mediated gastrointestinal
symptoms. GMP can also downregulate the LPS-induced pro-inflammatory response and
inhibit the protein expression of NF-
κ
B-p65 in LPS-stimulated cells, potentially mitigating
the inflammation induced by LPS [
147
]. Most studies attribute GMP’s toxin-binding
capacity to its glycosylation (particularly sialic acid residues) [55].
GMP’s ability to bind bacterial toxins could have potential implications for managing
IBS. By preventing the binding and interaction of toxins with host cells, GMP could help
reduce the inflammatory response and alleviate symptoms in individuals with IBS. Further
research is needed to explore whether GMP can limit toxin binding
in vivo
in humans and
reduce IBS symptoms.
4.2. Gut Motility
People with IBS often have dysregulated gut motility, leading to constipation, diarrhea,
or a mix of both [
156
]. Stress, diet, alterations in the gut microbiome, and hormonal
changes can influence gut motility [
157
]. Stress can trigger the release of hormones and
neurotransmitters that affect motility [
157
]. Diet can modulate gut motility, with insoluble
fiber-rich foods promoting transit [
158
], high-fat and processed foods potentially slowing
digestion [
159
] and certain carbohydrates (fermentable oligosaccharides, disaccharides,
monosaccharides, and polyols) impacting bloating and faster motility [
160
]. Imbalances in
the gut microbiota promote gut motility [
157
]. Hormonal fluctuations, such as increased or
decreased levels of progesterone or estrogen, can affect muscle contractions in the intestinal
walls, leading to stronger or weaker contractions resulting in diarrhea, constipation, or
alternating bowel habits [
161
]. In addition to directly inducing bowel habit changes
associated with IBS, these factors’ influence on gut motility can lead to changes in the gut
microflora, which contribute to the development of IBS [162].
Regarding IBS management, GMP has shown potential in modulating gastric secretion
and stomach motility [
149
–
151
] (Table 3). Intravenous injections of GMP in dogs inhibited
gastric secretion and motility [
149
–
151
]. Whether GMP consumed as a food or supplement
has similar effects is unknown.
GMP’s potential to slow gastric motility may be particularly beneficial for people with
IBS-D, as it could help modulate the dysregulated motility experienced by these patients.
Further research is needed to elucidate the specific mechanisms by which GMP affects gut
motility and whether these effects are transferable to humans.
4.3. Barrier Function
The intestinal barrier plays a pivotal role in health, as it prevents harmful pathogens
and toxins from entering the bloodstream and facilitates the uptake of essential nutri-
ents. This barrier can be compromised in IBS, particularly within its IBS-D and PI-IBS
subtypes, leading to symptomatic manifestations such as abdominal pain and bowel dis-
turbances [
163
]. Gastrointestinal infections can compromise intestinal barrier function, as
some pathogens are adept at altering tight junctions [
164
]. This compromise can facilitate
the migration of bacteria and their products from the intestinal lumen into the blood-
stream, igniting immune responses and subsequent inflammation [
164
]. Such inflammatory
responses can further exacerbate intestinal permeability [156].
GMP has improved gut barrier function in cell models and animal studies (Table 3).
For example, Arbizu et al. found that in HT29-MTX and Caco-2 cell lines, which were
subjected to LPS-induced disruptions, GMP treatment upregulated tight junction proteins
(claudin-1, claudin-3, occludin, and zonula occludens-1) [
147
]. Such proteins are essential
for preserving the structural integrity of the intestinal barrier. In the same study, GMP was
observed to mitigate the permeability induced by TNF-
α
in Caco-2/HT29-MTX co-cultured
monolayers. This mitigation was comparable to the effects of TGF-
β
1, a protein known

Nutrients 2023,15, 3991 15 of 22
to enhance epithelial barrier function [
147
]. Additionally, Feeney et al. demonstrated
that GMP could significantly reduce the adhesion of pathogenic E. coli to HT29 and Caco-
2, underlining its potential to bolster gastrointestinal barrier defense against harmful
bacteria [70].
GMP’s effects on barrier function have been shown in animal models. For example,
supplementing GMP to weaning piglets challenged with an E. coli K88 helped prevent
infection-induced increases in intestinal barrier permeability [
83
]. This protection con-
tributed to the overall health of the piglets and reduced the impact of infection.
By enhancing the integrity of the intestinal barrier, GMP can prevent the translocation
of harmful substances and pathogens, which could help prevent inflammation and promote
overall gut health. These findings suggest that GMP may hold promise for improving
intestinal barrier function in individuals with IBS. Further research is needed to determine
whether GMP can enhance barrier function in humans and whether this improved barrier
function can support IBS management.
5. Conclusions and Future Perspective
The current body of research indicates that the diverse properties of GMP (antimi-
crobial, prebiotic, immunomodulatory, toxin-binding, gut motility-modulating, barrier
function-enhancing) align well with the recognized pathophysiological aspects of IBS (mi-
crobiome imbalances, immune system alterations, altered gut function). Therefore, GMP
may have potential as a therapeutic agent in IBS management.
GMP was shown to prevent the binding of pathogenic bacteria and toxins to models
of the human intestine (HT29 and Caco-2 cancer cell lines). These cell lines can differentiate
into cells resembling normal intestinal enterocytes, serving as useful models for research.
However, the results of these cell line experiments may not accurately reflect human
physiology. Future work should also examine the extent to which GMP exerts these effects
on primary cell lines and enteroids.
Current research predominantly indicates that GMP has anti-inflammatory activity,
which could be useful in alleviating chronic inflammation often associated with IBS. Al-
though some studies indicate its pro-inflammatory effects, further investigations are needed
to clarify GMP’s immunomodulatory effects and identify their precise mechanisms.
GMP’s toxin-binding, gut motility-modulating, and barrier function-enhancing prop-
erties may be useful in IBS management. Studies have demonstrated GMP’s ability to bind
and neutralize harmful bacterial toxins, which could prevent characteristic symptoms of
IBS, including toxin-induced inflammation and increased gut permeability. GMP’s ability to
decrease gut motility could be useful in cases of IBS-D. GMP’s ability to enhance intestinal
barrier function could also help mitigate symptoms associated with IBS.
However, no direct studies have investigated the effects of GMP supplementation
on the symptoms, microbiome, immune profile, and gut health of individuals with IBS.
Clinical trials into GMP’s effects on these aspects of IBS management are needed. Future
research should also examine GMP’s optimal dosage, formulation, and treatment duration
for IBS treatment. Moreover, research should examine how GMP’s effects differ across vari-
ous IBS subtypes, which could facilitate the development of subtype-specific therapeutic
approaches. By focusing on these critical areas, research communities can develop a new
therapeutic strategy for IBS.
Author Contributions:
Methodology, analysis, preparation of original manuscript draft—Y.Q. manuscript
editing—S.H.P. conceptualization, methodology development, manuscript editing, supervision, funding
acquisition—D.C.D. All authors have read and agreed to the published version of the manuscript.
Funding: This work was supported by funding from BUILD Dairy and Agropur, Inc.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.

Nutrients 2023,15, 3991 16 of 22
Acknowledgments:
We thank Haley C. Paxton for her contributions to Section 2.1 on IBS subtype
gut bacterial composition.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Seyedmirzaee, S.; Hayatbakhsh, M.M.; Ahmadi, B.; Baniasadi, N.; Bagheri Rafsanjani, A.M.; Nikpoor, A.R.; Mohammadi, M.
Serum Immune Biomarkers in Irritable Bowel Syndrome. Clin. Res. Hepatol. Gastroenterol.
2016
,40, 631–637. [CrossRef] [PubMed]
2.
Hungin, A.P.S.; Chang, L.; Locke, G.R.; Dennis, E.H.; Barghout, V. Irritable Bowel Syndrome in the United States: Prevalence,
Symptom Patterns and Impact. Aliment. Pharmacol. Ther. 2005,21, 1365–1375. [CrossRef] [PubMed]
3.
Enck, P.; Aziz, Q.; Barbara, G.; Farmer, A.D.; Fukudo, S.; Mayer, E.A.; Niesler, B.; Quigley, E.M.M.; Rajili´c-Stojanovi´c, M.;
Schemann, M.; et al. Irritable Bowel Syndrome. Nat. Rev. Dis. Primers 2016,2, 16014. [CrossRef] [PubMed]
4. Choung, R.S.; Locke, G.R. Epidemiology of IBS. Gastroenterol. Clin. N. Am. 2011,40, 1–10. [CrossRef]
5.
Oka, P.; Parr, H.; Barberio, B.; Black, C.J.; Savarino, E.V.; Ford, A.C. Global Prevalence of Irritable Bowel Syndrome According to
Rome III or IV Criteria: A Systematic Review and Meta-Analysis. Lancet Gastroenterol. Hepatol. 2020,5, 908–917. [CrossRef]
6.
Tornkvist, N.T.; Aziz, I.; Whitehead, W.E.; Sperber, A.D.; Palsson, O.S.; Hreinsson, J.P.; Simrén, M.; Törnblom, H. Health Care
Utilization of Individuals with Rome IV Irritable Bowel Syndrome in the General Population. United Eur. Gastroenterol. J.
2021
,9,
1178–1188. [CrossRef]
7.
Saito, Y.A.; Schoenfeld, P.; Locke, G.R., 3rd. The Epidemiology of Irritable Bowel Syndrome in North America: A Systematic
Review. Am. J. Gastroenterol. 2002,97, 1910–1915. [CrossRef]
8.
Mazzawi, T.; Lied, G.A.; Sangnes, D.A.; El-Salhy, M.; Hov, J.R.; Gilja, O.H.; Hatlebakk, J.G.; Hausken, T. The Kinetics of Gut
Microbial Community Composition in Patients with Irritable Bowel Syndrome Following Fecal Microbiota Transplantation. PLoS
ONE 2018,13, e0194904. [CrossRef]
9.
Lesbros-Pantoflickova, D.; Michetti, P.; Fried, M.; Beglinger, C.; Blum, A.L. Meta-Analysis: The Treatment of Irritable Bowel
Syndrome. Aliment. Pharmacol. Ther. 2004,20, 1253–1269. [CrossRef]
10.
Cook, I.J.; Irvine, E.J.; Campbell, D.; Shannon, S.; Reddy, S.N.; Collins, S.M. Effect of Dietary Fiber on Symptoms and Rectosigmoid
Motility in Patients with Irritable Bowel Syndrome. A Controlled, Crossover Study. Gastroenterology 1990,98, 66–72. [CrossRef]
11.
Hebden, J.M.; Blackshaw, E.; D’Amato, M.; Perkins, A.C.; Spiller, R.C. Abnormalities of GI Transit in Bloated Irritable Bowel
Syndrome: Effect of Bran on Transit and Symptoms. Am. J. Gastroenterol. 2002,97, 2315–2320. [CrossRef]
12.
Thimister, P.W.L.; Hopman, W.P.M.; Van Roermund, R.F.C.; Willems, H.L.; Rosenbusch, G.; Woestenborghs, R.; Jansen, J.B.M.J.
Inhibition of Pancreaticobiliary Secretion by Loperamide in Humans. Hepatology 1997,26, 256–261. [CrossRef] [PubMed]
13.
Cann, P.A.; Read, N.W.; Holdsworth, C.D.; Barends, D. Role of Loperamide and Placebo in Management of Irritable Bowel
Syndrome (IBS). Dig. Dis. Sci. 1984,29, 239–247. [CrossRef] [PubMed]
14.
Dobrilla, G.; Piazzi, L.; Bensi, G.; Dobrilla, G. Longterm Treatment of Irritable Bowel Syndrome with Cimetropium Bromide:
A Double Blind Placebo Controlled Clinical Trial. Gut 1990,31, 355. [CrossRef] [PubMed]
15.
Passaretti, S.; Guslandi, M.; Imbimbo, B.P.; Daniotti, S.; Tittobello, A. Effects of Cimetropium Bromide on Gastrointestinal Transit
Time in Patients with Irritable Bowel Syndrome. Aliment. Pharmacol. Ther. 1989,3, 267–276. [CrossRef] [PubMed]
16.
Milo, R. Use of the Peripheral Dopamine Antagonist, Domperidone, in the Management of Gastro-Intestinal Symptoms in
Patients with Irritable Bowel Syndrome. Curr. Med. Res. Opin. 1980,6, 577–584. [CrossRef] [PubMed]
17.
Farup, P.G.; Hovdenak, N.; Wetterhus, S.; Lange, O.J.; Hovde, Ø.; Trondstad, R. The Symptomatic Effect of Cisapride in Patients
with Irritable Bowel Syndrome and Constipation. Scand. J. Gastroenterol. 2009,33, 128–131. [CrossRef]
18.
Schütze, K.; Brandstätter, G.; Dragosics, B.; Judmaier, G.; Hentschel, E. Double-Blind Study of the Effect of Cisapride on
Constipation and Abdominal Discomfort as Components of the Irritable Bowel Syndrome. Aliment. Pharmacol. Ther.
1997
,11,
387–394. [CrossRef]
19.
Myren, J.; Groth, H.; Larssen, S.E.; Larsen, S. The Effect of Trimipramine in Patients with the Irritable Bowel Syndrome. A
Double-Blind Study. Scand. J. Gastroenterol. 1982,17, 871–875. [CrossRef]
20.
Rajagopalan, M.; Kurian, G.; John, J. Symptom Relief with Amitriptyline in the Irritable Bowel Syndrome. J. Gastroenterol. Hepatol.
1998,13, 738–741. [CrossRef]
21.
Fayyaz, M.; Lackner, J.M. Serotonin Receptor Modulators in the Treatment of Irritable Bowel Syndrome. Ther. Clin. Risk Manag.
2008,4, 41. [CrossRef] [PubMed]
22.
Coulie, B.; Szarka, L.A.; Camilleri, M.; Burton, D.D.; McKinzie, S.; Stambler, N.; Cedarbaum, J.M. Recombinant Human Neu-
rotrophic Factors Accelerate Colonic Transit and Relieve Constipation in Humans. Gastroenterology
2000
,119, 41–50. [CrossRef]
[PubMed]
23.
Fioramonti, J.; Gaultier, E.; Toulouse, M.; Sanger, G.J.; Bueno, L. Intestinal Anti-Nociceptive Behaviour of NK3 Receptor
Antagonism in Conscious Rats: Evidence to Support a Peripheral Mechanism of Action. Neurogastroenterol. Motil.
2003
,15,
363–369. [CrossRef] [PubMed]
24.
Okano, S.; Ikeura, Y.; Inatomi, N. Effects of Tachykinin NK1 Receptor Antagonists on the Viscerosensory Response Caused by
Colorectal Distention in Rabbits. J. Pharmacol. Exp. Ther. 2002,300, 925–931. [CrossRef]

Nutrients 2023,15, 3991 17 of 22
25.
Sanger, G.J. Neurokinin NK1 and NK3 Receptors as Targets for Drugs to Treat Gastrointestinal Motility Disorders and Pain. Br. J.
Pharmacol. 2004,141, 1303–1312. [CrossRef]
26.
Tsigos, C.; Chrousos, G.P. Hypothalamic-Pituitary-Adrenal Axis, Neuroendocrine Factors and Stress. J. Psychosom. Res.
2002
,53,
865–871. [CrossRef]
27.
Elsenbruch, S.; Orr, W.C. Diarrhea- and Constipation-Predominant IBS Patients Differ in Postprandial Autonomic and Cortisol
Responses. Am. J. Gastroenterol. 2001,96, 460–466. [CrossRef]
28.
Camilleri, M.; Kim, D.Y.; McKinzie, S.; Kim, H.J.; Thomforde, G.M.; Burton, D.D.; Low, P.A.; Zinsmeister, A.R. A Randomized,
Controlled Exploratory Study of Clonidine in Diarrhea-Predominant Irritable Bowel Syndrome. Clin. Gastroenterol. Hepatol.
2003
,
1, 111–121. [CrossRef]
29.
Bazzocchi, G.; Gionchetti, P.; Almerigi, P.F.; Amadini, C.; Campieri, M. Intestinal Microflora and Oral Bacteriotherapy in Irritable
Bowel Syndrome. Dig. Liver Dis. 2002,34 (Suppl. S2), S48–S53. [CrossRef]
30.
Coutinho, S.V.; Plotsky, P.M.; Sablad, M.; Miller, J.C.; Zhou, H.; Bayati, A.I.; McRoberts, J.A.; Mayer, E.A. Neonatal Maternal
Separation Alters Stress-Induced Responses to Viscerosomatic Nociceptive Stimuli in Rat. Am. J. Physiol. Gastrointest. Liver Physiol.
2002,282, G307–G316. [CrossRef]
31.
Gholamrezaei, A.; Ardestani, S.K.; Emami, M.H. Where Does Hypnotherapy Stand in the Management of Irritable Bowel
Syndrome? A Systematic Review. J. Altern. Complement. Med. 2006,12, 517–527. [CrossRef] [PubMed]
32.
Akiho, H.; Ihara, E.; Nakamura, K. Low-Grade Inflammation Plays a Pivotal Role in Gastrointestinal Dysfunction in Irritable
Bowel Syndrome. World J. Gastrointest. Pathophysiol. 2010,1, 97–105. [CrossRef] [PubMed]
33.
Rodríguez, L.A.; Ruigómez, A. Increased Risk of Irritable Bowel Syndrome after Bacterial Gastroenteritis: Cohort Study. BMJ
1999,318, 565–566. [CrossRef] [PubMed]
34.
Schmulson, M.; Bielsa, M.V.; Carmona-Sánchez, R.; Hernández, A.; López-Colombo, A.; Vidal, Y.L.; Peláez-Luna, M.; Remes-
Troche, J.M.; Tamayo, J.L.; Valdovinos, M.A. Microbiota, Gastrointestinal Infections, Low-Grade Inflammation, and Antibiotic
Therapy in Irritable Bowel Syndrome (IBS): An Evidence-Based Review. Rev. Gastroenterol. Méx. 2014,79, 96–134. [CrossRef]
35.
Principi, N.; Cozzali, R.; Farinelli, E.; Brusaferro, A.; Esposito, S. Gut Dysbiosis and Irritable Bowel Syndrome: The Potential Role
of Probiotics. J. Infect. 2018,76, 111–120. [CrossRef]
36.
Casén, C.; Vebø, H.C.; Sekelja, M.; Hegge, F.T.; Karlsson, M.K.; Ciemniejewska, E.; Dzankovic, S.; Frøyland, C.; Nestestog, R.;
Engstrand, L.; et al. Deviations in Human Gut Microbiota: A Novel Diagnostic Test for Determining Dysbiosis in Patients with
IBS or IBD. Aliment. Pharmacol. Ther. 2015,42, 71–83. [CrossRef]
37.
Karantanos, T.; Markoutsaki, T.; Gazouli, M.; Anagnou, N.P.; Karamanolis, D.G. Current Insights in to the Pathophysiology of
Irritable Bowel Syndrome. Gut Pathog. 2010,2, 3. [CrossRef]
38.
Jeffery, I.B.; O’Toole, P.W.; Öhman, L.; Claesson, M.J.; Deane, J.; Quigley, E.M.M.; Simrén, M. An Irritable Bowel Syndrome
Subtype Defined by Species-Specific Alterations in Faecal Microbiota. Gut 2012,61, 997–1006. [CrossRef]
39. Collins, S.M. A Role for the Gut Microbiota in IBS. Nat. Rev. Gastroenterol. Hepatol. 2014,11, 497–505. [CrossRef]
40.
Matricon, J.; Meleine, M.; Gelot, A.; Piche, T.; Dapoigny, M.; Muller, E.; Ardid, D. Review Article: Associations between Immune
Activation, Intestinal Permeability and the Irritable Bowel Syndrome. Aliment. Pharmacol. Ther. 2012,36, 1009–1031. [CrossRef]
41.
Quigley, E.M.M. Therapies Aimed at the Gut Microbiota and Inflammation: Antibiotics, Prebiotics, Probiotics, Synbiotics,
Anti-Inflammatory Therapies. Gastroenterol. Clin. N. Am. 2011,40, 207–222. [CrossRef] [PubMed]
42.
Farrell Jr, H.M.; Jimenez-Flores, R.; Bleck, G.T.; Brown, E.M.; Butler, J.E.; Creamer, L.K.; Hicks, C.L.; Hollar, C.M.; Ng-Kwai-Hang,
K.F.; Swaisgood, H.E. Nomenclature of the Proteins of Cows’ Milk--Sixth Revision. J. Dairy Sci.
2004
,87, 1641–1674. [CrossRef]
[PubMed]
43.
Eigel, W.N.; Butler, J.E.; Ernstrom, C.A.; Farrell, H.M., Jr.; Harwalkar, V.R.; Jenness, R.; Whitney, R.M. Nomenclature of Proteins of
Cow’s Milk: Fifth Revision. J. Dairy Sci. 1984,67, 1599–1631. [CrossRef]
44.
Thomä-Worringer, C.; Sørensen, J.; López-Fandiño, R. Health Effects and Technological Features of Caseinomacropeptide. Int.
Dairy J. 2006,16, 1324–1333. [CrossRef]
45.
Qu, Y.; Kim, B.J.; Koh, J.; Dallas, D.C. Analysis of Bovine Kappa-Casein Glycomacropeptide by Liquid Chromatography–Tandem
Mass Spectrometry. Foods 2021,10, 2028. [CrossRef] [PubMed]
46.
O’Riordan, N.; Kane, M.; Joshi, L.; Hickey, R.M. Structural and Functional Characteristics of Bovine Milk Protein Glycosylation.
Glycobiology 2014,24, 220–236. [CrossRef]
47.
Arunkumar, A.; Etzel, M.R. Fractionation of Glycomacropeptide from Whey Using Positively Charged Ultrafiltration Membranes.
Foods 2018,7, 166. [CrossRef]
48.
Ney, D.M.; Hull, A.K.; van Calcar, S.C.; Liu, X.; Etzel, M.R. Dietary Glycomacropeptide Supports Growth and Reduces the
Concentrations of Phenylalanine in Plasma and Brain in a Murine Model of Phenylketonuria. J. Nutr.
2008
,138, 316–322.
[CrossRef]
49.
Furlanetti, A.M.; Prata, L.F. Free and Total GMP (Glycomacropeptide) Contents of Milk during Bovine Lactation. Food Sci. Technol.
2003,23, 121–125. [CrossRef]
50.
Yvon, M.; Beucher, S.; Guilloteau, P.; Le Huerou-Luron, I.; Corring, T. Effects of Caseinomacropeptide (CMP) on Digestion
Regulation. Reprod. Nutr. Dev. 1994,34, 527–537. [CrossRef]
51.
Kawasaki, Y.; Isoda, H.; Shinmoto, H.; Tanimoto, M.; Dosako, S.; Idota, T.; Nakajima, I. Inhibition by
κ
-Casein Glycomacropeptide
and Lactoferrin of Influenza Virus Hemagglutination. Biosci. Biotechnol. Biochem. 1993,57, 1214–1215. [CrossRef]

Nutrients 2023,15, 3991 18 of 22
52.
Janer, C.; Díaz, J.; Peláez, C.; Requena, T. The effect of caseinomacropeptide and whey protein concentrate on streptococcus
mutans adhesion to polystyrene surfaces and cell aggregation. J. Food Qual. 2004,27, 233–238. [CrossRef]
53.
Robitaille, G. Growth-Promoting Effects of Caseinomacropeptide from Cow and Goat Milk on Probiotics. J. Dairy Res.
2013
,80,
58–63. [CrossRef] [PubMed]
54.
Vara, E.J.; Brokstad, K.A.; Hausken, T.; Lied, G.A. Altered Levels of Cytokines in Patients with Irritable Bowel Syndrome Are Not
Correlated with Fatigue. Int. J. Gen. Med. 2018,11, 285–291. [CrossRef] [PubMed]
55.
Kawasaki, Y.; Isoda, H.; Tanimoto, M.; Dosako, S.; Idota, T.; Ahiko, K. Inhibition by Lactoferrin and
κ
-Casein Glycomacropeptide
of Binding of Cholera Toxin to Its Receptor. Biosci. Biotechnol. Biochem. 1992,56, 195–198. [CrossRef]
56.
Brück, W.M.; Graverholt, G.; Gibson, G.R. A Two-Stage Continuous Culture System to Study the Effect of Supplemental Alpha-
Lactalbumin and Glycomacropeptide on Mixed Cultures of Human Gut Bacteria Challenged with Enteropathogenic Escherichia
coli and Salmonella Serotype Typhimurium. J. Appl. Microbiol. 2003,95, 44–53. [CrossRef]
57.
Brück, W.M.; Kelleher, S.L.; Gibson, G.R.; Graverholt, G.; Lönnerdal, B.L. The Effects of Alpha-Lactalbumin and Glycomacropep-
tide on the Association of CaCo-2 Cells by Enteropathogenic Escherichia coli,Salmonella typhimurium and Shigella flexneri.FEMS
Microbiol. Lett. 2006,259, 158–162. [CrossRef]
58.
Wang, L.; Alammar, N.; Singh, R.; Nanavati, J.; Song, Y.; Chaudhary, R.; Mullin, G.E. Gut Microbial Dysbiosis in the Irritable
Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies. J. Acad. Nutr. Diet.
2020
,120, 565–586.
[CrossRef]
59.
Wilson, B.; Rossi, M.; Dimidi, E.; Whelan, K. Prebiotics in Irritable Bowel Syndrome and Other Functional Bowel Disorders
in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Am. J. Clin. Nutr.
2019
,109, 1098–1111.
[CrossRef]
60.
Pozuelo, M.; Panda, S.; Santiago, A.; Mendez, S.; Accarino, A.; Santos, J.; Guarner, F.; Azpiroz, F.; Manichanh, C. Reduction of
Butyrate- and Methane-Producing Microorganisms in Patients with Irritable Bowel Syndrome. Sci. Rep.
2015
,5, 12693. [CrossRef]
61.
Carroll, I.M.; Ringel-Kulka, T.; Keku, T.O.; Chang, Y.H.; Packey, C.D.; Balfour Sartor, R.; Ringel, Y. Molecular Analysis of the
Luminal- and Mucosal-Associated Intestinal Microbiota in Diarrhea-Predominant Irritable Bowel Syndrome. Am. J. Physiol.
Gastrointest. Liver Physiol. 2011,301, G799–G807. [CrossRef]
62.
Liu, Y.; Zhang, L.; Wang, X.; Wang, Z.; Zhang, J.; Jiang, R.; Wang, X.; Wang, K.; Liu, Z.; Xia, Z.; et al. Similar Fecal Microbiota
Signatures in Patients with Diarrhea-Predominant Irritable Bowel Syndrome and Patients with Depression. Clin. Gastroenterol.
Hepatol. 2016,14, 1602–1611.e5. [CrossRef] [PubMed]
63.
Rangel, I.; Sundin, J.; Fuentes, S.; Repsilber, D.; de Vos, W.M.; Brummer, R.J. The Relationship between Faecal-Associated and
Mucosal-Associated Microbiota in Irritable Bowel Syndrome Patients and Healthy Subjects. Aliment. Pharmacol. Ther.
2015
,42,
1211–1221. [CrossRef] [PubMed]
64.
Durbán, A.; Abellán, J.J.; Jiménez-Hernández, N.; Salgado, P.; Ponce, M.; Ponce, J.; Garrigues, V.; Latorre, A.; Moya, A. Structural
Alterations of Faecal and Mucosa-Associated Bacterial Communities in Irritable Bowel Syndrome. Environ. Microbiol. Rep.
2012
,4,
242–247. [CrossRef]
65.
Rigsbee, L.; Agans, R.; Shankar, V.; Kenche, H.; Khamis, H.J.; Michail, S.; Paliy, O. Quantitative Profiling of Gut Microbiota of
Children with Diarrhea-Predominant Irritable Bowel Syndrome. Am. J. Gastroenterol.
2012
,107, 1740–1751. [CrossRef] [PubMed]
66.
Tap, J.; Derrien, M.; Törnblom, H.; Brazeilles, R.; Cools-Portier, S.; Doré, J.; Störsrud, S.; Le Nevé, B.; Öhman, L.; Simrén, M.
Identification of an Intestinal Microbiota Signature Associated with Severity of Irritable Bowel Syndrome. Gastroenterology
2017
,
152, 111–123.e8. [CrossRef] [PubMed]
67. Labus, J.S.; Hollister, E.B.; Jacobs, J.; Kirbach, K.; Oezguen, N.; Gupta, A.; Acosta, J.; Luna, R.A.; Aagaard, K.; Versalovic, J.; et al.
Differences in Gut Microbial Composition Correlate with Regional Brain Volumes in Irritable Bowel Syndrome. Microbiome
2017
,
5, 49. [CrossRef] [PubMed]
68.
Pittayanon, R.; Lau, J.T.; Yuan, Y.; Leontiadis, G.I.; Tse, F.; Surette, M.; Moayyedi, P. Gut Microbiota in Patients With Irritable
Bowel Syndrome-A Systematic Review. Gastroenterology 2019,157, 97–108. [CrossRef]
69.
Jahng, J.; Jung, I.S.; Choi, E.J.; Conklin, J.L.; Park, H. The Effects of Methane and Hydrogen Gases Produced by Enteric Bacteria on
Ileal Motility and Colonic Transit Time. Neurogastroenterol. Motil. 2012,24, 185-e92. [CrossRef]
70.
Villanueva-Millan, M.J.; Leite, G.; Wang, J.; Morales, W.; Parodi, G.; Pimentel, M.L.; Barlow, G.M.; Mathur, R.; Rezaie, A.;
Sanchez, M.; et al. Methanogens and Hydrogen Sulfide Producing Bacteria Guide Distinct Gut Microbe Profiles and Irritable
Bowel Syndrome Subtypes. Am. J. Gastroenterol. 2022,117, 2055–2066. [CrossRef]
71.
Singer-Englar, T.; Rezaie, A.; Gupta, K.; Pichetshote, N.; Sedighi, R.; Lin, E.; Chua, K.S.; Pimentel, M. 182—Competitive Hydrogen
Gas Utilization by Methane- and Hydrogen Sulfide-Producing Microorganisms and Associated Symptoms: Results of a Novel
4-Gas Breath Test Machine. Gastroenterology 2018,154, 47. [CrossRef]
72.
Quan, X.; Luo, H.; Liu, Y.; Xia, H.; Chen, W.; Tang, Q. Hydrogen Sulfide Regulates the Colonic Motility by Inhibiting Both L-Type
Calcium Channels and BKCa Channels in Smooth Muscle Cells of Rat Colon. PLoS ONE
2015
,10, e0121331. [CrossRef] [PubMed]
73.
Parkes, G.C.; Rayment, N.B.; Hudspith, B.N.; Petrovska, L.; Lomer, M.C.; Brostoff, J.; Whelan, K.; Sanderson, J.D. Distinct
Microbial Populations Exist in the Mucosa-Associated Microbiota of Sub-Groups of Irritable Bowel Syndrome. Neurogastroenterol.
Motil. 2012,24, 31–39. [CrossRef] [PubMed]

Nutrients 2023,15, 3991 19 of 22
74.
El-Salhy, M.; Hatlebakk, J.G.; Gilja, O.H.; Bråthen Kristoffersen, A.; Hausken, T. Efficacy of Faecal Microbiota Transplantation
for Patients with Irritable Bowel Syndrome in a Randomised, Double-Blind, Placebo-Controlled Study. Gut
2020
,69, 859–867.
[CrossRef]
75.
Crouzet, L.; Gaultier, E.; Del’Homme, C.; Cartier, C.; Delmas, E.; Dapoigny, M.; Fioramonti, J.; Bernalier-Donadille, A. The Hyper-
sensitivity to Colonic Distension of IBS Patients Can Be Transferred to Rats through Their Fecal Microbiota. Neurogastroenterol.
Motil. 2013,25, e272–e282. [CrossRef]
76.
Whorwell, P.J.; Altringer, L.; Morel, J.; Bond, Y.; Charbonneau, D.; O’Mahony, L.; Kiely, B.; Shanahan, F.; Quigley, E.M.M. Efficacy
of an Encapsulated Probiotic Bifidobacterium Infantis 35624 in Women with Irritable Bowel Syndrome. Am. J. Gastroenterol.
2006
,
101, 1581–1590. [CrossRef]
77.
O’Mahony, L.; McCarthy, J.; Kelly, P.; Hurley, G.; Luo, F.; Chen, K.; O’Sullivan, G.C.; Kiely, B.; Collins, J.K.; Shanahan, F.; et al.
Lactobacillus and Bifidobacterium in Irritable Bowel Syndrome: Symptom Responses and Relationship to Cytokine Profiles.
Gastroenterology 2005,128, 541–551. [CrossRef]
78.
Enck, P.; Zimmermann, K.; Menke, G.; Müller-Lissner, S.; Martens, U.; Klosterhalfen, S. A Mixture of Escherichia coli (DSM 17252)
and Enterococcus faecalis (DSM 16440) for Treatment of the Irritable Bowel Syndrome—A Randomized Controlled Trial with
Primary Care Physicians. Neurogastroenterol. Motil. 2008,20, 1103–1109. [CrossRef]
79.
Choi, S.C.; Kim, B.J.; Rhee, P.L.; Chang, D.K.; Son, H.J.; Kim, J.J.; Rhee, J.C.; Kim, S.I.; Han, Y.S.; Sim, K.H.; et al. Probiotic
Fermented Milk Containing Dietary Fiber Has Additive Effects in IBS with Constipation Compared to Plain Probiotic Fermented
Milk. Gut Liver 2011,5, 22–28. [CrossRef]
80.
Clarke, G.; Cryan, J.F.; Dinan, T.G.; Quigley, E.M. Review Article: Probiotics for the Treatment of Irritable Bowel Syndrome—Focus
on Lactic Acid Bacteria. Aliment. Pharmacol. Ther. 2012,35, 403–413. [CrossRef]
81.
O’Sullivan, M.A.; O’Morain, C.A. Bacterial Supplementation in the Irritable Bowel Syndrome. A Randomised Double-Blind
Placebo-Controlled Crossover Study. Dig. Liver Dis. 2000,32, 294–301. [CrossRef]
82.
Gustavo Hermes, R.; Molist, F.; Francisco Pérez, J.; De Segura, A.G.; Ywazaki, M.; Davin, R.; Nofrarías, M.; Korhonen, T.K.;
Virkola, R.; Martín-Orúe, S.M. Casein Glycomacropeptide in the Diet May Reduce Escherichia coli Attachment to the Intestinal
Mucosa and Increase the Intestinal Lactobacilli of Early Weaned Piglets after an Enterotoxigenic E. coli K88 Challenge. Br. J. Nutr.
2013,109, 1001–1012. [CrossRef] [PubMed]
83.
Rong, Y.; Lu, Z.; Zhang, H.; Zhang, L.; Song, D.; Wang, Y. Effects of Casein Glycomacropeptide Supplementation on Growth Per-
formance, Intestinal Morphology, Intestinal Barrier Permeability and Inflammatory Responses in Escherichia coli K88 Challenged
Piglets. Anim. Nutr. 2015,1, 54–59. [CrossRef] [PubMed]
84.
Nakajima, K.; Tamura, N.; Kobayashi-Hattori, K.; Yoshida, T.; Hara-Kudo, Y.; Ikedo, M.; Sugita-Konishi, Y.; Hattori, M. Prevention
of Intestinal Infection by Glycomacropeptide. Biosci. Biotechnol. Biochem. 2005,69, 2294–2301. [CrossRef] [PubMed]
85.
Rhoades, J.R.; Gibson, G.R.; Formentin, K.; Beer, M.; Greenberg, N.; Rastall, R.A. Caseinoglycomacropeptide Inhibits Adhesion of
Pathogenic Escherichia coli Strains to Human Cells in Culture. J. Dairy Sci. 2005,88, 3455–3459. [CrossRef] [PubMed]
86.
Brück, W.M.; Redgrave, M.; Tuohy, K.M.; Lönnerdal, B.; Graverholt, G.; Hernell, O.; Gibson, G.R. Effects of Bovine
α
-Lactalbumin
and Casein Glycomacropeptide-Enriched Infant Formulae on Faecal Microbiota in Healthy Term Infants. J. Pediatr. Gastroenterol.
Nutr. 2006,43, 673–679. [CrossRef]
87.
Feeney, S.; Ryan, J.T.; Kilcoyne, M.; Joshi, L.; Hickey, R. Glycomacropeptide Reduces Intestinal Epithelial Cell Barrier Dysfunction
and Adhesion of Entero-Hemorrhagic and Entero-Pathogenic Escherichia coli in Vitro. Foods 2017,6, 93. [CrossRef]
88.
Malinen, E.; Krogius-Kurikka, L.; Lyra, A.; Nikkilä, J.; Jääskeläinen, A.; Rinttilä, T.; Vilpponen-Salmela, T.; von Wright, A.J.;
Palva, A. Association of Symptoms with Gastrointestinal Microbiota in Irritable Bowel Syndrome. World J. Gastroenterol.
2010
,16,
4532–4540. [CrossRef]
89.
Inness, V.L.; McCartney, A.L.; Khoo, C.; Gross, K.L.; Gibson, G.R. Molecular Characterisation of the Gut Microflora of Healthy
and Inflammatory Bowel Disease Cats Using Fluorescence in Situ Hybridisation with Special Reference to Desulfovibrio Spp. J.
Anim. Physiol. Anim. Nutr. 2007,91, 48–53. [CrossRef]
90.
Kushkevych, I.; Dordevi´c, D.; Kollár, P. Analysis of Physiological Parameters of Desulfovibrio Strains from Individuals with
Colitis. Open Life Sci. 2019,13, 481–488. [CrossRef]
91.
Wernlund, P.G.; Hvas, C.L.; Dahlerup, J.F.; Bahl, M.I.; Licht, T.R.; Knudsen, K.E.B.; Agnholt, J.S. Casein Glycomacropeptide Is
Well Tolerated in Healthy Adults and Changes Neither High-Sensitive C-Reactive Protein, Gut Microbiota nor Faecal Butyrate:
A Restricted Randomised Trial. Br. J. Nutr. 2021,125, 1374–1385. [CrossRef] [PubMed]
92.
Montanari, C.; Ceccarani, C.; Corsello, A.; Zuvadelli, J.; Ottaviano, E.; Dei Cas, M.; Banderali, G.; Zuccotti, G.; Borghi, E.;
Verduci, E. Glycomacropeptide Safety and Its Effect on Gut Microbiota in Patients with Phenylketonuria: A Pilot Study. Nutrients
2022,14, 1883. [CrossRef] [PubMed]
93.
Yu, X.; Xing, Y.; Liu, H.; Chang, Y.; You, Y.; Dou, Y.; Liu, B.; Wang, Q.; Ma, D.; Chen, L.; et al. Effects of a Formula with
ScGOS/LcFOS (9:1) and Glycomacropeptide (GMP) Supplementation on the Gut Microbiota of Very Preterm Infants. Nutrients
2022,14, 1901. [CrossRef] [PubMed]
94.
Hansen, K.E.; Murali, S.; Chaves, I.Z.; Suen, G.; Ney, D.M. Glycomacropeptide Impacts Amylin-Mediated Satiety, Postprandial
Markers of Glucose Homeostasis, and the Fecal Microbiome in Obese Postmenopausal Women. J. Nutr.
2023
,153, 1915–1929.
[CrossRef] [PubMed]

Nutrients 2023,15, 3991 20 of 22
95.
Sawin, E.A.; De Wolfe, T.J.; Aktas, B.; Stroup, B.M.; Murali, S.G.; Steele, J.L.; Ney, D.M. Glycomacropeptide Is a Prebiotic That
Reduces Desulfovibrio Bacteria, Increases Cecal Short-Chain Fatty Acids, and Is Anti-Inflammatory in Mice. Am. J. Physiol.
Gastrointest. Liver Physiol. 2015,309, G590–G601. [CrossRef]
96.
Jiménez, M.; Cervantes-García, D.; Muñoz, Y.H.; García, A.; Haro, L.M.; Salinas, E. Novel Mechanisms Underlying the Therapeutic
Effect of Glycomacropeptide on Allergy: Change in Gut Microbiota, Upregulation of TGF-
β
, and Inhibition of Mast Cells. Int.
Arch. Allergy Immunol. 2016,171, 217–226. [CrossRef]
97.
Ntemiri, A.; Ribière, C.; Stanton, C.; Ross, R.P.; O’Connor, E.M.; O’Toole, P.W. Retention of Microbiota Diversity by Lactose-Free
Milk in a Mouse Model of Elderly Gut Microbiota. J. Agric. Food Chem. 2019,67, 2098–2112. [CrossRef] [PubMed]
98.
Yuan, Q.; Zhan, B.; Chang, R.; Du, M.; Mao, X. Antidiabetic Effect of Casein Glycomacropeptide Hydrolysates on High-Fat Diet
and STZ-Induced Diabetic Mice via Regulating Insulin Signaling in Skeletal Muscle and Modulating Gut Microbiota. Nutrients
2020,12, 220. [CrossRef]
99.
Chen, Q.; Cao, J.; Jia, Y.; Liu, X.; Yan, Y.; Pang, G. Modulation of Mice Fecal Microbiota by Administration of Casein Glyco-
macropeptide. Microbiol. Res. 2012,3, e3. [CrossRef]
100.
Wu, Y.; Zhang, X.; Tao, S.; Pi, Y.; Han, D.; Ye, H.; Feng, C.; Zhao, J.; Chen, L.; Wang, J. Maternal Supplementation with Combined
Galactooligosaccharides and Casein Glycomacropeptides Modulated Microbial Colonization and Intestinal Development of
Neonatal Piglets. J. Funct. Foods 2020,74, 104170. [CrossRef]
101.
Azuma, N.; Yamauchi, K.; Mitsuoka, T. Bifidus Growth-Promoting Activity of a Glycomacropeptide Derived from Human
K-Casein. Agric. Biol. Chem. 1984,48, 2159–2162. [CrossRef]
102.
Tian, Q.; Wang, T.T.; Tang, X.; Han, M.Z.; Leng, X.J.; Mao, X.Y. Developing a Potential Prebiotic of Yogurt: Growth of Bifi-
dobacterium and Yogurt Cultures with Addition of Glycomacropeptide Hydrolysate. Int. J. Food Sci. Technol.
2015
,50, 120–127.
[CrossRef]
103.
Ntemiri, A.; Chonchúir, F.N.; O’Callaghan, T.F.; Stanton, C.; Ross, R.P.; O’Toole, P.W. Glycomacropeptide Sustains Microbiota
Diversity and Promotes Specific Taxa in an Artificial Colon Model of Elderly Gut Microbiota. J. Agric. Food Chem.
2017
,65,
1836–1846. [CrossRef] [PubMed]
104.
O’Riordan, N.; O’Callaghan, J.; Buttò, L.F.; Kilcoyne, M.; Joshi, L.; Hickey, R.M. Bovine Glycomacropeptide Promotes the Growth
of Bifidobacterium longum ssp. infantis and Modulates Its Gene Expression. J. Dairy Sci. 2018,101, 6730–6741. [CrossRef]
105.
Morozumi, M.; Wada, Y.; Tsuda, M.; Tabata, F.; Ehara, T.; Nakamura, H.; Miyaji, K. Cross-Feeding among Bifidobacteria on
Glycomacropeptide. J. Funct. Foods 2023,103, 105463. [CrossRef]
106.
McGuckin, M.A.; Lindén, S.K.; Sutton, P.; Florin, T.H. Mucin Dynamics and Enteric Pathogens. Nat. Rev. Microbiol.
2011
,9,
265–278. [CrossRef]
107.
Zeber-Lubecka, N.; Kulecka, M.; Ambrozkiewicz, F.; Paziewska, A.; Goryca, K.; Karczmarski, J.; Rubel, T.; Wojtowicz, W.;
Mlynarz, P.; Marczak, L.; et al. Limited Prolonged Effects of Rifaximin Treatment on Irritable Bowel Syndrome-Related Differences
in the Fecal Microbiome and Metabolome. Gut Microbes 2016,7, 397–413. [CrossRef]
108.
Nagel, R.; Traub, R.J.; Allcock, R.J.N.; Kwan, M.M.S.; Bielefeldt-Ohmann, H. Comparison of Faecal Microbiota in Blastocystis-
Positive and Blastocystis-Negative Irritable Bowel Syndrome Patients. Microbiome 2016,4, 47. [CrossRef]
109.
Chung, C.-S.; Chang, P.-F.; Liao, C.-H.; Lee, T.-H.; Chen, Y.; Lee, Y.-C.; Wu, M.-S.; Wang, H.-P.; Ni, Y.-H. Differences of Microbiota
in Small Bowel and Faeces between Irritable Bowel Syndrome Patients and Healthy Subjects. Scand. J. Gastroenterol.
2016
,51,
410–419. [CrossRef]
110.
Rowan, F.; Docherty, N.G.; Murphy, M.; Murphy, B.; Calvin Coffey, J.; O’Connell, P.R. Desulfovibrio Bacterial Species Are
Increased in Ulcerative Colitis. Dis. Colon Rectum 2010,53, 1530–1536. [CrossRef]
111.
Fukuda, S.; Toh, H.; Hase, K.; Oshima, K.; Nakanishi, Y.; Yoshimura, K.; Tobe, T.; Clarke, J.M.; Topping, D.L.; Suzuki, T.; et al.
Bifidobacteria Can Protect from Enteropathogenic Infection through Production of Acetate. Nature
2011
,469, 543–547. [CrossRef]
[PubMed]
112.
Hamilton, M.K.; Boudry, G.; Lemay, D.G.; Raybould, H.E. Changes in Intestinal Barrier Function and Gut Microbiota in High-Fat
Diet-Fed Rats Are Dynamic and Region Dependent. Am. J. Physiol. Gastrointest. Liver Physiol.
2015
,308, G840–G851. [CrossRef]
[PubMed]
113.
Qu, Y.; Kim, B.-J.; Koh, J.; Dallas, D.C. Comparison of Solid-Phase Extraction Sorbents for Monitoring the In Vivo Intestinal
Survival and Digestion of Kappa-Casein-Derived Caseinomacropeptide. Foods 2023,12, 299. [CrossRef] [PubMed]
114.
Koh, J.; Kim, B.J.; Qu, Y.; Dallas, D.C. Mass Spectral Profiling of Caseinomacropeptide Extracted from Feeding Material and
Jejunal Fluid Using Three Methods-Ethanol Precipitation, Perchloric Acid Precipitation, and Ultrafiltration. Food Chem.
2023
,
398, 133864. [CrossRef]
115.
Koh, J.; Kim, B.J.; Qu, Y.; Huang, H.; Dallas, D.C. Top-Down Glycopeptidomics Reveals Intact Glycomacropeptide Is Digested to
a Wide Array of Peptides in Human Jejunum. J. Nutr. 2022,152, 429–438. [CrossRef]
116.
Chadwick, V.S.; Chen, W.; Shu, D.; Paulus, B.; Bethwaite, P.; Tie, A.; Wilson, I. Activation of the Mucosal Immune System in
Irritable Bowel Syndrome. Gastroenterology 2002,122, 1778–1783. [CrossRef]
117.
Zhang, L.; Song, J.; Hou, X. Mast Cells and Irritable Bowel Syndrome: From the Bench to the Bedside. J. Neurogastroenterol. Motil.
2016,22, 181–192. [CrossRef]
118.
Simrén, M.; Öhman, L. Pathogenesis of IBS: Role of Inflammation, Immunity and Neuroimmune Interactions. Nat. Rev.
Gastroenterol. Hepatol. 2010,7, 163–173. [CrossRef]

Nutrients 2023,15, 3991 21 of 22
119.
Bennet, S.M.P.; Polster, A.; Törnblom, H.; Isaksson, S.; Capronnier, S.; Tessier, A.; Le Nevé, B.; Simrén, M.; Öhman, L. Global
Cytokine Profiles and Association with Clinical Characteristics in Patients With Irritable Bowel Syndrome. Am. J. Gastroenterol.
2016,111, 1165–1176. [CrossRef]
120.
Gonsalkorale, W.M.; Miller, V.; Afzal, A.; Whorwell, P.J. Long Term Benefits of Hypnotherapy for Irritable Bowel Syndrome. Gut
2003,52, 1623–1629. [CrossRef]
121.
Chang, L. The Role of Stress on Physiologic Responses and Clinical Symptoms in Irritable Bowel Syndrome. Gastroenterology
2011,140, 761–765. [CrossRef] [PubMed]
122.
Choghakhori, R.; Abbasnezhad, A.; Hasanvand, A.; Amani, R. Inflammatory Cytokines and Oxidative Stress Biomarkers in
Irritable Bowel Syndrome: Association with Digestive Symptoms and Quality of Life. Cytokine
2017
,93, 34–43. [CrossRef]
[PubMed]
123.
Schmulson, M.; Pulido-London, D.; Rodriguez, O.; Morales-Rochlin, N.; Martinez-García, R.; Gutierrez-Ruiz, M.C.;
López-Alvarenga, J.C.; Robles-Díaz, G.; Gutiérrez-Reyes, G. Lower Serum IL-10 Is an Independent Predictor of IBS among
Volunteers in Mexico. Am. J. Gastroenterol. 2012,107, 747–753. [CrossRef] [PubMed]
124.
Chang, L.; Adeyemo, M.; Karagiannidis, I.; Videlock, E.J.; Bowe, C.; Shih, W.; Presson, A.P.; Yuan, P.Q.; Cortina, G.; Gong, H.; et al.
Serum and Colonic Mucosal Immune Markers in Irritable Bowel Syndrome. Am. J. Gastroenterol. 2012,107, 262–272. [CrossRef]
125.
Hasler, W.L.; Grabauskas, G.; Singh, P.; Owyang, C. Mast Cell Mediation of Visceral Sensation and Permeability in Irritable Bowel
Syndrome. Neurogastroenterol. Motil. 2022,34, e14339. [CrossRef]
126.
Zhen, Y.; Chu, C.; Zhou, S.; Qi, M.; Shu, R. Imbalance of Tumor Necrosis Factor-
α
, Interleukin-8 and Interleukin-10 Production
Evokes Barrier Dysfunction, Severe Abdominal Symptoms and Psychological Disorders in Patients with Irritable Bowel Syndrome-
Associated Diarrhea. Mol. Med. Rep. 2015,12, 5239–5245. [CrossRef]
127.
Li, F.; Ma, J.; Geng, S.; Wang, J.; Ren, F.; Sheng, X. Comparison of the Different Kinds of Feeding on the Level of Fecal Calprotectin.
Early Hum. Dev. 2014,90, 471–475. [CrossRef]
128.
Melchior, C.; Aziz, M.; Aubry, T.; Gourcerol, G.; Quillard, M.; Zalar, A.; Coëffier, M.; Dechelotte, P.; Leroi, A.-M.; Ducrotté, P. Does
Calprotectin Level Identify a Subgroup among Patients Suffering from Irritable Bowel Syndrome? Results of a Prospective Study.
United Eur. Gastroenterol. J. 2017,5, 261–269. [CrossRef]
129.
Choi, Y.J.; Jeong, S.J. Is Fecal Calprotectin Always Normal in Children with Irritable Bowel Syndrome? Intest. Res.
2019
,17,
546–553. [CrossRef]
130.
Chang, M.H.; Chou, J.W.; Chen, S.M.; Tsai, M.C.; Sun, Y.S.; Lin, C.C.; Lin, C.P. Faecal Calprotectin as a Novel Biomarker for
Differentiating between Inflammatory Bowel Disease and Irritable Bowel Syndrome. Mol. Med. Rep.
2014
,10, 522–526. [CrossRef]
131.
Waugh, N.; Cummins, E.; Royle, P.; Kandala, N.B.; Shyangdan, D.; Arasaradnam, R.; Clar, C.; Johnston, R. Faecal Calprotectin
Testing for Differentiating amongst Inflammatory and Non-Inflammatory Bowel Diseases: Systematic Review and Economic
Evaluation. Health Technol. Assess. 2013,17, xv–xix. [CrossRef]
132.
Thabane, M.; Kottachchi, D.T.; Marshall, J.K. Systematic Review and Meta-Analysis: The Incidence and Prognosis of Post-
Infectious Irritable Bowel Syndrome. Aliment. Pharmacol. Ther. 2007,26, 535–544. [CrossRef] [PubMed]
133.
Hvas, C.L.; Dige, A.; Bendix, M.; Wernlund, P.G.; Christensen, L.A.; Dahlerup, J.F.; Agnholt, J. Casein Glycomacropeptide for
Active Distal Ulcerative Colitis: A Randomized Pilot Study. Eur. J. Clin. Investig. 2016,46, 555–563. [CrossRef] [PubMed]
134.
Daddaoua, A.; Puerta, V.; Zarzuelo, A.; Suárez, M.D.; Sánchez De Medina, F.; Martínez-Augustin, O. Bovine Glycomacropeptide
Is Anti-Inflammatory in Rats with Hapten-Induced Colitis. J. Nutr. 2005,135, 1164–1170. [CrossRef]
135.
Requena, P.; Daddaoua, A.; Martínez-Plata, E.; González, M.; Zarzuelo, A.; Suárez, M.D.; Sánchez de Medina, F.;
Martínez-Augustin, O. Bovine Glycomacropeptide Ameliorates Experimental Rat Ileitis by Mechanisms Involving Downregula-
tion of Interleukin 17. Br. J. Pharmacol. 2008,154, 825–832. [CrossRef]
136.
Requena, P.; González, R.; López-Posadas, R.; Abadía-Molina, A.; Suárez, M.D.; Zarzuelo, A.; de Medina, F.S.; Martínez-Augustin,
O. The Intestinal Antiinflammatory Agent Glycomacropeptide Has Immunomodulatory Actions on Rat Splenocytes. Biochem.
Pharmacol. 2010,79, 1797–1804. [CrossRef] [PubMed]
137.
López-Posadas, R.; Requena, P.; González, R.; Suárez, M.D.; Zarzuelo, A.; Sánchez de Medina, F.; Martínez-Augustin, O. Bovine
Glycomacropeptide Has Intestinal Antiinflammatory Effects in Rats with Dextran Sulfate-Induced Colitis. J. Nutr.
2010
,140,
2014–2019. [CrossRef]
138.
Ortega-González, M.; Capitán-Cañadas, F.; Requena, P.; Ocón, B.; Romero-Calvo, I.; Aranda, C.; Suárez, M.D.; Zarzuelo, A.;
Sánchez De Medina, F.; Martínez-Augustin, O. Validation of Bovine Glycomacropeptide as an Intestinal Anti-Inflammatory
Nutraceutical in the Lymphocyte-Transfer Model of Colitis. Br. J. Nutr. 2014,111, 1202–1212. [CrossRef]
139.
Sawin, E.; Aktas, B.; DeWolfe, T.; Stroup, B.; Murali, S.; Steele, J.; Ney, D. Glycomacropeptide Shows Prebiotic and Immune
Modulating Properties in Phenylketonuria and Wild Type Mice. FASEB J. 2015,29, 1010–1012. [CrossRef]
140.
Muñoz, F.C.; Cervantes, M.M.; Cervantes-García, D.; Jiménez, M.; Ventura-Juárez, J.; Salinas, E. Glycomacropeptide Attenuates
Inflammation, Pruritus, and Th2 Response Associated with Atopic Dermatitis Induced by 2,4-Dinitrochlorobenzene in Rat. J.
Immunol. Res. 2017,2017, 6935402. [CrossRef]
141.
Cervantes-García, D.; Bahena-Delgado, A.I.; Jiménez, M.; Córdova-Dávalos, L.E.; Palacios, V.R.E.; Sánchez-Alemán, E.; Martínez-
Saldaña, M.C.; Salinas, E. Glycomacropeptide Ameliorates Indomethacin-Induced Enteropathy in Rats by Modifying Intestinal
Inflammation and Oxidative Stress. Molecules 2020,25, 2351. [CrossRef] [PubMed]

Nutrients 2023,15, 3991 22 of 22
142.
Reyes-Pavón, D.; Cervantes-García, D.; Bermúdez-Humarán, L.G.; Córdova-Dávalos, L.E.; Quintanar-Stephano, A.; Jiménez, M.;
Salinas, E. Protective Effect of Glycomacropeptide on Food Allergy with Gastrointestinal Manifestations in a Rat Model through
Down-Regulation of Type 2 Immune Response. Nutrients 2020,12, 2942. [CrossRef]
143.
Mikkelsen, T.L.; Bakman, S.; Sørensen, E.S.; Barkholt, V.; Frøkiær, H. Sialic Acid-Containing Milk Proteins Show Differential
Immunomodulatory Activities Independent of Sialic Acid. J. Agric. Food Chem. 2005,53, 7673–7680. [CrossRef]
144.
Cheng, X.; Gao, D.; Chen, B.; Mao, X. Endotoxin-Binding Peptides Derived from Casein Glycomacropeptide Inhibit
Lipopolysaccharide-Stimulated Inflammatory Responses via Blockade of NF-KB Activation in Macrophages. Nutrients
2015
,7,
3119–3137. [CrossRef] [PubMed]
145.
Li, T.; Cheng, X.; Du, M.; Chen, B.; Mao, X. Upregulation of Heme Oxygenase-1 Mediates the Anti-Inflammatory Activity of
Casein Glycomacropeptide (GMP) Hydrolysates in LPS-Stimulated Macrophages. Food Funct.
2017
,8, 2475–2484. [CrossRef]
[PubMed]
146.
Foisy-Sauvé, M.; Ahmarani, L.; Delvin, E.; Sané, A.T.; Spahis, S.; Levy, E. Glycomacropeptide Prevents Iron/Ascorbate-Induced
Oxidative Stress, Inflammation and Insulin Sensitivity with an Impact on Lipoprotein Production in Intestinal Caco-2/15 Cells.
Nutrients 2020,12, 1175. [CrossRef]
147.
Arbizu, S.; Chew, B.; Mertens-Talcott, S.U.; Noratto, G. Commercial Whey Products Promote Intestinal Barrier Function with
Glycomacropeptide Enhanced Activity in Downregulating Bacterial Endotoxin Lipopolysaccharides (LPS)-Induced Inflammation
in Vitro. Food Funct. 2020,11, 5842–5852. [CrossRef]
148.
Lu, Y.; Liu, J.; Li, Z.; Li, W.; Liu, J.; Huang, L.; Wang, Z. Comparative Mass Spectrometry Analysis and Immunomodulatory
Effects of Casein Glycomacropeptide O-Glycans in Bovine and Caprine Whey Powder. J. Agric. Food Chem.
2022
,70, 8746–8754.
[CrossRef]
149.
Vasilevskaia, L.S.; Stan, E.I.; Chernikov, M.P.; Shlygin, G.K. Inhibiting Action of Glycomacropeptide on Stomach Secretion Induced
by Various Humoral Stimulants. Vopr. Pitan. 1977,4, 21–24.
150. Stan, E.I.; Chernikov, M.P. Physiological Activity of Kappa-Casein Glycomacropeptide. Vopr. Med. Khim. 1979,25, 348–352.
151.
Stan, E.I.; Gro
˘
ısman, S.D.; Krasil’shchikov, K.B.; Chernikov, M.P. Effect of Kappa-Casein Glycomacropeptide on Gastrointestinal
Motility in Dogs. Biull. Eksp. Biol. Med. 1983,96, 10–12. [CrossRef] [PubMed]
152.
Beatty, J.K.; Bhargava, A.; Buret, A.G. Post-Infectious Irritable Bowel Syndrome: Mechanistic Insights into Chronic Disturbances
Following Enteric Infection. World J. Gastroenterol. WJG 2014,20, 3976. [CrossRef] [PubMed]
153.
Pokkunuri, V.; Pimentel, M.; Morales, W.; Jee, S.-R.; Alpern, J.; Weitsman, S.; Marsh, Z.; Low, K.; Hwang, L.; Khoshini, R.; et al.
Role of Cytolethal Distending Toxin in Altered Stool Form and Bowel Phenotypes in a Rat Model of Post-Infectious Irritable
Bowel Syndrome. J. Neurogastroenterol. Motil. 2012,18, 434–442. [CrossRef] [PubMed]
154.
Guo, S.; Al-Sadi, R.; Said, H.M.; Ma, T.Y. Lipopolysaccharide Causes an Increase in Intestinal Tight Junction Permeability in Vitro
and in Vivo by Inducing Enterocyte Membrane Expression and Localization of TLR-4 and CD14. Am. J. Pathol.
2013
,182, 375.
[CrossRef]
155.
Piche, T.; Barbara, G.; Aubert, P.; Bruley des Varannes, S.; Dainese, R.; Nano, J.L.; Cremon, C.; Stanghellini, V.; De Giorgio, R.;
Galmiche, J.P.; et al. Impaired Intestinal Barrier Integrity in the Colon of Patients with Irritable Bowel Syndrome: Involvement of
Soluble Mediators. Gut 2009,58, 196–201. [CrossRef]
156. Camilleri, M. Peripheral Mechanisms in Irritable Bowel Syndrome. N. Engl. J. Med. 2013,368, 578–579. [CrossRef]
157.
Simrén, M.; Barbara, G.; Flint, H.J.; Spiegel, B.M.R.; Spiller, R.C.; Vanner, S.; Verdu, E.F.; Whorwell, P.J.; Zoetendal, E.G.; Committee,
R.F. Intestinal Microbiota in Functional Bowel Disorders: A Rome Foundation Report. Gut 2013,62, 159–176. [CrossRef]
158.
Anderson, J.W.; Baird, P.; Davis, R.H.; Ferreri, S.; Knudtson, M.; Koraym, A.; Waters, V.; Williams, C.L. Health Benefits of Dietary
Fiber. Nutr. Rev. 2009,67, 188–205. [CrossRef]
159.
Camilleri, M.; Gores, G.J. Therapeutic Targeting of Bile Acids. Am. J. Physiol. Gastrointest. Liver Physiol.
2015
,309, G209. [CrossRef]
160.
Gibson, P.R.; Shepherd, S.J. Evidence-Based Dietary Management of Functional Gastrointestinal Symptoms: The FODMAP
Approach. J. Gastroenterol. Hepatol. 2010,25, 252–258. [CrossRef]
161.
Heitkemper, M.M.; Chang, L. Do Fluctuations in Ovarian Hormones Affect Gastrointestinal Symptoms in Women with Irritable
Bowel Syndrome? Gend. Med. 2009,6(Suppl. S2), 152–167. [CrossRef] [PubMed]
162.
Barbara, G.; Feinle-Bisset, C.; Ghoshal, U.C.; Santos, J.; Vanner, S.J.; Vergnolle, N.; Zoetendal, E.G.; Quigley, E.M. The Intestinal
Microenvironment and Functional Gastrointestinal Disorders. Gastroenterology 2016,150, 1305–1318.e8. [CrossRef]
163.
Hanning, N.; Edwinson, A.L.; Ceuleers, H.; Peters, S.A.; De Man, J.G.; Hassett, L.C.; De Winter, B.Y.; Grover, M. Intestinal Barrier
Dysfunction in Irritable Bowel Syndrome: A Systematic Review. Ther. Adv. Gastroenterol.
2021
,14, 1756284821993586. [CrossRef]
[PubMed]
164.
Guttman, J.A.; Finlay, B.B. Tight Junctions as Targets of Infectious Agents. Biochim. Biophys. Acta
2009
,1788, 832–841. [CrossRef]
[PubMed]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.