Glycomacropeptide Sustains Microbiota Diversity and Promotes Specific Taxa in an Artificial Colon Model of Elderly Gut Microbiota

The potential of food-derived peptides in alleviating depressed mood: Function, evaluation and mechanism

Food-derived peptides offer a promising approach to alleviating depressive symptoms due to their safety and natural origin, avoiding the adverse side effects of conventional pharmacological treatments. This review aims to explore their potential in mitigating depressive symptoms. Antidepressant peptides from both animal and plant sources have been reviewed, while the animal models and evaluation methods used to assess their efficacy have been summarized. The review highlights four major mechanisms underlying their effects, namely modulation of gut microbiota and production of neuroactive metabolites, alteration of molecules associated with nervous system, normalization of hypothalamic-pituitary-adrenal axis dysregulation to reduce cortisol production, and suppression of pro-inflammatory cytokines linked to neuroinflammation. It also highlights the role of gut-brain axis in mediating the mechanisms, which has been insufficiently elucidated. However, the efficacy of antidepressant peptides for clinical use has not been established. The present review provides a reference for developing dietary interventions with food-derived peptides to supplement current therapeutic approaches.

In vitro digestibility of bioprocessed brewer's spent yeast: Demonstrating protein quality and gut microbiome modulation potential

With an ever-increasing global population and dwindling natural resources, a shift towards more sustainable food systems is required. Important aspects to aid in this transition are the reduction of food waste, and a movement towards non-animal protein sources. Brewers spent yeast (BSY) is an abundant by-product of the brewing industry, which is generally regarded as waste, despite its high nutritional value. Previous work has shown that fermentation of BSY with Lactobacillus amylovorus FST 2.11 resulted in changes in composition, functionality, and improved palatability of the processed raw material (PBSY). In this study, in vitro protein digestibility, amino acid bioaccessability, and protein quality of PBSY was explored using the static INFOGEST in vitro model. In vitro protein digestibility of PBSY (73.0 %) was almost two-fold higher than that of CBSY (40.0 %), while PBSY also displayed significantly higher in vitro bioaccessability values for all essential amino acids, except for tryptophan. Investigation of protein quality using the digestible indispensable amino acid score (DIAAS) values and the FAO recommended amino acid scoring pattern for individuals >3 years old showed that the protein quality for CBSY was low (DIAAS of 17.0 %), while PBSY was considered to be of "good" protein quality (DIAAS of 98.2 %). Investigation of the modulation potential of PBSY on the gut microbiome using an in vitro colon model system showed an increase in gut microbiome α-diversity indices and an abundance of beneficial Mediterranean diet-responsive taxa after 24 h. Overall, this study highlights the potential of BSY as raw material for the production of a high-quality food ingredient with potential prebiotic effects, aiding in the reduction food waste and supporting global food systems.

The protein ingredient quality of infant formula influences colonic physiology and microbiota and the serum metabolomic profile in neonatal mini-piglets

Despite the WHO recommendations in favor of breastfeeding, most infants receive infant formulas (IFs), which are complex matrices involving numerous ingredients and processing steps. Our aim was to understand the impact of the quality of the protein ingredient in IFs on gut microbiota and physiology, blood metabolites and brain gene expression. Three IFs were produced using whey proteins (WPs) from cheese whey (IF-A) or ideal whey (IFs-C and -D) and caseins, either in a micellar form (IFs-A and -C) or partly in a non-micellar form (IF-D). Twenty-four Yucatan minipiglets received one of the IFs from 2- to 21-days of age. The piglets were then euthanized 84 min postprandially. Blood, ileal and colonic digesta and tissues, the liver and the hypothalamus were sampled. Gut microbiota composition and activity, the expression of intestinal and brain genes involved in barrier, immune, endocrine, nutrient carrier and neuronal functions and serum metabolite levels were determined. Intestinal paracellular permeability was assessed with an ex vivo Ussing chamber. The data were analyzed using multifactorial and univariate analyses. The colon was the main site to be physiologically affected by the quality of the dairy protein ingredients used in IFs. Colonic paracellular permeability was significantly higher in IF-D-fed piglets than in those receiving IFs-A and -C, in line with the expression of genes encoding tight junction proteins (OCLN, CLDN3 and CLDN4). IF-D up-regulated the colonic expression of genes involved in the immune function (SOCS3, PIGR and TNFα) when compared to IF-A. Although intestinal α- and β-diversities did not significantly differ among IFs, some specific differences were observed, such as the abundances of Campylobacterota phylum and Bacteroides genera and fecal butyrate production, which were increased with IFs-C and -D versus IF-A. The kynurenine pathway was favored in piglets fed IF-D compared to IF-A, based on colonic gene expression and serum metabolites. In addition, levels of some serum metabolites, particularly putrescine, spermidine and spermine, were higher in piglets fed IF-D than IFs-A and -C. Overall, IF-D, which combined ideal WPs and some non-micellar caseins, appeared to differ most from IF-A in terms of its physiological consequences, suggesting that both WP and casein ingredient quality may mediate the physiological properties of IFs, probably through changes to the colonic microbiota composition and activity.

Potential Prebiotic Properties of Whey Protein and Glycomacropeptide in Gut Microbiome

Proteins in whey have prebiotic and antimicrobial properties. Whey protein comprises numerous bioactive proteins and peptides, including glycomacropeptide (GMP), a hydrophilic casein peptide that separates with the whey fraction during cheese making. GMP has traditionally been used as a protein source for individuals with phenylketonuria and also has prebiotic (supporting the growth of Bifidobacterium and lactic acid bacteria) and antimicrobial activities. GMP supplementation may help positively modulate the gut microbiome, help treat dysbiosis-related gastrointestinal disorders and improve overall health in consumers.

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

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.

Glycomacropeptide Impacts Amylin-Mediated Satiety, Postprandial Markers of Glucose Homeostasis, and the Fecal Microbiome in Obese Postmenopausal Women

BACKGROUND

Obesity with metabolic syndrome is highly prevalent and shortens lifespan.

OBJECTIVES

In a dose-finding crossover study, we evaluated the effect of glycomacropeptide (GMP) on satiety, glucose homeostasis, amino acid concentrations, inflammation, and the fecal microbiome in 13 obese women.

METHODS

Eligible women were ≤10 yr past menopause with a body mass index [BMI (in kg/m2)] of 28 to 35 and no underlying inflammatory condition affecting study outcomes. Participants consumed GMP supplements (15 g GMP + 10 g whey protein) twice daily for 1 wk and thrice daily for 1 wk, with a washout period between the 2 wk. Women completed a meal tolerance test (MTT) on day 1 (soy MTT) and day 7 (GMP MTT) of each week. During each test, subjects underwent measures of glucose homeostasis, satiety, cytokines, and the fecal microbiome compared with that of usual diet, and rated the acceptability of consuming GMP supplements.

RESULTS

The mean ± SE age of the 13 women was 57 ± 1 yr, with a median of 8 yr (range: 3-9 yr) past menopause and a BMI of 30 (IQR: 29-32). GMP was highly acceptable to participants, permitting high adherence. Metabolic effects were similar for twice or thrice daily GMP supplementation. Glucose, insulin, and cytokine concentrations were no different. The postprandial area under the curve (AUC) for glucagon concentrations was significantly lower, and the insulin-glucagon ratio was significantly higher with GMP than that with the soy MTT. Postprandial AUC amylin concentration was significantly higher with GMP than that with the soy MTT and correlated with C-peptide (P < 0.001; R2 = 0.52) and greater satiety. Ingestion of GMP supplements twice daily reduced members of the genus Streptococcus (P = 0.009) and thrice daily consumption reduced overall α diversity.

CONCLUSIONS

GMP is shown to increase amylin concentrations, improve glucose homeostasis, and alter the fecal microbiome. GMP can be a helpful nutritional supplement in obese postmenopausal women at risk for metabolic syndrome. Further investigation is warranted. This trial was registered at clinicaltrials.gov as NCT05551091.

Mass spectral profiling of caseinomacropeptide extracted from feeding material and jejunal fluid using three methods-ethanol precipitation, perchloric acid precipitation, and ultrafiltration

The ability of bovine κ-casein-derived caseinomacropeptide (CMP) to exert bioactivity in the human gut depends on its digestive survival. Sampling from the human jejunum after feeding CMP and top-down glycopeptidomics analysis facilitates the determination of CMP survival. To reduce interference from non-target molecules in mass spectrometric analysis, CMP must be isolated from digestive fluid. To identify an optimal extraction method, this study compared the profiles of CMP extracted from feeding material (commercial CMP in water) and digestive fluid by ethanol precipitation, perchloric acid (PCA) precipitation, and ultrafiltration. Ethanol precipitation yielded the highest ion abundances for aglycosylated CMP and glycosylated CMP in both feeding material and jejunal samples. Notably, PCA precipitation yielded the highest abundance of partially digested CMP-derived fragments in jejunal samples. Overall, ethanol precipitation was the most effective among the methods tested for intact CMP extraction from jejunal fluids, whereas PCA precipitation was optimal for extraction of CMP fragments.

Comparison between frail and non-frail older adults' gut microbiota: A systematic review and meta-analysis

BACKGROUND

Emerging evidence suggests that the intestinal microbiota (IM) undergoes remodelling as we age, and this impacts the ageing trajectory and mortality in older adults. The aim was to investigate IM diversity differences between frail and non-frail older adults by meta-analysing previous studies.

METHODS

The protocol of this systematic review with meta-analysis was registered on PROSPERO (CRD42021276733). We searched for studies comparing IM diversity of frail and non-frail older adults indexed on PubMed, Embase, Cochrane, and Web of Science in November 2021.

RESULTS

We included 11 studies with 1239 participants, of which 340 were meta-analysed. Frailty was defined by a variety of criteria (i.e. Fried Scale, European Consensus on Sarcopenia). There were no differences in the meta-analyses between the frail and non-frail groups for species richness index (SMD = -0.147; 95% CI = -0.394, 0.100; p = 0.243) and species diversity index (SMD = -0.033; 95% CI = -0.315, 0.250; p = 0.820). However, we identified almost 50 differences between frail and non-frail within the relative abundance of bacteria phyla, families, genera, and species in the primary studies.

CONCLUSIONS

The evidence to prove that there are differences between frail and non-frail IM diversity by meta-analysis is still lacking. The present results suggest that further investigation into the role of specific bacteria, their function, and their influence on the physiopathology of frailty is needed.

Glycomacropeptide Safety and Its Effect on Gut Microbiota in Patients with Phenylketonuria: A Pilot Study

Glycomacropeptide (GMP) represents a good alternative protein source in Phenylketonuria (PKU). In a mouse model, it has been suggested to exert a prebiotic role on beneficial gut bacteria. In this study, we performed the 16S rRNA sequencing to evaluate the effect of 6 months of GMP supplementation on the gut microbiota of nine PKU patients, comparing their bacterial composition and clinical parameters before and after the intervention. GMP seems to be safe from both the microbiological and the clinical point of view. Indeed, we did not observe dramatic changes in the gut microbiota but a specific prebiotic effect on the butyrate-producer Agathobacter spp. and, to a lesser extent, of Subdoligranulum. Clinically, GMP intake did not show a significant impact on both metabolic control, as phenylalanine values were kept below the age target and nutritional parameters. On the other hand, an amelioration of calcium phosphate homeostasis was observed, with an increase in plasmatic vitamin D and a decrease in alkaline phosphatase. Our results suggest GMP as a safe alternative in the PKU diet and its possible prebiotic role on specific taxa without causing dramatic changes in the commensal microbiota.

Glycomacropeptide in PKU-Does It Live Up to Its Potential?

The use of casein glycomacropeptide (CGMP) as a protein substitute in phenylketonuria (PKU) has grown in popularity. CGMP is derived from κ casein and is a sialic-rich glycophosphopeptide, formed by the action of chymosin during the production of cheese. It comprises 20–25% of total protein in whey products and has key biomodulatory properties. In PKU, the amino acid sequence of CGMP has been adapted by adding the amino acids histidine, leucine, methionine, tyrosine and tryptophan naturally low in CGMP. The use of CGMP compared to mono amino acids (L-AAs) as a protein substitute in the treatment of PKU promises several potential clinical benefits, although any advantage is supported only by evidence from non-PKU conditions or PKU animal models. This review examines if there is sufficient evidence to support the bioactive properties of CGMP leading to physiological benefits when compared to L-AAs in PKU, with a focus on blood phenylalanine control and stability, body composition, growth, bone density, breath odour and palatability.

A synthetic consortium of 100 gut commensals modulates the composition and function in a colon model of the microbiome of elderly subjects

Administration of cultured gut isolates holds promise for modulating the altered composition and function of the microbiota in older subjects, and for promoting their health. From among 692 initial isolates, we selected 100 gut commensal strains (MCC100) based on emulating the gut microbiota of healthy subjects, and retaining strain diversity within selected species. MCC100 susceptibility to seven antibiotics was determined, and their genomes were screened for virulence factor, antimicrobial resistance and bacteriocin genes. Supplementation of healthy and frail elderly microbiota types with the MCC100 in an in vitro colon model increased alpha-diversity, raised relative abundance of taxa including Blautia luti, Bacteroides fragilis, and Sutterella wadsworthensis; and introduced taxa such as Bifidobacterium spp. Microbiota changes correlated with higher levels of branched chain amino acids, which are health-associated in elderly. The study establishes that the MCC100 consortium can modulate older subjects' microbiota composition and associated metabolome in vitro, paving the way for pre-clinical and human trials.

Casein Glycomacropeptide: An Alternative Protein Substitute in Tyrosinemia Type I

Tyrosinemia type I (HTI) is treated with nitisinone, a tyrosine (Tyr) and phenylalanine (Phe)-restricted diet, and supplemented with a Tyr/Phe-free protein substitute (PS). Casein glycomacropeptide (CGMP), a bioactive peptide, is an alternative protein source to traditional amino acids (L-AA). CGMP contains residual Tyr and Phe and requires supplementation with tryptophan, histidine, methionine, leucine, cysteine and arginine. Aims: a 2-part study assessed: (1) the tolerance and acceptability of a low Tyr/Phe CGMP-based PS over 28 days, and (2) its long-term impact on metabolic control and growth over 12 months. Methods: 11 children with HTI were recruited and given a low Tyr/Phe CGMP to supply all or part of their PS intake. At enrolment, weeks 1 and 4, caregivers completed a questionnaire on gastrointestinal symptoms, acceptability and ease of PS use. In study part 1, blood Tyr and Phe were assessed weekly; in part 2, weekly to fortnightly. In parts 1 and 2, weight and height were assessed at the study start and end. Results: Nine of eleven children (82%), median age 15 years (range 8.6–17.7), took low Tyr/Phe CGMP PS over 28 days; it was continued for 12 months in n = 5 children. It was well accepted by 67% (n = 6/9), tolerated by 100% (n = 9/9) and improved gastrointestinal symptoms in 2 children. The median daily dose of protein equivalent from protein substitute was 60 g/day (range 45–60 g) with a median of 20 g/day (range 15 to 30 g) from natural protein. In part 2 (n = 5), a trend for improved blood Tyr was observed: 12 months pre-study, median Tyr was 490 μmol/L (range 200–600) and Phe 50 μmol/L (range 30–100); in the 12 months taking low Tyr/Phe CGMP PS, median Tyr was 430 μmol/L (range 270–940) and Phe 40 μmol/L (range 20–70). Normal height, weight and BMI z scores were maintained over 12 months. Conclusions: In HTI children, CGMP was well tolerated, with no deterioration in metabolic control or growth when studied over 12 months. The efficacy of CGMP in HTI needs further investigation to evaluate the longer-term impact on blood Phe concentrations and its potential influence on gut microflora

Prebiotic effects of pectooligosaccharides obtained from lemon peel on the microbiota from elderly donors using an in vitro continuous colon model (TIM-2)

The development of new prebiotics capable of modulating the gut microbiota in the elderly has become an area of great interest due to the particular vulnerability and frailty of this population. In the present work, mixtures of pectin-derived oligosaccharides (POS) were manufactured from lemon peel waste and evaluated for their capability to modulate the gut microbiota using, as inoculum, a pool of faeces from elderly donors. Both changes in the microbiota and the metabolic activity were assessed and compared with commercial fructooligosaccharides (FOS) and the standard ileal efflux medium (SIEM) using the TIM-2 in vitro colon model. POS fermentation led to similar or even better effects than FOS at phylum, family and genus levels. Higher increments in beneficial species such as Faecalibacterium prausnitzii and larger alpha diversity values were observed with POS in comparison with FOS and in some cases with SIEM. The PCoA analyses revealed that the microbial profiles resulting from POS and FOS bacterial fermentation were rather similar and differed from those observed after SIEM fermentation. Finally, although butyrate cumulative production was comparable among substrates, the highest short chain fatty acid (SCFA) and the lowest branched chain fatty acid (BCFA) cumulative production was observed in POS experiments. These results support the potential of pectin-derived oligosaccharides as prebiotic candidates targeting gut health in the elderly.

Commercial whey products promote intestinal barrier function with glycomacropeptide enhanced activity in downregulating bacterial endotoxin lipopolysaccharides (LPS)-induced inflammation in vitro

Cheese whey contains bioactive compounds which have shown multiple health-promoting benefits. This study aimed to assess the commercial whey products (CWP) whey protein isolate (WPI), galacto-oligosaccharide-whey protein concentrate (GOS-W) and glycomacropeptide (GMP) for their potential to improve intestinal health in vitro using HT29-MTX intestinal goblet and Caco-2 epithelial cells. Results from HT29-MTX culture showed that WPI mitigated reactive oxygen species (ROS) production at a higher extent compared to GOS-W or GMP. However, GMP downregulated the lipopolysaccharide (LPS)-induced TLR-4 inflammatory pathway with the highest potency compared to the other CWP. Biomarkers of epithelial integrity assessed on both cell lines showed tight junction proteins claudin-1, claudin-3, occludin (OCC), and zonula occludens-1 (ZO-1) upregulation by GMP in HT29-MTX (1.33-1.93-fold of control) and in Caco-2 cells (1.56-2.09-fold of control). All CWP increased transepithelial electrical resistance (TEER) in TNF-α challenged Caco-2/HT29-MTX co-culture monolayer (p < 0.05), but only GMP was similar to the positive control TGF-β1, known for its role in promoting epithelial barrier function. The TNF-α-induced co-culture monolayer permeability was prevented at similar levels by all CWP (p < 0.05). In conclusion, CWP may be used as functional food ingredients to protect against intestinal disorders with emphasis on the GMP enhanced anti-inflammatory and intestinal barrier function properties. Further in vivo studies are guaranteed to validate these findings.

Glycomacropeptide: A Bioactive Milk Derivative to Alleviate Metabolic Syndrome Outcomes

Significance: Metabolic syndrome (MetS) represents a cluster of cardiometabolic disorders, which accelerate the risk of developing diabetes, nonalcoholic fatty liver disease, and cardiovascular disorders such as atherosclerosis. Oxidative stress (OxS) and inflammation contribute to insulin resistance (IR) that greatly promotes the clinical manifestations of MetS components. Given the growing prevalence of this multifactorial condition, its alerting comorbidities, and the absence of specific drugs for treatment, there is an urgent need of prospecting for alternative nutraceutics as effective therapeutic agents for MetS. Recent Advances: There is a renewed interest in bioactive peptides derived from human and bovine milk proteins given their high potential in magnifying health benefits. Special attention has been paid to glycomacropeptide (GMP), a bioactive and soluble derivative from casein and milk whey, because of the wide range of its health-promoting functions perceived in the MetS and related complications. Critical Issues: In the present review, the challenging issue relative to clinical utility of GMP in improving MetS outcomes will be critically reported. Its importance in alleviating obesity, OxS, inflammation, IR, dyslipidemia, and hypertension will be underlined. The mechanisms of action will be analyzed, and the various gaps of knowledge in this area will be specified. Future Directions: Valuable data from cellular, preclinical, and clinical investigations have emphasized the preventive and therapeutic actions of GMP toward the MetS. However, additional efforts are needed to support its proofs of principle and causative relationship to translate its concept into the clinic. Antioxid. Redox Signal. 34, 201-222.

Nutrition, Microbiota and Role of Gut-Brain Axis in Subjects with Phenylketonuria (PKU): A Review

The composition and functioning of the gut microbiota, the complex population of microorganisms residing in the intestine, is strongly affected by endogenous and exogenous factors, among which diet is key. Important perturbations of the microbiota have been observed to contribute to disease risk, as in the case of neurological disorders, inflammatory bowel disease, obesity, diabetes, cardiovascular disease, among others. Although mechanisms are not fully clarified, nutrients interacting with the microbiota are thought to affect host metabolism, immune response or disrupt the protective functions of the intestinal barrier. Similarly, key intermediaries, whose presence may be strongly influenced by dietary habits, sustain the communication along the gut-brain-axis, influencing brain functions in the same way as the brain influences gut activity. Due to the role of diet in the modulation of the microbiota, its composition is of high interest in inherited errors of metabolism (IEMs) and may reveal an appealing therapeutic target. In IEMs, for example in phenylketonuria (PKU), since part of the therapeutic intervention is based on chronic or life-long tailored dietetic regimens, important variations of the microbial diversity or relative abundance have been observed. A holistic approach, including a healthy composition of the microbiota, is recommended to modulate host metabolism and affected neurological functions.

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

Casein glycomacropeptide (CGMP) is a bioactive milk-derived peptide with potential anti-inflammatory effects. Animal studies suggest that CGMP may work by altering gut microbiota composition and enhancing butyrate production. Its effects on intestinal homoeostasis, microbiota and metabolites in humans are unknown. The aim of the present study was to assess both the intestinal and systemic immunomodulatory effects of orally ingested CGMP. We hypothesised that daily oral CGMP intake would reduce high-sensitive C-reactive protein (hsCRP) in healthy adults. In a single-centre limited but randomised, double-blinded, reference-controlled study, we compared the effects of a 4-week intervention of either 25 g of oral powder-based chocolate-flavoured CGMP or a reference drink. We included twenty-four healthy adults who all completed the study. CGMP had no systemic or intestinal immunomodulatory effects compared with a reference drink, with regard to either hsCRP or faecal calprotectin level, faecal microbiota composition or faecal SCFA content. CGMP ingestion did not affect satiety or body weight, and it caused no severe adverse events. The palatability of CGMP was acceptable, and adherence was high. CGMP did not induce or change gastrointestinal symptoms. In conclusion, we found no immunomodulatory effects of CGMP in healthy adults. In a minor group of healthy adults, oral ingestion of 25 g of CGMP during 4 weeks was safe, well tolerated, had acceptable palatability and was without any effects on body weight.

Whole Blueberry and Isolated Polyphenol-Rich Fractions Modulate Specific Gut Microbes in an In Vitro Colon Model and in a Pilot Study in Human Consumers

Blueberry (BB) consumption is linked to improved health. The bioconversion of the polyphenolic content of BB by fermentative bacteria in the large intestine may be a necessary step for the health benefits attributed to BB consumption. The identification of specific gut microbiota taxa that respond to BB consumption and that mediate the bioconversion of consumed polyphenolic compounds into bioactive forms is required to improve our understanding of how polyphenols impact human health. We tested the ability of polyphenol-rich fractions purified from whole BB-namely, anthocyanins/flavonol glycosides (ANTH/FLAV), proanthocyanidins (PACs), the sugar/acid fraction (S/A), and total polyphenols (TPP)-to modulate the fecal microbiota composition of healthy adults in an in vitro colon system. In a parallel pilot study, we tested the effect of consuming 38 g of freeze-dried BB powder per day for 6 weeks on the fecal microbiota of 17 women in two age groups (i.e., young and older). The BB ingredients had a distinct effect on the fecal microbiota composition in the artificial colon model. The ANTH/FLAV and PAC fractions were more effective in promoting microbiome alpha diversity compared to S/A and TPP, and these effects were attributed to differentially responsive taxa. Dietary enrichment with BB resulted in a moderate increase in the diversity of the microbiota of the older subjects but not in younger subjects, and certain health-relevant taxa were significantly associated with BB consumption. Alterations in the abundance of some gut bacteria correlated not only with BB consumption but also with increased antioxidant activity in blood. Collectively, these pilot data support the notion that BB consumption is associated with gut microbiota changes and health benefits.

The Impact of the Use of Glycomacropeptide on Satiety and Dietary Intake in Phenylketonuria

Protein is the most satiating macronutrient, increasing secretion of gastrointestinal hormones and diet induced thermogenesis. In phenylketonuria (PKU), natural protein is restricted with approximately 80% of intake supplied by a synthetic protein source, which may alter satiety response. Casein glycomacropeptide (CGMP-AA), a carbohydrate containing peptide and alternative protein substitute to amino acids (AA), may enhance satiety mediated by its bioactive properties. Aim: In a three-year longitudinal; prospective study, the effect of AA and two different amounts of CGMP-AA (CGMP-AA only (CGMP100) and a combination of CGMP-AA and AA (CGMP50) on satiety, weight and body mass index (BMI) were compared. Methods: 48 children with PKU completed the study. Median ages of children were: CGMP100; (n = 13), 9.2 years; CGMP50; (n = 16), 7.3 years; and AA (n = 19), 11.1 years. Semi-quantitative dietary assessments and anthropometry (weight, height and BMI) were measured every three months. Results: The macronutrient contribution to total energy intake from protein, carbohydrate and fat was similar across the groups. Adjusting for age and gender, no differences in energy intake, weight, BMI, incidence of overweight or obesity was apparent between the groups. Conclusion: In this three-year longitudinal study, there was no indication to support a relationship between CGMP and satiety, as evidenced by decreased energy intake, thereby preventing overweight or obesity. Satiety is a complex multi-system process that is not fully understood.

Sex effects of dietary protein source and acid load on renal and bone status in the Pahenu2 mouse model of phenylketonuria

The low‐phenylalanine (Phe) diet with amino acid (AA) medical foods is associated with low bone mineral density (BMD) and renal dysfunction in human phenylketonuria (PKU). Our objective was to determine if diets differing in dietary protein source and acid load alter bone and renal outcomes in Pah^−/− and wild‐type (WT) mice. Female and male Pah^−/− (Pah^enu2/enu2) and WT littermates (C57BL/6 background) were fed high‐acid AA, buffered AA (BAA), glycomacropeptide (GMP), or high‐Phe casein diets from 3 to 24 weeks of age. The BAA diet significantly reduced the excretion of renal net acid and ammonium compared with the AA diet. Interestingly, the BAA diet did not improve renal dilation in hematoxylin and eosin (H&E) stained renal sections, femoral biomechanical parameters, or femoral bone mineral content (BMC). Significantly lower femoral BMC and strength occurred in Pah^−/− versus WT mice, with greater decline in female Pah^−/− mice. Polyuria and mild vacuolation in the proximal convoluted tubules were observed in male Pah^−/− and WT mice fed the high‐acid AA diet versus absent/minimal cortical vacuolation in males fed the GMP, BAA, or casein diets. Vacuole contents in male mice were proteinaceous. Cortical vacuolation was absent in female mice. Dilated medullary tubules were observed in all Pah^−/− mice, except for male Pah^−/− mice fed the GMP diet. In summary, the PKU genotype and diet showed differential effects on renal and bone status in male and female mice. Renal status improved in male Pah^−/− mice fed the GMP diet.

An In Vitro Enrichment Strategy for Formulating Synergistic Synbiotics

Research on the role of diet on gut and systemic health has led to considerable interest toward identifying novel therapeutic modulators of the gut microbiome, including the use of prebiotics and probiotics. However, various host responses have often been reported among many clinical trials. This is in part due to competitive exclusion as a result of the absence of ecological niches as well as host-mediated constraints via colonization resistance. In this research, we developed a novel in vitro enrichment (IVE) method for isolating autochthonous strains that can function as synergistic synbiotics and overcome these constraints. The method relied on stepwise in vitro fecal fermentations to enrich for and isolate Bifidobacterium strains that ferment the prebiotic xylooligosaccharide (XOS). We subsequently isolated Bifidobacterium longum subsp. longum CR15 and then tested its establishment in 20 unique fecal samples with or without XOS. The strain was established in up to 18 samples but only in the presence of XOS. Our findings revealed that the IVE method is suitable for isolating potential synergistic probiotic strains that possess the genetic and biochemical ability to ferment specific prebiotic substrates. The IVE method can be used as an initial high-throughput screen for probiotic selection and isolation prior to further characterization and in vivo tests.IMPORTANCE This study describes an in vitro enrichment method to formulate synergistic synbiotics that have potential for establishing autochthonous strains across multiple individuals. The rationale for this approach-that the chance of survival of a bacterial strain is improved by providing it with its required resources-is based on classic ecological theory. From these experiments, a human-derived strain, Bifidobacterium longum subsp. longum CR15, was identified as a xylooligosaccharide (XOS) fermenter in fecal environments and displayed synergistic effects in vitro The high rate of strain establishment observed in this study provides a basis for using synergistic synbiotics to overcome the responder/nonresponder phenomenon that occurs frequently in clinical trials with probiotic and prebiotic interventions. In addition, this approach can be applied in other protocols that require enrichment of specific bacterial populations prior to strain isolation.

Gut and immune effects of bioactive milk factors in preterm pigs exposed to prenatal inflammation

Prenatal inflammation may predispose to preterm birth and postnatal inflammatory disorders such as necrotizing enterocolitis (NEC). Bioactive milk ingredients may help to support gut maturation in such neonates, but mother's milk is often insufficient after preterm birth. We hypothesized that supplementation with bioactive ingredients from bovine milk [osteopontin (OPN), caseinoglycomacropeptide (CGMP), colostrum (COL)] supports gut, immunity, and NEC resistance in neonates born preterm after gram-negative infection before birth. Using preterm pigs as a model for preterm infants, fetal pigs were given intraamniotic injections of lipopolysaccharide (LPS; 1 mg/fetus) and delivered 3 days later (90% gestation). For 5 days, groups of LPS-exposed pigs were fed formula (FOR), bovine colostrum (COL), or formula enriched with OPN or CGMP. LPS induced intraamniotic inflammation and postnatal systemic inflammation but limited effects on postnatal gut parameters and NEC. Relative to FOR, COL feeding to LPS-exposed pigs showed less diarrhea, NEC severity, reduced gut IL-1β and IL-8 levels, greater gut goblet cell density and digestive enzyme activities, and blood helper T-cell fraction. CGMP improved neonatal arousal and gut lactase activities and reduced LPS-induced IL-8 secretion in intestinal epithelial cells (IECs) in vitro. Finally, OPN tended to reduce diarrhea and stimulated IEC proliferation in vitro. No effects on villus morphology, circulating cytokines, or colonic microbiota were observed among groups. In conclusion, bioactive milk ingredients exerted only modest effects on gut and systemic immune parameters in preterm pigs exposed to prenatal inflammation. Short-term, prenatal exposure to inflammation may render the gut less sensitive to immune-modulatory milk effects. NEW & NOTEWORTHY Prenatal inflammation is a risk factor for preterm birth and postnatal complications including infections. However, from clinical studies, it is difficult to separate the effects of only prenatal inflammation from preterm birth. Using cesarean-delivered preterm pigs with prenatal inflammation, we documented some beneficial gut effects of bioactive milk diets relative to formula, but prenatal inflammation appeared to decrease the sensitivity of enteral feeding. Special treatments and diets may be required for this neonatal population.

Glycomacropeptide Bioactivity and Health: A Review Highlighting Action Mechanisms and Signaling Pathways

Food-derived bioactive peptides are reported as beneficial and safe for human health. Glycomacropeptide (GMP) is a milk-protein-derived peptide that, in addition to its nutritional value, retains many biological properties and has therapeutic effects in several inflammatory disorders. GMP was shown under in vitro and in vivo conditions to exert a number of activities that regulate the physiology of important body systems, namely the gastrointestinal, endocrine, and immune systems. This review represents a comprehensive compilation summarizing the current knowledge and updated information on the major biological properties associated with GMP. GMP bioactivity is addressed with special attention on mechanisms of action, signaling pathways involved, and structural characteristics implicated. In addition, the results of various studies dealing with the effects of GMP on models of inflammatory diseases are reviewed and discussed.

Retention of Microbiota Diversity by Lactose-Free Milk in a Mouse Model of Elderly Gut Microbiota

Prebiotics may improve aging-related dysbiosis. Milk is a source of nutrients including oligosaccharides whose prebiotic potential remains largely unexplored. We used a murine model to explore the effect of milk products on high diversity and lower diversity faecal microbiota from healthy and frail elderly subjects, respectively. Mice were treated with antibiotics and subsequently "humanized" with human faecal microbiota. The mice received lactose-free or whole milk, glycomacropeptide, or soy protein (control) supplemented diets for one month. The faecal microbiota was analyzed by 16S rRNA gene amplicon sequencing. Lactose-free milk diet was as efficient as the control diet in retaining faecal microbiota diversity in mice. Both milk diets had a significant effect on the relative abundance of health-relevant taxa (e.g., Ruminococcaceae, Lachnospiraceae). The glycomacropeptide prebiotic activity previously observed in vitro was not replicated in vivo. However, these data indicate the novel prebiotic potential of bovine milk for human nutrition.

Bovine glycomacropeptide promotes the growth of Bifidobacterium longum ssp. infantis and modulates its gene expression

Bovine milk glycomacropeptide (GMP) is derived from κ-casein, with exclusively o-linked glycosylation. Glycomacropeptide promoted the growth of Bifidobacterium longum ssp. infantis in a concentration-dependent manner, and this activity was lost following periodate treatment of the GMP (GMP-P), which disables biological recognition of the conjugated oligosaccharides. Transcriptional analysis of B. longum ssp. infantis following exposure to GMP revealed a substantial response to GMP relative to bacteria treated with GMP-P, with a greater number of differentially expressed transcripts and larger fold changes versus the control. Therefore, stimulation of B. longum ssp. infantis growth by GMP is intrinsically linked to the peptide's O-linked glycosylation. The pool of differentially expressed transcripts included 2 glycoside hydrolase (family 25) genes, which were substantially upregulated following exposure to GMP, but not GMP-P. These GH25 genes were present in duplicated genomic islands that also contained genes encoding fibronectin type III binding domain proteins and numerous phage-related proteins, all of which were also upregulated. Homologs of this genomic arrangement were present in other Bifidobacterium species, which suggest it may be a conserved domain for the utilization of glycosylated peptides. This study provides insights into the molecular basis for the prebiotic effect of bovine milk GMP on B. longum ssp. infantis.

Phenylketonuric diet negatively impacts on butyrate production

BACKGROUND AND AIMS

Phenylalanine (Phe) restricted diet, combined with Phe-free l-amino acid supplementation, is the mainstay of treatment for phenylketonuria (PKU). Being the diet a key factor modulating gut microbiota composition, the aim of the present paper was to compare dietary intakes, gut microbiota biodiversity and short chain fatty acids (SCFAs) production in children with PKU, on low-Phe diet, and in children with mild hyperphenylalaninemia (MHP), on unrestricted diet.

METHODS AND RESULTS

We enrolled 21 PKU and 21 MHP children matched for gender, age and body mass index z-score. Dietary intakes, including glycemic index (GI) and glycemic load (GL), and fecal microbiota analyses, by means of denaturing gradient gel electrophoresis (DGGE) and Real-time PCR were assessed. Fecal SCFAs were quantified by gas chromatographic analysis.

RESULTS

We observed an increased carbohydrate (% of total energy), fiber and vegetables intakes (g/day) in PKU compared with MHP children (p = 0.047), as well a higher daily GI and GL (maximum p < 0.001). Compared with MHP, PKU showed a lower degree of microbial diversity and a decrease in fecal butyrate content (p = 0.02). Accordingly, two of the most abundant butyrate-producing genera, Faecalibacterium spp. and Roseburia spp., were found significantly depleted in PKU children (p = 0.02 and p = 0.03, respectively).

CONCLUSION

The low-Phe diet, characterized by a higher carbohydrate intake, increases GI and GL, resulting in a different quality of substrates for microbial fermentation. Further analyses, thoroughly evaluating microbial species altered by PKU diet are needed to better investigate gut microbiota in PKU children and to eventually pave the way for pre/probiotic supplementations.

Metabolomic Markers of Essential Fatty Acids, Carnitine, and Cholesterol Metabolism in Adults and Adolescents with Phenylketonuria

Background

Individuals with phenylketonuria (PKU) have a risk of cognitive impairment and inflammation. Many follow a low-phenylalanine (low-Phe) diet devoid of animal protein in combination with medical foods (MFs).

Objective

To assess lipid metabolism in participants with PKU consuming amino acid MFs (AA-MFs) or glycomacropeptide MFs (GMP-MFs), we conducted fatty acid and metabolomics analyses.

Methods

We used subsets of fasting plasma and urine samples from our randomized crossover trial in which participants with early-treated classical and variant (milder) PKU consumed a low-Phe diet combined with AA-MFs or GMP-MFs for 3 wk each. Fatty acid profiles of red blood cell (RBC) membranes were determined for 25 adults (aged 18-49 y) with PKU and 143 control participants. Metabolomics analyses of plasma and urine samples were conducted by Metabolon for 9-10 adolescent and adult participants with PKU and for 15 control participants.

Results

RBC fatty acid profiles were not significantly different with AA-MFs or GMP-MFs. PKU participants showed higher total n-6:n-3 (ω-6:ω-3) fatty acids (mean ± SD percentages of total fatty acids: AA-MF = 5.45% ± 1.07%; controls = 4.33%; P < 0.001) and lower docosahexaenoic acid (DHA; AA-MF = 3.21% ± 0.98%; controls = 3.70% ± 1.01%; P = 0.02) and eicosapentaenoic acid (AA-MF = 0.33% ± 0.12%; controls = 0.60% ± 0.43%; P < 0.001) in RBCs than did control participants. Despite higher carnitine intake from AA-MFs than GMP-MFs (mean ± SE intake: AA-MFs = 58.6 ± 5.3 mg/d; GMP-MFs = 0.3 ± 0.01 mg/d; P < 0.001), plasma concentrations of carnitine were similar and not different from those in the control group (AA-MF compared with GMP-MF, P = 0.73). AA-MFs resulted in higher urinary excretion of trimethylamine N-oxide (TMAO), which is synthesized by bacteria from carnitine, compared with GMP-MFs (mean ± SE scaled intensity-TMAO: AA-MFs = 1.2 ± 0.1, GMP-MFs = 0.9 ± 0.1; P = 0.005). Plasma deoxycarnitine was lower in PKU participants than in control participants, suggesting reduced carnitine biosynthesis in PKU (AA-MF = 0.9 ± 0.1; GMP-MF = 1.0 ± 0.1; controls = 1.3 ± 0.1; AA-MF compared with controls, P = 0.01; GMP-MF compared with controls, P = 0.04).

Conclusions

Supplementation with DHA is needed in PKU. Carnitine supplementation of AA-MFs shows reduced bioavailability due, in part, to bacterial degradation to TMAO, whereas the bioavailability of carnitine is greater with prebiotic GMP-MFs. This trial was registered at www.clinicaltrials.gov as NCT01428258.

Glycomacropeptide Reduces Intestinal Epithelial Cell Barrier Dysfunction and Adhesion of Entero-Hemorrhagic and Entero-Pathogenic Escherichia coli in Vitro

In recent years, the potential of glycosylated food components to positively influence health has received considerable attention. Milk is a rich source of biologically active glycoconjugates which are associated with antimicrobial, immunomodulatory, anti-adhesion, anti-inflammatory and prebiotic properties. Glycomacropeptide (GMP) is the C-terminal portion of kappa-casein that is released from whey during cheese-making by the action of chymosin. Many of the biological properties associated with GMP, such as anti-adhesion, have been linked with the carbohydrate portion of the protein. In this study, we investigated the ability of GMP to inhibit the adhesion of a variety of pathogenic Escherichia coli strains to HT-29 and Caco-2 intestinal cell lines, given the importance of E. coli in causing bacterial gastroenteritis. GMP significantly reduced pathogen adhesion, albeit with a high degree of species specificity toward enteropathogenic E. coli (EPEC) strains O125:H32 and O111:H2 and enterohemorrhagic E. coli (EHEC) strain 12900 O157:H7. The anti-adhesive effect resulted from the interaction of GMP with the E. coli cells and was also dependent on GMP concentration. Pre-incubation of intestinal Caco-2 cells with GMP reduced pathogen translocation as represented by a decrease in transepithelial electrical resistance (TEER). Thus, GMP is an effective in-vitro inhibitor of adhesion and epithelial injury caused by E. coli and may have potential as a biofunctional ingredient in foods to improve gastrointestinal health.

Metabolomic changes demonstrate reduced bioavailability of tyrosine and altered metabolism of tryptophan via the kynurenine pathway with ingestion of medical foods in phenylketonuria

BACKGROUND

Deficiencies of the monoamine neurotransmitters, such as dopamine synthesized from Tyr and serotonin synthesized from Trp, are of concern in PKU. Our objective was to utilize metabolomics analysis to assess monoamine metabolites in subjects with PKU consuming amino acid medical foods (AA-MF) and glycomacropeptide medical foods (GMP-MF).

METHODS

Subjects with PKU consumed a low-Phe diet combined with AA-MF or GMP-MF for 3weeks each in a randomized, controlled, crossover study. Metabolomic analysis was conducted by Metabolon, Inc. on plasma (n=18) and urine (n=9) samples. Catecholamines and 6-sulfatoxymelatonin were measured in 24-h urine samples.

RESULTS

Intake of Tyr and Trp was ~50% higher with AA-MF, and AA-MF were consumed in larger quantities, less frequently during the day compared with GMP-MF. Performance on neuropsychological tests and concentrations of neurotransmitters derived from Tyr and Trp were not significantly different with AA-MF or GMP-MF. Plasma serotonin levels of gut origin were higher in subjects with variant compared with classical PKU, and with GMP-MF compared with AA-MF in subjects with variant PKU. Metabolomics analysis identified higher levels of microbiome-derived compounds synthesized from Tyr, such as phenol sulfate, and higher levels of compounds synthesized from Trp in the kynurenine pathway, such as quinolinic acid, with ingestion of AA-MF compared with GMP-MF.

CONCLUSIONS

The Tyr from AA-MF is less bioavailable due, in part, to greater degradation by intestinal microbes compared with the Tyr from prebiotic GMP-MF. Research is needed to understand how metabolism of Trp via the kynurenine pathway and changes in the intestinal microbiota affect health for individuals with PKU. This trial is registered at www.clinicaltrials.gov as NCT01428258.