Top-Down Glycopeptidomics Reveals Intact Glycomacropeptide Is Digested to a Wide Array of Peptides in Human Jejunum

Dietary delivery of glycomacropeptide within the whey protein matrix is not effective in mitigating tissue ceramide deposition and obesity in mice fed a high-fat diet

Obesity is often accompanied by heightened circulating and tissue inflammation along with an increase in sphingolipids (e.g., ceramides) in metabolically active and insulin-sensitive organs. Whey protein isolate (WPI) has been shown to decrease inflammation and increase insulin sensitivity when given during a high-fat diet (HFD) intervention in rodents. The whey protein bioactive peptide glycomacropeptide (GMP) has also been linked to having anti-inflammatory properties and regulating lipogenesis. Therefore, the purpose of the study was to determine the effect of dietary GMP within the whey protein matrix on tissue inflammation, adiposity, and tissue ceramide accumulation in an obesogenic rodent model. Young adult male mice (10 wk old) underwent a 10-wk 60% HFD intervention. Glycomacropeptide was absent in the control low-fat diet and HFD WPI (-GMP) groups. The HFD WPI (1×GMP) treatment contained a standard amount of GMP, and HFD WPI (2×GMP) had double the amount. We observed no differences in weight gain or reductions in adiposity when comparing the GMP groups to HFD WPI (-GMP). Similarly, insulin resistance and glucose intolerance were not offset with GMP, and skeletal muscle and liver tissue ceramide content was unaltered with the GMP intervention. In contrast, the additional amount of GMP (2×GMP) might adversely affect tissue obesity-related pathologies. Together, dietary GMP given in a whey protein matrix during an HFD intervention does not alter weight gain, insulin resistance, glucose intolerance, and sphingolipid accumulation in the liver and skeletal muscle.

Macrophage-Immunomodulatory Actions of Bovine Whey Protein Isolate, Glycomacropeptide, and Their In Vitro and In Vivo Digests

Whey protein isolate (WPI) consists of an array of proteins and peptides obtained as a byproduct of the cheesemaking process. Research suggests that WPI, along with its peptides such as glycomacropeptide (GMP), possesses immunomodulatory properties. These properties hold potential for alleviating the adverse effects of inflammatory conditions such as inflammatory bowel disease. Although promising, the immunoregulatory properties of the digested forms of WPI and GMP-those most likely to interact with the gut immune system-remain under-investigated. To address this knowledge gap, the current study examined the effects of in vitro-digested WPI and GMP, in vivo-digested WPI, and undigested WPI and GMP on the secretion of pro-inflammatory cytokines (TNF-α and IL-1β) in lipopolysaccharide-stimulated macrophage-like cells. Our results indicate that digested WPI and GMP reduced the expression of TNF-α and IL-1β, two pro-inflammatory cytokines. Whole WPI had no effect on TNF-α but reduced IL-1β levels. In contrast, in vivo-digested WPI reduced TNF-α but increased IL-1β. Undigested GMP, on the other hand, increased the secretion of both cytokines. These results demonstrate that digestion greatly modifies the effects of WPI and GMP on macrophages and suggest that digested WPI and GMP could help mitigate gastrointestinal inflammation. Further clinical studies are necessary to determine the biological relevance of WPI and GMP digestion products within the gut and their capacity to influence gut inflammation.

Evaluating the Potential of Casein Glycomacropeptide in Adult Irritable Bowel Syndrome Management: A Pilot Study

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that affects 10-15% of the global population and presents symptoms such as abdominal discomfort, bloating and altered bowel habits. IBS is believed to be influenced by gut microbiota alterations and low-grade inflammation. Bovine kappa-casein glycomacropeptide (GMP), a bioactive dairy-derived peptide, possesses anti-adhesive, prebiotic and immunomodulatory properties that could potentially benefit IBS patients. This pilot study investigated the effects of daily supplementation with 30 g of GMP for three weeks on gut health in five people with IBS. We assessed alterations in gut microbiota composition, fecal and blood inflammatory makers, and gut-related symptoms before, during and after the GMP feeding period. The results revealed no changes in fecal microbiota, subtle effects on systemic and intestinal immune makers, and no changes in gut-related symptoms during and after the GMP supplementation. Further research is needed to assess the potential benefits of GMP in IBS patients, including the examination of dosage and form of GMP supplementation.

Fingerprinting of Proteases, Protease Inhibitors and Indigenous Peptides in Human Milk

The presence of proteases and their resulting level of activity on human milk (HM) proteins may aid in the generation of indigenous peptides as part of a pre-digestion process, of which some have potential bioactivity for the infant. The present study investigated the relative abundance of indigenous peptides and their cleavage products in relation to the abundance of observed proteases and protease inhibitors. The proteomes and peptidomes in twelve HM samples, representing six donors at lactation months 1 and 3, were profiled. In the proteome, 39 proteases and 29 protease inhibitors were identified in 2/3 of the samples. Cathepsin D was found to be present in higher abundance in the proteome compared with plasmin, while peptides originating from plasmin cleavage were more abundant than peptides from cathepsin D cleavage. As both proteases are present as a system of pro- and active- forms, their activation indexes were calculated. Plasmin was more active in lactation month 3 than month 1, which correlated with the total relative abundance of the cleavage product ascribed to plasmin. By searching the identified indigenous peptides in the milk bioactive peptide database, 283 peptides were ascribed to 10 groups of bioactivities. Antimicrobial peptides were significantly more abundant in month 1 than month 3; this group comprised 103 peptides, originating from the β-CN C-terminal region.

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.