Analysis of Bovine Kappa-Casein Glycomacropeptide by Liquid Chromatography-Tandem Mass Spectrometry

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.

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.

Caseins: Versatility of Their Micellar Organization in Relation to the Functional and Nutritional Properties of Milk

The milk of mammals is a complex fluid mixture of various proteins, minerals, lipids, and other micronutrients that play a critical role in providing nutrition and immunity to newborns. Casein proteins together with calcium phosphate form large colloidal particles, called casein micelles. Caseins and their micelles have received great scientific interest, but their versatility and role in the functional and nutritional properties of milk from different animal species are not fully understood. Caseins belong to a class of proteins that exhibit open and flexible conformations. Here, we discuss the key features that maintain the structures of the protein sequences in four selected animal species: cow, camel, human, and African elephant. The primary sequences of these proteins and their posttranslational modifications (phosphorylation and glycosylation) that determine their secondary structures have distinctively evolved in these different animal species, leading to differences in their structural, functional, and nutritional properties. The variability in the structures of milk caseins influence the properties of their dairy products, such as cheese and yogurt, as well as their digestibility and allergic properties. Such differences are beneficial to the development of different functionally improved casein molecules with variable biological and industrial utilities.

Comparison of Solid-Phase Extraction Sorbents for Monitoring the In Vivo Intestinal Survival and Digestion of Kappa-Casein-Derived Caseinomacropeptide

Kappa-casein-derived caseinomacropeptide (CMP)-a 64-amino-acid peptide-is released from kappa-casein after rennet treatment and is one of the major peptides in whey protein isolate (WPI). CMP has anti-inflammatory and antibacterial activities. It also has two major amino acid sequences with different modifications, including glycosylation, phosphorylation, and oxidation. To understand the potential biological role of CMP within the human body, there is a need to examine the extent to which CMP and CMP-derived fragments survive across the digestive tract, where they can exert these functions. In this study, three solid-phase extraction (SPE) methods-porous graphitized carbon (PGC), hydrophilic interaction liquid chromatography (HILIC), and C18 chromatography-were evaluated to determine which SPE sorbent is the most efficient to extract intact CMP and CMP-derived peptides from WPI and intestinal digestive samples prior to LC-MS/MS acquisition. The C18 SPE sorbent was the most efficient in extracting intact CMP and CMP-derived peptides from WPI, whereas the PGC SPE sorbent was the most efficient in extracting CMP-derived peptides from intestinal digesta samples.

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.

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

BACKGROUND

Bovine milk κ-casein-derived caseinomacropeptide (CMP) is produced in large quantities during cheese-making and has various biological activities demonstrated via in vitro and in vivo experiments. Previous studies examined protein degradation and peptide release after casein or whey protein consumption. However, whether purified intact CMP that is partially glycosylated survives intact to its presumed site of bioactivity within the gut remains unknown.

OBJECTIVES

The aim of this study was to determine the extent to which purified intact CMP (including glycosylated forms) is digested into peptide fragments within the jejunum of healthy human adults after consumption.

METHODS

Jejunal fluids were collected from 3 adult participants (2 men and 1 woman, age: 27 ± 7 y; BMI: 23 ± 1 kg/m2) for 3 h after consuming 37.5 g of purified intact CMP. CMP and CMP-derived peptides were isolated from the collected jejunal fluids by ethanol precipitation and solid-phase extraction and identified by MS-based top-down glycopeptidomics. Relative abundances of CMP and CMP-derived peptides were compared qualitatively between the feed and the jejunal fluids.

RESULTS

Intact CMP was dominant in feeding material, accounting for 90% of the total ion abundance of detected peptides, and in very low abundance (<2%) in the jejunal fluids. CMP-derived fragment peptides ranging from 11 to 20 amino acids in length were predominant (accounting for 68-88% of the total peptide ion abundance) in jejunal fluids during 1-3 h post consumption.

CONCLUSIONS

This study demonstrates that intact CMP (including glycosylated forms) is mostly digested in the human jejunum, releasing a wide array of CMP-derived peptide fragments. Some of the CMP-derived peptides with high homology to known bioactive peptides consistently survived across 3 h of digestion. Therefore, future research should examine the biological effects of the partially digested form-the CMP-derived fragments-rather than those of intact CMP.