Appetite is not influenced by a unique milk peptide: caseinomacropeptide (CMP)

Fermented Soy and Fish Protein Dietary Sources Shape Ileal and Colonic Microbiota, Improving Nutrient Digestibility and Host Health in a Piglet Model

Suitable protein sources are essential requirements for piglet growth and health. Typically, intestinal microbiota co-develops with the host and impact its physiology, which make it more plastic to dietary protein sources at early stages. However, the effects of fermented soybean meal (FSB) and fish meal (FM) on foregut and hindgut microbiota, and their relationship with nutrient digestion and host health remain unclear. In this study, we identified interactions between ileac and colonic microbiota which were reshaped by FSB and FM, and assessed host digestibility and host health in a piglet model. Eighteen weaned piglets (mean weight = 8.58 ± 0.44 kg) were divided into three dietary treatments, with six replicates/treatment. The level of dietary protein was 16%, with FSB, FM, and a mixture of fermented soybean meal and fish meal (MFSM) applied as protein sources. During days 1-14 and 1-28, diets containing MFSM generated higher piglet body weight and average daily gain, but lower feed to weight gain ratios when compared with the FM diet (P < 0.05). Piglets in MFSM and FM groups had lower apparent total tract digestibility (ATTD) of crude protein (CP) compared with the FSB group (P < 0.05). Serum immunoglobulins (IgM and IgG) in MFSM and FM groups were significantly higher on day 28, but serum cytokines (interleukin-6 and tumor necrosis factor-α) were significantly lower than the FSB group on days 14 and 28 (P < 0.05). When compared with FSB and FM groups, dietary MFSM significantly increased colonic acetic acid and butyric acid levels (P < 0.05). Compared with the FM and MFSM groups, the FSB diet increased the relative abundance of ileac Lactobacillus and f_Lactobacillaceae, which were significant positively correlated with CP ATTD (P < 0.05). Compared with the FSB group, the relative abundance of f_Peptostreptococcaceae and Romboutsia in MFSM or FM groups were increased and were significant positively correlated with total carbohydrate (TC) ATTD (P < 0.05). Piglets fed FSB had higher α-diversity in colonic microbiota when compared with other groups (P < 0.05). The relative abundance of colonic unidentified_Clostridiales and Romboutsia in MFSM and FSB groups were significantly higher than in the FM group (P < 0.05). Dietary MFSM or FM increased the relative abundance of colonic Streptococcaceae and Streptococcus, but decreased the relative abundance of Christensenellaceae when compared with the FSB group (P < 0.05). These bacteria showed a significantly positive correlation with serum cytokine and immunoglobulin levels (P < 0.05). Therefore, dietary FSB improved CP digestibility by increasing the relative abundance of ileac f_Lactobacillaceae and Lactobacillus, while dietary MFSM benefited TC digestibility by increasing f_Peptostreptococcaceae and Romboutsia. Dietary MFSM and FM enhanced immunoglobulin secretion by increasing colonic f_Streptococcaceae and Streptococcus prevalence, while dietary FSB promoted cytokine production by increasing microbiota diversity and Romboutsia and Christensenellaceae. Our data provide a theoretical dietary basis for young animals using plant and animal protein sources.

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.

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.

The Metabolic Concept of Meal Sequence vs. Satiety: Glycemic and Oxidative Responses with Reference to Inflammation Risk, Protective Principles and Mediterranean Diet

With increasing exposure to eating opportunities and postprandial conditions becoming dominant states, acute effects of meals are garnering interest. In this narrative review, meal components, combinations and course sequence were questioned vis-à-vis resultant postprandial responses, including satiety, glycemic, oxidative and inflammatory risks/outcomes vs. protective principles, with reference to the Mediterranean diet. Representative scientific literature was reviewed and explained, and corresponding recommendations discussed and illustrated. Starting meals with foods, courses and/or preloads high in innate/added/incorporated water and/or fibre, followed by protein-based courses, delaying carbohydrates and fatty foods and minimizing highly-processed/sweetened hedonic foods, would increase satiety-per-calorie vs. obesogenic passive overconsumption. Similarly, starting with high-water/fibre dishes, followed by high-protein foods, oils/fats, and delayed/reduced slowly-digested whole/complex carbohydrate sources, optionally closing with simpler carbohydrates/sugars, would reduce glycaemic response. Likewise, starting with foods high in innate/added/incorporated water/fibre/antioxidants, high monounsaturated fatty acid foods/oils, light proteins and whole/complex carbohydrate foods, with foods/oils low in n-6 polyunsaturated fatty acids (PUFA) and n-6:n-3 PUFA ratios, and minimal-to-no red meat and highly/ultra-processed foods/lipids, would reduce oxidative/inflammatory response. Pyramids illustrating representative meal sequences, from most-to-least protective foods, visually communicate similarities between axes, suggesting potential unification for optimal meal sequence, consistent with anti-inflammatory nutrition and Mediterranean diet/meal principles, warranting application and outcome evaluation.

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.

Postprandial metabolic responses to ingestion of bovine glycomacropeptide compared to a whey protein isolate in prediabetic volunteers

PURPOSE

Whey protein was shown to reduce blood glucose responses in humans and various other positive effects have been attributed to this protein. In contrast, studies using glycomacropeptide (GMP) as part of the whey fraction of bovine milk are rare. We, therefore, studied the postprandial responses to GMP administration in humans with impaired glucose tolerance compared to the effects of pure whey protein in a random design.

METHODS

Fifteen prediabetic volunteers received on different occasions one of three test drinks containing 50 g of maltodextrin19 (MD19) alone or in combination with either 50 g GMP or 50 g whey protein isolate (WPI). Blood was collected over 4 h with analysis of blood glucose and hormones, gastric emptying rate as well as plasma amino- and fatty acids, β-hydroxybutyrate and acylcarnitines.

RESULTS

The WPI drink reduced the AUC of venous blood glucose compared to the MD19 drink in the prediabetic group by 11% (p = 0.0018) whereas GMP reduced the AUC by 18% (p < 0.0001), significantly different to the WPI drink (p = 0.0384). The reduction in blood glucose after the GMP drink was accompanied by a significantly lower AUC of insulin (- 34%) than for the WPI drink. Levels of C-peptide and of glucose insulinotropic polypeptide (GIP) were highly increased after the WPI drink over the MD19 control drink but remained in essence unaffected by the GMP.

CONCLUSION

GMP reduced the glycemic response more potently than whey protein, whereas insulin output was less affected making GMP an interesting protein to control postprandial glucose responses.

Therapeutic Potential of Milk Whey

Milk whey—commonly known as cheese whey—is a by-product of cheese or casein in the dairy industry and contains usually high levels of lactose, low levels of nitrogenous compounds, protein, salts, lactic acid and small amounts of vitamins and minerals. Milk whey contains several unique components like immunoglobulins (Igs), lactoferrin (Lf), lactoperoxidase (Lp), glycomacropeptide (GMP) and sphingolipids that possess some important antimicrobial and antiviral properties. Some whey components possess anticancer properties such as sphingomyelin, which have the potential to inhibit colon cancer. Immunoglobulin-G (IgGs), Lp and Lf concentrated from whey participates in host immunity. IgGs binds with bacterial toxins and lowers the bacterial load in the large bowel. There are some whey-derived carbohydrate components that possess prebiotic activity. Lactose support lactic acid bacteria (such as Bifidobacteria and Lactobacilli). Stallic acids, an oligosaccharide in whey, are typically attached to proteins, and possess prebiotic properties. The uniqueness of whey proteins is due to their ability to boost the level of glutathione (GSH) in various tissues and also to optimize various processes of the immune system. The role of GSH is very critical as it protects the cells against free radical damage, infections, toxins, pollution and UV exposure. Overall GSH acts as a centerpiece of the body’s antioxidant defense system. It has been widely observed that individuals suffering from cancer, HIV, chronic fatigue syndrome and many other immune-compromising conditions have very poor levels of glutathione. The sulphur-containing amino-acids (cysteine and methionine) are also found in high levels in whey protein. Thus, the present review will focus on the therapeutic potential of milk whey such as antibiotic, anti-cancer, anti-toxin, immune-enhancer, prebiotic property etc.

The Macronutrients, Appetite, and Energy Intake

Each of the macronutrients-carbohydrate, protein, and fat-has a unique set of properties that influences health, but all are a source of energy. The optimal balance of their contribution to the diet has been a long-standing matter of debate. Over the past half century, thinking has progressed regarding the mechanisms by which each macronutrient may contribute to energy balance. At the beginning of this period, metabolic signals that initiated eating events (i.e., determined eating frequency) were emphasized. This was followed by an orientation to gut endocrine signals that purportedly modulate the size of eating events (i.e., determined portion size). Most recently, research attention has been directed to the brain, where the reward signals elicited by the macronutrients are viewed as potentially problematic (e.g., contribute to disordered eating). At this point, the predictive power of the macronutrients for energy intake remains limited.

Casein glycomacropeptide for active distal ulcerative colitis: a randomized pilot study

BACKGROUND

In ulcerative colitis (UC), dietary supplements may have anti-inflammatory properties and improve disease course. We investigated the effects of casein glycomacropeptide (CGMP), a fraction of bovine whey protein, in active UC.

MATERIALS AND METHODS

In a randomized open-label intervention study, 24 patients with active UC involving 10-40 cm of the distal colon were randomized in a 2 : 1 ratio into two groups. The first group was administered their usual treatment plus a daily supplement of CGMP 30 g, and the second group was administered a dose escalation to 4800 mg oral mesalamine daily (standard treatment) for 4 weeks. Clinical, endoscopic, mucosal and circulating disease activity markers were monitored. Acceptance of and adherence to CGMP up to 8 weeks were documented.

RESULTS

After 4 weeks of treatment, 10 of 16 (63%) patients who received CGMP had an unchanged or decreased Simple Clinical Colitis Activity Index (SCCAI), which was similar to the four of eight (50%) (P = 0·67) patients on the standard treatment. The number of patients in which SCCAI decreased by three or more did not differ between the two groups: nine of 16 (56%) in the CGMP group vs. four of eight (50%) in the standard treatment group (P = 0·77). Changes in disease extent and severity were similar between the two groups. CGMP was well tolerated and accepted by the patients.

CONCLUSIONS

The addition of CGMP as a nutritional therapy to standard treatment was safe and accepted by patients with active distal UC. The disease-modifying effect of CGMP was similar to that of the mesalamine dose escalation.

Do small differences in hydration status affect mood and mental performance?

Although it has been suggested that many in the general population are dehydrated to the extent that mood and cognition are disrupted, there has been little research investigating mild levels of dehydration. When dehydration reduces body mass by more than 2%, it has been consistently reported that mood is influenced, fatigue is greater, and alertness is lower. In contrast, the effects on cognition have been less consistent. Only a few studies have looked at females and these studies made little attempt to consider hormones that influence kidney functioning. In particular, there has been virtually no attempt to look at changes in hydration status in the range that occurs in individuals with a sedentary lifestyle in a temperate climate. There is a consequent need to study individuals who have lost up to 1% of body mass due to dehydration. While 4 intervention trials have found that the cognition of children improved in response to water consumption, the effects of water consumption on cognition in older adults, another high-risk group, have been largely ignored.

Trigonella foenum-graecum seeds lowers postprandial blood glucose in overweight and obese individuals

This study determined the effects of fenugreek on postprandial plasma glucose (PPG) and satiety among overweight and obese individuals. Fourteen subjects were studied in the morning after overnight fasts on four separate occasions. Glycaemic responses elicited by 50 g carbohydrate portions of white bread and jam with or without 5.5 g of fenugreek and fried rice with or without 5.5 g fenugreek were determined over 2 h. The primary endpoint was the incremental area under the plasma glucose response curve (IAUC). Adding fenugreek to both foods significantly reduced the IAUC compared to the food alone: white bread and jam, 180 ± 22 versus 271 ± 23 mmol × min/L (P = 0.001); fried rice, 176 ± 20 versus 249 ± 25 mmol × min/L (P = 0.001). Fenugreek also significantly reduced the area under the satiety curve for white bread with jam (134 ± 27 versus 232 ± 33 mm × hr, P = 0.01) and fried rice (280 ± 37 versus 379 ± 36 mm × hr, P = 0.01). It is concluded that fenugreek significantly decreased the PPG response and increased satiety among overweight and obese individuals.

Evidence of enhanced serum amino acid profile but not appetite suppression by dietary glycomacropeptide (GMP): a comparison of dairy whey proteins

OBJECTIVE

There is evidence that high-protein foods increase satiety and may aid weight loss, yet little is known of differential effects of protein composition. The aim of the study was to compare the acute effects of 4 whey proteins on satiety and food intake and to evaluate possible relationships with postprandial serum amino acid concentrations.

METHODS

Isoenergetic high-protein shakes (∼1 MJ) containing 25 g whey protein were given to 18 lean male participants using a crossover design. Three protein fractions identified as satiating in a rat model, glycomacropeptide (GMP), beta-lactoglobulin (ß-lac), and colostrum whey protein concentrate (WPC), were compared with a WPC control. A standardized 2.5MJ breakfast was given at 0830 hours, followed by the preload beverages at 1130 hours. Participants rated appetite sensations using visual analogue scales (VAS) prior to the beverage (baseline, 0 minutes) and then at 15, 30, 45, 60, 90, 150, and 210 minutes. Energy and macronutrient intake was measured by covert weighing of an ad libitum lunch meal at 90 minutes. Repeat blood samples were collected via venous cannulation.

RESULTS

Serum amino acid (a.a.) concentrations differed between whey fractions (p=0.012) and were higher following GMP compared to ß-lac (p=0.051) and colostrum WPC (p=0.044) but not the WPC control (p=0.20). There was no difference in VAS-rated hunger, satisfaction, or thoughts of food between whey fractions, but fullness did differ (p=0.032) and was highest following the ß-lac beverage. Energy intake was not suppressed relative to control by any of the 3 whey fractions.

CONCLUSIONS

We conclude that total serum a.a. concentration was a poor indicator of satiety, with little evidence of differential satiety between these whey proteins other than a modest enhancement of fullness by ß-lac.

Novel nutritional treatment for manic and psychotic disorders: a review of tryptophan and tyrosine depletion studies and the potential of protein-based formulations using glycomacropeptide

RATIONALE

Current amino acid (AA) mixtures used in acute tryptophan (Trp) and tyrosine (Tyr) plus phenylalanine (Phe) depletion and loading tests are unpalatable and lack specificity. Specificity is improved by reducing content of branched-chain amino acids (BCAA) and palatability to a certain extent by dose reduction.

OBJECTIVES

This study aims to identify a palatable naturally occurring alternative(s) to amino acids with the desired BCAA content for use in the above tests.

METHODS

A palatable alternative lacking in Trp, Tyr and Phe has been identified in the whey protein fraction caseino-glycomacropeptide (c-GMP). The absence of these three aromatic amino acids renders GMP suitable as a template for seven formulations for separate and combined depletion or loading and a placebo control. The absence of Phe and Tyr enables GMP to provide a unique nutritional therapy of manic and psychotic disorders by inhibition of cerebral dopamine synthesis and release and possibly also by enhancing glutamatergic function, in general, and in patients resistant to anti-psychotic medication, in particular.

RESULTS

Seven GMP-based formulations for the above tests are proposed, two of which can be used in the above nutritional therapy and a third formulation as a placebo control in clinical trials.

CONCLUSIONS

Development of these formulations should advance the above research and diagnostic tests, open new avenues for neuroscience research on monoamine function, and improve the therapy of bipolar and psychotic disorders and enhance the quality of life of sufferers.

Possible role of milk-derived bioactive peptides in the treatment and prevention of metabolic syndrome

The growing prevalence of metabolic syndrome as well as its impact on public health has garnered increased attention in recent years. As a result, metabolic syndrome is now considered one of the world's leading public health problems. Bioactive peptides deriving from milk proteins may play an important role in the prevention and treatment of metabolic syndrome and its complications via several mechanisms, such as the satiety response, the regulation of insulinemia levels and blood pressure, the uptake of free radicals, and alteration of the lipid profile. These peptides can be incorporated into functional foods or administered via nutraceuticals to decrease the risk of obesity, atherogenesis, arterial hypertension, and type 2 diabetes. Recent findings have generated considerable scientific and commercial interest in milk-derived bioactive peptides, leading to numerous publications on the effectiveness of these substances. This review summarizes the current knowledge on bioactive peptides derived from milk proteins and examines the potential value of these peptides in the treatment and prevention of metabolic syndrome and its complications.

Acute effect of soybean beta-conglycinin hydrolysate ingestion on appetite sensations in healthy humans

A hydrolysate prepared from soybean beta-conglycinin reduced food intake through cholecystokinin release in rats; however, effects of the hydrolysate on human appetites are unknown. In this study, healthy volunteers ingested 3g of the beta-conglycinin hydrolysate (BconB) and/or a soy protein hydrolysate (HN) contained in a beverage or in a jelly. Appetite profiles (hunger, fullness and prospective consumption) after the ingestion and palatability of test jellies were recorded. Fullness was rated higher, and hunger was rated lower after BconB ingestion as compared to HN ingestion. These results demonstrate that 3g of BconB is effective to enhance fullness and reduce hunger sensations in healthy humans.

Breakfast with glycomacropeptide compared with amino acids suppresses plasma ghrelin levels in individuals with phenylketonuria

Phenylketonuria (PKU) requires a lifelong low-phenylalanine (phe) diet where protein needs are met by consumption of a phe-free amino acid (AA) formula; complaints of persistent hunger are common. Foods made with glycomacropeptide (GMP), an intact protein that contains minimal phe and may promote satiety, provide an alternative to AA formula. The objective was to assess the ability of a GMP breakfast to promote satiety and affect plasma concentrations of AAs, insulin, and the appetite stimulating hormone ghrelin in those with PKU, when compared to an AA-based breakfast. Eleven PKU subjects (8 adults and 3 boys ages 11-14) served as their own controls in an inpatient metabolic study with two 4-day treatments: an AA-based diet followed by a diet replacing all AA formula with GMP foods. Plasma concentrations of AAs, insulin and ghrelin were obtained before and/or 180 min after breakfast. Satiety was assessed using a visual analog scale before, immediately after and 150 min after breakfast. Postprandial ghrelin concentration was significantly lower (p=0.03) with GMP compared to an AA-based breakfast, with no difference in fasting ghrelin. Lower postprandial ghrelin concentrations were associated with greater feelings of fullness after breakfast suggesting greater satiety with GMP compared to AAs. Postprandial concentrations of insulin and total plasma AAs were higher after a GMP breakfast compared to an AA-based breakfast consistent with slower absorption and less degradation of AAs from GMP. These results show sustained ghrelin suppression, and suggest greater satiety with ingestion of a meal containing GMP compared with AAs.

Effect of glycomacropeptide fractions on cholecystokinin and food intake

Glycomacropeptide (GMP) is the hydrophilic 64-amino acid C-terminal glycopeptide released into cheese whey when kappa-casein is cleaved by chymosin. GMP exists as a mixture of different glycoforms due to the carbohydrates sialic acid (N-acetylneuraminic acid, NeuNAc), galactose (Gal), galactosamine and glucosamine attached by O-glycosidic linkages. GMP reportedly stimulates the release of cholecystokinin (CCK), which may promote satiety. The objectives of the present study were to manufacture three glycoforms of GMP, minimally glycosylated GMP (3.5 (sd 0.1) % NeuNAc and 1.5 (sd 0.1) % Gal), glycosylated GMP (12.0 (sd 0.3) % NeuNAc and 4.2 (sd 0.2) % Gal) and a GMP-depleted whey protein concentrate, and to assess the effects of these fractions relative to glucose on CCK, subjective measures of satiety and food intake. In a randomised double-blind acute study, twenty overweight/obese males (56.9 (sd 7.2) years, 97.4 (sd 8.1) kg, 31.5 (sd 3.0) kg/m2) were recruited to consume four 50 g preloads (two GMP preparations, GMP-depleted whey and glucose) containing 895 kJ. Blood samples and subjective measures of satiety were collected before and at 15, 30, 60, 90, 120 and 180 min after the consumption of preload, and CCK levels were measured. A lunchtime meal of hot food was provided from which subjects ate ad libitum until satisfied. Energy and nutrient intakes from the food consumed were calculated. There was no significant difference in CCK levels, subjective measures of satiety or food intake between treatments at the given preload level. These results suggest that the protein fractions at the dose employed do not influence satiety, CCK levels or energy intake at a subsequent meal.

Hunger and thirst: issues in measurement and prediction of eating and drinking

Associations between hunger and eating and between thirst and drinking are generally weak. This stems, in part, from limitations in the measurement of these sensations which generally rely on temporal, motivational, metabolic and/or self-reported descriptive indices. Each is critically reviewed. Also problematic is the fact that the deterministic depletion-repletion concept of ingestive behavior fails to account for influences of a multitude of contravening cognitive, social, sensory and logistical factors. Although hunger and thirst serve some parallel purposes, sharp distinctions are also present with health implications. Of particular note are the observations that thirst ratings are higher and more stable over the day compared to hunger and thirst may be more motivating to drink than hunger is to eat. Coupling these observations with evidence that beverages have limited satiety value, they pose particular challenges and opportunities. Beverages can facilitate the delivery of nutrients to those desiring or requiring them, but also to those where they are not desired or required. The benefits and risks are a function of their use rather than their inherent properties.

Effects of complete whey-protein breakfasts versus whey without GMP-breakfasts on energy intake and satiety

AIM

To compare the effects of whey versus whey without glycomacropeptide (GMP) in a high and a normal amount of protein in a breakfast custard on satiety and energy intake (EI), taking concentrations of amino acids (AA), glucose, insulin, glucagon-like peptide 1 (GLP-1) and ghrelin into account.

METHODS

Twenty-five healthy subjects (mean+/-S.E.M., BMI: 23.9+/-0.3 kg/m(2); age: 22+/-1 years) received a breakfast containing whey or whey without GMP as protein type with 10/55/35 or 25/55/20 En% protein/carbohydrate/fat in a randomized, single-blind design. Appetite profile (Visual Analogue Scale, VAS), glucose, insulin, GLP-1, ghrelin and AA concentrations were measured, and the adequate moment for ad libitum lunch was determined based on differences in ghrelin concentration. In a second set of experiments subjects received the same breakfasts; ad libitum lunch was offered at the pre-determined moment.

RESULTS

After a breakfast with 25 En% protein increases in insulin and GLP-1 and decreases in ghrelin concentrations were larger; increases in satiety ratings were lower than after 10 En% (p<0.05); there was a treatment x time interaction effect on glucose and insulin concentrations (p<0.001). After a breakfast with whey without GMP insulin concentrations were increased more than after whey (p<0.05). EI at lunch was lower after whey than after whey without GMP (2877+/-165 kJ versus 3208+/-178 kJ, p<0.05), coinciding with more increased concentrations of serine, threonine, alanine, alpha-aminobutyric acid and isoleucine (p<0.05).

CONCLUSION

GMP as a whey-fraction reduced energy intake coinciding with increased concentrations of certain amino acids, irrespective of the concentration of whey-protein. Although between different concentrations of whey-protein differences in hormone responses were observed, these were unrelated to satiety ratings or energy intake.

The influence of whey protein and glycomacropeptide on satiety in adult humans

Protein is often considered the most satiating macronutrient. The objective was to determine the short-term effect of mixtures of whey protein and glycomacropeptide (GMP) versus a carbohydrate control on satiety in healthy adult humans. The study was a randomised crossover Latin Square design. On 4 separate days, fifty healthy subjects (19 males and 31 females) received a subject-specific breakfast (08:00 h), a preload drink (12:00 h) and lunch (12:30 h). The preload drink was presented as a milkshake with either maltodextrin carbohydrate (control), whey protein isolate (WPI) with no GMP, WPI with naturally present 21% GMP or WPI with naturally present 21% GMP plus added GMP. Satiety was assessed using visual analogue scales (VAS) and by determining ad libitum food intake during a cafeteria style meal offered 30 min after the preload. The VAS indicated that the lower GMP treatment induced a greater feeling of fullness immediately after consumption of the preload compared with the other treatments. Energy and macronutrient intake at lunch did not differ significantly (p>0.05) between treatments although subjects chose to eat foods higher in carbohydrate and lower in protein after the protein preloads. Women consumed the least amount of protein after the protein preloads whereas no difference was found in men. There was some evidence that whey proteins and their components enhance satiety over a short-term period compared to carbohydrate but there was no consistent effect of either whey protein alone or glycomacropeptide.

Glycosylations of kappa-casein-derived caseinomacropeptide reduce its accessibility to endo- but not exointestinal brush border membrane peptidases

Caseinomacropeptide (CMP) is a peptide obtained from kappa-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV) were used to digest glycosylated and unglycosylated CMP. Our results demonstrated that whatever was the glycosylated state of CMP, they were digested by BBMV intestinal enzymes, from macropeptides to free amino acids. The digestion of unglycosylated and glycosylated CMP throughout the action of exopeptidases was similar, but the activity of endopeptideases on glycosylated CMP was limited, certainly due to the attached O-glycosylations. Consequently, much more peptides were identified from the unglycosylated than from the glycosylated CMP. In addition, the glycosylation core as well as the number of the attached glycosylated chain modified the kinetic of digestion; the most heavily glycosylated forms being the slowest digested.

The effect of meal replacements high in glycomacropeptide on weight loss and markers of cardiovascular disease risk

BACKGROUND

Glycomacropeptide (GMP) is a peptide that has been shown to stimulate release of cholecystokinin, which may promote satiety.

OBJECTIVE

The aim of this one-year study was to examine whether greater weight loss could be achieved and sustained with a GMP-enriched whey powder supplement compared with a skim milk powder supplement.

DESIGN

In a double-blind, randomized, parallel-design study using meal replacements, weight, body composition (determined by dual-energy X-ray absorptiometry), blood pressure, fasting lipids, glucose, and insulin were measured at baseline, 6, and 12 mo. Meal replacements contained 15 g protein from GMP-enriched whey protein isolate (GMP-WPI) or skim milk powder (SMP) and 900 kJ/sachet. Volunteers consumed 2 sachets/d instead of 2 meals for 6 mo and 1 sachet/d for a further 6 mo. Of the 127 participants (95 women, 32 men, 95.5 +/- 15.4 kg, body mass index 33.4 +/- 3.4 kg/m(2), 50.0 +/- 12.4 y), 82 completed the 6-mo study and 72 of those completed the 12-mo study.

RESULTS

At 6 mo, weight loss was 9.5 +/- 5.8 kg compared with 11.0 +/- 6.0, GMP-WPI and SMP, respectively, and 9.9 +/- 8.8 kg compared with 10.8 +/- 7.4 GMP-WPI and SMP, respectively, at 12 mo (P < 0.001 compared with baseline, at both timepoints) with no differences between treatments. Total and LDL cholesterol, triacylglycerols, glucose, insulin, and systolic and diastolic blood pressure decreased at 6 and 12 mo (all P < 0.01 compared with baseline with no difference between treatments). HDL cholesterol increased at 12 mo (P < 0.001 compared with baseline).

CONCLUSIONS

Meal replacements containing GMP had no additional effect on the overall sustained 12-mo weight loss of 10 kg. There were improvements in cardiovascular disease risk markers.

Protein, weight management, and satiety

Obesity, with its comorbidities such as metabolic syndrome and cardiovascular diseases, is a major public health concern. To address this problem, it is imperative to identify treatment interventions that target a variety of short- and long-term mechanisms. Although any dietary or lifestyle change must be personalized, controlled energy intake in association with a moderately elevated protein intake may represent an effective and practical weight-loss strategy. Potential beneficial outcomes associated with protein ingestion include the following: 1) increased satiety--protein generally increases satiety to a greater extent than carbohydrate or fat and may facilitate a reduction in energy consumption under ad libitum dietary conditions; 2) increased thermogenesis--higher-protein diets are associated with increased thermogenesis, which also influences satiety and augments energy expenditure (in the longer term, increased thermogenesis contributes to the relatively low-energy efficiency of protein); and 3) maintenance or accretion of fat-free mass--in some individuals, a moderately higher protein diet may provide a stimulatory effect on muscle protein anabolism, favoring the retention of lean muscle mass while improving metabolic profile. Nevertheless, any potential benefits associated with a moderately elevated protein intake must be evaluated in the light of customary dietary practices and individual variability.

Relationships between human thirst, hunger, drinking, and feeding

There is a widely held view that hunger prompts feeding to ensure energy needs are met, while thirst cues drinking to address hydration requirements. However, recent changes in the nature of the food supply and eating patterns have raised questions about the functionality of these relationships with respect to maintaining energy balance. The increasing consumption of energy-yielding beverages and foods with diluted energy density, through the use of ingredients such as high-intensity sweeteners and fat replacers, poses new challenges to presumed homeostatic energy regulatory mechanisms. This review draws on findings from a recent observational study and other published evidence to explore whether shifts of food composition and use patterns may be disrupting relationships between thirst, hunger, drinking, and eating, resulting in positive energy balance (e.g., drinking low satiety, energy-yielding beverages in response to hunger). The observational study entailed collecting hourly appetitive ratings and dietary recalls from 50 adults for seven consecutive days. These data reveal a clear bimodal daily hunger pattern, whereas thirst is stronger and more stable throughout the day. Further, approximately 75% of fluid intake occurs peri-prandially, with the majority derived from energy-yielding beverages. While there is published evidence that drinking is responsive to feeding, support for the view that drinking is the more tightly regulated behavior is stronger. Our data indicates that, due to a number of plausible factors, neither absolute values nor changes of hunger or thirst are strong predictors of energy intake. However, it is proposed that stable, high thirst facilitates drinking, and with the increased availability and use of energy-yielding beverages that have low satiety properties, can promote positive energy balance. There are marked individual differences in mean daily hunger and thirst ratings with unknown implications for energy balance.

Emerging health properties of whey proteins and their clinical implications

The nursery rhyme "Little Miss Muffet sat on a tuffet (small stool) eating her curds and whey. ..." is recognition of the fact that over the centuries "curds and whey", the two major components of cow's milk, have been widely accepted as part of a healthy diet. Milk provides complete nourishment for the neonate for six months from birth, containing factors that help develop various organ systems including the brain, immune system, and the intestine. Importantly it provides immune protection at a time when the neonates own immune system, though fully developed, is albeit immature. Many adult consumers include cow's milk as part of a healthy diet as it provides protein and essential nutrients, vitamins, and minerals, in particular calcium for strong bones. There is a growing appreciation that milk, and in particular whey, contains components that not only provide nutrition, but can also prevent and attenuate disease, or augment conventional therapies, when delivered in amounts that exceed normal dietary intakes. This paper reviews the emerging health properties of whey proteins and their clinical implications.

Whey proteins in the regulation of food intake and satiety

Whey protein has potential as a functional food component to contribute to the regulation of body weight by providing satiety signals that affect both short-term and long-term food intake regulation. Because whey is an inexpensive source of high nutritional quality protein, the utilization of whey as a physiologically functional food ingredient for weight management is of current interest. At present, the role of individual whey proteins and peptides in contributing to food intake regulation has not been fully defined. However, Whey protein reduces short-term food intake relative to placebo, carbohydrate and other proteins. Whey protein affects satiation and satiety by the actions of: (1) whey protein fractions per se; (2) bioactive peptides; (3) amino-acids released after digestion; (4) combined action of whey protein and/or peptides and/or amino acids with other milk constituents. Whey ingestion activates many components of the food intake regulatory system. Whey protein is insulinotropic, and whey-born peptides affect the renin-angiotensin system. Therefore whey protein has potential as physiologically functional food component for persons with obesity and its co-morbidities (hypertension, type II diabetes, hyper- and dislipidemia). It remains unclear, however, if the favourable effects of whey on food intake, subjective satiety and intake regulatory mechanisms in humans are obtained from usual serving sizes of dairy products. The effects described have been observed in short-term experiments and when whey is consumed in much higher amounts.

Whey protein isolate and glycomacropeptide decrease weight gain and alter body composition in male Wistar rats

The effect of feed protein type on body composition and growth has been examined. Evidence exists that whey protein concentrate is effective at limiting body fat expansion. The presence of caseinomacropeptide, a mixture of glycosylated and non-glycosylated carbohydrate residues, in particular glycomacropeptide (GMP) in whey protein concentrate may be important for this effect. The influence of whey protein isolate (WPI) and GMP on weight gain and body composition was examined by feeding Wistar rats ad libitum for 7 weeks with five semi-purified American Institute of Nutrition-based diets differing in protein type: (1) casein; (2) barbequed beef; (3) control WPI (no GMP); (4) WPI+GMP at 100 g/kg; (5) WPI+GMP at 200 g/kg. Body composition was assessed, and plasma samples were assayed for TAG, insulin and glucose. Body-weight gain was lower (- 21 %) on the control WPI diet relative to casein, with a non-significant influence associated with GMP inclusion (- 30 %), the effect being equivalent at both levels of GMP addition. Renal and carcass fat mass were reduced in the highest GMP diet when compared with WPI (P < 0.05). Plasma insulin was lowered by GMP at the highest addition compared with WPI alone (- 53 %; P < 0.01). Plasma TAG in the WPI+GMP (200 g/kg) group were lower (- 27 %; P < 0.05) than the casein and beef groups. In conclusion, GMP appears to have a significant additional influence when combined with WPI on fat accumulation. WPI alone appears to have the predominant influence accounting for 70 % of the overall effect on body-weight gain. Mechanisms for this effect have not been identified but food intake was not responsible.

Glycomacropeptide (GMP) is not critical to whey-induced satiety, but may have a unique role in energy intake regulation through cholecystokinin (CCK)

BACKGROUND

Whey protein is more satiating than other protein types, including casein. We hypothesized that enhanced satiety with whey protein is related to glycomacropeptide (GMP) content, a stimulator of cholecystokinin (CCK).

OBJECTIVES

To investigate the role of GMP in whey protein-induced satiety, as measured by subjective satiety, CCK release and food intake at a test meal in healthy weight men and women.

DESIGN

In a within-subjects design, twenty subjects (n=10 men, 10 women) consumed 1 of 4 preload shakes (300 mL, 1 MJ), 1 week apart. Preloads differed by protein source and content: Whey; whey protein isolate, Whey (-)GMP; whey protein without GMP, Control; low protein, GMP; GMP isolate. Protein energy of preloads was 44, 44, 2 and 3%, respectively. Subjective satiety and CCK were measured at 0, 15, 30, 45, 60, 75 and 105 min post-preload consumption. A lunch test meal was provided at 75 min. Food records were completed weekly.

RESULTS

Pre-meal satiety was greater after whey protein preloads compared to Control and GMP preloads in women, but no difference was evident in men (sex by preload, p<0.03). CCK concentrations followed a pattern that predicted the subjective satiety in women, but not in men. Test meal intake was not different by preload; however, compensation relative to usual daily intake was achieved after whey-containing- and GMP-containing preloads in women and after GMP and Control preloads in men.

CONCLUSIONS

GMP alone is not critical in pre-meal whey-induced satiety; however, it may have a unique role in compensatory intake regulation managing daily energy intake.

Effect of increased dairy consumption on appetitive ratings and food intake

OBJECTIVE

The influence of dairy product consumption on food intake and appetitive sensations was explored in a cross-over design study with individuals who were habitually low (<1 serving/d) or high (>3 servings/d) dairy consumers.

RESEARCH METHODS AND PROCEDURES

Fifty-eight participants were required to eat one portion of dairy each day (low dairy) or three portions of dairy each day (high dairy) for 7 days. After a 7-day washout period, the opposite treatment condition was completed. Food intake and appetitive ratings were measured on each day of the treatment periods.

RESULTS

During the high-dairy period, participants consumed 209 kcal/d more than during the low dairy period (p < 0.05). There were no significant differences in subjective appetite ratings. Habitual dairy use did not influence either the appetitive or dietary findings.

DISCUSSION

These data indicate that increasing dairy consumption may lead to increased energy intake, which could potentially cause weight gain.

Dietary proteins in the regulation of food intake and body weight in humans

This review presents 4 lines of evidence supporting a role for proteins in the regulation of food intake and maintenance of healthy body weights. It is concluded that the protein content of food, and perhaps its source, is a strong determinant of short-term satiety and of how much food is eaten. Although the role of protein in the regulation of long-term food intake and body weight is less clear, the evidence reviewed suggests that further research to define its role is merited. Such research has the potential to lead to new functional foods, food formulations, and dietary recommendations for achieving healthy body weights.

Functional properties of whey, whey components, and essential amino acids: mechanisms underlying health benefits for active people (review)

Whey proteins and amino acid supplements have a strong position in the sports nutrition market based on the purported quality of proteins and amino acids they provide. Recent studies employing stable isotope methodology demonstrate the ability of whey proteins or amino acid mixtures of similar composition to promote whole body and muscle protein synthesis. Other developing avenues of research explore health benefits of whey that extend beyond protein and basic nutrition. Many bioactive components derived from whey are under study for their ability to offer specific health benefits. These functions are being investigated predominantly in tissue culture systems and animal models. The capacity of these compounds to modulate adiposity, and to enhance immune function and anti-oxidant activity presents new applications potentially suited to the needs of those individuals with active lifestyles. This paper will review the recent literature that describes functional properties of essential amino acids, whey proteins, whey-derived minerals and other compounds and the mechanisms by which they may confer benefits to active people in the context that exercise is a form of metabolic stress. The response to this stress can be positive, as with the accretion of more muscle and improved functionality or greater strength. However, overall benefits may be compromised if immune function or general health is challenged in response to the stress. From a mechanistic standpoint, whey proteins, their composite amino acids, and/or associated compounds may be able to provide substrate and bioactive components to extend the overall benefits of physical activity.