A dipeptide and an amino acid present in whey protein hydrolysate increase translocation of GLUT-4 to the plasma membrane in Wistar rats

Lactobacillus brevis M2-Fermented Whey Protein Hydrolysate Increases Slow-Wave Sleep via GABAA Receptors in Rodent Models

In this study, we investigated the effects of whey protein hydrolysate (WPH) fermented with Lactobacillus brevis on sleep behavior and GABAergic mechanisms in rodent models. Fermentation converted the glutamate in WPH to high (3.15 ± 0.21 mg/mL) levels of γ-aminobutyric acid (GABA). Fermented WPH (WP-SF) enhanced sleep duration in mice by increasing GABA content in the brain. The increase in sleep duration induced by WP-SF resulted from an increase in delta wave activity during non-rapid eye movement sleep, and its sleep-promoting effect in a caffeine-induced insomnia model was characterized by an increase in delta waves. WP-SF increased GABAergic receptors at both mRNA and protein levels. Cotreatment with GABAA receptor antagonists abolished the sleep-promoting effects of WP-SF, indicating that WP-SF shares binding sites with antagonists on GABAA receptors. Collectively, WP-SF effectively increased sleep duration by enhancing delta wave activity through GABAergic activation; thus, it is suggested as a functional food-grade ingredient for promoting sleep.

Anti-diabetic mechanism and potential bioactive peptides of casein hydrolysates in STZ/HFD-induced diabetic rats

BACKGROUND

Casein hydrolysates have attracted much interest as anti-diabetic food, but their hypoglycemic mechanism and biopeptides are not well understood. This study aimed to explore the anti-diabetic mechanism and potential biopeptides of casein hydrolysates in streptozotocin/high-fat-diet-induced diabetic rats and HepG2 cells.

RESULTS

Oral administration of casein hydrolysate prepared with papain-Flavourzyme combination (P-FCH) decreased fasting blood glucose, improved oral glucose tolerance, and reduced HbA1c values in diabetic rats. P-FCH was ineffective in alleviating insulin resistance (homeostasis model assessment and insulin sensitivity index) and enhancing hepatic insulin signaling transduction (phosphorylated Akt, hexokinase activity, and pyruvate kinase activity) in diabetic rats. However, P-FCH significantly upregulated adenosine monophosphate-activated protein kinase phosphorylation and glucose transporter-2 expression, inhibited phosphoenolpyruvate carboxylase kinase activity, and elevated glycogen content in liver tissue of diabetic rats. Furthermore, P-FCH increased glucose consumption independently in normal and insulin-resistant HepG2 cells without the presence of insulin. The peptide composition of P-FCH was characterized. The potential biopeptides in P-FCH showed the sequence characteristic of a Val at the N-terminal or a Pro at the P2 position, and the hypoglycemic activity of Val-Pro-Leu-Gly (the most potential biopeptide in P-FCH) was verified by oral glucose tolerance test in mice.

CONCLUSION

These results suggested that activation of the non-insulin-mediated AMPK pathway might be the determinant mechanism of P-FCH on the hypoglycemic effect. The novel peptide Val-Pro-Leu-Gly in P-FCH was effective in reducing blood glucose levels when orally administered to mice. © 2023 Society of Chemical Industry.

The Degree of Hydrolysis and Peptide Profile Affect the Anti-Fatigue Activities of Whey Protein Hydrolysates in Promoting Energy Metabolism in Exercise Mice

The purpose of this study was to investigate the effects of characteristics of whey protein hydrolysates (WPHs) on energy metabolism in exercise mice. Results showed that high-degree of hydrolysis (DH) hydrolysates (22%, H-Alc and H-AXH) showed better anti-fatigue effects than low-DH hydrolysates (10%, L-Alc and L-AXH) in enhancing energy substances and reducing metabolic byproducts. It might be related to the higher content of components less than 3 kDa in H-Alc and H-AXH (92.35 and 81.05%, respectively) and higher intensities of small peptides containing two to nine residues. Moreover, Western blot results revealed that WPHs maintained the energy balance in exercise mice by regulating the AMP-activated protein kinase (AMPK) and mTOR signaling pathways. Notably, H-Alc had higher intensities of peptides containing two to five residues than H-AXH and these peptides were rich in essential amino acids, which might explain why H-Alc exhibited better effects in decreasing protein metabolites. Meanwhile, H-AXH contained more free amino acids, especially Leu, which might contribute to its ability to promote glucose consumption in muscle. Furthermore, 40 peptides with two to nine residues and high intensities (>5 × 10⁵) were screened from H-Alc and H-AXH and predicted by bioinformatics tools. Among them, LLL, LLF, GTW, AGTW, and ALPM showed high bioavailability, cell permeability, and potential bioactivity.

Anti-Fatigue Peptides from the Enzymatic Hydrolysates of Cervus elaphus Blood

Red deer (Cervus elaphus) blood is widely used as a health product. Mixed culture fermentation improves the flavor and bioavailability of deer blood (DB), and both DB and its enzymatic hydrolysates exhibit anti-fatigue activities in vivo. To elucidate the bioactive ingredients, enzymatic hydrolysates were fractioned into different peptide groups using reversed phase resin chromatography, and then evaluated using an exhaustive swimming mice model to assess swimming time and biochemical parameters. The structures of the bioactive peptides were elucidated by high performance liquid chromatography with tandem mass detection. Thirty-one compounds were identified as glutamine or branched-chain amino acids containing short peptides, of which Val-Ala-Asn, Val-Val-Ser-Ala, Leu(Ile)-Leu(Ile)-Val-Thr, Pro-His-Pro-Thr-Thr, Glu-Val-Ala-Phe and Val-Leu(Ile)-Asp-Ala-Phe are new peptides. The fractions containing glutamine or valine short peptides, Ala-Gln, Val-Gln, Val-Val-Ser-Ala, Val-Leu(Ile)-Ser improved exercise endurance by increasing hepatic glycogen (HG) storage. The peptides group containing Leu(Ile)-Leu(Ile), Asp-Gln, Phe- Leu(Ile), Val-Val-Tyr-Pro contributed to decreased muscle lactic acid (MLA)accumulation and to an increase in HG. The anti-fatigue activities of DB hydrolysates were attributed to the synergistic effects of different types of peptides.

The Antioxidant Effects of Whey Protein Peptide on Learning and Memory Improvement in Aging Mice Models

This study investigated the antioxidant effects of whey protein peptide on learning and memory in aging C57BL/6N mice. A total of 72 SPF male C57BL/6N mice were used. Twelve mice were randomly selected as the control group, and the other mice were intraperitoneally injected with D-galactose (100 mg/kg body weight for 6 weeks), during which, the mice in the control group were intraperitoneally injected with the same amount of normal saline. After 6 weeks, the blood was taken from the epicanthus and the serum MDA level was measured, according to which, the mice were randomly divided into the model control group, the whey protein group (1.5 g/kg body weight), and three Whey protein peptide (WHP) intervention groups (0.3 g/kg body weight, 1.5 g/kg body weight, 3.0 g/kg body weight). The water solution of the test sample was administered by oral gavage every day. The intervention period was 30 days, during which, the model control group, the whey protein group, and the whey protein peptide group continued receiving intraperitoneal injections of D-galactose, while the control group continued receiving intraperitoneal injections of normal saline. After the intervention, behavioral experiments were conducted in the following order: open field test, water maze test, and new object recognition test. After the behavioral experiment, the morphology of hippocampal formation was observed by HE staining and TUNEL labeling. Oxidative stress-related indexes in the serum, liver, and brain were detected. Expression levels of the cholinergic system-related enzymes and proinflammatory cytokines in brain tissue were detected. Western blot was used to detect the expression of synaptic plasticity-related proteins in the mouse brain. The results showed that WHP could significantly improve the accumulation of MDA and PC, increase the activities of SOD and GSH-Px, resist oxidative stress injury, and enhance the potential of endogenous antioxidant defense mechanisms. WHP can significantly improve the decline of aging-related spatial exploration, body movement, and spatial and non-spatial learning/memory ability. Its specific mechanism may be related to reducing the degeneration of hippocampal nerve cells, reducing the apoptosis of nerve cells, improving the activity of AChE, reducing the expression of inflammatory factors (TNF-α and IL-1β) in brain tissue, reducing oxidative stress injury, and improving the expression of p-CaMKⅡ and BDNF synaptic plasticity protein. These results indicate that WHP can improve aging-related oxidative stress, as well as learning and memory impairment.

Carbohydrate-Restricted Exercise With Protein Increases Self-Selected Training Intensity in Female Cyclists but Not Male Runners and Cyclists

ABSTRACT

Oosthuyse, T, Florence, GE, Correia, A, Smyth, C, and Bosch, AN. Carbohydrate-restricted exercise with protein increases self-selected training intensity in female cyclists but not male runners and cyclists. J Strength Cond Res 35(6): 1547-1558, 2021-Carbohydrate-restricted training challenges preservation of euglycemia and exercise intensity that precludes ergogenic gains, necessitating countering strategies. We investigated the efficacy of ingesting casein protein hydrolysate in overnight-fasted male runners, male cyclists, and female cyclists. Twenty-four overnight-fasted athletes ingested 15.8 g·h-1 casein hydrolysate or placebo-water during exercise (60-80 minutes) comprising an incremental test to exhaustion, steady-state exercise (70% Vmax or 60% peak power output, 87 ± 4% HRmax), and 20-minute time trial (TT) in a double-blind randomized crossover design, with p < 0.05 accepted as significant. Ingesting protein vs. placebo increased metabolic demand {oxygen consumption, +4.7% (95% confidence interval [CI] ± 4%), p = 0.0297; +3.2% (95% CI ± 3.4%), p = 0.061}, heart rate (p = 0.0083; p = 0.007) and rating of perceived exertion (RPE) (p = 0.0266; p = 0.0163) in male cyclists and runners, respectively, but not female cyclists. Protein vs. placebo increased carbohydrate oxidation (+0.26 [95% CI ± 0.13] g·min-1, p = 0.0007) in female cyclists alone. Cyclists reported +2 ± 1 higher RPE than runners (p = 0.0062). Glycemia was maintained only in runners and increased with protein vs. placebo after 20 minutes of steady-state exercise (+0.63 [95% CI ± 0.56] mmol·L-1, p = 0.0285). TT performance with protein vs. placebo ingestion was modestly compromised in runners (-2.8% [95% CI ± 2.2%], p = 0.0018), unchanged in male cyclists (+1.9% [95% CI ± 5.6%], p = 0.5794), and modestly improved in female cyclists (+2.5% [95% CI ± 1.8%], p = 0.0164). Casein hydrolysate ingestion during moderate to hard carbohydrate-restricted exercise increases glycemia in runners, but not cyclists. Casein hydrolysate increases metabolic demand in male athletes and carbohydrate oxidation in female cyclists and is suitable for improving carbohydrate-restricted training intensity in female but not male endurance athletes.

Whey Proteins and Its Derivatives: Bioactivity, Functionality, and Current Applications

With the increased consumer demand for nutritional foods, it is important to develop value-added products, which will not only catch the attention of a wider consumer group but also provide greater benefits in terms of enhanced nutrition and functionality. Milk whey proteins are one of the most valued constituents due to their nutritional and techno-functional attributes. Whey proteins are rich in bioactive peptides, possessing bioactive properties such as being antioxidant and antihypertensive as well as having antimicrobial activities, which, when ingested, confers several health benefits. These peptides have the potential to be used as an active food ingredient in the production of functional foods. In addition to their bioactivities, whey proteins are known to possess enhanced functional attributes that allow them to be utilized in broad applications, such as an encapsulating agent or carrier materials to entrap bioactive compounds, emulsification, and in edible and active packaging. Hence, over the recent years, several whey protein-based ingredients have been developed and utilized in making formulations for a wide range of foods to harness their beneficial properties. This review highlights the bioactive properties, functional characteristics, associated processing limitations, and applications of different whey protein fractions and derivatives in the field of food formulations, encapsulation, and packaging.

Characteristics of Potential Protein Nutraceuticals of Plant Origin with Antioxidant Activity

This study used selected plant proteins and the tools available in the BIOPEP-UWM database to profile proteins and release antioxidant nutraceuticals from their primary structures. The frequency of the occurrence of fragments with antioxidant activity in a protein sequence (the A parameter) was determined. A simulated monocatalytic proteolysis was carried out using ficin or stem bromelain or pepsin (pH > 2), and the theoretical degree of hydrolysis (DHt) and the frequency (including relative frequency) of the release of fragments with a particular antioxidant activity by a selected enzyme (the AE and W parameters, respectively). Both barley hordoindolines and the protein group of "actins and other rice proteins" were characterised by the best antioxidant potential. On the other hand, among the main analysed cereal protein groups or species, the best nutraceutical sources included kafirins, rice glutelins and α-gliadins. Potentially the most nutraceutical molecules were released by pepsin (HL, VY, PHQ and PWQ biopeptides) from gliadins, but the most analysed proteins were hydrolysed (66% on average) and the DHt for ficin and bromelain amounted to 27% and 31%, respectively. However, based on the calculated AE mean values, it can be concluded that nutraceuticals were more frequently released from rice protein structures (IY and VY biopeptides), and less frequently released from barley and other cereal protein species, which may be of significance in the context of designing nutraceutical food.

Trypsin-Treated β-Lactoglobulin Improves Glucose Tolerance in C57BL/6 Mice by Enhancing AMPK Activation and Glucose Uptake in Hepatocytes

It was reported that trypsin-treated β-lactoglobulin (β-LG) had a glucose-lowering effect in the oral glucose tolerance test (OGTT) in mice and a dipeptidyl peptidase-4 (DPP-4) inhibition activity in vitro. However, whether trypsin-treated β-LG improves glucose tolerance by inhibiting DPP-4 in vivo has not yet been examined, and the mechanism of the glucose-lowering effect of trypsin-treated β-LG is thus unclear. Here we investigated the detailed mechanism underlying the glucose tolerance effect of trypsin-treated β-LG. The oral administration of trypsin-treated β-LG significantly decreased the blood glucose concentrations in both the OGTT and an intraperitoneal glucose tolerance test (IPGTT). However, trypsin-treated β-LG did not increase the insulin secretion after glucose loading. Trypsin-treated β-LG potently increased the level of phosphorylated AMP-activated protein kinase (AMPK) in human hepatocellular carcinoma (HepG2) cells and in mice hepatocytes. Moreover, trypsin-treated β-LG significantly enhanced glucose uptake into the HepG2 cells. These results indicate that trypsin-treated β-LG decreases blood glucose levels after glucose loading by upregulating AMPK activation and glucose uptake in the liver, which could contribute to the reduction of postprandial hyperglycemia.

Effects of ultrasound treatment on physico-chemical, functional properties and antioxidant activity of whey protein isolate in the presence of calcium lactate

BACKGROUND

The aim of this study was to investigate the effects of ultrasound applied at various powers (0, 200, 400, 600 or 800 W) and for different times (20 or 40 min) on the physico-chemical, functional properties and antioxidant activities of whey protein isolate (WPI) dispersions in the presence of 1.20 mmol L^-1 calcium lactate.

RESULTS

Surface hydrophobicity and free sulfhydryl group of the WPI dispersions containing 1.2 mmol L^-1 calcium lactate were significantly enhanced after sonication. Furthermore, particle size of WPI dispersions containing 1.20 mmol L^-1 calcium lactate was minimised after sonication. Scanning electron microscopy of sonicated WPI suspensions containing 1.20 mmol L^-1 calcium lactate showed that WPI microstructure had significantly changed. After WPI dispersions were treated by sonication assisted with calcium lactate, its gel strength enhanced and solubility decreased. Gel strength of sonicated WPI dispersions (600 W, 40 min) was the maximum among all the WPI treatments. Emulsification activity of sonicated WPI dispersions reduced while its emulsion stability increased. The DPPH radical scavenging activity and ferrous reducing power of sonicated WPI dispersions mostly increased.

CONCLUSION

Ultrasound treatments induced structural changes in WPI molecules, leading to different microstructure and improved gel strength of WPI in the presence of calcium lactate. © 2017 Society of Chemical Industry.

BCAA Metabolism and Insulin Sensitivity - Dysregulated by Metabolic Status?

Branched-chain amino acids (BCAAs) appear to influence several synthetic and catabolic cellular signaling cascades leading to altered phenotypes in mammals. BCAAs are most notably known to increase protein synthesis through modulating protein translation, explaining their appeal to resistance and endurance athletes for muscle hypertrophy, expedited recovery, and preservation of lean body mass. In addition to anabolic effects, BCAAs may increase mitochondrial content in skeletal muscle and adipocytes, possibly enhancing oxidative capacity. However, elevated circulating BCAA levels have been correlated with severity of insulin resistance. It is hypothesized that elevated circulating BCAAs observed in insulin resistance may result from dysregulated BCAA degradation. This review summarizes original reports that investigated the ability of BCAAs to alter glucose uptake in consequential cell types and experimental models. The review also discusses the interplay of BCAAs with other metabolic factors, and the role of excess lipid (and possibly energy excess) in the dysregulation of BCAA catabolism. Lastly, this article provides a working hypothesis of the mechanism(s) by which lipids may contribute to altered BCAA catabolism, which often accompanies metabolic disease.

Bioactivity of food peptides: biological response of rats to bovine milk whey peptides following acute exercise

Background: Several physiologically beneficial effects of consuming a whey protein hydrolysate (WPH) have been attributed to the greater availability of bioactive peptides.

Aims: The aim was to investigate the effect of four branched-chain amino acid- (BCAA-)containing dipeptides, present in WPH, on immune modulation, stimulation of HSP expression, muscle protein synthesis, glycogen content, satiety signals and the impact of these peptides on the plasma free amino acid profiles.

Methods: The animals were divided in groups: control (rest, without gavage), vehicle (water), L-isoleucyl-L-leucine (lle-Leu), L-leucyl-L-isoleucine (Leu-lle), L-valyl-Lleucine (Val-Leu), L-leucyl-L-valine (Leu-Val) and WPH. All animals were submitted to acute exercise, except for control.

Results: lle-Leu stimulated immune response, hepatic and muscle glycogen and HSP60 expression, whereas Leu-Val enhanced HSP90 expression. All dipeptides reduced glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, no changes were observed on leptin. All peptides inhibited NF-kB expression. The plasma amino acid time-course showed peptide-specific and isomer-specific metabolic features, including increases of the BCAAs.

Conclusion: The data indicate that lle-Leu was effective to attenuate immune-suppression exercise-induced, promoted glycogen content and stimulated anti-stress effect (HSP). Furthermore, Leu-Val increased HSP90, p-4EBP1, p-mTOR and p-AMPK expression. The data suggest the involvement of these peptides in various beneficial functions of WPH consumption.

Modulatory effects of arginine, glutamine and branched-chain amino acids on heat shock proteins, immunity and antioxidant response in exercised rats

Heat shock proteins (HSPs) are endogenous proteins whose function is to maintain the cell's tolerance to insult, including intense exercise.

Intragastric administration of leucine or isoleucine lowers the blood glucose response to a mixed-nutrient drink by different mechanisms in healthy, lean volunteers

BACKGROUND

The branched-chain amino acids leucine and isoleucine lower blood glucose after oral glucose ingestion, and the intraduodenal infusion of leucine decreases energy intake in healthy, lean men.

OBJECTIVE

We investigated the effects of the intragastric administration of leucine and isoleucine on the gastric emptying of, and blood glucose responses to, a physiologic mixed-macronutrient drink and subsequent energy intake.

DESIGN

In 2 separate studies, 12 healthy, lean subjects received on 3 separate occasions an intragastric infusion of 5 g leucine (leucine-5g) or an intragastric infusion of 10 g leucine (leucine-10g), an intragastric infusion of 5 g isoleucine (isoleucine-5g) or an intragastric infusion of 10 g isoleucine (isoleucine-10g), or a control. Fifteen minutes later, subjects consumed a mixed-nutrient drink (400 kcal, 56 g carbohydrates, 15 g protein, and 12 g fat), and gastric emptying (¹³C-acetate breath test) and blood glucose, plasma insulin, C-peptide, glucagon, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (leucine study only) were measured for 60 min. Immediately afterward, energy intake from a cold, buffet-style meal was assessed.

RESULTS

Compared with the control, leucine-10g decreased the blood glucose area under the curve (AUC) (P < 0.05) and tended to reduce peak blood glucose (P = 0.07), whereas effects of leucine-5g were NS. Leucine-10g, but not leucine-5g, increased plasma insulin and C-peptide AUCs (P < 0.01 for both), but neither dose affected glucagon, GLP-1, GIP, cholecystokinin, gastric emptying, or energy intake. Compared with the control, isoleucine-10g reduced the blood glucose AUC and peak blood glucose (P < 0.01), whereas effects of isoleucine-5g were NS. Neither load affected insulin, C-peptide, glucagon, GLP-1, or GIP. Isoleucine-10g, but not isoleucine-5g, slowed gastric emptying (P < 0.05), but gastric emptying was not correlated with the blood glucose AUC. Isoleucine did not affect energy intake.

CONCLUSIONS

In healthy subjects, both leucine and isoleucine reduced blood glucose in response to a mixed-nutrient drink but did not affect subsequent energy intake. The mechanisms underlying glucose lowering appear to differ; leucine stimulated insulin, whereas isoleucine acted insulin independently. These trials were registered at www.anzctr.org.au as 12613000899741 and 12614000837628.

The Effect of a High-Protein Diet and Exercise on Cardiac AQP7 and GLUT4 Gene Expression

High-protein (HP) diets are commonly consumed by athletes despite their potential health hazard, which is postulated to enforce a negative effect on bone and renal health. However, its effects on heart have not been known yet. Aquaporin-7 (AQP7) is an aquaglyceroporin that facilitates glycerol and water transport. Glycerol is an important cardiac energy production substrate, especially during exercise, in conjunction with fatty acids and glucose. Glucose transporter 4 (GLUT4) is an insulin-sensitive glucose transporter in heart. We aimed to investigate the effect of HPD on AQP7 and GLUT4 levels in the rat heart subjected to exercise. Male Sprague-Dawley rats were divided into control (n = 12), exercise (E) training (n = 10), HPD (n = 12), and HPD-E training (n = 9) groups. The HPD groups were fed a 45 % protein-containing diet 5 weeks. The HPD-E and E groups were performed the treadmill exercise during the 5-week study period. Real-time polymerase chain reaction and immunohistochemistry techniques were used to determine the gene expression and localization of AQP7 and GLUT4 in heart tissue. Results of relative gene expression were calculated by the 'Pfaffl' mathematical method using the REST program. Differences in AQP7 and GLUT4 gene expression were expressed as fold change compared to the control group. Heart weight/tibia ratio and ventricular wall thickness were evaluated as markers of cardiac hypertrophy. Further, serum glucose, glycerol, and insulin levels were also measured. AQP7 gene expression was found to be increased in the E (3.47-fold, p < 0.001), HPD (5.59-fold, p < 0.001), and HPD-E (3.87-fold, p < 0.001) groups compared to the control group. AQP7 protein expression was also increased in the HPD and HPD-E groups (p < 0.001). Additionally, cardiac mRNA expression levels of GLUT4 showed a significant increase in the E (2.16-fold, p < 0.003), HPD (7.14-fold, p < 0.001), and HPD-E (3.43-fold, p < 0.001) groups compared to the control group. GLUT4 protein expression was significantly increased in the E, HPD, and HPD-E groups compared to the control group (p = 0.024, p < 0.001, and p < 0.001, respectively). Furthermore, Serum glucose levels were significantly different between groups (p < 0.005). This difference was observed between the HPD groups and normal-protein diet groups (C and E). Serum insulin levels were higher for HPD groups compared with the normal-protein diet groups (p < 0.001), whereas no differences were observed between the exercise and sedentary groups (p = 0.111). Serum glycerol levels were significantly increased in the HPD groups compared with control and E groups (p < 0.05 and p < 0.05, respectively). Consumption of HPD supplementation caused the increased effects on AQP7 and GLUT4 expression in rat heart.

Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate only versus carbohydrate plus whey or casein hydrolysate

Cardiac function is often suppressed following prolonged strenuous exercise and this may occur partly because of an energy deficit. This study compared left ventricular (LV) function by 2-dimensional echocardiography and tissue Doppler imaging (TDI) before and after ∼2.5 h of cycling (2-h steady-state 60% peak aerobic power output plus 16 km time trial) in 8 male cyclists when they ingested either placebo, carbohydrate-only (CHO-only), carbohydrate-casein hydrolysate (CHO-casein), or carbohydrate-whey hydrolysate (CHO-whey). No treatment-by-time interactions occurred, but pre-to-postexercise time effects occurred selectively. Although diastolic function measured by pulsed-wave Doppler early-to-late (E/A) transmitral blood flow velocity was suppressed in all trials from pre- to postexercise (mean change post-pre exercise: -0.53 (95% CI -0.15 to -0.91)), TDI early-to-late (e'/a') tissue velocity was significantly suppressed pre- to postexercise only with placebo, CHO-only, and CHO-whey (septal and lateral wall e'/a' average change: -0.62 (95% CI -1.12 to -0.12); -0.69 (95% CI -1.19 to -0.20); and -0.79 (95% CI -1.28 to -0.29), respectively) but not with CHO-casein (-0.40 (95% CI -0.90 to 0.09)). LV contractility was, or tended to be, significantly reduced pre- to postexercise with placebo, CHO-only, and CHO-whey (systolic blood pressure/end systolic volume change, mm Hg·mL(-1): -0.8 (95% CI -1.2 to -0.4), p = 0.0003; -0.5 (95% CI -0.9 to -0.02), p = 0.035; and -0.4 (95% CI -0.8 to 0.04), p = 0.086, respectively), but not with CHO-casein (-0.3 (95% CI -0.8 to 0.1), p = 0.22). However, ejection fraction (EF) and ventricular-arterial coupling were significantly reduced pre- to postexercise only with placebo (placebo change: EF, -4.6 (95% CI -8.4 to -0.7)%; stroke volume/end systolic volume, -0.3 (95% CI -0.6 to -0.04)). Despite no treatment-by-time interactions, pre-to-postexercise time effects observed with specific beverages may be meaningful for athletes. Tentatively, the order of beverages with least-to-most variables displaying a time effect indicating suppression of LV function following exercise was CHO-casein < CHO-only and CHO-whey < placebo, and calls for further verification.

Dietary Whey and Casein Differentially Affect Energy Balance, Gut Hormones, Glucose Metabolism, and Taste Preference in Diet-Induced Obese Rats

BACKGROUND

Dietary whey and casein proteins decrease food intake and body weight and improve glycemic control; however, little is known about the underlying mechanisms.

OBJECTIVE

We determined the effects of dietary whey, casein, and a combination of the 2 on energy balance, hormones, glucose metabolism, and taste preference in rats.

METHODS

In Expt. 1, Obesity Prone CD (OP-CD) rats were fed a high-fat control diet (33% fat energy) for 8 wk, and then randomly assigned to 4 isocaloric dietary treatments (n = 12/group): the control treatment (CO; 14% protein energy from egg white), the whey treatment (WH; 26% whey + 14% egg white), the casein treatment (CA; 26% casein + 14% egg white), or the whey plus casein treatment (WHCA; 13% whey + 13% casein + 14% egg white) for 28 d. Measurements included food intake, energy expenditure, body composition, metabolic hormones, glucose tolerance and key tissue markers of glucose and energy metabolism. In Expt. 2, naïve OP-CD rats were randomly assigned to 3 groups (n = 8/group). During an 8 d conditioning period, each group received on alternate days either the CO or WH, CO or CA, or CO or WHCA. Subsequently, preferences for the test diets were assessed on 2 consecutive days with food intake measurements at regular intervals.

RESULTS

In Expt. 1, food intake was decreased by 17-37% for the first 14 d in the WH and CA rats, and by 18-34% only for the first 4 d in the WHCA compared with the CO rats. Fat mass decreased by 21-28% for the WH rats and 17-33% for the CA rats from day 14 onward, but by 30% only on day 28 in WHCA rats, relative to CO rats. Thus, food intake, body weight, and fat mass decreased more rapidly in WH and CA rats than in WHCA rats. Energy expenditure in WH rats decreased for the first 4 d compared with CA and WHCA rats, and for the first 7 d compared with the CO rats. Circulating leptin, glucose-dependent insulinotropic polypeptide, interleukin 6, and glucose concentrations were lower in WH, CA, and WHCA rats than in CO rats. Plasma glucagon-like peptide 1 concentrations were greater in WH than in CA or WHCA rats. The improvements in glucose tolerance were greater in WH than in WHCA rats. The plasma membrane glucose transporter 4 (GLUT4)-to-total GLUT4 ratio in skeletal muscle was greater in CA and WHCA rats than in CO rats; other markers of glucose and energy metabolism in the adipose and cardiac tissues did not differ. In Expt. 2, during 4 conditioning trials, daily food intake was decreased in WH, CA, and WHCA rats by 26-37%, 30-43%, and 23-33%, respectively, compared with CO rats. Preferences for WH and CA rats were 45% and 31% lower, respectively, than those for CO rats, but that for WHCA rats did not differ.

CONCLUSION

Together, these data demonstrate that in obese rats, whey, casein, and their combination improve energy balance through differential effects on food intake, taste preference, energy expenditure, glucose tolerance, and gut hormone secretion.

Emerging trends in nutraceutical applications of whey protein and its derivatives

The looming food insecurity demands the utilization of nutrient-rich residues from food industries as value-added products. Whey, a dairy industry waste has been characterized to be excellent nourishment with an array of bioactive components. Whey protein comprises 20 % of total milk protein and it is rich in branched and essential amino acids, functional peptides, antioxidants and immunoglobulins. It confers benefits against a wide range of metabolic diseases such as cardiovascular complications, hypertension, obesity, diabetes, cancer and phenylketonuria. The protein has been validated to boost recovery from resistance exercise-injuries, stimulate gut physiology and protect skin against detrimental radiations. Apart from health invigoration, whey protein has proved its suitability as fat replacer and emulsifier. Further, its edible and antimicrobial packaging potential renders its highly desirable in food as well as pharmaceutical sectors. Considering the enormous nutraceutical worth of whey protein, this review emphasizes on its established and emerging biological roles. Present and future scopes in food processing and dietary supplement formulation are discussed. Associated hurdles are identified and how technical advancement might augment its applications are explored. This review is expected to provide valuable insight on whey protein-fortified functional foods, associated technical hurdles and scopes of improvement.

Whey protein hydrolysate enhances HSP90 but does not alter HSP60 and HSP25 in skeletal muscle of rats

Whey protein hydrolysate (WPH) intake has shown to increase HSP70 expression. The aim of the present study was to investigate whether WPH intake would also influences HSP90, HSP60 and HSP25 expression, as well as associated parameters. Forty-eight male Wistar rats were divided into sedentary (unstressed) and exercised (stressed) groups, and were fed with three different sources of protein: whey protein (WP), whey protein hydrolysate (WPH) and casein (CAS) as a control, based on the AIN93G diet for 3 weeks. WPH intake increased HSP90 expression in both sedentary and exercised animals compared to WP or CAS, however no alteration was found from exercise or diet to HSP60 or HSP25. Co-chaperone Aha1 and p-HSF1 were also increased in the exercised animals fed with WPH in comparison with WP or CAS, consistent with enhanced HSP90 expression. VEGF and p-AKT were increased in the WPH exercised group. No alteration was found in BCKDH, PI3-Kinase (p85), GFAT, OGT or PGC for diet or exercise. The antioxidant system GPx, catalase and SOD showed different responses to diet and exercise. The data indicate that WPH intake enhanced factors related to cell survival, such as HSP90 and VEGF, but does not alter HSP60 or HSP25 in rat skeletal muscle.