Whey protein precludes lipid and protein oxidation and improves body weight gain in resistance-exercised rats

Association between the use of muscle-building supplements and DNA damage in resistance training practitioners

OBJECTIVES

Little is known about the relationship between the supplements used for sport and safety, especially regarding the induction of genotoxicity. Therefore, more knowledge about a DNA damage possibly caused using sport supplements is necessary. The aim of this study was to investigate the potential association between the use of muscle-building supplements and DNA damage in resistance training practitioners.

METHODS

Muscle-building supplements were classified into three categories based on evidence of efficacy and safety: Strong Evidence to Support Efficacy and Apparently Safe (SESEAS); Limited or Mixed Evidence to Support Efficacy (LMESE), and Little to No Evidence to Support Efficacy and/or Safety (LNESES). DNA damage was evaluated by the comet assay (DNA damage index and frequency) and buccal micronucleus by the cytome assay (micronuclei and nuclear buds). In the sequence, the adjusted analysis of covariance was performed. This study included 307 individuals ages 37.99 ± 13.95 y (52.1% men), of which 157 consumed supplements.

RESULTS

The results of the comet assay revealed that participants who used supplements had higher DNA damage indexes (P = 0.018) and damage frequency (P = 0.045) than those who reported using no supplements. Moreover, the comet assay also indicated that the participants who used supplements classified into the SESEAS category presented the highest DNA damage index (P = 0.025) and frequency (P = 0.044) compared with those who used no supplements. However, we found no significant difference in the micronuclei and nuclear buds in the evaluated groups (P > 0.05).

CONCLUSION

Supplement use is not associated with permanent damage, suggesting that SESEAS supplements are safe for consumption.

Influence of shortened recovery between resistance exercise sessions on muscle-hypertrophic effect in rat skeletal muscle

Resistance exercise training induces muscle hypertrophy, and recovery between sessions is one of the major determinants of this effect. However, the effect of the recovery period between sessions on muscle hypertrophy following resistance exercise training remains unclear. To elucidate the effect of recovery period on hypertrophy, in the present study, we investigated changes in protein degradation systems and hypertrophic responses in rat skeletal muscle to resistance training with variable recovery periods. In the conventional recovery group (exercised every 72 h) and a shorter recovery group (exercised every 24 h), 18 bouts of resistance exercise consisting of 50 repetitions of a 3-sec maximal isometric contraction caused muscle hypertrophy and slight activation of muscle protein degradation systems. By contrast, in an excessively shorter recovery group (exercised every 8 h), 18 bouts of resistance exercise did not cause hypertrophy and markedly activated protein degradation systems, accompanied by inflammatory responses. These observations indicate that excessive shortening of recovery between sessions does not cause skeletal muscle hypertrophy, likely due to the activation of proteolysis induced by inflammatory responses to resistance exercise training.

Whey proteins: targets of oxidation, or mediators of redox protection

Bovine whey proteins are highly valued dairy ingredients. This is primarily due to their amino acid content, digestibility, bioactivities and their processing characteristics. One of the reported bioactivities of whey proteins is antioxidant activity. Numerous dietary intervention trials with humans and animals indicate that consumption of whey products can modulate redox biomarkers to reduce oxidative stress. This bioactivity has in part been assigned to whey peptides using a range of biochemical or cellular assays in vitro. Superimposing whey peptide sequences from gastrointestinal samples, with whey peptides proven to be antioxidant in vitro, allows us to propose peptides from whey likely to exhibit antioxidant activity in the diet. However, whey proteins themselves are targets of oxidation during processing particularly when exposed to high thermal loads and/or extensive processing (e.g. infant formula manufacture). Oxidative damage of whey proteins can be selective with regard to the residues that are modified and are associated with the degree of protein unfolding, with α-Lactalbumin more susceptible than β-Lactoglobulin. Such oxidative damage may have adverse effects on human health. This review summarises how whey proteins can modulate cellular redox pathways and conversely how whey proteins can be oxidised during processing. Given the extensive processing steps that whey proteins are often subjected to, we conclude that oxidation during processing is likely to compromise the positive health attributes associated with whey proteins.

Repeated bouts of resistance exercise with short recovery periods activates mTOR signaling, but not protein synthesis, in mouse skeletal muscle

The recovery period between bouts of exercise is one of the major factors influencing the effects of resistance exercise, in addition to exercise intensity and volume. However, the effects of shortening the recovery time between bouts of resistance exercise on subsequent protein synthesis remain unclear. In this study, we investigated the consequences of shortening the recovery time between bouts of resistance exercise on protein synthesis and related processes in mouse skeletal muscles. Eighteen male C57BL/6J mice were randomly subjected to three bouts of resistance exercise with 72 (72H), 24 (24H), or 8 h (8H) of recovery periods between bouts. Resistance exercise, consisting of five sets of 3 s × 10 isometric contractions with 3 min rest between sets, was elicited on the right tibialis anterior muscle via percutaneous electrical stimulation on the deep peroneal nerve under isoflurane anesthesia. The left muscle served as an internal control. Six hours after the third bout of exercise, protein synthesis was found to be activated in the 72H and 24H groups, but not in the 8H group. Phosphorylation of p70S6K at Thr 389, a marker of mammalian target of rapamycin (mTOR) signaling, was increased in all groups, with the 8H group showing the highest magnitude. In contrast, protein carbonylation was observed only in mice in the 8H group. These results suggest that repeated bouts of resistance exercise with 8 h of recovery periods do not effectively increase the levels of muscle protein synthesis despite activation of the mTOR signaling pathway, which likely involves oxidative stress.

Invited review: Whey proteins as antioxidants and promoters of cellular antioxidant pathways

Oxidative stress contributes to cell injury and aggravates several chronic diseases. Dietary antioxidants help the body to fight against free radicals and, therefore, avoid or reduce oxidative stress. Recently, proteins from milk whey liquid have been described as antioxidants. This review summarizes the evidence that whey products exhibit radical scavenging activity and reducing power. It examines the processing and treatment attempts to increase the antioxidant bioactivity and identifies 1 enzyme, subtilisin, which consistently produces the most potent whey fractions. The review compares whey from different milk sources and puts whey proteins in the context of other known food antioxidants. However, for efficacy, the antioxidant activity of whey proteins must not only survive processing, but also upper gut transit and arrival in the bloodstream, if whey products are to promote antioxidant levels in target organs. Studies reveal that direct cell exposure to whey samples increases intracellular antioxidants such as glutathione. However, the physiological relevance of these in vitro assays is questionable, and evidence is conflicting from dietary intervention trials, with both rats and humans, that whey products can boost cellular antioxidant biomarkers.

Effects of sheep/goat whey protein dietary supplementation on the redox status of rats

The purpose of the present study is to estimate the effects of sheep/goat whey protein dietary supplementation on the redox status of blood and tissues of rats. Twelve male Wistar rats were divided into the control group (standard commercial diet) and whey group [standard commercial diet + sheep/goat whey protein (1 g kg b.w/day)] (6 rats/group). The animals were maintainted on their respective diet for 28 days. At the end of the experimental period, reduced glutathione, catalase activity, total antioxidant capacity, thiobarbituric reactive substances, protein carbonyls and the decomposition rate of H₂O₂ were measured in blood and tissues of rats. According to the results, the rats fed with the sheep/goat whey protein exhibited improved antioxidant status and decreased free radical-induced toxic effects on lipids and proteins. Specifically, in blood, GSH and CAT levels were significantly increased while TBARS and protein carbonyl levels were significantly decreased compared to the control group. Regarding the effects on tissues, it was observed that GSH levels were significantly increased in small intestine, quadriceps muscle, pancreas and lung tissue compared to the control group. The decomposition rate of H₂O₂ was significantly decreased in liver, brain and quadriceps muscle, but was significantly increased in spleen tissue compared to the control group. TBARS levels were significantly decreased in liver, brain, quadriceps muscle, pancreas, lung and spleen tissue compared to the control group. Finally, protein carbonyl levels were significantly decreased in brain, small intestine, kidney, pancreas and spleen tissue compared to the control group. Thus, the present findings show the beneficial effects of sheep/goat whey protein, a by-product of cheese manufacturing, on the redox status in an in vivo model.

Effect of administration of high-protein diet in rats submitted to resistance training

PURPOSE

Although there is limited evidence regarding the pathophysiological effects of a high-protein diet (HD), it is believed that this type of diet could overload the body and cause damage to the organs directly involved with protein metabolism and excretion. The aim of this study was to verify the effects of HD on biochemical and morphological parameters of rats that completed a resistance training protocol (RT; aquatic jump) for 8 weeks.

METHODS

Thirty-two adult male Wistar rats were divided into four groups (n = 8 for each group): sedentary normal protein diet (SN-14%), sedentary high-protein diet (SH-35%), trained normal protein diet (TN-14%), and trained high-protein diet (TH-35%). Biochemical, tissue, and morphological measurements were made.

RESULTS

Kidney (1.91 ± 0.34) and liver weights (12.88 ± 1.42) were higher in the SH. Soleus muscle weight was higher in the SH (0.22 ± 0.03) when compared to all groups. Blood glucose (123.2 ± 1.8), triglycerides (128.5 ± 44.0), and HDL cholesterol levels (65.7 ± 20.9) were also higher in the SH compared with the other experimental groups. Exercise reduced urea levels in the trained groups TN and TH (31.0 ± 4.1 and 36.8 ± 6.6), respectively. Creatinine levels were lower in TH and SH groups (0.68 ± 0.12; 0.54 ± 0.19), respectively. HD negatively altered renal morphology in SH, but when associated with RT, the apparent damage was partially reversed. In addition, the aquatic jump protocol reversed the damage to the gastrocnemius muscle caused by the HD.

CONCLUSIONS

A high-protein diet promoted negative metabolic and morphological changes, while RT was effective in reversing these deleterious effects.

Animal models of resistance exercise and their application to neuroscience research

BACKGROUND

Numerous studies have demonstrated that participation in regular resistance exercise (e.g., strength training) is associated with improvements in mental health, memory, and cognition. However, less is known about the neurobiological mechanisms mediating these effects. The goal of this mini-review is to describe and evaluate the available animal models of resistance exercise that may prove useful for examining CNS activity.

NEW METHOD

Various models have been developed to examine resistance exercise in laboratory animals.

COMPARISON WITH EXISTING METHODS

Resistance exercise models vary in how the resistance manipulation is applied, either through direct stimulation of the muscle (e.g., in situ models) or through behavior maintained by operant contingencies (e.g., whole organism models). Each model presents distinct advantages and disadvantages for examining central nervous system (CNS) activity, and consideration of these attributes is essential for the future investigation of underlying neurobiological substrates.

RESULTS

Potential neurobiological mechanisms mediating the effects of resistance exercise on pain, anxiety, memory, and drug use have been efficiently and effectively investigated using resistance exercise models that minimize stress and maximize the relative contribution of resistance over aerobic factors.

CONCLUSIONS

Whole organism resistance exercise models that (1) limit the use of potentially stressful stimuli and (2) minimize the contribution of aerobic factors will be critical for examining resistance exercise and CNS function.

Effects of Whey Powder Supplementation on Dry-Aged Meat Quality

The objective of this study was to determine the effect of dietary supplementation with whey powder (WP, 1g/kg feed) from weaning to slaughter (150 d) on dry-aged loin quality of pigs. Fifty-eight pigs were randomly divided into two dietary treatment groups (seven replications of four pigs per treatments). Basal diet with 0.1% whey powder was supplied to the WP group. Basal diet was used for the control group (CON). Diet whey protein did not appear to influence the moisture or protein contents. However, ash and fat contents were significantly (p<0.05) decreased in the WP group compared to the control group. Drip loss was significantly (p<0.05) lower in the WP group than that of the control group. Increasing redness with decreasing lightness was found in the inner loin of the WP group. Calcium and iron contents in the WP group were significantly higher than those in the control group. Protein degradation was higher in the WP group than that in the control group (p<0.05), whereas shear force was lower in the WP group than that in the control group (p<0.05). In conclusion, the basal diet supplemented with 0.1% whey powder influence negatively the lipid oxidation of meat whereas the texture property and mineral composition of meat from whey powder fed pigs are developed.

The effects of resistance exercise on cocaine self-administration, muscle hypertrophy, and BDNF expression in the nucleus accumbens

BACKGROUND

Exercise is associated with positive outcomes in drug abusing populations and reduces drug self-administration in laboratory animals. To date, most research has focused on aerobic exercise, and other types of exercise have not been examined. This study examined the effects of resistance exercise (strength training) on cocaine self-administration and BDNF expression, a marker of neuronal activation regulated by aerobic exercise.

METHODS

Female rats were assigned to either exercising or sedentary conditions. Exercising rats climbed a ladder wearing a weighted vest and trained six days/week. Training consisted of a three-set "pyramid" in which the number of repetitions and resistance varied across three sets: eight climbs carrying 70% body weight (BW), six climbs carrying 85% BW, and four climbs carrying 100% BW. Rats were implanted with intravenous catheters and cocaine self-administration was examined. Behavioral economic measures of demand intensity and demand elasticity were derived from the behavioral data. BDNF mRNA expression was measured via qRT-PCR in the nucleus accumbens following behavioral testing.

RESULTS

Exercising rats self-administered significantly less cocaine than sedentary rats. A behavioral economic analysis revealed that exercise increased demand elasticity for cocaine, reducing consumption at higher unit prices. Exercising rats had lower BDNF expression in the nucleus accumbens core than sedentary rats.

CONCLUSIONS

These data indicate that resistance exercise decreases cocaine self-administration and reduces BDNF expression in the nucleus accumbens after a history of cocaine exposure. Collectively, these findings suggest that strength training reduces the positive reinforcing effects of cocaine and may decrease cocaine use in human populations.

Antioxidant Effects of Sheep Whey Protein on Endothelial Cells

Excessive production of reactive oxygen species (ROS) may cause endothelial dysfunction and consequently vascular disease. In the present study, the possible protective effects of sheep whey protein (SWP) from tert-butyl hydroperoxide- (tBHP-) induced oxidative stress in endothelial cells (EA.hy926) were assessed using oxidative stress biomarkers. These oxidative stress biomarkers were glutathione (GSH) and ROS levels determined by flow cytometry. Moreover, thiobarbituric acid-reactive substances (TBARS), protein carbonyls (CARB), and oxidized glutathione (GSSG) were determined spectrophotometrically. The results showed that SWP at 0.78, 1.56, 3.12, and 6.24 mg of protein mL⁻¹ increased GSH up to 141%, while it decreased GSSG to 46.7%, ROS to 58.5%, TBARS to 52.5%, and CARB to 49.0%. In conclusion, the present study demonstrated for the first time that SWP protected endothelial cells from oxidative stress. Thus, SWP may be used for developing food supplements or biofunctional foods to attenuate vascular disturbances associated with oxidative stress.

Whey protein improves exercise performance and biochemical profiles in trained mice

Purpose

The objective of this study is to verify the beneficial effects of whey protein (WP) supplementation on health promotion and enhance exercise performance in an aerobic-exercise training protocol.

Methods

In total, 40 male Institute of Cancer Research mice (4 wk old) were divided into four groups (n = 10 per group): sedentary control with vehicle (SC) or WP supplementation (4.1 g·kg⁻¹, SC + WP), and exercise training with vehicle (ET) or WP supplementation (4.1 g·kg⁻¹, ET + WP). Animals in the ET and ET + WP groups underwent swimming endurance training for 6 wk, 5 d·wk⁻¹. Exercise performance was evaluated by forelimb grip strength and exhaustive swimming time as well as by changes in body composition and biochemical parameters at the end of the experiment.

Results

ET significantly decreased final body and muscle weight and levels of albumin, total protein, blood urea nitrogen, creatinine, total cholesterol, and triacylglycerol. ET significantly increased grip strength; relative weight (%) of liver, heart, and brown adipose tissue (BAT); and levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase, and total bilirubin. WP supplementation significantly decreased final body, muscle, liver, BAT, and kidney weight and relative weight (%) of muscle, liver, and BAT as well as levels of aspartate aminotransferase, lactate dehydrogenase, creatine kinase, and uric acid. In addition, WP supplementation slightly increased endurance time and significantly increased grip strength and levels of albumin and total protein.

Conclusion

WP supplementation improved exercise performance, body composition, and biochemical assessments in mice and may be an effective ergogenic aid in aerobic exercise training.

Protective effect of corn peptides against alcoholic liver injury in men with chronic alcohol consumption: a randomized double-blind placebo-controlled study

BACKGROUND

Corn peptides (CPs) are a novel food prepared from corn gluten meal, which is a main by-product of the corn starch industry. Recently, significant beneficial effects of CPs on early alcoholic liver injury in rats and on acute alcoholic injury in mice were observed. To our knowledge, the present study is the first report showing that CPs supplementation has beneficial effects on lipid profile, oxidative stress and alcoholic liver injury in men with chronic alcohol consumption.

METHODS

A 9-week, randomized, double-blind, placebo-controlled study was conducted between September 2011 and August 2012 to assess the hepatoprotective effect of CPs. A total of 161 men were randomized to receive CPs (n=53), whey protein (n=54), or corn starch placebo (n=54) at the same dose of 2 g twice daily. 146 participants completed the study. Serum lipid profile, serum markers of liver injury, oxidative stress and inflammation, and fatty liver based on the results of abdominal ultrasonography were assessed at the beginning and end of the intervention.

RESULTS

CPs supplementation (4 g/d) for 9 weeks significantly lowered serum levels or activities of total cholesterol, triglyceride, alanine aminotransferase, aspartate aminotransferase, malondialdehyde and tumor necrosis factor-α, and significantly increased serum activities of superoxide dismutase and glutathione peroxidase, but the same dose of whey protein and corn starch (placebo) did not demonstrate these effects.

CONCLUSIONS

Our results indicate that CPs may have protective effects on alcohol-induced liver damage via modulation of lipid metabolism and oxidative stress. CPs may potentially be used as a functional food for the management of alcoholic liver disease in subjects with chronic alcohol consumption.

Anti-atherogenic effect of hydrogen sulfide by over-expression of cystathionine gamma-lyase (CSE) gene

Hydrogen sulfide (H₂S) is an important gaseous signaling molecule that functions in physiological and pathological conditions, such as atherosclerosis. H₂S dilates vessels and therefore has been suggested as an anti-atherogenic molecule. Since cystathionine gamma-lyase (CSE) enzyme is responsible for producing H₂S in the cardiovascular system, we hypothesized that up-regulation of CSE expression in vivo with preservation of H₂S bioactivity can slow down plaque formation and, can serve as a therapeutic strategy against atherosclerosis. In this study, C57BL/6 wild type mice (WT), ApoE knockout mice (KO) and transgenic ApoE knockout mice overexpressing CSE (Tg/KO) at four weeks of age were weaned. They were then fed with either normal or atherogenic diet for 12 weeks. At week 16, serial plasma lipid levels, body weight, and blood pressure were measured prior to euthanization of the mice and the size of atherosclerotic plaques at their aortic roots was measured. Tg/KO mice showed an increase in endogenous H₂S production in aortic tissue, reduced atherosclerotic plaque sizes and attenuation in plasma lipid profiles. We also showed an up-regulation in plasma glutathionine peroxidase that could indicate reduced oxidative stress. Furthermore, there was an increase in expression of p-p53 and down regulation of inflammatory nuclear factor-kappa B (NF-κB) in aorta. To conclude, alteration of endogenous H₂S by CSE gene activation was associated with reduced atherosclerosis in ApoE-deficient mice. Up-regulation of CSE/H₂S pathway attenuates atherosclerosis and this would be a potential target for therapeutic intervention against its formation.

Four-month course of soluble milk proteins interacts with exercise to improve muscle strength and delay fatigue in elderly participants

BACKGROUND

The benefit of protein supplementation on the adaptive response of muscle to exercise training in older people is controversial.

OBJECTIVE

To investigate the independent and combined effects of a multicomponent exercise program with and without a milk-based nutritional supplement on muscle strength and mass, lower-extremity fatigue, and metabolic markers.

DESIGN

A sample of 48 healthy sedentary men aged 60.8 ± 0.4 years were randomly assigned to a 16-week multicomponent exercise training program with a milk-based supplement containing, besides proteins [total milk proteins 4 or 10 g/day or soluble milk proteins rich in leucine (PRO) 10 g/day], carbohydrates and fat. Body composition, muscle mass and strength, and time to task failure, an index of muscle fatigue, were measured. Blood lipid, fibrinogen, creatine phosphokinase, glucose, insulin, C-reactive protein, interleukin-6, tumor necrosis factor-α soluble receptors, and endothelial markers were assessed.

RESULTS

Body fat mass was reduced after the 4-month training program in groups receiving 10 g/day of protein supplementation (P < .01). The training program sustained with the daily 10 g/day PRO was associated with a significant increase in dominant fat free mass (+5.4%, P < .01) and in appendicular muscle mass (+4.5%, P < .01). Blood cholesterol was decreased in the trained group receiving 10 g/day PRO. The index of insulin resistance (homeostasis model assessment-insulin resistance) and blood creatine phosphokinase were reduced in the groups receiving 10 g/day PRO, irrespective of exercise. The inflammatory and endothelial markers were not different between the groups. Training caused a significant improvement (+10.6% to 19.4%, P < .01) in the maximal oxygen uptake. Increased maximum voluntary contraction force was seen in the trained groups receiving 10 g/day of proteins (about 3%, P < .05). Time to task failure was improved in the trained participants receiving a 10 g/day supplementation with PRO (P < .01).

CONCLUSIONS

Soluble milk proteins rich in leucine improved time to muscle failure and increase in skeletal muscle mass and strength after prolonged multicomponent exercise training in healthy older men.

Glutathione homeostasis and functions: potential targets for medical interventions

Glutathione (GSH) is a tripeptide, which has many biological roles including protection against reactive oxygen and nitrogen species. The primary goal of this paper is to characterize the principal mechanisms of the protective role of GSH against reactive species and electrophiles. The ancillary goals are to provide up-to-date knowledge of GSH biosynthesis, hydrolysis, and utilization; intracellular compartmentalization and interorgan transfer; elimination of endogenously produced toxicants; involvement in metal homeostasis; glutathione-related enzymes and their regulation; glutathionylation of sulfhydryls. Individual sections are devoted to the relationships between GSH homeostasis and pathologies as well as to developed research tools and pharmacological approaches to manipulating GSH levels. Special attention is paid to compounds mainly of a natural origin (phytochemicals) which affect GSH-related processes. The paper provides starting points for development of novel tools and provides a hypothesis for investigation of the physiology and biochemistry of glutathione with a focus on human and animal health.