Effect Of Whey Protein Intake Research Articles

Consecutive-Day Intake of Whey Protein Upregulates mTOR mRNA and Protein Expression in Resting Skeletal Muscle of Mice

Background: Although the effect of whey protein intake on protein metabolism in exercise-loaded skeletal muscle has been well documented, little has been reported on its effect on resting muscle. The effects of whey protein intake on protein metabolism in resting mouse skeletal muscle were investigated. Methods: Mice were fed AIN-93G composed of either casein or whey protein as the protein source for 3 or 7 consecutive days. The gastrocnemius muscle was excised, and the expression levels of the regulatory factor, mTOR, and its subunits, Raptor and Rictor, were measured by real-time PCR. The protein expression levels of mTOR and its phosphorylated form were measured by immunofluorescent western blotting. The effects of whey protein were compared to those of the case in control. Results: mTOR expression increased in the gastrocnemius muscle of mice fed whey protein for 7 consecutive days. The expression of Raptor significantly increased, whereas that of Rictor did not change, suggesting a dominant formation of mTORC1 relating to the upregulation of protein synthesis. The protein levels of mTOR and its phosphorylated form significantly increased in mice fed whey protein, indicating enhanced protein synthesis. Increased mTOR expression was not seen in the gastrocnemius muscle of mice fed whey protein for 3 consecutive days. Conclusions: These results indicate that the intake of whey protein for 7 consecutive days, but not 3 days, upregulates the mRNA and protein expression of mTOR in the resting gastrocnemius muscle of mice, suggesting its ability to enhance protein synthesis. Consecutive-day intake of whey protein may induce constitutive alteration of the skeletal muscle, including continuous upregulation of muscle protein synthesis.

Whey Protein Intake Modulates Lipid Metabolism by Transcriptionally Affecting PPARs and SREBP1c and Their Downstream Enzymes in Mice

Background: The effects of whey protein intake on the transcriptional expression of genes related to lipid metabolism in mice were investigated herein. Methods: For 4 weeks, mice were fed AIN-93G composed of either casein or whey protein as the protein source. Then the gastrocnemius muscle, liver, and epididymal adipose tissue were excised. Expression levels of the transcription factors, PPARα, PPARγ, and SREBP1c, and those of the enzymes modulated by these factors, HSL, LPL, ACCα, and FAS, were measured by real-time PCR. The effects of whey protein were compared to those of the case in control. Results: The mRNA expression of PPARα was enhanced in the gastrocnemius muscle, while that of PPARγ was increased in the liver and epididymal adipose tissue. The expression of HSL and LPL was increased in the epididymal adipose tissue and gastrocnemius muscle, respectively. The mRNA expression of SREBP1c was suppressed in all of the three tissues. The expression of ACCα was suppressed in the gastrocnemius muscle and liver, while that of FAS was suppressed in all of the three tissues. Conclusions: These results indicate that whey protein intakes transcriptionally modulate PPARs and SREBP1c directing lipid metabolism toward the enhancement of triglyceride breakdown and suppression of fatty acid synthesis.

Whey protein-derived peptide sensing by enteroendocrine cells compared with osteoblast-like cells: Role of peptide length and peptide composition, focussing on products of β-lactoglobulin hydrolysis

The short-term satiating effect of whey protein intake is higher than that obtained with other dietary proteins. The molecular basis underlying the secretagogue effect of whey proteins on the release of cholecystokinin, a gut hormone involved in appetite suppression, has not been deeply investigated. Using STC-1 enteroendocrine cells we analysed the effects of synthetic peptides and protein hydrolysates. The hypothesis that specific molecular features in terms of short amino acid sequences released after enzymatic digestion may exert a primary role in the cholecystokinin secretagogue activity of dietary proteins was not supported. However, the length of the peptide fragments derived from a protein during enzymatic digestion is relevant to this activity. Regarding the complexities of how food can interact with different cellular systems, our data suggest a novel biological activity of ALPMH, a known bioactive peptide product of β-lactoglobulin digestion, on cell growth and a related signalling pathway in osteoblast-like cells.

Whey protein hydrolysate enhances the exercise-induced heat shock protein (HSP70) response in rats

Whey protein has been suggested to be potential protective agent against various forms of stress. The heat shock protein HSP70 confers greater cellular tolerance against stressors. The present study evaluated the effects of whey protein intake on HSP70 expression. Forty-eight male Wistar rats were divided into sedentary and exercised groups, and each group was fed as a protein source casein (CAS), whey protein (WP) or whey protein hydrolysate (WPH) for 3weeks. Exercise on a treadmill was used as the source of stress in the animals from the exercised group. The results showed a larger increase in HSP70 expression in the soleus, gastrocnemius and lung of the WPH-fed rats than WP or casein-fed rats. HSP70 expression in the sedentary rats was very low, independent of the diet or tissue. Protein carbonyls were lower in the group that consumed WPH. These data suggest that the consumption of WPH enhances HSP70 expression.