Effects of Whey, Caseinate, or Milk Protein Ingestion on Muscle Protein Synthesis after Exercise

Abstract

Whey protein (WP) is characterized as a “fast” protein and caseinate (CA) as a “slow” protein according to their digestion and absorption rates. We hypothesized that co-ingestion of milk proteins (WP and CA) may be effective for prolonging the muscle protein synthesis response compared to either protein alone. We therefore compared the effect of ingesting milk protein (MP) to either WP or CA alone on muscle protein synthesis after exercise in rats. We also compared the effects of these milk-derived proteins to a control, soy protein (SP). Male Sprague-Dawley rats swam for two hours. Immediately after exercise, one of the following four solutions was administered: WP, CA, MP, or SP. Individual rats were euthanized at designated postprandial time points and triceps muscle samples collected for measurement of the protein fractional synthesis rate (FSR). FSR tended to increase in all groups post-ingestion, although the initial peaks of FSR occurred at different times (WP, peak time = 60 min, FSR = 7.76%/day; MP, peak time = 90 min, FSR = 8.34%/day; CA, peak time = 120 min, FSR = 7.85%/day). Milk-derived proteins caused significantly greater increases (p < 0.05) in FSR compared with SP at different times (WP, 60 min; MP, 90 and 120 min; CA, 120 min). Although statistical analysis could not be performed, the calculated the area under the curve (AUC) values for FSR following this trend were: MP, 534.61; CA, 498.22; WP, 473.46; and SP, 406.18. We conclude that ingestion of MP, CA or WP causes the initial peak time in muscle protein synthesis to occur at different times (WP, fast; MP, intermediate; CA, slow) and the dairy proteins have a superior effect on muscle protein synthesis after exercise compared with SP.

The Combination of Fasting, Acute Resistance Exercise, and Protein Ingestion Led to Different Responses of Autophagy Markers in Gastrocnemius and Liver Samples

“…The EXE/Suppl-imm and EXE/Suppl-1h groups displayed increased levels of insulin compared to the other groups, while the EXE/Suppl-imm group also had elevated levels of glucose. Kanda et al [27] visualized the peak of intramuscular and plasma leucine levels in male Sprague-Dawley rats that swam and received milk protein (whey protein and casein) at 60 min, but without significant alterations of plasma insulin concentrations. Further, Dijk et al [31] observed elevated levels of intramuscular and plasma leucine in C57/BL6RJ mice at 25 months of age after 60, 75, and 90 min of leucine-enriched whey protein gavage, but with no changes in glucose concentrations measured at 60 and 75 min.…”

“…Protein fractions such as whey protein (WP) and casein (CA) are found in milk. WP has a higher content of branched-chain amino acids (BCAA) and is considered a "fast" protein, while CA is considered a "slow" protein due to its structure that affects the absorption speed [27,28]. Although post-exercise protein feeding has been extensively used as a nutritional strategy by athletes [29,30], the combined effects of acute resistance exercise and protein ingestion after a fasting period on the autophagy pathway are not completely understood.…”

Post-Exercise Muscle Protein Synthesis in Rats after Ingestion of Acidified Bovine Milk Compared with Skim Milk

“…Bovine milk proteins are of the highest quality because they possess a complete profile of essential amino acids [ 10 ], have high amino acid digestibility and absorptivity [ 11 , 12 ], and are associated with marked changes in MPS [ 13 , 14 ] through the activation of signaling of the mammalian target of rapamycin (mTOR) [ 15 ]. Furthermore, milk has the potential to be a good protein supplement over the course of a long training period [ 16 ].…”

The mTORC1-Signaling Pathway and Hepatic Polyribosome Profile Are Enhanced after the Recovery of a Protein Restricted Diet by a Combination of Soy or Black Bean with Corn Protein

“…It has been widely reported that the combination of cereals and legumes complement the limiting amino acids in each source [ 8 , 9 , 10 ]. Although several studies have demonstrated the effect of dietary protein, mainly casein or whey [ 11 , 12 ], on growth and protein synthesis [ 13 , 14 , 15 ], less is known about the effect of different dietary protein sources or combinations of vegetable proteins to activate liver and muscle mTORC1 (mechanistic target of rapamycin)-signaling pathway. Clinical and consumer market interest is increasingly directed toward the use of plant-based proteins as dietary components to increase protein synthesis; however, there is controversy about whether the ingestion of a plant-based diet results in lower protein synthesis compared to animal-derived proteins.…”

“…However, diets as consumed inevitably consist of mixtures of proteins, which improve the quality of the protein by complementing the limiting amino acids in each source. Most studies have assessed muscle protein synthesis after the ingestion of free amino acids, milk, whey or casein [ 12 ]. In contrast, few studies have assessed the impact of plant-based protein ingestion on mTORC1-signaling pathway involved in protein synthesis.…”