Post-Exercise Muscle Protein Synthesis in Rats after Ingestion of Acidified Bovine Milk Compared with Skim Milk
Food Science Research Labs., Meiji Co., Ltd., 540 Naruda, Odawara, Kanagawa 250-0862, Japan
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Nutrients 2017, 9(10), 1071; https://doi.org/10.3390/nu9101071
Received: 11 September 2017 / Revised: 22 September 2017 / Accepted: 25 September 2017 / Published: 27 September 2017
(This article belongs to the Special Issue Protein for Post-Exercise Recovery and Performance)
Bovine milk proteins have a low absorption rate due to gastric acid-induced coagulation. Acidified milk remains liquid under acidic conditions; therefore, the absorption rate of its protein may differ from that of untreated milk. To investigate how this would affect muscle protein synthesis (MPS), we compared MPS after ingestion of acidified versus skim milk in rats. Male Sprague-Dawley rats swam for 2 h and were immediately administered acidified or skim milk, then euthanized at 30, 60, 90, and 120 min afterwards. Triceps muscle samples were excised for assessing fractional synthetic rate (FSR), plasma components, intramuscular free amino acids and mTOR signaling. The FSR in the acidified milk group was significantly higher than in the skim milk group throughout the post-ingestive period. Plasma essential amino acids, leucine, and insulin levels were significantly increased in the acidified milk group at 30 min after administration compared to the skim milk group. In addition, acidified milk ingestion was associated with greater phosphorylation of protein kinase B (Akt) and ribosomal protein S6 kinase (S6K1), and sustained phosphorylation of 4E-binding protein 1 (4E-BP1). These results indicate that compared with untreated milk, acidified milk ingestion is associated with greater stimulation of post-exercise MPS.
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Keywords:
milk protein; leucine; FSR; mTOR signaling; hyperaminoacidemia
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MDPI and ACS Style
Nakayama, K.; Kanda, A.; Tagawa, R.; Sanbongi, C.; Ikegami, S.; Itoh, H. Post-Exercise Muscle Protein Synthesis in Rats after Ingestion of Acidified Bovine Milk Compared with Skim Milk. Nutrients 2017, 9, 1071.
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