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Mechanistic target of rapamycin pathway components and proteins associated with amino acid metabolism differ among adipose depots and mammary gland in late-lactation Holstein cows.

Y. Liang

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06-23-2020

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Abstract:

T58
Mechanistic target of rapamycin pathway components and proteins associated with amino acid metabolism differ among adipose depots and mammary gland in late-lactation Holstein cows.
Y. Liang*1, N. Ma1,2, D. N. Coleman1, F. Liu1,3, Y. Li1,4, H. Y. Ding1,4, F. F. Cardoso1, F. C. Cardoso1, J. J. Loor1. 1Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana Urbana, IL, 2College of Veterinary Medicine, Nanjing Agricultural University Nanjing, China, 3Department of Animal Science and Veterinary Medicine, Henan Agricultural University Zhengzhou, China, 4Department of Veterinary Medicine, College of Animal Science and Technology, Anhui Agricultural University Hefei, China.

Branched-chain amino acids (BCAA), leucine in particular, are well-known regulators of the mechanistic target of rapamycin (mTOR), hence, they exert control on protein synthesis and cell growth. Mammary gland is a major site for protein synthesis during lactation, while adipose depots (AT) might be major sites for BCAA uptake and initial catabolism. The objective of this study was to characterize the protein profiles of mTOR pathway components, AA transporters, and BCAA catabolism among mammary gland, omental, mesenteric and s.c. AT. Four Holstein cows (parity 4 � 1.4, DIM 248 � 38 before slaughter; mean � SD) were used in this study. All cows were fed a common lactation diet before slaughter. Subcutaneous, omental, and mesenteric AT along with mammary gland tissue were collected immediately after slaughter. Statistical analysis was performed using the MIXED model in SAS 9.4 with tissue as fixed effect. Adipose tissue had greater phosphorylated (p) ratio of protein kinase B (AKT) to total AKT than mammary gland (P < 0.05). Mesenteric and SAT had greater activation of AKT (p-AKT/total AKT) than omental AT (P < 0.05) suggesting the later might be less insulin-sensitive (at least in late-lactation). Omental and SAT had greater activation of mTOR (p-mTOR/total mTOR) compared with mammary tissue (P < 0.05). However, compared with mesenteric AT, mammary tissue had greater activation of mTOR (P < 0.05). Branched-chain ketoacid dehydrogenase kinase (BCKDK) is a key enzyme in regulating BCAA catabolism. Glutathione S-transferase Mu 1 (GSTM1) modulates glutathione synthesis. Compared with mammary gland, AT depots had greater protein abundance of BCKDK and GSTM1 (P < 0.05), suggesting that AT depots might play an important role in regulating BCAA catabolism and oxidative stress. Solute carrier family 1 member 5 (SLC1A5) was only detectable in SAT and omental AT. Overall, data suggest that adipose depots play a role in BCAA metabolism and have antioxidant mechanisms that might help preserve tissue function such as insulin sensitivity.

Keywords: adipose depots, branched-chain amino acid, mechanistic target of rapamycin.

Biography: I am Yusheng Liang, a third year PhD student of animal sciences from University of Illinois.