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Methionine and arginine supplementation alters mechanistic target of rapamycin (mTOR) and insulin signaling in bovine subcutaneous adipose explants challenged with C2-ceramide.

Y. Liang

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06-23-2020

Abstract:

205
Methionine and arginine supplementation alters mechanistic target of rapamycin (mTOR) and insulin signaling in bovine subcutaneous adipose explants challenged with C2-ceramide.
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.

Periparturient cows are exposed to increased circulating levels of ceramide which contributes to insulin resistance. Both Met and Arg promote protein synthesis via the mechanistic target of rapamycin (mTOR) and synthesis of polyamines and glutathione (antioxidants). Our previous work underscored the potential for Met supply to enhance insulin sensitivity in s.c. adipose tissue (SAT). The objective of this study was to investigate effects of enhanced Met and Arg supply alone or in combination on protein abundance of mTOR and insulin signaling pathways in adipose explants during ceramide stimulation. SAT from the tail-head of 4 Holstein cows (parity 4 � 1.4, DIM 248 � 38 before slaughter; mean � SD) was incubated in duplicate for 4 h with one of the following media: ideal profile of essential AA as the control (IPAA; Lys:Met 2.9:1, Lys:Arg 2:1), increased Met (incMet; Lys:Met 2.5:1), increased Arg (incArg; Lys:Arg 1:1), or incMet plus incArg (Lys:Met 2.5:1 Lys:Arg 1:1) with or without exogenous C2:0-ceramide (100 μM). Total protein extracted from tissue explants was used for Western blotting. Data were analyzed as a 2 � 2 � 2 factorial using the MIXED procedure of SAS 9.4. There was a triple interaction between Met, Arg and ceramide for phosphorylated (p) protein kinase B (AKT) and p-mTOR (P < 0.05). Ceramide stimulation downregulated overall abundance of p-mTOR and p-AKT (P < 0.05). Without ceramide stimulation, enhanced Met and Arg alone or in combination led to lower p-mTOR (P < 0.05). However, compared with IPAA challenged with ceramide, increased Met or Arg led to greater p-AKT and p-mTOR, with a more pronounced response due to Arg and Met individually (P < 0.05). Compared with IPAA challenged with ceramide, enhanced Met or Arg supply resulted in greater activation of mTOR (p-mTOR/total mTOR) and AKT (p-AKT/total AKT), with a more pronounced response due to Arg. Overall, data suggest that greater Met or Arg supply might help preserve SAT functionality during the periparturient period when systemic ceramide concentrations increase.

Keywords: ceramide, amino acid, mechanistic target of rapamycin.

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