Inflammation- and lipid metabolism-related gene network expression in visceral and subcutaneous adipose depots of Holstein cows

Abstract

This experiment was conducted to determine the effects of energy overfeeding on gene expression in mesenteric (MAT), omental (OAT), and subcutaneous (SAT) adipose tissue (AT) from nonpregnant and nonlactating Holstein cows. Eighteen cows were randomly assigned to either a controlled energy [LE, net energy for lactation (NE(L)) = 1.35 Mcal/kg of dry matter (DM)] or moderate energy-overfed group (HE, NE(L) = 1.62 Mcal/kg of DM) for 8 wk. Cows were then euthanized and subsamples of MAT, OAT, and SAT were harvested for transcript profiling via quantitative PCR of 34 genes involved in lipogenesis, triacylglycerol (TAG) synthesis, lactate signaling, hepatokine signaling, lipolysis, transcription regulation, and inflammation. The interaction of dietary energy and adipose depot was not significant for any gene analyzed except LPL, which indicated a consistent response to diet. Expression of ACACA and FASN was greater in SAT than MAT, whereas expression of SCD and ADFP were greatest in SAT, intermediate in OAT, and lowest in MAT. However, the 2 visceral depots had greater expression of THRSP, ACLY, LPL, FABP4, GPAM, and LPIN1 compared with SAT. The transcription factor SREBF1 was more highly expressed in MAT and SAT than in OAT. The expression of PNPLA2 was greater in visceral AT sites than in SAT, but other lipolysis-related genes were not differentially expressed among AT depots. Visceral AT depots had greater expression of LEP, ADIPOQ, and SAA3 compared with SAT. Moreover, MAT had greater expression than SAT of proinflammatory cytokines (IL1B and IL6), IL6 receptor (IL6R), and chemokines (CCL2 and CCL5). However, TNF expression was greatest in SAT, lowest in OAT, and intermediate in MAT. Overall, results indicated that visceral AT might be more active in uptake of preformed long-chain fatty acids than SAT, whereas de novo fatty acid synthesis could make a greater contribution to the intracellular pool of fatty acids in SAT than in visceral AT. The visceral AT compared with SAT seem to have a greater capacity for expression (and potentially for secretion) of proinflammatory cytokines; thus, excessive accumulation of visceral lipid due to a long-term overfeeding energy may be detrimental to liver function and overall health of dairy cows, particularly during the transition period.

Keywords: gene expression; inflammation; lipogenesis; visceral adipose tissue.