Body condition and insulin resistance interactions with periparturient gene expression in adipose tissue and lipid metabolism in dairy cows

摘要

Adipose tissue plays an important role in a cow’sability to adapt to the metabolic demands of lactation,because of its central involvement in energy metabolismand immunity. High adiposity and adipose tissueresistance to insulin are associated with excessive lipidmobilization. We hypothesized that the response to aglucose challenge differs between cows of different bodycondition 21 d before and after calving and that theresponses are explainable by gene expression in subcutaneousadipose tissue (SAT). In addition, we aimed toinvestigate insulin resistance with gene expression inSAT and lipid mobilization around parturition. MultiparousHolstein cows were grouped according to bodyconditions score (BCS) 4 wk before calving, as follows:BCS ≤ 3.0 = thin (T, n = 14); BCS 3.25 to 3.5 = optimal(O, n = 14); BCS ≥ 3.75 = over-conditioned (OC,n = 14). We collected SAT on d −21 and d 21 relativeto calving. A reverse-transcriptase quantitative (RT-q)PCR was used to measure gene expression related tolipid metabolism. One hour after the collection of adiposetissue, an intravenous glucose tolerance test wascarried out, with administration of 0.15 g of glucoseper kg of body weight (with a 40% glucose solution).Once weekly from the first week before calving to thethird week after calving, a blood sample was taken. Thetransition to lactation was associated with intensifiedrelease of energy stored in adipose tissue, a decrease inthe lipogenic genes lipoprotein lipase (LPL) and diacylglycerolO-acyltransferase 2 (DGAT2), and an increasein the lipolytic gene hormone-sensitive lipase (LIPE).On d −21, compared with T cows, OC cows had lowermRNA abundance of LPL and DGAT2, and the latencyof fatty acid response after glucose infusion was alsolonger (8.5 vs. 23.3 min) in OC cows. Cows with higherinsulin area under the curve on d −21 had concurrentlylower LPL and DGAT2 gene expression and greaterconcentration of fatty acids on d −7, d 7, and d 14.In conclusion, high adiposity prepartum lowers thewhole-body lipid metabolism response to insulin andcauses reduced expression of lipogenic genes in SAT3 weeks before calving. In addition, more pronouncedinsulin release after glucose infusion on d −21 is relatedto higher lipid mobilization around calving, indicatingan insulin-resistant state, and is associated with lowerexpression of lipogenic genes in SAT.