Abstract #M195

# M195
Coordination of adipose tissue lipolysis during the transition period in dairy cows.
S. J. Erb*1, R. S. Pralle1, H. M. White1, 1University of Wisconsin-Madison, Madison, WI.

Mobilization of triacylglycerols (TAG) during the transition period is crucial to mitigate negative energy balance (NEB). Lipolysis is mediated by lipases; however, known regulators of lipolysis in nonruminants are not upregulated during the transition period in dairy cows. The objective of this study was to determine the coordinated response of bovine adipose lipases to mobilize TAG during the transition period. Multiparous pregnant dairy cows were blocked by anticipated calving date and randomly assigned to either the control group (n = 3), fed an ad libitum diet, or fatty liver induction (FLI) group (n = 8; overfed prepartum and feed restricted postpartum) until clinical ketosis onset. Adipose tissue and blood samples were collected at −14, +1, and +14 d relative to calving (DRTC) for NEFA and lipase quantification. Additional samples (n = 3) were taken once during a period of positive energy balance (PEB) to utilize as PEB controls. Protein abundance of abhydrolase domain containing 5 (ABHD5), lipoprotein lipase (LPL), perilipin 1 (PLIN), and patatin-like phospholipase domain containing 3 (PNPLA3) were determined through Western blot analysis, normalized to total lane protein, and expressed relative to −14 DRTC samples. Data were non-normal; therefore, the log(relative abundance +1) was analyzed (PROC MIXED, SAS 9.4) for effect of DRTC, treatment, and DRTC x treatment. Correlations were explored using PROC CORR. During the transition period, ABHD5 (P = 0.04) was increased at +14 DRTC compared with +1 DRTC. Abundance of LPL was greater (P = 0.05) in FLI cows, and +1 LPL was correlated with NEFA (r = 0.62) at +14 DRTC across treatments. At +14 DRTC, abundance of ABHD5 (r = 0.64) and PLIN (r = 0.60) were correlated with NEFA concentration at +1 DRTC. Interestingly, PNPLA3 abundance (P = 0.04) was increased 3.8-fold from PEB to −14 DRTC, and was highly correlated with abundance of both PLIN (r = 0.71) and phosphorylated PLIN (r = 0.74) at +1 DRTC. Previously thought to not be expressed in bovine adipose tissue, PNPLA3 may be a key lipase during the transition period; however, the mechanistic relationship between these lipases needs to be further explored.

Key Words: lipase, negative energy balance, NEFA