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Hepatic lipid-associated protein abundances vary by day relative to calving and are associated with hepatic triglyceride content in transition dairy cows.

H. T. Holdorf

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06-23-2020

Abstract:

170
Hepatic lipid-associated protein abundances vary by day relative to calving and are associated with hepatic triglyceride content in transition dairy cows.
H. T. Holdorf*, R. S. Pralle, S. J. Erb, H. M. White. University of Wisconsin-Madison Madison, WI.

The objectives of this study were to determine protein abundance of hepatic lipid-associated proteins (HLAP) in liver homogenates and interrogate a potential relationship with peripartum liver triglyceride (LVTG) content. Multiparous Holstein cows (n = 25) were blocked by expected calving date and randomly assigned to control or a fatty liver induction (FLI) treatment (TRT). Liver samples were collected via biopsy at −28, −14, +1, +14, +28, +42, and +56 d relative to calving (DRTC). Content of LVTG was determined and expressed on a % dry matter basis. Western blotting was used to analyze the abundance of HLAP: abhydrolase domain containing 5 (ABHD5), hormone sensitive lipase (HSL), phosphorylated HSL (PHSL), adipose triglyceride lipase (ATGL), perilipin 1 (PLIN) and phosphorylated PLIN (PPLIN). Data was analyzed using PROC MIXED in SAS 9.4. Evidence was considered significant if P ≤ 0.05, and a tendency if 0.05 < P ≤ 0.1. When P ≤ 0.1 for the main effects, means were separated by Bonferroni adjustment and presented as least squares means � SEM with comparison P-values. No evidence was observed for effects of TRT or TRT � DRTC (P > 0.1) on LVTG content or HLAP abundance. Mean LVTG content was greater (P ≤ 0.05) postpartum compared with prepartum and peaked at +14 DRTC (P ≤ 0.0004). Greater ATGL abundance was observed (P ≤ 0.04) at +14 and +28 DRTC (� = 1.89 � 0.02 arbitrary units [AU]) compared with +1 (1.83 � 0.03 AU) DRTC. Abundance of PLIN tended to be greater (P = 0.08) at +14 (0.79 � 0.02 AU) compared with +1 DRTC (0.72 � 0.03 AU). Conversely, PPLIN was decreased (P ≤ 0.003) at +1, +14, +28, and +42 (� = 1.67 � 0.02 AU) compared with −14 DRTC (1.74 � 0.01 AU). As linear regressors, PPLIN predicted (P = 0.05; β = −0.44) and ATGL tended to predict (P = 0.09; β = −0.33) LVTG content across all DRTC. Variation in HLAP abundance by DRTC and their associations with LVTG suggest a potential role in the accumulation and subsequent remobilization of LVTG. The impact of coordinated regulation of HLAP on the etiology of fatty liver onset and recovery peripartum warrants further exploration.

Keywords: lipase, fatty liver, peripartum.