Lipolysis in early lactation is associated with an increase in phosphorylation of adenosine monophosphate-activated protein kinase (AMPK)α1 in adipose tissue of dairy cows

Abstract

Adenosine monophosphate-activated protein kinase (AMPK)α1 is activated in the context of triacylglycerol hydrolysis in adipose tissue in monogastric animals. This study describes AMPKα1 protein expression and the occurrence of its phosphorylated form (pAMPKα1) in different adipose tissue depots as influenced by time and postpartum diet in dairy cows. Biopsy samples were obtained from subcutaneous (SCAT) and retroperitoneal (RPAT) adipose tissues of 20 Holstein cows 21d prepartum (ap) and 1 and 21d postpartum (pp). After d 1 pp, cows were randomly assigned to 2 groups (n=10) and fed different amounts of concentrate until the third biopsy sampling at 21d pp. Protein expression of AMPK and the extent of its phosphorylation in adipose tissue were measured by semiquantitative Western blotting. Results were not influenced by postpartum feeding. Therefore, both groups were pooled and data analyzed together. Expression of AMPKα1 in SCAT showed a decrease over time, resulting in lower expression at 1d pp compared with 21d ap. Expression in RPAT was maintained over time. Phosphorylation increased in SCAT, showing a greater extent of phosphorylation at d 21 pp compared with 21d ap. In RPAT, this could be seen as a trend. The proportion of pAMPKα1 to AMPKα1 significantly increased over time in both tissues. In the first adipose tissue sampling (21d ap), AMPKα1 protein expression and extent of phosphorylation were significantly higher in RPAT than in SCAT. Lipolysis in early lactation of dairy cows was associated with an increase in phosphorylation of AMPKα1 and ratio of pAMPKα1 to AMPKα1 in bovine adipose tissues. This indicates that AMPKα1 may be involved in the regulation of energy metabolism of bovine adipose tissues.