Adaptations in lipid metabolism of bovine adipose tissue in lactogenesis and lactation.

The timing and magnitude of metabolic adaptations in adipose tissue during lactogenesis and lactation were determined in first lactation bovines. In vitro rates of lipogenesis and palmitate esterification were measured to estimate in vivo synthesis. Lipolysis was measured in the basal state and as maximally stimulated by norepinephrine or epinephrine to estimate physiological adaptations as well as the changes in catecholamine responsiveness. Subcutaneous adipose tissue was biopsied at -1, -0.5, +0.5, 1, 2, and 6 months from parturition. From 1 to 0.5 months prepartum there was a 54% reduction in lipogenesis, a 16% reduction in esterification, a 54 and 77% increase in norepinephrine- and epinephrine-stimulated free fatty acid (FFA) release, respectively, and a 28% increase in epinephrine-stimulated glycerol release. The immediate postpartum period (0.5 and 1 month) was marked by a decrease in lipogenesis to 5% and esterification to 50% of -1 month rates. During this period, norepinephrine-stimulated FFA release increased 50% above -1 month rates, epinephrine-stimulated FFA release increased 128%, and norepinephrine- and epinephrine-stimulated glycerol release increased 30 and 87%, respectively. Midlactation (2 and 6 months) was marked by a dramatic rebound in lipogenesis and esterification to 14-fold and 2.5-fold prepartum rates, respectively. Basal glycerol release doubled during this period, while basal FFA release declined to near prepartum levels. Catecholamine-stimulated FFA and glycerol release decreased from the peak during midlactation, but remained elevated compared to prepartum levels.(ABSTRACT TRUNCATED AT 250 WORDS)