Lipid synthesis and adipocyte growth in adipose tissue from sheep chronically fed a beta-adrenergic agent

The effects of the chronic ingestion of the beta-adrenergic agonist clenbuterol on ovine sc adipose tissue were investigated. Three groups of 10 wether lambs with an average initial weight of 22.7 kg were used as experimental animals. After culling 2 to 3 animals per group, one group of eight sheep was slaughtered (initial). The remaining two groups of sheep (control, n = 7 and clenbuterol-fed, n = 8) were fed either a control, high-energy diet or one containing 2 ppm clenbuterol for 40 to 44 d. At slaughter, sc adipose tissue was obtained from all animals for assays in vitro. Subcutaneous fat accretion observed over time in the control sheep was due primarily to an increase in the number of lipid-filled adipocytes. This phenomenon was not observed in the clenbuterol-fed sheep. The incorporation of acetate into lipid increased in the clenbuterol-fed group relative to the initial group and was numerically greater than the rate observed for the control group. Similar results were observed for lipogenic enzyme activities and fatty acid-binding protein activity. Palmitate esterification in vitro tended to be elevated in the clenbuterol-fed group, relative to the control group, suggesting increased triacylglycerol turnover. The in vitro data indicate that clenbuterol did not decrease sc fat accretion in sheep by inhibiting lipogenesis.