Glycerolipid biosynthesis in rat adipose tissue. Influence of adipose-cell size and site of adipose tissue on triacylglycerol formation in lean and obese rats.

The rates of lipid formation were compared in different fat-depots from lean and obese rats by using [14C]glycerol 3-phosphate, [14C]glucose or [14C]acetate as substrates. In lean animals, subcutaneous adipose tissue showed significantly lower rates of lipid synthesis than did perirenal and gonadal fat-tissue. In obese animals, the rates of lipid synthesis were significantly higher and did not vary from one fat-depot to another. Differences in the rates of lipid formation between lean and obese rats disappeared during dietary restriction of obese animals. The isolated adipocyte preparation did not reflect the true metabolic activity of the adipose organ, since this preparation was mainly derived from smaller adipocytes that were metabolically less active than larger adipocytes. The present study suggests that it is better to use whole tissue preparations to measure lipogenesis and esterification reactions, because these measurements represent the contribution of both larger and smaller adipocytes towards lipid formation.