ADIPOSE-TISSUE LIPOGENESIS AND FAT DEPOSITION IN LEANER BROILER-CHICKENS

Rates of hepatic lipogenesis and secretion of plasma triglyceride-rich lipoproteins in 6- to 7-wk-old broiler chickens were similar to the overall rate of fat deposition in these birds, although -20% of [C-14]-labeled VLDL was oxidized to CO2 within 8 h. Only 6-7% of VLDL and portomicron triglyceride was taken up by the abdominal fat pad, but this proportion of total triglyceride flux could account for about 80-85% of the total fatty acids accumulating in that depot. The rate of lipogenesis in adipose tissue was much lower than that in the liver, but it could account for much of the remaining fatty acids. Lipogenesis from [C-14]acetate in cultured chicken adipocytes was markedly inhibited by adding VLDL as an exogenous source of fatty acids. However, adipose tissue lipogenesis was not increased in vivo by reduction of plasma lipoprotein flux by genetic selection, by the feeding of a high protein diet or by immunological intervention. The results confirm that adipose tissue lipogenesis makes only a small contribution to adipose tissue growth in normal broilers. Its importance does not increase in response to the reductions in hepatic lipogenesis that accompany genetic or nutritional manipulation of body composition.