Endocrine control of sheep adipose tissue fatty acid synthesis: depot specific differences in response to lactation.

The effects of lactation and insulin, growth hormone and dexamethasone (a glucocorticoid analogue) have been assessed on the rate of fatty acid synthesis in adipose tissue from omental (abdominal), subcutaneous and popliteal (intermuscular) depots of sheep. Adipocyte mean cell volume was greatest in omental tissue but the rate of fatty acid synthesis was similar in omental and subcutaneous adipose tissue in non-lactating ewes. Insulin increased the rate of fatty acid synthesis in tissue from all three depots and this was antagonised by growth hormone. The effects of growth hormone were less in omental adipose tissue from non-lactating sheep than in the other two depots. Lactation decreased the rate of fatty acid synthesis in all three depots, but to a lesser extent in omental than the other depots. Insulin resistance was apparent in subcutaneous and popliteal tissues from lactating ewes but not in omental tissue. Omental adipose tissue, thus differs in several aspects from the two carcass depots. Differences in response to hormones in omental adipose tissue were apparent in young sheep before the onset of fattening when omental adipocytes are similar in size to subcutaneous adipocytes.