EFFECTS OF TRIIODOTHYRONINE ADMINISTRATION ON DIETARY [C-14] TRIOLEINPARTITIONING BETWEEN DEPOSITION IN ADIPOSE-TISSUE AND OXIDATION TO [C-14] CO2 IN AD LIBITUM-FED OR FOOD-RESTRICTED RATS
Ml. Cruz et Dh. Williamson, EFFECTS OF TRIIODOTHYRONINE ADMINISTRATION ON DIETARY [C-14] TRIOLEINPARTITIONING BETWEEN DEPOSITION IN ADIPOSE-TISSUE AND OXIDATION TO [C-14] CO2 IN AD LIBITUM-FED OR FOOD-RESTRICTED RATS, Biochimica et biophysica acta, 1168(2), 1993, pp. 205-212
Refeeding a chow meal containing [1-C-14]triolein to food-restricted r
ats results in increased accumulation of [C-14]lipid in carcass and ep
ididymal adipose tissue and lower oxidation to [C-14]CO2 compared to a
d libitum-fed rats (Biochem. J. 285, 773-778, 1992). In the present ex
periments the effects of treatment with triiodothyronine (T3) for thre
e days on lipid accumulation in refed food-restricted rats has been ex
amined. T3 decreased accumulation of [C-14]lipid in carcass and epidid
ymal adipose tissue (32 and 77%, respectively) of food-restricted rats
on refeeding the chow-[1-C-14]triolein meal. This decreased accumulat
ion of [C-14]lipid was accompanied by increased [C-14]CO2 production (
77%) and decreased heparin-elutable lipoprotein lipase activity in the
epididymal fat pad (90%) and subCUtaneous adipose tissue (80%). ACCum
ulation of [C-14]lipid in the latter did not decrease significantly. I
n contrast, T3 treatment of ad libitum-fed rats increased [C-14]lipid
deposition in carcass (44%) and in subcutaneous adipose tissue (240%)
on refeeding, when compared to untreated ad libitum rats. Lipoprotein
lipase activity in the two adipose tissue depots of the refed ad libit
um + T3 rats, however, decreased. Thus, the effects of T3 on [C-14]lip
id deposition are adipose-tissue-depot-specific and depend on the prev
ious dietary intake (over 14 days) of the rat. T3-treatment increased
the lipoprotein lipase activity released from perfused hearts to a sim
ilar extent in both food-restricted and ad libitum-fed rats compared t
o the corresponding untreated groups. The rates of lipogenesis in-vivo
in liver, epididymal and subcutaneous adipose tissue of food-restrict
ed rats refed chow were not altered by T3. It is concluded that the in
creased deposition of dietary lipid in the food-restricted rat can be
partially reversed by treatment with T3, suggesting that the low-T3 st
ate associated with this condition may be in part responsible.