Reduced lipogenesis in rats fed a high-protein, carbohydrate-free diet: participateion of liver and four adipose depots

ABSTRACT

Rates of in vivo fatty acid (FA) synthesis were assessed with 3 H2O in carcass, liver intestines, muscle and four adipose depots from rats fed a high-protein, carbohydrate-free diet (70% casein, 8% fat, w/w) or a balanced diet (66% carbohydrate, 17% casein, 8% fat) for 25-30 days). rats adapted to the high protein (HP) diet showed a marked reduction of total FA synthesis from all carbon sources, which was due to a decreasedsynthesis of triacyglycerols. Rates of phospholipid-fatty acid synthesis in both carcans and liver were not liver were not affected by the diet. Rates of triacyglycerol-fatty acid (TAG-FA) synthesis were markedly reduced in adipose tissue from four different sites: epididymal (79%), retroperitoneal (78%)), subcutaneous (65%) anmd intermuscular (82%). In rats fed the balanced control diet, TAG-FA synthesis in adipose tissue accounted for about 75% of synthesis in whole carcass, whereas it was reduced to 36% in rats under the HP regimen. Although hepatic lipogenesis was also reduced in HP-fed rats, the contribution of the liver to total TAG-FA synthesis was approximately the same in HP (24%) and control (20%) rats, whereas the contribution of adipose tissue was only 26% in HP-fed animals compared to 57% in controls. Force-feeding fed rats with components of their own diets results in a significant (100%) increase of liver TAG-FA synthesis in animals fed the control diet, but did not significantly affect liver lip[ogenesis in HP rats