Regulation of PPAR gamma but not obese gene expression by dietary fat supplementation

Leptin, the product of the obese gene, and peroxisome proliferator activate d receptor gamma (PPAR gamma) are important regulators of energy metabolism , adipogenesis, and immune function. In rodent models, both genes seen to r espond at the mRNA and/or protein levels to dietary fat consumption. To det ermine the effect(s) of dietary saturated and polyunsaturated fatty acids o n the expression (mRna abundance) of these genes, adipose tissue was obtain ed from pigs fed there different dietary fat sources. Corn-soybean meal die ts containing no added fat (NO, control) or 10% beef tallow (BT), safflower oil (SO), or fish oil (FO) were fed ad libitum (n = 12) for 12 weeks. The abundance of obese, PPAR gamma 1, and PPAR gamma 2 mRNA was quantified rela tive to 18S rRNA using ribonuclease protection assays. The gain:feed ratio was improved (P < 0.05) 21% by all fats with a corresponding reduction (P < 0.05) in feed intake. Relative to pigs fed NO, serum total cholesterol was increased (P < 0.01) in pigs fed BT and triglyceride and nonesterified fat ty acid concentrations were reponsive to added fat ( > 0.15). However, the abundance of PPAR gamma 2 mRNA was increased fourfold by SO compared with t he NO diet. These data indicate that the abundance of obese mRNA is indepen tent of dietary fat consumption per se, whether saturated or unsaturated, w hen feed consumption is reduced due to greater dietary caloric density. Fur thermore, we provide evidence that expression of the PPAR gamma 2 gene in p orcine adipose tissue is selectively reponsive to SO (presumably linoleic a cid, 18:2n-6). (C) Elsevier Science Inc. 2000. All rights reserved.