Submitted on August 12, 2002
Revised on January 30, 2003
Accepted on January 31, 2003
EFFECTS OF DIETARY FAT TYPE AND ENERGY RESTRICTION ON ADIPOSE TISSUE FATTY ACID COMPOSITION AND LEPTIN PRODUCTION IN RATS
Geoffrey R. Hynes, Jode Heshka, Kris Chadee, and Peter J. H. Jones
Dietetics and Human Nutrition, McGill University, Montreal, Qc H9X 3V9
Corresponding Author: jonesp{at}macdonald.mcgill.ca
To investigate whether dietary fatty acid (FA) composition and energy restriction (ER) interactively influence visceral adipose obese (ob) gene expression, rats (n=72) consumed diets containing beef tallow, safflower or fish oil (20% wt/wt) ad libitum or at 60% ad libitum intake. Circulating leptin concentrations were higher (p<0.0001) after ad libitum feeding but were not influenced by dietary fat type. ER decreased (p<0.0001) weight gain and visceral adipose weight, the latter, which was positively correlated (r=0.40 p<0.001, r=0.58 p<0.0001) with circulating leptin levels. Visceral adipose ob mRNA levels were greatest after feeding fish oil, safflower oil and beef tallow, respectively. In particular, ob mRNA levels were greater after safflower oil feeding in epididymal and retroperitoneal fat pads, with ad libitum groups showing a greater abundance compared to ER animals. Circulating leptin levels did not correlate with those of ob mRNA except for higher levels detected in ad libitum depots, in comparison to ER animals. In addition, visceral FA profiles were reflective of the dietary fat source and were influenced by an interaction of dietary fat and energy. These data demonstrate that dietary fat; particularly plant or marine source and energy restriction interactively influence visceral ob mRNA levels in a tissue-specific manner. Alterations in ob mRNA do not confer changes in circulating leptin, with the exception of energy restriction which is a key determinant of circulating levels. Thus, dietary intake is an important regulator of leptin production; however, the significance of these modest changes in diet-induced obese animals requires further study.