Effects
of Linoleic Acid (LA) and Conjugated Linoleic Acid (CLA) on Leptin
Patti Plett, H. Weiler, A. Angel*
Department of Medicine and Nutritional Sciences, University of Manitoba,
Winnipeg, MB
Leptin is an important regulator of feeding behavior and metabolic rate
and its production is related to adipose mass. To determine the effects
of dietary lipid composition on adipose mass and leptin, C57 BL/6C mice
(n=7 or 8 per group) were fed semi-synthetic diets containing 20% Safflower
oil (SO, linoleic rich), 20% Flax oil (FX, linoleic rich), or standard
Chow for 70 days. On DEXA analysis of adipose mass, SO had significantly
more fat than FX and Chow mice (25.1 * 23g vs 20.2 * 0.6 and 14.6 * 4.2g,
mean SEM respectively). Serum leptin was greater in SO (90.7 * 3.7 ng/mL)
vs FX (74.9 * 5.6 ng/mL) and Chow (33.1 * 2.2 ng/mL). In contrast to LA,
dietary CLA is thought to reduce adipose mass, an effect that appears
to be isomer specific. Accordingly, the effects of C9-T11 and T10-C12
isomers of CLA on triglyceride and leptin production in differentiated
3T3-LI cells were examined. Dose response experiments (0.100uM) showed
that the C9-T10 isomer stimulated and T10-C12 CLA reduced adipocyte lipid
and leptin secretion. In time course experiments (0-11 days), a phasic
profile was evident with aa late fall in leptin secretion. These studies
demonstrate that CLA isomers either stimulate or inhibit adipose lipid
accumulation and leptin production, depending on isoform type and concentration.
The results also suggest that leptin production is greatest early during
lipid accumulation and decreases as lipid storage expands.
Supported by a grant from the Dairy Farmers of Canada
