Adipose tissue ob mRNA expression in humans: discordance with plasma leptin and relationship with adipose TNFalpha expression.

Elevated plasma leptin levels are found in obese humans, suggesting a defect in the function of leptin in regulating body weight and adiposity. In 53 subjects covering a broad range of adiposity, we examined the relationships between plasma leptin, adipose tissue ob mRNA levels, and adipose tissue TNF mRNA. There was a highly significant correlation between plasma leptin levels and every index of adiposity. In contrast, the relationship between ob mRNA levels and adiposity was weak. Adipose tissue from obese subjects demonstrated higher ob mRNA levels than adipose tissue from lean subjects (lean: 0.49+/-0.05; obese 0.87+/-0.09 arbitrary units, P< 0.05). However, there was no significant correlation between body fat and ob mRNA level. In addition, there was no significant relationship between ob mRNA levels and plasma leptin levels, which were measured in the same subjects. In addition to the measure of ob mRNA levels, adipose TNF mRNA levels were measured in 18 subjects. TNF mRNA levels varied with ob mRNA levels (r = 0.44, P = 0.06). These data show that plasma leptin levels are not directly related to adipose tissue ob mRNA levels, suggesting posttranscriptional regulation of leptin expression, either at the level of the adipocyte, or by alteration of plasma leptin degradation or clearance. In addition, the parallel changes in ob and TNF mRNA in adipose tissue suggest that these two important factors in the defense against obesity may be regulated similarly.