INSULIN AND BODY-FAT DISTRIBUTION HAVE NO DIRECT EFFECT ON PLASMA LEPTIN LEVELS IN OBESE CAUCASIAN WOMEN WITH AND WITHOUT TYPE-2 DIABETES-MELLITUS

Leptin, a hormone produced by adipose tissue, is potentially involved in the regulation of adiposity.The effects of insulin and body fat dis tribution on human plasma leptin have not yet been clearly defined. Th e present study investigated the relationships between plasma leptin a nd total and regional body fat parameters measured by anthropometry an d bienergetic absorptiometry associated or not with computed tomograph y, taking glucose metabolism into account. A cohort of 51 obese Caucas ian women (23 with normal glucose tolerance, 11 with impaired glucose tolerance, and 17 with Type 2 diabetes) was analysed. All non-diabetic subjects had an oral glucose tolerence test together with plasma gluc ose and insulin measurements. Moreover, a subgroup of 7 diabetic subje cts with failure to oral antidiabetic treatment was submitted to about 12 days of intensive subcutaneous insulin therapy. Plasma leptin was essentially dependent on total body fat mass (r=0.83, p < 0.0001, for the whole population), but not related to adipose tissue distribution. An independent correlation between leptin adjusted on body fat mass a nd fasting insulinaemia (R=0.72 p < 0.02) or C-peptide (R = 0.62, p < 0.03) was found significant only in the diabetic group. Insulin treatm ent was associated with a moderate and transient increase of plasma le ptin. The relative variations of plasma leptin levels were strongly ne gatively correlated with those of free fatty acids. The present data c onfirm that plasma leptin is not dependent on body fat distribution an d suggest an indirect effect of insulin on leptin secretion in clinica l conditions.