Leptin levels in diabetic and nondiabetic subjects

The role of leptin in human pathophysiology elicits considerable interest in view of its potential role as a treatment tool for obesity and other insulin resistant states, like type 2 diabetes mellitus (T2DM). Leptin has been extensively studied in obese humans, and much less so in other pathologic conditions. Leptin level has been reported to correlate with percent body fat mass (%FM), fasting serum insulin (FPI), insulin sensitivity and blood pressure. The aim of this study was to compare the leptin concentration, and its relationship with some anthropometric and biochemical parameters related to insulin resistance in 140 moderately obese type 2 diabetics (T2DM) and 160 age and weight matched non-diabetic controls in order to get a better insight into the possible role of leptin in the metabolic abnormalities of diabetes. The leptin levels were lower in the diabetic population only when both sexes were combined (p<0.05) and were higher in the females of both groups. Among the nondiabetics, the leptin levels appeared to be related to BMI, %FM, HDL and FPI, while this was not the case in the diabetics. After correction for BMI, leptin appeared to be correlated with the FPI levels only in the non-diabetic females. When plasma leptin was included in a multiple linear regression model with plasma leptin as a dependent variable, BMI, W:Hr and FPI levels were significantly related to leptin in the non diabetic population, while no relationship reached the level of statistical significance among the diabetics, with the exception of the borderline value for the FPI (p=.052). In conclusion, leptin levels were independent of any of the parameters examined in our diabetic population, possibly due to the progressive loss of the normal mechanisms of leptin regulation with advancing disease. Conclusive data can only be obtained from the longitudinal study of a cohort of newly diagnosed diabetic subjects.