Clinical implication of serial leptin measurement in subjects with type 2 diabetes mellitus

Plasma leptin concentration is closely associated with body fat in humans, with energy restriction inducing a greater decrease in plasma leptin than in body fat. Since adequate energy restriction is mandatory in diet therapy of diabetes mellitus especially in obese subjects, the present study was undertaken to evaluate the clinical implication of serial leptin measurement in the management of diabetic patients. Fifty-four consecutive subjects with type 2 diabetes, who were subjected to adjusted energy restriction during hospitalization, were enrolled in the study. During their hospitalization period (24+/-4 days), plasma leptin concentrations decreased from 6.9+/-0.7 to 5.7+/-0.6 microg/l (P<0.0001) in the overall subjects, and the %change in plasma leptin (-13.9%) was greater than the %changes in body mass index (BMI) and percent body fat (-1.7% and -4.7%, respectively). The %change in plasma leptin was positively correlated with the %changes in BMI and plasma C-peptide (r=0.526, P<0.0001 and r=0.446, P<0.002, respectively) and negatively with a %change in plasma ketone bodies (r=-0.516, P<0.005). Multiple regression analysis revealed that the %changes in BMI and plasma C-peptide were independent determinants of the %change in plasma leptin. In addition, 38 subjects were followed up after discharge. Three months after discharge, plasma leptin concentrations significantly increased by 25.6%, which was again much greater than the %change in BMI (+0.9%). In 28 subjects who showed increase in plasma leptin levels after discharge, BMI was also increased. In contrast, the remaining 10 subjects without the increase in plasma leptin kept their BMI unchanged. Throughout the observation period, the changes in plasma leptin were prominent in the subjects with BMI greater than 25 kg/m2. In conclusion, plasma leptin concentrations showed greater changes than the alterations in anthropometric indexes during the observation period. Serial leptin measurement may be useful to estimate adherence to energy restriction especially in obese subjects with type 2 diabetes.