Bassi livelli plasmatici di leptina nel diabete tipo 2 in buon controllo metabolico non sono in relazione con massa grassa e grado di insulino-resistenza

Plasma leptin concentrations are positively correlated with measures of obesity, and leptin metabolism is interrelated with insulin secretion and action. However, data in patients with type 2 diabetes mellitus are somewhat scarce and inconsistent. We have evaluated plasma leptin levels in type 2 diabetes in relation to obesity and insulin resistance, comparing male subjects with obesity and diabetes (n = 10), only obesity (n = 10), or normal weight (n = 10). Obese subjects with and without diabetes had similar degrees of adiposity (BMI 33.0 ± 2.0 and 34.5 ± 2.7 kg/m²; waist circumference 112 ± 8 and 113 ± 7 cm; and fat mass 32.4 ± 4.1 and 32.9 ± 4.9 kg). Insulin resistance measured by hyperinsulinemic euglycemic clamp was similar in diabetic obese and only obese subjects. Fasting plasma leptin concentrations were significantly lower in the diabetic obese subjects than in the only obese ones (9.5 ± 4.1 vs 24.3 ± 10.2 ng/ml, p <0.001). In the three groups combined, plasma leptin was correlated positively with fasting plasma insulin (r = 0.71, p <0.001) and negatively with whole-body insulin sensitivity expressed as M/I (r = -0.84, p <0.001). These results support factors other than obesity and insulin resistance as responsible for the reduced plasma leptin levels per body fat in diabetic patients, relative hypoinsulinemia likely playing a role.