The association between fasting serum leptin and specific insulin, proinsulin and insulin sensitivity in different glucose tolerance individuals

Objective To investigate the relationship between fasting serum leptin and specific insulin (SI), proinsulin (PI) and insulin sensitivity. Methods This study included 54 normal glucose tolerance (NGT) subjects, 33 impaired glucose tolerance (IGT) subjects and 47 newly diagnosed patients with type 2 diabetes mellitus (DM). Specific insulin and proinsulin during oral glucose tolerlance test (OGTT) at 0, 1/2, 1 and 2h and fasting serum leptin were measured by radioimmunoassay. Results (1) Sex, body mass index (BMI) and insulin sensitivity index (ISI) were three major factors related to the concentration of serum leptin, while serum leptin level did not relate to SI, PI and PI/SI during OGTT at 0, 1/2, 1 and 2h. (2) After adjusted by sex and BMI, there was no significant difference of serum leptin levels among three groups; while PI/SI was higher and ISI was lower in DM group than those in NGT and IGT groups (P0.01). Conclusion Sex, BMI and ISI are the major factors that affect the concentration of serum leptin; There is no significant difference of serum leptin level in different glucose torlerant states; DM group shows higher PI/SI and lower insulin sensitivity (calculated from SI levels).