Relationship between testosterone, sex hormone binding globulin, angiopoietin related growth factor and insulin resistance in normal weight and obese men

Background: Angiopoietin related growth factor (AGF) is a liver derived factor that potently antagonizes obesity and insulin resistance (IR). Aim: The objective of this work is to determine AGF serum levels and evaluate its relationship with total testosterone (TT), calculated free testosterone (cFT), sex hormone binding globulin (SHBG), insulin and IR in normal weight and obese men. Subjects: A total of 60 men were included: twenty normal weight subjects with body mass index (18.5–24.7 kg/m^2) and 40 obese men with BMI (30–39.5 kg/m^2). Methods: Serum AGF was measured by enzyme linked immunosorbent assay. Serum TT, SHBG, and insulin were analyzed by chemiluminescent immunoassay. Results: Angiopoietin related growth factor was significantly lower in the obese group as compared with normal weight group. In all subjects, AGF correlated positively with TT and SHBG and negatively with 2 h oral glucose tolerance test (OGTT) glucose and fatty liver index (FLI). In normal weight group, AGF correlated positively with age, SHBG, fasting insulin, HOMA-IR, AST and ALT and negatively with BMI, TC and LDL-C. In the obese group, it correlated positively with BMI and negatively with TG. Multiple linear regression analysis revealed that SHBG and fasting glucose were positive predictors of AGF serum levels. In the total sample, SHBG correlated negatively with BMI, fasting glucose, fasting insulin, HOMA-IR, FLI and positively with AGF, QUICKI and HDL-C. Conclusion: The present results revealed for the first time an association between SHBG and AGF serum levels. It could be suggested that they overlap to regulate metabolic homeostasis in normal weight men and that the disturbed inter-relationship could contribute to the pathogenesis of insulin resistance and obesity. Moreover, the observed relationship between SHBG and AGF in the present study could clarify the unresolved controversies regarding specific mechanistic relationships between SHBG abnormalities and abnormalities in glucose homeostasis.