Objective: The regulatory processes that modulate adiponectin production and the mechanisms involved in nuclear factor kB (NF-kB) transcriptional activity in human adipocytes are not yet fully known. The aim of our study was to evaluate the inter-relationships between body fat, fat distribution, systemic inflammation, insulin resistance, leptin and the serum and subcutaneous adipose tissue gene expression levels of tumor necrosis factor-alpha (TNF-alpha), adiponectin and the inhibitor kappa B-alpha (IkB-alpha), in subjects with a wide range of body mass index (BMI). We also wanted to determine which of these variables was most closely related to adiponectin gene expression and adipocyte NF-kB transcriptional power.
Methods: A total of 27 women aged between 50 and 80 years, with BMI ranging from 22.1 to 53.3 kg/m(2), were studied. In all subjects BMI, waist circumference, body composition by dual X-ray absorptometry, triglycerides, cholesterol, high-density lipoprotein cholesterol (HDL-Ch), glucose, insulin, homeostasis model assessment of insulin resistance (HOMA), high-sensitive C-reactive protein (hs-CRP), serum adiponectin, leptin and TNF-alpha were evaluated. Subcutaneous adipose tissue biopsies were taken from the abdomen of all subjects and the mRNA levels of adiponectin, TNF-alpha and IkB-alpha were determined.
Results: BMI and waist circumference were associated positively with leptin, HOMA, and hs-CRP, and negatively with HDL-Ch; waist was also associated with adiponectin and IkB-alpha mRNA. HOMA was negatively associated with serum adiponectin and adiponectin mRNA. Hs-CRP was negatively associated with IkB-alpha mRNA, and was positively associated with HOMA. Step-down multiple regression analysis was performed to determine the joint effects of BMI, waist circumference, triglycerides, HDL-Ch, HOMA, hs-CRP, leptin, serum and TNF-alpha mRNA on adiponectin gene expression: waist circumference and leptin were both included in the best fitting regression equation for predicting adiponectin gene expression (R(2)=0.403, P=0.006). Stepwise multiple regression analysis was performed, considering IkB-alpha mRNA as a dependent variable and BMI, waist, HDL-Ch, HOMA, hs-CRP and adiponectin mRNA as independent variables. Adiponectin mRNA was the only variable to enter the regression (R(2)=0.406, P<0.001).
Conclusion: Our results suggest that abdominal adiposity and leptin are independent predictors of adiponectin gene expression and that in human adipocytes, adiponectin gene expression is strongly related to IkB-alpha mRNA.