Metformin increases serum concentration of high molecular weight (HMW-adiponectin) in nondiabetic obese subjects

Obesity is associated with low-intensity chronic systemic inflammation. To evaluate the efficacy of two different doses of metformin in comparison with placebo on increased serum levels of high molecular weight (HMW) adiponectin. An experimental design was developed with a crossover complete treatment and balanced design; 28 female and eight male nondiabetic obese adults participated. All participants received, during a week and in randomized order: placebo or metformin 500 or 850 mg twice daily; there was a week washout period between each treatment. The HMW adiponectin serum concentration (0 and 120 minutes) at the end of each treatment was measured. Analyses of variance (ANOVA), Bonferroni test, and size effect calculations were performed. Differences in concentrations of HMW adiponectin (t0', t120') were measured for each treatment by ANOVA, having values of p = 0.03 and 0.002, respectively. The post hoc analysis reported differences favoring treatment with metformin 850 mg (p = 0.025). The sizes of the effect at times t0 and t120 for metformin 500 mg were 34 and 35%, and for metformin 850 mg, 65 and 84%, respectively.