Polycystic ovary syndrome (PCOS) is a chronic dysfunction associated with
obesity and metabolic disorders that can be ameliorated by treatment with
metformin. Brown adipose tissue (BAT) has been recently identified in adult humans, and irisin is a
myokine that induces BAT formation. The aim of this randomized controlled trial was to evaluate whether a short term treatment with
metformin alters BAT activity and plasma irisin levels in women with PCOS. The participants were randomly assigned to receive
metformin (1500 mg/day, n=21) or placebo (n=24) during 60 days. BAT activity was assessed by
18F-FDG positron emission tomography-computed tomography (PET-CT) and plasma irisin levels were measured by
enzyme immunoassay. The groups were similar in age, body measures, metabolic profile and PCOS phenotypes. BAT activity did not change significantly in the women treated with
metformin (median Δ SUVmax=-0.06 g/ml, interquartile interval -2.81 to 0.24 g/ml, p=0.484, Wilcoxon's test) or placebo (median Δ SUVmax=0.98 g/ml, interquartile interval -2.94 to 4.60 g/ml, p=0.386). In addition, plasma irisin levels remained unchanged in the groups treated with
metformin (median Δ=-98 ng/ml, interquartile interval -366 to 60 ng/ml, p=0.310) and placebo (median Δ=28 ng/ml, interquartile interval -1260 to 215 ng/ml, p=0.650). These results suggest that in PCOS women BAT activity and plasma irisin levels may not change after a brief treatment with
metformin.