Tecido adiposo marrom em mulheres com Síndrome dos Ovários Policísticos: relação com medidas corporais, níveis de irisina no plasma e uso de metformina

Abstract

The Polycystic Ovary Syndrome (PCOS) is a chronic endocrine-reproductive dysfunction associated with obesity and metabolic disorders. Brown adipose tissue (BAT), which has high metabolic activity, has been recently identified in human adults through positron emission tomography/computed tomography (PET/CT). Irisin is a myokine that induces browning of white adipocytes. This study was designed to evaluate (i) if BAT activity is altered in women with PCOS, (ii) to correlate irisin levels in women with PCOS, and (iii) if these parameters can be altered by short-term treatment with metformin. The study included 70 women aged 18 to 45 years, divided into a PCOS group (n=45) and a healthy control group (n=25), matched for age and body mass index (BMI). Participants were recruited between April 2015 and September 2017, from two centers. BAT activity was measured using PET-CT with 18F-FDG, while plasma irisin levels were analyzed using ELISA. Total BAT activity was significantly reduced in women with PCOS (standardized uptake value [SUVmax]: median 7.4 g/ml, interquartile range 0.9 to 15.4) compared to controls (median 13.0 g/ml, interquartile range 4.7 to 18.4, p = 0.047). However, this difference was not maintained significant after adjusting for covariates such as waist circumference, a marker of central adiposity. In the PCOS group, total BAT activity was inversely correlated with BMI (Spearman's r = -0.63, p<0.001) and waist circumference (r = -0.59, p<0.001) but not with plasma irisin levels (r = -0.25, p=0.10). The 45 participants in the PCOS group were randomized into a metformin subgroup (1,500 mg/day, for 60 days, n = 21) and a placebo subgroup (n = 24). Neither metformin nor placebo resulted in significant changes in any anatomical region of BAT evaluated or in plasma irisin levels. In conclusion, BAT activity was reduced in women with PCOS, possibly due to increased central adiposity. In women with PCOS, BAT activity did not correlate with plasma irisin levels and did not change after short-term treatment with metformin.