Circulating apelin level in relation to nutritional status in polycystic ovary syndrome and its association with metabolic and hormonal disturbances

Abstract

The aim of the study was to analyse relationships between plasma apelin-36 and apelin-12 levels, nutritional status, insulin resistance and hormonal disturbances, as well as plasma adiponectin, leptin and resistin concentrations in PCOS women. A cross-sectional study involving 87 PCOS (48 obese) and 67 non-PCOS women (36 obese). Anthropometric parameters and body composition were determined. Serum glucose, androgens, FSH, LH, SHBG, insulin, apelin-36, apelin-12, adiponectin, leptin and resistin were measured in the fasting state. Plasma apelin-36 and apelin-12 levels were significantly higher in normal weight women than in the obese women with PCOS (3·1 ± 2·2 vs 1·2 ± 0·7 μg/l, P < 0·001; 2·9 ± 2·4 vs 0·5 ± 0·7 μg/l; P < 0·001 respectively). Both plasma apelin-36 and -12 levels correlated positively with adiponectin levels, and inversely with leptin or resistin levels. There was a negative correlation between plasma apelin-36, apelin-12 and serum LH levels. In addition, an inverse correlation between apelin-12 level and LH to FSH ratio was found. In multiple regression analysis 9% of LH variability was explained by apelin-12 levels (β = -0·14; P < 0·001). Nutritional status seems to have different effects on apelin release, particularly, its active isoform, in women with PCOS compared with women without PCOS. This may be partially caused by changes in leptin and resistin secretion and may enhance pituitary-ovarian axis disturbances. The association between both isoforms of apelin and insulin resistance seems to be bidirectional.