Leptin secretory burst mass correlates with body mass index and insulin in normal women but not in women with polycystic ovary syndrome

Abstract

Leptin secretion exhibits a pulsatile, circadian pattern and may play a role in reproduction. No previous studies have compared leptin secretory burst characteristics in normal eumenorrheic women and women with polycystic ovary syndrome (PCOS) who are appropriately matched for body mass index (BMI). To determine if leptin secretory burst characteristics and/or the relationships of BMI, insulin, or testosterone to these characteristics differ between PCOS and normal women, we studied 9 normal eumenorrheic women and 9 women with PCOS. Each woman underwent blood sampling every 10 minutes for 24 hours to measure leptin and insulin under controlled conditions. Leptin secretory bursts were identified and characterized using multiparameter deconvolution procedures (Deconv), and the 24-hour periodicity of leptin was characterized with cosinor analysis. Relationships between BMI, area under the curve (AUC) insulin, and testosterone and leptin secretory burst characteristics in PCOS and normal women were sought using linear regression. There were no significant differences in mean serum leptin concentrations or in secretory burst characteristics between PCOS and normal women. Although the 24-hour serum leptin concentration correlated with BMI in both normal and PCOS women, leptin secretory burst mass correlated with BMI only in normal women. Similarly, the 24-hour serum leptin concentration correlated with serum insulin AUC in both normal and PCOS women; but insulin AUC correlated with leptin burst mass only in normal women. Although there was a strong trend toward a correlation between both mean 24-hour serum leptin concentration and leptin secretory burst mass with the serum testosterone concentration in normal women, such trends were not seen in PCOS women. Both normal and PCOS women exhibited a diurnal rhythm of leptin secretion with the peak occurring at night. However, neither the peak amplitude nor the timing of the peak amplitude differed between normal and PCOS women. The presence of strong relationships between BMI and insulin with both mean serum leptin and leptin secretory burst mass in normal women as opposed to PCOS women suggests that the mechanisms subserving leptin secretion differ in these 2 groups.