Adipocyte insulin action during the normal menstrual cycle

Abstract

The relationship between the menstrual cycle and insulin sensitivity is unclear. The aim of this study was to investigate insulin sensitivity during the normal menstrual cycle using the physiological insulin target organ adipose tissue. A total of 23 normal healthy volunteers were studied, nine of whom were in the follicular phase, and 14 of whom were age and body mass index-matched and in the luteal phase of the menstrual cycle. Adipocyte insulin receptor binding was measured and adipocyte insulin action was assessed by measuring initial rates of 3-O-methylglucose uptake and by inhibition of lipolysis. The maximum specific insulin receptor binding was significantly higher in subjects studied during the follicular phase of the menstrual cycle compared to subjects studied during the luteal phase (1.81 ± 0.13 versus 1.36 ± 0.15% per 10 cm2 cell surface, P < 0.05). Maximum rates of 3-O-methylglucose transport were 1.70 ± 0.22 versus 1.75 ± 0.22 pmol/10 cm2/5 s in the follicular and luteal phase respectively and were not significantly different between the two groups. The maximum percentage lipolysis inhibition observed was 42.5 ± 7.5% in the follicular phase and 39.9 ± 7.4% in the luteal phase (not significant). This study demonstrated that there is a reduction in insulin receptor binding in the luteal phase of the normal ovulatory menstrual cycle. The post-receptor action of insulin is not affected between the two phases of the menstrual cycle.