Association of High Intracellular Calcium Levels with Insulin Resistance in Women with Polycystic Ovary Syndrome

Oh, Jee Young; Lee, Hye Jin; Hong, Young Sun; Chung, Hye Won; Sung, Yeon Ah

Abstract

BACKGROUND: Insulin resistance is an intrinsic defect of polycystic ovary syndrome (PCOS), and elevated levels of cytosolic free calcium in insulin target cells may cause insulin resistance. To our knowledge, the relationship between intracellular calcium and insulin resistance in PCOS has not been investigated. The purpose of this study was to determine whether the levels of intracelluar calcium are changed and if they have any association with insulin resistance in women with PCOS.
METHODS
The intracellular calcium levels in the platelets and the insulin sensitivity were measured by fluorescent spectrophotometry and the euglycemic hyperinsulinemic clamp technique, respectively, in 16 women with PCOS and 6 normal cycling women. A 2h, 75 g oral glucose tolerance test was performed to determine the glucose tolerance.
RESULTS
The insulin sensitivity measured by the glucose disposal rate(the M-value), was significantly lower in women with PCOS(4.6+/-1.5mg/kg/min vs. 7.0+/-1.3mg/kg/min, p<0.01), but the intracellular calcium levels were significantly higher in women with PCOS compared to the controls(122.7+/-36.7 vs 59.1+/-29.3mmol/L, p<0.01). When the women with PCOS were divided into the overweight or obese(n=9, BMI ?23kg/m2) and lean(n=7, BMI<23kg/m2) groups, both groups had significantly lower M values compared to the control subjects(3.9+/-1.3, 5.5+/-1.2 vs. 7.0+/-1.3mumg/kg/min, p<0.001), and these levels between the overweight/obese and lean PCOS groups showed a significant difference(p<0.001). The overweight/ obese and lean women with PCOS had significantly higher levels of intracellular calcium compared to the control subjects(131.3+/-39.6, 111.7+/-31.8 vs. 59.1+/-29.3nmol/L, p<0.01), but these levels did not differ significantly between the overweight/obese and lean women with PCOS. The intracellular calcium levels showed a significant positive correlation with age, and a negative correlation with the M value(r=-0.55, p<0.05). The BMI-adjusted partial correlation showed marginal significance between elevated levels of intracellular calcium and insulin sensitivity (r=-0.47, p=0.07).
CONCLUSION
Women with PCOS showed both insulin resistance and increased levels of intracellular calcium compared to the control subjects. Increased levels of intracellular calcium were associated with insulin resistance in women with PCOS.