Polymorphism of glycogen synthetase gene in polycystic ovary syndrome

Polycystic ovary syndrome is a heterogeneous disorder associated with a moderate degree of insulin resistance and a higher risk of developing NIDDM. The exact mechanism of insulin resistance is unclear. This study examines the frequency of an Xbal polymorphism of the glycogen synthetase gene (A2 allele) as a marker of insulin resistance and seeks to relate the presence of the A2 allele to indices of insulin sensitivity in women with polycystic ovary syndrome (PCOS).

Insulin sensitivity was assessed by fasting insulin measurements, as well as following oral glucose tolerance test. An i.v. insulin tolerance test was performed to measure the rate of endogenous blood glucose disposal following an i.v. bolus of insulin. Restriction fragment length polymorphism was performed with Xbal digestion of PCR amplified product to detect the presence of A1 and A2 allele.

Seventy-one obese (BMI > 25.1) and 19 non-obese (BMI < 25) women with PCOS, and 62 controls (33 obese and 29 non-obese) participated in the study.

Obese PCOS had significantly higher fasting insulin (P = 0.002) compared to obese controls. There was no difference between non-obese PCOS and controls. Twenty per cent of obese PCOS had impaired glucose tolerance. The A1A2 genotype was detected in 16 of the 150 (10.7%) subjects examined. Of these, 11/88 (12.5%) were PCOS and 5/62 (8%) were controls. The A2A2 genotype was not present in any of the subjects. The A1A2 genotype was not detected in any of the subjects with impaired glucose tolerance. There was no significant difference in the incidence of the A1A2 genotype between PCOS and controls or between the individual groups. There was no association between the presence of the A1A2 genotype and indices of insulin sensitivity.

The Xbal polymorphism (A2 allele) of the glycogen synthetase gene was not over represented in the PCOS subject and did not relate to the indices of insulin sensitivity or glucose intolerance.