Obesity and insulin resistance associated with lower plasma vitamin B12 in PCOS

Polycystic ovary syndrome (PCOS) shares some or most components of metabolic cardiovascular syndrome, manifested by abdominal obesity, insulin resistance, dyslipidaemia and atherosclerosis. It has been previously demonstrated that folate and vitamin B12 treatment improved insulin resistance in patients with metabolic syndrome. This study first investigated whether PCOS patients have lower or higher vitamin B12, folate and homocysteine concentrations when compared with healthy, age and body mass index matched controls, and, then examined associations between vitamin B12, folate, homocysteine and insulin resistance and obesity in PCOS patients. Homocysteine concentrations and homeostasis model assessment index were higher, whereas concentrations of vitamin B12 were lower in PCOS patients with insulin resistance compared with those without insulin resistance. Serum vitamin B12 concentrations were significantly lower in obese PCOS women in comparison with obese control women (P < 0.05). Fasting insulin, insulin resistance and homocysteine are independent determinants of serum vitamin B12 concentrations in PCOS patients. Insulin resistance, obesity, and elevated homocysteine were associated with lower serum vitamin B12 concentrations in PCOS patients.