Sex differences in the control of plasma concentrations and urinary excretion of glycine betaine in patients attending a lipid disorders clinic

Objectives: To find whether the control of betaine metabolism differs between male and female patients and identify the effects of insulin and other hormones. Design and methods: Data from non-diabetic lipid clinic patients (82♀ and 76♂) were re-analyzed by sex. Data on insulin, thyroid hormones and leptin were included in models to identify factors affecting the circulation and excretion of betaine and its metabolites. Results: Different factors influenced plasma concentrations and urinary excretion of betaine, dimethylglycine and homocysteine in males and females. In males, apolipoprotein B (negative), thyroid stimulating hormone (positive) and insulin (negative) predicted circulating betaine, consistent with betaine-homocysteine methyltransferase mediated control. In females, insulin positively predicted plasma dimethylglycine. Urinary betaine excretion positively predicted circulating homocysteine in males (p < 0.001), whereas dimethylglycine excretion (also indicating betaine loss) was a stronger positive predictor (p < 0.001) in females. Carnitine affected betaine homeostasis. Conclusions: Betaine metabolism is under endocrine control, and studies should use sex stratified groups.