Glycine betaine excretion is not directly linked to plasma glucose concentrations in hyperglycaemia

Diabetes mellitus subjects, type 1 and type 2, have increased glycine betaine excretion compared to normal subjects that correlated with plasma glucose and HbA(1C) concentrations. The current study was undertaken to determine whether elevated glucose concentration directly increases glycine betaine excretion in an animal model. Non-pregnant female Coopworth sheep received an intravenous glucose load (12.5,25 and 50% w/v; rate 200 ml/h) for 6 h followed by a 12 h physiological saline washout (0.9% w/v). Plasma and urine samples were analyzed for glycine betaine and glucose. Urine volumes and osmolality were also measured. Using the non-parametric Kruskal Wallis analysis of variance test we found no difference in glycine betaine excretion between glucose loaded and saline infused control animals (P=0.861). However, a significant negative correlation (r=-0.28, P<0.001) was observed between urine osmolality and glycine betaine excretion independent of treatment. We conclude that acute elevations of plasma glucose concentrations did not result in increased glycine betaine excretion and is therefore unlikely to be directly responsible for elevated glycine betaine excretion observed in diabetes mellitus subjects.