d-Ribose as a Contributor to Glycated Haemoglobin.

Glycated haemoglobin (HbA1c) is the most important marker of hyperglycaemia in diabetes mellitus. We show that d-ribose reacts with haemoglobin, thus yielding HbA1c. Using mass spectrometry, we detected glycation of haemoglobin with d-ribose produces 10 carboxylmethyllysines (CMLs). The first-order rate constant of fructosamine formation for d-ribose was approximately 60 times higher than that for d-glucose at the initial stage. Zucker Diabetic Fatty (ZDF) rat, a common model for type 2 diabetes mellitus (T2DM), had high levels of d-ribose and HbA1c, accompanied by a decrease of transketolase (TK) in the liver. The administration of benfotiamine, an activator of TK, significantly decreased d-ribose followed by a decline in HbA1c. In clinical investigation, T2DM patients with high HbA1c had a high level of urine d-ribose, though the level of their urine d-glucose was low. That is, d-ribose contributes to HbA1c, which prompts future studies to further explore whether d-ribose plays a role in the pathophysiological mechanism of T2DM.