Glucose flux in controlled hyperglycaemia before and after oral glucose ingestion in men with mild type 2 diabetes

Could thiamine pyrophosphate be a regulator of the nitric oxide synthesis in the endothelial cell of diabetic patients?

Thiamine (Vitamin B1) is considered an essential micronutrient for humans; its deficient intake brings about the Wernicke-Korsakoff syndrome (encephalopathy and psychosis) or beriberi (a neurological and cardiovascular disease). Once thiamine enters the cells it is phosphorylated by thiamine pyrophosphokinase (TPPK), and converted into the coenzyme thiamine pyrophosphate (TPP), the active form of thiamine. TPP is a relevant cofactor for transketolase (TK), α-ketoglutarate dehydrogenase (αKDH), and pyruvate dehydrogenase (PDH), all these enzymes are fundamental for glucose metabolism. Diabetes mellitus (DM), however, is considered both a deficient thiamine and deficient energy state, as a consequence of the limited TPP synthesis. Recent evidences have shown that the administration of thiamine or lipid-soluble derivatives, such as benfotiamine (developed to improve the bioavailability of thiamine), has positive effects in the diabetic patient (after thiamine is transformed into TPP). For this reason, administration of supplements with TPP in the diabetic patients is recommended to avoid complications, like neuropathy and nephropathy. It has been suggested that these beneficial effects are a consequence of the activation of TK (pentose pathway) or the PDH complex in mitochondria. Nitric oxide (NO) is synthesized by the endothelial cell and is also an important element for the viability and functionality of this cell type. However, in the DM patient, a deficient synthesis of NO has been reported. It is relevant to mention that recent evidences have led to propose mitochondrial activity as an important regulator of nitric oxide synthesis (ON). We consider that the exogenous administration of TPP facilitates the utilization of this molecule, regulating some metabolic processes such as phosphorylation of thiamine by TPPK, energy consumption (ATP), as well as mitochondrial activity, inducing eventually NO synthesis. If this is confirmed, the administration of TPP to the diabetic patient would provide additional protection to endothelial cells, reducing the risk of vascular damage, to which the diabetic patient is highly susceptible.