Chronic oxidative stress leads to the accumulation of reversibly oxidised thiamine derivatives in tissues: effects of thiamine and cholecalciferol.

There is limited data on oxidised thiamine (vitamin B1) derivatives in animal and human tissues. Some studies suggest that oxidative stress (OS) leads to their formation. This study aimed to estimate the proportion of reversibly oxidised (disulfide) thiamine derivatives in the total vitamin B1 pool in rat tissues exposed to various chronic OS forms, and to investigate the possibility of reducing these derivatives to a cyclic form. Rat models of thiamine deficiency and chronic alcoholism were used in experiments. The thiochrome method was used to analyse thiamine, with pretreatment of samples with a reducing agent and hydrolysis of thiamine phosphates performed separately under optimal conditions. The analysis of active and oxidised forms of vitamin B1, standard markers of OS and blood levels of 25(OH)D3 was performed in tissue samples. The corrective effect of thiamine and vitamin D3 supplementation was studied. In both models of OS, there was a decrease in the proportion of the active (cyclic) form of thiamine and a sharp increase in its oxidised (disulfide) forms, reaching levels of ∼50-70% of the total thiamine pool. High doses of thiamine (2 mg/kg) or vitamin D3 (2000 IU/kg) completely or partially normalized the situation with regard to OS indicators and also reduced the proportion of oxidised thiamine. Our results show that OS causes thiamine deficiency and tissue accumulation of thiamine disulfide derivatives. Red blood cell thiamine disulfide levels serve as a reliable marker of chronic OS, whereas a positive vitamin D deficiency test can mask actual vitamin B1 deficiency.