Hepatic metabolism and transport in thiamine deficiency

Thiamine deficiency often accompanies alcoholism which causes liver disease, but the role of thiamine depletion per se in modifying hepatic metabolism and function is uncertain. Thiamine is the coenzyme for transketolase and pyruvate decarboxylase in tissues. Decreased pyruvate decarboxylase activity theoretically may impair synthesis of acetyl CoA and then of ATP, the ultimate tissue energy source. In this study, hepatic metabolism, especially ATP stores, and the transport of Rose Bengal across the liver, were assessed in rats with encephalopathy due to dietary thiamine deprivation, and in asymptomatic pair-fed controls. Compared to controls, in the thiamine-deficient rats, (a) hepatic transketolase and pyruvate decarboxylase activity were 89 and 74% lower (P<0.01) respectively; however, (b) hepatic acetyl CoA and ATP concentrations decreased only 21 and 12% (P<0.01), hepatic morphology was normal, and transport of Rose Bengal-¹³¹l across the liver was unimpaired. Depressed hepatic pyruvate decarboxylase activity and ATP concentration in thiamine-deficient rats in vivo responded to exogenous thiamine much more slowly than it did in brain, heart or kidney. In vitro, however, hepatic pyruvate decarboxylase activity rose briskly when exogenous thiamine pyrophosphate was added, indicating that the apoenzyme was not impaired. In conclusion, in severe thiamine deficiency, hepatic acetyl CoA and ATP stores are only slightly decreased, and hepatic transport of Rose Bengal is normal.