The Role of Dietary Fat in Protecting the Rat against Oxythiamine-produced Thiamine Deficiency

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Abstract
Dietary fat decreases the thiamine requirements of the rat and provides extended protection against the thiamine antagonist oxythiamine. We have measured the changes in the activities of three major thiamine-requiring enzymes of the brain and liver in rats fed low fat and high fat oxythiamine diets. Brain activities were unchanged with both diets. Liver and blood transketolase activities were decreased to the same extent with both diets. With the high fat oxythiamine diet, the oxidation of pyruvate by the liver was decreased to 51% of the control, whereas with the low-fat oxythiamine diet, it was decreased to 26% of the control (significantly lower than for the high-fat oxythiamine diet). These data provide additional evidence to support the idea that dietary fat spares thiamine by supplying energy through a route which requires a minimum of thiamine. On the basis of the results from our study, it appears that the cause of death in the thiamine deficiency produced by oxythiamine is a decreased ability of the rat to convert dietary carbohydrate into utilizable energy. The importance of the hexose monophosphate shunt in the metabolism of fat is discussed.