The effect of bacterial infections on ketone concentrations in rat liver and blood and on free fatty acid concentrations in rat blood.

The concentrations of cytoplasmic lactate and pyruvate and the NAD+/NADH ratio and the concentrations of mitochondrial acetoacetate, beta-hydroxybutyrate, and the NAD+/NADH ratio were determined in normal, fed, and fasted rats, and in rats infected with Streptococcus pneumoniae, Francisella tularensis, and Salmonella typhimurium. The various infections were found to have little or no effect on the cytoplasmic parameters. In normal rats, fasting caused a marked increase in blood and hepatic ketone concentration and in serum free fatty acid content. Fasted infected rats, however, did not show the increase in ketone bodies or serum free fatty acids normally associated with fasting alone. The mitochondrial NAD+/NADH ratio increased as the infections progressed, reversing the normal trend. The introduction of an infection during the fasting state when ketone bodies and serum free fatty acids were elevated caused a marked depression in their concentration. These data have led to a postulation of decreased lipolysis in the infected host to account for the lowered hepatic and blood ketone bodies and the decreased level of serum free fatty acids.