Anti-ketogenic effect of glucose in the lactating cow deprived of food

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Abstract
The effect of a constant glucose infusion on ketosis that is observed when dairy cows are deprived of food in early lactation was studied. Cows in early lactation were first deprived of food for 96 h to induce a fasting ketosis. Glucose was then infused i.v. at a constant rate of 0.75 g/min for 48 h while food deprivation was maintained. At the end of this 48 h period, blood and liver ketone-body concentrations had decreased to values well below those found in healthy fed cows. On the assumption that the anti-ketogenic effect of glucose was mainly due to suppression of hepatic ketogenesis, 2 anti-ketogenic mechanisms were identified. These were a decrease in the availability of free fatty acids for hepatic oxidation and anti-ketogenic changes within the liver itself. These latter anti-ketogenic changes were 2-fold. The 1st was a major increase in the hepatic concentrations of citrate and 2-oxoglutarate. The 2nd was an increase in the degree of oxidation of the hepatic cytosol. Both intrahepatic changes may indicate an augmentation of the quantity of oxaloacetate available for condensation with acetyl-CoA derived from fat oxidation. Hepatic glycerol 1-phosphate concentration fell substantially after glucose infusion. Glucose infusion into fed cows produced qualitatively similar effects to those observed in the unfed cows; but blood and liver ketone-body concentrations were not decreased to the same extent in the fed cows as in the unfed cows.