Origin of Fasting Ketosis in the Rat Following a Diet Low in Choline and Protein

Abstract

When rats are fasted they develop a ketonemia and frequently it is high enough to produce a measurable ketonuria. The height of the ketosis is determined by many factors. When the diet is low in choline and in protein the liver becomes fatty 1 and on subsequent fasting there is a very substantial ketonuria. 2 3 It seemed probable that this was incident to the fatty liver. However, since we have been unable to obtain a good correlation between the degree of ketosis and the amount of fat in the liver we have examined the factors which determine the extent of the fasting ketosis in question.

Deuel, et al., 4 have found that choline administered during the period of fasting does not appreciably affect the ketosis of fasting fatty liver rats. We have confirmed this observation. Neither does the addition of choline to the diet prior to fasting, although it prevents the accumulation of fat in the liver, influence the subsequent ketosis. The only possibility left is that the ketosis of fasting rats is determined by their protein intake prior to fasting. This has been demonstrated in diets containing variable concentrations of casein, all containing 0.5% choline hydrochloride which insured livers low in fat when the fasting was commenced. The “0” protein diet was composed of sucrose 60, cod liver oil 2.5, Crisco 30, Standard Salt Mixture (Osborne and Mendel) 5, and Yeast Extract (Vitamin B Powder, The Harris Laboratories) 2. The other diets contained 5, 15 and 30% of casein respectively at the expense of the sucrose. Each group consisted of 5 adult male rats with an average body weight of 324 g. They had been receiving the special diets for 10 days before fasting was commenced.