LIPID STORAGE UNDER ABNORMAL CONDITIONS 695 



elusions, on the basis of experiments in which fat or carbohydrate was for- 

 cibly fed over periods of three to six weeks. Ketonuria occurred only in 

 the fat-fed rats, in spite of the fact that the protein intake and nitrogen 

 excretion during fasting had been the same in the two groups. These 

 workers concluded 909 that the fasting ketosis is a reflection of accelerated fat 

 metabolism initiated during feeding, and continued after withdrawal of the 

 food. This phenomenon is referred to as a preferential utilization. 



The administration of betaine to rats having fatty livers but receiving an 

 ordinary diet resulted in a more rapid reduction in liver lipids than occurred 

 when no supplement was given. Moreover, the rats did not respond to a sub- 

 sequent fast period with such a marked rise in liver lipid as did those animals 

 which had not received the lipotropic agent. However, the effect of betaine 

 on ketonuria was not immediate. After the feeding of betaine for seven days 

 a marked endogenous ketonuria still obtained over a subsequent five-day 

 fasting period. The average level of acetone bodies was somewhat re- 

 duced below the control value. 



Table 27 summarizes the data on the liver fats and ketonuria of rats, 

 fed a stock diet, which developed fatty livers. 



d'. Effect on Glucose Tolerance Tests: One would expect that, when 

 the liver cells are congested with lipid, the ability to store glycogen would 

 be reduced and a decrease in glucose tolerance might be observed. Bodan- 

 sky 910 reported that a lower tolerance for glucose existed in dogs whose livers 

 had previously been damaged with chloroform or phosphorus than in 

 normal dogs. 



In the case of animals having the dietary type of fatty liver, MacLean et 

 aZ. 904 found that, while the liver was able to store appreciable quantities of 

 glycogen in the presence of large amounts of fat, the glycogen storage re- 

 sulting from given amounts of carbohydrate was less when the liver was 

 extremely fat. Treadwell and associates 911 noted a marked decrease in 

 glucose tolerance by rats on a diet high in fat and low in lipotropic factors. 

 Their results were confirmed by Deuel and Davis. 912 The latter workers 

 found that the fasting blood sugar levels were significantly higher in rats of 

 both sexes which had fatty livers than in animals having a normal content 

 of liver lipid. The rise in blood sugar level after glucose feeding was signi- 

 ficantly greater in female rats with fatty livers than in those having a nor- 

 mal level of liver lipids. However, these workers were unable to demon- 

 strate abnormal glucose tolerance curves in male rats with fatty livers. 



910 M. Bodansky, /. Biol. Chem., 58, 515-522~( 1923-1924). 



911 C. R. Treadwell, W. C. King, K. C. Bebb, and H. C. Tidwell, /. Biol. Chem., US, 

 203-209 (1943). 



912 H. J. Deuel, Jr., and A. Davis, /. Biol. Chem., 146, 649-653 (1942). 



