TRIGLYCERIDES AND FATTY ACIDS 173 



D-mannose,^^^ and cellobiose^^ also exhibit the same ketolytic properties as 

 does ghicose, or are even more effective. In addition to the above-men- 

 tioned sugars, the hexitols,^^^ a series of glucose intermediates^^^ including 

 L-lactic acid, pyruvic acid, and glycerol, as well as the glucose-forming 

 amino acids"'^'^^^-^^^'^-^''^^'^®^"^^^-^" produce similar responses in phlorhizi- 

 nized animals when tested for "extra sugar" formation, for the production 

 of liver glycogen, and for their ability to reduce ketonuria.^-^ However, 

 the ketolytic effect of sorbitol was only 50% that of glucose in tests of 

 ketonuria, and only 25% in endogenous ketonuria.^^^ Sharp and Berg^^^ 

 found that DL-lysine monohydrochloride fed to fasted rats produced no 

 greater gl^ycogen deposition than was observed in fasted controls, and that 

 the average total excretion of acetone bodies was slightly greater 

 than in the corresponding control groups which had received no 

 lysine. Cahill,^^^ in his chapter on Metabolism of Proteins and Amino 

 Acids, included a table showing the comparative carbohydrate-forming 

 activity of various amino acids when evaluated by these three methods. 



The results obtained with the hexitol, sorbitol, present some interesting 

 features. When this polyhydric alcohol is fed to rats having an exogenous 

 ketonuria, it exerts approximately 50% of the ketolytic effect which is 

 produced by an equivalent amount of glucose. On the other hand, when 

 it is fed to fasting rats in which an endogenous ketonuria exists, it is only 

 approximately 25% as effective as glucose. ^^^ Johnston and DeueP^^ 

 believe that the latter result may be attributed to the fact that the func- 

 tional activity of the fatty livers in the rats is presumably sufficiently 

 reduced to slow do^vn the conversion of sorbitol to glucose in this organ. 

 This is the first essential step in the metabolism of sorbitol if this substance 

 is to exert its depressing action on ketonuria. 



Edson"" reported that, when sorbitol was tested for its ability to reduce 

 the spontaneous ketogenesis in the liver slices obtained from fasted rats, 

 sorbitol was more effective than glucose or fructose. L-Iditol was likewise 



661 J. S. Butts, M. S. Dunn, and L. F. Hallman, J. Biol. Chem., 112, 263-274 (1935- 

 1936). 



«2 J. S. Butts, H. Blunden, and M. S. Dunn, /. Biol. Chem., 119, 247-255 (1937). 



6" J. S. Butts, H. Blunden, and M. S. Dunn, J. Biol. Chem., 124, 709-714 (1938). 



56^. S. Butts and R. O. Sinnhuber, J. Biol. Chem., I40, 597-602 (1941). 



5« L. F. Remmert and J. S. Butts, /. Biol. Chem., 144, 41-46 (1942). 



566 H. J. Deuel, Jr., E. M. MacKay, P. W. Jewel, M. Gulick, and C. F. Grunewald, 

 /. Biol. Chem., 101, 301-322 (1933). 



56' W. K. Hall, J. R. Dotv, and A. G. Eaton, Am. J. Physiol, 131, 252-255 (1940). 



668 G. O. Sharp and C. P. Berg, /. Biol. Chem., I4I, 739-745 (1941). 



66' W. M. Cahill, Metabolism of Proteins and Amino Acids, in M. Sahj^um, Outline of 

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6™ N. L. Edson, Biochem. J., SO, 1862-1869 (1936). 



