130 III. OXIDATION AND METABOLISM 



are not entirely conclusive. Uhlmann-^^ also tentatively recommended 

 the treatment of diabetics with fats composed of an odd number of carbons. 

 Synthetic fats made in Germany from petroleum, during World War II, 

 contained a considerable proportion of fatty acids having an uneven num- 

 ber of carbons. Flossner'^'* and Kabehtz^°° both reported that a lower 

 degree of ketonuria occurs in diabetics when synthetic fat is used than when 

 natural fats are ingested, although the latter author states that the metab- 

 olism of unstabilized diabetics was severely upset by the excess of synthetic 

 fat. Divergent conclusions have been reported by a number of other 

 workers. ^"^"^"^ 



(e) Formation from Branched-Chain Acids. In addition to isovaleric 

 acid, which is believed to be an intermediate of leucine, and a-ketovaleric 

 acid, which arises from valine, a number of other branched-chain fatty 

 acids have been investigated, to determine their ketogenic activity. These 

 results are summarized in Table 2. 



In the oxidation of fatty acids, /3-oxidation will occur unless the molecule 

 is altered by the introduction of a new group. The amino group, when 

 introduced into the or-position, which is the normal one in the physiologic 

 amino acids, will have the net effect of shortening the acid by one carbon 

 insofar as oxidation is concerned. ^"^ Thus, an a-amino acid with an even 

 number of carbons will suffer the fate of the odd-carbon fatty acid with one 

 less carbon ; on the other hand, the a-amino acid containing an odd num- 

 ber of carbons will behave, on oxidation, like the even-chain fatty acid 

 with one less carbon. The introduction of methyl or ethyl groups into the 

 fatty acids tends to block /3-oxidation. Thus, Wick ^"^ was unable to in- 

 duce ketosis in the rabbit with a-methylbutyric acid, a-ethylbutyric acid, 

 or with a-methyl-valeric acid. Carter ^^ reviewed the subject of the oxida- 

 tion of branched-chain acids. 



(/) Formation from Amino Acids. Although most of the amino acids 

 are glucose-formers, there is convincing evidence that leucine and possibly 

 several other amino acids can give rise to ketone bodies. 



a'. Leucine: Embden, Salomon, and Schmidf reported that, when 

 leucine was added to the perfusing fluid passed through a surviving liver, 

 acetone bodies were formed in large amounts. The natural isomer was 



298 R. Uhlmann, Deut. Arch. klin. Med., 161, 165-173 (1928). 

 "9 O. Flossner, Erndhrung, 8, 89-93 (1943). 



300 G. Kabelitz, Klin. Wochschr., 23, 13-16 (1944). 



301 H. Luiidin, J. Metabolic Research, 4, 151-176 (1923). 



302 F. S. Modern, /. Metabolic Research, 4, 177-188 (1923). 



303 D. M. Lyon, W. Robson, and A. C. White, Brit. Med. J., 1925, 1, 207-210. 



304 A. N. Wick, /. Biol. Chem., I4I. 897-903 (1941). 



