528 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



the odd-carbon fatty acids form no ketone bodies, or limited amounts of 

 the latter. 34 ' 36 ' 37 Moreover, the acids can be transformed to glycogen to 

 the extent that they are converted to propionic acid. 35 



It is therefore quite suprising to find that triundecylin (Cu) can be readily 

 deposited in the fat storage depots of the rat. Visscher 38 reported that as 

 much as 24% of the fatty acids present in the tissues consisted of unde- 

 cylic acid, after triundecylin had been fed to the rats over a six-week period. 



Appel, Bohm and associates, also, 39 have reported that the saturated odd- 

 carbon acids from Cu to Ow, which occur in the fat synthesized from par- 

 affin, are stored in depot fat as the corresponding C 9 to Cio unsaturated 

 acids. Only minimum amounts of the branched-chain acids were found 

 to be deposited in animal fats, the greater amount being excreted in the 

 urine as Ce to Cio dicarboxylic acids. 



c. The Effect of Unsaturated Fats in the Diet on the Composition of 

 Storage Fat. (a) Oleic Acid. Oleic acid, CH 3 (CH 2 ) 7 CH:CH(CH 2 ) 7 - 

 COOH, is the most important unsaturated fatty acid found in animal as 

 well as in vegetable fats, both from a qualitative and from a quantitative 

 standpoint. The concentration of this fatty acid in the tissue fats is less 

 influenced by diet than is that of the other unsaturated acids. This is 

 probably to be ascribed to the fact that tissue oleic acid possesses a dual 

 origin. In the first place, along with many other fatty acids, oleic acid in 

 the fat depots may represent that originating from the diet. Secondly, 

 oleic acid may be synthesized from saturated fatty acids which, in turn, 

 may be derived from carbohydrate and protein. 



Schoenheimer and Rittenberg 40 - 42 have shown that the body is able to 

 desaturate stearic acid and other saturated acids to produce unsaturated 

 acids such as oleic. In fact, the reverse reaction may also take place in 

 the tissues; this may indicate that an equilibrium exists which is able to 

 control the proportion of oleic acid laid down in body fat. On the other 

 hand, the animal body is unable to produce a dienoic acid either from a 

 monoethenoid acid or from a saturated acid, 43 although Reiser 44 has shown 

 that such acids may originate from more highly unsaturated ones. In 



36 J. S. Butts, C. H. Cutler, L. F. Hallman, and H. J. Deuel, Jr., J. Biol. Chem., 109, 

 597-613(1935). 



37 E. M. MacKay, A. N. Wick, and C. P. Barnum, J. Biol. Chem., 186, 503-507 (1940). 



38 F. E. Visscher, /. Biol. Chem., 162, 129-132 (1946). 



39 H. Appel, H. Bohm, W. Keil, and G.Schiller, Z.physiol. Chem., 282, 220-244 (1947). 



40 R. Schoenheimer and D. Rittenberg, J. Biol. Chem., 113, 505-510 (1936). 



41 R. Schoenheimer and D. Rittenberg, /. Biol. Chem., 114, 381-396 (1936). 



42 D. Rittenberg and R. Schoenheimer, J. Biol. Chem., 121, 235-253 (1937). 



43 K. Bernhard and R. Schoenheimer, /. Biol, Chem., 183, 707-712 (1940). 



44 R. Reiser, Arch. Biochem. Biophys., 32, 113-120 (1951). 



