684 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



H H H 



CO CO CO 



/\ II /\ !! ^ n / \ II 



HC C— C— OH +C Hr HC C— C +H;0 , HC C— C— OH 



HC CH HC CH 



H A 



I 



CH 



N N+ 0- N + 



I I (OH)- 



CH.3 CH 3 



Nicotinic acid Trigonelline 



The detoxication of nicotinic acid in the animal body (5) 



Tyner, Lewis, and Eckstein 865 reported that the fattening effect of cystine 

 on the liver is exerted only when the animals have a low nicotinic acid in- 

 take. 



The physiologic effect of nicotinic acid in producing fatty livers, on diets 

 low in choline or in methionine, can be reversed when the N'-methylnico- 

 tinamide is given to rats receiving glycocyamine as a lipogenic agent. The 

 lipotropic action of N'-methyl-nicotinamide was shown by Najjar and 

 Deal 866 to be associated with a demethylation resulting in a marked increase 

 in the daily urinary output of nicotinic acid. Rats which received the N'- 

 methylnicotinamide averaged half the amount of liver fat which was pres- 

 ent in the controls. 



(h) Fatty Livers Resulting from Hormones, a'. Pancreatic Hormones: 

 Insulin has been shown to bring about a six-fold increase in the fatty acid 

 content of the liver of the alloxan-diabetic rat within four days. 867 Pre- 

 sumably this condition results largely because of an increased hepatic lipo- 

 genesis, as demonstrated by the rate at which C 14 is incorporated into such 

 fatty acids when pyruvate-2-C 14 is metabolized. However, Osborn, Felts, 

 and Chaikoff 867 noted that this insulin-induced fatty infiltration is transi- 

 tory; the fatty acid content of the liver decreases abruptly after the fourth 

 day of insulin injections, and returns almost to the original diabetic level 

 within six days. It is suggested that a homeostatic control regulates the 

 rate of hepatic lipogenesis. The effect of lipocaic has been discussed earlier 

 (see page 670). 



b'. Hormones of the Anterior Pituitary Gland: (a') Ketogenic Hor- 

 mone. — Best and associates 432,434589 demonstrated that a pronounced fat 

 mobilization occurs in the liver following the injection of the ketogenic 

 hormone into mice, rats, and guinea pigs. The fattening of the liver was not 

 prevented by choline, although this lipotropic agent accelerated the removal 



865 E. P. Tyner, H. B. Lewis, and H. C. Eckstein, /. Biol. Chem., 187, 651-654 (1950). 



866 V. A. Najjar and C. C. Deal, J. Biol. Chem., 162, 741-742 (1946). 



867 M. J. Osborn, J. M. Felts, and I. L. Chaikoff, J. Biol. Chem., 203, 173-181 (1953). 



