430 THE BIOCHEMISTRY OF B VITAMINS 



by folic acid and vitamin B 12 indicates indeed that PABA is intimately 

 related to these substances (see Chapter HID). In view of these con- 

 siderations it is remarkable that the physiological effects of PABA and 

 its deficiency in the higher animals are not more pronounced. 



Inositol Deficiency. Inositol deficiency is little understood, probably 

 because of the paucity of evidence regarding this avitaminosis in man. 

 Possibly the only effect known in man is its prevention of the fatty liver 

 induced by cholesterol feeding. Mice and rats apparently require inositol 

 for normal growth, and mice on deficiency diets become hairless and 

 develop a severe dermatitis. Rats develop a spectacle-eyed appearance 

 and a high-cholesterol fatty liver. The alopoecia and other symptoms 

 undergo remission on inositol administration. The fatty livers induced 

 by biotin or liver extract are similarly cured by inositol, but not choline. 198 

 Inositol does not affect "fat type" fatty livers as does choline, however. 

 Along with the association of inositol as one of the lipocaic factors of 

 the pancreas, other relationships appear. Inositol has recently been 

 reported to be highly efficacious in the treatment of diabetes mellitus, 

 and despite the caution that must be used in viewing such reports, it 

 seems probable that as yet unknown dietary considerations will even- 

 tually be shown to play an integral role in the etiology of this disease. 

 The relationship is more interesting in view of the possible role of 

 inositol as a coenzyme in amylase (p. 125) . 199 - 20 ° 



One other aspect of inositol deserves mention at this point. Beyond its 

 wide occurrence in the free state and as its esters and their salts, inositol 

 is found in certain cephalins called "lipositols," which occur in brain 

 tissue, soybean oil, etc. Regardless of what other roles they play, these 

 cephalins undoubtedly function in the mobilization and transport of 

 fat, and the lipotropic activity of inositol may be due to its occurrence 

 in lipositols. Beyond this, the antagonistic activities between streptomycin 

 and lipositol in bacteria suggest that lipositol may play an integral role 

 in cellular function. 201 



Choline Deficiency. Choline deficiency occurs naturally among domes- 

 tic fowls and it is thought to occur on rare occasion in other animals, but 

 it may be readily induced in most species. An important function of 

 choline is as a supply of methyl groups for transmethylation, 202 and 

 although this function is vital, it is not a vitamin function. For this 

 reason, and because the topic is a large and important one in its own 

 right, 203 the function of choline as a raw material for methionine synthesis 

 cannot be considered at length in this monograph. It is recognized, how- 

 ever, that choline may function as a vitamin by acting catalytically as 

 a carrier of methyl groups, or as a donor in the methylation of some other 

 catalyst. It is difficult to attribute a vitamin function to choline by virtue 



