824 XIII. ESSENTIAL FATTY ACIDS 



than in those who had partaken exclusively of a diet containing animal fats. 

 In studies on rats fourteen years later, Kramar and Levine^^^ were able to 

 prove decisively that the resistance of the skin capillaries of immature rats, 

 fed a diet devoid of fats or fatty acids, or one containing 5% of methyl 

 stearate, began to decrease at fifty days, and soon reached pathologically 

 low levels. This change in capillary resistance was shown to be inversely 

 proportional to the increase in capillary permeability. This increased 

 capillary permeability occurred simultaneously with the flattening of the 

 growth curve, but before other symptoms of EFA deficiency were evident. 

 Caudal necrosis did not occur. 



The low capillary resistance of the fat-deficient rat could be restored to 

 normal by the administration of small amounts of linseed oil or of linoleic 

 acid itself. It would appear that one must consider decreased capillary 

 resistance (or increased capillary permeability) as an additional manifesta- 

 tion of the fat-deficiency syndrome in rats, and also in man. 



{6) Relation to Cholesterol Metabolism 



Fats have been widely maligned as a food in recent years, both as a 

 carrier of cholesterol (animal fats) and as a source of endogenous cholesterol 

 (animal and vegetable fats). Since the acetate molecule is known to be 

 incorporated in newly synthesized cholesterol, and because acetate is formed 

 on the oxidation of the fatty acid molecule, it has been suggested that the 

 ingestion of fat stimulates the synthesis of cholesterol. However, the rate 

 of synthesis of cholesterol is independent of the amount of fat available; 

 furthermore, the acetate required in this reaction can originate from dietary 

 carbohydrate, either directly from the ingested carbohydrate, or indirectly 

 from the fat formed from it. In order to prevent an overproduction of 

 cholesterol, because of its supposed relationship to arteriosclerosis, patients 

 have been given diets practically devoid of all fats. It has been recently 

 reported, in the case of the rat, that the administration of a fat-free diet 

 does result in a reduction of blood cholesterol; however, there is a concomi- 

 tant increase of liver and adrenal cholesterol which may reach twice the 

 normal level, according to Alfin-Slater et al}^-^^ The normal liver choles- 

 terol, 2.06 mg. per g. liver, which was found in the group of rats receiving 

 the diet containing 12.5% of cottonseed oil, compares with averages of 3.60 

 mg. per g. in one group on the fat-free regimen, and of 4.48 mg. per g. in 

 another group which received no fat. On the other hand, the plasma choles- 

 terol was only 44.4 and 43.0 mg. % in the case of the groups on the fat- 



"5 J. Kiamdr and V. E. Levine, /. Nutrition, 50, 149-160 (1953). 



