BIOSYNTHESIS OF CHOLESTEROL 377 



Exceedingly high blood cholesterol values have been reported in cases of 

 diabetes mellitus, in which condition hyperlipemia has also been noted. 

 Blood cholesterol levels as high as 1.5% and 1.41% were recorded by 

 Imrie^^'* and by Herbert, '^^ respectively; in these cases, cholesterol com- 

 prised 14.1% and 22% of the total blood lipid. Cochrane, Michaels, and 

 KjnselF^^ observed that the substitution of a vegetable fat for "animal fat" 

 in the high-protein, high-fat diabetic diets resulted in a major decline in the 

 levels of plasma cholesterol and of phospholipids. It has been suggested 

 that inositol is the effective agent in reducing both cholesterol and lipid P 

 in the case of hypercholesterolemic diabetics.^" Another condition, re- 

 lated to diabetes, known as essential xantliomatosis or essential cholesterol- 

 emia, is characterized by blood cholesterol values 400 to 500% of that of 

 normal subjects. Arteriosclerosis is another condition which is considered 

 by many to be related to hypercholesterolemia. For an extended discus- 

 sion of the subject of blood cholesterol under normal and pathologic condi- 

 tions, the reader is referred to Chapter V, Volume II, The Lipids. Pages 

 466 to 481 in the above chapter deal especially with the subject of choles- 

 terol in relation to arteriosclerosis. 



5. The Biosynthesis of Cholesterol 



(/) Evidence Proving Cholesterol Synthesis 



The ability of living tissue to synthesize cholesterol has long been recog- 

 nized. Among the earher experimental work, that of Beumer and Leh- 

 mann^*^ on dogs, and the findings of Randies and Knudson^^^ who studied 

 rats, were particularly convincing. Gamble and Blackf an, ^^^ investigating 

 infants, and Gardner and Fox^^^ studying adults, in both cases on a mixed 

 diet, interpreted their data as evidence of cholesterol sjaithesis in man. 



The experiments of Schonheimer'*^ with, herbivorous animals indicate 

 that the Herbivora are forced to synthesize practically all of the cholesterol 

 necessary for their tissues, since they ordinarily obtain only plant sterols in 

 the diet ; phytosterols are reported to be incapable either of absorption or 



154 C. G. Imrie, J. Biol. Chem., 20, 87-90 ( 1915). 

 1" F. K. Herbert, Biochem. J., 29, 1887-1893 (1935). 



i5« G. C. Cochrane, G. D. Michaels, and L. W. Kinsell, /. Clin. Nutrition, 1, 295-298 

 (1953). 



1" W. C. Felch and L. B. Dotti, Proc. Soc. Exptl. Biol. Med., 72, 376-378 (1949). 



158 H. Beumer and F. Lehmann, Z. ges. exptl. Med., 37, 274-280 (1923). 



159 F. S. Randies and A. Knudson, J. Biol. Chem., 66, 459-466 (1928). 



'«" J. L. Gamble and K. D. Blackfan, J. Biol. Chem., 42, 401-409 (1920). 



'61 J. A. Gardner and F. \Y. Fox, Proc. Roy. Soc. {London), B 92, 358-367 (1921). 



