The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

A novel pathway for biosynthesis of cholestanol with 7 alpha-hydroxylated C27-steroids as intermediates, and its importance for the accumulation of cholestanol in cerebrotendinous xanthomatosis.

A mixture of 7 alpha-3H- and 4-14C-labeled cholesterol was administered intravenously to rats. Cholestanol with 20-30% lower ratio between 3H and 14C than in cholesterol could be isolated from different organs. In a healthy human control, cholestanol isolated from feces had a 3H/14C ratio which was 28% lower than in administered cholesterol. Cholesterol and coprostanol reisolated in these experiments had the same ratio between 3H and 14C as in the precursor. A previously unknown pathway for formation of cholestanol, involving 7 alpha-hydroxylated intermediates, may explain these results. Under normal conditions, this pathway is responsible for at most 30% of the cholestanol synthesized from cholesterol. Intravenous administration of the 7 alpha-3H- and 4-14C-labeled cholesterol to a patient with cerebrotendinous xanthomatosis (CTX) resulted in formation of cholestanol which had 70-75% lower 3H/14C ratio. It is concluded that the novel pathway involving 7 alpha-hydroxylated intermediates is accelerated in patients with CTX. This acceleration may contribute essentially to the accumulation of cholestanol, which is a predominant feature of this disease. 7 alpha-Hydroxycholesterol and 7 alpha-hydroxy-4-cholesten-3-one might be intermediates in the novel pathway to cholestanol. After intravenous administration of 7 beta-3H-labeled 7 alpha-hydroxycholesterol in a patient with CTX, significant amounts of 3H were incorporated into plasma and fecal cholestanol. Only small amounts of 7 alpha-hydroxycholesterol and 7 alpha-hydroxy-4-cholesten-3-one are excreted into the intestine, and we therefore conclude that the 7 alpha-dehydroxylation step mainly occurs in the liver. In CTX, the synthesis of cholestanol may be accelerated because the concentrations of 7 alpha-hydroxylated bile acid intermediates in the liver are increased. A possible mechanism for the conversion of a minor fraction of 7 alpha-hydroxycholesterol into cholestanol is suggested.[1]

References

 
WikiGenes - Universities