Cholesterol, Neurosteroid Hormones, Vitamin D3, and Bile

This isoform was found as the result of a mouse deficient in the oxysterol 7a-hydroxylase gene (CYP7B1 in humans), which nonetheless did not accumulate 24-hydroxy cholesterol from the CYP46pathway, suggesting the existence of another 7ot-hydroxylase (Li-Hawkins et al., 2000). However, very httle evidence exists for its expression in human brain. Nishimura et al. quantified CYP39A1 mRNA by RT-RT-PCR and reported some 100-fold less than they reported for CYP51 mRNA (Nishimura et al., 2003). There is no other evidence for the expression of this isoform in the brain as of this writing and this is beheved to be the first report of its kind. The isoform has been shown to be sexually dimorphic in the liver (Li-Hawkins et al., 2000). 

A striking feature of the collection of human brain cytochrome P450s discussed in the present review is the obvious major classes they fall into. With the exception of CYP26A1, which appears to be alone in the retinoic acid metabolic pathway, all the other brain P450s, including those normally considered xenobiotic-metabolizing, are either involved in the metabolism (or synthesis, in the case of CYP51, the 

Infants require a substantial supplementation of AA, which is normally supplied through breast milk. Almost 10% of the membrane phospholipid content of breast fed infants was found to be AA in one study (Koletzko et ah, 1996). A crucial factor of the developing infant brain is the amount and type of polyunsaturated fatty acids they receive from their diet. That is, the ratio of dietary n-3 fatty acids (those in which the unsaturation begins 3 carbons from the terminal carbon) to n-6 fatty acids can be optimized to 

Cytochrome P450 pathways in human brain arachidonic acid cascade 

Phospholipid ( 9% of fatty acid in plasma membrane is arachidonic acid Koletzko, 1996) 

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