PubMed · 6107438
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G E Williams. 1980-09-20. The clofibrate problem.. https://doi.org/10.1016/s0140-6736(80)90317-7
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Some chiral analogs of clofibric acid, the active metabolite of the antilipidemic drug clofibrate, show different configurational stability in basic conditions. Also, extensive racemization occurs when the corresponding optically active acid chlorides are treated with 3 alpha-tropanol, whereas no racemization takes place with 3 alpha-tropanol as hydrochloride salt and with 3 beta-tropanol and 1-methyl-4-hydroxy-piperidine as either the free base or hydrochloride salt. For these aminoalcohols, experimental evidence supports the hypothesis that a ketene intermediate is involved in the racemization process. Formation of intramolecular hydrogen bond is evoked to explain the different ability of aminoalcohols to induce ketene formation and consequent racemization.
The chemical tagging of a cytochrome P-450-dependent lauric acid omega-hydroxylase from clofibrate-treated Vicia sativa seedlings with [1-14C]11-dodecynoic acid allowed the isolation of a full-length cDNA designated CYP94A1. We describe here the functional expression of this novel P-450 in two Saccharomyces cerevisiae strains overproducing their own NADPH-cytochrome P-450 reductase or a reductase from Arabidopsis thaliana. The results show a much higher efficiency of the yeast strain overproducing the plant reductase compared with the yeast strain overproducing its own reductase for expressing CYP94A1. The methyl end of saturated (from C-10 to C-16) and unsaturated (C18:1, C18:2 and C18:3) fatty acids was mainly oxidized by CYP94A1. Both E/Z and Z/E configurations of 9, 12-octadecadienoic acids were omega-hydroxylated. Lauric, myristic and linolenic acids were oxidized with the highest turnover rate (24 min-1). The strong regioselectivity of CYP94A1 was clearly shifted with sulphur-containing substrates, since both 9- and 11-thia laurate analogues were sulphoxidized. Similar to animal omega-hydroxylases, this plant enzyme was strongly induced by clofibrate treatment. Rapid CYP94A1 transcript accumulation was detected less than 20 min after exposure of seedlings to the hypolipidaemic drug. The involvement of CYP94A1 in the synthesis of cutin monomers and fatty acid detoxification is discussed.
Pharmacological treatment of neonatal jaundice is again topical. At the beginning of the eighties, clofibrate was added to phenobarbital which was difficult to use and inefficient. Clofibrate is a better enhancer of glucuronosyl transferase induction than phenobarbital and causes 100% increase of hepatic bilirubin clearance within 6 hours. In the treatment of early jaundice in full term neonate, it significantly reduces bilirubinemia in 16 hours, and decreases the intensity and duration of jaundice and also phototherapy requirement. At the end of the eighties, new molecules inhibiting hepatic production of heme to bilirubin, like metalloporphyrins, were introduced. These molecules block the transformation of heme to biliverdin and bilirubin. Among them, the Sn-mesoporphyrin seems to have the best efficacy when used prophylactically in premature infants between 30 and 36 weeks of gestational age, and also curatively in full-term neonates, with minimal side effects. However the product is not yet manufactured and can not be used in pediatrics practice. Therefore clofibrate represents the only pharmacological treatment of neonatal jaundice actually available.