Fidarestat

Polycystic ovary syndrome (PCOS) represents a spectrum of disorders, associated with hyperandrogenism, oligoanovulation, and polycystic ovaries. Aldose reductase (AR), a rate-limiting enzyme of polyol pathway, is responsible for maintenance of intracellular osmotic balance, facilitation of oocyte development, and organization of the granulosa cells in the ovary. Cyclic changes in the aldose reductase level were found during the 4-5 days estrus cycle in rat, which is regulated by gonadotropin-releasing hormone (GnRH). Irregular GnRH secretion in PCOS patients may lead to altered aldose reductase expression and ovarian dysfunction. Treatment with a novel AR inhibitor, fidarestat, has been reported to improve erythrocyte sorbitol content in diabetic patients. Hence, the potential role AR in pathogenesis of PCOS was investigated by inhibiting AR with fidarestat in PCOS-induced rats. Pre-pubertal female Sprague-Dawley rats were divided into five groups. PCOS is induced either by administering letrozole or by feeding high-fat diet for 90 days. After induction of PCOS, fidarestat treatment was given for 28 days and various parameters were measured. In PCOS-induced rats, parameters like food intake, body weight, insulin, OGTT, triglycerides, cholesterol, prolonged diestrus phase, ovary weight, and immunohistological localization AR were found to be significantly altered. Fidarestat treatment significantly improved ovary weight, ovarian aldose reductase localization in PCOS-induced rats. Improvement in all these parameters suggest involvement of aldose reductase in the pathogenesis of PCOS.

(S)-Efavirenz (EFV) is a reverse transcriptase inhibitor and an antiviral drug. In addition, (S)-EFV can interact off target with CYP46A1, the major cholesterol hydroxylating enzyme in the mammalian brain, and allosterically activate CYP46A1 at a small dose in mice and humans. Studies with purified CYP46A1 identified two allosteric sites on the enzyme surface, one for (S)-EFV and the second site for L-Glu, a neurotransmitter, which also activates CYP46A1 either alone or in the presence of (S)-EFV. Previously, we found that (rac)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, (S)-8-hydroxyefavirenz, and (rac)-8,14-dihydroxyefavirenz, compounds with the hydroxylation positions corresponding to the metabolism of (S)-EFV in the liver, activated CYP46A1 in vitro. Yet, these compounds differed from (S)-EFV in how they allosterically interacted with CYP46A1. Herein, we further characterized (rac)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, (S)-8-hydroxyefavirenz, and (rac)-8,14-dihydroxyefavirenz, and, in addition, (R)-EFV, (S)-7-hydroxyefavirenz, (rac)-7,8-dihydroxyefavirenz, (S)-7,8-dihydroxyefavirenz, and (S)-8,14-dihydroxyefavirenz for activation and binding to CYP46A1 in vitro. We found that the spatial configuration of all tested compounds neither affected the CYP46A1 activation nor the sites of binding to CYP46A1. Yet, the hydroxylation position determined whether the hydroxylated metabolite interacted with the allosteric site for (S)-EFV [(R)-EFV, (rac)-7,8-dihydroxyefavirenz, and (S)-7,8-dihydroxyefavirenz], L-Glu [(rac)- and (S)-8,14-dihydroxyefavirenz] or both [(rac)-7-hydroxyefavirenz, (S)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, and (S)-8-hydroxyefavirenz]. This difference in binding to the allosteric sites determined, in turn, how CYP46A1 activity was changed in the co-incubations with (S)-EFV and either its metabolite or L-Glu. The results suggest EFV metabolites that could be more potent for CYP46A1 activation in vivo than (S)-EFV. Significance Statement We found that not only efavirenz but also all its hydroxylated metabolites allosterically activate CYP46A1 in vitro The enzyme activation depended on the hydroxylation position but not the metabolite spatial configuration, and involved either one or two allosteric sites - for efavirenz, L-Glu or both. The results suggest that the hydroxylated efavirenz metabolites may differ from efavirenz in how they interact with the CYP46A1 allosteric and active sites.