Cortisol-Metabolizing Enzymes in Polycystic Ovary Syndrome.

OBJECTIVE: The aim of this study was to assess the activity of cortisol-metabolizing enzymes in women with polycystic ovary syndrome (PCOS), using a fully quantitative gas chromatography/mass spectrometry (GCMS) method. DESIGN: We investigated the glucocorticoid degradation pathways that include 11ß-hydroxysteroid dehydrogenase (11ß-HSD) type 1, 5α-reductase (5α-R) and 5ß-reductase (5ß-R), 3α-hydroxysteroid dehydrogenase, and 20α- and 20ß-hydroxysteroid dehydrogenase (20α-HSD and 20ß-HSD, respectively) in young nonobese women with PCOS, using a fully quantitative GCMS method. SETTING: This study was conducted in a tertiary referral hospital in Israel. PATIENTS: This study group consisted of 13 young women, aged 20.1 ± 2.8 years (mean ± SD), with the body mass index (BMI) of 22.6 ± 3.7 kg/m(2), diagnosed with PCOS according to the Rotterdam criteria. The control group consisted of 14 healthy young women matched for weight, height, and BMI. INTERVENTIONS: Urine samples were analyzed using GCMS. We measured urinary steroid metabolites that represent the products and substrates of the study enzymes and calculated the product/substrate ratios to represent enzyme activity. MAIN OUTCOME MEASURES: The calculation of enzymatic activity, based on glucocorticoid degradation metabolites, was done by GCMS in PCOS vs. controls. RESULTS: All glucocorticoid degradation metabolites were higher in the PCOS group than in controls. Of the adrenal enzymes, the activities of 21-hydroxylase and 17α-hydroxylase were reduced, whereas the activity of 17,20-lyase was enhanced in PCOS. Of the degradation enzymes, the activity of 11ß-HSD type 1 was reduced in women with PCOS only when calculated from cortoles and cortolones ratios. The activities of 5α-R/5ß-R were increased only when calculating the 11-hydroxy metabolites of androgens. The activity of 20α-HSD was elevated in the patients with PCOS and its relation with the substrate levels was lost. CONCLUSIONS: We confirm PCOS association with low 21-hydroxylase activity. PCOS is associated with dysregulation in glucocorticoid degradation. The activity of 5α-R is enhanced only through the backdoor pathway. Marked increase in the activity of 20α-HSD suggests a hitherto unknown derangement in PCOS.

Epigenetic control of female puberty.

The timing of puberty is controlled by many genes. The elements coordinating this process have not, however, been identified. Here we show that an epigenetic mechanism of transcriptional repression times the initiation of female puberty in rats. We identify silencers of the Polycomb group (PcG) as principal contributors to this mechanism and show that PcG proteins repress Kiss1, a puberty-activating gene. Hypothalamic expression of two key PcG genes, Eed and Cbx7, decreased and methylation of their promoters increased before puberty. Inhibiting DNA methylation blocked both events and resulted in pubertal failure. The pubertal increase in Kiss1 expression was accompanied by EED loss from the Kiss1 promoter and enrichment of histone H3 modifications associated with gene activation. Preventing the eviction of EED from the Kiss1 promoter disrupted pulsatile gonadotropin-releasing hormone release, delayed puberty and compromised fecundity. Our results identify epigenetic silencing as a mechanism underlying the neuroendocrine control of female puberty.

The transcriptional control of female puberty.

The initiation of mammalian puberty requires a sustained increase in pulsatile release of gonadotrophin releasing hormone (GnRH) from the hypothalamus. This increase is brought about by coordinated changes in transsynaptic and glial-neuronal communication, consisting of an increase in neuronal and glial stimulatory inputs to the GnRH neuronal network and the loss of transsynaptic inhibitory influences. GnRH secretion is stimulated by transsynaptic inputs provided by excitatory amino acids (glutamate) and at least one peptide (kisspeptin), and by glial inputs provided by growth factors and small bioactive molecules. The inhibitory input to GnRH neurons is mostly transsynaptic and provided by GABAergic and opiatergic neurons; however, GABA has also been shown to directly excite GnRH neurons. There are many genes involved in the control of these cellular networks, and hence in the control of the pubertal process as a whole. Our laboratory has proposed the concept that these genes are arranged in overlapping networks internally organized in a hierarchical fashion. According to this concept, the highest level of intra-network control is provided by transcriptional regulators that, by directing expression of key subordinate genes, impose genetic coordination to the neuronal and glial subsets involved in initiating the pubertal process. More recently, we have begun to explore the concept that a more dynamic and encompassing level of integrative coordination is provided by epigenetic mechanisms.

Gene networks and the neuroendocrine regulation of puberty.

A sustained increase in pulsatile release of gonadotrophin releasing hormone (GnRH) from the hypothalamus is an essential, final event that defines the initiation of mammalian puberty. This increase depends on coordinated changes in transsynaptic and glial-neuronal communication, consisting of activating neuronal and glial excitatory inputs to the GnRH neuronal network and the loss of transsynaptic inhibitory tone. It is now clear that the prevalent excitatory systems stimulating GnRH secretion involve a neuronal component consisting of excitatory amino acids (glutamate) and at least one peptide (kisspeptin), and a glial component that uses growth factors and small molecules for cell-cell signaling. GABAergic and opiatergic neurons provide transsynaptic inhibitory control to the system, but GABA neurons also exert direct excitatory effects on GnRH neurons. The molecular mechanisms that provide encompassing coordination to this cellular network are not known, but they appear to involve a host of functionally related genes hierarchically arranged. We envision that, as observed in other gene networks, the highest level of control in this network is provided by transcriptional regulators that, by directing expression of key subordinate genes, impose an integrative level of coordination to the neuronal and glial subsets involved in initiating the pubertal process. The use of high-throughput and gene manipulation approaches coupled to systems biology strategies should provide not only the experimental bases supporting this concept, but also unveil the existence of crucial components of network control not yet identified.