Polycystic Ovary Syndrome: An Evolutionary Adaptation to Lifestyle and the Environment

Polycystic ovary syndrome (PCOS) is increasingly recognized as a complex metabolic disorder that manifests in genetically susceptible women following a range of negative exposures to nutritional and environmental factors related to contemporary lifestyle. The hypothesis that PCOS phenotypes are derived from a mismatch between ancient genetic survival mechanisms and modern lifestyle practices is supported by a diversity of research findings. The proposed evolutionary model of the pathogenesis of PCOS incorporates evidence related to evolutionary theory, genetic studies, in utero developmental epigenetic programming, transgenerational inheritance, metabolic features including insulin resistance, obesity and the apparent paradox of lean phenotypes, reproductive effects and subfertility, the impact of the microbiome and dysbiosis, endocrine-disrupting chemical exposure, and the influence of lifestyle factors such as poor-quality diet and physical inactivity. Based on these premises, the diverse lines of research are synthesized into a composite evolutionary model of the pathogenesis of PCOS. It is hoped that this model will assist clinicians and patients to understand the importance of lifestyle interventions in the prevention and management of PCOS and provide a conceptual framework for future research. It is appreciated that this theory represents a synthesis of the current evidence and that it is expected to evolve and change over time.

Developmental origins and transgenerational inheritance of polycystic ovary syndrome

BACKGROUND

There has been increasing awareness that polycystic ovary syndrome (PCOS) phenotypes may represent a mismatch between ancient genetically programmed metabolic and reproductive survival mechanisms and modern lifestyle practices. In-utero developmental programming of metabolic and endocrine pathways may play an important role in activating gene variants that predispose the offspring to develop PCOS when exposed to specific postnatal conditions. Postnatal exposure to lifestyle factors such as poor-quality diet and endocrine disrupting chemicals may modulate epigenetically programmed pathways that result in the observed pathophysiological changes and clinical features seen in women with PCOS.

AIM

To review the developmental origins and transgenerational transmission of PCOS and the impact of lifestyle, androgens and endocrine disrupting chemicals on fetal epigenetic programming.

MATERIALS AND METHODS

The literature was reviewed using Google, Google Scholar, Medline and PubMed databases. The results are presented as a narrative review.

RESULTS

Human observational and animal experimental data support the hypothesis that PCOS is an inherited condition that arises as a result of developmental programming of normal gene variants. It is likely that these genes can be amplified by in-utero androgen exposure and activated by a range of postnatal lifestyle and environmental factors. Endocrine disrupting chemicals have the potential to influence developmental programming of PCOS susceptibility genes.

CONCLUSIONS

The current evidence suggests that developmental epigenetic programming following exposure to an adverse maternal metabolic and endocrine environment contributes to the pathogenesis of PCOS. Lifestyle interventions, as recommended by the International Guidelines, have the potential to reduce both symptoms and transgenerational transmission of PCOS.

Enhanced thecal androgen production is prenatally programmed in an ovine model of polycystic ovary syndrome

One of the hallmarks of polycystic ovary syndrome (PCOS) is increased ovarian androgen secretion that contributes to the ovarian, hormonal, and metabolic features of this condition. Thecal cells from women with PCOS have an enhanced capacity for androgen synthesis. To investigate whether this propensity is a potential cause, rather than a consequence, of PCOS, we used an ovine prenatal androgenization model of PCOS and assessed ewes at 11 months of age. Pregnant Scottish Greyface ewes were administered 100 mg testosterone propionate (TP) or vehicle control twice weekly from d 62 to 102 of gestation, and female offspring (TP = 9, control = 5) were studied. Prenatal TP exposure did not alter ovarian morphology or cyclicity, or plasma androgen, estrogen, and gonadotropin concentrations, at this stage. However, follicle function was reprogrammed in vivo with increased proportions of estrogenic follicles (P < 0.05) in the TP-exposed cohort. Furthermore, in vitro the thecal cells of follicles (>4 mm) secreted more LH-stimulated androstenedione after prenatal androgenization (P < 0.05), associated with increased basal expression of thecal StAR (P < 0.01), CYP11A (P < 0.05), HSD3B1 (P < 0.01), CYP17 (P < 0.05), and LHR (P < 0.05). This provides the first evidence of increased thecal androgenic capacity in the absence of a PCOS phenotype, suggesting a thecal defect induced during fetal life.

Prenatal androgen exposure leads to alterations in gene and protein expression in the ovine fetal ovary

Exposure of a female fetus to increased androgens in utero results in an adult phenotype reminiscent of polycystic ovary syndrome. We investigated whether prenatal androgens could directly alter the structure and function of the fetal ovary. We examined fetal ovarian cell proliferation, germ cell volume, and the expression of steroid receptors and steroidogenic enzymes. In addition, we studied the inhibitors of differentiation (Ids) and the SLIT/Roundabout developmental pathways. Female fetuses were collected from ewes treated with 100 mg testosterone propionate (TP) or vehicle control (C), twice weekly from d 60 to 70 (C = 3, TP = 6) or d 90 (C = 6, TP = 8). Female fetuses were also collected at d 70 after a single injection of TP (20 mg) or vehicle C into the fetal flank at d 60 (C = 4, TP = 8). Prenatal androgenization had no effect on fetal ovarian morphology, cell proliferation, or germ cell volume. However, there was a reduction in the expression of StAR, CYP11A, CYP17, and LHR at d 90 of gestation. There was also an increase in Id1 immunostaining at d 90 and an increase in Id3 immunostaining at d 70. Direct injection of TP into the fetus down-regulated ovarian CYP11A, estrogen receptor α and β mRNA, and ROBO1 and up-regulated CYP19, androgen receptor immunostaining, and Id3 mRNA and protein. Although at d 90 prenatal androgenization does not result in structural changes of the fetal ovary, there are functional changes that may impact on ovarian development. TP has direct actions on the fetal ovary, and these may contribute to the adult ovarian phenotype in the ovine model of polycystic ovary syndrome.

Experimentally induced gestational androgen excess disrupts glucoregulation in rhesus monkey dams and their female offspring

Discrete fetal androgen excess during early gestation in rhesus monkeys (Macaca mulatta) promotes endocrine antecedents of adult polycystic ovary syndrome (PCOS)-like traits in female offspring. Because developmental changes promoting such PCOS-like metabolic dysfunction remain unclear, the present study examined time-mated, gravid rhesus monkeys with female fetuses, of which nine gravid females received 15 mg of testosterone propionate (TP) subcutaneously daily from 40 to 80 days (first to second trimesters) of gestation [term, mean (range): 165 (155-175) days], whereas an additional six such females received oil vehicle injections over the same time interval. During gestation, ultrasonography quantified fetal growth measures and was used as an adjunct for fetal blood collections. At term, all fetuses were delivered by cesarean section for postnatal studies. Blood samples were collected from dams and infants for glucose, insulin, and total free fatty acid (FFA) determinations. TP injections transiently accelerated maternal weight gain in dams, very modestly increased head diameter of prenatally androgenized (PA) fetuses, and modestly increased weight gain in infancy compared with concurrent controls. Mild to moderate glucose intolerance, with increased area-under-the-curve circulating insulin values, occurred in TP-injected dams during an intravenous glucose tolerance test in the early second trimester. Moreover, reduced circulating FFA levels occurred in PA fetuses during a third trimester intravenous glucagon-tolbutamide challenge (140 days gestation), whereas excessive insulin sensitivity and increased insulin secretion relative to insulin sensitivity occurred in PA infants during an intravenous glucose-tolbutamide test at ∼1.5 mo postnatal age. Data from these studies suggest that experimentally induced fetal androgen excess may result in transient hyperglycemic episodes in the intrauterine environment that are sufficient to induce relative increases in pancreatic function in PA infants, suggesting in this nonhuman primate model that differential programming of insulin action and secretion may precede adult metabolic dysfunction.