More than 1 out of 10 women worldwide are diagnosed with polycystic ovary syndrome (PCOS), the leading cause of female reproductive and metabolic dysfunction. Despite its high prevalence, PCOS and its accompanying morbidities are likely underdiagnosed, averaging > 2 years and 3 physicians before women are diagnosed. Although it has been intensively researched, the underlying cause(s) of PCOS have yet to be defined. In order to understand PCOS pathophysiology, its developmental origins, and how to predict and prevent PCOS onset, there is an urgent need for safe and effective markers and treatments. In this review, we detail which animal models are more suitable for contributing to our understanding of the etiology and pathophysiology of PCOS. We summarize and highlight advantages and limitations of hormonal or genetic manipulation of animal models, as well as of naturally occurring PCOS-like females.

Adiponectin, together with adipocyte size, is the strongest factor associated with insulin resistance in women with polycystic ovary syndrome (PCOS). This study investigates the causal relationship between adiponectin levels and metabolic and reproductive functions in PCOS. Prepubertal mice overexpressing adiponectin from adipose tissue (APNtg), adiponectin knockouts (APNko), and their wild-type (WT) littermate mice were continuously exposed to placebo or dihydrotestosterone (DHT) to induce PCOS-like traits. As expected, DHT exposure led to reproductive dysfunction, as judged by continuous anestrus, smaller ovaries with a decreased number of corpus luteum, and an increased number of cystic/atretic follicles. A two-way between-groups analysis showed that there was a significant main effect for DHT exposure, but not for genotype, indicating adiponectin does not influence follicle development. Adiponectin had, however, some protective effects on ovarian function. Similar to in many women with PCOS, DHT exposure led to reduced adiponectin levels, larger adipocyte size, and reduced insulin sensitivity in WTs. APNtg mice remained metabolically healthy despite DHT exposure, while APNko-DHT mice were even more insulin resistant than their DHT-exposed littermate WTs. DHT exposure also reduced the mRNA expression of genes involved in metabolic pathways in gonadal adipose tissue of WT and APNko, but this effect of DHT was not observed in APNtg mice. Moreover, APNtg-DHT mice displayed increased pancreatic mRNA levels of insulin receptors, Pdx1 and Igf1R, suggesting adiponectin stimulates beta cell viability/hyperplasia in the context of PCOS. In conclusion, adiponectin improves metabolic health but has only minor effects on reproductive functions in this PCOS-like mouse model.

If and how obesity and elevated androgens in women with polycystic ovary syndrome (PCOS) affect their offspring’s psychiatric health is unclear. Using data from Swedish population health registers, we showed that daughters of mothers with PCOS have a 78% increased risk of being diagnosed with anxiety disorders. We next generated a PCOS-like mouse (F₀) model induced by androgen exposure during late gestation, with or without diet-induced maternal obesity, and showed that the first generation (F₁) female offspring develop anxiety-like behavior, which is transgenerationally transmitted through the female germline into the third generation of female offspring (F₃) in the androgenized lineage. In contrast, following the male germline, F₃ male offspring (mF₃) displayed anxiety-like behavior in the androgenized and the obese lineages. Using a targeted approach to search for molecular targets within the amygdala, we identified five differentially expressed genes involved in anxiety-like behavior in F₃ females in the androgenized lineage and eight genes in the obese lineage. In mF₃ male offspring, three genes were dysregulated in the obese lineage but none in the androgenized lineage. Finally, we performed in vitro fertilization (IVF) using a PCOS mouse model of continuous androgen exposure. We showed that the IVF generated F₁ and F₂ offspring in the female germline did not develop anxiety-like behavior, while the F₂ male offspring (mF₂) in the male germline did. Our findings provide evidence that elevated maternal androgens in PCOS and maternal obesity may underlie the risk of a transgenerational transmission of anxiety disorders in children of women with PCOS.

Insulin-induced hypoglycemia is a major treatment barrier in type-1 diabetes (T1D). Accordingly, it is important that we understand the mechanisms regulating the circulating levels of glucagon. Varying glucose over the range of concentrations that occur physiologically between the fed and fuel-deprived states (8 to 4 mM) has no significant effect on glucagon secretion in the perfused mouse pancreas or in isolated mouse islets (in vitro), and yet associates with dramatic increases in plasma glucagon. The identity of the systemic factor(s) that elevates circulating glucagon remains unknown. Here, we show that arginine-vasopressin (AVP), secreted from the posterior pituitary, stimulates glucagon secretion. Alpha-cells express high levels of the vasopressin 1b receptor (V1bR) gene (Avpr1b). Activation of AVP neurons in vivo increased circulating copeptin (the C-terminal segment of the AVP precursor peptide) and increased blood glucose; effects blocked by pharmacological antagonism of either the glucagon receptor or V1bR. AVP also mediates the stimulatory effects of hypoglycemia produced by exogenous insulin and 2-deoxy-D-glucose on glucagon secretion. We show that the A1/C1 neurons of the medulla oblongata drive AVP neuron activation in response to insulin-induced hypoglycemia. AVP injection increased cytoplasmic Ca²⁺in alpha-cells (implanted into the anterior chamber of the eye) and glucagon release. Hypoglycemia also increases circulating levels of AVP/copeptin in humans and this hormone stimulates glucagon secretion from human islets. In patients with T1D, hypoglycemia failed to increase both copeptin and glucagon. These findings suggest that AVP is a physiological systemic regulator of glucagon secretion and that this mechanism becomes impaired in T1D.

Aims: Polycystic ovary syndrome (PCOS) is a common endocrinopathy that is suggested to increase the risk for cardiovascular disease. How PCOS may lead to adverse cardiac outcomes is unclear and here we hypothesized that prenatal exposure to dihydrotestosterone (DHT) and/or maternal obesity in mice induce adverse metabolic and cardiac programming in female offspring that resemble the reproductive features of the syndrome. Methods and results: The maternal obese PCOS phenotype was induced in mice by chronic high-fat–high-sucrose consumption together with prenatal DHT exposure. The prenatally androgenized (PNA) female offspring displayed cardiac hypertrophy during adulthood, an outcome that was not accompanied by aberrant metabolic profile. The expression of key genes involved in cardiac hypertrophy was up-regulated in the PNA offspring, with limited or no impact of maternal obesity. Furthermore, the activity of NADPH oxidase, a major source of reactive oxygen species in the cardiovascular system, was down-regulated in the PNA offspring heart. We next explored for early transcriptional changes in the heart of newly born PNA offspring, which could account for the long-lasting changes observed in adulthood. Neonatal PNA hearts displayed an up-regulation of transcription factors involved in cardiac hypertrophic remodelling and of the calcium-handling gene, Slc8a2. Finally, to determine the specific role of androgens in cardiovascular function, female mice were continuously exposed to DHT from pre-puberty to adulthood, with or without the antiandrogen flutamide. Continuous exposure to DHT led to adverse left ventricular remodelling, and increased vasocontractile responses, while treatment with flutamide partly alleviated these effects. Conclusion: Taken together, our results indicate that intrauterine androgen exposure programmes long-lasting heart remodelling in female mouse offspring that is linked to left ventricular hypertrophy and highlight the potential risk of developing cardiac dysfunction in daughters of mothers with PCOS.

Polycystic ovary syndrome (PCOS) is associated with a low‐grade inflammation, but it is unknown how hyperandrogenism, the hallmark of PCOS, affects the immune system. Using a PCOS‐like mouse model, it is demonstrated that hyperandrogenism affects immune cell populations in reproductive, metabolic, and immunological tissues differently in a site‐specific manner. Co‐treatment with an androgen receptor antagonist prevents most of these alterations, demonstrating that these effects are mediated through androgen receptor activation. Dihydrotestosterone (DHT)‐exposed mice displayed a drastically reduced eosinophil population in the uterus and visceral adipose tissue (VAT). A higher frequency of natural killer (NK) cells and elevated levels of IFN‐γ and TNF‐α are seen in uteri of androgen‐exposed mice, while NK cells in VAT and spleen displayed a higher expression level of CD69, a marker of activation or tissue residency. Distinct alterations of macrophages in the uterus, ovaries, and VAT are also found in DHT‐exposed mice and can potentially be linked to PCOS‐like traits of the model. Indeed, androgen‐exposed mice are insulin‐resistant, albeit unaltered fat mass. Collectively, it is demonstrated that hyperandrogenism causes tissue‐specific alterations of immune cells in reproductive organs and VAT, which can have considerable implications on tissue function and contribute to the reduced fertility and metabolic comorbidities associated with PCOS.