Proteomic analysis shows decreased type I fibers and ectopic fat accumulation in skeletal muscle from women with PCOS

Reappraising the relationship between hyperinsulinemia and insulin resistance in PCOS

Polycystic ovary syndrome (PCOS), a reproductive endocrine disorder with quintessential features of metabolic dysfunction, affects millions of women worldwide. Hyperinsulinemia (i.e., elevated insulin without hypoglycemia) is a common metabolic feature of PCOS that worsens its reproductive symptoms by exacerbating pituitary hormone imbalances and increasing levels of bioactive androgens. Hyperinsulinemia in PCOS is often attributed to insulin resistance, based on the concept that impaired insulin-mediated glucose disposal would induce compensatory insulin hypersecretion. However, it is challenging to define the sequential relationship between insulin sensitivity and insulin secretion, as they are tightly interlinked, and evidence suggests that hyperinsulinemia can alternatively precede insulin resistance. Notably, other drivers of hyperinsulinemia (outside of insulin resistance) may be highly relevant in the context of PCOS. For instance, high androgen levels can augment both hyperinsulinemia and insulin resistance, generating a self-perpetuating cycle of reproductive and metabolic dysfunction. In this review, we evaluate the cause-and-effect relationships between insulin resistance and hyperinsulinemia in PCOS. We examine evidence for the prevailing theory of insulin resistance as the primary defect that causes secondary compensatory hyperinsulinemia, and an alternative framework of hyperinsulinemia as the earlier defect that perpetuates reproductive and metabolic features of PCOS. Considering the heterogeneous nature of PCOS, it is improbable that its metabolic characteristics always follow the same progression. Comprehensively examining all mechanistic regulators of hyperinsulinemia and insulin resistance in PCOS might thereby lead to improved prevention and management strategies, and address critical knowledge gaps in the progression of PCOS pathogenesis.

Hyperandrogenaemia, polycystic ovary syndrome, and physical fitness in women-a Northern Finland birth cohort study

OBJECTIVE

To investigate the independent associations of hyperandrogenaemia (HA) and polycystic ovary syndrome (PCOS) with physical fitness in women among the general population.

DESIGN

A population-based birth cohort study including 5889 women.

METHODS

Longitudinal associations of serum testosterone (T), free androgen index (FAI), and PCOS with cardiorespiratory fitness (CRF) (measured by heart rate after a submaximal exercise test) and grip strength over the 31 to 46 years of age timespan were examined using multivariable linear mixed models adjusted for time, body mass index, homeostatic model assessment of insulin resistance, physical activity and smoking. The results are reported as regression coefficients (β) with corresponding 95% confidence intervals [95% CI].

RESULTS

The third and fourth T and FAI quartiles were associated positively with higher heart rate after the submaximal exercise test in multivariable models indicating poorer CRF compared with women in Q1 of T and FAI (Q3: β of T = 1.58 [95% CI: 0.21 to 2.96], β of FAI = 1.97 [0.54 to 3.39]; Q4: β of T = 1.88 [0.46 to 3.30], β of FAI = 2.70 [1.15 to 4.25]). The second, third, and fourth quartiles of FAI were associated with higher grip strength in multivariable models compared with women in Q1 (Q2: β = 0.59 [0.04 to 1.14], Q3: β = 0.74 [0.16 to 1.30], Q4: β = 0.68 [0.06 to 1.27]). Excluding women with PCOS did not alter these results, while PCOS itself was not associated with CRF or grip strength.

CONCLUSION

Hyperandrogenaemia in premenopausal women was associated with poorer CRF but better grip strength, independently of PCOS, which suggests that HA, rather than PCOS, has an independent and complex association with physical fitness in premenopausal women.

The impact of high-intensity interval training on insulin resistance, oxidative stress, and muscle function in a PCOS rat model

Polycystic ovary syndrome (PCOS) is one of the most common endocrine and metabolic disorders . This study aimed to investigate the effects of high-intensity interval training (HIIT) on insulin resistance, oxidative stress, soleus muscle function, and myokine levels in a PCOS rat model. Female rats were assigned to four groups: Control, PCOS, PCOS+Exercise, and Exercise (n=15 each). PCOS was induced by subcutaneous administration of dehydroepiandrosterone (DHEA) for 3 weeks, and exercise groups underwent HIIT for 12 weeks. Insulin resistance (HOMA-IR), serum oxidative stress markers, hormone levels (FSH, LH), soleus myokine expression, and muscle function were analyzed. Results showed that the PCOS group exhibited increased blood pressure and insulin resistance compared to controls, with a significant reduction in FSH and LH levels in the PCOS+Exercise group. Exercise improved insulin sensitivity and reduced insulin resistance in the PCOS+Exercise group. Serum oxidative stress markers did not differ significantly between groups. Soleus muscle IL-6 levels were significantly reduced in the PCOS+Exercise group. Histological analysis revealed a larger cross-sectional area of the soleus muscle in the PCOS+Exercise group compared to the PCOS group, suggesting improved muscle morphology. Furthermore, exercise improved the functional capacity of soleus muscles, as evidenced by weightlifting performance. These findings indicate that HIIT has beneficial effects on insulin resistance, reproductive hormone levels in PCOS. Exercise also shows potential in slowing oocyte loss and improving follicle health, highlighting its role as a therapeutic intervention for reproductive health in PCOS. This study suggests that HIIT could be a beneficial approach for managing PCOS, and further research is needed to better understand its underlying mechanisms and potential long-term benefits.

Mendelian randomization and multi-omics approach analyses reveal impaired glucose metabolism and oxidative phosphorylation in visceral adipose tissue of women with polycystic ovary syndrome

STUDY QUESTION

What is the significance of visceral adipose tissue (VAT) in the pathogenesis of polycystic ovary syndrome (PCOS) and its impact on the regulation of metabolic disorders in women with PCOS?

SUMMARY ANSWER

We revealed a potentially causal relationship between increased genetically predicted VAT and PCOS-related traits, and found that VAT exhibited impaired glucose metabolism and mitochondrial oxidative phosphorylation (OXPHOS) in women with PCOS.

WHAT IS KNOWN ALREADY

PCOS is a common reproductive endocrine disorder accompanied by many metabolic abnormalities. Adipose tissue is a metabolically active endocrine organ that regulates multiple physiological processes, and VAT has a much stronger association with metabolism than subcutaneous adipose tissue does.

STUDY DESIGN, SIZE, DURATION

Mendelian randomization (MR) analysis was used to investigate the potential causal association between genetically predicted VAT and the risk of PCOS. Data for MR analysis were extracted from European population cohorts. VAT samples from sixteen PCOS patients and eight control women who underwent laparoscopic surgery were collected for proteomics and targeted metabolomics analyses.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PCOS was diagnosed according to the 2003 Rotterdam Criteria. The control subjects were women who underwent laparoscopic investigation for infertility or benign indications. Proteomics was performed by TMT labeling and liquid chromatography-tandem mass spectrometry analysis, and targeted metabolomics was performed by ultra-performance liquid chromatography-tandem mass spectrometry analysis. The key differentially expressed proteins (DEPs) were validated by immunoblotting.

MAIN RESULTS AND THE ROLE OF CHANCE

MR analysis revealed a potentially causal relationship between increased genetically predicted VAT and PCOS, as well as related traits, such as polycystic ovaries, total testosterone, bioavailable testosterone, and anti-Müllerian hormone, while a negative relationship was found with sex hormone-binding globulin. Enrichment pathway analysis of DEPs indicated the inhibition of glycolysis and activation of mitochondrial OXPHOS in the VAT of PCOS patients. MR analysis revealed that key DEPs involved in glycolysis and OXPHOS were significantly linked to PCOS and its related traits. Dot blot assay confirmed a significant decrease in glycolysis enzymes PKM2 and HK1, and an increase in mitochondrial Complex I and III subunits, NDUFS3 and UQCR10. Moreover, metabolomics analysis confirmed down-regulated metabolites of energy metabolic pathways, in particular glycolysis. Further analysis of PCOS and control subjects of normal weight revealed that dysregulation of glucose metabolism and OXPHOS in VAT of women with PCOS was independent of obesity.

LARGE SCALE DATA

The mass spectrometry proteomics data have been deposited to the iProX database (http://www.iprox.org) with the iProX accession: IPX0005774001.

LIMITATIONS, REASONS FOR CAUTION

There may be an overlap in some exposure and outcome data, which might affect the results in the MR analysis.

WIDER IMPLICATIONS OF THE FINDINGS

The changes in protein expression of key enzymes affect their activities and disrupt the energy metabolic homeostasis in VAT, providing valuable insight for identifying potential intervention targets of PCOS.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Key Research and Development Project of China (2021YFC2700402), the National Natural Science Foundation of China (82071608, 82271665), the Key Clinical Projects of Peking University Third Hospital (BYSY2022043), and the CAMS Innovation Fund for Medical Sciences (2019-I2M-5-001). All authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Polycystic ovary syndrome

Despite affecting ~11-13% of women globally, polycystic ovary syndrome (PCOS) is a substantially understudied condition. PCOS, possibly extending to men's health, imposes a considerable health and economic burden worldwide. Diagnosis in adults follows the International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome, requiring two out of three criteria - clinical or biochemical hyperandrogenism, ovulatory dysfunction, and/or specific ovarian morphological characteristics or elevated anti-Müllerian hormone. However, diagnosing adolescents omits ovarian morphology and anti-Müllerian hormone considerations. PCOS, marked by insulin resistance and hyperandrogenism, strongly contributes to early-onset type 2 diabetes, with increased odds for cardiovascular diseases. Reproduction-related implications include irregular menstrual cycles, anovulatory infertility, heightened risks of pregnancy complications and endometrial cancer. Beyond physiological manifestations, PCOS is associated with anxiety, depression, eating disorders, psychosexual dysfunction and negative body image, collectively contributing to diminished health-related quality of life in patients. Despite its high prevalence persisting into menopause, diagnosing PCOS often involves extended timelines and multiple health-care visits. Treatment remains ad hoc owing to limited understanding of underlying mechanisms, highlighting the need for research delineating the aetiology and pathophysiology of the syndrome. Identifying factors contributing to PCOS will pave the way for personalized medicine approaches. Additionally, exploring novel biomarkers, refining diagnostic criteria and advancing treatment modalities will be crucial in enhancing the precision and efficacy of interventions that will positively impact the lives of patients.