Antioxidant supplements relieve insulin resistance but do not improve lipid metabolism in women with polycystic ovary syndrome: a meta-analysis of randomized clinical trials

The effect of long-term exposure to moderate high altitude on adipokines and insulin sensitivity

BACKGROUND

High altitude area refers to plateau area with an altitude of 1500 m or above. Short-term (less than 30 days) exposure to high-altitude environments (hypoxia, low temperature, low pressure) might affect the adipokines level and insulin sensitivity. However, whether long-term exposure to moderate high altitude would have an impact on adipokines and insulin sensitivity remains unknown.

OBJECTIVE

This study aimed to explore the effect of long-term exposure (12 months) to moderate high altitudes (2900 m) on changes in adipokines level and insulin sensitivity.

METHODS

48 healthy adults from Guangdong Province (the average altitude less than 50 m) to Nyingchi (an average altitude of 2900 m) were included with follow-up of 12 months. Before entering Nyingchi, baseline anthropometric indicators (height, weight, blood pressure), metabolic indicators: fasting plasma glucose (FPG), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), insulin resistance index (HOMA-IR), adipokines: adiponectin and leptin, inflammatory indicators: tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6); hypoxia-inducible factor 1alpha (HIF-1α), oxidative stress indicator: malondialdehyde (MDA), antioxidant indicators: superoxide dismutase (SOD) and glutathione (GSH) were determined. After entering Nyingchi, the above indicators were retested at the 1st, 6th, and 12th month. The control group consist of 47 local residents in Nyingchi. Linear mixed effect model was used to analyze the trend of index changes. Multivariate linear regression analysis was analyzed to explore the influence factors of adiponectin at 12th month.

RESULTS

After 12 months exposure to high altitude, the body mass index (BMI), systolic blood pressure (SBP) and FPG of subjects decreased from baseline of 23.51 ± 2.68 kg/m2, 123.68 ± 14.94 mmHg and 5.05 ± 0.36 mmol/L to 22.59 ± 2.56 kg/m2, 116.10 ± 14.68 mmHg and 4.65 ± 0.46 mmol/L respectively, HDL-C increased from baseline of 1.30 ± 0.26 mmol/L to 1.37 ± 0.30 mmol/L. HOMA-IR decreased from baseline 1.70 (1.19, 2.22) to 1.25(1.04, 1.78). Adiponectin increased from 3.85(3.05, 4.98) to 4.75(3.33, 5.88) μg/mL, leptin decreased from 1022.10(496.30, 2508.60) to 729.60(308.78, 1670.20) pg/mL. TNFα decreased from 6.81(5.37, 8.49) to 5.50(4.00, 6.74) pg/mL. The level of HIF-1α increased from baseline 1.91 (1.32, 5.09) to 2.94 (1.65, 15.45) pg/mL. SOD increased from 0.20(0.15, 0.24) to 0.25(0.20, 0.28) U/mL. Multivariate linear regression analysis showed that HIF-1α (β = 0.006, 95 %CI, 0.001-0.012, p = 0.033) and SOD (β = 7.318, 95 %CI, 0.486-14.149, p = 0.037) was the factors that influenced adiponectin level at 12th month after exposure to high altitude.

CONCLUSION

Long-term exposure to moderate high-altitude environments could improve insulin sensitivity and adipocyte function in healthy adults. Elevated HIF-1α and SOD during altitude acclimatization were the beneficial factors for improvement of adipocyte function. It is worthwhile to further explore the effect and the potential therapeutic value of long-term moderate altitude exposure on adults with metabolic disorders.

Efficacy and safety of dietary polyphenol administration as assessed by hormonal, glycolipid metabolism, inflammation and oxidative stress parameters in patients with PCOS: a meta-analysis and systematic review

BACKGROUND

The current knowledge about the efficacy and safety of dietary polyphenol administration in patients with polycystic ovarian syndrome (PCOS) is divergent.

OBJECTIVE

To evaluate the pooled efficacy and safety of dietary polyphenol administration in the treatment of patients with PCOS.

METHODS

The pubmed, Embase, Scopus, Cochrane Library, and Web of Science databases were searched for randomized controlled trials (RCTs) of dietary polyphenol administration for the treatment of PCOS. English-language RCTs involving adults with PCOS were thoroughly searched in electronic databases from the time of their establishment to May 2024. Random-effects models were used because heterogeneity was derived from differences in intervention materials and study duration, among other confounding factors. The effect sizes of the outcomes in the pooled analysis are expressed as weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

A total of 15 RCTs involving 934 patients were finally included. Compared with control treatments, dietary polyphenol administration significantly reduced luteinizing hormone (LH) (WMD: -0.85, 95% CI [-1.32 to -0.38], p = 0.00), and prolactin levels (WMD: -3.73, 95% CI [-6.73 to -0.74], p = 0.01). Dietary polyphenol administration significantly reduced insulin levels (WMD: -0.85, 95% CI [-1.32 to -0.38], p = 0.00). Regarding lipid metabolism, dietary polyphenol administration only reduced triglyceride levels (WMD: -8.96, 95% CI [-16.44 to -1.49], p = 0.02). Malondialdehyde (MDA) (WMD: -0.65, 95% CI [-0.68 to -0.62], p = 0.00), tumor necrosis factor (TNF-α) (WMD: -1.39, 95% CI [-2.41 to -0.37], p = 0.01) concentrations were significantly reduced by dietary polyphenol administration. None of the interventions significantly affected weight, body mass index (BMI), waist circumference (WC), homeostatic model-insulin resistance (HOMA-IR), fasting blood sugar (FBS), glycated hemoglobin (HBA1c), follicle-stimulating hormone (FSH), testosterone (T), dehydroepiandrosterone (DHEA), estradiol (E2), anti-Müllerian hormone (AMH), quantitative insulin-sensitivity check index (QUICKI), sex hormone-binding globulin (SHBG), total antioxidant capacity (TAC), C-peptide, C-reactive protein (CRP), high-density lipoprotein (HDL), low-density lipoprotein (LDL), cholesterol, cholesterol/HDL, acne score, thyroid-stimulating hormone (TSH), aspartate aminotransferase (AST), alanine aminotransferase (ALT) or alkaline phosphatase (ALP).

CONCLUSION

Dietary polyphenol administration was efficacious in patients with PCOS in our study. This review might provide new insight into the treatment of patients with PCOS and the potential of daily polyphenol supplementation in patients with PCOS. Nevertheless, these results must be interpreted carefully as a result of the heterogeneity and risk of bias among the studies and we expect that more high-quality RCTs evaluating the efficacy and safety of dietary polyphenol adnimistration in patients with PCOS will be conducted in the future.

SYSTEMATIC REVIEW REGISTRATION

CRD42024498494.

Efficacy of antioxidant supplementation in improving endocrine, hormonal, inflammatory, and metabolic statuses of PCOS: a meta-analysis and systematic review

Background and aim: A large number of recent studies have reported on the use of antioxidants in patients with polycystic ovary syndrome (PCOS). This study aimed to evaluate the antioxidant effects on PCOS. Methods: We searched PubMed, Embase, Web of Science, and The Cochrane Library to identify randomized controlled trials investigating the use of antioxidants in treating PCOS. Statistical analysis was performed using Review Manager 5.4. Stata17.0 software was used to conduct sensitivity analyses. Results: This meta-analysis included 49 articles and 62 studies. The sample comprised 1657 patients with PCOS from the antioxidant group and 1619 with PCOS from the placebo group. The meta-analysis revealed that the fasting blood glucose levels [standardized mean difference (SMD): -0.31, 95% confidence interval (CI): -0.39 to -0.22, P < 0.00001], the homeostatic model assessment of insulin resistance (SMD: -0.68, 95% CI: -0.87 to -0.50], P < 0.00001), and insulin levels (SMD: -0.68, 95% CI: -0.79 to -0.58, P < 0.00001) were significantly lower in patients with PCOS taking antioxidants than those in the placebo group. Further, total cholesterol levels (SMD: -0.38, 95% CI: -0.56 to -0.20, P < 0.001), low-density lipoprotein cholesterol levels (SMD: -0.24, 95% CI: -0.37 to -0.10, P = 0.0008), and very low-density lipoprotein levels (SMD: -0.53, 95% CI: -0.65 to -0.41, P < 0.00001) were lower in patients with PCOS taking antioxidant supplements compared with the placebo group. Total testosterone (TT) level (SMD: -0.78, 95% CI: -1.15 to -0.42, P < 0.0001), dehydroepiandrosterone level (SMD: -0.42, 95% CI: -0.58 to -0.25, P < 0.00001), and mean standard deviation modified Ferriman-Gallway (MF-G scores) (SMD: -0.63, 95% CI: -0.98 to -0.28, P = 0.0004) were lower in patients taking antioxidant supplements. C-reactive protein (CRP) levels (SMD: -0.48, 95% CI: -0.63 to -0.34, P < 0.000001), body mass index [mean difference (MD): -0.27, 95% CI: -0.50 to -0.03, P = 0.03], weight (MD: -0.73, 95% CI: -1.35 to -0.11, P = 0.02), and diastolic blood pressure (MD: -3.78, 95% CI: -6.30 to -1.26, P = 0.003) were significantly lower. Moreover, the levels of sex hormone-binding protein (SMD: 0.23, 95% CI: 0.07-0.38, P = 0.004), high-density lipoprotein cholesterol (SMD: 0.11, 95% CI: 0.01-0.20, P = 0.03), total antioxidant capacity (SMD: 0.59, 95% CI: 0.31-0.87, P < 0.0001), and quantitative insulin sensitivity index (SMD: 0.01, 95% CI: 0.01-0.02, P < 0.00001) were higher in patients with PCOS who took antioxidant supplements compared with the placebo group. Antioxidant supplements did not affect other analyzed parameters in these patients, including follicle-stimulating hormone, free androgen index, nitric oxide, glutathione, malondialdehyde, and diastolic blood pressure. Conclusions: Antioxidants are beneficial in treating PCOS. Our study might provide a new treatment strategy for patients with clinical PCOS. We hope that more high-quality studies evaluating the effects of antioxidants on patients with PCOS will be conducted in the future. Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42023448088.

Therapeutic Effects and Molecular Mechanism of Chlorogenic Acid on Polycystic Ovarian Syndrome: Role of HIF-1alpha

Chlorogenic acid (CGA) is a powerful antioxidant polyphenol molecule found in many diets and liquid beverages, playing a preventive and therapeutic role in various diseases caused by oxidative stress and inflammation. Recent research has found that CGA can not only improve clinical symptoms in PCOS patients but also improve follicular development, hormone status, and oxidative stress in PCOS rats, indicating the therapeutic effect of CGA on PCOS. Notably, our previous series of studies has demonstrated the expression changes and regulatory mechanisms of HIF-1alpha signaling in PCOS ovaries. Considering the regulatory effect of CGA on the HIF-1alpha pathway, the present article systematically elucidates the therapeutic role and molecular mechanisms of HIF-1alpha signaling during the treatment of PCOS by CGA, including follicular development, steroid synthesis, inflammatory response, oxidative stress, and insulin resistance, in order to further understand the mechanisms of CGA effects in different types of diseases and to provide a theoretical basis for further promoting CGA-rich diets and beverages simultaneously.