Myostatin and its association with abdominal obesity, androgen and follistatin levels in women with polycystic ovary syndrome

Follistatin and follistatin-like 3 in metabolic disorders

Follistatin (FST) is a glycoprotein which main role is antagonizing activity of transforming growth factor β superfamily members. Folistatin-related proteins such as follistatin-like 3 (FSTL3) also reveal these properties. The exact function of them has still not been established, but it can be bound to the pathogenesis of metabolic disorders. So far, there were performed a few studies about their role in type 2 diabetes, obesity or gestational diabetes and even less in type 1 diabetes. The outcomes are contradictory and do not allow to draw exact conclusions. In this article we summarize the available information about connections between follistatin, as well as follistatin-like 3, and metabolic disorders. We also emphasize the strong need of performing further research to explain their exact role, especially in the pathogenesis of diabetes and obesity.

Signaling pathways and targeted therapeutic strategies for polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among women of reproductive age. Although promising strides have been made in the field of PCOS over the past decades, the distinct etiologies of this syndrome are not fully elucidated. Prenatal factors, genetic variation, epigenetic mechanisms, unhealthy lifestyles, and environmental toxins all contribute to the development of this intricate and highly heterogeneous metabolic, endocrine, reproductive, and psychological disorder. Moreover, interactions between androgen excess, insulin resistance, disruption to the hypothalamic-pituitary-ovary (HPO) axis, and obesity only make for a more complex picture. In this review, we investigate and summarize the related molecular mechanisms underlying PCOS pathogenesis from the perspective of the level of signaling pathways, including PI3K/Akt, TGF-β/Smads, Wnt/β-catenin, and Hippo/YAP. Additionally, this review provides an overview of prospective therapies, such as exosome therapy, gene therapy, and drugs based on traditional Chinese medicine (TCM) and natural compounds. By targeting these aberrant pathways, these interventions primarily alleviate inflammation, insulin resistance, androgen excess, and ovarian fibrosis, which are typical symptoms of PCOS. Overall, we hope that this paper will pave the way for better understanding and management of PCOS in the future.

Serum Follistatin Levels are Independently Associated with Exercise Tolerance in Patients with Obesity

OBJECTIVE

Follistatin (FST)/myostatin (MST) myokine-signaling axis is important for muscle metabolism and pathogenesis of obesity. FST, mainly secreted by skeletal muscle and liver, inhibits MST and affects skeletal muscle synthesis. This study aimed to identify the characteristics of myokines and independent predictors of serum FST levels in patients with obesity.

METHODS

In this retrospective cross-sectional study, 226 patients (mean age, 46.6 years; men, 35.4%) with obesity who initially visited an outpatient clinic between June 2014 and September 2020, were included and classified into obesity (25.0 ≤ body mass index (BMI) < 35.0 kg/m2) and severe obesity (BMI ≥35 kg/m2) groups based on the guidelines of the Japan Society for the Study of Obesity. Body composition was measured using bioelectrical impedance analysis and computed tomography. Muscle strength, exercise tolerance, metabolic parameters, and myokines were measured, including serum levels of FST, MST, irisin, and brain-derived neurotrophic factor.

RESULTS

Serum FST levels were significantly higher in the severe obesity group than in the obesity group (median: 768.4 vs. 895.1 pg/mL, P = 0.020). However, the levels of other myokines showed no significant differences between the groups. In Model 1, which included factors that significantly correlated with FST levels, stepwise multivariate regression analysis revealed peak oxygen uptake (VO2) as an independent predictor of FST levels based on the significance of the univariate analysis. Additionally, Model 2 was analyzed by adding myokine level to Model 1, revealing that peak VO2, MST, and irisin levels were independent predictors of FST levels.

CONCLUSION

Serum FST levels were higher in patients in the severe obesity group compared to those in the obesity group. There was an independent association between low exercise tolerance and elevated serum FST levels.

Cord blood myostatin concentrations by gestational diabetes mellitus and fetal sex

INTRODUCTION

Myostatin is a member of the transforming growth factor β superfamily, and is mainly secreted from skeletal muscle. Animal studies have demonstrated that deficiency in myostatin promotes muscle growth and protects against insulin resistance. In humans, gestational diabetes mellitus (GDM) affects fetal insulin sensitivity. Females are more insulin resistant and weigh less than males at birth. We sought to assess whether cord blood myostatin concentrations vary by GDM and fetal sex, and the associations with fetal growth factors.

METHODS

In a study of 44 GDM and 66 euglycemic mother-newborn dyads, myostatin, insulin, proinsulin, insulin-like growth factor (IGF)-1, IGF-2 and testosterone were measured in cord blood samples.

RESULTS

Cord blood myostatin concentrations were similar in GDM vs. euglycemic pregnancies (mean ± SD: 5.5 ± 1.4 vs. 5.8 ± 1.4 ng/mL, P=0.28), and were higher in males vs. females (6.1 ± 1.6 vs. 5.3 ± 1.0 ng/mL, P=0.006). Adjusting for gestational age, myostatin was negatively correlated with IGF-2 (r=-0.23, P=0.02), but not correlated with IGF-1 (P=0.60) or birth weight (P=0.23). Myostatin was strongly correlated with testosterone in males (r=0.56, P<0.001), but not in females (r=-0.08, P=0.58) (test for difference in r, P<0.001). Testosterone concentrations were higher in males vs. females (9.5 ± 6.4 vs. 7.1 ± 4.0 nmol/L, P=0.017), and could explain 30.0% (P=0.039) of sex differences in myostatin concentrations.

DISCUSSION

The study is the first to demonstrate that GDM does not impact cord blood myostatin concentration, but fetal sex does. The higher myostatin concentrations in males appear to be partly mediated by higher testosterone concentrations. These findings shed novel insight on developmental sex differences in insulin sensitivity regulation relevant molecules.

Free-androgen Index in Women with Polycystic Ovarian Syndrome: A Meta-Analysis

Objectives Hyperandrogenism, a key feature of polycystic ovarian syndrome (PCOS), is caused by excess androgen secretion, most commonly of ovarian origin. Although the serum total testosterone (TT) levels have long been used as a traditional measure of hyperandrogenemia in women with PCOS, it is associated with many fallacies due to the fact that a component of TT is linked to sex hormone-binding globulin (SHBG). Recent research has discovered that measuring free testosterone levels and computing the free androgen index (FAI), which is a ratio of TT and SHBG, are better predictors of androgen excess in PCOS. The aim of this meta-analysis is to determine the association of FAI in diagnosing hyperandrogenism and its ability to discriminate PCOS from controls.

Materials and Methods The publicly available databases PubMed, Scopus and Web of Science were searched using MeSH terms, ‘Polycystic Ovarian Syndrome’ OR ‘PCOS’ OR ‘PCOD’ AND ‘Testosterone’ AND ‘Sex Hormone Binding Globulin’ OR ‘SHBG’ to collect the full-text articles for the retrieval of related data of case–control and cross-sectional studies. The studies quality was assessed using the Newcastle–Ottawa scale, and a sub-group analysis and publication bias between the studies was evaluated by funnel plot.

Statistical Analysis The R program (v4.0.3) and R packages ‘metafor’ and ‘dmetar’ were used for statistical analyses of quantitative data and the plots were generated using ‘ggplot2’ package through a comparison of pooled SMD by Egger's linear regression and Beggs-Mazumdar tests.

Results Twenty-four studies involving 7,847 participants including 3,290 controls and 4,557 PCOS were included in the meta-analysis. The pooled data analysis of the included studies showed that the PCOS women had higher FAI than controls, with SMD of 1.56 (95%CI 1.08–2.04; p < 0.01). The publication bias was tested using a funnel plot and Egger's regression asymmetry test, which revealed no risk of publishing bias (p = 0.1727). Additionally, the sub-group meta-analysis of geographic region revealed that FAI levels were more significant in PCOS subjects of Asia and Europe, compared with the American region.

Conclusion Overall, this meta-analysis indicates that FAI could be a reliable marker to differentiate PCOS patients from controls in Asian and European ethnicities.

Myostatin: a multifunctional role in human female reproduction and fertility - a short review

Myostatin (MSTN) is member of the transforming growth factor β (TGF-β) superfamily and was originally identified in the musculoskeletal system as a negative regulator of skeletal muscle growth. The functional roles of MSTN outside of the musculoskeletal system have aroused researchers' interest in recent years, with an increasing number of studies being conducted in this area. Notably, the expression of MSTN and its potential activities in various reproductive organs, including the ovary, placenta, and uterus, have recently been examined. Numerous studies published in the last few years demonstrate that MSTN plays a critical role in human reproduction and fertility, including the regulation of follicular development, ovarian steroidogenesis, granule-cell proliferation, and oocyte maturation regulation. Furthermore, findings from clinical samples suggest that MSTN may play a key role in the pathogenesis of several reproductive disorders such as uterine myoma, preeclampsia (PE), ovary hyperstimulation syndrome (OHSS), and polycystic ovarian syndrome (PCOS). There is no comprehensive review regarding to MSTN related to the female reproductive system in the literature. This review serves as a summary of the genes in reproductive medicine and their potential influence. We summarized MSTN expression in different compartments of the female reproductive system. Subsequently, we discuss the role of MSTN in both physiological and several pathological conditions related to the female fertility and reproduction-related diseases.

Decreased myostatin in response to a controlled DASH diet is associated with improved body composition and cardiometabolic biomarkers in older adults: results from a controlled-feeding diet intervention study

BACKGROUND

Elevated concentrations of myostatin inhibit muscle growth, function and strength. Myostatin is a mediator of sarcopenia and is associated with insulin resistance. For this study we tested the response of a calorie-restricted Dietary Approaches to Stop Hypertension (DASH) diet on changes in myostatin, follistatin, and mystatin:follistatin ratio levels after 12 weeks in comparison to basline in adults aged 65 years and older. Furthermore we evaluated correlations between changes in myostatin, body composition and cardiometabolic biomarkers in this cohort of older adults.

METHODS

This was a controlled-feeding diet intervention study in which females (n = 17) and males (n = 11) aged 65 years and older consumed either 85 g (n = 15) or 170 g (n = 13) of fresh lean beef within a standardized DASH diet for 12-weeks. Myostatin and follistatin concentrations were measured from fasted blood samples collected at 5 timepoints throughout the 12-week feeding intervention period. Correlations were assessed between changes in myostatin and follistatin levels and measures of body composition and cardiometabolic biomarkers.

RESULTS

There were no differences (p > 0.05) in circulating myostatin or follistatin levels between the beef intake groups. However, with beef groups combined myostatin decreased by 17.6% (p = 0.006) and the myostatin-to-follistatin ratio decreased by 16.5% (p < 0.001) in response to the study diet. Decreased myostatin was positively correlated with reductions in waist circumference (R² = 0.163; p = 0.033) and fat mass (R² = 0.233; p = 0.009). There was an inverse relationship between decreased myostatin and increased strength-to-weight ratio (R² = 0.162; p = 0.034). The change in myostatin-to-follistatin ratio was associated with the change in skeletal muscle mass-to-fat mass ratio (R² = 0.176; p = 0.026). Decreased myostatin was positively correlated with reductions in total cholesterol (R² = 0.193; p = 0.012), LDL-C (R² = 0.163; p = 0.031), insulin (R² = 0.234; p = 0.009), and HOMA-IR (R² = 0.248; P = 0.007). There was no change (p > 0.05) in circulating follistatin concentrations in response to the diet intervention.

CONCLUSIONS

The outcomes from this study suggest that a calorie-restricted DASH diet has the potential to reduce myostatin concentrations in older adults. Furthermore these outcomes support interrelationships between myostatin, body composition and cardiometabolic health in adults aged 65 years and older.

TRIAL REGISTRATION

ClinicalTrials.gov; Identifier: NCT04127240 ; Registration Date: 15/10/ 2019.

Intensity Dependent Effects of Interval Resistance Training on Myokines and Cardiovascular Risk Factors in Males With Obesity

OBJECTIVE

To determine the effects of different intensities of interval resistance training (IRT) protocols on the levels of select myokines (decorin, follistatin, myostatin, activin A, transforming growth factor beta-1 [TGF-β1]), and cardiometabolic and anthropometric measures in males with obesity.

METHODS

Forty-four obese males (age: 27.5 ± 9.4 yr.; height: 165.4 ± 2.8 cm; weight: 97.9 ± 2.6 kg and BMI: 35.7 ± 4.3 kg/m²) were randomly assigned to one of four groups (n=11 per group): low-intensity interval resistance training (LIIRT), moderate-intensity interval resistance training (MIIRT), high-intensity interval resistance training (HIIRT) or control (C). The LIIRT group performed 10 exercises in 3 sets of 40% (20 repetitions), the MIIRT group performed 10 exercises in three sets of 60% (13 repetitions), and the HIIRT group performed 10 exercises in three sets of 80% (10 repetitions) of one maximum repetition (1RM), which were followed with active rest of 20% of 1RM and 15 repetitions. The resistance training groups exercised ~70 min per session, 3 days per week, for 12 weeks. Measurements were taken at baseline and after 12 weeks of exercise training.

RESULTS

Baseline levels of myokines, cardiovascular risk factors, anthropometry, body composition, and cardio-respiratory fitness were not different between the four groups (p>0.05). The group x time interactions for decorin, activin A, follistatin, myostatin, and TGF-β1, total cholesterol (TC), triglyceride (TG), high-density cholesterol (HDL), low-density cholesterol (LDL), anthropometry, body composition, and cardio-respiratory fitness were statistically significant (p<0.05). There were increases in post-test values for decorin, follistatin, HDL (p<0.05) and decreases in TC, TG, TGF-β1, LDL, and myostatin levels in the LIIRT, MIIRT, and HIIRT groups compared to pretest values (p<0.05). Changes in fat mass, VO_2peak, HDL, TG, glucose, activin A, decorin were not significant in LIIRT compared to the control group, while changes in activin A, follistatin, and TFG-β1 levels were greater in HIIRT and MIIRT groups compared to the LIIRT group (p<0.05).

CONCLUSION

The LIIRT, MIIRT, and HIIRT protocols all produced beneficial changes in decorin, activin A, follistatin, myostatin, and TGF-β1 levels, and cardiometabolic risk factors, with greater effects from the MIIRT and HIIRT protocols compared to LIIRT.

Characterizing skeletal muscle dysfunction in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine condition affecting women. It has traditionally been viewed as a primarily reproductive disorder; however, it is increasingly recognized as a lifelong metabolic disease. Women with PCOS are at increased risk of insulin resistance (IR), type 2 diabetes mellitus, non-alcoholic fatty liver disease and cardiovascular disease. Although not currently a diagnostic criterion, IR is a cardinal pathophysiological feature and highly prevalent in women with PCOS. Androgens play a bidirectional role in the pathogenesis of IR, and there is a complex interplay between IR and androgen excess in women with PCOS. Skeletal muscle has a key role in maintaining metabolic homeostasis and is also a metabolic target organ of androgen action. Skeletal muscle is the organ responsible for the majority of insulin-mediated glucose disposal. There is growing interest in the relationship between skeletal muscle, androgen excess and mitochondrial dysfunction in the pathogenesis of metabolic disease in PCOS. Molecular mechanisms underpinning defects in skeletal muscle dysfunction in PCOS remain to be elucidated, but may represent promising targets for future therapeutic intervention. In this review, we aim to explore the role of skeletal muscle in metabolism, focusing particularly on perturbations in skeletal muscle specific to PCOS as observed in recent molecular and in vivo human studies. We review the possible role of androgens in the pathophysiology of skeletal muscle abnormalities in PCOS, and identify knowledge gaps, areas for future research and potential therapeutic implications. Despite increasing interest in the area of skeletal muscle dysfunction in women with PCOS, significant challenges and unanswered questions remain, and going forward, novel innovative approaches will be required to dissect the underlying mechanisms.

Regulatory Role and Potential Importance of GDF-8 in Ovarian Reproductive Activity

Growth differentiation factor-8 (GDF-8) is a member of the transforming growth factor-beta superfamily. Studies in vitro and in vivo have shown GDF-8 to be involved in the physiology and pathology of ovarian reproductive functions. In vitro experiments using a granulosa-cell model have demonstrated steroidogenesis, gonadotrophin responsiveness, glucose metabolism, cell proliferation as well as expression of lysyl oxidase and pentraxin 3 to be regulated by GDF-8 via the mothers against decapentaplegic homolog signaling pathway. Clinical data have shown that GDF-8 is expressed widely in the human ovary and has high expression in serum of obese women with polycystic ovary syndrome. GDF-8 expression in serum changes dynamically in patients undergoing controlled ovarian hyperstimulation. GDF-8 expression in serum and follicular fluid is correlated with the ovarian response and pregnancy outcome during in vitro fertilization. Blocking the GDF-8 signaling pathway is a potential therapeutic for ovarian hyperstimulation syndrome and ovulation disorders in polycystic ovary syndrome. GDF-8 has a regulatory role and potential importance in ovarian reproductive activity and may be involved in folliculogenesis, ovulation, and early embryo implantation.

Metabolic Syndrome in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age. Although its essential clinical manifestation includes a plethora of symptoms and signs, which largely reflects the underlying hyperandrogenism, oligo/anovulation, and polycystic ovarian morphology, PCOS may also be associated with many metabolic derangements. These metabolic derangements happen to overlap with many of the core constituents of the metabolic syndrome (MBS)—increased insulin resistance, central obesity, and dyslipidemia. The two disorders also display similarly increased risks for certain metabolic and vascular diseases, such as type 2 diabetes mellitus, hypertension, and cardiovascular diseases. Due to the many similarities between metabolic syndrome and PCOS, this review aims to examine the evidence concerning the overlapping features, the risks for comorbidities, possible shared mechanisms, and treatment strategies in patients with coexisting PCOS and MBS.

Skeletal muscle myostatin gene expression and sarcopenia in overweight and obese middle‐aged and older adults

Background

Myostatin (MSTN) is a key negative regulator of muscle mass in humans and animals, having direct and indirect influences on molecular regulators of atrophy and hypertrophy, thus potentially impacting fitness and physical function. We have shown that myostatin is elevated in conditions of chronic disability (e.g. paretic limb of stroke). Our hypothesis is that myostatin would be elevated in older adults with sarcopenia. The purpose of this study was to examine the role of skeletal muscle myostatin in sarcopenia.

Methods

Sixty-four overweight to obese aged 45–81 years underwent a maximal aerobic capacity (VO₂max) test, dual-energy X-ray absorptiometry (DXA) scan to determine appendicular lean tissue (ALM), and vastus lateralis muscle biopsy to determine myostatin mRNA expression by quantitative real time PCR (Q-RT-PCR). Rates of sarcopenia were determined using (ALM/BMI), and sarcopenia was defined as <0.789 in men and <0.512 in women. Subjects had low fitness (VO₂max: 22.7 ± 0.7 mL/kg/min) and on average 40.9 ± 1% body fat.

Results

The prevalence of sarcopenia in this cohort was 16%. BMI, % body fat, and fat mass were higher in adults with sarcopenia than those without sarcopenia (all P < 0.001). Myostatin mRNA expression was lower in those without sarcopenia than those with sarcopenia (P < 0.05) and higher in men than women (P < 0.001). Myostatin expression was associated with BMI (r = 0.36, P < 0.01) and mid-thigh intramuscular fat (r = 0.29, P < 0.05).

Conclusion

Given that myostatin is important in muscle atrophy, fat accumulation, and sarcopenia, further work could address its implication in other aging cohorts of disability and chronic disease.

Association of Serum Myostatin with Body Weight, Visceral Fat Volume, and High Sensitivity C-Reactive Protein But Not With Muscle Mass and Physical Fitness in Premenopausal Women

BACKGROUND

The myokine myostatin regulates muscle mass and has been linked to insulin resistance and metabolic syndrome. However, data on its role in humans is still limited. We, therefore, investigated the associations of serum myostatin with muscle mass, physical fitness, and components of the metabolic syndrome in a cohort of premenopausal women.

METHODS

We undertook a cross-sectional analysis of 233 women from the monocenter study PPSDiab, conducted in Munich, Germany. Participants had recently completed a pregnancy with or without gestational diabetes. Our analysis included medical history, anthropometrics, oral glucose tolerance testing, laboratory chemistry, cardiopulmonary exercise testing, and magnetic resonance imaging (n=142) of visceral fat volume, left quadriceps muscle mass, and muscle fat content. Serum myostatin was quantified by a competitive enzyme-linked immunosorbent assay.

RESULTS

We observed positive correlations of serum myostatin with body mass index (ρ=0.235; p=0.0003), body fat percentage (ρ=0.166; p=0.011), waist circumference (ρ=0.206; p=0.002), intraabdominal fat volume (ρ=0.182; p=0.030) and high-sensitivity C-reactive protein (ρ=0.175; p=0.008). These correlations were reproduced in linear regression analyses with adjustment for age and time after delivery. We saw no correlations with muscle mass, physical fitness, insulin sensitivity, triglycerides, HDL cholesterol, and blood pressure.

CONCLUSIONS

Our observation of elevated serum myostatin in women with a higher body fat percentage, visceral obesity, and elevated c-reactive protein suggests that this myokine contributes to the altered muscle-adipose tissue crosstalk in metabolic syndrome. Elevated myostatin may advance this pathophysiologic process and could also impair the efficacy of exercise interventions. Further mechanistic studies, therefore, seem warranted.

Differential Effects of Various Androgens on Polycystic Ovary Syndrome

The hyperandrogenism in polycystic ovary syndrome (PCOS) is associated with the risk for the future development of the cardiovascular disease. The objective of the study is to verify whether different androgens have the same harmful effect. This cross-sectional study enrolled 823 women with PCOS: 627 (76.2%) with biochemical hyperandrogenism and 196 (23.8%) with normal androgen levels. The role of individual androgen was evaluated using univariate and multivariate logistic regression. In normoandrogenemic PCOS (NA-PCOS), free androgen index (FAI) predicted significant abnormality in visceral adipose index (VAI, OR=9.2, p=0.002) and dehydroepiandrosterone (DHEA) predicted against alteration in β-cell function (OR=0.5, p=0.007). In hyperandrogenemic PCOS (HA-PCOS), FAI predicted derangements in waist triglyceride index (WTI), VAI, and lipid accumulation product (LAP) (OR ranging from 1.6 to 5.8, p<0.05). DHEA weakly predicted against VAI (OR 0.7, p=0.018), dehydroepiandrosterone sulfate (DHEAS) tended to predict against the conicity index (OR=0.7, p=0.037). After multiple regression, FAI retained significant strength to predict various anthropometric and metabolic abnormalities (OR ranging from 1.1 to 3.0, p<0.01), DHEA was kept as a protector factor against WTI, LAP, and VAI (OR ranging from 0.6 to 0.9; p<0.01) and DHEAS against the conicity index (OR=0.5, p<0.001). In conclusion, the free androgen index was the most powerful predictor of anthropometric and metabolic abnormalities of polycystic ovary syndrome. Conversely, DHEA and DHEAS demonstrated protective effects against disorders in some markers of obesity and abnormal metabolism.

Regulation of circulating CTRP-2/CTRP-9 and GDF-8/GDF-15 by intralipids and insulin in healthy control and polycystic ovary syndrome women following chronic exercise training

Background

Polycystic ovary syndrome (PCOS) is associated with obesity, diabetes, and insulin resistance. The circulating C1Q/TNF-related proteins (CTRP-2, CTRP-9) and growth differentiation factors (GDF-8, GDF-15) contribute to glucose and lipid homeostasis. The effects of intralipids and insulin infusion on CTRP-2, CTRP-9, GDF-8 and GDF-15 in PCOS and control subjects before and after chronic exercise training were examined.

Methods

Ten PCOS and nine healthy subjects were studied at baseline status and after moderate-intensity chronic exercise training (1 h exercise, 3 times per week, 8 weeks). All participants were infused with 1.5 mL/min of saline or intralipids (20%) for 5 h, and during the last 2 h of saline or intralipids infusion hyperinsulinemic-euglycemic clamp (HIEC) was performed. CTRP-2, CTRP-9, GDF-8 and GDF-15 levels were measured at 0, 3 and 5 h.

Results

Intralipids dramatically increased CTRP-2 levels in PCOS (P = 0.02) and control (P = 0.004) subjects, which was not affected by insulin infusion or by exercise. Intralipids alone had no effects on CTRP-9, GDF-8, or GDF-15. Insulin increased the levels of GDF-15 in control subjects (P = 0.05) during the saline study and in PCOS subjects (P = 0.04) during the intralipid infusion. Insulin suppressed CTRP9 levels during the intralipid study in both PCOS (P = 0.04) and control (P = 0.01) subjects. Exercise significantly reduced fasting GDF-8 levels in PCOS (P = 0.03) and control (P = 0.04) subjects; however, intralipids infusion after chronic exercise training increased GDF-8 levels in both PCOS (P = 0.003) and control (P = 0.05) subjects and insulin infusion during intralipid infusion reduced the rise of GDF-8 levels.

Conclusion

This study showed that exogenous lipids modulate CTRP-2, which might have a physiological role in lipid metabolism. Since chronic exercise training reduced fasting GDF-8 levels; GDF-8 might have a role in humoral adaptation to exercise. GDF-15 and CTRP-9 levels are responsive to insulin, and thus they may play a role in insulin responses.

Circulating resistin and follistatin levels in obese and non-obese women with polycystic ovary syndrome: A systematic review and meta-analysis

This meta-analysis was performed to resolve the inconsistencies regarding resistin and follistatin levels in women with polycystic ovary syndrome (PCOS) by pooling the available evidence. A systematic literature search using PubMed and Scopus was carried out through November 2020 to obtain all pertinent studies. Weighted mean differences (WMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between the levels of resistin and follistatin with PCOS in the overall and stratified analysis by obesity status. A total of 47 publications, 38 for resistin (2424 cases; 1906 controls) and 9 studies for follistatin (815 cases; 328 controls), were included in the meta-analysis. Resistin levels were significantly higher in PCOS women compared with non-PCOS controls (WMD = 1.96 ng/ml; 95%CI = 1.25–2.67, P≤0.001) as well as in obese PCOS women vs. obese controls, and in non-obese PCOS women compared with non-obese controls, but not in obese PCOS vs. non-obese PCOS patients,. A significantly increased circulating follistatin was found in PCOS patients compared with the controls (WMD = 0.44 ng/ml; 95%CI = 0.30–0.58, P≤0.001) and in non-obese PCOS women compared with non-obese controls and in obese PCOS women vs. obese controls, but, no significant difference in follistatin level was observed in obese PCOS compared with non-obese PCOS women. Significant heterogeneity and publication bias was evident for some analyses. Circulating levels of resistin and follistatin, independent of obesity status, are higher in women with PCOS compared with controls, showing that these adipokines may contribute to the pathology of PCOS.

Spirulina supplementation during gradual weight loss in competitive wrestlers

We aimed to assess the effects of spirulina supplementation during gradual weight loss on serum concentrations of follistatin (FST), myostatin (MST), insulin-like growth factor 1 (IGF-1), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and body composition in competitive wrestlers. Forty competitive wrestlers (age: 22 (sem 2) years) were randomly assigned to one of two groups: gradual weight loss + spirulina (SP; n 20) or gradual weight loss + placebo (PL; n 20). Subjects in both groups lost weight according to a designed diet over 12 d and were required to reduce baseline body mass (BM) by 4%. Subjects in the SP group received two tablets of spirulina, while subjects in the PL received two tablets of placebo before each meal. Concentrations of mentioned serum markers and body composition were measured before and after the interventions. BM (SP = -3·1 kg and PL = -2·9 kg), body fat percentage (BFP) (SP = -2·1 % and PL = -0·6 %), fat mass (FM) (SP = -2·2 kg and PL = -0·9 kg) and skeletal muscle mass (SP = -1·4 kg and PL = -1·5 kg) significantly decreased in both groups (P < 0·05). The changes in BFP and FM were significantly greater in SP compared with the PL group (P < 0·001). Additionally, MST (SP = -0·1 ng/ml), AST (SP = -2·1 u/l) and ALT (SP = -2·7 u/l) concentrations significantly diminished in SP group (P = 0·005), while FST (PL = -0·1 ng/ml) and IGF-1 (PL = -2·6 ng/ml) concentrations significantly decreased in PL group (P < 0·05). Spirulina supplementation during gradual weight loss is beneficial in reducing BFP, FM, MST and liver enzymes while maintaining IGF-1 and FST concentrations in competitive wrestlers.

The Exploration of Poor Ovarian Response-Related Risk Factors: A Potential Role of Growth Differentiation Factor 8 in Predicting Ovarian Response in IVF-ET Patient

Controlled ovarian hyperstimulation (COH) is the most common therapeutic protocol to obtain a considerable number of oocytes in IVF-ET cycles. To date, the risk factors affecting COH outcomes remain elusive. Growth differentiation factor 8 (GDF-8), a member of transforming growth factor β (TGF-β) superfamily, has been long discerned as a crucial growth factor in folliculogenesis, and the aberrant expression of GDF-8 is closely correlated with the reproductive diseases. However, less is known about the level of GDF-8 in IVF-ET patients with different ovarian response. In the present study, the potential risk factors correlated with ovarian response were explored using logistic regression analysis methods. Meanwhile, the expression changes of GDF-8 and its responsible cellular receptors in various ovarian response patients were determined. Our results showed that several factors were intensely related to poor ovarian response (POR), including aging, obesity, endometriosis, surgery history, and IVF treatment, while irregular menstrual cycles and PCOS contribute to hyperovarian response (HOR). Furthermore, POR patients exhibited a decrease in numbers of MII oocytes and available embryos, thereby manifesting a lower clinical pregnancy rate. The levels of GDF-8, ALK5, and ACVR2B in POR patients were higher compared with those in control groups, whereas the expression level of ACVR2A decreased in poor ovarian response patients. In addition, clinical correlation analysis results showed that the concentration of GDF-8 was negatively correlated with LH and estradiol concentration and antral follicle count. Collectively, our observations provide a novel insight of ovarian response-associated risk factors, highlighting the potential role of GDF-8 levels in ovarian response during COH process.

Aberrant elevation of GDF8 impairs granulosa cell glucose metabolism via upregulating SERPINE1 expression in patients with PCOS

Clinical investigations have demonstrated that polycystic ovary syndrome (PCOS) is often accompanied by insulin resistance (IR) in more than 70% of women with PCOS. However, the etiology of PCOS with IR remains to be characterized. Growth differentiation factor 8 (GDF8) is an intraovarian factor that plays a vital role in the regulation of follicle development and ovulation. Previous studies have reported that GDF8 is a pathogenic factor in glucose metabolism disorder in IR patients. To date, the role of GDF8 on glucose metabolism of granulosa cell in PCOS patients remains to be determined. In the current study, we demonstrated that the expression and accumulation of GDF8 in human granulosa-lutein (hGL) cells and follicular fluid from PCOS patients were higher compared with those of non-PCOS women. GDF8 treatment caused glucose metabolism defects in hGL cells. Transcriptome sequencing results showed that SERPINE1 mediated GDF8-induced impairment of hGL glucose metabolism defects. Using pharmacological and small interfering RNA (siRNA)-mediated knockdown approaches, we demonstrated that GDF8 upregulated the expression of SERPINE1 via the ALK5-mediated SMAD2/3-SMAD4 signaling pathway. Interestingly, the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway was also activated with GDF8 treatment but did not participate in the effect of GDF8 on SERPINE1 expression. Our results also showed that TP53 was required for the GDF8-stimulated increase in SERPINE1 expression. Importantly, our study demonstrated that SB-431542 treatment significantly improved DHEA-induced PCOS-like ovaries. These findings support a potential role for GDF8 in metabolic disorders in PCOS.

Serum myostatin levels are positively associated with diabetic retinopathy in individuals with type 2 diabetes mellitus

AIM

To examine the relationship between serum myostatin levels and diabetic retinopathy in individuals with type 2 diabetes mellitus (DM).

METHODS

This cross-sectional study evaluated 246 individuals with type 2 DM. Analysis of covariance was performed after adjusting for confounders. A logistic regression model was used to evaluate the relationship between serum myostatin levels and diabetic retinopathy.

RESULTS

Serum myostatin levels were significantly higher in individuals with diabetic retinopathy than in those without. After adjusting for other covariates, the mean serum myostatin levels were significantly different according to the severity of retinopathy (without diabetic retinopathy, 2234 pg/mL; non-proliferative diabetic retinopathy, 2698 pg/mL; and proliferative diabetic retinopathy, 3076 pg/mL; p for trend = 0.004). The multivariate analysis showed that serum myostatin levels were significantly associated with diabetic retinopathy (odds ratio for every 1 standard deviation-increase in logarithmic value, 1.77; 95% confidence interval: 1.21-2.59; p = 0.003).

CONCLUSION

Serum myostatin levels were positively associated with diabetic retinopathy in individuals with type 2 DM.

Follicular localization of growth differentiation factor 8 and its receptors in normal and polycystic ovary syndrome ovaries

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age and its etiology has not been characterized. Growth differentiation factor 8 (GDF8) is a member of the transforming growth factor-β superfamily that plays a critical role in the regulation of ovarian functions. However, the expression pattern of GDF8 in the human ovary is not yet clear. This study examined the cellular distribution of GDF8 and its putative cellular receptors (ACVR2A, ACVR2B, and ALK5) in a series of normal (n = 34) and PCOS ovaries (n = 14). The immunostaining of GDF8, ACVR2A, ACVR2B, and ALK5 was detected in the oocytes regardless of the developmental stage. All these proteins were localized in antral follicles in normal and PCOS ovaries, and the expression of these proteins increased with increasing follicle diameter. A significantly higher expression of GDF8 was detected in the granulosa cells than in the matched theca cells (TCs). These proteins were also localized in the luteal cells of the corpus luteum. Granulosa cells and TCs of large antral follicles in PCOS ovaries display a higher expression of these proteins. The higher expression levels of GDF8 and its functional receptors (ACVR2A, ACVR2B, and ALK5) in antral follicles of PCOS ovaries than those in normal ovaries suggest the possible involvement of dysregulated GDF8 in the pathogenesis of PCOS.

Major determinants of circulating myostatin in polycystic ovary syndrome

The present study was designed to investigate the possible impact of hormonal and demographic parameters of patients with polycystic ovary syndrome (PCOS) on the circulating levels of myostatin. The study cohort comprised 46 patients with PCOS and 42 healthy female controls, and all subjects were of normal weight. Multiple regression analysis was applied to investigate the possible associations between serum myostatin levels and other laboratory parameters. Evaluation of the levels of myostatin revealed no significant differences between the PCOS and control groups (P>0.05). In the control group, no significant correlations were identified between the myostatin levels and any other laboratory parameters. Only low-density-lipoprotein cholesterol (LDL-C) levels in the PCOS group were revealed to be significantly, although negatively, associated with myostatin levels (P=0.018). In the regression model of the PCOS group, an increase in LDL-C and prolactin (PRL) were associated with a decrease in myostatin (P=0.001 and P=0.013, respectively). Furthermore, a decrease in sex hormone-binding globulin (SHBG), fasting blood glucose (FBG) and monocytes were associated with an increase in myostatin (P=0.028, P<0.001 and P=0.026, respectively). An increase in triglycerides was also associated with an increase in myostatin (P=0.001). In the regression model of the control group, a decrease in LDL-C was associated with an increase in myostatin (P=0.003) and a decrease in thyroid-stimulating hormone was associated with a decrease in myostatin (P=0.028). These results indicated that the normal range of myostatin levels in patients with PCOS is regulated by changes in the circulating levels of PRL, LDL-C, SHBG, triglycerides, monocytes and FBG.

Tight interplay in early pregnancy between follistatin and anti-mullerian hormone in women with polycystic ovarian syndrome (PCOS)

PURPOSE

Follistatin levels increase during the course of pregnancy and may play a role in ovarian arrest, reflected by the simultaneous decrease of anti-mullerian-hormone (AMH) levels. The aim of the study was to investigate AMH and follistatin levels during the hormonal window at the beginning of pregnancy. Since both parameters are described as deregulated in polycystic ovarian syndrome (PCOS), subgroup analysis of PCOS patients may additionally elucidate their interplay and effects on ovarian activity.

METHODS

Serum samples were retrospectively analyzed using the AMH Gen II ELISA and the Human Follistatin Quantikine ELISA Kit. Samples were collected longitudinally from 57 patients (32 with PCOS and 25 controls) before conception and during the first trimester. In 18 patients, measurements from the early and the late first trimester were available. Potential associations of AMH and follistatin levels with PCOS-related parameters were compared between the subgroups as well as longitudinally before and in the first trimester of pregnancy. For statistical analysis, the Spearman's correlation, Wilcoxon test, t test, Friedman test and multiple linear regression analysis was performed.

RESULTS

In contrast to AMH, follistatin levels differed not between controls and PCOS patients before and in pregnancy. In both subgroups, AMH levels significantly decreased and follistatin levels significantly increased in longitudinally performed measurements before conceiving and in the first trimester of pregnancy.

CONCLUSION

Follistatin levels are not suited as a biomarker for PCOS, but could be involved in suppressing ovarian activity, as reflected by AMH levels at the beginning of pregnancy.

Oocyte-somatic cell interactions in the human ovary-novel role of bone morphogenetic proteins and growth differentiation factors

BACKGROUND

Initially identified for their capability to induce heterotopic bone formation, bone morphogenetic proteins (BMPs) are multifunctional growth factors that belong to the transforming growth factor β superfamily. Using cellular and molecular genetic approaches, recent studies have implicated intra-ovarian BMPs as potent regulators of ovarian follicular function. The bi-directional communication of oocytes and the surrounding somatic cells is mandatory for normal follicle development and oocyte maturation. This review summarizes the current knowledge on the physiological role and molecular determinants of these ovarian regulatory factors within the human germline-somatic regulatory loop.

OBJECTIVE AND RATIONALE

The regulation of ovarian function remains poorly characterized in humans because, while the fundamental process of follicular development and oocyte maturation is highly similar across species, most information on the regulation of ovarian function is obtained from studies using rodent models. Thus, this review focuses on the studies that used human biological materials to gain knowledge about human ovarian biology and disorders and to develop strategies for preventing, diagnosing and treating these abnormalities.

SEARCH METHODS

Relevant English-language publications describing the roles of BMPs or growth differentiation factors (GDFs) in human ovarian biology and phenotypes were comprehensively searched using PubMed and the Google Scholar database. The publications included those published since the initial identification of BMPs in the mammalian ovary in 1999 through July 2016.

OUTCOMES

Studies using human biological materials have revealed the expression of BMPs, GDFs and their putative receptors as well as their molecular signaling in the fundamental cells (oocyte, cumulus/granulosa cells (GCs) and theca/stroma cells) of the ovarian follicles throughout follicle development. With the availability of recombinant human BMPs/GDFs and the development of immortalized human cell lines, functional studies have demonstrated the physiological role of intra-ovarian BMPs/GDFs in all aspects of ovarian functions, from follicle development to steroidogenesis, cell–cell communication, oocyte maturation, ovulation and luteal function. Furthermore, there is crosstalk between these potent ovarian regulators and the endocrine signaling system. Dysregulation or naturally occurring mutations within the BMP system may lead to several female reproductive diseases. The latest development of recombinant BMPs, synthetic BMP inhibitors, gene therapy and tools for BMP-ligand sequestration has made the BMP pathway a potential therapeutic target in certain human fertility disorders; however, further clinical trials are needed. Recent studies have indicated that GDF8 is an intra-ovarian factor that may play a novel role in regulating ovarian functions in the human ovary.

WIDER IMPLICATIONS

Intra-ovarian BMPs/GDFs are critical regulators of folliculogenesis and human ovarian functions. Any dysregulation or variations in these ligands or their receptors may affect the related intracellular signaling and influence ovarian functions, which accounts for several reproductive pathologies and infertility. Understanding the normal and pathological roles of intra-ovarian BMPs/GDFs, especially as related to GC functions and follicular fluid levels, will inform innovative approaches to fertility regulation and improve the diagnosis and treatment of ovarian disorders.

Serum GDF-8 levels change dynamically during controlled ovarian hyperstimulation in patients undergoing IVF/ICSI-ET

Growth differentiation factor-8 (GDF-8) is found in the human serum, follicular fluid and granulosa cells. Our previous studies have shown that the human cumulus expansion and steroidogenesis can be regulated by GDF-8. However, thus far, the expression profile of GDF-8 in serum and whether the level of serum GDF-8 influences pregnancy results for patients treated with in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET) is totally unknown. In this study, we showed that GDF-8 had a dynamic trend during controlled ovarian hyperstimulation (COH) procedure. On human chorionic gonadotropin (hCG) administration day, patients with a GDF-8 level higher than 4.7 ng/ml had lower progesterone levels and a higher pregnancy rate. From hCG day to oocyte pick-up day, patients with a GDF-8 decrease greater than 1.3 ng/ml had a higher progesterone increase and a higher pregnancy rate. Importantly, the levels of GDF-8 were negatively correlated with progesterone levels. Our findings provide evidences that GDF-8 plays an important role in ensuring successful pregnancy by regulating progesterone levels.

Hepatic manifestations of women with polycystic ovary syndrome

Women with polycystic ovary syndrome (PCOS) have a higher prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) than the general population. The link between NAFLD/NASH and PCOS is not just a coincidence. Indeed, both of these disorders comprise common risk factors, including central obesity, insulin resistance, chronic low-grade inflammation, and hyperandrogenemia. The characteristics of hyperandrogenemia in women with PCOS include elevated total and free testosterone levels and low sex hormone-binding globulin levels and are reported to be associated with NAFLD and elevated liver enzymes; however, not all elevated androgen levels in women with PCOS have the same adverse effects on the liver. With the exception of weight loss and encouraging exercise in obese women, few evidence-based effective treatments target NAFLD/NASH in women with PCOS. Selective antiandrogens and insulin sensitizers might be beneficial in treating NAFLD/NASH in women with PCOS, but further elucidation is needed.

Functional microarray analysis of differentially expressed genes in granulosa cells from women with polycystic ovary syndrome related to MAPK/ERK signaling

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age. Although its aetiology and pathogenesis remain unclear, recent studies suggest that the dysfunction of granulosa cells may partly be responsible. This study aimed to use cDNA microarray technology to compare granulosa cell gene expression profiles in women with and without PCOS to identify genes that may be aetiologically implicated in the pathogenesis of PCOS. The study cohort included 12 women undergoing in vitro fertilization, six with PCOS and six without PCOS. Differential gene expression profiles were classified by post-analyses of microarray data, followed by western blot analyses to confirm the microarray data of selected genes. In total, 243 genes were differentially expressed (125 upregulated and 118 downregulated) between the PCOS and non-PCOS granulosa cells. These genes are involved in reproductive system development, amino acid metabolism and cellular development and proliferation. Comparative analysis revealed genes involved in the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) signaling pathways. Western blot analyses confirmed that mitogen-activated protein kinase kinase kinase 4 and phospho-ERK1/2 were decreased in PCOS granulosa cells. This study identified candidate genes involved in MAPK/ERK signaling pathways that may influence the function of granulosa cells in PCOS.

Myostatin as a mediator of sarcopenia versus homeostatic regulator of muscle mass: insights using a new mass spectrometry-based assay

BACKGROUND

Myostatin is a protein synthesized and secreted by skeletal muscle that negatively regulates muscle mass. The extent to which circulating myostatin levels change in the context of aging is controversial, largely due to methodological barriers.

METHODS

We developed a specific and sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) assay to measure concentrations of myostatin and two of its key inhibitors, follistatin-related gene (FLRG) protein and growth and serum protein-1 (GASP-1) in 80 younger (<40 years), 80 older (>65 years), and 80 sarcopenic older women and men.

RESULTS

Older women had 34 % higher circulating concentrations of myostatin than younger women. Per unit of lean mass, both older and sarcopenic older women had >23 % higher myostatin levels than younger women. By contrast, younger men had higher myostatin concentrations than older men with and without sarcopenia. Younger men had approximately twofold higher concentrations of myostatin than younger women; however, older women and sarcopenic older women had significantly higher relative myostatin levels than the corresponding groups of men. In both sexes, sarcopenic older subjects had the highest concentrations of FLRG. Circulating concentrations of myostatin exhibited positive, but not robust, correlations with relative muscle mass in both sexes.

CONCLUSIONS

Our data suggest that myostatin may contribute to the higher prevalence of sarcopenia in women but acts as a homeostatic regulator of muscle mass in men. Moreover, this new LC-MS/MS-based approach offers a means to determine the extent to which myostatin serves as a biomarker of muscle health in diverse conditions of muscle loss and deterioration.

Growth differentiation factor 8 down-regulates pentraxin 3 in human granulosa cells

Growth differentiation factor 8 (GDF8), also known as myostatin, is highly expressed in the mammalian musculoskeletal system and plays critical roles in the regulation of skeletal muscle growth. Though not exclusively expressed in the musculoskeletal system, the expression and biological function of GDF8 has never been examined in the human ovary. Pentraxin 3 (PTX3) plays a key role in the assembly of extracellular matrix, which is essential for cumulus expansion, ovulation and in vivo fertilization. The aim of this study was to investigate GDF8 expression and function in human granulosa cells and to examine its underlying molecular determinants. An established immortalized human granulosa cell line (SVOG), granulosa cell tumor cell line (KGN) and primary granulosa-lutein cells were used as study models. We now demonstrate for the first time that GDF8 is expressed in human granulosa cells and follicular fluid. All 16 follicular fluid samples tested contained GDF8 protein at an average concentration of 3 ng/ml. In addition, GDF8 treatment significantly decreased PTX3 mRNA and protein levels. These suppressive effects, along with the induction of SMAD2/3 phosphorylation, were abolished by co-treatment with the ALK4/5/7 inhibitor SB431542. Knockdown of ALK5, ACVR2A/ACVR2B or SMAD4 reversed the effects of GDF8-induced PTX3 suppression. These results indicate that GDF8 down-regulates PTX3 expression via ACVR2A/ACVR2B-ALK5-mediated SMAD-dependent signaling in human granulosa cells. These novel findings support a potential role for GDF8 in the regulation of follicular function, likely via autocrine effects on human granulosa cells.

Symptom patterns and phenotypic subgrouping of women with polycystic ovary syndrome: association between endocrine characteristics and metabolic aberrations

STUDY QUESTION

What are the potential endocrine characteristics related to risk and severity of metabolic disturbances in women with polycystic ovary syndrome (PCOS)?

SUMMARY ANSWER

Women with PCOS could be subtyped into four subgroups according to heterogeneous endocrine characteristics and the major predictive endocrine factors for metabolic aberrations among different subgroups were free androgen index (FAI) and luteinizing hormone (LH) levels.

WHAT IS KNOWN ALREADY

Women diagnosed with PCOS present with highly heterogeneous phenotypes, including endocrine and metabolic aberrations. Different strategies have been proposed to predict the metabolic outcomes but whether the endocrine factors can solely predict the metabolic aberrations is still inconclusive.

STUDY DESIGN, SIZE, DURATION

A cross-sectional study including 460 patients recruited from a reproductive endocrinology outpatient clinic of a tertiary medical center.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients with PCOS diagnosed according to the 2003 Rotterdam criteria were studied. Clinical history recorded by questionnaires, anthropometric measurements, biochemistry tests after an overnight fast, and pelvic ultrasonography were collected from all patients.

MAIN RESULTS AND THE ROLE OF CHANCE

Applying a matrix visualization and clustering approach (generalized association plots), the patients were divided into four distinct clusters according to the correlation with four endocrine parameters. Each cluster exhibited specific endocrine characteristics and the prevalence of metabolic syndrome (MS) was significantly different among the clusters (P < 0.0001). The high-risk subgroups for MS included one cluster with higher mean (SD) FAI (39.6 (14.7) in cluster 4), and another one with lower mean (SD) FAI (10 (6.4) in cluster 2). A common endocrine characteristic of these two metabolically unhealthy clusters was relatively lower LH level. Contrarily, higher LH level (≧15 mIU/ml) during early follicular phase was found to be the best indicator of the metabolically healthy cluster (cluster 1). While high FAI level did correlate with more severe metabolic aberrations, high LH level showed better predictive value than low FAI level to become a metabolically healthy cluster.

LIMITATIONS, REASONS FOR CAUTION

The results should be applied to other populations with caution due to racial or environmental differences. Another limitation is a lack of normal non-PCOS control in our study.

WIDER IMPLICATIONS OF THE FINDINGS

Stratifying women with PCOS into meaningful subtypes could provide a better understanding of related risk factors and potentially enable the design and delivery of more effective screening and treatment intervention.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by grant NSC 100-2314-B002-027-MY3 from the National Science Council of Taiwan.

TRIAL REGISTRATION NUMBER

Nil.