Effects of Short Term Metformin Treatment on Brown Adipose Tissue Activity and Plasma Irisin Levels in Women with Polycystic Ovary Syndrome: A Randomized Controlled Trial

GDF-15 levels in patients with polycystic ovary syndrome treated with metformin: a combined clinical and in silico pathway analysis

Objective

Polycystic ovary syndrome (PCOS) is an endocrine disease characterized by metabolic, reproductive, and psychological manifestations. Growth and differentiation factor 15 (GDF-15) is a cytokine associated with metabolic and inflammatory disorders. Metformin is commonly used for the treatment of PCOS. We investigated the relationship between GDF-15 levels and PCOS, the effect of metformin on GDF-15 levels, and potential biologic pathways related to GDF-15.

Subjects and methods

The study included 35 women with PCOS and 32 women without PCOS (controls). Both groups were compared in terms of GDF-15 levels. Additional analysis was conducted on samples from 22 women with PCOS who were treated with either metformin (n = 7) or placebo (n = 15), retrieved from a previous randomized, controlled trial. Levels of GDF-15 were measured using MILLIPLEX. The biologic pathways related to GDF-15 were evaluated using the databases STRING, SIGNOR, and Pathway Commons. The statistical analysis was conducted using the software SPSS.

Results

Levels of GDF-15 were higher in the PCOS group compared with the non-PCOS group (p = 0.039). Among women with PCOS, GDF-15 levels were higher in those treated with metformin compared with placebo (p = 0.007). The proteins related to GDF-15 overlapped between the databases, and a significant interaction was found between GDF-15 and proteins related to PCOS and its complications, including those related to estrogen response, oxidative stress, ovarian infertility, interleukin (IL)-18, IL-4, the ratio of advanced glycation end products to their receptor (AGE/RAGE), leptin, transforming growth factor beta (TGF-β), adipogenesis, and insulin.

Conclusion

The findings of the present study suggest a relationship between GDF-15 and PCOS and a potential increase in GDF-15 levels with metformin treatment. An additional finding was that GDF-15 could be involved in biologic pathways related to PCOS complications.

Role of Brown Adipose Tissue in Metabolic Health and Efficacy of Drug Treatment for Obesity

(1) Background: Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis, and its activation has become a new object as both a determinant of metabolic health and a target for therapy. This study aimed to identify the relationships between the presence of BAT, parameters that characterize metabolic health (glucose, lipids, blood pressure (BP)), and the dynamics of body mass index (BMI) during weight-reducing therapy. (2) Methods: The study included 72 patients with obesity. We investigated metabolic parameters, anthropometric parameters, and BP. Dual-energy X-ray absorptiometry (DXA) and positron emission tomography and computed tomography (PET/CT) imaging with 18F-fluorodeoxyglucose (18F-FDG) were performed. (3) Results: Before weight-reducing therapy, BAT was revealed only in 19% patients with obesity. The presence of BAT was associated with a lower risk of metabolic deviations that characterize metabolic syndrome: shorter waist circumference (WC) (p = 0.02) and lower levels of glucose (p = 0.03) and triglycerides (p = 0.03). Thereafter, patients were divided into four groups according to the type of therapy (only lifestyle modification or with Liraglutide or Reduxin or Reduxin Forte). We did not find a relationship between the presence of BAT and response to therapy: percent weight reduction was 10.4% in patients with BAT and 8.5% in patients without BAT (p = 0.78) during six months of therapy. But we noted a significant positive correlation between the volume of BAT and the effectiveness of weight loss at 3 months (r = 0.52, p = 0.016). The dynamic analysis of BAT after 6 months of therapy showed a significant increase in the volume of cold-induced metabolically active BAT, as determined by PET/CT with 18F-FDG in the Liraglutide group (p = 0.04) and an increase in the activity of BAT standardized uptake value (SUV mean and SUV max) in the Reduxin (p = 0.02; p = 0.01, respectively) and Liraglutide groups (p = 0.02 in both settings). (4) Conclusions: The presence of brown adipose tissue is associated with a lower risk of metabolic abnormalities. In general, our study demonstrated that well-established drugs in the treatment of obesity (Liraglutide and Reduxin) have one more mechanism for implementing their effects. These drugs have the ability to increase the activity of BAT. A significant positive relationship between the total volume of BAT and the percentage of weight loss may further determine the priority mechanism of the weight-reducing effect of these medicaments.

Molecular Imaging in Gynecology: Beyond Cancer

Gynecological pathologies account for approximately 4.5% of the overall global disease burden. Although cancers of the female reproductive system have understandably been the focus of a great deal of research, benign gynecological conditions-such as endometriosis, polycystic ovary syndrome, and uterine fibroids-have remained stubbornly understudied despite their astonishing ubiquity and grave morbidity. This historical inattention has frequently become manifested in flawed diagnostic and treatment paradigms. Molecular imaging could be instrumental in improving patient care on both fronts. In this Focus on Molecular Imaging review, we will examine recent advances in the use of PET, SPECT, MRI, and fluorescence imaging for the diagnosis and management of benign gynecological conditions, with particular emphasis on recent clinical reports, areas of need, and opportunities for growth.

Serum Irisin in Polycystic Ovary Syndrome and its Alteration with Metformin Intervention

Introduction

Studies investigating the alterations of serum irisin and its change with metformin therapy in patients with polycystic ovary syndrome (PCOS) are conflicting. Our aim is to study serum irisin in PCOS patients and the change of irisin levels with metformin therapy over 6 months.

Methods

This is a randomized control study conducted in 187 PCOS cases and 94 age-matched controls aged 18-40 years. Detailed evaluation of anthropometric, biochemical, and hormonal parameters was performed. A subset of 99 overweight/obese patients with body mass index (BMI) ≥23 kg/m2 were stratified into a metformin group (n = 67) receiving 500 mg thrice daily and a lifestyle intervention-only group (n = 32). The effect of metformin therapy on serum irisin levels was measured at the end of 6 months. Statistical analyses were performed with SPSS version 26.0 Software.

Results

Serum irisin was higher in PCOS patients than in controls [12.47 (8.1-17.7) vs 8.3 (7.0-9.6) ng/ml, P < 0.001], independent of BMI. Serum irisin showed a significant positive association with BMI (β =0.168), waist-to-hip ratio (β =0.166), leutinizing hormone (β =0.225), TG (β =0.305), FAI (β =0.151), and testosterone (β =0.135). Serum irisin showed a significant positive association with homeostatic model assessment of insulin resistance (HOMA-IR) (β =0.14, P = 0.04) in overweight/obese PCOS patients only (n = 146) but not in the whole PCOS cohort (n = 187). Metformin reduced the median serum irisin levels significantly (13.9 to 12.1 ng/ml, P < 0.001), and the delta change in irisin levels was associated with HOMA-IR in the metformin group.

Conclusion

Serum irisin is increased in PCOS patients independent of BMI. Metformin therapy reduced serum irisin levels in overweight/obese PCOS patients by improving insulin resistance.

18F-FDG PET/CT technology for the assessment of brown adipose tissue: an updated review

INTRODUCTION

This review provides an update of 18 F-fluorodeoxyglucose ([18F] FDG) for Brown adipose tissue (BAT) activity quantification, whose role is not completely understood.

AREAS COVERED

We conducted an unstructured search of the literature for any studies employing the [18F] FDG PET in BAT assessment. We explored BAT quantification both in healthy individuals and in different pathologies, after cold exposure and as a metabolic biomarker. The assessment of possible BAT modulators by using [18F] FDG PET is shown. Further PET tracers and novel developments for BAT assessments are also described.

EXPERT OPINION

Further PET tracers and imaging modalities are under investigation, but the [18F] FDG PET is currently the method of choice for the evaluation of BAT and further multicentric trials are needed for a better understanding of the BAT physiopathology, also after cold stimuli. The modulation of BAT activity, assessed by [18F] FDG PET imaging, seems a promising tool for the management of conditions such as obesity and type 2 diabetes. Moreover, an interesting possible correlation of BAT activation with prognostic [18F] FDG PET indices in cancer patients should be assessed with further multicentric trials.

Anti-Obesity Effects of Metformin: A Scoping Review Evaluating the Feasibility of Brown Adipose Tissue as a Therapeutic Target

Brown adipose tissue (BAT) is increasingly recognized as the major therapeutic target to promote energy expenditure and ameliorate diverse metabolic complications. There is a general interest in understanding the pleiotropic effects of metformin against metabolic complications. Major electronic databases and search engines such as PubMed/MEDLINE, Google Scholar, and the Cochrane library were used to retrieve and critically discuss evidence reporting on the impact of metformin on regulating BAT thermogenic activity to ameliorate complications linked with obesity. The summarized evidence suggests that metformin can reduce body weight, enhance insulin sensitivity, and improve glucose metabolism by promoting BAT thermogenic activity in preclinical models of obesity. Notably, this anti-diabetic agent can affect the expression of major thermogenic transcriptional factors such as uncoupling protein 1 (UCP1), nuclear respiratory factor 1 (NRF1), and peroxisome-proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α) to improve BAT mitochondrial function and promote energy expenditure. Interestingly, vital molecular markers involved in glucose metabolism and energy regulation such as AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21) are similarly upregulated by metformin treatment in preclinical models of obesity. The current review also discusses the clinical relevance of BAT and thermogenesis as therapeutic targets. This review explored critical components including effective dosage and appropriate intervention period, consistent with the beneficial effects of metformin against obesity-associated complications.

Polycystic ovary syndrome and adipose tissue

Polycystic ovary syndrome (PCOS) is the most common endocrine metabolic disorder in women of reproductive age. Typically, it is associated with ovulatory dysfunction: dysovulation or anovulation, and symptoms of hyperandrogenism. It incurs risk of metabolic disorders such as diabetes, dyslipidemia and fatty liver. As a key endocrine organ in metabolic homeostasis, adipose tissue is often implicated in these complications. Studies of white adipose tissue (WAT) in PCOS have focused on the mechanism of insulin resistance in this tissue. Clinically, abnormalities in WAT distribution are seen, with decreased waist-to-hip ratio and increased ratio of adipose to lean mass. Such abnormalities are greater when total circulating androgens are elevated. At tissue level, white adipocyte hyperplasia occurs, along with infiltration of macrophages. Secretion of adipokines, cytokines and chemo-attractant proteins is increased in a pro-inflammatory manner, leading to reduced insulin sensitivity via alteration of glucose transporters, and hence decreased glucose uptake. The kinetics of non-esterified fatty acids (or free fatty acids) is also altered, leading to lipotoxicity. In recent years, brown adipose tissue (BAT) has been studied in women with PCOS. Although abundance is low in the body, BAT appears to play a significant role in energy expenditure and metabolic parameters. Both supra-clavicular skin temperature, which reflects BAT activity, and BAT mass are reduced in women with PCOS. Moreover, BAT mass and body mass index (BMI) are inversely correlated in patients. In the adipocyte, increased total circulating androgen levels reduce expression of uncoupling protein 1 (UCP1), a key protein in the brown adipocyte, leading to reduced biogenesis and mitochondrial respiration and hence a reduction in post-prandial thermogenesis. BAT is currently being investigated as a possible new therapeutic application.

Irisin enhances longevity by boosting SIRT1, AMPK, autophagy and telomerase

Ageing is characterised by the accumulation of molecular and cellular damage through time, leading to a decline in physical and mental abilities. Currently, society has experienced a rapid increase in life expectancy, which has led to an increase in age-associated diseases. Therefore, it is crucial to study the process of ageing to guarantee the best conditions in the final stages of life. In recent years, interest has increased in a myokine known as irisin, which is secreted during physical exercise. This polypeptide hormone is produced by various organs, mainly muscle, and once it is released into the blood, it performs a wide variety of functions that are involved in metabolic control and may be relevant during some of the diseases associated with ageing. The aim of this review is to highlight the recent studies of irisin, such as its mechanism of expression, blood release, distribution, tissue target and participation in various cellular metabolic reactions and the relationship with key anti-ageing pathways such as adenosine monophosphate-activated protein kinase, silent information regulator T 1, autophagy and telomerase. In conclusion, irisin is a key player during the ageing process and it could be a novel target molecule for the therapeutic approach to boost longevity pathways. However, more research will be necessary to use this promising hormone for this gain.

Brown fat triglyceride content is associated with cardiovascular risk markers in adults from a tropical region

Brown adipose tissue (BAT) is regarded as an interesting potential target for the treatment of obesity, diabetes, and cardiovascular diseases, and the detailed characterization of its structural and functional phenotype could enable an advance in these fields. Most studies evaluating BAT structure and function were performed in temperate climate regions, and we are yet to know how these findings apply to the 40% of the world's population living in tropical areas. Here, we used 18F-fluorodeoxyglucose positron emission tomography - magnetic resonance imaging to evaluate BAT in 45 lean, overweight, and obese volunteers living in a tropical area in Southeast Brazil. We aimed at investigating the associations between BAT activity, volume, metabolic activity, and BAT content of triglycerides with adiposity and cardiovascular risk markers in a sample of adults living in a tropical area and we showed that BAT glucose uptake is not correlated with leanness; instead, BAT triglyceride content is correlated with visceral adiposity and markers of cardiovascular risk. This study expands knowledge regarding the structure and function of BAT in people living in tropical areas. In addition, we provide evidence that BAT triglyceride content could be an interesting marker of cardiovascular risk.

Effect of metformin intervention on circulating irisin levels in polycystic ovary syndrome: a systematic review and collaborative meta-analysis

BACKGROUND

Irisin is an adipo-myokine with potential implications in metabolic disorders such as polycystic ovary syndrome (PCOS). Despite of a strong evidence showing increased irisin level in PCOS, there is no conclusive evidence on the effect of metformin intervention on circulatory irisin in PCOS.

AIM

The aim of this meta-analysis was to compare the circulatory (serum/plasma) irisin levels before and after metformin intervention in subjects with PCOS.

METHODS

Relevant studies were retrieved by online database and manual searching. The standardized mean differences (SMDs) with 95% confidence intervals (CIs) were obtained by a random-effects meta-analysis. A one-study leave-out sensitivity analysis was conducted to validate the overall obtained results.

RESULTS

A total of five observations were included in this meta-analysis. The results based on random effects meta-analysis indicated that irisin levels were significantly decreased after metformin intervention as compared to the baseline pretreatment levels in PCOS (SMD: -1.00, 95% CI: -1.60 to -0.41, Z: 3.29, p = .001). The sensitivity analysis leaving-out a particular observation at a time and repeating the meta-analysis validated the robustness of the overall finding suggesting the significant effect of metformin treatment on irisin levels in PCOS.

CONCLUSION

Circulating irisin levels were significantly decreased upon metformin intervention in PCOS patients. The higher pretreatment irisin levels in PCOS may recede once the altered metabolic state is restored upon metformin intervention. Well-designed randomized trials with large sample sizes are warranted to further substantiate the reported evidence reported and to establish the possible mechanisms.

Climate Change and Obesity

Global warming and the rising prevalence of obesity are well described challenges of current mankind. Most recently, the COVID-19 pandemic arose as a new challenge. We here attempt to delineate their relationship with each other from our perspective. Global greenhouse gas emissions from the burning of fossil fuels have exponentially increased since 1950. The main contributors to such greenhouse gas emissions are manufacturing and construction, transport, residential, commercial, agriculture, and land use change and forestry, combined with an increasing global population growth from 1 billion in 1800 to 7.8 billion in 2020 along with rising obesity rates since the 1980s. The current Covid-19 pandemic has caused some decline in greenhouse gas emissions by limiting mobility globally via repetitive lockdowns. Following multiple lockdowns, there was further increase in obesity in wealthier populations, malnutrition from hunger in poor populations and death from severe infection with Covid-19 and its virus variants. There is a bidirectional relationship between adiposity and global warming. With rising atmospheric air temperatures, people typically will have less adaptive thermogenesis and become less physically active, while they are producing a higher carbon footprint. To reduce obesity rates, one should be willing to learn more about the environmental impact, how to minimize consumption of energy generating carbon dioxide and other greenhouse gas emissions, and to reduce food waste. Diets lower in meat such as a Mediterranean diet, have been estimated to reduce greenhouse gas emissions by 72%, land use by 58%, and energy consumption by 52%.

The "irisin system": From biological roles to pharmacological and nutraceutical perspectives

The scientific interest in irisin, a myokine discovered in 2012, has grown exponentially in recent years. Irisin, which is mainly produced in skeletal muscle, influences the browning process of adipose tissue and lipid and energy metabolism. Recent discoveries highlight that the potential of this hormone may have been underestimated. In the first part of this review, reports on irisin structure and molecules involved in its metabolic pathway are shown. Furthermore, data related to unclear aspects are also reported: distribution, different gene expression of its precursors in different tissues, physiological levels of circulating irisin, and pharmacokinetic and pharmacodynamic profile. The second part of this work focuses on exogenous stimuli and pharmacological agents which regulate the metabolic pathway of irisin and its serum concentration. In addition to physical exercise and exposure to low temperatures, which were early recognized as exogenous stimuli able to promote the production of this myokine, preclinical and clinical evidence demonstrates the ability of natural and synthetic molecules to interfere with this metabolic pathway. Current experimental data on irisin cannot dissolve all doubts related to this interesting molecule, but they certainly underline its potential for therapeutic purposes. Thus, identification of new pharmacological tools able to act on the irisin pathway is a challenging issue for biomedical research.