The impact of metformin treatment on adiponectin and resistin levels in women with polycystic ovary syndrome: a prospective clinical study

Adipose tissue and ovarian aging: Potential mechanism and protective strategies

Ovarian aging occurs approximately 10 years prior to the natural age-associated functional decline of other organ systems. With the increase of life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Therefore, understanding the causes and molecular mechanisms of ovarian aging is very essential for the inhibition of age-related diseases and the promotion of health and longevity in women. Recently, studies have revealed an association between adipose tissue (AT) and ovarian aging. Alterations in the function and quantity of AT have profound consequences on ovarian function because AT is central for follicular development, lipid metabolism, and hormonal regulation. Moreover, the interplay between AT and the ovary is bidirectional, with ovary-derived signals directly affecting AT biology. In this review, we summarize the current knowledge of the complex molecular mechanisms controlling the crosstalk between the AT and ovarian aging, and further discuss how therapeutic targeting of the AT can delay ovarian aging.

Effect of metformin on adiponectin in PCOS: A meta-analysis and a systematic review

BACKGROUND

Conflicting results have been reported regarding the effect of metformin on adiponectin levels in women with polycystic ovary syndrome (PCOS). This meta-analysis reviewed all studies comparing adiponectin levels before and after metformin treatment in PCOS women. Additionally, changes in other indicators, including long-term complications associated with PCOS, such as inflammatory, metabolism factors and hormonal profile, were investigated following metformin treatment. We conducted subgroup analysis based on body mass index (BMI) stratification and appropriate pooling.

METHODS

We searched literature in PUBMED, EMBASE, the Cochrane Library, and CNKI databases. The main meta-analysis included 11 studies containing data on 353 subjects.

RESULTS

Metformin treatment was associated with significantly increased serum adiponectin concentrations [10 studies, random-effects SMD (95% CI) -0.58 [-1.03, -0.13]; I² = 86%; P = 0.01]. Additionally, the meta-analysis revealed that circulating tumor necrosis factor-α(TNF-α) and C-reactive protein (CRP) concentrations were significantly decreased after metformin treatment, with corresponding SMDs of 1.01 (95% CI: 0.74-1.28, P＜0.00001) and 0.48(95% CI: 0.35-0.60, P＜0.00001).

CONCLUSION

Following metformin administration, serum adiponectin concentrations of PCOS women were found to be significantly increased, accompanied by a significant improvement in other indicators. Further investigation with a larger sample size should be conducted to validate optimal dose and duration of metformin.

Adipocyte and steroidogenic cell cross-talk in polycystic ovary syndrome

BACKGROUND

Metabolic and endocrine alterations in women with polycystic ovary syndrome (PCOS) affect adipose tissue mass and distribution. PCOS is characterised by hyperandrogenism, obesity and adipocyte dysfunction. Hyperandrogenism in PCOS drives dysfunctional adipocyte secretion of potentially harmful adipocytokines. Glucocorticoids and sex-steroids modulate adipocyte development and function. For their part, adipocyte products interact with adrenal and ovarian steroidogenic cells. Currently, the relationship between adipocyte and steroidogenic cells is not clear, and for these reasons, it is important to elucidate the interrelationship between these cells in women with and without PCOS.

OBJECTIVE AND RATIONALE

This comprehensive review aims to assess current knowledge regarding the interrelationship between adipocytes and adrenal and ovarian steroidogenic cells in animal models and humans with or without PCOS.

SEARCH METHODS

We searched for articles published in English and Portuguese in PubMed. Keywords were as follows: polycystic ovary syndrome, steroidogenesis, adrenal glands, theca cells, granulosa cells, adipocytes, adipocytokines, obesity, enzyme activation, and cytochrome P450 enzymes. We expanded the search into the references from the retrieved articles.

OUTCOMES

Glucocorticoids and sex-steroids modulate adipocyte differentiation and function. Dysfunctional adipocyte products play important roles in the metabolic and endocrine pathways in animals and women with PCOS. Most adipokines participate in the regulation of the hypothalamic-pituitary-adrenal and ovarian axes. In animal models of PCOS, hyperinsulinemia and poor fertility are common; various adipokines modulate ovarian steroidogenesis, depending on the species. Women with PCOS secrete unbalanced levels of adipocyte products, characterised by higher levels of leptin and lower levels of adiponectin. Leptin expression positively correlates with body mass index, waist/hip ratio and levels of total cholesterol, triglyceride, luteinising hormone, oestradiol and androgens. Leptin inhibits the production of oestradiol and, in granulosa cells, may modulate 17-hydroxylase and aromatase enzyme activities. Adiponectin levels negatively correlate with fat mass, body mass index, waist-hip ratio, glucose, insulin and triglycerides, and decrease androgen production by altering expression of luteinising hormone receptor, steroidogenic acute regulatory protein, cholesterol-side-chain cleavage enzyme and 17-hydroxylase. Resistin expression positively correlates with body mass index and testosterone, and promotes the expression of 17-hydroxylase enzyme in theca cells. The potential benefits of adipokines in the treatment of women with PCOS require more investigation.

WIDER IMPLICATIONS

The current data regarding the relationship between adipocyte products and steroidogenic cells are conflicting in animals and humans. Polycystic ovary syndrome is an excellent model to investigate the interrelationship among adipocyte and steroidogenic cells. Women with PCOS manifest some pathological conditions associated with hyperandrogenism and adipocyte products. In animals, cross-talk between cells may vary according to species, and the current review suggests opportunities to test new medications to prevent or even reverse several harmful sequelae of PCOS in humans. Further studies are required to investigate the possible therapeutic application of adipokines in women with obese and non-obese PCOS. Meanwhile, when appropriate, metformin use alone, or associated with flutamide, may be considered for therapeutic purposes.

Impact of Treatment with Metformin on Adipocytokines in Patients with Polycystic Ovary Syndrome: A Meta-Analysis

Background

Metformin is effective for the treatment of polycystic ovary syndrome, but conflicting results regarding its effect on adipocytokine levels (adiponectin, resistin, visfatin, and leptin) in patients with polycystic ovary syndrome receiving metformin treatment have been reported. To provide high-quality evidence about the effect of metformin treatment on adipocytokines in patients with polycystic ovary syndrome, relevant studies that assessed the levels of adipocytokines (adiponectin, resistin, visfatin, and leptin) in patients with polycystic ovary syndrome receiving treatment with metformin administration were reviewed and analyzed.

Methods

A literature search was conducted in the SCI, PUBMED, EMBASE, and Elsevier databases, and personal contact was made with the authors. Standard mean differences and 95% confidence intervals were calculated and combined appropriately. To ensure synthesis of the best available evidence, sensitivity analyses were performed.

Results

A total of 34 data sets were included in 4 different outcomes, involving 744 women with polycystic ovary syndrome and adipocytokine levels measured both before and after metformin administration. Metformin treatment was associated with significantly elevated serum adiponectin concentrations (standard mean differences [95% confidence interval], −0.43 [−0.75 to −0.11]) and decreased serum leptin concentrations (0.65 [0.26 to 1.04]), whereas no significant difference in resistin level (−0.01 [−0.49 to 0.45]) or visfatin level (−0.04 [−1.55 to 1.46]) was found.

Conclusions

Metformin administration was associated with increased serum adiponectin concentrations and decreased serum leptin levels. Further study is needed to elucidate whether this apparent effect decreases the incidence of type 2 diabetes and other metabolic diseases in patients with polycystic ovary syndrome later in life.