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      A nontargeted study of muscle proteome in severely obese women with androgen excess compared with severely obese men and nonhyperandrogenic women

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          Abstract

          Objective

          Androgen excess in women is frequently associated with muscle insulin resistance, especially in obese women with polycystic ovary syndrome. However, whether this is a primary event or the result of indirect mechanisms is currently debated.

          Design

          This is an observational study.

          Methods

          We obtained skeletal muscle biopsies during bariatric surgery from severely obese men ( n=6) and women with ( n=5) or without ( n=5) androgen excess. We used two-dimensional differential gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight mass spectrometry to identify muscle proteins showing differences in abundance between the groups of obese subjects.

          Results

          Women with hyperandrogenism presented the lowest abundances of glycogen phosphorylase, pyruvate kinase, β-enolase, glycerol-3-phosphate dehydrogenase, creatine kinase M-type, and desmin, whereas the abundances of these molecules were similar in control women and men.

          Conclusion

          According to our nontargeted proteomic approach, women with hyperandrogenism show a specific alteration of the skeletal muscle proteome that could contribute to their insulin resistance. Because men do not show similar results, this alteration does not appear to be the direct effect on muscle of androgen excess, but rather the consequence of indirect mechanisms that merit further studies.

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          Most cited references23

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          Muscles, exercise and obesity: skeletal muscle as a secretory organ.

          During the past decade, skeletal muscle has been identified as a secretory organ. Accordingly, we have suggested that cytokines and other peptides that are produced, expressed and released by muscle fibres and exert either autocrine, paracrine or endocrine effects should be classified as myokines. The finding that the muscle secretome consists of several hundred secreted peptides provides a conceptual basis and a whole new paradigm for understanding how muscles communicate with other organs, such as adipose tissue, liver, pancreas, bones and brain. However, some myokines exert their effects within the muscle itself. Thus, myostatin, LIF, IL-6 and IL-7 are involved in muscle hypertrophy and myogenesis, whereas BDNF and IL-6 are involved in AMPK-mediated fat oxidation. IL-6 also appears to have systemic effects on the liver, adipose tissue and the immune system, and mediates crosstalk between intestinal L cells and pancreatic islets. Other myokines include the osteogenic factors IGF-1 and FGF-2; FSTL-1, which improves the endothelial function of the vascular system; and the PGC-1α-dependent myokine irisin, which drives brown-fat-like development. Studies in the past few years suggest the existence of yet unidentified factors, secreted from muscle cells, which may influence cancer cell growth and pancreas function. Many proteins produced by skeletal muscle are dependent upon contraction; therefore, physical inactivity probably leads to an altered myokine response, which could provide a potential mechanism for the association between sedentary behaviour and many chronic diseases.
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            The polycystic ovary syndrome associated with morbid obesity may resolve after weight loss induced by bariatric surgery.

            The polycystic ovary syndrome (PCOS) is frequently associated with obesity. However, there are very few data about PCOS in morbid obesity, especially with regard to its evolution after bariatric surgery. The objective of this study was to evaluate the response of PCOS to the sustained and marked weight loss achieved by bariatric surgery in morbidly obese women. This was a longitudinal prospective nonrandomized evaluation. The study was performed at an academic hospital. Thirty-six consecutive premenopausal women submitted to bariatric surgery were screened for PCOS, which was present in 17. Bariatric surgery was performed. Hyperandrogenism, menstrual function, and insulin resistance were estimated before and at least 6 months after bariatric surgery in 12 patients with PCOS. Weight loss (41 +/- 9 kg after 12 +/- 5 months) was paralleled by decreases in the hirsutism score (from 9.5 +/- 6.8 to 4.9 +/- 4.2; P = 0.001), total (69 +/- 32 to 42 +/- 19 ng/dl; P < 0.02) and free testosterone (from 1.6 +/- 0.7 to 0.6 +/- 0.3 ng/dl; P < 0.005), androstenedione (from 4.1 +/- 1.5 to 3.0 +/- 0.9 ng/ml; P < 0.02), and dehydroepiandrosterone sulfate (from 2000 +/- 1125 to 1353 +/- 759 ng/ml; P < 0.005); amelioration of insulin resistance estimated by homeostasis model assessment (from 6.0 +/- 3.0 to 1.6 +/- 1.0; P < 0.001); and restoration of regular menstrual cycles and/or ovulation in all patients. The PCOS is a frequent finding in women with morbid obesity and may resolve after weight loss induced by bariatric surgery.
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              Global adiposity rather than abnormal regional fat distribution characterizes women with polycystic ovary syndrome.

              Obesity-related predisposition to polycystic ovary syndrome (PCOS) could reflect overall adiposity and/or regional accumulation of abdominal visceral fat. The objective of the study was to compare distributions of visceral, abdominal sc, and gluteofemoral sc adipose tissue in PCOS cases vs. control women. This was a cross-sectional study. Fat depot measurements from axial magnetic resonance imaging scans taken at anatomically predefined sites were compared between 22 body mass index (BMI)/fat mass-matched pairs of PCOS cases and controls; whole-group comparisons included 50 PCOS cases vs. 28 female controls. All subjects were of UK British/Irish origin. We measured cross-sectional areas of adipose tissue within visceral (mid-L4), abdominal (mid-L4) sc, and gluteofemoral (greater trochanteric and midfemoral) sc fat depots. Other measurements included fat mass, BMI, testosterone, SHBG, and homeostasis model assessment of insulin resistance (a measure of insulin sensitivity). Whole-group analyses were adjusted for fat mass and age. There were no significant differences in fat-depot measurements between BMI/fat mass-matched pairs of PCOS cases and controls: mid-L4 visceral (P=0.40), abdominal sc (P=0.22), gluteal sc (P=0.67), and midfemoral sc (P=0.37) depots. Whole-group comparisons gave similar results after adjustments for fat mass and age. Fasting serum insulin concentrations (P=0.03) and homeostasis model assessment of insulin resistance (P=0.03) were significantly higher in the PCOS group than BMI/fat mass-matched controls. PCOS cases and BMI/fat mass-matched control women are indistinguishable with respect to distribution of fat within visceral, abdominal sc, and gluteofemoral sc depots, despite significant differences in insulin resistance between these two groups.
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                Author and article information

                Journal
                European Journal of Endocrinology
                Bioscientifica
                0804-4643
                1479-683X
                March 2016
                March 2016
                : 174
                : 3
                : 389-398
                Article
                10.1530/EJE-15-0912
                26671973
                d67394ac-bd48-4044-9706-6c511482a81e
                © 2016

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