Exercise and insulin resistance in PCOS: muscle insulin signalling and fibrosis.

OBJECTIVE: Mechanisms of insulin resistance in polycystic ovary syndrome (PCOS) remain ill defined, contributing to sub-optimal therapies. Recognising skeletal muscle plays a key role in glucose homeostasis we investigated early insulin signalling, its association with aberrant transforming growth factor ß (TGFß)-regulated tissue fibrosis. We also explored the impact of aerobic exercise on these molecular pathways. METHODS: A secondary analysis from a cross-sectional study was undertaken in women with (n = 30) or without (n = 29) PCOS across lean and overweight BMIs. A subset of participants with (n = 8) or without (n = 8) PCOS who were overweight completed 12 weeks of aerobic exercise training. Muscle was sampled before and 30 min into a euglycaemic-hyperinsulinaemic clamp pre and post training. RESULTS: We found reduced signalling in PCOS of mechanistic target of rapamycin (mTOR). Exercise training augmented but did not completely rescue this signalling defect in women with PCOS. Genes in the TGFß signalling network were upregulated in skeletal muscle in the overweight women with PCOS but were unresponsive to exercise training except for genes encoding LOX, collagen 1 and 3. CONCLUSIONS: We provide new insights into defects in early insulin signalling, tissue fibrosis, and hyperandrogenism in PCOS-specific insulin resistance in lean and overweight women. PCOS-specific insulin signalling defects were isolated to mTOR, while gene expression implicated TGFß ligand regulating a fibrosis in the PCOS-obesity synergy in insulin resistance and altered responses to exercise. Interestingly, there was little evidence for hyperandrogenism as a mechanism for insulin resistance.

Effect of exercise training on insulin sensitivity, mitochondria and computed tomography muscle attenuation in overweight women with and without polycystic ovary syndrome.

AIMS/HYPOTHESIS: Polycystic ovary syndrome (PCOS) is an insulin resistant (IR) state. Increased skeletal muscle lipid content and impaired mitochondrial biogenesis have been implicated in the pathogenesis of IR. We investigated whether differences in these variables explain the IR of women affected by PCOS and whether improvements in IR with exercise are reflected by changes in these variables. METHODS: Sixteen PCOS and 13 non-PCOS overweight women were assessed, and eight PCOS and seven non-PCOS women were reassessed after 12 weeks of moderate and vigorous exercise training. Outcomes included insulin sensitivity (glucose infusion rate [GIR]), skeletal muscle gene expression and protein abundance, enzyme activity of selected mitochondrial components, and computed tomography (CT) attenuation-estimated muscle lipid. RESULTS: GIR was lower in women with PCOS versus those without (p = 0.01) and increased with exercise in both groups. Baseline CT muscle attenuation suggested a trend to less muscle lipid in PCOS, which increased with exercise training, with a difference in the change in muscle lipid (p = 0.01, age-corrected), compared with non-PCOS women. GIR correlated with PGC1A gene expression across the whole group; skeletal muscle expression of mitochondrial biogenesis markers was not different between groups at baseline, or after training. Neither lipid changes nor mitochondrial changes correlated with changes in GIR. CONCLUSIONS/INTERPRETATION: Differences in IR in women with and without PCOS were not explained by differences in skeletal muscle lipid or mitochondrial parameters. Improvements in IR with exercise were dissociated from mitochondrial parameters. CT muscle attenuation suggested a differential capacity of PCOS muscle to store lipid compared with non-PCOS. TRIAL REGISTRATION: Clinicaltrials.gov ISRCTN84763265. FUNDING: National Health & Medical Research Council (Grant number 606553), Monash University and The Jean Hailes Foundation.

Exercise decreases anti-müllerian hormone in anovulatory overweight women with polycystic ovary syndrome: a pilot study.

Polycystic ovary syndrome (PCOS) is a common condition in women associated with menstrual irregularity and anovulation. While obesity worsens and weight loss or exercise improves reproduction function in PCOS, the mechanism for this is unclear. The aim of this study was to examine the effect of exercise on ovarian hormones [anti-Müllerian hormone (AMH)] and menstrual and ovulatory function in women with and without PCOS. Overweight women with (n=7) and without (n=8) PCOS of comparable age, weight and BMI undertook a 12-week intensified endurance exercise training program (1 h 3 times/week) with no structured energy restriction. Primary outcomes were AMH, ovulation (weekly urinary pregnanediol) and menstrual regularity. Secondary outcomes were insulin resistance (euglycemic hyperinsulinemic clamp) and body composition (computed tomography and dual X-ray absorptiometry). Exercise decreased BMI, total and android fat mass and improved insulin sensitivity for all women. AMH was significantly higher in women with PCOS compared to controls before (p<0.001) and after exercise (p=0.001). There was a significant interaction between AMH changes with exercise and PCOS status (p=0.007) such that women without PCOS had no change in AMH (+1.4±5.2 pmol/l, p=0.48) while women with PCOS had a decrease in AMH (- 13.2±11.7 pmol/l, p=0.025). Exercise is associated with improvements in ovarian hormones in women with abnormal ovarian function. This suggests that mechanisms associated with ovarian dysfunction can be improved by exercise in PCOS.

Novel inflammatory markers in overweight women with and without polycystic ovary syndrome and following pharmacological intervention.

BACKGROUND: Polycystic ovary syndrome (PCOS) is associated with reproductive and metabolic abnormalities. AIM: The aim of this study was to assess novel inflammatory markers [adipokines leptin, adiponectin, and leptinadiponectin ratio (L/A)] in overweight women with and without PCOS and to examine alterations in these markers [aldosterone, leptin, adiponectin, and L/A] with pharmacological interventions modulating insulin resistance (IR) in PCOS. MATERIALS/SUBJECTS AND METHODS: Overweight age, and body mass index (BMI)-matched women with (no.=80) or without PCOS (no.=27) were assessed cross-sectionally. Subjects with PCOS were then randomised to 6 months metformin (1 g b.d, no.=26) or oral contraceptive pill (OCP) (35 g ethinyl estradiol/2 mg cytoproterone acetate, no.=30). Outcome measures were leptin, adiponectin, L/A, aldosterone, highly sensitive C-reactive protein, lipid profile, IR, and androgen levels. RESULTS: Leptin levels were lower (156.4+/-85.9 vs 208.5+/-105.2 ng/ml, p=0.015) while adiponectin and L/A were not different between women with and without PCOS. Following intervention, IR increased for the OCP and decreased for metformin, however leptin and aldosterone decreased equivalently with the OCP and metformin with no difference between each treatment (p=0.583 and p=0.801, respectively). There was no change in adiponectin or L/A with the OCP or metformin. On multiple regression, the only baseline predictor of leptin was BMI (r(2)=0.485, p<0.001) and the strongest predictor of change in leptin was change in weight (r(2)=0.402, p<0.001). CONCLUSIONS: Alterations in leptin between women with and without PCOS and following pharmacological interventions are primarily related to adiposity and not IR. Aldosterone was reduced equivalently with metformin and the OCP despite differential effects on IR.

Enzyme replacement therapy in fibroblasts from a patient with cholesteryl ester storage disease.

Enzyme replacement has long been considered only a remote possibility in the treatment of a wide range of genetic disorders, many manifested as lysosomal storage diseases. The complexity of having a particular enzyme gain access to the lysosomal compartment in a specific cell seemed insurmountable. We report here on an attempt to introduce the enzyme cholesteryl esterase into fibroblasts from a patient with cholesteryl ester storage disease (CESD). The enzyme gains access to the lysosomal compartment and the accumulating cholesteryl ester by virtue of being carried into the cell conjugated to a ligand (insulin or apoprotein B [apoB]) that binds to its own specific receptor and is internalized by the well-described process of receptor-mediated endocytosis. Regardless of whether the enzyme enters the cell via the insulin receptor or via the low-density lipoprotein (ApoB) receptor, it can be found associated with a lysosomal fraction and is effective in lowering levels of accumulated substrate, cholesteryl ester. The time course of the substrate degradation and the dependence on the receptor density and receptor density and receptor-ligand interaction indicate that the enzyme is simply being carried to the site of substrate accumulation by virtue of the fact that that is the destination of the ligand (along with its conjugated enzyme) following internalization.