Polycystic Ovary Syndrome (PCOS) is a complex endocrine disorder that increases a woman’s risk of developing cardiovascular disease and metabolic disease. Women with PCOS tend to have elevated sympathetic nerve activity and are more likely to be obese and insulin resistant. The current working theory is that obesity and insulin resistance contribute to the sympathetic over activity in PCOS. While few treatment options for women with PCOS target both elevated sympathetic nerve activity and insulin resistance, passive heat exposure shows promise as a novel intervention for improving cardiovascular and metabolic health in this population. PURPOSE: To examine changes in sympathetic nerve activity and metabolic health in obese women with PCOS following 8 weeks of chronic passive heat exposure (CPHE). METHODS: Three women with PCOS (Age: 25±8y, BMI 41±1 kg·m2) underwent CPHE, consisting of 30 one-hour hot tub sessions over 8-10 weeks (3-4 per week) in 40.5˚C water. Muscle sympathetic nerve activity (MSNA) was measured at 0, 4, and 8 weeks through microneurography of the peroneal nerve, and metabolic function was assessed using a 2-hr oral glucose tolerance test [OGTT] at 0, 4, and 8 weeks. Height and weight were measured to calculate BMI at each time point. Results were analyzed using a one-way repeated measures ANOVA and significance was accepted at p<0.05. RESULTS: No change in BMI was observed over the 8 weeks of CPHE (p=0.38). MSNA significantly decreased from 0 to 4 weeks (0weeks: 21±6 bursts/min; 4weeks: 15±4 bursts/min p=0.03) and remained lower following 8 weeks (14±6 bursts/min; p=0.015 vs 0 weeks) of CPHE. Fasting glucose was in the impaired range [>100mg/dl] at 0 (108±9 mg/dl) and 4 weeks (110±10 mg/dl), but decreased significantly at 8 weeks to within the ideal range (88±10 mg/dl; p=0.001 vs 0 weeks). Similarly, 2-hr glucose was in the insulin resistant range [>140mg/dl] at 0 (171±20 mg/dl) and 4 (171±8 mg/dl) weeks, but tended to decrease at the 8-week time point (143±26 mg/dl; p=0.22 vs 0 weeks). CONCLUSION: CPHE significantly decreases MSNA in women with PCOS, and appears to improve metabolic health. However, these improvements happen in the absence of weight changes and on different timelines, suggesting that obesity and insulin resistance are not driving sympathetic over activity in PCOS, and improvements in metabolic health are not directly responsible for the observed decreases in MSNA. These pilot data show promise for CPHE as a treatment option for women with PCOS to improve cardiovascular and metabolic profiles, and further research is needed to elucidate the mechanisms.

Supported by American Heart Association Predoctoral Fellowship 16PRE27780085, Eugene & Clarissa Evonuk Memorial Fellowship

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