Cardio-respiratory Fitness Affects Glucose Control And Thus Cardiovascular Disease Risk In Postmenopausal Women.

Abstract

Increased glucose levels above a threshold of 4.9 mmol/L are associated with a greater risk of cardiovascular disease (CVD). The menopause has been associated with impaired glucose control, including poor glucose tolerance, increased glycosylated haemoglobin (HbA1C) and fasting insulin concentration. The positive effect of increased cardio-respiratory fitness (CRF) upon glucose control in postmenopausal women (PM-women) is unclear. PURPOSE: To determine the effects of CRF upon glucose control in PM-women. METHODS: CRF was assessed via Bruce treadmill test in 79 sedentary-to-moderately active and 10 marathon running (MR) PM-women. Sedentary-to-moderately active women were classified into low, medium or high CRF levels according to VO2 peak, MR were a separate group. Assessment of glucose control included analysis of fasting venous glucose and insulin (thus the homeostasis model assessment (HOMA)) and HbA1c concentrations The following additional CVD risk factors were assessed: body composition (skinfold analysis/waist and hip circumferences, BMI and body mass), flow mediated dilation (reactive hyperaemia) as an index of endothelial function, total cholesterol, high and low density lipoproteins, triglycerides and high sensitivity C-reactive protein (hsCRP). CRF level differences in glucose control variables were analysed via ANCOVA (all other variables as covariates), and multiple regression assessed which variables best predicted glucose control variables. RESULTS: Fasting plasma glucose concentration was the only glucose control variable to differ between CRF levels with the MR group having significantly lower concentrations (4.1mmol/L) than all other CRF levels (low CRF 5.7; medium CRF 5.5; high CRF 5.5 mmol/L). Additionally, MR women were the only group to have a glucose concentration less that 4.9 mmol/L (threshold for CVD risk). CRF was found to be the strongest predictor for glucose concentration. Conversely, body mass, waist circumference and hsCRP were the strongest predictors of insulin concentration and HOMA, whereas CRF had little predictive influence. CONCLUSION: Very high levels of CRF similar to marathon runners may be required to lower glucose concentration in PM-women to levels below the threshold for increased risk of CVD. Supported by a Heart Research UK grant 2508/06/08