Loss of the normal coupling between the anaerobic threshold and insulin sensitivity in chronic heart failure

Abstract

Objective - To explore whether the anaerobic threshold, a measure of the balance between aerobic and anaerobic cellular metabolism, is related to whole body insulin sensitivity in healthy individuals and in patients with chronic heart failure, which involves is an imbalance of aerobic and anaerobic metabolism. Design - Case-control study. Setting - A teaching hospital department specialising in heart failure. Patients - 20 healthy individuals (mean (SEM) age 55.2 (2.7) years) and 36 patients with chronic heart failure (59.1 (2.0) years, New York Heart Association class I-IV, anaerobic threshold 11.8 (0.7) ml/kg/min, left ventricular ejection fraction 26 (2)%). Interventions - An intravenous glucose tolerance test for assessment of insulin sensitivity (minimal model analysis) and a maximum treadmill exercise test for assessment of the anaerobic threshold, derived from measurement of oxygen consumption and carbon dioxide output. Main outcome measures - Relation between insulin sensitivity and the anaerobic threshold in patients with chronic heart failure. Results - While anaerobic threshold was positively correlated with insulin sensitivity in healthy controls (r = 0.72, p < 0.001), no such relation was observed in patients with chronic heart failure. In stepwise multiple linear regression analyses of variables in healthy individuals, insulin sensitivity emerged as the only predictor of anaerobic threshold (standardised coefficient = 0.72, p < 0.001), while fasting insulin, incremental insulin area, and total body fat (dual photon x ray absorptiometry) failed to enter into final models (joint R = 0.52, p < 0.001). Conclusions - In healthy individuals, whole body insulin sensitivity is related, or 'coupled,' to the anaerobic threshold. The absence of such metabolic coupling in patients with chronic heart failure provides further evidence of disturbed cellular metabolism in patients with this condition.