Distinct effects of type 2 diabetes and obesity on cardiopulmonary performance

Aim: Effort intolerance is frequent in patients with overweight/obesity and/or type 2 diabetes (T2D) free from cardiac and respiratory disease. We sought to quantify the independent effects of T2D and body mass index (BMI) on cardiopulmonary capacity and gain insights on the possible pathophysiology by case-control and regression analyses. Methods: Patients at high/moderate cardiovascular risk, with or without T2D, underwent spirometry and combined echocardiography-cardiopulmonary exercise test as part of their clinical workup. Subjects with evidence of cardiopulmonary disease were excluded. The effects of T2D and obesity were estimated by multivariable models accounting for known/potential confounders and the major pathophysiological determinants of oxygen uptake at peak exercise (VO2peak) normalized for fat-free mass (FFM). Results: In total, 109 patients with T2D and 97 controls were included in the analysis. The two groups had similar demographic and anthropometric characteristics except for higher BMI in T2D (28.6 ± 4.6 vs. 26.3 ± 4.4 kg/m2, p =.0003) but comparable FFM. Patients with T2D achieved lower VO2peak than controls (18.5 ± 4.4 vs. 21.7 ± 8.3 ml/min/kg, p =.0006). Subclinical cardiovascular dysfunctions were observed in T2D: concentric left ventricular remodelling, autonomic dysfunction, systolic dysfunction and reduced systolic reserve. After accounting for confounders and major determinants of VO2peakFFM, T2D still displayed reduced VO2peak by 1.0 (−1.7/−0.3) ml/min/kgFFM, p =.0089, while the effect of BMI [−0.2 (−0.3/0.1) ml/min/kgFFM, p =.06 per unit increase], was largely explained by a combination of chronotropic incompetence, reduced peripheral oxygen extraction, impaired systolic reserve and ventilatory (in)efficiency. Conclusions: T2D is an independent negative determinant of VO2peak whose effect is additive to other pathophysiological determinants of oxygen uptake, including BMI.