Acto-myosin crossbridge kinetics in humans with coronary artery disease: Influence of sex and diabetes mellitus

Risk of heart failure (HF) is influenced by sex and diabetes mellitus (DM). To better understand these interactions, sub-epicardial myocardium from 26 patients with coronary artery disease (CAD) undergoing coronary bypass surgery was examined in vitro using sinusoidal length perturbation analysis at varying [Ca2+] to determine the viscoelastic properties of myofilaments related to acto-myosin crossbridge kinetics. Half of the patients had CAD only (four female, F-CAD; nine male, M-CAD), while the other half had both CAD and Type 2 DM (six F-DM; seven M-DM). At maximal and sub-maximal myofilament Ca2+ activation there was a significant effect of sex and disease on frequency of maximum oscillatory work output during sinusoidal perturbation (P < 0.05). Myofilaments from F-CAD produced oscillatory work at significantly higher frequencies compared with M-CAD, while myofilaments from F-DM and M-DM produced work at similar frequencies. Correspondingly, minimum viscoelastic stiffness at maximum Ca2+ activation occurred at significantly higher frequencies in F-CAD (5.0 ± 0.3 Hz) than M-CAD (3.3 ± 0.3 Hz), but at similar frequencies in F-DM (3.7 ± 0.3 Hz) and M-DM (4.3 ± 0.2 Hz). Thus, sex influences acto-myosin crossbridge kinetics in myofilaments isolated from CAD patients. These sex-related differences were absent in DM, suggesting that differences in the properties of cardiac muscle contribute to reported sex differences in the incidence and mortality of HF in DM.