Abstract
Coronary microvessel endothelial dysfunction and nitric oxide (NO) depletion contribute to elevated passive tension of cardiomyocytes, diastolic dysfunction and predispose the heart to heart failure with preserved ejection fraction. We examined if diastolic dysfunction at the level of the cardiomyocytes precedes coronary endothelial dysfunction in prediabetes. Further, we determined if myofilaments other than titin contribute to impairment. Utilizing synchrotron microangiography we found young prediabetic male rats showed preserved dilator responses to acetylcholine in microvessels. Utilizing synchrotron X-ray diffraction we show that cardiac relaxation and cross-bridge dynamics are impaired by myosin head displacement from actin filaments particularly in the inner myocardium. We reveal that increased PKC activity and mitochondrial oxidative stress in cardiomyocytes contributes to rho-kinase mediated impairment of myosin head extension to actin filaments, depression of soluble guanylyl cyclase/PKG activity and consequently stiffening of titin in prediabetes ahead of coronary endothelial dysfunction.