Increased oxidative stress alters coronary microvascular tone in exercising swine with multiple comorbidities

Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Netherlands CardioVascular Research Initiative: an initiative with support of the Dutch Heart Foundation Introduction Diabetes mellitus (DM), chronic kidney disease (CKD) and hypercholesterolemia either alone or in combination, induce sustained systemic inflammation, increased oxidative stress and coronary endothelial dysfunction. The resulting alterations in microvascular tone may contribute to impaired myocardial perfusion in patients chronically affected by these comorbidities. Purpose We tested, in exercising swine, the hypothesis that increased production of reactive oxygen species (ROS) due to DM, CKD and high fat diet (HFD) results in loss of NO bioavailability in the coronary microvasculature leading to altered myocardial perfusion. Methods In 12 female swine, DM (streptozotocin 3x50mg/kg iv), CKD (renal embolization), and hypercholesterolemia (via high fat diet, HFD) were induced for 6 months (DM+HFD+CKD). 10 female healthy swine on normal pig chow served as controls (Normal). The role of ROS in the regulation of coronary flow was studied at rest and during graded treadmill exercise with or without ROS scavengers (MPG+Tempol). Results 6 months after the induction of comorbidities, DM+HFD+CKD animals had sustained hyperglycemia (19.5±1.1 vs 8.7±0.5mmol/L), renal dysfunction (plasma creatinine: 163±7 vs 120±3 µmol/l), hypercholesterolemia (12.7±2.1 vs 1.7±0.1mmol/l) and sustained systemic inflammation (TNF 52±5 vs 25±6 pg/ml, all P<0.05). Myocardial superoxide production was increased in DM+HFD+CKD animals due to NADPH oxidase activation and eNOS uncoupling, (Sorop et al, CVR 2018) and total antioxidant capacity was reduced (Fig. A), which was associated with a lower myocardial NO production, (P<0.05). In vivo experiments showed that myocardial oxygen delivery was impaired in DM+HFD+CKD swine at rest and during exercise, requiring an increased myocardial oxygen extraction (MO2ex) compared to Healthy (compare control runs in panels C and D, P<0.05), that is due to a loss of NO vasodilator influence (van de Wouw et al. BRIC 2021). Interestingly, scavenging of ROS had no effect in Healthy but resulted in increased MO2ex in DM+HFD+CKD (Fig. C, D), indicating that increased oxidative stress resulted in increased production of vasodilator ROS, most likely H2O2. The latter was also supported by an increase in ceramide production (138±34 vs 45±4 nmol/ml, P<0.05) and increased activity of catalase in the myocardium (Fig. B, P<0.05). Conclusion In swine, 6 months exposure to multiple comorbidities resulted in increased oxidative stress associated with impaired myocardial oxygen delivery, due to a loss of NO that was partially compensated for by increased H2O2-mediated coronary vasodilation.