Mitochondrial bioenergetics deficit linked to endothelial dysfunction and ER stress induced by obesity in coronary arteries

Obesity and metabolic syndrome are major drivers of metabolic heart disease, characterized by profound cardiac energy deficits, structural remodeling, and progression to heart failure. While myocardial mitochondrial dysfunction in obesity is well established, its impact on coronary arteries remains underexplored. This study investigates how high-fat diet (HFD)-induced obesity affects coronary bioenergetics, mitochondrial REDOX balance, and endothelial function. Male Wistar rats were fed a HFD (60% kcal fat) for 15–16 weeks after weaning as a model of diet-induced obesity, and tunicamycin-treated rats as a model of chemically-induced ER stress in vivo were used. Myograph experiments to assess coronary endothelial function, reactive oxygen species (ROS) measurements, and mitochondrial respiration experiments in a Seahorse analyzer were comprehensively conducted. After 15–16 weeks of HFD rats developed metabolic syndrome features, including weight gain, hyperglycemia, hypertriglyceridemia, and elevated lactate. Coronary arteries exhibited endothelial dysfunction, evidenced by impaired acetylcholine- and isoprenaline-induced relaxations, mediated by NADPH oxidase 1 (NOX1)-derived ROS, as selective NOX1 inhibition (NoxA1ds-tat) restored vasodilation. Mitochondrial ROS (mtROS) levels increased in arteries but not myocardium, along with preserved hydrogen peroxide (H 2 O 2 )-mediated signaling. Protein analysis revealed down-regulated endothelial NOX4 and manganese superoxide dismutase (MnSOD), reduced respiratory complex IV (COX-IV) and uncoupling protein 2 (UCP2), and blunted mitochondrial respiration across basal, ATP-linked, and maximal states. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) up-regulation indicated adaptive biogenesis. HFD also activated endoplasmic reticulum (ER) stress. Notably, tunicamycin-induced ER stress recapitulated these deficits, impairing relaxation, H 2 O 2 production, and respiration, yet up-regulating protective NOX4/MnSOD/PGC-1α. These findings couple coronary mitochondrial impairment to obesity-driven heart disease, highlighting impaired coronary bioenergetics, mitochondrial oxidative stress, and ER stress as key mechanisms. Thus, coronary artery mitochondria emerge as therapeutic targets to improve microvascular perfusion and mitigate progression to heart failure in obesity.