Overfed Ossabaw swine with early stage metabolic syndrome have normal coronary collateral development in response to chronic ischemia

Ossabaw miniswine have been naturally selected to efficiently store large amounts of lipids offering them a survival advantage. Our goal was to evaluate the myocardial response to chronic ischemia of the Ossabaw consuming a hypercaloric, high-fat/cholesterol diet with and without metformin supplementation. At 6 weeks of age animals were fed either a regular diet (OC, n = 9), a hypercaloric high-fat/cholesterol diet (OHC, n = 9), or a hypercaloric high-fat/cholesterol diet supplemented with metformin (OHCM, n = 8). At 9 weeks, all animals underwent ameroid constrictor placement to the left circumflex coronary artery to simulate chronic ischemia. Seven weeks after ameroid placement, all animals underwent hemodynamic and functional measurements followed by cardiac harvest. Both OHC and OHCM animals developed significantly greater weight gain, total cholesterol, and LDL:HDL ratio compared to OC controls. Metformin administration reversed diet-induced hypertension and glucose intolerance. There were no differences in global and regional contractility, myocardial perfusion, capillary and arteriolar density, or total protein oxidation between groups. Myocardial protein expression of VEGF, PPAR-alpha, gamma, and delta was significantly increased in the OHC and OHCM groups. Microvessel reactivity was improved in the OHC and OHCM groups compared to controls, and correlated with increased p-eNOS expression. Overfed Ossabaw miniswine develop several components of metabolic syndrome. However, impairments of myocardial function, neovascularization and perfusion were not present, and microvessel reactivity was paradoxically improved in hypercholesterolemic animals. The observed cardioprotection despite metabolic derangements may be clue to lipid-dependant upregulation of the PPAR pathway which is anti-inflammatory and governs myocardial fatty acid metabolism.