Effects of GLP‐1 receptor agonist on Ca2+ handling in coronary smooth muscle cells from metabolic syndrome Ossabaw swine with coronary artery disease

Abstract

Chronic effects of glucagon‐like peptide (GLP‐1) receptor agonists were studied in Ossabaw swine with metabolic syndrome (MetS). MetS was induced by hypercaloric atherogenic diet for 6 months. Subcutaneous injections were given twice daily for 6 months after induction of MetS. Consistent with clinical effects, food consumption and weight gain were attenuated. MetS increases coronary artery disease (CAD) and coronary smooth muscle (CSM) Ca2+ dysfunction. CSM cells were isolated enzymatically from the coronary arteries and Ca2+ was digitally imaged with fluorescent fura‐2. In normal physiological salt solution we released sarcoplasmic reticulum (SR) stores with caffeine. Treated cells showed a larger Ca2+ transient, ΔF360/380=0.26±0.02, compared to placebo cells, ΔF360/380=0.16±0.01 (p<0.001). In lean CSM, acute exposure to exenatide markedly increased activity of the sarcoplasmic‐endoplasmic reticulum Ca2+ ATPase (SERCA). This activity was confirmed by cyclopizaonic acid block. The increased SERCA activity may explain increased SR Ca2+ store in chronic MetS CSM. Acute exposure of placebo MetS CSM to exenatide has shown no effect on SERCA activity (n=43). Evidence for myocardial resistance to GLP‐1 in MetS is consistent with the lack of acute response. Our interpretation is that chronic exposure attenuates the decline in CSM Ca2+ handling associated with more severe CAD and dedifferentiation of CSM.(Support: NIH HL062552, TL1 TR000162, Amylin Pharmaceuticals Inc.)