Abstract 620: Molecular Mechanisms and Therapeutic Approaches to Myofilament Glycation as a Result of Diabetes

Abstract

Methylglyoxal (MG), a glycolysis byproduct, is significantly elevated in the blood of patients with diabetes and modifies proteins by reacting with arginine and lysine residues to form irreversible adducts. We previously found that patients with diabetes and heart failure (dbHF) exhibited an increase in MG-modifications on cardiac myofilament proteins compared to non-failing hearts. We discovered these modifications reduced myofilament calcium sensitivity and maximal calcium-activated force, and despite being primarily on actin and myosin, did not affect their direct binding. The aim of this study was to elucidate MG’s molecular effects on muscle mechanics as well as to identify effective therapeutic options for dbHF patients. We first utilized a custom loaded fiber system to simultaneously measure isometric force and ATPase activity. When mouse fibers were treated with 100 μM Mg for 20 mins, similar to previous studies, there was a decrease in force production, but there was a concomitant decrease in ATPase activity as well. Thus, the tension cost was not altered by MG, supporting our hypothesis that MG modifications on myosin do not alter myosin function, instead altering its interactions with thin filament proteins. MG modifications are irreversible so therapeutic approaches should compensate for the functional defects induced. We pre-treated mouse skinned myocytes with MG, and then measured force-calcium relationships before and after treatment with different drugs. We first used 1 mM aminoguanidine (AG), an MG scavenger that has been efficacious in basic science studies but failed in clinical trials. Agreeing with the clinical trial, we show AG cannot reverse MG’s effects. We then treated the myocytes with omecamtiv mecarbil (OM), a myosin activator currently in clinical trials. In myocytes not pretreated with MG, OM increased calcium sensitivity and decreased maximum force, as reported previously. Interestingly, OM had no effect of calcium sensitivity but still decreased Fmax, suggesting OM may have less effect in patients with diabetes. Overall, in this study we further elucidate the mechanism of MG effect’s on the myofilament, and also show these modifications may reduce the efficacy of OM, a small molecule currently in clinical trials.