Abstract 20503: Dynamic Metabolic Profiling of Atrial Energetics: Age-dependent Decline in ATP Cycling and Glycerol-3-phosphate Shuttle Activity
Integration of mitochondrial and cytosolic ATP-consuming and substrate supply processes is critical for sustaining adequate atrial bioenergetics and normal electrical activity. Here we employed advanced oxygen-18 labeling methodology and mass spectrometry (18O-assisted GC/MS) to determine mechanisms of age dependent decline in atrial energetics which may contribute to increase susceptibility to fibrillation. Intact atrial myocardium from adult and aged rats, 6 and 24 month old respectively, were subjected to metabolite 18O-labeling procedure and extracts were analyzed using HPLC fractionation and 18O-assisted GC/MS techniques. Turnover rates of inorganic phosphate (Pi), an indicator of ATP utilization, and glycerol-3-phosphate (G3P), an indicator of substrate shuttle activity, were determined using 18O-assisted GC/MS after HPLC separation, metoxymation and derivatization using MSTFA plus TMCS. Data analysis indicates a significant lower ATP utilization and overall ATP turnover rates in atrial myocardium of aged rats compared to adult counterparts. Moreover, reduced incorporation of 18O into 2nd (18O2), 3rd (18O3) and 4th (18O4) positions of Pi indicate diminished cycling of Pi and ATP between cellular ATPases and mitochondria. Labeling of G3P with 18O was significantly depressed in aged atrial myocardium compared to adult indicating deficient G3P shuttle activity and substrate supply to mitochondria. Incorporation of 18O into 2nd (18O2) and 3rd (18O3) positions of phosphoryl of G3P was lower in aged atria reflecting reduced dynamics of G3P and impeded cycling between glycolytic NADH generation sites and mitochondria. These alterations were along with gene array data showing reduced transcript levels of genes in ATP and G3P metabolism in aged hearts. Thus, stable isotope assisted dynamic metabolic profiling of atrial energetics uncovers developing simultaneous ATP cycling and mitochondrial substrate shuttle deficit in aging myocardium.
- © 2010 by American Heart Association, Inc.