Poster Topical Area: Aging and Chronic Disease
Poster Board Number: 100
Objective: In many metabolic diseases, mitochondrial inner membrane phospholipids undergo significant acyl chain remodeling. One paradoxical event that occurs in the cardiac mitochondrial phospholipidome is an increase in docosahexaenoic acid (DHA) levels. Therefore, the purpose of this study was to determine how dietary DHA impacted murine cardiac mitochondrial phospholipid composition and mitochondrial respiratory enzyme activities. Furthermore, biophysical studies were conducted to study DHA's role in mitochondrial lipid-lipid and lipid-protein interactions.
Methods: Mice were administered a western diet in the absence or presence of DHA and their metabolic profile was monitored. Phospholipidomic assays were performed via mass spectrometry. Respiratory enzyme specific activity measurements were performed via UV-Vis spectroscopy and select biophysical measurements were performed using biomimetic membranes and surface plasmon resonance.
Results: Phospholipidomic analyses revealed that DHA dramatically remodeled the acyl chains of cardiac mitochondrial phospholipids phosphatidylcholine, phosphatidylethanolamine, and cardiolipin (CL). These changes were accompanied by decreased complex I, IV, V, and I+III enzyme activities, which was not driven by changes in mitochondrial respiratory protein abundance or supercomplex formation. Instead, we found that the replacement of tetralinoleoyl-CL [(18:2)4CL] with tetradocosahexaenoyl-CL [(22:6)4CL] in biomimetic membranes prohibited the formation of lipid microdomains due to DHA's influence on thermodynamics of lipid-lipid mixing. Furthermore, (22:6)4CL modified CL-protein binding kinetics relative to (18:2)4CL. The reintroduction of (18:2)4CL to mitochondria isolated from mice consuming DHA, rescued the major losses in the mitochondrial phospholipidome and the specific enzymatic activities of complexes, I, IV, and V.
Conclusions: These results suggest that increased mitochondrial membrane DHA decreases cardiac mitochondrial respiratory enzymatic activities, which are rescued with linoleic acid, potentially through lipid-lipid and lipid-protein mediated mechanisms. This has major implications for the ongoing debate regarding n-6 and n-3 polyunsaturated fatty acids and cardiac health.
Graduate Student Researcher
Department of Biochemistry & Molecular Biology, East Carolina Diabetes & Obesity Institute, Brody School of Medicine, East Carolina University
Raleigh, North Carolina