H(2)O(2) release from the very long chain acyl-CoA dehydrogenase

Enhanced mitochondrial generation of oxidants, including hydrogen peroxide (H(2)O(2)), is related to a large number of pathological conditions, including diet-induced obesity and steatohepatosis. Indeed, we have previously shown that high fat diets increase the generation of H(2)O(2) in liver mitochondria energized by activated fatty acids. Here, we further study fatty-acid induced H(2)O(2) release in liver mitochondria, and determine the characteristics that regulate it. We find that this production of H(2)O(2) is independent of mitochondrial inner membrane integrity and insensitive to purine nucleotides. On the other hand, palmitate-induced H(2)O(2) production is strongly enhanced by high fat diets and is pH-sensitive, with a peak at a matrix pH of ~8.5. Using recombinantly expressed human very long chain acyl-CoA dehydrogenase, we are able to demonstrate that palmitate-induced H(2)O(2) release may be ascribed to the activity of this enzyme alone, acting as an oxidase. Our results add to a number of findings indicating that sources outside of the electron transport chain can generate significant, physiopathologically relevant, amounts of oxidants in mitochondria.