Mitochondrial ATP-sensitive K+ channels as redox signals to liver mitochondria in response to hypertriglyceridemia

Abstract

We have recently demonstrated that hypertriglyceridemic (HTG) mice present both elevated body metabolic rates and mild mitochondrial uncoupling in the liver owing to stimulated activity of the ATP-sensitive potassium channel (mitoKATP). Because lipid excess normally leads to cell redox imbalance, we examined the hepatic oxidative status in this model. Cell redox imbalance was evidenced by increased total levels of carbonylated proteins, malondialdehydes, and GSSG/GSH ratios in HTG livers compared to wild type. In addition, the activities of the extramitochondrial enzymes NADPH oxidase and xanthine oxidase were elevated in HTG livers. In contrast, Mn-superoxide dismutase activity and content, a mitochondrial matrix marker, were significantly decreased in HTG livers. Isolated HTG liver mitochondria presented lower rates of H2O2 production, which were reversed by mitoKATP antagonists. In vivo antioxidant treatment with N-acetylcysteine decreased both mitoKATP activity and metabolic rates in HTG mice. These data indicate that high levels of triglycerides increase reactive oxygen generation by extramitochondrial enzymes that promote mitoKATP activation. The mild uncoupling mediated by mitoKATP increases metabolic rates and protects mitochondria against oxidative damage. Therefore, a biological role for mitoKATP as a redox sensor is shown here for the first time in an in vivo model of systemic and cellular lipid excess