Peroxisome-Generated Hydrogen Peroxide as Important Mediator of Lipotoxicity in Insulin-Producing Cells

摘要

Objective-type 2 diabetes is a complex disease that is accompanied by elevated levels of nonesterifled fatty acids (nefas), which contribute to p-cell dysfunction and 3-cell loss, referred to as lipotoxicity. Experimental evidence suggests that oxidative stress is involved in lipotoxicity. In this study, we analyzed the molecular mechanisms of reactive oxygen species-mediated lipotoxicity in insulin-producing rinm5f cells and ins-ie cells as well as in primary rat islet cells. Research design and methods-the toxicity of saturated nefas with different chain lengths upon insulin-producing cells was determined by mtt and propidium iodide (pi) viability assays. Catalase or superoxide dismutase overexpressing cells were used to analyze the nature and the cellular compartment of reactive oxygen species formation. With the new h_2o_2-sensitive fluorescent protein hyper h_2o_2 formation induced by exposure to palmitic acid was determined. Results-only long-chain (>c14) saturated nefas were toxic to insulin-producing cells. Overexpression of catalase in the peroxisomes and in the cytosol, but not in the mitochondria, significantly reduced h_2o_2 formation and protected the cells against palmitic acid-induced toxicity. With the hyper protein, h_2o_2 generation was directly detectable in the peroxisomes of rinm5f and ins-ie insulin-producing cells as well as in primary rat islet cells. Conclusions-the results demonstrate that h_2o_3 formation in the peroxisomes rather than in the mitochondria are responsible for nefa-induced toxicity. Therefore, we propose a new concept of fatty acid-induced β-cell lipotoxicity mediated via reactive oxygen species formation through peroxisomal 3-oxidation.