Peroxisome-generated hydrogen peroxide as important mediator of lipotoxicity in insulin-producing cells.
OBJECTIVE
Type 2 diabetes is a complex disease that is accompanied by elevated levels of nonesterified fatty acids (NEFAs), which contribute to β-cell dysfunction and β-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-1E cells as well as in primary rat islet cells.


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 H₂O₂-sensitive fluorescent protein HyPer H₂O₂ 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 H₂O₂ formation and protected the cells against palmitic acid-induced toxicity. With the HyPer protein, H₂O₂ generation was directly detectable in the peroxisomes of RINm5F and INS-1E insulin-producing cells as well as in primary rat islet cells.


CONCLUSIONS
The results demonstrate that H₂O₂ 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 β- oxidation.
Institute of Clinical Biochemistry, Hannover Medical School, Germany.
Matthias
M
Elsner
Wiebke
W
Gehrmann
Sigurd
S
Lenzen
D000818:Animals; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D017931:DNA Primers; D005109:Extracellular Matrix / Q000502:physiology; D005452:Fluoresceins / Q000494:pharmacology; D056945:Hep G2 Cells / Q000473:pathology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D016086:Lentivirus / Q000502:physiology; D008297:Male; D018384:Oxidative Stress; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000502:physiology; D016133:Polymerase Chain Reaction; D051381:Rats; D011917:Rats, Inbred Lew; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics
D017931:DNA Primers; D005452:Fluoresceins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D006861:Hydrogen Peroxide; C018506:diacetylfluorescein