Obesity, a risk factor for dyslipidemia, diabetes mellitus and cardiovascular disease, is induced by the increase of lipid-accumulating adipocytes. Oxidative stress can trigger development of adipocyte and/or cell death depending on the intracellular condition. Although intracellular hydrogen peroxide (H₂O₂) increase during differentiation into adipocytes, the effect of H₂O₂ on lipid accumulation is unclear. In general, intracellular H₂O₂ is mainly produced in mitochondria, but also in large amounts in peroxisomes. Catalase which is abundant in peroxisomes may be involved in the regulation of H₂O₂ level in peroxisomes. In this study, we investigated the effect of peroxisomal H₂O₂ on lipid accumulation during differentiation into adipocytes.
Differentiation into adipocytes was induced by treatment with insulin, dexamethasone, 3-isobutyl-1-methylxanthine. 3-Amino-1,2,4-triazole (ATZ), a catalase activity inhibitor, was added at the time of medium exchange on day 0 and day 3 of differentiation. H₂O₂ overlapped on labeled peroxisomes using fluorescent staining was observed as peroxisomal H₂O₂.
Treatment of ATZ induced inhibition of catalase activity and reduction of lipid accumulation and increase of intracellular H₂O₂ level during differentiation into adipocytes. We demonstrated that H₂O₂ in ATZ untreated adipocytes was mostly present in peroxisomes. Inhibition of catalase activity significantly increased peroxisomal H₂O₂ level and decreased peroxisome content during differentiation into adipocytes. Inhibition of catalase activity also resulted in an increase of autophagosomes and LC3II/I ratio, indicating an increase in autophagy. Treatment with Spautin-1, an autophagy inhibitor, recovered the reduction of lipid accumulation by inhibition of catalase activity.
These results suggest that peroxisomal H₂O₂ reduced peroxisome content via the induction of autophagy ,which might reduce lipid accumulation during differentiation into adipocytes.