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Podocyte injury is an important factor in the pathogenesis of diabetic nephropathy. Podocytes are characterized by large numbers of mitochondria. However, mitochondrial dysfunction as it relates to kidney pathology remains poorly understood. The present study found that podocyte mitochondria in different animal models of diabetes mellitus became elongated with the development of albuminuria, suggesting a change in mitochondrial dynamics. We then treated cells with a combination of glucose, fatty acids, and angiotensin II (GFA) to mimic the diabetic milieu. Cultured podocytes exposed to GFA showed megamitochondria formation and decreased autophagosome degradation. We also found that GFA treatment decreased the binding of the autophagosome to the lysosome. Our results suggest that megamitochondria are common in podocytes during diabetic nephropathy and that insufficient autophagy flux may underlie this effect. These findings have expanded our understanding of the pathogenesis of diabetic nephropathy and identified a potential pharmacological target for treatment.

Considering the increase in cases of non-alcoholic steatohepatitis (NASH), the use of appropriate animal model of NASH is essential to understand the underlying pathogenesis mechanism. To date, several mice models have been used; however, significant differences in the etiologies and food administered affected the results, with inconsistent conclusions. Therefore, it is necessary to understand these models and their differences to be able to choose appropriate models. Inspired by the fact that mitochondrial (mt)DNA content is changed in non-alcoholic fatty liver disease in humans, we investigated the mtDNA copy number in the NASH mice models induced by high-fat diet (HFD) and methionine/choline-deficient diet (MCD) to understand the differences between these models. Megamitochondria were observed in both MCD and HFD groups. However, the MCD group showed significant decrease in liver mtDNA content compared with that in the HFD group. These changes were associated with significant upregulation of mitochondrial biogenesis- and degradation-related genes in MCD model than in HFD model. Thus, stability of mtDNA is associated with the differences between MCD and HFD-induced NASH models often used in studies; these findings could help in choosing appropriate models for studies on NASH.