Diet-induced obesity and kidney disease - In search of a susceptible mouse model.

Obesity and metabolic syndrome are independent risk factors for chronic kidney disease, even without diabetes or hyperglycemia. Here, we compare two mouse models that are susceptible to diet-induced obesity: the relatively renal injury resistant C57BL/6J strain and the DBA2/J strain which is more sensitive to renal injury. Our studies focused on characterizing the effects of high fat diet feeding on renal oxidative stress, albuminuria, fibrosis and podocyte loss/insulin resistance. While the C57BL/6J strain does not develop significant pathological changes in the kidney, at least on lard based diets within the time frame investigated, it does show increased renal iNOS and nitrotyrosine levels and elevated mitochondrial respiration which may be indicative of mitochondrial lipid overfueling. Restricting the high fat diet to decrease adiposity decreased the levels of cellular oxidative stress markers, indicating that adiposity-related proinflammatory changes such as increased iNOS levels may trigger similar responses in the kidney. Mitochondrial respiration remained higher, suggesting that eating excess lipids, despite normal adiposity may still lead to renal mitochondrial overfueling. In comparison, DBA/2J mice developed albuminuria on similar diets, signs of fibrosis, oxidative stress, early signs of podocyte loss (evaluated by the markers podocin and WT-1) and podocyte insulin resistance (unable to phosphorylate their glomerular Akt when insulin was given). To summarize, while the C57BL/6J strain is not particularly susceptible to renal disease, changes in its mitochondrial lipid handling combined with the easy availability of transgenic technology may be an advantage to design new knockout models related to mitochondrial lipid metabolism. The DBA/2J model could serve as a basis for studying podocyte insulin resistance and identifying early renal markers in obesity before more severe kidney disease develops. Based on our observations, we encourage further critical evaluation of mouse models for obesity related chronic kidney disease.