Podocyte Specific Deletion of Acid Ceramidase Predisposes Mice to Obesity‐Induced Glomerular Injury

Abstract

Acid ceramidase (AC) as a key regulatory enzyme involved in ceramide metabolism plays a critical role in the intracellular lipid metabolism and molecular trafficking. Given recent reports that obesity enhances ceramide production, leading to the activation of NADPH oxidase and consequent development of glomerular sclerosis, the present study was designed to test whether AC contributes to the development of glomerular injury associated with obesity. First, we generated and characterized the podocyte‐specific AC knockout mice by cross breeding loxP‐floxed AC‐/‐ and nephrin cre promoter mice. The podocyte specific AC knockout (Ac‐/‐/Nephcre) and wild type (AC+/+) mice were fed a high fat diet (HFD) or normal chow (ND) for 10 weeks to produce obesity. Immunohistochemical analysis demonstrated that AC expression was reduced in glomeruli of Ac‐/‐/Nephcre mice compared to AC+/+ mice. In contrast, the ceramide level, and desmin expression were higher in glomeruli of Ac‐/‐/Nephcre than AC+/+ mice. Furthermore, Western blot, real time RT‐PCR and Immunohistochemical analyses showed that HFD significantly decreased the AC expression in Ac‐/‐/Nephcre mice, but not in AC+/+ mice. Correspondingly, the urinary protein excretion was significantly higher in HFD fed Ac‐/‐/Nephcre than Ac+/+ mice. In in vitro studies of podocytes, AC inhibitor, D‐NMAPPD decreased the podocin expression, VEGF level and increased the desmin expression compared to control cells. In conclusion, our observations reveal that normal expression of AC contributes to the function of podocytes and the defect of this gene expression is a critical mechanism triggering podocyte injury and ultimately resulting in obesity‐associated end‐stage renal disease.