Abstract
Differentially altered expression of transcripts of retinoic acid receptors α, β, γ (Rarα, β, γ), which mediate the actions of all-trans retinoic acid (RA), is observed in glomeruli of nephrotic syndrome (NS) patients vs normal individuals, with Rarβ reduced and both RARα and RARγ increased. Thus, we generated a mouse model (PCRB) with Rarβ specifically deleted in podocytes to define the glomerular actions of Rarβ. Rarβ deletion in PCRB mice results in podocyte loss, podocyte foot process effacement, glomerular basement membrane (GBM) thickening, reduced podocyte adhesion to the GBM, lipid accumulation in glomeruli, and hyperfiltration leading to albuminuria. Genome-wide transcriptomics and proteomics studies of glomeruli revealed that Rarβ deletion increased Mogat, Dgat, and Hmgcs mRNAs, which catalyze triglyceride and cholesterol synthesis, and Slc27a2 and Cd36, which mediate fatty acid uptake, recapitulating NS symptoms. Surprisingly, podocyte-specific Rarβ deletion also increased key mRNAs and proteins involved in fatty acid uptake and lipid biosynthesis in the liver, promoting steatohepatitis and systemic hyperlipidemia. These data indicate that Rarβ signaling in the kidney has a profound impact on both kidney and liver functions and suggest that Rarβ plays an important role in regulating kidney-liver crosstalk. PCRB mice may be a useful model of NS.