Circadian clock disruption and growth of kidney cysts in autosomal dominant polycystic kidney disease

Abstract

AbstractBackgroundAutosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in thePKD1andPKD2genes, and often progresses to kidney failure. ADPKD progression is not uniform among patients, suggesting that factors secondary to thePKD1/2gene mutation could regulate the rate of disease progression. Here we tested the effect of circadian clock disruption on ADPKD progression. Circadian rhythms are regulated by cell-autonomous circadian clocks composed of clock proteins. BMAL1 is a core constituent of the circadian clock.MethodsTo disrupt the circadian clock, we deletedBmal1gene in the renal collecting ducts of thePkd1RC/RC(RC/RC) mouse model of ADPKD (RC/RC;Bmal1f/f;Pkhd1cre, called DKO mice), and inPkd1knockout mouse inner medullary collecting duct cells (Pkd1Bmal1KO mIMCD3 cells). Only male mice were used.ResultsHuman nephrectomy ADPKD kidneys andPkd1KO mIMCD3 cells showed reducedBmal1gene expression compared to normal controls. When compared to RC/RC kidneys, DKO kidneys showed significantly altered clock gene expression, increased cyst growth, cell proliferation, apoptosis and fibrosis. DKO kidneys also showed increased lipogenesis and cholesterol synthesis-related gene expression, and increased tissue triglyceride levels compared to RC/RC kidneys. Similarly,in vitro, Pkd1Bmal1KO cells showed altered clock genes, increased lipogenesis and cholesterol synthesis-related genes, and reduced fatty-acid oxidation-related gene expression compared toPkd1KOcells. ThePkd1Bmal1KO cells showed increased cell proliferation compared toPkd1KOcells, which was rescued by pharmacological inhibition of lipogenesis.ConclusionRenal collecting duct specificBmal1gene deletion disrupts the circadian clock and triggers accelerated ADPKD progression by altering lipid metabolism-related gene expression.Key pointsLack of BMAL1, a circadian clock protein in renal collecting ducts disrupted the clock and increased cyst growth and fibrosis in an ADPKD mouse model.BMAL1 gene deletion increased cell proliferation by increasing lipogenesis in kidney cells.Thus, circadian clock disruption could be a risk factor for accelerated disease progression in patients with ADPKD.