Renal tubule epithelial cells are high-energy demanding polarized epithelial cells. Liver kinase B1 (LKB1) is a key regulator of polarity, proliferation, and cell metabolism in epithelial cells, but the function of LKB1 in the kidney is unclear. Our unbiased gene expression studies of human control and CKD kidney samples identified lower expression of LKB1 and regulatory proteins in CKD. Mice with distal tubule epithelial-specific Lkb1 deletion (Ksp-Cre/Lkb1 flox/flox ) exhibited progressive kidney disease characterized by flattened dedifferentiated tubule epithelial cells, interstitial matrix accumulation, and dilated cystic-appearing tubules. Expression of epithelial polarity markers b-catenin and E-cadherin was not altered even at later stages. However, expression levels of key regulators of metabolism, AMP-activated protein kinase (Ampk), peroxisome proliferative activated receptor gamma coactivator 1-a (Ppargc1a), and Ppara, were significantly lower than those in controls and correlated with fibrosis development. Loss of Lkb1 in cultured epithelial cells resulted in energy depletion, apoptosis, less fatty acid oxidation and glycolysis, and a profibrotic phenotype. Treatment of Lkb1-deficient cells with an AMP-activated protein kinase (AMPK) agonist (A769662) or a peroxisome proliferative activated receptor alpha agonist (fenofibrate) restored the fatty oxidation defect and reduced apoptosis. In conclusion, we show that loss of LKB1 in renal tubular epithelial cells has an important role in kidney disease development by influencing intracellular metabolism. 27: 439-453, 201627: 439-453, . doi: 10.1681 Renal tubular epithelial cells (TECs) display strict apico-basal polarity. They allow a highly regulated uptake or excretion of substances at its apical surface, while keeping a closed, impenetrable surface through the formation of tight intercellular junctions in the basolateral membrane. The establishment and maintenance of TEC polarity is incompletely understood. The liver kinase B1 (LKB1) is an important regular of polarity. Early studies indicated that single intestinal epithelial cells polarize in a cell-autonomous fashion in response to LKB1 expression. 1 The LKB1 or STK11 gene encodes an evolutionarily conserved serine/threonine protein kinase. Following LKB1 expression, intestinal epithelial cells reorganized their cytoskeleton to form an apical brush border, demonstrating LKB1's critical role in establishing epithelial polarity. On the other hand, the effect of LKB1 on cell polarity appears to be cell type specific and deletion of LKB1 did not alter polarity of lung epithelial and pancreatic cells. 2
J Am Soc Nephrol