Decreased bone density and increased phosphaturia in gene-targeted mice lacking functional serum- and glucocorticoid-inducible kinase 3

• Published in: Kidney international Vol. 80; no. 1; pp. 61 - 67
• Main Authors: Bhandaru, Madhuri, Kempe, Daniela S., Rotte, Anand, Capuano, Paola, Pathare, Ganesh, Sopjani, Mentor, Alesutan, Ioana, Tyan, Leonid, Huang, Dan Yang, Siraskar, Balasaheb, Judenhofer, Martin S., Stange, Gerti, Pichler, Bernd J., Biber, Jürg, Quintanilla-Martinez, Leticia, Wagner, Carsten A., Pearce, David, Föller, Michael, Lang, Florian
• Format: Journal Article
• Language: English
• Published: Basingstoke Elsevier Inc 01.07.2011; Nature Publishing Group; Elsevier Limited
• Subjects: 1,25(OH)2D3; Animals; Biological and medical sciences; Biological Transport, Active; Bone (cortical); Bone (trabecular); Bone density; Bone Density - genetics; Bone Density - physiology; Calcitriol; calcium; Calcium (blood); Calcium (urinary); Calcium - metabolism; Diets; Excretion; Female; Fibroblast growth factor 23; Filtration; Fluid intake; Genotypes; Humans; Hypophosphatemia, Familial - enzymology; Hypophosphatemia, Familial - etiology; Hypophosphatemia, Familial - genetics; In Vitro Techniques; Insulin; Kidney; Kidney Tubules - metabolism; Medical sciences; Mice; Mice, Knockout; mineralization; Nephrology. Urinary tract diseases; Oocytes; Oocytes - metabolism; Parathyroid hormone; Phosphate; Phosphates - metabolism; Phosphaturia; Protein-Serine-Threonine Kinases - deficiency; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; PTH; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Signal Transduction; Sodium-Phosphate Cotransporter Proteins, Type IIa - genetics; Sodium-Phosphate Cotransporter Proteins, Type IIa - metabolism; Urine; Xenopus; phosphate; 1,25(OH)2D3; mineralization; calcium; insulin; PTH; Phosphates; Pancreatic hormone; Nephrology; Calcium; Targeting; D; Inorganic element; Density; Glucocorticoid; Urology; Osteoarticular system; Gene; Mineralization; Genetics; Serum; 1,25(OH); Enzyme; Transferases; Rodentia; Insulin; Phosphaturia; Vertebrata; Mammalia; Mouse; Kinase; Animal; Bone
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1038/ki.2011.67

Insulin and growth factors activate the phosphatidylinositide-3-kinase pathway, leading to stimulation of several kinases including serum- and glucocorticoid-inducible kinase isoform SGK3, a transport regulating kinase. Here, we explored the contribution of SGK3 to the regulation of renal tubular phosphate transport. Coexpression of SGK3 and sodium-phosphate cotransporter IIa significantly enhanced the phosphate-induced current in Xenopus oocytes. In sgk3 knockout and wild-type mice on a standard diet, fluid intake, glomerular filtration and urine flow rates, and urinary calcium ion excretion were similar. However, fractional urinary phosphate excretion was slightly but significantly larger in the knockout than in wild-type mice. Plasma calcium ion, phosphate concentration, and plasma parathyroid hormone levels were not significantly different between the two genotypes, but plasma calcitriol and fibroblast growth factor 23 concentrations were significantly lower in the knockout than in wild-type mice. Moreover, bone density was significantly lower in the knockouts than in wild-type mice. Histological analysis of the femur did not show any differences in cortical bone but there was slightly less prominent trabecular bone in sgk3 knockout mice. Thus, SGK3 has a subtle but significant role in the regulation of renal tubular phosphate transport and bone density.