title: Thiazide-sensitive Na+ -Cl- cotransporter (NCC) gene inactivation results in increased duodenal Ca2+ absorption, enhanced osteoblast differentiation and elevated bone mineral density.
abstract: Inactivation of the thiazide-sensitive sodium chloride cotransporter (NCC) due to genetic mutations in Gitelman's syndrome (GS) or pharmacological inhibition with thiazide diuretics causes hypocalciuria and increased bone mineral density (BMD) with unclear extrarenal calcium (Ca(2+) ) regulation. We investigated intestinal Ca(2+) absorption and bone Ca(2+) metabolism in nonsense Ncc Ser707X (S707X) homozygous knockin mice (Ncc(S707X/S707X) mice). Compared to wild-type and heterozygous knockin littermates, Ncc(S707X/S707X) mice had increased intestinal absorption of (45) Ca(2+) and expression of the active Ca(2+) transport machinery (transient receptor potential vanilloid 6, calbindin-D9K , and plasma membrane Ca(2+) ATPase isoform 1b). Ncc(S707X/S707X) mice had also significantly increased Ca(2+) content accompanied by greater mineral apposition rate (MAR) in their femurs and higher trabecular bone volume, cortical bone thickness, and BMD determined by μCT. Their osteoblast differentiation markers, such as bone alkaline phosphatase, procollagen I, osteocalcin, and osterix, were also significantly increased while osteoclast activity was unaffected. Analysis of marrow-derived bone cells, either treated with thiazide or directly cultured from Ncc S707X knockin mice, showed that the differentiation of osteoblasts was associated with increased phosphorylation of mechanical stress-induced focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). In conclusion, NCC inhibition stimulates duodenal Ca(2+) absorption as well as osteoblast differentiation and bone Ca(2+) storage, possibly through a FAK/ERK dependent mechanism.
authors.affiliation: Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Yu-Juei
authors.initials: YJ
authors.lastname: Hsu
authors.forename: Sung-Sen
authors.initials: SS
authors.lastname: Yang
authors.forename: Chih-Jen
authors.initials: CJ
authors.lastname: Cheng
authors.forename: Shu-Ting
authors.initials: ST
authors.lastname: Liu
authors.forename: Shih-Ming
authors.initials: SM
authors.lastname: Huang
authors.forename: Tom
authors.initials: T
authors.lastname: Chau
authors.forename: Pauling
authors.initials: P
authors.lastname: Chu
authors.forename: Donald M
authors.initials: DM
authors.lastname: Salter
authors.forename: Herng-Sheng
authors.initials: HS
authors.lastname: Lee
authors.forename: Shih-Hua
authors.initials: SH
authors.lastname: Lin
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D004386:Duodenum / Q000166:cytology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism; D055879:Gene Knock-In Techniques; D007408:Intestinal Absorption / Q000502:physiology*; D017136:Ion Transport / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D064486:Solute Carrier Family 12, Member 3 / Q000235:genetics / Q000378:metabolism
chemical_list: C578875:Slc12a3 protein, mouse; D064486:Solute Carrier Family 12, Member 3; D051417:Focal Adhesion Kinase 1; C496051:Ptk2 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium
keywords: CALCIUM; GITELMAN'S SYNDROME; INTESTINE; OSTEOBLAST DIFFERENTIATION; THIAZIDES