title: Alteration of tight junction gene expression by calcium- and vitamin D-deficient diet in the duodenum of calbindin-null mice.
abstract: Calcium absorption is regulated by both active (transcellular) and passive (paracellular) pathways. Although each pathway has been studied, correlations between the two pathways have not been well elucidated. In previous investigations, the critical transcellular proteins, calbindin-D9k (CaBP-9k) and -D28k (CaBP-28k), were shown to affect other transcellular pathways by buffering intracellular calcium concentrations. The rate of paracellular calcium transport in the duodenum is generally determined by the expression of tight junction genes. In the present study, the effect of dietary calcium and/or vitamin D supplementation on the expression of tight junction genes (occludin, ZO-1 and claudin 2, 10b, 12 and 15) in the duodenum of CaBP-9k- and/or -28k-deficient mice was examined. With a normal diet, the expression of most tight junction genes in the duodenum was significantly increased in CaBP-9k knockout (KO) mice compared to wild-type (WT) animals. With a calcium- and vitamin D-deficient diet, tight junction gene expression was significantly decreased in the duodenum of the CaBP-9k KO mice. These findings suggest that expression of paracellular tight junction genes is regulated by transcellular CaBP proteins, suggesting that active and passive calcium transport pathways may function cooperatively.
authors.affiliation: Laboratory of Veterinary Biochemistry and Molecular Biology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea. ebjeung@chungbuk.ac.kr.
authors.forename: Inho
authors.initials: I
authors.lastname: Hwang
authors.forename: Hyun
authors.initials: H
authors.lastname: Yang
authors.forename: Hong-Seok
authors.initials: HS
authors.lastname: Kang
authors.forename: Changhwan
authors.initials: C
authors.lastname: Ahn
authors.forename: Eui-Ju
authors.initials: EJ
authors.lastname: Hong
authors.forename: Beum-Soo
authors.initials: BS
authors.lastname: An
authors.forename: Eui-Bae
authors.initials: EB
authors.lastname: Jeung
mesh_terms: D000818:Animals; D064026:Calbindins / Q000235:genetics* / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000378:metabolism*; D004032:Diet; D004386:Duodenum / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D018345:Mice, Knockout; D019108:Tight Junctions / Q000235:genetics*; D014807:Vitamin D / Q000008:administration & dosage / Q000378:metabolism*
chemical_list: D064026:Calbindins; D002136:Calcium, Dietary; D014807:Vitamin D