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Varying dietary calcium (Ca), but not vitamin D (VD), influences bone and calcium metabolism in mature mice
Author(s) -
Schoch Ryan D.,
Smolinski Justin,
McCreedy Rebecca,
Clinton Steven K.,
Fleet James C.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.946.1
Subject(s) - endocrinology , medicine , calcium , vitamin d and neurology , bone remodeling , calcium metabolism , weaning , calbindin , homeostasis , biology , chemistry
During growth, Ca restriction activates the VD endocrine system to regulate Ca homeostasis. However, some research shows that aging blunts this adaptation while other research suggests that serum 25 hydroxyVD 3 (25OHD) levels should be raised to ≥ 80 nmol/L for optimal bone health. We examined whether mature mice adapt to low Ca intake and whether improved VD status enhances this response. At weaning, male mice were fed one of 6 diets with increasing levels of Ca (0.2, 0.5, or 1.5%) and VD (25 or 150 IU/kg diet) for 7‐months. Ca restriction significantly elevated renal 1α hydroxylase mRNA and suppressed renal 24‐hydroxylase mRNA leading to elevated serum 1,25‐dihydroxyVD 3 . As a result, mRNA for VD‐target genes in the duodenum (calbindin D 9k ) and kidney (calbindin D 28k , calbindin D 9k ) were significantly increased. Despite this adaptation, Ca restriction decreased bone mineral density (−5.8%). Changing VD intake increased serum 25OHD from 49±3 to 79±3 nmol/L. However, this had no effect on bone or markers of Ca metabolism. These data show that habitual Ca restriction within ranges relevant to human intakes can stimulate adaptive mechanisms of Ca metabolism in mature mice but that this is insufficient to protect bone. In addition, using VD intake to raise serum 25OHD to 80 nmol/L does not benefit bone health and Ca metabolism nor blunt the negative impact of calcium restriction. Supported by NIH awards DK054111 and CA101113.