Calcium absorption, endogenous excretion, and endocrine changes during and after long-term bed rest

LeBlanc, Adrian; Schneider, Victor; Spector, Elisabeth R.; Evans, Harlan J.; Rowe, Richard C.; Lane, Helen W.; Demers, Lawrence M.; Lipton, Allan

doi:10.1016/s8756-3282(95)80193-6

Cited by 56 publications

(38 citation statements)

References 15 publications

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“…Plasma PTH concentrations were not significantly different in S and R rats and were unaffected by hind limb unloading, as was previously reported for S and R rats fed 0.3% salt [9]. Plasma PTH concentrations have been reported to decrease [1, 5–6, 30–31] and to remain unchanged [2, 4, 37] as a result of bed rest. Plasma PTH concentrations were decreased, compared with baseline, in African-American men at day 7 of bed rest when salt intake was high, but not when salt intake was low [3].…”

Section: Discussionsupporting

confidence: 71%

“…Serum concentrations of vitamin D hormone (1,25-dihydroxyvitamin D, 1,25-(OH) 2 D) were decreased within one week of bed rest [1–3], after long-term bed rest [4–6], and after long-term space flight [7–8]. The Dahl salt-sensitive (S) female rat, but not the Dahl salt-resistant (R) rat, also demonstrated a decrease in plasma 1,25-(OH) 2 D concentration when hind limb unloaded (a disuse and space flight model) for 28 days [9].…”

Section: Introductionmentioning

confidence: 99%

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Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats

Thierry-Palmer

Cephas

2010

The Journal of Steroid Biochemistry and Molecular Biology

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Plasma 1,25-dihydroxyvitamin D (1,25-(OH)2D) concentration was shown to decrease during bed rest in several studies when baseline plasma 25-hydroxyvitamin D (25-OHD) concentration was sub-optimal. Dahl salt-sensitive female (S) rats, but not Dahl salt-resistant female (R) rats, demonstrated a 50% decrease in plasma 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) concentration after 28 days of hind limb unloading (HU, disuse model) during low salt intake (0.3%). We tested the vitamin D endocrine system response of female S rats to hind limb unloading during high salt intake (2%, twice that of standard rat chow to mimic salt intake in the USA). Hind limb unloading resulted in lower plasma 25-OHD3 concentrations in S-HU rats than in R-HU rats (P < 0.05) and greater urinary loss of 25-OHD3 by S-HU rats than by S rats (P < 0.05). Plasma 1,25-(OH)2D3 concentration of S-HU rats was half that of S rats, but was unchanged in R-HU rats. The association of low plasma 25-OHD concentration with decrease in plasma 1,25-(OH)2D concentration of hind limb unloaded rats and of bed rest participants (published studies) suggests that low vitamin D status might be a risk factor for decrease in plasma vitamin D hormone concentration during long-term immobilization or bed rest.

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Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats

Thierry-Palmer

Cephas

2010

The Journal of Steroid Biochemistry and Molecular Biology

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“…Evidence from bone biopsy and histomorphometry suggests that, during bed rest, bone formation decreases (30, 31) . However, evidence from measuring biochemical markers and calcium kinetics suggests that bone formation is unchanged or decreased (7, 32–34) . This difference likely reflects the anatomic level at which measurements were made: site‐specific (biopsy) versus systemic (biochemical markers, calcium kinetics).…”

Section: Discussionmentioning

confidence: 99%

Bone Markers, Calcium Metabolism, and Calcium Kinetics During Extended-Duration Space Flight on the Mir Space Station

Smith

Wastney

O’Brien

et al. 2005

Journal of Bone and Mineral Research

217

180

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Bone loss is a current limitation for long-term space exploration. Bone markers, calcitropic hormones, and calcium kinetics of crew members on space missions of 4-6 months were evaluated. Spaceflight-induced bone loss was associated with increased bone resorption and decreased calcium absorption.Introduction: Bone loss is a significant concern for the health of astronauts on long-duration missions. Defining the time course and mechanism of these changes will aid in developing means to counteract these losses during space flight and will have relevance for other clinical situations that impair weight-bearing activity. Materials and Methods: We report here results from two studies conducted during the Shuttle-Mir Science Program. Study 1 was an evaluation of bone and calcium biochemical markers of 13 subjects before and after long-duration (4-6 months) space missions. In study 2, stable calcium isotopes were used to evaluate calcium metabolism in six subjects before, during, and after flight. Relationships between measures of bone turnover, biochemical markers, and calcium kinetics were examined. Results: Pre-and postflight study results confirmed that, after landing, bone resorption was increased, as indicated by increases in urinary calcium (p < 0.05) and collagen cross-links (N-telopeptide, pyridinoline, and deoxypyridinoline were all increased >55% above preflight levels, p < 0.001). Parathyroid hormone and vitamin D metabolites were unchanged at landing. Biochemical markers of bone formation were unchanged at landing, but 2-3 weeks later, both bone-specific alkaline phosphatase and osteocalcin were significantly (p < 0.01) increased above preflight levels. In studies conducted during flight, bone resorption markers were also significantly higher than before flight. The calcium kinetic data also validated that bone resorption was increased during flight compared with preflight values (668 ± 130 versus 427 ± 153 mg/day; p < 0.001) and clearly documented that true intestinal calcium absorption was significantly lower during flight compared with preflight values (233 ± 87 versus 460 ± 47 mg/day; p < 0.01). Weightlessness had a detrimental effect on the balance in bone turnover such that the daily difference in calcium retention during flight compared with preflight values approached 300 mg/day (−234 ± 102 versus 63 ± 75 mg/day; p < 0.01). Conclusions: These bone marker and calcium kinetic studies indicated that the bone loss that occurs during space flight is a consequence of increased bone resorption and decreased intestinal calcium absorption.

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“…Previous studies have shown that bed rest is associated with increases in urinary pyridinoline and DPD (10,(21)(22)(23)(24). In one 17-week study in which significant bone was lost (8), urinary pyridinolines and DPD were almost 40% higher than before the bed rest (10).…”

mentioning

confidence: 88%

Collagen Cross-Link Excretion during Space Flight and Bed Rest1

Smith¹,

Nillen

LeBlanc

et al. 1998

The Journal of Clinical Endocrinology &Amp; Metabolism

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Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this bone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PYD) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short (14-day) and long (119-day) bed-rest studies. During space flight, the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden.

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Calcium absorption, endogenous excretion, and endocrine changes during and after long-term bed rest

Cited by 56 publications

References 15 publications

Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats

Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats

Bone Markers, Calcium Metabolism, and Calcium Kinetics During Extended-Duration Space Flight on the Mir Space Station

Collagen Cross-Link Excretion during Space Flight and Bed Rest1

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