Low serum vitamin D is associated with higher cortical porosity in elderly men.

BACKGROUND: Bone loss at peripheral sites in the elderly is mainly cortical and involves increased cortical porosity. However, an association between bone loss at these sites and 25-hydroxyvitamin D has not been reported. OBJECTIVE: To investigate the association between serum levels of 25-hydroxyvitamin D, bone microstructure and areal bone mineral density (BMD) in elderly men. METHODS: A population-based cohort of 444 elderly men (mean ± SD age 80.2 ± 3.5 years) was investigated. Bone microstructure was measured by high-resolution peripheral quantitative computed tomography, areal BMD by dual-energy X-ray absorptiometry and serum 25-hydroxyvitamin D and parathyroid hormone levels by immunoassay. RESULTS: Mean cortical porosity at the distal tibia was 14.7% higher (12.5 ± 4.3% vs. 10.9 ± 4.1%, P < 0.05) whilst cortical volumetric BMD, area, trabecular bone volume fraction and femoral neck areal BMD were lower in men in the lowest quartile of vitamin D levels compared to the highest. In men with vitamin D deficiency (<25 nmol L-1 ) or insufficiency [25-49 nmol L-1 , in combination with an elevated serum level of parathyroid hormone (>6.8 pmol L-1 )], cortical porosity was 17.2% higher than in vitamin D-sufficient men (P < 0.01). A linear regression model including age, weight, height, daily calcium intake, physical activity, smoking vitamin D supplementation and parathyroid hormone showed that 25-hydroxyvitamin D independently predicted cortical porosity (standardized ß = -0.110, R2 = 1.1%, P = 0.024), area (ß = 0.123, R2 = 1.4%, P = 0.007) and cortical volumetric BMD (ß = 0.125, R2 = 1.4%, P = 0.007) of the tibia as well as areal BMD of the femoral neck (ß = 0.102, R2 = 0.9%, P = 0.04). CONCLUSION: Serum vitamin D is associated with cortical porosity, area and density, indicating that bone fragility as a result of low vitamin D could be due to changes in cortical bone microstructure and geometry.

Risk factors for vitamin D inadequacy among women with osteoporosis: an international epidemiological study.

A serum 25-hydroxyvitamin D [25(OH)D] level of 75 nmol/l (30 ng/ml) has been proposed as the minimum for adequate vitamin D nutrition as lower levels are associated with increases in serum parathyroid hormone in otherwise healthy adults. Amongst 2589 community-dwelling, postmenopausal women with osteoporosis from 18 countries, recruited to determine risk factors for vitamin D inadequacy, 64% had vitamin D inadequacy. General health, education, ethnicity, sun exposure, skin reactivity, diet, recent travel to sunny climates, vitamin D supplementation, body mass index (BMI), season and latitude were assessed using logistic regression models. Asian ethnicity, BMI >or=30 kg/m(2), living in non-equatorial countries, inadequate vitamin D supplementation, poor/fair health, no education about vitamin D, skin reactivity and no recent travel to sunny areas were significant predictors. Several modifiable risk factors are associated with vitamin D inadequacy worldwide, suggesting potentially simple ways to increase vitamin D and improve bone health in postmenopausal women.

Addressing the musculoskeletal components of fracture risk with calcium and vitamin D: a review of the evidence.

Osteoporotic fractures are an extremely common and serious health problem in the elderly. This article presents the rationale for calcium and vitamin D supplementation in the prevention and treatment of osteoporotic fractures and reviews the literature evidence on the efficacy of this strategy. Two musculoskeletal risk factors are implicated in osteoporotic fractures in the elderly: the loss of bone mass due to secondary hyperparathyroidism and the increased propensity to falls. Calcium and vitamin D reverse secondary hyperparathyroidism with resultant beneficial effects on bone mineral density (BMD). Additionally, calcium and vitamin D supplementation significantly improves body sway and lower extremity strength, reducing the risk of falls. The effects of combined calcium and vitamin D on parathyroid function and BMD provide a strong rationale for the use of this therapy in the prevention and treatment of osteoporosis and osteoporotic fractures. There is general agreement that, in patients with documented osteoporosis, calcium and vitamin D supplementation should be an integral component of the management strategy, along with antiresorptive or anabolic treatment. Frail elderly individuals constitute another major target population for calcium and vitamin D because evidence from randomized studies in institutionalized elderly subjects demonstrates that these supplements reduce osteoporotic fracture risk, particularly in the presence of dietary deficiencies. However, the results of trials in community-dwelling subjects have been equivocal. Within the primary-care setting, further research is required to establish appropriate target subgroups for calcium and vitamin D supplementation; overall, the data are consistent with a benefit individuals with insufficient calcium and/or vitamin D, although patients with documented osteoporosis will derive further benefit in terms of fracture prevention from the addition of an antiresorptive agent.

Longitudinal bone loss in postmenopausal women with primary biliary cirrhosis and well-preserved liver function.

OBJECTIVES/DESIGN: Increased rate of bone loss has been reported in women with primary biliary cirrhosis (PBC) and varying degree of liver dysfunction. Whether bone loss is increased in patients without liver dysfunction is unclear. The aim of this study was to estimate retrospectively the rate of bone loss in postmenopausal women with PBC and well-preserved liver function. SUBJECTS/INTERVENTIONS: Forty-three women with PBC, and classified as Child-Pugh class A, were included. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry at the lumbar spine and the femoral neck. RESULTS: Median time between measurements of BMD was 26 months (range, 12-48 months). Twenty women were not receiving any bone protective treatment, i.e. hormone replacement therapy (HRT), bisphosphonates or vitamin D/calcium supplementation, whilst 23 women received such treatment. Mean annual bone loss in the former group was 0.38 +/- 2.56% and 0.42 +/- 2.29% at the lumbar spine and the femoral neck, respectively. Women receiving treatment, however, increased their BMD by 1.92 +/- 3.76% and 0.15 +/- 2.75% at the lumbar spine and the femoral neck, respectively. At the lumbar spine the difference with regard to changes in BMD between untreated and treated women was statistically significant (P = 0.02). Women who received HRT (n = 11) increased their BMD at the lumbar spine by 2.95 +/- 3.91%, P = 0.03 when compared with untreated women. CONCLUSION: Bone loss in postmenopausal women with PBC and well-preserved liver function is not increased above normal. Treatment with bone protective treatment, mainly HRT, improves BMD at the lumbar spine.

Thrombin, but not bradykinin, stimulates proliferation in isolated human osteoblasts, via a mechanism not dependent on endogenous prostaglandin formation.

Osteolysis or osteosclerosis often occurs in bone tissue adjacent to chronic inflammatory processes. Numerous cytokines and inflammatory mediators have been implicated as osteoclast-activating agents, explaining inflammation-induced bone resorption. In many cases, the cause of the sclerosis seen in these lesions is less thoroughly investigated. We have studied the effects of thrombin and bradykinin, 2 inflammatory mediators, on the rate of proliferation in isolated human osteoblasts (hOBs). Thrombin, at and above 1 U/mL, stimulated the rate of thymidine incorporation into hOBs. The absolute cell number also increased, as measured by an assay based on the detection of cell metabolism. A synthetic peptide ligand for the thrombin receptor enhanced the rate of [3H]thymidine incorporation in hOBs, indicating that thrombin-induced proliferation is mediated via the tetheric thrombin receptor. The thrombin-induced proliferation was not affected by indomethacin, excluding prostanoids as mediators of this effect. Bradykinin did not affect either the rate of thymidine incorporation, or number of cells in long-term cultures of hOBs. In conclusion, the inflammatory mediator, thrombin, stimulates proliferation in isolated human osteoblasts probably via the recently described G-protein-coupled tetheric thrombin receptor. Thrombin may therefore be involved as a mediator of inflammation-induced sclerosis and bone formation.