Platelet vitamin D receptor is reduced in osteoporotic patients.

AIM: It is well known that vitamin D plays an important role in maintaining bone homeostasis and in regulating calcium absorption. The active form of vitamin D interacts with its receptor the VDR that is expressed in multiple tissues and it is involved in platelets (PLTs) function. In the present study we evaluate PLTs' VDR expression in osteoporotic as opposed to healthy subjects. METHODS: We enrolled in the study 77 women with postmenopausal osteoporosis, 33 healthy women of childbearing age, 49 healthy men, and 11 healthy women matched with patients for age and postmenopausal period. Thirty-nine patients had had one femoral fracture occurred after the age of fifty and attributable to primary osteoporosis. Bone mineral density, markers of bone metabolism and VDR levels were measured in all the subjects. RESULTS: Our data show that VDR level is lower in patients as respect to controls and is positively correlated with bone density, but not with markers of bone metabolism. We also found a decrease in the phosphorus levels in patients without differences in vitamin D levels and in the dietary calcium intake. CONCLUSION: The lower VDR expression in osteoporotic could indicate a lower ability to respond to vitamin D, and could be the explanation of the increase in the PTH and decrease in the phosphorus levels in patients with respect to controls.

Alendronate reduces osteoclast precursors in osteoporosis.

UNLABELLED: This study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women. We suggest that it acts on mature bone resorbing osteoclasts after 3 months of treatment, whereas, after 1 year, it diminishes their formation by reducing their precursors and serum RANKL. INTRODUCTION: Osteoclasts are the target cells of bisphosphonates, though the most drug-sensitive steps of their formation and activity have not been determined. The present study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women. METHODS: The study was conducted on 35 osteoporotic women; 15 were pretreated with alendronate 70 mg/week, whereas, 20 were treated with calcium 1 g/day and vitamin D 800 IU/day. After 3 months, 30 received alendonate 70/mg, vitamin D 2800 IU/week, and calcium 1 g/day for 12 months (combined therapy), whereas, the other five patients remained on calcium 1 g/day and vitamin D 800 IU/day. The following parameters were assessed before and after therapy: changes in bone resorption markers, circulating osteoclast precursors, formation of osteoclasts in peripheral blood mononuclear cell cultures, their viability, and variations in cytokines production. RESULTS: After 3 months of alendronate, there was no significant reduction in the number of osteoclast precursors, osteoclast formation and viability, and cytokine levels, whereas, there was a significant reduction of bone resorption markers. One year of the combined therapy, on the other hand, reduced osteoclast precursors, osteoclast formation, and serum RANKL, whereas, calcium plus vitamin D alone had no effect. CONCLUSIONS: We suggest that alendronate mainly acts on mature bone resorbing osteoclasts in the short term, whereas, its long-term administration diminishes their formation by reducing their precursors and serum RANKL.

HDL cholesterol and bone mineral density in normal-weight postmenopausal women: is there any possible association?

AIM: Epidemiological investigation of the association between lipid profile, atherosclerosis and bone mass has produced conflicting RESULTS: The present paper reports the assessment of the lipid profile, bone mineral density (BMD) and turnover in a cohort of Italian women. METHODS: In this cross sectional study we enrolled 173 women in menopause (101 osteoporotic and 72 normal). In each subject the authors evaluated BMD, bone turnover, lipid profile (total cholesterol, high density lipoprotein [HDL], low density lipoprotein [LDL] and triglycerides), and risk factors for osteoporosis, cardiovascular diseases and eating habits using a questionnaire. RESULTS: HDL was significantly higher in osteoporotic patients than in controls and the risk of osteoporosis was significantly higher in women with higher level of HDL. The authors suggest that the level of HDL could be used as screening for postmenopausal osteoporosis: the cut-off points recommended are HDL >61 mg/dL to detect women with a high risk (sensitivity 74%) and <45 mg/dL to detect those with a low risk (specificity 83%). CONCLUSION: This study provides evidences of the relation between HDL, but not total cholesterol or LDL levels with BMD in a cohort of normal-weight women and equally distributed cardiovascular risks. It also suggests that a proatherogenic lipid profile is associated with higher bone mineral density, and that HDL can be used in deciding whether a patient's BMD should be measured.