Patrizia D’Amelio

Effects of potassium citrate supplementation on bone metabolism.

Western diets rich in animal protein result in long-term acid loading that, despite corresponding increases in net renal acid excretion, may induce a chronic state of acidemia. This may have deleterious effects on both the kidney and bone, by increasing the risk of calcium stone in the former and leading to chemical dissolution of mineral alkaline salts in the latter. Whereas supplementation with alkaline citrate has been shown to reduce stone recurrences, its effect on bone turnover has received less attention. The aim of the present study was to evaluate whether potassium citrate favorably affects bone turnover markers in postmenopausal females with low bone density. Thirty women, aged 58 ± 8.1 years, were enrolled and studied on basal conditions and after a 3-month course of potassium citrate supplementation (0.08–0.1 g/kg b.w. daily). Twenty-two women concluded the study while 8 withdrew. Twenty-four age-matched healthy women were taken as control cases. All were evaluated for electrolyte and acid–base balance-related parameters, bone turnover, markers and renal function. A significant decrease in net acid excretion was observed upon citrate supplementation, and this was paralleled by a significant decrease of urinary deoxypyridinolines, hydroxyproline-to-creatinine ratios, and, to a lesser extent, serum osteocalcin. Percent variations of urine citrate were inversely related to those of deoxypyridinolines and hydroxyproline. No change in these chemistries occurred in the control group. Our results suggest that treatment with an alkaline salt, such as potassium citrate, can reduce bone resorption thereby contrasting the potential adverse effects caused by chronic acidemia of protein-rich diets.

Bone and bone marrow pro-osteoclastogenic cytokines are up-regulated in osteoporosis fragility fractures

SummaryThis study evaluates cytokines production in bone and bone marrow of patients with an osteoporotic fracture or with osteoarthritis by real time PCR, Western blot and immunohistochemistry. We demonstrate that the cytokine pattern is shifted towards osteoclast activation and osteoblast inhibition in patients with osteoporotic fractures.IntroductionFragility fractures are the resultant of low bone mass and poor bone architecture typical of osteoporosis. Cytokines involved in the control of bone cell maturation and function are produced by both bone itself and bone marrow cells, but the roles of these two sources in its control and the amounts they produce are not clear. This study compares their production in patients with an osteoporotic fracture and those with osteoarthritis.MethodsWe evaluated 52 femoral heads from women subjected to hip-joint replacement surgery for femoral neck fractures due to low-energy trauma (37), or for osteoarthritis (15). Total RNA was extracted from both bone and bone marrow, and quantitative PCR was used to identify the receptor activator of nuclear factor kB Ligand (RANKL), osteoprotegerin (OPG), macrophage colony stimulating factor (M-CSF), transforming growth factor β (TGFβ), Dickoppf-1 (DKK-1) and sclerostin (SOST) expression. Immunohistochemistry and Western blot were performed in order to quantify and localize in bone and bone marrow the cytokines.ResultsWe found an increase of RANKL/OPG ratio, M-CSF, SOST and DKK-1 in fractured patients, whereas TGFβ was increased in osteoarthritic bone. Bone marrow produced greater amounts of RANKL, M-CSF and TGFβ compared to bone, whereas the production of DKK-1 and SOST was higher in bone.ConclusionsWe show that bone marrow cells produced the greater amount of pro-osteoclastogenic cytokines, whereas bone cells produced higher amount of osteoblast inhibitors in patients with fragility fracture, thus the cytokine pattern is shifted towards osteoclast activation and osteoblast inhibition in these patients.

Primary breast cancer stem-like cells metastasise to bone, switch phenotype and acquire a bone tropism signature

Background:Bone metastases represent a common and severe complication in breast cancer, and the involvement of cancer stem cells (CSCs) in the promotion of bone metastasis is currently under discussion. Here, we used a human-in-mice model to study bone metastasis formation due to primary breast CSCs-like colonisation.Methods:Primary CD44+CD24− breast CSCs-like were transduced by a luciferase-lentiviral vector and injected through subcutaneous and intracardiac (IC) routes in non-obese/severe-combined immunodeficient (NOD/SCID) mice carrying subcutaneous human bone implants. The CSCs-like localisation was monitored by in vivo luciferase imaging. Bone metastatic CSCs-like were analysed through immunohistochemistry and flow cytometry, and gene expression analyses were performed by microarray techniques.Results:Breast CSCs-like colonised the human-implanted bone, resulting in bone remodelling. Bone metastatic lesions were histologically apparent by tumour cell expression of epithelial markers and vimentin. The bone-isolated CSCs-like were CD44−CD24+ and showed tumorigenic abilities after injection in secondary mice. CD44−CD24+ CSCs-like displayed a distinct bone tropism signature that was enriched in genes that discriminate bone metastases of breast cancer from metastases at other organs.Conclusion:Breast CSCs-like promote bone metastasis and display a CSCs-like bone tropism signature. This signature has clinical prognostic relevance, because it efficiently discriminates osteotropic breast cancers from tumour metastases at other sites.

Effects of lifestyle and risk factors on bone mineral density in a cohort of Italian women: suggestion for a new decision rule.

In this study the authors analyzed the role of risk factors in postmenopausal osteoporosis in a cohort of Italian women and evaluated predictive values of decision rules for early identification of osteoporotic women. Furthermore, the authors investigated the prevalence of secondary osteoporosis in this population. Women who underwent bone densitometry were asked to answer a questionnaire about the common risk factors for osteoporosis. Patients were classified as nonosteoporotic, nonosteopenic, and osteoporotic. Risk factors were compared among the groups by use of analysis of variance (ANOVA). National Osteoporosis Foundation (NOF) recommendation, Osteoporosis Risk Assessment Instruments (ORAIs), Osteoporosis Self-Assessment Tools (OST) score, and weight criterion were applied to this population. The authors proposed a new decision rule based on a new score. A total of 525 women received the questionnaire: 47.4% women were osteoporotic, 32.2% were osteopenic, and 20.4% nonosteoporotic. Risk factors that differed significantly between these groups were: age, age at menarche, postmenopausal period, and body mass index (BMI); the aforementioned risk factors appear to be significant predictors of bone density (BMD) in linear regression model. The incidence of secondary osteoporosis was 13%.In conclusion, the authors (1) confirmed the role played by nonmodifiable risk factors in determining BMD; (2) showed that the use of NOF guidelines, ORAI, OST score, and weight criterion is not satisfactory in our cohort; (3) suggested a new score, based upon the features that were significantly different between patients and controls; and (4) demonstrated the relatively high prevalence of secondary osteoporosis and suggest a primary screening for secondary osteoporosis in all patients with low BMD.

Hypovitaminosis D in Internal Medicine Inpatients

Some studies have suggested that hypovitaminosis D may be a consequence of protein-calorie malnutrition. This study assessed both the relationship between vitamin D status, malnutrition, calcium and phosphorus metabolism indices and the importance attached by internists to these alterations. There were 239 patients admitted to an internal medicine division who underwent examinations to assess nutritional state, liver and renal function, and bone metabolism. At the end of the study, the clinical data included in the discharge letter, the treatment prescribed, and the diagnosis assigned to patients on their hospital discharge form were collected. Hypovitaminosis D was found in 72% and hypoalbuminemia in 34.3% of patients. Subjects with hypovitaminosis were generally older and had lower albumin levels than those with mild or no hypovitaminosis. 25-Hydroxyvitamin D was inversely related with parathyroid hormone and directly related with albumin. Alterations of calcium and phosphorus metabolism were present in 55.6% and recorded by the division’s physicians for only 13.53% of patients, of whom 72.37% were not specifically treated. There is a direct correlation between 25-hydroxyvitamin D and albumin levels. The high incidence and the metabolic consequence of hypovitaminosis D and of protein-calorie malnutrition is significantly underestimated and undertreated by physicians.

Teriparatide increases the maturation of circulating osteoblast precursors

SummaryThis study shows that teriparatide promotes the circulating osteoblast (OB) precursor degree of maturation in patients affected by postmenopausal osteoporosis.IntroductionAnabolic treatment with teriparatide has proven effective for the therapy of postmenopausal osteoporosis and significantly reduces the risk of non-vertebral fragility fractures. The aim of this study was to investigate the effect of teriparatide on circulating OB precursors.MethodsWe evaluated by flow cytometry and real-time PCR the expression of OBs typical markers in peripheral blood mononuclear cells during treatment with teriparatide plus calcium and vitamin D, raloxifene plus calcium and vitamin D or calcium and vitamin D alone at various time points. Serum bone alkaline phosphatase and osteocalcin (OC) were measured as markers of bone turnover.ResultsOur results show that circulating OB precursors are more numerous and more immature in patients affected by fragility fractures than in osteoporotic patients without fractures. We also show that teriparatide treatment increases the expression of alkaline phosphatase and of OC in OB precursors; thus, it increases their degree of maturation.ConclusionsWe suggest that teriparatide acts as anabolic agents also by promoting the maturation of OB precursors.

Interactions between the immune system and bone.

The relationship between the immune system, estrogen deficiency and bone loss is an intriguing and, as yet, unexplained challenge of the past two decades. Here we summarize the evidence that links immune cells, inflammation, cytokine production and osteoclast formation and activity with particular regard to humans.

Multinucleated giant cells with an osteoclast phenotype derived from caprine peripheral blood mononuclear cells

Formation of multinucleated giant cells (MGCs) by macrophage fusion is a typical cytopathic effect of lentiviral replication in caprine monocytes and MGC formation from cultured caprine peripheral blood mononuclear cells (PBMCs) has been considered to be diagnostic for small ruminant lentivirus (SRLV) infection. In this study, formation of MGCs was observed after 7-14 days when PBMCs were cultured from healthy goats free from SRLV infection. These MGCs expressed tartrate-resistant acid phosphatase, calcitonin receptor, integrin αVβ3, cathepsin K and matrix metalloproteinase 9 and were able to resorb bone in vitro in the absence of RANKL and macrophage colony stimulating factor, consistent with an osteoclast phenotype.

Microdamage Accumulation Changes According to Animal Mass: An Intraspecies Investigation

The fatigue life of a structure is also influenced by its size. Statistically, a bone from a large animal is expected to bear a higher risk of stress fracture if compared to the same bone from a small animal of the same species. This is not documented in the dog, where individuals can have a 40 times difference in body mass. We investigated the effect of body size on cortical bone microdamage accumulation, cortical microstructural organization (porosity, osteon area, and osteocyte lacunar density), and turnover in dogs with a wide body mass range. The aim was to understand and mathematically model how the bone tissue copes with the microdamage accumulation linked to body mass increase. Calcified transverse cortical sections of 18 canine radii of remarkably different size were examined by means of a standard bulk-staining technique and histomorphometric standard algorithms. Relationships between the investigated histomorphometric variables age, sex and mass were analyzed by general linear multivariate models and exponential equations. Type and location of microdamage and bone turnover were not influenced by body mass. Gender did not influence any parameter. Age influenced bone turnover and activation frequency. Microcrack density was influenced by bone mass. Bones had a similar microstructural organization within the same species regardless of the subject’s dimension. Microdamage accumulation is inversely related to bone mass, whereas bone turnover is mass-invariant. We theorize a mass-related change in the bone fracture toughness targeted to reach an optimal unique dimensionless curve for fatigue life.

Parathyroid Hormone Secretion and Action

The parathyroid hormone (PTH) in physiological conditions is secreted into the circulation in response to low calcium levels and its principal activity is to regulate the concentration of calcium in the blood circulation, modulating movement of calcium into and out of the bone and reabsorption from renal tubules so as to maintain serum calcium concentration within a narrow range [1].