Indices Of Bone Resorption Research Articles

Morbid obesity attenuates the skeletal abnormalities associated with leptin deficiency in mice.

Leptin-deficient ob/ob mice are morbidly obese and exhibit low total bone mass and mild osteopetrosis. In order to disassociate the skeletal effects of leptin deficiency from those associated with morbid obesity, we evaluated bone mass, architecture, gene expression, and indices of bone turnover in WT mice, ob/ob mice allowed to feed ad libitum (ob/ob), and ob/ob mice pair-fed equivalent to WT mice (pair-fed ob/ob). Mice were maintained at 32 °C (thermoneutral) from 6 to 18 weeks of age to minimize differences in resting energy expenditure. ob/ob mice were heavier, had more abdominal white adipose tissue (WAT), and were hyperglycemic compared with WT mice. Femur length, bone mineral content (BMC) and bone mineral density, and midshaft femur cortical thickness were lower in ob/ob mice than in WT mice. Cancellous bone volume (BV) fraction was higher but indices of bone formation and resorption were lower in ob/ob mice compared with WT mice; reduced bone resorption in ob/ob mice resulted in pathological retention of calcified cartilage. Pair-fed ob/ob mice were lighter and had lower WAT, uterine weight, and serum glucose than ob/ob mice. Similarly, femoral length, BMC, and cortical thickness were lower in pair-fed ob/ob mice compared with ob/ob mice, as were indices of cancellous bone formation and resorption. In contrast, bone marrow adiposity, calcified cartilage, and cancellous BV fraction were higher at one or more cancellous sites in pair-fed ob/ob mice compared with ob/ob mice. These findings indicate that the skeletal abnormalities caused by leptin deficiency are markedly attenuated in morbidly obese ob/ob mice.

Bioactive Propolis and Bone Loss Reduction in an Ovariectomized Rat Model of Hypogonadal Osteoporosis

Osteoporosis particularly affects post-menopausal women for which the ovariectomized (OVX) rat is an established model and validation tool for agents of bone loss prevention. Objective: The potency of the natural substance propolis was investigated with regard to bone loss in ovariectomized animals. Methods: The complex chemical nature of propolis extract was confirmed by HPLC. Adult female albino rats (n=70; weight 150 – 200 gm), all ovariectomized at 24 weeks were randomly divided into controls (Group I, n=35; OVX/ H2O-supplement), for comparison with treatment (Group II, n=35; OVX/ propolis-supplement) administered as 400 mg of propolis/kg daily for 9 weeks. Blood biochemical analysis included serum calcium (Ca), phosphorus (P), magnesium (Mg), alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP), with serum osteocalcin (OC) determined by enzyme-linked immunosorbent assay (ELISA). Urine biochemical analysis measured Ca, P and creatinine (Cr). In addition, the corresponding densitometry of bone status comprised the bone mineral content (BMC) and density (BMD) at the proximal, distal and total femur by dual energy X-ray absorptiometry (DEXA; PIXImus), while the morphometry of the femoral shaft thickness was determined in longitudinal sections using an automated image analyzer. Results: A total of 27 compounds including flavonoids was identified in the propolis extract by HPLC. In comparison with OVX controls the skeleton was more substantial morphometrically in the animals receiving propolis, in terms of femoral shaft width (p<0.01) and BMD and BMC (p< 0.01). Simultaneously, the urine biochemical indices of Ca, P, Cr and Ca:Cr were significantly reduced (p<0.01) by propolis, while serum TRAP (an index of bone resorption) was also significantly lower (p<0.05), as were serum OC and ALP (indices of bone formation; p<0.05). Conclusion: Propolis is chemically complex and statistically bioactive in the oestrogen-deficient rodent, maintaining bone mass by reducing remodeling possibly by interaction with oestrogen receptors.

Marginal Bone Levels and Soft Tissue Conditions Around Single-Tooth Implants with a Scalloped Neck Design: Results of a Prospective 3-Year Study

Scalloped implants were developed to better maintain marginal bone. Therefore, this study evaluated marginal bone levels (MBLs) and soft tissue around single implants with scalloped necks in the esthetic zone prospectively over a 3-year period. MBLs were compared to those of conventional flat-platform implants at 1 and 3 years. Patients received anterior single-tooth implants and were divided into two groups; the test group included implants with a scalloped neck design and the control group included conventional rough-surface implants with external hex. MBLs were compared radiographically at 1 and 3 years after crown insertion. For the test group, soft and hard tissue assessments were made at six different time points, beginning at abutment connection. Mesial and distal interproximal papillae and probing depths were assessed clinically. Data were analyzed with the Student t test and repeated measures analysis of variance on ranks (P < .05). Twenty-four patients (17 men, 7 women) took part; each group included 12 implants. The test group had significantly more marginal bone resorption than the control group at each time point (P < .001). With respect to changes in MBL values over time, a significant difference was detected between groups mesially (P < .001) but not distally. Statistical analyses demonstrated obvious significant increases with time (P < .001) in bone resorption and mesial papilla index. A significant increase over time in probing depths was demonstrated distally (P = .003) but not mesially. The scalloped implant did not stabilize interproximal bone remodeling and caused more bone loss than conventional implants. Soft tissue levels were not maintained around the scalloped implants.

Intermittent minodronic acid treatment with sufficient bone resorption inhibition prevents reduction in bone mass and strength in ovariectomized rats with established osteopenia comparable with daily treatment

This study examined and compared the effects of four-week intermittent and daily administrations of minodronic acid, a highly potent nitrogen-containing bisphosphonate, on bone mineral density (BMD), bone strength, bone turnover, and histomorphometry on established osteopenia in ovariectomized (OVX) rats. Fourteen-week-old female F344 rats were OVX or sham-operated. At 12weeks post surgery, minodronic acid was orally administered once every 4weeks at 0.2, 1, and 5mg/kg and once daily at 0.006, 0.03, and 0.15mg/kg for 12months. The total dosing amount was comparable between the two dosing regimens. The levels of urinary deoxypyridinoline and serum osteocalcin were measured to assess bone turnover. BMD as assessed via dual-energy X-ray absorptiometry, bone structure and dynamical changes in vertebral trabecula and biomechanical properties were measured ex vivo at 12months to assess bone content and material properties. Minodronic acid dose-dependently ameliorated the decrease in BMD of lumbar vertebrae and the femur in both treatment regimens similarly. Minodronic acid suppressed elevated urinary levels of deoxypyridinoline, a bone resorption marker, and reduced the serum levels of osteocalcin, a bone formation marker. In the mechanical test at 12months of treatment, minodronic acid dose-dependently ameliorated the reduction in bone strength in femur and vertebral body. There is no significant difference in parameters between the two regimens except maximal load of lower doses in lumbar vertebral body and absorption energy of middle doses in femur. With these parameters with significant differences, values of the intermittent regimen were significantly lower than that of daily repeated regimen. Bone histomorphometric analysis of the lumbar vertebral body showed that minodronic acid significantly ameliorated the decrease in bone mass, trabecular thickness and number, and the increase in trabecular separation, bone resorption indices (Oc.S/BS and N.Oc/BS), and bone formation indices (BFR/BS, MAR and OV/BV) in both regimens. Minodronic acid suppressed OVX-induced increases in bone turnover at the tissue level and ameliorated all structural indices, thereby improving the deterioration of bone quality under osteoporotic disease conditions regardless of the regimen. In conclusion, a four-week intermittent treatment of minodronic acid suppressed increased bone resorption as daily treatment when considering the total administered dose in OVX rats with established osteopenia. The improvement of microarchitectural destruction in low dose of intermittent treatment was weaker than that observed in a daily repeated regimen; however the effects of high and middle doses of intermittent treatment were equivalent to that observed in daily repeated regimen accompanied by sufficient bone resorption inhibition in rats. These findings suggest that minodronic acid at an appropriate dose in an intermittent regimen may be as clinically useful in osteoporosis therapy as in daily treatment.

Use of Medicinal Plants and Natural Products for Treatment of Osteoporosis and Its Complications

Osteoporosis is characterized by low bone mass with susceptibility to fracture. It may only be discovered when fractures of the osteoporotic bone have occurred. Therefore, prevention and early treatment of osteoporosis are important to avoid its complications. Some of the commercially available antiosteoporotic drugs are associated with serious side effects. Research is ongoing to find alternative antiosteoporotic agents with comparable effectiveness but minimal side effects. It is hoped that the increased ethnobotanical and ethnopharmacological research may pave the way to the development of novel drug candidates. In this special issue, 28 papers were published addressing various aspects of natural products on osteoporosis and its complications. Of these, 7 were review articles and the rest were original articles. All the published papers contribute significantly towards providing scientific evidence for future use in research and clinical settings. Amongst the natural products, vitamin E, in particular tocotrienol, was the most studied, whereby 7 papers (4 original articles and 3 review articles) were published. The topics discussed were wide-ranging, including effects on bone structure and strength, mechanisms of action, and effects on osteoporotic fracture healing. S. Abdul-Majeed et al. reported on the effects of a combination of tocotrienol derived from annatto beans and lovastatin on bone resorption and formation indices. N. A. Manan et al. reported an in vivo study on the effects of γ-tocotrienol on osteoblasts. In conclusion, vitamin E of the tocotrienol type was shown to protect against experimental osteoporosis, whereby the mechanisms of these effects may be via its antioxidant or mevalonate suppressor properties, or both. Other natural herbal products discussed were Eurycoma longifola, Labisia pumila, virgin coconut oil, Cosmos caudatus, curcumin, Nigella sativa, Sambucus nigra, and Trifolium sp. These were mainly extracts from the whole plant or specific parts of the plants, such as the fruit, leaves, or roots. However, S.-W. Choi et al. reported on fisetin, an alkaloid found in several different plants, where they described the mechanisms of the osteoclast inhibitory effects of fisetin. In general, these studies found encouraging effects of these natural products on bone metabolism, structure, and strength, as well as in improving the rate of osteoporotic fracture healing. However, further studies are needed to confirm these effects as well as to elucidate the precise mechanisms of action. The effects of Chinese herbal products on osteoporosis were well represented in four papers. These studies included in vivo animal studies, in vitro cell culture studies, as well as a population-based study on usage of Chinese herbal medication in Taiwan. One study used the fermented product from Chinese herbal medication. In general, the animal studies showed that the Chinese medications studied had positive effects on bone. The population based-study identified patterns of Chinese herbal products used for the treatment of osteoporosis. However, further research is required to fully elucidate the efficacy and safety of these Chinese herbal products. Overall, this special issue described studies on the effects of a plethora of natural products on different aspects of osteoporosis and osteoporotic fracture healing. These studies contribute greatly to the existing knowledge regarding prevention and treatment options for osteoporosis. It is anticipated that some of these products may be further developed into pharmacotherapy for osteoporosis and osteoporotic fracture healing. Ima Nirwana Soelaiman Srijit Das Ahmad Nazrun Shuid Huanbiao Mo Norazlina Mohamed

Immediate vs. early loading of SLA implants in the posterior mandible: 5‐year results of randomized controlled clinical trial

The aim of this study was to compare clinical results of immediate and early loading (EL) self-tapping implants placed in posterior mandibles. Twelve patients with bilateral edentulous posterior mandibular were randomly assigned to treatment either with immediate (test) or early loaded implants (control). Seventy-two self-tapping implants with SLA surface (Ø 4, 1/4, 8 mm; length 8 and 10 mm) were analyzed in this study. Test implants (36) were loaded on the day of surgery and control implants 6 weeks later. The measuring of implant stability quotient (ISQ) was performed on 0, 6th, 12th, and 52nd week after implant insertion. The bone resorption, modified plaque, and bleeding index were notified at 1 and 5 years later. After 5 years, survival in the both groups was 100%. The mean value of primary implant stability was 76.92 ± 0.79 ISQ. In the first 6 weeks, ISQ values significantly increased in the test group (77.92 ± 1.16 vs. 79.61 ± 0.90) as well as in the control group (7.92 ± 1.05 vs. 77.55 ± 0.99). A significant longitudinal increase in ISQ value was recorded in test and control group. The differences between immediate and early loaded implants were statistically insignificant (P > 0.05). At the 5 years, no statistically significant differences were found between immediate and early loaded implants with respect to mean crestal bone loss measurements (0.4 ± 0.24 vs. 0.8 ± 0.15 mm), mean bleeding index (0.22 ± 0.11 vs. 0.25 ± 0.11), and mean plaque index (0.17 ± 0.15 vs. 0.19 ± 0.20). Based on these results, the self-tapping implants inserted in posterior mandible can provide adequate primary stability value as the main factor for immediate and EL protocol.

Selective tyrosine kinase inhibition of insulin-like growth factor-1 receptor inhibits human and mouse breast cancer–induced bone cell activity, bone remodeling, and osteolysis

Insulin-like growth factor 1 (IGF-1) plays an important role in both bone metabolism and breast cancer. In this study, we investigated the effects of the novel IGF-1 receptor tyrosine kinase inhibitor cis-3-[3-(4-methyl-piperazin-l-yl)-cyclobutyl]-1-(2-phenyl-quinolin-7-yl)-imidazo[1,5-a]pyrazin-8-ylamine (PQIP) on osteolytic bone disease associated with breast cancer. Human MDA-MB-231 and mouse 4T1 breast cancer cells enhanced osteoclast formation in receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) stimulated bone marrow cultures, and these effects were significantly inhibited by PQIP. Functional studies in osteoclasts showed that PQIP inhibited both IGF-1 and conditioned medium-induced osteoclast formation by preventing phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) activation without interfering with RANKL or M-CSF signaling. Treatment of osteoblasts with PQIP significantly inhibited the increase in RANKL/osteoprotegerin (OPG) ratio by IGF-1 and conditioned medium and totally prevented conditioned medium-induced osteoclast formation in osteoblast-bone marrow (BM) cell cocultures, thereby suggesting an inhibitory effect on osteoblast-osteoclast coupling. PQIP also inhibited IGF-1-induced osteoblast differentiation, spreading, migration, and bone nodule formation. Treatment with PQIP significantly reduced MDA-MB-231 conditioned medium-induced osteolytic bone loss in a mouse calvarial organ culture system ex vivo and in adult mice in vivo. Moreover, once daily oral administration of PQIP significantly decreased trabecular bone loss and reduced the size of osteolytic bone lesions following 4T1 intratibial injection in mice. Quantitative histomorphometry showed a significant reduction in bone resorption and formation indices, indicative of a reduced rate of cancer-associated bone turnover. We conclude that inhibition of IGF-1 receptor tyrosine kinase activity by PQIP suppresses breast cancer-induced bone turnover and osteolysis. Therefore, PQIP, and its novel derivatives that are currently in advanced clinical development for the treatment of a number of solid tumors, may be of value in the treatment of osteolytic bone disease associated with breast cancer.

Hijikia fusiforme protects against ovariectomy-induced bone loss in rats.

The prophylactic effects of Hijikia fusiforme on bone metabolism were examined using in vitro indices of bone formation and resorption. As the indices of bone formation, osteoblast proliferation and differentiation were measured through mitochondrial enzyme activity [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay] and bone marker alkaline phosphatase (ALP) activity. The aqueous extract of H. fusiforme stimulated the proliferation of the human osteoblast-like cell line MG63 and the ALP activity of the mouse osteoblast-like cell line MC3T3-E1. Moreover, extracellular matrix mineralization was accelerated by the addition of H. fusiforme. As the indices of bone resorption, differentiation of the murine macrophage/osteoclast precursor cell line RAW 264.7 by receptor activator of nuclear factor-κB ligand (RANKL) was measured as tartrate-resistant acid phosphatase-positive multinucleated cells, which were suppressed by H. fusiforme. Additionally, H. fusiforme lowered the secreted amount of RANKL that is required for the osteoclastic differentiation and activation, but the amount of osteoprotegerin as a decoy receptor for RANKL was not affected. The bone-protective effects of H. fusiforme in estrogen-deficient ovariectomized rats were also investigated. Osteoporosis was induced in female Sprague-Dawley rats by ovariectomy for 15 weeks, and then H. fusiforme was orally administered at a dose of 100 mg/kg of body weight every day for 6 weeks. Bone mineral density in the group orally administered H. fusiforme was increased, compared with ovariectomized rats, but not significantly (P>.05). Oral administration of H. fusiforme improved microarchitecture of bone in terms of bone volume (bone volume/total volume ratio) and trabecular separation (P<.05). The amounts of osteocalcin and C-telopeptide type I collagen in serum were measured as the biomarkers for bone formation and resorption. The level of osteocalcin in serum was increased, but not significantly. However, the level of C-telopeptide type I collagen in serum was significantly decreased (P<.05). When the results are taken together, the present study indicates that H. fusiforme might be useful in the treatment of osteoporosis.

A Comparative Study of Intravenous Ibandronate and Pamindronate in Patients With Bone Metastases From Breast or Lung Cancer: Effect on Metastatic Bone Pain

We compared the effects of ibandronate and pamindronate in patients with bone metastases from breast or lung cancer and we found that ibandronate is superior to pamindronate in alleviating pain, improving mobility and quality of life, and reducing bone resorption indices in patients with bone metastases from breast or lung cancer.

Simultaneous free and glycosylated pyridinium crosslink determination in urine: Validation of an HPLC-fluorescence method using a deoxypyridinoline homologue as internal standard

Pyridinoline (Pyr), deoxypyridinoline (D-Pyr), galactosyl-pyridinoline (Gal-Pyr) and glucosyl–galactosyl pyridinoline (GluGal-Pyr) are enzymatic mature pyridinium crosslinks. Generally, only total Pyr and D-Pyr urinary amounts (free + bound forms) are evaluated by HPLC as indices of bone resorption. This report describes the validation of an HPLC-fluorescence method for the simultaneous evaluation of free Pyr and D-Pyr, together with GluGal-Pyr and Gal-Pyr, in urine of healthy women ( n = 20, aged 27–41) and girls ( n = 20, aged 5–10). The use of an unnatural D-Pyr homologue, here proposed for the first time as internal standard, and of pure Pyr, D-Pyr, GluGal-Pyr and Gal-Pyr synthesized to be used as primary calibrators, guarantees method specificity and correct crosslink quantification. Urine, spiked with IS, was solid-phase extracted prior to HPLC analysis. Total Pyr and D-Pyr amounts were also evaluated after urine hydrolysis. The HPLC method was validated for selectivity, sensitivity, linearity, precision, accuracy, recovery and stability for all measured crosslinks. Both free and total Pyr and D-Pyr as well as GluGal-Pyr and Gal-Pyr amounts were significantly higher in girls than in women ( p < 0.0001), indicating an increased collagen turnover rather than only bone turnover. Gal-Pyr, for the first time evaluated in girls, was under its lower quantification limit (<LLOQ, <21.20 pmol/mL) in women. The measurement of free and glycosylated pyridinium crosslinks might provide more information on the degradation of various types of collagen than only that of total Pyr and D-Pyr. Moreover, this validated method could be a useful non-invasive technique for studying pathological conditions characterized by modified glycosylation enzyme activity and for more clinical investigation on bone fragility.

Effects of Risedronate in Runx2 Overexpressing Mice, an Animal Model for Evaluation of Treatment Effects on Bone Quality and Fractures

Young mice overexpressing Runx2 specifically in cells of the osteoblastic lineage failed to gain bone mass and exhibited a dramatic increase in bone resorption, leading to severe osteopenia and spontaneous vertebral fractures. The objective of the current study was to determine whether treatment with a bisphosphonate (risedronate, Ris), which reduces fractures in postmenopausal as well as in juvenile osteoporosis, was able to improve bone quality and reduce vertebral fractures in mice overexpressing Runx2. Four-week-old female Runx2 mice received Ris at 2 and 10 μg/kg subcutaneously twice a week for 12 weeks. Runx2 and wild-type mice received vehicle (Veh) as control. We measured the number of new fractures by X-ray and bone mineral density (BMD) by DEXA. We evaluated bone quality by histomorphometry, micro-CT, and Fourier transform infrared imaging (FTIRI). Ris at 20 μg/kg weekly significantly reduced the average number of new vertebral fractures compared to controls. This was accompanied by significantly increased BMD, increased trabecular bone volume, and reduced bone remodeling (seen in indices of bone resorption and formation) in the vertebrae and femoral metaphysis compared to Runx2 Veh. At the femur, Ris also increased cortical thickness. Changes in collagen cross-linking seen on FTIRI confirmed that Runx2 mice have accelerated bone turnover and showed that Ris affects the collagen cross-link ratio at both forming and resorbing sites. In conclusion, young mice overexpressing Runx2 have high bone turnover-induced osteopenia and spontaneous fractures. Ris at 20 μg/kg weekly induced an increase in bone mass, changes in bone microarchitecture, and decreased vertebral fractures.

Fragility Fractures in Men with Idiopathic Osteoporosis Are Associated with Undermineralization of the Bone Matrix without Evidence of Increased Bone Turnover

The pathogenesis of primary osteoporosis in younger individuals is still elusive. An important determinant of the biomechanical competence of bone is its material quality. In this retrospective study we evaluated bone material quality based on quantitative backscattered electron imaging to assess bone mineralization density distribution (BMDD) in bone biopsies of 25 male patients (aged 18-61 years) who sustained fragility fractures but were otherwise healthy. BMDD of cancellous bone was compared with previously established adult reference data. Complementary information was obtained by bone histomorphometry. The histomorphometric results showed a paucity of osteoblasts and osteoclasts on the bone surface in the majority of patients. BMDD revealed a significant shift to lower mineralization densities for cancellous bone values: CaMean (weighted mean Ca content, -5.9%), CaPeak (mode of the BMDD, -5.6%), and CaHigh (portion of fully mineralized bone, -76.8%) were decreased compared to normative reference; CaWidth (heterogeneity in mineralization, +18.5%) and CaLow (portion of low mineralized bone, +68.8; all P < 0.001) were significantly increased. The shift toward lower mineral content in the bone matrix in combination with reduced indices of bone formation and bone resorption suggests an inherent mineralization defect leading to undermineralized bone matrix, which might contribute to the susceptibility to fragility fractures of the patients. The alteration in bone material might be related to osteoblastic dysfunction and seems fundamentally different from that in high bone turnover osteoporosis with a negative bone balance.

Imatinib Mesylate Does Not Increase Bone Volume In Vivo

Imatinib mesylate is a tyrosine kinase inhibitor used in the management of disorders in which activation of c-Abl, PDGFR, or c-Kit signaling plays a critical role. In vitro, imatinib stimulates osteoblast differentiation, inhibits osteoblast proliferation and survival, and decreases osteoclast development. Patients treated with imatinib exhibit altered bone and mineral metabolism, with stable or increased bone mass. However, recovery from the underlying disease and/or weight gain might contribute to these effects. We therefore investigated the skeletal effects of imatinib in healthy rats. We evaluated the effects of imatinib on bone volume, markers of bone turnover, and bone histomorphometry in mature female rats treated for 5weeks with either vehicle, imatinib 40mg/kg daily, or imatinib 70mg/kg daily. Compared to vehicle, imatinib reduced trabecular bone volume/tissue volume (mean [SD]: vehicle 26.4% [5.4%], low-dose imatinib 24.8% [4.9%] [P=0.5], high-dose imatinib 21.1% [5.7%] [P=0.05]), reduced osteoblast surface (mean [SD]: vehicle 12.8% [5.8%], low-dose 6.8% [1.9%] [P<0.01], high-dose 7.8 [3.1%] [P<0.05]), and reduced serum osteocalcin (mean change from baseline [95% CI]: vehicle -8.2 [-26.6 to 10.2]ng/ml, low dose -79.7 [-97.5 to -61.9]ng/ml [P<0.01 vs. vehicle], high-dose -66.0 [-82.0 to -50.0]ng/ml [P<0.05 vs. vehicle]). Imatinib did not affect biochemical or histomorphometric indices of bone resorption. These results suggest that, in healthy animals, treatment with imatinib does not increase bone mass and that the improvements in bone density reported in patients receiving imatinib may not be a direct effect of the drug.

Tenofovir Disoproxil Fumarate and Bone Mineral Density: A 60-Month Longitudinal Study in a Cohort of H V -Infected Youths

Decreased bone mineral density (BMD) has been associated with the use of tenofovir disoproxil fumarate (TDF) in HIV-infected adults. The data in HIV-infected children are conflicting. The aim of this study was to assess the safety of a TDF-containing antiretroviral (ARV) regimen on BMD in paediatric patients. We report the results of a longitudinal 60-month follow-up study. A total of 21 vertically HIV-infected Caucasian youths (10 male and 11 female) on ARV treatment containing lamivudine, efavirenz and TDF were enrolled (age range 4.9-17.9 years at baseline). BMD was measured at the lumbar spine and in the whole skeleton by DXA. Bone-specific alkaline phosphatase (BAP) was measured as a bone formation marker and urinary N-telopeptide of type-I collagen (NTx) was measured as a bone resorption index. Baseline mean (±sd) BMD measurements of HIV-infected patients expressed as z-scores were -0.7 (±0.9) for lumbar spine and -0.13 (±1.0) for the whole skeleton. BMD measurements did not change significantly during the 60-month observation period. Both BAP and NTx concentrations were higher than a reference group of controls at baseline and remained unchanged throughout the study. Our data indicate that a TDF-containing regimen does not decrease the BMD of HIV-infected youths.

CXC receptor knockout mice: Characterization of skeletal features and membranous bone healing in the adult mouse

The potential role of CXC chemokines bearing the glu-leu-arg (ELR) motif in bone repair was studied using a cranial defect (CD) model in mice lacking the CXC receptor (mCXCR −/− knockout mice), which is homologous to knockout of the human CXC receptor 2 (CXCR2) gene. During the inflammatory stage of bone repair, ELR CXC chemokines are released by inflammatory cells and serve as chemotactic and angiogenic factors. mCXCR −/− mice were smaller in weight and length from base of tail to nose tip, compared to WT littermates. DEXA analysis indicated that bone mineral density (BMD), bone mineral content (BMC), total area (TA), bone area (BA), and total tissue mass (TTM) were decreased in the mCXCR −/− mice at 6, 12, and 18 weeks of age. Trabecular bone characteristics in mCXCR −/− (% bone, connectivity, number, and thickness) were reduced, and trabecular spacing was increased as evidenced by μCT. There was no difference in bone formation or resorption indices measured by bone histomorphometry. Trabecular BMD was not altered. Cortical bone volume, BMD, and thickness were reduced; whereas, bone marrow volume was increased in mCXCR −/−. Decreased polar moment of inertia ( J) in the tibias/femurs suggested that the mCXCR −/− long bones are weaker. This was confirmed by three-point bending testing of the femurs. CDs created in 6-week-old male mCXCR −/− and WT littermates were not completely healed at 12 weeks; WT animals, however, had significantly more bone in-growth than mCXCR −/−. New bone sites were identified using polarized light and assessed for numbers of osteocyte (OCy) lacunae and blood vessels (BlV) around the original CD. In new bone, the number of BlV in WT was > 2× that seen in mCXCR −/−. Bone histomorphometry parameters in the cranial defect did not show any difference in bone formation or resorption markers. In summary, studies showed that mCXCR −/− mice have (1) reduced weight and size; (2) decreased BMD and BMC; (3) decreased amounts of trabecular and cortical long bone; (4) decreased femur bone strength; and (5) significantly reduced intramembranous bone formation and number of BlV in new calvarial bone during bone repair.

Caloric restriction leads to high marrow adiposity and low bone mass in growing mice

The effects of caloric restriction (CR) on the skeleton are well studied in adult rodents and include lower cortical bone mass but higher trabecular bone volume. Much less is known about how CR affects bone mass in young, rapidly growing animals. This is an important problem because low caloric intake during skeletal acquisition in humans, as in anorexia nervosa, is associated with low bone mass, increased fracture risk, and osteoporosis in adulthood. To explore this question, we tested the effect of caloric restriction on bone mass and microarchitecture during rapid skeletal growth in young mice. At 3 weeks of age, we weaned male C57Bl/6J mice onto 30% caloric restriction (10% kcal/fat) or normal diet (10% kcal/fat). Outcomes at 6 (n = 4/group) and 12 weeks of age (n = 8/group) included body mass, femur length, serum leptin and insulin-like growth factor 1 (IGF-1) values, whole-body bone mineral density (WBBMD, g/cm(2)), cortical and trabecular bone architecture at the midshaft and distal femur, bone formation and cellularity, and marrow fat measurement. Compared with the normal diet, CR mice had 52% and 88% lower serum leptin and 33% and 39% lower serum IGF-1 at 6 and 12 weeks of age (p < .05 for all). CR mice were smaller, with lower bone mineral density, trabecular, and cortical bone properties. Bone-formation indices were lower, whereas bone-resorption indices were higher (p < .01 for all) in CR versus normal diet mice. Despite having lower percent of body fat, bone marrow adiposity was elevated dramatically in CR versus normal diet mice (p < .05). Thus we conclude that caloric restriction in young, growing mice is associated with impaired skeletal acquisition, low leptin and IGF-1 levels, and high marrow adiposity. These results support the hypothesis that caloric restriction during rapid skeletal growth is deleterious to cortical and trabecular bone mass and architecture, in contrast to potential skeletal benefits of CR in aging animals.

Effects of a Twelve-Week Once versus Twice a Day Power Training Program on Bone Turnover Markers and Bone Quality

Physical activity, especially high impact activities, can improve bone. Recently, it has been suggested that increased osteogenic or bone promoting properties may result when high impact training is broken into two sessions per day compared to one. PURPOSE: To compare the effectiveness of performing one vs. two sessions per day of osteogenic-impacting power training on bone in college-aged males and females. METHODS: Nineteen volunteers (8 Males, 11 Females; age 22.1 ± 4.4 yr) were placed into either control (CON, n=4) or exercise groups: 1×/d (n=10) or 2×/d (n=5). Subjects in the exercise groups performed non-linear periodized training on a 3PQ leg press machine 3d/wk for 12 wks. Training groups were matched for total exercise volume but the 2x/d group had a calculated 24% greater osteogenic index by separating same day sessions by 8 hours. Basal serum markers of bone formation (BAP and P1NP) and resorption (CTx and TRAP5b) were evaluated at baseline and 12 wks. Total bone mineral density (BMD), content(BMC) and area (BA) were assessed by pQCT at 4, 38, & 66% of tibial length. Polar strength strain indices (SSIP) were also assessed at the 38 and 66% sites. Baseline and 12 wk one repetition maximum (1-RM) was used to assess changes in overall strength. Repeated measures ANOVA was employed for statistical analysis and significance was set at p<0.05. RESULTS: In all participants, BAP increased significantly over time (pre=22.9±12.6 vs. post= 26.6±13.5 U/L, p<0.03) with no between-group differences. P1NP was suppressed only in the CON group after 12 wks (pre=110±91.4 vs. post=76.2±39.2 ng/mL) (p<0.03). A slight but significant increase in BMD at the 38% site was observed after 12 wks in all participants (pre=916.5±59.1 vs. post=921.5±60.6 mg/cm3) (p<0.03) with no between group differences. Over 12 wks, 1×/d and 2×/d training groups significantly increased their 1-RM with the 2×/d group showing greater improvements (27% vs. 36%, p<0.05). No changes were observed in any groups for bone parameters at the 4 or 66% sites or in markers of resorption. CONCLUSION: Overall engaging in power training was able to maintain bone formation markers with no subsequent effect on bone resorption indices. Although both programs increased BMD, no differences were observed in the measures of bone quality with once vs. twice a day power training programs.

Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with 'platform-shifting' in a dog model. Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. The SCL groups' indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone-to-implant contact and histological bone density. The subcrestal placement of contiguous Morse cone connection implants with 'platform shifting' was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions.

The TRPV1 ion channel antagonist capsazepine inhibits osteoclast and osteoblast differentiation in vitro and ovariectomy induced bone loss in vivo

The vanilloid type 1 ion channel (TRPV1) is known to play an important role in the regulation of pain and inflammation. Pharmacological ligands of TRPV1 regulate human osteoclast formation in vitro, but the effects of these agents on osteoblast function have not been studied and their effects on bone loss in vivo are unknown. Here we examined the effects of the TRPV1 ion channel antagonist capsazepine on mouse osteoclast and osteoblast differentiation in vitro and ovariectomy induced bone loss in vivo. Capsazepine inhibited osteoclast formation and bone resorption in a dose dependent manner in bone marrow–osteoblast co-cultures and RANKL generated osteoclast cultures, whereas the TRPV1 agonist capsaicin enhanced RANKL and M-CSF stimulated osteoclast formation. Capsazepine also suppressed RANKL induced IκB and ERK1/2 phosphorylation and caused apoptosis of mature osteoclasts and also inhibited alkaline phosphatase activity and bone nodule formation in calvarial osteoblast cultures. Studies in vivo showed that capsazepine (1 mg/kg/day) inhibited ovariectomy induced bone loss in mice and histomorphometric analysis showed inhibitory effects on indices of bone resorption and bone formation. We conclude that pharmacological blockade of TRPV1 ion channels by capsazepine inhibits osteoclastic bone resorption and protects against ovariectomy induced bone loss in mice, but also inhibits osteoblast activity and bone formation.

Treatment with a Potent Cathepsin K Inhibitor Preserves Cortical and Trabecular Bone Mass in Ovariectomized Monkeys

The cysteine protease cathepsin K is involved in osteoclast-mediated bone resorption. We evaluated the effect of daily oral dosing of an inhibitor of human cathepsin K (SB-462795 [relacatib]) for 9 months on bone turnover, mass, and architecture in estrogen-deficient cynomolgus monkeys. Ovariectomized animals were treated orally with relacatib at 1, 3, or 10 mg/kg/day, or oral vehicle plus alendronate at 0.05 mg/kg by IV injection once every 2 weeks. The control groups, ovariectomized and sham-ovariectomized animals, received vehicle (all groups n = 20 animals). Samples for biomarker analysis were collected at various times, bone mass changes were evaluated at 6 and 9 months of treatment, and histomorphometric analysis was performed at 9 months. Relacatib significantly reduced urinary N-telopeptide excretion within 1 week of treatment at all dose levels, an effect that was maintained at the highest dose level. At some time points bone formation markers were elevated at the lowest dose of relacatib. Animals treated with relacatib had dose-dependent preservation of areal bone mineral density reaching statistical significance in distal femur. In femur neck there was significant preservation of total volumetric BMD (vBMD) by relacatib. By histomorphometry, relacatib reduced indices of bone resorption and formation at cancellous sites as did alendronate. In cortical bone, osteonal bone formation rate was reduced by alendronate but preserved at low and medium doses of relacatib. Thus, relacatib preserved cortical and cancellous bone mass in ovariectomized monkeys.