Effects of insulin therapy on porosity,non-enzymatic glycation and mechanical competence in the bone of rats with type 2 diabetes mellitus

Type 2 diabetes mellitus increases skeletal fragility; however, the contributing mechanisms and optimal treatment strategies remain unclear. We studied the effects of diabetes and insulin therapy on non-enzymatic glycation (NEG), cortical porosity (Ct.Po) and biomechanics of the bone tissue in Zucker Diabetic Fatty (ZDF) rats.Eleven-week old ZDF diabetic and non-diabetic rats were given insulin to achieve glycaemic control or vehicle seven days per week over twelve weeks (insulin dose adapted individually 0.5 international units (IU) at week 1 to 13.0 IU at week 12). The right femora were excised, micro-CT scanned, and tested in 3-point bending to measure biomechanics. NEG of the midshaft was determined from bulk fluorescence.Diabetes led to increased NEG (+ 50.1%, p = 0.001) and Ct.Po (+ 22.9%, p = 0.004), as well as to reduced mechanical competence (max. stress: − 14.2%, p = 0.041, toughness: − 29.7%, p = 0.016) in the bone tissue. NEG and Ct.Po both correlated positively to serum glucose (NEG: R² = 0.41, p < 0.001, Ct.Po: R² = 0.34, p = 0.003) and HbA1c (NEG: R² = 0.42, p < 0.001, Ct.Po: R² = 0.28, p = 0.008) levels, while NEG correlated negatively with bone biomechanics (elastic modulus: R² = 0.21, p = 0.023, yield stress: R² = 0.17, p = 0.047). Twelve weeks of insulin therapy had no significant effect on NEG or Ct.Po, and was unable to improve the mechanical competence of the bone tissue.A reduction of mechanical competence was observed in the bone tissue of the diabetic rats, which was explained in part by increased collagen NEG. Twelve weeks of insulin therapy did not alter NEG, Ct.Po or bone biomechanics. However, significant correlations between NEG and serum glucose and HbA1c were observed, both of which were reduced with insulin therapy. This suggests that a longer duration of insulin therapy may be required to reduce the NEG of the bone collagen and restore the mechanical competence of diabetic bone.     

Cortical measurements of the tibia from high resolution peripheral quantitative computed tomography images: A comparison with synchrotron radiation micro-computed tomography

High resolution-peripheral quantitative computed tomography (HR-pQCT) measurements are carried out in clinical research protocols to analyze cortical bone. Micro-computed tomography (micro-CT) is a standard tool for ex vivo examination of bone in 3D. The aim of this work was to evaluate cortical measurements derived from HR-pQCT images compared to those from synchrotron radiation (SR) micro-CT in a distal position (4.2 cm from the distal pilon).Twenty-nine tibia specimens were scanned with HR-pQCT using protocols provided by the manufacturer. The standard measured outcomes included volumetric bone density (g HA/cm³) of the cortical region (Dcomp), and the cortical thickness (Ct.Th, mm). New features, such as cortical porosity (Ct.Po) and mean pore diameter (Ct.Po.Dm), were measured by an auto-contouring process. All tibias were harvested from the posterior region and imaged with SR micro-CT (voxel size = 7.5μm). The cortical thickness, (Ct.Th_micro-CT), porosity (PoV/TV), pore diameter, pore spacing, pore number, and degree of mineralization of bone (DMB) were obtained for SR micro-CT images. For standard measurements on HR-pQCT images, site matched analyses with micro-CT were completed to obtain Dcomp_local and Ct.Th_local.Dcomp was highly correlated to PoV/TV (r = − 0.84,p < 10^− 4) but not to DMB. Dcomp_local was correlated to PoV/TV (r = − 0.72, p < 10^− 4) and to DMB (r = 0.40, p > 0.05). Ct.Th_local and Ct.Th_micro-CT were moderately correlated (r = 0.53,p < 0.01). Ct.Th and Ct.Po results from the autocontouring process are influenced by the level of trabecularization of the cortical bone and need manual correction of the endosteal contour.Distal tibia is a reliable region to study cortical bone with Dcomp as the best parameter because it reflects both the micro-porosity (Havers canals) and macro-porosity (resorption lacunae) of the cortical bone.     

The pitfall of treating low bone turnover: Effects on cortical porosity

Although it is recognized that cortical bone contributes significantly to the mechanical strength of the skeleton, little is known about this compartment from bone biopsy studies, particularly in CKD patients. In addition, there is no prospective data on the effects of CKD-MBD therapy on cortical porosity (Ct.Po). This is a post hoc analysis on data from a randomized controlled trial on the effects of different phosphate binders on bone remodelling. Therapy was adjusted according to the first biopsy, and included sevelamer or calcium acetate, calcitriol and changes in calcium dialysate concentration. We measured Ct.Po at baseline and one year after. Fifty-two patients (46 ± 13 years old, 67% women and 60% white) were enrolled. Ct.Po was already high at baseline in 85% of patients [30% (17, 46)] and correlated with PTH (p = 0.001). Low bone turnover was seen in 28 patients (54.9%). After one-year treatment, PTH increased in patients with low turnover, as intended. However, increased Ct.Po was seen in 49 patients (94%). This increase correlated with the delta of phosphate (p = 0.015) and the delta of PTH (p = 0.03); it was also higher among non-white patients than in white patients (p = 0.039). The risk of increase in Ct.Po was 4.5 higher among non-white patients. Adjusted multiple regression analysis showed that the delta of Ct.Po was dependent on delta PTH and race (r² = 0.193). We concluded that in an attempt to increase bone turnover, the increase in PTH levels might be associated with higher cortical porosity, particularly in non-white patients. Whether this finding leads to a high risk of fracture deserves further investigation.     

Dynamic acoustic radiation force retains bone structural and mechanical integrity in a functional disuse osteopenia model

Disuse osteopenia and bone loss have been extensively reported in long duration space mission and long term bed rest. The pathology of the bone loss is similar to osteoporosis but highly confined to weight bearing bones. The current anabolic and/or anti-resorptive drugs have systemic effects and are costly over extended time, with concerns of long term fracture risk. This study use Low Intensity Pulsed Ultrasound (LIPUS) as a non-invasive acoustic force and anabolic stimulus to countermeasure disuse induced bone loss. Four-month old C57BL/6 mice were randomized into five groups, 1) age-matched (AM), 2) non-suspended sham (NS), 3) non-suspended-LIPUS (NU), 4) suspended sham (SS), and 5) suspended-LIPUS (SU) groups. After four weeks of suspension, μCT analyses showed significant decreases in trabecular bone volume fraction (BV/TV) (− 36%, p < 0.005), bone tissue mineral density (TMD) (− 3%, p < 0.05), trabecular thickness (Tb.Th) (− 12.5%, p < 0.005), and increase in bone surface/bone volume (+ BS/BV) (+ 16%, p < 0.005), relative to age-matched (AM). The application of LIPUS for 20 min/day for 5 days/week, significantly increased TMD (+ 3%, p < 0.05), Tb.Th (+ 6%, p < 0.05), and decreased BS/BV (− 10%, p < 0.005), relative to suspension alone (SS) mice. Histomorphometry analyses showed a breakdown of bone microstructure under disuse conditions consist with μCT results. In comparison to SS mice, LIPUS treated bone showed increased structural integrity with increased bone formation rates at metaphysical endosteal and trabecular surfaces (+ 0.104 ± 0.07 vs 0.031 ± 0.30 μm³/μm²/day) relative to SS. Four-point bending mechanical tests of disused SS femurs showed reduced elastic modulus (− 53%, p < 0.05), yield (− 33%, p < 0.05) and ultimate strength (− 45%, p < 0.05) at the femoral diaphysis relative to AM bone. LIPUS stimulation mitigated the adverse effects of disuse on bone elastic modulus (+ 42%, p < 0.05), yield strength (+ 29%, p < 0.05), and ultimate strength (+ 39%, p < 0.05) relative to SS femurs. LIPUS provides the essential mechanical stimulus to retain bone morphological and mechanical integrity in disuse conditions. This study demonstrates LIPUS potential as regional therapeutic agent to countermeasure disuse induced bone loss while maintaining bone's integrity.     

Serum FGF-21 levels are associated with worsened radial trabecular bone microarchitecture and decreased radial bone strength in women with anorexia nervosa

BackgroundAnorexia nervosa (AN) is a psychiatric disorder characterized by self-induced starvation and low body weight. Women with AN have impaired bone formation, low bone mass and an increased risk of fracture. FGF-21 is a hormone secreted by the liver in starvation and FGF-21 transgenic mice have significant bone loss due to an uncoupling of bone resorption and bone formation. We hypothesized that FGF-21 may contribute to the low bone mass state of AN.Subjects and methodsWe studied 46 women: 20 with AN (median age [interquartile range]: 27.5 [25, 30.75] years) and 26 normal-weight controls (NWC) of similar age (25 [24, 28.5] years). We investigated associations between serum FGF-21 and 1) aBMD measured by dual energy X-ray absorptiometry, 2) parameters of bone microarchitecture in the distal radius and tibia measured by high-resolution peripheral quantitative CT and 3) bone strength, estimated by microfinite element analysis.ResultsFGF-21 levels were similar in AN and NWC (AN: 33.1 [18.1, 117.0] pg/ml vs. NWC: 57.4 [23.8, 107.1] pg/ml; p = 0.54). There was a significant inverse association between log FGF-21 and trabecular number in the radius in both AN (R = − 0.57, p < 0.01) and NWC (R = − 0.53, p < 0.01) and a significant positive association between log FGF-21 and trabecular separation in the radius in AN (R = 0.50, p < 0.03) and NWC (R = 0.52, p < 0.01). Estimates of radial bone strength were inversely associated with log FGF-21 in AN (R = − 0.50, p < 0.03 for both stiffness and failure load). There were no associations between FGF-21 and aBMD, cortical parameters or tibial parameters in the AN or NWC groups.ConclusionsFGF-21 may be an important determinant of trabecular skeletal homeostasis in AN.     

Inverse association between bone microarchitecture assessed by HR-pQCT and coronary artery calcification in patients with end-stage renal disease

It is a matter of debate whether vascular calcification and bone loss are simultaneously occurring but largely independent processes or whether poor bone health predisposes to vascular calcification, especially in patients with kidney disease. Here we investigated the association between the changes of microarchitecture in weight bearing bone and the extent of coronary artery calcification in patients with chronic renal failure.The bone microarchitecture of the tibia using high-resolution peripheral quantitative computed tomography (HR-pQCT), bone mineral density using dual X-ray absorptiometry (DXA) of the lumbar spine, femoral neck and distal radius as well as coronary artery calcification using multi-slice CT and reported as Agatston score were measured in 66 patients with end-stage renal disease on chronic hemodialysis. Markers of bone turnover, vitamin D status and intact parathyroid hormone (iPTH) were assessed.CAC score was found to be < 100 in 39% and ≥ 100 in 61% of patients. The median [95% CI] total CAC score was 282 [315–2587]. By univariate analysis, significant correlations between CAC and age (R = 0.52, p < 0.001), weight (R = 0.3, p < 0.01) and serum cross laps (CTX, R = − 0.39, p < 0.01) were found, and parameters of bone microarchitecture were numerically but not significantly lower in patients with CAC scores ≥ 100. In multivariate analysis stratifying for gender and correcting for age, tibial density (D_tot) and bone volume/total volume (BV/TV) were significantly lower in patients with CAC scores ≥ 100 (p < 0.05 for both).Low trabecular bone volume and decreased cortical bone density are associated with coronary artery calcification in dialysis patients.     

Effect of odanacatib on bone turnover markers,bone density and geometry of the spine and hip of ovariectomized monkeys: A head-to-head comparison with alendronate

Odanacatib (ODN) is a selective and reversible Cathepsin K (CatK) inhibitor currently being developed as a once weekly treatment for osteoporosis. Here, effects of ODN compared to alendronate (ALN) on bone turnover, DXA-based areal bone mineral density (aBMD), QCT-based volumetric BMD (vBMD) and geometric parameters were studied in ovariectomized (OVX) rhesus monkeys. Treatment was initiated 10 days after ovariectomy and continued for 20 months. The study consisted of four groups: L-ODN (2 mg/kg, daily p.o.), H-ODN (8/4 mg/kg daily p.o.), ALN (15 μg/kg, twice weekly, s.c.), and VEH (vehicle, daily, p.o.). L-ODN and ALN doses were selected to approximate the clinical exposures of the ODN 50-mg and ALN 70-mg once-weekly, respectively. L-ODN and ALN effectively reduced bone resorption markers uNTx and sCTx compared to VEH. There was no additional efficacy with these markers achieved with H-ODN. Conversely, ODN displayed inversely dose-dependent reduction of bone formation markers, sP1NP and sBSAP, and L-ODN reduced formation to a lesser degree than ALN. At month 18 post-OVX, L-ODN showed robust increases in lumbar spine aBMD (11.4%, p < 0.001), spine trabecular vBMD (13.7%, p < 0.001), femoral neck (FN) integral (int) vBMD (9.0%, p < 0.001) and sub-trochanteric proximal femur (SubTrPF) int vBMD, (6.4%, p < 0.001) compared to baseline. L-ODN significantly increased FN cortical thickness (Ct.Th) and cortical bone mineral content (Ct.BMC) by 22.5% (p < 0.001) and 21.8% (p < 0.001), respectively, and SubTrPF Ct.Th and Ct.BMC by 10.9% (p < 0.001) and 11.3% (p < 0.001) respectively. Compared to ALN, L-ODN significantly increased FN Ct. BMC by 8.7% (p < 0.05), and SubTrPF Ct.Th by 7.6% (p < 0.05) and Ct.BMC by 6.2% (p < 0.05). H-ODN showed no additional efficacy compared to L-ODN in OVX-monkeys in prevention mode. Taken together, the results from this study have demonstrated that administration of ODN at levels which approximate clinical exposure in OVX-monkeys had comparable efficacy to ALN in DXA-based aBMD and QCT-based vBMD. However, FN cortical mineral content clearly demonstrated superior efficacy of ODN versus ALN in this model of estrogen-deficient non-human primates.     

Raman spectral classification of mineral- and collagen-bound water's associations to elastic and post-yield mechanical properties of cortical bone

Water that is bound to bone's matrix is implied as a predictor of fracture resistance; however, bound water is an elusive variable to be measured nondestructively. To date, the only nondestructive method used for studying bone hydration status is magnetic resonance variants (NMR or MRI). For the first time, bone hydration status was studied by short-wave infrared (SWIR) Raman spectroscopy to investigate associations of mineral-bound and collagen-bound water compartments with mechanical properties. Thirty cortical bone samples were used for quantitative Raman-based water analysis, gravimetric analysis, porosity measurement, and biomechanical testing. A sequential dehydration protocol was developed to replace unbound (heat drying) and bound (ethanol treatment) water in bone. Raman spectra were collected serially to track the OH-stretch band during dehydration. Four previously identified peaks were investigated: I₃₂₂₀/I₂₉₄₉, I₃₃₂₅/I₂₉₄₉ and I₃₄₅₃/I₂₉₄₉ reflect status of organic-matrix related water (mostly collagen-related water) compartments and collagen portion of bone while I₃₅₈₄/I₂₉₄₉ reflects status of mineral-related water compartments and mineral portion of bone. These spectroscopic biomarkers were correlated with elastic and post-yield mechanical properties of bone. Collagen–water related biomarkers (I₃₂₂₀/I₂₉₄₉ and I₃₃₂₅/I₂₉₄₉) correlated significantly and positively with toughness (R² = 0.81 and R² = 0.79; p < 0.001) and post-yield toughness (R² = 0.65 and R² = 0.73; p < 0.001). Mineral-water related biomarker correlated significantly and negatively with elastic modulus (R² = 0.78; p < 0.001) and positively with strength (R² = 0.46; p < 0.001). While MR-based techniques have been useful in measuring unbound and bound water, this is the first study which probed bound-water compartments differentially for collagen and mineral-bound water. For the first time, we showed an evidence for contributions of different bound-water compartments to mechanical properties of wet bone and the reported correlations of Raman-based water measurements to mechanical properties underline the necessity for enabling approaches to assess these new biomarkers noninvasively in vivo to improve the current diagnosis of those who may be at risk of bone fracture due to aging and diseases.     

Plasma ghrelin and leptin in adult cystic fibrosis patients

BackgroundWeight loss in cystic fibrosis (CF) may be associated with altered levels of appetite stimulating peptide ghrelin and the appetite decreasing peptide leptin. However, prior data on leptin in CF are conflicting, while the data on ghrelin are scarce. We hypothesized that weight loss in CF is associated with low levels ghrelin and elevated levels of leptin.MethodsPlasma ghrelin, leptin, TNF-α, IL-1 and IL-6, BMI, fat free mass (FFM), fat mass (FM) were measured in 74 CF adults and 20 controls. CF subjects were divided into 3 groups based on lung disease: mild (n = 19), moderate (n = 30) and severe (n = 25).ResultsSevere CF patients (% predicted FEV1 27 ± 7; median BMI 21 kg/m²) had significantly elevated ghrelin and decreased leptin compared to controls and other CF subjects. Ghrelin correlated (r value, p value) with BMI (− 0.35,< 0.001), FFM (− 0.22,< 0.05), FM (− 0.41,< 0.0001), FEV1 (− 0.62,< 0.001), TNF-α (0.51,< 0.0001), IL-1 (0.56,< 0.0001), and IL-6 (0.33,< 0.01). Leptin correlated (r value, p value) with BMI (0.40,< 0.0001), FM (0.56,< 0.0001), FEV1 (0.34,< 0.05), IL-1 (− 0.51,< 0.05) and TNF-α (− 0.43,< 0.0001). BMI and FEV1 were independent predictors of ghrelin (− 0.35,< 0.05;−0.59,< 0.001). FM was a predictor of leptin (0.56,< 0.0001). Cytokines were elevated only in severe CF (severe CF vs. controls, pg/ml): TNF-α (3.4 ± 0.6 vs. 1.2 ± 0.4), IL-1 (3.5 ± 1 vs. 0.2 ± 0.1), IL-6 (17.4 ± 4 vs. 2.4 ± 2).ConclusionsElevated ghrelin and decreased leptin levels are a consequence rather than a cause of weight loss in advanced CF.     

Changes in cortical microarchitecture are independent of areal bone mineral density in patients with fragility fractures

Dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) are commonly used to assess the areal bone mineral density (aBMD) and peripheral microstructure, respectively. While DXA is the standard to diagnose osteoporosis, HR-pQCT provides information about the cortical and trabecular architecture. Many fragility fractures occur in patients who do not meet the osteoporosis criterion (i.e., T-score ≤ −2.5). We hypothesize that patients with T-score above −2.5 and fragility fracture may have abnormal bone microarchitecture. Therefore, in this retrospective clinical study, HR-pQCT data obtained from patients with fragility fractures and T-scores ≥ −2.5 (n = 71) were compared to corresponding data from patients with fragility fractures and T-scores ≤ −3.5 (n = 56). Types of secondary osteoporosis were excluded from the study. To verify the dependency of alterations in bone microarchitecture and T-score, the association between HR-pQCT values and aBMD as reflected by the T-score at both proximal femora, was assessed. At the distal tibia, cortical thickness was lower (p < 0.001), cortical porosity was similar (p = 0.61), trabecular number was higher (p < 0.001), and bone volume fraction (BV/TV) was higher (p < 0.001) in patients with T-scores ≥ −2.5 than in patients with T-scores ≤ −3.5. Trabecular number and BV/TV correlated with T-score (r = 0.68, p < 0.001; r = 0.61, p < 0.001), whereas the cortical values did not. Our results thus demonstrate the importance of bone structure, as assessed by HR-pQCT, in addition to the standard DXA T-score in the diagnosis of osteoporosis.     

Fractures on bisphosphonates in osteoporosis pseudoglioma syndrome (OPPG): pQCT shows poor bone density and structure

Osteoporosis pseudoglioma syndrome (OPPG) is a rare autosomal recessive disorder of childhood osteoporosis and blindness due to inactivating mutations in LDL receptor-like protein 5 (LRP5). We and others have reported improvement in areal bone mineral density (aBMD) by DXA in OPPG on short term bisphosphonates. Long-term data on bisphosphonate use in OPPG and measures of volumetric BMD (vBMD) and cortical structure are not available. In addition, no long-term DXA data on untreated OPPG is available. The aims of this study were to: (1) record low trauma fractures and longitudinal aBMD by DXA in 5 OPPG patients on chronic bisphosphonate treatment, and in 4 OPPG patients never treated (2) to perform tibia peripheral quantitative CT (pQCT) to evaluate volumetric bone mineral density (vBMD), cortical structure and calf muscle area in 6 OPPG patients and 14 unaffected first degree family members. pQCT results were converted to sex-specific Z-scores for age and adjusted for tibia length based on data in > 700 reference participants. We observed 4 fractures (3 femoral shafts) in 3 OPPG patients while on bisphosphonates, after each achieved significant improvement in aBMD. OPPG participants had significantly lower mean trabecular vBMD (− 1.51 vs. 0.17, p = 0.002), cortical area (− 2.36 vs. 0.37; p < 0.001) and periosteal circumference (− 1.86 vs. − 0.31, p = 0.001) Z-scores, compared with unaffected participants and had a trend toward lower muscle area Z-score (− 0.69 vs. 0.47, p = 0.12). These data demonstrate substantial bone fragility despite improvements in aBMD. The pQCT data provide insight into the fragility with substantial deficits in trabecular vBMD and cortical dimensions, consistent with OPPG effects of bone formation. Treatment that improves bone quality is needed to reduce fractures in OPPG.     

Subtle changes in bone mineralization density distribution in most severely affected patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is associated with low aBMD as measured by DXA and altered microstructure as assessed by bone histomorphometry and microcomputed tomography. Knowledge of bone matrix mineralization is lacking in COPD. Using quantitative backscatter electron imaging (qBEI), we assessed cancellous (Cn.) and cortical (Ct.) bone mineralization density distribution (BMDD) in 19 postmenopausal women (62.1 ± 7.3 years of age) with COPD. Eight had sustained fragility fractures, and 13 had received treatment with inhaled glucocorticoids. The BMDD outcomes from the patients were compared with healthy reference data and were correlated with previous clinical and histomorphometric findings.In general, the BMDD outcomes for the patients were not significantly different from the reference data. Neither the subgroups of with or without fragility fractures or of who did or did not receive inhaled glucocorticoid treatment, showed differences in BMDD. However, subgroup comparison according to severity revealed 10% decreased cancellous mineralization heterogeneity (Cn.CaWidth) for the most severely affected compared with less affected patients (p = 0.042) and compared with healthy premenopausal controls (p = 0.021). BMDD parameters were highly correlated with histomorphometric cancellous bone volume (BV/TV) and formation indices: mean degree of mineralization (Cn.CaMean) versus BV/TV (r = 0.58, p = 0.009), and Cn.CaMean and Ct.CaMean versus bone formation rate (BFR/BS) (r = -0.71, p < 0.001). In particular, those with lower BV/TV (< 50th percentile) had significantly lower Cn.CaMean (p = 0.037) and higher Cn.CaLow (p = 0.020) compared with those with higher (> 50th percentile) BV/TV.The normality in most of the BMDD parameters and bone formation rates as well as the significant correlations between them suggests unaffected mineralization processes in COPD. Our findings also indicate no significant negative effect of treatment with inhaled glucocorticoids on the bone mineralization pattern. However, the observed concomitant occurrence of relatively lower bone volumes with lower bone matrix mineralization will both contribute to the reduced aBMD in some patients with COPD.     

Age but not gender modulates the relationship between PTH and vitamin D

ContextIt is unclear whether the relationship between 25-OHD and PTH is modulated by age or gender.ObjectiveTo assess the 25-OHD–PTH relationship in 340 adolescents (10–17 years) and 443 elderly (65–85 years) of the same ethnic group, and living in the same sunny country.AssessmentsCalcium intake was estimated. Serum calcium, phosphorus, 25-OHD and PTH were measured. Body fat was determined by DXA.Results25-OHD levels were lower in the elderly in the overall group (p < 0.001) and within genders. 25-OHD levels were lower in females in the overall group and within age subgroups (p < 0.05). PTH levels were higher in the elderly in the overall population and in both genders (p < 0.001). There were no gender differences in PTH levels within age subgroups. For the same 25-OHD level, PTH levels were comparable across genders but were 1.5–2 folds higher in the elderly compared to adolescents (p < 0.001). PTH correlated positively with age (p < 0.001), body fat (p = 0.02), and negatively with calcium intake (p < 0.001), and 25-OHD (p < 0.001). The magnitude of the correlation with 25-OHD decreased after adjustment for age but not for gender. In multivariate analyses, age, 25-OHD and fat mass were independent predictors for PTH. In the elderly, after adjustment for serum creatinine, only 25-OHD and creatinine were independent predictors of PTH.ConclusionThe negative relationship between 25-OHD and PTH is modulated by age but not gender. Desirable 25-OHD levels derived from examining the 25-OHD–PTH relationship should therefore take into account the age of the population of interest.     

The association between plasma homocysteine levels and bone quality and bone mineral density parameters in older persons

IntroductionHigh plasma homocysteine levels have been associated with incident osteoporotic fractures, but the mechanisms underlying this association are still unknown. It has been hypothesized that homocysteine might interfere with collagen cross-linking in bone, thereby weakening bone structure. Therefore, we wanted to investigate whether plasma homocysteine levels are associated with bone quality parameters, rather than with bone mineral density.MethodsCross-sectional data of the B-PROOF study (n = 1227) and of two cohorts of the Rotterdam Study (RS-I (n = 2850) and RS-II (n = 2023)) were used. Data on bone mineral density of the femoral neck and lumbar spine were obtained in these participants using dual-energy X-ray assessment (DXA). In addition, participants of B-PROOF and RS-I underwent quantitative ultrasound measurement of the calcaneus, as a marker for bone quality. Multiple linear regression analysis was used to investigate the associations between natural-log transformed plasma levels of homocysteine and bone mineral density or ultrasound parameters.ResultsNatural-log transformed homocysteine levels were inversely associated with femoral neck bone mineral density in the two cohorts of the Rotterdam Study (B = − 0.025, p = 0.004 and B = − 0.024, p = 0.024). In B-PROOF, no association was found. Pooled data analysis showed significant associations between homocysteine and bone mineral density at both femoral neck (B = − 0.032, p = 0.010) and lumbar spine (B = − 0.098, p = 0.021). Higher natural-log transformed homocysteine levels associated significantly with lower bone ultrasound attenuation in B-PROOF (B = − 3.7, p = 0.009) and speed of sound in both B-PROOF (B = − 8.9, p = 0.001) and RS-I (B = − 14.5, p = 0.003), indicating lower bone quality. Pooled analysis confirmed the association between homocysteine and SOS (B = − 13.1, p = 0.016). Results from ANCOVA-analysis indicate that differences in SOS and BUA between participants having a plasma homocysteine level above or below median correspond to 0.14 and 0.09 SD, respectively.DiscussionIn this study, plasma levels of homocysteine were significantly inversely associated with both bone ultrasound parameters and with bone mineral density. However, the size of the associations seems to be of limited clinical relevance and may therefore not explain the previously observed association between plasma homocysteine and osteoporotic fracture incidence.     

The resistance of cortical bone tissue to failure under cyclic loading is reduced with alendronate

Bisphosphonates are the most prescribed preventative treatment for osteoporosis. However, their long-term use has recently been associated with atypical fractures of cortical bone in patients who present with low-energy induced breaks of unclear pathophysiology. The effects of bisphosphonates on the mechanical properties of cortical bone have been exclusively studied under simple, monotonic, quasi-static loading. This study examined the cyclic fatigue properties of bisphosphonate-treated cortical bone at a level in which tissue damage initiates and is accumulated prior to frank fracture in low-energy situations. Physiologically relevant, dynamic, 4-point bending applied to beams (1.5 mm × 0.5 mm × 10 mm) machined from dog rib (n = 12/group) demonstrated mechanical failure and micro-architectural features that were dependent on drug dose (3 groups: 0, 0.2, 1.0 mg/kg/day; alendronate [ALN] for 3 years) with cortical bone tissue elastic modulus (initial cycles of loading) reduced by 21% (p < 0.001) and fatigue life (number of cycles to failure) reduced in a stress-life approach by greater than 3-fold with ALN1.0 (p < 0.05). While not affecting the number of osteons, ALN treatment reduced other features associated with bone remodeling, such as the size of osteons (− 14%; ALN1.0: 10.5 ± 1.8, VEH: 12.2 ± 1.6, × 10³ μm²; p < 0.01) and the density of osteocyte lacunae (− 20%; ALN1.0: 11.4 ± 3.3, VEH: 14.3 ± 3.6, × 10² #/mm²; p < 0.05). Furthermore, the osteocyte lacunar density was directly proportional to initial elastic modulus when the groups were pooled (R = 0.54, p < 0.01). These findings suggest that the structural components normally contributing to healthy cortical bone tissue are altered by high-dose ALN treatment and contribute to reduced mechanical properties under cyclic loading conditions.     

Associations among endocrine,inflammatory, and bone markers,body composition and weight loss induced bone loss

IntroductionWeight loss reduces co-morbidities of obesity, but decreases bone mass.PurposeOur aims were to 1) determine if adequate dairy intake attenuates weight loss-induced bone loss; 2) evaluate the associations of endocrine, inflammatory and bone markers, anthropometric and other parameters to bone mineral density and content (BMD, BMC) pre- and post-weight loss; and 3) model the contribution of these variables to post weight-loss BMD and BMC.MethodsOverweight/obese women (BMI: 28–37 kg/m²) were enrolled in an energy reduced (− 500 kcal/d; − 2092 kJ/d) diet with adequate dairy (AD: 3–4 servings/d; n = 25, 32.2 ± 8.8 years) or low dairy (LD: ≤ 1 serving/d; n = 26, 31.7 ± 8.4 years). BMD, BMC and body composition were measured by DXA. Bone markers (CTX, PYD, BAP, OC), endocrine (PTH, vitamin D, leptin, adiponectin, ghrelin, amylin, insulin, GLP-1, PAI-1, HOMA) and inflammatory markers (CRP, IL1-β, IL-6, IL-8, TNF-α, cortisol) were measured in serum or plasma. PA was assessed by accelerometry.ResultsFollowing weight loss, AD intake resulted in significantly greater (p = 0.004) lumbar spine BMD and serum osteocalcin (p = 0.004) concentration compared to LD. Pre- and post-body fat was negatively associated with hip and lumbar spine BMC (r = − 0.28, p = 0.04 to − 0.45, p = 0.001). Of note were the significant negative associations among bone markers and IL-1β, TNFα and CRP ranging from r = − 0.29 (p = 0.04) to r = − 0.34 (p = 0.01); magnitude of associations did not change with weight loss. Adiponectin was negatively related to change in osteocalcin. Factor analysis resulted in 8 pre- and post-weight loss factors. Pre-weight loss factors accounted for 13.7% of the total variance in pre-weight loss hip BMD; post-weight loss factors explained 19.6% of the total variance in post-weight loss hip BMD. None of the factors contributed to the variance in lumbar spine BMD.ConclusionAD during weight loss resulted in higher lumbar spine BMD and osteocalcin compared to LD. Significant negative associations were observed between bone and inflammatory markers suggesting that inflammation suppresses bone metabolism. Using factor analysis, 19.6% of total variance in post-weight loss hip BMD could be explained by endocrine, immune, and anthropometric variables, but not lumbar spine BMD.     

Comparison of the Relationship Between Bone Marrow Adipose Tissue and Volumetric Bone Mineral Density in Children and Adults

Several large-scale studies have reported the presence of an inverse relationship between bone mineral density (BMD) and bone marrow adipose tissue (BMAT) in adults. We aim to determine if there is an inverse relationship between pelvic volumetric BMD (vBMD) and pelvic BMAT in children and to compare this relationship in children and adults. Pelvic BMAT and bone volume (BV) was evaluated in 181 healthy children (5–17 yr) and 495 healthy adults (≥18 yr) with whole-body magnetic resonance imaging (MRI). Pelvic vBMD was calculated using whole-body dual-energy X-ray absorptiometry to measure pelvic bone mineral content and MRI-measured BV. An inverse correlation was found between pelvic BMAT and pelvic vBMD in both children (r = −0.374, p < 0.001) and adults (r = −0.650, p < 0.001). In regression analysis with pelvic vBMD as the dependent variable and BMAT as the independent variable, being a child or adult neither significantly contribute to the pelvic BMD (p = 0.995) nor did its interaction with pelvic BMAT (p = 0.415). The inverse relationship observed between pelvic vBMD and pelvic BMAT in children extends previous findings that found the inverse relationship to exist in adults and provides further support for a reciprocal relationship between adipocytes and osteoblasts.     

The role of bone intrinsic properties measured by infrared spectroscopy in whole lumbar vertebra mechanics: Organic rather than inorganic bone matrix?

Whole bone strength is determined by bone mass, microarchitecture and intrinsic properties of the bone matrix. However, few studies have directly investigated the contribution of bone tissue material properties to whole bone strength in humans. This study assessed the role of bone matrix composition on whole lumbar vertebra mechanics. We obtained 17 fresh frozen human lumbar spines (8 W, 9 M, aged 76 ± 11 years). L3 bone mass was measured by DXA and microarchitecture by μ-CT with a 35 μm-isotropic resolution. Microarchitectural parameters were directly measured: Tb.BV/TV, SMI, Tb.Th, DA, Ct.Th, Ct.Po and radius of anterior cortical curvature. Failure load (N), stiffness (N/mm) and work to failure (N.mm) were extracted from quasi-static uniaxial compressive testing performed on L3 vertebral bodies. FTIRM analysis was performed on 2 μm-thick sections from L2 trabecular cores, with a Perkin-Elmer GXII Auto-image Microscope equipped with a wide band detector. Twenty measurements per sample were performed at 30 1 100 μm of spatial resolution. Each spectrum was collected at 4 cm^− 1 resolution and 50 scans in transmission mode. Mineral and collagen maturity, and mineralization and crystallinity index were measured. There was no association between the bone matrix characteristics and bone mass or microarchitecture. Mineral maturity, mineralization and crystallinity index were not related to whole vertebra mechanics. However, collagen maturity was positively correlated with whole vertebra failure load and stiffness (r = 0.64, p = 0.005 and r = 0.54, p = 0.025, respectively). The collagen maturity (3rd step) in combination with bone mass (i.e. BMC, 1st step) and microarchitecture (i.e. Tb.Th, 2nd step) improved the prediction of whole vertebra mechanical properties in forward stepwise multiple regression models, together explaining 71% of the variability in whole vertebra stiffness (p = 0.001). In conclusion, we demonstrated a substantial contribution of collagen maturity, but not mineralization parameters, to whole bone strength of human lumbar vertebrae that was independent of bone mass and microarchitecture.     

Zoledronate prevents lactation induced bone loss and results in additional post-lactation bone mass in mice

In rodents, lactation is associated with a considerable and very rapid bone loss, which almost completely recovers after weaning. The aim of the present study was to investigate whether the bisphosphonate Zoledronate (Zln) can inhibit lactation induced bone loss, and if Zln interferes with recovery of bone mass after lactation has ceased.Seventy-six 10-weeks-old NMRI mice were divided into the following groups: Baseline, Pregnant, Lactation, Lactation + Zln, Recovery, Recovery + Zln, and Virgin Control (age-matched). The lactation period was 12 days, then the pups were removed, and thereafter recovery took place for 28 days. Zln, 100 μg/kg, was given s.c. on the day of delivery, and again 4 and 8 days later. Mechanical testing, μCT, and dynamic histomorphometry were performed. At L4, lactation resulted in a substantial loss of bone strength (− 55% vs. Pregnant, p < 0.01), BV/TV (− 40% vs. Pregnant, p < 0.01), and trabecular thickness (Tb.Th) (− 29% vs. Pregnant, p < 0.001). Treatment with Zln completely prevented lactation induced loss of bone strength, BV/TV, and Tb.Th at L4. Full recovery of micro-architectural and mechanical properties was found 28 days after weaning in vehicle-treated mice. Interestingly, the recovery group treated with Zln during the lactation period had higher BV/TV (+ 45%, p < 0.01) and Tb.Th (+ 16%, p < 0.05) compared with virgin controls. Similar results were found at the proximal tibia and femur. This indicates that Zln did not interfere with the bone formation taking place after weaning. On this background, we conclude that post-lactation bone formation is not dependent on a preceding lactation induced bone loss.