Forearm endothelial function and bone mineral loss in postmenopausal women

The association of microvascular disease and endothelial dysfunction with vertebral trabecular bone mineral density : The MESA study

Retinopathy and albuminuria are associated with hip fracture risk. We investigated whether these disorders and endothelial dysfunction (which underlies microvascular diseases) were associated with low trabecular bone density. No significant associations were found, suggesting that microvascular diseases are not related to fracture risk through low trabecular bone density.

PURPOSE

Microvascular diseases of the eye, kidney, and brain are associated with endothelial dysfunction and increased hip fracture risk. To explore the basis for higher hip fracture risk, we comprehensively examined whether markers of microvascular disease and/or endothelial dysfunction are related to trabecular bone mineral density (BMD), a proximate risk factor for osteoporotic fractures.

METHODS

Among 6814 participants in the Multi-Ethnic Study of Atherosclerosis study (MESA), we derived thoracic vertebral trabecular BMD from computed tomography of the chest and measured urine albumin to creatinine ratios (UACR), retinal arteriolar and venular widths, flow mediated dilation (FMD) of the brachial artery after 5 min of ischemia; and levels of five soluble endothelial adhesion markers (ICAM-1, VCAM-1, L-selectin, P-selectin, and E-selectin). Linear regression models were used to examine the association of trabecular BMD with markers of microvascular disease and with markers of endothelial dysfunction.

RESULTS

We observed no significant associations of UACR, retinal arteriolar or venular widths, or FMD with BMD. We also observed no statistically significant association of spine trabecular BMD with levels of endothelial adhesion markers. Men and women had largely similar results.

CONCLUSION

We conclude that there is little evidence to connect thoracic spine trabecular BMD to microvascular disorders or to endothelial dysfunction among multi-ethnic middle-aged and older adults. Other factors beyond trabecular BMD (e.g., bone quality or predisposition to falling) may be responsible for the associations of microvascular disease with osteoporotic fractures.

The associations of markers of endothelial dysfunction with hip fracture risk

Endothelial dysfunction underlies the development of atherosclerotic vascular disease, which in turn is associated with osteoporotic fractures. Here, we examined the association of two markers of endothelial dysfunction with incident hip fracture risk in older adults but found no statistically significant associations between them.

PURPOSE/INTRODUCTION

Endothelial dysfunction underlies the development of atherosclerotic vascular disease. Vascular disease, in turn, is associated with the risk of osteoporotic fractures, such as hip fractures. Here, we examine whether two measures of endothelial dysfunction are related to hip fracture risk.

METHODS

Participants for this study were 2792 individuals (mean age 78.6 years) who had flow-mediated dilation (FMD) measured after ischemia in the forearm and 2255 adults (mean age 73.3 years) with measured soluble intercellular adhesion molecule (siCAM) levels, a constitutive endothelial cell membrane protein associated with the initiation of atherosclerosis. Mean follow-up was 9.7 and 11.7 years, respectively. There were 375 and 265 incident hip fractures, respectively, in each group.

RESULTS

In Cox proportional hazards models, there was no significant association between FMD response and incident hip fracture (HR per 1% higher FMD was 0.98 [0.93, 1.04]; p = 0.44). In exploratory analyses, when data were examined dichotomously, participants in the lowest 80% of FMD (≤ 4.5%) had an adjusted 1.29 (0.98, 1.68; p = 0.067) higher hazard of hip fracture compared to participants in the upper 20% of FMD change. There were no significant associations between siCAM and incident hip fracture whether examined as a continuous or dichotomized variable.

CONCLUSIONS

Among older adults, two measures of endothelial dysfunction were not significantly associated with hip fracture risk. There was a trend for higher fracture risk with lower FMD.

Early vascular ageing biomarkers in osteoporotic outpatients: a pilot study

Osteoporosis and atherosclerosis are significant public health problems that often coexist, especially in the elderly. Although some studies have reported an age-dependent relationship, others have suggested a causal relationship between osteoporosis and atherosclerosis. The aim of our study was to evaluate the cardiovascular risk in a population of patients with osteoporosis by measuring carotid intima-media thickness (cIMT) and carotid-femoral pulse wave velocity (cf-PWV). A total of 58 patients with osteoporosis and an equal number of healthy control subjects were enrolled. All subjects underwent (1) a bone densitometry examination using dual X-ray absorptiometry, (2) a vascular evaluation for the measurements of cIMT and cf-PWV and (3) a blood sample for the evaluation of lipids and phosphocalcic metabolism. Patients with osteoporosis had a significant increase in cIMT and cf-PWV. There was also a significant inverse correlation between the femoral neck BMD and cf-PWV values. In conclusion, osteoporotic outpatients have earlier vascular ageing, with an increase of arterial stiffness. These data support a possible association between osteoporosis and atherosclerosis independent of age.

Evaluation of bone perfusion during open orthopedic surgery using quantitative dynamic contrast-enhanced fluorescence imaging

In this study, an indocyanine green (ICG)-based dynamic contrast- enhanced fluorescence imaging (DCE-FI) technique was evaluated as a method to provide objective real-time data on bone perfusion using a porcine osteotomy model. DCE-FI with sequentially increasing injury to osseous blood supply was performed in 12 porcine tibias. There were measurable, reproducible and predictable changes to DCE-FI data across each condition have been observed on simple kinetic curve-derived variables as well variables derived from a novel bone-specific kinetic model. The best accuracy, sensitivity and specificity of 89%, 88% and 90%, have been achieved to effectively differentiate injured from normal/healthy bone.

Estimating bone mineral density using MRI in medicine and dentistry: a literature review

OBJECTIVES

Studies performed in the medical area have shown that an indirect diagnosis of bone mineral density (BMD) is feasible by assessing the amount of bone marrow fat with non-ionizing magnetic resonance imaging (MRI). In dentistry, radiographic methods are still the most used for alveolar bone diagnosis. The present literature review aimed at addressing the role of MRI in assessing BMD in medicine and dentistry.

METHODS

MEDLINE and EMBASE databases were searched for articles published up to 2019.

RESULTS

A total of 428 potentially eligible papers were screened. Of these, 397 were excluded after title, abstract and keyword assessment, yielding 31 papers that potentially met the inclusion criteria. Eleven studies were then excluded because their full texts did not discuss the role of MRI in the indirect diagnosis of BMD. As a result, a total of 20 studies were finally identified as eligible for inclusion in this literature review. Most studies found satisfactory accuracy of MRI for indirectly assessing BMD by quantifying bone mineral fat (BMF). However, only one of these studies was on dentistry.

CONCLUSION

Within the limitations of this study, the present findings suggest that MRI is accurate to indirectly estimate bone density by assessing BMF, and could be clinically relevant during dental treatment planning.

Association between carotid intima-media thickness and bone mineral density: a cross-sectional study in Vietnamese men and women aged 50 years and older

OBJECTIVES

The association between osteoporosis and atherosclerosis remains controversial. We sought to define the relationship between carotid intima-media thickness and bone mineral density (BMD) in individuals of Vietnamese background.

DESIGN AND SETTING

Cross-sectional study in Ho Chi Minh City, Vietnam.

PARTICIPANTS

The study involved 1460 individuals (559 men) aged 50 years and older (average age 59 years) who were randomly recruited from the community.

OUTCOME MEASURES

BMD at the femoral neck and lumbar spine was measured by dual-energy X-ray absorptiometry (Hologic, Waltham, Massachusetts, USA). Carotid intima-media thickness (cIMT) was measured using a Philips Ultrasonography (HD7XE). The presence of atherosclerotic plaque was ascertained for each individual. The association between cIMT and BMD was analysed by a multiple linear regression model.

RESULTS

In unadjusted analysis, cIMT was positively associated with femoral neck BMD in men (p=0.005), but not in women (p=0.242). After adjusting for age, smoking, diabetes and hypertension, the association remained statistically significant in men (partial R²=0.005; p=0.015) but not in women (partial R²=0.008; p=0.369). When the analysis was limited to individuals aged 60 years and older, the association between cIMT and BMD was no longer statistically significant. There was no statistically significant association between cIMT and lumbar spine BMD in either men or women.

CONCLUSIONS

In Vietnamese individuals aged 50 years and older, there is a clinically non-significant but statistically significant association between carotid intima-media thickness and BMD in men, not in women.

A strong and reliable indicator for early postoperative major cardiac events after elective orthopedic surgery: Aortic arch calcification

BACKGROUND

Cardiovascular events after orthopedic surgery may result in mortality. Therefore, predictors of early cardiovascular events after elective orthopedic surgery are required.

AIM

The aim of this study is to investigate the relationship between aortic arch calcification and 30-day major adverse cardiac events following elective orthopedic surgery.

METHODS

Patients who had undergone orthopedic surgery were screened. Preoperative detailed anamnesis was taken. Echocardiography and standard chest x-ray were performed.Patients were followed in terms of perioperative 30-days major cardiac events and were classified into two groups according to development of perioperative major adverse cardiac events.Aortic arch calcification was evaluated by two cardiologists, blinded to study findings and was graded as 0 to 3 on chest x-ray.

RESULTS

A total of 1060 patients were approached for the study participation. Of these 714 were included in the study (mean age: 70.43, 65% female). Cardiovascular events occurred in 33 patients. As compared to the patients without cardiac events, the prevalence of aortic arch calcification, coronary artery disease, hypertension, and smoking were higher in patients with cardiac events. In addition, Lee index, left ventricular end-systolic, end-diastolic and left atrial diameter were significantly higher, GFR values were significantly lower in the group with cardiac events.Multivariate regression analysis showed that smoking (OR 5.031, 95% CI 1.602 to 15.794), presence of hypertension (OR 5.133, 95% CI 1.297 to 20.308) and aortic arch calcification (OR 6.920, 95% CI 3.890 to 12.310) are independent predictors of major cardiac events within 30-day of elective orthopedic surgery.

CONCLUSIONS

Presence of aortic arch calcification is associated with development of major cardiac events within 30-days after elective orthopedic surgery.

Regulation of bone blood flow in humans: The role of nitric oxide, prostaglandins, and adenosine

The mechanisms that regulate bone blood flow (BBF) in humans are largely unknown. Animal studies suggest that nitric oxide (NO) could be involved, and in this study, we investigated the effects of inhibition of nitric oxide synthase (NOS) alone and in combination with inhibition of cyclooxygenase (COX) enzyme, thus prostaglandin (PG) synthesis on femoral bone marrow blood flow by positron emission tomography in healthy young men at rest and during one-leg dynamic exercise. In an additional group of healthy men, the role of adenosine (ADO) in the regulation of BBF during exercise was investigated by use of an adenosine receptor blocker (aminophylline). Inhibitors were directly infused into the femoral artery. Resting BBF was 1.1 ± 0.4 mL 100 g^-1 min^-1 and increased to almost sixfold in response to exercise (6.3 ± 1.5 mL 100 g^-1  min^-1 ). Inhibition of NOS reduced BBF at rest to 0.7 ± 0.3 mL 100 g^-1  min^-1 (P = .036), but did not affect BBF significantly during exercise (5.5 ± 1.4 mL 100 g^-1  min^-1 , P = .25). On the other hand, while combined NOS and COX inhibition did not cause any further reduction of blood flow at rest (0.6 ± 0.2 mL 100 g^-1 min^-1 ), the combined blockade reduced BBF during exercise by ~21%, to 5.0 ± 1.8 mL 100 g^-1  min^-1 (P = .014). Finally, the ADO inhibition during exercise reduced BBF from 5.5 ± 1.9 mL 100 g^-1  min^-1 to 4.6 ± 1.2 mL 100 g^-1  min^-1 (P = .045). In conclusion, our results support the view that NO is involved in controlling bone marrow blood flow at rest, and NO, PG, and ADO play important roles in controlling human BBF during exercise.

Effect of teriparatide treatment on endothelial function, glucose metabolism and inflammation markers in patients with postmenopausal osteoporosis

OBJECTIVE

Teriparatide, an anabolic agent used in the treatment of postmenopausal osteoporosis, can induce effects similar to primary hyperparathyroidism. Our objective was to evaluate the effects of teriparatide on endothelial functions, glucose metabolism and inflammation markers in patients diagnosed with postmenopausal osteoporosis.

DESIGN, PATIENTS AND MEASUREMENTS

This was a single-centre, single-arm, 6-month prospective study. Twenty-three postmenopausal women over 65 years old with a lumbar spine or femoral neck T-score of -4·0 or lower and having at least two compression fractures in thoracic or lumbar spine were studied. Low-dose intermittent teriparatide (20 μg/day) was supplemented with calcium carbonate (1000 mg elemental calcium) and 880 IU cholecalciferol for 6 months. The biochemical parameters for glucose metabolism, inflammation and atherosclerosis were determined. For the assessment of vascular endothelial function, carotid intima-media thickness (CIMT), brachial artery intima-media thickness (BIMT), per cent change in flow-mediated dilation (FMD%) and nitroglycerine-induced dilations (NID%) were measured on ultrasonography.

RESULTS

The fasting plasma glucose, homoeostatic model assessment of insulin resistance, fibrinogen, homocysteine and high-density lipoprotein cholesterol increased significantly with teriparatide treatment (P < 0·05 for all). Baseline CIMT and BIMT did not change significantly with 6 months of teriparatide treatment (P > 0·05); however, FMD% and NID% showed significant decrease after treatment (P < 0·01 for both).

CONCLUSIONS

Intermittent teriparatide treatment may adversely affect some parameters of glucose metabolism, inflammation and endothelial function. On the basis of our findings, further large-scale and controlled studies are needed to clarify the exact effect of teriparatide treatment on glucose metabolism, inflammation and endothelial function.

Bone Strength and Arterial Stiffness Impact on Cardiovascular Mortality in a General Population

Osteoporosis and increased arterial stiffness independently have been found to be associated with higher cardiovascular events rates in the general population (GP). We examined 558 patients from GP by dual-energy X-ray absorptiometry (DXA) and pulse wave velocity (PWV) measurements at baseline, with 36-month follow-up period. DXA assessed bone mineral density of femoral neck (BMD FN) and lumbar spine (BMD LS). Carotid-femoral PWV was assessed by pulsed-Doppler. The aim of our study is to find correlation between bone strength and arterial stiffness and their impact on cardiovascular mortality in GP. The mean ± SD of BMD FN, BMD LS, and PWV was 0.852 ± 0.1432 g/cm(2), 0.934 ± 0.1546 g/cm(2), and 9.209 ± 1.9815 m/s. In multiple regression analysis we found BMD FN (βst = -6.0094, p < 0.0001), hypertension (βst = 1.7340, p < 0.0091), and diabetes (βst = 0.4595, p < 0.0046). With Cox-regression analysis, after 17 cardiovascular events, the significant covariates retained by the backward model were BMD FN (b = -2.4129, p = 0.015) and PWV (b = 0.2606, p = 0.0318). The cut-off values were PWV = 9.4 m/s, BMD FN = 0.783 g/cm(2), and BMD LS = 0.992 g/cm(2). The results for BMD FN and PWV hazard ratio risk were 1.116 and 1.297, respectively. BMD FN as a measure of bone strength and PWV as a measure of arterial stiffness are strong independent predictors of cardiovascular mortality in GP.

Prevalence of carotid artery calcification in postmenopausal women and its correlation with atherogenic risk factors

Aim:

The aim of the present study was to determine the prevalence of carotid artery calcification (CAC) in postmenopausal females on panoramic radiographs and to study the correlation of CAC with possible risk factors such as hypertension, osteoporosis, and hypercholesterolemia, among others.

Materials and Methods:

Totally, 1214 panoramic radiographs of postmenopausal females attending the Department of Oral Medicine and Radiology were examined for the presence of CAC. The subjects were also assessed for the presence of various risk factors and the possible correlation to CAC. Statistical analysis was done using Chi-square test, and P < 0.05 was considered to be statistically significant.

Results:

Two hundred and seventy-eight postmenopausal females presented with CAC and a prevalence of 22.9%. These patients presented with a medical history that was laden with risk factors, of which hypertension (71.2%) was the most common risk factor. Hypertension, hypercholesterolemia, osteoporosis, and obesity were significantly (P < 0.05) related to the presence of CAC while age, diabetes, and smoking were not significantly (P > 0.05) related to CAC.

Conclusion:

The incidental finding of CAC on panoramic radiographs during the routine dental examination can provide life-saving information for the identification of postmenopausal females who are at a higher risk for stroke. Oral clinicians should, therefore, record a proper medical history of such patients to identify the atherogenic risk factors and refer such patients to the physician for careful evaluation and conformation of the disease.

Effects of hindlimb unloading and ionizing radiation on skeletal muscle resistance artery vasodilation and its relation to cancellous bone in mice

Spaceflight has profound effects on vascular function as a result of weightlessness that may be further compounded by radiation exposure. The purpose of the present study was to assess the individual and combined effects of hindlimb unloading (HU) and radiation (Rad) on vasodilator responses in the skeletal muscle vasculature. Adult male C57BL/6J mice were randomized to one of four groups: control (Con), HU (tail suspension for 15 days), Rad (200 cGy of (137)Cs), and HU-Rad (15-day tail suspension and 200 cGy of (137)Cs). Endothelium-dependent vasodilation of gastrocnemius feed arteries was assessed in vitro using acetylcholine (ACh, 10(-9)-10(-4) M) and inhibitors of nitric oxide synthase (NOS) and cyclooxygenase (COX). Endothelium-independent vasodilation was assessed using Dea-NONOate (10(-9)-10(-4) M). Endothelium-dependent and -independent vasodilator responses were impaired relative to Con responses in all treatment groups; however, there was no further impairment from the combination of treatments (HU-Rad) relative to that in the HU and Rad groups. The NOS-mediated contribution to endothelium-dependent vasodilation was depressed with HU and Rad. This impairment in NOS signaling may have been partially compensated for by an enhancement of PGI2-mediated dilation. Changes in endothelium-dependent vasodilation were also associated with decrements in trabecular bone volume in the proximal tibia metaphysis. These data demonstrate that the simulated space environment (i.e., radiation exposure and unloading of muscle and bone) significantly impairs skeletal muscle artery vasodilation, mediated through endothelium-dependent reductions in NOS signaling and decrements in vascular smooth muscle cell responsiveness to NO.

Small vessel disease/white matter disease of the brain and its association with osteoporosis

BACKGROUND

Evidence now suggests the role of neural effect on bone mass control. The effect of small vessel disease of the brain on osteoporosis has not been studied. The aim of this study was to investigate the association of white matter disease (WMD) of the brain with osteoporosis in the elderly.

METHODS

In this retrospective cross-sectional study, 780 consecutive patient charts between 2010 and 2011 were reviewed in the Senior's Outpatient Clinic at the University of Alberta Hospital. Subjects with brain computerized tomography (CT) were included in the study. Subjects with incomplete information, intracranial hemorrhage, acute stroke, cerebral edema, and/or normal pressure hydrocephalus on the CT were excluded. WMD was quantified on CT using Wahlund's scoring protocol. Osteoporosis information was obtained from the chart, which has been diagnosed based on bone mineral density (BMD) information. Logistic regression analysis was done to determine the association of WMD severity with osteoporosis after controlling for confounding vascular risk factors.

RESULTS

Of the 505 subjects who were included in the study, 188 (37%) had osteoporosis and 171 (91%) of these osteoporotic subjects were females. The mean age was 79.8 ± 7.04 years. The prevalence of WMD in osteoporosis subjects was 73%. In the unadjusted logistic regression analysis, there was a significant association between WMD severity and osteoporosis (odds ratio (OR): 1.10; 95% confidence interval (CI): 1.05 - 1.14; P < 0.001) and the significance remained in the adjusted model, after correcting for age, sex and all vascular risk factors (OR: 1.11; 95% CI: 1.05 - 1.18; P < 0.001).

CONCLUSION

WMD severity of the brain was associated with osteoporosis in the elderly.

Effects of skeletal unloading on the vasomotor properties of the rat femur principal nutrient artery

Spaceflight and prolonged bed rest induce deconditioning of the cardiovascular system and bone loss. Previous research has shown declines in femoral bone and marrow perfusion during unloading and with subsequent reloading in hindlimb-unloaded (HU) rats, an animal model of chronic disuse. We hypothesized that the attenuated bone and marrow perfusion may result from altered vasomotor properties of the bone resistance vasculature. Therefore, the purpose of this study was to determine the effects of unloading on the vasoconstrictor and vasodilator properties of the femoral principal nutrient artery (PNA), the main conduit for blood flow to the femur, in 2 wk HU and control (CON) rats. Vasoconstriction of the femoral PNA was assessed in vitro using norepinephrine, phenylephrine, clonidine, KCl, endothelin-1, arginine vasopressin, and myogenic responsiveness. Vasodilation through endothelium-dependent [acetylcholine, bradykinin, and flow-mediated dilation (FMD)] and endothelium-independent mechanisms [sodium nitroprusside (SNP) and adenosine] were also determined. Vasoconstrictor responsiveness of the PNA from HU rats was not enhanced through any of the mechanisms tested. Endothelium-dependent vasodilation to acetylcholine (CON, 86 ± 3%; HU, 48 ± 7% vasodilation) and FMD (CON, 61 ± 9%; HU, 11 ± 11% vasodilation) were attenuated in PNAs from HU rats, while responses to bradykinin were not different between groups. Endothelium-independent vasodilation to SNP and adenosine were not different between groups. These data indicate that unloading-induced decrements in bone and marrow perfusion and increases in vascular resistance are not the result of enhanced vasoconstrictor responsiveness of the bone resistance arteries but are associated with reductions in endothelium-dependent vasodilation.

Rapid increase in marrow fat content and decrease in marrow perfusion in lumbar vertebra following bilateral oophorectomy: an MR imaging-based prospective longitudinal study

Objective

Bilateral oophorectomy leads to reduced bone mineral density (BMD), and reduced BMD is associated with increased marrow fat and reduced marrow perfusion. Purpose of this study was to investigate how soon these changes occur following surgical oophorectomy.

Materials and Methods

Six patients who underwent hysterectomy and bilateral salpingo-oophorectomy were studied. At baseline, mean patient age was 49.5 years (range: 45-54 years). Third lumbar vertebral body BMD measurement using quantitative CT, marrow fat fraction (FF) using MR spectroscopy and marrow perfusion using dynamic contrast enhanced MRI were conducted immediately prior to surgery and at 3, 9, and 21 months after surgery.

Results

Reduced BMD, increased marrow FF, and reduced marrow perfusion occurred synchronously post-oophorectomy. There was a sharp decrease of 12.5 ± 7.2% in BMD (n = 6), a sharp increase of 92.2 ± 46.3% (n = 6) in FF, a sharp decrease of 23.6 ± 3.9% in maximum contrast enhancement (n = 5), and of 45.4 ± 7.7% for enhancement slope (n = 5) during the initial 3 months post surgery. BMD and marrow perfusion continued to decrease, and marrow FF continued to increase at a slower rate during the following 18 months. Friedman test showed a significant trend for these changes (p < 0.05).

Conclusion

Bilateral oophorectomy leads to a rapid decrease in lumbar BMD, an increase in marrow fat content, and a decrease in marrow blood perfusion.

Prolyl hydroxylase inhibitors protect from the bone loss in ovariectomy rats by increasing bone vascularity

The hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathway is involved in skeletal development, bone repair, and postmenopausal osteoporosis. Inhibitors of prolyl hydroxylases (PHD) enhance vascularity, increase callus formation in a stabilized fracture model, and activate the HIF-1α/VEGF pathway. This study examined the effects of estrogen on the HIF-1α/VEGF pathway in osteoblasts and whether PHD inhibitors can protect from bone loss in postmenopausal osteoporosis. Osteoblasts were treated with estrogen, and expressions of HIF-1α and VEGF were measured at mRNA (qPCR) and protein (Western blot) levels. Further, osteoblasts were treated with inhibitors of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway, and levels of VEGF mRNA and protein expression were detected. In addition, ovariectomized rats were treated with PHD inhibitors, and bone microarchitecture and bone mechanical strength were assessed using micro-CT and biomechanical analyses (lower ultimate stress, modulus, and stiffness). Blood vessel formation was measured with India Ink Perfusion and immunohistochemistry. Estrogen, in a dose- and time-dependent manner, induced VEGF expression at both mRNA and protein levels and enhanced HIF-1α protein stability. Further, the estrogen-induced VEGF expression in osteoblasts involved the PI3K/Akt pathway. PHD inhibitors increased bone mineral density, bone microarchitecture and bone mechanical strength, and promoted blood vessel formation in ovariectomized rats. In conclusion, estrogen and PHD inhibitors activate the HIF-1α/VEGF pathway in osteoblasts. PHD inhibitors can be utilized to protect bone loss in postmenopausal osteoporosis by improving bone vascularity and angiogenesis in bone marrow.

Coronary microvascular endothelial dysfunction is an independent predictor of development of osteoporosis in postmenopausal women

BACKGROUND

A growing body of evidence links coronary artery atherosclerosis and calcification to osteoporosis in women. The endothelium plays a critical role in maintaining vascular integrity and may play a role in bone metabolism. We aimed to determine whether early coronary atherosclerosis, as detected by coronary microvascular endothelial dysfunction (CMED), predicts the development of osteoporosis in postmenopausal women.

METHODS

Coronary vascular reactivity was evaluated in 194 postmenopausal women greater than 50 years of age and with non-obstructive coronary arteries by administration of intracoronary acetylcholine during diagnostic angiography. CMED was defined as ≤50% increase in coronary blood flow from baseline in response to maximal dose. After a median follow-up of 7.0±0.3 years, patients were assessed by a questionnaire for development of osteoporosis.

RESULTS

The average age of the cohort was 60.9±7.4 years. Women with CMED were twice as likely to develop osteoporosis compared with women without endothelial dysfunction after adjustment for potential confounders (relative risk, 2.4; 95% confidence interval [CI], 1.1, 5.6, P=0.02). Epicardial endothelial dysfunction was not associated with development of osteoporosis.

DISCUSSION

Early coronary atherosclerosis with endothelial dysfunction is an independent marker for increased risk of developing osteoporosis in postmenopausal women greater than 50 years of age without obstructive coronary artery disease. The current study supports a link between coronary atherosclerosis and osteoporosis.

Sulfonylureas and risk of falls and fractures: a systematic review

BACKGROUND

Sulfonylureas have been linked to increased risk of hypoglycemia. Hypoglycemia may lead to falls, and falls may lead to fracture. However, studies quantifying the association between sulfonylureas and fractures are sparse and yield inconsistent results.

OBJECTIVE

The purpose of this article was to review the literature regarding sulfonylurea use and falls or fall-related fractures among older adults with type 2 diabetes mellitus and to delineate areas for future research.

DATA SOURCES

We searched MEDLINE (1966-March 2012) and CINAHL (1937-March 2012) for studies of patients with type 2 diabetes mellitus living in the community or nursing homes.

STUDY SELECTION

The search algorithms combined three domains: (1) diabetic patients, (2) sulfonylurea medications, and (3) fractures or falls. We included only publications in English that pertained to human subjects. We found 9 randomized trials and 12 non-experimental studies that met the inclusion criteria.

STUDY APPRAISAL AND SYNTHESIS METHODS

The guidelines provided by the Cochrane handbook or Agency for Healthcare Research and Quality (AHRQ) Methods Guide are too general to distinguish the quality of included non-experimental studies, so we developed several specific domains based on those general guidelines. These domains included study design, study population, follow-up time, comparison group, exposure definition, outcome definition, induction period, confounding adjustment, and attrition or missing data. The data were not amenable to a meta-analysis.

RESULTS

No clinical trials included fracture as a primary endpoint. Most clinical trials excluded older adults. Most studies were not designed to evaluate the risk of sulfonylureas on fractures or falls. Studies did not show an increased risk of falls/fractures with sulfonylurea.

LIMITATIONS

The data available from existing studies suffer from methodological limitations including insufficient events, lack of primary endpoints, exclusion of older adults, and lack of clarity or inappropriate comparison groups.

CONCLUSION

Future studies are needed to appropriately estimate the effect of sulfonylureas on falls or fall-related fractures in older adults who are at increased risk for hypoglycemia, the hypothesized mechanism for fractures related to sulfonylurea therapy.

Systemic treatment with telmisartan improves femur fracture healing in mice

Recent clinical studies indicated that angiotensin receptor blockers (ARBs) would decrease the risk of bone fractures in the elderly populations. There is little known about the role of the ARBs in the process of fracture healing. The purpose of the present study was to verify the hypothesis that systemic treatment with telmisartan has the ability to promote fracture healing. In this study, femur fractures were produced in 96 mature male BALB/c mice. Animals were treated with the ARBs telmisartan or vehicle. Fracture healing was analysed after 2, 5 and 10 weeks postoperatively using X-ray, biomechanical testing, histomorphometry, immunohistochemistry and micro-computed tomography (micro-CT). Radiological analysis showed the diameter of the callus in the telmisartan treated animals was significantly increased when compared with that of vehicle treated controls after two weeks of fracture healing. The radiologically observed promotion of callus formation was confirmed by histomorphometric analyses, which revealed a significantly increased amount of bone formation when compared with vehicle-treated controls. Biomechanical testing further showed a significantly greater peak torque at failure, and a higher torsional stiffness in telmisartan-treated animals compared with controls. There was an increased fraction of PCNA-positive cells and VEGF-positive cells in telmisartan-treated group compared with vehicle-treated controls. From the three-dimensional reconstruction of the bony callus, telmisartan-treated group significantly increased the values of BV/TV by 21.7% and CsAr by 26.0% compared to the vehicle-treated controls at 5 weeks post-fracture. In summary, we demonstrate in the current study that telmisartan could promote fracture healing in a mice model via increasing mechanical strength and improving microstructure. The most mechanism is probably by an increase of cell proliferation and neovascularization associated with a decreased VEGF expression in hypertrophic chondrocytes.

Endothelium and its alterations in cardiovascular diseases: life style intervention

The endothelium, which forms the inner cellular lining of blood vessels and lymphatics, is a highly metabolically active organ that is involved in many physiopathological processes, including the control of vasomotor tone, barrier function, leukocyte adhesion, and trafficking and inflammation. In this review, we summarized and described the following: (i) endothelial cell function in physiological conditions and (ii) endothelial cell activation and dysfunction in the main cardiovascular diseases (such as atherosclerosis, and hypertension) and to diabetes, cigarette smoking, and aging physiological process. Finally, we presented the currently available evidence that supports the beneficial effects of physical activity and various dietary compounds on endothelial functions.

Increased risk for bone loss in women with systemic sclerosis: a comparative study with rheumatoid arthritis

AIM

To assess bone mass in women with systemic sclerosis (SSc) in comparison to age and sex-matched patients with rheumatoid arthritis (RA), and to evaluate factors influencing bone mineral density (BMD).

METHODS

Patients were consecutively recruited and assessed for BMD at the lumbar spine and hip by dual-energy X-ray absorptiometry (DEXA) using a densitometer. In SSc, the extent of skin involvement, modified Rodnan skin thickness score (mRSS) and Medsger disease severity index were assessed.

RESULTS

Forty-three patients with SSc and 38 age-matched patients with RA were included. There was no difference in BMD measurements between patients with diffuse or limited SSc. Patients with SSc had similar risk factors associated with osteoporosis (OP) or low bone mass except for low body mass index (BMI) and low vitamin D levels compared to patients with RA. Lumbar spinal BMD and T score were similar between groups. Total hip and femoral neck BMD and T score at femoral neck and total hip were significantly lower in patient with SSc versus RA. There was significant association between mRSS, Medsger severity score (peripheral vascular involvement and skin) and femoral BMD.

CONCLUSION

There is an increased risk for bone loss in patients with SSc and the risk of OP is associated with disease severity, prolonged menopause and disease duration. The complex pathophysiology of bone metabolism as well as complex pathogenesis of the SSc pose some difficulty reaching clear-cut conclusions on the causal relationship between SSc and bone loss.

Pulse Wave Velocity in Postmenopausal Women

Cardiovascular disease (CVD) and osteoporosis are major causes of morbidity and mortality in postmenopausal women. The relationship between atherosclerosis and osteoporosis has been established by studies of the underlying pathophysiological mechanisms and biochemical pathways that seem to overlap in many places. Pulse wave velocity (PWV) is one of the known predictors of cardiovascular and all-cause mortality. Studies indicate that PWV in hypertensive postmenopausal women is increased, and hormone replacement therapy (HRT) attenuates this increase. In addition, recently, many studies have suggested a role for arterial stiffness in the association between CVD and osteoporosis. From these findings, it appears that estrogen deficiency combined with production of inflammatory cytokines plays a role in increased PWV closely associated with CVD and osteoporosis, although the mechanisms of arterial stiffness in postmenopausal women may be more complex. Accordingly, a possible role for PWV as a surrogate marker of CVD as well as osteoporosis in postmenopausal women is discussed in this review. First, menopause leads to increased arterial stiffness with aging in females. Further, epidemiological data evaluating arterial stiffness assessed by PWV provided evidence that most of the established CVD risk factors are determinants of PWV, and these risk factors are increased in patients with CVD. In turn, contrary to expectation, HRT did not always contribute to a lower incidence of CVD in postmenopausal women. By reviewing the current data available, it becomes clear that, at present, the effects of menopause including HRT on PWV remain controversial, and further studies are needed to clarify these associations.

Pancreas-kidney transplantation is associated with reduced fracture risk compared with kidney-alone transplantation in men with type 1 diabetes

Both type 1 diabetes mellitus and end stage renal disease are associated with increased fracture risk, likely due to metabolic abnormalities that reduce bone strength. Simultaneous pancreas-kidney transplantation is a treatment of choice for patients with both disorders, yet the effects of simultaneous pancreas-kidney versus kidney transplantation alone on post-transplantation fracture risk are unknown. From the United States Renal Data System we identified 11, 145 adults with type 1 diabetes undergoing transplantation of whom 4,933 had a simultaneous pancreas-kidney while 6, 212 had a kidney alone transplant between 2000 and 2006. Post-transplantation fractures resulting in hospitalization were identified from discharge codes. Time to first fracture was modeled and propensity score adjustment was used to balance covariates between groups. Fractures occurred in significantly fewer (4.7%) of pancreas-kidney compared to kidney-alone transplant (5.9%) cohorts. After gender stratification and adjustment for fracture covariates, pancreas-kidney transplantation was associated with a significant 31% reduction in fracture risk in men (hazard risk 0.69). Older age, white race, prior dialysis and pre transplantation fracture were also associated with increased fracture risk. Prospective studies are needed to determine the gender-specific mechanisms by which pancreas-kidney transplantation reduces fracture risk in men.

Bone Mineral Density as a Predictor of Atherosclerosis and Arterial Wall Stiffness in Obese African-American Women

Bone demineralization is associated with higher cardiovascular event rates, possibly due to vascular calcification and accelerated atherosclerosis. African-Americans have less bone loss and less calcium content within atherosclerotic plaques. However, whether loss of bone mass is related to atherosclerosis has not been examined in African-Americans. The objective of this study was to evaluate possible associations between bone mineral density (BMD), carotid intimal-medial thickness (CIMT), and arterial stiffness. We studied 100 obese African-American women (BMI: 26.6 ± 6.2; age: 63 ± 14 years) referred for BMD estimation by dual-energy X-ray absorptiometry scan. BMD (g/cm(2)) was obtained at the lumbar spine (L1-L4), femoral neck, and total hip. Arterial stiffness was evaluated by the heart rate-corrected augmentation index (AI@75) and pulse wave velocity (PWV) using applanation tonometry. CIMT was measured by vascular ultrasound. Mean CIMT, AI@75, and PWV were 0.72 ± 0.14 mm, 28.8 ± 9.0%, and 8.9 ± 1.6 m/s, respectively. Mean BMD values at the lumbar spine, femoral neck, and hip were 0.96 ± 0.19, 0.80 ± 0.16, and 0.91 ± 0.17 g/cm(2). Older subjects had higher CIMT (r = 0.61, p < 0.001) and AI@75 (r = 0.42, p < 0.001). There was a significant correlation between AI@75 and CIMT (r = 0.45, p < 0.001). BMD was negatively correlated with AI@75 (lumbar: r = -0.22, p = 0.03; femoral neck: r = -0.24, p = 0.01; hip: r = -0.21, p = 0.03). BMD was unrelated to CIMT (lumbar: r = -0.09, p = 0.42; femoral neck: r = -0.15, p = 0.17; hip: r = -0.13, p = 0.23). On multivariate analysis, age (p < 0.001), hypertension (p = 0.02), and lumbar BMD (p = 0.01, R(2) = 0.30) were independent predictors of increased AI@75 after adjusting for age, height, and cardiovascular risk factors. These findings were unchanged upon substitution of femoral neck BMD (p = 0.05, R(2) = 0.28) into the model. There was a trend with hip BMD (p = 0.06, R(2) = 0.28) in the regression model. Age-matched comparison between normal BMD (n = 25) and osteoporotic patients (n = 34) demonstrated a significant difference in AI@75 (26.6 ± 8.9 vs. 31.6 ± 9.1%, p = 0.04). In summary, women with lower BMD had increased arterial stiffness. There was no relationship between BMD and atherosclerosis. In conclusion, age, hypertension, and BMD are independent predictors of higher arterial stiffness. Vascular changes are related to bone mineral loss, suggesting lower BMD may increase cardiovascular risk in African-Americans.

Aging and estrogen status: a possible endothelium-dependent vascular coupling mechanism in bone remodeling

Bone loss with aging and menopause may be linked to vascular endothelial dysfunction. The purpose of the study was to determine whether putative modifications in endothelium-dependent vasodilation of the principal nutrient artery (PNA) of the femur are associated with changes in trabecular bone volume (BV/TV) with altered estrogen status in young (6 mon) and old (24 mon) female Fischer-344 rats. Animals were divided into 6 groups: 1) young intact, 2) old intact, 3) young ovariectomized (OVX), 4) old OVX, 5) young OVX plus estrogen replacement (OVX+E2), and 6) old OVX+E2. PNA endothelium-dependent vasodilation was assessed in vitro using acetylcholine. Trabecular bone volume of the distal femoral metaphysis was determined by microCT. In young rats, vasodilation was diminished by OVX and restored with estrogen replacement (intact, 82±7; OVX, 61±9; OVX+E2, 90±4%), which corresponded with similar modifications in BV/TV (intact, 28.7±1.6; OVX, 16.3±0.9; OVX+E2, 25.7±1.4%). In old animals, vasodilation was unaffected by OVX but enhanced with estrogen replacement (intact, 55±8; OVX, 59±7; OVX+E2, 92±4%). Likewise, modifications in BV/TV followed the same pattern (intact, 33.1±1.6; OVX, 34.4±3.7; OVX+E2, 42.4±2.1%). Furthermore, in old animals with low endogenous estrogen (i.e., intact and old OVX), vasodilation was correlated with BV/TV (R² = 0.630; P<0.001). These data demonstrate parallel effects of estrogen on vascular endothelial function and BV/TV, and provide for a possible coupling mechanism linking endothelium-dependent vasodilation to bone remodeling.

Osteoprotegerin, but not osteopontin, as a potential predictor of vascular calcification in normotensive subjects

We conducted a cross-sectional observation study that included 500 asymptomatic subjects to investigate the relationship between bone metabolism and coronary artery calcification (CAC) in hypertensive conditions. Osteoprotegerin (OPG) and osteopontin (OPN) levels and their associations with hypertension were analyzed to predict CAC in 316 subjects. Multislice computed tomography was used to quantify CAC. Multivariate analysis of variance was used to test the non-interactive effects of hypertension, CAC severity and biomarker levels, and the logistic regression model was applied to predict the risk of CAC. OPG and OPN concentrations were significantly higher in the hypertensive than the normotensive subjects, at 3.0 (2.3-4.0) pmol l(-1) and 51 (21-136) ng ml(-1) vs. 2.4 (2.0-3.0) pmol l(-1) and 41 (13-63) ng ml(-1), respectively. The OPG level, but not OPN level, increased with age (r = 0.29; P = 0.0001). Zero or minimal CAC (<10 Agatston units (AU)) was observed in 63% of the subjects, mild (11-100 AU) in 17%, moderate (101-400 AU) in 12% and severe (401-1000 AU)-to-extensive (>1000 AU) in 8%. In hypertensive subjects, only glomerular filtration rate (GFR) (β = -0.67) and gender (β = 0.52) were significant predictors for CAC (R = 0.68). In normotensive patients, GFR (β = -0.81), gender (β = 0.48) and log-transformed OPG levels (β = 0.15) were significant predictors for CAC. OPG levels were associated with an increased risk of CAC in normotensive subjects only (odds ratio: 3.37; 95% confidence interval (1.63-6.57); P = 0.0002). OPG predicted a premature state of vascular calcification in asymptomatic normotensive individuals, and renal function significantly contributed to this process in both hypertensive and normotensive subjects.

Acute myocardial infarction and atherosclerosis of the coronary arteries in patients treated with drugs against osteoporosis: calcium in the vessels and not the bones?

We studied the association between bisphosphonate use and risk of acute myocardial infarction (AMI) or atherosclerosis of the coronary vessels using a nationwide retrospective cohort from Denmark. All users of bisphosphonates and other drugs against osteoporosis between 1996 and 2006 (n = 103,562) comprised the exposed group and three age- and gender-matched controls from the general population (n = 310,683), the unexposed group. The main outcomes were occurrence of AMI or atherosclerosis of the coronary vessels. An excess risk of AMI was seen in users of alendronate compared to the unexposed. However, an inverse dose-response relationship was seen, with an increased risk in those with low adherence (≤0.66 DDD, HR = 1.50, 95% CI 1.24-1.82) and a nonsignificantly decreased risk in those who were adherent to the drug (≥1 DDD, HR = 0.80, 95% CI 0.59-1.09; P for trend <0.01). For etidronate and raloxifene, no excess risk was present and no dose-response relationship was seen. For atherosclerosis of the coronary vessels, a similar trend as for AMI was seen for alendronate but a protective effect was present at high doses (≥1 DDD, HR = 0.58, 95% CI 0.49-0.70). For etidronate, an increased risk of atherosclerosis was seen at all doses, with no dose-response relationship. For raloxifene, no excess of atherosclerosis was observed. At high doses of alendronate a decreased risk of atherosclerosis of the coronary vessels was seemingly present, whereas at low doses an increased risk was present. The finding may be spurious due to the "healthy user" effect, but a causal relationship cannot be excluded.

Nitrate patch prevents steroid-related bone necrosis

Avascular necrosis of the femoral head is a common complication with disabling effect for young patients after high-dose corticosteroid treatment. We could show that steroids have a vasoconstrictive effect on lateral epiphyseal arteries of the femoral head which could lead to ischemia and subsequent necrosis. In this study we investigated the preventive effect of a nitrate patch on steroid-related bone necrosis in a rabbit model. New Zealand White rabbits (male; 3-4.5 kg bodyweight) were injected with 20 mg/kg bodyweight methylprednisolone (GC group; n = 6). Control animals (n = 6) were treated with phosphate-buffered saline. A third group (GC + N; n = 6) additionally received a nitrate patch (0.675 mg/day). Four weeks after i.m. methylprednisolone injection the animals were sacrificed. For histology and immunohistochemistry, tissue samples were fixed in 3% paraformaldehyde, embedded in paraffin, sectioned, dewaxed, and stained with Ladewig. For quantification of empty lacunae, a histologic sign of FHN, histomorphometry was performed. Histomorphometry revealed a significant increase of empty lacunae in glucocorticoid-treated animals compared to controls and GC + N-treated animals. No significant difference in empty lacunae count was detected between the GC + N group and controls. HE staining revealed the different osteocyte amount in the GC versus GC and nitrate patch-treated groups. This study demonstrates an increased number of empty osteocyte lacunae representing a pathologic feature of osteonecrosis, in the GC group. Less empty lacunae were counted in the GC animals after additional treatment with a nitrate patch. This finding suggests that nitrate co-treatment has the potential to prevent steroid-associated FHN.

Osteoporotic fractures and heart failure in the community

PURPOSE

Recent findings suggest a role for heart failure in the etiology of osteoporotic fractures, yet the temporal sequence of occurrence of the 2 conditions needs clarification.

METHODS

Using the Rochester Epidemiology Project, the authors conducted a 2-phase study: a case-control study compared osteoporotic fracture history among Olmsted County, Minnesota, residents newly diagnosed with heart failure in 1979-2002 with age- and sex-matched community controls without heart failure (961 pairs; mean age 76 years; 54% women). Both groups were then followed to July 2009 to evaluate their subsequent fracture risk in a cohort study.

RESULTS

Prior fractures were more frequent in heart failure cases than controls (23.1% vs. 18.8%, P=.02). The adjusted odds ratio (OR) for heart failure associated with prior fracture was 1.39 (95% confidence interval [CI], 1.07-1.81), mainly driven by hip fractures (OR 1.82; 95% CI, 1.25-2.66) with little or no association with other fractures. Over a mean follow-up of 7.5 years, 444 individuals developed subsequent osteoporotic fractures. The adjusted fracture risk was marginally elevated in heart failure patients compared with controls (hazard ratio [HR] 1.32; 95% CI, 0.98-1.79), again largely attributable to hip fractures (HR 1.58; 95% CI, 1.03-2.41).

CONCLUSIONS

In this community, the association with fracture risk was about as strong before as after the diagnosis of heart failure and was nearly entirely attributable to hip fractures. Additional work is needed to identify common underlying mechanisms for heart failure and hip fracture, which may define prevention opportunities.

Prediction of bone loss in elderly female subjects by MR perfusion imaging and spectroscopy

OBJECTIVE

To determine whether MR perfusion indices or marrow fat content at baseline can predict areal bone mineral density (BMDa) loss.

METHODS

Repeat dual x-ray absorptiometry (DXA) of the hip was performed in female subjects at 2 years (n = 52) and 4 years (n = 45) following baseline MR perfusion imaging and spectroscopy of the hip.

RESULTS

Percentage reduction in femoral neck BMDa at 4 years post-baseline was greater in subjects with below median acetabulum enhancement slope (E(slope)) (-5.6 ± 1.2 Vs -1.1 ± 1.2 (mean ± standard error) p = 0.014) or muscle maximum enhancement (E(max)) (-5.7 ± 1.2 Vs -0.23 ± 1.2, p = 0.009) after adjusting for baseline co-variables. Baseline MR parameters correlated with reduction in BMDa at 4 years (acetabulum E(slope) r = 0.517, p = 0.0003; muscle E(max) r = 0.306, p = 0.043) as well as traditionally applied clinical risk factors. Acetabulum E(slope), femoral neck E(max) and marrow fat content at baseline had sensitivities of 89%, 81% and 72% respectively at distinguishing between fast (>1%/annum) (n = 18) and slow (<1%/annum) (n = 27) BMD losers.

CONCLUSION

Elderly female subjects with reduced perfusion indices at baseline had increased femoral neck bone loss at 4 years. Selected perfusion indices and marrow fat content have a moderate to high sensitivity in discriminating between fast and slow bone losers.

Osteopenia and endothelin-1-mediated vasconstrictor tone in postmenopausal women

Low bone mineral density is highly prevalent in postmenopausal women. Osteopenia in postmenopausal women is a predictor of adverse cardiovascular events. A potential mechanism contributing to the increased cardiovascular risk in postmenopausal women with osteopenia is endothelial vasomotor dysfunction. Endothelin (ET)-1 is a potent vasoconstrictor peptide that is associated with endothelial vasomotor dysfunction and increased cardiovascular risk. Currently, there is no information on osteopenia and ET-1 vasoconstrictor activity in postmenopausal women. We tested the hypothesis that ET-1 mediated vasoconstrictor activity is greater in postmenopausal women with osteopenia compared with those without. Forearm blood flow responses to intra-arterial infusion of BQ-123 (100 nmol/min for 60 min), a selective ET(A) receptor antagonist, were determined in postmenopausal women: 10 with osteopenia (age: 56+/-1 yr, lumbar spine T-score between -1.5 and -2.5) and 12 without osteopenia (age: 60+/-2 yr, T-score>-1.5). In women with osteopenia, forearm blood flow increased approximately 25% (P<0.05) in response to BQ-123. However, in the women without osteopenia, resting forearm blood flow was not significantly changed. In conclusion, these results suggest that osteopenia is associated with greater ET-1-mediated vasoconstrictor tone. Increased ET-1 vasoconstrictor activity may contribute to the elevated cardiovascular risk in postmenopausal women with osteopenia.

Lack of both bradykinin B1 and B2 receptors enhances nephropathy, neuropathy, and bone mineral loss in Akita diabetic mice

An insertion polymorphism of the angiotensin-I converting enzyme gene (ACE) is common in humans and the higher expressing allele is associated with an increased risk of diabetic complications. The ACE polymorphism does not significantly affect blood pressure or angiotensin II levels, suggesting that the kallikrein-kinin system partly mediates the effects of the polymorphism. We have therefore explored the influence of lack of both bradykinin receptors (B1R and B2R) on diabetic nephropathy, neuropathy, and osteopathy in male mice heterozygous for the Akita diabetogenic mutation in the insulin 2 gene (Ins2). We find that all of the detrimental phenotypes observed in Akita diabetes are enhanced by lack of both B1R and B2R, including urinary albumin excretion, glomerulosclerosis, glomerular basement membrane thickening, mitochondrial DNA deletions, reduction of nerve conduction velocities and of heat sensation, and bone mineral loss. Absence of the bradykinin receptors also enhances the diabetes-associated increases in plasma thiobarbituric acid-reactive substances, mitochondrial DNA deletions, and renal expression of fibrogenic genes, including transforming growth factor beta1, connective tissue growth factor, and endothelin-1. Thus, lack of B1R and B2R exacerbates diabetic complications. The enhanced renal injury in diabetic mice caused by lack of B1R and B2R may be mediated by a combination of increases in oxidative stress, mitochondrial DNA damage and over expression of fibrogenic genes.

Endothelial dysfunction and aging: an update

Aging is an important risk factor for the development of many cardiovascular diseases as atherosclerosis and hypertension with a common underlying circumstance: the progressive decline of endothelial function. Vascular endothelial dysfunction occurs during the human aging process and is accompanied by deterioration in the balance between vasodilator and vasoconstriction substances produced by the endothelium. This imbalance is mainly characterized by a progressive reduction of the bioavailability of nitric oxide (NO) and an increase in the production of cyclooxygenase (COX)-derived vasoconstrictor factors. Both circumstances are in turn related to an increased production of reactive oxygen and nitrogen species. The aim of this review is to describe the pathophysiological mechanisms involved in the endothelial function declination that accompanies the multifactorial aging process, including alterations related to oxidative stress and pro-inflammatory cytokines, senescence of endothelial cells and genetic factors.

Increased nitric oxide-mediated vasodilation of bone resistance arteries is associated with increased trabecular bone volume after endurance training in rats

Old age-associated osteoporosis is related to diminished bone blood flow and impaired nitric oxide (NO)-mediated vasodilation of the bone vasculature. Endurance exercise training restores the age-associated reduction of vasodilation in numerous vascular beds, as well as improving bone properties. The purpose of this study was to determine whether functional improvements in the bone vasculature are associated with increased bone properties after an endurance training intervention. Young adult (4-6 months) and old (24-26 months) male Fischer-344 rats remained sedentary or were trained (15 m/min walking, 15 degrees incline, 5 days/week, 10-12 weeks). Endothelium-dependent vasodilation of the femoral principal nutrient artery (PNA) was assessed in vitro using acetylcholine (ACh) and inhibitors of NO synthase (NOS) and cyclooxygenase (COX). PNA endothelium-dependent vasodilation was greater after training by 16% in young and by 24% in old animals. The NOS-mediated contribution to endothelium-dependent vasodilation was enhanced by 77% after training in old rats. Distal femur trabecular bone volume (BV/TV, %) was lower with old age in sedentary animals (young: 27+/-2%, old: 23+/-1%; P<0.05). Exercise-induced elevations in bone and marrow blood flow and the NOS signaling pathway were associated with greater BV/TV (young trained: 34+/-2%, old trained: 26+/-1%; P<0.05) relative to sedentary groups. These data demonstrate that training-induced increases in bone properties are associated with enhanced endothelium-dependent vasodilation through a NOS signaling pathway in the bone vasculature.

Differences in regional bone perfusion and turnover between lumbar spine and distal humerus: (18)F-fluoride PET study of treatment-naïve and treated postmenopausal women

The functional imaging technique of (18)F-fluoride positron emission tomography ((18)F-PET) allows the non-invasive assessment of regional bone blood perfusion and turnover. Bone perfusion and turnover measured using (18)F-PET correlate closely with those obtained experimentally and so they can be readily applied in clinical research studies. The aim of this study was to compare bone perfusion and turnover between the lumbar spine and humerus in both treatment naïve postmenopausal women (n=11) and those on stable antiresorptive therapy (n=12). All women had a BMD T-score of less than -2 at the spine and/or hip. Each woman had a dynamic PET scan of the lumbar spine and distal humerus after injection of 90 MBq (18)F-fluoride. Using a three-compartmental model bone perfusion (K(1)), the net plasma clearance of tracer to bone mineral (K(i)) reflecting regional bone turnover and the rate constants k(2)-k(4) describing the transport of fluoride between plasma, an extravascular bone compartment and bone mineral compartment were calculated. Mean bone perfusion (K(1)) and bone turnover (K(i)) were significantly higher at the lumbar spine compared to the humerus for both treatment-naïve and antiresorptive groups. K(1) values were on average 3 times greater while K(i) was approximately 50% greater at the lumbar spine. The rate constant k(2), the reverse transport of fluoride from the extravascular compartment to plasma, was significantly lower at the humerus compared to the lumbar spine in both groups. The ratio K(i)/K(1) describing the unidirectional extraction efficiency to bone mineral was significantly greater at the humerus compared to the lumbar spine for both study groups. No significant differences between skeletal sites were observed for k(3) or k(4). In conclusion a significant skeletal heterogeneity was observed in terms of bone perfusion and turnover between the lumbar spine and humerus. (18)F-PET may aid in our understanding of the importance of bone perfusion in osteoporosis and differences in regional bone turnover with disease and in response to therapy.

Reduced bone perfusion in proximal femur of subjects with decreased bone mineral density preferentially affects the femoral neck

Using dynamic contrast enhanced MR imaging, this study investigated perfusion of the proximal femur in subjects with normal BMD, low bone mass and osteoporosis. Study cohort comprised healthy elderly Hong Kong Chinese volunteers consisting of 107 males (74.4+/-4.2 years, mean+/-SD) and 135 females (73.9+/-4.3 years). Right proximal femur BMD measurement by DXA and MR perfusion imaging (maximum enhancement, E(max) and enhancement slope, E(slope)) of the femoral head, neck, and proximal shaft were carried out within a one month interval. Normal BMD, low bone mass and osteoporotic subjects accounted for 46.7%, 44.9%, and 8.4% of males; and 32.6%, 43.7%, and 23.7% of females. Perfusion indices showed that femoral head perfusion was less perfused compared to the femoral shaft (E(max) and E(slope) indices of head region=28% of shaft region). Compared with normal BMD subjects, E(max) of femoral head, neck, and proximal femur shaft were reduced by 15+/-5% (mean+/-standard error); 40+/-4%; 15+/-5% respectively for low bone mass subjects, and 36+/-4%; 50+/-6%; 47+/-6% respectively for osteoporotic subjects. E(slope) of femoral head, neck, and proximal femur shaft were reduced by 17+/-7%; 41+/-5%; 4+/-7% for low bone mass subjects and 50+/-5%, 62+/-5%, 34+/-8% for osteoporotic subjects. In low bone mass and osteoporotic subjects there was a tendency for perfusion in the femoral neck to reduce to a greater degree relative to that in the femoral head and shaft.

Could rusalatide acetate be the future drug of choice for diabetic foot ulcers and fracture repair?

Rusalatide acetate (Chrysalin) is an investigational drug being evaluated for treatment of chronic wounds and fractures. Rusalatide acetate interacts with cell surface receptors to stimulate a cascade of cellular and molecular wound healing events, including activation of nitric oxide signaling. Rusalatide acetate significantly accelerated healing of diabetic foot ulcers and distal radius fractures in Phase I/II clinical trials. Subsequently, in one of the largest Phase III fracture studies to date, rusalatide acetate showed significant acceleration of distal radius fracture healing radiographically but failed to meet its primary clinical endpoint - time to removal of immobilization - within the intent-to-treat population. Subset analysis showed that rusalatide acetate met this primary clinical endpoint and significantly accelerated radiographic healing in osteopenic women. Rusalatide acetate may therefore show its greatest efficacy in healing-impaired patients.

TP508 (Chrysalin) reverses endothelial dysfunction and increases perfusion and myocardial function in hearts with chronic ischemia

Endothelial dysfunction (ED) is characterized by impaired nitric oxide (NO) signaling, decreased NO-dependent vasodilatation, increased vascular inflammation, and diminished response to angiogenic factors. TP508 (Chrysalin), an angiogenic tissue repair peptide, was tested for potential effects on myocardial revascularization and ED using a porcine model of chronic myocardial ischemia. TP508 increased perfusion in ischemic regions up to16-fold (P < .02) and doubled myocardial wall thickening (P < .02) relative to placebo controls. Ischemic arterioles exhibited impaired NO-mediated vasodilation and diminished NO production. TP508 reversed ischemic effects, increasing NO-mediated vasodilation (P < .05), endothelial nitric oxide synthase (eNOS) expression, and NO production. In human endothelial cells, TP508 stimulated eNOS activation (1.84 +/- 0.2-fold; P < .02), increased NO production (85 +/- 18%; P < .02), and prevented hypoxia-induced eNOS downregulation (P < .01). Thus, TP508 reverses ED both in porcine ischemic hearts and cultured human endothelial cells. These results suggest potential therapeutic benefit of TP508 in myocardial revascularization and treatment of ED-related diseases.

Angiotensin II type 2 receptor blockade increases bone mass

Renin angiotensin system (RAS) regulates circulating blood volume and blood pressure systemically, whereas RAS also plays a role in the local milieu. Previous in vitro studies suggested that RAS may be involved in the regulation of bone cells. However, it was not known whether molecules involved in RAS are present in bone in vivo. In this study, we examined the presence of RAS components in adult bone and the effects of angiotensin II type 2 (AT2) receptor blocker on bone mass. Immunohistochemistry revealed that AT2 receptor protein was expressed in both osteoblasts and osteoclasts. In addition, renin and angiotensin II-converting enzyme were expressed in bone cells in vivo. Treatment with AT2 receptor blocker significantly enhanced the levels of bone mass, and this effect was based on the enhancement of osteoblastic activity as well as the suppression of osteoclastic activity in vivo. These results indicate that RAS components are present in adult bone and that blockade of AT2 receptor results in alteration in bone mass.

Compromised bone marrow perfusion in osteoporosis

A link between bone blood flow and osteoporosis may exist. Outside of the spine, the proximal femur is the most common site of osteoporotic fracture and is also an area prone to avascular necrosis and fracture nonunion. This study of the proximal femur investigates the relationship between BMD, bone marrow fat content, bone perfusion, and muscle perfusion. One hundred twenty healthy female subjects (mean age, 74 yr; age range, 67-89 yr) underwent DXA examination of the hip, proton MR spectroscopy, and dynamic contrast-enhanced MR imaging of the right proximal femur, acetabulum, and adductor thigh muscle. In all bone areas examined (femoral head, femoral neck, femoral shaft, acetabulum), perfusion indices (maximum enhancement, enhancement slope) were significantly reduced in subjects with osteoporosis compared with subjects with osteopenia or normal BMD. Adductor muscle perfusion was not affected by change in BMD. As marrow perfusion decreased in the proximal femur, marrow fat increased (r = 0.827). This increase in fat content seemed to account for the decrease in marrow perfusion more than a reduction in BMD. For normal BMD subjects, perfusion parameters in the femoral head were one third of those in the femoral neck or shaft and one fifth of those in the acetabulum. Perfusion throughout the proximal femur is reduced in osteoporotic subjects compared with osteopenic and normal subjects. This reduction in perfusion only affects bone and not those tissues outside of bone with the same blood supply. As bone perfusion decreased, there was a corresponding increase in marrow fat.

Nitroglycerin enhances proliferation and osteoblastic differentiation in human mesenchymal stem cells via nitric oxide pathway

AIM

To investigate the effect of nitroglycerin (NTG) on cell proliferation and osteoblastic differentiation of human bone marrow-derived mesenchymal stem cells (HBMSC) and its mechanisms.

METHODS

Primary HBMSC were cultured in osteogenic differentiation medium consisting of phenol red-free alpha-minimum essential media plus 10% fetal bovine serum (dextran-coated charcoal stripped) supplemented with 10 nmol/L dexamethasone, 50 mg/L ascorbic acid, and 10 mmol/L beta-glycerophosphate for inducing osteoblastic differentiation. The cells were treated with NTG (0.1-10 micromol/L) alone or concurrent incubation with different nitric oxide synthase (NOS) inhibitors. Nitric oxide (NO) production was measured by using a commercial NO kit. Cell proliferation was measured by 5-bromodeoxyuridine (BrdU) incorporation. The osteoblastic differentiation of HBMSC culture was evaluated by measuring cellular alkaline phosphatase (ALP) activity and calcium deposition, as well as osteoblastic markers by real-time RT-PCR.

RESULTS

The treatment of HBMSC with NTG (0.1-10 micromol/L) led to a dose-dependent increase of NO production in the conditional medium. The release of NO by NTG resulted in increased cell proliferation and osteoblastic differentiation of HBMSC, as evidenced by the increment of the BrdU incorporation, the induction of ALP activity in the early stage, and the calcium deposition in the latter stage. The increment of NO production was also correlated with the upregulation of osteoblastic markers in HBMSC cultures. However, the stimulatory effect of NTG (10 micromol/L) could not be abolished by either N(G ) -nitro-L-arginine methyl ester, an antagonist of endothelial NOS, or 1400W, a selective blocker of inducible NOS activity.

CONCLUSION

NTG stimulates cell proliferation and osteoblastic differentiation of HBMSC through a direct release of NO, which is independent on intracellular NOS activity.

Increased augmentation index and central aortic blood pressure in osteoporotic postmenopausal women

Osteoporosis has been associated with cardiovascular disease. We found increased augmentation index, a measure of wave reflections and arterial stiffness, and central pressures in osteoporotic postmenopausal women. They also showed a higher estimated aortic pulse wave velocity, indicating a stiffer aorta. These changes may increase cardiovascular risk in postmenopausal osteoporosis.

INTRODUCTION

Evidence suggests a link between osteoporosis and cardiovascular disease. We investigated whether augmentation index (AIx), a measure of pulse wave reflections and arterial stiffness, is increased and related to the osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL) system in postmenopausal osteoporosis.

METHODS

AIx and central aortic haemodynamics were assessed using pulse wave analysis in 182 cardiovascular disease-free osteoporotic postmenopausal women and in 160 controls. Statistical analysis was performed by unpaired t test, Mann-Whitney test, Spearman's correlation coefficient, and multivariate linear regression analysis.

RESULTS

AIx (37.2 +/- 7.0 vs. 29.6 +/- 9.2 %, P < 0.0001) and central aortic systolic (117.5 +/- 12.1 vs. 111.4 +/- 12.2 mmHg, P < 0.0001) and pulse (40.5 +/- 10.3 vs. 36.4 +/- 8.1 mmHg, P = 0.0007) pressures were significantly higher in osteoporotic patients than in controls. The estimated aortic pulse wave velocity (PWV) was also significantly higher in the osteoporotic group. In multivariate analysis for osteoporotic patients, femoral neck and lumbar spine bone mineral density T scores were independent negative predictors of AIx (P < 0.0001). AIx was not correlated with serum levels of OPG and RANKL.

CONCLUSIONS

Osteoporotic postmenopausal women show increased AIx and central aortic pressures, and a higher estimated aortic PWV, indicating a stiffer aorta. Such alterations may increase cardiovascular risk in postmenopausal osteoporosis.