Lipid oxidation products have opposite effects on calcifying vascular cell and bone cell differentiation. A possible explanation for the paradox of arterial calcification in osteoporotic patients

[Associations of lipoproteins with bone mass in postmenopausal women]

AIM

To study an association between blood lipid composition and bone mass in Russian postmenopausal women.

SUBJECTS AND METHODS

The cross-sectional study included 373 postmenopausal women aged 45-80 years who were examined to diagnose osteoporosis in outpatient settings. Height, body weight, and waist and hip circumferences (WC and HC) were measured before densitometry. Quetelet's index was calculated as a ratio of weight (kg) to height (m2). The concentration of lipids and apolipoproteins (apo) AІ and B were measured by enzyme immunoassay. Bone mineral density (BMD) in the spine and proximal femur (PF) was estimated by dual-energy X-ray absorptiometry.

RESULTS

According to bone mass, the patients were divided into three groups: 1) osteoporosis (OP); 2) osteopenia; 3) normal BMD. The levels of total cholesterol and high-density lipoprotein (HDL) cholesterol were significantly higher in the postmenopausal women with OP than in those with normal bone mass. There was a negative correlation of cholesterol and HDL cholesterol levels with lumbar spine BMD and that of HDL levels with BMD in the femoral neck (FN) and entire PF. The level of lipoprotein (a) (LPa) was significantly lower in the group of patients with OP and positively correlated with BMD in FN and entire PF. After adjustment for age, the duration of menopause, Quetelet's index, and WC/HC association remained only between LPa and FN BMD.

CONCLUSION

Multivariate regression analysis failed to confirm a trend towards decreased BMD and increased HDL cholesterol. This suggests that the association of HDL cholesterol with bone mass is apparently mediated by other factors and, above all, with age, postmenopausal hormonal status and body weight.

Calcific aortic stenosis

Calcific aortic stenosis (AS) is the most prevalent heart valve disorder in developed countries. It is characterized by progressive fibro-calcific remodelling and thickening of the aortic valve leaflets that, over years, evolve to cause severe obstruction to cardiac outflow. In developed countries, AS is the third-most frequent cardiovascular disease after coronary artery disease and systemic arterial hypertension, with a prevalence of 0.4% in the general population and 1.7% in the population >65 years old. Congenital abnormality (bicuspid valve) and older age are powerful risk factors for calcific AS. Metabolic syndrome and an elevated plasma level of lipoprotein(a) have also been associated with increased risk of calcific AS. The pathobiology of calcific AS is complex and involves genetic factors, lipoprotein deposition and oxidation, chronic inflammation, osteoblastic transition of cardiac valve interstitial cells and active leaflet calcification. Although no pharmacotherapy has proved to be effective in reducing the progression of AS, promising therapeutic targets include lipoprotein(a), the renin-angiotensin system, receptor activator of NF-κB ligand (RANKL; also known as TNFSF11) and ectonucleotidases. Currently, aortic valve replacement (AVR) remains the only effective treatment for severe AS. The diagnosis and staging of AS are based on the assessment of stenosis severity and left ventricular systolic function by Doppler echocardiography, and the presence of symptoms. The introduction of transcatheter AVR in the past decade has been a transformative therapeutic innovation for patients at high or prohibitive risk for surgical valve replacement, and this new technology might extend to lower-risk patients in the near future.

Circulating CD14(+) monocytes in patients with aortic stenosis

BACKGROUND

Calcific aortic stenosis (AS) is an active process sharing similarities with atherosclerosis and chronic inflammation. The pathophysiology of AS is notable for three cardinal components: inflammation, fibrosis and calcification. Monocytes play a role in each of these processes. The role of circulating monocytes in AS is not clear. The aim of the present study was to study an association between circulating apoptotic and non apoptotic CD14(+) monocytes and AS features.

METHODS

We assessed the number of CD14(+) monocytes and apoptotic monocytes in 54 patients with significant AS (aortic valve area 0.74 ± 0.27 cm(2)) and compared them to 33 patients with similar risk factors and no valvular disease. The level of CD14(+) monocytes and apoptotic monocytes was assessed by flow cytometry.

RESULTS

There was no difference in the risk factor profile and known coronary or peripheral vascular diseases between patients with AS and controls. Patients with AS exhibited increased numbers of CD14(+) monocytes as compared to controls (9.9% ± 4.9% vs. 7.7% ± 3.9%, P = 0.03). CD14(+) monocyte number was related to age and the presence and severity of AS. In patients with AS, both CD14(+) monocytes and apoptotic monocytes were inversely related to aortic valve area.

CONCLUSIONS

Patients with significant AS have increased number of circulating CD14(+) monocytes and there is an inverse correlation between monocyte count and aortic valve area. These findings may suggest that inflammation is operative not only in early valve injury phase, but also at later developed stages such as calcification when AS is severe.

Association of APOE Genotype with Bone Mineral Density in Men and Women: The Dong-gu and Namwon Studies

Many studies have investigated relationships between APOE genotype and bone mineral density (BMD). However, the results of these studies have been inconsistent. Few studies have been carried out in Asian populations. We studied the relationship of the APOE gene polymorphism and BMD in two large population-based studies. The datasets included the Dong-gu Study (3575 men and 5335 women) and the Namwon Study (2310 men, 3512 women). Lumbar spine and femoral neck BMD were measured by dual-energy X-ray absorptiometry. APOE genotypes were analyzed by polymerase chain reaction–restriction fragment length polymorphism. The APOE genotypes were classified into APOE E2 (E2/E2 and E2/E3), APOE E3 (E3/E3), and APOE E4 (E3/E4 and E4/E4). The genotype distribution of the study population was in Hardy-Weinberg equilibrium. There were no significant differences among APOE genotype groups in lumbar and femoral neck BMD in either cohort. Our data do not support the hypothesis that the APOE genotype is associated with BMD.

Cells and extracellular matrix interplay in cardiac valve disease: because age matters

Cardiovascular aging is a physiological process affecting all components of the heart. Despite the interest and experimental effort lavished on aging of cardiac cells, increasing evidence is pointing at the pivotal role of extracellular matrix (ECM) in cardiac aging. Structural and molecular changes in ECM composition during aging are at the root of significant functional modifications at the level of cardiac valve apparatus. Indeed, calcification or myxomatous degeneration of cardiac valves and their functional impairment can all be explained in light of age-related ECM alterations and the reciprocal interplay between altered ECM and cellular elements populating the leaflet, namely valvular interstitial cells and valvular endothelial cells, is additionally affecting valve function with striking reflexes on the clinical scenario. The initial experimental findings on this argument are underlining the need for a more comprehensive understanding on the biological mechanisms underlying ECM aging and remodeling as potentially constituting a pharmacological therapeutic target or a basis to improve existing prosthetic devices and treatment options. Given the lack of systematic knowledge on this topic, this review will focus on the ECM changes that occur during aging and on their clinical translational relevance and implications in the bedside scenario.

Lipoprotein (a) in calcific aortic valve disease: from genomics to novel drug target for aortic stenosis

Calcific aortic stenosis (AS) is the most common form of valve disease in the Western world and affects over 2.5 million individuals in North America. Despite the large burden of disease, there are no medical treatments to slow the development of AS, due at least in part to our incomplete understanding of its causes. The Cohorts for Heart and Aging Research in Genetic Epidemiology extra-coronary calcium consortium reported a genome-wide association study demonstrating that genetic variants in LPA are strongly associated with aortic valve (AV) calcium and clinical AS. Using a Mendelian randomization study design, it was demonstrated that the effect of this genetic variant is mediated by plasma lipoprotein (a) [Lp(a)], directly implicating elevations in Lp(a) as a cause of AV calcium and progression to AS. This discovery has sparked intense interest in Lp(a) as a modifiable cause for AV disease. Herein, we will review the mounting epidemiological and genetic findings in support of Lp(a)-mediated valve disease, discuss potential mechanisms underlying this observation, and outline the steps to translate this discovery to a much needed novel preventive and/or therapeutic strategy for AV disease.

Low bone mineral density is associated with intracranial posterior circulation atherosclerosis in women

Low bone mineral density (BMD) is associated with carotid atherosclerosis and the incidence of stroke. However, there are no data on the association of BMD with intracranial atherosclerosis. The study population consisted of 357 participants who underwent dual energy x-ray absorptiometric scanning of the lumbar spine and brain 3D time of flight magnetic resonance angiography as part of their voluntary health checks. The basilar, middle cerebral, intracranial internal carotid and intracranial vertebral arteries were evaluated. Low BMD was defined as a T-score of less than -1. All analyses were stratified by sex and intracranial atherosclerosis location. One hundred seventy-six women (53 years; 66.9% postmenopausal; 33.5% low BMD; 60.2% intracranial atherosclerosis in the anterior circulation (AC); 60.2% intracranial atherosclerosis in the posterior circulation (PC)) and 181 men (51 years; 28.7% low BMD; 61.9% intracranial atherosclerosis in the AC; 55.8% intracranial atherosclerosis in the PC) were included. In women, low BMD was significantly associated with intracranial atherosclerosis in the PC with the odds ratio of 2.57 (95% confidence interval 1.11-5.99). However, intracranial atherosclerosis in the AC was not associated with BMD in women. In men, there were no significant associations between BMD and intracranial atherosclerosis. In conclusion, this study shows that low BMD is associated with subclinical intracranial PC atherosclerosis in women but not in men.

Plasma Metabolic Profiles in Women are Menopause Dependent

Menopause is an endocrinological transition that greatly affects health and disease susceptibility in middle-aged and elderly women. To gain new insights into the metabolic process of menopause, plasma metabolic profiles in 115 pre- and post-menopausal women were systematically analyzed by ultra-performance liquid chromatography/mass spectrometry in conjunction with univariate and multivariate statistical analysis. Metabolic signatures revealed considerable differences between pre- and post-menopausal women, and clear separations were observed between the groups in partial least-squares discriminant analysis score plots. In total, 28 metabolites were identified as potential metabolite markers for menopause, including up-regulated acylcarnitines, fatty acids, lysophosphatidylcholines, lysophosphatidylethanolamines, and down-regulated pregnanediol-3-glucuronide, dehydroepiandrosterone sulfate, p-hydroxyphenylacetic acid and dihydrolipoic acid. These differences highlight that significant alterations occur in fatty acid β-oxidation, phospholipid metabolism, hormone metabolism and amino acid metabolism in post-menopausal women. In conclusion, our plasma metabolomics study provides novel understanding of the metabolic profiles related to menopause, and will be useful for investigating menopause-related diseases and assessing metabolomic confounding factors.

Saturated phosphatidic acids mediate saturated fatty acid-induced vascular calcification and lipotoxicity

Recent evidence indicates that saturated fatty acid-induced (SFA-induced) lipotoxicity contributes to the pathogenesis of cardiovascular and metabolic diseases; however, the molecular mechanisms that underlie SFA-induced lipotoxicity remain unclear. Here, we have shown that repression of stearoyl-CoA desaturase (SCD) enzymes, which regulate the intracellular balance of SFAs and unsaturated FAs, and the subsequent accumulation of SFAs in vascular smooth muscle cells (VSMCs), are characteristic events in the development of vascular calcification. We evaluated whether SMC-specific inhibition of SCD and the resulting SFA accumulation plays a causative role in the pathogenesis of vascular calcification and generated mice with SMC-specific deletion of both Scd1 and Scd2. Mice lacking both SCD1 and SCD2 in SMCs displayed severe vascular calcification with increased ER stress. Moreover, we employed shRNA library screening and radiolabeling approaches, as well as in vitro and in vivo lipidomic analysis, and determined that fully saturated phosphatidic acids such as 1,2-distearoyl-PA (18:0/18:0-PA) mediate SFA-induced lipotoxicity and vascular calcification. Together, these results identify a key lipogenic pathway in SMCs that mediates vascular calcification.

QCT Volumetric Bone Mineral Density and Vascular and Valvular Calcification: The Framingham Study

There is increasing evidence that bone and vascular calcification share common pathogenesis. Little is known about potential links between bone and valvular calcification. The purpose of this study was to determine the association between spine bone mineral density (BMD) and vascular and valvular calcification. Participants included 1317 participants (689 women, 628 men) in the Framingham Offspring Study (mean age 60 years). Integral, trabecular, and cortical volumetric bone density (vBMD) and arterial and valvular calcification were measured from computed tomography (CT) scans and categorized by sex-specific quartiles (Q4 = high vBMD). Calcification of the coronary arteries (CAC), abdominal aorta (AAC), aortic valve (AVC), and mitral valve (MVC) were quantified using the Agatston Score (AS). Prevalence of any calcium (AS >0) was 69% for CAC, 81% for AAC, 39% for AVC, and 20% for MVC. In women, CAC increased with decreasing quartile of trabecular vBMD: adjusted mean CAC = 2.1 (Q4), 2.2 (Q3), 2.5 (Q2), 2.6 (Q1); trend p = 0.04. However, there was no inverse trend between CAC and trabecular vBMD in men: CAC = 4.3 (Q4), 4.3 (Q3), 4.2 (Q2), 4.3 (Q1); trend p = 0.92. AAC increased with decreasing quartile of trabecular vBMD in both women (AAC = 4.5 [Q4], 4.8 [Q3], 5.4 [Q2], 5.1 [Q1]; trend p = 0.01) and men (AAC = 5.5 [Q4], 5.8 [Q3], 5.9 [Q2], 6.2 [Q1]; trend p = 0.01). We observed no association between trabecular vBMD and AVC or MVC in women or men. Finally, cortical vBMD was unrelated to vascular calcification and valvular calcification in women and men. Women and men with low spine vBMD have greater severity of vascular calcification, particularly at the abdominal aorta. The inverse relation between AAC and spine vBMD in women and men may be attributable to shared etiology and may be an important link on which to focus treatment efforts that can target individuals at high risk of both fracture and cardiovascular events.

Bone morphogenetic protein 6 and oxidized low-density lipoprotein synergistically recruit osteogenic differentiation in endothelial cells

AIMS

Vascular calcification contributes to mortality and morbidity in atherosclerosis, chronic kidney disease, and diabetes. Vascular calcific lesions contain osteoblast- and chondroblast-like cells, suggesting a process of endochondral or membranous ossification thought to result from the phenotypic plasticity of vascular cells. Bone morphogenetic protein (BMP) signalling potentiates atherosclerotic calcification, whereas BMP inhibition attenuates vascular inflammation and calcification in atherogenic mice. We hypothesized endothelial cells (ECs) may undergo osteogenic differentiation in response to BMP signalling and pro-atherogenic stimuli.

METHODS AND RESULTS

Among various BMP ligands tested, BMP6 and BMP9 elicited the most potent signalling in bovine aortic endothelial cells (BAEC), however, only BMP6 induced osteogenic differentiation. BMP6 and oxidized low-density lipoprotein (oxLDL) independently and synergistically induced osteogenic differentiation and mineralization, in a manner consistent with endothelial-to-mesenchymal transition. Treatment of ECs with BMP6 or oxLDL individually induced osteogenic and chondrogenic transcription factors Runx2 and Msx2, whereas treatment with BMP6 and oxLDL synergistically up-regulated Osterix and Osteopontin. Production of H2O2 was necessary for oxLDL-induced regulation of Runx2, Msx2, and Osterix in BAEC, and H2O2 was sufficient by itself to up-regulate these genes. Mineralization of ECs in response to BMP6 or oxLDL was abrogated by scavenging reactive oxygen species or inhibiting BMP type I receptor kinases. Similar synergistic effects of BMP and oxLDL upon osteogenic and chondrogenic transcription and phenotypic plasticity in human aortic endothelial cells were observed.

CONCLUSION

These findings provide a potential mechanism for the observed interactions of BMP signalling, oxidative stress, and inflammation in recruiting vascular calcification associated with atherosclerosis.

Tanshinol stimulates bone formation and attenuates dexamethasone-induced inhibition of osteogenesis in larval zebrafish

Background/Objective

Tanshinol is the main active component of Salvia miltiorrhiza Bunge, a significant Traditional Chinese Medicine used to treat cardiovascular disease. We have shown that tanshinol exerts an antiosteoporostic effect via the enhancement of bone formation in vivo and in vitro. However, the mechanism remains unclear. Based on the polyphenol group in the structure of tanshinol, we speculate the protective action on skeletal tissue is related to antioxidative capacity. Our in vitro evidence indicated that tanshinol stimulated osteoblastic differentiation by its antioxidaive capacity. In this study, we aim to further confirm the effect of tanshinol on bone formation and the underlying mechanism in zebrafish in vivo.

Methods

We used a Danio rerio (zebrafish) model, which has a bone formation process similar to humans, and evaluated the relationship between the dose and the effect of tanshinol on bone formation determined using alizarin red S staining or fluorescence intensity analysis in normal and glucocorticoid (GC)-induced inhibition of an osteogenesis model using wild-type zebrafish and cortical bone transgenic zebrafish tg(sp7:egfp). The expression of osteoblast-specific genes and reactive oxygen species (ROS) were tested.

Results

Our data showed that dexamethasone exerts a series of consequences, including the inhibition of bone formation, decrease of bone mass, downregulation of expression of osteoblast-specific genes (runx2a, ALP, osteocalcin, and sp7), as well as the accumulation of ROS generation and decreased capacity of antioxidants. Tanshinol showed a protective effect on promoting bone formation and bone mass both in wild-type larval zebrafish and transgenic zebrafish. Furthermore, tanshinol attenuated the inhibition of osteogenesis elicited by oxidative stress in the zebrafish exposed to dexamethasone.

Conclusion

The present findings suggest that tanshinol prevented decreased osteogenesis in GC-treated larval zebrafish via scavenging ROS and stimulated the expression of osteoblast-specific genes. Tanshinol treatment may be developed as a novel therapeutic approach under recent recognised conditions of GC-induced osteoporosis.

Childhood obesity, bone development, and cardiometabolic risk factors

Osteoporosis and obesity are both major public health concerns. It has long been considered that these are distinct disorders rarely found in the same individual; however, emerging evidence supports an important interaction between adipose tissue and the skeleton. Whereas overweight per se may augment bone strength, animal studies suggest that the metabolic impairment that accompanies obesity is detrimental to bone. Obesity during childhood, a critical time for bone development, likely has profound and lasting effects on bone strength and fracture risk. This notion has received little attention in children and results are mixed, with studies reporting that bone strength development is enhanced or impaired by obesity. Whether obesity is a risk factor for osteoporosis or childhood bone health, in general, remains an important clinical question. Here, we will focus on clarifying the controversial relationships between childhood obesity and bone strength development, and provide insights into potential mechanisms that may regulate the effect of excess adiposity on bone.

The Effects of a High Fat Diet Containing Diacylglycerol on Bone in C57BL/6J Mice

PURPOSE

In epidemiologic and animal studies, a high fat diet (HFD) has been shown to be associated with lower bone mineral density (BMD) and a higher risk of osteoporotic fractures. Meanwhile, consuming a HFD containing diacylglycerol (DAG) instead of triacylglycerol (TAG) is known to offer metabolically beneficial effects of reductions in body weight and abdominal fat. The purpose of this study was to investigate the effects of a HFD containing DAG (HFD-DAG) on bone in mice.

MATERIALS AND METHODS

Four-week-old male C57BL/6J mice (n=39) were divided into three weight-matched groups based on diet type: a chow diet group, a HFD containing TAG (HFD-TAG) group, and a HFD-DAG group. After 20 weeks, body composition and bone microstructure were analyzed using dual energy X-ray absorptiometry and micro-computed tomography. Reverse transcription-polymerase chain reaction (PCR) and real-time PCR of bone marrow cells were performed to investigate the expressions of transcription factors for osteogenesis or adipogenesis.

RESULTS

The HFD-DAG group exhibited lower body weight, higher BMD, and superior microstructural bone parameters, compared to the HFD-TAG group. The HFD-DAG group showed increased expression of Runx2 and decreased expression of PPARgamma in bone marrow cells, compared to the HFD-TAG group. The HFD-DAG group also had lower levels of plasma glucose, insulin, total cholesterol, and triglyceride than the HFD-TAG group.

CONCLUSION

Compared to HFD-TAG, HFD-DAG showed beneficial effects on bone and bone metabolism in C57BL/6J mice.

Blood and interstitial flow in the hierarchical pore space architecture of bone tissue

There are two main types of fluid in bone tissue, blood and interstitial fluid. The chemical composition of these fluids varies with time and location in bone. Blood arrives through the arterial system containing oxygen and other nutrients and the blood components depart via the venous system containing less oxygen and reduced nutrition. Within the bone, as within other tissues, substances pass from the blood through the arterial walls into the interstitial fluid. The movement of the interstitial fluid carries these substances to the cells within the bone and, at the same time, carries off the waste materials from the cells. Bone tissue would not live without these fluid movements. The development of a model for poroelastic materials with hierarchical pore space architecture for the description of blood flow and interstitial fluid flow in living bone tissue is reviewed. The model is applied to the problem of determining the exchange of pore fluid between the vascular porosity and the lacunar-canalicular porosity in bone tissue due to cyclic mechanical loading and blood pressure. These results are basic to the understanding of interstitial flow in bone tissue that, in turn, is basic to understanding of nutrient transport from the vasculature to the bone cells buried in the bone tissue and to the process of mechanotransduction by these cells.

Bone mineral density, adiposity, and cognitive functions

Cognitive decline and dementia due to Alzheimer's disease (AD) have been associated with genetic, lifestyle, and environmental factors. A number of potentially modifiable risk factors should be taken into account when preventive or ameliorative interventions targeting dementia and its preclinical stages are investigated. Bone mineral density (BMD) and body composition are two such potentially modifiable risk factors, and their association with cognitive decline was investigated in this study. 164 participants, aged 34–87 years old (62.78 ± 9.27), were recruited for this longitudinal study and underwent cognitive and clinical examinations at baseline and after 3 years. Blood samples were collected for apolipoprotein E (APOE) genotyping and dual energy x-ray absorptiometry (DXA) was conducted at the same day as cognitive assessment. Using hierarchical regression analysis, we found that BMD and lean body mass, as measured using DXA were significant predictors of episodic memory. Age, gender, APOE status, and premorbid IQ were controlled for. Specifically, the List A learning from California Verbal Learning Test was significantly associated with BMD and lean mass both at baseline and at follow up assessment. Our findings indicate that there is a significant association between BMD and lean body mass and episodic verbal learning. While the involvement of modifiable lifestyle factors in human cognitive function has been examined in different studies, there is a need for further research to understand the potential underlying mechanisms.

Influence of chronic stroke impairments on bone strength index of the tibial distal epiphysis and diaphysis

SUMMARY

The influence of various stroke impairments on bone health is poorly understood. This study showed that muscle function and small artery compliance were more strongly associated with the bone strength index at the tibial diaphyseal and epiphyseal regions, respectively. These impairments should be targeted in promoting bone health post-stroke.

INTRODUCTION

This study examined the bone structural properties of the tibial distal epiphysis and diaphysis after chronic stroke and identified the clinical correlates of the bone strength index measured at these sites.

METHODS

The tibial distal epiphysis (4% site) and diaphysis (66% site) were scanned on both sides in 66 chronic stroke patients and 23 control participants using peripheral quantitative computed tomography. Dynamic knee muscle strength, balance function, spasticity, arterial compliance, and endurance were also measured in the stroke group.

RESULTS

At the 4% site, multivariate analysis showed a significant side×group interaction effect (Wilk's lambda=3.977, p<0.001), with significant side-to-side differences in total volumetric bone mineral density (vBMD), trabecular vBMD, and bone strength index in the stroke group, but not in the control group. A significant side×group interaction was also found at the 66% site (Wilk's lambda=4.464, p<0.001), with significant side-to-side differences in cortical vBMD, cortical area, cortical thickness, and bone strength index in the stroke group only. Balance and endurance were independently associated with bone strength index at both tibial sites in the paretic leg (p<0.05) after adjusting for relevant factors in multivariate regression analysis. Small artery compliance and muscle strength were significantly associated with the bone strength index at the 4% site and 66% site, respectively.

CONCLUSIONS

The influence of various stroke impairments on bone was region-specific. While muscle function was more strongly associated with the bone strength index in the diaphyseal region, the effect of vascular health was more apparent in the tibial epiphysis in the paretic leg.

Relationships of serum lipid profiles and bone mineral density in postmenopausal Chinese women

OBJECTIVES

Recent studies suggest that serum lipid profiles are related to bone mineral density (BMD). But data about this relationship on Chinese population are scarce. We investigated the relationships between serum lipid and BMD in postmenopausal Chinese women.

METHODS

A cross-sectional study was conducted in 790 Chinese postmenopausal women. BMDs were measured by dual X-ray absorptiometry. Serum lipid profiles were obtained after a 12-h fasting.

RESULTS

Women with serum high-density lipoprotein cholesterol (HDL-C) levels of at least 1·55 mmol/l had a greater prevalence of osteoporosis compared with women with lower HDL-C (≤1·54 mmol/l). After controlling for age, menopausal duration, body mass index, serum creatinine levels, outdoor activity, smoking and alcohol intake, high HDL-C levels were associated with osteoporosis (OR = 1·64, 95%CI 1·16-2·33, P < 0·01). BMD at femoral neck and total hip was significantly lower in the higher HDL-C class than the lower class (0·722 ± 0·118 vs 0·744 ± 0·120 g/cm(2) , P < 0·01; 0·800 ± 0·126 vs 0·824 ± 0·125 g/cm(2) , P < 0·01, respectively). No association was found between total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) with BMD.

CONCLUSIONS

In Chinese postmenopausal women, elevated levels of serum HDL-C had a greater probability of being osteoporosis than the lower HDL-C levels. Our analysis showed higher HDL-C level that is favourable for cardiovascular diseases should be regarded as a risk factor for osteoporosis.

Association of serum paraoxonase concentration with serum lipid levels and bone mineral density measurements in early postmenopausal women

OBJECTIVE

To determine the association of serum paraoxonase concentration with serum lipid levels and bone mineral density in early postmenopausal Turkish women.

DESIGN

One hundred healthy postmenopausal women were included in a cross-sectional study in a University hospital clinic. Blood was drawn from women who had bone mineral density (BMD) measurements during routine visits. BMD of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry. The serum paraoxonase concentration and serum lipid levels were measured. Women were divided into two groups: those with normal lumbar vertebrae BMD and those with osteopenic lumbar vertebrae. Serum paraoxonase concentration was compared between the groups. The correlation between serum paraoxonase concentration and bone mass parameters was performed using Pearson's test.

RESULTS

The paraoxonase concentration in the osteopenic group was significantly lower than in the group with normal lumbar vertebrae BMD. The paraoxonase concentration was moderately correlated with total cholesterol, low density lipoprotein cholesterol and triglyceride levels among early postmenopausal Turkish women.

CONCLUSIONS

Early postmenopausal women with osteopenic lumbar vertebrae have significantly lower paraoxonase concentration than those with normal lumbar vertebrae BMD. Further studies are needed to clarify the associations between the osteoporosis risk factors and paraoxonase concentration during late postmenopausal years.

Association of low-density lipoprotein cholesterol-related genetic variants with aortic valve calcium and incident aortic stenosis

IMPORTANCE

Plasma low-density lipoprotein cholesterol (LDL-C) has been associated with aortic stenosis in observational studies; however, randomized trials with cholesterol-lowering therapies in individuals with established valve disease have failed to demonstrate reduced disease progression.

OBJECTIVE

To evaluate whether genetic data are consistent with an association between LDL-C, high-density lipoprotein cholesterol (HDL-C), or triglycerides (TG) and aortic valve disease.

DESIGN, SETTING, AND PARTICIPANTS

Using a Mendelian randomization study design, we evaluated whether weighted genetic risk scores (GRSs), a measure of the genetic predisposition to elevations in plasma lipids, constructed using single-nucleotide polymorphisms identified in genome-wide association studies for plasma lipids, were associated with aortic valve disease. We included community-based cohorts participating in the CHARGE consortium (n = 6942), including the Framingham Heart Study (cohort inception to last follow-up: 1971-2013; n = 1295), Multi-Ethnic Study of Atherosclerosis (2000-2012; n = 2527), Age Gene/Environment Study-Reykjavik (2000-2012; n = 3120), and the Malmö Diet and Cancer Study (MDCS, 1991-2010; n = 28,461).

MAIN OUTCOMES AND MEASURES

Aortic valve calcium quantified by computed tomography in CHARGE and incident aortic stenosis in the MDCS.

RESULTS

The prevalence of aortic valve calcium across the 3 CHARGE cohorts was 32% (n = 2245). In the MDCS, over a median follow-up time of 16.1 years, aortic stenosis developed in 17 per 1000 participants (n = 473) and aortic valve replacement for aortic stenosis occurred in 7 per 1000 (n = 205). Plasma LDL-C, but not HDL-C or TG, was significantly associated with incident aortic stenosis (hazard ratio [HR] per mmol/L, 1.28; 95% CI, 1.04-1.57; P = .02; aortic stenosis incidence: 1.3% and 2.4% in lowest and highest LDL-C quartiles, respectively). The LDL-C GRS, but not HDL-C or TG GRS, was significantly associated with presence of aortic valve calcium in CHARGE (odds ratio [OR] per GRS increment, 1.38; 95% CI, 1.09-1.74; P = .007) and with incident aortic stenosis in MDCS (HR per GRS increment, 2.78; 95% CI, 1.22-6.37; P = .02; aortic stenosis incidence: 1.9% and 2.6% in lowest and highest GRS quartiles, respectively). In sensitivity analyses excluding variants weakly associated with HDL-C or TG, the LDL-C GRS remained associated with aortic valve calcium (P = .03) and aortic stenosis (P = .009). In instrumental variable analysis, LDL-C was associated with an increase in the risk of incident aortic stenosis (HR per mmol/L, 1.51; 95% CI, 1.07-2.14; P = .02).

CONCLUSIONS AND RELEVANCE

Genetic predisposition to elevated LDL-C was associated with presence of aortic valve calcium and incidence of aortic stenosis, providing evidence supportive of a causal association between LDL-C and aortic valve disease. Whether earlier intervention to reduce LDL-C could prevent aortic valve disease merits further investigation.

Roles of parathyroid hormone (PTH) receptor and reactive oxygen species in hyperlipidemia-induced PTH resistance in preosteoblasts

Bioactive lipids initiate inflammatory reactions leading to pathogenesis of atherosclerosis. Evidence shows that they also contribute to bone loss by inhibiting parathyroid hormone receptor (PTH1R) expression and differentiation of osteoblasts. We previously demonstrated that bone anabolic effects of PTH(1-34) are blunted in hyperlipidemic mice and that these PTH effects are restored by antioxidants. However, it is not clear which osteoblastic cell developmental stage is targeted by bioactive lipids. To investigate the effects of hyperlipidemia at the cellular level, hyperlipidemic Ldlr(-/-) mice were bred with Col3.6GFPtpz mice, in which preosteoblasts/osteoblasts carry a topaz fluorescent label, and with Col2.3GFPcyan mice, in which more mature osteoblasts/osteocytes carry a cyan fluorescent label. Histological analyses of trabecular bone surfaces in femoral as well as calvarial bones showed that intermittent PTH(1-34) increased fluorescence intensity in WT-Tpz mice, but not in Tpz-Ldlr(-/-) mice. In contrast, PTH(1-34) did not alter fluorescence intensity in femoral cortical envelopes of either WT-Cyan or Ldlr(-/-)-Cyan mice. To test the mechanism of PTH1R downregulation, preosteoblastic MC3T3-E1 cells were treated with bioactive lipids and the antioxidant Trolox. Results showed that inhibitory effects of PTH1R levels by bioactive lipids were rescued by pretreatment with Trolox. The inhibitory effects on expression of PTH1R as well as on PTH-induced osteoblastic genes were mimicked by xanthine/xanthine oxidase, a known generator of reactive oxygen species. These findings suggest an important role of the preosteoblastic development stage as the target and downregulation of PTH receptor expression mediated by intracellular oxidant stress as a mechanism in hyperlipidemia-induced PTH resistance.

Porcine bone grafts defatted by lipase: efficacy of defatting and assessment of cytocompatibility

Defatting is an important procedure for the preparation of bone grafts because lipids in bone grafts strongly influence the osteointegration. Lipases have been widely used in different fields. However, study on the application to defatting process for bone grafts preparation has never been found so far. In this study, bone samples were treated respectively by lipase, NaHCO(3)/Na(2)CO(3), acetone and deionized water. The lipids content of processed bone grafts was calculated in Soxhlet extractor method. Surface morphology of the bone grafts was observed under scanning electron microscope (SEM). DNA content of processed bone grafts was measured. Cytocompatibility was evaluated by co-culturing mouse preosteoblasts (MC3T3-E1) on defatted bone cubes. Proliferation rates of MC3T3-E1 were examined by cell counting kit-8 (CCK-8) assay. No statistically significant difference was found between lipids amount of bone processed by lipase (0.46 ± 0.16 %) and acetone (1.11 ± 0.13 %) (P > 0.05). Both of them were significantly lower than that in groups processed by Na(2)CO(3)/NaHCO(3) (3.46 ± 0.69 %) and deionized water (8.88 ± 0.18 %) (P = 0.000). Only cell debris were discovered over the surface of bone processed by lipase or acetone, while lipid droplets were observed on bone processed by Na(2)CO(3)/NaHCO(3) or water by SEM. The difference of DNA concentration between the bone processed by lipase (3.16 ± 0.81 ng/μl) and acetone (4.14 ± 0.40 ng/μl) is not statistically significant (P > 0.05). Both of them are significantly lower than that groups processed by Na(2)CO(3)/NaHCO(3) (5.22 ± 0.38 ng/μl) and water (7.88 ± 0.55 ng/μl) (P < 0.05). MC3T3-E1 cells maintained their characteristic spreading on the trabecular surfaces of bone processed by lipase. There were no statistically significant differences among absorbance of lipase, acetone groups in CCK-8 assay. The application of lipase to bone tissue defatting appears to be a very promising technique for bone grafts preparation.

A novel osteogenic oxysterol compound for therapeutic development to promote bone growth: activation of hedgehog signaling and osteogenesis through smoothened binding

Osteogenic factors are often used in orthopedics to promote bone growth, improve fracture healing, and induce spine fusion. Osteogenic oxysterols are naturally occurring molecules that were shown to induce osteogenic differentiation in vitro and promote spine fusion in vivo. The purpose of this study was to identify an osteogenic oxysterol more suitable for clinical development than those previously reported, and evaluate its ability to promote osteogenesis in vitro and spine fusion in rats in vivo. Among more than 100 oxysterol analogues synthesized, Oxy133 induced significant expression of osteogenic markers Runx2, osterix (OSX), alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OCN) in C3H10T1/2 mouse embryonic fibroblasts and in M2-10B4 mouse marrow stromal cells. Oxy133-induced activation of an 8X-Gli luciferase reporter, its direct binding to Smoothened, and the inhibition of Oxy133-induced osteogenic effects by the Hedgehog (Hh) pathway inhibitor, cyclopamine, demonstrated the role of Hh pathway in mediating osteogenic responses to Oxy133. Oxy133 did not stimulate osteogenesis via BMP or Wnt signaling. Oxy133 induced the expression of OSX, BSP, and OCN, and stimulated robust mineralization in primary human mesenchymal stem cells. In vivo, bilateral spine fusion occurred through endochondral ossification and was observed in animals treated with Oxy133 at the fusion site on X-ray after 4 weeks and confirmed with manual assessment, micro-CT (µCT), and histology after 8 weeks, with equal efficiency to recombinant human bone morphogenetic protein-2 (rhBMP-2). Unlike rhBMP-2, Oxy133 did not induce adipogenesis in the fusion mass and resulted in denser bone evidenced by greater bone volume/tissue volume (BV/TV) ratio and smaller trabecular separation. Findings here suggest that Oxy133 has significant potential as an osteogenic molecule with greater ease of synthesis and improved time to fusion compared to previously studied oxysterols. Small molecule osteogenic oxysterols may serve as the next generation of bone anabolic agents for therapeutic development.

Relationship between serum total cholesterol level and serum biochemical bone turnover markers in healthy pre- and postmenopausal women

Background. The presence of common risk factors suggests that there is a relationship between osteoporosis and cardiovascular disease, possibly via dyslipidemia and inflammation. We investigated the relationships among the lipid profile, the inflammation marker high-sensitivity C-reactive protein (hsCRP), bone turnover markers, and bone mineral density (BMD) to assess the correlation between osteoporosis and cardiovascular disease and identify factors predicting osteoporosis. Methods. The study included 759 Korean women older than 20 years of age. The BMD, serum lipid profile, and levels of hsCRP, cross-linked C-terminal peptide (CTX), and osteocalcin were measured. We compared the serum biomarkers between groups with normal and low BMD and assessed the correlations between the levels of bone turnover markers and the lipid profile and hsCRP level. Results. The concentrations of CTX, osteocalcin, and total cholesterol were significantly higher in the low BMD group than in the normal BMD group in premenopausal women group. However, hsCRP was not correlated with these parameters. Multivariate logistic regression analysis revealed that TC (OR, 1.647; 95% CI, 1.190–2.279) and osteocalcin (OR, 1.044; 95% CI, 1.002–1.088) had an increased risk of low BMD in premenopausal women. Conclusions. These results indicate that total cholesterol concentration is correlated with the levels of bone turnover markers, suggesting that it might predict osteoporosis in premenopausal women.

Effects of growth hormone administration for 6 months on bone turnover and bone marrow fat in obese premenopausal women

PURPOSE

Abdominal adiposity is associated with low BMD and decreased growth hormone (GH) secretion, an important regulator of bone homeostasis. The purpose of our study was to determine the effects of a short course of GH on markers of bone turnover and bone marrow fat in premenopausal women with abdominal adiposity.

MATERIALS AND METHODS

In a 6-month, randomized, double-blind, placebo-controlled trial we studied 79 abdominally obese premenopausal women (21-45 y) who underwent daily sc injections of GH vs. placebo. Main outcome measures were body composition by DXA and CT, bone marrow fat by proton MR spectroscopy, P1NP, CTX, 25(OH)D, hsCRP, undercarboxylated osteocalcin (ucOC), preadipocyte factor 1 (Pref 1), apolipoprotein B (ApoB), and IGF-1.

RESULTS

GH increased IGF-1, P1NP, 25(OH)D, ucOC, bone marrow fat and lean mass, and decreased abdominal fat, hsCRP, and ApoB compared with placebo (p<0.05). There was a trend toward an increase in CTX and Pref-1. Among all participants, a 6-month increase in IGF-1 correlated with 6-month increase in P1NP (p=0.0005), suggesting that subjects with the greatest increases in IGF-1 experienced the greatest increases in bone formation. A six-month decrease in abdominal fat, hsCRP, and ApoB inversely predicted 6-month change in P1NP, and 6-month increase in lean mass and 25(OH)D positively predicted 6-month change in P1NP (p≤0.05), suggesting that subjects with greatest decreases in abdominal fat, inflammation and ApoB, and the greatest increases in lean mass and 25(OH)D experienced the greatest increases in bone formation. A six-month increase in bone marrow fat correlated with 6-month increase in P1NP (trend), suggesting that subjects with the greatest increases in bone formation experienced the greatest increases in bone marrow fat. Forward stepwise regression analysis indicated that increase in lean mass and decrease in abdominal fat were positive predictors of P1NP. When IGF-1 was added to the model, it became the only predictor of P1NP.

CONCLUSION

GH replacement in abdominally obese premenopausal women for 6 months increased bone turnover and bone marrow fat. Reductions in abdominal fat, and inflammation, and increases in IGF-1, lean mass and vitamin D were associated with increased bone formation. The increase in bone marrow fat may reflect changes in energy demand from increased bone turnover.

Bone: a new endocrine organ at the heart of chronic kidney disease and mineral and bone disorders

Recent reports of several bone-derived substances, some of which have hormonal properties, have shed new light on the bone-cardiovascular axis. Deranged concentrations of humoral factors are not only epidemiologically connected to cardiovascular morbidity and mortality, but can also be causally implicated, especially in chronic kidney disease. FGF23 rises exponentially with advancing chronic kidney disease, seems to reach maladaptive concentrations, and then induces left ventricular hypertrophy, and is possibly implicated in the process of vessel calcification. Sclerostin and DKK1, both secreted mainly by osteocytes, are important Wnt inhibitors and as such can interfere with systems for biological signalling that operate in the vessel wall. Osteocalcin, produced by osteoblasts or released from mineralised bone, interferes with insulin concentrations and sensitivity, and its metabolism is disturbed in kidney disease. These bone-derived humoral factors might place the bone at the centre of cardiovascular disease associated with chronic kidney disease. Most importantly, factors that dictate the regulation of these substances in bone and subsequent secretion into the circulation have not been researched, and could provide entirely new avenues for therapeutic intervention.

Hyperlipidemia affects multiscale structure and strength of murine femur

To improve bone strength prediction beyond limitations of assessment founded solely on the bone mineral component, we investigated the effect of hyperlipidemia, present in more than 40% of osteoporotic patients, on multiscale structure of murine bone. Our overarching purpose is to estimate bone strength accurately, to facilitate mitigating fracture morbidity and mortality in patients. Because (i) orientation of collagen type I affects, independently of degree of mineralization, cortical bone׳s micro-structural strength; and, (ii) hyperlipidemia affects collagen orientation and μCT volumetric tissue mineral density (vTMD) in murine cortical bone, we have constructed the first multiscale finite element (mFE), mouse-specific femoral model to study the effect of collagen orientation and vTMD on strength in Ldlr(-/-), a mouse model of hyperlipidemia, and its control wild type, on either high fat diet or normal diet. Each µCT scan-based mFE model included either element-specific elastic orthotropic properties calculated from collagen orientation and vTMD (collagen-density model) by experimentally validated formulation, or usual element-specific elastic isotropic material properties dependent on vTMD-only (density-only model). We found that collagen orientation, assessed by circularly polarized light and confocal microscopies, and vTMD, differed among groups and that microindentation results strongly correlate with elastic modulus of collagen-density models (r(2)=0.85, p=10(-5)). Collagen-density models yielded (1) larger strains, and therefore lower strength, in simulations of 3-point bending and physiological loading; and (2) higher correlation between mFE-predicted strength and 3-point bending experimental strength, than density-only models. This novel method supports ongoing translational research to achieve the as yet elusive goal of accurate bone strength prediction.

Lysophosphatidylcholine-induced cytotoxicity in osteoblast-like MG-63 cells: involvement of transient receptor potential vanilloid 2 (TRPV2) channels

Epidemiological studies indicate that patients suffering from atherosclerosis are predisposed to develop osteoporosis. Accordingly, atherogenic determinants such as oxidized low density lipoprotein (OxLDL) particles have been shown to alter bone cell functions. In this work, we investigated the cytotoxicity of lysophosphatidylcholine (lysoPC), a major phospholipid component generated upon LDL oxidation, on bone-forming MG-63 osteoblast-like cells. Cell viability was reduced by lysoPC in a concentration-dependent manner with a LC50 of 18.7±0.7 μM. LysoPC-induced cell death was attributed to induction of both apoptosis and necrosis. Since impairment of intracellular calcium homeostasis is often involved in mechanism of cell death, we determined the involvement of calcium in lysoPC-induced cytotoxicity. LysoPC promoted a rapid and transient increase in intracellular calcium attributed to mobilization from calcium stores, followed by a sustained influx. Intracellular calcium mobilization was associated to phospholipase C (PLC)-dependent mobilization of calcium from the endoplasmic reticulum since inhibition of PLC or calcium depletion of reticulum endoplasmic with thapsigargin prevented the calcium mobilization. The calcium influx induced by lysoPC was abolished by inhibition of transient receptor potential vanilloid (TRPV) channels with ruthenium red whereas gadolinium, which inhibits canonical TRP (TRPC) channels, was without effect. Accordingly, expression of TRPV2 and TRPV4 were shown in MG-63 cells. The addition of TRPV2 inhibitor Tranilast in the incubation medium prevent the calcium influx triggered by lysoPC and reduced lysoPC-induced cytotoxicity whereas TRPV4 inhibitor RN 1734 was without effect, which confirms the involvement of TRPV2 activation in lysoPC-induced cell death.

Time course-changes in phosphatidylcholine profile during oxidative modification of low-density lipoprotein

Background

Oxidized phosphatidylcholines (oxPC) and lysophosphatidylcholine (lysoPC) generated during the formation of oxidized low-density lipoprotein (oxLDL) are involved in atherosclerotic lesion development. We investigated the time course-changes in phosphatidylcholine (PC) molecular species during oxidation of LDL to determine how those atherogenic PCs are produced.

Methods

Human and rabbit LDLs were pretreated with or without a selective platelet-activating factor acetylhydrolase (PAF-AH) inhibitor. LDL was oxidized by incubation with copper sulfate, and PC profiles were analyzed by liquid chromatography-tandem mass spectrometry.

Results

When human LDL was oxidized, the peak areas for polyunsaturated fatty acid (PUFA)-containing PC species dramatically decreased after a short lag period, concomitantly lysoPC species increased sharply. Although a variety of oxPC species containing oxidized fatty acyl groups or cleaved acyl chains are formed during LDL oxidation, only a few oxPC products accumulated in oxLDL: 1-palmitoyl-2-(9-oxo-nonanoyl) PC and long-chain oxPC with two double bonds. Pretreatment of LDL with the PAF-AH inhibitor greatly reduced lysoPC production while it had no effect on lipid peroxidation reactions and oxPC profiles. Rabbit LDL, which has a different composition of PC molecular species and needs a longer time to reach achieve full oxidation than human LDL, also accumulated lysoPC during oxidation. The increase in lysoPC in rabbit oxLDL was suppressed by pretreatment with the PAF-AH inhibitor. The major oxPC species formed in rabbit oxLDL were almost the same as human oxLDL.

Conclusions

These results suggest that lysoPC species are the major products and PAF-AH activity is crucial for lysoPC generation during oxidation of LDL. The oxPC species accumulated are limited when LDL is oxidized with copper ion in vitro.

Effects of bioactive lipids and lipoproteins on bone

Although epidemiological studies from the past two decades show a link between atherosclerotic vascular disease and bone loss, that is independent of age, the mechanism is still unclear. This review focuses on evidence that suggests a role for atherogenic lipids and lipoproteins in the pathogenesis of bone loss, including direct effects of these bioactive lipids/lipoproteins on bone cells, inhibiting osteoblastic differentiation and promoting osteoclastic differentiation. It also addresses recent evidence that suggests that bioactive lipids blunt the effects of bone anabolic agents such as teriparatide and bone morphogenetic proteins. Systemic and intracellular oxidant stress and inflammation are implicated in mediating the effects of bioactive lipids/lipoproteins.

The anabolic effect of teriparatide is undermined by low levels of high-density lipoprotein cholesterol

Intermittent parathyroid hormone (PTH) administration has a potent ability to increase bone mass, regardless of underlying conditions or species. A recent study using LDLR(-/-) mice showed that the anabolic effect of PTH was blunted by hyperlipidemia, whereas PTH anabolism was rescued by enhancement of high-density lipoprotein cholesterol (HDL-C) function. We conducted a retrospective longitudinal study to determine whether lipid profiles also affect the anabolic effect of intermittent PTH treatment in humans. Fifty-two patients (8 males and 44 females, ages 38-85 years) with severe osteoporosis who had been treated with teriparatide (TPTD, recombinant human PTH(1-34) for 12 months were studied at Severance Hospital, Yonsei University. C-telopeptide (CTX) and osteocalcin (OCN) were measured at 0, 3, and 12 months; and total cholesterol, triglycerides, and HDL-C were measured at baseline. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry at 0 and 12 months. Lumbar spine BMD increased significantly after 12 months of treatment with TPTD (10.0 ± 9.3%, p < 0.001). Initial 3-month changes in CTX and OCN levels revealed positive correlations with the increase in lumbar BMD (r = 0.546, p = 0.001 and r = 0.500, p = 0.006, respectively). Moreover, percentage change in lumbar BMD at 12 months showed a negative correlation with baseline total cholesterol (r = -0.438, p = 0.009) and a positive correlation with HDL-C (r = 0.498, p = 0.016). A smaller 3-month increase in OCN and a lower HDL-C level at baseline were associated with a smaller lumbar BMD increase after TPTD treatment, even after adjustment for age, sex, and other confounding factors (β = 0.462, p = 0.031 for ΔOCN and β = 0.670, p = 0.004 for HDL-C). Plasma levels of lipids, especially HDL-C, seem to be associated with the extent of osteoanabolic effects of TPTD in humans.

Ceramide mediates Ox-LDL-induced human vascular smooth muscle cell calcification via p38 mitogen-activated protein kinase signaling

Vascular calcification is associated with significant cardiovascular morbidity and mortality, and has been demonstrated as an actively regulated process resembling bone formation. Oxidized low density lipoprotein (Ox-LDL) has been identified as a regulatory factor involved in calcification of vascular smooth muscle cells (VSMCs). Additionally, over-expression of recombinant human neutral sphingomyelinase (N-SMase) has been shown to stimulate VSMC apoptosis, which plays an important role in the progression of vascular calcification. The aim of this study is to investigate whether ceramide regulates Ox-LDL-induced calcification of VSMCs via activation of p38 mitogen-activated protein kinase (MAPK) pathway. Ox-LDL increased the activity of N-SMase and the level of ceramide in cultured VSMCs. Calcification and the osteogenic transcription factor, Msx2 mRNA expression were reduced by N-SMase inhibitor, GW4869 in the presence of Ox-LDL. Usage of GW4869 inhibited Ox-LDL-induced apoptosis in VSMCs, an effect which was reversed by C2-ceramide. Additionally, C2-ceramide treatment accelerated VSMC calcification, with a concomitant increase in ALP activity. Furthermore, C2-ceramide treatment enhanced Ox-LDL-induced VSMC calcification. Addition of caspase inhibitor, ZVAD-fmk attenuated Ox-LDL-induced calcification. Both Ox-LDL and C2-ceramide treatment increased the phosphorylation of p38 MAPK. Inhibition of p38 MAPK by SB203580 attenuated Ox-LDL-induced calcification of VSMCs. These data suggest that Ox-LDL activates N-SMase-ceramide signaling pathway, and stimulates phosphorylation of p38 MAPK, leading to apoptosis in VSMCs, which initiates VSMC calcification.

Decreased bone mineral density in subjects carrying familial defective apolipoprotein B-100

CONTEXT

Although numerous epidemiologic studies have documented associations between osteoporosis and cardiovascular disease, the mechanisms underlying this association remain to be clarified. One hypothesis is that hyperlipidemia may be a common predisposing factor to both atherosclerotic heart disease and bone fragility.

OBJECTIVE

To evaluate this, we compared bone mineral density (BMD) between subjects with and without the R3500Q APOB mutation, the cause of familial defective apolipoprotein B-100, which has been previously shown to markedly increase low-density lipoprotein cholesterol (LDL-C). We hypothesized that R3500Q carriers would have lower BMD due to lifetime, elevated LDL-C.

DESIGN

This was a a cross-sectional study in the Old Order Amish (OOA) population.

PARTICIPANTS

The R3500Q APOB mutation is present at a high frequency (∼6% vs <0.5%) in the OOA population due to a founder effect. Therefore, we conducted analysis on 1097 Amish individuals of whom 125 were R3500Q carriers.

MAIN OUTCOME MEASURE

BMD was measured by dual-energy x-ray absorptiometry.

RESULTS

After adjusting for age, age(2), sex, body mass index, and family structure, carriers for the Q risk allele had significantly lower BMD than noncarriers at the femoral neck (P = .037), lumbar spine (P = .035) and whole body (P = .016). Adjusting for LDL-C attenuated the association between R3500Q genotype and BMD but did not completely explain the relationship. Subgroup analyses showed no significant interactions with sex, age, or presence of metabolic syndrome.

CONCLUSION

These results use the unique genetic architecture of the OOA population to provide a novel line of evidence supporting a causal role for elevated LDL-C in lowering BMD.

High glucose concentration does not modulate the formation of arterial medial calcification in experimental uremic rats

High phosphate-induced phenotypic switching of smooth muscle cells (SMCs) into osteogenic cells is critical for the formation of arterial medial calcification in chronic kidney disease. Because vascular calcification is also prevalent in type 2 diabetes, we examined whether glucose concentration affects high phosphate-induced SMC phenotypic switching and calcification. First, the formation of arterial medial calcification was compared among 4 groups: adenine-fed uremic rats, streptozotocin-injected hyperglycemic rats, adenine-fed and streptozotocin-injected uremic/hyperglycemic rats, and control rats. Calcification was obvious in uremic and uremic/hyperglycemic rats, whereas it was undetectable in the others. Aortic calcium contents were significantly elevated in uremic and uremic/hyperglycemic rats, but they were not different between the two groups. Moreover, hyperglycemia had no effects on the reduced expression of SMC differentiation markers including smooth muscle α-actin and SM22α and on the increased expression of osteogenic markers, such as Runx2, in uremic rats. Second, cultured SMCs were incubated in the medium with various concentrations of phosphate (0.9-4.5 mmol/l) and glucose (5-50 mmol/l), and calcium deposition was measured. Although high phosphate dose-dependently increased calcium contents, they were unaffected by glucose concentration. Results suggest that glucose concentration does not directly modulate high phosphate-induced SMC phenotypic switching and arterial medial calcification.

Two neglected biologic risk factors in bone grafting and implantology: high low-density lipoprotein cholesterol and low serum vitamin D

Following a failure of a bone graft or an implant placement, the hypothesis of a biological abnormality is rarely considered as a possible cause. A systematic search of peer-reviewed literature for dyslipidemia or vitamin D deficiency may explain this lack of consideration. Excess low-density lipoprotein cholesterol (dyslipidemia) is responsible for a slower bone metabolism or lower dental implant osseointegration. In addition, vitamin D is a key factor for linking innate and adaptive immunity. Both of these factors are compromised under the conditions of vitamin D deficiency. Therefore, vitamin D deficiency slows implant osseointegration and increases the risk of graft infection. Vitamin D is also involved in immune function and therefore allergic reactions.

Trabecular bone mineral density and bone geometry of the distal radius at completion of pubertal growth in childhood type 1 diabetes

AIM

To identify disease-related risk factors for an altered bone mineral density (BMD) and geometry at young adulthood in patients with diabetes mellitus type 1 (DM1).

METHODS

Fifty-six DM1 patients (23 females, 33 males) with prepubertal onset of diabetes were studied after completion of skeletal growth. Bone parameters at the distal radius were investigated by peripheral quantitative computed tomography. Disease-related parameters, in particular average HbA1c during the 2 years around peak height velocity, were analyzed. Forty-seven healthy controls (32 females, 15 males) were studied.

RESULTS

Trabecular BMD was similar between DM1 patients and controls. The mean (±SD) cross-sectional bone area (CSA) was smaller in DM1 patients compared to controls (282.5 ± 45.4 vs. 326.7 ± 52.2 mm(2), p = 0.002 and males 391.0 ± 61.3 vs. 423.4 ± 81.9 mm(2), p = 0.1). In female DM1 patients, the CSA z-score correlated negatively with the body mass index z-score (r = -0.52, p = 0.01) and positively with the height z-score (r = 0.49, p = 0.02).

CONCLUSIONS

DM1 patients are at risk for smaller bone sizes at the distal radius at the end of pubertal growth, especially females with increased adiposity. Diabetes-specific parameters seem to have a low impact on forearm volumetric apparent mineral density.

Role of oxidative and nitrosative stress in autogenous bone grafts to the mandible using guided bone regeneration and a deproteinized bovine bone material

The aim of this study was to evaluate the role of oxidative and nitrosative stress in autogenous bone grafts to the mandible based on immunohistochemical analysis.

MATERIAL AND METHODS

Using a well-established sheep model autogenous bone grafts were harvested form the iliac bone. A combination of a Collagen Membrane (CM) and Deproteinized Bovine Bone Material (DBBM) was used to cover the bone graft (Experiment 2). This modification was compared with simple onlay bone grafts (Experiment 1). Immunohistochemically, the expression of specific stable degradation products of oxidative and nitrosative stress was compared between the two experimental groups.

RESULTS

Specific markers for oxidative and nitrosative stress showed statistically significant differences in expression in the different experimental groups. The influence of oxidative and nitrosative stress on osteoblasts (OB), osteoclasts (OC), and osteocytes (OCy) was analysed. Experiment 2 showed increased expression of markers in OB and decreased expression in OC.

CONCLUSIONS

Taking the result of this study and reports from the literature into consideration grafts in Experiment 2 showed less resorption and atrophy, higher activity of OB and inhibition of OC, and less expression of Reactive Oxygen and Nitrogen Species (RONS) as markers of oxidative stress within the graft. These data illustrate the improved remodelling processes in grafts using CM and DBBM.

Gender difference in bone loss and vascular calcification associated with age

BACKGROUND AND OBJECTIVES

It is widely known that both bone loss and vascular calcification are age-related processes. The purpose of this study was to investigate the relationship between coronary artery calcium (CAC) score or bone mineral density (BMD) with age and whether there is a gender difference factoring in the two conditions among healthy subjects.

SUBJECTS AND METHODS

Between March 2009 and August 2011, participants included 1727 subjects (mean age: 55±10 years, M : F=914 : 813) with routine health check-ups. After being categorized into three groups (normal, osteopenia, and osteoporosis) according to the World Health Organization (WHO) diagnostic classification, we estimated BMD by dual energy X-ray absorptiometry (DEXA) and CAC score by dual-source CT (DSCT).

RESULTS

There was a significant gender difference among the risk factors, including total-lumbar spine (1.213±0.176 g/cm(2) : 1.087±0.168 g/cm(2), p<0.001) and femur (1.024±0.131 g/cm(2) : 0.910±0.127 g/cm(2), p<0.001) in BMD by DEXA, and CAC score (68±227 : 27±116, p<0.001) in coronary artery calcification by DSCT. Age in male [odds ratio (OR): 1.138 {95% confidence interval (CI): 1.088-1.190}, p<0.001] and menopause in female subjects {OR: 12.370 (95% CI: 3.120-49.047), p<0.001} were, respectively, independently associated with osteopenia.

CONCLUSION

Although our results do not demonstrate a direct association between CAC score and BMD in both genders, there is a gender difference of CAC score in normal and osteopenia groups according to the WHO diagnostic classification. Additionally, we suggest that more specific therapeutic strategies be considered during any early bone loss period, especially in female subjects.

Panoramic images of white and black post-menopausal females evidencing carotid calcifications are at high risk of comorbid osteopenia of the femoral neck

OBJECTIVES

Femoral neck fractures in older females resulting from decreased bone mineral density (BMD; osteopenia) are associated with increased morbidity and mortality. Bone mineralization inhibition is probably controlled by proteins which also foster vascular calcification. Therefore, we evaluated the relationship between calcified carotid artery plaque (CCAP) on panoramic images and BMD on dual energy X-ray absorptiometry (DXA) bone scans.

METHODS

Images and hospital records identified by dentists defined two study groups (20 white females and 24 black females) having CCAP and an incidentally obtained bone scan. Ethnically matched (age±7 years, body mass index ±3 units) control groups with panoramic images devoid of CCAP and accompanying DXA scan were likewise constituted. A physician determined the BMD on the DXA.

RESULTS

Females with CCAP had significantly (p = 0.03) poorer BMD at the femoral neck than those without CCAP. Although mean femoral neck BMD was significantly lower (p = 0.009) for white than for black females, there was no significant interaction between race and CCAP (p = 0.80).

CONCLUSION

We observed a significant inverse association between the CCAP on panoramic images and femoral neck BMD in post-menopausal white females.

Bone mineral density is associated with site-specific atherosclerosis in patients with severe peripheral artery disease

Recent studies have highlighted a significant association between the severity of atherosclerosis and bone mineral density (BMD) among healthy subjects, although its connection to angiographically determined peripheral artery disease (PAD) has never been investigated. We evaluated the connection between the angiographic severity and site specificity of peripheral atherosclerosis and osteoporosis among patients with chronic lower limb ischemia. In our cross-sectional study we investigated 172 patients with PAD. The anatomic sites of the lesions were analyzed. The severity of atherosclerosis was diagnosed using the Bollinger angiographic score (BS). BMD was measured at the lumbar spine (l-BMD) and at femoral (f-BMD) and radial (r-BMD) sites by dual-energy X-ray absorptiometry. Dyslipidemia, the level of vitamin D(3), and different bone turnover markers were also noted. Among PAD patients, regardless of the lesion site, we did not find any association between BMD and BS. Among patients with iliac disease, BS was associated with l-BMD (p = 0.038, r = -0.467) and with f-BMD (p = 0.002, r = -0.642). The level of r-BMD among patients with iliac disease was not associated with BS (p = 0.233, r = -0.306). We did not find any difference between the group of patients with and that without dyslipidemia and low or normal levels of vitamin D(3). Our results show a connection between the severity of atherosclerosis and osteoporosis among patients with PAD, specific to the site of the lesion. The findings regarding dyslipidemia, bone markers, and site specificity support the hypothesis that reduced blood flow is the key factor responsible for the inverse association of BMD with atherosclerosis.

Vascular elasticity and grip strength are associated with bone health of the hemiparetic radius in people with chronic stroke: implications for rehabilitation

BACKGROUND

People with stroke often have increased bone loss and fracture rate. Increasing evidence has demonstrated a link between cardiovascular health and bone loss in other patient populations.

OBJECTIVE

The study objectives were: (1) to compare the bone density and geometry of the radius diaphysis on the left and right sides in people with chronic stroke and people who were matched for age (control participants) and (2) to examine the relationship between the bone strength index at the hemiparetic radius diaphysis and vascular health in people with chronic stroke.

DESIGN

This was a case-control study.

METHODS

The radius diaphysis on both sides was scanned with peripheral quantitative computed tomography in 65 participants with chronic stroke and 34 control participants. Large-artery and small-artery elasticity indexes were evaluated with a cardiovascular profiling system.

RESULTS

The paretic radius diaphysis had significantly lower values for cortical bone mineral density, cortical thickness, cortical area, and the bone strength index but a larger marrow cavity area than the nonparetic radius diaphysis in participants with chronic stroke, whereas no bone measurement showed a significant side-to-side difference in control participants. Multiple regression analyses showed that the large-artery elasticity index and grip strength remained significantly associated with the bone strength index at the hemiparetic radius diaphysis after controlling for age, sex, time since stroke diagnosis, body mass index, and physical activity (R(2)=.790).

LIMITATIONS

This study was cross-sectional and could not establish causality. The radius diaphysis is not the most common site of fracture after stroke.

CONCLUSIONS

Both the integrity of the vasculature and muscle strength were significantly associated with the bone strength index at the hemiparetic radius diaphysis in participants with chronic stroke. The results may be useful in guiding rehabilitative programs for enhancing bone health in the paretic arm after stroke.

Vascular calcification in diabetes: mechanisms and implications

Cardiovascular disease (CVD) remains the leading cause of death among adults with diabetes, and CVD prevention remains a major challenge. Coronary artery calcium (CAC) score measured by electron beam tomography (EBT) or multi-slice detector computed tomography correlates closely with plaque burden and coronary angiography, and predicts coronary events independently of other risk factors. Further, progression of CAC over several years has been shown to predict increased mortality. Coronary calcification is an active process strongly associated with atherosclerotic plaque evolution and is an accepted surrogate endpoint in studies of patients with diabetes older than 30. In this review, recent findings regarding the mechanisms and implications of vascular calcification in diabetes will be discussed.