Mechanisms linking osteoporosis with cardiovascular calcification

Aortic stenosis: a review on acquired pathogenesis and ominous combination with diabetes mellitus

BACKGROUND

Aortic stenosis (AS) is a progressive disease, with no pharmacological treatment. The prevalence of diabetes mellitus (DM) among AS patients is higher than in the general population. DM significantly increases the risk of AS development and progression from mild to severe. The interplay between AS and DM's mechanism is not entirely known yet.

MAIN BODY

The increased accumulation of advanced glycation end products (AGEs) was linked to increased valvular oxidative stress, inflammation, expression of coagulation factors, and signs of calcification, according to an analysis of aortic stenotic valves. It is interesting to note that in diabetic AS patients, valvular inflammation did not correlate with serum glucose levels but rather only with long-term glycemic management markers like glycated haemoglobin and fructosamine. Transcatheter aortic valve replacement, which has been shown to be safer than surgical aortic valve replacement, is advantageous for AS patients who also have concurrent diabetes. Additionally, novel anti-diabetic medications have been proposed to lower the risk of AS development in DM patients, including sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonist that target reduction of AGEs-mediated oxidative stress.

CONCLUSIONS

There are little data on the effects of hyperglycemia on valvular calcification, but understanding the interactions between them is essential to develop a successful treatment strategy to stop or at least slow the progression of AS in DM patients. There is a link among AS and DM and that DM negatively impacts the quality of life and longevity of AS patients. The sole successful treatment, despite ongoing efforts to find new therapeutic modalities, involves aortic valve replacement. More research is required to find methods that can slow the advancement of these conditions, enhancing the prognosis and course of people with AS and DM.

Abdominal aortic calcification, bone mineral density and fractures: a systematic review and meta-analysis of observational studies

BACKGROUND

Abdominal aortic calcification (AAC) has been inconsistently associated with skeletal health. We aimed to investigate the association of AAC with bone mineral density (BMD) and fracture risk by pooling the findings of observational studies.

METHODS

Medline, EMBASE, Web of Science and Google Scholar were searched (August 2021). All clinical studies that assessed the association between AAC and BMD or fracture were included. AAC was categorized into any/advanced (all higher reported groups) vs no/less advanced (lowest reported group). Pooled standardized mean differences (SMDs) and risk ratios (RRs) with 95% confidence intervals (CI) were determined for BMD and fracture, respectively, using random-effects models.

RESULTS

Of 2,192 articles screened, 86 (61,553 participants) were included in the review, while 42 provided data for meta-analysis. AAC was associated with lower BMD at the total hip [SMD=-1.05 (95%CI: -1.47 to -0.63); 16 studies], femoral neck [-0.25 (-0.46 to - 0.04); 10] and lumbar spine [-0.67 (-1.21 to -0.12); 20]. AAC was associated with a greater risk of any fracture [RR= 1.73 (95%CI: 1.48 to 2.02); 27]. AAC was also associated with vertebral, non-vertebral and hip fractures. In dose-response analysis, the highest AAC group had greater risks of any, vertebral and non-vertebral fractures.

CONCLUSIONS

AAC is associated with lower BMD and increased fracture risk at multiple sites, underscoring the potential importance of vascular disease on skeletal health. Detection of AAC at the time of BMD testing may provide clinicians with prognostic information about bone health to enhance osteoporosis screening programs and fracture risk prediction.

High cholesterol and low triglycerides are associated with total lumbar bone mineral density among adults aged 50 years and over: The NHANES 2017–2020

Background

The association between cholesterol and triglycerides with the lumbar bone mineral density (BMD) was widely investigated, but the results remained conflicting. This study aimed to investigate the relationship between total cholesterol, triglycerides, and total lumbar BMD in adults.

Materials and methods

This cross-sectional study included 1,985 individuals aged 50 years and over. The data on total cholesterol, triglycerides, total lumbar BMD, and other covariates were obtained from the National Health and Nutritional (NHANES) between 2017 and March 2020 pre-pandemic. Multivariate logistic regression models were utilized to investigate the association between cholesterol, triglycerides, and total lumbar BMD. Smooth curve fittings and generalized additive models were also used to analyze the potential non-linearity.

Results

A total of 901 men and 1,084 women with a mean age of 63.02 ± 8.72 years (age 50–80 years) were included in this study. In multivariate regression analysis, the association between cholesterol and total lumbar BMD was negative (β = −0.026, 95% CI: −0.033, −0.020). This relationship still existed after adjusted for gender and race (β = −0.018, 95% CI: −0.025, −0.012) and fully adjusted for all covariates (β = −0.022, 95% CI: −0.029, −0.015). The association between triglycerides and total lumbar BMD was positive (β = 0.024, 95% CI: 0.017, 0.031). This relationship still existed after adjusted for gender and race (β = 0.021, 95% CI: 0.015, 0.028) and fully adjusted for all covariates (β = 0.021, 95% CI: 0.014, 0.028). In threshold effect analysis, the relationship between triglycerides and total lumbar BMD was an inverted U-shaped curve with the inflection point at 2.597 mmol/L.

Conclusion

High levels of total cholesterol and relatively low levels of triglycerides are significantly associated with the total lumbar BMD in adults aged 50 years and over.

Is dual-energy absorptiometry accurate in the assessment of bone status of patients with chronic kidney disease?

Several patients with chronic kidney disease (CKD) have deteriorated bone status. Estimation of bone status using DXA has limitations especially in patients with CKD accompanying aortic calcifications. Quantitative CT and the trabecular bone score could be more accurate methods to estimate bone status for patients with CKD and vascular calcifications.

INTRODUCTION

It remains unclear whether dual-energy absorptiometry (DXA) is appropriate for the assessment of bone status in patients with chronic kidney disease (CKD), a disease that impacts bone health. The aims of this study were to compare DXA and central quantitative computed tomography (cQCT) and to evaluate bone status in patients with pre-dialysis CKD.

METHODS

This retrospective study included 363 healthy control subjects whose bone mineral density (BMD) was evaluated with DXA and 117 CKD patients whose BMD was evaluated using both cQCT and DXA. Diagnostic discordance was assessed between the lumbar spine (LS) and femur neck (FN) from DXA or between two modalities. The trabecular bone score (TBS) was extracted from DXA images. The volume of abdominal aortic calcification (AAC) was calculated using CT images from cQCT.

RESULTS

Using LS DXA T-score, osteoporosis was less common in the CKD group than in controls. Patients with normal LS BMD using DXA were reclassified into osteopenia or osteoporosis using cQCT in CKD patients. Among discordant subjects between FN and LS in DXA, a higher BMD of LS was more common in CKD patients than in controls. CKD patients had lower TBS than controls despite having the same diagnosis using DXA. AAC volume negatively correlated with BMD from cQCT and with TBS but not with BMD from DXA.

CONCLUSIONS

TBS and cQCT could accurately assess bone status in CKD patients since DXA may overestimate LS BMD, likely due to an increased AAC volume.

Expression of Calcification and Extracellular Matrix Genes in the Cardiovascular System of the Healthy Domestic Sheep (Ovis aries)

The maintenance of a healthy cardiovascular system requires expression of genes that contribute to essential biological activities and repression of those that are associated with functions likely to be detrimental to cardiovascular homeostasis. Vascular calcification is a major disruption to cardiovascular homeostasis, where tissues of the cardiovascular system undergo ectopic calcification and consequent dysfunction, but little is known about the expression of calcification genes in the healthy cardiovascular system. Large animal models are of increasing importance in cardiovascular disease research as they demonstrate more similar cardiovascular features (in terms of anatomy, physiology and size) to humans than do rodent species. We used RNA sequencing results from the sheep, which has been utilized extensively to examine calcification of prosthetic cardiac valves, to explore the transcriptome of the heart and cardiac valves in this large animal, in particular looking at expression of calcification and extracellular matrix genes. We then examined genes implicated in the process of vascular calcification in a wide array of cardiovascular tissues and across multiple developmental stages, using RT-qPCR. Our results demonstrate that there is a balance between genes that promote and those that suppress mineralization during development and across cardiovascular tissues. We show extensive expression of genes encoding proteins involved in formation and maintenance of the extracellular matrix in cardiovascular tissues, and high expression of hematopoietic genes in the cardiac valves. Our analysis will support future research into the functions of implicated genes in the development of valve calcification, and increase the utility of the sheep as a large animal model for understanding ectopic calcification in cardiovascular disease. This study provides a foundation to explore the transcriptome of the developing cardiovascular system and is a valuable resource for the fields of mammalian genomics and cardiovascular research.

Surgical management of bilateral hip fractures in a patient with fibrodysplasia ossificans progressiva treated with the RAR-γ agonist palovarotene: a case report

Background

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare disorder marked by painful, recurrent flare-ups and heterotopic ossification (HO) in soft and connective tissues, which can be idiopathic or provoked by trauma, illness, inflammation, or surgery. There are currently no effective treatments for FOP, or for patients with FOP who must undergo surgery. Palovarotene, an investigational retinoic acid receptor-γ agonist, offers a potential avenue to prevent HO formation.

Case presentation

The patient is a 32 year-old male, who at age 29 enrolled in a study evaluating palovarotene to prevent HO formation in FOP. One year after starting palovarotene, he fell resulting in a left intertrochanteric fracture. He underwent intramedullary nailing of the femur shaft with screw placement at the distal femur. After surgery, he received palovarotene at 20 mg/day for 4 weeks, then 10 mg/day for 8 weeks. Imaging 12 weeks after surgery showed new bridging HO at the site of intramedullary rod insertion and distal screw.

Nine months after the left hip fracture, the patient had a second fall resulting in a subdural hematoma, left parietal bone fracture, and right intertrochanteric fracture. He underwent intramedullary nailing of the right hip, in a modified procedure which did not require distal screw placement. Palovarotene 20 mg/day was started at fracture occurrence and continued for 4 weeks, then reduced to 10 mg/day for 8 weeks. HO also formed near the insertion site of the intramedullary rod. No HO developed at the right distal intramedullary rod. After each fracture, the patient had prolonged recurrent flare-ups around the hips.

Conclusion

Surgery is only rarely considered in FOP due to the high risks of procedural complications and potential for inducing HO. This case emphasizes the risks of increased flare activity and HO formation from injury and surgery in patients with FOP. The efficacy of HO prevention by palovarotene could not be assessed; however, our observation that palovarotene can be administered in an individual with FOP following surgery with no negative impact on clinical fracture healing, osteointegration, or skin healing will help facilitate future trials testing the role of palovarotene as a therapy for HO.

TREML4 Promotes Inflammatory Programs in Human and Murine Macrophages and Alters Atherosclerosis Lesion Composition in the Apolipoprotein E Deficient Mouse

The Triggering Receptor Expressed on Myeloid cells-like 4 (TREML4) is a member of the TREM receptor family, known modulators of inflammatory responses. We have previously found that TREML4 expression positively correlates with human coronary arterial calcification (CAC). However, the role of TREML4 in the pathogenesis of cardiovascular disease remains incompletely defined. Since macrophages play a key role in inflammatory conditions, we investigated if activated macrophages selectively expressed TREML4 and found that carriage of either one of the eQTL SNP's previously associated with increased TREML4 expression conferred higher expression in human inflammatory macrophages (M1) compared to alternatively activated macrophages (M2). Furthermore, we found that TREML4 expression in human M1 dysregulated several inflammatory pathways related to leukocyte activation, apoptosis and extracellular matrix degradation. Similarly, murine M1 expressed substantial levels of Treml4, as did oxLDL treated macrophages. Transcriptome analysis confirmed that murine Treml4 controls the expression of genes related to inflammation and lipid regulation pathways, suggesting a possible role in atherosclerosis. Analysis of Apoe-/-/Treml4-/- mice showed reduced plaque burden and lesion complexity as indicated by decreased stage scores, macrophage content and collagen deposition. Finally, transcriptome analysis of oxLDL-loaded murine macrophages showed that Treml4 represses a specific set of genes related to carbohydrate, ion and amino acid membrane transport. Metabolomic analysis confirmed that Treml4 deficiency may promote a beneficial relationship between iron homeostasis and glucose metabolism. Together, our results suggest that Treml4 plays a role in the development of cardiovascular disease, as indicated by Treml4-dependent dysregulation of macrophage inflammatory pathways, macrophage metabolism and promotion of vulnerability features in advanced lesions.

Effects of teriparatide on morphology of aortic calcification in aged hyperlipidemic mice

Calcific aortic vasculopathy correlates with bone loss in osteoporosis in an age-independent manner. Prior work suggests that teriparatide, the bone anabolic treatment for postmenopausal osteoporosis, may inhibit the onset of aortic calcification. Whether teriparatide affects the progression of preexisting aortic calcification, widespread among this patient population, is unknown. Female apolipoprotein E-deficient mice were aged for over 1 yr to induce aortic calcification, treated for 4.5 wk with daily injections of control vehicle (PBS), 40 µg/kg teriparatide (PTH40), or 400 µg/kg teriparatide (PTH400), and assayed for aortic calcification by microcomputed tomography (microCT) before and after treatment. In a followup cohort, aged female apolipoprotein E-deficient mice were treated with PBS or PTH400 and assayed for aortic calcification by serial microCT and micropositron emission tomography. In both cohorts, aortic calcification detected by microCT progressed similarly in all groups. Mean aortic ¹⁸F-NaF incorporation, detected by serial micropositron emission tomography, increased in the PBS-treated group (+14 ± 5%). In contrast, ¹⁸F-NaF incorporation decreased in the PTH400-treated group (-33 ± 20%, P = 0.03). Quantitative histochemical analysis by Alizarin red staining revealed a lower mineral surface area index in the PTH400-treated group compared with the PBS-treated group ( P = 0.04). Furthermore, Masson trichrome staining showed a significant increase in collagen deposition in the left ventricular myocardium of mice that received PTH400 [2.1 ± 0.6% vs. control mice (0.5 ± 0.1%), P = 0.02]. In summary, although teriparatide may not affect the calcium mineral content of aortic calcification, it reduces ¹⁸F-NaF uptake in calcified lesions, suggesting the possibility that it may reduce mineral surface area with potential impact on plaque stability. NEW & NOTEWORTHY Parathyroid hormone regulates bone mineralization and may also affect vascular calcification, which is an important issue, given that its active fragment, teriparatide, is widely used for the treatment of osteoporosis. To determine whether teriparatide alters vascular calcification, we imaged aortic calcification in mice treated with teriparatide and control mice. Although teriparatide did not affect the calcium content of cardiovascular deposits, it reduced their fluoride tracer uptake.

A novel quantitative approach to the measurement of abdominal aortic calcification as applied to the Canadian Multicenter Osteoporosis Study (CaMOS)

BACKGROUND AND AIMS

Lateral spine radiographs provide an inexpensive resource for characterizing abdominal aortic calcification (AAC). A widely accepted measurement of AAC is the semi-quantitative technique generated by the Framingham Heart Study (F-AAC-24). We sought to develop an analytical method to quantify ACC (Q_AAC) on lateral spine radiographs and compare the finding to conventional subjective measurements.

METHODS

Severity of AAC was quantified by measuring pixel intensities in the user-defined region of the aorta with internal standardization to the vertebral endplates and background calibration to the density of the vertebral body. The association between bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) and AAC measured by Q_AAC, F-AAC-24 and a modified Framingham score (F-AAC-12) was determined in 110 participants of the Canadian Multicenter Osteoporosis Study (CaMOS).

RESULTS

The inter-observer reliability for the Q_AAC was slightly higher than with the visual and semi-quantitative Framingham method and the pseudo-colored images illustrate the potential to meaningfully resolve severity of calcification. There was a significant negative association between Q_AAC and BMD measures of the hip and spine. This association remained significant after adjustment for age, sex, estimated glomerular filtration rate, phosphate and hypertension. Significant predictors of F-ACC-12 and 24 included age and hypertension.

CONCLUSIONS

The Q_AAC is a reproducible approach to measuring AAC. Whether it is capable of monitoring subtle calcific changes over time requires further study. This technique could be applied to large studies that seek to determine the impact of interventions that modify bone density as a treatment for vascular calcification and cardiovascular disease in the general population.

Novel association between bone mineral density scores and the prevalence of peripheral artery disease in both sexes

The purpose of the current study was to investigate the association between bone mineral density (BMD) scores and the prevalence of peripheral artery disease (PAD) in a large cohort of subjects who underwent arterial Doppler assessments and calcaneal bone densitometry. The study was performed using data obtained from Life Line Screening Inc. Subjects were self-selected and paid for screening tests. The prevalence of PAD was significantly higher in men with osteopenia (4.5%) and osteoporosis (10.9%) compared to men with normal BMD (3.0%) ( p<0.001). Osteopenia (odds ratio (OR) 1.3) and osteoporosis (OR 2.3) were found to be independent risk factors for the presence of PAD in men. The prevalence of PAD was significantly higher in women with osteopenia (4.8%) and osteoporosis (11.8%) compared to women with normal BMD (3.3%) ( p<0.001). Osteopenia (OR 1.15) and osteoporosis (OR 1.8) were found to be independent risk factors for the presence of PAD in women. The current study reports a strong association of abnormal BMD analysis with the prevalence of PAD, which persists even when controlling for age and associated atherosclerotic risk factors. Although the mechanism by which these two disease processes is related is not completely elucidated, the presence of osteoporosis should make clinicians aware of the possibility of occult PAD or associated atherosclerotic disease in appropriate patients.

Osteoporosis and vascular calcification in postmenopausal women: a cross-sectional study

Objectives To estimate the correlation between osteoporosis and vascular calcification in postmenopausal women and the influence of calcium/vitamin D supplements on vascular calcification. Methods A cross-sectional study was performed including 29 women with osteoporosis (15 not taking supplements) and 18 age-matched, non-osteoporotic women. They were evaluated for cardiovascular risk factors and blood tests, lateral X-ray of lumbar spine (assessment of abdominal aorta calcification, AAC) and carotid ultrasound (increased intima media thickness (iIMT) or calcified plaques) were performed. Results In univariate analysis, osteoporotic women were 16 times more likely to develop AAC (odds ratio (OR) 15.8, 95% confidence interval (CI) 1.9-135.4) and seven times more likely to develop iIMT (OR 6.8, 95% CI 1.8-25.4) compared to normal individuals. The odds of developing AAC and iIMT were increased each year after menopause (OR 1.11, 95% CI 1.01-1.2 and OR 1.18, 95% CI 1.05-1.3, respectively) and with aging (OR 1.27, 95% CI 1.1-1.47 and OR = 1.17, 95% CI 1.04-1.3, respectively). Calcified plaques were significantly correlated with osteoporosis (p = 0.014). In multivariate analysis, osteoporosis was an independent risk factor for AAC (OR 13.3, 95% CI 1.3-134.4) and iIMT (OR 4.7, 95% CI 1.1-19.9). Low doses of supplements did not appear to affect vascular calcification (p = 0.6). Conclusions Osteoporosis is associated with increased calcification of the abdominal aorta and carotids. Low doses of supplements do not appear to cause any increase in vascular calcification in osteoporotic women.

Identification of early vascular calcification with (18)F-sodium fluoride: potential clinical application

Vascular calcification plays a prominent role in cardiovascular disease. Once considered to be a passive consequence of aging, this pathological process is now accepted to be dynamic and tightly regulated, its onset triggered by inflammation and necrosis and its progression bearing key similarities to osteogenesis. A major potential advance in our ability to understand the natural history and clinical implications of vascular calcification is the detection of its early and dynamic stages through the use of the positron-emitting radiotracer, (18)F-sodium fluoride. Alongside anatomical information gained from computed tomography, hybrid positron emission and computed tomography (PET/CT) imaging with (18)F-sodium fluoride has, for the first time, enabled the non-invasive detection of microcalcification within the aortic valve, great vessels, and vulnerable coronary plaque. This has raised promise that exploring this process may allow improved risk prediction, better application of current therapies and ultimately the development of novel treatments to target this widespread pathology.

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.

Impact of lifestyle factors on fracture risk in older patients with cardiovascular disease: a prospective cohort study of 26,335 individuals from 40 countries

BACKGROUND

fractures are a major health concern among the elderly. People at risk for cardiovascular disease (CVD) are at an increased risk for fractures. The aim of this study was to assess the individual and combined effect of the CVD risk factors of smoking, alcohol consumption and physical activity on fracture risk in a large sample of older individuals with CVD or diabetes with end-organ damage.

METHODS

we analysed data for 26,335 adults, aged 55 years or older, who participated in two large antihypertensive drug treatment trials and who had no previous fracture at baseline. Lifestyle factors were assessed by the standardised questionnaire and their individual and combined effects on incident fracture risk were modelled using Cox proportional hazard regression.

RESULTS

during the 56-month follow-up, 1,079 incident fractures occurred; 508 (6.51%) among women and 571 (3.08%) among men. Smoking [hazard ratio (HR) 1.52, 95% confidence interval (CI) 1.27-1.82] and low physical activity (HR: 1.19, 95% CI: 1.05-1.36) were associated with an increased risk of any fracture, while high alcohol intake showed a directional, but non-significant, relationship with fracture risk (HR: 1.09, 95% CI: 0.64-1.84). Compared with participants with no lifestyle risk factors, those having one, two, or three risk factors had an increased risk of a future fracture (HR: 1.17, 95% CI: 1.03-1.34 for one risk factor; HR: 1.73, 95% CI: 1.38-2.16 for two risk factors; and HR: 2.37, 95% CI: 0.88-6.36 for three risk factors; P for trend <0.001).

CONCLUSIONS

a healthier lifestyle advocated to reduce the risk of CVD is associated with a significant and graded reduction in fracture risk.

Alkaline phosphatase and risk of stroke among Japanese: the Circulatory Risk in Communities Study (CIRCS)

Although serum alkaline phosphatase (ALP) levels have been associated with mortality from all-cause and from either ischemic or hemorrhagic stroke, no study has been published of the associations between ALP and the incidence of stroke. We therefore examined the associations of ALP with risk of stroke among Japanese, stratified by drinking status because ALP is known as an enzyme affected by alcohol consumption. We conducted a prospective cohort study of 10,754 Japanese subjects (4098 men and 6656 women) aged 40-69 years and living in 4 communities under systematic surveillance for stroke incidence. During the 16-year follow-up, we documented 264 strokes (164 ischemic strokes and 69 hemorrhagic strokes) for men and 225 strokes (118 ischemic strokes and 89 hemorrhagic strokes) for women. There was a U-shaped association between ALP level and stroke incidence in both men and women, which was confined primarily to nondrinkers. For nondrinkers, higher ALP levels were associated with an elevated risk of ischemic stroke for men and of hemorrhagic stroke for women, whereas lower ALP levels were associated with elevated risks of ischemic and hemorrhagic strokes in both men and women. Our data indicate that not only higher, but also lower, serum ALP level may be a predictor for the risk of stroke in nondrinking men and women.

Nuclear factor of activated T cells mediates oxidised LDL-induced calcification of vascular smooth muscle cells

AIMS/HYPOTHESIS

Vascular calcification is a prominent feature of both atherosclerosis and diabetes, and is clinically associated with osteoporosis. The expression of bone-regulatory factors and the impact of oxidative stress in aortic calcification are well-documented. Recently, nuclear factor of activated T cells (NFAT) cytoplasmic, calcineurin-dependent 1 (NFATc1) was identified in calcified aortic valves and has been implicated in vascular calcification. Therefore, we assessed the mechanisms of osteogenic transdifferentiation of vascular smooth muscle cells induced by oxidised LDL (oxLDL) and evaluated the role of NFAT in this process.

METHODS

Human coronary artery smooth muscle cells (HCASMCs) were cultured for 21 days in medium supplemented with oxLDL. NFAT was inhibited using the NFAT inhibitor VIVIT, or by knockdown with small interfering RNA (siRNA). Osteogenic transdifferentiation was assessed by gene expression, matrix mineralisation and alkaline phosphatase activity.

RESULTS

Exposure to oxLDL caused the transformation of HCASMCs towards an osteoblast-like phenotype based on increased mineral matrix formation and RUNX2 expression. NFATc1 blockade completely prevented oxLDL-induced osteogenic transformation of HCASMCs as well as oxLDL-induced stimulation of osteoblast differentiation. In contrast, matrix mineralisation induced by osteogenic medium was independent of the NFAT pathway. Of note, oxLDL-conditioned medium from HCASMCs transferred to bone cells promoted osteoblast mineralisation. Consistent with these in vitro findings, diabetic rats with a twofold increase in oxidised lipid levels displayed higher aortic calcium concentrations and increased expression of osteogenic markers and production of NFATc1.

CONCLUSIONS/INTERPRETATION

Our results identify the NFAT signalling pathway as a novel regulator of oxLDL-induced transdifferentiation of vascular smooth muscle cells towards an osteoblast-like phenotype.

Calcific aortic valve stenosis: methods, models, and mechanisms

Calcific aortic valve stenosis (CAVS) is a major health problem facing aging societies. The identification of osteoblast-like and osteoclast-like cells in human tissue has led to a major paradigm shift in the field. CAVS was thought to be a passive, degenerative process, whereas now the progression of calcification in CAVS is considered to be actively regulated. Mechanistic studies examining the contributions of true ectopic osteogenesis, nonosseous calcification, and ectopic osteoblast-like cells (that appear to function differently from skeletal osteoblasts) to valvular dysfunction have been facilitated by the development of mouse models of CAVS. Recent studies also suggest that valvular fibrosis, as well as calcification, may play an important role in restricting cusp movement, and CAVS may be more appropriately viewed as a fibrocalcific disease. High-resolution echocardiography and magnetic resonance imaging have emerged as useful tools for testing the efficacy of pharmacological and genetic interventions in vivo. Key studies in humans and animals are reviewed that have shaped current paradigms in the field of CAVS, and suggest promising future areas for research.

Molecular imaging insights into early inflammatory stages of arterial and aortic valve calcification

Traditional imaging modalities such as computed tomography, although perfectly adept at identifying and quantifying advanced calcification, cannot detect the early stages of this disorder and offer limited insight into the mechanisms of mineral dysregulation. This review presents optical molecular imaging as a promising tool that simultaneously detects pathobiological processes associated with inflammation and early stages of calcification in vivo at the (sub)cellular levels. Research into treatment of cardiovascular calcification is lacking, as shown by clinical trials that have failed to demonstrate the reduction of calcific aortic stenosis. Hence, the need to elucidate the pathways that contribute to cardiovascular calcification and to develop new therapeutic strategies to prevent or reverse calcification has driven investigations into the use of molecular imaging. This review discusses studies that have used molecular imaging methods to advance knowledge of cardiovascular calcification, focusing in particular on the inflammation-dependent mechanisms of arterial and aortic valve calcification.

Molecular imaging insights into early inflammatory stages of arterial and aortic valve calcification

Traditional imaging modalities such as computed tomography, although perfectly adept at identifying and quantifying advanced calcification, cannot detect the early stages of this disorder and offer limited insight into the mechanisms of mineral dysregulation. This review presents optical molecular imaging as a promising tool that simultaneously detects pathobiological processes associated with inflammation and early stages of calcification in vivo at the (sub)cellular levels. Research into treatment of cardiovascular calcification is lacking, as shown by clinical trials that have failed to demonstrate the reduction of calcific aortic stenosis. Hence, the need to elucidate the pathways that contribute to cardiovascular calcification and to develop new therapeutic strategies to prevent or reverse calcification has driven investigations into the use of molecular imaging. This review discusses studies that have used molecular imaging methods to advance knowledge of cardiovascular calcification, focusing in particular on the inflammation-dependent mechanisms of arterial and aortic valve calcification.

Biosynthesis of the vitamin K-dependent matrix Gla protein (MGP) in chondrocytes: a fetuin-MGP protein complex is assembled in vesicles shed from normal but not from osteoarthritic chondrocytes

OBJECTIVE

Mineralization has been observed in osteoarthritic cartilage but the mechanisms are incompletely understood. Vitamin K is an essential cofactor in post-translational modification of proteins where specific Glu residues become modified to Ca(++) binding gamma-carboxyglutamic acid residues (Gla). One such protein, matrix Gla protein (MGP), is a known mineralization inhibitor. This study determined if synthesis of MGP and formation of a fetuin-MGP protein complex was altered in chondrocytes and vesicles from osteoarthritis (OA) cartilage.

METHODS

Chondrocytes and vesicles were isolated from normal and OA human articular cartilage and lysates prepared. Specific antibodies were used in immunoblotting to detect the mature fully gamma-carboxylated form of MGP (cMGP) and non-gamma-carboxylated MGP (ucMGP) as well as fetuin and MGP-fetuin complexes. gamma-carboxylase activity was measured by (14)CO(2) incorporation into the carboxylase peptide substrate FLEEL. Immunocytochemistry was used to examine fetuin in cartilage sections and uptake of biotin-labeled fetuin by isolated chondrocytes.

RESULTS

Chondrocytes and vesicles from osteoarthritic tissue produced significantly less cMGP compared to those from normal cartilage. This correlated with significantly less vitamin K-dependent gamma-carboxylase enzyme activity in OA chondrocytes. Fetuin was found to be present in articular cartilage and cultured chondrocytes were capable of fetuin uptake. A fetuin-MGP complex was identified in normal chondrocytes and in vesicles shed from these cells but not in OA cells or vesicles.

CONCLUSIONS

The absence of cMGP and of the cMGP-fetuin complex in OA cells and OA vesicles may be an important mechanism for increased mineralization of osteoarthritic cartilage.

Bone mineral density and atherosclerosis: the Multi-Ethnic Study of Atherosclerosis, Abdominal Aortic Calcium Study

CONTEXT

Molecular and cell biology studies have demonstrated an association between bone and arterial wall disease, but the significance of a population-level association is less clear and potentially confounded by inability to account for shared risk factors.

OBJECTIVE

To test population-level associations between atherosclerosis types and bone integrity.

MAIN OUTCOME MEASURES

Volumetric trabecular lumbar bone mineral density (vBMD), ankle-brachial index (ABI), intima-media thickness (IMT) of the common carotid (CCA-IMT) and internal carotid (ICA-IMT) arteries, and carotid plaque echogenicity.

DESIGN, SETTING AND PARTICIPANTS

A random subset of participants from the Multi-Ethnic Study of Atherosclerosis (MESA) assessed between 2002 and 2005.

RESULTS

904 post-menopausal female (62.4 years; 62% non-white; 12% ABI <1; 17% CCA-IMT >1mm; 33% ICA-IMT >1mm) and 929 male (61.4 years; 58% non-white; 6% ABI <1; 25% CCA-IMT >1mm; 40% ICA-IMT >1mm) were included. In serial, sex-specific regression models adjusting for age, ethnicity, body mass index, dyslipidemia, hypertension, smoking, alcohol consumption, diabetes, homocysteine, interleukin-6, sex hormones, and renal function, lower vBMD was associated with lower ABI in men (p for trend <0.01) and greater ICA-IMT in men (p for trend <0.02). CCA-IMT was not associated with vBMD in men or women. Carotid plaque echogenicity was independently associated with lower vBMD in both men (trend p=0.01) and women (trend p<0.04). In all models, adjustment did not materially affect results.

CONCLUSIONS

Lower vBMD is independently associated with structural and functional measures of atherosclerosis in men and with more advanced and calcified carotid atherosclerotic plaques in both sexes.