Radiographic measure of aorta calcification is a site-specific predictor of bone loss and fracture risk at the hip

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Saturated fatty acids enhance osteoclast survival

Hyperlipidemia and marrow fat are associated with lowering bone density in vivo, suggesting that lipid contributes to bone loss. Using bone marrow-derived macrophages, we investigated the effect of saturated fatty acids (SFA) on osteoclastogenesis. The level of free fatty acids and adiposity in bone marrow was significantly elevated in obese mice. SFA increased osteoclast (OC) survival by preventing apoptosis. SFA caused the production of MIP-1alpha and led to activation of nuclear factor (NF)-kappaB in the OC. The absence of Toll-like receptor 4 (TLR4) or myeloid differentiation factor 88 (MyD88) abolished the survival effect of SFA on OC.

Osteoprotegerin as a predictor of coronary artery disease and cardiovascular mortality and morbidity

Osteoprotegerin (OPG) is a glycoprotein that acts as a decoy receptor for receptor activator of nuclear factor kappaB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand. The OPG/RANKL/receptor activator of nuclear factor kappaB axis plays an important regulatory role in the skeletal, immune, and vascular systems. The protective role of OPG, in animal models, against vascular calcification has not been replicated in human trials; moreover, increased OPG levels have been consistently associated with the incidence and prevalence of coronary artery disease. There seems to be some dichotomy in the role of OPG, RANKL, and tumor necrosis factor-related apoptosis-inducing ligand in atherosclerosis and plaque stability. In this review, we integrate the findings from some of the important studies and try to draw conclusions with a view to gaining some insight into the complex interactions of the OPG/RANKL/receptor activator of nuclear factor kappaB axis and tumor necrosis factor-related apoptosis-inducing ligand in the pathophysiology of atherosclerosis.

Serum alkaline phosphatase and phosphate and risk of mortality and hospitalization

BACKGROUND AND OBJECTIVES

Elevated alkaline phosphatase (AlkPhos) and phosphate levels are associated with cardiovascular morbidity and mortality in patients receiving dialysis. A retrospective cohort study was conducted to test these associations in outpatients with an estimated GFR > or =60 ml/min/1.73 m(2).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with serum AlkPhos and phosphate levels measured between 2000 and 2002 (n = 10,743) at Montefiore Medical Center (MMC) clinics were followed through September 11, 2008 (median 6.8 years). Mortality data were obtained via Social Security Administration records (n = 949 deaths). Hospitalization data were obtained from MMC records.

RESULTS

The mean age was 51 years, 64% were women, 22% were white, 26% were non-Hispanic black, 16% were Hispanic, 13% had a diagnosis of hypertension, 9% had diabetes mellitus, and 8% had cardiovascular disease at baseline. AlkPhos and phosphate were independently associated with mortality and cardiovascular-related hospitalization after multivariable adjustment. Comparing patients in the highest (> or =104 U/L) versus lowest quartile of AlkPhos (< or =66 U/L), the adjusted hazard ratio (HR) for mortality was 1.65 (P trend across quartiles <0.001). For the highest compared with the lowest quartile of serum phosphate (> or =3.8 mg/dl versus < or =3.0 mg/dl), the adjusted HR for mortality was 1.29 (P trend across quartiles = 0.008). High AlkPhos but not phosphate levels were also associated with all-cause, infection-related, and fracture-related hospitalization.

CONCLUSIONS

Higher levels of serum AlkPhos and phosphate were associated with increased mortality and cardiovascular-related hospitalization in an inner-city clinic population. Further studies are needed to elucidate mechanisms underlying these associations.

Bone mineral density and prediction of non-osteoporotic disease

It is widely recognized that bone mineral density (BMD) is one of the best predictors of osteoporotic fractures. Sex hormone status clearly affects bone either directly or indirectly and a longer estrogen exposure appears to be a major determinant of postmenopausal BMD. Accordingly, several studies have led to the hypothesis that BMD might represent a marker of the accumulated lifetime exposure of estrogen and therefore be used as a predictor factor of the risk of other postmenopausal conditions such as breast cancer or cardiovascular diseases (CVD). With regard to the risk of breast cancer, there is evidence that different surrogate markers of lifetime exposure to estrogen are associated with an increased risk for breast cancer. Most of these markers are the opposite of those for the risk of fracture. Furthermore, several studies have also reported that women with higher BMD have an increased risk of breast cancer compared to women with lower BMD. On the other hand, postmenopausal women with osteoporosis are at increased risk for acute cardiovascular events and mortality independently of age and cardiovascular risk factors. BMD has been shown to inversely correlate with surrogate markers of CVD including aortic calcifications and atherosclerosis. The underlying mechanisms of such a relationship are not fully understood. Several plausible molecular links are serum lipids, pro-inflammatory cytokines or the RANK/RANK ligand/osteoprotegerin system. Interestingly, all of these factors are modulated by estrogens. It could thus be hypothesized that the intensity of postmenopausal estrogen deficiency could be also the common pathogenic factor between atherosclerosis and osteoporosis.

PLCL1 rs7595412 variation is not associated with hip bone size variation in postmenopausal Danish women

BACKGROUND

Bone size (BS) variation is under strong genetic control and plays an important role in determining bone strength and fracture risk. Recently, a genome-wide association study identified polymorphisms associated with hip BS variation in the PLCL1 (phospholipase c-like 1) locus. Carriers of the major A allele of the most significant polymorphism, rs7595412, have around 17% larger hip BS than non-carriers. We therefore hypothesized that this polymorphism may also influence postmenopausal complications.

METHODS

The effects of rs7595412 on hip BS, bone mineral density (BMD), vertebral fractures, serum Crosslaps and osteocalcin levels were analyzed in 1,191 postmenopausal Danish women.

RESULTS

This polymorphism had no influence on hip and spine BS as well as on femur and spine BMD. Women carrying at least one copy of the A allele had lower levels of serum osteocalcin as compared with those homozygous for the G allele (p = 0.03) whereas no effect on serum Crosslaps was detected. Furthermore, women homozygous for the A allele were more affected by vertebral fractures than those carrying at least one copy of the G allele (p = 0.04).

CONCLUSIONS

In postmenopausal women, our results suggest that the PLCL1 rs7595412 polymorphism has no obvious effect on hip BS or BMD but may be nominally associated with increased proportion of vertebral fracture and increased levels of osteocalcin.

A radiographic study on the associations of age and prevalence of vertebral fractures with abdominal aortic calcification in Japanese postmenopausal women and men

The purpose of the present study was to determine the associations of age and history of non- and low-traumatic fractures with the severity of abdominal aortic calcification in Japanese postmenopausal women and men. Four hundred and one Japanese persons (24 men and 377 postmenopausal women, mean age: 73.8 years) for whom thoracic and lumbar spine radiographs had been obtained to evaluate their posture prior to patient participation in a fall-prevention exercise program were enrolled. The associations of sex, age, history of hip fracture, prevalence of vertebral fracture, and spondylosis grade (the Nathan degree) with the severity of abdominal aortic calcification (length of calcification, as evaluated according to the number of vertebral bodies) were analyzed. Nine subjects (2.2%) had a history of hip fracture, and 221 (55.1%) had at least one prevalent vertebral fracture. Two hundred and sixty-seven subjects (66.6%) had first-degree spondylosis. Age and the number of prevalent vertebral fractures, but not sex, history of hip fracture, or spondylosis grade, were significantly associated with the severity of abdominal aortic calcification. The present study confirmed that age and the number of vertebral fractures were associated with the severity of abdominal aortic calcification in Japanese postmenopausal women and men.

Association between low bone mass and aortic valve sclerosis in Koreans

BACKGROUND

Osteoporosis or low bone mass has been associated with cardiovascular disease and calcification in several clinical studies. However, few studies have assessed the relationship between bone mass and valvular calcification. The aim of this study was to evaluate the relationship between low bone mass and aortic valve sclerosis in Korean men and women.

METHODS

A total of 211 men and 117 women were included in this study. Each subject's bone mineral density (BMD) was measured with dual-energy X-ray absorptiometry, and aortic valve sclerosis was assessed using transthoracic echocardiography. Association between low bone mass and aortic valve sclerosis was assessed with multivariate logistic regression analysis in this cross-sectional study.

RESULTS

Of 328 total subjects enrolled in this study, 50 men (23.7%) and 18 women (15.4%) were found to have aortic valve sclerosis. The mean (+/-SD) BMD T-scores were -0.5 (+/-0.8) in men and -0.9 (+/-1.0) in women. After adjusting for covariates, only women with aortic valve sclerosis had significantly lower BMD T-scores than those without it. Multivariate logistic regression analysis showed that age, smoking and hypertension were independently associated with increased risk of aortic valve sclerosis in men. In women, however, logistic regression analysis showed that BMD T-score, as well as age, was an independent variable for aortic valve sclerosis. We also found that a T-score of less than -1.5 was significantly associated with increased risk of aortic valve sclerosis in women compared to normal T-scores.

CONCLUSION

Low bone mass might be independently associated with increased risk of aortic valve sclerosis in women, but not in men. Women with low bone mass should be further evaluated for the presence of aortic valve sclerosis and related cardiovascular diseases.

Lower bone mineral density is associated with higher coronary calcification and coronary plaque burdens by multidetector row coronary computed tomography in pre- and postmenopausal women

OBJECTIVES

There is growing evidence for the association between bone mineral density (BMD) and vascular calcification, which is related to cardiovascular disease. Coronary multidetector row computed tomography (MDCT) is a noninvasive tool developed to evaluate coronary status precisely. We used MDCT to evaluate this association.

DESIGN AND PATIENTS

Eight hundred and fifteen subjects received routine checkups. After excluding subjects with factors affecting bone metabolism and cardiovascular disease, 467 subjects were analysed.

MEASUREMENTS

Coronary calcification was measured with MDCT and BMD was measured with dual X-ray absorptiometry (DXA).

RESULTS

The BMD of the femur and the lumbar spine (L-spine) were negatively associated with the coronary calcium score (CCS) after adjusting for age in women but not in men. This inverse correlation was stronger in women with a longer time since menopause (r = -0.35 at femur, postmenopausal women vs. r = -0.10 at femur, premenopausal women, P < 0.05), and it was stronger at the femur than in the L-spine (r = -0.35 at femur vs. r = -0.16 at L-spine, P < 0.01). The relationship was also stronger in postmenopausal women with osteoporosis and osteopaenia than in women with normal BMD. The lower BMD was associated with higher coronary plaque burdens and multidiseased coronary vessels in both men and women (P < 0.01).

CONCLUSIONS

Increased CCS and subclinical atherosclerosis of plaque burdens as revealed by MDCT was associated with a low BMD in all women, independent of cardiovascular risk factors and age.

The effect of alendronate sodium on carotid artery intima-media thickness and lipid profile in women with postmenopausal osteoporosis

OBJECTIVE

Observational and experimental studies support that osteoporosis and atherosclerosis are two related phenomena. The aim of the present study was to investigate the probable effect of alendronate sodium, which is used in the treatment of osteoporosis, on carotid artery intima-media thickness (IMT), the lipid profile, and apolipoprotein A-I (ApoA-I) and apolipoprotein B (ApoB) levels, which are known to have a role in the atherosclerotic process.

METHODS

Carotid artery IMT was measured in 39 women in whom alendronate 70 mg/week was started due to osteoporosis and in 33 control participants at the start and the 6th and 12th months of the study. Triglyceride, high-density lipoprotein, low-density lipoprotein, ApoA-I, and ApoB levels were also measured at the same time points, and ApoB/ApoA-I rates were calculated.

RESULTS

Among the basal values, only the ApoA-I level was significantly lower in the alendronate group (P < 0.01). IMT measurement results (mean [SE]) of the alendronate group were 0.622 [0.015], 0.616 [0.014], and 0.597 [0.013] mm; those of the control group were 0.600 [0.010], 0.611 [0.011], and 0.620 [0.011] mm, respectively. In both groups, the difference between the start and 12-month values was significant (P < 0.05). A significant difference was not determined in the triglyceride and lipid measurement results between the groups and also within groups. ApoA and ApoB levels at the start and the 12th month of the study were as follows: 159.8 [3.6], 162.2 [3.4] (P > 0.05) and 96.2 [4.2], 101.5 [4.5] (P > 0.05) in the control group and 145.1 [4.0], 173.7 [4.3] (P < 0.05) and 98.7 [3.9], 84.6 [3.3] (P < 0.05) in the alendronate group, respectively. The ratios of ApoB/ApoA-I were 0.611 [0.029] is to 0.636 [0.031] (P > 0.05) in the control group and 0.703 [0.04] is to 0.498 [0.0] (P < 0.05) in the alendronate group.

CONCLUSIONS

We concluded that alendronate sodium resulted in a significant decrease in IMT during a 1-year period compared with matched controls. Also, alendronate was associated with a positive effect on the ApoB/ApoA-I ratio.

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

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

Vascular calcification and bone disease: the calcification paradox

Vascular calcification or ectopic mineralization in blood vessels is an active, cell-regulated process, increasingly recognized as a general cardiovascular risk factor. Remarkably, ectopic artery mineralization is frequently accompanied by decreased bone mineral density or disturbed bone turnover. This contradictory association, observed mainly in osteoporosis and chronic kidney disease, is called the 'calcification paradox'. Here, we review recent advances in our understanding of the calcification paradox, including protein expression patterns governing both normal and ectopic mineralization, the conversion of vascular smooth muscle cells to bone-like cells, and the regulatory pathways involved in both bone and vessel mineralization. Further elucidation of the mechanisms underlying the calcification paradox is crucial in order to develop preventive and therapeutic strategies to deal with vascular calcification and reduce the associated cardiovascular risk.

Mechanisms linking osteoporosis with cardiovascular calcification

Cardiovascular calcium deposition is associated with osteoporosis through various potential mechanisms involving molecular regulatory factors at the nanoscale level that govern skeletal bone and cardiovascular tissues. In this article, several possible mechanisms linking cardiovascular calcification and osteoporosis are discussed, including aging, tissue-specific responses to chronic inflammation, flow-limiting atherosclerosis of skeletal end arteries causing ischemic abnormalities in metabolism, shared endogenous regulatory factors that affect the two tissues in a reciprocal manner, and changes in a cysteine protease inhibitor, fetuin. Any or all of these factors and phenomena may contribute to the association.

Osteoprotegerin, vascular calcification and atherosclerosis

The association of bone pathologies with atherosclerosis has stimulated the search for common mediators linking the skeletal and the vascular system. Since its initial discovery as a key regulator in bone metabolism, osteoprotegerin (OPG) has become the subject of intense interest for its role in vascular disease and calcification. Studies in vitro and in animal models suggest that OPG inhibits vascular calcification. Paradoxically however, clinical studies suggest that serum OPG levels increase in association with vascular calcification, coronary artery disease, stroke and future cardiovascular events. This has led to an extensive debate on the potential of OPG as a biomarker of vascular disease. However the exact significance and mechanisms by which this bone-regulatory protein influences cardiovascular pathophysiology is still unclear. The need for a more complete picture is being addressed in increasing valuable research indicating OPG as not only a marker but also a mediator of vascular pathology modulating osteogenic, inflammatory and apoptotic responses. By integrating the results of recent experimental research, animal models and clinical studies, this review summarises the present understanding of the role of OPG in vascular disease and calcification.

Abdominal aortic calcification, BMD, and bone microstructure: a population-based study

To better define the relationship between vascular calcification and bone mass/structure, we assessed abdominal aortic calcification (AAC), BMD, and bone microstructure in an age-stratified, random sample of 693 Rochester, MN, residents. Participants underwent QCT of the spine and hip and high-resolution pQCT (HRpQCT) of the radius to define volumetric BMD (vBMD) and microstructural parameters. AAC was quantified with the Agatston scoring method. In men, AAC correlated with lower vertebral trabecular and femoral neck vBMD (p < 0.001), but not after age or multivariable (age, body mass index, smoking status) adjustment. Separation into <50 and >or=50 yr showed this pattern only in the older men. BV/TV and Tb.Th inversely correlated with AAC in all men (p < 0.001), and Tb.Th remained significantly correlated after age adjustment (p < 0.05). Tb.N positively correlated with AAC in younger men (p < 0.001) but negatively correlated in older men (p < 0.001). The opposite was true with Tb.Sp (p = 0.01 and p < 0.001, respectively). Lower Tb.N and higher Tb.Sp correlated with AAC in older men even after multivariable adjustment. Among all women and postmenopausal women, AAC correlated with lower vertebral and femoral neck vBMD (p < 0.001) but not after adjustment. Lower BV/TV and Tb.Th correlated with AAC (p = 0.03 and p = 0.04, respectively) in women, but not after adjustment. Our findings support an age-dependent association between AAC and vBMD. We also found that AAC correlates with specific bone microstructural parameters in older men, suggesting a possible common pathogenesis for vascular calcification and deterioration in bone structure. However, sex-specific differences exist.

Relationship of calcification of atherosclerotic plaque and arterial stiffness to bone mineral density and osteoprotegerin in postmenopausal women referred for osteoporosis screening

Arterial calcification leading to increased arterial stiffness, a powerful risk factor for cardiovascular disease, may underlie the association of osteoporosis with cardiovascular disease in postmenopausal women. Osteoprotegerin (OPG), an indirect inhibitor of osteoclastogenesis, may be involved in arterial calcification. We examined relationships between calcification of subclinical atherosclerotic plaque and arterial stiffness with bone mineral density (BMD) and OPG in a group of 54 postmenopausal women referred for routine osteoporosis screening by dual-energy X-ray absorptiometric scanning of the lumbar spine and hip. Presence of calcified and noncalcified plaque in carotid and femoral arteries was examined using ultrasonography. Pulse wave velocity (PWV), a measure of arterial stiffness, was determined by sequential tonometry over the carotid and femoral region. Fifty-nine percent of osteoporotic women had calcified (echogenic) plaque at one or more sites compared with 42% and 20% for women with osteopenia and normal BMD, respectively (P = 0.04). There was a significant negative correlation between PWV and hip BMD (r = -0.35, P = 0.01), which remained significant when age, mean arterial pressure, and serum lipids were taken into account (P = 0.05). No significant relationships were observed between serum concentrations of OPG and lumbar spine or total hip BMD or with the number of arterial sites with calcified or noncalcified plaque. However, there was a strong correlation between OPG and PWV (r = 0.44, P = 0.001), which remained significant when adjusted for age (P = 0.01). These findings suggest that decreased BMD is associated with arterial calcification and stiffening and raise the possibility that OPG is a marker of arterial stiffening, independent of any association with BMD.

Compromised bone marrow perfusion in osteoporosis

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

Bone metabolism and vascular calcification

Osteoporosis and atherosclerosis are chronic degenerative diseases which have been considered to be independent and whose common characteristic is increasing incidence with age. At present, growing evidence indicates the existence of a correlation between cardiovascular disease and osteoporosis, irrespective of age. The morbidity and mortality of osteoporosis is mainly related to the occurrence of fractures. Atherosclerosis shows a high rate of morbidity and especially mortality because of its clinical repercussions such as angina pectoris, acute myocardial infarction, stroke, and peripheral vascular insufficiency. Atherosclerotic disease is characterized by the accumulation of lipid material in the arterial wall resulting from autoimmune and inflammatory mechanisms. More than 90% of these fatty plaques undergo calcification. The correlation between osteoporosis and atherosclerosis is being established by studies of the underlying physiopathological mechanisms, which seem to coincide in many biochemical pathways, and of the risk factors for vascular disease, which have also been associated with a higher incidence of low-bone mineral density. In addition, there is evidence indicating an action of antiresorptive drugs on the reduction of cardiovascular risks and the effect of statins, antihypertensives and insulin on bone mass increase. The mechanism of arterial calcification resembles the process of osteogenesis, involving various cells, proteins and cytokines that lead to tissue mineralization. The authors review the factors responsible for atherosclerotic disease that correlate with low-bone mineral density.

Vitamin K and vitamin D status: associations with inflammatory markers in the Framingham Offspring Study

In vitro data suggest protective roles for vitamins K and D in inflammation. To examine associations between vitamins K and D and inflammation in vivo, the authors used multiple linear regression analyses, adjusted for age, sex, body mass index, triglyceride concentrations, use of aspirin, use of lipid-lowering medication, season, menopausal status, and hormone replacement therapy. Participants were from the Framingham Offspring Study (1997-2001; n = 1,381; mean age = 59 years; 52% women). Vitamin K status, measured by plasma phylloquinone concentration and phylloquinone intake, was inversely associated with circulating inflammatory markers as a group and with several individual inflammatory biomarkers (p < 0.01). Percentage of undercarboxylated osteocalcin, a functional measure of vitamin K status, was not associated with overall inflammation but was associated with C-reactive protein (p < 0.01). Although plasma 25-hydroxyvitamin D was inversely associated with urinary isoprostane concentration, an indicator of oxidative stress (p < 0.01), overall associations between vitamin D status and inflammation were inconsistent. The observation that high vitamin K status was associated with lower concentrations of inflammatory markers suggests that a possible protective role for vitamin K in inflammation merits further investigation.

Calcified atherosclerotic plaque and bone mineral density in type 2 diabetes: the diabetes heart study

The purpose of the present study was to determine the relationships between atherosclerotic calcified plaque (CP) and bone mineral density (BMD) in subjects with type 2 diabetes mellitus (DM2). CP in the coronary arteries, carotid bifurcation, and abdominal aorta was measured using computed tomography (CT) in 1023 diabetic subjects from 453 families. Trabecular volumetric BMD in thoracic (T-vBMD) and lumbar (L-vBMD) spine was measured with quantitative CT (QCT), while areal BMD (aBMD) in the lumbar spine and hip was measured by dual X-ray absorptiometry (DXA). Correlation coefficients were computed to assess the magnitude of associations and generalized estimating equations (GEE1) were used to make statistical inferences while accounting for familial correlation. Subjects were 53.8% female, 85% European American (EA) and 15% African American (AA). After adjustment for age, significant inverse associations between CP and vBMD persisted in EA men (correlations between -0.11 and -0.16, all p<0.05 with the exception of carotid CP vs. T-vBMD, p=0.076) and in AA women, excluding aortic CP (correlations between -0.16 and -0.25, all p<0.05). Estrogen use in AA but not EA women was consistently associated with an inverse relation between CP and vBMD. Significant inverse relationships between CP and vBMD were observed in EA men and AA women with DM2 after adjusting for age and other covariates. QCT determined vBMD was more strongly related to CP than aBMD by DXA. The relation between CP and BMD in diabetes is influenced by age, sex, and ethnicity, with further effect modification by hormone replacement therapy.

Calcifications in the abdominal aorta predict fractures in men: MINOS study

In a cohort of 781 men >or=50 yr of age followed up for 10 yr, extended calcifications in the abdominal aorta were associated with a 2- to 3-fold increase in the risk of osteoporotic fractures regardless of BMD and falls.

INTRODUCTION

Cardiovascular disease and osteoporotic fractures are public health problems that frequently coexist.

MATERIALS AND METHODS

We assessed the relation of the severity of aortic calcifications with BMD and the risk of fracture in 781 men >or=50 yr of age. During a 10-year follow-up, 66 men sustained incident clinical fractures. Calcifications in the abdominal aorta expressed as an aortic calcification score (ACS) were assessed by a semiquantitative method. BMD was measured at the lumbar spine, hip, whole body, and distal forearm.

RESULTS

ACS > 2 was associated with a 2-fold increase in the mortality risk after adjustment for age, weight, smoking, comorbidity, and medications. After adjustment for age, body mass index (BMI), smoking, and comorbidity, men in the highest quartile of ACS (>6) had lower BMD of distal forearm, ultradistal radius, and whole body than men in the lower quartiles. Log-transformed ACS predicted fractures when adjusted for age, BMI, age by BMI interaction, prevalent fractures, BMD, and history of two or more falls (e.g., hip BMD; OR = 1.44; p < 0.02). ACS, BMD at all the skeletal sites, and history of two or more falls were independent predictors of fracture. Men with ACS > 6 had a 2- to 3-fold increased risk of fracture after adjustment for confounding variables (OR = 2.54-3.04; p < 0.005-0.001 according to the site).

CONCLUSIONS

This long-term prospective study showed that elevated ACS (>6) is a robust and independent risk factor for incident fracture in older men regardless of age, BMI, BMD, prevalent fractures, history of two or more falls, comorbidities, and medications.

Osteoporosis and chronic kidney disease

Osteoporosis (OP), the most frequent bone disease affecting the general population, is associated with high fracture risk. Patients with impaired kidney function have bone and mineral disturbances leading to extraskeletal calcifications and complex changes in bone turnover that predispose them to increased fracture risk accompanied by increased morbidity and mortality. The combination of these two bone disorders seems to have an additive effect with regard to fracture risk and its outcome, so that appropriate diagnosis and treatment of this disorder should be of primary concern when approaching patients with kidney disease. Nevertheless, the clinical and laboratory diagnostic tools used to identify OP in the general population do not suit the requirement for detecting the complex bone and metabolic changes that occur with chronic kidney disease, leading to the lack of or the initiation of inappropriate therapy. This review will focus on the bone pathophysiologic processes involved in OP and renal osteodystrophy and address some of the problems associated with our current diagnostic tools and aspects of the therapeutic approaches.

Bone marrow-derived cells and arterial disease

This article reviews the association between bone and artery disease, with particular relevance to progenitor cells. The review was based on insight gained by analysis of previous publications and on-going work by the authors. A large number of studies have demonstrated a correlation between bone pathology, particularly osteoporosis, and atherosclerosis. In this review we highlight the particular aspect of bone marrow progenitor cells in the bone-artery link. Progenitor cells, primarily those believed to give rise to endothelial cells, have been inversely correlated with atherosclerosis severity and risk factors. Therapeutic approaches aimed at manipulating progenitor cells in revascularization and vascular repair have demonstrated some promising results. Subtypes of progenitor cells have also been linked with vascular pathology, however, and further studies are required to assess relative beneficial and pathologic effects of bone marrow-derived progenitors. Further understanding of the link between bone and artery pathophysiology is likely to be of significant value in developing new therapies for vascular disease.

Cardiovascular diseases and future risk of hip fracture in women

We used a population-based case-control study in women and linkage to the Swedish in-patient register to examine if there is an increased risk of hip fracture after a cardiovascular disease. There was a substantially increased risk of hip fracture after a diagnosis of a cardiovascular disease.

INTRODUCTION

Recent data have indicated that cardiovascular diseases (CVDs) might have a relationship to osteoporosis, which may explain the increased risk of mortality after hip fracture. It is uncertain, however, whether there is an increased risk of fracture after any cardiovascular disease and in subgroups of CVDs. The objective of this study was to determine whether there are associations between CVD and future hip fracture risk. Knowledge of the risk pattern would lead to better understanding of common pathologic pathways of osteoporosis and CVD.

METHODS

We conducted a population-based case-control study of 1,327 incident hip fracture cases and 3,170 randomly selected population controls among women 50-81 years old in Sweden. Information on cardiovascular and other diseases before the fracture was obtained by linkage to the Swedish National Inpatient Register. Odds ratios (OR) and 95% confidence intervals (CI) where calculated by unconditional logistic regression.

RESULTS

Before study entry, CVDs were diagnosed more than twice as commonly among fracture cases (25%) as among controls (12%). Also, after adjustment for variables including several chronic diseases, we found a doubled risk of hip fracture after a CVD event (OR 2.38; 95% CI 1.92-2.94). There was a gradient increase in risk of hip fracture with increasing number of hospitalizations for CVD and highest fracture risk occurred the first year after the CVD event. Hypertension, heart failure, and cerebrovascular lesions remained independent risk factors, with 2- to 3-fold increases in odds ratios, even after mutual adjustments for other CVDs.

CONCLUSION

There was a substantially increased risk of hip fracture in women after a diagnosis of a CVD, a finding compatible with the concept of common pathologic pathways for osteoporotic fractures and CVD.

Vascular calcification in middle age and long-term risk of hip fracture: the Framingham Study

Osteoporosis and atherosclerosis frequently occur in the same individuals and may share similar pathogenic mechanisms. This study examined the relation between severity of aortic calcification in middle-age years and subsequent risk of hip fracture in women and men in the population-based Framingham Study.

INTRODUCTION

We assessed vascular calcification in women and men in middle age and risk of hip fracture at advanced age.

MATERIALS AND METHODS

Participants included 2499 Framingham cohort members (mean age, 61 yr; range, 47-80 yr). Semiquantitative methods were used to determine severity of abdominal aortic calcification on baseline radiographs. Information on potential confounding factors was obtained from study examinations conducted at, or before, baseline radiography. Hip fractures were ascertained by active surveillance and confirmed by medical records.

RESULTS

Thirty-five-year cumulative incidence of hip fracture was 16% in women and 5% in men with prevalent aortic calcification at baseline (score 1+) and 14% in women and 4% in men without aortic calcification (score 0). Hazard ratios (HRs) and 95% CIs for hip fracture did not increase from the lowest to the highest category of aortic calcification. HRs were 1.0, 1.2 (95% CI, 0.9-1.8), 1.2 (95% CI, 0.7-1.9), 1.1 (95% CI, 0.7-1.7), and 1.4 (95% CI, 0.8-2.3) in women (p for trend = 0.44) and 1.0, 1.8 (95% CI, 0.8-3.8), 1.8 (95% CI, 0.7-4.6), 1.5 (95% CI, 0.6-3.9), and 1.2 (95% CI, 0.2-5.7) in men (p for trend = 0.29) for aortic calcification scores 0 (reference), 1-4, 4-5, 6-10, and 11+, respectively. However, aortic calcification score was strongly associated with increased risk of death (p for trend < 0.0001 in women and men). HRs (95% CIs) for mortality from the lowest to highest aortic calcification score were 1.0, 1.6 (1.4-1.9), 1.7 (1.4-2.1), 1.8 (1.5-2.2), and 2.1 (1.7-2.6) for women, and for men were 1.0, 1.4 (1.1-1.6), 1.4 (1.2-1.8), 1.6 (1.3-2.0), and 1.9 (1.5-2.5).

CONCLUSIONS

Vascular calcification in middle-aged adults does not increase long-term hip fracture risk.

The association of bone mineral density measures with incident cardiovascular disease in older adults

The associations of volumetric and areal bone mineral density (BMD) measures with incident cardiovascular disease (CVD) were studied in a biracial cohort of 2,310 older adults. BMD measures were inversely related to CVD in women and white men, independent of age and shared risk factors for osteoporosis and CVD.

INTRODUCTION

We investigated the associations of volumetric (vBMD) and areal (aBMD) bone mineral density measures with incident cardiovascular disease (CVD) in older adults enrolled in the Health, Aging, and Body Composition study.

METHODS

The incidence of CVD was ascertained in 2,310 well-functioning white and black participants (42% black; 55% women), aged 68-80 years. aBMD measures of the hip were assessed using DXA. Spine trabecular, integral, and cortical vBMD measures were obtained using QCT.

RESULTS

During an average follow-up of 5.4 years, 23% of men and 14% of women had incident CVD. Spine vBMD measures were inversely associated with incident CVD in white men [HR(integral)=1.39, 95% CI 1.03-1.87; HR(cortical)=1.38, 95% CI 1.03-1.84], but not in black men. In women, aBMD measures of the total hip (HR = 1.36, 95% CI 1.03-1.78), femoral neck (HR = 1.44, 95% CI 1.10-1.90), and trochanter (HR = 1.34, 95% CI 1.04-1.72) exhibited significant associations with CVD in blacks, but not in whites. All associations were independent of age and shared risk factors between osteoporosis and CVD, and were not explained by inflammatory cytokines or oxidized LDL.

CONCLUSION

Our results provide support for an inverse association between BMD and incident CVD. Further research should elucidate possible pathophysiological mechanisms linking osteoporosis and CVD.

Atherogenic phospholipids attenuate osteogenic signaling by BMP-2 and parathyroid hormone in osteoblasts

Cardiovascular disease, such as atherosclerosis, has been associated with reduced bone mineral density and fracture risk. A major etiologic factor in atherogenesis is believed to be oxidized phospholipids. We previously found that these phospholipids inhibit spontaneous osteogenic differentiation of marrow stromal cells, suggesting that they may account for the clinical link between atherosclerosis and osteoporosis. Currently, anabolic agents that promote bone formation are increasingly used as a new treatment for osteoporosis. It is not known, however, whether atherogenic phospholipids alter the effects of bone anabolic agents, such as bone morphogenetic protein (BMP)-2 and parathyroid hormone (PTH). Therefore we investigated the effects of oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (ox-PAPC) on osteogenic signaling induced by BMP-2 and PTH in MC3T3-E1 cells. Results showed that ox-PAPC attenuated BMP-2 induction of osteogenic markers alkaline phosphatase and osteocalcin. Ox-PAPC also inhibited both spontaneous and BMP-induced expression of PTH receptor. Consistently, pretreatment of cells with ox-PAPC inhibited PTH-induced cAMP production and expression of immediate early genes Nurr1 and IL-6. Results from immunofluorescence and Western blot analyses showed that inhibitory effects of ox-PAPC on BMP-2 signaling were associated with inhibition of SMAD 1/5/8 but not p38-MAPK activation. These effects appear to be due to ox-PAPC activation of the ERK pathway, as the ERK inhibitor PD98059 reversed ox-PAPC inhibitory effects on BMP-2-induced alkaline phosphatase activity, osteocalcin expression, and SMAD activation. These results suggest that atherogenic lipids inhibit osteogenic signaling induced by BMP-2 and PTH, raising the possibility that hyperlipidemia and atherogenic phospholipids may interfere with anabolic therapy.

Links between cardiovascular disease and osteoporosis in postmenopausal women: serum lipids or atherosclerosis per se?

INTRODUCTION AND HYPOTHESIS

Epidemiological observations suggest links between osteoporosis and risk of acute cardiovascular events and vice versa. Whether the two clinical conditions are linked by common pathogenic factors or atherosclerosis per se remains incompletely understood. We investigated whether serum lipids and polymorphism in the ApoE gene modifying serum lipids could be a biological linkage.

METHODS

This was an observational study including 1176 elderly women 60-85 years old. Women were genotyped for epsilon (epsilon) allelic variants of the ApoE gene, and data concerning serum lipids (total cholesterol, triglycerides, HDL-C, LDL-C, apoA1, ApoB, Lp(a)), hip and spine BMD, aorta calcification (AC), radiographic vertebral fracture and self-reported wrist and hip fractures, cardiovascular events together with a wide array of demographic and lifestyle characteristics were collected.

RESULTS

Presence of the ApoE epsilon 4 allele had a significant impact on serum lipid profile, yet no association with spine/hip BMD or AC could be established. In multiple regression models, apoA1 was a significant independent contributor to the variation in AC. However, none of the lipid components were independent contributors to the variation in spine or hip BMD. When comparing the women with or without vertebral fractures, serum triglycerides showed significant differences. This finding was however not applicable to hip or wrist fractures. After adjustment for age, severe AC score (>or=6) and/or manifest cardiovascular disease increased the risk of hip but not vertebral or wrist fractures.

CONCLUSION

The contribution of serum lipids to the modulators of BMD does not seem to be direct but rather indirect via promotion of atherosclerosis, which in turn can affect bone metabolism locally, especially when skeletal sites supplied by end-arteries are concerned. Further studies are needed to explore the genetic or environmental risk factors underlying the association of low triglyceride levels to vertebral fractures.

Vascular calcification and osteoporosis--from clinical observation towards molecular understanding

Patients with osteoporosis frequently suffer from vascular calcification, which was shown to predict both cardiovascular morbidity/mortality and osteoporotic fractures. Various common risk factors and mechanisms have been suggested to cause both bone loss and vascular calcification, including aging, estrogen deficiency, vitamin D and K abnormalities, chronic inflammation and oxidative stress. Major breakthroughs in molecular and cellular biology of bone metabolism and the characterization of knockout animals with deletion of bone-related genes have led to the concept that common signaling pathways, transcription factors and extracellular matrix interactions may account for both skeletal and vascular abnormalities. For example, mice that lack the cytokine decoy receptor osteoprotegerin or the hormone Klotho display a combined osteoporosis-arterial calcification phenotype. In this review, we summarize the current data and evaluate potential mechanisms of the osteoporosis-arterial calcification syndrome. We propose a unifying hypothesis of vascular calcification that combines both active and passive mechanisms of vascular mineralization with aspects of bone resorption and age-related changes.