Determinants of coronary artery calcification in diabetics with and without nephropathy

Obstructive sleep apnea, coronary calcification and arterial stiffness in patients with diabetic kidney disease

BACKGROUND AND AIMS

Obstructive sleep apnea (OSA) may accelerate arterial calcification, but the relation remains unexplored in diabetic kidney disease (DKD). We examined the associations between OSA, coronary calcification and large artery stiffness in patients with DKD and reduced renal function.

METHODS

Patients with type 2 diabetes, estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 and urine albumin-creatinine ratio (UACR) > 30 mg/g were tested for OSA quantified by the apnea-hypopnea index (AHI, events/hour). Patients without OSA (AHI< 5) were compared to patients with moderate (AHI 15-29) or severe (AHI ≥30) OSA and underwent computed tomography angiography with coronary Agatston scoring (CAS) to quantify coronary calcification. Arterial stiffness was determined as carotid-femoral pulse wave velocity (PWV).

RESULTS

Among 114 patients with acceptable AHI recordings had 43 no OSA, 33 mild OSA and 38 moderate-severe OSA. Mean age of the 74 patients completing the study was 71.5 ± 9.4 years (73% males), eGFR 32.2 ± 12.3 ml/min/1.73 m2 and UACR 533 (192-1707) mg/g. CAS (ln-transformed) was significantly higher in patients with OSA compared to patients without (6.6 ± 1.7 vs. 5.6 ± 2.4, p = 0.04), and the same was observed for PWV (11.9 ± 2.7 vs. 10.5 ± 2.2 m/s, p = 0.02). In multivariable linear regression analyses adjusted for sex, age, body mass index, UACR, and mean arterial pressure, moderate-severe OSA remained significantly associated with PWV but not with CAS. Dominance analysis revealed OSA as the third and second most important factor relative to CAS and PWV respectively.

CONCLUSIONS

In DKD patients, moderate-severe OSA is a significant predictor of arterial stiffness but is not independently associated with coronary calcification.

S100A9-RAGE Axis Accelerates Formation of Macrophage-Mediated Extracellular Vesicle Microcalcification in Diabetes Mellitus

OBJECTIVE

Vascular calcification is a cardiovascular risk factor and accelerated in diabetes mellitus. Previous work has established a role for calcification-prone extracellular vesicles in promoting vascular calcification. However, the mechanisms by which diabetes mellitus provokes cardiovascular events remain incompletely understood. Our goal was to identify that increased S100A9 promotes the release of calcification-prone extracellular vesicles from human macrophages in diabetes mellitus. Approach and Results: Human primary macrophages exposed to high glucose (25 mmol/L) increased S100A9 secretion and the expression of receptor for advanced glycation end products (RAGE) protein. Recombinant S100A9 induced the expression of proinflammatory and osteogenic factors, as well as the number of extracellular vesicles with high calcific potential (alkaline phosphatase activity, P<0.001) in macrophages. Treatment with a RAGE antagonist or silencing with S100A9 siRNA in macrophages abolished these responses, suggesting that stimulation of the S100A9-RAGE axis by hyperglycemia favors a procalcific environment. We further showed that an imbalance between Nrf-2 (nuclear factor 2 erythroid related factor 2) and NF-κB (nuclear factor-κB) pathways contributes to macrophage activation and promotes a procalcific environment. In addition, streptozotocin-induced diabetic Apoe^-/-S100a9^-/- mice and mice treated with S100a9 siRNA encapsulated in macrophage-targeted lipid nanoparticles showed decreased inflammation and microcalcification in atherosclerotic plaques, as gauged by molecular imaging and comprehensive histological analysis. In human carotid plaques, comparative proteomics in patients with diabetes mellitus and histological analysis showed that the S100A9-RAGE axis associates with osteogenic activity and the formation of microcalcification.

CONCLUSIONS

Under hyperglycemic conditions, macrophages release calcific extracellular vesicles through mechanisms involving the S100A9-RAGE axis, thus contributing to the formation of microcalcification within atherosclerotic plaques.

The Continuum of Chronic Kidney Disease and End-Stage Renal Disease: Challenges and Opportunities for Chronic Peritoneal Dialysis in the United States

End-stage renal disease (ESRD) patients undergoing renal replacement therapy have a high mortality rate and suffer from considerable morbidity. Degree of nutritional decline, disordered mineral metabolism, and vascular calcification are some of the abnormalities that predict an adverse outcome for ESRD patients. All these abnormalities begin early during the course of chronic kidney disease (CKD), long before the need for maintenance dialysis. Thus, CKD represents a continuum of metabolic and vascular abnormalities. Treatment of these abnormalities early during the course of CKD and a timely initiation of dialysis have the potential of improving patient outcomes. However, the thesis that successful management of these abnormalities will favorably modify the outcomes of dialysis patients remains untested.

The proportion of incident USA ESRD patients starting chronic peritoneal dialysis (CPD) has historically been low. Limited physician training and inadequate predialysis patient education appear to underlie the low CPD take-on in the USA. Furthermore, two key changes have occurred in the USA: steep decline in CPD take-on and progressive increase in the use of automated peritoneal dialysis. The decline in CPD take-on has afflicted virtually every subgroup examined and has occurred, paradoxically, when the CPD outcomes in the country have improved. Understanding the reasons for historically low CPD take-on and recent steep declines in utilization may allow the development of plans to reverse these trends.

Epicardial adipose tissue deposition in patients with diabetes and renal impairment: Analysis of the literature

Diabetes mellitus (DM) is defined as a chronic disease of disordered metabolism with an ongoing increase in prevalence and incidence rates. Renal disease in patients with diabetes is associated with increased morbidity and premature mortality, particularly attributed to their very high cardiovascular risk. Since this group of patients frequently lacks specific symptomatology prior to the adverse events, a screening tool for the identification of high-risk patients is necessary. The epicardial adipose tissue (EAT) is a biologically active organ having properties similar to visceral adipose tissue and has been associated with metabolic diseases and coronary artery disease. Superior to conventional cardiovascular risk factors and anthropometric measures, including body mass index and waist circumference, the EAT can early predict the development of coronary artery disease. Assessment of EAT can be performed by two-dimensional echocardiography, magnetic resonance imaging or computer tomography. However, its role and significance in patients with DM and nephropathy has not been thoroughly evaluated. The aim of the current editorial is to evaluate all available evidence regarding EAT in patients with DM and renal impairment. Systematic search of the literature revealed that patients with DM and nephropathy have increased EAT measurements, uncontrolled underlying disease, high body mass index and raised cardiovascular risk markers. Acknowledging the practical implications of this test, EAT assessment could serve as a novel and non-invasive biomarker to identify high-risk patients for cardiovascular adverse events.

Prevalence of coronary artery calcification and its association with mortality, cardiovascular events in patients with chronic kidney disease: a systematic review and meta-analysis

PURPOSE

To date, the prevalence and prognostic role of coronary artery calcification (CAC) in patients with chronic kidney disease (CKD) have been investigated in several studies, but have yielded conflicting results. The aim of this meta-analysis is to derive a more precise estimation of CAC prevalence in CKD patients and its association with cardiovascular events and mortality.

METHODS

The relevant literature was identified and evaluated from inception until July 2018 through multiple search strategies on PubMed, Embase, and Web of Science. Cross-sectional or cohort (baseline data) studies reporting CAC prevalence were included. Data extracted from eligible studies were used to calculate effect estimates (ESs) and 95% confidence intervals (95%CI). We searched databases for observational studies that explored baseline CAC and subsequent cardiovascular or all-cause mortality risk in CKD patients.

RESULTS

The meta-analysis included 47 studies; 38 of these were included in the final analysis of CAC prevalence. The pooled prevalence of CAC in random effect model was 60% (95%CI 53-68%). CAC was positively associated with an increased risk of all-cause mortality (hazard ratio [HR] 3.44; 95%CI 2.40-4.94), cardiovascular mortality (HR 3.87; 95%CI 2.06-7.26), and cardiovascular events (HR 2.09; 95%CI 1.19-3.67), when comparing individuals in the top CAC score group to those in the bottom CAC score group.

CONCLUSIONS

The pooled prevalence of CAC is highly prevalent. CAC is independently associated with all-cause and cardiovascular mortality risk as well as cardiovascular events among CKD patients. In view of the high heterogeneity, larger clinical trials are still needed.

Atherosclerosis and Microvascular Complications: Results From the Canadian Study of Longevity in Type 1 Diabetes

OBJECTIVE

Type 1 diabetes carries a significant risk for cardiovascular mortality, but it is unclear how atherosclerosis associates with microvascular complications. We aimed to determine the relationships between atherosclerotic burden and neuropathy, retinopathy, and diabetic kidney disease (DKD) in adults with a ≥50-year history of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Adults with type 1 diabetes (n = 69) underwent coronary artery calcification (CAC) volume scoring by wide-volume computerized tomography. Microvascular complications were graded as follows: neuropathy by clinical assessment, electrophysiology, vibration and cooling detection thresholds, heart rate variability, and corneal confocal microscopy; retinopathy by ultra-wide-field retinal imaging; and DKD by renal hemodynamic function measured by inulin and para-aminohippurate clearance at baseline and after intravenous infusion of angiotensin II. The cohort was dichotomized to high (≥300 Agatston units [AU]) or low (<300 AU) CAC and was stratified by diabetes status. A comparator group without diabetes (n = 73) matched for age and sex also underwent all study procedures except for retinal imaging.

RESULTS

CAC scores were higher in participants with type 1 diabetes (median Agatston score 1,000 [interquartile range = 222, 2,373] AU vs. 1 [0.75] AU in comparators, P < 0.001). In participants with type 1 diabetes, high CAC scores associated with markers of neuropathy and retinopathy, but not with DKD, or renal hemodynamic function at baseline or in response to angiotensin II.

CONCLUSIONS

The presence of high CAC in adults with longstanding type 1 diabetes was associated with large nerve fiber neuropathy and retinopathy but not with renal hemodynamic function, suggesting that neuropathy, retinopathy, and macrovascular calcification share common risk factors.

Coronary artery calcification in patients with diabetes mellitus and advanced chronic kidney disease

INTRODUCTION

Patients with chronic kidney disease (CKD) and diabetes mellitus (DM) have high cardiovascular risk. Both conditions are related to systemic atherosclerosis and vascular calcification. The prevalence and severity of coronary artery calcification (CaC) is higher in patients with DM, regardless of their renal function. Data about the long-term prognostic role of CaC in diabetic patients with CKD are scarce.

MATERIAL AND METHODS

We carried out a prospective longitudinal study enrolling 137 patients with advanced CKD. A non-enhanced multislice coronary computed tomography (CT) was performed at baseline. CaC was assessed using Agatston method. Patients were stratified according to their CaC score: severe calcification group (CaCs≥400HU) and mild-moderate calcification group (CaCs<400HU).

RESULTS

The median follow-up time was 87.5 months. DM was found in 28% of subjects. The patients with DM showed more severe CaC, lower albumin and higher C-reactive protein serum levels. Serum albumin was correlated with severe CaC (r=-0.45, P=.009). Overall mortality rate reached 58%. Patients with DM also tended to have higher mortality compared to non-diabetic subjects (X² 3.51, P=.061) especially those with severe CaC showed higher mortality than those with severe CaC without DM (93% vs.73%, P=.04).

CONCLUSIONS

Patients with advanced CKD and DM have more severe CaC, increased inflammation-malnutrition data and higher mortality compared to those without DM.

Serum amyloid a and risk of death and end-stage renal disease in diabetic kidney disease

AIMS

To determine if serum levels of serum amyloid A (SAA) predict death and end-stage renal disease in a cohort of people with diabetic kidney disease.

METHODS

In a longitudinal cohort study of 135 participants with type 2 diabetes and diabetic kidney disease, serum samples were assayed for SAA. Censored time-to-event analyses in Cox-proportional hazard models were utilized to assess SAA as a predictor of the primary outcome of death and end-stage renal disease.

RESULTS

Participants were 73% Mexican-American (99/135) and 55% men (75/135), with a mean±SD age of 57±7.5years. At baseline, participants had hemoglobin A1c of 8.6±2.3%, systolic blood pressure of 153±27mm Hg, body mass index of 31±9kg/m², median urine-albumin-to-creatinine ratio of 1861mg/g (interquartile range 720-3912mg/g), and estimated glomerular filtration rate of 55.7±22.3ml/min/1.73m². Over a median duration of follow-up of 3.5years, 44% (60/135) of participants experienced a primary outcome event. The hazards ratio for the primary outcome was 3.03 (95% CI 1.43-6.40, p=0.003) in the highest (>1.0 μg/ml) compared to the lowest (<0.55 μg/ml) SAA tertile in a model adjusted for urine-albumin-to-creatinine ratio, estimated glomerular filtration rate, age, sex, and race/ethnicity. Addition of SAA as a covariate improved the model C-statistic (Δ c=0.017).

CONCLUSIONS

In a longitudinal cohort study of participants with type 2 diabetes and DKD, higher levels of serum SAA predicted higher risk of death and ESRD. SAA is a promising targetable biomarker for DKD.

Assessment of abdominal aortic calcification at different stages of chronic kidney disease

PURPOSE

Vascular calcifications that may cause cardiovascular disease are highly prevalent in chronic kidney disease (CKD). In this study, we aimed to determine abdominal aorta calcifications (AAC) in predialysis and hemodialysis patients by lateral lumbar radiography and to investigate factors that were associated with the calcifications.

METHODS

Two hundred and fifty-nine adult chronic hemodialysis patients, 300 predialysis CKD patients and 60 healthy subjects with normal kidney function as a control group were enrolled in the study. Lateral lumbar radiography was used to measure AAC. Calcified deposits of the abdominal aorta wall at the level of the first through fourth lumbar vertebrae were graded by a 24-point scoring system.

RESULTS

AAC prevalence (AAC score ≥1) was significantly different in hemodialysis, predialysis and control groups (71.8, 45.7 and 33.3 %, respectively; p < 0.001). AAC prevalence in CKD stages 1, 2, 3, 4 and 5 predialysis patients was 26.6, 43.3, 40, 58.3 and 55 %, respectively. AAC scores of the hemodialysis group were higher than of the predialysis group (p < 0.001) and the control group (p < 0.001). AAC scores of the predialysis group were not higher than of the control group (p = 0.314). AAC scores of the hemodialysis group were significantly higher than of the control group (p < 0.001) and stage 1 (p < 0.001), stage 2 (p = 0.001) and stage 3 predialysis groups (p = 0.002). Age (p < 0.001), presence of diabetes mellitus (p < 0.001) and serum phosphorus levels (p = 0.011) were found to be independent predictors of calcification in the hemodialysis group. Age (p < 0.001), serum phosphorus levels (p = 0.007) and history of cardiovascular disease (p = 0.014) were found to be independent predictors of calcification in the predialysis group.

CONCLUSIONS

Abdominal aortic calcification is highly prevalent in the hemodialysis population. Strict phosphorus control should be implemented to the predialysis and hemodialysis patients.

Increased detection of coronary atherosclerosis on 320-slice computed tomographic angiography with burden of cardiovascular risk factors and complications in patients with type 2 diabetes

AIMS

The cardiovascular risk factors and diabetic complications are related to coronary atherosclerosis. However, the evaluation of the prevalence of coronary atherosclerosis based on their accumulation remains to be determined.

METHODS

247 consecutive Chinese subjects with type 2 diabetes but without history of coronary heart disease (CHD) underwent 320-slice computed tomographic coronary angiography, including no coronary atherosclerosis, non-obstructive atherosclerosis (<50% stenosis) and obstructive atherosclerosis (≥50% stenosis). Conventional cardiovascular risk factors, albuminuria, renal dysfunction and diabetic retinopathy (DR) were determined. Framingham Risk Score (FRS) was used to assess the 10-year CHD risk.

RESULTS

Increase in burden of cardiovascular risk factors and diabetic complications were significantly associated with the likelihood of being a higher coronary atherosclerosis category. In the analysis for trend through the categories of burden score or FRS stratification, the percentage of obstructive atherosclerosis was increased and the percentage of no atherosclerosis decreased as the burden score and FRS increased (all p<0.005), respectively. The areas under the receiver operator curve for the burden score versus FRS were greater at predicting coronary atherosclerosis and obstructive atherosclerosis (p=0.004 and p=0.002), respectively.

CONCLUSIONS

The prevalence of coronary atherosclerosis was increased with the accumulation of cardiovascular risk factors and diabetic complications. The burden of these clinical and biochemical risk factors has increased ability for prediction of the presence and severity of coronary atherosclerosis over FRS in type 2 diabetic patients.

Pathophysiology of Vascular Calcification

Vascular calcification can lead to cardiovascular morbidity and mortality. The initiating factors and clinical consequences depend on the underlying disease state and location of the calcification. The pathogenesis of vascular calcification is complex and involves a transformation of vascular smooth muscle cells to an osteo/chondrocytic cell that expresses RUNX2 and produces matrix vesicles. The imbalance of promoters (such as hyperphosphatemia and hypercalcemia) and inhibitors (e.g., fetuin-A) is critical in the development of vascular calcification. The altered mineral metabolism and deficiency in inhibitors are common in patients with chronic kidney disease (CKD) and is one reason why vascular calcification is so prevalent in that population.

Urine matrix metalloproteinase-7 and risk of kidney disease progression and mortality in type 2 diabetes

AIMS

The renin-angiotensin-aldosterone system (RAAS), bone morphogenetic protein (BMP) and WNT pathways are dysregulated in diabetic kidney disease (DKD). Urine excretion of angiotensinogen, gremlin-1 and matrix metalloproteinase-7 (MMP-7), components of the RAAS, BMP and WNT pathways, respectively, is increased in DKD. We asked if this increase is associated with subsequent progression to end-stage renal disease (ESRD) or death.

METHODS

Using time-to-event analyses, we examined the association of baseline urine concentration of these proteins with progression to ESRD or death in a predominantly Mexican-American cohort with type 2 diabetes and proteinuric DKD (n=141).

RESULTS

Progression to ESRD occurred for 38 participants over a median follow-up of 3.0years; 39 participants died over a median follow-up of 3.6years. Urine MMP-7 and gremlin-1 were associated with increased risk of ESRD after adjustment for demographic and clinical covariates. Angiotensinogen showed a U-shaped relationship with ESRD, with the middle tertile associated with lowest risk of ESRD. After additional adjustment for glomerular filtration rate and albuminuria, all associations with ESRD lost significance. Only urine MMP-7 was associated with mortality, and this association remained robust in the fully adjusted model with a Hazard ratio of 3.59 (95% confidence interval 1.31 to 9.85) for highest vs. lowest tertile. Serum MMP-7 was not associated with mortality and did not attenuate the association of urine MMP-7 with mortality (HR 4.03 for highest vs. lowest urine MMP-7 tertile).

CONCLUSIONS

Among people with type 2 diabetes and proteinuric DKD, urine MMP-7 concentration was strongly associated with subsequent mortality.

Coronary artery calcification, cardiovascular events, and death: a prospective cohort study of incident patients on hemodialysis

Background

Coronary calcification in patients with end-stage renal disease (ESRD) is associated with an increased risk of cardiovascular outcomes and death from all causes. Previous evidence has been limited by short follow-up periods and inclusion of a heterogeneous cluster of events in the primary analyses.

Objective

To describe coronary calcification in patients incident to ESRD, and to identify whether calcification predicts vascular events or death.

Design

Prospective substudy of an inception cohort.

Setting

Tertiary care haemodialysis centre in Ontario (St Joseph’s Healthcare Hamilton).

Participants

Patients starting haemodialysis who were new to ESRD.

Measurements

At baseline, clinical characterization and spiral computed tomography (CT) to score coronary calcification by the Agatston-Janowitz 130 scoring method. A primary outcome composite of adjudicated stroke, myocardial infarction, or death.

Methods

We followed patients prospectively to identify the relationship between cardiac calcification and subsequent stroke, myocardial infarction, or death, using Cox regression.

Results

We recruited 248 patients in 3 centres to our main study, which required only biochemical markers. Of these 164 were at St Joseph’s healthcare, and eligible to participate in the substudy; of these, 51 completed CT scanning (31 %). Median follow up was 26 months (Q₁, Q₃: 14, 34). The primary outcome occurred in 16 patients; 11 in the group above the median and 5 in the group below (p = 0.086). There were 26 primary outcomes in 16 patients; 20 (77 %) events in the group above the coronary calcification median and 6 (23 %) in the group below (p = 0.006). There were 10 deaths; 8 in the group above the median compared with 2 in the group below (p = 0.04). The hazard ratios for coronary calcification above, compared with below the median, for the primary outcome composite were 2.5 (95 % CI 0.87, 7.3; p = 0.09) and 1.7 (95 % CI 0.55, 5.4; p = 0.4), unadjusted and adjusted for age, respectively. For death, the hazard ratios were 4.6 (95 % CI 0.98, 21.96; p = 0.054) and 2.4 (95 % CI 0.45, 12.97; p = 0.3) respectively.

Limitations

We were limited by a small sample size and a small number of events.

Conclusions

Respondent burden is high for additional testing around the initiation of dialysis. High coronary calcification in patients new to ESRD has a tendency to predict cardiovascular outcomes and death, though effects are attenuated when adjusted for age.

Neuropathy and the vascular-bone axis in diabetes: lessons from Charcot osteoarthropathy

Emerging evidence from the last two decades has shown that vascular calcification (VC) is a regulated, cell-mediated process orchestrated by vascular smooth muscle cells (VSMCs) and that this process bears many similarities to bone mineralization. While many of the mechanisms driving VSMC calcification have been well established, it remains unclear what factors in specific disease states act to promote vascular calcification and in parallel, bone loss. Diabetes is a condition most commonly associated with VC and bone abnormalities. In this review, we describe how factors associated with the diabetic milieu impact on VSMCs, focusing on the role of oxidative stress, inflammation, impairment of the advanced glycation end product (AGE)/receptor for AGE system and, importantly, diabetic neuropathy. We also explore the link between bone and VC in diabetes with a specific emphasis on the receptor activator of nuclear factor κβ ligand/osteoprotegerin system. Finally, we describe what insights can be gleaned from studying Charcot osteoarthropathy, a rare complication of diabetic neuropathy, in which the occurrence of VC is frequent and where bone lysis is extreme.

Effect of smoking and other traditional risk factors on the onset of coronary artery calcification: results of the Heinz Nixdorf recall study

BACKGROUND

Coronary artery calcium (CAC) indicates coronary atherosclerosis and can be present in very early stages of the disease. The conversion from no CAC to any CAC reflects an important step of the disease process as cardiovascular risk is increased in persons even with mildly elevated CAC. We sought to identify risk factors that determined incident CAC>0 in men and women from an unselected general population with a special focus on the role of smoking.

METHODS

All 4814 persons that were initially studied in the Heinz Nixdorf Recall Study were invited to participate in the follow-up examination after 5.1 ± 0.3 years. All traditional Framingham risk factors were quantified using standard techniques. Smokers were categorized in never, former and present smokers. The CAC scores were measured from EBCT using the Agatston method.

RESULTS

Overall, out of 342 men and 919 women with zero CAC at baseline, 107 (31.3%) men and 210 (22.9%) women had CAC>0 at second examination. In multivariable analysis, age (OR estimate per 5 years: 1.34 (95%CI: 1.21-1.47)), LDL cholesterol (per 10 mg/dL: 1.05 (95%CI: 1.01-1.10)), systolic blood pressure (per 10 mmHg: 1.19 (95%CI: 1.11-1.28)) and current smoking (1.49 (95%CI: 1.04-2.15)) were independent predictors of CAC onset. The probability of CAC onset steadily increased with age from 23.3% (men) and 15.3% (women) at age 45-49 years to 66.7% (men) and 42.9% (women) at age 70-74 years. The difference in age-dependent conversion rates was quantified by years between reaching a given level of CAC onset probability. We found a consistent pattern with respect to smoking status: presently (formerly) smoking middle-aged men convert to positive CAC 10 (5) years earlier than never smokers, for women (middle-aged to elderly) this time span is 8 (5) years.

CONCLUSION

Several traditional CVD risk factors are associated with CAC onset during 5 years follow-up. CAC onset is accelerated by approximately 10 (5) years for present (former) compared to never smokers.

No independent association of serum phosphorus with risk for death or progression to end-stage renal disease in a large screen for chronic kidney disease

Whether higher serum phosphorus levels are associated with a higher risk for death and/or progression of chronic kidney disease (CKD) is not well established, and whether the association is confounded by access and barriers to care is unknown. To answer these questions, data of 10,672 individuals identified to have CKD (estimated glomerular filtration rate <60 ml/min per 1.73 m(2)) from those participating in a community-based screening program were analyzed. Over a median follow-up of 2.3 years, there was no association between quartiles of serum phosphorus and all-cause mortality (adjusted hazards ratio for serum phosphorus over 3.3 to 3.7, over 3.7 to 4.1, and over 4.1 mg/dl, respectively: 1.22 (0.95-1.56), 1.00 (0.76-1.32), and 1.00 (0.75-1.33); reference, serum phosphorus of 3.3 mg/dl and below). Individuals in the highest quartile for serum phosphorus had a significantly higher risk for progression to end-stage renal disease (ESRD) (unadjusted hazards ratio, 6.72 (4.16-10.85)); however, the risk became nonsignificant on adjustment for potential confounders. There was no appreciable change in hazards ratio with inclusion of variables related to access and barriers to care. Additional analyses in subgroups based on 12 different variables yielded similar negative associations. Thus, in the largest cohort of individuals with early-stage CKD to date, we could not validate an independent association of serum phosphorus with risk for death or progression to ESRD.

Vascular calcification: pathophysiology and risk factors

Vascular calcification can occur in nearly all arterial beds and in both the medial and intimal layers. The initiating factors and clinical consequences depend on the underlying disease state and location of the calcification. The best studied manifestation is coronary artery calcification, in part because of the obvious clinical consequences, but also because of CT-based imaging modalities. In the general population, the presence of coronary artery calcification increases cardiovascular risk above that predicted by traditional Framingham risk factors, suggesting the presence of nontraditional risk factors. In patients with chronic kidney disease (CKD), coronary artery calcification is more prevalent and markedly more severe than in the general population. In these CKD patients, nontraditional risk factors such as oxidative stress, advanced glycation end products, and disordered mineral metabolism are also more prevalent and more severe and offer mechanistic insight into the pathogenesis of vascular calcification.

25-Hydroxyvitamin D is lower in deprived groups, but is not associated with carotid intima media thickness or plaques: results from pSoBid

OBJECTIVE

The association of the circulating serum vitamin D metabolite 25-hydroxyvitamin D (25OHD) with atherosclerotic burden is unclear, with previous studies reporting disparate results.

METHOD

Psychological, social and biological determinants of ill health (pSoBid) is a study of participants aged 35-64 years from Glasgow who live at extremes of the socioeconomic spectrum. Vitamin D deficiency was defined as 25OHD < 25nmol/L, as per convention. Cross-sectional associations between circulating 25OHD concentrations and a range of socioeconomic, lifestyle, and biochemistry factors, as well as carotid intima media thickness (cIMT) and plaque presence were assessed in 625 participants.

RESULTS

Geometric mean levels of circulating 25OHD were higher among the least deprived (45.6 nmol/L, 1-SD range 24.4-85.5) versus most deprived (34.2 nmol/L, 1-SD range 16.9-69.2; p < 0.0001). In the least deprived group 15% were "deficient" in circulating 25OHD versus 30.8% in the most deprived (χ(2)p < 0.0001). Log 25OHD was 27% lower among smokers (p < 0.0001), 20% higher among the physically active versus inactive (p = 0.01), 2% lower per 1 kg/m(2) increase in body mass index (BMI) (p < 0.0001), and showed expected seasonal variation (χ(2)p < 0.0001). Log 25OHD was 13% lower in the most versus least deprived independent of the aforementioned lifestyle confounding factors (p = 0.03). One unit increase in log 25OHD was not associated with atherosclerotic burden in univariable models; cIMT (effect estimate 0.000 mm [95% CI -0.011, 0.012]); plaque presence (OR 0.88 [0.75, 1.03]), or in multivariable models.

CONCLUSION

There is no strong association of 25OHD with cIMT or plaque presence, despite strong evidence 25OHD associates with lifestyle factors and socioeconomic deprivation.

Repression of osteocyte Wnt/β-catenin signaling is an early event in the progression of renal osteodystrophy

Chronic kidney disease-mineral bone disorder (CKD-MBD) is defined by abnormalities in mineral and hormone metabolism, bone histomorphometric changes, and/or the presence of soft-tissue calcification. Emerging evidence suggests that features of CKD-MBD may occur early in disease progression and are associated with changes in osteocyte function. To identify early changes in bone, we utilized the jck mouse, a genetic model of polycystic kidney disease that exhibits progressive renal disease. At 6 weeks of age, jck mice have normal renal function and no evidence of bone disease but exhibit continual decline in renal function and death by 20 weeks of age, when approximately 40% to 60% of them have vascular calcification. Temporal changes in serum parameters were identified in jck relative to wild-type mice from 6 through 18 weeks of age and were subsequently shown to largely mirror serum changes commonly associated with clinical CKD-MBD. Bone histomorphometry revealed progressive changes associated with increased osteoclast activity and elevated bone formation relative to wild-type mice. To capture the early molecular and cellular events in the progression of CKD-MBD we examined cell-specific pathways associated with bone remodeling at the protein and/or gene expression level. Importantly, a steady increase in the number of cells expressing phosphor-Ser33/37-β-catenin was observed both in mouse and human bones. Overall repression of Wnt/β-catenin signaling within osteocytes occurred in conjunction with increased expression of Wnt antagonists (SOST and sFRP4) and genes associated with osteoclast activity, including receptor activator of NF-κB ligand (RANKL). The resulting increase in the RANKL/osteoprotegerin (OPG) ratio correlated with increased osteoclast activity. In late-stage disease, an apparent repression of genes associated with osteoblast function was observed. These data confirm that jck mice develop progressive biochemical changes in CKD-MBD and suggest that repression of the Wnt/β-catenin pathway is involved in the pathogenesis of renal osteodystrophy.

Prevalence and progression of peripheral vascular calcification in type 2 diabetes subjects with preserved kidney function

AIMS

To determine predictors of prevalence and progression of peripheral vascular calcification (VC) in type 2 diabetes (DM) subjects with preserved kidney function.

METHODS

Fifty-eight subjects (age 63 ± 11.6 years) with type 2 DM and serum creatinine <125 μmol/l were studied. A CT scan of femoral, posterior tibial and dorsalis pedis arteries was carried out at baseline and at one year. Serum osteoprotegerin (OPG) and RANKL were measured along with routine biochemistry.

RESULTS

Seventy-eight percent of patients had baseline VC, 47% with femoral VC, 49% with VC at two sites - femoral and foot, and 4% foot VC alone. Age, ethnicity, peripheral neuropathy and eGFR were independent predictors of baseline VC. Baseline calcification was the most important predictor of VC progression and was present in all subjects with progression compared to 35% of non-progressors (p < 0.001). Exclusion of demographic factors from models revealed neuropathy and serum OPG levels as independent predictors of both; baseline VC and progression.

CONCLUSIONS

Subjects with type 2 DM and well-preserved renal function had a high prevalence of VC, which was rapidly progressive especially in those with baseline VC. Age, ethnicity, neuropathy, smoking and eGFR were predictors of baseline VC and progression.

Dissociation between progression of coronary artery calcification and endothelial function in hemodialysis patients: a prospective pilot study

Chronic kidney disease profoundly disturbs calcium-phosphate metabolism and predisposes to premature atherosclerosis. Both coronary artery calcification (CAC) and endothelial dysfunction are common in hemodialysis (HD) patients. We hypothesized that a calcium-free phosphate binder would improve endothelial function and delay progression of vascular calcification in HD patients.

METHODS

This was a randomized parallel-group trial in HD patients comparing lanthanum carbonate (LC) with a non-LC phosphorus binders control group (non-LC) at a 1 : 1 randomization. CAC was obtained at baseline, 6, and 12 months, and endothelial function (brachial artery flow-mediated dilation - FMD) at baseline and 6 months.

RESULTS

13 patients were randomized (LC n = 7 and non-LC n = 6). CAC scores (Log ± SE) at baseline were 7.21 ± 0.62 (LC) and 6.07 ± 0.73 (control). CAC increased in the non-LC group (33 ± 17% and 77 ± 22% at 6 and 12 months), but tended to decrease in the LC group (-10 ± 11% and -2 ± 11% at 6 and 12 months). There was statistically less progression in CAC in the LC group compared to control at 6 (p = 0.002) and 12 months (p = 0.003). There was no difference between groups in FMD (p = 0.7). Markers of inflammation did not change significantly.

CONCLUSION

A slower rate of progression of CAC occurred in the LC group, independent of changes in FMD. This is the first study showing dissociation between progression of CAC and FMD in HD patients. Larger studies are warranted to elucidate the impact of different phosphate sequestration therapies on atherosclerosis in HD patients.

Cardiovascular disease among hispanics and non-hispanics in the chronic renal insufficiency cohort (CRIC) study

BACKGROUND AND OBJECTIVES

Hispanics are the largest minority group in the United States. The leading cause of death in patients with chronic kidney disease (CKD) is cardiovascular disease (CVD), yet little is known about its prevalence among Hispanics with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted cross-sectional analyses of prevalent self-reported clinical and subclinical measures of CVD among 497 Hispanics, 1638 non-Hispanic Caucasians, and 1650 non-Hispanic African Americans, aged 21 to 74 years, with mild-to-moderate CKD at enrollment in the Chronic Renal Insufficiency Cohort (CRIC) and Hispanic CRIC (HCRIC) studies. Measures of subclinical CVD included left ventricular hypertrophy (LVH), coronary artery calcification (CAC), and ankle-brachial index.

RESULTS

Self-reported coronary heart disease (CHD) was lower in Hispanics compared with non-Hispanic Caucasians (18% versus 23%, P = 0.02). Compared with non-Hispanic Caucasians, Hispanics had a lower prevalence of CAC >100 (41% versus 34%, P = 0.03) and CAC >400 (26% versus 19%, P = 0.02). However, after adjusting for sociodemographic factors, these differences were no longer significant. In adjusted analyses, Hispanics had a higher odds of LVH compared with non-Hispanic Caucasians (odds ratio 1.97, 95% confidence interval, 1.22 to 3.17, P = 0.005), and a higher odds of CAC >400 compared with non-Hispanic African Americans (odds ratio, 2.49, 95% confidence interval, 1.11 to 5.58, P = 0.03). Hispanic ethnicity was not independently associated with any other CVD measures.

CONCLUSIONS

Prevalent LVH was more common among Hispanics than non-Hispanic Caucasians, and elevated CAC score was more common among Hispanics than non-Hispanic African Americans. Understanding reasons for these racial/ethnic differences and their association with long-term clinical outcomes is needed.

Role of coronary artery calcification score on the decrease in GFR among subjects with CT coronary angiography

OBJECTIVE

Higher levels of coronary artery calcification score (CACS) are associated not only with an increased risk for cardiovascular death, but also with lower glomerular filtration rates (GFRs). However, its role in renal disease progression in patients has not been elucidated.

MATERIALS AND METHODS

We evaluated the change of estimated GFR in 279 nondialytic outpatients, who had undergone computed tomographic coronary angiography and follow-up over a period of 3 months.

RESULTS

The mean age of the participants was 57.7 ± 10.5 years, and the mean GFR was 88.2 ± 15.7 mL/min/1.73 m(2). Although there was no difference in baseline GFR between the CACS ≤ 200 AU group (n = 240) and the CACS > 200 AU group (n = 39), the latter group had a lower level of final GFR and higher annual reduction rate of GFR than the former group after an observation period of 13.1 ± 5.97 months. After adjusting for confounding variables, including age, gender, baseline GFR, albumin, and proteinuria, high levels of CACS showed an independent association with an annual reduction rate of GFR (r = -0.142, P = .048).

CONCLUSIONS

The results suggest that CACS was related to an annual decrease in GFR and may predict the faster decline in GFR in patients with symptoms requiring computed tomographic coronary angiography.

The risk for medial arterial calcification in CKD

BACKGROUND AND OBJECTIVES

CKD is a risk factor for medial artery calcification, but the CKD stage at which this risk begins is unknown. Because breast arterial calcification (BAC) is a marker of generalized medial arterial calcification, mammography was used to detect medial arterial calcification in women with different CKD stages.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a retrospective, cross-sectional study of women with and without CKD matched for age and diabetes and identified from mammograms obtained in 2006-2011. BAC was scored as present or absent per visual inspection.

RESULTS

A total of 146 women with stage 3 CKD and 54 with stage 4/5 CKD were identified. An additional 21 patients with ESRD were identified and added to a previous cohort of 71 patients. Mean age was 64 years for CKD 3, 63 for CKD 4, and 59 for ESRD. Half of each group had diabetes. Compared with controls, the odds ratios for BAC were 1.44 in CKD 3 (95% confidence interval [CI], 0.82-2.53), 2.69 in CKD 4 (95% CI, 1.14-6.33), and 7.19 in ESRD (95% CI, 3.77-13.7) and did not differ with diabetic status or race. In a multivariable logistic model, age (P<0.001) and estimated GFR (P=0.005) were independent predictors of BAC. The odds ratio for BAC increased 4% for each milliliter per minute per 1.73 m(2) decrease in estimated GFR. The prevalence of BAC in CKD was increased in each decade of age over 49 years.

CONCLUSIONS

CKD is an independent risk factor for medial arterial calcification.

Comparison of coronary artery calcification and some coronary artery calcification risk factors in patients on haemodialysis and in patients with type 2 diabetes

Patients on haemodialysis (HD) and patients with type 2 diabetes are at high-risk for coronary artery calcification (CAC). The coronary artery calcium score (CACS), quantified by computed tomography, cannot be completely explained by traditional cardiovascular disease risk factors. CAC was measured in 45 non-diabetic chronic kidney disease patients on HD and in 45 matched type 2 diabetes patients without diabetic nephropathy. Serum calcium, phosphate, 25-hydroxyvitamin D (25[OH]D), alkaline phosphatase, intact parathyroid hormone (iPTH), fetuin-A, high-sensitivity C-reactive protein (hsCRP), albumin, homocysteine, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides and femoral neck bone mineral density were also measured. No differences were observed in patient distribution across the CACS risk categories between the two groups. Significant differences were observed in serum calcium, phosphate, 25(OH)D, alkaline phosphatase, iPTH, fetuin-A, hsCRP, homocysteine and triglycerides between the two patient groups. Further research into the diverse, numerous and often interlinked factors that influence CAC in different groups of patients is warranted.

Relationship of estimated GFR and coronary artery calcification in the CRIC (Chronic Renal Insufficiency Cohort) Study

BACKGROUND

Coronary artery calcification (CAC) is associated with increased mortality risk in the general population. Although individuals with chronic kidney disease (CKD) are at markedly increased mortality risk, the incidence, prevalence, and prognosis of CAC in CKD are not well understood.

STUDY DESIGN

Cross-sectional observational study.

SETTING & PARTICIPANTS

Analysis of 1,908 participants who underwent coronary calcium scanning as part of the multiethnic CRIC (Chronic Renal Insufficiency Cohort) Study.

PREDICTOR

Estimated glomerular filtration rate (eGFR) computed using the Modification of Diet in Renal Disease (MDRD) Study equation, stratified by race, sex, and diabetic status. eGFR was treated as a continuous and a categorical variable compared with the reference value of >60 mL/min/1.73 m(2).

MEASUREMENTS

CAC detected using computed tomography (CT) using either an Imatron C-300 electron beam computed tomography (CT) scanner or multidetector CT scanner. CAC was computed using Agatston score as a categorical variable. Analyses were performed using ordinal logistic regression.

RESULTS

We found a strong and graded relationship between lower eGFR and increasing CAC. In unadjusted models, ORs increased from 1.68 (95% CI, 1.23-2.31) for eGFR of 50-59 mL/min/1.73 m(2) to 2.82 (95% CI, 2.06-3.85) for eGFR <30 mL/min/1.73 m(2). Multivariable adjustment only partially attenuated the results (OR, 1.53; 95% CI, 1.07-2.20) for eGFR <30 mL/min/1.73 m(2).

LIMITATIONS

Use of eGFR rather than measured GFR.

CONCLUSIONS

We showed a graded relationship between severity of CKD and CAC independent of traditional risk factors. These findings support recent guidelines that state that if vascular calcification is present, it should be considered as a complementary component to be included in the decision making required for individualizing CKD treatment.

Endothelin but Not Angiotensin II May Mediate Hypertension-Induced Coronary Vascular Calcification in Chronic Kidney Disease

To understand the relationship between putative neurohormonal factors operative in hypertension and coronary artery calcification (CAC), the relevant cellular actions of angiotensin (Ang II) and endothelin-1 (ET-1) are reviewed. There is compelling evidence to implicate ET-1 in CAC. ET-1 increases phosphate transport with a 42 to 73% increase in V_max. Increased cellular phosphate may induce CAC through increased Ca x phosphate product, transformation of vascular smooth muscle cells into a bone-producing phenotype or cell apoptosis that releases procalcific substances. ET-1 is increased in several models of vascular calcification. ET-1 inhibits inhibitors of calcification, matrix Gla and osteoprotegerin, while enhancing pro-calcific factors such as BMP-2 and osteopontin. In contrast, Ang II inhibits phosphate transport decreasing V_max by 38% and increases matrix Gla. Ang II also stimulates bone resorption. Vascular calcification is reduced by ET-1 A receptor antagonists and to a greater extent than angiotensin receptor blockade although both agents reduce blood pressure.

Study of coronary artery calcification risk in Egyptian adolescents with type-1 diabetes

The objective of the study is to assess coronary artery calcification (CAC) among adolescents with type-1 diabetes and to determine its relation with high-sensitivity C-reactive protein (hs-CRP), dyslipidaemia, glycaemic control and microvascular complications. The study included sixty patients with type-1 diabetes. Their ages ranged from 12 to 18 years and their diabetes duration ranged between 10 and 15 years. Patients were compared with 60 healthy subjects who served as controls. Clinical examination and laboratory investigations were done for evaluation of glycaemic control and presence of microvascular complications. Lipid profile, hs-CRP and multislice spiral computed tomography were done. Hs-CRP, total cholesterol, triglycerides and low-density lipoproteins levels were significantly higher in patients with diabetes compared to controls (P < 0.001). Twelve patients with diabetes (20%) had positive CAC. The mean calcium score was significantly higher in patients with diabetes compared to controls (P < 0.05). Smoking significantly affects CAC as 50% of smokers with diabetes had evidence of CAC compared to 9.1% of non-smokers with diabetes (P < 0.001). Fifty percent of patients with diabetes on angiotensin-converting enzyme inhibitor (ACEI) had evidence of CAC compared to 0% of patients without history of ACEI therapy (P < 0.001). Diabetics with CAC had significantly elder age, longer disease duration and higher mean glycosylated hemoglobin compared to diabetics without CAC (P < 0.05). Blood pressure percentiles, albumin creatinine ratio and serum lipids were significantly higher in patients with CAC compared to those without CAC (P < 0.001). All diabetics with severe retinopathy had positive CAC compared to 0% with normal Fundus (P < 0.001). All diabetics with overt nephropathy had positive CAC compared to 13.3% and 0% in micro- and normo-albuminuric patients (P < 0.001). Young patients with diabetes have evidence of CAC. Smoking, microvascular complications and dyslipidaemia might contribute to this risk.

Recent progress in the treatment of vascular calcification

Vascular calcification is common in patients with advanced chronic kidney disease and is associated with poorer outcomes. Although the pathophysiology is not completely understood, it is clear that it is a multifactorial process involving altered mineral metabolism, as well as changes in systemic and local factors that can promote or inhibit vascular calcification, and all of these are potential therapeutic targets. Current therapy is closely linked to strategies for preventing disordered bone and mineral metabolism in advanced kidney disease and involves lowering the circulating levels of both phosphate and calcium. The efficacy of compounds that specifically target calcification, such as bisphosphonates and thiosulfate, has been shown in animals but only in small numbers of humans, and safety remains an issue. Additional therapies, such as pyrophosphate, vitamin K, and lowering of pH, are supported by animal studies, but are yet to be investigated clinically. As the mineral composition of vascular calcifications is the same as in bone, potential effects on bone must be addressed with any therapy for vascular calcification.

Using vertebral bone densitometry to determine aortic calcification in patients with chronic kidney disease

BACKGROUND

Vascular calcification (VC) is a major contributor to increased cardiovascular (CV) disease in chronic kidney disease (CKD) and an independent predictor of mortality. VC is inversely correlated with bone mineral density (BMD). Screening for VC may be useful to determine those at greater CV risk and dual-energy X-ray absorptiometry (DXA) may have a dual role in providing VC measurement as well as BMD.

METHODS

We report cross-sectional data on 44 patients with CKD stages 3-4 and aim to determine and validate measurement of VC using DXA. Patients had computed tomography (CT) of abdominal aorta and DXA of lateral lumbar spine, to determine both aortic VC and BMD. Semi-quantitative measurement of VC from DXA was determined (blinded) using previously validated 8- and 24-point scales, and compared with VC from CT. BMD determination from L2 to L4 vertebrae on CT was compared with DXA-reported BMD.

RESULTS

Patients 66% male, 57% diabetic, had mean age 63.4 years and mean estimated glomerular filtration rate 31.4 +/- 12 mL/min. Aortic VC was present in 95% on CT, mean 564.9 +/- 304 Hounsfield units (HU). Aortic VC was seen in 68% on lateral DXA, mean scores 5.1 +/- 5.9 and 1.9 +/- 1.9 using 24- and 8-point scales, respectively. Strong correlation of VC measurement was present between CT and DXA (r 0.52, P < 0.001). For DXA VC 24-point score, intraclass correlations for intra-rater and inter-rater agreement were 0.91 and 0.64, respectively (8-point scale, intraclass correlations 0.90 and 0.69). Vertebral BMD measured by CT (mean 469.3 HU L2-4) also significantly correlated with lateral DXA-reported BMD (mean spine T-score -0.67 +/- 1.6) (r 0.56, P < 0.001).

CONCLUSION

Despite limitations in CKD, DXA may be useful as lateral DXA images provide concurrent assessment of aortic calcification as well as lumbar spine BMD, both correlating significantly with CT measurements. Lateral DXA may provide VC screening to determine patients at greater CV risk although more studies are needed to evaluate their potential role.

Prevalence and prognostic significance of renal artery calcification in patients with diabetes and proteinuria

BACKGROUND AND OBJECTIVES

Vascular calcification is common and severe in chronic kidney disease. Because the consequences of calcification may differ by vascular beds, we sought to test the hypothesis that patients who have diabetes with proteinuria and have significant renal artery calcification (RAC) have a higher risk for progression to ESRD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using electron-beam computed tomography, RAC was computed as the sum of Agatston scores at each of the two renal ostia and renal arteries. Time-to-event analysis was conducted to compare the risk in individuals with or without significant RAC (total score >10).

RESULTS

Of 172 patients with type 2 diabetes and overt proteinuria studied (estimated GFR 56 ± 25 ml/min per 1.73 m(2)), significant RAC was present in 31%. In 33 ± 21 months, 41 progressed to ESRD and 65 reached a composite outcome (ESRD or death). Serum phosphorus was a significant predictor of progression to ESRD but was replaced by the significant RAC in multivariate models that included the latter. Individuals with significant RAC had a higher risk for reaching the composite outcome. In contrast, there was no association between coronary artery calcification scores and progression to ESRD.

CONCLUSIONS

Significant RAC was an independent predictor of progression to ESRD as well as reaching the composite outcome. Understanding the pathogenesis of RAC would allow determination of whether this risk is potentially modifiable.

Cardiovascular complications in diabetic kidney disease

Diabetes mellitus (DM) is the leading cause of chronic kidney disease (CKD). Due to an explosion in the incidence and the prevalence of Type 2 DM, the burden of CKD is expected to increase proportionately. Both DM and CKD are associated with a high incidence of cardiovascular (CV) morbidity and mortality, and it is important to understand the unique nature of CV disease in patients with the combination of these two conditions. In this report, we review the traditional and nontraditional risk factors that underlie the high risk of CV disease in this population, with a particular focus on vascular calcification, mineral metabolism, and therapeutic paradigms for the treatment of cardiovascular disease in this unique and high-risk population.

Outcomes associated with serum calcium level in men with non-dialysis-dependent chronic kidney disease

BACKGROUND AND OBJECTIVES

Elevated serum calcium has been associated with increased mortality in dialysis patients, but it is unclear whether the same is true in non-dialysis-dependent (NDD) chronic kidney disease (CKD). Outcomes associated with low serum calcium are also not well-characterized.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined associations of baseline, time-varying, and time-averaged serum calcium with all-cause mortality in a historic prospective cohort of 1243 men with moderate and advanced NDD CKD by using Cox models.

RESULTS

The association of serum calcium with mortality varied according to the applied statistical models. Higher baseline calcium and time-averaged calcium were associated with higher mortality (multivariable adjusted hazard ratio (95% confidence interval): 1.31 (1.13, 1.53); P < 0.001 for a baseline calcium 1 mg/dl higher). However, in time-varying analyses, lower calcium levels were associated with increased mortality.

CONCLUSIONS

Higher serum calcium is associated with increased long-term mortality (as reflected by the baseline and time-averaged models), and lower serum calcium is associated with increased short-term mortality (as reflected by the time-varying models) in patients with NDD CKD. Clinical trials are warranted to determine whether maintaining normal serum calcium can improve outcomes in these patients.

Coronary calcification in patients with chronic kidney disease and coronary artery disease

BACKGROUND AND OBJECTIVES

A close linkage between chronic kidney disease (CKD) and cardiovascular disease (CVD) has been demonstrated. Coronary artery calcification (CAC) is considered to be the causal link connecting them. The aim of the study is to determine the relationship between level of kidney function and the prevalence of CAC.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Autopsy subjects known to have coronary artery disease and a wide range of kidney function were studied. Patients without CKD were classified into five groups depending on estimated GFR (eGFR) and proteinuria: eGFR > or =60 ml/min/1.73 m(2) without proteinuria; CKD1/2: eGFR > or =60 ml/min/1.73 m(2) with proteinuria; CKD3: 60 ml/min/1.73 m(2) >eGFR > or =30 ml/min/1.73 m(2); CKD4/5: eGFR <30 ml/min/1.73 m(2); and CKD5D: on hemodialysis. Intimal and medial calcification of the coronary arteries was evaluated. Risk factors for CVD and uremia were identified as relevant to CAC using logistic regression analysis.

RESULTS

Intimal calcification of plaques was present in all groups, but was most frequent and severe in the CKD5D group and less so in the CKD4/5 and CKD3 groups. Risk factors included luminal stenosis, age, smoking, diabetes, calcium-phosphorus product, inflammation, and kidney function. Medial calcification was seen in a small number of CKD4/5 and CKD5D groups. Risk factors were use of calcium-containing phosphate binders, hemodialysis treatment, and duration.

CONCLUSIONS

It was concluded that CAC was present in the intimal plaque of both nonrenal and renal patients. Renal function and traditional risks were linked to initimal calcification. Medial calcification occurred only in CKD patients.

Cardiovascular implications of proteinuria: an indicator of chronic kidney disease

Proteinuria, defined as urine protein excretion greater than 300 mg over 24 h, is a strong and independent predictor of increased risk for all-cause and cardiovascular mortality in patients with and without diabetes. Proteinuria is a sign of persistent dysfunction of the glomerular barrier and often precedes any detectable decline in renal filtration function. Measurement of proteinuria is important in stratifying the risk for cardiovascular disease and chronic kidney disease progression. A variety of basic pathophysiologic mechanisms that can partially explain simultaneous renal and cardiac disease will be discussed in this Review. In addition to being a prognostic marker, proteinuria is being considered as a therapeutic target in cardiovascular medicine. Therapeutic strategies for amelioration of proteinuria by achieving blood pressure targets, glycemic control in diabetes, treatment of hyperlipidemia, and reducing dietary salt and protein intake are also reviewed in this paper. Future clinical studies are needed to assess if proteinuria reduction should be a target of treatment to reduce the burden of end-stage renal disease, cardiovascular disease, and improve survival in this high-risk population.

Association of serum alkaline phosphatase with coronary artery calcification in maintenance hemodialysis patients

BACKGROUND AND OBJECTIVES

Recent in vitro studies have shown a link between alkaline phosphatase and vascular calcification in patients with chronic kidney disease (CKD). High serum levels of alkaline phosphatase are associated with increased death risk in epidemiologic studies of maintenance hemodialysis (MHD) patients. We hypothesized that coronary artery calcification is independently associated with increased serum alkaline phosphatase levels in MHD patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined the association of coronary artery calcification score (CACS) and alkaline phosphatase in 137 randomly selected MHD patients for whom markers of malnutrition, inflammation, and bone and mineral disorders were also measured.

RESULTS

Serum alkaline phosphatase was the only measure with significant and robust association with CACS (P < 0.003), whereas either other biochemical markers had no association with CACS or their association was eliminated after controlling for case-mix variables. Serum alkaline phosphatase >120 IU/L was a robust predictor of higher CACS and was particularly associated with the likelihood of CACS >400 (multivariate odds ratio 5.0 95% confidence interval 1.6 to 16.3; P = 0.007). Serum alkaline phosphatase of approximately 85 IU/L seemed to be associated with the lowest likelihood of severe coronary artery calcification, but in the lowest tertile of alkaline phosphatase, the CACS predictability was not statistically significant.

CONCLUSIONS

An association between serum alkaline phosphatase level and CACS exists in MHD patients. Given the high burden of vascular calcification in patients with CKD, examining potential therapeutic interventions to modulate the alkaline phosphatase pathway may be warranted.

Lanthanum carbonate reduces phosphorus burden in patients with CKD stages 3 and 4: a randomized trial

BACKGROUND AND OBJECTIVES

Lanthanum carbonate (FOSRENOL, Shire Pharmaceuticals) is an effective noncalcium, nonresin phosphate binder for the control of hyperphosphatemia in chronic kidney disease (CKD) stage 5 patients undergoing dialysis.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

A Phase 2, randomized, double-blind, placebo-controlled trial evaluating the efficacy and safety of lanthanum carbonate in CKD stage 3 and 4 patients. Of 281 patients screened, 121 were randomized (2:1) to lanthanum carbonate or placebo (80 versus 41). The modified intent-to-treat population included 90 patients (56 versus 34); 71 (43 versus 28) completed the study. After run-in, when any current phosphate binders were discontinued and dietary counseling reinforced, patients with serum phosphorus >4.6 mg/dl received lanthanum carbonate (titrated up to 3000 mg/d) or matching placebo for 8 wk.

RESULTS

At the end of treatment, 25 (44.6%) versus nine (26.5%) patients had serum phosphorus < or =4.6 mg/dl (difference 18.1%, P = 0.12) in the lanthanum carbonate and placebo groups, respectively. Statistically significant differences were observed between groups in change from baseline to end of treatment for serum phosphorus (P = 0.02), intact parathyroid hormone (P = 0.02), and urinary phosphorus excretion (P = 0.04). The safety profile and tolerability of lanthanum carbonate were similar to that of placebo.

CONCLUSIONS

Because <1% of phosphorus is in the extracellular fluid, serum measurements may not accurately reflect total body burden in patients with CKD stages 3 and 4. However, lanthanum carbonate is an effective phosphate binder in this patient population, with a safety profile and tolerability similar to that of placebo.

Phosphate binders in chronic kidney disease and end-stage renal disease: a patient-centered approach

Disorders of calcium and phosphorus metabolism are associated with significant morbidity and mortality in patients with advanced chronic kidney disease. These patients typically require oral phosphate binders to maintain phosphorus homeostasis, but the choice of which among several agents to use has been actively investigated and debated. Recent debate has been polarized between those who favor calcium-based binders for their proven efficacy and relatively low cost and those who favor sevelamer for its putative beneficial effects on inflammatory biomarkers and vascular calcification. This review summarizes the current state of the art of prescribing phosphate binders, ranging from large-scale clinical trials to focused mechanistic studies, and proposes that the available evidence does not conclusively prove the relative superiority of any one binder.

Bone and mineral disorders in pre-dialysis CKD

Disorders in calcium, phosphorus, and parathyroid hormone (PTH) are common in chronic kidney disease (CKD) and may be associated with poor outcomes including a higher rate of CKD progression and increased death risk. Although these abnormalities have been examined extensively in patients with CKD stage 5 who are receiving chronic maintenance dialysis, they have not been studied to the same extent at earlier stages of CKD, in spite of the much larger numbers of patients in the early CKD population. We summarize the available literature on outcomes associated with bone and mineral disorders in patients with CKD not yet receiving maintenance dialysis. We have reviewed novel data linking fibroblast growth factor 23 (FGF-23) to phosphorus and vitamin D homeostasis. More rapid CKD progression is linked to hyperphosphatemia and its associated hyperparathyroidism and vitamin D deficiency. Hence, hyperphosphatemia may play a central role in the diverse disorders characterizing CKD. We provide a brief overview of the available treatment recommendations for bone and mineral disorders, with an emphasis on areas needing further research.

Importance of low-grade albuminuria

The well-described association between chronic kidney disease and cardiovascular disease is typically thought to originate from loss of renal function, as estimated by the glomerular filtration rate. However, recent data suggest that urinary albumin excretion has an important role in this association. Albuminuria is a marker of underlying vascular dysfunction and has been correlated with structural and functional integrity of the vasculature. Although the traditional upper limit of normal daily albumin excretion has been 30 mg/d, recent epidemiologic data suggest that levels in the general population are actually much lower. Further, within this range of low-grade albuminuria (LGA), increasing excretion rates are associated with increasing risk of cardiovascular disease. This association is independent of renal function, and in the earliest stages of chronic kidney disease, LGA seems to be a more important determinant than the glomerular filtration rate. This emerging association underscores the complexity of albumin excretion, in which subtle changes in albumin excretion reflect widespread vascular processes. Using the key words albuminuria, low-grade albuminuria, and microalbuminuria in a PubMed search of literature from January 1, 1995, to February 29, 2008, this review summarizes the most recent data on LGA and its association with cardiovascular and renal disease.