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

Comparative Analysis of Protein Quantification by the SomaScan Assay versus Orthogonal Methods in Urine from People with Diabetic Kidney Disease

To our knowledge, calibration curves or other validations for thousands of SomaScan aptamers are not publicly available. Moreover, the abundance of urine proteins obtained from these assays is not routinely validated with orthogonal methods (OMs). We report an in-depth comparison of SomaScan readout for 23 proteins in urine samples from patients with diabetic kidney disease (n = 118) vs OMs, including liquid chromatography-targeted mass spectrometry (LC-MS), ELISA, and nephelometry. Pearson correlation between urine abundance of the 23 proteins from SomaScan 3.2 vs OMs ranged from -0.58 to 0.86, with a median (interquartile ratio, [IQR]) of 0.49 (0.18, 0.53). In multivariable linear regression, the SomaScan readout for 6 of the 23 examined proteins (26%) was most strongly associated with the OM-derived abundance of the same (target) protein. For 3 of 23 (13%), the SomaScan and OM-derived abundance of each protein were significantly associated, but the SomaScan readout was more strongly associated with OM-derived abundance of one or more "off-target" proteins. For the remaining 14 proteins (61%), the SomaScan readouts were not significantly associated with the OM-derived abundance of the targeted proteins. In 6 of the latest group, the SomaScan readout was not associated with urine abundance of any of the 23 quantified proteins. To sum, over half of the SomaScan results could not be confirmed by independent orthogonal methods.

The Usefulness of Calcium/Magnesium Ratio in the Risk Stratification of Early Onset of Renal Replacement Therapy

Background: A growing number of studies have reported a close relationship between high serum calcium (Ca)/low serum magnesium (Mg) and vascular calcification. Endothelial dysfunction and vascular inflammation seem plausible risk factors for the enhanced progression of kidney disease. The aim of this study was to evaluate the role of the Ca/Mg ratio as a predictor of the early onset of renal replacement therapy (RRT). Methods: This was a prospective study conducted in an outpatient low-clearance nephrology clinic, enrolling 693 patients with stages 4−5 of CKD. Patients were divided into two groups according to the start of renal replacement therapy (RRT). Results: The kidney’s survival at 120 months was 60% for a Ca−Mg ratio < 6 and 40% for a Ca−Mg ratio ≥ 6 (p = 0.000). Patients who started RRT had lower levels of Hb, Ca, Mg, albumin, and cholesterol and higher values of phosphorus, the Ca/Mg ratio, and PTH. High values of phosphorus and the Ca/Mg ratio and low levels of Mg and GFR were independent predictors of entry into RRT. A high Ca/Mg ratio, high phosphorus levels, and low levels of GFR were associated with a cumulative risk for initiation of RRT. Conclusions: In our population, the Ca/Mg ratio is an independent predictive factor for the initiation of a depurative technique.

Impact of the explanting surgeon's impression of donor arteriosclerosis on outcome of kidney transplantations from donors aged ≥65 years

PURPOSE

Careful donor selection is important for kidney transplantations (KT) from suboptimal donors aged ≥65 years. Several tools such as histopathological assessment of preimplant biopsies have been shown to predict allograft survival and can be applied for selection. Whether the explanting surgeon's appraisal is associated with outcomes of KTs from suboptimal donors is unknown.

METHODS

We compared outcomes of KTs from ≥65-year-old deceased donors performed at our centre between 1999 and 2018 for which grading of macroscopic 'donor arteriosclerosis' (n=104) and 'organ quality' (n=208) as judged by the explanting surgeon and documented on the Eurotransplant kidney organ report was available.

RESULTS

No association was observed between degree of macroscopic donor arteriosclerosis and death-censored graft survival in univariable or multivariable regression analyses. Compared to KTs from donors with no/mild arteriosclerosis, KTs from donors with moderate/severe arteriosclerosis were associated with a significantly impaired allograft function 3 months, 1 year and 3 years after transplantation (e.g. at 3 years: 176.8 µmol/l vs 137.0 µmol/l, P=0.003). Following multivariable regression analysis, these differences remained significant at 3 months and 3 years after KT. No association was observed between degree of macroscopic arteriosclerosis and mortality or primary non-function as well as no consistent association with delayed graft function and histological arteriosclerosis. Assessment of 'organ quality' was not associated with outcomes.

CONCLUSION

Our data suggest that the explanting surgeon's assessment of donor arteriosclerosis is associated with allograft function. Larger studies and better standardization of kidney inspection after explantation are required to further explore the impact of surgeon's appraisal in KT.

Burden of chronic kidney disease and rapid decline in renal function among adults attending a hospital-based diabetes center in Northern Europe

Introduction

This study aimed to determine the prevalence of diabetic kidney disease (DKD) and rapid renal function decline and to identify indices associated with this decline among adults attending a diabetes center in Northern Europe.

Research design and methods

This is a retrospective cohort study of 4606 patients who attended a diabetes center in Ireland between June 2012 and December 2016. Definition/staging of chronic kidney disease used the Kidney Disease: Improving Global Outcomes (KDIGO) 2012 classification based on data from the most recently attended appointment. Relevant longitudinal trends and variabilities were derived from serial records prior to index visit. Rapid renal function decline was defined based on per cent and absolute rates of estimated glomerular filtration rate (eGFR) change. Multiple linear regression was used to explore the relationships between explanatory variables and per cent eGFR change.

Results

42.0% (total), 23.4% (type 1 diabetes), 47.9% (type 2 diabetes) and 32.6% (other diabetes) had DKD. Rapid decline based on per cent change was more frequent in type 2 than in type 1 diabetes (32.8% vs 14.0%, p<0.001). Indices independently associated with rapid eGFR decline included older age, greater number of antihypertensives, higher log-normalized urine albumin to creatinine ratio (LNuACR), serum alkaline phosphatase, thyroid stimulating hormone, variability in systolic blood pressure and variability in LNuACR, lower glycated hemoglobin, high-density lipoprotein cholesterol and diastolic blood pressure, and lack of ACE inhibitor/angiotensin receptor blocker prescription.

Conclusions

DKD (using the KDIGO 2012 classification) and rapid eGFR decline were highly prevalent among adults attending a hospital-based diabetes clinic in a predominantly Caucasian Northern European country. The burden was greater for adults with type 2 diabetes. Expected as well as potentially novel clinical predictors were identified.

Acute on chronic kidney disease in cats: Etiology, clinical and clinicopathologic findings, prognostic markers, and outcome

Background

Chronic kidney disease (CKD) and acute decompensation of CKD (ACKD) are common in cats.

Objectives

To characterize the etiology, clinical and clinicopathologic findings, and the short‐ and long‐term prognosis of feline ACKD.

Animals

One hundred cats with ACKD.

Methods

Retrospective study, search of medical records for cats with ACKD.

Results

Common clinical signs included anorexia (85%), lethargy (60%), weight loss (39%), and vomiting (27%). Suspected etiologies included ureteral obstruction (11%), renal ischemia (9%), pyelonephritis (8%), others (6%), or unknown (66%). Hospitalization duration was longer in survivors versus nonsurvivors (median = 7 days, range = 2‐26 versus median = 3 days, range = 2‐20, respectively, P < .001). The survival rate to discharge was 58%. Age, serum creatinine, urea, and phosphorous concentrations were higher and venous blood pH was lower in nonsurvivors. However, only serum phosphorus remained associated with the short‐term outcome in the multivariable model (P = .02; 95% confidence interval = 1.03‐1.39). Survivors had a median survival time of 66 days after discharge. Serum creatinine concentrations at presentation as well as at discharge were associated with long‐term survival (P < .002 for both).

Conclusions

The short‐term prognosis of ACKD is comparable to acute kidney injury, while the long‐term prognosis is guarded.

Urine Complement Proteins and the Risk of Kidney Disease Progression and Mortality in Type 2 Diabetes

OBJECTIVE

We examined the association of urine complement proteins with progression to end-stage renal disease (ESRD) or death in people with type 2 diabetes and proteinuric diabetic kidney disease (DKD).

RESEARCH DESIGN AND METHODS

Using targeted mass spectrometry, we quantified urinary abundance of 12 complement proteins in a predominantly Mexican American cohort with type 2 diabetes and proteinuric DKD (n = 141). The association of urine complement proteins with progression to ESRD or death was evaluated using time-to-event analyses.

RESULTS

At baseline, median estimated glomerular filtration rate (eGFR) was 54 mL/min/1.73 m2 and urine protein-to-creatinine ratio 2.6 g/g. Sixty-seven participants developed ESRD or died, of whom 39 progressed to ESRD over a median of 3.1 years and 40 died over a median 3.6 years. Higher urine CD59, an inhibitor of terminal complement complex formation, was associated with a lower risk of ESRD (hazard ratio [HR] [95% CI per doubling] 0.50 [0.29-0.87]) and death (HR [95% CI] 0.56 [0.34-0.93]), after adjustment for demographic and clinical covariates, including baseline eGFR and proteinuria. Higher urine complement components 4 and 8 were associated with lower risk of death (HR [95% CI] 0.57 [0.41-0.79] and 0.66 [0.44-0.97], respectively); higher urine factor H-related protein 2, a positive regulator of the alternative complement pathway, was associated with greater risk of death (HR [95% CI] 1.61 [1.05-2.48]) in fully adjusted models.

CONCLUSIONS

In a largely Mexican American cohort with type 2 diabetes and proteinuric DKD, urine abundance of several complement and complement regulatory proteins was strongly associated with progression to ESRD and death.

Protection Effect of Exogenous Fibroblast Growth Factor 21 on the Kidney Injury in Vascular Calcification Rats

Background:

Chronic kidney disease (CKD) is closely related to the cardiovascular events in vascular calcification (VC). However, little has known about the characteristics of kidney injury caused by VC. Fibroblast growth factor 21 (FGF21) is an endocrine factor, which takes part in various metabolic actions with the potential to alleviate metabolic disorder diseases. Even FGF21 has been regarded as a biomarker in CKD, the role of FGF21 in CKD remains unclear. Therefore, in this study, we evaluate the FGF21 on the kidney injury in VC rats.

Methods:

The male Sprague-Dawley rats were divided into three groups: (1) control group, (2) Vitamin D3 plus nicotine (VDN)-induced VC group, (3) FGF21-treated VDN group. After 4 weeks, the rats were killed and the blood was collected for serum creatinine, urea nitrogen, calcium, and phosphate measurement. Moreover, the renal tissues were homogenized for alkaline phosphatases (ALPs) activity and calcium content. The levels of FGF21 protein were measured by radioimmunoassay. The levels of β-Klotho and FGF receptor 1 (FGFR1) protein were measured by enzyme-linked immunosorbent assay (ELISA). The structural damage and calcifications in aortas were stained by Alizarin-red S. Moreover, the structure of kidney was observed by hematoxylin and eosin staining.

Results:

The renal function impairment caused by VDN modeling was ameliorated by FGF21 treatment, inhibited the elevated serum creatinine and urea level by 20.5% (34.750 ± 4.334 μmol/L vs. 27.630 ± 2.387 μmol/L) and 4.0% (7.038 ± 0.590 mmol/L vs. 6.763 ± 0.374 mmol/L; P < 0.01), respectively, together with the structural damages of glomerular atrophy and renal interstitial fibrosis. FGF21 treatment downregulated the ALP activity, calcium content in the kidney of VC rats by 42.1% (P < 0.01) and 11.7% (P < 0.05) as well as ameliorated the aortic injury and calcification as compared with VDN treatment alone group, indicating an ameliorative effect on VC. ELISA assays showed that the expression of β-Klotho, a component of FGF21 receptor system, was increased in VDN-treated VC rats by 37.4% (6.588 ± 0.957 pg/mg vs. 9.054 ± 0.963 pg/mg; P < 0.01), indicating an FGF21-resistant state. Moreover, FGF21 treatment downregulated the level of β-Klotho in renal tissue by 16.7% (9.054 ± 0.963 pg/mg vs. 7.544 ± 1.362 pg/mg; P < 0.05). However, the level of FGFR1, the receptor of FGF21, kept unchanged under VDN and VDN plus FGF21 administration (0.191 ± 0.0376 ng/mg vs. 0.189 ± 0.032 ng/mg vs. 0.181 ± 0.034 ng/mg; P > 0.05).

Conclusions:

In the present study, FGF21 was observed to ameliorate the kidney injury in VDN-induced VC rats. FGF21 might be a potential therapeutic factor in CKD by cutting off the vicious circle between VC and kidney injury.

Relation Between Calcified Atherosclerosis in the Renal Arteries and Kidney Function (from the Multi-Ethnic Study of Atherosclerosis)

Renal artery calcium (RAC) has been shown to be associated with higher odds of hypertension (HTN). The purpose of this study was to determine if the presence and extent of RAC is associated with renal function. We analyzed cross-sectional data from the Multi-Ethnic Study of Atherosclerosis (MESA). A subsample of 1,226 participants underwent computed tomography of the abdomen and also had venous blood samples measured for kidney function. RAC was the primary predictor variable and the following measures of kidney function were the outcome variables: estimated glomerular filtration rate (eGFR), urinary albumin-to-creatinine ratio (UACR), and chronic kidney disease (CKD) stage. The analyses were adjusted for age, gender, race, height, visceral fat, dyslipidemia, diabetes, cigarette smoking, hypertension, interleukin-6 and abdominal aortic calcium (AAC). The average age of this cohort was 66.1 years (SD 9.7), 44.8% (549 of 1,226) were men, and nearly 30% had RAC >0. Compared with those with no RAC, those with RAC >0 were significantly older but not different by gender or race. After adjustment for age, gender, and race, those with RAC >0 had significantly higher visceral fat, were more likely to have dyslipidemia, diabetes, and hypertension, had a higher interleukin-6, and a higher prevalence of AAC >0. The mean eGFR and UACR among those without RAC were 80 ml/min/1.73 m2 and 21 mg/g, whereas these values were 78 ml/min/1.73 m2 and 55 mg/g among those with RAC. In fully adjusted multivariable linear regression models, the presence of RAC was associated with a lower eGFR (β = -2.21, p = 0.06) but not with UACR (β = 0.02, p = 0.79). In fully adjusted ordinal logistic regression, RAC as a continuous variable was associated with increased odds of being in a worse CKD category (odds ratio 1.14, p = 0.05). When measured by eGFR and CKD stage, there is a modest relation between RAC and kidney function. Further studies might involve clinical trials to assess the role of intensive cardiovascular disease risk factor management in patients with subclinical RAC to determine if this may prevent or delay the development and progression of CKD.

Abdominal Aortic Calcification in Living Kidney Donors

OBJECTIVE

This study assesses the association between abdominal aortic calcification (AAC) and renal function of living kidney donors and evaluate AAC as a surrogate marker for nephrosclerosis.

METHODS

Between January 2010 and March 2013, 287 donors who underwent living donor nephrectomy were enrolled. We analyzed computed tomography angiographies and quantified AAC scores by calculating the Agatston score for the abdominal aorta. The donors were stratified into the non-AAC group (AAC score = 0; n = 238) and the AAC group (AAC score >0; n = 49). The relationship between AAC and perioperative estimated glomerular filtration rate was analyzed. For the 180 donors consenting to implantation biopsy, the nephrosclerosis score was defined as the sum of abnormalities, including glomerulosclerosis, tubular atrophy, interstitial fibrosis, and arteriosclerosis.

RESULTS

The mean AAC score was 185.5 ± 263.3 in the AAC group. The AAC group was older than the non-AAC group (51.1 ± 6.1 vs 37.9 ± 11 years; P < .001). Perioperative renal function was not different between the 2 groups. However, among the AAC group, donors with an AAC score of >100 were associated with delayed renal function recovery (P = .035). Donors with AAC were more likely to have glomerulosclerosis (50.0% vs 29.1%; P = .022), tubular atrophy (62.5% vs 33.1%; P = .002), and a higher nephrosclerosis score (P = .002).

CONCLUSIONS

Living donors with an AAC score of >100 require close observation because they have a higher probability of delayed renal function recovery after donation. AAC is associated with nephrosclerosis in healthy adults.

Clinical impact of coexisting retinopathy and vascular calcification on chronic kidney disease progression and cardiovascular events

BACKGROUND AND AIMS

Retinopathy and vascular calcification (VC) are representative markers of microvascular and macrovascular dysfunction in patients with chronic kidney disease (CKD). However, their relationship and combined effects on clinical outcomes remain undetermined.

METHODS AND RESULTS

We included 523 patients with nondialysis-dependent CKD stage 3-5 who had been examined with fundus photography for diabetic or hypertensive retinopathy. Simple radiographs were analyzed for the presence of VC. The clinical significance of VC of the abdominal aorta and iliofemoral artery (apVC) and retinopathy was evaluated in terms of the rate of renal function decline and composite of any cardiovascular event or death. CKD patients with retinopathy showed higher prevalence of apVC than those without retinopathy (25.6% vs. 12.5%, P < 0.001).The presence of retinopathy was independently associated with apVC (OR 2.13, 95% CI 1.31, 3.49). In multivariate analysis, compared with subjects with neither apVC nor retinopathy, the coexistence of both apVC and retinopathy were independently associated with rapid renal function decline (β = -1.51; 95% CI -2.40, -0.61), whereas apVC or retinopathy alone were not. Compared with subjects with neither apVC nor retinopathy, the HRs for composite end points were 1.05 (95% CI 0.48, 2.27), 1.79 (95% CI 1.14, 2.80), and 2.07 (95% CI 1.17, 3.67) for patients with apVC only, those with retinopathy only, and those with both apVC and retinopathy, respectively.

CONCLUSION

The coexistence of VC and retinopathy was independently associated with CKD progression and cardiovascular events or deaths, and its combined effect was stronger than any separate condition.

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.

Magnesium modifies the association between serum phosphate and the risk of progression to end-stage kidney disease in patients with non-diabetic chronic kidney disease

It is known that magnesium antagonizes phosphate-induced apoptosis of vascular smooth muscle cells and prevents vascular calcification. Here we tested whether magnesium can also counteract other pathological conditions where phosphate toxicity is involved, such as progression of chronic kidney disease (CKD). We explored how the link between the risk of CKD progression and hyperphosphatemia is modified by magnesium status. A post hoc analysis was run in 311 non-diabetic CKD patients who were divided into four groups according to the median values of serum magnesium and phosphate. During a median follow-up of 44 months, 135 patients developed end-stage kidney disease (ESKD). After adjustment for relevant clinical factors, patients in the lower magnesium-higher phosphate group were at a 2.07-fold (95% CI: 1.23-3.48) risk for incident ESKD and had a significantly faster decline in estimated glomerular filtration rate compared with those in the higher magnesium-higher phosphate group. There were no significant differences in the risk of these renal outcomes among the higher magnesium-higher phosphate group and both lower phosphate groups. Incubation of tubular epithelial cells in high phosphate and low magnesium medium in vitro increased apoptosis and the expression levels of profibrotic and proinflammatory cytokine; these changes were significantly suppressed by increasing magnesium concentration. Thus, magnesium may act protectively against phosphate-induced kidney injury.

Renal artery calcium, cardiovascular risk factors, and indexes of renal function

Vascular calcium is well studied in the coronary and peripheral arteries, although there are limited data focusing on calcium deposits specific to renal arteries. The associations among renal artery calcium (RAC), cardiovascular disease risk factors, and indexes of renal function are unknown. We examined 2,699 Framingham Heart Study participants who were part of a multidetector computed tomography substudy from 2008 to 2011. RAC was measured as a calcified plaque of >130 HU and an area of >3 contiguous pixels. Detectable RAC was defined as an Agatston score >0. Chronic kidney disease was defined as an estimated glomerular filtration rate of <60 ml/min/1.73 m(2). Microalbuminuria was defined as an albumin/creatinine ratio of ≥17 mg/g for men and ≥25 mg/g for women. Multivariable adjusted logistic regression models were used to evaluate the associations between RAC, cardiovascular disease risk factors, and renal function. The associations were secondarily adjusted for coronary artery calcium (CAC) that was used as a marker of nonrenal systemic vascular calcium. The prevalence of RAC was 28.2%; this was similar in women (28.8%) and men (27.5%). Patients with RAC had a higher odds of microalbuminuria (odds ratio [OR] 1.79, 95% confidence interval [CI] 1.22 to 2.61, p = 0.003), hypertension (OR 2.11, 95% CI 1.69 to 2.64, p <0.001), and diabetes (OR 1.60, 95% CI 1.14 to 2.24, p = 0.01) but not chronic kidney disease (OR 0.87, 95% CI 0.58 to 1.32). After adjustment for CAC, the association with microalbuminuria and hypertension persisted, but the association with diabetes became nonsignificant. In conclusion, RAC is common and independently associated with microalbuminuria and hypertension after adjustment for nonrenal vascular calcium. RAC may be uniquely associated with these markers of renal end-organ damage.

Derivation and validation of a renal risk score for people with type 2 diabetes

OBJECTIVE

Diabetes has become the leading cause of end-stage renal disease (ESRD). Renal risk stratification could assist in earlier identification and targeted prevention. This study aimed to derive risk models to predict ESRD events in type 2 diabetes in primary care.

RESEARCH DESIGN AND METHODS

The nationwide derivation cohort included adults with type 2 diabetes from the New Zealand Diabetes Cohort Study initially assessed during 2000-2006 and followed until December 2010, excluding those with pre-existing ESRD. The outcome was fatal or nonfatal ESRD event (peritoneal dialysis or hemodialysis for ESRD, renal transplantation, or death from ESRD). Risk models were developed using Cox proportional hazards models, and their performance was assessed in a separate validation cohort.

RESULTS

The derivation cohort included 25,736 individuals followed for up to 11 years (180,497 person-years; 86% followed for ≥5 years). At baseline, mean age was 62 years, median diabetes duration 5 years, and median HbA1c 7.2% (55 mmol/mol); 37% had albuminuria; and median estimated glomerular filtration rate (eGFR) was 77 mL/min/1.73 m2. There were 637 ESRD events (2.5%) during follow-up. Models that included sex, ethnicity, age, diabetes duration, albuminuria, serum creatinine, systolic blood pressure, HbA1c, smoking status, and previous cardiovascular disease status performed well with good discrimination and calibration in the derivation cohort and the validation cohort (n=5,877) (C-statistics 0.89-0.92), improving predictive performance compared with previous models.

CONCLUSIONS

These 5-year renal risk models performed very well in two large primary care populations with type 2 diabetes. More accurate risk stratification could facilitate earlier intervention than using eGFR and/or albuminuria alone.

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.

Association of foot ulcer with tibial artery calcification is independent of peripheral occlusive disease in type 2 diabetes

AIMS

To determine the relationship between foot ulcers, arterial calcification, and peripheral occlusive disease in patients with type 2 diabetes.

METHODS

We performed a cross-sectional study on 162 patients with type 2 diabetes who underwent assessment of tibial artery calcification (TAC) by non-contrasted CT scan. Peripheral artery occlusive disease was assessed by angiography. Foot status including the presence or absence of ulcers was documented at presentation. A multivariable logistic regression model was used to evaluate the association between foot ulcers, arterial calcification, and the extent of peripheral atherosclerotic occlusive disease.

RESULTS

Patients with foot ulcers (N=31) were more likely to be older and have a history of tobacco use. They were also more likely to have higher TAC scores (median [IQR]: 4324.6 [609.9, 11163.6] vs. 9.4 [0.0, 343.9], P<0.001) and more advanced peripheral artery occlusive disease (occlusion index 5.5 [4.8, 6.4] vs. 2.2 [1.0, 3.6], P<0.001). Foot ulcer was strongly associated with elevated TAC scores in a multivariable regression model (odds ratio [95% CI]=2.76 [1.61, 4.75], P=0.0002).

CONCLUSIONS

There is a strong association between arterial calcification and diabetic foot ulcers that persists after adjusting for the extent of atherosclerosis in patients with type 2 diabetes.

Change in ankle-brachial index over time and mortality in diabetics with proteinuria

Peripheral arterial disease is common in diabetic chronic kidney disease (CKD) and is characterized either by abnormally low or high ankle-brachial index (ABI). Whether low or high ABI carries similar prognostic value is unknown. The association of baseline ABI with all-cause mortality over 40 ± 21 months (mean ± SD) was ascertained in 167 proteinuric diabetics (age 57 ± 7 years; median urine protein-creatinine, 2.5 mg/mg). Association of change in ABI with all-cause mortality was determined in 75 subjects with normal ABI (0.9 - 1.3) at baseline. Among 167 participants, 41% had an abnormal ABI: < 0.9, 18%; and > 1.3 or non-compressible arteries, 23%. Only individuals with low ABI had a significantly higher risk for all-cause mortality (hazards ratio (95% confidence interval), HR: 2.23 (1.07, 4.65)). In subjects with normal ABI at baseline with follow-up measurement (n = 75), vascular disease worsened in 39% over 23 ± 6 months: 17% had either a decrease in ABI by ≥ 0.1 or a final ABI < 0.9, and 21% had a final ABI > 1.3 or noncompressible arteries. Only individuals who had a decrease in ABI over time had a significantly higher risk for death (adjusted HR, 7.41 (1.63, 33.65)). Peripheral arterial disease is not uncommon and progresses rapidly in individuals with diabetes and proteinuria. Low or declining ABI is a strong predictor of all-cause mortality. Routine measurement of ABI is a simple bed-side procedure that may permit easy risk-stratification in diabetic CKD patients.

Renal artery calcification and mortality among clinically asymptomatic adults

OBJECTIVES

The goal of this study was to assess the associations between renal artery calcification (RAC) and mortality in a healthy outpatient cohort with no known cardiovascular disease (CVD).

BACKGROUND

Studies in individuals with known diabetes and kidney disease have suggested that RAC confers additional mortality risk independent of coronary artery calcification, but this hypothesis has not been explored in healthier populations.

METHODS

RAC was assessed by using computed tomography scan in healthy outpatients with no known CVD. Cox proportional hazards models were used to examine the association of RAC with mortality.

RESULTS

The mean age of participants was 57 years; 42.6% were women. RAC was present in 622 (14%) of 4,450 participants. Over a median follow-up of 8.2 years, there were 178 deaths. After adjustment for age, sex, diabetes, smoking, cholesterol, and family history of CVD, the presence of RAC conferred a >60% increased hazard for all-cause mortality (hazard ratio [HR]: 1.63 [95% confidence interval (CI): 1.17 to 2.29]). Adjustment for calcification in other vascular beds attenuated this association (HR: 1.40 [95% CI: 0.99 to 1.97]). Adjustment for hypertension, a potential mediator of the association, did not substantially change the results (HR: 1.44 [95% CI: 1.02 to 2.03]). Adding RAC to a model including Framingham risk and coronary artery calcification improved the predictive ability of the model, from 0.73 to 0.77 (p = 0.0002); the net reclassification index was 14.4% for the addition of RAC. Results for cardiovascular mortality were not significant and were limited by the small number of cardiovascular deaths.

CONCLUSIONS

RAC was associated with an increased risk of subsequent all-cause mortality in healthy outpatient individuals, independent of traditional cardiac risk factors. The risk was modestly attenuated by adjustment for vascular calcification in other vascular beds, suggesting partial confounding by systemic calcified atherosclerosis. The effect did not seem to be mediated by hypertension.

Cinacalcet: will it play a role in reducing cardiovascular events?

Secondary hyperparathyroidism is a common complication of chronic kidney disease and it is associated with high morbidity and mortality. It is characterized by high parathyroid hormone levels and bone turnover leading to bone pain, deformity and fragility. Furthermore, secondary hyperparathyroidism adversely affects the cardiovascular system and has been associated with cardiovascular calcification and cardiomyopathy. Cinacalcet, a type II calcimimetic, is an effective and well-tolerated oral therapy for the management of secondary hyperparathyroidism. It is an allosteric activator of the calcium-sensing receptor enhancing sensitivity of parathyroid cells to extracellular calcium, which leads to inhibition of parathyroid hormone secretion. The calcium-sensing receptor expression in cardiomyocytes, endothelial cells and vascular smooth muscle cells raises the possibility that this receptor may be implicated in the pathophysiology of cardiovascular disease and constitute a potential therapeutic target. This article reviews the role of the calcimimetic agent cinacalcet in the prevention and progression of cardiovascular calcification and uremic cardiomyopathy in the chronic kidney disease setting.

Clinicopathological variables predicting progression of azotemia in cats with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is common in geriatric cats, but often appears to be stable for long periods of time.

OBJECTIVES

To describe CKD progression and identify risk factors for progression in newly diagnosed azotemic cats.

ANIMALS

A total of 213 cats with CKD (plasma creatinine concentration > 2 mg/dL, urine specific gravity < 1.035) were followed up until progression occurred or for at least 1 year; 132, 73, and 8 cats were in International Renal Interest Society (IRIS) stages 2, 3, and 4, respectively.

METHODS

Progression was defined as a 25% increase in plasma creatinine concentration. Logistic regression was used to assess variables at diagnosis that were associated with progression within 1 year. Changes in IRIS stage during follow-up also were described. Cases that remained in stages 2 or 3, but did not have renal function assessed in the last 60 days of life, were excluded from analysis of the proportion reaching stage 4.

RESULTS

Of the cats, 47% (101) progressed within 1 year of diagnosis. High plasma phosphate concentration and high urine protein-to-creatinine ratio (UPC) predicted progression in all cats. Low PCV and high UPC independently predicted progression in stage 2 cats, whereas higher plasma phosphate concentration predicted progression in stage 3 cats; 19% (18/94) of cats diagnosed in stage 2; and 63% (34/54) of cats diagnosed in stage 3 reached stage 4 before they died.

CONCLUSIONS

Proteinuria, anemia, and hyperphosphatemia may reflect more progressive kidney disease. Alternatively, they may be markers for mechanisms of progression such as tubular protein overload, hypoxia, and nephrocalcinosis.

Noninvasive imaging for assessment of calcification in chronic kidney disease

Vascular calcification is highly prevalent in patients with chronic kidney disease and has a progressive course. Several cardiovascular and uremia-related risk factors, such as abnormalities in mineral metabolism, contribute to the development of vascular calcification, although the pathophysiological mechanisms are still unclear. The presence and extent of vascular calcification is associated with an increased risk of cardiovascular events and mortality. By contrast, patients who do not have calcification seem to have a good prognosis, with minimal or no calcification progression over an extended period of time. A number of noninvasive imaging methods are available to detect vascular calcification and may help clinicians to make therapeutic decisions. Cardiac CT remains the reference standard to detect and quantify coronary artery, aortic and cardiac valve calcification. However, the high cost of equipment, the inability to perform in-office testing and the expertise required limit its use on a routine basis. Other imaging methods, such as planar X-ray, ultrasound and echocardiography, are appropriate alternatives to evaluate vascular and valvular calcification. In this review, we discuss the noninvasive imaging methods most frequently used to assess vascular and valvular calcification, with their advantages and limitations.