HIV-infected persons have substantially higher risk of kidney failure than persons without HIV, but serum creatinine levels are insensitive for detecting declining kidney function. We hypothesized that urine markers of kidney injury would be associated with declining kidney function among HIV-infected women.
In the Women's Interagency HIV Study (WIHS), we measured concentrations of albumin-to-creatinine ratio (ACR), interleukin-18 (IL-18), kidney injury marker-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL) from stored urine among 908 HIV-infected and 289 uninfected participants. Primary analyses used cystatin C based estimated glomerular filtration rate (CKD-EPI eGFRcys) as the outcome, measured at baseline and two follow-up visits over eight years; secondary analyses used creatinine (CKD-EPI eGFRcr). Each urine biomarker was categorized into tertiles, and kidney decline was modeled with both continuous and dichotomized outcomes.
Compared with the lowest tertiles, the highest tertiles of ACR (−0.15ml/min/1.73m2, p<0.0001), IL-18 (−0.09ml/min/1.73m2, p<0.0001) and KIM-1 (−0.06ml/min/1.73m2, p<0.001) were independently associated with faster eGFRcys decline after multivariate adjustment including all three biomarkers among HIV-infected women. Among these biomarkers, only IL-18 was associated with each dichotomized eGFRcys outcome: ≥3% (Relative Risk 1.40; 95%CI 1.04-1.89); ≥5% (1.88; 1.30-2.71); and ≥10% (2.16; 1.20-3.88) for the highest versus lowest tertile. In alternative models using eGFRcr, the high tertile of KIM-1 had independent associations with 5% (1.71; 1.25-2.33) and 10% (1.78; 1.07-2.96) decline, and the high IL-18 tertile with 10% decline (1.97; 1.00-3.87).
Among HIV-infected women in the WIHS cohort, novel urine markers of kidney injury detect risk for subsequent declines in kidney function.
HIV; KIM-1; NGAL; IL-18; albumin-to-creatinine ratio; cystatin C; kidney injury
Whether elevations of urinary biomarkers of tubular injury (urine neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule 1 (KIM-1)) are associated with future risk of kidney disease has not been investigated.
1:1 nested case-control study
Setting & Participants
686 participants in the Multi-Ethnic Study of Atherosclerosis (MESA).
NGAL and KIM-1 were measured at baseline and expressed as log-transformed continuous variables and categorized into deciles.
Kidney function was estimated by cystatin C using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Incident CKD Stage 3 was defined as eGFR <60 ml/min/1.73m2 and a eGFR decline >1 ml/min/1.73m2 per year, and rapid kidney function decline (RKFD) was defined as decline of ≥3 ml/min/1.73m2 per year.
Cases were defined as persons with eGFR >60 ml/min/1.73m2 who subsequently developed incident CKD Stage 3 and/or had RKFD by MESA year 5 visit. Controls were matched for age, gender, race, diabetes, and baseline eGFR. We adjusted for age, hypertension and presence of albuminuria (ACR ≥30 mg/g).
Of the 343 cases, 145 had incident CKD Stage 3, 141 had RKFD and 57 had both. Mean eGFR for controls was 81 (±10) ml/min/1.73m2 at baseline and 80 (±10) at follow-up, compared with 82 (±13) and 58 (±10) for cases. Each doubling of KIM-1 (pg/ml) was associated with an OR of 1.15 (95% CI, 1.02-1.29) for incident CKD Stage 3 and/or RKFD. Compared to the lowest 90%, the highest decile of KIM-1 was associated with an OR of 2.02 (95% CI, 1.15-3.56) for the outcome; these associations were independent of albuminuria. NGAL levels (ng/ml) were not associated with incident CKD Stage 3 and/or RKFD (OR, 1.04; 95% CI, 0.99-1.10). Results were similar when KIM-1 and NGAL were standardized for urine creatinine.
The case-control design limits ability to account for persons who died or were not available for follow-up.
Urinary KIM-1 is associated with future risk of kidney disease independent of albuminuria. Urinary biomarkers of tubular injury are a promising tool for identifying persons at risk for CKD.
KIM-1; NGAL; kidney function decline
Higher serum phosphorus concentrations are associated with cardiovascular disease events and mortality. Low socioeconomic status is linked with higher serum phosphorus, but the reasons are unclear. Poor individuals disproportionately consume inexpensive processed foods commonly enriched with phosphorus-based food preservatives. Accordingly, we hypothesized that excess intake of these foods accounts for a relationship between lower socioeconomic status and higher serum phosphorus.
Setting and Participants
We examined a random cohort of 2,664 participants with available phosphorus measurements in the Multi-Ethnic Study of Atherosclerosis, a community-based sample of individuals free of clinically apparent cardiovascular disease from across the United States.
Socioeconomic status, the intake of foods commonly enriched with phosphorus additives (processed meats, sodas) and frequency of fast food consumption.
Fasting morning serum phosphorus concentrations.
In unadjusted analyses, lower income and lower educational achievement categories were associated with modestly higher serum phosphorus (by 0.02 to 0.10 mg/dL, P < 0.05 for all). These associations were attenuated in models adjusted for demographic and clinical factors, almost entirely due to adjustment for female gender. There were no statistically significant associations of processed meat intake or frequency of fast-food consumption with serum phosphorus in multivariable-adjusted analyses. In contrast, each serving per day higher soda intake was associated with 0.02 mg/dl lower serum phosphorus (95% confidence interval, −0.04, −0.01).
Greater intake of foods commonly enriched with phosphorus additives was not associated with higher serum phosphorus in a community-living sample with largely preserved kidney function. These results suggest that excess intake of processed and fast foods may not impact fasting serum phosphorus concentrations among individuals without kidney disease.
phosphorus; socioeconomic status; nutrition
In some older adults, higher blood pressure (BP) is associated with a lower risk of mortality. We hypothesized that higher BP would be associated with greater mortality in high-functioning elders and lower mortality in elders with lower functional status.
Participants were 1,562 Latino adults aged 60–101 years in the Sacramento Area Latino Study on Aging. Functional status was measured by self-reported walking speed, and BP was measured by automatic sphygmomanometer. Death information was determined from vital statistics records.
There were 442 deaths from 1998 to 2010; 53% were cardiovascular. Mean BP levels (mmHg) varied across fast, medium, and slow walkers: 136, 139, and 140 mmHg (systolic), p = .02 and 75, 76, and 77 mmHg (diastolic), p = .08, respectively. The relationship between systolic BP and mortality varied by self-reported walking speed: The adjusted hazard ratio for mortality in slow walkers was 0.96 per 10 mmHg higher systolic BP (95% confidence interval: 0.89, 1.02) and 1.29 (95% confidence interval: 1.08, 1.55) in fast walkers (p value for interaction <.001). We found a similar pattern for diastolic BP, although the interaction did not reach statistical significance; the adjusted hazard ratio per 10 mmHg higher diastolic BP was 0.89 (95% confidence interval: 0.78, 1.02) in slow walkers and 1.20 (95% confidence interval: 0.82, 1.76) in fast walkers (p value for interaction = .06).
In high-functioning older adults, elevated systolic BP is a risk factor for all-cause mortality. If confirmed in other studies, the assessment of functional status may help to identify persons who are most at-risk for adverse outcomes related to high BP.
Blood pressure; Functional status; Latinos
The strength and direction of the associations between inflammation and coagulation biomarkers with kidney disease onset and progression remains unclear, especially in a population-based setting.
Prospective observational study.
Setting & Participants
4,966 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) with a cystatin C-based estimate of glomerular filtration rate (eGFRcys) > 60 ml/min/1.73m2 and least one follow-up measure of kidney function. All participants were free of cardiovascular disease (CVD) at entry.
We evaluated the associations of C-reactive protein (CRP), interleukin-6 (IL-6), fibrinogen, factor VIII, and D-dimer with kidney function decline.
Outcomes and Measurements
Kidney function decline was assessed primarily by repeated measures of eGFRcys over 5 years. Rapid decline of kidney function was defined as an eGFR decrease of more than 3 ml/min/1.73m2 per year. Incident low eGFR was defined as the onset of eGFRcys<60 ml/min/1.73m2 at any follow up exam and eGFRcys decline ≥1 ml/min/1.73m2 per year.
Mean age was 60 years, 39% were white, 52% were women, and 11% had diabetes. Mean eGFRcys was 96 mL/min/1.73 m2 and 7% had albuminuria. Median follow up time was 4.77 years. Higher Factor VIII levels (per 1-standard deviation [SD] of biomarker) had the strongest association with kidney function decline (β= −0.25; 95% CI, −0.38 to −0.12; p<0.001), followed by IL-6 (β= −0.16; 95% CI, −0.29 to −0.03; p=0.01), CRP (β= −0.09; 95% CI, −0.22 to 0.03; p=0.1), and fibrinogen (β= −0.09; 95% CI, −0.22 to 0.04; p=0.2). Each 1-SD higher concentration of IL-6 (OR, 1.15; 95% CI, 1.07–1.23), Factor VIII (OR, 1.11; 95% CI, 1.03–1.18), and CRP (OR, 1.09; 95% CI, 1.02–1.16) at baseline was significantly associated with rapid kidney function decline. Only IL-6 was significantly associated with incident low eGFR (OR, 1.09; 95% CI, 1.00–1.19).
Observational study design and absence of measured GFR.
Inflammation and coagulation biomarkers are associated with declining kidney function in ambulatory adults without established CVD or CKD.
The association of hypertension and mortality is attenuated in elderly adults. Walking speed, as a measure of frailty, may identify which elders are most at risk for the adverse effects of hypertension. We hypothesized that elevated blood pressure (BP) would be associated with a greater risk of mortality in faster, but not slower, walking older adults.
Participants included 2,340 persons ≥65 years in the National Health and Nutrition Examination Survey, 1999–2000 and 2001–2002. Mortality data was linked to death certificates in the National Death Index. Walking speed was measured over a 20-foot walk and classified as faster (≥ 0.8 meters/second, n=1,307), slower (n=790), or incomplete (n=243). Potential confounders included age, sex, race, survey year, lifestyle and physiologic variables, health conditions, and antihypertensive medications.
There were 589 deaths through December 31st, 2006. The association of BP and mortality varied by walking speed. Among faster walkers, those with elevated systolic BP (≥140 mmHg) had a greater adjusted risk of mortality compared to those without (Hazard Ratio (HR): 1.35, 95% confidence interval (CI): 1.03, 1.77). Among slower walkers, neither elevated systolic nor diastolic BP (≥90 mmHg) was associated with mortality. In participants who did not complete the walk test, elevated BP was strongly and independently associated with a lower risk of death: HR: 0.38, 95% CI: 0.23, 0.62 (systolic) and HR: 0.10, 95% CI: 0.01, 0.81 (diastolic).
Walking speed could be a simple measure to identify elderly adults who are most at risk for adverse outcomes related to high BP.
Hypertension guidelines recommend screening for chronic kidney disease (CKD) using serum creatinine and urine dipstick; this strategy may lead to misclassification. Persons with occult CKD [i.e. missed by creatinine but detected by cystatin C or albumin-to-creatinine ratio (ACR)] have higher risks for death, cardiovascular events, and end-stage renal disease.
We studied occult CKD prevalence among nondiabetic, hypertensive adults in National Health and Nutrition Examination Survey 1988–1994 (N = 2088) and 1999–2002 (N = 737). We defined occult CKD as estimated glomerular filtration rate by cystatin C (eGFRcys) less than 60 ml/min per 1.73m2 and/or ACR at least 30 mg/g among persons with eGFRcreat more than 60 ml/min per 1.73m2. We studied occult CKD prevalence by either marker, stratified by age, race/ethnicity, and assessed clinical predictors associated with occult CKD presence.
In 1988–1994, occult CKD was prevalent among 25% of nondiabetic hypertensive persons, and it was 22% in 1999–2002. Each marker’s ability to detect occult CKD varied by age and race. Cystatin C detected occult CKD among 8.9% of persons more than 65 years, and among 3.8% of whites. ACR detected occult CKD among 9.3% of persons less than 45 years, 16.6% of Blacks, and 20.6% of Mexican–Americans. In multivariate models, each decade of advancing age was associated with a higher occult CKD prevalence by cystatin C (OR 3.1, 95% CI 2.5–3.8) in 1988–1994 and 1999–2002 (OR 2.9, 1.8–4.6).
Current hypertension guidelines may fail to detect a large proportion of high-risk individuals with CKD who can be identified by cystatin C or ACR. Future studies are needed to evaluate targeted use of multimarker renal panels among hypertensives.
albumin-to-creatinine ratio; chronic kidney disease; cystatin C; National Health and Nutrition Examination Survey
A triple-marker approach for chronic kidney disease (CKD) evaluation has not been well studied.
To evaluate whether combining creatinine, cystatin C, and urine albumin-to-creatinine ratio (ACR) would improve identification of risks associated with CKD compared with creatinine alone.
Design, Setting, and Participants
Prospective cohort study involving 26 643 US adults enrolled in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study from January 2003 to June 2010. Participants were categorized into 8 groups defined by estimated glomerular filtration rate (GFR) determined by creatinine and by cystatin C of either <60 or ≥60 mL/min/1.73 m2 and ACR of either <30 or ≥30 mg/g.
Main Outcome Measures
All-cause mortality and incident end-stage renal disease with median follow-up of 4.6 years.
Participants had a mean age of 65 years, 40% were black, and 54% were women. Of 26 643 participants, 1940 died and 177 developed end-stage renal disease. Among participants without CKD defined by creatinine, 24% did not have CKD by either ACR or cystatin C. Compared with those with CKD defined by creatinine alone, the hazard ratio for death in multivariable-adjusted models was 3.3 (95% confidence interval [CI], 2.0–5.6) for participants with CKD defined by creatinine and ACR; 3.2 (95% CI, 2.2–4.7) for those with CKD defined by creatinine and cystatin C, and 5.6 (95% CI, 3.9–8.2) for those with CKD defined by all biomarkers. Among participants without CKD defined by creatinine, 3863 (16%) had CKD detected by ACR or cystatin C. Compared with participants who did not have CKD by any measure, the HRs for mortality were 1.7 (95% CI, 1.4–1.9) for participants with CKD defined by ACR alone, 2.2 (95% CI, 1.9–2.7) for participants with CKD defined by cystatin C alone, and 3.0 (95% CI, 2.4–3.7) for participants with CKD defined by both measures. Risk of incident end-stage renal disease was higher among those with CKD defined by all markers (34.1 per 1000 person-years; 95% CI, 28.7–40.5 vs 0.33 per 1000 person-years; 95% CI, 0.05–2.3) for those with CKD defined by creatinine alone. The second highest end-stage renal disease rate was among persons missed by the creatinine measure but detected by both ACR and cystatin C (rate per 1000 person-years, 6.4; 95% CI, 3.6–11.3). Net reclassification improvement for death was 13.3% (P<.001) and for end-stage renal disease was 6.4% (P<.001) after adding estimated GFR cystatin C in fully adjusted models with estimated GFR creatinine and ACR.
Adding cystatin C to the combination of creatinine and ACR measures improved the predictive accuracy for all-cause mortality and end-stage renal disease.
Insulin resistance is a risk factor for cardiovascular and noncardiovascular diseases. Impaired kidney function is linked with insulin resistance and may affect relationships of insulin resistance with health outcomes.
RESEARCH DESIGN AND METHODS
We performed a cohort study of 3,138 Cardiovascular Health Study participants (age ≥65 years) without diabetes. Insulin sensitivity index (ISI) was calculated from fasting and 2-h postload insulin and glucose concentrations. Associations of ISI and fasting insulin concentration with all-cause mortality were tested using Cox proportional hazards models, adjusting for demographic variables, prevalent cardiovascular disease, lifestyle variables, waist circumference, and LDL cholesterol. Subsequent models were additionally adjusted for or stratified by glomerular filtration rate estimated using serum cystatin C (eGFR).
A total of 1,810 participants died during the 14.7-year median follow-up. Compared with the highest quartile of ISI, the lowest quartile (most insulin resistant) was associated with 21% (95% CI 6–41) and 11% (−3 to 29) higher risks of death without and with adjustment for eGFR, respectively. Compared with the lowest quartile of fasting insulin concentration, the highest quartile was associated with 22% (4–43) and 4% (−12 to 22) higher risks of death without and with adjustment for eGFR, respectively. Similar attenuation by eGFR was observed when blood pressure, triglycerides, HDL cholesterol, and C-reactive protein were included in models.
Insulin resistance measured as ISI or fasting insulin concentration is associated with increased risk of death among older adults, adjusting for conventional confounding characteristics. Impaired kidney function may mediate or confound this relationship.
Both anemia and secondary hyperparathyroidism are reflections of hormonal failure in chronic kidney disease (CKD). While the association of elevated levels of parathyroid hormone (PTH) and anemia has been studied among those with advanced CKD, less is known about this association in mild-to-moderate CKD.
In a cross-sectional analysis, the relationship between PTH and hemoglobin levels was investigated in 10,750 participants in the National Kidney Foundation's Kidney Early Evaluation Program with an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m2.
In the unadjusted analysis, higher PTH levels were associated with lower hemoglobin levels. However, after multivariable adjustment for age, race, gender, smoking status, education, cardiovascular disease, diabetes, hypertension, cancer, albuminuria, BMI, baseline eGFR, calcium, and phosphorus, the direction of association changed. As compared to the first PTH quintile, hemoglobin levels were 0.09 g/dl (95% CI: 0.01-0.18), 0.15 g/dl (95% CI: 0.07-0.24), 0.18 g/dl (95% CI: 0.09-0.26), and 0.13 g/dl (95% CI: 0.07-0.25) higher for the second, third, fourth, and fifth quintiles, respectively. Similarly, each standard deviation increase in natural log transformed PTH was associated with a 0.06 g/dl (95% CI: 0.03-0.09, p = 0.0003) increase in hemoglobin. However, a significant effect modification was seen for diabetes (p = 0.0003). Each standard deviation increase in natural log transformed PTH was associated with a 0.10 g/dl (95% CI: 0.054-0.138, p < 0.0001) increase in hemoglobin, while no association was seen among those without diabetes mellitus.
After multivariable adjustment, there was a small positive association between PTH and hemoglobin among diabetics but not among nondiabetics.
Chronic kidney disease; Anemia; Secondary hyperparathyroidism
Purpose of Review
The purpose of this review is to discuss novel studies in the last year that have examined the use of combinations of multiple markers to improve risk prediction in the setting of chronic kidney disease (CKD). We will focus on multi-marker panels to improve prediction of CKD onset; improve classification of CKD and risk-stratification of persons with CKD; and develop individual-level risk scores for progression to ESRD.
One study reported that several novel circulation biomarkers may aid in predicting incident CKD and microalbuminuria. Second, our group has shown that the combination of creatinine, cystatin C and albuminuria improves detection and risk stratification for death, heart failure, cardiovascular events, and end stage renal disease compared with creatinine alone. Finally, a highly accurate individual risk score was developed to predict progression to ESRD using readily available clinical markers.
The combination of multiple markers improves detection and risk stratification in CKD. Future research is needed in understanding the use of a “renal panel” for detection, classification and risk stratification in kidney disease in diverse populations. The studies presented here represent the beginning of a paradigm shift to multi-marker panels in nephrology.
Chronic kidney disease; albuminuria; creatinine; cystatin C; multi-marker
Pentraxin-3 is an inflammatory marker thought to be more specific to vascular inflammation than C-reactive protein (CRP). Whether pentraxin-3 is independently associated with adverse events among persons with stable coronary heart disease (CHD), independently of CRP, and whether kidney dysfunction influences these associations, is not known.
We evaluated the associations of baseline pentraxin-3 levels with all-cause mortality, cardiovascular events (myocardial infarction, stroke or CHD death), and incident heart failure during 37 months among ambulatory persons with stable CHD participating in the Heart and Soul Study. Cox proportional hazards models were adjusted for age, sex, race, hypertension, diabetes, smoking, and CRP.
Among 986 persons with stable CHD, each one unit increase in log pentraxin-3 at baseline was associated with an 80% increased risk of all-cause mortality (HR 1.8, 95% CI 1.5–2.1), a 50% increased risk of cardiovascular events (HR 1.5, 95% CI, 1.2–1.9), and an 80% greater risk of incident heart failure (HR 1.8, 95% CI, 1.3–2.5). Further adjustment for estimated glomerular filtration rate (eGFR) attenuated these associations to 1.6 (1.3–1.9) for mortality, 1.3 (1.0–1.6) for cardiovascular events and 1.5 (1.1–2.1) for incident heart failure. Stratification by eGFR above or below 60 ml/min/1.73m2 did not affect these associations (p interaction >0.3 for all outcomes).
Among persons with stable CHD, higher pentraxin-3 concentrations were associated with increased risk for all-cause mortality, cardiovascular events and incident heart failure independently of systemic inflammation. Adjustment for eGFR modestly attenuated these associations, suggesting that future studies of pentraxin-3 should adjust for kidney function.
cardiovascular diseases; heart failure; coronary disease; kidney
The association of subclinical vascular disease and early declines in kidney function has not been well studied.
Prospective cohort study
Setting & Participants
MESA participants with eGFR ≥60 ml/min/1.73m2 with follow-up of 5 years
Pulse pressure (pulse pressure), small and large arterial elasticity (SAE, LAE), and flow mediated dilation.
kidney function decline
SAE and LAE were measured by pulse contour analysis of the radial artery. Kidney function was measured by serum creatinine- and cystatin C-based eGFR.
Among 4,853 adults, higher pulse pressure and lower SAE and LAE had independent and linear associations with faster rates of kidney function decline. Compared to persons with pulse pressure 40–50mmHg, eGFRSCysC decline was 0.29 (p=0.006), 0.56 (p<0.001), and 0.91 (p<0.001) ml/min/1.73m2/year faster among persons with pulse pressure 50–60, 60–70, and >70mmHg, respectively. Compared to the highest quartile of SAE (most elastic), eGFRSCysC decline was 0.26 (p=0.009), 0.35 (p=0.001), and 0.70 (p<0.001) ml/min/1.73m2/year faster for the second, third and fourth quartiles respectively. For LAE, compared to the highest quartile, eGFRSCysC decline was 0.28 (p=0.004), 0.58 (p<0.001), and 0.83 (p<0.001) ml/min/1.73m2/year faster for each decreasing quartile of LAE. Findings were similar with creatinine-based eGFR. In contrast, among 2,997 adults with flow-mediated dilation and kidney function measures, flow-mediated dilation was not significantly associated with kidney function decline. For every 1-SD greater flow-mediated dilation, eGFRSCysC and eGFRSCr changed by 0.05 ml/min/1.73m2/year (p=0.3) and 0.06 ml/min/1.73m2/year (p=0.04), respectively.
We had no direct measure of GFR, in common with nearly all large population based studies.
Higher pulse pressure and lower arterial elasticity, but not flow-mediated dilation, were linearly and independently associated with faster kidney function decline among persons with eGFR ≥60 ml/min/1.73m2. Future studies investigate whether treatments to lower stiffness of large and small arteries may slow the rate of kidney function loss.
kidney function; arterial elasticity; chronic kidney disease; atherosclerosis
Background: Whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are associated with kidney function decline has not been well studied. Methods: We investigated associations of Lp-PLA2 antigen and activity with kidney function decline and rapid decline over 5.7 years in the Cardiovascular Health Study (n = 4,359). We estimated kidney function by cystatin C (eGFRcys) in repeated measures, and defined rapid decline as ≥3 ml/min/1.73 m2 per year. We stratified by baseline preserved GFR (≥60 ml/min/1.73 m2). Results: Mean age was 72 ± 5 years. Average eGFRcys decline was −1.79 ml/min/1.73 m2 (SD = 2.60) per year. Among persons with preserved GFR, compared to the lowest quartile of Lp-PLA2 antigen, eGFRcys decline was faster among persons in the second, β −0.31 (95% CI −0.52, −0.10), third −0.19 (–0.41, 0.02) and fourth quartiles −0.26 (–0.48, −0.04) after full adjustment. Persons in the highest quartile of Lp-PLA2 antigen had increased odds of rapid decline 1.34 (1.03, 1.75), compared to the lowest. There was no significant association between levels of Lp-PLA2 activity and eGFRcys decline or rapid decline. Associations were not statistically significant among persons with low eGFR (<60 ml/min/1.73 m2) at baseline. Conclusion: Higher levels of Lp-PLA2 antigen but not activity were significantly associated with faster rates of kidney function decline. These findings may suggest a novel vascular pathway for kidney disease progression.
Chronic kidney disease; Elderly; Estimated GFR; Kidney decline; Lipoprotein-associated phospholipase A2
African-Americans have a disproportionate burden of hypertension compared to Caucasians, while data on Hispanics is less well-defined. Mechanisms underlying these differences are unclear, but could be due in part to ancestral background and vascular function.
Methods and Results
660 African-Americans and 635 Hispanics from the Multi-Ethnic Study of Atherosclerosis (MESA) with complete data on genetic ancestry, pulse pressure (PP), and large and small arterial elasticity (LAE, SAE) were studied. LAE and SAE were obtained using the HDI PulseWave CR-2000 Research CardioVascular Profiling Instrument. Among African-Americans higher European ancestry was marginally associated with higher LAE (p=0.05) and lower PP (p=0.05) among African-Americans; results for LAE were attenuated after adjustment for potential mediators (p=0.30). Ancestry was not associated with SAE in African-Americans. Among Hispanics, higher Native American ancestry was associated with higher SAE (p=0.0006); higher African ancestry was marginally associated with lower SAE (p=0.07). Ancestry was not significantly associated with LAE or PP in Hispanics.
Among African-Americans, higher European ancestry may be associated with less large artery damage as measured by LAE and PP, although these associations warrant further study. Among Hispanics, ancestry is strongly associated with SAE. Future studies should consider information on genetic ancestry when studying hypertension burden in race/ethnic minorities, particularly among Hispanics.
large artery elasticity; small artery elasticity; admixture; pulse pressure
The evidence for the effectiveness of antihypertensive medication use for slowing decline in kidney function in older persons is sparse. We addressed this research question by the application of novel methods in a marginal structural model.
Change in kidney function was measured by two or more measures of cystatin C in 1,576 hypertensive participants in the Cardiovascular Health Study over 7 years of follow-up (1989–1997 in four U.S. communities). The exposure of interest was antihypertensive medication use. We used a novel estimator in a marginal structural model to account for bias due to confounding and informative censoring.
The mean annual decline in eGFR was 2.41 ± 4.91 mL/min/1.73 m2. In unadjusted analysis, antihypertensive medication use was not associated with annual change in kidney function. Traditional multivariable regression did not substantially change these estimates. Based on a marginal structural analysis, persons on antihypertensives had slower declines in kidney function; participants had an estimated 0.88 (0.13, 1.63) ml/min/1.73 m2 per year slower decline in eGFR compared with persons on no treatment. In a model that also accounted for bias due to informative censoring, the estimate for the treatment effect was 2.23 (−0.13, 4.59) ml/min/1.73 m2 per year slower decline in eGFR.
In summary, estimates from a marginal structural model suggested that antihypertensive therapy was associated with preserved kidney function in hypertensive elderly adults. Confirmatory studies may provide power to determine the strength and validity of the findings.
aged; kidney function; hypertension; marginal structural model
Functional biomarkers like large artery elasticity (LAE) and small artery elasticity (SAE) may predict cardiovascular disease (CVD) events beyond blood pressure. The authors examined the prognostic value of LAE and SAE for clinical CVD events among 6,235 Multi-Ethnic Study of Atherosclerosis participants who were initially aged 45–84 years and without symptomatic CVD. LAE and SAE were derived from diastolic pulse contour analysis. During a median 5.8 years of follow-up between 2000 and 2008, 454 adjudicated CVD events occurred, including 256 cases of coronary heart disease (CHD), 93 strokes, and 126 heart failures (multiple diagnoses were possible). After adjustment for age, race/ethnicity, sex, clinic, height, heart rate, body mass index, systolic and diastolic blood pressure, use of antihypertensive and cholesterol-lowering medications, smoking, total cholesterol, high density lipoprotein cholesterol, triglycerides, diabetes, and high-sensitivity C-reactive protein, the hazard ratio for any CVD per standard-deviation increase in SAE was 0.71 (95% confidence interval: 0.61, 0.83; P < 0.0001). The lowest (stiffest) SAE quartile had a hazard ratio of 2.28 (95% confidence interval: 1.55, 3.36) versus the highest (most elastic) quartile. The net reclassification index, conditional on base risk, was 0.11. SAE was significantly associated with future CHD, stroke, and heart failure. After adjustment, LAE was not significantly related to CVD. In asymptomatic participants free of overt CVD, lower SAE added prognostic information for CVD, CHD, stroke, and heart failure events.
arteries; cardiovascular diseases; elasticity; risk factors
Treatment of hypertension is difficult in chronic kidney disease (CKD), and blood pressure goals remain controversial. The association between each blood pressure component and end-stage renal disease (ESRD) risk is less well known.
We studied associations of systolic and diastolic blood pressure (SBP and DBP, respectively) and pulse pressure (PP) with ESRD risk among 16 129 Kidney Early Evaluation Program (KEEP) participants with an estimated glomerular filtration rate of 60 mL/min/1.73 m2 using Cox proportional hazards. We estimated the prevalence and characteristics associated with uncontrolled hypertension (SBP≥150 or DBP≥90 mm Hg).
The mean (SD) age of participants was 69 (12) years; 25% were black, 6% were Hispanic, and 43% had diabetes mellitus. Over 2.87 years, there were 320 ESRD events. Higher SBP was associated with higher ESRD risk, starting at SBP of 140 mm Hg or higher. After sex and age adjustment, compared with SBP lower than 130 mm Hg, hazard ratios (HRs) were 1.08 (95% CI, 0.74–1.59) for SBP of 130 to 139 mm Hg, 1.72 (95% CI, 1.21–2.45) for SBP of 140 to 149 mm Hg, and 3.36 (95% CI, 2.51–4.49) for SBP of 150 mm Hg or greater. After full adjustment, HRs for ESRD were 1.27 (95% CI, 0.88–1.83) for SBP of 140 to 149 mm Hg and 1.36 (95% CI, 1.02–1.85) for SBP of 150 mm Hg or higher. Persons with DBP of 90 mm Hg or higher were at higher risk for ESRD compared with persons with DBP of 60 to 74 mm Hg (HR, 1.81; 95% CI, 1.33–2.45). Higher PP was also associated with higher ESRD risk (HR, 1.44 [95% CI, 1.00–2.07] for PP≥80 mm Hg compared with PP<50 mm Hg). Adjustment for SBP attenuated this association. More than 33% of participants had uncontrolled hypertension (SBP≥150 mm Hg or DBP≥90 mm Hg), mostly due to isolated systolic hypertension (54%).
In this large, diverse, community-based sample, we found that high SBP seemed to account for most of the risk of progression to ESRD. This risk started at SBP of 140 mm Hg rather than the currently recommended goal of less than 130 mm Hg, and it was highest among those with SBP of at least 150 mm Hg. Treatment strategies that preferentially lower SBP may be required to improve BP control in CKD.
The growing burden and morbidity of chronic kidney disease (CKD) warrant effective strategies for identifying those at increased risk. We examined the association of cystatin C and albuminuria with development of CKD stage 3.
Prospective observational study.
Setting and Participants
5,422 participants from the Multi-Ethnic Study of Atherosclerosis with estimated glomerular filtration rate (eGFR) ≥ 60 ml/min/1.73m2.
Participants were categorized into four mutually exclusive groups: presence or absence of microalbuminuria (albumin-creatinine ratio >17 and > 25 µg/mg in men and women, respectively) in those with or without cystatin C ≥ 1.0 mg/L.
Outcomes and Measurements
Incident CKD stage 3 was defined as eGFR < 60 ml/min/1.73m2 at the 3rd or 4th visit and an annual decline of > 1 ml/min/1.73 m2. Poisson regression was used to evaluate incident rate ratios in unadjusted and adjusted analyses that include baseline eGFR.
Mean age was 61 years, 49% were men, 38% white, 11% had diabetes, 13.7% had cystatin C ≥ 1mg/L, 8.4% had microalbuminuria, and 2.7 % had cystatin C ≥ 1 mg/L with microalbuminuria. 554 (10%) participants developed CKD stage 3 over a median follow-up of 4.7 years and the adjusted incidence rate ratios (95% CI) were 1.57 (1.19–2.07), 1.37 (1.13–1.66), and 2.12 (1.61–2.80) in those with microalbuminuria, cystatin C ≥ 1 mg/L, and both, respectively, compared to those with neither.
Relatively short follow up and absence of measured GFR.
Cystatin C and microalbuminuria are independent risk factors for incident CKD stage 3 and could be useful as screening tools to identify those at increased risk.
Background. Pentraxin-3 (PTX3), an inflammatory marker thought to be related to vascular inflammation, is elevated in advanced chronic kidney disease (CKD). Whether PTX3 is associated with mild to moderate kidney dysfunction is unknown.
Methods. We tested associations of proteins in the pentraxin family [PTX3, C-reactive protein (CRP) and serum amyloid protein (SAP)] with estimated glomerular filtration rate by cystatin C (eGFRcys) and microalbuminuria among 2824 participants in the Multi-Ethnic Study of Atherosclerosis. Associations were tested using multivariable linear regression with adjustment for demographics (age, gender, annual income), comorbidities (diabetes, hypertension, smoking, body mass index, low-density lipoprotein, high-density lipoprotein, triglycerides, ACE inhibitor and statin use) and systemic inflammation [interleukin-6 (IL-6)].
Results. Among the 2824 participants, mean age was 62 years and mean eGFRcys was 94 mL/min/1.73 m2; 25% were white, 25% Chinese, 25% African-American and 25% Hispanic. Among all participants after full adjustment, higher PTX3 was associated with lower eGFRcys independently of IL-6 (β − 3.0 mL/min/1.73 m2 per unit increase in lnPTX3, P < 0.001). In contrast, CRP and SAP were associated with eGFRcys in demographic adjusted models, but these associations were attenuated after adjustment for comorbidities and IL-6 (lnCRP β − 0.06, P = 0.9; lnSAP β − 0.35, P = 0.7). There was a significant interaction with race/ethnicity (P < 0.001) in the association of PTX3 and eGFRcys. After adjustment for demographics, comorbidities and IL-6, this association was significant in blacks (β − 5.7 mL/min/1.73 m2 per unit increase in lnPTX3, P = 0.002) but not in Hispanics (β − 2.4, P = 0.1), Chinese (β − 0.91, P = 0.5) or whites (β − 0.26, P = 0.9). PTX3 and CRP, but not SAP, had correlations with microalbuminuria in unadjusted models (Spearman coefficients PTX3 0.05, P = 0.005; CRP 0.07, P < 0.001; SAP 0.013, P = 0.5), but these were attenuated after full adjustment.
Conclusions. Endovascular inflammation may be an important mechanism associated with early kidney dysfunction, particularly among blacks. This mechanism appears to be independent of IL-6-regulated pathways.
C-reactive protein; estimated glomerular filtration rate by cystatin; pentraxin-3; race/ethnicity; serum amyloid protein
Background. Acculturation affects health, but it has never been studied with kidney disease.
Methods. We studied the association of language spoken at home, generation and birth place with kidney function among Hispanics and Chinese in the Multi-Ethnic Study of Atherosclerosis (n = 2999). Kidney function was determined by cystatin C (eGFRcys) and albumin/creatinine ratio (ACR). We evaluated mediators in models: Model 1 = age, sex, income, education; Model 2 = Model 1 + behaviors; and Model 3 = Model 1 + comorbidities.
Results. Among Hispanics, speaking mixed Spanish/English was significantly associated with lower eGFRcys (− 2.83 mL/min/1.73 m2, − 5.69–0.04) and higher ACR (RD 40%, 17–68%) compared with speaking Spanish only; this was mildly attenuated by behaviors (− 2.29, − 5.33–0.75; RD 42%, 18–72%) but not comorbidities (− 3.04, − 5.83 to − 0.23); RD 35%, 14–59%). US-born Hispanics had lower eGFRcys compared with foreign-born Hispanics [1.83 mL/min/1.73 m2 lower (0.97–1.31) for Generation 1; 1.37 mL/min/1.73 m2 lower (0.75–1.57) for Generation ≥ 2].
In contrast, Chinese who spoke any English had higher eGFRcys (2.53, 95% CI: − 1.70–6.78), but similar ACR (RD − 5%, 95% CI: − 26–23%) compared with those speaking Chinese only, but associations were not statistically significant.
Conclusion. Higher acculturation was associated with worse kidney function in Hispanics, mediated perhaps by behavioral factors but not comorbidities. Associations may be in the opposite direction among Chinese. Future studies are needed to elucidate these mechanisms.
acculturation; cystatin C; kidney function
Using ∼60,000 SNPs selected for minimal linkage disequilibrium, we perform population structure analysis of 1,374 unrelated Hispanic individuals from the Multi-Ethnic Study of Atherosclerosis (MESA), with self-identification corresponding to Central America (n = 93), Cuba (n = 50), the Dominican Republic (n = 203), Mexico (n = 708), Puerto Rico (n = 192), and South America (n = 111). By projection of principal components (PCs) of ancestry to samples from the HapMap phase III and the Human Genome Diversity Panel (HGDP), we show the first two PCs quantify the Caucasian, African, and Native American origins, while the third and fourth PCs bring out an axis that aligns with known South-to-North geographic location of HGDP Native American samples and further separates MESA Mexican versus Central/South American samples along the same axis. Using k-means clustering computed from the first four PCs, we define four subgroups of the MESA Hispanic cohort that show close agreement with self-identification, labeling the clusters as primarily Dominican/Cuban, Mexican, Central/South American, and Puerto Rican. To demonstrate our recommendations for genetic analysis in the MESA Hispanic cohort, we present pooled and stratified association analysis of triglycerides for selected SNPs in the LPL and TRIB1 gene regions, previously reported in GWAS of triglycerides in Caucasians but as yet unconfirmed in Hispanic populations. We report statistically significant evidence for genetic association in both genes, and we further demonstrate the importance of considering population substructure and genetic heterogeneity in genetic association studies performed in the United States Hispanic population.
Using genotype data from about 60,000 distinct genetic markers, we examined population structure in 1,374 unrelated Hispanic individuals from the Multi-Ethnic Study of Atherosclerosis (MESA), with self-identification corresponding to Central America (n = 93), Cuba (n = 50), the Dominican Republic (n = 203), Mexico (n = 708), Puerto Rico (n = 192), and South America (n = 111). By comparing genetic ancestry of MESA Hispanic participants to reference samples representing worldwide diversity, we show major differences in ancestry of MESA Hispanics reflecting their Caucasian, African, and Native American origins, with finer differences corresponding to North-South geographic origins that separate MESA Mexican versus Central/South American samples. Based on our analysis, we define four subgroups of the MESA Hispanic cohort that show close agreement with the following self-identified regions of origin: Dominican/Cuban, Mexican, Central/South American, and Puerto Rican. We examine association of triglycerides with selected genetic markers, and we further demonstrate the importance of considering differences in genetic ancestry (or factors associated with genetic ancestry) when performing genetic studies of the United States Hispanic population.
Background. Despite a higher incidence of end-stage renal disease (stage 5), blacks have been shown to have the same or lower prevalence of chronic kidney disease (CKD stages 3 and 4). Current creatinine-based glomerular filtration rate (GFR)-estimating equations may misclassify young, healthy blacks.
Methods. Among 3501 young adults (mean age 45), we compared the prevalence of CKD in blacks and whites using the Modification of Diet in Renal Disease (MDRD) and the CKD Epidemiology Collaboration (CKD-EPI) equations. In addition, we used measured creatinine excretion rates to determine the actual excretion ratio for CARDIA (race coefficient 12%) and applied this to the CKD-EPI equation. We also studied the prevalence of CKD risk factors among black and white participants near the CKD threshold cut-off (eGFR CKD-EPI 60–80 mL/min/1.73 m2) to estimate the relative likelihood of misclassification in blacks and whites.
Results. Using the MDRD equation, prevalence of CKD stages 4 and 5 was higher for blacks compared with whites (0.6% vs. 0.1%, P-value 0.05). In contrast, prevalence of eGFR <60 mL/min/1.73 m2 was significantly higher for whites (3.6%) compared with blacks (1.9%), due to higher prevalence of stage 3 among whites. Prevalence of CKD was similar for blacks and whites using CKD-EPI equation (1.2%), but was higher among blacks when using the CARDIA-derived race coefficient (1.6% vs.1.2%, P-value = 0.03). Among persons with eGFR by CKD-EPI of 60–80 mL/min/1.73 m2, blacks had higher levels of albuminuria, uric acid, systolic blood pressure and higher diabetes prevalence.
Conclusions. CKD classification among young blacks is very sensitive to the race coefficients. Despite whites having higher rates of CKD stage 3, blacks with eGFRs just above the CKD threshold had higher rates of CKD risk factors. Current equations used to define CKD may systematically miss a high-risk group of blacks at a time in the disease course when interventions are crucial.
chronic kidney disease; glomerular filtration rate; race
Despite a higher burden of standard atrial fibrillation (AF) risk factors, African Americans have a lower risk of AF than whites. It is unknown if the higher riskis due to genetic or environmental factors. As African Americans have varying degrees of European ancestry, we sought to test the hypothesis that European ancestry is an independent risk factor for AF.
Methods and Results
We studied whites (n=4,543) and African Americans (n=822) in the Cardiovascular Health Study (CHS) and whites (n=10,902) and Africa Americans (n=3,517) in the Atherosclerosis Risk in Communities (ARIC) Study (n=3,517). Percent European ancestry in African Americans was estimated using 1,747 ancestry informative markers (AIMs) from the Illumina custom ITMAT-Broad-CARe (IBC) array. Among African Americans without baseline AF, 120 of 804 CHS participants and 181 of 3,517 ARIC participants developed incident AF. A meta-analysis from the two studies revealed that every 10% increase in European ancestry increased the risk of AF by 13% (HR 1.13, 95% CI 1.03–1.23, p=0.007). After adjusting for potential confounders, European ancestry remained a predictor of incident AF in each cohort alone, with a combined estimated hazard ratio for each 10% increase in European ancestry of 1.17 (95% CI 1.07–1.29, p=0.001). A second analysis using 3,192 AIMs from a genome wide Affymetrix 6.0 array in ARIC African Americans yielded similar results.
European ancestry predicted risk of incident AF. Our study suggests that investigating genetic variants contributing to differential AF risk in individuals of African versus European ancestry will be informative.
Atrial Fibrillation Genetics; Ancestry; African Americans
Chronic kidney disease (CKD) is an increasing global public health concern, particularly among populations of African ancestry. We performed an interrogation of known renal loci, genome-wide association (GWA), and IBC candidate-gene SNP association analyses in African Americans from the CARe Renal Consortium. In up to 8,110 participants, we performed meta-analyses of GWA and IBC array data for estimated glomerular filtration rate (eGFR), CKD (eGFR <60 mL/min/1.73 m2), urinary albumin-to-creatinine ratio (UACR), and microalbuminuria (UACR >30 mg/g) and interrogated the 250 kb flanking region around 24 SNPs previously identified in European Ancestry renal GWAS analyses. Findings were replicated in up to 4,358 African Americans. To assess function, individually identified genes were knocked down in zebrafish embryos by morpholino antisense oligonucleotides. Expression of kidney-specific genes was assessed by in situ hybridization, and glomerular filtration was evaluated by dextran clearance. Overall, 23 of 24 previously identified SNPs had direction-consistent associations with eGFR in African Americans, 2 of which achieved nominal significance (UMOD, PIP5K1B). Interrogation of the flanking regions uncovered 24 new index SNPs in African Americans, 12 of which were replicated (UMOD, ANXA9, GCKR, TFDP2, DAB2, VEGFA, ATXN2, GATM, SLC22A2, TMEM60, SLC6A13, and BCAS3). In addition, we identified 3 suggestive loci at DOK6 (p-value = 5.3×10−7) and FNDC1 (p-value = 3.0×10−7) for UACR, and KCNQ1 with eGFR (p = 3.6×10−6). Morpholino knockdown of kcnq1 in the zebrafish resulted in abnormal kidney development and filtration capacity. We identified several SNPs in association with eGFR in African Ancestry individuals, as well as 3 suggestive loci for UACR and eGFR. Functional genetic studies support a role for kcnq1 in glomerular development in zebrafish.
Chronic kidney disease (CKD) is an increasing global public health problem and disproportionately affects populations of African ancestry. Many studies have shown that genetic variants are associated with the development of CKD; however, similar studies are lacking in African ancestry populations. The CARe consortium consists of more than 8,000 individuals of African ancestry; genome-wide association analysis for renal-related phenotypes was conducted. In cross-ethnicity analyses, we found that 23 of 24 previously identified SNPs in European ancestry populations have the same effect direction in our samples of African ancestry. We also identified 3 suggestive genetic variants associated with measurement of kidney function. We then tested these genes in zebrafish knockdown models and demonstrated that kcnq1 is involved in kidney development in zebrafish. These results highlight the similarity of genetic variants across ethnicities and show that cross-species modeling in zebrafish is feasible for genes associated with chronic human disease.