Cardiovascular-Kidney-Metabolic Health: A Presidential Advisory From the American Heart Association.

Cardiovascular-kidney-metabolic health reflects the interplay among metabolic risk factors, chronic kidney disease, and the cardiovascular system and has profound impacts on morbidity and mortality. There are multisystem consequences of poor cardiovascular-kidney-metabolic health, with the most significant clinical impact being the high associated incidence of cardiovascular disease events and cardiovascular mortality. There is a high prevalence of poor cardiovascular-kidney-metabolic health in the population, with a disproportionate burden seen among those with adverse social determinants of health. However, there is also a growing number of therapeutic options that favorably affect metabolic risk factors, kidney function, or both that also have cardioprotective effects. To improve cardiovascular-kidney-metabolic health and related outcomes in the population, there is a critical need for (1) more clarity on the definition of cardiovascular-kidney-metabolic syndrome; (2) an approach to cardiovascular-kidney-metabolic staging that promotes prevention across the life course; (3) prediction algorithms that include the exposures and outcomes most relevant to cardiovascular-kidney-metabolic health; and (4) strategies for the prevention and management of cardiovascular disease in relation to cardiovascular-kidney-metabolic health that reflect harmonization across major subspecialty guidelines and emerging scientific evidence. It is also critical to incorporate considerations of social determinants of health into care models for cardiovascular-kidney-metabolic syndrome and to reduce care fragmentation by facilitating approaches for patient-centered interdisciplinary care. This presidential advisory provides guidance on the definition, staging, prediction paradigms, and holistic approaches to care for patients with cardiovascular-kidney-metabolic syndrome and details a multicomponent vision for effectively and equitably enhancing cardiovascular-kidney-metabolic health in the population.

Kidney function, bone-mineral metabolism markers, and calcification of coronary arteries, aorta, and cardiac valves in older adults.

BACKGROUND AND AIMS: The contribution of kidney dysfunction, especially at mild-to-moderate stages, and bone-mineral metabolism (BMM) markers to vascular calcification remains controversial or unclear. We comprehensively evaluated the association of kidney and BMM markers with coronary artery calcification (CAC) and extra-coronary calcification (ECC). METHODS: In 1931 ARIC participants (age 73-95 years) without coronary heart disease at visit 7 (2018-19), we investigated the associations of estimated glomerular filtration rate (eGFR) (with creatinine, cystatin C, and both) and five serum BMM markers (calcium, fibroblast growth factor 23, magnesium, parathyroid hormone, and phosphorus) with high CAC and ECC (sex-race specific ≥75th vs. <75th percentile Agatston score) or any vs. zero CAC and ECC using multivariable logistic regression. For eGFR and BMM markers, we took their weighted cumulative averages from visit 1 (1987-89) to visit 5 (2011-13). RESULTS: Lower eGFR, regardless of equations used, was not robustly associated with high CAC or ECC. Among BMM markers, only higher phosphorus levels, even within the normal range, showed robust associations with high CAC (only when modeled continuously) and ECC, independently of kidney function (e.g., odds ratio 1.94 [95%CI 1.38-2.73] for high aortic valve calcification, in the highest vs. lowest quartile). Results were generally consistent when analyzing any CAC or ECC, although cystatin C-based eGFR <60 mL/min/1.73 m2 became significantly associated with mitral valve calcification (odds ratio 1.69 [1.10-2.60]). CONCLUSIONS: Among kidney and BMM measures tested, only serum phosphorus demonstrated robust associations with both CAC and ECC, supporting a key role of phosphorus in the pathophysiology of vascular calcification.

Metabolites Associated with Coffee Consumption and Incident Chronic Kidney Disease.

BACKGROUND AND OBJECTIVES: Moderate coffee consumption has been associated with lower risk of CKD; however, the exact biologic mechanisms underlying this association are unknown. Metabolomic profiling may identify metabolic pathways that explain the association between coffee and CKD. The goal of this study was to identify serum metabolites associated with coffee consumption and examine the association between these coffee-associated metabolites and incident CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Using multivariable linear regression, we identified coffee-associated metabolites among 372 serum metabolites available in two subsamples of the Atherosclerosis Risk in Communities study (ARIC; n=3811). Fixed effects meta-analysis was used to pool the results from the two ARIC study subsamples. Associations between coffee and metabolites were replicated in the Bogalusa Heart Study (n=1043). Metabolites with significant associations with coffee in both cohorts were then evaluated for their prospective associations with incident CKD in the ARIC study using Cox proportional hazards regression. RESULTS: In the ARIC study, mean (SD) age was 54 (6) years, 56% were daily coffee drinkers, and 32% drank >2 cups per day. In the Bogalusa Heart Study, mean (SD) age was 48 (5) years, 57% were daily coffee drinkers, and 38% drank >2 cups per day. In a meta-analysis of two subsamples of the ARIC study, 41 metabolites were associated with coffee consumption, of which 20 metabolites replicated in the Bogalusa Heart Study. Three of these 20 coffee-associated metabolites were associated with incident CKD in the ARIC study. CONCLUSIONS: We detected 20 unique serum metabolites associated with coffee consumption in both the ARIC study and the Bogalusa Heart Study, and three of these 20 candidate biomarkers of coffee consumption were associated with incident CKD. One metabolite (glycochenodeoxycholate), a lipid involved in primary bile acid metabolism, may contribute to the favorable kidney health outcomes associated with coffee consumption. Two metabolites (O-methylcatechol sulfate and 3-methyl catechol sulfate), both of which are xenobiotics involved in benzoate metabolism, may represent potential harmful aspects of coffee on kidney health.

The Effects of Four Doses of Vitamin D Supplements on Falls in Older Adults : A Response-Adaptive, Randomized Clinical Trial.

BACKGROUND: Vitamin D supplementation may prevent falls in older persons, but evidence is inconsistent, possibly because of dosage differences. OBJECTIVE: To compare the effects of 4 doses of vitamin D3 supplements on falls. DESIGN: 2-stage Bayesian, response-adaptive, randomized trial. (ClinicalTrials.gov: NCT02166333). SETTING: 2 community-based research units. PARTICIPANTS: 688 participants, aged 70 years and older, with elevated fall risk and a serum 25-hydroxyvitamin D [25-(OH)D] level of 25 to 72.5 nmol/L. INTERVENTION: 200 (control), 1000, 2000, or 4000 IU of vitamin D3 per day. During the dose-finding stage, participants were randomly assigned to 1 of the 4 vitamin D3 doses, and the best noncontrol dose for preventing falls was determined. After dose finding, participants previously assigned to receive noncontrol doses received the best dose, and new enrollees were randomly assigned to receive 200 IU/d or the best dose. MEASUREMENTS: Time to first fall or death over 2 years (primary outcome). RESULTS: During the dose-finding stage, the primary outcome rates were higher for the 2000- and 4000-IU/d doses than for the 1000-IU/d dose, which was selected as the best dose (posterior probability of being best, 0.90). In the confirmatory stage, event rates were not significantly different between participants with experience receiving the best dose (events and observation time limited to the period they were receiving 1000 IU/d; n = 308) and those randomly assigned to receive 200 IU/d (n = 339) (hazard ratio [HR], 0.94 [95% CI, 0.76 to 1.15]; P = 0.54). Analysis of falls with adverse outcomes suggested greater risk in the experience-with-best-dose group versus the 200-IU/d group (serious fall: HR, 1.87 [CI, 1.03 to 3.41]; fall with hospitalization: HR, 2.48 [CI, 1.13 to 5.46]). LIMITATIONS: The control group received 200 IU of vitamin D3 per day, not a placebo. Dose finding ended before the prespecified thresholds for dose suspension and dose selection were reached. CONCLUSION: In older persons with elevated fall risk and low serum 25-(OH)D levels, vitamin D3 supplementation at doses of 1000 IU/d or higher did not prevent falls compared with 200 IU/d. Several analyses raised safety concerns about vitamin D3 doses of 1000 IU/d or higher. PRIMARY FUNDING SOURCE: National Institute on Aging.

Serum magnesium, bone-mineral metabolism markers and their interactions with kidney function on subsequent risk of peripheral artery disease: the Atherosclerosis Risk in Communities Study.

BACKGROUND: Few studies have investigated the association of magnesium levels with incident peripheral artery disease (PAD) despite emerging evidence of magnesium contributing to vascular calcification. Moreover, no data are available on whether the magnesium-PAD relationship is independent of or modified by kidney function. METHODS: A cohort of 11 839 participants free of PAD in the Atherosclerosis Risk in Communities Study at Visit 2 (1990-92) was studied. We investigated the association of serum magnesium and other bone-mineral metabolism markers [calcium, phosphorus, intact parathyroid hormone (iPTH) and intact fibroblast growth factor-23] with incident PAD using multivariable Cox proportional hazards regression. RESULTS: Over a median of 23 years, there were 471 cases of incident PAD. The hazard ratio for incident PAD in Quartile 1 (<1.5 mEq/L) versus Quartile 4 (>1.7 mEq/L) of magnesium was 1.96 (95% confidence interval 1.40-2.74) after adjustment for potential confounders. Lower magnesium levels were associated with greater incidence of PAD, particularly in those with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 (n = 11 606). In contrast, the association was largely flat in those with eGFR <60 mL/min/1.73 m2 (n = 233) with P-for-interaction 0.03. Among bone-mineral metabolism markers, only higher iPTH showed an interaction with kidney function (P-for-interaction 0.01) and iPTH >65 pg/mL was significantly related to PAD only in those with eGFR <60 mL/min/1.73 m2. CONCLUSIONS: Lower magnesium was independently associated with incident PAD, but this association was significantly weaker in those with reduced kidney function. In contrast, higher iPTH levels were particularly related to PAD risk in this clinical population.

Association Between Renin-Angiotensin System Blockade Discontinuation and All-Cause Mortality Among Persons With Low Estimated Glomerular Filtration Rate.

Importance: It is uncertain whether and when angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker (ARB) treatment should be discontinued in individuals with low estimated glomerular filtration rate (eGFR). Objective: To investigate the association of ACE-I or ARB therapy discontinuation after eGFR decreases to below 30 mL/min/1.73 m2 with the risk of mortality, major adverse cardiovascular events (MACE), and end-stage kidney disease (ESKD). Design, Setting, and Participants: This retrospective, propensity score-matched cohort study included 3909 patients from an integrated health care system that served rural areas of central and northeastern Pennsylvania. Patients who initiated ACE-I or ARB therapy from January 1, 2004, to December 31, 2018, and had an eGFR decrease to below 30 mL/min/1.73 m2 during therapy were enrolled, with follow-up until January 25, 2019. Exposures: Individuals were classified based on whether they discontinued ACE-I or ARB therapy within 6 months after an eGFR decrease to below 30 mL/min/1.73 m2. Main Outcomes and Measures: The association between ACE-I or ARB therapy discontinuation and mortality during the subsequent 5 years was assessed using multivariable Cox proportional hazards regression models, adjusting for patient characteristics at the time of the eGFR decrease in a propensity score-matched sample. Secondary outcomes included MACE and ESKD. Results: Of the 3909 individuals receiving ACE-I or ARB treatment who experienced an eGFR decrease to below 30 mL/min/1.73 m2 (2406 [61.6%] female; mean [SD] age, 73.7 [12.6] years), 1235 discontinued ACE-I or ARB therapy within 6 months after the eGFR decrease and 2674 did not discontinue therapy. A total of 434 patients (35.1%) who discontinued ACE-I or ARB therapy and 786 (29.4%) who did not discontinue therapy died during a median follow-up of 2.9 years (interquartile range, 1.3-5.0 years). In the propensity score-matched sample of 2410 individuals, ACE-I or ARB therapy discontinuation was associated with a higher risk of mortality (hazard ratio [HR], 1.39; 95% CI, 1.20-1.60]) and MACE (HR, 1.37; 95% CI, 1.20-1.56), but no statistically significant difference in the risk of ESKD was found (HR, 1.19; 95% CI, 0.86-1.65). Conclusions and Relevance: The findings suggest that continuing ACE-I or ARB therapy in patients with declining kidney function may be associated with cardiovascular benefit without excessive harm of ESKD.

Coffee consumption and liver-related hospitalizations and deaths in the ARIC study.

BACKGROUND/OBJECTIVES: Coffee consumption has been found to be associated with reduced risk of chronic conditions such as liver disease. However, less is known about the association between coffee and liver-related hospitalizations and deaths. SUBJECTS/METHODS: We conducted a prospective analysis on 14,208 participants aged 45-64 years from the Atherosclerosis Risk in Communities (ARIC) study. Coffee consumption (cups/day) was assessed using food frequency questionnaires at visit 1 (1987-89) and visit 3 (1993-95). Liver-related hospitalizations were defined as a hospitalization with any International Classification of Diseases, Ninth Revision (ICD-9) code related to liver disease identified through cohort surveillance. Liver-related death was defined as any death with a liver disease ICD-9 code listed anywhere on the death certificate form. RESULTS: There were 833 incident cases of liver-related hospitalizations over a median follow-up of 24 years and 152 liver-related deaths over a median follow-up of 25 years. Participants who were in the highest category of coffee consumption (≥ 3 cups/day) were more likely to be men, whites, current smokers, and current alcohol drinkers. In our fully adjusted model, consuming ≥ 3 cups/day of coffee was significantly associated with a reduced risk of liver-related hospitalizations compared with never drinkers (hazard ratio: 0.79, 95% CI: 0.63-0.99). There were no significant associations between coffee consumption and liver-related deaths after adjusting for covariates. CONCLUSIONS: Coffee drinkers may be at lower risk for liver-related hospitalizations. This supports current evidence that low and moderate levels of coffee may be protective to the liver.

Kidney Function, Polypharmacy, and Potentially Inappropriate Medication Use in a Community-Based Cohort of Older Adults.

BACKGROUND: Chronic kidney disease (CKD) afflicts many older adults and increases the risk for medication-related adverse events. OBJECTIVE: The aim of this study was to assess the prevalence and associated morbidity and mortality of polypharmacy (use of several medications concurrently), and potentially inappropriate medication (PIM) use in older adults, looking for differences by CKD status. METHODS: We quantified medication and PIM use (from Beers criteria, the Screening Tool of Older People's Prescriptions, and Micromedex®) by level of estimated glomerular filtration rate (eGFR) for participants aged 65 years or older attending a baseline study visit in the Atherosclerosis Risk in Communities study (n =6392). We used zero-inflated negative binomial and Cox proportional hazards regressions to assess the relationship between baseline polypharmacy, PIM use, and subsequent hospitalization and death. RESULTS: Mean age at baseline was 76 (± 5) years, 59% were female, and 29% had CKD (eGFR < 60 ml/min/1.73 m2). Overall, participants reported 6.1 (± 3.5) medications and 2.3 (± 2.2) vitamins/supplements; 16% reported ≥ 10 medications; 31% reported a PIM based on their age. On average, participants with CKD reported more medications. A PIM based on kidney function was used by 36% of those with eGFR < 30 ml/min/1.73 m2. Over a median of 2.6 years, more concurrent medications were associated with higher risk of hospitalization and death, but PIM use was not. While those with CKD had higher absolute risks, there was no difference in the relative risks associated with greater numbers of medications by CKD status. CONCLUSION: Polypharmacy and PIM use were common, with greater numbers of medications associated with higher risk of hospitalization and death; relative risks were similar for those with and without CKD.

The Dietary Fructose:Vitamin C Intake Ratio Is Associated with Hyperuricemia in African-American Adults.

Background: A high fructose intake has been shown to be associated with increased serum urate concentration, whereas ascorbate (vitamin C) may lower serum urate by competing with urate for renal reabsorption. Objective: We assessed the combined association, as the fructose:vitamin C intake ratio, and the separate associations of dietary fructose and vitamin C intakes on prevalent hyperuricemia. Methods: We conducted cross-sectional analyses of dietary intakes of fructose and vitamin C and serum urate concentrations among Jackson Heart Study participants, a cohort of African Americans in Jackson, Mississippi, aged 21-91 y. In the analytic sample (n = 4576), multivariable logistic regression was used to examine the separate associations of dietary intakes of fructose and vitamin C and the fructose:vitamin C intake ratio with prevalent hyperuricemia (serum urate ≥7 mg/dL), after adjusting for age, sex, smoking, waist circumference, systolic blood pressure, estimated glomerular filtration rate, diuretic medication use, vitamin C supplement use, total energy intake, alcohol consumption, and dietary intake of animal protein. Analyses for individual dietary factors (vitamin C, fructose) were adjusted for the other dietary factor. Results: In the fully adjusted model, there were 17% greater odds of hyperuricemia associated with a doubling of the fructose:vitamin C intake ratio (OR: 1.17; 95% CI: 1.08, 1.28), 20% greater odds associated with a doubling of fructose intake (OR: 1.20; 95% CI: 1.08, 1.34), and 13% lower odds associated with a doubling of vitamin C intake (OR: 0.87; 95% CI: 0.78, 0.97). Dietary fructose and the fructose:vitamin C intake ratio were more strongly associated with hyperuricemia among men than women (P-interaction ≤ 0.04). Conclusion: Dietary intakes of fructose and vitamin C are associated with prevalent hyperuricemia in a community-based population of African Americans.

Coffee Consumption and Incident Kidney Disease: Results From the Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: Moderate coffee consumption has been suggested to be associated with lower risk for chronic conditions such as diabetes, a major precursor to chronic kidney disease (CKD). However, the association between coffee and CKD has not been fully established. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 14,209 participants aged 45 to 64 years from the Atherosclerosis Risk in Communities (ARIC) Study. PREDICTORS: Coffee consumption (cups per day) was assessed at visits 1 (1987-1989) and 3 (1993-1995) using food frequency questionnaires. OUTCOMES: Incident CKD defined as estimated glomerular filtration rate < 60mL/min/1.73m2 accompanied by ≥25% estimated glomerular filtration rate decline, CKD-related hospitalization or death, or end-stage renal disease. RESULTS: There were 3,845 cases of incident CKD over a median of 24 years of follow-up. Men, whites, current smokers, and participants without comorbid conditions were more likely to consume higher amounts of coffee per day. After adjustment for demographic, clinical, and dietary factors, higher categories of coffee consumption were associated with lower risk for incident CKD compared with those who never consumed coffee (HR for <1 cup per day, 0.90 [95% CI, 0.82-0.99]; 1-<2 cups per day, 0.90 [95% CI, 0.82-0.99]; 2-<3 cups per day, 0.87 [95% CI, 0.77-0.97]; and ≥3 cups per day, 0.84 [95% CI, 0.75-0.94]). In continuous analysis, for each additional cup of coffee consumed per day, risk for incident CKD was lower by 3% (HR, 0.97; 95% CI, 0.95-0.99; P<0.001). LIMITATIONS: Self-reported coffee consumption and observational design. CONCLUSIONS: Participants who drank higher amounts of coffee had lower risk for incident CKD after adjusting for covariates. Coffee consumers may not be at adverse risk for kidney disease.

Kidney function, bone-mineral metabolism markers, and future risk of peripheral artery disease.

BACKGROUND AND AIMS: Reduced kidney function is a risk factor for lower-extremity peripheral artery disease (PAD). However, the associations of novel filtration markers with PAD are yet to be quantified. Moreover, little is known on whether bone-mineral metabolism (BMM) markers are related to incident PAD beyond kidney function. METHODS: Using data from 12,472 participants at baseline (1990-1992) of the Atherosclerosis Risk in Communities (ARIC) study, we comprehensively quantified the associations of kidney related markers with incident PAD (defined as hospitalizations with diagnosis of lower-extremity atherosclerosis, revascularization, or amputation). Kidney related markers of interest included estimated glomerular filtration rate (eGFR) (based on creatinine, cystatin C, and both), cystatin C, beta-2 microglobulin (B2M), and BMM markers (serum fibroblast growth factor 23, parathyroid hormone, calcium, and phosphorus). RESULTS: During a median follow-up of 21 years, 471 participants developed incident PAD. Low eGFR was significantly associated with future PAD risk, with slightly stronger relationship when cystatin C was used (adjusted hazard ratio [HR] 6.3-8.3 for eGFR <30 and 2.4-3.5 for eGFR 30-59 vs. eGFR ≥90 mL/min/1.73 m2). Among all filtration markers, B2M had the strongest association with incident PAD (HR for top vs. bottom quartile 2.60 [95% CI: 1.91-3.54] for B2M vs. 1.20 [0.91-1.58] for creatinine-based eGFR). Among BMM markers, only phosphorus remained significant for PAD risk beyond potential confounders, including kidney function (HR 1.47 [1.11-1.94] in top quartile). CONCLUSIONS: Kidney dysfunction was independently associated with future PAD risk, particularly when assessed with cystatin C and B2M. Among the BMM markers tested, phosphorus was most robustly associated with incident PAD beyond kidney function. Our results suggest the potential usefulness of novel filtration markers for PAD risk assessment and the possible role of phosphorus in the pathophysiology of PAD.

Global kidney health 2017 and beyond: a roadmap for closing gaps in care, research, and policy.

The global nephrology community recognises the need for a cohesive plan to address the problem of chronic kidney disease (CKD). In July, 2016, the International Society of Nephrology hosted a CKD summit of more than 85 people with diverse expertise and professional backgrounds from around the globe. The purpose was to identify and prioritise key activities for the next 5-10 years in the domains of clinical care, research, and advocacy and to create an action plan and performance framework based on ten themes: strengthen CKD surveillance; tackle major risk factors for CKD; reduce acute kidney injury-a special risk factor for CKD; enhance understanding of the genetic causes of CKD; establish better diagnostic methods in CKD; improve understanding of the natural course of CKD; assess and implement established treatment options in patients with CKD; improve management of symptoms and complications of CKD; develop novel therapeutic interventions to slow CKD progression and reduce CKD complications; and increase the quantity and quality of clinical trials in CKD. Each group produced a prioritised list of goals, activities, and a set of key deliverable objectives for each of the themes. The intended users of this action plan are clinicians, patients, scientists, industry partners, governments, and advocacy organisations. Implementation of this integrated comprehensive plan will benefit people who are at risk for or affected by CKD worldwide.

Practical Approaches for Whole-Genome Sequence Analysis of Heart- and Blood-Related Traits.

Whole-genome sequencing (WGS) allows for a comprehensive view of the sequence of the human genome. We present and apply integrated methodologic steps for interrogating WGS data to characterize the genetic architecture of 10 heart- and blood-related traits in a sample of 1,860 African Americans. In order to evaluate the contribution of regulatory and non-protein coding regions of the genome, we conducted aggregate tests of rare variation across the entire genomic landscape using a sliding window, complemented by an annotation-based assessment of the genome using predefined regulatory elements and within the first intron of all genes. These tests were performed treating all variants equally as well as with individual variants weighted by a measure of predicted functional consequence. Significant findings were assessed in 1,705 individuals of European ancestry. After these steps, we identified and replicated components of the genomic landscape significantly associated with heart- and blood-related traits. For two traits, lipoprotein(a) levels and neutrophil count, aggregate tests of low-frequency and rare variation were significantly associated across multiple motifs. For a third trait, cardiac troponin T, investigation of regulatory domains identified a locus on chromosome 9. These practical approaches for WGS analysis led to the identification of informative genomic regions and also showed that defined non-coding regions, such as first introns of genes and regulatory domains, are associated with important risk factor phenotypes. This study illustrates the tractable nature of WGS data and outlines an approach for characterizing the genetic architecture of complex traits.

Incident chronic kidney disease: trends in management and outcomes.

BACKGROUND: Management trends in early chronic kidney disease (CKD) and their associations with clinical outcomes have not previously been reported. METHODS: We evaluated incident (Stage G3A) CKD patients from an integrated health care system in 2004-06, 2007-09 and 2010-12 to determine adjusted trends in screening (urinary protein quantification), treatment [prescription for angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB), and statin] and nephrology referral. For the same time periods, adjusted rates for mortality, progression to Stage G4 CKD and hospitalization for myocardial infarction or heart failure were calculated and compared across time periods. RESULTS: There were 728, 788 and 956 patients with incident CKD in 2004-06, 2007-09 and 2010-12, respectively. Adjusted rates of proteinuria quantification (31, 39 and 51 screens/100 person-years), statin prescription (53, 63 and 64 prescriptions/100 person-years) and nephrology referral (2, 3 and 5 referrals/100 person-years) all increased over time (P for trend <0.001 in all cases). ACEI/ARB prescription rates did not change (88, 83 and 80 prescriptions/100 person-years, P = 0.68). Adjusted death rates (7, 5 and 6 deaths/100 person-years), CKD progression (9, 10 and 7 progressors/100 person-years) and cardiovascular hospitalization (10, 8 and 9 hospitalizations per 100/person-years) did not change (P for trend >0.4 in all cases). CONCLUSION: In this integrated health care system, management of incident CKD over the past decade has intensified.

A Metabolome-Wide Association Study of Kidney Function and Disease in the General Population.

Small molecules are extensively metabolized and cleared by the kidney. Changes in serum metabolite concentrations may result from impaired kidney function and can be used to estimate filtration (e.g., the established marker creatinine) or may precede and potentially contribute to CKD development. Here, we applied a nontargeted metabolomics approach using gas and liquid chromatography coupled to mass spectrometry to quantify 493 small molecules in human serum. The associations of these molecules with GFR estimated on the basis of creatinine (eGFRcr) and cystatin C levels were assessed in ≤1735 participants in the KORA F4 study, followed by replication in 1164 individuals in the TwinsUK registry. After correction for multiple testing, 54 replicated metabolites significantly associated with eGFRcr, and six of these showed pairwise correlation (r≥0.50) with established kidney function measures: C-mannosyltryptophan, pseudouridine, N-acetylalanine, erythronate, myo-inositol, and N-acetylcarnosine. Higher C-mannosyltryptophan, pseudouridine, and O-sulfo-L-tyrosine concentrations associated with incident CKD (eGFRcr <60 ml/min per 1.73 m(2)) in the KORA F4 study. In contrast with serum creatinine, C-mannosyltryptophan and pseudouridine concentrations showed little dependence on sex. Furthermore, correlation with measured GFR in 200 participants in the AASK study was 0.78 for both C-mannosyltryptophan and pseudouridine concentration, and highly significant associations of both metabolites with incident ESRD disappeared upon adjustment for measured GFR. Thus, these molecules may be alternative or complementary markers of kidney function. In conclusion, our study provides a comprehensive list of kidney function-associated metabolites and highlights potential novel filtration markers that may help to improve the estimation of GFR.

Race, Mineral Homeostasis and Mortality in Patients with End-Stage Renal Disease on Dialysis.

BACKGROUND: Abnormalities in mineral homeostasis are ubiquitous in patients on dialysis, and influenced by race. In this study, we determine the race-specific relationship between mineral parameters and mortality in patients initiating hemodialysis. METHODS: We measured the levels of fibroblast growth factor 23 (FGF23) and 25-hydroxyvitamin D (25 D) in 184 African American and 327 non-African American hemodialysis patients who enrolled between 1995 and 1998 in the Choices for Healthy Outcomes in Caring for ESRD Study. Serum calcium, phosphorus, parathyroid hormone (PTH) and total alkaline phosphatase levels were averaged from clinical measurements during the first 4.5 months of dialysis. We evaluated the associated prospective risk of mortality using multivariable Cox proportional hazards models stratified by race. RESULTS: PTH and total alkaline phosphatase levels were higher, whereas calcium, phosphorus, FGF23 and 25 D levels were lower in African Americans compared to those of non-African Americans. Higher serum phosphorus and FGF23 levels were associated with greater mortality risk overall; however, phosphorus was only associated with risk among African Americans (HR 5.38, 95% CI 2.14-13.55 for quartile 4 vs. 1), but not among non-African Americans (p-interaction = 0.04). FGF23 was associated with mortality in both groups, but more strongly in African Americans (HR 3.91, 95% CI 1.74-8.82 for quartiles 4 vs. 1; p-interaction = 0.09). Serum calcium, PTH, and 25 D levels were not consistently associated with mortality. The lowest and highest quartiles of total alkaline phosphatase were associated with higher mortality risk, but this did not differ by race (p-interaction = 0.97). CONCLUSIONS: Aberrant phosphorus homeostasis, reflected by higher phosphorus and FGF23, may be a risk factor for mortality in patients initiating hemodialysis, particularly among African Americans.

Serum magnesium, phosphorus, and calcium are associated with risk of incident heart failure: the Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: Heart failure (HF) is a major source of morbidity and mortality, particularly among the elderly. Magnesium, phosphorus, and calcium are micronutrients traditionally viewed in relation to bone health or chronic kidney disease. However, they also may be associated with risk of cardiovascular disease through a broad range of physiologic roles. OBJECTIVE: With the use of data from the Atherosclerosis Risk in Communities (ARIC) cohort, we tested the hypotheses that the incidence of HF is greater among individuals with low serum magnesium and those with high serum phosphorus and calcium. DESIGN: A total of 14,709 African Americans (27%) and whites from the ARIC cohort [aged 45-64 y at baseline (1987-1989)] were observed through 2009. Proportional hazards regression was used to explore associations between biomarkers and incident HF. Serum calcium was corrected for serum albumin. Models were adjusted for demographics, behaviors, and physiologic characteristics. RESULTS: A total of 2250 incident HF events accrued over a median follow-up of 20.6 y. Participants in the lowest (≤1.4 mEq/L) compared with the highest (≥1.8 mEq/L) category of magnesium were at greater HF risk (HR: 1.71; 95% CI: 1.46, 1.99). For phosphorus, there appeared to be a threshold whereby only those in the highest quintile were at greater HF risk [HR(Q5 vs Q1): 1.34; 95% CI: 1.16, 1.54]. Higher concentrations of calcium were also associated with greater risk of HF [HR(Q5 vs Q1): 1.24; 95% CI: 1.07, 1.43]. Results were not modified by race, sex, or kidney function and were similar when incident coronary heart disease was included as a time-varying covariate. CONCLUSIONS: Low serum magnesium and high serum phosphorus and calcium were independently associated with greater risk of incident HF in this population-based cohort. Whether these biomarkers will be useful candidates for HF risk prediction or targets for prevention remains to be seen.

Common genetic variants associate with serum phosphorus concentration.

Phosphorus is an essential mineral that maintains cellular energy and mineralizes the skeleton. Because complex actions of ion transporters and regulatory hormones regulate serum phosphorus concentrations, genetic variation may determine interindividual variation in phosphorus metabolism. Here, we report a comprehensive genome-wide association study of serum phosphorus concentration. We evaluated 16,264 participants of European ancestry from the Cardiovascular Heath Study, Atherosclerosis Risk in Communities Study, Framingham Offspring Study, and the Rotterdam Study. We excluded participants with an estimated GFR <45 ml/min per 1.73 m(2) to focus on phosphorus metabolism under normal conditions. We imputed genotypes to approximately 2.5 million single-nucleotide polymorphisms in the HapMap and combined study-specific findings using meta-analysis. We tested top polymorphisms from discovery cohorts in a 5444-person replication sample. Polymorphisms in seven loci with minor allele frequencies 0.08 to 0.49 associate with serum phosphorus concentration (P = 3.5 x 10(-16) to 3.6 x 10(-7)). Three loci were near genes encoding the kidney-specific type IIa sodium phosphate co-transporter (SLC34A1), the calcium-sensing receptor (CASR), and fibroblast growth factor 23 (FGF23), proteins that contribute to phosphorus metabolism. We also identified genes encoding phosphatases, kinases, and phosphodiesterases that have yet-undetermined roles in phosphorus homeostasis. In the replication sample, five of seven top polymorphisms associate with serum phosphorous concentrations (P < 0.05 for each). In conclusion, common genetic variants associate with serum phosphorus in the general population. Further study of the loci identified in this study may help elucidate mechanisms of phosphorus regulation.

Metabolic abnormalities are present in adults with elevated serum cystatin C.

Although metabolic anomalies are often seen in advanced chronic kidney disease (CKD), their presence in more mild states is unknown. We studied 6722 participants in the Third National Health and Nutrition Examination Survey, dividing them into three mutually exclusive groups consisting of those having a normal or mildly reduced estimated glomerular filtration rate (eGFR) (Modification of Diet in Renal Disease (MDRD) formula), those with normal or elevated serum cystatin C, and those with clinically relevant moderate or severely reduced eGFR (stage 3 or 4 of CKD). The prevalence of several metabolic abnormalities associated with moderate to advanced CKD was determined after standardization for age, race-ethnicity, and gender. In the absence of stage 3 or 4 CKD, patients with elevated serum cystatin C had a higher prevalence of low hemoglobin and elevated uric acid, homocysteine, phosphorus, fibrinogen, and C-reactive protein than patients with a normal serum cystatin C. Our results show that in adults with normal or mildly reduced eGFR, elevated serum cystatin C is associated with an increased prevalence of metabolic abnormalities traditionally found in moderate or severe CKD. Elevated serum cystatin C may identify patients with 'preclinical' kidney disease not detected by traditional serum creatinine measurements.

Exposure to radiologic contrast media and an increased risk of treated end-stage renal disease.

BACKGROUND: Radiologic contrast media can cause acute renal failure, but whether their repeated use is associated with end-stage renal disease (ESRD) is unknown. METHODS: We compared 716 incident case subjects of treated ESRD with 361 control subjects, frequency matched on age, drawn from the general population (age, 20-65 years). Participants were interviewed by telephone regarding their previous exposure (before initiation of dialysis for case subjects and the study interview for control subject) to various imaging procedures. RESULTS: As expected, the case subjects reported having more imaging procedures of the kidneys than did control subjects. Excluding persons who had been subjected to examinations of their kidney from the analysis and adjusting for ultrasound examinations and several possible confounders, persons who had a history of one [odds ratio (OR), 2.0; 95% confidence interval (CI), 1.0, 4.0], 2 or 3 (OR, 2.6; 95% CI, 1.2,5.9), or 4 or more (OR, 3.6; 95% CI, 1.0, 12.5) radiocontrast examinations were at higher risk of treated ESRD than persons who reported not having had such procedures. Ultrasound examinations and a history of barium enema were not associated with an increased risk of treated ESRD. CONCLUSION: In the current study, a graded association was present between increasing exposure to radiologic contrast media and higher risk of treated ESRD. Whether exposure to contrast media accelerates progression to ESRD or is merely a noncausal accompaniment to multiple disease processes occurring concurrently cannot be determined from our observational data. However, if these results are confirmed in future prospective studies, they will have important clinical implications.