Albuminuria within the Normal Range Can Predict All-Cause Mortality and Cardiovascular Mortality

The Urinary Glycopeptide Profile Differentiates Early Cardiorenal Risk in Subjects Not Meeting Criteria for Chronic Kidney Disease

Early diagnosis and treatment of chronic kidney disease (CKD) is a worldwide challenge. Subjects with albumin-to-creatinine ratio (ACR) ≥ 30 mg/g and preserved renal function are considered to be at no cardiorenal risk in clinical practice, but prospective clinical studies evidence increased risk, even at the high-normal (HN) ACR range (10-30 mg/g), supporting the need to identify other molecular indicators for early assessment of patients at higher risk. Following our previous studies, here we aim to stratify the normoalbuminuria range according to cardiorenal risk and identify the glycoproteins and N-glycosylation sites associated with kidney damage in subclinical CKD. Glycoproteins were analyzed in urine from hypertensive patients within the HN ACR range compared to control group (C; ACR < 10 mg/g) by mass spectrometry. A different cohort was analyzed for confirmation (ELISA) and sex perspective was evaluated. Patients' follow-up for 8 years since basal urine collection revealed higher renal function decline and ACR progression for HN patients. Differential N-glycopeptides and their N -glycosylation sites were also identified, together with their pathogenicity. N-glycosylation may condition pathological protein deregulation, and a panel of 62 glycoproteins evidenced alteration in normoalbuminuric subjects within the HN range. Haptoglobin-related protein, haptoglobin, afamin, transferrin, and immunoglobulin heavy constant gamma 1 (IGHG1) and 2 (IGHG2) showed increased levels in HN patients, pointing to disturbed iron metabolism and tubular reabsorption and supporting the tubule as a target of interest in the early progression of CKD. When analyzed separately, haptoglobin, afamin, transferrin, and IGHG2 remained significant in HN, in both women and men. At the peptide level, 172 N-glycopeptides showed differential abundance in HN patients, and 26 showed high pathogenicity, 10 of them belonging to glycoproteins that do not show variation between HN and C groups. This study highlights the value of glycosylation in subjects not meeting KDIGO criteria for CKD. The identified N-glycopeptides and glycosylation sites showed novel targets, for both the early assessment of individual cardiorenal risk and for intervention aimed at anticipating CKD progression.

The relationship between low levels of albuminuria and mortality among adults without major cardiovascular risk factors

AIMS

The determine if elevated levels of albuminuria within the low range (urinary albumin-to-creatinine ratio, UACR <30 mg/g) are linked to cardiovascular death in adults lacking major cardiovascular risk factors.

METHODS

The association between UACR and cardiovascular mortality was investigated among 12,835 participants in the 1999-2014 National Health and Nutrition Examination Survey using Cox proportional hazard models and confounder-adjusted survival curves. We excluded participants with baseline cardiovascular disease, hypertension, diabetes, pre-diabetes, estimated glomerular filtration rate (eGFR) <60ml/min/1.73m2, currently pregnant, and those who had received dialysis in the last year.

RESULTS

Over a median follow-up of 12.3 years, 110 and 621 participants experienced cardiovascular and all-cause mortality. In multivariable-adjusted models, each doubling of UACR was associated with a 36% higher risk of cardiovascular death [HR 1.36 (95% confidence interval (CI) 1.02-1.82)] and a 24% higher risk of all-cause mortality [HR 1.24 (95% CI 1.10-1.39)]. The 15-year adjusted cumulative incidences of cardiovascular mortality were 0.91%, 0.99%, and 2.1% for UACR levels of <4.18 mg/g, 4.18 to <6.91 mg/g, and ≥6.91 mg/g, respectively. The 15-year adjusted cumulative incidences of all-cause mortality were 5.1%, 6.1%, and 7.4% for UACR levels of <4.18 mg/g, 4.18 to <6.91 mg/g, and ≥6.91 mg/g, respectively.

CONCLUSIONS

Adults with elevated levels of albuminuria within the low range (UACR <30 mg/g) and no major cardiovascular risk factors had elevated risks of cardiovascular and all-cause mortality. The risks increased linearly with higher albuminuria levels. This emphasizes a risk gradient across all albuminuria levels, even within the supposedly normal range, adding to the existing evidence.

Association of Albuminuria With Chronic Kidney Disease Progression in Persons With Chronic Kidney Disease and Normoalbuminuria : A Cohort Study

BACKGROUND

Albuminuria is a major risk factor for chronic kidney disease (CKD) progression, especially when categorized as moderate (30 to 300 mg/g) or severe (>300 mg/g). However, there are limited data on the prognostic value of albuminuria within the normoalbuminuric range (<30 mg/g) in persons with CKD.

OBJECTIVE

To estimate the increase in the cumulative incidence of CKD progression with greater baseline levels of albuminuria among persons with CKD who had normoalbuminuria (<30 mg/g).

DESIGN

Multicenter prospective cohort study.

SETTING

7 U.S. clinical centers.

PARTICIPANTS

1629 participants meeting criteria from the CRIC (Chronic Renal Insufficiency Cohort) study with CKD (estimated glomerular filtration rate [eGFR], 20 to 70 mL/min/1.73 m2) and urine albumin-creatinine ratio (UACR) less than 30 mg/g.

MEASUREMENTS

Baseline spot urine albumin divided by spot urine creatinine to calculate UACR as the exposure variable. The 10-year adjusted cumulative incidences of CKD progression (composite of 50% eGFR decline or kidney failure [dialysis or kidney transplantation]) from confounder adjusted survival curves using the G-formula.

RESULTS

Over a median follow-up of 9.8 years, 182 of 1629 participants experienced CKD progression. The 10-year adjusted cumulative incidences of CKD progression were 8.7% (95% CI, 5.9% to 11.6%), 11.5% (CI, 8.8% to 14.3%), and 19.5% (CI, 15.4% to 23.5%) for UACR levels of 0 to less than 5 mg/g, 5 to less than 15 mg/g, and 15 mg/g or more, respectively. Comparing persons with UACR 15 mg/g or more to those with UACR 5 to less than 15 mg/g and 0 to less than 5 mg/g, the absolute risk differences were 7.9% (CI, 3.0% to 12.7%) and 10.7% (CI, 5.8% to 15.6%), respectively. The 10-year adjusted cumulative incidence increased linearly based on baseline UACR levels.

LIMITATION

UACR was measured once.

CONCLUSION

Persons with CKD and normoalbuminuria (<30 mg/g) had excess risk for CKD progression, which increased in a linear fashion with higher levels of albuminuria.

PRIMARY FUNDING SOURCE

None.

Association of Urine Albumin to Creatinine Ratio With Cardiovascular Outcomes in Patients With Type 2 Diabetes Mellitus

CONTEXT

The urinary albumin to creatinine ratio (UACR) is a widely used indicator of albuminuria and has predictive value for adverse cardiovascular events.

OBJECTIVE

To evaluate the correlation between the UACR and the risk of developing major adverse cardiovascular events (MACEs) and total mortality in patients with type 2 diabetes mellitus (T2DM).

METHODS

This post hoc analysis included 10 171 participants from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study and the ACCORD follow-up study (ACCORDION) with baseline UACR data. The natural logarithm (ln) of each UACR measurement was calculated. Univariate and multivariate Cox proportional hazard regression analyses were conducted to examine the association between the UACR and the risk of MACEs and total mortality. The additional predictive value of UACR was further evaluated. Similar methods were used to analyze the correlation between the UACR and MACEs and total mortality within the normal range.

RESULTS

During a median follow-up period of 8.83 years, 1808 (17.78%) participants experienced MACEs, and there were 1934 (19.01%) total deaths. After adjusting for traditional cardiovascular risk factors, the multivariate analysis revealed a significant association between the UACR and the risk of MACEs and total mortality. The inclusion of UACR in the conventional risk model enhanced the predictive efficacy for MACEs and total mortality.

CONCLUSION

An elevated UACR is associated with a higher risk of MACEs and total mortality in patients with T2DM, even when it falls within the normal range. The UACR improves prediction of MACE and total mortality risk in patients with T2DM.

Association of urine biomarkers of kidney health with subclinical cardiovascular disease among men with and without HIV

OBJECTIVE

The aim of this study was to determine whether urine biomarkers of kidney health are associated with subclinical cardiovascular disease among men with and without HIV.

DESIGN

A cross-sectional study within the Multicenter AIDS Cohort Study (MACS) among 504 men with and without HIV infection who underwent cardiac computed tomography scans and had urine biomarkers measured within the preceding 2 years.

METHODS

Our primary predictors were four urine biomarkers of endothelial (albuminuria), proximal tubule dysfunction (alpha-1-microglobulin [A1 M] and injury (kidney injury molecule-1 [KIM-1]) and tubulointerstitial fibrosis (pro-collagen-III N-terminal peptide [PIIINP]). These were evaluated for association with coronary artery calcium (CAC) prevalence, CAC extent, total plaque score, and total segment stenosis using multivariable regression.

RESULTS

Of the 504 participants, 384 were men with HIV (MWH) and 120 were men without HIV. In models adjusted for sociodemographic factors, cardiovascular disease risk factors, eGFR, and HIV-related factors, each two-fold higher concentration of albuminuria was associated with a greater extent of CAC (1.35-fold higher, 95% confidence interval 1.11-1.65), and segment stenosis (1.08-fold greater, 95% confidence interval 1.01-1.16). Associations were similar between MWH and men without HIV in stratified analyses. The third quartile of A1 M showed an association with greater CAC extent, total plaque score, and total segment stenosis, compared with the lowest quartile.

CONCLUSION

Worse endothelial and proximal tubule dysfunction, as reflected by higher urine albumin and A1 M, were associated with greater CAC extent and coronary artery stenosis.

A cross-sectional study investigating the relationship between urinary albumin creatinine ratio and abdominal aortic calcification in adults

Introduction

The presence of abdominal aortic calcification (AAC) is strongly linked to the development of atherosclerosis and the incidence of morbidity and mortality related to cardiovascular diseases (CVD). Urinary albumin creatinine ratio (UACR) was found related with the increased risk of CVD. The aim of this study is to explore the relationship between the UACR and severe AAC (SAAC).

Methods and Results

This study included a total of 2,379 individuals aged over 40 years, and their information was obtained from the National Health and Nutrition Examination Survey conducted (NHANES) in 2013-2014. The measurement of AAC was conducted through dual-energy x-ray absorptiometry and assessed using the Kauppila scoring system. SAAC was characterized by a Kauppila score of 6 or higher. Multivariate regression models were used to analyze the relationship between UACR level and SAAC, with covariate adjustment. In the completely adapted model, the top third subgroup exhibits increased likelihood of SAAC (odds ratio 1.50; 95%CI: 0.98, 2.29; p = 0.030) in contrast to the bottom third subgroup. The subgroup analyses revealed a more pronounced correlation among the older participants (p-value for interaction = 0.013).

Discussion

In the United States, SAAC was more likely to occur in adults who had a higher probability of UACR. The use of UACR has the potential to be a valuable method for forecasting the likelihood of SAAC.

The association of hemoglobin ethylene oxide levels with albuminuria in US adults: analysis of NHANES 2013-2016

Ethylene oxide (EO) is a common chemical contaminant in the environment and associated with the occurrence of multiple clinical diseases. This study aimed to explore the association of hemoglobin ethylene oxide (HbEO) levels with the risk of albuminuria in a representative sample of US adults. In total, 3523 participants from National Health and Nutrition Examination Survey (NHANES) 2013-2016 were enrolled and classified into four groups based on HbEO. Restricted cubic spline plots and multiple logistic regression were performed to investigate the connection between HbEO levels and albuminuria, and mediation analysis was applied to elucidate the potential mechanism for the effect of HbEO concentrations on albuminuria. In the results, compared with the extreme quartile of HbEO levels, the weighted prevalence of albuminuria was significantly increased in participants with highest quartile (Q4 vs Q1, 11.2% vs 8.1%). Restricted cubic spline plots revealed that the risk of albuminuria raised non-linearly and positively with elevated HbEO level. After adjusting for confounders, the logistic regression suggested that the risk of albuminuria was enhanced by 12% for each one-unit increase in log-2-transformed HbEO (OR = 1.12, 95% CI, 1.03-1.22, P = 0.007). Moreover, the multivariate ORs (95% CIs) on albuminuria was increased across the increasing HbEO quartiles (Q4 vs Q1, OR = 1.54, 95% CI, 1.09-2.17; P for trend = 0.029). Furthermore, the impact of high HbEO level on albuminuria was partially related to inflammation markers, including white blood cells (17.2%), neutrophils (22.1%), and lymphocytes (19.5%). To sum up, our study identified that high HbEO levels increased the risk of albuminuria in representative population of US adults, and several inflammatory mediators might be potentially involved in EO-associated albuminuria.

The relationship between low levels of albuminuria and cardiovascular mortality among apparently healthy adults

Background

Albuminuria is associated with cardiovascular events among adults with underlying cardiovascular disease and diabetes, even at low levels of urinary albumin excretion. We hypothesized that low levels of albuminuria in the 'normal' range (urinary albumin-to-creatine ratio (UACR) <30 mg/g) are associated with cardiovascular death among apparently healthy adults.

Methods

We studied adults who participated in the 1999-2014 National Health and Nutrition Examination Survey. We excluded participants with baseline cardiovascular disease, hypertension, diabetes, estimated glomerular filtration rate (eGFR) <60ml/min/1.73m2, those who were currently pregnant, and those who had received dialysis in the last year. After excluding these conditions, only 5.0% of the remaining population had UACR ≥30 mg/g (N=873) and were excluded. The final sample size was 16,247. We assessed the relationship between UACR and cardiovascular and all-cause mortality using multivariable-adjusted Cox proportional hazards models. Models were adjusted for age, sex, race or ethnicity, smoking status, systolic blood pressure, hemoglobin A1c, total cholesterol, health insurance, food insecurity, serum albumin, body mass index, use of statins, and eGFR.

Results

Mean age was 38.9 years (SD 13.6) and 53.7% were women. The median length of follow-up was 12.2 years. In multivariable-adjusted models, each doubling of UACR (within the <30 mg/g range) was associated with a 36% higher risk of cardiovascular death [HR 1.36 (95% confidence interval (CI) 1.11-1.65)] and a 28% higher risk of all-cause mortality [HR 1.28 (95%CI 1.17-1.41)]. The highest tertile of UACR (7.1-29.9 mg/g) was associated with an 87% higher risk of cardiovascular death [HR 1.87 (95%CI 1.20-2.92)] and 59% higher risk of all-cause mortality [HR 1.59 (95%CI 1.28-1.96)], compared with the lowest tertile (< 4.3 mg/g).

Conclusions

In a nationally representative sample of relatively healthy community-dwelling adults, higher levels of albuminuria in the conventionally "normal" range <30 mg/g in healthy individuals are associated with greater mortality. Overall, our findings contribute to the growing body of evidence on the existence of a risk gradient across all levels of albuminuria, even in the so-called normal range.

Review on adherence of the literature to official recommendations on albuminuria harmonization and standardization

Albuminuria standardization is a key issue to produce reliable and equivalent results between laboratories. We investigated whether official recommendations on albuminuria harmonization are followed in the literature. The PubMed database was searched from June 1 to September 26, 2021. The search terms included urine albumin, urine albumin-to-creatinine ratio (uACR), and albuminuria. A total of 159 articles were considered eligible; 50.9 % reported the type of urine collection. Specifically, 58.1 % collected a random spot urine specimen, 21 % collected a first morning void, and 6.2 % collected a 24-h specimen. Overall, 15 % of articles reported data on sample shipping, storage, and centrifugation and 13.3 % mentioned the preanalytical phase without any data on albuminuria. The method for albuminuria was properly described in 31.4 % of articles; of these, 54.9 % used immunological methods, and 8.9 % contained errors or missing data. Most articles (76.7 %) expressed test results as albuminuria-to-creatininuria ratio. Different decision levels were utilized in 130 articles; of these, 36 % used a decision level of ≤30 mg/g creatininuria and 23.7 % used three decision levels (≤30, 30-300, and ≥300 mg/g). The failure to follow guidelines on albuminuria harmonization was mainly found in the preanalytical phase. The poor awareness of the importance of preanalytical steps on test result may be a possible explanation.

Associations Between Albuminuria and Mortality Among US Adults by Demographic and Comorbidity Factors

Background Albuminuria is a known marker of mortality risk. Whether the association between albuminuria and mortality differs by demographic and comorbidity factors remains unclear. Therefore, we sought to determine whether albuminuria is differentially associated with mortality. Methods and Results This study included 49 640 participants from the National Health and Nutrition Examination Survey (1999-2018). All-cause mortality through 2019 was linked from the National Death Index. Multivariable-adjusted Poisson regression models were used to determine whether levels of urine albumin-to-creatinine ratio (ACR) were associated with mortality. Models were adjusted for demographic, socioeconomic, behavioral, and clinical factors. Mean age in the population was 46 years, with 51.3% female, and 30.3% with an ACR ≥10 mg/g. Over a median follow-up of 9.5 years, 6813 deaths occurred. Compared with ACR <10, ACR ≥300 was associated with increased risk of mortality by 132% overall (95% CI, 2.01-2.68), 124% among men (95% CI, 1.84-2.73), 158% among women (95% CI, 2.14-3.11), 130% among non-Hispanic White adults (95% CI: 1.89-2.79), 135% among non-Hispanic Black adults (95% CI, 1.82-3.04), and 114% among Hispanic adults (95% CI, 1.55-2.94). Compared with ACR <10, ACR ≥300 was associated with increased risk of mortality by 148% among individuals with neither hypertension nor hypercholesterolemia (95% CI, 1.69-3.64), 128% among individuals with hypertension alone (95% CI, 1.86-2.79), and 166% among individuals with both hypertension and hypercholesterolemia (95% CI, 2.18-3.26). Conclusions We found strong associations between albuminuria and mortality risk, even at mildly increased levels of albuminuria. Associations persisted across categories of sex, race or ethnicity, and comorbid conditions, with subtle differences.

Positive associations between different circulating trans fatty acids (TFAs) and urinary albumin excretion among adults in the U.S.: a population-based study

BACKGROUND

It is well established that the consumption of trans-fatty acids (TFAs) can increase the incidence of total mortality, cardiovascular disease, cancer, and diabetes. However, there are still no demographic studies on the effects of circulating TFA isoforms on the albumin-creatinine ratio (ACR), an early marker of chronic kidney disease. Our goal was to explore the possible relationships between TFAs and ACR.

METHODS

In this study, complete TFAs and urinary ACR data were collected from the National Health and Nutrition Examination Survey (NHANES) (2009-2010 and 1999-2000 cycles). The independent linear relationships between different circulating TFA isoforms and the ACR were examined by performing multivariable linear regression models. Machine learning was used to analyze the contribution of the different TFA isoforms to the ACR. To assess the nonlinearity of the relationship, smooth curve fitting and an analysis of threshold effect were performed, and a stratified analysis was conducted to identify possible susceptible populations.

RESULTS

Our analysis included a total of 3785 individuals. Elaidic acid, linolelaidic acid, and sum TFAs were shown to be positively associated with the ACR after full adjustment by weighted multivariable regression analysis. In the subgroup analysis, the positive associations were maintained in participants with hypertension and without diabetes. In the XGBoost model of the ACR, Sum TFAs were found to be the most crucial factor. In addition, smooth curve fitting showed that there was a nonlinear relationship between the different TFAs and the ACR, and there was a saturation point.

CONCLUSIONS

Our study demonstrated that TFA isoforms were positively and independently correlated with urinary albumin excretion, especially in participants with hypertension and without diabetes. This suggested that reducing trans fatty acid intake may reduce the risk of renal events.

Elevated urine albumin creatinine ratio increases cardiovascular mortality in coronary artery disease patients with or without type 2 diabetes mellitus: a multicenter retrospective study

BACKGROUND

Albuminuria has been suggested as an atherosclerotic risk factor among the general population. However, whether this association will be amplified in patients with coronary artery disease (CAD) is unknown. It is also unknown whether diabetes mellitus confounds the association. We aim to analyse the prognosis of elevated urine albumin creatinine ratio (uACR) in the CAD population with or without type 2 diabetes mellitus (T2DM).

METHODS

This multi-center registry cohort study included 5,960 patients with CAD. Patients were divided into T2DM and non-T2DM group, and baseline uACR levels were assessed on three grades (low: uACR < 10 mg/g, middle: 10 mg/g ≤ uACR < 30 mg/g, and high: uACR ≥ 30 mg/g). The study endpoints were cardiovascular mortality and all-cause mortality.

RESULTS

During the median follow-up of 2.2 [1.2-3.1] years, 310 (5.2%) patients died, of which 236 (4.0%) patients died of cardiovascular disease. CAD patients with elevated uACR had a higher risk of cardiovascular mortality (middle: HR, 2.32; high: HR, 3.22) than those with low uACR, as well as all-cause mortality. Elevated uACR increased nearly 1.5-fold risk of cardiovascular mortality (middle: HR, 2.33; high: HR, 2.34) among patients without T2DM, and increased 1.5- fold to 3- fold risk of cardiovascular mortality in T2DM patients (middle: HR, 2.49; high: HR, 3.98).

CONCLUSIONS

Even mildly increased uACR could increase the risk of cardiovascular mortality in patients with CAD, especially when combined with T2DM.

Albuminuria improves R2CHA2DS2-VASc score in predicting mortality in high cardiovascular risk population

BACKGROUND AND AIMS

The CHA₂DS₂-VASc score estimates the risk of cardioembolism in patients with atrial fibrillation (AF). It also predicts vascular events and death in different clinical settings, even in the absence of AF. The R₂CHA₂DS₂-VASc score, obtained by adding the glomerular filtration rate to CHA₂DS₂-VASc, shows a higher prediction ability for new events and all-cause mortality. The present study aims to assess whether the addition of albuminuria to R₂CHA₂DS₂-VASc score further improves its discrimination ability in predicting all-cause mortality in a sample of high cardiovascular risk population.

METHODS AND RESULTS

Prospective, monocentric, observational study, evaluating a subset of 737 subjects consecutively undergoing to coronary angiography at Coronary Unit of Scientific Institute "Casa Sollievo della Sofferenza" from June 2016 to December 2018. The presence of albuminuria was significantly associated with all-cause mortality (p < 0.0001). Any one-point increase of Alb-R₂CHA₂DS₂-VASc score increased mortality of about 1.5-fold (adjusted HR 1.49; 95%CI: 1.37-1.63; p < 0.0001). Considering tertiles of Alb-R₂CHA₂DS₂-VASc, the third tertile showed a 9.5-fold increased risk of mortality (HR 9.52; 95% CI: 5.15-17.60, p < 0.001). Comparing the two scores, the Alb-R₂CHA₂DS₂-VASc score (C-statistic = 0.751; 95%CI: 0.69-0.81) outperformed the R₂-CHA₂DS₂-VASc score (C-statistic = 0.736; 95%CI: 0.68-0.961) in predicting mortality (delta C-statistic = 0.015; 95%CI: 0.001-0.029). The better prediction ability of the Alb-R₂CHA₂DS₂-VASc score was also proven by an IDI of 0.024 (p < 0.0001) and a relative IDI of 24.11% (p < 0.0001), with an NRI = 0.608 (p < 0.00001).

CONCLUSIONS

The addition of albuminuria to R₂CHA₂DS₂-VASc significantly and independently predicts the risk of all-cause mortality in a sample of high CV risk patients. Moreover, Alb-R₂CHA₂DS₂-VASc outperforms R₂CHA₂DS₂-VASc.

Longitudinal changes in blood pressure are preceded by changes in albuminuria and accelerated by increasing dietary sodium intake

BACKGROUND

Dietary sodium is a well-known risk factor for cardiovascular and renal disease; however, direct evidence of the longitudinal changes that occur with aging, and the influence of dietary sodium on the age-associated alterations are scarce.

METHODS

C57BL/6 mice were maintained for 13 months on a low (LS, 0.02 % Na+), normal (NS, 0.3 % Na+) or high (HS, 1.6 % Na+) salt diet. We assessed 1) the longitudinal trajectories for two markers of cardiovascular and renal dysfunction (blood pressure (BP) and albuminuria), as well as hormonal changes, and 2) end-of-study cardiac and renal parameters.

RESULTS

The effect of aging on BP and kidney damage did not reach significance levels in the LS group; however, relative to baseline, there were significant increases in these parameters for animals maintained on NS and HS diets, starting as early as month 7 and month 5, respectively. Furthermore, changes in albuminuria preceded the changes in BP relative to baseline, irrespective of the diet. Circulating aldosterone and plasma renin activity displayed the expected decreasing trends with age and dietary sodium loading. As compared to LS - higher dietary sodium consumption associated with increasing trends in left ventricular mass and volume indices, consistent with an eccentric dilated phenotype. Functional and molecular markers of kidney dysfunction displayed similar trends with increasing long-term sodium levels: higher renovascular resistance, increased glomerular volumes, as well as higher levels of renal angiotensin II type 1 and mineralocorticoid receptors, and lower renal Klotho levels.

CONCLUSION

Our study provides a timeline for the development of cardiorenal dysfunction with aging, and documents that increasing dietary salt accelerates the age-induced phenotypes. In addition, we propose albuminuria as a prognostic biomarker for the future development of hypertension. Last, we identified functional and molecular markers of renal dysfunction that associate with long-term dietary salt loading.

Effect of Urinary Albumin Creatinine Ratio on Cardiovascular Morbidity and Mortality in Diabetes Patients with Atherosclerotic Disease

BACKGROUND

Diabetes mellitus (DM) patients with increased urinary albumin creatinine ratio (uACR) have higher risk of mortality, while it is unclear in DM patients with atherosclerotic cardiovascular disease (ASCVD).

METHODS

We analysed 2832 DM patients with ASCVD in this multi-center registry cohort study Cardiorenal ImprovemeNt II (CIN-II) in 5 Chinese tertiary hospitals from 2007 to 2020. Patients were divided into 3 groups according to their uACR level (normal group: uACR <30mg/g, moderately increased group: 30mg/g≤ uACR <300mg/g, severely increased group: 300mg/g≤ uACR). The main outcome of the study was cardiovascular mortality and all-cause mortality.

RESULTS

During a median follow-up of 2.1 years, among 2832 patients (mean age: 63.3 ± 9.9 years, 29.1% women), 434 patients (15.3%) had moderately increased uACR, and 203 patients (7.2%) had severely increased uACR. Compared to patients in normal group, patients had higher cardiovascular mortality in moderately increased group and severely increased group (2.5% vs 9.9% vs 16.7%, P < 0.001), as well as all-cause mortality. After adjusting confounders, the risk of cardiovascular mortality remained higher in moderately increased group (adjusted hazard ratio [aHR]: 3.13; 95% confidence interval [CI]: 2.04-4.81) and severely increased group (aHR: 4.54; 95% CI: 2.58-8.01) than in normal group, as well as all-cause mortality.

CONCLUSION

In our study, we found nearly a quarter of DM patients with ASCVD had increased uACR, and they have over 2- or 3-fold risk of cardiovascular mortality than those with normal uACR. UACR is a helpful indicator for risk stratification and treatment target for DM patients with ASCVD.

Prevention of cardiorenal damage: importance of albuminuria

Chronic kidney disease (CKD) is projected to become a leading global cause of death by 2040, and its early detection is critical for effective and timely management. The current definition of CKD identifies only advanced stages, when kidney injury has already destroyed &gt;50% of functioning kidney mass as reflected by an estimated glomerular filtration rate &lt;60 mL/min/1.73 m2 or a urinary albumin/creatinine ratio &gt;six-fold higher than physiological levels (i.e. &gt; 30 mg/g). An elevated urinary albumin-excretion rate is a known early predictor of future cardiovascular events. There is thus a ‘blind spot’ in the detection of CKD, when kidney injury is present but is undetectable by current diagnostic criteria, and no intervention is made before renal and cardiovascular damage occurs. The present review discusses the CKD ‘blind spot’ concept and how it may facilitate a holistic approach to CKD and cardiovascular disease prevention and implement the call for albuminuria screening implicit in current guidelines. Cardiorenal risk associated with albuminuria in the high-normal range, novel genetic and biochemical markers of elevated cardiorenal risk, and the role of heart and kidney protective drugs evaluated in recent clinical trials are also discussed. As albuminuria is a major risk factor for cardiovascular and renal disease, starting from levels not yet considered in the definition of CKD, the implementation of opportunistic or systematic albuminuria screening and therapy, possibly complemented with novel early biomarkers, has the potential to improve cardiorenal outcomes and mitigate the dismal 2040 projections for CKD and related cardiovascular burden.

Urinary A- and C-megalin predict progression of diabetic kidney disease: an exploratory retrospective cohort study

AIMS

Megalin, a proximal tubular endocytosis receptor, is excreted in urine in two forms: ectodomain (A-megalin) and full-length (C-megalin). We explored whether urinary megalin levels can be used as independent prognostic biomarkers in the progression of diabetic kidney disease (DKD).

METHODS

The associations between baseline urinary A-megalin/creatinine (Cr) and/or C-megalin/Cr levels and the subsequent estimated glomerular filtration rate (eGFR) slope were analyzed using a generalized estimating equation. Patients were categorized into higher or lower groups based on the optimal cutoff values, obtained from a receiver operating characteristic curve, of the two forms of urinary megalin.

RESULTS

We retrospectively analyzed 188 patients with type 2 diabetes. The eGFR slopes of the higher A-megalin/Cr and higher C-megalin/Cr groups were - 0.904 and -0.749 ml/min/1.73 m²/year steeper than those of the lower groups, respectively. Moreover, the eGFR slope was -1.888 ml/min/1.73 m²/year steeper in the group with both higher A- and higher C-megalin/Cr than in the other group. These results remained significant when adjusted for known urinary biomarkers (albumin, α₁-microglobulin, β₂-microglobulin, and N-acetyl-β-d-glucosaminidase).

CONCLUSIONS

Urinary A- and C-megalin/Cr levels are likely to be prognostic biomarkers in the progression of DKD independent of other urinary biomarkers.

Assessment of Cystatin C Level for Risk Stratification in Adults With Chronic Kidney Disease

Importance

Kidney function is usually estimated from serum creatinine level, whereas an alternative glomerular filtration marker (cystatin C level) associates more closely with future risk of cardiovascular disease (CVD) and mortality.

Objectives

To evaluate whether testing concordance between estimated glomerular filtration rates based on cystatin C (eGFRcys) and creatinine (eGFRcr) levels would improve risk stratification for future outcomes and whether estimations differ by age.

Design, Setting, and Participants

A prospective population-based cohort study (UK Biobank), with participants recruited between 2006-2010 with median follow-up of 11.5 (IQR, 10.8-12.2) years; data were collected until August 31, 2020. Participants had eGFRcr greater than or equal to 45 mL/min/1.73 m2, albuminuria (albumin <30 mg/g), and no preexisting CVD or kidney failure.

Exposures

Chronic kidney disease status was categorized by concordance between eGFRcr and eGFRcys across the threshold for hronic kidney disease (CKD) diagnosis (60 mL/min/1.73 m2).

Main Outcomes and Measures

Ten-year probabilities of CVD, mortality, and kidney failure were assessed according to CKD status. Multivariable-adjusted Cox proportional hazards models tested associations between CVD and mortality. Area under the receiving operating curve tested discrimination of eGFRcr and eGFRcys for CVD and mortality. The Net Reclassification Index assessed the usefulness of eGFRcr and eGFRcys for CVD risk stratification. Analyses were stratified by older (age 65-73 years) and younger (age <65 years) age.

Results

There were 428 402 participants: median age was 57 (IQR, 50-63) years and 237 173 (55.4%) were women. Among 76 629 older participants, there were 9335 deaths and 5205 CVD events. Among 351 773 younger participants, there were 14 776 deaths and 9328 CVD events. The 10-year probability of kidney failure was less than 0.1%. Regardless of the eGFRcr, the 10-year probabilities of CVD and mortality were low when eGFRcys was greater than or equal to 60 mL/min/1.73 m2; conversely, with eGFRcys less than 60 mL/min/1.73 m2, 10-year risks were nearly doubled in older adults and more than doubled in younger adults. Use of eGFRcys better discriminated CVD and mortality risk than eGFRcr. Across a 7.5% 10-year risk threshold for CVD, eGFRcys improved case Net Reclassification Index by 0.7% (95% CI, 0.6%-0.8%) in older people and 0.7% (95% CI, 0.7%-0.8%) in younger people; eGFRcr did not add to CVD risk estimation.

Conclusions and Relevance

The findings of this study suggest that eGFRcr 45 to 59 mL/min/1.73 m2 includes a proportion of individuals at low risk and fails to capture a substantial proportion of individuals at high-risk for CVD and mortality. The eGFRcys appears to be more sensitive and specific for CVD and mortality risks in mild CKD.

Decreasing the Lower Limit of Quantitation for Urine Albumin Improves Clinical Utility

Background

Urine albumin-to-creatinine ratio (uACR) is a screening assay for chronic kidney disease (CKD). A value of &gt;30 mg/g is flagged abnormal, but lower ratios have prognostic implications. Thus, to maximize diagnostic utility, urine albumin (uAlb) should be measurable to 3 mg/L to match the lowest creatinine concentration generally utilized (10 mg/dL). Most uAlb assays have lower limits of quantitation (LLOQs) 2- to 4-fold higher. We sought to determine the performance characteristics of a commonly used uAlb assay at 3 mg/L and to evaluate the clinical screening impact of reducing the LLOQ.

Methods

Urine was serially diluted to assess uAlb linearity and precision for concentrations near the claimed LLOQ (12 mg/L). Samples (n = 30) with uAlb &lt;12 mg/L were compared between laboratories. Sequential samples (n = 1239) were evaluated for clinical impact of reducing the measuring range to 3 mg/L.

Results

The assay was linear to 1.6 mg/L. Interday precision at 3.7 mg/L and 4.3 mg/L was 7.7% and 8.6%, respectively. Minimal bias was observed between labs (y = 1.091x − 0.75; average bias = −0.13 mg/L). Clinical validation demonstrated 501 of 1239 samples (40.4%) had uAlb &lt;12 mg/L. Using 11.9 mg/L as the numerator for samples with uAlb &lt;12 mg/dL and urine creatinine &gt;10 mg/L, 107 of 499 (21.4%) would have a ratio flagged abnormal at &gt;30 mg/g. Using the numeric value for these samples to 3 mg/L reduced alarm to &lt;1%.

Conclusions

A uAlb LLOQ of 3 mg/L improves screening utility of uACR by simplifying reporting and clinical interpretation when uAlb is low and provides clinical information for prognostic tools developed for people at risk of CKD.