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Adults with chronic kidney disease (CKD) are hospitalized more frequently than those without CKD, but the magnitude of this excess morbidity and the factors associated with hospitalizations are not well known. Data from 3,939 participants enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study between 2003 and 2008 at 7 clinical centers in the United States were used to estimate primary causes of hospitalizations, hospitalization rates, and baseline participant factors associated with all-cause, cardiovascular, and non-cardiovascular hospitalizations during a median follow up of 9.6 years. Multivariable-adjusted Poisson regression was used to identify factors associated with hospitalization rates, including demographics, blood pressure, estimated glomerular filtration rate (eGFR), and proteinuria. Hospitalization rates in CRIC were compared with rates in the Nationwide Inpatient Sample (NIS) from 2012. Of the 3,939 CRIC participants, 45.1% were female, and 41.9% identified as non-Hispanic black, with a mean age of 57.7 years, and the mean eGFR is 44.9 ml/min/1.73m2. CRIC participants had an unadjusted overall hospitalization rate of 35.0 per 100 person-years (PY) [95% CI: 34.3 to 35.6] and 11.1 per 100 PY [95% CI: 10.8 to 11.5] for cardiovascular-related causes. All-cause, non-cardiovascular, and cardiovascular hospitalizations were associated with older age (≥65 versus 45 to 64 years), more proteinuria (≥150 to <500 versus <150 mg/g), higher systolic blood pressure (≥140 versus 120 to <130 mmHg), diabetes (versus no diabetes), and lower eGFR (<60 versus ≥60 ml/min/1.73m2). Non-Hispanic black (versus non-Hispanic white) race/ethnicity was associated with higher risk for cardiovascular hospitalization [rate ratio (RR) 1.25, 95% CI: 1.16 to 1.35, p-value < 0.001], while risk among females was lower [RR 0.89, 95% CI: 0.83 to 0.96, p-value = 0.002]. Rates of cardiovascular hospitalizations were higher among those with ≥500 mg/g of proteinuria irrespective of eGFR. The most common causes of hospitalization were related to cardiovascular (31.8%), genitourinary (8.7%), digestive (8.3%), endocrine, nutritional or metabolic (8.3%), and respiratory (6.7%) causes. Hospitalization rates were higher in CRIC than the NIS, except for non-cardiovascular hospitalizations among individuals aged >65 years. Limitations of the study include possible misclassification by diagnostic codes, residual confounding, and potential bias from healthy volunteer effect due to its observational nature. In this study, we observed that adults with CKD had a higher hospitalization rate than the general population that is hospitalized, and even moderate reductions in kidney function were associated with elevated rates of hospitalization. Causes of hospitalization were predominantly related to cardiovascular disease, but other causes contributed, particularly, genitourinary, digestive, and endocrine, nutritional, and metabolic illnesses. High levels of proteinuria were observed to have the largest association with hospitalizations across a wide range of kidney function levels.

The metabolic syndrome is a common risk factor for cardiovascular disease. To examine the association between the metabolic syndrome and risk for chronic kidney disease and microalbuminuria. Cross-sectional study. The Third National Health and Nutrition Examination Survey. Participants 20 years of age or older were studied in the chronic kidney disease (n = 6217) and microalbuminuria (n = 6125) analyses. The metabolic syndrome was defined as the presence of 3 or more of the following risk factors: elevated blood pressure, low high-density lipoprotein cholesterol level, high triglyceride level, elevated glucose level, and abdominal obesity. Chronic kidney disease was defined as a glomerular filtration rate less than 60 mL/min per 1.73 m2, and microalbuminuria was defined as a urinary albumin-creatinine ratio of 30 to 300 mg/g. The multivariate-adjusted odds ratios of chronic kidney disease and microalbuminuria in participants with the metabolic syndrome compared with participants without the metabolic syndrome were 2.60 (95% CI, 1.68 to 4.03) and 1.89 (CI, 1.34 to 2.67), respectively. Compared with participants with 0 or 1 component of the metabolic syndrome, participants with 2, 3, 4, and 5 components of chronic kidney disease had multivariate-adjusted odds ratios of 2.21 (CI, 1.16 to 4.24), 3.38 (CI, 1.48 to 7.69), 4.23 (CI, 2.06 to 8.63), and 5.85 (CI, 3.11 to 11.0), respectively. The corresponding multivariate-adjusted odds ratios of microalbuminuria for participants with 3, 4, and 5 components were 1.62 (CI, 1.10 to 2.38), 2.45 (CI, 1.55 to 3.85), and 3.19 (CI, 1.96 to 5.19), respectively. These findings suggest that the metabolic syndrome might be an important factor in the cause of chronic kidney disease.

Background Insulin resistance contributes to the metabolic syndrome, which is associated with the development of kidney disease. However, it is unclear if insulin resistance independently contributes to an increased risk of chronic kidney disease (CKD) progression or CKD complications. Additionally, predisposing factors responsible for insulin resistance in the absence of diabetes in CKD are not well described. This study aimed to describe factors associated with insulin resistance and characterize the relationship of insulin resistance to CKD progression, cardiovascular events and death among a cohort of non-diabetics with CKD. Methods Data was utilized from Chronic Renal Insufficiency Cohort Study participants without diabetes ( N  = 1883). Linear regression was used to assess associations with insulin resistance, defined using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The relationship of HOMA-IR, fasting glucose, hemoglobin A1c (HbA1c), and C-peptide with CKD progression, cardiovascular events, and all-cause mortality was examined with Cox proportional hazards models. Results Novel positive associations with HOMA-IR included serum albumin, uric acid, and hemoglobin A1c. After adjustment, HOMA-IR was not associated with CKD progression, cardiovascular events, or all-cause mortality. There was a notable positive association of one standard deviation increase in HbA1c with the cardiovascular endpoint (HR 1.16, 95% CI: 1.00–1.34). Conclusion We describe potential determinants of HOMA-IR among a cohort of non-diabetics with mild-moderate CKD. HOMA-IR was not associated with renal or cardiovascular events, or all-cause mortality, which adds to the growing literature describing an inconsistent relationship of insulin resistance with CKD-related outcomes.

Background Hematuria is associated with chronic kidney disease (CKD), but has rarely been examined as a risk factor for CKD progression. We explored whether individuals with hematuria had worse outcomes compared to those without hematuria in the CRIC Study. Methods Participants were a racially and ethnically diverse group of adults (21 to 74 years), with moderate CKD. Presence of hematuria (positive dipstick) from a single urine sample was the primary predictor. Outcomes included a 50% or greater reduction in eGFR from baseline, ESRD, and death, over a median follow-up of 7.3 years, analyzed using Cox Proportional Hazards models. Net reclassification indices (NRI) and C statistics were calculated to evaluate their predictive performance. Results Hematuria was observed in 1145 (29%) of a total of 3272 participants at baseline. Individuals with hematuria were more likely to be Hispanic (22% vs. 9.5%, respectively), have diabetes (56% vs. 48%), lower mean eGFR (40.2 vs. 45.3 ml/min/1.73 m2), and higher levels of urinary albumin > 1.0 g/day (36% vs. 10%). In multivariable-adjusted analysis, individuals with hematuria had a greater risk for all outcomes during the first 2 years of follow-up: Halving of eGFR or ESRD (HR Year 1: 1.68, Year 2: 1.36), ESRD (Year 1: 1.71, Year 2: 1.39) and death (Year 1:1.92, Year 2: 1.77), and these associations were attenuated, thereafter. Based on NRIs and C-statistics, no clear improvement in the ability to improve prediction of study outcomes was observed when hematuria was included in multivariable models. Conclusion In a large adult cohort with CKD, hematuria was associated with a significantly higher risk of CKD progression and death in the first 2 years of follow-up but did not improve risk prediction.

The accuracy of ankle-brachial index (ABI) and toe-brachial index (TBI) in discriminating lower extremity peripheral artery disease (PAD) has not been evaluated in patients with chronic kidney disease (CKD). We measured ABI, TBI, and Doppler ultrasound in 100 predialysis patients with CKD without revascularization or amputation. Leg-specific ABI was calculated using higher systolic blood pressure (SBP) in posterior tibial or dorsalis pedis artery divided by higher brachial SBP; alternative ABI was calculated using lower SBP in posterior tibial or dorsalis pedis artery. PAD was defined as ≥50% stenosis detected by Doppler ultrasound. PAD risk classification score was calculated using cardiovascular disease risk factors. The area under the curve (AUC, 95% confidence interval [CI]) for discriminating ultrasound-diagnosed PAD was 0.78 (0.69 to 0.87) by ABI, 0.80 (0.71 to 0.89) by alternative ABI, and 0.74 (0.63 to 0.86) by TBI. Sensitivity and specificity were 25% and 97% for ABI ≤0.9, 41% and 95% for alternative ABI ≤0.9, and 45% and 93% for TBI ≤0.7, respectively. AUC (95% CI) of PAD risk classification score was 0.86 (0.78 to 0.94) with sensitivity and specificity of 95% and 60% for risk score ≥0.10, 76% and 76% for risk score ≥0.25, and 43% and 95% for risk score ≥0.55. Combining risk score with ABI, alternative ABI, and TBI increased AUC (95% CI) to 0.89 (0.82 to 0.96), 0.89 (0.80 to 0.98), and 0.87 (0.78 to 0.96), respectively. In conclusion, current ABI and TBI diagnostic criteria have high specificity but low sensitivity for classifying PAD in patients with CKD. PAD classification risk score based on cardiovascular disease risk factors improves the accuracy of PAD classification.

The interrelationship of multiple endothelial biomarkers and chronic kidney disease (CKD) has not been well studied. We measured asymmetric dimethylarginine (ADMA), L-arginine, soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular adhesion molecule-1 (sVCAM-1), soluble E-selectin (sE-selectin), von Willebrand factor (vWF), flow-mediated dilation (FMD), and nitroglycerin-induced dilation (NID) in 201 patients with CKD and 201 community-based controls without CKD. Multivariable analyses were used to examine the interrelationship of endothelial biomarkers with CKD. The multivariable-adjusted medians (interquartile ranges) were 0.54 (0.40, 0.75) in patients with CKD vs. 0.25 (0.22, 0.27) μmol /L in controls without CKD (p<0.0001 for group difference) for ADMA; 67.0 (49.6, 86.7) vs. 31.0 (27.7, 34.2) μmol/L (p<0.0001) for L-arginine; 230.0 (171.6, 278.6) vs. 223.9 (178.0, 270.6) ng/mL (p=0.55) for sICAM-1; 981.7 (782.6, 1216.8) vs. 633.2 (507.8, 764.3) ng/mL (p<0.0001) for sVCAM-1; 47.9 (35.0, 62.5) vs. 37.0 (28.9, 48.0) ng/mL (p=0.01) for sE-selectin; 1320 (1044, 1664) vs. 1083 (756, 1359) mU/mL (p=0.008) for vWF; 5.74 (3.29, 8.72) vs. 8.80 (6.50, 11.39)% (p=0.01) for FMD; and 15.2 (13.5, 16.9) vs. 19.1 (17.2, 21.0)% (p=0.0002) for NID, respectively. In addition, the severity of CKD was positively associated with ADMA, L-arginine, sVCAM-1, sE-selectin, and vWF and inversely associated with FMD and NID. Furthermore, FMD and NID were significantly and inversely correlated with ADMA, L-arginine, sVCAM-1, sE-selectin, and vWF. In conclusion, these data indicate that multiple dysfunctions of the endothelium were present among patients with CKD. Interventional studies are warranted to test the effects of treatment of endothelial dysfunction on CKD.

Significance How the kidney handles chloride reabsorption has long been a mystery. Here, we have discovered a pathway in the kidney that utilizes channel-activating protease 1 and claudin-4 to physiologically regulate tight junction permeability to chloride. Such a pathway not only is important in renal regulation of chloride but also may play key roles in chloride transport across many other epithelia such as the lung, the salivary gland, and the skin. This discovery also attests to a concept of “druggable” tight junction. Proteases or protease-dependent mechanisms may be developed as pharmacological tools to transiently regulate tight junction permeability in the kidney, the intestine, and the blood–brain barrier.

Since insulin resistance is thought to be the underlying mechanism for metabolic syndrome, affected individuals might be sensitive to a dietary sodium intervention. We aimed to examine the association between metabolic syndrome and salt sensitivity of blood pressure. 1906 Chinese participants without diabetes, aged 16 years or more, were selected to receive a low-sodium diet (51·3 mmol per day) for 7 days followed by a high-sodium diet (307·8 mmol per day) for an additional 7 days. Participants were excluded from the analysis if metabolic risk factor information was missing or if they did not complete their dietary interventions. Blood pressure was measured at baseline and on days 2, 5, 6, and 7 of each intervention. Metabolic syndrome was defined as the presence of three or more of: abdominal obesity, raised blood pressure, high triglyceride concentration, low HDL cholesterol, or high glucose. High salt sensitivity was defined as a decrease in mean arterial blood pressure of more than 5 mm Hg during low-sodium or an increase of more than 5 mm Hg during high-sodium intervention. This study is registered with ClinicalTrials.gov, number NCT00721721. Of the 1881 participants with information regarding metabolic syndrome, 283 had metabolic syndrome. 1853 participants completed the low-sodium diet and 1845 completed the high-sodium diet. Multivariable-adjusted mean changes in blood pressure were significantly greater in participants with metabolic syndrome than in those without on both low-sodium and high-sodium diets (p<0·0001 for all comparisons). Additionally, risk of salt sensitivity rose with increasing numbers of risk factors for metabolic syndrome. Compared with those with no risk factors, participants with four or five had a 3·54-fold increased odds (95% CI 2·05–6·11) of high salt-sensitivity during the low-sodium and a 3·13-fold increased odds (1·80–5·43) of high salt-sensitivity during the high-sodium intervention. These results suggest that metabolic syndrome enhances blood pressure response to sodium intake. Reduction in sodium intake could be an especially important component in reducing blood pressure in patients with multiple risk factors for metabolic syndrome. National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.

Risk for coronary heart disease is high among patients with chronic kidney disease. To compare the prevalence of low apolipoprotein A1 levels and elevated apolipoprotein B, plasma fibrinogen, lipoprotein(a), homocysteine, and C-reactive protein levels by estimated glomerular filtration rate (GFR). Cross-sectional study. Third National Health and Nutrition Examination survey. 12 547, 3180, and 744 persons with estimated GFRs of at least 90, 60 to 89, or less than 60 mL/min per 1.73 m2, respectively, who were at least 18 years of age. Chronic kidney disease was defined as an estimated GFR of less than 60 mL/min per 1.73 m2 based on the abbreviated Modification of Diet in Renal Disease formula. After standardization for age, race or ethnicity, and sex, lower estimated GFR (> or =90, 60 to 89, or <60 mL/min per 1.73 m2) was associated with lower average levels of apolipoprotein A1 (1.44, 1.43, and 1.35 g/L) and higher levels of apolipoprotein B (1.03, 1.06, and 1.08 g/L), plasma fibrinogen (8.43, 8.44, and 9.53 micromol/L), homocysteine (8.5, 10.0, and 13.2 micromol/L), and C-reactive protein (3.0, 2.9, and 3.9 mg/L) (P < 0.05 for all values). The multivariate-adjusted odds ratios of an apolipoprotein A1 level of less than 1.2 g/L, a serum lipoprotein(a) level of at least 1.61 micromol/L (> or =45.3 mg/dL), a plasma fibrinogen level of at least 10.35 micromol/L, a serum homocysteine level of at least 15 micromol/L, and a C-reactive protein level of at least 10.0 mg/L for participants with chronic kidney disease compared with those with a GFR of at least 90 mL/min per 1.73 m2 or greater were 1.92 (95% CI, 1.02 to 3.63), 1.82 (CI, 1.06 to 3.13), 1.74 (CI, 1.35 to 2.24), 8.23 (CI, 5.00 to 13.6), and 1.93 (CI, 1.33 to 2.81), respectively. Levels of apolipoprotein A1 are decreased and levels of homocysteine, lipoprotein(a), fibrinogen, and C-reactive protein are increased among patients with chronic kidney disease.

Background There are limited data on the associations of circulating angiogenic factors with chronic kidney disease (CKD). We investigate the associations of circulating vascular endothelial growth factor (VEGF)-A, angiopoietin-1, angiopoietin-1/VEGF-A ratio, VEGF receptor 1 (VEGFR-1), VEGFR-2, and pentraxin-3 with CKD. Methods We recruited 201 patients with CKD and 201 community controls without CKD from the greater New Orleans area. CKD was defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m 2 or presence of albuminuria. Multivariable quantile and logistic regression models were used to examine the relationship between angiogenesis-related factors and CKD adjusting for confounding factors. Results After adjusting for covariables including traditional cardiovascular disease (CVD) risk factors, C-reactive protein, and history of CVD, the medians (interquartile range) were 133.08 (90.39, 204.15) in patients with CKD vs. 114.17 (72.45, 170.32) pg/mL in controls without CKD ( p  = 0.002 for group difference) for VEGF-A; 3951.2 (2471.9, 6656.6) vs. 4270.5 (2763.7, 6537.2) pg/mL ( p  = 0.70) for angiopoietin-1; 25.87 (18.09, 47.90) vs. 36.55 (25.71, 61.10) ( p  = 0.0001) for angiopoietin-1/VEGF-A ratio; 147.81 (122.94, 168.79) vs. 144.16 (123.74, 168.05) ng/mL ( p  = 0.25) for VEGFR-1; 26.20 (22.67, 29.92) vs. 26.28 (23.10, 29.69) ng/mL ( p  = 0.31) for VEGFR-2; and 1.01 (0.79, 1.49)vs. 0.89 (0.58, 1.18) ng/mL ( p  = 0.01) for pentraxin-3, respectively. In addition, an elevated VEGF-A level and decreased angiopoietin-1/VEGF-A ratio were associated with increased odds of CKD. Conclusions These data indicate that plasma VEGF-A and pentraxin-3 levels were increased and the angiopoietin-1/VEGF-A ratio was decreased in patients with CKD. Future prospective studies are warranted to examine whether angiogenic factors play a role in progression of CKD.