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Chronic kidney disease (CKD), a major public health problem, is associated with decreased anabolic response to insulin contributing to protein-energy wasting. Targeted metabolic profiling of the response to oral glucose tolerance testing (OGTT) may help identify metabolic pathways contributing to disruptions to insulin response in CKD. Using targeted metabolic profiling, we examined plasma metabolome in 41 moderate-to-severe non-diabetic CKD patients with estimated glomerular filtration rate (eGFR)2 (38.9±12.7) and 20 healthy controls with normal eGFR (87.2±17.7) before and after 2h of 75g oral glucose load. Compared to controls, CKD participants had higher lactate: pyruvate (L:P) ratio both at fasting and after oral glucose challenge. Total energy production estimated through GTP:GDP ratio was impaired during OGTT despite similar fasting GTP:GDP ratio. CKD group had sustained elevation of vitamin B family members, TCA cycle metabolites, and purine nucleotides in response to glucose challenge. Metabolic profiling in response to OGTT suggests a broad disruption of mitochondrial energy metabolism in CKD patients. These findings motivate further investigation into insulin sensitizers in patients with non-diabetic CKD and their impact on energy metabolism.

BackgroundPatients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles as compared with the general population. Understanding the lipid composition of HDL may provide mechanistic insight. We tested associations of estimated glomerular filtration rate (eGFR) and albuminuria with relative HDL abundance of ceramides, sphingomyelins, and phosphatidylcholines in participants with CKD.MethodsWe studied 490 participants with CKD from the Seattle Kidney Study. HDL was isolated from plasma; targeted lipidomics was used to quantify the relative abundance of ceramides, sphingomyelins, and phosphatidylcholines per 10 µg of total HDL protein. We evaluated the associations of eGFR and albuminuria with levels of individual lipids and lipid classes (including 7 ceramides, 6 sphingomyelins, and 24 phosphatidylcholines) using multivariable linear regression, controlling for multiple comparisons via the false discovery rate.ResultsThe mean (SD) eGFR was 45 (24) mL/min/1.73 m2; the median (IQR[interquartile range]) albuminuria was 108 (16, 686) mg/g (12.2 [1.8, 77.6] mg/mmol) urine creatinine. After adjusting for demographics, past medical history, laboratory values, and medication use, eGFR was not associated with higher relative abundance of any class of lipids or individual lipids. Greater albuminuria was significantly associated with a higher relative abundance of total ceramides and moderate–long R-chain sphingomyelins, ceramides 22:0 and 24:1, hexosylceramide 16:0, sphingomyelin 16:0, and phosphatidylcholines 29:0, 30:1, and 38:2; the strongest association was for hexosylceramide 16:0 (increase per doubling of urine albumin to creatinine ratio 0.022 (95% CI, 0.012–0.032).ConclusionsGreater albuminuria was significantly associated with specific alterations in the lipid composition of HDL in participants with CKD.

BACKGROUND: Reduced 25-hydroxyvitamin D (25[OH]D) metabolism and secondary hyperparathyroidism are common with lower estimated glomerular filtration rate (eGFR) and may contribute to cardiovascular disease and cancer risk. METHODS: We assessed for heterogeneity by baseline eGFR of the effects of vitamin D(3) on cardiovascular and cancer outcomes in the Vitamin D and Omega-3 Trial (VITAL). Participants were randomized to 2000 IU vitamin D(3) and/or 1 g Ω-3 fatty acids daily using a placebo-controlled, two-by-two factorial design (5.3 years follow-up). Primary study end points were incident major cardiovascular events and invasive cancer. Changes in serum 25(OH)D and parathyroid hormone (PTH) were examined. RESULTS: Baseline eGFR was available for 15,917 participants. Participants’ mean age was 68 years, and 51% were women. Vitamin D(3) resulted in higher serum 25(OH)D compared with placebo (difference in change 12.5 ng/ml; 95% CI, 12 to 13.1 ng/ml), without heterogeneity by eGFR (P interaction, continuous eGFR=0.2). Difference in change in PTH between vitamin D(3) and placebo was larger with lower eGFR (P interaction=0.05): –6.9 (95% CI, –10.5 to –3.4), –5.8 (95% CI, –8.3 to –3.4), –4 (95% CI, –5.9 to –2.2), and –3.8 (95% CI, –5.6 to –2) pg/ml for eGFR

Secretion of solutes by the proximal tubules represents an intrinsic kidney function not directly reflected by the glomerular filtration rate (GFR). The early loss of secretory clearance may reflect unrecognized kidney dysfunction, portending future disease progression.We designed a nested case-control study within the Jackson Heart Study (JHS), a prospective study of African American adults in Mississippi, to associate baseline differences in proximal tubular secretion of 5 endogenously produced solutes with future estimated glomerular rate (eGFR) decline. We matched 127 pairs by creatinine-eGFR, age, diabetes, and sex among the patients who provided a 24-hour urine collection; cases had a ≥25% decline in eGFR compared to 10% in controls over 10 years of follow-up. We measured baseline plasma and urine concentrations of secretory solutes using liquid chromatography-mass spectrometry to determine the odds ratio of kidney disease progression.Mean age was 60 years; 76% were women; 30% had diabetes; mean baseline eGFR was 94±20 ml/min per 1.73 mWe found that in this community-based study of adults without significant kidney disease, lower proximal tubular secretory solute clearance is associated with future eGFR decline.

Heart failure (HF) is common in chronic kidney disease (CKD); identifying patients with CKD at high risk for HF may guide clinical care. We assessed the prognostic value of cardiac biomarkers and echocardiographic variables for 10-year HF prediction compared with a published clinical HF prediction equation in a cohort of participants with CKD.We studied 2147 Chronic Renal Insufficiency Cohort (CRIC) participants without prior HF with complete clinical, cardiac biomarker (N-terminal brain natriuretic peptide [NT-proBNP] and high sensitivity troponin-T [hsTnT]), and echocardiographic data (left ventricular mass [LVM] and left ventricular ejection fraction [LVEF] data). We compared the discrimination of the 11-variable Atherosclerosis Risk in Communities (ARIC) HF prediction equation with LVM, LVEF, hsTnT, and NT-proBNP to predict 10-year risk of hospitalization for HF using a Fine and Gray modeling approach. We separately evaluated prediction of HF with preserved and reduced LVEF (LVEF ≥50% and 50%, respectively). We assessed discrimination with internally valid C-indices using 10-fold cross-validation.Participants' mean (SD) age was 59 (11) years, 53% were men, 43% were Black, and mean (SD) estimated glomerular filtration rate (eGFR) was 44 (16) ml/min per 1.73 mThe ARIC HF prediction model for 10-year HF risk had modest discrimination among adults with CKD. NT-proBNP and hsTnT discriminated better than the ARIC HF model and at least as well as a model with echocardiographic variables. HF clinical prediction models tailored to adults with CKD are needed. Until then, measurement of NT-proBNP and hsTnT may be a low-burden approach to predicting HF in this population, as they offer moderate discrimination.

RATIONALE & OBJECTIVE: The utility of conventional upper reference limits (URL) for N-terminal pro brain natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hsTnT) in chronic kidney disease (CKD) remains debated. We analyzed the distribution of hsTnT and NT-proBNP in people with CKD in ambulatory settings to examine the diagnostic value of conventional URL in this population. STUDY DESIGN: Observational study. SETTING & PARTICIPANTS: We studied participants of the Chronic Renal Insufficiency Cohort with CKD and no self-reported history of cardiovascular disease (CVD). EXPOSURE: Estimated glomerular filtration rate (eGFR). OUTCOMES: NT-proBNP and hsTnT at baseline. ANALYTICAL APPROACH:. We described the proportion of participants above the conventional URL for NT-proBNP (125 pg/ml) and hsTnT (14 ng/L) overall, and by eGFR. We then estimated 99(th) percentile URL for NT-proBNP and hsTnT. Using quantile regression of the 99(th) percentile, we modeled the association of eGFR with NT-proBNP and hsTnT. RESULTS: Among 2,312 CKD participants, 40% and 43% had levels of NT-proBNP and hsTnT above conventional URL, respectively. In those with eGFR

OBJECTIVE Intensive glycemic control reduces the risk of kidney, retinal, and neurologic complications in type 1 diabetes (T1D), but whether it reduces the risk of lower-extremity complications is unknown. We examined whether former intensive versus conventional glycemic control among Diabetes Control and Complications Trial (DCCT) participants with T1D reduced the long-term risk of diabetic foot ulcers (DFUs) and lower-extremity amputations (LEAs) in the subsequent Epidemiology of Diabetes Interventions and Complications (EDIC) study. RESEARCH DESIGN AND METHODS DCCT participants (n = 1,441) completed 6.5 years on average of intensive versus conventional diabetes treatment, after which 1,408 were enrolled in EDIC and followed annually over 23 years for DFU and LEA occurrences by physical examination. Multivariable Cox proportional hazard regression models estimated associations of DCCT treatment assignment and time-updated exposures with DFU or LEA. RESULTS Intensive versus conventional glycemic control was associated with a significant risk reduction for all DFUs (hazard ratio 0.77 [95% CI 0.60, 0.97]) and a similar magnitude but nonsignificant risk reduction for first-recorded DFUs (0.78 [0.59, 1.03]) and first LEAs (0.70 [0.36, 1.36]). In adjusted Cox models, clinical neuropathy, lower sural nerve conduction velocity, and cardiovascular autonomic neuropathy were associated with higher DFU risk; estimated glomerular filtration rate CONCLUSIONS Early intensive glycemic control decreases long-term DFU risk, the most important antecedent in the causal pathway to LEA.

Background and objectives Atrial fibrillation (AF) is common in CKD and associated with poor kidney and cardiovascular outcomes. Prediction models developed using novel methods may be useful to identify patients with CKD at highest risk of incident AF. We compared a previously published prediction model with models developed using machine learning methods in a CKD population. Design, setting, participants, & measurements We studied 2766 participants in the Chronic Renal Insufficiency Cohort study without prior AF with complete cardiac biomarker (N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T) and clinical data. We evaluated the utility of machine learning methods as well as a previously validated clinical prediction model (Cohorts for Heart and Aging Research in Genomic Epidemiology [CHARGE]-AF, which included 11 predictors, using original and re-estimated coefficients) to predict incident AF. Discriminatory ability of each model was assessed using the ten-fold cross-validated C-index; calibration was evaluated graphically and with the Gronnesby and Borgan test. Results Mean (SD) age of participants was 57 (11) years, 55% were men, 38% were Black, and mean (SD) eGFR was 45 (15) ml/min per 1.73 m2; 259 incident AF events occurred during a median of 8 years of follow-up. The CHARGE-AF prediction equation using original and re-estimated coefficients had C-indices of 0.67 (95% confidence interval, 0.64 to 0.71) and 0.67 (95% confidence interval, 0.64 to 0.70), respectively. A likelihood-based boosting model using clinical variables only had a C-index of 0.67 (95% confidence interval, 0.64 to 0.70); adding N-terminal pro-B-type natriuretic peptide, high-sensitivity troponin T, or both biomarkers improved the C-index by 0.04, 0.01, and 0.04, respectively. In addition to N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T, the final model included age, non-Hispanic Black race/ethnicity, Hispanic race/ethnicity, cardiovascular disease, chronic obstructive pulmonary disease, myocardial infarction, peripheral vascular disease, use of angiotensin-converting enzyme inhibitor/angiotensin receptor blockers, calcium channel blockers, diuretics, height, and weight. Conclusions Using machine learning algorithms, a model that included 12 standard clinical variables and cardiac-specific biomarkers N-terminal pro-B-type natriuretic peptide and high-sensitivity troponin T had moderate discrimination for incident AF in a CKD population.

Rationale & Objective Circulating cardiac biomarkers may signal potential mechanistic pathways involved in heart failure (HF) and atrial fibrillation (AF). Single measures of circulating cardiac biomarkers are strongly associated with incident HF and AF in chronic kidney disease (CKD). We tested the associations of longitudinal changes in the N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP), high-sensitivity troponin T (hsTnT), galectin-3, growth differentiation factor 15 (GDF-15), and soluble ST-2 (sST-2) with incident HF and AF in patients with CKD. Study Design Observational, case-cohort study design. Setting & Participants Adults with CKD enrolled in the Chronic Renal Insufficiency Cohort study. Exposures Biomarkers were measured at baseline and 2 years later among those without kidney failure. We created 3 categories of absolute change in each biomarker: the lowest quartile, the middle 2 quartiles, and the top quartile. Outcomes The primary outcomes were incident HF and AF. Analytical Approach Cox proportional hazards regression models were used to test the associations of the change categories of each cardiac biomarker with each outcome (with the middle 2 quartiles of change as the referent group), adjusting for potential confounders and baseline concentrations of each biomarker. Results The incident HF analysis included 789 participants (which included 138 incident HF cases), and the incident AF analysis included 774 participants (123 incident AF cases). In multivariable models, the top quartile of NT-proBNP change (>232 pg/mL over 2 years) was associated with increased risk of incident HF (HR, 1.79 [95% CI, 1.06-3.04]) and AF (HR, 2.32 [95% CI, 1.37-3.93]) compared with the referent group. Participants in the top quartile of sST2 change (>3.37 ng/mL over 2 years) had significantly greater risk of incident HF (HR, 1.89 [95% CI, 1.13-3.16]), whereas those in the bottom quartile (≤−3.78 ng/mL over 2 years) had greater risk of incident AF (HR, 2.43 [95% CI, 1.39-4.22]) compared with the 2 middle quartiles. There was no association of changes in hsTnT, galectin-3, or GDF-15 with incident HF or AF. Limitations Observational study. Conclusions In CKD, increases in NT-proBNP were significantly associated with greater risk of incident HF and AF, and increases in sST2 were associated with HF. Further studies should investigate whether these markers of subclinical cardiovascular disease can be modified to reduce the risk of cardiovascular disease in CKD.

Background Analyses of blood biomarkers involved in the host response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral infection can reveal distinct biological pathways and inform development and testing of therapeutics for COVID-19. Our objective was to evaluate host endothelial, epithelial and inflammatory biomarkers in COVID-19. Methods We prospectively enrolled 171 ICU patients, including 78 (46%) patients positive and 93 (54%) negative for SARS-CoV-2 infection from April to September, 2020. We compared 22 plasma biomarkers in blood collected within 24 h and 3 days after ICU admission. Results In critically ill COVID-19 and non-COVID-19 patients, the most common ICU admission diagnoses were respiratory failure or pneumonia, followed by sepsis and other diagnoses. Similar proportions of patients in both groups received invasive mechanical ventilation at the time of study enrollment. COVID-19 and non-COVID-19 patients had similar rates of acute respiratory distress syndrome, severe acute kidney injury, and in-hospital mortality. While concentrations of interleukin 6 and 8 were not different between groups, markers of epithelial cell injury (soluble receptor for advanced glycation end products, sRAGE) and acute phase proteins (serum amyloid A, SAA) were significantly higher in COVID-19 compared to non-COVID-19, adjusting for demographics and APACHE III scores. In contrast, angiopoietin 2:1 (Ang-2:1 ratio) and soluble tumor necrosis factor receptor 1 (sTNFR-1), markers of endothelial dysfunction and inflammation, were significantly lower in COVID-19 (p Conclusions These studies demonstrate that, unlike other well-studied causes of critical illness, endothelial dysfunction may not be characteristic of severe COVID-19 early after ICU admission. Pathways resulting in elaboration of acute phase proteins and inducing epithelial cell injury may be promising targets for therapeutics in COVID-19.

BACKGROUND: Serum 25-hydroxyvitamin D [25(OH)D] concentration is an indicator of vitamin D exposure, but it is also influenced by clinical characteristics that affect 25(OH)D production and clearance. Vitamin D is the precursor to 25(OH)D but is analytically challenging to measure in biological specimens. OBJECTIVES: We aimed to develop and validate a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for quantification of vitamins D(3) and D(2) in serum and to explore the potential of circulating vitamin D as a biomarker of exposure in supplementation trials. METHODS: The method was validated using guideline C62-A from the Clinical and Laboratory Standards Institute and was applied in 2 pilot clinical trials of oral vitamin D(3) supplementation. Pilot study 1 included 22 adults randomly assigned to placebo or 2000 IU/d. Blood was collected at baseline, 1, 3, 6, and 12 mo. Pilot study 2 included 15 adults randomly assigned to 2000 or 4000 IU/d. Blood and subcutaneous (SUBQ) adipose tissue were collected at baseline and 3 mo. RESULTS: In study 1, mean change (baseline to 3 mo) in serum vitamin D(3) was −0.1 ng/mL in the placebo group and 6.8 ng/mL in the 2000 IU/d group (absolute difference: 6.9; 95% CI: 4.5, 9.3 ng/mL). In study 2, mean change (baseline to 3 mo) in serum vitamin D(3) was 10.4 ng/mL in the 2000 IU/d group and 22.2 ng/mL in the 4000 IU/d group (fold difference: 2.15; 95% CI: 1.40, 3.37). Serum and adipose tissue vitamin D(3) concentrations were correlated, and the dose-response of vitamin D(3) in adipose mirrored that in serum. CONCLUSIONS: We validated a sensitive, robust, and high-throughput LC-MS/MS method to quantify vitamins D(3) and D(2) in serum. Serum and SUBQ adipose tissue vitamin D(3) concentrations increased proportionally to dose with 3 mo of daily supplementation. These trials were registered at clinicaltrials.gov as NCT00552409 (pilot study 1) and NCT01477034 (pilot study 2).

Introduction Cardiovascular disease (CVD) is the leading cause of mortality among individuals with chronic kidney disease (CKD). Cardiac biomarkers of myocardial distention, injury, and inflammation may signal unique pathways underlying CVD in CKD. In this analysis, we studied the association of baseline levels and changes in 4 traditional and novel cardiac biomarkers with risk of all-cause, CV, and non-CV mortality in a large cohort of patients with CKD. Methods Among 3664 adults with CKD enrolled in the Chronic Renal Insufficiency Cohort Study, we conducted a cohort study to examine the associations of baseline levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP), cardiac high-sensitivity troponin T (hsTnT), growth differentiation factor−15 (GDF-15), and soluble ST-2 (sST-2) with risks of all-cause and cardiovascular (CV) mortality. Among a subcohort of 842 participants, we further examined the associations between change in biomarker levels over 2 years with risk of all-cause mortality. We used Cox proportional hazards regression models and adjusted for demographics, kidney function measures, cardiovascular risk factors, and medication use. Results After adjustment, elevated baseline levels of each cardiac biomarker were associated with increased risk of all-cause mortality: NT-proBNP (hazard ratio [HR] = 1.92, 95% confidence interval [CI] = 1.73−2.12); hsTnT (HR = 1.62, 95% CI = 1.48, 1.78]); GDF-15 (HR = 1.61, 95% CI = 1.46−1.78]); and sST-2 (HR = 1.26, CI = 1.16−1.37). Higher baseline levels of all 4 cardiac biomarkers were also associated with increased risk of CV. Declines in NT-proBNP (adjusted HR = 0.55, 95% CI = 0.36−0.86) and sST2 (HR = 0.55, 95% CI = 0.36−0.86]) over 2 years were associated with lower risk of all-cause mortality. Conclusion In a large cohort of CKD participants, elevations of NT-proBNP, hsTnT, GDF-15, and sST-2 were independently associated with greater risks of all-cause and CV mortality., Graphical abstract

BACKGROUND: Conversion of 25-hydroxyvitamin D (25[OH]D) to the active form of vitamin D occurs primarily in the kidney. Observational studies suggest 25(OH)D clearance from the circulation differs by kidney function and race. However, these potential variations have not been tested using gold-standard methods. METHODS: We administered intravenous, deuterated 25(OH)D(3) (d-25[OH]D(3)) in a pharmacokinetic study of 87 adults, including 43 with normal eGFR (≥60 ml/min per 1.73 m(2)), 24 with nondialysis CKD (eGFR

Context The kidneys eliminate insulin via glomerular and peritubular mechanisms; consequently, the kidney contribution to insulin clearance may be underestimated by the glomerular filtration rate (GFR) alone. Objective To determine associations of tubular secretory clearance with whole-body insulin clearance and sensitivity in a dedicated study of glucose and insulin metabolism. Design, Setting, and Participants We performed an ancillary, cross-sectional study of tubular secretion in the Study of Glucose and Insulin in Renal Disease (SUGAR). Hyperinsulinemic-euglycemic clamps were performed in 57 nondiabetic persons with chronic kidney disease and 38 persons without kidney disease. Intervention We measured plasma and 24-hour urine concentrations of endogenous solutes primarily eliminated by tubular secretion. Kidney clearances of secretory solutes were calculated as the amount of blood fully cleared of that solute per minute. Main Outcome Measures Whole-body insulin clearance, insulin sensitivity. Results Mean whole-body insulin clearance was 924 ± 228 mL/min. After adjustment for age, sex, Black race, fat and fat-free mass, each 20% lower estimated GFR was associated with a 13 mL/min lower insulin clearance (95% confidence interval [CI], 2-24 mL/min lower). Each 20% lower clearance of isovalerylglycine and xanthosine were associated with a 16 mL/min lower (95% CI, 5-26 mL/min lower) and 19 mL/min lower (95% CI, 7-31 mL/min lower) insulin clearance, respectively. Neither estimated GFR nor secretory solute clearances were associated with insulin sensitivity after adjustment. Conclusions These results highlight the importance of tubular secretory pathways to insulin elimination but suggest that kidney functions in aggregate contribute only modestly to systemic insulin clearance.

Background The secretion of organic solutes by the proximal tubules is an essential intrinsic kidney function. However, the clinical significance of the kidney's clearance of tubular secretory solutes is uncertain. Methods In this prospective cohort study, we evaluated 3416 participants with CKD from the Chronic Renal Insufficiency Cohort (CRIC) study. We measured plasma and 24-hour urine concentrations of endogenous candidate secretory solutes at baseline, using targeted liquid chromatography-tandem mass spectrometry. The study defined CKD progression by a ≥50% decline in the eGFR, initiation of maintenance dialysis, or kidney transplantation. We used Cox proportional hazards regression to test associations of secretory-solute clearances with CKD progression and mortality, adjusting for eGFR, albuminuria, and other confounding characteristics. Results Participants in this ancillary study had a mean age of 58 years and 41% were black; the median eGFR was 43 ml/min per 1.73 m2. After adjustment, lower kidney clearances of six solutes-kynurenic acid, pyridoxic acid, indoxyl sulfate, xanthosine, isovalerylglycine, and cinnamoylglycine-were associated with significantly greater risks of CKD progression, with clearance of kynurenic acid, a highly protein-bound solute, having the strongest association. Lower clearances of isovalerylglycine, tiglylglycine, hippurate, and trimethyluric acid were significantly associated with all-cause mortality after adjustment. Conclusions We found lower kidney clearances of endogenous secretory solutes to be associated with CKD progression and all-cause mortality, independent of eGFR and albuminuria. This suggests that tubular clearance of secretory solutes provides additional information about kidney health beyond measurements of glomerular function alone.

Background Phosphate binders are commonly used in the treatment of patients with hyperphosphatemia. While phosphate binders are used to lower phosphate, the effects of specific phosphate binder types on vitamin D metabolism are unknown. Methods We performed a secondary analysis of the Phosphate Normalization Trial in which patients with moderate to advanced chronic kidney disease were randomized to receive either placebo, sevelamer carbonate, lanthanum carbonate or calcium acetate for 9 months. We evaluated changes in serum concentrations of vitamin D metabolites including 24,25-dihydroxyvitamin D3 [24,25(OH)2D3], 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the ratio of 24,25(OH)2D3 to 25-hydroxyvitamin D [the vitamin D metabolite ratio (VMR)] and the ratio of serum 1,25(OH)2D to 25-hydroxyvitamin D. Results Compared with placebo, randomization to the calcium acetate arm was associated with a 0.6 ng/mL (95% CI 0.2, 1) and 13.5 pg/ng (95% CI 5.5, 21.5) increase in 24,25(OH)2D and VMR, respectively, and a 5.2 pg/mL (95% CI 1.1, 9.4) reduction in 1,25(OH)2D. Randomization to sevelamer carbonate was associated with a 0.5 ng/mL (95% CI −0.9, −0.1) and 11.8 pg/ng (95% CI −20, −3.5) reduction in 24,25(OH)2D3 and VMR, respectively. There was no association of the sevelamer arm with the change in 1,25(OH)2D3, and randomization to lanthanum carbonate was not associated with a change in any of the vitamin D metabolites. Conclusion Administration of different phosphate binders to patients with moderate to severe CKD results in unique changes in vitamin D metabolism.

BACKGROUND AND OBJECTIVES: Residual kidney function is important to the health and wellbeing of patients with ESKD. We tested whether the kidney clearances of proximal tubular secretory solutes are associated with burden of uremic and heart failure symptoms among patients on peritoneal dialysis with residual kidney function. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We enrolled 29 patients on incident peritoneal dialysis with residual urine output >250 ml daily. We used targeted liquid chromatography-mass spectrometry to quantify plasma, 24-hour urine, and peritoneal dialysate concentrations of ten tubular secretory solutes. We calculated the kidney and peritoneal dialysis clearances of each secretory solute, creatinine, and urea, and we estimated a composite kidney and peritoneal secretion score. We assessed for uremic symptoms using the Dialysis Symptom Index and heart failure–related symptoms using the Kansas City Cardiomyopathy Questionnaire. We used linear regression to determine associations of composite secretory solute clearances and GFR(urea+Cr) with Dialysis Symptom Index symptom score and Kansas City Cardiomyopathy Questionnaire summary score. RESULTS: Mean residual kidney clearances of creatinine and urea were 8±5 and 9±6 ml/min per 1.73 m(2), respectively, and mean GFR(urea+Cr) was 8±5 ml/min per 1.73 m(2). The residual kidney clearances of most secretory solutes were considerably higher than creatinine and urea clearance, and also, they were higher than their respective peritoneal dialysis clearances. After adjustments for age and sex, each SD higher composite kidney secretion score was associated with an 11-point lower Dialysis Symptom Index score (95% confidence interval, −20 to −1; P=0.03) and a 12-point higher Kansas City Cardiomyopathy Questionnaire score (95% confidence interval, 0.5- to 23-point higher score; P=0.04). Composite peritoneal dialysis secretion score was not associated with either symptom assessment. CONCLUSIONS: Residual kidney clearances of secretory solutes are higher than peritoneal dialysis clearances. Kidney clearances of secretory solutes are associated with patient-reported uremic and heart failure–related symptoms.

Objective: Intensive glycemic control reduces risk of kidney, retinal, and neurologic complications in type 1 diabetes (T1D), but whether it reduces risk of lower extremity complications is unknown. We examined whether former intensive versus conventional glycemic control among Diabetes Control and Complications Trial (DCCT) participants with T1D reduced the long-term risk of diabetic foot ulcers (DFU) and lower extremity amputations (LEA) in the subsequent Epidemiology of Diabetes Interventions and Complications (EDIC) study. Research Design and Methods: DCCT participants [n=1441] completed 6.5 years on average of intensive vs conventional diabetes treatment, after which 1408 were enrolled in EDIC and followed annually over 23 years for DFU and LEA occurrences by physical examination. Multivariable Cox models estimated associations of DCCT treatment assignment and time-updated exposures with DFU or LEA. Results: Intensive versus conventional glycemic control was associated with a significant risk reduction for all DFU (Hazard Ratio [HR] 0.77, 95% CI 0.60 to 0.97), and a similar magnitude but nonsignificant risk reduction for first recorded DFU (HR 0.78, 95% CI 0.59 to 1.03) and first LEA (HR 0.70, 95% CI 0.36 to 1.36). In adjusted Cox models, clinical neuropathy, lower sural nerve conduction velocity and cardiovascular autonomic neuropathy were associated with higher DFU risk; eGFR < 60 mL/min/1.73 m2, albuminuria, and macular edema with higher LEA risk; and any retinopathy and greater time-weighted mean DCCT/EDIC HbA1c with higher risk of both outcomes (p Conclusions: Early intensive glycemic control decreases long-term DFU risk, the most important antecedent in the causal pathway to LEA.

BACKGROUND: Adjudication of inpatient AKI in the Systolic Blood Pressure Intervention Trial (SPRINT) was based on billing codes and admission and discharge notes. The purpose of this study was to evaluate the effect of intensive versus standard BP control on creatinine-based inpatient and outpatient AKI, and whether AKI was associated with cardiovascular disease (CVD) and mortality. METHODS: We linked electronic health record (EHR) data from 47 clinic sites with trial data to enable creatinine-based adjudication of AKI. Cox regression was used to evaluate the effect of intensive BP control on the incidence of AKI, and the relationship between incident AKI and CVD and all-cause mortality. RESULTS: A total of 3644 participants had linked EHR data. A greater number of inpatient AKI events were identified using EHR data (187 on intensive versus 155 on standard treatment) as compared with serious adverse event (SAE) adjudication in the trial (95 on intensive versus 61 on standard treatment). Intensive treatment increased risk for SPRINT-adjudicated inpatient AKI (HR, 1.51; 95% CI, 1.09 to 2.08) and for creatinine-based outpatient AKI (HR, 1.40; 95% CI, 1.15 to 1.70), but not for creatinine-based inpatient AKI (HR, 1.20; 95% CI, 0.97 to 1.48). Irrespective of the definition (SAE or creatinine based), AKI was associated with increased risk for all-cause mortality, but only creatinine-based inpatient AKI was associated with increased risk for CVD. CONCLUSIONS: Creatinine-based ascertainment of AKI, enabled by EHR data, may be more sensitive and less biased than traditional SAE adjudication. Identifying ways to prevent AKI may reduce mortality further in the setting of intensive BP control.

Background Acute hypoxemic respiratory failure (HRF) is associated with high morbidity and mortality, but its heterogeneity challenges the identification of effective therapies. Defining subphenotypes with distinct prognoses or biologic features can improve therapeutic trials, but prior work has focused on ARDS, which excludes many acute HRF patients. We aimed to characterize persistent and resolving subphenotypes in the broader HRF population. Methods In this secondary analysis of 2 independent prospective ICU cohorts, we included adults with acute HRF, defined by invasive mechanical ventilation and PaO2-to-FIO2 ratio ≤ 300 on cohort enrollment (n = 768 in the discovery cohort and n = 1715 in the validation cohort). We classified patients as persistent HRF if still requiring mechanical ventilation with PaO2-to-FIO2 ratio ≤ 300 on day 3 following ICU admission, or resolving HRF if otherwise. We estimated relative risk of 28-day hospital mortality associated with persistent HRF, compared to resolving HRF, using generalized linear models. We also estimated fold difference in circulating biomarkers of inflammation and endothelial activation on cohort enrollment among persistent HRF compared to resolving HRF. Finally, we stratified our analyses by ARDS to understand whether this was driving differences between persistent and resolving HRF. Results Over 50% developed persistent HRF in both the discovery (n = 386) and validation (n = 1032) cohorts. Persistent HRF was associated with higher risk of death relative to resolving HRF in both the discovery (1.68-fold, 95% CI 1.11, 2.54) and validation cohorts (1.93-fold, 95% CI 1.50, 2.47), after adjustment for age, sex, chronic respiratory illness, and acute illness severity on enrollment (APACHE-III in discovery, APACHE-II in validation). Patients with persistent HRF displayed higher biomarkers of inflammation (interleukin-6, interleukin-8) and endothelial dysfunction (angiopoietin-2) than resolving HRF after adjustment. Only half of persistent HRF patients had ARDS, yet exhibited higher mortality and biomarkers than resolving HRF regardless of whether they qualified for ARDS. Conclusion Patients with persistent HRF are common and have higher mortality and elevated circulating markers of lung injury compared to resolving HRF, and yet only a subset are captured by ARDS definitions. Persistent HRF may represent a clinically important, inclusive target for future therapeutic trials in HRF.

BACKGROUND AND OBJECTIVES: Although patient-reported symptoms often precede acute presentations of cardiovascular disease, patients with nondialysis-requiring CKD are less likely to have typical symptoms of atherosclerotic disease when presenting with acute myocardial infarction. However, the associations between typical atherosclerotic symptoms and subsequent risk of myocardial infarction are unknown in ambulatory patients with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: To determine whether typical atherosclerotic symptoms are associated with risk for subsequent myocardial infarction in people with CKD, we examined participants from the Chronic Renal Insufficiency Cohort Study. Chest pain, shortness of breath, and inability to climb stairs were evaluated annually using the Kidney Disease Quality of Life Instrument. Associations between categorical time-updated symptoms and physician-adjudicated incident myocardial infarction were assessed using Cox regression models. RESULTS: Among 3910 participants (mean age of 58±11 years; mean eGFR =44±15 ml/min per 1.73 m(2)), there were 476 incident myocardial infarctions over a median follow-up period of 10.4 years (interquartile range, 5.36–12.6 years). Median time from symptom assessment to incident myocardial infarction was 213 days (interquartile range, 111–333 days). Compared with no symptoms, mild, and moderate or worse, symptoms of chest pain (hazard ratio, 1.30; 95% confidence interval, 1.01 to 1.67; and hazard ratio, 1.70; 95% confidence interval, 1.27 to 2.27, respectively) and shortness of breath (hazard ratio, 1.37; 95% confidence interval, 1.10 to 1.70; and hazard ratio, 1.33; 95% confidence interval, 1.05 to 1.69, respectively) were significantly associated with greater risks for subsequent myocardial infarction. Participants reporting mild and severe limitations in climbing stairs (versus no limitation) had significantly higher adjusted risk of myocardial infarction (hazard ratio, 1.44; 95% confidence interval, 1.10 to 1.89; and hazard ratio, 1.89; 95% confidence interval, 1.44 to 2.49, respectively). CONCLUSIONS: In a large ambulatory cohort of adults with CKD, symptoms of atherosclerotic cardiovascular disease were strongly associated with a higher risk for subsequent myocardial infarction. PODCAST: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2022_03_17_CJN12080921.mp3

To determine whether biomarkers of endothelial activation and inflammation provide added value for prediction of in-hospital mortality within 28 days when combined with physician judgment in critically ill emergency department patients.Prospective, observational study.Two urban, academic emergency departments, with ≈80,000 combined annual visits, between June 2016 and December 2017.Admitted patients, greater than 17 years old, with two systemic inflammatory response syndrome criteria and organ dysfunction, systolic blood pressure less than 90 mm Hg, or lactate greater than 4.0 mmol/L. Patients with trauma, intracranial hemorrhage known prior to arrival, or without available blood samples were excluded.Emergency department physicians reported likelihood of in-hospital mortality (0-100%) by survey at hospital admission. Remnant EDTA blood samples, drawn during the emergency department stay, were used to measure angiopoietin-1, angiopoietin-2, tumor necrosis factor receptor-1, interleukin-6, and interleukin-8.We screened 421 patients and enrolled 314. The primary outcome of in-hospital mortality within 28 days occurred in 31 (9.9%). When predicting the primary outcome, the best biomarker model included angiopoietin-2 and interleukin-6 and performed moderately well (area under the curve, 0.72; 95% CI, 0.69-0.75), as did physician judgment (area under the curve, 0.78; 95% CI, 0.74-0.82). Combining physician judgment and biomarker models improved performance (area under the curve, 0.85; 95% CI, 0.82-0.87), with area under the curve change of 0.06 (95% CI, 0.04-0.09; p0.01) compared with physician judgment alone.Predicting in-hospital mortality within 28 days among critically ill emergency department patients may be improved by including biomarkers of endothelial activation and inflammation in combination with emergency department physician judgment.

BACKGROUND AND OBJECTIVES: In autosomal dominant polycystic kidney disease (ADPKD), the GFR often remains normal despite significant nephron loss. Proximal tubular secretory clearance may be reduced in ADPKD before detectable changes in GFR. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We used targeted mass spectrometry to quantify secretory solutes from blood and urine samples from 31 patients with ADPKD and preserved GFR (mean eGFR =111±11 ml/min per 1.73 m(2)) and 25 healthy control individuals as well as from 95 patients with ADPKD and reduced GFR (mean eGFR =53±21 ml/min per 1.73 m(2)) and 92 individuals with non-ADPKD CKD. We used linear regression to compare the fractional excretion of each solute between ADPKD and control groups. Among 112 patients with ADPKD, we used linear regression to determine associations of solute fractional excretion with height-adjusted total kidney volume. RESULTS: After adjusting for demographics, clinical characteristics, and kidney function measures, the fractional excretions of three secretory solutes were lower in patients with ADPKD and preserved GFR compared with healthy individuals: 52% lower cinnamoylglycine excretion (95% confidence interval, 24% to 70%), 53% lower tiglylglycine excretion (95% confidence interval, 23% to 71%), and 91% lower xanthosine excretion (95% confidence interval, 83% to 95%). In addition to lower excretions of tiglylglycine and xanthosine, patients with ADPKD and reduced GFR also demonstrated 37% lower dimethyluric acid excretion (95% confidence interval, 21% to 50%), 58% lower hippurate excretion (95% confidence interval, 48% to 66%), 48% lower isovalerylglycine excretion (95% confidence interval, 37% to 56%), and 31% lower pyridoxic acid excretion (95% confidence interval, 16% to 42%) compared with patients with non-ADPKD CKD and comparable eGFR. Among patients with ADPKD, solute fractional excretions were not associated with differences in kidney volume. CONCLUSIONS: Patients with ADPKD and preserved and reduced GFR demonstrate lower tubular secretory solute excretion compared with healthy controls and patients with non-ADPKD CKD. Our results suggest that tubular secretion is impaired in ADPKD independent of GFR.

Objective— Albuminuria is an important risk factor for cardiovascular disease in diabetes mellitus. We determined whether albuminuria associates with alterations in the proteome of HDL (high-density lipoprotein) of subjects with type 1 diabetes mellitus and whether those alterations associated with coronary artery calcification. Approach and Results— In a cross-sectional study of 191 subjects enrolled in the DCCT (Diabetes Control and Complications Trial)/EDIC study (Epidemiology of Diabetes Interventions and Complications), we used isotope dilution tandem mass spectrometry to quantify 46 proteins in HDL. Stringent statistical analysis demonstrated that 8 proteins associated with albuminuria. Two of those proteins, AMBP (α1-microglobulin/bikunin precursor) and PTGDS (prostaglandin-H2 D-isomerase), strongly and positively associated with the albumin excretion rate ( P −6 ). Furthermore, PON (paraoxonase) 1 and PON3 levels in HDL strongly and negatively associated with the presence of coronary artery calcium, with odds ratios per 1-SD difference of 0.63 (95% CI, 0.43–0.92; P =0.018) for PON1 and 0.59 (95% CI, 0.40–0.87; P =0.0079) for PON3. Only 1 protein, PON1, associated with both albumin excretion rate and coronary artery calcification. Conclusions— Our observations indicate that the HDL proteome is remodeled in type 1 diabetes mellitus subjects with albuminuria. Moreover, low concentrations of the antiatherosclerotic protein PON1 in HDL associated with both albuminuria and coronary artery calcification, raising the possibility that alterations in HDL protein cargo mediate, in part, the known association of albuminuria with cardiovascular risk in type 1 diabetes mellitus. Visual Overview— An online visual overview is available for this article.

We propose a general class of 2-phase epidemiologic study designs for quantitative, longitudinal data that are useful when phase 1 longitudinal outcome and covariate data are available but data on the exposure (e.g., a biomarker) can only be collected on a subset of subjects during phase 2. To conduct a study using a design in the class, one first summarizes the longitudinal outcomes by fitting a simple linear regression of the response on a time-varying covariate for each subject. Sampling strata are defined by splitting the estimated regression intercept or slope distributions into distinct (low, medium, and high) regions. Stratified sampling is then conducted from strata defined by the intercepts, by the slopes, or from a mixture. In general, samples selected with extreme intercept values will yield low variances for associations of time-fixed exposures with the outcome and samples enriched with extreme slope values will yield low variances for associations of time-varying exposures with the outcome (including interactions with time-varying exposures). We describe ascertainment-corrected maximum likelihood and multiple-imputation estimation procedures that permit valid and efficient inferences. We embed all methodological developments within the framework of conducting a substudy that seeks to examine genetic associations with lung function among continuous smokers in the Lung Health Study (United States and Canada, 1986–1994).

Background The arteriovenous fistula (AVF) is central to haemodialysis treatment, but up to half of surgically created AVF fail to mature. Chronic kidney disease often leads to mineral metabolism disturbances that may interfere with AVF maturation through adverse vascular effects. This study tested associations between mineral metabolism markers and vein histology at AVF creation and unassisted and overall clinical AVF maturation. Methods Concentrations of fibroblast growth factor 23, parathyroid hormone, calcium, phosphate, and vitamin D metabolites: 1,25(OH)2D, 24,25(OH)2D, 25(OH)D, and bioavailable 25(OH)D were measured in pre-operative serum samples from 562 of 602 participants in the Haemodialysis Fistula Maturation Study, a multicentre, prospective cohort study of patients undergoing surgical creation of an autologous upper extremity AVF. Unassisted and overall AVF maturation were ascertained for 540 and 527 participants, respectively, within nine months of surgery or four weeks of dialysis initiation. Study personnel obtained vein segments adjacent to the portion of the vein used for anastomosis, which were processed, embedded, and stained for measurement of neointimal hyperplasia, calcification, and collagen deposition in the medial wall. Results Participants in this substudy were 71% male, 43% black, and had a mean age of 55 years. Failure to achieve AVF maturation without assistance occurred in 288 (53%) participants for whom this outcome was determined. In demographic and further adjusted models, mineral metabolism markers were not significantly associated with vein histology characteristics, unassisted AVF maturation failure, or overall maturation failure, other than a biologically unexplained association of higher 24,25(OH)2D with overall failure. This exception aside, associations were non-significant for continuous and categorical analyses and relevant subgroups. Conclusions Serum concentrations of measured mineral metabolites were not substantially associated with major histological characteristics of veins in patients undergoing AVF creation surgery, or with AVF maturation failure, suggesting that efforts to improve AVF maturation rates should increase attention to other processes such as vein mechanics, anatomy, and cellular metabolism among end stage renal disease patients.

BACKGROUND AND OBJECTIVES: Among people with diabetes mellitus, CKD may promote hypoglycemia through altered clearance of glucose-lowering medications, decreased kidney gluconeogenesis, and blunted counter-regulatory response. We conducted a prospective observational study of hypoglycemia among 105 individuals with type 2 diabetes treated with insulin or a sulfonylurea using continuous glucose monitors. DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS: We enrolled 81 participants with CKD, defined as eGFR

Introduction Hypertensive nephrosclerosis is among the leading causes of end-stage renal disease, but its pathophysiology is poorly understood. We wanted to explore early metabolic changes using gene expression and targeted metabolomics analysis. Methods We analyzed gene expression in kidneys biopsied from 20 patients with nephrosclerosis and 31 healthy controls with an Affymetrix array. Thirty-one amino acids were measured by liquid chromatography coupled with mass spectrometry (LC-MS) in urine samples from 62 patients with clinical hypertensive nephrosclerosis and 33 age- and sex-matched healthy controls, and major findings were confirmed in an independent cohort of 45 cases and 15 controls. Results Amino acid catabolism and synthesis were strongly underexpressed in hypertensive nephrosclerosis (13- and 7-fold, respectively), and these patients also showed gene expression patterns indicating decreased fatty acid oxidation (12-fold) and increased interferon gamma (10-fold) and cellular defense response (8-fold). Metabolomics analysis revealed significant distribution differences in 11 amino acids in hypertensive nephrosclerosis, among them tyrosine, phenylalanine, dopamine, homocysteine, and serine, with 30% to 70% lower urine excretion. These findings were replicated in the independent cohort. Integrated gene-metabolite pathway analysis showed perturbations of renal dopamine biosynthesis. There were also significant differences in homocysteine/methionine homeostasis and the serine pathway, which have strong influence on 1-carbon metabolism. Several of these disturbances could be interconnected through reduced regeneration of tetrahydrofolate and tetrahydrobiopterin. Conclusion Early hypertensive nephrosclerosis showed perturbations of intrarenal biosynthesis of dopamine, which regulates natriuresis and blood pressure. There were also disturbances in serine/glycine and methionine/homocysteine metabolism, which may contribute to endothelial dysfunction, atherosclerosis, and renal fibrosis., Graphical abstract

We investigated changes in and factors affecting American adolescents' subjective wellbeing during the early months (April - August 2020) of the coronavirus pandemic in the United States. Twenty-one teens (14 - 19 years) participated in interviews at the start and end of the study and completed ecological momentary assessments three times per week between the interviews. There was an aggregate trend toward increased wellbeing, with considerable variation within and across participants. Teens reported greater reliance on networked technologies as their unstructured time increased during lockdown. Using multilevel growth modeling, we found that how much total time teens spent with technology had less bearing on daily fluctuations in wellbeing than the satisfaction and meaning they derived from their technology use. Ultimately, teens felt online communication could not replace face-to-face interactions. We conducted two follow-up participatory design sessions with nine teens to explore these insights in greater depth and reflect on general implications for design to support teens' meaningful technology experiences and wellbeing during disruptive life events., Comment: 22 pages, 2 figures, 2 tables, Proceedings of the ACM Conference on Human Factors in Computing Systems (CHI '21)