Proton Pump Inhibitor Use, Fatigue, and Health-Related Quality of Life in Kidney Transplant Recipients: Results From the TransplantLines Biobank and Cohort Study

RATIONALE & OBJECTIVE

Prior studies report that the use of proton pump inhibitors (PPIs) can adversely affect gut microbiota and gastrointestinal uptake of micronutrients, in particular iron and magnesium, and are used frequently by kidney transplant recipients. Altered gut microbiota, iron deficiency, and magnesium deficiency have been implicated in the pathogenesis of chronic fatigue. Therefore, we hypothesized that PPI use may be an important and underappreciated cause of fatigue and reduced health-related quality of life (HRQoL) in this population.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

Kidney transplant recipients (≥1 year after transplantation) enrolled in the TransplantLines Biobank and Cohort Study.

EXPOSURE

PPI use, PPI type, PPI dosage, and duration of PPI use.

OUTCOME

Fatigue and HRQoL, assessed using the validated Checklist Individual Strength 20 Revised questionnaire and Short Form-36 questionnaire.

ANALYTICAL APPROACH

Logistic and linear regression.

RESULTS

We included 937 kidney transplant recipients (mean age 56±13 years, 39% female) at a median of 3 (1-10) years after transplantation. PPI use was associated with fatigue severity (regression coefficient 4.02, 95% CI, 2.18 to 5.85, P<0.001), a higher risk of severe fatigue (OR 2.05, 95% CI, 1.48 to 2.84, P<0.001), lower physical HRQoL (regression coefficient-8.54, 95% CI, -11.54 to-5.54, P<0.001), and lower mental HRQoL (regression coefficient-4.66, 95% CI, -7.15 to-2.17, P<0.001). These associations were independent of potential confounders including age, time since transplantation, history of upper gastrointestinal disease, antiplatelet therapy, and the total number of medications. They were present among all individually assessed PPI types and were dose dependent. Duration of PPI exposure was only associated with fatigue severity.

LIMITATIONS

Residual confounding and inability to assess causal relationships.

CONCLUSIONS

PPI use is independently associated with fatigue and lower HRQoL among kidney transplant recipients. PPI use might be an easily accessible target for alleviating fatigue and improving HRQoL among kidney transplant recipients. Further studies examining the effect of PPI exposure in this population are warranted.

Folate reference interval estimation in the Dutch general population

Background

Folate functions as an enzyme co-factor within the one-carbon metabolic pathway, providing key metabolites required for DNA synthesis and methylation. Hence, insufficient intake of folate can negatively affect health. As correct interpretation of folate status is dependent on a well-established reference interval, we set out to perform a new estimation following the restandardization of the Roche folate assay against the international folate standard.

Materials and methods

The folate reference interval was estimated using samples obtained from the Dutch population-based Lifelines cohort. The reference interval was estimated using two methods: a nonparametric estimation combined with bootstrap resampling and by fitting the data to a gamma distribution. The lower reference limit was verified in a patient cohort by combined measurement of folate and homocysteine.

Results

Dependent on the method used for estimation and in- or exclusion of individuals younger than 21 years of age, the lower reference limit ranged from 6.8 to 7.3 nmol/L and the upper reference limit ranged from 26 to 38.5 nmol/L. Applying a lower reference limit of 7.3 nmol/L resulted in the following percentage of folate deficiencies over a period of 12 months: general practitioner 15.5% (IQR 4.0%), general hospital 12.8% (IQR 5.3%), academic hospital 9.6% (IQR 4.3%).

Conclusions

We estimated the folate reference interval in the Dutch general population which is not affected by a folic acid fortification program and verified the obtained lower reference limit by homocysteine measurements. Based on our results, we propose a folate reference interval independent of age of 7.3–38.5 nmol/L

A novel diagnostic algorithm equipped on an automated hematology analyzer to differentiate between common causes of febrile illness in Southeast Asia

BACKGROUND

Distinguishing arboviral infections from bacterial causes of febrile illness is of great importance for clinical management. The Infection Manager System (IMS) is a novel diagnostic algorithm equipped on a Sysmex hematology analyzer that evaluates the host response using novel techniques that quantify cellular activation and cell membrane composition. The aim of this study was to train and validate the IMS to differentiate between arboviral and common bacterial infections in Southeast Asia and compare its performance against C-reactive protein (CRP) and procalcitonin (PCT).

METHODOLOGY/PRINCIPAL FINDINGS

600 adult Indonesian patients with acute febrile illness were enrolled in a prospective cohort study and analyzed using a structured diagnostic protocol. The IMS was first trained on the first 200 patients and subsequently validated using the complete cohort. A definite infectious etiology could be determined in 190 of 463 evaluable patients (41%), including 89 arboviral infections (81 dengue and 8 chikungunya), 94 bacterial infections (26 murine typhus, 16 salmonellosis, 6 leptospirosis and 46 cosmopolitan bacterial infections), 3 concomitant arboviral-bacterial infections, and 4 malaria infections. The IMS detected inflammation in all but two participants. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IMS for arboviral infections were 69.7%, 97.9%, 96.9%, and 77.3%, respectively, and for bacterial infections 77.7%, 93.3%, 92.4%, and 79.8%. Inflammation remained unclassified in 19.1% and 22.5% of patients with a proven bacterial or arboviral infection. When cases of unclassified inflammation were grouped in the bacterial etiology group, the NPV for bacterial infection was 95.5%. IMS performed comparable to CRP and outperformed PCT in this cohort.

CONCLUSIONS/SIGNIFICANCE

The IMS is an automated, easy to use, novel diagnostic tool that allows rapid differentiation between common causes of febrile illness in Southeast Asia.

Additional filtering of blood from a cell salvage device is not likely to show important additional benefits in outcome in cardiac surgery

BACKGROUND

Several authors and manufacturers of cell salvage devices recommend additional filtering of processed blood before transfusion. There is no evidence to support this practice. Therefore, we compared the clinical outcome and biochemical effects of cell salvage with or without additional filtering.

STUDY DESIGN AND METHODS

The patients, scheduled for coronary artery bypass grafting, valve replacement, or combined procedures were part of our randomized multicenter factorial study of cell salvage and filter use on transfusion requirements (ISRCTN 58333401). They were randomized to intraoperative cell salvage or cell salvage plus additional WBC depletion filter. We compared the occurrence of major adverse events (combined death/stroke/myocardial infarction) as primary outcome and minor adverse events (renal function disturbances, infections, delirium), ventilation time, and length of stay in the intensive care unit and hospital. We also measured biochemical markers of organ injury and inflammation.

RESULTS

One hundred eighty-nine patients had cell salvage, and 175 patients had cell salvage plus filter and completed the study. Demographic data, surgical procedures, and amount of salvaged blood were not different between the groups. There was no difference in the primary outcome with a risk of 6.3% (95% confidence interval [CI], 3.34-11.25) in the cell salvage plus filter group versus 5.8% (95% CI, 3.09-10.45) in the cell salvage group, a relative risk of 1.08 (95% CI, 0.48- 2.43]. There were no differences in minor adverse events and biochemical markers between the groups.

CONCLUSION

The routine use of an additional filter for transfusion of salvaged blood is unlikely to show important additional benefits.

HDL function is impaired in acute myocardial infarction independent of plasma HDL cholesterol levels

BACKGROUND

High-density lipoproteins (HDLs) protect against the development of atherosclerotic cardiovascular disease. HDL function represents an emerging concept in cardiovascular research.

OBJECTIVE

This study investigated the association between HDL functionality and acute myocardial infarction (MI) independent of HDL-cholesterol plasma levels.

METHODS

Participants (non-ST-segment elevation MI, non-STEMI, n = 41; STEMI, n = 37; non-MI patients, n = 33) from a prospective follow-up study enrolling patients with acute chest pain were matched for age and plasma HDL cholesterol. The in vitro capacity of HDL to (1) mediate cholesterol efflux from macrophage foam cells, (2) prevent low-density lipoprotein oxidation, and (3) inhibit TNF-α-induced vascular adhesion molecule-1 expression in endothelial cells was determined.

RESULTS

STEMI-HDL displayed reduced cholesterol efflux (P < .001) and anti-inflammatory functionality (P = .001), whereas the antioxidative properties were unaltered. Cholesterol efflux correlated with the anti-inflammatory HDL activity (P < .001). Not C-reactive protein levels, a marker of systemic inflammation, but specifically plasma myeloperoxidase levels were independently associated with impaired HDL function (efflux: P = .022; anti-inflammation: P < .001). Subjects in the higher risk quartile of efflux (odds ratio [OR], 5.66; 95% confidence interval [CI], 1.26-25.00; P = .024) as well as anti-inflammatory functionality of HDL (OR, 5.53; 95% CI, 1.83-16.73; P = .002) had a higher OR for MI vs those in the three lower risk quartiles combined.

CONCLUSION

Independent of plasma HDL cholesterol levels, 2 of 3 antiatherogenic HDL functionalities tested were significantly impaired in STEMI patients, namely cholesterol efflux and anti-inflammatory properties. Increased myeloperoxidase levels might represent a major contributing mechanism for decreased HDL functionality in MI patients.

Discovery and refinement of loci associated with lipid levels

Levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and total cholesterol are heritable, modifiable risk factors for coronary artery disease. To identify new loci and refine known loci influencing these lipids, we examined 188,577 individuals using genome-wide and custom genotyping arrays. We identify and annotate 157 loci associated with lipid levels at P < 5 × 10(-8), including 62 loci not previously associated with lipid levels in humans. Using dense genotyping in individuals of European, East Asian, South Asian and African ancestry, we narrow association signals in 12 loci. We find that loci associated with blood lipid levels are often associated with cardiovascular and metabolic traits, including coronary artery disease, type 2 diabetes, blood pressure, waist-hip ratio and body mass index. Our results demonstrate the value of using genetic data from individuals of diverse ancestry and provide insights into the biological mechanisms regulating blood lipids to guide future genetic, biological and therapeutic research.

Common variants associated with plasma triglycerides and risk for coronary artery disease

Triglycerides are transported in plasma by specific triglyceride-rich lipoproteins; in epidemiologic studies, increased triglyceride levels correlate with higher risk for coronary artery disease (CAD). However, it is unclear whether this association reflects causal processes. We used 185 common variants recently mapped for plasma lipids (P<5×10⁻⁸ for each) to examine the role of triglycerides on risk for CAD. First, we highlight loci associated with both low-density lipoprotein cholesterol (LDL-C) and triglycerides, and show that the direction and magnitude of both are factors in determining CAD risk. Second, we consider loci with only a strong magnitude of association with triglycerides and show that these loci are also associated with CAD. Finally, in a model accounting for effects on LDL-C and/or high-density lipoprotein cholesterol, a polymorphism's strength of effect on triglycerides is correlated with the magnitude of its effect on CAD risk. These results suggest that triglyceride-rich lipoproteins causally influence risk for CAD.

Seventy-five genetic loci influencing the human red blood cell

Anaemia is a chief determinant of global ill health, contributing to cognitive impairment, growth retardation and impaired physical capacity. To understand further the genetic factors influencing red blood cells, we carried out a genome-wide association study of haemoglobin concentration and related parameters in up to 135,367 individuals. Here we identify 75 independent genetic loci associated with one or more red blood cell phenotypes at P < 10(-8), which together explain 4-9% of the phenotypic variance per trait. Using expression quantitative trait loci and bioinformatic strategies, we identify 121 candidate genes enriched in functions relevant to red blood cell biology. The candidate genes are expressed preferentially in red blood cell precursors, and 43 have haematopoietic phenotypes in Mus musculus or Drosophila melanogaster. Through open-chromatin and coding-variant analyses we identify potential causal genetic variants at 41 loci. Our findings provide extensive new insights into genetic mechanisms and biological pathways controlling red blood cell formation and function.

Plasma Lp-PLA(2) mass and apoB-lipoproteins that carry Lp-PLA(2) decrease after sodium

BACKGROUND

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) is a novel cardiovascular risk marker, which is predominantly complexed to apolipoprotein (apo) B-containing lipoproteins in human plasma. As increasing dietary sodium intake may decrease plasma apoB-containing lipoproteins, we tested whether a sodium challenge lowers plasma Lp-PLA(2) mass, as well as the levels of apoB-containing lipoprotein particles carrying Lp-PLA(2) (apoB-Lp-PLA(2) ), employing a newly developed enzyme-linked immunosorbent assay.

MATERIALS AND METHODS

In 45 women and 31 men (mean age 44 ± 14 years), plasma Lp-PLA(2) mass (turbidimetric immunoassay), the level of apoB-Lp-PLA(2) , expressed in apoB concentration and lipoproteins were measured in response to a 3-day challenge with 9 g sodium chloride tablets daily.

RESULTS

Urinary sodium excretion increased from 165 ± 60 to 321 ± 70 mmol/24 h (P<0.001) after salt loading. Plasma Lp-PLA(2) mass decreased from 618 (493-719) to 588 (465-698) μg/L (P<0.001), and apoB-Lp-PLA(2) decreased from 0.276 (0.200-0.351) to 0.256 (0.189-0.328) g LDL protein/L (P=0.004) in response to the sodium challenge together with decreases in plasma total cholesterol, nonhigh-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, apolipoprotein B and the total cholesterol/HDL cholesterol ratio (P<0.01 for all). Changes in plasma Lp-PLA(2) mass were correlated positively with changes in total cholesterol, LDL cholesterol and non-HDL cholesterol (r=0.260-0.276, P<0.05 to P<0.02), whereas changes in apoB-Lp-PLA(2) were correlated positively with changes in non-HDL cholesterol and in the total cholesterol/HDL cholesterol ratio (r=0.232-0.385, P<0.05-0.01).

CONCLUSION

Both plasma Lp-PLA(2) mass levels and apoB-Lp-PLA(2) decrease in response to a short-term oral sodium challenge.

Simvastatin but not bezafibrate decreases plasma lipoprotein-associated phospholipase A₂ mass in type 2 diabetes mellitus: relevance of high sensitive C-reactive protein, lipoprotein profile and low-density lipoprotein (LDL) electronegativity

OBJECTIVE

Plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) levels predict incident cardiovascular disease, impacting Lp-PLA(2) as an emerging therapeutic target. We determined Lp-PLA(2) responses to statin and fibrate administration in type 2 diabetes mellitus, and assessed relationships of changes in Lp-PLA(2) with subclinical inflammation and lipoprotein characteristics.

METHODS

A placebo-controlled cross-over study (three 8-week treatment periods with simvastatin (40 mg daily), bezafibrate (400mg daily) and their combination) was carried out in 14 male type 2 diabetic patients. Plasma Lp-PLA(2) mass was measured by turbidimetric immunoassay.

RESULTS

Plasma Lp-PLA(2) decreased (-21 ± 4%) in response to simvastatin (p<0.05 from baseline and placebo), but was unaffected by bezafibrate (1 ± 5%). The drop in Lp-PLA(2) during combined treatment (-17 ± 3%, p<0.05) was similar compared to that during simvastatin alone. The Lp-PLA(2) changes during the 3 active lipid lowering treatment periods were related positively to baseline levels of high sensitive C-reactive protein, non-HDL cholesterol, triglycerides, the total cholesterol/HDL cholesterol ratio and less LDL electronegativity (p<0.02 to p<0.01), and inversely to baseline Lp-PLA(2) (p<0.01). LpPLA(2) responses correlated inversely with changes in non-HDL cholesterol, triglycerides and the total cholesterol/HDL cholesterol ratio during treatment (p<0.05 to p<0.02).

CONCLUSIONS

In type 2 diabetes mellitus, plasma Lp-PLA(2) is likely to be lowered by statin treatment only. Enhanced subclinical inflammation and more severe dyslipidemia may predict diminished LpPLA(2) responses during lipid lowering treatment, which in turn appear to be quantitatively dissociated from decreases in apolipoprotein B lipoproteins. Conventional lipid lowering treatment may be insufficient for optimal LpPLA(2) lowering in diabetes mellitus.

High-sensitive troponin T and N-terminal pro-B type natriuretic peptide are associated with cardiovascular events despite the cross-sectional association with albuminuria and glomerular filtration rate

AIMS

It has been suggested that troponins and natriuretic peptides can be falsely elevated in subjects with impaired kidney function because of decreased renal clearance. The value of these biomarkers in subjects with impaired kidney function has therefore been debated. We tested in a population-based cohort study, first, whether high-sensitive troponin T (hsTnT) and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) levels are cross-sectionally associated with the estimated glomerular filtration rate (eGFR) and albuminuria, and secondly, whether these markers are associated with cardiovascular outcome, independent of eGFR, albuminuria and conventional cardiovascular risk factors.

METHODS AND RESULTS

We included 8121 subjects from the PREVEND study with both values of hsTnT and NT-pro-BNP available. High-sensitive troponin T >0.01 µg/L and NT-pro-BNP >125 ng/L were defined as elevated. We first performed linear regression analyses with hsTnT and NT-pro-BNP as dependent variables. Next, we performed Cox-regression analyses, studying the associations of hsTnT and NT-pro-BNP with incident cardiovascular events. Of our cohort, 6.7% had an elevated hsTnT and 12.2% an elevated NT-pro-BNP. Also, the estimated glomerular filtration rate, albuminuria, and ECG-assessed ischaemia and left ventricular hypertrophy were all significantly associated with hsTnT and NT-pro-BNP in the linear regression analyses. Both hsTnT and NT-pro-BNP appeared associated with cardiovascular events, and these associations remained significant after adjustment for eGFR, albuminuria, age, gender and conventional cardiovascular risk factors (P= 0.03 and P< 0.001, respectively). Only a few subjects with markedly reduced renal function were included. The results presented are therefore mainly valid for a population with mildly impaired renal function.

CONCLUSION

These data indicate that a finding of an increased hsTnT or NT-pro-BNP in subjects with chronic kidney disease stages 1/3 should be taken seriously as a prognostic marker for a worse cardiovascular outcome and not be discarded as merely a reflection of decreased renal clearance.

New gene functions in megakaryopoiesis and platelet formation

Platelets are the second most abundant cell type in blood and are essential for maintaining haemostasis. Their count and volume are tightly controlled within narrow physiological ranges, but there is only limited understanding of the molecular processes controlling both traits. Here we carried out a high-powered meta-analysis of genome-wide association studies (GWAS) in up to 66,867 individuals of European ancestry, followed by extensive biological and functional assessment. We identified 68 genomic loci reliably associated with platelet count and volume mapping to established and putative novel regulators of megakaryopoiesis and platelet formation. These genes show megakaryocyte-specific gene expression patterns and extensive network connectivity. Using gene silencing in Danio rerio and Drosophila melanogaster, we identified 11 of the genes as novel regulators of blood cell formation. Taken together, our findings advance understanding of novel gene functions controlling fate-determining events during megakaryopoiesis and platelet formation, providing a new example of successful translation of GWAS to function.

Carotid intima media thickness is associated with plasma lipoprotein-associated phospholipase A2 mass in nondiabetic subjects but not in patients with type 2 diabetes

BACKGROUND

A recent meta-analysis showed that both plasma lipoprotein-associated phospholipase A(2) (Lp-PLA(2) ) mass and activity independently predict cardiovascular events. Notably, Lp-PLA(2) activity but not mass was found to be a determinant of cardiovascular outcome in type 2 diabetes mellitus. We questioned whether relationships of carotid intima media thickness (IMT), a measure of subclinical atherosclerosis, with Lp-PLA(2) mass differ between diabetic and nondiabetic subjects.

MATERIALS AND METHODS

Relationships of IMT with plasma Lp-PLA(2) mass (turbidimetric immunoassay) were compared in 74 patients with type 2 diabetes and in 64 nondiabetic subjects.

RESULTS

IMT was increased (P=0·016), but plasma Lp-PLA(2) mass was decreased in patients with diabetes compared to nondiabetic subjects (277±66 vs. 327±62μgL(-1) , P<0·001). In nondiabetic subjects, IMT was correlated positively with Lp-PLA(2) (r=0·325, P<0·009); multiple linear regression analysis confirmed an independent association of IMT with Lp-PLA(2) (ß=0·192, P=0·048). In contrast, IMT was unrelated to Lp-PLA(2) in patients with diabetes (r=0·021, P=0·86), and the relationship of IMT with Lp-PLA(2) was different in diabetic and control subjects (P<0·001). The relationship of Lp-PLA(2) with the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio also differed between diabetic and nondiabetic subjects (P<0·001).

CONCLUSIONS

Plasma Lp-PLA(2) may relate to early stages of atherosclerosis development. In diabetes mellitus, in contrast, the association of IMT with plasma Lp-PLA(2) mass is abolished, which could be partly ascribed to redistribution of Lp-PLA(2) mass from apolipoprotein B-containing lipoproteins towards HDL. These findings raise questions about the usefulness of plasma Lp-PLA(2) mass measurement as a marker of subclinical atherosclerosis in type 2 diabetes mellitus.

Renal function equations before and after living kidney donation: a within-individual comparison of performance at different levels of renal function

BACKGROUND AND OBJECTIVES

The Modification of Diet in Renal Disease (MDRD) study equation and the Cockcroft-Gault (CG) equation perform poorly in the (near-) normal range of GFR. Whether this is due to the level of GFR as such or to differences in individual characteristics between healthy individuals and patient with chronic kidney disease (CKD) is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated the performance of MDRD, CG per BSA (CG/(BSA)) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations compared with measured GFR (mGFR; I-iothalamate) at 4 months before and 2 months after donation in 253 consecutive living kidney donors.

RESULTS

mGFR declined from 103 ± 15 to 66 ± 11 ml/min per 1.73 m(2) after donation. All equations underestimated mGFR at both time points. Arithmetic performance analysis showed improved performance after donation of all equations, with significant reduction of bias after donation. Expressed as percentage difference, mGFR-estimated GFR (eGFR) bias was reduced after donation only for CG/(BSA). Finally, in 295 unselected individuals who were screened for donation, mGFR was below the cutoff for donation of 80 ml/min per 1.73 m(2) in 19 individual but in 166, 98, and 74 for MDRD, CDK-EPI, and CG/(BSA), respectively.

CONCLUSIONS

A higher level of GFR as such is associated with larger absolute underestimation of true GFR by eGFR. For donor screening purposes, eGFR should be interpreted with great caution; when in doubt, true GFR should be performed to prevent unjustified decline of prospective kidney donors.

Clinical correlates of arterial lactate levels in patients with ST-segment elevation myocardial infarction at admission: a descriptive study

Introduction

Blood lactate measurements can be used as an indicator of hemodynamic impairment and relate to mortality in various forms of shock. Little is known at the moment concerning the clinical correlates of systemic lactate in patients with ST-segment elevation myocardial infarction (STEMI).

Methods

To assess the relation of systemic arterial lactate levels in STEMI patients with clinical correlates at presentation in the catheterization laboratory, we measured arterial lactate levels with a rapid point-of-care technique, immediately following femoral sheath insertion. The study population (n= 1,176) was divided into tertiles with lactate levels ≤1.1 (n = 410), 1.2 to 1.7 (n = 398) and ≥1.8 mmol/l (n = 368). We compared both baseline characteristics and outcome measures of the three lactate groups.

Results

Factors independently associated with higher lactate levels were hypotension, heart rate, thrombolysis in myocardial infarction (TIMI) flow 0 to 1, diabetes and non-smoking. Mortality at 30 days in the three groups was 2.0%, 1.5% and 6.5%. The latter group also showed lower blush grades and greater enzymatic infarct sizes. An intra aortic balloon pump (IABP) was used more frequently in patients with higher lactate levels (4.2%, 7.6% and 14.7%).

Conclusions

In STEMI patients, impaired hemodynamics, worse TIMI flow and non-smoking were related to increased arterial lactate levels. Higher lactate levels were independently related with 30-day mortality and an overall worse response to percutaneous coronary intervention (PCI). In particular, acute mortality was related to admission lactates ≥1.8 mmol/L. Point-of-care measurement of arterial lactate at admission in patients with STEMI has the potential to improve acute risk stratification.