Renal Biomarkers in the Early Detection of Acute Kidney Injury After Off-Pump Coronary Artery Bypass Grafting

BACKGROUND

Cardiac surgery-associated (CSA) acute kidney injury (AKI) is a severe postoperative complication in patients undergoing off-pump coronary artery bypass grafting (OPCAB). Early detection of postoperative CSA-AKI may be key to improving patient outcomes. This study explored the use of renal biomarkers measured immediately after surgery for the early detection of CSA-AKI in patients undergoing OPCAB.Methods and Results: In all, 111 patients who underwent OPCAB at Kumamoto University Hospital between June 2020 and October 2022 were included in this study. Urinary neutrophil gelatinase-associated lipocalin, liver-type fatty acid-binding protein, and N-acetyl-β-D-glucosaminidase (NAG) were measured upon arrival in the intensive care unit (ICU) after surgery. AKI was diagnosed using KDIGO criteria. Of the 111 patients, 32 (28.8%) developed postoperative AKI. Regarding AKI staging, 19 (59.4%), 11 (34.4%), and 2 (6.3%) patients had Stage 1, 2, and 3 AKI, respectively. There were significant differences in chronic kidney disease, preoperative estimated glomerular filtration rate (eGFR), and NAG between the AKI and non-AKI groups. Multivariate analysis showed that preoperative eGFR (odds ratio [OR] for 5-mL/min/1.73 m2increase in eGFR 0.75; 95% confidence interval [CI] 0.63-0.89) and increasing urinary NAG concentrations at ICU admission (OR 2.44; 95% CI 1.30-4.60) were significant risk factors for CSA-AKI in OPCAB patients.

CONCLUSIONS

NAG and eGFR may be valuable biomarkers for the early detection of CSA-AKI in patients undergoing OPCAB.

Acute kidney injury biomarker olfactomedin 4 predicts furosemide responsiveness

BACKGROUND

Acute kidney injury (AKI) is associated with increased morbidity and mortality in critically ill patients. Olfactomedin 4 (OLFM4), a secreted glycoprotein expressed in neutrophils and stressed epithelial cells, is upregulated in loop of Henle (LOH) cells following AKI. We hypothesized that urine OLFM4 (uOLFM4) will increase in patients with AKI and may predict furosemide responsiveness.

METHODS

Urine from critically ill children was collected prospectively and tested for uOLFM4 concentrations with a Luminex immunoassay. Severe AKI was defined by KDIGO (stage 2/3) serum creatinine criteria. Furosemide responsiveness was defined as > 3 mL/kg/h of urine output in the 4 h after a 1 mg/kg IV furosemide dose administered as part of standard of care.

RESULTS

Fifty-seven patients contributed 178 urine samples. Irrespective of sepsis status or AKI cause, uOLFM4 concentrations were higher in patients with AKI (221 ng/mL [IQR 93-425] vs. 36 ng/mL [IQR 15-115], p = 0.007). uOLFM4 concentrations were higher in patients unresponsive to furosemide (230 ng/mL [IQR 102-534] vs. 42 ng/mL [IQR 21-161], p = 0.04). Area under the receiver operating curve for association with furosemide responsiveness was 0.75 (95% CI, 0.60-0.90).

CONCLUSIONS

AKI is associated with increased uOLFM4. Higher uOLFM4 is associated with a lack of response to furosemide. Further testing is warranted to determine whether uOLFM4 could identify patients most likely to benefit from earlier escalation from diuretics to kidney replacement therapy to maintain fluid balance. A higher resolution version of the Graphical abstract is available as Supplementary information.

Urine titin as a novel biomarker for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most severe form of muscular dystrophy that is caused by lack of dystrophin, a critical structural protein in skeletal muscle. DMD treatments, and quantitative biomarkers to assess the efficacy of potential treatments, are urgently needed. Previous evidence has shown that titin, a muscle cell protein, is increased in the urine of patients with DMD, suggesting its usefulness as a DMD biomarker. Here, we demonstrated that the elevated titin in urine is directly associated with the lack of dystrophin and urine titin responses to drug treatment. We performed a drug intervention study using mdx mice, a DMD mouse model. We showed that mdx mice, which lack dystrophin due to a mutation in exon 23 of the Dmd gene, have elevated urine titin. Treatment with an exon skipper that targets exon 23 rescued muscle dystrophin level and dramatically decreased urine titin in mdx mice and correlates with dystrophin expression. We also demonstrated that titin levels were significantly increased in the urine of patients with DMD. This suggests that elevated urine titin level might be a hallmark of DMD and a useful pharmacodynamic marker for therapies designed to restore dystrophin levels.

Association of urinary and ambient black carbon, and other ambient air pollutants with risk of prediabetes and metabolic syndrome in children and adolescents

The effects of exposure to black carbon (BC) on various diseases remains unclear, one reason being potential exposure misclassification following modelling of ambient air pollution levels. Urinary BC particles may be a more precise measure to analyze the health effects of BC. We aimed to assess the risk of prediabetes and metabolic syndrome (MetS) in relation to urinary BC particles and ambient BC and to compare their associations in 5453 children from IDEFICS/I. Family cohort. We determined the amount of BC particles in urine using label-free white-light generation under femtosecond pulsed laser illumination. We assessed annual exposure to ambient air pollutants (BC, PM_2.5 and NO₂) at the place of residence using land use regression models for Europe, and we calculated the residential distance to major roads (≤250 m vs. more). We analyzed the cross-sectional relationships between urinary BC and air pollutants (BC, PM_2.5 and NO₂) and distance to roads, and the associations of all these variables to the risk of prediabetes and MetS, using logistic and linear regression models. Though we did not observe associations between urinary and ambient BC in overall analysis, we observed a positive association between urinary and ambient BC levels in boys and in children living ≤250 m to a major road compared to those living >250 m away from a major road. We observed a positive association between log-transformed urinary BC particles and MetS (OR_{per unit increase} = 1.72, 95% CI = 1.21; 2.45). An association between ambient BC and MetS was only observed in children living closer to a major road. Our findings suggest that exposure to BC (ambient and biomarker) may contribute to the risk of MetS in children. By measuring the internal dose, the BC particles in urine may have additionally captured non-residential sources and reduced exposure misclassification. Larger studies, with longitudinal design including measurement of urinary BC at multiple time-points are warranted to confirm our findings.

Urinary protein biomarker panel predicts esophageal squamous carcinoma from control cases and other tumors

PURPOSE

Discovery of noninvasive urinary biomarkers for the early diagnosis of esophageal squamous carcinoma (ESCC).

METHODS

We conducted proteomic analyses of 499 human urine samples obtained from healthy individuals (n = 321) and ESCC (n = 83), bladder cancer (n = 17), breast cancer (n = 12), colorectal cancer (n = 16), lung cancer (n = 33) and thyroid cancer (n = 17) patients from multiple medical centers. Those samples were divided into a discovery set (n = 247) and an independent validation set (n = 157).

RESULTS

Among urinary proteins identified in the comprehensive quantitative proteomics analysis, we selected a panel of three urinary biomarkers (ANXA1, S100A8, TMEM256), and established a logistic regression model in the discovery set that can correctly classify the majority of ESCC cases in the validation sets with the area under the curve (AUC) values of 0.825. This urinary biomarker panel not only discriminates ESCC patients from healthy individuals but also differentiates ESCC from other common tumors. Notably, the panel distinguishes stage I ESCC patients from healthy individuals with AUC values of 0.886. On the analysis of stage-specific biomarkers, another combination panel of protein (ANXA1, S100A8, SOD3, TMEM256) demonstrated a good AUC value of 0.792 for stage I ESCC.

CONCLUSIONS

Urinary biomarker panel represents a promising auxiliary diagnostic tool for ESCC, including early-stage ESCC.

Potential urine biomarkers in bladder outlet obstruction-related detrusor underactivity

Detrusor underactivity (DU), an important but under-researched issue, is thought to be complex and multifactorial in etiology, pathophysiology, and diagnosis. Bladder outlet obstruction (BOO) is one of the important known etiologies of DU, with significant morphologic and physiologic changes of the urothelium, suburothelium, and detrusor muscle in the urinary bladder. Chronic urinary bladder ischemia and repeated cycles of ischemia and reperfusion injury cause excessive oxidative stress, and it is thought to be responsible for the development of DU. DU might be the late phase or decompensated status of BOO, with the possible mechanisms of afferent nervous dysfunction, increased inflammation, denervation of the detrusor muscle, and myogenic failure. Prostaglandin E2 (PGE2) involves in the physiological detrusor contraction, and might provide the prognostic value for the recoverability of DU. Neurotrophins, including nerve growth factor and brain-derived neurotrophic factor, involve in the neuroplastic changes in many inflammatory bladder diseases, including BOO and DU. Oxidative stress biomarkers, including 8-hydroxy-2-deoxyguanosine, F2-isoprostane, and the involved pro-inflammatory cytokines, have been applied in BOO due to their involvements in chronic bladder ischemia. PGE2, neurotrophins, inflammatory cytokines, and oxidative stress biomarkers are the potential urine biomarkers in BOO-related DU.

Associations of Urine Biomarkers with Kidney Function Decline in HIV-Infected and Uninfected Men

BACKGROUND

HIV-infected (HIV+) persons are at increased risk of chronic kidney disease, but serum creatinine does not detect early losses in kidney function. We hypothesized that urine biomarkers of kidney damage would be associated with subsequent changes in kidney function in a contemporary cohort of HIV+ and HIV-uninfected (HIV-) men.

METHODS

In the Multicenter AIDS Cohort Study, we measured baseline urine concentrations of 5 biomarkers from 2009 to 2011 in 860 HIV+ and 337 HIV- men: albumin, alpha-1-microglobulin (α1m), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), and procollagen type III N-terminal propeptide (PIIINP). We evaluated associations of urine biomarker concentrations with annual changes in estimated glomerular filtration rate (eGFR) using multivariable linear mixed models adjusted for demographics, traditional kidney disease risk factors, HIV-related risk factors, and baseline eGFR.

RESULTS

Over a median follow-up of 4.8 years, the average annual eGFR decline was 1.42 mL/min/1.73 m2/year in HIV+ men and 1.22 mL/min/1.73 m2/year in HIV- men. Among HIV+ men, the highest vs. lowest tertiles of albumin (-1.78 mL/min/1.73 m2/year, 95% CI -3.47 to -0.09) and α1m (-2.43 mL/min/1.73 m2/year, 95% CI -4.14 to -0.73) were each associated with faster annual eGFR declines after multivariable adjustment. Among HIV- men, the highest vs. lowest tertile of α1m (-2.49 mL/min/1.73 m2/year, 95% CI -4.48 to -0.50) was independently associated with faster annual eGFR decline. Urine IL-18, KIM-1, and PIIINP showed no independent associations with eGFR decline, regardless of HIV serostatus.

CONCLUSIONS

Among HIV+ men, higher urine albumin and α1m are associated with subsequent declines in kidney function, independent of eGFR.

Urinary biomarkers of tubular injury to predict renal progression and end stage renal disease in type 2 diabetes mellitus with advanced nephropathy: A prospective cohort study

BACKGROUND

Novel potential tubular biomarkers in diabetic nephropathy could improve risk stratification and prediction. The study aimed to evaluate the association of tubular damage markers with rapid renal progression and incidence of end stage renal disease (ESRD) in type 2 diabetes (T2DM).

METHODS

A prospective cohort study, involving a total of 257 patients with T2DM, was included. The baseline values of urine albumin, cystatin-C, angiotensinogen, kidney injury molecule-1 (KIM-1) and neutrophil-gelatinase associated lipocalin (NGAL) were measured. The composite outcomes included a rapid glomerular filtration rate (GFR) decline or incident of ESRD at 3-year follow-up.

MAIN FINDINGS

The composite outcomes were noted in 26.1%. Using univariate followed by multivariate COX proportional hazard regression analysis, the patients with highest quartiles of urine cystatin-C (HR 2.96, 95% CI, 1.38-6.35), urine angiotensinogen (HR 2.93, 95% CI, 1.40- 6.13) urine KIM-1 (HR 2.77, 95% CI, 1.27-6.05) and urine NGAL (HR 2.53, 95% CI, 1.11-5.76) were significantly associated with rapid renal progression when compared with the patients with the lowest quartiles of all tubular biomarkers.

CONCLUSIONS

Patients with T2DM with high levels of baseline urine tubular biomarkers (cystatin-C, angiotensinogen, KIM-1 and NGAL) had a greater incidence of ESRD and rapid GFR decline.

Smarter screening for prostate cancer

PURPOSE

Prostate cancer is the second commonest cancer among men. In the large European Randomized Study of Screening for Prostate Cancer (ERSPC) trial, prostate-specific antigen (PSA) screening has been shown to substantially reduce prostate cancer mortality. However, PSA screening is known to lead to more unnecessary prostate biopsies and over-diagnosis of clinically insignificant cancer. Therefore, it is imperative that smarter screening methods be developed to overcome the weaknesses of PSA screening. This review explores the novel screening tools that are available.

METHODS

A comprehensive literature search was performed using PubMed regarding newer biomarkers, imaging techniques and risk-predicting models that are used to screen for prostate cancer in mainly biopsy-naïve men.

RESULTS

Novel serum-based models like 4Kscore^® and prostate health index (PHI) are generally better than PSA alone in detecting clinically significant cancer. Similarly, urine-based biomarkers like prostate cancer antigen 3 (PCA3) and HOXC6/DLX1 have been shown to be more accurate than PSA screening. More recently, multiparametric magnetic resonance imaging (mpMRI) is gaining popularity for its ability to detect clinically significant cancer. There is also evidence that combining individual tests to develop prediction models can reliably predict high-risk prostate cancers while reducing the number of unnecessary biopsies. Combinations such as the Stockholm-3 model (STHLM3) and other novel combinations are presented in this review.

CONCLUSION

While we continue to find the smarter screening methods that are reliable, precise, and cost-effective, we continue to advocate shared decision-making in prostate cancer screening in order to work in our patients' best interests.

A panel of DNA methylation markers for the detection of prostate cancer from FV and DRE urine DNA

Background

Early screening for prostate cancer (PCA) remains controversial because of overdiagnosis and overtreatment of clinically insignificant cancers. Even though a number of diagnostic tests have been developed to improve on PSA testing, there remains a need for a more informative non-invasive test for PCA. The objective of this study is to identify a panel of DNA methylation markers suitable for a non-invasive diagnostic test from urine DNA collected following a digital rectal exam (DRE) and/or from first morning void (FV). A secondary objective is to determine if the cumulative methylation is indicative of biopsy findings.

Methods

DRE and FV urine samples were prospectively collected from 94 patients and analyzed using 24 methylation-specific quantitative PCR assays derived from 19 CpG islands. The methylation of individual markers and various combinations of markers was compared to biopsy results. A methylation threshold for cancer classification was determined using a target specificity of 70%. The average methylation and the number of positive markers were also compared to the result of the biopsy, and the area under the receiver operating characteristic curves (AUCs) were calculated.

Results

Methylation of all 19 markers was detected in FV and DRE DNAs. Combining the methylation of two or more markers improved on individual marker results. Using 6of19 methylated markers as the threshold for cancer classification yielded a specificity of 71% (95% CI, 0.57-0.86) from both DRE and FV and a sensitivity of 89% (95% CI, 0.79-0.97) from DRE and 94% (95% CI, 0.84-1.0) from FV. The negative predictive value at the 6of19 threshold was ≥ 90 for both DNA types.

Conclusions

PCA-specific methylation was detected in both FV and DRE DNA. There was no significant difference in diagnostic accuracy at the 6of19 threshold between DRE and FV urine DNA. The results support the development of a non-invasive diagnostic test to reduce unnecessary biopsies in men with elevated PSA. The test can also provide patients with personalized recommendations based on their own methylation profile.

Urinary Biomarkers of Kidney Tubular Damage and Risk of Cardiovascular Disease and Mortality in Elders

RATIONALE & OBJECTIVE

Novel urinary biomarkers have enabled earlier detection of kidney tubular damage, but their prognostic value for adverse cardiovascular outcomes is uncertain. We hypothesized that tubular damage, measured by urine α₁-microglobulin (A1M), amino-terminal propeptide of type III procollagen (PIIINP), and neutrophil gelatinase-associated lipocalin (NGAL), would be associated with higher risks for cardiovascular events and mortality among elders.

STUDY DESIGN

Case-cohort study.

SETTING & PARTICIPANTS

This study included a randomly selected subcohort (n=502), cardiovascular disease (CVD) cases (n=245), and heart failure cases (n=220) from the Health, Aging, and Body Composition (Health ABC) Study.

PREDICTORS

Baseline urine A1M, PIIINP, and NGAL concentrations.

OUTCOMES

Incident CVD, heart failure, and all-cause mortality.

ANALYTICAL APPROACH

Cox proportional hazards models were used to evaluate biomarker associations with each outcome.

RESULTS

At baseline, mean age was 74 years and estimated glomerular filtration rate was 73mL/min/1.73m². After adjustment for demographics, estimated glomerular filtration rate, albumin-creatinine ratio, and other cardiovascular risk factors, each doubling in biomarker concentration was associated with the following adjusted HRs for CVD: A1M, 1.51 (95% CI, 1.16-1.96); PIIINP, 1.21 (95% CI, 1.00-1.46); and NGAL, 1.12 (95% CI, 1.05-1.20). There were 248 deaths in the subcohort during a median follow-up of 12.4 years. Adjusted associations of each biomarker (HR per doubling) with all-cause mortality were: A1M, 1.29 (95% CI, 1.10-1.51); PIIINP, 1.05 (95%, 0.94-1.18); and NGAL, 1.07 (95% CI, 1.02-1.12). Biomarker concentrations did not have statistically significant associations with heart failure after multivariable adjustment.

LIMITATIONS

Urine biomarkers were measured at a single time point; no validation cohort available.

CONCLUSIONS

Kidney tubular damage is an independent risk factor for CVD and death among elders. Future studies should investigate mechanisms by which kidney tubular damage may adversely affect cardiovascular risk.

Promoter methylation of DNA damage repair (DDR) genes in human tumor entities: RBBP8/CtIP is almost exclusively methylated in bladder cancer

Background

Genome-wide studies identified pan-cancer genes and shared biological networks affected by epigenetic dysregulation among diverse tumor entities. Here, we systematically screened for hypermethylation of DNA damage repair (DDR) genes in a comprehensive candidate-approach and exemplarily identify and validate candidate DDR genes as targets of epigenetic inactivation unique to bladder cancer (BLCA), which may serve as non-invasive biomarkers.

Methods

Genome-wide DNA methylation datasets (2755 CpG probes of n = 7819 tumor and n = 659 normal samples) of the TCGA network covering 32 tumor entities were analyzed in silico for 177 DDR genes. Genes of interest were defined as differentially methylated between normal and cancerous tissues proximal to transcription start sites. The lead candidate gene was validated by methylation-specific PCR (MSP) and/or bisulfite-pyrosequencing in different human cell lines (n = 36), in primary BLCA tissues (n = 43), and in voided urine samples (n = 74) of BLCA patients. Urines from healthy donors and patients with urological benign and malignant diseases were included as controls (n = 78). mRNA expression was determined using qRT-PCR in vitro before (n = 5) and after decitabine treatment (n = 2). Protein expression was assessed by immunohistochemistry (n = 42). R 3.2.0. was used for statistical data acquisition and SPSS 21.0 for statistical analysis.

Results

Overall, 39 DDR genes were hypermethylated in human cancers. Most exclusively and frequently methylated (37%) in primary BLCA was RBBP8, encoding endonuclease CtIP. RBBP8 hypermethylation predicted longer overall survival (OS) and was found in 2/4 bladder cancer cell lines but not in any of 33 cancer cell lines from entities with another origin like prostate. RBBP8 methylation was inversely correlated with RBBP8 mRNA and nuclear protein expression while RBBP8 was re-expressed after in vitro demethylation. RBBP8 methylation was associated with histological grade in primary BLCA and urine samples. RBBP8 methylation was detectable in urine samples of bladder cancer patients achieving a sensitivity of 52%, at 91% specificity.

Conclusions

RBBP8 was identified as almost exclusively hypermethylated in BLCA. RBBP8/CtIP has a proven role in homologous recombination-mediated DNA double-strand break repair known to sensitize cancer cells for PARP1 inhibitors. Since RBBP8 methylation was detectable in urines, it may be a complementary marker of high specificity in urine for BLCA detection.

Development of a fully automated chemiluminescence immunoassay for urine monomeric laminin-γ2 as a promising diagnostic tool of non-muscle invasive bladder cancer

BACKGROUND

Monomeric laminin-γ2 in urine is a potential biomarker for bladder cancer. However, the current detection system uses an antibody that cannot discriminate between monomeric laminin-γ2 and the heterotrimeric γ2 chain of laminin-332, which may cause false-positive reactions. The present study aimed to develop a fully automated chemiluminescence immunoassay system using a specific monoclonal antibody against monomeric laminin-γ2.

METHODS

In total, 237 urine specimens (84 from patients with bladder cancer, 48 from patients with benign urological disease, and 105 from healthy donors) were collected, and monomeric laminin-γ2 values in the urine were measured using a fully automated chemiluminescence immunoassay.

RESULTS

The results revealed that laminin-γ2 values in patients with benign urological disease were comparable to those of healthy donors and that the chemiluminescence immunoassay's lower limit of detection was 10 pg/mL (approximately 20-fold better than the sandwich enzyme-linked immunosorbent assay's limit of 200 pg/mL). Moreover, the chemiluminescence immunoassay demonstrated that patients with bladder cancer, including non-muscle invasive bladder cancer (≤pT1), had higher laminin-γ2 values than patients with benign urological disease or healthy donors.

CONCLUSIONS

These results suggest that urine monomeric laminin-γ2 may be a promising biomarker to diagnose cases of non-muscle invasive bladder cancer using a fully automated chemiluminescence immunoassay system.

8-hydroxy-2'-deoxyguanosine (8-OHdG) biomarker detection down to picoMolar level on a plastic antibody film

An innovative biosensor assembly relying on a simple and straightforward in-situ construction is presented to monitor urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) down to the pmol/L level. The sensing film of the biosensor consisted of a molecularly imprinted polymer (MIP) layer for 8-OHdG assembled on a gold electrode through electropolymerization of monomer combined with the template. The analytical features of the resulting biosensor were assessed by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). Some experimental parameters such as the initial concentration of the monomer and the ratio template-monomer were investigated and optimized in order to finely tune the performance of the MIP-based sensor. Under optimal conditions, the developed biosensor was able to rebind 8-OHdG with a linear response against EIS from 0.1 to 100pg/ml 3.5-3500 pM. The interference of coexisting species was tested, also with calibrations on urine samples, and good selectivity towards 8-OHdG was obtained. RAMAN spectroscopy, FTIR and SEM evaluations of the prepared films confirmed the formation of a polyphenol thin-film on the electrode surface. The presence and distribution of the imprinted cavities on the MIP layer was confirmed by confocal microscopy imaging of the film, after a post-treatment with Fluorescein Isothiocyanate (FITC) labeled 8-OHdG antibody. Overall, this label-free biosensor for urinary 8-OHdG detection constitutes a promising low-cost alternative to the conventional immunoassay approaches, due to its simplicity, stability, high sensitivity and selectivity for biological sample assays, opening new doors for other applications.

Programmed cell death 6 interacting protein (PDCD6IP) and Rabenosyn-5 (ZFYVE20) are potential urinary biomarkers for upper gastrointestinal cancer

PURPOSE

Cancer of the upper digestive tract (uGI) is a major contributor to cancer-related death worldwide. Due to a rise in occurrence, together with poor survival rates and a lack of diagnostic or prognostic clinical assays, there is a clear need to establish molecular biomarkers.

EXPERIMENTAL DESIGN

Initial assessment was performed on urine samples from 60 control and 60 uGI cancer patients using MS to establish a peak pattern or fingerprint model, which was validated by a further set of 59 samples.

RESULTS

We detected 86 cluster peaks by MS above frequency and detection thresholds. Statistical testing and model building resulted in a peak profiling model of five relevant peaks with 88% overall sensitivity and 91% specificity, and overall correctness of 90%. High-resolution MS of 40 samples in the 2-10 kDa range resulted in 646 identified proteins, and pattern matching identified four of the five model peaks within significant parameters, namely programmed cell death 6 interacting protein (PDCD6IP/Alix/AIP1), Rabenosyn-5 (ZFYVE20), protein S100A8, and protein S100A9, of which the first two were validated by Western blotting.

CONCLUSIONS AND CLINICAL RELEVANCE

We demonstrate that MS analysis of human urine can identify lead biomarker candidates in uGI cancers, which makes this technique potentially useful in defining and consolidating biomarker patterns for uGI cancer screening.

DNA methylation modifies urine biomarker levels in 1,6-hexamethylene diisocyanate exposed workers: a pilot study

DNA methylation may mediate inter-individual responses to chemical exposure and, thus, modify biomarker levels of exposure and effects. We analyzed inter-individual differences in inhalation and skin exposure to 1,6-hexamethylene diisocyanate (HDI) and urine biomarker 1,6-hexamethylene diamine (HDA) levels in 20 automotive spray-painters. Genome-wide 5-methyl cytosine (CpG) DNA methylation was assessed in each individual's peripheral blood mononuclear cells (PBMC) DNA using the Illumina 450K CpG array. Mediation analysis using linear regression models adjusted for age, ethnicity, and smoking was conducted to identify and assess the association between HDI exposure, CpG methylation, and urine HDA biomarker levels. We did not identify any CpGs common to HDI exposure and biomarker level suggesting that CpG methylation is a mediator that only partially explains the phenotype. Functional significance of genic- and intergenic-CpG methylation status was tested using protein-protein or protein-DNA interactions and gene-ontology enrichment to infer networks. Combined, the results suggest that methylation has the potential to affect HDI mass transport, permeation, and HDI metabolism. We demonstrate the potential use of PBMC methylation along with quantitative exposure and biomarker data to guide further investigation into the mediators of occupational exposure and biomarkers and its role in risk assessment.