Jayanta Gupta

Association between Albuminuria, Kidney Function, and Inflammatory Biomarker Profile in CKD in CRIC

BACKGROUND AND OBJECTIVES Increased risk of mortality in patients with CKD has been attributed to inflammation. However, the association between kidney function, albuminuria, and biomarkers of inflammation has not been examined in a large cohort of CKD patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This study measured the plasma levels of IL-1β, IL-1 receptor antagonist (IL-1RA), IL-6, TNF-α, TGF-β, high-sensitivity C-reactive protein (hs-CRP), fibrinogen, and serum albumin in 3939 participants enrolled in the Chronic Renal Insufficiency Cohort study between June 2003 and September 2008. An inflammation score was established based on plasma levels of IL-1β, IL-6, TNF-α, hs-CRP, and fibrinogen. Estimated GFR (eGFR) and serum cystatin C were used as measures of kidney function. Albuminuria was quantitated by urine albumin to creatinine ratio (UACR). RESULTS Plasma levels of IL-1β, IL-1RA, IL-6, TNF-α, hs-CRP, and fibrinogen were higher among participants with lower levels of eGFR. Inflammation score was higher among those with lower eGFR and higher UACR. In regression analysis adjusted for multiple covariates, eGFR, cystatin C, and UACR were strongly associated with fibrinogen, serum albumin, IL-6, and TNF-α. Each unit increase in eGFR, cystatin C, and UACR was associated with a -1.2% (95% confidence interval, -1.4, -1), 64.9% (56.8, 73.3) and 0.6% (0.4, 0.8) change in IL-6, respectively (P<0.001). CONCLUSIONS Biomarkers of inflammation were inversely associated with measures of kidney function and positively with albuminuria.

The persistence of atopic dermatitis and filaggrin (FLG) mutations in a US longitudinal cohort.

BACKGROUND Atopic dermatitis (AD) is a common skin disease that is characterized by recurrent episodes of itching. Filaggrin (FLG) loss-of-function (FLG null) mutations have been associated with an increased risk of AD. OBJECTIVE We sought to evaluate the effect of individual FLG null mutations on the persistence of AD over time. METHODS We evaluated a multiyear prospective cohort study of children with AD with respect to FLG null mutations (R501X, 2282del4, R2447X, and S3247X). We evaluated the association of these mutations with the persistence of AD symptoms over time with respect to reports of no symptoms of AD and whether topical medication was needed for symptom resolution. RESULTS Eight hundred fifty-seven subjects were followed for 3684 person-years. One or more FLG null mutations were noted in 16.3% of subjects and specifically in 27.5% of white subjects and 5.8% of African American subjects. Subjects with an FLG null mutation were less likely (odds ratio [OR], 0.54; 95% CI, 0.41-0.71) to report that their skin was symptom free at any time compared with those without an FLG null mutation. The effect of these mutations was similar in white subjects (OR, 0.42; 95% CI, 0.31-0.57) and African-American subjects (OR, 0.53; 95% CI, 0.25-1.12; P = .62). Children with the R501X mutation (OR, 0.44; 95% CI, 0.22-0.88) were the least responsive to therapy. CONCLUSIONS In a US cohort with AD, FLG null mutations were common. Children with FLG null mutations were more likely to have persistent AD. Although these mutations were more common in those of European ancestry, their effect on persistence was similar in those of African ancestry. Response to therapy was not uniform among children with FLG null mutations.

Lack of Effectiveness of Hyperbaric Oxygen Therapy for the Treatment of Diabetic Foot Ulcer and the Prevention of Amputation: A cohort study

OBJECTIVE Hyperbaric oxygen (HBO) is a device that is used to treat foot ulcers. The study goal was to compare the effectiveness of HBO with other conventional therapies administered in a wound care network for the treatment of a diabetic foot ulcer and prevention of lower-extremity amputation. RESEARCH DESIGN AND METHODS This was a longitudinal observational cohort study. To address treatment selection bias, we used propensity scores to determine the “propensity” that an individual was selected to receive HBO. RESULTS We studied 6,259 individuals with diabetes, adequate lower limb arterial perfusion, and foot ulcer extending through the dermis, representing 767,060 person-days of wound care. In the propensity score–adjusted models, individuals receiving HBO were less likely to have healing of their foot ulcer (hazard ratio 0.68 [95% CI 0.63–0.73]) and more likely to have an amputation (2.37 [1.84–3.04]). Additional analyses, including the use of an instrumental variable, were conducted to assess the robustness of our results to unmeasured confounding. HBO was not found to improve the likelihood that a wound might heal or to decrease the likelihood of amputation in any of these analyses. CONCLUSIONS Use of HBO neither improved the likelihood that a wound would heal nor prevented amputation in a cohort of patients defined by Centers for Medicare and Medicaid Services eligibility criteria. The usefulness of HBO in the treatment of diabetic foot ulcers needs to be reevaluated.

Comparison of Two ELISA Methods and Mass Spectrometry for Measurement of Vitamin D‐Binding Protein: Implications for the Assessment of Bioavailable Vitamin D Concentrations Across Genotypes

Studies using vitamin D‐binding protein (DBP) concentrations to estimate free and bioavailable vitamin D have increased dramatically in recent years. Combinations of two single‐nucleotide polymorphisms (SNPs) produce three major DBP isoforms (Gc1f, Gc1s, and Gc2). A recent study showed that DBP concentrations quantified by liquid chromatography–tandem mass spectrometry (LC‐MS/MS) did not differ by race, whereas a widely used monoclonal enzyme‐linked immunosorbent assay (ELISA) quantified DBP differentially by isoform, yielding significantly lower DBP concentrations in black versus white individuals. We compared measurements of serum DBP using a monoclonal ELISA, a polyclonal ELISA, and LC‐MS/MS in 125 participants in the Chronic Renal Insufficiency Cohort (CRIC). Serum free and bioavailable 25OHD were calculated based on DBP concentrations from these three assays in homozygous participants, and race differences were compared. We confirmed that the monoclonal ELISA quantifies DBP differentially by isoform and showed that the polyclonal ELISA is not subject to this bias. Whereas ≤9% of the variability in DBP concentrations quantified using either LC‐MS/MS or the polyclonal ELISA was explained by genotype, 85% of the variability in the monoclonal ELISA‐based measures was explained by genotype. DBP concentrations measured by the monoclonal ELISA were disproportionately lower than LC‐MS/MS‐based results for Gc1f homozygotes (median difference –67%; interquartile range [IQR] –71%, –64%), 95% of whom were black. In contrast, the polyclonal ELISA yielded consistently and similarly higher measurements of DBP than LC‐MS/MS, irrespective of genotype, with a median percent difference of +50% (IQR +33%, +65%). Contrary to findings using the monoclonal ELISA, DBP concentrations did not differ by race, and free and bioavailable 25OHD were significantly lower in black versus white participants based on both the polyclonal ELISA and LC‐MS/MS, consistent with their lower total 25OHD. Future studies of DBP and free or bioavailable vitamin D metabolites should employ DBP assays that are not biased by DBP genotype.

Inflammation and Progression of CKD: The CRIC Study

BACKGROUND AND OBJECTIVES CKD is a global public health problem with significant mortality and morbidity. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We examined the multivariable association of plasma levels of IL-1, IL-1 receptor antagonist, IL-6, TNF-α, TGF-β, high-sensitivity C-reactive protein, fibrinogen, and serum albumin with progression of CKD in 3430 Chronic Renal Insufficiency Cohort study participants. RESULTS Over a median follow-up time of 6.3 years, 899 participants reached the composite end point of ≥50% decline in eGFR from baseline or onset of ESRD. Elevated plasma levels of fibrinogen, IL-6, and TNF-α and lower serum albumin were associated with a greater decline in eGFR over time. After adjusting for demographics, BP, laboratory variables, medication use, and baseline eGFR, hazard ratios for the composite outcome were greater for the patients in the highest quartile of fibrinogen (hazard ratio, 2.05; 95% confidence interval, 1.64 to 2.55; P<0.001), IL-6 (hazard ratio, 1.44; 95% confidence interval, 1.17 to 1.77; P<0.01), and TNF-α (hazard ratio, 1.94; 95% confidence interval, 1.52 to 2.47; P<0.001) compared with those in the respective lowest quartiles. The hazard ratio was 3.48 (95% confidence interval, 2.88 to 4.21; P<0.001) for patients in the lowest serum albumin quartile relative to those in the highest quartile. When also adjusted for albuminuria, the associations of fibrinogen (hazard ratio, 1.49; 95% confidence interval, 1.20 to 1.86; P<0.001), serum albumin (hazard ratio, 1.52; 95% confidence interval, 1.24 to 1.87; P<0.001), and TNF-α (hazard ratio, 1.42; 95% confidence interval, 1.11 to 1.81; P<0.001) with outcome were attenuated but remained significant. CONCLUSIONS Elevated plasma levels of fibrinogen and TNF-α and decreased serum albumin are associated with rapid loss of kidney function in patients with CKD.

Thymic Stromal Lymphopoietin Variation, Filaggrin Loss of Function, and the Persistence of Atopic Dermatitis

IMPORTANCE Atopic dermatitis (AD) is a common chronic illness of childhood. OBJECTIVE To evaluate the association between thymic stromal lymphopoietin (TSLP) variation and the persistence of skin symptoms of AD. DESIGN, SETTING, AND PARTICIPANTS A prospective cohort study was conducted in the general community. Participants included 796 children enrolled in the Pediatric Eczema Elective Registry. EXPOSURE Evaluation of TSLP variation. MAIN OUTCOMES AND MEASURES Self-reported outcome of whether a childs skin had no symptoms of AD and required no medications for 6 months at 6-month intervals. RESULTS We evaluated 14 variants of TSLP. The variant rs1898671 was significantly associated with the outcome in white children (P = .01). As measured by overlapping CIs, similar odds ratios (ORs) were noted among whites (OR, 1.72; 95% CI, 1.11-2.66) and African Americans (1.33; 0.52-3.45). Further within the subcohort of individuals with a filaggrin protein (FLG) loss-of-function mutation, those with TSLP variation were more likely to have less-persistent disease (OR, 4.92; 95% CI, 2.04-11.86). CONCLUSIONS AND RELEVANCE The TSLP variation is associated with less persistent AD. Therefore, TSLP may be a potential therapeutic target for the treatment of AD, especially in individuals with diminished barrier function due to FLG mutations. This is an attractive hypothesis that can be tested in clinical trials.

Exome Sequencing of Filaggrin and Related Genes in African-American Children with Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic relapsing disease. There is a considerable body of evidence supporting a genetic basis for AD (Bussman et al., 2011;Ellinghaus et al., 2013). Mutations in the Filaggrin (FLG) gene have been consistently found to be associated with AD in people of European and Asian ancestry (Brown and McLean, 2012). More than 40 FLG loss-of-function mutations have been described in Europeans and Asians, (Brown and McLean, 2012).However, FLG loss-of-function mutations have not commonly been found in Africans or African-Americans (Margolis et al., 2012;Brown and McLean, 2012;Winge et al., 2011a). Loss-of-function mutations in exon 3 of FLG result in diminished or absent filaggrin protein, most often due to a premature stop codon or a frameshift mutation resulting in a stop codon further downstream. Interestingly, the absence of profilaggrin protein (precursor of filaggrin) has also been noted in keratohyalin granules in the majority of those with ichthyosis vulgaris (IV) of European and Asian ancestry (Perusquia-Ortiz.A.M. et al., 2013;Thyssen et al., 2013;Fleckman and Brumbaugh, 2002).

Association between Inflammation and Cardiac Geometry in Chronic Kidney Disease: Findings from the CRIC Study

Background Left ventricular hypertrophy (LVH) and myocardial contractile dysfunction are independent predictors of mortality in patients with chronic kidney disease (CKD). The association between inflammatory biomarkers and cardiac geometry has not yet been studied in a large cohort of CKD patients with a wide range of kidney function. Methods Plasma levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), IL-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, high-sensitivity C-Reactive protein (hs-CRP), fibrinogen and serum albumin were measured in 3,939 Chronic Renal Insufficiency Cohort study participants. Echocardiography was performed according to the recommendations of the American Society of Echocardiography and interpreted at a centralized core laboratory. Results LVH, systolic dysfunction and diastolic dysfunction were present in 52.3%, 11.8% and 76.3% of the study subjects, respectively. In logistic regression analysis adjusted for age, sex, race/ethnicity, diabetic status, current smoking status, systolic blood pressure, urinary albumin- creatinine ratio and estimated glomerular filtration rate, hs-CRP (OR 1.26 [95% CI 1.16, 1.37], p<0.001), IL-1RA (1.23 [1.13, 1.34], p<0.0001), IL-6 (1.25 [1.14, 1.36], p<0.001) and TNF-α (1.14 [1.04, 1.25], p = 0.004) were associated with LVH. The odds for systolic dysfunction were greater for subjects with elevated levels of hs-CRP (1.32 [1.18, 1.48], p<0.001) and IL-6 (1.34 [1.21, 1.49], p<0.001). Only hs-CRP was associated with diastolic dysfunction (1.14 [1.04, 1.26], p = 0.005). Conclusion In patients with CKD, elevated plasma levels of hs-CRP and IL-6 are associated with LVH and systolic dysfunction.

Genome-Wide Association of CKD Progression: The Chronic Renal Insufficiency Cohort Study

The rate of decline of renal function varies significantly among individuals with CKD. To understand better the contribution of genetics to CKD progression, we performed a genome-wide association study among participants in the Chronic Renal Insufficiency Cohort Study. Our outcome of interest was CKD progression measured as change in eGFR over time among 1331 blacks and 1476 whites with CKD. We stratified all analyses by race and subsequently, diabetes status. Single-nucleotide polymorphisms (SNPs) that surpassed a significance threshold of P<1×10-6 for association with eGFR slope were selected as candidates for follow-up and secondarily tested for association with proteinuria and time to ESRD. We identified 12 such SNPs among black patients and six such SNPs among white patients. We were able to conduct follow-up analyses of three candidate SNPs in similar (replication) cohorts and eight candidate SNPs in phenotype-related (validation) cohorts. Among blacks without diabetes, rs653747 in LINC00923 replicated in the African American Study of Kidney Disease and Hypertension cohort (discovery P=5.42×10-7; replication P=0.039; combined P=7.42×10-9). This SNP also associated with ESRD (hazard ratio, 2.0 (95% confidence interval, 1.5 to 2.7); P=4.90×10-6). Similarly, rs931891 in LINC00923 associated with eGFR decline (P=1.44×10-4) in white patients without diabetes. In summary, SNPs in LINC00923, an RNA gene expressed in the kidney, significantly associated with CKD progression in individuals with nondiabetic CKD. However, the lack of equivalent cohorts hampered replication for most discovery loci. Further replication of our findings in comparable study populations is warranted.

Diabetes, lower extremity amputation, loss of protective sensation, and neuronal nitric oxide synthase associated protein in the Chronic Renal Insufficiency Cohort study

Lower extremity amputation (LEA) is a life‐altering complication of diabetes. The goal of our study was to investigate the possibility that genetic variation in neuronal nitric oxide synthase associated protein (NOS1AP) is associated with LEA and diabetic peripheral neuropathy (DPN). Our work used data from the Chronic Renal Insufficiency Cohort (CRIC) study. CRIC is a multicenter investigation undertaken to pursue the relationship between chronic renal insufficiency and cardiovascular disease. We evaluated 3,040 CRIC study subjects; 1,490 individuals were African Americans and 1,550 were whites. LEA occurred in 162 (5.3%) subjects, 93 (6.2%) of African Americans and 69 (4.4%) of whites. In whites, NOS1AP single nucleotide polymorphism rs1963645 was most strongly associated with LEA (1.73 [1.23, 2.44]). In African Americans three NOS1AP single nucleotide polymorphisms were associated with LEA: rs6659759 (1.65 [1.21, 2.24]); rs16849113 (1.58 [1.16, 2.14]); rs880296 (1.54 [1.14, 2.10]). We tested a subset of 100 CRIC participants for DPN using Semmes–Weinstein filaments. DPN in those with diabetes was associated with rs1963645 (16.97 [2.38, 120.97]) in whites and rs16849113 and rs6659759 (3.62 [1.11, 11.83] and 3.02 [0.82, 11.12], respectively) in African Americans. In conclusion, this is one of the first studies to show that NOS1AP gene variants are associated with DPN and LEA.