Lower urinary connective tissue growth factor levels and incident CKD stage 3 in the general population

Urinary Biomarkers of Renal Fibrosis

Renal fibrosis is the common pathological pathway of progressive CKD. The commonly used biomarkers in clinical practice are not optimal to detect injury or predict prognosis. Therefore, it is crucial to develop novel biomarkers to allow prompt intervention. Urine serves as a valuable resource of biomarker discovery for kidney diseases. Owing to the rapid development of omics platforms and bioinformatics, research on novel urinary biomarkers for renal fibrosis has proliferated in recent years. In this chapter, we discuss the current status and provide basic knowledge in this field. We present novel promising biomarkers including tubular injury markers, proteins related to activated inflammation/fibrosis pathways, CKD273, transcriptomic biomarkers, as well as metabolomic biomarkers. Furthermore, considering the complex nature of the pathogenesis of renal fibrosis, we also highlight the combination of biomarkers to further improve the diagnostic and prognostic performance.

Role of Epidermal Growth Factor Receptor (EGFR) and Its Ligands in Kidney Inflammation and Damage

Chronic kidney disease (CKD) is characterized by persistent inflammation and progressive fibrosis, ultimately leading to end-stage renal disease. Although many studies have investigated the factors involved in the progressive deterioration of renal function, current therapeutic strategies only delay disease progression, leaving an unmet need for effective therapeutic interventions that target the cause behind the inflammatory process and could slow down or reverse the development and progression of CKD. Epidermal growth factor receptor (EGFR) (ERBB1), a membrane tyrosine kinase receptor expressed in the kidney, is activated after renal damage, and preclinical studies have evidenced its potential as a therapeutic target in CKD therapy. To date, seven official EGFR ligands have been described, including epidermal growth factor (EGF) (canonical ligand), transforming growth factor-α, heparin-binding epidermal growth factor, amphiregulin, betacellulin, epiregulin, and epigen. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand. The direct activation of EGFR by its ligands can exert different cellular responses, depending on the specific ligand, tissue, and pathological condition. Among all EGFR ligands, CTGF/CCN2 is of special relevance in CKD. This growth factor, by binding to EGFR and downstream signaling pathway activation, regulates renal inflammation, cell growth, and fibrosis. EGFR can also be “transactivated” by extracellular stimuli, including several key factors involved in renal disease, such as angiotensin II, transforming growth factor beta (TGFB), and other cytokines, including members of the tumor necrosis factor superfamily, showing another important mechanism involved in renal pathology. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process. Better insights in EGFR signaling in renal disease could improve our current knowledge of renal pathology contributing to therapeutic strategies for CKD development and progression.

MMP-2 and 9 in Chronic Kidney Disease

Gelatinases are members of the matrix metalloproteinase (MMPs) family; they play an important role in the degradation of the extracellular matrix (ECM). This effect is also crucial in the development and progression of chronic kidney disease (CKD). Its expression, as well as its activity regulation are closely related to the cell signaling pathways, hypoxia and cell membrane structural change. Gelatinases also can affect the development and progression of CKD through the various interactions with tumor necrosis factors (TNFs), monocyte chemoattractant proteins (MCPs), growth factors (GFs), oxidative stress (OS), and so on. Currently, their non-proteolytic function is a hot topic of research, which may also be associated with the progression of CKD. Therefore, with the in-depth understanding about the function of gelatinases, we can have a more specific and accurate understanding of their role in the human body.

Risk Factors for Development and Progression of Chronic Kidney Disease: A Systematic Review and Exploratory Meta-Analysis

The risk factors influencing the natural course of chronic kidney disease (CKD) are complex and heterogeneous, and few systematic reviews to date have focused on this issue. The aim of the study is to identify the risk factors for disease development and progression in each stage of CKD. We conducted electronic literature searches of PubMed, MEDLINE, Scopus, and the Cochrane Library up to October 15, 2012, for observational studies evaluating the risk factors on the development or progression of CKD. Eligible studies should have collected repeated information that could evaluate changes in renal function. Extracted information from all the included studies was synthesized narratively. Quality assessments were performed using the Newcastle-Ottawa Scale. An exploratory random-effects meta-analysis was performed where feasible to pool effect sizes across studies for a specific risk factor in a specific outcome. We identified 38 cohort studies and 2 case-control studies from 40 articles, with a total of 318,898 participants from 14 countries. The follow-up duration ranged from 1.5 to 16 years. The majority of the included studies were of high quality. The baseline CKD stages of the included studies ranged from normal to later stages, and only 19 studies could be classified into a specific range of CKD stages during follow-up. Three risk factors from studies of the same baseline and follow-up CKD stages were eligible for the exploratory meta-analysis, including male sex, substantial proteinuria, and diabetes. The hazard ratios for the progression from CKD stages 3-5 to end-stage renal disease (ESRD) were 1.37 (95% confidence interval 1.17-1.62), 1.64 (1.01-2.66), and 1.16 (0.98-1.38) for male sex, substantial proteinuria, and diabetes, respectively. In conclusion, our analyses comprehensively summarize the initiating and perpetuating factors for CKD. Male sex and substantial proteinuria are significant perpetuating factors for the progression from late stage CKD to ESRD, and diabetes may play a minor role for the outcome of ESRD among patients with later stages of CKD.

Fat quality and incident cardiovascular disease, all-cause mortality, and cancer mortality

CONTEXT

Cellular characteristics of fat quality have been associated with cardiometabolic risk and can be estimated by computed tomography (CT) attenuation.

OBJECTIVE

The aim was to determine the association between CT attenuation (measured in Hounsfield units [HU]) and clinical outcomes.

METHODS

This was a prospective community-based cohort study using data from the Framingham Heart Study (n = 3324, 48% women, mean age 51 years) and Cox proportional hazard models.

MAIN OUTCOMES

The primary outcomes of interest were incident cardiovascular disease (CVD) and all-cause mortality. The secondary outcomes of interest were incident cancer, non-CVD death, and cancer death.

RESULTS

There were 111 incident CVD events, 137 incident cancers, 85 deaths including 69 non-CVD deaths, and 45 cancer deaths in up to 23 047 person-years of follow-up. A 1-SD increment in visceral adipose tissue (VAT) HU was inversely associated with incident CVD in the age- and sex-adjusted model (hazard ratio [HR] 0.78, P = .02) but not after multivariable adjustment (HR 0.83, P = .11). VAT HU was directly associated with all-cause mortality (multivariable HR 1.40, P = .003), which maintained significance after additional adjustment for body mass index (HR 1.53, P < .001) and VAT volume (HR 1.99, P < .001). Non-CVD death remained significant in all 3 models, including after adjustment for VAT volume (HR 1.97, P < .001). VAT HU was also associated with cancer mortality (HR 1.93, P = .002). Similar results were obtained for sc adipose tissue HU.

CONCLUSIONS

Fat quality, as estimated by CT attenuation, is associated with all-cause mortality, non-CVD death, and cancer death. These associations highlight how indirect indices of fat quality can potentially add to a better understanding of obesity-related complications.

Novel urinary biomarkers in early diabetic kidney disease

In diabetic kidney disease, detection of urinary albumin is recommended to aid in diagnosis, evaluate disease severity, and determine effects of therapy. However, because typical histopathologic changes in diabetic kidney disease or early progressive renal decline may occur in patients with normoalbuminuria, urinary albumin may not be sufficient to identify patients with early-stage diabetic kidney disease or to predict its progression. Therefore, intensive efforts have been made to identify novel noninvasive urinary biomarkers to discriminate patients with a higher risk of end-stage renal failure. Because diabetic kidney disease progression is associated with the extent of histologic changes in the glomeruli and the degree of tubulointerstitial changes, urinary biomarkers that accurately reflect the degree of histopathologic damage may be excellent biomarkers. This review article summarizes the clinical significance of new urinary biomarkers in the early detection of diabetic kidney disease.

Analysis of a urinary biomarker panel for incident kidney disease and clinical outcomes

Whether novel biomarkers improve the assessment of incident kidney disease and related adverse outcomes remains to be tested in longitudinal observational studies. We tested 14 urinary biomarkers for association with incident kidney, cardiovascular, and mortality outcomes in 2948 Framingham Heart Study participants. Baseline examinations were performed between 1995 and 1998; mean follow-up was 10.1 years for renal outcomes and 11.2 years for survival analyses. Primary outcomes were incident CKD, incident albuminuria, incident cardiovascular disease, and all-cause mortality. Secondary analyses assessed incident congestive heart failure (CHF) and mortality with coexistent kidney disease. Biomarkers were tested for association with renal end points using logistic regression and incident cardiovascular and mortality outcomes in proportional hazards models; α1-microglobulin, Kim-1, and TFF-3 predicted all-cause mortality (hazard ratio per SD increase in log-transformed biomarker [HR] range, 1.15 to 1.21; 95% confidence interval [CI] range, 1.04 to 1.34; P values=0.007 to <0.001), whereas α1-microglobulin, β2-microglobulin, KIM-1, and TFF-3 associated with death with coexistent kidney disease (HR range, 1.72-2.25; 95% CI, 1.17 to 3.24; P values<0.01). KIM-1 also associated with the risk of incident CHF (HR, 1.32; 95% CI, 1.07 to 1.63; P=0.008). CTGF associated nominally with CKD (HR, 0.83; 95% CI, 0.71 to 0.98; P=0.03), but no other biomarkers associated with incident CKD or albuminuria. Addition of α1-microglobulin and TFF-3 resulted in a nonsignificant net reclassification index (NRI) of 3% for all-cause mortality beyond clinical risk factors. In conclusion, components of a panel of 14 subclinical biomarkers of kidney injury were associated with important clinical outcomes and merit additional investigation.

Does HIV infection promote early kidney injury in women?

BACKGROUND

In HIV-infected women, urine concentrations of novel tubulointerstitial injury markers, interleukin-18 (IL-18) and kidney injury marker-1 (KIM-1), are associated with kidney function decline and all-cause mortality. We hypothesized that HIV-infected individuals with preserved kidney filtration function would have more extensive kidney injury, as determined by urine injury markers, compared to the uninfected controls, and that risk factors for tubulointerstitial injury would differ from risk factors for albuminuria.

METHODS

In this cross-sectional study, we compared urine concentrations of IL-18, KIM-1 and albumin-to-creatinine ratio (ACR) in 908 HIV-infected and 289 HIV-uninfected women enrolled in the Women's Interagency HIV Study, utilizing stored urine specimens from visits between 1999 and 2000.

RESULTS

After multivariate-adjusted linear regression analysis, mean urine concentrations were higher in HIV-infected individuals by 38% for IL-18 (P<0.0001), 12% for KIM-1 (P=0.081) and 47% for ACR (P<0.0001). Higher HIV RNA level (15% per 10-fold increase; P<0.0001), lower CD4(+) lymphocyte count (8% per doubling; P=0.0025), HCV infection (30%; P=0.00018) and lower high-density lipoprotein (5% per 10 mg/dl; P=0.0024) were each associated with higher IL-18 concentrations. In contrast, hypertension (81%; P<0.0001) and diabetes (47%; P=0.018) were among the strongest predictors of higher ACR, though HIV RNA level (15% per 10-fold increase; P=0.0004) was also associated with higher ACR.

CONCLUSIONS

HIV-infected women had more extensive tubulointerstitial and glomerular injury than uninfected women, but the associated factors differed among the urine biomarkers. Combinations of urinary biomarkers should be investigated to further characterize early kidney injury in HIV-infected women.

The C-terminal module IV of connective tissue growth factor is a novel immune modulator of the Th17 response

Connective tissue growth factor (CTGF/CCN2) is a matricellular protein susceptible to proteolytic degradation. CCN2 levels have been suggested as a potential risk biomarker in several chronic diseases. In body fluids, CCN2 full-length and its degradation fragments can be found; however, their in vivo effects are far from being elucidated. CCN2 was described as a profibrotic mediator, but this concept is changing to a proinflammatory cytokine. In vitro, CCN2 full-length and its C-terminal module IV (CCN2(IV)) exert proinflammatory properties. Emerging evidence suggest that Th17 cells, and its effector cytokine IL-17A, participate in chronic inflammatory diseases. Our aim was to explore whether CCN2(IV) could regulate the Th17 response. In vitro, stimulation of human naive CD4+ T lymphocytes with CCN2(IV) resulted in differentiation to Th17 phenotype. The in vivo effects of CCN2(IV) were studied in C57BL/6 mice. Intraperitoneal administration of recombinant CCN2(IV) did not change serum IL-17A levels, but caused an activation of the Th17 response in the kidney, characterized by interstitial infiltration of Th17 (IL17A+/CD4+) cells and upregulation of proinflammatory mediators. In CCN2(IV)-injected mice, elevated renal levels of Th17-related factors (IL-17A, IL-6, STAT3 and RORγt) were found, whereas Th1/Th2 cytokines or Treg-related factors (TGF-β and Foxp-3) were not modified. Treatment with an anti-IL-17A neutralizing antibody diminished CCN2(IV)-induced renal inflammation. Our findings unveil that the C-terminal module of CCN2 induces the Th17 differentiation of human Th17 cells and causes a renal Th17 inflammatory response. Furthermore, these data bear out that IL-17A targeting is a promising tool for chronic inflammatory diseases, including renal pathologies.

Advances in the use of multimarker panels for renal risk stratification

PURPOSE OF REVIEW

This review discusses novel studies in the past year that have examined the use of combinations of multiple markers to improve risk prediction in the setting of chronic kidney disease (CKD). We will focus on multimarker panels to: improve prediction of CKD onset; improve classification of CKD and risk stratification of persons with CKD; and develop individual-level risk scores for progression to end-stage renal disease (ESRD).

RECENT FINDINGS

One study reported that several novel circulation biomarkers may aid in predicting incident CKD and microalbuminuria. Second, our group has shown that the combination of creatinine, cystatin C, and albuminuria improves detection and risk stratification for death, heart failure, cardiovascular events, and ESRD compared with creatinine alone. Finally, a highly accurate individual risk score was developed to predict progression to ESRD using readily available clinical markers.

SUMMARY

The combination of multiple markers improves detection and risk stratification in CKD. Future research is needed in understanding the use of a 'renal panel' for detection, classification, and risk stratification in kidney disease in diverse populations. The studies presented here represent the beginning of a paradigm shift to multimarker panels in nephrology.

Associations of urinary levels of kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) with kidney function decline in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Whether elevations in levels of urinary biomarkers of tubular injury (urine neutrophil gelatinase-associated lipocalin [NGAL] and kidney injury molecule 1 [KIM-1]) are associated with future risk of kidney disease has not been investigated.

STUDY DESIGN

1:1 nested case-control study.

SETTING & PARTICIPANTS

686 participants in the Multi-Ethnic Study of Atherosclerosis (MESA).

PREDICTOR

NGAL and KIM-1 were measured at baseline, expressed as log-transformed continuous variables, and categorized into deciles.

OUTCOMES

Kidney function was estimated by cystatin C level using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Incident CKD stage 3 was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2) and an eGFR decrease >1 mL/min/1.73 m(2) per year, and rapid kidney function decrease was defined as decrease ≥3 mL/min/1.73 m(2) per year.

MEASUREMENTS

Cases were defined as persons with eGFR >60 mL/min/1.73 m(2) who subsequently developed incident CKD stage 3 and/or had rapid kidney function decrease by the MESA year-5 visit. Controls were matched for age, sex, race, diabetes, and baseline eGFR. We adjusted for age, hypertension, and presence of albuminuria (albumin-creatinine ratio ≥30 mg/g).

RESULTS

Of 343 cases, 145 had incident CKD stage 3, 141 had rapid kidney function decrease, and 57 had both. Mean eGFR for controls was 81 ± 10 mL/min/1.73 m(2) at baseline and 80 ± 10 mL/min/1.73 m(2) at follow-up compared with 82 ± 13 and 58 ± 10 mL/min/1.73 m(2) for cases. Each doubling of KIM-1 level (in picograms per milliliter) was associated with an OR of 1.15 (95% CI, 1.02-1.29) for incident CKD stage 3 and/or rapid kidney function decrease. Compared with the lowest 90%, the highest decile of KIM-1 level was associated with an OR of 2.02 (95% CI, 1.15-3.56) for the outcome; these associations were independent of albuminuria. NGAL levels (in nanograms per milliliter) were not associated with incident CKD stage 3 and/or rapid kidney function decrease (OR, 1.04; 95% CI, 0.99-1.10). Results were similar when KIM-1 and NGAL levels were standardized for urine creatinine.

LIMITATIONS

The case-control design limits the ability to account for persons who died or were not available for follow-up.

CONCLUSIONS

Urinary KIM-1 level is associated with future risk of kidney disease independent of albuminuria. Urinary biomarkers of tubular injury are a promising tool for identifying persons at risk of CKD.