Biochemistry and Clinical Role of Human Cystatin C

Serum Cystatin C as an Inflammatory Marker in Exacerbated and Convalescent COPD Patients

Chronic obstructive pulmonary disease (COPD) is a common chronic inflammatory disease with high morbidity and mortality rates. Cystatin C (Cys C) is a sensitive indicator for various chronic inflammatory diseases. In this study, we aimed to evaluate the role of Cys C in COPD patients comparing with the other well-known inflammatory markers. Ninety patients with acute exacerbated COPD were studied and were reassessed when convalescent. Ninety controls were matched for age, gender, body mass index, smoking index, and comorbidity. Serum Cys C was significantly increased in convalescent COPD patients compared with healthy controls and further increased in COPD patients with an acute exacerbation. Serum Cys C was positively correlated with hsCRP both in the exacerbation and convalescence periods of COPD and negatively correlated with FEV1% predicted and FEV1/FVC in the convalescent COPD patients. In conclusion, serum Cys C is a positive acute-phase reactant in COPD patients and might indicate systemic inflammation during the progression of COPD.

Dementia risk in renal dysfunction: A systematic review and meta-analysis of prospective studies

OBJECTIVE

Renal dysfunction has been linked with increased risk for cognitive impairment and dementia, but studies are conflicting. For that reason, the aim of the present systematic review and meta-analysis is to summarize the best available evidence on the prospective association between potential markers of renal dysfunction and development of cognitive impairment or dementia.

METHODS

Medline, Embase, and Cochrane Database of Systematic Reviews were searched for potential publications until August 1, 2016. Studies were eligible if they fulfilled the following criteria: population-based study, prospective design, ≥100 participants, aged ≥45 years, ≥1 year follow-up, and cognition/dementia outcomes. Where appropriate, random effects meta-analyses were conducted yielding pooled odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Twenty-two out of 8,494 abstracts fulfilled the eligibility criteria. Sufficient evidence was found for albuminuria, mixed results for estimated glomerular filtration rate (eGFR), insufficient support for cystatin C, and tentative evidence for serum creatinine and creatinine clearance. Meta-analyses of 5 studies representing 27,805 persons showed a 35% increased risk of cognitive impairment or dementia in those with albuminuria (OR 1.35, 95% CI 1.06-1.73, p = 0.015), whereas eGFR <60 mL/min/1.73 m² showed no significant association (OR 1.28, 95% CI 0.99-1.65, p = 0.063). No meta-analyses could be done for serum creatinine, creatinine clearance, or cystatin C.

CONCLUSIONS

The overall evidence for an association between renal dysfunction and cognitive impairment or dementia is modest. Evidence suggests that albuminuria is associated with higher odds of developing cognitive impairment or dementia.

Application of amide hydrogen/deuterium exchange mass spectrometry for epitope mapping in human cystatin C

Human cystatin C (hCC) is a small cysteine protease inhibitor whose oligomerization by propagated domain swapping is linked to certain neurological disorders. One of the ways to prevent hCC dimerization and fibrillogenesis is to enable its interaction with a proper antibody. Herein, the sites of interaction of hCC with dimer-preventing mouse monoclonal anti-hCC antibodies Cyst28 are studied and compared with the binding sites found for mAb Cyst10 that has almost no effect on hCC dimerization. In addition, hCC epitopes in complexes with native polyclonal antibodies extracted from human serum were studied. The results obtained with hydrogen-deuterium exchange mass spectrometry (HDX MS) were compared with the previous findings made using the excision/extraction MS approach. The main results from the two complementary MS-based approaches are found to be in agreement with each other, with some differences being attributed to the specificity of each method. The findings of the current studies may be important for future design of hCC dimerization inhibitors.

Isolation and characterization of autoantibodies against human cystatin C

Hereditary cystatin C amyloid angiopathy (HCCAA) is a severe neurodegenerative disorder related to the point mutation in cystatin C gene resulting in human cystatin C (hCC) L68Q variant. One of the potential immunotherapeutic approaches to HCCAA treatment is based on naturally occurring antibodies against cystatin C. A recent growing interest in autoantibodies, especially in the context of neurodegenerative diseases, emerges from their potential use as valuable diagnostic markers and for controlling protein aggregation. In this work, we present characteristics of natural anti-hCC antibodies isolated from the IgG fraction of human serum by affinity chromatography. The electrophoresis (1-D and 2-D) results demonstrated that the isolated NAbs are a polyclonal mixture, but their electrophoretic properties did not allow to classify the new autoantibodies to any particular type of IgG. The Fc-glycan status of the studied autoantibodies was assessed using mass spectrometry analysis. For the isolated NAbs, the epitopic fragments in hCC sequence were identified by MS-assisted proteolytic excision of the immune complex and compared with the ones predicted theoretically. The knowledge of hCC fragments binding to NAbs and other ligands may contribute to the search for new diagnostic methods for amyloidosis of different types and the search for their treatment.

Assessment of a multiple biomarker panel for diagnosis of amyotrophic lateral sclerosis

Background

The aim of the study was to assess a panel of promising biomarkers for their ability to improve diagnosis of sporadic amyotrophic lateral sclerosis (ALS).

Methods

Forty patients with sporadic ALS and 40 controls with other neurological diseases were evaluated. Levels of phosphorylated neurofilament heavy chain (pNfH), S100-β, cystatin C, and chitotriosidase (CHIT) in cerebrospinal fluid were assayed using two-site solid-phase sandwich ELISA.

Results

Patients with sporadic ALS showed higher levels of pNfH and CHIT than controls, but lower levels of cystatin C. Multivariate logistic regression that adjusted for patient age and sex identified significant associations between sporadic ALS and levels of pNfH, CHIT and cystatin C. Levels of pNfH correlated positively with rate of progression and decline based on the Amyotrophic Lateral Sclerosis Functional Rating Scale - Revised. Based on receiver operating curve analysis, a pNfH cut-off of 437 ng/L discriminated patients from controls with a sensitivity of 97.3 % and specificity of 83.8 %. A CHIT cut-off of 1593.779 ng/L discriminated patients from controls with a sensitivity of 83.8 % and specificity of 81.1 %. Combining the two biomarkers gave a sensitivity of 83.8 % and specificity of 91.9 %.

Conclusions

Levels of pNfH in cerebrospinal fluid may be a reliable biomarker for diagnosing ALS, and combining this biomarker with levels of CHIT may improve diagnostic accuracy.

Cystatin C and risk of mortality among patients undergoing percutaneous coronary intervention

AIMS

We tested the prognostic value of cystatin C in patients with documented coronary artery disease (CAD) who underwent percutaneous coronary artery intervention (PCI). We also tested the hypothesis that the incremental predictive value of cystatin C on all-cause mortality was superior to that of glomerular filtration rate (GFR) by the Modification of Diet in Renal Disease (MDRD) formula.

METHODS AND RESULTS

Included in the study were 2,757 patients (mean age 63 years, 77% men). Blood samples for cystatin C levels were collected immediately before PCI. During a median follow-up of two years, 114 patients died. In multivariable Cox analyses, after adjustment for several confounders, GFR (p=0.004) and cystatin C concentration (p<0.0001) were independent predictors of all-cause death. Cystatin C predicted all-cause death (c-statistic: 0.794) better than GFR estimate based on creatinine (c-statistic: 0.776, p=0.008 for comparison), and significantly reclassified 15% of patients into categories that reflected their actual likelihood of death more accurately (p=0.005). Adding cystatin C and GFR in the same multivariable survival model, only cystatin C level was a significant predictor of death.

CONCLUSIONS

This study presents for the first time the incremental predictive value of cystatin C over the creatinine-based MDRD formula on all-cause mortality for CAD patients undergoing PCI.

Relationship between pre-procedural microalbuminuria and renal functional changes after coronary computed tomography in diabetic patients

BACKGROUND

Diabetes is one of the risks for development of contrast-induced nephropathy (CIN). The percentage change in cystatin C (CyC), a recent new reliable marker for detecting subtle renal dysfunction, of ≥10% for 24h after procedure is an independent predictor for developing CIN. Urinary microalbumin is one of the markers for preclinical nephropathy in diabetic patients. We investigated the relationship between pre-procedural urinary microalbumin and renal functional changes using CyC after coronary computed tomography angiography (CCTA) in diabetic patients.

METHODS

Two hundred and six patients with diabetes scheduled for CCTA were enrolled. The serum creatinine and CyC levels were measured before and 24h after CCTA. The percentage change in CyC (%CyC) and absolute change in estimated glomerular filtration rate (eGFR) from pre- to post-procedure were calculated. The pre-procedural urinary microalbumin was measured. The patients were classified into 2 groups as follows: group A comprised 93 patients with pre-procedural urinary microalbumin of ≥30mg/g creatinine; and group B comprised 113 patients with one of <30mg/g creatinine.

RESULTS

The %CyC, fasting plasma glucose levels, and HbA1c were significantly greater in group A than in group B. The absolute change in eGFR was significantly less in group A than in group B. A significant correlation was seen between urinary microalbumin and %CyC (r=0.49, p<0.0001). Multivariate regression analysis revealed that pre-procedural urinary microalbumin and HbA1c were independent predictors for a %CyC≥10% (OR: 1.030, 95% CI: 1.020-1.039, p=0.008; and OR: 1.011, 95% CI: 1.007-1.016, p=0.004, respectively). The optimal cut-off value of a pre-procedural urinary microalbumin level was 64mg/g creatinine for predicting a %CyC≥10% using receiver-operating characteristic curve analysis with a sensitivity, specificity, and area under the curve of 56%, 88%, and 0.72, respectively.

CONCLUSIONS

Renal functional changes should be paid attention to after CCTA, particularly in diabetic patients exhibiting elevated pre-procedural urinary microalbumin even though they indicate preserved eGFR.

Epitope location for two monoclonal antibodies against human cystatin C, representing opposite aggregation inhibitory properties

Human cystatin C (hCC), like many other amyloidogenic proteins, dimerizes and possibly makes aggregates by subdomain swapping. Inhibition of the process should suppress the fibrillogenesis leading to a specific amyloidosis (hereditary cystatin C amyloid angiopathy, HCCAA). It has been reported that exogenous agents like monoclonal antibodies against cystatin C are able to suppress formation of cystatin C dimers and presumably control the neurodegenerative disease. We have studied in detail two monoclonal antibodies (mAbs) representing very different aggregation inhibitory potency, Cyst10 and Cyst28, to find binding sites in hCC sequence responsible for the immunocomplex formation and pave the way for possible immunotherapy of HCCAA. We used the epitope extraction/excision mass spectrometry approach with the use of different enzymes complemented by affinity studies with synthetic hCC fragments as a basic technique for epitope identification. The results were analyzed in the context of hCC structure allowing us to discuss the binding sites for both antibodies. Epitopic sequences for clone Cyst28 which is a highly potent dimerization inhibitor were found in N-terminus, loop 1 and 2 (L1, L2) and fragments of β2 and β3 strands. The crucial difference between conformational epitope sequences found for both mAbs seems to be the lack of interactions with hCC via N-terminus and the loop 1 in the case of mAb Cyst10. Presumably the interactions of mAbs with hCC via L1 and β sheet fragments make the hCC structure rigid and unable to undergo the swapping process.

The association of plasma cystatin C proteoforms with diabetic chronic kidney disease

Background

Cystatin C (CysC) is an endogenous cysteine protease inhibitor that can be used to assess the progression of kidney function. Recent studies demonstrate that CysC is a more specific indicator of glomerular filtration rate (GFR) than creatinine. CysC in plasma exists in multiple proteoforms. The goal of this study was to clarify the association of native CysC, CysC missing N-terminal Serine (CysC des-S), and CysC without three N-terminal residues (CysC des-SSP) with diabetic chronic kidney disease (CKD).

Results

Using mass spectrometric immunoassay, the plasma concentrations of native CysC and the two CysC truncation proteoforms were examined in 111 individuals from three groups: 33 non-diabetic controls, 34 participants with type 2 diabetes (DM) and without CKD and 44 participants with diabetic CKD. Native CysC concentrations were 1.4 fold greater in CKD compared to DM group (p = 0.02) and 1.5 fold greater in CKD compared to the control group (p = 0.001). CysC des-S concentrations were 1.55 fold greater in CKD compared to the DM group (p = 0.002) and 1.9 fold greater in CKD compared to the control group (p = 0.0002). CysC des-SSP concentrations were 1.8 fold greater in CKD compared to the DM group (p = 0.008) and 1.52 fold greater in CKD compared to the control group (p = 0.002). In addition, the concentrations of CysC proteoforms were greater in the setting of albuminuria. The truncated CysC proteoform concentrations were associated with estimated GFR independent of native CysC concentrations.

Conclusion

Our findings demonstrate a greater amount of CysC proteoforms in diabetic CKD. We therefore suggest assessing the role of cystatin C proteoforms in the progression of CKD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-016-0096-7) contains supplementary material, which is available to authorized users.

Cystatin C as a biomarker for estimating glomerular filtration rate

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) is rarely measured in clinical practice because of the complexity of the measurement. As such, kidney function is typically estimated using validated study equations, which use readily available data including age, sex, race, and serum creatinine as filtration marker. Contemporary research suggests that cystatin C may be an improved alternative to creatinine for inclusion in GFR estimating equations. The purpose of this article is to evaluate the benefits and limitations of using cystatin C as a biomarker of filtration.

RECENT FINDINGS

Cystatin C has fewer non-GFR determinants, when compared with serum creatinine. Use of serum cystatin C avoids the limitations related to both diet and muscle mass that affect serum creatinine. Cystatin C may be more accurate than serum creatinine in estimating GFR, and is more strongly associated with all-cause mortality and cardiovascular events.

SUMMARY

Cystatin C has some advantages over serum creatinine in estimating GFR. The use of cystatin C as a confirmatory biomarker in deciding medication dosages or as a confirmatory test in patients with an uncertain diagnosis of chronic kidney disease may be beneficial.

Biomarkers of Renal Function in Type 2 Diabetic Patients with Cognitive Impairment

Kidney disease is associated with cognitive impairment in studies of nondiabetic adults. We examined the cross-sectional relation between three measures of renal function and cognitive impairment (CI) in type 2 diabetic patients. A total of 357 patients with type 2 diabetes were prospectively enrolled. There were 108 patients with CI and 249 patients without CI (control). We calculated the urinary albumin/creatinine ratio (UACR) from morning spot urine and the estimated glomerular filtration rate (eGFR) in serum samples. Serum Cystatin C (Cys C) was measured with an automated particle-enhanced turbidimetric immunoassay. UACR and Cystatin C levels were significantly higher in patients with CI than those without CI (P<0.001), and the eGFR was lower in patients with CI than those without (P=0.003). A logistic regression analysis indicates that kidney impairment biomarkers levels were significantly associated with an increased risk of CI after adjustment for age and gender. The OR of each kidney biomarker (eGFR, UACR, Cystatin C) for CI status was 1.78 (0.89-3.27), 2.36 (1.29-4.42), and 2.77 (1.36-5.97), respectively. Among three kidney biomarkers (eGFR, UACR, Cystatin C), only elevated serum Cystatin C was associated with increased risk of CI in type 2 diabetic patients, with an OR of 1.42 (1.25-4.24) after additional adjustment for duration of diabetes, hypertension, hyperlipidemia, hemoglobin A1c (HbA1c), high-sensitivity C-reactive protein (Hs-CRP), intima-media thickness (IMT), ankle brachial index (ABI), and brachial-ankle pulse wave velocity (ba-PWV). Furthermore, combination of conventional risk factors and Cystatin C levels exhibited a fair diagnostic value for CI, with an area under the curve (AUC) of 0.91. Among three kidney impairment biomarkers (eGFR, UACR, Cystatin C), only elevated serum Cystatin C was associated with increased risk of CI in type 2 diabetic patients, independent of conventional risk factors. Furthermore, Cystatin C may be a better marker for CI than eGFR and UACR, and exhibited diagnostic value.

New developments and future opportunities in biomarkers for amyotrophic lateral sclerosis

Modern technology has improved the ability to probe effectively the underlying biology of ALS by examination of genomic, proteomic and physiological changes in patients with ALS, as well as to monitor functional and structural changes during the course of disease. While effective treatments for ALS are lacking, the discovery of sensitive biomarkers to disease activity offers clinicians tools for rapid diagnosis and insights into the pathophysiology of ALS. The ultimate aim is to lessen reliance on clinical measures and survival as trial endpoints and broaden the therapeutic options for patients with this disease.

Expression, purification, and characterization of human cystatin C monomers and oligomers

Human cystatin C (cysC) is a soluble basic protein belonging to the cysteine protease inhibitor family. CysC is a potent inhibitor of cathepsins--proteolytic enzymes that degrade intracellular and endocytosed proteins, remodel extracellular matrix, and trigger apoptosis. Inhibition is via tight reversible binding involving the N-terminus as well as two β-hairpin loops of cysC. As a significant component of cerebrospinal fluid, cysC has numerous other functions, including support of neural stem cell growth and differentiation. Several studies suggest that cysC may bind to the Alzheimer-related protein beta-amyloid (Aβ), and inhibit its aggregation and toxicity. Because of an increasing recognition of its important biological roles, there is considerable interest in methods to produce full-length recombinant human cysC. Several researchers have reported success, but with processes that require multiple purification steps. Here we report successful production of human cysC using an intein-based expression system and a simple one-column purification scheme. The recombinant protein so obtained was natively folded and active as an enzyme inhibitor. Unexpectedly, even mild concentration by ultrafiltration caused significant oligomerization. The oligomers are noncovalent and retain the native secondary structure and inhibitory activity of the monomer. The oligomers, but not the monomers, were highly effective at inhibiting aggregation of Aβ. These results demonstrate the critical importance of careful physicochemical characterization of recombinant cysC protein prior to evaluation of its biological functions.

Relationship of Changes in Cystatin-C With Serum Creatinine and Estimated Glomerular Filtration Rate in Kidney Transplantation

BACKGROUND

Serum creatinine (S-Cr) is the most commonly used marker for the assessment of renal function in kidney transplantation (KTx). Cystatin-C (Cys-C) has been proposed as an alternative marker of renal function for the estimated glomerular filtration rate (eGFR), which seems to be more accurate than S-Cr. The aim of this study was to investigate the relationship between changes in S-Cr, Cys-C, and eGFR measurements in KT patients during the early post-transplantation (post-Tx) period.

METHODS

Fifty consecutive patients, aged 15 to 70 years, were subjected to KT. Blood samples were collected at stable time-points on pre-Tx and post-Tx days 2, 6, and 14 and in the third month. Cys-C and S-Cr levels were measured, and GFR was estimated at all time-points using the Cockcroft-Gault and Le Bricon equations.

RESULTS

S-Cr and Cys-C levels decreased significantly post-Tx in all time-point determinations compared with pre-Tx levels. Both markers showed a parallel decrease, reaching normal levels in the third month. Estimated GFR post-Tx by S-Cr and Cys-C exhibited a parallel progressive increase without significant difference between the calculations. Correlation between S-Cr and Cys-C in all time-point determinations was positive and of high significance using Pearson's correlation (r = 0.969, P < .01; r = 0.951, P < .01; r = 0.969, P < .01; r = 0.701, P < .01). Also, the correlation between the eGFR by Cys-C and S-Cr was positive and of high significance in all post-Tx calculations (r = 0.896, P < .01; r = 0.935, P < .01; r = 0.929, P < .01; r = 0.861, P < .01). Ten recipients had acute rejection and were treated successfully with antirejection therapy. Their S-Cr, cys-C, and eGFR results were analyzed separately and showed a significant difference from no-rejection patients, with Cys-C being more sensitive to earlier eGFR changes.

CONCLUSION

Cystatin-C is an alternative and accurate marker of renal function in KT patients showing similar diagnostic characteristics to S-Cr. However, Cys-C appears superior to S-Cr in reflecting early GFR temporary changes, which is critical for the early detection of acute rejection.

Cystatin C and cardiovascular or all-cause mortality risk in the general population: A meta-analysis

BACKGROUND

Elevated cystatin C level was associated with excessive risk of cardiovascular events and mortality in the highly cardiovascular risk populations. We conducted this meta-analysis to investigate the relationship between serum cystatin C level and cardiovascular or all-cause mortality risk in the general population.

METHODS

We searched for all relevant studies published through May 2015 using PubMed, Embase, and Cochrane Library. Prospective studies that assessed the relationship between serum cystatin C level and cardiovascular or all-cause mortality risk in the general population were selected. Pooled adjust hazard risk (HR) and the corresponding 95% confidence intervals (CI) were calculated for continuous and category of cystatin C level.

RESULTS

Nine studies composed of 38,854 participants were analyzed. Elevated serum cystatin C level was associated with excessive risk of all-cause mortality (HR 1.72; 95% CI 1.37-2.16) and cardiovascular mortality (HR 2.74; 95% CI 2.04-3.68) comparing the highest to lowest category of cystatin C. Each standard deviation increment in serum cystatin C level increased 32% all-cause (HR 1.32; 95% CI 1.12-1.55) and 57% cardiovascular mortality (HR 1.57; 95% CI 1.31-1.88) risk.

CONCLUSIONS

Elevated serum cystatin C level is independently associated with excessive cardiovascular and all-cause mortality risk in elderly persons.

Comparison of Cystatin C and β-Trace Protein Versus 99mTc-DTPA Plasma Sampling in Determining Glomerular Filtration Rate in Chronic Renal Disease

Glomerular filtration rate (GFR) is the best indicator of renal function. The gold standard for GFR measurement is inulin clearance. However, its measurement is inconvenient, time-consuming, and costly. Thus, in both scientific studies and routine clinical practice nuclear medicine methods ((99m)Tc-diethylenetriaminepentaacetic acid [(99m)Tc-DTPA] and (51)Cr-ethylenediaminetetraacetic acid [(51)Cr-EDTA]) are preferred, and they correlate strongly with inulin clearance. In addition, cystatin C and β-trace protein have also recently been used for this purpose. In the literature, however, data are limited about the clinical value of cystatin C and β-trace protein in GFR measurement in chronic renal disease (CRD), and the results have been inconclusive. In this study, we aimed to determine the efficiency of cystatin C and β-trace protein in the determination of GFR in CRD patients.

METHODS

Eighty-four patients with CRD were included in the study (59 men and 25 women; age range, 21-88 y; mean age, 61 y). GFR was calculated using the gold-standard (99m)Tc-DTPA 2-sample plasma sampling method (TPSM) and 2 alternative methods: a formula using cystatin C and a formula using β-trace protein. The correlation between TPSM and the cystatin C and β-trace protein methods was assessed, and Bland-Altman analysis was used to graph scatterplots of the differences at a confidence interval of 95% (mean difference ± 1.96 SDs).

RESULTS

GFRs calculated using both alternative methods correlated strongly with those calculated using the gold standard. However, the correlation was stronger for the cystatin C method than for the β-trace protein method, and neither method produced reliably consistent GFRs.

CONCLUSION

This study demonstrated that cystatin C and β-trace protein do not reflect GFR with sufficient accuracy.

Cystatin C: An alternative dialysis adequacy marker in high flux hemodialysis

The conventional, low flux (LF) dialyzer allows the removal of small molecular solutes like urea and creatinine. High flux (HF) dialyzers allow the effective removal of middle molecules (MM) as well, and are associated with reduced hemodialysis-related morbidity and mortality. Cystatin C has attractive characteristics as a representative MM. The aim of this study was to determine cystatin C reduction ratio (CysCRR) in both LF and HF groups and to compare it with other markers of dialysis adequacy. Thirty-seven patients were subjected to both LF and HF hemodialysis 2 weeks apart. Serum urea, creatinine and cystatin C were measured pre- and post-dialysis. Cystatin C was measured by latex-enhanced immunoturbidimetry. Urea and creatinine reduction ratios were 72.3 ± 14.7% and 62.5 ± 13%, respectively in the LF group. The CysCRR was −9.7 ± 6.7% and 29.2 ± 11% in LF and HF hemodialysis, respectively. The statistically significant decrease in CysCRR in the HF group shows the effective clearance of MM by HF dialyzers. Hence, CysCRR could be applied to measure the MM clearance in HF hemodialysis. This study highlights the significance of cystatin C as an important dialysis adequacy marker replacing the conventional markers such as urea and creatinine in HF hemodialysis. Among the middle molecules cystatin C scores over beta-2 microglobulin.

Associations between biomarkers of renal function with cerebral microbleeds in hypertensive patients

BACKGROUND

Cerebral microbleeds (CMBs) have been observed in the elderly and have been regarded as a manifestation of small vessel disease (SVD). Cerebral and glomerular SVD may have a common source of pathogenesis because these organs are closely connected through anatomic and hemodynamic similarities. The purpose of this study was to clarify the associations between kidney biomarker levels and CMBs in hypertensive patients.

METHODS

The presence and number of CMBs were assessed on susceptibility-weighted imaging. We calculated the urinary albumin/creatinine ratio (UACR) from morning spot urine and the estimated glomerular filtration rate (eGFR) in serum samples. Serum cystatin C (CysC) was measured with an automated particle-enhanced turbidimetric immunoassay.

RESULTS

UACR and CysC levels were higher in the patients with CMBs than those without, and the eGFR was lower in the patients with CMBs than those without. A logistic regression analysis indicates that eGFR and UACR were independently associated with the prevalence of deep or infratentorial CMBs. The odds ratio (OR) (95% confidence interval (CI)) of eGFR and UACR was 1.95 (1.37-3.27) and 2.25 (1.66-4.46), respectively. CysC was independently associated with CMBs in both deep or infratentorial and lobar locations. The ORs (95% CI) were 2.59 (1.57-6.22) and 1.57 (1.15-4.85), respectively. Furthermore, CysC exhibited fair diagnostic value for CMBs, with an area under the curve of 0.80.

CONCLUSIONS

Kidney biomarker levels are associated with the presence of CMB in hypertensive patients without a history of transient ischemic attack (TIA) or stroke, independent of conventional risk factors, and CysC was a better marker for CMBs than eGFR and UACR.

Cystatin C and long term risk of community-acquired sepsis: a population-based cohort study

Background

Chronic kidney disease (CKD) and systemic inflammation are risk factors for sepsis. While often viewed as a marker of chronic kidney disease, Cystatin C (Cyst-C) may also reflect systemic inflammation. We sought to determine the association between elevated baseline Cyst-C and long-term rates of community-acquired sepsis, and to determine if this relationship is influenced by traditional markers of CKD (estimated glomerular filtration rate [eGFR], albumin-to-creatinine ratio [ACR]) and inflammation (high sensitivity C-reactive protein [hsCRP]).

Methods

We studied 30,239 adults ≥45 years old from the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. The primary exposure was elevated Cyst-C (>1.12 mg/dL) measured at study baseline. The primary outcome was the first sepsis hospitalization during a 10-year observation period. Using Cox regression, we evaluated the association between elevated Cyst-C and first sepsis event, adjusted for sociodemographics, health behaviors, chronic medical conditions, eGFR, ACR and hsCRP.

Results

Among participants, 1,532 experienced a sepsis event. Median Cyst-C levels were: sepsis 1.08 (IQR 0.91-1.33) mg/dL (43.8% >1.12 mg/dL), non-sepsis 0.94 (IQR 0.82-1.10) mg/dL (23.4% >1.12 mg/dL). Cyst-C > 1.12 mg/dL was independently associated with increased rates of sepsis, adjusted for participant demographics, health behaviors and chronic medical conditions (HR 1.75; 95% CI: 1.55-1.96). The addition of eGFR < 60 mg/min/1.73 m^2, ACR ≥ 30 mg/g and hsCRP > 3.0 mg/dL only partially attenuated the association between Cyst-C > 1.12 mg/dL and rates of sepsis (adjusted HR 1.51; 1.32-1.72).

Conclusions

Elevated Cyst-C is associated with increased long-term rates of community-acquired sepsis, independent of abnormal eGFR, ACR or hsCRP. Cyst-C may play a role in long-term sepsis risk prediction and prevention.

Renal Safety Pharmacology in Drug Discovery and Development

The kidney is a complex excretory organ playing a crucial role in various physiological processes such as fluid and electrolyte balance, control of blood pressure, removal of waste products, and drug disposition. Drug-induced kidney injury (DIKI) remains a significant cause of candidate drug attrition during drug development. However, the incidence of renal toxicities in preclinical studies is low, and the mechanisms by which drugs induce kidney injury are still poorly understood. Although some in vitro investigational tools have been developed, the in vivo assessment of renal function remains the most widely used methodology to identify DIKI. Stand-alone safety pharmacology studies usually include assessment of glomerular and hemodynamic function, coupled with urine and plasma analyses. However, as renal function is not part of the ICH S7A core battery, such studies are not routinely conducted by pharmaceutical companies. The most common approach consists in integrating renal/urinary measurements in repeat-dose toxicity studies. In addition to the standard analyses and histopathological examination of kidneys, novel promising urinary biomarkers have emerged over the last decade, offering greater sensitivity and specificity than traditional renal parameters. Seven of these biomarkers have been qualified by regulatory agencies for use in rat toxicity studies.

[Usefulness of cystatin C as a prognostic marker in venous thromboembolism]

BACKGROUND AND OBJECTIVE

Cystatin C (cysC) is a prognostic marker in patients with hypertension, coronary heart disease and heart failure. The aim of this study was to determine the prognostic value of cysC levels obtained at the time of diagnosis in patients with venous thromboembolism (VTE).

MATERIAL AND METHOD

Retrospective study of a cohort of 226 consecutive patients with VTE, followed for 6 months. Serum samples were obtained for the determination of cysC, creatinine, and the N-terminal fraction of the brain natriuretic peptide (NT-proBNP) at the time of diagnosis.

RESULTS

The highest discriminating power value of dying at 6 months for cysC was 1,175mg/dl (sensitivity 76%, specificity 65%, positive predictive value 26%, negative predictive value 94%). Above the cut-off, 17/48 patients died, versus 9/152 that had lower levels (odds ratio: 5.98, 95% confidence interval [95% CI]: 2.50-14.29, P<.001). The adjusted hazard ratio in a multivariate model was 3.76 (95% CI 1.46-9.66). The accuracy of this parameter was similar to that for creatinine (1.24mg/dl) but lower than the NT-proBNP (435pg/ml). Patients who exceeded the limit values of cysC and NT-proBNP together had no greater risk of death than those above NT-proBNP only (odds ratio: 9.43, 95% CI 3.90-22.81, P<.001). There was no value, which was significantly associated with bleeding episodes or recurrent thromboembolism.

CONCLUSION

CysC concentration at the time of diagnosis in VTE patients has prognostic value, which is similar to that of serum creatinine and lower than that of NT-proBNP.

Creatinine, arsenic metabolism, and renal function in an arsenic-exposed population in Bangladesh

Kidney disease is emerging as an arsenic (As)-linked disease outcome, however further evidence of this association is warranted. Our first objective for this paper was to examine the potential renal toxicity of As exposure in Bangladesh. Our second objective relates to examining whether the previously reported positive association between urinary creatinine (uCrn) and As methylation may be explained by renal function. We had hypothesized that these associations relate to supply and demand for s-adenosylmethionine, the methyl donor for both creatine synthesis and As methylation. Alternatively, renal function could influence both As and creatinine excretion, or the As metabolites may influence renal function, which in turn influences uCrn. We conducted a cross-sectional study (N = 478) of adults, composed of a sample recruited in 2001 and a sample recruited in 2003. We assessed renal function using plasma cystatin C, and calculated the estimated glomerular filtration rate (eGFR). Consistent with renal toxicity of As, log-uAs had a marginal inverse association with eGFR in the 2003 sample (b = -5.6, p = 0.07), however this association was not significant in the 2001 sample (b = -1.9, p = 0.24). Adjustment for eGFR did not alter the associations between uCrn and the %uAs metabolites, indicating that GFR does not explain these associations. Increased eGFR was associated with increased odds of having %uInAs >12.2% (2001: OR = 1.01, 95%CI (1.00,1.03); 2003: OR = 1.04, 95%CI (1.01,1.07)). In the 2003 sample only, there was a negative association between eGFR and %uDMA (b = -0.08, p = 0.02). These results may indicate differential effects of renal function on excretion of InAs and DMA. Alternatively, a certain methylation pattern, involving decreased %InAs and increased %DMA, may reduce renal function. Given that these studies were cross-sectional, we cannot distinguish between these two possibilities. Discrepancies between the samples may be due to the higher As exposure, poorer nutrition, and lower As methylation capacity in the 2003 sample.

Cystatin C in cerebrospinal fluid is upregulated in elderly patients with chronic osteoarthritis pain and modulated through matrix metalloproteinase 9-specific pathway

OBJECTIVES

Although high abundant cystatin c (CysC) in cerebrospinal fluid (CSF) is well known, its ambiguous role associated with pain still remains unclear. This study evaluated the effects of intrathecal CysC content from chronic pain caused by osteoarthritis (OA) and the novel relationship with matrix metalloproteinases 2 and 9 (MMP2 and MMP9) in CSF.

METHODS

Samples of CSF were obtained from 8 elderly patients (65 y and above) with OA with lower limb pain for at least 6 months (OA group) and 8 sex-matched and age-matched relatively healthy elderly individuals without any pain problems (control group). The intrathecal CysC, MMP2, and MMP9 were examined by Western blotting. The analysis of CysC cleavage under different conditions was performed through silver staining and using mass-spectroscopy (SELDI-TOF) on 2 groups.

RESULTS

Expression of full-length CysC and pro-MMP2 proteins showed statistically significant upregulation (P=0.0004 vs. 0.03), and expression of MMP9 protein showed downregulation (P=0.007) in the OA group. Both MMP9 and MMP2 initiated the mechanism for full-length CysC cleavage only in the presence of CSF. However, MMP9 showed greater ability than MMP2 for CysC cleavage in control and OA groups in sliver staining. Incubation of CSF with the MMP9 inhibitor led to the suppression of CysC cleavage in SELDI-TOF.

DISCUSSION

These findings provide the first in vivo evidence on a relationship between CysC and gelatinases (MMP2 and MMP9), and could facilitate further investigation of novel interactions among these proteins within the proteomics field, especially protein-protein interactions involved in pain.

Cystatin C: a new renal marker and its potential use in small animal medicine

The occurrence of chronic kidney disease is underestimated in both human and veterinary medicine. Glomerular filtration rate (GFR) is considered the gold standard for evaluating kidney function. However, GFR assessment is time-consuming and labor-intensive and therefore not routinely used in practice. The commonly used indirect GFR markers, serum creatinine (sCr) and urea, are not sufficiently sensitive or specific to detect early renal dysfunction. Serum cystatin C (sCysC), a proteinase inhibitor, has most of the properties required for an endogenous GFR marker. In human medicine, numerous studies have evaluated its potential use as a GFR marker in several populations. In veterinary medicine, this marker is gaining interest. The measurement is easy, which makes it an interesting parameter for clinical use. This review summarizes current knowledge about cystatin C (CysC) in humans, dogs, and cats, including its history, assays, relationship with GFR, and biological and clinical variations in both human and veterinary medicine.

Serum cystatin C and indices of lung function in elderly Chinese men with chronic obstructive pulmonary disease

OBJECTIVE

The aim of this cross-sectional case-control study was to determine the relationship between serum cystatin C (sCysC) levels and lung function in elderly male patients with chronic obstructive pulmonary disease (COPD).

METHODS

This study included 251 Chinese men (age ≥ 65 years) who were divided into COPD (n = 129) and non-COPD (n = 122) groups. Participants underwent lung function and laboratory testing, including measurement of sCysC levels. Relationships between sCysC concentration and indices of lung function were assessed by multiple regression analysis.

RESULTS

Participants in the COPD group displayed higher sCysC concentrations (P = 0.041) and lower lung function (P < 0.001) compared to participants in the non-COPD group. Multiple linear regression analyses revealed that the reciprocal of the sCysC concentration (1/sCysC) was positively associated with the predicted forced expiratory volume in 1 s in all subjects (β = 0.156, P = 0.009). The findings indicate that high sCysC levels were directly associated with decreased lung function in elderly Chinese men with COPD.

CONCLUSIONS

High sCysC concentration may be a potential indicator of impaired lung function, and its application may improve the diagnosis and assessment of COPD severity in elderly male patients.

Extracellular vesicle protein levels are related to brain atrophy and cerebral white matter lesions in patients with manifest vascular disease: the SMART-MR study

OBJECTIVES

Extracellular vesicles (EVs) and their protein levels have been identified as a potential risk marker for the development of vascular disease. In the present study, we assessed whether levels of four previously identified EV proteins (cystatin C, serpin G1, serpin F2 and CD14) are associated with cerebral white matter lesions (WMLs) and brain atrophy.

DESIGN

Cohort study; cross-sectional and prospective.

SETTING

Single centre, secondary and tertiary setting.

PARTICIPANTS

1309 patients with manifest vascular disease from the Second Manifestations of ARTerial disease-MR (SMART-MR) study, of which 994 had successful brain MRI and EV protein level measurements.

OUTCOMES

WML and brain parenchymal fraction (BPF), as parameter for brain atrophy, at baseline and follow-up.

STATISTICAL METHODS

The relationship between EV protein levels and WML volume (expressed as log transformed percentage of intracranial volume) and BPF (expressed percentage of intracranial volume) on 1.5 T brain MRI was assessed with multivariable linear regression modelling. Subsequently, the relationship between baseline EV protein levels and progression of atrophy and WML was analysed in 534 patients, in whom a follow-up MRI was obtained after 4 years.

RESULTS

Higher EV-cystatin C and EV-CD14 were significantly associated with larger WML volume (linear regression coefficient (95% CI) 0.10 log %/SD (0.04 to 0.17) and 0.14 log %/SD (0.07 to 0.20), respectively. Higher EV-CD14 was associated with more brain atrophy (-0.14%/SD; -0.27 to -0.01). Baseline EV-CD14 was significantly associated with increase of WMLs (0.11 log %/SD (0.04 to 0.18)). No relationship with EV-serpins was observed at baseline or at follow-up.

CONCLUSIONS

EV proteins cystatin C and CD14 are related to cerebral WMLs and the progression of brain atrophy in patients with manifest vascular disease, potentially identifying EVs in the aetiology of structural brain changes.

Cystatin C and lactoferrin concentrations in biological fluids as possible prognostic factors in eye tumor development

Objectives

To investigate the possible role of cystatin C in eye biological fluids locally and in serum and lactoferrin revealing anti-tumor activity in eye tumor development.

Background

The increased number of eye tumors was registered recently not only in the countries with high insolation, but also in the northern countries including Russia (11 cases per million of population). Search for new biological markers is important for diagnosis and prognosis in eye tumors. Cystatin C, an endogenous inhibitor of cysteine proteases, plays an important protective role in several tumors. Lactoferrin was shown to express anti-tumor and antiviral activities. It was hypothesized that cystatin C and lactoferrin could serve as possible biomarkers in the diagnosis of malignant and benign eye tumors.

Study design

A total of 54 patients with choroidal melanoma and benign eye tumors were examined (part of them undergoing surgical treatment). Serum, tear fluid and intraocular fluid samples obtained from the anterior chamber of eyes in patients with choroidal melanoma were studied.

Methods

Cystatin C concentration in serum and eye biological fluids was measured by commercial ELISA kits for human (BioVendor, Czechia); lactoferrin concentration – by Lactoferrin-strip D 4106 ELISA test systems (Vector-BEST, Novosibirsk Region, Russia).

Results

Cystatin C concentration in serum of healthy persons was significantly higher as compared to tear and intraocular fluids. In patients with choroidal melanoma, increased cystatin C concentration was similar in tear fluid of both the eyes. Lactoferrin level in tear fluid of healthy persons was significantly higher than its serum level. Significantly increased lactoferrin concentration in tear fluid was noted in patients with benign and malignant eye tumors.

Conclusion

Increased level of cystatin C in tear fluid seems to be a possible diagnostic factor in the eye tumors studied. However, it does not allow us to differentiate between malignant and benign eye tumors. Similar changes were noted for lactoferrin in tear fluid.

Three low molecular weight cysteine proteinase inhibitors of human seminal fluid: purification and enzyme kinetic properties

The cystatins form a superfamily of structurally related proteins with highly conserved structural folds. They are all potent, reversible, competitive inhibitors of cysteine proteinases (CPs). Proteins from this group present differences in proteinase inhibition despite their high level of structural similarities. In this study, three cysteine proteinase inhibitors (CPIs) of low molecular weight were isolated from human seminal fluid (HSF) by affinity chromatography on carboxymethyl (CM)-papain-Sepharose column, purified using various chromatographic procedures and checked for purity on sodium-dodecyl PAGE (SDS-PAGE). Matrix-assisted laser desorption-ionization-time-of flight-mass spectrometry (MALDI-TOF-MS) identified these proteins as cystatin 9, cystatin SN, and SAP-1 (an N-terminal truncated form of cystatin S). All three CPIs suppressed the activity of papain potentially and showed remarkable heat stability. Interestingly SAP-1 also inhibits the activity of trypsin, chymotrypsin, pepsin, and PSA (prostate specific antigen) and acts as a cross-class protease inhibitor in in vitro studies. Using Surface Plasmon Resonance, we have also observed that SAP-1 shows a significant binding with all these proteases. These studies suggest that SAP-1 is a cross-class inhibitor that may regulate activity of various classes of proteases within the reproductive systems. To our knowledge, this is the first report about purification of CPIs from HSF; the identification of such proteins could provide better insights into the physiological processes and offer intimation for further research.

Over-expression of human cystatin C in pterygium versus healthy conjunctiva

BACKGROUND

A prospective, non-randomised, transversal and comparative study, carried out in INOVA Vision Institute and Autonomous University of Aguascalientes. Pterygium is an important illness that affects 22% people from tropic and equatorial zones. Is an inflammatory process caused by UV rays, and it has a behavior similar to a neoplasm. For this study was taken into consideration 191 samples from the INOVA Vision Institute, Aguascalientes, Mexico. Include 73 pterygia samples, which were obtained during resection under sterile conditions. 44 normal conjunctiva samples were obtained from the same patients when harvesting the conjunctival autograft, or from other patients undergoing extracapsular cataract extraction from the superior bulbar region. Tears from patients with pterygium (n = 50) and normal volunteers (n = 24) were obtained using a calibrated glass micro capillary tube. The surgical conjunctiva and pterygia samples were subjected to reverse-transcription polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry. Tears were analyzed by enzyme-linked immunosorbent assays.

METHODS

This was a prospective, non-randomised study involving 191 biological samples taken from patients with pterygium and normal volunteers, whom were operated under local anaesthesia by either complete resection of the lesion with primary closure, or resection with conjunctival autograft. Tissue samples were fixed in 10% formaldehyde. Sections were routinely stained with hematoxylin and eosin. HCC expression was evaluated by reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and by western blotting. All tears samples were analyzed by enzyme-linked immunosorbent assays (ELISA).

RESULTS

Expression levels and distribution patterns of HCC in normal conjunctiva and pterygium. Higher levels of HCC mRNAs and proteins were detected in pterygium compared with a normal conjunctiva. Immunohistochemistry revealed that HCC was localized in the apical cells of the epithelium in the normal conjunctiva. In contrast, HCC was detected in all extension of epithelial tissue, from apical to basal cells in pterygia. The concentration of HCC protein in tears was higher in patients with pterygium versus controls.

CONCLUSION

HCC may play an important role in protecting normal conjunctiva, and regulating inflammatory conditions of the anterior ocular surface.

Alterations of CSF cystatin C levels and their correlations with CSF Αβ40 and Αβ42 levels in patients with Alzheimer's disease, dementia with lewy bodies and the atrophic form of general paresis

Immunohistochemical studies have revealed that cystatin C (CysC) co-localizes with amyloid-β (Αβ) in amyloid-laden vascular walls and in the senile plaque cores of amyloid. In vitro and in vivo animal studies suggest that CysC protects against neurodegeneration by inhibition of cysteine proteases, inhibition of Αβ aggregation, induction of autophagy and induction of cell division. CysC levels may be altered and may have a potential link with cerebrospinal fluid (CSF) Aβ levels in various types of dementia with characteristic amyloid deposits, such as Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and the atrophic form of general paresis (AF-GP). We assessed the serum and CSF levels of CysC and the CSF levels of Aβ40 and Aβ42 in patients with AD (n = 51), DLB (n = 26) and AF-GP (n = 43) and normal controls (n = 30). Using these samples, we explored the correlation between CSF CysC and CSF Aβ levels. We found that in comparison to the normal control group, both CSF CysC and CSF Aβ42 levels were significantly lower in all three dementia groups (all p<0.001); serum CysC levels were the same in the AD and DLB groups, and were lower in the AF-GP group (p = 0.008). The CSF CysC levels were positively correlated with both the CSF Aβ40 and Aβ42 levels in the AD, AF-GP and normal control groups (r = 0.306∼0.657, all p<0.05). Lower CSF CysC levels might be a common feature in dementia with characteristic amyloid deposits. Our results provide evidence for the potential role of CysC involvement in Aβ metabolism and suggest that modulation of the CysC level in the brain might produce a disease-modifying effect in dementia with characteristic amyloid deposits.

Interaction of serum amyloid A with human cystatin C--identification of binding sites

Serum amyloid A (SAA) is a multifunctional acute-phase protein whose natural role seems to be participation in many physiologic and pathological processes. Prolonged increased SAA level in a number of chronic inflammatory and neoplastic diseases gives rise to reactive systemic amyloid A amyloidosis, where the N-terminal 76-amino acid residue-long segment of SAA is deposited as amyloid fibrils. Recently, a specific interaction between SAA and the ubiquitous inhibitor of cysteine proteases--human cystatin C (hCC)--has been described. Here, we report further evidence corroborating this interaction, and the identification of the SAA and hCC binding sites in the SAA-hCC complex, using a combination of selective proteolytic excision and high-resolution mass spectrometry. The shortest binding site in the SAA sequence was determined as SAA(86-104), whereas the binding site in hCC sequence was identified as hCC(96-102). Binding specificities of both interacting sequences were ascertained by affinity experiments (ELISA) and by registration of mass spectrum of SAA-hCC complex.

Comparison of serum cystatin C, serum creatinine, measured GFR, and estimated GFR to assess the risk of kidney failure in American Indians with diabetic nephropathy

BACKGROUND

We compared values of baseline serum cystatin C (SCysC), serum creatinine (SCr), and measured glomerular filtration rate (mGFR) for predicting end-stage renal disease (ESRD) in patients with type 2 diabetes and elevated albuminuria.

STUDY DESIGN

Observational longitudinal study.

SETTING & PARTICIPANTS

Pima Indians with type 2 diabetes and elevated albumin-creatinine ratio (ACR ≥30 mg/g).

PREDICTORS

Baseline SCysC, SCr, and mGFR.

OUTCOMES & MEASUREMENTS

Individuals were followed up from their first examination with diabetes and ACR ≥30 mg/g until December 2010, onset of ESRD, or death, whichever came first. Incidence rates adjusted for age and sex were computed by Mantel-Haenszel stratification. The abilities of SCysC, SCr, and mGFR values to predict ESRD were compared with receiver operating characteristic curves.

RESULTS

Of 234 Pima Indians with a mean age of 42.8 years who were followed up for a median of 10.7 (range, 0.6-21.3) years, 68 (29%) developed ESRD. The incidence of ESRD was significantly higher in patients in the lowest versus highest tertile of 1/SCysC (incidence rate ratio, 2.43; 95% CI, 1.31-4.50). By contrast, mGFR and 1/SCr had J-shaped associations with ESRD. In unadjusted analyses, 1/SCysC had the highest area under the receiver operating characteristic curve (AUROC; 0.719 ± 0.035) and mGFR had the lowest (0.585 ± 0.042; P < 0.001); the AUROC for 1/SCr was intermediate (0.672 ± 0.040; P = 0.1 and P = 0.03 vs 1/SCysC and mGFR, respectively). In analyses adjusted for age, sex, diabetes duration, height, weight, hemoglobin A1c level, and ACR, 1/SCysC had the highest AUROC (0.845 ± 0.026). Models with mGFR or 1/SCr alone had similar AUROCs (P = 0.9) and both were lower than the model with 1/SCysC alone (P = 0.02 and P = 0.03, respectively).

LIMITATIONS

The predictive values of the filtration markers are limited to the extent that their precision is based on a single measurement.

CONCLUSIONS

SCysC level was a better predictor of ESRD than mGFR or SCr level in Pima Indians with type 2 diabetes and elevated albuminuria.

Is serum cystatin C a better marker than serum creatinine for monitoring renal function in pediatric intensive care unit?

In critically ill patients, mild to moderate reductions in glomerular filtration rate are not instantly followed by parallel changes in serum creatinine (SCr). The aim of this study was to identify a value of serum cystatin C (cys-C) level as a marker for monitoring renal function in critically ill pediatric patients. Creatinine clearance was used to estimate glomeruler filtration rate (eGFR). The correlation between the inverse of serum cys-C and eGFR (r = -0.70, p < 0.0001) was better than the correlation between the inverse of SCr and eGFR (r = -0.27, p = 0.008). Serum cys-C was found to be superior to SCr to predict renal impairment (area under the curve for cys-C, 0.932 and for SCr, 0.658). It can be concluded that cys-C is superior to SCr for the detection of renal impairment in critically ill children.

Plasma and Cerebrospinal Fluid-Based Protein Biomarkers for Motor Neuron Disease

Motor neuron diseases (MNDs) and, in particular, amyotrophic lateral sclerosis (ALS), are a heterogeneous group of neurologic disorders characterized by the progressive loss of motor function. In ALS, a selective and relentless degeneration of both upper and lower motor neurons occurs, culminating in mortality typically within 5 years of symptom onset. However, survival rates vary among individual patients and can be from a few months to >10 years from diagnosis. Inadequacies in disease detection and treatment, along with a lack of diagnostic and prognostic tools, have prompted many to turn to proteomics-based biomarker discovery efforts. Proteomics refers to the study of the proteins expressed by a genome at a particular time, and the proteome can respond to and reflect the status of an organism, including health and disease states. Although an emerging field, proteomic applications promise to uncover biomarkers critical for differentiating patients with ALS and other MNDs from healthy individuals and from patients affected by other diseases. Ideally, these studies will also provide mechanistic information to facilitate identification of new drug targets for subsequent therapeutic development. In addition to proper experimental design, standard operating procedures for sample acquisition, preprocessing, and storage must be developed. Biological samples typically analyzed in proteomic studies of neurologic diseases include both plasma and cerebrospinal fluid (CSF). Recent studies have identified individual proteins and/or protein panels from blood plasma and CSF that represent putative biomarkers for ALS, although many of these proteins are not unique to this disease. Continued investigations are required to validate these initial findings and to further pursue the role of these proteins as diagnostic biomarkers or surrogate markers of disease progression. Protein biomarkers specific to ALS will additionally function to evaluate drug efficacy in clinical trials and to identify novel targets for drug design. It is hoped that proteomic technologies will soon integrate the basic biology of ALS with mechanistic disease information to achieve success in the clinical setting.

Involvement of dopaminergic neuronal cystatin C in neuronal injury-induced microglial activation and neurotoxicity

Factors released from injured dopaminergic (DA) neurons may trigger microglial activation and set in motion a vicious cycle of neuronal injury and inflammation that fuels progressive DA neurodegeneration in Parkinson's disease. In this study, using proteomic and immunoblotting analysis, we detected elevated levels of cystatin C in conditioned media (CM) from 1-methyl-4-phenylpyridinium and dieldrin-injured rat DA neuronal cells. Immunodepletion of cystatin C significantly reduced the ability of DA neuronal CM to induce activation of rat microglial cells as determined by up-regulation of inducible nitric oxide synthase, production of free radicals and release of proinflammatory cytokines as well as activated microglia-mediated DA neurotoxicity. Treatment of the cystatin C-containing CM with enzymes that remove O- and sialic acid-, but not N-linked carbohydrate moieties markedly reduced the ability of the DA neuronal CM to activate microglia. Taken together, these results suggest that DA neuronal cystatin C plays a role in the neuronal injury-induced microglial activation and neurotoxicity. These findings from the rat DA neuron-microglia in vitro model may help guide continued investigation to define the precise role of cystatin C in the complex interplay among neurons and glia in the pathogenesis of Parkinson's disease.

Serum Beta 2-microglobulin/cystatin C index: a useful biomarker in lupus nephritis?

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with frequent flares. Our aim was to evaluate the beta 2-microglobulin/cystatin C (β2M/CysC) index versus other markers as a predictor factor for assessment of SLE reactivation.

METHODS

We prospectively analyzed 42 patients with lupus nephritis. Disease activity was classified using SLEDAI-2K and BILAG. Routine renal function and laboratory markers of SLE activity were performed, as well as serum β2M (Sβ2M)/serum CysC (SCysC) and Sβ2M/serum creatinine (SCreat) indexes determinations.

RESULTS

The 42 enrolled patients had a mean age of 37.7 ± 13.1 years, 88% were female and 67% Caucasians; mean estimated glomerular filtration rate was 61.9 ± 20.0 ml/min/1.73 m(2). There was a strong correlation between SCreat versus SCysC (r = 0.887), SCreat versus Sβ2M (r = 0.865), and SCysC versus Sβ2M (r = 0.880). Multivariate analysis showed that the Sβ2M/SCreat index is a prognostic factor predicting active lupus nephritis.

CONCLUSION

As SCysC is a good marker of renal function, it would be expected that the Sβ2M/SCysC index could be a better indicator of renal activity than Sβ2M/SCreat, but in the present study it did not add relevant clinical information in the assessment of renal activity in SLE.