Biochemistry and Clinical Role of Human Cystatin C

Investigation of serum cystatin C levels and their diagnostic value in combination with inflammatory ratios in patients with bipolar disorder

Background

It is thought that inflammation significantly contributes to the development of bipolar disorder (BD), and recent findings indicate a connection between cystatin C and immune-related inflammation. In this study, we investigated serum cystatin C levels in patients with BD and explored the relationship between cystatin C and inflammatory markers.

Methods

The study involved 3,647 individuals diagnosed with BD, comprising 2,431 with BD-manic (BD-M) and 1,216 with BD-depression (BD-D), alongside 3,500 healthy controls. The analysis covered cystatin C levels and inflammatory biomarkers obtained from complete blood counts across the various groups. The Spearman correlation test was used to examine the relationship between cystatin C and inflammatory markers. Logistic regression and ROC curve analyses assessed the predictive value of these markers for disease occurrence.

Results

Serum cystatin C levels were significantly elevated in BD patients, particularly those in manic episodes, compared to the healthy control group, with distinct correlation patterns with inflammatory biomarkers observed among the groups. Serum Cystatin C levels independently and positively indicated disease occurrence, showing improved diagnostic effectiveness when combined with inflammatory ratios.

Conclusion

Our research indicates that cystatin C could be involved in the pathophysiological mechanisms of BD by affecting pro-inflammatory processes. Additionally, it should be emphasized that cystatin C showed considerable predictive capacity in diagnosing BD, especially when used alongside various inflammatory markers.

Limitations

The cross-sectional study is limited to demonstrating associations rather than establishing causality. A thorough examination of sociodemographic factors and the severity of the disease could not be conducted.

Recent Advances on Integrating Porous Nanomaterials with Chemiluminescence Assays

Advanced porous nanomaterials have recently been the subject of considerable interest due to their high surface areas, tunable pore structures, high porosity, and ease of modification. In the chemiluminescence (CL) domain, the incorporation of additional pores into nanostructures not only enhances the loading capacity for signal amplification but also allows the confinement effect in a nanoscale microreactor and the controlled release of reaction agents. In light of this, increasing efforts have been made to fabricate various porous nanomaterials and explore their potential applications in CL assays. This review therefore aims to highlight the recent advances in preparation strategies and basic attributes of the CL-related porous nanomaterials. Moreover, it offers a comprehensive summary of the emerging CL sensing applications based on these materials. The key challenges and future perspectives of porous nanomaterials in CL assays are finally discussed.

Formation of molecularly imprinted polymers: Strategies applied for the removal of protein template (review)

The key step in the entire molecularly imprinted polymer (MIP) preparation process is the formation of the complementary cavities in the polymer matrix through the template removal process. The template is removed using chemical treatments, leaving behind selective binding sites for target molecules within the polymer matrix. Other MIP preparation steps include mixing monomers and template molecules in the appropriate solvent(s), monomer-template complex equilibration, and polymerisation of the monomers around the template. However, template removal is the most important among all the preparation steps because the final structure, which can be accepted and recognised as the MIP, is obtained only after the template removal. A thorough analysis of the studies dedicated to MIP applications demonstrates that this MIP preparation step, namely the template removal, is relatively understudied. MIP template removal is especially challenging in the synthesis, where the molecular template is a macromolecule such as a protein. This review aims to provide a deliberate, systematic, and consistent overview of protein removal as the MIP template molecules. The most prevalent template removal methods are outlined for removing protein templates from electrochemically synthesised MIPs, particularly thin layers on electrodes used in electrochemical sensors. Five protein template removal approaches involving chemical treatment are highlighted, which include the utilisation of (i) chaotropic agents, (ii) salt, (iii) acidic cleavage, (iv) alkaline, and finally, (v) proteolytic treatment focusing on studies conducted over the past decade. In addition, we discuss the interactions driving the removal of protein templates in each approach and associated challenges. This review provides insights into MIPs protein template removal strategies while highlighting the prevalent issue of this understudied step of template removal.

Emerging trends in the cystatin C sensing technologies: towards better chronic kidney disease management

Cystatin C (CysC), a protein, has replaced creatinine as a biomarker of kidney function and other diseases and has led to a surge in the research on the development of efficient CysC biosensors. The current CysC sensing technologies are remarkable in terms of selectivity and reproducibility. However, the complexity, cost, and space requirements of these methods render them unsuitable for real-time monitoring or point-of-care (PoC) implementations in healthcare settings. This review discusses the most recent developments in the field of CysC biosensing and to the best of our knowledge, this is the first focused review exclusively on CysC biosensing modalities. Our goal is to provide a thorough overview of the current state of CysC biosensors, and presenting mechanisms related to biosensor recognition and transduction. The review starts with clinical significance of CysC detection followed by detailed analysis of different CysC biosensing methods with emphasis on the necessity of PoC monitoring of CysC. We have also highlighted current challenges and an outlook on future perspectives. We anticipate that this study will play a key role in the understanding the working principle of CysC sensors and will aid in the designing of new efficient sensing modalities for the detection of CysC.

The influence of a dicationic surfactant on the aggregation process of the IVAGVN peptide derived from the human cystatin C sequence (56-61)

Human cystatin C (hCC) undergoes domain swapping and forms amyloid structures. Steric zipper motifs, which are important for hCC fibrillization, have been identified and studied in our previous work. In the present study, we analysed the influence of the selected dicationic surfactant (a derivative of dodecylimidazolium chloride: 3,3'-[α,ω-(dioxahexane)]bis(1-dodecylimidazolium)dichloride) on the structure of the aggregates formed by one such fragment, a peptide with the sequence IVAGVN, corresponding to residues 56-61 in the full-length protein. Changes in the secondary structure of the peptide induced by the surfactant were studied using circular dichroism (CD) and FTIR, and the aggregates were characterised using microscopic techniques (AFM and TEM) and NMR.

Preliminary Analysis of Potentially Overlapping Differentially Expressed Proteins in Both the Spinal Cord and Brain of SOD1 G93A Mice

OBJECTIVE

Proteomic elucidation is an essential step in improving our understanding of the biological properties of proteins in amyotrophic lateral sclerosis (ALS).

METHODS

Preliminary proteomic analysis was performed on the spinal cord and brain of SOD1 G93A (TG) and wild-type (WT) mice using isobaric tags for relative and absolute quantitation.

RESULTS

Partial up- and downregulated proteins showing significant differences between TG and WT mice were identified, of which 105 proteins overlapped with differentially expressed proteins in both the spinal cord and brain of progression mice. Bioinformatic analyses using Gene Ontology, a cluster of orthologous groups, and Kyoto Encyclopedia of Genes and Genomes pathway revealed that the significantly up- and downregulated proteins represented multiple biological functions closely related to ALS, with 105 overlapping differentially expressed proteins in the spinal cord and brain at the progression stage of TG mice closely related to 122 pathways. Differentially expressed proteins involved in a set of molecular functions play essential roles in maintaining neural cell survival.

CONCLUSION

This study provides additional proteomic profiles of TG mice, including potential overlapping proteins in both the spinal cord and brain that participate in pathogenesis, as well as novel insights into the up- and downregulation of proteins involved in the pathogenesis of ALS.

Recent discovery of natural substances with cathepsin L-inhibitory activity for cancer metastasis suppression

Cathepsin L (CTSL), a cysteine cathepsin protease of the papain superfamily, plays a crucial role in cancer progression and metastasis. Dysregulation of CTSL is frequently observed in tumor malignancies, leading to the degradation of extracellular matrix and facilitating epithelial-mesenchymal transition (EMT), a key process in malignant cancer metastasis. This review mainly provides a comprehensive information about recent findings on natural inhibitors targeting CTSL and their anticancer effects, which have emerged as potent anticancer therapeutic agents or metastasis-suppressive adjuvants. Specifically, inhibitors are categorized into small-molecule and macromolecule inhibitors, with a particular emphasis on cathepsin propeptide-type macromolecules. Additionally, the article explores the molecular mechanisms of CTSL involvement in cancer metastasis, highlighting its regulation at transcriptional, translational, post-translational, and epigenetic levels. This work underscores the importance of understanding natural CTSL inhibitors and provides researchers with practical insights to advance the relevant fields and discover novel CTSL-targeting inhibitors from natural sources.

Identification and functional characterization of a novel cystatin in amphioxus, ancient origin of vertebrate type-2 cystatin homologues

Cystatins are well known as a vast superfamily of functional proteins participated in the reversible competitive inhibition of cysteine proteases. Currently, increasing evidences point to the extensive phylogenetic diversity and crucial immune roles of type-2 cystatins in the vertebrate species. However, no information is available regarding the homologue in cephalochordate amphioxus, the representative of most basal living chordates, whose immune regulation are still ambiguous. Here, we clearly identified the presence of type-2 cystatin gene in amphioxus Branchiostoma japonicum, termed Bjcystatin-2, which was structurally characterized by typical wedge-shaped cystatin feature. Evolutionary analyses revealed that Bjcystatin-2 is the putative ancestral type-2 cystatin for chordates, with gene diversity emerging through duplication events. The expression of Bjcystatin-2 showed tissue-specific profile and was inducible upon invasive pathogens. Significantly, the recombinant Bjcystatin-2 exhibited not merely cathepsin L inhibitory activity, but also the ability to bind with bacteria and their characteristic molecules. Furthermore, Bjcystatin-2 also showed the capacity to enhance the macrophage-driven bacterial phagocytosis and to attenuate the generation of pro-inflammatory cytokines within macrophages. In summary, these findings demonstrate that Bjcystatin-2 exhibits dual role acting as both a protease inhibitor and an immunoactive molecule, greatly enriching our understanding of immune defense mechanisms of type-2 cystatin within the amphioxus.

Methods for monitoring protein-membrane binding. Comparison based on the interactions between amyloidogenic protein human cystatin C and phospholipid liposomes

A cell membrane is an essential cellular component providing protection against the outer environment. It is also a host for proteins and carbohydrates responsible for, e.g. transporter, receptor, or enzymatic functions. In parallel, the membrane may also be implicated in pathological processes leading, e.g. to the oligomerization of amyloid-forming proteins, a hallmark of i.a. Alzheimer's disease. The increasing need for detailed information on mechanisms driving the amyloid formation and the potential role of cell membranes in the process proves the research on protein-membrane interactions biologically relevant. Considering the potential and limitations of the relatively well established and newly developed methods, this study focused on selecting methods that allow a broad and comprehensive description of interactions between amyloidogenic protein human cystatin C and lipid bilayers. In the first step, dot-blot and ELISA tests were selected as techniques allowing fast screening for protein-ligand interactions. Next, surface plasmon resonance, spectral shift, biolayer interferometry, and switchSENSE® technology were used to determine kinetic parameters and binding constants for interactions between human cystatin C and the selected lipid bilayers. Based on the obtained results we have proposed the most promising candidates for monitoring of interactions and determining affinity between amyloidogenic proteins and membrane mimetics.

Sex inequalities in cardiovascular risk prediction

AIMS

Evaluate sex differences in cardiovascular disease (CVD) risk prediction, including use of (i) optimal sex-specific risk predictors and (ii) sex-specific risk thresholds.

METHODS AND RESULTS

Prospective cohort study using UK Biobank, including 121 724 and 182 632 healthy men and women, respectively, aged 38-73 years at baseline. There were 11 899 (men) and 9110 (women) incident CVD cases (hospitalization or mortality) with a median of 12.1 years of follow-up. We used recalibrated pooled cohort equations (PCEs; 7.5% 10-year risk threshold as per US guidelines), QRISK3 (10% 10-year risk threshold as per UK guidelines), and Cox survival models using sparse sex-specific variable sets (via LASSO stability selection) to predict CVD risk separately in men and women. LASSO stability selection included 12 variables in common between men and women, with 3 additional variables selected for men and 1 for women. C-statistics were slightly lower for PCE than QRISK3 and models using stably selected variables, but were similar between men and women: 0.67 (0.66-0.68), 0.70 (0.69-0.71), and 0.71 (0.70-0.72) in men and 0.69 (0.68-0.70), 0.72 (0.71-0.73), and 0.72 (0.71-0.73) in women for PCE, QRISK3, and models using stably selected variables, respectively. At current clinically implemented risk thresholds, test sensitivity was markedly lower in women than men for all models: at 7.5% 10-year risk, sensitivity was 65.1 and 68.2% in men and 24.0 and 33.4% in women for PCE and models using stably selected variables, respectively; at 10% 10-year risk, sensitivity was 53.7 and 52.3% in men and 16.8 and 20.2% in women for QRISK3 and models using stably selected variables, respectively. Specificity was correspondingly higher in women than men. However, the sensitivity in women at 5% 10-year risk threshold increased to 50.1, 58.5, and 55.7% for PCE, QRISK3, and models using stably selected variables, respectively.

CONCLUSION

Use of sparse sex-specific variables improved CVD risk prediction compared with PCE but not QRISK3. At current risk thresholds, PCE and QRISK3 work less well for women than men, but sensitivity was improved in women using a 5% 10-year risk threshold. Use of sex-specific risk thresholds should be considered in any re-evaluation of CVD risk calculators.

Development and Validation of an Accurate Creatinine-Based Equation to Estimate Glomerular Filtration Rate for the Adult Indian Population: Design and Methods

Background

Existing creatinine-based equations to estimate glomerular filtration rate (GFR), developed primarily in populations of European and African American ancestry, do not accurately reflect the GFR in the Indian population due to differences in body composition, diet, and other factors. This manuscript describes the rationale and methodology for developing a creatinine-based equation for more accurate GFR estimation in Indian subjects.

Materials and Methods

This cross-sectional study will be conducted in India's two geographically and demographically diverse locations: Chandigarh (north) and Puducherry (south). Participants will include a representative sample from the general population and subjects with chronic kidney disease (CKD), with the latter being recruited from outpatient clinics. A total of 1558 subjects will be enrolled in the discovery and cross-validation cohort and 620 subjects in the external validation cohort. The reference standard for measured GFR (mGFR) will be the plasma clearance of iohexol. Stepwise multiple regression on log-transformed data will determine a set of variables that jointly predict mGFR and identify factors influencing mGFR and estimated (eGFR) in the study population. This study will also explore the performance of mGFR by iohexol measurement from dried blood spots against mGFR from plasma clearance of iohexol.

Conclusion

Developing a more reliable and accurate creatinine-based GFR estimating equation will improve CKD diagnosis, classification, and management. The findings will have substantial implications for CKD research in India and other regions with similar populations.

Monomer-Dimer Equilibrium of Human Cystatin C During Internalization Into Cancer Cells

Human cystatin C (hCC) is a physiologically important protein that serves as intra- and extracellular cysteine proteinase inhibitor in homeostasis. However, in pathological states it dimerizes and further oligomerizes accumulating into a toxic amyloid. HCC forms an active monomer in the extracellular space and becomes an inactive dimer when internalized in cellular organelles. However, hCC cell penetration and its oligomeric state during this process are not well understood. To determine if and how the oligomeric state influences hCC transmembrane migration, we investigated the internalization of the hCC wild type protein as well as three different mutants, which exclusively exist in the monomeric or multimeric state into HeLa cells via confocal fluorescence microscopy. Our results showed that the preferred pathway was endocytosis and that the oligomeric state did not significantly influence the internalization because both monomeric and dimeric hCC migrated into HeLa cells. Considering the differences of the active monomeric and the passive dimeric states of hCC, our findings contribute to a better understanding of the intra and extra cellular functions of hCC and their interaction with cysteine proteases.

A Multimodal Fuzzy Approach in Evaluating Pediatric Chronic Kidney Disease Using Kidney Biomarkers

Chronic kidney disease (CKD) is one of the most important causes of chronic pediatric morbidity and mortality and places an important burden on the medical system. Current diagnosis and progression monitoring techniques have numerous sensitivity and specificity limitations. New biomarkers for monitoring CKD progression have been assessed. Neutrophil gelatinase-associated lipocalin (NGAL) has had some promising results in adults, but in pediatric patients, due to the small number of patients included in the studies, cutoff values are not agreed upon. The small sample size also makes the statistical approach limited. The aim of our study was to develop a fuzzy logic approach to assess the probability of pediatric CKD progression using both NGAL (urinary and plasmatic) and routine blood test parameters (creatinine and erythrocyte sedimentation rate) as input data. In our study, we describe in detail how to configure a fuzzy model that can simulate the correlations between the input variables ESR, NGAL-P, NGAL-U, creatinine, and the output variable Prob regarding the prognosis of the patient's evolution. The results of the simulations on the model, i.e., the correlations between the input and output variables (3D graphic presentations) are explained in detail. We propose this model as a tool for physicians which will allow them to improve diagnosis, follow-up, and interventional decisions relative to the CKD stage. We believe this innovative approach can be a great tool for the clinician and validates the feasibility of using a fuzzy logic approach in interpreting NGAL biomarker results for CKD progression.

Comparison of estimated GFR using cystatin C versus creatinine in pediatric kidney transplant recipients

BACKGROUND

An accurate, rapid estimate of glomerular filtration rate (GFR) in kidney transplant patients affords early detection of transplant deterioration and timely intervention. This study compared the performance of serum creatinine (Cr) and cystatin C (CysC)-based GFR equations to measured GFR (mGFR) using iohexol among pediatric kidney transplant recipients.

METHODS

CysC, Cr, and mGFR were obtained from 45 kidney transplant patients, 1-18 years old. Cr- and CysC-estimated GFR (eGFR) was compared against mGFR using the Cr-based (Bedside Schwartz, U25-Cr), CysC-based (Gentian CysC, CAPA, U25-CysC), and Cr-CysC combination (CKiD Cr-CysC, U25 Cr-CysC) equations in terms of bias, precision, and accuracy. Bland-Altman plots assessed the agreement between eGFR and mGFR. Secondary analyses evaluated the formulas in patients with biopsy-proven histological changes, and K/DOQI CKD staging.

RESULTS

Bias was small with Gentian CysC (0.1 ml/min/1.73 m2); 88.9% and 37.8% of U25-CysC estimations were within 30% and 10% of mGFR, respectively. In subjects with histological changes on biopsy, Gentian CysC had a small bias and U25-CysC were more accurate-both with 83.3% of and 41.7% of estimates within 30% and 10% mGFR, respectively. Precision was better with U25-CysC, CKiD Cr-CysC, and U25 Cr-CysC. Bland-Altman plots showed the Bedside Schwartz, Gentian CysC, CAPA, and U25-CysC tend to overestimate GFR when > 100 ml/min/1.72 m2. CAPA misclassified CKD stage the least (whole cohort 24.4%, histological changes on biopsy 33.3%).

CONCLUSIONS

In this small cohort, CysC-based equations with or without Cr may have better bias, precision, and accuracy in predicting GFR.

Human molybdenum exposure risk in industrial regions of China: New critical effect indicators and reference dose

Evidence increasingly suggests molybdenum exposure at environmental levels is still associated with adverse human health, emphasizing the necessity to establish a more protective reference dose (RfD). Herein, we conducted a study measuring 15 urinary metals and 30 clinical health indicators in 2267 participants residing near chemical enterprises across 11 Chinese provinces to investigate their relationships. The kidney and cystatin-C emerged as the most sensitive organ and critical effect indicator of molybdenum exposure, respectively. Odds of cystatin-C-defined chronic kidney disease (CKD) in the highest quantile of molybdenum exposure significantly increased by 133.5% (odds ratio [OR]: 2.34, 95% CI: 1.78, 3.11) and 75.8% (OR: 1.76, 95% CI: 1.24, 2.49) before and after adjusting for urinary 14 metals, respectively. Intriguingly, cystatin-C significantly mediated 15.9-89.5% of molybdenum's impacts on liver and lung function, suggesting nephrotoxicity from molybdenum exposure may trigger hepatotoxicity and pulmonary toxicity. We derived a new RfD for molybdenum exposure (0.87 μg/kg-day) based on cystatin-C-defined estimated glomerular filtration rate by employing Bayesian Benchmark Dose modeling analysis. This RfD is significantly lower than current exposure guidance values (5-30 μg/kg-day). Remarkably, >90% of participants exceeded the new RfD, underscoring the significant health impacts of environmental molybdenum exposure on populations in industrial regions of China.

Current Prognostic Biomarkers for Abdominal Aortic Aneurysm: A Comprehensive Scoping Review of the Literature

Abdominal aortic aneurysm (AAA) is a progressive dilatation of the aorta that can lead to aortic rupture. The pathophysiology of the disease is not well characterized but is known to be caused by the general breakdown of the extracellular matrix within the aortic wall. In this comprehensive literature review, all current research on proteins that have been investigated for their potential prognostic capabilities in patients with AAA was included. A total of 45 proteins were found to be potential prognostic biomarkers for AAA, predicting incidence of AAA, AAA rupture, AAA growth, endoleak, and post-surgical mortality. The 45 proteins fell into the following seven general categories based on their primary function: (1) cardiovascular health, (2) hemostasis, (3) transport proteins, (4) inflammation and immunity, (5) kidney function, (6) cellular structure, (7) and hormones and growth factors. This is the most up-to-date literature review on current prognostic markers for AAA and their functions. This review outlines the wide pathophysiological processes that are implicated in AAA disease progression.

An LC-MS/MS method for serum cystatin C quantification and its comparison with two commercial immunoassays

OBJECTIVES

The standardization of cystatin C (CysC) measurement has received increasing attention in recent years due to its importance in estimating glomerular filtration rate (GFR). Mass spectrometry-based assays have the potential to provide an accuracy base for CysC measurement. However, a precise, accurate and sustainable LC-MS/MS method for CysC is still lacking.

METHODS

The developed LC-MS/MS method quantified CysC by detecting signature peptide (T3) obtained from tryptic digestion. Stable isotope labeled T3 peptide (SIL-T3) was spiked to control matrix effects and errors caused by liquid handling. The protein denaturation, reduction and alkylation procedures were combined into a single step with incubation time of 1 h, and the digestion lasted for 3.5 h. In the method validation, digestion time-course, imprecision, accuracy, matrix effect, interference, limit of quantification (LOQ), carryover, linearity, and the comparability to two routine immunoassays were evaluated.

RESULTS

No significant matrix effect or interference was observed with the CysC measurement. The LOQ was 0.21 mg/L; the within-run and total imprecision were 1.33-2.05 % and 2.18-3.90 % for three serum pools (1.18-5.34 mg/L). The LC-MS/MS method was calibrated by ERM-DA471/IFCC and showed good correlation with two immunoassays traceable to ERM-DA471/IFCC. However, significant bias was observed for immunoassays against the LC-MS/MS method.

CONCLUSIONS

The developed LC-MS/MS method is robust and simpler and holds the promise to provide an accuracy base for routine immunoassays, which will promote the standardization of CysC measurement.

Monitoring the interactions between POPG phospholipid bilayer and amyloid-forming protein human cystatin C. Does the bilayer influence the oligomeric state and structure of the protein?

A biological membrane is a structure characteristic for various cells and organelles present in almost all living organisms. Even though, it is one of the most common structures in organisms, where it serves crucial functions, a phospholipid bilayer may also take part in pathological processes leading to severe diseases. Research indicates that biological membranes have a profound impact on the pathological processes of oligomerization of amyloid-forming proteins. These processes are a hallmark of amyloid diseases, a group of pathological states involving, e.g., Parkinson's or Alzheimer's disease. Even though amyloidogenic diseases reap the harvest in modern societies, especially in elderly patients, the mechanisms governing the amyloid deposition are not clearly described. Therefore, the presented study focuses on the description of interactions between a model biological membrane (POPG) and one of amyloid forming proteins - human cystatin C. For the purpose of the study molecular dynamics simulations were applied to confirm interactions between the protein and POPG membrane. Next the NMR techniques were used to verify how the data obtained in solution compared to MD simulations and determine fragments of the protein responsible for interactions with POPG. Finally, circular dichroism was used to monitor the changes in secondary structure of the protein and size exclusion chromatography was used to monitor its oligomerization process. Obtained data indicates that the protein interacts with POPG submerging itself into the bilayer with the AS region. However, the presence of POPG bilayer does not significantly affect the structure or oligomerization process of human cystatin C.

Association of Cystatin C Level with All-cause Mortality in Patients with Liver Cirrhosis: A Meta-analysis

BACKGROUND AND OBJECTIVE

Blood cystatin C level has been introduced as a promising biomarker to detect early kidney injury in cirrhotic patients. The purpose of this meta-analysis was to investigate the association of blood cystatin C level with allcause mortality in patients with liver cirrhosis.

METHODS

PubMed, ScienceDirect, and Embase databases were searched from the inception to November 15, 2022. Observational studies evaluating the value of blood cystatin C level in predicting all-cause mortality in patients with ACS were selected. The pooled hazard risk (HR) with 95% confidence intervals (CI) was calculated using a random effect model meta-analysis.

RESULTS

Twelve studies with 1983 cirrhotic patients were identified. The pooled adjusted HR of all-cause mortality was 3.59 (95% CI 2.39-5.39) for the high versus low group of cystatin C level. Stratified analysis by study design, characteristics of patients, geographical region, sample size, and length of follow-up further supported the predictive value elevated cystatin C level.

CONCLUSION

Elevated cystatin C level was an independent predictor of poor survival in patients with liver cirrhosis. Detection of blood cystatin C level may provide important prognostic information in cirrhotic patients.

Correlation between the Cognitive Status (SIRT1) and the Metabolic Function in Geriatric Patients Using the Indonesian Version of the Montreal Cognitive Assessment (MoCA-INA)

A growing life expectancy may result in a chronic medical condition and multimorbidity because the aging process leads to a decrease in cognitive and physiological function. These risks may affect the quality of life of geriatrics. The present study aims to determine the correlation between cognitive status (in terms of SIRT1, a nicotinamide adenine dinucleotide (NAD+)-dependent class III deacetylase) and metabolic function (in terms of the lipid profile, kidney function, and blood glucose) in geriatric patients. The differences in the parameters of metabolic function in the participants' cognitive status were determined by using the Indonesian version of the Montreal Cognitive Assessments (MoCA-Ina). The elderly participants (n = 120) were recruited at three sites in Indonesia from March to October 2022. Our study demonstrated a negative correlation between the cognitive status of geriatric patients and their metabolic function, represented by the MoCA-Ina score with a linear regression equation of y = 0.27 - 2.4 ×10-3x. Higher levels of LDL-C, cystatin C, and HbA1c were found in the Severe-Moderate Cognitive Impairment group. Determining the SIRT1 levels may be beneficial in predicting both the cognitive and metabolic status of geriatrics because this protein is among numerous metabolic sensors in the hypothalamus.

Serum cystatin C for risk stratification of prediabetes and diabetes populations

BACKGROUND

The association between serum cystatin C level and vascular outcomes has not been fully elucidated in diabetes and is unclear in prediabetes. We aim to evaluate whether cystatin C level predicts future risk for mortality and vascular outcomes in prediabetes and diabetes.

METHODS

A total of 85,371 participants with prediabetes and diabetes, and available baseline cystatin C in the UK biobank were included with a 14-year follow-up. Cox hazards models were used to calculate the associations between cystatin C level, mortality (all-cause, cause-specfic mortality) and vascular outcomes (myocardial infarction [MI], stroke, end-stage renal disease [ESRD] and diabetic retinopathy [DR]). The 1136 diabetes subjects in Guangzhou Diabetic Eye Study (GDES) were included for examing the impact of cystatin C on in vivo retinal degeneration and microvascular changes by using SS-OCT and OCTA.

RESULTS

The highest cystatin C quartile had increased risks of all-cause (hazard ratio [HR], 2.02; 95% confidence interval [CI] 1.86-2.19), cardiovascular (HR, 2.29; 95% CI 1.97-2.67), cancer (HR, 1.86; 95% CI 1.65-2.10) and other-cause mortality (HR, 2.24; 95% CI 1.90-2.64), MI (HR, 1.40; 95% CI 1.26-1.55), stroke (HR, 1.88; 95% CI, 1.57-2.26), ESRD (HR, 7.33; 95% CI, 5.02-10.71), DR (HR, 1.17; 95% CI 1.03-1.32) than those in the lowest quartile. Adding cystatin C to the conventional model improved C-statistic for all-cause (0.699-0.724), cardiovascular (0.762-0.789), cancer (0.661-0.674) and other-cause mortality (0.675-0.715), MI (0.748-0.750), stroke (0.712-0.718), and ESRD (0.808-0.827). The GDES analysis identified a strong association between increased cystatin C levels and diminished retinal neural layers, as well as microvascular rarefaction in both macular and optic disc regions (all P < 0.05).

CONCLUSIONS

Serum cystatin C refines the risk stratification for mortality and vascular outcomes among patients with prediabetes or diabetes.

The Urinary Concentrations of Neutrophil Gelatinase-Associated Lipocalin, Cystatin C and Osteopontin in the Healthy Term and Stable Preterm Neonates: A Pilot Study

BACKGROUND

In neonates, the assessment of kidney function with serum creatinine is limited; therefore, more effective biomarkers are needed.

AIM

The study aimed at analyzing the concentrations of renal biomarkers (osteopontin, cystatin C, and NGAL) in neonates.

MATERIAL AND METHODS

The study included 80 term and 20 preterm neonates aged 28-33 weeks of gestation. Biomarkers were measured in urine. Term neonates' urine was collected on the 1st day of life. Preterm neonates' urine was collected on the 1st, 8th, 15th, 22nd day of life. Biomarkers' concentrations were normalized to urinary creatinine (cr.) and presented as urinary biomarker/cr. ratios.

RESULTS

Median values of biomarker/creatine ratios in term and preterm neonates were the following: cystatin C/cr.: 7.26 and 439.49; osteopontin/cr.: 135.86 and 1633.37; NGAL/cr. in girls: 212.14 and 256.93; and NGAL/cr. in boys 27.123 and 65.29 ng/mg cr. In preterm neonates the cystatin C/cr. ratio was higher on the 1st than on the 8th day. The osteopontin/cr. ratio did not differ between the days. The NGAL/cr. ratio in girls was higher on the 8th than on the 22nd day, and in boys, the lowest was on the 22nd day.

CONCLUSIONS

Prematurity in stable, Caucasian neonates might cause higher osteopontin and cystatin C excretion, but not NGAL. The excretion of NGAL and cystatin C, but not osteopontin, may change during first weeks of premature neonate's life.

Mast cells in colorectal cancer tumour progression, angiogenesis, and lymphangiogenesis

The characteristics of the tumour cells, as well as how tumour cells interact with their surroundings, affect the prognosis of cancer patients. The resident cells in the tumour microenvironment are mast cells (MCs), which are known for their functions in allergic responses, but their functions in the cancer milieu have been hotly contested. Several studies have revealed a link between MCs and the development of tumours. Mast cell proliferation in colorectal cancer (CRC) is correlated with angiogenesis, the number of lymph nodes to which the malignancy has spread, and patient prognosis. By releasing angiogenic factors (VEGF-A, CXCL 8, MMP-9, etc.) and lymphangiogenic factors (VEGF-C, VEGF-D, etc.) stored in granules, mast cells play a significant role in the development of CRC. On the other hand, MCs can actively encourage tumour development via pathways including the c-kit/SCF-dependent signaling cascade and histamine production. The impact of MC-derived mediators on tumour growth, the prognostic importance of MCs in patients with various stages of colorectal cancer, and crosstalk between MCs and CRC cells in the tumour microenvironment are discussed in this article. We acknowledge the need for a deeper comprehension of the function of MCs in CRC and the possibility that targeting MCs might be a useful therapeutic approach in the future.

Clinical significance of serum cystatin C-to-creatinine ratio as a surrogate marker for incident osteoporotic fracture predictions

Background

Detection of appropriate indicators is valuable for preventing incidental osteoporotic fractures. We statistically evaluated the significance of serum cystatin C-to-creatinine ratio (CysC/Cr) as a surrogate marker for incident major osteoporotic fractures (MOF) prediction.

Methods

Eligible patients with simultaneous measurement of CysC/Cr and bone mineral density in the lumbar spine and proximal femur were selected, and their fracture histories until 5 years after baseline were observed in the retrospective area cohort data. Patients who were followed up until termination or the first osteoporotic fracture were included, and loss of follow-up or death was excluded. Candidate risk factors for osteoporotic fractures were tested for risk ratios using a cox regression analysis. Receiver operating characteristic tests were performed on factors with significantly higher risk ratios and evaluated with Kaplan-Meier survival analysis to determine the hazard ratios of the factors.

Results

A total of 175 patients of whom 28 had incident MOF, 38 men, and 137 women, were enrolled. The mean age was 70.2 years. A significantly higher risk ratio was shown in the presence of prevalent MOF, hyper fall-ability, lifestyle-related diseases, chronic kidney diseases ≥ Grade3a, and higher CysC/Cr. All parameters had cutoff indices and showed significantly higher hazard ratios.

Conclusions

These results suggested that CysC/Cr may be a predictive marker of incident osteoporotic fractures. It might work as a screening tool for MOF risk.

Optimizing Vancomycin Therapy in Critically Ill Children: A Population Pharmacokinetics Study to Inform Vancomycin Area under the Curve Estimation Using Novel Biomarkers

Area under the curve (AUC)-directed vancomycin therapy is recommended, but Bayesian AUC estimation in critically ill children is difficult due to inadequate methods for estimating kidney function. We prospectively enrolled 50 critically ill children receiving IV vancomycin for suspected infection and divided them into model training (n = 30) and testing (n = 20) groups. We performed nonparametric population PK modeling in the training group using Pmetrics, evaluating novel urinary and plasma kidney biomarkers as covariates on vancomycin clearance. In this group, a two-compartment model best described the data. During covariate testing, cystatin C-based estimated glomerular filtration rate (eGFR) and urinary neutrophil gelatinase-associated lipocalin (NGAL; full model) improved model likelihood when included as covariates on clearance. We then used multiple-model optimization to define the optimal sampling times to estimate AUC24 for each subject in the model testing group and compared the Bayesian posterior AUC24 to AUC24 calculated using noncompartmental analysis from all measured concentrations for each subject. Our full model provided accurate and precise estimates of vancomycin AUC (bias 2.3%, imprecision 6.2%). However, AUC prediction was similar when using reduced models with only cystatin C-based eGFR (bias 1.8%, imprecision 7.0%) or creatinine-based eGFR (bias -2.4%, imprecision 6.2%) as covariates on clearance. All three model(s) facilitated accurate and precise estimation of vancomycin AUC in critically ill children.

Monitoring of Serological, Cellular and Genomic Biomarkers in Transplantation, Computational Prediction Models and Role of Cell-Free DNA in Transplant Outcome

The process and evolution of an organ transplant procedure has evolved in terms of the prevention of immunological rejection with the improvement in the determination of immune response genes. These techniques include considering more important genes, more polymorphism detection, more refinement of the response motifs, as well as the analysis of epitopes and eplets, its capacity to fix complement, the PIRCHE algorithm and post-transplant monitoring with promising new biomarkers that surpass the classic serum markers such as creatine and other similar parameters of renal function. Among these new biomarkers, we analyze new serological, urine, cellular, genomic and transcriptomic biomarkers and computational prediction, with particular attention to the analysis of donor free circulating DNA as an optimal marker of kidney damage.

Cystatin C proteoforms in chronic kidney disease

Cystatin C, a cysteine protease inhibitor, is used as a biomarker of renal function. It offers several advantages compared to creatinine, and formulas for the estimation of the glomerular filtration rate based on cystatin C have been developed. Recently, several proteoforms of cystatin C have been discovered, including an intact protein with a hydroxylated proline at the N-terminus, and N-terminal truncated forms. There is little knowledge about the biological significance of these proteoforms.

METHODS

Cross-sectional study of patients with different stages of chronic renal disease (pre-dialysis n = 53; hemodialysis n = 51, renal transplant n = 53). Measurement of cystatin C proteoforms by MALDI-TOF MS, assessment of medicine prescription using the first two levels of the Anatomical Therapeutic chemical system from patients' records.

RESULTS

Patients receiving hemodialysis had the highest cystatin C concentrations, followed by pre-dialysis patients and patients with a renal transplant. In all groups, the most common proteoforms were native cystatin C and CysC 3Pro-OH while the truncated forms made up 28%. The distribution of the different proteoforms was largely independent of renal function and total cystatin C. However, the use of corticosteroids (ATC-L02) and immunosuppressants (ATC-H04) considerably impacted the distribution of proteoforms.

CONCLUSION

The different proteoforms of cystatin C increased proportionally with total cystatin C in patients with chronic kidney disease. Prescription of corticosteroids and immunosuppressants had a significant effect on the distribution of proteoforms. The biological significance of these proteoforms remains to be determined.

Mast cells inhibit colorectal cancer development by inducing ER stress through secreting Cystatin C

Mast cells (MCs) are abundantly distributed in the human intestinal mucosa and submucosa. However, their roles and mechanisms in the development of colorectal cancer (CRC) are still unclear. In the present research, we found that the infiltration density of MCs in CRC tissues was positively correlated with improved patients' prognoses. Moreover, MCs suppressed the growth and induced the apoptosis of CRC cells in vitro and in vivo but had no effect on normal colonic epithelial cells. The present study revealed that MCs specifically induced endoplasmic reticulum stress (ERS) and activated the unfolded protein response (UPR) in CRC cells but not in normal cells, which led to the suppression of CRC development in vivo. Furthermore, we found that the secreted Cystatin C protein was the key factor for the MC-induced ERS in CRC cells. This work is of significance for uncovering the antitumor function of MCs in CRC progression and identifying the potential of CRC to respond to MC-targeted immunotherapy.

Association between serum cystatin C level and cognition in older adults: a cross-sectional analysis

Introduction

Serum Cystatin C level, an indication of kidney function, has been implicated in the pathogenesis of Alzheimer's disease and cognitive impairment. In this cross-sectional study, we looked into the relation between serum Cystatin C levels and cognition in a group of U.S. older adults.

Method

The data of this study were from the National Health and Nutrition Examination Survey (NHANES) 1999-2002. A total of 4,832 older adults aged ≥60 who met the inclusion criteria were included. The Dade Behring N Latex Cystatin C assay, which is a particle-enhanced nephelometric assay (PENIA), was utilized to assess Cystatin C levels in participants' blood samples. Participants' cognition was examined using the digit symbol substitution test (DSST). Z-scores of the DSST were calculated based on sample means and standard deviations (SD). To investigate the relationships between the quartiles of serum Cystatin C level and DSST z scores, multiple linear regression models were developed while controlling for age, sex, race/ethnicity, and education.

Results

The average age of the participants was 71.1 (SD 7.8). The participants were about half female (50.5%), non-Hispanic White (61.2%), and (36.1%) who had completed at least some college. They had an average serum Cystatin C level of 1.0 mg/dl (SD 0.44). After performing multiple linear regression with a reference group consisting of participants in quartile one of plasma Cystatin C levels, we found that serum Cystatin C levels in quartiles three and four were independently associated with lower DSST z scores (β = -0.059, 95% CI -0.200 to -0.074 and β = -0.108, 95% CI -0.319 to -0.184, respectively).

Conclusion

Higher serum Cystatin C level is associated with worse processing speed, sustained attention, and working memory in older adults. Cystatin C level may be a biomarker for cognitive decline in older adults.

Association of plasma cystatin C with all-cause and cause-specific mortality among middle-aged and elderly individuals: a prospective community-based cohort study

We investigated the associations of plasma cystatin C with all-cause and cause-specific mortality risk and identified potential modifying factors affecting these associations in middle-aged and elderly people (≥ 50 years). This community-based prospective cohort study included 13,913 individuals aged ≥ 50 years from the Health and Retirement Study. Cox proportional hazard models were used to estimate the associations between cystatin C concentrations and the risk of all-cause and cardiovascular and cancer mortality after adjustment for sociodemographic characteristics, lifestyle factors, self-reported medical history, and other potential confounding factors. During a total of 71,988 person-years of follow-up (median: 5.8 years; interquartile range 3.3-7.6 years), 1893 all-cause deaths were documented, including 714 cardiovascular-related and 406 cancer-related deaths. The comparisons of the groups with the highest (quartile 4) and lowest (quartile 1) cystatin C concentrations revealed that the adjusted hazard ratios and 95% confidence intervals were 1.92 (1.62-2.28) for all-cause mortality, 1.98 (1.48-2.65) for cardiovascular mortality, and 1.62 (1.13-2.32) for cancer mortality. The associations of cystatin C concentrations with all-cause, cardiovascular and cancer mortality did not differ substantially when participants were stratified by sex, age, BMI, current smoking status, current alcohol consumption, and regular exercise (all P for interactions > 0.05). Our study indicates that an elevated plasma cystatin C concentration is associated with an increased risk of all-cause, cardiovascular and cancer mortality both men and women among the middle-aged and elderly individuals.

Cystatin C predicts cognitive decline in multiple system atrophy: A 1-year prospective cohort study

BACKGROUND

Accumulating evidence has suggested that cystatin C is associated with cognitive impairment in patients with neurodegenerative diseases. However, the association between cystatin C and cognitive decline in patients with multiple system atrophy (MSA) remains largely unknown.

OBJECTIVES

The objective was to determine whether cystatin C was independently associated with cognitive decline in patients with early-stage MSA.

METHODS

Patients with MSA underwent evaluation at baseline and the 1-year follow-up. Cognitive function was evaluated with Montreal cognitive assessment (MoCA). Changes in the MoCA score and the absolute MoCA score at the 1-year assessment were considered the main cognitive outcome. The cystatin C concentrations in patients with MSA and age, sex, and body mass index matched-healthy controls (HCs) were measured. A multiple linear regression model was used to test the association between cystatin C and cognitive decline.

RESULTS

A total of 117 patients with MSA and 416 HCs were enrolled in the study. The cystatin C levels were significantly higher in patients with MSA than in HCs (p < 0.001). Cystatin C levels were negatively correlated with MoCA score at baseline and at 1-year follow-up. Multiple linear regression model adjusted for potential confounders showed that baseline cystatin C levels were significantly associated with the MoCA score (p = 0.004) or change in the MoCA score (p = 0.008) at 1-year follow-up.

CONCLUSION

Our results suggested that cystatin C may serve as a potential biomarker of cognitive decline in patients with early-stage MSA.

Detection of urinary cystatin-c in IUGR neonates by immunoblot SDS-PAGE

BACKGROUND

it is known that intrauterine growth retardation (IUGR) represents a risk factor for the deterioration of renal function as it can adversely impact on the number of nephrons developed in the kidney during nephrogenesis. An interesting molecule is the Cystatin-C (cyst-C): it is considered to have the potency to detect both glomerular and proximal renal injury. Recently, using a quantitative EIA cyst-C detection kit, we found increased levels of cyst-C in the urine of neonates with IUGR. Since cyst-C molecules can be present in both monomer and/or polymer forms, the purpose of this study is to investigate in which forms this molecule is present in the urine of IUGR neonates by Immunoblot SDS-PAGE in order to verify if the presence or absence of a particular type of cyst-C conformation can give more information about the renal functioning.

METHODS

urine samples were collected from 64 neonates with IUGR, and 86 healthy controls defined as appropriate for gestational age (AGA). Urinary cyst-C was investigated by the Immunoblot SDS-PAGE.

RESULTS

in all urine samples, SDS-PAGE analysis showed a reactivity of the IgG anti cyst-C with a complex of about 70 kDa. The monomer form at 13 KDa appeared in 78% of IUGR neonates and in 12% of AGA neonates.

CONCLUSIONS

this study revealed the presence of monomer cyst-C in the urine of IUGR neonates, and suggests an insufficient and/or non-compensatory reabsorption by tubular cells. Monomeric cyst-C can be considered an early biochemical marker to identify and to select IUGR neonates who need to be monitored for risk of renal injury.

Endogenous markers of kidney function and renal drug clearance processes of filtration, secretion, and reabsorption

The kidneys are responsible for maintaining physiologic homeostasis. The kidneys clear a variety of drugs and other substances through passive (filtration) and active processes that utilize transport proteins. Renal clearance is comprised of the processes of glomerular filtration, tubular secretion, and tubular reabsorption. Endogenous biomarkers, such as creatinine and cystatin C, are routinely used to estimate renal clearance. Understanding the contributing components of renal function and clearance, through the use of biomarkers, is necessary in elucidating the renal pharmacology of drugs and other substances. While exogenous markers of kidney function have been known for decades, several complexities have limited their usage. Several endogenous markers are being evaluated and hold promise to elucidate the individual components of kidney function that represent filtration, secretion, and reabsorption.

High serum amyloid A predicts risk of cognitive impairment after lacunar infarction: Development and validation of a nomogram

Background

Post-stroke cognitive impairment (PSCI) after lacunar infarction was worth attention in recent years. An easy-to-use score model to predict the risk of PSCI was rare. This study aimed to explore the association between serum amyloid A (SAA) and cognitive impairment, and it also developed a nomogram for predicting the risk of PSCI in lacunar infarction patients.

Methods

A total of 313 patients with lacunar infarction were enrolled in this retrospective study between January 2021 and December 2021. They were divided into a training set and a validation set at 70%:30% randomly. The Chinese version of the Mini-Mental State Examination (MMSE) was performed to identify cognitive impairment 3 months after discharge. Univariate and multivariate logistic regression analyses were used to determine the independent risk factors for PSCI in the training set. A nomogram was developed based on the five variables, and the calibration curve and the receiver operating characteristic (ROC) curve were drawn to assess the predictive ability of the nomogram between the training set and the validation set. The decision curve analysis (DCA) was also conducted in both sets.

Results

In total, 52/313 (16.61%) participants were identified with PSCI. The SAA levels in patients with PSCI were significantly higher than non-PSCI patients in the training set (P < 0.001). After multivariate analysis, age, diabetes mellitus, white blood count, cystatin C, and SAA were independent risk predictors of PSCI. The nomogram demonstrated a good discrimination performance between the training set (AUC = 0.860) and the validation set (AUC = 0.811). The DCA showed that the nomogram had a well clinical utility in the two sets.

Conclusion

The increased SAA is associated with PSCI in lacunar infarction patients, and the nomogram developed with SAA can increase prognostic information for the early detection of PSCI.

Construction of a Nomogram Discriminating Malignancy-Associated Membranous Nephropathy From Idiopathic Membranous Nephropathy: A Retrospective Study

Background

Based on the etiology, membranous nephropathy (MN) can be categorized into idiopathic membranous nephropathy (IMN) and secondary membranous nephropathy. Malignancy-associated membranous nephropathy (MMN) is a common type of secondary MN. Its incidence is only second to that of lupus nephritis. As the treatment and prognosis of MMN differ significantly from those of other MNs, the identification of MMN is crucial for clinical practice. The purpose of this study was to develop a model that could efficiently discriminate MMN, to guide more precise selection of therapeutic strategies.

Methods

A total of 385 with IMN and 62 patients with MMN, who were hospitalized at the First Affiliated Hospital of Zhengzhou University between January 2017 and December 2020 were included in this study. We constructed a discriminant model based on demographic information and laboratory parameters for distinguishing MMN and IMN. To avoid an increased false positivity rate resulting from the large difference in sample numbers between the two groups, we matched MMN and IMN in a 1:3 ratio according to gender. Regression analysis was subsequently performed and a discriminant model was constructed. The calibration ability and clinical utility of the model were assessed via calibration curve and decision curve analysis.

Results

We constructed a discriminant model based on age, CD4⁺ T cell counts, levels of cystatin C, albumin, free triiodothyronine and body mass index, with a diagnostic power of 0.860 and 0.870 in the training and test groups, respectively. The model was validated to demonstrate good calibration capability and clinical utility.

Conclusion

In clinical practice, patients demonstrating higher scores after screening with this model should be carefully monitored for the presence of tumors in order to improve their outcome.

Association of inflammatory biomarkers and cardiovascular risk scores in an Italian cohort of HIV positive patient undergoing antiretroviral therapy

BACKGROUND

Several algorithms have been developed to predict cardiovascular risk (CVR) over time, however none of them seem to be accurate when applied to HIV patients.

OBJECTIVE

The aim of this study was to assess plasma inflammatory biomarkers in relation to multiple CVR scores (FRS, ASCVD, PROCAM and the DAD-5 Years-Estimated-Risk) in an Italian cohort of HIV patients undergoing a combined Antiretroviral Therapy (cART).

METHODS

We enrolled HIV patients undergoing cART without any change in the HIV-related pharmacological therapy over the last 48 weeks Demographic and anamnestic data were collected, and a biochemical panel including the following biomarkers was collected: CRP, Cystatin-C, microalbuminuria, IL-18, IL-2, IL-4, IL-6, IL-10, TNF-α and IFN- γ. CVR scores were obtained for each patient and compared to the biochemical panel to assess statistical correlation.

RESULTS

90 Caucasian HIV patients were enrolled. Assessment of CVR scores showed FRS values of 6.98±6.11%, ASCVD 7.18±6.25%, PROCAM 6.7±7.4% and DAD-5 Years Estimated Risk 3.10±3.41%. We found correlations between the levels of circulating cytokines measured and the cardiovascular risk prediction scores.

CONCLUSIONS

Our data showed that the values of selected inflammatory biomarkers strongly correlate with the CVR scores, suggesting that they can be employed as reliable predictors of cardiovascular disease in HIV patients. The routine use of selected biomarkers associated with systemic inflammation could be a valid and readily available tool for clinicians to assess and monitor cardiovascular risk in HIV patients.

.

The Most Promising Biomarkers of Allogeneic Kidney Transplant Rejection

Clinical transplantology is a constantly evolving field of medicine. Kidney transplantation has become standard clinical practice, and it has a significant impact on reducing mortality and improving the quality of life of patients. Allogenic transplantation induces an immune response, which may lead to the rejection of the transplanted organ. The gold standard for evaluating rejection of the transplanted kidney by the recipient's organism is a biopsy of this organ. However, due to the high invasiveness of this procedure, alternative diagnostic methods are being sought. Therefore, the biomarkers may play an essential predictive role in transplant rejection. A review of the most promising biomarkers for early diagnosis and prognosis prediction of allogenic kidney transplant rejection summarizes novel data on neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), C-X-C motif chemokine 10 (CXCL-10), cystatin C (CysC), osteopontin (OPN), and clusterin (CLU) and analyses the dynamics of changes of the biomarkers mentioned above in kidney diseases and the mechanism of rejection of the transplanted kidney.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Advancements in nanomedicines for the detection and treatment of diabetic kidney disease

In the diabetic kidneys, morbidities such as accelerated ageing, hypertension and hyperglycaemia create a pro-inflammatory microenvironment characterised by extensive fibrogenesis. Radiological techniques are not yet optimised generating inconsistent and non-reproducible data. The gold standard procedure to assess renal fibrosis is kidney biopsy, followed by histopathological assessment. However, this method is risky, invasive, subjective and examines less than 0.01% of kidney tissue resulting in diagnostic errors. As such, less than 10% of patients undergo kidney biopsy, limiting the accuracy of the current diabetic kidney disease (DKD) staging method. Standard treatments suppress the renin-angiotensin system to control hypertension and use of pharmaceuticals aimed at controlling diabetes have shown promise but can cause hypoglycaemia, diuresis and malnutrition as a result of low caloric intake. New approaches to both diagnosis and treatment are required. Nanoparticles (NPs) are an attractive candidate for managing DKD due to their ability to act as theranostic tools that can carry drugs and enhance image contrast. NP-based point-of-care systems can provide physiological information previously considered unattainable and provide control over the rate and location of drug release. Here we discuss the use of nanotechnology in renal disease, its application to both the treatment and diagnosis of DKD. Finally, we propose a new method of NP-based DKD classification that overcomes the current systems limitations.

Urinary cystatin C: pediatric reference intervals and comparative assessment as a biomarker of renal injury among children in the regions with high burden of CKDu in Sri Lanka

BACKGROUND

Cystatin C (Cys-C) is an emerging biomarker of renal diseases and its clinical use, particularly for screening the communities affected by chronic kidney disease of unknown etiology (CKDu), is hindered due to the lack of reference intervals (RIs) for diverse ethnic and age groups. The present study aimed to define RIs for urinary Cys-C (uCys-C) for a healthy pediatric population in Sri Lanka and in turn compare the renal function of the residential children in CKDu endemic and non-endemic regions in Sri Lanka.

METHODS

A cross-sectional study was conducted with 850 healthy children (10-17 years) from selected locations for reference interval establishment, while a total of 892 children were recruited for the comparative study. Urine samples were collected and analyzed for Cys-C, creatinine (Cr) and albumin. Cr-adjusted uCys-C levels were partitioned by age, and RIs were determined with quantile regression (2.5th, 50th and 97.5th quantiles) at 90% confidence interval.

RESULTS

The range of median RIs for uCys-C in healthy children was 45.94-64.44 ng/mg Cr for boys and 53.58-69.97 ng/mg Cr for girls. The median (interquartile range) uCys-C levels of children in the CKDu endemic and non-endemic regions were 58.18 (21.8-141.9) and 58.31 (23.9-155.3) ng/mg Cr with no significant difference (P = 0.781). A significant variation of uCys-C was noted in the children across age.

CONCLUSIONS

Notably high uCys-C levels were observed in children with elevated proteinuria. Thus, uCys-C could be a potential biomarker in identifying communities at high risk of CKDu susceptibility.

Prospective evaluation of high-dose methotrexate pharmacokinetics in adult patients with lymphoma using novel determinants of kidney function

High-dose methotrexate (HDMTX) pharmacokinetics (PKs), including the best estimated glomerular filtration rate (eGFR) equation that reflects methotrexate (MTX) clearance, requires investigation. This prospective, observational, single-center study evaluated adult patients with lymphoma treated with HDMTX. Samples were collected at predefined time points up to 96 h postinfusion. MTX and 7-hydroxy-MTX PKs were estimated by standard noncompartmental analysis. Linear regression determined which serum creatinine- or cystatin C-based eGFR equation best predicted MTX clearance. The 80 included patients had a median (interquartile range [IQR]) age of 68.6 years (IQR 59.2-75.6), 54 (67.5%) were men, and 74 (92.5%) were White. The median (IQR) dose of MTX was 7.6 (IQR 4.8-11.3) grams. Median clearance was similar across three dosing levels at 4.5-5.6 L/h and was consistent with linear PKs. Liver function, weight, age, sex, concomitant chemotherapy, and number of previous MTX doses did not impact clearance. MTX area under the curve (AUC) values varied over a fourfold range and appeared to increase in proportion to the dose. The eGFR_cys (ml/min) equation most closely correlated with MTX clearance in both the entire cohort and after excluding outlier MTX clearance values (r = 0.31 and 0.51, respectively). HDMTX as a 4-h infusion displays high interpatient pharmacokinetic variability. Population PK modeling to optimize MTX AUC attainment requires further evaluation. The cystatin C-based eGFR equation most closely estimated MTX clearance and should be investigated for dosing and monitoring in adults requiring MTX as part of lymphoma management.

Role of cystatin C in urogenital malignancy

Urogenital malignancy accounts for one of the major causes of cancer-related deaths globally. Numerous studies have investigated novel molecular markers in the blood circulation, tumor tissue, or urine in order to assist in the clinical identification of tumors at early stages, predict the response of therapeutic strategies, and give accurate prognosis assessment. As an endogenous inhibitor of lysosomal cysteine proteinases, cystatin C plays an integral role in diverse processes. A substantial number of studies have indicated that it may be such a potential promising biomarker. Therefore, this review was intended to provide a detailed overview of the role of cystatin C in urogenital malignancy.

OUP accepted manuscript

Background

Methods

Results

Conclusions

Association Between Serum Cystatin C and Thyroid Diseases: A Systematic Review and Meta-Analysis

Background

Cystatin C (CysC) is often used to diagnose and monitor renal diseases. Although some studies have investigated the association between serum CysC levels and thyroid diseases, their reported results were inconsistent. Therefore, the relationship between CysC levels and thyroid diseases remains controversial.

Aim

This meta-analysis aimed to statistically evaluate serum CysC levels in patients with thyroid diseases.

Methods

A literature search was conducted using the PubMed, Web of Science, Embase, EBSCO, and Wiley Online Library databases. The following search terms were used for the title or abstract: "Cystatin C" or "CysC" in combination with the terms "thyroid disease", "thyroid function", "hypothyroidism", or "hyperthyroidism". The results of the systematic analysis were presented as standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs).

Results

Eleven articles (1,265 cases and 894 controls) were included in the meta-analysis. The results of the meta-analysis showed that the serum CysC levels of patients with hyperthyroidism were significantly higher than those of the controls (SMD: 1.79, 95% CI [1.34, 2.25]), and the serum CysC levels of patients with hypothyroidism were significantly lower than those of the controls (SMD -0.59, 95% CI [-0.82, -0.36]). Moreover, the treatment of thyroid diseases significantly affected serum CysC levels.

Conclusions

To the best of our knowledge, this meta-analysis is the first to evaluate serum CysC levels in patients with thyroid diseases. Our findings suggest that thyroid function affects serum CysC levels and that serum CysC may be an effective marker for monitoring thyroid diseases.

Systematic Review Registration

PROSPERO [https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=258022], identifier CRD42021258022].

Associations of serum cystatin C with depressive symptoms and suicidal ideation in major depressive disorder

BACKGROUND

Individuals with major depressive disorder (MDD) have high suicidal ideation. There is evidence that serum cystatin C (Cys C) may be involved in the pathophysiology of MDD. The present study aimed to investigate Cys C concentration in patients with MDD and clarify its possible association with depressive symptoms and suicidal ideation.

METHODS

An online cross-sectional survey of 159 patients diagnosed with MDD was conducted. Serum Cys C levels were measured using ADVIA 2400 biochemical analyzer. The 24-item Hamilton Depression Scale (HAMD-24) was administered to evaluate the depressive symptoms. Generalized linear regression, logistic regression and restricted cubic spline models were used to examine the association of serum Cys C levels with depressive symptoms and suicidal ideation.

RESULTS

Serum Cys C levels were higher in MDD patients than in controls (p = 0.001) and were positively associated with scores on HAMD-24 in unadjusted (gender distribution, age, smoking, alcohol consumption, family history of depression and traumatic life events; (p = 0.003) and fully adjusted linear regression model (p = 0.005). The fully adjusted regression coefficient with 95% confidence intervals for serum Cys C levels and HAMD-24 score was 30.339 (9.602 to 51.077). The level of Cys C in the suicidal ideation (SI) group was significantly higher than that in the non-suicide ideation (non-SI) group (p = 0.001). Serum Cys C levels were positively associated with suicidal ideation in each logistic regression model (all p <  0.05).

CONCLUSION

Serum Cys C levels were elevated in MDD patients and appeared to be positively correlated with depressive symptoms and suicidal ideation. These findings suggest that the dysfunction of Cys C may be involved in the severity of depression and in the pathophysiological process of MDD. Thus, regulation of serum Cys C could potentially be an effective predictor of the severity of depression and potentially, play a role in reducing the risk of suicide in MDD patients.

Association Between CST3 Gene Polymorphisms and Large-Artery Atherosclerotic Stroke

Objective: Cystatin C, a marker of atherosclerosis, is encoded by CST3. We aimed to evaluate whether two single-nucleotide polymorphisms (SNPs) of CST3 are correlated with large-artery atherosclerotic stroke (LAAS) and prognosis.

Methods: This subgroup analysis of the Third China National Stroke Registry (CNSR-III) enrolled acute ischemic stroke (AIS) patients within 7 days from August 2015 to March 2018 in China. rs13038305 and rs911119 of CST3 were selected based on the strong association with cystatin C concentration.

Results: Two loci of CST3 (rs13038305 and rs911119) were analyzed in 3,833 ischemic stroke patients. Carriers of T allele in rs13038305 and C allele in rs911119 tend to have lower serum cystatin C levels (p < 0.05). Compared with C/C as a reference in rs13038305, odds ratio (OR) of T/T was 0.486, 95% CI 0.237–0.994, p = 0.048. Per C allele of rs13038305 also showed an increased level of low-density lipoprotein cholesterol (LDL-C), β (95% CI) was 1.335 (1.008–1.250), p = 0.044. No correlation was found between the selected SNPs and stroke prognosis (functional outcome, recurrence, and mortality).

Conclusions: Carriers of the T allele in rs13038305 tend to have a lower proportion of LAAS. rs13038305 and rs911119 polymorphisms were likely to affect cystatin C concentration independently of kidney function.

Aggregation of Cystatin C Changes Its Inhibitory Functions on Protease Activities and Amyloid β Fibril Formation

Cystatin C (CST3) is an endogenous cysteine protease inhibitor, which is implicated in cerebral amyloid angiopathy (CAA). In CAA, CST3 is found to be aggregated. The purpose of this study is to investigate whether this aggregation could alter the activity of the protein relevant to the molecular pathology of CAA. A system of CST3 protein aggregation was established, and the aggregated protein was characterized. The results showed that CST3 aggregated both at 80 °C without agitation, and at 37 °C with agitation in a time-dependent manner. However, the levels of aggregation were high and appeared earlier at 80 °C. Dot-blot immunoassay for oligomers revealed that CST3 could make oligomeric aggregates at the 37 °C condition. Electron microscopy showed that CST3 could make short fibrillary aggregates at 37 °C. Cathepsin B activity assay demonstrated that aggregated CST3 inhibited the enzyme activity less efficiently at pH 5.5. At 7.4 pH, it lost the inhibitory properties almost completely. In addition, aggregated CST3 did not inhibit Aβ_1-40 fibril formation, rather, it slightly increased it. CST3 immunocytochemistry showed that the protein was positive both in monomeric and aggregated CST3-treated neuronal culture. However, His6 immunocytochemistry revealed that the internalization of exogenous recombinant CST3 by an astrocytoma cell culture was higher when the protein was aggregated compared to its monomeric form. Finally, MTT cell viability assay showed that the aggregated form of CST3 was more toxic than the monomeric form. Thus, our results suggest that aggregation may result in a loss-of-function phenotype of CST3, which is toxic and responsible for cellular degeneration.

Role of Cystatin C in Predicting Disease Activity and Flare-Up in Systemic Lupus Erythematosus: A Longitudinal Follow-Up Study

Background:

We aimed to determine the sensitivity of serum cystatin C (Cys-C) in predicting lupus flare-up.

Methods:

In a longitudinal study, 77 patients were followed-up for up to 15 months. Cys-C, physician global assessment (PGA), and lupus activity index (SLEDAI) were recorded during each visit. Flare-up was defined as an increase ≥4 scores in SLEDAI compared to the last visit. The predictability of flare-up by Cys-C was evaluated by generalized linear-mixed effect model (GLMM) and generalized estimating equation (GEE). Predictive power of Cys-C, SLEDAI, and PGA was compared by the area under the curves (AUC) and application of receiver operating characteristic (ROC) curves.

Results:

Lupus flare-up was observed in 14 out of 77 patients on the 1^st visit, 3 out of 41 patients on the 2^nd visit, 2 out of 26 patients on the 3^rd visit, 1 out of 14 patients on the 4^th visit, and 1 out of 3 patients on the 5^th visit. Mean Cys-C levels in patients with flare-up vs. those with no flare-up in the 1^st, 2^nd, and 3^rd visits were 1769 vs. 1603 (P = 0.6), 5701 vs. 2117 (p = 0.2) and 1409 vs. 1731 (p = 0.9), respectively. Cys-C had lower predictive power than PGA and SLEDAI for either flare-up, active nephritis or SLEDAI in GLMM/GEE models. Cys-C also showed lower sensitivity (AUC = 0.701, 95%CI = 0.579-0.823, P = 0.003) than PGA and SLEDAI, to distinguish patients prone to flare-ups.

Conclusions:

Although Cys-C had some sensitivity for predicting flare-up, active nephritis or SLEDAI, its sensitivity was lower than that in PGA and SLEDAI.