Serum cystatin C as a new marker for noninvasive estimation of glomerular filtration rate and as a marker for early renal impairment

Fractional excretion of magnesium as an early indicator of renal tubular damage in normotensive diabetic nephropathy

Objectives

The aim of the present study is to evaluate the diagnostic powers of fractional magnesium, sodium and potassium as markers of renal tubular damage in normotensive type 2 diabetes mellitus (T2DM) patients with respect to microalbuminuria and estimated glomerular filtration rate (eGFR).

Materials and methods

Forty healthy volunteers and 91 normotensive T2DM patients were included in the study. Patient group was divided into two according to albuminuria level; 49 were normoalbuminuric and 42 were microalbuminuric. In addition to albumin in urine, urine and serum Na, K, Mg and creatinine values were measured to calculate fractional electrolyte excretion rates.

Results

In normoalbuminuric and microalbuminuric groups, fractional excretion of magnesium (FEMg) values were found to be significantly higher than the control group (p < 0.05). There was a moderate correlation between FEMg and albümin to cratinin ratio (ACR) (Spearman r = 0.3215, p < 0.05). In the ROC analysis for eGFR and FEMg based on microalbuminuria, the areas under the curve were 0.625 and 0.732, respectively (diagnostic sensitivity 59.52% and 66.67%; specificity 70.79% and 77.53%, p < 0.05).

Conclusion

For renal tubular damage predicted by microalbuminuria, FEMg could be accepted as a candidate biochemical marker with diagnostic and prognostic value.

Cystatin C, a Controversial Biomarker in Hypothyroid Patients under Levothyroxine Therapy: THYRenal, a Pilot Cohort Observational Study

BACKGROUND

Cystatin C (Cys-C) is recognized as one of the most reliable renal function parameters in the general population, although it might be biased by thyroid status. Herein, we tested Cys-C and conventional renal parameters in a cohort of hypothyroid patients treated with Levothyroxine.

METHODS

Eighty-four hypothyroid patients were recruited and subgrouped according to their serum thyroid-stimulating hormone (TSH) values as a paradigm for therapeutic targeting (n = 54, optimal TSH range = 0.5-2 µIU/mL; n = 30, TSH > 2µIU/mL). Serum Cys-C, creatinine, measured and estimated glomerular filtration rates (mGFR and eGFR) were assessed. Results-mGFR and eGFR were comparable among the two subgroups, whereas Cys-C was significantly higher in patients with suboptimal TSH values (>2 µIU/mL) (p < 0.0001). TSH significantly correlated with Cys-C in the overall patient group, and in the subgroup with TSH above the target value (>2 µIU/mL). Out of 20 patients with abnormal Cys-C, 19 had suboptimal TSH levels. Receiver operating characteristic (ROC) analysis indicated Cys-C as a moderately accurate diagnostic tool (AUC = 0.871) to assess Levothyroxine replacement efficacy in hypothyroid patients (63% sensitivity, and 98% specificity).

CONCLUSIONS

The observation of increased serum Cys-C in patients with suboptimal TSH would suggest the importance of a careful interpretation by clinicians of this biomarker in the case of hypothyroid patients.

Intensive Care Unit Management of the Adult with Congenital Heart Disease

PURPOSE

Adults with congenital heart disease (ACHD) are a rapidly growing population with ever-increasing complexity, and intensive care unit (ICU) management is often necessary. This review summarizes common cardiovascular and non-cardiovascular complications in ACHD and provides a framework for ICU care.

RECENT FINDINGS

Heart failure is the leading cause of hospitalization and mortality in ACHD. Varied anatomy and repairs, as well as differing physiological complications, limit generalized application of management algorithms. Recent studies suggest that earlier mechanical support in advanced cases is feasible and potentially helpful. Cardiac arrhythmias are poorly tolerated and often require immediate attention. Other complications requiring intensive care include infections such as endocarditis and COVID-19, pulmonary hypertension, renal failure, hepatic dysfunction, coagulopathy, and stroke. Successful ICU care in ACHD requires a multi-disciplinary approach with careful consideration of anatomy, physiology, and associated comorbidities. Few studies have formally examined ICU management in ACHD and further research is necessary.

Kidney biomarkers in tropical infections: an update

Neglected tropical diseases affect over 1 billion people, and cause 170,000 deaths each year. They result in disability, stigma and disfigurement, and also push families into poverty. Tropical infections can involve the kidney, presenting as a wide variety of ways, varying from transient urinary abnormalities to severe acute kidney injury (AKI). It is important to assess renal function in patients with tropical infections for earlier detection of AKI, appropriate treatment and prevention of Chronic Kidney Disease (CKD) outcome in some of them. There was an exponential increase in research on new kidney biomarkers that were earlier and specific for renal damage but few in the scope of tropical infections. In this review, we focus on kidney biomarkers that are being studied in some of the most prevalent tropical infections such as visceral leishmaniasis, leptospirosis, malaria, schistosomiasis and leprosy. Further studies are needed to evaluate the usefulness of renal biomarkers in the early diagnosis of renal diseases associated with tropical infections.

Cystatin C and α-1-Microglobulin Predict Severe Acute Kidney Injury in Patients with Hemorrhagic Fever with Renal Syndrome

Puumala orthohantavirus causes hemorrhagic fever with renal syndrome (HFRS) characterized by acute kidney injury (AKI), an abrupt decrease in renal function. Creatinine is routinely used to detect and quantify AKI; however, early AKI may not be reflected in increased creatinine levels. Therefore, kidney injury markers that can predict AKI are needed. The potential of the kidney injury markers urea, cystatin C, α1-microglobulin (A1M) and neutrophil gelatinase-associated lipocalin (NGAL) to detect early AKI during HFRS was studied by quantifying the levels of these markers in consecutively obtained plasma (P) and urine samples (U) for 44 HFRS patients. P-cystatin C and U-A1M levels were significantly increased during early HFRS compared to follow-up. In a receiver operating characteristic (ROC) curve analysis, P-cystatin C, U-A1M and P-urea predicted severe AKI with area under the curve 0.72, 0.73 and 0.71, respectively, whereas the traditional kidney injury biomarkers creatinine and U-albumin did not predict AKI. Nearly half of the HFRS patients (41%) fulfilled the criteria for shrunken pore syndrome, which was associated with the level of inflammation as measured by P-CRP. P-cystatin C and U-A1M are more sensitive and earlier markers compared to creatinine in predicting kidney injury during HFRS.

Effects of dose and type of corticosteroids on the divergence between estimated glomerular filtration rates derived from cystatin C and creatinine

WHAT IS KNOWN AND OBJECTIVE

Cystatin C (Cys-C) is a useful diagnostic marker for early renal dysfunction, but has the disadvantage of giving false-positive results when corticosteroids are administered. In this study, we aimed to evaluate the dose-dependent effect of corticosteroids on the divergence between estimated glomerular filtration rates based on Cys-C (eGFRcys) and creatinine (eGFRcreat) and calculate the cut-off value of corticosteroid dose having an impact on eGFRcys/eGFRcreat ratio.

METHODS

This retrospective study included 305 patients (1318 therapies) treated with oral or injectable corticosteroids between June 2014 and May 2018, who did not meet the exclusion criteria. All corticosteroid doses were converted to prednisolone equivalent.

RESULTS

Steroid dose correlated significantly with eGFRcys/eGFRcreat ratio for all corticosteroids and for prednisolone (r_s  = -.150 and -.273, respectively), whereas no correlation was observed for methylprednisolone and hydrocortisone. The cut-off value of prednisolone dose for eGFRcys/eGFRcreat ratio < 0.79 was 0.170 mg/kg/day, with 62.4% sensitivity and 84.7% specificity. The correlation coefficient (r_s  = -.434) between prednisolone dose and eGFRcys/eGFRcreat ratio for doses of 0.170 mg/kg/day and higher was markedly larger compared with all corticosteroids.

WHAT IS NEW AND CONCLUSION

These findings suggest that results should be interpreted with caution when using eGFRcys as renal function marker in patients treated with prednisolone at doses of 0.170 mg/kg/day and higher.

The Difference Between Cystatin C- and Creatinine-Based Estimated GFR and Associations With Frailty and Adverse Outcomes: A Cohort Analysis of the Systolic Blood Pressure Intervention Trial (SPRINT)

RATIONALE & OBJECTIVE

In prior research and in practice, the difference between estimated glomerular filtration rate (eGFR) calculated from cystatin C level and eGFR calculated from creatinine level has not been assessed for clinical significance and relevance. We evaluated whether these differences contain important information about frailty.

STUDY DESIGN

A cohort analysis of the Systolic Blood Pressure Intervention Trial (SPRINT).

SETTING & PARTICIPANTS

9,092 hypertensive SPRINT participants who had baseline measurements of serum creatinine, cystatin C, and frailty.

EXPOSURE

eGFRs calculated using CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations (eGFR_cys and eGFR_cr), and eGFR_Diff, calculated as eGFR_cys-eGFR_cr.

OUTCOMES

A validated 35-item frailty index that included questionnaire data for general and physical health, limitations of activities, pain, depression, sleep, energy level, self-care, and smoking status, as well as medical history, cognitive assessment, and laboratory data. We defined frailty as frailty index score>0.21 (range, 0-1). The incidence of injurious falls, hospitalizations, cardiovascular events, and mortality was also recorded.

ANALYTICAL APPROACH

We used logistic regression to model the cross-sectional association of baseline eGFR_Diff with frailty among all SPRINT participants. Adjusted proportional hazards regression was used to evaluate the association of eGFR_Diff with adverse outcomes and mortality.

RESULTS

Mean age was 68±9 (SD) years, mean eGFR_cys and eGFR_cr were 73±23 and 72±20mL/min/1.73m², and mean eGFR_Diff was 0.5±15mL/min/1.73m². In adjusted models, each 1-SD higher eGFR_Diff was associated with 24% lower odds of prevalent frailty (OR, 0.76; 95% CI, 0.71-0.81), as well as with lower incidence rate of injurious falls (HR, 0.84; 95% CI, 0.77-0.92), hospitalization (HR, 0.91; 95% CI, 0.88-0.95), cardiovascular events (HR, 0.89; 95% CI, 0.81-0.97), and all-cause mortality (HR, 0.71; 95% CI, 0.63-0.82); P<0.01.

LIMITATIONS

Gold-standard measure of kidney function and assessment of muscle mass were not available.

CONCLUSIONS

The difference between eGFR_cys and eGFR_cr is associated with frailty and health status. Positive eGFR_Diff is strongly associated with lower risks for longitudinal adverse outcomes and mortality, even after adjusting for chronic kidney disease stage and baseline frailty.

Cerebral Microbleeds and Chronic Kidney Disease in Acute Ischemic Stroke Patients with Atrial Fibrillation

BACKGROUND

Cerebral microbleeds (CMBs) are associated with the risk of intracerebral hemorrhage in stroke patients with atrial fibrillation (AF). We investigated the association between CMBs and chronic kidney disease (CKD) in patients with acute ischemic stroke and AF.

METHODS

We retrospectively examined consecutive patients with acute ischemic stroke and AF who underwent brain gradient-echo T2*-weighted magnetic resonance imaging. The number and distribution (lobar, deep or infratentorial, and mixed) of CMBs were assessed. Kidney function was assessed according to the estimated glomerular filtration rate (eGFR), which was calculated using a modified version of the Modification of Diet in Renal Disease equation.

RESULTS

Of the 357 included patients, 105 (29.4%) had CMBs. CKD (eGFR < 60 mL/min/1.73 m²) was found in 131 (36.7%) patients. Patients with CKD showed a higher prevalence of any form of CMB (41.2% versus 22.6%, P < .001), deep or infratentorial CMBs (19.9% versus 9.3%, P < .01), and mixed CMBs (14.5% versus 5.3%, P < .01) than those without CKD. After adjusting for age and other confounding factors, CKD was found to be independently associated with the presence of any form of CMB (odds ratio 1.89, P = .02) and mixed CMBs (odds ratio 3.10, P < .01). Moreover, moderate to severe CKD (eGFR < 45 mL/min/1.73 m²) was independently associated with the presence of multiple CMBs (odds ratio 2.31, P = .04).

CONCLUSIONS

CMBs and CKD are common in acute ischemic stroke patients with AF, and CKD may be a risk factor for CMBs. Further longitudinal studies are needed to evaluate whether maintaining kidney function can prevent the development of CMBs.

Association between Endothelial Dysfunction, Biomarkers of Renal Function, and Disease Severity in Sickle Cell Disease

Background

Endothelial dysfunction (ED), as ascertained by brachial artery flow-mediated dilation (FMD), is a known feature of sickle cell disease (SCD), which is present both in crisis and in steady state. The assessment of FMD was introduced to examine the vasodilator function. Our objective was to establish the relationship between ED determined by FMD, biomarkers of renal dysfunction, and biomarkers of disease severity in SCD subjects asymptomatic of renal disease.

Methods

We enrolled 44 patients with homozygous SCD in steady state and 33 age- and sex-matched controls between 2013 and 2014 in a tropical tertiary hospital. Ultrasonographic FMD of the right brachial artery, renal arterial Doppler, complete blood count, creatinine, fetal hemoglobin, soluble P-selectin, and cystatin C (Cys-C) levels were determined. Using the median FMD value of the control group, the SCD subjects were further classified into two groups for comparison.

Results

The median FMD in SCD subjects of 3.44 (IQR, 0.00-7.08) was significantly lower than that of controls, which was 5.35 (IQR, 3.60-6.78; P=0.04). There was negative correlation between FMD and Cys-C levels (r=-0.372; P=0.01) along with renal artery resistivity index (RARI; r=-0.307; P=0.04) in SCD subjects. Additionally, Cys-C level was significantly higher in SCD subjects with FMD<5.35.

Conclusions

Brachial artery FMD was significantly lower in SCD subjects compared with a control group. Cys-C and RARI show a negative correlation with FMD, indicating that renal function is related to ED in SCD.

Diagnosis and Treatment of Hereditary Transthyretin Amyloidosis (hATTR) Polyneuropathy: Current Perspectives on Improving Patient Care

Hereditary transthyretin amyloidosis (hATTR) with polyneuropathy (formerly known as Familial Amyloid Polyneuropathy) is a rare disease due to mutations in the gene encoding transthyretin (TTR) and characterized by multisystem extracellular deposition of amyloid, leading to dysfunction of different organs and tissues. hATTR amyloidosis represents a diagnostic challenge for neurologists considering the great variability in clinical presentation and multiorgan involvement. Generally, patients present with polyneuropathy, but clinicians should consider the frequent cardiac, ocular and renal impairment. Especially a hypertrophic cardiomyopathy, even if usually latent, is identifiable in at least 50% of the patients. Therapeutically, current available options act at different stages of TTR production, including synthesis inhibition (liver transplantation and/or gene-silencing drugs) or tetramer TTR stabilization (TTR stabilizers), increasing survival at different disease stages.

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Bendiocarb-induced nephrotoxicity in rats and the protective role of vitamins C and E

Bendiocarb is a pesticide carbamate which is used to protect agricultural products and animals. In this study, rats were given orally with bendiocarb and also other chemicals via gavage. Male rats were randomly divided into eight groups (n = 6): group 1 served as controls; group 2 received vitamin C (100 mg/kg bw); group 3 received vitamin E (100 mg/kg bw); group 4 received vitamins C plus E; group 5 received bendiocarb (0.8 mg/kg 1/50 LD₅₀); group 6 received both bendiocarb and vitamin C; group 7 received both bendiocarb and vitamin E; and group 8 received both bendiocarb and vitamin C and E via oral gavage. Degenerative changes and biochemical differences in rat kidney were investigated after 4 weeks of especially bendiocarb treatment. While biochemical values were normal in the control group, it was observed that CAT, SOD, GPx, and GST values decreased, while MDA, creatine, urea, and uric acid values increased in the pesticide-treated groups. It was also reported that bendiocarb caused cytopathological and histopathological changes in rat kidney. We have shown that the application of vitamins has a therapeutic effect on the evaluated parameters.

Serum cystatin C levels are negatively correlated with post-stroke cognitive dysfunction

Stroke is the leading cause of death and long-term disability worldwide, and cognitive impairment and dementia are major complications of ischemic stroke. Cystatin C (CysC) has been found to be a neuroprotective factor in animal studies. However, the relationship between CysC levels and cognitive dysfunction in previous studies has revealed different results. This prospective observational study investigated the correlation between serum CysC levels and post-stroke cognitive dysfunction at 3 months. Data from 638 patients were obtained from the China Antihypertensive Trial in Acute Ischemic Stroke (CATIS). Cognitive dysfunction was assessed using the Mini-Mental State Examination (MMSE) at 3 months after stroke. According to the MMSE score, 308 patients (52.9%) had post-stroke cognitive dysfunction. After adjusting for potential confounding factors, the odds ratio (95% CI) of post-stroke cognitive dysfunction for the highest quartile of serum CysC levels was 0.54 (0.30–0.98), compared with the lowest quartile. The correlation between serum CysC and cognitive dysfunction was modified by renal function status. We observed a negative linear dose-response correlation between CysC and cognitive dysfunction in patients with normal renal function (P_linearity = 0.044), but not in those with abnormal renal function. Elevated serum CysC levels were correlated with a low risk of 3-month cognitive dysfunction in patients with acute ischemic stroke, especially in those with normal renal function. The current results suggest that CysC is a protective factor for post-stroke cognitive dysfunction, and could be used to treat post-stroke cognitive dysfunction. The CATIS study was approved by the Institutional Review Boards at Soochow University from China (approval No. 2012-02) on December 30, 2012, and was registered at ClinicalTrials.gov (identifier No. NCT01840072) on April 25, 2013.

Effects of Cystatin C on Cognitive Impairment in Older Chinese Adults

OBJECTIVE

To find a suitable dividing value to classify cystatin C and evaluate the association between cognition and levels of cystatin C.

METHODS

Using data from the China Health and Retirement Longitudinal Study, We conducted a longitudinal analysis of a prospective cohort of 6,869 middle-aged and older Chinese without cognitive impairment at baseline. Levels of cystatin C were categorized into 2 groups by method of decision tree. Logistic regression models evaluated whether cystatin C was related to cognitive impairment.

RESULTS

Respondents were categorized as lower levels of cystatin C and higher levels of cystatin C, cut-point was 1.11 mg/L. Higher levels of cystatin C was associated with the odds of cognitive impairment (OR, 1.56; 95% CI, 1.10-2.22) after multivariable adjustment. Respondents with higher levels of cystatin C had worse cognition scores.

CONCLUSIONS

We found a suitable dividing value of cystatin C in middle-aged and older Chinese.

An LC-MS/MS assay with a label-free internal standard for quantitation of serum cystatin C

Cystatin C is considered as an alternative to the evaluation of glomerular filtration rate. In this study, we highlighted an LC-MS/MS approach for the absolute quantitation of serum cystatin C based on label-free internal standards. A tryptic peptide (ALDFAVGEYNK) was selected as the surrogate whilst analogue (ALDFAVGEYQK) served as an internal standard. After denaturation, reduction, alkylation, digestion and concentration, the target peptides were separated on an LC column and monitored under MRM. The calibration range was from 0.25 mg/L to 15 mg/L with LLOQ of 0.05 mg/L and LOD of 0.03 mg/L, respectively. The certified reference material (ERM-DA471) was determined at 5.12 mg/L with bias of 6.57%. The recovery was between 89.68% and 92.43%. The RSD of intra- and inter-assay imprecision were both <10%. Good stability was also observed. The assay also demonstrated that the quantification of native cystatin C in human serum could be achieved using label-free internal standards. The assay was robust, cheap and sensitive.

Unusual manifestation of monoclonal gammopathy of undetermined significance: a false serum creatinine elevation

A 72-year-old Japanese man with diabetes mellitus and hypertension presented with an acutely elevated serum creatinine level, from 1.02 to 4.13 mg/dL over 2 months as measured by the enzymatic method by pure-auto S CRE-N^®. Renal biopsy could not identify the etiology of the elevating sCr. However, an elevated total protein level (8.2 g/dL) and lowering of the BUN and sCr ratio from 14.5 to 2.7 were found, and bone marrow biopsy showed less than 10% lymphoplasmacytic infiltration, compatible with monoclonal gammopathy of undetermined significance. The diagnosis of a false serum creatinine elevation due to monoclonal gammopathy of undetermined significance was confirmed with the serum cystatin C level at 1.05 mg/dL and the creatinine level of 0.97 mg/dL using Shikarikid-S CRE^® method. Although cases of monoclonal gammopathy of undetermined significance with a false serum creatinine elevation as an initial presentation are rare, this condition should be considered in patients with paraproteinemia; measuring the renal function using cystatin C is important in such patients.

Cystatin C for Risk Stratification in Patients After an Acute Coronary Syndrome

Background

Cystatin C (Cys‐C) is a marker of renal function that has shown prognostic value for cardiovascular risk stratification across different patient populations. The incremental value of Cys‐C beyond established cardiac and renal biomarkers remains incompletely explored.

Methods and Results

SOLID‐TIMI 52 (Stabilization of Plaques Using Darapladib‐Thrombolysis in Myocardial Infarction 52; http://www.clinicaltrials.gov, NCT01000727) randomized patients ≤30 days post–acute coronary syndrome were treated with darapladib or placebo. The association between Cys‐C and long‐term risk (median follow‐up 2.5 years) was assessed in 4965 individuals with adjustments made for clinical variables and other risk markers (eg, estimated glomerular filtration rate, high‐sensitivity troponin I, brain‐type natriuretic peptide, and fibroblast growth factor‐23). The prespecified outcome of interest was cardiovascular death (CVD) or heart failure hospitalization. Cys‐C was strongly correlated with creatinine (r=0.60) and estimated glomerular filtration rate (r=−0.68), moderately correlated with fibroblast growth factor‐23 (r=0.39), and weakly correlated with brain‐type natriuretic peptide (r=0.28) and high‐sensitivity troponin I (r=0.06) (all P<0.0001). After multivariate adjustment, increasing concentration of Cys‐C (per SD of log‐transformed Cys‐C) was significantly associated with a 28% higher hazard of CVD or heart failure hospitalization (hazard ratio [HR] 1.28, 95% confidence interval [CI] 1.12‐1.46, P<0.001), including CVD (HR 1.24, 95% CI 1.04‐1.47, P=0.01) and heart failure hospitalization (HR 1.42, 95% CI 1.19‐1.69, P<0.001). Cys‐C was also associated with a higher hazard of CVD, myocardial infarction, or stroke (HR 1.15, 95% CI 1.04‐1.28, P<0.01), including myocardial infarction (HR 1.17, 95% CI 1.02‐1.33, P=0.02). The addition of Cys‐C to a fully adjusted model without estimated glomerular filtration rate improved the C‐statistic from 0.80 to 0.81 (P=0.03) for CVD or heart failure hospitalization. In contrast, the addition of estimated glomerular filtration rate to a fully adjusted model without Cys‐C failed to improve model discrimination (P=0.17).

Conclusions

Cys‐C is associated with the risk of adverse outcomes in patients after acute coronary syndrome. This relationship is independent of established and novel biomarkers of the cardiorenal axis.

Association of serum cystatin C with white matter abnormalities in patients with amnestic mild cognitive impairment

Aim

White matter hyperintensities (WMH) on MRI have been reported to be a risk factor for the conversion from mild cognitive impairment (MCI) to Alzheimer's disease, although the reason remains unclear. In the present study, we hence investigated the associations between WMH volumes and cognitive function, blood levels of various molecules, and the presence of lifestyle‐associated diseases in patients with amnestic MCI.

Methods

The initial data of 38 patients with amnestic MCI and 10 normal control individuals were analyzed. The volumes of periventricular hyperintensities (PVH) and deep WMH (DWMH) were measured on T2 fluid‐attenuated inversion recovery using the imaging software, 3D Slicer; and the association between PVH/DWMH volumes and cognitive function, blood levels of molecules (such as cystatin C [CysC], 25‐hydroxyvitamin D and homocysteine) and the presence of lifestyle‐associated diseases (such as hypertension, hyperlipidemia and diabetes mellitus) were analyzed.

Results

In the MCI group, the PVH volume : intracranial volume ratio significantly correlated with Trail Making Test‐A/B scores and CysC level by Pearson's analysis, and the PVH volume : intracranial volume ratio significantly correlated with only CysC levels, whereas the DWMH volume : intracranial volume ratio did not correlate with any items at all by linear multiple regression analysis.

Conclusions

PVH volume was closely associated with frontal lobe dysfunction, particularly with attention and executive dysfunction. Serum CysC level was associated with PVH volume, which suggests that CysC might be a useful marker for determining treatment strategies for white matter abnormalities in amnestic MCI. Geriatr Gerontol Int 2019; 19: 1036–1040.

Association Between Cystatin C and the Risk of Ischemic Stroke: a Systematic Review and Meta-analysis

Ischemic stroke is a disease that affects people^'s health and quality of life. Cystatin C has been found as a new biomarker of cardiovascular disease. We performed this meta-analysis to assess the relationship between cystatin C and the risk of ischemic stroke. The studies on looking at the association between cystatin C and ischemic stroke were identified from inception to November 18, 2018. We performed a random-effects meta-analysis using mean difference. Nine studies with a total of 3773 ischemic stroke patients were included into the meta-analysis. Our results showed that patients with ischemic stroke had significantly higher serum cystatin C concentrations compared with the participants without ischemic stroke (pooled mean difference, 0.11; 95% confidence interval (CI), 0.00-0.22; P = 0.04), in particular acute ischemic stroke and subclinical cerebral infarction (mean difference, 0.23; 95% CI, 0.11-0.36; P = 0.0003 and mean difference, 0.07; 95% CI, 0.05-0.09; P < 0.00001, respectively). Cystatin C was associated with ischemic stroke, and it could be considered a predictor for the risk of ischemic stroke, especially in acute ischemic stroke and subclinical cerebral infarction.

Kidney Size, Renal Function, Ang (Angiotensin) Peptides, and Blood Pressure in Young Adults Born Preterm

Preterm birth incurs a higher risk for adult cardiovascular diseases, including hypertension. Because preterm birth may impact nephrogenesis, study objectives were to assess renal size and function of adults born preterm versus full term and to examine their relationship with blood pressure (BP; 24-hour ambulatory BP monitoring) and circulating renin-Ang (angiotensin) system peptides. The study included 92 young adults born (1987-1997) preterm (≤29 weeks of gestation) and term (n=92) matched for age, sex, and race. Young adults born preterm had smaller kidneys (80±17 versus 90±18 cm³/m²; P<0.001), higher urine albumin-to-creatinine ratio (0.70; interquartile range, 0.47-1.14 versus 0.58, interquartile range 0.42 to 0.78 mg/mmol, P=0.007), higher 24-hour systolic (121±9 versus 116±8 mm Hg; P=0.001) and diastolic (69±5 versus 66±6 mm Hg; P=0.004) BP, but similar estimated glomerular filtration rate. BP was inversely correlated with kidney size in preterm participants. Plasma Ang I was higher in preterm versus term participants (36.3; interquartile range, 13.2-62.3 versus 19.4; interquartile range, 9.9-28.1 pg/mL; P<0.001). There was no group difference in renin, Ang II, Ang (1-7), and alamandine. In the preterm, but not in the term group, higher BP was significantly associated with higher renin and alamandine and lower birth weight and gestational age with smaller adult kidney size. Young adults born preterm have smaller kidneys, higher urine albumin-to-creatinine ratio, higher BP, and higher circulating Ang I levels compared with term controls. Preterm young adults with smaller kidneys have higher BP. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT03261609.

Disposable electrochemical immunosensor for analysis of cystatin C, a CKD biomarker

Specific monitoring of cystatin C (CysC) levels in biological fluids is critical for diagnosis, treatment and mechanistic understanding of a spectrum of diseases, particularly chronic kidney disease (CKD). Despite evidences that CysC correlates with the high risk and/or progression of CKD, its use in clinical practice is still scarce. In this context, we report the development of a simple and sensitive immunosensor for the detection of CysC. The biosensor combines the technology of cost-effective screen-printed electrodes with the high specificity of a sandwich immunoassay. Optimized conditions showed that the sensor operates in a linear range between 10 and 100 ng mL^-1, with a detection limit and a sensitivity of 6.0 ng mL^-1 and 6.4 ± 0.3 μA ng mL^-1 cm^-2, respectively. Moreover, the sensor provided precise results (RSD ≤ 6.2%) and the quantification of CysC in CKD serum samples revealed to be in agreement with the values obtained by a particle-enhanced nephelometric immunoassay. In this light, the proposed immunosensor qualifies for clinical application, constituting a step forward in the development of fast, sensitive and cost-effective diagnostic tools that can improve the current medical care settings of CKD patients.

Vision Impairment in CKD Patients: Epidemiology, Mechanisms, Differential Diagnoses, and Prevention

Eyes and kidneys have numerous structural, developmental, physiologic, and pathogenic pathways in common, suggesting that many kidney and eye diseases may be interlinked. Studies suggest that the prevalence of eye diseases and vision impairment are higher among persons with end-stage kidney disease and earlier stages of chronic kidney disease (CKD) than in those without. Ocular morbidity in persons with CKD and end-stage kidney disease may be due to the following risk factors: (1) underlying conditions and risk factors for CKD such as diabetes or hypertension, (2) metabolic disorders associated with CKD, (3) uremia and anemia, and (4) CKD treatment. Among the chief eye diseases, diabetic retinopathy and age-related macular degeneration are most consistently associated with CKD. Further research for eye diseases such as glaucoma and cataract is needed to determine their relationships with CKD. Despite the high prevalence and burden of vision impairment among persons with CKD, eye screening in patients with CKD is not currently recommended as standard practice. This review suggests that patients with CKD should be encouraged to undergo a complete eye examination. Furthermore, physicians should be aware that patients undergoing dialysis may develop acute eye problems such as acute glaucoma, and appropriate referral to ophthalmologists should be considered in those with a history of glaucoma or recent ocular surgery. Interdisciplinary collaboration between nephrologists and ophthalmologists will ensure enhanced and appropriate management of patients with CKD.

Association of serum cystatin C levels with acute coronary syndrome in patients of advanced age

Objective

This study was performed to investigate the relationship between the serum cystatin C (Cys C) level and acute coronary syndrome (ACS) in patients of advanced age.

Methods

The study included 184 patients with ACS and 46 healthy control subjects. Statistical analysis was performed using SPSS version 14.0 (SPSS Inc., Chicago, IL, USA).

Results

The serum Cys C level was significantly higher in patients with than without ACS (1.24 ± 0.30 vs. 1.42 ± 0.46 mg/L, respectively). Patients with more stenotic coronary arteries were significantly more likely to have higher median serum Cys C and creatinine levels and a lower estimated glomerular filtration rate. The multivariate logistic regression analysis demonstrated that the serum Cys C level was independently associated with the presence of ACS and the quantity of stenotic coronary arteries after adjustment for confounding factors. Additionally, the serum Cys C level was positively correlated with age, the creatinine level, and the N-terminal pro-B-type natriuretic peptide level in all patients but was negatively correlated with the estimated glomerular filtration rate.

Conclusion

A high serum Cys C level was independently associated with ACS and the quantity of stenotic coronary arteries in patients of advanced age regardless of renal function.

Relationship of High Circulating Cystatin C to Biochemical Markers of Bone Turnover and Bone Mineral Density in Elderly Males with a Chronic Heart Failure

Background

The aim of the study was to investigate the association of Cystatin C (CysC) to biochemical markers of bone turnover and bone mass, and to evaluate its prognostic significance in elderly males with chronic heart failure (CHF).

Methods

A prospective cohort study was executed on sixtyeight males (mean age 68±7 years) with mild to moderate CHF, together with 19 of corresponding age- and body mass index-matched healthy individuals who underwent cardio vascular, bone mineral density (BMD), and body com position assessment. Biochemical assessment of all subjects included NT-pro-BNP, parathyroid hormone (PTH), 25-hydroxy vitamin D (25(OH)D), CysC, and biochemical markers of bone turnover including osteocalcin (OC), alkaline phosphatase (ALP), β-CrossLaps (β-CTx), osteoprotegerin (OPG), and receptor activator of nuclear factor κB ligand (RANKL).

Results

Serum CysC was significantly increased in males with CHF in comparison to healthy control ones. A significant positive association was found between CysC levels and OC in males with CHF, while OC and β-CTx increased in increasing CysC tertiles. In multivariate regression analysis, OC and smoking were a significant determinant of CysC in males with CHF. Level of CysC was found to be positively associated with an increased fatal risk in males with CHF.

Conclusions

Serum osteocalcin is an independent predictor of CysC level in elderly males with CHF. Higher CysC level showed a negative relation to survival and bone loss in males with CHF. Further research is needed to confirm the potential role of CysC in the crosstalk between heart, kidney, bone, and energy metabolism in CHF.

Impact of thyroid function on cystatin C in detecting acute kidney injury: a prospective, observational study

BACKGROUND

Cystatin C (Cys C) used clinically for detecting early acute kidney injury (AKI) was reported to be associated with thyroid function. Therefore, whether the performance of Cys C is affected by thyroid hormones has raised concern in critically ill patients. This study aimed to investigate the impact of thyroid hormones on the diagnostic and predictive accuracy of Cys C for AKI, and hence optimize the clinical application of Cys C.

METHODS

A prospective observational study was conducted in the general intensive care units (ICUs). Serum creatinine (SCr), Cys C, and thyroid function were documented for all patients at ICU admission. Patients were separated into five quintiles based on free triiodothyronine (FT3) and total triiodothyronine (TT3), and two categories according to the presence of low T3 syndrome or not. The impact of thyroid function on the performance of Cys C in diagnosing and predicting AKI was assessed by area under the receiver operating characteristic curve (AUC).

RESULTS

The AKI incidence was 30.0% (402/1339); 225 patients had AKI upon entry, and 177 patients developed AKI during the subsequent 7 days. The AUCs for Cys C in detecting total AKI, established AKI, and later-onset AKI was 0.753, 0.797, and 0.669, respectively. The multiple linear regression analysis demonstrated that TT3 and FT3 were independently associated with Cys C. Overall, although Cys C did not yield any significant difference in AUCs for detecting AKI among patients with different thyroid hormones, the optimal cut-off value of Cys C to detect AKI was markedly different between patients with and without low T3 syndrome.

CONCLUSIONS

The thyroid function had no significant impact on the diagnostic and predictive accuracy of Cys C in detecting AKI in ICU patients. However, the optimal cut-off value of Cys C to detect AKI could be affected by thyroid function.

Serum cystatin C as an indicator for early detection of diabetic nephropathy in type 2 diabetes mellitus

BACKGROUND

Diabetes mellitus (DM) refers to a group of common metabolic disorders that share the phenotype of hyperglycemia. The metabolic dysregulations associated with DM causes secondary pathophysiological changes in multiple organ systems which result in various complications, responsible for the morbidity and mortality associated with the disease.

METHODS

The present study was carried out on 40 patients with type 2 diabetes mellitus, who were recruited from those attending outpatient clinic and inpatient of Internal Medicine Department at The National Institute of Diabetes and Endocrinology from January 2017 to june 2017.

RESULTS

The mean Cystatin C values in Group I were 0.74, group II were 1.07. and in Group III were 3.25, The results show that the Cystatin C values were raised even in the patients with Normoalbuminuria with GFR ≥90 whom clinical albuminuria had not yet started.

CONCLUSIONS

serum Cystatin C may be considered as an early marker, than microalbuminuria and serum creatinine, the commonly used marker for nephropathy, for declining renal function, in diabetic subjects. Further studies in larger population are needed to confirm this result.

Intima-media thickness of the common femoral artery as a marker of leg ulceration in sickle cell disease patients

Leg ulceration is a debilitating chronic complication of sickle cell disease (SCD) the pathogenesis of which is yet to be fully elucidated. We hypothesized that SCD patients with histories of previous leg ulcers would have intima hyperplasia of the common femoral artery (CFA). We enrolled 44 SCD patients and 33 age-matched and sex-matched controls with hemoglobin AA. Anthropometric measurements, biochemical parameters, and sonographic intima-media thickness (IMT) of the CFA were determined. The median CFA IMT in SCD limbs with history of leg ulcers (SWLU) was 1.0 mm, whereas it was 0.7 mm in SCD limbs with no history of leg ulcer (SNLU) and 0.60 mm in controls (P < .001). Among the SNLU, 70.3% had CFA IMT <0.9 mm, whereas only 29.7% had CFA IMT ≥0.9 mm. Conversely, only 20.8% of SWLU had CFA IMT <0.9 mm, whereas the remaining 79.2% had CFA IMT ≥0.9 mm. All the controls had CFA IMT <0.9 mm. Binary logistic regression to determine the odds of having leg ulcer among SCD limbs with CFA IMT of ≥0.9 mm yielded an odds ratio of 9, indicating that SCD limbs with CFA IMT ≥0.9 mm had a 9 times greater risk of having leg ulcer compared with those with CFA IMT <0.9 mm. There is a significant increase in the CFA IMT of SCD limbs with ulcer compared with controls and SCD limbs without ulcer, suggesting that arterial vasculopathy plays a major role in the formation of these ulcers.

From Analysis of Ischemic Mouse Brain Proteome to Identification of Human Serum Clusterin as a Potential Biomarker for Severity of Acute Ischemic Stroke

Ischemic stroke is a devastating neurological disease that can cause permanent brain damage, but to date, few biomarkers are available to reliably assess the severity of injury during acute onset. In this study, quantitative proteomic analysis of ischemic mouse brain detected the increase in expression levels of clusterin (CLU) and cystatin C (CST3). Since CLU is a secretary protein, serum samples (n = 70) were obtained from acute ischemic stroke (AIS) patients within 24 h of stroke onset and together with 70 matched health controls. Analysis of CLU levels indicated significantly higher levels in AIS patients than healthy controls (14.91 ± 4.03 vs. 12.79 ± 2.22 ng/L; P = 0.0004). Analysis of serum CST3 also showed significant increase in AIS patients as compared with healthy controls (0.90 ± 0.19 vs. 0.84 ± 0.12 ng/L; P = 0.0064). The serum values of CLU were also positively correlated with the NIH Stroke Scale (NIHSS) scores, the time interval after stroke onset, as well as major stroke risk factors associated with lipid profile. These data demonstrate that elevated levels of serum CLU and CST3 are independently associated with AIS and may serve as peripheral biomarkers to aid clinical assessment of AIS and its severity. This pilot study thus contributes to progress toward preclinical proteomic screening by using animal models and allows translation of results from bench to bedside.

The creatinine/cystatin C ratio provides effective evaluation of muscle mass in kidney transplant recipients

INTRODUCTION

Measuring muscle mass is an important step in detecting sarcopenia. The evaluation of sarcopenia is also important for kidney transplant recipients. Methods for estimating muscle mass have been established using computed tomography or magnetic resonance imaging, which are considered the gold standards. But these methods are invasive and costly, and there is a need for a more practical and simple method using blood samples from kidney transplant recipients.

METHODS

The study population was 62 patients who underwent kidney transplantation at Kansai Medical University Hospital, and were evaluated from August to October 2017. Muscle mass was measured using dual-energy X-ray absorptiometry. Serum creatinine and cystatin C levels were measured by immunoassay.

RESULTS

We analyzed 62 transplant recipients who met the inclusion criteria (20 females and 42 males, mean age of 45.6 ± 12.7 years). The creatinine/cystatin C ratio in the male group was > 1, whereas the creatinine/cystatin C ratio in the female group was < 1. Muscle mass was significantly larger in the male group than the female group. There was a significant positive correlation between the skeletal muscle index and creatinine/cystatin C ratio in the male (r = 0.553; p < 0.001) and female groups (r = 0.675; p < 0.001).

CONCLUSION

The creatinine/cystatin C ratio is appropriate for evaluating muscle mass in kidney transplant recipients.

Pretransplantation Cystatin C, but not Creatinine, Predicts 30-day Cardiovascular Events and Mortality in Liver Transplant Recipients With Normal Serum Creatinine Levels

BACKGROUND

The connection between renal dysfunction and cardiovascular dysfunction has been consistently shown. In patients with liver cirrhosis, renal dysfunction shows a tight correlation with prognosis after liver transplantation (LT); therefore, precise renal assessment is mandatory. Cystatin C, a sensitive biomarker for assessing renal function, has shown superiority in detecting mild renal dysfunction compared to classical biomarker creatinine. In this study, we aimed to compare cystatin C and creatinine in predicting 30-day major cardiovascular events (MACE) and all-cause mortality in LT recipients with normal serum creatinine levels.

PATIENTS AND METHODS

Between May 2010 and October 2015, 1181 LT recipients (mean Model for End-stage Liver Disease score 12.1) with pretransplantation creatinine level ≤1.4 mg/dL were divided into tertiles according to each renal biomarker. The 30-day MACE was a composite of troponin I >0.2 ng/mL, arrhythmia, congestive heart failure, death, and cerebrovascular events.

RESULTS

The highest tertile of cystatin C (≥0.95 mg/L) was associated with a higher risk for a 30-day MACE event (odds ratio: 1.62; 95% confidence interval: 1.07 to 2.48) and higher risk of death (hazard ratio: 1.96; 95% confidence interval: 1.04 to 3.67) than the lowest tertile (<0.74 mg/L) after multivariate adjustments. However, the highest tertile of creatinine level showed neither increasing MACE event rate nor worse survival rate compared with the lowest tertile (both insignificant after multivariate adjustment).

CONCLUSIONS

Pretransplantation cystatin C is superior in risk prediction of MACE and all-cause mortality in LT recipients with normal creatinine, compared to creatinine. It would assist further risk stratification which may not be detected with creatinine.

Prognostic ability of cystatin C and homocysteine plasma levels for long-term outcomes in very old acute myocardial infarction patients

Background and aims

This study sought to evaluate the prognostic powers of combined use of cystatin C (Cys C) and homocysteine (Hcy) at predicting adverse events of patients >80 years old with acute myocardial infarction (AMI).

Patients and methods

The analysis involved 753 patients >80 years old undergoing coronary angiography for chest pain in China from January 2006 to December 2012. Kaplan–Meier method was used for survival and major adverse cardiac events (MACE) rates. Multivariate Cox regression was performed to identify mortality predictors. Receiver operating characteristic curve analysis was performed to predict the cutoff values of Cys C and Hcy for all-cause mortality.

Results

The duration of follow-up was 40–116 months (median, 63 months; interquartile range, 51–74 months). The long-term survival and event-free survival rates of AMI patients were significantly lower than those of unstable angina pectoris patients (P<0.05), and were significantly different according to the tertile concentration of Cys C of AMI patients (P<0.01). Cys C and Hcy were independent risk factors for long-term all-cause mortality (odds ratio [OR] =3.72 [2.27–6.09]; OR =1.59 [1.04–2.61]) and MACE (OR =2.83 [1.82–4.40]; OR =1.09 [1.04–1.21]) of AMI patients. The predictive cutoff value of Cys C was 1.815 mg/L (82.8%, 86.4%) and that of Hcy was 15.06 μmol/L (84.4%, 83.1%) in AMI patients. Combined use of both biomarker’s cutoff values further increased the sensitivity and specificity of all-cause mortality.

Conclusion

Cys C is a strong independent predictor of long-term all-cause death and MACE in very old AMI patients. The combined use of Cys C and Hcy further improves the predictive accuracy.

Newer glomerular filtration rate estimating equations for the full age spectrum based on serum creatinine and cystatin C in predicting mortality in patients with ischemic stroke

BACKGROUND

Renal dysfunction is associated with increased risk of mortality. The novel Full Age Spectrum (FAS) equations estimating the glomerular filtration rate (GFR) based on serum creatinine (FAScrea) and cystatin C (FAScysC) are validated across the entire age spectrum and are superior markers of renal function compared to other equations. Possible association of these equations with mortality in patients with ischemic stroke is not known.

PATIENTS AND METHODS

We included 390 patients (207 men, 183 women) in our observational cohort study who had suffered from an ischemic stroke and followed-up on for 3 years. Serum creatinine and cystatin C were measured at admission; GFR was estimated according to the FAScrea, CKD-EPIcrea, FAScysC and CKD-EPIcysC equations. The values of estimated GFRs were divided into quintiles.

RESULTS

During the follow-up period, 173 (44.4%) patients died. The association of hazard ratios for FAScrea and CKD-EPIcrea with all-cause mortality was J-shaped and only significantly higher when comparing the fifth quintile hazard ratio for mortality with the first quintile (P < 0.001). For FAScysC and CKD-EPIcysC, hazard ratios increased from the first to the fifth quintile linearly. In an adjusted analysis, FAScrea and CKD-EPIcrea were not associated with all-cause mortality and the hazard ratios of the fifth quintile of FAScysC (P = 0.008) and CKD-EPIcysC (P = 0.042) were significantly associated with mortality compared to the first quintile.

CONCLUSIONS

In patients with an ischemic stroke, estimated GFR based on serum cystatin (FAScysC and CKD-EPIcysC) was a better predictor of all-cause and cardiovascular mortality than estimated GFR based on serum creatinine.

Prognostic significance of serum cystatin C in acute ischemic stroke patients according to lipid component levels

BACKGROUND AND AIMS

Serum cystatin C (CysC) is associated with the risk of ischemic stroke and may predict cardiovascular events and death after ischemic stroke onset. However, the association between serum CysC and functional outcome in ischemic stroke patients remains unclear, and whether lipid component level influences the relationship between them has not been studied.

METHODS

A total of 3348 ischemic patients from China Antihypertensive Trial in Acute Ischemic Stroke were included in the study. Serum CysC was used to calculate estimated glomerular filtration rate (eGFR_CysC) at baseline. The primary outcome was poor functional outcome (modified Rankin Scale score ≥3) at one year after ischemic stroke. Secondary outcomes were death, stroke recurrence, vascular events and combination of the aforementioned outcomes.

RESULTS

The association between eGFR_CysC and primary outcome was appreciably modified by low-density lipoprotein cholesterol (LDL-C) (p_interaction = 0.048). Low eGFR_CysC was associated with primary outcome only in ischemic stroke patients with LDL-C ≥4.14 mmol/l rather than all patients. The multivariable adjusted odds ratio (95% confidence interval) of poor functional outcome associated with low eGFR_CysC was 3.94 (1.04-14.98) and a positive linear dose-response relationship between them was observed among patients with LDL-C ≥4.14 mmol/l (p for linearity = 0.021). Subgroup analyses further confirmed these associations. There was no association between eGFR based on serum creatinine and poor functional outcome of stroke.

CONCLUSIONS

Low eGFR_CysC may be an independent predictor for 1-year poor functional outcome in ischemic stroke patients with LDL-C ≥4.14 mmol/l. Further studies are needed to replicate our findings and to clarify the potential mechanisms.

Serum cystatin C is an independent biomarker associated with the renal resistive index in patients with chronic kidney disease

Cystatin C is a cysteine protease inhibitor that is produced by nearly all human cells. The serum level of cystatin C is a stronger predictor of the renal outcome and the risk of cardiovascular events than the creatinine level. The resistive index (RI) on renal Doppler ultrasonography is a good indicator of vascular resistance as well as the renal outcomes in patients with chronic kidney disease (CKD). However, it is unclear whether serum cystatin C is associated with signs of vascular dysfunction, such as the renal RI. We measured the serum cystatin C levels in 101 CKD patients and investigated the relationships between cystatin C and markers of vascular dysfunction, including the renal RI, ankle-brachial pulse wave velocity (baPWV), intima-media thickness (IMT), and cardiac function. The renal RI was significantly correlated with the serum cystatin C level (p < 0.0001, r = 0.6920). The serum cystatin C level was found to be a significant determinant of the renal RI (p < 0.0001), but not the baPWV, in a multivariate regression analysis. The multivariate odds ratio of the serum cystatin C level for a renal RI of more than 0.66 was statistically significant (2.92, p = 0.0106). The area under the receiver-operating characteristic curve comparing the sensitivity and specificity of cystatin C for predicting an RI of more than 0.66 was 0.882 (cutoff value: 2.04 mg/L). In conclusion, the serum cystatin C level is an independent biomarker associated with the renal RI in patients with CKD.

Impact of diabetes-related gene polymorphisms on the clinical characteristics of type 2 diabetes Chinese Han population

We investigated the correlation between type 2 diabetes (T2D)-related genes and the clinical characteristics of T2D in the Chinese Han population. Our study included 319 patients and 387 controls. Age, gender, clinical features, medications intake and biochemical blood profiles were analyzed. Genotyping was performed on a total of 18 single nucleotide polymorphisms previously reported to be associated with T2D. Our analyses revealed that the CT genotype of ARHGAP22 rs4838605 is associated with T2D risk. Upon analyzing the subjects’ clinical characteristics, we found that for rs2811893, the TT genotype correlated with high creatinine levels, while the AA genotype of rs17045754 and the TT genotype of rs4838605 correlated with elevated triglyceride levels. In addition, the AA genotype of rs17376456 and the TT genotype of rs6214 (p = 0.006) correlated with elevated hemoglobin A1c levels. Lastly, those carrying the TT genotype of rs7772697 and the CA genotype of rs3918227 exhibited higher mean body mass index and Cystatin C than controls. Our results showing that the ARHGAP22 gene is associated with an increased risk of T2D, and that seven SNPs in MYSM1, PLXDC2, ARHGAP22 and HS6ST3 promote T2D progression and could help predict the clinical course of T2D in patients at risk.

Detection of a Peptide Biomarker by Engineered Yeast Receptors

Directed evolution of membrane receptors is challenging as the evolved receptor must not only accommodate a non-native ligand, but also maintain the ability to transduce the detection of the new ligand to any associated intracellular components. The G-protein coupled receptor (GPCR) superfamily is the largest group of membrane receptors. As members of the GPCR family detect a wide range of ligands, GPCRs are an incredibly useful starting point for directed evolution of user-defined analytical tools and diagnostics. The aim of this study was to determine if directed evolution of the yeast Ste2p GPCR, which natively detects the α-factor peptide, could yield a GPCR that detects Cystatin C, a human peptide biomarker. We demonstrate a generalizable approach for evolving Ste2p to detect peptide sequences. Because the target peptide differs significantly from α-factor, a single evolutionary step was infeasible. We turned to a substrate walking approach and evolved receptors for a series of chimeric intermediates with increasing similarity to the biomarker. We validate our previous model as a tool for designing optimal chimeric peptide steps. Finally, we demonstrate the clinical utility of yeast-based biosensors by showing specific activation by a C-terminally amidated Cystatin C peptide in commercially sourced human urine. To our knowledge, this is the first directed evolution of a peptide GPCR.

Inverse Relationship between Adherence to the Mediterranean Diet and Serum Cystatin C Levels

OBJECTIVE

The aim of the present study was to examine serum cystatin C levels in association with the Mediterranean diet in a healthy Greek population.

METHODS

Cystatin C together with basic clinical chemistry tests was measured in a total of 490 adults (46±16 years, 40% of males), who underwent an annual health check. Demographic, anthropometric and lifestyle characteristics were recorded, while adherence to the Mediterranean diet was evaluated through the MedDietScore (0-55).

RESULTS

The mean level of serum cystatin C was 0.84 mg/L, while men had increased serum cystatin C levels compared to women (0.86 mg/L vs. 0.83 mg/L, respectively, 0.017). After adjusting for age, gender, body mass index, smoking status, hypertension, diabetes, hypercholesterolemia, estimated glomerular filtration rate (eGFR), albumin and ferritin levels, each unit increase in MedDietScore led to 0.002 mg/dL drop off in cystatin C serum levels.

CONCLUSIONS

We have demonstrated an inverse relationship between the MedDietScore and serum cystatin C levels. Our finding that increases in MedDietScore are associated with decreases in serum cystatin C levels could imply that adherence to the Mediterranean diet may reduce the cardiovascular risk, as assessed by cystatin C, a prognostic marker of the cardiometabolic risk. This notion could have a great impact on public health.

Association between serum cystatin C and bone mineral density in Korean adults

Background

Serum cystatin C has been known as a novel marker of preclinical renal dysfunction, and higher cystatin C levels are associated with increased risks of hip and nonvertebral fractures. However, there are few reports on the association between serum cystatin C and bone mineral density (BMD), especially in the Asian population. We evaluated the association between cystatin C levels and BMD of the spine and hip in Korean adults.

Methods

A cross-sectional study was performed in 865 Korean adults (325 men and 540 women) who participated in a comprehensive medical examination program and underwent bone densitometry. Renal function was assessed by the estimated glomerular filtration rate (eGFR), which was calculated using an equation based on creatinine (eGFRcre) and cystatin C (eGFRcys).

Results

The serum cystatin C level was negatively correlated with different types of BMD, including the lowest lumbar, total lumbar, femoral neck, and total femur BMD, in women, but not in men. Higher cystatin C levels were associated with a higher prevalence of osteoporosis in women (odds ratio [OR], 3.68; 95% confidence interval [CI], 1.69-8.03; P=0.001), but not in men (OR, 0.85; 95% CI, 0.30-2.38; P=0.761). However, this association was attenuated in the multivariable model adjusted for age, body mass index, serum 25-hydroxyvitamin D₃, and creatinine (OR, 1.01; 95% CI, 0.38-2.71) in women. In addition, the eGFRcys showed a stronger positive correlation with BMD than the eGFRcre.

Conclusion

Our findings suggest that serum cystatin C levels might help identify women with osteoporosis who are susceptible to fractures.

Left atrial volume index in patients with heart failure and severely impaired left ventricular systolic function: the role of established echocardiographic parameters, circulating cystatin C and galectin-3

Backround: Left atrial (LA) enlargement plays an important role in the development of heart failure (HF) and is a robust prognostic factor. Fibrotic processes have also been advocated to evoke HF through finite signalling proteins.

METHODS

We examined the association of two such proteins, cystatin C (CysC) and galectin-3 (Gal-3), and other clinical, echocardiographic and biochemical parameters with LA volume index (LAVi) in patients with HF with severely impaired left ventricular ejection fraction (LVEF). Severe renal, liver, autoimmune disease and cancer were exclusion criteria.

RESULTS

A total of 40 patients with HF (31 men, age 66.6 ± 1.7) with LVEF = 25.4 ± 0.9% were divided into two groups according to the mean LAVi (51.03 ± 2.9 ml/m2) calculated by two-dimensional transthoracic echocardiography. Greater LAVi was positively associated with LV end-diastolic volume ( p = 0.017), LV end-systolic volume ( p = 0.025), mitral regurgitant volume (MRV) ( p = 0.001), right ventricular systolic pressure (RVSP) ( p < 0.001), restrictive diastolic filling pattern ( p = 0.003) and atrial fibrillation ( p = 0.005). Plasma CysC was positively correlated with LAVi ( R2 = 0.135, p = 0.019) and log-transformed plasma Gal-3 ( R2 = 0.109, p = 0.042) by simple linear regression analysis. Stepwise multiple linear regression analysis showed that only MRV ( t = 2.236, p = 0.032), CysC ( t = 2.467, p = 0.019) and RVSP ( t = 2.155, p = 0.038) were significant predictors of LAVi.

CONCLUSIONS

Apart from known determinants of LAVi, circulating CysC and Gal-3 were associated with greater LA dilatation in patients with HF with reduced LVEF. Interestingly, the correlation between these two fibrotic proteins was positive.

Prevention of Chemotherapy-Induced Nephrotoxicity in Children with Cancer

Children with cancer treated with cytotoxic drugs are frequently at risk of developing renal dysfunction. The cytotoxic drugs that are widely used for cancer treatment in children are cisplatin (CPL), ifosfamide (IFO), carboplatin, and methotrexate (MTX). Mechanisms of anticancer drug-induced renal disorders are different and include acute kidney injury (AKI), tubulointerstitial disease, vascular damage, hemolytic uremic syndrome (HUS), and intrarenal obstruction. CPL nephrotoxicity is dose-related and is often demonstrated with hypomagnesemia, hypokalemia, and impaired renal function with rising serum creatinine and blood urea nitrogen levels. CPL, mitomycin C, and gemcitabine treatment cause vascular injury and HUS. High-dose IFO, streptozocin, and azacitidine cause renal tubular dysfunction manifested by Fanconi syndrome, rickets, and osteomalacia. AKI is a common adverse effect of MTX, interferon-alpha, and nitrosourea compound treatment. These strategies to reduce the cytotoxic drug-induced nephrotoxicity should include adequate hydration, forced diuresis, and urinary alkalization. Amifostine, sodium thiosulfate, and diethyldithiocarbamate provide protection against CPL-induced renal toxicity.

Relationship between subtle urinary albumin excretion and risk of incident hypertension: modification by glomerular filtration rate

It has been reported that an increase in urinary albumin excretion (UAE) within the normal range could be a risk factor for incident hypertension. However, it remains unclear how the subtle increases in UAE and renal function interact in the development of hypertension. We examined the modification of UAE as a risk factor for incident hypertension by glomerular filtration rate (GFR) in the Japanese population. We prospectively followed 1281 normotensive individuals from Watari town (34.3% men; mean age, 58.0±12.3 years old) whose UAE was <30 mg g⁻¹· Cr. Hypertension was diagnosed as a systolic blood pressure (BP)⩾140 mm Hg and/or a diastolic BP⩾90 mm Hg, or antihypertensive medication use. The relationship between sex-specific quartiles of UAE and incident hypertension was examined with Cox proportional hazard analysis. During a mean follow-up of 3.7 years, 315 individuals developed hypertension. Multivariate Cox proportional hazard analysis revealed that a subtle increase in UAE was a risk factor for incident hypertension, but there was a significant interaction between UAE and estimated GFR (eGFR) (P=0.018). The risk of incident hypertension dose dependently increased in the highest eGFR quartile (⩾90 ml min⁻¹ per 1.73 m²). Decline in renal function alone increased the risk of incident hypertension but the increased risk with a subtle increase in UAE became smaller and less clear in the lower eGFR quartiles. The present data suggest that UAE as a risk factor for incident hypertension is largely dependent on eGFR levels.

Association of serum cystatin C levels with mortality in patients with acute type A aortic dissection

Increased serum cystatin C levels are related to the prognosis of cardiovascular diseases. This study aims to investigate the effect of admission serum cystatin C levels on short- and long-term mortality in patients with acute type A aortic dissection (ATAAD). From 2010 to 2014, 136 consecutive patients with ATAAD were enrolled and followed up. Clinical data and laboratory assays including were measured. During a median follow-up of 198.7 days, the short-term mortality (30-days) was 20.6%, whereas the long-term death rate was 10.2%. We identified that the expression of cystatin C and high-sensitivity C-reactive protein (hs-CRP) in the dying patients was higher than in the surviving patients (P < 0.01). Hs-CRP (HR = 1.41, 95% CI: 1.03–2.59, P = 0.037) was an independent risk factor of short-term death determined by univariate and multivariate Cox analyses. No impact of cystatin C was observed on the short-term mortality. For long-term mortality, cystatin C (HR = 1.49, 95% CI: 1.10–7.36, P = 0.013) was identified as an independent predictor at above the cut-off value ≥ 1.10 mg/L. ROC analysis showed the AUC values of cystatin C and hs-CRP were 0.772 (95% CI, 0.692–0.839) and 0.640 (95% CI, 0.574–0.739), respectively, in the prediction of long-term death. The combined AUC value of cystatin C and hs-CRP was 0.883 (95% CI, 0.826–0.935; P < 0.01). Taken together, high cystatin C levels (≥ 1.10 mg/L) on admission are independently associated with the long-term mortality in patients with ATAAD.

Evaluation of the renal function using serum Cystatin C following open and endovascular aortic aneurysm repair

Objectives

Controversies regarding renal function impairment after open and endovascular aortic aneurysm repair still exist. The purpose of this study was to evaluate the renal function following open repair and endovascular aneurysm repair using Cystatin C.

Methods

This prospective, observational case–control study was conducted in tertiary referral centre over 3 years, starting from 2012. In total, 60 patients operated due to infrarenal AAA either by means of open repair (30 patients) or endovascular aneurysm repair (30 patients) were included in the study. Biochemical markers of renal function (sCr, urea, potassium) were recorded pre-operatively and at these specific time points, immediately after the operation and at discharge, home (third postoperative day, endovascular aneurysm repair group) or from intensive care unit (third postoperative day, open repair group). Multivariate and propensity score adjustments were used to control for the baseline differences between the groups.

Results

Creatinine levels in serum remained unchanged during the hospital stay in both groups without significant differences at any time point. Cystatin C levels in endovascular aneurysm repair patients significantly increased postoperatively and restored to values comparable to baseline at the discharge (0.865 ± 0.319 vs. *0.962 ± 0.353 vs. 0.921 ± 0.322, * p < 0.001). Cystatin C levels in patients treated with the open surgery was decreasing over time but not statistically significant comparing to Cystatin C values at the admission. However, decrease in Cystatin C serum levels in patients treated with conventional surgery resulted in statistically significant lower values compared to endovascular aneurysm repair patients both postoperatively and at the time of discharge (0.760 ± 0.225 vs. 0.962 ± 0.353, p < 0.05; 0.750 vs. 0.156, p < 0.05). Both multivariate linear regression models and propensity score adjustment confirm that, even after correction for previously observed intergroup differences, type of surgery, i.e. endovascular aneurysm repair is independently associated with the higher levels of Cystatin C both postoperatively and at the discharge.

Conclusions

Dynamics of Cystatin C levels have been proven as a more vulnerable marker of renal dysfunction. Endovascular aneurysm repair is associated with higher levels of kidney injury markers.

The diagnostic value of serum creatinine and cystatin c in evaluating glomerular filtration rate in patients with chronic kidney disease: a systematic literature review and meta-analysis

BACKGROUND

Serum biomarkers, such as serum creatinine (SCr) and serum cystatin C (SCysC), have been widely used to evaluate renal function in patients who have chronic kidney disease (CKD).

OBJECTIVE

This article aims to assess the value of determining SCr and SCysC levels in patients that have long-term kidney disease. Approaches: MEDLINE, EmBase, the Cochrane Library and other databases were searched using both MeSH terms and text words to collect research that assessed the diagnostic value of using SCr and SCysC to evaluate Glomerular Filtration Rate (GFR) in patients with CKD. Data were converted into fourfold tables. Summary Receiver Operating Characteristic Curves and meta-analyses were accomplished via Meta-Disc version 1.4.

RESULTS

In total, 21 relevant articles involving 3112 study subjects were included in our review. Results showed that the collective sensitivity for SCr and SCysC was 0.77 (95% CI: 0.69-0.84) and 0.87 (95% CI: 0.82-0.91), respectively. The pooled specificity for SCr and SCysC was 0.91 (95% CI: 0.86-0.94) and 0.87 (95% CI: 0.82-0.91), respectively. Subgroup analyses demonstrated that when GFR cut-off values are set to 60 (ml/min/1.73 m²), the pooled sensitivity is 0.94 (95% CI: 0.90-0.96) for SCysC and 0.75 (95% CI: 0.68-0.82) for SCr.

CONCLUSIONS

The diagnostical accuracy for impaired kidney function favors SCysC. Confidence intervals for the pooled sensitivity and specificity for SCr and SCysC overlap. However, SCysC is more sensitive for estimating GFR than SCr when GFR cut-off values are set to 60 (ml/min/1.73 m²).