A sol particle homogeneous immunoassay for measuring serum cystatin C

Association between continuous glucose monitoring-derived glycemic control indices and urinary biomarkers of diabetic kidney disease: Hyogo Diabetes Hypoglycemia Cognition Complications study

AIMS

Glomerular damage and proximal tubular damage play an important role in the pathogenesis of diabetic kidney disease. This study aimed to investigate the relationship between the urinary markers of proximal tubular injury, including urinary liver-type fatty acid-binding protein-to-creatinine ratio (uL-FABP/Cr) and urinary N-acetyl-β-D-glucosaminidase-to-creatinine ratio (uNAG/Cr), and glycemic control status.

METHODS

This cross-sectional study included 245 and 39 patients with type 2 diabetes mellitus (T2DM) and non-T2DM (NDM), respectively. The participants of this study were fitted with retrospective CGM, and glycemic control indices, such as time in range (TIR) and glycemia risk index (GRI), were calculated.

RESULTS

The results were presented as medians (interquartile ranges). The uL-FABP/Cr was significantly higher in the microalbuminuria than in the normo-albuminuria group [4.2 (2.7-7.1) and 2.2 (1.4-3.4) μg/gCr, respectively, P < 0.001], while the uNAG/Cr in the normo-albuminuria group [6.3 (4.5-10.1) U/gCr] was significantly higher than that in the NDM group [5.3 (3.8-6.3) U/gCr, P = 0.048] but significantly lower than that in the microalbuminuria group [9.2 (6.4-11.1) U/gCr, P = 0.004]. The multivariate logistic regression analysis indicated that CGM-derived TIR was significantly associated with the urinary albumin-to-creatinine ratio [uAlb/Cr, odds ratio (OR) 0.985, 95% confidence interval (CI) 0.971-0.998, P = 0.029] and uNAG/Cr (OR 0.973, 95% CI 0.957-0.989, P = 0.001) independent of renal function. GRI was similarly associated with uAlb/Cr and uNAG/Cr.

CONCLUSION

The findings of this study indicated that uNAG/Cr was elevated before albuminuria development and was associated with CGM-derived TIR and GRI.

Effect of denosumab on renal function in women with osteoporosis evaluated using cystatin C

Objectives

To investigate renal function during denosumab therapy using the estimated glomerular filtration rate based on cystatin C (eGFRcys) which is more accurate than creatinine (eGFRcr) for renal function.

Methods

Bone mineral densities (BMDs) of lumbar spine and hip regions, eGFRcys, eGFRcr, creatinine clearance (Ccr), and serum total homocysteine (S-Hcy) were measured during 2-year denosumab therapy in 53 women with osteoporosis naïve to anti-osteoporosis drugs (new group) and 64 women who were switched from long-term bisphosphonate treatment to denosumab therapy (switch group).

Results

There were no significant differences in age, eGFRcr, Ccr, eGFRcys, and S-Hcy levels at baseline between the groups. BMDs in the lumbar spine, femoral neck, and total hip increased significantly after 2-year denosumab therapy in both groups. eGFRcr decreased in the switch group, and Ccr decreased in both groups; however, eGFRcys and S-Hcy levels did not change significantly in either group. To investigate the causal factors associated with the decrease in eGFRcr and Ccr, multiple regression analysis was performed in all patients. Denosumab initiation within 3 months after fracture and eGFRcr or Ccr at baseline were independent factors for the decrease in eGFRcr or Ccr during the 2-year denosumab therapy. Decline in creatinine-based renal function could be reflected by increased muscle mass during the ongoing recovery from fracture.

Conclusions

Renal function was preserved in all patients, including those in the switch group during denosumab therapy. Creatinine-based renal function should be cautiously interpreted during denosumab therapy in patients with recent fractures.

Synergistic association of the copper/zinc ratio under inflammatory conditions with diabetic kidney disease in patients with type 2 diabetes: The Asahi Diabetes Complications Study

AIMS/INTRODUCTION

We aimed to study the relationships among the copper (Cu)/zinc (Zn) ratio, inflammatory biomarkers, and the prevalence of diabetic kidney disease (DKD) in patients with type 2 diabetes.

MATERIALS AND METHODS

A cross-sectional study was performed on 651 patients with type 2 diabetes. DKD was defined as a urinary albumin-to-creatinine ratio of ≥30 mg/g creatinine and/or an estimated glomerular filtration rate using cystatin C of < 60 mL/min/1.73 m2 . Areas under the curves (AUCs), cutoff values, and thresholds for detecting DKD were determined for the Cu/Zn ratio, soluble tumor necrosis factor-α receptor 1 (sTNFαR1), and high-sensitivity C-reactive protein (hsCRP). Patients were categorized by each cutoff value of sTNFαR1 and the Cu/Zn ratio. Odds ratios (ORs) and biological interactions for the prevalence of DKD were determined.

RESULTS

DKD was identified in 220 patients. AUC/optimal cutoff values were 0.777/1300 pg/mL for sTNFαR1, 0.603/1.1648 for the Cu/Zn ratio, and 0.582/305 ng/mL for hsCRP. The ORs for DKD were higher, but not significantly, in the sTNFαR1 < 1300 and Cu/Zn ≥ 1.1648 group, significantly higher in the sTNFαR1 ≥ 1300 and Cu/Zn < 1.1648 group (P < 0.0001), and further synergistically elevated in the sTNFαR1 ≥ 1300 and Cu/Zn ≥ 1.1648 group (P < 0.0001) compared with the sTNFαR1 < 1300 and Cu/Zn < 1.1648 group after multivariable adjustment. Levels of sTNFαR1 were significantly higher in the sTNFαR1 ≥ 1300 and Cu/Zn ≥ 1.1648 group than in the sTNFαR1 ≥ 1300 and Cu/Zn < 1.1648 group (P = 0.0006).

CONCLUSIONS

Under an inflammatory initiation signal of elevated serum sTNFαR1 levels, an increase in the Cu/Zn ratio may further exacerbate inflammation and is synergistically associated with a high prevalence of DKD in patients with type 2 diabetes.

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.

Changeover Trial of Febuxostat and Topiroxostat for Hyperuricemia with Cardiovascular Disease: Sub-Analysis for Chronic Kidney Disease (TROFEO CKD Trial)

Background: The TROFEO trial demonstrated that febuxostat causes greater and more rapid reduction of serum uric acid (s-UA) than topiroxostat. We compared these drugs in patients with chronic kidney disease (CKD) by sub-analysis of the TROFEO trial.

Methods: This sub-analysis targeted patients with an estimated glomerular filtration rate (eGFR) ≤60 mL/min/1.73 m². The primary endpoint was the s-UA level. Secondary endpoints included creatinine, eGFR, urinary albumin, cystatin-C, oxidized low-density lipoprotein (Ox-LDL), eicosapentaenoic acid/arachidonic acid ratio, lipid biomarkers, high-sensitivity C-reactive protein, and B-type natriuretic peptide (BNP).

Results: There was no significant difference of s-UA between the two groups either before or after treatment. However, s-UA did not exceed 6.0 mg/dL in febuxostat group during the study period, but it exceeded this level in seven patients from topiroxostat group, with the number being significantly higher in topiroxostat group. Serum creatinine (s-Cr) and eGFR were significantly better after 6 months of febuxostat treatment compared with topiroxostat Cystatin-C was significantly lower after 6 months of febuxostat treatment compared with topiroxostat. The Ox-LDL was significantly lower after 3 and 6 months of febuxostat treatment compared with topiroxostat.

Conclusion: Febuxostat had stronger renoprotective and antioxidant effects than topiroxostat in patients with hyperuricemia and CKD.

Population pharmacokinetics of teicoplanin in hospitalized elderly patients using cystatin C as an indicator of renal function

OBJECTIVE

Serum cystatin C (CysC) has recently been proposed as an alternative marker to serum creatinine (SCR) for estimating renal clearance. In the present study, we performed a population pharmacokinetic analysis of teicoplanin (TEIC), which is mainly eliminated through the kidneys, using CysC as a predictor for renal clearance.

METHODS

Thirty-six patients with MRSA infections who were administrated to the National Hospital Organization Beppu Medical Center between January 2012 and December 2013 were enrolled and gave 123 sets of blood TEIC concentration data. Renal clearance was estimated by the Hoek equation using CysC, by creatinine clearance predicted by the Cockcroft-Gault equation using SCR, or directly by CysC. One compartment open model with inter-individual variabilities for renal clearance and the volume of distribution as well as an additional residual error model was used to estimate population pharmacokinetic parameters for TEIC.

RESULTS

The model with the best predictability was that with CysC as a predictor for renal clearance; it showed better significance than the models using estimated the glomerular filtration rate by the Hoek equation or CLcr. The final model was as follows: CL (L/hr) = 0.510 × (CysC/1.4)^-0.68 × Total body weight/60^0.81, omega (CL) = 19.8% CV, VC (L) = 78.1, omega (V) = 42.7% CV.

CONCLUSION

The present results show the usefulness of CysC to more accurately predict the pharmacokinetics of drugs mainly eliminated through the kidneys, such as TEIC. However, since the sample size in this study was relatively small, further investigations on renal clearance predictability using CysC are needed.

Cardio-Ankle Vascular Index and Indices of Diabetic Polyneuropathy in Patients with Type 2 Diabetes

The cardio-ankle vascular index (CAVI) is used to test vascular function and is an arterial stiffness marker and potential predictor of cardiovascular events. This study aimed to analyze the relation between objective indices of diabetic polyneuropathy (DPN) and the CAVI. One hundred sixty-six patients with type 2 diabetes mellitus were included in this study. We used nerve conduction studies (NCSs) and the coefficient of variation of the R-R interval to evaluate DPN. We estimated arteriosclerosis by the CAVI. Simple and multiple linear regression analyses were performed between neuropathy indices and the CAVI. In univariate analysis, the CAVI showed significant associations with sural sensory nerve conduction velocity and median F-wave conduction velocity. Multiple linear regression analysis for the CAVI showed that sural nerve conduction velocity and median F-wave conduction velocity were significant explanatory variables second only to age. In multiple linear regression analysis for sural nerve conduction velocity among neuropathy indices, the CAVI remained the most significant explanatory variable. In multiple linear regression analysis for median nerve F-wave conduction velocity among neuropathy indices, the CAVI remained the second most significant explanatory variable following HbA1c. These results suggest a close relationship between macroangiopathy and DPN.

A novel sol particle immunoassay for fecal calprotectin in inflammatory bowel disease patients

BACKGROUND

We introduce a new assay method to measure the concentration of fecal calprotectin that can be applied in exclusive analyzers. The assay method uses gold colloidal reagents. In addition, we report performance evaluation results for the new method and the results of comparisons with enzyme-linked immunosorbent assay (ELISA) methods.

METHODS

We evaluated the new method by linearity tests and within-run tests. In addition, we collected specimens from patients with a definitive diagnosis of inflammatory bowel disease (n=566) and examined them using the new method. The results were compared with those from 2 commercially available ELISA kits.

RESULTS

In the linearity tests, the correlation coefficients between the measured values and the theoretical values were 0.9980-0.9990. In the within-run tests, the CVs were 3.4-4.3%. The correlation coefficients for our method and the 2 ELISA kits showed high correlations of 0.945 and 0.942.

CONCLUSIONS

Our assay is capable of measuring calprotectin concentrations in feces, and has a similar performance to commercially available ELISA methods. Our method is an automated assay system, which is an easier, cheaper, and quicker measurement method than conventional ELISA kits. Therefore, our assay is suitable for daily clinical use.

Utility of creatinine/cystatin C ratio as a predictive marker for adverse effects of chemotherapy in lung cancer: A retrospective study

Objective

To determine whether the creatinine/cystatin C (Cr/CysC) ratio, which is influenced by muscle mass, can be used as a predictive marker of the adverse effects of chemotherapy.

Methods

This single-centre, retrospective, observational study assessed patients with lung cancer. Serum Cr and CysC levels were measured once within 1 month prior the commencement of chemotherapy.

Results

A total of 25 patients with lung cancer were enrolled in the study: 22 received first-line therapy; three received second-line therapy. A significant difference was noted regarding the Cr/CysC ratios between patients with nonsmall-cell lung cancer (NSCLC) and those with small-cell lung cancer (0.78 versus 0.92, respectively). A significant difference was also noted in the Cr/CysC ratios of patients with NSCLC with toxicity grades <3 and ≥3 (0.84 versus 0.70, respectively). Similar findings were observed in patients with NSCLC who received platinum-based combination therapy (toxicity grade < 3, 0.85; toxicity grade ≥3, 0.69).

Conclusion

The Cr/CysC ratio could serve as a useful predictive marker for chemotherapy-related adverse effects in patients with NSCLC.

Continuous intravenous infusion of nicorandil for 4 hours before and 24 hours after percutaneous coronary intervention protects against contrast-induced nephropathy in patients with poor renal function

BACKGROUND

We conducted a prospective randomized trial to assess the protective effect of continuous intravenous infusion of nicorandil against contrast-induced nephropathy (CIN) in patients with poor renal function.

METHODS AND RESULTS

We randomly assigned 213 patients who would subsequently undergo elective percutaneous coronary intervention (PCI) and who had a high serum cystatin C level to a saline group (n=107) or a nicorandil group (n=106, nicorandil infused in addition to saline for 4h before and 24h after PCI). There were no significant differences in baseline characteristics between the two groups. However, the average percent increases in serum creatinine and cystatin C following PCI were significantly smaller in the nicorandil group than the saline group. Likewise, the average percent decline in the estimated glomerular filtration rate was smaller in the nicorandil group. Correspondingly, the incidence of CIN was dramatically lower in the nicorandil group than the saline group (2.0% vs. 10.7%, p<0.02). Univariate regression analysis revealed nicorandil treatment to be the only significant predictor of CIN development (odds ratio: 0.173, 95% confidence interval: 0.037-0.812, p=0.026).

CONCLUSIONS

Nicorandil strongly prevents CIN in patients with poor renal function undergoing PCI.

Association between serum long-chain n-3 and n-6 polyunsaturated fatty acid profiles and glomerular filtration rate assessed by serum creatinine and cystatin C levels in Japanese community-dwellers

Background

Plasma concentration of n-3 polyunsaturated fatty acids (PUFAs) has been reported to be associated with renal function in Western populations. However, few studies have investigated the association between serum long-chain n-3 and n-6 PUFA profiles and renal function in a Japanese population with high marine-derived long-chain n-3 PUFA intake.

Methods

A cross-sectional study was performed in 549 Japanese rural community-dwellers aged 40 to 64 years. In adjusted analysis of covariance, we assessed the relationship between estimated glomerular filtration rate (eGFR) and tertiles of serum long-chain n-3 and n-6 PUFA profiles ([eicosapentaenoic acid {EPA} + docosahexaenoic acid {DHA}]:arachidonic acid [AA]). GFR was estimated by Japanese specific equations using serum creatinine and cystatin C (eGFR_cre and eGFR_cys). Using multivariate-adjusted linear regression models, we also assessed the relationships between eGFRs and several n-3 and n-6 PUFAs, which have been suggested to be associated with renal function.

Results

In all participants, higher dietary fish intake as assessed by a semi-quantitative questionnaire was associated with higher serum value of (EPA+DHA):AA. Participants in the higher (EPA+DHA):AA tertiles had non-significantly higher eGFR_cre and significantly higher eGFR_cys (P = 0.016). In addition, eGFR_cys in T₂+T₃ of (EPA+DHA):AA was significantly higher than that in T₁ (adjusted mean eGFR_cys, T₁: 87 ml/min/1.73 m², T₂+T₃: 91 ml/min/1.73 m²; P < 0.01). Among the PUFAs, only (EPA+DHA) was significantly associated with eGFR_cys.

Conclusions

Serum (EPA+DHA):AA, which reflects an individual’s fish intake, might be associated with eGFR_cys in Japanese community-dwellers.

Development of a Sol Particle Homogeneous Immunoassay for Measuring Full-Length Selenoprotein P in Human Serum

BACKGROUND

Selenoprotein P (SeP), a selenium-rich extracellular glycoprotein, is the primary selenoprotein in the plasma. SeP plays an important role in the maintenance of selenium levels in the peripheral tissues. We developed a new sol particle homogeneous immunoassay (SPIA) for measuring full-length SeP (FL-SeP) levels in the human serum.

METHODS

We used colloidal gold particles coated with two types of anti-SeP monoclonal antibodies, one recognizing the N-terminal side domain of SeP and the other recognizing the C-terminal side domain.

RESULTS

The assay range was 0.2-9 mg/l, and the linearity was excellent. The within-day and between-day coefficients of variation ranged from 0.73% to 2.24% and 0.45% to 1.11%, respectively. Serum samples (n = 200) were examined using the newly developed assay system (employing a Model 7070 Hitachi automatic clinical analyzer) and the conventional enzyme-linked immunosorbent assay. These two methods were compared using the Passing-Bablok regression analysis; the resulting regression equation and correlation coefficient were y = 0.940x + 0.165 and r = 0.954, respectively.

CONCLUSIONS

Our new SPIA assay is a fully automated homogeneous immunoassay that can be used in conjunction with various commercial analyzers. The assay was sensitive, precise, and suitable for clinical measurement of the FL-SeP in the human serum.

Incidence and predictors of sarcopenia onset in community-dwelling elderly Japanese women: 4-year follow-up study

OBJECTIVES

Several studies have explored the prevalence and risk factors of sarcopenia, but they have been based on cross-sectional data. The objective of this study was to determine the incidence and predictors of the onset of sarcopenia over 4 years in community-dwelling elderly women.

DESIGN

Four-year longitudinal follow-up study.

SETTING

Urban community in Tokyo, Japan.

PARTICIPANTS

A total of 538 nonsarcopenic women older than 75 years.

MEASUREMENTS

Body composition was determined by bioelectrical impedance analysis. Functional fitness measurements, including grip strength, usual walking speed, timed up and go (TUG), and interview surveys were conducted at baseline and 4-year follow-up. Blood samples were obtained to analyze serum albumin and hemoglobin A1c, and kidney function was analyzed using serum creatinine and cystatin C. Sarcopenia was defined based on the criteria suggested by the European Working Group on Sarcopenia in Older People, and the development of all stages, that is, presarcopenia, sarcopenia, and severe sarcopenia as well as the components of sarcopenia skeletal muscle index (SMI), grip strength, and walking speed, were analyzed.

RESULTS

The incidence of total sarcopenia was 39.6% (presarcopenia 23.8%, sarcopenia 11.2%, severe sarcopenia 4.6%). Older age was significantly predictive of the development of presarcopenia and severe sarcopenia. Body mass index (BMI) lower than 21.0 kg/m(2) was significantly predictive of the development of all stages of sarcopenia, as well as declines in SMI, grip strength, and walking speed. Slow TUG was a predictor of the development of presarcopenia and severe sarcopenia. Increased calf circumference showed protective effects from the development of all stages of sarcopenia. Greater albumin levels also showed lower risk of declines in SMI, walking speed, and development of presarcopenia. Cystatin C was positively associated with the development of severe sarcopenia (odds ratio 1.83, 95% confidence interval 1.08-3.12). Heart disease and hyperlipidemia history were associated with presarcopenia and sarcopenia, respectively.

CONCLUSION

Age, BMI, calf circumference, and TUG were consistent predictors of the various stages and components of sarcopenia. The data also suggest that cystatin C was associated with higher odds of incident severe sarcopenia, and further study into kidney function and onset of sarcopenia in large populations is needed.

Usefulness of a novel and rapid assay system for fecal calprotectin in pediatric patients with inflammatory bowel diseases

BACKGROUND AND AIM

Fecal calprotectin (FC) has become a reliable biomarker for intestinal inflammation in inflammatory bowel diseases (IBDs). However, a simple and rapid assay to replace conventional ELISA is necessary for wider use in clinical practice. In this study, we investigated the usefulness of a novel method for measuring FC using a colloidal gold aggregation (CGA) assay for assessing mucosal inflammation in pediatric IBDs.

METHODS

FC levels were determined by ELISA and CGA assay in 309 fecal samples (ulcerative colitis [UC]: 131; Crohn's disease [CD]: 121; healthy controls: 57). For endoscopic evaluation, the modified Matts' grading system for UC and the simple endoscopic score for CD were used.

RESULTS

A strong correlation was found between the FC values determined by the two methods (r = 0.98, P < 0.01). FC levels, determined by CGA assay, strongly correlated with the endoscopic score for UC (r = 0.70, P < 0.01) and CD (r = 0.58, P < 0.01). In the UC patients with endoscopic remission, the FC levels determined by CGA assay (median: 31.5 μg/g, n = 14) were as low as in healthy controls. For patients in clinical remission but showing an active status endoscopically, FC was more likely to be abnormal than commonly used laboratory markers.

CONCLUSIONS

Our simple and rapid assay system has excellent performance for assessing mucosal inflammation of IBDs and can be replaced for ELISA. Practical application of this assay system enables us to use FC measurement more widely in clinical practice.

Generation of a new cystatin C-based estimating equation for glomerular filtration rate by use of 7 assays standardized to the international calibrator

BACKGROUND

Many different cystatin C-based equations exist for estimating glomerular filtration rate. Major reasons for this are the previous lack of an international cystatin C calibrator and the nonequivalence of results from different cystatin C assays.

METHODS

Use of the recently introduced certified reference material, ERM-DA471/IFCC, and further work to achieve high agreement and equivalence of 7 commercially available cystatin C assays allowed a substantial decrease of the CV of the assays, as defined by their performance in an external quality assessment for clinical laboratory investigations. By use of 2 of these assays and a population of 4690 subjects, with large subpopulations of children and Asian and Caucasian adults, with their GFR determined by either renal or plasma inulin clearance or plasma iohexol clearance, we attempted to produce a virtually assay-independent simple cystatin C-based equation for estimation of GFR.

RESULTS

We developed a simple cystatin C-based equation for estimation of GFR comprising only 2 variables, cystatin C concentration and age. No terms for race and sex are required for optimal diagnostic performance. The equation, [Formula: see text] is also biologically oriented, with 1 term for the theoretical renal clearance of small molecules and 1 constant for extrarenal clearance of cystatin C.

CONCLUSIONS

A virtually assay-independent simple cystatin C-based and biologically oriented equation for estimation of GFR, without terms for sex and race, was produced.

Perfluoroalkyl substances during pregnancy and validated preeclampsia among nulliparous women in the Norwegian Mother and Child Cohort Study

Perfluoroalkyl substances (PFAS) are persistent and ubiquitous environmental contaminants, and human exposure to these substances may be related to preeclampsia, a common pregnancy complication. Previous studies have found serum concentrations of PFAS to be positively associated with pregnancy-induced hypertension and preeclampsia in a population with high levels of exposure to perfluorooctanoate. Whether this association exists among pregnant women with background levels of PFAS exposure is unknown. Using data from the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health, we carried out a study of nulliparous pregnant women enrolled in 2003-2007 (466 cases, 510 noncases) to estimate associations between PFAS concentrations and an independently validated diagnosis of preeclampsia. We measured levels of 9 PFAS in maternal plasma extracted midpregnancy; statistical analyses were restricted to 7 PFAS that were quantifiable in more than 50% of samples. In proportional hazards models adjusted for maternal age, prepregnancy body mass index (weight (kg)/height (m)(2)), educational level, and smoking status, we observed no strongly positive associations between PFAS levels and preeclampsia. We found an inverse association between preeclampsia and the highest quartile of perfluoroundecanoic acid concentration relative to the lowest quartile (hazard ratio = 0.55, 95% confidence interval: 0.38, 0.81). Overall, our findings do not support an increased risk of preeclampsia among nulliparous Norwegian women with background levels of PFAS exposure.

Utility of cystatin C for renal function in amyotrophic lateral sclerosis

OBJECTIVES

Creatinine (Cr) as a marker of renal function has limited value in amyotrophic lateral sclerosis (ALS) because patients with ALS have reduced muscle mass. Thus, there is a need for alternative methods of assessing renal function. Cystatin C (CysC), which is unaffected by muscle mass, is potentially an ideal biomarker of nephrotoxicity in ALS; however, its utility requires validation.

MATERIAL AND METHODS

One hundred and six subjects were recruited for the study: 76 ALS patients and 30 healthy controls. We compared the Cr-based estimated glomerular filtration rate (eGFR) with the CysC-based eGFR in the ALS patients and healthy controls. The results were further analysed according to the severity of ALS in the patients.

RESULTS

The mean Cr-based eGFRs were 257.2 ± 383.1 ml/min/1.73 m(2) in the ALS group and 98.1 ± 34.9 in the control group; however, the mean CysC-based eGFRs were not significantly different between both groups. Thus, the Cr-based eGFR in the ALS group was markedly higher than any of the other values. Although serum CysC levels did not correlate with the severity of ALS according to the ALS Functional Rating Scale-Revised, strong simple correlations were observed between serum Cr levels and the severity of ALS (correlation coefficient = 0.734, P < 0.001).

CONCLUSIONS

This study demonstrates the potential usefulness of CysC as a biomarker of renal function in ALS patients. Furthermore, its applicability could be extended to other neuromuscular diseases.

Effects of lipid-lowering therapy with rosuvastatin on kidney function and oxidative stress in patients with diabetic nephropathy

AIM

We aimed to assess the effects of rosuvastatin treatment on lipid levels, a biomarker of oxidative stress, albuminuria, and kidney function in patients with diabetic nephropathy.

METHODS

We conducted a prospective, open-label, parallel group, controlled study of 104 patients with diabetic nephropathy, low-density lipoprotein cholesterol (LDL-C) levels of > 120 mg/dL, and well-controlled blood pressure who were undergoing treatment with renin angiotensin system inhibitors. Patients were randomly assigned to two groups: the rosuvastatin group (n = 52; 2.5 mg/day rosuvastatin, increased to 10 mg/day) and the control group (n = 52; no rosuvastatin administered). We determined the efficacy of rosuvastatin by monitoring serum lipid profiles, high sensitivity C-reactive protein (hs-CRP), malondialdehyde-modified LDL (MDA-LDL), and cystatin C levels. In addition, urinary albumin, 8-hydroxydeoxyguanosine (8-OHdG) and liver-type fatty acid-binding protein (L-FABP) levels were measured before and 6 months after rosuvastatin was added to the treatment.

RESULTS

Rosuvastatin effectively reduced total cholesterol, LDL-C, triglycerides, non-high-density lipoprotein cholesterol (non-HDL-C) levels, and the LDL-C/ HDL-C ratio in the rosuvastatin group. These parameters remained unchanged in patients who were not treated with rosuvastatin. Although there was no significant change in the estimated glomerular filtration rate level, serum cystatin C levels and urinary albumin excretion rates were significantly decreased in the rosuvastatin group. In addition, rosuvastatin significantly reduced hs-CRP and MDA-LDL levels. Moreover, urinary 8-OHdG and L-FABP levels at baseline (13.5±5.1 and 41.7±26.1 ng/mgCr, respectively) decreased significantly at 6 months (11.5±4.0 and 26.9±13.4 ng/mgCr, respectively), and there was a significant correlation (r = 0.48, p < 0.01). Multivariate analysis revealed that albuminuria was significantly correlated with only rosuvastatin use (p = 0.0006, R(2)= 0.53).

CONCLUSION

Rosuvastatin administration reduced albuminuria, oxidative stress, and serum cystatin C levels, independent of blood pressure and lipid levels.

Effect of gold nanoparticle conjugation on the activity and stability of functional proteins

Immobilization of functional proteins such as enzymes on solid surfaces produces a variety of effects ranging from the reversal and strong inhibition to the enhancement of protein stability and function. Such effects are protein-dependent and are affected by the physical and chemical properties of the surfaces. Functional consequences of protein immobilization on the surface of gold nanoparticles (AuNPs) are protein-dependent and require thorough investigation using suitable functional tests. However, traditional approaches to making control samples, i.e., immobilized protein vs. protein in solution in absence of any nanoparticles do not provide sufficiently identical reaction conditions and complicate interpretation of the results. This report provides advice and methods for preparing AuNP-conjugated preparations generally suitable for studying the effects of immobilization on the activity and stability of different functional proteins. We use bovine catalase to illustrate our approach, but the methods are easily adaptable to any other enzyme or protein. The AuNP-immobilized enzyme showed increased stability at elevated temperatures compared to the same enzyme in solution.

Serum levels of cystatin C in elderly lung cancer patients

The purpose of this study was to confirm the correlation between serum levels of cystatin C (Cys-C) and those of creatinine (Cre), the most widely used index of renal function in clinical practice, and to evaluate serum levels of Cys-C, with a particular focus on the effects of aging, body mass index (BMI), C-reactive protein (CRP) and disease extent in patients with lung cancer. Serum Cys-C levels in a total of 39 patients (median 72 years), who were diagnosed as having lung cancer were analyzed retrospectively. The serum Cys-C was determined using colloidal gold particles coated with anti-Cys C antibodies. A significant correlation coefficient was found between serum levels of Cys-C and those of Cre (P=0.001), but only moderate agreement. Serum Cys-C levels increased in an age-dependent manner with significant differences among 3 age groups: patients younger than 65 years, those aged 65 to 74 years and those aged 75 years or older (P=0.001). However, no correlation was observed between Cys-C and BMI, Cys-C and CRP, or Cys-C and disease extent of lung cancer. Estimation of renal function is important since renal insufficiency is directly correlated to increased chemotherapeutic complications in oncological practice. Thus, estimation of serum Cys-C levels may be important, but adjustment of Cys-C for age should be taken into consideration.

Serum high-sensitivity cardiac troponin T is a significant biomarker of left-ventricular diastolic dysfunction in subjects with non-diabetic chronic kidney disease

Background

Chronic kidney disease (CKD) is associated with left-ventricular (LV) diastolic dysfunction (LVDD) which progresses to diastolic heart failure. However, biomarkers predicting LVDD in patients with CKD are largely unknown.

Methods

In 93 patients with non-diabetic CKD, the relationships among echocardiography, high-sensitivity cardiac troponin T (hs-cTnT), B-type natriuretic peptide (BNP), and renal function were evaluated. LV mass index, peak early diastolic mitral filling velocity (E), peak early diastolic mitral annular velocity (E′), and E/E′ were recorded.

Results

The E′ values were significantly decreased and E/E′, BNP, and hs-cTnT increased with increasing CKD stage. The CKD patients with LVDD with E′ <5 cm/s had a significantly higher hs-cTnT level as well as a significantly higher BNP level compared to those with E′ ≥5 cm/s. The area under the receiver-operating characteristic curve for hs-cTnT and BNP to detect E′ <5 cm/s was 0.880 (p = 0.0101) and 0.741 (p = 0.0570), respectively. In multivariate analysis, hs-cTnT and albuminuria were significantly associated with E′, and estimated glomerular filtration rate with the hs-cTnT level, after adjusting for age, cause of CKD, and other parameters.

Conclusions

These data suggest that hs-cTnT may be a useful biomarker of LVDD in non- diabetic CKD patients.

Efficacy analysis of the lipid-lowering and renoprotective effects of rosuvastatin in patients with chronic kidney disease

We aimed to assess the effects of rosuvastatin treatment on lipid levels, albuminuria, and kidney function in patients with chronic kidney disease (CKD). We conducted a prospective, open-label, study of 91 patients with CKD, low-density lipoprotein cholesterol (LDL-C) levels > 120 mg/dL, and well-controlled blood pressure who were undergoing treatment with renin-angiotensin system inhibitors. Subjects were treated with 2.5 mg/day rosuvastatin, which was increased to 10 mg/day for the 24-week study period. Rosuvastatin effectively reduced total cholesterol, LDL-C, triglycerides, non-high density lipoprotein cholesterol (non-HDL-C) levels, and the LDL-C/HDL-C ratio. Although there was no significant change in the estimated glomerular filtration rate (eGFR), serum cystatin C levels and urinary albumin/creatinine ratio were significantly decreased. Subjects were divided into 2 groups: with and without diabetes mellitus (DM). Percent changes of HDL-C, C-reactive protein (CRP), and malondialdehyde-modified (MDA)-LDL were significantly higher in the DM group than in the non-DM group. Furthermore, when the subjects were divided into 2 groups based on eGFR levels (60 mL/min/1.73 m(2) or more, normal-GFR group; less than 60 mL/min/1.73 m(2), decreased-GFR group), the percent reduction of non-HDL-C, CRP, MDA-LDL levels, and albuminuria of DM subjects in the decreased-GFR group were significantly higher than those in the non-DM subjects. Multivariate analysis identified a change in cystatin C to be associated with decreased albuminuria during rosuvastatin treatment. Rosuvastatin administration reduced albuminuria, serum cystatin C levels, and inflammation, and improved lipid profiles, regardless of the presence or absence of DM, and the degree of the eGFR.

Confocal detection of planar homogeneous and heterogeneous immunosorbent assays

Optically sectioned detection of fluorescence immunoassays using a confocal microscope enables the creation of both homo- and heterogeneous planar format assays. We report a set assays requiring optically sectioned detection using a model system and analysis procedures for separating signals of a surface layer from an overlying solution. A model sandwich assay with human immunoglobulin G as the target antigen is created on a glass substrate. The prepared surfaces are exposed to antigen and a FITC-labeled secondary antibody. The resulting preparations are either read directly to provide a homogeneous assay or after wash steps, giving a heterogeneous assay. The simplicity of the object shapes arising from the planar format makes the decomposition of analyte signals from the thin film bound to the surface and overlayer straightforward. Measured response functions of the thin film and overlayer fit well to the Cauchy-Lorentz and cumulative Cauchy-Lorentz functions, respectively, enabling the film and overlayer to be separated. Under the conditions used, the detection limits for the homogeneous and heterogeneous forms of the assay are 2.2 and 5.5 ng/ml, respectively. Planar format, confocally read fluorescence assays enable wash-free detection of antigens and should be applicable to a wide range of assays involving surface-bound species.

Comparisons of cystatin C with creatinine for evaluation of renal function in chronic kidney disease

BACKGROUND

Because of the limitations of creatinine (Cr) as a marker for the glomerular filtration rate (GFR), cystatin C (CysC) has been proposed as an alternative substance. The aim here was to clarify the characteristics of CysC compared with Cr.

METHODS

CysC and Cr were measured in 199 patients with chronic kidney disease. Regression analysis between CysC and Cr and comparisons of the effect of gender, inflammation, prescription of prednisolone, smoking and diabetes mellitus (DM) on these markers were performed. Sensitivity and specificity of CysC and Cr to discriminate estimated GFR of less than 50 ml/min/1.73 m(2) were computed and evaluated by the receiver-operating characteristic curve (ROC).

RESULTS

The correlation coefficient between natural logarithmic Cr [ln(Cr)] and ln(CysC) was higher than that between these variables per se (0.941 vs. 0.906). When Cr was lower than 1.10 mg/dl, CysC rose more sharply than Cr. CysC divided by Cr (CysC/Cr) was higher in females (1.35 +/- 0.33 vs. 1.16 +/- 0.30; p < 0.001), in patients with elevated CRP (1.33 +/- 0.40 vs. 1.21 +/- 0.29; p < 0.001) and in patients prescribed with prednisolone (1.42 +/- 0.33 vs. 1.20 +/- 0.30; p < 0.001). A stepwise multiple linear regression model indicated that ln(CysC) was positively correlated with ln(Cr), age, female gender, prednisolone prescription, elevated CRP and DM (R = 0.964, p < 0.001). The area under the ROC curve of Cr was 0.900 and that of CysC was 0.925.

CONCLUSION

CysC is a promising marker for GFR because it was not gender- or age-related. However, inflammation, prednisolone and DM caused CysC to deviate higher than expected from GFR. CysC can rise sensitively in early renal dysfunction.

Biochemistry and Clinical Role of Human Cystatin C

Low molecular-mass plasma proteins play a key role in health and disease. Cystatin C is an endogenous cysteine proteinase inhibitor belonging to the type 2 cystatin superfamily. The mature, active form of human cystatin C is a single non-glycosylated polypeptide chain consisting of 120 amino acid residues, with a molecular mass of 13,343-13,359 Da, and containing four characteristic disulfide-paired cysteine residues. Human cystatin C is encoded by the CST3 gene, ubiquitously expressed at moderate levels. Cystatin C monomer is present in all human body fluids; it is preferentially abundant in cerebrospinal fluid, seminal plasma, and milk. Cystatin C L68Q variant is an amyloid fibril-forming protein with a high tendency to dimerize. It forms self-aggregates with massive amyloid deposits in the brain arteries of young adults, leading to lethal cerebral hemorrhage. The main catabolic site of cystatin C is the kidney: more than 99% of the protein is cleared from the circulation by glomerular ultrafiltration and tubular reabsorption. The diagnostic value of cystatin C as a marker of kidney dysfunction has been extensively investigated in multiple clinical studies on adults, children, and in the elderly. In almost all the clinical studies, cystatin C demonstrated a better diagnostic accuracy than serum creatinine in discriminating normal from impaired kidney function, but controversial results have been obtained by comparing this protein with other indices of kidney disease, especially serum creatinine-based equations. In this review, we present and discuss most of the available data from the literature, critically reviewing conclusions and suggestions for the use of cystatin C in clinical practice. Despite the multitude of clinical data in the literature, cystatin C has not been widely used, perhaps because of a combination of factors, such as a general diffidence among clinicians, the absence of definitive cut-off values, conflicting results in clinical studies, no clear evidence on when and how to request the test, the poor commutability of results, and no accurate examination of costs and of its routine use in a stat laboratory.

Study of serum argininosuccinate lyase determination for diagnosis of liver diseases

The objectives of this research were to establish an automatic analysis method for the determination of serum argininosuccinate lyase (ASL) and to investigate the value of serum ASL test in the diagnosis of various liver disorders. According to the chemical reaction catalyzed by ASL, an enzyme-coupled reaction system was designed, and a methodology evaluation of this method was performed. A total of 291 patients with various liver diseases, 247 patients with nonliver disease and 32 healthy controls, were recruited, their serum levels of ASL and traditional hepatopathy markers, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and total bilirubin (TBil), were all determined, and their diagnostic values in liver diseases were analyzed and compared. Liver biopsy and the score of histopathological inflammation grading were performed in 31 patients with hepatopathy to explore the correlation between serum ASL level and hepatic histopathological change. A continuous monitoring assay method of serum ASL activity was established, which could be performed with automatic biochemistry analyzer. Methodological evaluation exhibited that the precision of this method was good indicated by the 4.0% intraassay coefficient of variation (CV), and 5.9% interassay CV. The mean recovery was 100.5%, linear range was from 0 to 167.7 U/L, and the lowest detection limit was approximately 0 U/L. All of the tested hepatopathy markers listed above were significantly increased in the liver disease group. However, levels of traditional markers of hepatopathy were all significantly increased at different degrees (all P<0.001) in patients with nonliver diseases; in contrast, there were no significantly increased ASL levels in all non-hepatopathy groups (P=0.335). The receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of ASL were 100% and 91.1% (cutoff value=8 U/L), respectively, in the assessment of liver diseases. In contrast, ALT levels were 97.6% and 24.7%, and AST levels were 83.8% and 28.3% (both cutoff values=40.0 U/L), respectively. A positive correlation (r=0.417, P=0.019) was observed between serum ASL levels (86.9+/-26.5) and scores of histopathological inflammation grading (SHIG) (9.83+/-3.36). The sensitivity and specificity of ALS is much higher than that of ALT and AST for the diagnosis of liver diseases. ASL may be a more valuable marker for estimating hepatopathy.

A protein assay based on colloidal gold conjugates with trypsin

The standard sol particle immunoassay (SPIA) is based on a biospecific aggregation of gold nanoparticle conjugates, followed by conventional spectrophotometry. Here we propose a novel SPIA format that uses microtitration immunological plates and an enzyme-linked immunosorbent assay reader. The novel and standard assays are exemplified by determination of immunoglobulin G by using 15-nm colloidal gold-protein A conjugates. We also describe a novel sol particle-trypsin assay using conjugates of gold nanoparticles with trypsin. The method is based on measuring spectral extinction changes caused by the addition of protein to a conjugate solution. The changes in the extinction spectra are presumed to be related to aggregation of gold nanoparticles caused by polyvalent binding of protein molecules to the trypsin molecules of the conjugates.