Influence of thyroid hormones and transforming growth factor-β1 on cystatin C concentrations

Assessment of the renal function of patients with anorexia nervosa

BACKGROUND

A decreased glomerular filtration rate (GFR), estimated using creatinine (Cr- eGFR), is often found at the initial presentation of anorexia nervosa (AN). Its pathophysiology has been explained mainly by dehydration, and chronic hypokalemia is also thought to be a cause. However, because we have often experienced cases of AN with decreased Cr-eGFR without these conditions, we must consider different etiologies. The focus of this paper is on low free triiodothyronine (FT3) syndrome. We also discuss the utility of eGFR, estimated using cystatin-C (CysC-eGFR), for these patients.

METHODS

The data of 39 patients diagnosed with AN between January 2005 and December 2023 was available for study. The characteristics of patients at the lowest and highest body mass index standard deviation score (BMI-SDS) were examined. Data on the parameters Cr-eGFR, CysC-eGFR, dehydration markers, potassium (K), and hormonal data and BMI-SDS were assessed during the treatment course to evaluate the correlations in these parameters. Blood hematocrit, uric acid (UA), blood urine nitrogen (BUN) level, and urine specific gravity were adopted as dehydration markers; FT3, free thyroxine, thyroid stimulating hormone, and insulin-like growth factor were adopted as hormonal data. Cr-eGFR and simultaneously evaluated dehydration markers, K, or hormonal data were extracted and correlations associated with the changes in BMI-SDS were examined. Furthermore, Cr-eGFR and simultaneously assessed CysC-eGFR were compared.

RESULTS

When the BMI-SDS was at the lowest value, low-FT3 syndrome was shown. Severe hypokalemia was not found in our study. A linear relation was not found between Cr-eGFR and BMI-SDS. A statistically significant correlation was found between Cr-eGFR and FT3 (p = 0.0025). Among the dehydration markers, statistically significant correlations were found between Cr-eGFR and BUN or UA. The difference between Cr-eGFR and CysC-eGFR was prominent, and CysC-eGFR showed much higher values.

CONCLUSIONS

Our data indicates that low-FT3 syndrome and dehydration were related to the renal function of our patients with AN. Furthermore, our data suggest that caution is needed in the interpretation of kidney function evaluation when using CysC-eGFR in cases of AN.

Systemic Activation of the Kynurenine Pathway in Graves Disease With and Without Ophthalmopathy

CONTEXT

Graves disease (GD) is one of the most common autoimmune disorders. Recent literature has shown an immune response involving several different inflammatory related proteins in these patients.

OBJECTIVE

This work aimed to characterize the kynurenine pathway, activated during interferon-γ (IFN-γ)-mediated inflammation and cellular (T-helper type 1 [Th1] type) immunity, in GD patients with and without thyroid eye disease (TED).

METHODS

We analyzed 34 biomarkers by mass spectrometry in serum samples from 100 patients with GD (36 with TED) and 100 matched healthy controls. The analytes included 10 metabolites and 3 indices from the kynurenine pathway, 6 microbiota-derived metabolites, 10 B-vitamers, and 5 serum proteins reflecting inflammation and kidney function.

RESULTS

GD patients showed significantly elevated levels of 7 biomarkers compared with healthy controls (omega squared [ω2] > 0.06; P < .01). Of these 7, the 6 biomarkers with the strongest effect size were all components of the kynurenine pathway. Factor analysis showed that biomarkers related to cellular immunity and the Th1 responses (3-hydroxykynurenine, kynurenine, and quinolinic acid with the highest loading) were most strongly associated with GD. Further, a factor mainly reflecting acute phase response (C-reactive protein and serum amyloid A) showed weaker association with GD by factor analysis. There were no differences in biomarker levels between GD patients with and without TED.

CONCLUSION

This study supports activation of IFN-γ inflammation and Th1 cellular immunity in GD, but also a contribution of acute-phase reactants. Our finding of no difference in systemic activation of the kynurenine pathway in GD patients with and without TED implies that the local Th1 immune response in the orbit is not reflected systemically.

Does cystatin C have an immunomodulatory role in Hashimoto's thyroiditis?

OBJECTIVES

Studies which report cystatin C's (Cys-C) role in immunological disorders are increasing. However, data in the pediatric age group is limited. In this study, we aimed to evaluate the association between serum Cys-C levels and thyroid autoantibodies in children and adolescents diagnosed with euthyroid Hashimoto's thyroiditis.

METHODS

The patient group was included 50 participants aged between 3 and 18 years, and the control group included 50 healthy children matched for age, gender, and body mass index. Patients with hypothyroidism or taking any medication were not included in the study. Fasting glucose, liver enzymes, urea, creatinine, lipid profile, Cys-C, free thyroxine (fT4), free triiodothyronine (fT3), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibodies (TGAb) levels were recorded in all subjects.

RESULTS

The mean age of control group was 13.5 ± 2.5 years, and the mean age of Hashimoto thyroiditis (HT) group was 14.2 ± 2.7 years, no statistically significant differences existed (p=0.205). Cys-C values were significantly higher in the HT group than in the control group (p=0.041). When all cases were evaluated, Cys-C levels were statistically positively correlated with fT3, TPOAb, and TGAb values (p<0.001, p=0.029, p=0.013 respectively).

CONCLUSIONS

Based on the results of our study, Cys-C levels in children and adolescents with euthyroid Hashimoto thyroiditis were statistically higher than their healthy peers. In conclusion, it can be said that Cys-C may be a factor in the etiopathogenesis of autoimmune thyroiditis, and even small changes in TSH values affect Cys-C levels.

Evaluation of renal injury and function biomarkers, including symmetric dimethylarginine (SDMA), in the rat passive Heymann nephritis (PHN) model

Symmetric dimethylarginine (SDMA) is a serum biomarker of excretory renal function which consistently correlates with glomerular filtration rate (GFR) across multiple species including rats, dogs, and humans. In human and veterinary clinical settings SDMA demonstrates enhanced sensitivity for detection of declining renal function as compared to other serum biomarkers, but application in preclinical study designs thus far has been limited. The purpose of this study was to determine the performance of serum SDMA in a rat passive Heyman nephritis model of glomerulopathy. In addition to SDMA other biomarkers of excretory renal function were measured including serum creatinine (sCr), blood urea nitrogen (BUN), and cystatin C along with creatinine clearance. Urinary renal biomarkers including microalbumin (μALB), clusterin (CLU), cystatin C, kidney injury marker-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and osteopontin (OPN) were also measured. PHN was induced using commercial sheep anti-Fx1A serum. Tissue, serum, and urine were collected from groups of control and anti-Fx1A-treated animals for biomarker evaluation, hematology, urinalysis, serum biochemistry, and histologic examination of kidney. Over the course of a 28-day study, concentrations of the urinary biomarkers μALB, CLU, cystatin C, NGAL, KIM-1 and the serum biomarker cystatin C increased significantly in anti-Fx1A-treated rats as compared to controls but no significant increase in serum SDMA, sCr, BUN, or creatinine clearance were noted in anti-Fx1A-treated rats. Given lack of direct GFR measurement or significant change in the renal function biomarkers sCr, BUN, and creatinine clearance, it is unclear if GFR differed significantly between control and anti-Fx1A-treated rats in this study, though urinary biomarkers and histopathologic findings supported renal injury in anti-Fx1A-treated rats over the time course investigated. This study is among the first to investigate serum SDMA in a rat model relevant to preclinical safety assessment and serves to inform future experimental designs and biomarker selection when evaluation of glomerular injury is of priority.

Cardiovascular protective effect of nano selenium in hypothyroid rats: protection against oxidative stress and cardiac fibrosis

BACKGROUND

Nano selenium (Nano Sel) has many therapeutic properties including antioxidant, anticancer, and anti-inflammatory actions.

OBJECTIVE

Impacts of Nano Sel administration against cardiac fibrosis and heart and aorta tissue oxidative damage observed in hypothyroid rats were explored.

METHODS

The animals were randomly grouped and treated as: 1) Control; 2) Propylthiouracil (PTU) in which PTU was added to the drinking water (0.05%) to induce hypothyroidism; 3-5) PTU-Nano Sel 50, PTU-Nano Sel 100, and PTU-Nano Sel 150 groups, which received daily PTU plus 50,100 or 150 µg/kg of Nano Sel for 6 weeks intraperitoneally. The heart and aorta tissues were removed under deep anesthesia and then biochemical parameters including malondialdehyde (MDA), total thiol groups, catalase (CAT), and superoxide dismutase (SOD), as well as cardiac fibrosis were assessed.

RESULTS

Hypothyroidism induced by PTU was remarkably associated with myocardial hypertrophy and perivascular fibrosis in Masson's trichrome staining. Moreover, hypothyroidism increased MDA level, while it subtracted total thiol group content and activity of SOD and CAT. Treatment with Nano Sel recovered hypothyroidism-induced cardiac fibrosis in the histological assessment. Nano Sel also promoted CAT and SOD activity and thiol content, whereas alleviated MDA levels in the heart and aorta tissues.

CONCLUSION

Results propose that administration of Nano Sel exerts a protective role in the cardio vascular system via preventing cardiac fibrosis and inhibiting oxidative stress.

Cystatin C relates to metabolism in healthy, pubertal adolescents

INTRODUCTION

The cystatin C (CysC) serum level is a marker of glomerular filtration rate and depends on age, gender, and pubertal stage. We hypothesize that CysC might overall reflect energy homeostasis and be regulated by components of the endocrine system and metabolites in pubertal adolescents.

METHODS

Serum CysC levels and further possible effector parameters in 5355 fasting, morning venous blood samples from 2035 healthy participants of the LIFE Child cohort study (age 8 to 18 years) were analyzed. Recruitment started in 2011, with probands followed up once a year. Linear univariate and stepwise multivariate regression analyses were performed.

RESULTS

Annual growth rate, serum levels of thyroid hormones, parathyroid hormone, insulin-like growth factor 1, hemoglobin A1c (HbA1c), uric acid, and alkaline phosphatase show relevant and significant associations with CysC serum concentrations (p <0.001). Furthermore, male probands' CysC correlated with the body mass index and testosterone among other sexual hormones. Multivariate analyses revealed that uric acid and HbA1c are associated variables of CysC independent from gender (p <0.001). In males, alkaline phosphatase (p <0.001) is additionally significantly associated with CysC. Thyroid hormones show significant correlations only in multivariate analyses in females (p <0.001).

CONCLUSIONS

The described associations strongly suggest an impact of children's metabolism on CysC serum levels. These alterations need to be considered in kidney diagnostics using CysC in adolescents. Additionally, further studies are needed on CysC in children.

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

Background

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

Aim

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

Methods

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

Results

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

Conclusions

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

Systematic Review Registration

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

Comparison of inulin clearance with 2-h creatinine clearance in Japanese pediatric patients with renal disease: open-label phase 3 study of inulin

Background

There is no approved dosage and administration of inulin for children. Therefore, we measured inulin clearance (Cin) in pediatric patients with renal disease using the pediatric dosage and administration formulated by the Japanese Society for Pediatric Nephrology, and compared Cin with creatinine clearance (Ccr) measured at the same time. We examined to what degree Ccr overestimates Cin, using the clearance ratio (Ccr/Cin), and confirmed the safety of inulin in pediatric patients.

Methods

Pediatric renal disease patients aged 18 years or younger were enrolled. Inulin (1.0 g/dL) was administered intravenously at a priming rate of 8 mL/kg/hr (max 300 mL/hr) for 30 min. Next, patients received inulin at a maintenance rate of 0.7 × eGFR mL/min/1.73 m² × body surface area (max 100 mL/hr) for 120 min. With the time the maintenance rate was initiated as a starting point, blood was collected at 30 and 90 min, while urine was collected twice at 60-min intervals. The primary endpoint was the ratio of Ccr to Cin (Ccr/Cin).

Results

Inulin was administered to 60 pediatric patients with renal disease; 1 patient was discontinued and 59 completed. The primary endpoint, Ccr/Cin, was 1.78 ± 0.52 (mean ± standard deviation). Regarding safety, five adverse events were observed in four patients (6.7%); all were non-serious. No adverse reactions were observed in this study.

Conclusions

The results in this study on the dosage and administration of inulin showed that inulin can safely and accurately determine GFR in pediatric patients with renal disease.

ClinicalTrials.gov identifier

NCT03345316.

Estimation of kidney function in patients with primary neuromuscular diseases: is serum cystatin C a better marker of kidney function than creatinine?

BACKGROUND

Using serum creatinine leads to an overestimation of kidney function in patients with primary neuromuscular disorders, and reduced kidney function may remain undetected. Cystatin C (CysC) could provide a better estimation.

AIM

To evaluate the precision, accuracy, and bias of two creatinine-, one cystatin C-based and one combined equation to estimate glomerular filtration rate (eGFR) in patients with primary neuromuscular disease.

PATIENTS AND METHODS

Of the 418 patients initially identified at the out-patient clinic, data on kidney function was obtained for 145 adult patients (age 46 ± 14 years, BMI 26 ± 6 kg/m²) with primary neuromuscular disease. Kidney function was measured by iohexol clearance, and blood samples for serum creatinine and CysC were drawn simultaneously. Bias was defined as the mean difference between eGFR and measured iohexol clearance, and accuracy as the proportion of eGFRs within ± 10% (P10) of measured clearance.

RESULTS

Kidney function (iohexol clearance) was 81 ± 19 (38-134) ml/min/1.73m². All equations overestimated kidney function by 22-60 ml/min/1.73m². eGFR CysC had the lowest bias overall 22 (95% CI 20-26) ml/min/1.73m² also at all levels of kidney function we evaluated (at 30-59 ml/min/1.73m² bias was 27 (95% CI 21-35), at 60-89 it was 25 (95% CI 20-28) and at ≥ 90 it was 12 (95% CI 7-22)). eGFR CysC also had the best accuracy in patients with reduced kidney function (P10 was 5.9% at 30-59 ml/min/1.73m²).

CONCLUSIONS

Cystatin C-based estimations of kidney function performed better than creatinine-based ones in patients with primary neuromuscular disease, but most importantly, all evaluated equations overestimated kidney function, especially in patients with reduced kidney function. Therefore, kidney function should be measured by gold-standard methods when precision and accuracy are needed.

Superiority of Cystatin C over Creatinine for Early Diagnosis of Acute Kidney Injury in Pediatric Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

The exact incidence of acute kidney injury (AKI) during chemotherapy for acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL) is unknown. Furthermore, childhood cancer survivors are at risk of AKI-chronic kidney disease transition. Thus, early diagnosis of AKI is crucial. This study aimed to elucidate the incidence of AKI in patients undergoing chemotherapy for pediatric ALL/LBL and to compare the usefulness of serum cystatin C (CysC)- and creatinine (Cr)-based estimated glomerular filtration rate (eGFR) as diagnostic measures. Data of 16 patients with ALL/LBL treated with a total of 75 courses of chemotherapy were retrospectively analyzed. CysC- and Cr-based eGFR were measured before and three times per week during therapy. To calculate the eGFR, an equation for Japanese children was used. AKI was diagnosed when eGFR dropped by ≥ 25% from the highest eGFR value obtained during the latest 2 weeks since the start of chemotherapy. AKI was graded based on the pediatric Risk, Injury, Failure, Loss, End Stage Renal Disease scale. All patients developed AKI during chemotherapy; however, more than 90% of the cases were mild and eventually recovered. No significant differences were found in the incidence of AKI between CysC- and Cr-based eGFR (p = 0.104). The median time to AKI diagnosis was significantly shorter in the CysC-based eGFR than in the Cr-based eGFR (8 vs. 17 days, p < 0.001). In this study, all patients with pediatric ALL/LBL could develop mild AKI during treatment. CysC-based eGFR is a more effective measure than Cr-based eGFR for the early diagnosis of AKI.

Serum Cystatin C Concentrations in Patients with Graves' Ophthalmopathy

Purpose

To evaluate the concentration of serum cystatin C (CysC) in patients with Graves’ ophthalmopathy (GO) and the usability of the serum CysC concentrations in the follow-up of the disease.

Methods

Thirty patients with GO and 30 healthy age-matched volunteers were included in this cross-sectional study. GO was diagnosed based on the European Group on Graves’ Orbitopathy consensus. Serum thyroid-stimulating hormone, free triiodothyronine, free thyroxine, and CysC concentrations were measured in the participants. The serum CysC concentrations were compared between patients with GO and controls. Patients with GO were subdivided into hyperthyroid and euthyroid patients, and their serum CysC concentrations were compared. In addition, the CysC concentrations in hyperthyroid and euthyroid patients with GO were compared separately with those of healthy subjects. Kruskal-Wallis test and Student’s t-test were used for statistical evaluation.

Results

The mean serum CysC concentrations in GO patients and controls were 1.04 ± 0.36 and 0.74 ± 0.09 mg/L, respectively. There was a statistically significant difference in the serum CysC concentrations between patients with GO and control subjects (p < 0.001). Fifteen patients had hyperthyroid status, and 15 patients had euthyroid status. The mean serum CysC concentrations in hyperthyroid and euthyroid patients with GO were 1.35 ± 0.22 and 0.72 ± 0.13 mg/L, respectively. Serum CysC concentrations were significantly higher in hyperthyroid patients than in euthyroid patients (p = 0.001). In addition, hyperthyroid patients had significantly higher serum CysC concentrations than healthy subjects. Among patients with GO, 21 and nine had mild and moderate-to-severe GO, respectively. Active and inactive GO were observed in eight and 22 patients, respectively.

Conclusions

The serum CysC concentrations in hyperthyroid patients were higher than those in healthy subjects. Moreover, hyperthyroid patients had higher serum CysC concentrations than euthyroid patients. Further studies with a larger sample size are needed to confirm these results.

Corticosteroids significantly increase cystatin C levels in the plasma by promoting cystatin C production in rats

Background: Several studies have shown that non-renal factors such as corticosteroids may increase plasma cystatin C levels without affecting kidney function. However, the mechanisms underlying this are unclear. We hypothesized that corticosteroids may increase cystatin C levels in the plasma by promoting its production in tissues. In the present study, we aimed to test our hypothesis in rats by investigating the effect of corticosteroids on cystatin C production in tissues and the glomerular filtration rate (GFR), as measured by the gold standard method (i.e., inulin clearance). Results: Dexamethasone treatment was associated with much higher concentrations of cystatin C in all organ tissue homogenates tested. Dexamethasone increased plasma cystatin C levels in rats, without any decrease in renal inulin clearance. The impact of dexamethasone on plasma and organ tissue cystatin C levels was abolished by RU486, indicating the effect was glucocorticoid receptor-mediated. Conclusions: Our study provides direct evidence that corticosteroids may increase cystatin C levels in the plasma by promoting its production, without any decrease in GFR.

Cystatin C in adipose tissue and stimulation of its production by growth hormone and triiodothyronine in 3T3-L1 cells

Cystatin C (CysC) is a marker for estimation of glomerular filtration rate (GFR). CysC levels may depend not only on clearance/GFR but possibly also on changes in production. Our studies on tissue distribution of CysC protein in mice showed that adipose tissue expresses significant amounts of CysC, suggesting that adipocytes could contribute to circulating CysC levels in vivo. As growth hormone (GH) and triiodothyronine (T₃) increase both GFR and CysC (increased in acromegaly and hyperthyroidism) in vivo, we studied whether they could increase CysC production in 3T3-L1 adipocytes in vitro. CysC accumulated in culture media of 3T3-L1 adipocytes in a time-dependent fashion. GH and T₃ both (10 nmol/l) increased accumulation of CysC, to 373 ± 14 and 422 ± 20, respectively, vs 298 ± 10 ng per well over 4 days in controls. Thus, GH and T₃ enhance the production of CysC by adipocytes in vitro.

Serum Cystatin C Predicts AKI and the Prognosis of Patients in Coronary Care Unit: a Prospective, Observational Study

BACKGROUND/AIMS

Acute Kidney Injury (AKI) is a serious clinical state associated with high morbidity and mortality, particularly in critical ill patients. We investigated the hypothesis that serum Cystatin C (sCysC) is a good predictor for AKI and may affect the short-term prognosis of coronary care unit (CCU) patients.

METHODS

In this prospective, observational study, we screened 412 adults admitted to the CCU from January 1, 2014 to June 1, 2015 at Zhongnan Hospital of Wuhan University. Serum samples were obtained at the time of admission, and sCysC was quantified through nephelometry. AKI was defined based on KDIGO-AKI criteria. After the patients' hospital discharge, the survivors in this study were followed up for up to 2 years. The primary endpoint was the incidence of AKI stratified by severity stage, while the second endpoints included 2-year mortality, rehospitalization and failure in renal recovery rates, as well as the progression of AKI to CKD.

RESULTS

According to the KDIGO-AKI criteria, AKI occurred in 130 (31.6%) patients. After multivariate adjustments, the highest quartile of sCysC was associated with a 9-fold increased risk of incident AKI compared with the lowest quartile. For predicting AKI, sCysC [area under the receiver operating characteristic curve (AUC=0.842)] outperformed β2-micro globulin (AUC=0.813) and the clinical model (AUC=0.777), and a cutoff of 1.255 mg/L yielded good sensitivity and specificity. After a median 19.8-month follow-up, 112 (27.2%) patients died within 2 years after admission. The sCysC independently predicted the risk of 2-year mortality [adjusted odds ratio (OR), 4.955; 95% confidence interval (95% CI), 2.853 to 8.603] and rehospitalization (OR, 3.128; 95% CI, 2.011 to 4.867), as well as renal recovery failure (OR, 3.618, 95% CI, 1.753 to 7.463).

CONCLUSIONS

Serum CysC is a strong predictor of AKI and the short-term prognosis of CCU patients.

Serum and urinary cystatin C in cats with feline immunodeficiency virus infection and cats with hyperthyroidism

OBJECTIVES

The objective of this study was to investigate serum cystatin C (sCysC) and urinary cystatin C (uCysC) in cats with hyperthyroidism and cats with feline immunodeficiency virus (FIV).

METHODS

Thirty cats with FIV, 26 hyperthyroid cats and 28 healthy cats were included. sCysC and uCysC:creatinine (uCysC/uCr) ratio were measured with a human particle-enhanced nephelometric immunoassay, previously validated for feline CysC measurement. Routine renal variables (serum creatinine [sCr], urine specific gravity, urinary protein:creatinine ratio [UPC]) were also measured in the three groups.

RESULTS

Cats with hyperthyroidism had significantly higher sCysC and higher uCysC/uCr ratio, lower sCr and a higher UPC than healthy cats. Cats with FIV infection did not show a significantly higher sCysC concentration but had a significantly higher sCr and UPC than healthy cats. uCysC could be detected in only four of them.

CONCLUSIONS AND RELEVANCE

This study demonstrated that sCysC is increased in cats with hyperthyroidism, in contrast with sCr, but not in cats with FIV. Many hyperthyroid cats, but only four cats with FIV, had an elevated uCysC/uCr ratio. Further studies may reveal if uCysC might be a valuable marker for tubular dysfunction in cats.

Paradoxical effects of thyroid function on glomerular filtration rate estimated from serum creatinine or standardized cystatin C in patients with Japanese Graves' disease

BACKGROUND

Estimated glomerular filtration rate (eGFR) is clinically valuable for evaluating renal function. Recently, serum cystatin C (sCysC) measurement has been standardized and has demonstrated utility as a novel indicator of renal function. Thyroid hormone is known to affect serum creatinine (sCr) and sCysC, however, the clinical significance of post-treatment renal function evaluation is yet to be completely elucidated. This study examined the effects of thyroid hormones on eGFR by sCr (eGFRCr), and standardized sCysC (eGFRCysC) in patients with Japanese Graves' disease (GD).

METHODS

Serum samples were obtained from 113 outpatients with GD. Following pharmacotherapy, 41 of the 113 outpatients with GD achieved remission. Renal function was evaluated by eGFRCr and eGFRCysC. Reference method used Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.

RESULTS

eGFRCr levels significantly increased whereas eGFRCysC levels significantly decreased with elevated FT3 and FT4 levels in patients with GD. In the remission group, eGFRCr levels significantly decreased and eGFRCysC levels significantly increased. No significant differences between eGFRCr and eGFRCysC levels were observed. Furthermore, CKD-EPI equations show a similar trend and eGFRCr-CysC levels were no significant differences regardless of before and after treatment.

CONCLUSIONS

Renal function evaluation by eGFRCr and eGFRCysC had clinical utility in post-treatment euthyroidism.

Decreased serum level of IL-7 in patients with active Graves' disease

BACKGROUND

Graves' disease (GD) is a common autoimmune disease which is one of the major causes of hyperthyroidism. Interleukin 7 (IL-7) has been recently reported to play an important role in various autoimmune diseases, but its role in the pathogenesis of GD has not been assessed. The aim of this study was to evaluate the levels of IL-7 and the soluble form of its receptor (sIL-7R) in the serum of GD patients, and to identify their association with disease activity.

METHODS

A total of 37 GD patients were enrolled into the experimental group and 16 individuals into the control group. All patients were further classified into three subgroups: a GD-active group (hyperthyroidism and TRAb (thyroid stimulating hormone receptor antibody) >7.5 U/L) (N=15), a GD-inactive group (euthyreosis and TRAb<1 U/L) (N=8), and other GD patients (euthyreosis and TRAb>1 U/L) (N=14). Concentrations of IL-7 and sIL-7R were assayed with ELISA. Additionally, the relationship between IL-7 and sIL-7R serum concentrations with disease activity (free triiodothyronine [FT3], free thyroxine [FT4], thyroid stimulating hormone [TSH] and TRAb) was also analyzed.

RESULTS

The serum concentrations of IL-7 in GD-active patients were significantly lower than those of the control group as well as the GD-inactive and GD-other groups. The serum level of IL-7 in GD patients negatively correlated with FT4 and TRAb concentrations. Moreover, no significant difference was observed in the serum level of sIL-7R in GD patients compared to the control group.

CONCLUSIONS

These observations suggest that IL-7 may play a role in the pathogenesis of GD and may be associated with its clinical activity. To this end, the serum level of IL-7 could be an additional diagnostic biomarker predictive of the disease and could be particularly valuable for TRAb-negative GD patients.

Cystatin C is a disease-associated protein subject to multiple regulation

A protease inhibitor, cystatin C (Cst C), is a secreted cysteine protease inhibitor abundantly expressed in body fluids. Clinically, it is mostly used to measure glomerular filtration rate as a marker for kidney function due to its relatively small molecular weight and easy detection. However, recent findings suggest that Cst C is regulated at both transcriptional and post‐translational levels, and Cst C production from haematopoietic cell lineages contributes significantly to the systematic pools of Cst C. Furthermore, Cst C is directly linked to many pathologic processes through various mechanisms. Thus fluctuation of Cst C levels might have serious clinical implications rather than a mere reflection of kidney functions. Here, we summarize the pathophysiological roles of Cst C dependent and independent on its inhibition of proteases, outline its change of expression by various stimuli, and elucidate the regulatory mechanisms to control this disease‐related protease inhibitor. Finally, we discuss the clinical implications of these findings for translational gains.

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

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

Improved glomerular filtration rate estimation using new equations combined with standardized cystatin C and creatinine in Chinese adult chronic kidney disease patients

OBJECTIVES

The newly developed glomerular filtration rate (GFR)-estimating equations developed by the CKD-EPI Collaboration and Feng et al. (2013) that are based on standardized serum cystatin C (ScysC), combined/not combined with serum creatinine (Scr), require further validation in China. We compared the performance of four new equations (CKD-EPIcys, CKD-EPIcr-cys, Fengcys, and Fengcr-cys equations) with the CKD-EPI creatinine equation (CKD-EPIcr) in adult Chinese chronic kidney disease (CKD) patients to clarify their clinical application.

DESIGN AND METHODS

GFR was measured using the dual plasma sampling (99m)Tc-DTPA method (mGFR) in 252 adult CKD patients enrolled from four centres. Scr and ScysC were measured by standardized assays in a central laboratory. Each equation's performance was assessed using bias, precision, accuracy, agreement, and correct classification of the CKD stage.

RESULTS

The measured GFR was 46 [25-83] mL/min per 1.73 m(2). The CKD-EPIcys, CKD-EPIcr-cys and Fengcys equations provided significantly higher accuracy (P15: 38.9%, 39.7%, and 38.9%) than the CKD-EPIcr equation (29.8%). The CKD-EPIcr-cys and Fengcr-cys equations presented higher precision (IQR of the difference, 16.4 and 17.3 mL/min per 1.73 m(2), respectively) and narrower acceptable limits in Bland-Altman analysis (56.6 and 50.8 mL/min per 1.73 m(2), respectively) than single marker-based equations. The CKD-EPIcr-cys equation achieved the highest overall correct proportion (61.5%) in classification of CKD stages.

CONCLUSIONS

Combining ScysC and Scr measurements for GFR estimation improves diagnostic performance. The Scr-ScysC equation showed better performance than equations based on either marker alone. The CKD-EPIcr-cys equation showed the best performance for GFR estimation in Chinese adult CKD patients.

Impact of thyroid function on serum cystatin C and estimated glomerular filtration rate: a cross-sectional study

OBJECTIVE

To determine the relationship between thyroid-stimulating hormone (TSH) and cystatin C (CysC) and estimated glomerular filtration rate calculated by Cys C (eGFR(CysC)).

METHODS

We conducted a cross-sectional study including 8,126 male participants. Serum creatinine (Cr), CysC, eGFR calculated by Cr (eGFR(Cr)), and eGFR(CysC) were determined and compared in euthyroid and subclinical thyroid dysfunction patients. Relationships between TSH and Cr, cystatin C, eGFR(Cr), and eGFR(CysC) were assessed by linear and quadratic trend analyses. Odds ratios (ORs) of chronic kidney disease (CKD; eGFR<60 mL/min/1.73 m2) were calculated according to categories of thyroid function using TSH values of 2.01-3.00 mIU/L as a reference.

RESULTS

Serum CysC level was significantly elevated, and eGFR(CysC) was significantly reduced in both subclinical hypothyroidism and subclinical hyperthyroidism. TSH was negatively and linearly associated with Cr and eGFR(Cr) (P<.001). Quadratic trends were found between TSH and cystatin C or eGFR(CysC) (P<.001). Compared with individuals with TSH of 2.01-3.00 mIU/L, the prevalence of CKD(CysC) was significantly higher in subjects with TSH<0.40 mIU/L, 3.01-4.00 mIU/L, and 4.01-7.00 mIU/L, while the prevalence of CKD(Cr) was only significantly higher in subjects with TSH>7.0 mIU/L.

CONCLUSIONS

Despite only studying male subjects and using eGFR rather than standard GFR, we conclude that thyroid function differentially affects serum CysC and Cr concentrations. Subclinical hypothyroidism and subclinical hyperthyroidism are both associated with elevated CysC, reduced eGFR(CysC), and higher prevalence of CKDCysC. Assessment of renal function with CysC should be avoided in patients with thyroid dysfunction.

The impacts of thyroid function on the diagnostic accuracy of cystatin C to detect acute kidney injury in ICU patients: a prospective, observational study

INTRODUCTION

Cystatin C (Cysc) could be affected by thyroid function both in vivo and in vitro and thereby may have limited ability to reflect renal function. We aimed to assess the association between Cysc and thyroid hormones as well as the effect of thyroid function on the diagnostic accuracy of Cysc to detect acute kidney injury (AKI).

METHODS

A total of 446 consecutive intensive care unit (ICU) patients were screened for eligibility in this prospective AKI observational study. Serum Cysc, thyroid hormones and serum creatinine (Scr) were measured upon entry to the ICU. We also collected each patient's baseline characteristics including the Acute Physiology and Chronic Health Evaluation II (APACHE-II) score. The diagnostic performance of Cysc was assessed from the area under the receiver operator characteristic curve (AUC) in each quartile of thyroid hormone(s).

RESULTS

A total of 114 (25.6%) patients had a clinical diagnosis of AKI upon entry to the ICU. The range of free thyroxine (FT4) value was 4.77 to 39.57 pmol/L. Multivariate linear regression showed that age (standardized beta = 0.128, P < 0.0001), baseline Scr level (standardized beta = 0.290, P < 0.0001), current Scr (standardized beta = 0.453, P < 0.0001), albumin (standardized beta = -0.086, P = 0.006), and FT4 (standardized beta = 0.062, P = 0.039) were related with Cysc. Patients were divided into four quartiles based on FT4 levels. The AUC for Cysc in detecting AKI in each quartile were as follows: 0.712 in quartile I, 0.754 in quartile II, 0.829 in quartile III and 0.797 in quartile IV. There was no significant difference in the AUC between any two groups (all P > 0.05). The optimal cut-off value of Cysc for diagnosing AKI increased across FT4 quartiles (1.15 mg/L in quartile I, 1.15 mg/L in quartile II, 1.35 mg/L in quartile III and 1.45 mg/L in quartile IV).

CONCLUSIONS

There was no significant impact of thyroid function on the diagnostic accuracy of Cysc to detect AKI in ICU patients. However, the optimal cut-off value of Cysc to detect AKI could be affected by thyroid function.

Plasma cystatin-C and risk of developing gestational diabetes mellitus

AIMS

Cystatin-C, a low molecular weight protein, is effectively applied to evaluate the risk of developing renal insufficiency, cardiovascular disorders, neural defects, and inflammatory states. However, the role of this biomarker to monitor different pregnancy-related complications remains controversial.

MATERIALS AND METHODS

In the present study, we compared serum cystatin-C concentration between pregnant women with gestational diabetes mellitus (GDM) and healthy pregnant women to assess value of this biomarker to predict presence of GDM in these women. The study consisted of 60 consecutive pregnant women (30 women suffered GDM and 30 healthy pregnant women) enrolled in Afzalipour hospital in Kerman, Iran in 2012. Fasting blood sample was collected to perform measurements on plasma glucose, lipids, serum creatinine, and C-cystatin. Serum cystatin-C level was quantified using ELISA techniques.

RESULTS

Unadjusted comparison of cystatin-C level between the two study group showed no significant discrepancy between them so that the level of this biomarker in GDM group was 593.00±204.81 mg/L and in healthy group was 531.67±87.52 mg/L (P=0.137); while in multivariable linear model with the presence of associated variables, GDM was a main determinant for increased level of cystatin-C (standardized beta of 0.355, P-value of 0.014).

CONCLUSION

Gestational age was also identified to be another indicator of elevated cystatin-C. In final, our study showed that cystatin-C can be a reliable, useful and promising marker of GDM appearance in pregnant women.

Impact of Growth Hormone on Cystatin C

Background

Cystatin C (CysC) is an alternative marker to creatinine for estimation of the glomerular filtration rate (GFR). Hormones such as thyroid hormones and glucocorticoids are known to have an impact on CysC. In this study, we examined the effect of growth hormone (GH) on CysC in patients with acromegaly undergoing transsphenoidal surgery.

Methods

Creatinine, CysC, GH and insulin-like growth factor-1 (IGF-1) were determined in 24 patients with acromegaly before and following transsphenoidal surgery. Estimated GFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration formula.

Results

In all patients, surgical debulking resulted in decreased clinical disease activity and declining GH/IGF-1 levels. Postoperatively, biochemical cure was documented in 20 out of 24 patients. Creatinine levels (mean ± SEM) increased from 72 ± 3 to 80 ± 3 µmol/l (p = 0.0004) and concurrently, estimated GFR decreased from 99 ± 3 to 91 ± 3 ml/min (p = 0.0008). In contrast to creatinine, CysC levels decreased from 0.72 ± 0.02 to 0.68 ± 0.02 mg/l (p = 0.0008).

Conclusions

Our study provides strong evidence for discordant effects of GH on creatinine and CysC in patients with acromegaly undergoing transsphenoidal surgery, thus identifying another hormone that influences CysC independent of renal function.

Impaired aortic distensibility in hypothyroid patients with negative coronary angiograms: Simultaneous evaluation with 128-slice multiple row detector computed tomography

Objective

To determine the relationship between arterial distensibility and hypothyroidism by simultaneous assessment of coronary angiography and aortic distensibility, measured using 128-slice retrospective electrocardiogram-gated multiple row detector computed tomography (MDCT).

Methods

Untreated hypothyroid patients and age-matched euthyroid patients, who underwent 128-slice retrospective electrocardiogram-gated MDCT to evaluate the coronary arteries, were assessed. Intraluminal aortic areas in systolic and diastolic phases of the cardiac cycle were measured with multiphase reformation at predefined locations including the ascending aorta, proximal descending aorta and distal descending aorta in the widest axial plane.

Results

The study included 21 hypothyroid and 21 euthyroid patients. Patients with hypothyroidism exhibited decreased aortic distensibility between each location in the thoracic aorta (ascending aorta, proximal descending aorta and distal descending aorta) compared with euthryoid patients.

Conclusions

Hypothyroidism was associated with preclinical vascular alteration, characterized by impaired aortic distensibility at each location of the thoracic aorta, which has been shown to be related to increased cardiovascular risk. Monitoring of aortic distensibility is relevant for evaluating coronary artery disease progression and treatment choices.

Multicenter study of creatinine- and/or cystatin C-based equations for estimation of glomerular filtration rates in Chinese patients with chronic kidney disease

OBJECTIVE

To establish equations for the estimation of glomerular filtration rates (eGFRs) based on serum creatinine (SCr) and/or serum cystatin C (SCysC) in Chinese patients with chronic kidney disease (CKD), and to compare the new equations with both the reference GFR (rGFR) and the literature equations to evaluate their applicability.

METHODS

The 788 Chinese CKD patients were randomly divided into two groups, the training group and the testing group, to establish new eGFR-formulas based on serum CysC and to validate the established formulas, respectively. (99m)Tc-DTPA clearance (as the rGFR), serum Cr, and serum CysC were determined for all patients, and GFR was calculated using the Cockcroft-Gault equation (eGFR1), the MDRD formula (eGFR2), the CKD-EPI formulas (eGFR3, eGFR4), and the Chinese eGFR Investigation Collaboration formulas (eGFR5, eGFR6). The accuracy of each eGFR was compared with the rGFR.

RESULTS

The training and testing groups' mean GFRs were 50.84±31.36 mL/min/1.73 m(2) and 54.16±29.45 mL/min/1.73 m(2), respectively. The two newly developed eGFR formulas were fitted using iterative computation: [Formula: see text] and [Formula: see text]. Significant correlation was observed between each eGFR and the rGFR. However, proportional errors and constant errors were observed between rGFR and eGFR1, eGFR2, eGFR4, eGFR5 or eGFR6, and constant errors were observed between eGFR3 and rGFR, as revealed by the Passing & Bablok plot analysis. The Bland-Altman analysis illustrated that the 95% limits of agreement of all equations exceeded the previously accepted limits of <60 mL/min •1.73 m(2), except the equations of eGFR7 and eGFR8.

CONCLUSION

The newly developed formulas, eGFR7 and eGFR8, provide precise and accurate GFR estimation using serum CysC detection alone or in combination with serum Cr detection. Differences in detection methods should be carefully considered when choosing literature eGFR equations to avoid misdiagnosis and mistreatment.

GFR estimation using standardized serum cystatin C in Japan

BACKGROUND

Recently, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed glomerular filtration rate (GFR)-estimating equations based on standardized serum cystatin C (CKD-EPI(cys)) and standardized serum creatinine plus standardized serum cystatin C (CKD-EPI(cr-cys)). We developed new GFR-estimating equations based on standardized cystatin C for a Japanese population and compared their accuracy with the CKD-EPI equations.

STUDY DESIGN

Accuracy of diagnostic test study.

SETTING & PARTICIPANTS

413 (development data set) and 350 individuals (validation data set).

INDEX TEST

CKD-EPI(cys); CKD-EPI(cr-cys); modifications to CKD-EPI(cys) and CKD-EPI(cr-cys) using Japanese coefficients; and newly developed Japanese eGFR equations based on standardized serum cystatin C (Eq(cys)), cystatin C with a nonrenal factor reflecting hypothesized extrarenal elimination (Eq(cys+nonrenal)), and creatinine in combination with cystatin C (Eq(cr-cys)). Standardized cystatin C values were determined by a colloidal gold immunoassay traceable to the international certified reference material ERM-DA471/IFCC.

REFERENCE TEST

Measured GFR by inulin renal clearance.

RESULTS

In a development data set, we calculated Japanese coefficients for CKD-EPI(cys) and CKD-EPI(cr-cys) of 0.977 (95% CI, 0.853-1.002) and 0.908 (95% CI, 0.889-0.928), respectively. In a validation data set, we compared CKD-EPI(cys), Eq(cys), and Eq(cys+nonrenal) with each other. Bias and accuracy were not significantly different among the 3 equations. The precision of CKD-EPI(cys) was significantly better than for Eq(cys) (P = 0.007) and not significantly different from Eq(cys+nonrenal) (P = 0.6). We then compared 0.908 × CKD-EPI(cr-cys), Eq(cr-cys), and Eq(average) (the average value of Eq(cr) [previous Japanese equation based on standardized serum creatinine] and Eq(cys+nonrenal)) with each other in the validation data set. Bias and accuracy were not significantly different among the 3 equations. The precision of 0.908 × CKD-EPI(cr-cys) was significantly better than for Eq(cr-cys) (P = 0.004) and not significantly different from Eq(average) (P = 0.06).

LIMITATIONS

Limited number of participants with measured GFR >90 mL/min/1.73 m(2). Extrarenal elimination of cystatin C was not measured.

CONCLUSIONS

CKD-EPI(cys) performed well in Japanese individuals, suggesting that equations based on serum cystatin C could be used in patients with different races without modification. Accounting for extrarenal elimination of cystatin C may improve the performance of estimating equations.

Performance of serum cystatin C versus serum creatinine as a marker of glomerular filtration rate as measured by inulin renal clearance

INTRODUCTION

Serum cystatin C was recently proposed as an alternative marker of glomerular filtration rate (GFR), with a suggested better performance than creatinine. However, detailed studies are limited. We evaluated the performance of cystatin C as a GFR marker.

METHODS

GFR was measured by inulin clearance in 763 Japanese subjects. Factors other than GFR influencing serum cystatin C or serum creatinine were analyzed by multivariate analyses.

RESULTS

After adjustment for GFR, the value of serum creatinine was 25.2% lower in females than males, and decreased by 5.2% for every 20 years of age. Serum cystatin C was 8.2% lower in females, and did not change significantly with aging. Creatinine but not cystatin C was significantly affected by body weight, height and body mass index after adjustment for GFR, gender and age. The correlation coefficient between GFR and 1/cystatin C was significantly higher than that of 1/creatinine in total subjects (0.866 and 0.810, respectively, p < 0.001). Unlike serum creatinine, serum cystatin C did not increase in association with the reduction of GFR in subjects with very low GFR. The regression line of 1/cystatin C against GFR showed a significantly negative intercept of about -8 ml/min/1.73 m(2).

CONCLUSION

The performance of serum cystatin C was not good in the subjects with very low GFR. Non-renal elimination of cystatin C may contribute to the result. The correlation between reciprocal cystatin C and GFR suggested its superiority in predicting GFR compared to creatinine in subjects with normal and mildly reduced GFR.