Impact of Growth Hormone on Cystatin C

Novel insight into pancreatic adenocarcinoma pathogenesis using liquid association analysis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy associated with a poor prognosis. High-throughput disease-related-gene expression data provide valuable information on gene interaction, which consequently lead to deeper insight about pathogenesis. The co-expression analysis is a common approach that is used to investigate gene interaction. However, such an approach solely is inadequate to reveal the complexity of the gene interaction. The three-way interaction model is known as a novel approach applied to decode the complex relationship between genes.

METHODS

In the current study, the liquid association method was used to capture the statistically significant triplets involved in the PDAC pathogenesis. Subsequently, gene set enrichment and gene regulatory network analyses were performed to trace the biological relevance of the statistically significant triplets.

RESULTS

The results of the current study suggest that "response to estradiol" and "Regulation of T-cell proliferation" are two critical biological processes that may be associated with the PDAC pathogenesis. Additionally, we introduced six switch genes, namely Lamc2, Klk1, Nqo1, Aox1, Tspan1, and Cxcl12, which might be involved in PDAC triggering.

CONCLUSION

In the current study, for the first time, the critical genes and pathways involved in the PDAC pathogenesis were investigated using the three-way interaction approach. As a result, two critical biological processes, as well as six potential biomarkers, were suggested that might be involved in the PDAC triggering. Surprisingly, strong evidence for the biological relevance of our results can be found in the literature.

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.

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.

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.

Cystatin-C and epicardial adipose tissue as noninvasive predictors of cardiovascular risk in acromegaly

BACKGROUND

Acromegaly (ACRO) is associated with elevated cardiovascular risk, although the prevalence of coronary artery disease (CAD) is unclear. Increased epicardial adipose tissue (EAT) and elevated cystatin-C (Cys-C) levels are cardiovascular risk factors, also related to the progression of CAD in several populations.

AIMS

To measure the severity and extent of CAD in patients with ACRO and to determine whether either EAT or Cys-C reflect higher cardiovascular risk in patients with ACRO than in healthy controls.

SUBJECTS AND METHODS

Case-control study, of 35 patients with ACRO (19 males, 17 with active disease) and 35 age-, gender- and body mass index (BMI)-matched healthy controls; mean age was 48·1 ± 8·1 years and mean BMI was 27·6 ± 4·8 kg/m² . Cys-C was measured by an immunoturbidimetric assay. The 10-year risk of developing a coronary event was calculated using the Framingham Risk Score (FRS). EAT index (volume indexed to body surface area), and severity and extent of CAD were measured using a 256-slice multidetector computed tomography scanner (iCT-256 Philips Healthcare, Amsterdam).

RESULTS

Coronary artery disease lesions, EAT index and severity/extent of CAD were similar between patients with ACRO and controls. Forty-four per cent of patients with ACRO had mild coronary lesions associated with greater EAT index (ß = 0·022, P = 0·036). Cys-C levels correlated with both EAT index (ρ = 0·386, P = 0·031) and FRS (ρ = 0·477, P = 0·004) in patients with ACRO only, despite similar prevalence of traditional cardiovascular risk factors. In a multiple linear regression model, both Cys-C levels (ß = 0·369, P = 0·007) and EAT index (ß = 0·29, P = 0·025) predicted FRS (R² = 0·613).

CONCLUSIONS

In patients with ACRO, both Cys-C and EAT index might be used as noninvasive predictors of cardiovascular risk.

Treatable glomerular hyperfiltration in patients with active acromegaly

OBJECTIVE

The glomerular filtration rate (GFR) is increased in patients with active acromegaly. The aim of this study is to elucidate whether renal function deteriorates in patients with acromegaly and whether this deterioration is reversible after surgical remission.

DESIGN/METHODS

A case-control study of 48 acromegalic patients who were surgically cured (cases) and 48 patients with nonfunctioning pituitary adenomas (NFomas, controls) was conducted. We performed clinical and biochemical examinations before surgery and 3months post-surgery. The GFR of each patient was estimated (estimated GFR, eGFR) using their serum creatinine, age, sex, and body surface area, and postoperative changes in the eGFR were assessed.

RESULTS

The preoperative eGFR was significantly higher in patients with acromegaly than in those with NFoma (99.8 vs 75.1mL/min respectively, P<0.01). In acromegalic patients, surgical remission was accompanied by a significant decline in the eGFR (from 99.8 to 86.2mL/min, P<0.01). Conversely, in patients with NFoma, the postoperative eGFR did not change significantly (from 75.1 to 81.9mL/min, P=0.12). Among the acromegalic patients, the postoperative decreases in the eGFR were more prominent in patients with a preoperatively high or normal vs low eGFR.

CONCLUSIONS

Our data demonstrated a significant post-surgical eGFR decrease in patients with acromegaly, but not in patients with NFomas. This change in the eGFR was reversible in acromegalic patients with a high/normal preoperative eGFR, but not in those with a low preoperative eGFR. This suggests that the reversible pathophysiological change in some patients is functional but not organic.

Serum cystatin is a useful marker for the diagnosis of acute kidney injury in critically ill children: prospective cohort study

Background

Acute kidney injury (AKI) has been associated with high morbidity and mortality rates among critically ill children. Cystatin C is a protease inhibitor, and studies have shown that it is a promising marker for the early diagnosis of AKI. Our goal in this study was to assess whether serum cystatin C could serve as an accurate marker for the diagnosis of AKI.

Methods

This prospective study was undertaken in the pediatric intensive care unit at King Abdulaziz University Hospital. Serum creatinine and serum cystatin C levels were both measured in patients on admission (0 h) and at 6, 12, and 24 h after admission. AKI was diagnosed according to the modified pRIFLE criteria. Receiver operating characteristic (ROC) curve analysis was performed to assess the utility of serum cystatin C for diagnosing AKI.

Results

A total of 62 patients were enrolled in this study, and 32 were diagnosed with AKI according to the modified pRIFLE criteria (51.4 %). The area under the ROC curve for serum cystatin indicated that it was a good marker for the diagnosis of AKI at 0, 6, 12 and 24 h, with sensitivities of 78, 94, 94 and 83 %, respectively. However, the specificities of serum cystatin C at 0, 6, 12, and 24 h were 57, 57, 60 and 50 %, respectively. The optimal cutoff value was 0.645 mg/L. The area under the ROC for serum creatinine showed sensitivities of 50, 65.4, 69.2 and 57.7 % and specificities of 67.7, 70, 60 and 70 % at 0, 6, 12 and 24 h, respectively. The optimal cutoff value for serum creatinine was 30 μmol/l. Comparisons of ROC curves revealed that serum cystatin C was superior to serum creatinine for the diagnosis of AKI at 12 h (p = 0.03), but no differences were detected at 0, 6 or 24 h.

Conclusion

Serum cystatin is a sensitive, but not a specific, marker for the diagnosis of AKI in critically ill children.

Renal dysfunction can be a common complication in patients with myotonic dystrophy 1

Although renal failure can be a life-threatening complication even in neuromuscular disorders (NMDs), renal dysfunction is easily overlooked because muscle atrophy decreases the serum creatinine level. Renal function was retrospectively assessed using cystatin C (CysC) in various NMDs to clarify the differences among diseases. As is in the general population, age was correlated to CysC, and female patients showed lower CysC levels. Although elevated CysC was frequent in myotonic dystrophy 1 (DM1: MIM 160900) and motor neuron disorders, an inter-disease comparison by sex adjusted for age showed that only DM1 had a higher CysC compared to other diseases. Multivariate linear regression with the stepwise method also suggested that the number of CTG repeats had an impact on CysC levels. In two autopsy DM1 cases, nephrosclerotic changes were observed even though they were in their forties. These facts suggested a disease-specific pathomechanism for renal dysfunction in DM1. Although further study is required, renal function should be carefully monitored in patients with DM1.

Estimated GFR is biased by non-traditional cardiovascular risk factors

BACKGROUND

Estimated glomerular filtration rate (eGFR) based on either cystatin C or creatinine performs similarly in estimating measured GFR, but associate differently with cardiovascular disease (CVD) and mortality. This could be due to confounding by non-GFR-related traits associated with cystatin C and creatinine levels. We investigated non-GFR-related associations between eGFR and two types of nontraditional risk factors for CVD and death: L-arginine/dimethylarginine metabolism and insulin resistance.

METHODS

GFR was measured via iohexol clearance in a cross-sectional study of 1,624 middle-aged persons from the general population without CVD, diabetes or chronic kidney disease. The dimethylarginines were measured using liquid chromatography tandem mass spectrometry (LC-MSMS). Insulin resistance was determined by the homeostasis model assessment (HOMA-IR).

RESULTS

Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), the L-arginine/ADMA ratio and insulin resistance were associated with creatinine-based eGFR after accounting for measured GFR in multivariable adjusted analyses. The cystatin C-based eGFR showed a similar residual association with SDMA; an oppositely directed, borderline significant association with ADMA; and a stronger residual association with insulin resistance compared with eGFR based on creatinine.

CONCLUSION

Both creatinine- and cystatin C-based eGFR are influenced by nontraditional risk factors, which may bias risk prediction by eGFR in longitudinal studies.