Urinary α-GST and π-GST for prediction of dialysis requirement or in-hospital death in established acute kidney injury

Biomarkers in Contrast-Induced Nephropathy: Advances in Early Detection, Risk Assessment, and Prevention Strategies

Contrast-induced nephropathy (CIN) represents a significant complication associated with the use of iodinated contrast media (ICM), especially in individuals with preexisting renal impairment. The pathophysiology of CIN encompasses oxidative stress, inflammation, endothelial dysfunction, and hemodynamic disturbances, resulting in acute kidney injury (AKI). Early detection is essential for effective management; however, conventional markers like serum creatinine (sCr) and estimated glomerular filtration rate (eGFR) exhibit limitations in sensitivity and timeliness. This review emphasizes the increasing significance of novel biomarkers in enhancing early detection and risk stratification of contrast-induced nephropathy (CIN). Recent advancements in artificial intelligence and computational analytics have improved the predictive capabilities of these biomarkers, enabling personalized risk assessment and precision medicine strategies. Additionally, we discuss mitigation strategies, including hydration protocols, pharmacological interventions, and procedural modifications, aimed at reducing CIN incidence. Incorporating biomarker-driven assessments into clinical decision-making can enhance patient management and outcomes. Future research must prioritize the standardization of biomarker assays, the validation of predictive models across diverse patient populations, and the exploration of novel therapeutic targets. Utilizing advancements in biomarkers and risk mitigation strategies allows clinicians to improve the safety of contrast-enhanced imaging and reduce the likelihood of renal injury.

Biomarkers in Contrast-Induced Acute Kidney Injury: Towards A New Perspective

Contrast-Induced Acute Kidney Injury (CI-AKI) remains a frequent iatrogenic condition since radiological procedures using intra-vascular iodinated contrast media (CM) are being widely administered for diagnostic and therapeutic purposes. Despite the improvement of the medical healthcare system worldwide, CI-AKI is still associated with direct short-term and indirect long-term outcomes including increased morbidity and mortality, especially in patients with underlying pre-existing renal function impairment, cardiovascular disease, or diabetes that could rapidly progress into Chronic Kidney Disease. Although the RIFLE (Risk, Injury, Failure, Loss, End-Stage Kidney Disease), AKIN (Acute Kidney Injury Network), and KDIGO (Kidney Disease Improving Global Outcomes) clinical criteria and recommendation guidelines are based on traditional "gold standard" biomarkers known as serum creatinine, glomerular filtration rate, and urinary output, new reliable serum and urinary biomarkers are still needed for an effective unified diagnostic strategy for AKI. Starting from previous and recent publications on the benefits and limitations of validated biomarkers responding to kidney injury, glomerular filtration, and inflammation among others, this review unravels the role of new emerging biomarkers used alone or in combination as reliable tools for early diagnosis and prognosis of CI-AKI, taking into account patients and procedures-risk factors towards a new clinical perspective.

Urinary Biomarkers α-GST and π-GST for Evaluation and Monitoring in Living and Deceased Donor Kidney Grafts

The aim of this study was to analyze the value of urine α- and π-GST in monitoring and predicting kidney graft function following transplantation. In addition, urine samples from corresponding organ donors was analyzed and compared with graft function after organ donation from brain-dead and living donors. Urine samples from brain-dead (n = 30) and living related (n = 50) donors and their corresponding recipients were analyzed before and after kidney transplantation. Urine α- and π-GST values were measured. Kidney recipients were grouped into patients with acute graft rejection (AGR), calcineurin inhibitor toxicity (CNI), and delayed graft function (DGF), and compared to those with unimpaired graft function. Urinary π-GST revealed significant differences in deceased kidney donor recipients with episodes of AGR or DGF at day one after transplantation (p = 0.0023 and p = 0.036, respectively). High π-GST values at postoperative day 1 (cutoff: >21.4 ng/mg urine creatinine (uCrea) or >18.3 ng/mg uCrea for AGR or DGF, respectively) distinguished between rejection and no rejection (sensitivity, 100%; specificity, 66.6%) as well as between DGF and normal-functioning grafts (sensitivity, 100%; specificity, 62.6%). In living donor recipients, urine levels of α- and π-GST were about 10 times lower than in deceased donor recipients. In deceased donors with impaired graft function in corresponding recipients, urinary α- and π-GST were elevated. α-GST values >33.97 ng/mg uCrea were indicative of AGR with a sensitivity and specificity of 77.7% and 100%, respectively. In deceased donor kidney transplantation, evaluation of urinary α- and π-GST seems to predict different events that deteriorate graft function. To elucidate the potential advantages of such biomarkers, further analysis is warranted.

Sensitivity of glutathione S-transferases to high doses of acrylamide in albino wistar rats: Affinity purification, biochemical characterization and expression analysis

The main objectives of this study were to purify the glutathione S-transfereses (GSTs) and assess the effect of high doses of acrylamide (ACR) on male albino Wistar rat liver, kidney, testis and bran GST activities, and expression analysis of GST. ACR (50 mg/300 ml) was ingested for 40 days (20 doses) in drinking water on alternative days, on 40 day post ingestion the control and treated tissues were collected for GST purification by affinity column and biochemical characterization of GSTs by substrate specificities, and GST expression by immuno dot blots. In the analysis of the purified GSTs, we observed that liver GSTs were resolved in to three bands known as Yc, Yb and Ya; kidney GSTs were resolved in to two bands known as Yc and Ya; testis and brain GSTs were resolved as four bands known as Yc, Yb, Yβ and Yδ on 12.5% sodium dodecyl sulfate polyacrylamide gel (SDS PAGE). In the analysis of biochemical characterization, we observed a significant decrease (p < 0.05) in the specific activities of liver GST isoforms with the substrates 1-chloro 2,4-dinitrobenzene (CDNB), bromosulfophthalein (BSP), p-nitrophenyl acetate (pNPA), p-nitrobenzyl chloride (pNBC) and cumene hydroperoxide (CHP), but showed no activity with ethacrynic acid (ECA) and significant decrease (p < 0.05) in the specific activities of kidney GST isoforms with the substrates CDNB, pNPA, pNBC and CHP, but showed no activity with BSP and ECA, and a significant decrease (p < 0.05) in the specific activities of testis and brain GST isoforms with the substrates CDNB, BSP, pNPA, pNBC, ECA and CHP. In the analysis of immuno dot blots, we observed a decreased expression of liver, kidney, testis and brain GSTs. Through the affinity purification and biochemical characterization, we observed a tissue specific distribution of GSTs that is liver GSTs possess Yc, Yb and Ya sub units known as alpha (α) and mu (μ) class GSTs; kidney GSTs possess Yc and Ya sub units known as (α) alpha class GST; testis and brain GSTs possess Yc, Yb, Yβ and Yδ sub units known as alpha (α), mu (μ) and pi (π) class GSTs. Purification studies, biochemical characterization and immuno dot blot analysis were revealed the GSTs were sensitive to high doses of ACR and the high level exposure to ACR cause the damage of detoxification function of GST due to decreased expression and hence lead to cellular dysfunction of vital organs.

Urinary π-glutathione S-transferase Predicts Advanced Acute Kidney Injury Following Cardiovascular Surgery

Urinary biomarkers augment the diagnosis of acute kidney injury (AKI), with AKI after cardiovascular surgeries being a prototype of prognosis scenario. Glutathione S-transferases (GST) were evaluated as biomarkers of AKI. Urine samples were collected in 141 cardiovascular surgical patients and analyzed for urinary alpha-(α-) and pi-(π-) GSTs. The outcomes of advanced AKI (KDIGO stage 2, 3) and all-cause in-patient mortality, as composite outcome, were recorded. Areas under the receiver operator characteristic (ROC) curves and multivariate generalized additive model (GAM) were applied to predict outcomes. Thirty-eight (26.9%) patients had AKI, while 12 (8.5%) were with advanced AKI. Urinary π-GST differentiated patients with/without advanced AKI or composite outcome after surgery (p < 0.05 by generalized estimating equation). Urinary π-GST predicted advanced AKI at 3 hrs post-surgery (p = 0.033) and composite outcome (p = 0.009), while the corresponding ROC curve had AUC of 0.784 and 0.783. Using GAM, the cutoff value of 14.7 μg/L for π-GST showed the best performance to predict composite outcome. The addition of π-GST to the SOFA score improved risk stratification (total net reclassification index = 0.47). Thus, urinary π-GST levels predict advanced AKI or hospital mortality after cardiovascular surgery and improve in SOFA outcome assessment specific to AKI.

Detection and adequacy evaluation of erythrocyte glutathione transferase on levels of circulating toxins in hemodialysis patients

To explore detection and adequacy evaluation of erythrocyte glutathione S transferase (GST) on levels of circulating toxins in hemodialysis patients in Qinhuangdao region in China, this study divided 84 cases of long-term, end-stage hemodialysis patients into 2 groups: one group of 33 cases of adequate hemodialysis (spKt/V ≥ 1.3) and another group of 51 cases of inadequate hemodialysis (spKt/V < 1.3), according to the urea index value of the unit chamber model (spKt/V). Another 50 cases of subjects found healthy by a physical examination were taken as the control group, and the differences in the related clinical and biochemical indexes of the 3 groups were compared and analyzed. The levels of GST, creatinine, high sensitivity C-reactive protein (hs-CRP), transferrin saturation (TSAT), parathyroid hormone (PTH), interleukin-2,6,8 (IL-2,6,8) and tumor necrosis factor-a (TNF-a) in the hemodialysis group were significantly higher than those in the control group (P < 0.05), and GST, IL-2, 6, 8, and TNF-a levels in the inadequate hemodialysis group were significantly higher than in the adequate hemodialysis group (P < 0.05). Pearson's relevant analysis showed that the levels of GST and spKt/V, IL-2, IL-6, IL-8, and TNF-a have a positive correlation (P < 0.05), and they have no correlation with levels of creatinine, hs-CRP, TSAT, and PHT (P > 0.05). There were 23 patients with levels of spKt/V ≥ 1.3 after adjusting the dialysis solution for 51 cases of inadequate hemodialysis patients, and the GST level after the adjustment was significantly lower than that before the adjustment, but still higher than that in the adequate dialysis group. This concludes that the maintenance of hemodialysis in patients has certain relevance on spKt/V and associated inflammatory factors. Through the study, it can be determined that GST can effectively respond to adequate hemodialysis, which has a guiding significance on adjusting the blood dialysis solution in clinical practice.

Urinary alpha- and pi-glutathione s-transferases in adult patients with type 1 diabetes

Background/Aims

Glutathione S-transferases (GSTs) are cytosolic enzymes excreted from renal tubules following tubular damage. α-GST primarily originates from proximal tubules, while π-GST from distal tubules and collecting ducts. We investigated if GST levels are associated with renal function in patients with type 1 diabetes.

Methods

We conducted a cross-sectional study including 189 Caucasian patients with type 1 diabetes and 16 nondiabetic controls. α- and π-GST were measured by ELISA and reported as GST/urinary creatinine excretion (μg/mmol).

Results

The subjects were 53 ± 14 years old, 66 (35%) were female and the estimated glomerular filtration rate was 85 ± 29 ml/min/1.73 m². Normo- (<30 mg/24 h), micro- (30-299 mg/24 h) and macroalbuminuria (≥300 mg/24 h) was present in 57, 61 and 71 patients, respectively. α- and π-GST/creatinine ratios in controls versus all patients were 0.07 (0-0.3) and 0.11 (0-0.8) μg/mmol versus 0.05 (0-2.3) and 0.16 (0-4.9) μg/mmol (p ≥ 0.16; adjusted for age and gender, p ≥ 0.18). The α-GST/creatinine ratio positively correlated with female gender (p = 0.04), while the π-GST/creatinine ratio was associated with age and female gender (p ≤ 0.016). Comparing normo-, micro- and macroalbuminuric patients, α- and π-GST levels were similar (p = 0.10; adjusted p = 0.11). Neither α- nor π-GST levels were significantly associated with renal function (p ≥ 0.34).

Conclusion

α- and π-GST/creatinine ratios were similar among controls and patients with type 1 diabetes. In addition, we did not find associations with albuminuria degree or level of renal function. The significance of increased or decreased excretion of α- and π-GST among patients with diabetes needs to be clarified.

Time of injury affects urinary biomarker predictive values for acute kidney injury in critically ill, non-septic patients

Background

The predictive value of acute kidney injury (AKI) urinary biomarkers may depend on the time interval following tubular injury, thereby explaining in part the heterogeneous performance of these markers that has been reported in the literature. We studied the influence of timing on the predictive values of tubular proteins, measured before the rise of serum creatinine (SCr) in critically ill, non-septic patients.

Methods

Seven hundred adult critically ill patients were prospectively included for urine measurements at four time-points prior to the rise in serum creatinine (T = 0, -16, -20 and -24 h). Patients with sepsis and or AKI at ICU entry were excluded. The urinary excretion of the proteins, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), which are up-regulated in the distal and proximal tubules, respectively, were measured as well as the constitutive cytoplasmatic enzymes, π- and α-glutathione-S-transferase (GST), which are released by the distal and proximal tubules, respectively.

Results

Five hundred and forty-three subjects were eligible for further analyses; however, 49 developed AKI in the first 48 h. Both NGAL (P = 0.001 at T = -24 vs. non-AKI patients) and KIM-1 (P < 0.0001 at T = 0 vs. non-AKI patients) concentrations gradually increased until AKI diagnosis, whereas π- and α-GST peaked at T = -24 before AKI (P = 0.006 and P = 0.002, respectively vs. non-AKI patients) and showed a rapid decline afterwards. The predictive values at T = -24 prior to AKI were modest for π- and α-GST, whereas NGAL sufficiently predicted AKI at T = -24 and its predictive power improved as the time interval to AKI presentation decreased (area under the receiver operating characteristic curve; AUC = 0.79, P < 0.0001). KIM-1 was a good discriminator at T = 0 only (AUC = 0.73, P < 0.0001).

Conclusions

NGAL, KIM-1, pi- and alpha-GST displayed unique and mutually incomparable time dependent characteristics during the development of non-sepsis related AKI. Therefore, the time-relationship between the biomarker measurements and the injurious event influences the individual test results.

Performance of urinary liver-type fatty acid-binding protein in acute kidney injury: a meta-analysis

BACKGROUND

Urinary liver-type fatty acid-binding protein (L-FABP) is a proximal tubular injury candidate biomarker for early detection of acute kidney injury (AKI), with variable performance characteristics depending on clinical settings.

STUDY DESIGN

Meta-analysis of diagnostic test studies assessing the performance of urinary L-FABP in AKI.

SETTING & POPULATION

Literature search in MEDLINE, EMBASE, Scopus, Google Scholar, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov using search terms "liver-type fatty acid-binding protein" and "L-FABP."

SELECTION CRITERIA FOR STUDIES

Studies of humans investigating the performance characteristics of urinary L-FABP for the early diagnosis of AKI and AKI-related outcomes, including dialysis requirement and mortality.

PREDICTOR

Urinary L-FABP.

OUTCOMES

Diagnosis of AKI, dialysis requirement, and in-hospital death.

RESULTS

15 prospective cohort and 2 case-control studies were identified. Only 7 cohort studies could be meta-analyzed. The estimated sensitivity of urinary L-FABP level for the diagnosis of AKI was 74.5% (95% CI, 60.4%-84.8%), and specificity was 77.6% (95% CI, 61.5%-88.2%). The estimated sensitivity of urinary L-FABP level for predicting dialysis requirement was 69.1% (95% CI, 34.6%-90.5%), and specificity was 42.7% (95% CI, 3.1%-94.5%); for in-hospital mortality, sensitivity and specificity were 93.2% (95% CI, 66.2%-99.0%) and 78.8% (95% CI, 27.0%-97.4%), respectively.

LIMITATIONS

Paucity and low quality of studies, different clinical settings, and variable definitions of AKI.

CONCLUSIONS

Although urinary L-FABP may be a promising biomarker for early detection of AKI and prediction of dialysis requirement and in-hospital mortality, its potential value needs to be validated in large studies and across a broader spectrum of clinical settings.

Kidney Injury Biomarkers in Hypertensive, Diabetic, and Nephropathy Rat Models Treated with Contrast Media

Contrast-induced nephropathy (CIN) refers to a decline in renal function following exposure to iodinated contrast media (CM). The present study was initiated to explore the role of known human risk factors (spontaneous hypertension, diabetes, protein-losing nephropathy) on CIN development in rodent models and to determine the effect of CM administration on kidney injury biomarkers in the face of preexisting kidney injury. Spontaneously hypertensive rats (hypertension), streptozotocin-treated Sprague Dawley rats (diabetes), and Dahl salt-sensitive rats (protein-losing nephropathy) were given single intravenous injections of the nonionic, low osmolar contrast medium, iohexol. Blood urea nitrogen (BUN), serum creatinine (sCr), and urinary biomarkers; albumin, lipocalin 2 (Lcn-2), osteopontin (Opn), kidney injury molecule 1 (Kim-1), renal papillary antigen 1 (Rpa-1), α-glutathione S-transferase (α-Gst), µ-glutathione S-transferase (µ-Gst), and beta-2 microglobulin (β2m) were measured in disease models and appropriate controls to determine the response of these biomarkers to CM administration. Each disease model produced elevated biomarkers of kidney injury without CM. Preexisting histopathology was exacerbated by CM but little or no significant increases in biomarkers were observed. When 1.5-fold or greater sCr increases from pre-CM were used to define true positives, receiver–operating characteristic curve analysis of biomarker performance showed sCr was the best predictor of CIN across disease models. β2m, Lcn-2, and BUN were the best predictors of histopathology defined kidney injury.