Glomerular and Tubular Functions in Children and Adults with Transfusion-Dependent Thalassemia

Evaluating Renal Glomerular Function in Beta-Thalassemia Patients Receiving Deferasirox Using Serum Cystatin-C and Creatinine: A Cross-Sectional Study

The introduction of iron chelation therapies has notably extended the life expectancy of individuals with β-thalassemia, thereby presenting the potential for the emergence of new complications such as renal impairments. Because creatinine levels are influenced by body mass and nutritional status, there is a need for a more sensitive and reliable indicator of renal glomerular function. Here, we studied 27 individuals with β-thalassemia undergoing iron chelation therapy with Deferasirox. The serum levels of cystatin-C, a highly sensitive biomarker for renal dysfunction, were quantified using an immunoturbidimetry assay. We subsequently analyzed the data, examining correlations with other clinical and laboratory parameters. We determined the glomerular filtration rate (GFR) using both creatinine and cystatin-C-based equations. According to the creatinine equation, none of the patients had a reduced GFR, but 59% exhibited a reduced GFR value based on the cystatin-C equation. Patients with elevated cystatin-C levels exhibited higher serum creatinine (p < 0.001) and BUN (p = 0.002) and lower ferritin (p = 0.023) levels. Our study revealed a positive correlation between cystatin-C and creatinine (p = 0.002), BUN (p = 0.018), and BMI (p = 0.046), while a negative correlation was observed with ferritin (p = 0.006). We found no correlation between cystatin-C and age, weight, height, Deferasirox therapy duration, or blood transfusion frequency. Multiple regression analysis indicated that ferritin (p = 0.003) significantly affected cystatin-C levels, while other variables did not. Additionally, no independent variables had a significant impact on creatinine levels. Since there is a high likelihood of subclinical renal impairment in these patients, we recommend regular monitoring of serum cystatin-C as a screening tool.

Iron and ferroptosis in kidney disease: molecular and metabolic mechanisms

Maintaining iron homeostasis is necessary for kidney functioning. There is more and more research indicating that kidney disease is often caused by iron imbalance. Over the past decade, ferroptosis' role in mediating the development and progression of renal disorders, such as acute kidney injury (renal ischemia-reperfusion injury, drug-induced acute kidney injury, severe acute pancreatitis induced acute kidney injury and sepsis-associated acute kidney injury), chronic kidney disease (diabetic nephropathy, renal fibrosis, autosomal dominant polycystic kidney disease) and renal cell carcinoma, has come into focus. Thus, knowing kidney iron metabolism and ferroptosis regulation may enhance disease therapy. In this review, we discuss the metabolic and molecular mechanisms of iron signaling and ferroptosis in kidney disease. We also explore the possible targets of ferroptosis in the therapy of renal illness, as well as their existing limitations and future strategies.

Existing Tubular Injury in β-Thalassemia Major Patients Receiving Iron Chelating Agents with Normal Creatinine Level in East Java, Indonesia

Patients suffering from thalassemia are recipients of routine transfusions leading to hemosiderosis. Taking iron chelating agents is mandatory. Several studies have shown different results regarding the occurrence of kidney complications in thalassemia patients who received iron-chelating agents. In this study, we were looking for kidney complications by examining human NAG urine/serum and NGAL urine/serum in thalassemia community in East Java community. The study was conducted cross-sectionally in the thalassemia community in East Java with a total sample of 91 patients aged 13-48 years. All thalassemia patients filled in demographic data, transfusion routines, duration of taking iron chelating agents, and length of time diagnosed with thalassemia. Laboratory tests included routine blood tests for ferritin, ureum, serum creatinine, human NAG urine or serum, and human NGAL urine or serum. Comparison tests (t-test, Mann-Whitney, and ANOVA, Kruskal-Wallis) were conducted to see if there were significant differences in the levels of human NAG urine and human NGAL urine serum based on age, sex, blood group, duration of transfusion, routine of transfusion, duration of taking iron chelating agents, and types of iron chelating drugs. Multivariate analysis was conducted to see whether some of these categories were related to abnormalities in human NAG urine or serum and human NGAL urine or serum. All 91 patients had normal creatinine values, yet some had abnormal serum NAG. There is a significant difference in urine human NAG and urine human NGAL levels at ages over 23 years (p = 0.05 and p = 0.01). Significant differences in human NGAL serum were also found in working and student patients (p = 0.028). Serum NGAL also differed in those taking deferasirox (p = 0.030) and significantly different human NGAL urine was also found in iron overload status (Ferritin ≥ 1000 ng.ml) (p = 0.006). There is no difference between human NAG urine/serum and human NGAL urine/serum based on sex, body mass index, blood type, hemoglobin less than 10 g/dl, routine transfusion once a month, duration of using iron chelation for more than 10 years, or splenomegaly status (splenomegaly, splenectomy, or no splenomegaly). The multivariate logistic regression results showed that age above 23 was a factor associated with abnormal urine human NAG levels (aOR = 3.79, 95% CI = 1.08-13.28). Students (aOR = 4.89, 95% CI = 1.48-16.16) with ages above 23 years (aOR = 3.69, 95% CI = 1.09-12.43) showed higher risk for an abnormal serum human NGAL levels. Patients with beta-thalassemia major exhibit noticeable tubular damage. Further research is encouraged to determine other factors behind tubular damage in the thalassemia community, particularly in Indonesia.

Renal function in β-thalassemia major patients treated with two different iron-chelation regimes

BACKGROUND

Renal injury in transfusion dependent β thalassemia patients (TDT) has been attributed to iron overload, chronic anemia and iron-chelation therapy (ICT) toxicity. We studied renal function in TDT patients treated with two different ICT regimes.

PATIENTS AND METHODS

We studied 36 TDT patients: 26 received deferasirox (DFX) and 10 were treated with deferoxamine (DFO) +/- deferiprone (DFP).

RESULTS

Increased uNAG was found in 30% of the DFX group vs. 10% of the DFO+/-DFP group, the mean uNAG level in the DFX group was significantly higher than in the DFO+/-DFP group, (P < 0.05). A moderate negative correlation was found between uNAG levels and mean serum ferritin for the prior 10 years (P = 0.03), more pronounced for the DFO+/-DFP group. Twenty nine patients had had their renal function evaluated 10 years earlier; eGFR significantly declined in patients switched to DFX (P = 0.0093) but not in patients who continued DFO+/-DFP.

CONCLUSIONS

A high prevalence of renal tubular damage was observed in our TDT patients, particularly those treated with DFX; uNAG was negatively associated with mean 10-year serum ferritin, suggesting ICT's involvement in tubular injury. A significant decline in eGFR compared to a decade earlier was observed only in patients currently treated with DFX. Strict follow-up of renal function in TDT patients is warranted.

Comparing different markers of tubular dysfunction in transfusion-dependent thalassemia patients

BACKGROUND

Renal tubular dysfunction was reported in transfusion-dependent thalassemia (TDT) patients and ranges from mild to severe. The objectives of our study were identification of the best marker of early renal tubular dysfunction in TDT patients among the three most commonly used urinary biomarkers, named neutrophil gelatinase-associated lipocalin (NGAL), retinol-binding protein (RBP) and N-acetyl-D-glucosaminidase (NAG) and correlation of these biomarkers with different patient variables.

METHODOLOGY

Sixty-one TDT patients and another 62 healthy children were enrolled in a cross-sectional study. Morning urine samples were taken for measurement of calcium, phosphorus, creatinine, microalbumin and markers of tubular dysfunction (NGAL, NAG and RBP). Urine NGAL/creatinine (UrNGAL/Cr), urine NAG/creatinine (UrNAG/Cr) and urine RBP/creatinine (UrRBP/Cr) ratios were used for accuracy. Patients were classified into 2 groups: group A, with tubular dysfunction and group b, without tubular dysfunction.

RESULTS

Group A showed statistically significant higher UrNGAL/Cr (p < 0.001), UrRBP/Cr (p < 0.001) and UrNAG/Cr (p <0.001) than group B. In group A, microalbuminuria was detected only in 7 patients (28%) while it was detected in 12 patients (33.3%) in group B. By using ROC curve analysis, the diagnostic cutoff values for UrNGAL/Cr, UrRBP/Cr and UrNAG/Cr were 3713.38, 1614.85 and 56.56 ng/g, respectively. We found a statistically significant superiority of UrNGAL/Cr over UrRBP/Cr (p < 0.001) and UrRBP/Cr over UrNAG/Cr (p < 0.001).

CONCLUSION

Evaluation of UrNGAL/Cr, UrRBP/Cr and UrNAG/Cr could early discriminate tubular dysfunction TDT patients from those with normal tubular function. UrNGAL/Cr is more accurate in early detection of tubular dysfunction when compared with the other two biomarkers.

β2-Microglobulin, Neutrophil Gelatinase-Associated Lipocalin, and Endocan Values in Evaluating Renal Functions in Patients with β-Thalassemia Major

Chronic anemia, transfusion-associated iron deposition, and chelating agents lead to renal impairment in β-thalassemia (β-thal) patients. The present study aimed to determine the most reliable and practical method in assessing and predicting renal injury in β-thal major (β-TM) patients. Therefore, we assessed the predictive values of urine β2-microglobulin (β2-MG) and neutrophil gelatinase-associated lipocalin (NGAL) levels, their ratios to urine creatinine, and serum endocan level. Sixty β-TM patients and 30 healthy controls were included. Renal functions of the patients and controls were evaluated by means of urine protein/creatinine ratio, urine β2-MG, urine NGAL, and serum endocan level. The β-TM and control groups were comparable in terms of the demographic characteristics. Of the β-TM patients, 26.7% had glomerular hyperfiltration and 41.7% had proteinuria. Compared with the control group, the β-TM group had significantly higher levels of urine protein/creatinine, urine β2-MG, urine β2-MG/creatinine, urine NGAL, urine NGAL/creatinine, and serum endocan. These parameters did not differ between the chelating agent subgroups in the patient group. Urine β2-MG/creatinine and NGAL/creatinine ratios were the parameters with high specificity in predicting proteinuria. There were significant correlations of urine β2-MG, urine NGAL, and serum endocan levels with serum ferritin concentration. Urine β2-MG/creatinine, NGAL/creatinine, and protein/creatinine ratios were correlated with each other in the patient group. Positive correlations of urine β2-MG, urine NGAL, and serum endocan levels with serum ferritin concentration indicated that iron deposition was associated with endothelial damage and renal injury.

The multifaceted role of iron in renal health and disease

Iron is an essential element that is indispensable for life. The delicate physiological body iron balance is maintained by both systemic and cellular regulatory mechanisms. The iron-regulatory hormone hepcidin assures maintenance of adequate systemic iron levels and is regulated by circulating and stored iron levels, inflammation and erythropoiesis. The kidney has an important role in preventing iron loss from the body by means of reabsorption. Cellular iron levels are dependent on iron import, storage, utilization and export, which are mainly regulated by the iron response element-iron regulatory protein (IRE-IRP) system. In the kidney, iron transport mechanisms independent of the IRE-IRP system have been identified, suggesting additional mechanisms for iron handling in this organ. Yet, knowledge gaps on renal iron handling remain in terms of redundancy in transport mechanisms, the roles of the different tubular segments and related regulatory processes. Disturbances in cellular and systemic iron balance are recognized as causes and consequences of kidney injury. Consequently, iron metabolism has become a focus for novel therapeutic interventions for acute kidney injury and chronic kidney disease, which has fuelled interest in the molecular mechanisms of renal iron handling and renal injury, as well as the complex dynamics between systemic and local cellular iron regulation.

Iron handling by the human kidney: glomerular filtration and tubular reabsorption both contribute to urinary iron excretion

In physiological conditions, circulating iron can be filtered by the glomerulus and is almost completely reabsorbed by the tubular epithelium to prevent urinary iron wasting. Increased urinary iron concentrations have been associated with renal injury. However, it is not clear whether increased urinary iron concentrations in patients are the result of increased glomerular iron filtration and/or insufficient tubular iron reabsorption and if these processes contribute to renal injury. We measured plasma and urine iron parameters and urinary tubular injury markers in healthy human subjects ( n = 20), patients with systemic iron overload ( n = 20), and patients with renal tubular dysfunction ( n = 18). Urinary iron excretion parameters were increased in both patients with systemic iron overload and tubular dysfunction, whereas plasma iron parameters were only increased in patients with systemic iron overload. In patients with systemic iron overload, increased urinary iron levels were associated with elevated circulating iron, as indicated by transferrin saturation (TSAT), and increased body iron, as suggested by plasma ferritin concentrations. In patients with tubular dysfunction, enhanced urinary iron and transferrin excretion were associated with distal tubular injury as indicated by increased urinary glutathione S-transferase pi 1-1 (GSTP1-1) excretion. In systemic iron overload, elevated urinary iron and transferrin levels were associated with increased injury to proximal tubules, indicated by increased urinary kidney injury marker 1 (KIM-1) excretion. Our explorative study demonstrates that both glomerular filtration of elevated plasma iron levels and insufficient tubular iron reabsorption could increase urinary iron excretion and cause renal injury.