Transferrina y ceruloplasmina en orina de pacientes con lupus eritematoso sistémico. ¿Son útiles para diferenciar pacientes con nefritis lúpica? / Utility of urinary transferrin and ceruloplasmin in patients with systemic lupus erythematosus for differentiating patients with lupus nephritis

ANTECEDENTES Y OBJETIVO: El diagnóstico de la nefritis lúpica (NL) se suele hacer con la biopsia renal, que es una técnica invasiva que conlleva múltiples riesgos. Por lo tanto, han surgido diferentes biomarcadores en orina como posibles alternativas para el diagnóstico de la NL. Sin embargo, los estudios de biomarcadores en orina de pacientes latinoamericanos con lupus eritematoso sistémico (LES) son escasos; por lo tanto, el objetivo del presente estudio fue determinar el valor diagnóstico de la transferrina (TF) y la ceruloplasmina (CP) en orina, para diferenciar los pacientes que tienen compromiso renal de aquellos que no. MATERIALES Y MÉTODOS: Se incluyeron prospectivamente pacientes con diagnóstico de LES de acuerdo a los criterios del American College of Rheumatology (ACR). Se excluyeron los pacientes con otra enfermedad autoinmune concomitante, infección activa (de vías urinarias o sistémica), terapia de reemplazo renal, infección por virus de la inmunodeficiencia humana y embarazo. A cada paciente se le tomó una muestra de orina. El diagnóstico de NL se realizó mediante los criterios ACR para la definición de NL. La actividad y la cronicidad de la NL en la biopsia renal fueron medidas con el índice de Austin. La determinación de los niveles de TF y CP se realizó con kits comerciales de ELISA. Se utilizó la prueba t de Student y la prueba U de Mann Whitney para comparar los datos. Para determinar las asociaciones entre las variables se utilizaron los coeficientes de correlación de Spearman. Por último, se construyeron curvas ROC. RESULTADOS: Se incluyeron 120 pacientes con LES, de los cuales el 85% fueron de sexo femenino. El 76% fueron de raza mestiza. Presentaron una edad media de 32,8+/-12,1años, y una media del SLEDAI de 8,4+/-8,9, y un 64% presentaron compromiso renal. Los niveles de ambos biomarcadores fueron significativamente mayores en pacientes con NL comparados con aquellos sin NL. De igual manera, los niveles de ambos biomarcadores fueron significativamente mayores en pacientes con NL activa comparados con aquellos con NL inactiva. Los niveles de TF fueron significativamente mayores en pacientes afro-latinoamericanos. Por otro lado, las concentraciones de TF se correlacionaron con el SLEDAI y el rango de proteinuria, y las concentraciones de TF y CP se correlacionaron entre sí. Las curvas ROC para ambos biomarcadores mostraron un buen valor diagnóstico de la NL. CONCLUSIONES: En nuestra cohorte de pacientes con LES encontramos que la TF y la CP son potenciales biomarcadores para el diagnóstico de la NL e, incluso, de la actividad de la NL

BACKGROUND AND OBJECTIVE: Diagnosis of lupus nephritis (LN) is usually based on renal biopsy, which is an invasive technique that involves multiple risks. Therefore, different biomarkers have emerged as alternatives for the diagnosis of LN. Nonetheless, studies regarding urinary biomarkers in Latin American patients are limited. The objective of this study was to assess the diagnostic value of urinary transferrin and ceruloplasmin to differentiate patients who have renal involvement from those who do not. MATERIALS AND METHODS: Systemic lupus erythematosus (SLE) patients that met the revised American College of Rheumatology (ACR) classification criteria were recruited. Patients with another autoimmune disease, active infection (urinary tract or systemic infection), renal replacement therapy, human immunodeficiency virus infection or pregnancy were excluded. A urine sample was collected from each patient. LN was diagnosed according to ACR criteria. The activity and chronicity of LN were measured using the Austin indices. Urinary transferrin and ceruloplasmin levels were measured using commercial enzyme-linked immunosorbent assay (ELISA) kits. Mann-Whitney U test and Student's t-test were used to compare data. Spearman's rank correlation was used to determine associations. Lastly, receiver operating characteristic (ROC) curves were created. RESULTS: The study involved 120 SLE patients. In all, 85% were female, 76% mestizo, the mean age was 32.8+/-12.1years and mean systemic lupus erythematosus disease activity index (SLEDAI) was 8.4+/-8.9; 64% had renal involvement. Urinary levels of the two biomarkers were significantly higher in patients with LN compared to those without LN. Similarly, urinary levels of both biomarkers were significantly higher in patients with active LN compared to those with inactive LN. Furthermore, urinary transferrin levels were significantly higher in Afro-Latin American patients. On the other hand, urinary transferrin levels correlated with SLEDAI and proteinuria, and transferrin and ceruloplasmin levels correlated with each other. The diagnostic value of ROC curves for these urinary biomarkers for LN were good. CONCLUSIONS: In our cohort of SLE patients, we found that transferrin and ceruloplasmin were potential biomarkers for LN, and can even differentiate active LN

Diabetic rats present higher urinary loss of proteins and lower renal expression of megalin, cubilin, ClC-5, and CFTR.

Diabetic nephropathy (DN) occurs in around 40% of those with diabetes. Proteinuria is the main characteristic of DN and develops as a result of increased permeability of the glomerulus capillary wall and/or decreased proximal tubule endocytosis. The goal of this work was to evaluate renal function and the expression of megalin, cubilin, CFTR (cystic fibrosis transmembrane conductance regulator), and ClC-5 in the proximal tubule and renal cortex of rats with type 1 diabetes. Male Wistar rats were randomly assigned to control (CTRL) and diabetic (DM) groups for 4 weeks. Renal function was assessed in 24-h urine sample by calculating clearance and fractional excretion of solutes. The RNA and protein contents of ClC-5, CFTR, megalin, and cubilin were determined in the renal proximal tubule and cortex using real-time polymerase chain reaction and western blotting techniques, respectively. The results showed higher creatinine clearance and higher urinary excretion of proteins, albumin, and transferrin in the DM group than in the CTRL group. Furthermore, the renal cortex and proximal tubule of diabetic animals showed downregulation of megalin, cubilin, ClC-5, and CFTR, critical components of the endocytic apparatus. These data suggest dysfunction in proximal tubule low-molecular-weight endocytosis and protein glomerulus filtration in the kidney of diabetic rats.