Diagnostic value of brush border enzymes of the proximal renal tubules in rheumatoid arthritis.

BACKGROUND: Proximal tubules of the kidney have a dominant function in the excretion of different enzymes in the urine. These enzymes can be used as markers for secondary renal damage under the action of different diseases, medicines, and toxins. The aim of this study was to evaluate the values of alanine aminopeptidase (AAP), gamma-glutamyl transferase (gamma-GT), and beta2 microglobulin (beta2m) in urine of patients with untreated rheumatoid arthritis (RA) and to define the possible association between untreated rheumatoid arthritis and tubular function at the brush border region. METHODS: We used a kinetic assay for AAP, standard methods by the International Federation for Clinical Chemistry (IFCC) for gamma-GT and Microparticle Enzyme Immunoassay (MEIA), (Abbott A(x)SYM System) for the determination of beta2m in urine of 70 participants (35 untreated RA patients and 35 healthy volunteers (HC)). RESULTS: From the total of 35 RA patients, AAP enzymuria was found in 24 patients with test sensitivity (68.57%), gamma-GT in 16 patients with test sensitivity (45.71%), while the presence of urinary beta2m was found in a very low percentage of cases. Out of 18 rheumatoid factor (RF) negative patients, 14 patients were AAP and 10 patients were gamma-GT positive, while the presence of beta2m in urine was not detected. Among 17 RF positive RA patients, the presence of AAP and gamma-GT was noticed in 10 and 6 patients, respectively, while the presence of beta2m in urine was not detected. CONCLUSIONS: In conclusion, AAP had a higher sensitivity than gamma-GT and beta2m in detection of asymptomatic renal lesions in untreated RA.

Symmetric dimethyl arginine and N-acetyl-ß-D-glucosaminidase lysozimuria of proximal renal tubules as a target for nephrotoxicity in patients with rheumatoid arthritis treated with disease modifying antirheumatic drugs.

BACKGROUND: The aim of this study was to determine the effect of initial therapy with some disease modifying antirheumatic drugs (DMARDs) (Methotrexate and Ketoprofen) on glomerular and tubular integrity in patients with Rheumatoid arthritis (RA). OBJECTIVES: To determine whether there is a change in clinical and laboratory indicators of renal function in course of the follow up of treatment and whether that change correlates with the dynamics of the quantity of enzymes excreted in urine and reactants of the acute phase. MATERIALS AND METHODS: Using colorimetric method for determination of NAG, samples of 70 participants were examined (35 RA patients treated with Ketoprofen only, 35 RA patients treated with combined use of Methotrexate and Ketoprofen). The follow up was 5 time-intervals in the course of 24 weeks. RESULTS: There was moderate correlation between NAG and microalbuminuria (r=0,34) in the group of patients treated with Ketoprofen only, while statistically significant correlation (r=0,21) was seen in group of patients with combined use of Methotrexate and Ketoprofen. NAG enzymuria in size, number of patients registered, and time of appearance were greater and appears earlier in the group with the combined use of Methotrexate and Ketoprofen compared with the mono-therapy with Ketoprofen. Mean urinary NAG induction was increasing with the concomitant use of Methotrexate and Ketoprofen. CONCLUSIONS: Methotrexate is more potent NAG inductor than Ketoprofen and provokes greater tubular enzymuria than Ketoprofen.