Does renal function influence plasma levels of advanced glycation and oxidation protein products in patients with chronic rheumatic diseases complicated by secondary amyloidosis?

Abstract

Background: The aim of the study was to assess the contribution of carbonyl and oxidative stresses to the development of amyloidosis in patients suffering from chronic rheumatic diseases, and the potential influence of renal function to their concentrations was considered.

Methods: We investigated 17 patients with chronic rheumatological diseases and histologically proven diagnosis of AA amyloidosis (group AA-RA), 26 patients suffering from rheumatoid arthritis without any signs of AA amyloidosis (group nonAA-RA) and 20 healthy volunteers (Co). In all patients, advanced glycation end products (AGEs), advanced oxidation protein products (AOPP), pregnancy-associated plasma protein A (PAPP-A) and other selected proinflammatory markers were measured.

Results: An increase in serum levels of AOPP and AGEs was found in the AA-RA group in comparison with nonAA-RA patients and also with Co (p < 0.001 for all comparisons). AGEs positively correlated with serum creatinine (r = 0.67, p = 0.004) and negatively with glomerular filtration rate (r = -0.54, p = 0.027). We did not find a correlation between AOPP and any other assessed parameters including proteins and renal parameters. PAPP-A levels were not significantly increased in any group of patients (AA-RA, nonAA-RA) in comparison with Co.

Conclusions: Increased plasma levels of AGEs and AOPP in the group of patients with AA-RA may have been partly explained by the diminished renal clearance. However, the increase in AOPP levels was higher than what is expected in this degree of renal failure (glomerular filtration rate in the AA-RA group corresponding to chronic kidney disease stage III).