7.3.5. Urinary APs in Other Chronic Diseases

Sorokman et al. [142] measured urinary levels of renal-specific enzymes (neutral α-glucosidase, L-alanine aminopeptidase, and γ-glutamyltranspeptidase) as markers of proximal tubule damage in children with pyelonephritis, the most common cause of fever in patients with urinary system disorders. They observed an increase in urinary levels of these enzymes during the active phase of pyelonephritis, which correlated with leukocyturia and C-Reactive Protein levels. Finally, Spasovski et al. [143] studied urinary levels of brush border enzymes of the proximal renal tubules (e.g., APN, gamma-glutamyl transferase, and beta2 microglobulin) in patients with untreated rheumatoid arthritis to explore the possible relationship between this disease and dysfunction of the brush border of proximal tubules. They found that urinary APN activity was a superior indicator of asymptomatic renal lesions in untreated rheumatoid arthritis patients compared with measurements of gamma-GT or beta2m.

**Author Contributions:** All authors have contributed to the review and have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
