COVID-19-induced acute renal tubular injury associated with elevation of serum inflammatory cytokine.

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome Coronavirus 2 has rapidly spread worldwide, with acute kidney injury (AKI) as one of the manifestations with unknown causal mechanisms. We aimed to investigate tubular injury by assessing tubular markers and their association with the severity of Coronavirus disease 2019 (COVID-19). METHODS: We examined the associations between laboratory markers and urinary levels of N-acetyl-ß-D-glucosaminidase (uNAG), ß2-microglobulin (u ß2MG), α1-microglobulin (u α1MG), and liver-type fatty acid binding protein (L-FABP). We studied 18 COVID-19 patients without previous chronic kidney disease and analyzed the relationship between the urinary biomarkers and inflammatory markers in patients with severe (n = 7) or non-severe (n = 11) COVID-19, defined by requirements of supplemental oxygen. RESULTS: Fourteen patients (78%) showed abnormal urinalysis findings and two (11%) developed AKI. Patients with severe COVID-19 had significantly higher levels of proteinuria, uNAG, uß2MG, uα 1MG, and L-FABP than those with non-severe disease. Serum levels of interleukin-6 (IL-6) were significantly higher on admission in all severe COVID-19 cases and correlated with the levels of L-FABP, uß2MG, uα1MG, uNAG, and proteinuria. Moreover, the changes in serum IL-6 (ΔIL-6) levels from baseline to 7 days after admission significantly correlated with ΔL-FABP and Δuß2MG. CONCLUSIONS: Levels of tubular injury markers, especially L-FABP and uß2MG, were significantly associated with IL-6 levels even in patients with no evident AKI. This suggests that L-FABP and uß2MG could be useful as early detective biomarkers for COVID-19 associated renal injury.