Surfactant protein-D (SP-D) gene polymorphisms and serum level as predictors of susceptibility and prognosis of acute kidney injury in the Chinese population

Jiao Liu,Zhiyong Liu,Guirong Wang,Guang Li,Qingshan Zhou,Dechang Chen,Lianghai Li

doi:10.1186/s12882-017-0485-x

Abstract

BackgroundInjury to the kidney epithelial barrier is a characteristic feature of acute kidney injury (AKI). Serum surfactant protein-D (SP-D), a known biomarker of damaged alveolar epithelium, is also secreted by renal tubular epithelial cells. Therefore, the aim of this study was to examine the possible association of SP-D with AKI susceptibility and prognosis.MethodsIn this study, 159 AKI patients and 120 healthy individuals were included. SP-D polymorphisms Thr11Met and Thr160Ala, AKI patient serum SP-D levels at days 1, 3 and 7 and urine KIM-1 levels in both AKI patients and controls were examined. The obtained results were correlated with the AKI stage, duration of renal replacement therapy (RRT) and prognosis.ResultsSerum SP-D level in AKI patients was higher than controls (p < 0.01). SP-D 11Thr/Thr genotype was more frequent in AKI patients than in controls (p < 0.01). Furthermore, AKI patients with SP-D 11Thr/Thr genotype had significantly higher serum SP-D levels (p < 0.05) compared to other genotypes. Serum SP-D levels corrected to the progression of AKI with a peak at day 3. Furthermore, the SP-D 11Thr/Thr genotype frequency and baseline serum SP-D level were higher in patients who subsequently died. Baseline serum SP-D levels positively correlated with the urine KIM-1 levels, AKI stage and RRT duration.ConclusionIn our study, elevated serum SP-D was associated with worse AKI clinical outcomes and patients with SP-D 11Thr/Thr genotype were more susceptible to AKI. Collectively, these findings suggest that SP-D may be useful as a biomarker of AKI susceptibility and prognosis.

Highlights

Injury to the kidney epithelial barrier is a characteristic feature of acute kidney injury (AKI)
In our study, elevated serum surfactant protein-D (SP-D) was associated with worse AKI clinical outcomes and patients with SP-D 11Thr/Thr genotype were more susceptible to AKI
From all AKI patients in 89 (56%) AKI was caused by sepsis, in 30 (18.9%) AKI was caused by trauma, in 25 (15.7%) AKI was caused by cardiovascular disease, and in 15 (9.4%) AKI was caused by other diseases

Summary

Introduction

Injury to the kidney epithelial barrier is a characteristic feature of acute kidney injury (AKI). The recognition of acute kidney injury (AKI) has increased dramatically worldwide [1]. Surfactant protein D (SP-D) is a member of the C-type lectin family and expression and secretion were initially described in lung alveolar epithelial type II cells [4]. A previous study has demonstrated that levels of inflammatory cytokines IL-6 and TNF-α in SP-D knockout mice with radiation-induced lung injury were significantly higher than those in wild-type mice [6]. We have shown in our recent studies that besides expression in the lung, SP-D is expressed in several other organs such as the pancreas [7] and kidney [8]. We have shown that in a CLP-induced sepsis model, SP-D knockout mice showed a higher degree of severity of kidney injury than wild-type mice [9]

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