Abstract Body (Do not enter title and authors here): Background
Acute kidney injury (AKI) is among the most common complications after cardiac surgery, with an 18% prevalence and is associated with an increased risk of death. Cardiopulmonary bypass surgery generates danger-associated molecular patterns that trigger a release of proinflammatory molecules that can lead to AKI. Obesity is also associated with chronic low-grade inflammation and an increased risk for AKI. We investigated the utility of inflammatory molecules in the diagnosis of AKI in obese and non-obese cardiac surgery patients.

Methods
A panel of 13 circulating plasma molecules, including CXCL1, CXCL10, CXCL13, CCL22, IL-5,6,8,10,16, SLPI, TIM1, Properdin, Serpins E1 and A3, was measured using MAGPIX. The samples were collected from 95 MaRACAS patients (NCT02315183) before and 6-72 hours (h) after surgery. Obesity was defined as BMI>=32, based on our previous study.

Results
There was no significant difference in the incidence of AKI between obese (46%) and non-obese patients (58%). The levels of the selected molecules were compared between AKI and non-AKI groups in patients with and without obesity. In obese patients with AKI, the levels of serpin E1 were lower before surgery (22.16 vs 40.94ng/mL, q=0.03) and higher 6h post-surgery (49.26 vs 21.65ng/mL, q=0.02), while properdin was lower 72h post-surgery (11.12 vs 14.35ng/mL, q=0.01). In the non-obese group, CXCL10 was higher in the AKI group 6-48h post-surgery, peaking at 6h (218.5pg/mL vs 131.38pg/mL, q=0.02); CXCL13 was higher at 6h (435.78 vs 291.0pg/mL, q=0.04) and 24h (215.18 vs 157.49pg/mL, q=0.04); IL-16 was higher at 6h (256.01 vs 174.44, q=0.04) and 24h (344.94 vs 174.02, q=0.02); and SLPI was higher 6-72h post-surgery, peaking at 6h (50.44 vs 33.53 at 6h, q<0.01). ROC AUC analyses showed that Serpin E1 had a diagnostic value for AKI in obese patients pre (75.6%, 58.3%-92.8%) and 6h post-surgery (80%, 64.6%-95.4%); while SLPI had a diagnostic value in non-obese patients 6h after surgery (75.0%, 62.2%-87.8%).

Conclusions
AKI leads to different expression levels of proinflammatory molecules in obese and non-obese patients undergoing cardiac surgery. SLPI and Serpin E1 have diagnostic potential as biomarkers, but should be validated in larger cohorts.