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Background More than 50% of patients with infective endocarditis (IE) develop an indication for surgery. Despite its benefit, surgery is associated with a high incidence of multiple organ dysfunction syndrome (MODS) and mortality, which may be linked to increased release of inflammatory mediators during cardiopulmonary bypass (CPB). We therefore assessed plasma cytokine profiles in patients undergoing valve surgery with or without IE. Methods We performed a prospective case-control pilot study comparing patients undergoing cardiac valve surgery with or without IE. Plasma profiles of inflammatory mediators were measured at 7 defined time points and reported as median (interquartile). The degree of MODS was measured using sequential organ failure assessment (SOFA) score. Results Between May and December 2016 we included 40 patients (20 in each group). Both groups showed similar distribution of age and gender. Patients with IE had higher preoperative SOFA (6.9± 2.6 vs 3.8 ± 1.1, p<0.001) and operative risk scores (EuroSCORE II 18.6±17.4 vs. 1.8±1.3, p<0.001). In-hospital mortality was higher in IE patients (35% vs. 5%; p<0.001). Multiple organ failure was the cause of death in all non-survivors. At the end of CPB, median levels of following inflammatory mediators were higher in IE compared to control group: IL-6 (119.73 (226.49) vs. 24.48 (40.09) pg/ml, p = 0.001); IL-18 (104.82 (105.99) vs. 57.30 (49.53) pg/ml, p<0.001); Mid-regional pro-adrenomedullin (MR-proADM) (2.06 (1.58) vs. 1.11 (0.53) nmol/L, p = 0.003); MR-pro-atrial natriuretic peptide (MR-proANP) (479.49 (224.74) vs. 266.55 (308.26) pmol/l, p = 0.028). IL-1β and TNFα were only detectable in IE patients and first after starting CPB. Plasma levels of IL-6, IL-18, MRproADM, and MRproANP during CPB were significantly lower in survivors than in those who died.

Background & Aims Retention of bile acids in the blood is a hallmark of liver failure. Recent studies have shown that increased serum bile acid levels correlate with bacterial infection and increased mortality. However, the mechanisms by which circulating bile acids influence patient outcomes still are elusive. Methods Serum bile acid profiles in 33 critically ill patients with liver failure and their effects on Takeda G-protein–coupled receptor 5 (TGR5), an immunomodulatory receptor that is highly expressed in monocytes, were analyzed using tandem mass spectrometry, novel highly sensitive TGR5 bioluminescence resonance energy transfer using nanoluciferase (NanoBRET, Promega Corp, Madison, WI) technology, and in vitro assays with human monocytes. Results Twenty-two patients (67%) had serum bile acids that led to distinct TGR5 activation. These TGR5-activating serum bile acids severely compromised monocyte function. The release of proinflammatory cytokines (eg, tumor necrosis factor α or interleukin 6) in response to bacterial challenge was reduced significantly if monocytes were incubated with TGR5-activating serum bile acids from patients with liver failure. By contrast, serum bile acids from healthy volunteers did not influence cytokine release. Monocytes that did not express TGR5 were protected from the bile acid effects. TGR5-activating serum bile acids were a risk factor for a fatal outcome in patients with liver failure, independent of disease severity. Conclusions Depending on their composition and quantity, serum bile acids in liver failure activate TGR5. TGR5 activation leads to monocyte dysfunction and correlates with mortality, independent of disease activity. This indicates an active role of TGR5 in liver failure. Therefore, TGR5 and bile acid metabolism might be promising targets for the treatment of immune dysfunction in liver failure.