SULM – Schweizerische Union für Labormedizin | Union Suisse de Médecine de Laboratoire | Swiss Union of Laboratory Medicine

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G KLINKE1, T RASSELLI2, A WYSS2, N PERKINS1, J MARTI-JAUN1, G ROGLER2, B MISSELWITZ2, M HERSBERGER1

1Division of Clinical Chemistry and Biochemistry, Children’s Research Center, University Children’s Hospital Zurich, Switzerland, 2Division of Gastroenterology and Hepatology, University Hospital Zurich, Switzerland

Inflammatory bowel diseases (IBDs) are a group of chronic relapsing immune-mediated disorders of the gastrointestinal tract with still badly understood pathophysiology. A set of oxysterol receptors have re-cently been implicated in IBD, namely the Epstein-Barr virus-induced G-protein coupled receptor 2 (EBI2), the Liver X receptors (LXRs) and the RAR-related orphan receptor gamma t (RORγt). We surmised that the oxysterols triggering these receptors may play a role in the pathophysiology of IBD and that there are differences in plasma levels between healthy controls and different IBD forms.

We established a LC-MS/MS (ESI+) method to measure 24(S)-hydroxycholesterol (24(S)-OHC), 25-hydroxycholesterol (25-OHC), 27-hydroxycholesterol (27-OHC), 7α,24(S)-dihydroxycholesterol (7α,24(S)-OHC), 7α,25-dihydroxycholesterol (7α,25-OHC), 7β,25-dihydroxycholesterol (7β,25-OHC), 7α,27-dihydroxycholesterol (7α,27-OHC), and 7β,27-dihydroxycholesterol (7β,27-OHC) in human plasma. The method was subsequently applied to determine the oxysterol profile in plasma of healthy volunteers (n=22) and patients with Crohn’s disease (CD) (n=20) and Ulcerative colitis (UC) (n=23) during active and inactive disease stages.

The reported method is linear (r >0.99), sensitive (detection limit ranging from 0,0018 nM to 1,09 nM) and precise, with a median intra-day imprecision of 12 % and 8,8 % and a median inter-day imprecision of 4,5 % and 5,7 % for dihydroxycholesterols and monohydroxycholesterols, respectively. Recoveries for all oxysterols in the inter-day assay ranged between 82 % and 124 %.

With this method, 24(S)-OHC, 25-OHC, 27-OHC, 7α,25-OHC and 7α,27-OHC could be detected in human plasma of controls and IBD patients. The levels of 27-OHC and 25-OHC were lower in CD and UC pa-tients compared to the control group, while the level of the other oxysterols did not differ. The results indicate that IBD patients have lower 27-OHC and eventually 25-OHC levels in the active and the remis-sion phases compared to controls, indicating a role for the oxysterol-LXR-axis in IBD.

 

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