Serum phosphatidylinositol depletion associates with fecal calprotectin and disease severity in female and male IBD patients

Phosphatidylinositol (PI) is a phospholipid that exerts anti-inflammatory effects when injected during experimental colitis. The levels of PI species in the serum of patients with inflammatory bowel disease (IBD) and their association with disease activity have not yet been determined. This exploratory study investigates whether the levels of PI species in the serum are associated with the severity of the disease. Serum concentrations of 14 PI species were assessed using direct flow injection analysis with a triple quadrupole mass spectrometer. The study involved 16 healthy controls and 57 patients (including 26 females and 31 males) diagnosed with IBD. Similar levels of all PIs measured were exhibited by patients with IBD and controls. Nine PI species were found to be higher in female patients, prompting a sex-specific analysis. Almost all PI species exhibited a negative correlation with fecal calprotectin in both sexes. Negative correlations of PI species with CRP were mostly found in males. PI 34:1, 36:1, 36:2, and 40:5 were significantly reduced in male and female patients with active disease compared to those with quiescent disease. In the entire patient cohort, all PI species significantly declined in active disease compared to patients with inactive disease and compared to healthy controls. Serum PI species levels were not associated with disease localisation in patients with Crohn’s disease, but were increased in ulcerative colitis patients with proctosigmoiditis in comparison to patients with pancolitis. The levels of PI 38:4, 38:5, 40:4, and 40:5 were higher in the serum of patients with Crohn’s disease than in those with ulcerative colitis, despite having similar disease activity. This study demonstrates that serum PI species decline in active IBD in both sexes. Specific PI species may evolve new biomarkers to discriminate patients with Crohn´s disease from patients with ulcerative colitis.