LAUSR

Introduction South Asians (SA) with Crohn’s disease (CD) display a different disease phenotype and course (Walker, 2011. AJG.), as well as a different urinary metabolic profile (Marchesi, 2008. J. Proteome Res.). Metabolic profiling of faecal water has distinguished CD from controls previously, but only in Caucasian (Cau) cohorts, characterised by a reduction in short chained fatty acids. In this study, we aimed to compare the metabolic profiles of faecal water in CD patients and healthy controls (H) from Caucasian and South Asian backgrounds. Methods Samples from 28 CD patients (15 Cau and 13 SA) and 44 healthy controls (20 Cau and 24 SA) were analysed by H1NMR spectroscopy. Data was assessed using orthogonal partial least squares discriminant analysis (OPLSDA). Hypothesis-led univariate analysis was also performed using metabolites that have been previously shown to distinguish CD from controls (Marchesi, 2008). These metabolites were as follows: Acetate, Butyrate, Propionate, Lactate, Methylamine, Glutamine, Alanine, Taurine, Valine, and 2-Hydroxybutyrate (2-HIB). Results Multivariate analysis (table 1) demonstrated that the faecal metabolites driving the separation between CD and controls were similar regardless of ethnicity, although statistically significant separation could not be achieved by multivariate analysis in the smallest group (CD v H in Caucasians).Abstract PTH-113 Table 1 Model OPLSDA n R2X Q2 P value CV-ANOVA Metabolites driving separation in CD CD : HCAll 72(28:44) 0.145 0.197 <0.001 Acetate ↓Butyrate ↓Glutamine ↓Alanine ↓Creatine ↓Tryptophan ↓2-HIB ↓Methylamine ↓ CD : HCaucasian 35 (15:20) 0.122 0.126 0.117 Acetate ↓Butyrate ↓Glutamine ↓Alanine ↓Creatine ↓Tryptophan ↓2-HIB ↓Methylamine ↓ CD : HSouth Asians 37 (13:24) 0.196 0.290 0.024 Acetate ↓Butyrate ↓Glutamine ↓Alanine ↓Creatine ↓Tryptophan ↓2-HIB ↓Methylamine ↓ Univariate analysis demonstrated a statistically significant reduction in Butyrate, Acetate, 2-HIB, and Methylamine (p < 0.05) in Cau CD patients compared to controls consistent with previous studies, but only a reduction in 2-HIB and Methylamine were seen with statistical significance in SA patients. When directly comparing Cau and SA patients with CD, Butyrate and 2-HIB were significantly different (p = 0.034 and 0.035 respectively) between these ethnic groups. Conclusions Despite observing consistent changes in the metabolites driving separation between Caucasian and SA patients compared to controls, univariate analysis reveals differences relating to ethnicity, showing that ethnicity influences faecal water metabolic profiles. The effect of ethnicity is likely to be a combination of genetics, diet and environment. Ethnicity therefore must be accounted for as a potential confounder in this type of analysis.