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P355. The association between plasma histidine level and the efficacy of elemental diet therapy in Crohn's disease patients

M. Nakano1, K. Tominaga1, M. Hoshino1, K. Kanke1, H. Hiraishi1, 1Dokkyo Medical University, Department of Gastroenterology, Mibu-machi, Japan

Background

Several randomized controlled studies have shown the efficacy and safety of elemental diet (ED) therapy as remission induction and maintenance therapy for Crohn's disease (CD), and it has also been used as a fundamental therapy in Japan. In addition to bowel rest and stable nutrient absorption/supply, the involvement of amino acids with anti-inflammatory effect, has recently been recognized as part of the therapeutic efficacy mechanism of ED. In particular, abnormal metabolic balance of amino acids such as histidine has been reported to be associated with the condition of CD patients. This study was performed to clarify the relationship between plasma histidine levels and the efficacy of ED in CD patients.

Methods

Crohn's disease activity index (CDAI), C-reactive protein level, blood biochemistry data, and plasma histidine level were evaluated at baseline and at 12 weeks of treatment in 25 patients with active CD who received ED therapy as the primary remission induction therapy between October 2010 and December 2011. The association between changes in plasma histidine level and the therapeutic effect was assessed.

Results

Remission was induced in 17 patients (mean CDAI decreased from 242.1 to 100.4) but not in 8 despite a mean CDAI decrease (from 250.3 to 189.6). The plasma histidine level significantly increased from 64.1 to 76.8 umol/L in patients who achieved remission (p = 0.009) while no significant change was noted in those who failed to achieve remission (72.2 to 71.9 umol/L; p = 0.954). The results suggest the plasma histidine level is more strongly correlated with the condition of CD compared with the nutritional status. The CDAI decreased from pre-treatment 232.1 to 107.1 in 15 patients with better ED treatment adherence while it decreased from 263.8 to 161.6 in 10 with poorer treatment adherence. The plasma histidine level significantly increased from 71.3 to 81.3 umol/L in patients with better ED treatment adherence (p = 0.027) while no significant change was noted in those with poorer treatment adherence (59.8 to 66.1 umol/L; p = 0.227). In patients with better treatment adherence, the increase in plasma histidine level observed was considered to be attributable to the decreased disease activity associated with the enhanced efficacy of ED.

Conclusion

The results of this study confirmed the importance of ED therapy for CD in terms of the usefulness of plasma histidine level as a non-invasive CD marker and the direct anti-inflammatory effect of this amino acid.