In vivo measurement of colonic butyrate metabolism in patients with quiescent ulcerative colitis

Background-Butyrate, a short chain fatty acid produced by bacterial ferment ation, is a major fuel source for the colonocyte. In vitro work has shown t hat ulcerative colitis may be characterised by a metabolic defect in colono cyte butyrate oxidation. Aims-To investigate the rate of metabolism of rectally administered butyrat e in patients with quiescent colitis. Methods-[1-C-13]-butyrate enemas were administered to 11 patients with long standing quiescent ulcerative colitis and to 10 control patients. The rate of production of (CO2)-C-13 in exhaled breath over four hours was measured by isotope ratio mass spectrometry combined with indirect calorimetry in o rder to measure CO2 production. This allowed calculation of the patients' r esting energy expenditure and respiratory quotient. Results-Over a four hour period, 325 (SEM 21) mu mol (CO2)-C-13 was recover ed in breath samples from the colitis group compared with 322 (17) mu mol f rom the control group (NS). The respiratory quotient of the colitic group w as significantly lower than that of the control group. Conclusion-There was no difference in the rate of metabolism of butyrate be tween the two groups. It is unlikely that there is a primary metabolic defe ct of butyrate metabolism in patients with quiescent ulcerative colitis.