Kinetics of butyrate metabolism in the normal colon and in ulcerative colitis: the effects of substrate concentration and carnitine on the b-oxidation pathway V. De Preter, K. P. Geboes, V. Bulteel, G. Vandermeulen, P. Suenaert, P. Rutgeerts & K. Verbeke Translational Research Center for Gastrointestinal Disorders (TARGID) and Leuven Food Science and Nutrition Research Centre (LFoRCe), KULeuven, Leuven, Belgium. Correspondence to: Dr K. Verbeke, Translational Research Center for Gastrointestinal Disorders (TARGID) KULeuven, Herestraat 49, B-3000 Leuven, Belgium. E-mail: kristin.verbeke@med. kuleuven.be Publication data Submitted 14 March 2011 First decision 9 April 2011 Resubmitted 23 May 2011 Accepted 9 June 2011 EV Pub Online 26 June 2011 SUMMARY Background Butyrate, a colonic metabolite of carbohydrates, is considered as the major energy source for the colonic mucosa. An impaired butyrate metabolism has been reported in ulcerative colitis (UC), however, the cause still remains unknown. Aim In the present study, we investigated whether higher butyrate concentra- tions could normalise the oxidation rate in UC. Furthermore, it was investi- gated whether carnitine could enhance the butyrate oxidation. Methods Mucosal biopsies from a total of 26 UC patients and 25 controls were incu- bated with 14 C-labelled Na-butyrate and the produced 14 CO 2 was measured. First, the rate of oxidative metabolism was compared at three different con- centrations of Na-butyrate (0.05 mM,1mM and 10 mM). Then, incubations of biopsies were performed with carnitine alone or combined with ATP. Results Overall, butyrate oxidation in UC was significantly lower than that in con- trols. The maximum rate of butyrate oxidation was achieved in UC and control subjects from 1 mM onwards. Increasing the butyrate concentration to a level to be present in the colonic lumen, i.e. 10 mM, did not increase the rate of butyrate oxidation in UC to the rate observed in controls. Addi- tion of carnitine alone or combined with ATP caused no effects. Conclusions Saturation of butyrate kinetics was achieved from 1 mM in UC and control subjects. The rate of butyrate metabolism was significantly impaired in active ulcerative colitis. The addition of compounds interfering with the b-oxidation pathway had no effect on the butyrate metabolism in UC. Aliment Pharmacol Ther 2011; 34: 526–532 526 ª 2011 Blackwell Publishing Ltd doi:10.1111/j.1365-2036.2011.04757.x Alimentary Pharmacology and Therapeutics