The short chain fatty acids, butyrate and propionate, have differential effects on the motility of the guinea pig colon

BackgroundColonic microbiota digest resistant starches producing short chain fatty acids (SCFAs). The main SCFAs produced are acetate, propionate, and butyrate. Both excitatory and inhibitory effects of SCFAs on motility have been reported. We hypothesized that the effect of SCFAs on colonic motility varies with chain length and aimed to determine the effects of SCFAs on propagating and non-propagating contractions of guinea pig proximal and distal colon. MethodsIn isolated proximal colonic segments, Krebs solution alone or containing 10-100mM acetate, propionate, or butyrate was injected into the lumen, motility was videorecorded over 10min, and spatiotemporal maps created. In distal colon, the lumen was perfused with the same solutions of SCFAs at 0.1mL/min, the movement of artificial fecal pellets videorecorded, and velocity of propulsion calculated. Key ResultsIn proximal colon, butyrate increased the frequency of full-length propagations, decreased short propagations, and had a biphasic effect on non-propagating contractions. Propionate blocked full and short propagations and had a biphasic effect on non-propagating contractions. Acetate decreased short and total propagations. In distal colon, butyrate increased and propionate decreased velocity of propulsion. Conclusions & InferencesThe data suggest that luminal SCFAs have differing effects on proximal and distal colonic motility depending on chain length. Thus, the net effect of SCFAs on colonic motility would depend on the balance of SCFAs produced by microbial digestion of resistant starches.