Abstract
Background/AimsLuminal factors such as short-chain fatty acids are increasingly recognized for playing a regulatory role in peristaltic activity. Our objective was to understand the roles of butyrate and propionate in regulating peristaltic activity in relation to distention-induced activities.MethodsButyrate and propionate were perfused intraluminally under varying intraluminal pressures in murine colons bathed in Krebs solution. We used video recording and spatiotemporal maps to examine peristalsis induced by the intrinsic rhythmic colonic motor complex (CMC) as well as pellet-induced peristaltic reflex movements.ResultsThe CMC showed several configurations at different levels of excitation, culminating in long distance contractions (LDCs) which possess a triangular shape in murine colon spatiotemporal maps. Butyrate increased the frequency of CMCs but was a much weaker stimulus than distention and only contributed to significant changes under low distention. Propionate inhibited CMCs by decreasing either their amplitudes or frequencies, but only in low distention conditions. Butyrate did not consistently counteract propionate-induced inhibition likely due to the multiple and distinct mechanisms of action for these signaling molecules in the lumen. Pellet movement occurred through ongoing CMCs as well as pellet induced peristaltic reflex movements and butyrate augmented both types of peristaltic motor patterns to decrease the amount of time required to expel each pellet.ConclusionsButyrate is effective in promoting peristalsis, but only when the level of colonic activity is low such as under conditions of low intraluminal pressure. This suggests that it may play a significant role in patients with poor fiber intake, where there is low mechanical stimulation in the lumen.
Highlights
Colonic motility is dependent on stimuli, and colonic distention is a major stimulus for the initiation of motor patterns
In support of this hypothesis, we recently found that abnormal motor patterns in germ-free mice can be reversed to normal by luminal butyrate (Vincent et al, 2018)
The resultant change in mean intraluminal pressure did not increase to the same degree: the mean intraluminal pressure started at 1.47 ± 0.43 and increased to 4.16 ± 0.59 cmH2O, likely due to adaptive relaxation in the colon (N = 7)
Summary
Colonic motility is dependent on stimuli, and colonic distention is a major stimulus for the initiation of motor patterns. The content causes distension of the colon and/or increases in luminal pressure that evokes motor activity; at the same time, microbial fermentation produces metabolites that might activate [e.g., butyrate (Hurst et al, 2014), 5-HT (Fukumoto et al, 2003)] or inhibit [e.g., propionate (Hurst et al, 2014)] motility. The colon appears to find a balance between different stimuli to generate motor patterns that facilitate digestion, absorption, and microbiota homeostasis. Poor colonic motility may be caused by an imbalance in these factors. In support of this hypothesis, we recently found that abnormal motor patterns in germ-free mice can be reversed to normal by luminal butyrate (Vincent et al, 2018). Knowledge of butyrate’s effects could indicate whether its potential roles can be leveraged as an intraluminal prokinetic in motility disorders
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