Nutrient sensing; transcriptomic response and regulation of gut motility in an agastric vertebrate

The transcriptome of nutrient sensing and the regulation of gut motility by nutrients in a stomachless fish with a short digestive tract; the ballan wrasse (Labrus berggylta) were investigated. Using an in vitro model, we differentiate how signals initiated by physical stretch and nutrients modulate the gut evacuation rate and motility patterns, and transcriptomic changes. Stretch on the intestine by inert cellulose initiated fast evacuation out of the anterior intestine compared to the digestible protein and lipid. Stretch on the intestine upregulated genes associated with increased muscle activity, whereas nutrients stimulated pathways related to ribosomal activity and the increase in the expression of several neuropeptides which are directly involved in gut motility regulation. Our findings show that physical pressure in the intestine initiate contractions propelling the matter towards the exit, whereas the sensing of nutrients modulates the motility to prolong the residence of digesta in the digestive tract for optimal digestion. Summary statementPressure by food speed up peristalsis in the intestine, but the intestines ability to sense nutrients slow down peristalsis for better digestion. This is partly controlled by genetic regulation.