Butyrylated starch increases large bowel butyrate levels and lowers colonic smooth muscle contractility in rats

Abstract 

The short-chain fatty acids acetate, propionate, and butyrate are produced by colonic bacterial fermentation of carbohydrates. Butyrate is important in the regulation of the colonocyte cell cycle and gut motility and may also reduce the risk of large bowel cancer. We have shown that dietary butyrylated starch can deliver butyrate to the large bowel in a sustained manner. We hypothesized that ingestion of butyrylated starch increases large bowel butyrate levels and decreases colonic contractility. Groups of male Sprague-Dawley rats (n = 8) were fed AIN-93G-based diet containing a highly digestible low-amylose maize starch (LAMS) control or 5% or 10% butyrylated LAMS (LAMSB) for 10 days. We found that cecal but not colonic tissue weight as well as cecal and distal colonic digesta weights and fecal output were higher in LAMSB fed rats. Butyrylated LAMS lowered digesta pH throughout the large bowel. Cecal, proximal, and distal colonic butyrate pools and portal venous butyrate concentrations were higher in rats fed LAMSB. Electrically stimulated and receptor-dependent carbachol and prostaglandin E₂–induced isotonic contractions were lower in isolated intact sections of proximal colon (P < .05) but not the terminal ileum after 10% LAMSB ingestion. These results demonstrated that elevation of butyrate levels in the large bowel of the rat correlated with reduction of contractile activity of the colonic musculature, which may assist in the reabsorption of water and minerals.

Abbreviations: AUC, area under the curve, EC₅₀, the molar concentration of an agonist that produces 50% of the maximal possible effective response for that agonist, LAMS, low-amylose maize starch, LAMSB, butyrylated low-amylose maize starch, PGE₂, prostaglandin E₂, RS, resistant starch, SCFA, short-chain fatty acids

Keywords: Rats, Short-chain fatty acid, Butyrate, Contractility, Carbachol, PGE₂, Ileum, Colon, Smooth muscle