Enteric capsuled protein reduced food intake and inhibited high-fat diet-induced weight gain in mice

To understand the mechanisms of food intake reduction after metabolic bariatric surgery, we investigated the potential antiobesity effects of undigested proteins delivered to the small intestine using enteric capsules. We utilized EUDRAGIT-coated capsules (enteric capsules) to deliver contents not into the stomach but into the small intestine. Wild-type mice were administered various proteins (soy, pea, chicken, or whey) in the enteric capsules, and the amount of food intake and weight gain by the high-fat diet were evaluated. Protein aggregation by heat treatment and vagal nerve ablation by capsaicin treatment were conducted to determine whether they affect food intake. We found that: (1) Single administration of less than 4 milligrams of soy protein in enteric capsules significantly reduced food intake. Similar effects were observed with other proteins. (2) Heat treatment increased the food intake reduction effect of whey protein with increasing levels of the enteric hormone PYY. Vagal nerve ablation by capsaicin abolished the effects of such food intake reduction. (3) Multiple administrations of soy protein in enteric capsules reduced body weight gain and liver triglyceride accumulation under high-fat diet conditions. We concluded that proteins delivered to the small intestine via enteric capsules reduced food intake and inhibited high-fat diet-induced weight gain in mice. The aggregation of protein and the capsaicin-sensitive vagal afferent nerve might play a role in this effect.