Feeding appetite suppressing thylakoids to pigs alters pancreatic lipase/colipase secretion

The mechanism for a new appetite suppressor named thylakoids (membrane proteins derived from spinach leaves) was examined in vivo in pigs. Thylakoids inhibit the lipase/colipase hydrolysis of triacylglycerols (TG) in vitro and suppress food intake, decrease body weight gain and raise the circulating satiety hormone cholecystokinin (CCK) in rats but its mechanism in vivo remains unclear. We hypothesized that a thylakoid-enriched diet prolongs intestinal digestion of food and therefore promote satiety signaling. Five pigs were surgically prepared with a fistula in the duodenum for collection of digesta and with two catheters, one in v. jugularis and one in v. porta, for blood collection. After 1 week of recovery and an overnight fast the pigs were fed a high-fat diet with and without supplementation with thylakoids. Duodenal content and blood samples were taken before and 15, 30, 60, 120, 240 and 360 min after feeding. Pancreatic lipase and colipase enzymes were measured in duodenal digesta. Blood samples were analyzed for the satiety hormone CCK as well as insulin and glucose.We found that pancreatic lipase/colipase level increased and stayed elevated for a longer time in the duodenum in the pigs receiving thylakoids compared to the control. CCK levels were unchanged. Insulin levels were significantly reduced by the thylakoid treatment without any change in blood glucose. In conclusion, thylakoids increased lipase/colipase secretion. The mechanism for this secretion appears not to be related to CCK and may be an effect of vagal activation. Thylakoids gave reduced insulin levels without any change in glucose levels.