Rapid synthesis and secretion of intestinal apolipoprotein A-IV after gastric fat loading in rats

To further investigate the possible role of apolipoprotein A-IV (apo A-IV) in the short-term control of food intake, we examined the kinetics of intestinal apo A-IV synthesis and release into lymph and plasma after intragastric delivery of physiological amounts of lipid. Within 30 min of intragastric administration of 0.1 g of triglyceride, plasma and lymph levels of apo A-IV were similar to those produced by exogenous apo A-IV that inhibit food intake. Within 15 min, 5% of gastrically delivered radioactive lipid reached the distal small bowel and cecum; by 30 min radioactivity was evenly distributed throughout the small intestine, with 10-15% of the load in the distal gut. By 30 min, synthesis of apo A-IV was significantly stimulated in proximal and distal jejunum and distal ileum and remained elevated up to 4 h after the delivery of lipid. Our results indicate that the delivery of physiological amounts of lipid into the stomach produces a significant and rapid stimulation of apo A-IV secretion into lymph and plasma, together with a rapid delivery of lipid and increases in mucosal synthesis of apo A-IV along the entire length of the small intestine. The results support a possible role for apo A-IV in the short-term control of food intake and suggest a role for the entire gut in the integrative response of apo A-IV to a fat meal.