Stimulation of jejunal synthesis of apolipoprotein A-IV by ileal lipid infusion is blocked by vagotomy

We examined the role of vagal innervation in lipid-stimulated increases in expression and synthesis of intestinal apolipoprotein A-IV (apoA-IV). In ra ts with duodenal cannulas and superior mesenteric lymph fistulas given duod enal infusions of lipid emulsion, vagotomy had no effect on either intestin al lipid transport, lymphatic apoA-IV output, or jejunal mucosal apoA-IV sy nthesis. In rats with jejunal Thiry-Vella fistulas, ileal lipid infusion el icited a twofold Stimulation of apoA-IV synthesis without affecting apoA-IV mRNA levels; vagotomy blocked this increase in apoA-IV synthesis. Direct p erfusion of jejunal. Thiry-Vella fistulas produced 2- to 2.5-fold increases in both apoA-IV synthesis and mRNA levels in the Thiry-Vella segment; thes e effects were not influenced by vagal denervation. These results suggest t wo mechanisms whereby lipid stimulates intestinal apoA-IV production: 1) a vagal-dependent stimulation of jejunal apoA-IV synthesis by distal gut lipi d that is independent of changes in apoA-IV mRNA levels and 2) a direct sti mulatory effect of proximal gut lipid on both synthesis and mRNA levels of jejunal apoA-IV that is independent of vagal innervation.