Apolipoprotein A-IV synthesis in rat intestine: regulation by dietary triglyceride.
Apolipoprotein A-IV (apoA-IV) synthesis rates were measured in vivo in rat enterocytes by immunoprecipitation after administration of [3H]leucine into in situ loops of jejunum and ileum. Basal apoA-IV synthesis rates (percent total protein synthesis) were significantly higher in jejunal enterocytes (2.05 +/- 0.54%) compared with ileal enterocytes (0.48 +/- 0.32%) from the same fasted animals. After an acute triglyceride bolus, significant and sustained elevations of apoA-IV synthesis rates were seen in both jejunal and ileal enterocytes with maximal effects noted at 4-6 h. Animals fed diets containing 30% wt/wt triglyceride as saturated (SF) or polyunsaturated (UF) fats for 6 wk had similarly increased rates of apoA-IV synthesis in jejunal enterocytes with both SF (3.73 +/- 0.83%) and UF (3.33 +/- 0.64%) but no change in ileal enterocytes. By contrast, animals consuming a fat-free diet for 3 wk had jejunal apoA-IV synthesis rates indistinguishable from basal values (2.40 +/- 0.45%). Translatable intestinal mRNA levels for pre-apoA-IV after triglyceride increased in parallel to synthesis rates with a 50% increase in jejunum and a 350% increase in ileum observed at 4-6 h. These results suggest that apoA-IV synthesis by rat small intestine increases in response to acute and chronic dietary triglyceride, is maintained in the absence of dietary triglyceride, and may be under pretranslational control.
D000818:Animals; D001054:Apolipoproteins A / Q000096:biosynthesis* / Q000235:genetics; D004032:Diet; D007158:Immunologic Techniques; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000494:pharmacology*
D001054:Apolipoproteins A; D012333:RNA, Messenger; D014280:Triglycerides; C022205:apolipoprotein A-IV