triolein and Fistula

Apolipoprotein A-V (apoA-V), a liver-synthesized apolipoprotein discovered in 2001, strongly modulates fasting plasma triglycerides (TG). Little is reported on the effect of apoA-V on postprandial plasma TG, an independent predictor for atherosclerosis. Overexpressing apoA-V in mice suppresses postprandial TG, but mechanisms focus on increased lipolysis or clearance of remnant particles. Unknown is whether apoA-V suppresses the absorption of dietary lipids by the gut. This study examines how apoA-V deficiency affects the steady-state absorption and lymphatic transport of dietary lipids in chow-fed mice. Using apoA-V knockout (KO, n = 8) and wild-type (WT, n = 8) lymph fistula mice, we analyzed the uptake and lymphatic transport of lipids during a continuous infusion of an emulsion containing [(3)H]triolein and [(14)C]cholesterol. ApoA-V KO mice showed a twofold increase in (3)H (P < 0.001) and a threefold increase in (14)C (P < 0.001) transport into the lymph compared with WT. The increased lymphatic transport was accompanied by a twofold reduction (P < 0.05) in mucosal (3)H, suggesting that apoA-V KO mice more rapidly secreted [(3)H]TG out of the mucosa into the lymph. ApoA-V KO mice also produced chylomicrons more rapidly than WT (P < 0.05), as measured by the transit time of [(14)C]oleic acid from the intestinal lumen to lymph. Interestingly, apoA-V KO mice produced a steadily increasing number of chylomicron particles over time, as measured by lymphatic apoB output. The data suggest that apoA-V suppresses the production of chylomicrons, playing a previously unknown role in lipid metabolism that may contribute to the postprandial hypertriglyceridemia associated with apoA-V deficiency.

Topics: Administration, Oral; Animals; Apolipoprotein A-V; Apolipoproteins; Cholesterol; Chylomicrons; Disease Models, Animal; Duodenum; Fistula; Intestinal Absorption; Lymph; Lymphatic Diseases; Lymphatic System; Male; Mice, Inbred C57BL; Mice, Knockout; Postprandial Period; Time Factors; Triolein; Up-Regulation

In most experimental designs, the inhibitory effect of water-soluble dietary fibers on lipid absorption is evaluated by the decrease in plasma lipid concentration or the increase in fecal lipid output. The aim of this study was to evaluate the acute effect of a water-soluble polysaccharide, polydextrose, on lipid transport to the mesenteric lymph using lymph-fistula rats. The mesenteric lymph duct of rats was cannulated, and an infusion tube was introduced into the duodenum. After recovery, a lipid emulsion containing radioactive triolein and cholesteryl oleate was infused into the duodenum for 8 hr. The tested group was infused with the lipid emulsion containing 5% or 10% polydextrose as dietary fiber. Samples from the lymph-fistula were collected, and the luminal contents and mucosa were collected at the end of infusion. Lymph flow in the mesenteric lymph decreased in the polydextrose group after the infusion. The amounts of both triglyceride and cholesterol remaining in the lumen were greater in the polydextrose group, due to decreased transport of lipid into the lymph. These effects were dose dependent in the 5% and 10% polydextrose groups. The results of this study indicate that polydextrose retarded the transport of triolein and cholesterol into the mesenteric lymph.

Topics: Animals; Biological Transport; Catheterization; Cholesterol; Fistula; Glucans; Intestinal Absorption; Intestinal Mucosa; Lipid Metabolism; Lymph; Male; Mesentery; Rats; Rats, Sprague-Dawley; Triolein

The ability of the intestinal cell to export triacylglycerol (TG) is a physiologically regulatable function. The intracellular site where this occurs is unknown, although available evidence suggests that the step between the endoplasmic reticulum (ER) and the Golgi is the most likely. We studied this process in rat enterocytes that were isolated from the proximal intestine. A novel system was developed in which [3H]TG was transported from ER to the Golgi. This process was time, ATP, temperature, and cytosol dependent. The cytosolic factor(s) was heat and trypsin sensitive. TG transport was directly proportional to the amount of added nonradiolabeled acceptor Golgi. The rate of TG transported to the Golgi was the fastest in cells isolated from rats that had been intraduodenally infused in vivo with glyceryltrioleate (TO) plus phosphatidylcholine and slowest in cells isolated from bile-fistulated rats infused with TO in vivo compared with cells from in vivo TO-infused, bile duct intact rats, mimicking the relative transport rates seen in vivo. TG transport in vitro could not be quenched by adding TG emulsions, chylomicrons, liposomes, or guanosine 5'-O-(3-thiotriphosphate). Cytosol from the liver and kidney supported TG transport, but the Golgi from liver or kidney did not accept TG from intestinal ER. We conclude that an intestinally specific, active transport mechanism transports TG from the ER to the Golgi and that this might be a regulatory step in TG export from the intestinal cell.

Topics: Adenosine Triphosphate; Animals; Apolipoprotein B-48; Apolipoproteins B; Cell Fractionation; Chylomicrons; Cytosol; Duodenum; Endoplasmic Reticulum; Fistula; Gallbladder; Golgi Apparatus; In Vitro Techniques; Intestinal Mucosa; Intestine, Small; Intracellular Membranes; Kinetics; Microscopy, Electron; Phosphatidylcholines; Rats; Rats, Sprague-Dawley; Triolein

We tested the hypothesis that stimulation of synthesis and secretion of intestinal apolipoprotein A-IV (apo A-IV) by intestinally infused lipid is mediated by capsaicin-sensitive afferent signals. Vehicle or capsaicin (125 mg/kg) was systemically administered to rats; then the effects of intestinal infusion of lipid emulsions on lymph lipid and apo A-IV transport were determined in rats equipped with duodenal infusion cannulas and mesenteric lymph fistulas. Capsaicin treatment did not significantly affect lymph outputs of triglyceride, phospholipid, and apo A-IV during duodenal infusion of triglyceride emulsion. In separate studies the effect of capsaicin treatment on ileal lipid-elicited stimulation of intestinal mucosal apo A-IV synthesis was also examined. Ileal lipid infusion increased apo A-IV synthesis in distal ileum, proximal jejunum, and jejunal Thirty-Vella fistulas; this finding was unaffected by capsaicin pretreatment. However, capsaicin treatment significantly attenuated the inhibitory effects of duodenal acid and fat on gastric emptying. These results do not support a role for capsaicin-sensitive, sensory afferent nerves in the stimulation of intestinal apo A-IV by dietary lipid.

Topics: Afferent Pathways; Animals; Apolipoproteins A; Capsaicin; Duodenum; Fat Emulsions, Intravenous; Fatty Acids, Nonesterified; Fistula; Gastric Emptying; Glycerides; Ileum; Intestinal Absorption; Intestinal Mucosa; Jejunum; Lymph; Male; Rats; Rats, Sprague-Dawley; Triolein

The transport of triacylglycerol (TG) in mesenteric lymph was studied in rats with duodenal and mesenteric lymphatic cannulas with or without bile fistulas. Rats were infused with 135 mumol glycerol trioleate (TO) for 4 h, followed by 5 h of NaCl infusion. Rats with intact fistulas prefed 20% corn oil had nearly twice the maximum output of TG in lymph as controls. Decay from peak values was zero order for controls and indeterminate for rats prefed corn oil. In rats with bile fistulas, less TG was transported in lymph than in those in which 2 mM phosphatidylcholine (PC) was added to the infusate. The decay from maximum values was zero order for controls and first order for rats infused with PC and TO. Recovery of infused [3H]glycerol trioleate in controls was 43% and increased to 68% on inclusion of PC in the infusate. We conclude that in chow-fed rats lymph TG delivery rates were well below infusion rates, suggesting alternate TG transport routes, TG transport was improved by supplementing the infusate with PC or prefeeding with 20% TG in chow, and PC may be limiting in TG transport in rats with bile fistulas.

Topics: Animals; Bile Ducts; Chylomicrons; Fistula; Lymph; Male; Mesentery; Phosphatidylcholines; Rats; Rats, Inbred Strains; Triglycerides; Triolein

Topics: Absorption; Alkanes; Animals; Bile Acids and Salts; Carbon Isotopes; Chromatography, Gas; Colloids; Fistula; Lymph; Oleic Acids; Palmitic Acids; Rats; Solubility; Stearic Acids; Thoracic Duct; Triglycerides; Triolein

Topics: Absorption; Animals; Biliary Fistula; Biological Transport; Carbon Isotopes; Fistula; Intestinal Absorption; Lymph; Oleic Acids; Radiometry; Rats; Thoracic Duct; Triolein

Topics: Contrast Media; Fistula; Humans; Lymphatic Vessels; Radiography; Triolein; Urinary Fistula; Urinary Tract