We examined the intestinal delivery of conjugated linoleic acids (CLA) given in their triacylglycerol form in the mesenteric lymph of rats. Emulsions containing a mixture of the trilinolein/triester of CLA (9:1) and a tri-[1-(14)C]-linoleyl-sn-glycerol tracer were administered by force-feeding. Lymph was collected over two time periods (0-6 and 6-24 h), and the apparent recovery of CLA was determined relative to that of [1-(14)C]-18:2(n-6). A mixture of CLA-triester/trilinolein (1:9), trilinolein or CLA-triester was separately subjected to pancreatic lipase hydrolysis in vitro to determine whether the lymphatic recovery of CLA was correlated with the initial step of digestion. Lymphatic recovery of CLA was similar to that of 18:2(n-6) (95.6+/-9.0% of the linoleic acid recovery), and isomer repartition was similar in lymph and in the oil fed, indicating that all the CLA isomers were equally absorbed by the enterocytes. Unexpectedly, the in vitro release of CLA into the absorbable forms (free fatty acids and 2-monoacyl-sn-glycerol) was consistently lower than that of 18:2(n-6). Moreover, the 9c, 11t-isomer of CLA was also released faster into the absorbable forms than its 10t,12c homolog (P = 0.05). We cannot ascribe a distinct cellular accumulation or a difference in the biological effects of different CLA isomers on the ground of a selective intestinal absorbability. Also, the physiological conditions prevailing in vivo in the digestive tract are likely to overcome the relative resistance of CLA ester bonds to pancreatic lipase hydrolysis and allow a lymphatic recovery of CLA similar to that of linoleic acid.

These studies were designed to investigate the lymph absorption of a lipid emulsion in rats prefed different long-term high-fat diets. Particular emphasis was placed on the consequences of endogenous fatty acid alteration on the lymph recovery of two labeled fatty acids. Male Wistar rats were fed a standard diet (LF) containing 3.5 g/100 g fat or high-fat diets containing 15 g/100 g sunflower oil (HSFO), menhaden oil (HMO) or medium-chain triglyceride oil (HMCT) for 4 wk. The lymph was collected for 3 h before and after the intraduodenal infusion of a 90 μmol lipid emulsion (30 μmol monopalmitin, 30 μmol oleic acid, 25 μmol linoleic acid, 5 μmol arachidonic acid) labeled with [3H] oleic (OA) and [14C] arachidonic (AA) acids. The [3H] OA and [14C] AA lymph recoveries were measured and the lymph samples were tested for fatty acid, phospholipid and triglyceride content. Prefeeding an HSFO or HMO diet led to a 65 or 32% greater total lymph fatty acid output, respectively, compared with rats prefed the LF diet. In rats prefed both the HSFO and HMO diets, lymph fatty acid characteristics provided evidence of a dilution of exogenous fatty acids coming from the emulsion by endogenous fatty acids. In rats prefed the HMCT diet, the total lymph fatty acid output after the infusion of the lipid emulsion was not greater than that of starved rats. Nevertheless, 27% [3H] OA and 21% [14C] AA were recovered in the lymph, suggesting a limited dilution of exogenous fatty acids by endogenous fatty acids. In rats prefed the HMCT diet, some exogenous long-chain fatty acids must have been transported by the portal vein in response to low biliary phopholipid production, as indicated by the proportions of [3H] OA and [14C] AA taken up by the mucosa and not recovered in the lymph. Thus we demonstrated that during absorption of a single long-chain fatty acid meal a dilution of exogenous fatty acids by endogenous fatty acids occurred. The nature and the quantity of these endogenous fatty acids could alter the absorption efficiency of long-chain fatty acids by the lymphatic pathway and modify the fatty acid characteristics of lymph lipoprotein.

A study was undertaken to compare the influence of different high fat diets on fatty acid composition and output of bile and lymph lipids in fasting rats. Moreover, the lipid fatty acid composition and concentration of adipose tissue and liver on the one hand and plasma on the other hand were determined. Male Wistar rats were fed a normolipidic diet (NL) or hyperlipidic diets containing 15% sunflower oil (HSFO), 15% menhaden oil (HMO) or 15% medium chain triglyceride (HMCT) for 4 weeks. The appearance of the characteristic fatty acids of the diets or of those resulting of their hepatic metabolism at the different levels of the organism was emphasized. Indeed the HSFO diet led to an increased fatty acid concentration in adipose tissue, the lipemia was increased by HMCT diet and decreased by HMO diet. An original result was the significant decreases in bile flow and fatty acid output observed with the HSFO diet when compared to the NL diet. Biliary fatty acid outputs were subjected to variations which did not lead, in all groups, to concommitant modifications of lymph lipid fatty acid outputs. Particularly, after a HMCT diet, the total biliary fatty acid output was significantly reduced and was roughly one quarter of the lymph fatty acid output while it was roughly half after a NL, HSFO or HMO feeding. So the contribution of plasma fatty acids to the constitution of lymph lipoproteins was thought to be more important in the HMCT prefed rat group. For example, fatty acids like 16:0, 18:0, or 20:4n-6 were undoubtly provided by the plasma according to their low biliary concentrations and their relative high proportions in the lymph. These data showed the central role of the liver in determining the fatty acid composition of plasma and bile and consequently of intestinal lymph in the fasting rat and probably in the postprandial state.

We have investigated the bioconversion of the two essential polyunsaturated fatty acids (EFA), linoleic acid (18:2, n = 6) and a linolenic acid (18:3, n = 3) by homogenates or microsomes of rat intestinal mucosa and

During the last years, the knowledge about the intestinal absorption of lipids has made great strides. The cloning of several plasma membrane and cytosolic proteins involved in both the uptake and the cellular trafficking of long chain fatty acids allows now to study the molecular mechanisms of each step. This article briefly describes the recent data in this field of research. The direct involvement of long chain fatty acid in the gene regulation is also discussed.

Biology of the CellVolume 86, Issue 2-3 p. 194-194 IMMUNOLOCALISATION OF FATTY ACID TRANSPORTER (FAT) AND LIVER FATTY ACID BINDING PROTEIN (L-FABPC) IN THE SMALL INTESTINE Pascal DEGRACE, Pascal DEGRACE Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorHe´le`ne POIRIER, He´le`ne POIRIER Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorIsabelle NIOT, Isabelle NIOT Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorClaude CASELLI, Claude CASELLI Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorPhillipe BESNARD, Phillipe BESNARD Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorAndre´ BERNARD, Andre´ BERNARD Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this author Pascal DEGRACE, Pascal DEGRACE Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorHe´le`ne POIRIER, He´le`ne POIRIER Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorIsabelle NIOT, Isabelle NIOT Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorClaude CASELLI, Claude CASELLI Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorPhillipe BESNARD, Phillipe BESNARD Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this authorAndre´ BERNARD, Andre´ BERNARD Département de Physiologie de la Nutrition, EA. DRED N° 580, Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, 1 Esplanade Erasme, Université de Bourgogne, 21000 — Dijon, FranceSearch for more papers by this author First published: 1996 https://doi.org/10.1016/0248-4900(96)84815-5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume86, Issue2-31996Pages 194-194 RelatedInformation

Adult male rats were surgically given a drainage catheter in the main mesenteric lymph duct. After an overnight fast, five groups of rats received intragastrically, in one bolus, butter, corn oil (CO), cod liver oil (CLO), menhaden oil (MO), or ethyl esters of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids (K80). Intestinal lymph was collected in these conscious animals, each hour during the first 6 h and in a single sample for the next 18 h. The absorption peak appeared earlier after MO and CO than after CLO administration. The quantities of triglycerides recovered during the first 6 h were significantly lower after butter (91 mg) and K80 (54 mg) administration than for the other three oils. No difference was observed between the vegetable oil and the two marine oils (CO=173 mg, CLO=148 mg, MO=180 mg). The total triglyceride recovered in 24 h was highest after CLO (410 mg) and lowest with K80 (146 mg). An increase in the weight percentage of some characteristic fatty acids of the lipid mixtures was observed: oleic acid for butter, oleic and linoleic acids for CO, EPA and DHA for CLO, MO, and K80. Chylomicrons were the largest with CO, more numerous and smaller with CLO, and the smallest with K80. Results obtained illustrated the relation between gastrointestinal hydrolysis, enterocyte biochemical events, and lymph triglyceride absorption profiles as related to the composition and distribution of triglyceride fatty acids.

The present study examines the suggestion that in the absence of adequate bile and pancreatic juice, which support the absorption from the gut of long-chain fatty acids into lymph, the fatty acids are absorbed directly into the portal blood. Oleic acid (18:1) partitioning between lymph and portal blood was investigated in intact and bile- and pancreatic juice-diverted rats. In a first set of experiments, 18:1 absorption from the gut into lymph and blood was studied by continuous recovery of the mesenteric lymph for 6 h and mesenteric portal venous blood for 1 h. In a second set of experiments, esterification processes were investigated by study of the mucosal distribution of labelled lipids and by mono- and diacylglycerol acyltransferase (EC 2.3.1.22 and EC 2.3.1.20 respectively) specific activities. In the bile- and pancreatic juice-diverted rats the absorption of labelled 18:1 into lymph was significantly reduced during the first 3 h of intraluminal infusion of this substrate. In such rats a compensatory absorption of labelled 18:1 into mesenteric portal blood was not observed. At 6 h after micellar lipid-mixture infusion, the overload of lipids both in free form and as triacylglycerols persisting in the mucosa paralleled the lower acyltransferase specific activities observed in bile- and pancreatic juice-diverted rats. These studies demonstrate the absence of a previously proposed compensatory absorption of 18:1 into portal blood when absorption into lymph is impaired by an inadequate supply of bile and pancreatic juice.

Mesenteric lymph recoveries and profiles of labeled eicosapentaenoic acid were explored in rats after intraduodenal infusions of 90 μmol of lipid mixtures composed either of 5 μmol of eicosapentaenoic acid, 25 μmol of arachidonic acid, 30 μmol of oleic acid, and 30 μmol of monopalmitin or equimolar in eicopentaenoic acid, linoleic acid, and monoolein. Biochemical and morphologic studies were simultaneously carried out on mesenteric lymph lipoproteins. When administered in free form in the presence of monoglycerides, eicosapentaenoic acid absorption modalities closely resembled those of arachidonic acid given in a similar design, with a mesenteric lymph recovery of 44% of the infused radioactivity for the 6-h time period following the onset of the lipid infusion. In spite of 61–71% of eicosapentaenoic acid incorporation into lymph triglycerides, a significant incorporation into lymph phospholipids occurred (13–21%). By increasing the degree of unsaturation of the lipid mixture infused, the lymph lipoprotein size increased.

The arachidonic acid (C20:4, n-6) appearing in intestinal lymph during linoleic acid (C18:2, n-6) absorption may originate from enterocyte synthesis or from the liver either after secretion in biliary phospholipids at the same time dietary linoleic acid absorption occurs or via plasma. The radioactivity measured in the total bile collected during the 6 hours of linoleic acid absorption is too small to explain hepatic origin of the C20:4 detected by high performance liquid chromatography analysis of labeled fatty acids recovered in the lymph, in the intestinal mucosa, and the intestinal wall at the peak of linoleic acid intestinal absorption. This study confirms the probability that under in vivo conditions, during the absorption processes, rat intestine is able to convert dietary linoleic acid independent of liver desaturases and elongase activities.

1. Lactase, sucrase, maltase, trehalase and alkaline phosphatase activities of rat proximal jejunum were measured in 3, 6, 9, 12, 18 and 24-month-old rats fed with diets differing in their fatty acid composition. 2. A drop of 47-53% of the specific enzyme activity was observed with disaccharidases against a decrease of 71% for alkaline phosphatase in the 24-month-old rats compared to the 3-month-old rats. 3. Changes in dietary fatty acid composition, either in the saturated or monounsaturated ratio, or in the polyunsaturated fatty acid composition, did not significantly interfere with this aging effect.

Polyunsaturated fatty acids play an important part in the structure and function of cellular membranes and are precursors of lipid mediators which play a key role in cardiovascular and inflammatory diseases. Dietary sources of essential fatty acids are vegetable oils for either linoleic or alpha-linolenic acids, and sea fish oils for eicosapentaenoic and docosahexaenoic acids. Because of the specificity of the pancreatic lipid hydrolases, triglyceride fatty acid distribution is an essential parameter in the digestibility of fats. The efficiency of the intestinal uptake depends on the hydrolysis and especially on their micellarization. n-3 polyunsaturated fatty acid ethyl ester digestion is recognized to be impaired, but n-3 polyunsaturated fatty acid triglyceride hydrolysis remains a controversial point, and to some authors explains differences observed between vegetable and fish oil absorption. So additional studies are required to investigate this intestinal step. In enterocytes, morphological and biochemical absorption processes involve reesterification of long-chain fatty acids and lipoprotein formation. At this level, specific affinity of I- and L-FABPc (cytosolic fatty acid binding proteins) to polyunsaturated fatty acids requires further investigation. A better understanding of the role of these FABPc might bring to light the esterification step, particularly the integration of polyunsaturated fatty acids into phospholipids. With reference to differences published between fish and vegetable oil absorption, longer-term absorption studies appear essential to some authors. Polyunsaturated fatty acid absorption is thought to be not very dissimilar to that of long-chain mono-unsaturated fatty acid absorption. However, several digestion and absorption specific steps are worth studying with reference to the crucial role of polyunsaturated fatty acids in the organism, and for example adaptation of possible dietary supplements.

1-C-14 linoleic acid intestinal absorption and simultaneous biochemical events were followed up on rats under vascular perfusion and on main mesenteric lymphatic duct fistulated rats. 1-C-14 linoleic acid was introduced in the duodenum alone in doses from 1.2 to 90-mu-mol or in the presence of oleic acid and monopalmitin (30/30/30-mu-mol/mu-mol/mu-mol). Mesenteric portal venous blood and chyle, respectively, were collected continuously for 1 and 6 h after the infusions. Blood-labeled lipid recovery varied from 4.7 to 2.2% of the C-14 linoleic acid infused as the C-14 linoleic acid dose infused increased, and dropped to 1.8% with the mixed lipid infusate. Lymph-labeled lipid recovery increased from 25.7 to 31.8% of the C-14 linoleic acid infused as the dose infused increased, and rose to 48.1% with the mixed lipid infusate. The oxidation of 1-C-14 linoleic acid remained low: 0.8-3% of the infused radioactivity. A desaturation and elongation of C-14 linoleic acid into C-14 arachidonic acid was detected and discussed. We can conclude that the linoleic lymph absorption pathway remained preferential in our experimental conditions, simultaneous to a low rate of oxidation and an eventual ability for the enterocyte to convert this essential fatty acid to arachidonic acid.

Metabolism of Erucic Acid was studied in rat heart in comparison with that of oleic acid, particularly in relation with diet lipids. Rats were fed for 3 or 60 days a diet containing 30% of the calories of either Rapessed Oil, rich in erucic acid or sunflower seed oil rich in linoleic acid. They were I.V. injected with tritiated erucic or oleic acid. After 1 or 15 min the radioactivity recovered in heart lipids was very low whatever the diet (1 to 2%). One minute after injection of erucic acid the radioactivity was mainly recovered in the free fatty acid fraction and as untransformed erucic acid. After 15 min the major part of radioactivity was recovered in the triacylglycerol fraction which contained a high proportion of labelled oleic acid formed by shortening of erucic acid. When oleic was injected, the radioactivity was principally recovered in triacylglycerols as untransformed oleic acid whatever the experimental conditions. Electron microscopy showed that a much higher proportion of peroxisomes, was present in heart cells, following sunflower seed oil diet as compared to rapeseed oil diet. In all cases mitochondria supported the greater part of radioactivity, especially when erucic acid was injected in rats fed rapeseed oil. After sunflower seed oil, a noticeable radioactivity was observed in peroxisomes, most of them containing silver grains, especially when oleic acid was injected. According to the data reported, peroxisomes do not seem more implicated than mitochondria in the metabolism of erucic acid in myocardium.

The intestinal absorption and metabolism of 14 C erucic acid was investigated after intraduodenal infusion of an equimolar lipid emulsion of either 10-14C or 1-14C erucic acid, oleic acid and monopalmitin. Labelled catabolites were analyzed in the mesenteric portal blood. Absorbed labelled lipids were studied both on the mesenteric portal blood and on the intestinal lymph from two groups of rats. Our results revealed: 1) A low catabolism of 1-14C erucic acid. 2) A preferential lymph transport of erucic acid but a significantly lower lymphatic recovery rate than oleic acid. 3) A preferential incorporation of erucic acid in VLDL all along its absorption. 4) A recovery in the lymph lipids of labelled oleic acid which agrees with the concept of the chain shortening of labelled 10-14C erucic acid in the intestine. Most of these observations confirm the long chain saturated fatty acid characteristic of this monounsaturated long chain fatty acid.