The Effect of Dietary Fat Load on the Size and Composition of Chylomicrons in Thoracic Duct Lymph

Fraser, Robin; Cliff, W. J.; Courtice, F. C.

doi:10.1113/expphysiol.1968.sp001984

Cited by 68 publications

(26 citation statements)

References 15 publications

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“…Smaller particles (such as VLDL) with a larger surface-to-volume ratio, would therefore be expected to contain relatively more protein, phospholipid, and cholesterol, and less triglyceride. Fraser, Cliff, and Courtice have also obtained evidence suggesting that differences in triglyceride-to-phospholipid ratios of thoracic duct lymph chylomicrons and VLDL can be explained by differences in particle size (33). The relative decrease in triglyceride content would in turn result in an increased particle density, while the relative increase in polar surface components could at least in part account for an increased electrophoretic mobility, Thus, several of the features which distinguish VLDL from chylomicrons could be explained solely on the basis of differences in particle size between the two lipoprotein classes.…”

Section: Discussionmentioning

confidence: 98%

Very low density lipoproteins in intestinal lymph: origin, composition, and role in lipid transport in the fasting state

Ockner¹,

Hughes²,

Isselbacher³

1969

J. Clin. Invest.

198

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A B S T R A C T The transport of endogenous lipids in the lipoproteins of mesenteric lymph was studied in fasting rats with mesenteric lymph fistulas. The lymph was found to contain, in addition to chylomicrons (Sf > 400), a significant amount of another, more dense, triglyceride-rich fraction, the very low density lipoproteins (VLDL), which showed a peak Sf of 102. The VLDL differed from chylomicrons not only in flotation, but also in per cent lipid composition and electrophoretic mobility in agarose gel. The VLDL fraction was found to contain 47% of the triglyceride and 54% of the cholesterol of fasting lymph and, in the fasting state, was the major lipoprotein species present.When cholestyramine resin was administered intraduodenally, or bile flow was acutely diverted from the intestine, it was demonstrated that the lipids in lymph VLDL, like those in chylomicrons, were derived from the intestine and bile. These data indicate that the VLDL in intestinal lymph are not derived from the plasma but are of intestinal origin.Because certain properties of lymph VLDL were similar to those reported for plasma VLDL (per cent lipid composition, flotation coefficient, and continuing entry into plasma in the fasting state), additional comparisons between these fractions were made. Although lymph VLDL moved to the as region in agarose gel, when they were mixed with VLDL-free serum immediately before electrophoresis they showed the a, mobility of rat serum VLDL. Furthermore, immunoelectrophoretic comparison of partially delipidated lymph and serum VLDL revealed that these fractions shared in

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Section: Discussionmentioning

confidence: 98%

Very low density lipoproteins in intestinal lymph: origin, composition, and role in lipid transport in the fasting state

Ockner¹,

Hughes²,

Isselbacher³

1969

J. Clin. Invest.

198

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“…However, the amount of lipids transported during the postprandial state is severalfold greater than that transported during the fasting state. Increased transport of fat with similar amounts of apoB48 occurs because of an increase in the size of the particles during the postprandial state (42,43,54,63,72,173). Fat feeding also increases the expression of apoA-IV, which serves as a surface component for apoB48 particles in the enterocyte (77,135).…”

Section: Assembly Secretion and Regulation Of Intestinal Lipoproteinsmentioning

confidence: 99%

Intestinal lipid absorption

Iqbal¹,

Hussain²

2009

American Journal of Physiology-Endocrinology and Metabolism

666

484

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Our knowledge of the uptake and transport of dietary fat and fat-soluble vitamins has advanced considerably. Researchers have identified several new mechanisms by which lipids are taken up by enterocytes and packaged as chylomicrons for export into the lymphatic system or clarified the actions of mechanisms previously known to participate in these processes. Fatty acids are taken up by enterocytes involving protein-mediated as well as proteinindependent processes. Net cholesterol uptake depends on the competing activities of NPC1L1, ABCG5, and ABCG8 present in the apical membrane. We have considerably more detailed information about the uptake of products of lipid hydrolysis, the active transport systems by which they reach the endoplasmic reticulum, the mechanisms by which they are resynthesized into neutral lipids and utilized within the endoplasmic reticulum to form lipoproteins, and the mechanisms by which lipoproteins are secreted from the basolateral side of the enterocyte. apoB and MTP are known to be central to the efficient assembly and secretion of lipoproteins. In recent studies, investigators found that cholesterol, phospholipids, and vitamin E can also be secreted from enterocytes as components of high-density apoB-free/apoAI-containing lipoproteins. Several of these advances will probably be investigated further for their potential as targets for the development of drugs that can suppress cholesterol absorption, thereby reducing the risk of hypercholesterolemia and cardiovascular disease.intestine; dietary fat; triacylglycerol; cholesterol; phospholipids; fat-soluble vitamins; microsomal triglyceride transfer protein DIETARY FATS CONSIST OF A WIDE ARRAY of polar and nonpolar lipids (32, 33). Triacylglycerol (TAG) is the dominant fat in the diet, contributing 90 -95% of the total energy derived from dietary fat. Dietary fats also include phospholipids (PLs), sterols (e.g., cholesterol), and many other lipids (e.g., fatsoluble vitamins). The predominant PL in the intestinal lumen is phosphatidylcholine (PC), which is derived mostly from bile (10 -20 g/day in humans) but also from the diet (ϳ1-2 g/day). The predominant dietary sterols are cholesterol (mostly of animal origin) and ␤-sitosterol (the major plant sterol). Although ␤-sitosterol accounts for 25% of dietary sterols, it is not absorbed by humans under physiological conditions.Researchers have been investigating the various steps involved in lipid digestion, absorption, and metabolism to identify factors that could serve as targets for the development of drugs capable of reducing the risk of lipid-associated disorders, including dyslipidemias and cardiovascular disease. In so doing, they have explored key aspects of lipid digestion hydrolysis, emulsification, and micelle formation. They have also explored key issues of absorption, e.g., the uptake of the products of lipid hydrolysis by enterocytes (the epithelial cells lining the walls of the intestinal lumen) and their transport to intracellular compartments, where fatty acids and sterols are...

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“…Zilversmit et al (1967) showed that in rabbits fed normal low fat diets, the lipids absorbed from the small intestines were also transported in lymph in the comparatively small lipoproteins. However, it was subsequently demonstrated that the sizes of these lymph lipoproteins were dependent on the amount of ingested dietary triacylglycerols and that the size increased with the intake of triacylglycerol (Fraser et al 1968;Ockner et al 1969;Fraser and Courtice 1969), accounting for the appearance of chylomicrons in plasma after the consumption of high fat diets (Simmonds 1972).…”

Section: Distribution Of Radioactivity In Lymph Lipoproteinsmentioning

confidence: 99%

“…The lymph sample remaining after removal of the chylomicrons was subjected to an 'infinite' ultracentrifugation at 100000 g at density 1·006 gil (Fraser et al 1968) to isolate the intestinal VLDL of All the samples of lymph lipoproteins were purified by washing through saline at density 1·006 gil for appropriate times in the ultracentrifuge and reconstituted to their original volume (Fraser 1970).…”

Section: Preparative Ultracentrifugationmentioning

confidence: 99%

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Size of Lipoproteins in Intestinal Lymph of Sheep and Suckling Lambs

Gooden¹,

Fraser²,

Bosanquet³

et al. 1979

Aust. Jnl. Of Bio. Sci.

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The relative importance of chylomicrons (Sf> 400) and very low density lipoproteins in transporting lipids in lymph was investigated in surgically prepared adult sheep and pre-ruminant lambs fed low fat diets or infused intraduodenally with corn oil. The concentration of triacylglycerol in the intestinal lymph of sheep and lambs was increased from 520 and 925 mg/1oo ml to 2326 and 2367 mg/loo ml respectively when corn oil was infused into the duodenum and the ratio of triacylglycerol to phospholipid changed from 3 ·7 and 5 . 5 to 9·5 and 9·7 respectively. The flow of lymph also increased. Electron microscopy and analytical and preparative ultracentrifugation showed that lymph lipoproteins from sheep and lambs fed low fat diets consisted mainly of lipoproteins 50 nm in diameter and that very low density lipoproteins (Sf 20-400) contributed up to 75 % of the Sf > 20 lipoproteins. There were no lipoproteins with diameters above 150 nm.Infusion of corn oil into the duodenum of sheep and lambs increased the diameters of lymph lipoproteins. Most were 80--100 nm in diameter but substantial numbers above 150 and up to 400 nm were observed. The maximum contribution of very low density lipoproteins to lipoproteins of Sf> 20 was 27-30%.The above findings demonstrate that the size of intestinal lymph lipoprotein particles increases with the amount of lipid absorbed from the small intestines and that the transport of lymph lipids, in ruminants, is similar to that previously found in rats, rabbits and man.

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The Effect of Dietary Fat Load on the Size and Composition of Chylomicrons in Thoracic Duct Lymph

Cited by 68 publications

References 15 publications

Very low density lipoproteins in intestinal lymph: origin, composition, and role in lipid transport in the fasting state

Very low density lipoproteins in intestinal lymph: origin, composition, and role in lipid transport in the fasting state

Intestinal lipid absorption

Size of Lipoproteins in Intestinal Lymph of Sheep and Suckling Lambs

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