Lipoprotein Very high-density

Part of a minor fraction known as very high density lipoproteins (VHDL). 

FIGURE 3.2.2 Metabolic pathways of carotenoids such as p-carotene. CM = chylomicrons. VLDL = very low-density lipoproteins. LDL = low-density lipoproteins. HDL = high-density lipoproteins. BCO = p-carotene 15,15 -oxygenase. BCO2 = p-carotene 9, 10 -oxygenase. LPL = lipoprotein lipase. RBP = retinol binding protein. SR-BI = scavenger receptor class B, type I. 

Many of the globulins act as transport proteins. Of particular interest are those proteins which are combined with lipids, themselves synthesized in the liver, to form lipoprotein complexes. High density lipoprotein (HDL), which contains predominantly apoproteins A and C combined with mainly phospholipids (most of the cholesterol found in mature HDL is added later) and very low density lipoprotein... 

Contains very high-density lipoproteins and albu-... 

CHYL = chylomicron VLDL = very low-, LDL = low-, HDL = high-, and VHDL = very high-density lipoprotein. 

Fic. 3. Protein components of human serum very high-density lipoprotein (VLDL) apoprotein (Apo). According to the experience gained in this laboratory, this component is negligible. As shown by Brown et al. (B9, BIO), it becomes relevant in VLDL of patients with types IV and V hyperlipoproteinemia,... 

Fig. 6. Amino acid sequence of serum very high-density lipoprotein Di or Ci (apo Lp-Ser). Data from Shulman et al. (S35).

Choi, cholesterol TG, triglyceride CHD, coronary heart disease LDL, low density lipoproteins LPL, lipoprotein lipase VLDL, very low density lipoprotein HDL, high-density lipoprotein IDL, intermediate-density lipoprotein. 

The effects of coenzyme Q10 on coronary artery disease and chronic stable angina are modest but appear promising. A theoretical basis for such benefit could be metabolic protection of the ischemic myocardium. Double-blind, placebo-controlled trials have demonstrated that coenzyme Q10 supplementation improved a number of clinical measures in patients with a history of acute myocardial infarction (AMI). Improvements have been observed in lipoprotein a, high-density lipoprotein cholesterol, exercise tolerance, and time to development of ischemic changes on the electrocardiogram during stress tests. In addition, very small reductions in cardiac deaths and rate of reinfarction in patients with previous AMI have been reported (absolute risk reduction 1.5%). 

Figure 3.11 Composition (%) of human serum lipoproteins VLDL, very low density lipoproteins LDL, low density lipoproteins HDL, high density lipoproteins.

Major plasma proteins serum albumin, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), high-density lipoproteins (HDL), immunoglobulins (hundreds of kinds), fibrinogen, prothrombin, many specialized transport proteins such as transferrin... 

FIG. 1 Schematic diagram of cholesterol transport in the tissues, with sites of action of the main drug affecting lipoprotein metabolism (C = cholesterol CE = cholesteryl ester TG = triglycerides MV A = mevalonate HMG-CoA reductase = 3-hydroxy-3-methyl-glutaryl-CoA reductase YLDL = very low density lipoproteins LDL = low density lipoproteins HDL = high density lipoproteins). (Reprinted from Rang et al (1999), with permission from Elsevier Science.)... 

Lipoproteins are assembled in two organs, the small intestine and the liver. The lipoproteins assembled in the intestine contain the lipids assimilated from the diet. These lipoproteins, called chylomicrons, leave the enterocyte and enter the bloodstream via the Lymphatic system. The lipoproteins assembled in the liver contain lipids originating from the bloodstream and from de novo synthesis in the liver. The term de novo simply means "newly made from simple components" as opposed to "acquired from the diet" or "recycled from preexisting complex components." These lipoproteins, called very-low-dcnslty lipoproteins (VLDLs), are secreted from the liver into the bloodstream. The liver also synthesizes and secretes other Lipoproteins called high-density Lipoproteins (HDLs), which interact with the chylomicrons and VLDLs in the bloodstream and promote their maturation and function. The data in Table 6-4 show that chylomicrons contain a small proportion of protein, whereas HDLs have a relatively high protein content. Of greater interest is the identity and function of the proteins that constitute these particles. These proteins confer specific properties to lipoprotein particles, as detailed later in this chapter. 

Abbreviations GcL, Geotrichum candidum lipase hPL, human pancreatic lipase RmL, Rhizomucor miehei lipase hHL, human hepatic lipase hLPL, human lipoprotein lipase hLAL, human lysosomal acid lipase hGL, human gastric lipase BAL, bile salt-activated lipase HSL, hormone-sensitive lipase CLP, colipase AChE, Torpedo cal omica acetylcholinesterase cDNA, complementary deoxyribonucleic acid VLDL, very low-density lipoprotein IDL, intermediate-density lipoprotein HDL, high-density lipoprotein apoC-II, apolipoprotein C-II. 

Vertebrate, especially mammalian, lipoproteins have been extensively studied. In the invertebrate world, only insect lipoproteins have received serious attention. Whereas vertebrates rely on a battery of lipoproteins (chylomicrons, very low-density lipoproteins, low-density lipoproteins, and high-density lipoproteins) to effect lipid transport, insects use primarily a single type of lipoprotein, lipophorin, for lipid transport. Lipophorin is both more versatile than vertebrate lipoproteins in terms of the diverse lipids it transports and more efficient than vertebrate lipoproteins in that, for the most part, it delivers lipids to tissues without being internalized and destroyed. We believe that new insights can be obtained from an understanding of insect lipoproteins, and in this article we review the current state of knowledge about the structure and metabolism of lipophorins. 

The lipid transfer particle (LTP) is a very high-density lipoprotein having a molecular mass greater than 650 kDa. LTP contains about 15% lipid and three apolipoproteins with = 320,000, 85,000, and 55,000. First discovered in M. sexta (Ryan et al., 1986a), LTP has been purified... 

Eggs from Hyalophora cecropia (Telfer, 1960), Samina cynthia (Chino et al., 1977), M. sexta (Kawooya et al., 1988), and R. prolixus (Gondim et al., 1989b) have been shown to contain a very high-density lipophorin, VHDLp-E, which is derived from HDLp-A in the hemolymph by a receptor-mediated process (Kawooya et al., 1988 Telfer and Pan, 1988 Kulakosky and Telfer, 1990) this represents the only known exception to the generalization that lipophorin delivers its lipids to tissues without internalization. The conversion of HDLp-A to VHDLp-E involves removal of DG, which is catalyzed by a lipoprotein lipase found in the yolk body of the egg (Van Antwerpen and Law, 1992). However, in spite of the presence of lipophorin in the egg, 90% of the lipid in the egg is... 

Figure 6-1. Overview of lipid metabolism in the fed state. TG = triacylglycerol 2-MG = 2-monoacylglyceroi FA = fatty acid LPL = lipoprotein lipase VLDL = very-low-density lipoprotein HDL = high-density lipoprotein circled TG = triacylglycerols of VLDL and chylomicrons.

Koudinov A, Matsubara E, Frangione B, Ghiso J. 1994. The soluble form of Alzheimer s amyloid beta protein is com-plexed to high density lipoprotein 3 and very high density lipoprotein in normal human plasma. Biochem. Biophys. Res. Commun. 205(2) 1164-71... 

VLDL, Very low-density lipoproteins IDL, intermediate-density lipoproteins LDL, low-density lipoproteins HDL high-density lipoproteins Lp(a), lipoprotein (a). 

LCAT=Lecithin-cholesterolacyltranferase LPL=Iipoprotein lipase VLDL=very-low-density lipoprotein LDL=low-density lipoprotein HDL= high-density lipotrotein IDL=intermediate density lipoprotein. 

VLDL = very low-density lipoprotein LDL = low-density lipoprotein HDL = high-density lipoprotein. 

Lipid panel includes total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride and/or very low-density lipoprotein (VLDL). 

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