Cholesterols removal

Chinetti G, Lestavel S, Bocher V, Re-maley AT, Neve B, Torra IP, et al. PPAR-alpha and PPAR-gamma activators induce cholesterol removal from human macrophage foam cells through stimulation of the ABCA1 pathway. Nature Med 2001 7 53-58. 

Cholesterol Remove free fatty acids 3. Add 10 ml n-heptane, reflux for another 2 to 3 min, and cool to room temperature. 4. Quantitatively transfer the refluxed solution to a separatory funnel and add 5 ml saturated NaCl solution. 

A, Inhibition of proteolytic enzymes B, dissociation of hexameric to monomeric form of insulin C, loosening of tight junctions D, increase in membrane fluidity due to cholesterol removal E, reversible ciliostasis F, mucoadhesion and prolonged residence time G, incorporation into lipid bilayer and membrane perturbation H, insulin internalization, increased transcellular transport and I, correlation with CMC. 

Cholesterol has an alcohol group. One could also dehydrate cholesterol (removing one water molecule by heating). Show the structure you would expect from the dehydration of cholesterol. 

Similarly, removal of cholesterol from liquid egg yolk using /1-cyclodextrin has been reported. This involved the formation of an insoluble complex by binding with cholesterol in the oil-water interface of egg yolk. As the amount of added /1-cyclodextrin increased, the cholesterol removal efficiency was increased but valuable nutrients of egg yolk also decreased. As a result, it was concluded that the molar ratio of 3 1 5 1 for /l-cyclodextrin cholesterol was most effective at removing cholesterol from egg yolk [49]. 

Gow, C.Y. and Li, J.T. (1995) Cholesterol removal from a lard-water mixture with beta-cyclodextrin, J. Food Sci., 60, 561-564. 

Yen, G.C. and Chen, C.I. (2000) Effects of fractionation and the refining process of lard on cholesterol removal by beta-cyclodextrin. J. Food Sci., 65, 622-624. 

Cholesterol is present in milk at a level of 0.25-0.46%. The interest in removing cholesterol from milk fat has been driven primarily by consumer concern about the possible link between cholesterol and heart disease. Although there is still some debate about the causal relationship between dietary cholesterol and heart disease, a marketing position has been created for low-cholesterol products and this has spurred interest in examining alternative ways of cholesterol removal in the 1980s and 1990s (Schlimme, 1990). A number of physical, chemical and biological processes have been used to reduce the level of cholesterol in milk fat (Boudreau and Arul, 1993). Cholesterol-reduced butter has been introduced on the market in Europe (Anon, 1992). 

Alternative adsorbents for cholesterol are food-grade saponins. Com-plexation of cholesterol in milk fat with saponins in aqueous solutions, followed by separation of the cholesterol-saponin complex has been shown to be technically feasible for cholesterol removal (Sundfeld et al., 1993). 

Micich, T.J, Foglia, T.A., Holsinger, V.H. 1992. Polymer-supported saponins an approach to cholesterol removal from butteroil. J. Agric. Food Chem. 40, 1321-1325. 

Versteeg, C. 1991. Milkfat fractionation and cholesterol removal. CSIRO Food Research Quarterly 51, 32-42. 

HDLs also acquire cholesterol by extracting it from cell-surface membranes. This process has the effect of lowering the level of intracellular cholesterol, since the cholesterol stored within cells as cholesteryl esters will be mobilised to replace the cholesterol removed from the plasma membrane. 

Vacuum Steam Distillation. There has been direct application of cholesterol removal by vacuum steam distillation, an old technology. This process is widely used in the fats and oils industry for deodorization. 

The process for cholesterol removal from anhydrous milkfat was patented by General Mills (41). Fractionment Tirtiaux also disclosed the development of a vacuum steam distillation system called the LAN cylinder (38). The steam distillation process (Figure 2) was commercialized, producing a 90-95% cholesterol reduction in anhydrous milkfat with a 95% yield that was reconstituted into 2% fat fluid milk (42). The major disadvantage to the process is that it strips or removes most all volatile flavor components from the fat. These flavor components must be captured (i.e., vacreation) before the distillation process to attempt to reproduce the delicate flavors so desired for reconstitution into a butter product. 

This process appears to provide considerable economic and practical advantages over alternative cholesterol reduction technologies, such as steam distillation and supercritical carbon dioxide fluid extraction. For instance, there is no absorption of vitamins, it is a low-temperature operation, and it has a low capital cost. The only economic concern is that the ratio of the addition of p-cyclodextrin to the cholesterol removed is high, creating the potential for a high-cost process. Even so, the Europeans have commercialized the process, and reduced-cholesterol butter and cheese products have been introduced into the marketplace (49). 

Supercritical Fluid Extraction. The supercritical fluid extraction process created extensive excitement in the mid-1980s in the research community as a preferred process for cholesterol removal. Extensive research at various universities was initiated to evaluate its potential, and significant publicity was generated within the dairy industry (45, 46, 52-56). 

By the late 1980s, technologies for the removal of cholesterol with supercritical carbon dioxide were offered by a number of companies (38). Commercialization was never attempted by any major food company for removal of cholesterol. Successful scale-up and commercialization was achieved by the General Foods Corporation for removal of caffeine from coffee (45). The primary disadvantages for the dairy industry were the low yields, low cholesterol removal, and the very high capital and operating costs of the equipment. 

Enzymatic. Biological procedures for cholesterol removal make use of microorganisms that produce enzymes to convert cholesterol into innocuous compounds. Several enzymatic systems are being investigated in different cormtries of the world. Most systems use a cholesterol reductase that converts the cholesterol into coprostanol and coprosterol (52, 57). These converted compounds are very poorly absorbed by the digestive system and pass through intact. Several investigators have isolated and characterized Eubacteria able to convert cholesterol into coprostanol from rat, baboon, and human feces. Leaves of cucumber, soybeans, corn, and beans are known to contain similar enzymes (45, 57, 58). Lactobacillus acidophilus has also been reported to metabolize cholesterol (51). 

Regulatory-Nutritional. Many of the processes for cholesterol removal will meet with regulatory hurdles because of residues, unapproved additives, or byproduct formation. But the real burden for the U.S. dairy industry was the 1993 Nutritional Labeling and Education Act (54). This act created commercial prohibitions,... 

HDLs are secreted in nascent form by hepatocytes and en-terocytes (Figure 20-7). Loss of surface components, including phospholipids, free cholesterol, and protein from chylomicrons and VLDL as they are acted on by lipoprotein lipase, may also contribute to formation of HDL in plasma. Discoidal, nascent HDL is converted to spherical, mature HDL by acquiring free cholesterol from cell membranes or other lipoproteins. This function of HDL in peripheral cholesterol removal may underlie the strong inverse relationship between plasma HDL levels and incidence of coronary heart disease. After esterification of HDL surface cholesterol by LCAT, which is activated by apo A-I, HDL sequesters the cholesteryl ester in its hydrophobic core. This action increases the gradient of free cholesterol between the cellular plasma membrane and HDL particles. Cholesteryl esters are also transferred from HDL to VLDL and LDL via apo D, the cholesteryl ester transfer protein (Figure 20-8). 

Role of HDL in peripheral cholesterol removal. Free cholesterol in plasma membranes of peripheral tissues is transferred to apo A-I containing pre-/ -HDL (nascent HDL), via an ATP-binding cassette transporter 1 (ABCl). Cholesterol is esterified by LCAT and stored in the core of the HDL particle. In the presence of suitable acceptor lipoproteins (VLDL or LDL), cholesteryl esters are transferred from HDL via apo D and CETP to the lower density lipoproteins, thereby shortening the half-life of plasma cholesterol since VLDL and LDL have a much faster turnover time than HDL. PL = Phospholipid. 

The mechanism by which albumin (in many cases bovine serum albumin BSA) promotes capacitation in mammalian sperm is intriguing as it is believed to function during capacitation in vitro as a sink for the removal of cholesterol from the sperm plasma membrane (Go and Wolf, 1985 Langlais and Roberts, 1998 Cross, 1998). The association between cholesterol removal from the sperm plasma membrane, albumin, and capacitation was first proposed by Davis and colleagues (1980). Removal of this sterol likely accounts for the membrane fluidity changes observed during capacitation (Wolf et al., 1986). The consequence of the removal of this sterol is that the cholesterol to phospholipid ratio in the membrane decreases, and such changes in... 

Modulation of the cholesterol content of membranes affects passive permeability to water and other molecules. For example, permeability to Na and is known to increase at the boundary between domains of rigid and fluid phospholipid within a bilayer which may result from cholesterol removal [72,73]. 

How does cholesterol leave the cell Since most cells do not secrete cholesterol esters (the known exceptions are hepatocytes and intestinal epithelial cells), free cholesterol must take its way to the outer bilayer of the cell membrane, where it may be removed by appropriate acceptors. It is likely that a net loss from the cell membrane involves movement of cholesterol from an area in the membrane with a high cholesterol-phospholipid ratio to an area with a lower ratio in the acceptor. The appropriate acceptors for cholesterol removal include any phospholipid bilayer system that contains little or no free cholesterol [125]. In vivo this is intact or nascent HDL [126,127]. Nascent HDL is a disc of phospholipid surrounded on its hydro-phobic perimeter by detergent-like apoproteins, such as the arginine-rich apoprotein and the HDL apoproteins, apo AI and apo All [128]. It is secreted from the liver and probably from the intestine (Chapter 5) into the plasma. Cholesterol enters nascent or intact HDL, and the lecithin-cholesterol acyltransferase (LCAT) reaction converts it to cholesterol ester [129,130] (Chapter 4). Since the ester is insoluble in the phospholipid bilayer it oils out into the centre of the particle. In this way. nascent discs are converted to spheres, and space for a new substrate, cholesterol, is created at the surface of the particle. Lipoproteins in lymph may also produce. similar effects on the cell surfaces exposed to this fluid. 

HDL promotes cholesterol removal, and the level should be greater than 60 mg/dL. The client s HDL is low, less than 40 mg/dL, which indicates the medication is not effective. 

CDs are effectively used for the removal of cholesterol fi-om animal products, such as eggs and dairy products with the need of nutrition properties. The immobilized /3-CD glass beads prepared by silanization and immobilization reaction can generate 41% of cholesterol removal in milk and a recycling efficiency of almost 100% [41]. It is also reported that the crosslinked fi-CD can obviously reduce the cholesterol and retain most of physicochemical and sensory properties of mayonnaise [42]. Another previous study has been carried out to estimate the functional properties of cholesterol-removed whipping cream by -CD, indicating that the cholesterol is almost eliminated and less time is needed for cream whipping, after the treatment of /3-CD [43]. 

Kwak, HS, SH Kim, JH Kim, HJ Choi and J feng(2004). Immobilized bcyclodextrin as a simple and recyclable method for cholesterol removal in milk. Archiers ofPharmacal... 

Shim, SY, J Ahn and HS Kwak (2003). Functional properties of cholesterol-removed whipping cream treated by /3-cyclodextrin. Journal of Dairy Science, 86, 2767-2772. 

Liong, M.T. and Shah, N.P. (2005) Production of organic acids from fermentation of mannitol, fruc-tooligosaccharide and inulin by a cholesterol removing Lactobacillus acidophilus strain. /. Appl Microbiol, 99, 783-793. 

Food purification COj Coffee decaffeination Cholesterol removal from egg yolk... 

Food purification CO2 Oil purification Cholesterol removal from miUc fat... 

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