Sterol

About: Sterol is a research topic. Over the lifetime, 8117 publications have been published within this topic receiving 309926 citations. The topic is also known as: sterols & sterol lipids.

Roles of carbonyl oxygens at the bilayer interface in phospholipid-sterol interaction.

Abstract: FROM many recent studies on the phospholipid–sterol interaction, it has become increasingly clear that the 3 α-and 3 β-hydroxy isomers of a range of sterols have quite different effects on the molecular mobility and functional property of lipid bilayer membranes1,2. For example, the addition of cholesterol or Δ5-cholesten-3 β-ol to liposomes decreases their permeability, whereas epicholesterol, a 3 α-isomer of cholesterol, exerts no apparent effect. It has been proposed that the 3 β-hydroxyl group engages in hydrogen bonding with the carbonyl oxygen of the fatty acyl groups in phospholipids in the bilayer3. Evidence supporting such hydrogen bond formation is strong4. The problem is, then, why does the 3 β-OH group of cholesterol, but not the 3 α-OH group of epicholesterol form such bonds?

Microbial cleavage of sterol side chains.

Abstract: Publisher Summary This chapter discusses the microbial cleavage of sterol side chains. The recent interest in the microbial conversion of sterols to C19 steroids was caused by the increased demand for steroid drugs and the shortage of diosgenin. As the microbial process has to compete with chemical methods, high conversion efficiencies in the presence of large substrate concentrations have to be obtained. These processes are now used on an industrial scale for the production of 17-ketosteroids. Conventional chemical oxidation of the saturated aliphatic chain results in very low yields. However, in using remote oxidation, the removal of the cholesterol side chain proceeds rather efficiently. For the chemical oxidation of unsaturated sterol side chains, there exist few methods. As alternative to chemical methods, the microbial removal of the aliphatic side chain of phytosterols offers a promising method for use of these sterols and has been studied for some time. Recently, processes for the commercial conversion of sterols to C19-steroids by microorganisms have been developed.

Lipoprotein receptors, cholesterol metabolism, and atherosclerosis

Abstract: Deposition of cholesterol esters in the arterial intima is a characteristic feature of human atherosclerosis. Very little is known about the mechanisms by which cells normally regulate their cholesterol ester content. Recent studies in cultured human cells demonstrate the existence of a cell surface receptor that binds plasma low density lipoproteins and regulates the sterol content of cells by modulating the rates of uptake, esterification, and synthesis of cholesterol. A possible role for this lipoprotein receptor in the pathogenesis of atherosclerosis is discussed.

Hydroxymethylglutaryl-CoA reductase, a key enzyme in phytosterol synthesis?

Abstract: Hydroxymethylglutaryl-CoA reductase (HMGR) regulates the synthesis of mevalonic acid (MVA), the precursor of the myriad of isoprenoid compounds functional in plant cells, with phytosterols representing one class of major importance. Recently, it has shown possible to solubilize and purify the membrane-bound enzyme from a heavy membrane fraction (P 16,000×g) isolated from a cell-free homogenate of etiolated radish seedlings. What is presently known about the molecular and kinetic properties of radish HMGR is reported. Mevinolin, a highly specific competitive inhibitor of HMGR, has been valuable as a research tool in studying the regulatory role of HMGR activity for the growth and development of intact seedlings and cell cultures. The results obtained indicate a primary effect of mevinolin on phytosterol accumulation, whereas other endproducts of the multibranched isoprenoid pathway, such as ubiquinone in the mitochondria or chlorophylls and carotenoids in the plastids, are less or not at all affected. This and other data can be interpreted to mean that the organelles are autonomous in their capacity to synthesize MVA. Since the mevinolin-induced drop in free sterol accumulation is paralleled by significant plant growth retardation, a rate-limiting role of HMGR activity for phytosterol synthesis and normal development of plants is suggested.

Soy protein enhances the cholesterol-lowering effect of plant sterol esters in cholesterol-fed hamsters.

Abstract: This study aimed to investigate whether the combination of plant sterol esters (PSE) with soy protein or soy isoflavones may have extra cholesterol-lowering effects. Male hamsters (n=20/group) were fed diets containing (g/100 g diet) (A) 20 casein (control), (B) 0.24 PSE, (C) 20 intact soy protein (replacing casein), (D) 0.02 soy isoflavones, (E) 0.24 PSE plus 20 soy protein (replacing casein), or (F) 0.24 PSE plus 0.02 soy isoflavones, for 5 wk. All diets contained 0.08 g cholesterol/100 g diet. Compared with the control diet, the PSE and soy protein diets significantly lowered the plasma total cholesterol concentration by 13% (P<0.05) and 9% (P<0.05), respectively, whereas the isoflavone diet (D) had no effect. The combination of PSE and soy protein (diet E) decreased plasma total cholesterol by 26% (P<0.05). The decrease in plasma cholesterol concentration was mainly in the non-HDL fraction. In addition, the combination of PSE and soy protein significantly decreased plasma triacylglycerol concentration (37%, P<0.05) and reduced cholesterol accumulation in the liver. The abundance of hepatic LDL-receptors was not influenced by any of the test diets. PSE selectively increased fecal excretion of neutral sterols by 190% (P<0.05), whereas soy protein increased fecal excretion of neutral sterols and bile acids by 66% (P<0.05) and 130% (P<0.05), respectively. The combination of PSE and soy protein increased the fecal excretion of neutral sterols and bile acids compared with PSE and soy protein alone. In conclusion, the combination of PSE and soy protein more dramatically lowers plasma lipids than the individual ingredients.