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.

Plasma lipoprotein metabolism in perfused rat livers. ii. transfer of free and esterified cholesterol into the plasma

Abstract: When cholesterol was a dietary component (2% of the diet), it was dissolved in olive oil and fed for 5 to 7 days, except in the experiments described in Tables VI, VII, and VIII; in those, cholesterol was fed for 12 to 14 days in order to produce livers of very high lipid content. Liver perfusion. The technique of perfusion of Miller and associates (6, 7) was used. Mevalonic acid-2-C'4 was used as sterol precursor. In some experiments, 3.3 to 5.5 ,sc (0.7 to 1.2 mg) was added directly to the perfusing blood; one-third of the total was added at the start of the experiment, and the rest, by continuous injection during the perfusion (2 to 4 hours). In other experiments, designed to study the transfer of labeled cholesterol from liver to plasma, 11 ,uc of mevalonic acid-2-C"4 was given in two ip injections to the rats used as liver donors, at 16 hours and 3 hours before removal of their livers.

Serum cholestanol and plant sterol levels in relation to cholesterol metabolism in middle-aged men.

Abstract: Serum cholestanol was studied in relation to fecal cholestanol excretion and cholesterol metabolism in a random middle-aged population of 61 men. The serum concentrations of cholestanol ranged from 1.6 to 10.8 mumol/L and were positively correlated with those of serum total LDL and HDL cholesterol. In terms of millimole per mole of cholesterol, these correlations disappeared; inverse associations were found with VLDL cholesterol and triglyceride levels, the P/S ratio of dietary fat, and the amount of fecal plant sterols, but not with fecal cholestanol. The serum contents of cholestanol (1) were also closely positively associated with those of serum plant sterols (campesterol and sitosterol) and fractional cholesterol absorption, (2) were inversely related to the fecal excretion of neutral sterols and cholesterol synthesis which were measured either by the sterol balance technique or serum cholesterol precursor sterols (desmosterol and lathosterol), and (3) were unrelated to bile acid synthesis. Fecal cholestanol (mean = 12.5 mg/d) was (1) clearly higher than the dietary cholestanol intake (less than 2 mg/d), (2) unrelated to serum cholestanol, and (3) positively correlated with the intestinal cholesterol (dietary plus endogenous) flux as well as fecal plant sterols, neutral sterols, and bacterial products of cholesterol. The study emphasizes that, in normal men, high serum cholestanol levels reflect high efficiency of intestinal sterol absorption and low cholesterol synthesis. Thus, the changes in the serum contents of cholestanol are parallel with those of plant sterols and opposite to those of cholesterol precursor sterols.

A critical role of sterols in embryonic patterning and meristem programming revealed by the fackel mutants of Arabidopsis thaliana

Abstract: Here we report a novel Arabidopsis dwarf mutant, fackel-J79, whose adult morphology resembles that of brassinosteroid-deficient mutants but also displays distorted embryos, supernumerary cotyledons, multiple shoot meristems, and stunted roots. We cloned the FACKEL gene and found that it encodes a protein with sequence similarity to both the human sterol reductase family and yeast C-14 sterol reductase and is preferentially expressed in actively growing cells. Biochemical analysis indicates that the fk-J79 mutation results in deficient C-14 sterol reductase activity, abnormal sterol composition, and reduction of brassinosteroids (BRs). Unlike other BR-deficient mutants, the defect of hypocotyl elongation in fk-J79 cannot be corrected by exogenous BRs. The unique phenotypes and sterol composition in fk-J79 indicate crucial roles of sterol regulation and signaling in cell division and cell expansion in embryonic and post-embryonic development in plants.

Molecular cloning and expression of the human Δ7-sterol reductase

Abstract: Inhibitors of the last steps of cholesterol biosynthesis such as AY9944 and BM15766 severely impair brain development. Their molecular target is the Δ7-sterol reductase (EC 1.3.1.21), suspected to be defective in the Smith–Lemli–Opitz syndrome, a frequent inborn disorder of sterol metabolism. Molecular cloning of the cDNA revealed that the human enzyme is a membrane-bound protein with a predicted molecular mass of 55 kDa and six to nine putative transmembrane segments. The protein is structurally related to plant and yeast sterol reductases. In adults the ubiquitously transcribed mRNA is most abundant in adrenal gland, liver, testis, and brain. The Δ7-sterol reductase is the ultimate enzyme of cholesterol biosynthesis in vertebrates and is absent from yeast. Microsomes from Saccharomyces cerevisiae strains heterologously expressing the human cDNA remove the C7–8 double bond in 7-dehydrocholesterol. The conversion to cholesterol depends on NADPH and is potently inhibited by AY9944 (IC50 0.013 μM), BM15766 (IC50 1.2 μM), and triparanol (IC50 14 μM). Our work paves the way to clarify whether a defect in the Δ7-sterol reductase gene underlies the Smith–Lemli–Opitz syndrome.