Sterol synthesis in the human arterial intima

Steroid Fingerprint Analysis of Endangered Caspian Seal (Pusa caspica) through the Gorgan Bay (Caspian Sea)

The profile of steroid congeners was evaluated in Caspian seals Pusa caspica by age, sex, and tissue-specific bioaccumulation, and compared with that of abiotic matrices (seawater, surface sediment, and suspended particulate materials, SPMs) from Miankaleh Wildlife/Gorgan Bay, (Caspian Sea, Iran). To identify the level of human fecal contamination, ∑25 sterol congeners were measured in all abiotic/biotic samples, revealing coprostanol, a proxy for human feces, as the most abundant sterol (seawater: 45.1-20.3 ng L^-1; surface sediment: 90.2-70.3 ng g^-1 dw; SPMs: 187.7-157.6 ng g^-1 dw). The quantification of ∑25 sterols in seals followed the order of brain > liver > kidney > heart > blood > spleen > muscle > intestine > blubber > fur, and in both sexes coprostanol level (8.95-21.01% of ∑25s) was higher in blubber and fur, followed by cholesterol in brain, liver, kidney, heart, and blood, cholestanone in intestine and muscle, and β-sitosterol in spleen. Though no age/sex differentiation was observed, the mean concentration of ∑25s was higher in male than females and pup. Different diagnostic ratios revealed sterols originating from human and nonhuman sewage sources. Findings pinpoint the urgent necessity to investigate the ecotoxicity of fecal sterols in mammals, and consequent implications for human health.

Cholesterol absorption, synthesis, and fecal output in postmenopausal women with and without coronary artery disease

Hypercholesterolemia is a prominent risk factor for coronary artery disease (CAD), yet cholesterol metabolism has not been evaluated in women with CAD. The objective of this study was to determine the interrelations of CAD, serum squalene and sterols, and cholesterol metabolism with each other in postmenopausal women. For this purpose, we measured serum squalene and sterols and fecal steroids (cholesterol and bile acids) and squalene by gas-liquid chromatography and evaluated cholesterol absorption and synthesis in postmenopausal women with CAD (n=29) and age-matched controls (n=20). On similar dietary lipid intake, the cholesterol absorption efficiency and mean serum cholesterol level were comparable, but the squalene-to-cholesterol ratio was higher in cases than in controls. The presence of CAD was inversely associated with fecal total steroids (logistic regression coefficient beta/SE=-2.11, P=0.04) and cholesterol synthesis (beta/SE=-2.14, P=0.04) and turnover (beta/SE=-2.19, P=0.03) after adjustment for dietary cholesterol, family history of CAD, smoking, low and high density lipoprotein cholesterol, and serum triglyceride levels. A high serum squalene ratio was not related to cholesterol synthesis but was inversely related to fecal squalene excretion, which was lower in cases than in controls. In conclusion, the presence of CAD in postmenopausal women is independently associated with altered cholesterol metabolism, as reflected by low synthesis and inefficient elimination of cholesterol.

Studies on rat liver plasma membrane. Altered protein and phospholipid metabolism after injection of D-galactosamine

1. The metabolism of protein and phospholipid in rat liver plasma membranes isolated by the method of Neville [(1960) J. Biophys. Biochem. Cytol. 8, 413-422] was investigated 3 and 6 h after the injection of D-galactosamine in vivo. During this time, all the biochemical and morphological alterations associated with hepatitis developed. 2. After the injection of D-galactosamine the concentration of sphingomyelin in the plasma membrane decreased to below 60% of the control values. 3. The activity of 5'-nucleotidase (EC 3.1.3.5), which has been purified as a sphingomyelin-protein complex, decreased in the total homogenate as well as in the plasma-membrane fraction of livers of rats treated with galactosamine, to about 60% of the control values. 4. Protein synthesis, as measured by the incorporation of [14C]leucine into plasma membranes, was decreased to 45% of that of the controls. However, only small differences were observed in the amino acid composition of the plasma membrane after D-galactosamine treatment. 5. The protein composition of the plasma membranes was determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The results showed a change from low- to high-molecular-weight proteins after the injection of galactosamine. 6. These results demonstrate different metabolic processes of the plasma membrane altered during the induction of galactosamine hepatitis.

Non-human primate platelets and arterial tissue cannot convert preformed [14C]lanosterol into[14C]cholesterol in vivo

In contrast with the prevailing view, we report the inability of non-human primate platelets or arterial tissue to complete the biosynthesis of [14C]cholesterol from [14C]mevalonic acid in vitro or in vivo, or from performed [14C]lanosterol in vivo. The latter observation suggests that these tissues lack one or more components of the methyl sterol demethylase system.

The lipid metabolism of the arterial wall and its abnormalities in diabetes

Arteries are not simply conduits for the transport of blood, but consist of metabolically active tissue which has the capacity to synthesize all the components of the atherosclerotic lesion. The smooth muscle cell appears to be the most important metabolically active cell in the arterial wall. There is little information on arterial metabolism in human diabetes. Experimental diabetes depressed all aspects of arterial lipid metabolism and this effect is reversed by insulin. Insulin promotes changes in arterial metabolism which are similar to those an atherosclerosis. Thus the relationship of human diabetes to the metabolism of the arterial wall is complex and little understood.

Lipid metabolism in perfused human and dog coronary arteries

The paper represents a summary of our studies in which in vitro perfusion of human and animal coronary vessels was carried out. Formation and uptake of lipids in perfused human coronary arteries were studied under a vairety of experimental conditions, including exposure to carbon monoxide. The effect of collagenase on lipid synthesis and transport in carotid arteries of dogs was also studied. Human plasma with hydrogen-3-labeled cholesterol and carbon-14-acetate was used to perfuse human blood vessels. Autologous plasma was employed. Inhibition of cholesterol uptake was accomplished by the addition of 7-ketocholesterol (concentrations of 0.005 to 1 mum/ml) to the perfusate. Both atherosclerotic and normal human coronary arteries incorporated 14C-acetate into lipids but failed to synthesize either cholesterol of cholesterol esters. Similar results were obtained in human saphenous veins perfused at arterial pressure. Cholesterol uptake from the perfusion fluid was demonstrated in atherosclerotic and normal human coronary arteries as well as in human saphenous veins. Carbon monoxide increased permeability of the arterial wall to cholesterol uptake. In dog arteries exposed to collagenase marked increases in cholesterol uptake were found, but total lipid synthesis was reduced; the relative synthesis individual lipids remained unchanged. The addition of 7-ketocholesterol to the perfusate reduced cholesterol uptake by the vessel by 90 percent. Inhibition of cholesterol uptake was present in all species and was not due to oxidation of cholesterol to 7-detocholesterol in the perfusate. The results illustrate that human coronary arteries as well as human saphenous veins synthesize lipids but not cholesterol. Cholesterol flux into the artery is augmented by carbon monoxide and collagenase. The data also show that active inhibition of cholesterol uptake in the arterial wall can be accomplished by competitive inhibition with 7-ketocholesterol.