Plasma Campesterol Research Articles

Effects of variable dietary sitostanol concentrations on plasma lipid profile and phytosterol metabolism in hamsters

To examine how variable sitostanol (SI) levels in phytosterol-supplemented diets influence plasma and hepatic lipid concentrations, fifty hamsters were divided into five groups and fed semipurified diets containing 0.25% (w/w) cholesterol for 45 days ad libitum. Four groups were fed this diet with 1% (w/w) phytosterol mixtures which contained 0.01% (w/w) SI derived from soybean, 0.2% (w/w) SI derived from tall oil, 0.2% (w/w) synthetic SI mixture (SIM) and 1% (w/w) pure SI, respectively. A control group did not receive phytosterols. Dietary SI supplementation at 1% (w/w) decreased total and non-apolipoprotein-A cholesterol levels in plasma by 34% ( P=0.001) and 55% ( P=0.04), respectively, whereas mean plasma total cholesterol level in the 0.2% (w/w) SI group was 23% ( P=0.001) lower than that of the control group. Conversely, plasma lipid profile in hamsters fed 1 or 0.2% (w/w) SI did not differ from the 0.01% (w/w) SI group. Liver weights were 15 and 20% ( P=0.012) higher in the control group compared with those fed 0.01% and 1% (w/w) SI, respectively, while the hepatic cholesterol content in the control group was greater ( P<0.0001) than that of all other groups. Plasma campesterol levels were higher ( P=0.04) in the 0.01% and 0.2% (w/w) SI fed groups than in the control, 0.2% (w/w) SIM and 1% (w/w) SI groups. Hepatic sitosterol content was elevated ( P=0.002) in the SIM fed group compared to other groups. We conclude that dietary SI effect is proportional to its concentration in phytosterol mixtures and in the diet. Dietary SI lowered plasma cholesterol levels at concentrations higher than 0.2% (w/w) in hamsters.

Enhanced efficacy of sitostanol-containing versus sitostanol-free phytosterol mixtures in altering lipoprotein cholesterol levels and synthesis in rats

To investigate the action and mechanism of a dietary phytosterol mixture naturally containing sitostanol, derived from tall-oil, on circulating cholesterol and lipoprotein levels, five groups of rats were fed a control elemental diet (group 1), a control elemental diet with 1% cholesterol alone (group 2) or with sitostanol mixtures or a sitostanol-free mixture supplemented at 0.2% (group 3), 0.5% (group 4) or 1% (group 5) of dietary levels. One per cent supplementation of sitostanol (21%) compared with sitostanol-free mixtures decreased ( P < 0.02) total serum cholesterol. Dietary sitostanol (16% or 21%) mixture at 1% dietary levels decreased ( P < 0.05) low density lipoprotein (LDL) cholesterol and increased ( P < 0.05) high density lipoprotein (HDL) cholesterol levels. The decrease of LDL and increase of HDL cholesterol were correlated ( P < 0.01) with the level of sitostanol mixture in the diet. Consumption of the sitostanol-containing mixture (1% dietary levels) caused a compensatory increase in cholesterol synthesis as indicated by elevated ( P < 0.05) lathosterol/cholesterol ratios in plasma and hepatic cholesterol fractional synthesis rate (FSR) ( P < 0.02). Both sitostanol and sitostanol-free mixtures at 0.5% or 1% dietary intake levels increased plasma campesterol and β-sitosterol levels, while plasma sitostanol levels were negligible. The absence of sitostanol in plasma and the increase in cholesterol synthesis induced by dietary sitostanol mixtures in addition to elevation of plasma campesterol and β-sitosterol by sitostanol or sitostanol-free mixtures suggest that sitostanol mixtures effectively modify circulating lipoprotein cholesterol concentrations at the level of the intestine, rather than internally at the level of cholesterogenesis.

Plasma lathosterol and campesterol in detection of ileal dysfunction.

Plasma lathosterol levels reflect cholesterol synthesis, especially that induced by bile acid malabsorption, whereas plasma plant sterol contents change in parallel with cholesterol and fat absorption. The significance of lathosterols and plant sterols (campesterol and sitosterol) was therefore studied in detection of ileal dysfunction in 29 patients with ileal resection (7 with no malabsorption, 8 with only bile acid malabsorption, and 15 with bile acid, fat, and cholesterol malabsorption) and in 8 jejunoileal bypass patients with fat, bile acid, and cholesterol malabsorption. Ileal dysfunction-induced faecal loss of bile acids was proportionate to cholesterol synthesis, which, in turn, was proportionate to the plasma levels of lathosterols, so that the lathosterols contents were also closely correlated (r = 0.880) to faecal bile acids. The lower the cholesterol absorption, the lower was the plasma campesterol (less consistently, beta-sitosterol) level and the higher the faecal fat. Thus, elevated plasma lathosterol content is highly suggestive of bile acid malabsorption in a patient with suspected ileal dysfunction. High plasma content of lathosterols combined with a low campesterol level points to associated fat malabsorption, indicating that the lathosterol to campesterol ratio in plasma is frequently increased in patients with ileal dysfunction associated with steatorrhoea.

Regulation of plasma plant sterol levels in patients with gut resections

The role of cholesterol and bile acid malabsorption in the regulation of plasma plant sterol levels was studied in 30 patients with an ileal resection (seven without any malabsorption, eight with bile acid malabsorption alone and 15 with bile acid, fat and cholesterol malabsorption) and nine with jejunoileal bypass (modest bile acid, and severe cholesterol and fat malabsorption). In contrast to cholesterol, plant sterols are not synthesized by the body, and so the plasma levels are regulated by their intestinal absorption and biliary secretion. In fact, the plant sterol, especially campesterol, levels were low in patients with cholesterol and fat malabsorption. Cholesterol absorption efficiency was a significant determinant of the plant sterol levels, suggesting that it reflects overall sterol absorption efficiency and that the plasma plant sterol levels, in turn, reflect cholesterol absorption. Bile acid malabsorption, though it appeared to promote biliary plant sterol secretion, had little direct effect on the plasma plant sterol contents. The results indicate that plasma campesterol levels can be used to evaluate cholesterol absorption efficiency in general and may reveal clinically significant steatorrhoea in patients with gut exclusion.

Beziehungen zwischen Indolessigsäure-induziertem Wachstum und dem Steringehalt der Plasmamembran-Fraktion bei Avena-Koleoptilen

Summary After etiolated Avena coleoptiles have been incubated either for 1 h or 20 h in buffered 10-4 or 10-5 MIAA, the plasma membrane fraction was isolated by means of homogenization and centrifugation on a linear sucrose gradient of 15-45 % (w/w). Centrifugation concentrated plasma membrane material in the sucrose gradient fractions of 33-37 %. This material was identified by electron microscopy and with the aid of marker enzymes. After extraction of the plasma membrane fraction, cholesterol, campesterol, stigmasterol, and sitosterol could be detected in the purified extract by means of gc-ms-analysis. Quantitative determinations of the sterols contained in the plasma membrane after IAA-treatment revealed that, in comparison to the untreated control, 10-5 M IAA applied 1 h before analysis leads to an increased concentration (11-24 %) of the four identified sterols, whereas incubation for 20 h in 10-4 M IAA shows a weaker promotive effect (2-15 %); in fact, the concentration of sitosterol deereases. As it is well known that sterols can influence microviscosity and permeability in biomembranes, it may be concluded from the above-mentioned results that a relationship exists between the primary action of the tested auxin and the sterol composition of the plasma membrane. However, these alterations in the sterol concentration observed in extracts of complete membranes are rather small; but with regard to this observation, it must be taken into consideration (ORCI et al. 1980) that the distribution of sterols in membranes is not homogeneous. Thus, it might be possible that sterol concentrations underwent strongly localized alterations after IAA treatment of the plasma membrane. These locations could be situated near transport proteins or ATPases responsible for proton pumping. It seems reasonable to believe that many effects observed after steroid treatment of plants may be attributable to the interrelation of auxins and sterols at the membrane level.

Absorbability of Plant Sterols in the Rhesus Monkeys

High- and low-responding rhesus monkeys were fed a semisynthetic high or low cholesterol diet with 2% plant sterols for 6 weeks to determine the absorbability of the plant sterols. No plant sterols were detected in the plasma of either high- or low-responding animals fed either high or low cholesterol diet containing low levels of plant sterols. After addition of 2% plant sterols to either of the diets, only campesterol was found in the plasma of all animals. The final plasma campesterol concentrations in the high-responders on high and low cholesterol diets containing high levels of plant sterols were 0.91 ± 0.14(SE)and 1.16 ± 0.27 mg/dl, respectively. Similar values in the low-responders were 0.51 ± 0.06 and 0.24 ± 0.16 mg/dl, respectively. Sitosterol was occasionally detected in trace amounts in some animals of both groups on either high or low cholesterol diet. Stigmasterol was not detected in the plasma of any animals. We conclude, based on the plasma sterol levels, that rhesus monkeys absorb campesterol and probably do not absorb sitosterol or stigmasterol in any significant amount. The study also shows that the high-responders absorb higher amounts of campesterol than the low-responders; a finding similar in respect to cholesterol absorption in the high-responders.

Absorbability of plant sterols and their distribution in rabbit tissues

Rabbits were fed a low cholesterol diet containing 2% plant sterols for 10 weeks to determine the absorbability of these sterols and their deposition in the tissues. We found campesterol and β-sitosterol in the blood and tissues. The Plasma campesterol levels were 4.34–13.3 mg/100 ml, whereas, β-sitosterol levels were 0.41–1 mg/100 ml. Stigmasterol was not detected. The total plasma plant sterol concentration was about 10% of the total plasma sterol. The mean terminal plasma cholesterol concentration averaged 60% higher (55 vs. 88 mg/ 100 ml, P < 0.001) than the mean initial value. Campesterol was the preponderant sterol in all tissues studied, including the aorta. Sitosterol was found in small amounts in the tissues of the abdominal organs. Stigmasterol was not detected in any tissue studied. Esterified campesterol and sitosterol were detected in trace amounts in most tissues. Campesterol and sitosterol, particularly the former, accumulated in the tissues including the aorta.