Effect of esterified 4-desmethylsterols and -stanols or 4,4′-dimethylsterols on cholesterol and bile acid metabolism in hamsters

Abstract

4-Desmethylsterols and -stanols reduce plasma total cholesterol (TC) and LDL cholesterol by inhibition of intestinal cholesterol absorption, while the cholesterol-lowering potential of 4,4 0 -dimethylsterols is less well defined. The present study aimed to compare the effects of 4-desmethylsterols, -stanols, and 4,4 0 -dimethylsterols on plasma and hepatic cholesterol, sterol excretion and bile acid metabolism. Male golden Syrian hamsters were fed diets containing 13 g/100 g fat, 0·08 g/100 g cholesterol and 0 (control), 0·24 or 0·48 % (w/w) esterified 4-desmethylsterols (sterols) and esterified hydrogenated 4-desmethylsterols (stanols) from common vegetable oils or esterified 4,4 0 -dimethylsterols from rice bran oil for 5 weeks. Sterol and stanol esters at the dose of 0·24 % were equally effective and significantly (P,0·05) lowered TC by 15 %, while 0·24 % 4,4-dimethylsterols reduced TC by 10 %. Liver total and esterified cholesterol concentrations were significantly (P,0·05) lowered by 40, 22, 43 and 31 % in hamsters fed 0·48 % sterols, 0·24 % stanols, 0·48 % stanols or 0·48 % dimethylsterols, respectively. Daily faecal bile acid excretion and hepatic cholesterol 7a-hydroxylase activity were not altered, indicating that sterols, stanols and dimethylsterols had no effect on the intestinal re-absorption of bile acids or on hepatic bile acid synthesis. Daily excretion of cholesterol was significantly higher in hamsters fed esterified sterols and stanols, but was only slightly increased in those fed dimethylsterols. The results indicate that esterified sterols and stanols were equally effective in lowering plasma TC and LDL cholesterol, while dimethylsterol esters caused a weaker cholesterol-lowering effect. Sterols and stanols achieve their cholesterol-lowering effect by stimulating faecal cholesterol excretion through inhibiting intestinal cholesterol absorption, but do not affect bile acid excretion. Other mechanisms need to be considered to explain the effect on plasma and hepatic cholesterol of dimethylsterols. Plant sterols, also called phytosterols, are components of a normal diet, mainly coming from plant sources, e.g. vegetable oils, seeds, nuts and grain-based products. The typical consumption of plant sterols with Western diets ranges between 200 and 400 mg/d, whereas the intake of phytostanols, the saturated form of plant sterols, is negligible (Jones et al. 1997). The most common plant sterols are the 4-desmethylsterols b-sitosterol, campesterol and stigmasterol; their saturated counterparts are sitostanol and campestanol.

Phytosterol stearate esters elicit similar responses on plasma lipids and cholesterol absorption but different responses on fecal neutral sterol excretion and hepatic free cholesterol in male Syrian hamsters

“…Whereas stearic acid-enriched phytosterol esters fed to hamsters at 5% of the diet lowered non-HDL cholesterol [6], our 2.5% PSE treatments did not lower plasma total, non-HDL, or HDL cholesterol. In contrast, hamsters fed a much lower amount (0.24% of the diet) of phytosterol esters made with unsaturated fatty acids (canola oil) exhibited reductions in plasma non-HDL cholesterol [30,31]. We recently reported that phytosterol esters containing unsaturated fatty acids (oleate) are hydrolyzed in vitro to a much greater extent than phytosterol esters containing saturated fatty acids [22], suggesting that hydrolysis and liberation of free sterol may be important factors in decreasing cholesterol absorption and/or plasma non-HDL cholesterol concentration.…”

“…When fed PSE at 2.5% of the diet-assuming approximately 5% hydrolysis and the fact that the sterol moiety is 60% of PSE mass-the maximum amount of free phytosterol liberated from hydrolysis would be equivalent to feeding free phytosterol at 0.075% of the diet. In comparison, feeding 0.24% phytosterol esters made with unsaturated fatty acids [30,31], assuming 90% hydrolysis, would be equivalent to feeding free phytosterol at 0.13% of the diet. If cholesterol-lowering efficacy is indeed dependent on the presence of free phytosterol, then our treatment using stearate esters may have had the disadvantage of resisting hydrolysis and limiting the amount of free phytosterol.…”

Nutrition Discussion Forum

“…Besides the viscous and highly fermentable DF components, some other constituents of the wholegrain barley products may affect steroid metabolism: phytosterols, tocotrienols and/or a-linolenic aid as shown in several studies (Lupton et al 1994;McIntosh et al 1995;Jadhav et al 1998;Kerckhoffs et al 2002;Moreau et al 2002;Trautwein et al 2002). But concentration of phytosterols is relatively low in barley compared with maize products or maize oil.…”

“…The feeding of 30 g barley-bran flour or 3 g barley oil in the daily diet lowered total and LDL-cholesterol in hypercholesterolaemic human volunteers (Lupton et al 1994). In several studies, it was shown that phytosterols also, as the counterparts of cholesterol in man and animals, are able to reduce plasma lipids and to increase cholesterol excretion (Moghadasian, 2000;Kerckhoffs et al 2002;Moreau et al 2002;Trautwein et al 2002). Compared with maize, the phytosterol content of barley is relatively low (Piironen et al 2000).…”

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“…It was reported that the differences between effects of different plant oils on blood lipid profiles may be related to their content of plant sterols [46-49]. Indeed, there has been renewed interest in the cholesterol lowering properties of speciality grains and unprocesses oils rich in plant sterols including amaranth oil [50,51], rice bran oil [52] (Berger et al, submitted), avocado oil [53], extra virgin olive oil [54], macadamian nut [55], and argan oil [56]. …”