Dietary sesame lignans decrease lipid peroxidation in rats fed docosahexaenoic acid.

We have previously reported that dietary sesamin and sesaminol, major lignans of sesame seed, elevate the alpha-tocopherol concentration and decrease the thiobarbituric acid reactive substance (TBARS) concentration in the plasma and liver of rats. In this study, the effects of dietary sesamin and sesaminol on the lipid peroxidation in the plasma and tissues of rats fed docosahexaenoic acid (DHA, 22:6 n-3) were examined. Male Wistar rats (4-wk-old) were divided into the following six experimental groups: control group, fed a basal diet: sesamin group, fed a diet with sesamin (2 g/kg); sesaminol group, fed a diet with sesaminol (2 g/kg); DHA group, fed a diet containing DHA (5 g/kg); DHA + sesamin group, fed a diet containing DHA with sesamin; and DHA + sesaminol group, fed a diet containing DHA with sesaminol. Each diet contained either 0.01 or 0.05 g D-alpha-tocopherol/kg, and the rats were fed the respective experimental diet for 5 wk. The dietary DHA elevated the TBARS concentration and also increased the red blood-cell hemolysis induced by the dialuric acid. The dietary sesamin and sesaminol lowered the TBARS concentrations and decreased the red blood hemolysis. The dietary sesamin and sesaminol elevated the alpha-tocopherol concentrations in the plasma, liver, and brain of the rats fed a diet with or without DHA. These results suggest that dietary sesame lignans decrease lipid peroxidation as a result of elevating the alpha-tocopherol concentration in rats fed DHA.

Dietary alpha-tocopherol decreases alpha-tocotrienol but not gamma-tocotrienol concentration in rats.

We previously showed that alpha- and gamma-tocotrienols accumulate in adipose tissue and skin but not in plasma or other tissues of rats fed a tocotrienol-rich fraction extracted from palm oil containing alpha-tocopherol and alpha- and gamma-tocotrienols. To clarify the nature of tocotrienol metabolism, we studied the distribution of alpha- or gamma-tocotrienol in rats fed alpha- or gamma-tocotrienol without alpha-tocopherol, and the effect of alpha-tocopherol on their distribution. Wistar rats (4-wk-old) were fed a diet with 50 mg alpha-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 1, and a diet with 50 mg gamma-tocotrienol/kg alone or with 50 mg alpha-tocopherol/kg in expt. 2, for 8 wk. alpha-Tocotrienol was detected in various tissues and plasma of the rats fed alpha-tocotrienol alone, and the alpha-tocotrienol concentrations in those tissues and plasma decreased (P < 0.05) by the dietary alpha-tocopherol in the rats fed alpha-tocotrienol with alpha-tocopherol. However, gamma-tocotrienol preferentially accumulated in the adipose tissue and skin of the rats fed gamma-tocotrienol alone, and the dietary alpha-tocopherol failed either to decrease (P >/= 0.05) gamma-tocotrienol concentrations in the adipose tissue and skin or to increase (P >/= 0.05) in the urinary excretion of 2,7,8-trimethyl-2(2'-carboxymethyl)-6-hydroxycroman, a metabolite of gamma-tocotrienol, in the rats fed gamma-tocotrienol with alpha-tocopherol. These data suggest that alpha-tocopherol enhances the alpha-tocotrienol metabolism but not the gamma-tocotrienol metabolism in rats.

Dietary sesame seed and its lignans inhibit 2,7,8-trimethyl- 2(2'-carboxyethyl)-6-hydroxychroman excretion into urine of rats fed gamma-tocopherol.

We showed previously that dietary sesame seed and its lignans elevate the tocopherol concentration in rats. To clarify their effect on tocopherol metabolism, we determined in this study the urinary excretion of 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC), a gamma-tocopherol metabolite, in rats fed sesame seed or its lignans. Rats were fed diets with or without sesame seed for 28 d in Experiment 1, and for 1, 3 and 7 d in Experiment 2. On d 28, dietary sesame seed elevated (P < 0.05) gamma-tocopherol concentrations in liver, kidney, brain and serum, and decreased (P < 0.05) urinary excretion of gamma-CEHC. The excretion was completely inhibited by feeding sesame seed on d 1 and 3. In Experiment 3, the effects of dietary sesamin and sesaminol (major lignans in sesame seed) or ketoconazole (a selective inhibitor of cytochrome P(450) (CYP)3A on urinary excretion of gamma-CEHC in rats fed gamma-tocopherol were examined. The urinary gamma-CEHC in rats fed sesamin or sesaminol was markedly lower than in rats fed gamma-tocopherol alone (P < 0.05). Dietary ketoconazole also inhibited (P < 0.05) urinary excretion of gamma-CEHC, and elevated (P < 0.05) gamma-tocopherol concentrations in tissues and serum of rats fed gamma-tocopherol. These data suggest that sesame seed and its lignans elevate gamma-tocopherol concentration due to the inhibition of CYP3A-dependent metabolism of gamma-tocopherol.