Biomedical subjects

Saiko Ikeda

Publications and source records attributed to Saiko Ikeda.

5 recordsLinked to original sources

PubMed2003

Comparative effects of flaxseed and sesame seed on vitamin E and cholesterol levels in rats.

Flaxseed and sesame seed both contain more than 40% fat, about 20% protein, and vitamin E, mostly gamma-tocopherol. Furthermore, both contain considerable amounts of plant lignans. However, flaxseed contains 54% alpha-linolenic acid, but sesame seed only 0.6%, and the chemical structures of flaxseed and sesame lignans are different. In this study, we investigated the differential effects of flaxseed and sesame seed on plasma and tissue gamma-tocopherol, TBARS, and cholesterol concentrations. Rats were fed experimental diets for 4 wk: vitamin E-free, (-VE), gamma-tocopherol, flaxseed (FS), sesame seed (SS), flaxseed oil (FO), FO with sesamin (FOS), and defatted flaxseed (DFF). SS and FOS diets induced significantly higher gamma-tocopherol concentrations in plasma and liver compared with FS, FO, and DFF diets. Groups fed FS, FO, and FOS showed lower plasma total cholesterol compared with the SS and DFF groups. Higher TBARS concentrations in plasma and liver were observed in the FS and FO groups but not in the FOS group. These results suggest that sesame seed and its lignans induced higher gamma-tocopherol and lower TBARS concentrations, whereas flaxseed lignans had no such effects. Further, alpha-linolenic acid produced strong plasma cholesterol-lowering effects and higher TBARS concentrations.

Animals↗

PubMed2003

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.

Adipose Tissue↗

PubMed2003

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.

Animals↗

PubMed2002

Effect of sesaminol on plasma and tissue alpha-tocopherol and alpha-tocotrienol concentrations in rats fed a vitamin E concentrate rich in tocotrienols.

We have shown that sesame lignans added to rat diet resulted in significantly greater plasma and tissue concentrations of alpha- and gamma-tocopherol concentrations in supplemented rats than in rats without supplementation. In the present studies we examined whether sesaminol, a sesame lignan, enhances tocotrienol concentrations in plasma and tissues of rats fed diets containing a tocotrienol-rich fraction of palm oil (T-mix). In Experiment 1, effects of sesaminol on tocotrienol concentrations in plasma, liver, and kidney were evaluated in rats fed diets containing 20 mg/kg of T-mix (20T) and 50 mg/kg of T-mix (50T) with or without 0.1% sesaminol. Although the T-mix contained 23% alpha-tocopherol, 22% alpha-tocotrienol, and 34% gamma-tocotrienol, alpha-tocopherol constituted most or all of the vitamin E in plasma and tissue (from 97% in kidney to 100% in plasma), with no or very little alpha-tocotrienol and no gamma-tocotrienol at all. Addition of sesaminol to the T-mix resulted in significantly higher plasma, liver, and kidney alpha-tocopherol concentrations compared to values for T-mix alone. Further, T-mix with sesaminol resulted in significantly higher alpha-tocotrienol concentrations in kidney, although the concentration was very low. In Experiment 2, we examined whether sesaminol caused enhanced absorption of alpha-tocopherol and alpha-tocotrienol in a dosage regimen supplying T-mix and sesaminol on alternating days and observed significantly higher levels of alpha-tocopherol and alpha-tocotrienol in rats fed sesaminol, even without simultaneous intake, compared to those in rats without sesaminol. In Experiment 3, alpha-tocopherol was supplied to the stomach with and without sesaminol, and alpha-tocopherol concentrations in the lymph fluid were measured. a-Tocopherol concentrations were not different between groups. These results indicated that sesaminol produced markedly higher alpha-tocopherol concentrations in plasma and tissue and significantly greater alpha-tocotrienol concentrations in kidney and various other tissues, but the concentrations of alpha-tocotrienol were extremely low compared to those of a-tocopherol (Exps. 1 and 2). However, the sesaminol-induced increases of a-tocopherol and a-tocotrienol concentrations in plasma and tissue were not caused by their enhanced absorption since sesaminol did not enhance their absorption.

Animals↗

PubMed2002

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.

Animals↗