Circadian rhythm-dependent induction of hepatic lipogenic gene expression in rats fed a high-sucrose diet.

Metabolic syndrome has become a global health challenge and was recently reported to be positively correlated with increased sucrose consumption. Mechanistic analyses of excess sucrose-induced progression of metabolic syndrome have been focused mainly on abnormal hepatic lipogenesis, and the exact contribution of excess sucrose to metabolic disorders remains controversial. Considering that carbohydrate and lipid metabolisms exhibit clear circadian rhythms, here we investigated the possible contribution of diurnal oscillations to responses of hepatic lipid metabolism to excess sucrose. We found that excess sucrose dose-dependently promotes fatty liver and hyperlipidemia in in rats fed a high-sucrose diet (HSD). We observed that excess sucrose enhances the oscillation amplitudes of the expression of clock genes along with the levels of hepatic lipid and carbohydrate metabolism-related mRNAs that increase lipogenesis. We did not observe similar changes in the levels of the transcription factors regulating the expression of these genes. This suggested that the excess sucrose-induced, circadian rhythm-dependent amplification of lipogenesis is post-transcriptionally regulated via the stability of metabolic gene transcripts. Of note, our findings also provide evidence that fructose causes some of the HSD-induced, circadian rhythm-dependent alterations in lipogenic gene expression. Our discovery of HSD-induced circadian rhythm-dependent alterations in lipogenesis at the post-transcriptional level may inform future studies investigating the complex relationships among sucrose uptake, circadian rhythm, and metabolic enzyme expression. Our findings could contribute to the design of chrono-nutritional interventions to prevent or manage the development of fatty liver and hyperlipidemia in sucrose-induced metabolic syndrome.

Hydrogen produced in rat colon improves in vivo reduction-oxidation balance due to induced regeneration of α-tocopherol.

We investigated whether non-digestible saccharide fermentation-derived hydrogen molecules (H2) in rat colon could improve the in vivo reduction-oxidation (redox) balance via regeneration of α-tocopherol, by assessing their effect on hydroxyl radicals, the α-tocopherol concentration and the redox balance. In Expt 1, a Fenton reaction with phenylalanine (0 or 1·37 mmol/l of H2) was conducted. In Expt 2, rats received intraperitoneally maize oil containing phorone (400 mg/kg) 7 d after drinking ad libitum water containing 0 or 4 % fructo-oligosaccharides (FOS) (groups CP and FP, respectively). In Expt 3, rats unable to synthesise ascorbic acid drank ad libitum for 14 d water with 240 mg ascorbic acid/l (group AC), 20 mg of ascorbic acid/l (group DC) or 20 mg of ascorbic acid/l and 4 % FOS (group DCF). In the Fenton reaction, H2 reduced tyrosine produced from phenylalanine to 72 % when platinum was added and to 92 % when platinum was excluded. In Expt 2, liver glutathione was depleted by administration of phorone to rats. However, compared with CP, no change in the m-tyrosine concentration in the liver of FP was detected. In Expt 3, net H2 excretion was higher in DCF than in the other rats after 3 d of the experiment. Furthermore, the concentrations of H2 and α-tocopherol and the redox glutathione ratio in perirenal adipose tissue of rats were significantly higher in DCF than in DC. To summarise, in rat colon, fermentation-derived H2 further shifted the redox balance towards a more reducing status in perirenal adipose tissue through increased regeneration of α-tocopherol.

Vitamin E supplementation improves high-densitiy lipoprotein and endothelial functions in end-stage kidney disease patients undergoing hemodialysis
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BACKGROUND AND AIMS: Patients with end-stage kidney disease (ESKD) undergoing hemodialysis (HD) have been shown to be at increased risk for cardiovascular disease (CVD). Decreased high-density lipoprotein cholesterol (HDL-C) and impaired cholesterol efflux capacity (CEC) have been reported in such patients, and effects of vitamin E supplementation on HDL functions are poorly understood. Therefore, the present study aimed to investigate effects of vitamin E supplementation on HDL and endothelial functions in ESKD patients undergoing HD. We also assessed the influence of diabetes and haptoglobin (Hp) phenotype on the effects of vitamin E. MATERIALS AND METHODS: Vitamin E (300 mg daily) was supplemented for 12 weeks, followed by a 10-week washout phase in 40 ESKD patients undergoing HD (20 diabetic and 20 nondiabetic patients). HDL functions, including CEC, antioxidant capacity, and anti-inflammatory activity, were investigated. In diabetic patients, endothelial function, as represented by flow-mediated vasodilatation (FMD), was also assessed. The findings were compared according to diabetic condition or Hp phenotype. RESULTS: Vitamin E significantly increased CEC, whereas antioxidant capacity and anti-inflammatory activity remained unchanged. Further, the improvement in CEC was maintained after the 10-week washout phase. Endothelial function was significantly improved in diabetic patients. Subanalyses based on diabetes or Hp phenotype revealed that neither diabetes nor Hp phenotype influenced the effects of vitamin E. CONCLUSION: In ESKD patients undergoing hemodialysis, vitamin E supplementation significantly improved the HDL function of CEC and, in diabetic patients, endothelial function. These effects were independent of Hp phenotype.
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Physical inactivity and breakfast skipping caused visceral fat accumulation in rats.

Physical inactivity as well as breakfast skipping is known as risk factor for various metabolic diseases, such as obesity and type 2 diabetes. We have previously reported that a breakfast skipping model, in which the timing of feeding is delayed, induces abnormal lipid metabolism by altering the circadian rhythm of lipid metabolism-related genes in rats. The purpose of this study was to elucidate the synergistic effect of physical inactivity and breakfast skipping on lipid metabolism. We adopted sciatic neurectomized rats as physically inactive models, because we confirmed that the rats mildly decreased their spontaneous locomotor activity compared to sham-operated rats. And then the physically inactive model rats were fed a mild high-fat diet during zeitgeber time (ZT) 12-0 in the control group and ZT16-0 in the breakfast skipping group for 11 days. Body weight gain and total food intake were similar in both groups. Breakfast skipping induced a significant visceral fat accumulation, which was not observed in our previous breakfast skipping or physically inactive studies. The mRNA levels of clock and lipogenesis-related genes were altered by breakfast skipping in the liver and epididymal adipose tissue, and serum insulin level was altered by breakfast skipping. These results suggest that physical inactivity and breakfast skipping synergistically induces drastic visceral fat accumulation due to the alteration of circadian clock and lipid metabolism in the liver and adipose tissue. Therefore, regular feeding timing plays an important role in the health of a sedentary modern society.

Dietary sesame seed and its lignan, sesamin, increase tocopherol and phylloquinone concentrations in male rats.

We have shown that intake of sesame seed and its lignan increases vitamin E concentrations and decreases urinary excretion levels of vitamin E metabolites in male Wistar rats, suggesting inhibition of vitamin E catabolism by sesame lignan. The aim of this study was to examine whether dietary sesame seed also increased vitamin K concentrations, because its metabolic pathway is similar to that of vitamin E. To test the effect of sesame lignan on vitamin K concentrations, male Wistar rats were fed a control diet or a diet with 0.2% sesamin (a sesame lignan) for 7 d in experiment 1. Liver phylloquinone (PK), menaquinone-4 (MK-4), and γ-tocopherol were greater in rats fed sesamin than in control rats. To test the effect of sesame seed on vitamin K concentrations, male Wistar rats were fed a control diet or a diet with 1, 5, or 10% sesame seed for 3 d in experiment 2. Liver and kidney PK and γ-tocopherol but not MK-4 were greater in rats fed sesame seed than in control rats, although differences in dietary amounts of sesame seed did not affect the PK concentrations. For further confirmation of the effect of sesame seed, male Wistar rats were fed a control diet or a diet with 20% sesame seed for 40 d in experiment 3. Kidney, heart, lung, testis, and brain PK and brain MK-4 were greater in rats fed sesame seed than in control rats. The present study revealed for the first time, to our knowledge, that dietary sesame seed and sesame lignan increase not only vitamin E but also vitamin K concentrations in rat tissues.

Delayed feeding of a high-sucrose diet led to increased body weight by affecting the circadian rhythm of body temperature and hepatic lipid-metabolism genes in rats.

Skipping breakfast is an irregular feeding behavior, typically in young people. In our previous study, we established a 4 h-delayed feeding protocol for rats as a breakfast-skipping model and showed that the 4 h-delayed feeding of a high-fat diet led to body weight gain in rats. Excess sucrose induces metabolic syndrome and fatty liver. Recently, excess sucrose intake has received increased attention. Young people generally consume more sugar than adults do. In the present study, we investigated whether a 4 h-delayed feeding promoted high-sucrose diet-induced abnormalities in lipid metabolism, such as fatty liver and obesity in rats. The 4 h-delayed feeding rats showed increased body weight gain, although it did not induce fatty liver and hyperlipidemia compared to normal feeding rats. Serum insulin concentration during the feeding period was higher than in the control rats, suggesting that slight insulin resistance was induced by the 4 h-delayed feeding. The surge in body temperature was also delayed by 4 h in response to the 4 h-delayed feeding. This delay would result in less energy expenditure to increase body weight. The oscillations of hepatic lipid and glucose metabolism-related gene expression were delayed by almost 2-4 h, and the clock genes were delayed by approximately 2 h. The 4 h-delayed feeding induced weight gain by affecting body temperature, insulin resistance, and circadian oscillation of lipid metabolism-related genes in rats fed a high-sucrose diet, suggesting that a high sucrose intake with breakfast skipping leads to obesity.

C3H/HeNSlc mouse with low phospholipid transfer protein expression showed dyslipidemia.

High serum levels of triglycerides (TG) and low levels of high-density lipoprotein cholesterol (HDL-C) increase the risk of coronary heart disease in humans. Herein, we first reported that the C3H/HeNSlc (C3H-S) mouse, a C3H/HeN-derived substrain, is a novel model for dyslipidemia. C3H-S showed hypertriglyceridemia and low total cholesterol (TC), HDL-C, and phospholipid (PL) concentrations. To identify the gene locus causing dyslipidemia in C3H-S, we performed genetic analysis. In F2 intercrosses between C3H-S mice and strains with normal serum lipids, the locus associated with serum lipids was identified as 163-168 Mb on chromosome 2. The phospholipid transfer protein (Pltp) gene was a candidate gene within this locus. Pltp expression and serum PLTP activity were markedly lower in C3H-S mice. Pltp expression was negatively correlated with serum TG and positively correlated with serum TC and HDL-C in F2 mice. Genome sequencing analysis revealed that an endogenous retrovirus (ERV) sequence called intracisternal A particle was inserted into intron 12 of Pltp in C3H-S. These results suggest that ERV insertion within Pltp causes aberrant splicing, leading to reduced Pltp expression in C3H-S. This study demonstrated the contribution of C3H-S to our understanding of the relationship between TG, TC, and PL metabolism via PLTP.

High sucrose diet-induced dysbiosis of gut microbiota promotes fatty liver and hyperlipidemia in rats.

Excess sucrose intake has been found to be a major factor in the development of metabolic syndrome, especially in promoting nonalcoholic fatty liver disease. The excess fructose is believed to targets the liver to promote de novo lipogenesis, as described in major biochemistry textbooks. On the contrary, in this study, we explored the possible involvement of gut microbiota in excess sucrose-induced lipid metabolic disorders, to validate a novel mechanism by which excess sucrose causes hepatic lipid metabolic disorders via alterations to the gut microbial community structure. Wistar male rats were fed either a control starch diet or a high-sucrose diet for 4 weeks. Half of the rats in each group were treated with an antibiotic cocktail delivered via drinking water for the entire experimental period. After 4 weeks, rats fed with the high-sucrose diet showed symptoms of fatty liver and hyperlipidemia. The architecture of cecal microbiota was altered in rats fed with high-sucrose diet as compared to the control group, with traits including increased ratios of the phyla Bacteroidetes/Firmicutes, reduced α-diversity, and diurnal oscillations changes. Antibiotic administration rescued high-sucrose diet-induced lipid accumulation in the both blood and liver. Levels of two microbial metabolites, formate and butyrate, were reduced in rats fed with the high-sucrose diet. These volatile short-chain fatty acids might be responsible for the sucrose-induced fatty liver and hyperlipidemia. Our results indicate that changes in the gut microbiota induced by a high-sucrose diet would promote the development of nonalcoholic fatty liver disease via its metabolites, such as short-chain fatty acids.

Delayed Meal Timing, a Breakfast Skipping Model, Increased Hepatic Lipid Accumulation and Adipose Tissue Weight by Disintegrating Circadian Oscillation in Rats Fed a High-Cholesterol Diet.

Background: To investigate whether shifted timing of eating, breakfast skipping, induces alterations in the circadian clock and abnormal lipid metabolism, we have established a delayed meal timing (DMT) protocol for rats, which started eating food 4 h delay. In the present study, control and DMT rats were fed a high-cholesterol diet during zeitgeber time (ZT) 12-24 and ZT 16-4, respectively. The DMT protocol increased the hepatic lipids and epididymal adipose tissue weight without changes in food intake and body weight. The surge in body temperature was delayed by 4 h in the DMT group, suggesting that energy expenditure was decreased in response to DMT. The peaks of the diurnal rhythm of serum non-esterified fatty acids and insulin were delayed by 2 and 4 h due to DMT, respectively. The oscillation peaks of hepatic de novo fatty acid synthesis gene expression was delayed by 4 h in response to DMT, whereas the peak of hepatic clock genes were 2 h delayed or not by DMT. Although metabolic oscillation is considered to be controlled by clock genes, the disintegration rhythms between the clock genes and lipid metabolism-related genes were not observed in rats fed a high-fat diet in our previous study. These data suggest that the circadian rhythm of de novo fatty acid metabolism is regulated by timing of eating, but is not directly controlled by clock genes. The present study suggests that breakfast skipping would complicate fatty liver and body fat accumulation.

Complexation of tocotrienol with gamma-cyclodextrin enhances intestinal absorption of tocotrienol in rats.

To determine the bioavailability of tocotrienol complex with gamma-cyclodextrin, the effects of tocotrienol/gamma-cyclodextrin complex on tocotrienol concentration in rat plasma and tissues were studied. Rats were administered by oral gavage an emulsion containing tocotrienol, tocotrienol with gamma-cyclodextrin, or tocotrienol/gamma-cyclodextrin complex. At 3 h after administration, the plasma gamma-tocotrienol concentration of the rats administered tocotrienol/gamma-cyclodextrin complex was higher than that of the rats administered tocotrienol and gamma-cyclodextrin. In order to determine the effect of complexation on tocotrienol absorption, rats were injected with Triton WR1339, which prevents the catabolism of triacylglycerol-rich lipoprotein by lipoprotein lipase, and then administered by oral gavage an emulsion containing tocotrienol, tocotrienol with gamma-cyclodextrin, or tocotrienol/gamma-cyclodextrin complex. The plasma gamma-tocotrienol concentration of the Triton-treated rats administered tocotrienol/gamma-cyclodextrin complex was higher than that of the other Triton-treated rats. These results suggest that complexation of tocotrienol with gamma-cyclodextrin elevates plasma and tissue tocotrienol concentrations by enhancing intestinal absorption.

Gut Microbiota Is Not Involved in the Induction of Acute Phase Protein Expression Caused by Vitamin C Deficiency.

Using rats, we previously found that vitamin C deficiency increases serum levels of interleukin-6 (IL-6) and glucocorticoid, and changes the gene expression of acute phase proteins (APP) in the liver. However, it remains unclear how vitamin C deficiency causes these inflammation-like responses. In this study, we investigated the possibility that changes in gut microbiota are involved in the induction of APP gene expression by vitamin C deficiency. ODS rats that cannot genetically synthesize vitamin C were divided into 4 groups based on the presence or absence of vitamin C or antibiotics and were raised for 15 d. Neomycin, vancomycin, and ampicillin were used as antibiotics, and 300 mg L-ascorbic acid/kg was added to the AIN93G diet. Vitamin C deficiency affected neither the wet tissue weights nor relative abundance of bacteria in the cecal contents. Antibiotic administration increased wet weights of the cecum, cecal contents, and colon, changed the relative abundance of some bacteria in the cecal contents, and decreased serum IL-6 level. However, antibiotic administration had no effect on serum concentrations of corticosterone and α1-acid glycoprotein (AGP), vitamin C concentration in the liver, and mRNA levels of haptoglobin and AGP in the liver. Therefore, disturbance of gut microbiota did not attenuate the increase in glucocorticoid level and induction of APP gene expression due to vitamin C deficiency. This suggests that gut microbiota is not involved in the inflammation-like responses caused by vitamin C deficiency.

Impacts of high-sucrose diet on circadian rhythms in the small intestine of rats.

Excessive sucrose intake, known as fructose toxicity, leads to fatty liver, hyperlipidemia, and metabolic syndrome. Circadian disorders also contribute to metabolic syndrome. Here, we investigated the effect of excessive sucrose intake on circadian rhythms of the small intestine, the main location of sucrose absorption, to elucidate a mechanism of sucrose-induced abnormal lipid metabolism. Male Wistar rats were fed control starch or high-sucrose diets for 4 weeks. High-sucrose diet-induced fatty liver and hypertriglyceridemia in rats. Amplitudes of PER1/2 expression oscillations in the small intestine were reduced by excessive sucrose, while gene expression of GLUT5 and gluconeogenic enzymes was enhanced. These changes would contribute to interfering in lipid homeostasis as well as adaptive responses to control fructose toxicity in rats.

γ-Tocopherol Is Metabolized Faster than α-Tocopherol in Young Japanese Women.

To elucidate the characteristics of γ-tocopherol metabolism, serum concentrations of α- and γ-tocopherol, and urinary excretion of their metabolites after ingestion of α- or γ-tocopherol, major isoforms in our diet, were compared. Six healthy Japanese women (age 22.7±1.7 y old, BMI 21.4±0.9) ingested 134 mg of α- or γ-tocopherol, and blood and urine were collected until 72 h later. After α-tocopherol intake, the serum concentration of α-tocopherol increased at 12-24 h, and urinary excretion of 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (α-CEHC), an α-tocopherol metabolite, increased at 12-36 h. However, after γ-tocopherol intake, the serum concentration of γ-tocopherol increased at 6-12 h, and excretion of 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (γ-CEHC), a γ-tocopherol metabolite, increased at 3-12 h. The area under the curve from 0 to 72 h and serum maximal concentration of γ-tocopherol were lower than those of α-tocopherol. The time to maximal concentration of γ-tocopherol was faster than that of α-tocopherol. The ratio of urinary excretion of carboxyethyl-hydroxychroman to tocopherol intake was 2.9% for α-CEHC and 7.7% for γ-CEHC. These results revealed that γ-tocopherol is metabolized faster than α-tocopherol in healthy young women.

Time-restricted feeding suppresses excess sucrose-induced plasma and liver lipid accumulation in rats.

The etiology of metabolic syndrome involves several complicated factors. One of the main factors contributing to metabolic syndrome has been proposed to be excessive intake of sucrose, which disturbs hepatic lipid metabolism, resulting in fatty liver. However, the mechanism by which sucrose induces fatty liver remains to be elucidated. Considering feeding behavior important for metabolism, we investigated whether time-restricted feeding of high sucrose diet (HSD), only in the active phase (the dark phase of the daily light/dark cycle), would ameliorate adverse effects of sucrose on lipid homeostasis in rats. Male Wistar rats, fed either an ad libitum (ad lib.) or time-restricted control starch diet (CD) or HSD were investigated. Rats fed ad lib. (CD and HSD) completed approximately 20% of food intake in the daytime. Time-restricted feeding did not significantly suppress total food intake of rats. However, time-restricted feeding of HSD significantly suppressed the increased plasma triglyceride levels. Moreover, time-restricted feeding also ameliorated HSD-induced liver lipid accumulation, whereas circadian oscillations of liver clock gene or transcriptional factor gene expression for lipid metabolism were not altered significantly. These results demonstrated that restricting sucrose intake only during the active phase in rats ameliorates the abnormal lipid metabolism caused by excess sucrose intake.

Delayed first active-phase meal, a breakfast-skipping model, led to increased body weight and shifted the circadian oscillation of the hepatic clock and lipid metabolism-related genes in rats fed a high-fat diet.

The circadian clock is closely related to human health, such as metabolic syndrome and cardiovascular disease. Our previous study revealed that irregular feeding induced abnormal lipid metabolism with disruption of the hepatic circadian clock. We hypothesized that breakfast skipping induces lipid abnormalities, such as adiposity, by altering the hepatic circadian oscillation of clock and lipid metabolism-related genes. Here, we established a delayed first active-phase meal (DFAM) protocol as a breakfast-skipping model. Briefly, rats were fed a high-fat diet during zeitgeber time (ZT) 12-24 in a control group and ZT 16-4 in the DFAM group. The DFAM group showed increased body weight gain and perirenal adipose tissue weight without a change in total food intake. The circadian oscillations of hepatic clock and de novo fatty acid synthesis genes were delayed by 2-4 h because of DFAM. The peaks of serum insulin, a synchronizer for the liver clock, bile acids, and non-esterified fatty acid (NEFA) were delayed by 4-6 h because of DFAM. Moreover, DFAM delayed the surge in body temperature by 4 h and may have contributed to the increase in body weight gain and adipose tissue weight because of decreased energy expenditure. These data indicated a potential molecular mechanism by which breakfast skipping induces abnormal lipid metabolism, which is related to the altered circadian oscillation of hepatic gene expression. The results also suggested that the delayed peaks of serum NEFA, bile acids, and insulin entrain the circadian rhythm of hepatic clock and lipid metabolism-related genes.

α-Tocopherol Intake Decreases Phylloquinone Concentration in Bone but Does Not Affect Bone Metabolism in Rats.

Previous studies have shown that α-tocopherol intake lowers phylloquinone (PK) concentration in some extrahepatic tissues in rats. The study's aim was to clarify the effect of α-tocopherol intake on vitamin K concentration in bone, as well as the physiological action of vitamin K. Male Wistar rats were divided into 4 groups. Over a 3-mo period, the K-free group was fed a vitamin K-free diet with 50 mg RRR-α-tocopherol/kg, the E-free group was fed a diet containing 0.75 mg PK/kg without vitamin E, the control group was fed a diet containing 0.75 mg PK/kg with 50 mg RRR-α-tocopherol/kg, and the E-excess group was fed a diet containing 0.75 mg PK/kg with 500 mg RRR-α-tocopherol/kg. PK concentration in the liver was higher in E-excess rats than in E-free rats, was lower in the tibias of control rats than in those of E-free rats, and was lower in E-excess rats than in control rats. Menaquinone-4 (MK-4) concentration in the liver was higher in E-excess rats than in E-free and control rats. However, MK-4 concentrations in the tibias of E-free, control, and E-excess rats were almost the same. Blood coagulation activity was lower in K-free rats than in the other rats but was not affected by the level of α-tocopherol intake. Additionally, dietary intake of PK and α-tocopherol did not affect uncarboxylated-osteocalcin concentration in the serum, femur density, or expression of the genes related to bone resorption and formation in the femur. These results suggest that α-tocopherol intake decreases PK concentration in bone but does not affect bone metabolism in rats.

Tissue Distribution of Menaquinone-7 and the Effect of α-Tocopherol Intake on Menaquinone-7 Concentration in Rats.

We have reported that vitamin E intake lowers phylloquinone (PK) concentration in extrahepatic tissues of rats. In this study, we aimed to clarify the characteristic of the distribution of menaquinone-7 (MK-7), a vitamin K contained in fermented foods, by comparison with other vitamin K distributions and to clarify the effect of vitamin E intake on MK-7 concentration in rats. Rats were fed a vitamin K-free diet (Free group), a diet containing 0.75 mg PK/kg (PK group), a 0.74 mg menaquinone-4 (MK-4)/kg diet (MK-4 group), a 1.08 mg MK-7/kg diet (MK-7 group), or a 0.29 mg menadione (MD)/kg diet (MD group) for 16 wk. MK-7 mainly accumulated in the liver, spleen, and adrenal gland of the MK-7 group, although PK accumulated in the serum and all tissues of the PK group. Conversely, MK-4 was present in all tissues of the PK, MK-4, MK-7, and MD groups. MK-4 concentration in the serum, liver, adipose tissue, and spleen was higher in the MK-4 group than in the other groups; however, MK-4 concentration in the kidney, testis, tibia, and brain was lower in the MK-4 group than in the PK, MK-7, and MD groups. Next, vitamin E- and K-deficient rats were orally administered MK-7 with or without α-tocopherol. α-Tocopherol did not affect MK-7 or MK-4 concentration in the serum and various tissues. These results suggested that MK-7 is particularly liable to accumulate in the liver, and MK-7 concentration is not affected by vitamin E intake.

Cytochrome P450-dependent metabolism of vitamin E isoforms is a critical determinant of their tissue concentrations in rats.

The aim of this study was to clarify the contribution of cytochrome P450 (CYP)-dependent metabolism of vitamin E isoforms to their tissue concentrations. We studied the effect of ketoconazole, a potent inhibitor of CYP-dependent vitamin E metabolism in cultured cells, on vitamin E concentration in rats. Vitamin E-deficient rats fed a vitamin E-free diet for 4 weeks were administered by oral gavage a vitamin E-free emulsion, an emulsion containing alpha-tocopherol, gamma-tocopherol or a tocotrienol mixture with or without ketoconazole. Alpha-tocopherol was detected in the serum and various tissues of the vitamin E-deficient rats, but gamma-tocopherol, alpha- and gamma-tocotrienol were not detected. Ketoconazole decreased urinary excretion of 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman after alpha-tocopherol or a tocotrienol mixture administration, and that of 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC) after gamma-tocopherol or a tocotrienol mixture administration. The gamma-tocopherol, alpha- and gamma-tocotrienol concentrations in the serum and various tissues at 24 h after their administration were elevated by ketoconazole, while the alpha-tocopherol concentration was not affected. The gamma-tocopherol or gamma-tocotrienol concentration in the jejunum at 3 h after each administration was also elevated by ketoconazole. In addition, significant amount of gamma-CEHC was in the jejunum at 3 h after gamma-tocopherol or gamma-tocotrienol administration, and ketoconazole inhibited gamma-tocopherol metabolism to gamma-CEHC in the jejunum. These results showed that CYP-dependent metabolism of gamma-tocopherol and tocotrienol is a critical determinant of their concentrations in the serum and tissues. The data also suggest that some amount of dietary vitamin E isoform is metabolized by a CYP-mediated pathway in the intestine during absorption.

Dietary sesame seed decreases urinary excretion of alpha- and gamma-tocopherol metabolites in rats.

We previously showed that dietary sesame seed and its lignan inhibited gamma-tocopherol metabolism to 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC), a gamma-tocopherol metabolite, and markedly elevated tissue gamma-tocopherol concentration in rats. The aim of this study was to clarify the effect of dietary sesame seed on alpha-tocopherol metabolism. Vitamin E-deficient rats fed a vitamin E-free diet for 4 wk were fed a diet containing alpha-tocopherol, alpha- and gamma-tocopherol, or alpha-tocopherol with sesame seed for 7 d. Urinary excretion of 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC), a alpha-tocopherol metabolite, in rats fed alpha-tocopherol with sesame seed was inhibited (p<0.05) as compared with that in rats fed alpha-tocopherol alone, or alpha- and gamma-tocopherol. The gamma-CEHC excretion was also less (p<0.05) in rats fed alpha-tocopherol with sesame seed than that in rats fed alpha- and gamma-tocopherol. The inhibition of alpha- and gamma-CEHC excretion by sesame seed was accompanied by elevation (p<0.05) of the alpha- and gamma-tocopherol concentration in the liver. These results suggest that dietary sesame seed inhibits not only gamma-tocopherol metabolism to gamma-CEHC but also alpha-tocopherol metabolism to alpha-CEHC in rats.

Dietary sesame seed and its lignan increase both ascorbic acid concentration in some tissues and urinary excretion by stimulating biosynthesis in rats.

We previously showed that the intake of sesamin, a major lignan in sesame seed, decreased lipid peroxidation and elevated tocopherol concentration in rat tissues. In this study, we examined the effect of dietary sesame seed and sesamin on the ascorbic acid concentration in rat tissues. Rats (4-wk-old) were fed either a vitamin E-free diet, or a diet containing 50 mg gamma-tocopherol/kg, one containing 2 g sesamin/kg, one containing 50 mg gamma-tocopherol/kg and 2 g sesamin/kg, or one containing 200 g sesame seed/kg for 28 d. The dietary sesamin and sesame seed elevated ascorbic acid concentrations in the liver and kidney, and increased urinary excretion in those Wistar rats. The dietary sesamin also elevated the hepatic mRNA levels of cytochrome P450 (CYP) 2B, and UDP-glucuronosyltransferase (UGT) 1A and 2B. In contrast, neither the sesamin nor the sesame seed affected the liver concentration of ascorbic acid in ODS rats with a hereditary defect in ascorbic acid synthesis, though the dietary sesame seed elevated the UGT1A and 2B mRNA levels in the liver. In addition, the sesame seed elevated the gamma-tocopherol concentration in the various ODS rat tissues and the ascorbic acid concentrations in the kidney, heart and lung, while reducing the thiobarbituric acid reactive substance concentration in the heart and kidney. These results suggest that dietary sesame seed and its lignan stimulate ascorbic acid synthesis as a result of the induction of UGT1A and the 2B-mediated metabolism of sesame lignan in rats. The data of ODS rat studies also suggest that dietary sesame seed enhances antioxidative activity in the tissues by elevating the levels of two antioxidative vitamins, vitamin C and E.