Anti-inflammatory Effects of Food Ingredients on Mice Adipose Tissues and Adipocytes.

In 2021, we published three papers related to the anti-inflammatory effects of food ingredients. The present paper reports the effects of vitamin E homologs and sweet basil powder. In these papers, we investigated whether inflammation occurs in the adipose tissue of mice fed a high-fat and high-sucrose diet for 16 weeks. Inflammatory cytokine gene expression was significantly higher in the epididymal fat of the high-fat and high-sucrose diet group than in that of the control diet group. However, the addition of α-tocopherol or δ-tocopherol to the diet could not restrain the inflammation of mice epididymal fats. Thereafter, we investigated the anti-inflammatory effects of α- and δ-tocopherols using the co-cultured cells. Consequently, we clarified that δ-tocopherol inhibited the increase in the gene expressions of inflammatory cytokines. We also examined the effect of sweet basil powder on a similar obese mice model. The final body weight in the high-fat and high-sucrose group that received sweet basil powder was significantly lower than that in the high-fat and high-sucrose diet group. Liver weights were also significantly lower in the high-fat and high-sucrose diet group that received sweet basil powder than in the high-fat and high-sucrose diet group, although adipose tissue weights were unchanged in both groups. Furthermore, sweet basil powder tended to inhibit in lipid synthesis in the mice livers. Therefore, we suggested that sweet basil powder inhibited fatty acid synthesis in mice livers, thereby suppressing liver enlargement, and resulting in body weight loss. Moreover, the gene expression of MCP-1 in the adipose tissue of mice fed a high-fat and high-sucrose diet added with sweet basil powder was significantly lower than that of mice fed a high-fat and high-sucrose diet for 12 weeks. Therefore, sweet basil powder inhibited inflammation onset in the adipose tissue of mice. Taken together, the results suggested that food ingredients, especially vitamin E homologs and sweet basil powder, have anti-inflammatory effects on mice adipose tissue and mice adipocyte-induced inflammation.

Delta-Tocopherol Suppresses the Dysfunction of Thermogenesis due to Inflammatory Stimulation in Brown Adipocytes.

Brown adipose tissue (BAT) functions as a radiator for thermogenesis and helps maintain body temperature and regulate metabolism. Inflammatory signals have been reported to inhibit PGC-1α activation and UCP1-mediated thermogenesis in brown adipocytes. Inflammation is mainly caused by cell hypertrophy and macrophage invasion due to obesity, and invading macrophages secrete inflammatory cytokines, including TNF-α, IL1ß, and IL6, which suppress the thermogenesis in BAT. Tocopherol is a lipid-soluble vitamin with anti-inflammatory effects is expected to contribute to the suppression of inflammation in adipose tissue. In this study, we investigated the protective effect of tocopherols, α-tocopherol (α-toc) and δ-tocopherol (δ-toc), against brown adipocyte inflammation and thermogenesis dysfunction.Inflammatory stimulation by TNF-α, a major inflammatory cytokine, significantly decreased the protein expression levels of UCP1 and PGC-1α in rat primary brown adipocytes. The pre-incubation of α-toc or δ-toc significantly suppressed the decrease in UCP1 and PGC-1α expression and lipid accumulation. Additionally, α-toc and δ-toc suppress the induction of ERK1/2 gene expression, implying that an antiinflammatory effect is involved in this protective effect. We fed mice a high-fat diet for 16 weeks and investigated the effects of α-toc and δ-toc in the diet. Intake of α-toc and δ-toc significantly suppressed weight gain and hypertrophy of brown adipocytes. Our results suggest that α-toc and δ-toc suppress the dysfunction of thermogenesis in brown adipocytes due to inflammation and contribute to the treatment of obesity and obesity-related metabolic diseases.

Tocotrienols Attenuate White Adipose Tissue Accumulation and Improve Serum Cholesterol Concentration in High-Fat Diet-Treated Mice.

Tocotrienols (T3s), which are vitamin E homologs, have not only antioxidant function but also inhibitory effects on body weight gain and hepatic lipid droplet accumulation. However, the mechanisms of the anti-obesity effects of T3s are not yet understood. In this study, C57BL/6 mice were fed a high-fat diet in the presence or absence of T3s. Treatment with T3s inhibited white adipose tissue accumulation and elevation of serum cholesterol concentrations. Additionally, to clarify the relationship between obesity-induced cognitive dysfunction and the neuroprotective effect of T3s, cognitive function, brain oxidation, and protein expression levels of brain-derived neurotrophic factor (BDNF), which is strongly involved in neuronal growth and differentiation, were measured. Although mice behaviors were improved by oral T3 intake, there were no significant differences in brain oxidation levels and BDNF expression. These results suggest that T3s attenuate obesity via inhibition of body fat and serum cholesterol increase.

Absorption, transportation, and distribution of vitamin E homologs.

Vitamin E has eight different naturally occurring forms: four tocopherols and four tocotrienols. Because α-tocopherol has three asymmetric carbons, both natural α-tocopherol (RRR-α-tocopherol) and synthetic α-tocopherol (all-rac-α-tocopherol) are utilized in both pharmaceutical products and food additives. Therefore, determining the distribution of vitamin E in the body is very important. With regard to absorption, and transportation of vitamin E, it is suggested that the pathways mediated by three proteins (CD36, SR-BI, and NPC1L1) as well as passive diffusion affect absorption of vitamin E. Vitamin E homologs are mainly transported by very low-density lipoprotein (VLDL) with the α-tocopherol being recognized by the α-tocopherol transfer protein in liver. However, it is also suggested that chylomicrons (CMs) and high-density lipoprotein (HDL) are involved in transportation of vitamin E homologs from the small intestine to each section of peripheral tissue. In particular, it is speculated that vitamin E homologs transportation by CMs and HDL from enterocytes to peripheral tissues such as adipose tissue greatly affects the distribution of vitamin E homologs, excluding α-tocopherol. However, how lipoprotein lipase affects the incorporation of vitamin E homologs containing lipoprotein into peripheral tissues is unclear. Whether there is biodiscrimination when vitamin E homologs are incorporated into peripheral tissues from lipoprotein is an interesting question. It is likely that future research will reveal how individual vitamin E homologs are incorporated into peripheral tissue, especially the brain, adipose tissue, and skin.

Effect of δ-Tocopherol on Mice Adipose Tissues and Mice Adipocytes Induced Inflammation.

The study aim was to evaluate the potential anti-inflammatory effects of vitamin E analogs, especially α-tocopherol and δ-tocopherol. We used male C57BL/6JJcl mice, which were divided into four groups: the control (C), high-fat and high-sucrose diet (H), high-fat and high-sucrose diet+α-tocopherol (Ha) and high-fat and high-sucrose diet+δ-tocopherol (Hd) groups. The mice were fed for 16 weeks. To the high-fat and high-sucrose diet, 800 mg/kg of α-tocopherol or δ-tocopherol was added more. The final body weight was significantly higher in the H group than in the C group. On the other hand, the final body weight was drastically lower in the Ha group and Hd group than in the H group. However, the energy intake was not significantly different among all groups. Therefore, we assumed that α-tocopherol and δ-tocopherol have potential anti-obesity effect. Besides, inflammatory cytokine gene expression was significantly higher in the epididymal fat of the H group than in the C group. These results showed that inflammation was induced by epididymal fat of mice fed a high-fat and high-sucrose diet for 16 weeks. Unfortunately, addition of α-tocopherol or δ-tocopherol to the diet did not restrain inflammation of epididymal fat. Investigation of the anti-inflammatory effects of α-tocopherol or δ-tocopherol in co-cultured 3T3-L1 cells and RAW264.7 cells showed that δ-tocopherol inhibited increased gene expression of the inflammatory cytokines, IL-1ß, IL-6, and iNOS. These results suggest that an anti-inflammatory effect in the δ-tocopherol is stronger than that in the α-tocopherol in vitro. We intend to perform an experiment by in vivo sequentially in the future.

Improvement Effect of Sweet Basil (Ocimum basilicum L.) Powder Intake on Obese Mice Fed a High-fat and High-sucrose Diet.

This study aimed to determine if there are anti-inflammatory and anti-obesity effects of sweet basil, an herb, in mice. Sweet basil was administered as a powder to male C57BL/6JJcl mice, which were divided into three groups: the (control [C], high-fat and high-sucrose diet [H], and high-fat and high-sucrose diet plus sweet basil powder [HB]) groups. The mice were fed for 12 weeks and the dry sweet basil powder comprised 1% per kg of the diet. From experiment third week, the average body weight was significantly higher in the H group than in the C group. The average body weight was significantly lower in the HB group than in the H group, but food intake did not significantly differ between the H and HB groups. Liver weight was drastically lower in the HB group than in the H group. Perirenal fat weight and epididymal fat weight were not significantly different between the H and HB groups. Therefore, we assumed that body-weight reduction caused by sweet basil powder intake depended on inhibition of liver enlargement. We then examined lipid metabolism-related gene expression in the mice livers. Expression of the sterol response element binding protein 1-c gene tended to be lower in the HB group than in the H group (p=0.056). We speculated that sweet basil inhibited liver enlargement by suppressing fatty acid synthesis. Moreover, expression of the monocyte chemoattractant protein-1 gene in epididymal fat was significantly lower in the HB group than in the H group. Sweet basil powder appears to have a potent anti-inflammatory effect in the adipose tissue of mice fed a high-fat and high-sucrose diet.

δ-Tocopherol Slightly Accumulates in the Adipose Tissue of Mice.

This study aimed to compare the distribution of vitamin E analogs, particularly α-tocopherol and δ-tocopherol, in mice fed with a normal diet and a high-fat and high-sucrose diet separately. We used male C57BL/6JJcl strain mice, which were divided into six groups (control [C], Cα, Cδ, high-fat and high-sucrose [H], Hα, and Hδ groups) and bred for 4 weeks. The additional quantity of α-tocopherol or E-mix D (containing 86.7% δ-tocopherol) into diet was 800 mg/kg diet. The final body weight was significantly higher in the H group than in the C group. However, the effects of vitamin E analog intake had no significant difference, with no synergy between vitamin E and diet. Similar results were obtained in epididymal fat weight. Moreover, α-tocopherol was mainly distributed in the liver in both the Cα group and Hα group, whereas δ-tocopherol mostly accumulated in the epididymal fat, in both the Cδ group and Hδ group. Also, δ-tocopherol was detected in all tissues in both groups. Both the α-tocopherol and δ-tocopherol levels in the epididymal fat were significantly lower in the H group than in the C group. In conclusion, our results suggest that a portion of δ-tocopherol was incorporated into the adipose tissue by chylomicron before arriving at the liver, and then it is metabolized in the liver.

Anti-inflammatory Effects of Extracts of Sweet Basil (Ocimum basilicum L.) on a Co-culture of 3T3-L1 Adipocytes and RAW264.7 Macrophages.

Obesity, a lifestyle disease resulting from excessive caloric intake and insufficient physical activity, results in a state of chronic inflammation. A food ingredient that suppresses chronic inflammation could help prevent associated diseases. Sweet basil (Ocimum basilicum L.) is a herb from the Lamiaceae family with some reported anti-inflammatory effects. Via this in vitro study, we aimed to investigate whether sweet basil exerts anti-inflammatory effects in obese patients. Fresh sweet basil leaves were freeze-dried and powered. After that, this was extracted with 80% methanol. After 3T3-L1 adipocytes were cultured with sweet basil extracts at final concentrations of either 5 or 25 µg/mL for 24h, RAW264.7 macrophages were seeded onto this adipocytes and co-cultured for 12h. We determined the effects of sweet basil extracts on inflammatory cytokine expression by real-time PCR or western blotting. Sweet basil extracts reduced the expression of inflammatory cytokine mRNA induced by co-culture, including that of IL-6 (Il6), IL-1ß (Il1b), TNF-α (Tnf), and CCL2 (Ccl2). In addition, sweet basil extracts suppressed the mRNA expression of NF-κB (Nfκb1), a transcription factor of inflammatory cytokines. In an investigation of costimulatory CD137 (Tnfrsf9)/CD137L inflammatory signaling, a member of the TNF super-family, sweet basil extracts inhibited Tnfrsf9 expression induced by the co-culture. Therefore, the results of this study indicated that sweet basil extracts have an anti-inflammatory effect against adipocyte-induced inflammation, possibly through suppression of Tnfrsf9 expression.

δ-Tocopherol promotes thermogenic gene expression via PGC-1α upregulation in 3T3-L1 cells.

Activation of thermogenic adipocytes (brown and beige) has been considered an attractive target for weight loss and treatment of metabolic disease. Peroxisome proliferator-activated receptor γ co-activator-1 α (PGC1-α) is a master regulator of thermogenic gene expression in thermogenic adipocytes. We previously reported that α-tocopherol upregulated PGC-1α gene expression and promoted thermogenic adipocyte differentiation in mammalian adipocytes. In this study, we investigated the effects of the vitamin E analogs (α-, γ- and δ-tocopherol) on PGC-1α and uncoupling protein 1 (UCP1) gene expression in 3T3-L1 cells. The expression of PGC-1α and UCP1 increased significantly with the addition of δ-tocopherol. In δ-tocopherol-treated cells, nuclear translocation of PGC-1α increased, as did p38 mitogen-activated protein kinase (MAPK) expression and phosphorylation. Our results suggest that p38 MAPK activation by δ-tocopherol contributes to PGC-1α activation and UCP1 induction.

Promoting Effect of α-Tocopherol on Beige Adipocyte Differentiation in 3T3-L1 Cells and Rat White Adipose Tissue.

Thermogenic adipocytes that are distinct from classical brown adipocytes (beige adipocytes) were identified in 2012. Beige adipocytes are also called inducible brown adipocytes because their differentiation is induced by a number of physiological stimuli, including adrenaline or myokines. PPARγ is the master regulator of adipogenesis and promotes thermogenic adipocyte differentiation. A PPARγ agonist also promotes thermogenic adipocyte differentiation in mouse white adipose tissues. The vitamin E analog α-tocopherol promotes PPARγ expression and induces mRNA expression of target genes. This study investigated the effects of vitamin E analogs on thermogenic adipocyte differentiation in mouse preadipocytes and rat white adipose tissues. We determined the effects of vitamin E analogs (α-tocopherol and γ-tocopherol) on PPARγ, PGC-1α, and uncoupling protein 1 (UCP1) gene expression in 3T3-L1 cells. UCP1 expression and the mitochondrial contents were confirmed in the cells using immunofluorescence. In an in vivo study, male SD-IGS rats were fed a high-fat diet (HFD), α-tocopherol-enriched HFD, or γ-tocopherol-enriched HFD for 8 weeks before the analysis of PPARγ, PGC-1α, UCP1, and CD137 gene expression, and pathological examinations of white adipose tissues. The expression of PPARγ, PGC-1α, and UCP1 increased in 3T3-L1 cells following α-tocopherol treatment in a concentration-dependent manner. UCP1 expression and mitochondrial content also increased in α-tocopherol-treated cells. According to the histopathological examinations of rat white adipose tissues, multilocular cells were observed in the α-tocopherol intake group. Furthermore, the gene expression levels of PGC-1α, UCP1, and CD137 increased in the α-tocopherol intake group. Our results suggest that α-tocopherol promotes thermogenic adipocyte differentiation in mammalian white adipose tissues.

Changes in the concentrations of vitamin E analogs and their metabolites in rat liver and kidney after oral administration.

Vitamin E analog, such as α- and γ-tocopherol, can undergo ω-oxidation without cleavage of the chroman ring, and this pathway is responsible for generation of the major urinary vitamin E metabolite, carboxyethyl hydroxychroman. However, it is still unclear how carboxyethyl hydroxychroman is changed in various tissues after vitamin E intake. We therefore investigated changes in the concentrations of α- and γ-tocopherol and their metabolites in rat liver and kidney. The concentration of α-tocopherol in rat liver increased until 6 h after oral administration, and then decreased. The change in the concentration of α-carboxyethyl hydroxychroman in rat liver in the α-Toc group slowly increased until 12 h after oral administration. Cytochrome P450 3A1 mRNA expression significantly increased from 12 h after the start of α-tocopherol administration. The change in the concentration of γ-carboxyethyl hydroxychroman in rat liver in the γ-Toc group markedly increased until 12 h after oral administration. On the other hand, γ-carboxyethyl hydroxychroman in rat kidney showed greater accumulation than α-carboxyethyl hydroxychroman from 3 h to 24 h after oral administration. From these results, we considered that γ-carboxyethyl hydroxychroman formed in the liver continues to be released into the bloodstream and is transported to the kidney rapidly.

Effects of tocotrienol on tumor necrosis factor-α/d-galactosamine-induced steatohepatitis in rats.

It has been reported that α-tocopherol (α-Toc), a vitamin E analog, is effective for treatment of non-alcoholic steatohepatitis (NASH). However, it is unknown whether or not other vitamin E analogs are effective. Therefore we designed a new rat model of steatohepatitis induced by tumor necrosis factor-α (TNF-α) stimulation, and used it to investigate the effects of vitamin E analogs. The rat liver triglyceride content increased with the dosage of TNF-α/d-galactosamine (GalN), but was suppressed by intake of both tocotrienol (T3) and α-tocopherol. Moreover, lipid peroxides (thiobarbituric acid-reactive substances) level in the liver level was also lower in both groups after tocotrienol and α-Toc intake. Intake of both tocotrienol and α-tocopherol also tended to control the increase of liver damage marker activity. In the tocotrienol and α-tocopherol groups, increases of inflammatory cytokines mRNA expression in the liver were inhibited, and these effects were considered to contribute to improvement of inflammation and fibrosis. The expression of mRNAs for inflammatory cytokines in rat primary hepatocytes was increased by TNF-α stimulation, but was inhibited by addition of α-tocotrienol and γ-tocotrienol. Transforming growth factor-ß1 mRNA expression in particular was significantly inhibited by γ-tocotrienol. These findings suggest that tocotrienol species are effective for amelioration of steatohepatitis, and that tocotrienol and α-tocopherol exert a synergistic effect.

Gamma-tocotrienol reduces the triacylglycerol level in rat primary hepatocytes through regulation of fatty acid metabolism.

The present study was carried out to investigate the effect of vitamin E analogs, especially gamma-tocotrienol (γ-T3), on hepatic TG accumulation and enzymes related to fatty acid metabolism in three types of rat primary hepatocytes: (1) normal hepatocytes, (2) hepatocytes incubated in the presence of palmitic acid (PA), and (3) hepatocytes with fat accumulation. Our results showed that γ-T3 significantly reduced the TG content of normal hepatocytes. γ-T3 also increased the expression of carnitine palmitoyltransferase 1 (CPT1A) mRNA, and tended to reduce that of sterol regulatory element binding protein 1c (SREBP-1c) mRNA. In addition, γ-T3 markedly suppressed the gene expression of both C/EBP homologous protein (CHOP) and SREBP-1c induced by PA. As these two genes are located downstream of endoplasmic reticulum (ER) stress, their suppression by γ-T3 might result from a decrease of ER stress. Moreover, γ-T3 suppressed the expression of interleukin 1ß (IL-1ß), which lies downstream of CHOP signaling. Taken together, our data suggest that γ-T3 might prevent hepatic steatosis and ameliorate ER stress and subsequent inflammation in the liver.

Protective Effects of Vitamin E Analogs against Carbon Tetrachloride-Induced Fatty Liver in Rats.

Recently, it has been reported that α-tocopherol (α-Toc) is effective for amelioration of liver damage. However, it is unknown whether other vitamin E analogs are effective. In this study, we investigated the effects of γ-tocopherol (γ-Toc) and tocotrienols (T3) in rats with fatty liver. Rats fed a vitamin E-deficient diet for four weeks were divided into eight groups: Control, carbon tetrachloride (CCl(4)), α-Toc, α-Toc + CCl(4), γ-Toc, γ-Toc + CCl(4), T3 mix, T3 mix + CCl(4). After a 24 h fast, the rats were administered 20 mg of each of the vitamin E analogs, respectively. Moreover, the CCl(4) group were given 0.5 ml/kg body weight corn oil preparation containing CCl(4) 6 h after vitamin E administration. We measured the activities of aspartate aminotransferase and alanine aminotransferase (ALT) in plasma, and the contents of triglyceride (TG), total cholesterol (T-Chol) and vitamin E analogs in the liver. Also, we determined the hepatic expression of mRNA for inflammatory cytokines. The liver TG content in the γ-Toc + CCl(4) and T3 mix + CCl(4) groups was decreased in comparison with the CCl(4) group. Moreover, ALT activity in the T3 mix + CCl(4) group was significantly lower than CCl(4) group. These findings suggest that γ-Toc and T3 are effective for amelioration of fatty liver.

Effect of collagen hydrolysates from salmon and trout skins on the lipid profile in rats.

The effect of collagen hydrolysates from fish skins on lipid profile was assessed in rats administered chum salmon or rainbow trout collagen peptide. Single oral administration of soybean oil with or without one of either type of fish collagen peptide demonstrated that rat plasma triglycerides were significantly decreased 2 h later after the intake of oil and peptide mixtures (p < 0.05). The free and peptide forms of hydroxyproline derived from fish collagen peptides were statistically higher than those of zero time after oral administration. To test the effect of fish collagen peptides on continuous administration, rats were fed an AIN-93G purified diet containing 0.17% fish collagen peptide. The peptide groups had lower levels of plasma total lipids and triglycerides compared with the control group. However, the body, liver, and fat weights of rats were not significantly different between groups. These results suggest that fish collagen hydrolysates affect lipid absorption and metabolism in rats and may be useful in suppressing the transient increase of plasma triglycerides.

Tocotrienol suppresses adipocyte differentiation and Akt phosphorylation in 3T3-L1 preadipocytes.

In vivo studies show that alpha-tocotrienol and gamma-tocotrienol accumulate in adipose tissue. Furthermore, a recent study reports that the oral administration of gamma-tocotrienol from a tocotrienol-rich fraction from palm oil (TRF) decreases body fat levels in rats. The objective of this study was to evaluate the effect of TRF and its components on adipocyte differentiation in 3T3-L1 preadipocytes, which differentiated into adipocytes in the presence of 1.8 micromol/L insulin. TRF suppressed the insulin-induced mRNA expression of adipocyte-specific genes such as PPARgamma, adipocyte fatty acid-binding protein (aP2), and CCAAT/enhancer-binding protein-alpha (C/EBPalpha) compared with the differentiation of 3T3-L1 preadipocytes into adipocytes only in the presence of insulin. To confirm the suppressive effect of TRF, the major components of TRF, such as alpha-tocotrienol, gamma-tocotrienol, and alpha-tocopherol, were investigated. Alpha-tocotrienol and gamma-tocotrienol decreased the insulin-induced PPARgamma mRNA expression by 55 and 90%, respectively, compared with insulin, whereas alpha-tocopherol increased the mRNA expression. In addition, gamma-tocotrienol suppressed the insulin-induced aP2 and C/EBPalpha mRNA expression, triglyceride accumulation, and PPARgamma protein levels compared with insulin. The current results also revealed that gamma-tocotrienol inhibited the insulin-stimulated phosphorylation of Akt but not extracellular signal-regulated kinase (ERK)1/2 in the insulin signaling pathway of 3T3-L1 preadipocytes. Thus, the antiadipogenic effect of TRF depends on alpha-tocotrienol and gamma-tocotrienol, and gamma-tocotrienol may be a more potent inhibitor of adipogenesis than alpha-tocotrienol. Therefore, the results of this study suggest that tocotrienol suppresses insulin-induced differentiation and Akt phosphorylation in 3T3-L1 preadipocytes. Furthermore, tocotrienol could act as an antiadipogenic vitamin in the nutrient-mediated regulation of body fat through its effects on differentiation.

The coantioxidative effects of carboxyethyl-6-hydroxychromans and alpha-Tocopherol.

alpha-Tocopherol (alpha-Toc) is abundant in LDL and thought to prevent the oxidation of LDL together with various water-soluble antioxidants. Recently, it was reported that alpha-Toc and gamma-Toc metabolites, alpha-carboxyethyl-6-hydroxychromans (CEHC) and gamma-CEHC, are water-soluble antioxidants. In this study, we investigated the interaction between alpha-Toc and CEHC against 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and LDL oxidation. We administered 600 mg of alpha-Toc to healthy male volunteers to obtain LDL including high levels of alpha-Toc before antioxidant administration. The alpha-Toc content of their LDL was increased after consumption at 24 h (18.3 microg/mL) above the level before consumption (6.6 microg/mL). The lag time of LDL at 24 h after alpha-Toc consumption (alpha-Toc rich LDL) with alpha-CEHC (98.5+/-8.2 min) or gamma-CEHC (101.3+/-9.0 min) was longer than that of only alpha-Toc-rich LDL (78.1+/-9.0 min). Furthermore, we examined the interaction of LDL with CEHC and alpha-Toc in vitro (5-20 microg/mL). The lag times of 5 and 10 microg/mL alpha-Toc were 65.5+/-18.9 min and 69.5+/-15.5 min, and that of 20 microg/mL alpha-Toc (83.5+/-20.2 min) was longer than the control value (55.7+/-14.1 min). The lag time of 20 microg/mL alpha-Toc with alpha-CEHC (98.7+/-25.7 min) or gamma-CEHC (100.6+/-25.3 min) was longer than that of only alpha-Toc (83.5+/-20.2 min). These results suggest that CEHC has the potential to delay the oxidation of LDL, while enhancing the antioxidative activity of alpha-Toc both in vitro and ex vivo.

gamma-Tocopherol Accelerated Sodium Excretion in a Dose-Dependent Manner in Rats with a High Sodium Intake.

We have previously reported that gamma-tocopherol (gamma-Toc) displays a natriuretic potency in rats fed a NaCl diet and administered 20 mg gamma-Toc. In this study, we investigated whether gamma-Toc has natriuretic potency at a dose lower or higher than 20 mg in rats given a NaCl diet. Male rats were fed a control diet or a NaCl diet and administered either placebo or 10, 20 or 40 mg of gamma-Toc. The rat urine was collected for 24 hours (divided into 6 hour periods) and the 2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC) level, the sodium excretion content, and the urine volume were determined. The 24-hour gamma-CEHC and sodium levels in the urine of the NaCl groups given 20 mg or 40 mg gamma-Toc were significantly higher than those in the placebo group. The peak levels of urine sodium and gamma-CEHC in the NaCl group given 40 mg gamma-Toc appeared at 0-6 h, which was a more rapid increase than that seen in the group given 20 mg gamma-Toc. The 24-hour urine volumes of the NaCl groups given 10 and 20 mg gamma-Toc were significantly higher than the urine volume of the placebo group. Our findings suggested that gamma-Toc increased sodium excretion in a dose-dependent manner in rats fed a NaCl diet. Moreover, a high dose of gamma-Toc may accelerate its metabolism and cause an increase in the rate of sodium excretion.

Effect of docosahexaenoic acid intake on lipid peroxidation in diabetic rat retina under oxidative stress.

Docosahexaenoic acid (DHA) plays an important role in visual function but has a highly oxidation-prone chemical structure. Therefore, we investigated how dietary DHA affects the generation of lipid peroxides in rat retina under oxidative stress in diabetes with/without vitamin E (VE) deficiency. Streptozotocin-induced (50 mg i.p./kg B.W.) diabetic Sprague-Dawley (SD) rats were assigned to four groups: (i) control/VE(+), (ii) DHA/VE(+), (iii) control/VE( - ) and (iv) DHA/VE( - ), and raised for 28 days. We then measured lipid peroxide levels in the retina, serum and liver. With a normal intake of VE, dietary DHA increased only the retinal level of thiobarbituric acid-reactive substances (TBARS) slightly. In contrast, in rats with VE deficiency, dietary DHA increased serum and liver lipid peroxide levels but not in the retina. These results suggest that dietary DHA does not necessarily promote lipid peroxidation in the retina even under high oxidative stress.

Antioxidant activities of black and yellow soybeans against low density lipoprotein oxidation.

Several studies have demonstrated that the daily intakes of soy foods were associated with a reduced cardiovascular risk. The aim of our study was to investigate the inhibitory effect of black soybeans on low density lipoprotein (LDL) oxidation in comparison to yellow soybeans. The extract from black soybean had a longer LDL oxidation lag time than that from yellow soybean (205 +/- 16 and 65 +/- 3 min, respectively). When both soybeans were divided into the seed coat and the mixture of the germ and cotyledon, the diluted extract solution from the black soybean seed coat prolonged the lag time significantly more than the original extract of the yellow soybean seed coat. On the other hand, antioxidant effects of the extract from the mixture of germs and cotyledons were similar in both soybeans. Regarding total polyphenol contents, the seed coat of black soybean had a higher polyphenol content than that of yellow soybean (29.0 +/- 0.56 and 0.45 +/- 0.02 mg/g, respectively). Interestingly, the mixture of the germ and cotyledon hydrolyzed by beta-glucosidase in both soybeans showed a stronger inhibitory effect on LDL oxidation than that before being hydrolyzed by beta-glucosidase. These results suggest that black soybeans may be more effective in inhibiting LDL oxidation than yellow soybeans because of total polyphenols contents in its seed coat. In addition, aglycones, which are rich in soybeans fermented or hydrolyzed by beta-glucosidase, may play a crucial role in the prevention of oxidation-related diseases.