α‑Tocopherol Attenuates the Triglyceride- and Cholesterol-Lowering Effects of Rice Bran Tocotrienol in Rats Fed a Western Diet

Previous studies demonstrated the ability of tocotrienol (T3) to lower levels of lipids, including cholesterol (Cho) and triglycerides (TG). Although α-tocopherol (α-Toc) reportedly inhibits the hypocholesterolemic effect of T3, there is no information about whether α-Toc influences the TG-lowering effect of T3 in vivo. In this study, we investigated the influence of α-Toc on the antihyperlipidemic effects (Cho- and TG-lowering) of rice bran tocotrienols (RBT3) in F344 rats fed a western diet. α-Toc attenuated both the Cho- and TG-lowering effects of RBT3 in vivo, whereas α-Toc alone exhibited no hypolipidemic effects. RBT3-induced <i>Cpt-1a</i> and <i>Cyp7a1</i> gene expression was reduced by α-Toc. Furthermore, coadministration of α-Toc decreased liver and adipose tissue concentrations of tocotrienols in F344 rats. These results indicate that α-Toc has almost no antihyperlipidemic effect in vivo, but abrogates the antihyperlipidemic effect of RBT3 by reducing tissue concentrations of tocotrienols and regulating expression of genes involved in lipid metabolism. Understanding the underlying mechanism of the beneficial effects of T3 on lipid metabolism and the interaction with α-Toc will be important for developing T3-based therapeutics

Identification of a Genetic Factor Required for High γ‑Isoform Concentration in Rice Vitamin E

The γ-isoforms of tocopherols (Tc) and tocotrienols (T3) possess high biological activities in comparison to the α-isoforms. The concentrations of Tc and T3 isoforms in rice (Oriza sativa) was cultivar-dependent. Using chromosome segment substitution lines (CSSLs) and near isogenic lines (NILs) of indica cultivar “Kasalath” in a japonica cultivar “Koshihikari” genetic background, the Kasalath genomic segment on chromosome 2 was determined to be responsible for the high γ-isoform concentration: γ-tocopherol methyltransferase (<i>γ-TMT</i>) was identified as a candidate gene. An amino acid substitution in the coding region and several nucleotide polymorphisms, including an insertion of 10 base pairs in the promoter region, were identified. Gene expression analysis revealed that low expression levels of the <i>γ-TMT</i> gene in Kasalath were not associated with the γ-isoform concentration. Genetic variations in the coding region of the <i>γ-TMT</i> gene may play a major role in determining the γ-isoform concentration. This information could be used to breed rice with a high γ-isoform content

Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Seven Kinds of Rice Bran Extracts in Ethanol Solution. Development of an Aroxyl Radical Absorption Capacity (ARAC) Assay Method

Recently, a new assay method that can quantify the aroxyl radical (ArO•) absorption capacity (ARAC) of antioxidants (AOHs) was proposed. In the present work, the second-order rate constants (<i>k</i>_s^Extract) and ARAC values for the reaction of ArO• with seven kinds of rice bran extracts 1–7, which contain different concentrations of α-, β-, γ-, and δ-tocopherols and -tocotrienols (α-, β-, γ-, and δ-Tocs and -Toc-3s) and γ-oryzanol, were measured in ethanol at 25 °C using stopped-flow spectrophotometry. The <i>k</i>_s^Extract value (1.26 × 10^–2 M^–1 s^–1) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 × 10^–3) of Milyang-23 (extract 7) with the lowest activity. The concentrations (in mg/100 g) of α-, β-, γ-, and δ-Tocs and -Toc-3s and γ-oryzanol found in the seven extracts 1–7 were determined using HPLC-MS/MS and UV–vis absorption spectroscopy, respectively. From the results, it has been clarified that the ArO•-scavenging rates (<i>k</i>_s^Extract) (that is, the relative ARAC value) obtained for the seven extracts 1–7 may be approximately explained as the sum of the product {Σ <i>k</i>_s^{AOH‑<i>i</i>} [AOH-<i>i</i>]/10⁵} of the rate constant (<i>k</i>_s^{AOH‑<i>i</i>}) and the concentration ([AOH-<i>i</i>]/10⁵) of AOH-<i>i</i> (Tocs, Toc-3s, and γ-oryzanol) included in rice bran extracts. The contribution of γ-oryzanol to the <i>k</i>_s^Extract value was estimated to be between 3.0–4.7% for each extract. Taken together, these results suggest that the ARAC assay method is applicable to general food extracts

Correlation between RBC astaxanthin and Aβ40 (A) or Aβ42 (B) concentrations after 12 weeks administration of astaxanthin (N = 30).

<p>X-axis is the concentration of RBC Aβ. Y-axis is concentration of RBC astaxanthin that had been measured in our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a>.</p

Correlation between RBC PLOOH and Aβ40 (A) or Aβ42 (B) concentration after 12 weeks administration of astaxanthin (N = 30).

<p>X-axis is concentration of RBC Aβ. Y-axis is concentration of RBC PLOOH [phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH)] that had been measured in our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a>.</p

Changes in Amyloid β levels in RBC and plasma before and after a 12 week administration of 0, 6 or 12 mg astaxanthin.

<p>Means ± SE are shown.</p><p>Significantly different between before and after astaxanthin administration: *<i>P</i><0.05.</p><p>Blood samples (RBC and plasma) that had been obtained from our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a> were subjected to Aβ determination.</p

Kinetic study of the quenching reaction of singlet oxygen by seven rice bran extracts in ethanol solution. Development of a singlet oxygen absorption capacity (SOAC) assay method

<p>Measurements of singlet oxygen (¹O₂) quenching rates (<i>k</i>_Q (<i>S</i>)) and the relative singlet oxygen absorption capacity (SOAC) values were performed for seven rice bran extracts 1–7, which contained different concentrations of antioxidants (AOs) (such as α-, β-, γ-, and δ-tocopherols and -tocotrienols, three carotenoids (lutein, β-carotene, and zeaxanthin), and γ-oryzanol), in ethanol at 35 °C using UV–vis spectrophotometry. The concentrations of four tocopherols and four tocotrienols, three carotenoids, and γ-oryzanol contained in the extracts were determined using HPLC-MS/MS, UV-HPLC, and UV–vis absorption spectroscopy, respectively. Furthermore, comparisons of <i>k</i>_Q (<i>S</i>) (Obsd.) values observed for the above extracts 1–7 with the sum of the product { [AO-<i>i</i>]} of the values obtained for each AO-<i>i</i> and the concentration ([AO-<i>i</i>]) of AO-<i>i</i> contained in extracts 1–7 were performed. From the results, it has been ascertained that the SOAC method is applicable to general food extracts to evaluate their ¹O₂-quenching activity.</p> <p>Measurements of the quenching rate (<i>k</i>_Q) of singlet oxygen were performed for seven rice bran extracts in ethanol to evaluate their singlet oxygen quenching activity.</p

Metabolic Fate of Luteolin in Rats: Its Relationship to Anti-inflammatory Effect

Luteolin is a naturally occurring flavone that reportedly has anti-inflammatory effects. Because most luteolin is conjugated following intestinal absorption, free luteolin is likely present at low levels in the body. Therefore, luteolin metabolites are presumably responsible for luteolin bioactivity. Here we confirmed that luteolin glucuronides, especially luteolin-3′-<i>O</i>-glucuronide, are the major metabolites found in plasma after oral administration of luteolin (aglycone) or luteolin glucoside (luteolin-7-<i>O</i>-glucoside) to rats. Luteolin-4′-<i>O</i>-glucuronide and luteolin-7-<i>O</i>-glucuronide were also detectable together with luteolin-3′-<i>O</i>-glucuronide in the liver, kidney, and small intestine. Next, we prepared these luteolin glucuronides and compared the anti-inflammatory effects of luteolin and luteolin glucuronides on gene expression in lipopolysaccharide-treated RAW264.7 cells. Luteolin glucuronides, especially luteolin-7-<i>O</i>-glucuronide, reduced expression of inflammatory genes in the cells, although their effects were weaker than those of luteolin. These results indicate that the active compound responsible for the anti-inflammatory effect of luteolin in vivo would be luteolin glucuronide and/or residual luteolin

The transition of plasma DNJ concentration.

<p>The rats received orally administered sucrose (2 g/kg B.W.) 15 minutes after each samples administration (equivalent to 5 mg DNJ or miglitol/kg B.W.). Blood was collected from tail venous vein and plasma DNJ or miglitol concentration was determined using LC-MS/MS. Results are given as means ± SE. Means without a common letter differ significantly (p < 0.05).</p

The recovery rate of ¹⁵N from DNJ in urine and feces until 48 hours after sample administration.

<p>The recovery rate of ¹⁵N from DNJ in urine and feces until 48 hours after sample administration. After 12 hours fasting, the rats were received ¹⁵N-labeled DNJ (10 mg). Urine and feces were collected and the amount of ¹⁵N from DNJ was analyzed. (a) The time course of recovery rate of ¹⁵N in urine. (b) Total recovery rate of ¹⁵N in urine and feces. Results are given as means ± SE.</p