Masayuki Abe

Cytotoxic effect of conjugated trienoic fatty acids on mouse tumor and human monocytic leukemia cells.

The cytotoxicity of fatty acids from seed oils containing conjugated linolenic acids (CLN) was studied. Fatty acids from pomegranate, tung, and catalpa were cytotoxic to human monocytic leukemia cells at concentrations exceeding 5 μM for pomegranate and tung and 10 μM for catalpa, but fatty acids from pot marigold oil had no effect at concentrations ranging up to 163 μM. The main conjugated fatty acids of pomegranate, tung, catalpa, and pot marigold were cis(c)9, trans(t)11, c13-CLN (71.7%), c9,t11,t13-CLN (70.1%), t9,t11,c13-CLN (31.3%), and t8,t10,c12-CLN (33.4%), respectively. Therefore, the cytotoxicities of fatty acids from pomegranate, tung, and catalpa were supposed to be due to 9,11,13-CLN isomers. To elucidate the cytotoxicity of these CLN, we separated each CLN isomer from the fatty acid mixtures by high-performance liquid chromatography and analyzed its cytotoxicity. The cytotoxicities of c9,t11,c13-CLN, c9,t11,t13-CLN, and t9,t11,c13-CLN were much stronger than that of t8,t10,c12-CLN. Therefore, the higher cytotoxicity of fatty acids from pomegranate, tung, and catalpa than those from pot marigold would be derived from the different activities of 9,11,13-CLN and 8,10,12-CLN. Since there was little difference in the cytotoxicities of c9,t11,c13-CLN, c9,t11,t13-CLN, and t9,t11,c13-CLN, it is suggested that the cis/trans configuration of 9,11,13-CLN isomers had little effect on their cytotoxic effects. The mechanism of the cytotoxicity of the four fatty acids above may involve lipid peroxidation, because the order of toxicity of the fatty acids was consistent with their susceptibility to peroxidation in aqueous phase. This was supported by the decrease in the cytotoxicity of the fatty acids by addition of butylated hydroxytoluene.

The allenic carotenoid fucoxanthin, a novel marine nutraceutical from brown seaweeds.

Obesity and type 2 diabetes are pathologies with rapidly growing prevalence throughout the world. A few molecular targets offer the most hope for anti-obesity and anti-diabetic therapeutics. One of the keys to success will be the induction of uncoupling protein 1 (UCP1) in abdominal white adipose tissue (WAT) and the regulation of cytokine secretions from both abdominal adipose cells and macrophage cells infiltrated into adipose tissue. Anti-obesity and anti-diabetic effects of fucoxanthin, a characteristic carotenoid found in brown seaweeds, have been reported. Nutrigenomic studies reveal that fucoxanthin induces UCP1 in abdominal WAT mitochondria, leading to the oxidation of fatty acids and heat production in WAT. Fucoxanthin improves insulin resistance and decreases blood glucose levels through the regulation of cytokine secretions from WAT. The key structure of carotenoids for the expression of anti-obesity effect is suggested to be the carotenoid end of the polyene chromophore, which contains an allenic bond and two hydroxyl groups.

Effect of Brown Seaweed Lipids on Fatty Acid Composition and Lipid Hydroperoxide Levels of Mouse Liver

Brown seaweed lipids from Undaria pinnatifida (Wakame), Sargassum horneri (Akamoku), and Cystoseira hakodatensis (Uganomoku) contained several bioactive compounds, namely, fucoxanthin, polyphenols, and omega-3 polyunsaturated fatty acids (PUFA). Fucoxanthin and polyphenol contents of Akamoku and Uganomoku lipids were higher than those of Wakame lipids, while Wakame lipids showed higher total omega-3 PUFA content than Akamoku and Uganomoku lipids. The levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) in liver lipids of KK-A(y) mouse significantly increased by Akamoku and Uganomoku lipid feeding as compared with the control, but not by Wakame lipid feeding. Fucoxanthin has been reported to accelerate the bioconversion of omega-3 PUFA and omega-6 PUFA to DHA and AA, respectively. The higher hepatic DHA and AA level of mice fed Akamoku and Uganomoku lipids would be attributed to the higher content of fucoxanthin of Akamoku and Uganomoku lipids. The lipid hydroperoxide levels of the liver of mice fed brown seaweed lipids were significantly lower than those of control mice, even though total PUFA content was higher in the liver of mice fed brown seaweed lipids. This would be, at least in part, due to the antioxidant activity of fucoxanthin metabolites in the liver.

Pharmacological characterization of 5‐hydroxytryptamine‐induced excitation of afferent cervical vagus nerve in anaesthetized rats

1 An excitatory response to 5‐hydroxytryptamine (5‐HT) was measured from the afferent vagus nerve of anaesthetized rats. Measurements were determined by an extracellular recording from the whole nerve. 2 Intravenous bolus injection of 5‐HT (1.56–100 μg kg−1) evoked a dose‐dependent excitation of afferent vagus nerve activity. This response was blocked not only by a selective 5‐HT3 receptor antagonist, GR38032F (10 and 100 μg kg−1), but also by a 5‐HT2 receptor antagonist, ketanserin (10 and 100 μg kg−1). 3 Both a 5‐HT3 receptor agonist, 2‐methyl‐5‐HT (3.12–100 μg kg−1), and a 5‐HT2 receptor agonist, α‐methyl‐5‐HT (3.12–50 μg kg−1), produced a dose‐dependent excitation of afferent vagus nerve activity. These excitatory effects were antagonized by GR38032F (10 μg kg−1) and ketanserin (10 μg kg−1), respectively. 4 A 5‐HT1 like receptor agonist, 5‐carboxamidotryptamine (50 μg kg−1), and a putative 5‐HT4 receptor agonist, 5‐methoxytryptamine (100 μg kg−1), failed to produce excitatory effects on the afferent vagus nerve. 5 These results suggest that the 5‐HT‐induced excitatory response of the afferent vagus nerve might be mediated not only via 5‐HT3 receptors but also via 5‐HT2 receptors in anaesthetized rats. It is unlikely, however, that either 5‐HT1‐like or putative 5‐HT4 receptors are involved in the excitatory response of the afferent vagus nerve to 5‐HT.

Oxidative Stability of Lipids Rich in EPA and DHA Extracted from Fermented Scallop Ovary

A novel seafood paste was developed by the fermentation of scallop ovary using rice malt (koji) and yeast culture. Chemical analysis of the product showed the formation of high level of free amino acids and organic acids during the fermentation. The product color and flavor resembled to Japanese traditional soybean miso. The contents of total lipids (TLs) extracted from the fermented products were ranged from 9.18% to 11.59% or 11.38% to 13.57%/dry sample weight. Although the TL was rich in oxidatively unstable polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), little decrease was found in these PUFAs during the fermentation, showing the high oxidative stability of the TL from the fermented scallop ovary. Moreover, the oxidative stability of the TL extracted from the fermented products increased with increasing the fermentation time. This would be mainly due to the formation of lipid soluble antioxidants such as tocopherols, which might be derived from yeast used for fermentation.