Kiyotaka Nakagawa

ANTIANGIOGENIC AND ANTICANCER POTENTIAL OF UNSATURATED VITAMIN E (TOCOTRIENOL)

Several lines of evidence support the beneficial effect of tocotrienol (T3; an unsaturated vitamin E) on inhibition of tumor development. Many factors, including decrease in oxidative stress and modulation of cell signaling pathways in tumor and endothelial cells, have been implicated in such anticancer action of T3, while the in vivo potency and exact intracellular mechanisms for the anticancer properties of T3 remain not fully understood. We have hypothesized that the inhibitory effect of T3 on cancer may be attributable to the antiangiogenic activity of T3, and we found that T3 acts as a potent regulator of growth-factor-dependent signaling in endothelial cells and as an antiangiogenic agent minimizing tumor growth. In this work, we review the history and biological action (i.e., anticancer) of vitamin E and describe current research on the antiangiogenic effects of T3 and its mechanisms.

MicroRNAs in plasma and cerebrospinal fluid as potential markers for Alzheimer's disease.

The development of Alzheimers disease (AD) biomarkers remains an unmet challenge, and new approaches that can improve current AD biomarker strategies are needed. Recent reports suggested that microRNA (miRNA) profiling of biological fluids has emerged as a diagnostic tool for several pathologic conditions. In this study, we measured six candidate miRNAs (miR-9, miR-29a, miR-29b, miR-34a, miR-125b, and miR-146a) in plasma and cerebrospinal fluid (CSF) of AD and normal subjects by using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) to evaluate their potential usability as AD biomarkers. The qRT-PCR results showed that plasma miR-34a and miR-146a levels, and CSF miR-34a, miR-125b, and miR-146a levels in AD patients were significantly lower than in control subjects. On the other hand, CSF miR-29a and miR-29b levels were significantly higher than in control subjects. Our results provide a possibility that miRNAs detected in plasma and CSF can serve as biomarkers for AD.

Synthetically prepared Amadori-glycated phosphatidylethanolamine can trigger lipid peroxidation via free radical reactions

This study for the first time confirmed the peroxidative role of the Amadori product derived from the glycation of phosphatidylethanolamine (PE), namely Amadori–PE. The product was synthesized from the reaction of dioleoyl PE with D‐glucose, and then purified by a solid‐phase extraction procedure, which was a key step in the next HPLC technique for the isolation of essentially pure Amadori–PE. When the synthetically prepared Amadori–PE was incubated with linoleic acid in the presence of Fe3+ in micellar system, a remarkable formation of thiobarbituric acid reactive substances was observed together with increases in lipid hydroperoxides. In addition, the lipid peroxidation caused by Amadori–PE was effectively inhibited by superoxide dismutase, mannitol, catalase and metal chelator. These results indicated that Amadori–PE triggers oxidative modification of lipids via the generation of superoxide, and implied the involvement of ‘lipid glycation’ along with membrane lipid peroxidation in the pathogenesis of diabetes and aging.

Anti-angiogenic activity of tocotrienol.

The anti-angiogenic property of vitamin E compounds, with particular emphasis on tocotrienol, has been investigated in vitro. Tocotrienol, but not tocopherol, inhibited both the proliferation and tube formation of bovine aortic endothelial cells, with δ-tocotrienol appearing the highest activity. Also, δ-tocotrienol reduced the vascular endothelial growth factor-stimulated tube formation by human umbilical vein endothelial cells. Our findings suggest that tocotrienol has potential use as a therapeutic dietary supplement for minimizing tumor angiogenesis.

Tocotrienol Inhibits Secretion of Angiogenic Factors from Human Colorectal Adenocarcinoma Cells by Suppressing Hypoxia-Inducible Factor-1α

Tocotrienol (T3), unsaturated vitamin E, has recently gained considerable attention as a potent antiangiogenic agent minimizing tumor growth, the exact intracellular mechanisms of which remain poorly understood. Because hypoxia-inducible factor-1alpha (HIF-1alpha), its downstream target vascular endothelial growth factor (VEGF), and other angiogenic factors such as interleukin-8 (IL-8) and cyclooxygenase 2 (COX-2) play critical roles in neovascularization, we tested the hypothesis that the inhibitory effect of T3 on tumor angiogenesis is via regulation of these angiogenic factors. We used 2 cancer cell lines, human colorectal adenocarcinoma cells (DLD-1) and human hepatoma cells (HepG2). T3 isomers (2 micromol/L) inhibited hypoxia-induced VEGF secretion from DLD-1, with delta-T3 showing potent inhibition. Delta-T3 suppressed hypoxia-induced VEGF and IL-8 expression in DLD-1 at both mRNA and protein levels, and we found the inhibitory mechanism of delta-T3 by reducing HIF-1alpha protein expression or increasing HIF-1alpha degradation. Also, delta-T3 (2 micromol/L) did not affect hypoxia-induced COX-2 mRNA expression; however, delta-T3 tended to suppress (P = 0.044) hypoxia-induced COX-2 protein expression, implying a possible post-transcriptional mechanism by delta-T3. Overall, our results confirmed that T3 has an inhibitory effect on angiogenic factor secretion from cancer cells and revealed the possible mechanisms, providing new information about the antiangiogenic effects of T3.

Long-term intake of fish oil increases oxidative stress and decreases lifespan in senescence-accelerated mice

OBJECTIVE The effects of fish oil including ω-3 polyunsaturated fatty acids on aging and lifespan are not well understood. In this study, the influence of long-term ingestion of fish oil on lifespan was examined in senescence-accelerated (SAMP8) mice. METHODS We investigated the effects of dietary fish oil on lifespan and on lipid composition and oxidative stress in plasma and liver in SAMP8 mice. Male mice were fed a fish oil diet (5% fish oil and 5% safflower oil) or a safflower oil diet (10% safflower oil) from 12 wk of age. RESULTS The SAMP8 mice fed fish oil did not have a longer maximum lifespan and had a shorter average lifespan than mice fed safflower oil. To examine the mechanism underlying these results, the effects on oxidative stress of long-term ingestion of fish oil were also examined. SAMP8 mice fed fish oil for 28 wk showed strong oxidative stress that caused hyperoxidation of membrane phospholipids and a diminished antioxidant defense system due to a decrease in tocopherol compared with mice fed safflower oil. CONCLUSION These findings suggest that intake of fish oil increases oxidative stress, decreases cellular function, and causes organ dysfunction in SAMP8 mice, thereby promoting aging and shortening the lifespan of the mice.

Tumor anti-angiogenic effect and mechanism of action of δ-tocotrienol

Anti-angiogenic therapy mediated by drugs and food components is an established strategy for cancer prevention. Our previous cell-culture studies identified a food-derived anti-angiogenic compound, tocotrienol (T3, an unsaturated vitamin E), as a potential angiogenic inhibitor. Among T3 isomers, delta-T3 is considered as the most potent compound. The purpose of this study was therefore to evaluate the inhibitory effect of delta-T3 on tumor angiogenesis. As growth factors (e.g., vascular endothelial growth factor and fibroblast growth factor) play critical roles in tumor angiogenesis, a conditioned medium rich in these growth factors from human colorectal adenocarcinoma cells (DLD-1-CM) was used as an angiogenic stimulus. Delta-T3 (2.5-5 microM) significantly suppressed DLD-1-CM-induced tube formation, migration, and adhesion on human umbilical vein endothelial cells. These effects were partly associated with reactive oxygen species generation by delta-T3. Western blot analysis revealed that the anti-angiogenic effect of delta-T3 is attributable to regulation of growth factor-dependent phosphatidylinositol-3 kinase (PI3K)/phosphoinositide-dependent protein kinase (PDK)/Akt signaling as well as to induction stress response in endothelial cells. Moreover, we conducted an in vivo mouse Matrigel plug angiogenesis assay, and found that delta-T3 (10-20 microg) exhibits dose-dependent inhibition of DLD-1-induced vessel formation. These results suggest that T3 has potential use as a therapeutic dietary supplement for minimizing tumor angiogenesis.

Intake of mulberry 1-deoxynojirimycin prevents diet-induced obesity through increases in adiponectin in mice

In this study, the anti-obesity effect of 1-deoxynojirimycin (DNJ) was examined in the diet-induced obese mouse model. Mulberry DNJ was administered to the obese mice for 12 weeks. As a result, DNJ decreased both the visceral fat weight and adipocyte size. To determine the influence of DNJ on lipid metabolism, lipid parameters of the plasma and the liver and the activities of several molecules related to lipid metabolism in the liver were measured. DNJ activated the β-oxidation system, suppressed lipid accumulation in the liver and reduced plasma triacylglycerol. Since it was thought that the factor activated in the β-oxidation system was adiponectin, plasma adiponectin levels were measured and it was shown that plasma adiponectin was increased with DNJ. Therefore, it was suggested that DNJ promoted an increase in plasma adiponectin and activated the β-oxidation system. Overall, it was shown that DNJ prevents diet-induced obesity through an increase in adiponectin.

Jacaric acid, a linolenic acid isomer with a conjugated triene system, has a strong antitumor effect in vitro and in vivo

In this study, we compared the cytotoxic effects of natural conjugated linolenic acids (CLnAs) on human adenocarcinoma cells (DLD-1) in vitro, with the goal of finding CLnA isomers with strong cytotoxic effects. The antitumor effect of the CLnA with the strongest cytotoxic effect was then examined in mice. The results showed that all CLnA isomers have strong cytotoxic effects on DLD-1 cells, with jacaric acid (JA) having the strongest effect. Examination of the mechanism of cell death showed that CLnAs induce apoptosis in DLD-1 cells via lipid peroxidation. The intracellular levels of incorporated CLnAs were measured to examine the reason for differences in cytotoxic effects. These results showed that JA was taken into cells efficiently. Collectively, these results suggest that the cytotoxic effect of CLnAs is dependent on intracellular incorporation and induction of apoptosis via lipid peroxidation. JA also had a strong preventive antitumor effect in vivo in nude mice into which DLD-1 cells were transplanted. These results suggest that JA can be used as a dietary constituent for prevention of cancer.

Intake of 1-deoxynojirimycin suppresses lipid accumulation through activation of the β-oxidation system in rat liver.

It was recently shown that administration of 1-deoxynojirimycin (DNJ) extracted from mulberry suppresses an increase in postprandial blood glucose in humans. These findings are of interest, but other physiological functions of DNJ are unknown. This study examined the effects of oral administration of DNJ (1 mg/kg of body weight/day) or mulberry extracts enriched in DNJ (meDNJ; 100 or 200 mg of extract/kg of body weight/day, equivalent to 0.53 or 1.06 mg of DNJ/kg of body weight/day) in male Sprague-Dawley rats for 4 weeks. DNJ and meDNJ enhanced expression of adiponectin mRNA in white adipose tissue; increased plasma adiponectin levels, enhanced expression of AMPK mRNA, activated the beta-oxidation system, and suppressed lipid accumulation in the liver. Intake of DNJ and meDNJ did not cause hepatic dysfunction and led to a reduction of oxidative stress. These results indicate the efficacy and safety of DNJ and meDNJ.