Taro Honma

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.

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.

Continuous intake of a high-fat diet beyond one generation promotes lipid accumulation in liver and white adipose tissue of female mice

Lipid metabolism in a child may be altered when the mother has a high-fat diet (HFD), but it is unclear whether the lipid metabolism of future offspring (grandchildren) is also changed under these circumstances. In this study, we examined the influence of intake of an HFD beyond one generation on offspring in normal mice. Parent mice fed an HFD were bred and the resultant second and third generations were also fed an HFD. The diets used in the study had approximately 20% more energy than a standard chow diet. Changes in lipid metabolism were examined in each generation. Intake of an HFD from generation to generation promoted lipid accumulation in the white adipose tissue of female mice, increased lipid, glucose and insulin levels in the serum, increased the activities of enzymes associated with fatty acid metabolism in the liver, promoted lipid accumulation in hepatocytes and adipocytes and increased the mRNA levels of Cdkn1a in the liver and white adipose tissue. These results suggest that activation of Cdkn1a promoted lipid accumulation in the liver and white adipose tissue of third-generation female mice that were offspring from earlier generations fed HFDs. Moreover, intake of a high-energy diet beyond one generation led to offspring with obesity, fatty liver and hyperinsulinemia.

Increased Monocytic Adhesion by Senescence in Human Umbilical Vein Endothelial Cells

We investigated whether replicative senescence of endothelial cells contributed to the pathogenesis of atherosclerosis in human umbilical vein endothelial cells (HUVECs). HUVECs at a population-doubling level of 30 (PDL30) divided much more slowly than those at PDL9. The percentage of SA-β-Gal-positive cells and the mRNA expression levels of PAI-1 and p21 at PDL30 were significantly higher than those at PDL9. The changes induced by aging were evaluated according to the mRNA expression level of genes related to the endothelial cell function. The expression level of many adhesion molecules promoting monocytic adhesion was significantly increased, and monocytic adhesion on HUVECs was found to be significantly promoted by aging. Monocytic adhesion is an essential early event in the development of atherosclerosis, and our results suggest that replicative senescence of the vascular endothelial cells induced increased expression of adhesion molecules. The consequent increase in monocytic adhesion may then promote the pathogenesis of atherosclerosis.

1-Deoxynojirimycin attenuates high glucose-accelerated senescence in human umbilical vein endothelial cells

The influence of 1-deoxynojirimycin (DNJ) derived from mulberry on senescence of endothelial cells was examined with the goal of discovery of a method for prevention of senescence of blood vessels. The effect of DNJ on senescence of human umbilical vein endothelial cells (HUVECs) promoted under high glucose condition was determined. HUVECs were cultured in normal glucose (5.6mmol/L, NG group), normal glucose plus DNJ (10μmol/L, DNJ group), high glucose (30mmol/L, HG group), or high glucose plus DNJ (10μmol/L, HG+DNJ group) and passaged until they reached senescence. The proliferation rate was markedly decreased in the HG group compared with the NG group, and this phenomenon was reversed by DNJ. The frequency of senescent (SA-ß-Gal-positive) cells and the expression level of senescence genes (PAI-1 and p21) were significantly higher in the HG group compared with the NG group, and these changes were blocked by DNJ. Monocyte adhesion, NF-kB activity, and reactive oxygen species production, all of which promote cellular senescence, were significantly increased in the HG group compared with the NG group, and again these changes were blocked by DNJ. Therefore, these results show that DNJ delays cellular senescence that is promoted under high glucose condition.

jacaric acid, a linolenic acid isomer with a conjugated triene system, reduces stearoyl-CoA desaturase expression in liver of mice.

Conjugated fatty acid is a collective term used for fatty acids with conjugated double bond systems. Seed oils from certain plants include conjugated linolenic acids, which have a conjugated triene system and are geometrical and positional isomers of α-linolenic acid. One of these isomers, jacaric acid (JA, 8c, 10t, 12c-18:3), has not been examined widely. Therefore, we investigated the absorption and metabolism of JA in normal animals (ICR mice). An oral dose of JA of 5 mg/day for 1 week had no effects on body weight, food intake and tissue weight of mice. JA was detected in the serum, kidney, liver, lung and epididymal white adipose tissue. Analysis of the fatty acid composition in liver and white adipose tissue showed a tendency to increase levels of saturated fatty acids (SFAs) such as palmitic acid (16:0) and stearic acid (18:0) and to decrease levels of monounsaturated fatty acids (MUFAs) such as palmitoleic acid (16:1) and oleic acid (18:1). Thus, JA treatment decreased the desaturation index (16:1/16:0, 18:1/18:0) in liver and white adipose tissue. This index is used as an indicator of the activity of stearoyl coenzyme A desaturase (SCD), an endoplasmic reticulum enzyme that catalyzes the biosynthesis of MUFAs from SFAs. The change in this index indicates that JA inhibited SCD activity in ICR mice, and further experiments showed that JA also decreased the expression level of SCD-1 mRNA. Inhibition of SCD activity may have anti-obesity and anti-diabetes effects, and therefore the findings in this study suggest that JA may be effective for preventing obesity and diabetes.

Aging decreases antioxidant effects and increases lipid peroxidation in the Apolipoprotein E deficient mouse.

In this study, to study the effect of aging and Apolipoprotein E (ApoE) deficiency on antioxidant ability in mice, we examined whether lipid peroxidation is promoted by aging in ApoE deficient (ApoE−/−) mice, which have a shorter lifespan than normal mice. The levels of thiobarbituric acid-reactive substances (TBARS), a biomarker of lipid peroxidation, were measured in plasma and liver in ApoE−/− mice aged 12 weeks (young) and 52 weeks (early stage of senescence). TBARS in plasma and liver were significantly increased by aging. Next, we examined the reasons why lipid peroxidation was promoted by aging, based on measurement of protein and mRNA levels for antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in liver in ApoE−/− mice aged 12 and 52 weeks. The levels of superoxide dismutase 1 and 2 in liver were significantly decreased by aging. The mRNA level of catalase was also significantly decreased and the mRNA levels of superoxide dismutase 1, superoxide dismutase 2 and glutathione peroxidase 1 all showed a tendency to decrease with age. These results suggest that lipid peroxidation is caused by reduction of antioxidant activity with aging and that this promotes senescence and shortens lifespan in ApoE−/− mice.

The Japanese diet from 1975 delays senescence and prolongs life span in SAMP8 mice

OBJECTIVE Life expectancy in Japan is high, suggesting that the Japanese diet, Nihon shoku (Japanese food), has significant health benefits. However, these benefits have been called into question over the past 50 y, during which time the Japanese diet has become increasingly Westernized. The aim of the present study was to focus on senescence delay and to examine the effects of Japanese diets from different years to identify which Japanese diet is most effective in enhancing life expectancy and delaying senescence. METHODS Weekly menus from the years 1960, 1975, 1990, and 2005 were reproduced based on the National Health and Nutrition Survey in Japan and prepared as powdered foods. The senescence-accelerated mouse prone 8 (SAMP8) mice were fed standard laboratory chow supplemented with a 30% mix of Japanese meals from various years ad libitum throughout their lifetime. Additionally, the control group was given standard laboratory chow only, to examine the development of mice reared under standard conditions. RESULTS In the group that ingested the traditional 1975 Japanese diet, life span was prolonged, senescence was delayed, and learning and memory capacities were maintained compared with the group fed the 2005 Japanese diet. The life span of the group that ingested the 1990 Japanese diet showed a tendency to be longer than SAMP8 mice fed the 2005 diet. CONCLUSION The results of the present study suggested that the traditional Japanese diet is more effective in enhancing life expectancy and delaying senescence than the current Japanese diet.

Atopic dermatitis causes lipid accumulation in the liver of NC/Nga mouse

Various factors have been reported to influence lipid metabolism and cause metabolic syndrome. However, the influence of allergy on the liver that plays important role of lipid metabolism has not been clarified. The aim of this study was to examine the influence of allergy on lipid metabolism of liver. A model of atopic dermatitis was developed in the NC/Nga mouse using picryl chloride to induce allergy. Lipid metabolism parameters were measured and the mechanism of changes in these parameters was examined using DNA microarray analysis and quantitative reverse transcriptase PCR. Triacylglycerol accumulation was promoted in the liver in the mouse atopic dermatitis model despite reductions in food intake, body weight gain, and serum glucose. As this mechanism, it was thought that atopic dermatitis caused the suppression of fatty acid β-oxidation. These results suggest that atopic dermatitis causes lipid accumulation in the liver.