Effect of dietary oils enriched with n-3 fatty acids on survival of mice

Effect of dietary lipids on longevity and memory in the SAMP8 mice

The senescence-accelerated mouse (SAMP8) is an animal model used in studies of aging. The purpose of this study was to investigate the effect of different types of dietary lipids on longevity and age-related deterioration in memory in SAMP8 mice. Eight-month-old mice were fed diets with 5% lard (Lard group), 5% soybean oil (Soy group), 2% lecithin +3% soybean oil (Lecithin+Soy group) or 2% fish oil+3% soybean oil (Fish+Soy group), and learning and memory were examined by passive avoidance test at 8 and 10 mo of age. At the end of the experiment, the mice were killed, and the brain fatty acid composition was analyzed. The results indicated that the survival rates at 12 mo decreased in the order: Fish+Soy>Soy>Lecithin+Soy>Lard and were 50, 40, 30 and 20%, respectively. The rate of the lard group was lower than that of the Fish+Soy group, but this difference was not statistically significant. At 10 mo of age, the passive avoidance times of the Fish+Soy, Lecithin+Soy, Soy and Lard groups were 166, 170, 149 and 127 s, respectively. The passive avoidance times of the Fish+Soy and Lecithin+Soy groups were longer than that of the Lard group (p<0.01) at 10 mo. The brain DHA concentration was the highest in the Fish+Soy group SAMP8 mice, the linoleic acid levels was highest in the Soy group and the palmitic acid level was lowest in the Lard group (p<0.05). In conclusion, compared with SAMP8 mice fed a high saturated fatty acid diet, SAMP8 mice given a high poly-unsaturated fatty acid diet had higher brain concentrations of poly-unsaturated acid, better memory and greater longevity.

Feeding into old age: long-term effects of dietary fatty acid supplementation on tissue composition and life span in mice

Smaller mammals, such as mice, possess tissues containing more polyunsaturated fatty acids (PUFAs) than larger mammals, while at the same time live shorter lives. These relationships have been combined in the 'membrane pacemaker hypothesis of aging'. It suggests that membrane PUFA content might determine an animal's life span. PUFAs in general and certain long-chain PUFAs in particular, are highly prone to lipid peroxidation which brings about a high rate of reactive oxygen species (ROS) production. We hypothesized that dietary supplementation of either n-3 or n-6 PUFAs might affect (1) membrane phospholipid composition of heart and liver tissues and (2) life span of the animals due to the altered membrane composition, and subsequent effects on lipid peroxidation. Therefore, we kept female laboratory mice from the C57BL/6 strain on three diets (n-3 PUFA rich, n-6 PUFA rich, control) and assessed body weights, life span, heart, and liver phospholipid composition after the animals had died. We found that while membrane phospholipid composition clearly differed between feeding groups, life span was not directly affected. However, we were able to observe a positive correlation between monounsaturated fatty acids in cardiac muscle and life span.

Dietary polyunsaturated fatty acids suppress acute hepatitis, alter gene expression and prolong survival of female Long-Evans Cinnamon rats, a model of Wilson disease

In the Long-Evans Cinnamon rat, copper accumulates in the liver because of a mutation in the copper-transporting ATPase gene, and peroxidative stresses are supposed to be augmented. We examined the effects of dietary fatty acids on hepatitis, hepatic gene expression, and survival. Rats were fed a conventional, low-fat diet (CE2), a CE2 diet supplemented with 10 wt% of lard (Lar), high-linoleic soybean oil (Soy), or a mixture of docosahexaenoic acid (DHA)-rich fish oil and soybean oil (DHA/Soy). Among female rats, the mean survival times of the DHA/Soy and the Soy groups were longer by 17 approximately 20% than in the Lar and the CE2 groups. Among male rats, the survival times were much longer than in the females, but no significant difference in survival was observed among the dietary groups. Serum ceruloplasmin levels in female and male rats of all of the dietary groups were similar. Serum transaminase levels of the DHA/Soy group tended to be lower than in the CE2 group. Histological examinations revealed a marked degeneration in hepatic tissue integrity in the Lar and CE2 groups but not in the DHA/Soy group. Hepatic levels of metal-related genes, transferrin and ceruloplasmin, as well as those related to bile acid synthesis were up-regulated, and an inflammation-related gene (cyclooxygenase [COX]-2) was down-regulated in the DHA/Soy group. Some proliferation-related genes were also affected by the dietary fatty acids. These results indicate that polyunsaturated fatty acids suppress the development of acute hepatitis and prolong survival in females, regardless of whether they are of the n-6 or n-3 type, which are associated with altered gene expressions.

Factors other than phytosterols in some vegetable oils affect the survival of SHRSP rats

Unusual survival-shortening activities of some vegetable oils were detected in stroke-prone spontaneously hypertensive (SHRSP) rats, and phytosterol (PS) in the oils and the tissue tocopherol status have been suggested to be the factors for the activities. Here, we re-evaluated the contribution of PS to the survival-shortening, and examined the hepatic tocopherol status. A basal diet for rodents and a test oil were mixed at a 9:1 ratio, and the diet was given to male SHRSP rats upon weaning. The total and major PS contents of the diets and tissue lipids did not correlate with relative survival time. The free fatty acid fractions obtained by lipase and alkaline hydrolyses of canola oil (Can) and the original Can contained PS in comparable amounts but the free fatty acid fractions did not exhibit survival-shortening activities compared with the soybean oil (Soy) group. The activity was not detected in the ethyl acetate extracts of the aqueous phase after the hydrolysis. When a commercially available PS preparation was added to the Soy diet at an amount 2.8-fold higher than that in the Can diet, the mean survival time was shortened but was still significantly longer than that of the Can group. The hepatic tocopherol level was significantly higher in the Can group than in the hydrogenated Soy group and Soy group, but the former two groups exhibited a survival-shortening activity. These results indicate that factors other than PS, tocopherol status and fatty acid composition in some vegetable oils are critical for the survival-shortening activity observed in SHRSP rats.

Effects of Western, Vegetarian, and Japanese Dietary Fat Model Diets with or without Green Tea Extract on the Plasma Lipids and Glucose, and Liver Lipids in Mice

BACKGROUND/AIMS

The purpose of this study was to investigate the long-term effects of three model diets containing different fats, with or without a small amount of green tea extract (GTE), on plasma lipids and glucose, and liver lipids in mice.

METHODS

Male mice (2 months old) fed 10% fat diets with Western (W), Vegetarian (V), and Japanese (J) fat compositions with or without 0.03% GTE for 7 months.

RESULTS

The concentrations of plasma and liver total cholesterol in animals fed the W diet were not significantly different from those fed the J diet. Plasma triacylglycerol (TG) concentrations were significantly different from one another in the following order: V > J > W diet groups. GTE supplementation significantly reduced plasma and liver TG content only in V diet group. Plasma glucose (Glu) concentrations were in the following order: W > V > J diet groups, and the GTE supplementation reduced the concentration of Glu in each diet group. The ratios of plasma n-6 to n-3 fatty acids were in the following order: V > W > J diet groups, regardless of GTE supplementation.

CONCLUSION

These findings show the possibility that Japanese eating habits combined with drinking green tea might be a factor in preventing the onset of non-insulin-dependent diabetes mellitus.

Cholesterol synthesis in mice is suppressed but lipofuscin formation is not affected by long-term feeding of n-3 fatty acid-enriched oils compared with lard and n-6 fatty acid-enriched oils

Hypocholesterolemic activity of dietary polyunsaturated fatty acids is observed after relatively short-term but not long-term feedings, and their long-term feedings are suspected to accelerate aging through tissue accumulation of lipid peroxides and age pigments (lipofuscin). To define the long-term effects of fats and oils in more detail, female mice were fed a conventional basal diet supplemented with lard (Lar), high-linoleic (n-6) safflower oil (Saf), rapeseed oil (Rap), high-alpha-linolenic (n-3) perilla oil (Per), or a mixture of ethyl docosahexaenoate and soybean oil (DHA/Soy) from 17 weeks to 71 weeks of age. The DHA/Soy and Per groups had decreased serum cholesterol levels compared with the Lar and Saf groups, but the difference between the Lar and Saf groups was not significant. The 3-hydroxy-3-methyglutary-CoA (HMG-CoA) reductase activity in the liver was also significantly lower in the Per and DHA/Soy groups. However, no significant difference in lipofuscin contents in the brain and liver was observed among the 5 dietary groups, despite significant differences in peroxidizability indices of the dietary and/or tissue lipids. These results indicate that n-3 fatty acid-rich oils are hypocholesterolemic by suppressing hepatic HMG-CoA reductase activity compared with animal fats and high-linoleic (n-6) oil, but tissue lipofuscin contents are not affected by a long-term feeding of fats and oils with different degree of unsaturation in mice.

Dietary fish oil does not protect rats exposed to restraint or sleep deprivation stress

It has been suggested that fish oil (FO) prevents weight loss caused by physiological stress such as cancer, injury, or cardiovascular disorders. Previously, we observed that a high-fat diet containing corn and coconut oil exaggerated weight loss caused by the mixed physiological and psychological stress of repeated restraint (RR). This experiment tested the effects of a high-fat diet containing FO as the predominant lipid source in rats exposed to the mixed physiological and psychological stress of either RR or sleep deprivation (SD). FO did not prevent stress-induced hypophagia or weight loss in RR or SD rats but exaggerated the negative effects of stress on body weight in SD rats by promoting loss of lean body mass. RR caused a reduction in body fat content irrespective of dietary treatment. In SD rats, both stress and FO independently reduced body fat mass. FO did not have any effect on adrenal and thymus weights during RR or SD and did not influence corticosterone levels after 1 h of RR or after 48 or 96 h of SD. In conclusion, our results suggest that high levels of dietary FO do not improve the response to stress in rats exposed to mixed stressors.