SummaryThe effect of dietary docosahexaenoic acid (DHA, C22:6 n -3) with two lipid types on lipid peroxidation of the brain was investigated in streptozotocin (STZ)-induced diabetic mice. Each group of female Balb/c mice was fed a diet containing DHA-connecting phospholipids (DHA-PL) or DHA-connecting triacylglycerols (DHA-TG) for 5 wk. Safflower oil was fed as the control. The lipid peroxide level of the brain was significantly lower in the mice fed the DHA-PL diet when compared to those fed the DHA-TG and safflower oil diets, while the ␣ -tocopherol level was significantly higher in the mice fed the DHA-PL diet than in those fed the DHA-TG and safflower oil diets. The DHA level of phosphatidylethanolamine in the brain was significantly higher in the mice fed the DHA-PL diet than in those fed the safflower oil diet. The dimethylacetal levels were significantly higher in the mice fed the DHA-PL diet than in those fed the safflower oil and DHA-TG diets. These results suggest that the dietary DHA-connecting phospholipids have an antioxidant activity on the brain lipids in mice, and the effect may be related to the brain plasmalogen.

SummaryThe effects of dietary docosahexaenoic acid (DHA, C22:6 n -3) connecting phospholipids on the learning ability and fatty acid composition of the brain were investigated in hypercholesterolemic mice. ICR mice were subjected to a very low level of n -3 fatty acids through two generations. At 4 wk of age, the F 1 generation, n -3 fatty acid deficient male mice were provided with an experimental diet containing four kinds of lipids (safflower oil: Saf, DHA connecting triacylglycerols: DHA-TG, DHA connecting phospholipids: DHA-PL, soybean phospholipids: Soy-PL) for 5 wk. Another group of ICR mice were obtained and fed a commercial diet (CE-2, CLEA Japan, Inc.) as a control. The learning and memory abilities of the mice were evaluated by the modified avoidance procedure. The learning and memory ability level was significantly higher in mice fed the DHA-PL diet than in those fed the Saf and Soy-PL diets, and was the same level as the control. The DHA levels of phosphatidylethanolamine in the brain were significantly higher in the mice fed the two types of DHA-containing diets than in those fed the Saf and Soy-PL diets and was not significantly different between DHA-TG and DHA-PL. The dimethylacetal levels in the brain were significantly higher in the mice fed the DHA-PL diet than in those fed the Saf and DHA-TG diets. These results suggest that the dietary DHA connecting phospholipids have the effect of improving memory learning, and may be related to the both the DHA and plasmalogen levels in the brain.

Lipid class and fatty acid composition of phospholipids from the gonads of skipjack tuna were examined to evaluate effective utilization of the processing of by-products. The predominant phospholipids in the ovaries were phosphatidylcholine (PC; 47.9%), phosphatidylethanolamine (PE; 19.3%) and lyso-phosphatidylcholine (LPC; 19.1%). In contrast, those in the testes were PC (40.1%), PE (29.3%) and phosphatidylserine (PS; 9.6%). The percentage of docosahexaenoic acid (DHA) was markedly high at more than 50% in LPC of the ovaries, and PE and PS of the testes were also high. The percentages of DHA at sn-position 2 of the predominant phospholipids, except for PC in the testes, were more than 60%, in particular PE in the testes was remarkably high at 81.9%. After storage for 2 days at 5 ∞ C, the LPC content in the ovaries increased twofold and the DHA level of LPC was the same as before, though the contents of other phospholipids decreased.

Non‐destructive determinations of the fat content in frozen skipjack by the portable and desktop near infrared (NIR) spectrophotometers were performed. In both spectrophotometers, the RPD value, which is an index of the accuracy, was higher at the abdominal part than at the central part of the body. The RPD value obtained by the portable instrument was higher than that of the desktop instrument when measured at the abdominal part. The rapid determination of the fat content in frozen skipjack was possible by determining the NIR spectra at the abdominal part of the fish body using the portable spectrophotometer.

Lipid contents and fatty acid compositions were compared among 110 muscle samples of Japanese wild, Japanese cultured, and Chinese cultured ocellate puffer Takifugu rubripes. The effects of diet on muscle lipids in cultured ocellate puffer were also investigated. There was no noticeable difference between the wild and cultured fish with regard to the lipid content, but there were significant differences in the fatty acid composition ratio such as C16:0, C16:1n-7, and C20:4n-6. Moreover, the percentages of the fatty acids C18:2n-6 and C22:5n-3 were correlated with those in the diet. These results suggest that the muscle lipid content was not affected by diet, whereas fatty acid composition was affected. There were significant differences in fatty acid composition among Japanese wild fish, Japanese cultured fish, and Chinese cultured fish. The results suggest that the fatty acid composition is applicable as a tool to distinguish between wild and cultured ocellate puffer as well as those cultured in Japan and China.

SummaryThe effects of dietary sialic acid in dams on the learning abilities of their pups after weaning were investigated using rats deficient in n-3 fatty acids. Nine-week-old female Wistar rats were fed an n-3 fatty acid-deficient diet for 3 wk and were mated at 12 wk of age. During pregnancy and lactation, the female rats were fed the n-3 fatty acid-deficient diet, and were given water or water containing 1% N-acetylneuraminic acid (NANA) ad libitum. After weaning, the learning abilities of the pups were evaluated using a novel object recognition test. The recognition index of pups nursed by dams fed on water containing 1% NANA (NANA-intake dams) was significantly higher than that of pups nursed by dams fed only on water (NANA non-intake dams). There were no significant differences in the total sialic acid or docosahexaenoic acid contents in the cerebral cortex or hippocampus of pups nursed by dams fed on either type of water. The total dimethylacetal (DMA, from plasmalogen) level in the cerebral cortex of pups nursed by NANA-intake dams was significantly higher than that of pups nursed by NANA non-intake dams. These results suggest that dietary sialic acid in dams during pregnancy and lactation might be beneficial for the learning abilities of pups after weaning, which may be related to the plasmalogen level in the brain of pups.

No abstract

The phospholipid class composition, fatty acid composition and phospholipase A1 (PLA1) activity from the ovaries of skipjack tuna were compared with those of six other species of marine fish. In the skipjack ovaries, the lysophosphatidylcholine (LPC) proportion for the phospholipid, the docosahexaenoic acid (DHA) percentage for the total fatty acids of the phospholipids and the PLA1 activity of the crude enzyme were the highest among those of the seven species. The optimum pH and temperature for the PLA1 activity of the crude enzyme from the skipjack ovaries were in the range of pH 6-7 and 20-30°C, respectively, and calcium ions were not required. As a substrate, phosphatidylcholine was more easily hydrolyzed than phosphatidylethanolamine by this enzyme, and the plasmalogen-type phospholipid was much lower than the acyl-type phospholipid. After a 6-h hydrolysis reaction of the purified phospholipid extracted from the mixed ovaries of skipjack and yellowfin tuna by this enzyme, the LPC ratio of the phospholipid increased from 20 to 72.6% and the percentage of DHA for the total fatty acids of the phospholipid also increased. Thus, skipjack ovaries might possibly be used as a source of PLA1.