Phospholipids (PL) containing n-3 polyunsaturated fatty acids (PUFA) have beneficial effects of maintaining and promoting health compared with triacylglycerols (TAG) containing n-3 PUFA or general PL. This study evaluated the effects of dietary PL containing n-3 PUFA and elucidated the effects of the glycerophosphate structure and n-3 PUFA on fatty acid (FA) metabolism in rats. Rats were fed a basal diet containing soybean oil alone, TAG containing n-3 PUFA (1.8%), soybean PL (2.7%), PL containing n-3 PUFA (2.7%), or TAG containing n-3 PUFA (1.8%) + soybean PL (2.7%). The present n-3 PUFA-supplemented diets had similar FA compositions, and the PL diets had similar PL compositions. TAG containing n-3 PUFA reduced serum TAG contents, but did not affect serum cholesterol contents compared with soybean oil alone. PL diets containing n-3 PUFA and the combination of TAG containing n-3 PUFA and soybean PL resulted in decreased serum and liver TAG contents compared with the diet containing soybean oil alone, reflecting enhanced liver FA β-oxidation. The results of this study show that TAG containing n-3 PUFA with added soybean PL affects serum and liver TAG and cholesterol contents to a similar degree as PL containing n-3 PUFA. TAG containing n-3 PUFA and soybean PL are widely used as functional food ingredients and pharmaceutical constituents and are inexpensive compared with PL containing n-3 PUFA. Therefore, the combination of TAG containing n-3 PUFA and soybean PL has potential as a useful and inexpensive component of functional foods.

Protamine has been used as an antiheparin drug and a natural preservative in various food products. However, limited studies have evaluated the physicochemical and functional properties of protamine. Hence, we assessed the mechanisms underlying the inhibition of lipid absorption following salmon protamine intake in in vitro and in vivo studies. In initial experiments, a salmon protamine hydrolyzate (PH) was prepared using in vitro simulated gastrointestinal digestion suppressed pancreatic lipase activity and micellar cholesterol solubility. This PH had higher bile acid-binding capacity and emulsion breakdown activity than casein hydrolyzate and l-arginine. However, the hypolipidemic functions of protamine were dramatically reduced by pancreatin digestion. In further experiments, groups of male Wistar rats were fed an AIN-93G diet containing 5% (wt/wt) salmon protamine or a protamine amino acid mixture. After 4 wk of feeding with experimental diets, reductions in serum and liver triacylglycerol (TAG) and cholesterol contents were observed in the presence of protamine, reflecting inhibition of TAG, cholesterol, and bile acid absorption. These data suggest that the formation of insoluble PH-bile acid complexes is critical before the bile acid-binding capacity is reduced. Therefore, dietary salmon protamine may ameliorate lifestyle-related diseases such as hyperlipidemia and obesity.

Lysophospholipids have been recognized as potent biologically active lipid mediators. However, attention has not been paid to the health benefits of dietary partial hydrolysate of phospholipids (PH‐PL), which is rich in docosahexaenoic acid (DHA)‐bound lysophospholipids. In this study, the effects of PH‐PL on serum and liver lipid profiles of rats upon administration of PH‐PL are demonstrated in comparison to those of fish oil (FO), which comprises eicosapentaenoic acid (EPA) and DHA‐bound triglyceride (TG). PH‐PL containing EPA and DHA was prepared via enzymatic modification of squid (Todarodes pacificus) meal that is rich in phospholipids. Male Wistar rats were fed a basal diet containing soybean oil alone (7%), FO, and PH‐PL. The FO and PH‐PL diets had similar EPA and DHA contents. After the rats had been fed their respective diets for 28 d, their serum and liver lipid contents, fecal lipid excretion, and hepatic gene expression level were measured. The results demonstrated that compared with the soybean oil diet alone, the PH‐PL diet decreased serum and liver TG contents partially because of the enhancement of liver acyl‐CoA oxidase activity and suppression of liver fatty acid synthase activity. In addition, compared with the soybean oil diet, the PH‐PL group exhibited lower serum cholesterol content at least in part because of the reduction of hepatic 3‐hydroxy‐3‐methylglutaryl‐CoA reductase mRNA expression level. We found that dietary administration of EPA and DHA containing PH‐PL has a hypolipidemic effect that may help prevent the development lifestyle‐related diseases.

Introduction Docosahexaenoic acid DHA-and eicosapentaenoic acid EPA-bound triacylglycerol TAG and ethyl-ester EE forms of purified DHA and EPA are used as supplements and pharmaceutical products. Protection against hyperlipidemia 1 , cardiovascular diseases 2 , hypertension 3 , and Alzheimer s disease 4 is provided by n-3 polyunsaturated fatty acids PUFA , namely EPA and DHA. Fishery by-products are rich in DHA and EPA and are a viable source of n-3 PUFA. Utilization of these bioresources would result in a worldwide reduction in waste. Fishery by-products, such as squid skin, muscle, and connective tissues and the testis