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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.

Tuna muscle consists of light and dark muscle in approximately equal proportions. However, besides for the light muscle of tuna, cod, sardine, and salmon, few researches have assessed the health-promoting functions of fish protein. Therefore, we evaluated the mechanisms underlying the alteration of lipid storage and cholesterol metabolism following the intake of tuna dark muscle protein (TDMP) by obese type-2 diabetic/obese mice. Four-week-old male KK-Ay mice were separated into 2 dietary groups, with one group receiving a casein-based diet and the other receiving a diet with the substitution of part of the protein (50%, w/w) by TDMP (TDMP diet) for 4 wk. The TDMP diet significantly increased the content of serum high-density lipoprotein cholesterol, partly due to the reduction of the expression of scavenger receptor class B member 1 in epididymal white adipose tissue. In addition, dietary TDMP decreased the content of hepatic triacylglycerol, which could be due to the enhancement of carnitine palmitoyltransferase-2 activity through the activation of the expression of the peroxisome proliferative activated receptor-α in the liver. These results suggest that TDMP could have the potential to prevent the development of obesity-related diseases by suppressing the storage of hepatic triacylglycerol and cholesterol.

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.

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.

Tuna muscle consists of light and dark muscle in approximately equal proportions. However, besides for the light muscle of tuna, cod, sardine, and salmon, few researches have assessed the health-promoting functions of fish protein. Therefore, we evaluated the mechanisms underlying the alteration of lipid storage and cholesterol metabolism following the intake of tuna dark muscle protein (TDMP) by obese type-2 diabetic/obese mice. Four-week-old male KK-A

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.

Trans and conjugated fatty acids may exhibit either beneficial or detrimental bioactive effects depending on their metabolic properties. This study was conducted to elucidate if isomerization and conjugation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) demonstrate more favorable bioactivity on lipid metabolism compared to unmodified EPA and DHA. The effects of dietary intake of trans and conjugated forms of EPA and DHA on lipid metabolism were evaluated in animal trials and compared to a control group fed soybean oil. None of the experimental diets showed significant differences from the control in terms of body weight; however, the white adipose tissue weight of rodents fed trans DHA, conjugated EPA (CEPA), and conjugated DHA (CDHA) was significantly lower than the control. Triacylglycerol levels in plasma were significantly decreased in groups fed trans DHA (17.2 mg/dL) and CDHA (31.9 mg/dL) relative to the control (51.3 mg/dL). The total cholesterol concentrations were significantly lower than the control (68.0 mg/dL) in all experimental groups (47.3 to 53.7 mg/dL) except CEPA (58.3 mg/dL). Fatty acid compositions of lipids extracted from rodent livers were influenced by the dietary fatty acid profiles, with all groups showing higher concentrations of stearic acid and lower levels of linoleic acid compared to the control. Rodents fed trans DHA did not have detectable levels of these fatty acid isomers in their livers, suggesting either quick metabolism or a difficulty with bio-absorption.