Dietary Phospholipids Prepared From Scallop Internal Organs Attenuate the Serum and Liver Cholesterol Contents by Enhancing the Expression of Cholesterol Hydroxylase in the Liver of Mice

In this study, we successfully prepared scallop oil (SCO), which contains high levels of phospholipids (PL) and eicosapentaenoic acid (EPA), from the internal organs of the Japanese giant scallop (Patinopecten yessoensis), one of the most important underutilized fishery resources in Japan. The intake of SCO lowers the serum and liver cholesterol contents in mice; however, whether the fatty acids (FA) composition or PL of SCO exhibits any cholesterol-lowering effect remains unknown. To elucidate whether the cholesterol-lowering function is due to FA composition or PL of SCO, and investigate the cholesterol-lowering mechanism by SCO, in the present study, mice were fed SCO's PL fraction (SCO-PL), triglyceride (TG)-type oil with almost the same FA composition as SCO-PL, called SCO's TG fraction (SCO-TG), soybean oil (SOY-TG), and soybean's PL fraction (SOY-PL). Male C57BL/6J mice (5-week-old) were fed high-fat and cholesterol diets containing 3% (w/w) experimental oils (SOY-TG, SOY-PL, SCO-TG, and SCO-PL) for 28 days. The SCO-PL diet significantly decreased the serum and liver cholesterol contents compared with the SOY-TG diet, but the intake of SOY-PL and SCO-TG did not show this effect. This result indicated that the serum and liver cholesterol-lowering effect observed in the SCO intake group was due to the effect of SCO-PL. The cholesterol-lowering effect of SCO-PL was in part related to the promotion of liver cholesterol 7α-hydroxylase (CYP7A1) expression, which is the rate-limiting enzyme for bile acid synthesis. In contrast, the expression levels of the ileum farnesoid X receptor (Fxr) and fibroblast growth factor 15 (Fgf15), which inhibit the expression of liver CYP7A1, were significantly reduced in the SCO-PL group than the SOY-TG group. From these results, the increase in the liver CYP7A1 expression by dietary SCO-PL was in part through the reduction of the ileum Fxr/Fgf15 regulatory pathway. Therefore, this study showed that SCO-PL may be a health-promoting component as it lowers the serum and liver cholesterol contents by increasing the liver CYP7A1 expression, which is not seen in SOY-PL and SCO-TG.

Comparison of the Cholesterol-Lowering Effect of Scallop Oil Prepared from the Internal Organs of the Japanese Giant Scallop (Patinopecten yessoensis), Fish Oil, and Krill Oil in Obese Type II Diabetic KK-A y Mice

Due to the growing demand of n-3 polyunsaturated fatty acids (PUFA) as supplements and pharmaceutical products worldwide, there are concerns about the exhaustion of n-3 PUFA supply sources. We have successfully prepared high-quality scallop oil (SCO), containing high eicosapentaenoic acid and phospholipids contents, from the internal organs of the Japanese giant scallop (Patinopecten yessoensis), which is the largest unutilized marine resource in Japan. This study compared the cholesterol-lowering effect of SCO with fish oil (menhaden oil, MO) and krill oil (KO) in obese type II diabetic KK-A ^y mice. Four-week-old male KK-A ^y mice were divided into four groups; the control group was fed the AIN93G-modified high-fat (3 wt% soybean oil + 17 wt% lard) diet, and the other three groups (SCO, MO, and KO groups) were fed a high-fat diet, in which 7 wt% of the lard in the control diet was replaced with SCO, MO, or KO, respectively. After the mice were fed the experimental diet for 42 days, their serum, liver, and fecal lipid contents as well as their liver mRNA expression levels were evaluated. The SCO group had significantly decreased cholesterol levels in the serum and liver; this decrease was not observed in the MO and KO groups. The cholesterol-lowering effect of SCO was partly mediated by the enhancement of fecal total sterol excretion and expression of liver cholesterol 7α-hydroxylase, a rate-limiting enzyme for bile acid synthesis. These results indicate that dietary SCO exhibits serum and liver cholesterol-lowering effects that are not found in dietary MO and KO and can help prevent lifestyle-related diseases.

Effects of dietary oils prepared from the internal organs of the Japanese giant scallop (Patinopecten yessoensis) on cholesterol metabolism in obese type-II diabetic KK-Ay mice

Our research team has successfully prepared high-quality scallop oil (SCO), containing high eicosapentaenoic acid (EPA) and phospholipids (PL) from the internal organs of Japanese giant scallop (Patinopecten yessoensis) which is the largest unutilized marine resource in Japan. In this study, we prepared SCOs from scallop internal organs obtained from Mutsu (Aomori) and Uchiura (Hokkaido) bays in Japan, and named them SCO-M and SCO-U, respectively. This study aimed to investigate the effects of dietary SCO-M and SCO-U on cholesterol metabolism in obese type-II diabetic KK-Ay mice. Four-week-old male KK-Ay mice were divided into four groups. The Control group was fed with AIN93G-modified high-fat (3 wt% soybean oil + 17 wt% lard) diet, and the other groups were fed with high-fat diet, in which 7 wt% of the lard contained in the Control diet was replaced with SCO-M, SCO-U, or tuna oil (TO). After the mice had been fed with the experimental diet for 49 days, their serum, liver, and fecal lipid contents, as well as their liver messenger ribonucleic acid expression levels, were evaluated. The SCO-M and SCO-U groups were significantly decreased liver cholesterol contents compared to those of the Control and TO groups, partially through the enhancement of the fecal neutral sterol excretions and the tendency to increase the cholesterol 7α-hydroxylase expression level of the liver. These results indicated that dietary SCO-M and SCO-U exhibited cholesterol-lowering functions in the liver that can help prevent the development of lifestyle-related diseases.

Single and Repeated Dose 28-Day and 13-Week Toxicity Studies of Oil Prepared from the Internal Organs of the Japanese Giant Scallop (Patinopecten yessoensis) in Mice

Internal organs of discarded scallops are rich in omega-3 polyunsaturated fatty acids, but it is not used as a food ingredient due to the presence of toxic substances. Recently, our research team prepared high-quality scallop oil (SCO) from the internal organs of the Japanese giant scallop (Patinopecten yessoensis), in which cadmium and diarrhetic shellfish toxin are below regulated levels. In this study, SCO was prepared from the internal organs of scallops obtained from Mutsu and Uchiura bays in Japan, and was referred to as SCO-M (scallop oil from Mutsu bay) and SCO-U (scallop oil from Uchiura bay), respectively. Acute and subacute toxicity studies were performed to assess the safety of the prepared SCO. In acute toxicity study, mice were orally administered SCO-M and SCO-U at a single dose of 5,000 mg/kg body weight. In a 28-day repeated oral dose toxicity study, the mice were fed diets containing 1% and 5% SCO-M and SCO-U; and in a 13-week repeated oral dose toxicity study, the mice were fed 5% SCO-M and SCO-U. There were no toxicologically significant changes in clinical signs, hematology, blood chemistry, and organ weights at any dose during the experiment. Therefore, it was concluded that SCO-M and SCO-U are safe for use as food ingredients under the experimental conditions of this study.