Salmon Protamine Decreases Serum and Liver Lipid Contents by Inhibiting Lipid Absorption in anIn VitroGastrointestinal Digestion Model and in Rats

Effects of Marine-Derived Components on Cardiovascular Disease Risk Factors and Gut Microbiota Diversity

Cardiovascular diseases (CVDs), which comprise coronary heart disease, hypertension, and stroke, collectively represent the number one cause of death globally. Atherosclerosis is the dominant cause of CVDs, and its risk factors are elevated levels of low-density lipoprotein cholesterol and triglycerides, hypertension, cigarette smoking, obesity, and diabetes mellitus. In addition, diverse evidence highlights the role played by inflammation and clonal haematopoiesis, eventually leading to immunity involvement. The human microbiota project and subsequent studies using next-generation sequencing technology have indicated that thousands of different microbial species are present in the human gut. Disturbances in the gut microbiota (GM) composition, i.e., gut dysbiosis, have been associated with diseases ranging from localised gastrointestinal disorders to metabolic and cardiovascular illnesses. Of note, experimental studies suggested that GM, host immune cells, and marine-derived ingredients work together to ensure intestinal wall integrity. This review discusses current evidence concerning the links among GM, marine-derived ingredients, and human inflammatory disease. In detail, we summarise the impact of fish-derived proteins/peptides and algae components on CVD risk factors and gut microbiome. Furthermore, we describe the interplay among these dietary components, probiotics/prebiotics, and CVDs.

Protamine-derived peptide RPR (Arg-Pro-Arg) ameliorates oleic acid-induced lipogenesis via the PepT1 pathway in HepG2 cells

The protamine-derived peptide arginine-proline-arginine (RPR) can ameliorate lifestyle-related diseases such as obesity and hypercholesterolemia. Thus, we hypothesized that the hypolipidemic activity of RPR could attenuate events leading to non-alcoholic fatty liver disease. Addition of 2 m m oleic acid (OA) to the culture medium induced fatty liver conditions in HepG2 cells. The OA + RPR group showed significantly decreased cellular or medium triglyceride (TG) level compared with the OA group. Stearoyl-CoA desaturase-1 (SCD1) or sterol regulatory element-binding protein 1 (SREBP1) protein level was significantly lower in the OA + RPR group than in the OA group. In the R + P + R amino acid mixture-treated group, the TG level was not significantly different from that in the OA-treated group. The OA + RP- or OA + PR-treated groups showed significantly decreased cellular TG level compared with the OA group. Moreover, the effect of RPR disappeared when the peptide transporter 1 (PepT1) was knocked down with a siRNA. Collectively, our results demonstrated that RPR effectively ameliorated hepatic steatosis in HepG2 cells via the PepT1 pathway.

Effects of diets containing proteins from fish muscles or fish by-products on the circulating cholesterol concentration in rodents: a systematic review and meta-analysis

A high circulating cholesterol concentration is considered an important risk factor for the development of CVD. Since lean fish intake and fish protein supplementation have been associated with lower cholesterol concentration in some but not all clinical studies, the main aim of this study was to investigate the effect of diets containing proteins from fish muscles and fish by-products on the serum/plasma total cholesterol (TC) concentration in rodents. A systematic literature search was performed using the databases PubMed, Web of Science and Embase, structured around the population (rodents), intervention (type of fish and fraction, protein dose and duration), comparator (casein) and the primary outcome (circulating TC). Articles were assessed for risk of bias using the SYRCLE's tool. A meta-analysis was conducted in Review Manager v. 5·4·1 (the Cochrane Collaboration) to determine the effectiveness of proteins from fish on the circulating TC concentration. Thirty-nine articles were included in the systematic review and meta-analysis, with data from 935 rodents. The risk of bias is unclear since few of the entries in the SYRCLE's tool were addressed. Consumption of proteins from fish resulted in a significantly lower circulating TC concentration when compared with control groups (mean difference -0·24 mmol/l, 95 % CI - 0·34, -0·15, P < 0·00001), with high statistical heterogeneity (I² = 71 %). To conclude, proteins from fish muscles and by-products show promise as a functional dietary ingredient or supplement by preventing high cholesterol concentration in rodents, thus reducing one of the most important risk factors for developing CVD.

Anti-Obesity and Hypocholesterolemic Actions of Protamine-Derived Peptide RPR (Arg-Pro-Arg) and Protamine in High-Fat Diet-Induced C57BL/6J Mice

Dietary protamine can ameliorate hyperlipidemia; however, the protamine-derived active peptide and its hypolipidemic mechanism of action are unclear. Here, we report the discovery of a novel anti-obesity and hypocholesterolemic peptide, RPR (Arg-Pro-Arg), derived from protamine in mice fed a high-fat diet for 50 days. Serum cholesterol levels were significantly lower in the protamine and RPR groups than in the control group. White adipose tissue weight was significantly decreased in the protamine and RPR groups. The fecal excretion of cholesterol and bile acid was significantly higher in the protamine and RPR groups than in the control group. We also observed a significant decrease in the expression of hepatic SCD1, SREBP1, and adipocyte FAS mRNA, and significantly increased expression of hepatic PPARα and adipocyte PPARγ1 mRNA in the protamine group. These findings demonstrate that the anti-obesity effects of protamine are linked to the upregulation of adipocyte PPARγ1 and hepatic PPARα and the downregulation of hepatic SCD1 via SREBP1 and adipocyte FAS. RPR derived from protamine has a crucial role in the anti-obesity action of protamine by evaluating the effective dose of adipose tissue weight loss.

Dietary Alaska pollock protein alters insulin sensitivity and gut microbiota composition in rats

Fish protein is not only nutritional but also promotes health by improving insulin sensitivity and hypercholesterolemia. Few studies have examined the relationship between gut microbiota and the enhanced insulin sensitivity due to the intake of Alaska pollock protein (APP). Hence, we assessed the glycolytic enzyme inhibitory activity of APP in in vitro study and the alteration of blood glucose level in insulin tolerance test (ITT) and glucose tolerance test (GTT) and gut microbiota following APP intake in the in vivo study. In initial experiments, the glycolytic enzyme (α-amylase, α-glucosidase, and sucrase) inhibitory activities of APP and its digest were not drastically altered compared with that of casein and its digests. In further experiments, rats fed an AIN-93G diet containing 20% (w/w) casein or APP for 8 weeks, and the composition of fecal microbiota analyzed by 16S rRNA amplicon sequence analysis. In addition, at 6 and 7 weeks of administration of experimental diet, insulin and glucose tolerance tests were evaluated, respectively. Compared with dietary casein, dietary APP has blood glucose-lowering activity as evident in the ITT and GTT. Moreover, APP group altered the structure of fecal microbiota, and area under the curves of the ITT and GTT and the relative abundance of Blautia, which is associated with glucose metabolism, tended to be positively correlated (P = 0.08 and 0.10, respectively). This study illustrates a novel finding that APP intake could alter the composition of gut microbiota and improve insulin sensitivity. PRACTICAL APPLICATION: Studies in animals and humans have shown that Alaska pollock protein (APP) intake improves insulin sensitivity, allowing the body to utilize blood glucose more effectively, thereby keeping blood sugar levels under control. Microorganisms residing in the human gut are associated with glucose metabolism. This study shows that the relative APP intake alters the composition of these gut microorganisms, more than casein intake and therefore might prevent hyperglycemia and type 2 diabetes.

Differential Effects of Cod Proteins and Tuna Proteins on Serum and Liver Lipid Profiles in Rats Fed Non-Cholesterol- and Cholesterol-Containing Diets

Fish muscles are classified into white and red muscles, and the chemical composition of the two fish muscles have many differences. Few reports have assessed the health-promoting functions of white fish muscle proteins (WFP) and red fish muscle proteins (RFP). We therefore evaluated the mechanisms underlying the alteration of lipid profiles and cholesterol metabolism following the intake of WFP prepared from cod and RFP prepared from light muscles of tuna. Male Wistar rats were divided into six dietary groups: casein (23%), WFP (23%), and RFP (23%), with or without 0.5% cholesterol and 0.1% sodium cholate. Compared to the WFP-containing diet, the RFP-containing diet supplemented with cholesterol and sodium cholate significantly increased serum and liver cholesterol contents. However, in the RFP groups, an alteration in cholesterol metabolism including an increased tendency to excrete fecal sterols and hepatic cholesterol 7α-hydroxylase was related to the reduction of hepatic cholesterol contents. This phenomenon might be related to the tendency of an increased food intake in RFP-containing diets. These results highlight the differential effects of WFP and RFP on serum and liver lipid profiles of Wistar rats fed non-cholesterol- or cholesterol-containing diets under no fasting condition.

Porcine hemoglobin promotes lipid excretion to feces more strongly than globin protein in rats

In an effort to clarify whether the lipid-lowering effect of hemoglobin is due to globin protein or heme, this study investigated the effects of dietary porcine hemoglobin (PH) and porcine globin (PG) on lipids contents of serum, liver, and feces in rats. Five-week-old male Wistar rats were divided into 3 dietary groups of 7 rats each, with one group receiving a control diet and the other groups receiving diets containing 1.25% (w/w) PH or 1.18% (w/w) PG for 4 weeks. The PH diet decreased triacylglycerol content in serum and cholesterol in serum and liver, whereas the PG diet reduced triacylglycerol content in serum and cholesterol in liver. Fecal lipid excretion in the PH group was significantly higher than in the PG group. Therefore, PH affected lipid excretion to feces due to globin protein as well as heme.