Alaska Pollack Protein Prevents the Accumulation of Visceral Fat in Rats Fed a High Fat Diet

Dietary Alaska Pollack Protein Induces Acute and Sustainable Skeletal Muscle Hypertrophy in Rats

Our previous studies suggested that Alaska pollack protein (APP) intake increases skeletal muscle mass and that it may cause a slow-to-fast shift in muscle fiber type in rats fed a high-fat diet after 56 days of feeding. In this study, we explored whether dietary APP induces acute and sustainable skeletal muscle hypertrophy in rats fed a normal-fat diet. Male 5-week-old Sprague–Dawley rats were divided into four groups and fed a purified ingredient-based high-fat diet or a purified ingredient-based normal-fat diet with casein or APP, containing the same amount of crude protein. Dietary APP significantly increased gastrocnemius muscle mass (105~110%) after 2, 7 days of feeding, regardless of dietary fat content. Rats were separated into two groups and fed a normal-fat diet with casein or APP. Dietary APP significantly increased gastrocnemius muscle mass (110%) after 56 days of feeding. Dietary APP significantly increased the cross-sectional area of the gastrocnemius skeletal muscle and collagen-rich connective tissue after 7 days of feeding. It decreased the gene expression of Mstn /Myostatin, Trim63/MuRF1, and Fbxo32/atrogin-1, but not other gene expression, such as serum IGF-1 after 7 days of feeding. No differences were observed between casein and APP groups with respect to the percentage of Type I, Type IIA, and Type IIX or IIB fibers, as determined by myosin ATPase staining after 7 days of feeding. In the similar experiment, the puromycin-labeled peptides were not different between dietary casein and APP after 2 days of feeding. These results demonstrate that APP induces acute and sustainable skeletal muscle hypertrophy in rats, regardless of dietary fat content. Dietary APP, as a daily protein source, may be an approach for maintaining or increasing muscle mass.

Dietary Alaska Pollock Protein Attenuates the Experimental Colitis Induced by Dextran Sulfate Sodium via Regulation of Gut Microbiota and Its Metabolites in Mice

Protein derived from fish has not only nutritional properties but also health-promoting properties. Few studies have examined the effect of dietary Alaska pollock protein (APP) on the anticolitis effect reported to be associated with metabolic syndrome (MetS). This study investigated the effect of APP intake on colitis symptoms, gut microbiota, and its metabolites in the experimental colitis mouse model induced by dextran sulfate sodium (DSS). Male C57BL/6J mice were divided into three groups: (1) DSS-untreated mice fed an American Institute of Nutrition (AIN) 93G diet (protein source is casein), (2) DSS-treated mice fed an AIN93G diet, and (3) DSS-treated mice fed an APP diet. After the mice were fed the diets for 21 days, experimental colitis was induced by three cycles of 2% DSS administration for 5 days followed by washouts over the course of 5 days. APP-reduced body weight loss increased the disease activity index, and elevated spleen weight and alleviated colon length shortening and colonic tissue damage. Furthermore, APP altered the structure and composition of the microbiota and short-chain fatty acids in feces. Since APP intake alleviates experimental colitis induced by DSS administration through alterations in the gut microbiota and its metabolites, we deduced that APP would inhibit MetS progression via colitis suppression.

Selar (Selar crumenophthalmus) Fish Protein Hydrolysate Has Antidiabetic Properties Possibly through GLP-1

Background :

Enzymatic hydrolysis of fish protein using protease or fish protein hydrolysate can form bioactive peptides that have antidiabetic activity. One potential mechanism of fish protein hydrolysate is reducing blood glucose through increased endogenous glucagon like peptide (GLP)-1 production. Tempeh is soy fermented food that has protease which is potential biocatalyst in producing fish protein hydrolysate.

Objective:

To evaluate the antidiabetic properties of Selar (Selar crumenophthalmus) fish protein hydrolysate using tempeh protease as biocatalyst and duodenal gene expression of GLP-1.

Methods:

Selar fish protein isolate was digested for 8 hours at 37°C using crude tempeh protease. Diabetes mellitus was induced in rats by intraperitoneal injection of streptozotosin (65 mg/kg bw) and nicotinamide (230 mg/kg bw). Fish protein isolate and hydrolysate in dose of 300 mg/bw and 500 mg/ bw were orally administered daily for 4 weeks. Blood was drawn for fasting serum glucose and lipid profile analysis. Total RNAs were isolated from duodenum and quantitative real time PCR was performed to quantify mRNA expression of GLP-1. Data were analyzed using one way ANOVA and gene expression analysis were performed using Livak.

Results and Discussion:

There is a significant difference on fasting serum glucose, total cholesterol, triglyceride, LDL-cholesterol, HDL-cholesterol and duodenal GLP-1 mRNA expression level between groups (p<0.05). The duodenal GLP-1 mRNA expression was the highest in rats who received hydrolyzed fish protein 500 mg/ bw.

Conclusion:

Hydrolysis of selar fish protein using tempeh protease has anti-diabetic properties possibly through GLP-1 production.

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.

Seafood intake and the development of obesity, insulin resistance and type 2 diabetes

We provide an overview of studies on seafood intake in relation to obesity, insulin resistance and type 2 diabetes. Overweight and obesity development is for most individuals the result of years of positive energy balance. Evidence from intervention trials and animal studies suggests that frequent intake of lean seafood, as compared with intake of terrestrial meats, reduces energy intake by 4–9 %, sufficient to prevent a positive energy balance and obesity. At equal energy intake, lean seafood reduces fasting and postprandial risk markers of insulin resistance, and improves insulin sensitivity in insulin-resistant adults. Energy restriction combined with intake of lean and fatty seafood seems to increase weight loss. Marine n-3 PUFA are probably of importance through n-3 PUFA-derived lipid mediators such as endocannabinoids and oxylipins, but other constituents of seafood such as the fish protein per se, trace elements or vitamins also seem to play a largely neglected role. A high intake of fatty seafood increases circulating levels of the insulin-sensitising hormone adiponectin. As compared with a high meat intake, high intake of seafood has been reported to reduce plasma levels of the hepatic acute-phase protein C-reactive protein level in some, but not all studies. More studies are needed to confirm the dietary effects on energy intake, obesity and insulin resistance. Future studies should be designed to elucidate the potential contribution of trace elements, vitamins and undesirables present in seafood, and we argue that stratification into responders and non-responders in randomised controlled trials may improve the understanding of health effects from intake of seafood.

Fish protein hydrolysate exhibits anti-obesity activity and reduces hypothalamic neuropeptide Y and agouti-related protein mRNA expressions in rats

Fish protein is a source of animal protein that is consumed worldwide. Although it has been reported that the intake of Alaska pollack protein (APP) reduces body fat accumulation and increases muscle weight in rats, the mechanisms underlying these effects are poorly understood. As a possibility, peptides released from APP in the gastrointestinal tract are important to the functions of APP. In the present study, we examined the effects of APP hydrolysate digested artificially with pepsin and pancreatin on white adipose tissue and skeletal muscle. We found that APP hydrolysate group shows significantly lower weight of white adipose tissue and higher weight of soleus muscle than the control group. We also found that APP hydrolysate group reduces food intake and mRNA expressions of neuropeptide Y and agouti-related protein in the hypothalamus compared with the control group. These results may imply that APP hydrolysate exhibits anti-obesity activity by the reduction of appetite and the enhancement of basal energy expenditure by skeletal muscle hypertrophy in rats. The downregulation of orexigenic gene by APP hydrolysate in the hypothalamus may contribute to the reduction of appetite. These results suggest that the effect of APP on anti-obesity and muscle hypertrophy may be induced by peptides released from APP in the gastrointestinal tract.

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.

A novel Alaska pollack-derived peptide, which increases glucose uptake in skeletal muscle cells, lowers the blood glucose level in diabetic mice

We found that the tryptic digest of Alaska pollack protein (APP) and novel APP-derived peptide exhibited a glucose-lowering effect in KK-Ay mice, a type II diabetic mice.

Fish protein intake induces fast-muscle hypertrophy and reduces liver lipids and serum glucose levels in rats

In our previous study, fish protein was proven to reduce serum lipids and body fat accumulation by skeletal muscle hypertrophy and enhancing basal energy expenditure in rats. In the present study, we examined the precise effects of fish protein intake on different skeletal muscle fiber types and metabolic gene expression of the muscle. Fish protein increased fast-twitch muscle weight, reduced liver triglycerides and serum glucose levels, compared with the casein diet after 6 or 8 weeks of feeding. Furthermore, fish protein upregulated the gene expressions of a fast-twitch muscle-type marker and a glucose transporter in the muscle. These results suggest that fish protein induces fast-muscle hypertrophy, and the enhancement of basal energy expenditure by muscle hypertrophy and the increase in muscle glucose uptake reduced liver lipids and serum glucose levels. The present results also imply that fish protein intake causes a slow-to-fast shift in muscle fiber type.

Seafood consumption and components for health

In recent years, in developed countries and around the world, lifestyle-related diseases have become a serious problem. Numerous epidemiological studies and clinical trials have demonstrated that diet is one of the major factors that influences susceptibility to lifestyle-related diseases, especially the middle-senile state. Studies examining dietary habits have revealed the health benefits of seafood consumption. Seafood contains functional components that are not present in terrestrial organisms. These components include n-3-polyunsaturated fatty acids, such as eicosapentaenoic acid and docosahexsaenoic acid, which aid in the prevention of arteriosclerotic and thrombotic disease. In addition, seafood is a superior source of various nutrients, such as protein, amino acids, fiber, vitamins, and minerals. This review focuses on the components derived from seafood and examines the significant role they play in the maintenance and promotion of health.

Fish protein decreases serum cholesterol in rats by inhibition of cholesterol and bile acid absorption

Fish protein has been shown to decrease serum cholesterol content by inhibiting absorption of cholesterol and bile acid in laboratory animals, though the mechanism underlying this effect is not yet fully understood. The purpose of this study was to elucidate the mechanism underlying the inhibition of cholesterol and bile acid absorption following fish protein intake. Male Wistar rats were divided into 2 dietary groups of 7 rats each, 1 group receiving a diet consisting of 20% casein and the other receiving a diet consisting of 10% casein and 10% fish protein. Both experimental diets also contained 0.5% cholesterol and 0.1% sodium cholate. After the rats had been on their respective diets for 4 wk, their serum and liver cholesterol contents and fecal cholesterol, bile acid, and nitrogen excretion contents were measured. Fish protein consumption decreased serum and liver cholesterol content and increased fecal cholesterol and bile acid excretion and simultaneously increased fecal nitrogen excretion. In addition, fish protein hydrolyzate prepared by in vitro digestion had lower micellar solubility of cholesterol and higher binding capacity for bile acids compared with casein hydrolyzate. These results suggest that the hypocholesterolemic effect of fish protein is mediated by increased fecal cholesterol and bile acid excretion, which is due to the digestion products of fish protein having reduced micellar solubility of cholesterol and increased bile acid binding capacity.

Fast-twitch muscle hypertrophy partly induces lipid accumulation inhibition with Alaska pollack protein intake in rats

Fish protein is a source of animal protein that is consumed worldwide. Although it has been reported that the intake of Alaska pollack protein (APP) reduces serum triglyceride and body fat accumulation in rats, the mechanisms underlying these effects are poorly understood. In the present study, we fed 5-week-old male Sprague-Dawley rats a high-fat diet with APP or casein for 4 weeks. We reconfirmed that the intake of APP decreases serum triglycerides and inhibits visceral body fat accumulation in rats. We found that APP had a higher non-digestive protein content than casein, and the amount of protein in feces was higher in the APP group than in the casein group. However, the amount of total lipids in feces did not differ significantly between the groups. We also found that the gastrocnemius muscle, a fast-twitch muscle, tended to increase in weight, and that the epididymal fat weight correlated negatively with gastrocnemius muscle weight in the APP group. These results imply that the enhancement of basal energy expenditure by fast-twitch muscle hypertrophy, rather than the enhancement of lipid excretion via feces, partly causes APP-induced inhibition of lipid accumulation in rats.