Study On The Nutritional Values And Immunity Activity Of Decapterus Maruadsi Peptide Powder

Decapterus maruadsi is an important economic fish,especially in Fujian Province due to its high content of protein and minerals.However,it has great nutritional value but lower economic added value.In order to further improve the utilization rate and value-added of decapterus maruadsi resource,in the present work,the peptide powder was obtained by enzymatic hydrolysis of decapterus maruadsi as the research material,based on the analysis and evaluation of its major nutrient components,the effect of peptide powder on the nutritional and physiological function were investigated in rats;the effect of decapterus maruadsi peptide powder on the expression of PEPT1 in rats intestine was further explored.Finally,the immune function was performed in hypoimmune mice.The main research contents and results were showed as follows:1.Analysis and evaluation of nutrient components-of decapterus maruadsi peptide powder.The main nutrient components and amino acid contents were analyzed and evaluated using conventional food nutrient content determination methods.The results showed that peptide powder of decapterus maruadsi protein content was 72%,crude fat was 0.3%,crude ash was 12%;the highest constant element was potassium which was 9.92 X 103 mg/kg in decapterus maruadsi peptide powder;the molecular weight of decapterus maruadsi protein peptide was 72.023%below 1000Da.The ratios of essential amino acid to total amino acid of peptide powder were 33%;Meanwhile,the ratios of delicious amino acids to total amino acids was 46.4%;and the first-limiting amino acids was valine.2.Nutritional and physiological functions of decapterus maruadsi peptide powder.The SD rats fed with casein as the protein source were treated as control group,and the nutritional and physiological functions were studied by using the decapterus maruadsi powder and the decapterus maruadsi peptide powder as the protein source of feed in rats.The results showed that the peptide powder protein digestibility was significantly higher than the fish powder(P<0.01),besides the biological value and net protein utilization were significantly higher than casein(P<0.01).Compared with casein control group,the peptide powder group rats low density lipoprotein content was significantly lower than that of control group(P<0.05),hematocrit was increased in the peptide powder group(P<0.05),and mean corpuscular volume,mean corpuscular hemoglobin and mean hemoglobin concentration were decreased(P<0.05).Compared with the fish powder,the alkaline phosphatase(ALP)content of the peptide powder group rats was lower than the fish powder group(P<0.05).The creatinine content was higher than the fish powder group(P<0.05).The total iron binding capacity of the rats was significantly higher than the fish powder(P<0.05).3.Effect of decapterus maruadsi peptide powder on expression of PEPT1 in rat small intestine.The results showed that,compared with with casein control group,the peptide powder group and fish powder group on PEPT1 mRNA and protein expression significantly were lower in the duodenum(P<0.01),PEPT1 protein expression of jejunums was also significantly decreased in both rats(P<0.01),but protein peptide group on the PEPT1 protein expression had no significant difference in jejunum(P>0.05),The PEPT1 protein expression in jejunum of fish meal group was significantly lower(P<0.01).Compared with fish meal group,the mRNA expression of PEPT1 in jejunum was significantly higher than fish powder group(P<0.01),and the PEPT1 protein expression was significantly higher than fish powder group(P<0.05).The mRNA expression of PEPT1 and its protein expression in duodenum were no significant difference between the peptide powder group and fish powder group(P>0.05).4.Effect of decapterus maruadsi peptide powder on immune function in hypoimmune mice.The hypoimmune mice model was established by intraperitoneal injection of cyclophosphamide,the effect of decapterus maruadsi peptide powder immune organ index,cellular immunity,humoral immunity and non-specific immune function in hypoimmune mice were studied.The results showed that,it may have a protective effect;a range of doses of decapterus maruadsi protein peptide significantly increased immune organ index in hypoimmune mice(P<0.05);it could heighten delayed-type hypersensitivity(P<0.05),spleen lymphocyte transformation(P<0.001)significantly,and NK cell killing activity(P<0.05,P<0.001)significantly,and it was indicated that it could improve the function of cellular immunity in hypoimmune mice.The level of hemolysin in mice serum was significantly increased(P<0.001)within a certain dose range,and the levels of IgA,IgG,IgM in serum were significantly increased(P<0.01,P<0.001),and promote the function of humoral immunity in hypoimmune mice;it could significantly enhance phagocytosis rate and phagocytic index of peritoneal macrophages in hypoimmune mice(P<0.001),and carbon clearance ability(P<0.01,P<0.001),indicating that it could promote non-specific immunity in hypoimmune mice.In this study,the nutritional values,nutrient physiological function,expression of PEPT1 in rats and immunity activity of decapterus maruadsi peptide powder were preliminary investigated.The research results show that decapterus maruadsi peptide powder has high protein,low fat,rich mineral content and reasonable amino acid ratio.It is very beneficial for digestion and absorption when compare to the decapterus maruadsi powder without any further treantment,and it has the effect of immune regulation function as high-quality protein resource.The research results can provide important theoretical guidance for highly valued utilization of decapterus maruadsi protein resources in the future.