Study On Hypoglycemic Bioactivities And Mechanisms Of Proteins From Four Black Teas

Black tea is rich in nutritional value and medicinal value.In this paper,the hypoglycemic activity of four common black tea proteins,such as HMJ,FZ,HZ,and QL,is studied.The inhibitory effect of?-amylase,?-glucosidase and dipeptidyl peptidase?DPP4?of four kinds of black tea crude protein extracts and their hydrorates generated by Trypsin and Alcalase were evaluated.The fractions with stronger effect were treated by ultrafiltration-HPLC-MS,and the peptide sequence were analyzed and synthesized.Then,the inhibitory effect of the synthetic peptides on DPP4 and?-glucosidase were determined.Finally,the hypoglycemic effect of the crude protein of the black tea was evaluated in hyperglycemic mice,and the hypoglycemic mechanism of the black tea protein was preliminarily studied by analyzing the differential expression of genes in brain and spleen.The results of this study are shown as follow:?1?The extraction rate of four kinds of black tea crude protein are:HMJ:50.62%,FZ:42.78%,HZ:61.26%,QL:55.28%.The fraction shown the strongest inhibitory effect on?-amylase was QL,whose IC₅₀0 value was 1.2710±0.1725 mg/mL.Moreover,HMJ and QL had the stronger inhibitory effect on?-glucosidase,whose IC₅₀0 values were 0.0942±0.0267mg/mL and 0.0103±0.0545 mg/mL,respectively.The fraction FZ-T showed the strongest inhibitory effect on DPP4.The IC₅₀0 value of FZ-T was 0.1011±0.0256 mg/mL.?2?A total of 12 peptides with credibility of more than 50%were separated from HMJ,and CGKKFVR and TAELLPR were finally selected for further study.11 peptides with credibility of more than 70%were separated from QL.AVPANLVDLNVPALLK and VVDLVFFAAAKwere selected for further study.11 peptides with credibility of more than70%were separated from FZ-T,and QGQELGGALNFK and MSYLPR were selected for further study.?3?The inhibitory activity of four peptides to?-glucosidase were determined in vitro.Their IC₅₀0 values can be show as followed:VVDLVFFAAAK?0.0435±0.0367mg/mL?>TEALLPR?0.4300±0.0314 mg/mL?>CGKKFVR?0.5179±0.0945mg/mL?>AVPANLVDLNVPALLK?1.0261±0.1286mg/mL?.The IC₅₀0 value of two DPP4inhibitory peptides are MSYLPR?1.3564±0.1545mg/mL?,QGQELGGALNFK?3.8915±0.2233 mg/mL??4?Through the animal test,we found that black tea crude protein had good effect on inhibiting the body weight growth of the mice.Moreover,the crude protein of the black tea can significantly lowen the blood sugar of the hyperglycemic mice,and the ingestion of the black tea protein is beneficial to glucose tolerance in hyperglycemic mice bodies.?5?According to the differential expression analysis of genes in brain and spleen tissue of mice,52 differentially expressed genes related to glucose metabolism were found in spleen,including Try5,Try4,etc.,while 47 genes related to glucose metabolism were found in brain,such as Cpne7,Pcsk9,etc.?6?According to ipath pathway map,black tea protein influenced the pathway includespolysaccharides biosynthesis and metabolism,energy metabolism and fat metabolism.The polysaccharides biosynthesis and metabolism pathway reffered to the biosynthesis ofmucopolysaccharide,the metabolism of amino sugar and nucleic acid sugar.The energymetabolism mainly reffered to phosphate and phosphite metabolism,TCA cycle,glycolysis and oxidative phosphorylation.The metabolism of fat was reflected in the synthesis ofunsaturated fatty acids,the metabolism of glycerin phospholipids,and the synthesis and metabolism of sheath lipids.