| Apple(Malus domestica)belongs to the family of Rosaceae with sweet taste and abundant nutrition,and is widely favored by consumers.During the growth period,in order to ensure apple yield and quality,fruit farmers commonly remove young apples in the middle of April every year,producing a large amount of young apples that are abandoned in the orchard.However,young apples are rich in phenolic compounds(about 10 times as much as mature apples).It is of great significance for agriculture and food industry to collect discarded young apples and develop their potential application value.Type 2 diabetes is one of the most common diseases in the world,and hyperglycemia is the leading cause of type 2 diabetes.It has been reported that young apple polyphenols(YAP)can effectively inhibit the activity of ?-amylase,regulating the level of blood glucose indirectly.However,it is still obscure about the specific adjusting mechanisms of YAP on blood glucose level.Based on this,in this study,the phenolic components of YAP were analyzed,and the effects of YAP on ?-amylase activity and postprandial blood glucose in mice were studied in vitro and in vivo.The ameliorating effect of YAP on insulin resistance(IR)was further investigated by insulin resistant HepG2 cells model.The wheat starch(WS)-YAP complexes were constructed to study the effect of YAP on the digestion and fermentation characteristics of WS via in vitro experiments.Then,WS-YAP complex were used to interfere mice with high fat diet,in order to study the effect of the WS-YAP complexes on mice blood glucose balance with different diets and the possible mechanisms.The detailed results are as follows:1)The effect of YAP on ?-amylase activity and postprandial blood glucose level in mice.Qualitative and quantitative analysis of YAP extracted by ethanol and purified by X-5 macroporous resin was carried out by HPLC and HPLC-MS/MS.The results showed that 14 phenolics were identified in YAP,and phlorizin,chlorogenic acid and tannic acid were the main components.Next,the ?-amylase inhibitory effect of YAP and three main individual phenols was studied,and the results showed that YAP could effectively inhibit ?-amylase activity.In addition,the effects of YAP and three main individual phenols on postprandial blood glucose levels in mice were studied by acute experiment and one week intervention experiment.It was found that the four phenols could delay the increase of postprandial blood glucose and insulin levels in mice,with the effect following the order of tannic acid>phlorizin>YAP>chlorogenic acid,indicating that YAP possesses significant effect on delaying the increase of postprandial blood glucose level.2)Regulation of YAP on insulin resistant HepG2 cells model.Insulin resistant HepG2 cells model was established by glucose and palmitic acid(PA),and YAP phlorizin and chlorogenic acid were used to intervene the model,respectively.The results showed that the consumption and uptake of glucose in the model cells were significantly decreased,indicating that the IR cell model was successfully established.The intervention of YAP,phlorizin and chlorogenic acid significantly increased the consumption and uptake of glucose.Also,YAP and phlorizin can activate PI3K/AKT pathway by activating the phosphorylation of IRS2,promote the phosphorylation of downstream GSK3? and FOXO1,promote glycogen synthesis,reduce gluconeogenesis,and alleviate IR.Moreover,YAP and phlorizin can also significantly reduce intracellular oxidative pressure caused by IR,increase the production of ATP and the level of mitochondrial membrane potential(MMP),improve mitochondrial function and promote glucose metabolism,suggesting that YAP can improve IR by activating the signal transduction pathway IRS2/PI3K/AKT and improving mitochondrial function,the main component of phlorizin plays a decisive role.3)The influence of WS-YAP complexes on starch digestion and intestinal microflora.WS-YAP,WS-chlorogenic acid(CA)and WS-phlorizin(P)complexes were constructed and gelatinized before study.A combined analysis of SEM,XRD and FTIR showed that the crystal structure of untreated wheat starch(NWS)was partially destroyed during the gelatinization process,and the addition of YAP,CA and P improved the short-range crystal structure of gelatinized WS,but had no significant effect on the overall crystal structure.Subsequently,the gelatinized WS and WS-phenolic compound complexes were digested in vitro,and the results showed that the WS-phenolic compound complexes could significantly reduce WS digestion rate and increase the proportion of resistant starch(RS)in WS.Moreover,undigested WS and WS-phenolic compound complexes were fermented by human feces in vitro for 24 h.It was found that the residual product of WS-YAP complexes after digestion could significantly increase the production of short chain fatty acids(SCFAs),especially acetic acid and propionic acid,and promote the growth of Prevotella,which is a probiotic that is closely related to the production of SCFAs,glucose metabolism and IR.Therefore,YAP can be used as a functional component to improve IR and delay the rise of blood glucose level by inhibiting the digestion rate of starch and promoting the growth of probiotics.4)The effect of WS-YAP complex on blood glucose balance and intestinal microflora in mice fed with high fat diet.Normal C57 mice were fed with high-fat diet for 8 weeks to investigate the effect of WS-YAP complex on blood glucose,insulin resistance and intestinal microflora of mice.The results showed that the weight gain,liver and fat index,serum TC,TG,LDL-C,ALT and AST contents of mice in the WS-YAP complex intervened group were significantly lower,the pancreas index and HDL-C content were significantly higher compared with high fat diet group.The WS-YAP complex intervened group could effectively inhibit the accumulation of liver fat and improve the liver injury caused by high-fat diet.In addition,through the analysis of fasting blood glucose,serum insulin,glucose tolerance and insulin tolerance of mice,it was found that WS-YAP complex intervention can effectively reduce the blood glucose level of mice,increase the body's sensitivity to insulin,and improve insulin resistance.Through the analysis of fecal flora,it was found that WS-YAP complex intervention can affect the diversity and richness of intestinal flora in mice,change the relative abundance of Firmicutes and Bacteroidetes at phylum level,enhance the growth of genus Akkermansia that is beneficial to improve the blood glucose level,and inhibit the reproduce of genus Desulfovibrionaceae that is higher in diabetic,suggesting that WS-YAP complex can maintain the blood glucose balance by improving the composition of gut microbiota.In conclusion,the inhibitory effect of YAP on ?-amylase activity and the improving effect of YAP on IR were studied,and WS-YAP complex was constructed.The physiological function of YAP and the health-promoting effect of RS were explored.These results indicated YAP and its complexes can effectively regulate blood glucose balance and improve body sub-health,which provides theoretical basis for the design and manufacture of starchy food with low glycemic index. |
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