| BackgroundDiabetes mellitus (DM), which is characterized by high blood glucose levels, is one of the most challenging chronic diseases facing health care professionals today. Its increasing prevalence puts a large burden on society and the public health sector. It is estimated that the number of DM patients will increase to300million by2025. The incidence rate of DM increased rapidly, especially in developing countries. And the number of DM patients in China only less than India, ranking second in the world. Diabetic has many complications which are very serious. Its complications mainly display by coronary heart disease, cerebrovascular and peripheral blood vessels’ lesion, nephropathy and retinopathy, diabetic osteoporosis and so on. The current treatment of diabetes and its complications is still not satisfactory. Therefore, hypoglycemic drugs and function food is one of most important steps to prevent and improve diabetes and its complications.In recent decade, more and more researches about hypoglycemic effect of polysaccharides have been done by animal study. The mainly hypoglycemic mechanism contain for the following aspects:(1) Improve islet cell form and function, and promote the insulin secretion;(2) Raise insulin sensitivity;(3) Improve the sugar metabolism, promote the peripheral tissues and targets such as liver, muscle etc on sugar utilization;(4) Reduce blood sugar by adjust autoimmunity and scavenging free radicals;(5)Improve sugar metabolism related enzyme activity;(6) Slow down the metabolic rate of insulin in human body;(7) Inhibit the a glycosidase enzymes activity, delay the glucose absorption.Peach resin is a kind of semi-transparent gum which is from the trunk of rosaceae by the mechanical damage (such as insect bites, cuts, etc.), or some disease. Its main compositions are polysaccharides and protein. Also contain few of other materials. The polysaccharides constitute of galactose, arabinose, rhamnose, glucuronic acid and so on. Different researcher reported quite different results about the kinds of peach resin monose and percentage composition. The most probably reason for the difference maybe relate with varieties and producing area. There are still many questions about of the physical and chemical properties of Peach resin, such as the molecular weight of polysaccharide isolated from peach resin (PPR), molecular structure, solubility, hydrophile lipophile balance, critical micelle concentration, rheological type, surface tension etc. Ding Ting etc intragastric administration the alloxan induced diabetic rats with peach resin. Found that peach resin have effects on the diabetic rats of enhance insulin level, reduce the blood glucose, reduce low-density lipoprotein cholesterol, triglyceride and total cholesterol. Meanwhile there has dose-effect relationship. Hong Yuzhi etc give30DM patients with30g peach resin and100g steamed bread. And then they found that tested patients’ postprandial hyperglycemia and the glucose area under curve were significantly lower than the control day. This suggests that peach resin has the similar hyperglycemic mechanism with other plant dietary fiber. That is peach resin defer the absorption of sugar in intestine, which cause gastric inhibitory polypeptide secreted decrease, blood insulin level drop. Because peach resin do not increase blood insulin level meanwhile improve postprandial glucose tolerance, so peach resin not only do not worsen hyperinsulinmia of insulin resistance type2diabetes patients, but also can reduce the dose of insulin or oral antidiabetic agents to DM patients.Our country has rich resources and wide distribution of peach resin. Guangdong, Hebei, Shanxi, Gansu, Jiangxi, Jiangsu etc, all of these provinces is the origin of it. Peach resin has large production and cheap prince, about2500yuan/ton. The hyperglycemic research of PPR can provides theory basis for the development of new glucose-lowering drugs and health care products. PPR was extracted by the method of water extraction and alcohol precipitation in this research, and then observed the hyperglycemic effects of different molecular. Also we observed the influence on amylase, invertase, maltase etc, conjectured the probable hyperglycemic mechanism of PPR.2. Methods2.1The extraction and separation of polysaccharidePPR were extracted from fresh peach resin by next steps, defecate, rinse, freeze-drying, grinding, extraction in90℃hot water, Sevage method to take off the protein, Gradient alcohol sink(the alcohol concentrations in mixed liquor were50%,70%,90%), purification by Glucan gel chromatography column.2.2Establishment of experimental animal modelSelect80SPF SD rats,180-220g, male, free diet and water. One week later, rats were randomly divided by weight into normal group (10) and the group for replicating diabetes model (70). During the experiment, the normal group was fed with basic feedings, the group for model fed with high-energy diet which is rich in fat and sugar. After adaptation for one week, fasting (without limiting the water)12h,2%Alloxan solution freshly prepared with the saline (above ice and in darkness),120,80,60mg/kg, were injected respectively (every other day) into abdominal cavity. After72h, fasting blood glucose were examined with fasting12h. Rats with fasting blood glucose values between11.1mmol/L and25mmol/L were investigated and were randomly divided into PPR of low, medium and high molecular group, acarbose group and model group,8in each group.2.3. Hyperglycemic research of PPR(1) Influence of different molecular weight PPR and acarbose on DM model rats’ fasteing plasma glucose (FPG) and postprandial plasma glucose (PPG).(2) Influence of different molecular weight PPR and acarbose on DM model rats’ insulin and C-peptide.2.4. Experimental study of digestive enzymes decompose PPR2.5. Experimental study of PPR on digestive enzymes affection.(1) Experimental study of PPR and acarbose on amylase activity affection.(2) Experimental study of PPR and L-arabinose on invertase activity affection.(3) Experimental study of PPR on maltase activity affection.2.6. Statistical MethodsStatistical software SPSS13.0was used to analyze experimental, the data were expressed by mean±standard deviation (x±s).Independent test and ONE-WAY ANOVA were used in the text. The single factor analysis of variance (ONE-WAY ANOVA) was used when the variance is homogenous, and the smallest significant difference (LSD method) was used in multiple comparisons between groups. Welch method similar to F test was used when the variance is not homogenous, and Dunnett ’T3method was used in multiple comparisons between groups. α=0.05indicates the level for the statistical significance.3. Results3.1. The extraction and separation of polysaccharideThree kinds of PPR with different molecular weight were extracted by hot water extraction, Sevage method to take off the protein, Gradient alcohol sink, purification by Glucan gel chromatography column. PPR status to beige solid powder, yield is29.8%.3.2. Rats’ general situation after model establishmentNormal rats, in good spirit, fed, drank, urinate and defecate well, with a rapid response. Its dorsal seta is smooth, thick and shiny. They grew rapidly. The diabetic rats drank, ate and urinated more than before, with the white floated flocculent fat above the urine. The diabetic rats with light yellow and less shiny hair were in low spirit, without more activity. During the entire experiment, only three diabetic rat died. After model establishment, the FPG of rats showed that the variance was not homogenous by the Levene test (F=3.350, P=0.012). There was significant difference among groups in rats’ FPG (F=46.484, P=0.000). Dunnett T3test, there was significant difference between normal group and model group (P<0.01). The PPG of rats showed that the variance was homogenous by the Levene test (F=1.489, P=0.214). There was significant difference among groups in rats’ PPG (F=54.771, P=0.000). LSD test, there was significant difference between normal group and model group (P<0.01).3.3. Experimental study of digestive enzymes (amylase, invertase, maltase, lactase) decompose PPRThe experiment proves that PPR can’t be decomposed by amylase, invertase, maltose and lactase.3.4. Influence of different molecular weight PPR and acarbose on DM model rats’ plasma glucose.Treat with PPR two weeks later, compared with model group, rats in medicated group have lighter in hair color, better spirit, more activities, and more sensitive reaction. There was significant difference among groups in rats’ FPG (F=19.428, P=0.000), further set of two comparison between groups. FPG in model group is significant higher than normal group (P<0.01). There is no significant difference between PPR groups and acarbose group in rats’ FPG. There is significant difference between PPR groups model group (P<0.01), also with normal group (P<0.05). These results indicate that PPR can reduce FPG in DM model rats, and has the similar effect with acarbose.There was significant difference among groups in rats’ PPG (F=44.996, P=0.000), further set of two comparison between groups. PPG in model group is significant higher than normal group (P<0.05). There is no significant difference between PPR groups and acarbose group in rats’ PPG. There is significant difference between PPR groups model group (P<0.05), also with normal group (P<0.05). These results indicate that PPR can reduce PPG in DM model rats, and has the similar effect with acarbose.3.5. Influence of different molecular weight PPR and acarbose on DM model rats’insulin and C-peptide.There was significant difference among groups in rats’ insulin (F=0.995, P=0.443), C-peptide (F=2.276, P=0.064). Need not further set of two comparisons between groups. Indicate that PPR can not improveβ cell function directly.3.6. Animal experimental study of PPR on digestive enzymes affection.3.6.1Animal experimental study of PPR and acarbose on amylase activity affection.PPR, acarbose mixed starch solution respectively, pure starch solution were given to normal rats by intragastric administration respectively. Blood glucose was determined at0,10,30,60,90,120min. There was significant difference among groups in rats’ blood glucose (P=0.000). Comparison between groups (LSD method), PPR group and acarbose group have significant difference with pure starch group in blood glucose at six timing.(P=0.000). There was no significant difference between PPR group and acarbose group (P=0.239). These results suggest that PPR can reduce rats’ PPG and has the similar effect with acarbose. The hypoglycemic mechanism may through restrain amylase activity, further delay the carbohydrate intake, achieve the aim of reduce postprandial blood glucose.3.6.2. Animal experimental study of PPR and L-arabinose on invertase activity affection.PPR, L-arabinose mixed sugar solution respectively, pure sugar solution were given to normal rats by intragastric administration respectively. Blood glucose was determined at0,10,30,60,90,120min. There was no significant difference among groups in rats’ blood glucose (P=0.151). These results suggest that PPR and L-arabinose can not restrain invertase activity. It means that when rat intake food rich with sugar, PPR can not reduce rats’ postprandial blood glucose.3.6.3. Animal experimental study of PPR on maltase activity affection.PPR mixed maltose solution, pure maltose solution were given to normal rats by intragastric administration respectively. Blood glucose was determined at0,10,30,60,90,120min. There was significant difference between groups in rats’ blood glucose (P=0.002). These results suggest that PPR can restrain maltase activity. It means that when rat intake food rich with sugar, PPR can not reduce rats’ postprandial blood glucose. The hypoglycemic mechanism may through restrain maltase activity, further delay the carbohydrate intake, achieve the aim of reduce postprandial blood glucose.4. Research conclusion1. PPS can’t be digestive by main enzymes of human. That means it can not decompose and absorb in the stomach and small intestine, also can’t get in the circulation of the blood.2. Different molecular weight of PPS can reduce both fasting blood glucose and postprandial blood glucose of DM model rats. The hypoglycemic effect has no difference with acarbose. All three kinds of PPS and acarbose have no effect on DM model rats’ insulin and c-peptide. This means that PPS can’t directly improve islet function, but through influence sugar decomposition and monose absorption to reduce the blood sugar.3. PPS can restrain amylase and maltose enzyme activity, it means that the hypoglycemic mechanism of PPS is by inhibiting digestive enzymes, further delay the carbohydrate intake, achieve the aim of reduce postprandial blood glucose.4. Because of acarbose only can inhibit the amylase activity, can’t restrain maltose enzyme activity. This research shows that, PPS not only can inhibit the amylase activity, but also can inhibit the maltose enzyme activity. Therefore, this research provide theoretical basis for further research that find the function parts of PPS which can inhibit the amylase and maltose enzyme activity to develop new digestive enzymes inhibitors for drugs.5. PPS can not inhibit invertase activity, when animal intake sucrose primarily food, PPS without the effect of reduce blood sugar.6. We used more PPS than acarbose in this study. But PPS has advantages of high yield and low cost. This result provides theoretical basis for further research that develop PPS into new lower blood sugar health food. |
