Effect Of Resistant Starch On Intestinal Physiological Environment And Gastrointestinal Function In Rats/mice

Resistant starch (RS) is added to foods as a low-calorie starch, which can play with the physiological functions of dietary fiber:such as weight control, prevention constipation colorectal cancer and other intestinal diseases, improving the intestinal flora, reducing blood lipid and glucose.Compared with dietary fiber, RS has become the central issue because of its good processing properties. It can be added into different kinds of foods.Different types of resistant starch have different effects on body intestinal physiological environment and gastrointestinal function because of different fermentation patterns. There are few dates about different types of resistant starch and contentsresistant starch on body intestinal physiological environment and gastrointestinal function in domestic and international studies.To examine the effect of different types(RS2、RS3、RS4) and contents (5%、10%、15%)of resistant starch on intestinal environment and gastrointestinal function, Sprague-Dawley rats and mice experimental model were fed diet containing resistant starch. This study provides theoretical basis on the mechanism of intestinal health for further study about resistant starch. The main conclusions of the research are as follows:(1) To examine the effect of different types and contents of resistant starch on intestinal metabolites and serum lipids, Sprague-Dawley rats were fed diet containing resistant starch for four weeks. The results showed that:compared to the control group, different types and contents of resistant starch can increase food intake, lower food efficiency and body weight gain. The pH of experimental groups was lower than the control group. The free ammonia concentration of caecal and fecal contents of experimental groups was lower than the control group. Cecal contents and feces of experimental groups was more moist and softer than the control group. The concentration of acetate, propionate, butyrate and total short-chain fatty acids of caecal and fecal contents of experimental groups were higher than the control group. It can lower the concentration of bad metabolites and higher the concentration of good metabolites. The AI and concentrations of TG, TC and LDL-C of experimental groups were lower than the control group. The overall effects were:compared with the other two RS groups, RS3group was more significant on reducing weight, improving the intestinal physiological environment and lowering serum lipids in rats.15%RS group was better at weight control, increasing the wet weight and moisture content of cecal contents;10%RS group was better at increasing intestinal main product SCFAs,reducing the free ammonia content, reducing the pH value, increasing fecal wet weight and moisture content and serum lipids.(2) To examine the effect of different types and contents of resistant starch on intestinal morphology, Sprague-Dawley rats were fed diet containing resistant starch for four weeks. The results showed that:the total cecal weight, cecal wall weight, weight of cecal contents of experimental groups were higher than the control group. But there was a significant difference between the different types of RS group, compared to the RS2and RS4group, RS3group had the most obvious effect with increasing their weight. Change of small intestine, cecum and colon morphology were:15%RS>10%RS>5%RS. Compared with the control group,5%RS group had no significant effect on the morphology of small intestine, cecum, colon. However,10%RS3group was better than RS2、RS4group at changing significantly the structure of the intestinal mucosa,and15%RS4group was better at changing significantly the structure of the intestinal mucosa.In short,high, medium and low contents of resistant starch group did not cause pathological changes in the small intestine, cecum and colon.(3) The impact of different types and contents of resistant starch on intestinal microbial flora by nested PCR-DGGE technique showed that compared to the control group, the resistant starch group had4dominant bacterias, they were Clostridium cellobioparum,Acetivibriocellulolyticus,Bifidobacterium adolescentis and Lactobacillus oligofermentans. The control group had3dominant bacterias, they were Coprococcus catus.Ruminococcus gauvreauii and Blautia schinkii. Allobaculum stercoricanis only existed in RS2and RS4group, not in the control group and RS3group.By real-time PCR technology, the results showed that:different types and contents of resistant starch could significantly increase the growth of Bifidobacteria and Lactobacilli, and reduce the growth of the Enterobacteriaceae. RS3showed the best acticity in three kinds of resistant starch.10%RS group was better than5%RS and15%RS group in the effect of promoting the growth of bifidobacteria and lactobacilli, and controlling the number of Enterobacteriaceae. During the whole experiment, compared to the control group, three types of resistant starch group could not significant impact on the change of Enterococcus in rat feces. The conclusions were consistent with the results of DGGE level electrophoresis.(4) Effect of different types of15%resistant starch in activated carbon-induced constipation mice showed that resistant starch had the preventive effect of active-carbon induced constipation in mice which was regarded as a functional food. According to the results of RS3, it found that first black stool defecation shorten time was only a little longer than bisacodyl, gastrointestinal transit was longer than control and similar to bisacodyl, various serum levels such as MTL, Gas, ET, AchE, SP and VIP in resistant starch dose mice were higher than control mice, the SS levels showed opposite tendency. These results suggested that resistant starch had a significant preventive effect on activated carbon induced constipation mice, and RS3showed the best acticity.(5) This study demonstrates that different types of15%resistant starch is effective in the prevention of HCl/ethanol-induced gastric injury in SD rats. The protective effects of resistant starch may be because of the decreased the proinflammatory cytokines such as IL-6and TNF-a. The stomach appearance also showed that resistant starch could prevent HCl/ethanol-induced injury in the stomach. Furthermore, mRNA and protein expression levels of inflammation-related genes in the stomach, including iNOS, COX-2, TNF-α and IL-1β were significantly reduced in the resistant starch-treated rats. These results suggested that resistant starch was potentially useful in the treatment or prevention of chemical-induced gastric injury in vivo. And the RS3showed the best activity.Through PCR-DGGE and and real-time quantitative PCR technology, this paper analyzed the changes of microbial flora in different types and contents of resistant starch fermentation process in the large intestine. The results showed that:4kinds of dominant flora (Clostridium cellobioparum,Acetivibrio cellulolyticus,Bifidobacterium adolescentis and Lactobacillus oligofermentans) in resistant starch groups, and3kinds of dominant flora in the control group (Coprococcus catus, Ruminococcus gauvreauii.and the Blautia schinkii interaction) were interacted and leaded the change of major metabolite (SCFA); indirectly, caused the change of intestinal pH value, contents of free ammonia, blood lipids as well as the changes of intestinal morphology. Those microbial flora played a important role in improving the intestinal environment and lowering blood lipids. Allobaculum stercoricanis bacteria that existed only in the RS2and RS4group may lead to the RS3group,which had the best activity in improving intestinal environment and reducing serum lipids. However, different types and contents of resistant starch affect the mechanism of intestinal function by changing the intestinal microbial flora also are required in-depth testing.The major metabolite in gut, such as SCFA、free ammonia content, serum lipids changing in pH and gut morphology consistented with the change of the type and quantity of intestinal microbial flora.This experiment made the model of activated carbon-induced constipation mice and HCl/ethanol-induced gastric injury rats, to study the impact of high concents of different types of resistant starch on gastrointestinal functional on body, through reverse transcription-polymerase chain reaction, enzyme-linked immuno sorbent assay and western blot. The results showed that:the high concentration of the different types of RS did have good improvement in gastrointestinal function of the body, Althought the effect of drug (bisacodyl) was better than RS, but resistant starch did improve symptoms of constipation in activated carbon-induced constipation mice.The effect of prevention and inhibition of gastrointestine was good in HCI/ethanol-induced gastric injury rats. In the three different types of resistant starch, the RS3showed the best activity, which consistented preferably with previous experimental results. Resistant starch did have a protective effect on the gastrointestine.The paper provided experimental evidences for study effects of resistant starch in physiological environment of the gut and gastrointestinal function. These results contributed to development health functional food containing resistant starch,and to alleviation the symptoms of intestinal diseases.