Study On The Mechanism Of Pretreated Oat Bran Improving Intestinal Flora And Glucolipid Metabolism

Over the past few years,numerous studies have demonstrated the crucial role of gut microbiota in the development and progression of obesity and its complications.Among various factors affecting gut microbiota,the diet has been identified as the most significant one.Dietary fiber supplementation has been shown to regulate gut microbiota,decrease hunger,extend satiety,and reduce energy intake.Oat bran,which is the primary by-product of oat processing,is an excellent source of low-calorie,nutrient-rich dietary fiber that contains a substantial amount of water-soluble β-glucan fiber.However,the unpleasant taste and rancid deterioration of oat bran limit its processing and storage,necessitating pretreatment to improve its quality.Although research has been conducted on pretreatment,few studies have explored the mechanisms underlying oat bran’s impact on gut microbiota and glucose and lipid metabolism.In this study,we examined the effects of different pretreatment methods(steaming,microwaving,and hot air drying)on the starch digestibility,gut microbiota,and short-chain fatty acids of in vitro simulated digestion and fermentation of steamed oat bran.We also investigated the mechanism by which steamed oat bran affects gut microbiota,glucose homeostasis,lipogenesis,and food intake in obese rat models induced by a high-fat diet.The following sections outline the specific research findings.(1)Effects of pretreatment and removal of non-starch components on nutritional composition and physicochemical properties of oat bran.The results indicated that steaming,microwaving,and hot air drying effectively preserved the nutritional composition of oat bran.However,steaming was found to be the most effective in reducing the starch digestibility of oat bran,resulting in a decrease in the HI and e GI values.On the other hand,pretreatment of oat bran by removing non-starch components such as lipids,proteins,and β-glucans increased starch digestibility,decreased the resistant starch content,and increased the HI and e GI values,while the starch crystal type remained unchanged.These findings demonstrated that the intact structure of oat bran effectively slowed down starch digestion and reduced blood glucose levels,and steaming treatment was the most beneficial.(2)In vitro fermentation characteristics of pretreated oat bran.The results showed that oat bran treated with steaming,microwaving,and hot air drying had no significant change in total dietary fiber content and no loss in β-glucan content after in vitro simulated digestion.Pretreatment of oat bran significantly influenced the gut microbial α-diversity,altered the relative abundance of Phylum Firmicutes,inhibited the propagation of Escherichia-Shigella,and promoted the growth of Faecalibacterium prausnitzii.Compared to microwaving and hot air drying,steaming produced more acetic,propionic,and butyric acids,indicating that steaming treatment improved the fermentation ability of oat bran and optimized the balance of gut microbiota.(3)Effect of oat bran on obesity in rats fed with high-fat diet.In this study,an obesity model was established in SD rats by feeding them a high-fat diet.The rats were then divided into groups and fed a high-fat diet supplemented with 10%,20%,or 30% steamed oat bran for 8 weeks.The results indicate that oat bran had significant positive effects on the rats’ health.It reduced body weight and food intake,decreased fat accumulation and adipocyte hypertrophy,improved glucose tolerance and insulin resistance,and reduced serum levels of TC,TG,and LDL-C while increasing HDL-C.Oat bran also improved the disturbance of blood lipid levels,protected the ileal barrier,and improved liver injury in a dose-dependent manner.Overall,the study suggests that oat bran can inhibit excessive fat accumulation,improve dyslipidemia,and reduce the degree of obesity.(4)Impact of oat bran on gut microbiota,short-chain fatty acids,and plasma metabolites in obese rats.The study found that oat bran increased the α-diversity of the gut microbiota,up-regulated the Allobaculum,Blautia,and Lactobacillus bacteria,while down-regulated the Akkermansia and Ruminococcaceaea UCG-005.Moreover,it increased the levels of acetic acids,propionic acids,and butyric acids in the gut.The study also revealed significant changes in the plasma metabolites of obese rats,with 39 differential metabolites being affected,mostly associated with fatty acid biosynthesis,metabolic pathways,cholesterol,bile secretion,and tryptophan metabolism.These findings suggest that oat bran has the potential to improve gut microbiota and metabolites,thereby positively affecting overall body health.(5)Regulation of oat bran on hepatic glucose and lipid metabolism in obese rats.Results showed that oat bran intake led to a reduction in insulin resistance and an increase in the synthesis and storage of liver glycogen.It inhibited the activities of enzymes,viz.,HK,G-6-P and PEPCK,and inhibited the gluconeogenesis in a dose-dependent manner.It significantly increased the AMPK activity of key pathways of liver lipid metabolism.In addition to that,it also significantly increased the HSL and ATGL activities,promoted lipolysis,inhibited ACC1,FAS,PPARγ,and SREBP-1,and increased the LPL and C/EBPαactivities.Results showed that oat bran ameliorated glucose and lipid metabolism disorders by mediating AMPK signaling pathways.(6)The mechanism of oat bran interfering with signaling molecules of the gut-brain axis.Consumption of oat bran significantly increased GABA and ghrelin levels and levels of the appetite-suppressing hormones GLP-1 and PYY in the colon and hypothalamus of obese rats in a dose-dependent manner and reduced insulin and leptin resistance.Furthermore,the study found a significant correlation between the key enzyme activities involved in glucose and lipid metabolism,as well as the signal molecules of the gut-brain axis pathway and certain gut microbes.These findings suggest that oat bran can increase feelings of fullness,regulate the signal molecules of the gut-brain axis pathway,reduce appetite,and control energy intake,ultimately helping to manage obesity.In conclusion,dietary supplementation with oat bran can effectively regulate blood glucose balance and prevent the development of obesity by regulating gut microbes and their metabolites,as well as by regulating hepatic glucose and lipid metabolism and hypothalamic appetite factors,improving insulin and leptin resistance,and addressing abnormal glucose and lipid metabolism.