Anti-obesity And Glucose Homeostasis Regulation By Dietary Fiber And Starch In A Whole-grain Like Structural Form

In recent years,the prevalence of obesity has increased at an alarming rate due to changes in eating habits and lifestyles,and has become a growing and disturbing global public health crisis.Obesity is a risk factor for many chronic diseases,such as insulin resistance,type 2diabetes,hypertension and atherosclerosis.Studies have confirmed that whole grain foods have the function of inhibiting obesity and regulating glucose homeostasis,among which dietary fiber and phytochemicals are considered to be the main substances for their physiological effects.However,cereal starch,as the main glucose provider in cereal based foods,the contribution and mechanism of endosperm starch to the beneficial effects of whole grain foods have rarely been investigated.Therefore,this study constructed a whole-grain structural form?WGLSF?using corn starch and oat as raw materials,to explore the nutritional property and physiological functions of starch in whole-grain like structrual form.The effects and mechanism of a long-term dietary intervention and prevention with WGLSF on anti-obesity and glucose homeostasis in mice were investigated.The main research contents and results are as follows:1.According to the principle of bionics and the natural arrangement of cell wall and starch in whole grain,WGLSF was constructed that the starch granules were encapsulate d in the Ca²⁺-induced alginate gel network in the presence of?-glucan,and the digestion property of the embedded starch was studied.In vitro digestion experiments,it showed that the slowly digestible starch content of WGLSF?44.33%?is higher than that of the physical mixture?21.17%?,indicating the importance of the physical structure to the slow digestion property of WGLSF.Scanning electron microscope?SEM?and confocal laser scanning microscope?CLSM?observation demonstrated that the starch granules were embedded in the?-glucan-alginate co-formed gel matrix with a cell wall-like structure,which might cause the decrease of enzyme accessibility to the substrate,and ultimately to the slow digestion profile of starch.2.The fermentation characteristics of WGLSF were studied by in vitro fermentation.The amount of gas produced by microbiota growing on WGLSF during the 24-hour fermentation period was the lowest,and the pH values of WGLSF also changed slower than that of physical mixture and individual?-glucan.These results demonstrated that WGLSF was a slow fermenting material during the 24 h.In addition,the short chain fatty acid?SCFA?content was different among WGLSF,physical mixture and individual?-glucan,indicating the fermentation characteristics of WGLSF was affected by the network-like form.According to the results of postprandial glycemic response,WGLSF can reduced glycaemic response,which is beneficial to postprandial blood glucose balance.3.Obese mouse model was induced by 60%high-fat diets,and it was selected to study the anti-obesity effect of a long-term intervention of the whole-grain like structural form.WGLSF effectively reduced the body weight gain,abdominal fat accumulation,serum triglycerides?TG?and total cholesterol?TC?levels in obese mice induced by HF diet.Meanwhile,WGLSF treatment also improved the fat metabolism,which was evidenced by reduced fat accumulation in the liver and adipocyte size in the white adipose tissue.Therefore,WGLSF could lower the increasing rate of obese mice'body weight,improve lipid metabolism in obese rats and prevent the formation of fatty liver.Moreover,feeding on WGLSF significantly increased the heat production and ambulatory movements of mice.WGLSF could up-regulated pro-opiomelanocortin?POMC?mRNA and down-regulated neuropeptide Y?NPY?mRNA in hypothalamus,which play a crucial role in energy homeostasis regulation by adjusting both the energy intake and energy expenditure through activation of the gut-brain axis.In addition,WGLSF could down-regulated lipogenic transcription factor of sterol regulatory element-binding protein-1c?SREBP-1c?and fatty acid synthase?FAS?,and up-regulated the lipid-oxidation related transcription factor of peroxisome proliferator-activated receptor-??PPAR-??and phosphorylated AMP-activated protein kinase?p-AMPK?,which improved hepatic gluconeogenesis,promoted fatty acid oxidation,and reduced fat accumulation.4.High-fat diet-induced obese mice were also used to study the effects of a long-term intervention of whole-grain like structural form on hepatic insulin resistance in obese mice.After 8-week treatment,the body weight gain and insulin resistance were significantly reduced.The hepatic Akt,which is the key component in insulin signaling,was activated,and the hepatic expression and protein levels of glucose-6-phosphatase?G-6-P?and phosphoenolpyruvate carboxykinase?PEPCK?were reduced.Moreover,WGLSF effectively reduced the hepatic levels of the pro-inflammatory cytokines of TNF-?and IL-6.These results demonstrated that starch and WGLSF has the potential as a dietary strategy to ameliorate obesity-induced hepatic insulin resistance favoring glucose homeostasis.5.Mice fed with different diets were used to explore the prevention of WGLSF on obesity and insulin resistance.The body weight,the fat content,fasting blood glucose,insulin,TG and TC levels of WGLSF diets fed mice were significantly lower than those in high-fat diets fed mice.Meanwhile,WGLSF can significantly lower liver fat accumulation and fat cell enlargement,and as a result,the steatosis of liver was mitigated in mice fed with WGLSF at a high-fat condition.Therefore,WGLSF could lower the rate of increase in body weights,reverse the disorders of glucose metabolism and ameliorate the symptoms of insulin resistance in mice.In addition,WGLSF could improve lipid metabolism and prevent the formation of fatty liver.Moreover,the metabolite in blood was analyzed by metabolome.The results showed the content of butyric acid in WGLSF fed mice was significantly higher than in high-fat fed mice,and glycoside amino acids,such as arginine and norleucine,were significantly lower than those in high-fat diet group,indicating that WGLSF can improve the glucose and lipid metabolism disorder by regulation lipid metabolism and amino acid metabolism.Based on high throughput technology,the effect of WGLSF on intestinal microflora in mice was analyzed.The results showed that the abundance of Bacteroidetes in WGLSF fed group was higher,and the bacteria of Lachnospiraceae which promoted the development and progression of diabetes was lower than in high-fat fed mice.It indicated that WGLSF have a beneficial effect on the health by improving the intestinal flora disorder.In conclusion,a whole-grain structural form with a whole-grain microstructure has been constructed,which combined the advantages of the physiological functions of dietary fiber and the health benefits of slow-digested starch.WGLSF can effectively reduce obesity and favor glucose homeostasis in obese mice.The research of the WGLSF will provide theoretical and technological guidance to healthy foods with the physiological functions of whole grain foods.