| In recent years,domestic and foreign scholars have conducted many studies on the effects of dietary fiber on glycolipid metabolism.Many dietary fibers have been proven to regulate glycolipid metabolism,and the source and type of dietary fibers are important factors influencing their health benefits.Studies concerning the effects of flaxseed insoluble and soluble dietary fiber on glycolipid metabolism homeostasis are still limited,and the underlying mechanisms are still not clear.Flaxseed cake is a by-product of flaxseed following oil extraction,and it is a valuable resource for dietary fibers,though it has not been fully commercially exploited.Based on this,flaxseed cake was enzymatically hydrolyzed to extract flaxseed cake insoluble dietary fiber(FIDF)and flaxseed cake soluble dietary fiber(FSDF).This study characterized the in vitro prebiotic properties of FIDF and FSDF firstly,and then explored the regulatory effects of FIDF and FSDF dietary supplementation on glycolipid metabolism homeostasis in high-fat-diet induced obese mice.The underlying mechanisms were analyzed by measuring the expression of genes related to glycolipid metabolism and sequencing the intestinal microorganism.Our findings demonstrated the potential of FIDF and FSDF as novel dietary fiber resources.The main research contents and results are as follows:Firstly,the physicochemical properties and in vitro fermentation characteristics of FIDF and FSDF were analyzed.Physicochemical properties analysis results showed that the loose porous structure of FIDF and FSDF contributed to their strong water retention,oil retention and expansion capabilities.FSDF had better hydration properties than FIDF,and FIDF had higher oil holding power than FSDF.The ability of FSDF to adsorb glucose and cholesterol and delay glucose diffusion was stronger than that of FIDF.The results of in vitro human colonic fermentation showed that both FIDF and FSDF had good in vitro fermentation characteristics,they could reduce the ratio of Firmicutes to Bacteroidetes and regulate intestinal microbial community structure.FSDF was more efficient to produce short-chain fatty acids than FIDF.Crucial propionic acid producing bacteria g＿Prevotella＿9 was significantly enriched in both FIDF and FSDF fermentation(p<0.01),while the co-fermentation of FIDF and FSDF significantly enriched g＿Bifidobacterium(p<0.001).Secondly,a high-fat-diet induced C57BL/6J obese mice model was constructed.The mice were fed high-fat-diets with FIDF alone(FIDF group)or FSDF alone(FSDF group)or FIDF combined with FSDF(MIX group)for 5 weeks.The results showed that both FIDF and FSDF could improve glycolipid metabolism in obese mice.The supplementation with FSDF alone or FIDF and FSDF together significantly reduced the weight gain of obese mice(especially FSDF alone dietary supplementation).Compared with the HFD mice,the fasting blood glucose level of the FSDF mice and the MIX mice was decreased by 21.54% and 11.84%,respectively.And the area under OGTT curve which represented oral glucose tolerance of the FSDF mice and the MIX mice was decreased by 26.54% and 26.75%,respectively.The serum TC level of the FSDF mice and the MIX mice was decreased by 20.33% and 19.84%,respectively.And the serum TG level of the FSDF mice and the MIX mice was decreased by 25.35% and 30.99%,respectively.Although the supplementation with FIDF alone did not inhibit the body weight gain and fat accumulation,it significantly alleviated the liver steatosis of obese mice.The liver TC level and liver TG level were decreased by 45.38% and 43.94%,respectively,compared with that of HFD mice.The supplementation with FIDF alone also had a certain regulatory effect on glucose metabolism,and the effect of FSDF intervention was stronger than that of FIDF intervention.Finally,the mechanisms of dietary supplementation of FIDF and FSDF on glycolipid metabolism homeostasis regulation were analyzed.The supplementation with FSDF activated the PPARα-LXRa-CYP7A1 pathway in liver,thus enhanced β-oxidation of fatty acids,and promoted cholesterol metabolism.The supplementation with FSDF also significantly upregulated the expression of PPARγ in adipose tissue(p<0.05).The dietary supplementation with FSDF alone or FIDF and FSDF together significantly enriched g＿Akkermansia(p<0.001)and g＿norank＿f＿Muribaculaceae(p<0.001).Correlation analysis showed that the two characteristic bacteria were significantly negatively correlated with body weight,fasting blood glucose,insulin resistance indexes and so on.The dietary supplementation of FIDF alone restored the richness and diversity of the gut microbiota,enriched some short-chain fatty acid producing bacteria,e.g.,g＿Blautia and g＿Bifidobacterium(p<0.05).The content of short-chain fatty acids in the intestinal tract of FIDF mice was significantly increased by 208.39% compared with that of HFD mice. |
