Functional Fiber Reduces Mice Obesity By Regulating Intestinal Microbiota

Obesity has become a global public health problem,and caused metabolic syndrome which has potential dangerous to health Dietary fibers(DFs)alleviate obesity and metabolic syndrome by regulating intestinal microbiota.Supplemented 6% functional fiber(FF)with high-fat diet(HFD)improved insulin sensitivity of obese mice,while has no effect on body weight.Therefore,we invstigated the effect of FF supplementation during HFD-diets,which influenced the obesity and intestine microbiota.58 C57BL/6 male mice aged 5-6 weeks were fed HFD-diets for 9 weeks,and obtained total of 35 obese mice.We randomly divided into 5 groups according to their average body weight.Normal mice fed with low fat diet considered as LFD,fed with high fat diet considered as HFD,and considered as 8% FF or 12% FF which has supplemented with FF with HFD-diets.Supplemented with 12% FF and treated with antibiotics(12% FF+AB),7 normal mice fed with the same batch of ordinary diets were set as the control group(Con group).Recorded the weight of each body weekly and the feed intake daily for 12 weeks.At the end of the 11 th week,fasting serum was collected for 2 hours to analyze the level of inflammatory factorsand the composition of blood lipids.Insulin tolerance test(ITT)and glucose tolerance test(Glucose insulin tolerance,GTT)were performed on the second day after blood collection.Collected feces at the end of the experiment to detect the concentration of short-chain fatty acids(SCFAs)in the feces by gas chromatography-mass spectrometry and the composition of gut microbiota by 16 S r RNA gene sequencing technology.Mice sacrificed at the end of the 12 th week.Oil red O slices were used to measured liver lipid content and observed the morphological of brown fat,epididymal white fat and colon tissue which stained with H&E.RT-PCR was used to measure the m RNA expression of liver lipid synthesis genes and brown fat thermogenic genes.The main findings are as follows:1.The cumulative energy intake of mice in the HFD group increased significantly(P< 0.01),while has no effect with functional fiber supplementation(P < 0.05).The body weight gain of HFD group was significantly increased compared with control group andlow-fat group(P < 0.01)and 12% FF was significantly lower the body weight than HFD group(P <0.05),while 12% FF+AB group was significantly increased the body weight compared to the 12% FF group(P < 0.01).The epididymal adipocytes of the HFD group increased significantly with HFD-diets(P < 0.01).Compared with the HFD group,the epididymal adipocyte area of obese mice in the 8% and 12% FF groups was significantly reduced(P < 0.01).The above results indicated that 12% FF not effectively reduce energy intake under the condition of HFD,while significantly reduce the body weight and epididymal fat cell area of mice and improve obesity;the addition of antibiotics will inhibit the effect of functional fiber on improving obesity.2.The concentration of non-esterified fatty acids(NEFA)in the serum of mice in the HFD group was significantly reduced than control group(P < 0.05);the levels of high-density lipoprotein-cholesterol and NEFA in the serum of mice were significantly increased with 12% FF supplemented(P < 0.05),while the levels of high-density lipoprotein-cholesterol and NEFA in 12%FF+AB group were significantly lower than 12%FF group(P < 0.05).The liver weight,liver fat content and fat vesicle size of mice in the HFD group increased significantly(P < 0.01).Supplemented 12% FF can reduce the liver weight and the size of liver fat bubbles under high-fat feeding conditions.The levels of bilirubin(T-BIL)and alanine aminotransferase(ALT)in the serum of mice in the HFD group were significantly increased(P < 0.05).3.Compared with the HFD group,the m RNA expression of the brown fat thermogenesis gene(UCP1)and lipid transport gene(FABP)in the 12% FF group increased significantly(P < 0.05).The above results indicate that 12% FF stimulated brown adipose tissue browning by promoting thermogenesis and lipid decomposition and transport of brown fat.4.The glucose AUC values of IGTT and IITT of HFD group mice were significantly higher than control group and LFD group(P < 0.01);compared with HFD group,FF supplementation significantly reduced the glucose AUC value of IGTT(P < 0.05).Antibiotic supplementation significantly increased the glucose AUC values of IGTT and IITT in obese mice with 12% FF intervention(P < 0.01).Compared with the HFD group,the serum insulin level of the mice in the 12% FF group was significantly decreased(P <0.05).The above results indicate that 8% and 12% FF alleviated glucose tolerance and improved insulin sensitivity compared with the HFD group,while the supplementation of antibiotics reversed the above-mentioned index.5.Compared with control group,the inflammatory factors(LPS and leptin)in HFD group increased significantly(P < 0.05).Adding 8% FF or 12% FF under HFD-dietssignificantly reduced the levels of leptin(P < 0.01),and the levels of LPS and TNF-αwere significantly reduced in 8% FF group(P < 0.05).Antibiotics supplementation significantly reduced the concentration of IL-6 compared to 12%FF group(P < 0.05).The above results indicate that supplementation of 8% FF or 12% FF alleviated systemic inflammation.6.Compared with the HFD group,the concentration of acetic acid in the 8% and 12%FF groups was significantly increased(P < 0.05).Compared with the 12% FF group,the12% FF+AB group significantly reduced acetic acid,propionic acid,butyric acid,and total short chain fatty acids(SCFAs)(P < 0.01).The above results indicate that the supplementation of 8% FF or 12% FF regulated the metabolic activity of fecal microorganisms and significantly increased the production of acetic acid.7.The 16 S r RNA gene sequencing results showed that compared with control group,the Observed species index in the colon of HFD group was decreased significantly(P <0.05);compared with the HFD group,Chao1 index and Oberserved species index of 8%FF group and 12% FF group increased significantly(P < 0.05).the relative abundance of Firmicutes in control group,LFD group and 12% FF group were significantly decreased(P < 0.01),and the Actinobacteria increased clearly in the feces(P < 0.05).In colon,the relative abundance of Coprococcus and unclassified genera from Ruminococcaceae and Coliobacteriaceae in 12%FF group were significantly higher than HFD group(P < 0.05),while the relative abundance of Adlercreutzia,Streptococcus,Lactococcus,Leuconostoc and Subdoligranulum were significantly decreased(P < 0.05).In feces,compared with the HFD group,Bifidobacterium and unclassified genera from Coriobacteriaceae and Bacteria in 12% FF group were significantly increased(P < 0.05),and Dehalobacterium,AF12,and unclassified genera from Clostridiales were significantly decreased(P < 0.05),Clostridiales,Lachnospiraceae,and Rikenellaceae unclassified genera tended to decrease(P < 0.1).The above results indicated that 12% FF reshaped the gut microbial diversity and composition of obese mice,reduced the abundance of Firmicutes,and increased the abundance of Bifidobacterium,Coprococcus and other beneficial bacteria.8.Spearman correlation analysis showed that the increased abundance in 12% FF group has significantly negative correlation between Coprococcus and insulin resistance(insulin,HOMA-IR)(P < 0.05).Oscillospira was extremely negative correlation with serum leptin levels(P < 0.01).The 6 reduced abundance genera(including Streptococcus,Clostridium,Adlercreutzia,Lactococcus,Subdoligranulum,Leuconostoc)were significantly positive correlation with body weight gain(P < 0.05).In feces,the increased abundance in 12% FF group has significantly negative correlation between Bifidobacterium and insulin levels(P < 0.05),Olsenella is significantly negative correlation with body weight gain(P < 0.05),and Corynebacterium is associated with insulin resistance(blood sugar,insulin,HOMA-IR)which was significantly negative correlation(P < 0.05).Bifidobacterium,Anaerostipes,Olsenella,Corynebacterium,and unclassified genera from Bacteria and Coriobacteriaceae were significantly negative correlation with serum leptin levels(P < 0.05).