The Change And Intervention Measures Of The Aging Gut Microbial Ecology

With the development of the economic and technology,people in China are living a better life,and China has entered the aging society,many aging related disease and health status of elderly has gained much attention,intestinal microbial ecology refers to the composition,structure and function of the intestinal bacteria and the relationship between the host,it plays an important role in the human health and development process of some disease,with the development of next generation sequencing and various "omics",we had learned more about the intestinal microbial ecology.In our whole life course,gut microbial ecology is not static,it can be affected by diet,lifestyle,and many other effects,after aging,due to some physiological reasons,intestinal microbial ecology have certain changes,so intestinal microbial ecology has great plasticity,it can be a target that to improve the health and prevent age-related diseases of aging.Some research of aging gut microbiota has been done,these researches involve different national and area,research sample numbers and age are different,research methods are also not same,so the conclusion of these studies are not unified,the change law of the aging gut microbiota is not clear.Between these findings,there are no research of China aging people,so this paper is aim to study aging gut microbiota of China and study the intervention measures to improve the aging gut microbial ecology with mice as model.In order to study the aging gut microbiota in China,we collected 102 samples in Henan province,it includes 59 aging people(men 29,women 30),the mean age is 77.6 years,15 middle-aged people(men 10,women 5),the mean age is 48 years,28 young people(men 18,women 10),the mean age is 32 years.We did the sequencing of gut microbiota using the 16 s high-throughput sequencing method,the ratios of gut microbiota at the phylum level in the three groups are all Bacteroidetes and Firmicutes,accounted for more than 80% of the gut microbiota,Bacteroidetes is the most abundant phylum,in the aging people,the ratio of Bacteroidetes is 52.4%,Firmicutes is 27.9%,in the middle aged people,the ratio of Bacteroidetes is 55.2%,Firmicutes is 31.7%,in the young people,the ratio of Bacteroidetes is 49.2%,Firmicutes is 36.2%,Proteobacteria is the third phylum,the ratio in the aging,middle aged and young people is 17.7%,11.1% and 12.0%.It is different from the data that is reported.The variation tendency of the gut microbiota during aging is that the ratio of Bacteroidetes increased and the Firmicutes decreased,the Firmicutes/Bacteroidetes ratio in the young adults,middle aged group,elderly group is 0.73,0.57,0.53 respectively,it can reflect the variation tendency more directly.For the whole structure of the gut microbiota,we did PcoA and NMDS analysis to study the change of gut microbiota,in these two analysis,the dot which represent the aging people and young adults is far from each other,that means the structure of the gut microbiota is different between them.In the aged group,the dot is more dispersed than that in the young group,it indicates that the within-group variation is large in the aged group than that in the young group.We did metastats analyze to study the different bacteria in genus level,The percentage of butyrate-producing bacteria was different between the two groups,Faecalibacterium and Roseburia are both more abundant in the young group than that in the aged group.Gemella species produce a mixture of acetic and lactic acids,while Propionibacterium species can synthesize propionic acid,both of which were found to have lower abundance in the elderly in our study.With regard to the genus Bifidobacterium,which is commonly accepted that the elderly had lower abundance,no statistically significant difference has been observed in its abundance between young adults group and the aged group.Another genus that drew our attention is Akkermansia,its abundance in the elderly was higher than that in the young adults.It have been conducted because of its association with human metabolism and health.The animal model in this study is BALB/c mice,the intervention measure is the branched-chain amino acid-enriched mixture(BCAAem),we study the gut microbiota,the metabolomics of the faecal extracts and the immune status of the body.The time for the intervention measure is from the age of 11 month to 15 month,that is from middle age to old age.For the gut microbiota,the BCAAem-supplemented group had richer microbial diversity than that in the control group at 15 months of age.Bacteroidetes and Firmicutes were the dominant phyla in both the supplemented and control groups,representing more than 95% of the total gut microbiota.The most abundant phylum is Bacteroidetes which ratio is more than 50%,and the ratio of Firmicutes is about 40%.At the age of 11 month,in the control group,the average proportion of Bacteroidetes is 51.37%,the Firmicutes is 46.24%,for the BCAAem group,the Bacteroidetes is 51.68%,and the Firmicutes is 44.91%.At the age of 15 month,in the control group,the average proportion of Bacteroidetes is 59.64%,the Firmicutes is 38.16%,for the BCAAem group,the Bacteroidetes is 55.85%,and the Firmicutes is 41.78%.The proportion of the Bacteroidetes increased and the Firmicutes decreased during aging,it has the same trend with the aged people.In the control group,compared with proportions measured at 11 months,the average proportion of the Bacteroidetes phylum increased 8.27%,while that of the Firmicutes phylum decreased 8.08% at 15 months.In the supplemented group,the average proportion of the Bacteroidetes phylum increased 4.17%,while that of the Firmicutes phylum decreased 3.13% at 15 months.In the supplemented group,the rate of change in the two dominant phyla due to age was slowed by BCAAem supplementation.As the Bacteroidetes and Firmicutes are the dominant phyla in the gut,their relative ratios may be used as a structural indicator of the gut microbiota.In the control group,the Firmicutes/Bacteroidetes ratio at 11 months of age was 0.90,while that at 15 months was 0.64.In the supplemented group,the Firmicutes/Bacteroidetes ratio at 11 months was 0.87,while that at 15 months was 0.75.Thus,at 15 months of age,the Firmicutes/Bacteroidetes ratio of the supplemented group was higher than the control group and was closer to the ratio observed in 11-month-old mice.In addition,it is worth mentioning that as the third most abundant phylum,the proportion of Proteobacteria in the 15-month-old supplemented group was about half of the control group.The Proteobacteria phylum includes some pathogenic bacteria such as enterobacteria,which are considered pathobionts and can cause pathogenic infections in certain circumstances.Thus,BCAAem supplementation may help control the proportion of Proteobacteria in the gut microbiota and improve the gut health.In order to validate the 16 s sequencing method and detect the bacteria of low ratio,we detect Bifidobacterium,Lactobacillus,Clostridium leptum and Prevotella using q PCR,The abundance of bifidobacteria decreased in both group during aging,but in the supplemented group,the downturn is slower,at age of 14 and 15 month,bifidobacteria were more abundant than in the control group,so the BCAAem can increase the abundance of bifidobacteria.Lactobacillus and Prevotella have no significant difference between the two group.During aging,Clostridium leptum increased in the two group,and in the BCAAem group,it increased more,at the age of 15 month,in the supplemented group,bifidobacteria were more abundant than in the control group.In order to study the immune status of the host,we detect two proinflammatory cytokines TNF-αand IL-1β,one anti-inflammatory cytokine IL-10,at the age of 15 month,in the control group,the concentration of TNF-αis 57.6pg/ml,in the BCAAem group,the concentration is 46.1pg/ml,for IL-1β,in the control group,the concentration is 182.0pg/ml,in the BCAAem group,the concentration is 158.3pg/ml,the concentration of TNF-αand IL-1βis lower in the BCAAem group.For IL-10,at the age of 15 month,in the control group,the concentration is 34.6pg/ml,in the BCAAem group,the concentration is 96.2 pg/ml,it is higher than the control group.We also detect the lipopolysaccharide binding protein(LBP),which can reflect the antigen load in the host,at the age of 15 month,in the BCAAem group,the concentration is 20.3pg/ml,and the control group is 39.7pg/ml,it is lower in the BCAAem group than that in the control group.All the data shows that BCAAem can weakens the immune response and the antigen load so that improve the immune status of the host.In the study of the metabolomics of the faecal extracts,we found that the faecal metabolites of the BCAAem-supplemented mice were significantly different from those in the control mice,the different metabolites between the two groups are Octadecenoic acid,Cholesterol,Oleic acid,Deoxycholic acid,Glycerol,Fructose,Sucrose,Erythritol,1-monooleoylglycerol,Xylitol,Phenyllactic acid,Stigmasterol.In the BCAAem group,the Octadecenoic acid,Cholesterol,Oleic acid,Deoxycholic acid,Glycerol have relatively high proportion,and the Fructose,Sucrose,Erythritol,1-monooleoylglycerol,Xylitol,Phenyllactic acid,Stigmasterol have relatively low proportion.The difference between the two groups is about sugar metabolism and lipid metabolism.In summary,the BCAAem can change the metabolites of the fecal,especially sugar metabolism and lipid metabolism,these metabolites can lay a foundation for the study of the influence to the gut of the BCAAem.In conclusion,this paper studied the change of aging gut microbiota in China for the first time,the structure and bacteria in each level are different with that of young people,we also studied the influence of BCAAem on aging gut microbial ecology using BALB/c mice,BCAAem can slowed the change speed of gut microbiota which is due to age,change the gut metabolism,improve the gut immune condition,so BCAAem could improve the aging gut microbial ecology.