Correlation Between Gut Microbiota And Inflammatory Indexes In Patients With First Episode Depression

Objective:Depression is a common mental illness,which seriously affects people’s physical and mental health.Previous studies have shown that the occurrence of depression is closely related to gut microbiota and inflammation.Therefore,the levels of gut microbiota,short chain fatty acids and inflammatory factors in patients with depression were analyzed to explore the relationship between them in this study,aiming to provide new ideas and strategies for the study of the mechanism of depression.Methods:Thirty-five patients with first-episode untreated depression and 31 healthy control were collected.We collected the general demographic data of the subjects.The 17-item Hamilton Depression Scale(HAMD-17)was used to evaluate the severity of depression.We detected the sequence of gut microbiota of the two groups by 16 S r RNA gene sequencing technology,analysed the species composition and diversity gut microbiota by QIIME2 software.The different species of the two groups were identified by LEf Se analysis.The levels of short chain fatty acids in plasma were detected by gas chromatography-mass spectrometry(GC-MS)and the levels of inflammatory factors in plasma were detected by Enzyme linked-immuno-sorbent assay(ELISA).The differences of gut microbiota,short chain fatty acids and inflammatory factors between the two groups were compared,and the correlation between gut microbiota and shortchain fatty acids and inflammatory factors was analyzed.Results:1.There was no statistically significant difference in general demographic data between the depression group and the healthy control group in gender,age,years of education,BMI,smoking,drinking,eating habits,etc(P>0.05).2.In this study,a total of 7422832 sequences were obtained from the fecal samples of66 subjects.Vsearch software was used to splice the obtained sequences,mass filtration,deduplication,and chimerism removal,and finally 4,337,329 high-quality sequences were obtained.The length of these sequences mainly concentrated between 400-430 bp.A total of28468 operational taxons were obtained by clustering at 97% similarity level.Species composition analysis showed that at the phylum level,the main gut microbiota of patients with depression and healthy people were Firmicutes,Bacteroidetes,Proteobacteria and Actamobacteria.The relative abundance of these four phyla was more than 99%,and Firmicutes was the absolute dominant phyla in the two groups.At the family level,we counted the top 20 bacterial communities with relative abundance.Among the patients with depression,the relative abundance of the gut microbiota was greater than 1% :Lachnospiraceae,Ruminococcaceae,Bacteroidaceae,Veillonellaceae,Enterobacteriaceae,Bifidobacteriaceae,Streptococcaceae,and Rikenellaceae.In addition to the above groups of bacteria with relative abundance greater than 1% in healthy people,there are also families of Porphyromonadaceae and Clostridiaceae.At the genus level,we counted the top 20 bacterial communities with relative abundance.In depressed patients and healthy people,the gut microbiota relative abundance that is more than 1% mainly included Bacteroides Roseburia,Faecalibacterium,Gemmiger,Blautia,Bifidobacterium,Shigella,Ruminococcaceae＿Ruminococcus,Ruminococcus,Coprococcus,Streptococcus,Dialister,Alistipes,Phascolarctobacterium,Lachnospiraceae＿Clostridium.In addition,the relative abundance of more than 1% of the bacteria in patients with depression included Megamonas and Dorea,and the relative abundance of more than 1% of the bacteria in healthy people included Megasphaera,Parabacteroides and Oscillospira.Compared with the healthy control group,the Simpson index and Pielou’s evenness index of gut microbiota in the depressed group were decreased(P=0.0025,P=0.031).Sparse curves indicated that the sequencing depth is sufficient to reflect the diversity contained in the current sample.Beta diversity analysis showed greater inter-group differences than intra-group differences between the two groups(P=0.001).LEf Se analysis in two groups were identified in 13 significantly different microbes(?<0.05,LDA > 2).Four of them,Sphingomonadales,Sphingomonadaceae,Moraxellaceae,and Acinetobacter,were concentrated in patients with depression.Nine were lower in people with depression,They were Turicibacterales,Turicibacteraceae,Clostridiaceae,Marinilabiaceae,Clostridium,Lachnospira,Macellibacteroides,Enterobacter and Turicibacter respectively.3.Compared with healthy control group,the levels of acetic acid,propionic acid and butyric acid in depression group were decreased(P<0.05).The correlation analysis between different strains and short chain fatty acids showed that butyric acid was positively correlated with Clostridium(r=0.349,P=0.040).4.Compared with healthy control group,peripheral blood CRP in depression group was significantly higher(P=0.013).The correlation analysis between different strains and inflammatory factors showed that IL-6 was negatively correlated with Turicibacteraceae(r=-0.441,P=0.008),and IL-6 was negatively correlated with Turicibacter(r=-0.462,P= 0.005).Conclusion:1.Compared with healthy people,the composition of the gut microbiota in depressed people changed and the diversity of the microbiota decreased.2.Compared with healthy people,the levels of acetic acid,propionic acid and butyric acid in the peripheral blood of patients with depression decreased,and the levels of CRP increased,which may be related to the changes of gut microbiota.