Abstract Body (Do not enter title and authors here): Introduction
Several studies have shown that alterations of gut microbiome are associated with various diseases, such as atherosclerosis. Published literature often compared the gut microbiome of healthy individuals only and those with atherosclerotic coronary artery disease (CAD). Data on the gut microbiome structure of high-risk individuals, who are neither completely healthy nor diseased, were missed and largely unknown.

Objective and Hypothesis
This study aimed to investigate human gut microbiome association and atherosclerotic coronary artery disease risk status. We hypothesize that risk factors drive alterations in the gut microbiome, which are associated with the overall risk of developing CAD. We further propose that these changes in the gut microbiome composition occur before significant disease development.

Methods
The study recruited 30 patients from a tertiary hospital: at low risk (LR) (n=10), at high risk (HR) (n=10), and with CAD (CD) (n=10). The risk of developing CAD was determined by ASCVD Risk Score. Microbial DNA was isolated from stool samples and sequenced using Illumina MiSeq. The taxonomic and functional profiles of the gut microbiome were determined by MetaPhlAn2 and HUMAnN2. Data were analyzed using the Kruskal-Wallis H test and multiple pairwise comparisons by the Mann-Whitney U test.

Results
Taxonomic profiling demonstrated that relative abundance of Proteobacteria, Enterobacteriaceae, Bacteroides, and Collinsella were increased in individuals with high-risk status and CAD while, Bifidobacterium and Lactobacillus were higher in the gut of low-risk individuals. The relative abundance of Streptococcaceae and Akkermansia muciniphila were highest in the gut microbiota of high-risk individuals. Gut microbiome diversity was noted to be richer as the risk of CAD becomes higher. Functionally, this study revealed that microbial genes for nitrogen utilization, DNA repair, and DNA conformation change were associated with healthier gut microbiome while, transport of nutrients, harnessing of energy from dietary sources, cell wall component biosynthesis, phosphorylation, signal transduction, and biosynthesis of certain amino acids and phospholipids appeared to be linked with the risk of atherosclerotic CAD.

Conclusion
Metagenomic profiling of the gut microbiome across various risk statuses of atherosclerotic CAD identifies distinct taxonomic and functional signatures. Thus, the altered gut microbiome signatures may serve as early predictor for CAD.