Analyzing Probiotic-Induced Shifts to the Microbiome in a Murine Model of Atherosclerosis Öffentlichkeit

Abstract

Atherosclerosis is a leading cause of death worldwide, as the build-up of fatty deposits in blood vessels can lead to both ischemic strokes and ischemic heart attacks. Recently, the gut microbiome has been implicated in both driving and inhibiting atherogenesis. Thus, probiotics have emerged as novel therapeutic paradigms to lessen atherosclerotic disease burden. Notably, Lactococcus lactis subspecies cremoris (L. cremoris; LLC), a probiotic commonly utilized in dairy fermentation processes, has been shown to elicit protection against detrimental cardiometabolic phenotypes in mice fed a Western-style (high-fat, high-sugar) diet. Therefore, in order to better characterize the potential mechanisms by which L. cremoris drives its protective phenotypes, this study aims to compare the effects of L. cremoris and Lactobacillus rhamnosus GG (L. rhamnosus; LGG), another widely-used probiotic, on gut microbial composition in a murine model of atherosclerosis. To assess the impact of probiotic administration on bacterial communities, the QIIME bioinformatics pipeline was utilized to analyze alpha diversity, beta diversity, and taxa abundance metrics following 16S rRNA sequencing of fecal samples at the V3-V4 region. In the results of this study, we have found that in comparison to treatment with either L. rhamnosus or a vehicle saline solution, L. cremoris significantly increased the abundance of Odoribacter, a butyrate-producing bacterium with beneficial anti-inflammatory activity. Additionally, L. cremoris treatment resulted in a significant reduction of microbes typically associated with weight gain, increased gut permeability, and atherogenesis. In mice administered L. cremoris, decreases in the abundance of the Marvinbryantia and Akkermansia genera, as well as the Clostridiaceae and Ruminococcaceae bacterial families were observed. Furthermore, while an increase in the Firmicutes/Bacteroidetes ratio has been previously identified as a marker of diet-induced obesity, L. cremoris treatment resulted in a reduction of this ratio. Thus, dietary supplementation of L. cremoris results in differential alterations to the gut microbial profile, relative to those induced by either L. rhamnosus or vehicle treatments. Because L. cremoris is generally regarded as safe for consumption and has previously been shown to attenuate metabolic complications, this bacterium’s impact on the microbiome serves as an exciting avenue for future therapeutic exploration.

Table of Contents

Abbreviations ........................................................................................................................................... 1

Introduction ............................................................................................................................................. 1

The Gut Microbiome's Impact on Host Health ............................................................................................. 1

Tales of Men in Mice: Experimental Approaches for Studying the Microbiome in Disease States ..................... 2

At the Heart of the Matter: The Gut Microbiome in Atherosclerosis .............................................................. 4

Figure 1 ................................................................................................................................................... 5

From Food to Factory to Pharmacy: The Potential of Probiotic-Based Therapeutic Interventions for

Atherosclerosis ........................................................................................................................................ 6

Figure 2 ................................................................................................................................................... 8

Materials and Methods ............................................................................................................................. 8

Dietary Regimen and Probiotic Administration in Animal Models ................................................................ 8

Table 1 ................................................................................................................................................... 10

Probiotic Culture .................................................................................................................................... 10

DNA Extraction and Sample Preparation .................................................................................................. 10

Bioinformatics Analysis .......................................................................................................................... 11

Statistical Analysis ................................................................................................................................. 11

Results .................................................................................................................................................. 12

L. cremoris treatment significantly altered the abundance of certain genera ............................................... 12

Figure 3 ................................................................................................................................................. 12

Figure 4 ................................................................................................................................................. 13

Figure 5 ................................................................................................................................................. 14

L. cremoris treatment significantly impacted the abundance of certain bacterial families ............................ 14

Figure 6 ................................................................................................................................................. 15

Figure 7 ................................................................................................................................................. 16

Probiotic treatments alter the composition of the gut microbiome ............................................................. 16

Figure 8 ................................................................................................................................................. 17

Analyzing the impact of probiotic treatment on alpha and beta diversity .................................................... 19

Figure 9 ................................................................................................................................................. 19

Discussion ............................................................................................................................................. 20

Conclusions and Perspectives ..................................................................................................................24

References ............................................................................................................................................. 25

About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Bioinformatics Biology, Microbiology Health Sciences, General
Stichwort	Probiotics Cardiometabolic Disease Cardiovascular Disease Lactobacillus rhamnosus GG Gut Microbiome Western Diet Atherosclerosis Lactococcus lactis subspecies cremoris
Committee Chair / Thesis Advisor	Rheinallt Jones, Emory University
Committee Members	Simbarashe Nkomo, Emory University Roger Deal, Emory University

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