Attempted Isolations of Cholesterol-to-Coprostanol Reducing Bacteria in the Human Gut
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Biotechnology (MPBIO), MSc
Publicerad
2023
Författare
Antonsson, Selma
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of death globally. In early development of atherosclerosis, retention of cholesterol in artery walls is a key step. Cholesterol both endogenously produced and absorbed from the diet ends up in the gut, where bacteria may reduce it to coprostanol. Unlike cholesterol, coprostanol cannot be reabsorbed into circulation from the intestines, leading to long-standing hypotheses that high cholesterol-to-coprostanol conversion may lower blood cholesterol and thus the risk of ASCVD. Metagenomic evidence for both conversion being health-associated and ASCVD being a microbiota-modulated disease is mounting, emphasising the potential importance of microbial cholesterol metabolism in the gut. This project thus aimed to isolate cholesterol-converting bacteria from the human gut to further characterise them. Conversion was initially studied in a pure Eubacterium coprostanoligenes culture as a positive control. However, the type strain was quickly outcompeted by a contaminant whereupon culturing of faecal samples from two healthy donors was initiated. Over four sample series, several media compositions and cultivation approaches were investigated. Coprostanol was not observed in any culture. Pathway intermediates could not be analysed and as such it is possible, although improbable, that partial conversion took place. There was also no way of detecting the potential presence coprostanoligenic but non-converting bacteria. Altogether, these results reiterate on the previously established
fastidiousness of coprostanoligenic bacteria. Further attempts would benefit from more research determining the conditionssupporting cholesterol conversion, as a better understanding of those conditions is a first step in characterising the bacteria performing conversion. Eventually, this might enable research on supporting their growth using prebiotics or the feasibility of their application as next-generation probiotics for improved cardiovascular health.
Beskrivning
Ämne/nyckelord
cholesterol, coprostanol, gut microbiota, atherosclerosis