Investigating the Effect of Alcohol on the Gut Microbiome of Pregnant Women

Bain, Chane (2020-03)

Thesis (MSc)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Alcohol is the second most abused drug in the world and has been found to induce changes in the microbial composition of the gut microbiome (the collection of microbial organisms together with their genetic material). The effects of alcohol on the microbiome of pregnant women have not been well studied. The gut microbiome is established early in life, primarily through vertical transmission from the gastrointestinal and reproductive tracts of the mother and evolves through the lifespan of an individual. Although there exist studies on animal models, limited research has been conducted on the effect that alcohol has on the gut microbiome during pregnancy. We therefore sought to characterise the gut microbiota in a cohort of pregnant women (N=86) to determine if alcohol consumption during pregnancy is associated with alterations in the gut microbiota. Informed consent was obtained from 86 pregnant women belonging to the South African Coloured population, ranging in age from 18-44 years. The sample-set was divided into two groups based on levels of the alcohol use biomarker phosphatidylethanol (PEth) detected in the blood. A PEth measurement of > 8 ng/mL represents the PEth+ group (N=35), who have drinking positive values versus no alcohol biomarker detection (PETh < 8 ng/mL) in the control group (N=51). Microbial DNA was extracted from the stool of each subject and sent for 16S rRNA sequencing on the Illumina MiSeq, amplifying the V3-V4 region. The bacterial diversity within samples (alpha diversity) was estimated by the calculation of Simpson, Dominance, Shannon, and Shannon Equitability metrics. As a vast number of factors have been found to affect the human gut microbiome (Kho et al., 2018), multivariate statistical analysis was conducted using Multivariate Association with Linear Models (MaAsLin). This method enabled correcting for age, body mass index, Bristol Stool Scale, gestational weeks, and smoking. After correcting for age, body mass index, Bristol Stool Scale and nicotine or tobacco use, we observed no significant differences in the gut microbiome of women who consumed alcohol during pregnancy compared to those who did not drink alcohol. Furthermore, age was significantly different between the PEth+ and the control group (p = 0.001). The study was done on a small sample size; a bigger sample size will provide more power, a smaller margin of error and more accurate mean values. Another possible limitation is that the participants were all in different trimesters of pregnancy. A larger sample size will also identify outliers that could skew the data in a smaller sample size. The gut microbiome is a complex ecology that is impacted by various factors. Also, the gut microbiome impacts on the human body and should thus be approached holistically in future studies, taking trimesters into account.

AFRIKAANSE OPSOMMING: Alkohol is die tweede mees misbruikte dwelm ter wêreld en daar is bevind dat dit veranderinge in die mikrobiese samestelling van die dermmikrobioom (die versameling van mikrobiese organismes tesame met hul genetiese materiaal) teweeg bring. Daar is beperkte navorsing beskikbaar oor die effek van alkohol op die mikrobioom van swanger vroue. Die dermmikrobioom word vroeg tydens die begin van lewe gevestig, hoofsaaklik deur vertikale oordrag deur middel van die maag en voortplantingskanale vanaf die moeder en hou aan ontwikkel deur die lewensduur van die individu. Alhoewel studies op diere gedoen is, is navorsing op die effek van alkohol op die menslike mikrobioom tydens swangerskap beperk. Dit was daarom noodsaaklik om te mik om die dermmikrobioom te karakteriseer vir ‘n steekproef van swanger vroue (N = 86) ten einde te bepaal of alkoholverbruik tydens swangerskap met veranderings in die dermmikrobioom geassosieer kan word en om veranderinge in die samestelling van die dermmikrobioom te vergelyk met die metadata. Om die primêre data te verkry is toestemming verkry van 86 swanger vrouens wat aan die SuidAfrikaanse Kleurling groepering behoort, in die ouderdoms groep 18-44 jaar. Die deelnemers is opgedeel in twee groepe na aanleiding van die teenwoordigheid van hul alkohol gebruik biomerker (fosfatidieletanol (FEth)) vlakke. Die FEth+ groep met FEth vlakke van ≥ 8 ng/mL (N=35) en die kontrole groep met FEth+ vlakke van < 8ng/mL (N=51). Mikrobiese DNA is onttrek uit ‘n stoelmonster van elke deelnemer en gevolglik gestuur vir 16S rRNA Sequencing (volgordebepaling) op die Illumina MiSeq, vir amplifisering van die V3/V4 streek. Die bakteriële diversiteit van die monsters (alfa-diversiteit) is bepaal deur middel van Simpson, Dominance, Shannon en Shannon Equitability statistiese berekeninge. Om die effek van alkohol op die dermmikrobioom, onafhanklik van ander faktore, te ondersoek is ‘n meerveranderlike statistiese analise op MaAsLin gedoen, met aanpassings vir ourderdom, liggaamsmassa-indeks, ‘Bristol Stool Scale’ en die gebruik van tabak en/of sigarette. Na die aanpassings vir ouderdom, liggaamsmassa-indeks, ‘Britstol Stool Scale’ en tabak en/of sigaret gebruik, is daar gevind dat alkohol tydens swangerskap geen beduidende verskille in die dermikrobioom veroorsaak nie. Die rede hiervoor kan wees dat die vroue in verskillende trimesters van swangerskap was of dat die steekproefgrootte te klein was. ‘n Groter steekproefgrootte sal moontlik meer statistiese krag, ‘n kleiner foutmarge en meer akkurate gemiddelde waardes oplewer. Ouderdom het aansienlik verskil tussen die FEth + en die kontrolegroep (p = 0.001). Die swanger dermmikrobioom kan gesien word as ‘n komplekse ekologie wat deur verskeie faktore beïnvloed kan word. Daarbenewens het die dermmikrobioom ook ‘n invloed op die menslike liggaam en moet dit in ‘n holistiese manier in toekomstige studies benader word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/108473
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