Črevesna mikrobiota nosečnic z gestacijskim diabetesom in pojav makrosomije

Molan, Katja (author), Žgur Bertok, Darja (mentor), Ambrožič Avguštin, Jerneja (comentor)

Črevesna mikrobiota ima pomembno vlogo za razvoj in zdravje človeka. Črevesne disbioze so povezane s številnimi obolenji, vključno s sladkorno boleznijo in debelostjo. Pojavnost obeh, kakor tudi gestacijskega diabetesa mellitus (GDM) zlasti v razvitem svetu narašča. GDM je eden od pomembnih dejavnikov tveganja za rojstvo otroka s preveliko telesno maso, kar imenujemo makrosomija. Slednja predstavlja nevarnost za obporodne poškodbe ter za pojav debelosti in sladkorne bolezni tipa 2 pri otrocih. Zanimalo nas je ali obstajajo povezave med črevesno mikrobioto matere z GDM in pojavom makrosomije. V raziskavo smo vključili 47 nosečnic z GDM in opredelili glavne razlike med mikrobioto nosečnic z GDM, ki so rodile makrosomnega otroka v primerjavi s skupino z nemakrosomnim otrokom. 30 odstotkov nosečnic z GDM je rodilo makrosomnega otroka. Iz 18 vzorcev fecesa v našo raziskavo vključenih nosečnic smo izolirali celokupno DNA in opravili metataksonomsko analizo. V ta namen smo sekvencirali gene za 16S rRNA iz fecesa nosečnic 2. in 3. trimestra (skupaj 36 metagenomov). Na nivoju debel je bila poglavitna razlika med skupinama v relativni zastopanosti Firmicutes in Proteobacteria. Dokazali smo nižji odstotek Firmicutes in višji delež Proteobacteria v skupini nosečnic z makrosomnim otrokom, na račun nižjega odstotka razreda Clostridia in višjega vrste Bilophila wadsworthia. Zaradi naravno raznolike mikrobiote pri posameznikih z analizo sekvenciranega gena za 16S rRNA pogosto ne vidimo jasnih korelacij med sestavo mikrobiote in preučevanim fenotipom gostitelja. Poleg tega zaradi plastičnosti genomov nekaterih bakterijskih vrst lahko na fenotip gostitelja vplivajo le določeni sevi, ki jih s tarčnim sekvenciranjem ne razlikujemo med sabo. V ta namen smo v doktorskem delu okarakterizirali bakterijsko vrsto Escherichia coli. Nosečnice z GDM, ki so rodile makrosomnega otroka so imele v fecesu drugačne populacije E. coli kot nosečnice, ki so rodile nemakrosomnega otroka. Pokazali smo tudi, da je struktura populacij E. coli odvisna od več dejavnikov med drugim od indeksa telesne mase nosečnice pred zanositvijo in od uživanja dodatkov železa ter, da se filogenetska skupina B2 pojavlja v mikrobioti z višjo pestrostjo taksonov v primerjavi z ostalimi filogenetskimi skupinami. Posebno pozornost smo namenili genotoksinom, saj prevalenca sevov E. coli iz skupine B2, ki imajo pogosto zapise za sintezo genotoksinov, v razvitem svetu narašča. 42 odstotkov izolatov iz skupine B2 je imelo zapis za kolibaktin in zapis se je izključno pojavil pri filogenetski skupini B2. Kar 95,5 odstotka izolatov iz B2 je imelo genski zapis za Usp ter tudi 90 odstotkov izolatov iz skupine F. Producent genotoksina je zaščiten pred delovanjem lastnega toksina. Mehanizmi zaščite lahko delujejo širše in zaščitijo bakterijo tudi pred drugimi toksini, kar verjetno daje selektivno prednost sevom, ki se srečujejo s stresnimi pogoji tudi v gostitelju.

• Language: Slovenian
• Keywords: črevesna mikrobiota, nosečnost, gestacijski diabetes mellitus, debelost, kratkoverižne maščobne kisline, Escherichia coli, filogenetske skupine, dejavniki virulence, odpornost proti antibiotikom, genotoksini, protein imunosti ClbS
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Publisher: [K. Molan]
• Year: 2019
• PID: 20.500.12556/RUL-113424
• UDC: 612.63:616.379-008.64(043.3)
• COBISS.SI-ID: 942199
• Publication date in RUL: 02.01.2020

Secondary language

• Language: English
• Title: The gut microbiota of pregnant women with gestational diabetes and emergence of macrosomia

Abstract

The gut microbiota plays an important role in human development and health. Gut dysbiosis has been associated with many diseases, including diabetes and obesity. The incidence of both as well as gestational diabetes mellitus (GDM) is increasing especially in the developed countries. GDM is one of the important risk factors for the birth of an overweight baby, called macrosomia. The latter is associated with birth-related injuries of mother and child as well as increased risk of obesity and diabetes type 2 of the child. In the doctoral thesis, we investigated whether there were links between the gut microbiota of the GDM-women and the occurrence of macrosomia. The study included 47 GDM-women. We defined the main differences between the microbiota of GDM-women with macrosomic baby and the microbiota of GDM-women with non-macrosomic baby. 30 percent of GDM-women gave birth to a macrosomic baby. 18 metagenomes from feces, from the 2nd and 3rd trimesters (in total 36 metagenomes) were included in the NGS analyzes of 16S rRNA gene sequences. At the phyla level, the main differences between the groups were in the relative abundances of Firmicutes and Proteobacteria. We detected a lower percentage of Firmicutes and a higher percentage of Proteobacteria in the group of GDM-women with a macrosomic baby, due to a lower percentage of Clostridia and higher levels of Bilophila wadsworthia. However, we often find that NGS data do not always show clear correlations between microbiota composition and the studied host phenotype, due to microbiota interindividual diversity. In addition, due to genome plasticity of certain bacterial species, only particular strains, which cannot be identified by target sequencing, can be responsible for a particular phenotype. Therefore, we characterized bacteria Escherichia coli. GDM-women who gave birth to a macrosomal baby had different populations of E. coli in the faeces compared to GDM-women who gave birth to a normal weight baby. We have also shown that the structures of E. coli populations depend on several factors, including the body mass index before pregnancy and the consumption of iron supplements, and also that E. coli from B2 phylogroup is associated with microbiota with higher taxa richness. We paid special attention to genotoxins as the prevalence of E. coli strains from B2 group, that often carries genes for genotoxins, has increased significantly in developed countries. 42 percent of the isolates from B2 group had a gene for colibactin and gene was exclusively present in the B2 phylogenetic group. As many as 95,5 percent of B2 isolates had a gene for Usp and also 90 percent of isolates from F group. The genotoxin producer is protected against the action of its own toxin. Mechanisms to protect a producer from the action of their own toxin can act more broadly and can protect the bacteria from other toxins, presumably providing a selective advantage for bacterial strains encountering stressful conditions also within the host.

• Keywords: gut microbiota, pregnancy, gestational diabetes mellitus, obesity, short-chain fatty acids, Escherichia coli, phylogenetic groups, virulence factors, antibiotic resistance, genotoxins, immunity protein ClbS