Page 29 - EJMO-9-2

Eurasian Journal of
Medicine and Oncology Gut microbiome effects on obesity

are Bacillota and Bacteroidota. Until recent years, the first contact with the maternal microbiota during birth
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majority of gut microorganisms remained unidentified, and culminating in a highly dense and diverse microbial
mainly due to their anerobic nature, which made them community. It has been shown that facultative anerobic
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difficult to cultivate. The advent of the polymerase chain bacteria are usually the first colonizers, followed by strictly
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reaction targeting the 16S rRNA gene, coupled with next- anerobic genera, including Bacteroides, Bifidobacterium,
generation sequencing and advanced bioinformatics tools, Eubacterium, and Clostridium. 98,99
has facilitated the precise identification of various bacterial Breast milk also has a potential role in GM development.
strains and the functional attributes of GM. 83,84 A study of 94 premature mother-child dyads found that 30
Many factors, including nutritional, chemical, and – 40% of the bacteria present in an infant’s gut were also
immunological gradients along the gut, can affect found in breast milk, suggesting bacterial transfer. These
the composition and density of GM. Indeed, it varies interactions were influenced by dietary practices and
according to different intestinal regions, where pH levels, antibiotic use. 100
oxygen tension, host secretions, and substrate availability The GM of a newborn takes around 2 – 3 years to develop
fluctuate. 85 and stabilize into a profile similar to that of an adult. In
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In the small intestine, transit time is short, with generally normal and healthy individuals, the GM is principally
elevated levels of acids, oxygen, and antimicrobials. These dominated by Firmicutes, Bacteroidetes, Proteobacteria,
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properties hinder bacterial proliferation, allowing only and Actinobacteria. An analysis of GM in Moroccan
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facultative anerobes characterized by rapid growth and residents showed a large percentage of Bacteroides (62.6%).
adherence to epithelia or mucus to survive. 86 In addition, the genera Prevotella, Prevotella copri, and
Meanwhile, the colon provides different conditions that Prevotella stercorea, as well as Fecalibacterium prosnitzi,
support a diverse bacterial community, mainly anerobes were significantly dominant in these samples. 103
capable of metabolizing complex carbohydrates that go Throughout life, human GM undergoes multiple
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through incomplete digestion in the small intestine. It changes related to lifestyle. A high-fiber diet increases the
has been shown that Firmicutes (60 – 80%), Bacteroidetes abundance of beneficial bacteria such as Lactobacillus,
(20 – 40%), the Verrucomicrobia, the Actinobacteria, and a Akkermansia, and Bifidobacterium while reducing
reduced presence of Proteobacteria are five predominantly opportunistic pathogenic bacteria such as Desulfovibrio
phyla of bacteria in the normal human GM. 88 and Klebsiella. In 2010, researchers compared the GM
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of European children to that of children living in a rural
3.1. GM: Coevolution with human life village of Burkina Faso, where a fiber-rich diet is common.
The human fetus has long been considered microbiologically The results have showed significant differences in microbial
sterile. The predominant assumption suggests that the first composition. Burkinabe children had a high abundance
human encounter and interaction with bacteria occur of Bacteroides and a clear reduction in Firmicutes, with
at birth when the newborn comes into contact with the increased Prevotella and Xylanibacter, both adapted to fiber
surrounding environment. 89,90 However, some studies degradation, and higher short-chain fatty acid (SCFA)
suggest that the human GM is generally established before levels (P < 0.001). Moreover, pathogenic bacteria such us
birth. 91 Shigella and Escherichia were significantly less common in
these children than in European children. 105
This exposure to microbiota is highly beneficial and
plays a critical role in programming the maturation of Poor sleep also affects GM, as shown by the critical role
an infant’s immunity during fetal life. Bacterial DNA is a of the brain-gut-microbiota axis in sleep intensification.
key factor in this process. Other research indicates that Recent research has explored the impact of sleep disorders
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contact with maternal microbiota through the placenta has such as fragmentation, sleep deprivation, obstructive sleep
been associated with adverse outcomes, including preterm apnea, insomnia, and circadian rhythm sleep disorders on
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birth, spontaneous abortion, and intrauterine infections, GM composition. Similarly, physical activity could affect
as observed in cases of listeriosis throughout pregnancy. 93 GM by increasing beneficial bacteria, while a healthy GM
The mode of delivery is a key factor shaping the may, in turn, improve exercise performance. 107
composition of an infant’s microbiota. 94,95 Infants delivered The GM presents diurnal oscillations on a global scale,
by cesarean section (C-section) have a different GM with its levels and rhythms fluctuating in accordance with
composition and colonization timeline compared to a 24-h cycle. Using cosinor-based rhythmometry, diurnal
those delivered vaginally. 95,96 The colonization of bacteria signals were detected across different taxonomic levels
in an infant’s gut occurs gradually, beginning with the of the GM, with 57% of phyla following a 24-h rhythmic

Volume 9 Issue 2 (2025) 21 doi: 10.36922/ejmo.8318