Effect of Microgravity on the Gut Microbiota Bacterial Composition in a Hindlimb Unloading Model

Abstract

We utilised a ground-based microgravity hindlimb unloading (HU) mouse model to elucidate the gut microbiota bacterial changes in mice under a simulated microgravity environment. Four-month-old, male C57/Bl6 mice were randomly divided into ground-based controls and the HU groups and kept under controlled environmental conditions. For the microgravity environment, the mice were suspended in special cages individually for 20 days. At the end of the suspension, the mice were sacrificed; gut dissections were performed, followed by a metagenomic analysis of bacterial species, which was carried out by extracting DNA and 16S rRNA analysis. The results revealed that the gut bacterial communities of mice under gravity and microgravity were different. Notably, our findings revealed differences in the bacterial community structure. Around 449 bacterial OTUs were specific to mice kept under normal gravity versus 443 bacterial OTUs under microgravity conditions. In contrast, 694 bacterial OTUs were common to both groups. When the relative abundance of taxa was analyzed, Bacteroidetes dominated the gut (64.7%) of normal mice. Conversely, mice in the microgravity environment were dominated by Firmicutes (42.7%), and the relative abundance of Bacteroidetes differed significantly between the two groups (p < 0.05). The distribution of Muribaculaceae between normal mice versus microgravity mice was significantly different, at 62% and 36.4%, respectively (p < 0.05). Furthermore, a significant decrease in 11 bacteria was observed in mice under simulated microgravity, including Akkermansia muciniphila, Eubacterium coprostanoligenes, Bacteroides acidifaciens, Clostridium leptum, Methylorubrum extorquens, Comamonas testosterone, Desulfovibrio fairfieldensis, Bacteroides coprocola, Aerococcus urinaeequi, Helicobacter hepaticus, and Burkholderiales. Further studies are needed to elucidate gut bacterial metabolites of these identified bacterial species in microgravity conditions and normal environment. Notably, the influence of these metabolites on obesity, neuroprotection, musculoskeletal and cardiovascular dysfunction, longevity, inflammation, health, and disease in astronauts ought to be investigated and will be important in developing procedures against adverse effects in astronauts following space travel.

The microbiota of long-living and cancer-free blind mole rat $\textit{(Nannospalax xanthodon)}$ from the edge of its distribution in Northern Anatolia

“…Interestingly, the possible role of the Muribaculaceae family on extended life span was discussed by [44]. It should be noted, however, that Muribaculaceae also has a high abundance in short-living rodents [47,53,54] and other (possibly long-living) members of the family Spalacidae [55]. The association of this family with the host longevity thus deserves a more thorough and focused study.…”

How the adaptation of the human microbiome to harsh space environment can determine the chances of success for a space mission to Mars and beyond

“…Microgravity may affect various cellular functions, such as cell morphology, growth rate, biofilm formation, gene expression, microbial mutations, antibiotic resistance, virulence, and resistance to adapt to simulated microgravity ( Table 1 ). Moreover, microgravity stress has been reported to alter bacterial microbiome diversity and composition in animal models ( Wang et al, 2020 ; Siddiqui et al, 2022 ; Yuan et al, 2023 ). Disruption of microbiome and metabolites may be associated with dysbiosis-related diseases such as inflammatory bowel disease, obesity, autism, allergy, diabetes, and some gastrointestinal cancers ( Degruttola et al, 2016 ; Figure 3 ).…”

“…Using a ground-based microgravity hindlimb unloading (HU) mouse model, Siddiqui et al (2022) have shown that the amount of several bacterial species is significantly lower in mice in microgravity conditions compared to in mice on Earth. Additionally, several changes were observed perceived in the ratio of Bacteroidetes to Firmicutes under simulated microgravity conditions.…”

Prospective Use of Probiotics to Maintain Astronaut Health during Spaceflight

“…A study by Siddiqui et al [ 22 ] used a hindlimb unloading (HU) mouse model on the ground to simulate microgravity conditions to investigate changes in the gut microbiota bacterial composition. They found that hindlimb unloading causes changes in the gut microbiota, including a decrease in the diversity of useful gut microbiota which can lead to increased permeability and gut inflammation.…”

“…Firmicutes play a role in host metabolism and nutrition, while Bacteroidetes are associated with immunomodulation. These results suggest that changes in the gut microbiota may contribute to negative health effects experienced in spaceflight [ 22 ].…”