The Role of 4-Phenylbutyric Acid in Gut Microbial Dysbiosis in a Mouse Model of Simulated Microgravity

Enhancing microbial diversity as well as multi-organ health in hind-limb unloaded mice

During space travel, the gut microbiota is changed which can lead to health-related issues. Previously, we utilized the hind-limb unloaded (HU) mouse, which is an established ground-based in-vivo model of microgravity and observed altered gut microbiota. In this study, we evaluated the beneficial effects of novel bacterial conditioned media in HU mice to understand if they can offset the effects of unloading in the HU mouse model. We aimed to explore the influence of bacterial conditioned media on diversity and quantity of intestinal microbes in HU mice, and investigated the microarchitecture of mice retinas and kidneys to evaluate the potential systemic effects of bacterial conditioned media in HU mice. Four-month-old, male C57/Bl6 mice were separated into groups: including the ground-based control group, the HU group mice fed with vehicle as placebo (HU-placebo mice), and the HU group fed with bacterial conditioned media (HU-CP mice) and kept under controlled environmental conditions for three weeks. Next, mice were sacrificed; gut dissections were conducted, and metagenomic analysis of bacterial species was performed via DNA extraction and 16S rRNA analysis. The results revealed an HU-induced reduction in intestinal microbial diversity, and an increase in pathogenic bacteria dominated by Firmicutes (45%). In contrast, supplementation with bacterial conditioned media for three weeks led to a significant increase in gut microbial diversity with noticeable changes in the OTUs abundance in the HU mice. Additionally, HU-induced muscle weakness and structural abnormalities in the retina and kidney were partially prevented with bacterial conditioned media. Moreover, a greater diversity of several bacteria in the HU-CP was observed including, Bacteriodota, Firmicutes, Proteobacteria, Actionobacteriota, Verrucomicorbiota, Cyanobacteria, Gemmatimonadota, Acidobacteriota, Chloroflexi, Myxococcota, and others. Prospective research involving molecular mechanistic studies are needed to comprehend the systemic effects of bacterial metabolites conditioned media on experimental animal models under chronic stress.

Serum multi-omics analysis in hindlimb unloading mice model: Insights into systemic molecular changes and potential diagnostic and therapeutic biomarkers

Microgravity, in space travel and prolonged bed rest conditions, induces cardiovascular deconditioning along with skeletal muscle mass loss and weakness. The findings of microgravity research may also aid in the understanding and treatment of human health conditions on Earth such as muscle atrophy, and cardiovascular diseases. Due to the paucity of biomarkers and the unknown underlying mechanisms of cardiovascular and skeletal muscle deconditioning in these environments, there are insufficient diagnostic and preventative measures. In this study, we employed hindlimb unloading (HU) mouse model, which mimics astronauts in space and bedridden patients, to first evaluate cardiovascular and skeletal muscle function, followed by proteomics and metabolomics LC-MS/MS-based analysis using serum samples. Three weeks of unloading caused changes in the function of the cardiovascular system in c57/Bl6 mice, as seen by a decrease in mean arterial pressure and heart weight. Unloading for three weeks also changed skeletal muscle function, causing a loss in grip strength in HU mice and atrophy of skeletal muscle indicated by a reduction in muscle mass. These modifications were partially reversed by a two-week recovery period of reloading condition, emphasizing the significance of the recovery process. Proteomics analysis revealed 12 dysregulated proteins among the groups, such as phospholipid transfer protein, Carbonic anhydrase 3, Parvalbumin alpha, Major urinary protein 20 (Mup20), Thrombospondin-1, and Apolipoprotein C-IV. On the other hand, metabolomics analysis showed altered metabolites among the groups such as inosine, hypoxanthine, xanthosine, sphinganine, l-valine, 3,4-Dihydroxyphenylglycol, and l-Glutamic acid. The joint data analysis revealed that HU conditions mainly impacted pathways such as ABC transporters, complement and coagulation cascades, nitrogen metabolism, and purine metabolism. Overall, our results indicate that microgravity environment induces significant alterations in the function, proteins, and metabolites of these mice. These observations suggest the potential utilization of these proteins and metabolites as novel biomarkers for assessing and mitigating cardiovascular and skeletal muscle deconditioning associated with such conditions.

Metabolomics analysis reveals the differences between Abrus cantoniensis Hance and Abrus mollis Hance

BACKGROUND

Abrus cantoniensis Hance. (Ac) and Abrus mollis (Am), two edible and medicinal plants with economic value in southern China, belong to the Abrus genus. Due to its growth characteristics, Am often replaces Ac in folk medicine. However, the latest National Pharmacopeia of China only recommends Ac. The differences in the metabolite composition of the plants are directly related to the differences in their clinical efficacy.

RESULTS

The difference in metabolites were analyzed using an untargeted metabolomic approach based on ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC‒ESI‒MS/MS). The roots (R), stems (S) and leaves (L) of the two varieties were examined, and 635 metabolites belonging to 8 classes were detected. A comparative study revealed clear variations in the metabolic profiles of the two plants, and the AmR group had more active ingredients (flavonoids and terpenoids) than the AcR group. The metabolites classified as flavonoids and triterpene saponins showed considerable variations among the various samples. Both Ac and Am had unique metabolites. Two metabolites (isovitexin-2''-xyloside and soyasaponin V) specifically belong to Ac, and nine metabolites (vitexin-2"-O-galactoside, ethyl salicylate, 6-acetamidohexanoic acid, rhein-8-O-glucoside, hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)-glucoside, methyl dioxindole-3-acetate, veratric acid, isorhamnetin-3-O-sophoroside-7-O-rhamnoside, and isorhamnetin-3-O-sophoroside) specifically belong to Am.

CONCLUSIONS

The metabolite differences between Ac and Am cause the differences in their clinical efficacy. Our findings serve as a foundation for further investigation of biosynthesis pathways and associated bioactivities and provide guidance for the clinical application of traditional Chinese medicine.

Current Knowledge about the Impact of Microgravity on Gene Regulation

Microgravity (µg) has a massive impact on the health of space explorers. Microgravity changes the proliferation, differentiation, and growth of cells. As crewed spaceflights into deep space are being planned along with the commercialization of space travelling, researchers have focused on gene regulation in cells and organisms exposed to real (r-) and simulated (s-) µg. In particular, cancer and metastasis research benefits from the findings obtained under µg conditions. Gene regulation is a key factor in a cell or an organism’s ability to sustain life and respond to environmental changes. It is a universal process to control the amount, location, and timing in which genes are expressed. In this review, we provide an overview of µg-induced changes in the numerous mechanisms involved in gene regulation, including regulatory proteins, microRNAs, and the chemical modification of DNA. In particular, we discuss the current knowledge about the impact of microgravity on gene regulation in different types of bacteria, protists, fungi, animals, humans, and cells with a focus on the brain, eye, endothelium, immune system, cartilage, muscle, bone, and various cancers as well as recent findings in plants. Importantly, the obtained data clearly imply that µg experiments can support translational medicine on Earth.

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

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.