High-altitude exposure decreases bone mineral density and its relationship with gut microbiota: Results from the China multi-ethnic cohort (CMEC) study

High-altitude-induced alterations in intestinal microbiota

In high-altitude environments characterized by low pressure and oxygen levels, the intestinal microbiota undergoes significant alterations. Whether individuals are subjected to prolonged exposure or acute altitude changes, these conditions lead to shifts in both the diversity and abundance of intestinal microbiota and changes in their composition. While these alterations represent adaptations to high-altitude conditions, they may also pose health risks through certain mechanisms. Changes in the intestinal microbiota induced by high altitudes can compromise the integrity of the intestinal mucosal barrier, resulting in gastrointestinal dysfunction and an increased susceptibility to acute mountain sickness (AMS). Moreover, alterations in the intestinal microbiota have been implicated in the induction or exacerbation of chronic heart failure. Targeted modulation of the intestinal microbiota holds promise in mitigating high-altitude-related cardiac damage. Dietary interventions, such as adopting a high-carbohydrate, high-fiber, low-protein, and low-fat diet, can help regulate the effects of intestinal microbiota and their metabolic byproducts on intestinal health. Additionally, supplementation with probiotics, either through dietary sources or medications, offers a means of modulating the composition of the intestinal microbiota. These interventions may offer beneficial effects in preventing and alleviating AMS following acute exposure to high altitudes.

Polymorphic transposable elements provide new insights on high-altitude adaptation in the Tibetan Plateau

Several studies demonstrated that populations living in the Tibetan plateau are genetically and physiologically adapted to high-altitude conditions, showing genomic signatures ascribable to the action of natural selection. However, so far most of them relied solely on inferences drawn from the analysis of coding variants and point mutations. To fill this gap, we focused on the possible role of polymorphic transposable elements in influencing the adaptation of Tibetan and Sherpa highlanders. To do so, we compared high-altitude and middle/low-lander individuals of East Asian ancestry by performing in silico analyses and differentiation tests on 118 modern and ancient samples. We detected several transposable elements associated with high altitude, which map genes involved in cardiovascular, hematological, chem-dependent and respiratory conditions, suggesting that metabolic and signaling pathways taking part in these functions are disproportionately impacted by the effect of environmental stressors in high-altitude individuals. To our knowledge, our study is the first hinting to a possible role of transposable elements in the adaptation of Tibetan and Sherpa highlanders.

Antimicrobial resistance and genomic investigation of Salmonella isolated from retail foods in Guizhou, China

Introduction

Salmonella is a major foodborne pathogen worldwide that causes severe morbidity and mortality. It is mainly caused by consuming contaminated food, with retail food considered the primary source.

Methods

In Guizhou, China, 102 Salmonella strains isolated from 2016 to 2021 underwent phenotypic antimicrobial resistance testing and whole-genome sequencing (WGS) to understand Salmonella diversity, including serotypes, sequencing types (STs), antimicrobial genes, virulence genes, plasmid types, multi-locus sequence types (MLST), and core genome MLST (cgMLST).

Results and discussion

S.Typhimurium was the dominant serotype, and O:4(B) was the leading serogroup. The most prevalent genotype was ST40. Phenotypic antimicrobial resistance identified 66.7% of the sampled isolates as multi-drug resistant (MDR). S.Enteritidis (n = 7), S.Typhimurium (n = 1), S.Indiana (n = 1), S.Kentucky (n = 1), S.Uganda (n = 1), all of which were MDR, were resistant to Colistin. Resistance rates varied significantly across different strains and food types, particularly meat products exhibiting higher resistance. Notably, significant increases in resistance were observed from 2016 to 2021 for the following: ≥ 1 resistant (P = 0.001), MDR (P = 0.001), ampicillin (P = 0.001), tetracycline (P < 0.001), chloramphenicol (P = 0.030), and trimethoprim/sulfamethoxazole (P = 0.003). The marked escalation in drug resistance over the recent years, coupled with the varying resistance rates among food sources, underscores the growing public health concern. Our findings highlight the need for a coordinated approach to effectively monitor and respond to Salmonella infections in Guizhou, China.

Targeting the gut microbiota-related metabolites for osteoporosis: The inextricable connection of gut-bone axis

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass, destruction of bone microstructure, raised bone fragility, and enhanced risk of fractures. The correlation between gut microbiota and bone metabolism has gradually become a widespread research hotspot in recent years, and successive studies have revealed that the alterations of gut microbiota and its-related metabolites are related to the occurrence and progression of osteoporosis. Moreover, several emerging studies on the relationship between gut microbiota-related metabolites and bone metabolism are also underway, and extensive research evidence has indicated an inseparable connection between them. Combined with latest literatures and based on inextricable connection of gut-bone axis, this review is aimed to summarize the relation, potential mechanisms, application strategies, clinical application prospects, and existing challenges of gut microbiota and its-related metabolites on osteoporosis, thus updating the knowledge in this research field and providing certain reference for future researches.

Lactobacillus plantarum attenuates glucocorticoid-induced osteoporosis by altering the composition of rat gut microbiota and serum metabolic profile

Introduction

Osteoporosis, one of the most common non-communicable human diseases worldwide, is one of the most prevalent disease of the adult skeleton. Glucocorticoid-induced osteoporosis(GIOP) is the foremost form of secondary osteoporosis, extensively researched due to its prevalence.Probiotics constitute a primary bioactive component within numerous foods, offering promise as a potential biological intervention for preventing and treating osteoporosis. This study aimed to evaluate the beneficial effects of the probiotic Lactobacillus plantarum on bone health and its underlying mechanisms in a rat model of glucocorticoid dexamethasone-induced osteoporosis, using the osteoporosis treatment drug alendronate as a reference.

Methods

We examined the bone microstructure (Micro-CT and HE staining) and analyzed the gut microbiome and serum metabolome in rats.

Results and discussion

The results revealed that L. plantarum treatment significantly restored parameters of bone microstructure, with elevated bone density, increased number and thickness of trabeculae, and decreased Tb.Sp. Gut microbiota sequencing results showed that probiotic treatment increased gut microbial diversity and the ratio of Firmicutes to Bacteroidota decreased. Beneficial bacteria abundance was significantly increased (Lachnospiraceae_NK4A136_group, Ruminococcus, UCG_005, Romboutsia, and Christensenellaceae_R_7_group), and harmful bacteria abundance was significantly decreased (Desulfovibrionaceae). According to the results of serum metabolomics, significant changes in serum metabolites occurred in different groups. These differential metabolites were predominantly enriched within the pathways of Pentose and Glucuronate Interconversions, as well as Propanoate Metabolism. Furthermore, treatment of L. plantarum significantly increased serum levels of Pyrazine and gamma-Glutamylcysteine, which were associated with inhibition of osteoclast formation and promoting osteoblast formation. Lactobacillus plantarum can protect rats from DEX-induced GIOP by mediating the "gut microbial-bone axis" promoting the production of beneficial bacteria and metabolites. Therefore L. plantarum is a potential candidate for the treatment of GIOP.

Diets intervene osteoporosis via gut-bone axis

Osteoporosis is a systemic skeletal disease that seriously endangers the health of middle-aged and older adults. Recently, with the continuous deepening of research, an increasing number of studies have revealed gut microbiota as a potential target for osteoporosis, and the research concept of the gut-bone axis has gradually emerged. Additionally, the intake of dietary nutrients and the adoption of dietary patterns may affect the gut microbiota, and alterations in the gut microbiota might also influence the metabolic status of the host, thus adjusting bone metabolism. Based on the gut-bone axis, dietary intake can also participate in the modulation of bone metabolism by altering abundance, diversity, and composition of gut microbiota. Herein, combined with emerging literatures and relevant studies, this review is aimed to summarize the impacts of different dietary components and patterns on osteoporosis by acting on gut microbiota, as well as underlying mechanisms and proper dietary recommendations.

Moderate altitude exposure impacts host fasting blood glucose and serum metabolome by regulation of the intestinal flora

Moderate altitude exposure has shown beneficial effects on diabetes incidence but the underlying mechanisms are not understood. Our study aimed to investigate how the human gut microbiome impacted the serum metabolome and associated with glucose homeostasis in healthy Chinese individuals upon moderate-altitude exposure. Faecal microbiome composition was assessed using shotgun metagenomic sequencing. Serum metabolome was acquired by untargeted metabolomics technology, and amino acids (AAs) and propionic acid in serum were quantified by targeted metabolomics technology. The results indicated that the moderate-altitude exposed individuals presented lowered fasting blood glucose (FBG) and propionic acid, increased circulating L-Glutamine but decreased L-Glutamate and L-Valine, which correlated with enriched Bacteroidetes and decreased Proteobacteria. Additionally, the silico causality associations among gut microbiota, serum metabolome and host FBG were analyzed by mediation analysis. It showed that increased Bacteroides ovatus (B. ovatus) and decreased Escherichia coli (E. coli) were identified as the main antagonistic species driving the association between L-Glutamate and FBG in silico causality. Furthermore, the high-fat diet (HFD) fed mice subjected to faecal microbiota transplantation (FMT) were applied to validate the cause-in-fact effects of gut microbiota on the beneficial glucose response. We found that microbiome in the moderate-altitude exposed donor could predict the extent of the FBG response in recipient mice, which showed lowered FBG, L-Glutamate and Firmicutes/Bacteroidetes ratio. Our findings suggest that moderate-altitude exposure targeting gut microbiota and circulating metabolome, may pave novel avenues to counter dysglycemia.

Microbiota and mycobiota in bronchoalveolar lavage fluid of silicosis patients

BACKGROUND

The contribution of bronchoalveolar lavage fluid (BALF) microbiota and mycobiota to silicosis has recently been noticed. However, many confounding factors can influence the accuracy of BALF microbiota and mycobiota studies, resulting in inconsistencies in the published results. In this cross-sectional study, we systematically investigated the effects of "sampling in different rounds of BALF" on its microbiota and mycobiota. We further explored the relationship between silicosis fatigue and the microbiota and mycobiota.

METHODS

After obtaining approval from the ethics board, we collected 100 BALF samples from 10 patients with silicosis. Demographic data, clinical information, and blood test results were also collected from each patient. The characteristics of the microbiota and mycobiota were defined using next-generation sequencing. However, no non-silicosis referent group was examined, which was a major limitation of this study.

RESULTS

Our analysis indicated that subsampling from different rounds of BALF did not affect the alpha- and beta-diversities of microbial and fungal communities when the centrifuged BALF sediment was sufficient for DNA extraction. In contrast, fatigue status significantly influenced the beta-diversity of microbes and fungi (Principal Coordinates Analysis, P = 0.001; P = 0.002). The abundance of Vibrio alone could distinguish silicosis patients with fatigue from those without fatigue (area under the curve = 0.938, 95% confidence interval [CI] 0.870-1.000). Significant correlations were found between Vibrio and haemoglobin levels (P < 0.001, ρ = -0.64).

CONCLUSIONS

Sampling in different rounds of BALF showed minimal effect on BALF microbial and fungal diversities; the first round of BALF collection was recommended for microbial and fungal analyses for convenience. In addition, Vibrio may be a potential biomarker for silicosis fatigue screening.

Association of long-term exposure to ambient PM2.5 and its constituents with gut microbiota: Evidence from a China cohort

Accumulating animal experiments and epidemiological studies have found that exposure to fine particulate matter (PM_2.5) is associated with altered gut microbiota (GM). However, it is unclear what kind of role the PM_2.5 constituents play in the PM_2.5-GM association. Therefore, this study aimed to investigate the association of long-term exposure to PM_2.5 and its constituents (PM_cons) with GM. This study included 1583 participants from a cohort in Southwest China. Satellite remote sensing and chemical transport modelling were used to determine the yearly average concentrations of PM_cons. GM data were derived from 16 s sequencing based on stool samples. Generalized propensity score weighting regression and Bayesian Kernel Machine Regression (BKMR) were used to estimate the individual and joint association of exposure to PM_cons with the Shannon index. The weighted correlation analysis was used to estimate the association of PM_cons with the composition of GM. The result showed that an interquartile range increase of 3-year average black carbon (BC), ammonium, nitrate, organic matter (OM), sulfate, and soil particles (SOIL) were negatively associated with Shannon index with mean difference (95 % confidence interval) being -0.144 (-0.208, -0.080), -0.141 (-0.205, -0.078), -0.126 (-0.184, -0.068), -0.117 (-0.172, -0.062), -0.153 (-0.221, -0.085), and - 0.153 (-0.222, -0.085). BKMR indicated joint exposure to PM_cons was associated with decreased Shannon index, and BC had the largest posterior inclusion probability (0.578). Weighted correlation analyses indicated PM_cons were associated with decreased Bacteroidetes (r = -0.204, P < 0.001 for PM_2.5) and increased Proteobacteria (r = 0.273, P < 0.001 for PM_2.5). These results revealed that long-term exposure to PM_cons was associated with GM. BC was the most important constituent in the association, indicating that the source of BC should be controlled to mitigate the negative effects of PM_2.5 on GM.

Oral mycobiota and pancreatic ductal adenocarcinoma

Early detection of pancreatic ductal adenocarcinoma (PDAC) is essential for survival. Preliminary research demonstrated significant associations between structural alternation of mycobiota and PDAC. In this study, we investigated the associations between oral mycobiota and PDAC. We further explored mycobiota biomarkers for PDAC detection. We enrolled 34 PDAC patients and 35 matched healthy controls from West China hospital in Southwest China. Demographic data, clinical information, and salivary samples were collected. Mycobiota characteristics were defined using Internal Transcribed Spacer (ITS) ribosomal RNA sequencing. We found that the PDAC patients had significant increase in fungal abundance (P < 0.001) and significant decrease in fungal diversity (P < 0.001) in comparison to the healthy controls. A higher abundance of Basidiomycota and Unclassifed_p_Ascomycota was associated with an increased risk of PDAC. With each increase of abundance of g__unclassified_k__Fungi and g__unclassified_p__Ascomycota in PDAC patients, the risk of pancreatic cancer increased by 1.359 odds and 1.260 odds, respectively. Aspergillus (AUC = 0.983, 95% CI 0.951-1.000) and Cladosporium (AUC = 0.969, 95% CI 0.921-1.000) achieved high classification powers to distinguish PDAC patients from the healthy controls. The rapid, inexpensive tests of ITS1 sequencing of mycobiota and PCR detection of potential fungal biomarkers make it promising for the clinical practice to use oral microbes for PDAC early detection and prevention. Results of our study provide evidence that salivary mycobiota may provide insights into cancer risk, prevention, and detection.