Urinary Metabolites as Predictors of Acute Mountain Sickness Severity

Urine metabolite profiling in Indian males exposed to high-altitude: a longitudinal pilot study

People who visit high-altitude for research and development work, pilgrimage, recreational purposes and deployments are exposed to different environmental conditions such as low temperature and atmospheric pressure, leading to hypoxia, high radiation, dry air, and non-availability of fresh food and vegetables. These environmental stressors have significant physiological effects on the human body. Among these challenges, hypobaric hypoxia at high-altitude affects aerobic metabolism and thereby reduces the supply of metabolic energy. Metabolic alterations may further lead to extreme environment related maladaptation as evidenced by alterations in the levels of metabolites and metabolic pathways. To investigate the variation in the metabolite profile, urine samples were collected from 16 individuals at baseline (BL, 210 m) and high-altitude (HA, 4200 m). Untargeted urinary metabolic profiling was performed by liquid chromatography-mass spectrometry (LC-MS) in conjunction with statistical analysis. Univariate and multivariate statistical analyses revealed 33 differentially abundant metabolites based on fold change, VIP score and p value. These distinct metabolites were primarily associated with pathways related to phenylalanine, tyrosine and tryptophan biosynthesis; metabolism of phenylalanine, biotin, tyrosine, cysteine and methionine along with alanine, aspartate and glutamate metabolism. Thes pathways are also linked with pentose and glucuronate interconversions, citrate cycle, vitamin B6 and porphyrin metabolism. Furthermore, receiver operating characteristic curve analysis detected five metabolites namely, 2-Tetrahydrothiopheneacetic acid, 1-Benzyl-7,8-dimethoxy-3-phenyl-3H-pyrazolo [3,4-c] isoquinoline, Abietin, 4,4'-Thiobis-2-butanone, and Hydroxyisovaleroyl carnitine with high range of sensitivity and specificity. In summary, this longitudinal study demonstrated novel metabolic variations in humans exposed to high-altitude, utilising the potential of LC-MS based metabolomics. Thus, the present findings shed light on the impact of hypoxic exposure on metabolic adaptation and provide a better understanding about the pathophysiological mechanisms underlying high-altitude illnesses correlated to tissue hypoxia.

Metabolic insights into hypoxia adaptation in adolescent athletes at different altitudes: a cross-sectional study

Athletes use hypoxic training methods to enhance their performance under altitude conditions. Comparative studies involving populations from low (500-2,000 m) and moderate (2,000-3,000 m) altitudes offer an opportunity to understand the mechanisms behind adaptations to hypoxia. The present study combined data from metabolomics analysis based on gas- and liquid-chromatography mass spectrometry (GC-MS and LC-MS) to compare plasma profiles from 80 adolescent athletes at moderate- or low altitudes. 161 metabolites were identified, including 84 elevated and 77 decreased in moderate-altitude adolescents compared to their low-altitude counterparts. Pathway analysis revealed that metabolites related to carbohydrates, amino acids, and lipid metabolism differed between groups. Lipid metabolism was significantly altered in moderate-altitude athletes, including pathways such as linolenic and linoleic acid, sphingolipid, and arachidonic acid, as well as processes involving the transfer of acetyl groups into mitochondria and fatty acid biosynthesis. Biomarker analysis looking for signatures of chronic adaptation to moderate altitude identified glycerol and 5-oxoproline metabolites amongst the variables with the strongest sensitivity and specificity. This study demonstrates differences in metabolic profiles between moderate- and low-altitude populations and highlights the potential of these differential metabolites and associated metabolic pathways to provide new insights into the mechanisms of adaptation to moderate altitude.

[Status of Research on Molecular Mechanisms and Management of Acute Mountain Sickness]

Acute mountain sickness (AMS), a condition characterized primarily by symptoms such as headache and nausea, has a high incidence and seriously affects the life and health of individuals undertaking rapid ascensions to high altitudes. The main pathophysiological manifestations of AMS include cerebral vasodilation and transient increases in intracranial pressure, with severe cases potentially incurring cerebral edema. The occurrence and development of AMS is associated with factors such as the susceptibility, physiological state, and psychological state of an individual. The molecular mechanisms involved include inflammatory responses, oxidative stress, immune regulation, and energy metabolism at the levels of genes, proteins, and metabolism. The management of AMS includes both prevention and treatment strategies. This article provides a comprehensive discussion of AMS from several aspects, including diagnosis, pathophysiological manifestations, susceptibility factors, molecular mechanisms, and prevention and treatment strategies.

A global view on quantitative proteomic and metabolic analysis of rat livers under different hypoxia protocols

Hypobaric hypoxia causes altitude sickness and significantly affects human health. As of now, focusing on rats different proteomic and metabolic changes exposed to different hypoxic times at extreme altitude is blank. Our study integrated in vivo experiments with tandem mass tag (TMT)- and gas chromatography time-of-flight (GC-TOF)-based proteomic and metabolomic assessments, respectively. Male Sprague-Dawley rats were exposed to long-term constant hypoxia for 40 days or short-term constant hypoxia for three days, and their responses were compared with those of a normal control group. Post-hypoxia, serum marker assays related to lipid metabolism revealed significant increases in the levels of low-density lipoprotein (LDL), triglycerides (TG), and total cholesterol (TC) in the liver. In contrast, high-density lipoprotein (HDL) levels were upregulated in the long-term constant hypoxia cohorts and were significantly reduced in the short-term constant hypoxia cohorts. Furthermore, metabolic pathway analysis indicated that glycerolipid and glycerophospholipid metabolisms were the most significantly affected pathways in long-term hypoxia group. Subsequently, RT-qPCR analyses were performed to corroborate the key regulatory elements, including macrophage galactose-type lectin (MGL) and Fatty Acid Desaturase 2 (FADS2). The results of this study provide new information for understanding the effects of different hypobaric hypoxia exposure protocols on protein expression and metabolism in low-altitude animals.

Hyperoxic recovery interferes with the metabolic imprint of hypoxic exercise

Supplemental oxygen (hyperoxia) improves physical performance during hypoxic exercise. Based on the analysis of metabolome and iron homeostasis from human athlete blood samples, we show that hyperoxia during recovery periods interferes with metabolic alterations following hypoxic exercise. This may impair beneficial adaptations to exercise and/or hypoxia and highlights risks of oxygen supplementation in hypoxia.

Recent advances in predicting acute mountain sickness: from multidimensional cohort studies to cutting-edge model applications

High-altitude illnesses, encompassing a spectrum of health threats including Acute Mountain Sickness (AMS), pose significant challenges to individuals exposed to high altitude environments, necessitating effective prophylaxis and immediate management. Given the variability in individual responses to these conditions, accurate prediction of high-altitude illnesses onset is of paramount importance. This review systematically consolidates recent advancements in research on predicting AMS by evaluating existing cohort data, predictive models, and methodologies, while also delving into the application of emerging technologies. Through a thorough analysis of scholarly literature, we discuss traditional prediction methods anchored in physiological parameters (e.g., heart rate, respiratory frequency, blood pressure) and biochemical markers, as well as the integration and utility of novel technologies such as biosensors, genetic testing, and artificial intelligence within high-altitude prediction research. While conventional pre-diction techniques have been extensively used, they are often constrained by limitations in accuracy, reliability, and multifactorial influences. The advent of these innovative technologies holds promise for more precise individual risk assessments and personalized preventive and therapeutic strategies across various forms of AMS. Future research endeavors must pivot decisively towards the meticulous identification and stringent validation of innovative predictive biomarkers and models. This strategic re-direction should catalyze intensified interdisciplinary cooperation to significantly deepen our mechanistic insights into the pathogenesis of AMS while refining existing prediction methodologies. These groundbreaking advancements harbor the potential to fundamentally transform preventive and therapeutic frameworks for high-altitude illnesses, ultimately securing augmented safety standards and wellbeing for individuals operating at elevated altitudes with far-reaching global implications.

Rapid altitude displacement induce zebrafish appearing acute high altitude illness symptoms

Rapid ascent to high-altitude areas above 2500 m often leads to acute high altitude illness (AHAI), posing significant health risks. Current models for AHAI research are limited in their ability to accurately simulate the high-altitude environment for drug screening. Addressing this gap, a novel static self-assembled water vacuum transparent chamber was developed to induce AHAI in zebrafish. This study identified 6000 m for 2 h as the optimal condition for AHAI induction in zebrafish. Under these conditions, notable behavioral changes including slow movement, abnormal exploration behavior and static behavior in the Novel tank test. Furthermore, this model demonstrated changes in oxidative stress-related markers included increased levels of malondialdehyde, decreased levels of glutathione, decreased activities of superoxide dismutase and catalase, and increased levels of inflammatory markers IL-6, IL-1β and TNF-α, and inflammatory cell infiltration and mild edema in the gill tissue, mirroring the clinical pathophysiology observed in AHAI patients. This innovative zebrafish model not only offers a more accurate representation of the high-altitude environment but also provides a high-throughput platform for AHAI drug discovery and pathogenesis research.

A sportomics soccer investigation unveils an exercise-induced shift in tyrosine metabolism leading to hawkinsinuria

Tyrosine metabolism has an intense role in the synthesis of neurotransmitters. Our study used an untargeted, sportomics-based analysis of urine samples to investigate changes in metabolism during a soccer match in 30 male junior professional soccer players. Samples were collected before and after the match and analyzed using liquid chromatography and mass spectrometry. Results showed significant changes in tyrosine metabolism. Exercise caused a downregulation of the homogentisate metabolites 4-maleylacetoacetate and succinylacetone to 20% (p = 4.69E-5) and 16% (p = 4.25E-14), respectively. 4-Hydroxyphenylpyruvate, a homogentisate precursor, was found to be upregulated by 26% (p = 7.20E-3). The concentration of hawkinsin and its metabolite 4-hydroxycyclohexyl acetate increased ~six-fold (p = 1.49E-6 and p = 9.81E-6, respectively). Different DOPA metabolism pathways were also affected by exercise. DOPA and dopaquinone increased four-to six-fold (p = 5.62E-14 and p = 4.98E-13, respectively). 3-Methoxytyrosine, indole-5,6-quinone, and melanin were downregulated from 1 to 25%, as were dopamine and tyramine (decreasing to up to 5% or 80%; p= 5.62E-14 and p = 2.47E-2, respectively). Blood TCO₂ decreased as well as urinary glutathione and glutamate (40% and 10% respectively) associated with a two-fold increase in pyroglutamate. Our study found unexpected similarities between exercise-induced changes in metabolism and the inherited disorder Hawkinsinuria, suggesting a possible transient condition called exercise-induced hawkinsinuria (EIh). Additionally, our research suggests changes in DOPA pathways may be involved. Our findings suggest that soccer exercise could be used as a model to search for potential countermeasures in Hawkinsinuria and other tyrosine metabolism disorders.

AZU1 (HBP/CAP37) and PRKCG (PKC-gamma) may be candidate genes affecting the severity of acute mountain sickness

BACKGROUND

Acute Mountain Sickness (AMS) is one of the diseases that predispose to sudden ascent to high altitudes above 2500 m. Among the many studies on the occurrence and development of AMS, there are few studies on the severity of AMS. Some unidentified phenotypes or genes that determine the severity of AMS may be vital to elucidating the mechanisms of AMS. This study aims to explore the underlying genes or phenotypes associated with AMS severity and to provide evidence for a better understanding of the mechanisms of AMS.

METHODS

GSE103927 dataset was downloaded from the Gene Expression Omnibus database, and a total of 19 subjects were enrolled in the study. Subjects were divided into a moderate to severe AMS (MS-AMS, 9 subjects) group and a no or mild AMS (NM-AMS, 10 subjects) group based on the Lake Louise score (LLS). Various bioinformatics analyses were used to compare the differences between the two groups. Another dataset, Real-time quantitative PCR (RT-qPCR), and another grouping method were used to validate the analysis results.

RESULT

No statistically significant differences in phenotypic and clinical data existed between the MS-AMS and NM-AMS groups. Eight differential expression genes are associated with LLS, and their biological functions are related regulating of the apoptotic process and programmed cell death. The ROC curves showed that AZU1 and PRKCG had a better predictive performance for MS-AMS. AZU1 and PRKCG were significantly associated with the severity of AMS. The expression of AZU1 and PRKCG were significantly higher in the MS-AMS group compared to the NM-AMS group. The hypoxic environment promotes the expression of AZU1 and PRKCG. The results of these analyses were validated by an alternative grouping method and RT-qPCR results. AZU1 and PRKCG were enriched in the Neutrophil extracellular trap formation pathway, suggesting the importance of this pathway in influencing the severity of AMS.

CONCLUSION

AZU1 and PRKCG may be key genes influencing the severity of acute mountain sickness, and can be used as good diagnostic or predictive indicators of the severity of AMS. Our study provides a new perspective to explore the molecular mechanism of AMS.

Metabolomic and Proteomic Identification of Serum Exosome for Hypoxic Preconditioning Participants

Background

In high-altitude areas, hypoxic stress can elicit a series of physiological responses in humans. Exosomes play important roles in both local and distal cellular communications.

Methods

We used ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) studies to analyze the differentially expressed metabolomics and proteomics in serum exosome of hypoxic preconditioning participants and control subjects in the hypoxic conditions.

Results

Fifty-seven military personnel were divided into hypoxic preconditioning group (n = 27) and control group (n = 30). One hundred thirty-six differentially expressed serum exosomal metabolites were found between the hypoxic preconditioning and control groups in the hypoxic conditions, and these differentially expressed metabolites were enriched in pathways related to lysine degradation, butanoate metabolism, GABAergic synapse, histidine metabolism, and linoleic acid metabolism. In addition, hypoxic preconditioning participants showed 102 excellent differential expressions of proteomics compared to controls, which involved actin cytoskeleton organization, hemostasis, complement and coagulation cascades, vesicle-medicated transport, wound healing, etc.

Conclusions

We revealed that the expression of exosomal metabolites and proteomics in hypoxic preconditioning participants was significantly different compared to controls in hypoxic conditions.

Metabolomic analysis of human plasma sample after exposed to high altitude and return to sea level

When ascending to high altitude, it is a rigorous challenge to people who living in the low altitude area to acclimatize to hypoxic environment. Hypoxia exposure can cause dramatic disturbances of metabolism. This longitudinal cohort study was conducted to delineate the plasma metabolomics profile following exposure to altitude environments and explore potential metabolic changes after return to low altitude area. 25 healthy volunteers living in the low altitude area (Nor; 40m) were transported to high altitude (HA; 3,650m) for a 7-day sojourn before transported back to the low altitude area (HAP; 40m). Plasma samples were collected on the day before ascending to HA, the third day on HA(day 3) and the fourteenth day after returning to low altitude(14 day) and analyzed using UHPLC-MS/MS tools and then the data were subjected to multivariate statistical analyses. There were 737 metabolites were obtained in plasma samples with 133 significantly changed metabolites. We screened 13 differential metabolites that were significantly changed under hypoxia exposure; enriched metabolic pathways under hypoxia exposure including tryptophan metabolism, purine metabolism, regulation of lipolysis in adipocytes; We verified and relatively quantified eight targeted candidate metabolites including adenosine, guanosine, inosine, xanthurenic acid, 5-oxo-ETE, raffinose, indole-3-acetic acid and biotin for the Nor and HA group. Most of the metabolites recovered when returning to the low altitude area, however, there were still 6 metabolites that were affected by hypoxia exposure. It is apparent that high-altitude exposure alters the metabolic characteristics and two weeks after returning to the low altitude area a small portion of metabolites was still affected by high-altitude exposure, which indicated that high-altitude exposure had a long-term impact on metabolism. This present longitudinal cohort study demonstrated that metabolomics can be a useful tool to monitor metabolic changes exposed to high altitude, providing new insight in the attendant health problem that occur in response to high altitude.

High Intensity Concentric-Eccentric Exercise Under Hypoxia Changes the Blood Metabolome of Trained Athletes

The aim of this study was to determine alterations of the metabolome in blood plasma in response to concentric-eccentric leg exercise performed at a simulated altitude of 3,500 m. To do so, we recruited 11 well-trained subjects and performed an untargeted metabolomics analysis of plasma samples obtained before, 20 min after as well as on day 8 after five sets of maximal, concentric-eccentric leg exercises that lasted 90 s each. We identified and annotated 115 metabolites through untargeted liquid chromatography-mass spectrometry metabolomics and used them to further calculate 20 sum/ratio of metabolites. A principal component analysis (PCA) revealed differences in-between the overall metabolome at rest and immediately after exercise. Interestingly, some systematic changes of relative metabolite concentrations still persisted on day 8 after exercise. The first two components of the PCA explained 34% of the relative concentrations of all identified metabolites analyzed together. A volcano plot indicates that 35 metabolites and two metabolite ratios were significantly changed directly after exercise, such as metabolites related to carbohydrate and TCA metabolism. Moreover, we observed alterations in the relative concentrations of amino acids (e.g., decreases of valine, leucine and increases in alanine) and purines (e.g., increases in hypoxanthine, xanthine and uric acid). In summary, high intensity concentric-eccentric exercise performed at simulated altitude systematically changed the blood metabolome in trained athletes directly after exercise and some relative metabolite concentrations were still changed on day 8. The importance of that persisting metabolic alterations on exercise performance should be studied further.