Acute Exposure to Simulated High-altitude Hypoxia Alters Gut Microbiota in Mice

Gut microbiota bears adaptive potential to different environments, but little is known regarding its responses to acute high-altitude exposure. This study aimed to evaluate the microbial changes after acute exposure to simulated high-altitude hypoxia. C57BL/6J mice were divided into hypoxia and normoxia groups. The hypoxia group was exposed to a simulated altitude of 5500 m for 24 hours above sea level. The normoxia group was maintained in low-altitude of 10 m above sea level. Colonic microbiota was analyzed using 16S rRNA V4 gene sequencing. Compared with the normoxia group, shannon, simpson and Akkermansia were significantly increased, while Firmicutes to Bacteroidetes ratio and Bifidobacterium were significantly decreased in the hypoxia group. The hypoxia group exhibited lower mobile element containing and higher potentially pathogenic and stress tolerant phenotypes than those in the normoxia group. Functional analysis indicated that environmental information processing was significantly lower, metabolism, cellular processes and organismal systems were significantly higher in the hypoxia group than those in the normoxia group. In conclusion, acute exposure to simulated high-altitude hypoxia alters gut microbiota diversity and composition, which may provide a potential target to alleviate acute high-altitude diseases.

Variations in HIF-1α Contributed to High Altitude Hypoxia Adaptation via Affected Oxygen Metabolism in Tibetan Sheep

The Tibetan sheep is an indigenous species of the Tibetan plateau and has been well adapted to high-altitude hypoxia. In comparison to lowland sheep breeds, the blood gas indicators have changed and the HIFs signaling pathway is activated in Tibetan sheep. These phenotypic and genetic alterations in Tibetan sheep are thought to be an important basis for adaptation to high-altitude hypoxia and variation in genes encoding the subunits that make up HIFs, such as HIF-1α can affect blood gas indicators. In this study, exons 9, 10, 12 of the HIF-1α gene were sequenced to find variations and 3 SNPs were detected, and these 3 SNPs were genotyped by KASP in 341 Hu sheep and 391 Tibetan sheep. In addition, 197 Hu sheep, 160 Tibetan sheep and 12 Gansu alpine merino sheep were used for blood gas indicators analysis. The results showed significant differences between the blood gas indicators of high-altitude breeds (Tibetan sheep and Gansu alpine merino sheep) and low-altitude breeds (Hu sheep), implying that the differences in blood gas indicators are mainly caused by differences in altitude. The haplotype combinations H2H3 and H1H3 were more frequent in the Tibetan sheep population, H2H3 increases O2 carrying capacity by increasing hematocrit and hemoglobin concentrations; H1H3 makes O2 dissociate more readily from oxyhemoglobin by decreasing partial pressure of oxygen and oxygen saturation. These results suggest that variants at the HIF-1α promote the ability of oxygen utilization in Tibetan sheep, which may underpin the survival and reproduction of Tibetan sheep on the Tibetan plateau.

Recruitments of Sherpa highlanders and non-Sherpa lowlanders v1

In order to carry out the research project of genetic adaptation to high-altitude hypoxia in Sherpa highlanders, we recruited Sherpa highlanders in Namche Bazaar village at a high altitude of 3,440 meters (m) above sea level and non-Sherpa lowlanders in Kathmandu city at 1,300 m in Nepal. Venous blood was sampled to obtain plasma and extract DNA in each subject. The concentrations of factors in plasma were measured. The single-nucleotide polymorphisms (SNPs) in the hypoxia-associated genes were genotyped.

Selection of Species Specific Panel of Reference Genes Across Native Livestock Species Adapted to Trans-Himalayan Region of Leh-ladakh

The identification of appropriate references genes is an integral component of any gene expression-based study for getting accuracy and reliability in data interpretation. In this study, we evaluated the expression stability of 10 candidate reference genes (GAPDH, RPL4, EEF1A1, RPS9, HPRT1, UXT, RPS23, B2M, RPS15, ACTB) in peripheral blood mononuclear cells of livestock species that are adapted to high altitude hypoxia conditions of Leh-Ladakh. A total of 37 PBMCs samples from six native livestock species of leh-Ladakh region such as Ladakhi cattle (LAC), Ladakhi yak (LAY), Ladakhi donkey (LAD), Chanthangi goat (CHG), Double hump cattle (DHC) and Zanskar ponies (ZAP) were included in this study. The commonly used statistical algorithms such as geNorm, NormFinder, BestKeeper and RefFinder were employed to assess the stability of these RGs in all the livestock species. Our study has identified different panel of reference genes in each species; for example, EEF1A1, RPL4 in Ladakhi cattle; GAPDH, RPS9, ACTB in Ladakhi yak; HPRT1, B2M, ACTB in Ladakhi donkey; HPRT1, B2M, ACTB in Double hump camel, RPS9, HPRT1 in Changthangi goat, HPRT1 and ACTB in Zanskar ponies. To the best of our knowledge, this is the first systematic attempt to identify panel of RGs across different livestock species types adapted to high altitude hypoxia conditions. In future, the findings of the present study would be quite helpful in conducting any transcriptional studies to understand the molecular basis of high altitude adaptation of native livestock population of Leh-Ladakh.

Comparative Analysis of Long Non-Coding RNA and mRNA Expression Provides Insights Into Adaptation to Hypoxia in Tibetan Sheep

Tibetan sheep have lived on the Qinghai-Tibetan Plateau for thousands of years and they have a good adaptability to the hypoxic environment and strong disease resistance. However, the molecular mechanism of the Tibetan sheep adapting to this extreme environment, especially the role of genetic regulation is still unknown. Emerging evidence suggests that long non-coding RNAs (lncRNAs) participate in the regulation of a diverse range of biological processes. To explore the potential lncRNAs involved in Tibetan sheep adapting to high altitude hypoxia environment, we analyzed the expression profile of lncRNAs and mRNAs in liver and lung tissue of sheep based on the comparative transcriptome analysis between four Tibetan sheep populations (high altitude) and Hu sheep (low altitude). The results showed a total of 7848 differentially expressed (DE) lncRNAs transcripts and 22971 DE mRNAs transcripts were detected by pairwise comparison. The expression patterns of selected mRNAs and lncRNAs were validated by qRT-PCR and the results correlated well with the transcriptome data. Moreover, the functional annotation analysis based on the Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) databases showed that DE mRNAs and the target genes of the lncRNAs were significantly enriched in organ morphogenesis, response to stimulus, heme binding, immune system, arginine and proline metabolism, and fatty acid biosynthesis. The prediction of mRNA-mRNA and lncRNA-mRNA interaction networks further revealed transcripts potentially involved in adaptation to high altitude hypoxia, the hub genes that DDX24, PDCD11, EIF4A3, NDUFA11, SART1, PRPF8 and TCONS_00306477, TCONS_00306029, TCONS_00139593, TCONS_00293272, TCONS_00313398 were selected. Additionally, a set of target genes, PIK3R1, IGF1R, FZD6, IFNB2, ATF3, MB, CYP2B4, PSMD13, and TGFB1 were also identified as candidate genes associated with high altitude hypoxia adaptation. In conclusion, a collection of aberrantly expressed lncRNA, a set of target genes and biological pathways known to be relevant for altitude adaptation were identified by comparative transcriptome analysis between Tibetan sheep and Hu sheep. Our results first identified the characterization and expression profile of lncRNAs between Tibetan sheep and Hu sheep and provides insights into the genetic regulation mechanisms for Tibetan sheep adaptation to high altitude hypoxia environments.

Modulation of Perturbed Cardiac Metabolism in Rats Under High-Altitude Hypoxia by Combination Treatment With L-carnitine and Trimetazidine

High-altitude hypoxia has long been recognized as a vital etiology for high-altitude illnesses. High-altitude myocardial injury (HAMI) usually occurs in people who suffered from high-altitude exposure. To date, the molecular mechanism of HAMI remains elusive, which seriously hinders the prevention and treatment of HAMI. L-carnitine and trimetazidine are classic cardiovascular protective medicines. In this study, we used the metabolomic method, based on GC/MS, to explore the changes in metabolites in rats exposed to high-altitude hypoxia and then illustrate the metabolic pathways associated with the modulatory effect of L-carnitine combined with trimetazidine on rats with high-altitude exposure. The results showed that metabolites in the myocardium in rats under high-altitude hypoxia were markedly changed, such as branched-chain amino acids (BCAA, leucine, isoleucine, and valine), taurine, succinic acid, fumaric acid, lactic acid, pyruvic acid, 3-hydroxybutyrate, and docosahexaenoic acid (DHA), while L-carnitine combined with trimetazidine modulated and improved the abnormal changes in energy substances caused by high-altitude hypoxia. L-carnitine mainly promoted the metabolism of fatty acids, while trimetazidine enhanced the glycolysis process. The combined administration of the two components not only increased the metabolism of fatty acids but also promoted aerobic glycolysis. Meanwhile, it contributed to the decrease in the elevation in some of the intermediates of the tricarboxylic acid (TCA) cycle, decrease in the production of 3-hydroxybutyric acid, and relief of the abnormal energy metabolism process in organisms and the cardiac tissue. Our analysis delineates the landscape of the metabolites in the myocardial tissue of rats that were exposed to high altitude. Moreover, L-carnitine combined with trimetazidine can relieve the HAMI through modulated and improved abnormal changes in energy substances caused by high-altitude hypoxia.

Pharmacokinetics of Acetaminophen and Metformin Hydrochloride in Rats After Exposure to Simulated High Altitude Hypoxia

The pharmacokinetic characteristics of drugs were altered under high altitude hypoxia, thereby affecting the absorption, distribution, metabolism, and excretion of drug. However, there are few literatures on the pharmacokinetic changes of antipyretic and pain-relieving drugs and cardiovascular system drugs at high altitude. This study aimed to evaluate the pharmacokinetics of acetaminophen and metformin hydrochloride in rats under simulated high altitude hypoxia condition. Mechanically, the protein and mRNA expression of uridine diphosphate glucuronyltransferase 1A1 (UGT1A1) and organic cation transporter 2 (OCT2) were investigated by enzyme linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Compared with the normoxia group, the t1/2 and AUC of acetaminophen were significantly increased, and the CL/F was significantly decreased in rats after exposure to simulated high altitude hypoxia. The t1/2 of metformin hydrochloride was significantly increased by simulated high altitude hypoxia. No significant differences in AUC and CL/F of metformin hydrochloride were observed when comparing the hypoxia group with the normoxia group. The protein and mRNA expression of UGT1A1 and OCT2 were decreased significantly under hypoxia in rats. This study found obvious changes in the pharmacokinetics of acetaminophen and metformin hydrochloride in rats after exposure to simulated high altitude hypoxia, and they might be due to significant decreases in the expressions of UGT1A1 and OCT2. To sum up, our data suggested that the pharmacokinetics of acetaminophen and metformin hydrochloride should be reexamined, and the optimal dose should be reassessed under hypoxia exposure.

Selective Sweeps Uncovering the Genetic Basis of Horn and Adaptability Traits on Fine-Wool Sheep in China

Long-term natural and artificial selection leads to change in certain regions of the genome, resulting in selection signatures that can reveal genes associated with selected traits, such as horns (i.e., polled/horned), high-quality wool traits, and high-altitude hypoxia adaptability. These are complex traits determined by multiple genes, regulatory pathways, and environmental factors. A list of genes with considerable effects on horn and adaptability traits has not been found, although multiple quantitative trait loci (QTL) have been identified. Selection signatures could be identified using genetic differentiation (FST), polymorphism levels θπ, and Tajima’s D. This study aimed to identify selection signatures in fine-wool sheep and to investigate the genes annotated in these regions, as well as the biological pathways involved in horn and adaptability traits. For this purpose, the whole-genome sequence of 120 individuals from four breeds, which come from different elevations and habitats in China, was used to analyze selection signatures for horn and adaptability traits. Annotation of the consensus regions of FST and θπ ratios revealed a list of identified genes associated with polled/horned and high-altitude hypoxia adaptability traits, such as RXPF2, EERFC4, MSH6, PP1R12A, THBS1, ATP1B2, RYR2, and PLA2G2E. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified genes related primarily to mismatch repair, metabolism, vascular smooth muscle contraction, and cardiac muscle contraction. This is the first study to demonstrate that selection signatures play an important role in the polled/horned and high-altitude hypoxia adaptability traits of fine-wool sheep breeds that have undergone high-intensity selection and adapted to different ecological environments in China. Changes observed in the genome of fine-wool sheep may have acted on genomic regions that affect performance traits and provide a reference for genome design and breeding.