Hypoxia-inducible factor-2α promotes fibrosis in non-alcoholic fatty liver disease by enhancing glutamine catabolism and inhibiting yes-associated protein phosphorylation in hepatic stellate cells.

Non-alcoholic fatty liver disease (NAFLD) has a high global prevalence and affects approximately one-third of adults, owing to high-fat dietary habits and a sedentary lifestyle. The role of hypoxia-inducible factor 2α (HIF-2α) in NAFLD progression remains unknown. This study aimed to investigate the effects of chronic hypoxia on NAFLD progression by examining the role of hypoxia-inducible factor 2α (HIF-2α) activation and that of hepatic stellate cell (HSC)-derived myofibroblasts through glutaminolysis. We hypothesised that hypoxia exacerbates NAFLD by promoting HIF-2α upregulation and inhibiting phosphorylated yes-associated protein (YAP), and that increasing YAP expression enhances HSC-derived myofibroblasts. We studied patients with NAFLD living at high altitudes, as well as animal models and cultured cells. The results revealed significant increases in HSC-derived myofibroblasts and collagen accumulation caused by HIF-2α and YAP upregulation, both in patients and in a mouse model for hypoxia and NAFLD. HIF-2α and HIF-2α-dependent YAP downregulation reduced HSC activation and myofibroblast levels in persistent chronic hypoxia. Furthermore, hypoxia-induced HIF-2α upregulation promoted YAP and inhibited YAP phosphorylation, leading to glutaminase 1 (GLS1), SLC38A1, α-SMA, and Collagen-1 overexpression. Additionally, hypoxia restored mitochondrial adenosine triphosphate production and reactive oxygen species (ROS) overproduction. Thus, chronic hypoxia-induced HIF-2α activation enhances fibrosis and NAFLD progression by restoring mitochondrial ROS production and glutaminase-1-induced glutaminolysis, which is mediated through the inhibition of YAP phosphorylation and increased YAP nuclear translocation. In summary, HIF-2α plays a pivotal role in NAFLD progression during chronic hypoxia.

Mitochondria in hypoxic pulmonary hypertension, roles and the potential targets.

Mitochondria are the centrol hub for cellular energy metabolisms. They regulate fuel metabolism by oxygen levels, participate in physiological signaling pathways, and act as oxygen sensors. Once oxygen deprived, the fuel utilizations can be switched from mitochondrial oxidative phosphorylation to glycolysis for ATP production. Notably, mitochondria can also adapt to hypoxia by making various functional and phenotypes changes to meet the demanding of oxygen levels. Hypoxic pulmonary hypertension is a life-threatening disease, but its exact pathgenesis mechanism is still unclear and there is no effective treatment available until now. Ample of evidence indicated that mitochondria play key factor in the development of hypoxic pulmonary hypertension. By hypoxia-inducible factors, multiple cells sense and transmit hypoxia signals, which then control the expression of various metabolic genes. This activation of hypoxia-inducible factors considered associations with crosstalk between hypoxia and altered mitochondrial metabolism, which plays an important role in the development of hypoxic pulmonary hypertension. Here, we review the molecular mechanisms of how hypoxia affects mitochondrial function, including mitochondrial biosynthesis, reactive oxygen homeostasis, and mitochondrial dynamics, to explore the potential of improving mitochondrial function as a strategy for treating hypoxic pulmonary hypertension.

Metabolomic profiling of early inactive hepatic alveolar and cystic echinococcosis.

Hepatic alveolar echinococcosis (AE) and cystic echinococcosis (CE) are severe helminthic zoonoses and leading causes of parasitic liver damage. They pose a high mortality risk due to invisible clinical signs, especially at the early inactive stage. However, the specific metabolic profiles induced by inactive AE and CE lesions remain largely unclear. Therefore, we used gas chromatography-mass spectrometry-based metabolomic profiling to identify the global metabolic variations in AE and CE patient sera to differentiate between the two diseases and reveal the mechanisms underlying their pathogenesis. In addition, specific serum biomarkers of inactive hepatic AE and CE were screened using receiver operating curves, which can contribute to the clinical diagnosis of both diseases, especially in the earlier phase. These differential metabolites are involved in glycine, serine, tyrosine, and phenylalanine metabolism. Further analysis of key metabolic pathways showed that inactive AE lesions strongly alter amino acid metabolism in the host. CE lesions have an altered metabolism of oxidative stress response. These changes suggest these metabolite-associated pathways can serve as biomarkers to distinguish individuals with inactive AE and CE from healthy populations. This study also investigated the differences in serum metabolic profiles in patients with CE and AE. The biomarkers identified belonged to different metabolic pathways, including lipid, carnitine, androgen, and bile acid metabolism. Taken together, by investigating the different phenotypes of CE and AE with metabolomic profiling, serum biomarkers facilitating early diagnosis were identified.

Biofunctional roles of estrogen in coronavirus disease 2019: Beyond a steroid hormone.

The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), epidemic poses a major global public health threat with more than one million daily new infections and hundreds of deaths. To combat this global pandemic, efficient prevention and management strategies are urgently needed. Together with the main characteristics of COVID-19, impaired coagulation with dysfunctions of the immune response in COVID-19 pathophysiology causes high mortality and morbidity. From recent clinical observations, increased expression of specific types of estrogen appears to protect patients from SARS-CoV-2 infection, thereby, reducing mortality. COVID-19 severity is less common in women than in men, particularly in menopausal women. Furthermore, estrogen levels are negatively correlated with COVID-19 severity and mortality. These findings suggest that estrogen plays a protective role in the pathophysiology of COVID-19. In this review, we discuss the potential roles of estrogen in blocking the SARS-CoV-2 from invading alveolar cells and replicating, and summarize the potential mechanisms of anti-inflammation, immune modulation, reactive oxygen species resistance, anti-thrombosis, vascular dilation, and vascular endothelium protection. Finally, the potential therapeutic effects of estrogen against COVID-19 are reviewed. This review provides insights into the role of estrogen and its use as a potential strategy to reduce the mortality associated with COVID-19, and possibly other viral infections and discusses the possible challenges and pertinent questions.

Hypoxia-inducible factor-2 promotes liver fibrosis in non-alcoholic steatohepatitis liver disease via the NF-κB signalling pathway.

Non-alcoholic steatohepatitis (NASH) is one of the most common chronic liver diseases. Chronic hypoxia is related to the pathogenesis of NASH. HIF-2α is the key gene for lipid metabolism, fibrosis, and inflammation in many cells. To identify the molecular mechanism through which hypoxia exposure increases the morbidity of NASH, the expression level of HIF-2α was analysed and was found to be upregulated in human NASH liver. By constructing the NASH model of chronic hypoxia, the mice were housed at an altitude of 4300 m for 4 and 8 weeks, compared to the control groups that were housed at an altitude of 50 m. Histological studies showed that exposure to hypoxia promoted the activation of NF-κB by upregulating the expression of HIF-2α, as well as that of the genes related to inflammation and fibrosis, thereby promoting the development of NASH both in vivo and in vitro. In summary, hypoxia-exposure could upregulate HIF-2α to aggravate tissue fibrosis and inflammation by upregulating inflammation-related genes and fibrosis-related genes metabolites via the activated NF-κB pathway in NASH. Our results suggest that for NASH patients living at high altitudes, drug therapy could focus on treating tissue fibrosis and inflammation, and thus provides a new strategy for NASH treatment.

WY14643 improves left ventricular myocardial mitochondrial and systolic functions in obese rats under chronic persistent hypoxia via the PPARα pathway.

AIMS: Peroxisome proliferator-activated receptor (PPAR) α, a key regulator of lipid metabolism, plays a role in maintaining the homeostasis of myocardial energy metabolism. Both hypoxia and obesity inhibit the expression of PPARα in the myocardium. In this study, we verified the inhibitory effects of hypoxia and obesity on PPARα and examined whether WY14643 (4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid), an agonist of PPARα, ameliorates myocardial mitochondrial dysfunction and protects cardiac function in obese rats under chronic persistent hypoxia. MAIN METHODS: Sprague-Dawley rats were randomly divided into six groups: a control group (normal chow diet, normal oxygen), a high-fat diet (HFD) group (normal oxygen), a chronic persistent hypoxia normal chow diet group, a chronic persistent hypoxia HFD group, a chronic persistent hypoxia HFD group with WY14643 treatment, and a chronic persistent hypoxia HFD group with vehicle treatment. KEY FINDINGS: Hypoxia and obesity increased myocardial lipid accumulation, mitochondrial dysfunction, and left ventricular systolic dysfunction. Myocardial lipid metabolism-related genes, including those encoding PPARα, PPARγ coactivator 1α (PGC1α), and carnitine palmitoyl transferase 1α (CPT1α), were downregulated, while acetyl-CoA carboxylase 2 (ACC2) was upregulated under a combination of hypoxia and obesity. WY14643 upregulated PPARα, PGC1α, and CPT1α, and downregulated ACC2. WY14643 alleviated hypoxia- and obesity-induced myocardial lipid accumulation and improved mitochondrial and left ventricular systolic functions. SIGNIFICANCE: WY14643 improved myocardial mitochondrial and left ventricular systolic functions in obese rats under chronic persistent hypoxia. Thus, WY14643 possibly exerts its effects by regulating the PPARα pathway and shows potential as a therapeutic target for cardiovascular diseases associated with obesity and hypoxia.

Adipose-derived exosomal miR-210/92a cluster inhibits adipose browning via the FGFR-1 signaling pathway in high-altitude hypoxia.

Cold and hypoxia are critical drivers of adaptation to high altitudes. Organisms at high altitudes have adapted to maximize the efficiency of oxygen utilization and are less prone to obesity and diabetes than those at low altitudes. Brown adipose tissue (BAT) dissipates energy in the form of heat in both humans and rodents; it also serves to regulate metabolism to curb obesity. However, the role of BAT in high-altitude populations is poorly understood. Serum exosomes can be easily obtained, enabling the study of BAT functions and identification of biomarkers in serum exosomes, both of which contribute to understanding the role of BAT in high-altitude populations. 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography integrated with computed tomography (PET/CT) is the gold standard for studying BAT in human adults. Here, we studied BAT in healthy high-altitude populations via PET/CT and serum exosomal microRNAs (miRNAs). The observations were validated in mouse tissues and demonstrated that high-altitude hypoxia activated BAT through attenuated white adipose tissue (WAT) secreted exosomal miR-210/92a, which enhanced the FGFR-1 expression in BAT.

Increased Insulin Sensitivity by High-Altitude Hypoxia in Mice with High-Fat Diet-Induced Obesity Is Associated with Activated AMPK Signaling and Subsequently Enhanced Mitochondrial Biogenesis in Skeletal Muscles.

BACKGROUND: This study aimed to investigate whether and how high altitude-associated ambient hypoxia affects insulin sensitivity in mice fed a high-fat diet (HFD). METHODS: Mice were randomly divided into a control group (with normal diet feeding and low-altitude housing), LA/HFD group (with HFD feeding and low-altitude housing), and HA/HFD group (with HFD feeding and high-altitude housing). RESULTS: After 8 weeks, mice in the HA/HFD group showed improved insulin sensitivity-related indices compared with the LA/HFD group. In mice residing in a low-altitude region, HFD significantly impaired mitochondrial respiratory function and mitochondrial DNA content in skeletal muscles, which was partially reversed in mice in the HA/HFD group. In addition, the fatty acid oxidation-related enzyme gene CPT1 (carnitine palmitoyltransferase 1) and genes related to mitochondrial biogenesis such as peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (Tfam) were upregulated in the skeletal muscles of mice housed at high altitude, in comparison to in the LA/HFD group. Furthermore, AMPK (adenosine monophosphate-activated protein kinase) signaling was activated in the skeletal muscles, as evidenced by a higher expression of phosphorylated AMPK (p-AMPK) and protein kinase B (p-AKT) in the HA/HFD group than in the LA/HFD group. CONCLUSION: Our study suggests that high-altitude hypoxia improves insulin sensitivity in mice fed an HFD, which is associated with AMPK activation in the skeletal muscle and consequently enhanced mitochondrial biogenesis and fatty acid oxidation. This work provides a molecular explanation for why high altitude is associated with a reduced incidence of insulin resistance in the obese population.

High-altitude chronic hypoxia ameliorates obesity-induced non-alcoholic fatty liver disease in mice by regulating mitochondrial and AMPK signaling.

AIMS: High-fat intake induces obesity and non-alcoholic fatty liver disease (NAFLD). However, high-altitude chronic hypoxia might alleviate NAFLD progression through improved mitochondrial function and AMP-activated protein kinase (AMPK) signaling. We hypothesized that high-altitude chronic hypoxia would have protective effects against NAFLD development. MAIN METHODS: C57BL/6J mice were randomly divided into control (normal diet and altitude 50 m), CHH (normal diet and altitude 4300 m), HFD (high-fat diet and altitude 50 m), and HFD-CHH (high-fat diet and altitude 4300 m) groups. After being maintained for 8 weeks under the appropriate conditions, mice were evaluated. KEY FINDINGS: The degree of liver lipid accumulation and expression of the lipid synthesis-related genes acetyl-CoA carboxylase1 (ACC1), fatty acid synthesis (FAS), and sterol regulatory element binding protein-1c (SREBP-1c) were reduced in the HFD-CHH group; however, expression of the lipolysis-related gene carnitine palmitoyl transferase 1 (CPT1) was increased. Furthermore, in addition to increased expression of mitochondrial biogenesis-related genes, mitochondrial respiratory function and mitochondrial DNA content were elevated in the HFD-CHH group compared to those in the HFD group. The HFD-CHH group also exhibited significantly increased antioxidation activity and decreased reactive oxygen species production (P < 0.05). Finally, AMPK signaling in the liver was activated and the expression of phosphorylated-AMPK (P-AMPK) was significantly increased in the HFD-CHH group. SIGNIFICANCE: Collectively, our findings suggest that high altitude-induced hypoxia might improve impaired mitochondrial function and activate AMPK signaling in obesity-induced NAFLD. High-altitude chronic hypoxia could be a new treatment strategy for obesity-induced NAFLD.

The human platelet transcriptome and proteome is altered and pro-thrombotic functional responses are increased during prolonged hypoxia exposure at high altitude.

Exposure to hypoxia, through ascension to high altitudes (HAs), air travel, or human disease, is associated with an increased incidence of thrombosis in some settings. Mechanisms underpinning this increased thrombosis risk remain incompletely understood, and the effects of more sustained hypoxia on the human platelet molecular signature and associated functional responses have never been examined. We examined the effects of prolonged (≥2 months continuously) hypobaric hypoxia on platelets isolated from subjects residing at HA (3,700 meters) and, for comparison, matched subjects residing under normoxia conditions at sea level (50 meters). Using complementary transcriptomic, proteomic, and functional methods, we identified that the human platelet transcriptome is markedly altered under prolonged exposure to hypobaric hypoxia at HA. Among the significantly, differentially expressed genes (mRNA and protein), were those having canonical roles in platelet activation and thrombosis, including membrane glycoproteins (e.g. GP4, GP6, GP9), integrin subunits (e.g. ITGA2B), and alpha-granule chemokines (e.g. SELP, PF4V1). Platelets from subjects residing at HA were hyperactive, as demonstrated by increased engagement and adhesion to fibrinogen, fewer alpha granules by transmission electron microscopy, increased circulating PF4 and ADP, and significantly enhanced clot retraction. In conclusion, we identify that prolonged hypobaric hypoxia exposure due to HA alters the platelet transcriptome and proteome, triggering increased functional activation responses that may contribute to thrombosis. Our findings may also have relevance across a range of human diseases where chronic hypoxia, platelet activation, and thrombosis are increased.

Gut microbiota adaptation to high altitude in indigenous animals.

Limited is known about role of gut microbiota in the metabolism of high-altitude-living herbivores, and potential co-evolution between gut microbiome and host genome during high altitude adaptation were not fully understood. Here, DNA from faecal samples was used to investigate the gut microbial compositions and diversity in three host species endemic to the high-altitude Tibetan plateau, the Tibetan antelope (Pantholops hodgsonii, T-antelope, 4300 m) and the Tibetan wild ass (Equus kiang, T-ass, 4300 m), and in the Tibetan sheep (Ovis aries, T-sheep) collected from two different altitudes (T-sheep [k], 4300 m and T-sheep [l] 3000 m). Ordinary sheep (O. aries, sheep) from low altitudes (1800 m) were used for comparison. 16S rRNA gene sequencing revealed that the genera Ruminococcus (22.78%), Oscillospira (20.00%), and Clostridium (10.00%) were common taxa in all high-altitude species (T-antelope, T-ass and T-sheep [k]). Ruminococcaceae, Clostridiales, Clostridia, and Firmicutes showed greater enrichment in the T-antelopes' gut microbiota than in the microbiota of lower-altitude sheep (T-sheep [l] and sheep). The T-antelopes' gut microbiota displayed a higher ratio of Firmicutes to Bacteroidetes than lower-altitude sheep (T-sheep [l] and sheep). A functional capacity analysis of the paired-end metagenomics sequences of the gut metagenomes of high-altitude T-antelopes and T-sheep annotated over 80% of the unique genes to metabolism (especially carbohydrate metabolism pathways) and genetic information processing in the Kyoto Encyclopedia of Genes and Genomes database. The gut metagenome of the T-antelope may have co-evolved with the host genomes (e.g. glycolysis and DNA repair). The higher-altitude herbivores tended to have similar gut microbial compositions, with similar functional capacities, suggesting that their gut microbiota could involved in their high-altitude adaptation.

Iron down-regulates leptin by suppressing protein O-GlcNAc modification in adipocytes, resulting in decreased levels of O-glycosylated CREB.

We previously reported that iron down-regulates transcription of the leptin gene by increasing occupancy of phosphorylated cAMP response element-binding protein (pCREB) at two sites in the leptin gene promoter. Several nutrient-sensing pathways including O-GlcNAcylation also regulate leptin. We therefore investigated whether O-glycosylation plays a role in iron- and CREB-mediated regulation of leptin. We found that high iron decreases protein O-GlcNAcylation both in cultured 3T3-L1 adipocytes and in mice fed high-iron diets and down-regulates leptin mRNA and protein levels. Glucosamine treatment, which bypasses the rate-limiting step in the synthesis of substrate for glycosylation, increased both O-GlcNAc and leptin, whereas inhibition of O-glycosyltransferase (OGT) decreased O-GlcNAc and leptin. The increased leptin levels induced by glucosamine were susceptible to the inhibition by iron, but in the case of OGT inhibition, iron did not further decrease leptin. Mice with deletion of the O-GlcNAcase gene, either via whole-body heterozygous deletion or through adipocyte-targeted homozygous deletion, exhibited increased O-GlcNAc levels in adipose tissue and increased leptin levels that were inhibited by iron. Of note, iron increased the occupancy of pCREB and decreased the occupancy of O-GlcNAcylated CREB on the leptin promoter. These patterns observed in our experimental models suggest that iron exerts its effects on leptin by decreasing O-glycosylation and not by increasing protein deglycosylation and that neither O-GlcNAcase nor OGT mRNA and protein levels are affected by iron. We conclude that iron down-regulates leptin by decreasing CREB glycosylation, resulting in increased CREB phosphorylation and leptin promoter occupancy by pCREB.

Chronic cold exposure results in subcutaneous adipose tissue browning and altered global metabolism in Qinghai-Tibetan plateau pika (Ochotona curzoniae).

The plateau pika (Ochotona curzoniae), one of the indigenous animals of the Qinghai-Tibet Plateau, is adapted to life in a cold and hypoxic environment. We conducted a series of genomic, proteomic and morphological studies to investigate whether changes in energy metabolism contribute to adaptation of the plateau pika to cold stress by analyzing summer and winter cohorts. The winter group showed strong morphological and histological features of brown adipose tissue (BAT) in subcutaneous white adipose tissue (sWAT). To obtain molecular evidence of browning of sWAT, we performed reverse transcription and quantitative real-time PCR, which revealed that BAT-specific genes, including uncoupling protein 1 (UCP-1) and PPAR-γ coactivator 1α (PGC-1α), were highly expressed in sWAT from the winter group. Compared with the summer group, Western blot analysis also confirmed that UCP-1, PGC-1α and Cox4 protein levels were significantly increased in sWAT from the winter group. Increased BAT mass in the inter-scapular region of the winter group was also observed. These results suggest that the plateau pika adapts to cold by browning sWAT and increasing BAT in order to increase thermogenesis. These changes are distinct from the previously reported adaptation of highland deer mice. Understanding the regulatory mechanisms underlying this adaptation may lead to novel therapeutic strategies for treating obesity and metabolic disorders.

Metabolic Alterations of Qinghai-Tibet Plateau Pikas in Adaptation to High Altitude.

Cao, Xue-Feng, Zhen-Zhong Bai, Lan Ma, Shuang Ma, and Ri-Li Ge. Metabolic alterations of Qinghai-Tibet plateau pikas in adaptation to high altitude. High Alt Med Biol. 18:219-225, 2017.-To determine specific metabolic alterations in the myocardium of plateau pikas (Ochotona curzoniae) and potential metabolic biomarkers involved in their adaptation to the high-altitude environment of the Qinghai-Tibet Plateau. Ten pikas were captured by traps in the Kekexili Reserve (4630 m a.s.l; n = 5) and at the foot of the Laji Mountain (2600 m a.s.l; n = 5) on the Qinghai-Tibet Plateau, Qinghai Province, China. Metabolite levels were determined by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) metabolomics, and multivariate statistical analysis was performed. Several metabolites involved in carbohydrate, fat, energy, and redox homeostasis pathways were significantly altered in pikas living at 4630 m. In addition, those pikas showed increased levels of lactic acid, sarcosine, 4-hydroxybutyrate, methionine, tartaric acid, ribose, tyrosine, pentadecanoic acid, 2-monoolein, 3,5-dihydroxyphenylglycine, trehalose-6-phosphate, succinic acid, myoinositol, fumaric acid, taurine, 2-hydroxybutanoic acid, gluconic acid, citrulline, and glutathione, but decreased levels of oleic acid and 2'-deoxyadenosine 5'-monophosphate. Metabolic activity is significantly altered in the myocardium of pikas in the high-altitude areas of the Qinghai-Tibet Plateau. This study provides important insights into metabolic biomarkers related to the adaptation of pikas to high-altitude hypoxia.

Cross-talk between EPAS-1/HIF-2α and PXR signaling pathway regulates multi-drug resistance of stomach cancer cell.

EPAS-1/HIF-2α (Endothelial PAS domain-containing protein 1/hypoxia-inducible transcription factors 2α) is a transcription factor expressed in a wide range of human cancers, including stomach cancer. Although EPAS-1 has been studied for years, its function in oncogenic transformation processes needs to be further investigated. In this study, we found that EPAS-1 would promote the growth of stomach cancer cell line BGC-823. Our results revealed that EPAS-1 interacts with Pregnane X Receptor (PXR), a nuclear receptor that regulates multiple genes' transcription involved in multi-drugs resistance (MDR) process. Protein-protein interaction between EPAS-1 and PXR was identified by co-immunoprecipitation and GST-pull down assays. By this interaction, EPAS-1 recruited PXR to its response elements in promoter/enhancer regions of CYP3A4, a PXR target gene. Over-expression of EPAS-1 increased the expression of PXR responsive genes, enhanced the proliferation of BGC-823 cells and boosted the resistance of BGC-823 cells against the cytotoxicity of chemotherapeutic drugs, e.g. Mitomycin C and Paclitaxel. Reduction of EPAS-1 level via its siRNA disrupted the proliferation, and enhanced the susceptibility of BGC-823 cells to those chemotherapeutic drugs. Our findings suggested that EPAS-1 and PXR may cooperatively participate in development and especially MDR process of stomach cancer. These findings may contribute to more effective targeted drugs discovery for the stomach cancer therapy.

The Local HIF-2α/EPO Pathway in the Bone Marrow is Associated with Excessive Erythrocytosis and the Increase in Bone Marrow Microvessel Density in Chronic Mountain Sickness.

AIM: Chronic mountain sickness (CMS) is characterized by excessive erythrocytosis, and angiogenesis may be involved in the pathogenesis of this disease. The bone marrow niche is the primary site of erythropoiesis and angiogenesis. This study was aimed at investigating the associations of the levels of hypoxia-inducible factors (HIFs), erythropoietin (EPO), and erythropoietin receptor (EPOR), as well as microvessel density (MVD) in the bone marrow with CMS. RESULTS: A total of 34 patients with CMS and 30 control subjects residing in areas at altitudes of 3000-4500 m were recruited for this study. The mRNA and protein expression of HIF-2α and EPO in the bone marrow cells was significantly higher in the CMS patients than in the controls. Moreover, changes in HIF-2α expression in CMS patients were significantly correlated with EPO and hemoglobin levels. In contrast, the expression of mRNA and protein expression of HIF-1α and EPOR did not differ significantly between the CMS and control patients. Increased MVD was observed in the bone marrow of the patients with CMS and it was significantly correlated with hemoglobin. CONCLUSIONS: Bone marrow cells of CMS patients may show enhanced activity of the HIF-2α/EPO pathway, and EPO may regulate the erythropoiesis and vasculogenesis through autocrine or/and paracrine mechanisms in the bone marrow niche. The increased MVD in the bone marrow of CMS patients appears to be involved in the pathogenesis of this disease.

Comparative ventilatory strategies of acclimated rats and burrowing plateau pika (Ochotona curzoniae) in response to hypoxic-hypercapnia.

The objective of this study was to compare the different ventilatory strategies that help in coping with hypoxic-hypercapnia environment among two species: use acclimated rats and plateau pikas (Ochotona curzoniae) that live in Tibetan plateaus, and have been well adjusted to high altitude. Arterial blood samples taken at 4100 m of elevation in acclimatized rats and adapted pikas revealed inter-species differences with lower hemoglobin and hematocrit and higher blood pH in pikas. A linear and significant increase in minute ventilation was observed in pikas, which help them to cope with hypoxic-hypercapnia. Pikas also displayed a high inspiratory drive and an invariant respiratory timing regardless of the conditions. Biochemical analysis revealed that N-methyl-D-aspartate receptor (NMDA) receptor gene and nNOS gene are highly conserved between rats and pikas, however pikas have higher expression of NMDA receptors and nNOS compared to rats at the brainstem level. Taken together, these results suggest that pikas have developed a specific ventilatory pattern supported by a modification of the NMDA/NO ventilatory central pathways to survive in extreme conditions imposed on the Tibetan plateaus. These physiological adaptive strategies help in maintaining a better blood oxygenation despite high CO2 concentration in burrows at high altitude.

Role of glutamate and serotonin on the hypoxic ventilatory response in high-altitude-adapted plateau Pika.

The highland "plateau Pika" is considered to be adapted to chronic hypoxia. We hypothesized that glutamate N-methyl-D-aspartate (NMDA) and non-NMDA receptors, nitric oxide (NO) synthase, and serotonin are involved in hypoxic ventilatory response (HVR) in Pikas. We tested the effects of NMDA (memantine) and non-NMDA receptors (DNQX) antagonists, NO synthase inhibitor (L-NAME), and selective serotonin reuptake inhibitors (fluoxetine) on ventilation and HVR in Pikas. Ventilatory parameters were measured before and after drug (or vehicle) injections in conscious Pikas at their natural living altitude (PIO2 86 mmHg) and after a hypoxic challenge (PIO2 57 mmHg, 3 min) to assess the influence of peripheral chemoreceptor on HVR. Minute ventilation (VI) and tidal volume (Vt) increased during hypoxic challenge after vehicle injection, whereas the Ti/Ttot ratio remained unchanged. The increase in VI and Vt observed with vehicle at PIO2-57, when compared with PIO2-86, was inhibited after memantine and fluoxetine injection, whereas the DNQX injection increased HVR. At PIO2-57, L-NAME induced an increase in the Ti/Ttot ratio when compared with vehicle. Therefore, the glutamate through NMDA-R/AMPA receptor bindings and serotonin pathway are implicated at the peripheral chemoreceptor level in HVR in Pikas. However, NO influences the ventilatory pattern of Pikas at their habitual living altitude.

Intermittent cold exposure results in visceral adipose tissue "browning" in the plateau pika (Ochotona curzoniae).

The plateau pika has developed tolerance to cold and hypoxia in order to adapt to living in the extreme environment of the Qinghai-Tibetan Plateau. One mammalian mechanism for cold adaptation is thermogenesis by brown adipose tissue (BAT), but the degree to which pika exploits this mechanism or how it may be modified by the additional stresses of high altitude is not known. Intermittent Cold Exposure (ICE) is an approachable method to study cold adaptation in rodents. To investigate the role of adipose tissue in the adaptation of pika to cold temperatures, we have studied pika during ICE. We find that pika kept in warm temperatures has little classical brown fat, but "browning" of white adipose tissues is observed rapidly upon cold exposure. This is demonstrated by the increased expression of several markers of brown fat differentiation including uncoupling protein 1 (UCP-1). Surprisingly, this occurs mainly in visceral rather than epididymal adipose tissue. In addition, ICE increases the expression of several general adipose differentiation markers at both the mRNA and protein levels. These substantial changes in the distribution of fat are accomplished without changes in weight or blood levels of glucose and triglycerides, suggesting that the adaptable changes are coordinated and self-compensated. Together, our results demonstrate that ICE promotes recruitment of BAT in pika, and unlike small mammals in at lower altitudes, pika can activate visceral WAT to adapt to cold stress without major changes overall energy balance.

Sleep disturbances in long-term immigrants with chronic mountain sickness: a comparison with healthy immigrants at high altitude.

The aim of this study was to examine sleep disturbances in patients with chronic mountain sickness (CMS). The sleep of 14 patients with CMS and 11 healthy controls with or without sleep disorders (control N: without sleep disorders; control D: with sleep disorders) was studied by polysomnography. Hypopnea was the sleep disorder most commonly suffered by CMS patients and control D subjects. No major differences were observed in sleep structure between CMS and control groups, with the exception of shorter rapid eye movement latency in controls and increased deep non-rapid eye movement in the control N group. Periodic breathing was observed in only two study participants, one each in the CMS and control D groups. The level of saturated oxygen was significantly lower in the CMS group during sleep than the control groups (P<0.05). CMS scores were positively correlated with the apnea-hypopnea index, and negatively correlated with saturated oxygen levels. These results demonstrate that sleep disorders and nocturnal hypoxia are important in the development of CMS.