The role of hypoxia-inducible factors in metabolic diseases

The Impact of Cirrhosis on Outcomes of Patients Admitted With Diabetic Ketoacidosis: A Nationwide Study

Introduction Diabetic ketoacidosis (DKA) is the most common acute hyperglycemic emergency in people with diabetes mellitus (DM). Cirrhosis is a consequence of chronic inflammation that is followed by hepatic fibrosis. It has been noted that cirrhosis is associated with an increased risk of developing type II DM due to altered glucose homeostasis. The prognostic value of DM in cirrhotic patients has been studied before and was found to be associated with lower survival. However, the risk of mortality and adverse events in cirrhotic patients admitted with DKA needs further evaluation. The aim of this study is to compare outcomes in patients with cirrhosis admitted to the hospital with DKA compared to non-cirrhotic patients. Methods The data for this study were extracted from the National Inpatient Sample (NIS) 2016-2019. The NIS was queried for all patients who had a discharge diagnosis of DKA. Patients with cirrhosis were identified and subclassified into compensated and decompensated cirrhosis using the International Classification of Diseases 10th revision, Clinical Modification (ICD-10-CM) codes. Patients without cirrhosis were the control group. ICD-10-CM codes that have been validated for cirrhosis were utilized. The primary outcome was in-hospital mortality. Secondary outcomes were hospital charges, length of stay (LOS), and in-hospital complications, including shock, mechanical ventilation, and acute kidney injury (AKI) requiring dialysis. Results We included 1,098,875 hospitalizations with a discharge diagnosis of DKA. Overall, 9,190 patients had compensated cirrhosis and 4,355 had decompensated cirrhosis. Cirrhotic patients had overall worse outcomes compared to non-cirrhotics. Decompensated cirrhotics had the highest mortality (11.26%; 95% confidence interval [CI]: 9.36% to 13.49%) compared to compensated cirrhotics (3.54%; 95% CI: 2.79% to 4.48%) and non-cirrhotics (2.15%; 95% CI: 1.89% to 2.43%). Similarly, decompensated cirrhotics also had the highest LOS, total charges, and in-hospital complications among the groups. On multivariate analysis, decompensated cirrhosis, rather than compensated cirrhosis, was an independent predictor of higher mortality (adjusted odds ratio [AOR]: 2.30; 95% CI: 1.81 to 2.92), LOS (regression coefficient: +1.82 days; 95% CI: +1.19 to +2.44 days), hospital charges (regression coefficient: +$28,497; 95% CI: +$18,107 to +$38,887), shock (AOR: 2.31; 95% CI: 1.68 to 3.18), mechanical ventilation (AOR: 1.91; 95% CI: 1.58 to 2.29), and AKI requiring dialysis (AOR: 2.31; 95% CI: 1.68 to 3.18). Conclusion This study showed that patients with decompensated liver cirrhosis who were admitted with DKA had the worst in-hospital outcomes. Additionally, only decompensated cirrhosis was an independent predictor of worse outcomes. Decompensated cirrhotics who develop DKA should be approached with more caution with a probable lower threshold for intensive care unit admission for a higher level management.

Characterization of EPO H131S as a key mutation site in the hypoxia-adaptive evolution of Gymnocypris dobula

Erythropoietin (EPO) is a glycoprotein hormone involved in proerythropoiesis, antioxidation, and antiapoptosis. It also contributes to cellular immune function in high-altitude species, such as the schizothoracine fish Gymnocypris dobula. Six mutation sites previously identified in EPO from G. dobula (GD-EPO) were injected into zebrafish embryos, and their effects were compared with EPO from the low-altitude schizothoracine Schizothorax prenanti. The key mutation site in GD-EPO was identified as H131S. Under hypoxic conditions, the levels of superoxide dismutase and malondialdehyde were decreased, whereas that of nitric oxide was increased in zebrafish injected with GD-EPO compared with those injected with S. prenanti-EPO (SP-EPO). The results suggest that EPO in high-altitude schizothoracine species is both antioxidative and antiapoptotic, driven by the H131S mutation site. Thus, this enhanced the ability of this species to adapt to the high-altitude hypoxic environment. These results provide a basis for investigating further the hypoxia adaptation mechanisms of teleosts.

Berberine reduces hepatic ceramide levels to improve insulin resistance in HFD-fed mice by inhibiting HIF-2α

Several studies have documented the effects of hypoxia and ceramides on lipid and glucose metabolism, resulting in insulin resistance. However, the roles of ceramide in hepatic hypoxia and hepatic insulin resistance remain to be clarified. This study aimed to explore the relationship between hypoxia, ceramide synthesis, and hepatic insulin resistance in high-fat diet (HFD)-fed mice. Given the interaction of hypoxia-inducible factors 2α(HIF-2α) and berberine determined using molecular docking, this study also assessed the pharmacological effects of berberine on the HIF-2α-ceramide-insulin resistance pathway. In the preliminary phase of the study, gradually aggravated hepatic hypoxia and varying levels of ceramides were observed with the development of type 2 diabetes mellitus (T2DM) due to increasing HIF-2α accumulation. Lipidomic analyses of animal and cell models revealed that berberine reduced hypoxia-induced ceramide production and attenuated ceramide-induced insulin resistance. This research provides timely and necessary evidence for the role of ceramide in hypoxia and insulin resistance in the liver. It also contributes to a better understanding of the pharmacological effects of berberine on ameliorating hypoxia and insulin resistance in T2DM therapy.

Action Sites and Clinical Application of HIF-1α Inhibitors

Hypoxia-inducible factor-1α (HIF-1α) is widely distributed in human cells, and it can form different signaling pathways with various upstream and downstream proteins, mediate hypoxia signals, regulate cells to produce a series of compensatory responses to hypoxia, and play an important role in the physiological and pathological processes of the body, so it is a focus of biomedical research. In recent years, various types of HIF-1α inhibitors have been designed and synthesized and are expected to become a new class of drugs for the treatment of diseases such as tumors, leukemia, diabetes, and ischemic diseases. This article mainly reviews the structure and functional regulation of HIF-1α, the modes of action of HIF-1α inhibitors, and the application of HIF-1α inhibitors during the treatment of diseases.

Potential role of selenium in alleviating obesity-related iron dyshomeostasis

Obesity is a serious health problem in modern life and increases the risk of many comorbidities including iron dyshomeostasis. In contrast to malnourished anemia, obesity-related iron dyshomeostasis is mainly caused by excessive fat accumulation, inflammation, and disordered gut microbiota. In obesity, iron dyshomeostasis also induces disorders associated with gut microbiota, neurodegenerative injury, oxidative damage, and fat accumulation in the liver. Selenium deficiency is often accompanied by obesity or iron deficiency, and selenium supplementation has been shown to alleviate obesity and overcome iron deficiency. Selenium inhibits fat accumulation and exhibits anti-inflammatory activity. It regulates gut microbiota, prevents neurodegenerative injury, alleviates oxidative damage to the body, and ameliorates hepatic fat accumulation. These effects theoretically meet the requirements for the inhibition of factors underlying obesity-related iron dyshomeostasis. Selenium supplementation may have a potential role in the alleviation of obesity-related iron dyshomeostasis. This review verifies this hypothesis in theory. All the currently reported causes and results of obesity-related iron dyshomeostasis are reviewed comprehensively, together with the effects of selenium. The challenges and strategies of selenium supplementation are also discussed. The findings demonstrate the possibility of selenium-containing drugs or functional foods in alleviating obesity-related iron dyshomeostasis.

Hua-Tan-Sheng-Jing Decoction Treats Obesity With Oligoasthenozoospermia by Up-Regulating the PI3K-AKT and Down-Regulating the JNK MAPK Signaling Pathways: At the Crossroad of Obesity and Oligoasthenozoospermia

Background: Oligoasthenozoospermia is the leading cause of male infertility, seriously affecting men's health and increasing the societal medical burden. In recent years, obesity-related oligoasthenozoospermia has attracted increased attention from researchers to find a cure. This study aimed to evaluate the efficacy of Hua-Tan-Sheng-Jing decoction (HTSJD) in treating obesity with oligoasthenozoospermia, determine its active ingredients and identify its mechanism of action. Methods: The ingredients of HTSJD were determined by combining the ultra-performance liquid chromatography with mass spectrometry (UPLC-MS/MS) and systems pharmacology approach. The common pathogenesis of obesity and oligoasthenozoospermia and the potential mechanism of HTSJD against obesity with oligoasthenozoospermia were obtained through target fishing, network construction, and enrichment analyses. Further, molecular docking of the key ingredients with the upstream receptors of the key signaling pathways of the potential mechanism was used to predict their affinity. Finally, high-fat-induced obesity with oligoasthenozoospermia rat model was constructed to determine the effects of HTSJD on semen concentration, sperm motility, body weight, and serum lipid metabolism. The key proteins were validated by immunohistochemistry (IHC). Results: A total of 70 effective components and 847 potential targets of HTSJD (H targets) were identified, of which 743 were common targets related to obesity and oligoasthenozoospermia (O-O targets) mainly enriched in the pathways related to inflammation, oxidative stress and hormone regulation. Finally, 143 common targets (H-O-O targets) for HTSJD against obesity with oligoasthenozoospermia were obtained. Combining the hub genes and the results of Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of H-O-O targets, PI3K-AKT and MAPK signaling pathways were identified as the key pathways. Molecular docking results showed that Diosgenin, Kaempferol, Quercetin, Hederagenin, Isorhamnetin may act on the related pathways by docking EGFR, IGF1R and INSR. The animal-based in vivo experiments confirmed that HTSJD improves the sperm quality of high-fat diet-fed rats by reducing their body weight and blood lipid levels, influencing the PI3K-AKT and MAPK signaling pathways and altering the corresponding protein expressions. Conclusion: HTSJD treats obesity with oligoasthenozoospermia by up-regulating the PI3K-AKT signaling pathway and down-regulating the MAPK signaling pathway, which are at the crossroad of obesity and oligoasthenozoospermia.

Identification of oleoylethanolamide as an endogenous ligand for HIF-3α

Hypoxia-inducible factors (HIFs) are α/β heterodimeric transcription factors modulating cellular responses to the low oxygen condition. Among three HIF-α isoforms, HIF-3α is the least studied to date. Here we show that oleoylethanolamide (OEA), a physiological lipid known to regulate food intake and metabolism, binds selectively to HIF-3α. Through crystallographic analysis of HIF-3 α/β heterodimer in both apo and OEA-bound forms, hydrogen-deuterium exchange mass spectrometry (HDX-MS), molecular dynamics (MD) simulations, and biochemical and cell-based assays, we unveil the molecular mechanism of OEA entry and binding to the PAS-B pocket of HIF-3α, and show that it leads to enhanced heterodimer stability and functional modulation of HIF-3. The identification of HIF-3α as a selective lipid sensor is consistent with recent human genetic findings linking HIF-3α with obesity, and demonstrates that endogenous metabolites can directly interact with HIF-α proteins to modulate their activities, potentially as a regulatory mechanism supplementary to the well-known oxygen-dependent HIF-α hydroxylation.

Oxygen sensors mediated HIF-1α accumulation and translocation: A pivotal mechanism of fine particles-exacerbated myocardial hypoxia injury

Epidemiological studies have demonstrated a strong association of ambient fine particulate matter (PM_2.5) exposure with the increasing mortality by ischemic heart disease (IHD), but the involved mechanisms remain poorly understood. Herein, we found that the chronic exposure of real ambient PM_2.5 led to the upregulation of hypoxia-inducible factor-1 alpha (HIF-1α) protein in the myocardium of mice, accompanied by obvious myocardial injury and hypertrophy. Further data from the hypoxia-ischemia cellular model indicated that PM_2.5-induced HIF-1α accumulation was responsible for the promotion of myocardial hypoxia injury. Moreover, the declined ATP level due to the HIF-1α-mediated energy metabolism remodeling from β-oxidation to glycolysis had a critical role in the PM_2.5-increased myocardial hypoxia injury. The in-depth analysis delineated that PM_2.5 exposure decreased the binding of prolyl hydroxylase domain 2 (PHD2) and HIF-1α and subsequent ubiquitin protease levels, thereby leading to the accumulation of HIF-1α. Meanwhile, factor-inhibiting HIF1 (FIH1) expression was down-regulated by PM_2.5, resulting in the enhanced translocation of HIF-1α to the nucleus. Overall, our study provides valuable insight into the regulatory role of oxygen sensor-mediated HIF-1α stabilization and translocation in PM-exacerbated myocardial hypoxia injury, we suggest this adds significantly to understanding the mechanisms of haze particles-caused burden of cardiovascular disease.

Morbid Obesity in Women Is Associated with an Altered Intestinal Expression of Genes Related to Cancer Risk and Immune, Defensive, and Antimicrobial Response

Background: Little is known about the relation between morbid obesity and duodenal transcriptomic changes. We aimed to identify intestinal genes that may be associated with the development of obesity regardless of the degree of insulin resistance (IR) of patients. Material and Methods: Duodenal samples were assessed by microarray in three groups of women: non-obese women and women with morbid obesity with low and high IR. Results: We identified differentially expressed genes (DEGs) associated with morbid obesity, regardless of IR degree, related to digestion and lipid metabolism, defense response and inflammatory processes, maintenance of the gastrointestinal epithelium, wound healing and homeostasis, and the development of gastrointestinal cancer. However, other DEGs depended on the IR degree. We mainly found an upregulation of genes involved in the response to external organisms, hypoxia, and wound healing functions in women with morbid obesity and low IR. Conclusions: Regardless of the degree of IR, morbid obesity is associated with an altered expression of genes related to intestinal defenses, antimicrobial and immune responses, and gastrointestinal cancer. Our data also suggest a deficient duodenal immune and antimicrobial response in women with high IR.

Hypoxia-Inducible Factor Protects Against Acute Kidney Injury via the Wnt/β-Catenin Signaling Pathway

Promoting adaptive repair (AR) in acute kidney injury (AKI) is an effective strategy to preventprogression from AKI to chronic kidney disease (CKD). However, the mechanisms involved in renal repair after AKI remain unclear. In this study, we investigated the role of hypoxia-inducible factor (HIF), an important regulator of ischemic and hypoxic injury, in AKI during the repair phase. We established mouse models of ischemia-reperfusion injury (IRI)-induced AKI with AR or maladaptive repair (MAR). We found that after injury, the activation of HIF in the AR group was rapid, while in the MAR group, HIF activation was relatively delayed, and its expression was significantly lower than that in the AR group during the early repair phase. To further investigate the mechanism of HIF, we regulated the expression of HIF-1α and HIF-2α in HK-2 cells and EA.hy926 cells, respectively. Silencing HIF expression reduced proliferation and increased apoptosis in cells injured by hypoxia/reoxygenation (H/R). Self-healing ability was further reduced due to the downregulation of HIF. Moreover, HIF overexpression had the opposite effect. HIF increased the expression of β-catenin and its downstream target genes. Activation of Wnt/β-catenin by the small molecule activator SKL2001 mitigated the damaging effect of HIF knockdown, while blocking β-catenin with the inhibitor IWR-1-endo reduced the protective effects of HIF. In conclusion, HIF, which is highly expressed in the early stage after AKI, promotes renal repair by interacting with the Wnt/β-catenin signaling pathway.

A new perspective on NAFLD: Focusing on lipid droplets

Lipid droplets (LDs) are complex and metabolically active organelles. They are composed of a neutral lipid core surrounded by a monolayer of phospholipids and proteins. LD accumulation in hepatocytes is the distinctive characteristic of non-alcoholic fatty liver disease (NAFLD), which is a chronic, heterogeneous liver condition that can progress to liver fibrosis and hepatocellular carcinoma. Though recent research has improved our understanding of the mechanisms linking LD accumulation to NAFLD progression, numerous aspects of LD biology are either poorly understood or unknown. In this review, we provide a description of several key mechanisms that contribute to LD accumulation in hepatocytes, favouring NAFLD progression. First, we highlight the importance of LD architecture and describe how the dysregulation of LD biogenesis leads to endoplasmic reticulum stress and inflammation. This is followed by an analysis of the causal nexus that exists between LD proteome composition and LD degradation. Finally, we describe how the increase in size of LDs causes activation of hepatic stellate cells, leading to liver fibrosis and hepatocellular carcinoma. We conclude that acquiring a more sophisticated understanding of LD biology will provide crucial insights into the heterogeneity of NAFLD and assist in the development of therapeutic approaches for this liver disease.

Evolutionarily conserved transcription factors as regulators of longevity and targets for geroprotection

Aging is the single largest risk factor for many debilitating conditions, including heart diseases, stroke, cancer, diabetes, and neurodegenerative disorders. While far from understood in its full complexity, it is scientifically well-established that aging is influenced by genetic and environmental factors, and can be modulated by various interventions. One of aging's early hallmarks are aberrations in transcriptional networks, controlling for example metabolic homeostasis or the response to stress. Evidence in different model organisms abounds that a number of evolutionarily conserved transcription factors, which control such networks, can affect lifespan and healthspan across species. These transcription factors thus potentially represent conserved regulators of longevity and are emerging as important targets in the challenging quest to develop treatments to mitigate age-related diseases, and possibly even to slow aging itself. This review provides an overview of evolutionarily conserved transcription factors that impact longevity or age-related diseases in at least one multicellular model organism (nematodes, flies, or mice), and/or are tentatively linked to human aging. Discussed is the general evidence for transcriptional regulation of aging and disease, followed by a more detailed look at selected transcription factor families, the common metabolic pathways involved, and the targeting of transcription factors as a strategy for geroprotective interventions.

Integration of Adverse Outcome Pathways, Causal Networks and ‘Omics to Support Chemical Hazard Assessment

Several approaches have been used in an attempt to simplify and codify the events that lead to adverse effects of chemicals including systems biology, ‘omics, in vitro assays and frameworks such as the Adverse Outcome Pathway (AOP). However, these approaches are generally not integrated despite their complementary nature. Here we propose to integrate toxicogenomics data, systems biology information and AOPs using causal biological networks to define Key Events in AOPs. We demonstrate this by developing a causal subnetwork of 28 nodes that represents the Key Event of regenerative proliferation – a critical event in AOPs for liver cancer. We then assessed the effects of three chemicals known to cause liver injury and cell proliferation (carbon tetrachloride, aflatoxin B₁, thioacetamide) and two with no known cell proliferation effects (diazepam, simvastatin) on the subnetwork using rat liver gene expression data from the toxicogenomic database Open TG-GATEs. Cyclin D1 (Ccnd1), a gene both causally linked to and sufficient to infer regenerative proliferation activity, was overexpressed after exposures to carbon tetrachloride, aflatoxin B₁ and thioacetamide, but not in exposures to diazepam and simvastatin. These results were consistent with known effects on rat livers and liver pathology of exposed rats. Using these approaches, we demonstrate that transcriptomics, AOPs and systems biology can be applied to examine the presence and progression of AOPs in order to better understand the hazards of chemical exposure.

The WWOX/HIF1A Axis Downregulation Alters Glucose Metabolism and Predispose to Metabolic Disorders

Recent reports indicate that the hypoxia-induced factor (HIF1α) and the Warburg effect play an initiating role in glucotoxicity, which underlies disorders in metabolic diseases. WWOX has been identified as a HIF1α regulator. WWOX downregulation leads to an increased expression of HIF1α target genes encoding glucose transporters and glycolysis’ enzymes. It has been proven in the normoglycemic mice cells and in gestational diabetes patients. The aim of the study was to determine WWOX’s role in glucose metabolism regulation in hyperglycemia and hypoxia to confirm its importance in the development of metabolic disorders. For this purpose, the WWOX gene was silenced in human normal fibroblasts, and then cells were cultured under different sugar and oxygen levels. Thereafter, it was investigated how WWOX silencing alters the genes and proteins expression profile of glucose transporters and glycolysis pathway enzymes, and their activity. In normoxia normoglycemia, higher glycolysis genes expression, their activity, and the lactate concentration were observed in WWOX KO fibroblasts in comparison to control cells. In normoxia hyperglycemia, it was observed a decrease of insulin-dependent glucose uptake and a further increase of lactate. It likely intensifies hyperglycemia condition, which deepen the glucose toxic effect. Then, in hypoxia hyperglycemia, WWOX KO caused weaker glucose uptake and elevated lactate production. In conclusion, the WWOX/HIF1A axis downregulation alters glucose metabolism and probably predispose to metabolic disorders.

Constructing Morphologically Tunable Copper Oxide-Based Nanomaterials on Cu Wire with/without the Deposition of Manganese Oxide as Bifunctional Materials for Glucose Sensing and Supercapacitors

Morphologically tunable copper oxide-based nanomaterials on Cu wire have been synthesized through a one-step alkali-assisted surface oxidation process for non-enzymatic glucose sensing. Subsequently, copper oxide-based nanomaterials on Cu wire as a supporting matrix to deposit manganese oxide for the construction of heterostructured Mn-Cu bimetallic oxide architectures through spontaneous redox reaction in the KMnO4 solution for supercapacitors. Field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed that morphological and phase transformation from Cu(OH)2 to CuO occurred in copper oxide-based nanomaterials on Cu wire with different degrees of growth reaction. In non-enzymatic glucose sensing, morphologically tunable copper oxide-based nanomaterials owned the high tunability of electrocatalytically active sites and intrinsic catalytic activity to meet efficient glucose electrooxidation for obtaining promoted non-enzymatic glucose sensing performances (sensitivity of 2331 μA mM-1 cm-2 and the limit of detection of 0.02 mM). In the supercapacitor, heterostructured Mn-Cu bimetallic oxide-based nanomaterials delivered abundant redox-active sites and continuous conductive network to optimize the synergistic effect of Mn and Cu redox species for boosting the pseudo-capacitance performance (areal capacitance value of 79.4 mF cm-2 at 0.2 mA cm-2 current density and capacitance retention of 74.9% after 1000 cycles). It concluded that morphologically tunable copper oxide-based nanomaterials on Cu wire with/without deposition of manganese oxide could be good candidates for the future design of synergistic multifunctional materials in electrochemical techniques.

Driving role of macrophages in transition from acute kidney injury to chronic kidney disease

Acute kidney injury (AKI), characterized by acute renal dysfunction, is an increasingly common clinical problem and an important risk factor in the subsequent development of chronic kidney disease (CKD). Regardless of the initial insults, the progression of CKD after AKI involves multiple types of cells, including renal resident cells and immune cells such as macrophages. Recently, the involvements of macrophages in AKI-to-CKD transition have garnered significant attention. Furthermore, substantial progress has also been made in elucidating the pathophysiological functions of macrophages from the acute kidney to repair or fibrosis. In this review, we highlight current knowledge regarding the roles and mechanisms of macrophage activation and phenotypic polarization, and transdifferentiation in the development of AKI-to-CKD transition. In addition, the potential of macrophage-based therapy for preventing AKI-to-CKD transition is also discussed.

Adipose tissue dysfunction and MAFLD in obesity on the scene of COVID-19

Obesity is a known risk factor for respiratory infection and many other chronic diseases, including metabolic dysfunction-associated fatty liver disease (MAFLD), previously known as nonalcoholic fatty liver disease (NAFLD). Recently, it has been considered an important and independent predictor for coronavirus disease 2019 (COVID-19) complications in adults, especially cardiopulmonary, presenting in a great number of individuals in critical care. In obesity, adipose tissue (AT) undergoes expansion via several processes: expansion of adipocytes and insufficient vascularization lead to hypoxia; adipocyte apoptosis/necrosis; irregular fatty acid flux; and enhanced secretion of inflammatory adipokines, cytokines, and chemokines. In individuals with obesity the liver can also become a target of COVID-19 infection, although major liver damage is uncommon. COVID-19 acute pandemic often develops in patients with major metabolic abnormalities, including fatty liver disease, which is part of a chronic pandemic together with body fat accumulation. During metabolic abnormalities, the expansion of metabolically active fat parallels chronic inflammatory changes, the development of Insulin Resistance (IR), and in the liver, the accumulation of fat, possibly, an underlying fibrosis. SARS-Cov-2 virus might affect the liver by direct or indirect mechanisms. The current epidemic of obesity and related metabolic diseases has extensively contributed to increase the number of severe cases and deaths from COVID-19, resulting in a health, political and economic crisis with long-lasting consequences. In this review, the authors explore the relationship between AT dysfunction and MAFLD in obesity on the scene of COVID-19.

Role of mitochondrial reactive oxygen species in homeostasis regulation

Mitochondria are the main source of reactive oxygen species (ROS) in cells. Early studies have shown that mitochondrial reactive oxygen species (mROS) are related to the occurrence and adverse outcomes of many diseases, and are thus regarded as an important risk factor that threaten human health. Recently, increasing evidence has shown that mROS are very important for an organism’s homeostasis. mROS can regulate a variety of signaling pathways and activate the adaptation and protection behaviors of an organism under stress. In addition, mROS also regulate important physiological processes, such as cell proliferation, differentiation, aging, and apoptosis. Herein, we review the mechanisms of production, transformation, and clearance of mROS and their biological roles in different physiological processes.

Overcoming Radiation Resistance in Gliomas by Targeting Metabolism and DNA Repair Pathways

Gliomas represent a wide spectrum of brain tumors characterized by their high invasiveness, resistance to chemoradiotherapy, and both intratumoral and intertumoral heterogeneity. Recent advances in transomics studies revealed that enormous abnormalities exist in different biological layers of glioma cells, which include genetic/epigenetic alterations, RNA expressions, protein expression/modifications, and metabolic pathways, which provide opportunities for development of novel targeted therapeutic agents for gliomas. Metabolic reprogramming is one of the hallmarks of cancer cells, as well as one of the oldest fields in cancer biology research. Altered cancer cell metabolism not only provides energy and metabolites to support tumor growth, but also mediates the resistance of tumor cells to antitumor therapies. The interactions between cancer metabolism and DNA repair pathways, and the enhancement of radiotherapy sensitivity and assessment of radiation response by modulation of glioma metabolism are discussed herein.

Exploring synthetic biology for the development of a sensor cell line for automated bioprocess control

Unfavorable process conditions lead to adverse cultivation states, limited cell growth and thus hamper biotherapeutic protein production. Oxygen deficiency or hyperosmolality are among the most critical process conditions and therefore require continuous monitoring. We established a novel sensor CHO cell line with the ability to automatically sense and report unwanted process conditions by the expression of destabilized fluorescent proteins. To this end, an inducible real-time system to detect hypoxia by hypoxia response elements (HREs) of vascular endothelial growth factor (VEGF) origin reporting limitations by the expression of destabilized green fluorescent protein (GFP) was created. Additionally, we established a technique for observing hyperosmolality by exploiting osmotic response elements (OREs) for the expression of unstable blue fluorescent protein (BFP, FKBP-BFP), enabling the simultaneous automated supervision of two bioprocess parameters by using a dual sensor CHO cell line transfected with a multiplexable monitoring system. We finally also provided a fully automated in-line fluorescence microscopy-based setup to observe CHO cells and their response to varying culture conditions. In summary, we created the first CHO cell line, reporting unfavorable process parameters to the operator, and provided a novel and promising sensor technology accelerating the implementation of the process analytical technology (PAT) initiative by innovative solutions.

Identification of Hypoxia-Immune-Related Gene Signatures and Construction of a Prognostic Model in Kidney Renal Clear Cell Carcinoma

Introduction: Kidney renal clear cell carcinoma (KIRC), a kind of malignant disease, is a severe threat to public health. Tracking the information of tumor progression and conducting a related dynamic prognosis model are necessary for KIRC. It is crucial to identify hypoxia-immune-related genes and construct a prognostic model due to immune interaction and the influence of hypoxia in the prognosis of patients with KIRC. Methods: The hypoxia and immune status of KIRC patients were identified by utilizing t-SNE and ImmuCellAI for gene expression data. COX and Lasso regression were used to identify some hypoxia-immune-related signature genes and further construct a prognostic risk model based on these genes. Internal and external validations were also conducted to construct a prognostic model. Finally, some potentially effective drugs were screened by the CMap dataset. Results: We found that high-hypoxia and low-immune status tend to induce poor overall survival (OS). Six genes, including PLAUR, UCN, PABPC1L, SLC16A12, NFE2L3, and KCNAB1, were identified and involved in our hypoxia-immune-related prognostic risk model. Internal verification showed that the area under the curve (AUC) for the constructed models for 1-, 3-, 4-, and 5-year OS were 0.768, 0.754, 0.775, and 0.792, respectively. For the external verification, the AUC for 1-, 3-, 4-, and 5-year OS were 0.768, 0.739, 0.763, and 0.643 respectively. Furthermore, the decision curve analysis findings demonstrated excellent clinical effectiveness. Finally, we found that four drugs (including vorinostat, fludroxycortide, oxolinic acid, and flutamide) might be effective and efficient in alleviating or reversing the status of severe hypoxia and poor infiltration of immune cells. Conclusion: Our constructed prognostic model, based on hypoxia-immune-related genes, has excellent effectiveness and clinical application value. Moreover, some small-molecule drugs are screened to alleviate severe hypoxia and poor infiltration of immune cells.

Susceptibility to Metabolic Diseases in COVID-19: To be or Not to be an Issue

Despite the passage of more than 17 months from the beginning of the COVID-19 pandemic, challenges regarding the disease and its related complications still continue in recovered patients. Thus, various studies are underway to assay the long-term effects of COVID-19. Some patients, especially those with severe symptoms, experience susceptibility to a range of diseases and substantial organ dysfunction after recovery. Although COVID-19 primarily affects the lungs, multiple reports exist on the effect of this infection on the kidneys, cardiovascular system, and gastrointestinal tract. Studies have also indicated the increased risk of severe COVID-19 in patients with diabetes. On the other hand, COVID-19 may predispose patients to diabetes, as the most common metabolic disease. Recent studies have shown that Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) binds to Angiotensin-Converting Enzyme 2 (ACE2) receptors, which are expressed in the tissues and organs involved in regulating the metabolic status including pancreas, adipose tissue, gastrointestinal tract, and kidneys. Therefore, SARS-CoV-2 may result in metabolic disturbance. However, there are still many unknowns about SARS-CoV-2, which are required to be explored in basic studies. In this context, special attention to molecular pathways is warranted for understanding the pathogenesis of the disease and achieving therapeutic opportunities. Hence, the present review aims to focus on the molecular mechanisms associated with the susceptibility to metabolic diseases amongst patients recovered from COVID-19.

Reduction of ROS-HIF1α-driven glycolysis by taurine alleviates Streptococcus uberis infection

Antibiotic-resistant strains of Streptococcus uberis (S. uberis) frequently cause clinical mastitis in dairy cows resulting in enormous economic losses. The regulation of immunometabolism is a promising strategy for controlling this bacterial infection. To investigate whether taurine alleviates S. uberis infection by the regulation of host glycolysis via HIF1α, the murine mammary epithelial cell line (EpH4-Ev) and C57BL/6J mice were challenged with S. uberis. Our data indicate that HIF1α-driven glycolysis promotes inflammation and damage in response to the S. uberis challenge. The activation of HIF1α is dependent on mTOR-mediated ROS production. These results were confirmed in vivo. Taurine, an intracellular metabolite present in most animal tissues, has been shown to effectively modulate HIF1α-triggered metabolic reprogramming and contributes to a reduction of inflammation, which reduces mammary tissue damage and prevents mammary gland dysfunction in S. uberis-induced mastitis. These data provide a novel putative prophylactic and therapeutic strategy for amelioration of dairy cow mastitis and bacterial inflammation.

Adipose Stromal/Stem Cell-Derived Extracellular Vesicles: Potential Next-Generation Anti-Obesity Agents

Over the last decade, several compounds have been identified for the treatment of obesity. However, due to the complexity of the disease, many pharmacological interventions have raised concerns about their efficacy and safety. Therefore, it is important to discover new factors involved in the induction/progression of obesity. Adipose stromal/stem cells (ASCs), which are mostly isolated from subcutaneous adipose tissue, are the primary cells contributing to the expansion of fat mass. Like other cells, ASCs release nanoparticles known as extracellular vesicles (EVs), which are being actively studied for their potential applications in a variety of diseases. Here, we focused on the importance of the contribution of ASC-derived EVs in the regulation of metabolic processes. In addition, we outlined the advantages/disadvantages of the use of EVs as potential next-generation anti-obesity agents.

Aged Mouse Hippocampus Exhibits Signs of Chronic Hypoxia and an Impaired HIF-Controlled Response to Acute Hypoxic Exposures

Altered hypoxia-inducible factor-alpha (HIF-α) activity may have significant consequences in the hippocampus, which mediates declarative memory, has limited vascularization, and is vulnerable to hypoxic insults. Previous studies have reported that neurovascular coupling is reduced in aged brains and that diseases which cause hypoxia increase with age, which may render the hippocampus susceptible to acute hypoxia. Most studies have investigated the actions of HIF-α in aging cortical structures, but few have focused on the role of HIF-α within aged hippocampus. This study tests the hypothesis that aging is associated with impaired hippocampal HIF-α activity. Dorsal hippocampal sections from mice aged 3, 9, 18, and 24 months were probed for the presence of HIF-α isoforms or their associated gene products using immunohistochemistry and fluorescent in situ hybridization (fISH). A subset of each age was exposed to acute hypoxia (8% oxygen) for 3 h to investigate changes in the responsiveness of HIF-α to hypoxia. Basal mean intensity of fluorescently labeled HIF-1α protein increases with age in the hippocampus, whereas HIF-2α intensity only increases in the 24-month group. Acute hypoxic elevation of HIF-1α is lost with aging and is reversed in the 24-month group. fISH reveals that glycolytic genes induced by HIF-1α (lactose dehydrogenase-a, phosphoglycerate kinase 1, and pyruvate dehydrogenase kinase 1) are lower in aged hippocampus than in 3-month hippocampus, and mRNA for monocarboxylate transporter 1, a lactose transporter, increases. These results indicate that lactate, used in neurotransmission, may be limited in aged hippocampus, concurrent with impaired HIF-α response to hypoxic events. Therefore, impaired HIF-α may contribute to age-associated cognitive decline during hypoxic events.

Protective Effect of Mesenchymal Stem Cells on Isolated Islets Survival and Against Hypoxia Associated With the HIF-1α/PFKFB3 Pathway

Islets have a high demand for oxygen and most of them will die of hypoxia injury before and after transplantation. Hypoxic damage is one of the key factors associated with islet graft dysfunction. Mesenchymal stem cells (MSCs) have multiple functions and can enhance the therapeutic effect of islet transplantation. In this study, islets were cultured together with or without MSCs derived from umbilical cord (hUC-MSCs) under normal and hypoxic conditions. The effect of hUC-MSCs on the survival and function of isolated islets was detected by immunofluorescence and ELISA. Hypoxia-inducible factor 1 alpha (HIF-1α) and PFKFB3 mRNA and protein expression in different conditions were tested by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blot. The islets co-cultured with hUC-MSCs have improved viability and function compared with islets cultured alone. The mRNA transcription of HIF-1α in the co-cultured group increased. The protein expression of PFKFB3 increased with the increase of HIF-1α. This study found that hUC-MSCs could protect islets from dysfunction caused by hypoxia, and HIF-1α/PFKFB3 played an important role in hypoxic resistance, suggesting a potential strategy to improve the outcome of islet transplantation.

miR-29cb2 promotes angiogenesis and osteogenesis by inhibiting HIF-3α in bone

Coordination between osteogenesis and angiogenesis is required for bone homeostasis. Here, we show that miR-29cb2 is a bone-specific miRNA and plays critical roles on angiogenesis-osteogenesis coupling during bone remodeling. Mice with deletion of miR-29cb2 exhibit osteopenic phenotypes and osteoblast impairment, accompanied by pronounced decreases in specific H vessels. The decrease in bone miR-29cb2 was associated with pathological ovariectomy stimuli. Mechanistically, hypoxia-inducible factor (HIF)-3α, as a target for miR-29cb2, inhibits HIF-1α activity by competitively bonding with HIF-1β. Notably, miR-29cb2 in peripheral blood (PB) nearly is undetectable in sham and significantly increases in ovariectomy mice. Further evaluation from osteoporosis patients demonstrates similar signatures. ROC analysis shows miR-29cb2 in PB has higher sensitivity and specificity for diagnosing osteoporosis when compared with four clinical biomarkers. Collectively, these findings reveal that miR-29cb2 is essential for bone remodeling by inhibiting HIF-3α and elevated bone-specific miR-29cb2 in PB, which may be a promising biomarker for bone loss.

Trophoblast-derived Lactic Acid Orchestrates Decidual Macrophage Differentiation via SRC/LDHA Signaling in Early Pregnancy

Lactic acid (LA) metabolism in the tumor microenvironment contributes to the establishment and maintenance of immune tolerance. This pathway is characterized in tumor associated macrophages. However, the role and pathway of LA metabolism at maternal-fetal interface during early pregnancy, especially in decidual macrophage differentiation, are still unclear. Herein, for the first time, we discovered that LA can trigger either M2 or M1 macrophage polarization via oxidative phosphorylation and glycolysis regulation under normoxia or hypoxia, respectively. Also, LA metabolism played a vital role in decidual macrophages-mediated recurrent pregnancy loss (RPL), through HIF-1α/SRC/LDHA pathway. Moreover, blockade of LA intake with AZD3965 (MCT-1 inhibitor) could rescue pregnancy in an abortion-prone mouse model, suggesting a potential therapeutic target in RPL. Collectively, the present study identifies the previously unknown functions of LA metabolism in the differentiation of decidual macrophages in early normal pregnancy and RPL, and provides a potential therapeutic strategy in RPL by manipulating decidual macrophages' functions through LA metabolic pathway.

Combined Association Between ADIPOQ, PPARG, and TNF Genes Variants and Obstructive Sleep Apnea in Chinese Han Population

PURPOSE

Obstructive sleep apnea (OSA) is a common chronic polygenic disease. Multiple genetic markers associated with OSA have been identified by genome-wide association studies. Here, we aimed to construct a polygenic risk score (PRS) and examine the association with the presence of OSA in a Chinese Han Population.

PATIENTS AND METHODS

This study included 1057 individuals who were genotyped for nine susceptibility loci from three genes (ADIPOQ, PPARG, and TNF), from which each individual's PRS was calculated by summing the number of risk alleles. The associations between PRS and OSA were determined by logistic regression analyses. Model discrimination was assessed by a receiver operating characteristic (ROC) curve using bootstrapping with 1000 resamples.

RESULTS

The subjects included 874 with OSA and 183 controls. A higher PRS was associated with an increased apnea-hypopnea index (AHI). The PRS was an important risk factor for the development of OSA (OR = 1.237 per SD, P = 0.030). Subjects with higher PRS had a 2.88-fold (95% CI: 1.393-5.955, P = 0.004) and 5.402-fold (95% CI: 2.311-12.624, P<0.001) greater risk for having OSA and moderate-to-severe OSA, respectively, compared with those with lower genetic risk. More importantly, compared with determination of risk based solely on clinical factors, addition of the PRS increased discriminatory accuracy for both OSA (AUC from 0.75 to 0.78, P = 0.02) and moderate-to-severe OSA (AUC from 0.80 to 0.83, P = 0.02).

CONCLUSION

Our study suggests that the PRS is independently associated with AHI and OSA. Combining PRS with conventional risk factors could improve the discrimination of OSA.

Chronic constant light exposure aggravates high fat diet-induced renal injury in rats

Obesity-related kidney disease is now recognized as a global health issue, with a substantial number of patients developing progressive renal failure and end-stage renal disease. Interestingly, recent studies indicate light pollution is a novel environmental risk factor for chronic kidney disease. However, the impact of light pollution on obesity-related kidney disease remains largely unknown, with its underlying mechanism insufficiently explained. Renal hypoxia induced factor 1α (HIF1α) is critical in the development of glomerulosclerosis and renal fibrosis. The present study explored effects of constant light exposure on high fat diet (HFD) -induced renal injury and its association with HIF1α signal pathway. Thirty-two male Sprague Dawley rats were divided into four groups according to diet (HFD or normal chow diet) and light cycles (light/dark or constant light). After 16 weeks treatment, rats were sacrificed and pathophysiological assessments were performed. In normal chow fed rats, constant light exposure led to glucose abnormalities and dyslipidemia. In HFD fed rats, constant light exposure exacerbated obesity, glucose abnormalities, insulin resistance, dyslipidemia, renal functional decline, proteinuria, glomerulomegaly, renal inflammation and fibrosis. And, constant light exposure caused an increase in HIF1α and a decrease in prolyl hydroxylase domain 1 (PHD1) and PHD2 expression in kidneys of HFD-fed rats. Then, we demonstrated that BMAL1 bound directly to the promoters of PHD1 in mouse podocyte clone 5 cell line (MPC5) by ChIP assays. In conclusion, chronic constant light exposure aggravates HFD-induced renal injuries in rats, and it is associated with activation of HIF1α signal pathway.

Oxygenation therapies for improved wound healing: Current trends and technologies

Degree of oxygenation is one of the important parameters governing various processes, including cell proliferation, angiogenesis, extracellular matrix production, and even combating the microbial burden at the wound site, all...

HIF-1α switches the functionality of TGF-β signaling via changing the partners of smads to drive glucose metabolic reprogramming in non-small cell lung cancer

BACKGROUND

Most cancer cells have fundamentally different metabolic characteristics, particularly much higher glycolysis rates than normal tissues, which support the increased demand for biosynthesis and promote tumor progression. We found that transforming growth factor (TGF)-β plays a dual function in regulating glycolysis and cell proliferation in non-small cell lung cancer.

METHODS

We used the PET/MRI imaging system to observe the glucose metabolism of subcutaneous tumors in nude mice. Energy metabolism of non-small cell lung cancer cell lines detected by the Seahorse XFe96 cell outflow analyzer. Co-immunoprecipitation assays were used to detect the binding of Smads and HIF-1α. Western blotting and qRT-PCR were used to detect the regulatory effects of TGF-β and HIF-1α on c-MYC, PKM1/2, and cell cycle-related genes.

RESULTS

We discovered that TGF-β could inhibit glycolysis under normoxia while significantly promoting tumor cells' glycolysis under hypoxia in vitro and in vivo. The binding of hypoxia-inducible factor (HIF)-1α to the MH2 domain of phosphorylated Smad3 switched TGF-β function to glycolysis by changing Smad partners under hypoxia. The Smad-p107-E2F4/5 complex that initially inhibited c-Myc expression was transformed into a Smad-HIF-1α complex that promoted the expression of c-Myc. The increased expression of c-Myc promoted alternative splicing of PKM to PKM2, resulting in the metabolic reprogramming of tumor cells. In addition, the TGF-β/Smad signal lost its effect on cell cycle regulatory protein p15/p21. Furthermore, high expression of c-Myc inhibited p15/p21 and promoted the proliferation of tumor cells under hypoxia.

CONCLUSIONS

Our results indicated that HIF-1α functions as a critical factor in the dual role of TGF-β in tumor cells, and may be used as a biomarker or therapeutic target for TGF-β mediated cancer progression.

Metabolic Syndrome and PCOS: Pathogenesis and the Role of Metabolites

Polycystic ovary syndrome (PCOS) is one of the most common endocrine diseases among women of reproductive age and is associated with many metabolic manifestations, such as obesity, insulin resistance (IR) and hyperandrogenism. The underlying pathogenesis of these metabolic symptoms has not yet been fully elucidated. With the application of metabolomics techniques, a variety of metabolite changes have been observed in the serum and follicular fluid (FF) of PCOS patients and animal models. Changes in metabolites result from the daily diet and occur during uncommon physiological routines. However, some of these metabolite changes may provide evidence to explain possible mechanisms and new approaches for prevention and therapy. This article reviews the pathogenesis of PCOS metabolic symptoms and the relationship between metabolites and the pathophysiology of PCOS. Furthermore, the potential clinical application of some specific metabolites will be discussed.

Intestinal HIF-2α Regulates GLP-1 Secretion via Lipid Sensing in L-Cells

BACKGROUND & AIMS

Compelling evidence shows that glucagon-like peptide-1 (GLP-1) has a profound effect in restoring normoglycemia in type 2 diabetic patients by increasing pancreatic insulin secretion. Although L-cells are the primary source of circulating GLP-1, the current therapies do not target L-cells to increase GLP-1 levels. Our study aimed to determine the molecular underpinnings of GLP-1 secretion as an impetus to identify new interventions to target endogenous L-cells.

METHODS

We used genetic mouse models of intestine-specific overexpression of hypoxia-inducible factor (HIF)-1α and HIF-2α (VhlΔIE), conditional overexpression of intestinal HIF-2α (Hif-2αLSL;Vilin-Cre/ERT2), and intestine-specific HIF-2α knockout mice (Hif-2αΔIE) to show that HIF signaling, especially HIF-2α, regulates GLP-1 secretion.

RESULTS

Our data show that intestinal HIF signaling improved glucose homeostasis in a GLP-1-dependent manner. Intestinal HIF potentiated GLP-1 secretion via the lipid sensor G-protein-coupled receptor (GPR)40 enriched in L-cells. We show that HIF-2α regulates GPR40 in L-cells and potentiates fatty acid-induced GLP-1 secretion via extracellular regulated kinase (ERK). Using a genetic model of intestine-specific overexpression of HIF-2α, we show that HIF-2α is sufficient to increase GLP-1 levels and attenuate diet-induced metabolic perturbations such as visceral adiposity, glucose intolerance, and hepatic steatosis. Lastly, we show that intestinal HIF-2α signaling acts as a priming mechanism crucial for postprandial lipid-mediated GLP-1 secretion. Thus, disruption of intestinal HIF-2α decreases GLP-1 secretion.

CONCLUSIONS

In summary, we show that intestinal HIF signaling, particularly HIF-2α, regulates the lipid sensor GPR40, which is crucial for the lipid-mediated GLP-1 secretion, and suggest that HIF-2α is a potential target to induce endogenous GLP-1 secretion.

A review of surface-enhanced Raman spectroscopy in pathological processes

With the continuous growth of the human population and new challenges in the quality of life, it is more important than ever to diagnose diseases and pathologies with high accuracy, sensitivity and in different scenarios from medical implants to the operation room. Although conventional methods of diagnosis revolutionized healthcare, alternative analytical methods are making their way out of academic labs into clinics. In this regard, surface-enhanced Raman spectroscopy (SERS) developed immensely with its capability to achieve single-molecule sensitivity and high-specificity in the last two decades, and now it is well on its way to join the arsenal of physicians. This review discusses how SERS is becoming an essential tool for the clinical investigation of pathologies including inflammation, infections, necrosis/apoptosis, hypoxia, and tumors. We critically discuss the strategies reported so far in nanoparticle assembly, functionalization, non-metallic substrates, colloidal solutions and how these techniques improve SERS characteristics during pathology diagnoses like sensitivity, selectivity, and detection limit. Moreover, it is crucial to introduce the most recent developments and future perspectives of SERS as a biomedical analytical method. We finally discuss the challenges that remain as bottlenecks for a routine SERS implementation in the medical room from in vitro to in vivo applications. The review showcases the adaptability and versatility of SERS to resolve pathological processes by covering various experimental and analytical methods and the specific spectral features and analysis results achieved by these methods.

Cell line development for continuous high cell density biomanufacturing: Exploiting hypoxia for improved productivity

Oxygen deficiency (hypoxia) induces adverse effects during biotherapeutic protein production leading to reduced productivity and cell growth. Hypoxic conditions occur during classical batch fermentations using high cell densities or perfusion processes. Here we present an effort to create novel engineered Chinese hamster ovary (CHO) cell lines by exploiting encountered hypoxic bioprocess conditions to reinforce cellular production capacities. After verifying the conservation of the hypoxia-responsive pathway in CHO cell lines by analyzing oxygen sensing proteins HIF1a, HIF1β and VDL, hypoxia-response-elements (HREs) were functionally analyzed and used to create hypoxia-responsive expression vectors. Subsequently engineered hypoxia sensitive CHO cell lines significantly induced protein expression (SEAP) during adverse oxygen limitation encountered during batch fermentations as well as high cell density perfusion processes (2.7 fold). We also exploited this novel cell system to establish a highly effective oxygen shift as innovative bioprocessing strategy using hypoxia induction to improve production titers. Thus, substantial improvements can be made to optimize CHO cell productivity for novel bioprocessing challenges as oxygen limitation, providing an avenue to establish better cell systems by exploiting adverse process conditions for optimized biotherapeutic production.

Priming, Triggering, Adaptation and Senescence (PTAS): A Hypothesis for a Common Damage Mechanism of Steatohepatitis

Understanding the pathomechanism of steatohepatitis (SH) is hampered by the difficulty of distinguishing between causes and consequences, by the broad spectrum of aetiologies that can produce the phenotype, and by the long time-span during which SH develops, often without clinical symptoms. We propose that SH develops in four phases with transitions: (i) priming lowers stress defence; (ii) triggering leads to acute damage; (iii) adaptation, possibly associated with cellular senescence, mitigates tissue damage, leads to the phenotype, and preserves liver function at a lower level; (iv) finally, senescence prevents neoplastic transformation but favours fibrosis (cirrhosis) and inflammation and further reduction in liver function. Escape from senescence eventually leads to hepatocellular carcinoma. This hypothesis for a pathomechanism of SH is supported by clinical and experimental observations. It allows organizing the various findings to uncover remaining gaps in our knowledge and, finally, to provide possible diagnostic and intervention strategies for each stage of SH development.

Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis

Osteoarthritis (OA) is significantly associated with diabetes, but how hyperglycemia induces or aggravates OA has not been shown. The synovium plays a critical role in cartilage metabolism and substance exchange. Herein, we intended to investigate whether and how hyperglycemia affects the occurrence and progression of OA by influencing the synovium. In patients with knee OA and diabetes (DM OA), we found a more severe inflammatory response, higher endoplasmic reticulum stress (ERS) levels, and more advanced glycosylation end products (AGEs) accumulation in the synovium than in patients without diabetes. Subsequently, we found similar results in the DM OA group in a rat model. In the in vitro cocultivation system, high glucose-stimulated AGEs accumulation, ERS, and inflammation in rat fibroblast-like synoviocytes (FLSs), which resulted in chondrocyte degeneration due to inflammatory factors from FLSs. Furthermore, in the synovium of the DM OA group and FLSs treated with high glucose, the expression of glucose transporter 1 (GLUT1) and its regulatory factor hypoxia-inducible factor (HIF)-1α was increased significantly. Inhibitors of HIF-1α, GLUT1 or AGEs receptors attenuated the effect of high glucose on chondrocyte degradation in the FLS-chondrocyte coculture system. In summary, we demonstrated that hyperglycemia caused AGEs accumulation in FLSs via the HIF-1α-GLUT1 pathway, which increases the release of inflammatory factors from FLSs, subsequently inducing chondrocyte degradation and promoting OA progression.

LncRNA-MCM3AP-AS1 Promotes the Progression of Infantile Hemangiomas by Increasing miR-138-5p/HIF-1α Axis-Regulated Glycolysis

Infantile hemangioma (IH) is a common benign tumor of endothelial cells in infants. Most hemangiomas are self-limited, but a few may develop and lead to serious complications that affect the normal life of children. Therefore, finding an effective treatment strategy for IH is a pressing need. Recent studies have demonstrated that non-coding RNAs affect the progression of multiple tumors. This study aims to investigate the mechanism by which LncRNA-MCM3AP-AS1 promotes glycolysis in the pathogenesis of IH. We first documented that the expression of LncRNA MCM3AP-AS1 was significantly upregulated in IH. Furthermore, we demonstrated that MCM3AP-AS1 bound to miR-106b-3p which promotes glycolysis in IH. In addition, we found that inhibition of HIF-1α contributed to the transformation of glycolysis to normal aerobic oxidation, partially reversed the promoting effect on glycolysis by the up-regulation of LncRNA MCM3AP-AS1 in IH disease. More importantly, we demonstrated this phenomenon existed in IH patients. Taken together, we demonstrate that LncRNA-MCM3AP-AS1 promotes the progression of infantile hemangiomas by increasing the glycolysis via regulating miR-138-5p/HIF-1α axis.

Hypoxia-Inducible Factors as Key Players in the Pathogenesis of Non-alcoholic Fatty Liver Disease and Non-alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) and its more severe form non-alcoholic steatohepatitis (NASH) are a major public health concern with high and increasing global prevalence, and a significant disease burden owing to its progression to more severe forms of liver disease and the associated risk of cardiovascular disease. Treatment options, however, remain scarce, and a better understanding of the pathological and physiological processes involved could enable the development of new therapeutic strategies. One process implicated in the pathology of NAFLD and NASH is cellular oxygen sensing, coordinated largely by the hypoxia-inducible factor (HIF) family of transcription factors. Activation of HIFs has been demonstrated in patients and mouse models of NAFLD and NASH and studies of activation and inhibition of HIFs using pharmacological and genetic tools point toward important roles for these transcription factors in modulating central aspects of the disease. HIFs appear to act in several cell types in the liver to worsen steatosis, inflammation, and fibrosis, but may nevertheless improve insulin sensitivity. Moreover, in liver and other tissues, HIF activation alters mitochondrial respiratory function and metabolism, having an impact on energetic and redox homeostasis. This article aims to provide an overview of current understanding of the roles of HIFs in NAFLD, highlighting areas where further research is needed.

Intestinal hypoxia-inducible factor 2α regulates lactate levels to shape the gut microbiome and alter thermogenesis

Accumulating evidence suggests that the gut microbiota regulates obesity through metabolite-host interactions. However, the mechanisms underlying such interactions have been unclear. Here, we found that intestinal hypoxia-inducible factor 2α (HIF-2α) positively regulates gut lactate by controlling the expression of intestinal Ldha. Intestine-specific HIF-2α ablation in mice resulted in lower lactate levels, and less Bacteroides vulgatus and greater Ruminococcus torques abundance, respectively. Together, these changes resulted in elevated taurine-conjugated cholic acid (TCA) and deoxycholic acid (DCA) levels and activation of the adipose G-protein-coupled bile acid receptor, GPBAR1 (TGR5). This activation upregulated expression of uncoupling protein (UCP) 1 and mitochondrial creatine kinase (CKMT) 2, resulting in elevation of white adipose tissue thermogenesis. Administration of TCA and DCA mirrored these phenotypes, and colonization with B. vulgatus and R. torques inhibited and induced thermogenesis, respectively. This work deepens our understanding of how host genes regulate the microbiome and provides novel strategies for alleviating obesity.

Metabolic dysfunction associated fatty liver disease and coronavirus disease 2019: clinical relationship and current management

The coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). At present, the COVID-19 has been prevalent worldwide for more than a year and caused more than four million deaths. Liver injury was frequently observed in patients with COVID-19. Recently, a new definition of metabolic dysfunction associated fatty liver disease (MAFLD) was proposed by a panel of international experts, and the relationship between MAFLD and COVID-19 has been actively investigated. Several previous studies indicated that the patients with MAFLD had a higher prevalence of COVID-19 and a tendency to develop severe type of respiratory infection, and others indicated that liver injury would be exacerbated in the patients with MAFLD once infected with COVID-19. The mechanism underlying the relationship between MAFLD and COVID-19 infection has not been thoroughly investigated, and recent studies indicated that multifactorial mechanisms, such as altered host angiotensin converting enzyme 2 (ACE2) receptor expression, direct viral attack, disruption of cholangiocyte function, systemic inflammatory reaction, drug-induced liver injury, hepatic ischemic and hypoxic injury, and MAFLD-related glucose and lipid metabolic disorders, might jointly contribute to both of the adverse hepatic and respiratory outcomes. In this review, we discussed the relationship between MAFLD and COVID-19 based on current available literature, and summarized the recommendations for clinical management of MAFLD patients during the pandemic of COVID-19.

Beneficial Metabolic Effects of TREM2 in Obesity Are Uncoupled From Its Expression on Macrophages

Obesity-induced white adipose tissue (WAT) hypertrophy is associated with elevated adipose tissue macrophage (ATM) content. Overexpression of the triggering receptor expressed on myeloid cells 2 (TREM2) reportedly increases adiposity, worsening health. Paradoxically, using insulin resistance, elevated fat mass, and hypercholesterolemia as hallmarks of unhealthy obesity, a recent report demonstrated that ATM-expressed TREM2 promoted health. Here, we identified that in mice, TREM2 deficiency aggravated diet-induced insulin resistance and hepatic steatosis independently of fat and cholesterol levels. Metabolomics linked TREM2 deficiency with elevated obesity-instigated serum ceramides that correlated with impaired insulin sensitivity. Remarkably, while inhibiting ceramide synthesis exerted no influences on TREM2-dependent ATM remodeling, inflammation, or lipid load, it restored insulin tolerance, reversing adipose hypertrophy and secondary hepatic steatosis of TREM2-deficient animals. Bone marrow transplantation experiments revealed unremarkable influences of immune cell-expressed TREM2 on health, instead demonstrating that WAT-intrinsic mechanisms impinging on sphingolipid metabolism dominate in the systemic protective effects of TREM2 on metabolic health.

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

Macrophage HIF-2α suppresses NLRP3 inflammasome activation and alleviates insulin resistance

The interrelation between hypoxia and immune response has pivotal roles in the pathogenesis of chronic metabolic diseases. However, the role of macrophage HIF-2α in NLRP3 inflammasome activation remains unclear. Here, we show that deficiency of HIF-2α in macrophages results in excessive activation of the NLRP3 inflammasome in a manner dependent on CPT1A-mediated enhancement of fatty acid oxidation (FAO). Mechanistically, HIF-2α binds directly to the Cpt1a promoter and is involved in the regulation of H3K27me3 methylation during NLRP3 inflammasome activation. Myeloid-specific Hif2α knockout mice exhibit exacerbated insulin resistance and increased activation of NLRP3 inflammasome in macrophages. Overexpression of the Hif2α gene or stabilization of the protein by FG-4592 ameliorates insulin resistance and reduces NLRP3 inflammasome activation in macrophages. Taken together, our results suggest that macrophage HIF-2α inhibits FAO-mediated activation of the NLRP3 inflammasome and alleviates insulin resistance.