High glucose activates HIF-1-mediated signal transduction in glomerular mesangial cells through a carbohydrate response element binding protein

High glucose/ChREBP-induced Hif-1α transcriptional activation in CD4+ T cells reduces the risk of diabetic kidney disease by inhibiting the Th1 response

AIMS/HYPOTHESIS

Diabetic kidney disease (DKD) features intrarenal inflammation, in which T cells play a part. Hypoxia-inducible factor-1α (HIF-1α), a key transcription factor regulating cellular responses to hypoxia, is reportedly involved in the course of inflammation. The role of HIF-1α in DKD has been investigated, but the conclusions are controversial so far. We report a previously unrecognised high glucose/carbohydrate response element binding protein (ChREBP)/Hif-1α transcription axis in CD4+ T cells.

METHODS

Lck-Cre+Hif1aloxp/loxp (Hif-1α-/-) mice were generated to explore the role of T cell HIF-1α in the pathogenesis of DKD. CD4+ T cells sorted from T cell-specific Hif-1α-ablated mice and wild-type mice were used for functional studies and transcriptional profiling.

RESULTS

In this study, we used Lck-Cre transgenic mice to specifically disrupt Hif-1α in T cells and found that ablation of Hif-1α greatly accelerated the progression of DKD in a streptozocin-induced model of diabetes. Adoptive transfer of splenic CD4+ T cells from Hif-1α-/- mice rather than wild-type controls to diabetic mice elicited severe renal damage. Compared with wild-type controls, Hif-1α knockout markedly promoted IFN-γ secretion by CD4+ T cells in response to high glucose. Additional Ifn-γ ablation negated the effect of Hif-1α knockout on DKD progression. Mechanistically, the background Hif-1α mRNA synthesis rate in resting T cells was very low, but culture of T cells under high glucose led to significantly promoted Hif-1α expression, which was dependent on the transcription factor ChREBP. Consistent with results from Hif-1α-/- CD4+ T cells, adoptive transfer of Chrebp-/- CD4+ T cells to wild-type diabetic mice also elicited severe diabetic renal damage. By contrast, Chrebp-/-Ifn-γ-/- CD4+ T cells failed to show nephrotoxic effects. Examination of the Hif-1α promoter identified a ChREBP-binding sequence that mediated transcriptional upregulation of Hif-1α by high glucose.

CONCLUSIONS/INTERPRETATION

Our study reveals a previously unrecognised high glucose/ChREBP/Hif-1α transcription axis in CD4+ T cells, which serves as a self-protection mechanism against DKD progression via limiting T helper 1 response.

YY1/HIF-1α/mROS positive-feedback loop exacerbates glomerular mesangial cell proliferation in mouse early diabetic kidney disease

Mesangial cells (MCs) are the most active intrinsic cells in the glomerulus. MCs excessively proliferate at the early stage of diabetic kidney disease (DKD), eventually causing glomerular sclerosis and even renal failure; inhibiting glomerular MC proliferation in early DKD is a promising prevention and treatment strategy for early DKD. Our previous study shows that Yin Yang 1 (YY1), a zinc finger protein, is a novel regulator of DKD-induced renal fibrosis. In this study we investigated the role of YY1 in glomerular MC proliferation in DKD in vivo and in vitro. We first showed that YY1 expression levels were significantly increased in the glomerular MCs of DKD patients and db/db mice and in high glucose (HG)-treated SV40-MES13 cells. By using YY1 expression/knockdown plasmids, we confirmed that YY1 contributed to glomerular MC proliferation in vitro. We demonstrated that YY1 upregulated hypoxia-inducible factor-1 alpha (HIF-1α) expression and activity in HG-treated SV40-MES13 cells, leading to overproduction of mROS. Moreover, mROS contributed to positive feedback regulation of YY1/HIF-1α signaling, and the YY1/HIF-1α/mROS positive feedback loop exacerbated glomerular MC proliferation in HG-treated SV40-MES13 cells. In addition, renal-specific YY1 overexpression promoted glomerular MC proliferation in normal mice, whereas renal-specific YY1 knockdown mitigated MC proliferation in early diabetic mice by inactivating HIF-1α/ROS signaling. In conclusion, the YY1/HIF-1α/mROS positive feedback loop might be an attractive therapeutic target for overcoming glomerulosclerosis in early DKD.

Evaluating the prognostic role of glucose-to-lymphocyte ratio in patients with metastatic renal cell carcinoma treated with tyrosine kinase inhibitors in first line: a study by the Turkish Oncology Group Kidney Cancer Consortium (TKCC)

PURPOSE

Identifying prognostic indicators for risk stratification in metastatic renal cell carcinoma (mRCC) is crucial for optimizing treatment strategies and follow-up plans. This study aims to investigate the prognostic role of the glucose-to-lymphocyte ratio (GLR) in patients with mRCC receiving tyrosine kinase inhibitors (TKIs) as first-line therapy.

METHODS

A retrospective cohort study was conducted using data from the Turkish Oncology Group Kidney Cancer Consortium Database. GLR was calculated by dividing the fasting glucose (mmol/L) by the lymphocyte count (×109/L). We categorized patients into two categories based on their median GLR level.

RESULTS

The analysis included a total of 598 patients. We found that progression-free survival (PFS) was significantly longer in the GLR-low group, with a median PFS of 15.05 months (95% CI 12.7-17.4) compared to 7.79 months (95% CI 6.6-9.0) in the GLR-high group (p < 0.001). Multivariate analysis identified GLR as an independent risk factor for poor PFS (HR 1.39, 95% CI 1.12-1.72; p = 0.003). Overall survival (OS) was also significantly longer in the GLR-low group, with a median OS of 38.47 months (95% CI, 30.9-46.0) compared to 24.15 months (95% CI 18.0-30.2) in the GLR-high group (p = 0.001). GLR was an independent predictor for OS in multivariate analysis (HR 1.45, 95% CI 1.12-1.86; p = 0.004).

CONCLUSION

The GLR can be a valuable prognostic marker for glucose metabolism and systemic inflammatory status in this patient population. Our research highlights the potential prognostic value of GLR in patients with mRCC receiving TKIs, indicating its potential as a useful tool for clinical decision-making.

Effects of a Rosmarinus officinalis L. Extract and Rosmarinic Acid in Improving Streptozotocin-Induced Aortic Tissue Damages in Rats

BACKGROUND/AIM

Rosmarinus officinalis L. (R. officinalis) is an aromatic medicinal species with important nutraceutical potential, having rosmarinic acid (RA) as one of its main metabolites. The present study aims to evaluate the effects of an extract obtained from the leaves of this species and of its main metabolite in improving the streptozotocin-induced damage of hearts and aorta of diabetic rats.

METHODS

The leaves of the species were used to obtain a hydroethanolic extract, which was analyzed using the LC/MS method. Diabetes mellitus was induced by intraperitoneal streptozotocin administration in rats. After two weeks, oxidative stress parameters were evaluated from the heart and aorta homogenates. NOS3, AMPK, and adiponectin levels were quantified using ELISA tests, and thoracic aorta rings were isolated for contractility evaluation in the organ bath. Phospho-NF-κB, NRF2, HIF1 alfa, iNOS, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) quantification were performed using the Western blot technique.

RESULTS

Carnosic acid, together with rosmarinic acid, were proven to be the main metabolites identified in the composition of the tested extract. Administration of the extract and of RA improved the relaxation response to acetylcholine and the redox status, with the reduction in malondialdehyde (MDA), nitric oxide synthase 3 (NOS 3), AMP-activated protein kinase (AMPK), adiponectin, reduced (GSH) and oxidized glutathione (GSSG) levels, and superoxide dismutase (SOD) activity. RA significantly enhanced the expression of HIF 1α, NRF2, and pNFkB in the heart.

CONCLUSIONS

Administration of the R. officinalis extract and of RA-alleviated oxidative stress, proving vascular and cardiac antioxidant properties in the hearts and aorta of diabetic rats.

The Association of Cell-Free LncH19 and miR-29b Expression with the PI3K/AKT/HIF-1/VEGF Pathway in Patients with Diabetic Nephropathy: In Silico Prediction and Clinical Validation

Diabetic nephropathy (DN) affects about one-third of patients with diabetes and can lead to end-stage renal disease despite numerous trials aimed at improving diabetic management. Non-coding RNAs (ncRNAs) represent a new frontier in DN research, as increasing evidence suggests their involvement in the occurrence and progression of DN. A growing body of evidence suggests that long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) in DN signaling pathways might serve as novel biomarkers or therapeutic targets, although this remains to be fully explored. Our study included four groups, each comprising 40 adults: patients with diabetes (a) without albuminuria, (b) with microalbuminuria, (c) with macroalbuminuria, and a control group. All participants underwent history-taking and clinicolaboratory assessments, including CBC, fasting blood sugar, HbA1c, lipid profile, liver function, and renal function tests. Additionally, expressions of lncRNA H19, miRNA-29b, PI3K, AKT, mTOR, and HIF-1 alpha were assessed using qPCR. lncRNA H19 expression was upregulated in patients with albuminuria compared to the DM group. Furthermore, based on qPCR, the level of lncRNA H19 was negatively correlated with eGFR and miRNA-29b expression. On the other hand, the lncRNA H19 level was positively correlated with PI3K, AKT, mTOR, and HIF-1 alpha levels. We also found that the lncH19/miRNA-29b ratio was significantly increased in patients with DN and macroalbuminuria. In conclusion, lncRNA H19 was upregulated in patients with DN, and this increase was associated with miRNA29b downregulation. Therefore, our study suggests a novel link between the lncH19/miRNA-29b ratio and DN, indicating that it might serve as a potential biomarker for the dynamic monitoring of DN.

Taohe Chengqi decoction improves diabetic cognitive dysfunction by alleviating neural stem cell senescence through HIF1α-driven metabolic signaling

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is characterized by numerous long-term complications, in which progressive cognitive decline represents a significant risk factor for dementia and other neurodegenerative disorders. Taohe Chengqi decoction (THCQ) is a common traditional Chinese formula for treating T2DM; however, the neuroprotective effect of THCQ on diabetes-associated cognitive dysfunction remains unclear. Hence, the present study investigated the therapeutic effects of THCQ on cognitive impairment associated with T2DM and elucidated the underlying mechanisms.

METHODS

A stable high-fat diet (HFD) and streptozotocin (STZ)-induced T2DM mouse model was established and received intragastrical THCQ administration. Blood and tissue samples were investigated for biochemical parameters and neuropathology, whereas hippocampal tissue underwent transcriptome analyses and the role of neural stem cell (NSC) senescence was detected both in vivo and in vitro. Network pharmacology analysis and subsequent primary NSC experiments were conducted to explore the involvement of the HIF1α signaling pathway in THCQ-mediated hippocampal NSC senescence. Furthermore, a lentivirus vector overexpressing HIF1α was used to verify the THCQ potential therapeutic effects on HIF1α/PDKs metabolic signaling that influenced NSC senescence.

RESULTS

THCQ alleviated cognitive dysfunction and metabolic abnormalities in HFD/STZ mice, and relieved hippocampal neurodegeneration. Transcriptome analyses and validation experiments revealed THCQ-induced neuroprotective effects by targeting high glucose-mediated hippocampal neuropathy and NSC senescence. Bioinformatic analysis indicated that HIF1α signaling played a significant role in THCQ therapeutic outcomes; while HIF1α overexpression impaired the effects of THCQ on high glucose-induced metabolic disorders and NSC senescence.

CONCLUSION

The present study demonstrated that THCQ improved diabetic cognitive dysfunction and hippocampal neurogenesis, the effects of which were mainly attributed to the restoration of metabolic homeostasis and inhibition of NSC senescence through HIF1α signaling. Our results provide novel insights into the therapeutic framework for diabetic neuropathy and indicate that THCQ might be a promising candidate for the management of T2DM-related cognitive disorders.

Acute hyperglycemia exacerbates neuroinflammation and cognitive impairment in sepsis-associated encephalopathy by mediating the ChREBP/HIF-1α pathway

OBJECTIVES

Delirium is a prominent symptom of sepsis-associated encephalopathy (SAE) and is highly prevalent in septic patients hospitalized in the intensive care unit, being closely connected with raised mortality rates. Acute hyperglycemia (AH) has been recognized as a separate risk factor for delirium and a worse prognosis in critically sick patients. Nevertheless, the exact contribution of AH to the advancement of SAE is still unknown.

METHODS

This research retrospectively evaluated the connection between blood glucose levels (BGLs) and the incidence of delirium and death rates in septic patients in the ICU of a tertiary comprehensive hospital. In addition, a septic rat model was induced through cecal ligation and puncture (CLP), after which continuous glucose infusion was promptly initiated via a central venous catheter post-surgery to evaluate the potential implications of AH on SAE. Next, septic rats were assigned to four groups based on target BGLs: high glucose group (HG, ≥ 300 mg/dL), moderate glucose group (MG, 200-300 mg/dL), normal glucose group (NG, < 200 mg/dL), and a high glucose insulin-treated group (HI, 200-300 mg/dL) receiving recombinant human insulin treatment (0.1 IU/kg/min). The sham group (SG) received an equivalent volume of saline infusion and denoted the NG group. The effects of AH on neuroinflammation and cognitive function in septic rats were evaluated using behavioral tests, histopathological examination, TUNEL staining, ELISA, and Western blot. The effects of glucose levels on microglial activation and glucose metabolism following lipopolysaccharide (LPS, 1 μg/mL) exposure were assessed using CCK8 assay, qRT-PCR, Western blot, and ELISA.

RESULTS

Our findings revealed that AH during sepsis was a separate risk factor for delirium and assisted in predicting delirium occurrence. AH raised the levels of systemic and central inflammatory cytokines in septic rats, promoting neuronal apoptosis, blood-brain barrier disruption, and cognitive impairment. In addition, both in vivo and in vitro, an elevated glucose challenge increased the ChREBP, HIF-1α, glycolytic enzymes, and inflammatory cytokines expressions in microglia after exposure to CLP or LPS.

CONCLUSIONS

These results collectively suggest that hyperglycemia can exacerbate neuroinflammation and delirium by enhancing microglial glycolysis under septic conditions, potentially mediated by upregulation of the ChREBP/HIF-1α signaling pathway.

Knockout of the Carbohydrate Responsive Element Binding Protein Enhances Proliferation and Tumorigenesis in Renal Tubules of Mice

Glycogen-storing so-called clear cell kidney tubules (CCTs), precursor lesions of renal cell carcinoma, have been described in diabetic rats and in humans. The lesions show upregulation of the Akt/mTOR-pathway and the related transcription factor carbohydrate responsive element binding protein (ChREBP), which is supposedly pro-oncogenic. We investigated the effect of ChREBP-knockout on nephrocarcinogenesis in streptozotocin-induced diabetic and normoglycemic mice. Diabetic, but not non-diabetic mice, showed CCTs at 3, 6 and 12 months of age. Glycogenosis was confirmed by periodic acid schiff reaction and transmission electron microscopy. CCTs in ChREBP-knockout mice consisted of larger cells and occurred more frequently compared to wildtype mice. Progression towards kidney tumors was observed in both diabetic groups but occurred earlier in ChREBP-knockout mice. Proliferative activity assessed by BrdU-labeling was lower in 1-week-old but higher in 12-month-old diabetic ChREBP-knockout mice. Surprisingly, renal neoplasms occurred spontaneously in non-diabetic ChREBP-knockout, but not non-diabetic wildtype mice, indicating an unexpected tumor-suppressive function of ChREBP. Immunohistochemistry showed upregulated glycolysis and lipogenesis, along with activated Akt/mTOR-signaling in tumors of ChREBP-knockout groups. Immunohistochemistry of human clear cell renal cell carcinomas revealed reduced ChREBP expression compared to normal kidney tissue. However, the molecular mechanisms by which loss of ChREBP might facilitate tumorigenesis require further investigation.

Targeting hypoxia and thrombospondin-2 in diabetic wound healing

Impaired wound healing in diabetic patients is the leading cause of diabetes-associated hospitalizations and approximately 50% of lower limb amputations. This is due to multiple factors, including elevated glucose, sustained hypoxia, and cell dysfunction. Previously, diabetic wounds were found to contain excessive levels of the matricellular protein thrombospondin-2 (TSP2) and genetic ablation of TSP2 in diabetic mice or treatment of wounds with a hydrogel derived from TSP2-null mouse skin improved healing. Previously, TSP2 has been shown to be repressed by hypoxia, but in the present study we observed sustained hypoxia and overlapping TSP2 deposition in diabetic wounds. We determined this observation was due to the insufficient HIF-1α activation verified by western blot and immunofluorescent analysis of wound tissues and in vitro hypoxia experiments. Application of Dimethyloxalylglycine (DMOG), which can stabilize HIF-1α, inhibited TSP2 expression in diabetic fibroblasts in hypoxic conditions. Therefore, we prepared DMOG-containing TSP2KO hydrogel and applied it to the wounds of diabetic mice. In comparison to empty TSP2KO hydrogel or DMOG treatment, we observed improved wound healing associated with a reduction of TSP2, reduced hypoxia, and increased neovascularization. Overall, our findings shed light on the intricate interplay between hyperglycemia, hypoxia, and TSP2 in the complex environment of diabetic wounds.

Citropten Inhibits Vascular Smooth Muscle Cell Proliferation and Migration via the TRPV1 Receptor

Vascular smooth muscle cell (VSMC) proliferation and migration play critical roles in arterial remodeling. Citropten, a natural organic compound belonging to coumarin and its derivative classes, exhibits various biological activities. However, mechanisms by which citropten protects against vascular remodeling remain unknown. Therefore, in this study, we investigated the inhibitory effects of citropten on VSMC proliferation and migration under high-glucose (HG) stimulation. Citropten abolished the proliferation and migration of rat vascular smooth muscle cells (RVSMCs) in a concentration-dependent manner. Also, citropten inhibited the expression of proliferation-related proteins, including proliferating cell nuclear antigen (PCNA), cyclin E1, cyclin D1, and migration-related markers such as matrix metalloproteinase (MMP), MMP2 and MMP9, in a concentration-dependent manner. In addition, citropten inhibited the phosphorylation of ERK and AKT, as well as hypoxia-inducible factor-1α (HIF-1α) expression, mediated to the Krüppel-like factor 4 (KLF4) transcription factor. Using pharmacological inhibitors of ERK, AKT, and HIF-1α also strongly blocked the expression of MMP9, PCNA, and cyclin D1, as well as migration and the proliferation rate. Finally, molecular docking suggested that citropten docked onto the binding site of transient receptor potential vanilloid 1 (TRPV1), like epigallocatechin gallate (EGCG), a well-known agonist of TRPV1. These data suggest that citropten inhibits VSMC proliferation and migration by activating the TRPV1 channel.

SGLT2 Inhibitors and Kidney Protection: Mechanisms Beyond Tubuloglomerular Feedback

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk for kidney failure and are a key component of guideline-directed therapy for CKD. While SGLT2 inhibitors' ability to activate tubuloglomerular feedback and reduce hyperfiltration-mediated kidney injury is considered to be the central mechanism for kidney protection, recent data from experimental studies raise questions on the primacy of this mechanism. This review examines SGLT2 inhibitors' role in tubuloglomerular feedback and summarizes emerging evidence on following of SGLT2 inhibitors' other putative mechanisms for kidney protection: optimization of kidney's energy substrate utilization and delivery, regulation of autophagy and maintenance of cellular homeostasis, attenuation of sympathetic hyperactivity, and improvement in vascular health and microvascular function. It is imperative to examine the effect of SGLT2 inhibition on these different physiologic processes to help our understanding of mechanisms underpinning kidney protection with this important class of drugs.

Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications

Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased activity of glycolytic enzymes-unscheduled glycolysis-produces increased levels of glycolytic intermediates with overspill into effector pathways of cell dysfunction and pathogenesis. HK1 is saturated with glucose in euglycemia and, where it is the major HK, provides for basal glycolytic flux without glycolytic overload. HK2 has similar saturation characteristics, except that, in persistent hyperglycemia, it is stabilized to proteolysis by high intracellular glucose concentration, increasing HK activity and initiating glycolytic overload and unscheduled glycolysis. This drives the development of vascular complications of diabetes. Similar HK2-linked unscheduled glycolysis in skeletal muscle and adipose tissue in impaired fasting glucose drives the development of peripheral insulin resistance. Glucokinase (GCK or HK4)-linked glycolytic overload and unscheduled glycolysis occurs in persistent hyperglycemia in hepatocytes and beta-cells, contributing to hepatic insulin resistance and beta-cell glucotoxicity, leading to the development of type 2 diabetes. Downstream effector pathways of HK-linked unscheduled glycolysis are mitochondrial dysfunction and increased reactive oxygen species (ROS) formation; activation of hexosamine, protein kinase c, and dicarbonyl stress pathways; and increased Mlx/Mondo A signaling. Mitochondrial dysfunction and increased ROS was proposed as the initiator of metabolic dysfunction in hyperglycemia, but it is rather one of the multiple downstream effector pathways. Correction of HK2 dysregulation is proposed as a novel therapeutic target. Pharmacotherapy addressing it corrected insulin resistance in overweight and obese subjects in clinical trial. Overall, the damaging effects of hyperglycemia are a consequence of HK-gated increased flux of glucose metabolism without increased glycolytic enzyme activities to accommodate it.

Resveratrol attenuates high glucose-induced inflammation and improves glucose metabolism in HepG2 cells

Diabetes mellitus (DM) is characterized by impaired glucose and insulin metabolism, resulting in chronic hyperglycemia. Hyperglycemia-induced inflammation is linked to the onset and progression of diabetes. Resveratrol (RES), a polyphenol phytoalexin, is studied in diabetes therapeutics research. This study evaluates the effect of RES on inflammation and glucose metabolism in HepG2 cells exposed to high glucose. Inflammation and glucose metabolism-related genes were investigated using qPCR. Further, inflammatory genes were analyzed by applying ELISA and Bioplex assays. High glucose significantly increases IKK-α, IKB-α, and NF-kB expression compared to controls. Increased NF-kB expression was followed by increased expression of pro-inflammatory cytokines, such as TNF-α, IL-6, IL-β, and COX2. RES treatment significantly reduced the expression of NF-kB, IKK-α, and IKB-α, as well as pro-inflammatory cytokines. High glucose levels reduced the expression of TGFβ1, while treatment with RES increased the expression of TGFβ1. As glucose levels increased, PEPCK expression was reduced, and GCK expression was increased in HepG2 cells treated with RES. Further, HepG2 cells cultured with high glucose showed significant increases in KLF7 and HIF1A but decreased SIRT1. Moreover, RES significantly increased SIRT1 expression and reduced KLF7 and HIF1A expression levels. Our results indicated that RES could attenuate high glucose-induced inflammation and enhance glucose metabolism in HepG2 cells.

Hypoxia induces mitochondrial protein lactylation to limit oxidative phosphorylation

Oxidative phosphorylation (OXPHOS) consumes oxygen to produce ATP. However, the mechanism that balances OXPHOS activity and intracellular oxygen availability remains elusive. Here, we report that mitochondrial protein lactylation is induced by intracellular hypoxia to constrain OXPHOS. We show that mitochondrial alanyl-tRNA synthetase (AARS2) is a protein lysine lactyltransferase, whose proteasomal degradation is enhanced by proline 377 hydroxylation catalyzed by the oxygen-sensing hydroxylase PHD2. Hypoxia induces AARS2 accumulation to lactylate PDHA1 lysine 336 in the pyruvate dehydrogenase complex and carnitine palmitoyltransferase 2 (CPT2) lysine 457/8, inactivating both enzymes and inhibiting OXPHOS by limiting acetyl-CoA influx from pyruvate and fatty acid oxidation, respectively. PDHA1 and CPT2 lactylation can be reversed by SIRT3 to activate OXPHOS. In mouse muscle cells, lactylation is induced by lactate oxidation-induced intracellular hypoxia during exercise to constrain high-intensity endurance running exhaustion time, which can be increased or decreased by decreasing or increasing lactylation levels, respectively. Our results reveal that mitochondrial protein lactylation integrates intracellular hypoxia and lactate signals to regulate OXPHOS.

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

Mechanistic insights into the alterations and regulation of the AKT signaling pathway in diabetic retinopathy

In the early stages of diabetic retinopathy (DR), diabetes-related hyperglycemia directly inhibits the AKT signaling pathway by increasing oxidative stress or inhibiting growth factor expression, which leads to retinal cell apoptosis, nerve proliferation and fundus microvascular disease. However, due to compensatory vascular hyperplasia in the late stage of DR, the vascular endothelial growth factor (VEGF)/phosphatidylinositol 3 kinase (PI3K)/AKT cascade is activated, resulting in opposite levels of AKT regulation compared with the early stage. Studies have shown that many factors, including insulin, insulin-like growth factor-1 (IGF-1), VEGF and others, can regulate the AKT pathway. Disruption of the insulin pathway decreases AKT activation. IGF-1 downregulation decreases the activation of AKT in DR, which abrogates the neuroprotective effect, upregulates VEGF expression and thus induces neovascularization. Although inhibiting VEGF is the main treatment for neovascularization in DR, excessive inhibition may lead to apoptosis in inner retinal neurons. AKT pathway substrates, including mammalian target of rapamycin (mTOR), forkhead box O (FOXO), glycogen synthase kinase-3 (GSK-3)/nuclear factor erythroid 2-related factor 2 (Nrf2), and nuclear factor kappa-B (NF-κB), are a research focus. mTOR inhibitors can delay or prevent retinal microangiopathy, whereas low mTOR activity can decrease retinal protein synthesis. Inactivated AKT fails to inhibit FOXO and thus causes apoptosis. The GSK-3/Nrf2 cascade regulates oxidation and inflammation in DR. NF-κB is activated in diabetic retinas and is involved in inflammation and apoptosis. Many pathways or vital activities, such as the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and mitogen-activated protein kinase (MAPK) signaling pathways, interact with the AKT pathway to influence DR development. Numerous regulatory methods can simultaneously impact the AKT pathway and other pathways, and it is essential to consider both the connections and interactions between these pathways. In this review, we summarize changes in the AKT signaling pathway in DR and targeted drugs based on these potential sites.

Persistence and expansion of hypoxia detected by pimonidazole adduct immunostaining during progression of diabetic nephropathy in diabetic mice

Hypoxia and oxidative stress are considered to be underlying factors in the deterioration of renal function and pathogenesis in acute kidney injury (AKI) and chronic kidney disease, including diabetic nephropathy (DN). However, the long-term role of hypoxia in DN is unknown. Here, we investigated the distribution, severity, and time course of hypoxia during DN development in our well-established severely diabetic transgenic (Tg) DN mouse model that mimics human DN up to 80 wk of age, using pimonidazole adduct immunohistochemistry. The relationship between pimonidazole adduct distribution and hypoxia-inducible factor (HIF) expression was also examined. We found 1) persistent pimonidazole immunostaining mainly in the outer zone of the outer medulla, extending into the inner zone, 2) significant expansion of area and intensity up to 40 wk of age, and 3) characteristic subcellular localization mainly at apical sites in vesicular form by laser scanning microscopy of thin slices. The distribution of pimonidazole adducts was different from that of HIF reported previously, indicating that hypoxia does not directly contribute to persistent abnormal HIF expression. These results suggest that pimonidazole adducts produced under low [Formula: see text] conditions are sustained by a mechanism distinct from direct ischemia. We propose that in the long course of DN development, persistent hyperfiltration and hyperexcretion of glucose, albumin, and water increase metabolism and energy expenditure in the tubules, and such chronic stimulation leads to relative ischemia and local hypoxia, which may contribute in part to the loss of nephrons.NEW & NOTEWORTHY This study provides new insights into hypoxia during the long course of diabetic nephropathy development. Hypoxia was persistently localized only in limited areas and its distribution differed significantly from that of hypoxia-inducible factors. These findings suggests that in the long course of diabetic nephropathy development, increased energy requirements and limited blood supply may lead to relative ischemia and induction of local and persistent hypoxia, which may contribute in part to the loss of nephrons.

miR-34a/SIRT1/HIF-1α axis is involved in cardiac angiogenesis of type 2 diabetic rats: The protective effect of sodium butyrate combined with treadmill exercise

Type 2 diabetes mellitus (T2DM) is one of the most common metabolic disorders worldwide. Recent research has indicated that sodium butyrate (NaB) affects glucose metabolism and exercise has an anti-hyperglycemic effect in diabetes. This study aimed to evaluate the effects of NaB and treadmill exercise on heart angiogenesis through the miR-34a/SIRT1/FOXO1-HIF-1α pathway. Diabetic animals received NaB (400 mg/kg daily, orally) and treadmill exercise for 6 weeks. The effect of NaB and treadmill exercise, alone or combined, on miR-34a expression, SIRT1, FOXO1, HIF-1α levels, and angiogenesis in diabetic heart tissue was measured. Diabetes caused increased miR-34a (p < 0.01) and FOXO1 (p < 0.001) expression levels. Also, SIRT1 (p < 0.001) and HIF-1α (not significant) expression levels were reduced in diabetic rats. NaB and treadmill exercise decreased miR-34a (respectively p < 0.05 and not significant) and FOXO1 (both p < 0.001) expression levels and improved SIRT1 (both not significant) and HIF-1α (respectively p < 0.01 and p < 0.001) levels. Also, NaB combined with treadmill exercise decreased miR-34a (p < 0.001) and FOXO1 (p < 0.001) expression levels, and elevated SIRT1 (p < 0.05) and HIF-1α (p < 0.001) levels in comparison with the diabetic group. NaB and treadmill exercises modulate the expression of miR-34a and the levels of SIRT1, FOXO1, and HIF-1α proteins, thus increasing angiogenesis in the heart tissue of diabetic rats. It can be concluded that NaB and treadmill exercise, alone or combined, may be useful in the treatment of diabetes through the miR-34a/SIRT1/FOXO1-HIF-1α pathway.

The "sweet" path to cancer: focus on cellular glucose metabolism

The hypoxia-inducible factor-1α (HIF-1α), a key player in the adaptive regulation of energy metabolism, and the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2), a critical regulator of glucose consumption, are the main drivers of the metabolic rewiring in cancer cells. The use of glycolysis rather than oxidative phosphorylation, even in the presence of oxygen (i.e., Warburg effect or aerobic glycolysis), is a major metabolic hallmark of cancer. Aerobic glycolysis is also important for the immune system, which is involved in both metabolic disorders development and tumorigenesis. More recently, metabolic changes resembling the Warburg effect have been described in diabetes mellitus (DM). Scientists from different disciplines are looking for ways to interfere with these cellular metabolic rearrangements and reverse the pathological processes underlying their disease of interest. As cancer is overtaking cardiovascular disease as the leading cause of excess death in DM, and biological links between DM and cancer are incompletely understood, cellular glucose metabolism may be a promising field to explore in search of connections between cardiometabolic and cancer diseases. In this mini-review, we present the state-of-the-art on the role of the Warburg effect, HIF-1α, and PKM2 in cancer, inflammation, and DM to encourage multidisciplinary research to advance fundamental understanding in biology and pathways implicated in the link between DM and cancer.

The Sweet Side of HIPK2

HIPK2 is an evolutionary conserved protein kinase which modulates many molecular pathways involved in cellular functions such as apoptosis, DNA damage response, protein stability, and protein transcription. HIPK2 plays a key role in the cancer cell response to cytotoxic drugs as its deregulation impairs drug-induced cancer cell death. HIPK2 has also been involved in regulating fibrosis, angiogenesis, and neurological diseases. Recently, hyperglycemia was found to positively and/or negatively regulate HIPK2 activity, affecting not only cancer cell response to chemotherapy but also the progression of some diabetes complications. The present review will discuss how HIPK2 may be influenced by the high glucose (HG) metabolic condition and the consequences of such regulation in medical conditions.

ChREBP-β/TXNIP aggravates frucose-induced renal injury through triggering ferroptosis of renal tubular epithelial cells

High fructose intake is an essential risk factor for kidney injury. However, the specific mechanism underlying high fructose-induced kidney injury remains unclarified. Carbohydrate response element-binding protein (ChREBP) is a key transcriptional activator that regulates fructose metabolism. ChREBP-β exhibits sustained activity due to the lack of a low glucose inhibitory domain, and is thus described as the active form of ChREBP. In this study, a mouse model with specific overexpression of ChREBP-β in the renal tubule was established by using the Cre/LoxP method. Quantitative proteomic analysis and experimental verification results suggest that ChREP-β overexpression leads to ferroptosis of renal tubular epithelial cells and kidney injury. ChREPB-β promotes the gene transcription of thioredoxin-interacting protein (TXNIP) and thereby increases its expression level. TXNIP is associated with activation of ferroptosis. TXNIP can initiate ferroptosis and eventually contribute to high fructose-induced renal tubular epithelial cell damage. Through down-regulating ChREBP-β, metformin can inhibit gene transcription of TXNIP, attenuate high fructose-induced ferroptosis in renal tubular epithelial cells, and alleviate kidney injury. In conclusion, ChREBP-β mediates fructose-induced ferroptosis of renal tubular epithelial cells, and metformin with a ChREBP-β inhibitory effect may be a potential treatment for ferroptosis of renal tubular epithelial cells.

High glucose induced HIF-1α/TREK1 expression and myometrium relaxation during pregnancy

Background

The incidence of gestational diabetes mellitus (GDM) is increasing worldwide. GDM patients have a significantly higher rate of cesarean section and postpartum hemorrhage, suggesting changes in uterine contractility. TWIK-1-related potassium channel (TREK1) expressed in the pregnant uterus and its role in uterine contraction. In this study, we examined the expression of HIF-1α and TREK1 proteins in GDM uterine and investigated whether high glucose levels are involved in the regulation of human uterine smooth muscle cells (HUSMCs) contraction through TREK1, and verified the role of HIF-1α in this process.

Methods

Compared the uterine contractility between GDM and normal patients undergoing elective lower segment cesarean section. The HUSMCs were divided into normal glucose group, high glucose group, normal glucose with CoCl2 group, CoCl2 with echinomycin/L-Methionine group, and high glucose with echinomycin/L-Methionine group; Compare the cell contractility of each group. Compared the expression of hypoxia-inducible factor-1α (HIF-1α) and TREK1 protein in each group.

Results

The contractility of human uterine strips induced by both KCl and oxytocin was significantly lower in patients with GDM compared with that in normal individuals, with increased TREK1 and HIF-1α protein expression. The contractility of cultured HUSMCs was significantly decreased under high glucose levels, which was consistent with increased expression of HIF-1α and TREK1 proteins. The contractility of HUSMCs was decreased when hypoxia was induced by CoCl2 and increased when hypoxia was inhibited by echinomycin. The TREK1 inhibitor L-methionine also recovered the decreased contractility of HUSMCs under high glucose levels or hypoxia.

Discussion

The high glucose levels decreased the contractility of the myometrium, and increased expression of HIF-1a and TREK1 proteins play a role in changes in uterus contractility.

YY1-induced upregulation of LncRNA-ARAP1-AS2 and ARAP1 promotes diabetic kidney fibrosis via aberrant glycolysis associated with EGFR/PKM2/HIF-1α pathway

Objectives: Dimeric pyruvate kinase (PK) M2 (PKM2) plays an important role in promoting the accumulation of hypoxia-inducible factor (HIF)-1α, mediating aberrant glycolysis and inducing fibrosis in diabetic kidney disease (DKD). The aim of this work was to dissect a novel regulatory mechanism of Yin and Yang 1 (YY1) on lncRNA-ARAP1-AS2/ARAP1 to regulate EGFR/PKM2/HIF-1α pathway and glycolysis in DKD. Materials and methods: We used adeno-associated virus (AAV)-ARAP1 shRNA to knocked down ARAP1 in diabetic mice and overexpressed or knocked down YY1, ARAP1-AS2 and ARAP1 expression in human glomerular mesangial cells. Gene levels were assessed by Western blotting, RT-qPCR, immunofluorescence staining and immunohistochemistry. Molecular interactions were determined by RNA pull-down, co-immunoprecipitation, ubiquitination assay and dual-luciferase reporter analysis. Results: YY1, ARAP1-AS2, ARAP1, HIF-1α, glycolysis and fibrosis genes expressions were upregulated and ARAP1 knockdown could inhibit dimeric PKM2 expression and partly restore tetrameric PKM2 formation, while downregulate HIF-1α accumulation and aberrant glycolysis and fibrosis in in-vivo and in-vitro DKD models. ARAP1 knockdown attenuates renal injury and renal dysfunction in diabetic mice. ARAP1 maintains EGFR overactivation in-vivo and in-vitro DKD models. Mechanistically, YY1 transcriptionally upregulates ARAP1-AS2 and indirectly regulates ARAP1 and subsequently promotes EGFR activation, HIF-1α accumulation and aberrant glycolysis and fibrosis. Conclusion: Our results first highlight the role of the novel regulatory mechanism of YY1 on ARAP1-AS2 and ARAP1 in promoting aberrant glycolysis and fibrosis by EGFR/PKM2/HIF-1α pathway in DKD and provide potential therapeutic strategies for DKD treatments.

Functions of the aryl hydrocarbon receptor (AHR) beyond the canonical AHR/ARNT signaling pathway

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor regulating adaptive and maladaptive responses toward exogenous and endogenous signals. Research from various biomedical disciplines has provided compelling evidence that the AHR is critically involved in the pathogenesis of a variety of diseases and disorders, including autoimmunity, inflammatory diseases, endocrine disruption, premature aging and cancer. Accordingly, AHR is considered an attractive target for the development of novel preventive and therapeutic measures. However, the ligand-based targeting of AHR is considerably complicated by the fact that the receptor does not always follow the beaten track, i.e. the canonical AHR/ARNT signaling pathway. Instead, AHR might team up with other transcription factors and signaling molecules to shape gene expression patterns and associated physiological or pathophysiological functions in a ligand-, cell- and micromilieu-dependent manner. Herein, we provide an overview about some of the most important non-canonical functions of AHR, including crosstalk with major signaling pathways involved in controlling cell fate and function, immune responses, adaptation to low oxygen levels and oxidative stress, ubiquitination and proteasomal degradation. Further research on these diverse and exciting yet often ambivalent facets of AHR biology is urgently needed in order to exploit the full potential of AHR modulation for disease prevention and treatment.

The therapeutic prospect of zinc oxide nanoparticles in experimentally induced diabetic nephropathy

Diabetic nephropathy (DN) is the most frequent cause of end-stage renal failure. Zinc oxide nanoparticles (ZnO-NPs) are promising antidiabetic agents. Our aim was to evaluate the prospective efficacy of ZnO-NPs in treating DN in streptozotocin-induced diabetic rats. Rats were randomly dispersed into three sets: control group, DN group and DN + ZnO-NPs group. ZnO-NPs were given at a dose of 10 mg/kg/day by oral gavage for 4 weeks. Urine and blood samples were processed for biochemical analyses. Kidney samples were managed for light and electron microscopy studies. Immune histochemical staining of P53, aquaporin11 (AQP11) and mechanistic target of rapamycin (mTOR) were performed. Gene analyses of nephrin, podocin, beclin-1, LC3 and p62 were done. Administration of ZnO-NPs ameliorated the functional and histopathological alterations of the kidney in a rat model of diabetic nephropathy. ZnO-NPs retained the constancy of the glomerular filtration barrier and restored almost normal renal structure. This was confirmed by upregulation of mRNA expression of podocyte markers (nephrin and podocin) and AQP11 immune histochemical expression in the renal tubules. The beneficial outcomes of ZnO-NPs might be attributed to activation of autophagy through inhibiting mTOR signaling pathway. ZnO-NPs enhanced beclin-1 and LC3 mRNA expressions and reduced p62 mRNA expression. ZnO-NPs also exerted anti-apoptotic potential (evidenced by the decrease in p53 immune expression), anti-inflammatory and anti-oxidant effect [endorsed by suppression of serum cyclooxygenase-2 (COX-2) enzyme activity, tissue nuclear factor kappa beta (NF-κB) level and blood hypoxia-inducible factors (HIF-1α) level]. These results may point the way to an effective therapy of DN.Abbreviations: AQP11 Aquaporin11; BUN: Blood urea nitrogen; COX-2: Cyclooxygenase-2; DAB: 3, 3'-diaminobenzidine; DM: Diabetes mellitus; DN: Diabetic nephropathy; ELISA: Enzyme-linked immunosorbent assay; H&E: Hematoxylin & eosin; HIF-1α: Hypoxia-inducible factors; iNOS: inducible nitric oxide synthase; LC3: Microtubule-associated protein 1 light chain 3; mTOR: Mechanistic target of rapamycin; NF-κB: Nuclear factor kappa beta; NPs: Nanoparticles; PAS: Periodic acid Schiff; PCR: Polymerase chain reaction; PGE2: Prostaglandin E2; ROS: Reactive oxygen species; STZ: Streptozotocin; X ± SEM: Mean ± standard error of means; Zn: Zinc; ZnO-NPs: Zinc oxide nanoparticles.

Integrative analyses of biomarkers and pathways for diabetic nephropathy

Background: Diabetic nephropathy (DN) is a widespread diabetic complication and a major cause of terminal kidney disease. There is no doubt that DN is a chronic disease that imposes substantial health and economic burdens on the world's populations. By now, several important and exciting advances have been made in research on etiopathogenesis. Therefore, the genetic mechanisms underlying these effects remain unknown. Methods: The GSE30122, GSE30528, and GSE30529 microarray datasets were downloaded from the Gene Expression Omnibus database (GEO). Analyses of differentially expressed genes (DEGs), enrichment of gene ontology (GO), the Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) were performed. Protein-protein interaction (PPI) network construction was completed by the STRING database. Hub genes were identified by Cytoscape software, and common hub genes were identified by taking intersection sets. The diagnostic value of common hub genes was then predicted in the GSE30529 and GSE30528 datasets. Further analysis was carried out on the modules to identify transcription factors and miRNA networks. As well, a comparative toxicogenomics database was used to assess interactions between potential key genes and diseases associated upstream of DN. Results: Samples from 19 DNs and 50 normal controls were identified in the GSE30122 dataset. 86 upregulated genes and 34 downregulated genes (a total of 120 DEGs). GO analysis showed significant enrichment in humoral immune response, protein activation cascade, complement activation, extracellular matrix, glycosaminoglycan binding, and antigen binding. KEGG analysis showed significant enrichment in complement and coagulation cascades, phagosomes, the Rap1 signaling pathway, the PI3K-Akt signaling pathway, and infection. GSEA was mainly enriched in the TYROBP causal network, the inflammatory response pathway, chemokine receptor binding, the interferon signaling pathway, ECM receptor interaction, and the integrin 1 pathway. Meanwhile, mRNA-miRNA and mRNA-TF networks were constructed for common hub genes. Nine pivotal genes were identified by taking the intersection. After validating the expression differences and diagnostic values of the GSE30528 and GSE30529 datasets, eight pivotal genes (TYROBP, ITGB2, CD53, IL10RA, LAPTM5, CD48, C1QA, and IRF8) were finally identified as having diagnostic values. Conclusion: Pathway enrichment analysis scores provide insight into the genetic phenotype and may propose molecular mechanisms of DN. The target genes TYROBP, ITGB2, CD53, IL10RA, LAPTM5, CD48, C1QA, and IRF8 are promising new targets for DN. SPI1, HIF1A, STAT1, KLF5, RUNX1, MBD1, SP1, and WT1 may be involved in the regulatory mechanisms of DN development. Our study may provide a potential biomarker or therapeutic locus for the study of DN.

Hyperglycemic conditions induce rapid cell dysfunction-promoting transcriptional alterations in human aortic endothelial cells

Hyperglycemia is a major risk factor in the development of diabetic complications and promotes vascular complications through dysregulation of endothelial cell function. Various mechanisms have been proposed for endothelial cell dysregulation but the early transcriptomic alterations of endothelial cells under hyperglycemic conditions are not well documented. Here we use deep time-series RNA-seq profiling of human aortic endothelial cells (HAECs) following exposure to normal (NG) and high glucose (HG) conditions over a time course from baseline to 24 h to identify the early and transient transcriptomic changes, alteration of molecular networks, and their temporal dynamics. The analysis revealed that the most significant pathway activation/inhibition events take place in the 1- to 4-h transition and identified distinct clusters of genes that underlie a cascade of coordinated transcriptional events unique to HG conditions. Temporal co-expression and causal network analysis implicate the activation of type 2 diabetes (T2D) and growth factor signalling pathways including STAT3 and NF-κB. These results document HAEC transcriptional changes induced by hyperglycemic conditions and provide basic insight into the rapid molecular alterations that promote endothelial cell dysfunction.

Mutual Regulation between Redox and Hypoxia-Inducible Factors in Cardiovascular and Renal Complications of Diabetes

Oxidative stress and hypoxia-inducible factors (HIFs) have been implicated in the pathogenesis of diabetic cardiovascular and renal diseases. Reactive oxygen species (ROS) mediate physiological and pathophysiological processes, being involved in the modulation of cell signaling, differentiation, and survival, but also in cyto- and genotoxic damage. As master regulators of glycolytic metabolism and oxygen homeostasis, HIFs have been largely studied for their role in cell survival in hypoxic conditions. However, in addition to hypoxia, other stimuli can regulate HIFs stability and transcriptional activity, even in normoxic conditions. Among these, a regulatory role of ROS and their byproducts on HIFs, particularly the HIF-1α isoform, has received growing attention in recent years. On the other hand, HIF-1α and HIF-2α exert mutually antagonistic effects on oxidative damage. In diabetes, redox-mediated HIF-1α deregulation contributes to the onset and progression of cardiovascular and renal complications, and recent findings suggest that deranged HIF signaling induced by hyperglycemia and other cellular stressors associated with metabolic disorders may cause mitochondrial dysfunction, oxidative stress, and inflammation. Understanding the mechanisms of mutual regulation between HIFs and redox factors and the specific contribution of the two main isoforms of HIF-α is fundamental to identify new therapeutic targets for vascular complications of diabetes.

Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Significance: The disturbance of the hypoxia response system is closely related to human diseases, because it is essential for the maintenance of homeostasis. Given the significant role of the hypoxia response system in human health, therapeutic applications targeting prolyl hydroxylase-hypoxia-inducible factor (HIF) signaling have been attempted. Thus, systemically reviewing the hypoxia response-based therapeutic strategies is of great significance. Recent Advances: Disturbance of the hypoxia response is a characteristic feature of various diseases. Targeting the hypoxia response system is, thus, a promising therapeutic strategy. Interestingly, several compounds and drugs are currently under clinical trials, and some have already been approved for use in the treatment of certain human diseases. Critical Issues: We summarize the molecular mechanisms of the hypoxia response system and address the potential therapeutic implications in kidney diseases. Given that the effects of hypoxia response in kidney diseases are likely to depend on the pathological context, specific cell types, and the differences in the activation pattern of HIF isoforms, the precise application is critical for the treatment of kidney diseases. Although HIF-PHIs (HIF-PHD inhibitors) have been proven to be effective and well tolerated in chronic kidney disease patients with anemia, the potential on-target consequence of HIF activation and some outstanding questions warrant further consideration. Future Direction: The mechanism of the hypoxia response system disturbance remains unclear. Elucidation of the molecular mechanism of hypoxia response and its precise effects on kidney diseases warrants clarification. Considering the complexity of the hypoxia response system and multiple biological processes controlled by HIF signaling, the development of more specific inhibitors is highly warranted. Antioxid. Redox Signal. 37, 936-955.

HIF-1α Expression Increases Preoperative Concurrent Chemoradiotherapy Resistance in Hyperglycemic Rectal Cancer

Purpose: Preoperative concurrent chemoradiotherapy (CCRT) is the standard treatment for locally advanced rectal cancer patients. However, the poor therapeutic efficacy of CCRT was found in rectal cancer patients with hyperglycemia. This study investigated how hyperglycemia affects radiochemotherapy resistance in rectal cancer. Methods and Materials: We analyzed the correlation between prognosis indexes with hypoxia-inducible factor-1 alpha (HIF-1α) in rectal cancer patients with preoperative CCRT. In vitro, we investigated the effect of different concentrated glucose of environments on the radiation tolerance of rectal cancers. Further, we analyzed the combined HIF-1α inhibitor with radiation therapy in hyperglycemic rectal cancers. Results: The prognosis indexes of euglycemic or hyperglycemic rectal cancer patients after receiving CCRT treatment were investigated. The hyperglycemic rectal cancer patients (n = 13, glycosylated hemoglobin, HbA1c > 6.5%) had poorer prognosis indexes. In addition, a positive correlation was observed between HIF-1α expression and HbA1c levels (p = 0.046). Therefore, it is very important to clarify the relationship between HIF-1α and poor response in patients with hyperglycemia receiving pre-operative CCRT. Under a high glucose environment, rectal cancer cells express higher levels of glucose transport 1 (GLUT1), O-GlcNAc transferase (OGT), and HIF-1α, suggesting that the high glucose environment might stimulate HIF-1α expression through the GLUT1-OGT-HIF-1α pathway promoting tolerance to Fluorouracil (5-FU) and radiation. In the hyperglycemic rectal cancer animal model, rectal cancer cells confirmed that radiation exposure reduces apoptosis by overexpressing HIF-1α. Combining HIF-1α inhibitors was able to reverse radioresistance in a high glucose environment. Lower HIF-1α levels increased DNA damage in tumors leading to apoptosis. Conclusions: The findings here show that hyperglycemia induces the expression of GLUT1, OGT, and HIF-1α to cause CCRT tolerance in rectal cancer and suggest that combining HIF-1α inhibitors could reverse radioresistance in a high glucose environment. HIF-1α inhibitors may be useful for development as CCRT sensitizers in patients with hyperglycemic rectal cancer.

A Glimpse of Inflammation and Anti-Inflammation Therapy in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common complication of diabetes mellitus and a major cause of end-stage kidney disease (ESKD). The pathogenesis of DKD is very complex and not completely understood. Recently, accumulated evidence from in vitro and in vivo studies has demonstrated that inflammation plays an important role in the pathogenesis and the development of DKD. It has been well known that a variety of pro-inflammatory cytokines and related signaling pathways are involved in the procession of DKD. Additionally, some anti-hyperglycemic agents and mineralocorticoid receptor antagonists (MRAs) that are effective in alleviating the progression of DKD have anti-inflammatory properties, which might have beneficial effects on delaying the progression of DKD. However, there is currently a lack of systematic overviews. In this review, we focus on the novel pro-inflammatory signaling pathways in the development of DKD, including the nuclear factor kappa B (NF-κB) signaling pathway, toll-like receptors (TLRs) and myeloid differentiation primary response 88 (TLRs/MyD88) signaling pathway, adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathways, inflammasome activation, mitochondrial DNA (mtDNA) release as well as hypoxia-inducible factor-1(HIF-1) signaling pathway. We also discuss the related anti-inflammation mechanisms of metformin, finerenone, sodium-dependent glucose transporters 2 (SGLT2) inhibitors, Dipeptidyl peptidase-4 (DPP-4) inhibitors, Glucagon-like peptide-1 (GLP-1) receptor agonist and traditional Chinese medicines (TCM).

Hypoxia signaling in human health and diseases: implications and prospects for therapeutics

Molecular oxygen (O₂) is essential for most biological reactions in mammalian cells. When the intracellular oxygen content decreases, it is called hypoxia. The process of hypoxia is linked to several biological processes, including pathogenic microbe infection, metabolic adaptation, cancer, acute and chronic diseases, and other stress responses. The mechanism underlying cells respond to oxygen changes to mediate subsequent signal response is the central question during hypoxia. Hypoxia-inducible factors (HIFs) sense hypoxia to regulate the expressions of a series of downstream genes expression, which participate in multiple processes including cell metabolism, cell growth/death, cell proliferation, glycolysis, immune response, microbe infection, tumorigenesis, and metastasis. Importantly, hypoxia signaling also interacts with other cellular pathways, such as phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling, nuclear factor kappa-B (NF-κB) pathway, extracellular signal-regulated kinases (ERK) signaling, and endoplasmic reticulum (ER) stress. This paper systematically reviews the mechanisms of hypoxia signaling activation, the control of HIF signaling, and the function of HIF signaling in human health and diseases. In addition, the therapeutic targets involved in HIF signaling to balance health and diseases are summarized and highlighted, which would provide novel strategies for the design and development of therapeutic drugs.

Amelioration of Murine Diabetic Nephropathy with a SGLT2 Inhibitor Is Associated with Suppressing Abnormal Expression of Hypoxia-Inducible Factors

Diabetic nephropathy (DN), once manifested, is unlikely to completely recover. Factors that influence DN progression were explored by investigating the process of glomerulosclerosis and interstitial fibrosis and chronological changes in glucose, albuminuria, hyperfiltration, and expressions of sodium-glucose cotransporter 2 (SGLT2) and hypoxia-inducible factors (HIFs) up to 50 weeks in inducible cAMP early repressor transgenic mice, a model of severe DN. Long-term intervention with the SGLT2 inhibitor canagliflozin or islet transplantation or heminephrectomy was used. Inducible cAMP early repressor transgenic mice exhibited progressive diabetic glomerulosclerosis and mild interstitial fibrosis, and expressed extensive HIF-1α and HIF-2α in glomerulus and tubules, with sustained hyperfiltration up to 50 weeks. Canagliflozin ameliorated glomerulosclerosis/interstitial fibrosis gradually and reduced HIF overexpression. Islet-transplanted mice exhibited no amelioration. None of the heminephrectomized diabetic mice survived the hyperfiltration overload, but all of the canagliflozin-treated mice survived with re-expressions of HIF-1α and HIF-2α. These results suggest that persistent glomerular hyperfiltration might initiate glomerular injury, and persistent overexpression of HIFs could promote the development of glomerulosclerosis and interstitial fibrosis. Canagliflozin attenuated both changes. Oxidative stress or hypoxia was undetectable in this model. The abnormal expression of HIF-1α and HIF-2α may be a potential therapeutic target for preventing glomerulosclerosis and interstitial fibrosis.

The physiological and pathophysiological roles of carbohydrate response element binding protein in the kidney

Glucose is not only the energy fuel for most cells, but also the signaling molecule which affects gene expression via carbohydrate response element binding protein (ChREBP), a Mondo family transcription factor. In response to high glucose conditions, ChREBP regulates glycolytic and lipogenic genes by binding to carbohydrate response elements (ChoRE) in the regulatory region of its target genes, thus elucidating the role of ChREBP for converting excessively ingested carbohydrates to fatty acids as an energy storage in lipogenic tissues such as the liver and adipose tissue. While the pathophysiological roles of ChREBP for fatty liver and obesity in these tissues are well known, much of the physiological and pathophysiological roles of ChREBP in other tissues such as the kidney remains unclear despite its high levels of expression in them. This review will thus highlight the roles of ChREBP in the kidney and briefly introduce the latest research results that have been reported so far.

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.

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.

Mitochondrial dysfunction-induced high hCG associated with development of fetal growth restriction and pre-eclampsia with fetal growth restriction

Fetal growth restriction (FGR) and pre-eclampsia with fetal growth restriction (PE/FGR) are high-risk perinatal diseases that may involve high levels of human chorionic gonadotropin (hCG) and mitochondrial dysfunction. However, little is known about how these factors affect placental function. We investigated how mitochondrial dysfunction and high hCG expression affected placental function in unexplained FGR and PE/FGR. We observed elevated expression of hCGβ and growth differentiation factor 15 mRNA and protein levels in the placenta with both diseases. Likewise, antiangiogenic factors, such as Ang2, IP10, sFlt1, IL8, IL1B, and TNFα, were also upregulated at the mRNA level. In addition, the expression of COXI and COXII which encoded by mitochondrial DNA were significantly decreased in both diseases, suggesting that mitochondrial translation was impaired. Treatment with hCG increased Ang2, IP10, IL8, and TNFα mRNA levels in a dose-dependent manner via the p38 and JNK pathways. Mitochondrial translation inhibitors increased hCGβ expression through stabilization of HIF1α, and increased IL8 and TNFα mRNA expression. These results revealed that high expression of hCG due to mitochondrial translational dysfunction plays an important role in the pathogenesis of FGR and PE/FGR.

Hexokinase-2-Linked Glycolytic Overload and Unscheduled Glycolysis-Driver of Insulin Resistance and Development of Vascular Complications of Diabetes

The recent discovery of the glucose-induced stabilization of hexokinase-2 (HK2) to proteolysis in cell dysfunction in model hyperglycemia has revealed a likely key initiating factor contributing to the development of insulin resistance and vascular complications in diabetes. Consequently, the increased flux of glucose metabolism without a change in the expression and activity of glycolytic enzymes produces a wave of increased glycolytic intermediates driving mitochondrial dysfunction and increased reactive oxygen species (ROS) formation, the activation of hexosamine and protein kinase C pathways, the increased formation of methylglyoxal-producing dicarbonyl stress, and the activation of the unfolded protein response. This is called HK2-linked glycolytic overload and unscheduled glycolysis. The conditions required to sustain this are GLUT1 and/or GLUT3 glucose uptake and the expression of HK2. A metabolic biomarker of its occurrence is the abnormally increased deposition of glycogen, which is produced by metabolic channeling when HK2 becomes detached from mitochondria. These conditions and metabolic consequences are found in the vasculature, kidneys, retina, peripheral nerves, and early-stage embryo development in diabetes and likely sustain the development of diabetic vascular complications and embryopathy. In insulin resistance, HK2-linked unscheduled glycolysis may also be established in skeletal muscle and adipose tissue. This may explain the increased glucose disposal by skeletal uptake in the fasting phase in patients with type 2 diabetes mellitus, compared to healthy controls, and the presence of insulin resistance in patients with type 1 diabetes mellitus. Importantly, glyoxalase 1 inducer—trans-resveratrol and hesperetin in combination (tRES-HESP)—corrected HK2-linked glycolytic overload and unscheduled glycolysis and reversed insulin resistance and improved vascular inflammation in overweight and obese subjects in clinical trial. Further studies are now required to evaluate tRES-HESP for the prevention and reversal of early-stage type 2 diabetes and for the treatment of the vascular complications of diabetes.

Transcription Factor ChREBP Mediates High Glucose-Evoked Increase in HIF-1α Content in Epithelial Cells of Renal Proximal Tubules

Hyperglycemia/diabetes appears to be accompanied by the state of hypoxia, which especially affects kidneys. The aim of the study was to elucidate the mechanism of high glucose action on HIF-1α expression in renal proximal tubule epithelial cells. The research hypotheses included: (1) the participation of transcription factor ChREBP; and (2) the involvement of the effects resulting from pseudohypoxia, i.e., lowered intracellular NAD+/NADH ratio. The experiments were performed on HK-2 cells and primary cells: D-RPTEC (Diseased Human Renal Proximal Tubule Epithelial Cells—Diabetes Type II) and RPTEC (Renal Proximal Tubule Epithelial Cells). Protein and mRNA contents were determined by Western blot and RT-qPCR, respectively. ChREBP binding to DNA was detected applying chromatin immunoprecipitation, followed by RT-qPCR. Gene knockdown was performed using siRNA. Sirtuin activity and NAD⁺/NADH ratio were measured with commercially available kits. It was found that high glucose in HK-2 cells incubated under normoxic conditions: (1) activated transcription of HIF-1 target genes, elevated HIF-1α and ChREBP content, and increased the efficacy of ChREBP binding to promoter region of HIF1A gene; and (2), although it lowered NAD⁺/NADH ratio, it affected neither sirtuin activity nor HIF-1α acetylation level. The stimulatory effect of high glucose on HIF-1α expression was not observed upon the knockdown of ChREBP encoding gene. Experiments on RPTEC and D-RPTEC cells demonstrated that HIF-1α content in diabetic proximal tubular cells was lower than that in normal ones but remained high glucose-sensitive, and the latter phenomenon was mediated by ChREBP. Thus, it is concluded that the mechanism of high glucose-evoked increase in HIF-1α content in renal proximal tubule endothelial cells involves activation of ChREBP, indirectly capable of HIF1A gene up-regulation.

ChREBP deficiency alleviates apoptosis by inhibiting TXNIP/oxidative stress in diabetic nephropathy

AIMS

In the present study, we investigated the effect of carbohydrate responsive element binding protein (ChREBP) on the TXNIP/oxidative stress and apoptosis in diabetic nephropathy.

METHODS

ChREBP^-/- mice (8-week old) were produced using the CRISPR/Cas9 gene editing approach. Diabetes was induced in C57BL/6 mice with streptozotocin. HK-2 cells was transfected with plasmid containing either ChREBP shRNA or TXNIP siRNA.

RESULTS

Renal expression of ChREBP and thioredoxin-interacting protein (TXNIP) was increased in patients with type 2 diabetes mellitus (T2DM) and diabetic mice. ChREBP deficiency improved renal function, apoptosis as well as endoplasmic reticulum (ER) stress in diabetic mice. In addition, ChREBP deficiency prevented expression levels of TXNIP and NADPH oxidase 4 (Nox4), 8-hydroxydeoxyguanosine (8-OHdG) and heme oxygenase-1 (HO-1) in diabetic kidneys. The increased urinary 8-OHdG level induced by diabetes was also attenuated in ChREBP deficiency mice. Similarly, HG was shown to induce ChREBP expression and nuclear translocation in HK-2 cells. HG-induced apoptosis was inhibited by transfection of ChREBP shRNA plasmid. Moreover, we found that knockdown of ChREBP suppressed HG-induced TXNIP and Nox4 expression, reactive oxygen species (ROS) generation and ER stress in HK-2 cells. Furthermore, TXNIP knockdown effectively abrogated HG-induced apoptosis in HK-2 cells.

CONCLUSIONS

These results suggest that ChREBP deficiency prevents diabetes-induced apoptosis via inhibiting oxidative stress and ER stress, highlighting ChREBP as a potential therapy target for diabetic nephropathy.

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.

Sodium-Glucose Cotransporter 2 Inhibitors Work as a "Regulator" of Autophagic Activity in Overnutrition Diseases

Several large clinical trials have shown renal and cardioprotective effects of sodium–glucose cotransporter 2 (SGLT2) inhibitors in diabetes patients, and the protective mechanisms need to be elucidated. There have been accumulating studies which report that SGLT2 inhibitors ameliorate autophagy deficiency of multiple organs. In overnutrition diseases, SGLT2 inhibitors affect the autophagy via various signaling pathways, including mammalian target of rapamycin (mTOR), sirtuin 1 (SIRT1), and hypoxia-inducible factor (HIF) pathways. Recently, it turned out that not only stagnation but also overactivation of autophagy causes cellular damages, indicating that therapeutic interventions which simply enhance or stagnate autophagy activity might be a “double-edged sword” in some situations. A small number of studies suggest that SGLT2 inhibitors not only activate but also suppress the autophagy flux depending on the situation, indicating that SGLT2 inhibitors can “regulate” autophagic activity and help achieve the appropriate autophagy flux in each organ. Considering the complicated control and bilateral characteristics of autophagy, the potential of SGLT2 inhibitors as the regulator of autophagic activity would be beneficial in the treatment of autophagy deficiency.

Normalizing HIF-1α Signaling Improves Cellular Glucose Metabolism and Blocks the Pathological Pathways of Hyperglycemic Damage

Intracellular metabolism of excess glucose induces mitochondrial dysfunction and diversion of glycolytic intermediates into branch pathways, leading to cell injury and inflammation. Hyperglycemia-driven overproduction of mitochondrial superoxide was thought to be the initiator of these biochemical changes, but accumulating evidence indicates that mitochondrial superoxide generation is dispensable for diabetic complications development. Here we tested the hypothesis that hypoxia inducible factor (HIF)-1α and related bioenergetic changes (Warburg effect) play an initiating role in glucotoxicity. By using human endothelial cells and macrophages, we demonstrate that high glucose (HG) induces HIF-1α activity and a switch from oxidative metabolism to glycolysis and its principal branches. HIF1-α silencing, the carbonyl-trapping and anti-glycating agent ʟ-carnosine, and the glyoxalase-1 inducer trans-resveratrol reversed HG-induced bioenergetics/biochemical changes and endothelial-monocyte cell inflammation, pointing to methylglyoxal (MGO) as the non-hypoxic stimulus for HIF1-α induction. Consistently, MGO mimicked the effects of HG on HIF-1α induction and was able to induce a switch from oxidative metabolism to glycolysis. Mechanistically, methylglyoxal causes HIF1-α stabilization by inhibiting prolyl 4-hydroxylase domain 2 enzyme activity through post-translational glycation. These findings introduce a paradigm shift in the pathogenesis and prevention of diabetic complications by identifying HIF-1α as essential mediator of glucotoxicity, targetable with carbonyl-trapping agents and glyoxalase-1 inducers.

Network pharmacology-based analysis of the anti-hyperglycemic active ingredients of roselle and experimental validation

Diabetes mellitus is one of the top four leading causes of death among noncommunicable diseases worldwide, according to the World Hibiscus sabdariffa 2019. Roselle (Hibiscus sabdariffa L.), a traditional herbal medicine, has shown significant clinical anti-hyperglycemic efficacy. However, the mechanism of the treatment is not yet clear. We found that Roselle has a certain protective effect on vascular endothelial cells through this study. This study was based on network pharmacology and experimental validation. The present study made a comprehensive analysis by combining active ingredient screening, target prediction and signaling pathway analysis to elucidate the active ingredients and possible molecular mechanism of roselle for the first time, which provided theoretical and experimental basis for the development and application of roselle as an antidiabetic drug.

HIF-1α is transcriptionally regulated by NF-κB in acute kidney injury

Oxygen homeostasis disturbances play a critical role in the pathogenesis of acute kidney injury (AKI). The transcription factor hypoxia-inducible factor-1 (HIF-1) is a master regulator of adaptive responses to hypoxia. Aside from posttranslational hydroxylation, the mechanism of HIF-1 regulation in AKI remains largely unclear. In this study, the mechanism of HIF-α regulation in AKI was investigated. We found that tubular HIF-1α expression significantly increased at the transcriptional level in ischemia-reperfusion-, unilateral ureteral obstruction-, and sepsis-induced AKI models, which was closely associated with macrophage-dependent inflammation. Meanwhile, NF-κB, which plays a central role in the inflammation response, was involved in the increasing expression of HIF-1α in AKI, as evidenced by pharmacological modulation (NF-κB inhibitor BAY11-7082). Mechanistically, NF-κB directly bound to the HIF-1α promoter and enhanced its transcription, which occurred not only under hypoxic conditions but also under normoxic conditions. Moreover, the induced HIF-1α by inflammation protected against tubular injury in AKI. Thus, our findings not only provide novel insights into HIF-1 regulation in AKI but also offer to understand the pathophysiology of kidney diseases.NEW & NOTEWORTHY Here, the mechanism of hypoxia-inducible factor-α (HIF-α) regulation in acute kidney injury (AKI) was investigated. We found that tubular HIF-1α expression significantly increased at the transcriptional level, which was closely associated with macrophage-dependent inflammation. Meanwhile, NF-κB was involved in the increasing expression of HIF-1α in AKI. Mechanistically, NF-κB directly bound to the HIF-1α promoter and enhanced its transcription. Our findings not only provide novel insights into HIF-1 regulation in AKI but also offer to understand the pathophysiology of kidney diseases.

The prognostic outcome of 'type 2 diabetes mellitus and breast cancer' association pivots on hypoxia-hyperglycemia axis

Type 2 diabetes mellitus and breast cancer are complex, chronic, heterogeneous, and multi-factorial diseases; with common risk factors including but not limited to diet, obesity, and age. They also share mutually inclusive phenotypic features such as the metabolic deregulations resulting from hyperglycemia, hypoxic conditions and hormonal imbalances. Although, the association between diabetes and cancer has long been speculated; however, the exact molecular nature of this link remains to be fully elucidated. Both the diseases are leading causes of death worldwide and a causal relationship between the two if not addressed, may translate into a major global health concern. Previous studies have hypothesized hyperglycemia, hyperinsulinemia, hormonal imbalances and chronic inflammation, as some of the possible grounds for explaining how diabetes may lead to cancer initiation, yet further research still needs to be done to validate these proposed mechanisms. At the crux of this dilemma, hyperglycemia and hypoxia are two intimately related states involving an intricate level of crosstalk and hypoxia inducible factor 1, at the center of this, plays a key role in mediating an aggressive disease state, particularly in solid tumors such as breast cancer. Subsequently, elucidating the role of HIF1 in establishing the diabetes-breast cancer link on hypoxia-hyperglycemia axis may not only provide an insight into the molecular mechanisms underlying the association but also, illuminate on the prognostic outcome of the therapeutic targeting of HIF1 signaling in diabetic patients with breast cancer or vice versa. Hence, this review highlights the critical role of HIF1 signaling in patients with both T2DM and breast cancer, potentiates its significance as a prognostic marker in comorbid patients, and further discusses the potential prognostic outcome of targeting HIF1, subsequently establishing the pressing need for HIF1 molecular profiling-based patient selection leading to more effective therapeutic strategies emerging from personalized medicine.

Hypoxia and hypoxia-inducible factors in diabetes and its complications

Hypoxia-inducible factors (HIFs) are the key regulators of oxygen homeostasis in response to hypoxia. In diabetes, multiple tissues are hypoxic but adaptive responses to hypoxia are impaired due to insufficient activation of HIF signalling, which results from inhibition of HIF-1α stability and function due to hyperglycaemia and elevated fatty acid levels. In this review, we will summarise and discuss current findings about the regulation of HIF signalling in diabetes and the pathogenic roles of hypoxia and dysregulated HIF signalling in the development of diabetes and its complications. The therapeutic potential of targeting HIF signalling for the prevention and treatment of diabetes and related complications is also discussed.

Identification of a novel association for the WWOX/HIF1A axis with gestational diabetes mellitus (GDM)

Background

Although the WW-domain-containing oxidoreductase (WWOX)/Hypoxia-inducible factor 1 (HIF1) pathway is a well-known regulator of cellular glucose and energy metabolism in pathophysiological processes, its role in gestational diabetes mellitus (GDM), remains elusive. We undertook this study to determine the effect of WWOX/HIF1A signaling on the expression of glucose metabolism genes in GDM patients.

Methods

Leukocytes were obtained from 135 pregnant women with (n = 98) or without (n = 37) GDM and, in turn, 3 months (n = 8) and 1 year (n = 12) postpartum. Quantitative RT-PCR was performed to determine gene expression profiles of the WWOX/HIF1A-related genes, including those involved in glucose transport (SLC2A1, SLC2A4), glycolytic pathway (HK2, PKM2, PFK, LDHA), Wnt pathway (DVL2, CTNNB1), and inflammatory response (NFKB1).

Results

GDM patients displayed a significant downregulation of WWOX with simultaneous upregulation of HIF1A which resulted in approximately six times reduction in WWOX/HIF1A ratio. As a consequence, HIF1A induced genes (SLC2A1, HK2, PFK, PKM) were found to be overexpressed in GDM compared to normal pregnancy and negative correlate with WWOX/HIF1A ratio. The postpartum WWOX expression was higher than during GDM, but its level was comparable to that observed in normal pregnancy.

Conclusions

The obtained results suggest a significant contribution of the WWOX gene to glucose metabolism in patients with gestational diabetes. Decreased WWOX expression in GDM compared to normal pregnancy, and in particular reduction of WWOX/HIF1A ratio, indicate that WWOX modulates HIF1α activity in normal tissues as described in the tumor. The effect of HIF1α excessive activation is to increase the expression of genes encoding proteins directly involved in the glycolysis which may lead to pathological changes in glucose metabolism observed in gestational diabetes.