N6-methyladenine RNA methylation epigenetic modification and diabetic microvascular complications.

N6-methyladensine (m6A) has been identified as the best-characterized and the most abundant mRNA modification in eukaryotes. It can be dynamically regulated, removed, and recognized by its specific cellular components (respectively called "writers," "erasers," "readers") and have become a hot research field in a variety of biological processes and diseases. Currently, the underlying molecular mechanisms of m6A epigenetic modification in diabetes mellitus (DM) and diabetic microvascular complications have not been extensively clarified. In this review, we focus on the effects and possible mechanisms of m6A as possible potential biomarkers and therapeutic targets in the treatment of DM and diabetic microvascular complications.

Inhibition of CCL7 improves endothelial dysfunction and vasculopathy in mouse models of diabetes mellitus.

Diabetic vascular disease is a major complication of diabetes mellitus (DM). Chemokine C-C motif ligand 7 (CCL7) attracts macrophages and monocytes, amplifying inflammatory processes in the vasculature. We hypothesized a causal role for CCL7 in diabetic vasculopathy. CCL7 concentrations were higher in the plasma of patients with type 2 DM, as well as in supernatants from their endothelial progenitor cells (EPCs). High-glucose stimulation increased the secretion of CCL7 from human dermal microvascular endothelial cells (HDMECs) through the c-Fos and c-Jun signaling pathways. CCL7 inhibition using knockdown or neutralization antibody treatment reversed the high glucose-induced impaired tube formation and migration abilities of EPCs, human aortic endothelial cells, human coronary artery endothelial cells, and HDMECs. Administration of recombinant human CCL7 protein impaired tube formation and migration abilities by down-regulating the AKT-endothelial nitric oxide synthase and AKT/nuclear factor erythroid 2-related factor 2/heme oxygenase-1/vascular endothelial growth factor/stromal cell-derived factor-1 pathways and by up-regulating ERK/phosphorylated p65/interleukin-1ß/interleukin-6/tumor necrosis factor-α pathways through CC chemokine receptor 3 in endothelial cells. Ccl7 knockout in streptozotocin-treated mice showed improved neovasculogenesis in ischemic limbs and accelerated wound repair, with increased circulating EPCs and capillary density. CCL7 antibody treatment in db/db mice and high-fat diet-induced hyperglycemia mice showed improved neovasculogenesis in ischemic limbs and wound areas, accompanied by up-regulation of angiogenic proteins and down-regulation of inflammatory proteins. Endothelial cell-specific Ccl7-knockout mice showed ameliorated diabetic vasculopathy in streptozotocin-induced DM. This study highlights the potential of CCL7 as a therapeutic target for diabetic vasculopathy.

Role of long noncoding RNAs in diabetes-associated peripheral arterial disease.

Diabetes mellitus (DM) is a metabolic disease that heightens the risks of many vascular complications, including peripheral arterial disease (PAD). Various types of cells, including but not limited to endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and macrophages (MΦs), play crucial roles in the pathogenesis of DM-PAD. Long non-coding RNAs (lncRNAs) are epigenetic regulators that play important roles in cellular function, and their dysregulation in DM can contribute to PAD. This review focuses on the developing field of lncRNAs and their emerging roles in linking DM and PAD. We review the studies investigating the role of lncRNAs in crucial cellular processes contributing to DM-PAD, including those in ECs, VSMCs, and MΦ. By examining the intricate molecular landscape governed by lncRNAs in these relevant cell types, we hope to shed light on the roles of lncRNAs in EC dysfunction, inflammatory responses, and vascular remodeling contributing to DM-PAD. Additionally, we provide an overview of the research approach and methodologies, from identifying disease-relevant lncRNAs to characterizing their molecular and cellular functions in the context of DM-PAD. We also discuss the potential of leveraging lncRNAs in the diagnosis and therapeutics for DM-PAD. Collectively, this review provides a summary of lncRNA-regulated cell functions contributing to DM-PAD and highlights the translational potential of leveraging lncRNA biology to tackle this increasingly prevalent and complex disease.

1,8-cineole ameliorates experimental diabetic angiopathy by inhibiting NLRP3 inflammasome-mediated pyroptosis in HUVECs via SIRT2.

Accumulating evidence strongly support the key role of NLRP3-mediated pyroptosis in the pathogenesis and progression of vascular endothelial dysfunction associated with diabetes mellitus. Various studies have demonstrated that the activation or upregulation of Silent Information Regulation 2 homolog 2 (SIRT2) exerts inhibitory effect on the expression of NLRP3. Although 1,8-cineole has been found to protect against endothelial dysfunction and cardiovascular diseases, its role and mechanism in diabetic angiopathy remain unknown. Therefore, the aim of this study was to investigate the ameliorative effect of 1,8-cineole through SIRT2 on pyroptosis associated with diabetic angiopathy in human umbilical vein endothelial cells (HUVECs) and to elucidate the underlying mechanism. The findings revealed that 1,8-cineole exhibited a protective effect against vascular injury and ameliorated pathological alterations in the thoracic aorta of diabetic mice. Moreover, it effectively mitigated pyroptosis induced by palmitic acid-high glucose (PA-HG) in HUVECs. Treatment with 1,8-cineole effectively restored the reduced levels of SIRT2 and suppressed the elevated expression of pyroptosis-associated proteins. Additionally, our findings demonstrated the occurrence of NLRP3 deacetylation and the physical interaction between NLRP3 and SIRT2. The SIRT2 inhibitor AGK2 and siRNA-SIRT2 effectively attenuated the effect of 1,8-cineole on NLRP3 deacetylation in HUVECs and compromised its inhibitory effect against pyroptosis in HUVECs. However, overexpression of SIRT2 inhibited PA-HG-induced pyroptosis in HUVECs. 1,8-Cineole inhibited the deacetylation of NLRP3 by regulating SIRT2, thereby reducing pyroptosis in HUVECs. In conclusion, our findings suggest that PA-HG-induced pyroptosis in HUVECs plays a crucial role in the development of diabetic angiopathy, which can be mitigated by 1,8-cineole.

Umbilical Cord Mesenchymal Stem Cells Combined with Fufang Xueshuantong Capsule Attenuate Oxidative Stress and Vascular Lesions in Diabetic Rats by Activating Nrf-2/HO-1 Signaling Pathway.

BACKGROUND: Macrovascular lesions are the main cause of death and disability in diabetes mellitus, and excessive accumulation of cholesterol and lipids can lead to long-term and repeated damage of vascular endothelial cells. Umbilical cord mesenchymal stem cells (UCMSCs) can attenuate vascular endothelial damage in type 1 diabetic mice, while Fufang Xueshuantong capsule (FXC) has a protective effect on endothelial function; however, whether FXC in combination with UCMSCs can improve T2DM macrovascular lesions as well as its mechanism of action are not clear. Therefore, the aim of this study was to reveal the role of FXC + UCMSCs in T2DM vasculopathy and their potential mechanism in the treatment of T2DM. METHODS: The control and T2DM groups were intragastrically administered with equal amounts of saline, the UCMSCs group was injected with UCMSCs (1×106, resuspended cells with 0.5 mL PBS) in the tail vein, the FXC group was intragastrically administered with 0.58 g/kg FXC, and the UCMSCs + FXC group was injected with UCMSCs (1×106) in the tail vein, followed by FXC (0.58 g/kg), for 8 weeks. RESULTS: We found that FXC+UCMSCs effectively reduced lipid levels (TG, TC, and LDL-C) and ameliorated aortic lesions in T2DM rats. Meanwhile, Nrf2 and HO-1 expression were upregulated. We demonstrated that inhibition of Nrf-2 expression blocked the inhibitory effect of FXC+UCMSCs-CM on apoptosis and oxidative stress injury. CONCLUSION: Our data suggest that FXC+UCMSCs may attenuate oxidative stress injury and macroangiopathy in T2DM by activating the Nrf-2/HO-1 pathway.

Glucoselysine, a unique advanced glycation end-product of the polyol pathway and its association with vascular complications in type 2 diabetes.

Glucoselysine (GL) is an unique advanced glycation end-product derived from fructose. The main source of fructose in vivo is the polyol pathway, and an increase in its activity leads to diabetic complications. Here, we aimed to demonstrate that GL can serve as an indicator of the polyol pathway activity. Additionally, we propose a novel approach for detecting GL in peripheral blood samples using liquid chromatography-tandem mass spectrometry and evaluate its clinical usefulness. We successfully circumvent interference from fructoselysine, which shares the same molecular weight as GL, by performing ultrafiltration and hydrolysis without reduction, successfully generating adequate peaks for quantification in serum. Furthermore, using immortalized aldose reductase KO mouse Schwann cells, we demonstrate that GL reflects the downstream activity of the polyol pathway and that GL produced intracellularly is released into the extracellular space. Clinical studies reveal that GL levels in patients with type 2 diabetes are significantly higher than those in healthy participants, while Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine (MG-H1) levels are significantly lower. Both GL and MG-H1 show higher values among patients with vascular complications; however, GL varies more markedly than MG-H1 as well as hemoglobin A1c, fasting plasma glucose, and estimated glomerular filtration rate. Furthermore, GL remains consistently stable under various existing drug treatments for type 2 diabetes, whereas MG-H1 is impacted. To the best of our knowledge, we provide important insights in predicting diabetic complications caused by enhanced polyol pathway activity via assessment of GL levels in peripheral blood samples from patients.

N6-methyladenosine demethylase fat mass and obesity-associated protein suppresses hyperglycemia-induced endothelial cell injury by inhibiting reactive oxygen species formation via autophagy promotion.

INTRODUCTION: Hyperglycemia-induced endothelial cell injury is one of the main causes of diabetic vasculopathy. Fat mass and obesity-associated protein (FTO) was the first RNA N6-methyladenosine (m6A) demethylase identified; it participates in the pathogenesis of diabetes. However, the role of FTO in hyperglycemia-induced vascular endothelial cell injury remains unclear. MATERIALS AND METHODS: The effects of FTO on cellular m6A, autophagy, oxidative stress, proliferation, and cytotoxicity were explored in human umbilical vein endothelial cells (HUVECs) treated with high glucose (33.3 mmol/mL) after overexpression or pharmacological inhibition of FTO. MeRIP-qPCR and RNA stability assays were used to explore the molecular mechanisms by which FTO regulates autophagy. RESULTS: High glucose treatment increased m6A levels and reduced FTO protein expression in HUVECs. Wild-type overexpression of FTO markedly inhibited reactive oxygen species generation by promoting autophagy, increasing endothelial cell proliferation, and decreasing the cytotoxicity of high glucose concentrations. The pharmacological inhibition of FTO showed the opposite results. Mechanistically, we identified Unc-51-like kinase 1 (ULK1), a gene responsible for autophagosome formation, as a downstream target of FTO-mediated m6A modification. FTO overexpression demethylated ULK1 mRNA and inhibited its degradation in an m6A-YTHDF2-dependent manner, leading to autophagy activation. CONCLUSIONS: Our study demonstrates the functional importance of FTO-mediated m6A modification in alleviating endothelial cell injury under high glucose conditions and indicates that FTO may be a novel therapeutic target for diabetic vascular complications.

The role of glucagon-like peptide-1/GLP-1R and autophagy in diabetic cardiovascular disease.

Diabetes leads to a significantly accelerated incidence of various related macrovascular complications, including peripheral vascular disease and cardiovascular disease (the most common cause of mortality in diabetes), as well as microvascular complications such as kidney disease and retinopathy. Endothelial dysfunction is the main pathogenic event of diabetes-related vascular disease at the earliest stage of vascular injury. Understanding the molecular processes involved in the development of diabetes and its debilitating vascular complications might bring up more effective and specific clinical therapies. Long-acting glucagon-like peptide (GLP)-1 analogs are currently available in treating diabetes with widely established safety and extensively evaluated efficacy. In recent years, autophagy, as a critical lysosome-dependent self-degradative process to maintain homeostasis, has been shown to be involved in the vascular endothelium damage in diabetes. In this review, the GLP-1/GLP-1R system implicated in diabetic endothelial dysfunction and related autophagy mechanism underlying the pathogenesis of diabetic vascular complications are briefly presented. This review also highlights a possible crosstalk between autophagy and the GLP-1/GLP-1R axis in the treatment of diabetic angiopathy.

Oxidative and Nitrous Stress Underlies Vascular Malfunction Induced by Ionizing Radiation and Diabetes.

Oxidative stress results from the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in quantities exceeding the potential activity of the body's antioxidant system and is one of the risk factors for the development of vascular dysfunction in diabetes and exposure to ionizing radiation. Being the secondary products of normal aerobic metabolism in living organisms, ROS and RNS act as signaling molecules that play an important role in the regulation of vital organism functions. Meanwhile, in high concentrations, these compounds are toxic and disrupt various metabolic pathways. The various stress factors (hyperglycemia, gamma-irradiation, etc.) trigger free oxygen and nitrogen radicals accumulation in cells that are capable to damage almost all cellular components including ion channels and transporters such as Na+/K+-ATPase, BKCa, and TRP channels. Vascular dysfunctions are governed by interaction of ROS and RNS. For example, the reaction of ROS with NO produces peroxynitrite (ONOO-), which not only oxidizes DNA, cellular proteins, and lipids, but also disrupts important signaling pathways that regulate the cation channel functions in the vascular endothelium. Further increasing in ROS levels and formation of ONOO- leads to reduced NO bioavailability and causes endothelial dysfunction. Thus, imbalance of ROS and RNS and their affect on membrane ion channels plays an important role in the pathogenesis of vascular dysfunction associated with various disorders.

Role of endothelial Raptor in abnormal arteriogenesis after lower limb ischaemia in type 2 diabetes.

AIMS: Proper arteriogenesis after tissue ischaemia is necessary to rebuild stable blood circulation; nevertheless, this process is impaired in type 2 diabetes mellitus (T2DM). Raptor is a scaffold protein and a component of mammalian target of rapamycin complex 1 (mTORC1). However, the role of the endothelial Raptor in arteriogenesis under the conditions of T2DM remains unknown. This study investigated the role of endothelial Raptor in ischaemia-induced arteriogenesis during T2DM. METHODS AND RESULTS: Although endothelial mTORC1 is hyperactive in T2DM, we observed a marked reduction in the expression of endothelial Raptor in two mouse models and in human vessels. Inducible endothelial-specific Raptor knockout severely exacerbated impaired hindlimb perfusion and arteriogenesis after hindlimb ischaemic injury in 12-week high-fat diet fed mice. Additionally, we found that Raptor deficiency dampened vascular endothelial growth factor receptor 2 (VEGFR2) signalling in endothelial cells (ECs) and inhibited VEGF-induced cell migration and tube formation in a PTP1B-dependent manner. Furthermore, mass spectrometry analysis indicated that Raptor interacts with neuropilin 1 (NRP1), the co-receptor of VEGFR2, and mediates VEGFR2 trafficking by facilitating the interaction between NRP1 and Synectin. Finally, we found that EC-specific overexpression of the Raptor mutant (loss of mTOR binding) reversed impaired hindlimb perfusion and arteriogenesis induced by endothelial Raptor knockout in high-fat diet fed mice. CONCLUSION: Collectively, our study demonstrated the crucial role of endothelial Raptor in promoting ischaemia-induced arteriogenesis in T2DM by mediating VEGFR2 signalling. Thus, endothelial Raptor is a novel therapeutic target for promoting arteriogenesis and ameliorating perfusion in T2DM.

Apolipoprotein-CIII O-Glycosylation Is Associated with Micro- and Macrovascular Complications of Type 2 Diabetes.

Apolipoprotein-CIII (apo-CIII) inhibits the clearance of triglycerides from circulation and is associated with an increased risk of diabetes complications. It exists in four main proteoforms: O-glycosylated variants containing either zero, one, or two sialic acids and a non-glycosylated variant. O-glycosylation may affect the metabolic functions of apo-CIII. We investigated the associations of apo-CIII glycosylation in blood plasma, measured by mass spectrometry of the intact protein, and genetic variants with micro- and macrovascular complications (retinopathy, nephropathy, neuropathy, cardiovascular disease) of type 2 diabetes in a DiaGene study (n = 1571) and the Hoorn DCS cohort (n = 5409). Mono-sialylated apolipoprotein-CIII (apo-CIII1) was associated with a reduced risk of retinopathy (ß = -7.215, 95% CI -11.137 to -3.294) whereas disialylated apolipoprotein-CIII (apo-CIII2) was associated with an increased risk (ß = 5.309, 95% CI 2.279 to 8.339). A variant of the GALNT2-gene (rs4846913), previously linked to lower apo-CIII0a, was associated with a decreased prevalence of retinopathy (OR = 0.739, 95% CI 0.575 to 0.951). Higher apo-CIII1 levels were associated with neuropathy (ß = 7.706, 95% CI 2.317 to 13.095) and lower apo-CIII0a with macrovascular complications (ß = -9.195, 95% CI -15.847 to -2.543). In conclusion, apo-CIII glycosylation was associated with the prevalence of micro- and macrovascular complications of diabetes. Moreover, a variant in the GALNT2-gene was associated with apo-CIII glycosylation and retinopathy, suggesting a causal effect. The findings facilitate a molecular understanding of the pathophysiology of diabetes complications and warrant consideration of apo-CIII glycosylation as a potential target in the prevention of diabetes complications.

Ion channel Piezo1 activation aggravates the endothelial dysfunction under a high glucose environment.

BACKGROUND: Vasculopathy is the most common complication of diabetes. Endothelial cells located in the innermost layer of blood vessels are constantly affected by blood flow or vascular components; thus, their mechanosensitivity plays an important role in mediating vascular regulation. Endothelial damage, one of the main causes of hyperglycemic vascular complications, has been extensively studied. However, the role of mechanosensitive signaling in hyperglycemic endothelial damage remains unclear. METHODS: Vascular endothelial-specific Piezo1 knockout mice were generated to investigate the effects of Piezo1 on Streptozotocin-induced hyperglycemia and vascular endothelial injury. In vitro activation or knockdown of Piezo1 was performed to evaluate the effects on the proliferation, migration, and tubular function of human umbilical vein endothelial cells in high glucose. Reactive oxygen species production, mitochondrial membrane potential alternations, and oxidative stress-related products were used to assess the extent of oxidative stress damage caused by Piezo1 activation. RESULTS: Our study found that in VECreERT2;Piezo1flox/flox mice with Piezo1 conditional knockout in vascular endothelial cells, Piezo1 deficiency alleviated streptozotocin-induced hyperglycemia with reduced apoptosis and abscission of thoracic aortic endothelial cells, and decreased the inflammatory response of aortic tissue caused by high glucose. Moreover, the knockout of Piezo1 showed a thinner thoracic aortic wall, reduced tunica media damage, and increased endothelial nitric oxide synthase expression in transgenic mice, indicating the relief of endothelial damage caused by hyperglycemia. We also showed that Piezo1 activation aggravated oxidative stress injury and resulted in severe dysfunction through the Ca2+-induced CaMKII-Nrf2 axis in human umbilical vein endothelial cells. In Piezo1 conditional knockout mice, Piezo1 deficiency partially restored superoxide dismutase activity and reduced malondialdehyde content in the thoracic aorta. Mechanistically, Piezo1 deficiency decreased CaMKII phosphorylation and restored the expression of Nrf2 and its downstream molecules HO-1 and NQO1. CONCLUSION: In summary, our study revealed that Piezo1 is involved in high glucose-induced oxidative stress injury and aggravated endothelial dysfunction, which have great significance for alleviating endothelial damage caused by hyperglycemia.

l-thyroxine attenuates extracellular Hsp90α-induced vascular endothelial calcification in diabetes mellitus, as revealed by parallel metabolic profiles.

BACKGROUND AND AIMS: Diabetic atherosclerotic vascular disease is characterized by extensive vascular calcification. However, an elevated blood glucose level alone does not explain this pathogenesis. We investigated the metabolic markers underlying diabetic atherosclerosis and whether extracellular Hsp90α (eHsp90α) triggers vascular endothelial calcification in this particular metabolic environment. METHODS: A parallel human/animal model metabolomics approach was used. We analyzed 40 serum samples collected from 24 patients with atherosclerosis and from the STZ-induced ApoE-/- mouse model. A multivariate statistical analysis of the data was performed, and mouse aortic tissue was collected for the assessment of plaque formation. In vitro, the effects of eHsp90α on endothelial cell calcification were assessed by serum analysis, Western blotting and immunoelectron microscopy. RESULTS: Diabetic ApoE-/- mice showed more severe plaque lesions and calcification damage. Stearamide, oleamide, l-thyroxine, l-homocitrulline and l-citrulline are biomarkers of diabetic ASVD; l-thyroxine was downregulated in both groups, and the thyroid sensitivity index was correlated with serum Hsp90α concentration. In vitro studies showed that eHsp90α increased Runx2 expression in endothelial cells through the LRP1 receptor. l-thyroxine reduced the increase in Runx2 levels caused by eHsp90α and affected the distribution and expression of LRP1 through hydrogen bonding with glutamine at position 1054 in the extracellular segment of LRP1. CONCLUSIONS: This study provides a mechanistic link between characteristic serum metabolites and diabetic atherosclerosis and thus offers new insight into the role of extracellular Hsp90α in promoting vascular calcification.

BAG3 promotes proliferation and migration of arterial smooth muscle cells by regulating STAT3 phosphorylation in diabetic vascular remodeling.

BACKGROUND: Diabetic vascular remodeling is the most important pathological basis of diabetic cardiovascular complications. The accumulation of advanced glycation end products (AGEs) caused by elevated blood glucose promotes the proliferation and migration of vascular smooth muscle cells (VSMCs), leading to arterial wall thickening and ultimately vascular remodeling. Therefore, the excessive proliferation and migration of VSMCs is considered as an important therapeutic target for vascular remodeling in diabetes mellitus. However, due to the lack of breakthrough in experiments, there is currently no effective treatment for the excessive proliferation and migration of VSMCs in diabetic patients. Bcl-2-associated athanogene 3 (BAG3) protein is a multifunctional protein highly expressed in skeletal muscle and myocardium. Previous research has confirmed that BAG3 can not only regulate cell survival and apoptosis, but also affect cell proliferation and migration. Since the excessive proliferation and migration of VSMCs is an important pathogenesis of vascular remodeling in diabetes, the role of BAG3 in the excessive proliferation and migration of VSMCs and its molecular mechanism deserve further investigation. METHODS: In this study, BAG3 gene was manipulated in smooth muscle to acquire SM22αCre; BAG3FL/FL mice and streptozotocin (STZ) was used to simulate diabetes. Expression of proteins and aortic thickness of mice were detected by immunofluorescence, ultrasound and hematoxylin-eosin (HE) staining. Using human aorta smooth muscle cell line (HASMC), cell viability was measured by CCK-8 and proliferation was measured by colony formation experiment. Migration was detected by transwell, scratch experiments and Phalloidin staining. Western Blot was used to detect protein expression and Co-Immunoprecipitation (Co-IP) was used to detect protein interaction. RESULTS: In diabetic vascular remodeling, AGEs could promote the interaction between BAG3 and signal transducer and activator of transcription 3 (STAT3), leading to the enhanced interaction between STAT3 and Janus kinase 2 (JAK2) and reduced interaction between STAT3 and extracellular signal-regulated kinase 1/2 (ERK1/2), resulting in accumulated p-STAT3(705) and reduced p-STAT3(727). Subsequently, the expression of matrix metallopeptidase 2 (MMP2) is upregulated, thus promoting the migration of VSMCs. CONCLUSIONS: BAG3 upregulates the expression of MMP2 by increasing p-STAT3(705) and decreasing p-STAT3(727) levels, thereby promoting vascular remodeling in diabetes. This provides a new orientation for the prevention and treatment of diabetic vascular remodeling.

Endothelial dysfunction in vascular complications of diabetes: a comprehensive review of mechanisms and implications.

Diabetic vascular complications are prevalent and severe among diabetic patients, profoundly affecting both their quality of life and long-term prospects. These complications can be classified into macrovascular and microvascular complications. Under the impact of risk factors such as elevated blood glucose, blood pressure, and cholesterol lipids, the vascular endothelium undergoes endothelial dysfunction, characterized by increased inflammation and oxidative stress, decreased NO biosynthesis, endothelial-mesenchymal transition, senescence, and even cell death. These processes will ultimately lead to macrovascular and microvascular diseases, with macrovascular diseases mainly characterized by atherosclerosis (AS) and microvascular diseases mainly characterized by thickening of the basement membrane. It further indicates a primary contributor to the elevated morbidity and mortality observed in individuals with diabetes. In this review, we will delve into the intricate mechanisms that drive endothelial dysfunction during diabetes progression and its associated vascular complications. Furthermore, we will outline various pharmacotherapies targeting diabetic endothelial dysfunction in the hope of accelerating effective therapeutic drug discovery for early control of diabetes and its vascular complications.

New insights into the roles of Irisin in diabetic cardiomyopathy and vascular diseases.

Diabetes mellitus (DM) is a prevalent chronic disease in the 21st century due to increased lifespan and unhealthy lifestyle choices. Extensive research indicates that exercise can play a significant role in regulating systemic metabolism by improving energy metabolism and mitigating various metabolic disorders, including DM. Irisin, a well-known exerkine, was initially reported to enhance energy expenditure by indicating the browning of white adipose tissue (WAT) through peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) signaling. In this review, we summarize the potential mechanisms underlying the beneficial effects of Irisin on glucose dysmetabolism, including reducing gluconeogenesis, enhancing insulin energy expenditure, and promoting glycogenesis. Additionally, we highlight Irisin's potential to improve diabetic vascular diseases by stimulating nitric oxide (NO) production, reducing oxidative and nitrosative stress, curbing inflammation, and attenuating endothelial cell aging. Furthermore, we discuss the potential of Irisin to improve diabetic cardiomyopathy by preventing cardiomyocyte loss and reducing myocardial hypertrophy and fibrosis. Given Irisin's promising functions in managing diabetic cardiomyopathy and vascular diseases, targeting Irisin for therapeutic purposes could be a fruitful avenue for future research and clinical interventions.

Aberrant splicing of CaV1.2 calcium channel induced by decreased Rbfox1 enhances arterial constriction during diabetic hyperglycemia.

Diabetic hyperglycemia induces dysfunctions of arterial smooth muscle, leading to diabetic vascular complications. The CaV1.2 calcium channel is one primary pathway for Ca2+ influx, which initiates vasoconstriction. However, the long-term regulation mechanism(s) for vascular CaV1.2 functions under hyperglycemic condition remains unknown. Here, Sprague-Dawley rats fed with high-fat diet in combination with low dose streptozotocin and Goto-Kakizaki (GK) rats were used as diabetic models. Isolated mesenteric arteries (MAs) and vascular smooth muscle cells (VSMCs) from rat models were used to assess K+-induced arterial constriction and CaV1.2 channel functions using vascular myograph and whole-cell patch clamp, respectively. K+-induced vasoconstriction is persistently enhanced in the MAs from diabetic rats, and CaV1.2 alternative spliced exon 9* is increased, while exon 33 is decreased in rat diabetic arteries. Furthermore, CaV1.2 channels exhibit hyperpolarized current-voltage and activation curve in VSMCs from diabetic rats, which facilitates the channel function. Unexpectedly, the application of glycated serum (GS), mimicking advanced glycation end-products (AGEs), but not glucose, downregulates the expression of the splicing factor Rbfox1 in VSMCs. Moreover, GS application or Rbfox1 knockdown dynamically regulates alternative exons 9* and 33, leading to facilitated functions of CaV1.2 channels in VSMCs and MAs. Notably, GS increases K+-induced intracellular calcium concentration of VSMCs and the vasoconstriction of MAs. These results reveal that AGEs, not glucose, long-termly regulates CaV1.2 alternative splicing events by decreasing Rbfox1 expression, thereby enhancing channel functions and increasing vasoconstriction under diabetic hyperglycemia. This study identifies the specific molecular mechanism for enhanced vasoconstriction under hyperglycemia, providing a potential target for managing diabetic vascular complications.

Novel Angiogenesis Role of GLP-1(32-36) to Rescue Diabetic Ischemic Lower Limbs via GLP-1R-Dependent Glycolysis in Mice.

BACKGROUND: Restoring the capacity of endothelial progenitor cells (EPCs) to promote angiogenesis is the major therapeutic strategy of diabetic peripheral artery disease. The aim of this study was to investigate the effects of GLP-1 (glucagon-like peptide 1; 32-36)-an end product of GLP-1-on angiogenesis of EPCs and T1DM (type 1 diabetes) mice, as well as its interaction with the classical GLP-1R (GLP-1 receptor) pathway and its effect on mitochondrial metabolism. METHODS: In in vivo experiments, we conducted streptozocin-induced type 1 diabetic mice as a murine model of unilateral hind limb ischemia to examine the therapeutic potential of GLP-1(32-36) on angiogenesis. We also generated Glp1r-/- mice to detect whether GLP-1R is required for angiogenic function of GLP-1(32-36). In in vitro experiments, EPCs isolated from the mouse bone marrow and human umbilical cord blood samples were used to detect GLP-1(32-36)-mediated angiogenic capability under high glucose treatment. RESULTS: We demonstrated that GLP-1(32-36) did not affect insulin secretion but could significantly rescue angiogenic function and blood perfusion in ischemic limb of streptozocin-induced T1DM mice, a function similar to its parental GLP-1. We also found that GLP-1(32-36) promotes angiogenesis in EPCs exposed to high glucose. Specifically, GLP-1(32-36) has a causal role in improving fragile mitochondrial function and metabolism via the GLP-1R-mediated pathway. We further demonstrated that GLP-1(32-36) rescued diabetic ischemic lower limbs by activating the GLP-1R-dependent eNOS (endothelial NO synthase)/cGMP/PKG (protein kinase G) pathway. CONCLUSIONS: Our study provides a novel mechanism with which GLP-1(32-36) acts in modulating metabolic reprogramming toward glycolytic flux in partnership with GLP-1R for improved angiogenesis in high glucose-exposed EPCs and T1DM murine models. We propose that GLP-1(32-36) could be used as a monotherapy or add-on therapy with existing treatments for peripheral artery disease. REGISTRATION: URL: www.ebi.ac.uk/metabolights/; Unique identifier: MTBLS9543.

Heparanase inhibition as a systemic approach to protect the endothelial glycocalyx and prevent microvascular complications in diabetes.

BACKGROUND: Diabetes mellitus is a chronic disease which is detrimental to cardiovascular health, often leading to secondary microvascular complications, with huge global health implications. Therapeutic interventions that can be applied to multiple vascular beds are urgently needed. Diabetic retinopathy (DR) and diabetic kidney disease (DKD) are characterised by early microvascular permeability changes which, if left untreated, lead to visual impairment and renal failure, respectively. The heparan sulphate cleaving enzyme, heparanase, has previously been shown to contribute to diabetic microvascular complications, but the common underlying mechanism which results in microvascular dysfunction in conditions such as DR and DKD has not been determined. METHODS: In this study, two mouse models of heparan sulphate depletion (enzymatic removal and genetic ablation by endothelial specific Exotosin-1 knock down) were utilized to investigate the impact of endothelial cell surface (i.e., endothelial glycocalyx) heparan sulphate loss on microvascular barrier function. Endothelial glycocalyx changes were measured using fluorescence microscopy or transmission electron microscopy. To measure the impact on barrier function, we used sodium fluorescein angiography in the eye and a glomerular albumin permeability assay in the kidney. A type 2 diabetic (T2D, db/db) mouse model was used to determine the therapeutic potential of preventing heparan sulphate damage using treatment with a novel heparanase inhibitor, OVZ/HS-1638. Endothelial glycocalyx changes were measured as above, and microvascular barrier function assessed by albumin extravasation in the eye and a glomerular permeability assay in the kidney. RESULTS: In both models of heparan sulphate depletion, endothelial glycocalyx depth was reduced and retinal solute flux and glomerular albumin permeability was increased. T2D mice treated with OVZ/HS-1638 had improved endothelial glycocalyx measurements compared to vehicle treated T2D mice and were simultaneously protected from microvascular permeability changes associated with DR and DKD. CONCLUSION: We demonstrate that endothelial glycocalyx heparan sulphate plays a common mechanistic role in microvascular barrier function in the eye and kidney. Protecting the endothelial glycocalyx damage in diabetes, using the novel heparanase inhibitor OVZ/HS-1638, effectively prevents microvascular permeability changes associated with DR and DKD, demonstrating a novel systemic approach to address diabetic microvascular complications.

Angiotensin II reduces glyoxalase 1 activity and expression in vascular smooth muscle cells: Implications for diabetic vascular complications.

Angiotensin II (Ang II), a key mediator of vascular diseases, is linked to methylglyoxal (MGO) formation, a by-product of glucose metabolism implicated in vascular complications. The glyoxalase system, consisting of glyoxalase 1 (Glo1) and reduced glutathione (GSH), is responsible for detoxifying MGO. This study investigated the effect of Ang II on Glo1 activity and expression in vascular smooth muscle cells (VSMCs). Primary VSMCs were isolated from rat aortas and exposed to Ang II under standard or high glucose conditions. We examined Glo1 activity, expression, intracellular GSH, and methylglyoxal-derived hydroimidazolone 1 (MG-H1) levels. We also analyzed the expressions of nuclear factor-κB (NF-κB) p65 and nuclear factor erythroid 2-related factor 2 (Nrf2) as potential regulators of Glo1 expression. The results demonstrated that Ang II reduced Glo1 activity, expression, and GSH levels while increasing MG-H1 levels in VSMCs. Telmisartan and irbesartan, AT1R blockers, restored Glo1 activity, expression, and GSH levels and alleviated MG-H1 levels. Treatment with AT1R blockers or inhibitors targeting signaling pathways involved in Ang II-induced responses mitigated these effects. High glucose exacerbated the reduction in Glo1 activity and expression. In conclusion, this study provides evidence that Ang II reduces Glo1 activity and expression in VSMCs, which may contribute to developing vascular complications in diabetes. AT1R blockers and inhibitors targeting specific signaling pathways show potential in restoring Glo1 function and mitigating MGO-associated damage. These findings highlight the complex interactions between RAS, MGO, and vascular diseases, highlighting potential therapeutic targets for diabetic vascular complications.