Diabetes-induced Vascular Dysfunction Research Articles

ER stress CHOP Knockout in Beta Cells protects from type 2 diabetes-induced vascular dysfunction

Introduction: Cardiovascular complications are the primary causes of morbidity and mortality in patients with type 2 diabetes (T2D). T2D is a significant risk factor for cardiovascular diseases such as coronary artery disease, stroke, peripheral vascular disease, and heart failure for millions of people in the US. In the present study, we determined the role of the endoplasmic reticulum stress (ER) stress C/EBP homologous protein (CHOP) in beta cells on type 2 diabetes-induced vascular endothelial dysfunction. Methods: male and female CHOPflox/flox and CHOPbeta cells −/− mice were fed a high-fat diet (HFD) for 12 weeks. We measured body weight, running distance, heart/lung/pancreas/kidney weights, glucose tolerance test (GTT), vascular endothelial function, and signaling. Results: Our research indicates that mice with the ER stress CHOPflox/flox genotype, when fed a high-fat diet for 12 weeks, develop obesity and show impaired GTT and running distance. Additionally, they exhibit an increase in the weight of organs such as the heart, lungs, pancreas, and kidneys and experience vascular endothelial dysfunction and a reduction in phosphorylated eNOS levels. However, it's interesting to note that mice that lack the ER stress CHOPbeta cells−/− and were fed the same high-fat diet for 12 weeks displayed a protective effect. Conclusion: The data indicates that beta cell ER stress CHOP plays an essential role in type 2 diabetes. Disrupting the ER stress CHOP, specifically in beta cells, has been shown to protect mice from the vascular endothelial dysfunction caused by type 2 diabetes. Therefore, targeting ER stress CHOP, specifically in beta cells, could be a promising therapeutic approach to safeguard vascular endothelial function. NIH-HL150014 (Matrougui) and NIH-HL151616 (Matrougui). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Adding SGLT2 Cotransporter Inhibitor to PPARγ Activator Does Not Provide an Additive Effect in the Management of Diabetes-Induced Vascular Dysfunction

Introduction: Endothelial dysfunction (ED) plays a key role in the pathogenesis of diabetic vascular complications. In monotherapy, dapagliflozin (Dapa) as well as pioglitazone (Pio) prevent the progression of target organ damage in both type 1 (T1DM) and type 2 diabetes. We investigated whether the simultaneous PPAR-γ activation and SGLT2 cotransporter inhibition significantly alleviate ED-related pathological processes and thus normalize vascular response in experimental T1DM. Methods: Experimental diabetes was induced by streptozotocin (STZ; 55 mg/kg, i.p.) in Wistar rats. Dapa (10 mg/kg), Pio (12 mg/kg), or their combination were administrated to the STZ rats orally. Six weeks after STZ administration, the aorta was excised for functional studies and real-time qPCR analysis. Results: In the aorta of diabetic rats, impaired endothelium-dependent and independent relaxation were accompanied by the imbalance between vasoactive factors (eNos, Et1) and overexpression of inflammation (Tnfα, Il1b, Il6, Icam, Vcam) and oxidative stress (Cybb) markers. Pio monotherapy normalized response to vasoactive substances and restored balance between Et1-eNos expression, while Dapa treatment was ineffective. Nevertheless, Dapa and Pio monotherapy significantly reverted inflammation and oxidative stress markers to normal values. The combination treatment exhibited an additive effect in modulating Il6 expression, reaching the effect of Pio monotherapy in other measured parameters. Conclusion: Particularly, Pio exerts a vasoprotective character when used in monotherapy. When combined with Dapa, it does not exhibit an expected additive effect within modulating vasoreactivity or oxidative stress, though having a significant influence on IL6 downregulation.

FTO fuels diabetes-induced vascular endothelial dysfunction associated with inflammation by erasing m6A methylation of TNIP1.

Endothelial dysfunction is a critical and initiating factor of the vascular complications of diabetes. Inflammation plays an important role in endothelial dysfunction regulated by epigenetic modifications. N6-methyladenosine (m6A) is one of the most prevalent epigenetic modifications in eukaryotic cells. In this research, we identified an m6A demethylase, fat mass and obesity-associated protein (FTO), as an essential epitranscriptomic regulator in diabetes-induced vascular endothelial dysfunction. We showed that enhanced FTO reduced the global level of m6A in hyperglycemia. FTO knockdown in endothelial cells (ECs) resulted in less inflammation and compromised ability of migration and tube formation. Compared with EC Ftofl/fl diabetic mice, EC-specific Fto-deficient (EC FtoΔ/Δ) diabetic mice displayed less retinal vascular leakage and acellular capillary formation. Furthermore, methylated RNA immunoprecipitation sequencing (MeRIP-Seq) combined with RNA-Seq indicated that Tnip1 served as a downstream target of FTO. Luciferase activity assays and RNA pull-down demonstrated that FTO repressed TNIP1 mRNA expression by erasing its m6A methylation. In addition, TNIP1 depletion activated NF-κB and other inflammatory factors, which aggravated retinal vascular leakage and acellular capillary formation, while sustained expression of Tnip1 by intravitreal injection of adeno-associated virus alleviated endothelial impairments. These findings suggest that the FTO-TNIP1-NF-κB network provides potential targets to treat diabetic vascular complications.

A Selective Mineralocorticoid Receptor Blocker, Esaxerenone, Attenuates Vascular Dysfunction in Diabetic C57BL/6 Mice.

Pharmacological blockade of mineralocorticoid receptors (MRs) is a potential therapeutic approach to reduce cardiovascular complications since MRs play a crucial role in cardiovascular regulation. Recent studies suggest that MR antagonists affect several extrarenal tissues, including vessel function. We investigated the effect of a novel nonsteroidal selective MR blocker, esaxerenone, on diabetes-induced vascular dysfunction. Diabetes was induced by a single dose of streptozotocin in 8-week-old male C57BL/6 mice. Esaxerenone (3 mg/kg/day) or a vehicle was administered by gavage to diabetic mice for 3 weeks. Metabolic parameters, plasma aldosterone levels, and parameters related to renal function were measured. Endothelium-dependent or -independent vascular responses of the aortic segments were analyzed with acetylcholine or sodium nitroprusside, respectively. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro study. Induction of diabetes elevated plasma aldosterone level (P＜0.05) and impaired endothelium-dependent vascular relaxation (P＜0.05). The administration of esaxerenone ameliorated the endothelial dysfunction (P＜0.01) without the alteration of metabolic parameters, blood pressure, and renal function. Esaxerenone improved the eNOSSer1177 phosphorylation in the aorta obtained from diabetic mice (P＜0.05) compared with that in the vehicle-treated group. Furthermore, a major MR agonist, aldosterone, decreased eNOSSer1177 phosphorylation and increased eNOSThr495 phosphorylation in HUVECs, which recovered with esaxerenone. Esaxerenone ameliorated the endothelium-dependent vascular relaxation caused by aldosterone in the aortic segments obtained from C57BL/6 mice (P＜0.001). Esaxerenone attenuates the development of diabetes-induced endothelial dysfunction in mice. These results suggest that esaxerenone has potential vascular protective effects in individuals with diabetes.

Increased eHSP70-to-iHSP70 ratio disrupts vascular responses to calcium and activates the TLR4-MD2 complex in type 1 diabetes

AimsVascular dysfunction is a clinical hallmark of diabetes. While various pathways drive vascular alterations in diabetes, many gaps persist in understanding this process. Heat-shock protein 70 (HSP70) has a long-recognized role in diabetes, but the contributions of HSP70 to the diabetic vasculature remain largely unknown. Main methodsWe determined the systemic and local (aorta) levels of HSP70 in control (CTL) and streptozotocin (STZ)-induced diabetic rats. Functional studies were conducted in a wire myograph in the presence or absence of a pharmacological inhibitor for HSP70 (VER155008). Calcium (Ca2+) dynamics was indirectly evaluated as a function of change in force development in vehicle and VER-treated vessels, as well as in the presence of inhibitors for voltage-dependent and -independent plasmalemmal Ca2+ channels. Furthermore, mimicking the extracellular diabetic environment, we exposed aortic rings to serum from CTL and STZ-induced animals, which contains higher levels of HSP70, as well as to purified recombinant HSP70. Then, we performed functional studies following the modulation of Toll-like receptor 4 (TLR4) and its co-adaptor MD2, which interact with HSP70. Key findingsHSP70 plays a dual role in diabetes-induced vascular dysfunction: intracellular (i)HSP70 affects Ca2+ handling mechanisms, and extracellular (e)HSP70 modulates the TLR4-MD2 complex. SignificanceThese newly discovered roles of HSP70 push forward the field of vascular biology and open research avenues for other diseased states associated with altered vascular responses.

Impairment in endothelial bioenergetics contributes to diabetes‐induced vascular dysfunction

Diabetes, whether insulin‐dependent or independent is a major cause of endothelial dysfunction and a leading risk factor for cardiovascular disease. While compelling evidence indicates that endothelial dysfunction is a precursor and contributor to cardiovascular disease, the etiology of diabetes‐induced endothelial dysfunction remains ill‐defined. Recently alteration in endothelial cell bioenergetics has emerged as a new contributor to vascular diseases. However, whether alterations in endothelial glycolysis, the main endothelial cell bioenergetic pathway contributes to endothelial dysfunction is unknown. Herein, we tested the hypothesis that diabetes‐associated endothelial dysfunction involved increases in endothelial cells glycolysis and upregulation of its primary regulator, 6‐phosphofructo‐2‐kinase/fructose‐2, 6‐bisphosphatase 3 (PFKFB3). Measurement of glycolytic activity via Seahorse analyzer in primary human aortic endothelial cells (HAEC) from control and diabetic patients revealed a significant increase in basal glycolysis in diabetic subjects (p<0.05). We also employed Akita mice, a mouse model of type 1 diabetes. Male Akita mice showed a diabetic phenotype with 3‐folds increase in blood glucose. Seahorse analysis in intact aortic explants revealed a 1.7‐fold increase in basal glycolysis and a 1.3‐fold increase in maximal glycolysis in Akita mice (P<0.05). The increase in glycolysis was endothelial‐derived as aortic denudation significantly decreased glycolysis in Akita mice and abolished the difference between groups. No significant difference in mitochondrial function was depicted in the mito‐stress test between Akita and WT aortic explants (p>0.05). Additionally, endothelial cells extracted from aortas of Akita mice exhibited a 2‐fold increase in PFKFB3 mRNA expression(P<0.05). Interestingly, inhibition of PFKFB3 using 3PO (20μM) restored endothelial function in Akita mice. Similarly, Non‐obese diabetic females (NOD), a model for type‐1 diabetes, showed 4‐fold increases in PFKFB3 mRNA expression in aortic endothelial cells and impaired EDR which was restored with 3PO (p<0.05). To further evaluate the role of PFKFB3 in vascular endothelial function we overexpressed PFKFB3 in WT aortas with adenovirus (Ad‐PFKFB3), and reported impaired aorta EDR(P<0.05). Transduction of HAEC with Ad‐PFKFB3 showed a significant increase in ROS producing enzyme (NOX1). Also, inhibition of NOX1 using the selective inhibitor GKT771 restored EDR in Akita and Ad‐PFKFB3‐transduced WT aortas. In Conclusion, our data identified for the first time a role for endothelial glycolysis in the control of vascular relaxation and showed a crucial role of PFKFB3‐mediated endothelial glycolysis in vascular endothelial dysfunction associated with Type‐1 diabetes in males and females. The underlying mechanism potentially involves NOX1 as a downstream target for PFKFB3. Thus, Inhibitors of PFKFB3 could be a potential therapeutic target for diabetes‐induced vascular endothelial dysfunction.

Salvianolic acid B alleviates diabetic endothelial and mitochondrial dysfunction by down-regulating apoptosis and mitophagy of endothelial cells

ABSTRACT Endothelial dysfunction is a critical mediator in the pathogenesis of vascular complications of diabetes. Herein, this study was conducted to investigate the therapeutic effects of Salvianolic acid B (Sal B) on diabetes-induced endothelial dysfunction and the underlying mechanisms. Diabetic models were established both in db/db mice and high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs). Moreover, HUVECs were exposed to carbonyl cyanide m-chlorophenyl hydrazone (CCCP) to induce endothelial cell damage. Following Sal B treatment, pathological changes of thoracic aorta were investigated by hematoxylin and eosin, alcian blue (AB), elastic fiber, Masson, and reticular fiber staining. BCL2-associated X (BAX), B-cell lymphoma-2 (Bcl-2), Beclin1, Parkin and PTEN Induced Kinase 1 (Pink1) expression was detected by Western blot, immunohistochemistry, and immunofluorescence in thoracic aorta, HG- and CCCP-induced HUVECs. Cell scratch test, MitoTracker Red CMXRos staining and Flou-4 AM staining were separately presented to detect migration, mitochondrial activity and intracellular Ca2+ in HUVECs. Our results showed that Sal B significantly ameliorated hyperlipidemia, hyperglycemia, hyperinsulinemia, and insulin resistance in db/db mice. Furthermore, it significantly alleviated diabetes-induced vascular endothelial dysfunction according to histopathology analysis. In diabetic thoracic aorta, HG- and CCCP-induced HUVECs, Sal B distinctly increased Bcl-2 expression and reduced BAX, Beclin1, Parkin and Pink1 expression, thereby protecting endothelial cells from apoptosis and mitophagy. Moreover, Sal B markedly enhanced migration, mitochondrial activity and intracellular Ca2+ levels both in HG- and CCCP-induced HUVECs. Collectively, Sal B exhibited a potential to improve diabetes-induced endothelial and mitochondrial dysfunction through down-regulating apoptosis and mitophagy of endothelial cells. Abbreviations: DM: diabetes mellitus; T2DM: type 2 diabetes mellitus; Sal B: Salvianolic acid B; HG: high glucose; FBG: fasting blood glucose; TC: total cholesterol; TG: triglycerides; LDL-C: low-density lipoprotein cholesterol; HDL-C: high-density lipoprotein cholesterol; FINS: fasting insulin; HOMA-IR: homeostasis model assessment insulin resistance; QUICKI: quantitative insulin-sensitivity check index; H&E: hematoxylin and eosin; HUVECs: human umbilical vein endothelial cells; IHC: immunohistochemistry; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; FCM: flow cytometry; CCK-8: cell counting kit-8

IGF-I combined with exercise improve diabetes-induced vascular dysfunction in heart of male Wistar rats.

Introduction: This research investigates the impact of insulin-like growth factor-I (IGF -I)and exercise on mediators associated with angiogenesis (VEGF-A, TSP-1, and NF-кβ) and capillarization status of the diabetic rats’ hearts. Methods: Splitting of forty Wistar male rats into five groups occurred as following: control,diabetes, diabetes+IGF-I, diabetes+exercise, and diabetes+exercise+IGF-I.Through intraperitoneal administration of 60 mg/kg streptozotocin, the condition of Type 1diabetes was escalated. After four weeks of treatment with IGF-I (2 mg/kg/day) or treadmill exercise (17 m/min, zero degrees slope, 30 min/day), in the heart, microvascular density and protein levels of VEGF-A, TSP-1, and NF-кβ were determined by H&E staining and ELISA,respectively. Results: Within the diabetic group, observations present a significant decrease in VEGF-A and MVD levels, whereas an increase in the TSP-1 and NF-Κb levels. While these impacts were reversed by either IGF-I or exercise treatments, simultaneous treatment had synergistic effects. Moreover, among diabetic rats, undesirable histologic alterations of the heart were demonstrated, including myonecrosis, interstitial edema, hemorrhage, and mononuclear immune cell infiltration, whereas treatments improved these changes. Conclusion: These data manifest that IGF-I and exercise can increase the cardiac angiogenesis of diabetic rats through increasing expression of VEGF-A, and decreasing TSP-1 and NF-кβproteins level, also can improve myocardial tissue damages.

Diacerein attenuates vascular dysfunction by reducing inflammatory response and insulin resistance in type 2 diabetic rats

AimTo examine the effect of diacerein on vascular dysfunction in type 2 diabetic rats and elucidate the mechanism of diacerein. MethodsIn a rat model, type 2 diabetes was induced by high-fat diet and streptozotocin. Vascular function was assessed in vascular reactivity experiment. The effect of diacerein (10 or 20 mg/kg/day) on blood glucose, inflammation and insulin signaling, and modulators in vascular tissue in diabetic rats were investigated by molecular and biochemical approaches. ResultsIn this study, diacerein inhibited diabetes-induced vascular dysfunction. Diacerein treatment normalized blood glucose, insulin tolerance test, inflammatory cytokine levels and nitric oxide synthases expression in diabetic rats. Moreover, diacerein inhibited NF-κB and NLRP3 pathways and activated insulin signaling pathway related proteins IRS-1 and AKT in diabetic rats. ConclusionDiacerein improved vascular function effectively in diabetic rats by suppressing inflammation and reducing insulin resistance. These results suggest that diacerein may represent a novel therapy for patients with diabetes.

Whole body hypoxic preconditioning-mediated multiorgan protection in db/db mice via nitric oxide-BDNF-GSK-3β-Nrf2 signaling pathway.

The beneficial effects of hypoxic preconditioning are abolished in the diabetes. The present study was designed to investigate the protective effects and mechanisms of repeated episodes of whole body hypoxic preconditioning (WBHP) in db/db mice. The protective effects of preconditioning were explored on diabetes-induced vascular dysfunction, cognitive impairment and ischemia-reperfusion (IR)-induced increase in myocardial injury. Sixteen-week old db/db (diabetic) and C57BL/6 (non-diabetic) mice were employed. There was a significant impairment in cognitive function (Morris Water Maze test), endothelial function (acetylcholine-induced relaxation in aortic rings) and a significant increase in IR-induced heart injury (Langendorff apparatus) in db/db mice. WBHP stimulus was given by exposing mice to four alternate cycles of low (8%) and normal air O2 for 10 min each. A single episode of WBHP failed to produce protection; however, two and three episodes of WBHP significantly produced beneficial effects on the heart, brain and blood vessels. There was a significant increase in the levels of brain-derived neurotrophic factor (BDNF) and nitric oxide (NO) in response to 3 episodes of WBHP. Moreover, pretreatment with the BDNF receptor, TrkB antagonist (ANA-12) and NO synthase inhibitor (L-NAME) attenuated the protective effects imparted by three episodes of WBHP. These pharmacological agents abolished WBHP-induced restoration of p-GSK-3β/GSK-3β ratio and Nrf2 levels in IR-subjected hearts. It is concluded that repeated episodes of WHBP attenuate cognitive impairment, vascular dysfunction and enhancement in IR-induced myocardial injury in diabetic mice be due to increase in NO and BDNF levels that may eventually activate GSK-3β and Nrf2 signaling pathway to confer protection.

Synergistic effect of Ocimum Sanctum and Andrographis Paniculata against Diabetic Complications

The present study explored the effect of Ocimum sanctum, Andrographis paniculata and their combination for the management of experimental diabetic vascular complications. Diabetes associated dyslipidemia and free radical generation have been connected to the pathogenesis of diabetes-induced vascular complications. Ocimum sanctum, Andrographis paniculata, possess hypolipidemic and antioxidant property, thus we evaluated their vaso-protective potential. Hydroalcoholic extract of Ocimum sanctum (200 mg/kg p.o) and hydroalcoholic extract of Andrographis paniculata (400 mg/kg p.o) were noted to possess vascular protective potential in experimental chronic diabetes. Experimental diabetes mellitus was induced by Streptozotocin (55 mg/kg i.p., once) to Wistar rats. The induction of diabetes and its associated vascular complications were assessed biochemically. Diabetes-associated dyslipidemia and tissue oxidative stress were also assessed. Treatment of combination of Ocimum sanctum + Andrographis paniculata (300mg/kg p.o) was noted to be more efficient against the diabetes-induced vascular endothelial dysfunction and renal impairment as compared to either treatment with Ocimum sanctum (400mg/kg p.o) or Andrographis paniculata (200mg/kg p.o) or Lisinopril (1 mg/kg/day p.o.) (a reference agent). To conclude, diabetes associate oxidative stress and dyslipidemia are majorly accountable for the induction of vascular and renal impairment. The combination of Ocimum sanctum + Andrographis paniculata (300mg/kg p.o) shown the synergistic effect and may have prevented the progression of diabetes-induced vascular endothelial dysfunction and nephropathy by preventing the alteration lipid profile, restoring the serum nitrate/nitrite concentration, and decreasing the renal oxidative stress.

Knockout of vascular smooth muscle EGF receptor in a mouse model prevents obesity-induced vascular dysfunction and renal damage in vivo

Aims/hypothesisObesity causes type 2 diabetes leading to vascular dysfunction and finally renal end-organ damage. Vascular smooth muscle (VSM) EGF receptor (EGFR) modulates vascular wall homeostasis in part via serum response factor (SRF), a major regulator of VSM differentiation and a sensor for glucose. We investigated the role of VSM-EGFR during obesity-induced renovascular dysfunction, as well as EGFR–hyperglycaemia crosstalk.MethodsThe role of VSM-EGFR during high-fat diet (HFD)-induced type 2 diabetes was investigated in a mouse model with inducible, VSM-specific EGFR-knockout (KO). Various structural and functional variables as well as transcriptome changes, in vivo and ex vivo, were assessed. The impact of hyperglycaemia on EGFR-induced signalling and SRF transcriptional activity and the underlying mechanisms were investigated at the cellular level.ResultsWe show that VSM-EGFR mediates obesity/type 2 diabetes-induced vascular dysfunction, remodelling and transcriptome dysregulation preceding renal damage and identify an EGFR–glucose synergism in terms of SRF activation, matrix dysregulation and mitochondrial function. EGFR deletion protects the animals from HFD-induced endothelial dysfunction, creatininaemia and albuminuria. Furthermore, we show that HFD leads to marked changes of the aortic transcriptome in wild-type but not in KO animals, indicative of EGFR-dependent SRF activation, matrix dysregulation and mitochondrial dysfunction, the latter confirmed at the cellular level. Studies at the cellular level revealed that high glucose potentiated EGFR/EGF receptor 2 (ErbB2)-induced stimulation of SRF activity, enhancing the graded signalling responses to EGF, via the EGFR/ErbB2–ROCK–actin–MRTF pathway and promoted mitochondrial dysfunction.Conclusions/interpretationVSM-EGFR contributes to HFD-induced vascular and subsequent renal alterations. We propose that a potentiated EGFR/ErbB2–ROCK–MRTF–SRF signalling axis and mitochondrial dysfunction underlie the role of EGFR. This advanced working hypothesis will be investigated in mechanistic depth in future studies. VSM-EGFR may be a therapeutic target in cases of type 2 diabetes-induced renovascular disease.Data availabilityThe datasets generated during and/or analysed during the current study are available in: (1) share_it, the data repository of the academic libraries of Saxony-Anhalt (https://doi.org/10.25673/32049.2); and (2) in the gene expression omnibus database with the study identity GSE144838 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE144838).Graphical abstract

455-P: Pan-ErbB Inhibition Attenuates Diabetes-Induced Vascular Dysfunction in an Experimental Model of Diabetes

The underlying mechanisms leading to diabetes-induced vascular complications are not fully understood. We have previously shown that epidermal growth factor receptor (EGFR), which is part of the four membered family of EGFR/ErbB receptor tyrosine kinases, appears to play a detrimental role. However, the role of the other ErbB family members (ErbB2, ErbB3, and ErbB4)- that regulate cell growth, proliferation, differentiation and apoptosis- is not fully known and was further evaluated in this study. In a streptozotocin-rat model of type 1 diabetes, 4-weeks of diabetes induced significant vascular dysfunction, as assessed by abnormally high vasoconstrictor responses to norepinephrine in the mesenteric vascular bed (MVB). Diabetes also led to increased phosphorylation of all ErbB receptors with subsequent increased phosphorylation of downstream ERK1/2 in the MVB. Chronic 4-week in vivo administration of a novel pan-ErbB inhibitor, generation 7 polyamidoamine dendrimer (G7PAMAM; 20mg/kg daily i.p), or the well-established pan-ErbB inhibitor, Genistein (1mg/kg i.p. alt diem) to diabetic rats led to a marked attenuation in the hyperphosphorylation of all ErbBs, ERK1/2 and to a significant correction in NE-mediated hyper-responsiveness of the diabetic MVB. Furthermore, pan-ErbB inhibitors attenuated high glucose-induced ErbBs-ERK1/2 signaling in primary vascular smooth muscle cells grown in high (25mM) glucose. These data show for the first time that pan-ErbB inhibition attenuates diabetes-induced vascular dysfunction in an experimental model of diabetes. Therefore, pan-ErbB inhibition might represent a novel strategy for the treatment of diabetes-induced vascular complications. Disclosure S. Akhtar: None. B. Chandrasekhar: None. I. Benter: None. Funding Qatar University (QUCG-CMED-19/20-3)

Vascular Endothelial Growth Factor and Diabetic Nephropathy

According to the edition of International Diabetes Federation Atlas in 2009, the estimated diabetes prevalence for 2010 had risen to 285 million, representing 6.6% of the world’s adult population, with a prediction that by 2030 the number of people with diabetes in the world will have risen to 438 million1, with the majority of the new diabetic population coming from Asia. Diabetes-induced vascular dysfunction and pathologies are the major causes of morbidity and mortality in diabetic patients. Diabetic complications are a result of interactions among systemic metabolic changes, such as hyperglycemia, differential local tissue responses to toxic metabolites of glucose metabolism, and genetic and epigenetic modulators. Factors such as Vascular Endothelial Growth Factor (VEGF) seem to get involved in the above process.

Supplementation of dietary nitrate attenuated oxidative stress and endothelial dysfunction in diabetic vasculature through inhibition of NADPH oxidase

The metabolic disorders in diabetes, which are usually accompanied by oxidative stress and impaired nitric oxide (NO) bioavailability, increase the risk of detrimental cardiovascular complications. Herein, we investigated the therapeutic potential of dietary nitrate, which is found in high content in green leafy vegetables, on vascular oxidative stress and endothelial dysfunction in diabetic mice induced by high-fat diet and streptozotocin injection. Dietary nitrate in drinking water fuelled a nitrate–nitrite–NO pathway, which inhibited vascular oxidative stress, endothelial dysfunction and many features of metabolic syndrome in diabetic mice. These beneficial effects of nitrate on diabetic mice were abolished by PTIO (NO scavenger) treatment and significantly prevented by febuxostat (xanthine oxidoreductase inhibitor), demonstrating the central importance of NO in bioactivation of nitrate. The favorable effects of nitrate were not further influenced by apocynin (NADPH oxidase inhibitor), suggesting NADPH oxidase as a possible target. In high glucose-incubated vascular endothelial cells, NO donor attenuated oxidative stress and endothelial dysfunction via the inhibition of NADPH oxidase, where a heme oxygenase-1 (HO-1)-dependent mechanism was demonstrated for the antioxidant abilities of NO. Altogether, boosting this nitrate–nitrite–NO signaling pathway resulted in the decreases of NADPH oxidase-derived oxidative stress, endothelial dysfunction and metabolic disorders in diabetic vasculature. These findings may have novel implications for the preventive strategy against diabetes-induced vascular dysfunction and associated complications.

Heme oxygenase-1 contributes to the protective effect of resveratrol against endothelial dysfunction in STZ-induced diabetes in rats

Endothelial dysfunction is a common complication of diabetes that mainly stems from increased reactive oxygen species, which makes antioxidants of great benefit. Resveratrol (RSV) is an antioxidant that shows protective effects in a variety of disease models where the ameliorative effect appears to be mediated, in part, via heme oxygenase-1 (HO-1) induction. However, the pathophysiological relevance of HO-1 in the ameliorative response of RSV in endothelial dysfunction is not clearly defined. The present study was conducted to investigate whether HO-1 plays a role in diabetes-induced vascular dysfunction. Streptozotocin-diabetic rats were treated with RSV (10 mg/kg) in presence or absence of an HO-1 blocker, Zinc protoporphyrin (ZnPP) to assess vascular function and indicators of disease status. We found that RSV treatment significantly abrogated diabetes induced vascular dysfunction. This improvement was associated with the ability of RSV to decrease oxidative stress markers alongside a reduction in the aortic TGF-β expression, elevation of NOS3 expression and aortic nitrite concentration as well as HO activity. These ameliorative effects were diminished when ZnPP was administered prior to RSV. Our results clearly demonstrate the protective effects of RSV in diabetes-associated endothelial dysfunction and verified a causal role of HO-1 in this setting.

Salidroside ameliorates endothelial inflammation and oxidative stress by regulating the AMPK/NF-κB/NLRP3 signaling pathway in AGEs-induced HUVECs

Endothelial dysfunction plays important roles in vascular dysfunction under diabetic conditions. The generation of advanced glycation end products (AGEs), which can induce inflammation and oxidative stress, is pivotal in endothelial dysfunction. Salidroside, a major active compound in Rhodiola rosea, exerts protective effects against vascular diseases. To study the effects and mechanism of salidroside in diabetes-induced vascular endothelial dysfunction, an in vitro model was established with AGEs-induced human umbilical vein endothelial cells (HUVECs). Then, cell viability, cell apoptosis, pro-inflammatory cytokines and oxidative biomarkers were tested to determine the effects of salidroside at 10, 50 and 100 μM doses on AGEs induced HUVECs. Additionally, RNA-Seq and bioinformatics analyses were used to search for the underlying mechanism of salidroside. The results showed that salidroside promoted cell viability and significantly alleviated cell apoptosis in AGEs-induced HUVECs. Furthermore, salidroside remarkably decreased the levels of the pro-inflammatory cytokines TNF-α, IL-1β and IL-6 and impeded the expression of VCAM-1 and ICAM-1 induced by AGEs. Additionally, salidroside promoted superoxide dismutase (SOD) activity and increased catalase (CAT) and glutathione peroxidase (GSH-Px) levels while inhibiting the intracellular generation of reactive oxygen species (ROS) and malondialdehyde (MDA) in AGEs-induced HUVECs. Importantly, salidroside alleviated endothelial inflammation and oxidative stress by activating AMPK phosphorylation and inhibiting NF-ĸB p65 and NLRP3 inflammasome activation. Therefore, we used compound C, an accepted AMPK inhibitor, to further demonstrate the mechanism. Interestingly, the phenomenon produced by salidroside was abolished. Our findings suggest that salidroside ameliorates AGEs-induced endothelial inflammation and oxidative stress, partially via the AMPK/NF-κB/NLRP3 signaling pathway.

587-P: miR34a-Induced Loss of Nicotinamide Phosphoribosyltransferase Mediates Diabetes-Induced Retinal Vascular Senescence

Stress-associated premature senescence (SAPS) has been implicated in diabetes-induced vascular dysfunction. We have shown that microRNA34a (miR-34a) is involved in promoting senescence of the retinal microvasculature. Loss of nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme of NAD+ biosynthesis from nicotinamide mononucleotide (NMN), has been implicated in aging and metabolic diseases. Interestingly NAMPT is a target of miR34a, therefore, herein, we investigated the role and reciprocal relationship of miR34a and NAMPT on diabetes-induced senescence of the retinal vasculature. NAMPT expression and NAD+ content were significantly reduced in retina of streptozotocin-induced diabetic rats (STZ-rats, 8-12 weeks of hyperglycemia) and in human postmortem diabetic retinas. On the contrary, miR34a expression was found increased and positively correlated with augmented levels of senescence markers. Exposure of human retinal endothelial cells (HuREC) to glucidic stress (25mM) also decreased NAMPT and NAD+ levels while augmented the expression of miR34a and of senescence markers. Transfection of HuREC with miR-34a mimic, but not a scramble construct, in normal glucose conditions inhibited the expression of NAMPT and reduced NAD+ levels while promoting the expression of senescence markers. These effects of miR34a mimic on HuREC were halted by supplementation with NMN (0.05-1mM), but without modifying NAMPT expression. Lastly, NMN supplementation also prevented high glucose-induced loss of NAD+ and elevation of senescence markers. Our data show that high glucose/diabetes-induced SAPS in the retinal microvasculature involves miR34a-mediated blockade of NAMPT and consequent loss of NAD+. Moreover, our data suggest that NMN supplementation could be a viable therapeutic strategy to improve endothelial dysfunction in diabetic retinopathy. Disclosure M. Bartolli: None. R. Jadeja: None. M. Thounaojam: None. D. Gutsaeva: None. P. Martin: None. Funding National Institutes of Health (EY022416, EY028714)

Chronic administration of nano-sized PAMAM dendrimers in vivo inhibits EGFR-ERK1/2-ROCK signaling pathway and attenuates diabetes-induced vascular remodeling and dysfunction

We investigated whether chronic administration of nano-sized polyamidoamine (PAMAM) dendrimers can have beneficial effects on diabetes-induced vascular dysfunction by inhibiting the epidermal growth factor receptor (EGFR)-ERK1/2-Rho kinase (ROCK)—a pathway known to be critical in the development of diabetic vascular complications. Daily administration of naked PAMAMs for up to 4 weeks to streptozotocin-induced diabetic male Wistar rats inhibited EGFR-ERK1/2-ROCK signaling and improved diabetes-induced vascular remodeling and dysfunction in a dose, generation (G6 > G5) and surface chemistry-dependent manner (cationic > anionic > neutral). PAMAMs, AG1478 (a selective EGFR inhibitor), or anti-EGFR siRNA also inhibited vascular EGFR-ERK1/2-ROCK signaling in vitro. These data showed that naked PAMAM dendrimers have the propensity to modulate key (e.g. EGFR) cell signaling cascades with associated pharmacological consequences in vivo that are dependent on their physicochemical properties. Thus, PAMAMs, alone or in combination with vasculoprotective agents, may have a beneficial role in the potential treatment of diabetes-induced vascular complications.

Hyperglycemia-impaired aortic vasorelaxation mediated through arginase elevation: Role of stress kinase pathways

Diabetes-induced vascular endothelial dysfunction has been reported to involve hyperglycemia-induced increases in arginase activity. However, upstream mediators of this effect are not clear. Here, we have tested involvement of Rho kinase, ERK1/2 and p38 MAPK pathways in this process. Studies were performed with aortas isolated from wild type or hemizygous arginase 1 knockout (Arg1+/-) mice and bovine aortic endothelial cells exposed to high glucose (HG, 25 mmol/l) or normal glucose (NG, 5.5 mmol/l) conditions for different times. Effects of inhibitors of arginase, p38 MAPK, ERK1/2 or ROCK and ex vivo adenoviral delivery of active Arg1 and inactive (D128-Arg1) cDNA were also determined. Exposure in wild type aorta or endothelial cells to HG significantly increased arginase activity and Arg1 expression and impaired aortic relaxation. Transduction of wild type aorta with active Arg1 cDNA impaired vascular relaxation, whereas inactive Arg1 had no effect. The HG-induced vascular endothelial dysfunction was associated with increased phosphorylation (activation) of ERK1/2 and p38 MAPK. Pretreatment with inhibitors of ERK1/2, p38 MAPK, ROCK or arginase blocked HG-induced elevation of arginase activity and Arg1 expression and prevented the vascular dysfunction. Inhibition of ROCK blunted the HG-induced activation of ERK1/2 and p38 MAPK. In summary, activated ROCK and subsequent activation of ERK1/2 or p38 MAPK elevates arginase activity and Arg1 expression in hyperglycemic states. Targeting this pathway may provide an effective means for preventing diabetes/hyperglycemia-induced vascular endothelial dysfunction.