Impaired nitric oxide-mediated vasodilation in patients with non-insulin-dependent diabetes mellitus

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

Inhibition of eNOS by L-NAME resulting in rat hind limb developmental defects through PFKFB3 mediated angiogenetic pathway

l-arginine/NOS/NO signaling pathway plays a critical role in controlling variety of vascular diseases. However, whether NOS inhibition by L-NAME suppresses late embryonic development is undefined. The aim of this study is to determine whether NOS inhibition by L-NAME is critical for late embryonic rat hind limb development. The pregnant rat at E13.5 administrated L-NAME by consecutive intraperitoneal injection. The embryos been harvested from E16.5 to E 20.5. Hematoxylin and Eosin Staining, Immunofluorescence and Immunohistochemistry performed to determine hind limb Vasculogenesis, HUVEC culture, Adenoviral PFKFB3 infection, Real time PCR and western blot were performed to determine whether l-arginine/NOS/NO pathway controlling late embryonic hind limb development through PFKFB3 mediated angiogenetic pathway. NOS inhibition by L-NAME resulting in late embryonic hind limb developmental defects characterized by severe hemorrhage. The in vivo studies showed that NOS inhibition strongly suppressed hind limb angiogenetic remodeling by impairing differentiation of endothelial cells and smooth muscle cells, and extracellular matrix synthesis. For underlie mechanism, our studies indicated that L-NAME treatment dramatically suppresses PFKFB3 expression in hematopoietic progenitor cells, tubulogenetic endothelial cells and smooth muscle cells. Knockdown of PFKFB3 dramatically inhibits the expression of angiogenetic genes, as well as tubulogenesis and extracellular matrix related genes. Taken together, our data in this study demonstrated that l-arginine-eNOS-NO pathway is important for rat hind limb development during late embryonic stage. This could be both a useful animal model and a promising therapeutic treatment for defects of late embryonic developmental hind limbs.

Pre-impaired fasting glucose state is a risk factor for endothelial dysfunction: Flow-mediated Dilation Japan (FMD-J) study

INTRODUCTION

Diabetes mellitus is associated with endothelial dysfunction. However, there is little information on the relationships of fasting blood glucose (FBG), including high normal blood glucose and impaired fasting glucose (IFG) with endothelial function. The purpose of this study was to evaluate the relationship between FBG level and flow-mediated vasodilation (FMD) using a large sample size.

RESEARCH DESIGN AND METHODS

This study was a cross-sectional study. We measured FMD in 7265 subjects at 31 general hospitals. The subjects were divided into four groups based on FBG levels: <100, 100-109, 110-125, and ≥126 mg/dL or known diabetes. The subjects were also divided into six groups based on FBG levels: <90, 90-94, 95-99, 100-109, 110-125, and ≥126 mg/dL or known diabetes.

RESULTS

FMD decreased in relation to increase in FBG level. There was a significant difference in FMD between the FBG of <100 mg/dL group and the other three groups (6.7±3.1% vs 5.9±2.8%, 5.7±3.1%, and 5.1±2.6%, respectively; p<0.001). After adjustment for confounding factors, the odds of having the lowest quartile of FMD were significantly higher in the FBG of 95-99, 100-104, 105-109, 110-125, and ≥126 mg/dL or known diabetes groups than in the FBG of the <90 mg/dL group.

CONCLUSIONS

These findings suggest that FBG of 100-109 mg/dL and FBG of 110-125 mg/dL are similarly associated with endothelial dysfunction and that a pre-IFG state (FBG of 95-99 mg/dL) is also a risk for endothelial dysfunction compared with FBG of <90 mg/dL.

TRIAL REGISTRATION NUMBER

UMIN000012950, UMIN000012951, UMIN000012952, and UMIN000003409.

Individual Responses to Heat Stress: Implications for Hyperthermia and Physical Work Capacity

Background

Extreme heat events are increasing in frequency, severity, and duration. It is well known that heat stress can have a negative impact on occupational health and productivity, particularly during physical work. However, there are no up-to-date reviews on how vulnerability to heat changes as a function of individual characteristics in relation to the risk of hyperthermia and work capacity loss. The objective of this narrative review is to examine the role of individual characteristics on the human heat stress response, specifically in relation to hyperthermia risk and productivity loss in hot workplaces. Finally, we aim to generate practical guidance for industrial hygienists considering our findings. Factors included in the analysis were body mass, body surface area to mass ratio, body fat, aerobic fitness and training, heat adaptation, aging, sex, and chronic health conditions.

Findings

We found the relevance of any factor to be dynamic, based on the work-type (fixed pace or relative to fitness level), work intensity (low, moderate, or heavy work), climate type (humidity, clothing vapor resistance), and variable of interest (risk of hyperthermia or likelihood of productivity loss). Heat adaptation, high aerobic fitness, and having a large body mass are the most protective factors during heat exposure. Primary detrimental factors include low fitness, low body mass, and lack of heat adaptation. Aging beyond 50 years, being female, and diabetes are less impactful negative factors, since their independent effect is quite small in well matched participants. Skin surface area to mass ratio, body composition, hypertension, and cardiovascular disease are not strong independent predictors of the heat stress response.

Conclusion

Understanding how individual factors impact responses to heat stress is necessary for the prediction of heat wave impacts on occupational health and work capacity. The recommendations provided in this report could be utilized to help curtail hyperthermia risk and productivity losses induced by heat.

Cardiovascular Therapeutic Potential of the Redox Siblings, Nitric Oxide (NO•) and Nitroxyl (HNO), in the Setting of Reactive Oxygen Species Dysregulation

Reactive oxygen species (ROS) dysregulation is a hallmark of cardiovascular disease, characterised by an imbalance in the synthesis and removal of ROS. ROS such as superoxide (•O₂^-), hydrogen peroxide (H₂O₂), hydroxyl (OH•) and peroxynitrite (ONOO^-) have a marked impact on cardiovascular function, contributing to the vascular impairment and cardiac dysfunction associated with diseases such as angina, hypertension, diabetes and heart failure. Central to the vascular dysfunction is a reduction in bioavailability and/or physiological effects of vasoprotective nitric oxide (NO•), leading to vasoconstriction, inflammation and vascular remodelling. In a cardiac context, increased ROS generation can also lead to modification of key proteins involved in cardiac contractility. Whilst playing a key role in the pathogenesis of cardiovascular disease, ROS dysregulation also limits the clinical efficacy of current therapies, such as nitrosovasodilators. As such, alternate therapies are sought. This review will discuss the impact of ROS dysregulation on the therapeutic utility of NO• and its redox sibling, nitroxyl (HNO). Both nitric oxide (NO) and nitroxyl (HNO) donors signal through soluble guanylyl cyclase (sGC). NO binds to the Fe(II) form of sGC and nitroxyl possibly to both sGC heme and thiol groups. In the vasculature, nitroxyl can also signal through voltage-dependent (K_v) and ATP-sensitive (K_ATP) K⁺ channels as well as calcitonin gene-related peptide (CGRP). In the heart, HNO directly targets critical thiols to increase myocardial contractility, an effect not seen with NO. The qualitative effects via elevation of cGMP are similar, i.e. lusitropic in the heart and inhibitory on vasoconstriction, inflammation, aggregation and vascular remodelling. Of pathophysiological significance is the fact the efficacy of NO donors is impaired by ROS, e.g. through chemical scavenging of NO, to generate reactive nitrogen oxide species (RNOS), whilst nitroxyl is apparently not.

Co-administration of prazosin and propranolol with glibenclamide improves anti-oxidant defense system in endothelial tissue of streptozotocin-induced diabetic Wistar rats

Background Due to increasing prevalence of diabetes and associated endothelial dysfunction, this study was carried out to investigate the effects of co-administration of adrenoceptor blockers (prazosin and propranolol) and glibenclamide on plasma biomarkers of endothelial functions in diabetic rats. Methods Experiments were carried out on 35 male Wistar rats (170-200 g). They were divided into seven groups (n=5) as follows: normal control, diabetic control, diabetic + glibenclamide (GLB-5mg/kg/day), diabetic+ prazosin (PRZ-0.5 mg/kg/day), diabetic + PRZ + GLB, diabetic + propranolol (PRP-10 mg/kg/day), diabetes + PRP + GLB. Experimental diabetes was induced with streptozotocin (60 mg/kg) and drugs were administered orally for 3 weeks. Blood pressure was measured and animals were sacrificed afterwards. Blood samples were collected by cardiac puncture, and major marker of endothelial functions, nitric oxide derivatives (NOx), as well as superoxide dismutase (SOD) and malondialdehyde (MDA) were measured on the plasma. The aorta was harvested for histological examination. Data were subjected to descriptive statistics and analysed using ANOVA at α 0.05. Results There was a significant increase in levels of NOx and SOD, and a decrease in MDA level in diabetic treated groups compared to diabetic control. Mean blood pressure increased in diabetic control and diabetic + GLB group when compared with normal control, while it was mildly reduced in diabetic group treated with PRZ and PRP, and co-administered GLB. More so, Aorta histology was altered in diabetic control groups when compared with normal control and all diabetic treated groups. Conclusions Results from this study suggest that PRZ, PRP, and GLB (singly and in combined therapy) could have a restorative effect on endothelial functions in diabetes.

Nitroxyl: A Novel Strategy to Circumvent Diabetes Associated Impairments in Nitric Oxide Signaling

Diabetes is associated with an increased mortality risk due to cardiovascular complications. Hyperglycemia-induced oxidative stress underlies these complications, leading to an impairment in endogenous nitric oxide (NO•) generation, together with reductions in NO• bioavailability and NO• responsiveness in the vasculature, platelets and myocardium. The latter impairment of responsiveness to NO•, termed NO• resistance, compromises the ability of traditional NO•-based therapeutics to improve hemodynamic status during diabetes-associated cardiovascular emergencies, such as acute myocardial infarction. Whilst a number of agents can ameliorate (e.g. angiotensin converting enzyme [ACE] inhibitors, perhexiline, statins and insulin) or circumvent (e.g. nitrite and sGC activators) NO• resistance, nitroxyl (HNO) donors offer a novel opportunity to circumvent NO• resistance in diabetes. With a suite of vasoprotective properties and an ability to enhance cardiac inotropic and lusitropic responses, coupled with preserved efficacy in the setting of oxidative stress, HNO donors have intact therapeutic potential in the face of diminished NO• signaling. This review explores the major mechanisms by which hyperglycemia-induced oxidative stress drives NO• resistance, and the therapeutic potential of HNO donors to circumvent this to treat cardiovascular complications in type 2 diabetes mellitus.

An exploratory, randomised, placebo-controlled, 14 day trial of the soluble guanylate cyclase stimulator praliciguat in participants with type 2 diabetes and hypertension

AIMS/HYPOTHESIS

Praliciguat (IW-1973), a soluble guanylate cyclase stimulator, amplifies nitric oxide signalling. This exploratory trial investigated the safety, tolerability, pharmacokinetic profile and pharmacodynamic effects of praliciguat in individuals with type 2 diabetes and hypertension.

METHODS

This Phase IIA, double-blind, placebo-controlled trial investigated praliciguat in 26 participants with type 2 diabetes and hypertension on stable glucose- and BP-lowering therapies. Participants were randomly allocated in a 3:5:5 ratio to three groups: placebo (n = 6), praliciguat 40 mg once daily for days 1-14 (n = 10), or praliciguat 20 mg twice daily for days 1-7 then 40 mg once daily for days 8-14 (n = 10). Assessments were made in clinic and included treatment-emergent adverse events, pharmacokinetics, metabolic variables, 24 h BP and heart rate, platelet function, reactive hyperaemia index (RHI) and plasma biomarkers. Participants, the sponsor, the investigator and clinic study staff (except designated pharmacy personnel) were blinded to group assignment.

RESULTS

Participants treated for 14 days with praliciguat had least-square mean change-from-baseline differences vs placebo (95% CI) of -0.7 (-1.8, 0.4) mmol/l for fasting plasma glucose, -0.7 (-1.1, -0.2) mmol/l for total cholesterol, -0.5 (-1.0, -0.1) mmol/l for LDL-cholesterol, -23 (-56, 9) for HOMA-IR in those not being treated with insulin, and -5 (-10, 1) mmHg and 3 (-1, 6) beats/min for average 24 h mean arterial pressure and heart rate, respectively. Apart from one serious adverse event (SAE; upper gastrointestinal haemorrhage), praliciguat was well tolerated. Praliciguat did not affect platelet function or RHI. Among exploratory biomarkers, plasma levels of asymmetric dimethylarginine decreased in praliciguat vs placebo recipients.

CONCLUSIONS/INTERPRETATION

In participants with type 2 diabetes and hypertension on standard therapies, over 14 days praliciguat was well tolerated, except for a single SAE, and showed positive trends in metabolic and BP variables. These results support further clinical investigation of praliciguat.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03091920.

FUNDING

This trial was funded by Cyclerion Therapeutics.

Why the endothelium? The endothelium as a target to reduce diabetes-associated vascular disease

Over the past 66 years, our knowledge of the role of the endothelium in the regulation of cardiovascular function and dysfunction has advanced from the assumption that it is a single layer of cells that serves as a barrier between the blood stream and vascular smooth muscle to an understanding of its role as an essential endocrine-like organ. In terms of historical contributions, we pay particular credit to (1) the Canadian scientist Dr. Rudolf Altschul who, based on pathological changes in the appearance of the endothelium, advanced the argument in 1954 that "one is only as old as one's endothelium" and (2) the American scientist Dr. Robert Furchgott, a 1998 Nobel Prize winner in Physiology or Medicine, who identified the importance of the endothelium in the regulation of blood flow. This review provides a brief history of how our knowledge of endothelial function has advanced and now recognize that the endothelium produces a plethora of signaling molecules possessing paracrine, autocrine, and, arguably, systemic hormone functions. In addition, the endothelium is a therapeutic target for the anti-diabetic drugs metformin, glucagon-like peptide I (GLP-1) receptor agonists, and inhibitors of the sodium-glucose cotransporter 2 (SGLT2) that offset the vascular disease associated with diabetes.

Empagliflozin improved systolic blood pressure, endothelial dysfunction and heart remodeling in the metabolic syndrome ZSF1 rat

Background

Empagliflozin (empa), a selective sodium–glucose cotransporter (SGLT)2 inhibitor, reduced cardiovascular mortality and hospitalization for heart failure in patients with type 2 diabetes at high cardiovascular risk independent of glycemic control. The cardiovascular protective effect of empa was evaluated in an experimental model of metabolic syndrome, the obese ZSF1 rat, and its’ lean control.

Methods

Lean and obese ZSF1 rats were either non-treated or treated with empa (30 mg/kg/day) for 6 weeks. Vascular reactivity was assessed using mesenteric artery rings, systolic blood pressure by tail-cuff sphygmomanometry, heart function and structural changes by echocardiography, and protein expression levels by Western blot analysis.

Results

Empa treatment reduced blood glucose levels from 275 to 196 mg/dl in obese ZSF1 rats whereas normoglycemia (134 mg/dl) was present in control lean ZSF1 rats and was unaffected by empa. Obese ZSF1 rats showed increased systolic blood pressure, and blunted endothelium-dependent relaxations associated with the appearance of endothelium-dependent contractile responses (EDCFs) compared to control lean rats. These effects were prevented by the empa treatment. Obese ZSF1 rats showed increased weight of the heart and of the left ventricle volume without the presence of diastolic or systolic dysfunction, which were improved by the empa treatment. An increased expression level of senescence markers (p53, p21, p16), tissue factor, VCAM-1, SGLT1 and SGLT2 and a down-regulation of eNOS were observed in the aortic inner curvature compared to the outer one in the control lean rats, which were prevented by the empa treatment. In the obese ZSF1 rats, no such effects were observed. The empa treatment reduced the increased body weight and weight of lungs, spleen, liver and perirenal fat, hyperglycemia and the increased levels of total cholesterol and triglycerides in obese ZSF1 rats, and increased blood ketone levels and urinary glucose excretion in control lean and obese ZSF1 rats.

Conclusion

Empa reduced glucose levels by 28% and improved both endothelial function and cardiac remodeling in the obese ZSF1 rat. Empa also reduced the increased expression level of senescence, and atherothrombotic markers at arterial sites at risk in the control lean, but not obese, ZSF1 rat.

The effect of hyperglycemia on neurovascular coupling and cerebrovascular patterning in zebrafish

Neurovascular coupling (through which local cerebral blood flow changes in response to neural activation are mediated) is impaired in many diseases including diabetes. Current preclinical rodent models of neurovascular coupling rely on invasive surgery and instrumentation, but transgenic zebrafish coupled with advances in imaging techniques allow non-invasive quantification of cerebrovascular anatomy, neural activation, and cerebral vessel haemodynamics. We therefore established a novel non-invasive, non-anaesthetised zebrafish larval model of neurovascular coupling, in which visual stimulus evokes neuronal activation in the optic tectum that is associated with a specific increase in red blood cell speed in tectal blood vessels. We applied this model to the examination of the effect of glucose exposure on cerebrovascular patterning and neurovascular coupling. We found that chronic exposure of zebrafish to glucose impaired tectal blood vessel patterning and neurovascular coupling. The nitric oxide donor sodium nitroprusside rescued all these adverse effects of glucose exposure on cerebrovascular patterning and function. Our results establish the first non-mammalian model of neurovascular coupling, offering the potential to perform more rapid genetic modifications and high-throughput screening than is currently possible using rodents. Furthermore, using this zebrafish model, we reveal a potential strategy to ameliorate the effects of hyperglycemia on cerebrovascular function.

The protective role of calcitonin gene-related peptide (CGRP) in high-glucose-induced oxidative injury in rat aorta endothelial cells

Endothelial dysfunction is considered to be an initial indicator in diabetes-induced macrovascular complications. Evidence has shown that CGRP is an important neuropeptide active in vascular system, especially in vasorelaxation. This study aimed to investigate the role of CGRP in high-glucose-induced endothelial dysfunction in rat aorta endothelial cells (RAECs). Quantitative-real time PCR and western blots were used to determine the efficiency of overexpression and interference of CGRP. After incubation with normal glucose (5.5 mM) or high glucose (33 mM), the cell viability and cell apoptosis were tested. Afterwards, the Nitric Oxide (NO) production, the mRNA expression of inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS) and angiotensin II (Ang II) and the level of reactive oxygen species (ROS) were determined. The involvement of ERK1/2-NOX4 was determined through western blots and the translocation of p47phox was also observed via cell immunofluorescence. CGRP alleviated the high-glucose-induced cell apoptosis while CGRP did not have an obvious impact on cell viability. Meanwhile, CGRP increased the NO production as well as the eNOS mRNA expression and reversely decreased the stimulated expression of iNOS and Ang II by high glucose. In addition, CGRP attenuated the high-glucose-stimulated intracellular ROS production by ERK1/2-NOX4 and the translocation of p47phox. These results indicated the protective role of CGRP in high-glucose-induced oxidative injury in RAECs possibly through inhibiting ERK1/2-NOX4. Our findings might help to further understand the potential role and possible mechanism of CGRP in endothelial dysfunction caused by high glucose.

Endothelial Function Assessed by Digital Volume Plethysmography Predicts the Development and Progression of Type 2 Diabetes Mellitus

Background

Endothelial dysfunction is a consequence of type 2 diabetes mellitus, but it is unclear whether endothelial dysfunction of conductance versus resistance vessels may also precede type 2 diabetes mellitus development.

Methods and Results

In a population‐based cohort of 15 010 individuals from the GHS (Gutenberg Health Study) (aged 35–74 years at enrollment in 2007–2012), we identified 1610 cases of incident pre–diabetes mellitus and 386 cases of incident type 2 diabetes mellitus by hemoglobin A_1c (HbA_1c) and/or medical history between 2012 and 2017. Endothelial function of conductance and resistance vessels was measured by flow‐mediated dilation and digital volume plethysmography–derived reactive hyperemia index, respectively. Multivariable regression modeling was used to estimate β coefficients of HbA_1c levels at follow‐up and relative risks of incident (pre–)diabetes mellitus. Reactive hyperemia index was independently associated with HbA_1c after multivariable adjustment for baseline HbA_1c, sex, age, socioeconomic status, arterial hypertension, waist/height ratio, pack‐years of smoking, non–high‐density lipoprotein/high‐density lipoprotein ratio, physical activity, family history of myocardial infarction/stroke, prevalent cardiovascular disease, medication use, and C‐reactive protein (β=−0.020; P=0.0029). The adjusted relative risk per SD decline in reactive hyperemia index was 1.08 (95% CI, 1.02–1.15; P=0.012) for incident pre–diabetes mellitus and 1.16 (95% CI, 1.01–1.34; P=0.041) for incident type 2 diabetes mellitus. Flow‐mediated dilation independently increased the relative risk for developing pre–diabetes mellitus by 8% (95% CI, 1.02–1.14; P=0.012), but it was not independently associated with incident type 2 diabetes mellitus (relative risk, 1.01; 95% CI, 0.86–1.19; P=0.92) and with HbA_1c (β=−0.003; P=0.59).

Conclusions

Endothelial dysfunction of resistance rather than conductance vessels may precede the development of (pre–)diabetes mellitus. Assessment of endothelial function by digital volume plethysmography may help to identify subjects at risk for development of type 2 diabetes mellitus.

Sodium nitroprusside prevents the detrimental effects of glucose on the neurovascular unit and behaviour in zebrafish

Diabetes is associated with dysfunction of the neurovascular unit, although the mechanisms of this are incompletely understood and currently no treatment exists to prevent these negative effects. We previously found that the nitric oxide (NO) donor sodium nitroprusside (SNP) prevents the detrimental effect of glucose on neurovascular coupling in zebrafish. We therefore sought to establish the wider effects of glucose exposure on both the neurovascular unit and on behaviour in zebrafish, and the ability of SNP to prevent these. We incubated 4-days post-fertilisation (dpf) zebrafish embryos in 20 mM glucose or mannitol for 5 days until 9 dpf, with or without 0.1 mM SNP co-treatment for 24 h (8-9 dpf), and quantified vascular NO reactivity, vascular mural cell number, expression of a klf2a reporter, glial fibrillary acidic protein (GFAP) and transient receptor potential cation channel subfamily V member 4 (TRPV4), as well as spontaneous neuronal activation at 9 dpf, all in the optic tectum. We also assessed the effect on light/dark preference and locomotory characteristics during free-swimming studies. We find that glucose exposure significantly reduced NO reactivity, klf2a reporter expression, vascular mural cell number and TRPV4 expression, while significantly increasing spontaneous neuronal activation and GFAP expression (all in the optic tectum). Furthermore, when we examined larval behaviour, we found that glucose exposure significantly altered light/dark preference and high and low speed locomotion while in light. Co-treatment with SNP reversed all these molecular and behavioural effects of glucose exposure. Our findings comprehensively describe the negative effects of glucose exposure on the vascular anatomy, molecular phenotype and function of the optic tectum, and on whole-organism behaviour. We also show that SNP or other NO donors may represent a therapeutic strategy to ameliorate the complications of diabetes on the neurovascular unit.This article has an associated First Person interview with the first author of the paper.

Receptor for advanced glycation end products gene polymorphisms in cardiac syndrome X

Endothelial and microvascular dysfunction serve important roles in the formation and pathogenesis of cardiac syndrome X (CSX). Expression of receptor for advanced glycation end products (RAGE) is suggested to be increased in several conditions, including diabetes, inflammation and vascular diseases. In the present study, RAGE gene polymorphisms in patients with CSX and healthy controls were investigated. A total of 114 patients, diagnosed with CSX using coronary angiography results following complaints of angina and objective ischemia, and 103 healthy controls participated in the study. Whether there was a difference in genotype distributions of RAGE gene -374T/A, -429T/C and Glys82Ser polymorphisms between patients with CSX and healthy controls was investigated. Following DNA isolation from blood samples of the participants, the polymorphic regions were examined by quantitative polymerase chain reaction, and the genotyping results were statistically analyzed. When the genotypic distributions of -374T/A, -429T/C and Gly82Ser polymorphisms were investigated in patients with CSX and healthy controls, no statistically significant differences were identified between the two groups (P>0.05). Likewise, no statistically significant differences were observed in the allelic distributions of all 3 polymorphic regions (P>0.05). To the best of our knowledge, the present study also investigated the association between CSX and RAGE gene polymorphisms for the first time. No statistically significant differences in RAGE gene polymorphisms between the CSX and control groups were observed. We hypothesized that significant results may be obtained by increasing the numbers of patients and healthy controls in future studies.

Oral administration of α-ketoglutarate enhances nitric oxide synthesis by endothelial cells and whole-body insulin sensitivity in diet-induced obese rats

Obesity is a risk factor for many chronic diseases, including hypertension, type-2 diabetes, and cancer. Interestingly, concentrations of branched-chain amino acids (BCAAs) in plasma are commonly associated with endothelial dysfunction in humans and animals with obesity. Because L-leucine inhibits nitric oxide synthesis by endothelial cells (EC), we hypothesized that dietary supplementation with AKG (a substrate for BCAA transaminase) may stimulate BCAA catabolism in the small intestine and extra-intestinal tissues, thereby reducing the circulating concentrations of BCAAs and increasing nitric oxide synthesis by endothelial cells. Beginning at four weeks of age, male Sprague-Dawley rats were fed a low-fat or a high-fat diet for 15 weeks. At 19 weeks of age, lean or obese rats continued to be fed for 12 weeks their respective diets and received drinking water containing 0 or 1% AKG ( n =  8/group). At 31 weeks of age, the rats were euthanized to obtain tissues. Food intake did not differ ( P >  0.05) between rats supplemented with or without AKG. Oral administration of AKG (250 mg/kg BW per day) reduced ( P <  0.05) concentrations of BCAAs, glucose, ammonia, and triacylglycerols in plasma, adiposity, and glutamine:fructose-6-phosphate transaminase activity in endothelial cells, and enhanced ( P <  0.05) concentrations of the reduced form of glutathione in tissues, nitric oxide synthesis by endothelial cells, and whole-body insulin sensitivity (indicated by oral glucose tolerance test) in both low-fat and high-fat rats. AKG administration reduced ( P <  0.05) white adipose tissue weights of rats in the low-fat and high-fat groups. These novel results indicate that AKG can reduce adiposity and increase nitric oxide production by endothelial cells in diet-induced obese rats.

Impact statement

Obesity is associated with elevated concentrations of branched-chain amino acids, including L-leucine. L-Leucine inhibits the synthesis of nitric oxide from L-arginine by endothelial cells, contributing to impairments in angiogenesis, blood flow, and vascular dysfunction, as well as insulin resistance. Reduction in the circulating levels of branched-chain amino acids through dietary supplementation with α-ketoglutarate to promote their transamination in the small intestine and other tissues can restore nitric oxide synthesis in the vasculature and reduce the weights of white adipose tissues, thereby improving metabolic profiles and whole-body insulin sensitivity (indicated by oral glucose tolerance test) in diet-induced obese rats. Our findings provide a simple and effective nutritional means to alleviate metabolic syndrome in obese subjects. This is highly significant to combat the current obesity epidemic and associated health problems in humans worldwide.

Influence of type 2 diabetes on muscle deoxygenation during ramp incremental cycle exercise

We tested the hypothesis that type 2 diabetes (T2D) alters the profile of muscle fractional oxygen (O₂) extraction (near-infrared spectroscopy) during incremental cycle exercise. Seventeen middle-aged individuals with uncomplicated T2D and 17 controls performed an upright ramp test to exhaustion. The rate of muscle deoxygenation (i.e. deoxygenated haemoglobin and myoglobin concentration, Δ[HHb+Mb]) profiles of the vastus lateralis muscle were normalised to 100% of the response, plotted against % power output (PO) and fitted with a double linear regression model. Peak oxygen uptake was significantly (P < 0.05) reduced in individuals with T2D. The %Δ[HHb+Mb]/%PO slope of the first linear segment of the double linear regression function was significantly (P < 0.05) steeper in T2D than controls (1.59 (1.14) vs 1.23 (0.51)). Both groups displayed a near-plateau in Δ[HHb+Mb] at an exercise intensity (%PO) not different amongst them. Such findings suggest that a reduced O₂ delivery to active muscles is an important underlying cause of exercise intolerance during a maximum graded test in middle-aged individuals with T2D.

Microvascular capillary assessment in relation to forearm blood flow

OBJECTIVE

To study whether vascular reactivity as assessed by the methods forearm blood flow (FBF) and postocclusive reactive hyperaemia (PRH) in the nail fold was related as a measure of endothelium-dependent vasodilation in the microcirculation.

METHODS

Microvascular reactivity was assessed in forearm blood flow and in the nail fold by vital capillaroscopy of individual microvessels as postocclusive reactive hyperaemia. Vascular reactivity was assessed at baseline (n = 25) as well as after infusion of acetylcholine and of sodium nitroprusside (n = 13). We also performed a multivariate regression analysis to assess whether forearm blood flow or flow-mediated dilatation related to postocclusive reactive hyperaemia.

RESULTS

This study showed a distinct microvascular response to both acetylcholine (endothelium-dependent vasodilation) and sodium nitroprusside (endothelium-independent vasodilation) during forearm blood flow assessment and postocclusive reactive hyperaemia assessment in the nail fold (n = 13). These changes were inversely related (r- = -0·57; P<0·05).

CONCLUSIONS

Forearm blood flow was inversely correlated to postocclusive reactive hyperaemia. Postocclusive reactive hyperaemia was shortened after infusion with both acetylcholine and sodium nitroprusside. This occurred in parallel with the expected increase in forearm blood flow, conceivably reflecting that both methods can be used to assess endothelium-dependent vasodilation in the microcirculation.

Subclinical vascular disease in patients with diabetes is associated with insulin resistance

Patients with diabetes experience increased cardiovascular risk that is not fully explained by deficient glycemic control or traditional cardiovascular risk factors such as smoking and hypercholesterolemia. Asymptomatic patients with diabetes show structural and functional vascular damage that includes impaired vasodilation, arterial stiffness, increased intima-media thickness and calcification of the arterial wall. Subclinical vascular injury associated with diabetes predicts subsequent manifestations of cardiovascular disease, such as ischemic heart disease, peripheral artery disease and stroke. Noninvasive detection of subclinical vascular disease is commonly used to estimate cardiovascular risk associated to diabetes. Longitudinal studies in normotensive subjects show that arterial stiffness at baseline is associated with a greater risk for future hypertension independently of established risk factors. In patients with type 2 diabetes, vascular disease begins to develop during the latent phase of insulin resistance, long before the clinical diagnosis of diabetes. In contrast, patients with type 1 diabetes do not manifest vascular injury when they are first diagnosed due to insulin deficiency, as they lack the preceding period of insulin resistance. These findings suggest that insulin resistance plays an important role in the development of early vascular disease associated with diabetes. Cross-sectional and prospective studies confirm that insulin resistance is associated with subclinical vascular injury in patients with diabetes, independently of standard cardiovascular risk factors. Asymptomatic vascular disease associated with diabetes begins to occur early in life having been documented in children and adolescents. Insulin resistance should be considered a therapeutic target in order to prevent the vascular complications associated with diabetes.

Reduced insulin sensitivity in young, normoglycaemic subjects alters microvascular tissue oxygenation during postocclusive reactive hyperaemia

NEW FINDINGS

What is the central question of the study? Are measures of reduced insulin sensitivity in young, normoglycaemic subjects correlated with near-infrared spectroscopy-derived microvascular responsiveness [tissue oxygen saturation reperfusion rate (STO₂ upslope)] during postocclusive reactive hyperaemia? What is the main finding and its importance? A sevenfold range of hepatic insulin sensitivity is significantly correlated (r = 0.44, P = 0.02) with STO₂ upslope after transient tissue ischaemia. Near-infrared spectroscopy may be an important tool for determining altered microvascular function before onset of hyperglycaemia. Identification of pre-type 2 diabetes much earlier than with the present clinical criteria is important for pre-emptive measures against microvascular deterioration.

ABSTRACT

Near-infrared spectroscopy (NIRS) measurement of postocclusive reactive hyperaemia (PORH) tissue oxygen saturation reperfusion rate [STO₂ upslope (as a percentage per minute)] has recently been correlated with the percentage of flow-mediated dilatation (%FMD). Cardiovascular disease is associated with impairments in %FMD. Reduced insulin sensitivity may negatively affect the vascular system for many years before prediabetes/type 2 diabetes states. The aim of this study was to determine whether static and dynamic STO₂ parameters during PORH are correlated with reduced insulin sensitivity in young, normoglycaemic subjects. Glucose and insulin were measured during an oral glucose tolerance test in 18- to 26-year-old, healthy subjects (11 men and 11 women), and STO₂ was measured during PORH of antebrachial muscle. Hepatic (ISI_HOMA ) and whole-body (ISI_COMP ) insulin sensitivities were calculated. The STO₂ upslope was negatively correlated with minimal STO₂ (r = -0.5, P = 0.01). The change of STO₂ from minimum to baseline (ΔSTO₂ ) was significantly negatively correlated with fasting insulin (r = -0.5, P = 0.01) and a positively correlated with ISI_HOMA (r = 0.65, P = 0.001). The minimum STO₂ was significantly negatively correlated with ISI_HOMA , and STO₂ upslope was significantly positively correlated with ISI_HOMA (r = 0.44, P = 0.02). The minimum STO₂ (a measure of O₂ extraction while the cuff was inflated), ΔSTO₂ (a measure of the amount of reperfusion) and STO₂ upslope (a measure of responsiveness of the microcirculation to ischaemia) were all positively correlated with ISI_HOMA , one of the longest-used measures of insulin sensitivity. The NIRS-derived STO₂ might be a useful tool for assessing how levels of reduced insulin sensitivity in young, normoglycaemic adults affect the microvasculature.

Canagliflozin Inhibits Human Endothelial Cell Proliferation and Tube Formation

Recent clinical trials revealed that sodium-glucose co-transporter 2 (SGLT2) inhibitors significantly reduce cardiovascular events in type 2 diabetic patients, however, canagliflozin increased limb amputations, an effect not seen with other SGLT2 inhibitors. Since endothelial cell (EC) dysfunction promotes diabetes-associated vascular disease and limb ischemia, we hypothesized that canagliflozin, but not other SGLT2 inhibitors, impairs EC proliferation, migration, and angiogenesis. Treatment of human umbilical vein ECs (HUVECs) with clinically relevant concentrations of canagliflozin, but not empagliflozin or dapagliflozin, inhibited cell proliferation. In particular, 10 μM canagliflozin reduced EC proliferation by approximately 45%. The inhibition of EC growth by canagliflozin occurred in the absence of cell death and was associated with diminished DNA synthesis, cell cycle arrest, and a striking decrease in cyclin A expression. Restoration of cyclin A expression via adenoviral-mediated gene transfer partially rescued the proliferative response of HUVECs treated with canagliflozin. A high concentration of canagliflozin (50 μM) modestly inhibited HUVEC migration by 20%, but markedly attenuated their tube formation by 65% and EC sprouting from mouse aortas by 80%. A moderate 20% reduction in HUVEC migration was also observed with a high concentration of empagliflozin (50 μM), while neither empagliflozin nor dapagliflozin affected tube formation by HUVECs. The present study identified canagliflozin as a robust inhibitor of human EC proliferation and tube formation. The anti-proliferative action of canagliflozin occurs in the absence of cell death and is due, in part, to the blockade of cyclin A expression. Notably, these actions are not seen with empagliflozin or dapagliflozin. The ability of canagliflozin to exert these pleiotropic effects on ECs may contribute to the clinical actions of this drug.

Angiotensin II-induced redox-sensitive SGLT1 and 2 expression promotes high glucose-induced endothelial cell senescence

High glucose (HG)-induced endothelial senescence and dysfunction contribute to the increased cardiovascular risk in diabetes. Empagliflozin, a selective sodium glucose co-transporter2 (SGLT2) inhibitor, reduced the risk of cardiovascular mortality in type 2 diabetic patients but the protective mechanism remains unclear. This study examines the role of SGLT2 in HG-induced endothelial senescence and dysfunction. Porcine coronary artery cultured endothelial cells (ECs) or segments were exposed to HG (25 mmol/L) before determination of senescence-associated beta-galactosidase activity, protein level by Western blot and immunofluorescence staining, mRNA by RT-PCR, nitric oxide (NO) by electron paramagnetic resonance, oxidative stress using dihydroethidium and glucose uptake using 2-NBD-glucose. HG increased ECs senescence markers and oxidative stress, down-regulated eNOS expression and NO formation, and induced the expression of VCAM-1, tissue factor, and the local angiotensin system, all these effects were prevented by empagliflozin. Empagliflozin and LX-4211 (dual SGLT1/2 inhibitor) reduced glucose uptake stimulated by HG and H₂ O₂ in ECs. HG increased SGLT1 and 2 protein levels in cultured ECs and native endothelium. Inhibition of the angiotensin system prevented HG-induced ECs senescence and SGLT1 and 2 expression. Thus, HG-induced ECs ageing is driven by the local angiotensin system via the redox-sensitive up-regulation of SGLT1 and 2, and, in turn, enhanced glucotoxicity.

Impaired Vascular Redox Signaling in the Vascular Complications of Obesity and Diabetes Mellitus

Significance: Oxidative stress, a crucial regulator of vascular disease pathogenesis, may be involved in the vascular complications of obesity, systemic insulin resistance (IR), and diabetes mellitus (DM). Recent Advances: Excessive production of reactive oxygen species in the vascular wall has been linked with vascular disease pathogenesis. Recent evidence has revealed that vascular redox state is dysregulated in cases of obesity, systemic IR, and DM, potentially participating in the well-known vascular complications of these disease entities. Critical Issues: The detrimental effects of obesity and the metabolic syndrome on vascular biology have been extensively described at a clinical level. Further, vascular oxidative stress has often been associated with the presence of obesity and IR as well as with a variety of detrimental vascular phenotypes. However, the mechanisms of vascular redox state regulation under conditions of obesity and systemic IR, as well as their clinical relevance, are not adequately explored. In addition, the notion of vascular IR, and its relationship with systemic parameters of obesity and systemic IR, is not fully understood. In this review, we present all the important components of vascular redox state and the evidence linking oxidative stress with obesity and IR. Future Directions: Future studies are required to describe the cellular effects and the translational potential of vascular redox state in the context of vascular disease. In addition, further elucidation of the direct vascular effects of obesity and IR is required for better management of the vascular complications of DM.

Targeting transcriptional control of soluble guanylyl cyclase via NOTCH for prevention of cardiovascular disease

Soluble guanylyl cyclase (sGC) is an effector enzyme of nitric oxide (NO). Recent work has unravelled how levels of this enzyme are controlled, and highlighted a role in vascular disease. We provide a timely summary of available knowledge on transcriptional regulation of sGC, including influences from the NOTCH signalling pathway and genetic variants. It is speculated that hypertension-induced repression of sGC starts a vicious circle that can be initiated by periods of stress, diet or genetic factors, and a key tenet is that reduction in sGC further raises blood pressure. The idea that dysregulation of sGC contributes to syndromes caused by defective NOTCH signalling is advanced, and we discuss drug repositioning for vascular disease prevention. The advantage of targeting sGC expression rather than activity is also considered. It is argued that transcriptional inputs on sGC arise from interactions with other cells, the extracellular matrix and microRNAs (miRNAs), and concluded that the promise of sGC as a target for prevention of cardiovascular disease has increased in recent time.

Early Effects of Hyperbaric Oxygen on Inducible Nitric Oxide Synthase Activity/Expression in Lymphocytes of Type 1 Diabetes Patients: A Prospective Pilot Study

This study aimed at examining the early effects of hyperbaric oxygen therapy (HBOT) on inducible nitric oxide synthase (iNOS) activity/expression in lymphocytes of type 1 diabetes mellitus (T1DM) patients. A group of 19 patients (mean age: 63 ± 2.1) with T1DM and with the peripheral arterial disease were included in this study. Patients were exposed to 10 sessions of HBOT in the duration of 1 h to 100% oxygen inhalation at 2.4 ATA. Blood samples were collected for the plasma C-reactive protein (CRP), plasma free fatty acid (FFA), serum nitrite/nitrate, and serum arginase activity measurements. Expression of iNOS and phosphorylation of p65 subunit of nuclear factor-κB (NFκB-p65), extracellular-regulated kinases 1/2 (ERK1/2), and protein kinase B (Akt) were examined in lymphocyte lysates by Western blot. After exposure to HBOT, plasma CRP and FFA were significantly decreased (p < 0.001). Protein expression of iNOS and serum nitrite/nitrate levels were decreased (p < 0.01), while serum arginase activity was increased (p < 0.05) versus before exposure to HBOT. Increased phosphorylation of NFκB-p65 at Ser⁵³⁶ (p < 0.05) and decreased level of NFκB-p65 protein (p < 0.001) in lymphocytes of T1DM patients were observed after HBOT. Decreased phosphorylation of ERK1/2 (p < 0.05) and Akt (p < 0.05) was detected after HBOT. Our results indicate that exposure to HBO decreased iNOS activity/expression via decreasing phosphorylation of ERK1/2 and Akt followed by decreased activity of NFκB.

Vascular endothelial dysfunction, a major mediator in diabetic cardiomyopathy

Diabetes mellitus is currently a major public health problem. A common complication of diabetes is cardiac dysfunction, which is recognized as a microvascular disease that leads to morbidity and mortality in diabetic patients. While ischemic events are commonly observed in diabetic patients, the risk for developing heart failure is also increased, independent of the severity of coronary artery disease and hypertension. This diabetes-associated clinical entity is considered a distinct disease process referred to as "diabetic cardiomyopathy". However, it is not clear how diabetes promotes cardiac dysfunction. Vascular endothelial dysfunction is thought to be one of the key risk factors. The impact of diabetes on the endothelium involves several alterations, including hyperglycemia, fatty acid oxidation, reduced nitric oxide (NO), oxidative stress, inflammatory activation, and altered barrier function. The current review provides an update on mechanisms that specifically target endothelial dysfunction, which may lead to diabetic cardiomyopathy.

Mitochondrial regulation of diabetic vascular disease: an emerging opportunity

Diabetes-related vascular complication rates remain unacceptably high despite guideline-based medical therapies that are significantly more effective in individuals without diabetes. This critical gap represents an opportunity for researchers and clinicians to collaborate on targeting mechanisms and pathways that specifically contribute to vascular pathology in patients with diabetes mellitus. Dysfunctional mitochondria producing excessive mitochondrial reactive oxygen species (mtROS) play a proximal cell-signaling role in the development of vascular endothelial dysfunction in the setting of diabetes. Targeting the mechanisms of production of mtROS or mtROS themselves represents an attractive method to reduce the prevalence and severity of diabetic vascular disease. This review focuses on the role of mitochondria in the development of diabetic vascular disease and current developments in methods to improve mitochondrial health to improve vascular outcomes in patients with DM.

Modified redox signaling in vasculature after chronic infusion of the insulin receptor antagonist, S961

BACKGROUND

Type 2 diabetes and associated vascular complications cause substantial morbidity and mortality. It is important to investigate mechanisms and test therapies in relevant physiological models, yet few animal models adequately recapitulate all aspects of the human condition.

OBJECTIVE

We sought to determine the potential of using an insulin receptor antagonist, S961, in mice for investigating vascular pathophysiology.

METHODS

S961 was infused into mice for 4 weeks. Blood glucose was monitored, and insulin was measured at the end of the protocol. Blood pressure and pressor responses to vasodilators were measured in cannulated mice, and vascular reactive oxygen and nitrogen species were measured in isolated tissue.

RESULTS

S961 infusion-induced hyperglycemia and hyperinsulinemia. There was evidence of increased vascular reactive oxygen and nitrogen species and modification of NO-mediated signaling. Pressor responses to a NO donor were attenuated, but responses to bradykinin were preserved.

CONCLUSIONS

Infusion of S961, an insulin receptor antagonist, results in the production of a mouse model of type 2 diabetes that may be useful for investigating redox signaling in the vasculature of insulin-resistant mice over the short term. It is limited by both the transient nature of the hyperglycemia and incomplete functional analogy to the human condition.

Ultrafiltration binding analyses of glycated albumin with a 3D-printed syringe attachment

Protein-ligand binding assays facilitate the understanding of biomolecular interactions. Classical equilibrium dialysis methods are often used for accurate determination of binding properties. While accurate, the long equilibration times associated with the technique (> 6 h) hinder throughput. Here, in an attempt to gather high-accuracy results while reducing total analysis time, a low pressure ultrafiltration method that relies on a simple membrane-containing syringe attachment was developed. A minimal portion (1-2%) of the solution containing the binding analytes of interest is driven through the membrane pores and collected for analysis. Specifically, the device was used to investigate the binding affinity between Zn²⁺ and either normal human serum albumin (nHSA) or a commercially purchased glycated human serum albumin (gHSA). Both of these ligand/protein-binding systems have implications in type 1 diabetes. The device was then used to investigate the binding between the various albumin types and C-peptide, the 31 amino acid peptide that is co-secreted with insulin from pancreatic β cells. Results for nHSA/Zn²⁺ binding obtained using the ultrafiltration method (K_d = 5.77 ± 0.19 × 10^-7 M) were statistically equivalent with results reported using other methods. Importantly, the amount of Zn²⁺ bound to the nHSA was significantly different from the gHSA (97 ± 2% protein bound vs. 91 ± 3%, respectively p < 0.05). The binding affinity of C-peptide to nHSA (K_d = 2.4 ± 0.3 × 10^-6 M) agreed with values reported in the literature using standard techniques. Unlike Zn²⁺ binding, the binding of C-peptide to nHSA was statistically equal to its binding to gHSA (77.7 ± 6.2 and 78.8 ± 7.4%, respectively), suggesting that C-peptide replacement therapy in people with T1D may be strongly dependent upon the characteristics of Zn²⁺ binding to human serum albumin. Graphical abstract ᅟ.

Role of plasma glucose level on myocardial perfusion in ST-segment elevation myocardial infarction patients

AIMS

Hyperglycemia is frequent in patients with ST elevation myocardial infarction (STEMI) and is associated with adverse outcome. Aim of our study was to evaluate the correlation between admission plasma glucose level (PGL) and coronary arteries flow velocity.

METHODS

We enrolled 149 STEMI patients successfully treated with primary percutaneous coronary intervention (pPCI). The study population was divided into two groups based on PGL (< or >140 mg/dl) and on history of diabetes, and the groups compared in terms of corrected TIMI frame count (cTFC).

RESULTS

Hyperglycemic patients had a significantly higher cTFC in both the culprit (p < 0.0001) and non-culprit vessel (p: 0.0002); diabetes history impairs as well cTFC of the culprit (p < 0.0001) and non-culprit vessel (p: 0.0001). Within the subpopulation of diabetic patients hyperglycemic ones showed higher cTFC in both the culprit (p 0.0013) and non-culprit vessel (p: 0.0006). Moreover in the whole population cTFC values of both arteries increase linearly with the increment of admission PGL.

CONCLUSIONS

Admission PGL affects coronary flow of both culprit and non-culprit vessel. The impairment of coronary flow is also demonstrated in known diabetic patients, suggesting to consider hyperglycemia an additional risk factor. We finally demonstrated for the first time a positive linear relationship between PGL and cTFC.

Metformin, lipids and atherosclerosis prevention

PURPOSE OF REVIEW

We provide an overview of recent publications that extend clinically relevant knowledge relating to metformin's effects on lipids and atherosclerotic vascular disease and/or provide insights into the drug's mechanisms of action on the heart and vasculature.

RECENT FINDINGS

We focus on original research in humans or in human tissues. Several recently completed randomized clinical trials have reported effects of metformin on surrogate measures of atherosclerotic vascular disease, including carotid-intima media thickness, vascular reactivity and calcification in people with Type 1 (T1D) and Type 2 (T2D) diabetes as well as nondiabetic dysglycaemia. In addition, observational studies have provided novel insights into the mechanisms of metformin's effects on carotid plaque, monocytes/macrophages, vascular smooth muscle and endothelial cells, including via 5'-adenosine monophosphate-activated protein kinase (AMPK) activation.

SUMMARY

Recent trials based on surrogate outcome measures have provided further data suggesting protective effects of metformin against vascular disease in youth and adults with Type 1 diabetes, as well as in adults with prediabetes and Type 2 diabetes. In parallel, human tissue and cell studies have provided new insights into pleiotropic effects of metformin and suggest novel drug targets. As metformin is an inexpensive agent with an established safety profile, larger scale clinical trials based on hard clinical outcomes [cardiovascular disease (CVD) events] are now indicated.

Multicenter, randomized controlled, observer-blinded study of a nitric oxide generating treatment in foot ulcers of patients with diabetes-ProNOx1 study

The aim of this multicenter, prospective, observer-blinded, parallel group, randomized controlled trial was to assess the safety and efficacy of EDX110, a nitric oxide generating medical device, in the treatment of diabetic foot ulcers in a patient group reflecting "real world" clinical practice compared against optimal standard care. Participants were recruited from ten hospital sites in multidisciplinary foot ulcer clinics. The ulcers were full thickness, with an area of 25-2,500 mm² and either a palpable pedal pulse or ankle brachial pressure index > 0.5. Infected ulcers were included. Treatment lasted 12 weeks, or until healed, with a 12-week follow-up period. Both arms were given optimal debridement, offloading and antimicrobial treatment, the only difference being the fixed used of EDX110 as the wound dressing in the EDX110 group. 135 participants were recruited with 148 ulcers (EDX110-75; Control-73), 30% of which were clinically infected at baseline. EDX110 achieved its primary endpoint by attaining a median Percentage Area Reduction of 88.6% compared to 46.9% for the control group (p = 0.016) at 12 weeks in the intention-to-treat population. There was no significant difference between wound size reduction achieved by EDX110 after 4 weeks and the wound size reduction achieved in the control group after 12 weeks. EDX110 was well tolerated. Thirty serious adverse events were reported (12 in the EDX110 group, of which 4 were related to the ulcer; 18 in the control group, of which 10 were related and 1 possibly related to the ulcer), with significant reduction in serious adverse events related to the ulcer in EDX group. There was no significant difference in adverse events. This study, in a real world clinical foot ulcer population, demonstrates the ability of EDX110 to improve healing, as measured by significantly reducing the ulcer area, compared to current best clinical practice.

Comparison of Pulmonary and Systemic NO- and PGI2-Dependent Endothelial Function in Diabetic Mice

Diabetes increases the risk of pulmonary hypertension and is associated with alterations in pulmonary vascular function. Still, it is not clear whether alterations in the phenotype of pulmonary endothelium induced by diabetes are distinct, as compared to peripheral endothelium. In the present work, we characterized differences between diabetic complications in the lung and aorta in db/db mice with advanced diabetes. Male, 20-week-old db/db mice displayed increased HbA1c and glucose concentration compatible with advanced diabetes. Diabetic lungs had signs of mild fibrosis, and pulmonary endothelium displayed significantly ultrastructural changes. In the isolated, perfused lung from db/db mice, filtration coefficient (K_f,c) and contractile response to TXA₂ analogue were enhanced, while endothelial NO-dependent modulation of pulmonary response to hypoxic ventilation and cumulative production of NO₂⁻ were impaired, with no changes in immunostaining for eNOS expression. In turn, 6-keto-PGF_1α release from the isolated lung from db/db mice was increased, as well as immunostaining of thrombomodulin (CD141). In contrast to the lung, NO-dependent, acetylcholine-induced vasodilation, ionophore-stimulated NO₂⁻ generation, and production of 6-keto-PGF_1α were all impaired in aortic rings from db/db mice. Although eNOS immunostaining was not changed, that of CD141 was clearly lowered. Interestingly, diabetes-induced nitration of proteins in aorta was higher than that in the lungs. In summary, diabetes induced marked ultrastructural changes in pulmonary endothelium that were associated with the increased permeability of pulmonary microcirculation, impaired NO-dependent vascular function, with compensatory increase in PGI₂ production, and increased CD141 expression. In contrast, endothelial dysfunction in the aorta was featured by impaired NO-, PGI₂-dependent function and diminished CD141 expression.

Effects of Vitamin D Restricted Diet Administered during Perinatal and Postnatal Periods on the Penis of Wistar Rats

Vitamin D deficiency is common in pregnant women and infants. The present study aimed to investigate the effects of vitamin D restricted diet on the Wistar rats offspring penis morphology. Mother rats received either standard diet (SC) or vitamin D restricted (VitD) diet. At birth, offspring were divided into SC/SC (from SC mothers, fed with SC diet) and VitD/VitD (from VitD mothers, fed with VitD diet). After euthanasia the penises were processed for histomorphometric analysis. The VitD/VitD offspring displayed metabolic changes and reduction in the cross-sectional area of the penis, corpus cavernosum, tunica albuginea, and increased area of the corpus spongiosum. The connective tissue, smooth muscle, and cell proliferation percentages were greater in the corpus cavernosum and corpus spongiosum in the VitD/VitD offspring. The percentages of sinusoidal spaces and elastic fibers in the corpus cavernosum decreased. The elastic fibers in the tunica albuginea of the corpus spongiosum in the VitD/VitD offspring were reduced. Vitamin D restriction during perinatal and postnatal periods induced metabolic and structural changes and represented important risk factors for erectile dysfunction in the penis of the adult offspring. These findings suggest that vitamin D is an important micronutrient in maintaining the cytoarchitecture of the penis.

Vascular endothelium dysfunction: a conservative target in metabolic disorders

AIM

Vascular endothelium plays a role in capillary transport of nutrients and drugs and regulates angiogenesis, homeostasis, as well as vascular tone and permeability as a major regulator of local vascular homeostasis. The present study has been designed to investigate the role of endothelium in metabolic disorders.

METHODS

The endothelium maintains the balance between vasodilatation and vasoconstriction, procoagulant and anticoagulant, prothrombotic and antithrombotic mechanisms.

RESULTS

Diabetes mellitus causes the activation of aldose reductase, polyol pathway and advanced glycation-end-product formation that collectively affect the phosphorylation status and expression of endothelial nitric oxide synthatase (eNOS) and causes vascular endothelium dysfunction. Elevated homocysteine levels have been associated with increase in LDL oxidation, generation of hydrogen peroxides, superoxide anions that increased oxidative degradation of nitric oxide. Hyperhomocysteinemia has been reported to increase the endogenous competitive inhibitors of eNOS viz L-N-monomethyl arginine (L-NMMA) and asymmetric dimethyl arginine (ADMA) that may contribute to vascular endothelial dysfunction. Hypercholesterolemia stimulates oxidation of LDL cholesterol, release of endothelins, and generation of ROS. The increased cholesterol and triglyceride level and decreased protective HDL level, decreases the activity and expression of eNOS and disrupts the integrity of vascular endothelium, due to oxidative stress. Hypertension also stimulates release of endothelins, vasoconstrictor prostanoids, angiotensin II, inflammatory cytokines, xanthine oxidase and, thereby, reduces bioavailability of nitric oxide.

CONCLUSION

Thus, the cellular and molecular mechanisms underlying diabetes mellitus, hyperhomocysteinemia, hypercholesterolemia hypertension and hyperuricemia leads to an imbalance of phosphorylation and dephosphorylation status of lipid and protein kinase that cause modulation of vascular endothelial L-arginine/nitric oxide synthetase (eNOS), to produce vascular endothelium dysfunction.

Mechanisms and Clinical Significance of Endothelial Dysfunction in High-Risk Pregnancies

The maternal cardiovascular system undergoes critical anatomic and functional adaptations to achieve a successful pregnancy outcome which, if disrupted, can result in complications that significantly affect maternal and fetal health. Complications that involve the maternal cardiovascular system are among the most common disorders of pregnancy, including gestational hypertension, preeclampsia, gestational diabetes, and impaired fetal growth. As a central feature, maternal endothelial dysfunction is hypothesized to play a predominant role in mediating the pathogenesis of these high-risk pregnancies, and as such, might proceed and precipitate the clinical presentation of these pregnancy disorders. Improving or normalizing maternal endothelial function in high-risk pregnancies might be an effective therapeutic strategy to ameliorate maternal and fetal clinical outcomes.

Evolution of Hemodialysis Access Resistance: A Longitudinal 5-Year Model using Functional Principal Components Analysis

Purpose

Arteriovenous fistulae (AVF) and grafts (AVG) are the preferred accesses in hemodialysis (HD). By monitoring Access Resistance (AR) one can potentially identify problems with an established HD access, but little is known about how these changes in AR occur, or the variations between the two access types as they mature longitudinally. We postulated that AR evolves differentially between AVF and AVG, a critical aspect to further understanding of the natural history of HD accesses. To describe these changes, we applied a novel statistical methodology of Functional Principal Component (FPC) analysis.

Methods

Using ultrasound dilution flow studies, we retrospectively studied 479 functional HD accesses in which a total of 4573 assessments were made. Accounting for patient factors of age, race, gender and diabetes mellitus (DM) status, we employed a multivariate, mixed-effects model. Using the mean effects of those covariates, we then applied FPC analyses to assess the longitudinal, time-dependent changes between AVFs and AVGs over a 5-year period.

Results

Both types of upper-arm access were associated with a lower initial AR. Older age and DM were associated with a higher AR. Longitudinal AR varied significantly for both AVF and AVG, between the upper arm and lower arm. As a function of time, AVG was associated with an increasing AR. Conversely, AVF, especially upper-arm ones, demonstrated a longitudinal drop in AR.

Conclusions

Evolutionally AR can be predicted not only by the type of access, but also by the location along the arm of that access and by clinical patient factors. Longitudinal change in AR does differ between AVG and AVF. Our report provides the foundation of observed changes over time and provides insight as to how these variations are affected. We endorse ongoing surveillance to screen for clinical sequelae, even years from initial placement.

There Is No Impact of Diabetes on the Endothelial Function of Chronic Kidney Disease Patients

BACKGROUND

Patients with chronic kidney disease (CKD) and type 2 diabetes mellitus (DM) have increased risk of endothelial dysfunction, cardiovascular disease, and mortality. Several studies have separately analyzed endothelial function in these populations. However, data of patients with both CKD and DM are scarce. The aim of this study was to evaluate whether the presence of DM has any additional effect on the endothelial dysfunction of CKD patients.

METHODS

We measured endothelial progenitor cells (EPCs), stromal-derived factor 1 alpha (SDF-1α), serum and urinary nitric oxide (NO), flow-mediated dilation (FMD), and pulse wave velocity (PWV) in 37 CKD patients with DM (CKD-DM group) and in 37 without DM (CKD group).

RESULTS

CKD-DM group had a higher prevalence of obesity (P < 0.01), previous myocardial infarction (P = 0.02), myocardial revascularization (P = 0.04), and a trend for more peripheral artery disease (P = 0.07). Additionally, CKD-DM group had higher EPC (P = 0.001) and PWV (P < 0.001) values. On the other hand, no difference in SDF-1α and serum or urinary NO and FMD was observed between the groups.

CONCLUSIONS

Endothelial dysfunction is frequent in CKD patients, and an additive effect of diabetes cannot be implicated, suggesting the predominant role of uremia in this condition.

Thrombogenicity and central pulse pressure to enhance prediction of ischemic event occurrence in patients with established coronary artery disease: The MAGMA-ischemia score

BACKGROUND AND AIMS

Conventional cardiovascular risk estimators based on clinical demographics have limited prediction of coronary events. Markers for thrombogenicity and vascular function have not been explored in risk estimation of high-risk patients with coronary artery disease. We aimed to develop a clinical and biomarker score to predict 3-year adverse cardiovascular events.

METHODS

Four hundred eleven patients, with ejection fraction ≥40% undergoing coronary angiography, and found to have a luminal diameter stenosis ≥50%, were included in the analysis. Thrombelastography indices and central pulse pressure (CPP) were determined at the time of catheterization.

RESULTS

We identified predictors of death, myocardial infarction (MI) or stroke and developed a numerical ischemia risk score. The primary endpoint of cardiovascular death, MI or stroke occurred in 22 patients (5.4%). The factors associated with events were age, prior PCI or CABG, diabetes, CPP, and thrombin-induced platelet-fibrin clot strength, and were included in the MAGMA-ischemia score. The MAGMA-ischemia score showed a c-statistic of 0.85 (95% Confidence Interval [CI] 0.80-0.87; p<0.001) for the primary endpoint. In the subset of patients who underwent revascularization, the c-statistic was 0.90 (p<0.001). Patients with MAGMA-ischemia score greater than 5 had highest risk to develop clinical events, hazard ratio for the primary endpoint: 13.9 (95% CI 5.8-33.1, p<0.001) and for the secondary endpoint: 4.8 (95% CI 2.3-9.6, p<0.001). When compared to previous models, the MAGMA-ischemia score yielded a higher discrimination.

CONCLUSIONS

Inclusion of CPP and assessment of thrombogenicity in a novel score for patients with documented CAD enhanced the prediction of events.

THE EFFECT OF DIABETES ON CARDIOVASCULAR SYSTEM

Diabetes mellitus (DM) is a critical and long-term disorder due to the insufficient production of insulin by the pancreas or ineffective use of insulin by the body. Importantly, cardiovascular disease (CVD) has long been thought to be linked with diabetes. Despite more diabetic individuals surviving from better medications and treatments, there has been significant rise in the morbidity and mortality from CVD. Indeed, the classification of DM based on the electrocardiogram signals of the heart will be an advantageous system. Further, computer-aided classification of DM with integrated algorithms may enhance the execution of the system. In this paper, we have reviewed various studies using heart rate variability signals for automated classification of diabetes. Furthermore, the different techniques used to extract the features and the efficiency of the classification systems are discussed.

Impaired BKCa channel function in native vascular smooth muscle from humans with type 2 diabetes

Large-conductance Ca2+-activated potassium (BKCa) channels are key determinants of vascular smooth muscle excitability. Impaired BKCa channel function through remodeling of BKCa β1 expression and function contributes to vascular complications in animal models of diabetes. Yet, whether similar alterations occur in native vascular smooth muscle from humans with type 2 diabetes is unclear. In this study, we evaluated BKCa function in vascular smooth muscle from small resistance adipose arteries of non-diabetic and clinically diagnosed type 2 diabetic patients. We found that BKCa channel activity opposes pressure-induced constriction in human small resistance adipose arteries, and this is compromised in arteries from diabetic patients. Consistent with impairment of BKCa channel function, the amplitude and frequency of spontaneous BKCa currents, but not Ca2+ sparks were lower in cells from diabetic patients. BKCa channels in diabetic cells exhibited reduced Ca2+ sensitivity, single-channel open probability and tamoxifen sensitivity. These effects were associated with decreased functional coupling between BKCa α and β1 subunits, but no change in total protein abundance. Overall, results suggest impairment in BKCa channel function in vascular smooth muscle from diabetic patients through unique mechanisms, which may contribute to vascular complications in humans with type 2 diabetes.

Salidroside inhibits high-glucose induced proliferation of vascular smooth muscle cells via inhibiting mitochondrial fission and oxidative stress

The mitochondria are highly dynamic organelles, carefully maintaining network homeostasis by regulating mitochondrial fusion and fission. Mitochondrial dynamics are involved in the regulation of a variety of pathophysiological processes, including cell proliferation. Oxidative stress serves an important role in the remodeling of arterial vascular tissue in diabetic patients by affecting the proliferation of vascular smooth muscle cells (VSMCs). Salidroside is the primary active component of Rhodiola rosea and has been demonstrated to be an antioxidant with cardio- and vascular-protective effects, in addition to improving glucose metabolism. Therefore, the present study aimed to examine the impact of Salidroside on VSMC proliferation, reactive oxygen species (ROS) generation and mitochondrial dynamics under high glucose conditions and the potential mechanisms involved. The current study used Salidroside and a mitochondrial division inhibitor, specifically of Drp1 (Mdivi-1) to treat VSMCs under high glucose conditions for 24 h and assessed VSMCs proliferation, the state of mitochondrial fission and fusion and the expression level of proteins related to mitochondrial dynamics including dynamin-related protein (Drp1) and mitofusin 2 (Mfn2), ROS level and nicotinamide adenine dinucleotide phosphate oxidase activity. The results of the present study indicate that Salidroside and Mdivi-1 inhibit VSMC proliferation, Drp1 expression and oxidative stress and upregulate Mfn2 expression (all P<0.05). The inhibitive effect on VSMC proliferation may be partly reversed by exogenous ROS. In addition, the inhibitive effect on VSMCs proliferation and oxidative stress may also be in part reversed by Mfn2-siRNA. Collectively, these data suggest that Salidroside inhibits VSMCs proliferation induced by high-glucose and may perform its therapeutic effect via maintaining mitochondrial dynamic homeostasis and regulating oxidative stress level, with Mfn2 as a therapeutic target.

Rationale and design of a multicenter placebo-controlled double-blind randomized trial to evaluate the effect of empagliflozin on endothelial function: the EMBLEM trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is characterized by systemic metabolic abnormalities and the development of micro- and macrovascular complications, resulting in a shortened life expectancy. A recent cardiovascular (CV) safety trial, the EMPA-REG OUTCOME trial, showed that empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, markedly reduced CV death and all-cause mortality and hospitalization for heart failure in patients with T2DM and established CV disease (CVD). SGLT2 inhibitors are known to not only decrease plasma glucose levels, but also favorably modulate a wide range of metabolic and hemodynamic disorders related to CV pathways. Although some experimental studies revealed a beneficial effect of SGLT2 inhibitors on atherosclerosis, there is a paucity of clinical data showing that they can slow the progression of atherosclerosis in patients with T2DM. Therefore, the EMBLEM trial was designed to investigate whether empagliflozin treatment can improve endothelial function, which plays a pivotal role in the pathogenesis of atherosclerosis, in patients with T2DM and established CVD.

METHODS

The EMBLEM trial is an ongoing, prospective, multicenter, placebo-controlled double-blind randomized, investigator-initiated clinical trial in Japan. A total of 110 participants with T2DM (HbA1c range 6.0-10.0%) and with established CVD will be randomized (1:1) to receive either empagliflozin 10 mg once daily or a placebo. The primary endpoint of the trial is change in the reactive hyperemia (RH)-peripheral arterial tonometry-derived RH index at 24 weeks from baseline. For comparison of treatment effects between the treatment groups, the baseline-adjusted means and their 95% confidence intervals will be estimated by analysis of covariance adjusted for the following allocation factors: HbA1c (<7.0 or ≥7.0%), age (<65 or ≥65 years), systolic blood pressure (<140 or ≥140 mmHg), and current smoking status (nonsmoker or smoker). Key secondary endpoints include the change from baseline for other vascular-related markers such as arterial stiffness, sympathetic nervous activity, and parameters of cardiac and renal function. Importantly, serious adverse effects independently on the causal relationship to the trial drugs and protocol will be also evaluated throughout the trial period.

DISCUSSION

EMBLEM is the first trial to assess the effect of empagliflozin on endothelial function in patients with T2DM and established CVD. Additionally, mechanisms associating empagliflozin-mediated actions with endothelial function and other CV markers will be evaluated. Thus, the trial is designed to elucidate potential mechanisms by which empagliflozin protects CV systems and improves CV outcomes. Trial registration Unique Trial Number, UMIN000024502 ( https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000028197 ).