Arterial Calcification in Diabetes Mellitus: Preclinical Models and Translational Implications

Diabetes mellitus increasingly afflicts our aging and dysmetabolic population. Type 2 diabetes mellitus and the antecedent metabolic syndrome represent the vast majority of the disease burden-increasingly prevalent in children and older adults. However, type 1 diabetes mellitus is also advancing in preadolescent children. As such, a crushing wave of cardiometabolic disease burden now faces our society. Arteriosclerotic calcification is increased in metabolic syndrome, type 2 diabetes mellitus, and type 1 diabetes mellitus-impairing conduit vessel compliance and function, thereby increasing the risk for dementia, stroke, heart attack, limb ischemia, renal insufficiency, and lower extremity amputation. Preclinical models of these dysmetabolic settings have provided insights into the pathobiology of arterial calcification. Osteochondrogenic morphogens in the BMP-Wnt signaling relay and transcriptional regulatory programs driven by Msx and Runx gene families are entrained to innate immune responses-responses activated by the dysmetabolic state-to direct arterial matrix deposition and mineralization. Recent studies implicate the endothelial-mesenchymal transition in contributing to the phenotypic drift of mineralizing vascular progenitors. In this brief overview, we discuss preclinical disease models that provide mechanistic insights-and point to challenges and opportunities to translate these insights into new therapeutic strategies for our patients afflicted with diabetes mellitus and its arteriosclerotic complications.

Hmox1 Deficiency Sensitizes Mice to Peroxynitrite Formation and Diabetic Glomerular Microvascular Injuries

OBJECTIVE

Indirect evidence suggests a role for heme oxygenase-1 (HO-1) in limiting diabetic vasculopathy. The goal of this study was to assess the role of HO-1 in the development of microvascular lesions within glomeruli during diabetes mellitus using a mouse model with specific alteration of the Hmox1 gene.

APPROACH AND RESULTS

The effects of Hmox1 haploinsufficiency were studied as a means of assessing the intrinsic contribution of HO-1 in the development of renal microvascular lesions during diabetes. Renal function and histology were analyzed 10 weeks after diabetes induction with streptozotocin. Diabetic Hmox1^+/- mice showed higher levels of albuminuria and blood urea compared to their wild-type diabetic littermates. More severe glomerular microvascular lesions were also observed in the diabetic Hmox1^+/- mice. This was associated with a renal increase in the expression of the oxidative stress marker, nitrotyrosine.

CONCLUSIONS

Genetic Hmox1 partial deficiency is sufficient to sensitize mice to the development of diabetic glomerular microvascular lesions. HO-1 exerts antioxidant effects in the kidney during diabetes mellitus. These have protective effects on the development of glomerular endothelial injury.

Increased levels of inflammatory mediators and proinflammatory monocytes in patients with type I diabetes mellitus and nephropathy

AIMS

To investigate and describe the relationship between diabetic nephropathy and systemic inflammation in patients with type 1 diabetes mellitus (T1DM).

METHODS

Patients with T1DM, with or without reduced renal function due to diabetic nephropathy, were included. Differences in inflammatory mediators, adhesion molecules, markers of endothelial dysfunction and subsets of monocytes were studied in patients with mean disease duration of 31years.

RESULTS

Patients with T1DM with and without renal failure were compared. Patients with nephropathy had increased plasma levels of proinflammatory monocytes, as well as circulatory PAI-1, syndecan-1, VEGF, IL-1β, IL-1Ra and CCL4. Peripheral blood mononuclear cells from patients with nephropathy numerically increased soluble ICAM and PAI-1 in co-culture with primary endothelial cells compared to cells from patients without nephropathy.

CONCLUSIONS

T1DM patients with kidney failure have higher levels of proinflammatory monocytes and circulatory inflammatory mediators compared to patients with T1DM alone. The results highlight the importance of inflammation and endothelial dysfunction in diabetic nephropathy with reduced GFR.

Role of endoplasmic reticulum stress signalling in diabetic endothelial dysfunction and atherosclerosis

It is well established that diabetes mellitus accelerates atherosclerotic vascular disease. Endothelial injury has been proposed to be the initial event in the pathogenesis of atherosclerosis. Endothelium not only acts as a semi-selective barrier but also serves physiological and metabolic functions. Diabetes or high glucose in circulation triggers a series of intracellular responses and organ damage such as endothelial dysfunction and apoptosis. One such response is high glucose-induced chronic endoplasmic reticulum stress in the endothelium. The unfolded protein response is an acute reaction that enables cells to overcome endoplasmic reticulum stress. However, when chronically persistent, endoplasmic reticulum stress response could ultimately lead to endothelial dysfunction and atherosclerosis. Herein, we discuss the scientific advances in understanding endoplasmic reticulum stress-induced endothelial dysfunction, the pathogenesis of diabetes-accelerated atherosclerosis and endoplasmic reticulum stress as a potential target in therapies for diabetic atherosclerosis.

Investigation of the Effects and Mechanisms of Mai Tong Formula on Lower Limb Macroangiopathy in a Spontaneous Diabetic Rat Model

A new Chinese herbal formula called Mai Tong Formulae (MTF) has recently been used to treat lower limb macroangiopathy in type 2 diabetes mellitus (T2DM) patients. In this study, we investigated the effect of MTF on lower limb macroangiopathy in a spontaneous diabetic rat model (GK rats). We found that MTF treatment significantly reduced serum fasting blood glucose (FBG), triglycerides (TG), total cholesterol (TC), IL6, and VEGF and increased serum insulin in this model. Histological and ultrastructural observations showed that MTF treatment significantly reduced vascular endothelial cell shedding and improved endothelium injuries. We further detect proteome alteration following MTF treatment. 25 differential proteins (DPs) abnormally expressed in GK rats were normalized by MTF treatment. These DPs significantly are enriched in biological processes and pathways that regulate muscle contraction and cGMP-PKG signaling pathway and so on. Additional protein-protein interaction (PPI) network analyses of the DPs showed that Fasn and Prkar2a are involved in the AMPK signaling pathway, and Gnas, Myh11, and Myh6 are involved in vascular smooth muscle contraction; these 5 DPs were validated by Western blotting. These results indicate that MTF treatment effectively treats lower limb macroangiopathy by regulating key proteins involved in AMPK signaling pathway and vascular smooth muscle contraction.

Arginase Inhibition Improves Microvascular Endothelial Function in Patients With Type 2 Diabetes Mellitus

OBJECTIVES

The development of microvascular complications in diabetes is a complex process in which endothelial dysfunction is important. Emerging evidence suggests that arginase is a key mediator of endothelial dysfunction in type 2 diabetes mellitus by reciprocally regulating nitric oxide bioavailability. The aim of this prospective intervention study was to test the hypothesis that arginase activity is increased and that arginase inhibition improves microvascular endothelial function in patients with type 2 diabetes and microvascular dysfunction.

DESIGN

Microvascular endothelium-dependent and -independent dilatation was determined in patients with type 2 diabetes (n = 12) and healthy age-matched control subjects (n = 12) with laser Doppler flowmetry during iontophoretic application of acetylcholine and sodium nitroprusside, respectively, before and after administration of the arginase inhibitor N^ω-hydroxy-nor-L-arginine (120 min). Plasma ratios of amino acids involved in arginase and nitric oxide synthase activities were determined. The laser Doppler flowmetry data were the primary outcome variable.

RESULTS

Microvascular endothelium-dependent dilatation was impaired in subjects with type 2 diabetes (P < .05). After administration of N^ω-hydroxy-nor-L-arginine, microvascular endothelial function improved significantly in patients with type 2 diabetes to the level observed in healthy controls. Endothelium-independent vasodilatation did not change significantly. Subjects with type 2 diabetes had higher levels of ornithine and higher ratios of ornithine/citrulline and ornithine/arginine (P < .05), suggesting increased arginase activity.

CONCLUSION

Arginase inhibition improves microvascular endothelial function in patients with type 2 diabetes and microvascular dysfunction. Arginase inhibition may represent a novel therapeutic strategy to improve microvascular endothelial function in patients with type 2 diabetes.

Protective role of sulphoraphane against vascular complications in diabetes

Context Diabetes is a global health challenge. Although large prospective clinical trials have shown that intensive control of blood glucose or blood pressure reduces the risk for development and progression of vascular complications in diabetes, a substantial number of diabetic patients still experience renal failure and cardiovascular events, which could account for disabilities and high mortality rate in these subjects. Objective Sulphoraphane is a naturally occurring isothiocyanate found in widely consumed cruciferous vegetables, such as broccoli, cabbage and Brussels sprouts, and an inducer of phase II antioxidant and detoxification enzymes with anticancer properties. We reviewed here the protective role of sulphoraphane against diabetic vascular complications. Methods In this review, literature searches were undertaken in Medline and in CrossRef. Non-English language articles were excluded. Keywords [sulphoraphane and (diabetes, diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, diabetic complications, vascular, cardiomyocytes, heart or glycation)] have been used to select the articles. Results There is accumulating evidence that sulphoraphane exerts beneficial effects on vascular damage in both cell culture and diabetic animal models via antioxidative properties. Furthermore, we have recently found that sulphoraphane inhibits in vitro formation of advanced glycation end products (AGEs), suppresses the AGE-induced inflammatory reactions in rat aorta by reducing receptor for AGEs (RAGE) expression and decreases serum levels of AGEs in humans. Conclusion These findings suggest that blockade of oxidative stress and/or the AGE-RAGE axis by sulphoraphane may be a novel therapeutic strategy for preventing vascular complications in diabetes.

Extracellular microRNAs and endothelial hyperglycaemic memory: a therapeutic opportunity?

Type 2 diabetes mellitus (T2DM) is a major cause of cardiovascular (CV) disease. Several large clinical trials have shown that the risk for patients with diabetes of developing CV complications is only partially reduced by early, intensive glycaemic control and lifestyle interventions, and that such complications result from changes in complex, not fully explored networks that contribute to the maintenance of endothelial function. The accumulation of senescent cells and the low-grade, systemic, inflammatory status that accompanies aging (inflammaging) are involved in the development of endothelial dysfunction. Such phenomena are modulated by epigenetic mechanisms, including microRNAs (miRNAs). MiRNAs can modulate virtually all gene transcripts. They can be secreted by living cells and taken up in active form by recipient cells, providing a new communication tool between tissues and organs. MiRNA deregulation has been associated with the development and progression of a number of age-related diseases, including the enduring gene expression changes seen in patients with diabetes. We review recent evidence on miRNA changes in T2DM, focusing on the ability of diabetes-associated miRNAs to modulate endothelial function, inflammaging and cellular senescence. We also discuss the hypothesis that miRNA-containing extracellular vesicles (i.e. exosomes and microvesicles) could be harnessed to restore a 'physiological' signature capable of preventing or delaying the harmful systemic effects of T2DM.

Treatment for diabetic ulcer wounds using a fern tannin optimized hydrogel formulation with antibacterial and antioxidative properties

ETHNOPHARMACOLOGICAL RELEVANCE

Blechnum orientale Linn. (B. orientale) is a fern traditionally used by the natives as a poultice to treat wounds, boils, ulcers, blisters, abscesses, and sores on the skin.

AIM OF THE STUDY

To investigate the wound healing ability of a concentrated extract of B. orientale in a hydrogel formulation in healing diabetic ulcer wounds.

MATERIALS AND METHODS

The water extract from the leaves of B. orientale was separated from the crude methanolic extract and subjected to flash column chromatography techniques to produce concentrated fractions. These fractions were tested for phytochemical composition, tannin content, antioxidative and antibacterial activity. The bioactive fraction was formulated into a sodium carboxymethylcellulose hydrogel. The extract-loaded hydrogels were then characterized and tested on excision ulcer wounds of streptozotocin-induced diabetic rats. Wound size was measured for 14 days. Histopathological studies were conducted on the healed wound tissues to observe for epithelisation, fibroblast proliferation and angiogenesis. All possible mean values were subjected to statistical analysis using One-way ANOVA and post-hoc with Tukey's T-test (P<0.05).

RESULTS

One fraction exhibited strong antioxidative and antibacterial activity. The fraction was also highly saturated with tannins, particularly condensed tannins. Fraction W5-1 exhibited stronger antioxidant activity compared to three standards (α-Tocopherol, BHT and Trolox-C). Antibacterial activity was also present, and notably bactericidal towards Methicillin-resistant Staphylococcus aureus (MRSA) at 0.25mg/ml. The extract-loaded hydrogels exhibited shear-thinning properties, with high moisture retention ability. The bioactive fraction at 4% w/w was shown to be able to close diabetic wounds by Day 12 on average. Other groups, including controls, only exhibited wound closure by Day 14 (or not at all). Histopathological studies had also shown that extract-treated wounds exhibited re-epithelisation, higher fibroblast proliferation, collagen synthesis, and angiogenesis.

CONCLUSION

The ethnopharmacological effects of using B. orientale as a topical treatment for external wounds was validated and was also significantly effective in treating diabetic ulcer wounds. Thus, B. orientale extract hydrogel may be presented as a potential treatment for diabetic ulcer wounds.

Probucol normalizes cholesteryl ester transfer in type 2 diabetes

AIMS

Accelerated cholesteryl ester transfer (CET) protein (CETP) activity is believed to promote macrovascular disease in patients with type 2 diabetes (T2D) by increasing the cholesterol burden of the apoB - containing triglyceride-rich lipoprotein (TGRLP) CE acceptors and promoting small dense LDL formation. While previous studies have shown that this same abnormality is present in patients with type 1 diabetes (T1D) and was normalized by the anti-oxidant drug probucol, its effects on CET in T2D are unknown.

PATIENTS AND METHODS

The net mass transfer of CE from HDL to the apoB lipoproteins (VLDL+LDL) was studied in intact plasma from seven T2D patients before and two months after treatment with probucol (1g/day).

RESULTS

Before treatment, CET was significantly greater than controls at 1 and 2h (p<.005). Recombination studies showed that this disturbance was attributable to dysfunction of VLDL and not due to altered behavior of HDL or CETP. Probucol treatment normalized CET in all subjects and significantly lowered plasma cholesterol (pre-Rx: 197±4.5 vs post-Rx: 162±27.1mg/dL; mean±S.D.; p<.025) and HDL-C (pre-Rx: 46.4±7.5 vs post-Rx: 39.1±4.0; p<.025) without changing glycemic control.

CONCLUSIONS

By normalizing CET in T2D, probucol likely reduces the formation of atherogenic lipoproteins. This effect on CET is achieved through qualitative alterations in CETP's lipoprotein substrates and not through changes in CETP or HDL. Since probucol also has potent anti-oxidative and anti-inflammatory properties, it may have a new role to play in lipoprotein remodeling that reduce cardiovascular risk in T2D.

Combination Therapy of Nifedipine and Sulphonylureas Exhibits a Mutual Antagonistic Effect on the Endothelial Cell Dysfunction Induced by Hyperglycemia Linked to Vascular Disease

BACKGROUND/AIMS

By inducing severe endothelial impairment, hypertension and diabetes are two leading causes of morbidity and mortality. Hypertensive patients with concomitant diabetes must take both antihypertensive and hypoglycaemic medications, for which there is a lack of experimental and clinical guidelines. This study aimed to examine the interaction between these two types of medication on the endothelial cell function.

METHODS

The effect of antihypertensive (nifedipine and irbesartan) and anti-diabetic (metformin and glibenclamide/glimepiride) drugs on human umbilical vein cells (HUVECs) function was examined using a modified Boyden chamber assay. The intracellular NO and O2- levels of HUVECs were detected through flow cytometry.

RESULTS

Our findings showed that nifedipine/sulphonylurea monotherapy significantly attenuated high glucose-induced (33 mM) HUVECs migration incapacity, while combination therapy of nifedipine and glibenclamide/glimepiride showed no protective effect. Both nifedipine/metformin monotherapy and combined therapy significantly mitigated the migration incapacity induced by high glucose in HUVECs. Combined with either metformin or sulphonylureas, irbesartan therapy was able to attenuate the high glucose-induced migration incapacity of HUVECs. Nifedipine monotherapy decreased the O2- levels and increased the NO levels in in vitro-cultured HUVECs treated with high glucose. However, the combination therapy of nifedipine and glibenclamide increased the O2- levels and decreased the NO levels compared to the nifedipine monotherapeutic group.

CONCLUSION

The nifedipine and glibenclamide/glimepiride combination exerted a mutual antagonistic effect on the protection from high glucose-induced impairment in endothelial cells, which might be partially attributed to the increased O2- level and decreased NO level. These results imply that calcium channel blockers + sulphonylurea combination therapy warrants further attention in patients suffering from both hypertension and diabetes.

Diabetes mellitus: The linkage between oxidative stress, inflammation, hypercoagulability and vascular complications

BACKGROUND

Vascular complications are the leading cause of morbidity and mortality among patients with type 1 and type 2 diabetes mellitus. These vascular abnormalities result of a chronic hyperglycemic state, which leads to an increase in oxidative stress and inflammatory responses.

AIM

This review addresses the relationships among endothelial dysfunction, hypercoagulability and inflammation and their biomarkers in the development of vascular complications in type 1 and type 2 diabetes.

RESULTS

Inflammation, endothelial dysfunction, and hypercoagulability are correlated to each other, playing an important role in the development of vascular complications in diabetic patients. Moreover, it has been observed that several endothelial, inflammatory and pro-coagulant biomarkers, such as VWF, IL-6, TNF-α, D-dimer and PAI-1, are increased in diabetic patients who have microvascular and macrovascular complications, including nephropathy or cardiovascular disease.

CONCLUSION

It is promising the clinical and laboratory use of endothelial, inflammatory and pro-coagulant biomarkers for predicting the risk of cardiovascular and renal complications in diabetic patients and for monitoring these patients.

Multidrug resistance associated protein-1 (MRP1) deficiency attenuates endothelial dysfunction in diabetes

AIM

The multidrug resistance associated protein-1 (MRP1) is the main transporter of oxidized glutathione in endothelial cells, and blockade of MRP1 improves endothelial cell dysfunction induced by reactive oxygen species. We therefore investigated the role of MRP1 in hyperglycemia-induced endothelial dysfunction and ROS production.

METHODS AND RESULTS

Diabetes was induced in 12 week old male MRP1(-/-)- or corresponding FVB wild-type (wt) mice by injection of streptozotocin (50mg/kg for 5 days). Eight weeks thereafter acetylcholine-induced endothelium-dependent vasorelaxation was blunted in aortic rings from diabetic wt mice (blood glucose levels >250 mg/dl) compared with nondiabetic animals (Rmax 74 ± 2% vs. 94 ± 2%, p<0.001). However in aortae from diabetic mice lacking MRP1, endothelium-dependent vasorelaxation was only mildly impaired (Rmax 87 ± 3%, p<0.001 vs. wt). Endothelium-independent relaxation induced by DEA-NONOate was not different among the groups. Streptozotocin-induced diabetes significantly increased aortic superoxide anion and hydrogen peroxide production in wild-type but not in MRP1(-/-) mice. Aortic levels of glutathione were significantly diminished in STZ-treated FVB mice, while preserved in MRP1(-/-) mice. Further, in cultured human aortic endothelial cells, high glucose levels (30 mmol/l) over 5 days significantly increased superoxide production which was inhibited by downregulation of MRP1 via siRNA.

CONCLUSIONS

These data indicate that MRP1 plays an important role for endothelial dysfunction and reactive oxygen species production in diabetes and under conditions of hyperglycemia. MRP1 therefore may represent a therapeutic target in treatment of diabetes induced vascular dysfunction.

Diabetes medications: Impact on inflammation and wound healing

Chronic wounds are a common complication in patients with diabetes that often lead to amputation. These non-healing wounds are described as being stuck in a persistent inflammatory state characterized by accumulation of pro-inflammatory macrophages, cytokines and proteases. Some medications approved for management of type 2 diabetes have demonstrated anti-inflammatory properties independent of their marketed insulinotropic effects and thus have underappreciated potential to promote wound healing. In this review, the potential for insulin, metformin, specific sulfonylureas, thiazolidinediones, and dipeptidyl peptidase-4 inhibitors to promote healing is evaluated by reviewing human and animal studies on inflammation and wound healing. The available evidence indicates that diabetic medications have potential to prevent wounds from becoming arrested in the inflammatory stage of healing and to promote wound healing by downregulating pro-inflammatory cytokines, upregulating growth factors, lowering matrix metalloproteinases, stimulating angiogenesis, and increasing epithelization. However, no clinical recommendations currently exist on the potential for specific diabetic medications to impact healing of chronic wounds. Thus, we encourage further research that may guide physicians on providing personalized diabetes treatments that achieve glycemic goals while promoting healing in patients with chronic wounds.

Kinase-SUMO networks in diabetes-mediated cardiovascular disease

Type II diabetes mellitus (DM) is a common comorbidity in patients with cardiovascular disease (CVD). Epidemiological studies including the Framingham, UKPDS, and MRFIT studies have shown diabetes to be an independent risk factor for cardiovascular disease associated with increased incidence of morbidity and mortality. However, major randomized controlled clinical trials including ADVANCE, VAD, and ACCORD have failed to demonstrate a significant reduction in CVD complications from longstanding DM with strict glycemic control. This suggests that despite the strong clinical correlation between DM and CVD, the precise mechanisms of DM-mediated CVD pathogenesis remain unclear. Signal transduction investigations have shed some light on this question with numerous studies demonstrating the role of kinase pathways in facilitating DM and CVD pathology. Abnormalities in endothelial, vascular smooth muscle, and myocardial function from the pathological insults of hyperglycemia and oxidative stress in diabetes are thought to accelerate the development of cardiovascular disease. Extensive interplay between kinase pathways that regulate the complex pathology of DM-mediated CVD is heavily regulated by a number of post-translational modifications (PTMs). In this review, we focus on the role of a dynamic PTM known as SUMOylation and its role in regulating these kinase networks to provide a mechanistic link between DM and CVD.

Glucocorticoids Suppress Mitochondrial Oxidant Production via Upregulation of Uncoupling Protein 2 in Hyperglycemic Endothelial Cells

Diabetic complications are the leading cause of morbidity and mortality in diabetic patients. Elevated blood glucose contributes to the development of endothelial and vascular dysfunction, and, consequently, to diabetic micro- and macrovascular complications, because it increases the mitochondrial proton gradient and mitochondrial oxidant production. Therapeutic approaches designed to counteract glucose-induced mitochondrial reactive oxygen species (ROS) production in the vasculature are expected to show efficacy against all diabetic complications, but direct pharmacological targeting (scavenging) of mitochondrial oxidants remains challenging due to the high reactivity of some of these oxidant species. In a recent study, we have conducted a medium-throughput cell-based screening of a focused library of well-annotated pharmacologically active compounds and identified glucocorticoids as inhibitors of mitochondrial superoxide production in microvascular endothelial cells exposed to elevated extracellular glucose. The goal of the current study was to investigate the mechanism of glucocorticoids' action. Our findings show that glucocorticoids induce the expression of the mitochondrial UCP2 protein and decrease the mitochondrial potential. UCP2 silencing prevents the protective effect of the glucocorticoids on ROS production. UCP2 induction also increases the oxygen consumption and the "proton leak" in microvascular endothelial cells. Furthermore, glutamine supplementation augments the effect of glucocorticoids via further enhancing the expression of UCP2 at the translational level. We conclude that UCP2 induction represents a novel experimental therapeutic intervention in diabetic vascular complications. While direct repurposing of glucocorticoids may not be possible for the therapy of diabetic complications due to their significant side effects that develop during chronic administration, the UCP2 pathway may be therapeutically targetable by other, glucocorticoid-independent pharmacological means.

Serum apelin and ADMA levels in type 2 diabetics with and without vascular complications

AIMS

Type 2 diabetes mellitus (T2DM) is a metabolic and chronic disease which is characterized by hyperglycemia, and that is the major causes of various micro and macrovascular complications. Asymmetrical dimethylarginine (ADMA), formed by the hydrolysis of proteins containing methylated arginine residues, is an endogenous inhibitor of nitric oxide synthase (NOS), which oxidize l-arginine to citruline and nitric oxide (NO), related to hyperinsulinaemia and hyperlipidaemia. Apelin is a recently discovered peptide, present in a number of tissues and play role in insulin sensitivity improvement. In this study, our aim was to determine the levels of apelin and ADMA with glycated haemoglobin (HbA1c) in type 2 diabetic patients with or without vascular complications.

METHODS

This study included (a total of) 59 diabetic patients. Of the patients, 30 were diabetic with complications, and 29 without complications. In serum samples obtained from the patients, serum ADMA and apelin levels were measured with Enzyme Linked Immunosorbent Assay (ELISA) method.

RESULTS

Our study totally enrolled 59 patients in two groups. No significant differences were found in sex, age, HbA1c and glucose levels among groups. Apelin and ADMA levels of group with complications were lower than those of group without complications, but no statistically significant difference of apelin and ADMA levels (p>0.05).

CONCLUSION

The results of this study have been showed no statistically significant relationship present between ADMA-apelin levels and complications of T2DM. Further studies involving larger patients populations and healthy controls should be done to clarify the pathogenetic significance of apelin and ADMA in diabetic vascular complications.

Sonic hedgehog improves ischemia-induced neovascularization by enhancing endothelial progenitor cell function in type 1 diabetes

The Sonic hedgehog (Shh) pathway is downregulated in type 1 diabetes, and it has been reported that augmentation of this pathway may alleviate diabetic complications. However, the cellular mechanisms underlying these protective effects are poorly understood. Recent studies indicate that impaired function of endothelial progenitor cells (EPCs) may contribute to cardiovascular problems in diabetes. We hypothesized that impaired Shh signaling contribute to endothelial progenitor cell dysfunction and that activating the Shh signaling pathway may rescue EPC function and promote diabetic neovascularization. Adult male C57/B6 mice and streptozotocin (STZ)-induced type 1 diabetic mice were used. Gli1 and Ptc1 protein levels were reduced in EPCs from diabetic mice, indicating inhibition of the Shh signaling pathway. EPC migration, tube formation ability, and mobilization were impaired in diabetic mice compared with non-diabetic controls (p < 0.05 vs control), and all were improved by in vivo administration of the Shh pathway receptor agonist SAG (p < 0.05 vs diabetes). SAG significantly increased capillary density and blood perfusion in the ischemic hindlimbs of diabetic mice (p < 0.05 vs diabetes). The AKT activity was lower in EPCs from diabetic mice than those from non-diabetic controls (p < 0.05 vs control). This decreased AKT activity led to an increased GSK-3β activity and degradation of the Shh pathway transcription factor Gli1/Gli2. SAG significantly increased the activity of AKT in EPCs. Our data clearly demonstrate that an impaired Shh pathway mediated by the AKT/GSK-3β pathway can contribute to EPC dysfunction in diabetes and thus activating the Shh signaling pathway can restore both the number and function of EPCs and increase neovascularization in type 1 diabetic mice.

Glucose variability, HbA1c and microvascular complications

Microvascular complications in diabetes are associated with poor long-term diabetes control as measured by HbA1c levels. Glucose fluctuations are related to oxidative stress, endothelial dysfunction, and inflammation, factors traditionally associated with the pathogenesis of vascular damage. Glucose variability has been associated with macrovascular disease in some studies but any association with microvascular disease remains controversial. This overview summarizes recent findings in the field of glucose variability and its possible relationship with retinopathy, nephropathy and neuropathy. It is concluded that randomized prospective follow-up trials could possibly help estimate whether short-term glucose variability should be considered as an independent risk factor for microvascular complications in diabetes.

Influence of Postprandial Hyperglycemic Conditions on Arterial Stiffness in Patients With Type 2 Diabetes

CONTEXT

Patients with type 2 diabetes (T2D) are at an increased risk of cardiovascular disease.

OBJECTIVE

The objective of the study was to determine whether postprandial hyperglycemia affects arterial function in T2D.

DESIGN

A single-center, open-label study of three groups of men were studied: 1) T2D patients with albuminuria (n = 22), 2) T2D patients without albuminuria (n = 24), and 3) nondiabetic controls (n = 25). Patients were randomized to a two-period crossover study schedule, ingesting breakfast, with or without insulin lispro (to induce low or high postprandial glycemia).

MAIN OUTCOME MEASURES

Arterial stiffness was assessed by calculating pulse wave velocity (PWV) and augmentation index using applanation tonometry, and endothelial dysfunction was assessed using peripheral arterial tonometry, 30 minutes before breakfast and up to 240 minutes after breakfast.

RESULTS

At baseline, arterial stiffness was increased in patients. When adjusted for age and body mass index, in a combined group of patients with and without albuminuria, brachial PWV was higher during low (P = .032) and high (P = .038) postprandial glycemia vs controls. These differences were driven by the albuminuria group vs controls during low (P = .014) and high (P = .018) postprandial glycemia. No differences were observed in aortic PWV, augmentation index, or peripheral arterial tonometry ratio between patients and controls. Endothelin-1 and IL-6 were higher, and superoxide dismutase was lower, during postprandial hyperglycemia in T2D patients vs controls.

CONCLUSIONS

In patients with T2D and albuminuria, brachial PWV was higher under postprandial hyperglycemic conditions, relative to controls. These data suggest that hyperglycemia induces an increase in stiffness of intermediate-sized arteries. We found no changes in other parts of the arterial bed.

Elevated Glucose Levels Promote Contractile and Cytoskeletal Gene Expression in Vascular Smooth Muscle via Rho/Protein Kinase C and Actin Polymerization

Both type 1 and type 2 diabetes are associated with increased risk of cardiovascular disease. This is in part attributed to the effects of hyperglycemia on vascular endothelial and smooth muscle cells, but the underlying mechanisms are not fully understood. In diabetic animal models, hyperglycemia results in hypercontractility of vascular smooth muscle possibly due to increased activation of Rho-kinase. The aim of the present study was to investigate the regulation of contractile smooth muscle markers by glucose and to determine the signaling pathways that are activated by hyperglycemia in smooth muscle cells. Microarray, quantitative PCR, and Western blot analyses revealed that both mRNA and protein expression of contractile smooth muscle markers were increased in isolated smooth muscle cells cultured under high compared with low glucose conditions. This effect was also observed in hyperglycemic Akita mice and in diabetic patients. Elevated glucose activated the protein kinase C and Rho/Rho-kinase signaling pathways and stimulated actin polymerization. Glucose-induced expression of contractile smooth muscle markers in cultured cells could be partially or completely repressed by inhibitors of advanced glycation end products, L-type calcium channels, protein kinase C, Rho-kinase, actin polymerization, and myocardin-related transcription factors. Furthermore, genetic ablation of the miR-143/145 cluster prevented the effects of glucose on smooth muscle marker expression. In conclusion, these data demonstrate a possible link between hyperglycemia and vascular disease states associated with smooth muscle contractility.

Ursodeoxycholic Acid (UDCA) Exerts Anti-Atherogenic Effects by Inhibiting RAGE Signaling in Diabetic Atherosclerosis

A naturally occurring bile acid, ursodeoxycholic acid (UDCA), is known to alleviate endoplasmic reticulum (ER) stress at the cellular level. However, the detailed action mechanisms of UDCA in atherosclerosis are not fully understood. In this study, we demonstrated whether UDCA exerts anti-atherogenic activity in diabetic atherosclerosis by targeting ER stress and “receptor for advanced glycation endproduct” (RAGE) signaling. UDCA markedly reduced ER stress, RAGE expression, and pro-inflammatory responses [including NF-κB activation and reactive oxygen species (ROS) production] induced in endothelial cells (ECs) by high glucose (HG). In particular, UDCA inhibited HG-induced ROS production by increasing the Nrf2 level. In macrophages, UDCA also blocked HG-induced RAGE and pro-inflammatory cytokine expression and inhibited foam cell formation via upregulation of the ATP-binding cassette (ABC) transporters, ABCA1 and ABCG1. In the diabetic mouse model, UDCA inhibited atheromatous plaque formation by decreasing ER stress, and the levels of RAGE and adhesion molecules. In conclusion, UDCA exerts an anti-atherogenic activity in diabetic atherosclerosis by targeting both ER stress and RAGE signaling. Our work implicates UDCA as a potential therapeutic agent for prevention or treatment of diabetic atherosclerosis.