Pathophysiology of peripheral arterial disease in diabetes mellitus

Type 2 Diabetes and Cardiovascular Factors Contrasted with Fibrinolysis Disorders in the Blood of Patients with Peripheral Arterial Disease

Background and objectives: Both in the pathogenesis of type 2 diabetes (DM 2) and Peripheral Arterial Disease (PAD), a vital role is played by endothelial dysfunction. Metabolic disorders found in DM 2 (hyperglycemia, insulin resistance), endothelial dysfunction, and increased inflammation lead to intensified atherothrombosis. The fibrinolysis system comprises a natural compensatory mechanism in case of hypercoagulability. The aim of this study was to assess concentrations of selected fibrinolysis parameters in the blood of patients with symptomatic PAD, including in particular concurrent DM 2 and other cardiovascular factors. Materials and Methods: In the group of 80 patients with PAD (27 F/53 M) and 30 healthy volunteers (10 F/20 M), the following parameters were measured: Concentrations of fibrinogen, tissue-Plasminogen Activator (t-PA Ag), Plasminogen Activator Inhibitor-1 (PAI-1 Ag), D-dimer, and platelet (PLT) count. Results: In the blood of patients with PAD and concomitant DM 2 significantly higher concentrations of fibrinogen were found in comparison with patients with PAD and without diabetes (p = 0.044). No significant impact was observed in individuals with atherosclerotic complications (manifested by coronary artery disease, atherosclerosis of cerebral arteries) and selected cardiovascular risk factors (smoking, LDL and triglyceride concentrations, BP values) on the levels of t-PA, PAI-1, D-dimer, and PLT count. It was found that t-PA Ag and PAI-1 Ag values tended to rise along with a BMI increase in the subgroups of subjects (with normal body mass, overweight, and obesity), but no statistically significant differences were observed. However, two significant positive correlations were reported between t-PA Ag and BMI, as well as between PAI-1 Ag and BMI. Conclusions: Type 2 diabetes in peripheral arterial disease affects the concentration of fibrinogen causing its increase, which is connected with the inflammation and prothrombotic process in the course of both conditions. The concurrence of atherosclerosis of coronary or cerebral arteries, smoking, LDL and TG concentrations, and BP value do not have a significant impact on the levels of analyzed fibrinolysis parameters. A positive correlation between BMI and t-PA Ag and PAI-1 Ag concentrations needs to be supported in further studies on a larger number of overweight and obese patients.

Evaluation of Risk Factors for Major Amputation in Patients With Diabetes and Peripheral Artery Disease Receiving Antiplatelet Therapy - Post Hoc Analysis of a Prospective Observational Multicenter Cohort Study (SEASON)

BACKGROUND

Guidelines for peripheral arterial disease (PAD) recommend long-term antiplatelet therapy in symptomatic patients to reduce cardiovascular morbidity and mortality risk. Although diabetes is a known risk factor for PAD, PAD has been undertreated in these patients. This study aimed to evaluate risk factors for major amputation in patients with diabetes undergoing antiplatelet therapy for PAD.Methods and Results:This retrospective analysis of a 2-year observational cohort study (1,745 clinics in Japan, September 2009-2013) evaluated predictors of amputation in patients with diabetes undergoing antiplatelet therapy for PAD. Among 4,016 eligible patients, 52 had an amputation during follow-up. Amputation risk (Cox regression analysis) was predicted at baseline by history of lower extremity revascularization/amputation (hazard ratio [HR]: 2.92; 95% confidence interval [CI]: 1.39, 6.14), chronic kidney disease (HR: 4.19; 95% CI: 1.95, 8.97), and comorbid cerebrovascular and heart disease (HR: 3.32; 95% CI: 1.19, 9.30), and was unaffected by choice of oral antiplatelet therapy. In patients with PAD and diabetes, amputation event rate was highest for those with ankle-brachial pressure index (ABI) <0.40 and progressively decreased at higher ABI cut-offs.

CONCLUSIONS

These findings inform real-world understanding of PAD in diabetic patients receiving antiplatelet therapy in Japan, and showed that ABI <0.4 was the strongest risk factor for amputation.

Imaging the Proangiogenic Effects of Cardiovascular Drugs in a Diabetic Model of Limb Ischemia

Purpose

Peripheral artery disease (PAD) causes narrowing of arteries in the limbs, leading to tissue ischemia, gangrene, and eventually limb amputation. The presence of diabetes greatly exacerbates the course of PAD, accounting for the majority of lower limb amputations. Therapeutic strategies focussing on macrovascular repair are less effective in diabetic patients where smaller vessels are affected, and proangiogenic therapies offer a viable adjunct to improve vascularisation in these at risk individuals. The purpose of the current study was to assess the proangiogenic effects of drugs routinely used to treat cardiovascular disease in a diabetic murine model of hind limb ischemia longitudinally using multimodal imaging.

Procedures

Diabetic mice underwent surgical intervention to induce hind limb ischemia and were treated with simvastatin, metformin, or a combination orally for 28 days and compared to diabetic and nondiabetic mice. Neovascularisation was assessed using [¹⁸F]FtRGD PET imaging, and macrovascular volume was assessed by quantitative time of flight MRI. At each imaging time point, VEGF expression and capillary vessel density were quantified using immunohistochemical analysis, and functional recovery and disease progression were assessed.

Results

Combined use of simvastatin and metformin significantly increased neovascularisation above levels measured with either treatment alone. Early angiogenic events were accurately assessed using PET [¹⁸F]FtRGD, showing maximal retention in the ischemic hind limb by day 8, which translated to a sustained increase in vascular volume at later time points. Immunohistochemical analysis shows that combined therapy significantly increased VEGF expression and capillary density (CD31⁺) in a similar time course and also slowed disease progression while simultaneously improving functional foot use.

Conclusions

Combined treatment with simvastatin and metformin led to a significant improvement in limb angiogenesis, vascular volume, and sustained functional recovery in a diabetic murine model of HLI. PET imaging with [¹⁸F]FtRGD provides a robust method for early detection of these proangiogenic effects preclinically and may be useful for the assessment of proangiogenic therapies used clinically to treat diabetic PAD patients.

Low molecular-weight fucoidan protects against hindlimb ischemic injury in type 2 diabetic mice through enhancing endothelial nitric oxide synthase phosphorylation

BACKGROUND

Diabetes mellitus (DM) complications are associated with ischemic injury. Angiogenesis is a therapeutic strategy for diabetic foot. The aim of this study was to investigate the possible angiogenic effect of low molecular weight fucoidan (LMWF) in diabetic peripheral arterial disease (PAD).

METHODS

Diabetic db/db mice and age-matched C57BL/6 mice underwent femoral artery ligation followed by LMWF (30, 60, 80 mg/kg per day, p.o.) or cilostazol (30 mg/kg/day, p.o.) treatment for 6 weeks. Endothelium-dependent vasodilation and blood flow of the hindlimb were measured. Histological and western blot analyses of CD34, vascular endothelial growth factor (VEGF), eNOS, and inflammatory factors in the gastrocnemius were performed. The effects of LMWF were confirmed in human umbilical vein endothelial cells (HUVEC).

RESULTS

Diabetic mice with ligation exhibited hindlimb ulceration, hydrosarca, and necrosis, increased expression of inflammatory factors, and decreased levels of VEGF and eNOS phosphorylation. Treatment with LMWF markedly ameliorated foot lesions, suppressed expression of inflammatory factors, and improved plantar perfusion by promoting endothelium-dependent vasodilation and revascularization in diabetic PAD mice. In high-glucose treated HUVEC, LMWF (40 μg/mL) reversed blunted endothelial cell proliferation, migration, and tube formation, and promoted eNOS phosphorylation and VEGF expression, whereas HUVEC pretreatment with 100 μmol/L N^G -nitro-l-arginine methyl ester, an eNOS antagonist, markedly inhibited the effects of LMWF.

CONCLUSION

This study demonstrates that LMWF alleviates hindlimb ischemic damage, at least in part by promoting eNOS phosphorylation, nitric oxide production, and VEGF expression, resulting in enhanced angiogenesis in the ischemic region.

Role of Hyperglycemia-Induced Advanced Glycation End Product (AGE) Accumulation in Atherosclerosis

There is a growing body of evidence that cumulative hyperglycemic exposure plays a central role in the development and progression of atherosclerotic cardiovascular disease in diabetic patients. Monosaccharides, such as glucose, fructose, and glyceraldehyde can react non-enzymatically with amino groups of proteins, lipids, nucleic acids to form senescent macromolecules termed advanced glycation end products (AGEs), whose formation and accumulation has been known to progress in diabetic patients, especially in those with a long history of disease. The sustained accumulation of AGEs could contribute to the phenomenon of metabolic memory or legacy effects observed in long-term follow-up clinical studies of diabetic patients. AGE modification alters the structural integrity and function of various types of macromolecules, and interaction of AGEs with a receptor for AGEs (RAGE) has been shown to evoke inflammatory and thrombotic reactions. Therefore, the AGE–RAGE axis is a novel therapeutic target of atherosclerotic cardiovascular disease in diabetic patients. In this paper, we briefly review the pathological role of AGEs and their receptor RAGE system in atherosclerotic cardiovascular disease, including peripheral artery disease and discuss the clinical utility of measuring AGEs in evaluating the severity of atherosclerosis in patients with diabetes.

A Review of Distribution of Atherosclerosis in the Lower Limb Arteries of Patients With Diabetes Mellitus and Peripheral Vascular Disease

OBJECTIVE

There is a generally accepted hypothesis that patients with diabetes mellitus (DM) have a higher burden of atherosclerotic disease below the knee compared to patients without DM (NDM). The aim of this review was to summarize the evidence regarding this hypothesis.

METHODS

The literature was searched for papers that compared the anatomical distribution of atherosclerotic disease in patients with DM and those without using radiological imaging. Search terms used included "diabetes mellitus," "peripheral vascular disease," "distribution of disease," "angiography," "computed tomography angiography," and "magnetic resonance angiography." Where possible, the number of patients with disease in each arterial segment was extracted and included in a forest plot. A descriptive approach was taken when this was not possible or a scoring system was used.

RESULTS

Fourteen studies were included in the review and it was possible to summarize data from 9 of these in a forest plot. Fifteen different arterial segments were described; however, the most commonly used segments that differentiated between proximal and distal disease were aortoiliac (A-I; DM = 466 patients, NDM = 458), femoropopliteal (F-P; DM = 568, NDM = 585), tibial (DM = 306, NDM = 417). The resulting forest plot showed that those with DM were significantly less likely to have disease in the A-I segment (odds ratio [OR]: 0.25 [0.15-0.42]) and significantly more likely to have disease in the tibial segment (OR 1.94 [1.27-2.96]). In the DM group, there was a trend toward relative sparing in the F-P segment, but this does not reach significance (0.66 [0.33-1.31]).

CONCLUSIONS

These results support the hypothesis that patients with DM are more likely to have atherosclerotic disease in the tibial vessels than NDM. There is however limited information on how individual vessels are affected. Further information on this and a greater understanding of why the distal vessels are more affected are avenues for future research.

Role of Ligands of Receptor for Advanced Glycation End Products (RAGE) in Peripheral Artery Disease

Atherosclerotic cardiovascular disease, including peripheral artery disease (PAD), is more common and severe in diabetic patients compared with nondiabetic individuals. Indeed, diabetes is associated with the increased risk of limb amputation and all-cause mortality in patients with symptomatic PAD. Proteins and lipids are nonenzymatically modified by sugars, resulting in the formation and accumulation of advanced glycation end products (AGEs), whose process is accelerated under diabetic conditions, especially patients with a long duration of diabetes. Accumulating evidence shows that nonenzymatic modification by sugars alters the structural integrity of collagens and lipoproteins in large vessels, thereby being involved in vascular stiffness and atherosclerotic plaque instability. Furthermore, engagement of receptor for AGEs (RAGE) with its ligands, such as AGEs, high mobility group box 1, and S100A proteins evokes inflammatory and thrombotic reactions, thus playing a central role in the development and progression of atherosclerotic cardiovascular disease. In this article, we review the pathophysiological role of RAGE ligands in PAD and discuss the clinical utility of measurement of plasma, serum, or tissue RAGE ligands for assessment of the severity and prognosis of PAD. This review suggests that RAGE ligands may be a novel biomarker and also a therapeutic target of PAD, especially in patients with diabetes.

Prognostic efficacy of circulating asymmetric dimethylarginine in patients with peripheral arterial disease: A meta-analysis of prospective cohort studies

Background Asymmetric dimethylarginine is suggested to be a marker of poor prognosis in patients with atherosclerosis. However, the predictive role of circulating asymmetric dimethylarginine for clinical outcome in patients with peripheral arterial disease has not been determined. Aims To quantitatively assess the predictive value of circulating asymmetric dimethylarginine for clinical outcome in patients with peripheral arterial disease in a meta-analysis of prospective cohort studies. Methods Relevant studies were identified by systematically searching of PubMed and Embase databases. A random-effect model was used to synthesize the results. Sensitivity analyses by omitting one study at a time were performed to evaluate the robustness of the results. Results Six studies with 2535 peripheral arterial disease patients were included. Patients with higher circulating asymmetric dimethylarginine at baseline were associated with higher risk of all-cause mortality (adjusted hazard ratio: 1.63, 95% confidence interval: 1.28-2.06, I² = 16%), and major adverse cardiovascular events (adjusted hazard ratio: 2.01, 95% confidence interval: 1.08-3.73, I² = 78%) as compared with those with lower circulating asymmetric dimethylarginine at baseline. Specifically, every increment of 0.1 µmol/l of asymmetric dimethylarginine was associated with 18% (adjusted hazard ratio: 1.18, 95% confidence interval: 1.06-1.31) increased risk for all-cause mortality and 14% (adjusted hazard ratio: 1.14, 95% confidence interval: 1.04-1.25) increased risk for major adverse cardiovascular disease. Sensitivity analyses by omitting one study at a time did not significantly change the results. Conclusion Higher circulating asymmetric dimethylarginine at baseline may be associated with higher incidence of cardiovascular events and mortality in patients with peripheral arterial disease.

Anemia complicating type 2 diabetes: Prevalence, risk factors and prognosis

AIMS

To determine the prevalence, risk factors and prognosis of anemia in representative community-based patients with type 2 diabetes.

METHODS

Data from the Fremantle Diabetes Study Phase II (FDS2; n=1551, mean age 65.7years, 51.9% males) and Busselton Diabetes Study (BDS; n=186, mean age 70.2years, 50.0% males) cohorts, and from 186 matched BDS participants without diabetes, were analyzed. The prevalence of anemia (hemoglobin ≤130g/L males, ≤120g/L females) was determined in each sample. In FDS2, associates of anemia were assessed using multiple logistic regression and Cox proportional hazards modeling identified predictors of death during 4.3±1.2years post-recruitment.

RESULTS

The prevalence of anemia at baseline was 11.5% in FDS2 participants, 17.8% in BDS type 2 patients and 5.4% in BDS participants without diabetes. In FDS2, 163 of 178 patients with anemia (91.6%) had at least one other risk factor (serum vitamin B₁₂<140pmol/L, serum ferritin <30μg/L and/or transferrin saturation<20%, serum testosterone <10nmol/L (males), glitazone therapy, estimated glomerular filtration rate (eGFR) <60mL/min 1.73m², malignancy, hemoglobinopathy). More anemic than non-anemic FDS2 patients died (28.7% versus 8.0%; P<0.001). After adjustment for other independent predictors (age as time-scale, male sex, Aboriginality, marital status, smoking, eGFR), anemia was associated with a 57% increase in mortality (P=0.015).

CONCLUSIONS

Type 2 diabetes at least doubles the risk of anemia but other mostly modifiable risk factors are usually present. Anemia is associated with an increased risk of death after adjustment for other predictors.

Elevated serum fibroblast growth factor 23 levels as an indicator of lower extremity atherosclerotic disease in Chinese patients with type 2 diabetes mellitus

Background

Recently, basic and clinical studies have provided evidence supporting the relationship between circulating levels of fibroblast growth factor (FGF) 23 and the development of atherosclerosis. Given that diabetes is an established risk factor for lower extremity atherosclerotic disease (LEAD), the goal of the present study was to explore the relationship between serum FGF23 levels and LEAD, as well as the related factors, in Chinese patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 401 hospitalized T2DM patients (201 subjects with LEAD and 200 subjects without LEAD) were enrolled in this study. Serum FGF23 levels were determined by a sandwich enzyme-linked immunosorbent assay. Femoral intima-media thickness (F-IMT) and lower limb atherosclerotic plaque were assessed through color Doppler ultrasound.

Results

The median (interquartile range) serum FGF23 levels in the entire study population was 42.08 (35.59–49.17) pg/mL. Subjects with LEAD had significantly higher serum FGF23 levels compared with those without LEAD (44.00 [37.54–51.30] pg/mL versus 40.42 [32.61–48.23] pg/mL, P < 0.001). Logistic regression showed that serum FGF23 levels were independently and positively correlated with the presence of LEAD (odds ratio 1.039, 95% confidence interval 1.012–1.067, P = 0.004). In addition, multiple liner regression analysis revealed that serum FGF23 levels were positively associated with F-IMT (standardized β = 0.175, P < 0.001). Furthermore, this relationship remained significant after additional adjustment for gender and factors potentially affecting serum FGF23 levels (serum calcium, serum phosphorus, and glomerular filtration rate), respectively (both P < 0.01).

Conclusions

In Chinese patients with T2DM, serum FGF23 levels were independently and positively correlated with the presence of LEAD.