Current concepts and controversies in the pathogenesis, prevention, and treatment of the macrovascular complications of diabetes

Diabetes, subclinical atherosclerosis and multiple cardiovascular risk factors in hard-to-reach asymptomatic patients

AIM

To examine the association of cardiovascular disease risk factors with and their cumulative effect on coronary artery calcium in hard-to-reach asymptomatic patients with diabetes.

METHODS

A total of 2563 community-dwelling asymptomatic subjects from Central Appalachia participated in coronary artery calcium screening at a heart centre. Binary variable was used to indicate that coronary artery calcium was either present or absent. Independent variables consisted of demographic and modifiable risk factors and medical conditions. Descriptive statistics and multinomial logistic regression analyses were conducted.

RESULTS

In total, 55.8% and 13.7% of study participants had subclinical atherosclerosis (coronary artery calcium ⩾1) and diabetes, respectively. The presence of coronary artery calcium was higher in subjects with diabetes (68.5%) than those without (53.8%). Compared to subjects without diabetes with coronary artery calcium = 0, obesity, hypertension, hypercholesterolaemia and smoking increased the odds of the presence of coronary artery calcium (coronary artery calcium score ⩾1) regardless of diabetes status; however, with larger odds ratios in subjects with diabetes. Compared to subjects without diabetes with coronary artery calcium score = 0, having 3, 4 and ⩾5 risk factors increased the odds of presence of coronary artery calcium in subjects with diabetes by 14.06 (confidence interval = 3.26-62.69), 32.30 (confidence interval = 7.41-140.82) and 47.12 (confidence interval = 10.35-214.66) times, respectively.

CONCLUSION

There is a need for awareness about subclinical atherosclerosis in patients with diabetes and more research about coronary artery calcium in subpopulations of patients.

Carotid intima-media thickness: an index for subclinical atherosclerosis in type 1 diabetes

Cardiovascular disease and the development of coronary artery atherosclerosis play a pivotal role in increasing mortality in patients with diabetes. The aim of the present study was to determine the presence of subclinical atherosclerosis (measured as carotid intima-media thickness [cIMT] and to study possible associated risk factors in adolescents with type 1 diabetes. Forty type 1 diabetic subjects, aged 11-30 years, with duration of diabetes 3-25 years and 40 normal healthy controls, were included. Blood pressure (BP) measurement, as well as screening for diabetic complications, was performed. Lipid profile, albumin/creatinine ratio, renal functions and glycosylated hemoglobin (HB A(1)c) were assayed. Carotid intima-media thickness (cIMT) was measured using ultrasound. The mean aggregate cIMT was higher in diabetics than controls (0.6 mm 00 +/- 0.1 vs. 0.4 mm +/- 0.1, p = 0.000). Moreover, it was higher in patients with positive family history of type 2 diabetes than in those with negative family history (mean 0.7 mm +/- 0.1 vs. 0.6 mm +/- 0.1, p = 0.018). cIMT was found to positively correlate with: age in both diabetics and controls (r = 0.76, p = 0.000, r = 0.74, p = 0.000 respectively), body mass index (BMI) in diabetics but not controls (r = 0.82, p = 0.000, r = 0.30, p = 0.06 respectively). In diabetics, mean aggregate cIMT positively correlated with duration of diabetes (r = 0.66, p = 0.000), systolic blood pressure (r = 0.82, p = 0.000), diastolic BP (r = 0.83, p = 0.000), as well as HB A1c (r = 0.40, p = 0.004) and correlated negatively with high density lipoprotein -cholesterol (HDL-C) (r = -0.88, p = 0.000). As cardiovascular morbidity is high in diabetes, non-invasive methods for monitoring vascular changes as cIMT might be useful in clinical practice for early diagnosis of subclinical atherosclerosis, which can allow for strategies designed to reduce the cardiovascular event rate in those patients.

Arterial reconstruction with donor iliac vessels during pancreas transplantation: an intraoperative approach to arterial injury or inadequate flow

BACKGROUND

Outcome of pancreas transplantation (PTX) has improved because of use of novel immunosuppression and advances in surgical technique. It is not uncommon for severe atherosclerosis in patients with type 1 insulin-dependent diabetes mellitus or the presence of a previously transplanted organ to limit the options for vascular anastomosis. Herein we report the novel application of donor iliac arterial interposition grafts for arterial reconstruction in patients with severe iliac artery arteriosclerosis, and/or previous transplant who develop an arterial injury or stenosis during surgery.

METHODS

In five patients undergoing PTX, the external iliac artery was severely atherosclerotic and/or occupied by a previous vascular anastomosis. In four of the five patients, an arterial intimal dissection became apparent. The external iliac artery was excised and reconstructed with donor iliac artery interposition graft (end-to-end anastomosis). Pancreas or kidney was engrafted onto this arterial interposition graft (end-to-side anastomosis).

RESULTS

There was no operative morbidity related to this surgical approach. All grafts functioned well after transplantation. Distal lower extremities have no evidence of vascular insufficiency with mean follow-up of 26 months (7-45 months).

CONCLUSION

This surgical technique is an acceptable option during PTX for the patient with severe iliac artery arteriosclerosis with intraoperative intimal dissection or stenosis, or perhaps those with challenging arterial access.

Vascular protective actions of a nitric oxide aspirin analog in both in vitro and in vivo models of diabetes mellitus

BACKGROUND

Defective endothelium-dependent relaxation is observed in experimental and human diabetes mellitus. The nature of this defect is not fully understood but may involve decreased nitric oxide (NO) bioactivity due to enhanced production of reactive oxygen species (ROS). In this paper, we examine the benefits and actions of a novel NO-donating, antioxidant called 2-acetoxybenzoic acid 2-(2-nitrooxymethyl) phenyl ester, and denoted as NCX4016, on NO-mediated endothelium-dependent relaxation in normal arteries exposed to acute elevations in glucose or in arteries derived from chronic diabetic animals.

MATERIAL AND METHODS

Intrinsic free radical scavenging by NO-NSAIDs in solution were evaluated using electron paramagnetic resonance (EPR) spectroscopy and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). In acute studies, normal rat aortas were exposed in tissue culture for 18 h to 5.5 mM or 40 mM in the presence or absence of NCX4016, a NO-donating NSAID unrelated to aspirin (NCX2216) or aspirin. Vascular reactivity of thoracic aortic rings to endothelium-dependent relaxation to acetylcholine in vitro was determined. For chronic hyperglycemia, diabetes was induced in rats by intravenous injection with streptozotocin. Vascular reactivity of thoracic aortic rings to endothelium-dependent relaxation to acetylcholine in vitro was determined after 8 wks in untreated animals or animals chronically-treated with NCX4016. Antioxidant efficacy in vivo was determined by measurement of plasma isoprostanes and by nuclear binding activity of NF-kappaB in nuclear fractions of aortae.

RESULTS

Incubation with NCX4016 and NCX2216 produced a concentration-dependent inhibition of DMPO-OH formation indicating scavenging of hydroxyl radicals (HO(*)). In contrast, little efficacy to scavenge superoxide anion radicals was noted. Acute incubation of normal arteries with elevated glucose concentration caused inhibition of normal relaxation to acetylcholine. This impairment was prevented by co-incubation with NCX4106 but not by mannitol, the parent compound (aspirin) or by NCX2216. In addition, chronic treatment with NCX4016 prevented the development of defective endothelium-dependent relaxation to acetylcholine. This protection did not occur as a result to any changes in blood glucose concentration or hemoglobin glycation. Treatment with NCX4016 did decrease the elevation in plasma isoprostanes and normalized the diabetes-induced increase in NF-kappaB binding activity in nuclear fractions derived from aortic tissue.

CONCLUSIONS

Collectively, these studies suggest that antioxidant interventions using NO-donating NSAIDs may provide an important novel therapeutic strategy to protect the diabetic endothelium.

Increased prevalence of significant coronary artery calcification in patients with diabetes

OBJECTIVE

Coronary artery disease is the major cause of morbidity and mortality in patients with diabetes. Detection of coronary artery disease before the first myocardial infarction and before anginal symptoms will allow for strategies designed to reduce the cardiovascular event rate in this group of patients. Electron beam-computed tomography (EBCT) is a noninvasive technology for evaluating the extent of coronary artery atherosclerosis that relies on the detection of coronary artery calcium (CAC). We used EBCT to detect significant coronary artery atherosclerosis in diabetic patients without symptoms of heart disease.

RESEARCH DESIGN AND METHODS

We used EBCT to evaluate calcium in the coronary arteries of 139 consecutive diabetic patients scanned over a 20-month period. The CAC scores in this group were compared with a randomly selected nondiabetic control group and a control group that was selected to match a number of established cardiovascular risk factors.

RESULTS

Patients with diabetes had a significant increase in the prevalence of CAC scores > or =400 (25.9%) compared with the randomly selected (7.2%) and matched (14.4%) nondiabetic control groups. Scores in this range have been reported to be highly predictive for abnormal stress myocardial perfusion tomography and subsequent coronary events.

CONCLUSIONS

Our results, therefore, indicate a substantial prevalence of significant coronary artery disease in an asymptomatic diabetic patient population compared with nondiabetic control subjects. They also suggest that EBCT may be a useful approach for selecting a group of diabetic subjects who would benefit most from additional evaluation for subclinical coronary artery disease.

Concentration of leukocyte elastase in plasma and polymorphonuclear neutrophil extracts in type 2 diabetes

The concentration of leukocyte elastase/alpha1-proteinase inhibitor complexes in plasma and polymorphonuclear neutrophil extracts, and plasma trypsin inhibitory capacity were determined in 88 patients with type 2 diabetes and 47 control subjects. Higher values of these variables were found in patients as compared to controls (p < 0.001). The concentration of elastase was higher in obese patients than in lean ones (p < 0.05 for plasma, p < 0.01 for polymorphonuclear leukocytes). Only leukocyte elastase levels were significantly higher in the group with both micro- and macroangiopathy in comparison to the group with microangiopathy (p < 0.01) or macroangiopathy (p < 0.05) alone. Poor short-term glycaemic control was associated with higher elastase concentration in plasma and neutrophils (p < 0.05). The present study demonstrates that measurements of plasma polymorphonuclear neutrophil elastase level can be considered as a marker of development of diabetic angiopathy.