Carotid intima-media thickness and apolipoprotein B/apolipoprotein A-I ratio in middle-aged patients with Type 2 diabetes

AIMS

To explore the association between carotid intima-media thickness (IMT) and the apolipoprotein B (apoB)/apolipoprotein A-I (apoA-I) ratio compared with conventional lipids in middle-aged patients with Type 2 diabetes.

METHODS

We analysed data from 247 patients with Type 2 diabetes, aged 55-66 years, in the Cardiovascular Risk factors in Patients with Diabetes-a Prospective study in Primary care (CARDIPP-1) study. Primary care nurses measured blood pressure and anthropometric characteristics. Blood samples were taken for laboratory analyses. The carotid IMT was determined by ultrasonography at the University Hospital in Linköping and at the County Hospital Ryhov, Jönköping, Sweden.

RESULTS

The ApoB/apoA-I ratio (r = 0.207, P = 0.001), apoB (r = 0.166, P = 0.009) and non-high-density lipoprotein cholesterol (non-HDL-c) (r = 0.129, P = 0.046) correlated with IMT. Conventional lipids, high-sensitivity C-reactive protein (hsCRP), glycated haemoglobin (HbA(1c)) and systolic blood pressure were not significantly correlated to IMT. A stepwise logistic regression analysis was conducted with IMT as the dependent variable and the apoB/apoA-I ratio, HbA(1c), hsCRP, low-density lipoprotein cholesterol (LDL-c), total cholesterol, non-HDL-c and treatment with statins as independent variables. Following adjustment for age and gender, only the apoB/apoA-I ratio remained significantly associated with IMT (odds ratio 4.3, 95% confidence intervals 1.7-10.8, P = 0.002).

CONCLUSIONS

We conclude that there was a significant association between the apoB/apoA-I ratio and IMT in middle-aged patients with Type 2 diabetes. The association was independent of conventional lipids, hsCRP, glycaemic control and use of statins.

Association between plasma osteoprotegerin concentrations and urinary albumin excretion in Type 2 diabetes

AIMS

Osteoprotegerin (OPG) is a recently identified inhibitor of bone resorption. Recent studies indicate that OPG is also associated with endothelial dysfunction in Type 2 diabetes. The aim was to investigate the relationship between plasma OPG levels and urinary albumin excretion (UAE) in Type 2 diabetic patients.

METHODS

This study included 154 newly diagnosed Type 2 diabetic patients and 46 healthy subjects. Plasma OPG and 24-h UAE were measured. High-resolution ultrasound was used to measure flow-mediated (endothelium-dependent arterial) dilation (FMD).

RESULTS

Compared with the normoalbuminuric subgroup, OPG levels in the microalbuminuric subgroup were significantly higher, and OPG levels in macroalbuminuria subgroup were significantly higher than those in the normoalbuminuria and albuminuria subgroups. Multiple regression analysis showed that only FMD (r = -0.26), C-reactive protein (r = 0.23), fasting blood glucose (r = 0.25), 2-h blood glucose (r = 0.21), HbA(1c) (r = 0.28), UAE (r = 0.27) and retinopathy (r = 0.27) were significant factors associated with OPG. Pearson's correlation analyses showed a positive correlation between OPG and logUAE (r = 0.440) and negative correlations between OPG and FMD (r = -0.284), and between FMD and logUAE (r = -0.602).

CONCLUSIONS

Plasma OPG levels are significantly associated with UAE in Type 2 diabetic patients.

Connective tissue growth factor and cardiac fibrosis

Cardiac fibrosis is a major pathogenic factor in a variety of cardiovascular diseases and refers to an excessive deposition of extracellular matrix components in the heart, which leads to cardiac dysfunction and eventually overt heart failure. Evidence is accumulating for a crucial role of connective tissue growth factor (CTGF) in fibrotic processes in several tissues including the heart. CTGF orchestrates the actions of important local factors evoking cardiac fibrosis. The central role of CTGF as a matricellular protein modulating the fibrotic process in cardiac remodelling makes it a possible biomarker for cardiac fibrosis and a potential candidate for therapeutic intervention to mitigate fibrosis in the heart.

Peritoneal protein losses in diabetic patients starting peritoneal dialysis: is there a relationship with diabetic vascular lesions?

During peritoneal dialysis (PD), a significant amount of protein is lost through the peritoneal membrane, and these losses could influence the patient's nutrition status. It has been reported that peritoneal protein loss (PPL) is greater in diabetic (D) patients than in nondiabetic (ND) patients, but the topic is still controversial, and the factors involved are not totally defined. We studied 23 patients on continuous ambulatory PD (12 with diabetes) who had experienced no episodes of infection during the preceding months. We measured peritoneal transport, PPL, proteinuria, and parameters of inflammation and nutrition. Our study was carried out during the first months of PD (2 - 4 months), which coincided with the first evaluation of peritoneal transport. The PPL was higher in D patients than in ND patients (8.4 +/- 2.2 g vs. 5.7 +/- 1.7 g daily, p < 0.001), as was proteinuria (3.7 +/- 2.7 g vs. 0.9 +/- 0.7 g daily, p = 0.003). In 83% of D patients and 54% of ND patients, peritoneal transport (p = 0.002) was high or high-average. Dialysate-to-plasma creatinine in D patients was 0.77 +/- 0.12 as compared with 0.66 +/- 0.09 in ND patients (p = 0.031). Parameters of nutrition and inflammation were normal in both groups of patients and showed no significant differences, except for serum total protein, which was significantly lower in D patients. Ultrafiltration, Kt/V, and weekly creatinine clearance were similar in both groups. The D patients with a higher PPL had the highest proteinuria values. We conclude that the higher PPL seen in D patients starting PD seems to be related to high membrane transport in these patients. The condition of high transport in D patients could be a result of diabetic microvascular lesions that cause a similar pattern of permeability in the peritoneal and glomerular membranes.

An association between ethnicity and cardiovascular outcomes for people with Type 2 diabetes in New Zealand

AIMS

To investigate the association between ethnicity and risk of first cardiovascular (CV) event for people with Type 2 diabetes in New Zealand.

METHODS

A prospective cohort study using routinely collected data from a national primary health care diabetes annual review programme linked to national hospital admission and mortality data. Ethnicity was recorded as European, Maori, Pacific, Indo-Asian, East-Asian or Other. A Cox proportional hazards model was used to investigate factors associated with first CV event. Data was collected from 48,444 patients with Type 2 diabetes, with first data collected between 1 January 2000 and 20 December 2005, no previous cardiovascular event at entry and with complete measurements. Risk factors included ethnicity, gender, socio-economic status, body mass index, smoking, age at diagnosis, duration of diabetes, systolic blood pressure, serum lipids, glycated haemoglobin and urine albumin : creatinine ratio. The main outcome measures were time to first fatal or non-fatal CV event.

RESULTS

Median follow-up was 2.4 years. Using combined European and Other ethnicities as a reference, hazard ratios for first CV event were 1.30 for Maori (95% confidence interval 1.19-1.41), 1.04 for Pacific (0.95-1.13), 1.06 for Indo-Asian (0.91-1.24) and 0.73 for East-Asian (0.62-0.85) after controlling for all other risk factors.

CONCLUSIONS

Ethnicity was independently associated with time to first CV event in people with Type 2 diabetes. Maori were at 30% higher risk of first CV event and East-Asian 27% lower risk compared with European/Other, with no significant difference in risk for Pacific and Indo-Asian peoples.

Glycated haemoglobin and cardiovascular outcomes in people with Type 2 diabetes: a large prospective cohort study

AIMS

To investigate the association between long-term glycaemic control, measured by glycated haemoglobin (HbA(1c)), and time to first cardiovascular disease (CVD) event for people with Type 2 diabetes in New Zealand.

METHODS

A prospective cohort study including people with Type 2 diabetes but no previous CVD. The primary outcome measure was time to first recorded fatal or non-fatal CVD event (ischaemic heart disease, cerebrovascular accident, transient ischaemic attack or peripheral vascular disease) as identified from linked primary care, hospital and mortality records between January 2000 and December 2005. A Cox proportional hazards model was used to examine the association between HbA(1c) and time to CVD event, adjusting for age at diagnosis, duration of diabetes, gender, ethnicity, socio-economic status, smoking, blood pressure (BP), serum total cholesterol : high-density lipoprotein ratio, body mass index (BMI) and urine albumin : creatinine ratio.

RESULTS

Participants included 48 444 people with Type 2 diabetes. Fifty-one per cent (n = 24 721) were women, median age 60 years. Median duration of diabetes was 3 years, median BMI 31 kg/m(2), median HbA(1c) 7.1% and mean BP was 138/81 mmHg. During the study period (median follow-up 2.4 years), there were 5667 first CVD events (11.7% of cohort). Each 1% increase in HbA(1c) was associated with an increase in hazard ratio (HR) for CVD of 1.08 (95% confidence interval 1.06-1.10, P < 0.001), myocardial infarction [HR 1.08 (1.04, 1.11)] and stroke [HR 1.09 (1.04, 1.13)].

CONCLUSION

This study has confirmed in a large prospective cohort that increased HbA(1c) is an independent risk factor for cardiovascular disease after controlling for traditional risk factors.

Inflammation and immunity in diabetic vascular complications

PURPOSE OF REVIEW

Diabetes is associated with an increased risk for cardiovascular disease. The purpose of this review is to discuss possible mechanisms through which diabetes can contribute to a more aggressive atherosclerotic disease process with a particular focus on the role of innate and adaptive immunity.

RECENT FINDINGS

The observation that adaptive immune responses to oxidized LDL modulate atherosclerotic plaque development has led to development of pilot vaccines that inhibit atherosclerosis in experimental animals. Recent studies have shown that similar immune responses operate against self-antigens modified by glycation in diabetes. Diabetes has also been shown to activate proinflammatory innate immune receptors and intracellular oxidative stress.

SUMMARY

There are many similarities between the autoimmune responses against oxidized LDL and proteins modified by glycation. The role of autoimmune responses against modified self-antigens in the development of diabetic vascular complications represents a relatively unexplored concept that potentially could provide significant new mechanistic insight into the underlying disease process and identify novel targets for intervention.

Neutrophil surface expression of CD11b and CD62L in diabetic microangiopathy

The aims of the study are (1) assessment of cell surface expression of adhesion molecules CD11b and CD62L on peripheral blood neutrophils in patients with type 2 diabetes and microangiopathy; (2) analysis of serum levels of soluble adhesion molecules: E-selectin (sE-selectin), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1) and von Willebrand factor (vWF) and; (3) evaluation of systemic inflammatory markers like interleukin-6 (IL-6), soluble interleukin-6 receptor (IL-6Rs), high sensitivity C-reactive protein (hsCRP) and fibrinogen. Thirty patients with type 2 diabetes and microangiopathy were enrolled in the study. The study group was compared to 22 patients with type 2 diabetes without microangiopathic compliations. The control group included 20 healthy volunteers. Flow cytometry was used to analyse surface expression of adhesion molecules. Both inflammatory markers and soluble adhesion molecules were determined by immunoenzymatic assay. A significant increase in neutrophil surface CD11b expression (P < 0.01) as well as decrease in surface CD62L expression (P < 0.01) were observed in the group with diabetic microangiopathy in comparison with diabetic group without microangiopathic complications and healthy controls. Moreover, significantly higher concentrations of sICAM-1 (P < 0.05), sVCAM-1 (P < 0.05), sE-selectin (P < 0.05), vWF (P < 0.01), hsCRP (P < 0.01), IL-6 (P < 0.01) and fibrinogen (P < 0.001) were also found in patients with microangiopathy in comparison with the control group. IL-6Rs concentrations did not significantly vary between groups. We concluded (1) diabetic microangiopathy is accompanied by increase in CD11b expression and decrease in CD62L expression on peripheral blood neutrophils; (2) in diabetic microangiopathy rise in CD11b expression indicates neutrophil activation and intensified adhesion; (3) the development of diabetic microangiopathy is accompanied by an increase in soluble adhesion molecules and inflammatory markers concentrations in the blood.

Carbon monoxide and nitric oxide mediate cytoskeletal reorganization in microvascular cells via vasodilator-stimulated phosphoprotein phosphorylation: evidence for blunted responsiveness in diabetes

OBJECTIVE

We examined the effect of the vasoactive agents carbon monoxide (CO) and nitric oxide (NO) : n the phosphorylation and intracellular redistribution of vasodilator-stimulated phosphoprotein (VASP), a critical actin motor protein required for cell migration that also controls vasodilation and platelet aggregation.

RESEARCH DESIGN AND METHODS

We examined the effect of donor-released CO and NO in endothelial progenitor cells (EPCs) and platelets from nondiabetic and diabetic subjects and in human microvascular endothelial cells (HMECs) cultured under low (5.5 mmol/l) or high (25 mmol/l) glucose conditions. VASP phosphorylation was evaluated using phosphorylation site-specific antibodies.

RESULTS

In control platelets, CO selectively promotes phosphorylation at VASP Ser-157, whereas NO promotes phosphorylation primarily at Ser-157 and also at Ser-239, with maximal responses at 1 min with both agents on Ser-157 and at 15 min on Ser-239 with NO treatment. In diabetic platelets, neither agent resulted in VASP phosphorylation. In nondiabetic EPCs, NO and CO increased phosphorylation at Ser-239 and Ser-157, respectively, but this response was markedly reduced in diabetic EPCs. In endothelial cells cultured under low glucose conditions, both CO and NO induced phosphorylation at Ser-157 and Ser-239; however, this response was completely lost when cells were cultured under high glucose conditions. In control EPCs and in HMECs exposed to low glucose, VASP was redistributed to filopodia-like structures following CO or NO exposure; however, redistribution was dramatically attenuated under high glucose conditions.

CONCLUSIONS

Vasoactive gases CO and NO promote cytoskeletal changes through site- and cell type-specific VASP phosphorylation, and in diabetes, blunted responses to these agents may lead to reduced vascular repair and tissue perfusion.

PPAR-alpha: therapeutic role in diabetes-related cardiovascular disease

Among individuals with diabetes mellitus, cardiovascular disease remains the leading cause of death, despite the many treatment modalities that have been developed over time. The PPAR family, including PPAR-alpha, play important roles in glucose and lipid metabolism and atherosclerosis and thus are potential therapeutic targets. Fibrates act upon PPAR-alpha and appear to target the typical dyslipidaemia of diabetes. Several large prospective clinical trials have shown both primary prevention and secondary prevention benefit with fibrates, although they only had small subgroups of patients with diabetes. The first large outcome study to exclusively study those with diabetes was the FIELD study, which showed no reduction in the primary cardiovascular end-point and only some benefit in the secondary end-point. There are many potential explanations for these results; however, it would appear that at present, there is no role for fibrates as monotherapy for the reduction of cardiovascular risk among those with diabetes. However, their potential role in combination with statin therapy remains to be further elucidated with ongoing studies.

[The mechanisms responsible for the development of diabetic nephroangiopathy]

Metabolic, hemodynamic, blood rheological, hormonal, immune, age- and other related mechanisms are involved in the development of nephroangiopathy in types 1 and 2 diabetes mellitus. The initial increase in glomerular filtration rapidly gives way to progressive sclerosis and hyalinosis of glomeruli and afferent and efferent arterioles. These changes can be arrested only in early stages of diabetic nephroangiopathy.

Association of glycosylated haemoglobin level and diabetes mellitus duration with the severity of coronary artery disease

Diabetes mellitus (DM) is known to cause microvascular and possibly macrovascular complications. This study was performed to find the association between glycosylated haemoglobin (HbA1C) level and the severity of coronary artery disease. One hundred and ten consecutive patients admitted to hospital with acute myocardial infarction were studied. Seventy-eight patients (70.9%) had DM, 73 (93.58%) had HbA1C > 7%, 52 (47.3%) were hypertensive, 19 (17.3%) had a history of smoking and 37 (33.6%) had raised cholesterol. Coronary angiography was carried out in 87 (79.1%) patients and the severity of disease was assessed using the Gensini score. The mean Gensini score was 53.36+/-36.94 and the mean HbA1C was 8.4+/-2.39%. There was a significant association between Gensini score and DM (p=0.003) and between Gensini score and hypertension (p=0.018). HbA1C (r=0.427, p=0.001) and duration of DM (r=0.362, p=0.004) had a positive linear correlation with the Gensini score. Multiple regression analysis showed HbA1C to be an independent factor that influenced the Gensini score (p=0.021).

Metabolic phenotypes, vascular complications, and premature deaths in a population of 4,197 patients with type 1 diabetes

OBJECTIVE

Poor glycemic control, elevated triglycerides, and albuminuria are associated with vascular complications in diabetes. However, few studies have investigated combined associations between metabolic markers, diabetic kidney disease, retinopathy, hypertension, obesity, and mortality. Here, the goal was to reveal previously undetected association patterns between clinical diagnoses and biochemistry in the FinnDiane dataset.

RESEARCH DESIGN AND METHODS

At baseline, clinical records, serum, and 24-h urine samples of 2,173 men and 2,024 women with type 1 diabetes were collected. The data were analyzed by the self-organizing map, which is an unsupervised pattern recognition algorithm that produces a two-dimensional layout of the patients based on their multivariate biochemical profiles. At follow-up, the results were compared against all-cause mortality during 6.5 years (295 deaths).

RESULTS

The highest mortality was associated with advanced kidney disease. Other risk factors included 1) a profile of insulin resistance, abdominal obesity, high cholesterol, triglycerides, and low HDL(2) cholesterol, and 2) high adiponectin and high LDL cholesterol for older patients. The highest population-adjusted risk of death was 10.1-fold (95% CI 7.3-13.1) for men and 10.7-fold (7.9-13.7) for women. Nonsignificant risk was observed for a profile with good glycemic control and high HDL(2) cholesterol and for a low cholesterol profile with a short diabetes duration.

CONCLUSIONS

The self-organizing map analysis enabled detailed risk estimates, described the associations between known risk factors and complications, and uncovered statistical patterns difficult to detect by classical methods. The results also suggest that diabetes per se, without an adverse metabolic phenotype, does not contribute to increased mortality.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a relevant target for diabetic vasculopathy?

Mechanisms through which major risk factors accelerate diabetic angiopathy include low density lipoprotein (LDL) oxidation and advanced glycation end products (AGEs) formation. Lectin-like oxidized LDL receptor (LOX-1) is a newly identified vascular receptor for oxidized LDL (oxLDL) and AGEs. LOX-1 is up-regulated in vascular endothelium of diabetic animals and thus may be relevant to the development and progression of human diabetic vasculopathy. The mechanisms responsible for LOX-1 induction in diabetes remain unclear but appear to involve metabolic and inflammatory stimuli relevant to diabetes. Such factors may impact on LOX-1-mediated pro-atherogenic events, including endothelial dysfunction and plaque destabilization. Previous studies have shown that drugs commonly used in the treatment of type 2 diabetic patients, including statins and antidiabetic agents, inhibit endothelial LOX-1 expression. This review summarizes recent advances related to the role of LOX-1 in macrovascular diseases, its regulation by some derangements commonly found in diabetic patients and its modulation by vasculoprotective drugs.

Glycation of paraoxonase-1 inhibits its activity and impairs the ability of high-density lipoprotein to metabolize membrane lipid hydroperoxides

AIMS

High-density lipoprotein (HDL) protects against atherosclerosis development. Defective functioning of HDL in Type 2 diabetes may be one cause of increased cardiovascular disease associated with Type 2 diabetes. HDL modulates low-density lipoprotein and cell membrane oxidation through the action of paraoxonase-1 (PON1), which is one of the major mechanisms by which HDL is anti-atherogenic.

METHODS

We have compared the ability of HDL from Type 2 diabetic patients without coronary heart disease (CHD) (n = 36) to metabolize membrane lipid hydroperoxides with HDL from healthy control subjects (n = 19) and people with CHD but no diabetes (n = 37).

RESULTS

HDL from subjects with Type 2 diabetes and CHD metabolized 20% less membrane hydroperoxides than HDL from control subjects (P < 0.05). The PON1-192RR was least efficient in all the study groups. PON1 was glycated in vivo: (7.5% control, 12% CHD, 17% Type 2 diabetes P < 0.01) with QQ isoforms most glycated. In vitro glycation of PON1 reduced its ability to metabolize membrane hydroperoxides by 50% (P < 0.001); however, glyoxidation reduced it by 80% (P < 0.001). In the control group only there was a significant negative correlation between PON1 activity and the ability of HDL to metabolize membrane hydroperoxides (r = -0.911, P < 0.001).

CONCLUSIONS

HDL from Type 2 diabetic patients without CHD has decreased ability to metabolize membrane lipid hydroperoxides, which could lead to increased susceptibility to cardiovascular disease.

Adiponectin gene and cardiovascular risk in type 2 diabetic patients: a review of evidences

Diabetic patients have a 3-fold higher risk of developing atherosclerosis and its clinical complications as compared to non-diabetic individuals. Part of the cardiovascular risk associated with diabetes is probably due to genetic determinants influencing both glucose homeostasis and the development of atherosclerosis. However, type 2 diabetes frequently coexists with other cardiovascular risk factors like arterial hypertension, central obesity and dyslipidemia. Genetic variability affecting many areas such as lipid and energy metabolisms, hypertension and haemodynamic mechanisms, blood clotting homeostasis, inflammation, and matrix turnover in the vascular wall will have an impact on the development of macrovascular complications in diabetic patients. Adiponectin is abundantly secreted by adipocytes. It plays important roles in lipid and glucose metabolisms and has direct anti-inflammatory and anti-atherogenic effects. In this review, we summarize recent data from the literature suggesting an implication of allelic variations of the adiponectin gene (ADIPOQ) in the genetic determinants of cardiovascular disease in diabetic subjects.

Exercise restores endothelial function independently of weight loss or hyperglycaemic status in db/db mice

AIMS/HYPOTHESIS

Exercise ameliorates oxidative stress-mediated diabetic vascular endothelial dysfunction through poorly defined mechanisms. We hypothesised that, in addition to improving metabolic parameters, upregulation of antioxidants such as superoxide dismutase (SOD) mediates exercise-induced reductions of oxidative stress and increased nitric oxide (NO) bioavailability, and also restores vasodilatation.

METHODS

Type 2 diabetic db/db and normoglycaemic wild-type mice were exercised at moderate intensity for 1 h a day for 7 weeks, leading to a 10% body weight loss. Sedentary animals or those undergoing a low-intensity exercise regimen causing non-significant weight loss were also used. We examined aortic endothelial cell function, NO bioavailability and various biomarkers of oxidative stress.

RESULTS

Moderate-intensity exercise lowered body weight, increased mitochondrial manganese SOD (MnSOD) and both total and phosphorylated (Ser1177) endothelial nitric oxide synthase (eNOS) protein production; it also reduced whole-body (plasma 8-isoprostane) and tissue oxidative stress (nitrotyrosine immunostaining or protein carbonyl levels in the aorta). Low-intensity exercise did not alter body weight; however, it upregulated cytosolic Cu/Zn-SOD instead of MnSOD, and still demonstrated all the above benefits in the db/db aorta. Importantly, both exercise protocols improved endothelial-dependent vasodilatation and NO bioavailability without altering hyperglycaemic status in db/db mice.

CONCLUSIONS/INTERPRETATION

Exercise reverses diabetic vascular endothelial dysfunction independently of improvements in body weight or hyperglycaemia. Our data suggest that upregulation of eNOS and specific SOD isoforms could play important roles in improving NO bioavailability, as well as in reversing endothelial dysfunction in type 2 diabetes patients through lifestyle modifications in the management of diabetes.

Elevated epidermal growth factor receptor phosphorylation induces resistance artery dysfunction in diabetic db/db mice

OBJECTIVE

We previously showed epidermal growth factor receptor (EGFR) transactivation to be key mechanism in the regulation of resistance artery myogenic tone. Type 2 diabetes is associated with microvascular complications. We hypothesized that elevated EGFR phosphorylation contributes to resistance artery dysfunction in type 2 diabetes.

RESEARCH DESIGN AND METHODS AND RESULTS

Diabetic db/db and nondiabetic (control) mice were treated with EGFR inhibitor (AG1478; 10 mg x kg(-1) x day(-1)) for 2 weeks. Isolated coronary artery and mesenteric resistance artery (MRA) were mounted in an arteriograph. Pressure-induced myogenic tone was increased in MRA and coronary artery from diabetic mice and normalized by AG1478. Phenylephrine-induced contraction and nitric oxide donor-induced relaxation were similar in all groups. Endothelium-dependent relaxation in response to shear stress and acetylcholine of MRA and coronary artery from diabetic mice was altered and associated with reduced endothelial nitric oxide synthase (eNOS) expression and phosphorylation. Treated diabetic mice with AG1478 improved coronary artery and MRA endothelial function and restored eNOS expression. Immunostaining and Western blot analysis showed increased endothelial and smooth muscle cell EGFR phosphorylation of MRA and coronary artery from diabetic mouse, which was reduced by AG1478. Primary cultured endothelial cells from resistance arteries treated with high glucose for 48 h showed an increase of EGFR phosphorylation associated with eNOS expression and phosphorylation decrease in response to calcium ionophore. Pretreatment of endothelial cells with AG1478 prevented the effect of high glucose.

CONCLUSIONS

This study provides evidence of the role of elevated EGFR phosphorylation in coronary artery and MRA dysfunction in diabetic db/db mice. Therefore, EGFR should be a potential target for overcoming diabetic small artery complications.

Assessment of oxidative stress and endothelial dysfunction in Asian Indians with type 2 diabetes mellitus with and without macroangiopathy

BACKGROUND

Enhanced oxidative stress coupled with increased expression of adhesion molecules (e.g. VCAM-1, ICAM-1) and decreased nitric oxide (NO) levels are implicated in development of atheromatous vascular lesion in diabetes. The present study addresses the correlation between oxidative stress, vascular cell adhesion molecules-1 (VCAM-1), NO end products and macroangiopathic complications in type 2 diabetes mellitus (DM).

DESIGN AND METHODS

The study population consisted of three groups (i) diabetic patients with macroangiopathy (Group I); (ii) diabetic patients without macroangiopathy (Group II) and (iii) healthy controls (Group III) (n = 30, each group).

RESULTS

Serum malondialdehyde(MDA) concentration was significantly higher in diabetic patients as compared to controls. Group I had significantly higher malondialdehyde level as compared to Group II (P < 0.05) (5.12 +/- 1.83 micromol/l vs. 4.22 +/- 1.03 micromol/l), suggesting higher oxidative stress in patients with macroangiopathy. Significant reduction in NO end products was observed in diabetic patients compared to controls. Levels of serum NO end products levels were further reduced in patients with macroangiopathy compared to those without macroangiopathy. Group I (971.67 +/- 230.13 ng/ml) and Group II (823.55 +/- 197.74 ng/ml) had significantly higher level of sVCAM-1 compared to healthy controls (541.14 +/- 118.25 ng/ml) (P < 0.001). Also, patients with macroangiopathy had significantly higher levels of sVCAM-1 compared to those without macroangiopathy (P < 0.05). Multiple regression analysis indicated that post-prandial blood glucose, GSH and MDA were independent predictors of sVCAM-1 level (R = 0.690, P = 0.000).

CONCLUSION

It can be concluded from the present study that an enhanced oxidative stress coupled with endothelial dysfunction as indicated by reduced activity of NO pathway and enhanced expression of sVCAM-1 play an important intermediary role in the pathogenesis of macrovascular complications in type 2 DM.

Reduced expression of ATP-binding cassette transporter G1 increases cholesterol accumulation in macrophages of patients with type 2 diabetes mellitus

BACKGROUND

Patients with type 2 diabetes mellitus are at increased risk for the development of atherosclerosis. A pivotal event in the development of atherosclerosis is macrophage foam cell formation. The ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 regulate macrophage cholesterol efflux and hence play a vital role in macrophage foam cell formation. We have previously found that chronic elevated glucose reduces ABCG1 expression. In the present study, we examined whether patients with type 2 diabetes mellitus had decreased ABCG1 and/or ABCA1, impaired cholesterol efflux, and increased macrophage foam cell formation.

METHODS AND RESULTS

Blood was collected from patients with and without type 2 diabetes mellitus. Peripheral blood monocytes were differentiated into macrophages, and cholesterol efflux assays, immunoblots, histological analysis, and intracellular cholesteryl ester measurements were performed. Macrophages from patients with type 2 diabetes mellitus had a 30% reduction in cholesterol efflux with a corresponding 60% increase in cholesterol accumulation relative to control subjects. ABCG1 was present in macrophages from control subjects but was undetectable in macrophages from patients with type 2 diabetes mellitus. In contrast, ABCA1 expression in macrophages was similar in both control subjects and patients with type 2 diabetes mellitus. Macrophage expression of ABCG1 in both patients and control subjects was induced by treatment with the liver X receptor agonist TO-901317. Upregulation of liver X receptor dramatically reduced foam cell formation in macrophages from patients with type 2 diabetes mellitus.

CONCLUSIONS

ABCG1 expression and cholesterol efflux are reduced in patients with type 2 diabetes mellitus. This impaired ABCG1-mediated cholesterol efflux significantly correlates with increased intracellular cholesterol accumulation. Strategies to upregulate ABCG1 expression and function in type 2 diabetes mellitus could have therapeutic potential for limiting the accelerated vascular disease observed in patients with type 2 diabetes mellitus.