Dyslipoproteinaemia and hyperoxidative stress in the pathogenesis of endothelial dysfunction in non-insulin dependent diabetes mellitus: an hypothesis

Mitochondrial Dysfunction and Cardiovascular Disease: Pathophysiology and Emerging Therapies

Mitochondria ensure the supply of cellular energy through the production of ATP via oxidative phosphorylation. The alteration of this process, called mitochondrial dysfunction, leads to a reduction in ATP and an increase in the production of reactive oxygen species (ROS). Mitochondrial dysfunction can be caused by mitochondrial/nuclear DNA mutations, or it can be secondary to pathological conditions such as cardiovascular disease, aging, and environmental stress. The use of therapies aimed at the prevention/correction of mitochondrial dysfunction, in the context of the specific treatment of cardiovascular diseases, is a topic of growing interest. In this context, the data are conflicting since preclinical studies are numerous, but there are no large randomized studies.

Effects of inverted photoperiods on the blood pressure and carotid artery of spontaneously hypertensive rats and Wistar-Kyoto rats

OBJECTIVE

The objective of this study was to investigate the effects of inverted photoperiods on the blood pressure and carotid arteries in spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats (homologous control group).

METHODS AND RESULTS

This study used two inverted photoperiods [inverted light:dark (ILD)16 : 8 and ILD12 : 12] to create the model. A total of 27 male SHR and 27 male WKY rats were randomly divided into six groups (nine rats per group): SHR (LD12 : 12), SHR (ILD16 : 8), SHR (ILD12 : 12), WKY (LD12 : 12), WKY (ILD16 : 8) and WKY (ILD12 : 12). We recorded the trajectory of the activity rhythm of the rats and performed carotid vascular ultrasound examination, MRI (arterial spin labelling) analysis and carotid biopsy. The results showed that inverted photoperiods increased the blood pressure, carotid intima-media thickness, resistance index and blood flow velocity. In addition, inverted photoperiods led to the development of carotid arterial thrombosis, significantly reduced cerebral blood flow and increased the number of collagen fibres. Moreover, it increased the expression of angiotensin receptor and low-density lipoprotein receptor in the carotid arteries, leading to decreased expression of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase and nitric oxide synthase. Inverted photoperiods induced the formation of atherosclerotic plaque. Multiple results of SHR were worse than those of WKY rats.

CONCLUSION

Taken together, inverted photoperiods can produce a series of adverse consequences on blood pressure and carotid arteries. Hypertension can aggravate the adverse effects of inverted photoperiods.

Bridging the Gap Between Diabetes and Stroke in Search of High Clinical Relevance Therapeutic Targets

Diabetes affects more than 425 million people worldwide, a scale approaching pandemic proportion. Diabetes represents a major risk factor for stroke, and therefore is actively addressed for stroke prevention. However, how diabetes affects stroke severity has not yet been extensively considered, which is surprising given the evident but understudied common mechanistic features of both pathologies. The increase in number of diabetic people, incidence of stroke in the presence of this specific risk factor, and the exacerbation of ischemic brain damage in diabetic conditions (at least in animal models) warrants the need to integrate this comorbidity in preclinical studies of brain ischemia to develop novel therapeutic approaches. Therefore, a better understanding of the commonalties involved in the course of both diseases would offer the promise of discovering novel neuroprotective pathways that would be more appropriated to clinical scenarios. In this article, we will review the relevant mechanisms that have been identified as common traits of both pathologies and that could be, to our knowledge, potential targets in both pathologies.

High-density lipoprotein metabolism and reverse cholesterol transport: strategies for raising HDL cholesterol

A key to effective treatment of cardiovascular disease is to understand the body’s complex lipoprotein transport system. Reverse cholesterol transport (RCT) is the process of cholesterol movement from the extrahepatic tissues back to the liver. Lipoproteins containing apoA-I [high-density lipoprotein (HDL)] are key mediators in RCT, whereas non-high-density lipoproteins (non-HDL, lipoproteins containing apoB) are involved in the lipid delivery pathway. HDL particles are heterogeneous; they differ in proportion of proteins and lipids, size, shape, and charge. HDL heterogeneity is the result of the activity of several factors that assemble and remodel HDL particles in plasma: ATP-binding cassette transporter A1 (ABCA1), lecithin cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), hepatic lipase (HL), phospholipid transfer protein (PLTP), endothelial lipase (EL), and scavenger receptor class B type I (SR-BI). The RCT pathway consists of the following steps: 1. Cholesterol efflux from peripheral tissues to plasma, 2. LCAT-mediated esterification of cholesterol and remodeling of HDL particles, 3. direct pathway of HDL cholesterol delivery to the liver, and 4. indirect pathway of HDL cholesterol delivery to the liver via CETP-mediated transfer There are several established strategies for raising HDL cholesterol in humans, such as lifestyle changes; use of drugs including fibrates, statins, and niacin; and new therapeutic approaches. The therapeutic approaches include CETP inhibition, peroxisome proliferator-activated receptor (PPAR) agonists, synthetic farnesoid X receptor agonists, and gene therapy. Results of clinical trials should be awaited before further clinical management of atherosclerotic cardiovascular disease.

Molecular diagnosis of coenzyme Q10 deficiency: an update

INTRODUCTION

Coenzyme Q₁₀ (CoQ) deficiency syndromes comprise a growing number of genetic disorders. While primary CoQ deficiency syndromes are rare diseases, secondary deficiencies have been related to both genetic and environmental conditions, which are the main causes of biochemical CoQ deficiency. The diagnosis is the essential first step for planning future treatment strategies, as the potential treatability of CoQ deficiency is the most critical issue for the patients. Areas covered: While the quickest and most effective tool to define a CoQ-deficient status is its biochemical determination in biological fluids or tissues, this quantification does not provide a definite diagnosis of a CoQ-deficient status nor insight about the genetic etiology of the disease. The different laboratory tests to check for CoQ deficiency are evaluated in order to choose the best diagnostic pathway for the patient. Expert commentary: New insights are being discovered about the implication of new proteins in the intricate CoQ biosynthetic pathway. These insights reinforce the idea that next generation sequencing diagnostic strategies are the unique alternative in terms of rapid and accurate molecular diagnosis of CoQ deficiency.

Increased serum levels of fetuin B in patients with coronary artery disease

BACKGROUND

Recent evidence indicates a pivotal role for fetuin B, one of the cystatin superfamily of cysteine protease inhibitors, in the pathogenesis of metabolic diseases. This study investigated whether serum fetuin B levels are associated with the presence of coronary artery disease.

METHODS

Serum fetuin B levels were assessed in 87 patients with coronary artery disease (41 with acute coronary syndromes and 46 with stable angina pectoris) and 87 healthy controls using an enzyme-linked immunosorbent assay. The association of serum fetuin B levels with cardiac risk factors was analyzed.

RESULTS

Serum fetuin B levels were significantly higher in patients with coronary artery disease than those in healthy controls (90.7 ± 32.1 vs. 110.0 ± 32.7 μg/ml, P < 0.001), extremely elevated in group with acute coronary syndromes (115.0 ± 35.2 μg/ml). Pearson correlation analysis showed that serum fetuin B levels were positively associated with the levels of total cholesterol (r = 0.276, P < 0.001), low-density lipoprotein cholesterol (r = 0.363, P < 0.001), and fasting blood glucose (r = 0.159, P < 0.05). In addition, multiple logistic regression analyses revealed that fetuin B was independently associated with the presence of coronary artery disease (OR, 1.019; 95% CI, 1.009 to 1.029; P < 0.001) and acute coronary syndromes (OR, 1.017; 95% CI, 1.006 to 1.028; P < 0.01).

CONCLUSIONS

Our data revealed that high fetuin B levels are associated with the presence of coronary artery disease and acute coronary syndromes, and that fetuin B may serve as a potential biomarker for coronary artery disease.

Cilostazol improves endothelial function in acute cerebral ischemia patients: a double-blind placebo controlled trial with flow-mediated dilation technique

Background

In order to evaluate the impact of cilostazol on endothelial function, we compared the changes of flow-mediated dilation (FMD) between aspirin and cilostazol groups in patients with acute cerebral ischemia.

Methods

Patients presenting with acute cerebral ischemic events were randomly assigned into aspirin (n = 40) or cilostazol (n = 40) group in a double-blinded manner. FMD was measured at baseline (T0) and 90 days (T1). We measured L-arginine at baseline (a precursor of biologically active nitric oxides). Serious and non-serious adverse events were described.

Results

Despite no difference in the baseline FMD values (p = 0.363), there was a significant increase of FMD values in cilostazol group (7.9 ± 2.4 to 8.9 ± 2.3%, p = 0.001) and not in aspirin group (8.5 ± 2.6 to 9.3 ± 2.8%, p = 0.108). In the multiple regression analysis performed in cilostazol group, serum L–arginine levels were inversely correlated with FMD at T1 (ß = −0.050, SE: 0.012, p < 0.001) with age, total cholesterol levels, and C-reactive protein as confounders. While T0 FMD values in both aspirin and cilostazol groups did not show any correlation with serum L-arginine levels, the correlation is restored in the cilostazol group at T1 (r = 0.467, p = 0.007), while such is not shown in the aspirin group. There was no difference of serious adverse events between the two groups (p = 0.235). Adverse events were more common in the cilostazol group (35/40 vs. 25/40, p = 0.010), due to frequent headaches (14/40 vs. 3/30, p = 0.003) which was well tolerated.

Conclusion

Cilostazol improved endothelial function in acute cerebral ischemia patients. It also restored an inverse correlation between 3-month FMD and baseline L-arginine levels.

Trial registration

NCT03116269, 04/12/2017, retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s12883-017-0950-y) contains supplementary material, which is available to authorized users.

Review: Endothelial dysfunction and pre-symptomatic atherosclerosis in type 1 diabetes — pathogenesis and identification

The vascular endothelium offers an attractive model for detecting functional abnormalities prior to structural changes in the vasculature. Demonstration of progression from endothelial dysfunction through to atherosclerosis is required. Measurements of forearm bloodflow, biochemical markers and biophysical assessments of the endothelium have been employed as research tools for investigating pre-symptomatic atherosclerosis.

However, studies examining endothelial function in type 1 diabetes have been sparse and conflicting. Differences in methodology and the study populations were potential confounding factors. Augmented vasodilatory prostanoids compensate for reduced nitric oxide bioavailability in determining endothelial function in type 1 diabetes. Hyperglycaemia appears to be the initiating event in type 1 diabetes which promotes a variety of biochemical events which are pathogenic to the endothelium.

Improved understanding of the endothelium may facilitate the development of novel diagnostic tools and interventions targeting the accelerated atherosclerosis associated with type 1 diabetes.

Impaired endothelial function in siblings of patients with diabetic mellitus type 2

Background

Endothelial dysfunction is considered as a risk factor for cardiovascular disease, which is a consistent finding in diabetic mellitus type 2 (DMT2). First-degree relatives of DMT2 patients have a higher risk of developing DMT2 later on the life. We aimed to investigate whether impaired endothelial function exists in siblings of DMT2 patients.

Methods

As endothelial function markers, plasma E-selectin, soluble inter-cellular adhesion molecule-1 (sICAM-1), and endothelin-1 (ET-1) were measured on 27 DMT2 patients (9 m/18f; mean age: 48.48 ± 6.75 years), 28 siblings of DMT2 patients (14 m/14f; mean age: 44.54 ± 7.10 years), and 30 control subjects (18 m/12f; mean age: 44.72± 7.56 years) without any family history of diabetes. All the groups were matched by gender, age, and body mass index (BMI).

Results

Plasma levels of ET-1, sICAM-1, and E-selectin were significantly higher in the DMT2 group compared to the control group (ET-1:0.79 ± 1.63 pg/ml vs. 0.33 ± 0.08 pg/ml; P_CD = 0.049, sICAM-1: 71.15 ± 27.20 ng/ml vs. 34.57 ± 22.56 ng/ml; P_CD = 0.001, E-selectin: 22.45 ± 11.57 ng/ml vs. 16.28 ± 7.50 ng/ml; P_CD =0.026). There was a significant difference in sICAM-1 levels between siblings (62.08 ± 26.37 ng/ml) and controls (P_CS = 0.002), but not between siblings and DMT2 patients (P_SD = 0.411). Moreover, a significant difference was observed in ET-1 levels between siblings (0.75 ± 1.26 pg/ml) and controls (P_CS = 0.031), but not between siblings and DMT2 patients (P_SD = 0.751). There was also a significant difference in E-selectin levels between DMT2 patients and siblings (16.56 ± 8.71 ng/ml; P_SD =0.028); however, the difference in E-selectin levels was not statistically significant between siblings and controls (P_CS = 0.919).

Conclusion

Endothelial function markers in the siblings of DMT2 patients are increased in comparision to the control group Therefore; family history in the DMT2 patients seems to be a risk factor for endothelial function. Furthermore, endothelial dysfunction is available very early in the DMT2 patients, even before overt hyperglycemia ensues (in siblings), and may play a key role in the etiopathology of the vasculopathy associated with DMT2.

Diabetes and cardiovascular disease: Epidemiology, biological mechanisms, treatment recommendations and future research

The incidence of diabetes mellitus (DM) continues to rise and has quickly become one of the most prevalent and costly chronic diseases worldwide. A close link exists between DM and cardiovascular disease (CVD), which is the most prevalent cause of morbidity and mortality in diabetic patients. Cardiovascular (CV) risk factors such as obesity, hypertension and dyslipidemia are common in patients with DM, placing them at increased risk for cardiac events. In addition, many studies have found biological mechanisms associated with DM that independently increase the risk of CVD in diabetic patients. Therefore, targeting CV risk factors in patients with DM is critical to minimize the long-term CV complications of the disease. This paper summarizes the relationship between diabetes and CVD, examines possible mechanisms of disease progression, discusses current treatment recommendations, and outlines future research directions.

Epigallocatechin-3-gallate modulates anti-oxidant defense enzyme expression in murine submandibular and pancreatic exocrine gland cells and human HSG cells

Sjogren's syndrome (SS) and type-1 diabetes are prevalent autoimmune diseases in the USA. We reported previously that epigallocatechin-3-gallate (EGCG) prevented and delayed the onset of autoimmune disease in non-obese diabetic (NOD) mice, a model for both SS and type-1 diabetes. EGCG also normalized the levels of proteins related to DNA repair and anti-oxidant activity in NOD.B10.Sn-H2 mice, a model for primary SS, prior to disease onset. The current study examined the effect of EGCG on the expression of anti-oxidant enzymes in the submandibular salivary gland and the pancreas of NOD mice and cultured human salivary gland acinar cells. NOD mice consuming 0.2% EGCG daily dissolved in water showed higher protein levels of peroxiredoxin 6 (PRDX6), a major anti-oxidant defense protein, and catalase, while the untreated NOD mice exhibited significantly lowered levels of PRDX6. Similarly, pancreas samples from water-fed NOD mice were depleted in PRDX6 and superoxide dismutase, while EGCG-fed mice showed high levels of these anti-oxidant enzymes. In cultured HSG cells EGCG increased PRDX6 levels significantly, and this was inhibited by p38 and JNK inhibitors, suggesting that the EGCG-mediated increase in protective anti-oxidant capacity is regulated in part through mitogen-activated protein kinase pathway signaling. This mechanism may explain the higher levels of PRDX6 found in EGCG-fed NOD mice. These preclinical observations warrant future preclinical and clinical studies to determine whether EGCG or green tea polyphenols could be used in novel preventive and therapeutic approaches against autoimmune diseases and salivary dysfunction involving oxidative stress.

Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment

Type 2 diabetes (T2D) markedly increases the risk of cardiovascular disease. Endothelial dysfunction (ED), an early indicator of diabetic vascular disease, is common in T2D and independently predicts cardiovascular risk. Although the precise pathogenic mechanisms for ED in T2D remain unclear, at inception they probably involve uncoupling of both endothelial nitric oxide synthase activity and mitochondrial oxidative phosphorylation, as well as the activation of vascular nicotinamide adenine dinucleotide phosphate oxidase. The major contributing factors include dyslipoproteinemia, oxidative stress, and inflammation. Therapeutic interventions are designed to target these pathophysiological factors that underlie ED. Therapeutic interventions, including lifestyle changes, antiglycemic agents and lipid-regulating therapies, aim to correct hyperglycemia and atherogenic dyslipidemia and to improve ED. However, high residual cardiovascular risk is seen in both research and clinical practice settings. Well-designed studies of endothelial function in appropriately selected volunteers afford a good opportunity to test new therapeutic interventions, paving the way for clinical trials and utilization in the care of the diabetic patient. However, based on the results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled low-density lipoprotein cholesterol.

Atherogenic dyslipidemia and combination pharmacotherapy in diabetes: recent clinical trials

Patients with type 2 diabetes (T2D) are at a markedly increased risk of cardiovascular disease (CVD). Dyslipidemia is a common risk factor and a strong predictor of CVD in T2D patients. Although statins decrease the incidence of CVD in T2D, residual cardiovascular risk remains high despite the achievement of optimal or near-optimal plasma low-density lipoprotein (LDL) cholesterol concentrations. This may, in part, be due to uncorrected atherogenic dyslipidemia. Hypertriglyceridemia, the driving force behind diabetic dyslipidemia, results from hepatic overproduction and/or delayed clearance of triglyceride-rich lipoproteins. In patients treated with a statin to LDL-cholesterol goals, the addition of ezetimibe, fenofibrate, niacin, or n-3 fatty acid ethyl esters may be required to correct the persistent atherogenic dyslipidemia. Clinical trial evidence describing best practice is limited, but recent data supports the strategy of adding fenofibrate to a statin, and suggests specific benefits in dyslipidemic patients and in the improvement of diabetic retinopathy. However, based on results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled LDL-cholesterol. Further evidence is required to support the role of ezetimibe and n-3 fatty acids in treating residual CVD risk in statin-treated T2D patients.

Atherogenic dyslipidemia and combination pharmacotherapy in diabetes: recent clinical trials

Patients with type 2 diabetes (T2D) are at a markedly increased risk of cardiovascular disease (CVD). Dyslipidemia is a common risk factor and a strong predictor of CVD in T2D patients. Although statins decrease the incidence of CVD in T2D, residual cardiovascular risk remains high despite the achievement of optimal or near-optimal plasma low-density lipoprotein (LDL) cholesterol concentrations. This may, in part, be due to uncorrected atherogenic dyslipidemia. Hypertriglyceridemia, the driving force behind diabetic dyslipidemia, results from hepatic overproduction and/or delayed clearance of triglyceride-rich lipoproteins. In patients treated with a statin to LDL-cholesterol goals, the addition of ezetimibe, fenofibrate, niacin, or n-3 fatty acid ethyl esters may be required to correct the persistent atherogenic dyslipidemia. Clinical trial evidence describing best practice is limited, but recent data supports the strategy of adding fenofibrate to a statin, and suggests specific benefits in dyslipidemic patients and in the improvement of diabetic retinopathy. However, based on results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled LDL-cholesterol. Further evidence is required to support the role of ezetimibe and n-3 fatty acids in treating residual CVD risk in statin-treated T2D patients.

Impact of diabetes on cardiovascular disease: an update

Cardiovascular diseases are the most prevalent cause of morbidity and mortality among patients with type 1 or type 2 diabetes. The proposed mechanisms that can link accelerated atherosclerosis and increased cardiovascular risk in this population are poorly understood. It has been suggested that an association between hyperglycemia and intracellular metabolic changes can result in oxidative stress, low-grade inflammation, and endothelial dysfunction. Recently, epigenetic factors by different types of reactions are known to be responsible for the interaction between genes and environment and for this reason can also account for the association between diabetes and cardiovascular disease. The impact of clinical factors that may coexist with diabetes such as obesity, dyslipidemia, and hypertension are also discussed. Furthermore, evidence that justify screening for subclinical atherosclerosis in asymptomatic patients is controversial and is also matter of this review. The purpose of this paper is to describe the association between poor glycemic control, oxidative stress, markers of insulin resistance, and of low-grade inflammation that have been suggested as putative factors linking diabetes and cardiovascular disease.

Pharmacokinetic comparison of a generic coenzyme Q₁₀ solubilizate and a formulation with soybean phytosterols

Coenzyme Q₁₀ (CoQ₁₀) is essential for all cells, and deficiency has been implicated in cardiovascular disease. Plant phytosterols inhibit cholesterol absorption, and may thereby also reduce cardiovascular risk. This study compared the relative bioavailability of CoQ₁₀ solubilized in low-dose soybean phytosterols (SterolQ₁₀) with a generic CoQ₁₀ solubilizate. In a randomized, cross-over design, 36 healthy males received a single 100 mg dose of CoQ₁₀, as SterolQ₁₀ or generic CoQ₁₀, with a two-week washout between treatments. Plasma CoQ₁₀ was analysed at baseline, and at 2, 4, 6, 8 and 10 h after supplement ingestion. Subjects were then administered either 100 mg/day of generic CoQ₁₀ or SterolQ₁₀ for 4 weeks. Fasting plasma CoQ₁₀ levels were measured at baseline and following supplementation. The two preparations were bioequivalent in regard to the area under the curve (AUC(0-10h) ) and maximum increase in concentration (C(max) ), with geometric mean ratios of 0.89 (CI 0.81-0.98) and 0.88 (CI 0.80-0.96), respectively. Four-weeks of CoQ₁₀ resulted in a comparable twofold increase in CoQ₁₀ levels for both formulations (p < 0.001), which was similar between preparations (p = 0.74). The combined CoQ₁₀ and phytosterol formulation, SterolQ₁₀, showed bioequivalence to the generic CoQ₁₀ following a single CoQ₁₀ dose, and demonstrated comparable bioavailability following multiple dose administration.

The Effects of Ananas comosus L. Leaves on Diabetic-Dyslipidemic Rats Induced by Alloxan and a High-Fat/High-Cholesterol Diet

The aim of this study is to demonstrate the effects of Ananas comosus L. leaves on diabetic-dyslipidemic rats. Hypoglycemic and hypolipidemic activities of the ethanolic extract of Ananas comosus L. leaves (EEACL) were evaluated in normal and alloxan-induced diabetic rats by oral glucose tolerance test and an olive oil load test. Anti-diabetic, anti-hyperlipidemic and anti-oxidative activities of EEACL were also investigated in diabetic-dyslipidemic rats induced by alloxan and a high-fat/high-cholesterol diet. EEACL at the dose of 0.40 g/kg significantly inhibited the increase in blood glucose in diabetic rats in oral glucose tolerance test, but did not cause any hypoglycerimic activity in normal rats. It also significantly inhibited the increase in postprandial triglycerides (TG) levels in both normal and diabetic rats in olive oil load test. After 15 days of treatment of diabetic dyslipidemic rats, EEACL significantly decreased blood glucose (-51.0%, P<0.01), TG (-50.1%, P<0.01), TC (-23.3%, P<0.01), LDL-c (-47.9%, P<0.01) and glycated albumin (-25.4%, P<0.01) levels, significantly increased serum high-density lipoprotein cholesterol levels (66.2%, P<0.01) and prevented lower body weight of diabetes (11.8%, P<0.05), significantly lowered lipid peroxidation productions of blood (-27.8%, P<0.01), brain (-31.6%, P<0.05), liver (-44.5%, P<0.01) and kidneys (-72.2%, P<0.05) compared with those in untreated diabetic dyslipidemic rats. These data suggest that EEACL has anti-diabetic, anti-dyslipidemic and anti-oxidative activities, which may be developed into a new plant medicine for treatment of diabetes and its complications.

High-intensity aerobic training improves endothelium-dependent vasodilation in patients with metabolic syndrome and type 2 diabetes mellitus

BACKGROUND

The aim of this study is to compare the effect of physical exercise program on the endothelial function of patients with metabolic syndrome and type 2 diabetes mellitus.

METHODS

Patients were randomized for high intensity aerobic training (HI: 80% maximum heart rate, n=10), low intensity aerobic training (LI: 55% of maximum heart rate, n=10) and control (n=11). Before and after 6 weeks of training, subjects performed the maximal exercise test and a study of the endothelial function, through a high resolution ultrasound of the brachial artery, which was assessed after reactive hyperemia (endothelium dependent vasodilation) and nitrate administration (endothelium independent vasodilation).

RESULTS

A total of 31 patients with metabolic syndrome and type 2 diabetes mellitus were studied, with mean age of 58±6 years, The percentage diameter difference of the vessel after hyperemia was significantly higher for the high intensity group (HI before 2.52±2.85% and after 31.81±12.21%; LI before 3.23±3.52% and after 20.61±7.76%; controls before 3.56±2.33% and after 2.43±2.14%; p<0.05).

CONCLUSIONS

High intensity aerobic training improved the functional capability and endothelium dependent vasodilator response, but it does not improve the endothelium independent vasodilation in patients with metabolic syndrome and type 2 diabetes mellitus.

Coenzyme Q(10) , endothelial function, and cardiovascular disease

Since the time a precise role of coenzyme Q(10) (CoQ(10) ) in myocardial bioenergetics was established, the involvement of CoQ in the pathophysiology of heart failure was hypothesized. This provided the rationale for numerous clinical trials of CoQ(10) as adjunctive treatment for heart failure. A mild hypotensive effect of CoQ was reported in the early years of clinical use of this compound. We review early human and animal studies on the vascular effects of CoQ. We then focus on endothelial dysfunction in type 2 diabetes and the possible impact on this condition of antioxidants and nutritional supplements, and in particular the therapeutic effects of CoQ. The effect of CoQ(10) on endothelial dysfunction in ischemic heart disease is also reviewed together with recent data highlighting that treatment with CoQ(10) increases extracellular SOD activity.

Gliclazide Attenuates the Intracellular Ca2+Changes InducedIn Vitroby Ischemia in the Retinal Slices of Rats with Streptozotocin-Induced Diabetes

PURPOSE

To investigate the dynamics of the intracellular Ca2+ concentration ([Ca2+]i) during retinal ischemia in rats with streptozotocin (STZ)-induced diabetes and the effect of gliclazide, a sulfonylurea with a potent free-radical scavenging activity on ischemia-induced [Ca2+]i dynamics.

METHODS

Rats with STZ (65 mg/kg) induced diabetes were divided into three groups: the untreated diabetic group, the gliclazide-treated group, and the glibenclamide-treated group. An ischemic condition was imposed in vitro on the retinal slices by perfusion with an oxygen/glucose deprived solution. The [Ca2+]i was measured in individual layers of the rat retinal slices loaded with the Ca2+ indicator fluo-3.

RESULTS

As compared to that in the normal rat retina, both the amplitude and the kinetics of the [Ca2+]i increase were suppressed in the intermediate layers of the retinal slices from the diabetic rats under the ischemic condition. These changes were attenuated by the administration of gliclazide but not by that of glibenclamide.

CONCLUSIONS

Hyperglycemia influences ischemia-induced [Ca2+]i dynamics predominantly in the intermediate layers of the retina, and gliclazide, as compared to glibenclamide without a free radical scavenging activity, potently attenuates the ischemia-induced changes in the calcium dynamics.

Endothelial dysfunction in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease, even in the presence of intensive glycemic control. Substantial clinical and experimental evidence suggest that both diabetes and insulin resistance cause a combination of endothelial dysfunctions, which may diminish the anti-atherogenic role of the vascular endothelium. Both insulin resistance and endothelial dysfunction appear to precede the development of overt hyperglycemia in patients with type 2 diabetes. Therefore, in patients with diabetes or insulin resistance, endothelial dysfunction may be a critical early target for preventing atherosclerosis and cardiovascular disease. Microalbuminuria is now considered to be an atherosclerotic risk factor and predicts future cardiovascular disease risk in diabetic patients, in elderly patients, as well as in the general population. It has been implicated as an independent risk factor for cardiovascular disease and premature cardiovascular mortality for patients with type 1 and type 2 diabetes mellitus, as well as for patients with essential hypertension. A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. The role of chronic hyperglycemia in the development of diabetic microvascular complications and in neuropathy has been clearly established. However, the biochemical or cellular links between elevated blood glucose levels, and the vascular lesions remain incompletely understood. A number of trials have demonstrated that statins therapy as well as angiotensin converting enzyme inhibitors is associated with improvements in endothelial function in diabetes. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes. In the present review we provide the up to date details on this subject.

Postprandial lipemia: an under-recognized atherogenic factor in patients with diabetes mellitus

Atherosclerotic disease is the leading cause of both morbidity and mortality in patients with type 2 diabetes. In these patients, postprandial dyslipidemia include not only quantitative but also qualitative abnormalities of lipoproteins which are potentially atherogenic and seems to be a significant risk factor for cardiovascular disease since there is evidence that it results in endothelial dysfunction and enhanced oxidative stress. The most common pattern of postprandial dyslipidemia in diabetes consists of high concentrations of triglycerides, higher VLDLs production by the liver and a decrease in their clearance, a predominance of small dense LDL particles, and reduced levels of HDL. The cause of this postprandial dyslipidemia in diabetes is complex and involves a variety of factors including hyperinsulinemia, insulin resistance, hyperglycemia and disturbed fatty acid metabolism. Numerous clinical studies have shown that postprandial dyslipidemia is associated with endothelial dysfunction in type 2 diabetes and with alterations in other surrogate markers in the cascade of atherosclerosis. Current published guidelines indicate that in diabetics the primary lipid target is LDL<100 mg/dL (70 mg/dL in very high-risk patients) and the most appropriate class of drugs are statins although the issue of postprandial dyslipidemia has not been specifically addressed so far. Moreover, several other classes of medications (fibrates, niacin and antidiabetic drugs) as well as non-pharmacological interventions (i.e. diet, smoking cessation and exercise) can be used to treat lipid and lipoprotein abnormalities associated with insulin resistance and type 2 diabetes. These type of interventions may be more appropriate to ameliorate postprandial dyslipidemia. However, this remains to be confirmed on clinical grounds.

Therapeutic regulation of endothelial dysfunction in type 2 diabetes mellitus

Endothelial dysfunction is universal in diabetes, being intimately involved with the development of cardiovascular disease. The pathogenesis of endothelial dysfunction in diabetes is complex. It is initially related to the effects of fatty acids and insulin resistance on 'uncoupling' of both endothelial nitric oxide synthase activity and mitochondrial function. Oxidative stress activates protein kinase C (PKC), polyol, hexosamine and nuclear factor kappa B pathways, thereby aggravating endothelial dysfunction. Improvements in endothelial function in the peripheral circulation in diabetes have been demonstrated with monotherapies, including statins, fibrates, angiotensin-converting enzyme (ACE) inhibitors, metformin and fish oils. These observations are supported by large clinical end point trials. Other studies show benefits with certain antioxidants, L-arginine, folate, PKC-inhibitors, peroxisome proliferator activated receptor (PPAR)-alpha and -gamma agonists and phosphodiesterase (PDE-5) inhibitors. However, the benefits of these agents remain to be shown in clinical end point trials. Combination treatments, for example, statins plus ACE inhibitors and statins plus fibrates, have also been demonstrated to have additive benefits on endothelial function in diabetes, but there are no clinical outcome data to date. Measurement of endothelial dysfunction in cardiovascular research can provide fresh opportunities for exploring the mechanism of benefit of new therapeutic regimens and for planning and designing large clinical trials.

The role of hypertriglyceridemia in atherosclerosis

Atherosclerosis is a chronic disease associated with accumulation of lipids in lesions along blood vessels, leading to the occlusion of blood flow. Much of the focus has been on the role of low-density lipoprotein (LDL), and of oxidatively modified LDL, in the initiation and progression of this disease. LDL is in fact a metabolic end-product of the triglyceride-rich lipoproteins (ie, very-low density lipoproteins). Over the years, univariate analyses have implicated triglycerides as a contributor in atherosclerosis. However, depending on the studies, the significance of this relationship is either reduced or nullified when other co-variates are taken into account. This review summarizes more recent data that support the role of triglyceride-rich lipoproteins in the atherosclerotic process, both in the fasted as well as in the postprandial state.

The role of tobacco smoke induced mitochondrial damage in vascular dysfunction and atherosclerosis

The majority of individuals chronically exposed to tobacco smoke will eventually succumb to cardiovascular disease (CVD). However, despite the major cardiovascular health implications of tobacco smoke exposure, concepts of how such exposure specifically results in cardiovascular cell dysfunction that leads to CVD development are still being explored. Moreover, surprisingly little is known about the effects of prenatal and childhood tobacco smoke exposure on adult CVD development. Herein, it is proposed that the mitochondrion is a central target for environmental oxidants, including tobacco smoke. By virtue of its multiple, essential roles in cell function including energy production, oxidant signaling, apoptosis, immune response, and thermogenesis, damage to the mitochondrion will likely play an important role in the development of multiple common forms of human disease, including CVD. Specifically, this review will discuss the potential role of tobacco smoke and environmental oxidant exposure in the induction of mitochondrial damage which is related to CVD development. Furthermore, mechanisms of how mitochondrial damage can initiate and/or contribute to CVD are discussed, as are experimental results that are consistent with the hypothesis that mitochondrial damage and dysfunction will increase CVD susceptibility. Aspects of both adult and developmental (fetal and childhood) exposure to tobacco smoke on mitochondrial damage, function and disease development are also discussed, including the future implications and direction of studies involving the role of the mitochondrion in influencing disease susceptibility mediated by environmental factors.

Effect of treatment with nebivolol on parameters of oxidative stress in type 2 diabetics with mild to moderate hypertension

AIM

The aim of this study was to examine the effect of the cadioselective B(1)-adrenoceptor blocker nebivolol on glycaemic control, lipid profile and markers of oxidative stress in patients with type 2 diabetes over a 6-month period.

METHODS

Twenty-six patients with mild to moderate hypertension (140-160 mmHg systolic, 90-105 mmHg diastolic) confirmed on 24-h blood pressure monitoring, were treated with nebivolol 5 mg daily for 6 months. Total serum cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) subfractions, lipid hydroperoxides (LHPs) and total antioxidant capacity (TAC) were measured before and after 6 months of treatment.

RESULTS

Nebivolol, as expected, reduced mean daytime systolic and diastolic pressures on ambulatory monitoring (149 +/- 9 to 140 +/- 13 mmHg, P = 0.02 and 84 +/- 7 to 77 +/- 9 mmHg, P < 0.001). There were no significant changes in serum cholesterol or triglycerides following treatment but a significant increase in HDL cholesterol was noted (1.12 +/- 0.19 to 1.25 +/- 0.36 mmol/L, P = 0.008). Patients showed a highly significant reduction in TAC from 501 +/- 57 to 422 +/- 29 trolox equivalent (P < 0.001). Baseline LHPs were very high and showed no significant change over the 6-month period (18.7 +/- 7.4 and 18.7 +/- 10.9 micromol/L). The LDL score increased significantly from 1.7 +/- 0.7 to 2.3 +/- 0.7 (P = 0.0002) at 6 months suggesting a change to a more atherogenic lipid profile. Neither weight nor glycaemic control changed during treatment.

CONCLUSION

Nebivolol appears to be lipid neutral and may even have a positive effect on HDL cholesterol. Despite this it may promote the formation of potentially atherogenic LDL subfractions possibly as a result of reduced antioxidant defences. Further studies are needed to clarify the changes observed in parameters of oxidative stress.

The effects of lipid-lowering drug therapy on cardiovascular responsiveness in type 2 diabetic patients

Type 2 diabetes is associated with a high prevalence of dyslipidaemia and a high incidence of cardiovascular disease. Lipid lowering therapy with HMG Co-A reductase inhibitors (statins) reduce the risk of cardiovascular events in type 2 diabetic and non-diabetic patients, effects which are believed to be partly due to improvements in vascular function. The aetiology of abnormal vascular function in type 2 diabetics is likely to be multifactorial and the pattern of vascular dysfunction in type 2 diabetes may differ from that which occurs in non-diabetic patients with dyslipidaemia. Abnormalities in endothelium derived hyperpolarising factor (EDHF) mediated vasodilation in resistance vessels may be more prominent in both type 1 and type 2 diabetes than in non-diabetic patients with endothelial dysfunction. The effects of lipid lowering therapy on vascular responsiveness may differ in type 2 diabetic patients from those found in non-diabetic patients. Statin therapy does not appear to improve responses to endothelial dependent vasodilators in type 2 diabetics, but may alter the ratio between nitric oxide (NO) and EDHF mediated responses. Fibrate therapy improves flow mediated dilation of brachial arteries in type 2 diabetic patients, but only appears to improve endothelium dependant vasodilator responses in resistance vessels when given in conjunction with co-enzyme Q.

Basal production of nitric oxide (NO) and non-NO vasodilators in the forearm microcirculation in Type 2 diabetes: associations with blood pressure and HDL cholesterol

We examined basal forearm microcirculatory blood flow (FBF) using venous occlusive strain-gauge plethysmography in 47 middle-aged men and women [55+/-1 years] with Type 2 diabetes and 15 age-matched healthy individuals [52+/-3 years], all receiving aspirin. Blood flow was also measured following infusion of N(G)-monomethyl-L-arginine into the brachial artery to inhibit basal NO release (FBF+L-NMMA). Acetylcholine (ACh) and sodium nitroprusside (SNP) were administered to assess endothelium-dependent and endothelium-independent functions. Compared with controls, diabetic subjects had significantly lower vasodilatory responses to ACh and SNP (p<0.05 for each). Basal FBF and FBF+L-NMMA were increased in diabetic subjects compared with controls (2.4+/-0.2 ml/100ml/min versus 1.7+/-0.2 ml/100ml/min, p=0.02 and 1.9+/-0.1 ml/100ml/min versus 1.2+0.1 ml/100ml/min, p=0.01, respectively) whereas the change in FBF following L-NMMA was greater in the controls (-27% versus -19%, p=0.05). Amongst the diabetic subjects, pulse pressure and HDL cholesterol were independent predictors of FBF (b=0.04+/-0.01, adjusted r2=0.21 and p=0.001, and b=3.3+/-1.2, adjusted r2=0.12 and p=0.007, respectively) and FBF+L-NMMA (b=0.03+/-0.01, adjusted r2=0.20, p=0.002 and b=2.1+/-0.9, adjusted r2=0.09 and p=0.02, respectively). Diastolic blood pressure predicted the change in FBF with L-NMMA (b=-1.02+/-0.32, adjusted r2=0.20 and p=0.003). Our findings suggest that well controlled T2DM patients have impaired agonist-mediated vasodilatation of the forearm resistance arteries that is associated with impaired basal release of nitric oxide but an increase in the release of non-NO vasodilators. The latter may be a compensatory response to increased arterial stiffness and may be facilitated by an effect of HDL.

Postprandial hypertriglyceridemia and oxidative stress in patients of type 2 diabetes mellitus with macrovascular complications

BACKGROUND

Oxidative stress has been implicated in vascular complications of diabetes mellitus (DM). This study aims to evaluate the relationship between postprandial hypertriglyceridemia (PP-HTG) and oxidative stress in Indian patients of type 2 DM with macrovascular complications.

METHODS

Plasma triglycerides (TG), thiobarbituric acid reactive substances (TBARS), erythrocyte reduced glutathione (GSH) and superoxide dismutase (SOD) were measured in fasting and postprandial (PP) state at 2, 4, 6 and 8 h after a high fat meal challenge in controls (Group I) and patients of type 2 DM without (Group II) and with macrovascular complications (Group III).

RESULTS

Postprandial TGs increased significantly in patients with type 2 DM, which showed an exaggerated response to high fat meal challenge in Group III as compared to Group II. Highest PP-TBARS were also observed in Group III which correlated positively with TG. However, GSH and SOD were lower in both groups of diabetics as compared to controls.

CONCLUSIONS

The magnitude of PP-HTG appears to be the major determinant of oxidative stress in type 2 DM, which along with a compromised antioxidant status may lead to endothelial dysfunction and macrovascular complications.

Effect of ascorbic acid on microcirculation in patients with Type II diabetes: a randomized placebo-controlled cross-over study

Manifestations of vascular disease, including microvascular changes, constitute the major part of the morbidity and mortality in diabetic patients. Oxidative stress has been suggested to play an important role in the vascular dysfunction of diabetic patients. Furthermore, epidemiological observations indicate a beneficial effect of an increased dietary intake of antioxidants. The present study tested the hypothesis that the antioxidant ascorbic acid influences microcirculatory function in patients with Type II diabetes. Patients with Type II diabetes were treated with 1 g of ascorbic acid three times a day for 2 weeks in a randomized placebo-controlled double-blind cross-over design. Microvascular reactivity was assessed by vital capillaroscopy and PRH (post-occlusive reactive hyperaemia). hs-CRP (high-sensitivity C-reactive protein), IL-6 (interleukin-6), IL-1ra (interleukin-1 receptor antagonist) and ox-LDL (oxidized low-density lipoprotein) were analysed. The results showed no significant change in microvascular reactivity assessed after 2 weeks of ascorbic acid treatment. TtP (time to peak) was 12.0+/-3.3 s before and 11.2+/-3.5 s after ascorbic acid (n=17). In comparison, TtP was 11.5+/-2.9 s before and 10.6+/-2.8 s after placebo (not significant). IL-1ra, IL-6, hs-CRP and ox-LDL did not change significantly after ascorbic acid, neither as absolute or relative values. In conclusion, in contrast with some studies reported previously, we could not demonstrate an effect of continuous oral treatment with ascorbic acid on microvascular reactivity assessed at the level of individual capillaries. Furthermore, we found no indication of an effect on inflammatory cytokines or ox-LDL.

Mitochondrial dysfunction in cardiovascular disease

Whereas the pathogenesis of atherosclerosis has been intensively studied and described, the underlying events that initiate cardiovascular disease are not yet fully understood. A substantial number of studies suggest that altered levels of oxidative and nitrosoxidative stress within the cardiovascular environment are essential in the development of cardiovascular disease; however, the impact of such changes on the subcellular or organellar components and their functions that are relevant to cardiovascular disease inception are less understood. In this regard, studies are beginning to show that mitochondria not only appear susceptible to damage mediated by increased oxidative and nitrosoxidative stress, but also play significant roles in the regulation of cardiovascular cell function. In addition, accumulating evidence suggests that a common theme among cardiovascular disease development and cardiovascular disease risk factors is increased mitochondrial damage and dysfunction. This review discusses aspects relating mitochondrial damage and function to cardiovascular disease risk factors and disease development.

Effects of cerivastatin on forearm vascular responses, blood pressure responsiveness and ambulatory blood pressure in type 2 diabetic men

OBJECTIVE

The objective of the study was to investigate the effects of cerivastatin therapy on forearm endothelial dependent acetylcholine (ACH) and independent (nitroprusside) vasodilator responses, blood pressure (BP) responses to intravenous infusions of angiotensin II (AII) and noradrenaline (NA) and on 24-h ambulatory BP recordings in type 2 diabetic men.

DESIGN

Eleven type 2 diabetic men aged 59 +/- 9 years with total cholesterol levels of 5.0 +/- 1.26 mmol/l, triglycerides of 2.23 mmol/l and high-density lipoprotein cholesterol levels of 1.24 mmol/l completed a double-blind, randomized, crossover trial comparing 8 weeks of cerivastatin therapy (800 microg of nocte) with placebo. Forearm vascular resistance (FVR) responses to intrabrachial-arterial infusions of ACH (3-24 microg/min), nitroprusside (2-16 microg/min), the nitric oxide(NO) synthase inhibitor l-nitro-mono-methyl arginine (l-nmma) (8 micromol/min), ACH during l-NMMA infusion and BP responses to intravenous infusions of AII (12.5-50 ng/min) and NA (20-400 ng/min) were measured at the end of each treatment period. Twenty-four-hour ambulatory BP recordings were also performed.

RESULTS

FVR responses to ACH during l-NMMA infusion were significantly (p = 0.026) greater during cerivastatin than during placebo therapy. In contrast, FVR responses to ACH in the absence of NO synthase inhibition did not differ significantly between cerivastatin and placebo therapies (p = 0.81). FVR increased by 31.4 +/- 57.3% in response to l-NMMA infusion during cerivastatin therapy compared with 6.1 +/- 41.2% during placebo therapy (p = 0.20). FVR responses to nitroprusside did not differ between cerivastatin and placebo therapies (p = 0.28), nor did BP responses to AII (systolic BP, p = 0.99; diastolic BP, p = 0.98) or NA (systolic BP, p = 0.21; diastolic BP, p = 0.48). Mean 24-h BP was similar during cerivastatin (123 +/- 10 or 70 +/- 7 mmHg) and placebo therapies (129 +/- 11 or 74 +/- 7 mmHg) (systolic BP, p = 0.26; diastolic BP, p = 0.41).

CONCLUSION

Cerivastatin increases FVR responses to ACH in type 2 diabetic men with mild dyslipidaemia but only following NO synthase inhibition. This may indicate an improvement in endothelium-derived hyperpolarizing factor-mediated responses.

Statin therapy improves brachial artery vasodilator function in patients with Type 1 diabetes and microalbuminuria

AIMS

Type 1 diabetes mellitus patients with microalbuminuria have endothelial dysfunction associated with the degree of albuminuria but not with LDL-cholesterol levels. Lipid-lowering agents such as statins may still be of benefit as they can correct endothelial dysfunction by both lipid and non-lipid mechanisms. We therefore examined the effects of atorvastatin on brachial artery endothelial dysfunction in these patients.

METHODS

In a double-blind, randomized crossover study, 16 Type 1 diabetes mellitus patients with microalbuminuria received 6 weeks of atorvastatin 40 mg/day or placebo, separated by a 4-week washout. Brachial artery, endothelium-dependent, flow-mediated dilatation (FMD) and endothelium-independent, glyceryl trinitrate-mediated dilatation (GTNMD) were measured.

RESULTS

Compared with placebo, atorvastatin produced a significant decrease in apolipoprotein B (34.2%), LDL-cholesterol (44.1%) (all P < 0.001), and oxidized-LDL (35.7%, P = 0.03). There was a non-significant increase in plasma cGMP (P = 0.13) on atorvastatin. FMD and GTNMD increased significantly on atorvastatin (FMD: atorvastatin +1.8 +/- 0.4%; placebo +0.2 +/- 0.4%, P = 0.007); (GTNMD: atorvastatin +1.3 +/- 0.9%; placebo -1.2 +/- 0.6%, P = 0.04). An increase in cGMP was independently correlated with an increase in FMD on atorvastatin (adjusted (R2) 0.41, P = 0.02).

CONCLUSION

Atorvastatin improves endothelium-dependent and independent vasodilator function of the brachial artery in Type 1 diabetes mellitus patients with microalbuminuria. This may relate to pleiotropic effects of statins, in particular reduced oxidative stress and increased availability of nitric oxide.

The equine metabolic syndrome peripheral Cushing's syndrome

Certain management practices tend to promote the development of obesity (metabolic syndrome) in mature horses as they enter their teenage years. These management practices include the provision of starch-rich (high glycemic index) and fat-supplemented rations to healthy horses that are relatively inactive. Some horse breeds and ponies appear to be genetically predisposed to metabolic syndrome. The accretion of intra-abdominal adiposity by equids is associated with the development of insulin insensitivity (hyperinsulinemia), glucose intolerance, dyslipidemia, hypertension, and insidious-onset laminitis. Omental adipocytes are metabolically active, secreting free fatty acids and hormonally active mediators including cortisol, leptin, and resistin that might contribute to persistence and worsening of insulin refractoriness and the obese phenotype. We have hypothesized that obesity-associated laminitis arises as a consequence of vascular changes and a hypercoagulable state, similar to the development of atherosclerosis in human type 2 diabetes. Several molecular mechanisms that might serve to explain the development of insulin insensitivity as a result of excessive adiposity have been incriminated. Little investigation into the relationship between obesity, insulin insensitivity, and laminitis in horses has been reported to date. Insulin sensitivity and glucose tolerance can be improved by dietary restriction and exercise aimed at reversing omental obesity. Management practices that promote the development of obesity are likely initiated during the first 10 years of the horse's life. Veterinarians and horse owners must recognize that mature-onset obesity in adult horses is associated with a risk for development of laminitis. Obesity and insulin insensitivity might be prevented if horse owners can be educated to feed rations with a relatively lower glycemic index to inactive horses. Investigative research pertaining to the development of antiobesity drugs for human patients is continuing. Greater than 30 new pharmaceuticals are in various stages of research. However, it will likely take many years before any of these drugs are shown to be useful and safe in horses. Lifestyle changes in the form of diet and exercise patterns are still the crux of therapy for both human and equine patients.

Mechanisms, Significance and Treatment of Vascular Dysfunction in Type 2 Diabetes Mellitus

Endothelial dysfunction and increased arterial stiffness occur early in the pathogenesis of diabetic vasculopathy. They are both powerful independent predictors of cardiovascular risk. Advances in non-invasive methodologies have led to widespread clinical investigation of these abnormalities in diabetes mellitus, generating a wealth of new knowledge concerning the mechanisms of vascular dysfunction, risk factor associations and potential treatment targets. Endothelial dysfunction primarily reflects decreased availability of nitric oxide (NO), a critical endothelium-derived vasoactive factor with vasodilatory and anti-atherosclerotic properties. Techniques for assessing endothelial dysfunction include ultrasonographic measurement of flow-mediated vasodilatation of the brachial artery and plethysmography measurement of forearm blood flow responses to vasoactive agents. Arterial stiffness may be assessed using pulse wave analysis to generate measures of pulse wave velocity, arterial compliance and wave reflection. The pathogenesis of endothelial dysfunction in type 2 diabetes is multifactorial, with principal contributors being oxidative stress, dyslipidaemia and hyperglycaemia. Elevated blood glucose levels drive production of reactive oxidant species (ROS) via multiple pathways, resulting in uncoupling of mitochondrial oxidative phosphorylation and endothelial NO synthase (eNOS) activity, reducing NO availability and generating further ROS. Hyperglycaemia also contributes to accelerated arterial stiffening by increasing formation of advanced glycation end-products (AGEs), which alter vessel wall structure and function. Diabetic dyslipidaemia is characterised by accumulation of triglyceride-rich lipoproteins, small dense low-density lipoprotein (LDL) particles, reduced high-density lipoprotein (HDL)-cholesterol and increased postprandial free fatty acid flux. These lipid abnormalities contribute to increasing oxidative stress and may directly inhibit eNOS activity. Although lipid-regulating agents such as HMG-CoA reductase inhibitors (statins), fibric acid derivatives (fibrates) and fish oils are used to treat diabetic dyslipidaemia, their impact on vascular function is less clear. Studies in type 2 diabetes have yielded inconsistent results, but this may reflect sampling variation and the potential over-riding influence of oxidative stress, dysglycaemia and insulin resistance on endothelial dysfunction. Results of positive intervention trials suggest that improvement in vascular function is mediated by both lipid and non-lipid mechanisms, including anti-inflammatory, anti-oxidative and direct effects on the arterial wall. Other treatments, such as renin-angiotensin-aldosterone system antagonists, insulin sensitisers and lifestyle-based interventions, have shown beneficial effects on vascular function in type 2 diabetes. Novel approaches, targeting eNOS and AGEs, are under development, as are new lipid-regulating therapies that more effectively lower LDL-cholesterol and raise HDL-cholesterol. Combination therapy may potentially increase therapeutic efficacy and permit use of lower doses, thereby reducing the risk of adverse drug effects and interactions. Concomitant treatments that specifically target oxidative stress may also improve endothelial dysfunction in diabetes. Vascular function studies can be used to explore the therapeutic potential and mechanisms of action of new and established interventions, and provide useful surrogate measures for cardiovascular endpoints in clinical trials.

Coenzyme Q10 and diabetic endotheliopathy: oxidative stress and the 'recoupling hypothesis'

Increased oxidative stress in diabetes mellitus may underlie the development of endothelial cell dysfunction by decreasing the availability of nitric oxide (NO) as well as by activating pro-inflammatory pathways. In the arterial wall, redox imbalance and oxidation of tetrahydrobiopterin (BH4) uncouples endothelial nitric oxide synthase (eNOS). This results in decreased production and increased consumption of NO, and generation of free radicals, such as superoxide and peroxynitrite. In the mitochondria, increased redox potential uncouples oxidative phosphorylation, resulting in inhibition of electron transport and increased transfer of electrons to molecular oxygen to form superoxide and other oxidant radicals. Coenzyme Q10 (CoQ), a potent antioxidant and a critical intermediate of the electron transport chain, may improve endothelial dysfunction by 'recoupling' eNOS and mitochondrial oxidative phosphorylation. CoQ supplementation may also act synergistically with anti-atherogenic agents, such as fibrates and statins, to improve endotheliopathy in diabetes.

Flow mediated dilatation and carotid intimal media thickness in South Indian type 2 diabetic subjects

OBJECTIVE

The aims of this study were to determine: (1). endothelial function in type 2 diabetic subjects with and without diabetic microvascular complications using flow mediated dilatation method (FMD); (2). influence of other variables on FMD; and (3). the correlation between FMD and carotid intimal media thickness (IMT).

RESEARCH, DESIGN AND METHODS

In this cross-sectional study, flow mediated dilatation (FMD) and intimal media thickness (IMT) were determined using high resolution ultrasonography in 20 non-diabetic subjects, in 23 type 2 diabetic subjects without any complications and in 23 type 2 diabetic patients with nephropathy and retinopathy.

RESULTS

Age-adjusted mean (S.D.) FMD value in diabetic subjects (8.9 +/- 5%) was lower (P < 0.0001) when compared with the group of control subjects (18.8 +/- 7.5 %. However, there was no difference in the age-adjusted FMD values between diabetic subjects with and without complications (7.3 +/- 3.3 % versus 10.5 +/- 5.9 %). FMD levels did not vary significantly between sexes in both non-diabetic and diabetic groups. FMD correlated negatively with carotid IMT (r = -0.23, P < 0.05). In multiple linear regression analysis, age adjusted FMD was associated only with type 2 diabetes with complications (P = 0.012). The variance explained was 21.9%.

CONCLUSION

Abnormal FMD and increased carotid IMT were present in type 2 diabetes. Both these parameters negatively correlated with each other supporting an association between impaired FMD and atherogenesis. As these abnormalities existed even in diabetic subjects with no microvascular complications, it is likely that they preceded the development of these complications.

Oxidative Stress and Antioxidant Supplementation in the Management of Diabetic Cardiovascular Disease

The diabetic state confers an increased propensity to accelerated atherogenesis. In addition to the established risk factors, there is evidence for increased oxidative stress in diabetes. Increased oxidative stress is manifested by increased lipid peroxidation, increased F2-isoprostanes, increased nitrotyrosine, and increased DNA damage. Also, in diabetics, there is increased superoxide release. With regard to diabetes, antioxidants such as α-tocopherol, α-lipoate, and ascorbic acid supplementation have been shown to be beneficial. Most importantly, α-tocopherol therapy, especially at high doses, clearly shows a benefit with regard to low-density lipoprotein oxidation, isoprostanes, and monocyte superoxide release. Thus, it appears that, in diabetes, antioxidant therapy could alleviate the increased attendant oxidative stress and emerge as an additional therapeutic modality.

Alterations in high-density lipoprotein metabolism and reverse cholesterol transport in insulin resistance and type 2 diabetes mellitus: role of lipolytic enzymes, lecithin:cholesterol acyltransferase and lipid transfer proteins

Insulin resistance and type 2 diabetes mellitus are generally accompanied by low HDL cholesterol and high plasma triglycerides, which are major cardiovascular risk factors. This review describes abnormalities in HDL metabolism and reverse cholesterol transport, i.e. the transport of cholesterol from peripheral cells back to the liver for metabolism and biliary excretion, in insulin resistance and type 2 diabetes mellitus. Several enzymes including lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyltransferase (LCAT), as well as cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), participate in HDL metabolism and remodelling. Lipoprotein lipase hydrolyses lipoprotein triglycerides, thus providing lipids for HDL formation. Hepatic lipase reduces HDL particle size by hydrolysing its triglycerides and phospholipids. A decreased postheparin plasma LPL/HL ratio is a determinant of low HDL2 cholesterol in insulin resistance. The esterification of free cholesterol by LCAT increases HDL particle size. Plasma cholesterol esterification is unaltered or increased in type 2 diabetes mellitus, probably depending on the extent of triglyceride elevation. Subsequent CETP action results in transfer of cholesteryl esters from HDL towards triglyceride-rich lipoproteins, and is involved in decreasing HDL size. An increased plasma cholesteryl ester transfer is frequently observed in insulin-resistant conditions, and is considered to be a determinant of low HDL cholesterol. Phospholipid transfer protein generates small pre beta-HDL particles that are initial acceptors of cell-derived cholesterol. Its activity in plasma is elevated in insulin resistance and type 2 diabetes mellitus in association with high plasma triglycerides and obesity. In insulin resistance, the ability of plasma to promote cellular cholesterol efflux may be maintained consequent to increases in PLTP activity and pre beta-HDL. However, cellular cholesterol efflux to diabetic plasma is probably impaired. Besides, cellular abnormalities that are in part related to impaired actions of ATP binding cassette transporter 1 and scavenger receptor class B type I are likely to result in diminished cellular cholesterol efflux in the diabetic state. Whether hepatic metabolism of HDL-derived cholesterol and subsequent hepatobiliary transport is altered in insulin resistance and type 2 diabetes mellitus is unknown. Specific CETP inhibitors have been developed that exert major HDL cholesterol-raising effects in humans and retard atherosclerosis in animals. As an increased CETP-mediated cholesteryl ester transfer represents a plausible metabolic intermediate between high triglycerides and low HDL cholesterol, studies are warranted to evaluate the effects of these agents in insulin resistance- and diabetes-associated dyslipidaemia.

Combined effect of coenzyme Q10 and fenofibrate on forearm microcirculatory function in type 2 diabetes

Arteriopathy is the principal complication of type 2 diabetes mellitus. It develops from endothelial dysfunction, which we have hypothesised occurs in diabetes primarily as a consequence of dyslipidaemia and oxidative stress. Fenofibrate and CoQ may improve endothelial function by regulating dyslipidaemia and oxidative stress, respectively. We therefore aimed to assess the independent and combined effects of fenofibrate and coenzyme Q(10) (CoQ) on endothelium-dependent and endothelium-independent vasodilator function of the forearm microcirculation in type 2 diabetes. Eighty dyslipidaemic type 2 diabetics were randomized to receive fenofibrate (200 mg/daily), CoQ (200 mg/daily), fenofibrate plus CoQ (200+200 mg daily), or placebo for 12 weeks. Forearm microcirculatory function was assessed with venous occlusion plethysmography during the infusion of acetylcholine (ACh), bradykinin (BK), sodium nitroprusside (SNP) and N(G)-monomethyl-L-arginine (L-NMMA) into the brachial artery. Blood flow responses were calculated as area under the curve (AUC). Fenofibrate significantly lowered plasma cholesterol, triglyceride and fibrinogen (P<0.001), and elevated HDL-cholesterol and homocysteine (P<0.001). CoQ did not change plasma isoprostanes, but significantly lowered systolic blood pressure and HbA(1c) (P<0.05). Fenofibrate plus CoQ significantly improved (P<0.05) the AUC for ACh, BK and SNP without significantly altering basal responses to L-NMMA. Fenofibrate or CoQ alone did not significantly alter blood flow responses. Improvements in blood flow were independent of changes in plasma lipids, blood pressure, homocysteine and isoprostanes, but were correlated (P=0.013) with HbA(1c). In conclusion, in this factorial trial we found that only the combination of fenofibrate and CoQ markedly improved endothelial and non-endothelial forearm vasodilator function in dyslipidemic type 2 diabetic patients. The favourable vascular effect of this therapeutic combination could be due to increase in the bioactivity of and/or responses to endothelium-derived relaxing factors, including nitric oxide, and this may entail synergistic stimulation of peroxisome proliferator-activated receptors.

Effects of insulin lispro and chronic vitamin C therapy on postprandial lipaemia, oxidative stress and endothelial function in patients with type 2 diabetes mellitus

BACKGROUND

Insulin therapy may influence cardiovascular disease (CVD) and lipid metabolism in type 2 diabetes (T2D). Exaggerated postprandial lipaemia (PPL) is a feature of diabetic dyslipidaemia affecting CVD via enhanced oxidative stress (OS) and endothelial dysfunction. We assessed endothelial function and OS during PPL following insulin and vitamin C. Twenty (17 M) T2D patients were studied (mean Hba1c 8.4%) at baseline, following 6 weeks of insulin lispro (0.2 Iu kg-1) and vitamin C 1-g daily. Eight-h lipid and glucose profiles were measured following a fatty meal. Endothelial function (flow-mediated vasodilatation: FMD) and OS were measured at fasting, 4 h and 8 h.

MATERIALS AND METHODS

Glucose, body mass index, and total and LDL cholesterol remained unchanged. FMD improved. Placebo group: fasting, 1.1 +/- 1.2 to 4.2 +/- 1.1% (P < 0.001); 4-h, 0.3 +/- 1.2 to 3.1 +/- 0.9% (P < 0.01); 8-h, 0.7 +/- 1.1 to 3.76 +/- 1.1% (P < 0.001). Vitamin C group: fasting, 0.9 +/- 1.1 to 6.1 +/- 1.3% (P < 0.001); 4-h, 0.7 +/- 1.5 to 4.9 +/- 2.1% (P < 0.001); 8-h, 0.8 +/- 0.9 to 5.8 +/- 0.6% (P < 0.01). Post-prandial lipaemia was attenuated: TG area-under-curve (mmol L-1 8 h-1), 52.6 +/- 11 to 39.1 +/- 12.5 (placebo group), P < 0.02; and 56.9 +/- 8 to 40.1 +/- 10.3 (vitamin C group), P < 0.02. Oxidative stress was reduced, with greater changes in the vitamin C group.

CONCLUSION

Insulin may thus exert vascular benefits in T2D, by modifying fasting and postprandial lipid metabolism resulting in reduced OS and improved EF. Vitamin C therapy may augment the vascular benefits of insulin in T2D through additional effects on OS and EF.