Close relationship of abnormal glucose tolerance with endothelial dysfunction in hypertension

The Effect of Acute Hyperglycaemia Induced by Oral Glucose Load on Heart Rate Variability and Skin Microvascular Reactivity in Young Adults

We aimed to elucidate the effects of acute hyperglycaemia, induced by an oral glucose tolerance test (OGTT), on the autonomic nervous system (ANS) and skin microvascular reactivity at the time point of peak plasma glucose concentration (cglc) in 20 young, healthy participants. We assessed their heart rate variability (HRV) as a measure of the ANS activity and the parameters of post-occlusive reactive hyperaemia (PORH) to estimate skin microvascular reactivity as measured by laser Doppler (LD) fluxmetry. The tests were repeated 30 min after a standard OGTT (75 g glucose dissolved in 250 mL water) and, in a separate control experiment, after drinking the same amount of water. Participants had their cglc and serum insulin measured at three consecutive time-points according to the testing protocol. The low-frequency (LF) spectral power, the LF to high-frequency (LF/HF) ratio, and the diastolic blood pressure increased significantly more after water than after OGTT, and there was a trend of the peak LD flux of PORH decreasing more after OGTT than after water. Significant correlations between some PORH and all the HRV parameters and cglc increase after OGTT were found, implying diminished vascular reactivity evoked by hyperglycaemia in healthy subjects with lower glucose tolerance.

Effect of vinyl chloride exposure on cardiometabolic toxicity

Vinyl chloride (VC) is an organochlorine mainly used to manufacture its polymer polyvinyl chloride, which is extensively used in the manufacturing of consumer products. Recent studies suggest that chronic low dose VC exposure affects glucose homeostasis in high fat diet-fed mice. Our data suggest that even in the absence of high fat diet, exposure to VC (0.8 ppm, 6 h/day, 5 day/week, for 12 weeks) induces glucose intolerance (1.0 g/kg, i.p.) in male C57BL/6 mice. This was accompanied with the depletion of hepatic glutathione and a modest increase in lung interstitial macrophages. VC exposure did not affect the levels of circulating immune cells, endothelial progenitor cells, platelet-immune cell aggregates, and cytokines and chemokines. The acute challenge of VC-exposed mice with LPS did not affect lung immune cell composition or plasma IL-6. To examine the effect of VC exposure on vascular inflammation and atherosclerosis, LDL receptor-KO mice on C57BL/6 background maintained on western diet were exposed to VC for 12 weeks (0.8 ppm, 6 h/day, 5 day/week). Unlike the WT C57BL/6 mice, VC exposure did not affect glucose tolerance in the LDL receptor-KO mice. Plasma cytokines, lesion area in the aortic valve, and markers of lesional inflammation in VC-exposed LDL receptor-KO mice were comparable with the air-exposed controls. Collectively, despite impaired glucose tolerance and modest pulmonary inflammation, chronic low dose VC exposure does not affect surrogate markers of cardiovascular injury, LPS-induced acute inflammation in C57BL/6 mice, and chronic inflammation and atherosclerosis in the LDL receptor-KO mice.

Evaluation of antihypertensive potential of Ficus carica fruit

CONTEXT

Ficus carica L. (Moraceae) fruit is said to possess cardiovascular activity and has been used empirically in traditional phytotherapies for the treatment of hypertension and various other cardiovascular diseases.

OBJECTIVE

This study investigated the antihypertensive and cardioinhibitory activity of the aqueous-methanol extract of F. carica fruit in rats.

MATERIALS AND METHODS

Extract in 250, 500 and 1000 mg/kg doses (p.o.) were administered to normotensive Sprague Dawley rats and blood pressure was measured using non-invasive technique. Hypertension was induced in rats by oral administration of 10% glucose for 3 weeks. Hypotensive effect of extract (1000 mg/kg p.o) was studied in normotensive and glucose-treated hypertensive rats. Langendorff's isolated heart technique was used to assess the effect of crude extract on force of contraction and heart rate. In addition, antioxidant potential, TPC, TFC were also assessed by DPPH free radical scavenging activity, Folin-Ciocalteu reagent and AlCl3 assay, respectively. Furthermore, phenolic compounds were analyzed using HPLC-DAD technique.

RESULTS AND DISCUSSION

The 1000 mg/kg dose decreased blood pressure significantly in normotensive and glucose-treated hypertensive rats. The isolated heart study showed that the extract produced negative inotropic and chronotropic effects but it failed to block the stimulatory effect of both adrenaline and CaCl2. HPLC studies on the F. carica extract indicated the presence of quercetin, gallic acid, caffeic acid, vanillic acid, syringic acid, coumaric acid and chromotropic acid.

CONCLUSIONS

This study demonstrated that aqueous methanol extract of F. carica fruit exerted hypotensive and antihypertensive effects in glucose-induced hypertensive rats.

2-h postchallenge plasma glucose predicts cardiovascular events in patients with myocardial infarction without known diabetes mellitus

BACKGROUND AND PURPOSE

The incidence of cardiovascular events remains high in patients with myocardial infarction (MI) despite advances in current therapies. New and better methods for identifying patients at high risk of recurrent cardiovascular (CV) events are needed. This study aimed to analyze the predictive value of an oral glucose tolerance test (OGTT) in patients with acute myocardial infarction without known diabetes mellitus (DM).

METHODS

The prospective cohort study consisted of 123 men and women aged between 31-80 years who had suffered a previous MI 3-12 months before the examinations. The exclusion criteria were known diabetes mellitus. Patients were followed up over 6.03 ± 1.36 years for CV death, recurrent MI, stroke and unstable angina pectoris. A standard OGTT was performed at baseline.

RESULTS

2-h plasma glucose (HR, 1.27, 95% CI, 1.00 to 1.62; P < 0.05) and smoking (HR, 3.56, 95% CI, 1.02 to 12.38; P < 0.05) proved to be independent predictors of CV events in multivariate statistical analysis after adjustments for age, sex, total cholesterol, and other baseline characteristics.

CONCLUSIONS

In this study population, with previous MI and without known DM, 2-h PG and smoking were significant predictors of CV death, recurrent MI, stroke and unstable angina pectoris, independent of baseline characteristics and medical treatment.

The aqueous extract of Terminalia superba (Combretaceae) prevents glucose-induced hypertension in rats

AIM OF THE STUDY

The stem bark of Terminalia superba (Combretaceae) (TS) is used in traditional Cameroonian medicine as antihypertensive remedy. The aim of this study was to investigate the hypotensive and the antihypertensive effects of the aqueous extract of the stem bark of Terminalia superba.

MATERIALS AND METHODS

Hypertension was obtained in rats by oral administration of 10% D-glucose for 3 weeks. The acute effects of Terminalia superba were studied on blood pressure (BP) and heart rate (HR) after intravenous administration in normotensive rats (NTR) and glucose hypertensive rats (GHR). The antihypertensive effects were studied after oral administration of the extract (50 and 100 mg/kg/day) or nifedipine (10 mg/kg/day) for 3 weeks. At the end of the experiment, BP and HR were measured and reduced glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) activity levels were measured in heart, aorta, liver and kidney.

RESULTS

Intravenous administration of the aqueous extract of Terminalia superba induced a significant hypotensive response without any change in HR. The hypotensive effect of the extract was unaffected by atropine or propranolol but decreased by reserpine (5 mg/kg) and yohimbine (0.1 mg/kg). In addition, the oral administration of the extract significantly prevented the rise in BP in glucose-hypertensive rats. Finally, the treatment with plant extract significantly blunted the decrease in GSH and the increase in MDA levels associated with hypertension, and significantly prevents the increase in aortic SOD activity.

CONCLUSIONS

The present study demonstrates that the aqueous extract of the stem bark of Terminalia superba exhibits hypotensive and anti-hypertensive properties that are, at least in part, related to a withdrawal of sympathetic tone and to an improvement of the antioxidant status, respectively. Overall data validate the use of Terminalia superba as antihypertensive therapy in traditional medicine.

Are adverse pregnancy outcomes risk factors for development of end-stage renal disease in women with diabetes?

BACKGROUND

It is unknown whether adverse pregnancy-related outcomes in women with pregestational diabetes are associated with later development of end-stage renal disease (ESRD) or death.

METHODS

We linked data from the Medical Birth Registry of Norway with data from the Norwegian Renal Registry and the Norwegian Cause of Death Registry. Data from up to three pregnancies for women with a first singleton delivery from 1967 to 1994 were included and analysed in a cohort design using Cox regression.

RESULTS

Altogether, 639,018 women were included in the analyses, among whom 2204 women had diabetes mellitus before pregnancy. Their first pregnancy was complicated by pre-eclampsia in 13.2%, low birth weight offspring (<2.5 kg) in 11.0% and preterm birth in 25.1%, and their risk of ESRD and death in the follow-up period of up to 37 years was markedly higher. In women with pregestational diabetes, pre-eclampsia and preterm birth were associated with significantly increased risks of ESRD and death in women with only one pregnancy, but not in women with two or more pregnancies.

CONCLUSIONS

In women with pregestational diabetes, pre-eclampsia and preterm birth were associated with long-term increased risk of ESRD and death, but only in women who had only one pregnancy.

Relationship of insulin resistance to macro- and microvasculature reactivity in hypertension

BACKGROUND

Although insulin resistance (IR) is thought to be related to vascular dysfunction, the difference in the relationship of IR to microvasculature and macrovasculature reactivity has not yet been clarified. The present study was conducted to clarify whether the IR is more closely related to the macrovasculature reactivity (flow-mediated vasodilatation of the brachial artery induced by reactive hyperemia: FMD) or microvasculature reactivity (skin reactive hyperemia as assessed by laser Doppler flowmetry: SRH) in patients with hypertension.

METHODS

In 75 consecutive hypertensive patients (61 +/- 11 years of age) without obvious cardiovascular (CV) disease and/or risk factors for CV disease other than hypertension, FMD, SRH, and homeostasis model assessment index of IR (HOMA(IR)) were measured.

RESULTS

No significant relationship was observed between FMD with the parameters of SRH. In the univariate linear regression analysis, HOMA(IR) showed a significant correlation with the FMD (R(2) = 0.05, P < 0.05), but not with the parameters of SRH. Multivariate linear regression analysis demonstrated a significant association between HOMA(IR) and FMD, even after adjustments for covariates, including the use of medication for hypertension. (R(2) = 0.32, beta = -0.29, P = 0.02).

CONCLUSIONS

The complication of IR in hypertensive patients without obvious CV disease/risk factors may be related to impaired macrovasculature rather than microvasculature reactivity, apart from the influence of antihypertensive medication on the reactivity of the vasculature and insulin sensitivity.

An evaluation of glucose tolerance in essential hypertension

PURPOSE

This study aimed to determine the impaired glucose tolerance and diabetes prevalence in patients with essential hypertension (HT) and to compare the developed microvascular complications of these groups.

MATERIALS AND METHODS

An oral glucose tolerance test (OGTT) was performed on 338 essential hypertensive cases and glucose tolerances were classified according to ADA-2002 criteria.

RESULTS

Of the 338 cases, 32 people had diabetes (DM, 9.46%), 78 people had glucose intolerance (IGT, 23.1%), and 228 people had only hypertension but not IGT and DM (67.4%). Both the mean ages of the DM group (56.9 +/- 6.7 years, p = 0.002) and IGT group (56.3 +/- 8.4 years, p = 0.003) were older than the mean age of the control group (51.1 +/- 6.4 years). The risk of IGT development was found to be four times greater in male cases than female cases when compared to the control group (p = 0.004, add ratio = 4.194). There were no significant differences in the body mass indexes (BMI's), hypertension durations, and microvascular complications between the groups.

CONCLUSION

In conclusion, the risk of IGT and DM development in hypertensive cases increases with aging and longer hypertension duration. The risk of IGT development in hypertensive cases is four times more in males.

Postchallenge plasma glucose and glycemic spikes are associated with pulse pressure in patients with impaired glucose tolerance and essential hypertension

Elevated pulse pressure (PP) is associated with an increased risk of cardiovascular events. We examined whether PP is associated with post-challenge hyperglycemia in Japanese patients with essential hypertension and impaired glucose tolerance (IGT). In a total of 70 untreated essential hypertensive patients (age: 57+/-4 years, mean+/-SD; males=35, females=35), 24-h ambulatory blood pressure (ABP) monitoring, 75 g oral glucose tolerance testing (OGTT), metabolic analysis and echocardiography were performed. Patients were categorized into a high PP group (PP>or=60 mmHg, n=33) or a normal PP group (PP<60 mmHg, n=37). In all patients, 24-h systolic ABP, daytime systolic ABP, nighttime systolic ABP, and nighttime heart rate were significantly higher in the high PP group. Additionally, fasting immunoreactive insulin (F-IRI), homeostasis model assessment (HOMA) index, left ventricular mass index (LVMI) were also elevated in the high PP group. Finally, the high PP group exhibited impaired insulin secretion, increased post-challenge glucose concentrations and greater glucose spikes (PGS) during 75 g OGTT. Of the parameters measured, 24-h PP correlated positively with age, triglyceride, uric acid, F-IRI, HOMA index, 1-h postload glucose and insulin, 2-h postload glucose and insulin, PGS60, PGS120, PGSmax, LVMI, and deceleration time but correlated negatively with HDL-cholesterol and E/A ratio. Multiple regression analysis revealed that PP level was independently predicted by age, LVMI, and PGS120. Our results show that age, LVMI, and PGS120 are significantly associated with high PP in Japanese patients with IGT and essential hypertension.

Potential impact of carbohydrate and fat intake on pathological left ventricular hypertrophy

Currently, a high carbohydrate/low fat diet is recommended for patients with hypertension; however, the potentially important role that the composition of dietary fat and carbohydrate plays in hypertension and the development of pathological left ventricular hypertrophy (LVH) has not been well characterized. Recent studies demonstrate that LVH can also be triggered by activation of insulin signaling pathways, altered adipokine levels, or the activity of peroxisome proliferator-activated receptors (PPARs), suggesting that metabolic alterations play a role in the pathophysiology of LVH. Hypertensive patients with high plasma insulin or metabolic syndrome have a greater occurrence of LVH, which could be due to insulin activation of the serine-threonine kinase Akt and its downstream targets in the heart, resulting in cellular hypertrophy. PPARs also activate cardiac gene expression and growth and are stimulated by fatty acids and consumption of a high fat diet. Dietary intake of fats and carbohydrate and the resultant effects of plasma insulin, adipokine, and lipid concentrations may affect cardiomyocyte size and function, particularly in the setting of chronic hypertension. This review discusses potential mechanisms by which dietary carbohydrates and fats ca affect cardiac growth, metabolism, and function, mainly in the context of pressure overload-induced LVH.

Comprehensive assessment of postischemic vascular reactivity in Hispanic children and adults with and without diabetes mellitus

BACKGROUND

To examine the whole postischemic hyperemic response period in Hispanic children and adults with and without type 2 diabetes mellitus (T2DM) and offer insight into the potential adaptive mechanisms involved in the arterial response to disturbances in vascular homeostasis.

METHODS

Ninety-eight adults and 124 children of Hispanics participated in the study. Endothelial function was assessed in the brachial artery using high-resolution ultrasonography (HRU). A continuous scan was taken for 5 min during the hyperemic response, flow velocity (FV) recordings and diameter measurements were obtained, and brachial arterial blood flow (BF) was calculated after the cuff deflation.

RESULTS

The increment in FV during the reactive hyperemic period was higher in obese and in diabetic children than in lean healthy children, although the time to reach peak brachial artery diameter (BAD) and the per cent increase in peak diameter were comparable in all three groups. In subjects with impaired glucose tolerance (IGT), the hyperemic peak increase in FV was comparable to those in healthy adults. In diabetic patients, the peak increase in BAD as well as the per cent increment in the diameter were reduced at 50-60 s after the release of the arm cuff. The time to reach the peak increase in diameter also was prolonged in diabetics when compared with healthy adults.

CONCLUSION

Our study demonstrates clear differences in the normal vascular response between healthy children and healthy adults and discloses the presence of additional abnormalities in the flow-mediated vasodilation in diabetic and 'prediabetic' subjects.

Vascular adrenergic tone and structural narrowing constrain reactive hyperemia in skeletal muscle of obese Zucker rats

Previous studies have demonstrated that skeletal muscle perfusion is impaired in obese Zucker rats (OZR) under control conditions and with elevated metabolic demand versus responses in lean Zucker rats (LZR). To further our understanding of processes contributing to impaired perfusion, we determined whether hyperemic responses following periods of occlusion were altered in skeletal muscle of OZR versus LZR. In isolated hindlimbs, basal blood flow in OZR was less than in LZR, and total perfusion responses after 30, 90, and 180 s of occlusion were reduced. Treatment of animals with an antioxidant (polythethylene glycol-superoxide dismutase) had no effect on reactive hyperemia, although blockade of alpha-adrenoreceptors (alpha1 > alpha2) improved responses to 30 and 90 s of occlusion; responses to 180 s of occlusion were unaltered. Pump perfusion of a dilated distal hindlimb demonstrated that increased volume flow elicited a greater increase in perfusion pressure in OZR versus LZR, suggesting structural contributions to an increased vascular resistance. Responses were comparable for in situ cremaster muscle because reactive hyperemia following serial arteriolar occlusion was attenuated in OZR versus LZR, treatment with polythethylene glycol-superoxide dismutase was ineffective, and hyperemic responses were improved following inhibition of alpha-adrenoreceptors (alpha1 > alpha2). Treatment of cremaster muscle with adenosine (10(-3) M) caused flow to increase to a level comparable to that following 180 s of occlusion in both strains, although this level was reduced in OZR versus LZR. These results suggest that increased adrenergic tone may constrain reactive hyperemia in OZR with brief occlusion, although structural increases in vascular resistance can contribute to constrained perfusion after longer periods of occlusion.

ERK1/2 activation by angiotensin II inhibits insulin-induced glucose uptake in vascular smooth muscle cells

Clinical evidence suggests a relationship between hypertension and insulin resistance, and cross-talk between angiotensin II (Ang II) and insulin signaling pathways may take place. We now report the effect of Ang II on insulin-induced glucose uptake and its intracellular mechanisms in vascular smooth muscle cells (VSMC). We examined the translocation of glucose transporter-4 (GLUT-4) and glucose uptake in rat aortic smooth muscle cells (RASMC). Mitogen-activated protein (MAP) kinases and Akt activities, and phosphorylation of insulin receptor substrate-1 (IRS-1) at the serine and tyrosine residues were measured by immunoprecipitation and immunoblotting. As a result, Ang II inhibited insulin-induced GLUT-4 translocation from cytoplasm to the plasma membrane in RASMC. Ang II induced extracellular signal-regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase (JNK) activation and IRS-1 phosphorylation at Ser307 and Ser616. Ang II-induced Ser307 and Ser616 phophorylation of IRS-1 was inhibited by a MEK inhibitor, PD98059, and a JNK inhibitor, SP600125. Ang II inhibition of insulin-stimulated IRS-1 tyrosyl phophorylation and Akt activation were reversed by PD98059 but not by SP600125. Ang II inhibited insulin-induced glucose uptake, which was also reversed by PD98059 but not by SP600125. It is shown that Ang II-induced ERK1/2 activation inhibits insulin-dependent glucose uptake through serine phophorylation of IRS-1 in RASMC.

Impaired glucose tolerance: is there a case for pharmacologic intervention?

Impaired glucose tolerance (IGT) is determined by measuring plasma glucose levels 2 hours after glucose loading in the oral glucose tolerance test. There is good evidence from epidemiologic and prospective trials [e.g. Diabetes Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe (DECODE)] linking IGT with the development of type 2 diabetes mellitus and cardiovascular disease (CVD). IGT is characterized by an increase in postprandial glucose levels, which is considered the earliest metabolic abnormality in type 2 diabetes mellitus. It is one of a series of risk factors for CVD (hypertension, high triglyceride levels, low high-density lipoprotein-cholesterol and central obesity), known as the metabolic syndrome. The different factors making up this syndrome are intimately related. An impaired lipid profile can contribute to insulin resistance, as IGT may play a pathogenic role on other cardiovascular risk factors. IGT is the first easily identifiable step in the pathophysiology of type 2 diabetes mellitus. It is associated with high risk for type 2 diabetes mellitus and subsequent vascular morbidity and mortality. It is currently unknown whether treating IGT will reduce the incidence of macrovascular complications, as studies addressing this issue have yet to be conducted. Therefore, the main reason to identify and treat IGT is to prevent or delay the onset of type 2 diabetes mellitus. It has been demonstrated that lifestyle intervention with diet and exercise can reduce the incidence of type 2 diabetes mellitus. Pharmacologic intervention with metformin and acarbose is also effective. Other drugs, such as those indicated to treat other parameters of the metabolic syndrome, may also be useful. We can now be assured that prevention or delay of onset of type 2 diabetes mellitus is possible in individuals with IGT, either by changes in lifestyle or by pharmacotherapy.

Diabetes is a vascular disease: the role of endothelial dysfunction in pathophysiology of cardiovascular disease in diabetes

Diabetes is a vascular disease. Endothelial dysfunction is the initial process in vascular manifestations of diabetes mellitus (DM). There are multiple pathways involved in the pathophysiologic process related to endothelial dysfunction in DM. Most of these abnormalities occur secondary to insulin resistance. In this article the role of insulin, glucose,dyslipidemia, oxidative stress and various cellular mechanisms related to endothelial dys-function in diabetes are discussed in detail.

A novel approach to treatment of hypertension in diabetic patients - a multicenter, double-blind, randomized study comparing the efficacy of combination therapy of Eprosartan versus Ramipril with low-dose Hydrochlorothiazide and Moxonidine on blood pressure levels in patients with hypertension and associated diabetes mellitus type 2 - rationale and design [ISRCTN55725285]

Hypertension and diabetes mellitus are closely interrelated and coexist in as many as two-thirds of patients with type 2 diabetes. The consequent risk of such an association is an accelerated development of atherosclerotic cardiovascular disease and nephropathy complications.In choosing an antihypertensive agent, effectiveness needs to be accompanied by favourable metabolic, cardioprotective, and nephroprotective properties. Given the multifactorial nature of hypertension, the approach that has gained widespread agreement is treatment with more than one agent. Agents with different mechanisms of action increase antihypertensive efficacy because of synergistic impacts on the cardiovascular system. Combination therapy allows the use of lower doses of each antihypertensive agent which accounts for the excellent tolerability of combination products.The aim of the present study is to quantify the efficacy of combination therapy of Eprosartan 600 mg respectively Ramipril 5 mg with low-dose Hydrochlorothiazide and Moxonidine on blood pressure levels in patients with essential hypertension and associated diabetes mellitus type 2.The use of monotherapy (Eprosartan or Ramipril) followed by addition of low-dose Hydrochlorothiazide as second agent and of Moxonidine as a third agent will be individualized to the severity of hypertension in the particular patient and to his/her degree of response to current treatment.

Insulin secretion, sensitivity, and metabolic profile of young healthy offspring of hypertensive parents

Hyperinsulinemia and insulin resistance are commonly observed in essential hypertension, which is part of the metabolic syndrome. The aim of this study was to examine whether insulin secretion abnormalities or alterations in insulin sensitivity and glucose tolerance are also present in healthy men, offspring of patients with essential hypertension. Twelve young (27 +/- 3.6 years), lean normotensive offspring were compared with 14 age-, sex-, and body mass index (BMI)-matched controls without a family history of hypertension, diabetes mellitus, and coronary heart disease. We studied glucose tolerance, insulin secretion, and sensitivity using 10-hour hyperglycemic and 10-hour hyperinsulinemic-euglycemic clamps (HIC). Glucose tolerance was comparable in the offspring and controls. However, the offspring had higher insulin and C-peptide levels during the hyperglycemic clamp (HGC) compared with controls (P <.05). There was no difference in the early phase of insulin secretion between the groups. The insulin sensitivity index (glucose infusion rate/serum insulin) was significantly lower in the offspring during both clamps. Moreover, the offspring had higher systolic (P <.001) and diastolic (P <.001) blood pressure and had higher serum cholesterol (P <.01) and triglyceride (P <.05) levels. Apparently healthy, young, lean individuals with a genetic predisposition to essential hypertension and with normal glucose tolerance had higher insulin secretion and lower insulin sensitivity than controls. These abnormalities, together with higher blood pressure and altered lipid metabolism, may play a role in the development of hypertension and an increased risk of cardiovascular morbidity and mortality in these individuals.

Effects of ACE inhibition and AT1-receptor antagonism on endothelial function and insulin sensitivity in essential hypertensive patients

OBJECTIVE

Disturbed endothelial function is closely associated with hyperinsulinaemia and insulin resistance in essential hypertension. The aims of this study were: 1) to evaluate whether the two alternative drugs, angiotensin-converting enzyme (ACE) inhibitors and Angiotensin II (Ang II) antagonists, had comparable effects on glucose metabolism and endothelial function. 2) to determine whether they improve endothelial dysfunction through modulating insulin resistance and oxidative stress.

STUDY DESIGN AND METHODS

Essential hypertensive patients were randomised into two groups: Twelve (nine patients in final analysis) patients were given enalapril (enalapril group), and twelve (nine patients in final analysis) were given losartan (losartan group). Twelve sex- and age-matched normotensive volunteers were included as controls. Before and after six months of treatment, endothelial function, insulin sensitivity and lipid peroxidation (TBARs) and NO metabolites (NOx) were evaluated.

RESULTS

Endothelial function, measured as flow mediated dilatation (FMD), was improved in both of the treatment groups (p=0.0001). Calculated insulin sensitivity index also improved in the enalapril-treated group (p=0.05) but not in the losartan-treated group, compared with baseline levels. TBARS values decreased significantly in the enalapril group compared with baseline levels (p<0.001). FMD was positively correlated with insulin sensitivity index (r=0.32, p<0.05) and NOx levels (r=0.39, p=0.01) and negatively correlated with TBARS levels (r=-0.53, p=0.0002) in hypertensive patients.

CONCLUSION

Inhibition of the renin-angiotensin system, either with ACE inhibitors or AT(1)-receptor blockers improves endothelial dysfunction. ACE inhibition has prominent effects on improving insulin sensitivity and decreasing oxidative stress in essential hypertensive patients.

Mechanisms of endothelial dysfunction in the metabolic syndrome

Cardiovascular disease is a leading cause of death and disability in patients with diabetes or metabolic syndrome (MS). The available data suggest that many patients with diabetes or MS already have vascular abnormalities by the time they are diagnosed with their metabolic disorder. Endothelial dysfunction (ED), which is one of the initial steps in the process of vascular disease, is often present in patients with diabetes or MS. Although the precise mechanism(s) by which diabetes or MS causes ED remains to be elucidated, several possibilities exist. Hyperglycemia, hyperinsulinemia, increased oxidative stress, and diabetic dyslipidemia can all contribute to ED individually or in concert with one another. ED in the setting of diabetes or MS can subsequently result in the activation of a variety of pathways that alter vascular function and participate in the process of vascular remodeling and atherosclerosis. Because insulin resistance is the predominant mechanism responsible for various perturbations seen in MS or diabetes, it is essential to develop a therapeutic strategy that can improve insulin sensitivity with the hope that such interventions would reduce the risk of future cardiovascular events.

Influences of increased oxidative stress on endothelial function, platelets function, and fibrinolysis in hypertension associated with glucose intolerance

The effect of oxidative stress on endothelial function, platelet function, and fibrinolysis in hypertension with or without glucose intolerance was examined. The endothelium, platelets and fibrinolysis play important roles in the progression of atherosclerosis and interact with each other. We have previously demonstrated that glucose intolerance impairs endothelial function in hypertension, but its precise mechanisms have not been clarified. Hypertensive patients were divided by the results of 75-g oral glucose tolerance test into a normal glucose metabolism group (n = 65) and a glucose intolerance group (n = 47). The plasma level of thiobarbituric acid-reactive substances (TBARS) was assessed as a marker of oxidative stress. Endothelial function was assessed by flow-mediated dilatation (FMD), platelet function by the concentration of ADP dose inducing half-maximal aggregation (EC50), and fibrinolytic parameters by radioimmunoassay. These functions were assessed before and after acute administration of vitamin C. FMD was reduced while TBARS and fibrinolytic parameters were higher in patients with glucose intolerance than in those with a normal glucose metabolism. Vitamin C increased FMD and reduced fibrinolytic parameters significantly in the glucose intolerance group, but not in the group with normal glucose metabolism. On the other hand, the EC50 was similar in both groups. In conclusion, glucose intolerance aggravates oxidative stress, thereby contributing to the impairment of endothelial function in patients with hypertension. These abnormalities affect fibrinolysis but not platelet function.

Pharmacotherapy of diabetes mellitus: implications for the prevention and treatment of cardiovascular disease

Diabetes mellitus in adults is associated with an increased risk of premature vascular disease and a higher mortality rate. The presence of other risk factors, often seen in diabetic patients, such as systemic hypertension, augments the rate of vascular diseases. Evidence is growing that tight control of hyperglycemia using insulin and/or oral hypoglycemic agents will modify this risk. More aggressive control of concomitant hypertension and/or hyperlipidemia is also required. Diabetic patients who have myocardial infarctions do worse than nondiabetic patients. Various strategies to improve outcomes include the use of tight blood glucose control, and various coronary interventions are currently under clinical study.