Lifestyle modification improves endothelial function in obese subjects with the insulin resistance syndrome

Effects of weight loss from a very-low-carbohydrate diet on endothelial function and markers of cardiovascular disease risk in subjects with abdominal obesity

BACKGROUND

The effects of a very-low-carbohydrate, high-saturated-fat weight-loss diet (LC) on brachial artery flow-mediated dilatation (FMD) and markers of endothelial function are unknown.

OBJECTIVE

The effect of an LC on markers of endothelial function and cardiovascular disease (CVD) risk was compared with that of an isocaloric high-carbohydrate, low-saturated-fat diet (HC).

DESIGN

FMD and markers of endothelial function (n = 70) and CVD risk were measured before and after 8 wk of weight loss. Ninety-nine subjects aged 50.0 +/- 8.3 y with a body mass index (in kg/m2) of 33.7 +/- 4.1 completed the study.

RESULTS

Mean (+/-SD) FMD did not change significantly (P = 0.55) with either diet. Pulse wave velocity improved with both diets (P < 0.01). Endothelial markers, E- and P selectin, intracellular and cellular-adhesion molecule-1, tissue-type plasminogen activator, and plasminogen activator inhibitor-1 decreased (P < 0.001), with no diet effect. Adiponectin did not change significantly. More weight (P = 0.05 for diet x time interaction) and more abdominal fat mass (P = 0.05 for diet x time interaction) were lost with the LC than with the HC. LDL cholesterol decreased more with the HC than with the LC (P < 0.05, time x diet), and C-reactive protein decreased more with the HC than with the LC (P < 0.05 for diet x time interaction). Homocysteine increased more with the LC (P < 0.01 for diet x time interaction). Folate decreased with the LC and increased with the HC (P < 0.05, time; P < 0.001 for diet x time interaction).

CONCLUSION

An LC does not impair FMD. We observed beneficial effects of both diets on most of the CVD risk factors measured. This trial was registered with the Australian Clinical Trials Registry as ACTR N0 12606000203550.

Improved endothelial function following a 14-month resistance exercise training program in adults with type 2 diabetes

OBJECTIVE

We examined the effect of a 14-month progressive resistance training (PRT) program on endothelial function in both a supervised training (Center) group and non-supervised training (Home) group of patients with type 2 diabetes. We studied 28 men and women with type 2 diabetes who participated in a 14-month PRT involving an initial 2-month supervised program and a 12-month maintenance program.

METHODS

Endothelial function testing was performed through laser doppler flow responses in the skin microcirculation to iontophoresis of acetylcholine (ACh) and sodium nitroprusside (NaNP) and doses of 4, 8 and 16mC were used. Measurements of vascular response (VR), HbA1c, weight and blood pressure were performed at 0, 2 and 14 months.

RESULTS

VR to ACh and NaNP was significantly increased at 14 months compared with baseline in both the Center and Home groups. However, no between-group differences were observed. A significant correlation was observed between HbA1c and VR to ACh at baseline and 8 weeks using 8mC dose of ACh. There was a strong correlation between HbA1c at baseline and VR at 14 months using all three doses of ACh (4mC:r=-0.546, p=0.003, 8mC:r=-0.470, p=0.002, 16mC:r=-0.547, p=0.006).

CONCLUSIONS/INTERPRETATION

Endothelial function is improved following 14 months of PRT in type 2 diabetes both in a supervised and non-supervised program. Strong correlations with HbA1c including initial HbA1c levels suggest that glycemic control may be an important factor in long-term regulation of endothelial function.

Secondary prevention of cardiovascular disease in type 2 diabetes and prediabetes: a cardiologist's perspective

Patients with type 2 diabetes mellitus (T2DM) and prediabetes have a substantially greater risk of developing cardiovascular (CV) disease than the general population. This increased risk of CV disease is due to a complex cluster of risk factors including insulin resistance, hyperglycaemia, diabetic dyslipidaemia, hypertension and systemic inflammation. As a result of this cluster of risk factors, life expectancy is reduced by up to 10 years upon diagnosis of T2DM, principally because of fatal CV events. Patients with T2DM are not only more likely to sustain a CV event, but also have a higher risk of a fatal outcome from this event. Therefore, whilst primary prevention is critical in determining the prognosis of patients newly diagnosed with T2DM, many will go on to suffer CV events and represent a high-risk group requiring intensive secondary prevention techniques. Recent data demonstrate that contemporary prevention therapies do not afford equal benefits to T2DM sufferers after acute myocardial infarction compared with their non-diabetic counterparts. This finding highlights the need for more effective secondary preventative strategies to prevent recurrent CV events in patients with T2DM and prediabetes. The cardiologist's role in the multidisciplinary management of T2DM is to improve patient outcomes by optimising use of evidence-based strategies for the prevention of recurrent CV events.

Long-term cardiac rehabilitation and exercise training programs improve metabolic parameters in metabolic syndrome patients with and without coronary heart disease

BACKGROUND AND AIMS

The effectiveness of long-term cardiac rehabilitation and exercise training programs on metabolic parameters was evaluated in metabolic syndrome subjects with and without coronary heart disease (CHD).

METHODS AND RESULTS

Fifty-nine CHD and 81 non-coronary patients with metabolic syndrome (59+/-8 vs 56+/-9years) were identified retrospectively at entry into identical cardiac rehabilitation and exercise-training programs. Metabolic syndrome was defined using modified Adult Treatment Panel III criteria. Exercise training occurred approximately twice per week. Metabolic and exercise testing data were collected at baseline and after 12months during the course of the program. Mean duration of cardiac rehabilitation and exercise training programs was over one year in both coronary and non-coronary patients (366+/-111 vs 414+/-102days for CHD and non-coronary CHD cohorts respectively, p<0.01). Significant improvements in bodyweight, body mass index, blood lipids, triglyceride/HDL ratio and exercise tolerance were noted in both cohorts. At the end of follow-up, 31% of CHD and 20% of non-CHD subjects no longer possessed diagnostic criteria for metabolic syndrome (p<0.0001 and p<0.001 respectively).

CONCLUSIONS

A long-term cardiac rehabilitation program reduces metabolic syndrome prevalence in CHD patients and results in a similar improvement in risk factor control for metabolic syndrome patients without CHD.

Endothelial dysfunction in obesity: etiological role in atherosclerosis

PURPOSE OF REVIEW

To review studies of vascular endothelial dysfunction in obesity, discuss potential mechanisms of disease, and address the therapeutic effects of weight loss interventions on arterial health.

RECENT FINDINGS

Endothelial dysfunction represents the earliest abnormality in the development of vascular disease, and is pathophysiologically linked to subsequent atherosclerosis progression and cardiovascular disease events. Obesity is closely associated with a number of established cardiovascular risk factors, including diabetes mellitus, insulin resistance, dyslipidemia, and hypertension that are cumulatively damaging to the endothelium. In addition, there is now a growing recognition of non-traditional risk factors as potential modulators of the endothelial phenotype in obesity, including fat tissue production of proatherogenic adipokines, oxidative stress, and chronic inflammation. Clinical studies have demonstrated that even modest weight loss reverses endothelial dysfunction, and the restoration of arterial homeostasis could potentially reduce cardiovascular risk.

SUMMARY

Obesity is associated with altered arterial homeostasis and endothelial dysfunction. Mechanisms of disease are related to a complex interplay of metabolic and inflammatory factors that coordinately improve along with arterial function in response to weight loss interventions.

Diabetes mellitus do tipo 2, síndrome metabólica e modificação no estilo de vida

O Diabetes Mellitus do Tipo 2 favorece o aumento da morbidade e da mortalidade por doenças cardiovasculares. Essas doenças apresentam mesmo componente genético e mesmos antecedentes ambientais, sendo a resistência insulínica considerada um dos principais possíveis antecedentes. A síndrome metabólica é um transtorno complexo, representado por um conjunto de fatores de risco cardiovascular, usualmente relacionados à deposição central de gordura e à resistência à insulina. A modificação do comportamento alimentar inadequado e a perda ponderal, associadas à prática de atividade física regular, são consideradas terapias de primeira escolha para o tratamento da síndrome metabólica, por favorecer a redução da circunferência abdominal e da gordura visceral, melhorar a sensibilidade à insulina e diminuir as concentrações plasmáticas de glicose e triglicérides, aumentar os valores de HDL colesterol e, conseqüentemente, reduzir os fatores de risco para o desenvolvimento de Diabetes Mellitus do Tipo 2 e doenças cardiovasculares. Dessa forma, o presente artigo objetivou descrever e analisar alguns dos principais estudos publicados nas últimas décadas, os quais mostraram que a adoção de um estilo de vida adequado possibilita a prevenção primária do Diabetes Mellitus do Tipo 2. As mudanças no estilo de vida impróprio podem ser estimuladas por meio de uma intervenção educacional, dando ênfase ao aspecto nutricional e à atividade física, visando à redução dos fatores de risco relacionados à síndrome metabólica e às doenças cardiovasculares, em diferentes populações.

Health behaviors and endothelial function

An unhealthy lifestyle, including excess caloric intake, lack of exercise, smoking, and excessive alcohol consumption, increases one's risk of developing cardiovascular disease (CVD). However, the exact mechanisms by which these behaviors influence the development and progression of CVD have yet to be determined. Endothelial function (EF) has been shown to be a potent predictor of CVD, yet the effects of health behaviors on EF are not clear. The literature assessing the role of four health behaviors, obesity (a proxy of excess caloric intake), smoking, physical inactivity, and alcohol consumption, on the development of endothelial dysfunction is reviewed. Potential mechanisms through which these behaviors may influence EF are discussed. Smoking, being overweight or obese, and physical inactivity are all associated with decreased EF. A direct causal relationship between these measures and EF is suggested by the fact that improvements in these behaviors leads to parallel improvements in EF. The influence of alcohol consumption is somewhat more contentious, with some studies indicating a dose-response relationship such that those with greater consumption have poor EF. However, other studies have shown that those who drink moderately have the best EF. Although there is a growing body of literature implicating poor health behaviors in the development of endothelial dysfunction, more work is needed to establish the exact mechanisms by which this occurs. To our knowledge, there are no studies that have assessed the impact of multiple health behaviors or the interaction of health behaviors on EF.

Rationale for the use of insulin sensitizers to prevent cardiovascular events in type 2 diabetes mellitus

Cardiovascular events in patients with type 2 diabetes mellitus are a major problem in clinical practice, and patients with diabetes have derived less benefit from advances in preventive and interventional cardiology. Tighter goals for metabolic management and attention to nontraditional risk factors may be needed in this patient group. Insulin resistance rather than hyperinsulinemia is thought to underlie cardiovascular disease in patients with diabetes. Insulin resistance is associated with cardiovascular events and a wide range of traditional and nontraditional risk factors for cardiovascular disease (e.g., endothelial dysfunction, dyslipidemia, inflammation, vascular wall abnormalities). Therapy with lifestyle modifications, metformin, or thiazolidinediones (TZDs) corrects many of the abnormalities associated with diabetes in addition to lowering blood glucose and correcting diabetic dyslipidemia. TZDs, acting via the peroxisome proliferator-activated receptor-gamma, affect a number of mediators involved in the development of the cardiovascular complications of diabetes, including lipid profiles, vascular changes, and inflammatory mediators. TZDs decrease plasminogen activator-1 and C-reactive protein levels. They also reduce the extent of thickening of the carotid artery and reduce hyperplasia after coronary stent implantation. Insulin-sensitizing therapy with TZDs is a promising intervention for patients with diabetes at risk for adverse cardiovascular outcomes.

Oxidative stress-mediated arterial dysfunction in patients with metabolic syndrome: Effect of ascorbic acid

Arterial dysfunction is a hallmark of early atherosclerosis; however, its behavior in patients with metabolic syndrome (MS) is still unclear. We investigated the role of oxidative stress on ischemia-induced flow-mediated dilatation (FMD) in patients with MS. FMD and oxidative stress, as assessed by serum levels of 8-hydroxy-2-deoxy-2-deoxyguanosine (8-OHdG), were studied in 18 MS and 30 control subjects. Thereafter, in the 18 MS patients, FMD was assessed after iv infusion of 1 g vitamin C or placebo in a randomized, double-blind, crossover design; serial blood samples were taken in peripheral circulation before and after FMD to analyze 8-OHdG. Compared to controls, MS patients had higher 8-OHdG (p<0.001) and lower FMD (p<0.001); 8-OHdG and FMD were inversely correlated (R=-0.74; p<0.01). In MS patients, placebo administration did not change FMD, whereas vitamin C significantly enhanced it (p<0.001). After placebo, ischemia-induced FMD was associated with a significant increase in 8-OHdG (p<0.001), an effect that was counteracted by vitamin C. Vitamin C infusion was associated with an inverse correlation between the changes in FMD and oxidative stress (R=-0.67; p<0.01). The present study shows that arterial dilatation is impaired and that enhanced oxidative stress may play a key role in patients with MS.

Cardiovascular actions of insulin

Insulin has important vascular actions to stimulate production of nitric oxide from endothelium. This leads to capillary recruitment, vasodilation, increased blood flow, and subsequent augmentation of glucose disposal in classical insulin target tissues (e.g., skeletal muscle). Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways regulating endothelial production of nitric oxide share striking parallels with metabolic insulin-signaling pathways. Distinct MAPK-dependent insulin-signaling pathways (largely unrelated to metabolic actions of insulin) regulate secretion of the vasoconstrictor endothelin-1 from endothelium. These and other cardiovascular actions of insulin contribute to coupling metabolic and hemodynamic homeostasis under healthy conditions. Cardiovascular diseases are the leading cause of morbidity and mortality in insulin-resistant individuals. Insulin resistance is typically defined as decreased sensitivity and/or responsiveness to metabolic actions of insulin. This cardinal feature of diabetes, obesity, and dyslipidemia is also a prominent component of hypertension, coronary heart disease, and atherosclerosis that are all characterized by endothelial dysfunction. Conversely, endothelial dysfunction is often present in metabolic diseases. Insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling that in vascular endothelium contributes to a reciprocal relationship between insulin resistance and endothelial dysfunction. The clinical relevance of this coupling is highlighted by the findings that specific therapeutic interventions targeting insulin resistance often also ameliorate endothelial dysfunction (and vice versa). In this review, we discuss molecular mechanisms underlying cardiovascular actions of insulin, the reciprocal relationships between insulin resistance and endothelial dysfunction, and implications for developing beneficial therapeutic strategies that simultaneously target metabolic and cardiovascular diseases.

Diabetes mellitus as a prothrombotic condition

Diabetes mellitus (DM) is characterized by fasting hyperglycaemia and a high risk of atherothrombotic disorders affecting the coronary, cerebral and peripheral arterial trees. The risk of myocardial infarction (MI) is 3-5 fold higher in Type 2 DM and a DM subject with no history of MI has the same risk as a non-DM subject with a past history of MI. In total around 70% of deaths are vascular with poorer outcomes to both acute events and cardiological interventions. It was proposed that clustering of vascular risk factors (hyperinsulinaemia, dysglycaemia, dyslipidaemia and hypertension) around insulin resistance (IR) accounted for the increase in risk with Type 2 DM. The importance of this became apparent with the recognition that risk clustering occurs in normoglycaemic and impaired glucose tolerance (IGT) subjects with IR, in total around 25% of the population in addition to long-standing Type 1 subjects with renal disease. Evidence indicates that thrombotic risk clustering also occurs in association with IR, suppression of fibrinolysis due to elevated concentrations of the fibrinolytic inhibitor, plasminogen activator inhibitor-1 (PAI-1) is invariable with IR and there is evidence that this is regulated by the effects of triglyceride on the PAI-1 gene promoter. Other studies indicated that prothrombotic risk (coagulation factors VII, XII and fibrinogen) also associates with the IR syndrome. The development of endothelial cell dysfunction with suppression of nitric oxide and prostacyclin synthesis, combined with platelet resistance to the anti-aggregatory effects of these hormones leads to loss of control over platelet activation. In addition, hyperglycaemia and glycation have marked effects on fibrin structure function, generating a clot which has a denser structure, resistant to fibrinolysis. The combination of increased circulating coagulation zymogens, inhibition of fibrinolysis, changes in fibrin structure/function and alterations in platelet reactivity creates a thrombotic risk clustering which underpins the development of cardiovascular disease.

Insulin action and insulin resistance in vascular endothelium

PURPOSE OF REVIEW

Vasodilator actions of insulin are mediated by phosphatidylinositol 3-kinase dependent insulin signaling pathways in endothelium, which stimulate production of nitric oxide. Insulin-stimulated nitric oxide mediates capillary recruitment, vasodilation, increased blood flow, and subsequent augmentation of glucose disposal in skeletal muscle. Distinct mitogen-activated protein kinase dependent insulin signaling pathways regulate secretion of the vasoconstrictor endothelin-1 from endothelium. These vascular actions of insulin contribute to the coupling of metabolic and hemodynamic homeostasis that occurs under healthy conditions. Insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase dependent signaling in both metabolic and vascular insulin target tissues. Here we discuss consequences of pathway-specific insulin resistance in endothelium and therapeutic interventions targeting this selective impairment.

RECENT FINDINGS

Shared causal factors such as glucotoxicity, lipotoxicity, and inflammation selectively impair phosphatidylinositol 3-kinase dependent insulin signaling pathways, creating reciprocal relationships between insulin resistance and endothelial dysfunction. Diet, exercise, cardiovascular drugs, and insulin sensitizers simultaneously modulate phosphatidylinositol 3-kinase and mitogen-activated protein kinase dependent pathways, improving metabolic and vascular actions of insulin.

SUMMARY

Pathway-specific impairment in insulin action contributes to reciprocal relationships between endothelial dysfunction and insulin resistance, fostering clustering of metabolic and cardiovascular diseases in insulin-resistant states. Therapeutic interventions that target this selective impairment often simultaneously improve both metabolic and vascular function.

Effects of diet with or without exercise on leptin and anticoagulation proteins levels in obesity

Obesity is a risk factor for cardiovascular disease and thromboembolic events. We investigated the effects of weight reduction by a 12-week calorie-restricted diet with or without aerobic exercise (diet group and diet plus exercise group) on leptin and anticoagulation proteins levels. Forty-two obese nondiabetic individuals were evaluated for blood levels of leptin, protein C activity, free protein S antigen and for body fat area calculated on computerized tomography before and after intervention. Before intervention, serum levels of leptin and free protein S antigen correlated positively with several adiposity-related parameters. After the program, body weight and fat area were significantly decreased in both groups. Body mass index and leptin levels decreased in both groups, with a larger change in the diet plus exercise group than in the diet group. Although protein C activity levels did not change in both groups, free protein S antigen levels decreased significantly in the diet plus exercise group. In conclusion, the 12-week programs had significant effects on the initial weight reduction and body fat mass, decreasing lepin levels in obese nondiabetic individuals. To clarify whether aerobic exercise has additional or direct effects on the anticoagulation system, a study in a large number of individuals is needed.

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.

ED2: erectile dysfunction = endothelial dysfunction

Erectile dysfunction (ED) is a common condition in men, and increases with age. Cardiovascular disease (CVD) is the leading cause of death in men and also increases in prevalence with advancing years. The common link between the two conditions is endothelial dysfunction that leads to vascular insufficiency of the coronary and penile arteries. Because the penile arteries are smaller, symptoms of ED may precede those of CVD by several years. It is logical, therefore, that a patient complaining of ED should alert the physician to look for cardiovascular risk factors. Early treatment of these risk factors may help to prevent or retard symptoms of vascular insufficiency.

Effects of weight loss on a low-carbohydrate diet on flow-mediated dilatation, adhesion molecules and adiponectin

Our aim was to determine whether short-term weight loss on a low-carbohydrate/low-saturated fat diet improved endothelial function compared with a conventional high-carbohydrate diet, as this diet is expected to lower both blood glucose and LDL-cholesterol. In a randomised parallel design of two energy-restricted diets in an outpatient setting, thirty-six subjects (BMI 33 (sem 4) kg/m2) were randomised to a low- or high-carbohydrate diet both low in saturated fat. Flow-mediated dilatation (FMD), fasting glucose, insulin, lipids, adiponectin and adhesion molecules were measured at baseline, during weight loss and at 52 weeks. FMD did not change with either diet (5.2 (sem 0.6) to 5.5 (sem 0.6) %) despite weight loss of 5 % and significant reductions in glucose and insulin and LDL-cholesterol and was not different after sustained weight loss of 5 % at 52 weeks. Adiponectin fell by 6 % at 12 weeks (P = 0.1) with weight loss but rose by 17 % at 12 months (P < 0.05) with 5 % weight loss. There were no effects of diet. In contradistinction, adhesion molecules fell at 12 weeks, vascular cell adhesion molecule-1 by 14 % and intracellular adhesion molecule-1 by 13 % (both P < 0.05). There were correlations between change in adiponectin at 12 months and change in HDL (r 0.778, P < 0.01) and glucose (r - 0.563, P = 0.057). In summary, weight loss does not improve FMD. Novel cardiovascular risk factors improved at 12 weeks but the improvement in adiponectin was delayed.

Healthy endothelium: The scientific basis for cardiovascular health promotion and chronic disease prevention

The vascular endothelium plays a critical role both in health and in the pathogenesis of chronic diseases, including cardiovascular disease. This review explores the underlying role of normal endothelial function in core public health interventions for health promotion and in the prevention and control of cardiovascular disease and its risk factors, as well as the application of endothelial science toward innovative public health programs and further research. Increased collaboration among basic scientists, clinician-investigators, prevention research centers, and all public health practitioners is needed to facilitate the translation of the endothelial science into practice.

Obese adults with primary growth hormone resistance (Laron Syndrome) have normal endothelial function

OBJECTIVE

Classic Laron Syndrome (LS) is a recessive disease of insulin-like growth factor I (IGF-I) deficiency and primary growth hormone insensitivity, clinically characterized by dwarfism and marked obesity. The aim of the current study was to investigate the impact of long-term IGF-I deficiency on flow-mediated dilation (FMD) in 11 non-IGF-I-treated LS adults with long-term IGF-I deficiency who on stress echocardiography were found to have reduced cardiac dimensions and output, but normal left ventricular (LV) ejection fraction at rest and LV contractile reserve following stress.

DESIGN

Following an overnight fast we assessed percent improvement in endothelium-dependent FMD (%FMD) and endothelium-independent nitroglycerin (%NTG)-mediated vasodilation non-invasively in the brachial artery, using high resolution ultrasound in 11 non-treated adult patients with LS without known coronary artery disease, and compared them to 11 age- and sex-matched healthy controls. All subjects underwent symptom-limited exercise testing (Bruce protocol).

RESULTS

LS patients had a significantly higher body mass index (29+/-6 vs. 25+/-2 kg/m(2), p=0.04), lower low-density lipoprotein cholesterol (142+/-28 vs. 176+/-12 mg/dl, p=0.03) and a smaller mean brachial artery diameter (4.63+/-0.72 vs. 5.70+/-1.06 mm, p=0.01) compared to controls. However, brachial artery %FMD and %NTG were not significantly different between the LS patients and controls (13.1+/-6.2% vs. 15.4+/-5.2%, p=0.28 and 22.3+/-6.0% vs. 18.9+/-6.2%, p=0.30; respectively). Cardiac performance, assessed by exercise duration time and metabolic equivalents (METs), was significantly greater in control subjects than in LS patients (10.3+/-2.0 vs. 6.0+/-1.4 min, p<0.01 and 10.2+/-2.0 vs. 7.2+/-1.4 METs, p<0.01; respectively).

CONCLUSIONS

FMD was found to be within normal limits in non-IGF-I-treated adult patients with LS, despite congenital absence of IGF-I and obesity.

The influence of obesity on calf blood flow and vascular reactivity in older adults

OBJECTIVE

To determine whether differences in vascular reactivity existed among normal weight, overweight, and obese older men and women, and to examine the association between abdominal fat distribution and vascular reactivity.

METHODS

Eighty-seven individuals who were 60 years of age or older (age = 69 +/- 7 yrs; mean +/- SD) were grouped into normal weight (BMI < 25; n = 30), overweight (BMI > or = 25 and < 30; n = 28), or obese (BMI > or = 30; n = 29) categories. Calf blood flow (BF) was assessed by venous occlusion strain-gauge plethysmography at rest and post-occlusive reactive hyperemia.

RESULTS

Post-occlusive reactive hyperemia BF was lower (p = 0.038) in the obese group (5.55 +/- 4.67%/min) than in the normal weight group (8.34 +/- 3.89%/min). Additionally, change in BF from rest to post-occlusion in the obese group (1.93 +/- 2.58%/min) was lower (p = 0.001) than in the normal weight group (5.21 +/- 3.59%/min), as well as the percentage change (75 +/- 98% vs. 202 +/- 190%, p = 0.006, respectively). After adjusting for age, prevalence in hypertension and calf skinfold thickness, change in BF values remained lower (p < 0.05) in obese subjects compared to the normal weight subjects. Lastly, the absolute and percentage change in BF were significantly related to BMI (r = -0.44, p < 0.001, and r = -0.37, p < 0.001, respectively) and to waist circumference (r = -0.36, p = 0.001, and r = -0.32, p = 0.002).

CONCLUSION

Obesity and abdominal adiposity impair vascular reactivity in older men and women, and these deleterious effects on vascular reactivity are independent of conventional risk factors.

Impaired skin microvascular reactivity in painful diabetic neuropathy

OBJECTIVE

The pathogenesis of painful diabetic neuropathy (PDN) is not clear. Following our in vivo observations of increased sural nerve epineurial blood flow in patients with PDN, we investigated the cutaneous microcirculation of the foot by laser Doppler flowmetry to determine if the epineurial findings were just confined to the nerve or more widespread in other vascular beds.

RESEARCH DESIGN AND METHODS

We measured foot skin vasodilator responses to acetylcholine (Ach) and sodium nitroprusside (SNP) and vasoconstrictor responses to sympathetic (deepest possible gasp) stimulation in 5 healthy control subjects, 10 non-neuropathic diabetic (NND) patients, 10 diabetic patients with painless neuropathy (PLDN), and 8 diabetic patients with PDN.

RESULTS

In PDN, there were significantly reduced responses to Ach (ANOVA P = 0.003) and vasoconstrictor inspiratory gasp (ANOVA P < 0.001) but not to SNP (NS). Post hoc analysis showed significant differences in Ach-induced vasodilation between PDN and nondiabetic control subjects (P < 0.05) as well as between PDN and NND (P < 0.05) but not PDN and PLDN (NS). There were no significant differences for SNP-induced vasodilation. However, there were significant differences in the vasoconstrictor response between PDN and control, NND, and PLDN (P < 0.01).

CONCLUSIONS

We found an impairment of cutaneous endothelium-related vasodilation and C-fiber-mediated vasoconstriction in PDN. Inappropriate local blood flow regulation may have a role in the pathogenesis of pain in diabetic neuropathy. Prospective studies are required to determine the temporal relationship of these changes in relation to the emergence of neuropathic pain.

An exercise intervention without weight loss decreases circulating interleukin-6 in lean and obese men with and without type 2 diabetes mellitus

Obesity and type 2 diabetes mellitus (T2DM) have been associated with a state of chronic low-grade inflammation. We examined the effect of exercise without weight loss on circulating inflammatory biomarkers in previously sedentary lean men and obese men with and without T2DM. Middle-aged men (8 lean, 8 obese, and 8 obese with T2DM) performed 60 minutes of aerobic exercise 5 times per week for 12 weeks without a reduction in body weight. Subjects underwent a hyperinsulinemic-euglycemic clamp before and after the 12-week exercise program to assess insulin sensitivity. Circulating interleukin-6 (IL-6), plasminogen activator inhibitor-1 (PAI-1), and C-reactive protein concentrations were measured by sandwich enzyme-linked immunosorbent assay before and after the exercise intervention. Body fat was measured using magnetic resonance imaging, and waist circumference was recorded for each subject pre- and postexercise intervention. Waist circumference and plasma IL-6 concentrations were significantly lower (P < .05) after exercise training despite no change in body weight or insulin sensitivity. There were no correlations between insulin sensitivity and IL-6. Fasting plasma PAI-1 concentration was significantly lower in the lean group compared with the obese group both pre- and postexercise intervention (P < .05). There were no changes in C-reactive protein or PAI-1 concentrations after exercise training. A 12-week exercise intervention led to reductions in waist circumference and fasting IL-6 concentrations in previously sedentary lean and obese men with or without T2DM, demonstrating significant changes in clinically relevant diabetes-related parameters despite no change in body weight.

Vascular function in the metabolic syndrome and the effects on skeletal muscle perfusion: lessons from the obese Zucker rat

The increased prevalence of obesity in Western society has been well established for many years, and with this trend, the prevalence of other associated pathologies including insulin resistance, dyslipidaemia, hypertension and the genesis of a proinflammatory and prothrombotic environment within individuals is also rapidly increasing, resulting in a condition known as the~metabolic syndrome. From a physiological perspective, one of the most severe consequences of the metabolic syndrome is a progressive inability of the cardiovascular system to adequately perfuse tissues and organs during either elevated metabolic demand and, if sufficiently severe, under basal levels of demand. For the study of the metabolic syndrome, the OZR (obese Zucker rat) represents an important tool in this effort, as the metabolic syndrome in these animals results from a chronic hyperphagia, and thus can be an excellent representation of the human condition. As in afflicted humans, OZR experience an attenuated functional and reactive hyperaemia, and can ultimately experience an ischaemic condition in their skeletal muscles at rest. The source of this progressive ischaemia appears to lie at multiple sites, as endothelium-dependent vasodilator responses are strongly impaired in OZR, and specific constrictor processes (e.g. adrenergic tone) may be enhanced. Whilst these active processes may contribute to a reduction in blood flow under resting conditions or with mild elevations in metabolic demand, an evolving structural alteration to individual microvessels (reduced distensibility) and microvascular networks (reduced microvessel density) also develop and may act to constrain perfusion at higher levels of metabolic demand. Given that constrained muscle perfusion in the metabolic syndrome appears to reflect a highly integrated, multi-faceted effect in OZR, and probably in humans as well, therapeutic interventions must be designed to address each of these contributing elements.

Obesity and Thrombosis

OBJECTIVES

To describe the pathophysiological mechanisms by which obesity increases the propensity to thrombosis, the leading cause of death in the Western World, with particular emphasis on the role of inflammation, oxidative stress, dyslipidaemia, insulin resistance and the coagulation cascade.

DESIGN

Review article.

MATERIALS AND METHODS

Medline (1966-2005) and Cochrane library review of literature examining the relationship between obesity and thrombosis. Search terms included obesity, overweight, body mass index, thrombosis, cardiovascular disease, venous thromboembolism, peripheral arterial disease, and coronary heart disease.

RESULTS

Obesity is an important and growing public health issue that is estimated to affect more than half of the UK adult population. Obesity, in particular central (visceral) obesity, is associated with significant, and largely preventable, morbidity and mortality including an increased incidence and prevalence of arterial and venous thrombotic events. The various mechanisms by which obesity may cause thrombosis include: the actions of so-called adipocytokines from adipose tissue, e.g. leptin and adiponectin; increased activity of the coagulation cascade and decreased activity of the fibrinolytic cascade; increased inflammation; increased oxidative stress and endothelial dysfunction; and disturbances of lipids and glucose tolerance in association with the metabolic syndrome.

CONCLUSIONS

Obesity appears to be associated with thrombosis via several mechanisms. These pro-thrombotic factors are all improved by weight loss.

Reciprocal relationships between abnormal metabolic parameters and endothelial dysfunction

PURPOSE OF REVIEW

Endothelial dysfunction plays a crucial role in the pathogenesis of atherosclerosis and related cardiovascular diseases. Glucotoxicity, lipotoxicity, and inflammation all independently contribute to development of both endothelial dysfunction and insulin resistance. We review pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance and recent insights from therapeutic interventions to improve both metabolic and vascular function.

RECENT FINDINGS

Shared causal factors such as glucotoxicity, lipotoxicity, and inflammation interact at multiple levels creating reciprocal relationships between insulin resistance and endothelial dysfunction that help to explain frequent clustering of metabolic and cardiovascular disorders. Metabolic abnormalities implicated in the development of insulin resistance, including hyperglycemia, elevated levels of free fatty acids, accumulation of advanced glycation end products, dyslipidemias, and decreased levels of adiponectin, also contribute importantly to endothelial dysfunction. Diet, exercise, cardiovascular drugs, and insulin sensitizers simultaneously improve endothelium-dependent vascular function, reduce inflammation, and improve insulin sensitivity by both distinct and interrelated mechanisms.

SUMMARY

Pathophysiological mechanisms underlying reciprocal relationships between endothelial dysfunction and insulin resistance contribute to clustering of metabolic and cardiovascular diseases represented by the metabolic syndrome. Therapeutic interventions that target endothelial dysfunction or insulin resistance often simultaneously improve both metabolic and vascular function.

Early diabetic neuropathy: Triggers and mechanisms

Peripheral neuropathy, and specifically distal peripheral neuropathy (DPN), is one of the most frequent and troublesome complications of diabetes mellitus. It is the major reason for morbidity and mortality among diabetic patients. It is also frequently associated with debilitating pain. Unfortunately, our knowledge of the natural history and pathogenesis of this disease remains limited. For a long time hyperglycemia was viewed as a major, if not the sole factor, responsible for all symptomatic presentations of DPN. Multiple clinical observations and animal studies supported this view. The control of blood glucose as an obligatory step of therapy to delay or reverse DPN is no longer an arguable issue. However, while supporting evidence for the glycemic hypothesis has accumulated, multiple controversies accumulated as well. It is obvious now that DPN cannot be fully understood without considering factors besides hyperglycemia. Some symptoms of DPN may develop with little, if any, correlation with the glycemic status of a patient. It is also clear that identification of these putative non-glycemic mechanisms of DPN is of utmost importance for our understanding of failures with existing treatments and for the development of new approaches for diagnosis and therapy of DPN. In this work we will review the strengths and weaknesses of the glycemic hypothesis, focusing on clinical and animal data and on the pathogenesis of early stages and triggers of DPN other than hyperglycemia.

Impact of weight reduction on production of platelet-derived microparticles and fibrinolytic parameters in obesity

INTRODUCTION

Generation of platelet-derived microparticle (PMP) is implicated in cardiovascular disease (CVD). However, the influence of adiposity and weight reduction on PMP generation remains to be fully elucidated. We compared PMP generation and fibrinolytic parameters between 49 non-diabetic obese (obese group) and 37 age-matched non-obese subjects (control group), and compared the effects of weight reduction on the parameters between a 12-week calorie restricted diet and diet with aerobic exercise in obese subjects.

MATERIALS AND METHODS

PMP, plasma levels of plasminogen activator inhibitor-1 (PAI-1) activity and tissue-type plasminogen activator (t-PA) antigen were measured before and after intervention.

RESULTS

Before intervention, PMP, PAI-1 activity and t-PA antigen values were elevated in the obese group compared with the control group. In all 86 subjects of both groups, these three parameters correlated with body mass index, waist circumference and fat tissue mass. There was a positive correlation between plasma levels of fibrinolytic parameters and visceral fat area (VFA). PMP values correlated with subcutaneous fat area (SFA). The intervention significantly reduced PMP, PAI-1 activity and t-PA antigen levels. There was a significant correlation between percentages of changes in PMP values and those in BMI, fat tissue mass and VFA in the obese group. No additional effect of exercise on PMP or fibrinolytic parameters was observed.

CONCLUSIONS

Overproduction of PMP and fibrinolytic abnormalities may be associated with excessive adipose tissue. Weight reduction by either calorie restriction with or without exercise improves fibrinolytic abnormalities and PMP overproduction, probably through reduction of adipose tissue.

Improvement of early vascular changes and cardiovascular risk factors in obese children after a six-month exercise program

OBJECTIVES

The present study aimed to assess the effect of a 6-month exercise program in obese children on flow-mediated vasodilation (FMD) carotid intima-media thickness (IMT) and cardiovascular risk factors (RF).

BACKGROUND

Childhood obesity contributes to adult obesity and subsequent cardiovascular disease. Physical inactivity is a major RF for obesity, endothelial dysfunction, and elevated carotid IMT, culminating in early atherosclerotic disease.

METHODS

Sixty-seven obese subjects (age 14.7 +/- 2.2 years) were randomly assigned to 6 months' exercise or non-exercise protocol. We examined the influence of exercises (1 h, 3 times/week) on FMD, IMT, and cardiovascular risk profile.

RESULTS

Compared with lean control subjects, obese children demonstrated at baseline significantly impaired FMD (4.09 +/- 1.76% vs. 10.65 +/- 1.95%, p < 0.001), increased IMT (0.48 +/- 0.08 mm vs. 0.37 +/- 0.05 mm, p < 0.001), and a number of obesity-related cardiovascular RF. Significant improvements were observed in the exercise group for IMT (0.44 +/- 0.08 mm, p = 0.012, -6.3%) and FMD (7.71 +/- 2.53%, p < 0.001, +127%). This improvement correlated with reduced RF, such as body mass index standard deviation scores, body fat mass, waist/hip ratio, ambulatory systolic blood pressure, fasting insulin, triglycerides, low-density lipoprotein/high-density lipoprotein ratio, and low-degree inflammation (C-reactive protein, fibrinogen).

CONCLUSIONS

The present study documented increased IMT, impaired endothelial function, and various elevated cardiovascular RF in young obese subjects. Regular exercise over 6 months restores endothelial function and improves carotid IMT associated with an improved cardiovascular risk profile in obese children.

Exercise training improves insulin-induced and insulin-like growth factor-1-induced vasorelaxation in rat aortas

Improved vasorelaxant response is one of the beneficial effects of exercise training on vascular function. The mechanism for this response is, however, poorly understood. The aim of this study was to investigate the effects of exercise training on insulin-induced and insulin-like growth factor-1 (IGF-1)-induced vasorelaxation. Fourteen 6-week-old male Wistar rats were randomly divided into sedentary control and exercise groups. For 12 weeks, the exercise group ran on a treadmill 60 min/day, 5 days/week. After exercise training, insulin-induced and IGF-1-induced vasorelaxant responses were evaluated by measuring the isometric tension of aortic rings. The vasorelaxant role of phosphatidylinositol 3-kinase (PI3K) and nitric oxide synthase (NOS) was examined by applying inhibitors, such as wortmannin (an inhibitor of PI3K) and N(omega)-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor). In addition, we examined the vascular response to the NO donor, sodium nitroprusside (SNP). We found that: (1) exercise training significantly enhanced both insulin-induced and IGF-1-induced vasorelaxation in rat aortas; (2) this vasorelaxant effect disappeared after the use of wortmannin or L-NAME; (3) there was no significant difference in SNP-induced vasorelaxation between control and exercise groups. Our findings indicate that exercise training enhances insulin-induced and IGF-1-induced vasorelaxant responses which are mediated through the PI3K-NOS-dependent pathway.

Six months of aerobic exercise does not improve microvascular function in type 2 diabetes mellitus

AIMS/HYPOTHESIS

Adults with type 2 diabetes mellitus have impaired microvascular function. It has been hypothesised that microvascular function may be restored through regular exercise. The aim of this study was to investigate whether 6 months of regular aerobic exercise would improve microvascular function in adults with type 2 diabetes.

MATERIALS AND METHODS

Fifty-nine patients with type 2 diabetes (32 males, age 62.9+/-7.6 years, HbA(1c) 6.8+/-0.9%) were randomised to either a 6-month aerobic exercise programme (30 min, three times a week, 70-80% of maximal heart rate) or a 'standard care' control group. Before and after the intervention period, microvascular function was assessed as the maximum skin hyperaemia to local heating and endothelial and non-endothelial responsiveness following the iontophoretic application of acetylcholine and sodium nitroprusside. Maximal oxygen uptake, as an index of aerobic fitness, was assessed using a maximal exercise test.

RESULTS

No significant improvement was seen in the exercise group compared with the control group for any of the variables measured: maximal oxygen uptake (control pre: 1.73+/-0.53 [means+/-SD] vs post: 1.67+/-0.40; exercise pre: 1.75+/-0.56 vs post: 1.87+/-0.62 l/min, p=0.10); insulin sensitivity (insulin tolerance test) (control pre: -0.17+/-0.06 vs post: -0.17+/-0.06; exercise pre: -0.16+/-0.1 vs post: -0.17+/-0.07 mmol l(-1) min(-1), p=0.97); maximal hyperaemia (control pre: 1.49+/-0.43 vs post: 1.52+/-0.57; exercise pre: 1.42+/-0.36 vs post: 1.47+/-0.33 V, p=0.85); peak response to acetylcholine (control pre: 1.37+/-0.47 vs post: 1.28+/-0.37; exercise pre: 1.27+/-0.44 vs post: 1.44+/-0.23 V, p=0.19) or to sodium nitroprusside (control pre: 1.09+/-0.50 vs post: 1.10+/-0.39; exercise pre: 1.12+/-0.28 vs post: 1.13+/-0.40 V, p=0.98).

CONCLUSIONS/INTERPRETATION

In this group of type 2 diabetic patients with good glycaemic control a 6-month aerobic exercise programme did not improve microvascular function or aerobic fitness.

Effect of a diet and exercise intervention on oxidative stress, inflammation and monocyte adhesion in diabetic men

Diabetes increases the risk of coronary artery disease. We examined the effects of lifestyle modification on key contributing factors to atherogenesis, including oxidative stress, inflammation and cell adhesion. Diabetic men (N=13) were placed on a high-fiber, low-fat diet in a 3-week residential program where food was provided ad libitum and daily aerobic exercise was performed. In each subject, pre- and post-intervention fasting blood was drawn for circulating levels of serum lipids, glucose and insulin, oxidative stress marker 8-isoprostaglandin F2alpha (8-iso-PGF2alpha), the inflammatory protein C-reactive protein (CRP), and soluble intracellular adhesion molecule (sICAM)-1 and sE-selectin as indicators of endothelial activation. Using subject sera and human aortic endothelial cell (HAEC) culture systems, serum-induced monocyte adhesion, ICAM-1, vascular cell adhesion molecule-1 (VCAM-1) and cell surface abundance, and monocyte chemotactic protein-1 (MCP-1) production were determined. Nitric oxide (NO), superoxide, and hydrogen peroxide production were measured in vitro by fluorometric detection. After 3 weeks, significant reductions (p<0.05) in BMI, all serum lipids including total cholesterol (pre: 188.9+/-10.1 mg/dL versus post: 146.3+/-3.8 mg/dL) and low-density lipoprotein (103.1+/-10.2 mg/dL versus 76.4+/-4.3 mg/dL), fasting serum glucose (157.5+/-10.1 mg/dL versus 126.7+/-8.7 mg/dL), insulin (33.8+/-4.0 microU/ml versus 23.8+/-3.4 microU/ml), homeostasis model assessment for insulin resistance, 8-iso-PGF2alpha, CRP, sICAM-1, and sE-selectin were noted. In vitro, serum-stimulated monocyte adhesion, cellular ICAM-1 and VCAM-1 expression (p<0.05), and fluorometric detection of superoxide and hydrogen peroxide production decreased, while a concomitant increase in NO production was noted (all p<0.01). A combination of diet and exercise ameliorates oxidative stress, inflammation, and monocyte-endothelial interaction. Intensive lifestyle modification may improve novel CAD risk factors in men with diabetes.

Variability of flow-mediated dilation measurements with repetitive reactive hyperemia

To capture the response of an acute intervention, multiple post intervention measurements of flow-mediated dilation (FMD) must be performed. The effect of repetitive reactive hyperemia on endothelial function and the measurement of FMD are unknown. The purpose of this investigation was (1) to examine the effect of repetitive reactive hyperemia on brachial artery FMD and (2) to determine whether brachial artery FMD is stable during a 2-h morning period. We investigated FMD in 20 apparently healthy college students on three randomized treatment days every 30 min (T30), 60 min (T60), and 120 min (T120) throughout a 2-h morning period (08.00 h to 10.00 h). An ANOVA (p > 0.05) and ICC (> 0.40) were both needed to confirm no difference among repetitive reactive hyperemia treatments. In response to repetitive reactive hyperemia, there was no difference (p = 0.307; ICC > 0.40) within the first and last FMD measurements of each treatment condition or between treatment conditions (p = 0.344; ICC > 0.40). FMD was similar (p = 0.348) throughout the 2-h morning period. In conclusion, repetitive reactive hyperemia over a 2-h period has no effect on FMD measurements in apparently healthy college students. In addition, this study found no time trends for FMD measurements during the 2-h morning period to allow for pre/post intervention FMD measurements.

Fatores dietéticos na prevenção e tratamento de comorbidades associadas à síndrome metabólica

A síndrome metabólica constitui um fator de risco cardiovascular, sendo caracterizada pela associação de hipertensão arterial sistêmica, obesidade abdominal, tolerância à glicose prejudicada, hipertrigliceridemia e baixas concentrações sangüíneas de HDL-colesterol, além dos estados pró-trombótico e pró-inflamatório observados. No entanto, a alimentação adequada, associada a outras modificações no estilo de vida, tais como prática regular de atividade física e abandono do tabagismo, contribui para um melhor controle da doença, prevenindo suas complicações e aumentando a qualidade de vida. Desse modo, o objetivo deste estudo foi revisar, na literatura científica, o papel da dieta na prevenção e tratamento da síndrome metabólica. Os trabalhos sobre o assunto informam que a terapia nutricional visa a limitar o consumo de gorduras saturadas e ácidos graxos trans isômeros, os principais envolvidos no aumento da colesterolemia. O aporte protéico deve ser semelhante às recomendações da população geral, com ênfase no consumo de proteínas de origem vegetal e de peixe. Outro fator importante refere-se ao índice glicêmico dos alimentos: dietas de alto índice glicêmico estão relacionadas à promoção da resistência insulínica, obesidade e diabetes mellitus tipo 2. Quanto às fibras alimentares, muitos estudos comprovam que a dieta rica em fibras diminui o risco de doenças coronarianas e diabetes mellitus tipo 2, além de contribuir para melhor controle glicêmico. Portanto, a alimentação adequada constitui um fator indispensável não somente no tratamento, como também na prevenção da síndrome metabólica.

Effect of a short-term diet and exercise intervention on oxidative stress, inflammation, MMP-9, and monocyte chemotactic activity in men with metabolic syndrome factors

The present study was designed to examine the effects of lifestyle modification on key contributing factors to atherogenesis, including oxidative stress, inflammation, chemotaxis, and cell adhesion. Obese men ( n = 31), 15 of whom had metabolic syndrome, were placed on a high-fiber, low-fat diet in a 3-wk residential program where food was provided ad libitum and daily aerobic exercise was performed. In each subject, pre- and postintervention fasting blood was drawn for circulating levels of serum lipids, glucose and insulin (for estimation of insulin sensitivity), oxidative stress-generating enzyme myeloperoxidase and marker 8-isoprostaglandin F2α, the inflammatory protein C-reactive protein, soluble ICAM-1 as an indicator of endothelial activation, sP-selectin as a marker of platelet activation, the chemokine macrophage inflammatory protein-1α, and total matrix metalloproteinase-9. Using subject sera and human aortic endothelial cell culture systems, we measured VCAM-1 cell surface abundance and monocyte chemotactic protein-1, nitric oxide, superoxide, and hydrogen peroxide production in vitro by fluorometric detection. Also determined in vitro was serum-induced, monocyte adhesion and monocyte chemotactic activity. After 3 wk, significant reductions ( P < 0.05) in body mass index, all serum lipids and lipid ratios, fasting glucose, insulin, homeostasis model assessment for insulin resistance, myeloperoxidase, 8-isoprostaglandin F2α, C-reactive protein, soluble ICAM-1, soluble P-selectin, macrophage inflammatory protein-1α, and matrix metalloproteinase-9 were noted. In vitro, serum-stimulated cellular VCAM-1 expression, monocyte chemotactic protein-1 production, and fluorometric detection of superoxide and hydrogen peroxide production decreased, whereas a concomitant increase in NO production was noted (all P < 0.01). Additionally, both monocyte adhesion ( P < 0.05) and MCA ( P < 0.01) decreased. Nine of 15 were no longer positive for metabolic syndrome postintervention. Intensive lifestyle modification may ameliorate novel coronary artery disease risk factors in men with metabolic syndrome factors before reversal of obesity.

Valsartan improves resting skin blood flow in type 2 diabetic patients and reduces poly(adenosine diphosphate-ribose) polymerase activation

OBJECTIVE

To examine the effect of a 12-week daily treatment with 160 mg of valsartan, an angiotensin II receptor blocker, on the microcirculation and macrocirculation of type 2 diabetic patients (T2DM) and healthy subjects.

METHODS

This was a prospective, randomized, double-blind, placebo-controlled crossover study. Thirteen T2DM with no severe complications and 13 healthy subjects completed the trial.

RESULTS

Treatment with valsartan in T2DM improved the resting forearm skin blood flow and increased the resting brachial artery diameter but had no effects on arterial blood pressure, large vessel vascular reactivity, or carotid intima-media thickness. Resting skin blood flow increased by 60% (2%-90%; median and 25th-75th percentiles) during valsartan treatment and by only 2% (-22% to 27%) during placebo treatment (P < .05). No changes were observed in the nondiabetic subjects. Immunostaining studies of forearm skin biopsy samples from T2DM and healthy subjects showed that valsartan reduced poly(adenosine diphosphate-ribose) polymerase (PARP) activity in 50% (6/12) of the subjects. PARP activity remained unchanged in placebo-treated subjects (P < .02). In addition, valsartan treatment increased CD31 staining in 33% (4/12) of the subjects, whereas no change was noted in sequential skin biopsy samples of placebo-treated subjects (P = .057). Valsartan had no effect on the biochemical markers of endothelial cell activation and other cytokines, including CAMs, interleukin 6, tumor necrosis factor alpha, C-reactive protein, adiponectin, and plasma activator inhibitor 1.

CONCLUSIONS

Valsartan increases the resting skin blood flow in T2DM, likely through reduction of PARP activity.

Does microvascular dysfunction link obesity with insulin resistance and hypertension?

Obesity and obesity-associated clinical disorders are becoming an increasing public health burden. In this perspective, we postulate that impairment of microvascular function links obesity with insulin resistance and hypertension. Obesity is characterized by generalized microvascular dysfunction, which is associated with, and may precede, the development of insulin resistance and hypertension. Understanding of mechanisms involved in obesity-associated microvascular dysfunction may reveal new therapeutic targets. In obesity, cellular regulatory mechanisms of vasoreactivity are shifted towards vasoconstriction, with an increased role for endothelin-1 and a decreased role for nitric oxide. In addition, communicative pathways between adipose tissue and the microvasculature comprise increased release of adipokines and increased sympathetic activity. Although one mechanism may dominate, microvascular defects in obesity are probably caused by an integrated response consisting of endocrine, vasocrine and neurogenic mechanisms. This remains a fruitful area for future research.

The dysregulated adipose tissue: a connecting link between insulin resistance, type 2 diabetes mellitus and atherosclerosis

An emerging paradigm supports the view that adipose tissue (AT) dysregulation might play a crucial role in the pathogenesis of insulin-resistance and atherosclerosis. The net result of such a dysregulation is a state of low-grade, chronic, systemic inflammation that, in turn, links both the metabolic and the vascular pathologies. Overwhelming evidence shows that high circulating levels of markers of chronic inflammation predict the development of T2DM and atherosclerotic manifestations. Therefore, atherosclerotic cardiovascular disease and T2DM seem to arise from a "common soil", and chronic inflammation is a candidate. In this scenario, the dysfunctional AT provide a common hallmark for these apparently divergent disorders. An important question then is whether dysregulated and inflamed AT can be converted to healthy fat and, consequently, the development or the progression of metabolic and vascular impairment can be prevented or reversed by the modulation of the inflammatory profile. The beneficial effects of weight loss on obesity-related complications are clearly associated with the modification of the inflammatory profile in the AT. Furthermore, the thiazolidinediones (TZDs) possess both anti-inflammatory and anti-atherogenic properties. Intriguingly, in contrast to the paradoxical weight gain, TZDs influence favorably the pattern of adipokines. In conclusion, accepting the paradigm of AT dysfunction, the use of TZDs will represent an additional therapeutic approach that, in association with lifestyle interventions, would improve inflammation, ameliorate insulin sensitivity, and alleviate the related risk of atherosclerosis.

The effect of moxonidine on endothelial dysfunction in metabolic syndrome

BACKGROUND

Endothelial dysfunction has been reported in patients with type 2 diabetes mellitus and even in healthy obese individuals with a normal metabolic profile. Sympathetic activity commonly is increased in obese hypertensive patients, and moxonidine is effective in lowering BP and improving insulin sensitivity.

OBJECTIVE

To evaluate the effect of moxonidine on endothelial dysfunction in patients with metabolic syndrome.

METHODS

Twenty-six patients with mild hypertension were treated with moxonidine and a hypocaloric diet for 3 months, while a second normotensive group (n = 26) were followed-up with calorie restriction alone. Anthropometric (body mass index, waist and hip circumferences, and waist-to-hip ratio) and metabolic features (fasting plasma glucose and insulin, aminotransferases, gamma-glutamyl transpeptidase, triglycerides, and cholesterol levels) and flow-mediated dilatation (FMD) were evaluated. Insulin resistance was calculated by using the homeostasis model assessment formula. Insulin sensitivity was calculated according to the quantitative insulin-sensitivity check index (QUICKI).

RESULTS

SBP and DBP (both p < 0.001) and waist circumference (p = 0.02) were higher, and QUICKI (p = 0.043) and FMD (p = 0.01) were lower in the hypertensive group at baseline. After 3 months, nearly all the study parameters improved in both treatment groups. The decrease in BP, increase in FMD, and improvements in metabolic and anthropometric parameters were significantly greater in the moxonidine-treated group than in those treated with diet alone.

CONCLUSION

Moxonidine is proposed as a valuable option for treating mild-to-moderate hypertension in obese and insulin-resistant patients with metabolic syndrome as it appears to improve endothelial dysfunction in these patients.

Endothelial and erectile dysfunction, diabetes mellitus, and the metabolic syndrome: common pathways and treatments?

The past decade has witnessed a dramatic increase in the prevalence of obesity. Comorbidities of obesity include type 2 diabetes mellitus, hypertension, and lipid abnormalities, all of which contribute to cardiovascular disease (CVD) and are associated with endothelial dysfunction. These abnormalities frequently cluster in individuals, and the term metabolic syndrome is now widely used to define this cluster. The syndrome is frequently (although not invariably) associated with insulin resistance and CVD. Diabetes is associated with CVD, which may be asymptomatic in some cases, particularly when associated with autonomic neuropathy. This has implications for guidelines on the evaluation of patients with erectile dysfunction (ED) and CVD. Treatment of ED in men with diabetes has been revolutionized by the introduction of phosphodiesterase 5 inhibitors. However, men with diabetes tend to respond less positively to these agents, at least as currently prescribed. This decreased responsiveness may be related to the severity of endothelial function in patients with diabetes. Additional therapeutic strategies may be needed to overcome this problem.

Relation of endothelial cell function to erectile dysfunction: implications for treatment

The prevalence of both cardiovascular disease (CVD) and erectile dysfunction (ED) increases with advancing age. These conditions share the common risk factors of diabetes mellitus, hypertension, hyperlipidemia, smoking, and obesity. They also share a pathophysiologic mechanism of decreased vascular blood flow via endothelial dysfunction. There are several lines of evidence that endothelial dysfunction in men with ED can be detected well before overt manifestations of vascular damage, including atherosclerotic effects. Some evidence shows that ED can be improved not only with phosphodiesterase 5 inhibitors but also by treating the risk factors directly. This includes cessation of smoking, correction of hyperlipidemia, and amelioration of obesity through weight loss. Conversely, ED may be prevented through maintenance of lean body mass, consistency of physical activity, and smoking abstinence, similar to other risk factors for CVD.

Mechanisms of endothelial dysfunction in obesity

Obesity is a chronic disease, whose incidence is alarmingly growing, affecting not only adults but also children and adolescents. It is associated with severe metabolic abnormalities and increased cardiovascular morbidity and mortality. Adipose tissue secretes a great number of hormones and cytokines that not only regulate substrate metabolism but may deeply and negatively influence endothelial physiology, a condition which may lead to the formation of the atherosclerotic plaque. In this review, the physiology of the endothelium is summarised and the mechanisms by which obesity, through the secretory products of adipose tissue, influences endothelial function are explained. A short description of methodological approaches to diagnose endothelial dysfunction is presented. The possible pathogenetic links between obesity and cardiovascular disease, mediated by oxidative stress, inflammation and endothelial dysfunction are described as well.

Improved fibrinolysis by an intensive lifestyle intervention in subjects with impaired glucose tolerance. The Finnish Diabetes Prevention Study

AIMS/HYPOTHESIS

The aim of this study was to investigate the effects of lifestyle intervention on the levels of plasminogen activator inhibitor (PAI-1) and fibrinogen in subjects participating in the Finnish Diabetes Prevention Study (DPS).

METHODS

In five DPS centres, 321 subjects with impaired glucose tolerance (intervention group, n=163; control group, n=158) had their PAI-1 and fibrinogen levels measured at baseline and at the 1-year follow-up. Additional 3-year follow-up assessments were carried out in a sample of 97 subjects in one of the DPS centres (Turku). The intervention programme included an intensive lifestyle intervention aiming at weight reduction, healthy diet and increased physical activity.

RESULTS

During the first intervention year, PAI-1 decreased by 31% in the intervention group but showed no change in the control group (p<0.0001). In the Turku subgroup, the decrease in PAI-1 persisted throughout the 3-year follow-up. Changes in PAI-1 were associated with the number of lifestyle changes made during the first year (p=0.008). Weight reduction was the most important factor explaining the decrease in PAI-1. Changes in fibrinogen levels did not differ between the groups.

CONCLUSIONS/INTERPRETATION

In addition to the previously reported reduction in the risk of type 2 diabetes in DPS participants with impaired glucose tolerance, the intensive dietary and exercise intervention had beneficial long-term effects on fibrinolysis as indicated by the reduced levels of PAI-1. These results suggest that elevated PAI-1 levels in obese subjects with impaired glucose tolerance are mostly reversible by lifestyle changes, especially those geared to weight reduction.

Endothelial function and its assessment

Endothelial dysfunction is a characteristic aspect of most of the conditions associated with atherosclerosis and is commonly found as an early feature in atherothrombotic vascular disease. An appreciation of the underlying mechanisms of endothelial function, as well as dysfunction, is essential as this has critical influence on the different methods in the assessment of endothelial function and effects of various treatments on its quantification. Furthermore, endothelial dysfunction is recognised as a type of 'target organ damage' in common cardiovascular conditions (e.g., hypertension) and the area is of increasing interest for new drug development, as therapies that modulate the endothelium will have added advantages; thus, for the development of new/experimental drugs, an awareness of ways to assess the endothelium is necessary. In this review, an overview of different methods including biochemical markers, and invasive and non-invasive tools, to determine endothelial function is presented as well as their clinical relevance. Furthermore, the effects of various treatments on endothelial dysfunction and their underlying mechanisms are elucidated.

Hypertension-independent microvascular rarefaction in the obese Zucker rat model of the metabolic syndrome

OBJECTIVE

To test the hypothesis that reduced skeletal muscle microvessel density (MVD) in obese Zucker rats (OZR) is independent of chronic elevations in mean arterial pressure (MAP).

METHODS

Microvessels in cross sections of gastrocnemius muscle from lean Zucker rats (LZR) and OZR were labeled with Griffonia simplicifolia I lectin, visualized with fluorescence microscopy and vessel number within sections was determined using imaging software. Rats were used at different ages to assess correlations between the temporal development of hypertension and microvascular rarefaction. Additionally, rats were chronically treated with captopril or hydralazine as antihypertensive therapies to examine the development of microvascular rarefaction in the absence of elevated blood pressure.

RESULTS

MVD in muscle of OZR was reduced by approximately 17% versus LZR by 10-11 weeks of age, prior to any elevation in MAP. By 15-17 weeks, OZR exhibited a approximately 23% reduction in MVD and a approximately 25 mmHg increase in MAP. Treatment with hydralazine prevented elevated MAP in OZR, although this was not associated with an improved MVD. Captopril treatment also prevented elevated MAP in OZR, although a partial recovery of MVD toward normal levels was observed. This observation was associated with an improved insulin resistance.

CONCLUSIONS

These results suggest that microvessel rarefaction in skeletal muscle of OZR manifesting the metabolic syndrome does not depend on an elevated mean arterial pressure and that other factors associated with the metabolic syndrome, possibly insulin resistance, may underlie the progressive reduction in MVD in these animals.

Rolle des Körpergewichts für die Prävention der koronaren Herzkrankheit

The prevalence of obesity has increased considerably in recent years; only one third of our population displays a desirable, healthy weight. Persons with increased body fat mass are in a constant pro-inflammatory and pro-thrombotic condition; in addition they are often insulin-resistant und show cardiovascular risk factors. Therefore, obesity induces the development of atherosclerosis as an independent risk factor as well as a promoter for other risk factors. In addition, congestive heart failure is more frequent in obese subjects. By reducing body weight with a decrease of predominantly visceral fat all risk factors are improved as well as endothelial function. Effects on coronary atherosclerosis and congestive heart disease are until now insufficiently investigated.

Effect of weight loss on inflammatory and endothelial markers and FMD using two low-fat diets

OBJECTIVE

Cardiovascular disease is strongly associated with obesity and there is evidence that weight loss has positive effects on cardiovascular disease risk. The aims of this study were to compare meal replacements (MR) with a conventional low-fat diet as weight loss strategies and to examine the effect of weight loss on flow-mediated dilatation (FMD) and other markers of endothelial function in overweight Australians with raised triglycerides (TG) (> 2 mmol/l).

RESEARCH METHODS

Subjects matched for age, gender, fasting plasma TG and body mass index were randomized to two low- fat high- carbohydrate weight loss strategies (both < 6000 kJ), one using MR and the other a structured eating plan, control (C). Subjects followed both diets for 3 months. In total, 55 subjects completed the study. FMD, pulse wave velocity and blood pressure (BP) were measured at baseline and at 3 months, as were fasting blood samples for lipids, glucose, insulin, C reactive protein (CRP) and endothelium-derived factors.

RESULTS

Mean weight loss was 6.3 +/- 3.7 kg (6.0 +/- 4.2 vs 6.63 +/- 3.35 kg, MR vs C) with no difference between diet groups. TG, insulin, CRP, plasminogen activator inhibitor 1 (PAI-1) and soluble intracellular adhesion molecule-1 (sICAM1) fell after weight loss, but FMD did not change. Systolic BP fell by 8 mmHg and pulse wave velocity improved.

DISCUSSION

In subjects with elevated TG, weight loss resulted in significant improvements in cardiovascular risk markers, particularly endothelium-derived factors (PAI-1 and sICAM1). However, FMD did not improve with weight loss.

Metabolic and vascular abnormalities in subjects at risk for type 2 diabetes: the early start of a dangerous situation

Various groups at risk for type 2 diabetes have been identified, including individuals with family history of type 2 diabetes, obesity, prior gestational diabetes, polycystic ovary syndrome, metabolic syndrome, hypertension, dyslipidemia and particularly those with pre-diabetes (impaired glucose tolerance and/or impaired fasting glucose). To various degrees, all these groups have also been identified with significant vascular abnormalities that range from endothelial dysfunction and low-grade or sub-clinical inflammation to evident atherosclerosis. The mechanisms involved in establishing a link between the risk of type 2 diabetes and vascular dysfunction are multiple and complex. The presence in the circulation of various cytokines, hormones and substrates associated with increased visceral fat and insulin resistance, the frequent appearance of associated cardiovascular risk factors and/or the possibility of some genetically determined intrinsic vascular abnormalities are all explanatory mechanisms that are being evaluated in clinical research. Whereas the possibility of appreciating a significant reduction in cardiovascular outcomes in long-term prospective clinical trials in all these groups at risk for type 2 diabetes is still lacking, understanding these mechanisms and recognizing how various interventions may improve vascular health is a worthwhile area of research that may translate into important clinical strategies to reduce the burden of type 2 diabetes and cardiovascular disease.