Selective Rac-1 Inhibition Protects From Diabetes-Induced Vascular Injury

Diabetes mellitus is a main risk factor for vascular diseases. Vascular injury induced by diabetes mellitus is characterized by endothelial dysfunction attributable to an increased oxidative stress. So far, the molecular mechanisms involved in the vasculotoxic effects of diabetes are only partially known. We examined the effect of diabetes mellitus on oxidative stress and Rac-1 activation, a small G-protein involved in the activation of NADPH oxidase. Our results show that oxidative stress in vessels of different murine models of diabetes mellitus and in endothelial cells treated with high glucose is associated with an increased Rac-1/PAK binding and Rac-1 translocation from cytosol to plasma membrane, thus demonstrating an enhanced Rac-1 activity. More important, selective Rac-1 inhibition by an adenoviral vector carrying a dominant negative mutant of Rac-1 protected from oxidative stress and vascular dysfunction induced by diabetes mellitus. Our study demonstrates that Rac-1 plays a crucial role in diabetes-induced vascular injury, and it could be a target of novel therapeutic approaches to reduce vascular risk in diabetes mellitus.

Strict glycemic control ameliorates the increase of carotid IMT in patients with type 2 diabetes

The aim of this study was to investigate the effect of strict glycemic control on the carotid artery intima-media thickness (IMT) in type 2 diabetic patients who initially had good glycemic control (HbA1c between 5.8 and 6.4 %). The subjects were 67 patients showing deterioration of the mean HbA1c over 3 years by more than 0.2% from baseline (D group) and 33 subjects showing improvement of the mean HbA1c by more than 0.2% from baseline (A group). The clinical characteristics and annual change of IMT during the observation period were compared between the two groups in a 3-year retrospective longitudinal study. The baseline characteristics and the mean values of BMI, blood pressure, and serum lipids during the study period did not differ significantly between the two groups. However, the mean HbA1c of A group was significantly lower than that of D group (5.67 +/- 0.10 vs. 6.28 +/- 0.08, mean +/- SE, p<0.001). The adjusted annual increase rate of IMT was significantly less in A group than in D group (-0.035 +/- 0.019 vs. 0.036 +/- 0.015 mm, M +/- SEM, p<0.001). These results indicate that further improvement of glycemic control from a good HbA1c value can prevent an increase of IMT in type 2 diabetic patients.

High-sensitivity C-reactive protein as cardiovascular risk marker in patients with diabetes mellitus

C-reactive protein (CRP) is a liver-derived pattern recognition molecule that is increased in inflammatory states. It rapidly increases within hours after tissue injury, and it is suggested that it is part of the innate immune system and contributes to host defense. Since cardiovascular disease is at least in part an inflammatory process, CRP has been investigated in the context of arteriosclerosis and subsequent vascular disorders. Based on multiple epidemiological and intervention studies, minor CRP elevation [high-sensitivity CRP (hsCRP)] has been shown to be associated with future major cardiovascular risk (hsCRP:<1 mg/L=low risk; 1-3 mg/L=intermediate risk; 3-10 mg/L=high risk; >10 mg/L=unspecific elevation). It is recommended by the American Heart Association that patients at intermediate or high risk of coronary heart disease may benefit from measurement of hsCRP with regard to their individual risk prediction. Elevation of hsCRP is associated with increased risk of type 2 diabetes development in patients with all levels of metabolic syndrome. In type 1 and type 2 diabetes mellitus, hemoglobin A1c significantly correlates with hsCRP levels and future cardiovascular risk. Also, hsCRP levels increase with the stage of beta-cell dysfunction and insulin resistance. Non-diabetes drugs that have been shown to reduce hsCRP concentrations include aspirin, statins, cyclooxygenase-2 inhibitors, and fibrates. Recent intervention studies have also demonstrated the distinct efficacy of different anti-diabetes treatments on a variety of cardiovascular risk markers. Intensive insulin therapy may reduce inflammation, but this effect may be influenced by the degree of weight gain. Treatment with peroxisome proliferator-activated receptor gamma has lead to substantial reduction of hsCRP and other cardiovascular risk markers in several comparator studies. Since this effect was shown to be independent of the degree of glycemic improvement, it can be regarded as a classspecific effect. Whether these findings translate into a reduction of overall cardiovascular mortality will soon be shown by the currently running thiazolidinedione outcome studies. Positive results in these trials will further strengthen the value and acceptance of hsCRP, which is recommended as a predictive laboratory marker for cardiovascular disease risk also in patients with diabetes mellitus.

An overview of inflammatory markers in type 2 diabetes from the perspective of the clinical chemist

C-reactive protein (CRP), when measured by a highly sensitive method, is a measure of lowgrade, chronic inflammation and is an independent risk factor for type 2 diabetes (T2D) and cardiovascular disease (CVD). CRP also has the capacity to interact with other risk factors to increase the risk for T2D and CVD. Population distributions divided into tertiles provide the capacity to predict onset of T2D and associated CVD. Preanalytical as well as analytical sources of variation in high-sensitivity CRP (hsCRP) measurements need to be standardized in order for CRP results to be optimally useful. The Centers for Disease Control and Prevention and the American Heart Association have issued guidelines for clinical usefulness of hsCRP measurements. The Centers for Disease Control and Prevention has taken steps to standardize hsCRP assays by evaluating secondary reference materials to be used by manufacturers to calibrate their assays.

"Anti-inflammatory" drugs and their effects on type 2 diabetes

There is a growing body of evidence for the role of inflammation in type 2 diabetes. In addition to the evidence presented elsewhere, evidence is emerging that many drugs that have apparent "anti-inflammatory" properties may reduce the incidence and/or delay the onset of type 2 diabetes. Statins have been found to lower inflammatory markers, and a post hoc analysis of the West of Scotland Coronary Prevention Study (WOSCOPS) suggested that pravastatin may reduce the risk of developing diabetes, although the Lipid Lowering Arm of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) found no statistically significant effect of atorvastatin on risk of developing diabetes. Fibrates have been found to lower some markers of inflammation, and a prospective trial found that bezafibrate reduces risk of developing diabetes. Angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers appear to reduce some markers of inflammation, and a meta-analysis concluded that ACE inhibitors and angiotensin receptor blockers reduce risk of developing type 2 diabetes. Metformin is known to reduce the risk of developing diabetes, and more recent evidence suggests it also lowers C-reactive protein, in part because of its modest weight-reducing effect. Thiazolidinediones reduce risk of developing diabetes, and consistently lower inflammatory markers independent of adiposity effects. High-dose aspirin inhibits cyclooxygenase and IkappaB kinase-beta and reduces fasting plasma glucose concentration, although there has not, as yet, been a large-scale trial to examine the effect of aspirin on the risk of developing diabetes. We conclude that although many drugs with potential anti-inflammatory properties reduce the risk of developing diabetes, it is difficult to prove that such anti-inflammatory properties contribute to their diabetes prevention since nearly all drugs have other, often more pronounced, actions. Studies with more specific inhibitors of inflammatory pathways (e.g., interleukin- 6 blockers) and mendelian randomization (genetic studies) will help determine whether targeting the inflammation axis is a fertile mechanism to treat or prevent type 2 diabetes.

Nutritional influences on inflammation and type 2 diabetes risk

There is a clear role for inflammation in the development of type 2 diabetes and its associated co-morbidities. Circulating inflammatory markers such as C-reactive protein, sialic acid, and interleukin- 6 are all significant independent predictors of disease. A number of nutritional components are hypothesized to modulate inflammation, and hence impact on disease risk. The most extensively studied nutrients are the long-chain n-3 polyunsaturated fatty acids. However, evidence is also emerging with respect to whole grain or low glycemic index foods and antioxidant vitamins. Obesity, resulting from long-term dietary energy excess, is also strongly linked to raised inflammatory status and type 2 diabetes. To date, much of the evidence for the effect of nutrients or foods on disease risk has been based on epidemiological associations. However, the links among diet, inflammation, and type 2 diabetes are supported by some data from human dietary intervention trials and/or mechanistic studies in animals. Further research is required to quantify the precise role and refine the evidence base. However, the proposed "anti-inflammatory" strategies to tackle type 2 diabetes are broadly consistent with current public health nutrition guidelines: to achieve and maintain a healthy weight, to reduce saturated fat, to increase the proportion of less refined forms of carbohydrate, and to increase intake of fruits and vegetables.

Lessons learnt from the 4D trial

Renal dysfunction alters the pathogenesis of cardiovascular disease (CVD) profoundly conferring a very high-risk to the patients. Currently strategies are developed to combat CVD and clinical studies test a number of hypothesis. In this setting the results of the 4D study, comparing atorvastatin with placebo on cardiovascular outcomes in 1255 type 2 diabetic patients on maintenance hemodialysis, came as a great and unsuspected surprise. After a median follow-up of 4 years atorvastatin (20 mg/d) decreased the relative risk by 8% (95% confidence interval, 0.77-1.10; P=0.37) despite a high number of cardiovascular events and an overall 24% cardiovascular mortality. This indicates, that the risk in type 2 diabetic patients on hemodialysis origins from factors other than an atherogenic lipoprotein phenotype alone. Due to non-significant effects of atorvastatin on the primary endpoint and the different quality of such endpoints in dialysis patients as well as an unexplained higher rate of fatal strokes in atorvastatin treated patients we do not recommend to initiate statin treatment in patients with type 2 diabetes mellitus undergoing hemodialysis therapy at the present time. Statin therapy should be implemented earlier during the course of progressive vascular damage.

Exercise, fitness, and cardiovascular disease risk in type 2 diabetes and the metabolic syndrome

This article highlights research supporting the concept that increased physical activity and cardiorespiratory fitness attenuate risk of cardiovascular disease, type 2 diabetes, and the metabolic syndrome. Increased activity and fitness also attenuate risk of developing cardiovascular disease in persons who have type 2 diabetes or the metabolic syndrome. Although controversial, relationships between physical activity/physical fitness and type 2 diabetes/metabolic syndrome are largely independent of body weight. Thus, physical inactivity and poor cardiorespiratory fitness are not only important determinants of cardiovascular and metabolic diseases, but they can also be considered common features of these conditions, much like traditional risk factors such as obesity and insulin resistance.

[Type 2 diabetes mellitus and cardiovascular diseases: evaluation, treatment and prevention strategies]

Patients with type 2 diabetes mellitus are at high risk for cardiovascular events and heart failure. The major serious complication of this disorder is large vessel atherosclerosis leading to myocardial infarction and stroke. Aggressive target setting for modifiable cardiovascular risk factors such as dyslipidemia, hypertension, and a procoagulant state, and judicious choice of efficacious therapies have been shown to produce significant reductions in cardiovascular events. The effectiveness of percutaneous coronary intervention (PCI) in diabetes is discussed, and the factors that may influence outcomes are explored. A major unresolved question is the potential role of tight glucose control for reducing macrovascular complications in patients with diabetes. With the increased attention being given to cardiovascular risk factor reduction, the opportunity exists to substantially decrease the largest causes of mortality in diabetic patients. This article reviews the current and emerging therapeutic strategies for these purposes from the cardiologists' point of view.

The renin-angiotensin system and its blockade in diabetic renal and cardiovascular disease

Diabetic nephropathy, the most common cause of end-stage renal disease in the United States, is also associated with increased cardiovascular mortality. The renin-angiotensin-aldosterone system (RAAS) plays a central role in the development and progression of kidney disease and cardiovascular disease. Randomized, controlled trials have demonstrated renoprotection with the use of angiotensin receptor blockers (ARBs) in type 2 and angiotensin-converting enzyme inhibitors (ACEIs) in type 1 diabetes. More recent studies have demonstrated similar cardiovascular benefits with the use of ARBs compared with ACEIs. The combination of the two classes of RAAS blockers has been investigated in large studies of patients with heart failure and after myocardial infarction, and a few small studies of patients with diabetic nephropathy. In this review, we summarized the results of the studies on the benefits of ARBs, ACEIs, and their combination in patients with diabetic nephropathy or cardiovascular diseases.

[Advanced glycation end products and hyperglycaemia]

Hyperglycaemia leads to increased formation and accumulation of advanced glycation end products, and these molecules play an important role in the development of micro- and macrovascular complications in diabetes. The formation of advanced glycation end products are complex reactions that take place both intra- and extracellularly. Advanced glycation end products affect gene regulation by binding to receptors, but can also modify proteins, DNA and lipids directly. The amount in serum and tissues depends upon several factors. The extent of hyperglycaemia is the main determining factor for levels of glycation products in the body, but the ability to break down and excrete these products in the urine is also important. The most effective way of preventing late complications in diabetes caused by glycation products is strict regulation of blood sugar levels. Drugs that inhibit advanced glycation end products could potentially be important in the prevention of late complications in diabetes, but this needs further investigation.

Inhibitors of Advanced Glycation End Product Formation and Neurovascular Dysfunction in Experimental Diabetes

Advanced glycation and lipoxidation end products (AGEs/ALEs) have been implicated in the pathogenesis of the major microvascular complications of diabetes mellitus: nephropathy, neuropathy, and retinopathy. This article reviews the evidence regarding the peripheral nerve and its vascular supply. Most investigations done to assess the role of AGEs/ALEs in animal models of diabetic neuropathy have used aminoguanidine as a prototypic inhibitor. Preventive or intervention experiments have shown treatment benefits for motor and sensory nerve conduction velocity, autonomic nitrergic neurotransmission, nerve morphometry, and nerve blood flow. The latter depends on improvements in nitric oxide-mediated endothelium-dependent vasodilation and is responsible for conduction velocity improvements. A mechanistic interpretation of aminoguanidine's action in terms of AGE/ALE inhibition is made problematic by the relative lack of specificity. However, other unrelated compounds, such as pyridoxamine and pyridoxamine analogues, have recently been shown to have beneficial effects similar to aminoguanidine, as well as to improve pain-related measures of thermal hyperalgesia and tactile allodynia. These data also stress the importance of redox metal ion-catalyzed AGE/ALE formation. A further approach is to decrease substrate availability by reducing the elevated levels of hexose and triose phosphates found in diabetes. Benfotiamine is a transketolase activator that directs these substrates to the pentose phosphate pathway, thus reducing tissue AGEs. A similar spectrum of improvements in nerve and vascular function were noted when using benfotiamine in diabetic rats. Taken together, the data provide strong support for an important role for AGEs/ALEs in the etiology of diabetic neuropathy.

Influences of Statins on Glucose Tolerance in Patients with Type 2 Diabetes Mellitus

Atorvastatin is frequently administered for the treatment of hypercholesterolemia associated with type 2 diabetes mellitus. However, a marked deterioration of glycemic control has been reported in some patients treated with atorvastatin. No study has been done to determine whether atorvastatin adversely affects glycemic control. In this study, we retrospectively compared an atorvastatin-treated group (Group A, n = 76) with a pravastatin-treated group (Group P, n = 78) to examine the effects of the 2 statins on glycemic control from the onset of administration to 3 months thereafter. No change occurred in the antidiabetic drug dose in 62 patients of Group A and 68 patients of Group P. In those patients, arbitrary blood glucose levels increased from 147 +/- 50 (mean +/- SD) mg/dL to 177 +/- 70 mg/dL in Group A and from 140 +/- 38 mg/dL to 141 +/- 32 mg/dL in Group P. HbA(1c) increased from 6.8 +/- 0.9% to 7.2 +/- 1.1% in Group A and from 6.9 +/- 0.9% to 6.9 +/- 1.0% in Group P. The increase was significant only in Group A, and the extent of the increase was also significantly greater in Group A. These results suggest a predisposition to a deterioration of glycemic control in type 2 diabetic patients treated with atorvastatin.

Early diabetic complications in a population of young patients with type 1 diabetes mellitus despite intensive treatment

AIM

To describe the prevalence of early complications in an unselected population of patients with type 1 diabetes mellitus (DM1) diagnosed in childhood with intensive insulin treatment from diagnosis.

METHODS

Eighty children and adolescents with DM1, age 7-22 years and DM1 duration >3 years, were studied. Neuropathy was defined as abnormal nerve conduction finding in > or = 2 of 4 nerves (sural and peroneal nerves), nephropathy as albumin excretion rate > or = 20 microg/min and retinopathy as all grades of retinal changes in fundus photographs.

RESULTS

The prevalence of neuropathy was 59%, of retinopathy 27% and of nephropathy 5% after 13 years DM1 duration. Mean (SD) long-term HbA1c was 8.4 (0.9)% (DCCT-corrected value).

CONCLUSION

Even in a population with intensive insulin treatment from the beginning and fairly good metabolic control, the prevalence of subclinical neuropathy was high, while other diabetic complications were lower than usually reported.

[Prophylactic and therapeutic application of thiamine (vitamin B1)--a new point of view]

Usefulness and application of vitamin B1 (thiamine) and it's derivatives (benfotiamine, sulfotiamine) in some environmental diseases like congestive heart failure and diabetes is described. Possibility of its use in geriatry and in pain-associated diseases is also analysed. Concise description of the role of thiamine in the human organism, its content in some food products and results of this vitamin deficiency are also presented.

Diabetes mellitus and stroke

The aim of this article was to describe (i) the epidemiology and outcomes of stroke relating to diabetes; (ii) the pathophysiology of diabetes as a risk factor for stroke; (iii) the management of acute stroke in patients with diabetes; (iv) the evidence of primary and secondary prevention of stroke in patients with diabetes; and (v) the risk of new-onset diabetes using older antihypertensive agents. The combination of diabetes and stroke disease is a major cause of morbidity and mortality worldwide. Evidence from large clinical trials performed in patients with diabetes supports the need for aggressive and early intervention to target patients' cardiovascular (CV) risks in order to prevent the onset, recurrence and progression of acute stroke. Identification of at-risk patients with diabetes and metabolic syndrome has also allowed the delivery of early and effective intervention to reduce stroke risks, while active treatment during the acute phase of stroke will reduce long-term neurological and functional deficits. While the ongoing debate on the risk benefits of different antihypertensive, lipid-lowering and antiplatelet agents should not detract clinicians from pursuing aggressive CV risk reduction, the application of evidence-based medicine specifically in patients with diabetes will facilitate the use of appropriate agents to improve clinical outcomes. The overall management of patients with diabetes and acute stroke or at risk of secondary stroke should also include multifactorial intervention that not only targets patient's CV risk but also includes behavioural, lifestyle and, where appropriate, surgical intervention.

[Target of glycemic control of elderly diabetes mellitus patients]

Although the number of older diabetes mellitus patients is growing rapidly all over the world including Japan, there has been little evidence regarding the target of plasma glucose levels in elderly diabetes mellitus patients. Older persons with diabetes mellitus have higher rates of functional disability and coexisting illness. Plasma glucose levels should be controlled properly in elderly, however, the levels must be determined individually considering their complications. Because the risks of hypoglycemia, and/or drug-drug interactions are higher in the older patients, the medical providers must balance benefits and risks for every patient. RCT in older diabetes mellitus patients would be required.

Improving macrovascular outcomes in type 2 diabetes: Outcome studies in cardiovascular risk and metabolic control

BACKGROUND

Type 2 diabetes is accompanied by a host of potentially modifiable cardiovascular disease risk factors. Consequently, people with type 2 diabetes have a higher risk of macrovascular disease than the non-diabetic population, and a poor prognosis following an event. Several large-scale primary and secondary outcome studies have included large diabetes subgroups for post-hoc analysis, and a limited number of studies have focused specifically on type 2 diabetes.

SCOPE

This review provides an overview of macrovascular outcome studies in type 2 diabetes and discusses potential new targets for therapy based upon a MEDLINE literature search from January 1990 to April 2006.

FINDINGS

Large cardiovascular outcome studies show that treating cardiovascular disease risk factors significantly reduces the risk of primary and secondary macrovascular events in patients with type 2 diabetes. The evidence for targeting hypertension (using renin-angiotensin system inhibitors), dyslipidemia (statins), and coagulation factors (aspirin) appears robust. However, the macrovascular benefits of improved glucose control remain to be proven definitively, although metformin may have advantages over other glucose-lowering agents. Nevertheless, these studies reveal that significant excess residual risk remains, highlighting the need for new therapies. It is also apparent that some agents (e.g. metformin, statins, renin-angiotensin system inhibitors) may also have pleiotropic mechanisms. Newer strategies are investigating other lipid targets (especially HDL cholesterol) or using agents, such as thiazolidinediones, that address multiple established and emerging risk factors. A recent study with pioglitazone suggests that macrovascular risk can be reduced in very high-risk patients with type 2 diabetes who are already receiving contemporary lipid, anti-hypertensive, and anti-platelet therapy.

CONCLUSION

The core therapeutic paradigm targeting glycemia, hypertension, dyslipidemia, and coagulation factors has failed to remove excess residual risk in patients with type 2 diabetes completely. Emerging data, and on-going trials, should provide better guidance on new therapeutic opportunities in this high-risk patient group.

Metabolic effects of the incretin mimetic exenatide in the treatment of type 2 diabetes

Interventional studies have demonstrated the impact of hyperglycemia on the development of vascular complications associated with type 2 diabetes, which underscores the importance of safely lowering glucose to as near-normal as possible. Among the current challenges to reducing the risk of vascular disease associated with diabetes is the management of body weight in a predominantly overweight patient population, and in which weight gain is likely with many current therapies. Exenatide is the first in a new class of agents termed incretin mimetics, which replicate several glucoregulatory effects of the endogenous incretin hormone, glucagon-like peptide-1 (GLP-1). Currently approved in the US as an injectable adjunct to metformin and/or sulfonylurea therapy, exenatide improves glycemic control through multiple mechanisms of action including: glucose-dependent enhancement of insulin secretion that potentially reduces the risk of hypoglycemia compared with insulin secretagogues; restoration of first-phase insulin secretion typically deficient in patients with type 2 diabetes; suppression of inappropriately elevated glucagon secretion to reduce postprandial hepatic output; and slowing the rate of gastric emptying to regulate glucose appearance into the circulation. Clinical trials in patients with type 2 diabetes treated with subcutaneous exenatide twice daily demonstrated sustained improvements in glycemic control, evidenced by reductions in postprandial and fasting glycemia and glycosylated hemoglobin (HbA(1c)) levels. Notably, improvements in glycemic control with exenatide were coupled with progressive reductions in body weight, which represents a distinct therapeutic benefit for patients with type 2 diabetes. Acute effects of exenatide on beta-cell responsiveness along with significant reductions in body weight in patients with type 2 diabetes may have a positive impact on disease progression and potentially decrease the risk of associated long-term complications.