Prevention of type 2 diabetes mellitus through inhibition of the Renin-Angiotensin system

Blockade of the renin-angiotensin system improves insulin sensitivity in thermal injury

Insulin resistance after burn is associated with alterations in postreceptor insulin signaling and abnormal glucose homeostasis. The renin-angiotensin system (RAS) exerts a largely inhibitory role on insulin action and is activated after burn injury. We hypothesized that upregulation of RAS is involved in the development of insulin resistance in burned rats. We examined the possibility that an angiotensin II type 1 (AT1) receptor blocker, losartan, enhances insulin sensitivity and thereby increases glucose tolerance in thermally injured rats. A 30% body surface area burn was induced by immersion of the dorsum into water with a temperature level of 95 degrees C for 15 s. Sham-burned rats were immersed in water with a temperature level of 23 degrees C. Losartan (30 mg/kg per day) or placebo (water) was given by gavage immediately after the burn injury and daily for 3 days postburn injury, resulting in sham-burned, burn placebo, and burn losartan groups. Plasma angiotensin II levels between burn placebo and sham-burned groups were not different 3 days after burn injury. However, losartan significantly increased plasma angiotensin II levels (P < 0.05), suggesting blockade of the AT1 receptor. An oral glucose tolerance test was performed 3 days postburn injury. There was an increase in the area under the curve for insulin and the glucose insulin index in burn placebo group as compared with sham-burned group, indicating insulin resistance. Losartan treatment abolished the insulin resistance in burn as evidenced by an area under the curve for insulin and glucose insulin index lower than that in the burn placebo group and similar to that in the sham-burned group. This suggests that insulin resistance and glucose intolerance associated with burn injury is, in part, caused by RAS.

ACE inhibitors and angiotensin receptor antagonists and the incidence of new-onset diabetes mellitus: an emerging theme

The prevalence of type 2 diabetes mellitus continues to rise. Given the associated co-morbidities of obesity, hypertension and cardiovascular disease, the rising incidence of diabetes has important health consequences and efforts to reduce this incidence are critical. Although lifestyle modifications, including weight loss and exercise, are instrumental in the prevention of diabetes, pharmacological therapies that reduce the incidence of diabetes have the significant potential to lower risk. The results of several large clinical trials have demonstrated that treatment with ACE inhibitors and angiotensin receptor antagonists (angiotensin receptor blockers; ARBs) may prevent or delay the onset of diabetes. These trials have demonstrated an approximately 15-30% reduction in the new onset of diabetes in those receiving ACE inhibitors and ARBs when compared with placebo or other active therapy. Although the exact mechanism underlying the effects are not entirely clear, multiple animal and human studies have demonstrated that the renin-angiotensin system plays an important role in glucose homeostasis. Although future prospective studies to clarify the role of ACE inhibitors and ARBs in preventing diabetes are ongoing, there is substantial existing evidence from completed trials that these agents may prevent the onset of diabetes.

Combination pharmacotherapy in hypertension

Combination pharmacotherapy with two or more drugs is required in order to reach the currently recommended blood pressure goals in the majority of hypertensive patients, particularly those with a goal of <130/80 mm Hg. Further to the potentiation of the antihypertensive effects, benefits of combination therapy include the potential of fewer adverse affects and of improvement of patients' compliance. Current guidelines recommend that combination pharmacotherapy might also be considered as initial treatment in patients with significant elevation of blood pressure and evidence of complications. Several effective and well-tolerated antihypertensive drug classes available today offer multiple options for combination therapy. The choice of antihypertensive agents should be made on the basis of current recommendations regarding first line drugs and compelling indications. Specific drug combinations might have additional beneficial or detrimental long-term metabolic effects, beyond their effects on blood pressure. However, more outcome data comparing antihypertensive drug combinations are required. The implementation of an intensive up-titration treatment strategy, together with a systematic use of full doses of multiple drug combinations, is expected to achieve optimal blood pressure control in the vast majority of hypertensive patients.

Carvedilol-induced antagonism of angiotensin II: a matter of alpha1-adrenoceptor blockade

OBJECTIVE

To investigate whether renin-angiotensin system blockade might underlie the favorable metabolic effects of the nonselective beta + alpha1-adrenoceptor blocker carvedilol as compared with the selective beta1-adrenoceptor blocker metoprolol.

METHODS

Human coronary microarteries (HCMAs), obtained from 32 heart valve donors, were mounted in myographs.

RESULTS

Angiotensin II and the alpha1-adrenoceptor agonist phenylephrine constricted HCMAs to maximally 63 +/- 10 and 46 +/- 15% of the contraction to 100 mmol/l K. Neither carvedilol, metoprolol, the nonselective beta-adrenoceptor antagonist propranolol, nor the alpha1-adrenoceptor antagonist prazosin affected the constrictor response to angiotensin II. alpha1-adrenoreceptors and beta-adrenoceptors are thus not involved in the direct constrictor effects of angiotensin II. When added to the organ bath at a subthreshold concentration, angiotensin II greatly amplified the response to phenylephrine. Both carvedilol and the angiotensin II type 1 (AT1) receptor antagonist irbesartan inhibited this angiotensin II-induced potentiation. Furthermore, carvedilol blocked the angiotensin II-induced amplification of phenylephrine-induced inositol phosphate accumulation in cardiomyocytes.

CONCLUSIONS

AT1-alpha1-receptor crosstalk, involving inositol phosphates, sensitizes HCMAs to alpha1-adrenoceptor agonists. Our results suggest that, in the presence of an increased sympathetic tone, carvedilol provides AT1 receptor blockade via its alpha1-adrenoceptor blocking effects. This could explain the favorable effects of carvedilol versus metoprolol.

Review Paper � CME. Insulin Resistance, Diabetes, Hypertension, and Renin?Angiotensin System Inhibition: Reducing Risk for Cardiovascular Disease

Insulin resistance, diabetes mellitus, and hypertension are associated with significant cardiovascular morbidity and mortality. Lifestyle modifications effectively decrease the risk of progression to diabetes in high-risk patients, but intensive interventions can be costly and difficult for patients to maintain. The addition of pharmacotherapy is often necessary to treat hyperglycemia and hypertension and lower the risk of cardiovascular complications. Clinical trial data suggest the use of insulin-sensitizing and antihyperglycemic agents to delay the progression to diabetes. Similarly, analysis of data from clinical trials of angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers indicate that the use of these agents results in fewer cases of new-onset diabetes among patients with hypertension, when compared with other antihypertensive agents. Angiotensin II has direct and indirect effects on insulin and its signaling pathways, providing support for the biologic mechanism underlying the benefits of renin-angiotensin system inhibition in preventing diabetes and cardiovascular events. Clinical trials now under way will further evaluate the role of renin-angiotensin system inhibition in preventing diabetes and its microvascular and macrovascular complications.

Telmisartan improves insulin sensitivity in nondiabetic patients with essential hypertension

Hypertension is a cardiovascular risk factor commonly associated with insulin resistance, the metabolic syndrome, and type 2 diabetes mellitus. Recent in vitro data indicate that certain angiotensin receptor antagonists, for example, telmisartan, activate peroxisome proliferator-activated receptor gamma (PPAR-gamma) and increase adiponectin protein content in adipocytes. By this means, they may improve insulin sensitivity in vivo. To investigate the effect of antihypertensive treatment on insulin sensitivity and fasting adiponectin serum levels, 37 nondiabetic patients with essential hypertension were randomized to receive telmisartan, the calcium channel blocker nisoldipine, or their combination for 6 weeks in a prospective, parallel group study. Fasting serum glucose, insulin, and adiponectin were evaluated before, 3 weeks (low dose), and 6 weeks (high dose) after initiation of treatment. Furthermore, the effect of telmisartan on PPAR-gamma receptor activity was investigated in vitro using a PPAR-gamma reporter gene assay. As reported previously, telmisartan significantly enhanced PPAR-gamma receptor activity in vitro. At baseline, a positive correlation between insulin serum levels and body mass index of investigated subjects was observed, whereas body mass index and serum adiponectin levels were negatively associated. High-dose treatment with telmisartan but not with nisoldipine reduced serum insulin levels as well as the homeostasis model assessment of insulin resistance, but did not affect serum adiponectin levels. In conclusion, in our study cohort of nondiabetic patients with essential hypertension, telmisartan improved insulin sensitivity by mechanisms apparently not involving adiponectin induction. Future studies will demonstrate whether these telmisartan-induced effects may contribute to a blood pressure-independent reduction in cardiovascular morbidity.

Molecular activation of PPARγ by angiotensin II type 1-receptor antagonists

OBJECTIVE AND DESIGN

Elevated blood pressure and insulin resistance are strongly associated in patients. We explored the potential for the anti-hypertensive angiotensin II type 1-receptor (ATR(1)) antagonists to improve insulin sensitivity through modulation of the nuclear receptor PPARgamma, in vitro and in vivo compared to the potent insulin sensitizer, rosiglitazone.

METHODS

PPARgamma modulation by ATR(1) antagonists was measured first by direct recruitment of PGC-1, followed by trans-activation reporter assays in cells, and promotion of adipogenesis in fibroblast and pre-adipocyte cell lines. Improvement of insulin sensitivity was measured as changes in levels of glucose, insulin, and adiponectin in ob/ob mice.

RESULTS

Telmisartan, candesartan, irbesartan, and losartan (but not valsartan or olmesartan) each served as bona fide PPARgamma ligands in vitro, with EC(50) values between 3 and 5 micro mol/l. However, only telmisartan, and to a lesser extent candesartan, resulted in significant PPARgamma agonism in cells. In vivo, although rosiglitazone significantly lowered both glucose (33%, p<0.01) and insulin (61%, p<0.01) levels and increased expression of adiponectin (74%, p<0.001), sartan treatment had no effect.

CONCLUSIONS

Many members of the sartan family of ATR(1) antagonists are PPARgamma ligands in cell-free assays but their modulation of PPARgamma in cells is relatively weak. Furthermore, none appear to improve insulin sensitivity in a rodent model under conditions where other insulin sensitizers, including rosiglitazone, do. These results question whether reported effects of sartans on insulin sensitivity may be through other means, and should guide further efforts to develop dual agents to treat hypertension and insulin resistance.

Drug interactions of clinical importance with antihyperglycaemic agents: an update

Because management of type 2 diabetes mellitus usually involves combined pharmacological therapy to obtain adequate glucose control and treatment of concurrent pathologies (especially dyslipidaemia and arterial hypertension), drug-drug interactions must be carefully considered with antihyperglycaemic drugs. Additive glucose-lowering effects have been extensively reported when combining sulphonylureas (or the new insulin secretagogues, meglitinide derivatives, i.e. nateglinide and repaglinide) with metformin, sulphonylureas (or meglitinide derivatives) with thiazolidinediones (also called glitazones) and the biguanide compound metformin with thiazolidinediones. Interest in combining alpha-glucosidase inhibitors with either sulphonylureas (or meglitinide derivatives), metformin or thiazolidinediones has also been demonstrated. These combinations result in lower glycosylated haemoglobin (HbA(1c)), fasting glucose and postprandial glucose levels than with either monotherapy. Even if modest pharmacokinetic interferences have been reported with some combinations, they do not appear to have important clinical consequences. No significant adverse effects, except a higher risk of hypoglycaemic episodes that may be attributed to better glycaemic control, occur with any combination. Challenging the classical dual therapy with sulphonylurea plus metformin, there is a recent trend to use alternative dual combinations (sulphonylurea plus thiazolidinedione or metformin plus thiazolidinedione). In addition, triple therapy with the addition of a thiazolidinedione to the metformin-sulphonylurea combination has been recently evaluated and allows glucose targets to be reached before insulin therapy is considered. This triple therapy appears to be safe, with no deleterious drug-drug interactions being reported so far.Potential interferences may also occur between glucose-lowering agents and other drugs, and such drug-drug interactions may have important clinical implications. Relevant pharmacological agents are those that are widely coadministered in diabetic patients (e.g. lipid-lowering agents, antihypertensive agents); those that have a narrow efficacy/toxicity ratio (e.g. digoxin, warfarin); or those that are known to induce (rifampicin [rifampin]) or inhibit (fluconazole) the cytochrome P450 (CYP) system. Metformin is currently a key compound in the pharmacological management of type 2 diabetes, used either alone or in combination with other antihyperglycaemics. There are no clinically relevant metabolic interactions with metformin, because this compound is not metabolised and does not inhibit the metabolism of other drugs. In contrast, sulphonylureas, meglitinide derivatives and thiazolidinediones are extensively metabolised in the liver via the CYP system and thus, may be subject to drug-drug metabolic interactions. Many HMG-CoA reductase inhibitors (statins) are also metabolised via the CYP system. Even if modest pharmacokinetic interactions may occur, it is not clear whether drug-drug interactions between oral antihyperglycaemic agents and statins may have clinical consequences regarding both efficacy and safety. In contrast, a marked pharmacokinetic interference has been reported between gemfibrozil and repaglinide and, to a lesser extent, between gemfibrozil and rosiglitazone. This leads to a drastic increase in plasma concentrations of each antihyperglycaemic agent when they are coadministered with the fibric acid derivative, and an increased risk of adverse effects. Some antihypertensive agents may favour hypoglycaemic episodes when co-prescribed with sulphonylureas or meglitinide derivatives, especially ACE inhibitors, but this effect seems to result from a pharmacodynamic drug-drug interaction rather than from a pharmacokinetic drug-drug interaction. No, or only modest, interferences have been described with glucose-lowering agents and other pharmacological compounds such as digoxin or warfarin. The effects of inducers or inhibitors of CYP isoenzymes on the metabolism and pharmacokinetics of the glucose-lowering agents of each pharmacological class has been tested. Significantly increased (with CYP inhibitors) or decreased (with CYP inducers) plasma levels of sulphonylureas, meglitinide derivatives and thiazolidinediones have been reported in healthy volunteers, and these pharmacokinetic changes may lead to enhanced or reduced glucose-lowering action, and thus hypoglycaemia or worsening of metabolic control, respectively. In addition, some case reports have evidenced potential drug-drug interactions with various antihyperglycaemic agents that are usually associated with a higher risk of hypoglycaemia.

The metabolic syndrome and endothelial dysfunction: common highway to type 2 diabetes and CVD

Due to global lifestyle changes, obesity (the main driver of type 2 diabetes and cardiovascular disease ) is reaching pandemic proportions. The metabolic syndrome, which is regarded as a prediabetic state, is characterized by a concurrence of interrelated cardiovascular risk factors, including abdominal obesity, insulin resistance, hypertension, dyslipidemia, and glucose intolerance. Endothelial dysfunction (ED) is common in the metabolic syndrome and is associated with increased risk for T2D and CVD. This review focuses on the mechanisms linking ED to the metabolic syndrome, T2D, and CVD, and the possible therapies that may improve ED and reduce T2D and CVD risk.

The metabolic syndrome: evolving evidence that thiazolidinediones provide rational therapy

The metabolic syndrome, also known as the dysmetabolic syndrome, syndrome X or the insulin resistance syndrome, refers to the clustering of cardiovascular disease risk factors that are present in many individuals who are at increased risk for both cardiovascular events and type 2 diabetes. Prediabetic subjects typically exhibit an atherogenic pattern of cardiovascular risks that is associated with hyperinsulinaemia. Thus, identification of components of the metabolic syndrome is important if patients are to be treated early enough to prevent cardiovascular events and other complications related to diabetes. Therapies targeted to specific components of the metabolic syndrome such as improving glycaemic control, managing dyslipidaemia and reducing the prothrombotic state should help to minimize cardiovascular risk, particularly if initiated early. Traditional pharmacologic agents used to manage the individual components of the metabolic syndrome do not typically impact the other components. The thiazolidinediones, a new class of agents that improve insulin resistance, have the ability, in addition to their glucose-lowering effects, to exert several powerful anti-atherogenic properties, including anti-inflammatory effects in the vascular endothelium, redistribution of visceral fat and reduction of insulin resistance, hyperinsulinaemia and hyperproinsulinaemia. This makes the thiazolidinediones ideal candidates for the early treatment of many components associated with the metabolic syndrome.

Involvement of the Pancreatic Renin-Angiotensin System in Insulin Resistance and the Metabolic Syndrome

The cardiometabolic syndrome consists of several major components: hypertension, hyperinsulinemia, hyperlipidemia, and hyperglycemia. Central to this syndrome are insulin resistance and generation of reactive oxygen species; these features are particularly prominent in patients with type 2 diabetes mellitus. In this context, large clinical trials have shown that blockade of the renin-angiotensin system (RAS) is protective against type 2 diabetes. In spite of these solid clinical data, the mechanistic pathways by which RAS blockade achieves these protective effects have yet to be resolved. A recently identified local pancreatic islet RAS has, however, been implicated in this regard. Furthermore, RAS blockade was recently shown to enhance islet blood flow, oxygen tension, and insulin biosynthesis, thus improving beta-cell function and glucose tolerance. Meanwhile, RAS activation may also influence islet cell inflammatory responses, apoptosis, fibrosis, and superoxide anion production. This RAS-associated oxidative stress can induce islet cell dysfunction in the pancreas and insulin resistance in peripheral tissues.

Effect of antihypertensive agents on the development of type 2 diabetes mellitus

People with hypertension have a high prevalence of insulin resistance and are at relatively high risk of developing type 2 diabetes mellitus. It is becoming increasingly evident that antihypertensive agents have disparate metabolic effects. For example, recent clinical trials indicate that agents that interrupt the renin-angiotensin axis reduce the risk of developing diabetes compared with other classes of antihypertensive agents. Blockade of the effects of angiotensin II might improve blood flow to insulin-sensitive tissues. Furthermore, interruption of the renin-angiotensin system might provide metabolic benefit through such mechanisms as reduced oxidative stress and restored nitric oxide production, which could lead to improved insulin signaling. Alternatively, collective trials suggest that both diuretics and beta-blockers accelerate the appearance of new-onset type 2 diabetes mellitus in patients with hypertension. Therefore, the risk of new-onset diabetes-associated cardiovascular risks should be factored into future treatment recommendations for patients who require antihypertensive therapy. This will become even more important as the number of insulin-resistant patients with hypertension increases in parallel with the steady growth in the number of sedentary, obese, and aged persons in our population.

Diabetes prevention: is there more to it than lifestyle changes?

Over the past years, there has been an explosive increase in the prevalence of type 2 diabetes (T2DM) and this is expected to continue, entailing associated morbidity and mortality. An increasing number of studies explore the different ways T2DM could be prevented. On-going lifestyle modifications need to be addressed. High-risk patients should be given counselling on weight loss, possibly using a low glycaemic index diet, with a target of around 7-10% over 6-12 months, as well as instruction for increasing physical activity to around 150 min of physical exercise weekly (NNT = 4-8). Moderate alcohol consumption and coffee consumption may also be of benefit (NNT = 89 and 66, respectively). Metformin (NNT = 14), acarbose (NNT = 11) and troglitazone (NNT = 6) have been shown to prevent/delay T2DM and angiotensin-converting enzyme (ACE) inhibitors and statins appear to have an adjunctive role (NNT = 42 and 112, respectively). Trials with orlistat and bariatric surgery have also prevented T2DM (NNT = 36 and 6, respectively), and forthcoming treatment with GLP1 mimetics appears promising. Diabetes prevention studies should help create well-defined strategies for screening and treating high-risk populations in the real world, as prevention is our only chance to alleviate the ever growing burden of diabetes mellitus in the world.

Nutritive blood flow as an essential element supporting muscle anabolism

PURPOSE OF REVIEW

Much of the recent literature concerning hormonal effects on muscle assumes that full perfusion occurs at all times such that nutrient and hormone delivery is complete. New methods to measure the extent of nutritive blood flow in muscle show that this is not the case and that anabolic hormones such as insulin increase nutritive flow and that other agents that increase bulk flow have little effect. This review examines the latest developments concerning insulin action to increase nutritive perfusion of muscle and agents that interact with this effect and which could potentially modulate anabolism.

RECENT FINDINGS

We examine recent attempts to define the anatomical nature of non-nutritive flow route in muscle, the quick onset of insulin action to recruit nutritive blood flow at doses lower than that which activates glucose uptake and bulk blood flow, actions of the inflammatory cytokine tumour necrosis factor alpha TNFalpha to oppose physiologic insulin action, interfibrillar fat depots that grow on the non-nutritive vasculature of muscle and underpin a 'vascrine hypothesis', and drugs that reduce insulin resistance by ameliorating vascular dysfunction.

SUMMARY

Recognition that nutrient and hormone delivery to muscle is controlled by microvascular perfusion and not necessarily by bulk blood flow is the key issue.

Angiotensin II antagonists: clinical experience in the treatment of hypertension, prevention of cardiovascular outcomes and renal protection in diabetic nephropathy and proteinuria

Angiotensin II antagonists (AIIAs) were introduced to treat hypertension about 10 years ago. During this period they were evaluated not only in terms of efficacy and safety but also in several large studies with clinical outcomes. They are efficacious in all clinical forms of hypertension and are effective also in all ethnic groups. Cardiovascular and renal protection in proteinuric diabetic nephropathy beyond blood pressure reduction was proved in major clinical studies: Losartan Intervention For Endpoint reduction in hypertension study (LIFE), Reduction of Endpoint in Non-Insulin dependent Diabetes Mellitus with the AII Antagonist Losartan (RENAAL) and Irbesartan Type 2 Diabetic Nephropathy Trial (IDNT). Their blood pressure independent protective effect is also mentioned by the blockade of AT1 receptor. As a class AIIs have a tolerability profile similar to placebo.

Cardioprotective effects of rosiglitazone are associated with selective overexpression of type 2 angiotensin receptors and inhibition of p42/44 MAPK

Current evidence points to renin-angiotensin system as a key mediator in ischemia-reperfusion injury. Rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand, has recently been shown to confer cardioprotection against ischemia-reperfusion in animal models. We sought to examine the expression of ANG II receptors during PPAR-gamma-mediated cardioprotection. Male Sprague-Dawley rats (nondiabetic) were fed either regular rat chow (control diet group, n = 9) or rosiglitazone-rich diet (rosiglitazone-rich diet group, n = 9) and were subjected to 1 h of myocardial ischemia followed by 1 h of reperfusion. A third group of rats had only thoracotomy and pericardiotomy and served as a sham control group (n = 9). Hemodynamics, infarct size, and expression of ANG II type 1 and type 2 receptors (AT1 and AT2) were measured in all groups. There was a 58% reduction of infarct size in the rosiglitazone-rich diet group (P < 0.01 vs. control diet group). Increased myocardial expression of AT(1) receptors in the ischemic-reperfused myocardium was attenuated in the rosiglitazone-rich diet group (P < 0.05 vs. control diet group). Importantly, myocardial AT2 mRNA and protein expression were significantly increased (by >100-fold) in the rosiglitazone-rich diet group (P < 0.05). These changes were accompanied by inhibition of p42/44 MAPK in the rosiglitazone-rich diet group, while the Akt1 expression, believed to mediate insulin sensitization, remained similar in all three groups. The cardioprotective effects of rosiglitazone against myocardial ischemia-reperfusion injury are independent of its insulin-sensitizing properties and are associated with significant overexpression of AT2 receptors along with inhibition of p42/44 MAPK.

New-onset diabetes and antihypertensive drugs

Observational studies have provided evidence that a consistent fraction (approximately 15-20%) of hypertensive patients displays a glucose intolerance state that may be aggravated by antihypertensive drug regimens based on thiazide diuretics or beta-blockers. This review examines the relative and absolute diabetogenic effects of antihypertensive drugs, by comparing the impact of 'new' (calcium antagonists, angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists) versus 'old' (diuretics and beta-blockers) drugs on new-onset diabetes in recent clinical trials. Evidence is provided that compared with diuretics and beta-blockers, new-onset diabetes is less common with 'new' drugs, and that conventional antihypertensive compounds, particularly when combined together, may amplify the natural time-dependent tendency towards the development of this metabolic disease. This paper provides new insights into the potential mechanisms responsible for the phenomenon and the clinical significance of antihypertensive drug-induced diabetes.

The multi-faceted cross-talk between the insulin and angiotensin II signaling systems

Insulin and angiotensin II are hormones that play pivotal roles in the control of two vital and closely related systems, the metabolic and the circulatory systems, respectively. A failure in the proper action of each of these hormones results, to a variable degree, in the development of two highly prevalent and commonly overlapping diseases-diabetes mellitus and hypertension. In recent years, a series of studies has revealed a tight connection between the signal transduction pathways that mediate insulin and angiotensin II actions in target tissues. This molecular cross-talk occurs at multiple levels and plays an important role in phenomena that range from the action of anti-hypertensive drugs to cardiac hypertrophy and energy acquisition by the heart. At the extracellular level, the angiotensin-converting enzyme controls angiotensin II synthesis but also interferes with insulin signaling through the proper regulation of angiotensin II and through the accumulation of bradykinin. At an early intracellular level, angiotensin II, acting through JAK-2/IRS-1/PI3-kinase, JNK and ERK, may induce the serine phosphorylation and inhibition of key elements of the insulin-signaling pathway. Finally, by inducing the expression of the regulatory protein SOCS-3, angiotensin II may impose a late control on the insulin signal. This review will focus on the main advances obtained in this field and will discuss the implications of this molecular cross-talk in the common clinical association between diabetes mellitus and hypertension.

Obesity and the renin- angiotensin-aldosterone system

The renin-angiotensin-aldosterone system (RAAS) is a key regulator of cardiovascular function. RAAS activity is upregulated in obesity despite concurrent renal sodium retention, which is a hallmark and principle determinant of obesity-associated hypertension. The contribution of adipose tissue to increased angiotensinogen and aldosterone plasma levels in obesity is probably due to the secretion of angiotensinogen and, as yet, unidentified aldosterone secretagogues by adipocytes. Increased circulating renin activity, on the other hand, is probably due to increased sympathetic activity in the obese. Modest weight reduction significantly reduces RAAS activity by uncertain mechanisms. Pharmacological blockade of the RAAS yielded promising results, both with regard to cardiovascular function and metabolic complications of obesity. These studies suggest that the activated RAAS is a prime pharmacological target for reducing the cardiometabolic risk in obese patients.

Angiotensin II antagonists--therapeutic benefits spanning the cardiovascular disease continuum from hypertension to heart failure and diabetic nephropathy

BACKGROUND

The cardiovascular benefits of angiotensin II antagonists (AIIAs) have been evaluated not only in terms of their ability to lower blood pressure but also on their ability to prevent strokes, cardiac events, and target organ damage. This review summarizes the body of evidence-based data demonstrating the efficacy of AIIAs across the spectrum of cardiovascular disease.

METHODS

A PubMed/MEDLINE search of English-language articles (1990 to September 2005) was used to identify articles describing clinical studies, particularly outcome trials, or mechanisms of therapeutic action pertinent to the therapy of cardiovascular disease or nephropathy.

FINDINGS

The antihypertensive efficacy of AIIAs is apparent across a wide spectrum of hypertensive patients, including black and Asian patients and patients with isolated systolic hypertension. More importantly, large outcome-based studies have demonstrated the efficacy of AIIAs across the continuum of cardiovascular disease, including hypertension, heart failure, post-myocardial infarction, and diabetic nephropathy. The Losartan Intervention For Endpoint reduction in hypertension study (LIFE), Reduction of Endpoints in Non-insulin-dependent Diabetes Mellitus with the AII Antagonist Losartan (RENAAL), and the Irbesartan Type 2 Diabetic Nephropathy Trial (IDNT) indicate that AIIAs confer cardiovascular and renal protective effects beyond their ability to lower blood pressure. These bloodpressure independent protective benefits of AIIAs may arise not only by blocking the deleterious effects of AII mediated via the AT1-receptor but may also be due to beneficial molecule-specific effects. As a class, AIIAs are well tolerated with an overall adverse event profile generally comparable to placebo and superior to that typically seen with calcium channel blockers, ACE inhibitors, diuretics, and beta-blockers.

CONCLUSIONS

By utilizing the body of clinical trial evidence as a guide to rational prescribing of AIIAs, practitioners can expect to deliver clinical benefits to their patients in terms of survival, prognosis, and quality of life.

Did a reform strategy in drug management improve doctors’ prescribing habits in Montenegro: The example for the cardiovascular drugs

Background/Aim. A comprehensive reform strategy in drug management has been applying for a few years in Montenegro in order to promote a rational use of drugs. The reform strategy covered: an information system named ?The Control of Distribution and Use of Drugs?, a new List of Essential Drugs (that are reimbursed by the Republic Fund for Health), legislative and regulatory measures in order to establish a better control of drug prescribing and more efficient processing of the prescriptions. The aim of this study was to evaluate the effects of the reform strategy on the doctors' prescribing habits and the subsequent use of cardiovascular drugs within the outpatient setting of Montenegro. Methods. A retrospective-prospective pharmacoepidemiologic study included a sample of 100% of cardiovascular drugs that were taken with prescription from state pharmacies during 2000 and 2004. The results were presented by the number of defined daily doses (DDD) per 1000 inhabitants per day. All the drugs were classified according to the uniform anatomical-therapeutic-chemical (ATC) classification of the drugs. The Wilcoxon test for matched pairs was used in order to calculate the significance of difference in cardiovascular drugs utilization before and after the introduction of new measures. Results. Although prescribing and the resulting outpatient use of cardiovascular drugs (ATC group C) that were reimbursed by the Republic Fund for Health was increased approximately by 13% in 2004 in comparison with 2000 (67.98 vs. 60.17 DDD/1000 inh./day), we did not find a statistically significant difference (p > 0.05). Prescribing of ACE inhibitors (C09A) increased approximately by 45% during the investigated period (15.30 vs. 22.17 DDD/1000 inh./day). The selection of drugs was also altered: cilazapril, ramipril and quinapril were left out, captopril and enalapril were more prescribed, and a newly-included fosinopril was prescribed mostly (31.5%). Calcium-channel blockers (C08) were prescribed 33.7% more (7.12 vs. 9.52 DDD/1000 inh./day), mostly because of seven times higher prescribing of amlodipine in 2004. Pentaerythritol tetranitrate was left out, but isosorbide dinitrate and isosorbide mononitrate were prescribed more frequently. High-priced atorvastatin was replaced with the older simvastatin, that was prescribed three times more. Conclusion. The reform strategy in drug management mostly improved the doctors' prescribing habits and the subsequent use of cardiovascular drugs within the outpatient setting. For the most part, the noticed changes were in accordance with the actual recommendations, but some cases need additional measures. Regulatory policy, however, could not compensate for the continual education of doctors that prescribe drugs.

Review article: the metabolic syndrome and non-alcoholic fatty liver disease

Metabolic syndrome represents a common risk factor for premature cardiovascular disease and cancer whose core cluster includes diabetes, hypertension, dyslipidaemia and obesity. The liver is a target organ in metabolic syndrome patients in which it manifests itself with non-alcoholic fatty liver disease spanning steatosis through hepatocellular carcinoma via steatohepatitis and cirrhosis. Given that metabolic syndrome and non-alcoholic fatty liver disease affect the same insulin-resistant patients, not unexpectedly, there are amazing similarities between metabolic syndrome and non-alcoholic fatty liver disease in terms of prevalence, pathogenesis, clinical features and outcome. The available drug weaponry for metabolic syndrome includes aspirin, metformin, peroxisome proliferator-activated receptor agonists, statins, ACE (angiotensin I-converting enzyme) inhibitors and sartans, which are potentially or clinically useful also to the non-alcoholic fatty liver disease patient. Studies are needed to highlight the grey areas in this topic. Issues to be addressed include: diagnostic criteria for metabolic syndrome; nomenclature of non-alcoholic fatty liver disease; enlargement of the clinical spectrum and characterization of the prognosis of insulin resistance-related diseases; evaluation of the most specific clinical predictors of metabolic syndrome/non-alcoholic fatty liver disease and assessment of their variability over the time; characterization of the importance of new risk factors for metabolic syndrome with regard to the development and progression of non-alcoholic fatty liver disease.

Role of insulin-sensitizing property of telmisartan, a commercially available angiotensin II type 1 receptor blocker in preventing the development of atrial fibrillation

Atrial fibrillation (Af) is the most common disorder of cardiac rhythm and is responsible for substantial morbidity and mortality in the general population. A recent community-based observational study revealed that diabetes and hypertension were associated with the development of Af. Since there is no definite evidence to show that type 1 diabetes is at increased risk for the development of Af, insulin resistance rather than hyperglycemia per se could explain the link between diabetes and Af. Several clinical trials suggest that the renin-angiotensin system (RAS) plays a pivotal role in the pathogenesis of insulin resistance. Indeed, interruption of the RAS with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II type 1 receptor blockers (ARBs) has been shown to prevent the onset of diabetes in hypertensive patients. Further, several experimental and clinical studies showed the beneficial role for the inhibition of the RAS in preventing Af as well. However, to what extent the insulin-sensitizing effects of ARBs could account for the prevention of Af remains to be clarified. Recently, telmisartan, an ARB, was found to act as a partial agonist of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma influences the gene expression involved in carbohydrate metabolism. In animal study, telmisartan administration caused a significant attenuation of weight gain and reduced glucose, insulin, and triglyceride levels in rats fed a high-fat, high-carbohydrate diet, compared with treatments of losartan, another type of ARB. Furthermore, recently, some clinical papers also reported the insulin-sensitizing effects of telmisartan in hypertensive patients. In this paper, we would like to propose the possible ways of clarifying to what extent the insulin-sensitizing effects of ARBs could account for the prevention of Af. (1) Does telmisartan reduce the development of Af in insulin resistant hypertensive patients? (2) When adjusted for blood pressure, is the effect of telmisartan superior to other ARBs? (3) Does this beneficial effect of telmisartan correlate to its insulin-sensitizing properties? Ongoing clinical trial (ONTARGET) has been designed the efficacy of telmisartan with an ACEI, ramipril, alone or in combination. This randomized, double-blind, multicenter international studies will provide further information whether telmisartan can improve insulin resistance and subsequently reduce the development of Af in high-risk hypertensive patients.

The impact of ACE inhibitors or angiotensin II type 1 receptor blockers on the development of new-onset type 2 diabetes

OBJECTIVE

Angiotensin II has been shown to increase hepatic glucose production and decrease insulin sensitivity. Patients who utilize either an ACE inhibitor (ACEI) or angiotensin receptor blocker (ARB) may experience a decreased incidence of new-onset type 2 diabetes.

RESEARCH DESIGN AND METHODS

Three reviewers conducted a systematic literature search of Medline, EMBASE, CINAHL, and the Cochrane Library (1966 to present) to extract a consensus of trial data involving an ACEI or ARB with an end point of new-onset type 2 diabetes. Studies were included if they were randomized controlled trials verses placebo/routine therapy. A random-effects model was utilized. Subgroup and sensitivity analyses were conducted.

RESULTS

Eleven trials were identified, including 66,608 patients. An ACEI or ARB prevented new-onset type 2 diabetes (odds ratio 0.78 [95% CI 0.73-0.83]). The influence of either an ACEI (six trials) or an ARB (five trials) alone on new-onset type 2 diabetes was similar (0.79 [0.71-0.89] and 0.76 [0.70-0.82], respectively). Regardless of indication for use, hypertension (seven trials), coronary artery disease (two trials), or heart failure (two trials), reductions in new-onset type 2 diabetes were maintained (0.79 [0.72-0.85], 0.76 [0.60-0.95], and 0.70 [0.50-0.96], respectively). No statistical heterogeneity was observed for any evaluation (P > 0.1 for all comparisons). ACEIs and ARBs did not reduce the odds of mortality, cardiovascular, or cerebrovascular events versus control therapy among all of these studies combined or the hypertension trials. ACEIs and ARBs did reduce the odds of these outcomes among the coronary artery disease studies versus control therapy.

CONCLUSIONS

ACEIs or ARBs may decrease patients' odds of developing new-onset type 2 diabetes but does not reduce the odds of mortality, cardiovascular, or cerebrovascular outcomes over the study follow-up periods among patients with hypertension.

PPARγ-Activating Angiotensin Type-1 Receptor Blockers Induce Adiponectin

The adipose-specific protein adiponectin has been recently discovered to improve insulin sensitivity. Angiotensin type-1 receptor (AT1R) blockers (ARBs) reduce the incidence of type 2 diabetes mellitus by mostly unknown molecular mechanisms. To identify new antidiabetic mechanisms of ARBs, we studied the regulation of adiponectin by angiotensin II (Ang II) and different ARBs in murine 3T3-L1 adipocytes and obese Zucker rats. Adiponectin protein expression was markedly stimulated by Ang II (5 nmol/L), which was inhibited by blockade of the AT2R, and further enhanced by the ARB irbesartan. Irbesartan-mediated adiponectin upregulation started beyond the concentrations needed for AT1R blockade and was also present in the absence of Ang II, implicating an AT1R-independent mechanism of action. Recently, certain ARBs (irbesartan, telmisartan) were identified as ligands of the peroxisome proliferator-activated receptor (PPAR)γ. Telmisartan also stimulated adiponectin protein expression, whereas the non-PPARγ-activating ARB eprosartan had no effect. Blockade of PPARγ activation by the PPARγ antagonist GW9662 markedly inhibited irbesartan-induced adiponectin expression. Cognate mRNA levels of adiponectin were not affected by ARBs. Kinetic studies using the protein synthesis inhibitor cycloheximide showed that irbesartan prevented the cellular depletion of adiponectin protein. Finally, administration of irbesartan to obese Zucker rats improved insulin sensitivity and attenuated adiponectin serum depletion. The present study demonstrates that AT2R activation and certain ARBs induce adiponectin in adipocytes, which was associated with an improvement of parameters of insulin sensitivity in vivo. ARB-induced adiponectin stimulation is likely to be mediated via PPARγ activation involving a post-transcriptional mechanism.

Detection and treatment of hypertension in general health-care practice: a patient-based study

The aim of this study was to describe the pattern of blood pressure (BP) distribution in a multiethnic primary care practice in relation to sociodemographic characteristics, lifestyle and risk factors. Another aim was to analyse the quality of diagnosis and effectiveness of hypertension (HT) treatment. In all, 470 adult patients (> or =16 years old) who visited the Jordbro Health Centre (JHC), Haninge Municipality, participated in this study. A general questionnaire with questions about sociodemographic characteristics, lifestyle, health status and chronic disease was used. Medical records: information on consultations with the general practitioner and prescriptions were collected from the medical records for the year 2001. Furthermore, a medical examination was performed: this consisted of weight, height, systolic (SBP) and diastolic (DBP) blood pressure, and laboratory analyses including fasting blood glucose, serum cholesterol, serum triglycerides, electrocardiogram and spirometry. Out of 464 patients, 114 (24.6%) reported HT. Among the HT patients, 93 (81.6%) had SBP > or =140 mmHg and 52 (45.6%) DBP > or =90 mmHg. Among the nonhypertensive patients (n=350), 120 (34.3%) had SBP > or =140 mmHg and 50 (14.3%) DBP > or =90 mmHg. Furthermore, there are some patients with high BP who are unknown or undetected. HT treatment among this population is unsatisfactory and greater efforts are required to identify people with high BP and to ensure that they are managed according to the best available evidence.

Neointimal hyperplasia and vascular endothelial growth factor expression are increased in normoglycemic, insulin resistant, obese fatty rats

OBJECTIVE

Insulin resistance is associated with a constellation of factors that enhance the artherosclerotic process. Vessel injury results in the formation of a markedly increased neointima in type 2 diabetes. Increased neointimal hyperplasia (NH) and vascular endothelial growth factor (VEGF) expression may lead to restenosis post angioplasty. We studied NH and VEGF expression in an obese, insulin resistant, but normoglycemic rat model, after carotid balloon injury.

METHODS AND RESULTS

Diabetic rats (ZDF, n=10), normoglycemic, insulin-resistant rats (ZDF-normoglycemic, n=6) as well as Zucker fatty rats (FZ, n=6), and lean Zucker rats (LZ, n=6), all 13-16 weeks old, were subjected to right carotid injury by an angioplasty catheter introduced via the femoral artery. Three weeks later the rats were sacrificed and serum and carotids obtained. The intima-media ratio (I/M) was then calculated. ZDF-normoglycemic, FZ and ZDF-diabetic rats were all hyperinsulinemic and hypertriglyceridemic when compared to LZ rats. ZDF diabetic rats were hyperglycemic while FZ, ZDF-normoglycemic and LZ rats were normoglycemic. The I/M ratio for ZDF and FZ rats were significantly greater than for LZ rats. The VEGF expression was significantly greater in ZDF and FZ rats than LZ rats.

CONCLUSIONS

In conclusion, insulin resistance increases neointimal hyperplasia and VEGF expression even with normoglycemia, after carotid angioplasty in rats.

The metabolic syndrome

The metabolic syndrome is a common metabolic disorder that results from the increasing prevalence of obesity. The disorder is defined in various ways, but in the near future a new definition(s) will be applicable worldwide. The pathophysiology seems to be largely attributable to insulin resistance with excessive flux of fatty acids implicated. A proinflammatory state probably contributes to the syndrome. The increased risk for type 2 diabetes and cardiovascular disease demands therapeutic attention for those at high risk. The fundamental approach is weight reduction and increased physical activity; however, drug treatment could be appropriate for diabetes and cardiovascular disease risk reduction.

Insulin Response to Oral Glucose Loading and Coronary Artery Disease in Nondiabetics

Hyperinsulinemia is related to coronary artery disease (CAD), as an indication of decreased insulin sensitivity. Although there are many studies showing the relation between fasting insulin levels and insulin resistance, there are fewer studies on postprandial insulin levels. The aim of the present study was to investigate the relationship between postprandial insulin levels and CAD and its extent in our patients. For this purpose, oral glucose tolerance testing was performed in 222 patients with no known diabetes and who were scheduled to undergo diagnostic coronary angiography. The patients were first separated into two groups, one group (group I) having an insulin response within reference values to oral glucose loading, and the other group (group II) with a higher than normal insulin response. The presence and extent of CAD in the two groups were compared. While 65% of the patients in group 1 had CAD, this rate increased to 79% in group 2 patients (P = 0.02). The mean vessel scores were 0.92 +/- 0.78 in group 1 and 1.67 +/- 0.99 (P < 0.0001) in group 2 patients. The stenosis scores were 2.192 +/- 2.077 in group 1 and 5.588 +/- 3.519 (P < 0.001) in group 2, while the extent scores were 1.230 +/- 1.292 in group 1 and 2.729 +/- 1.847 in group 2 (P < 0.0001). The differences between the two groups were significant. Postprandial insulin values were positively correlated with CAD (P = 0.001, r = 0.214), vessel scores (P < 0.0001, r = 0.326), stenosis scores (P < 0.0001, r = 0.261), and extent scores (P < 0.0001, r = 0.419). Logistic regression analysis revealed hyperinsulinemia increased CAD independent from the other risk factors (OR = 5.742, CI 95%: 1.809-18.227, P = 0.003).

Renin-angiotensin system inhibition prevents type 2 diabetes mellitus

The inhibition of the renin-angiotensin system (RAS) with either angiotensin converting enzyme inhibitors (ACEIs) or AT1 angiotensin receptor blockers (ARBs) consistently and significantly reduces the incidence of type 2 diabetes in patients with hypertension or congestive heart failure. The mechanisms underlying this protective effect appear to be complex and may involve an improvement of both insulin sensitivity and insulin secretion. These two effects may result, at least in part, from the well known effects of these pharmacological agents on the vascular system on the one hand, on the ionic balance on the other hand. Indeed, the vasodilation induced by ACEIs or ARBs could improve the blood circulation in skeletal muscles, thus favouring peripheral insulin action, but also in the pancreas, thus promoting insulin secretion. Preserving cellular potassium and magnesium pools by blocking the aldosterone effects could also improve both cellular insulin action and insulin secretion. However, besides these classical effects, new mechanisms have been recently suggested. A direct effect of the inhibition of angiotensin and/or of the enhancement of bradykinin on various steps of the insulin cascade signalling has been described as well an increase in GLUT4 glucose transporters after RAS inhibition. Furthermore, it has been demonstrated that angiotensin II inhibits adipogenic differentiation of human adipocytes via A1 receptors and, therefore, it has been hypothesised that RAS blockade may prevent diabetes by promoting the recruitment and differentiation of adipocytes. Finally, some lipophilic ARBs appear to induce PPAR-gamma activity in the adipose tissue. Hence, the protection against type 2 diabetes observed after RAS inhibition may be partially linked to a thiazolidinedione-like effect. In conclusion, numerous physiological and biochemical mechanisms could explain the protective effect of RAS inhibition against the development of type 2 diabetes in individuals with arterial hypertension or congestive heart failure. What might be the main mechanism in the overall protection effect of ACEIs or ARBs remains an open question.

Renin-angiotensin system inhibition prevents type 2 diabetes mellitus

Most individuals with arterial hypertension or congestive heart failure are insulin-resistant and at a higher risk of developing type 2 diabetes (T2DM). The inhibition of the renin-angiotensin system (RAS), using an angiotensin converting enzyme inhibitor (ACEI) or a selective angiotensin receptor AT1 blocker (ARB), may exert favourable metabolic effects capable of preventing T2DM in high risk individuals. We performed a meta-analysis of randomised clinical trials (RCTs) assessing the effects of RAS inhibition on the incidence of new cases of T2DM in patients with arterial hypertension or congestive heart failure. Ten RCTs with cardiovascular prognosis as primary endpoints analysed the incidence of T2DM as secondary endpoints or as post-hoc analysis after a mean follow-up of 1 to 6 years: five with an ACEI and five with an ARB, compared with a placebo (n=4) or a reference drug (beta-blocker or diuretic: n=5; amlodipine: n=2). Eight RCTs concerned hypertensive patients: STOP Hypertension-2 (lisinopril or enalapril vs beta-blocker or diuretic), CAPPP (captopril vs thiazide or beta-blocker), HOPE (ramipril vs placebo), ALLHAT (lisinopril vs chlorthalidone and lisinopril vs amlodipine), LIFE (losartan vs atenolol), SCOPE (candesartan vs placebo), ALPINE (candesartan vs placebo) and VALUE (valsartan vs amlodipine). Two RCTs concerned patients with congestive heart failure: SOLVD (enalapril vs placebo) and CHARM-overall programme (candesartan vs placebo). Overall, 2 675 new cases of T2DM (7.40%) were observed in the group of 36 167 patients receiving a treatment with ACEI or ARA as compared with 3 842 events (9.63%) in the group of 39 902 control patients. A mean weighed relative risk reduction of new T2DM of 22% (95% CI: 18, 26; p<0.00001) was observed after RAS inhibition. The beneficial effect was similar with ACEIs and with ARBs as well as in patients with hypertension and in those with heart failure, and was also present whatever the comparator (placebo or beta-blockers/diuretics or amlodipine). The number needed-to-treat to avoid one new case of T2DM averaged 45 patients over 4-5 years. In conclusion, RAS inhibition consistently and significantly reduces the incidence of T2DM in individuals with arterial hypertension or with congestive heart failure. Considering the pandemic of T2DM, such pharmacological approach deserves further attention among the strategies aiming at preventing T2DM.