Renin-angiotensin-system blockade in the prevention of diabetes

Hepatic structural enhancement and insulin resistance amelioration due to AT1 receptor blockade

Over the last decade, the role of renin-angiotensin system (RAS) on the development of obesity and its comorbidities has been extensively addressed. Both circulating and local RAS components are up-regulated in obesity and involved in non-alcoholic fatty liver disease onset. Pharmacological manipulations of RAS are viable strategies to tackle metabolic impairments caused by the excessive body fat mass. Renin inhibitors rescue insulin resistance, but do not have marked effects on hepatic steatosis. However, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARB) yield beneficial hepatic remodeling. ARBs elicit body mass loss and normalize insulin levels, tackling insulin resistance. Also, this drug class increases adiponectin levels, besides countering interleukin-6, tumoral necrosis factor-alpha, and transforming growth factor-beta 1. The latter is essential to prevent from liver fibrosis. When conjugated with peroxisome proliferator-activated receptor (PPAR)-alpha activation, ARB fully rescues fatty liver. These effects might be orchestrated by an indirect up-regulation of MAS receptor due to angiotensin II receptor type 1 (AT1R) blockade. These associations of ARB with PPAR activation and ACE2-angiotensin (ANG) (1-7)-MAS receptor axis deserve a better understanding. This editorial provides a brief overview of the current knowledge regarding AT1R blockade effects on sensitivity to insulin and hepatic structural alterations as well as the intersections of AT1R blockade with peroxisome proliferator-activated receptor activation and ACE2-ANG (1-7) - MAS receptor axis.

Higher blood aldosterone level in metabolic syndrome is independently related to adiposity and fasting plasma glucose

BACKGROUND

Hypoadiponectinemia is a well-known state associated with metabolic syndrome (MetS) and insulin resistance (IR). Recently aldosterone has been highly associated with high blood pressure, and may thus be a possible biomarker for MetS and IR. In this study, we investigate the association of aldosterone with MetS and IR, and compare it with that of adiponectin.

METHODS

In this cross-sectional study, we recruited 556 women receiving physical examinations at a general hospital in central Taiwan. At the time of examination, we collected data on various demographic and physical characteristics and measured blood levels of aldosterone, adiponectin and a variety of metabolic factors. Multiple linear regression analysis was performed using adiponectin or aldosterone as the dependent variables.

RESULTS

We found an inverse correlation between blood adiponectin and aldosterone (γ = -0.11, P = 0.009). Adiponectin levels were lower and aldosterone levels higher in women with MetS that those without (8.1 ± 0.4 vs. 11.5 ± 0.2 μg/mL, P < 0.001 and 691 ± 50 vs. 560 ± 11 pmol/L, P = 0.013, respectively), as they were in women with and without IR (adiponectin 10.4 ± 0.5 vs. 11.3 ± 0.2 μg/mL, P = 0.003 and aldosterone 635 ± 31 vs. 560 ± 11 pmol/L, P = 0.022). Although aldosterone was significantly related to body fat %, fasting plasma glucose and serum creatinine levels, the relationship between adiponectin and aldosterone was not obvious after adjustment in the multivariate analysis.

CONCLUSION

Although aldosterone was related to metabolic factors, including body fat % and fasting plasma glucose in our female subjects, the relationship between aldosterone and adiponectin remains unclear.

Angiotensin (1-7) counteracts the negative effect of angiotensin II on insulin signalling in HUVECs

AIMS

Angiotensin II participates to the regulation of cardiovascular physiology and it is involved in molecular mechanisms of insulin resistance. Angiotensin (1-7), derived from angiotensin II metabolism, is able to counteract many of the haemodynamic and non-haemodynamic actions of angiotensin II. In this study, we investigated in human umbilical vein endothelial cells (HUVECs) the possible action of angiotensin (1-7) on the insulin signalling pathway.

METHODS AND RESULTS

We stimulated HUVECs with insulin, angiotensin II and angiotensin (1-7), testing the effects on endothelial nitric oxide synthase (eNOS) enzyme activation and on insulin receptor substrate-1 (IRS1) phosphorylation. Moreover, we analysed the involvement of angiotensin type1, type2, and Mas receptors in these actions. Finally, we measured the nitric oxide (NO) production, the intracellular cGMP and the PKG-related activity in HUVECs, and the subsequent functional vasoactive effect of angiotensin (1-7) in mesenteric arteries of mice. Angiotensin II inhibits the insulin-induced Akt and eNOS phosphorylation, reducing the NO production. On the other hand, angiotensin (1-7) counteracts the inhibitory effect of angiotensin II, being able to restore the insulin-induced Akt/eNOS activation and the NO production. This effect is mediated by the Mas receptor. The inhibitory effects of angiotensin II on insulin signalling are, at least in part, mediated by an increased serine phosphorylation of IRS₁. Angiotensin (1-7) inhibits the serine phosphorylation of IRS1 induced by angiotensin II.

CONCLUSION

In endothelial cells angiotensin (1-7) counteracts the negative effects of angiotensin II on insulin signalling and NO production. The balance between angiotensin II and angiotensin (1-7) could represent a key mechanism in the pathophysiological processes leading to endothelial dysfunction and insulin-resistance.

Offspring sex determines the impact of the maternal ACE I/D polymorphism on maternal glycaemic control during the last weeks of pregnancy

HYPOTHESIS/ INTRODUCTION: : We recently demonstrated that fetal sex may affect maternal glycaemic control in genetically prone mothers. We tested the hypothesis that fetal sex/fetal Y/X chromosomes might affect maternal glycaemic control during pregnancy depending on the maternal angiotensin converting enzyme (ACE) I/D polymorphism.

MATERIAL AND METHODS

: One thousand, three hundred and thirty-two Caucasian women without pre-existing diabetes and pre-existing hypertension with singleton pregnancies delivering consecutively at the Charité obstetrics department were genotyped. Glycaemic control was analysed by measuring total glycated haemoglobin at birth. Correction for confounding factors and multiple testing was done.

RESULTS

: Maternal ACE I/D polymorphism showed significant interaction with fetal sex concerning maternal total glycated haemoglobin. Total glycated haemoglobin in DD mothers delivering boys was 6.42 ± 0.70% vs. 6.21 ± 0.66% in DD mother delivering girls (p < 0.005), whereas the II carrying mothers showed the opposite effect. II mothers delivering a girl had a higher (p = 0.044) total glycated haemoglobin at birth (6.40 ± 0.80%) compared to II mothers delivering boys (6.21 ± 0.81%). There was no interaction of the ACE I/D polymorphism and fetal sex with respect to new onset proteinuria, new onset edema and pregnancy-induced hypertension.

CONCLUSIONS

: Maternal glycaemic control during the last weeks of pregnancy seems to be influenced by an interaction of the ACE I/D genotyp and fetal sex.

New evidence for the fetal insulin hypothesis: fetal angiotensinogen M235T polymorphism is associated with birth weight and elevated fetal total glycated hemoglobin at birth

BACKGROUND

Low birth weight is associated with an increased risk of cardiovascular events in later life. Insulin resistance is a key finding in adult patients with cardiovascular diseases. The neonatal phenotype of an individual with insulin resistance might be low birth weight, as insulin influences fetal growth. The renin-angiotensin-aldosterone system has been associated with cardiovascular disease and insulin resistance. We analyzed whether fetal polymorphisms of the angiotensinogen (AGT) and angiotensin-converting enzyme genes influence birth weight and/or fetal total glycated hemoglobin (fTGH), a surrogate parameter of fetal insulin resistance at birth.

METHOD

In 1132 white women delivering singletons, neonatal umbilical blood samples and clinical data of the mothers and newborns were obtained. Newborns were genotyped with respect to the AGT M235T and angiotensin-converting enzyme insertion/deletion polymorphism.

RESULTS

The AGT M235T TT polymorphism is associated with reduced birth weight (TT: 3288 g versus TM + MM: 3435 g, P < 0.05). Furthermore, newborns with a high percentage of fTGH (>6.5%) are more likely to have the TT genotype than those with normal fTGH (<or=6.5%, P < 0.05). With higher cutoffs for fTGH, the significance increases to P less than 0.005. No association was seen between these parameters and the fetal angiotensin-converting enzyme insertion/deletion phenotype.

CONCLUSION

The fetal AGT M235T polymorphism is associated with low birth weight and elevated fetal fTGH at birth. Previous findings show that elevated fetal fTGH correlates with low birth weight and that higher activity of the renin-angiotensin-aldosterone system is an independent risk factor for the development of diabetes mellitus and coronary artery disease. Therefore, our data are supportive of the fetal insulin hypothesis.

Maitake mushroom extracts ameliorate progressive hypertension and other chronic metabolic perturbations in aging female rats

OBJECTIVE

We assessed the ability of two commercially-available fractions labeled SX and D derived from the edible maitake mushroom to overcome many age-associated metabolic perturbations such as progressive, age-related elevation of blood pressure, over activity of the renin-angiotensin system (RAS), decreased insulin sensitivity, and inflammation in an in vivo laboratory model.

DESIGN AND METHOD

We divided forty mature, female Sprague-Dawley rats (SD) into five groups of eight. SD ingested regular rat chow containing added sucrose (20% w/w). The groups received baseline diet alone (control) or baseline diet containing captopril, niacin-bound chromium, maitake fraction SX, or maitake fraction D. In addition to blood pressure readings, the following procedures were implemented: losartan and insulin challenges, evaluation of serum ACE activity, glucose tolerance testing, blood chemistries, LNAME challenge, and measurement of various circulating cytokines.

RESULTS

We found that implementation of all test conditions stopped the gradual elevation of systolic blood pressure (SBP) in the SD over the four months of study, even reversing some of the previous elevation that occurred over time. In general, the treatment groups showed decreased activity of the RAS estimated by less lowering of SBP after losartan challenge and decreased serum ACE activity and were more sensitive to exogenous insulin challenge. TNFa levels decreased in all four test groups suggesting a lessening of the inflammatory state.

CONCLUSIONS

We believe our data suggest that maitake mushroom fractions lessen age-related hypertension, at least in part, via effects on the RAS; enhance insulin sensitivity; and reduce some aspects of inflammation--actions that should lead to a longer, healthier life span.

Prevention of type 2 diabetes mellitus to reduce cardiovascular morbidity and mortality: a review of the evidence

J Clin Hypertens (Greenwich). 2009;11:512-519. (c)2009 Wiley Periodicals, Inc.Cardiovascular disease accounts for the majority of deaths in patients with type 2 diabetes mellitus. Lifestyle interventions aimed at weight loss and increased physical activity and therapy with antidiabetic drugs have proven effective in reducing the risk of new-onset diabetes in high-risk individuals. Substantial evidence also suggests that drugs that inhibit the renin-angiotensin system, namely angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, also prolong the time to onset of clinical diabetes. An open question is whether delay of new-onset diabetes with antidiabetic or antihypertensive agents reduces cardiovascular morbidity and mortality. A large ongoing study is investigating whether therapy with an oral antidiabetic drug or an angiotensin II receptor blocker reduces the incidence of new-onset diabetes and cardiovascular events in high-risk patients.

Effect of metformin on weight gain during antihypertensive treatment with a beta-blocker in Chinese patients

BACKGROUND

Overweight and obesity are associated with cardiovascular disease (CVD). This study was designed to investigate whether combined use of nitrendipine and atenolol has any effect on body weight (BW) and whether metformin can prevent antihypertensive medication-induced weight gain and has any effect on blood glucose (BG).

METHODS

Included in the present study were 94 hypertensive patients with a body mass index (BMI) > or =25 kg/m(2), of whom 45 patients were treated with nitrendipine plus atenolol (N/A group), and the remaining 49 patients were treated with nitrendipine, atenolol, and metformin (N/A/M group). The mean follow-up duration was 14 months. BW and glucose tolerance were measured.

RESULTS

In N/A group, BW and fasting BG significantly increased from 73.5 +/- 9.6 kg to 74.2 +/- 9.7 kg (P < 0.05) and from 94.2 +/- 10.5 mg/dl to 97.9 +/- 11.3 mg/dl (P < 0.01), respectively, whereas postprandial BG did not change significantly. In N/A/M group, BW slightly decreased from 72.7 +/- 10.1 kg to 72.3 +/- 10.2 kg (P = 0.30), and fasting BG did not change significantly (93.5 +/- 10.4 mg/dl vs. 92.7 +/- 10.2 mg/dl, P = 0.59), whereas 2-h postprandial BG significantly decreased from 133.7 +/- 30.5 mg/dl to 124.0 +/- 29.6 mg/dl (P < 0.05). Furthermore, a significant difference was observed in difference value of BW before and after treatment between the two groups (0.7 (95% confidence interval, 0.1-1.3) kg in N/A group vs. -0.4 (95% confidence interval, -1.3 to 0.4) kg in N/A/M group, P < 0.05).

CONCLUSIONS

Combination therapy of nitrendipine and atenolol may significantly increase BW and fasting BG in overweight or obese patients with hypertension. Metformin may prevent BW gain and improve BG levels in hypertensive patients who received combination therapy of nitrendipine and atenolol.

Use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker therapy to reduce cardiovascular events in high-risk patients: part 2

As presented previously in Part 1 of this 2-part article, many long-term clinical trials provide overwhelming evidence of the benefits of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) across the cardiovascular continuum. Trials also indicate additive or synergistic effects of combination therapy in renal disease and heart failure. Part 2, which is presented here, discusses the extensive interaction of the renin-angiotensin system (RAS) with the cellular and molecular pathophysiology of cardiovascular disease and the cross-continuum effects of ARBs and ACE inhibitors, which raises the possibility that RAS inhibition can offer protection in high-risk patients who do not have symptoms. Although trial evidence supports the effectiveness of monotherapy, the benefits of combined ACE inhibitor/ARB therapy in high-risk patients await confirmation. Ongoing clinical research will provide new and important information regarding the efficacy of specific combination (ACE inhibitor/ARB) therapies.

Antihypertensive therapy, new-onset diabetes, and cardiovascular disease

Type 2 diabetes mellitus is a worldwide epidemic with considerable health and economic consequences. Diabetes is an important risk factor for cardiovascular disease, which is the leading cause of death in diabetic patients, and decreasing the incidence of diabetes may potentially reduce the burden of cardiovascular disease. This article discusses the clinical trial evidence for modalities associated with a reduction in the risk of new-onset diabetes, with a focus on the role of antihypertensive agents that block the renin-angiotensin system. Lifestyle interventions and the use of antidiabetic, anti-obesity, and lipid-lowering drugs are also reviewed. An unresolved question is whether decreasing the incidence of new-onset diabetes with non-pharmacologic or pharmacologic intervention will also lower the risk of cardiovascular disease. A large ongoing study is investigating whether the treatment with an oral antidiabetic drug or an angiotensin-receptor blocker will reduce the incidence of new-onset diabetes and cardiovascular disease in patients at high risk for developing diabetes.

Prediabetic and diabetic in vivo modification of circulating low-density lipoprotein attenuates its stimulatory effect on adrenal aldosterone and cortisol secretion

Modification of low-density lipoprotein (LDL) and abnormal aldosterone and cortisol metabolism have been implicated in the pathogenesis of type 2 diabetes (DM2) and diabetic vascular disease. Since LDL serves as a major cholesterol source for adrenal steroidogenesis, we investigated whether LDL modification in prediabetic and diabetic subjects influences adrenocortical aldosterone and cortisol release. LDL was isolated from 30 subjects with normal glucose tolerance (NGT-LDL), 30 subjects with impaired glucose tolerance (IGT-LDL), and 26 patients with DM2 (DM2-LDL). Oxidation and glycoxidation characteristics of LDL apolipoprotein B100 of each individual was assessed by gas chromatography-mass spectrometry analysis. Human adrenocortical cells (NCI-H295R) were incubated for 24 h with 100 microg/ml LDL and after removal of supernatants stimulated for a further 24 h with angiotensin II (AngII). In supernatants, aldosterone and cortisol secretion was measured. IGT-LDL and DM2-LDL were substantially more modified than NGT-LDL. Each of the five measured oxidation/glycoxidation markers was significantly positively associated with glycemic control, measured as HbA(1c). LDL from all subjects stimulated both the basal and AngII-induced aldosterone and cortisol release from adrenocortical cells. However, hormone secretion was significantly inversely related to the degree of LDL oxidation/glycoxidation. We conclude that LDL modifications in IGT and DM2 subjects may have significant clinical benefits by counteracting prediabetic and diabetic overactivity of the renin-angiotensin-aldosterone system and enhanced cortisol generation.

Newly developed angiotensin II-infused experimental models in vascular biology

Angiotensin II is a major vasoactive peptide in the renin-angiotensin system (RAS). In vitro evidence demonstrates that this peptide can modulate the function of various adhesion molecules, chemokines, cytokines and growth factors, and ultimately contributes to cell proliferation, hypertrophy and inflammation. Moreover, in vivo studies further support that angiotensin II induces several vascular alterations including sustained elevations of blood pressure, enhanced inflammatory response, increased medial thickness of the aortas, and formation of aortic dissection and aneurysms. Thus, it has been a long time that angiotensin II-induced hypertension, atherosclerosis and abdominal aortic aneurysms emerge as important experimental models with respect to vascular biology. Applications of these models to investigate the vascular diseases have dramatically improved our understanding in the pathogenesis of these diseases. However, the pathophysiology of angiotensin II in vivo remains to be determined in many other vascular diseases where angiotensin II has been implicated as the detrimental factor, at least in part due to the limit availability of animal models. Recently some new exciting experimental models based on angiotensin II infusion have been reported to replicate the human diseases, such as postmenopausal hypertension, preeclampsia, vascular remodeling, vascular aging and neovascularization. In this review, we will focus on the rationales and anticipated applications of these newly developed models, with special emphasis placed on those relevant to the vascular biology. We will also discuss the limitations of the method of chronic angiotensin II infusion and additional approaches to overcome these limitations. These experimental models will provide great opportunity for us to investigate the molecular mechanisms of angiotensin II and evaluate therapeutic approaches, particularly to finely tune the potential role of RAS activation in various vascular events using genetically engineered mice.

Effect of delapril/manidipine vs olmesartan/ hydrochlorothiazide combination on insulin sensitivity and fibrinogen in obese hypertensive patients

OBJECTIVE

To compare the effect of delapril/manidipine vs olmesartan/hydrochlorothiazide (HCTZ) combination on insulin sensitivity and plasma fibrinogen in obese hypertensive patients.

PATIENTS AND METHODS

After a 4-week placebo period, 88 obese, hypertensive (DBP >95 and <110 mmHg) outpatients were randomized to delapril 30 mg/manidipine 10 mg combination or to olmesartan 20 mg/HCTZ 12.5 mg combination for 24 weeks according to a prospective, randomized, open-label, blinded endpoint, parallel group design. At the end of the placebo period and treatment period, clinical BP, fasting plasma glucose (FPG), plasma insulin, insulin sensitivity (by euglycemic hyperinsulinemic clamp) and plasma fibrinogen were evaluated. Insulin sensitivity was expressed as the amount of glucose infused during the last 30 minutes (glucose infusion rate, GIR) in mg/Kg/min. The total glucose requirement (TGR) to maintain a steady-state blood glucose level in response to a defined increase in plasma insulin concentration was also evaluated.

RESULTS

Both combinations significantly reduced SBP/DBP values (-22.3/16.4 mmHg and -22.6/17.2 mmHg, respectively, all p <0.001 vs placebo). GIR was significantly increased only by delapril/manidipine (+3.01 mg/min/Kg, p=0.038 vs placebo), the difference between treatments being significant (p <0.05). TGR was significantly increased by delapril/manidipine (+9.7 g, p=0.034), while it was unaffected by olmesartan/HCTZ. Plasma insulin as well as fibrinogen were significantly reduced by delapril/manidipine (-17.8 pmol/l, p=0.047 and -67.5 mg/dl, p=0.021, respectively), but not by olmesartan/HCTZ, the difference between the two treatments being statistically significant (p <0.05).

CONCLUSION

In obese hypertensive patients the delapril/manidipine combination but not the olmesartan/HCTZ combination significantly decreased insulin resistance and plasma fibrinogen levels, despite the similar BP lowering efficacy.

Management of hypertension in diabetes mellitus

Overall, approximately 40% of diabetic patients have hypertension at the time of diagnosis of diabetes and a similar percentage may develop hypertension during their follow-up. Factors contributing to this high prevalance of hypertension in diabetes include obesity, old age, insulin resistance, increased extracelluar volume, diabetic nephropathy and increased arterial stiffness. Well-conducted clinical trials that have been completed in the last decade demonstrated a major impact of hypertension on the micro- and macrovascular complications of diabetes and remarkable benefits of its control. Based on this large trial database, the currently accepted level of blood pressure used in diabetes for definition and target of therapy is 130/80 mmHg. Dietary and behavioral lifestyle modifications should be an intergral part of any management regimen. These include weight reduction, low sodium diet, exercise, moderate alcohol intake and smoking cessation. Effective control of blood pressure to target levels is more important than the drug(s) used. Combination drug therapy is needed frequently to achieve a target blood pressure. Although blockers of the renin-angiotensin-aldosterone system seem to have a favorable effect in diabetes, high-level evidence suggests that low-dose thiazide diuretics, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and calcium channel blockers are all good choices, both as initial and add-on therapy. Frequently, more than one drug is needed, and a low-dose thiazide diuretic combined with an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker is a commonly used effective combination. Other drugs that can be added include calcium channel blockers and β-blockers. In certain clinical situations, specific drug classes are indicated. These include angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers in the case of diabetic nephropathy, β-blockers in the case of ischemic heart disease, and calcium channel blockers and loop diuretics in the case of advanced renal insufficiency, where the use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers carries a significant risk of hyperkalemia.