Prevention of diabetes in hypertensive patients: results and implications from the VALUE trial

No Association of Angiotensin-Converting Enzyme Insertion/Deletion (ACE I/D) Gene Polymorphism in the Susceptibility to Diabetic Retinopathy in Type 2 Diabetes Mellitus Patients: An Updated Meta-Analysis

Diabetic retinopathy (DR) is a complex and multifactorial pathology encompassing environmental, metabolic, and polygenic influences. Among the genes possibly involved in the development and progression of DR, the Angiotensin I-converting enzyme (ACE) gene stands out, which presents an insertion (I) or deletion (D) polymorphism of a 287 bp Alu repetitive sequence in intron 16. Thus, this study aimed to perform a systematic review with meta-analysis to elucidate the relationship between the ACE gene (I/D) polymorphism (rs1799752) and the development and progression of DR in type 2 diabetic patients. PubMed/MEDLINE, Embase, Web of Science, and Scopus databases were systematically searched to retrieve articles that investigated the association between ACE gene (I/D) polymorphism in DR patients. Sixteen articles were included in the systematic review. The results describe no significant association between the polymorphism and DR risk (OR = 1.12; CI = 0.96-1.31; and p = 0.1359) for genotypic analysis by the dominant model (II vs. ID+DD). Moreover, we also observed no significant association between the D allele on the allele frequency analysis (I vs. D) and the DR risk (OR = 1.10; CI = 0.98-1.23; and p = 0.1182). Forest plot analysis revealed that the discrepancy between previous studies most likely arose from variations in their sample sizes. In conclusion, I/D polymorphism appears to be not involved in the susceptibility to and progression of the DR in type 2 diabetic patients.

Perindopril prevents development of obesity and hypertension in middle aged diet-induced obese rat models of metabolic syndrome

AIMS

The therapeutic properties of anti-hypertensive medications that extend beyond blood pressure lowering have started to become important clinical targets in recent years. This study aimed to assess the cardioprotective effects of perindopril in attenuating complications associated with metabolic syndrome in diet induced obese rats.

MAIN METHODS

Male Wistar-Kyoto (WKY) rats aged 16 weeks were fed either standard rat chow (SC) or given a high-fat-high-carbohydrate (HFHC) diet for 20 weeks. Perindopril treatment (1 mg/kg/day) was administered to a subset of WKY rats commencing at week 8 of the 20 week HFHC feeding period. Body weights, food, water and energy intakes, blood pressure, heart rate and glucose tolerance were measured throughout the treatment period. Oxidative stress and inflammatory markers, lipid levels, cardiac collagen deposition, vascular function, aortic and cardiac electrical function were examined after the treatment.

KEY FINDINGS

WKY rats developed metabolic syndrome after 20 weeks of HFHC feeding, evidenced by the presence of abdominal obesity, dyslipidaemia, glucose intolerance and hypertension. Perindopril treatment prevented the development of obesity and hypertension in WKY-HFHC. Perindopril improved blood lipid profiles in HFHC rats with decreases in LDL cholesterol, triglycerides and total cholesterol. Type I collagen levels were decreased in WKY-HFHC rats along with decreases in left ventricle mass. Perindopril treated rats also showed improved cardiac electrical function indicated by decreases in action potential at 90 % of repolarisation in WKY-HFHC rats.

SIGNIFICANCE

These results show that perindopril has a profound effect on preventing the development of metabolic syndrome in animals fed a HFHC diet.

Clinical Predictors of Diabetic Retinopathy Progression; A Systematic Review

OBJECTIVE

This study was conducted to discuss the clinical value of published Diabetic Retinopathy Progression determinants.

METHODS

The data for systematic review was collected from the published studies through PubMed and Medline. These studies discussed the clinical predictors of Diabetic Retinopathy (DR) progression. The common keywords used were diabetic Retinopathy, diabetes mellitus, systolic blood pressure, hemoglobin, and albuminuria.

RESULTS

Diabetic Retinopathy is one of the common causes of irreversible visual impairment among adults. Poor glycemic control, systemic hypertension, diabetes duration, dyslipidemia, and microalbuminuria are the major risk factors for the development and progression of diabetic retinopathy. Recently, increased aortic stiffness has been identified as a prognostic marker of diabetic retinopathy and peripheral neuropathy.

CONCLUSION

Certain groups of diabetic individuals are at higher risk to have progressive diabetic retinopathy and eventually visual impairment. Clinical determinants and predictors are considered as prognostic markers and could help physicians to develop an effective risk-based screening program for this condition.

Efficacy and Tolerability of Antihypertensive Drugs in Diabetic and Nondiabetic Patients

OBJECTIVES OF THE STUDY

The aim of the study was to compare the efficacy and tolerability of different classes of antihypertensive drugs in diabetic and nondiabetic patients (NDPs) with essential hypertension.

MATERIAL AND METHODS

The study was conducted in Mayo Hospital, Punjab Institute of Cardiology, and National Defence Hospital, Lahore, Pakistan, on 200 hypertensive patients with diabetes and 230 hypertensive patients without (Three hospitals) diabetes. Both male and female patients of age between 30 and 80 years with systolic blood pressure (SBP) above 130 mmHg and diastolic blood pressure (DBP) above 80 mmHg were enrolled in the study. Angiotensin converting enzyme inhibitors (ACEI), beta-blocker (βB), calcium-channel blocker (CCB), diuretics (D), angiotensin receptor blocker (ARB) as well as α-blocker classes of antihypertensive drugs were used. These drugs were used as monotherapy as well as combination therapy. The study was conducted for 4 months (July-October). After 4 months, patients were assessed for efficacy by monitoring blood pressure (BP) and tolerability by assessing safety profile on renal function, liver function as well as lipid profile.

RESULTS

Significant control in mean BP by all drug groups was observed in "both groups that is patients with diabetes and without diabetes." The efficacy and tolerability data revealed that in diabetic patients with hypertension, the highest decrease in SBP and DBP was observed using monotherapy with ACEI, two-drug combination therapy with ACEI plus diuretic, ARBs plus diuretic, ACEI plus CCBs, three-drug combination therapy with ACEI plus CCBs plus diuretic, and four drug combination therapy with ACEI plus CCBs plus diuretic plus βBs, ARB's plus CCBs plus diuretic plus βBs while in NDPs, monotherapy with diuretic, two-drug combination therapy with ACEI plus CCBs, ACEI plus βBs, three-drug combination therapy with βBs plus ACEI plus D was found more effective in controlling SBP as well as DBP. Adverse effects observed were dry cough, pedal edema, dizziness, muscular cramps, constipation, palpitations, sweating, vertigo, tinnitus, paresthesia, and sexual dysfunction.

CONCLUSION

All classes of antihypertensives were found to control blood pressure significantly in both groups of patients that is diabetic patients with hypertesion and non-diabetic patients with hypertension.

The Role of Systemic Risk Factors in Diabetic Retinopathy

Diabetic retinopathy is an increasingly common medical issue in the United States. The risk of developing the disease or having the disease progress is caused by many systemic health factors. This article examines the existing literature on the links between glycemic control, arterial hypertension, high cholesterol and hyperlipidemia, obesity, inflammatory markers, sleep-disordered breathing, and exercise with risk of diabetic retinopathy development and prevention. The literature shows benefit for good glycemic and blood pressure control. The effects of cholesterol, and lipid control, inflammatory markers, sleep-disordered breathing, obesity, and exercise are less well established.

A systematic review of the role of renin angiotensin aldosterone system genes in diabetes mellitus, diabetic retinopathy and diabetic neuropathy

BACKGROUND

The renin angiotensin aldosterone system (RAAS) plays a vital role in regulating glucose metabolism and blood pressure, electrolyte and fluid homeostasis. The aim of this systematic review is to assess the association of the RAAS genes with diabetes mellitus (DM) and its complications of retinopathy, neuropathy and cardiovascular disease (CVD).

MATERIALS AND METHODS

The relevant English-language studies were identified using the key words of DM, type 1 diabetes mellitus (T1DM), T2DM, renin angiotensin aldosterone polymorphisms or genotypes and RAAS from the search engines of MEDLINE/PubMed, and Scopus from January 1, 1995 to July 30, 2014. Inclusion criteria for selecting relevant studies were reporting the role of RAAS gene variants in the pathogenesis of T1DM or T2DM, diabetic retinopathy (DR), diabetic neuropathy and cardiovascular complication of DM.

RESULTS

The reviewers identified 204 studies of which 73 were eligible for inclusion in the present systematic review. The review indicates the angiotensinogen (AGT) M235T polymorphism might not affect the risk of DM. The role of angiotensin converting enzyme insertion/deletion (ACE I/D) and angiotensin II type 1 receptor gene (AT1R) A1166C polymorphisms in the pathogenesis of DM could not be established. Studies indicate the absence of an association between three polymorphisms of AGT M235T, ACE I/D and AT1R A1166C and DR in DM patients. A protective role for ACE II genotype against diabetic peripheral neuropathy has been suggested. Also, the ACE I/D polymorphism might be associated with the risk of CVD in DM patients.

CONCLUSION

More studies with adequate sample size that investigate the influence of all RAAS gene variants together on the risk of DM and its complications are necessary to provide a more clear picture of the RAAS genes polymorphisms involvement in the pathogenesis of DM and its complications.

Renin-angiotensin system blocking drugs

The two major classes of drugs that target the RAS are the angiotensin-converting enzyme (ACE) inhibitors and the selective AT1 receptor blockers (ARBs). Although both of these drug classes target angiotensin II, the differences in their mechanisms of action have implications for their effects on other pathways and receptors that may have therapeutic implications. Both ACEIs and ARBs are effective antihypertensive agents that have been shown to reduce the risk of cardiovascular and renal events. Direct inhibition of renin -the most proximal aspect of the RAS -became clinically feasible from 2007 with the introduction of aliskiren. This latter drug has been shown to be efficacious for the management of hypertension. Combined therapy of direct renin-inhibitors with ACEIs or ARBs has been tested in some clinical situations as congestive HF and proteinuria with diverse results. This article tries to offer an updated review of current knowledge on the use of RAS blocking drugs in clinical settings.

Link between the renin-angiotensin system and insulin resistance: implications for cardiovascular disease

The incidence of metabolic syndrome is rapidly increasing in the United States and worldwide. The metabolic syndrome is a complex metabolic and vascular disorder that is associated with inappropriate activation of the renin-angiotensin-aldosterone system (RAAS) in the cardiovascular (CV) system and increased CV morbidity and mortality. Insulin activation of the phosphatidylinositol-3-kinase (PI3K) pathway promotes nitric oxide (NO) production in the endothelium and glucose uptake in insulin-sensitive tissues. Angiotensin (Ang) II inhibits insulin-mediated PI3K pathway activation, thereby impairing endothelial NO production and Glut-4 translocation in insulin-sensitive tissues, which results in vascular and systemic insulin resistance, respectively. On the other hand, Ang II enhances insulin-mediated activation of the mitogen-activated protein kinase (MAPK) pathway, which leads to vasoconstriction and pathologic vascular cellular growth. Therefore, the interaction of Ang II with insulin signaling is fully operative not only in insulin-sensitive tissues but also in CV tissues, thereby linking insulin resistance and CV disease. This notion is further supported by an increasing number of experimental and clinical studies indicating that pharmacological blockade of RAAS improves insulin sensitivity and endothelial function, as well as reduces the incidence of new-onset diabetes in high-risk patients with CV disease. This article reviews experimental and clinical data elucidating the physiological and pathophysiological role of the interaction between insulin and RAAS in the development of insulin resistance as well as CV disease.

Cardiorespiratory fitness determines the reduction in blood pressure and insulin resistance during lifestyle intervention

OBJECTIVE

Lifestyle intervention is not always effective for improving arterial hypertension and other cardiovascular risk factors, and the parameters determining the outcome are not known. Because high cardiorespiratory fitness (CRF) protects from cardiovascular disease and mortality, we determined whether CRF at baseline predicts the improvement of blood pressure and other cardiovascular risk factors during a lifestyle intervention.

METHODS

A total of 219 patients at risk for type 2 diabetes, who underwent a 9-month lifestyle intervention with diet modification and increase in physical activity, and had measurement of CRF, were studied. Insulin sensitivity was estimated during a 75-g oral glucose tolerance test. Total body, visceral and liver fat were measured by magnetic resonance (MR) tomography and H-MR spectroscopy. CRF was estimated using two different methods, an incremental cycle exercise (maximal aerobic capacity-VO2max) test and a motorized treadmill (individual anaerobic threshold) test.

RESULTS

After 9 months of intervention adiposity, glycemia, CRF, insulin sensitivity, SBP and serum lipids (except high-density lipoprotein cholesterol, P = 0.65) improved (all other P ≤ 0.006). DBP did not change significantly (P = 0.06). High CRF at baseline predicted decreases in SBP (P ≤ 0.0002) and DBP (P ≤ 0.004), and increase in insulin sensitivity (P ≤ 0.04), but not change in serum lipids (all P ≥ 0.06). For 1 SD increase in baseline CRF the odds ratio for resolution of hypertension or prehypertension was 2.26 (individual anaerobic threshold; 95% CI 1.40-3.80) and 1.75 (VO2max; 95% CI 1.08-2.89).

CONCLUSION

CRF at baseline predicts the effectiveness of a lifestyle intervention in improving insulin sensitivity, and particularly blood pressure.

Mechanisms underlying altered extracellular nucleotide-induced contractions in mesenteric arteries from rats in later-stage type 2 diabetes: effect of ANG II type 1 receptor antagonism

Little is known about the vascular contractile responsiveness to, and signaling pathways for, extracellular nucleotides in the chronic stage of type 2 diabetes or whether the ANG II type 1 receptor blocker losartan might alter such responses. We hypothesized that nucleotide-induced arterial contractions are augmented in diabetic Goto-Kakizaki (GK) rats and that treatment with losartan would normalize the contractions. Here, we investigated the vasoconstrictor effects of ATP/UTP in superior mesenteric arteries isolated from GK rats (37-42 wk old) that had or had not received 2 wk of losartan (25 mg·kg(-1)·day(-1)). In arteries from GK rats (vs. those from Wistar rats), 1) ATP- and UTP-induced contractions, which were blocked by the nonselective P2 antagonist suramin, were enhanced, and these enhancements were suppressed by endothelial denudation, by cyclooxygenase (COX) inhibitors, or by a cytosolic phospholipase A(2) (cPLA(2)) inhibitor; 2) both nucleotides induced increased release of PGE(2) and PGF(2α); 3) nucleotide-stimulated cPLA(2) phosphorylations were increased; 4) COX-1 and COX-2 expressions were increased; and 5) neither P2Y2 nor P2Y6 receptor expression differed, but P2Y4 receptor expression was decreased. Mesenteric arteries from GK rats treated with losartan exhibited (vs. untreated GK) 1) reduced nucleotide-induced contractions, 2) suppressed UTP-induced release of PGE(2) and PGF(2α), 3) suppressed UTP-stimulated cPLA(2) phosphorylation, 4) normalized expressions of COX-2 and P2Y4 receptors, and 5) reduced superoxide generation. Our data suggest that the diabetes-related enhancement of ATP-mediated vasoconstriction was due to P2Y receptor-mediated activation of the cPLA(2)/COX pathway and, moreover, that losartan normalizes such contractions by a suppressing action within this pathway.

Olmesartan severely weakened the development of NASH in an animal model of hypercholesterolemia

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is characterized by a broad spectrum of liver damage. In a rat model of non-alcoholic steatohepatitis (NASH), olmesartan attenuated steatosis and fibrosis.

OBJECTIVE

To assess the potential preventive action of olmesartan, an angiotensin II type 1 receptor blocker, on NAFLD in hypercholesterolemic rabbits.

METHODS

Thirty-four white adult male rabbits were selected. The animals were divided into three groups: group I (GI), control group, 13 rabbits; group II (GII), olmesartan group, 12 rabbits; and group III (GIII), normal group, 9 rabbits. The animals from GI and GII were fed with a specific diet plus 1% cholesterol. Animals from GIII were fed only with a specific diet. The GII animals were treated with olmesartan.

RESULTS

Steatosis was present in all animals from GI and GII; no steatosis was observed in animals from GIII. When GI and GII where compared, the steatosis had higher scores in GI (p < 0.013). Perisinusoidal and periportal fibrosis occurred in 46.2% of the animals from GI. There was no fibrosis in GII or GIII. Lobular inflammation occurred in 84.6% of the animals from GI. Animals from GII and GIII had no inflammation. The NAFLD activity score was higher in animals from GI when compared to animals from GII and GIII (p < 0.001 for both groups); the NAFLD score was significantly higher in animals from GII when compared to animals from GIII (p < 0.001).

CONCLUSIONS

In hypercholesterolemic rabbits, olmesartan significantly attenuated hepatic steatosis and prevented the development of lobular inflammation and liver fibrosis. Based on the NAFLD activity score, olmesartan significantly weakened the development of NASH in rabbits fed a high cholesterol diet.

Angiotensin II enhances insulin-stimulated whole-body glucose disposal but impairs insulin-induced capillary recruitment in healthy volunteers

CONTEXT

Angiotensin II (AngII) increases insulin-mediated glucose uptake in healthy individuals. The underlying mechanisms are undefined. AngII may increase glucose uptake through a direct effect on muscle cell insulin signaling or through increasing insulin delivery to muscle cells through effects on the microvasculature.

OBJECTIVE

Our objective was to determine whether AngII increases insulin-mediated glucose uptake through effects on insulin-induced capillary recruitment.

DESIGN

We examined the effects of AngII on hyperinsulinemia-induced capillary density by measuring skin capillary density, capillary recruitment, and capillary density during venous congestion in 18 healthy subjects in the basal state, during systemic hyperinsulinemia, and during hyperinsulinemia with coinfusion of AngII or phenylephrine (pressor control). In addition, whole-body glucose uptake and blood pressure were measured.

RESULTS

Capillaroscopy data of 13 subjects were available for analysis. Compared with the basal state, hyperinsulinemia increased baseline capillary density (51.5+/-9.0 vs. 55.2+/-10.8 n/mm2, P<0.01), capillary recruitment (67.8+/-6.8 vs. 70.6+/-7.5 n/mm2, P<0.05), and capillary density during venous congestion (78.5+/-12.0 vs. 80.3+/-12.0 n/mm2, P<0.01). Infusion of AngII, but not phenylephrine, reduced insulin-induced capillary recruitment (69.3+/-8.6 vs. 65.2+/-8.0 n/mm2, P<0.05) and capillary density during venous congestion (79.7+/-15.3 vs. 73.9+/-12.1, P<0.05) while enhancing glucose uptake [2.40+/-0.7 vs. 2.68+/-0.6 (mg/kg.min per pmol/l)x100, P<0.01)] (n=18).

CONCLUSION

AngII increases insulin-mediated glucose uptake in healthy individuals. This increase was probably not related to increases in microvascular perfusion because infusion of AngII during hyperinsulinemia reduced insulin-mediated skin capillary recruitment. Additional studies are needed to investigate whether AngII directly affects insulin delivery through increasing insulin transport across the microvasculature.

Short-term angiotensin-1 receptor antagonism in type 2 diabetic Goto-Kakizaki rats normalizes endothelin-1-induced mesenteric artery contraction

Endothelin (ET)-1 and angiotensin II (Ang II) are likely candidates for a key role in diabetic vascular complications. We demonstrated previously that an enhanced ET-1-induced contraction is present in mesenteric arteries from Goto-Kakizaki (GK) rats at the chronic stage of type 2 diabetes. Here, we investigated whether short-term treatment of such rats with losartan, an angiotensin type 1 receptor antagonist, might normalize the ET-1-induced contraction. In mesenteric arteries from GK rats at the chronic stage (34-38 weeks) (vs. those from age-matched control Wistar rats): (1) the ET-1-induced contraction was enhanced, (2) the levels of ET-1 and Ang II were increased, (3) ET-1-stimulated ERK2 phosphorylation was increased, and (4) the ACh-induced endothelium-dependent relaxation was reduced. Mesenteric arteries isolated from such GK rats following treatment with losartan (25mg/kg/day for 2 weeks) exhibited reduced ET-1- and Ang II-induced contractions, suppressed ET-1-stimulated ERK phosphorylation, and increased ACh-induced relaxation, while the rats exhibited normalized plasma NO metabolism and their mesenteric arteries exhibited increased basal NO formation. However, such losartan treatment did not alter the increased levels of ET-1 and Ang II seen in GK mesenteric arteries. Our data suggest that within the timescale studied here, losartan normalizes ET-1-induced mesenteric artery contraction through a suppression of ERK activities and/or by normalizing endothelial function.

Mechanisms underlying the losartan treatment-induced improvement in the endothelial dysfunction seen in mesenteric arteries from type 2 diabetic rats

It is well known that type 2 diabetes mellitus is frequently associated with vascular dysfunction and an elevated systemic blood pressure, yet the underlying mechanisms are not completely understood. We previously reported that in mesenteric arteries from established type 2 diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats, which exhibit endothelial dysfunction, there is an imbalance between endothelium-derived vasodilators [namely, nitric oxide (NO) and hyperpolarizing factor (EDHF)] and vasoconstrictors [contracting factors (EDCFs) such as cyclooxygenase (COX)-derived prostanoids]. Here, we investigated whether the angiotensin II receptor antagonist losartan might improve endothelial dysfunction in OLETF rats at the established stage of diabetes. In mesenteric arteries isolated from OLETF rats [vs. those from age-matched control Long-Evans Tokushima Otsuka (LETO) rats]: (1) the acetylcholine (ACh)-induced relaxation was impaired, (2) the NO- and EDHF-mediated relaxations were reduced, (3) the ACh-induced EDCF-mediated contraction and the production of prostanoids were increased, and (4) superoxide generation was increased. After such OLETF rats had received losartan (25 mg/kg/day p.o. for 4 weeks), their isolated mesenteric arteries exhibited: (1) improvements in ACh-induced NO- and EDHF-mediated relaxations, (2) reduced EDCF- and arachidonic acid-induced contractions, (3) suppressed production of prostanoids, (4) reduced PGE(2)-mediated contraction, and (5) reduced superoxide generation. Within the timescale studied here, losartan did not change the protein expressions of endothelial NO synthase, COX1, or COX2 in mesenteric arteries from either OLETF or LETO rats. Losartan thus normalizes vascular dysfunction in this type 2 diabetic model, and the above effects may contribute to the reduction of adverse cardiovascular events seen in diabetic patients treated with angiotensin II receptor blockers.