Losartan and other angiotensin II antagonists for nephropathy in type 2 diabetes mellitus: A review of the clinical trial evidence

Anterior Diabetic Retinopathy Studied by Ultra-widefield Angiography

Purpose

To evaluate the prevalence of anterior type diabetic retinopathy (DR) using ultra-widefield fluorescein angiography and to identify the factors associated with anterior type DR incidence.

Methods

A retrospective case review was used in this study. Patients with non-proliferative diabetic retinopathy (NPDR) underwent examination by ultra-widefield fluorescein angiography, and were classified into anterior, posterior, or diffuse DR groups. Anterior DR was defined if diabetic retinal changes were noted only at the location anterior to the imaginary circle bordered by the Early Treatment Diabetic Retinopathy Study seven-standard fields. Correlations between demographic data, as well as systemic and ocular factors, and the incidence of NPDR types were evaluated.

Results

Among the 234 eyes of 234 patients with NPDR, 25 eyes (10.7%) demonstrated anterior DR. Anterior DR was observed in 10 eyes (30.3%) of patients having mild NPDR, three eyes (4.8%) of moderate NPDR patients, and in 12 eyes (7.1%) of severe NPDR patients (p < 0.001). The incidence of anterior DR positively correlated with lower hemoglobin A1c levels and with greater high-density lipoprotein levels following multiple logistic regression analysis (p < 0.001). The mean hemoglobin A1c level was 7.03 ± 0.99% in anterior DR, 7.99 ± 1.74% in posterior DR, and 7.94 ± 1.39% in diffuse DR patients (p = 0.003). The mean high-density lipoprotein level was 51.2 ± 12.5 mg/dL in anterior, 49.7 ± 15.2 mg/dL in posterior, and 45.2 ± 13.1 mg/dL in diffuse DR patients (p = 0.010).

Conclusions

Diabetic retinal changes confined to an anterior location were more frequently noted in earlier stages of NPDR. The incidence of DR sparing posterior retinal involvement was related to favorable blood sugar and lipid profiles.

The Telmisartan Renoprotective Study from Incipient Nephropathy to Overt Nephropathy – Rationale, Study Design, Treatment Plan and Baseline Characteristics of the Incipient to Overt: Angiotensin II Receptor Blocker, Telmisartan, Investigation on Type 2 Diabetic Nephropathy (INNOVATION) Study

We planned the INNOVATION study to determine whether telmisartan, an angiotensin-2-receptor blocker, delays the progression of renal disease from incipient nephropathy to overt nephropathy in hypertensive or normotensive Japanese patients with type 2 diabetes mellitus. The INNOVATION study is a randomized, double-blind, placebo-controlled trial. Eligible patients must have incipient nephropathy (defined as a urinary albumin to creatinine ratio of 100-300 mg/g creatinine) and a serum creatinine concentration of < 1.5 mg/dl for men and < 1.3 mg/dl for women. Patients who need treatment with angiotensin II receptor blockers or angiotensin-converting enzyme inhibitors are excluded. Eligible patients are randomly assigned to three groups: telmisartan titrated to 40 mg; telmisartan titrated to 80 mg; or placebo. The primary endpoint is the time from baseline visit to first detection of overt nephropathy (defined by a urinary albumin to creatinine ratio that is > 300 mg/g creatinine and 30% higher than the baseline on at least two consecutive visits). A total of 1855 patients have been enrolled from 160 study centres. In 527 randomized patients (28.4% of the enrolled patients), mean (SD) urinary albumin to creatinine ratio and serum creatinine concentration at baseline were 173.3 (47.2) mg/g creatinine and 0.78 (0.19) mg/dl. Sixty-eight per cent of the patients had hypertension at baseline. Mean (SD) systolic and diastolic blood pressures at baseline were 137.1 (14.6) and 77.5 (10.3) mmHg. The INNOVATION study will determine whether telmisartan, an angiotensin II receptor blocker, provides clinical benefits in hypertensive or normotensive patients with diabetes mellitus and diabetic nephropathy.

Examining the Association of Olmesartan and Other Angiotensin Receptor Blockers With Overall and Cause-Specific Mortality

Concerns about an increased cardiovascular risk with the angiotensin receptor blocker, olmesartan, prompted the current study to examine associations between olmesartan and other angiotensin receptor blockers with overall and cause-specific mortalities. We collected patients who started to use losartan, valsartan, irbesartan, candesartan, telmisartan, and olmesartan between January 1, 2004, and December 31, 2009, from Taiwan’s National Health Insurance claims database. Prescribed drug types, dosage, and other clinical information were collected. Overall mortality and cause-specific mortality were ascertained through linkages with Taiwan’s National Death Registry. Two follow-up analyses, labeled intention-to-treat and as-treated, were conducted. A Cox proportional hazard regression model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) using losartan as the reference group. A total of 690 463 subjects were included, with a mean follow-up ranging from a low of 2.8 years for olmesartan to a high of 4.1 years for irbesartan. Subjects who began with valsartan had a modest but significantly increased risk of overall mortality (HR, 1.04; 95% CI, 1.02–1.06) compared with losartan. Irbesartan (HR, 0.96; 95% CI, 0.94–0.99), candesartan (HR, 0.95; 95% CI, 0.92–0.99), telmisartan (HR, 0.93; 95% CI, 0.90–0.96), and olmesartan (HR, 0.93; 95% CI, 0.88–0.97) were associated with a slightly lower overall mortality risk than losartan. The analysis indicates that the differences in mortality risk among individual angiotensin receptor blockers were only marginal and thus less likely to be clinically important. Although uncontrolled confounding might still exist, olmesartan does not seem to increase cardiovascular risk compared with losartan.

Telmisartan provides better renal protection than valsartan in a rat model of metabolic syndrome

BACKGROUND

Angiotensin receptor blockers (ARB), telmisartan, and valsartan were compared for renal protection in spontaneously hypertensive rats (SHR) fed high fat diet. We hypothesized that in cardiometabolic syndrome, telmisartan an ARB with peroxisome proliferators activated receptor-γ (PPAR-γ) activity will offer better renal protection.

METHODS

SHR were fed either normal (SHR-NF, 7% fat) or high fat (SHR-HF, 36% fat) diet and treated with an ARB for 10 weeks.

RESULTS

Blood pressure was similar between SHR-NF (190 ± 3 mm Hg) and SHR-HF (192 ± 4 mm Hg) at the end of the 10 week period. Telmisartan and valsartan decreased blood pressure to similar extents in SHR-NF and SHR-HF groups. Body weight was significantly higher in SHR-HF (368 ± 5 g) compared to SHR-NF (328 ± 7 g). Telmisartan but not valsartan significantly reduced the body weight gain in SHR-HF. Telmisartan was also more effective than valsartan in improving glycemic and lipid status in SHR-HF. Monocyte chemoattractant protein-1 (MCP-1), an inflammatory marker, was higher in SHR-HF (24 ± 2 ng/d) compared to SHR-NF (14 ± 5 ng/d). Telmisartan reduced MCP-1 excretion in both SHR-HF and SHR-NF to a greater extent than valsartan. An indicator of renal injury, urinary albumin excretion increased to 85 ± 8 mg/d in SHR-HF compared to 54 ± 9 mg/d in SHR-NF. Telmisartan (23 ± 5 mg/d) was more effective than valsartan (45 ± 3 mg/d) in lowering urinary albumin excretion in SHR-HF. Moreover, telmisartan reduced glomerular damage to a greater extent than valsartan in the SHR-HF.

CONCLUSIONS

Collectively, our data demonstrate that telmisartan was more effective than valsartan in reducing body weight gain, renal inflammation, and renal injury in a rat model of cardiometabolic syndrome.

Angiotensin inhibition and longevity: a question of hydration

With the advancement of medical and investigative science, it is somewhat surprising that although it is possible to stabilise medical patients with hypertension and the associated kidney dysfunction, obesity, diabetes and even cancer, there is still no clear method of significantly reducing these chronic disease pathologies, and thus, extending life expectancy. There is one hormone common to these pathologies, the antagonism of which goes some way to clinical improvements, and this is angiotensin, which is released during hypovolaemia. Angiotensin antagonists are used to treat many of these pathologies, and it has been shown in the obesity literature that angiotensin antagonists decrease weight, but also increase the drinking of water. Increased cellular hydration, and hence, improved mitochondrial metabolism could be one of the mechanisms for the reduction in weight seen in these studies, as well as for reducing the other pathologies, all showing metabolic dysfunction. It appears that the application of straightforward physiological regulation might be an appropriate medical approach to the prevention of hypertension, kidney disease, obesity, diabetes and cancer, and thus, to an increased life expectancy.

The role of angiotensin II type 1 receptor blockers in the prevention and management of diabetes mellitus

Angiotensin II Receptor blockers (ARBs) are an important addition to the current range of medications available for treating a wide spectrum of diseases including cardiovascular diseases. Coronary heart disease (CHD) is the most common cause of death in the United Kingdom and worldwide. More importantly, the presence of the metabolic syndrome and the likelihood of diabetes mellitus taking on epidemic proportions in the years to come all threaten to maintain the mortality rate due to CHD. This review article focuses on the clinical studies that have helped define the trends in the usage of these agents in the prevention and treatment of diabetes mellitus and its complications and also explores possible mechanisms of action and future developments.

Lost in publication: Half of all renal practice evidence is published in non-renal journals

Physicians often scan a select number of journals to keep up to date with practice evidence for patients with kidney conditions. This raises the question of where relevant studies are published. We performed a bibliometric analysis using 195 renal systematic reviews. Each review used a comprehensive method to identify all primary studies for a focused clinical question relevant to patient care. We compiled all the primary studies included in these reviews, and considered where each study was published. Of the 2779 studies, 1351 (49%) were published in the top 20 journals. Predictably, this list included Transplantation Proceedings (5.9% of studies), Kidney International (5.3%), American Journal of Kidney Diseases (4.7%), Nephrology Dialysis Transplantation (4.3%), Transplantation (4.2%), and Journal of the American Society of Nephrology (2.4%). Ten non-renal journals were also on this list, including New England Journal of Medicine (2.4%), Lancet (2.3%), and Diabetes Care (2.2%). The remaining 1428 (51%) studies were published across other 446 journals. When the disciplines of all journals were considered, 59 were classified as renal or transplant journals (42% of articles). Other specialties included general and internal medicine (16%), endocrinology (diabetes) and metabolism (6.5%), surgery (6.2%), cardiovascular diseases (6.1%), pediatrics (4.3%), and radiology (3.3%). About half of all renal practice evidence is published in non-renal journals. Browsing the top journals is important. However, relevant studies are also scattered across a large range of journals that may not be routinely scanned by busy physicians, and keeping up with this literature requires other continuing education strategies.

Telmisartan inhibits expression of a receptor for advanced glycation end products (RAGE) in angiotensin-II-exposed endothelial cells and decreases serum levels of soluble RAGE in patients with essential hypertension

There is a growing body of evidence that the advanced glycation end product (AGE)-their receptor (RAGE) system plays a central role in the pathogenesis of diabetic vascular complication. The renin-angiotensin system (RAS) contributes to the development and progression of diabetic angiopathy as well. However, the cross-talk between the AGE-RAGE system and the RAS is not fully understood. In this study, we examined the role of angiotensin II (Ang II) type 1 receptor system for RAGE expression in cultured endothelial cells (ECs) and in patients with essential hypertension. Ang II up-regulated RAGE mRNA levels of microvascular ECs and subsequently increased the soluble form of RAGE (sRAGE) expression in the medium of ECs, both of which were completely blocked by telmisartan, a commercially available Ang II type 1 receptor antagonist. Furthermore, telmisartan was found to decrease serum levels of sRAGE in patients with essential hypertension. These results demonstrate that sRAGE is released from the cell surface of Ang-II-exposed ECs. Our present study indicates that a cross-talk exists between the AGE-RAGE system and the RAS and suggests that serum levels of sRAGE may reflect endothelial RAGE expression.

Pharmacoeconomics of angiotensin II antagonists in type 2 diabetic patients with nephropathy: implications for decision making

Angiotensin II receptor antagonists (angiotensin II receptor blockers; ARBs) are a class of antihypertensive drugs that are generally considered comparable to ACE inhibitors in the prevention of heart and kidney failure. However, these two classes of agents do interfere in different stages of the renin-angiotensin system. In patients with type 2 diabetes mellitus, advantages for ARBs over conventional (non-ACE inhibitor) therapy on progression from micro- to macroalbuminuria and overt nephropathy and end-stage renal disease have been shown in clinical trials. In patients with type 2 diabetes and end-stage renal disease, the need for dialysis and/or transplantation results in the use of major healthcare resources. This paper reviews the available economic evidence on treatment with ARBs in type 2 diabetic patients with advanced renal disease.Within-trial analytic and Markov model economic evaluations of the RENAAL (Reduction of Endpoint in Non-insulin dependent diabetes mellitus with Angiotensin II Antagonist Losartan), IDNT (Irbesartan Diabetic Nephropathy Trial) and IRMA (IRbesartan in type 2 diabetes with MicroAlbuminuria)-2 studies suggest that treatment with ARBs in patients with type 2 diabetes with overt or incipient nephropathy confers health gains and net cost savings compared with conventional (non-ACE inhibitor) therapy. For reimbursement and reference pricing decisions, there is a need for a head-to-head comparison of an ACE inhibitor with ARBs to model all possible costs and effects of ACE inhibitors and ARBs. This will result in a proper pharmacoeconomic outcome, where both types of drugs can be compared for healthcare decisions.

Adjuvant strategies for prevention of glomerulosclerosis

The glomerulosclerosis which frequently complicates diabetes and severe hypertension is mediated primarily by increased mesangial production and activation of transforming growth factor-beta (TGF-beta), which acts on mesangial cells to boost their production of matrix proteins while suppressing extracellular proteolytic activity. Hyperglycemia and glomerular hypertension work in various complementary ways to stimulate superoxide production via NADPH oxidase in mesangial cells; the resulting oxidant stress results in the induction and activation of TFG-beta. Nitric oxide, generated by glomerular capillaries and by mesangial cells themselves, functions physiologically to oppose mesangial TGF-beta overproduction; however, NO bioactivity is compromised by oxidant stress. In addition to low-protein diets and drugs that suppress angiotensin II activity, a variety of other agents and measures may have potential for impeding the process of glomerulosclerosis. These include vitamin E, which blunts the rise in mesangial diacylglycerol levels induced by hyperglycemia; statins and (possibly) policosanol, which down-regulate NADPH oxidase activity by diminishing isoprenylation of Rac1; lipoic acid, whose potent antioxidant activity antagonizes the impact of oxidant stress on TGF-beta expression; pyridoxamine, which inhibits production of advanced glycation endproducts; arginine, high-dose folate, vitamin C, and salt restriction, which may support glomerular production of nitric oxide; and estrogen and soy isoflavones, which may induce nitric oxide synthase in glomerular capillaries while also interfering with TGF-beta signaling. Further research along these lines may enable the development of complex nutraceuticals which have important clinical utility for controlling and preventing glomerulosclerosis and renal failure. Most of these measures may likewise reduce risk for left ventricular hypertrophy in hypertensives, inasmuch as the signaling mechanisms which mediate this disorder appear similar to those involved in glomerulosclerosis.

Molecular-specific effects of angiotensin II antagonists: clinical relevance to treating hypertension?

Angiotensin II receptor blockers (ARBs) may produce a number of molecule-specific effects that appear to be independent of interaction with the angiotensin II type 1 (AT1)-receptor. These include antagonism of the thromboxane A2 receptor, inhibition of platelet aggregation, induction of peroxisome proliferator- activated receptor gamma (PPARgamma) activity, and reduction of serum uric acid levels. However, definitive evidence is lacking that these molecule-specific effects give rise to a therapeutic advantage of one ARB over another. Currently, the possibility of a link between a molecule-specific effect of an ARB and an improvement in clinical outcomes is best illustrated by a reduction in serum uric acid levels with losartan. Data from Losartan Intervention For Endpoint reduction in hypertension (LIFE) study suggest a treatment-induced decrease in serum uric acid may contribute to the treatment benefit of a losartan-based versus atenolol-based therapy on the composite endpoint (death, myocardial infarction, or stroke). This finding should prompt further studies to investigate the long-term cardioprotective benefits issue of reducing hyperuricaemia in hypertensive patients.

Telmisartan is a promising cardiometabolic sartan due to its unique PPAR-gamma-inducing property

The metabolic syndrome is strongly associated with insulin resistance and consists of a constellation of factors such as hypertension and hyperlipidemia that raise the risk for cardiovascular diseases and diabetes mellitus. Indeed, hypertension occurs approximately twice as frequently in patients with diabetes compared with in non-diabetic controls. Conversely, hypertensive patients are more likely than normotensive persons to develop diabetes. In addition, up to 75% of CVD in diabetic patients can be attributed to hypertension. Therefore, the primary goals of treating hypertensive patients with insulin resistance are prevention of type 2 diabetes and cardiovascular events. Then, what is the optimal anti-hypertensive approach to target organ protection in these patients? Several clinical trials suggest that the renin-angiotensin system (RAS) plays a pivotal role in the pathogensis of insulin resistance and CVD in diabetes. Interruption of the RAS with angiotensin-coverting enzyme inhibitors (ACEIs) or angiotensin II type 1 receptor blockers (ARBs) has been shown to prevent the onset of diabetes in hypertensive patients and to reduce cardiovascular and renal disease progression in diabetic patients with hypertension. However, whether we should recommend ARBs for insulin resistant-hypertensive patients or type 2 diabetic patients without nephropathy due to its insulin-sensitizing property remains to be clarified. Recently, telmisartan, an ARB, was found to act as a patrtial agonist of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma influences the gene expression involved in carbohydrate metabolism, and pioglitazone and rosiglitazone, ligands for PPAR-gamma, improve insulin resistance in diabetic patients. Furthermore, there is a growing body of evidence that activators of PPAR-gamma exert anti-inflammatory, anti-oxidative and anti-proliferative effects on vascular wall cells, thus decreasing the risks for atherosclerosis. We hypothesize here that due to its unique PPAR-gamma-modulating activity, telmisartan will become a promising 'cardiometabolic sartan', that targets both diabetes and CVD in hypertensive patients. In this paper, we would like to propose the possible ways of testing our hypothesis. Does telmisartan reduce the development of diabetes and CVD in insulin resistant patients pretreated with maximal doses of other ARBs? Does co-treatment with an activator of PPAR-gamma attenuate the effects of telmisartan in these patients? These clinical studies will provide further information whether the beneficial cardiometabolic actions of telmisartan could be ascribed to its PPAR-gamma-inducing property.

Matrix metalloproteinases and diabetic vascular complications

Diabetes mellitus (DM) is associated with an increased incidence of cardiovascular events and microvascular complications. These complications contribute to the morbidity and mortality associated with DM. There is increasing evidence supporting a role for matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of matrix metalloproteinases - TIMPs) in the atherosclerotic process. However, the relationship between MMPs/TIMPs and diabetic angiopathy is less well defined. Hyperglycemia directly or indirectly (eg, via oxidative stress or advanced glycation products) increases MMP expression and activity. These changes are associated with histologic alterations in large vessels. On the other hand, low proteolytic activity of MMPs contributes to diabetic nephropathy. Within atherosclerotic plaques an imbalance between MMPs and TIMPs may induce matrix degradation, resulting in an increased risk of plaque rupture. Furthermore, because MMPs enhance blood coagulability, MMPs and TIMPs may play a role in acute thrombotic occlusion of vessels and consequent cardiovascular events. Some drugs can inhibit MMP activity. However, the precise mechanisms involved are still not defined. Further research is required to demonstrate the causative relationship between MMPs/TIMPs and diabetic atherosclerosis. It also remains to be established if the long-term administration of MMP inhibitors can prevent acute cardiovascular events.

Diabetic nephropathy: the proteinuria hypothesis

BACKGROUND/AIMS

Proteinuria, nearly a universal finding in progressive kidney disease, has been the subject of frequent recent analyses in the renal literature. Proteinuria is a hallmark of diabetic nephropathy: microalbuminuria is the principal early predictor for progression of diabetic glomerulopathy, and proteinuria may be viewed as a measure of the severity and promoter of progression of nephropathy.

METHODS

This article critically reviews for the first time the full scope of diabetic proteinuria--complex molecular mechanisms, natural history, and analysis of treatment trials--in order to address the validity of 'the proteinuria hypothesis', i.e., that diabetic proteinuria is a modifiable determinant of renal progression. This hypothesis is analyzed in detail, including recent studies on the primary therapy of diabetic nephropathy, renin-angiotensin blockade.

RESULTS

As fully developed, this hypothesis consists of three postulates: that higher amounts of proteinuria predict progressive loss of function, that proteinuria reduction correlates with slowing progression, and that proteinuria is a surrogate endpoint for clinical trials. The latter postulate has not before been adequately linked to growing information about the first two postulates as they apply to diabetic kidney disease.

CONCLUSION

While diabetic nephropathy is a disease model for the potential use of proteinuria as a surrogate marker for renal progression, this shift in perspective will require prospective data from additional clinical trials, particularly of non-renin-angiotensin blocking drugs, to be complete.

Antiproteinuric effect of RAS blockade: New mechanisms

Experimental and clinical studies have shown that blockade of the renin-angiotensin system (RAS) is effective in reducing proteinuria in conditions such as diabetes by reducing systemic and intraglomerular hydrostatic pressure. However, increasing evidence suggests that nonhemodynamic effects, such as preservation of the podocyte slit diaphragm structure and function, may also mediate the antiproteinuric effects of RAS blockade. In this review, we analyze in detail the evidence for known and novel mechanisms considered to play important roles in mediating the antiproteinuric effect of RAS blockers, with a particular focus on diabetic nephropathy.