PPARγ-Activating Angiotensin Type-1 Receptor Blockers Induce Adiponectin

Effects of Ang II receptor blocker irbesartan on adipose tissue function in mice with metabolic disorders

Recent studies indicate that the functional renin-angiotensin system (RAS) exists in the adipose tissue. The adipose tissue RAS is proposed in the pathophysiology of metabolic disorders. In the present study, we examined therapeutic effects of irbesartan, an angiotensin II (Ang II) type 1 receptor (AT1R)-specific blocker, in genetically obese diabetic KKAy mice, a model of human metabolic disorders without any dietary loading, with our focus on the analysis on possible effect of irbesartan on the adipose tissue. The treatment with irbesartan significantly lowered systolic blood pressure with a concomitant decrease in body weight in KKAy mice. In addition, irbesartan significantly decreased the adipose leptin mRNA expression and tended to decrease IL-6 mRNA expression in the adipose tissue of KKAy mice. Furthermore irbesartan preserved the adipose gene expression of AT1R-associated protein (ATRAP), an endogenous inhibitory molecule of tissue AT1R signaling, with a concomitant tendency of up-regulation of adipose tissue ATRAP/AT1R ratio. Collectively, these results suggest that the irbesartan-induced beneficial suppressive effect on the leptin-IL-6 axis in the adipose tissue in KKAy mice is partly mediated by a trend of up-regulation of the adipose ATRAP/AT1R ratio as one of pleiotropic effects of irbesartan.

A meta-analysis of the association between angiotensin-converting enzyme insertion/ deletion gene polymorphism and the risk of overweight/obesity

BACKGROUND AND OBJECTIVE

The association between angiotensin-converting enzyme insertion/deletion (ACE I/D) gene polymorphism and the risk of overweight/obesity remains controversial. A meta-analysis was conducted to evaluate the association between ACE I/D gene polymorphism and overweight/obesity susceptibility.

METHOD

All eligible studies were included in this meta-analysis by searching PubMed, Embase and Cochrane databases through April 2013 according to a predefined criteria.

RESULTS

Fourteen case-control studies including 3371 cases and 4490 controls were recruited for the analysis of the association between ACE I/D gene polymorphism and overweight/obesity susceptibility. A significant association was observed between DD genotype and overweight/obesity risk in overall populations and Africans (p=0.014 and 0.010, respectively). D allele was associated with the risk of overweight/ obesity in Africans (p=0.026). However, II genotype might not be a protective factor against overweight/obesity risk in overall populations, Africans, Caucasians and Asians.

CONCLUSIONS

DD genotype is a risk factor for the overweight/obesity susceptibility in overall populations, particularly in Africans. D allele is a risk factor for the overweight/obesity susceptibility in Africans. Further larger studies are needed to confirm our findings.

The renin-angiotensin system in adipose tissue and its metabolic consequences during obesity

Obesity is a worldwide disease that is accompanied by several metabolic abnormalities such as hypertension, hyperglycemia and dyslipidemia. The accelerated adipose tissue growth and fat cell hypertrophy during the onset of obesity precedes adipocyte dysfunction. One of the features of adipocyte dysfunction is dysregulated adipokine secretion, which leads to an imbalance of pro-inflammatory, pro-atherogenic versus anti-inflammatory, insulin-sensitizing adipokines. The production of renin-angiotensin system (RAS) components by adipocytes is exacerbated during obesity, contributing to the systemic RAS and its consequences. Increased adipose tissue RAS has been described in various models of diet-induced obesity (DIO) including fructose and high-fat feeding. Up-regulation of the adipose RAS by DIO promotes inflammation, lipogenesis and reactive oxygen species generation and impairs insulin signaling, all of which worsen the adipose environment. Consequently, the increase of circulating RAS, for which adipose tissue is partially responsible, represents a link between hypertension, insulin resistance in diabetes and inflammation during obesity. However, other nutrients and food components such as soy protein attenuate adipose RAS, decrease adiposity, and improve adipocyte functionality. Here, we review the molecular mechanisms by which adipose RAS modulates systemic RAS and how it is enhanced in obesity, which will explain the simultaneous development of metabolic syndrome alterations. Finally, dietary interventions that prevent obesity and adipocyte dysfunction will maintain normal RAS concentrations and effects, thus preventing metabolic diseases that are associated with RAS enhancement.

Adipose tissue renin-angiotensin-aldosterone system (RAAS) and progression of insulin resistance

This review focuses on the expression of the key components of the renin-angiotensin-aldosterone axis in fat tissue. At the center of this report is the role of RAAS in normal and excessive fat mass enlargement, the leading etiology of insulin resistance. Understanding the expression and regulation of RAAS components in various fat depots allows insight not only into the processes by which these complex patterns are modified by the enlargement of adipose tissue, but also into their impact on local and systemic response to insulin.

Inhibition of ERK1/2 pathway suppresses adiponectin secretion via accelerating protein degradation by Ubiquitin-proteasome system: relevance to obesity-related adiponectin decline

OBJECTIVE

Predominantly secreted by adipose tissue, adiponectin possesses insulin-sensitizing, anti-atherogenic, anti-inflammatory, and anti-angiogenic properties. Paradoxically, obesity is associated with declined plasma adiponectin levels; however, the underlying mechanisms remain elusive. In this study, we investigated the mechanistic involvement of MEK/ERK1/2 pathway in obesity-related adiponectin decrease.

MATERIALS/METHODS

C57 BL/6 mice exposed to a high-fat diet (HFD) were employed as animal obesity model. Both fully-differentiated 3T3-L1 and mouse primary adipocytes were used in the in vitro experiments.

RESULTS

Obesity and plasma adiponectin decline induced by prolonged HFD exposure were associated with suppressed ERK1/2 activation in adipose tissue. In adipocytes, specific inhibition of MEK/ERK1/2 pathway decreased intracellular and secretory adiponectin levels, whereas adiponectin gene expression was increased, suggesting that MEK/ERK1/2 inhibition may promote adiponectin protein degradation. Cycloheximide (CHX)-chase assay revealed that MEK/ERK1/2 inhibition accelerated adiponectin protein degradation, which was prevented by MG132, a potent proteasome inhibitor. Immunoprecipitation assay showed that intracellular MEK/ERK1/2 activity was negatively associated with ubiquitinated adiponectin protein levels. Consistently, long-term HFD feeing in mice increased ubiquitinated adiponectin levels in the epididymal fat pads.

CONCLUSIONS

Adipose tissue MEK/ERK1/2 activity can differentially regulate adiponectin gene expression and protein abundance and its suppression in obesity may play a mechanistic role in obesity-related plasma adiponectin decline.

Predictive value of adiponectin in patients with multivessel coronary atherosclerosis detected on computed tomography angiography

AIM

Multislice computed tomography coronary angiography (CTCA) can be used to detect coronary plaques that predict the risk of cardiovascular events. This study aimed to identify the risk factors associated with the extent of coronary plaques detected using CTCA and to determine the value of adiponectin measurement for identifying high-risk patients with multivessel coronary atherosclerosis.

METHODS

The study included 298 patients who underwent CTCA for coronary artery disease (CAD) screening between July 2008 and October 2011. We investigated the relationship between the extent of coronary atherosclerosis in terms of the number of diseased vessels and various risk factors, including the serum adiponectin level.

RESULTS

The adiponectin level was found to be significantly associated with multivessel coronary atherosclerosis in a univariate analysis (p=0.001). A multivariate analysis revealed the adiponectin level to also be significantly associated with multivessel coronary atherosclerosis (p=0.01), independent of other significant risk factors, including an advanced age, male gender, diabetes mellitus (DM) and hypertension (HT). A receiver operating characteristic curve analysis revealed that a combination of these factors significantly predicted multivessel coronary atherosclerosis (area under the curve, 0.73;95% confidence interval, 0.67-0.78). As the number of these factors increased, the proportion of patients with multivessel coronary atherosclerosis increased, while the proportion of patients with normal coronary arteries decreased (p < 0.0001).

CONCLUSIONS

A low adiponectin level combined with an advanced age, male gender, DM, and HT is independently and incrementally associated with multivessel coronary atherosclerosis. The number of factors may predict the extent of coronary atherosclerosis in patients without documented CAD.

Preventive effect of irbesartan on bleomycin-induced lung injury in mice

BACKGROUND

Idiopathic pulmonary fibrosis is a specific form of chronic fibrosing interstitial pneumonia that is limited to the lung. Angiotensin receptor blockers (ARBs) and peroxisome proliferator-activated receptor (PPAR) γ ligands have anti-inflammatory and anti-fibrotic effects. We investigated the effects of irbesartan-an ARB with PPAR γ activity-on the development of bleomycin-induced pulmonary fibrosis in mice.

METHODS

Lung injury was induced in imprinting control region (ICR) mice by intratracheal instillation of 2mg/kg of bleomycin. The treatment group orally received 20mg/kg of irbesartan for 5 consecutive days before instillation. The mice were sacrificed and were evaluated 14 days after bleomycin instillation.

RESULTS

Irbesartan reduced the fluid content and hydroxyproline level in the lung and improved the pathological findings as indicated by the Ashcroft score. Total cell counts, the numbers of macrophages, neutrophils, and lymphocytes, and the levels of transforming growth factor (TGF) β1 and monocyte chemotactic protein (MCP) 1 in the bronchoalveolar lavage fluid (BALF) were decreased. Treatment with a PPARγ antagonist GW9662 reversed some of the effects of irbesartan.

CONCLUSIONS

The results of this study indicated that irbesartan attenuated the development of bleomycin-induced pulmonary fibrosis in mice by decreasing TGF-β1 and MCP-1 via blocking of ATI, by binding to CCR2b, and by PPARγ-mediated inhibition of inflammation.

Tissue-specific peroxisome proliferator activated receptor gamma expression and metabolic effects of telmisartan

BACKGROUND

The angiotensin receptor blocker telmisartan has unique chemical properties that enable it to partially activate the peroxisome proliferator activated receptor gamma (PPARG) as well as block angiotensin II type 1 receptors.

METHODS

To directly test whether some of the metabolic effects of telmisartan require the presence of PPARG, we studied mice in which the gene (Pparg) for PPARG had been deleted in fat or in muscle.

RESULTS

We found that knockout of Pparg in fat tissue greatly impaired the ability of telmisartan to increase adiponectin levels and to enhance sensitivity to insulin-stimulated glucose incorporation into adipose tissue lipids. In contrast, muscle-specific Pparg knockout had relatively little or no impact on the ability of telmisartan to increase adiponectin levels or affect glucose metabolism either in fat or muscle. These findings provide compelling evidence that the ability of telmisartan to increase adiponectin levels and stimulate glucose use in adipose tissue may depend on the presence of PPARG in fat.

CONCLUSIONS

We conclude that PPARG in adipose tissue is required for at least several of the metabolic actions of telmisartan.

A systematic comparison of the properties of clinically used angiotensin II type 1 receptor antagonists

Angiotensin II type 1 receptor antagonists (ARBs) have become an important drug class in the treatment of hypertension and heart failure and the protection from diabetic nephropathy. Eight ARBs are clinically available [azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan]. Azilsartan (in some countries), candesartan, and olmesartan are orally administered as prodrugs, whereas the blocking action of some is mediated through active metabolites. On the basis of their chemical structures, ARBs use different binding pockets in the receptor, which are associated with differences in dissociation times and, in most cases, apparently insurmountable antagonism. The physicochemical differences between ARBs also manifest in different tissue penetration, including passage through the blood-brain barrier. Differences in binding mode and tissue penetration are also associated with differences in pharmacokinetic profile, particularly duration of action. Although generally highly specific for angiotensin II type 1 receptors, some ARBs, particularly telmisartan, are partial agonists at peroxisome proliferator-activated receptor-γ. All of these properties are comprehensively reviewed in this article. Although there is general consensus that a continuous receptor blockade over a 24-hour period is desirable, the clinical relevance of other pharmacological differences between individual ARBs remains to be assessed.

Angiotensin II type 2 receptor promotes adipocyte differentiation and restores adipocyte size in high-fat/high-fructose diet-induced insulin resistance in rats

This study was aimed at establishing whether specific activation of angiotensin II (ANG II) type 2 receptor (AT2R) modulates adipocyte differentiation and function. In primary cultures of subcutaneous (SC) and retroperitoneal (RET) preadipocytes, both AT2R and AT1R were expressed at the mRNA and protein level. Cells were stimulated with ANG II or the AT2R agonist C21/M24, alone or in the presence of the AT1R antagonist losartan or the AT2R antagonist PD123,319. During differentiation, C21/M24 increased PPARγ expression in both RET and SC preadipocytes while the number of small lipid droplets and lipid accumulation solely increased in SC preadipocytes. In mature adipocytes, C21/M24 decreased the mean size of large lipid droplets. Upon abolishment of AT2R expression using AT2R-targeted shRNAs, expressions of AT2R, aP2, and PPARγ remained very low, and cells were unable to differentiate. In Wistar rats fed a 6-wk high-fat/high-fructose (HFHF) diet, a significant shift toward larger adipocytes was observed in RET and SC adipose tissue depots. C21/M24 treatments for 6 wk restored normal adipocyte size distribution in both these tissue depots. Moreover, C21/M24 and losartan decreased hyperinsulinemia and improved insulin sensitivity impaired by HFHF diet. A strong correlation between adipocyte size area and glucose infusion rate during euglycemic-hyperinsulinemic clamp was observed. These results indicate that AT2R is involved in early adipocyte differentiation, while in mature adipocytes and in a model of insulin resistance AT2R activation restores normal adipocyte morphology and improves insulin sensitivity.

Angiotensin AT(2) receptor contributes towards gender bias in weight gain

Obesity is a major disease condition, in turn leading to pathological changes collectively recognized as metabolic syndrome. Recently angiotensin receptor AT(2)R has been associated negatively with body weight (BW) gain in male mice. However, the gender differences in AT(2)R and BW changes have not been studied. To understand the gender based role of AT(2)R involving BW changes, we fed male and female wild type (WT) and AT(2)R knock out (AT(2)KO) mice with C57BL6 background with high fat diet (HFD) for 16 weeks. The male AT(2)KO had higher HFD calorie intake (WT: 1280±80; AT(2)KO:1680±80 kcal) but gained less BW compared with the WT (WT: 13; AT(2)KO: 6 g). Contrary to the male animals, the female AT(2)KO mice with equivalent caloric intake (WT: 1424±48; AT(2)KO:1456±80 kcal) gained significantly more BW than the WT mice (WT: 9 g; AT(2)KO: 15 g). The male AT(2)KO on HFD displayed lower plasma insulin level, less impaired glucose tolerance (GT), and higher plasma T3 compared with WT males on HFD; whereas the female AT(2)KO mice on HFD showed elevated levels of plasma insulin, more impaired GT, lower plasma T3 and higher free fatty acid and hepatic triglycerides compared with WT females on HFD. Interestingly, compared with WT, AT(2)KO female mice had significantly lower estrogen, which was further reduced by HFD. These results suggest that AT(2)R in female mice via potentially regulating estrogen may have protective role against BW gain and impaired glucose tolerance and lipid metabolism.

The Angiotensin II Type 2 Receptor in Brain Functions: An Update

Angiotensin II (Ang II) is the main active product of the renin-angiotensin system (RAS), mediating its action via two major receptors, namely, the Ang II type 1 (AT₁) receptor and the type 2 (AT₂) receptor. Recent results also implicate several other members of the renin-angiotensin system in various aspects of brain functions. The first aim of this paper is to summarize the current state of knowledge regarding the properties and signaling of the AT₂ receptor, its expression in the brain, and its well-established effects. Secondly, we will highlight the potential role of the AT₂ receptor in cognitive function, neurological disorders and in the regulation of appetite and the possible link with development of metabolic disorders. The potential utility of novel nonpeptide selective AT₂ receptor ligands in clarifying potential roles of this receptor in physiology will also be discussed. If confirmed, these new pharmacological tools should help to improve impaired cognitive performance, not only through its action on brain microcirculation and inflammation, but also through more specific effects on neurons. However, the overall physiological relevance of the AT₂ receptor in the brain must also consider the Ang IV/AT₄ receptor.

Telmisartan modulates mitochondrial function in vascular smooth muscle cells

The development of atherosclerosis is associated with disturbances in mitochondrial function that impair effective adenosine triphosphate (ATP) production, increase generation of superoxide and induce subsequent apoptosis in vascular smooth muscle cells (VSMCs). As peroxisome proliferator-activated receptor gamma (PPARγ) has a potentially important role in the regulation of mitochondrial metabolism, we studied effects of the partial PPARγ agonist and angiotensin receptor blocker telmisartan, on mitochondria-related cellular responses in VSMC. In human VSMC, telmisartan increased ATP levels and activation of mitochondrial complex II, succinate dehydrogenase, reduced the release of H2O2 and attenuated H2O2-induced increases in caspase 3/7 activity, a marker of cellular apoptosis. Eprosartan, an angiotensin II receptor blocker that lacks the ability to activate PPARγ, had no effect on these mitochondria-related cellular responses in VSMC. Studies in PPARγ-deficient VSMC revealed that the effects of telmisartan on mitochondrial function were largely independent of PPARγ although the presence of PPARγ modulated effects of telmisartan on H2O2 levels. These findings demonstrate that telmisartan can have significant effects on mitochondrial metabolism in VSMC that are potentially relevant to the pathogenesis of cardiovascular disease and that involve more than just angiotensin receptor blockade and activation of PPARγ.

Effects of telmisartan and valsartan on insulin sensitivity in obese diabetic mice

Telmisartan and valsartan have angiotensin II receptor blocking activity. Because telmisartan has also an agonistic action for peroxisome proliferators-activator receptor (PPAR)-γ, it is speculated that an effect of telmisartan on insulin sensitivity is different from that of valsartan, which lacks of PPAR-γ agonistic activity. To address the issue, effects of telmisartan and valsartan on insulin sensitivity, adipocytokines and PPAR-γ target genes were evaluated in obese diabetic mice. KK-A(y) mice were treated with telmisartan (5mg/kg) and valsartan (15 mg/kg), once daily for 3 weeks. Insulin tolerance test was performed on day 14, and plasma adiponectin concentration and mRNA expression levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in adipose tissues were measured on day 21. Time-course of plasma glucose level after the injection of insulin in mice with telmisartan was not significantly different from that of animals with valsartan. In addition, PPAR-γ antagonist did not diminished the improvement of insulin sensitivity by telmisartan. Telmisartan and valsartan elevated plasma adiponectin concentration and suppressed the mRNA expressions of TNF-α and IL-6 in adipose tissues. These variables of the telmisartan- and valsartan-treated groups did not significantly differ. Influence of telmisartan on the PPAR-γ target genes (ap2 and fatty acid synthase) mRNA expressions was not detected in adipose tissues under the present condition. These data suggest that the effect of telmisartan on insulin sensitivity is similar to that of valsartan, and a role of PPAR-γ-mediated stimuli is small in the telmisartan-induced improvement of insulin sensitivity.

Improvement of metabolic syndrome by irbesartan via the PPARγ/HGF pathway in apolipoprotein E knockout mice

Irbesartan, a partial agonist of peroxisome proliferators activated receptor-γ (PPARγ), has been reported to improve insulin resistance and lipid profile in patients with diabetes mellitus or metabolic syndrome (MS). However, the down effectors of PPARγ have yet to be elucidated. Thus, in this study, we focused on the role of the hepatocyte growth factor (HGF) in the anti-metabolic effects of irbesartan, using apolipoprotein E (ApoE) knockout (KO) mice. ApoE KO mice placed on a high-fat diet (HFD) for 12 weeks were divided into four groups: i) the control (HFD only), ii) the HFD + irbesartan (5 mg/kg/day), iii) the HFD + irbesartan + GW9662, a PPARγ antagonist (0.5 mg/kg/day) and iv) the HFD + irbesartan + anti-HGF neutralizing antibody (200 μg/week). The liver and epididymal adipose tissues were evaluated histologically. Serum adiponectin and HGF levels were also measured by ELISA. Fatty liver (as detected by oil-red O staining) and macrophage infiltration were markedly reduced by irbesartan. Irbesartan treatment also reduced macrophage infiltration into epididymal adipose tissue and hypertrophy of adipocytes. However, these effects of irbesartan were attenuated by GW9662 as well as by anti-HGF neutralizing antibody. Serum and hepatic HGF levels were also markedly increased by irbesartan, whereas GW9662 decreased the HGF level. In conclusion, irbesartan, an angiotensin (Ang) receptor blocker (ARB) and partial agonist of PPARγ (metabosartan), demonstrated a reduction in fatty liver and chronic inflammation, such as macrophage infiltration, beyond its blood pressure-lowering effect. These favorable characteristics of irbesartan might be due to local HGF activation through its partial PPARγ agonistic action, in addition to Ang II blockade. Upregulation of local HGF by irbesartan might provide a novel advantage in a strategy for the prevention and treatment of cardiovascular diseases (CVDs).

Inhibition of smooth muscle cell proliferation by adiponectin requires proteolytic conversion to its globular form

Accelerated atherosclerosis is the primary cardiovascular manifestation of diabetes and correlates inversely with levels of circulating adiponectin, an anti-atherosclerotic adipokine that declines in diabetes. We therefore initiated a study to examine the mechanisms by which adiponectin, a hormone released from adipose tissue, influences the proliferation of vascular smooth muscle cells (SMCs). Addition of adiponectin to quiescent porcine coronary artery SMCs increased both protein and DNA synthesis and concurrently activated ERK1/2 and Akt. By contrast, globular adiponectin, a truncated form of this protein, exhibited anti-mitogenic properties as indicated by the inhibition of protein and DNA synthesis in SMCs stimulated with platelet-derived growth factor (PDGF). Whereas globular adiponectin did not stimulate growth-related signal transduction pathways, it was able to block the PDGF-dependent phosphorylation of eukaryotic elongation factor 2 kinase, a regulator of protein synthesis. Proteolysis of adiponectin with trypsin, which produces globular adiponectin, reversed the growth-stimulating actions of the undigested protein. As the existence of globular adiponectin remains controversial, western blotting was used to establish its presence in rat serum. We found that globular adiponectin was detectable in rat serum, but this result was not obtained with all antibodies. The contrasting properties of adiponectin and its globular form with respect to SMC proliferation suggest that protection against atherosclerosis may therefore be mediated, in part, by the level of globular adiponectin.

Relationship between telmisartan dose and glycaemic control in Japanese patients with type 2 diabetes mellitus and hypertension: a retrospective study

BACKGROUND AND OBJECTIVES

Telmisartan has been reported to have beneficial effects on insulin resistance and lipid profiles by acting as a peroxisome proliferator-activated receptor-γ (PPARγ) agonist. In this study we investigated the relationship between telmisartan dose and glycaemic control in Japanese subjects with type 2 diabetes mellitus and hypertension.

METHODS

Patients (n = 263) who were prescribed telmisartan 20, 40 or 80 mg/day at our clinic were retrospectively identified from our clinical database. Only patients without changes in their treatments for diabetes and hypertension for 6 months after starting telmisartan were included in this study. Glycosylated haemoglobin A(1c) (HbA(1c)) levels were measured at 0, 3 and 6 months after starting telmisartan.

RESULTS

At 3 and 6 months after starting telmisartan, HbA(1c) levels were significantly decreased in patients treated with telmisartan 40 or 80 mg/day but not in patients treated with telmisartan 20 mg/day (mean ± standard error change at 6 months: -0.29 ± 0.10%, p < 0.001; -0.48 ± 0.15%, p < 0.001; and -0.03 ± 0.10%, p = 0.33; respectively). When patients were classified into two groups by telmisartan dose (20 vs ≥40 mg/day), there was no significant correlation between baseline HbA(1c) and change in HbA(1c) levels over time in the 20 mg/day group. However, in patients treated with ≥40 mg/day of telmisartan, baseline HbA(1c) was negatively correlated with the change in HbA(1c) at 6 months. Multiple regression analysis confirmed that baseline HbA(1c) and telmisartan dose were the predictive factors.

CONCLUSION

Our results suggest that telmisartan influences glycaemic control in a dose-dependent manner; doses ≥40 mg/day may be needed to improve glycaemic control. Our data also suggest that patients with higher baseline HbA(1c) may experience greater improvements in glycaemic control with telmisartan.

Relationship between telmisartan dose and glycaemic control in Japanese patients with type 2 diabetes mellitus and hypertension: a retrospective study

BACKGROUND AND OBJECTIVES

Telmisartan has been reported to have beneficial effects on insulin resistance and lipid profiles by acting as a peroxisome proliferator-activated receptor-γ (PPARγ) agonist. In this study we investigated the relationship between telmisartan dose and glycaemic control in Japanese subjects with type 2 diabetes mellitus and hypertension.

METHODS

Patients (n = 263) who were prescribed telmisartan 20, 40 or 80 mg/day at our clinic were retrospectively identified from our clinical database. Only patients without changes in their treatments for diabetes and hypertension for 6 months after starting telmisartan were included in this study. Glycosylated haemoglobin A(1c) (HbA(1c)) levels were measured at 0, 3 and 6 months after starting telmisartan.

RESULTS

At 3 and 6 months after starting telmisartan, HbA(1c) levels were significantly decreased in patients treated with telmisartan 40 or 80 mg/day but not in patients treated with telmisartan 20 mg/day (mean ± standard error change at 6 months: -0.29 ± 0.10%, p < 0.001; -0.48 ± 0.15%, p < 0.001; and -0.03 ± 0.10%, p = 0.33; respectively). When patients were classified into two groups by telmisartan dose (20 vs ≥40 mg/day), there was no significant correlation between baseline HbA(1c) and change in HbA(1c) levels over time in the 20 mg/day group. However, in patients treated with ≥40 mg/day of telmisartan, baseline HbA(1c) was negatively correlated with the change in HbA(1c) at 6 months. Multiple regression analysis confirmed that baseline HbA(1c) and telmisartan dose were the predictive factors.

CONCLUSION

Our results suggest that telmisartan influences glycaemic control in a dose-dependent manner; doses ≥40 mg/day may be needed to improve glycaemic control. Our data also suggest that patients with higher baseline HbA(1c) may experience greater improvements in glycaemic control with telmisartan.

Effect of telmisartan on the expression of adiponectin receptors and nicotinamide adenine dinucleotide phosphate oxidase in the heart and aorta in type 2 diabetic rats

BACKGROUND

Diabetic cardiovascular disease is associated with decreased adiponectin and increased oxidative stress. This study investigated the effect of telmisartan on the expression of adiponectin receptor 2 (adipoR2) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits in the heart and the expression of adiponectin receptor 1 (adipoR1) in aorta in type 2 diabetic rats.

METHODS

Type 2 diabetes was induced by high-fat and high-sugar diet and intraperitoneal injection of a low dose of streptozotocin (STZ). Heart function, adipoR2, p22phox, NOX4, glucose transporter 4(GLUT4), monocyte chemoattractant protein-1(MCP-1) and connective tissue growth factor (CTGF)in the heart, and adipoR1, MCP-1 and nuclear factor kappa B (NF-κB) in aorta were analyzed in controls and diabetic rats treated with or without telmisartan (5mg/kg/d) by gavage for 12 weeks.

RESULTS

Heart function, plasma and myocardial adiponectin levels, the expression of myocardial adipoR2 and GLUT4 were significantly decreased in diabetic rats (P <0.05). The expression of myocardial p22phox, NOX4, MCP-1, and CTGF was significantly increased in diabetic rats (P <0.05). The expression of adipoR1 was decreased and the expression of MCP-1 and NF-κB was increased in the abdominal aorta in diabetic rats (P <0.05). Telmisartan treatment significantly attenuated these changes in diabetic rats (P <0.05).

CONCLUSIONS

Our results suggest that telmisartan upregulates the expression of myocardial adiponectin, its receptor 2 and GLUT4. Simultaneously, it downregulates the expression of myocardial p22phox, NOX4, MCP-1, and CTGF, contributing so to the improvement of heart function in diabetic rats. Telmisartan also induces a protective role on the vascular system by upregulating the expression of adipoR1 and downregulating the expression of MCP-1 and NF-κB in the abdominal aorta in diabetic rats.

Double blockade of angiotensin II (AT(1) )-receptors and ACE does not improve weight gain and glucose homeostasis better than single-drug treatments in obese rats

BACKGROUND AND PURPOSE

Combination therapies are becoming increasingly important for the treatment of high blood pressure. Little is known about whether double blockade of angiotensin II (AT(1) ) receptors and angiotensin-converting enzyme (ACE) exert synergistic metabolic effects.

EXPERIMENTAL APPROACH

Spontaneously hypertensive rats were allowed to choose between palatable chocolate bars and standard chow and were simultaneously treated with the AT(1) blocker telmisartan (8 mg·kg(bw) (-1) ·day(-1) ), the ACE inhibitor ramipril (4 mg·kg(bw) (-1) ·day(-1) ) or a combination of the two (8 + 4 mg·kg(bw) (-1) ·day(-1) ) for 12 weeks.

KEY RESULTS

Although food-dependent energy intake was increased by telmisartan and telmisartan + ramipril compared with ramipril or controls, body weight gain, abundance of fat and plasma leptin levels were decreased. Increased insulin levels in response to an oral glucose tolerance test were comparably attenuated by telmisartan and telmisartan + ramipril, but not by ramipril. During an insulin tolerance test, glucose utilization was equally as effectively improved by telmisartan and telmisartan + ramipril. In response to a stress test, ACTH, corticosterone and glucose increased in controls. These stress reactions were attenuated by telmisartan and telmisartan + ramipril.

CONCLUSIONS AND IMPLICATIONS

The combination of telmisartan + ramipril was no more efficacious in regulating body weight and glucose homeostasis than telmisartan alone. However, telmisartan was more effective than ramipril in improving metabolic parameters and in reducing body weight. The association between the decrease in stress responses and the diminished glucose levels after stress supports our hypothesis that the ability of telmisartan, as an AT(1) receptor blocker, to alleviate stress reactions may contribute to its hypoglycaemic actions.

Adiponectin and cardiovascular health: an update

The global epidemic of obesity is accompanied by an increased prevalence of cardiovascular disease (CVD), in particular stroke and heart attack. Dysfunctional adipose tissue links obesity to CVD by secreting a multitude of bioactive lipids and pro-inflammatory factors (adipokines) with detrimental effects on the cardiovascular system. Adiponectin is one of the few adipokines that possesses multiple salutary effects on insulin sensitivity and cardiovascular health. Clinical investigations have identified adiponectin deficiency (hypoadiponectinaemia) as an independent risk factor for CVD. In animals, elevation of plasma adiponectin by either pharmacological or genetic approaches alleviates obesity-induced endothelial dysfunction and hypertension, and also prevents atherosclerosis, myocardial infarction and diabetic cardiomyopathy. Furthermore, many therapeutic benefits of the peroxisome-proliferator activated receptor gamma agonists, the thiazolidinediones, are mediated by induction of adiponectin. Adiponectin protects cardiovascular health through its vasodilator, anti-apoptotic, anti-inflammatory and anti-oxidative activities in both cardiac and vascular cells. This review summarizes recent findings in the understanding of the physiological role and clinical relevance of adiponectin in cardiovascular health, and in the identification of the receptor and postreceptor signalling events that mediate the cardiovascular actions of adiponectin. It also discusses adiponectin-targeted drug discovery strategies for treating obesity, diabetes and CVD.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Comparison of the efficacy and safety of irbesartan and olmesartan in patients with hypertension (EARTH study)

Fifty-four patients were randomly divided into irbesartan and olmesartan groups. Blood pressure (BP) was significantly decreased in all patients at 12 weeks. In particular, BP in patients who initially received irbesartan showed significant reductions. The equality of variance of BP in the irbesartan group was significantly smaller than that in the olmesartan group at 12 weeks. Blood concentrations of adiponectin were significantly increased in the irbesartan group at 12 weeks. Log [pentraxin-3] in the irbesartan group were significantly decreased. In conclusion, the ability of irbesartan to reduce BP is comparable to that of olmesartan with equivalent safety.

Exploring metabolic dysfunction in chronic kidney disease

Impaired kidney function and chronic kidney disease (CKD) leading to kidney failure and end-stage renal disease (ESRD) is a serious medical condition associated with increased morbidity, mortality, and in particular cardiovascular disease (CVD) risk. CKD is associated with multiple physiological and metabolic disturbances, including hypertension, dyslipidemia and the anorexia-cachexia syndrome which are linked to poor outcomes. Specific hormonal, inflammatory, and nutritional-metabolic factors may play key roles in CKD development and pathogenesis. These include raised proinflammatory cytokines, such as interleukin-1 and −6, tumor necrosis factor, altered hepatic acute phase proteins, including reduced albumin, increased C-reactive protein, and perturbations in normal anabolic hormone responses with reduced growth hormone-insulin-like growth factor-1 axis activity. Others include hyperactivation of the renin-angiotensin aldosterone system (RAAS), with angiotensin II and aldosterone implicated in hypertension and the promotion of insulin resistance, and subsequent pharmacological blockade shown to improve blood pressure, metabolic control and offer reno-protective effects. Abnormal adipocytokine levels including leptin and adiponectin may further promote the insulin resistant, and proinflammatory state in CKD. Ghrelin may be also implicated and controversial studies suggest activities may be reduced in human CKD, and may provide a rationale for administration of acyl-ghrelin. Poor vitamin D status has also been associated with patient outcome and CVD risk and may indicate a role for supplementation. Glucocorticoid activities traditionally known for their involvement in the pathogenesis of a number of disease states are increased and may be implicated in CKD-associated hypertension, insulin resistance, diabetes risk and cachexia, both directly and indirectly through effects on other systems including activation of the mineralcorticoid receptor. Insight into the multiple factors altered in CKD may provide useful information on disease pathogenesis, clinical assessment and treatment rationale such as potential pharmacological, nutritional and exercise therapies.

Candesartan cilexetil improves angiotensin II type 2 receptor-mediated neurite outgrowth via the PI3K-Akt pathway in fructose-induced insulin-resistant rats

We have shown previously that stimulation of the angiotensin II type 2 receptor (AT(2)R) results in nerve facilitation. In this study, we determined the capacity of candesartan to correct expression patterns characteristic of neuropathy and AT(2)R-mediated neurite outgrowth in the fructose-induced insulin-resistant rat, which is one of the human hyperinsulinemia models. Wistar rats received a 15% (w/v) fructose solution in their drinking water for 4 weeks (fructose-drinking rats [FDRs]), with or without candesartan (5 mg/kg/day). We evaluated physiological and behavioral parameters and performed immunohistochemical studies. We found that the FDR developed insulin resistance and downregulated both AT(2)R neuronal function and phosphorylated Akt expression in dorsal root ganglia (DRG) neurons. Candesartan improved neurite outgrowth in the FDR, which was associated with the restoration of AT(2)R and phosphorylated Akt expression. Furthermore, downregulation of phosphoinositide 3-kinase (PI3K) inhibited AT(2)R-mediated neurite outgrowth in control DRG cells. PI3K activation increased AT(2)R-mediated neurite outgrowth and phosphorylated Akt expression in FDR DRG cells. These results suggest that the decrease of AT(2)R-mediated neurite outgrowth in FDRs is likely to be the result of decreased PI3K-dependent Akt activation. Candesartan improved AT(2)R neuronal function and Akt phosphorylation, which were associated with sensory nerve defects and insulin sensitivity in the FDR.

Adiponectin elevation by telmisartan ameliorates ischaemic myocardium in Zucker diabetic fatty rats with metabolic syndrome

AIM

This study investigated whether telmisartan, a selective angiotensin type 1 (AT1) receptor antagonist and gamma peroxisome proliferator-activated receptor (PPAR-γ) partial agonist, reduces myocardial ischaemia/reperfusion (I/R) injury in an experimental model of metabolic syndrome.

METHODS

Zucker Diabetic Fatty (ZDF) rats were treated for 3 weeks with telmisartan at doses of 2, 7 and 12 mg/kg/day. After treatment, rats were subjected to a 25-min occlusion of the left descending coronary artery followed by 2-h reperfusion (I/R).

RESULTS

Telmisartan reduced the extension of the infarct size in a dose-dependent fashion and decreased the levels of plasma troponin I, a specific marker of myocardial damage. Telmisartan also caused a dose-dependent increase in adiponectin both in plasma and cardiac tissue of infarcted ZDF rats. These levels were minimally increased (p < 0.05 vs. vehicle) by telmisartan 7 mg/kg/day and reached the maximum values with the highest dose of 12 mg/kg/day (p < 0.01 vs. vehicle). In contrast, within the infarcted tissue telmisartan decreased the expression of markers of inflammation such as the transcription factor NF-κB, the toll-like receptors TLR2 and TLR4 as well as TNF-α cytokine. Nitrosative stress was maximal in vehicle-treated infarcted hearts as evidenced by increased expression of iNOS, which was almost abolished after treatement with telmisartan.

CONCLUSIONS

Treatment of ZDF rats for 3 weeks with telmisartan, a dual angiotensin II receptor antagonist and partial PPAR-γ receptor agonist, resulted in a significant reduction of myocardial damage induced by I/R and was associated with increased adiponectin and a decrease in inflammatory markers.

Improved insulin sensitivity after long-term treatment with AT1 blockers is not associated with PPARγ target gene regulation

In both cell culture experiments and in vivo studies, a number of angiotensin II type 1 (AT(1)) receptor antagonists activated the peroxisome proliferator-activated receptor-γ (PPARγ). This mechanism has been discussed to be, at least in part, responsible for the improvement in glucose metabolism observed in animal studies and clinical trials. To investigate whether the PPARγ-dependent mechanism may represent a valid target for chronic therapy, spontaneously hypertensive rats (SHR) were fed either with a cafeteria diet (CD) or standard chow. CD-fed SHR were simultaneously treated with either telmisartan (TEL; 8 mg/kg(body weight)· d) or candesartan (CAND; 10 mg/kg(body weight)· d) for 3 months because TEL, but not CAND, has been demonstrated to be a strong activator of PPARγ. After 3 months, chow- and CD-fed controls were hypertensive, whereas TEL and CAND treatment resulted in normalized blood pressures in SHR. Body weight and the amount of abdominal fat (determined by magnetic resonance imaging) were higher in CD- than in chow-fed SHR. After TEL or CAND, body weight, abdominal fat quantity, and adipocyte size returned to normal. In glucose tolerance tests, the glucose responses were comparable in the TEL- and CAND-treated SHR and obese controls, whereas the insulin response was almost halved by AT(1) blockade. Expression of PPARγ target genes aP2, FAT CD36, FASn, and PEPCK remained unaltered at the protein level in visceral fat after TEL and CAND compared with the CD-fed controls. Because the expression of examined PPARγ target genes was not affected, we concluded that improved insulin sensitivity after long-term treatment with AT(1) blockers was not related to a PPARγ-dependent mechanism.

Telmisartan: just an antihypertensive agent? A literature review

INTRODUCTION

The modulation of the renin angiotensin aldosterone system (RAAS) is an important pathway in managing high blood pressure, and its overexpression plays a key role in target end-organ damage. Telmisartan is an angiotensin II receptor blocker (ARB) with unique pharmacologic properties, including the longest half-life among all ARBs; this leads to a significant and 24-h sustained reduction of blood pressure. Telmisartan has well-known antihypertensive properties, but there is also strong clinical evidence that it reduces left ventricular hypertrophy, arterial stiffness and the recurrence of atrial fibrillation, and confers renoprotection.

AREAS COVERED

This paper reviews telmisartan's pharmacological properties in terms of efficacy for hypertension control and, importantly, focuses on its new therapeutic indications and their clinical implications.

EXPERT OPINION

ONTARGET (ongoing telmisartan alone and in combination with ramipril global endpoint trial) demonstrated, that telmisartan confers cardiovascular protective effects similar to those of ramipril, but with a better tolerability. Moreover, recent investigations focused on the capability of telmisartan to modulate the peroxisome proliferator-activated receptor-gamma (PPAR-γ), an established target in the treatment of insulin resistance, diabetes and metabolic syndrome, whose activation is also correlated to anti-inflammatory and, finally, anti-atherosclerotic properties. Telmisartan shows peculiar features that go beyond blood pressure control. It presents promising and unique protective properties against target end-organ damage, potentially able to open a scenario of new therapeutic approaches to cardiovascular disease.

4-Hydroxynonenal differentially regulates adiponectin gene expression and secretion via activating PPARγ and accelerating ubiquitin-proteasome degradation

Although well-established, the underlying mechanisms involved in obesity-related plasma adiponectin decline remain elusive. Oxidative stress is associated with obesity and insulin resistance and considered to contribute to the progression toward obesity-related metabolic disorders. In this study, we investigated the effects of 4-hydroxynonenal (4-HNE), the most abundant lipid peroxidation end product, on adiponectin production and its potential implication in obesity-related adiponectin decrease. Long-term high-fat diet feeding led to obesity in mouse, accompanied by decreased plasma adiponectin and increased adipose tissue 4-HNE content. Exposure of adipocytes to exogenous 4-HNE resulted in decreased adiponectin secretion in a dose-dependent manner, which was consistent with significantly decreased intracellular adiponectin protein abundance. In contrast, adiponectin gene expression was significantly elevated by 4-HNE treatment, which was concomitant with increased peroxisome proliferator-activated receptor gamma (PPAR-γ) gene expression and transactivity. The effect was abolished by T0070907, a PPAR-γ antagonist, suggesting that PPAR-γ activation plays a critical role in this process. To gain insight into mechanisms involved in adiponectin protein decrease, we examined the effects of 4-HNE on adiponectin protein degradation. Cycloheximide (CHX)-chase assay revealed that 4-HNE exposure accelerated adiponectin protein degradation, which was prevented by MG132, a potent proteasome inhibitor. Immunoprecipitation assay showed that 4-HNE exposure increased ubiquitinated adiponectin protein levels. These data altogether indicated that 4-HNE enhanced adiponectin protein degradation via ubiquitin-proteasome system. Finally, we demonstrated that supplementation of HF diet with betaine, an antioxidant and methyl donor, alleviated high-fat-induced adipose tissue 4-HNE increase and attenuated plasma adiponectin decline. Taken together, our findings suggest that the lipid peroxidation product 4-HNE can differentially regulates adiponectin gene expression and protein abundance and may play a mechanistic role in obesity-related plasma adiponectin decline.

Involvement of PPAR-γ in the neuroprotective and anti-inflammatory effects of angiotensin type 1 receptor inhibition: effects of the receptor antagonist telmisartan and receptor deletion in a mouse MPTP model of Parkinson's disease

BACKGROUND

Several recent studies have shown that angiotensin type 1 receptor (AT1) antagonists such as candesartan inhibit the microglial inflammatory response and dopaminergic cell loss in animal models of Parkinson's disease. However, the mechanisms involved in the neuroprotective and anti-inflammatory effects of AT1 blockers in the brain have not been clarified. A number of studies have reported that AT1 blockers activate peroxisome proliferator-activated receptor gamma (PPAR γ). PPAR-γ activation inhibits inflammation, and may be responsible for neuroprotective effects, independently of AT1 blocking actions.

METHODS

We have investigated whether oral treatment with telmisartan (the most potent PPAR-γ activator among AT1 blockers) provides neuroprotection against dopaminergic cell death and neuroinflammation, and the possible role of PPAR-γ activation in any such neuroprotection. We used a mouse model of parkinsonism induced by the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and co-administration of the PPAR-γ antagonist GW9662 to study the role of PPAR-γ activation. In addition, we used AT1a-null mice lesioned with MPTP to study whether deletion of AT1 in the absence of any pharmacological effect of AT1 blockers provides neuroprotection, and investigated whether PPAR-γ activation may also be involved in any such effect of AT1 deletion by co-administration of the PPAR-γ antagonist GW9662.

RESULTS

We observed that telmisartan protects mouse dopaminergic neurons and inhibits the microglial response induced by administration of MPTP. The protective effects of telmisartan on dopaminergic cell death and microglial activation were inhibited by co-administration of GW9662. Dopaminergic cell death and microglial activation were significantly lower in AT1a-null mice treated with MPTP than in mice not subjected to AT1a deletion. Interestingly, the protective effects of AT1 deletion were also inhibited by co-administration of GW9662.

CONCLUSION

The results suggest that telmisartan provides effective neuroprotection against dopaminergic cell death and that the neuroprotective effect is mediated by PPAR-γ activation. However, the results in AT1-deficient mice show that blockage of AT1, unrelated to the pharmacological properties of AT1 blockers, also protects against dopaminergic cell death and neuroinflammation. Furthermore, the results show that PPAR-γ activation is involved in the anti-inflammatory and neuroprotective effects of AT1 deletion.

D3 dopamine receptor regulation of D5 receptor expression and function in renal proximal tubule cells

Dopamine receptor, via D(1)-like and D(2)-like receptors, increases sodium excretion in kidney. We have reported positive interactions between D(3) and D(1) receptors in renal proximal tubule (RPT) cells. These reports, however do not preclude that there may be also interaction between D(3) and D(5) receptors, because of the lack of selective D(1) and D(5) receptor agonists or antagonists. We hypothesize that D(3) receptors can regulate D(5) receptors, and that D(3) receptor regulation of D(5) receptors in RPTs is impaired in spontaneously hypertensive rats (SHRs). It showed that a D(3) receptor agonist, PD128907, by the activation of protein kinase C activity, increased the expression of D(5) receptors in a concentration- and time-dependent manner in RPT cells from Wistar-Kyoto (WKY) rats. The stimulatory effect of the D(3) receptor on D(5) receptor expression was impaired in RPT cells from SHRs. The effect of D(3) receptor on D(5) receptor is functionally relevant; stimulation of D(5) receptor decreases Na(+)-K(+) adenosine triphosphatase (ATPase) activity in WKY cells. Pretreatment with D(3) receptor agonist for 24 h enhances the D(5) receptor expression and D(5) receptor-mediated inhibitory effect on Na(+)-K(+) ATPase activity in WKY cells, but decreases them in SHR cells. The effect of D(3) receptor on D(5) receptor expression and function was also confirmed in the D(5) receptor-transfected HEK293 cells. It indicates that activation of D(3) receptor increases D(5) receptor expression and function. Altered regulation of D(3) receptor on D(5) receptors may have a role in the pathogenesis of hypertension.

Prophylactic treatment with telmisartan induces tissue-specific gene modulation favoring normal glucose homeostasis in Cohen-Rosenthal diabetic hypertensive rats

The objectives were to assess the potential of long-term prophylactic administration of telmisartan, an angiotensin II receptor antagonist and a partial peroxisome proliferator activator receptor (PPAR)γ agonist, in preventing the development of hypertension and hyperglycemia and to demonstrate the alteration in gene expression associated with the development of hyperglycemia and insulin resistance in Cohen-Rosenthal diabetic hypertensive rat, a unique model of hypertension and type 2 diabetes mellitus comorbidity. Cohen-Rosenthal diabetic hypertensive rats were continuously treated with telmisartan (3 mg/[kg d]) starting at age 6 to 8 weeks before developing hypertension or diabetes. Weight changes, blood pressure, blood insulin, adiponectin, glucose tolerance, and insulin sensitivity were monitored. Fat, liver, and muscle messenger RNAs were examined for the expression of genes potentially involved in the onset of insulin resistance. In addition to the expected antihypertensive effect of prophylactic telmisartan, diabetes was blunted, evidenced at the end of the study by a significantly lower glucose level. This was accompanied by improved glucose tolerance, increased sensitivity to insulin, reduction in fasting insulin levels and homeostasis model assessment index, as well as an increase in serum adiponectin. Telmisartan also prevented the increase in serum triglycerides and the associated appearance of lipid droplets in the liver. Diabetes induced tissue-specific changes in messenger RNAs expression of the following selected genes, which were restored by telmisartan treatment: PPARγ, PPARδ, PPARγ coactivator 1α, adiponectin, adiponectin receptor 1, adiponectin receptor 2, phosphotyrosine binding domain and a pleckstrin homology domain-containing adaptor protein, adenosine monophosphate kinase, and glucose translocator 4. Telmisartan blunted the development of hypertension, insulin resistance, and diabetes in prediabetic Cohen-Rosenthal diabetic hypertensive rats through pleiotropic activity, involving specific gene regulation of target organs.

Screening for adiponectin secretion regulators

Adiponectin is an adipokine secreted from adipocytes and plays important roles in the suppression of metabolic syndromes that can result in type 2 diabetes, obesity, and atherosclerosis. Adiponectin is a promising drug target because a number of studies have shown that upregulation of adiponectin has a number of therapeutic benefits. Extensive efforts have revealed various adiponectin regulators, such as cytokines, transcription factors, and drugs. Cytokines, such as tumor necrosis factor α, IL-6, and IL-18, downregulate adiponectin production. On the other hand, transcription factors such as peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT-enhancer-binding protein α, and forkhead box O1 (FoxO1) upregulate adiponectin expression, although the activating transcription factor 3 and cAMP response element-binding protein downregulate it. Although a number of therapeutic drugs have been reported as adiponectin secretion regulators, most of them act through PPARγ-dependent mechanisms, leaving PPARγ-derived side effects as a concern. Using high-throughput screening, we have identified PPARγ-independent adiponectin secretion regulators as potential drug candidates with a novel mechanism of action.

Hypertension in obesity

Obesity and HTN are on the rise in the world. HTN seems to be the most common obesity-related health problem and visceral obesity seems to be the major culprit. Unfortunately, only 31% of hypertensives are treated to goal. This translates into an increased incidence of CVD and related morbidity and mortality. Several mechanisms have been postulated as the causes of obesity-related HTN. Activation of the RAAS, SNS, insulin resistance, leptin, adiponectin, dysfunctional fat, FFA, resistin, 11 Beta dehydrogenase, renal structural and hemodynamic changes, and OSA are some of the abnormalities in obesity-related HTN. Many of these factors are interrelated. Treatment of obesity should begin with weight loss via lifestyle modifications, medications, or bariatric surgery. According to the mechanisms of obesity-related HTN, it seems that drugs that blockade the RAAS and target the SNS should be ideal for treatment. There is not much evidence in the literature that one drug is better than another in controlling obesity-related HTN. There have only been a few studies specifically targeting the obese hypertensive patient, but recent trials that emphasize the importance of BP control have enrolled both overweight and obese subjects. Until we have further studies with more in-depth information about the mechanisms of obesity-related HTN and what the targeted treatment should be, the most important factor necessary to control the obesity-related HTN pandemic and its CVD and CKD consequences is to prevent and treat obesity and to treat HTN to goal.

Glucagon-like peptide-1 and candesartan additively improve glucolipotoxicity in pancreatic β-cells

Glucagon-like peptide-1 (GLP-1) and angiotensin II type 1 receptor blocker reduce β-cell apoptosis in diabetes, but the underlying mechanisms are not fully understood. We examined the combination effects of GLP-1 and candesartan, an angiotensin II type 1 receptor blocker, on glucolipotoxicity-induced β-cell apoptosis; and we explored the possible mechanisms of the antiapoptotic effects. The effects of GLP-1 and/or candesartan on glucolipotoxicity-induced apoptosis and the phosphorylation of insulin receptor substrate-2 (IRS-2), protein kinase B (PKB), and forkhead box O1 (FoxO1) were evaluated by using MIN6 cells and isolated mouse pancreatic islets. Although palmitate significantly enhanced the high-glucose-induced apoptosis in both islets and MIN6 cells, GLP-1 and candesartan significantly inhibited apoptosis; and combination treatment additively prevented apoptosis. Whereas palmitate significantly decreased the phosphorylation of IRS-2, PKB, and FoxO1 in MIN6 cells, these changes were significantly inhibited by treatment with GLP-1 and/or candesartan. In addition, wortmannin, an inhibitor of phosphoinositide 3-kinase, markedly inhibited GLP-1- and/or candesartan-mediated PKB and FoxO1 phosphorylation. The present results suggest that GLP-1 and candesartan additively prevent glucolipotoxicity-induced apoptosis in pancreatic β-cells through the IRS-2/phosphoinositide 3-kinase/PKB/FoxO1 signaling pathway.

Effects of telmisartan and losartan on cardiovascular protection in Japanese hypertensive patients

The Telmisartan and Losartan Cardiac Evaluation Trial, a multicenter, prospective, randomized, open-labeled, blinded-endpoint trial, was designed to compare the effects of two angiotensin II receptor blockers (ARBs), telmisartan and losartan, on cardiovascular protection in Japanese patients with mild to moderate essential hypertension. We compared the effects of telmisartan and losartan on left ventricular (LV) hypertrophy, cardiac function, atherosclerosis of carotid arteries and surrogate markers related to the actions of peroxisome proliferator-activated receptor-γ. A total of 58 patients were enrolled in the present trial and the follow-up period was 1 year. There were no significant differences in blood pressure (BP) levels between the telmisartan group and the losartan group throughout the trial. The percentage of the patients treated with ARB monotherapy was significantly higher in the telmisartan group compared with the losartan group. In addition, the progression of intima-media thickness of common carotid artery was significantly inhibited in the telmisartan group compared with the losartan group. Neither group experienced significant changes in cardiac function and LV mass index. There were no differences between the groups with respect to changes in surrogate markers such as serum adiponectin, creatinine, homeostasis model assessment index, plasminogen activator inhibitor-1 and high sensitivity C-reactive protein. Although BP levels were equal and well controlled in both groups, telmisartan showed more protective vascular effects than losartan.

Irbesartan improves endothelial dysfunction, abnormal lipid profile, proteinuria and liver dysfunction in Zucker diabetic fatty rats independent of glucose and insulin levels

Treatment with angiotensin type 1 receptor blockers (ARBs) is known to improve renal dysfunction and glucose metabolism in obese diabetic animal models and humans. This study examined the effects of irbesartan, a unique ARB with PPARγ activation, on endothelial dysfunction, renal dysfunction, abnormal lipid profile, and liver dysfunction in obese fa/fa Zucker diabetic fatty (ZDF) rats. ZDF rats were administered irbesartan (30 mg/kg/day p.o.) for 12 weeks. Blood pressure, glucose metabolism, lipid profile and renal function were measured every 4 weeks. Response of mesenteric artery rings to acetylcholine was also evaluated as an index of endothelial function after 12 weeks of treatment. Although irbesartan did not affect glucose and insulin levels in both glucose and insulin tolerance tests, decreases in systolic blood pressure, dyslipidemia, and urinary protein excretion were noted from 4 weeks after the start of treatment and continued until 12 weeks. Endothelial and liver dysfunctions were also improved after 12 weeks of treatment. Compared to previous reports showing the effects of irbesartan at later time points such as 6 or 12 months, the present study demonstrated that a low-dose of irbesartan had favorable effects from the early period of treatment, independent of glucose metabolism. Our findings suggest that a low-dose of irbesartan improves diabetic complications quickly after starting treatment, and may support the use of irbesartan for preventing progression of diabetic complications.

Angiotensin II upregulation of cardiomyocyte adiponectin production is nitric oxide/cyclic GMP dependent

INTRODUCTION

Adiponectin is a circulating cytokine that is now known to be synthesized by cardiomyocytes. Accumulating evidence has shown that adiponectin production is upregulated in patients with heart failure, with activation of the renin-angiotensin system and increased formation of angiotensin (Ang) II playing a critical role in left ventricular remodeling and heart failure. To determine whether Ang II upregulates adiponectin in hypertrophic cardiomyocytes, the authors need to explore the underlying mechanisms that could be involved.

METHODS

To test this hypothesis, neonatal rat ventricular myocytes (NRVMs) were treated with various concentrations of Ang II, and adiponectin expression was measured by quantitative real-time reverse transcription-polymerase chain reaction and Western immunoblotting.

RESULTS

Adiponectin mRNA expression was significantly increased by Ang II at concentrations from 10(-6) to 10(-8) M and was increased in a time-dependent manner at concentrations of 10(-7) M. Angiotensin type-2 receptor activation is required for Ang II-stimulated effects on adiponectin. A nitric oxide synthase inhibitor (Nx-nitro-l-arginine methyl ester hydrochloride) and an analog of cGMP antagonist (Rp-8-Br-CGMP-S) blocked Ang II-mediated upregulation of adiponectin.

CONCLUSIONS

These data suggest a mechanism whereby Ang II upregulates adiponectin in NRVMs via the angiotensin type-2 receptor/nitric oxide/cGMP/ protein kinase G signaling pathway.

Inhibitory effect of the D(3) dopamine receptor on insulin receptor expression and function in vascular smooth muscle cells

BACKGROUND

Vascular smooth muscle cell (VSMC) proliferation is regulated by numerous hormones and humoral factors. Our previous study found that stimulation of D(1)-like dopamine receptors inhibited insulin receptor expression and function in VSMCs. We hypothesize that there is also an interaction between D(3) dopamine and insulin receptors, i.e., stimulation of the D(3) receptor inhibits insulin receptor expression and function.

METHODS

Receptor expression was determined by immunoblotting, immunohistochemisty, and reverse transcriptase-PCR; VSMC proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-diphenyl-tetrazolium bromide (MTT) assay and cell number.

RESULTS

Insulin receptor protein is increased in the aorta of D(3) receptor deficient mice. Stimulation of the D(3) receptor inhibited insulin receptor mRNA and protein expression and insulin-mediated VSMC proliferation, and increased protein kinase A (PKA) activity, insulin receptor phosphorylation, and degradation in immortalized aortic VSMCs (A10 cells). These effects were blocked by a PKA inhibitor, indicating that the D(3) receptor-mediated decrease in insulin receptor expression was related to a decrease in transcription/post-transcription and increased degradation, involving PKA signaling.

CONCLUSIONS

D(3) receptor stimulation may be a target to reduce the adverse effect of insulin in hypertension by inhibition of insulin receptor expression and function in arterial VSMCs.

Telmisartan provides protection against development of impaired vasodilation independently of metabolic effects in SHRSP.Z-Lepr(fa)/IzmDmcr rats with metabolic syndrome

Metabolic syndrome is known to facilitate the development of cardiovascular disease. We have demonstrated that mesenteric arteries of SHRSP.Z-Lepr(fa)/IzmDmcr (SHRSP-fatty) rats with metabolic syndrome display an impaired vasorelaxation response mediated by nitric oxide. We examined whether the condition could be alleviated by treatment with telmisartan, an angiotensin II type 1 (AT1) receptor antagonist with PPAR-γ-activating properties and compared the results with those from pioglitazone, a PPAR-γ agonist. Telmisartan (5 mg·kg(-1)·day(-1)) or pioglitazone (2.5 mg·kg(-1)·day(-1)) was orally administered to male SHRSP-fatty rats for 8 weeks. Serum triglyceride and cholesterol levels were determined, and the oral glucose tolerance test was performed to evaluate insulin resistance. Vasodilations in response to acetylcholine and nitroprusside were determined by wire myographs under isometric tension conditions, protein expressions of soluble guanylyl cyclase in mesenteric arteries by Western blotting, and the contents of 3-nitrotyrosine in aortas by high-performance liquid chromatography with electrochemical detection. Telmisartan exerted antihypertensive effects, while pioglitazone ameliorated metabolic abnormalities in SHRSP-fatty rats. Telmisartan increased acetylcholine- and nitroprusside-induced relaxation and soluble guanylyl cyclase protein expression in mesenteric arteries and reduced 3-nitrotyrosine content in aortas. Pioglitazone displayed no such alleviating effects on vascular functions. These findings indicate that telmisartan protects against vasodilation disturbance through anti-oxidative and -nitrative stress independently of metabolic effects in SHRSP-fatty rats with metabolic syndrome.

Interaction between Adiponectin and Aldosterone

More than two thirds of the US population are considered overweight or obese. Adipocytes are now appreciated as important endocrine organs, secreting various factors with hormonal effects. Several different adipokines have been identified, including adiponectin, which is associated with improved insulin sensitivity, a better lipoprotein profile, and lower rates of vascular inflammation and cardiovascular disease. Several studies have identified the renin-angiotensin-aldosterone system as important in the regulation of adiponectin. These studies lay the fundamental groundwork for developing targeted therapies with potential to reduce the burden of obesity-associated diseases, such as the cardiorenal metabolic syndrome.

Molecular determinants of the cardiometabolic phenotype

The metabolic syndrome represents a clustering of risk factors that has been shown to predict adverse cardiovascular outcomes. Although the precise mechanisms contributing to the cardiometabolic syndrome (CMS) remain poorly defined, accumulating evidence identifies two intersecting candidate pathways responsible for inflammation and energy homeostasis in the pathophysiology that underlie cardiometabolic traits. Although currently no pharmacologic interventions specifically target CMS, future drug development efforts should attempt to capitalize on molecular nodes at the intersections of these pathways in the CMS.

Weight loss and hypophagia after high-dose AT1-blockade is only observed after high dosing and depends on regular leptin signalling but not blood pressure

AT(1)-blockade has been shown to induce weight loss in animals or patients. The aim of this study was to investigate whether weight reduction after AT(1)-blockade is dependent on dose, blood pressure reduction and leptin signalling. Spontaneously hypertensive rats (SHR) and lean and obese Zucker rats were treated for 4 weeks with candesartan (0, 2, 6 or 16 mg/kg/day). Body weight, food intake and hypothalamic mRNA levels of (an)orexigenic peptides were determined. Obese Zucker rats served as a model of primary leptin resistance. In SHR, body mass index and food intake were decreased selectively by 16 mg/kg/day candesartan but not after using normal (2 mg/kg/day) or supranormal (6 mg/kg/day) doses. Correlation analysis between blood pressure and body weight indicated no relationship of hypotensive potency on weight loss. The hypothalamic mRNA levels of the orexigenic peptide MCH (melanin-concentrating hormone) were diminished in parallel. Consistent to the results in SHRs, 16 mg/kg/day candesartan revealed a decrease of body weight, food intake and hypothalamic MCH mRNA levels in lean Zucker rats. In obese Zucker rats, none of these parameters were reduced by candesartan. Loss of body weight and hypophagia are not general features of AT(1)-blockers, since neither was seen after normal or moderately supranormal doses, but they were, after the highest doses. These actions of AT(1)-blockers occur independently of their ability to lower blood pressure. They do depend on an intact leptin signalling, since they were absent in obese Zucker rats that feature a genetic mutation of the leptin receptor.

Pharmacological and non-pharmacological interventions to influence adipose tissue function

Obesity is associated with metabolic derangements such as insulin resistance, inflammation and hypercoagulobility which can all be understood as consequences of adipose tissue dysfunction. The potential role for adipose tissue derived cytokines and adipokines in the development of vascular disease and diabetes may produce a clinical need to influence adipose tissue function. Various pharmacological and non-pharmacological interventions affect plasma cytokine and adipokine levels. The effects of these interventions depend on weight loss per se, changes in fat distribution without weight loss and/or direct effects on adipose tissue inflammation.

Weight loss, as a result of diet, pharmacology and surgery, positively influences plasma adipokines and systemic inflammation. Several classes of drugs influence systemic inflammation directly through their anti-inflammatory actions. PPAR-γ agonism positively influences adipose tissue inflammation in several classes of intervention such as the thiazolidinediones and perhaps salicylates, CB1-antagonists and angiotensin II receptor blockers. Furthermore, within drug classes there are differential effects of individual pharmacologic agents on adipose tissue function.

It can be concluded that several commonly used pharmacological and non-pharmacological interventions have unintended influences on adipose tissue function. Improving adipose tissue function may contribute to reducing the risk of vascular diseases and the development of type 2 diabetes.

Discovery and development of selective PPAR gamma modulators as safe and effective antidiabetic agents

IMPORTANCE OF THE FIELD

PPARgamma full agonists (pioglitazone and rosiglitazone) are the mainstay drugs for the treatment of type 2 diabetes; however, mechanism-based side effects have limited their full therapeutic potential. In recent years, much progress has been achieved in the discovery and development of selective PPARgamma modulators (SPPARgammaMs) as safer alternatives to PPARgamma full agonists.

AREAS COVERED IN THIS REVIEW

This review focuses on the preclinical and clinical data of all the SPPARgammaMs discovered so far, retrieved by searching PubMed, Prous Integrity database and company news updates from 1999 to date.

WHAT THE READER WILL GAIN

Here we thoroughly discuss SPPARgammaMs' mode of action, briefly examine new ways to identify superior SPPARgammaMs, and finally, compare and contrast the pharmacological and safety profile of various agents.

TAKE HOME MESSAGE

The preclinical and clinical findings clearly suggest that selective PPARgamma modulators have the potential to become the next generation of PPARgamma agonists: effective insulin sensitizers with a superior safety profile to that of PPARgamma full agonists.