Telmisartan prevents the glitazone-induced weight gain without interfering with its insulin-sensitizing properties

Telmisartan versus metformin in downregulating myostatin gene expression and enhancing insulin sensitivity in the skeletal muscles of type 2 diabetic rat model

Objective: Telmisartan is an angiotensin receptor blocker (ARB) that specifically blocks angiotensin II type-1 receptors (AT1R). Telmisartan has been proven to have antidiabetic effects via a variety of mechanisms, and it can be utilized in some diabetic patients due to its dual benefit for hypertensive patients with type 2 DM (T2DM) and when the other oral antidiabetic medications are intolerable or contraindicated. However, its precise underlying hypoglycemic mechanism is still obscure. Aim of work: We sought to establish a link between telmisartan administration and myostatin expression in skeletal muscles of T2DM rat model as a potential hypoglycemic mechanism of telmisartan. Materials and Methods: 32 male albino rats were included in the study; 8 rats served as controls (group I). T2DM was inducted in the other 24 rats, which were then randomly subdivided into 3 groups (8 in each): (group II) the Diabetic group and (groups III and IV) which were treated with either telmisartan (8 mg/kg/day) or metformin (250 mg/kg/day) respectively via oral gavage for a 4-week period. Results: Telmisartan administration resulted in a significant improvement in OGTT, HOMA-IR, glucose uptake, and muscle mass/body ratios in Telmisartan group as compared to Diabetic group (p < 0.05). Additionally, telmisartan induced a significant boost in adiponectin and IL-10 serum levels with a substantial drop in TNF-α and IL-6 levels in Telmisartan group compared to diabetic rats (p < 0.05). Moreover, telmisartan significantly boosted SOD and GSH, and decreased MDA levels in the skeletal muscles of telmisartan group. Furthermore, a significant downregulation of myostatin and upregulation of insulin receptor, IRS-1, and IRS-3 genes in the skeletal muscles of Telmisartan group were also detected. Histologically, telmisartan attenuated the morphological damage in the skeletal muscle fibers compared to diabetic rats, as evidenced by a considerable decrease in the collagen deposition area percentage and a reduction in NF-kB expression in the muscle tissues of group III. Conclusion: Telmisartan administration dramatically reduced myostatin and NF-kB expressions in skeletal muscles, which improved insulin resistance and glucose uptake in these muscles, highlighting a novel antidiabetic mechanism of telmisartan in treating T2DM.

Peroxisome proliferator-activated receptors-alpha and gamma synergism modulate the gut-adipose tissue axis and mitigate obesity

AIM

To evaluate the effects of single PPARα or PPARγ activation, and their synergism (combined PPARα/γ activation) upon the gut-adipose tissue axis, focusing on the endotoxemia and upstream interscapular brown adipose tissue (iBAT) function in high-saturated fat-fed mice.

METHODS

Male C57BL/6 mice received a control diet (C, 10% lipids) or a high-fat diet (HF, 50% lipids) for 12 weeks. Then, the HF group was divided to receive the treatments for four weeks: HFγ (pioglitazone, 10 mg/kg), HFα (WY-14643, 3.5 mg/kg), and HFα/γ (tesaglitazar, 4 mg/kg).

RESULTS

The HF group exhibited overweight, oral glucose intolerance, gut dysbiosis, altered gut permeability, and endotoxemia, culminating in iBAT whitening. The downregulation of LPS-Tlr4 signaling underpinned reduced inflammation and improved lipid metabolism in iBAT in the HFα/γ group, the unique to show normalized body mass and increased energy expenditure.

CONCLUSION

PPARα/γ synergism treated obesity by ameliorating the gut-adipose tissue axis, where restored gut microbiota and permeability controlled endotoxemia and rescued iBAT whitening through favored thermogenesis.

A Role for Peroxisome Proliferator-Activated Receptor Gamma Agonists in Counteracting the Degeneration of Cardiovascular Grafts

ABSTRACT

Aortic valve replacement for severe stenosis is a standard procedure in cardiovascular medicine. However, the use of biological prostheses has limitations especially in young patients because of calcifying degeneration, resulting in implant failure. Pioglitazone, a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist, was shown to decrease the degeneration of native aortic valves. In this study, we aim to examine the impact of pioglitazone on inflammation and calcification of aortic valve conduits (AoC) in a rat model. Cryopreserved AoC (n = 40) were infrarenally implanted into Wistar rats treated with pioglitazone (75 mg/kg chow; n = 20, PIO) or untreated (n = 20, controls). After 4 or 12 weeks, AoC were explanted and analyzed by histology, immunohistology, and polymerase chain reaction. Pioglitazone significantly decreased the expression of inflammatory markers and reduced the macrophage-mediated inflammation in PIO compared with controls after 4 (P = 0.03) and 12 weeks (P = 0.012). Chondrogenic transformation was significantly decreased in PIO after 12 weeks (P = 0.001). Calcification of the intima and media was significantly reduced after 12 weeks in PIO versus controls (intima: P = 0.008; media: P = 0.025). Moreover, echocardiography revealed significantly better functional outcome of the AoC in PIO after 12 weeks compared with control. Interestingly, significantly increased intima hyperplasia could be observed in PIO compared with controls after 12 weeks (P = 0.017). Systemic PPAR-gamma activation prevents inflammation as well as intima and media calcification in AoC and seems to inhibit functional impairment of the implanted aortic valve. To further elucidate the therapeutic role of PPAR-gamma regulation for graft durability, translational studies and long-term follow-up data should be striven for.

Vitamin D/VDR regulates peripheral energy homeostasis via central renin-angiotensin system

Introduction

Some epidemiological studies have revealed that vitamin D (VD) deficiency is closely linked with the prevalence of obesity, however, the role of VD in energy homeostasis is yet to be investigated, especially in central nervous system. Given that VD negatively regulates renin in adipose tissue, we hypothesized that central VD might play a potential role in energy homeostasis.

Objectives

The present study aims to investigate the potential role of VD in energy homeostasis in the CNS and elaborate its underlying mechanisms.

Methods

This study was conducted in Cyp27b1^−/− mice, VD-treated and wild-type mice. After the intraventricular injection of renin or its inhibitors, the changes of renin-angiotensin system (RAS) and its down-stream pathway as well as their effects on metabolic rate were examined.

Results

The RAS activity was enhanced in Cyp27b1^−/− mice, exhibiting a increased metabolic rate. Additionally, corticotropin-releasing hormone (CRH), a RAS-mediated protein regulating energy metabolism in the hypothalamus, increased significantly in Cyp27b1^−/− mice. While in VD-treated group, the RAS and sympathetic nerve activities were slightly inhibited, hence the reduced metabolic rate.

Conclusion

Collectively, the present study demonstrates that the VD/vitamin D receptor (VDR) has a significant impact on energy homeostasis through the modulation of RAS activity in the hypothalamus, subsequently altering CRH expression and sympathetic nervous activity.

Effects of telmisartan and pioglitazone on high fructose induced metabolic syndrome in rats

Metabolic syndrome (MS) is a cluster of hypertension, insulin resistance, dyslipidaemia, and hyperuricemia. This study was designed to assess the effect of telmisartan and pioglitazone on high fructose induced MS. Thirty-five male albino rats were classified into 5 groups: A, normal diet; B, high-fructose diet (HFD) subdivided into B1 (HFD only), B2 (telmisartan, 5 mg/kg), B3 (pioglitazone, 10 mg/kg), and B4 (telmisartan + pioglitazone). Administration of the drugs was started after the rats had been on HFD for 4 weeks and continued for 4 weeks. Body mass (BM), blood pressure (BP), uric acid (UA), total cholesterol, triglycerides (TG), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c), blood urea nitrogen (BUN), creatinine, and nitric oxide (NO) were measured and the levels of fasting glucose and fasting insulin were estimated. Compared with group B1, telmisartan treatment significantly decreased BP, BM, serum glucose, insulin, UA, urea, cholesterol, TGA, and LDL and significantly increased HDL, whereas pioglitazone treatment significantly decreased BP, serum glucose, insulin, UA, urea, creatinine, cholesterol, TGA, and LDL and significantly increased HDL. Co-administration of pioglitazone + telmisartan significantly decreased insulin, urea, and creatinine compared with telmisartan alone. Combined telmisartan + pioglitazone allowed better control of BP, hyperglycaemia, insulin resistance, and the amelioration of BM increase that may be associated with pioglitazone treatment.

Effect of telmisartan on the therapeutic efficacy of pitavastatin in high-fat diet induced dyslipidemic guinea pigs

Angiotensin II-receptor blockers (ARBs), similar to HMG-CoA reductase inhibitors (statins), could improve lipid metabolism abnormalities. There might be some cross-talking pathways between statins and ARBs to produce additive beneficial effects on lipid metabolism in dyslipidemia. However, few studies investigate the effects of ARBs on the therapeutic efficacy of statins in dyslipidemia. The present study was designed to systematically evaluate the effects of telmisartan on the therapeutic efficacy of pitavastatin on lowering lipid level and reducing fat deposition by employing a dyslipidemia model, guinea pigs. 48 Male guinea pigs fed with high-fat diet were randomly grouped and treated with vehicle, telmisartan, pitavastatin or telmisartan/pitavastatin combinations. After treatment for eight weeks, telmisartan could significantly enhance the therapeutic efficacy of pitavastatin by extremely reducing body weight gain, weight of adipose tissue and adipocyte size. However, telmisartan/pitavastatin combinations could not further improve lipid levels on the basis of pitavastain, though single telmisartan markedly decreased triglyceride (TG) and slightly increased high density lipoprotein cholesterol (HDL-C). Moreover, telmisartan/pitavastatin combinations significantly upregulated the gene expression level of peroxisome proliferator-activated receptor (PPAR)-δ, but no effects on the expression of PPAR-α/γ, leptin and adiponectin compared to monotherapy. Taken together, our studies provided new evidences that telmisartan has an additive beneficial influence on decreasing fat deposition and weight gain through PPAR-δ pathway but cannot enhance the therapeutic efficacy of pitavastatin on lowering lipid levels. The combinational administration of telmisartan and pitavastatin could be a potential therapeutic strategy for dyslipidemia related obesity and worthy of further investigation in obese animal models.

Preventing leptin resistance by blocking angiotensin II AT1 receptors in diet-induced obese rats

BACKGROUND AND PURPOSE

AT1 receptor blockers (ARBs) represent an approach for treating metabolic syndrome due to their potency in reducing hypertension, body weight and onset of type 2 diabetes. The mechanism underlying ARB-induced weight loss is still unclear.

EXPERIMENTAL APPROACH

Leptin resistance tests (LRTs) in diet-induced obese or lean rats were conducted to determine whether telmisartan (8 mg·kg(-1) ·day(-1) , 14 days) enhances leptin sensitivity. Phosphorylation of signal transducer and activator of transcription 3 (pSTAT3) staining was performed in hypothalami to determine leptin transport across the blood-brain barrier.

KEY RESULTS

Telmisartin reduced weight gain, food intake and plasma leptin but blood pressure remained unchanged. The 24 h profiles of plasma leptin after saline injections were similar in controls and telmisartan-treated rats, but after leptin injections were higher in controls and slightly lower in telmisartan-treated animals. After telmisartan, energy intake during LRT was lower in leptin- than in saline-pretreated rats, but remained unchanged in controls, irrespectively of whether rats received saline or leptin. Leptin minimized the gain in body weight during LRT in telmisartan-treated rats as compared with saline-treated animals. pSTAT3 staining was reduced in cafeteria diet-fed rats as compared with chow-fed rats but this was normalized by telmisartan. Telmisartin reduced hypothalamic mRNA levels of the orexigenic peptides melanin-concentrating hormone and prepro-orexin.

CONCLUSIONS AND IMPLICATIONS

Rats fed a cafeteria diet develop leptin resistance after 2 weeks. Leptin sensitivity was preserved by telmisartan treatment even in rats fed a cafeteria diet. This pleiotropic effect is not related to the hypotensive action of telmisartan.

Chronic blockade of angiotensin AT₁ receptors improves cardinal symptoms of metabolic syndrome in diet-induced obesity in rats

BACKGROUND AND PURPOSE

AT₁ receptor antagonists decrease body weight gain in models of murine obesity. However, fewer data are available concerning the anti-obesity effects of these antagonists, given as a treatment after obesity had been established.

EXPERIMENTAL APPROACH

In spontaneously hypertensive rats, obesity was established by cafeteria diet (CD) feeding for 19 weeks. Rats were then were treated with telmisartan (8 mg·kg⁻¹·d⁻¹) or amlodipine (10 mg·kg⁻¹·d⁻¹; serving as blood pressure control) or telmisartan + amlodipine (2 + 10 mg·kg⁻¹·d⁻¹; to control for dose-dependency) for 17 weeks. Rats receiving only chow (C(chow)) or CD-fed rats treated with vehicle (C(CD)) served as controls.

KEY RESULTS

The CD feeding induced obesity, hyperphagia, hyperlipidaemia, and leptin and insulin resistance. Telmisartan reduced the CD-induced increase in body weight and abdominal fat mass. Whereas energy intake was higher rather than lower, the respiratory ratio was lower. After telmisartan, leptin-induced energy intake was reduced and respiratory ratio was increased compared with C(CD) rats. Telmisartan also decreased plasma levels of triglycerides, free fatty acids and low-density lipoprotein. Amlodipine alone or the combination telmisartan + amlodipine did not affect body weight and eating behaviour. Telmisartan, but not amlodipine and telmisartan + amlodipine, improved glucose utilization. The decrease in BP reduction was almost the same in all treatment groups.

CONCLUSIONS AND IMPLICATIONS

Telmisartan exerted anti-obesity effects and restored leptin sensitivity, given as a treatment to rats with obesity. Such effects required high doses of telmisartan and were independent of the decrease in blood pressure.

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.

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.

Metabolic rate regulation by the renin-angiotensin system: brain vs. body

Substantial evidence supports a role for the renin-angiotensin system (RAS) in the regulation of metabolic function, but an apparent paradox exists where genetic or pharmacological inhibition of the RAS occasionally has similar physiological effects as chronic angiotensin infusion. Similarly, while RAS targeting in animal models has robust metabolic consequences, effects in humans are more subtle. Here, we review the data supporting a role for the RAS in metabolic rate regulation and propose a model where the local brain RAS works in opposition to the peripheral RAS, thus helping to explain the paradoxically similar effects of RAS supplementation and inhibition. Selectively modulating the peripheral RAS or brain RAS may thus provide a more effective treatment paradigm for obesity and obesity-related disorders.

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.

Adipogenesis and insulin sensitivity in obesity are regulated by retinoid-related orphan receptor gamma

Obesity is a well-known risk factor for the development of secondary complications such as type 2 diabetes. However, only a part of the obese population develops secondary metabolic disorders. Here, we identify the transcription factor retinoid-related orphan receptor gamma (RORγ) as a negative regulator of adipocyte differentiation through expression of its newly identified target gene matrix metalloproteinase 3. In vivo differentiation of adipocyte progenitor cells from Rorγ-deficient mice is enhanced and obese Rorγ^−/− mice show decreased adipocyte sizes. These small adipocytes are highly insulin sensitive, leading to an improved control of circulating free fatty acids. Ultimately, Rorγ^−/− mice are protected from hyperglycemia and insulin resistance in the state of obesity. In adipose stromal-vascular fraction from obese human subjects, Rorγ expression is correlated with adipocyte size and negatively correlated with adipogenesis and insulin sensitivity. Taken together, our findings identify RORγ as a factor, which controls adipogenesis as well as adipocyte size and modulates insulin sensitivity in obesity. RORγ might therefore serve as a novel pharmaceutical target to treat obesity-associated insulin resistance.

Pancreatic ultrastructural enhancement due to telmisartan plus sitagliptin treatment in diet-induced obese C57BL/6 mice

OBJECTIVE

We sought to evaluate the effects of telmisartan, sitagliptin, or their combination on pancreatic ultrastructural alterations in high-fat-fed C57BL/6 mice.

METHODS

Three-month-old C57BL/6 mice were fed with standard chow (SC, 10% lipids) or high-fat diet (HF, 60% lipids) during 10 weeks to induce obesity and its comorbidities. After this period, treatment began (lasted 6 weeks), and the HF group was divided into 4 subgroups: untreated HF, HF plus telmisartan (5 mg/kg per day), HF plus sitagliptin (1.1 g/kg per day), and HF plus telmisartan plus sitagliptin. Drugs were mixed with diet. Biochemical analyses, radioimmunoassay, immunofluorescence, stereology, and transmission electron microscopy were performed to assess pancreatic remodeling.

RESULTS

Overweight, hyperinsulinemia, hyperglycemia, and dyslipidemia were found in the HF group, but these outcomes were controlled by the different treatments. Untreated HF animals also showed alterations concerning distribution of α/β cell followed by large and numerous lipid droplets within pancreas. Telmisartan and sitagliptin as monotherapy alleviated these findings, and a complete reversal of pancreatic steatosis was observed after treating with the combination of the 2 drugs.

CONCLUSIONS

AT1 receptor blockade, partial peroxisome proliferator-activated receptor gamma activation, and extended incretin action emerge as feasible strategies to control pancreatic steatosis and avoid progression of pancreatic diseases due to lipotoxicity.

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.

Telmisartan ameliorates hyperglycemia and metabolic profile in nonobese Cohen-Rosenthal diabetic hypertensive rats via peroxisome proliferator activator receptor-gamma activation

The importance of hypertension treatment has expanded beyond blood pressure management to include additional risk factors, mainly diabetes. It was considered of interest to test the effect of telmisartan, an angiotensin receptor 1 antagonist and peroxisome proliferator activator receptor-gamma partial agonist, on Cohen-Rosenthal diabetic hypertensive nonobese (CRDH) rats, a unique model combining both pathologies. Its effect was examined on fat-derived and inflammatory agents in CRDH. To determine the extent of the drug's peroxisome proliferator activator receptor-gamma modulating beneficial metabolic actions, results were compared with those obtained with valsartan and rosiglitazone in CRDH and Cohen diabetic rat (CDR). Telmisartan and valsartan were given in drinking water at 3 and 12 mg/kg/d, whereas rosiglitazone (3 mg/kg/d) was given as food admixture for a period of 5 months. Blood pressure, glucose, insulin, adiponectin, leptin, and tumor necrosis factor alpha were examined. Telmisartan and valsartan significantly (P < .01) reduced blood pressure, whereas telmisartan and rosiglitazone considerably reduced blood glucose levels to normoglycemic levels (P < .01) in these 2 strains. Insulin levels were not affected by telmisartan and valsartan but were slightly reduced by rosiglitazone in CDR. In contrast to valsartan, adiponectin was significantly (60%, P < .01) increased by telmisartan in both CDR and CRDH, whereas rosiglitazone induced a 60% and 180% increase in CRDH and CDR animals, respectively, on day 30 of treatment. Co-treatment with GW9662 averted telmisartan-induced rise of adiponectin. Tumor necrosis factor alpha declined in telmisartan-treated rats, less so with rosiglitazone, but not valsartan. Telmisartan also induced downsizing of epididymal adipocytes compared with valsartan. Leptin levels were significantly increased by valsartan (P < .05) but reduced by telmisartan and rosiglitazone. The telmisartan-induced increase in adiponectin was most probably associated with a decrease in glucose and tumor necrosis factor alpha levels. Therefore, in addition to its hypotensive effect, telmisartan demonstrated beneficial thiazolidinedione-like effects.

Telmisartan alleviates rosiglitazone-induced bone loss in ovariectomized spontaneous hypertensive rats

In the present study, we systematically examined telmisartan, an angiotensin AT(1) receptor antagonist, on rosiglitazone-induced bone loss in ovariectomized spontaneously hypertensive rats. Telmisartan (5 mg/kg/d, 90 days) was found to be able to significantly alleviate rosiglitazone (10 mg/kg/d, 90 days)-induced decrease in BMD of femur and lumbar vertebrae. The BMD changes were associated with positive biomechanical changes of lumbar vertebrae, improvements in microarchitecture of tibial metaphysic and normalized serum osteocalcin (OC) levels and urinary deoxypyridinoline/creatinine (DPD/Cr) ratio. MicroCT analysis of the tibial metaphysis showed that telmisartan significantly prevented the decreases in bone volume/tissue volume (BV/TV), connect density (Conn. D.), trabecular number (Tb. N.) and trabecular thickness (Tb. Th.), and increase in trabecular separation (Tb. Sp.) induced by rosiglitazone. Histomorphometric analysis also showed that telmisartan had protective effects on rosiglitazone-reduced bone formation indices such as histomorphometric bone volume fraction (BV/TV-Histo), mineralizing surface/bone surface (MS/BS), mineral apposition rate (MAR) and bone formation rate (BFR/BS). Our study clearly showed that telmisartan alleviated rosiglitazone-induced bone loss in ovariectomized spontaneous hypertensive rats. The relief of bone loss provides a possible therapeutic application of telmisartan with rosiglitazone for the treatment of elderly women patients afflicted with metabolic syndrome.

Comparative effects of telmisartan, sitagliptin and metformin alone or in combination on obesity, insulin resistance, and liver and pancreas remodelling in C57BL/6 mice fed on a very high-fat diet

The aim of the present study was to evaluate the effects of monotherapies and combinations of drugs on insulin sensitivity, adipose tissue morphology, and pancreatic and hepatic remodelling in C57BL/6 mice fed on a very HF (high-fat) diet. Male C57BL/6 mice were fed on an HF (60% lipids) diet or SC (standard chow; 10% lipids) diet for 10 weeks, after which time the following drug treatments began: HF-T (HF diet treated with telmisartan; 5.2 mg x kg-1 of body weight x day-1), HF-S (HF diet treated with sitagliptin; 1.08 g x kg-1 of body weight.day-1), HF-M (HF diet treated with metformin; 310.0 mg x kg-1 of body weight x day-1), HF-TM (HF diet treated with telmisartan+metformin), HF-TS (HF diet treated with telmisartan+sitagliptin) and HF-SM (HF diet treated with sitagliptin+metformin). Treated groups also had free access to the HF diet, and treatments lasted for 6 weeks. Morphometry, stereological tools, immunostaining, ELISA, Western blot analysis and electron microscopy were used. The HF diet yielded an overweight phenotype, an increase in oral glucose intolerance, hyperinsulinaemia, hypertrophied islets and adipocytes, stage 2 steatosis (>33%), and reduced liver PPAR-alpha (peroxisome-proliferator-activated receptor-alpha) and GLUT-2 (glucose transporter-2) levels, concomitant with enhanced SREBP-1 (sterol-regulatory-element-binding protein-1) expression (P<0.0001). Conversely, all drug treatments resulted in significant weight loss, a reversal of insulin resistance, islet and adipocyte hypertrophy, and alleviated hepatic steatosis. Only the HF-T and HF-TS groups had body weights similar to the SC group at the end of the experiment, and the latter treatment reversed hepatic steatosis. Increased PPAR-alpha immunostaining in parallel with higher GLUT-2 and reduced SREBP-1 expression may explain the favourable hepatic outcomes. Restoration of adipocyte size was consistent with higher adiponectin levels and lower TNF-alpha (tumour necrosis factor-alpha) levels (P<0.0001) in the drug-treated groups. In conclusion, all of the drug treatments were effective in controlling the metabolic syndrome. The best results were achieved using telmisartan and sitagliptin as monotherapies or as a dual treatment, combining partial PPAR-gamma agonism and PPAR-alpha activation in the liver with extended incretin action.

Telmisartan: a different angiotensin II receptor blocker protecting a different population?

The ONgoing Telmisartan Alone and in combination with Ramipril Global Endpoint Trial (ONTARGET()) showed that the angiotensin II receptor blocker (ARB) telmisartan was as protective as the reference-standard ramipril in a broad cross-section of patients at increased cardiovascular risk, but was better tolerated. Telmisartan has a unique profile among ARBs, with a high affinity for the angiotensin II type 1 receptor, a long duration of receptor binding, a high lipophilicity and a long plasma half life. This leads to sustained and powerful blood pressure lowering when compared with the first marketed ARBs, such as losartan and valsartan. Some pharmacological properties of telmisartan clearly distinguish it from other members of the ARB class and may contribute to the clinical effects seen with telmisartan. A class effect for ARBs cannot be assumed. To date, telmisartan is the only ARB that has been shown to reduce cardiovascular risk in at-risk cardiovascular patients.

Telmisartan prevents weight gain and obesity through activation of peroxisome proliferator-activated receptor-delta-dependent pathways

Telmisartan shows antihypertensive and several pleiotropic effects that interact with metabolic pathways. In the present study we tested the hypothesis that telmisartan prevents adipogenesis in vitro and weight gain in vivo through activation of peroxisome proliferator-activated receptor (PPAR)-delta-dependent pathways in several tissues. In vitro, telmisartan significantly upregulated PPAR-delta expression in 3T3-L1 preadipocytes in a time- and dose-dependent manner. Other than enhancing PPAR-delta expression by 68.2+/-17.3% and PPAR-delta activity by 102.0+/-9.0%, telmisartan also upregulated PPAR-gamma expression, whereas neither candesartan nor losartan affected PPAR-delta expression. In vivo, long-term administration of telmisartan significantly reduced visceral fat and prevented high-fat diet-induced obesity in wild-type mice and hypertensive rats but not in PPAR-delta knockout mice. Administration of telmisartan did not influence food intake in mice. Telmisartan influenced several lipolytic and energy uncoupling related proteins (UCPs) and enhanced phosphorylated protein kinase A and hormone sensitive lipase but reduced perilipin expression and finally inhibited adipogenesis in 3T3-L1 preadipocytes. Telmisartan-associated reduction of adipogenesis in preadipocytes was significantly blocked after PPAR-delta gene knockout. Chronic telmisartan treatment upregulated the expressions of protein kinase A, hormone-sensitive lipase, and uncoupling protein 1 but reduced perilipin expression in adipose tissue and increased uncoupling protein 2 and 3 expression in skeletal muscle in wild-type mice but not in PPAR-delta knockout mice. We conclude that telmisartan prevents adipogenesis and weight gain through activation of PPAR-delta-dependent lipolytic pathways and energy uncoupling in several tissues.

The insulin sparing effect of telmisartan in a case of type 2 diabetes mellitus associated with schizophrenia under treatment of risperidone

A male patient was diagnosed with diabetes mellitus at age 37 and insulin treatment was introduced at age 49. About 2 years after the introduction of insulin, the antihypertensive agent was switched from candesartan (4 mg/day) to telmisartan (20 mg/day). The alteration improved his glycemic control dramatically, with the HbA1c levels decreasing from 8.3% to 6.0% in 6 months. Gradual marked reduction in insulin requirement was observed as it was reduced from 62 U/day to 46 U/day in 6 months and to 18 U/day in 15 months. Also his body weight was reduced from 81 kg to 65 kg in 15 months without remarkable life-style modification. Throughout the whole clinical course mentioned above, he was under treatment for schizophrenia with drugs including risperidone which possibly affects glucose metabolism. The medication for schizophrenia was not changed during this period. We present here the marked glycemia improvement effect and insulin sparing effect of telmisartan in a case of type 2 diabetes mellitus.

Neuroendocrine characterization and anorexigenic effects of telmisartan in diet- and glitazone-induced weight gain

Telmisartan is an angiotensin II receptor blocker with peroxisome proliferator-activated receptor-gamma agonistic properties. Telmisartan prevents weight gain and decreases food intake in models of obesity and in glitazone-treated rodents. This study further investigates the influence of telmisartan and pioglitazone and their association on weight gain and body composition by examining their influence on neuroendocrine mediators involved in food intake. Male C57/Black 6 mice were fed a high-fat diet, weight matched, and randomized in 4 treatment groups: vehicle, pioglitazone, telmisartan, and pioglitazone-telmisartan. Weight gain, food and water intake, body composition, plasma leptin levels, and the hypothalamic expression of neuroendocrine mediators were analyzed. Additional studies were performed with irbesartan and in angiotensin II 1(A) receptor-knockout mice. Telmisartan abolished weight and fat gain in vehicle- and pioglitazone-treated mice while decreasing food intake, the hypothalamic expression of the agouti-related protein, and plasma leptin levels. Modifications in neuropeptide Y and proopiomelanocortin were not consistent with changes in food intake. The effects on weight gain and expression of the agouti-related protein were intermediate with irbesartan. The effects of telmisartan on weight gain were even more pronounced in angiotensin II 1(A) receptor-knockout mice. This study confirms the anorexigenic effects of telmisartan in mice fed a high-fat diet and suggests for the first time a functional role of telmisartan on hypothalamic orexigenic agouti-related protein regulation. These anorexigenic properties abolish both weight gain and body composition modifications in fat-fed and glitazone-treated mice. The anorexigenic properties are independent from the angiotensin II 1(A) receptor.

Evidence against a direct role of klotho in insulin resistance

The klotho gene may be involved in the aging process. Klotho is a coactivator of FGF23, a regulator of phosphate and vitamin D metabolism. It has also been reported to be downregulated in insulin resistance syndromes and paradoxically to directly inhibit IGF-1 and insulin signaling. Our aim was to study klotho's regulation and effects on insulin and IGF-1 signaling to unravel this paradox. We studied klotho tissue distribution and expression by quantitative real-time polymerase chain reaction and Western blotting in obese Zucker rats and high-fat fed Wistar rats, two models of insulin resistance. Klotho was expressed in kidneys but at much lower levels (<1.5%) in liver, muscle, brain, and adipose tissue. There were no significant differences between insulin resistant and control animals. We next produced human recombinant soluble klotho protein (KLEC) and studied its effects on insulin and IGF-1 signaling in cultured cells. In HEK293 cells, FGF23 signaling (judged by FRS2-alpha and ERK1/2 phosphorylation) was activated by conditioned media from KLEC-producing cells (CM-KLEC); however, IGF-1 signaling was unaffected. CM-KLEC did not inhibit IGF-1 and insulin signaling in L6 and Hep G2 cells, as judged by Akt and ERK1/2 phosphorylation. We conclude that decreased klotho expression is not a general feature of rodent models of insulin resistance. Further, the soluble klotho protein does not inhibit IGF-1 and/or insulin signaling in HEK293, L6, and HepG2 cells, arguing against a direct role of klotho in insulin signaling. However, the hypothesis that klotho indirectly regulates insulin sensitivity via FGF23 activation remains to be investigated.

Aliskiren reduces body-weight gain, adiposity and plasma leptin during diet-induced obesity

BACKGROUND AND PURPOSE

Overfeeding increases adipose tissue mass and leptin production and up-regulates the renin-angiotensin system in adipose tissue in rodents. Here, we determined the effect of chronic treatment with the renin inhibitor, aliskiren, in a model of diet-induced obesity in mice, on: (i) body weight, adipose tissue weight and plasma leptin; (ii) food intake and caloric efficiency; and (iii) angiotensin II (Ang II) in adipose tissue.

EXPERIMENTAL APPROACH

Four-week-old C57BL/6J mice (n= 40) received aliskiren (50 mg.kg(-1).day(-1); 6 weeks) by means of a subcutaneous osmotic Alzet minipump. Animals were given either a low-fat (10% kcal from fat) or a high-fat diet (45% kcal from fat) during this period. Food-intake and body-weight variation were monitored during treatment.

KEY RESULTS

In addition to a decrease of plasma renin activity, aliskiren reduced body-weight gain, adipose pads and plasma leptin concentration, independent of the diet. In adipose tissue, local concentrations of Ang II were also reduced by aliskiren.

CONCLUSIONS AND IMPLICATIONS

Aliskiren limited the gain of adiposity in young mice. This effect was not due to changes in food intake or caloric efficiency and might be related to a down-regulation of the local renin-angiotensin system in adipose tissue. These effects were accompanied by reduced plasma leptin levels. As Ang II favours differentiation of adipocytes, it is possible that the decreased adipose tissue was linked to changes in adipocyte size and number.

Renin-angiotensin-aldosterone system-mediated redox effects in chronic kidney disease

The renin-angiotensin-aldosterone system (RAAS) is central to the pathogenesis of hypertension, cardiovascular disease, and kidney disease. Evidence supports various pathways through which a local renal RAAS can affect kidney function, hypertension, and cardiovascular disease. A prominent mechanism seems to be the loss of reduction-oxidation (redox) homeostasis and the formation of excessive free radicals. Free radicals such as reactive oxygen species (ROS) are necessary in normal physiologic processes, which include the development of nephrons, erythropoeisis, and tubular sodium transport. However, the loss of redox homeostasis contributes to proinflammatory and profibrotic pathways in the kidney that in turn lead to decreased vascular compliance, podocyte pathology, and proteinuria. Both the blockade of the RAAS and the oxidative stress produce salutary effects on hypertension and glomerular filtration barrier injury. Thus, the focus of current research is on understanding the pathophysiology of chronic kidney disease in the context of an increased RAAS and unbalanced redox mechanisms.

Pair feeding-mediated changes in metabolism: stress response and pathophysiology in insulin-resistant, atherosclerosis-prone JCR:LA-cp rats

Rats of the JCR:LA-cp strain, which are homozygous for the cp gene (cp/cp), are obese, insulin-resistant, and hyperinsulinemic. They exhibit associated micro- and macrovascular disease and end-stage ischemic myocardial lesions and are highly stress sensitive. We subjected male cp/cp rats to pair feeding (providing the rats each day with the amount of food eaten by matched freely fed animals), a procedure that alters the diurnal feeding pattern, leading to a state of intermittent caloric restriction. Effects on insulin, glucose, and lipid metabolism, response to restraint stress, aortic contractile/relaxant response, and myocardial lesion frequency were investigated. Pair-fed young (12-wk-old) cp/cp rats had lower insulin and glucose levels (basal and following restraint), consistent with increased insulin sensitivity, but a greater increase in plasma nonesterified fatty acids in response to restraint. These effects were unrelated to lipolytic rates in adipose tissue but may be related to reduced fatty acid oxidation in skeletal muscle. Older (24-wk-old) pair-fed cp/cp rats had significantly reduced plasma triglyceride levels, improved micro- and macrovascular function, and reduced severity of ischemic myocardial lesions. These changes indicate a significant amelioration of end-stage disease processes in this animal model and the complexity of metabolic/physiological responses in studies involving alterations in food intake. The effects illustrate the sensitivity of the JCR:LA-cp rat, an animal model for the metabolic syndrome and associated cardiovascular disease, to the environmental and experimental milieu. Similar stress-related mechanisms may play a role in metabolically induced cardiovascular disease in susceptible human beings.