The effect of amlodipine besylate, losartan potassium, olmesartan medoxomil, and other antihypertensives on central aortic blood pressure and biomarkers of vascular function

Soluble (pro)renin receptor induces endothelial dysfunction and hypertension in mice with diet-induced obesity via activation of angiotensin II type 1 receptor

Until now, renin-angiotensin system (RAS) hyperactivity was largely thought to result from angiotensin II (Ang II)-dependent stimulation of the Ang II type 1 receptor (AT1R). Here we assessed the role of soluble (pro)renin receptor (sPRR), a product of site-1 protease-mediated cleavage of (pro)renin receptor (PRR), as a possible ligand of the AT1R in mediating: (i) endothelial cell dysfunction in vitro and (ii) arterial dysfunction in mice with diet-induced obesity. Primary human umbilical vein endothelial cells (HUVECs) treated with a recombinant histidine-tagged sPRR (sPRR-His) exhibited IκBα degradation concurrent with NF-κB p65 activation. These responses were secondary to sPRR-His evoked elevations in Nox4-derived H2O2 production that resulted in inflammation, apoptosis and reduced NO production. Each of these sPRR-His-evoked responses was attenuated by AT1R inhibition using Losartan (Los) but not ACE inhibition using captopril (Cap). Further mechanistic exploration revealed that sPRR-His activated AT1R downstream Gq signaling pathway. Immunoprecipitation coupled with autoradiography experiments and radioactive ligand competitive binding assays indicate sPRR directly interacts with AT1R via Lysine199 and Asparagine295. Important translational relevance was provided by findings from obese C57/BL6 mice that sPRR-His evoked endothelial dysfunction was sensitive to Los. Besides, sPRR-His elevated blood pressure in obese C57/BL6 mice, an effect that was reversed by concurrent treatment with Los but not Cap. Collectively, we provide solid evidence that the AT1R mediates the functions of sPRR during obesity-related hypertension. Inhibiting sPRR signaling should be considered further as a potential therapeutic intervention in the treatment and prevention of cardiovascular disorders involving elevated blood pressure.

Receptors | Angiotensin Receptors

The renin-angiotensin-aldosterone system (RAS) is a vital hormone-receptor system that regulates cardiovascular and renal functions. In this article, we discuss exciting new findings in the RAS field. Recently solved active state crystal structures of Angiotensin II type 1 (AT1R) and type 2 receptor (AT2R) helped in understanding receptor activation mechanisms in detail. Also, considerable attention is given to the developments in characterizing the counter-regulatory RAS axis due to current hope for harnessing this axis for the development of protective therapies against various cardiovascular diseases. We describe the RAS component, angiotensin-converting enzyme 2 (ACE2) functioning as cellular entry receptor for the causative agent of COVID-19 pandemic, SARS-CoV-2. Altogether, these discoveries paved the way for developing novel therapies targeting different components of the RAS in the future.

The non-biphenyl-tetrazole angiotensin AT1 receptor antagonist eprosartan is a unique and robust inverse agonist of the active state of the AT1 receptor

BACKGROUND AND PURPOSE

Conditions such as hypertension and renal allograft rejection are accompanied by chronic, agonist-independent, signalling by angiotensin II AT1 receptors. The current treatment paradigm for these diseases entails the preferred use of inverse agonist AT1 receptor blockers (ARBs). However, variability in the inverse agonist activities of common biphenyl-tetrazole ARBs for the active state of AT1 receptors often leads to treatment failure. Therefore, characterization of robust inverse agonist ARBs for the active state of AT1 receptors is necessary.

EXPERIMENTAL APPROACH

To identify the robust inverse agonist for active state of AT1 receptors and its molecular mechanism, we performed site-directed mutagenesis, competition binding assay, inositol phosphate production assay and molecular modelling for both ground-state wild-type AT1 receptors and active-state N111G mutant AT1 receptors.

KEY RESULTS

Although candesartan and telmisartan exhibited weaker inverse agonist activity for N111G- compared with WT-AT1 receptors, only eprosartan exhibited robust inverse agonist activity for both N111G- and WT- AT1 receptors. Specific ligand-receptor contacts for candesartan and telmisartan are altered in the active-state N111G- AT1 receptors compared with the ground-state WT-AT1 receptors, suggesting an explanation of their attenuated inverse agonist activity for the active state of AT1 receptors. In contrast, interactions between eprosartan and N111G-AT1 receptors were not significantly altered, and the inverse agonist activity of eprosartan was robust.

CONCLUSIONS AND IMPLICATIONS

Eprosartan may be a better therapeutic option than other ARBs. Comparative studies investigating eprosartan and other ARBs for the treatment of diseases caused by chronic, agonist-independent, AT1 receptor activation are warranted.

Elevated serum adiponectin and tumor necrosis factor-α and decreased transthyretin in Japanese elderly women with low grip strength and preserved muscle mass and insulin sensitivity

OBJECTIVE

To determine if adiponectin levels are associated with low grip strength among the elderly independently of insulin resistance and inflammation.

RESEARCH DESIGN AND METHODS

Cross-sectional associations were analyzed by logistic regression between low grip strength and body composition, elevated serum adiponectin (≥20 mg/L), and biomarkers of nutritious stasis, insulin resistance and inflammation in 179 community-living Japanese women. Sarcopenia was evaluated using the Asian criteria.

RESULTS

No women had sarcopenia. In bivariate analyses, low grip strength (n=68) was positively associated with age, log tumor necrosis factor-α (TNF-α) and hyperadiponectinemia (n=37) and inversely with body weight, height, skeletal muscle mass, serum albumin, transthyretin (TTR), fat mass, serum zinc and hemoglobin (all p<0.01). In a fully adjusted model, TTR (0.90: 0.83-0.98, p=0.01) in addition to age (p=0.007), height (p=0.004) and skeletal muscle mass (p=0.008) emerged as independent determinants of low grip strength. When TTR was removed from the full model, TNF-α was associated with low grip strength (7.7; 1.3-45.8, p=0.02). Mean waist circumference and high-density lipoprotein cholesterol did not differ between women with and without low grip strength and were within the respective normal range. Women with hyperadiponectinemia had higher percentage of women with low grip strength and lower grip strength (both p<0.01).

CONCLUSIONS

Hyperadiponectinemia and elevated TNF-α in addition to decreased TTR, a biomarker of age-related catabolic states, were found in community-living Japanese elderly women with low grip strength and preserved muscle mass and insulin sensitivity.

Current topics in angiotensin II type 1 receptor research: Focus on inverse agonism, receptor dimerization and biased agonism

Although the octapeptide hormone angiotensin II (Ang II) regulates cardiovascular and renal homeostasis through the Ang II type 1 receptor (AT1R), overstimulation of AT1R causes various human diseases, such as hypertension and cardiac hypertrophy. Therefore, AT1R blockers (ARBs) have been widely used as therapeutic drugs for these diseases. Recent basic research and clinical studies have resulted in the discovery of interesting phenomena associated with AT1R function. For example, ligand-independent activation of AT1R by mechanical stress and agonistic autoantibodies, as well as via receptor mutations, has been shown to decrease the inverse agonistic efficacy of ARBs, though the molecular mechanisms of such phenomena had remained elusive until recently. Furthermore, although AT1R is believed to exist as a monomer, recent studies have demonstrated that AT1R can homodimerize and heterodimerize with other G-protein coupled receptors (GPCR), altering the receptor signaling properties. Therefore, formation of both AT1R homodimers and AT1R-GPCR heterodimer may be involved in the pathogenesis of human disease states, such as atherosclerosis and preeclampsia. Finally, biased AT1R ligands that can preferentially activate the β-arrestin-mediated signaling pathway have been discovered. Such β-arrestin-biased AT1R ligands may be better therapeutic drugs for cardiovascular diseases. New findings on AT1R described herein could provide a conceptual framework for application of ARBs in the treatment of diseases, as well as for novel drug development. Since AT1R is an extensively studied member of the GPCR superfamily encoded in the human genome, this review is relevant for understanding the functions of other members of this superfamily.

Association of Metabolic Syndrome with Chronic Kidney Disease in Elderly Japanese Women: Comparison by Estimation of Glomerular Filtration Rate from Creatinine, Cystatin C, and Both

BACKGROUND

Associations between metabolic syndrome (MetS) and chronic kidney disease (CKD) has not been extensively studied in elderly Asians, who in general have lower body mass index (BMI) than European populations.

METHODS

A cross-sectional analysis was conducted including 159 community-living elderly Japanese women. MetS was defined by the modified National Cholesterol Education Program Adult Treatment Panel III criteria, but using a BMI ≥25 kg/m(2) instead of waist circumference and renal function was assessed according to the Kidney Disease Outcomes Quality Initiative CKD classification. Creatinine-based and cystatin C-based estimated glomerular filtration rate (eGFR) and the average of the two eGFRS were used.

RESULTS

Prevalence of CKD was much higher when creatinine-based eGFR was used than the prevalence obtained when cystatin-C based equations were used (46.5% vs. 12.6%, P < 0.001). Eighteen (11.3%) women met MetS criteria. Both the presence of MetS and the number of MetS components were associated with higher prevalence of CKD using the average eGFR (all P < 0.05) but not using creatinine-based (P = 0.86) and cystatin C-based (P = 0.12) eGFR alone. Lower average eGFR and higher prevalence of CKD using average eGFR were evident in even women with only one MetS component, 89% of whom had elevated blood pressure.

CONCLUSIONS

Prevalence of CKD varied substantially depending on the used equation. In nonobese, elderly Japanese women, both the presence of MetS and the number of MetS components were associated with higher prevalence of CKD and elevated blood pressure may play an important role in these associations. These findings should be confirmed in studies employing more participants with MetS diagnosed using standard criteria (waist circumference instead of BMI).

Structure-Function Basis of Attenuated Inverse Agonism of Angiotensin II Type 1 Receptor Blockers for Active-State Angiotensin II Type 1 Receptor

Ligand-independent signaling by the angiotensin II type 1 receptor (AT1R) can be activated in clinical settings by mechanical stretch and autoantibodies as well as receptor mutations. Transition of the AT1R to the activated state is known to lower inverse agonistic efficacy of clinically used AT1R blockers (ARBs). The structure-function basis for reduced efficacy of inverse agonists is a fundamental aspect that has been understudied not only in relation to the AT1R but also regarding other homologous receptors. Here, we demonstrate that the active-state transition in the AT1R indeed attenuates an inverse agonistic effect of four biphenyl-tetrazole ARBs through changes in specific ligand-receptor interactions. In the ground state, tight interactions of four ARBs with a set of residues (Ser109(TM3), Phe182(ECL2), Gln257(TM6), Tyr292(TM7), and Asn295(TM7)) results in potent inverse agonism. In the activated state, the ARB-AT1R interactions shift to a different set of residues (Val108(TM3), Ser109(TM3), Ala163(TM4), Phe182(ECL2), Lys199(TM5), Tyr292(TM7), and Asn295(TM7)), resulting in attenuated inverse agonism. Interestingly, V108I, A163T, N295A, and F182A mutations in the activated state of the AT1R shift the functional response to the ARB binding toward agonism, but in the ground state the same mutations cause inverse agonism. Our data show that the second extracellular loop is an important regulator of the functional states of the AT1R. Our findings suggest that the quest for discovering novel ARBs, and improving current ARBs, fundamentally depends on the knowledge of the unique sets of residues that mediate inverse agonistic potency in the two states of the AT1R.

Effects of nebivolol on aortic compliance in patients with diabetes and maximal renin angiotensin system blockade: the EFFORT study

The beneficial effects of nebivolol on arterial stiffness and endothelial dysfunction are well documented in untreated hypertensive patients and differ from nonvasodilatory β-blockers. This study tests the hypothesis that the addition of nebivolol in predominantly African American patients with type 2 diabetes already receiving maximally tolerated doses of renin-angiotensin system (RAS) blockers will further improve large artery compliance. Patients with type 2 diabetes and hypertension on maximal RAS blockade (n=70) were randomized to nebivolol or metoprolol succinate daily. Doses were titrated until systolic blood pressure (SBP) was <130 mm Hg. Radial artery applanation tonometry and pulse wave velocity (PWV) analysis were used to derive central aortic pressures and hemodynamic indices at repeated visits at intervals during a 6-month period. Both metoprolol succinate and nebivolol groups demonstrated reductions in brachial SBP (-8.2±4.3 mm Hg [P=.01] and -7.8±3.7 [P=.002], respectively) and aortic DBP (-2.4±1.8 [P=.039] and -4.0±2.9 mm Hg [P=.013], respectively). Aortic SBP decreased in the nebivolol group only (125.3±8 to 121.6±8.2, P=.025). There were no between group differences in aortic SBP, DBP, augmentation index, or PWV reduction. A significant increase in hemoglobin A1c was observed only in the metoprolol group. In patients with well-controlled type 2 diabetes and hypertension treated with maximally tolerated RAS blockade, nebivolol does not offer significant reductions in aortic BP over metoprolol succinate but maintains a stable metabolic profile.