The blood pressure lowering effects of glucagon-like peptide-1 receptor agonists: A mini-review of the potential mechanisms

Potential kidney protective effects of glucagon-like peptide-1 receptor agonists

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have gained increasing attention for their potential benefits in people with type 2 diabetes (T2DM) with chronic kidney disease (CKD). This class of medication has demonstrated promising results in reducing albuminuria, preserving estimated glomerular filtration rate (eGFR), and mitigating cardiovascular (CV) risk, making them potential therapeutic options for individuals with CKD. The kidney protective effects of GLP-1RAs extend beyond glycaemic control, and are thought to be attributed to their anti-inflammatory, antioxidant, and natriuretic properties. Despite these promising findings, the use of GLP-RAs has yet to be definitively shown to slow progression to chronic kidney failure, or reduce CV and kidney related death in people with T2DM and CKD. The Research Study to See How Semaglutide (a once weekly subcutaneous administered GLP-1RA) Works Compared to Placebo in People with Type 2 Diabetes and Chronic Kidney Disease (FLOW trial) was recently stopped because of efficacy. The primary end point for the FLOW trial consists of a composite endpoint of (i) onset of chronic kidney failure; (ii) death from kidney failure; (iii) cardiovascular death; and (iv) onset of a persistent ≥50% reduction in eGFR from baseline. It has also been reported by the sponsors of the trial that the primary end point of the trial was reduced by 24% with both CKD and CV outcomes contributing to risk reduction. In anticipation of the results of the FLOW trial being published, we review the current evidence surrounding kidney outcomes and proposed kidney protective pathways associated with GLP-1RA use.

The role of gut microbiota in the development of salt-sensitive hypertension and the possible preventive effect of exercise

INTRODUCTION

The aim of the present study is to analyze the data indicating an association between high salt intake and the gastrointestinal microbiota in the development of salt-sensitive hypertension in animals and men. It is also, to discuss the preventive effects of exercise on gut-induced hypertension by favorably modifying the composition of gut microbiota.

AREAS COVERED

Salt sensitivity is quite common, accounting for 30%-60% in hypertensive subjects. Recently, a novel cause for salt-sensitive hypertension has been discovered through the action of gut microbiota by the secretion of several hormones and the action of short chain fatty acids (SCFAs). In addition, recent studies indicate that exercise might favorably modify the adverse effects of gut microbiota regarding their effects on BP. To identify the role of gut microbiota on the incidence of hypertension and CVD and the beneficial effect of exercise, a Medline search of the English literature was conducted between 2018 and 2023 and 42 pertinent papers were selected.

EXPERT OPINION

The analysis of data from the selected papers disclosed that the gut microbiota contribute significantly to the development of salt-sensitive hypertension and that exercise modifies their gut composition and ameliorates their adverse effects on BP.

GLP-1 in the Hypothalamic Paraventricular Nucleus Promotes Sympathetic Activation and Hypertension

Glucagon-like peptide-1 (GLP-1) and its analogs are widely used for diabetes treatment. The paraventricular nucleus (PVN) is crucial for regulating cardiovascular activity. This study aims to determine the roles of GLP-1 and its receptors (GLP-1R) in the PVN in regulating sympathetic outflow and blood pressure. Experiments were carried out in male normotensive rats and spontaneously hypertensive rats (SHR). Renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded. GLP-1 and GLP-1R expressions were present in the PVN. PVN microinjection of GLP-1R agonist recombinant human GLP-1 (rhGLP-1) or EX-4 increased RSNA and MAP, which were prevented by GLP-1R antagonist exendin 9-39 (EX9-39) or GLP-1R antagonist 1, superoxide scavenger tempol, antioxidant N-acetylcysteine, NADPH oxidase (NOX) inhibitor apocynin, adenylyl cyclase (AC) inhibitor SQ22536 or protein kinase A (PKA) inhibitor H89. PVN microinjection of rhGLP-1 increased superoxide production, NADPH oxidase activity, cAMP level, AC, and PKA activity, which were prevented by SQ22536 or H89. GLP-1 and GLP-1R were upregulated in the PVN of SHR. PVN microinjection of GLP-1 agonist increased RSNA and MAP in both WKY and SHR, but GLP-1 antagonists caused greater effects in reducing RSNA and MAP in SHR than in WKY. The increased superoxide production and NADPH oxidase activity in the PVN of SHR were augmented by GLP-1R agonists but attenuated by GLP-1R antagonists. These results indicate that activation of GLP-1R in the PVN increased sympathetic outflow and blood pressure via cAMP-PKA-mediated NADPH oxidase activation and subsequent superoxide production. GLP-1 and GLP-1R upregulation in the PVN partially contributes to sympathetic overactivity and hypertension.

Effect of GLP-1 Receptor Agonist on Ischemia Reperfusion Injury in Rats with Metabolic Syndrome

Metabolic syndrome (MetS) represents an important factor that increases the risk of myocardial infarction, and more severe complications. Glucagon Like Peptide-1 Receptor Agonists (GLP-1RAs) exhibit cardioprotective potential, but their efficacy in MetS-related myocardial dysfunction has not been fully explored. Therefore, we aimed to assess the effects of exenatide and dulaglutide on heart function and redox balance in MetS-induced rats. Twenty-four Wistar albino rats with induced MetS were divided into three groups: MetS, exenatide-treated (5 µg/kg), dulaglutide-treated (0.6 mg/kg). After 6 weeks of treatment, in vivo heart function was assessed via echocardiography, while ex vivo function was evaluated using a Langendorff apparatus to simulate ischemia-reperfusion injury. Heart tissue samples were analyzed histologically, and oxidative stress biomarkers were measured spectrophotometrically from the coronary venous effluent. Both exenatide and dulaglutide significantly improved the ejection fraction by 3% and 7%, respectively, compared to the MetS group. Histological analyses corroborated these findings, revealing a reduction in the cross-sectional area of cardiomyocytes by 11% in the exenatide and 18% in the dulaglutide group, indicating reduced myocardial damage in GLP-1RA-treated rats. Our findings suggest strong cardioprotective potential of GLP-1RAs in MetS, with dulaglutide showing a slight advantage. Thus, both exenatide and dulaglutide are potentially promising targets for cardioprotection and reducing mortality in MetS patients.

The effect of semaglutide on blood pressure in patients with type-2 diabetes: a systematic review and meta-analysis

OBJECTIVE

To evaluate the blood pressure (BP) lowering ability of semaglutide, a glucagon-like peptide-1 receptor agonist (GLP-1 RA), in individuals with type-2 diabetes (T2D).

METHODS

Randomized controlled trials (RCTs) comparing subcutaneous or oral semaglutide with placebo or other antihyperglycemic agents (AHAs) in T2D patients were identified by searching PubMed, Embase, Web of Science, ClinicalTrials.gov and Cochrane Library. These screened studies included the outcomes of interest: systolic and/or diastolic BP. Weighted mean differences (WMDs) and 95 % confidence intervals (CIs) were used to present the meta-analysis results. Pooled and sensitivity analyses were performed, and the risk of bias was evaluated.

RESULTS

Twenty-nine RCTs with a total of 26985 participants were recruited in the final analysis. The WMD in change from baseline in systolic BP (SBP) of semaglutide versus placebo or other AHAs was -2.31 mmHg (95% CI: -3.11 to -1.51), while that for diastolic BP (DBP) was 0.09 mmHg (95% CI: -0.16 to 0.33). It also reduced glycated hemoglobin A1c (HbA1c) by 0.75% (95% CI: -0.92 to -0.58) and body weight loss by 2.80 kg (95% CI: -3.51 to -2.08). The reduction in SBP was similar for subcutaneous and oral administration of semaglutide, with -2.36 (95% CI: -3.38 to -1.35) and -2.50 (95% CI: -3.48 to -1.53), respectively.

CONCLUSIONS

In T2D, SBP decreased significantly in the semaglutide group compared with placebo or other active controls. According to the efficacy results from this meta-analysis, subcutaneous and oral semaglutide have similar SBP-reducing effects. Therefore, the treatment of T2D patients with subcutaneous semaglutide or oral preparations is beneficial for reducing SBP.

Effects of dipeptidyl peptidase 4 inhibition on the endothelial control of the vascular tone

Dipeptidyl peptidase 4 (DPP4) is a serine protease known to cleave incretin hormones, which stimulate insulin secretion after food intake, a fact that supported the development of its inhibitors (DPP4i or gliptins) for the treatment of type 2 diabetes mellitus. In addition to their glucose-lowering effects, DPP4i show benefits for the cardiovascular system that could be related, at least in part, to their protective action on vascular endothelium. DPP4i have been associated with the reversal of endothelial dysfunction, an important predictor of cardiovascular events and a hallmark of diseases such as atherosclerosis, diabetes mellitus, hypertension, and heart failure. In animal models of these diseases, DPP4i increase nitric oxide bioavailability and limits oxidative stress, thereby improving the endothelium-dependent relaxation. Similar effects on flow-mediated dilation and attenuation of endothelial dysfunction have also been noted in human studies, suggesting a value for gliptins in the clinical scenario, despite the variability of the results regarding the DPP4i used, treatment duration, and presence of comorbidities. In this mini-review, we discuss the advances in our comprehension of the DPP4i effects on endothelial regulation of vascular tone. Understanding the role of DPP4 and its involvement in the signaling mechanisms leading to endothelial dysfunction will pave the way for a broader use of DPP4i in conditions that endothelial dysfunction is a pivotal pathophysiological player.