Long-Acting GLP-1 Receptor Agonist Exenatide Influence on the Autonomic Cardiac Sympatho-Vagal Balance

The impact of GLP-1 signalling on the energy metabolism of pancreatic islet β-cells and extrapancreatic tissues

Glucagon-like peptide-1 signalling impacts glucose homeostasis and appetite thereby indirectly affecting substrate availability at the whole-body level. The incretin canonically produces an insulinotropic effect, thereby lowering blood glucose levels by promoting the uptake and inhibiting the production of the sugar by peripheral tissues. Likewise, GLP-1 signalling within the central nervous system reduces the appetite and food intake, whereas its gastric effect delays the absorption of nutrients, thus improving glycaemic control and reducing the risk of postprandial hyperglycaemia. We review the molecular aspects of the GLP-1 signalling, focusing on its impact on intracellular energy metabolism. Whilst the incretin exerts its effects predominantly via a Gs receptor, which decodes the incretin signal into the elevation of intracellular cAMP levels, the downstream signalling cascades within the cell, acting on fast and slow timescales, resulting in an enhancement or an attenuation of glucose catabolism, respectively.

The handgrip test - A historical test for diabetic autonomic neuropathy or a marker of something else?

Cardiovascular autonomic neuropathy (CAN) is a frequent complication of diabetes mellitus and is associated with increased morbidity and mortality in patients with diabetes. Hence, early and correct diagnosis of CAN is crucial. Standard cardiovascular reflex rests (CARTs) have been the gold standard of CAN assessment. Originally, CARTs consisted of five reflex tests, but measuring diastolic blood pressure response to sustained handgrip exercise has no longer been suggested as an established clinical test. Increasing body of evidence suggests that isometric handgrip test should no longer be used for the evaluation of sympathetic dysfunction during cardiovascular autonomic neuropathy assessment in diabetic patients. The associations of isometric handgrip test results with parameters of hypertension and markers of hypertension-related target-organ damage in diabetic and non-diabetic individuals point toward its potential role as a screening tool to identify patients with high cardiovascular risk. The current review summarizes historical view of standard cardiovascular reflex tests and latest data on isometric handgrip test.

Treatment of hypothalamic obesity in people with hypothalamic injury: new drugs are on the horizon

Hypothalamic obesity (HO) is a complex and rare disorder affecting multiple regulatory pathways of energy intake and expenditure in the brain as well as the regulation of the autonomic nervous system and peripheral hormonal signaling. It can be related to monogenic obesity syndromes which often affect the central leptin-melanocortin pathways or due to injury of the hypothalamus from pituitary and hypothalamic tumors, such as craniopharyngioma, surgery, trauma, or radiation to the hypothalamus. Traditional treatments of obesity, such as lifestyle intervention and specific diets, are still a therapeutic cornerstone, but often fail to result in meaningful and sustained reduction of body mass index. This review will give an update on pharmacotherapies of HO related to hypothalamic injury. Recent obesity drug developments are promising for successful obesity intervention outcomes.

Association of glucagon-like peptide-1 receptor agonists with cardiac arrhythmias in patients with type 2 diabetes or obesity: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have been highly recommended for glycemic control and weight reduction. However, evidence has accumulated that GLP-1 RAs treatment is related to an increase in heart rate, which could potentially induce cardiac arrhythmias. This study aims to investigate the association of GLP-1 RAs therapy with incident arrhythmias in diabetic and obese patients.

METHODS

MEDLINE, EMBASE, Cochrane Library, and ClinicalTrials.gov were systematically searched from inception up to May 25, 2022. Randomized controlled trials (RCTs) comparing GLP-1 RAs with placebo or active control for adults with type 2 diabetes or obesity were included. The outcomes of interest were prespecified as incident atrial fibrillation (AF), atrial flutter (AFL), ventricular arrhythmias (VAs), and sudden cardiac death (SCD). Mantel-Haenszel relative risk (MH-RR) with a corresponding 95% confidence interval (95% CI) was estimated using a fixed-effects model.

RESULTS

A total of 56 RCTs involving 79,720 participants (44,028 GLP-1 RAs vs 35,692 control: mean age 57.3 years) were included from 7692 citations. GLP-1 RAs use overall did not significantly increase the risk of AF (RR 0.97, 95% CI 0.83-1.12), AFL (RR 0.83, 95% CI 0.59-1.17), VAs (RR 1.24, 95% CI 0.92-1.67), and SCD (RR 0.89, 95% CI 0.67-1.19), compared with controls. In further subgroup analyses, we observed an increasing trend toward incident AF with dulaglutide (RR 1.40, 95% CI 1.03-1.90) while an inverse trend with oral semaglutide (RR 0.43, 95% CI 0.21-0.87). Additionally, higher doses of GLP-1 RAs (RR 1.63, 95% CI 1.11-2.40) and higher baseline BMI (RR 1.60, 95% CI 1.04-2.48) might significantly increase the risk of VAs. No significant differences were identified in other subgroup analyses.

CONCLUSIONS

GLP-1 RAs therapy was not associated with an overall higher risk of arrhythmias, demonstrating an assuring cardiovascular safety profile. Further studies are required to determine whether the potential antiarrhythmic or arrhythmogenic effect of GLP-1 RAs is drug-specific and varies from doses or baseline BMI.

TRIAL REGISTRATION

PROSPERO Identifier: CRD42022339389.

Effect of the Glucagon-Like Peptide-1 Receptor Agonists on Autonomic Function in Subjects with Diabetes: A Systematic Review and Meta-Analysis

BACKGROUND

In addition to the metabolic effects in diabetes, glucagon-like peptide 1 receptor (GLP-1R) agonists lead to a small but substantial increase in heart rate (HR). However, the GLP-1R actions on the autonomic nervous system (ANS) in diabetes remain debated. Therefore, this meta-analysis evaluates the effect of GLP-1R agonist on measures of ANS function in diabetes.

METHODS

According to the Cochrane Collaboration and Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement, we conducted a meta-analysis considering clinical trials in which the autonomic function was evaluated in diabetic subjects chronically treated with GLP-1R agonists. The outcomes were the change of ANS function measured by heart rate variability (HRV) and cardiac autonomic reflex tests (CARTs).

RESULTS

In the studies enrolled, HR significantly increased after treatment (P<0.001), whereas low frequency/high frequency ratio did not differ (P=0.410); no changes in other measures of HRV were detected. Considering CARTs, only the 30:15 value derived from lying-to-standing test was significantly lower after treatment (P=0.002), but only two studies reported this measurement. No differences in other CARTs outcome were observed.

CONCLUSION

The meta-analysis confirms the HR increase but seems to exclude an alteration of the sympatho-vagal balance due to chronic treatment with GLP-1R agonists in diabetes, considering the available measures of ANS function.

Safety of Semaglutide

The glucagon-like peptide-1 receptor agonist (GLP-1RA) semaglutide is the most recently approved agent of this drug class, and the only GLP-1RA currently available as both subcutaneous and oral formulation. While GLP-1RAs effectively improve glycemic control and cause weight loss, potential safety concerns have arisen over the years. For semaglutide, such concerns have been addressed in the extensive phase 3 registration trials including cardiovascular outcome trials for both subcutaneous (SUSTAIN: Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes) and oral (PIONEER: Peptide InnOvatioN for the Early diabEtes tReatment) semaglutide and are being studied in further trials and registries, including real world data studies. In the current review we discuss the occurrence of adverse events associated with semaglutide focusing on hypoglycemia, gastrointestinal side effects, pancreatic safety (pancreatitis and pancreatic cancer), thyroid cancer, gallbladder events, cardiovascular aspects, acute kidney injury, diabetic retinopathy (DRP) complications and injection-site and allergic reactions and where available, we highlight potential underlying mechanisms. Furthermore, we discuss whether effects are specific for semaglutide or a class effect. We conclude that semaglutide induces mostly mild-to-moderate and transient gastrointestinal disturbances and increases the risk of biliary disease (cholelithiasis). No unexpected safety issues have arisen to date, and the established safety profile for semaglutide is similar to that of other GLP-1RAs where definitive conclusions for pancreatic and thyroid cancer cannot be drawn at this point due to low incidence of these conditions. Due to its potent glucose-lowering effect, patients at risk for deterioration of existing DRP should be carefully monitored if treated with semaglutide, particularly if also treated with insulin. Given the beneficial metabolic and cardiovascular actions of semaglutide, and the low risk for severe adverse events, semaglutide has an overall favorable risk/benefit profile for patient with type 2 diabetes.

Cardiovascular effects of glucagon-like peptide 1 receptor agonists: from mechanistic studies in humans to clinical outcomes

Type 2 diabetes mellitus (T2DM) is currently one of the most prevalent diseases, with as many as 415 million patients worldwide. T2DM is characterized by elevated blood glucose levels and is often accompanied by several comorbidities, such as cardiovascular disease. Treatment of T2DM is focused on reducing glucose levels by either lifestyle changes or medical treatment. One treatment option for T2DM is based on the gut-derived hormone glucagon-like peptide 1 (GLP-1). GLP-1 reduces blood glucose levels by stimulating insulin secretion, however, it is rapidly degraded, and thereby losing its glycaemic effect. GLP-1 receptor agonists (GLP-1RAs) are immune to degradation, prolonging the glycaemic effect. Lately, GLP-1RAs have spiked the interest of researchers and clinicians due to their beneficial effects on cardiovascular disease. Preclinical and clinical data have demonstrated that GLP-1 receptors are abundantly present in the heart and that stimulation of these receptors by GLP-1 has several effects. In this review, we will discuss the effects of GLP-1RA on heart rate, blood pressure, microvascular function, lipids, and inflammation, as measured in human mechanistic studies, and suggest how these effects may translate into the improved cardiovascular outcomes as demonstrated in several trials.

Heart rate variability in type 2 diabetic subjects randomized to liraglutide or glimepiride treatment, both in combination with metformin: A randomized, open, parallel-group study

AIMS

Reduced heart rate variability (HRV) and increased heart rate (HR) are associated with cardiovascular (CV) mortality. In the Liraglutide Effect and Action in Diabetes outcome trial, it was demonstrated a lower rate of CV events in type 2 diabetes (T2D) patients treated with liraglutide compared to placebo. We aimed to investigate the effects of liraglutide compared with glimepiride treatment in T2D patients on the CV risk parameters HR and HRV.

METHODS

This was a post hoc study whereas sixty-two T2D individuals (45 males) were randomized to once daily 1.8 mg liraglutide or once daily 4 mg glimepiride, both in combination with 1 g metformin. HR and measurement of sympathetic activity, that is standard deviation (SD) of beat-to-beat (NN) intervals (SDNN), was assessed by 24-hour Holter monitoring system. Parasympathetic activity was analysed by root mean square of successive differences (RMSSD) in NN intervals and high-frequency (HF), low-frequency (LF) and very low-frequency power.

RESULTS

Baseline clinical characteristics for liraglutide (n = 33) and glimepiride (n = 29) groups were well matched. There was a persistent increase in diurnal HR followed by a significantly increased HR at daytime 5.4 beats per minute, P = 0.011 in the liraglutide-treated group. There was no treatment change between groups in SDNN and RMSSD, or in HF and LF frequency power analysis.

CONCLUSIONS

Liraglutide treatment increased diurnal variation in hourly mean HR followed by an increase in mean daytime HR, independently of changes in sympathetic or parasympathetic activity.

Update on the Impact, Diagnosis and Management of Cardiovascular Autonomic Neuropathy in Diabetes: What Is Defined, What Is New, and What Is Unmet

The burden of diabetic cardiovascular autonomic neuropathy (CAN) is expected to increase due to the diabetes epidemic and its early and widespread appearance. CAN has a definite prognostic role for mortality and cardiovascular morbidity. Putative mechanisms for this are tachycardia, QT interval prolongation, orthostatic hypotension, reverse dipping, and impaired heart rate variability, while emerging mechanisms like inflammation support the pervasiveness of autonomic dysfunction. Efforts to overcome CAN under-diagnosis are on the table: by promoting screening for symptoms and signs; by simplifying cardiovascular reflex tests; and by selecting the candidates for screening. CAN assessment allows for treatment of its manifestations, cardiovascular risk stratification, and tailoring therapeutic targets. Risk factors for CAN are mainly glycaemic control in type 1 diabetes mellitus (T1DM) and, in addition, hypertension, dyslipidaemia, and obesity in type 2 diabetes mellitus (T2DM), while preliminary data regard glycaemic variability, vitamin B12 and D changes, oxidative stress, inflammation, and genetic biomarkers. Glycaemic control prevents CAN in T1DM, whereas multifactorial intervention might be effective in T2DM. Lifestyle intervention improves autonomic function mostly in pre-diabetes. While there is no conclusive evidence for a disease-modifying therapy, treatment of CAN manifestations is available. The modulation of autonomic function by SGLT2i represents a promising research field with possible clinical relevance.