Simultaneous GLP-1 and insulin administration acutely enhances their vasodilatory, antiinflammatory, and antioxidant action in type 2 diabetes

Reducing the mitochondrial oxidative burden alleviates lipid-induced muscle insulin resistance in humans

Preclinical models suggest mitochondria-derived oxidative stress as an underlying cause of insulin resistance. However, it remains unknown whether this pathophysiological mechanism is conserved in humans. Here, we used an invasive in vivo mechanistic approach to interrogate muscle insulin action while selectively manipulating the mitochondrial redox state in humans. To this end, we conducted insulin clamp studies combining intravenous infusion of a lipid overload with intake of a mitochondria-targeted antioxidant (mitoquinone). Under lipid overload, selective modulation of mitochondrial redox state by mitoquinone enhanced insulin-stimulated glucose uptake in skeletal muscle. Mechanistically, mitoquinone did not affect canonical insulin signaling but augmented insulin-stimulated glucose transporter type 4 (GLUT4) translocation while reducing the mitochondrial oxidative burden under lipid oversupply. Complementary ex vivo studies in human muscle fibers exposed to high intracellular lipid levels revealed that mitoquinone improves features of mitochondrial bioenergetics, including diminished mitochondrial H2O2 emission. These findings provide translational and mechanistic evidence implicating mitochondrial oxidants in the development of lipid-induced muscle insulin resistance in humans.

The Role of Obesity as a Cardiac Disease Risk Factor in Patients with Type 2 Diabetes

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is the leading cause of death globally and is closely associated with obesity and type 2 diabetes mellitus (T2DM). This review examines the interplay between obesity, T2DM, and CVD, highlighting the increasing prevalence and economic burden of these conditions.

RECENT FINDINGS

Pharmacologic therapies, particularly glucagon-like peptide-1 receptor agonists, show promise in substantial weight loss and subsequent reduction of adverse cardiovascular events in obese individuals with and without diabetes. Obesity significantly contributes to the development of insulin resistance and T2DM, further escalating CVD risk. The common co-occurrence of these three conditions may involve several other pathophysiological mechanisms, such as chronic inflammation, increased visceral adiposity, and endothelial dysfunction. Until recently, lifestyle modifications and bariatric surgery had been the primary methods for weight loss and mitigating obesity-associated cardiovascular risk. Newer pharmacological options have led to a paradigm shift in our approach to obesity management as they provide substantial benefits in weight loss, glycemic control, and cardiovascular risk reduction.

IDegLira improves time in range in a cohort of patients with type 2 diabetes: TiREX study

AIMS

To assess the effects of IDegLira on glucometric indices deriving from intermittently scanned Continuous Glucose Monitoring (isCGM) in patients with type 2 diabetes (T2D).

METHODS

Retrospective, observational, cohort, multi-center, "pre - post" study. All adults consecutively identified in the medical records who started treatment with IDegLira, and for whom an isCGM report before and after the initiation of IDegLira was available were included in the study. Time in range (TIR) represented the primary endpoint. Additional glucometric indices, insulin doses and body weight were also assessed.

RESULTS

Overall, 87 patients were included by 5 diabetes centers [mean age 70.2 ± 11.0 years, mean duration of T2D 15.5 ± 9.6 years; BMI 29.4 ± 5.4 kg/m2, baseline HbA1c 9.1 ± 2.1%, 33% insulin naïve, 20.7% treated with basal-oral therapy (BOT), and 46% treated with multiple daily injections of insulin (MDI)]. After an average of 1.7 weeks from IDegLira initiation, TIR significantly increased from 56.8 ± 23.5% to 81.3 ± 13.5% (p < 0.0001), TAR decreased from 42.3 ± 24.2% to 17.1 ± 13.6% (p < 0.0001), while TBR remained steadily low (from 1.3 ± 2.3% to 1.4 ± 2.6%; p = 0.62). Estimated HbA1c decreased from 9.1 ± 2.1% to 6.7 ± 0.6% (p < 0.0001) and percentage of patients with a blood glucose coefficient of variation ≥ 36% dropped from 33.2 to 13.8% (p = 0.0005). In patients on MDI, the reduction in the total insulin dose was substantial (from 55.8 ± 31.2 IU to 27.2 ± 12.3 U).

CONCLUSIONS

In T2D patients with poor metabolic control, either insulin naïve or treated with BOT or MDI, the introduction of IDegLira produces a significant increase in the time spent in good metabolic control and a marked reduction in glycemic fluctuations.

Skipping breakfast does not accelerate the hyperglycemia-induced endothelial dysfunction but reduces blood flow of the brachial artery in young men

PURPOSE

Postprandial hyperglycemia is assumed to have a negative impact on flow-mediated dilation (FMD), an index of endothelial function, and blood flow of the peripheral conduit arteries. This study aimed to determine whether the enhancement of postprandial hyperglycemia by skipping breakfast accelerates endothelial dysfunction and reduces the blood flow in the brachial artery in young men.

METHODS

Using a randomized cross-over design, ten healthy men completed two trials: with and without breakfast (Eating and Fasting trials, respectively). Venous blood sampling and brachial FMD tests were conducted before, 30, 60, 90, and 120 min after a 75-g oral glucose tolerance test (OGTT).

RESULTS

Skipping breakfast boosted post-OGTT glucose levels than having breakfast (P = 0.01). The magnitude of the decrease in FMD via OGTT did not vary between trials (main effect of trial P = 0.55). Although brachial blood flow tended to decrease after OGTT in both trials (interaction and main effect of time P = 0.61 and P = 0.054, respectively), the decrease in blood flow following OGTT was greater in the Fasting trial than in the Eating trial (main effect of trial, mean difference =  - 15.8 mL/min [95%CI =  - 25.6 to - 6.0 mL/min], P < 0.01).

CONCLUSION

Skipping breakfast did not enhance the magnitude of the decrease in FMD following glucose loading, but did accelerate hyperglycemia-induced reduction in brachial blood flow. Current findings suggest that even missing one breakfast has negative impacts on the blood flow regulation of the peripheral conduit arteries in young men who habitually eat breakfast.

The Role of Oxidative Stress Enhanced by Adiposity in Cardiometabolic Diseases

Cardiometabolic diseases (CMDs), including cardiovascular disease (CVD), metabolic syndrome (MetS), and type 2 diabetes (T2D), are associated with increased morbidity and mortality. The growing prevalence of CVD is mostly attributed to the aging population and common occurrence of risk factors, such as high systolic blood pressure, elevated plasma glucose, and increased body mass index, which led to a global epidemic of obesity, MetS, and T2D. Oxidant–antioxidant balance disorders largely contribute to the pathogenesis and outcomes of CMDs, such as systemic essential hypertension, coronary artery disease, stroke, and MetS. Enhanced and disturbed generation of reactive oxygen species in excess adipose tissue during obesity may lead to increased oxidative stress. Understanding the interplay between adiposity, oxidative stress, and cardiometabolic risks can have translational impacts, leading to the identification of novel effective strategies for reducing the CMDs burden. The present review article is based on extant results from basic and clinical studies and specifically addresses the various aspects associated with oxidant–antioxidant balance disorders in the course of CMDs in subjects with excess adipose tissue accumulation. We aim at giving a comprehensive overview of existing knowledge, knowledge gaps, and future perspectives for further basic and clinical research. We provide insights into both the mechanisms and clinical implications of effects related to the interplay between adiposity and oxidative stress for treating and preventing CMDs. Future basic research and clinical trials are needed to further examine the mechanisms of adiposity-enhanced oxidative stress in CMDs and the efficacy of antioxidant therapies for reducing risk and improving outcome of patients with CMDs.

The vascular function effects of adding exenatide or meal insulin to basal insulin therapy in early type 2 diabetes

OBJECTIVE

Basal insulin glargine has a neutral effect on cardiovascular risk in type 2 diabetes (T2DM). In practice, basal insulin is often paired with a glucagon-like peptide-1 receptor agonist (GLP1-RA) or meal insulin; however, the cardiovascular implications of these combinations have not been fully elucidated. In this context, we sought to evaluate the vascular function effects of adding the GLP1-RA exenatide or meal insulin lispro to basal glargine therapy in early T2DM.

METHODS

In this 20-week trial, adults with T2DM of < 7-years duration were randomized to 8-weeks treatment with (i) insulin glargine (Glar), (ii) glargine + thrice-daily lispro (Glar/Lispro), or (iii) glargine + twice-daily exenatide (Glar/Exenatide), followed by 12-weeks washout. At baseline, 8-weeks, and washout, fasting endothelial function was assessed with reactive hyperemia index (RHI) measurement by peripheral arterial tonometry.

RESULTS

At baseline, there were no differences in blood pressure (BP), heart rate (HR) or RHI between participants randomized to Glar (n = 24), Glar/Lispro (n = 24), and Glar/Exenatide (n = 25). At 8-weeks, Glar/Exenatide decreased systolic BP (mean - 8.1 mmHg [95%CI - 13.9 to - 2.4], p = 0.008) and diastolic BP (mean - 5.1 mmHg [- 9.0 to - 1.3], p = 0.012) compared to baseline, with no significant changes in HR or RHI. Notably, baseline-adjusted RHI (mean ± SE) did not differ between the groups at 8-weeks (Glar 2.07 ± 0.10; Glar/Lispro 2.00 ± 0.10; Glar/Exenatide 1.81 ± 0.10; p = 0.19), nor did baseline-adjusted BP or HR. There were no differences between the groups in baseline-adjusted RHI, BP or HR after 12-weeks washout.

CONCLUSION

Adding either exenatide or lispro to basal insulin therapy does not appear to affect fasting endothelial function in early T2DM.

TRIAL REGISTRATION

ClinicalTrials.Gov NCT02194595.

Effects of treatment of non-alcoholic fatty liver disease on heart failure with preserved ejection fraction

In the past few decades, non-alcoholic fatty liver disease (NAFLD) and heart failure with preserved ejection fraction (HFpEF) have become the most common chronic liver disease and the main form of heart failure (HF), respectively. NAFLD is closely associated with HFpEF by sharing common risk factors and/or by boosting systemic inflammation, releasing other secretory factors, and having an expansion of epicardial adipose tissue (EAT). Therefore, the treatments of NAFLD may also affect the development and prognosis of HFpEF. However, no specific drugs for NAFLD have been approved by the Food and Drug Administration (FDA) and some non-specific treatments for NAFLD are applied in the clinic. Currently, the treatments of NAFLD can be divided into non-pharmacological and pharmacological treatments. Non-pharmacological treatments mainly include dietary intervention, weight loss by exercise, caloric restriction, and bariatric surgery. Pharmacological treatments mainly include administering statins, thiazolidinediones, glucagon-like peptide-1 receptor agonists, sodium-glucose cotransporter 2 inhibitors, and metformin. This review will mainly focus on analyzing how these treatments may affect the development and prognosis of HFpEF.

Glucose-lowering drugs with cardiovascular benefits as modifiers of critical elements of the human life history

The life history theory assumes that all organisms are under selective pressure to harvest external resources and allocate them to maximise fitness: only organisms making the best use of energy obtain the greatest fitness benefits. The trade-off of energy spans four functions: maintenance, growth, reproduction, and defence against pathogens. The innovative antihyperglycaemic agents glucagon-like peptide 1 (GLP-1) receptor agonists and sodium-glucose cotransporter 2 (SGLT2) inhibitors decrease bodyweight and have the potential to counter low-grade inflammation. These key activities could rewire two components of the life history theory operative in adulthood-ie, maintenance and defence. In this Personal View, we postulate that the benefits of these medications on the cardiovascular system, beyond their glucose-lowering effects, could be mediated by the reduction of the maintenance cost driven by obesity and efforts spent on blunting low-grade inflammation.

Reactive Oxygen Species/Reactive Nitrogen Species as Messengers in the Gut: Impact on Physiology and Metabolic Disorders

Significance: The role of reactive oxygen/nitrogen species as "friend" or "foe" messengers in the whole body is well characterized. Depending on the concentration in the tissue considered, these molecular actors exert beneficial or deleterious impacts leading to a pathological state, as observed in metabolic disorders such as type 2 diabetes and obesity. Recent Advances: Among the tissues impacted by oxidation and inflammation in this pathological state, the intestine is a site of dysfunction that can establish diabetic symptoms, such as alterations in the intestinal barrier, gut motility, microbiota composition, and gut/brain axis communication. In the intestine, reactive oxygen/nitrogen species (from the host and/or microbiota) are key factors that modulate the transition from physiological to pathological signaling. Critical Issues: Controlling the levels of intestinal reactive oxygen/nitrogen species is a complicated balance between positive and negative impacts that is in constant equilibrium. Here, we describe the synthesis and degradation of intestinal reactive oxygen/nitrogen species and their interactions with the host. The development of novel redox-based therapeutics that alter these processes could restore intestinal health in patients with metabolic disorders. Future Directions: Deciphering the mode of action of reactive oxygen/nitrogen species in the gut of obese/diabetic patients could result in a future therapeutic strategy that combines nutritional and pharmacological approaches. Consequently, preventive and curative treatments must take into account one of the first sites of oxidative and inflammatory dysfunctions in the body, that is, the intestine. Antioxid. Redox Signal. 37, 394-415.

The anti-inflammatory and immunological properties of GLP-1 Receptor Agonists

In the last few years, a great interest has emerged in investigating the pleiotropic effects of Glucagon Like Peptide-1 Receptor Agonists (GLP-1RAs). While GLP-1RAs ability to lower plasma glucose and to induce weight loss has allowed them to be approved for the treatment of diabetes and obesity, consistent evidences from in vitro studies and preclinical models suggested that GLP-1RAs have anti-inflammatory properties and that may modulate the immune-system. Notably, such anti-inflammatory effects target different pathways in different tissues, underling the broad spectrum of GLP-1RAs actions. This review examines some of the currently proposed molecular mechanisms of GLP-1RAs actions and explores their potential benefits in reducing inflammatory responses, which may well suggest a future therapeutic use of GLP-1RAs in new indications.

Significance of Glycemic Variability in Diabetes Mellitus

The goal of diabetes treatment is to maintain good glycemic control, prevent the development and progression of diabetic complications, and ensure the same quality of life and life expectancy as healthy people. Hemoglobin A1c (HbA1c) is used as an index of glycemic control, but strict glycemic control using HbA1c as an index may lead to severe hypoglycemia and cardiovascular death. Glycemic variability (GV), such as excessive hyperglycemia and hypoglycemia, is associated with diabetic vascular complications and has been recognized as an important index of glycemic control. Here, we reviewed the definition and evaluated the clinical usefulness of GV, and its relationship with diabetic complications and therapeutic strategies to reduce GV.

Protective Effects and Mechanisms of Polyethylene Glycol Loxenatide Against Hyperglycemia and Liver Injury in db/db diabetic Mice

Background: Type 2 diabetes mellitus (T2DM) is a metabolic disorder with insulin resistance and impaired insulin secretion that can cause complications, including liver injury. Polyethylene glycol loxenatide (PEG-Loxe), a glucagon-like peptide-1 (GLP-1) analog, is widely used to treat T2DM. However, its specific glucose-lowering and hepatoprotective mechanisms of action have not been established yet.

METHODS: Using a high glucose-induced hepatocyte injury model and a type 2 diabetic db/db mouse model, we assessed PEG-Loxe’s impact on reducing blood glucose and improving liver injury in T2DM and revealed its mechanism.

RESULTS: PEG-Loxe treatment significantly reduced body weight and fasting glucose, increased glucose tolerance, improved serum and liver biochemical parameters (glycated hemoglobin, serum insulin, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, alanine aminotransferase, and aspartate aminotransferase), and attenuated hepatic steatosis and liver and pancreatic tissue damages in db/db mice. Additionally, PEG-Loxe considerably inhibited oxidative stress, decreased pro-inflammatory factor (TNF-α, IL-6, and MCP-1) levels, and increased anti-inflammatory factor IL-10 levels. PEG-Loxe possibly inhibits hepatic lipid synthesis, oxidative stress, and inflammatory response by upregulating Sirt1, p-AMPK, and p-ACC expressions in the Sirt1/AMPK/ACC pathway of lipid metabolism, thereby improving T2DM liver injury. PEG-Loxe most likely also promotes GLP-1R expression by inhibiting β-cell apoptosis, which in turn activates the insulin PI3K/AKT pathway to promote insulin synthesis and secretion, thereby exerting hypoglycemic effects. In vitro cellular experiments further confirmed that PEG-Loxe possibly exerts hypoglycemic effects by activating the insulin PI3K/AKT pathway.

Conclusion: PEG-Loxe improved liver injury in T2DM probably by activating Sirt1/AMPK/ACC lipid metabolism pathway, and exerted hypoglycemic effects through activation of insulin PI3K/AKT pathway.

Inflammation and Oxidative Stress in Diabetic Kidney Disease: The Targets for SGLT2 Inhibitors and GLP-1 Receptor Agonists

The incidence of type 2 diabetes (T2D) has been increasing worldwide, and diabetic kidney disease (DKD) remains one of the leading long-term complications of T2D. Several lines of evidence indicate that glucose-lowering agents prevent the onset and progression of DKD in its early stages but are of limited efficacy in later stages of DKD. However, sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor (GLP-1R) agonists were shown to exert nephroprotective effects in patients with established DKD, i.e., those who had a reduced glomerular filtration rate. These effects cannot be solely attributed to the improved metabolic control of diabetes. In our review, we attempted to discuss the interactions of both groups of agents with inflammation and oxidative stress—the key pathways contributing to organ damage in the course of diabetes. SGLT2i and GLP-1R agonists attenuate inflammation and oxidative stress in experimental in vitro and in vivo models of DKD in several ways. In addition, we have described experiments showing the same protective mechanisms as found in DKD in non-diabetic kidney injury models as well as in some tissues and organs other than the kidney. The interaction between both drug groups, inflammation and oxidative stress appears to have a universal mechanism of organ protection in diabetes and other diseases.

How glucagon-like peptide 1 receptor agonists work

In recent years, glucagon-like peptide 1 receptor agonists (GLP-1RAs) have become central in the treatment of type 2 diabetes (T2D). In addition to their glucose-lowering properties with low risk of hypoglycaemia, GLP-1RAs reduce body weight and show promising results in reducing cardiovascular risk and renal complications in high-risk individuals with T2D. These findings have changed guidelines on T2D management over the last years, and GLP-1RAs are now widely used in overweight patients with T2D as well as in patients with T2D and cardiovascular disease regardless of glycaemic control. The currently available GLP-1RAs have different pharmacokinetic profiles and differ in their ability to improve glycaemia, reduce body weight and in their cardio- and renal protective potentials. Understanding how these agents work, including insights into their pleiotropic effects on T2D pathophysiology, may improve their clinical utilisation and be useful for exploring other indications such as non-alcoholic steatohepatitis and neurodegenerative disorders. In this review, we provide an overview of approved GLP-1RAs, their clinical effects and mode of action, and we offer insights into the potential of GLP-1RAs for other indications than T2D. Finally, we will discuss the emerging data and therapeutic potential of using GLP-1RAs in combinations with other receptor agonists.

Incretin drugs in diabetic kidney disease: biological mechanisms and clinical evidence

As the prevalence of diabetes continues to climb, the number of individuals living with diabetic complications will reach an unprecedented magnitude. The emergence of new glucose-lowering agents - sodium-glucose cotransporter 2 inhibitors and incretin therapies - has markedly changed the treatment landscape of type 2 diabetes mellitus. In addition to effectively lowering glucose, incretin drugs, which include glucagon-like peptide 1 receptor (GLP1R) agonists and dipeptidyl peptidase 4 (DPP4) inhibitors, can also reduce blood pressure, body weight, the risk of developing or worsening chronic kidney disease and/or atherosclerotic cardiovascular events, and the risk of death. Although kidney disease events have thus far been secondary outcomes in clinical trials, an ongoing phase III trial in patients with diabetic kidney disease will test the effect of a GLP1R agonist on a primary kidney disease outcome. Experimental data have identified the modulation of innate immunity and inflammation as plausible biological mechanisms underpinning the kidney-protective effects of incretin-based agents. These drugs block the mechanisms involved in the pathogenesis of kidney damage, including the activation of resident mononuclear phagocytes, tissue infiltration by non-resident inflammatory cells, and the production of pro-inflammatory cytokines and adhesion molecules. GLP1R agonists and DPP4 inhibitors might also attenuate oxidative stress, fibrosis and cellular apoptosis in the kidney.

Mechanisms and Potential Roles of Glucose-Lowering Agents in COVID-19: A Review

OBJECTIVE

To explore mechanistic benefits of glucose-lowering agents that extend beyond glycemic control with the potential to mitigate coronavirus disease 2019 (COVID-19) complications.

DATA SOURCES

The following PubMed literature search terms were used from July 2020 to January 2, 2021: diabetes, COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), glucose-lowering agents, and pharmacology.

STUDY SELECTION AND DATA EXTRACTION

English-language studies reporting on the association between diabetes, COVID-19 adverse outcomes, and the potential roles of glucose-lowering agents were reviewed.

DATA SYNTHESIS

Selected glucose-lowering agents have benefits beyond glycemic control, with the potential to reduce the risks of severe complications during SARS-CoV-2 infection. Key benefits include anti-inflammatory, anticoagulant, immune modulating, and enzyme/receptor effects.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review summarizes the current knowledge of glucose-lowering agents and their potential roles in COVID-19 outcomes. Considering beneficial mechanisms on COVID-19 outcomes that extend beyond glycemic control as well as safety profiles, current data suggest that dipeptidyl peptidase-IV (DPP-IV) inhibitors and metformin may have the most promise and warrant further investigation.

CONCLUSIONS

Certain glucose-lowering agents may offer additional benefits beyond glucose control-namely, by modulating the mechanisms contributing to adverse outcomes related to COVID-19 in patients with diabetes. DPP-IV inhibitors and metformin appear to have the most promise. However, current published literature on diabetes medications and COVID-19 should be interpreted with caution. Most published studies are retrospective and consist of convenience samples, and some lack adequate analytical approaches with confounding biases. Ongoing trials aim to evaluate the effects of glucose-lowering agents in reducing the severity of COVID-19 outcomes.

Efficacy of dulaglutide on vascular health indexes in subjects with type 2 diabetes: a randomized trial

Background

Recent cardiovascular outcome trials have shown significant reductions in major cardiovascular (CV) events with glucagon-like peptide (GLP)-1 receptor agonists. Additionally, adjunctive surrogates for cardiovascular risk validated by some studies include arterial stiffness and endothelial function indexes. To date, no randomized trial has addressed the possible effects of antidiabetic interventional drugs such as GLP1 agonists on endothelial and arterial stiffness indexes as surrogate markers of vascular damage.

Aims

We aimed to evaluate metabolic efficacy and surrogate vascular efficacy endpoints of once-weekly dulaglutide (1.5 mg) plus traditional antidiabetic treatment compared with traditional antidiabetic treatment alone in subjects with type 2 diabetes.

Methods

Men and women (aged ≥ 50 years) with established or newly detected type 2 diabetes whose HbA1c level was 9.5% or less on stable doses of up to two oral glucose­ lowering drugs with or without basal insulin therapy were eligible for randomization. Subcutaneous dulaglutide was initiated at the full dose (1.5 mg/day weekly). Arterial stiffness (PWV: pulse wave velocity and augmentation index) and endothelial function (RHI: reactive hyperaemia index) were evaluated at baseline and at three-month and nine-month examination visits. At each visit (at 3 and 9 months), the subjects were also evaluated for glycaemic variables such as fasting plasma glucose (FPG) and HbA1c and lipid variables such as total cholesterol, LDL cholesterol, HDL cholesterol and triglyceride levels.

Results

At the three-month follow-up, the subjects treated with dulaglutide showed significantly lower serum levels of FPG and HbA1c than control subjects treated with conventional therapy. At the 9-month follow-up, subjects treated with dulaglutide showed significant lower values of the mean diastolic blood pressure, BMI, total serum cholesterol, LDL cholesterol, FPG, HbA1c and PWV and higher mean RHI values than control subjects treated with conventional therapy.

Conclusions

Our randomized trial showed that subjects with type 2 diabetes treated with conventional therapy plus 1.5 mg/day of subcutaneous dulaglutide compared with subjects treated with conventional therapy alone showed favourable metabolic effects associated with positive effects on vascular health markers such as arterial stiffness and endothelial function markers. These findings are consistent with previous study findings indicating the strict relationship between cardiovascular risk factors such as systolic blood pressure, total serum cholesterol and LDL levels and cardiovascular events and vascular health surrogate markers.

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.

Downregulation of the GLP-1/CREB/adiponectin pathway is partially responsible for diabetes-induced dysregulated vascular tone and VSMC dysfunction

BACKGROUND

The dysfunction of vasculature is observed in diabetes and might be responsible for the increased incidence of vascular events. Previous studies indicated that supplementation of GLP-1 analogues is beneficial to the cardiovascular functions in diabetic patients, but the mechanisms are not clear.

METHODS

A type 1 diabetic model was constructed. Vascular constrictions were measured using wire myograph. Western blotting and quantitative PCR were adopted to analyze the expression profiles of key molecules. Mitochondrial functions were analyzed in both vascular tissues or vascular smooth muscle cells (VSMCs). Dual-luciferase reporter assay was used to investigate the mechanism of adiponectin regulation.

RESULTS

In this study, abnormal vascular hypertrophy and increased vascular tones were observed in both diabetic patients and animals. ROS productions were increased in vessels and VSMCs from diabetic patients and animals, and the ROS scavenger mitoTEMPO partially attenuated the abnormal vascular tones and hypertension. In addition, decreased GLP-1 levels were observed, while GLP-1 supplementation improved the mitochondrial functions and vascular tones. Furthermore, it was shown that GLP-1 supplementation enhanced adiponectin expressions, while adiponectin facilitated the phosphorylation of AMPK and Sirt1 expressions. Also, CREB phosphorylation was enhanced upon GLP-1 supplementation and promoted the transcriptions of adiponectin. Finally, CREB inhibition partially attenuated the effects of GLP-1 on mitochondrial functions and adiponectin expressions.

CONCLUSION

GLP-1 downregulation might be an important mechanism of abnormal mitochondrial function and vascular tone in diabetes. Targeting GLP-1/CREB/adiponectin axis might become a promising therapeutic strategy in alleviating diabetes-related cardiovascular dysfunctions.

Saccharin Supplementation Inhibits Bacterial Growth and Reduces Experimental Colitis in Mice

Non-caloric artificial sweeteners are frequently discussed as components of the “Western diet”, negatively modulating intestinal homeostasis. Since the artificial sweetener saccharin is known to depict bacteriostatic and microbiome-modulating properties, we hypothesized oral saccharin intake to influence intestinal inflammation and aimed at delineating its effect on acute and chronic colitis activity in mice. In vitro, different bacterial strains were grown in the presence or absence of saccharin. Mice were supplemented with saccharin before or after induction of acute or chronic colitis using dextran sodium sulfate (DSS) and the extent of colitis was assessed. Ex vivo, intestinal inflammation, fecal bacterial load and composition were studied by immunohistochemistry analyses, quantitative PCR, 16 S RNA PCR or next generation sequencing in samples collected from analyzed mice. In vitro, saccharin inhibited bacterial growth in a species-dependent manner. In vivo, oral saccharin intake reduced fecal bacterial load and altered microbiome composition, while the intestinal barrier was not obviously affected. Of note, DSS-induced colitis activity was significantly improved in mice after therapeutic or prophylactic treatment with saccharin. Together, this study demonstrates that oral saccharin intake decreases intestinal bacteria count and hence encompasses the capacity to reduce acute and chronic colitis activity in mice.

Exendin‑4 inhibits lipotoxicity‑induced oxidative stress in β‑cells by inhibiting the activation of TLR4/NF‑κB signaling pathway

The present study aimed to investigate the relationship between the protective effects of exendin‑4 (EX‑4) on lipotoxicity‑induced oxidative stress and meta‑inflammation in β‑cells and the toll‑like receptor 4 (TLR4)/NF‑κB signaling pathway. Lipotoxicity, hydrogen peroxide (H2O2)‑induced oxidative stress in β cells, obese Sprague Dawley rats and TLR4 truncation rats were utilized in the present study. The expression levels were detected by western blotting; cell apoptosis was detected by TUNEL assay; and the intracellular reactive oxygen species (ROS) levels were analyzed using a ROS assay kit. The findings of the present study showed that EX‑4 inhibited the expression of TLR4, NF‑κB p65 subunit and p47phox in a concentration‑dependent manner, and decreased the intracellular level of ROS. Additionally, silencing of TLR4 expression enhanced the protective effects of EX‑4, while overexpression of TLR4 attenuated these protective influences. Simultaneously, it was demonstrated that TLR4 was involved in the process of EX‑4 intervention to inhibit H2O2‑induced oxidative stress in islet β‑cells. Moreover, it was found that EX‑4 also inhibited TLR4‑ or NF‑κB agonist‑induced oxidative stress. These results were also confirmed in an animal model of obese rats, in which EX‑4 was able to improve the function of β‑cells, attenuate oxidative stress, and inhibit the expression levels of TLR4 and NF‑κB p65 subunit in the pancreas of the diet‑induced obese rats. Furthermore, truncation of the TLR4 gene in SD rats delayed the aforementioned damage. In summary, EX‑4 may inhibit lipotoxicity‑induced oxidative stress in β‑cells by inhibiting the activation of the TLR4/NF‑κB signaling pathway.

Randomized Study Comparing Vildagliptin vs Glibenclamide on Glucose Variability and Endothelial Function in Patients with Type 2 Diabetes Mellitus and Hypertension

BACKGROUND

Glucose variability (GV) is considered an important factor for cardiovascular disease (CVD) in patients with type 2 diabetes mellitus (T2DM). High GV causes endothelial dysfunction and increased oxidative stress. Dipeptidyl peptidase-4 (DPP-4) inhibitors may improve endothelial function and decrease GV. The aim of this study was to investigate the effects of vildagliptin, a DPP-4 inhibitor, compared with glibenclamide in GV and endothelial function in patients with T2DM and arterial hypertension.

METHODS

This is a prospective, randomized, open and drug-controlled study. Fifty patients older than 35 years with T2DM and hypertension without CVD were randomized to receive vildagliptin (n=25) or glibenclamide (n=25), both in added-on metformin. Laboratory tests and analysis of endothelial function were performed before and 12 weeks after treatment. Endothelial function, defined by reactive hyperemia index (RHI), was analyzed by peripheral artery tonometry (endo-PAT2000). GV was evaluated by capillary glucose with intermittent monitoring device, six measurements per day, for three days, before and after treatment. The median of standard deviation (SD) of mean blood glucose (MBG) was used to evaluate GV.

RESULTS

GV decreased in the vildagliptin group (35.2 to 30.7, P=0.037) but did not change with glibenclamide (37.6 to 37.5, P=0.765). Glycated hemoglobin was similar in both groups. MBG decreased only in glibenclamide group, without difference with vildagliptin group (P=0.374). There were no changes in the RHI in both groups and there was no correlation between GV and RHI (P=0.658).

CONCLUSION

Vildagliptin reduces GV; however, the action on endothelial function was not demonstrated. In addition, there was no correlation between GV and endothelial function.

GLP-1 Is a Coronary Artery Vasodilator in Humans

Background

The mechanism underlying the beneficial cardiovascular effects of the incretin GLP‐1 (glucagon‐like peptide 1) and its analogues in humans is elusive. We hypothesized that activating receptors located on vascular smooth muscle cells to induce either peripheral or coronary vasodilatation mediates the cardiovascular effect of GLP‐1.

Methods and Results

Ten stable patients with angina awaiting left anterior descending artery stenting underwent forearm blood flow measurement using forearm plethysmography and post–percutaneous coronary intervention coronary blood flow measurement using a pressure‐flow wire before and after peripheral GLP‐1 administration. Coronary sinus and artery bloods were sampled for GLP‐1 levels. A further 11 control patients received saline rather than GLP‐1 in the coronary blood flow protocol. GLP‐1 receptor (GLP‐1R) expression was assessed by immunohistochemistry using a specific GLP‐1R monoclonal antibody in human tissue to inform the physiological studies. There was no effect of GLP‐1 on absolute forearm blood flow or forearm blood flow ratio after GLP‐1, systemic hemodynamics were not affected, and no binding of GLP‐1R monoclonal antibody was detected in vascular tissue. GLP‐1 reduced resting coronary transit time (mean [SD], 0.87 [0.39] versus 0.63 [0.27] seconds; P=0.02) and basal microcirculatory resistance (mean [SD], 76.3 [37.9] versus 55.4 [30.4] mm Hg/s; P=0.02), whereas in controls, there was an increase in transit time (mean [SD], 0.48 [0.24] versus 0.83 [0.41] seconds; P<0.001) and basal microcirculatory resistance (mean [SD], 45.9 [34.7] versus 66.7 [37.2] mm Hg/s; P=0.02). GLP‐1R monoclonal antibody binding was confirmed in ventricular tissue but not in vascular tissue, and transmyocardial GLP‐1 extraction was observed.

Conclusions

GLP‐1 causes coronary microvascular dilation and increased flow but does not influence peripheral tone. GLP‐1R immunohistochemistry suggests that GLP‐1 coronary vasodilatation is indirectly mediated by ventricular‐coronary cross talk.

Cardioprotective anti-hyperglycaemic medications: a review of clinical trials

Despite extensive clinical efforts to achieve stricter glycaemic control over the past few decades, cardiovascular (CV) disease remains the leading cause of death among diabetic patients. Recently, sodium-glucose cotransporter-2 (SGLT-2) inhibitors and glucagon-like peptide-1 receptor (GLP-1-R) agonists have gained attention due to their apparent effects in reducing CV mortality. Four CV randomized controlled trials: EMPA-REG, CANVAS, LEADER, and SUSTAIN-6, found a decrease in CV events among patients with type 2 diabetes on empagliflozin, canagliflozin, liraglutide, and semaglutide, respectively. In light of this data, the US Food and Drug Administration has recently approved empagliflozin for CV mortality reduction in type 2 diabetic patients, making it the first diabetes medication approved for such an indication. The purpose of this review is to summarize the results of novel anti-hyperglycaemic medication trials, and shed light on their mode of action and cardioprotective pathways.

Consensus recommendations for management of patients with type 2 diabetes mellitus and cardiovascular diseases

The recent American Diabetes Association and the European Association for the Study of Diabetes guideline mentioned glycaemia management in type 2 diabetes mellitus (T2DM) patients with cardiovascular diseases (CVDs); however, it did not cover the treatment approaches for patients with T2DM having a high risk of CVD, and treatment and screening approaches for CVDs in patients with concomitant T2DM. This consensus guideline undertakes the data obtained from all the cardiovascular outcome trials (CVOTs) to propose approaches for the T2DM management in presence of CV comorbidities. For patients at high risk of CVD, metformin is the drug of choice to manage the T2DM to achieve a patient specific HbA1c target. In case of established CVD, a combination of glucagon-like peptide-1 receptor agonist with proven CV benefits is recommended along with metformin, while for chronic kidney disease or heart failure, a sodium-glucose transporter proteins-2 inhibitor with proven benefit is advised. This document also summarises various screening and investigational approaches for the major CV events with their accuracy and specificity along with the treatment guidance to assist the healthcare professionals in selecting the best management strategies for every individual. Since lifestyle modification and management plays an important role in maintaining the effectiveness of the pharmacological therapies, authors of this consensus recommendation have also briefed on the patient-centric non-pharmacological management of T2DM and CVD.

Nonglycemic Effects of GLP-1 Agonists: From a Starling to Lizards to People

With the approval of exenatide in 2005, physicians had a new class of hypoglycemic agents available for the treatment of type 2 diabetes-the glucagon-like peptide-1 receptor agonists (or GLP-1 receptor agonists). As of this writing, there are seven drugs in this class available in the United States. In addition to demonstrating either cardiovascular risk neutrality or overt benefit, as now mandated by the United States Food and Drug Administration (FDA), many of these drugs have other, unexpected actions. It is our goal to outline these actions, some beneficial, some not. We have reviewed English-language articles in this area, not for an exhaustive study, but rather a broad search to define current understanding and perhaps generate further investigation.

GLP-1 Limits Adipocyte Inflammation and Its Low Circulating Pre-Operative Concentrations Predict Worse Type 2 Diabetes Remission after Bariatric Surgery in Obese Patients

OBJECTIVE

Glucagon-like peptide (GLP)-1 has been proposed as a key candidate in glucose improvements after bariatric surgery. Our aim was to explore the role of GLP-1 in surgically-induced type 2 diabetes (T2D) improvement and its capacity to regulate human adipocyte inflammation.

METHODS

Basal circulating concentrations of GLP-1 as well as during an oral glucose tolerance test (OGTT) were measured in lean and obese volunteers with and without T2D (n = 93). In addition, GLP-1 levels were determined before and after weight loss achieved by Roux-en-Y gastric bypass (RYGB) (n = 77). The impact of GLP-1 on inflammation signalling pathways was also evaluated.

RESULTS

We show that the reduced (p < 0.05) circulating levels of GLP-1 in obese T2D patients increased (p < 0.05) after RYGB. The area under the curve was significantly lower in obese patients with (p < 0.01) and without (p < 0.05) T2D compared to lean volunteers while obese patients with T2D exhibited decreased GLP-1 levels at baseline (p < 0.05) and 120 min (p < 0.01) after the OGTT. Importantly, higher (p < 0.05) pre-operative GLP-1 concentrations were found in patients with T2D remission after RYGB. We also revealed that exendin-4, a GLP-1 agonist, downregulated the expression of inflammation-related genes (IL1B, IL6, IL8, TNF) and, conversely, upregulated the mRNA levels of ADIPOQ in human visceral adipocytes. Furthermore, exendin-4 blocked (p < 0.05) LPS-induced inflammation in human adipocytes via downregulating the expression and secretion of key inflammatory markers.

CONCLUSIONS

Our data indicate that GLP-1 may contribute to glycemic control and exert a role in T2D remission after RYGB. GLP-1 is also involved in limiting inflammation in human visceral adipocytes.

Glucagon-like peptide-1 attenuates endothelial barrier injury in diabetes via cAMP/PKA mediated down-regulation of MLC phosphorylation

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) showed protective effects on endothelium-dependent dilatation. Since endothelial barrier dysfunction also plays a pivotal role in atherosclerosis, this study was designed to investigate the effects of GLP-1 on endothelial barrier function in diabetic aortic endothelium and explore the underlying mechanism.

METHODS

For in vivo studies, diabetic rats were established and subjected to 12- and 24-week treatment of exenatide. The morphological changes of aortic endothelium were observed with transmission electron microscope. A permeability assay of aortic endothelium was performed using the surface biotinylation technique. Protein expression was detected by immunohistochemical analysis and Western blots. For in vitro studies, human umbilical vein endothelial cells (HUVECs) were cultured in medium enriched with advanced glycation end products (AGEs) or AGEs plus GLP-1 and other reagents. The integrity of endothelium was evaluated by endothelial monolayer permeability assay and transendothelial resistance. The in vitro expressions of relevant proteins in signaling pathways were also detected by immunofluorescence and Western blots.

RESULTS

In vivo, the enhanced aortic endothelial permeability in diabetic aortas were attenuated by exenatide treatment. Additionally, myosin light chain (MLC) phosphorylation, related to actomyosin contractility, and activation of its upstream targets in diabetic aorta were inhibited after administration of exenatide. In vitro, the endothelial monolayer permeability and the assembly of stress fibers were reduced by GLP-1 intervention under diabetic condition. Meanwhile, AGE-induced MLC phosphorylation mediating ECs contractility was inhibited by GLP-1. Furthermore, GLP-1 down-regulated the upstream targets of MLC phosphorylation, including RAGE, Rho/ROCK and MAPK signaling pathways. Intriguingly, the effects of GLP-1 elicited on ECs contractility and barrier function in diabetes were blunted by inhibition of GLP-1R, cAMP or PKA and stimulation of Rho/ROCK and MAPK signaling pathways.

CONCLUSION

The findings of this study suggest that the stabilizing effect of GLP-1 on the endothelial barrier and contraction of AGE-treated ECs is caused by GLP-1R/cAMP/PKA activation and the subsequent inactivation of RAGE/Rho/ROCK as well as MAPK signaling pathways.

Glucagon-Like Peptide-1 Is a Marker of Systemic Inflammation in Patients Treated with High-Dose Chemotherapy and Autologous Stem Cell Transplantation

Autologous stem cell transplantation (ASCT) is challenged by side effects that may be propagated by chemotherapy-induced mucositis, resulting in bacterial translocation and systemic inflammation. Because gastrointestinal damage appears as an early event in this cascade of reactions, we hypothesized that markers reflecting damage to the intestinal barrier could serve as early predictive markers of toxicity. Glucagon-like peptide-1 (GLP-1), a well-known regulator of blood glucose, has been found to promote intestinal growth and repair in animal studies. We investigated fasting GLP-1 plasma levels in 66 adults undergoing ASCT for lymphoma and multiple myeloma. GLP-1 increased significantly after chemotherapy, reaching peak levels at day +7 post-transplant (median, 8 pmol/L [interquartile range, 4 to 12] before conditioning versus 10 pmol/L [interquartile range, 6 to 17] at day +7; P = .007). The magnitude of the GLP-1 increase was related to the intensity of conditioning. GLP-1 at the day of transplantation (day 0) was positively associated with peak C-reactive protein (CRP) levels (46 mg/L per GLP-1 doubling, P < .001) and increase in days with fever (32% per GLP-1 doubling, P = .0058). Patients with GLP-1 above the median at day 0 had higher CRP levels from days +3 to +10 post-transplant than patients with lower GLP-1 (P ≤ .041) with peak values of 238 versus 129 mg/L, respectively. This study, which represents the first clinical investigation of fasting GLP-1 in relation to high-dose chemotherapy, provides evidence that GLP-1 plays a role in regulation of mucosal defenses. Fasting GLP-1 levels may serve as an early predictor of systemic inflammation and fever in patients receiving high-dose chemotherapy.

Effect of Dulaglutide Versus Liraglutide on Glucose Variability, Oxidative Stress, and Endothelial Function in Type 2 Diabetes: A Prospective Study

INTRODUCTION

To compare the effect of dulaglutide and liraglutide on oxidative stress and endothelial function in patients with type 2 diabetes mellitus (T2DM).

METHODS

Twenty-two patients with T2DM who received treatment with liraglutide for at least 12 weeks were randomized to either continue liraglutide or receive dulaglutide for 24 weeks. The primary end points were changes in the diacron-reactive oxygen metabolite (d-ROMs) test, as a marker of oxidative stress, and endothelial function, as determined by the reactive hyperemia index (RHI). The secondary end points were changes in body weight (BW), glucose variability, diabetes treatment satisfaction questionnaire (DTSQ) score, and eating behavior.

RESULTS

There were no significant differences in changes in d-ROMs and logarithmic-scaled RHI (L-RHI) between the two groups after 24 weeks of treatment. Notably, the treatment with dulaglutide was superior to that with liraglutide in terms of mean glucose levels and mean amplitude of glycemic excursions following the 24-week treatment. However, in this regard, the outcome following the treatment with dulaglutide was maintained, whereas that with the treatment with liraglutide was aggravating. The DTSQ score for "convenience" improved in the dulaglutide group. No statistically significant changes in fasting plasma glucose, hemoglobin A1c, and BW were observed between the two groups.

CONCLUSION

We showed that once-weekly dulaglutide was comparable to once-daily liraglutide in terms of oxidative stress and endothelial function. Switching from liraglutide to dulaglutide improved convenience by decreasing the number of injections without deteriorating glucose metabolism.

TRIAL REGISTRATION

This trial was registered with the University Hospital Medical Information Network (UMIN no. 000034353) on 10 October 2018.

Effects of Acute GLP-1 Infusion on Pulmonary and Systemic Hemodynamics in Patients With Heart Failure: A Pilot Study

PURPOSE

Cardiovascular-safety studies assessing glucagon-like peptide (GLP)-1 receptor agonists and dipeptidyl peptidase 4 inhibitors have provided inconsistent data on the risk for developing heart failure. Animal studies have shown that GLP-1 is a vasodilator; if confirmed in humans, this may ameliorate heart failure symptoms.

METHODS

In a single-center, observational pilot study, we recruited 10 patients with advanced heart failure undergoing right heart catheterization, and we recorded pulmonary hemodynamic measures, including cardiac output calculated by thermodilution and the indirect Fick method before and after a 15-minute continuous infusion of native GLP-1 (7-36) NH₂.

FINDINGS

There was a neutral effect of GLP-1 on all pressure and hemodynamics indices as derived by cardiac output calculated by thermodilution. However, there was a small but consistent reduction in cardiac output as calculated by the indirect Fick method after GLP-1 infusion (baseline, 4.0 [1.1] L/min vs GLP-1, 3.6 [0.9] L/min; P = 0.003), driven by a consistent reduction in mixed venous oxygen saturation after GLP-1 infusion (baseline, 62.2% [7.0%] vs GLP-1, 59.3% [6.8%]; P < 0.001), whereas arterial saturation remained constant (baseline, 96.8% [3.3%] vs GLP-1, 97.0% [3.2%]; P = 0.34). This resulted in an increase in systemic vascular resistance by Fick (baseline, 1285 [228] dyn · s/cm⁵ vs GLP-1, 1562 [247] dyn · s/cm⁵; P = 0.001).

IMPLICATIONS

Acute infusion of GLP-1 has a neutral hemodynamic effect, when assessed by thermodilution, in patients with heart failure. However, GLP-1 reduces mixed venous oxygen saturation. ClinicalTrials.gov identifier: NCT02129179.

Prevalence and pathophysiology of early dumping in patients after primary Roux-en-Y gastric bypass during a mixed-meal tolerance test

BACKGROUND

Early dumping is a poorly defined and incompletely understood complication after Roux-en-Y gastric (RYGB).

OBJECTIVE

We performed a mixed-meal tolerance test in patients after RYGB to address the prevalence of early dumping and to gain further insight into its pathophysiology.

SETTING

The study was conducted in a regional hospital in the northern part of the Netherlands.

METHODS

From a random sample of patients who underwent primary RYGB between 2008 and 2011, 46 patients completed the mixed-meal tolerance test. The dumping severity score for early dumping was assessed every 30 minutes. A sum score at 30 or 60 minutes of ≥5 and an incremental score of ≥3 points were defined as indicating a high suspicion of early dumping. Blood samples were collected at baseline, every 10 minutes during the first half hour, and at 60 minutes after the start.

RESULTS

The prevalence of a high suspicion of early dumping was 26%. No differences were seen for absolute hematocrit value, inactive glucagon-like peptide-1, and vasoactive intestinal peptide between patients with or without early dumping. Patients at high suspicion of early dumping had higher levels of active glucagon-like peptide-1 and peptide YY.

CONCLUSION

The prevalence of complaints at high suspicion of early dumping in a random population of patients after RYGB is 26% in response to a mixed-meal tolerance test. Postprandial increases in both glucagon-like peptide-1 and peptide YY are associated with symptoms of early dumping, suggesting gut L-cell overactivity in this syndrome.

After the LEADER trial and SUSTAIN-6, how do we explain the cardiovascular benefits of some GLP-1 receptor agonists?

Recent cardiovascular outcome trials - the LEADER with liragutide and SUSTAIN-6 with semaglutide - have shown significant reductions of major cardiovascular (CV) events with these glucagon-like peptide (GLP)-1 receptor agonists. Progressive separation of the treatment and placebo curves, starting clearly between 12 and 18 months of the trial period, and significant reductions in the risk of myocardial infarction and stroke, indicate that the beneficial CV effects observed with GLP-1 receptor agonists could be due to an antiatherogenic effect. So far, the reasons for such an effect of GLP-1 receptor agonists have not been entirely clear, although several hypotheses may be proposed. As the reductions in glycated haemoglobin and systolic blood pressure (SBP) in these trials were modest, and both trials lasted only a short period of time, reductions in hyperglycaemia and SBP are unlikely to be involved in the beneficial CV effects of GLP-1 receptor agonists. On the other hand, their effect on lipids and, in particular, the dramatic decrease in postprandial hypertriglyceridaemia may explain their beneficial CV actions. Reduction of body weight, including a significant decrease in visceral fat in patients using GLP-1 receptor agonists, may also have beneficial CV effects by reducing chronic proatherogenic inflammation. In addition, there are in-vitro data showing a direct anti-inflammatory effect with these agents that could also be involved in their beneficial CV effects. Moreover, studies in humans have shown significant beneficial effects on ischaemic myocardium after a very short treatment period, suggesting a direct effect of GLP-1 receptor agonists on myocardium, although the precise mechanism remains unclear. Finally, as a reduction in insulin resistance has been associated with a decrease in CV risk, it cannot be ruled out that the lowering of insulin resistance induced by GLP-1 receptor agonists might also be involved in their beneficial CV actions.

Molecular Mechanisms Underlying the Cardiovascular Benefits of SGLT2i and GLP-1RA

PURPOSE OF REVIEW

In addition to their effects on glycemic control, two specific classes of relatively new anti-diabetic drugs, namely the sodium glucose co-transporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) have demonstrated reduced rates of major adverse cardiovascular events (MACE) in subjects with type 2 diabetes (T2D) at high risk for cardiovascular disease (CVD). This review summarizes recent experimental results that inform putative molecular mechanisms underlying these benefits.

RECENT FINDINGS

SGLT2i and GLP-1RA exert cardiovascular effects by targeting in both common and distinctive ways (A) several mediators of macro- and microvascular pathophysiology: namely (A1) inflammation and atherogenesis, (A2) oxidative stress-induced endothelial dysfunction, (A3) vascular smooth muscle cell reactive oxygen species (ROS) production and proliferation, and (A4) thrombosis. These agents also exhibit (B) hemodynamic effects through modulation of (B1) natriuresis/diuresis and (B2) the renin-angiotensin-aldosterone system. This review highlights that while GLP-1RA exert direct effects on vascular (endothelial and smooth muscle) cells, the effects of SGLT2i appear to include the activation of signaling pathways that prevent adverse vascular remodeling. Both SGLT2i and GLP-1RA confer hemodynamic effects that counter adverse cardiac remodeling.

Improvements of ambient hyperglycemia and glycemic variability are associated with reduction in oxidative stress for patients with type 2 diabetes

AIMS

We aimed to evaluate which parameters of improvement in glucose metabolism reduce oxidative stress for patients with Type 2 diabetes mellitus (T2DM).

METHODS

Sixty-seven outpatients with T2DM underwent 72 h of continuous glucose monitoring (CGM) and were measured for oxidative stress before and after a 24-week intervention with the following targets: fasting plasma glucose (FPG), <130 mg/dl; postprandial plasma glucose (PPG), <180 mg/dl; and glycated hemoglobin (HbA1c), <7% (53 mmol/mol). The mean glucose level (MGL), mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), percentage coefficient of variation for glucose (%CV) and area under the postprandial plasma glucose curve (AUC_PP) were calculated from the CGM data. Oxidative stress was estimated using the diacron-reactive oxygen metabolites (d-ROMs) test. Finally, the association between the improvements in glucose metabolism and oxidative stress was evaluated.

RESULTS

FPG, MGL, HbA1c, MAGE, MODD, %CV, AUC_PP, and d-ROMs significantly improved after 24 weeks of intervention. The change in d-ROMs was significantly correlated with that in FPG (r = 0.414), MGL (r = 0.402), HbA1c (r = 0.271), MAGE (r = 0.457), MODD (r = 0.371), and AUC_PP (r = 0.352). The correlation of the change in d-ROMs with that in FPG, MAGE, and MODD and the use of glucose-like peptide 1 receptor agonists and statins remained significant after adjustment for other markers of diabetes control (multiple R² = 0.406).

CONCLUSIONS

Improvements in glucose metabolism, including FPG and daily and day-to-day glucose variability, were all correlated with reduced oxidative stress for patients with T2DM.

Protective effects of melatonin and glucagon-like peptide-1 receptor agonist (liraglutide) on gastric ischaemia-reperfusion injury in high-fat/sucrose-fed rats

Ischaemia-reperfusion (I-R) injury is a serious pathology that is often encountered with thrombotic events, during surgery when blood vessels are cross-clamped, and in organs for transplantation. Increased oxidative stress is the main pathology in I-R injury, as assessed in studies on the heart, kidney, and brain with little data available on gastric I-R (GI-R). Liraglutide is a GLP-1 receptor agonist that has insulinotropic and weight reducing actions, and melatonin that has been much studied as a chronotropic hormone; have also studied as being anti-oxidative stress agents. Herein, we aimed to explore the effects of liraglutide and melatonin on GI-R injury with high-fat/sucrose diet. Rats were divided into six groups; two diet-control, two melatonin- and two liraglutide-pretreated groups. All rats were subjected to 30 minutes of gastric ischaemia followed by 1 hour of reperfusion. Gastric tissues were assessed for the percentage of DNA fragmentation, myeloperoxidase activity, total oxidant status, total antioxidant capacity, oxidative stress index, BMI and histopathological examination. We showed that high-fat feeding for four weeks prior to GI-R significantly increased BMI, oxidative stress indices and decreased total antioxidant capacity, with a neutral effect on apoptosis compared to controls. Pretreatment with either melatonin (10 mg/kg per day orally) or liraglutide (25 μg/kg per day ip) reverses these effects. Furthermore, both drugs reduced weight only in HFS-fed rats. Both liraglutide and melatonin have nearly similar protective effects on gastric I-R injury through decreasing the oxidative stress and apoptosis.

Coagonist of glucagon-like peptide-1 and glucagon receptors ameliorates nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is often associated with obesity and type 2 diabetes. Coagonists of glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) are under clinical investigation for the treatment of obesity and type 2 diabetes. In this study, we have demonstrated the effect of a balanced coagonist in the treatment of NAFLD using mouse models. GLP-1R agonist exendin-4, glucagon, and coagonist (Aib2 C24 chimera2) were administered to C57BL6/J mice, in which NAFLD was induced by carbon tetrachloride (CCl₄) treatment after high-fat diet (HFD) feeding, and choline-deficient, L-amino-acid-defined HFD (CDAHFD) feeding. Repeated dose administration of coagonist significantly attenuated liver inflammation and steatosis induced by acute and long-term treatment with CCl₄ in HFD-fed mice. Coagonist markedly attenuated the CDAHFD-induced expression of TIMP-1, MMP-9, TNF-α, MCP-1, COL1A1, and α-SMA. It also inhibited progression of hepatic steatosis and fibrosis in mice. Exendin-4 was better than glucagon, but coagonist was most effective in reduction of hepatic inflammation as well as steatosis. Coagonist of GLP-1R and GCGR improved NAFLD in C57BL6/J mice. This effect is mediated by reduction in lipotoxicity and inflammation in liver.

Incretins: Beyond type 2 diabetes

While the use of incretins, including GLP-1 receptor agonists and PDD-IV inhibitors, is well established in the treatment of type 2 diabetes, many other aspects of these agents are yet to be discovered and utilized for their potential clinical benefit. These include the potential role of GLP-1 receptor agonists in the induction of weight loss, blood pressure reduction, anti-inflammatory and nephro- and cardio-protective actions. Their potential benefit in type 1 diabetes is also being investigated. This review will attempt to comprehensively describe novel discoveries in the field of incretin pathophysiology and pharmacology beyond their classical role in the treatment of type 2 diabetes.

Extrapancreatic effects of incretin hormones: evidence for weight-independent changes in morphological aspects and oxidative status in insulin-sensitive organs of the obese nondiabetic Zucker rat (ZFR)

Incretin‐based therapies are widely used to treat type 2 diabetes. Although hypoglycemic actions of incretins are mostly due to their insulinotropic/glucagonostatic effects, they may also influence extrapancreatic metabolism. We administered exendin‐4 (Ex‐4), a long‐acting glucagon‐like peptide receptor agonist, at low dose (0.1 nmol/kg/day) for a short period (10 days), in obese nondiabetic fa/fa Zucker rats (ZFRs). Ex‐4‐treated ZFRs were compared to vehicle (saline)‐treated ZFRs and vehicle‐ and Ex‐4‐treated lean rats (LRs). Blood glucose levels were measured at days 0, 9, and 10. Ingested food and animal weight were recorded daily. On the day of sacrifice (d10), blood was sampled along with liver, epididymal, subcutaneous, brown adipose, and skeletal muscle tissues from animals fasted for 24 h. Plasma insulin and blood glucose levels, food intake, and body and epididymal fat weight were unchanged, but gross morphological changes were observed in insulin‐sensitive tissues. The average size of hepatocytes was significantly lower in Ex‐4‐treated ZFRs, associated with decreased number and size of lipid droplets and 4‐hydroxy‐2‐nonenal (HNE) staining, a marker of oxidative stress (OS). Myocytes, which were smaller in ZFRs than in LRs, were significantly enlarged and depleted of lipid droplets in Ex‐4‐treated ZFRs. Weak HNE staining was increased by Ex‐4. A similar observation was made in brown adipose tissue, whereas the elevated HNE staining observed in epididymal adipocytes of ZFRs, suggestive of strong OS, was decreased by Ex‐4. These results suggest that incretins by acting on OS in insulin‐sensitive tissues may contribute to weight‐independent improvement in insulin sensitivity.

Lowest Glucose Variability and Hypoglycemia Are Observed With the Combination of a GLP-1 Receptor Agonist and Basal Insulin (VARIATION Study)

OBJECTIVE

There is a dearth of published literature comparing glucose variability (GV) between different insulin regimens in type 2 diabetes. This cohort study compares GV using continuous glucose monitoring (CGM) in patients with well-controlled type 2 diabetes using four common insulin regimens: basal insulin + oral drugs (BO), basal insulin + glucagon-like peptide 1 receptor agonist (GLP-1 RA) (BGLP), premixed insulin (PM), and basal-bolus insulin (BB).

RESEARCH DESIGN AND METHODS

Consecutive patients from three endocrinology clinics who met study criteria-type 2 diabetes, age 18 to 80 years, BMI ≤ 45 kg/m², stable insulin regimen for a minimum of 6 months, and stable A1C value ≤7.5% (58 mmol/mol) before study enrollment-underwent 6-day masked CGM. Hypoglycemia was defined as a sensor glucose concentration <70 mg/dL on CGM.

RESULTS

A total of 160 patients with comparable baseline characteristics formed four equal insulin regimen cohorts. The daily glucose SD (the primary outcome) was significantly lower in the BGLP cohort versus the BO, PM, and BB cohorts (P = 0.03, P = 0.01, and P < 0.01, respectively), and remained so after adjusting for age, BMI, type 2 diabetes duration, and A1C. Similarly, daily hypoglycemia outcomes on CGM were least for the BGLP cohort.

CONCLUSIONS

The lowest GV and lowest hypoglycemia were observed in patients using the combination of basal insulin with a GLP-1 RA, supporting the complementary glycemic action of these agents in type 2 diabetes. These observed benefits in GV and hypoglycemia may contribute to the cardiovascular outcome reduction seen with GLP-1 RA therapy and should be investigated further.

Differential effects of glucagon-like peptide-1 receptor agonists on heart rate

While glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are known to increase heart rate (HR), it is insufficiently recognized that the extent varies greatly between the various agonists and is affected by the assessment methods employed. Here we review published data from 24-h time-averaged HR monitoring in healthy individuals and subjects with type 2 diabetes mellitus (T2DM) treated with either short-acting GLP-1 RAs, lixisenatide or exenatide, or long-acting GLP-1 RAs, exenatide LAR, liraglutide, albiglutide, or dulaglutide (N = 1112; active-treatment arms). HR effects observed in two independent head-to-head trials of lixisenatide and liraglutide (N = 202; active-treatment arms) are also reviewed. Short-acting GLP-1 RAs, exenatide and lixisenatide, are associated with a transient (1-12 h) mean placebo- and baseline-adjusted 24-h HR increase of 1-3 beats per minute (bpm). Conversely, long-acting GLP-1 RAs are associated with more pronounced increases in mean 24-h HR; the highest seen with liraglutide and albiglutide at 6-10 bpm compared with dulaglutide and exenatide LAR at 3-4 bpm. For both liraglutide and dulaglutide, HR increases were recorded during both the day and at night. In two head-to-head comparisons, a small, transient mean increase in HR from baseline was observed with lixisenatide; liraglutide induced a substantially greater increase that remained significantly elevated over 24 h. The underlying mechanism for increased HR remains to be elucidated; however, it could be related to a direct effect at the sinus node and/or stimulation of the sympathetic nervous system, with this effect related to the duration of action of the respective GLP-1 RAs. In conclusion, this review indicates that the effects on HR differ within the class of GLP-1 RAs: short-acting GLP-1 RAs are associated with a modest and transient HR increase before returning to baseline levels, while some long-acting GLP-1 RAs are associated with a more pronounced and sustained increase during the day and night. Findings from recently completed trials indicate that a GLP-1 RA-induced increase in HR, regardless of magnitude, does not present an increased cardiovascular risk for subjects with T2DM, although a pronounced increase in HR may be associated with adverse clinical outcomes in those with advanced heart failure.

The Cardiovascular Biology of Glucagon-like Peptide-1

Glucagon-like peptide-1, produced predominantly in enteroendocrine cells, controls glucose metabolism and energy homeostasis through regulation of islet hormone secretion, gastrointestinal motility, and food intake, enabling development of GLP-1 receptor (GLP-1R) agonists for the treatment of diabetes and obesity. GLP-1 also acts on the immune system to suppress inflammation, and GLP-1R signaling in multiple tissues impacts cardiovascular function in health and disease. Here we review how GLP-1 and clinically approved GLP-1R agonists engage mechanisms that influence the risk of developing cardiovascular disease. We discuss how GLP-1R agonists modify inflammation, cardiovascular physiology, and pathophysiology in normal and diabetic animals through direct and indirect mechanisms and review human studies illustrating mechanisms linking GLP-1R signaling to modification of the cardiovascular complications of diabetes. The risks and benefits of GLP-1R agonists are updated in light of recent data suggesting that GLP-1R agonists favorably modify outcomes in diabetic subjects at high risk for cardiovascular events.

The simultaneous control of hyperglycemia and GLP-1 infusion normalize endothelial function in type 1 diabetes

BACKGROUND

To test the effect of normoglycemia and glucagon-like peptide-1 (GLP-1), alone or in combination, on the possible normalization of endothelial function in type 1 diabetes.

METHODS

Fifteen people with type 1 diabetes participated in three experiments: reaching and maintaining normoglycemia for 4h; reaching and maintaining hyperglycemia plus GLP-1 infusion for 4h; and reaching and maintaining normoglycemia for 4h with simultaneous infusion of GLP-1.

RESULTS

Both normoglycemia and GLP-1 infusion restored endothelial function and decreased and plasma 8-iso prostaglandin F2α levels. However, only the combination of normoglycemia and GLP-1 was able to normalize endothelial function.

CONCLUSIONS

This study confirms that long-lasting hyperglycemia in type 1 diabetes induces a permanent alteration which contributes to maintaining endothelial dysfunction even when glycemia is normalized, and that in the presence of normoglycemia, GLP-1 can contribute to normalizing endothelial function.