Incretin-based therapies and renin-angiotensin system: Looking for new therapeutic potentials in the diabetic milieu

Gut Molecules in Cardiometabolic Diseases: The Mechanisms behind the Story

Atherosclerotic cardiovascular disease is the most common cause of morbidity and mortality worldwide. Diabetes mellitus increases cardiovascular risk. Heart failure and atrial fibrillation are associated comorbidities that share the main cardiovascular risk factors. The use of incretin-based therapies promoted the idea that activation of alternative signaling pathways is effective in reducing the risk of atherosclerosis and heart failure. Gut-derived molecules, gut hormones, and gut microbiota metabolites showed both positive and detrimental effects in cardiometabolic disorders. Although inflammation plays a key role in cardiometabolic disorders, additional intracellular signaling pathways are involved and could explain the observed effects. Revealing the involved molecular mechanisms could provide novel therapeutic strategies and a better understanding of the relationship between the gut, metabolic syndrome, and cardiovascular diseases.

Benefits of GLP-1 Mimetics on Epicardial Adiposity

The epicardial adipose tissue, which is referred to as fats surrounding the myocardium, is an active organ able to induce cardiovascular problems in pathophysiologic conditions through several pathways, such as inflammation, fibrosis, fat infiltration, and electrophysiologic problems. So, control of its volume and thickness, especially in patients with diabetes, is highly important. Incretin-based pharmacologic agents are newly developed antidiabetics that could provide further cardiovascular benefits through control and modulating epicardial adiposity. They can reduce cardiovascular risks by rapidly reducing epicardial adipose tissues, improving cardiac efficiency. We are at the first steps of a long way, but current evidence demonstrates the sum of possible mechanisms. In this study, we evaluate epicardial adiposity in physiologic and pathologic states and the impact of incretin-based drugs.

The effect of Glucagon-like peptide-1 receptor agonists on serum uric acid concentration: A systematic review and meta-analysis

AIMS

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a class of medications mainly used for the treatment of type 2 diabetes. They improve glucose tolerance, increase insulin secretion, and induce weight loss. There is controversy about the effect of GLP-1RAs on serum uric acid (SUA) concentration. Our systematic review aims to objectively answer whether GLP-1RAs affect SUA levels.

METHODS

We performed a systematic search on PubMed, Web of Science, Embase, Scopus, and Google Scholar datasets up to 27August,2021 with a language restriction of English only. Randomized controlled trials, observational studies, uncontrolled trials, and conference abstracts were included. Studies with insufficient data, irrelevant types of study, and follow-up duration of less than a month were excluded from the review. After critical appraisal by the Joanna Briggs Institute checklists, articles underwent data extraction using a pre-specified Microsoft Excel sheet.

RESULTS

Of 1004 identified studies, 17 were eligible for inclusion in this systematic review. Pre- to post-administration analysis of GLP-1RA effects on SUA demonstrated that GLP-1RAs could significantly reduce SUA concentration (difference in means=-0.341;SE=0.063;P-value<0.001). However, when compared to placebo, GLP-1 RAs did not perform any better in lowering SUA concentration (difference in means=-0.455;SE=0.259;P-value=0.079). Surprisingly, the active controls, that included insulin, metformin, sodium-glucose co-transporter 2 (SGLT-2) inhibitors, and dipeptidyl-peptidase 4 (DPP-4) inhibitors, did outperform GLP-1RAs in reducing SUA concentration (difference in means=0.250;SE=0.038;P-value<0.001).

CONCLUSIONS

Administration of GLP-1RAs can result in a significant reduction in SUA concentration. However, this reduction is less than that seen with the use of insulin, metformin, and SGLT-2 inhibitors.

Mechanisms of antidiabetic drugs and cholesterol efflux: a clinical perspective

Reverse cholesterol transport (RCT) is a physiological process that reduces excess cholesterol in the body. Cholesterol efflux (CE), an important step in RCT, is mainly mediated by ATP-binding cassette transporters A1 and G1 and has a significant role in atheroprotection. Moreover, impairments in CE can lead to the development of diabetes and fatty liver disease. In this review, we summarize the possible effects of hypoglycemic agents on CE and how this might influence atherosclerosis and dyslipidemia-related pathologies. Newer antidiabetic agents could have significant potential for targeting CE and preventing or alleviating atherosclerosis, obesity, and liver steatosis, and simultaneously improving insulin secretion. However, more research is warranted to interpret the clinical relevance of these data.

The Impact of Incretin-Based Medications on Lipid Metabolism

Pathophysiological pathways that are induced by chronic hyperglycemia negatively impact lipid metabolism. Thus, diabetes is commonly accompanied by varying degrees of dyslipidemia which is itself a major risk factor for further macro- and microvascular diabetes complications such as atherosclerosis and nephropathy. Therefore, normalizing lipid metabolism is an attractive goal for therapy in patients with diabetes. Incretin-based medications are a novel group of antidiabetic agents with potent hypoglycemic effects. While the impact of incretins on glucose metabolism is clear, recent evidence indicates their positive modulatory roles on various aspects of lipid metabolism. Therefore, incretins may offer additional beneficial effects beyond that of glucose normalization. In the current review, how these antidiabetic medications can regulate lipid homeostasis and the possible cellular pathways involved are discussed, incorporating related clinical evidence about incretin effects on lipid homeostasis.

Sirt6-mediated Nrf2/HO-1 activation alleviates angiotensin II-induced DNA DSBs and apoptosis in podocytes

Recent studies suggested that DNA double-strand breaks (DSBs) were associated with the pathogenesis of chronic kidney disease (CKD). The purpose of this investigation was to determine the role of Sirtuin6 (Sirt6), a histone deacetylase related to DNA damage repair, in angiotensin (Ang) II-induced DNA DSBs and the cell injury of podocytes and explore the possible mechanism. Here we showed that an increase of DNA DSBs was accompanied by a reduction in Sirt6 expression in the glomeruli of patients with hypertensive nephropathy (HN). Similar results were found in rat kidneys infused with Ang II and in cultured podocytes stimulated with Ang II. Sirt6 overexpression inhibited Ang II-induced ROS generation and DNA DSBs, and thus served as a protection against Ang II-induced apoptosis in podocytes. Moreover, Sirt6 activation enhanced Nrf2 and HO-1 gene expressions in podocytes after Ang II treatment. Furthermore, Nrf2 knockdown could partly reverse the cytoprotective effects of Sirt6 activation. In conclusion, our observations demonstrated that the Sirt6-Nrf2-HO-1 pathway played a vital role in relieving Ang II-mediated oxidative DNA damage and podocyte injury.

The Effects of Glucagon-Like Peptide-1 Receptor Agonists and Dipeptydilpeptidase-4 Inhibitors on Blood Pressure and Cardiovascular Complications in Diabetes

Glucagon-like peptide-1 receptor (GLP-1R) agonists are a class of newly introduced antidiabetic medications that potentially lower blood glucose by several molecular pathways. DPP-4 inhibitors are the other type of novel antidiabetic medications which act by preventing GLP-1 inactivation and thereby increasing the activity levels of GLP-1, leading to more glucose-induced insulin release from islet β-cells and suppression of glucagon release. Most patients with diabetes have concurrent hypertension and cardiovascular disorder. If antihyperglycemic agents can attenuate the risk of hypertension and cardiovascular disease, they will amplify their overall beneficial effects. There is conflicting evidence on the cardiovascular benefits of GLP-1R induction in laboratory studies and clinical trials. In this study, we have reviewed the main molecular mechanisms by which GLP-1R induction may modulate the cardiovascular function and the results of cardiovascular outcome clinical trials.

The role of incretins and incretin-based drugs in autoimmune diseases

Incretin hormones, including glucagon-like peptide (GLP)-1, GLP-2 and glucose-dependent insulinotropic polypeptide (GIP), are gastrointestinal peptides secreted from enteroendocrine cells. These hormones play significant roles in many physiological processes via binding to G-protein coupled receptors (GPCRs) on different organs and tissues; one of them is the immunomodulatory effect on the immune system and its molecular components such as cytokines and chemokines. Anti-inflammatory effects of incretins and dependent molecules involving long-acting analogs and DPP4 inhibitors through regulation of T and B cell activation may attenuate autoimmune diseases caused by immune system disorders in mistakenly recognizing self as the foreign agent. In this review, we investigate incretin effects on the immune system response and the potential benefits of incretin-based therapy for treating autoimmune diseases.

Antioxidative Potentials of Incretin-Based Medications: A Review of Molecular Mechanisms

Glucagon-like peptide 1 receptor agonists and dipeptidyl-peptidase 4 inhibitors are medications used for managing diabetes, mimicking the metabolic effects of incretin hormones. Recent evidence suggests that these medications have antioxidative potentials in the diabetic milieu. The pathophysiology of most diabetic complications involves oxidative stress. Therefore, if incretin-based antidiabetic medications can alleviate the free radicals involved in oxidative stress, they can potentially provide further therapeutic effects against diabetic complications. However, the molecular mechanisms by which these medications protect against oxidative stress are not fully understood. In the current review, we discuss the potential molecular mechanisms behind these pharmacologic agents' antioxidative properties.

Effect of linagliptin on glucose metabolism and pancreatic beta cell function in patients with persistent prediabetes after metformin and lifestyle

The goal of the study was to evaluate the effect of adding linagliptin to metformin and lifestyle on glucose levels and pancreatic β-cell function in patients with persistent impaired glucose tolerance (IGT) after 12 months of metformin and lifestyle. A single center parallel double-blind randomized clinical trial with 6 months of follow-up was performed in patients with persistent IGT after 12 months of treatment with metformin and lifestyle; patients were randomized to continue with metformin 850 mg twice daily (M group, n = 12) or linagliptin/metformin 2.5/850 mg twice daily (LM group, n = 19). Anthropometric measurements were obtained by standard methods and by bioelectrical impedance; glucose was measured by dry chemistry, insulin by chemiluminescence, and pancreatic β-cell function was calculated with the disposition index using glucose and insulin values during oral glucose tolerance test (OGTT) and adjusting by insulin sensitivity. The main outcomes were glucose levels during OGTT and pancreatic β-cell function. Patients in the LM group had a reduction in weight (-1.7 ± 0.6, p < 0.05) and body mass index (BMI, -0.67 ± 0.2, p < 0.05). Glucose levels significantly improved in LM group with a greater reduction in the area under the glucose curve during OGTT (AUCGluc_{0_120min}) as compared to the M group (-4425 ± 871 vs -1116 ± 1104 mg/dl/120 min, p < 0.001). Pancreatic β-cell function measured with the disposition index, improved only in LM group (2.3 ± 0.23 vs 1.7 ± 0.27, p 0.001); these improvements persisted after controlling for OGTT glucose levels. The differences in pancreatic β-cell function persisted also after pairing groups for basal AUCGluc_{0_120min}. The addition of linagliptin to patients with persistent IGT after 12 months of treatment with metformin and lifestyle, improved glucose levels during OGTT and pancreatic β-cell function after 6 months of treatment.Trial registration: Clinicaltrials.gov with the ID number NCT04088461.