Incretins: Beyond type 2 diabetes

Anti-atherosclerotic effect of incretin receptor agonists

Incretin receptor agonists (IRAs), primarily composed of glucagon-like peptide-1 receptor agonists (GLP-1RAs) and glucose-dependent insulinotropic polypeptide receptor agonists (GIPRAs), work by mimicking the actions of the endogenous incretin hormones in the body. GLP-1RAs have been approved for use as monotherapy and in combination with GIPRAs for the management of type 2 diabetes mellitus (T2DM). In addition to their role in glucose regulation, IRAs have demonstrated various benefits such as cardiovascular protection, obesity management, and regulation of bone turnover. Some studies have suggested that IRAs not only aid in glycemic control but also exhibit anti-atherosclerotic effects. These agents have been shown to modulate lipid abnormalities, reduce blood pressure, and preserve the structural and functional integrity of the endothelium. Furthermore, IRAs have the ability to mitigate inflammation by inhibiting macrophage activation and promoting M2 polarization. Research has also indicated that IRAs can decrease macrophage foam cell formation and prevent vascular smooth muscle cell (VSMC) phenotype switching, which are pivotal in atheromatous plaque formation and stability. This review offers a comprehensive overview of the protective effects of IRAs in atherosclerotic disease, with a focus on their impact on atherogenesis.

Beyond the Cardiovascular Effects of Glucagon-like Peptide-1 Receptor Agonists: Body Slimming and Plaque Stabilization. Are New Statins Born?

Atherosclerosis is a chronic inflammatory disease characterized by lipid and inflammatory cell deposits in the inner layer of large- and medium-sized elastic and muscular arteries. Diabetes mellitus (DM) significantly increases the risk of cardiovascular diseases and the overall and cardiovascular mortality, and it is a pro-atherogenic factor that induces atherosclerosis development and/or accelerates its progression through a multifactorial process. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a new class of drugs, belonging to the armamentarium to fight type 2 DM, that have shown robust reductions in atherosclerotic events and all-cause mortality in all studies. Preclinical studies have shown that GLP-1RAs play a role in the immunomodulation of atherosclerosis, affecting multiple pathways involved in plaque development and progression. In this review, we wanted to explore the translational power of such preclinical studies by analyzing the most recent clinical trials investigating the atheroprotective effect of GLP-1RAs.

Cardiovascular protective effects of GLP-1:A focus on the MAPK signaling pathway

Cardiovascular and related metabolic diseases are significant global health challenges. Glucagon-like peptide 1 (GLP-1) is a brain-gut peptide secreted by ileal endocrine that is now an established drug target in type 2 diabetes (T2DM). GLP-1 targeting agents have been shown not only to treat T2DM, but also to exert cardiovascular protective effects through regulating multiple signaling pathways. The mitogen-activated protein kinase (MAPK) pathway, a common signal transduction pathway for transmitting extracellular signals to downstream effector molecules, is involved in regulating diverse cell physiological processes, including cell proliferation, differentiation, stress, inflammation, functional synchronization, transformation and apoptosis. The purpose of this review is to highlight the relationship between GLP-1 and cardiovascular disease (CVD), and discuss how GLP-1 exerts cardiovascular protective effects through MAPK signaling pathway. This review also discusses the future challenges in fully characterizing and evaluating the CVD protective effects of GLP-1 receptor agonists (GLP-1RA) at the cellular and molecular level. A better understanding of MAPK signaling pathway that are disregulated in CVD may aid in the design and development of promising GLP-1RA.

Effect of combined therapy of mesenchymal stem cells with GLP-1 receptor agonist, exenatide, on early-onset nephropathy induced in diabetic rats

Diabetic nephropathy is the principal cause of end-stage renal failure and current interventions for its recession remains unsatisfactory. Mesenchymal stem cells (MSCs) hold an attractive source for renovating injured tissues. Unfortunately, limited self-renewal and migration capacity of MSCs after transplantation hinder their clinical applicability which demands a new policy for enhancing their biological functions. This study aimed to investigate whether the renoprotective potential of adipose-derived MSCs (ADMSCs) in diabetic rats could be promoted by exenatide, a glucagon-like peptide-1 (GLP-1) analogue. These effects were studied in type 2 diabetes mellitus rats which were administrated ADMSCs, exenatide or their combination four weeks post-induction. Four weeks later, renal function parameters were evaluated. To address the possible underlying mechanisms, parameters indicating glycolipid metabolism tolerance and oxidative stress biomarkers were assessed in renal tissues alongside evaluation of protein expression of tumor necrosis factor-alpha, transforming growth factor-beta1 and cleaved caspase-3. The results showed that the combined therapy had superior renoprotective effect as evident by significant improvement in kidney function and renal architecture changes through rebalancing of inflammatory, fibrotic and apoptotic markers. Based on these outcomes, ADMSCs with exenatide were supposed to effectively ameliorate diabetic renal dysfunction compared to ADMSCs solely, presenting a promise therapy for diabetic nephropathy with further clinical studies warranted to validate this effect.

Comprehensive analysis of body composition and insulin traits associated with intra-pancreatic fat deposition in healthy individuals and people with new-onset prediabetes/diabetes after acute pancreatitis

Current knowledge of biomarkers of intra-pancreatic fat deposition (IFD) is limited. We aimed to analyse comprehensively body composition and insulin traits as biomarkers of IFD in healthy normoglycaemic individuals as well as in individuals with new-onset prediabetes or diabetes after acute pancreatitis (NODAP). A total of 29 healthy individuals and 34 individuals with NODAP took part in this cross-sectional study. The studied biomarkers belonged to the following domains: body composition (anthropometric and MRI-derived variables); indices of insulin secretion; indices of insulin sensitivity; incretins and related peptides; and pancreatitis-related factors. All MRI-derived variables (including IFD) were measured using ImageJ software. Univariate and step-wise regression analyses were conducted to determine variables that best explained variance in IFD. Visceral fat volume and oxyntomodulin were the best biomarkers of IFD in normoglycaemic healthy individuals, contributing to 64% variance. The Raynaud index was the best biomarker of IFD in individuals with NODAP, contributing to 20% variance. Longitudinal studies are warranted to investigate the cause and effect relationship between oxyntomodulin and IFD in healthy individuals, as well as insulin sensitivity and IFD in individuals with NODAP.

Targeting inflammation to reduce ASCVD in type 2 diabetes

ASCVD is the leading cause of mortality in T2DM. Inflammation appears to be pivotal in the genesis of ASCVD. As T2DM is also a pro-inflammatory state, our aim was to determine the benefit of anti-inflammatory strategies on ASCVD in T2DM. PubMed searches were conducted using the keywords of T2DM, ASCVD, Inflammation and clinical trials. Our data review suggests that the Mediterranean diet, GLP1 receptor agonists and a monoclonal antibody against IL-1 reduces ASCVD events in T2DM. The former 2 therapies appear to be safe. Anti-IL-1 therapy resulted in an increase mortality from infections. We conclude that only the Mediterranean diet and GLP1 receptor agonists can be safely incorporated into mainstay therapy for patients with T2DM to reduce ASCVD. Further studies are required with respect to biologics targeting Inflammation to establish benefit to risk ratio.

Early effects of roflumilast on insulin sensitivity in adults with prediabetes and overweight/obesity involve age-associated fat mass loss - results of an exploratory study

PURPOSE

Roflumilast (Daliresp, Daxas) is a FDA-approved phosphodiesterase 4 (PDE4) inhibitor for the treatment of moderate-to-severe chronic obstructive pulmonary disease. In mice and in limited human studies, this oral medication can cause weight loss and improve insulin sensitivity. We set out to determine the mechanism of its effect on insulin sensitivity.

PATIENTS AND METHODS

Eight adults with overweight/obesity and prediabetes received roflumilast for 6 weeks. Before and after roflumilast, subjects underwent tests of insulin sensitivity, mixed meal test, body composition, markers of inflammation, and mitochondria function. Dietary intake and physical activity were also assessed. Our primary outcome was the change in peripheral insulin sensitivity, as assessed by the hyper-insulinemic euglycemic clamp.

RESULTS

This study was underpowered for the primary outcome. Pre- and post-roflumilast mean peripheral insulin sensitivity were 48.7 and 70.0 mg/g fat free mass/minute, respectively, (P-value=0.18), respectively. Among the mixed meal variables, roflumilast altered glucagon-like peptide 1 (GLP-1) hormone the most, although the average effect was not statistically significant (P=0.18). Roflumilast induced a trend toward significance in 1) decreased energy intake (from 11,095 KJ to 8,4555 KJ, P=0.07), 2) decreased fat mass (from 34.53 to 32.97 kg, P=0.06), 3) decreased total and LDL cholesterol (P=0.06 for both variables), and 4) increased plasma free fatty acids (from 0.40 to 0.50 mEq/L, P=0.09) The interval changes in adiposity and free fatty acid were significantly associated with the subject's age (P-value range= <0.001 to 0.02 for the correlations). Inflammatory and adhesion markers, though unchanged, significantly correlated with one another and with incretin hormones only after roflumilast.

CONCLUSION

We demonstrate, for the first time in humans, increasing percentage of fat mass loss from roflumilast with increasing age in adults with prediabetes and overweight/obesity. We also demonstrate novel associations among roflumilast-induced changes in incretin hormones, inflammatory markers, peripheral insulin sensitivity, and adiposity. We conclude that roflumilast's early effects on insulin sensitivity is indirect and likely mediated through roflumilast's prioritization of lipid over glucose handling.

CLINICAL TRIALS REGISTRATION

NCT01862029.