Glucagon-like Peptide-1 Treatment Research Articles

GLP-1(7–36) protected against oxidative damage and neuronal apoptosis in the hippocampal CA region after traumatic brain injury by regulating ERK5/CREB

BackgroundGlucagon-like peptide-1 (GLP-1) (7–36) amide, an endogenous active form of GLP-1, has been shown to modulate oxidative stress and neuronal cell survival in various neurological diseases.ObjectiveThis study investigated the potential effects of GLP-1(7–36) on oxidative stress and apoptosis in neuronal cells following traumatic brain injury (TBI) and explored the underlying mechanisms.MethodsTraumatic brain injury (TBI) models were established in male SD rats for in vivo experiments. The extent of cerebral oedema was assessed using wet-to-dry weight ratios following GLP-1(7–36) intervention. Neurological dysfunction and cognitive impairment were evaluated through behavioural experiments. Histopathological changes in the brain were observed using haematoxylin and eosin staining. Oxidative stress levels in hippocampal tissues were measured. TUNEL staining and Western blotting were employed to examine cell apoptosis. In vitro experiments evaluated the extent of oxidative stress and neural apoptosis following ERK5 phosphorylation activation. Immunofluorescence colocalization of p-ERK5 and NeuN was analysed using immunofluorescence cytochemistry.ResultsRats with TBI exhibited neurological deterioration, increased oxidative stress, and enhanced apoptosis, which were ameliorated by GLP-1(7–36) treatment. Notably, GLP-1(7–36) induced ERK5 phosphorylation in TBI rats. However, upon ERK5 inhibition, oxidative stress and neuronal apoptosis levels were elevated, even in the presence of GLP-1(7–36).ConclusionIn summary, this study suggested that GLP-1(7–36) suppressed oxidative damage and neuronal apoptosis after TBI by activating ERK5/CREB.

The Utilization of Glucagon-like Peptide 1 Agonists and Risk of Following External Eye Diseases in Type 2 Diabetes Mellitus Individuals: A Population-Based Study.

The glucagon-like peptide 1 (GLP-1) agonist showed anti-hyperglycemic and anti-inflammatory effects, which may retard the risk of external eye disease. The protective effect of GLP-1 agonist and dry eye disease (DED) was found, while the relationship between GLP-1 agonist and other corneal diseases was not clear. Herein, we aim to evaluate the association between the usage of GLP-1 agonists and the development of the following external eye disease in type 2 diabetes mellitus (T2DM) patients. A retrospective cohort study using the National Health Insurance Research Database (NHIRD) of Taiwan was conducted. The T2DM patients were divided into those with GLP-1 treatment and those without GLP-1 treatment and matched with a 1:2 ratio. The main outcomes were the development of dry eye disease (DED), superficial keratitis, and infectious keratitis. The Cox proportional hazard regression was adopted to produce the adjusted hazard ratio (aHR) with a 95% confidence interval (CI) of external eye diseases between groups. There were 115, 54, and 11 episodes of DED, superficial keratitis, and infectious keratitis in the GLP-1 group. Another 280, 168, and 31 events of DED, superficial keratitis, and infectious keratitis were recorded in the control group. The GLP-1 group demonstrated a significantly lower incidence of DED (aHR: 0.853, 95% CI: 0.668-0.989, p = 0.0356) and superficial keratitis (aHR: 0.670, 95% CI: 0.475-0.945, p = 0.0107) compared to the control group. In the subgroup analyses, the correlation of GLP-1 agonist and DED development was more prominent in patients younger than 60 years old (p = 0.0018). In conclusion, the GLP-1 agonist treatments are significantly associated with a lower incidence of subsequent DED and superficial keratitis, while the relationship was not significant between GLP-1 agonist usage and infectious keratitis.

FRI027 Regulation Of A Novel Sortilin Splice Variant Expression In Human Diabetic Adipocytes By GLP-1 To Maintain Glucose Homeostasis

Abstract Disclosure: N.A. Patel: None. R.S. Patel: None. A. Liu: None. Type 2 diabetes mellitus (T2DM) is a chronic and progressive metabolic disease with no cure. 37.3 million Americans have T2DM as of 2021 and 96 million (1 in 3) are prediabetic. Globally 462 million people are estimated to be living with T2DM. T2DM is a complex, polygenic metabolic disease characterized by hyperglycemia and insulin resistance. Adipocytes play a crucial role in glucose homeostasis. In response to insulin, translocation of major glucose transporter-4 (Glut4) from cytoplasm to the plasma membrane facilitates uptake of glucose into the adipocytes. Sortilin, an important constituent of Glut4 storage vesicles, binds to Glut4 with its luminal domain while its C-terminal tail guides intracellular trafficking. In insulin resistant adipocytes, glucose uptake is impaired. In this study, we used human adipose stem cells (hASC) from diabetic (DM) and nondiabetic (NDM) donors and differentiated them in vitro to mature adipocytes. We report that in addition to constitutively spliced full-length sortilin (Sort_FL), we identified an alternatively spliced sortilin variant in human adipocytes. Results show that alternative exon inclusion resulted in inclusion of STOP codon which produced a truncated C-terminal (Sort_T) protein whose expression was significantly increased in DM adipocytes. We elucidated the role and function of Sort_T and our results show that hyperglycemic conditions promoted an increase in Sort_T levels in NDM adipocytes. Overexpression of Sort_T in NDM adipocytes resulted in reduced insulin-stimulated Glut4 translocation and decreased glucose uptake. However, overexpression of Sort_FL does not rescue glucose uptake in DM adipocytes. Computational modeling and molecular dynamics results suggested that Glut4 bound tightly to both Sort_T and Sort_FL. This was validated using co-immunoprecipitation assays which demonstrated robust binding of Sort_T to Glut4. Immunocytochemistry was performed to determine localization of sortilin variants in DM and NDM adipocytes. Results demonstrated that Glut4 co-localized with both Sort_T and Sort_FL and Pearson’s coefficient demonstrated increased Sort_T co-localization with Glut4 in DM adipocytes. Incretin hormone glucagon-like peptide-1 (GLP1) and its analog liraglutide is used to manage T2DM. We evaluated the effect of GLP1 and liraglutide treatment in DM adipocytes on sortilin variant expression and our results demonstrate decreased Sort_T levels at physiological doses (8nM). Using a sortilin splicing minigene, our results demonstrate that GLP1 regulates splicing of Sort_T pre-mRNA and splice factor SRSF10 is involved in GLP1-mediated sortilin alternative splicing in adipocytes. Our study concludes that Sort_T expression in diabetic adipocytes hinders glucose metabolism and Sort_T is a target of GLP1 for maintaining glucose homeostasis. Presentation: Friday, June 16, 2023

Glucagon-like peptide-1 treatment reduces the risk of diabetes-type 2 related amputations: A cohort study in Denmark

AimsTo assess the impact of Glucagon-like peptide-1 (GLP-1) agonists on the risk of lower extremity amputations in patients with type 2 diabetes mellitus (DM2). MethodsWe conducted a cohort study on 309,116 patients with DM2 using Danish National Register and Diabetes Database. We tracked the GLP-1 agonists over time along with the medication dose. Time-varying models are used to assess the risk of amputation for patients with/without GLP-1 treatment. ResultsPatients on GLP-1 treatment experience a notable reduction in the risk of amputation compared to those without the treatment with a hazard ratio (HR) of 0.5, 95% CI [0.54–0.74], indicating a statistically significant difference (p <.005). This risk reduction was consistent across different age groups, but notably most pronounced among middle income patients. The findings were further validated by using time-varying Cox models, which considered the patient’s comorbidity history. ConclusionsOur analysis reveals compelling evidence of a reduced risk of amputation among patients receiving GLP-1 therapy, an effect dominated by liraglutide, compared to those without the treatment, even after adjusting for various socio-economic factors. However, further investigation is required to identify and account for any other potential confounding variables that may impact the outcome.

Effect of incretins on skeletal health.

The incretin hormones, glucagon like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP), have been shown to decrease bone resorption in humans. The aim of this review is to collate evidence and current advances in the research within the last year on the effect of incretins on skeletal health. Preclinical studies show potential direct beneficial effects on bone by GLP-1 and GIP, however real world epidemiological data show no effects of GLP-1 receptor analogues on fracture risk. This may be due to the weight loss accompanied by GLP-1 treatment which may have detrimental effects on bone. GIP is shown to reduce bone resorption and increase bone formation. Further evidence suggests an additive effect of GIP and glucagon like peptide-2, which could affect bone by different mechanisms. GIP and GLP-1 based therapies are more widespread used and may have potential beneficial effects on bone, possibly counterbalanced by weight loss. Long-term effects and side-effects of GIP or GIP/ GLP-2 co-administration remain to be elucidated, and longer term treatment trials are needed.

Therapy of obesity in women with PCOS using GLP-1 analogues - benefits and limitations [Terapia otyłości u kobiet z PCOS przy zastosowaniu analogów GLP-1 - korzyści i ograniczenia

Polycystic ovary syndrome (PCOS) is a heterogeneous endocrine disorder among women of reproductive age. The incidence ranges from approx. 6% to 20%. PCOS is characterized by a spectrum of symptoms and clinical features that includes ovarian dysfunction, clinical and/or biochemical hyperandrogenism, and ultrasound evidence of morphologically polycystic ovaries. Obesity is present in 40-70% of patients with the syndrome. Adiposity is involved in exacerbating the negative effects of insulin resistance, hyperinsulinaemia, and hyperandrogenaemia in the course of PCOS. Therefore, it is essential to maintain normal weight or effectively treat overweight/obesity in patients suffering from this endocrinopathy. Apart from diet and lifestyle interventions, an appropriate pharmacological or surgical treatment should be selected for the individual patient. Evidence-based data have unequivocally proven the validity of the use of glucagon-like peptide 1 (GLP-1) analogues in the treatment of overweight/obese patients with PCOS. The result of the GLP-1 therapy is not only a reduction of body weight but also an improvement in insulin resistance and a decrease in hyperandrogenaemia. It also seems that this treatment method increases spontaneous and in-vitro pregnancy rates. Therefore, the GLP-1 treatment of obese PCOS women is a new therapeutic opportunity not only for weight loss but also for a wide range of benefits. This review summarizes and discusses findings regarding obesity and its relation to hyperandrogenism and insulin resistance in PCOS, with special attention paid to the pharmacological treatment of adiposity with GLP-1 analogues.

IDF21-0347 Treatment response in the first Emirati patient with diabetes associated with the A3243G mitochondrial point mutation

Background: Maternally inherited diabetes and deafness (MIDD) is estimated as the cause of 1% of cases of diabetes. Due to the small patient population, it is not clear which diabetes treatments are most effective in MIDD. Aim: We discuss the response to different classes of hypoglycaemic agents in the first Emirati patient reported with mitochondrial diabetes. Method: A 23-year old male presented with hyperglycaemia and features atypical for Type 1 Diabetes including retinal changes at diagnosis. MIDD was confirmed by presence of an A to G point mutation in the tRNALeu(UUR) gene at base pair 3243 (A3243G) of the mitochondrial genome using targeted next generation sequencing. We report his management and his clinical features at 3.8 years of follow-up. Results: At diagnosis, anti-GAD and anti-IA2 antibody titres were not elevated and insulin secretory reserve was maintained, with C-peptide of 0.631nmol/L and simultaneous plasma glucose of 11.6mmol/L. No objective hearing loss was detected at presentation. Microvascular disease was detected at 39 days after onset of diabetes with background retinopathy (R1) and maculopathy (M1), and elevated albumin-creatinine ratio (ACR) (3.7 mg/mmoL, with subsequent microalbuminuria of 3.1, 4.1, 3.1, and 5.6 mg/mmoL at 12, 14, 17, and 19 months, respectively). Pinhole visual acuity (VA) was 0.8 (left) and 0.7 (right). BMI, HbA1c, and triglycerides were 27.3 kg/m2, 8.5%, and 1.34mmol/L, respectively. MIDD was confirmed by genetic analysis in the patient’s mother, who had an established diagnosis of diabetes mellitus; his brother declined screening. He was initially managed with insulin and metformin (HbA1c from 8.5% to 6.9%). He was switched to sulphonylurea (gliclazide) after diagnosis of MIDD (HbA1c from 6.9% to 7.7%), with canagliflozin added at 12 weeks (HbA1c from 7.7% to 6.2%, subsequently to 9%) and sitagliptin combined at 48 weeks (HbA1c from 9% to 8.7%). Dulaglutide was added at 73 weeks, leading to a dramatic improvement in his HbA1c from 8.7% to 6.9% and BMI from 28.4 to 25.4kg/m2 within 4 months and cessation of insulin, canagliflozin and sulphonylurea treatment. Dulaglutide was discontinued due to intolerance with subsequent deterioration of glycaemic control (HbA1c 9.5%). At 3.8 years of follow-up, he progressed to pre-proliferative retinopathy (R2, M1); his ACR was 7.0mg/mmoL. Pinhole VA reduced to 0.4 (left) and 0.3 (right). He remained overweight (BMI, 27.6kg/m2). LDL was elevated at 3.5mmol/L, and triglycerides were 1.3mmol/L while taking atorvastatin 20 mg. Discussion: The use of glucagon-like peptide-1 (GLP-1) analogues in patients with MIDD has been shown to effectively improve HbA1c within 6 months in three recent case reports. In this case, a GLP-1 induced a dramatic improvement in HbA1c within 4 months with cessation of several concomitant medications, sustained until the GLP-1 was discontinued due to lack of tolerability, with subsequent deterioration in glycaemic control. Although a full case series is lacking, accumulating evidence from case reports suggests that GLP-1 treatment may be particularly effective in people with MIDD.

Methylation status of vault RNA 2-1 promoter is a predictor of glycemic response to glucagon-like peptide-1 analog therapy in type 2 diabetes mellitus

IntroductionTherapeutic efficiency of glucagon-like peptide-1 (GLP-1) analog is about 50%–70% in type 2 diabetes mellitus (T2DM). Discovery of potential genetic biomarkers for prediction of treatment efficiency of GLP-1 analog before...

The Neurotrophic Function of Glucagon-Like Peptide-1 Promotes Human Neuroblastoma Differentiation via the PI3K-AKT Axis.

Simple SummaryThe study demonstrated that the treatment with GLP-1 of SH-SY5Y human neuroblastoma cells increased the expression of AMPA receptors, NMDA receptors, dopamine receptors, synaptic proteins-synapsin 1, synaptophysin, and postsynaptic density protein 95, but not muscular and nicotinic acetylcholine receptors. In addition, the biomarker of dividing neuronal cells, vimentin, was decreased after treatment with GLP-1. Tuj1 immunostaining images showed that GLP-1 induced neurite processes and the development of neuronal morphologies. The GLP-1-differentiated neurons were able to be induced to generate action potentials by single cell patch-clamp. Our results also suggested that the PI3K-AKT axis is the dominant signaling pathway promoting the differentiation of SH-SY5Y cells into mature and functional neurons in response to GLP-1 receptor activation. The sequential treatment of retinoic acid and GLP-1 within a serum-free medium is able to trigger the differentiation of SH-SY5Y cells into morphologically and physiologically mature glutamatergic and dopaminergic neurons.Background: Neurons are terminally-differentiated cells that generally develop from neuronal stem cells stimulated by various neurotrophic factors such as NGF, BDNF, NT3, and NT-4. Neurotrophic factors have multiple functions for neurons, including enabling neuronal development, growth, and protection. Glucagon-like peptide-1 (GLP-1) is an intestinal-secreted incretin that enhances cellular glucose up-take to decrease blood sugar levels. However, many studies suggest that the function of GLP-1 is not limited to the regulation of blood sugar levels. Instead, it may also act as a neurotrophic factor with a role in ensuring neuronal survival and neurite outgrowth, as well as protecting synaptic plasticity and memory formation. Methods: The SH-SY5Y cells were differentiated by sequential treatments of retinoic acid and GLP-1 treatment within polyethylenimine-coated dishes under serum-free Neurobasal medium. PI3K inhibitor (LY294002) and MEK inhibitor (U0126) were used to determine the signaling pathway in regulation of neuronal differentiation. Neuronal marker (TUJ1) and synaptic markers (synapsin 1, synaptophysin, and PSD95) as well as single cell patch-clamp were applied to determine maturity of neurons. Antibodies of AMPA receptor, NMDA receptor subunit 2A, dopamine receptor D1, muscarinic acetylcholine receptor 2, and nicotinic acetylcholine receptor α4 were used to examine the types of differentiated neurons. Results: Our study’s results demonstrated that the treatment with GLP-1 of SH-SY5Y human neuroblastoma cells increased the expression of AMPA receptors, NMDA receptors, dopamine receptors, synaptic proteins-synapsin 1, synaptophysin, and postsynaptic density protein 95, but not muscular and nicotinic acetylcholine receptors. In addition, the biomarker of dividing neuronal cells, vimentin, was decreased after treatment with GLP-1. Tuj1 immunostaining images showed that GLP-1 induced neurite processes and the development of neuronal morphologies. The GLP-1-differentiated neurons were able to be induced to generate action potentials by single cell patch-clamp. Our study also suggested that the PI3K-AKT axis is the dominant signaling pathway promoting the differentiation of SH-SY5Y cells into mature and functional neurons in response to GLP-1 receptor activation. Conclusions: The sequential treatment of retinoic acid and GLP-1 within a serum-free medium is able to trigger the differentiation of SH-SY5Y cells into morphologically and physiologically mature glutamatergic and dopaminergic neurons.

Glucagon-like peptide 1 treatment reverses vascular remodelling by downregulating matrix metalloproteinase 1 expression through inhibition of the ERK1/2/NF-κB signalling pathway

In addition to serving as an incretin-based treatment of type 2 diabetes mellitus (T2DM), glucagon-like peptide 1 (GLP-1) can also reverse cardiovascular diseases caused by vascular remodelling. However, a detailed mechanism underlying how GLP-1 reverses vascular remodelling remains unclear. Here, Spontaneous hypertension rats (SHR) were used as an in vivo model of vascular remodelling. Treatment with a GLP-1 receptor (GLP-1R) agonist Liraglutide or dipeptidyl peptidase 4 (DPP4) inhibitor Alogliptin decreased systolic blood pressure (SBP), diastolic blood pressure (DBP), thickness of vascular wall, and overall collagen levels in SHR. In vitro vascular remodelling can be induced by exposing rat aortic smooth muscle cells (RASMC) to angiotensin II (Ang II); GLP-1 treatment attenuated AngII induction of RASMC proliferation, migration, and excessive extracellular matrix (ECM) degradation. Downregulation of matrix metalloproteinase 1 (MMP1) enhanced the inhibitory effects of GLP-1, and extracellular regulated protein kinase 1/2 (ERK1/2) and nuclear factor kappa-B (NF-κB) signalling participated in these processes. These results provide a new mechanistic understanding of key therapeutic strategies for the treatment of vascular remodelling-related diseases.

GLP-1 promotes osteogenic differentiation of human ADSCs via the Wnt/GSK-3β/β-catenin pathway

Glucagon-like peptide-1 (GLP-1) analogues are promising anti-diabetic drugs which had been shown to have beneficial effects on bone metabolism in clinical practice, but the molecular mechanism remains unclear. In this study, we evaluated whether GLP-1 can affect the “intestine-fat-bone axis” via the Wnt/GSK-3β/β-catenin pathway. We established a diabetic mouse model and then treated mice with GLP-1 analogue liraglutide. The results showed that after liraglutide treatment, glucose tolerance and insulin tolerance were significantly improved in diabetic mice as expected. Moreover, osteogenic markers such as collagenⅠ, Runx2 and OCN were upregulated; and the adipogenic differentiation markers C/EBP-α and PPAR-γ were downregulated, these results indicated that liraglutide could ameliorate the osteogenic metabolism in diabetic mice. In the cell model, human ADSCs (hADSCs) were cultured and induced to undergo osteogenic and adipogenic differentiation under high glucose conditions in vitro and then treated with GLP-1. The results showed that GLP-1 repressed the induction of adipocyte differentiation biomarkers and the secretion of GSK-3β in a dose-dependent manner. In addition, GLP-1 enhanced the expression of osteoblastogenic biomarkers, such as OCN, Runx2 and collagenⅠ, and promoted osteoblastic mineralization. These effects were substantially suppressed by the Wnt signal recombinant human DKK-1 or activated by Wnt pathway agonist LiCl. Silencing of GSK-3β showed that the levels of β-catenin, GSK-3β and Runx2 were significantly increased by 2.46-, 2.05-, 4.44-fold after GLP-1 treatment compared to that observed in the GSK-3β lentiviral group, respectively. We conclude that GLP-1 promotes the osteogenic differentiation of hADSCs via the Wnt/GSK-3β/β-catenin pathway.

Glucagon-like peptide 1 reverses myocardial hypertrophy through cAMP/PKA/RhoA/ROCK2 signaling.

Myocardial hypertrophy is a major pathological and physiological process during heart failure. Glucagon-like peptide 1 (GLP-1) is a glucagon incretin hormone released from the gut endocrine L-cells that has protective effects on various cardiovascular diseases, including hypertension, atherosclerosis, and myocardial hypertrophy. However, the protective mechanisms of GLP-1 in myocardial hypertrophy remain unclear. Here, we showed that the GLP-1 agonist liraglutide and dipeptidyl peptidase 4 inhibitor alogliptin decreased heart weight and cardiac muscle cell volume in spontaneously hypertensive rats (SHR). In H9C2 cell hypertensive models induced by angiotensin II, GLP-1 treatment reduced myocardial cell volume, inhibited the expressions of atrial natriuretic peptide, brain/B-type natriuretic peptide, β-myosin heavy chain, RhoA, and ROCK2, and decreased MLC and MYPT1 phosphorylation. When H9C2 cells were treated with H89, a PKA inhibitor, the inhibitory effect of GLP-1 disappeared, while the inhibitory role was enhanced under the treatment of Y-27632, a ROCK2 inhibitor. These results suggested that GLP-1 might reverse myocardial hypertrophy through the PKA/RhoA/ROCK2 signaling pathway.

P4476Cardiovascular benefits of GLP-1 (liraglutide) treatment in experimental arterial hypertension are mediated by the endothelial GLP-1 receptor

Abstract Objective The LEADER trial demonstrated that glucagon-like peptide-1 (GLP-1) analogs like Liraglutide (Lira) reduce the risk of cardiovascular events in T2DM, an effect beyond glycemic control. A detailed evaluation of the precise mechanisms underlying the cardiovascular protective effects of GLP-1 has been hampered by the fact that the GLP-1 receptor is expressed on different cell types in the vasculature including platelets, neuronal, endothelial and inflammatory cells. We used endothelial and myeloid cell-specific knockout mice of the GLP-1 receptor (GLP-1r) in an angiotensin-II (ATII)-induced model of hypertension. The aim of the recent study was to investigate the cardioprotective effects of GLP-1 in ATII-induced arterial hypertension and to characterize the cell-specific contribution of GLP-1r signaling. Methods Arterial hypertension was induced by s.c. ATII administration (0.5mg/kg/d; 7 days) in WT (C57/BL6J) as well as endothelial and myeloid cell-specific GLP-1r knockout mice (Cdh5crexGLP-1rfl/fl and LysMcrexGLP-1rfl/fl mice). Animals were treated with Lira (2x30μg/d; 7 days). Blood pressure was measured by tail-cuff. Vascular function was tested by isometric tension recording. Aortic and cardiac tissue was used for Western blotting, qRT-PCR, FACS, IHC and HPLC to determine the extent of inflammation, oxidative stress and fibrosis. ELISA was used to determine GLP-1 and insulin levels in plasma. Results Endogenous GLP-1 (7–36 and 9–36) was reduced in hypertensive animals. Lira ameliorated blood pressure and improved endothelial dysfunction, vascular oxidative stress and inflammation caused by ATII, in both WT and myeloid cell-specific GLP-1r knockout mice. Hypertension led to infiltration of inflammatory monocytes (Ly6G-Ly6Chigh) and neutrophils (Ly6G+Ly6C+) into the vascular wall, which was prevented by Lira. In accordance, Lira suppressed vascular oxidative stress and mRNA expression of iNOS, CD11b and Nox2. Endothelial NO synthase (eNOS) was S-glutathionylated with ATII treatment indicating uncoupled eNOS. Thus, aortic NO levels were reduced, all of which was restored by Lira. Furthermore, vascular fibrosis and cardiac hypertrophy were tremendously reduced by GLP-1. Interestingly, all of these beneficial cardiovascular effects of GLP-1 were abolished in endothelial cell-specific GLP-1r knockout mice. Conclusion We show that Lira reduces blood pressure and improves vascular function, fibrosis and cardiac hypertrophy in experimental arterial hypertension in mice. Mechanistically, Lira prevents the infiltration of inflammatory cells to the vascular wall, leading to reduced oxidative stress and improved NO bioavailability. Beneficial effects of GLP-1 are mediated by the GLP-1r expressed on endothelial and not myeloid cells. With the present study we provide a mechanistic approach to explain the cardioprotective effects of GLP-1 analogs like Lira, for which the endothelial GLP-1 receptor is indispensable. Acknowledgement/Funding Deutsche Forschungsgesellschaft (DFG), Bundesministerium für Bildung und Forschung (BMBF)

Protective effects of glucagon-like peptide-1 on cardiac remodeling by inhibiting oxidative stress through mammalian target of rapamycin complex1/p70 ribosomal proteinS6 kinase pathway in diabetes mellitus.

Aims/IntroductionAlthough increased reactive oxygen species (ROS) generation is a major mechanism leading to cardiac remodeling in diabetes mellitus, research into the effects of anti‐oxidation on diabetic cardiac remodeling remains scarce and controversial. Glucagon‐like peptide‐1 (GLP‐1) shows potential anti‐oxidative effects besides lowering blood glucose. The objective of this research was to investigate the effects of GLP‐1 on cardiac remodeling and the molecular mechanism involved in diabetes mellitus.Materials and MethodsStreptozotocin‐induced diabetic rats received exenatide treatment for 3 months. Cardiac function, cardiac weight index and myocardial interstitial fibrosis were measured. Cardiomyocytes were cultured in high‐glucose medium with GLP‐1 treatment. The ROS production, apoptosis and the levels of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase protein expression in cardiomyocytes were analyzed.ResultsExperimental diabetes mellitus showed impaired cardiac diastolic function, increased brain natriuretic peptide expression and increased interstitial collagen deposition in the myocardium, which were ameliorated by exenatide treatment. Exenatide reduced myocardial ROS production and apoptosis in diabetes mellitus. Also, high glucose‐induced ROS generation and apoptosis in cardiomyocytes were inhibited by GLP‐1, as well as the levels of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase phosphorylation. Furthermore, GLP‐1 treatment upregulated adenosine monophosphate‐activated protein kinase activity in high‐glucose‐induced cardiomyocyte.ConclusionsGlucagon‐like peptide‐1 protects the cardiomyocytes from oxidative stress and apoptosis in diabetes mellitus, which might contribute to the improvement of cardiac remodeling. The cardiac protection of GLP‐1 might be dependent on inhibition of mammalian target of rapamycin complex 1/p70 ribosomal protein S6 kinase, through an adenosine monophosphate‐activated protein kinase‐mediated pathway.

New Insights into the Mechanisms of Action of Topical Administration of GLP-1 in an Experimental Model of Diabetic Retinopathy.

The main goals of this work were to assess whether the topical administration of glucagon-like peptide-1 (GLP-1) could revert the impairment of the neurovascular unit induced by long-term diabetes (24 weeks) in diabetic mice and to look into the underlying mechanisms. For that reason, db/db mice were treated with eye drops of GLP-1 or vehicle for 3 weeks. Moreover, db/+ mice were used as control. Studies performed in vivo included electroretinogramand the assessment of vascular leakage by using Evans Blue. NF-κB, GFAP and Ki67 proteins were analyzed by immunofluorescence (IF). Additionally, caspase 9, AMPK, IKBα, NF-κB, AKT, GSK3, β-catenin, Bcl-xl, and VEGF were analyzed by WB. Finally, VEGF, IL-1β, IL-6, TNF-α, IL-18, and NLRP3 were studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. We found that topical administration of GLP-1 reverted reactive gliosis and albumin extravasation, and protected against apoptosis and retinal dysfunction. Regarding the involved mechanisms, GLP-1 exerted an anti-inflammatory action by decreasing NF-κB, inflammosome, and pro-inflammatory factors. In addition, it also decreased VEGF expression. Furthermore, GLP-1 promoted cell survival by increasing the anti-apoptotic protein Bcl-xl and the signaling pathway Akt/GSK3b/β-catenin. Finally, Ki67 results revealed that GLP-1 treatment could induce neurogenesis. In conclusion, the topical administration of GLP-1 reverts the impairment of the neurovascular unit by modulating essential pathways involved in the development of diabetic retinopathy (DR). These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of GLP-1 in early stages of DR.

Glucagon-Like Peptide-1 Cleavage Product Improves Cognitive Function in a Mouse Model of Down Syndrome.

Currently there is no effective therapy available for cognitive impairments in Down syndrome (DS), one of the most prevalent forms of intellectual disability in humans associated with the chromosomes 21 trisomy. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that maintains glucose homeostasis by stimulating insulin secretion. Its natural cleavage product GLP-1 (9-36) lacks insulinotropic effects and has a low binding affinity for GLP-1 receptors; thus, GLP-1 (9-36) has historically been identified as an inactive metabolite. Conversely, recent work has demonstrated interesting physiological properties of GLP-1 (9-36) such as cardioprotection and neuroprotection. We have previously shown that GLP-1 (9-36) administration enhances neuronal plasticity in young WT mice and ameliorates cognitive deficits in a mouse model of Alzheimer’s disease. Here, we report that systemic administration of GLP-1 (9-36) in Ts65Dn DS model mice of either sex resulted in decreased mitochondrial oxidative stress in hippocampus and improved dendritic spine morphology, increase of mature spines and reduction of immature spines. Importantly, these molecular alterations translated into functional changes in that long-term potentiation failure and cognitive impairments in TsDn65 DS model mice were rescued with GLP-1 (9-36) treatment. We also show that chronic GLP-1 (9-36) treatment did not alter glucose tolerance in either WT or DS model mice. Our findings suggest that GLP-1 (9-36) treatment may have therapeutic potential for DS and other neurodegenerative diseases associated with increased neuronal oxidative stress.

Early treatment with GLP-1 after severe trauma preserves renal function in obese Zucker rats.

Early posttrauma hyperglycemia (EPTH) is correlated with later adverse outcomes, including acute kidney injury (AKI). Controlling EPTH in the prehospital setting is difficult because of the variability in the ideal insulin dosage and the potential risk of hypoglycemia, especially in those with confounding medical comorbidities of obesity and insulin resistance. Glucagon-like peptide-1 (GLP-1) controls glucose levels in a glucose-dependent manner and is a current target in antidiabetic therapy. We have shown that after orthopedic trauma, obese Zucker rats exhibit EPTH and a later development of AKI (within 24 h). We hypothesized that GLP-1 treatment after trauma decreases EPTH and protects renal function in obese Zucker rats. Obese Zucker rats (~12 wk old) were fasted for 4 h before trauma. Soft tissue injury, fibula fracture, and homogenized bone component injection were then performed in both hind limbs to induce severe extremity trauma. Plasma glucose levels were measured before and 15, 30, 60, 120, 180, 240, and 300 min after trauma. GLP-1 (3 μg·kg-1·h-1, 1.5 ml/kg total) or saline was continuously infused from 30 min to 5 h after trauma. Afterwards, rats were placed in metabolic cages overnight for urine collection. The following day, plasma interleukin (IL)-6 levels, renal blood flow (RBF), glomerular filtration rate (GFR), and renal oxygen delivery (Do2) and consumption (V̇o2) were measured. EPTH was evident within 15 min after trauma but was significantly ameliorated during the 5 h of GLP-1 infusion. One day after trauma, plasma IL-6 was markedly increased in the trauma group and decreased in GLP-1-treated animals. RBF, GFR, and Do2 all significantly decreased with trauma, but renal V̇o2 was unchanged. GLP-1 treatment normalized RBF, GFR, and Do2 without affecting V̇o2. These results suggest that GLP-1 decreases EPTH and protects against a later development of AKI. Early treatment with GLP-1 (or its analogs) to rapidly, effectively, and safely control EPTH may be beneficial in the prehospital care of obese patients after trauma.

Sodium butyrate reduces high-fat diet-induced non-alcoholic steatohepatitis through upregulation of hepatic GLP-1R expression

Glucagon-like peptide-1 (GLP-1) has a broad spectrum of biological activity by regulating metabolic processes via both the direct activation of the class B family of G protein-coupled receptors and indirect nonreceptor-mediated pathways. GLP-1 receptor (GLP-1R) agonists have significant therapeutic effects on non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) in animal models. However, clinical studies indicated that GLP-1 treatment had little effect on hepatic steatosis in some NAFLD patients, suggesting that GLP-1 resistance may occur in these patients. It is well-known that the gut metabolite sodium butyrate (NaB) could promote GLP-1 secretion from intestinal L cells. However, it is unclear whether NaB improves hepatic GLP-1 responsiveness in NAFLD. In the current study, we showed that the serum GLP-1 levels of NAFLD patients were similar to those of normal controls, but hepatic GLP-1R expression was significantly downregulated in NAFLD patients. Similarly, in the NAFLD mouse model, mice fed with a high-fat diet showed reduced hepatic GLP-1R expression, which was reversed by NaB treatment and accompanied by markedly alleviated liver steatosis. In addition, NaB treatment also upregulated the hepatic p-AMPK/p-ACC and insulin receptor/insulin receptor substrate-1 expression levels. Furthermore, NaB-enhanced GLP-1R expression in HepG2 cells by inhibiting histone deacetylase-2 independent of GPR43/GPR109a. These results indicate that NaB is able to prevent the progression of NAFL to NASH via promoting hepatic GLP-1R expression. NaB is a GLP-1 sensitizer and represents a potential therapeutic adjuvant to prevent NAFL progression to NASH.

Cardiovascular benefits of GLP-1 agonists in type 2 diabetes: a comparative review

Type 2 diabetes (T2D) carries risks of both cardiovascular (CV) (myocardial infarction, stroke, and peripheral vascular disease) and microvascular (retinopathy/nephropathy/neuropathy) complications. Glucose-lowering is an effective strategy for preventing microvascular complications, but the extent to which it can reduce CV complications is less certain. Glucagon-like peptide-1 (GLP-1) agonists are potent glucose-lowering agents but also have potentially beneficial effects on other traditional (body weight, blood pressure (BP), and LDL cholesterol) and non-traditional risk factors (low grade inflammation and endothelial dysfunction). The results of four large CV outcome trials with GLP-1 agonists are now available. These have compared lixisenatide (ELIXA), liraglutide (LEADER), semaglutide (SUSTAIN-6), and long-acting exenatide (EXSCEL) with placebo and standard of care over 2-4 years; four others (including with dulaglutide and albiglutide) are ongoing. LEADER and SUSTAIN-6 have demonstrated reductions in rates of major adverse CV events with active GLP-1 treatment but ELIXA and EXSCEL have not. In this review, we discuss the mechanisms by which GLP-1 receptor agonists act on the CV system and the design and conduct of these trials. Contrary to the assertions that (a) all GLP-1 agonists reduce CV disease in T2D but to different extents or (b) the magnitude of CV protection is predominantly related to glucose-lowering, we argue that CV benefit is specific to agents that provide longer acting agonism at the GLP-1 receptor. The mechanisms involve reduction in body weight and BP, and lowering of LDL-cholesterol and glucose, but pleiotropic effects-including suppression of low grade inflammation, vasodilation, and natriuresis-are also likely relevant.

Effect of Glucagon Like Peptide-1 on Serum Kisspeptin Level in Adult Male Albino Rats Treated by Anabolic Androgenic Steroid

AbstractBackground: Anabolic Androgenic Steroids (AAS) are widely used among youth and athletes for improving their physical appearance and performance. However, its use has adverse effects on sexual health and metabolism. Glucagon Like Peptide-1 (GLP-1) is a gut hormone that participates in the neuroendocrine control of hypothalamic-pituitary axis (HPG), and may play an important role in the reproductive functions as a component of GIT-brain axis. Also, the hypoth-alamic neuropeptide kisspeptin stimulates the Hypothalamic Pituitary Gonadal (HPG) axis and controls gonadotropin secretion. Few researches were performed to study the rela-tionship between each of GLP-1 and kisspeptin with HPG axis.Aim: To evaluate the potential protective role of (GLP-1) against some altered sexual, metabolic, and histopathologic changes induced by the use of AAS in adult male albino rats.Material and Methods: 40 adult male albino rats were divided into 4 groups; Group I (control or vehicle treated), Group II (GLP-1 + vehicle treated), Group III (AAS-treated) and Group IV (GLP-1 + AAS). In all groups, Body Weight (BW) was measured and Body Mass Index (BMI) was calcu-lated. Serum testosterone, Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH), kisspeptin, glucose and insulin levels were measured, homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was calculated, and lipid profile was estimated. The changes in the histopathological aspects of testis were examined. The testicular weight, testicular coefficient, epidydimal sperm count and motility were inves-tigated.Results: The study revealed that peripheral injection of GLP-1 for 5 weeks to androgen treated-rats in Group IV (GLP-1 + AAS) significantly increased levels of serum kisspep-tin, LH, FSH, testosterone and consequently epidydimal sperm count and motility compared with rats in Group III (AAS-treated). In addition, GLP-1 treatment induced significant reductions in the values of fasting serum glucose and HOMA-IR, serum total cholesterol and LDL levels with no significant changes in serum insulin, HDL and TG levels in Group IV compared with Group III.Conclusion: The administered GLP-1 may attenuate some altered sexual, metabolic and histopathological adverse effects induced by AAS use in adult male rats. Therefore, it may be a novel approach for managing AAS abuse.