Effects Of GLP-1 Research Articles

Santral GLP-1'in Gastrik Mukozal Kan Akımına Etkisi; Spesifik Reseptörlerin Rolü

Amaç: İntraserebroventriküler (ICV) olarak enjekte edilen 'glucagon like peptid-1 (GLP-1)'in sıçanlarda gastrik mukozal kan akımı [gastric mucosal blood flow (GMBF)]'na etkisi, bu etkide santral spesifik reseptörlerinin rolü ve ayrıca absolu etanolün GMBF'de neden olduğu değişikliklerin üzerindeki etkisinin araştırılmasıdır. Gereç ve Yöntemler: ICV enjeksiyonlar için izofloran (%4) anestezisi altında sıçanların kafatasına orta hattın 1,5 mm sağ yanında ve bregmanın 1-1,5 mm arkasında olacak şekilde bir delik açıldı. Bu delikten sağ lateral ventriküle, dik olarak ve alt ucu kafatası yüzeyinden 4,2-4,5 mm kadar derinliğe inecek şekilde 10 mm uzunluğunda bir kanül yerleştirildi. GMBF 'Laser Doppler flowmetre' ile ölçülerek, veriler 'MP30 Data Acquisition System' aracılığıyla bilgisayara aktarıldı. Ölçümler için anestezi altındaki sıçanlarda mide hazırlandıktan sonra mide mukozasına prob yerleştirilerek kalibrasyon için 30 dk beklendi ve bazal kan akımı ölçümleri kaydedildi. GLP-1'in GMBF'deki etkisini araştırmak amacıyla, GLP-1 (3, 10 ve 30 μg/10 μL; ICV) veya serum fizyolojik (10 μL; ICV) enjekte edildi. Spesifik reseptör antagonisti exendin-(9-39) (1 μg/10 μL; ICV) enjekte edildikten 5 dk sonra 10 μg GLP- 1 enjekte edildi. Enjeksiyonları takiben gastrik çember içine serum fizyolojik (1,5 mL) uygulandı ve 30 dak süresince her 5 dk'da gastrik kan akımı kaydedildi. Absolu etanolün GMBF'de neden olduğu değişikler üzerinde GLP-1'in etkisini araştırmak için sıçanlara 10 μg GLP-1 enjeksiyonundan 5 dk sonra gastrik çember içine etanol (1,5 mL) uygulandı. Bulgular: 10 μg ICV GLP-1 GMBF'yi arttırdı ve ICV eksendin- (9-39) bu etkiyi antagonize etti. Ayrıca GLP-1 absolu etanolün GMBF'de oluşturduğu inhibisyonu azalttı. 3 ve 30 μg GLP-1 ise GMBF'yi azalttı. Sonuç: ICV olarak enjekte edilen 10 μg GLP-1'in GMBF'yi artırdığı ve bu etkide, santral spesifik reseptörlerinin rolü olduğu düşünülmektedir. Aynı zamanda santral GLP-1'in GMBF'deki etanol nedenli inhibisyonu önleyebildiği gözlenmiştir. Diğer dozlar ise GMBF'de azalmaya neden olmuştur.

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

PurposeCardiovascular-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. MethodsIn 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. FindingsThere 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). ImplicationsAcute 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.

Recombinant human glucagon-like peptide-1 protects against chronic intermittent hypoxia by improving myocardial energy metabolism and mitochondrial biogenesis

Background and aimsObstructive sleep apnea syndrome is a chronic disease associated with intermittent hypoxia (IH) and is an important risk factor for cardiovascular disease. Glucagon-like peptide (GLP-1) is a naturally occurring incretin used as a promising therapeutic agent in the treatment of acute myocardial infarction, dilated cardiomyopathy, and advanced heart failure. However, whether GLP-1 can protect against IH-induced cardiac injury is still unclear. Accordingly, in this study, we evaluated the effects of recombinant human GLP-1 (rhGLP-1) on cardiac health in mice. MethodsMice were subjected to repetitive 5% O2 for 30 s and 21% O2 for 30 s, for a total of 8 h/day for 4 weeks. Subsequently, mice received subcutaneous injection of saline or rhGLP-1 (100 μg/kg, three times per day). Cardiac function, myocardial apoptosis and fibrosis, energy metabolism, and mitochondrial biogenesis were examined for evaluation of cardiac injury. ResultsA reduction in diastolic function (E/A ratio) in mice exposed to IH was significantly reversed by rhGLP-1. IH induced marked cardiomyocyte apoptosis and myocardial fibrosis. Additionally, IH resulted in a shift from fatty acid to glucose metabolism in the myocardium with downregulation of peroxisome proliferator-activated receptor (PPAR) α and PPARγ. Moreover, IH caused a reduction in mitochondrial DNA (mtDNA) replication and transcription, together with reduced mtDNA content and impaired mitochondrial ultrastructure. These changes were abolished by rhGLP-1 via activation of PGC-1α and Akt signaling. ConclusionsrhGLP-1 protects against IH-induced cardiac injury by improving myocardial energy metabolism and enhancing the early adaptive changes of mitochondrial biogenesis.

Role of β Cell Precursors in the Regeneration of Insulin-Producing Pancreatic β Cells under the Influence of Glucagon-Like Peptide 1.

The effects of the pegylated form of glucagon-like peptide 1 (pegGLP-1) on oligopotent β cell precursors (CD45-TER119-CD133+CD49flow) in the pancreas were studied in C57Bl/6 mice. Under conditions of streptozotocin-induced type 1 diabetes mellitus, intraperitoneal injection of pegGLP1 increased the content of β cell precursors and dithizone-stained cells in the pancreas. β Cell precursors of mice with diabetes demonstrated high self-maintenance potential. In contrast to pegGLP-1, native GLP-1 did not affect β cell precursors in diabetic animals. Treatment of a culture of β cell precursors from mice with diabetes induced the yield of dithizone-stained mononuclears. In conditioned mediums of dithizone-positive cells obtained as a result of differentiation of β cell precursors from mice with diabetes, insulin was detected after administration of pegGLP-1 (10-7 M) and glucose (3 mmol/liter); the level of insulin increased with increasing glucose concentration (to 20 mmol/liter). The in vitro effect of pegGLP-1 did not differ from the effect of GLP-1 (10-7 M).

Glepaglutide, a long-acting glucagon-like peptide-2 analog, alters postprandial intestinal hormone levels but not glucose homeostasis in patients with short bowel syndrome

Rationale: Native glucagon-like peptide (GLP)-2 as well as GLP-2 analogs have been shown to improve intestinal function in patients with short bowel syndrome (SBS). Since the effects of GLP-2 on endogenous meal-stimulated intestinal hormone release and glucose homeostasis are largely unknown, we aimed to elucidate these relationships in patients with SBS treated with glepaglutide, a long-acting GLP-2 analog.

PO-453 Effect of GLP-1 on proliferation and migration in pheochromocytoma and colorectal cancer cells

IntroductionIncretin-based therapy (like GLP-1R agonists) have been recently widely used as for treatment of diabetes and obesity. They have favourable effect on proliferation of beta cells of pancreas. GLP-1 mediates an incretin effect, by which oral glucose has a greater stimulatory effect on insulin secretion than intravenous glucose. GLP-1 binds to a specific GLP-1 receptor (GLP-1R), which is expressed in many tissues including; pancreatic beta cells, gastric mucosa, kidney, lung, heart, skin, immune cells, and the hypothalamus. In addition, those receptors are expressed in some types of cancers; including medullary thyroid, ovarian and colorectal cancers. The aim of our study is to explore the effect of GLP-1R agonist (exendin-4) and GLP-1 antagonist (exendin 9–39) on human pheochromocytoma (hPheo1) and colorectal cancer (HT29) cell proliferation and migration.Material and methodsGLP-1 receptor expression was detected by Western Blotting and real time PCR in 4 different cell lines; colorectal HT29, HCT116, [m1] pheochromocutoma (hPheo1) and neuroblastoma (SH-SY-5Y). Different concentrations (0.1–100 µM) of exendin-4 and exendin 9–39 (5 and 10 µM) were applied on hPheo1 and HT29 cell lines. The effect on proliferation was detected after 48 and 72 hours by cell viability assay (MTT). Cell migration assay was detected by wound healing experiment through measuring migration distance rate. Statistical significance was assessed using ANOVA, followed by post hoc Tukey Kramer test when groups were significantly different.Results and discussionsThe GLP1R gene is expressed in all 4 cell lines cell lines. Exendin-4 increased proliferation of hPheo and HT29 cell lines at 0.1μM and 1μM concentrations, as compared to control group (p<0.001). No proliferative effect was observed of exendin-4 at 10 μM, or exendin 9–39 in both hPheo1 and HT29 cell. Combination of exendin 4 and exendin 9–39 significantly decreased cell proliferation in both cell lines (p<0.001). There was no significant difference on cell migration distance rate after 24 hour-treatment of cells with either exendin-4 or exendin 9–39 or combination of both.ConclusionThe GLP-1R agonists may increase the proliferation of cancer cells initially and at low doses, whereas higher doses decreases the proliferation rate. They are likely to have no effect, or potentially favourable suppressing effect on cancer cell proliferation and migration in pheochromocytoma and colorectal cancer.

Effect of Biased GLP-1/Glucagon Receptor Co-agonists on Insulin Secretion

Introduction: The effect of dual GLP-1 and glucagon analogues on insulin secretion remains unclear. Here, we investigated the effect of novel GLP-1 / glucagon receptor (GLP-1R/GCGR) co-agonists on beta cell lines, finding augmented insulin release compared to reference agonist Exendin-4. This effect was related to signalling bias at the GLP-1R. Methods: GLP-1R/GCGR co-agonists were designed, based on the sequence of oxyntomodulin. INS-1 832/3 beta cells and MIN6B1 beta cells were used to perform 24 hour insulin secretion assays. Ligand-directed signal bias was determined from cyclic adenosine monophosphate (cAMP) and β arrestin-1/2 responses measured by enzyme fragment complementation in CHO-K1 cells expressing GLP-1R or GCGR. Results: Several co-agonists show enhanced maximal insulin release compared to Exendin-4 (representative co-agonist Peptide A vs. Exendin-4 fold insulin release, normalized to 11mM glucose: INS-1 823/3 cells 4.45 ± 0.24 vs. 2.55 ± 0.22, p = 0.0002; MIN6B1 cells 2.28 ± 0.22 vs. 1.57 ± 0.08, p = 0.002). At the GLP-1 receptor, co-agonists were biased towards cAMP generation, compared to the β arrestin-2 pathway (delta log (τ/KA) -0.70 ± 0.11 [Peptide A], vs. 0.29 ± 0.11 [Exendin-4], p= &amp;lt;0.0001). At the GCGR, no significant change in bias was seen relative to native glucagon. Conclusion: GLP-1R/GCGR co-agonists show enhanced insulin release in vitro compared to exendin-4. As canonical effects of β arrestin recruitment include desensitisation and loss of cell surface receptors via endocytosis, the observed signal bias with these peptides may be linked to their insulinotropic effect. These findings may inform the design of more potent insulinotropic compounds for therapeutic use in type 2 diabetes. Disclosure G. Farooq: None. B. Jones: None. J.S. Minnion: None. S.R. Bloom: None.

Elevated Insulin Clearance Contributes to the Reduced Peripheral Insulin Concentration Observed in Obese Young Asian with Type 2 Diabetes

Introduction: The importance of insulin clearance (CLins) on insulin dynamics and the role exerted in controlling glucose in type 2 subjects has recently been appreciated. Moreover, evidence in mice showed that CLins is reduced by incretin hormones at physiological levels. Aim: To evaluate in 29 young (19±1 years) multi-ethnic Asian type 2 subjects (T2D) the contribution of CLins to insulin dynamics and if an association exists with GLP-1. Methods: T2D (15F/14M; BMI=30.2±0.9 kg/m2; HbA1c=8.8±0.4% [73±4.4 mmol/mol]; mean duration of disease 2.5 years) had fasting glucose Gb=192±14 mg/mL and insulin Ib=19±3 µU/mL. They were compared to 17 (8F/9M) age-matched nondiabetic overweight (BMI=27.8±1.0, p=0.1) control subjects (CT, Gb=82±1, p&amp;lt;0.0001; Ib=12±2, p=0.09). All underwent a 75g 2h OGTT with measurements of glucose, insulin, C-peptide and GLP-1. Insulin secretion (ISR) was assessed by deconvolution from peripheral C-peptide; CLins) by ISR/AUCinsulin; beta cell function (BCF) by AUCC-peptide/AUCglucose; insulin sensitivity by OGIS model. GLP-1 effect on BCF (GLPE) was empirically calculated as BCF/AUCGLP-1. Results: T2D were insulin resistant (OGIS=277±16 mL/min m2 vs. 424±14) and had low BCF (82±11 pmolC-peptide/mmolglucose vs. 123±10), both p&amp;lt;0.0001. Lower total AUCinsulin was observed in T2D (4.7±0.7 U/L 2h vs. 11.0±1.4, p&amp;lt;0.0001), with higher CLins (2.06±0.19 L/min) than in CT (1.46±0.10, p=0.023). CLins directly correlated with OGIS in CT (R=0.55, p=0.02), but not in T2D (p=0.98). Despite no difference was observed in AUCGLP-1 (1.6±0.1 nmol/L 2h vs. 1.7±0.1 in CT, p=0.63), which did not correlate with CLins (p&amp;gt;0.2), GLPE was lower in T2D (6.2±0.9 vs. 23.4±2.3, p&amp;lt;0.0001). Conclusion: Reduced peripheral insulin availability in obese young Asian T2D is due not only to a markedly impaired beta cell function and reduced GLP-1 effect, but also to an increased insulin clearance, which however shows no association to GLP-1 response. Disclosure G. Pacini: None. A. Tura: None. C. Hor: None. S. Lim: None. F. Tan: None. C. Tong: None. J.Y.H. Hong: None. F. Md Zain: None. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. Board Member; Self; Zealand Pharma A/S. Speaker's Bureau; Self; Merck Sharp &amp; Dohme Corp., AstraZeneca. Research Support; Self; Danish Diabetes Academy, Novo Nordisk Foundation. Other Relationship; Self; Antag Therapeutics. Other Relationship; Spouse/Partner; Antag Therapeutics. W. Mohamud: None. T. Yeow: None.

Effect of a Novel Long-Acting GLP-1/GIP/Glucagon Triple Agonist (HM15211) in a NASH and Fibrosis Animal Model

Nonalcoholic steatohepatitis (NASH), a potential consequence of NAFLD, may lead to end stage liver disease including cirrhosis and hepatocellular carcinoma. Despite its severity and prevalence, NASH currently lacks effective treatment. In this respect, we developed a novel long-acting, GLP-1/GIP/Glucagon triple agonist, HM15211. With a unique activity profile, HM15211 could provide synergistic benefits on body weight loss and lipid profile improvement while avoiding hyperglycemic risk. Previously, we showed that HM15211 exerts potent reductions in body weight and hepatic TG (triglycerides) in DIO mice, and showed a liver preferential distribution, suggesting HM15211 as a potential treatment for NASH. Here, we evaluated the effect of HM15211 in NASH and fibrosis using MCD-diet mice with various disease induction periods. In MCD-diet mice (6 weeks induction), HM15211 treatment led to significant decrease in hepatic TG (-82.6% vs. vehicle) and TBARS (oxidative stress marker, -60.7% vs. vehicle), which coincided with significant reduction in ALT and bilirubin. Time course MRI/MRS imaging further confirmed the progressive steatosis resolution by HM15211. Furthermore, histopathological analysis indicated that HM15211 significantly reduced hepatic inflammatory gene expression and NAFLD activity score (1.3 for HM15211, 3.4 for liraglutide, and 2.7 for vehicle). To further evaluate the therapeutic potential in fibrosis, MCD-diet mice was used for an extended period (10 weeks induction) to achieve overt liver fibrosis. In line with NASH improvement, HM15211 successfully resolved liver fibrosis as demonstrated in histological evaluation. Histological improvements were accompanied by a remarkable decrease in disease biomarkers including hepatic hydroxyproline. Based on these observations, HM15211 may offer a therapeutic potential for NASH and fibrosis as well as obesity. Disclosure I. Choi: Employee; Self; Hanmi Pharmaceutical. Stock/Shareholder; Self; Hanmi Pharmaceutical. J. Kim: Employee; Self; Hanmi Pharmaceutical. Stock/Shareholder; Self; Hanmi Pharmaceutical. J. Lee: Employee; Self; Hanmi Pharmaceutical. Stock/Shareholder; Self; Hanmi Pharmaceutical. E. Park: Employee; Self; Hanmi Pharmaceutical. Y. Kim: Employee; Self; Hanmi Pharmaceutical. S. Jung: None. S. Kim: Employee; Self; Hanmi Pharmaceutical. Stock/Shareholder; Self; Hanmi Pharmaceutical.

The Effect of Nutritional Transition on the Differentiation of Bone Marrow Stem Cells and the Therapeutic Effect of GLP-1

Background: Catch up growth is associated with glucose and lipid metabolism disorders, that can lead to osteoporosis and related fractures. Glucagon-like peptide-1 receptor agonists, such as liraglutide, exert an anabolic effect on bone in insulin resistant mice, but the mechanism for the action remains unclear. We established an animal model of catch-up growth to explore the actions of GLP-1 on bone mass and structure. Methods: 30 male C57BL/6 mice were randomly divided into the normal diet (ND, n=10), the catch-up growth model (RH, n=10) and the catch-up growth model +GLP-1 (RH+GLP-1, n=10) groups. Liraglutide was subcutaneously administered (200ug/kg, twice a day, for four weeks). After killing, tibia and fibula were removed for bone histomorphometry, bilateral femoral bone marrow mesenchymal stem cells were collected to evaluate their differentiation ability. Results: GLP-1 administration decreased weight of visceral fat tissue, body weight, ratio between them, and blood lipids of the RH group. GLP-1 decreased triglyceride levels, and fatty acids in the liver, visceral fat tissue, subcutaneous fat tissue and skeletal muscle tissue. Compared to the ND group, GLP-1 secretion decreased in the RH group, but noticeably increased after GLP-1 administration. The areas under curves of intraperitoneal glucose tolerance test and insulin tolerance test and HOMA-IR in RH+GLP-1 group significantly declined. GLP-1 reversed deteriorated tibial and fibular bone structure in RH mice and induced osteoblastic differentiation. Conclusion: Decreased ability of osteoblastic/osteogenesis differentiation of MSCs in RH mice led to impaired bone formation and GLP-1 intervention reversed the damage and enhanced insulin sensitivity. Disclosure W. Xia: None. L. Chen: None. Q. Zhang: None.

A GLP-1:CCK fusion peptide harnesses the synergistic effects on metabolism of CCK-1 and GLP-1 receptor agonism in mice

Combination approaches for the treatment of metabolic diseases such as obesity and diabetes are becoming increasingly relevant. Co-administration of a glucagon-like peptide-1 receptor (GLP-1R) agonist with a cholecystokinin receptor-1 (CCKR1) agonist exert synergistic effects on weight loss in obese rodents. Here, we report on the effects of a novel fusion peptide (C2816) comprised of a stabilized GLP-1R agonist, AC3174, and a CCKR1-selective agonist, AC170222. C2816 was constructed such that AC3174 was linked to the N-terminus of AC170222, thus preserving the C-terminal amide of the CCK moiety. In functional in vitro assays C2816 retained full agonism at GLP-1R and CCKR1 at lower potency compared to parent molecules, whereas a previously reported fusion peptide in the opposite orientation, (pGlu-Gln)-CCK-8/exendin-4, exhibited no activity at either receptor. Acutely, in vivo, C2816 increased cFos in key central nuclei relevant to feeding behavior, and reduced food intake in wildtype (WT), but less so in GLP-1R-deficient (GLP-1RKO), mice. In sub-chronic studies in diet-induced obese (DIO) mice, C2816 exerted superior reduction in body weight compared to co-administration of AC3174 and AC170222 albeit at a higher molar dose. These data suggest that the synergistic pharmacological effects of GLP-1 and CCK pathways can be harnessed in a single therapeutic peptide.

Gglucagon-like peptide-1 analogue liraglutide (Saxenda®): mechanism of action, efficacy for the treatment of obesity

The development of effective methods of obesity treatment with the goal of preventing many associated diseases is among the priorities of modern biomedical research. In 2016 glucagon-like peptide-1 analog (GLP-1) liraglutide 3 mg (Saxenda) was approved in the Russian Federation for the treatment of obesity. This review presents literature data on the effects of GLP-1 and liraglutide on appetite and body weight as well as an analysis of the effectiveness and safety of drug Saxenda based on the results of major clinical trials.

Novel role of GLP-1 receptor signaling in energy expenditure during chronic high fat diet feeding in rats

ObjectiveGlucagon-like peptide-1 (GLP-1) secreted from intestinal L-cells plays a major role in meal termination and glucose-dependent insulin secretion. Several lines of evidence indicate, however, that the acute satiating and incretin effects of GLP-1 are attenuated with high fat diet (HFD) exposure. Here we tested the hypothesis that endogenous GLP-1 differentially affects energy balance and glucose homeostasis dependent on whether rats are fed chow or HFD (60% energy from fat). MethodsWe blocked GLP-1 receptor (GLP-1R) signaling by daily intraperitoneal (IP) injection of the GLP-1R antagonist exendin (9–39) (Ex9, 10 μg/kg) or vehicle for 5 weeks in male Sprague-Dawley rats fed either chow or HFD, recorded body weight (BW) and food intake throughout, and assessed energy expenditure (3rd week) and glucose tolerance (4th week). ResultsFive week daily Ex9 injections reduced BW gain in HFD-fed rats, but did not affect BW in chow-fed rats. On the other hand, chronic Ex9 treatment did not affect daily food intake in either chow or HFD-fed rats during the entire study. The reduced BW gain in HFD-fed rats was associated with an increase in energy expenditure. Interestingly, chronic Ex9 treatment induced glucose intolerance in chow-fed rats, but not in HFD-fed rats, suggesting a differential role of GLP-1R signaling in glucose metabolism during chow and HFD feeding. ConclusionsOur findings reveal a novel role of GLP-1R signaling, modulating energy expenditure rather than eating behavior during HFD feeding. Furthermore, these results suggest a previously unrecognized contribution of GLP-1R signaling to the pathophysiology of obesity.

Glucagon-like peptide-1 contributes to increases ABCA1 expression by downregulating miR-758 to regulate cholesterol homeostasis

Abnormal regulation of lipid metabolism is associated with type 2 diabetes mellitus (T2DM). GLP-1 as a new treatment for T2DM, has unique effects in modulating cholesterol homeostasis. However, the mechanism of this effect is largely missing. The aim of this study was to determine the effects of GLP-1 on cholesterol-induced lipotoxicity in hepatocytes and examine the underlying mechanisms. The cell viability was determined, and caspase-3 was used to detect the effects of GLP-1 on cholesterol-induced apoptosis. The alterations of miR-758 and ATP-binding cassette transporter A1 (ABCA1) resulting from cholesterol incubation or GLP-1 were detected by qRT-PCR and Western blot assays. Overexpression of miR-758 abrogated the GLP-1-mediated ABCA1 expression, and conversely, down-regulation of miR-758 aggravated GLP-1's action and revealed significant promotion effects. BODIPY-Cholesterol efflux assay revealed that treatment with miR-758 inhibitor significantly enhanced ABCA1-dependent cholesterol efflux, resulting in reduced total cholesterol. Furthermore, Oil red O staining and cholesterol measurement were used to detect lipid accumulation. As a result, cholesterol significantly attenuated cell viability, promoted cell apoptosis, and facilitated lipid accumulation, and these effects were reversed by GLP-1. This study provides evidence that, in HepG2 cells, GLP-1 may affect cholesterol homeostasis by regulating the expression of miR-758 and ABCA1. These data can inform the development of biomarkers for miR-758, and potentially other drugs, on the key pathways of lipid metabolism.

Protective Effect of GLP-1 on AGEs-Induced Apoptosis of Fibroblast Cells

Protective Effect of GLP-1 on AGEs-Induced Apoptosis of Fibroblast Cells

Recombinant human GLP-1(rhGLP-1) alleviating renal tubulointestitial injury in diabetic STZ-induced rats

GLP-1-based treatment improves glycemia through stimulation of insulin secretion and inhibition of glucagon secretion. Recently, more and more findings showed that GLP-1 could also protect kidney from diabetic nephropathy. Most of these studies focused on glomeruli, but the effect of GLP-1 on tubulointerstitial and tubule is not clear yet. In this study, we examined the renoprotective effect of recombinant human GLP-1 (rhGLP-1), and investigated the influence of GLP-1 on inflammation and tubulointerstitial injury using diabetic nephropathy rats model of STZ-induced. The results showed that rhGLP-1 reduced urinary albumin without influencing the body weight and food intake. rhGLP-1 could increased the serum C-peptide slightly but not lower fasting blood glucose significantly. In diabetic nephropathy rats, beside glomerular sclerosis, tubulointerstitial fibrosis was very serious. These lesions could be alleviated by rhGLP-1. rhGLP-1 decreased the expression of profibrotic factors collagen I, α-SMA, fibronectin, and inflammation factors MCP-1 and TNFα in tubular tissue and human proximal tubular cells (HK-2 cells). Furthermore, rhGLP-1 significantly inhibited the phosphorylation of NF-κB, MAPK in both diabetic tubular tissue and HK-2 cells. The inhibition of the expression of TNFα, MCP-1, collagen I and α-SMA in HK-2 cells by GLP-1 could be mimicked by blocking NF-κB or MAPK. These results indicate that rhGLP-1 exhibit renoprotective effect by alleviation of tubulointerstitial injury via inhibiting phosphorylation of MAPK and NF-κB. Therefore, rhGLP-1 may be a potential drug for treatment of diabetic nephropathy.

Incretins modulate progesterone biosynthesis by regulating bone morphogenetic protein activity in rat granulosa cells

The effects of incretins on ovarian steroidogenesis have not been clarified. In this study, we investigated the effects of incretins, including GIP and GLP-1, on ovarian steroidogenesis using rat primary granulosa cells. Treatment with incretins significantly suppressed progesterone synthesis in the presence of FSH, and the effect of GIP was more potent than that of GLP-1. In contrast, incretins had no significant effect on estrogen synthesis by rat granulosa cells. In accordance with the effects of incretins on steroidogenesis, GIP and GLP-1 suppressed the expression of progesterogenic factors and enzymes, including StAR, P450scc, 3βHSD, but not P450arom, and cellular cAMP synthesis induced by FSH. In addition, incretins moderately increased FSHR mRNA expression in granulosa cells. Of note, treatment with GIP, but not treatment with GLP-1, augmented Smad1/5/8 phosphorylation and transcription of the BMP target gene Id-1 induced by BMP-6 stimulation, suggesting that GIP upregulates BMP receptor signaling that can inhibit FSH-induced progesterone synthesis in rat granulosa cells. On the other hand, BMP-6 treatment suppressed the expression of GIP receptor but not that of GLP-1 receptor. Expression of the BMP type-I receptor ALK-3 was upregulated by treatment with GIP and GLP-1 and that of ALK-6 was also increased by GIP, while inhibitory Smad6 expression was impaired by GIP and GLP-1 in rat granulosa cells. Collectively, the results indicate that incretins, particularly GIP, impair FSH-induced progesterone production, at least in part, by upregulating BMP signaling in rat granulosa cells. The modulatory effects of incretins on endogenous BMP activity may be applicable to treatment of dysregulated steroidogenesis such as polycystic ovary syndrome.

Development and characterisation of a novel glucagon like peptide-1 receptor antibody

Aims/hypothesisGlucagon like peptide-1 (GLP-1) enhances glucose-dependent insulin secretion by binding to GLP-1 receptors (GLP1Rs) on pancreatic beta cells. GLP-1 mimetics are used in the clinic for the treatment of type 2 diabetes, but despite their therapeutic success, several clinical effects of GLP-1 remain unexplained at a mechanistic level, particularly in extrapancreatic tissues. The aim of this study was to generate and characterise a monoclonal antagonistic antibody for the GLP1R for use in vivo.MethodsA naive phage display selection strategy was used to isolate single-chain variable fragments (ScFvs) that bound to GLP1R. The ScFv with the highest affinity, Glp1R0017, was converted into a human IgG1 and characterised further. In vitro antagonistic activity was assessed in a number of assays: a cAMP-based homogenous time-resolved fluorescence assay in GLP1R-overexpressing cell lines, a live cell cAMP imaging assay and an insulin secretion assay in INS-1 832/3 cells. Glp1R0017 was further tested in immunostaining of mouse pancreas, and the ability of Glp1R0017 to block GLP1R in vivo was assessed by both IPGTT and OGTT in C57/Bl6 mice.ResultsAntibodies to GLP1R were selected from naive antibody phage display libraries. The monoclonal antibody Glp1R0017 antagonised mouse, human, rat, cynomolgus monkey and dog GLP1R. This antagonistic activity was specific to GLP1R; no antagonistic activity was found in cells overexpressing the glucose-dependent insulinotropic peptide receptor (GIPR), glucagon like peptide-2 receptor or glucagon receptor. GLP-1-stimulated cAMP and insulin secretion was attenuated in INS-1 832/3 cells by Glp1R0017 incubation. Immunostaining of mouse pancreas tissue with Glp1R0017 showed specific staining in the islets of Langerhans, which was absent in Glp1r knockout tissue. In vivo, Glp1R0017 reversed the glucose-lowering effect of liraglutide during IPGTTs, and reduced glucose tolerance by blocking endogenous GLP-1 action in OGTTs.Conclusions/interpretationGlp1R0017 is a monoclonal antagonistic antibody to the GLP1R that binds to GLP1R on pancreatic beta cells and blocks the actions of GLP-1 in vivo. This antibody holds the potential to be used in investigating the physiological importance of GLP1R signalling in extrapancreatic tissues where cellular targets and signalling pathways activated by GLP-1 are poorly understood.

Exenatide modulates tumor-endothelial cell interactions in human ovarian cancer cells.

Diabetes and cancer are prevalent diseases whose incidence is increasing globally. Diabetic women have a moderate risk increase in ovarian cancer, suggested to be due to an interaction between these two disorders. Furthermore, patients manifesting both diseases have associated worse prognosis, reduced survival and shorter relapse-free survival. According to current recommendations, incretin drugs such as Exenatide, a synthetic analog of Exendin-4, and Liraglutide are used as therapy for the type 2 diabetes (T2D). We studied the effects of GLP-1 and Exendin-4 on migration, apoptosis and metalloproteinase production in two human ovarian cancer cells (SKOV-3 and CAOV-3). Exendin-4 inhibited migration and promoted apoptosis through caspase 3/7 activation. Exendin-4 also modulated the expression of key metalloproteinases (MMP-2 and MMP-9) and their inhibitors (TIMP-1 and TIMP-2). Vascular endothelial cells, which contribute to the formation and progression of metastasis, were also analyzed. TNF-α-stimulated endothelial cells from iliac artery after Exendin-4 treatment showed reduced production of adhesion molecules (ICAM-1 and VCAM-1). Additionally, incretin treatment inhibited activation of apoptosis in TNF-α-stimulated endothelial cells. In the same experiment, MMPs (MMP-1 and MMP-9), which are relevant for tumor development, were also reduced. Our study demonstrated that incretin drugs may reduce cancer cell proliferation and dissemination potential, hence limiting the risk of metastasis in epithelial ovarian cancer.

Exploring the molecular mechanisms underlying α- and β-cell dysfunction in diabetes.

Pancreatic islet dysfunction, including impaired insulin secretion in β cells and dysregulated glucagon secretion in α cells, is the chief pathology of diabetes. In β cells, oxidative stress, evoked by chronic hyperglycemia, was found to induce dysfunction of a critical transcription factor, PDX1, caused by its nucleocytoplasmic translocation via interactions with the insulin and JNK signaling pathways and another transcription factor, FOXO1. The significance of α-cell insulin signaling in the physiological and pathological regulation of α-cell biology was demonstrated in α-cell-specific insulin receptor knockout mice, which exhibited dysregulated glucagon secretion. Moreover, a high-glucose load directly induced excessive glucagon secretion in a glucagon-secreting cell line and isolated islets, together with impairment of insulin signaling. These findings indicate that disordered insulin signaling is central to the pathophysiology of islet dysfunction in both α and β cells. On the other hand, certain beneficial effects of GLP-1 on dysfunctional α and β cells indicate that it has therapeutic potential for diabetes patients who exhibit insulin resistance in islets. These studies, involving basic medical research approaches, have-at least in part-clarified the molecular mechanisms underlying α- and β-cell dysfunction in diabetes, and offer important clues that should aid the development of future therapeutic approaches to the disease.