Liraglutide Reduces Both Atherosclerosis and Kidney Inflammation in Moderately Uremic LDLr-/- Mice

Therapy Combining Glucagon-Like Peptide-1 Receptor Agonist with Sodium-Glucose Cotransporter 2 Inhibitor Suppresses Atherosclerosis in Diabetic ApoE-Deficient Mice

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter 2 inhibitors (SGLT2i) have beneficial effects on cardiovascular disease in addition to their glucose-lowering effects. In this study, the effects of these drugs, when used individually or in combination, on cardiovascular atherosclerotic lesion development were compared in diabetic ApoE-deficient (ApoE KO) hyperlipidemic mice.

METHODS

ApoE-KO mice were treated with streptozotocin and nicotinamide, generating a type 2 diabetes model. The mice were randomly divided into four groups: vehicle-treated (untreated), liraglutide (LIRA), ipragliflozin (IPRA), and combination therapy (combo). These mice, as well as non-diabetic controls, were fed a high-fat diet. After 8 weeks of drug administration, the heart and aorta were removed and analyzed.

RESULTS

Atherosclerotic lesions evaluated by oil red O (ORO) staining were significantly larger in the untreated group (13.4±0.8% of the total aortic area) than in the non-diabetic controls (4.4±0.5%, p<0.01), while being reduced in the combo group (6.0±1.0%, p<0.01) as compared with the untreated group. The ORO stain-positive area in the LIRA and IPRA groups tended to be reduced but their differences were not statistically significant. Transcript levels of Mcp1 and Sirt1 were significantly reduced and increased, respectively, in the combo compared with the untreated group, while no significant changes were observed in the monotherapy groups.

CONCLUSIONS

The data suggest that combination therapy with liraglutide and ipragliflozin may be an efficient regimen for preventing the development of atherosclerosis in diabetic mice deficient in ApoE.

The expanding incretin universe: from basic biology to clinical translation

Incretin hormones, principally glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1(GLP-1), potentiate meal-stimulated insulin secretion through direct (GIP + GLP-1) and indirect (GLP-1) actions on islet β-cells. GIP and GLP-1 also regulate glucagon secretion, through direct and indirect pathways. The incretin hormone receptors (GIPR and GLP-1R) are widely distributed beyond the pancreas, principally in the brain, cardiovascular and immune systems, gut and kidney, consistent with a broad array of extrapancreatic incretin actions. Notably, the glucoregulatory and anorectic activities of GIP and GLP-1 have supported development of incretin-based therapies for the treatment of type 2 diabetes and obesity. Here we review evolving concepts of incretin action, focusing predominantly on GLP-1, from discovery, to clinical proof of concept, to therapeutic outcomes. We identify established vs uncertain mechanisms of action, highlighting biology conserved across species, while illuminating areas of active investigation and uncertainty that require additional clarification.

Effects of liraglutide on extraglycemic inflammatory markers and renal hemodynamic parameters in diabetic kidney disease (DKD)

Diabetic kidney disease (DKD) was the leading cause of kidney disease, which has been a crucial public health. Liraglutide is a drug, widely used for DKD treatment globally. However, the extraglycemic inflammatory markers and renal hemodynamic parameters of DKD patients treated with liraglutide has been not reported. In this study, 160 patients with early DKD were enrolled, 80 cases in the control group and 80 cases in the treatment group, respectively. The individuals in the control group were treated with metformin, while the individuals in the treatment group were treated with liraglutide and metformin for 3 months. The urinary microalbumin and urinary creatinine was measured to calculate the ratio (UACR), while the Doppler ultrasound were measured before and after treatment. After 3 months of treatment, body mass index (BMI), waist circumference (WC) and low-density lipoprotein cholesterol (LDL) in the treatment group were significantly decreased compared with before and after treatment in the control group; the levels of cystatin and UACR in treatment group were lower than before treatment and control group; The end-diastolic blood flow velocity (EDV) of renal artery and segment artery in treatment group was significantly higher than that before treatment and control group; The levels of CRP, TNF-α and IL-6 in the treatment group after treatment were lower than those before treatment and those in the control group. After 3 months of treatment, blood cystatin in the treatment group decreased significantly compared with before treatment and after treatment in the control group, with statistical significance After 3 months of treatment, the EDV of renal artery and renal segment in treatment group was significantly higher than that before treatment and control group, the peak systolic blood flow velocity (PSV) and EDV of renal interlobar artery in treatment group were significantly higher than those before treatment and control group. The resistance index (RI) was significantly lower than that before treatment and control group. Liraglutide can reduce inflammatory indicators, renal artery blood flow and renal function indicators in early DKD patients.

Lack of Rab27a attenuates foam cell formation and macrophage inflammation in uremic apolipoprotein E knockout mice

As the most common cardiovascular disease, atherosclerosis (AS), is a leading cause of high mortality in patients with chronic renal failure. Rab27a has been reported to regulate the progression of cardiovascular and renal diseases. Nevertheless, little studies investigated the role and mechanism of Rab27a in uremic-accelerated AS (UAAS). An animal model of UAAS was established in apolipoprotein E knockout (apoE^-/-) mice using 5/6 nephrectomy (NX). We conducted in vitro and in vivo functional experiments to explore the role of Rab27a in UAAS, including the presence of oxidized low-density lipoprotein (ox-LDL). Rab27a expression was upregulated in the plaque tissues of NX apoE^-/- mice. The knockout of Rab27a (Rab27a^-/-) reduced AS-induced artery injury, as manifested by the reductions of plaque area, collagen deposition, inflammation and lipid droplet. Besides, cholesterol efflux was increased, while the expression of lipid metabolism-related proteins and the secretions of pro-inflammatory factors were decreased in ox-LDL-induced NX Rab27a^-/- apoE^-/- mice group. Further, Rab27a deletion inhibited the activation of nuclear factor κB (NF-κB) pathway. In conclusion, our study indicated that Rab27a deficiency attenuated foam cell formation and macrophage inflammation, depending on the NF-κB pathway activation, to inhibit AS progression in uremic apoE^-/- mice. This finding may provide a new targeting strategy for UAAS therapy.

Nephroprotective Effects of Semaglutide as Mono- and Combination Treatment with Lisinopril in a Mouse Model of Hypertension-Accelerated Diabetic Kidney Disease

Background: Obesity, hyperglycemia and hypertension are critical risk factors for development of diabetic kidney disease (DKD). Emerging evidence suggests that glucagon-like peptide-1 receptor (GLP-1R) agonists improve cardiovascular and renal outcomes in type 2 diabetes patients. Here, we characterized the effect of the long-acting GLP-1R agonist semaglutide alone and in combination with an ACE inhibitor (lisinopril) in a model of hypertension-accelerated, advanced DKD facilitated by adeno-associated virus-mediated renin overexpression (ReninAAV) in uninephrectomized (UNx) female diabetic db/db mice. Methods: Female db/db mice received a single intravenous injection of ReninAAV 1 week prior to UNx. Six weeks post-nephrectomy, db/db UNx-ReninAAV mice were administered (q.d.) vehicle, semaglutide (30 nmol/kg, s.c.) or semaglutide (30 nmol/kg, s.c.) + lisinopril (30 mg/kg, p.o.) for 11 weeks. Endpoints included blood pressure, plasma/urine biochemistry, kidney histopathology and RNA sequencing. Results: Vehicle-dosed db/db UNx-ReninAAV mice developed hallmarks of DKD characterized by severe albuminuria and advanced glomerulosclerosis. Semaglutide robustly reduced hyperglycemia, hypertension and albuminuria concurrent with notable improvements in glomerulosclerosis severity, podocyte filtration slit density, urine/renal kidney injury molecule-1 (KIM-1) levels and gene expression markers of inflammation and fibrogenesis in db/db UNx-ReninAAV mice. Co-administration of lisinopril further ameliorated hypertension and glomerulosclerosis. Conclusions: Semaglutide improves disease hallmarks in the db/db UNx-ReninAAV mouse model of advanced DKD. Further benefits on renal outcomes were obtained by adjunctive antihypertensive standard of care. Collectively, our study supports the development of semaglutide for management of DKD.

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

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

Glucose-dependent insulinotropic polypeptide and tissue inflammation: Implications for atherogenic cardiovascular disease

Glucose-dependent insulinotropic polypeptide (GIP) has pleiotropic actions on pancreatic endocrine function, adipose tissue lipid metabolism, and skeletal calcium metabolism. Recent data indicate a potential new role for GIP in the pathogenesis of cardiovascular disease. This review focuses on the emerging literature that highlights GIP’s role in inflammation—an established process in the initiation and progression of atherosclerosis. In vasculature tissue, GIP may reduce concentrations of circulating inflammatory cytokines, attenuate vascular endothelial inflammation, and directly limit atherosclerotic vascular damage. Important to recognize is that evidence exists to support both pro- and anti-inflammatory effects of GIP even within the same tissue/cell type. Therefore, future study designs must account for factors such as model heterogeneity, physiological relevance of doses/exposures, potential indirect effects on inflammatory pathways, and the glucose-dependent insulinotropic polypeptide receptor (GIPR) agonist form. Elucidating the specific effects of enhanced GIP signaling in vascular inflammation and atherosclerosis is crucial given the existing widespread use of DPP4 inhibitors and the emergence of dual-incretin receptor agonists for type 2 diabetes treatment.

Liraglutide protects against lethal renal ischemia-reperfusion injury by inhibiting high-mobility group box 1 nuclear-cytoplasmic translocation and release

Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, has been reported to exert protective effects against myocardial, hepatic, and gastric ischemia-reperfusion injury (IRI), but whether it can protect against renal IRI remains unknown. Here, a lethal renal IRI model was established with a 100% mortality rate in untreated mice. Treatment with liraglutide involving a regimen of multiple doses resulted in 100% survival, remarkable preservation of renal function, a significant reduction in pathological damage, and blunted upregulation of TNF-α, IL-1β, IL-6, MCP-1, TLR-2, TLR-4, and RAGE mRNA. We found that liraglutide treatment dramatically inhibited ischemia-induced nucleocytoplasmic translocation and release of HMGB1. This inhibition was associated with a marked decrease (~ 60%) in nuclear histone acetyltransferase activity. In addition, the protective effects of liraglutide on renal IRI were largely abolished by the administration of exogenous HMGB1. When the GLP-1R antagonist exendin (9-39) was given to mice before each liraglutide administration, or GLP-1R-/- mice were used for the renal IRI experiments, the protective effect of liraglutide on renal IRI was partially reversed. Moreover, liraglutide pretreatment significantly inhibited HMGB1 nucleocytoplasmic translocation during hypoxic culture of HK-2 cells in vitro, but the addition of exendin (9-39) significantly eliminated this inhibition. We demonstrate here that liraglutide can exert a strong protective effect on lethal renal IRI in mice. This protection appears to be related to the inhibition of HMGB1 nuclear-cytoplasmic translocation and release and partially depends on GLP-1R. Thus, liraglutide may be therapeutically useful for the clinical prevention and treatment of organ IRI.

The chicken pan-genome reveals gene content variation and a promoter region deletion in IGF2BP1 affecting body size

Domestication and breeding have reshaped the genomic architecture of chicken, but the retention and loss of genomic elements during these evolutionary processes remain unclear. We present the first chicken pan-genome constructed using 664 individuals, which identified an additional ∼66.5 Mb sequences that are absent from the reference genome (GRCg6a). The constructed pan-genome encoded 20,491 predicated protein-coding genes, of which higher expression level are observed in conserved genes relative to dispensable genes. Presence/absence variation (PAV) analyses demonstrated that gene PAV in chicken was shaped by selection, genetic drift, and hybridization. PAV-based GWAS identified numerous candidate mutations related to growth, carcass composition, meat quality, or physiological traits. Among them, a deletion in the promoter region of IGF2BP1 affecting chicken body size is reported, which is supported by functional studies and extra samples. This is the first time to report the causal variant of chicken body size QTL located at chromosome 27 which was repeatedly reported. Therefore, the chicken pan-genome is a useful resource for biological discovery and breeding. It improves our understanding of chicken genome diversity and provides materials to unveil the evolution history of chicken domestication.

Mechanisms of Cardiorenal Protection of Glucagon-Like Peptide-1 Receptor Agonists

The worldwide prevalence of type 2 diabetes (T2D) is steadily increasing, and it remains a challenging public health problem for populations in both developing and developed countries around the world. Despite the recent advances in novel antidiabetic agents, diabetic kidney disease and cardiovascular disease remain the leading causes of morbidity and mortality in T2D. Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs), incretin hormones that stimulate postprandial insulin secretion, serve as a promising avenue for treatment of T2D as they result in a variety of antihyperglycemic effects including increased endogenous insulin secretion, decreased gluconeogenesis, inhibition of pancreatic α-cell glucagon production, decreased pancreatic β-cell apoptosis, and increased β-cell proliferation. GLP-1RAs have also been found to delay gastric emptying, promote weight loss, increase satiety, decrease hypertension, improve dyslipidemia, reduce inflammation, improve albuminuria, induce natriuresis, improve cardiovascular function, and prevent thrombogenesis. In this review, we will present risk factors for the development of cardiac and kidney disease in individuals with T2D and discuss possible mechanisms for the cardiorenal protective effects seen with GLP-1RAs. We will also present the possibility of dual- and tri-receptor agonist therapies with GLP-1, gastric inhibitory peptide, and glucagon RAs as an area of possible mechanistic synergy in the treatment of T2D and the prevention of cardiorenal complications.

GLP-1 receptor agonists (GLP-1RAs): cardiovascular actions and therapeutic potential

Type 2 diabetes mellitus (T2DM) is closely associated with cardiovascular diseases (CVD), including atherosclerosis, hypertension and heart failure. Some anti-diabetic medications are linked with an increased risk of weight gain or hypoglycemia which may reduce the efficacy of the intended anti-hyperglycemic effects of these therapies. The recently developed receptor agonists for glucagon-like peptide-1 (GLP-1RAs), stimulate insulin secretion and reduce glycated hemoglobin levels without having side effects such as weight gain and hypoglycemia. In addition, GLP1-RAs demonstrate numerous cardiovascular protective effects in subjects with or without diabetes. There have been several cardiovascular outcomes trials (CVOTs) involving GLP-1RAs, which have supported the overall cardiovascular benefits of these drugs. GLP1-RAs lower plasma lipid levels and lower blood pressure (BP), both of which contribute to a reduction of atherosclerosis and reduced CVD. GLP-1R is expressed in multiple cardiovascular cell types such as monocyte/macrophages, smooth muscle cells, endothelial cells, and cardiomyocytes. Recent studies have indicated that the protective properties against endothelial dysfunction, anti-inflammatory effects on macrophages and the anti-proliferative action on smooth muscle cells may contribute to atheroprotection through GLP-1R signaling. In the present review, we describe the cardiovascular effects and underlying molecular mechanisms of action of GLP-1RAs in CVOTs, animal models and cultured cells, and address how these findings have transformed our understanding of the pharmacotherapy of T2DM and the prevention of CVD.

Dulaglutide exerts beneficial anti atherosclerotic effects in ApoE knockout mice with diabetes: the earlier, the better

There has been no report about the mechanism for anti-atherosclerotic effects of dulaglutide (Dula) and/or about the difference of its effectiveness between in an early and a late phase of diabetes. To address such questions, streptozotocin (STZ) was intraperitoneally injected to ApoE knockout mice at 8 weeks of age. Either Dula or vehicle was administered to STZ-induced diabetic ApoE knockout mice from 10 to 18 weeks of age as an early intervention group and from 18 to 26 weeks as a late intervention group. Next, non-diabetic ApoE knockout mice without STZ injection were subcutaneously injected with either Dula or vehicle. In an early intervention group, atherosclerotic lesion in aortic arch and Mac-2 and CD68-positive areas in aortic root were significantly smaller in Dula group. In abdominal aorta, expression levels of some villain factors were lower in Dula group. In a late intervention group, there were no immunohistological differences in aortic root and expression levels of various factors between two groups. Furthermore, even in non-diabetic ApoE knockout mice, expression levels of inflammatory and macrophage markers were reduced by treatment with Dula. Taken together, Dula exerts more beneficial anti-atherosclerotic effects in an early phase of diabetes rather than in a late phase.

Enteropeptidase inhibition improves kidney function in a rat model of diabetic kidney disease

AIM

To examine the effects of an enteropeptidase inhibitor, SCO-792, on kidney function in rats.

MATERIALS AND METHODS

The pharmacological effects of SCO-792 were evaluated in Wistar fatty (WF) rats, a rat model of diabetic kidney disease (DKD).

RESULTS

Oral administration of SCO-792 increased faecal protein content and improved glycaemic control in WF rats. SCO-792 elicited a rapid decrease in urine albumin-to-creatinine ratio (UACR). SCO-792 also normalized glomerular hyperfiltration and decreased fibrosis, inflammation and tubular injury markers in the kidneys. However, pioglitazone-induced glycaemic improvement had no effect on kidney variables. Dietary supplementation of amino acids (AAs), which bypass the action of enteropeptidase inhibition, mitigated the effect of SCO-792 on UACR reduction, suggesting a pivotal role for enteropeptidase. Furthermore, autophagy activity in the glomerulus, which is impaired in DKD, was elevated in SCO-792-treated rats. Finally, a therapeutically additive effect on UACR reduction was observed with a combination of SCO-792 with irbesartan, an angiotensin II receptor blocker.

CONCLUSIONS

This study is the first to demonstrate that enteropeptidase inhibition is effective in improving disease conditions in DKD. SCO-792-induced therapeutic efficacy is likely to be independent of glycaemic control and mediated by the regulation of AAs and autophagy. Taken together with a combination effect of irbesartan, SCO-792 may be a novel therapeutic option for patients with DKD.

Nephroprotective effects of GLP-1 receptor agonists: where do we stand?

Glucagon-like peptide (GLP)-1 receptor agonists are the cornerstone in the treatment of hyperglycemia in many people suffering from type 2 diabetes (T2D). These drugs have potent glucose-lowering actions and, additionally, lower body weight through satiety induction while reducing blood pressure and dyslipidemia. Partly through these actions, GLP-1 receptor agonism was shown to reduce cardiovascular disease (CVD) in people with T2D with previous CVD or at high-risk thereof. In these cardiovascular safety trials, in secondary or exploratory analyses, GLP-1 receptor agonists were also shown to reduce macro-albuminuria, an accepted surrogate marker for diabetic kidney disease (DKD), a condition that still represents a major unmet medical need. In this review we will discuss the evidence which suggests renoprotection induced by GLP-1 receptor agonists and the potential mechanisms that may be involved. These include mitigation of hyperglycemia, overweight and insulin resistance, systemic and glomerular hypertension, dyslipidemia, sodium retention, inflammation and renal hypoxia. The recently initiated large-sized FLOW trial investigating the effects of semaglutide on hard renal outcomes in patients with DKD will provide clarity whether GLP-1 receptor agonists may reduce the burden of DKD in addition to their other beneficial metabolic and cardiovascular effects.

Liraglutide Improves the Kidney Function in a Murine Model of Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) is a global health burden, and the current treatment options only slow down the disease progression. GLP-1 receptor agonists (GLP-1 RA) have shown a renal protective effect in models of CKD; however, the mechanism behind the beneficial effect is not understood. In this study, we investigate the effect of the GLP-1 RA liraglutide in the nephrotoxic serum nephritis (NTN) CKD model. Moreover, we compare the gene expression pattern of liraglutide-treated mice to the gene expression pattern of mice treated with the angiotensin converting enzyme inhibitor, enalapril.

METHODS

The effect of liraglutide was tested in the NTN model by evaluating the glomerular filtration rate (GFR), albuminuria, mesangial expansion, renal fibrosis, and renal inflammation. Furthermore, the regulation of selected genes involved in CKD and in glomerular, cortical tubulointerstitial, and whole kidney structures was analyzed using a gene expression array on samples following laser capture microdissection.

RESULTS

Treatment with liraglutide improved CKD hallmarks including GFR, albuminuria, mesangial expansion, renal inflammation, and renal fibrosis. The gene expression revealed that both liraglutide and enalapril reversed the regulation of several fibrosis and inflammation associated genes, which are also regulated in human CKD patients. Furthermore, liraglutide and enalapril both regulated genes in the kidney involved in blood pressure control.

CONCLUSIONS

Treatment with liraglutide improved the kidney function and diminished renal lesions in NTN-induced mice. Both liraglutide and enalapril reversed the regulation of genes involved in CKD and regulated genes involved in blood pressure control.

Conservation of glucagon like peptide-1 level with liraglutide and linagilptin protects the kidney against angiotensin II-induced tissue fibrosis in rats

This study tested the hypothesis that the enhancement of glucagon-like peptide-1 (GLP-1) level through either exogenous supply of GLP-1 agonist, liraglutide or prevention of endogenous GLP-1 degradation with dipeptidyl peptidease-4 inhibitor, lingaliptin ameliorates angiotensin II (Ang II)-induced renal fibrosis. Sprague-Dawley rats were randomly divided into four groups: 0.9% saline or Ang II (500 ng/kg/min) was infused with osmotic minipumps for 4 weeks, defined as sham and Ang II groups. In drug treated groups, liraglutide (0.3 mg/kg) was injected subcutaneously twice daily or linagliptin (8 mg/kg) was administered daily via oral gavage during Ang II infusion. Compared with Ang II stimulation, liraglutide or linagliptin comparatively down-regulated the protein level of the AT₁ receptor, and up-regulated the AT₂ receptor, as identified by a reduced AT₁/AT₂ ratio (all p < 0.05), consistent with less locally-expressed AT₁ receptor and enhanced AT₂ receptor in the glomerular capillaries and proximal tubules of the renal cortex. Furthermore, both drugs significantly increased the expression of GLP-1 receptor and attenuated the protein levels of TLR4, NOX4 and IL-6. The populations of macrophages and α-SMA expressing myofibroblasts decreased with treatment of liraglutide and linagliptin, in coincidence with the reduced expression of phosphor-Smad2/3, Smad4, TGFβ1, and up-regulated Smad7. Along with these modulations, renal morphology was preserved and synthesis of fibronectin/collagen I was down-regulated, as identified by small collagen-rich area in the renal cortex. These results suggest that the preservation of GLP-1 level using liraglutide or linagliptin might be considered as an add-on therapeutic option for inhibiting Ang II induced renal fibrosis and failure.

Liraglutide Attenuates Preestablished Atherosclerosis in Apolipoprotein E-Deficient Mice via Regulation of Immune Cell Phenotypes and Proinflammatory Mediators

We have shown that the glucagon-like peptide-1 receptor agonist (GLP-1RA) liraglutide (Lir) inhibits development of early atherosclerosis in vivo by modulating immune cell function. We hypothesized that Lir could attenuate pre-established disease by modulating monocyte or macrophage phenotype to induce atheroprotective responses. Human atherosclerotic plaques obtained postendarterectomy and human peripheral blood macrophages were treated ex vivo with Lir. In parallel, apolipoprotein E-deficient (ApoE^-/-) mice received a high-fat, high-cholesterol diet to induce atherosclerosis for 8 weeks, after which ApoE^-/- mice received 300 μg/kg of Lir daily or vehicle control for a further 4 weeks to investigate the attenuation of atherosclerosis. Lir inhibited proinflammatory monocyte chemoattractant protein-1 secretion from human endarterectomy samples and monocyte chemoattractant protein-1, tumor necrosis factor-α, and interleukin (IL)-1β secretion from human macrophages after ex vivo treatment. An increase in CD206 mRNA and IL-10 secretion was also detected, which implies resolution of inflammation. Importantly, Lir significantly attenuated pre-established atherosclerosis in ApoE^-/- mice in the whole aorta and aortic root. Proteomic analysis of ApoE^-/- bone marrow cells showed that Lir upregulated the proinflammatory cathepsin protein family, which was abolished in differentiated macrophages. In addition, flow cytometry analysis of bone marrow cells induced a shift toward reduced proinflammatory and increased anti-inflammatory macrophages. We concluded that Lir attenuates pre-established atherosclerosis in vivo by altering proinflammatory mediators. This is the first study to describe a mechanism through which Lir attenuates atherosclerosis by increasing bone marrow proinflammatory protein expression, which is lost in differentiated bone marrow-derived macrophages. This study contributes to our understanding of the anti-inflammatory and cardioprotective role of GLP-1RAs. SIGNIFICANCE STATEMENT: It is critical to understand the mechanisms through which liraglutide (Lir) mediates a cardioprotective effect as many type 2 diabetic medications increase the risk of myocardial infarction and stroke. We have identified that Lir reduces proinflammatory immune cell populations and mediators from plaque-burdened murine aortas in vivo and augments proresolving bone marrow-derived macrophages in attenuation of atherosclerotic disease, which provides further insight into the atheroprotective effect of Lir.

Liraglutide Inhibits Endothelial-to-Mesenchymal Transition and Attenuates Neointima Formation after Endovascular Injury in Streptozotocin-Induced Diabetic Mice

Hyperglycaemia causes endothelial dysfunction, which is the initial process in the development of diabetic vascular complications. Upon injury, endothelial cells undergo an endothelial-to-mesenchymal transition (EndMT), lose their specific marker, and gain mesenchymal phenotypes. This study investigated the effect of liraglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist, on EndMT inhibition and neointima formation in diabetic mice induced by streptozotocin. The diabetic mice with a wire-induced vascular injury in the right carotid artery were treated with or without liraglutide for four weeks. The degree of neointima formation and re-endothelialisation was evaluated by histological assessments. Endothelial fate tracing revealed that endothelium-derived cells contribute to neointima formation through EndMT in vivo. In the diabetic mouse model, liraglutide attenuated wire injury-induced neointima formation and accelerated re-endothelialisation. In vitro, a high glucose condition (30 mmol/L) triggered morphological changes and mesenchymal marker expression in human umbilical vein endothelial cells (HUVECs), which were attenuated by liraglutide or Activin receptor-like 5 (ALK5) inhibitor SB431542. The inhibition of AMP-activated protein kinase (AMPK) signaling by Compound C diminished the liraglutide-mediated inhibitory effect on EndMT. Collectively, liraglutide was found to attenuate neointima formation in diabetic mice partially through EndMT inhibition, extending the potential therapeutic role of liraglutide.

Largest single-centre experience of dulaglutide for management of diabetes mellitus in solid organ transplant recipients

Published data regarding the approach to management of diabetes mellitus in solid organ transplant (SOT) recipients are limited. We performed a retrospective chart review of SOT recipients with diabetes, above 18 years of age, who were usisng dulaglutide. There was a sustained, statistically significant reduction in the primary endpoints of weight, body mass index (BMI) and insulin requirement in 63 SOT recipients at 6, 12 and 24 months, respectively. A total of 59, 50 and 13 recipients were followed during 6, 12 and 24 months, with a mean paired difference for weight reduction of 2.07 (P value <0.003), 4.007 (P value <0.001) and 5.23 (P value <0.034) kgs and a BMI reduction of 0.80 (P value <0.001), 1.35 (P value <0.005) and 2.015 (P value <0.045) kg/m² , respectively. The mean paired difference for insulin reduction before and after dulaglutide treatment was 5.94 units (P value <0.0002). There was no increased risk of malignancy, cardiovascular morbidity, graft-failure or all-cause mortality. Gastrointestinal manifestations were rare, even in patients with advanced chronic kidney disease (CKD), and required no change in immunosuppressive agents. Thus, dulaglutide may be considered an important option for diabetes management in SOT.

Myeloperoxidase-derived oxidants damage artery wall proteins in an animal model of chronic kidney disease-accelerated atherosclerosis

Increased myeloperoxidase (MPO) levels and activity are associated with increased cardiovascular risk among individuals with chronic kidney disease (CKD). However, a lack of good animal models for examining the presence and catalytic activity of MPO in vascular lesions has impeded mechanistic studies into CKD-associated cardiovascular diseases. Here, we show for the first time that exaggerated atherosclerosis in a pathophysiologically relevant CKD mouse model is associated with increased macrophage-derived MPO activity. Male 7-week-old LDL receptor-deficient mice underwent sham (control mice) or 5/6 nephrectomy and were fed either a low-fat or high-fat, high-cholesterol diet for 24 weeks, and the extents of atherosclerosis and vascular reactivity were assessed. MPO expression and oxidation products-protein-bound oxidized tyrosine moieties 3-chlorotyrosine, 3-nitrotyrosine, and o,o'-dityrosine-were examined with immunoassays and confirmed with mass spectrometry (MS). As anticipated, the CKD mice had significantly higher plasma creatinine, urea nitrogen, and intact parathyroid hormone along with lower hematocrit and body weight. On both the diet regimens, CKD mice did not have hypertension but had lower cholesterol and triglyceride levels than the control mice. Despite the lower cholesterol levels, CKD mice had increased aortic plaque areas, fibrosis, and luminal narrowing. They also exhibited increased MPO expression and activity (i.e. increased oxidized tyrosines) that co-localized with infiltrating lesional macrophages and diminished vascular reactivity. In summary, unlike non-CKD mouse models of atherosclerosis, CKD mice exhibit increased MPO expression and catalytic activity in atherosclerotic lesions, which co-localize with lesional macrophages. These results implicate macrophage-derived MPO in CKD-accelerated atherosclerosis.

Glycation of human serum albumin impairs binding to the glucagon-like peptide-1 analogue liraglutide

The long-acting glucagon-like peptide-1 analogue liraglutide has proven efficiency in the management of type 2 diabetes and also has beneficial effects on cardiovascular diseases. Liraglutide's protracted action highly depends on its capacity to bind to albumin via its palmitic acid part. However, in diabetes, albumin can undergo glycation, resulting in impaired drug binding. Our objective in this study was to assess the impact of human serum albumin (HSA) glycation on liraglutide affinity. Using fluorine labeling of the drug and ¹⁹F NMR, we determined HSA affinity for liraglutide in two glycated albumin models. We either glycated HSA in vitro by incubation with glucose (G25- or G100-HSA) or methylglyoxal (MGO-HSA) or purified in vivo glycated HSA from the plasma of diabetic patients with poor glycemic control. Nonglycated commercial HSA (G0-HSA) and HSA purified from plasma of healthy individuals served as controls. We found that glycation decreases affinity for liraglutide by 7-fold for G100-HSA and by 5-fold for MGO-HSA compared with G0-HSA. A similarly reduced affinity was observed for HSA purified from diabetic individuals compared with HSA from healthy individuals. Our results reveal that glycation significantly impairs HSA affinity to liraglutide and confirm that glycation contributes to liraglutide's variable therapeutic efficiency, depending on diabetes stage. Because diabetes is a progressive disease, the effect of glycated albumin on liraglutide affinity found here is important to consider when diabetes is managed with this drug.

Liraglutide dictates macrophage phenotype in apolipoprotein E null mice during early atherosclerosis

BACKGROUND

Macrophages play a pivotal role in atherosclerotic plaque development. Recent evidence has suggested the glucagon-like peptide-1 receptor (GLP-1R) agonist, liraglutide, can attenuate pro-inflammatory responses in macrophages. We hypothesized that liraglutide could limit atherosclerosis progression in vivo via modulation of the inflammatory response.

METHODS

Human THP-1 macrophages and bone marrow-derived macrophages, from both wild-type C57BL/6 (WT) and apolipoprotein E null mice (ApoE-/-) were used to investigate the effect of liraglutide on the inflammatory response in vitro. In parallel, ApoE-/- mice were fed a high-fat (60% calories from fat) high-cholesterol (1%) diet for 8 weeks to induce atherosclerotic disease progression with/without daily 300 μg/kg liraglutide administration for the final 6 weeks. Macrophages were analysed for MΦ1 and MΦ2 macrophage markers by Western blotting, RT-qPCR, ELISA and flow cytometry. Atherosclerotic lesions in aortae from ApoE-/- mice were analysed by en face staining and monocyte and macrophage populations from bone marrow derived cells analysed by flow cytometry.

RESULTS

Liraglutide decreased atherosclerotic lesion formation in ApoE-/- mice coincident with a reduction in pro-inflammatory and increased anti-inflammatory monocyte/macrophage populations in vivo. Liraglutide decreased IL-1beta in MΦ0 THP-1 macrophages and bone marrow-derived macrophages from WT mice and induced a significant increase in the MΦ2 surface marker mannose receptor in both MΦ0 and MΦ2 macrophages. Significant reduction in total lesion development was found with once daily 300 μg/kg liraglutide treatment in ApoE-/- mice. Interestingly, liraglutide inhibited disease progression at the iliac bifurcation suggesting that it retards the initiation and development of disease. These results corresponded to attenuated MΦ1 markers (CCR7, IL-6 and TNF-alpha), augmented MΦ2 cell markers (Arg-1, IL-10 and CD163) and finally decreased MΦ1-like monocytes and macrophages from bone marrow-derived cells.

CONCLUSIONS

This data supports a therapeutic role for liraglutide as an atheroprotective agent via modulating macrophage cell fate towards MΦ2 pro-resolving macrophages.

The role of endothelial nitric oxide in the anti-restenotic effects of liraglutide in a mouse model of restenosis

Background

Previous animal studies have shown that glucagon-like peptide-1 receptor agonists (GLP-1RAs) suppress arterial restenosis, a major complication of angioplasty, presumably through their direct action on vascular smooth muscle cells. However, the contribution of vascular endothelial cells (VECs) to this process remains unknown. In addition, the potential interference caused by severe hyperglycemia and optimal treatment regimen remain to be determined.

Methods

Nine-week-old male C57BL6 (wild-type) and diabetic db/db mice were randomly divided into vehicle or liraglutide treatment groups (Day 1), and subject to femoral artery wire injuries (Day 3). The injured arteries were collected on Day 29 for morphometric analysis. Human umbilical vein endothelial cells (HUVECs) were used for in vitro experiments. One-way ANOVA, followed by Tukey’s test, was used for comparisons.

Results

In wild-type mice, liraglutide treatment (5.7, 17, or 107 nmol/kg/day) dose-dependently reduced the neointimal area (20, 50, and 65%) without inducing systemic effects, and caused an associated decrease in the percentage of vascular proliferating cells. However, these effects were completely abolished by the nitric oxide synthase (NOS) inhibitor N-omega-nitro-l-arginine methyl ester. Next, we investigated the optimal treatment regimen. Early treatment (Days 1–14) was as effective in reducing the neointimal area and vascular cell proliferation as full treatment (Days 1–29), whereas delayed treatment (Days 15–29) was ineffective. In HUVECs, liraglutide treatment dose-dependently stimulated NO production, which was dependent on GLP-1R, cAMP, cAMP-dependent protein kinase, AMP-activated protein kinase (AMPK), and NOS. Subsequently, we investigated the role of liver kinase B (LKB)-1 in this process. Liraglutide increased the phosphorylation of LKB-1, and siRNA-induced LKB-1 knockdown abolished liraglutide-stimulated NO production. In severe hyperglycemic db/db mice, liraglutide treatment also suppressed neointimal hyperplasia, which was accompanied by reductions in vascular cell proliferation and density. Furthermore, liraglutide treatment suppressed hyperglycemia-enhanced vascular inflammation 7 days after arterial injury.

Conclusions

We demonstrate that endothelial cells are targets of liraglutide, and suppress restenosis via endothelial NO. Furthermore, the protective effects are maintained in severe hyperglycemia. Our findings provide an evidence base for a future clinical trial to determine whether treatment with GLP-1RAs represents potentially effective pharmacological therapy following angioplasty in patients with diabetes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0603-x) contains supplementary material, which is available to authorized users.

The GLP-1 analogue lixisenatide decreases atherosclerosis in insulin-resistant mice by modulating macrophage phenotype

AIMS/HYPOTHESIS

Recent clinical studies indicate that glucagon-like peptide-1 (GLP-1) analogues prevent acute cardiovascular events in type 2 diabetes mellitus but their mechanisms remain unknown. In the present study, the impact of GLP-1 analogues and their potential underlying molecular mechanisms in insulin resistance and atherosclerosis are investigated.

METHODS

Atherosclerosis development was evaluated in Apoe ^-/- Irs2 ^+/- mice, a mouse model of insulin resistance, the metabolic syndrome and atherosclerosis, treated with the GLP-1 analogues lixisenatide or liraglutide. In addition, studies in Apoe ^-/- Irs2 ^+/- mice and mouse-derived macrophages treated with lixisenatide were performed to investigate the potential inflammatory intracellular pathways.

RESULTS

Treatment of Apoe ^-/- Irs2 ^+/- mice with either lixisenatide or liraglutide improved glucose metabolism and blood pressure but this was independent of body weight loss. Both drugs significantly decreased atheroma plaque size. Compared with vehicle-treated control mice, lixisenatide treatment generated more stable atheromas, with fewer inflammatory infiltrates, reduced necrotic cores and thicker fibrous caps. Lixisenatide-treated mice also displayed diminished IL-6 levels, proinflammatory Ly6C^high monocytes and activated T cells. In vitro analysis showed that, in macrophages from Apoe ^-/- Irs2 ^+/- mice, lixisenatide reduced the secretion of the proinflammatory cytokine IL-6 accompanied by enhanced activation of signal transducer and activator of transcription (STAT) 3, which is a determinant for M2 macrophage differentiation. STAT1 activation, which is essential for M1 phenotype, was also diminished. Furthermore, atheromas from lixisenatide-treated mice showed higher arginase I content and decreased expression of inducible nitric oxide synthase, indicating the prevalence of the M2 phenotype within plaques.

CONCLUSIONS/INTERPRETATION

Lixisenatide decreases atheroma plaque size and instability in Apoe ^-/- Irs2 ^+/- mice by reprogramming macrophages towards an M2 phenotype, which leads to reduced inflammation. This study identifies a critical role for this drug in macrophage polarisation inside plaques and provides experimental evidence supporting a novel mechanism of action for GLP-1 analogues in the reduction of cardiovascular risk associated with insulin resistance.