Glucose-Dependent Insulinotropic Polypeptide Prevents the Progression of Macrophage-Driven Atherosclerosis in Diabetic Apolipoprotein E-Null Mice

Aim: We recently reported that glucose-dependent insulinotropic polypeptide (GIP) prevents the development of atherosclerosis in apolipoprotein E-null (Apoe 2/2) mice. GIP receptors (GIPRs) are found to be severely down-regulated in diabetic animals. We examined whether GIP can exert anti-atherogenic effects in diabetes. Methods: Nondiabetic Apoe 2/2 mice, streptozotocin-induced diabetic Apoe 2/2 mice, and db/db mice were administered GIP (25 nmol/kg/day) or saline (vehicle) through osmotic mini-pumps for 4 weeks. The animals were assessed for aortic atherosclerosis and for oxidized low-density lipoprotein-induced foam cell formation in exudate peritoneal macrophages. Results: Diabetic Apoe 2/2 mice of 21 weeks of age exhibited more advanced atherosclerosis than nondiabetic Apoe 2/2 mice of the same age. GIP infusion in diabetic Apoe 2/2 mice increased plasma total GIP levels by 4-fold without improving plasma insulin, glucose, or lipid profiles. GIP infusion significantly suppressed macrophage-driven atherosclerotic lesions, but this effect was abolished by co-infusions with [Pro 3]GIP, a GIPR antagonist. Foam cell formation was stimulated by 3-fold in diabetic Apoe 2/2 mice compared with their nondiabetic counterparts, but this effect was halved by GIP infusion. GIP infusion also attenuated the foam cell formation in db/db mice. In vitro treatment with GIP (1 nM) reduced foam cell formation by 15 % in macrophages from diabetic Apoe 2/2 mice, and this attenuating effect was weaker than that attained by the same treatment of macrophages from nondiabetic counterparts (35%). While GIPR expression was reduced by onl

Nesfatin-1 suppresses peripheral arterial remodeling without elevating blood pressure in mice

Nesfatin-1 is a novel anorexic peptide hormone that also exerts cardiovascular protective effects in rodent models. However, nesfatin-1 treatment at high doses also exerts vasopressor effects, which potentially limits its therapeutic application. Here, we evaluated the vasoprotective and vasopressor effects of nesfatin -1 at different doses in mouse models. Wild-type mice and those with the transgene nucleobindin-2, a precursor of nesfatin-1, were employed. Wild-type mice were randomly assigned to treatment with vehicle or nesfatin-1 at 0.2, 2.0 or 10 μg/kg/day (Nes-0.2, Nes-2, Nes-10, respectively). Subsequently, mice underwent femoral artery wire injury to induce arterial remodeling. After 4 weeks, injured arteries were collected for morphometric analysis. Compared with vehicle, nesfatin-1 treatments at 2.0 and 10 μg/kg/day decreased body weights and elevated plasma nesfatin-1 levels with no changes in systolic blood pressure. Furthermore, these treatments reduced neointimal hyperplasia without inducing undesirable remodeling in injured arteries. However, nesfatin-1 treatment at 0.2 μg/kg/day was insufficient to elevate plasma nesfatin-1 levels and showed no vascular effects. In nucleobindin-2- transgenic mice, blood pressure was slightly higher but neointimal area was lower than those observed in littermate controls. In cultured human vascular endothelial cells, nesfatin-1 concentration-dependently increased nitric oxide production. Additionally, nesfatin-1 increased AMP-activated protein kinase phosphorylation, which was abolished by inhibiting liver kinase B1. We thus demonstrated that nesfatin-1 treatment at appropriate doses suppressed arterial remodeling without affecting blood pressure. Our findings indicate that nesfatin-1 can be a therapeutic target for improved treatment of peripheral artery disease

Combination Therapy with a Sodium-Glucose Cotransporter 2 Inhibitor and a Dipeptidyl Peptidase-4 Inhibitor Additively Suppresses Macrophage Foam Cell Formation and Atherosclerosis in Diabetic Mice

Dipeptidyl peptidase-4 inhibitors (DPP-4is), in addition to their antihyperglycemic roles, have antiatherosclerotic effects. We reported that sodium-glucose cotransporter 2 inhibitors (SGLT2is) suppress atherosclerosis in a glucose-dependent manner in diabetic mice. Here, we investigated the effects of combination therapy with SGLT2i and DPP-4i on atherosclerosis in diabetic mice. SGLT2i (ipragliflozin, 1.0 mg/kg/day) and DPP-4i (alogliptin, 8.0 mg/kg/day), either alone or in combination, were administered to db/db mice or streptozotocin-induced diabetic apolipoprotein E-null (Apoe−/−) mice. Ipragliflozin and alogliptin monotherapies improved glucose intolerance; however, combination therapy did not show further improvement. The foam cell formation of peritoneal macrophages was suppressed by both the ipragliflozin and alogliptin monotherapies and was further enhanced by combination therapy. Although foam cell formation was closely associated with HbA1c levels in all groups, DPP-4i alone or the combination group showed further suppression of foam cell formation compared with the control or SGLT2i group at corresponding HbA1c levels. Both ipragliflozin and alogliptin monotherapies decreased scavenger receptors and increased cholesterol efflux regulatory genes in peritoneal macrophages, and combination therapy showed additive changes. In diabetic Apoe−/− mice, combination therapy showed the greatest suppression of plaque volume in the aortic root. In conclusion, combination therapy with SGLT2i and DPP4i synergistically suppresses macrophage foam cell formation and atherosclerosis in diabetic mice

Glucagon-like Peptide-1 Suppresses the Proliferation and Migration of Vascular Smooth Muscle Cells: Implications for Preventive Effects on Atherosclerosis

Our group previously demonstrated the suppressive effect of glucagon-like peptide-1 (GLP-1) on macrophage-driven atherosclerosis in apolipoprotein E-deficient (apoE-/-) mice. In the present study we investigated the suppressive effect of GLP-1 on the atherogenic phenotype of vascular smooth muscle cells (VSMCs) in vivo using apoE-/- mice, and the proliferation and migration of human VSMCs in vitro. A 4-week infusion of GLP-1 in 17-week-old apoE-/- mice significantly reduced the proliferative VSMC phenotype stained with SMemb. Platelet-derived growth factor (PDGF) -BB significantly stimulated the proliferation of human aortic VSMCs by three fold. Both 0.1 and 1nmol/l GLP-1 significantly suppressed the PDGF-induced VSMC proliferation, and this suppressive effect was significantly abolished by the GLP-1 receptor antagonist exendin (9-39) (50nmol/l). The GLP-1 receptor agonists liraglutide (100nmol/l) and exendin-4 (100nmol/l) mimicked GLP-1, significantly suppressing PDGF-induced VSMC proliferation. PDGF-BB significantly stimulated the migration of human aortic VSMCs by 1.7 -fold, and this effect was significantly suppressed by 1nmol/l GLP-1. These findings suggest that GLP-1-related treatments may prevent the progression of atherosclerotic lesions by suppressing the proliferation and migration of VSMCs, which are characteristic features of atherosclerosis

Involvement of Vascular Endothelial Cells in the Anti-atherogenic Effects of Liraglutide in Diabetic Apolipoprotein E-null Mice

Glucagon-like peptide 1 receptor agonists （GLP-1RAs） have been shown to exert anti-atherosclerotic effects via multiple mechanisms on different types of cells. However, it is unclear which of these mechanisms are crucial. We investigated the role of vascular endothelial cells （VECs） in the anti-atherogenic effects of the GLP-1RA liraglutide in a mouse model of atherosclerosis. Streptozotocin-induced diabetic apolipoprotein E-null mice were randomly assigned to treatment with either vehicle （saline） or liraglutide （107nmol/kg/day）, and were subjected to femoral artery wire injury to remove VECs. After 4 weeks, vessel samples were collected for analysis. Streptozotocin-injected mice had fasting plasma glucose levels of ＞300mg/dl and hemoglobin A1c levels of ＞9％, indicating that the injections had induced severe hyperglycemia. However, there were no differences in metabolic characteristics such as levels of hemoglobin A1c, fasting plasma glucose, total cholesterol, and triglycerides between the vehicle and liraglutide groups. Analysis of atherosclerotic plaque formation revealed that liraglutide treatment significantly suppressed plaque formation in the aorta. In addition, liraglutide treatment reduced plaque volume and intra-plaque macrophage accumulation at the aortic sinus. Furthermore, liraglutide treatment suppressed vascular expression of pro-inflammatory cytokines. In uninjured femoral arteries, no plaques were observed; however, severe plaque formation occurred in femoral arteries that had been injured by wire insertion to remove VECs. Unlike in the uninjured aorta, liraglutide treatment did not affect plaque volume or arterial remodeling （intimal and medial thinning, and arterial dilation） in wire-injured femoral arteries. Of the various cells that liraglutide affects, VECs play a central role in liraglutide’s anti-atherogenic effects in diabetic mice

Amelioration of Hyperglycemia with a Sodium-Glucose Cotransporter 2 Inhibitor Prevents Macrophage-Driven Atherosclerosis through Macrophage Foam Cell Formation Suppression in Type 1 and Type 2 Diabetic Mice.

Direct associations between hyperglycemia and atherosclerosis remain unclear. We investigated the association between the amelioration of glycemia by sodium-glucose cotransporter 2 inhibitors (SGLT2is) and macrophage-driven atherosclerosis in diabetic mice. We administered dapagliflozin or ipragliflozin (1.0 mg/kg/day) for 4-weeks to apolipoprotein E-null (Apoe-/-) mice, streptozotocin-induced diabetic Apoe-/- mice, and diabetic db/db mice. We then determined aortic atherosclerosis, oxidized low-density lipoprotein (LDL)-induced foam cell formation, and related gene expression in exudate peritoneal macrophages. Dapagliflozin substantially decreased glycated hemoglobin (HbA1c) and glucose tolerance without affecting body weight, blood pressure, plasma insulin, and lipids in diabetic Apoe-/- mice. Aortic atherosclerotic lesions, atheromatous plaque size, and macrophage infiltration in the aortic root increased in diabetic Apoe-/- mice; dapagliflozin attenuated these changes by 33%, 27%, and 20%, respectively. Atherosclerotic lesions or foam cell formation highly correlated with HbA1c. Dapagliflozin did not affect atherosclerosis or plasma parameters in non-diabetic Apoe-/- mice. In db/db mice, foam cell formation increased by 4-fold compared with C57/BL6 mice, whereas ipragliflozin decreased it by 31%. Foam cell formation exhibited a strong correlation with HbA1c. Gene expression of lectin-like ox-LDL receptor-1 and acyl-coenzyme A:cholesterol acyltransferase 1 was upregulated, whereas that of ATP-binding cassette transporter A1 was downregulated in the peritoneal macrophages of both types of diabetic mice. SGLT2i normalized these gene expressions. Our study is the first to demonstrate that SGLT2i exerts anti-atherogenic effects by pure glucose lowering independent of insulin action in diabetic mice through suppressing macrophage foam cell formation, suggesting that foam cell formation is highly sensitive to glycemia ex vivo

Expression of GIPR in exudate peritoneal macrophages from nondiabetic and diabetic <i>Apoe</i>^−/− mice.

<p>GIPR was stained with goat polyclonal anti-GIPR antibody followed by anti-goat Alexa Fluor 568. Phalloidin/DAPI staining shows F-actin cytoskeleton and nuclear morphology of mouse macrophages. These images were merged. Representative results are shown.</p

Suppressive effects of GIP on the progression of atherosclerotic lesions in diabetic <i>Apoe</i>^−/− mice.

<p>Thirty-five mice at 15 weeks of age were made diabetes by peritoneal injection of STZ (50 mg/kg/day) for 5 days and 14 mice were untreated. The 17-week-old diabetic <i>Apoe</i>^−/− mice were infused for 4 weeks with vehicle (control), GIP (25 nmol/kg/day), or GIP+[Pro³]GIP (both 25 nmol/kg/day) by osmotic mini-pumps. The aortic surface was stained with oil red O. Cross-sections of the aortic root were stained with oil red O or anti-MOMA-2 antibody. Hematoxylin was used for nuclear staining. The areas occupied by atherosclerotic lesions and by macrophage infiltration in the aortic wall were determined.</p

A Dipeptidyl Peptidase-4 Inhibitor Suppresses Macrophage Foam Cell Formation in Diabetic db/db Mice and Type 2 Diabetes Patients

Dipeptidyl peptidase-4 (DPP-4) inhibitors could have antiatherosclerotic action, in addition to antihyperglycemic roles. Because macrophage foam cells are key components of atherosclerosis, we investigated the effect of the DPP-4 inhibitor teneligliptin on foam cell formation and its related gene expression levels in macrophages extracted from diabetic db/db (C57BLKS/J Iar -+Leprdb/+Leprdb) mice and type 2 diabetes (T2D) patients ex vivo. We incubated mouse peritoneal macrophages and human monocyte-derived macrophages differentiated by 7-day culture with oxidized low-density lipoprotein in the presence/absence of teneligliptin (10 nmol/L) for 18 hours. We observed remarkable suppression of foam cell formation by teneligliptin treatment ex vivo in macrophages isolated from diabetic db/db mice (32%) and T2D patients (38%); this effect was accompanied by a reduction of CD36 (db/db mice, 43%; T2D patients, 46%) and acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) gene expression levels (db/db mice, 47%; T2D patients, 45%). Molecular mechanisms underlying this effect are associated with downregulation of CD36 and ACAT-1 by teneligliptin. The suppressive effect of a DPP-4 inhibitor on foam cell formation in T2D is conserved across species and is worth studying to elucidate its potential as an intervention for antiatherogenesis in T2D patients

General characteristics and plasma measurements.

a<p> = vs. Nondiabetic,</p>b<p> = vs. Diabetic,</p>c<p> = Diabetic GIP at <i>P</i><0.001–0.05.</p