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Aim Glucagon-like peptide-1 (GLP1) is known to decrease glucagon release and may be beneficial for the reduction of elevated blood glucose. However, its role and mechanism of action in diabetes remain elusive. This study aimed to examine the function of GLP1 and analyze the mechanism of effect that GLP1exerts on inducible nitric oxide synthase (iNOS) in diabetic mice. Methods A diabetes model was established in ApoE-/- mice fed a high-fat diet and treated with GLP1 and/or lentivirus-expressing PARP1. PARP1, iNOS, and inflammatory factors in islets were detected by Western blot and ELISA. Islet α cells and β cells and CD8+ T lymphocytes were detected by immunostaining. Islet-cell apoptosis was detected by TUNEL. Results GLP1 inhibited the expression of PARP1 and iNOS in islets, alleviated decrease in β cells, and suppressed cell apoptosis induced by the high-fat diet. Moreover, GLP1 recovered the decline in insulin sensitivity and glucose tolerance in ApoE-/- mice fed the high-fat diet, and the effects of GLP1 were related to the inhibition of COX2 and NFκB expression. Conclusion GLP1 significantly alleviated the decrease in β-cell numbers, suppressed β-cell apoptosis induced by the high-fat diet, inhibited the expression of iNOS, and alleviated inflammatory islet injury via inhibiting the COX2-NFκB pathway.

Cardiac fibrosis is a key factor to determine the prognosis in patient with myocardial infarction (MI). The aim of this study is to investigate whether the transcriptional factor paired‐related homeobox 2 (Prrx2) regulates Wnt5a gene expression and the role in myocardial fibrosis following MI. The MI surgery was performed by ligation of left anterior descending coronary artery. Cardiac remodelling was assessed by measuring interstitial fibrosis performed with Masson staining. Cell differentiation was examined by analysis the expression of alpha‐smooth muscle actin (α‐SMA). Both Prrx2 and Wnt5a gene expressions were up‐regulated in mice following MI, accompanied with increased mRNA and protein levels of α‐SMA, collagen I and collagen III, compared to mice with sham surgery. Adenovirus‐mediated gene knock down of Prrx2 increased survival rate, alleviated cardiac fibrosis, decreased infarction sizes and improved cardiac functions in mice with MI. Importantly, inhibition of Prrx2 suppressed ischaemia‐induced Wnt5a gene expression and Wnt5a signalling. In cultured cardiac fibroblasts, TGF‐β increased gene expressions of Prrx2 and Wnt5a, and induced cell differentiations, which were abolished by gene silence of either Prrx2 or Wnt5a. Further, overexpression of Prrx2 or Wnt5a mirrored the effects of TGF‐β on cell differentiations of cardiac fibroblasts. Gene silence of Wnt5a also ablated cell differentiations induced by Prrx2 overexpression in cardiac fibroblasts. Mechanically, Prrx2 was able to bind with Wnt5a gene promoter to up‐regulate Wnt5a gene expression. In conclusions, targeting Prrx2‐Wnt5a signalling should be considered to improve cardiac remodelling in patients with ischaemic heart diseases.

Apoptosis is a key event involved in diabetic cardiomyopathy. The expression of high mobility group box 1 protein (HMGB1) is up-regulated in diabetic mice. However, the molecular mechanism of high glucose (HG)-induced cardiomyocyte apoptosis remains obscure. We aimed to determine the role of HMGB1 in HG-induced apoptosis of cardiomyocytes. Treating neonatal primary cardiomyocytes with HG increased cell apoptosis, which was accompanied by elevated levels of HMGB1. Inhibition of HMGB1 by short-hairpin RNA significantly decreased HG-induced cell apoptosis by reducing caspase-3 activation and ratio of Bcl2-associated X protein to B-cell lymphoma/leukemia-2 (bax/bcl-2). Furthermore, HG activated E26 transformation-specific sequence-1 (Ets-1), and HMGB1 inhibition attenuated HG-induced activation of Ets-1 via extracellular signal-regulated kinase 1/2 (ERK1/2) signalling. In addition, inhibition of Ets-1 significantly decreased HG-induced cardiomyocyte apoptosis. Similar results were observed in streptozotocin-treated diabetic mice. Inhibition of HMGB1 by short-hairpin RNA markedly decreased myocardial cell apoptosis and activation of ERK and Ets-1 in diabetic mice. In conclusion, inhibition of HMGB1 may protect against hyperglycaemia-induced cardiomyocyte apoptosis by down-regulating ERK-dependent activation of Ets-1.

Basal and adaptive β-cell regeneration capacity declines with old age, but the underlying molecular mechanisms remain incompletely understood. Poly (adenosine diphosphate [ADP]-ribose) polymerase 1 (PARP-1) is considered a multifunctional enzyme and transcription factor that regulates pancreatic β-cell death, regeneration and insulin secretion. We analyzed the capacity of β-cell regeneration in 2-month-old (young) and 12-month-old (old) wild-type (WT) and PARP-1⁻/⁻ mice before and after low-dose streptozotocin (STZ), a stimulus of β-cell regeneration and the underlying mechanism. Before STZ administration, young WT and PARP-1⁻/⁻ mice showed similar β-cell proliferation. By contrast, old WT but not old PARP-1⁻/⁻ mice showed severely restricted β-cell proliferation. In further assessment of the adaptive β-cell regeneration capacity with age, we observed that with a single low dose of STZ, young WT and PARP-1⁻/⁻ mice showed a similar increase in β-cell proliferation, with few changes in old WT mice. Surprisingly, adaptive β-cell proliferation capacity was significantly higher in old PARP-1⁻/⁻ mice than old WT mice after STZ administration. The ability of β-cell mass to expand was associated with increased levels of the regenerating (Reg) genes RegI and RegII but not RegIV. Therefore, PARP-1 is a key regulator in β-cell regeneration with advancing age in mice.

Atherosclerosis begins as local inflammation of arterial walls at sites of disturbed flow, such as vessel curvatures and bifurcations with low shear stress. c-Jun NH2-terminal kinase (JNK) is a major regulator of flow-dependent gene expression in endothelial cells in atherosclerosis. However, little is known about the in vivo role of JNK in low shear stress in atherosclerosis. We aimed to observe the effect of JNK on low shear stress-induced atherogenesis in apolipoprotein E-deficient (ApoE−/−) mice and investigate the potential mechanism in human umbilical vein endothelial cells (HUVECs). We divided 84 male ApoE−/− mice into two groups for treatment with normal saline (NS) (n = 42) and JNK inhibitor SP600125 (JNK-I) (n = 42). Perivascular shear stress modifiers were placed around the right carotid arteries, and plaque formation was studied at low shear stress regions. The left carotid arteries without modifiers represented undisturbed shear stress as a control. The NS group showed atherosclerotic lesions in arterial regions with low shear stress, whereas the JNK-I group showed almost no atherosclerotic lesions. Corresponding to the expression of proatherogenic vascular cell adhesion molecule 1 (VCAM-1), phospho-JNK (p-JNK) level was higher in low shear stress regions with NS than with JNK-I inhibitor. In HUVECs under low shear stress, siRNA knockdown and SP600125 inhibition of JNK attenuated nuclear factor (NF)-κB activity and VCAM-1 expression. Furthermore, siRNA knockdown of platelet endothelial cell adhesion molecule 1 (PECAM-1) (CD31) reduced p-JNK and VCAM-1 levels after low shear stress stimulation. JNK may play a critical role in low shear stress-induced atherogenesis by a PECAM-1-dependent mechanosensory pathway and modulating NF-κB activity and VCAM-1 expression.

Background High-mobility group box 1 (HMGB1) is an important mediator of the inflammatory response. Its expression is increased in diabetic cardiomyopathy (DCM), but its role is unclear. We investigated the potential role and mechanism of HMGB1 in diabetes-induced myocardial fibrosis and dysfunction in mice. Methods In vivo , type 1 diabetes was induced by streptozotocin (STZ) in mice. HMGB1 expression was knocked down by lentivirus-mediated short-hairpin RNA (shRNA). Cardiac function was assessed by echocardiography. Total collagen deposition was assessed by Masson's trichrome and Picrosirius red staining. HMGB1, collagen I and III, and transforming growth factor β1 (TGF-β1) expression was quantified by immunostaining and western bolt analysis. In vitro , isolated neonatal cardiac fibroblasts were treated with high glucose (HG) or recombinant HMGB1 (rHMGB1). Pharmacologic (neutralizing anti-HMGB1 antibody) or genetic (shRNA-HMGB1) inhibition of HMGB1 was used to investigate the role of HMGB1 in HG-induced functional changes of cardiac fibroblasts. Results In vivo , HMGB1 was diffusely expressed in the myocardium of diabetic mice. HMGB1 silencing ameliorated left ventricular dysfunction and remodeling and decreased collagen deposition in diabetic mice. In vitro , HG induced HMGB1 translocation and secretion in both viable cardiomyocytes and fibroblasts. Administration of rHMGB1 dose-dependently increased the expression of collagens I and III and TGF-β1 in cardiac fibroblasts. HMGB1 inhibition reduced HG-induced collagen production, matrix metalloproteinase (MMP) activities, proliferation, and activated mitogen-activated protein kinase signaling in cardiac fibroblasts. Conclusions HMGB1 inhibition could alleviate cardiac fibrosis and remodeling in diabetic cardiomyopathy. Inhibition of HMGB1 might have therapeutic potential in the treatment of the disease.

Objective— Inflammation plays an important role in atherosclerosis. Arginase I (Arg I) promotes the proliferation of vascular smooth muscle cells; however, the effect of Arg I on inflammation remains unknown. The present study investigated the role of Arg I in inflammation in vitro and in vivo. Methods and Results— Quantitative reverse transcription–polymerase chain reaction and Western blot analysis demonstrated that Arg I inhibited tumor necrosis factor-α production induced by lipopolysaccharide in human aortic smooth muscle cells. Inducible nitric oxide synthase substrate competition and nuclear factor-κB activation were main contributors to lipopolysaccharide-mediated inflammatory cytokine generation. However, Arg I could attenuate the function of inducible nitric oxide synthase and inhibit the subsequent nuclear factor-κB activation, leading to inhibition of tumor necrosis factor-α generation. Furthermore, upregulation of Arg I significantly decreased macrophage infiltration and inflammation in atherosclerotic plaque of rabbits, whereas downregulation of Arg I aggravated these adverse effects. Conclusion— The results indicate the antiinflammatory effects of Arg I and suggest an unexpected beneficial role of Arg I in inflammatory disease.

Although serum amyloid A (SAA) is an excellent marker for coronary artery disease, its direct effect on atherogenesis in vivo is obscure. In this study we investigated the direct effect of SAA on promoting the formation of atherosclerosis in apolipoprotein E-deficient (ApoE−/−) mice. Murine SAA lentivirus was constructed and injected into ApoE−/− mice intravenously. Then, experimental mice were fed a chow diet (5% fat and no added cholesterol) for 14 wks. The aortic atherosclerotic lesion area was larger with than without SAA treatment. With increased SAA levels, the plasma levels of interleukin-6 and tumor necrosis factor-α were significantly increased. Macrophage infiltration in atherosclerotic regions was enhanced with SAA treatment. A migration assay revealed prominent dose-dependent chemotaxis of SAA to macrophages. Furthermore, the expression of monocyte chemotactic protein-1 and vascular cell adhesion molecule-1 (VCAM-1) was upregulated significantly with SAA treatment. SAA-induced VCAM-1 production was detected in human aortic endothelial cells in vitro. Thus, an increase in plasma SAA directly accelerates the progression of atherosclerosis in ApoE−/− mice. SAA is not only a risk marker for atherosclerosis but also an active participant in atherogenesis.

Increasing studies suggest that the activity of GLP-1 might be of significant importance in the development of type 2 diabetes beyond its serum glucose-lowering effects. However, to date, the anti-apoptosis mechanism by which GLP-1 acts on MILE SVEN 1 (MS-1) cells has not been fully explored with regard to the intracellular signaling pathway. Increasing evidence shows that apoptosis of islet microvascular endothelial cells (IMECs) participates in the pathogenesis of diabetes. We wondered whether GLP-1 exerts its anti-apoptosis effects by inactivating the PARP-1/iNOS/NO pathway in oxidized low-density-lipoprotein (oxLDL)-induced apoptosis in mouse IMECs (MS-1 cells), which may linked to GLP-1R/cAMP levels. MTT assay revealed that 2-h pre-incubation with GLP-1 markedly restored the oxLDL-induced loss of MS-1 viability in a concentration-dependent manner. This effect was accompanied by a significant decrease in intracellular nitric oxide (NO) activity. Moreover, GLP-1 suppressed lipid peroxidation, restored the activities of endogenous antioxidants, and decreased the level of NO. Pre-incubating MS-1 cells with GLP-1 reduced cell apoptosis. Finally, GLP-1 could efficiently prevent the upregulation of poly(ADP-ribose) polymerase-1/nitrotyrosine and inducible NO synthase protein. Simultaneously, the expression of GLP-1 receptor and the level of cAMP was consistent with the administration of GLP-1. Our findings suggest that GLP-1 can effectively protect MS-1 cells against oxLDL-induced apoptosis, which may be important in preventing the pathogenesis of diabetes mellitus.

Lipid peroxidation plays a critical role in cardiovascular diseases. Aldehydes are the major end products of lipid peroxidation and can be metabolized into less reactive chemical species by aldehyde dehydrogenase 2 (ALDH2). However, ALDH2 dehydrogenase activity can be affected by many factors including reactive oxygen species. To elucidate how reactive oxygen species inhibit ALDH2 dehydrogenase activity, we stimulated human aortic endothelial cells (HAECs) with oxidized low-density lipoproteins (ox-LDL) and performed a myocardial ischemia–reperfusion model. Ox-LDL treatment and ischemia–reperfusion injury inhibited ALDH2 dehydrogenase activity. Poly(ADP-ribose) polymerase (PARP) was activated by ox-LDL stimulation and ischemia–reperfusion injury and PARP inhibition partly restored ALDH2 dehydrogenase activity in ox-LDL treated HAECs and ischemia–reperfusion rat hearts. SIRT3 was upregulated by ox-LDL stimulation and ischemia–reperfusion injury and downregulated by PARP inhibition. Using siRNA to knock down SIRT3, we demonstrated that SIRT3 mediated deacetylation decreased ALDH2 dehydrogenase activity and PARP inhibition partly restored ALDH2 dehydrogenase activity through preventing SIRT3 expression and subsequently preserving ALDH2 acetylation.