Transcriptional patterns of human retinal pigment epithelial cells under protracted high glucose.

BACKGROUND: The retinal pigment epithelium (RPE) is essential for retinal homeostasis. Comprehensively exploring the transcriptional patterns of diabetic human RPE promotes the understanding of diabetic retinopathy (DR). METHODS AND RESULTS: A total of 4125 differentially expressed genes (DEGs) were screened out from the human primary RPE cells subjected to prolonged high glucose (HG). The subsequent bioinformatics analysis is divided into 3 steps. In Step 1, 21 genes were revealed by intersecting the enriched genes from the KEGG, WIKI, and Reactome databases. In Step 2, WGCNA was applied and intersected with the DEGs. Further intersection based on the enrichments with the GO biological processes, GO cellular components, and GO molecular functions databases screened out 12 candidate genes. In Step 3, 13 genes were found to be simultaneously up-regulated in the DEGs and a GEO dataset involving human diabetic retinal tissues. VEGFA and ERN1 were the 2 starred genes finally screened out by overlapping the 3 Steps. CONCLUSION: In this study, multiple genes were identified as crucial in the pathological process of RPE under protracted HG, providing potential candidates for future researches on DR. The current study highlights the importance of RPE in DR pathogenesis.

VK2 Promotes Osteogenic Differentiation of BMSCs against High Glucose Exposure via Modulation of Intracellular Oxidative Stress.

INTRODUCTION: Diabetic osteoporosis (DOP) has gradually gained public attention. The clinical manifestations of DOP include bone mass loss, bone microstructural damage, and increased bone fragility.

Linc279227 contributes to mitochondrial dysfunction in high glucose-treated mouse renal tubular epithelial cells.

BACKGROUND: The aberrant expression of long noncoding RNAs (lncRNAs) has been associated with diabetic nephropathy (DN), a major complication of diabetes mellitus (DM). This study investigated the differential expression of lncRNAs in DM without renal damage and DM with renal damage, known as DN, and elucidated the functions of a pathogenic lncRNA. METHODS: High-throughput sequencing was performed on the kidneys of male db/db mice with kidney injury, db/db mice without kidney involvement and db/m control littermates. Linc279227 expression was confirmed by RT‒qPCR and fluorescence in situ hybridization. The effects of linc279227 on high glucose (HG)-treated renal tubular epithelial cells (RTECs) were evaluated by autophagy flux monitoring, Western blot determination and mitochondrial morphological detection. RESULTS: With high-throughput sequencing, we identified a 1024 nt long intergenic noncoding RNA, TCONS_00279227 (linc279227), whose expression was markedly increased in the kidneys of db/db mice with kidney injury compared to db/db mice without kidney injury and db/m control littermates. Fluorescence in situ hybridization confirmed that linc279227 was mainly located in the renal tubules of mice with DN. In vitro, linc279227 expression was found to be significantly increased in RTECs treated with high glucose (HG) for 48 h. Silencing linc279227 markedly restored the levels of autophagy-/mitophagy-associated proteins in HG-stimulated RTECs. Furthermore, silencing linc279227 reduced phosphorylated Drp1 expression and increased Mfn2 expression in RTECs exposed to HG. CONCLUSION: Our data suggest that linc279227 plays an important role in mitochondrial dysfunction in HG-treated RTECs and that silencing linc279227 rescues RTECs exposed to HG.

Empagliflozin activates JAK2/STAT3 signaling and protects cardiomyocytes from hypoxia/reoxygenation injury under high glucose conditions.

The morbidity and mortality rates of cardiovascular disease are markedly higher in patients with diabetes than in non-diabetic patients, including patients with ischemia-reperfusion injury (IRI). However, the cardiovascular protective effects of Empagliflozin (EMPA) on IRI in diabetes mellitus have rarely been studied. In this study, we established a cardiomyocyte hypoxia/reoxygenation (H/R) injury model to mimic myocardial I/R injuries that occur in vivo. H9C2 cells were subjected to high glucose (HG) treatment plus H/R injury to mimic myocardial I/R injuries that occur in diabetes mellitus. Next, different concentrations of EMPA were added to the H9C2 cells and its protective effect was detected. STAT3 knockdown with recombinant plasmids was used to determine its roles. Our results showed that H/R injury-induced cell apoptosis, necroptosis, oxidative stress, and endoplasmic reticulum stress were further promoted by HG conditions, and HG treatment plus an H/R injury inhibited the activation of JAK2/STAT3 signaling. EMPA was found to protect against H/R-induced cardiomyocyte injury under HG conditions and activate JAK2/STAT3 signaling, while down-regulation of STAT3 reversed the protective effect of EMPA. When taken together, these findings indicate that EMPA protects against I/R-induced cardiomyocyte injury by activating JAK2/STAT3 signaling under HG conditions. Our results clarified the mechanisms that underlie the cardiovascular protective effects of EMPA in diabetes mellitus and provide new therapeutic targets for IRI in diabetes mellitus.

Ginsenoside Rg1 attenuates the inflammation and oxidative stress induced by diabetic nephropathy through regulating the PI3K/AKT/FOXO3 pathway.

BACKGROUND: Diabetic nephropathy (DN) is one of the most common microvascular complications in diabetes mellitus. Ginsenoside Rg1 (Rg1) is an important active ingredient extracted from Panax ginseng. This study aimed to investigate the role and molecular mechanism of Rg1 in DN model. METHODS: The mesangial cell line HBZY-1 was induced by high glucose (HG; 30 mM D-glucose). HG-induced HBZY-1 cells were treated with Rg1 (2.5, 5, 10 µmol/L). Cell viability was measured by the MTT assay. Apoptosis was detected by flow cytometry. Related proteins were measured by western blot. Reactive oxygen species (ROS) production was measured by dichlorodihydrofluorescein diacetate (DCFH-DA). Inflammatory factors and molecules associated with oxidative stress were detected by enzyme-linked immunoassay (ELISA). DN rats model were treated with 50mg/kg/d Rg1 for 8 weeks, the histopathological changes and the expression of relevant markers were analyzed. RESULTS: We found that Rg1 treatment markedly elevated the survival rates of HG-induced HBZY-1 cells and reduced apoptosis induced by HG. Rg1 treatment attenuated the HG-induced inflammatory response by decreasing the high levels of TNF-α, IL-1ß, and IL-6. Furthermore, Rg1 treatment alleviated HG-induced oxidative stress by decreasing ROS generation, malondialdehyde (MDA), and lactate dehydrogenase (LDH) accumulation and increasing the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). After Rg1 (50 mg/kg/d) treatment, the severe glomerular thylakoid hyperplasia, glomerular atrophy, tubule dermal cell exfoliation, basement membrane exposure, interstitial edema and inflammatory cell cytoplasmic infiltration were alleviated in DN rats. DN rat model treated with Rg1 (50 mg/kg/d) showed good anti-inflammatory and antioxidant activities. Rg1 treatment also increased the levels of the phosphorylation of PI3K (p-PI3K) and AKT (p-AKT) and promoted the transfer of FOXO3 from the nucleus to the cytoplasm in vitro and in vivo. CONCLUSIONS: Rg1 exhibited protective effects on DN-induced inflammatory responses and oxidative stress via regulating the PI3K/AKT/FOXO3 pathway in in vitro and in vivo. The results suggest that Rg1 may be a potential therapeutic agent for DN treatment.

Ephrin B2 mediates high glucose induced endothelial-to-mesenchymal transition in human aortic endothelial cells.

BACKGROUND: Previous study revealed that high glucose (HG) induced endothelial cell (EC) damage via endothelial-to-mesenchymal transition (EndMT). Recent studies suggested the role of Ephrin B2 in mediate ECs damage. However, the underlying mechanism remains unclear. The aim of the present study was to investigate whether Ephrin B2 mediates HG-induced EndMT in human aortic ECs (HAECs) and to determine the possible downstream signaling effector. METHODS: Primary HAECs were exposed to normal glucose (NG, 5.5 mM), HG (30 mM) and HG+Ephrin B2 small interfering RNA (siRNA), respectively. The pathological changes were investigated by light microscope and confocal microscopy. To study the effects of focal adhesion kinase (FAK) activation on Ephrin B2 in HAECs, cells were incubated with FAK siRNA in HG group. The expression of EndMT-related markers (CD31 and FSP1), Ephrin B2 and FAK were detected by qRT-PCR and western blot. RESULTS: The results showed that HG significantly inhibited the expression of CD31 and increased FSP1 compared with NG group. Moreover, Ephrin B2 was increased after HG incubation. Ephrin B2 siRNA attenuated HG-induced expression of EndMT-related markers. Furthermore, HG increased the expression of FAK and phosphorylated FAK (pho-FAK) in HAECs. In contrast, blocking Ephrin B2 could partially attenuate HG-induced FAK activation. And FAK siRNA further inhibited the EndMT-related markers in HAECs treated with HG. CONCLUSIONS: HG-induced EndMT in HAECs might be partially mediated by Ephrin B2 and the downstream FAK pathway.

LncRNA ANRIL Silencing Alleviates High Glucose-Induced Inflammation, Oxidative Stress, and Apoptosis via Upregulation of MME in Podocytes.

Diabetic nephropathy (DN), characterized by glomerular injury, is a common complication of both type 1 and type 2 diabetes, accompanied by massive proteinuria. Podocytes are reported to play pivotal roles in maintaining the glomerular filtration barrier. In addition, the expression of long non-coding RNAs (lncRNAs) ANRIL was upregulated in type 2 diabetes patients. Hence, the aim of this study was to investigate the underlying mechanisms implicated the role of LncRNA ANRIL in podocyte injury in DN. The concentration of inflammatory cytokines was quantified by the corresponding enzyme-linked immunosorbent assay (ELISA) kits. The mRNA levels of the target gene were determined by reverse transcription and real-time quantitative PCR (RT-qPCR). The expressions of proteins were evaluated by Western blot. The activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), and malondialdehyde (MDA) level were measured by corresponding commercial kits. Finally, the apoptosis of podocytes was analyzed by TUNEL assay. In our study, LncRNA ANRIL was highly expressed in high glucose (HG)-induced podocytes. Moreover, LncRNA ANRIL silencing attenuated HG-induced inflammation, oxidative stress, and apoptosis and induced MME overexpression in podocytes. Interestingly, MME knockdown abolished the suppressive effect of LncRNA ANRIL silencing on HG-induced inflammation, oxidative stress, and apoptosis in podocytes. LncRNA ANRIL silencing alleviates HG-induced inflammation, oxidative stress, and apoptosis via upregulation of MME in podocytes. Hence, LncRNA ANRIL may be a novel and effective target to ameliorate podocyte injury in DN.

miR-503/Apelin-12 mediates high glucose-induced microvascular endothelial cells injury via JNK and p38MAPK signaling pathway.

INTRODUCTION: Diabetic patients are often accompanied by complications of diabetic vascular disease, which could lead to heart failure or stroke. In this work, we explored the role of miR-503/Apelin-12 in diabetic angiopathy (DA) in vitro. METHODS: ELISA and qPCR were applied to assess the expression of miR-503 and Apelin-12 in high glucose (HG)-treated microvascular endothelial cells (HMEC-1). The effects of miR-503 on apoptosis, inflammation and oxidative stress were assessed by flow cytometry, western blotting, qPCR, and ELISA. The interaction between miR-503 and Apelin-12 was evaluated by dual-luciferase reporter assay, qPCR and ELISA, respectively. Western blotting was performed to examine the function of miR-503/Apelin-12 on JNK and p38MAPK activation. RESULTS: MiR-503 was markedly increased and Apelin-12 was decreased in HG-treated HMEC-1 cells. MiR-503 inhibitor significantly assuaged apoptosis, inflammation and oxidative stress in HMEC-1 cells. MiR-503 could specifically bind to the 3'UTR of Apelin and inversely downregulate Apelin-12 expression. Furthermore, Apelin-12 suppressed apoptosis, inflammation and oxidative stress. Inhibition of Apelin-12 could partially reverse the decrease of p-JNK and p-p38 expression levels induced by miR-503 suppression. CONCLUSION: In HG-induced microvascular cells injury, miR-503/Apelin-12 enhances inflammation and oxidative stress by regulating JNK and p38MAPK pathway, suggesting a potential therapeutic target for DA.

FOXP1 inhibits high glucose-induced ECM accumulation and oxidative stress in mesangial cells.

Diabetic nephropathy (DN) is a common complication of diabetes that remains the major cause of end-stage renal disease (ESRD). Forkhead box P1 (FOXP1) is a member of FOX family involved in the progression of diabetes. However, the pathogenic role of FOXP1 in DN remains unclear. This study was aimed to explore the effects of FOXP1 on glomerular mesangial cells (MCs) in response to high glucose (HG) stimulation. We found that HG stimulation markedly inhibited the FOXP1 expression in MCs in dose-and time-dependent manner. CCK-8 assay proved that FOXP1 overexpression attenuated HG-induced cell proliferation in MCs. FOXP1 exhibited anti-oxidative activity in HG-induced MCs, as proved by the decreased production of ROS and expressions of ROS producing enzymes, NADPH oxidase (NOX) 2 and NOX4. Besides, FOXP1 suppressed the expression and secretion of extracellular matrix (ECM) proteins including collagen IV (Col IV) and fibronectin (FN). Furthermore, FOXP1 overexpression significantly prevented HG-induced activation of Akt/mTOR signaling in MCs, and Akt activator blocked FOXP1-mediated cell proliferation, ROS production and ECM accumulation in MCs. Collectively, FOXP1 prevented HG-induced proliferation, oxidative stress, and ECM accumulation in MCs via inhibiting the activation of Akt/mTOR signaling pathway. The findings suggested that FOXP1 might be a therapeutic target for the treatment of DN.

CTRP3 inhibits high glucose-induced oxidative stress and apoptosis in retinal pigment epithelial cells.

Diabetic retinopathy (DR) is one of the most common diabetic complications and remains the leading cause of vision loss among adults. C1q/TNF-related protein 3 (CTRP3) is a member of CTRP family that has been found to be involved in the progression of diabetes mellitus and diabetic complications. However, the role of CTRP3 in DR has not been fully understood. In the present study, the results showed that CTRP3 expression was significantly decreased in DR patients compared with controls. In vitro investigations proved that overexpression of CTRP3 improved cell viability of ARPE-19 cells in response to high glucose (HG) stimulation. CTRP3 also attenuated HG-induced oxidative stress in ARPE-19 cells with decreased levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and increased superoxide dismutase (SOD) activity. Apoptotic rate was significantly decreased in CTRP3 overexpressing ARPE-19 cells. Besides, bcl-2 expression was increased, while bax expression was decreased by CTRP3 overexpression. Moreover, overexpression of CTRP3 enhanced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway in HG-stimulated ARPE-19 cells, and Nrf2 knockdown reversed CTRP3-mediated oxidative stress and apoptosis. These findings suggested that CTRP3 attenuated HG-stimulated oxidative stress and apoptosis in ARPE-19 cells, which were mediated by activation of Nrf2/HO-1 pathway.

Reduced chemotherapeutic sensitivity in high glucose condition: implication of antioxidant response.

Resistance to chemotherapy represents a major obstacle to successful treatment. The generation of reactive oxygen species (ROS) has been directly linked to the cytotoxic effects of several antitumor agents, including Adriamycin (ADR), and modulation of the oxidative balance has been implicated in the development and/or regulation of resistance to chemotherapeutic drugs. We recently showed that high glucose (HG) markedly diminished the cancer cell death induced by anticancer agents such as ADR. In the present study we attempted to evaluate the mechanism that impaired the cytotoxic effect of ADR in HG. We found that, in colon cancer cells, HG attenuated ADR-induced ROS production that consequently diminished ADR-induced H2AX phosphorylation and micronuclei (MN) formation. Mechanistically, HG attenuation of ADR-induced ROS production correlated with increased antioxidant response promoted by NRF2 activity. Thus, pharmacologic inhibition of NRF2 pathway by brusatol re-established the ADR cytotoxic effect impaired by HG. Together, the data provide new insights into chemotherapeutic-resistance mechanisms in HG condition dictated by increased NRF2-induced antioxidant response and how they may be overcome in order to restore chemosensitivity and ADR-induced cell death.

Eriodictyol inhibits high glucose-induced extracellular matrix accumulation, oxidative stress, and inflammation in human glomerular mesangial cells.

Diabetic nephropathy (DN) is one of the major complications of diabetes mellitus. The progression of DN has been found to be associated with high glucose (HG)-induced oxidative stress and inflammation in diabetes mellitus. Eriodictyol is a flavonoid that possesses antioxidant and anti-inflammatory effects. However, the effect of eriodictyol on DN remains unknown. In the present study, we evaluated the role of eriodictyol in mesangial cells (MCs) in response to HG condition. The results showed that eriodictyol repressed cell proliferation of HG-stimulated MCs. Treatment with eriodictyol attenuated oxidative stress, which was evidenced by increased superoxide dismutase activity as well as decreased production of reactive oxygen species (ROS) and malondialdehyde. Besides, eriodictyol suppressed the expressions of two NADPH oxidase (NOX) isoforms, NOX2 and NOX4, which are responsible for the generation of ROS. Eriodictyol suppressed the production of extracellular matrix proteins including fibronectin and Collagen IV, as well as the secretion of inflammatory cytokines including TNF-α, IL-1ß, and IL-6 in HG-induced MCs. Moreover, the HG-induced activation of Akt/NF-κB pathway was mitigated by eriodictyol. In conclusion, eriodictyol protected MCs from HG stimulation though inhibition of Akt/NF-κB pathway.

MiR-137 Restricts the Viability and Migration of HTR-8/SVneo Cells by Downregulating FNDC5 in Gestational Diabetes Mellitus.

BACKGROUND: An increasing number of studies have described the pathological changes of placenta tissues in gestational diabetes mellitus (GDM), although the underlying mechanisms involved in this process remain uncertain. The aim of the present study was to verify the possible role of microRNA-137 (miR)-137 and FNDC5 in regulating the biological function of trophoblasts in high glucose (HG) conditions during the GDM period. METHODS: Expression levels of miR-137 and FNDC5 were measured in placenta specimens, the HG-treated trophoblast cell line HTR-8/SVneo and miR-137- overexpressing HTR-8/SVneo cells using reverse transcription quantitative-PCR or western blotting. The viability of HTR-8/SVneo cells was tested using a Cell Counting kit- 8 (CCK8) assay, with cell migration assessed using scratch and transwell assays. RESULTS: It was observed that the expression levels of miR-137 were increased and the expression levels of FNDC5 were decreased in the placenta tissues of women with severe GDM and in HG-exposed HTR-8/SVneo cells. In addition, upregulating miR-137 in HTR-8/SVneo cells downregulated the expression levels of FNDC5. The viability and migration of HTR-8/SVneo cells were suppressed by increased miR-137 expression levels, and upregulating FNDC5 in miR-137-overexpressing HTR-8/SVneo cells resulted in the reversal of all these effects. CONCLUSIONS: The data from the present study suggest that miR-137 suppresses the viability and migration of trophoblasts via downregulating FNDC5 in GDM, which may contribute to the pathology of placenta tissues and occurrence of adverse pregnancy outcomes.

Daphnetin inhibits high glucose-induced extracellular matrix accumulation, oxidative stress and inflammation in human glomerular mesangial cells.

Diabetic nephropathy (DN) is one of the most common causes of end-stage renal disease (ESRD). Oxidative stress and inflammation have been documented to play important roles in the pathogenesis of DN. Daphnetin, a natural coumarin compound, possesses antioxidant and anti-inflammatory activities. However, the role of daphnetin in DN has not yet been investigated. The aim of the present study was to explore the function of daphnetin in DN and the underlying mechanism in vitro. Our results demonstrated that daphnetin alleviated cell proliferation induced by high glucose (HG) in human mesangial cells (MCs). Daphnetin strikingly reduced reactive oxygen species (ROS) and malonaldehyde (MDA) levels, and induced the superoxide dismutase (SOD) activity in HG-stimulated MCs. Besides, the production of TNF-α, IL-1ß, IL-6, fibronectin (FN) and collagen IV (Col IV) was also inhibited by daphnetin in HG-stimulated MCs. In addition, daphnetin enhanced the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) and inhibited the levels of p-Akt and p-p65 in HG-stimulated MCs. The results indicated that daphnetin inhibited HG-induced oxidative stress, inflammatory response, and ECM accumulation in human MCs. The effect is partially mediated by Nrf2/keap1 and Akt/NF-κB pathways. The findings suggested that daphnetin might be a therapeutic or preventive agent for DN.

Hsa-miRNA-29a protects against high glucose-induced damage in human umbilical vein endothelial cells.

Sustained exposure to high glucose (HG) results in dysfunction of vascular endothelial cells. Hence, diabetic patients often suffer from secondary vascular damages, such as vascular sclerosis and thrombogenesis, which may eventually cause cardiovascular problems. Thus, elucidating how HG results in vascular endothelial cell damage and finding an approach for prevention are important to prevent and treat vascular damages in diabetic patients. In the current study, we first showed that 72-hour exposure to HG-decreased hsa-miRNA-29a and increased the expression of Bcl-2 associated X protein (Bax), which subsequently inhibited Bcl-2 and promoted the expression of apoptotic protease activating factor-1 and activation of caspase-3, thus directly triggering the mitochondrial apoptotic pathway in human umbilical vein endothelial cells (HUVECs). Study of the underlying mechanism showed that hsa-miRNA-29a/Bax plays an essential role in the decreased proliferation and increased apoptosis of HUVECs induced by HG, and overexpression of hsa-miRNA-29a effectively inhibits HG-induced apoptosis and restores the proliferation and tube formation of HUVECs exposed to HG by inhibiting its target gene Bax. In short, our study demonstrates that hsa-miRNA-29a is a promising target for the prevention and treatment of vascular injury in diabetic patients.

High glucose induces dysfunction of human umbilical vein endothelial cells by upregulating miR-137 in gestational diabetes mellitus.

Recent studies have revealed considerable dysfunction of vascular endothelial cells (VECs) and abnormal expression of microRNA (miR)-137 in women with gestational diabetes mellitus (GDM), and the aim of this study was to clarify the underlying mechanism and possible role of microRNA (miR)-137 in dysfunction of VECs during GDM. We found increased levels of miR-137 in the plasma of GDM women and high-glucose (HG)-exposed HUVECs. Upregulating miR-137 in HUVECs elevated the chemokine (C-C motif) ligand 2 (CCL2) secretion and enhanced the chemotaxis and adhesion of U937 and THP-1 (two human acute monocytic leukemia cell lines) cells to HUVECs in a co-culture system. Moreover, HG stimulation and/or overexpression of miR-137 inhibited the viability, upregulated the expression levels of vascular cell adhesion molecule-1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), E-selectin, and inflammatory cytokine interleukin (IL)-6, and downregulated the production of IL-8, vascular endothelial growth factor (VEGF), and angiogenesis of HUVECs in vitro. These results imply that up-regulated miR-137 by HG can restrict the viability and angiogenesis, promote the activation and inflammatory cytokine secretion of VECs, and stimulate the monocyte chemotaxis and adhesion to VECs. Ultimately, we have concluded that miR-137 is crucial to HG-induced VEC dysfunction and may be involved in pathology of GDM.

Low-Intensity Ultrasound Reduces High Glucose-Induced Nitric Oxide Generation in Retinal Pigment Epithelial Cells.

Diabetic retinopathy (DR) is a severe micro-vascular complication of diabetes. High glucose (HG)-evoked nitric oxide (NO) production mediated by increased oxidative stress is a key factor in DR pathogenesis. In this study, we examined whether low-intensity ultrasound (LIUS) stimulation can reduce HG-induced NO generation. We determined that LIUS stimulation decreased the HG-induced NO generation possibly via inhibition of reactive oxygen species (ROS) and subsequently diminished the associated pro-inflammatory pathway involving the induced expression of inducible nitric oxide synthase, cyclooxygenase-2 and vascular endothelial growth factor. In addition, we determined that LIUS stimulation reduced the quantity of NO produced by N-acetylcysteine, which was not mediated by ROS. These results indicate that LIUS can inhibit both ROS-dependent and -independent NO generation processes in ARPE-19 cells. We envision LIUS as a potential therapeutic alternative to treat DR. Further studies are required to understand the underlying mechanism of the LIUS-induced reduction of NO generation for DR therapy.

Cardiac apoptosis induced under high glucose condition involves activation of IGF2R signaling in H9c2 cardiomyoblasts and streptozotocin-induced diabetic rat hearts.

The insulin-like growth factor type 2 receptor (IGF2R) overexpression has been implicated in heart disease progression. Unregulated IGF2R signaling triggers cardiac hypertrophy, apoptosis, and cardiomyopathies. The present study investigated the role of IGF2R in cardiomyocyte apoptosis under high glucose (HG) levels and in streptozotocin (STZ) induced diabetic rat hearts. We found that IGF2 and IGF2R protein expression were highly upregulated under high glucose condition in H9c2 cells as well as in STZ induced diabetic rat hearts. Using immunoblotting and TUNEL assay, we found that elevated glucose condition induced IGF2R expression leads to activation of Gαq mediated calcineurin-dependent signaling pathway, which further leads to downstream activation and expression of cardiac hypertrophy related proteins, ANP and BNP. Further, we found that glucose-induced IGF2R expression downregulated survival protein p-Akt, p-Bad (Ser 155) and enhanced the expression of apoptosis-inducing proteins cytochrome c and cleaved Caspase-3. Our results suggested that hyperglycemic condition leads to cellular cardiomyocyte apoptosis both in vitro and in vivo models, via abnormally increased activation of the IGF2R signaling pathway.

NGF Attenuates High Glucose-Induced ER Stress, Preventing Schwann Cell Apoptosis by Activating the PI3K/Akt/GSK3ß and ERK1/2 Pathways.

Diabetic peripheral neuropathy (DPN) is one of the most common and troublesome complications of diabetes mellitus. It has been demonstrated that nerve growth factor (NGF) exerts a pivotal role in the regulation of neuronal growth and the promotion of DPN recovery. However, the exact molecular mechanisms are not well understood. Recent studies have indicated that as a novel therapeutic target, endoplasmic reticulum (ER) stress participates in the onset and progression of DPN. In the present study, it has been demonstrated that NGF prevents the sciatic nerve from degeneration and demyelination in DPN rats. Thus, RSC 96 cells, which retain the characteristic features of Schwann cells (SCs), were cultured in medium containing 30 mM glucose (high glucose, HG) to mimic SCs in DPN mice. The 50-ng/ml dose of NGF was identified to be the optimal concentration for treating an excessive ER stress level under HG conditions for 24 h. We found that NGF treatment significantly inhibits HG-induced ER stress and subsequently suppresses ER-related apoptosis. Further, NGF administration also activates the upstream signaling pathway of ER stress, PI3K/Akt/GSK3ß signaling and ERK1/2 signaling. Co-treatment with the PI3K inhibitor LY294002 or ERK1/2 inhibitor U0126 significantly reverses the protective role of NGF on HG-induced excessive ER stress and subsequent apoptosis. These observations suggest that the neuroprotective role of NGF in DPN is mediated by the inhibition of excessive ER stress via the activation of the PI3K/Akt/GSK3ß and ERK1/2 signaling pathways.

Ghrelin inhibits high glucose-induced 16HBE cells apoptosis by regulating Wnt/ß-catenin pathway.

Ghrelin has a protective effect on diabetes and its complications. To expound its probable molecular mechanisms, we investigated the effects of ghrelin on high glucose (HG)-induced cell apoptosis and intracellular signaling pathways in cultured human bronchial epithelial cells (16HBE). In this study, we firstly came to conclusion that HG-induced 16HBE apoptosis was significantly inhibited by co-treatment of ghrelin. The molecular mechanism of ghrelin-induced protective effects for lungs is still not understood. We reported here for the first time that ghrelin can not only eliminate apoptosis of 16HBE, but also regulate the disordered cell cycle caused by HG. We speculated here that ghrelin inhibits the apoptosis of 16HBE by regulating the abnormal cell cycle to some extent. The mechanism may be that ghrelin up-regulates the expression of cyclin D1 via regulating Wnt/ß-catenin pathway, which has an intimate relationship with lung diseases. These results suggested the possible role of ghrelin in treating diabetic lung diseases, especially in view of its low toxicity in humans.