Insulin Receptor Substrate-1 Expression Research Articles

Effects of standard wheat flour proportion in total dietary carbohydrates on blood glucose, lipid metabolism, and inflammation in mice

ABSTRACT We investigated the effects on lipid metabolism and inflammatory response of different proportions of standard wheat flour in the total dietary carbohydrates. Mice were supplemented with the daily food in which energy from standard wheat flour was 30% (G30), 40% (G40), 50% (G50), 60% (G60), or 70% (G70) during 10 weeks experiment. The results showed that when the percentage of energy from standard wheat flour was in the medium range, 40%–60%, TC, TG, and free fatty acid levels in the liver were relatively low. In the G70, the expression of insulin receptor substrate 2 (IRS2) mRNA in mouse liver increased, whereas 50%–60% energy from standard wheat flour significantly increased the expression of PPARα mRNA and reduced the inflammatory response. When the percentage of energy from standard wheat flour was low, the expression of NF-κB mRNA was low and the inflammatory responses were elevated.

EFFECT OF DORSOMEDIAL HYPOTHALAMUS NEUROPEPTIDE Y KNOCKDOWN ON HEPATIC INSULIN SENSITIVITY.

In this study we investigated the effect of dorsomedial hypothalamus (DMH) neuropeptide Y (NPY) knock-down on hepatic insulin sensitivity in high-fat (HF) diet-fed rats. Forty-eight Sprague-Dawley rats were randomly assigned to receive bilateral DMH injections of adeno-associated virus AAVshNPY or AAVshCTL and then accessed to regular chow. Five weeks after viral injection, half rats in each group were given access to the HF diet. At 16 weeks, rat livers were collected. Insulin receptor substrate-1 (IRS-1) and phosphoinositide 3-kinase (PI3K) mRNA expression was measured by qRT-PCR. Blood glucose levels were measured by the oxidase method, serum insulin, triglyceride, and TC levels were measured by Elisa. Pathological changes in the liver were assessed by hematoxylin-eosin (HE) staining. AKT, p-AKT, and GSK-3 levels were measured by western blotting. Compared with AAVshCTL-injected rats, AAVshNPY-injected rats showed a significant decrease in blood glucose concentrations; serum insulin, triglyceride, and TC; HOMA-IR; and IRS-1 and PI3K mRNA levels (P<0.05). ISI, GSK-3, and p-AKT levels were significantly increased (P<0.05). HE staining showed that AAVshNPY-injected rats fed the HF diet had mild fatty degeneration. These results suggest that DMH NPY knock-down improves hepatic insulin sensitivity in HF diet-fed rats by activating the hepatic PI3K/AKT insulin signalling pathway.

Identification of novel mutations of Insulin Receptor Substrate 1 (IRS1) in tumor samples of non-small cell lung cancer (NSCLC): Implications for aberrant insulin signaling in development of cancer.

Lung cancer is the leading cause of cancer-related death, and NSCLC constitutes nearly 85%–90% of all cases. The IRS proteins function as adaptors and transmit signals from multiple receptors. Upon binding of insulin to the insulin receptor (IR), IRS1 is phosphorylated at several YXXM motifs creating docking sites for the binding of PI3Kp85, which activates AKT kinase. Therefore, we thought that gain of function mutantions of IRS1 could be related to development of lung cancer. In line with this, we wanted determine whether the IRS1 gene was mutated in the coding regions surrounding YXXM motifs. We sequenced the coding regions surrounding YXXM motifs of IRS1 using tumor samples of 42 NSCLC patients and 40 matching controls and found heterozygote p.S668T mutation in nine of 42 samples and four of nine also had the p.D674H mutation. We generated IRS1 expression vectors harboring p.S668T, p.D674H and double mutants. Expression of the mutants differentially affected insulin-induced phosphorylation of IRS1, AKT, ERK, and STAT3. Also, our mutants induced proliferation, glucose uptake, inhibited the migration of 293T cells and affected the responsiveness of the cells to cisplatin and radiation. Our results suggest that these novel mutations play a role in the phenotype of lung cancer.

The effect of 8-week resistance training on IRS-1 gene expression in gastrocnemius muscle and glycemic profile in diabetes rats

Background: The insulin receptor substrate-1 (IRS-1) has an important role in insulin signaling pathways in the target tissue of obese or insulin-resistant individuals. This study aimed to assess the effect of resistance training on fasting glucose, insulin resistance, and IRS-1 gene expression in gastrocnemius muscle in male Wister rats with type 2 diabetes (T2D). Materials and Methods: For this purpose, T2D induced by high- fat diet (8 weeks) and STZ in fourteen male Wistar rats (220 ± 10 g) and then assigned into exercise (resistance training, 8 weeks, 5 days/weekly, n = 7) and control (no-training, n = 7) by randomly. Fasting blood samples were obtained for measuring glucose, insulin, and calculating insulin resistance (HOMA-IR). Also, the IRS-1 gene expression in gastrocnemius muscle was measured 48 hours after the last training session of both cases and controls. Results: Compared to control, IRS-1 gene expression in gastrocnemius muscle increased significantly by resistance training in exercise groups (p = 0.001). Fasting glucose (p < 0.001) and insulin resistance (p = 0.007) were reduced in the exercise rats compared to the control group. Conclusion: Based on the results, improved fasting glucose and insulin function after resistance training in T2D diabetes could be attributed to enhancing IRS-1 expression in gastrocnemius muscle by training.

THE ASSOCIATION BETWEEN THE GLY972ARG POLYMORPHISM IN IRS1 GENE AND THE RISK OF PREDIABETES AMONG VIETNAMESE WOMEN

Insulin receptor substrate 1 (IRS1) is a ligand of the insulin receptor tyrosine kinase and participates in the insulin receptor signal transduction pathway. Dysregulations in IRS1 expression and function increase incidence of insulin-resistant states such as prediabetes and type 2 diabetes. The study aimed to investigate the association of the Gly972Arg (rs1801278) polymorphism in IRS1 gene with prediabetes in Northern Vietnamese women. The case-control study consisted of 1617 women (250 prediabetic cases and 1367 normoglycemic controls). The IRS1 Gly972Arg polymorphism was genotyped in these subjects using polymerase chain reaction–restriction fragment length polymorphism. The frequency of the ‘‘A’’ allele of the Gly972Arg (G&gt;A) polymorphism was similar between the normal glucose and prediabetic subjects (2.7% and 2.6%, respectively). There was no significant difference in the genotypic frequency between the control and prediabetic cases (P = 0.673). The IRS1 Gly972Arg polymorphism was not associated with the risk of prediabetes in Vietnamese women before and after adjusted for socio-economic, lifestyles and clinical factors (P &gt; 0.05).

Insulin Reduces Reaction of Follicular Granulosa Cells to FSH Stimulation in Women With Obesity-Related Infertility During IVF.

Women with obesity usually need larger doses of FSH for ovarian stimulation, resulting in poor outcomes; however, the mechanism is still unclear. To investigate the molecular regulation of FSH receptor (FSHR) expression associated with obesity. Case-control study to improve in vitro fertilization (IVF) outcomes. Women with obesity (82) and women who were overweight (457) undergoing IVF and 1790 age-matched controls with normal weight from our reproductive medicine center. FSHR expression was decreased in parallel with body mass index (BMI), whereas the estradiol (E2) level on the human chorionic gonadotropin (hCG) trigger day was significantly lower. FSHR expression in human granulosa cells (hGCs), both mRNA (P = 0.02) and protein (P = 0.001) levels, was decreased in women who were overweight or obese. Both insulin (P < 0.001) and glucose (P = 0.0017) levels were positively correlated with BMI in fasting blood and follicle fluids (FFs) but not with FFs leptin level. We treated human granulosa-like tumor cells (KGN) cells with insulin; E2 production was compromised; the level of phosphorylated (p)-protein kinase B (p-Akt2) decreased, whereas p-glycogen synthase kinase 3 (GSK3) increased; and there were similar changes in hGCs from women with obesity. Stimulated hGCs from women with obesity with compound 21 (CP21), an inhibitor of GSK3β, resulted in upregulated β-catenin activation and increased FSHR expression. CP21 also increased the expression of insulin receptor substrate 1 and phosphatidylinositol 3-kinase (PI3K), as well as p-Akt2. Women with obesity in IVF were associated with reduced FSHR expression and E2 production caused by a dysfunctional insulin pathway. Decreased FSHR expression in hGCs from women with obesity and insulin-treated KGN cells could be rescued by an inhibitor of GSK3β, which might be a potential target for the improvement of the impaired FSH-stimulation response in women with obesity.

Cinnamaldehyde ameliorates STZ-induced rat diabetes through modulation of IRS1/PI3K/AKT2 pathway and AGEs/RAGE interaction.

Type 2 diabetes mellitus (T2D) is a chronic metabolic disorder considered to be the most predominant form of diabetes throughout the world. This study aimed to investigate the possible effects of cinnamaldehyde (CIN) on insulin signaling pathways in STZ-induced T2D rat model. T2D was originated by feeding rats with a high-fat diet (HFD) plus 25% fructose solution plus streptozotocin (STZ) (35mg/kg, i.p.). CIN effects were investigated on fasting blood glucose, insulin, oral glucose tolerance test (OGTT), insulin tolerance test (ITT), liver biomarkers, lipid profile, oxidative stress biomarkers, serum advanced glycation end products (AGEs) and its receptors (RAGE) in the aorta, and histopathology of the liver and aorta. Additionally, the mRNA expression of hepatic insulin signaling pathway genes, phosphorylated AKT (serine 473) (P-AKT ser473) level, and aortic nitric oxide synthase3 (eNOS) and NADPH oxidase4 (NOX4) were determined. CIN treatment for 30days significantly decreased OGTT, ITT, fasting blood glucose, insulin, and HOMA-IR and increased HOMA-β index when compared to diabetic rats. CIN also improved lipid profile and decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, serum AGEs, and aortic RAGE. Additionally, CIN treatment significantly decreased hepatic malondialdehyde (MDA), increased hepatic and aortic glutathione (GSH) and superoxide dismutase (SOD), and decreased steatosis and inflammation observed in liver tissue of rats. Additionally, significant elevation in mRNA expression of insulin receptor substrate1 (IRS1), phosphatidylinositol 3-kinase regulatory subunit1 (PI3K-P85 subunit), and AKT serine/threonine kinase2 (AKT2); increased levels of P-AKT ser473 and aortic eNOS; and decrease in mRNA expression of NOX4 were detected in CIN-treated group when compared to diabetic group. This study suggests antidiabetic and antioxidant effects of CIN probably through upregulation of eNOS and IRS1/PI3K/AKT2 signaling pathway and alleviating AGEs, RAGE, and NOX4 elevation.

MicroRNA‑766 inhibits papillary thyroid cancer progression by directly targeting insulin receptor substrate 2 and regulating the PI3K/Akt pathway.

MicroRNAs (miRNAs/miRs) are widely dysregulated in papillary thyroid cancer (PTC). Dysregulated miRNAs, together with their target genes, comprise a complex network that has been implicated in the regulation of PTC pathogenesis. Further knowledge of the functional roles of aberrantly expressed miRNAs in PTC, and the underlying molecular mechanisms, may assist in the identification of novel therapeutic targets. miR‑766 has been well studied in human cancer; however, the expression status, specific roles and regulatory mechanisms of miR‑766 in PTC remain unclear. The present study aimed to detect miR‑766 expression in PTC tissues and cell lines, to explore the biological roles of miR‑766 in the malignant biological behaviors of PTC cells, and to determine the underlying mechanism of action of miR‑766 in PTC cells. The results revealed that miR‑766 was downregulated in PTC tissues and cell lines, and its downregulation was strongly associated with TNM stage and lymph node metastasis. Overexpression of miR‑766 inhibited PTC cell proliferation, colony formation, migration and invasion, promoted cell apoptosis and reduced tumor growth invivo. Mechanistically, insulin receptor substrate2 (IRS2) was identified as a direct target of miR‑766 in PTC cells. IRS2 was upregulated in PTC tissues, and this was inversely correlated with miR‑766 expression. Inhibition of IRS2 simulated the tumor suppressor activity of miR‑766 in PTC cells. Restoration of IRS2 expression negated the tumor‑suppressing effects of miR‑766 overexpression on PTC cells. Notably, miR‑766 directly targeted IRS2 to inhibit activation of the phosphoinositide3‑kinase (PI3K)/protein kinaseB (Akt) pathway in PTC cells invitro and invivo. Overall, these findings indicated that miR‑766 may inhibit the malignant biological behaviors of PTC cells by directly targeting IRS2 and regulating the PI3K/Akt pathway, thus suggesting that this miRNA may be a promising therapeutic target for PTC.

Expression of dopamine signaling genes in the post-mortem brain of individuals with mental illnesses is moderated by body mass index and mediated by insulin signaling genes

Preclinical studies implicate insulin signaling as a modulator of dopamine transmission, but human data is currently limited. We hypothesize that changes in the expression of insulin receptor-related genes in the post-mortem brain tissue of patients with mood and psychotic disorders mediate the expression of dopamine regulation-related genes. From a database containing microarray data from the post-mortem dorsolateral prefrontal cortex (dlPFC) (healthy controls [HC]: n = 209; patients: n = 321) and hippocampus (HC: n = 180; patients: n = 196), we conducted a hypothesis-driven analysis through the a priori selection of 12 dopamine- and 3 insulin-related genes. Mediation and moderated mediation models, accounting for the role of body mass index (BMI), were used. In the dlPFC, expressions of insulin receptor- and dopamine regulation-related genes were moderated by BMI, with significantly lower expression in high BMI patients. In the hippocampus, there were significantly lower expressions of these genes, which were not moderated by BMI. Illnesses by BMI effects on expression of dopamine genes were fully mediated by expression of insulin receptor gene (INSR). Analysis of conditional indirect effects showed interactions between INSR and BMI, indicating significantly stronger indirect effects at higher BMI values. In the hippocampus we observed that expression of insulin receptor substrate 1 and 2 fully mediated the effects of illnesses on expression of dopamine genes. In conclusion, differential expression of dopamine-related genes was related to altered expression of insulin signaling genes. BMI had region-specific effects, supporting the hypothesis that metabolic systems are critical mediators of dopaminergic function.

The effect of cyanidin-3-O-β-glucoside and peptides extracted from yoghurt on glucose uptake and gene expression in human primary skeletal muscle myotubes from obese and obese diabetic participants

Incidence of type II diabetes mellitus (T2DM) is rapidly increasing worldwide. This study aimed to investigate whether cyanidin-3-O-β-glucoside (C3G), or peptides with angiotensin converting enzyme (ACE) inhibitory activity, alone or in combination, alter glucose regulation in human primary myotubes derived from obese and obese T2DM participants. In the obese group, both low and high concentration of peptides and the combination of these peptides with high C3G concentration significantly enhanced glucose uptake in the presence or absence of insulin, and high concentration of peptide alone and its combination with low C3G down-regulated the mRNA expression of angiotensin II receptor, type 1 (AGTR-1), and up-regulated the mRNA expression of insulin receptor substrate 1 (IRS-1), and glucose transporter 4 (GLUT4). However, only high peptide concentration increased glucose uptake in the absence of insulin in the obese T2DM group, and the expression of AGTR-1 was decreased with high peptide and its combinations of C3G.

Preventative effects of resveratrol and estradiol on streptozotocin-induced diabetes in ovariectomized mice and the related mechanisms.

Resveratrol, a non-flavonoid polyphenolic compound, is structurally and functionally similar to estrogen and has drawn great attention for its potentially beneficial effects on diabetes. However, it is not known whether it shares the same protective effect against diabetes as estrogen and the underlying mechanisms. The aim of the present study was to investigate the protective effects of phytoestrogen resveratrol and exogenous 17β-estradiol against streptozotocin (STZ)-induced type 1 diabetes. Female mice were ovariectomized (OVX) and chronically injected with different concentrations of resveratrol (0.1, 1 or 10 mg/kg) and 17β-estradiol (0.01, 0.1 or 1 mg/kg) subcutaneously for 4 weeks, and the levels of blood glucose, plasma insulin, plasma antioxidant capacity, the changes of pancreatic islet cells and the expressions of glucose transporter 4 (GLUT4), insulin receptor substrate 1 (IRS-1) and phosphorylation of extracellular signal-regulated kinase (p-ERK) were detected. Resveratrol and 17β-estradiol significantly inhibited the increase of the blood glucose level and the rise of plasma malondialdehyde in STZ-induced diabetic mice, improved the levels of plasma antioxidant capacity and plasma insulin, protected the pancreatic islet cells, and increased the expressions of GLUT4 and IRS-1, but decreased p-ERK expression in skeletal muscle and myocardial tissue. The results suggest that resveratrol or 17β-estradiol shows obvious protection against STZ-induced diabetes in OVX mice, the mechanisms probably involve their ameliorating antioxidant activities and islet function, promoting muscle glucose uptake and inhibiting the expression of p-ERK.

Rosiglitazone Elicits an Adiponectin-Mediated Insulin-Sensitizing Action at the Adipose Tissue-Liver Axis in Otsuka Long-Evans Tokushima Fatty Rats.

Rosiglitazone is an agonist of peroxisome proliferator-activated receptor- (PPAR-) γ that is principally associated with insulin action. The exact mechanisms underlying its insulin-sensitizing action are still not fully elucidated. It is well known that adiponectin mostly secreted in adipose tissue is an insulin sensitizer. Here, we found that treatment of Otsuka Long-Evans Tokushima Fatty (OLETF) rats with rosiglitazone (3 mg/kg, once daily, by oral gavage for 33 weeks) attenuated the increase in fasting plasma insulin concentrations and the index of the homeostasis model assessment of insulin resistance along with the age growth and glucose concentrations during an oral glucose tolerance test. In addition, the increase in plasma alanine aminotransferase activity, concentrations of fasting plasma nonesterified fatty acids and triglyceride, and hepatic triglyceride content was also suppressed. The hepatic protein expression profile revealed that rosiglitazone increased the downregulated total protein expression of insulin receptor substrate 1 (IRS-1) and IRS-2. Furthermore, the treatment suppressed the upregulated phosphorylation of IRS-1 at Ser307 and IRS-2 at Ser731. The results indicate that rosiglitazone ameliorates hepatic and systemic insulin resistance, hepatic inflammation, and fatty liver. Mechanistically, rosiglitazone suppressed hepatic protein overexpression of both phosphorylated nuclear factor- (NF-) κBp65 and inhibitory-κB kinase-α/β, a transcription factor that primarily regulates chronic inflammatory responses and the upstream NF-κB signal transduction cascades which are necessary for activating NF-κB, respectively. More importantly, rosiglitazone attenuated the decreases in adipose adiponectin mRNA level, plasma adiponectin concentrations, and hepatic protein expression of adiponectin receptor-1 and receptor-2. Thus, we can draw the conclusion that rosiglitazone elicits an adiponectin-mediated insulin-sensitizing action at the adipose tissue-liver axis in obese rats. Our findings may provide new insights into the mechanisms of action of rosiglitazone.

TAZ enhances mammary cell proliferation in 3D culture through transcriptional regulation of IRS1

WW domain-containing transcriptional regulator 1 (TAZ) is a transcriptional co-activator and effector of the Hippo signaling pathway. In certain breast cancer subtypes, Hippo signaling is dysregulated leading to activation of TAZ and altered expression of TAZ transcriptional targets. Over the past decade, we and others have found that TAZ transcriptionally regulates genes that affect multiple aspects of breast cancer cell behaviour. However, while cancer cell-intrinsic oncogenic functions of TAZ have emerged, less is known about whether TAZ might also contribute to tumourigenesis by sensitizing tumour cells to factors present in the tumour microenvironment or in systemic circulation. Here, we show that TAZ directly regulates the expression of insulin receptor substrate 1 (IRS1) in breast cancer cells. TAZ or IRS1 overexpression induces a similar proliferative transformation phenotype in MCF10A mammary epithelial cells. TAZ enhances IRS1 mRNA, protein levels and downstream signaling in MCF10A. Mechanistically, TAZ interacts with the IRS1 promoter through the TEAD family of transcription factors and enhances its activity. Critically, TAZ-induced IRS1 upregulation contributes to the proliferation of TAZ-overexpressing MCF10A in 3-dimensional (3D) Matrigel culture. Therefore, we offer compelling evidence that TAZ regulates signaling through the insulin pathway in breast cancer cells. These findings highlight an additional mechanism by which TAZ may promote breast cancer tumourigenesis and progression by modulating cancer cell responses to exogenously produced factors.

Protective effects of rutin on liver injury in type 2 diabetic db/db mice

The aim of this study was to evaluate the protective effect of rutin on the liver of type 2 diabetic mice and explore the correlation mechanism. The db/db mice, selected as the type 2 diabetes mellitus (T2DM) models, have random blood glucose (RBG) and glucose level after 2 h of oral glucose loading of more than 16.7 mmol/L. After administration of 120 mg/kg or 60 mg/kg rutin, to T2DM mice, RBG, oral glucose tolerance, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum, and advanced glycation end products (AGEs) in vivo and vitro of different groups were detected. The liver pathological changes were observed under light and electron microscopy. Western blotting was used to detect the protein expression of insulin receptor substrate 2 (IRS-2) and phosphorylation of phosphatidylinositol 3 kinase (PI3K) on p85, Akt on Ser473, glycogen synthase kinase 3β (GSK-3β) on Ser9, real-time quantitative PCR was used to detect IRS-2 mRNA expression. Moreover, dynamically observing the effect of rutin on the generation of AGEs in non-enzymatic protein glycosylated system, Cell Counting Kit-8 (CCK-8) method was used to detect the effect of rutin on proliferation activity of HepG2 liver cells. The results showed that RBG and glucose levels of oral glucose tolerance test (OGTT) of mice in model group were significantly higher than that of normal group, which were significantly reduced after the rutin treatment. Rutin could reduce the ALT, AST activities and AGEs level in serum and potentiate the expression of IRS-2, P-PI3K (p85), P-Akt (Ser473), P-GSK-3β (Ser9) protein and IRS-2 mRNA in the liver tissue of db/db mice. Moreover, rutin could significantly alleviate the structure disorder of liver, reduce the degeneration and necrosis of liver cells and formation of collagen fibers of db/db mice. The results in vitro also showed that rutin could obviously inhibit the generation of AGEs, and promoted the proliferation activity of high glucose-stimulating HepG2 cells. In general, the protective effect of rutin on the liver of T2DM may be mediated by facilitating signal transduction and activated state of insulin IRS-2/PI3K/Akt/GSK-3β signal pathway, promoting hepatocyte proliferation, reducing blood glucose level and generation of AGEs.

Association of IRS2 overexpression with disease progression in intrahepatic cholangiocarcinoma.

Insulin receptor substrate 2 (IRS2) is a candidate driver oncogene frequently amplified in cancer and is positively associated with IRS2 expression. The overexpression of IRS2 has been suggested to promote tumor metastasis. However, its function in intrahepatic cholangiocarcinoma (iCCA) has not been investigated extensively. The present study examined 86 cases of iCCA to analyze IRS2 expression and its correlation with clinicopathological characteristics using immunohistochemical assays. Three stable cell lines overexpressing IRS2 were established. The mobility potential of cells was compared in the basal condition and following manipulation using cell migration and invasion assays. Epithelial-mesenchymal transition (EMT)-associated proteins were assessed by western blotting. IRS2 was overexpressed in 29 iCCA cases (33.7%) and was significantly more frequent in cases with large tumor size (P=0.033), classified as an advanced stage by the American Joint Committee on Cancer (P=0.046). In comparison with the control cells, the three IRS2-overexpressing iCCA cell lines exhibited a statistically significant increase in mobility potential. Expression analysis of EMT markers demonstrated decreased epithelial marker levels and increased mesenchymal marker levels in IRS2-overexpressing cells compared with their corresponding control cells. The results of the present study indicate that IRS2 overexpression is characterized by a large tumor size and advanced tumor stage in iCCA, and that it may increase tumor mobility potential by regulating EMT pathways. Therefore, it is a valuable predictive indicator of metastasis and may provide a novel direction for targeted therapy in iCCA.

MicroRNA-15b participates in diabetic retinopathy in rats through regulating IRS-1 via Wnt/β-catenin pathway.

To explore the role of microRNA-15b in diabetic retinopathy (DR) and its underlying mechanism. Diabetic retinopathy rat model was first constructed. Retinal endothelial cells (EC) and retinal pericytes (RP) in DR rats were extracted. The mRNA expression of microRNA-15b in EC and RP cells was detected by qRT-PCR (quantitative Real Time-Polymerase Chain Reaction). Protein expression of insulin receptor substrate 1 (IRS-1) in EC and RP cells was detected by Western blot. After altering microRNA-15b expression by plasmid transfection, cell viability was detected by CCK-8 (cell counting kit-8) assay. Furthermore, the target gene of microRNA-15b was predicted by TargetScan analysis and the binding condition was verified by luciferase reporter gene assay. Finally, rescue experiments were carried out to explore the regulatory effect of microRNA-15b on IRS-1. MicroRNA-15b was lowly expressed, whereas IRS-1 was highly expressed in EC and RP cells. After overexpression of microRNA-15b, viabilities of EC and RP cells were decreased and β-catenin expression was inhibited. TargetScan predicted that IRS-1 was the downstream gene of microRNA-15b, which was further verified by luciferase reporter gene assay. Rescue experiments indicated that microRNA-15b was capable of regulating IRS-1 via Wnt/β-catenin signaling pathway. MicroRNA-15b participates in the development of diabetic retinopathy by targeting IRS-1 via Wnt/β-catenin signaling pathway.

Effects of Lactobacillus on Mice with Diabetes Induced by High-Fat Diet with Streptozotocin (STZ)

This study aimed to evaluate and compare the effects of heat-killed and live Lactobacillus on mice with diabetes induced by high-fat diet with streptozotocin (STZ). Results based on body weight and liver pathological changes, oral glucose tolerance test, and related serum index (AST (aspartate aminotransferase), ALT (alanine aminotransferase), MDA (malondialdehyde), TNF-α (tumor necrosis factor α), INS (insulin), and GC (glucagon) and gene expression of IL-1β (Interleukin 1β), IRS-1(Insulin receptor substrate 1), GLUT-4 (glucose transporter type 4), PPARγ (peroxisome proliferators-activated receptor γ), and SREBP-1c (sterol-regulatory element-binding protein-1c) levels indicated that Lactobacillus fermentum (LF) and Lactobacillus plantarum (LP) could increase the average weight, alleviate the degree of damage in the liver, and improve the glucose tolerance of mice with diabetes. LF and LP also participated in the downregulation of AST, ALT, MDA, TNF-α, INS, and GC in serum, as well as the inhibition of IL-1β, TNF-α, IRS-1, GLUT-4, PPARγ, and SREBP-1c expression. These regulating effects were remarkable, and the regulating effect of the live group was significantly better than that of the heat-killed group. This study suggested that LF and LP can significantly alleviate liver damage and hepatic insulin resistance in mice with diabetes and that the acting mechanisms of LF and LP were related to cellular components and their activities.

Tangganjian decoction ameliorates type 2 diabetes mellitus and nonalcoholic fatty liver disease in rats by activating the IRS/PI3K/AKT signaling pathway

AimPrevious clinical studies have demonstrated that tangganjian (TGJ), a modern Chinese prescribed medicine, has a clinical effect in the treatment of type 2 diabetes mellitus (T2DM) with nonalcoholic fatty liver disease (NAFLD). Our study aimed to investigate whether the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway is involved in this therapeutic effect. Materials and methodsT2DM and NAFLD rat models were constructed and treated with three different concentrations of TGJ. Pioglitazone was used as a positive control, along with the model and normal groups. For analyses, blood and livers were collected. Levels of glucose and lipid metabolism indicators, including fasting insulin and total cholesterol, were determined. The expression levels of insulin receptor substrate (IRS), PI3K, and AKT were also determined by western blotting and immunohistochemistry. Liver tissues were stained with hematoxylin & eosin. ResultsIn the high-dose TGJ-treated and positive groups, there was a significant increase in the HDL-C level and decreases in the levels of the fasting blood glucose, 2 h postprandial blood glucose, fasting insulin, triglyceride, total cholesterol, and low-density lipoprotein cholesterol, along with a significant increase in the expression of IRS, PI3K, and AKT in the liver. TGJ could also attenuate or counteract the effects of T2DM and NAFLD in the liver lobules. ConclusionA high concentration of TGJ can improve glucose and lipid metabolism by activating the IRS/PI3K/AKT signaling pathway.

MiR-7 regulates the PI3K/AKT/VEGF pathway of retinal capillary endothelial cell and retinal pericytes in diabetic rat model through IRS-1 and inhibits cell proliferation.

To investigate the role of miR-7 in diabetic retinopathy and the underlying mechanism. The rat model of diabetic retinopathy (DR) was established. After that, the endothelial cell (EC) and retinal pericyte (RP) were isolated. QRT-PCR was used to detect the expression of miR-7 and insulin receptor substrate-1 (IRS-1) in ECs and RPs cells while the protein level of IRS1 was detected by Western blot. miR-7 mimic and miR-7 inhibitor were transfected to achieve miR-7 overexpression or knockdown. Cell viability was detected by Cell Counting Kit-8 (CCK-8) assay after miR-7 overexpression or knockdown. Besides, the expression levels of PI3K, AKT, and VEGF were detected by Western Blot. The luciferase reporter assay was performed to investigate whether miR-7 could be combined with IRS-1. Conversely, whether miR-7 could affect IRS-1 was also verified. miR-7 expression was significantly decreased in ECs and RPs of the experimental group compared with the control group, while the mRNA and protein levels of IRS-1 were increased. The CCK-8 assay showed that overexpression of miR-7 decreased the cell activity in ECs and RPs. In contrast, knock-down of miR-7 could increase the cell viability. Besides, Western blot showed that after overexpression of miR-7, the expressions of PI3K, AKT, and VEGF in ECs and RPs cells were down-regulated. Meanwhile, miR-7 knockdown upregulated the protein levels of PI3K, AKT, and VEGF. The luciferase reporter assay suggested that the 3'UTR region of IRS-1 could be combined with miR-7, which may be the downstream target gene for miR-7. Moreover, knockdown of IRS-1 could reverse the effect of the miR-7 inhibitor on cell proliferation in the diabetic model. MiR-7 was lowly expressed in ECs and RPs cells. Overexpression of miR-7 can down-regulate the expression levels of PI3K, AKT, and VEGF by down-regulating its downstream target gene IRS-1, and ultimately inhibit the proliferation of retinal cells.

Resveratrol reduces the inflammatory response in adipose tissue and improves adipose insulin signaling in high-fat diet-fed mice.

BackgroundObesity-induced glucose metabolism disorder is associated with chronic, low-grade, systemic inflammation and is considered a risk factor for diabetes and metabolic syndrome. Resveratrol (RES), a natural anti-inflammatory compound, is observed to improve glucose tolerance and insulin sensitivity in obese rodents and humans. This study aimed to test the effects of RES administration on insulin signaling and the inflammatory response in visceral white adipose tissue (WAT) caused by a high-fat diet (HFD) in mice.MethodsA total of 40 wild-type C57BL/6 male mice were divided into four groups (10 in each group): the standard chow diet (STD) group was fed a STD; the HFD group was fed a HFD; and the HFD-RES/L and HFD-RES/H groups were fed a HFD plus RES (200 and 400 mg/kg/day, respectively). The L and H in RES/L and RES/H stand for low and high, respectively. Glucose tolerance, insulin sensitivity, circulating inflammatory biomarkers and lipid profile were determined. Quantitative PCR and Western blot were used to determine the expression of CC-chemokine receptor 2 (CCR2), other inflammation markers, glucose transporter 4 (GLUT4), insulin receptor substrate 1 (IRS-1) and pAkt/Akt and to assess targets of interest involving glucose metabolism and inflammation in visceral WAT.ResultsHFD increased the levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol and proinflammatory cytokines in serum, decreased the high-density lipoprotein cholesterol level in serum, and induced insulin resistance and WAT inflammation in mice. However, RES treatment alleviated insulin resistance, increased the expressions of pAkt, GLUT4 and IRS-1 in WAT, and decreased serum proinflammatory cytokine levels, macrophage infiltration and CCR2 expression in WAT.ConclusionOur results indicated that WAT CCR2 may play a vital role in macrophage infiltration and the inflammatory response during the development of insulin resistance in HFD-induced obesity. These data suggested that administration of RES offers protection against abnormal glucose metabolism and inflammatory adaptations in visceral WAT in mice with HFD-induced obesity.