OBJECTIVE: To investigate the effect CD36 deficiency on muscle insulin signaling in mice fed a normal-fat diet and explore the possible mechanism. METHODS: Wild-type (WT) mice and systemic CD36 knockout (CD36^-/-) mice with normal feeding for 14 weeks (n=12) were subjected to insulin tolerance test (ITT) after intraperitoneal injection with insulin (1 U/kg). Real-time PCR was used to detect the mRNA expressions of insulin receptor (IR), insulin receptor substrate 1/2 (IRS1/2) and protein tyrosine phosphatase 1B (PTP1B), and Western blotting was performed to detect the protein expressions of AKT, IR, IRS1/2 and PTP1B in the muscle tissues of the mice. Tyrosine phosphorylation of IR and IRS1 and histone acetylation of PTP1B promoter in muscle tissues were detected using co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation (ChIP), respectively. RESULTS: CD36^-/- mice showed significantly lowered insulin sensitivity with obviously decreased area under the insulin tolerance curve in comparison with the WT mice (P < 0.05). CD36^-/- mice also had significantly higher serum insulin concentration and HOMA-IR than WT mice (P < 0.05). Western blotting showed that the p-AKT/AKT ratio in the muscle tissues was significantly decreased in CD36^-/- mice as compared with the WT mice (P < 0.01). No significant differences were found in mRNA and protein levels of IR, IRS1 and IRS2 in the muscle tissues between WT and CD36^-/- mice (P>0.05). In the muscle tissue of CD36^-/- mice, tyrosine phosphorylation levels of IR and IRS1 were significantly decreased (P < 0.05), and the mRNA and protein levels of PTP1B (P < 0.05) and histone acetylation level of PTP1B promoters (P < 0.01) were significantly increased as compared with those in the WT mice. Intraperitoneal injection of claramine, a PTP1B inhibitor, effectively improved the impairment of insulin sensitivity in CD36^-/- mice. CONCLUSION CD36 is essential for maintaining muscle insulin sensitivity under physiological conditions, and CD36 gene deletion in mice causes impaired insulin sensitivity by up-regulating muscle PTP1B expression, which results in detyrosine phosphorylation of IR and IRS1.
Animals ; Gene Deletion ; Histones/genetics* ; Insulin ; Insulin Receptor Substrate Proteins/metabolism* ; Insulin Resistance/genetics* ; Membrane Cofactor Protein/genetics* ; Mice ; Mice, Knockout ; Muscles/metabolism* ; Phosphoric Monoester Hydrolases/metabolism* ; Protein Tyrosine Phosphatase, Non-Receptor Type 1/metabolism* ; Proto-Oncogene Proteins c-akt/metabolism* ; RNA, Messenger/metabolism* ; Receptor, Insulin/metabolism* ; Tyrosine/genetics* ; Up-Regulation

OBJECTIVE: To study the expression of tumor associated vascular insulin receptor (TVIR) in colorectal cancer with or without metabolic syndrome (MS) and its relationship with the pathological features of colorectal cancer. METHODS: The expression of TVIR in 220 colorectal cancer specimens was detected by tissue microarray and immunohistochemistry. The relationships between the expression of TVIR and the pathological features (pathological subtypes, histological grade, invasion depth, lymph node metastasis and TNM stage) of colorectal cancer with/without MS were analyzed. RESULTS: The insulin receptor expression was observed in colorectal cancer tissue or border area between cancer and normal tissue, but not in normal intestinal tissue. The high-expression rates of TVIR in MS group was remarkably lower than that of non-MS group (21.6%vs. 41.0%, CONCLUSIONS s: High-expression of TVIR is associated with aggressive pathological features such as invasion, lymph node metastasis and high TNM stage of colorectal cancer, especially for those patients without MS. TVIR could be a useful biological marker for prognosis of colorectal cancer.
Biomarkers, Tumor/genetics* ; Colorectal Neoplasms/physiopathology* ; Gene Expression Regulation, Neoplastic ; Humans ; Neoplasm Staging ; Prognosis ; Receptor, Insulin/genetics*

More and more evidence suggests that microRNA is widely involved in the regulation of cardiovascular function. Our preliminary experiment showed that miR-494-3p was increased in heart of diabetic rats, and miR-494-3p was reported to be related to metabolism such as obesity and exercise. Therefore, this study was aimed to explore the role of miR-494-3p in diabetic myocardial insulin sensitivity and the related mechanism. The diabetic rat model was induced by high fat diet (45 kcal% fat, 12 weeks) combined with streptozotocin (STZ, 30 mg/kg), and cardiac tissue RNA was extracted for qPCR. The results showed that the level of miR-494-3p was significantly up-regulated in the myocardium of diabetic rats compared with the control (P < 0.05). The level of miR-494-3p in H9c2 cells cultured in high glucose and high fat medium (HGHF) was significantly increased (P < 0.01) with the increase of sodium palmitate concentration, whereas down-regulation of miR-494-3p in HGHF treated cells led to an increase in insulin-stimulated glucose uptake (P < 0.01) and the ratio of p-Akt/Akt (P < 0.05). Over-expression of miR-494-3p in H9c2 cell line significantly inhibited insulin-stimulated glucose uptake and phosphorylation of Akt (P < 0.01). Bioinformatics combined with Western blotting experiments confirmed insulin receptor substrate 1 (IRS1) as a target molecule of miR-494-3p. These results suggest that miR-494-3p reduces insulin sensitivity in diabetic cardiomyocytes by down-regulating IRS1.
Animals ; Diabetes Mellitus, Experimental ; physiopathology ; Down-Regulation ; Insulin ; Insulin Receptor Substrate Proteins ; physiology ; Insulin Resistance ; MicroRNAs ; genetics ; Myocytes, Cardiac ; physiology ; Rats

BACKGROUND: Epidemiological studies have suggested that noise exposure may increase the risk of type 2 diabetes mellitus (T2DM), and experimental studies have demonstrated that noise exposure can induce insulin resistance in rodents. The aim of the present study was to explore noise-induced processes underlying impaired insulin sensitivity in mice. METHODS: Male ICR mice were randomly divided into four groups: a control group without noise exposure and three noise groups exposed to white noise at a 95-dB sound pressure level for 4 h/day for 1, 10, or 20 days (N1D, N10D, and N20D, respectively). Systemic insulin sensitivity was evaluated at 1 day, 1 week, and 1 month post-noise exposure (1DPN, 1WPN, and 1MPN) via insulin tolerance tests (ITTs). Several insulin-related processes, including the phosphorylation of Akt, IRS1, and JNK in the animals' skeletal muscles, were examined using standard immunoblots. Biomarkers of inflammation (circulating levels of TNF-α and IL-6) and oxidative stress (SOD and CAT activities and MDA levels in skeletal muscles) were measured via chemical analyses. RESULTS: The data obtained in this study showed the following: (1) The impairment of systemic insulin sensitivity was transient in the N1D group but prolonged in the N10D and N20D groups. (2) Noise exposure led to enhanced JNK phosphorylation and IRS1 serine phosphorylation as well as reduced Akt phosphorylation in skeletal muscles in response to exogenous insulin stimulation. (3) Plasma levels of TNF-α and IL-6, CAT activity, and MDA concentrations in skeletal muscles were elevated after 20 days of noise exposure. CONCLUSIONS Impaired insulin sensitivity in noise-exposed mice might be mediated by an enhancement of the JNK/IRS1 pathway. Inflammation and oxidative stress might contribute to insulin resistance after chronic noise exposure.
Animals ; Biomarkers ; metabolism ; Inflammation ; physiopathology ; Insulin Receptor Substrate Proteins ; genetics ; metabolism ; Insulin Resistance ; genetics ; immunology ; MAP Kinase Signaling System ; physiology ; Male ; Mice ; Mice, Inbred ICR ; Mitogen-Activated Protein Kinase 8 ; genetics ; metabolism ; Noise ; adverse effects ; Oxidative Stress ; physiology ; Proto-Oncogene Proteins c-akt ; genetics ; metabolism ; Random Allocation ; Time Factors

Angiogenesis is a crucial process in the development of inflammatory diseases, including cancer, psoriasis and rheumatoid arthritis. Recently, several alkaloids from Picrasma quassioides had been screened for angiogenic activity in the zebrafish model, and the results indicated that 1-methoxycarbony-β-carboline (MCC) could effectively inhibit blood vessel formation. In this study, we further confirmed that MCC can inhibit, in a concentration-dependent manner, the viability, migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro, as well as the regenerative vascular outgrowth of zebrafish caudal fin in vivo. In the zebrafish xenograft assay, MCC inhibited the growth of tumor masses and the metastatic transplanted DU145 tumor cells. The proteome profile array of the MCC-treated HUVECs showed that MCC could down-regulate several angiogenesis-related self-secreted proteins, including ANG, EGF, bFGF, GRO, IGF-1, PLG and MMP-1. In addition, the expression of two key membrane receptor proteins in angiogenesis, TIE-2 and uPAR, were also down-regulated after MCC treatment. Taken together, these results shed light on the potential therapeutic application of MCC as a potent natural angiogenesis inhibitor via multiple molecular targets.
Angiogenesis Inhibitors ; chemistry ; pharmacology ; Animals ; Carbolines ; chemistry ; pharmacology ; Cell Movement ; drug effects ; Cell Proliferation ; drug effects ; Epidermal Growth Factor ; genetics ; metabolism ; Fibroblast Growth Factors ; genetics ; metabolism ; Human Umbilical Vein Endothelial Cells ; cytology ; drug effects ; metabolism ; Humans ; Insulin-Like Growth Factor I ; genetics ; metabolism ; Neovascularization, Physiologic ; drug effects ; Picrasma ; chemistry ; Plant Extracts ; chemistry ; pharmacology ; Receptor, TIE-2 ; genetics ; metabolism ; Zebrafish ; embryology

Catalpol, a major bioactive component from Rehmannia glutinosa, which has been used to treat diabetes. The present study was designed to elucidate the anti-diabetic effect and mechanism of action for catalpol in db/db mice. The db/db mice were randomly divided into six groups (10/group) according to their blood glucose levels: db/db control, metformin (positive control), and four dose levels of catalpol treatment (25, 50, 100, and 200 mg·kg), and 10 db/m mice were used as the normal control. All the groups were administered orally for 8 weeks. The levels of fasting blood glucose (FBG), random blood glucose (RBG), glucose tolerance, insulin tolerance, and glycated serum protein (GSP) and the globe gene expression in liver tissues were analyzed. Our results showed that catalpol treatment obviously reduced water intake and food intake in a dose-dependent manner. Catalpol treatment also remarkably reduce fasting blood glucose (FBG) and random blood glucose (RBG) in a dose-dependent manner. The RBG-lowering effect of catalpol was better than that of metformin. Furthermore, catalpol significantly improved glucose tolerance and insulin tolerance via increasing insulin sensitivity. Catalpol treatment significantly decreased GSP level. The comparisons of gene expression in liver tissues among normal control mice, db/db mice and catalpol treated mice (200 and 100 mg·kg) indicated that there were significant increases in the expressions of 287 genes, whichwere mainly involved in lipid metabolism, response to stress, energy metabolism, and cellular processes, and significant decreases in the expressions of 520 genes, which were mainly involved in cell growth, death, immune system, and response to stress. Four genes expressed differentially were linked to glucose metabolism or insulin signaling pathways, including Irs1 (insulin receptor substrate 1), Idh2 (isocitrate dehydrogenase 2 (NADP), mitochondrial), G6pd2 (glucose-6-phosphate dehydrogenase 2), and SOCS3 (suppressor of cytokine signaling 3). In conclusion, catalpol ecerted significant hypoglycemic effect and remarkable therapeutic effect in db/db mice via modulating various gene expressions.
Animals ; Blood Glucose ; metabolism ; Diabetes Mellitus, Experimental ; drug therapy ; genetics ; metabolism ; Disease Models, Animal ; Dose-Response Relationship, Drug ; Drugs, Chinese Herbal ; administration & dosage ; analysis ; Gene Expression ; drug effects ; Glucosephosphate Dehydrogenase ; genetics ; metabolism ; Humans ; Hypoglycemic Agents ; administration & dosage ; Insulin ; metabolism ; Insulin Receptor Substrate Proteins ; genetics ; metabolism ; Iridoid Glucosides ; administration & dosage ; analysis ; Isocitrate Dehydrogenase ; genetics ; metabolism ; Liver ; drug effects ; metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Rehmannia ; chemistry ; Suppressor of Cytokine Signaling 3 Protein ; genetics ; metabolism

Obesity has become a severe public health problem across the world, and seriously affects the health and life quality of human beings. Here we generated lepr and mc4r mutant zebrafish via the CRISPR/Cas9 technique, and performed morphological and functional characterizations of those mutants. We observed that there was no significant phenotypic difference between homozygous mutants and wild-type controls before 2.5 months post-fertilization (mpf). However, the adult leprand mc4rindividuals displayed increased food intake, heavier weight, and higher body fat percentage, the characteristics of obesity phenotypes. Blood glucose test showed that overfeeding induced significantly impaired glucose tolerance in adult leprand mc4rzebrafish. Furthermore, we analyzed 76 energy metabolism-related transcripts in leprand mc4rzebrafish livers by using real-time RT-PCR, and compared the results with the published microarray data of Lepmouse livers, and found that the changes in the expression of insulin/IGF signaling (IIS) pathway genes in leprzebrafish and Lepmouse were positively correlated, suggesting that the IIS pathway maintains functional conservation between zebrafish and mammals during the evolution of the obesity-regulating molecule network.
Animals ; CRISPR-Cas Systems ; Gene Knockout Techniques ; Insulin ; metabolism ; Leptin ; Mutation ; Obesity ; genetics ; Receptor, Melanocortin, Type 4 ; genetics ; Receptors, Leptin ; genetics ; Signal Transduction ; Zebrafish ; Zebrafish Proteins ; genetics

Berberine (BBR) is an isoquinoline alkaloid extracted from Rhizoma coptidis and has been used for treating type 2 diabetes mellitus (T2DM) in China. The development of T2DM is often associated with insulin resistance and impaired glucose uptake in peripheral tissues. In this study, we examined whether BBR attenuated glucose uptake dysfunction through the cholinergic anti-inflammatory pathway in HepG2 cells. Cellular glucose uptake, quantified by the 2-[N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)-amino]-2-deoxy-D-glucose (2-NBDG), was inhibited by 21% after HepG2 cells were incubated with insulin (10(-6) mol/L) for 36 h. Meanwhile, the expression of alpha7 nicotinic acetylcholine receptor (α7nAChR) protein was reduced without the change of acetylcholinesterase (AChE) activity. The level of interleukin-6 (IL-6) in the culture supernatant, the ratio of phosphorylated I-kappa-B kinase-β (IKκβ) Ser181/IKKβ and the expression of nuclear factor-kappa B (NF-κB) p65 protein were also increased. However, the treatment with BBR enhanced the glucose uptake, increased the expression of α7nAChR protein and inhibited AChE activity. These changes were also accompanied with the decrease of the ratio of pIKKβ Ser181/IKKβ, NF-κB p65 expression and IL-6 level. Taken together, these results suggest that BBR could enhance glucose uptake, and relieve insulin resistance and inflammation in HepG2 cells. The mechanism may be related to the cholinergic anti-inflammatory pathway and the inhibition of AChE activity.
Berberine ; pharmacology ; Glucose ; metabolism ; Hep G2 Cells ; Humans ; Hypoglycemic Agents ; pharmacology ; I-kappa B Kinase ; metabolism ; I-kappa B Proteins ; metabolism ; Insulin ; metabolism ; Insulin Resistance ; Interleukin-6 ; metabolism ; Transcription Factor RelA ; metabolism ; alpha7 Nicotinic Acetylcholine Receptor ; genetics ; metabolism

BACKGROUNDMicroRNAs (miRNAs) contribute to tumorigenesis by acting as either oncogenes or tumor suppressor genes. In this study, we investigated the role of miR-145 in the pathogenesis of uveal melanoma.

METHODSExpression profiles of miRNAs in uveal melanoma were performed using Agilent miRNA array. Quantitative real-time polymerase chain reaction was used to screen the expression levels of miR-145 in normal uveal tissue, uveal melanoma tissue, and uveal melanoma cell lines. Lenti-virus expression system was used to construct MUM-2B and OCM-1 cell lines with stable overexpression of miR-145. Cell proliferation, cell cycle, and cell apoptosis of these miR-145 overexpression cell lines were examined by MTT assay and flow cytometry respectively. The target genes of miR-145 were predicted by bioinformatics and confirmed using a luciferase reporter assay. The expression of insulin-like growth factor-1 receptor (IGF-1R), insulin receptor substrate-1 (IRS-1) proteins was determined by Western blotting analysis. IRS-1 was knocked down in OCM-1 cells. TUNEL, BrdU, and flow cytometry assay were performed in IRS-1 knocked down OCM-1 cell lines to analyze its function.

RESULTSForty-seven miRNAs were up regulated in uveal melanoma and 61 were down regulated. miR-145 expression was significantly lower in uveal melanoma sample and the cell lines were compared with normal uveal sample. Overexpression of miR-145 suppressed cell proliferation by blocking the G1 phase entering S phase in uveal melanoma cells, and promoted uveal melanoma cell apoptosis. IRS-1 was identified as a potential target of miR-145 by dual luciferase reporter assay. Knocking down of IRS-1 had similar effect as overexpression of miR-145.

CONCLUSIONmiR-145 might act as a tumor suppressor in uveal melanoma, and downregulation of the target IRS-1 might be a potential mechanism.

Apoptosis ; genetics ; physiology ; Blotting, Western ; Cell Cycle ; genetics ; physiology ; Cell Line, Tumor ; Cell Proliferation ; genetics ; physiology ; Humans ; In Vitro Techniques ; Insulin Receptor Substrate Proteins ; genetics ; metabolism ; Melanoma ; genetics ; metabolism ; pathology ; MicroRNAs ; genetics ; metabolism ; Polymerase Chain Reaction ; Uveal Neoplasms ; genetics ; metabolism ; pathology

The worldwide prevalence of obesity is steadily increasing, nearly doubling between 1980 and 2008. Obesity is often associated with insulin resistance, a major risk factor for type 2 diabetes mellitus (T2DM): a costly chronic disease and serious public health problem. The underlying cause of T2DM is a failure of the beta cells of the pancreas to continue to produce enough insulin to counteract insulin resistance. Most current T2DM therapeutics do not prevent continued loss of insulin secretion capacity, and those that do have the potential to preserve beta cell mass and function are not effective in all patients. Therefore, developing new methods for preventing and treating obesity and T2DM is very timely and of great significance. There is now considerable literature demonstrating a link between inhibitory guanine nucleotide-binding protein (G protein) and G protein-coupled receptor (GPCR) signaling in insulin-responsive tissues and the pathogenesis of obesity and T2DM. These studies are suggesting new and emerging therapeutic targets for these conditions. In this review, we will discuss inhibitory G proteins and GPCRs that have primary actions in the beta cell and other peripheral sites as therapeutic targets for obesity and T2DM, improving satiety, insulin resistance and/or beta cell biology.
Animals ; Diabetes Mellitus, Type 2/drug therapy/*metabolism ; GTP-Binding Protein alpha Subunits/genetics/*metabolism ; Humans ; Insulin-Secreting Cells/metabolism ; Obesity/drug therapy/*metabolism ; Receptor, Melatonin, MT2/genetics/*metabolism ; Receptors, Adrenergic, alpha-1/genetics/*metabolism ; Receptors, Prostaglandin/genetics/*metabolism