Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clinical evidence has shown a correlation between Parkinson's disease (PD) and Type 2 Diabetes (T2D), as abnormal glucose tolerance has been reported in >50% of PD patients. The development of insulin resistance and the degeneration of nigrostriatal dopamine (DA) neurons are both mediated by oxidative mechanisms, and oxidative stress is likely a mechanistic link between these pathologies. Although glucose uptake in neuronal tissues is primarily non-insulin dependent, proteins involved in insulin signaling, such as insulin receptor substrate 2 (IRS2) and glucose transporter 4 (GLUT4), are present in the basal ganglia. The purpose of this study was to determine whether nigrostriatal DA depletion affects measures of insulin resistance in the striatum. Six weeks after 6-hydroxydopamine (6-OHDA) infusion into the medial forebrain bundle, rats were classified as having either partial (20-65%) or severe (90-99%) striatal DA depletion. Increased IRS2 serine phosphorylation, a marker of insulin resistance, was observed in the DA-depleted striatum. Additionally, severe depletion resulted in decreased total IRS2, indicating possible degradation of the protein. Decreased phosphorylation of AKT and expression of the kinase glycogen synthase kinase-3 alpha (GSK3-alpha) was also measured in the striatum of severely DA-depleted animals. Finally, expression of heat shock protein 25 (Hsp25), which is protective against oxidative damage and can decrease stress kinase activity, was decreased in the striatum of lesioned rats. Together, these results support the hypothesis that nigrostriatal DA depletion impairs insulin signaling in the basal ganglia.
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PMID:Measures of striatal insulin resistance in a 6-hydroxydopamine model of Parkinson's disease. 1880 3

An ethanol extract of rhubarb rhizome exhibited marked glucose transport activity in differentiated L6 rat myotubes. Activity-guided fractionation resulted in the isolation of two anthraquinones, chrysophanol-8-O-beta-D-glucopyranoside (1) and chrysophanol (2). The anti-diabetic effect was examined by glucose transport activity, glucose transporter 4 (Glut4) expression in myotubes, and the level of insulin receptor (IR) tyrosine phosphorylation as influenced by tyrosine phosphatase 1B, each of which is a major target of diabetes treatment. Chrysophanol-8-O-beta-D-glucopyranoside up to 25 microM dose-dependently activated glucose transport in insulin-stimulated myotubes. Increased tyrosine phosphorylation of IR due to tyrosine phosphatase 1B inhibitory activity with an IC50 value of 18.34+/-0.29 microM and unchanged Glut4 mRNA levels was observed following chrysophanol-8-O-beta-D-glucopyranoside treatment. Chrysophanol up to 100 microM exerted mild glucose transport activity and elevated the tyrosine phosphorylation of IR via tyrosine phosphatase 1B inhibition (IC50=79.86+/-0.12 microM); Glut4 mRNA expression was also significantly increased by 100 microM. The ED50 values of the two compounds were 59.38+/-0.66 and 79.69+/-0.03 microM, respectively. Therefore, these two anthraquinones from rhubarb rhizome, chrysophanol-8-O-beta-D-glucopyranoside and chrysophanol, have mild cytotoxicity and anti-diabetic properties and could play metabolic roles in the insulin-stimulated glucose transport pathway.
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PMID:Anti-diabetic properties of chrysophanol and its glucoside from rhubarb rhizome. 1898 91

GLUT4 (glucose transporter 4) plays important roles in glucose homoeostasis in vivo. GLUT4 expression and function are diminished in diabetic human and animal subjects. The goal of the present study is to develop a cell-based assay for identifying negative regulators of GLUT4 translocation as potential targets for the treatment of Type 2 diabetes. Traditional GLUT4 translocation assays performed in differentiated myocytes or adipocytes are difficult to perform, particularly in HTS (high-throughput screening) mode. In the present study, we stably co-expressed c-Myc and eGFP [enhanced GFP (green fluorescent protein)] dual-tagged recombinant GLUT4 with recombinant IRS1 (insulin receptor substrate 1) in HEK-293 cells (human embryonic kidney cells) (HEK-293.IRS1.GLUT4 cells). Insulin treatment stimulated both glucose uptake and GLUT4 translocation in these cells. GLUT4 translocation is quantified by a TRF (time-resolved fluorescence) assay in a 96-well HTS format. TRF assays confirmed insulin-stimulated GLUT4 translocation, which can be inhibited by PI3K (phosphoinositide 3-kinase) or Akt [also called PKB (protein kinase B)] inhibitors. Treatment with palmitate increased IRS1 serine phosphorylation and reduced insulin-stimulated Akt phosphorylation and GLUT4 translocation, indicating insulin resistance. Knockdown of PTEN (phosphatase and tensin homologue deleted on chromosome 10) and PTP1B (protein tyrosine phosphatase 1B) gene expression by siRNA (small interfering RNA) treatment significantly increased GLUT4 translocation only in cells treated with palmitate but not in untreated cells. Similar results were obtained on treatment with siRNA of JNK1 (c-Jun N-terminal kinase 1), S6K1 (ribosomal protein S6 kinase, 70 kDa, polypeptide 1) and PKC(theta) (protein kinase C theta). In summary, we have established and validated a novel GLUT4 translocation assay that is optimal for identifying negative regulators of GLUT4 translocation. In combination with more physiologically relevant secondary assays in myotubes and adipocytes, this assay system can be used to identify potential novel therapeutic targets for the treatment of Type 2 diabetes.
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PMID:Development of a novel GLUT4 translocation assay for identifying potential novel therapeutic targets for insulin sensitization. 1903 54

Recent investigations have demonstrated that activation of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in liver and adipose tissue is closely related to the pathogenesis of obesity and diabetes. However, the relationship between alteration of 11beta-HSD1 and the pathogenesis of type 2 diabetes in skeletal muscle is still unclear. A rat model of Type 2 diabetes was developed by high fat diet feeding combined with multiple low dose streptozotocin injection (30 mg/kg, i.p. twice). Intraperitoneal glucose tolerance test, insulin tolerance test were performed. Fasting blood glucose, fasting insulin, total cholesterol, triglyceride were measured. The protein and mRNA level of 11beta-HSD1 and glucocorticoid receptor in gastrocnemius muscle were determined. The alteration of insulin signaling pathway related protein was investigated. We found that the protein levels of 11beta-HSD1 and glucocorticoid receptor were significantly increased (P < 0.05); the mRNA level of 11beta-HSD1 was also elevated (P < 0.05); the mRNA level of glucocorticoid receptor was decreased (P < 0.05). After insulin stimulation, diabetic rats had no significant changes in the level of the insulin receptor beta-subunit (IR-beta), AKT, as in phosphorylated AKT in the gastrocnemius muscle compared to its basal state. Similar results were observed in the protein expression level of glucose transporter 4 (GLUT4). Our data indicate that the alteration of 11beta-HSD1 at protein and mRNA level may be related to the abnormality of insulin signal pathway in skeletal muscle, this effect may be mediated by glucocorticoid receptor.
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PMID:Alteration of 11beta-hydroxysteroid dehydrogenase type 1 in skeletal muscle in a rat model of type 2 diabetes. 1911 9

Oxidized LDL (oxLDL) increase in patients affected by type-2 diabetes, obesity, and metabolic syndrome. Likewise, insulin resistance, an impaired responsiveness of target tissues to insulin, is associated with those pathological conditions. To investigate a possible causal relationship between oxLDL and the onset of insulin resistance, we evaluated the response to insulin of 3T3-L1 adipocytes treated with oxLDL. We observed that oxLDL inhibited glucose uptake (-40%) through reduced glucose transporter 4 (GLUT4) recruitment to the plasma membrane (-70%), without affecting GLUT4 gene expression. These findings were associated to the impairment of insulin signaling. Specifically, in oxLDL-treated cells insulin receptor (IR) substrate-1 (IRS-1) was highly degraded likely because of the enhanced Ser(307)phosphorylation. This process was largely mediated by the activation of the inhibitor of kappaB-kinase beta (IKKbeta) and the c-Jun NH(2)-terminal kinase (JNK). Moreover, the activation of IKKbeta positively regulated the nuclear content of nuclear factor kappaB (NF-kappaB), by inactivating the inhibitor of NF-kappaB (IkappaBalpha). The activated NF-kappaB further impaired per se GLUT4 functionality. Specific inhibitors of IKKbeta, JNK, and NF-kappaB restored insulin sensitivity in adipocytes treated with oxLDL. These data provide the first evidence that oxLDL, by activating serine/threonine kinases, impaired adipocyte response to insulin affecting pathways involved in the recruitment of GLUT4 to plasma membranes (PM). This suggests that oxLDL might participate in the development of insulin resistance.
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PMID:Oxidized LDL impair adipocyte response to insulin by activating serine/threonine kinases. 1913 67

In type 2 diabetes (T2D), postprandial and fasting hyperglycemia are important predictors of cardiovascular diseases; however, few drugs are currently available to simultaneously suppress these conditions. Here, we report an enduring antidiabetic effect of the heme oxygenase (HO) inducer hemin on Goto-Kakizaki rats (GK), a nonobese insulin-resistant T2D model. HO breaks down the heme-moiety-generating antioxidants (biliverdin/bilirubin and ferritin) and carbon monoxide, which stimulate insulin secretion. Hemin induces HO-1 to potentiate HO activity and the HO-derived products. Chronically applied hemin (30 mg/kg ip) for a month reduced and maintained fasting glucose at physiological levels for 3 mo. Before therapy, glucose levels were 9.3 +/- 0.3 mmol/l (n = 14). At 1, 2, and 3 mo posttherapy, we recorded 6.7 +/- 0.13, 5.9 +/- 0.2, and 7.2 +/- 0.2 mmol/l, respectively. Hemin was also effective against postprandial hyperglycemia (14.6 +/- 1.1 vs. 7.5 +/- 0.4 mmol/l; n = 14; P < 0.01), and the effect remained sustained for 3 mo after therapy. The reduction of hyperglycemia was accompanied by enhanced HO-1, HO activity, and cGMP of the soleus muscle, alongside increased plasma bilirubin, ferritin, SOD, total antioxidant capacity, and insulin levels, whereas markers/mediators of oxidative stress like urinary-8-isoprostane and soleus muscle nitrotyrosine, NF-kappaB, and activator protein-1 and -2 were abated. Furthermore, inhibitors of insulin signaling including soleus muscle glycogen synthase kinase-3 and JNK were reduced, while the insulin-sensitizing adipokine, adiponectin, alongside AMPK were increased. Correspondingly, hemin improved glucose tolerance, suppressed insulin intolerance, reduced insulin resistance, and overturned the inability of insulin to enhance glucose transporter 4, a protein required for glucose uptake. Hemin also upregulated HO-1/HO activity and cGMP and lowered glucose in euglycemic Sprague-Dawley control rats albeit less intensely, suggesting greater selectivity of the HO system in diabetic conditions. In conclusion, reduced oxidative stress alongside the concomitant and paradoxical enhancement of insulin secretion and insulin-sensitizing pathways may account for the 3-mo-enduring antidiabetic effect. The synergistic interaction among HO, adiponectin, and GLUT4 may be explored against insulin-resistant diabetes.
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PMID:Upregulation of the heme oxygenase system ameliorates postprandial and fasting hyperglycemia in type 2 diabetes. 1920 58

Increases in adiposity trigger metabolic and inflammatory changes that interfere with insulin action in peripheral tissues, culminating in beta cell failure and overt diabetes. We found that the cAMP Response Element Binding protein (CREB) is activated in adipose cells under obese conditions, where it promotes insulin resistance by triggering expression of the transcriptional repressor ATF3 and thereby downregulating expression of the adipokine hormone adiponectin as well as the insulin-sensitive glucose transporter 4 (GLUT4). Transgenic mice expressing a dominant-negative CREB transgene in adipocytes displayed increased whole-body insulin sensitivity in the contexts of diet-induced and genetic obesity, and they were protected from the development of hepatic steatosis and adipose tissue inflammation. These results indicate that adipocyte CREB provides an early signal in the progression to type 2 diabetes.
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PMID:Adipocyte CREB promotes insulin resistance in obesity. 1925 72

Under the activation of insulin receptors, glucose transporter 4 (Glut4) translocation is regulated by two signal transduction pathways. These pathways are the PI 3-kinase-dependent pathway and the CAP/TC10 pathway. The adaptor protein Rap guanine exchange factor 1 (RAPGEF1) also known as C3G is a component of the CAP/TC10 pathway. Defects in the RAPGEF1 protein may contribute to insulin resistance and type 2 diabetes. Recently, the RAPGEF1 gene was suggested to be involved in the development of type 2 diabetes by FUSION study. To investigate this association in the Korean population, we sequenced the RAPGEF1 gene in 24 unrelated individuals and identified 39 sequence variants. Eleven single nucleotide polymorphisms (SNPs) were selected and genotyped in 1122 Korean patients with type 2 diabetes. There were 1138 non-diabetic controls. Using a logistic regression analysis, a significant association was found between SNP rs11243444 in the RAPGEF1 gene and type 2 diabetes [OR=0.490 (95% CI 0.296-0.813), p=0.006] in the recessive model, leading the protective effect of the GG genotype on the disease development. The present study examines genetic polymorphisms in the RAPGEF1 gene, and the positive association between one polymorphism and type 2 diabetes in the Korean population.
Diabetes Res Clin Pract 2009 May
PMID:RAPGEF1 gene variants associated with type 2 diabetes in the Korean population. 1929 53

Advanced glycation end products (AGEs) contribute to the pathogenesis of diabetes-associated complications. Previously, we reported the possible effect of pyridoxamine (K-163), an AGE inhibitor, on improvement of glucose intolerance in type 2 diabetes mellitus KK-A(y)/Ta mice. Recently, AGEs and oxidative stress have been shown to induce insulin resistance. The objective of the present study is to examine the effect of pyridoxamine on glucose intolerance and oxidative stress. C57BL/6J mice were divided into 3 groups as follows: low-fat diet, high-fat diet, and high-fat diet with pyridoxamine treatment. Body and adipose tissue weight, serum insulin, hydrogen peroxide, malondialdehyde and AGE, and urinary 8-hydroxy-2'-deoxyguanosine levels were measured. Nicotinamide adenine dinucleotide phosphate subunits, antioxidant enzymes, and adipocytokine messenger RNA expressions in the adipose tissues were evaluated. Akt/protein kinase B activity and glucose transporter 4 translocation in skeletal muscle were also evaluated. Body and adipose tissue weights of the pyridoxamine treatment group were significantly decreased compared with those of the high-fat diet group. Pyridoxamine attenuated serum hydrogen peroxide, malondialdehyde and AGE, and urinary 8-hydroxy-2'-deoxyguanosine and nicotinamide adenine dinucleotide phosphate oxidase expression; increased antioxidant enzyme expression; and improved dysregulation of adipocytokines in adipose tissues. Pyridoxamine improved blood glucose levels after glucose injection and fasting hyperinsulinemia. Suppressed Akt/protein kinase B activity and glucose transporter 4 translocation in skeletal muscle in high-fat diet mice were improved by pyridoxamine treatment. It appears that the antioxidative effect of pyridoxamine is associated with improvement of glucose intolerance and obesity in C57BL/6J mice fed a high-fat diet. We assume that pyridoxamine may be useful in the treatment of the obesity-associated metabolic syndrome.
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PMID:Effects of pyridoxamine (K-163) on glucose intolerance and obesity in high-fat diet C57BL/6J mice. 1942 56

A permanent increase in acute-phase serum amyloid A (A-SAA) level is observed in obesity and insulin resistance. Recently, A-SAA has been shown to correlate with obesity and insulin resistance in human. However, what triggers A-SAA up-regulation is poorly understood, and the mechanism of elevated A-SAA to insulin resistance has not been elucidated. In this study, we used two cellular models of insulin resistance, one induced by treatment with tumor necrosis factor-alpha (TNF-alpha) and the other with the glucocorticoid dexamethasone. Gene expression analysis showed that SAA3 mRNA levels were increased in both models of insulin resistance, and ELISA showed that A-SAA levels were increased in both models too. To assess the potential impact of A-SAA on insulin resistance, we treated 3T3-L1 adipocytes with recombinant human SAA (Rh-SAA) and found that Rh-SAA attenuated cellular insulin sensitivity, up-regulated the level of phosphor-JNK, and down-regulated the level of phosphotyrosine-IRS-1 and the expression of glucose transporter 4 (GLUT4) in 3T3-L1 adipocytes. Pre-treatment of cells with C-Jun amino-terminal kinases (JNK) inhibitor brought about partial restoration of Rh-SAA-induced insulin resistance. In sum, our findings suggest that serum amyloid A might be a marker of insulin resistance, and it might play a major role in the development of obesity-related insulin resistance. Moreover, in our study it has been proved that JNK is indeed a crucial component of the pathway responsible for SAA-induced insulin resistance in 3T3-L1 adipocytes, which suggests that a selective interference with JNK activity might be a useful strategy in the treatment of Type 2 diabetes and other insulin-resistant states.
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PMID:Serum amyloid A attenuates cellular insulin sensitivity by increasing JNK activity in 3T3-L1 adipocytes. 1947 23


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