Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The New Zealand obese mouse, a model of NIDDM, is characterized by hyperglycemia, hyperinsulinemia, and hepatic and peripheral insulin resistance. The aim of this study was to investigate the biochemical basis of hepatic insulin resistance in NZO mice. Glycolytic and gluconeogenic enzyme activities were measured in fed and overnight fasted 19- to 20-wk-old NZO and control New Zealand chocolate mice. The NZO mice were twice as heavy as the NZC mice. The activity of the glycolytic enzymes glucokinase and pyruvate kinase was higher, whereas that of the gluconeogenic enzymes PEPCK and glucose-6-phosphatase was lower in fed and fasted NZO mice. These enzyme changes are consistent with a normal response to the hyperinsulinemia in NZO mice. In contrast, the activity of the third regulated gluconeogenic enzyme, fructose-1,6-bisphosphatase, was similar in fed and fasted NZO and NZC mice despite the higher insulin and glucose levels in the NZO mouse. This enzyme is primarily regulated by the powerful inhibitor fructose-2,6-bisphosphate. The levels of this metabolite were measured and found to be increased in both the fed and fasted states in the NZO mouse, suggesting that the activity of the bifunctional enzyme that regulates the level of inhibitor (6-phosphofructo-2-kinase/fructose-2,6- bisphosphatase) is normally regulated in the NZO mouse. We conclude that most insulin-responsive gluconeogenic and glycolytic enzymes are normally regulated in the NZO mouse, but an abnormality in the regulation of fructose-1,6-bisphosphatase may contribute to the increase hepatic glucose production in these mice.
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PMID:Impaired regulation of hepatic fructose-1,6-bisphosphatase in the New Zealand obese mouse model of NIDDM. 824 19

The human PCK1 gene encoding phosphoenolpyruvate carboxykinase (GTP) (PEPCK) was isolated and sequenced. There is 91% amino acid sequence identity (567/622 residues) between the human and the rat proteins, with conservation of intron/exon borders. A polymorphic dinucleotide microsatellite with the structure (CA)16(TA)5(CA) was identified in the 3' untranslated region of the cloned human PCK1 gene. This highly informative genetic marker has an estimated PIC value of 0.79 and heterozygosity of 0.81. Analysis of the RW pedigree demonstrated recombination between PCK1 and the MODY gene on chromosome 20. Multipoint linkage analysis of the reference pedigrees of the Centre d'Etude du Polymorphisme Humain localized PCK1 on the genetic map of chromosome 20 at a position distal to markers that are closely linked to MODY. PCK1 is part of a conserved linkage group on mouse Chromosome 2 with identical gene order but expanded length in the human genome.
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PMID:Phosphoenolpyruvate carboxykinase (GTP): characterization of the human PCK1 gene and localization distal to MODY on chromosome 20. 832 43

Extrapancreatic action of sulfonylurea (SU) drugs were extensively summarized. Hypoglycemic SU drugs stimulate glycolytic pathway and inhibit gluconeogenic pathway in the liver through regulating key enzymes such as the bifunctional enzyme PFK2/F-2,6-P2ase and PEPCK. It is possible that SUs improve the primary defects in NIDDM through both pancreatic and extrapancreatic actions.
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PMID:Extrapancreatic effects of sulfonylurea drugs. 852 2

Insulin regulates the rate of expression of many hepatic genes, including PEPCK, glucose-6-phosphatase (G6Pase), and glucose-6-phosphate dehydrogenase (G6PDHase). The expression of these genes is also abnormally regulated in type 2 diabetes. We demonstrate here that treatment of hepatoma cells with 5-aminoimidazole-4-carboxamide riboside (AICAR), an agent that activates AMP-activated protein kinase (AMPK), mimics the ability of insulin to repress PEPCK gene transcription. It also partially represses G6Pase gene transcription and yet has no effect on the expression of G6PDHase or the constitutively expressed genes cyclophilin or beta-actin. Several lines of evidence suggest that the insulin-mimetic effects of AICAR are mediated by activation of AMPK. Also, insulin does not activate AMPK in H4IIE cells, suggesting that this protein kinase does not link the insulin receptor to the PEPCK and G6Pase gene promoters. Instead, AMPK and insulin may lie on distinct pathways that converge at a point upstream of these 2 gene promoters. Investigation of the pathway by which AMPK acts may therefore give insight into the mechanism of action of insulin. Our results also suggest that activation of AMPK would inhibit hepatic gluconeogenesis in an insulin-independent manner and thus help to reverse the hyperglycemia associated with type 2 diabetes.
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PMID:5-aminoimidazole-4-carboxamide riboside mimics the effects of insulin on the expression of the 2 key gluconeogenic genes PEPCK and glucose-6-phosphatase. 1086 40

A major action of insulin is to regulate the transcription rate of specific genes. The expression of these genes is dramatically altered in type 2 diabetes. For example, the expression of two hepatic genes, glucose-6-phosphatase and PEPCK, is normally inhibited by insulin, but in type 2 diabetes, their expression is insensitive to insulin. An agent that mimics the effect of insulin on the expression of these genes would reduce gluconeogenesis and hepatic glucose output, even in the presence of insulin resistance. The repressive actions of insulin on these genes are dependent on phosphatidylinositol (PI) 3-kinase. However, the molecules that lie between this lipid kinase and the two gene promoters are unknown. Glycogen synthase kinase-3 (GSK-3) is inhibited following activation of PI 3-kinase and protein kinase B. In hepatoma cells, we find that selectively reducing GSK-3 activity strongly reduces the expression of both gluconeogenic genes. The effect is at the level of transcription and is observed with induced or basal gene expression. In addition, GSK-3 inhibition does not result in the subsequent activation of protein kinase B or inhibition of the transcription factor FKHR, which are candidate regulatory molecules for these promoters. Thus, GSK-3 activity is required for basal activity of each promoter. Inhibitors of GSK-3 should therefore reduce hepatic glucose output, as well as increase the synthesis of glycogen from L-glucose. These findings indicate that GSK-3 inhibitors may have greater therapeutic potential for lowering blood glucose levels and treating type 2 diabetes than previously realized.
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PMID:Inhibition of GSK-3 selectively reduces glucose-6-phosphatase and phosphatase and phosphoenolypyruvate carboxykinase gene expression. 1133 36

Adipose tissue glyceroneogenesis generates glycerol 3-phosphate, which could be used for fatty acid esterification during starvation. To determine whether increased glyceroneogenesis leads to increased fat mass and to explore the role of obesity in the development of insulin resistance, we overexpressed PEPCK, a regulatory enzyme of glyceroneogenesis in adipose tissue. Transgenic mice showed a chronic increase in PEPCK activity, which led to increased glyceroneogenesis, re-esterification of free fatty acids (FFAs), increased adipocyte size and fat mass, and higher body weight. In spite of increased fat mass, transgenic mice showed decreased circulating FFAs and normal leptin levels. Moreover, glucose tolerance and whole-body insulin sensitivity were preserved. Skeletal muscle basal and insulin-stimulated glucose uptake and glycogen content were not affected, suggesting that skeletal muscle insulin sensitivity is normal in transgenic obese mice. Our results indicate the key role of PEPCK in the control of FFA re-esterification in adipose tissue and, thus, the contribution of glyceroneogenesis to fat accumulation. Moreover, they suggest that higher fat mass without increased circulating FFAs does not lead to insulin resistance or type 2 diabetes in these mice.
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PMID:Increased fatty acid re-esterification by PEPCK overexpression in adipose tissue leads to obesity without insulin resistance. 1187 59

The two major metabolic perturbations resulting in hyperglycaemia in type 2 diabetes are insulin resistance and insulin deficiency. Insulin resistance occurs in peripheral organs (muscle and fat), leading to decreased glucose uptake and utilisation, and in liver, leading to increased hepatic glucose production. Thiazolidinediones, pharmacological ligands for PPAR gamma, can modulate the expression of genes influencing carbohydrate and lipid metabolism. Pioglitazone, a recently introduced thiazolidinedione, improves glycaemic control and lipid profiles in people with type 2 diabetes. Some of the possible mechanisms of improving glycaemic control include (a) increase in GLUT-1 and GLUT-4, (b) enhancement of insulin signalling, (c) decrease in tumour necrosis factor-alpha action, (d) reduction in plasma free fatty acid and (e) decrease in PEPCK. Together these can increase glucose uptake and utilisation in the peripheral organs and decrease gluconeogenesis in the liver. Possible mechanisms resulting in more desirable lipid profiles include an increase in phosphodiesterase-3B resulting in reduced intra-cellular lipolysis in adipocytes and an increase in lipoprotein lipase resulting in enhanced clearance of triglyceride-rich lipoproteins(TRLs). Pioglitazone, used as monotherapy or in combination with sulphonylurea, biguanide or insulin, improves glycaemic control, lowers serum triglycerides and raises high density lipoprotein (HDL)-cholesterol. It enhances hepatic and peripheral insulin sensitivity. In clinical trials, there has been no evidence of hepatotoxicity or increased incidence of elevated serum ALT in subjects taking pioglitazone compared with placebo.
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PMID:Current treatment of insulin resistance in type 2 diabetes mellitus. 1196 33

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) converts inactive corticosteroids into biologically active corticosteroids, thereby regulating the local concentration of active glucocorticoids, such as cortisol. 11beta-HSD-1 is particularly expressed in adipocytes and liver and appears to be causally linked to the development of type 2 diabetes and the metabolic syndrome. Liver X receptor (LXR)-alpha and -beta are nuclear oxysterol receptors whose key role in lipid metabolic regulation has recently been established. In this study, we show that treatment of adipocytes derived from 3T3-L1 cells and mouse embryonic fibroblasts in vitro with synthetic or natural LXR agonists decreases mRNA expression of 11beta-HSD-1 by approximately 50%, paralleled by a significant decline in 11beta-HSD-1 enzyme activity. Downregulation of 11beta-HSD-1 mRNA by LXRs started after a lag period of 8 h and required ongoing protein synthesis. Moreover, long-term per os treatment with a synthetic LXR agonist downregulated 11beta-HSD-1 mRNA levels by approximately 50% in brown adipose tissue and liver of wild-type but not of LXRalpha(-/-)beta(-/-) mice and was paralleled by downregulation of hepatic PEPCK expression. In conclusion, LXR ligands could mediate beneficial metabolic effects in insulin resistance syndromes including type 2 diabetes by interfering with peripheral glucocorticoid activation.
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PMID:Liver X receptors downregulate 11beta-hydroxysteroid dehydrogenase type 1 expression and activity. 1214 54

Increased hepatic glucose output and decreased glucose utilization are implicated in the development of type 2 diabetes. We previously reported that the expression of a novel gene, Tanis, was upregulated in the liver during fasting in the obese/diabetic animal model Psammomys obesus. Here, we have further studied the protein and its function. Cell fractionation indicated that Tanis was localized in the plasma membrane and microsomes but not in the nucleus, mitochondria, or soluble protein fraction. Consistent with previous gene expression data, hepatic Tanis protein levels increased more significantly in diabetic P. obesus than in nondiabetic controls after fasting. We used a recombinant adenovirus to increase Tanis expression in hepatoma H4IIE cells and investigated its role in metabolism. Tanis overexpression reduced glucose uptake, basal and insulin-stimulated glycogen synthesis, and glycogen content and attenuated the suppression of PEPCK gene expression by insulin, but it did not affect insulin-stimulated insulin receptor phosphorylation or triglyceride synthesis. These results suggest that Tanis may be involved in the regulation of glucose metabolism, and increased expression of Tanis could contribute to insulin resistance in the liver.
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PMID:Elevation in Tanis expression alters glucose metabolism and insulin sensitivity in H4IIE cells. 1266 63

Insulin is the key hormone that controls glucose homeostasis. Dysregulation of insulin function causes diabetes mellitus. Among the two major forms of diabetes, type 2 diabetes accounts for over 90% of the affected population. The incidence of type 2 diabetes is highly related to obesity. To find novel proteins potentially involved in obesity-related insulin resistance and type 2 diabetes, a functional expression screen was performed to search for genes that negatively regulate insulin signaling. Specifically, a reporter system comprised of the PEPCK promoter upstream of alkaline phosphatase was used in a hepatocyte cell-based assay to screen an expression cDNA library for genes that reverse insulin-induced repression of PEPCK transcription. The cDNA library used in this study was derived from the white adipose tissue of ob/ob mice, which are highly insulin-resistant. The mitogen-activated dual specificity protein kinase phosphatase 4 (MKP-4) was identified as a candidate gene in this screen. Here we show that MKP-4 is expressed in insulin-responsive tissues and that the expression levels are up-regulated in obese insulin-resistant rodent models. Heterologous expression of MKP-4 in preadipocytes significantly blocked insulin-induced adipogenesis, and overexpression of MKP-4 in adipocytes inhibited insulin-stimulated glucose uptake. Our data suggest that MKP-4 negatively regulates insulin signaling and, consequently, may contribute to the pathogenesis of insulin resistance.
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PMID:Dual specificity mitogen-activated protein (MAP) kinase phosphatase-4 plays a potential role in insulin resistance. 1277 78


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