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)

Hyperglycemia can lead directly to a secondary state of insulin resistance or can worsen a preexisting insulin-resistant state. Troglitazone is an orally active hypoglycemic agent that has been shown to ameliorate insulin resistance and hyperinsulinemia in both diabetic animal models and NIDDM subjects. To determine whether this drug could prevent the development of hyperglycemia-induced insulin resistance and to investigate the mechanism by which this might occur, we studied troglitazone's effect on insulin action in rats made hyperglycemic or infused with glucosamine. Normal male SD rats were fed regular powdered diet with or without troglitazone as a food admixture (0.2%). After 2 weeks, rats were made hyperglycemic with glucose (52 mg x kg(-1) x min[-1]) and somatostatin (0.8 microg x kg(-1) x min[-1]) infusion or were infused with glucosamine (6.5 mg x kg(-1) x min[-1]) for 6.5 h. In vivo insulin action was measured by the hyperinsulinemic-euglycemic clamp technique at a submaximal (24 pmol x kg(-1) x min[-1]) or maximal (240 pmol x kg(-1) x min[-1]) insulin infusion rate. The infusion of glucose and somatostatin caused a pronounced rise in the plasma glucose concentration (19.8 +/- 0.6 mmol/l) compared with saline-infused animals (8.0 +/- 0.2 mmol/l; P < 0.001). Hyperglycemia resulted in insulin resistance, as evidenced by a marked reduction in the submaximal glucose disposal rate (GDR) (78 +/- 7 vs. 135 +/- 6 micromol x kg(-1) x min(-1); P < 0.01) and maximal GDR (141 +/- 9 vs. 237 +/- 6 micromol x kg(-1) x min(-1); P < 0.01) compared with the control group. Troglitazone treatment largely prevented the hyperglycemia-induced decline in submaximal (116 +/- 7 micromol x kg(-1) x min[-1]) and maximal GDR (209 +/- 9 micromol x kg(-1) x min(-1); P < 0.05). Glucosamine infusion also resulted in a marked reduction in the submaximal GDR (85 +/- 3 vs. 135 +/- 6 micromol x kg(-1) x min(-1); P < 0.01) and maximal GDR (137 +/- 14 vs. 237 +/- 6 micromol x kg(-1) x min(-1); P < 0.01) compared with the control group. In contrast to the results in the hyperglycemic animals, troglitazone treatment had no effect on glucosamine-induced insulin resistance. In summary, 1) in normal rats, experimental hyperglycemia, as well as glucosamine infusion, led to a marked state of peripheral and hepatic insulin resistance; 2) troglitazone treatment prevented the hyperglycemia-induced, but not the glucosamine-induced, insulin resistance; and 3) either troglitazone acts at one or more sites proximal to the entry of glucosamine into the hexosamine pathway, or the increased flux of glucose-derived products through the hexosamine pathway is not a major mechanism for the hyperglycemia-induced defect in insulin action in these animals.
Diabetes 1998 Mar
PMID:Troglitazone prevents hyperglycemia-induced but not glucosamine-induced insulin resistance. 951 45

Both, impaired beta-cell function and insulin resistance, predominantly of the skeletal muscle, are considered to be the key factors in the pathogenesis of type-2 diabetes (non-insulin-dependent diabetes; NIDDM). In the early stage of the disease, impaired insulin-mediated glucose disposal is accompanied by increased insulin secretion and hyperinsulinaemia. The thiazolidinediones (e.g. troglitazone), by improving insulin sensitivity of target tissues, appear to be a novel pathophysiologically interesting approach for the treatment of patients with NIDDM or impaired glucose tolerance. Troglitazone mainly elicits the following actions: Enhancement of insulin-mediated glucose disposal in patients with insulin resistance, impaired glucose tolerance and NIDDM, reduction of hyperglycaemia (blood glucose; HbA1c) and concomitant hyperinsulinaemia, improvement of dyslipidaemia in NIDDM. These actions are attained with monotherapy (200-600 mg once daily; plasma concentrations 0.3-3.0 micrograms/ml) or, with increased effects, when troglitazone is added to previously insufficient treatment with sulfonylureas or insulin. Potentially therapeutic actions with clinical relevance include (a) improvement of insulin resistance-associated hyperglycaemia-independent states of dyslipidaemia, (b) inhibition of LDL-oxidation and (c) amelioration of function and/or protection of beta-cells, an effect indicating to a beneficial modulation of the second pathogenetic relevant factor of NIDDM. Troglitazone appears to be well tolerated by the majority of patients. Post-marketing reports of partly severe liver injury including deaths from liver failure among Japanese and U.S. patients taking troglitazone require a critical evaluation of the benefit to risk ratio of the drug and a careful monitoring of the patients.
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PMID:[The thiazolidinones--a new therapeutic agent for type 2 diabetes]. 954 19

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of troglitazone are reviewed. Troglitazone is the first oral thiazolidinedione approved for use in treating non-insulin-dependent diabetes mellitus (NIDDM). The drug's mechanism of action has not been fully elucidated. Troglitazone acts as an insulin sensitizer. Cell-line and animal models indicate that troglitazone may decrease hepatic glucose output by decreasing the rate of gluconeogenesis in the liver or by increasing glycolysis. Troglitazone is rapidly absorbed after oral administration, with peak concentration occurring in two to three hours. Food increases absorption by 30-85%. The drug is extensively metabolized in the liver. Troglitazone has been shown to be efficacious in treating NIDDM, both as monotherapy and in combination with oral sulfonylureas. Patients who are obese or who have high fasting plasma insulin levels may derive the greatest benefit. Patients with impaired glucose tolerance, syndrome X, polycystic ovary syndrome, gestational diabetes, or Werner's syndrome may also benefit from troglitazone. Adverse effects, including hematologic abnormalities, liver toxicity, and hypoglycemia, have been rare in published trials; no life-threatening effects have been reported thus far. The recommended initial dosage is 200 mg once daily with meals, with an increase to 400 mg daily if satisfactory glycemic control is not achieved after two to four weeks. The average wholesale price is $348 for 100 200-mg tablets and $534 for 100 400-mg tablets. Troglitazone may be an effective agent for treating NIDDM, especially in patients who are obese or who have high fasting plasma insulin levels.
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PMID:Troglitazone: an antidiabetic agent. 958 50

The aim of this in vitro study was to investigate the effect of troglitazone, a new oral antidiabetic agent, on LDL catabolism. HepG2 cells, which are cells from a well-differentiated cell line of hepatoma cells, were cultured and used to study LDL catabolism. Different concentrations of troglitazone, all within the therapeutic range for humans, were incubated in culture medium with 125I-labeled LDL to measure cell-associated and degraded 125I-LDL. Troglitazone increased cell-associated and degraded 125I-LDL by approximately 30%. We also investigated if this effect occurred through a LDL receptor-mediated pathway or a non-LDL receptor pathway. By using dextran sulfate, a substance known to release bound LDL from its receptor, we found that troglitazone upregulated LDL receptor activity by approximately 35%. In addition, we found that troglitazone increased the expression of the LDL receptor mRNA. The effect of troglitazone was comparable with that of a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, fluvastatin, with troglitazone having an upregulatory effect similar to that of fluvastatin. Insulin within human physiological concentrations also increased LDL receptor activity. We found that troglitazone and insulin had an additive effect on LDL catabolism. Also, the effect of troglitazone on LDL catabolism was studied in the presence of cyclosporine, an immunosuppressant drug that reduces LDL catabolism mainly by decreasing LDL receptor activity. The results showed that troglitazone can compensate for the reduced LDL receptor activity induced by cyclosporine, but that cyclosporine had a residual effect on the action of troglitazone. Thus troglitazone enhanced LDL binding, cell association, and degradation by increasing LDL receptor mRNA expression, with a subsequent increase in LDL receptor activity.
Diabetes 1998 Aug
PMID:Troglitazone upregulates LDL receptor activity in HepG2 cells. 970 16

Troglitazone, besides improving insulin action in insulin-resistant subjects, is also a specific ligand for the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma). To determine whether troglitazone might enhance insulin action by stimulation of PPARgamma gene expression in muscle, total PPARgamma messenger RNA (mRNA), and protein were determined in skeletal muscle cultures from nondiabetic control and type II diabetic subjects before and after treatment of cultures with troglitazone (4 days +/- troglitazone, 11.5 microM). Troglitazone treatment increased PPARgamma mRNA levels up to 3-fold in muscle cultures from type II diabetics (277 +/- 63 to 630 +/- 100 x 10(3) copies/microg total RNA, P = 0.003) and in nondiabetic control subjects (200 +/- 42 to 490 +/- 81, P = 0.003). PPARgamma protein levels in both diabetic (4.7 +/- 1.6 to 13.6 +/- 3.0 AU/10 microg protein, P < 0.02) and nondiabetic cells (7.4 +/- 1.0 to 12.7 +/- 1.8, P < 0.05) were also upregulated by troglitazone treatment. Increased PPARgamma was associated with stimulation of human adipocyte lipid binding protein (ALBP) and muscle fatty acid binding protein (mFABP) mRNA, without change in the mRNA for glycerol-3-phosphate dehydrogenase, PPARdelta, myogenin, uncoupling protein-2, or sarcomeric alpha-actin protein. In summary, we showed that troglitazone markedly induces PPARgamma, ALBP, and mFABP mRNA abundance in muscle cultures from both nondiabetic and type II diabetic subjects. Increased expression of PPARgamma protein and other genes involved in glucose and lipid metabolism in skeletal muscle may account, in part, for the insulin sensitizing effects of troglitazone in type II diabetes.
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PMID:Troglitazone effects on gene expression in human skeletal muscle of type II diabetes involve up-regulation of peroxisome proliferator-activated receptor-gamma. 970 55

Englitazone (CP 68,722, Pfizer) is a member of a family of drugs known as thiazolidinediones. One member of this family, troglitazone (Rezulin), is currently utilized in the treatment of Type 2 diabetes. Previous studies have focused on the ability of englitazone to increase insulin sensitivity in various tissues. However, little information is available regarding the direct effect of englitazone on hepatic glucose metabolism in the absence of insulin. Therefore, the following studies were conducted to comparatively evaluate the effect of englitazone and glyburide (a representative sulfonylurea) on gluconeogenesis and glycolysis from various substrates in the isolated perfused rat liver (IPRL). In isolated perfused rat livers of 24-hr fasted rats infused with lactate (2 mM), englitazone (6.25 to 50 microM) produced a concentration-dependent decrease (32-93%) in hepatic gluconeogenesis. When dihydroxyacetone (1 mM) and fructose (1 mM) were used as metabolic substrates, englitazone inhibited gluconeogenesis by 31 and 15%, respectively, while increasing glycolysis by 42 and 50%. Similar effects on gluconeogenesis and glycolysis were observed with glyburide, even though the effects with glyburide were more acutely evident, reversible, and of a greater magnitude. Such data suggest alterations in hepatic glucose production may contribute to the decrease in plasma glucose concentrations observed in individuals treated with englitazone and glyburide. These alterations may include effects on several regulatory enzymes (e.g. fructose-1,6-bisphosphatase, pyruvate kinase, and phosphoenolpyruvate carboxykinase), which warrant further investigation.
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PMID:Comparative effects of englitazone and glyburide on gluconeogenesis and glycolysis in the isolated perfused rat liver. 971 10

Troglitazone and pioglitazone, antidiabetic thiazolidinediones, are known to improve insulin resistance. However, the effect of these drugs on platelet aggregation remains unclear. The chemical structure of troglitazone contains vitamin E. Accordingly, we studied the effect of troglitazone, pioglitazone, and vitamin E on thrombin-induced platelet aggregation, metabolism of phosphoinositide, protein phosphorylation, protein kinase C (PKC)-alpha and -beta, and phosphatidylinositol (PI) 3-kinase activation in vitro in human platelets. Maximum platelet aggregation by ADP, collagen, and thrombin decreased in the presence of 0.1-1 micromol/l troglitazone and 500 nmol/l vitamin E for 60 min compared with controls. However, pioglitazone did not inhibit ADP-, collagen-, or thrombin-induced platelet aggregation. Pretreatment with troglitazone and vitamin E, but not with pioglitazone, resulted in decreases in thrombin-induced phosphatidic acid production, hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C, and 47-kDa protein phosphorylation. Thrombin-induced PKC-alpha and -beta activation in membrane fraction was suppressed by pretreatment with troglitazone and vitamin E, but not with pioglitazone. Separately, troglitazone and pioglitazone stimulated PI 3-kinase activity, but thrombin-induced PI 3-kinase activation was suppressed by pretreatment with troglitazone and pioglitazone for 60 min. These results suggest that troglitazone and vitamin E, but not pioglitazone, have a potent inhibitory effect on platelet aggregation via suppression of the thrombin-induced activation of phosphoinositide signaling in human platelets. Finally, the chemical structure of vitamin E may contribute to the inhibitory effect of troglitazone on platelet aggregation in human platelets.
Diabetes 1998 Sep
PMID:Differential effect of the antidiabetic thiazolidinediones troglitazone and pioglitazone on human platelet aggregation mechanism. 972 40

The management of Type 2 diabetes mellitus with currently available oral agents may be complicated in the elderly by an increased frequency of side-effects. The effects of troglitazone, an insulin action enhancer, were studied in elderly patients with Type 2 diabetes in a double-blind, parallel-group, placebo-controlled trial. A total of 229 patients (41% male), mean age 75 (range 69-85) years, with two fasting capillary blood glucose values > or =7 and < or =15 mmol l(-1) (and within 4.0 mmol l(-1) of each other) and previously treated with either diet alone (30%) or oral hypoglycaemic agents, were randomized to placebo or troglitazone 400 mg once daily or 200 mg twice daily, or 800 mg once daily or 400 mg twice daily, for 12 weeks. After 12 weeks' treatment, fasting serum glucose was significantly lower in troglitazone-treated patients (troglitazone, adjusted geometric mean 9.4-10.4 mmol l(-1) vs placebo 12.7 mmol l(-1), p < 0.001). Adjusted geometric mean fructosamine was also lower in troglitazone-treated patients by 5 to 15% compared to placebo (P < 0.05 at all doses except 400 mg od). There was no significant difference between troglitazone doses for improvement in glycaemic control. Troglitazone lowered adjusted geometric mean fasting plasma insulin by 27-34% compared to placebo (P < 0.001) and insulin sensitivity (HOMA-S) improved by 9-15% in all troglitazone dose groups (p < 0.001). Troglitazone also lowered serum non-esterified fatty acids and triglyceride. Adverse event incidence in troglitazone-treated patients was similar to that in patients treated with placebo. No weight gain or symptomatic hypoglycaemia was recorded at any of the doses studied. Troglitazone is effective and well tolerated in elderly patients with Type 2 diabetes mellitus, providing improved glycaemic control in the absence of weight gain.
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PMID:Troglitazone, an insulin action enhancer, improves glycaemic control and insulin sensitivity in elderly type 2 diabetic patients. 973 7

To assess the effects of troglitazone monotherapy on glycemic control in patients with type 2 diabetes mellitus, we carried out a 6-month, randomized, double-blind, placebo-controlled study in 24 hospital and outpatient clinics in the United States and Canada. Troglitazone 100, 200, 400, or 600 mg or placebo once daily with breakfast was administered to 402 patients with type 2 diabetes with fasting serum glucose (FSG) > 140 mg/dL, glycosylated hemoglobin (HbA1c) > 6.5%, and fasting C-peptide > or = 1.5 ng/mL. Prior oral hypoglycemic therapy was withdrawn in patients who received it before the study. FSG, HbA1c, C-peptide, and serum insulin were evaluated at baseline and the end of the study. Analysis was performed on two subsets of patients based on prestudy therapy: Patients treated with diet and exercise only before the study (22% of patients), and those who had been receiving sulfonylurea therapy (78% of patients). Patients treated with 400 and 600 mg troglitazone had significant decreases from baseline in mean FSG and HbA1c at month 6 compared with placebo-treated patients (FSG: -51 and -60 mg/dL, respectively; HbA1c: -0.7 and -1.1%, respectively). In the diet-only subset, 600 mg troglitazone therapy resulted in a significant (P < 0.05) reduction in HbA1c (-1.35%) and a significant reduction in FSG (-42 mg/dL) compared with placebo. Patients previously treated with sulfonylurea therapy had significant (P < 0.05) decreases in mean FSG with 200-600 mg troglitazone therapy compared with placebo (-48, -61, and -66 mg/dL, respectively). Significant (P < 0.05) decreases in mean HbA1c occurred with 400 and 600 mg troglitazone therapy at month 6 (-0.8 and -1.2%, respectively) compared with placebo in this same subset. Significant (P < 0.05) decreases in triglycerides and free fatty acids occurred with troglitazone 400 and 600 mg, and increased high-density lipoprotein occurred with 600 mg troglitazone. We conclude that troglitazone monotherapy significantly improves HbA1c and fasting serum glucose, while lowering insulin and C-peptide in patients with type 2 diabetes. Troglitazone 600 mg monotherapy is efficacious for patients who are newly diagnosed and have never received pharmacological intervention for diabetes.
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PMID:Troglitazone monotherapy improves glycemic control in patients with type 2 diabetes mellitus: a randomized, controlled study. The Troglitazone Study Group. 1002 65

Troglitazone has recently been introduced in the treatment of Type 2 diabetes. In addition to its anti-diabetic effects it acts as a perixosome proliferator activated receptor-gamma (PPAR-gamma) agonist and has anti-inflammatory properties by inhibiting macrophage tumour necrosis factor-alpha (TNF-alpha) secretion. It also inhibits the production of endothelial selectin (e-selectin). Troglitazone also reduces interleukin-1alpha induced nitric oxide production in pancreatic beta-cells, which may be relevant in preventing nitric oxide mediated damage to these cells in the Type 1 diabetes process. We tested troglitazone in the spontaneous model of autoimmune diabetes, the non-obese diabetic (NOD) mouse, to determine its effect on the disease process. When administered by gavage from weaning at a dose of 400 mg/kg body weight (n = 32), troglitazone reduced the incidence of diabetes by 16 weeks compared to controls (n = 32) in a pattern that was maintained up to the conclusion of the experiment at 31 weeks of age (p < 0.05). Insulitis was unaltered (index = 1.05 +/- 0.71 vs. 1.13 +/- 0.82, treated vs. controls, p = 0.78). The study was repeated using troglitazone in the diet of NOD mice (n = 24) to give a dose of approximately 200 mg/kg body weight in order to provide a more consistent level of troglitazone during the time course of the experiment. There was a reduction of diabetes incidence in this group but it did not reach significance. Insulin levels were reduced in gavage treated mice although such reduction did not reach significance (p < 0.07). We conclude that, in view of its effect on this model of autoimmune diabetes and because of its known function as an insulin sensitiser, troglitazone might be considered for potential use in those patients with Type 1 masquerading as Type 2 diabetes.
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PMID:Troglitazone prevents insulin dependent diabetes in the non-obese diabetic mouse. 979 40


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