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[Diabetes update: preventing type 2 diabetes. Individualized stepwise therapy (oral antidiabetic agents). Multifactorial intervention].

Preclinical disorders of glucose metabolism should be systematically included in the high-risk group for diabetes mellitus and affected individuals provided with preventive measures. Their underlying insulin resistance is determined with the help of a checklist and a method called homeostasis model assessment (HOMA). Patients with impaired fasting glucose (IFG) must change their lifestyles. If this does not lead to a response or the patient is unable to modify behavior, medication is required. In the case of manifest type 2 diabetes mellitus, a graded schedule is used for differential management, which should be based on nutritional and exercise therapy. Oral medication with metformin is probably the drug of choice in both obese and non-obese patients. It is crucial not to delay raising the level of treatment until HbA1c has fallen to within an unsatisfactory range (wait-and-see strategy). Rather, the level should be intensified when persistent exacerbation starts to become apparent (proactive therapy). In diabetes mellitus, the same guidelines for secondary prevention apply to the associated cardiovascular risk factors as with coronary heart disease. An intensified and, especially, early treatment is to be preferred over a conservative, wait-and-see approach, in this case as well.

Cardiovascular Diseases↗

Hypoglycaemic and insulinotropic effects of a novel oral antidiabetic agent, (-)-N-(trans-4-isopropylcyclohexanecarbonyl)-D-phenylalanine (A-4166).

1. (-)-N-(trans-4-isopropylcyclohexanecarbonyl)-D-phenylalanine (A-4166), a novel oral hypoglycaemic agent is a non-sulphonylurea insulin secretagogue. 2. We investigated the insulin-releasing action and hypoglycaemic effect of A-4166 compared to sulphonylureas in vitro and in vivo. 3. A-4166 stimulated insulin secretion from rat freshly isolated pancreatic islets at concentrations from 3 x 10(-6) M to 3 x 10(-4) M in the presence of 2.8 mM glucose. There was no obvious difference in glucose dependency between the insulinotropic effect of A-4166 and that of glibenclamide, and no additive or synergistic effect was observed between these two drugs. 4. A-4166 displaced [3H]-glibenclamide bound to intact HIT-T15 cells in a concentration-dependent manner. The Ki value was 4.34 +/- 0.04 x 10(7) M, and the displacement potency of A-4166 was between that of glibenclamide and tolbutamide, being similar to that of gliclazide. 5. Inf fasted beagle dogs, A-4166 showed a dose-dependent hypoglycaemic effect after oral administration over the range 1 to 10 mg kg-1. The hypoglycaemic action of A-4166 showed an earlier onset and a shorter duration than that of sulphonylureas. 6. Simultaneous measurement of plasma insulin levels revealed that the hypoglycaemic effect of A-4166 was caused by a rapid-onset and brief burst of insulin secretion. 7. The pharmacokinetic profile of A-4166 was consistent with the changes of the blood glucose and plasma insulin levels. 8. Although the in vitro insulin-releasing effect of A-4166 was similar to that of sulphonylureas, its hypoglycaemic effect was more rapid and shorter-lasting, associated with rapid absorption and clearance. Thus, A-4166 may be useful in suppressing postprandial hyperglycaemia in patients with non-insulin-dependent diabetes mellitus.

Animals↗

Hypoglycaemic effects of the novel antidiabetic agent repaglinide in rats and dogs.

1. Repaglinide, a novel compound with a nonsulphonylurea structure, is currently being clinically tested as a therapeutic agent. In the present study, the hypoglycaemic effects of repaglinide in rats and dogs were investigated. 2. Whereas the R-enantiomer, AG-EE 624 ZW, showed only weak hypoglycaemic activity, the S-enantiomer, repaglinide, turned out to be a potent hypoglycaemic compound in rats after oral as well as after intravenous administration. Only 50% of the dose of repaglinide was needed to be equieffective with the racemic mixture AG-EE 388 ZW. The corresponding ED50 values calculated for the effects after 120 min p.a. (intravenous administration) were 3.4 micrograms kg-1 (repaglinide) and 6 micrograms kg-1 (AG-EE 388 ZW). 3. When compared to glimepiride or glibenclamide, repaglinide displayed a 18 to 25 times higher potency in fasted rats. The ED50 values calculated for the effects after 120 min p.a. (oral administration) were 10 micrograms kg-1 (repaglinide), 182 micrograms kg-1 (glimepiride) and 255 micrograms kg-1 (glibenclamide). 4. In glucose loaded rats (0.5, 1.0, 2.0 and 3.0 g kg-1 glucose, p.o.) repaglinide exerted a very strong antihyperglycaemic activity which was even more pronounced than under normoglycaemic conditions. So for a reduction in blood glucose of 1 mmol l-1, 10.3, 9.3, 7.0 8.4 and 7.2 micrograms kg-1 repaglinide were needed after glucose loads of 0.0, 0.5, 1.0, 2.0 and 3.0 g kg-1, respectively. 5. In beagle dogs repaglinide again showed a pronounced hypoglycaemic effect (ED50 28.3 micrograms kg-1) which lasted for up to 24 h. However, insulin levels were only transiently increased. 6. The in vivo data presented are well supported by recently published in vitro findings. From its activity profile, repaglinide appears to be a promising new therapeutic agent.

Animals↗

JTT-501, a novel oral antidiabetic agent, improves insulin resistance in genetic and non-genetic insulin-resistant models.

1. We investigated whether JTT-501 (4-[4-[2-(5-methyl-2-phenyl-4-oxazolyl)ethoxy]benzyl]-3,5-isoxa zolidinedione) would improve insulin resistance in genetic (Zucker fatty rats) and non-genetic (high-fat fed rats) rodent models of obesity. 2. JTT-501 (10-100 mg kg(-1) day(-1)) was administered orally to Zucker fatty rats for 7-21 days. In the high-fat fed rat model, JTT-501 (100 mg kg(-1) day(-1) was administered orally for 7 days. In both models, JTT-501 improved metabolic abnormalities by enhancing insulin action during the glucose tolerance test and the euglycaemic-hyperinsulinaemic clamp study. In ex vivo assays, JTT-501 ameliorated the impaired insulin-sensitive glucose oxidation and lipid synthesis in peripheral tissues. Furthermore, JTT-501 enhanced insulin receptor autophosphorylation in hindlimb muscle. 3. JTT-501 reduced serum leptin concentrations in both models, but did not affect body weight or epididymal fat weight. 4. Our observations indicate that JTT-501 improves the metabolic abnormalities in both genetic and non-genetic insulin-resistant models by enhancing insulin action in peripheral tissues. These effects of JTT-501 are due, at least in part, to enhanced insulin receptor autophosphorylation. In addition, JTT-501 is able to reduce serum leptin concentrations in hyperleptinaemia of the insulin-resistant model. We expect JTT-501 to show promise for treating non-insulin dependent diabetes mellitus patients with insulin resistance.

Animals↗

Introduction to the Kinases in Diabetes Biochemical Society Focused Meeting: are protein kinases good targets for antidiabetic drugs?

Insulin regulates whole-body glucose homoeostasis by modulating the activities of protein kinases in its target tissues: muscle, liver and fat. Defects in insulin's ability to modulate protein kinase activity lead to 'insulin resistance' or impaired insulin action. Insulin resistance in combination with defective insulin secretion from the pancreas results in the elevated blood glucose levels that are characteristic of diabetes mellitus. Pharmacological agents that selectively modulate protein kinase activities in insulin-resistant tissues may act either as insulin-sensitizing or insulin-mimetic drugs. Consistent with this, small molecule modulators of a number of protein kinases have demonstrated efficacy in animal models of insulin resistance and diabetes. Moreover, emerging data in humans suggest that marketed anti-diabetic agents may also act in part through modulating protein kinase activities. This meeting was convened to consider the potential to treat insulin resistance and Type II diabetes by modulating protein kinase activity.

Animals↗

Repaglinide, a new oral antidiabetic agent: a review of recent preclinical studies.

Repaglinide is a new carbamoylmethyl benzoic acid derivative that is structurally related to meglitinide. In common with all active oral hypoglycaemic agents, it displays a comparable U-shaped configuration. Repaglinide exerts its effects by binding to a site on the plasma membrane of beta-cells, thereby closing ATP-sensitive potassium channels. This causes depolarization of the beta-cell and the opening of voltage-sensitive calcium channels allowing the influx of extracellular calcium ions. This increase in intracellular calcium, in turn, stimulates insulin release. The insulinotropic effect of repaglinide is not related to its ionophoretic capacity. Repaglinide does not cause insulin release in the absence of exogenous glucose, nor does it inhibit the biosynthesis of proinsulin. In vivo administration of an ester of succinic acid potentiates the insulin secretory response to concomitantly administered repaglinide. Repaglinide causes a more rapid increase in plasma insulin levels in rats than either glibenclamide or glimepiride.

Administration, Oral↗

Traffic hypoglycaemias and accidents in patients with diabetes mellitus treated with different antidiabetic regimens.

OBJECTIVES: Insulin-treated patients with diabetes are at a higher risk than the general population in causing traffic accidents due to hypoglycaemias. Preceding investigations focused on insulin-treated patients and hypoglycaemia-induced accidents as "end-points". We studied the incidence of symptomatic hypoglycaemia and hypoglycaemia-induced accidents during driving and put it in relation to the different treatment modes of insulin therapy (Conventional Insulin Treatment = CT, Intensified Conventional Insulin Treatment = ICT, Continuous Subcutaneous Insulin Infusion = CSII) as well as to patients treated with oral hypoglycaemia-inducing agents and the two main types of diabetes mellitus. DESIGN SUBJECTS AND SETTING: We investigated 450 patients (122 treated with sulphonylureas, 151 with CT, 143 with ICT and 34 with CSII) by an anonymous questionnaire at different locations to avoid bias. A total of 176 persons had type 1 diabetes, 243 persons had type 2 diabetes, 31 subjects could not be classified. RESULTS: Symptomatic hypoglycaemias during driving were rare events with an occurrence of 0.19-8.26 (minimal and maximal mean, depending on the mode of treatment), if given as hypoglycaemias per 100 000 km on one treatment regimen, or 0.02-0.63, if given as events per year driven. Their incidence increased significantly with the degree of "strictness" between the treatment groups, except between the patients treated with ICT and CSII. Hypoglycaemia-induced accidents are rare with 0.01-0.49, if given as events per 100 000 km and 0.007-0.01, if given as events per year driven. These differences were not significant. Significant confounders influencing the traffic safety of the patients were age, duration of diabetes and concomitant antihypertensive medication. Analysing the data in accordance with the type of diabetes revealed a significantly higher rate of hypoglycaemic events in patients with type 1 diabetes. The number of hypoglycaemia-induced accidents was considerably higher in this group, but failed slightly to reach statistical significance. CONCLUSIONS: Hypoglycaemias during driving are rare events, their occurrence is significantly influenced by the treatment regimen and type of diabetes. Hypoglycaemia-induced accidents are extremely rare, presumably as a positive effect of patient education in our group.

Accidents, Traffic↗

Antidiabetic sulphonylureas stimulate acetylcholine release from striatal cholinergic interneurones through inhibition of K(ATP) channel activity.

The sulphonylureas tolbutamide and glibenclamide were shown to stimulate acetylcholine release from rat striatal slices. To determine the mechanism of this effect, whole-cell patch-clamp recordings were made from large neurones within the striatum that displayed morphological, electrophysiological, and pharmacological characteristics typical of cholinergic interneurones. Dialysis of these neurones with a pipette solution containing low concentrations of ATP produced a gradual hyperpolarisation that could be reversed by bath application of the sulphonylureas. In voltage-clamp studies, these compounds were shown to act through the inhibition of a potassium conductance. It is concluded that cholinergic interneurones within the rat striatum express sulphonylurea-sensitive ATP-sensitive potassium channel activity. These channels are probably cytoprotective and may prove to be novel sites of therapeutic modulation.

Acetylcholine↗

Long-term prognosis of diabetic patients with myocardial infarction: relation to antidiabetic treatment regimen. The TRACE Study Group.

AIMS: The present study was performed to evaluate pre-admission history, presentation, initial treatment and long-term mortality in patients with myocardial infarction and diabetes. METHODS AND RESULTS: Between 1990 and 1992, 6676 patients with acute myocardial infarction were screened for entry into the Trandolapril Cardiac Evaluation (TRACE) study. In this cohort 719 (11%) of the patients had a history of diabetes. Among the diabetic patients 19% were treated with insulin, 52% with oral hypoglycaemic agents and 29% with diet only. The diabetic patients were slightly older, more likely to be female and had a higher prevalence of known cardiovascular disease. Even though the diabetic patients had the same frequency of ST-segment elevation on the electrocardiogram and the same admission delay, treatment with thrombolysis and aspirin was less frequently prescribed to the diabetic patients than to patients without diabetes. The mortality rate was significantly increased in the diabetic patients, 7-year mortality being 79% in insulin-treated, 73% in tablet-treated and 62% in diet-treated diabetic patients compared with 46% in patients without diabetes. In a multivariate analysis only diabetic patients treated with oral hypoglycaemic agents or with insulin had an increased mortality compared with non-diabetic patients. CONCLUSIONS: Patients with diabetes mellitus and myocardial infarction are treated with thrombolysis to a lesser extent than non-diabetic patients. Diabetic patients treated with oral hypoglycaemic agents or insulin, but not those treated with diet alone, have a significantly increased mortality following acute myocardial infarction compared with non-diabetic patients.

Aged↗

Antidiabetic thiazolidinediones inhibit collagen synthesis and hepatic stellate cell activation in vivo and in vitro.

BACKGROUND & AIMS: The ligand-dependent transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed in hepatic stellate cells (HSC), and its transcriptional activity is reduced during cell transdifferentiation in culture. PPARgamma transcriptional activation decreases platelet-derived growth factor-induced proliferation and inhibits alpha-smooth muscle actin expression in cultured HSC. The aim of our study was to evaluate whether oral administration of synthetic PPARgamma ligands, thiazolidinediones (TZD), might affect collagen deposition in animal models of liver fibrosis. METHODS: The effect of 2 TZD (pioglitazone or rosiglitazone) was tested on liver fibrosis induced in rats by either toxin administration (dimethylnitrosamine or carbon tetrachloride) or bile duct ligation. In vivo PPARgamma activation was evaluated by gel shift assay using nuclear extracts from HSC isolated from control and treated rats. RESULTS: Oral administration of TZD reduced extracellular matrix deposition and HSC activation in both toxic and cholestatic models of liver fibrosis. PPARgamma-specific DNA binding was significantly impaired in nuclear extracts of HSC isolated from fibrotic rats compared with HSC from control rats. TZD administration restored PPARgamma DNA binding in HSC nuclei. In vitro, TZD-induced PPARgamma activation inhibited collagen and fibronectin synthesis induced by transforming growth factor (TGF)-beta1 in human HSC, as measured by enzyme-linked immunosorbent assay and Northen blotting. TZD also reduced the TGF-beta1-induced activity of a 3.5-kilobase procollagen type I promoter transfected in human HSC. CONCLUSIONS: These findings indicate that PPARgamma activation in HSC retards fibrosis in vivo and suggest the use of TZD for the treatment of liver fibrosis.

Animals↗

Lowering plasma free fatty acids with Acipimox mimics the antidiabetic effects of the beta 3-adrenergic agonist CL-316243 in obese Zucker diabetic fatty rats.

We previously reported that long-term treatment of Zucker diabetic fatty (ZDF) rats with the selective beta(3) agonist CL-316243 normalizes glycemia, decreases plasma free fatty acids (FFA) concentration, improves insulin responsiveness, and increases glucose uptake, not only in brown and white adipose tissues, but also in skeletal muscles. Because muscles do not express typical beta(3) adrenoceptors, we postulated that the muscle effect was indirect and that it was possibly mediated by an activation of the glucose-fatty acid cycle. To test this hypothesis, we investigated the effects of Acipimox, a potent inhibitor of lipolysis in adipose tissue. Similar to CL-316243, Acipimox (150 mg/kg orally) markedly decreased plasma FFA, glucose, and insulin concentrations and improved glucose tolerance while reducing the insulin response in obese (350 to 400 g) ZDF rats. Plasma FFA concentrations were significantly correlated with plasma glucose and insulin concentrations (r =.72 and.83, respectively; P <.01), indicating strong metabolic relationships between these parameters. Euglycemic-hyperinsulinemic clamps combined with the 2-[(3)H]deoxyglucose method revealed that Acipimox markedly improved insulin responsiveness and significantly increased glucose uptake (Rg') in the diaphragm, the heart, and various skeletal muscles. Unlike CL-316243, Acipimox did not increase glucose use in brown or white adipose tissues. This selectivity shows that it is possible to improve diabetes in obese ZDF rats without necessarily stimulating thermogenesis in adipose tissues. Thus, decreasing plasma FFA with 2 drugs (Acipimox or CL-316243) that act via different mechanisms (acute inhibition of lipolysis or chronic stimulation of FFA oxidation) is associated with increased glucose uptake in muscles and enhanced insulin responsiveness. These observations support the hypothesis that CL-316243 may indirectly stimulate glucose uptake in muscles of type II diabetic rats by first stimulating brown adipose tissue (increasing uncoupling protein content and fatty acid oxidation) and progressively decreasing the levels of circulating FFA, resulting in activation of the glucose-fatty acid cycle or other mechanisms regulating insulin responsiveness in skeletal muscles.

Adrenergic beta-3 Receptor Agonists↗

Antidiabetic actions of arachidonic acid and zinc in genetically diabetic Goto-Kakizaki rats.

In previous studies, we showed that feeding arachidonic acid (AA) supplemented with a fixed amount of zinc lowered blood glucose concentrations in the fed state and water intake in rats with streptozotocin-induced diabetes. The present study was designed to determine dose-dependent effects of AA supplemented with a fixed amount of zinc on fed blood glucose levels, water intake, and glucose tolerance in genetically type 2 diabetic Goto-Kakizaki (G-K) Wistar rats. In an acute study, 20 mg/kg AA plus 10 mg/kg zinc administered via gastric gavage significantly improved oral glucose tolerance in G-K rats when compared to rats given distilled water (DW) only. When rats were treated chronically (2 weeks) with increasing doses of AA in drinking water, fed blood glucose concentrations and water intake were maximally decreased with diets containing 20 or 30 mg/L AA plus 10 mg/L zinc. Three-hour average area-above-fasting glucose concentrations (TAFGC; index of oral glucose tolerance) in diabetic G-K rats treated with 10, 20, or 30 mg/L AA plus 10 mg/L zinc for 2 weeks were significantly decreased relative to DW-treated rats. The effect on TAFGC values was maintained for an additional 2 weeks after cessation of treatment. Plasma insulin levels significantly increased in rats treated with 20 mg/L AA only or 10 mg/L AA plus 10 mg/L zinc, but not in rats treated with 20 or 30 mg/L AA plus 10 mg/L zinc, which are the most effective doses for the improvement of clinical signs of diabetes in G-K rats. In in vitro assays, 0.2 mg/mL AA in the incubation media was optimal for glucose uptake in isolated soleus muscle slices. These results suggest that treatment of genetically diabetic G-K rats with AA plus zinc lowers blood glucose levels via improvement of insulin sensitivity.

Animals↗