Studies on the mechanism of action of sulphonylureas in type II diabetic subjects: gliquidone

Gliquidone ameliorates hepatic insulin resistance in streptozotocin-induced diabetic Sur1-/- rats

Gliquidone was suggested to exert hypoglycemic effect through enhancing hepatic insulin sensitivity. However, inadequate in vivo evidences make this statement controversial. The aim of the present study was to clarify the insulin-sensitizer role of gliquidone in liver and muscle, so as to confirm its extra-pancreatic effects in vivo. TALEN technique was used to create Sur1 knockout (Sur1^-/-) rats. Diabetic Sur1^-/- rat models were established by high-fat diet combined with streptozotocin, and which were randomly divided into three groups: gliquidone, metformin and saline, treated for 8 weeks. Fasting blood glucose (FBG) and body mass were tested each week. IPGTT, IPITT and hyperinsulinemic-euglycemic clamp tests were used to evaluate glucose tolerance and insulin sensitivity, respectively. Key mediators of glucose metabolism in liver and skeletal muscle and the activity of AKT and AMPK in these tissues were further analyzed. We found that gliquidone decreased FBG and increased insulin sensitivity without increasing insulin secretion in diabetic Sur1^-/- rats. Further exploration implied that gliquidone mainly increased hepatic glycogen storage and decreased gluconeogenesis, which were accompanied with activation of AKT, but not enhanced muscle GLUT4 expression. However, both these effects were still weaker than that of metformin. These results suggested that gliquidone could exerts an extra-pancreatic hypoglycemic effect by improving insulin sensitivity, which might be largely attributes to its additional insulin sensitizer role in hepatic glucose metabolism.

Eltrombopag is a potential target for drug intervention in SARS-CoV-2 spike protein

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is a current global threat for which there is an urgent need to search for an effective therapy. The transmembrane spike (S) glycoprotein of SARS-CoV-2 directly binds to the host angiotensin-converting enzyme 2 (ACE2) and mediates viral entrance, which is therefore considered as a promising drug target. Considering that new drug development is a time-consuming process, drug repositioning may facilitate rapid drug discovery dealing with sudden infectious diseases. Here, we compared the differences between the virtual structural proteins of SARS-CoV-2 and SARS-CoV, and selected a pocket mainly localizing in the fusion cores of S2 domain for drug screening. A virtual drug design algorithm screened the Food and Drug Administration-approved drug library of 1234 compounds, and 13 top scored compounds were obtained through manual screening. Through in vitro molecular interaction experiments, eltrombopag was further verified to possess a high binding affinity to S protein plus human ACE2 and could potentially affect the stability of the ACE2-S protein complex. Hence, it is worth further exploring eltrombopag as a potential drug for the treatment of SARS-CoV-2 infection.

Protective Effects of Glurenorm (Gliquidone) Treatment on the Liver Injury of Experimental Diabetes

Oxidative stress plays an important role in chronic complications of diabetes mellitus, and hence the regulation of free radicals is essential in the treatment of diabetes. The aim of the current study is to investigate the effect of glurenorm (10 mg/kg) on liver tissue in experimental diabetes. Diabetes was induced by intraperitoneal injection of 65 mg/kg streptozotocin. Glurenorm was administered to one diabetic and one control group separately, from days 14 to 42. On day 42, cardiac blood samples and liver tissue were taken from each rat. In diabetic rats, blood glucose, serum alkaline phosphatase and serum amino transferase activities, serum uric acid, serum sodium and potassium levels, liver nonenzymatic glycosylation, and lipid peroxidation increased, whereas body weight and liver glutathione levels decreased. The diabetic group given glurenorm blood glucose, serum alkaline phosphatase and aminotransferase activities, serum uric acid, sodium and potassium, liver nonenzymatic glycosylation, and lipid peroxidation levels decreased, and liver glutathione levels increased. As a result of all the biochemical findings obtained, it was concluded that glurenorm has a protective effect on damage of liver of streptozotocin-induced diabetes in rats.

Gliquidone Contributes to Improvement of Type 2 Diabetes Mellitus Management

Diabetes mellitus is a global health problem of steadily increasing proportions, with approximately 95% of patients being affected by the type 2 form of the disease. The growing challenge to healthcare systems presented by this disorder has prompted ongoing research into novel therapies with which to improve management. The sulfonylureas constitute a long-established group of drugs with a proven track record in the treatment of type 2 diabetes, but efforts to improve the overall metabolic profile and safety of these agents have led over time to the addition of newer agents such as the second-generation benzenesulfonylurea gliquidone. Gliquidone has extrapancreatic effects that result in increased numbers of insulin receptors in peripheral tissues. The drug is rapidly and almost completely absorbed after oral administration, and has a short elimination half-life (around 1.5 hours). Metabolism is maintained in patients with hepatic insufficiency, and accumulation does not take place in patients with impaired renal function. Plasma glucose levels are controlled for several hours as a result of glucose-induced insulin secretion, and beneficial effects on plasma lipids have been described. In clinical studies, gliquidone has been associated with less hypoglycaemia than glibenclamide (glyburide), and with metabolic control at least as good as that seen with a number of other sulfonylureas. Beneficial effects on platelet aggregation have been documented, and the drug is described by WHO as the preferred sulfonylurea for patients with mild to moderate renal insufficiency. Importantly, in the light of the well documented consequences of increased bodyweight and the large growth in obesity worldwide, gliquidone is not associated with significant bodyweight gain. Thus, gliquidone is a sulfonylurea with proven efficacy and good safety and metabolic profiles that is only rarely associated with hypoglycaemia. In particular, the metabolism and route of excretion of the drug allow its use in patients who have or may be at risk of diabetic nephropathy.

The effect of Glurenorm (gliquidone) on lenses and skin in experimental diabetes

The aim of this study was to investigate the effect of administering Glurenorm (gliquidone, 10 mg/kg) on the lenses and skins of streptozotocin-induced diabetic rats. The drug was given to both diabetic and control rats daily, until the end of the experiment, at day 42. The drug was administered to one diabetic and one control group from day 0 and for the other diabetic and control groups from day 14. On day 42, cardiac blood samples, skin samples, and lenses were taken from each rat. Blood glucose (BG) was measured by the o-toluidine method. The total protein, nonenzymatic glycosylation of proteins (NEG), lipid peroxidation (LPO), and glutathione (GSH) levels in the lens and skin homogenates were determined by the Lowry, thiobarbituric acid, Ledwozwy, and Ellman methods, respectively. Laemmli SDS polyacrylamide gel electrophoresis was also carried out on the lens or skin homogenates. After 42 d, Glurenorm given to the diabetic rats produced (i) significant reductions in BG, NEG, and total protein in the lenses; (ii) significant increases in GSH levels in the lenses; (iii) and no significant results in the skin. The body weights of the drug group dropped relative to day 0, but not significantly. SDS polyacrylamide gel electrophoresis revealed no significant differences in any of the protein bands between any of the groups. In the lenses, the gains in turns of reduced NEG and increased GSH may have been offset by the reduction in protein.

In obese individuals dexfenfluramine corrects molecular derangements reflecting insulin resistance

BACKGROUND

Circulating lymphocytes of obese individuals with and without type 2 diabetes have derangements of pyruvate dehydrogenase (PDH) that are described as reflecting a disorder underlying systemic insulin resistance, namely basal activity below normal and, in vitro, unresponsiveness to insulin at 33 pmol/l and activation at 330 pmol/l instead of activation and inhibition as in controls.

OBJECTIVE

To explore whether the above enzyme derangements are overcome in obese individuals on dexfenfluramine treatment, known to improve poor peripheral insulin sensitivity.

METHODS

Fifteen obese diabetic patients and 15 age-matched euglycaemic obese subjects with normal glucose tolerance were enrolled for a trial composed of two 21-day periods; in the first (D-21-D0), participants received a placebo, and in the second (D0-D21), dexfenfluramine (30 mg/day). At D-21, D0 and D21 participants were evaluated for weight, BMI, fasting glycaemia (FG), fasting insulinaemia (FI), fasting insulin resistance index (FIRI), area under the glycaemic (G-AUC) and insulinaemic (I-AUC) curves from an OGT test, and for PDH activity assayed in their circulating lymphocytes before (basal activity) and after incubation with 33 or 330 pmol/l insulin. At D2, basal PDH activity and clinical parameters were assayed.

RESULTS

In both groups of participants at D0 all parameters tested were constant with respect to D-21; at D2, only basal PDH activity rose significantly; at D21, basal and insulin stimulated PDH activities were normalized and weight decreased significantly, as did FG, FI, FIRI and G-AUC in the diabetic, and FI, FIRI, G-AUC and I-AUC in the non-diabetic participants.

CONCLUSION

In obese, non-diabetic and diabetic individuals on dexfenfluramine treatment, amelioration of clinical parameters and indexes of poor insulin sensitivity of blood glucose homeostasis are preceded by correction, in their circulating lymphocytes, of PDH derangements described as reflecting a disorder underlying insulin resistance.

Cardiovascular effects of oral hypoglycaemic drugs

1. There is increasing evidence that sulfonylurea and biguanide oral hypoglycaemic drugs have cardiovascular effects and influence risk factors for cardiovascular disease in patients with non-insulin-dependent diabetes because of actions that are unrelated to alterations in glycaemic control. 2. While sulfonylureas may have anti-arrhythmic effects following myocardial ischaemia, there is concern that their action on vascular ATP-sensitive potassium channels may contribute to elevated blood pressure and enhanced vascular responsiveness. 3. In contrast to sulfonylureas, metformin (a biguanide) appears to reduce blood pressure and have beneficial effects on plasma lipoproteins by reducing low-density lipoprotein cholesterol and possibly increasing high-density lipoprotein cholesterol levels. 4. The pharmacological basis and clinical significance of these effects of sulfonylureas and biguanides require further investigation.

Effects of glimepiride on in vivo insulin action in normal and diabetic rats

To evaluate the effects of glimepiride on insulin action in peripheral tissues, we investigated insulin-induced glucose uptake in normal and diabetic rats using the euglycemic clamp procedure (insulin infusion rates: 6 and 30 mU/kg/min). Normal rats: After oral administration of glimepiride (0.1 mg/kg/day; NG) or saline (NC) for 2 weeks, euglycemic clamp procedures were performed. During submaximal hyperinsulinemia (620 +/- 35 pmol/l, mean +/- S.E.M.), metabolic clearance rates of glucose (MCR) in NG were significantly higher than in NC (25.1 +/- 2.1 vs. 18.3 +/- 1.2 ml/kg/min, P < 0.05). During maximal hyperinsulinemia (5235 +/- 270 pmol/l), MCRs in NG were higher than in NC, but there was no statistical significance (43.3 +/- 2.8 and 38.9 +/- 2.8). Diabetic rats: streptozotocin-induced diabetic rats were divided into four groups, GI (glimepiride treatment, 0.1 mg/kg/day p.o., with insulin, 5 U/day s.c.), SI (insulin alone), SG (glimepiride alone), and SC (saline). MCRs in the four groups were similar during 6 mU/kg/min clamps. During 30 mU/kg/min clamps, MCRs in GI were significantly higher than those in SC, SG or SI (23.4 +/- 2.8 vs. 12.2 +/- 1.9 and 8.9 +/- 0.8, P < 0.01, and vs. 17.4 +/- 1.5, P < 0.05). Although MCRs in SI tended to be higher than in SC, there was no significant statistical difference between these two groups. These results suggest that glimepiride enhances insulin action in peripheral tissues, and that glimepiride treatment with insulin improves the insulin resistance observed in streptozotocin-induced diabetic rats.