Sulphonylurea dose-response relationships: relation to clinical practice

Antidiabetic sulfonylureas modulate farnesoid X receptor activation and target gene transcription

Background: The sulfonylureas glibenclamide and glimepiride are oral antidiabetic drugs that stimulate insulin secretion by closing pancreatic ATP-dependent potassium channels. The farnesoid X receptor (FXR) is a ligand-activated transcription factor that regulates the expression of several target genes involved in bile acid metabolism and lipid and glucose homeostasis. Methods: In this study we investigated the potential effects of sulfonylureas on the signaling of FXR using a reporter-gene assay, real-time qPCR and computational methods such as molecular docking and molecular dynamic simulations. Results: We demonstrate that glibenclamide and glimepiride modulate FXR activation in a reporter-gene assay and induce FXR target genes in HepG2 cells. Within the docking experiments and molecular dynamics simulation, we found glibenclamide interacting with the ligand-binding domain of FXR and with helix 12. Conclusion: Glibenclamide and glimepiride are potential ligands of FXR and modulate activation and signaling.

Comparison of nateglinide and gliclazide in combination with metformin, for treatment of patients with Type 2 diabetes mellitus inadequately controlled on maximum doses of metformin alone

AIM

To compare the effects of nateglinide plus metformin with gliclazide plus metformin on glycaemic control in patients with Type 2 diabetes.

METHODS

Double-blind, double-dummy, parallel group, randomized, multicentre study over 24 weeks. Patients with inadequate glucose control on maximal doses of metformin were randomized to additionally receive nateglinide (n = 133) or gliclazide (n = 129). Changes from baseline in HbA1c, fasting plasma glucose (FPG) and mealtime glucose and insulin excursions were examined.

RESULTS

HbA1c was significantly (P < 0.001) decreased from baseline in both treatment groups (mean changes: nateglinide -0.41%, gliclazide -0.57%), but with no significant difference between treatments. Proportions of patients achieving a reduction of HbA1c >or= 0.5% or an end point HbA1c < 7% were also similar (nateglinide 58.1%, gliclazide 60.2%). Changes from baseline in FPG were similarly significant in both treatment groups (nateglinide -0.63, gliclazide -0.82 mmol/l). Reduction from baseline in maximum postprandial glucose excursion were significant in the nateglinide group only (nateglinide -0.71, gliclazide -0.10 mmol/l; P = 0.037 for difference). Postprandial insulin levels were significantly higher with nateglinide compared with gliclazide. The overall rate of hypoglycaemia events was similar in the nateglinide group compared with the gliclazide group.

CONCLUSIONS

No significant difference was seen between nateglinide plus metformin and gliclazide plus metformin in terms of HbA1c. However, the nateglinide combination demonstrated better postprandial glucose control.

Effects of glimepiride and glyburide on glucose counterregulation and recovery from hypoglycemia

Severe hypoglycemia, the most serious side effect of sulfonylurea therapy, has been reported to occur more frequently with glyburide than glimepiride. The present studies were undertaken to test the hypothesis that a differential effect on glucagon secretion may be involved. We performed hyperinsulinemic hypoglycemic (approximately 2.5 mmol/L) clamps in 16 healthy volunteers who received in randomized order placebo, glyburide (10 mg), and glimepiride (4 mg) just before beginning the insulin infusion and measured plasma glucagon, insulin, C-peptide, glucagon, epinephrine, cortisol, and growth hormone levels during the clamp and during a 3-hour recovery period after discontinuation of the insulin infusion. Neither sulfonylurea altered glucagon responses or those of other counterregulatory hormones (except cortisol) during the clamp. However, glyburide delayed plasma glucose recovery from hypoglycemia (plasma glucose at end of recovery period: control, 4.9 +/- 0.2 mmol/L; glyburide, 3.7 +/- 0.2 mmol/L; P = .0001; glimepiride, 4.5 +/- 0.2 mmol/L; P = .08). Despite lower plasma glucose levels, glyburide stimulated insulin secretion during this period (0.89 +/- 0.13 vs 1.47 +/- 0.15 pmol x kg(-1) x min(-1), control vs glyburide; P = .001), whereas glimepiride did not (P = .08). Short-term administration of glyburide or glimepiride did not alter glucagon responses during hypoglycemia. In contrast, during recovery from hypoglycemia, glyburide but not glimepiride inappropriately stimulates insulin secretion at low plasma glucose levels. This differential effect on insulin secretion may be an important factor in explaining why glyburide causes severe hypoglycemia more frequently than glimepiride.

The role of sulphonylureas in the management of type 2 diabetes mellitus

The sulphonylureas act by triggering insulin release from the pancreatic beta cell. A specific site on the adenosine triphosphate (ATP)-sensitive potassium channels is occupied by sulphonylureas leading to closure of the potassium channels and subsequent opening of calcium channels. This results in exocytosis of insulin. The meglitinides are not sulphonylureas but also occupy the sulphonylurea receptor unit coupled to the ATP-sensitive potassium channel. Glibenclamide (glyburide), gliclazide, glipizide and glimepiride are the primary sulphonylureas in current clinical use for type 2 diabetes mellitus. Glibenclamide has a higher frequency of hypoglycaemia than the other agents. With long-term use, there is a progressive decrease in the effectiveness of sulphonylureas. This loss of effect is the result of a reduction in insulin-producing capacity by the pancreatic beta cell and is also seen with other antihyperglycaemic agents. The major adverse effect of sulphonylureas is hypoglycaemia. There is a theoretical concern that sulphonylureas may affect cardiac potassium channels resulting in a diminished response to ischaemia. There are now many choices for initial therapy of type 2 diabetes in addition to sulphonylureas. Metformin and thiazolidinediones affect insulin sensitivity by independent mechanisms. Disaccharidase inhibitors reduce rapid carbohydrate absorption. No single agent appears capable of achieving target glucose levels in the majority of patients with type 2 diabetes. Combinations of agents are successful in lowering glycosylated haemoglobin levels more than with a single agent. Sulphonylureas are particularly beneficial when combined with agents such as metformin that decrease insulin resistance. Sulphonylureas can also be given with a basal insulin injection to provide enhanced endogenous insulin secretion after meals. Sulphonylureas will continue to be used both primarily and as part of combined therapy for most patients with type 2 diabetes.

Characteristics and time course of severe glimepiride- versus glibenclamide-induced hypoglycaemia

OBJECTIVE

To compare the clinical characteristics and time course of severe hypoglycaemia (SH) on glimepiride and the reference drug glibenclamide.

METHODS

SH was defined as a symptomatic event requiring administration of i.v. glucose or of glucagon. Four hundred doctors working in acute care hospitals were randomly selected from the membership directory of the German Diabetes Association and sent a standardised questionnaire about sulphonylurea-induced SH that occurred between June 2001 and August 2002. Detailed data on history, medication, laboratory parameters, treatment and time course of the SH were analysed.

RESULTS

Altogether, 93 episodes of SH were registered, 37 on glimepiride and 56 on glibenclamide. The characteristics of the glimepiride- versus glibenclamide-induced SH were as follows: initial blood glucose 1.9+/-0.66 mmol/l versus 1.8+/-0.89 mmol/l, P=0.17; age 77+/-11.2 years versus 78+/-9.6 years, P=0.35; HbA1c 5.4+/-0.7% versus 5.2+/-0.9%, P=0.18; creatinine clearance 38+/-23 ml/min versus 54+/-32 ml/min, P=0.005; co-medication 6.2.+/-3 versus 3.6+/-3 preparations, P< 0.0001. Even very low doses of glimepiride (0.5 mg) and glibenclamide (0.88 mg) were associated with SH. Prolonged hypoglycaemia requiring more than 12 h i.v. glucose administration occurred in 8 of 37 of the glimepiride-treated subjects and 5 of 56 of those on glibenclamide. Prolonged hypoglycaemia necessitated infusion of 308+/-256 g (104-862 g) i.v. glucose over 43+/-16 h (24-64 h) in glimepiride-treated patients compared with 168+/-98 g (66-300 g) over 33+/-28 h (14-80 h) in glibenclamide-treated patients. Impaired renal function was present in 11 of 13 of all patients with prolonged hypoglycaemia and impaired liver function in 1 of 13.

CONCLUSION

In glimepiride- and glibenclamide-treated individuals with SH, no essential differences in the clinical characteristics or time course were shown; prolonged courses also occurred on glimepiride. Even in patients with only mild renal failure both preparations should be used with caution.