Therapeutical concentrations of tolbutamide, glibenclamide, gliclazide and gliquidone at different glucose levels: in vitro effects on pancreatic A- and B-cell function

Real-world evidence on health-related quality of life in patients with type 2 diabetes mellitus using sulphonylureas: An analysis of the Joint Asia Diabetes Evaluation (JADE) Register

AIMS

To describe health-related quality of life (HRQoL) and identify associated factors in patients with type 2 diabetes mellitus (T2DM) treated with oral glucose-lowering drugs (OGLDs).

METHODS

This retrospective, cross-sectional analysis included adults with T2DM from 11 Asian countries/regions prospectively enrolled in the Joint Asian Diabetes Evaluation (JADE) Register (2007-2019) with available EuroQol-5D (EQ-5D-3L) data.

RESULTS

Of 47,895 included patients, 42,813 were treated with OGLDs + lifestyle modifications (LSM) and 5,082 with LSM only. Among those treated with OGLDs, 60% received sulphonylureas (SUs), of whom 47% received gliclazide. The OGLD + LSM group had a lower mean EQ-5D-3L index score than the LSM-only group (p < 0.001). The most affected EQ-5D-3L dimensions in OGLD + LSM-treated patients were pain/discomfort (26.2%) and anxiety/depression (22.6%). On multivariate analysis, good HRQoL was positively associated with male sex, education level, balanced diet and regular exercise, and negatively with complications/comorbidities, self-reported hypoglycaemia, smoking, HbA1c, age, body mass index and disease duration. Patients receiving gliclazide vs non-gliclazide SUs had lower HbA1c and better HRQoL in all dimensions (p < 0.001).

CONCLUSIONS

Demographic, physical and psychosocial-behavioural factors were associated with HRQoL in patients with T2DM. Our real-world data add to previous evidence that gliclazide is an effective OGLD, with most treated patients reporting good HRQoL. A plain language summary of this manuscript is available here.

Alpha-cells and therapy of diabetes: Inhibition, antagonism or death?

Absolute or relative hyperglucagonaemia is a characteristic of both Type 1 and Type 2 diabetes, resulting in fasting hyperglycaemia due in part to increased hepatic glucose production and lack of postprandial suppression of circulating glucagon concentrations. Consequently, therapeutics that target glucagon secretion or biological action may be effective antidiabetic agents. In this regard, specific glucagon receptor (GCGR) antagonists have been developed that exhibit impressive glucose-lowering actions, but unfortunately may cause off-target adverse effects in humans. Further to this, several currently approved antidiabetic agents, including GLP-1 mimetics, DPP-4 inhibitors, metformin, sulphonylureas and pramlintide likely exert part of their glucose homeostatic actions through direct or indirect inhibition of GCGR signalling. In addition to agents that inhibit the release of glucagon, compounds that enhance the transdifferentiation of glucagon secreting alpha-cells towards an insulin positive beta-cell phenotype could also help curb excess glucagon secretion in diabetes. Use of alpha-cell toxins represents another possible strategy to address hyperglucagonaemia in diabetes. In that respect, research from the 1920 s with diguanides such as synthalin A demonstrated effective glucose-lowering with alpha-cell ablation in both animal models and humans with diabetes. However, further clinical use of synthalin A was curtailed due its adverse effects and the increased availability of insulin. Overall, these observations with therapeutics that directly target alpha-cells, or GCGR signaling, highlight a largely untapped potential for diabetes therapy that merits further detailed consideration.

Sulfonylureas in the Current Practice of Type 2 Diabetes Management: Are They All the Same? Consensus from the Gulf Cooperation Council (GCC) Countries Advisory Board on Sulfonylureas

Since their inception in the commercial market in the mid-twentieth century, sulfonylureas (SUs) have remained a therapeutic option in the management of type 2 diabetes (T2D). Despite their established glucose-lowering effects, there is no consensus among global experts and modern guidelines regarding the priority of SUs in relation to other therapeutic options, given the lack of evidence that SUs are associated with a low risk of macrovascular events and excess mortality. However, findings from recent trials and real-time observations have resolved this contentious issue somewhat, albeit to varying degrees. The present consensus discusses the role of SUs in contemporary diabetes management in the Gulf Cooperation Council (GCC) countries. Regional experts from these countries gathered virtually to formulate a consensus following presentations of topics relevant to SU therapy with an emphasis on gliclazide, including long-term efficacy, cost, end-organ benefits, and side effects, based on up-to-date evidence. The present narrative review reflects the conclusions of this assembly and provides a platform upon which future guidelines for the use of SUs in the GCC can be tailored.

Glucagonotropic and Glucagonostatic Effects of KATP Channel Closure and Potassium Depolarization

The role of depolarization in the inverse glucose-dependence of glucagon secretion was investigated by comparing the effects of KATP channel block and of high potassium. The secretion of glucagon and insulin by perifused mouse islets was simultaneously measured. Lowering glucose raised glucagon secretion before it decreased insulin secretion, suggesting an alpha cell-intrinsic signal recognition. Raising glucose affected glucagon and insulin secretion at the same time. However, depolarization by tolbutamide, gliclazide, or 15 mM KCl increased insulin secretion before the glucagon secretion receded. In contrast to the robust depolarizing effect of arginine and KCl (15 and 40 mM) on single alpha cells, tolbutamide was of variable efficacy. Only when applied before other depolarizing agents had tolbutamide a consistent depolarizing effect and regularly increased the cytosolic Ca2+ concentration. When tested on inside-out patches tolbutamide was as effective on alpha cells as on beta cells. In the presence of 1 µM clonidine, to separate insulinotropic from glucagonotropic effects, both 500 µM tolbutamide and 30 µM gliclazide increased glucagon secretion significantly, but transiently. The additional presence of 15 or 40 mM KCl in contrast led to a marked and lasting increase of the glucagon secretion. The glucagon secretion by SUR1 knockout islets was not increased by tolbutamide, whereas 40 mM KCl was of unchanged efficiency. In conclusion a strong and sustained depolarization is compatible with a marked and lasting glucagon secretion. KATP channel closure in alpha cells is less readily achieved than in beta cells, which may explain the moderate and transient glucagonotropic effect.

The Role of α-Cells in Islet Function and Glucose Homeostasis in Health and Type 2 Diabetes

Pancreatic α-cells are the major source of glucagon, a hormone that counteracts the hypoglycemic action of insulin and strongly contributes to the correction of acute hypoglycemia. The mechanisms by which glucose controls glucagon secretion are hotly debated, and it is still unclear to what extent this control results from a direct action of glucose on α-cells or is indirectly mediated by β- and/or δ-cells. Besides its hyperglycemic action, glucagon has many other effects, in particular on lipid and amino acid metabolism. Counterintuitively, glucagon seems also required for an optimal insulin secretion in response to glucose by acting on its cognate receptor and, even more importantly, on GLP-1 receptors. Patients with diabetes mellitus display two main alterations of glucagon secretion: a relative hyperglucagonemia that aggravates hyperglycemia, and an impaired glucagon response to hypoglycemia. Under metabolic stress states, such as diabetes, pancreatic α-cells also secrete GLP-1, a glucose-lowering hormone, whereas the gut can produce glucagon. The contribution of extrapancreatic glucagon to the abnormal glucose homeostasis is unclear. Here, I review the possible mechanisms of control of glucagon secretion and the role of α-cells on islet function in healthy state. I discuss the possible causes of the abnormal glucagonemia in diabetes, with particular emphasis on type 2 diabetes, and I briefly comment the current antidiabetic therapies affecting α-cells.

Sulfonylurea derivatives and cancer, friend or foe?

Type 2 diabetes mellitus (T2DM) is associated with a higher risk of cancer and cancer-related mortality. Increased blood glucose and insulin levels in T2DM patients may be, at least in part, responsible for this effect. Indeed, lowering glucose and/or insulin levels pharmacologically appears to reduce cancer risk and progression, as has been demonstrated for the biguanide metformin in observational studies. Studies investigating the influence of sulfonylurea derivatives (SUs) on cancer risk have provided conflicting results, partly due to comparisons with metformin. Furthermore, little attention has been paid to within-class differences in systemic and off-target effects of the SUs. The aim of this systematic review is to discuss the available preclinical and clinical evidence on how the different SUs influence cancer development and risk. Databases including PubMed, Cochrane, Database of Abstracts on Reviews and Effectiveness, and trial registries were systematically searched for available clinical and preclinical evidence on within-class differences of SUs and cancer risk. The overall preclinical and clinical evidence suggest that the influence of SUs on cancer risk in T2DM patients differs between the various SUs. Potential mechanisms include differing affinities for the sulfonylurea receptors and thus differential systemic insulin exposure and off-target anti-cancer effects mediated for example through potassium transporters and drug export pumps. Preclinical evidence supports potential anti-cancer effects of SUs, which are of interest for further studies and potentially repurposing of SUs. At this time, the evidence on differences in cancer risk between SUs is not strong enough to guide clinical decision making.

Hypoglycaemia when adding sulphonylurea to metformin: a systematic review and network meta-analysis

AIMS

The risk of hypoglycaemia may differ among sulphonylureas (SUs), but evidence from head-to-head comparisons is sparse. Performing a network meta-analysis to use indirect evidence from randomized controlled trials (RCTs), we compared the relative risk of hypoglycaemia with newer generation SUs when added to metformin.

METHODS

A systematic review identified RCTs lasting 12-52 weeks and evaluating SUs added to inadequate metformin monotherapy (≥1000 mg/day) in type 2 diabetes. Adding RCTs investigating the active comparators from the identified SU trials, we established a coherent network. Hypoglycaemia of any severity was the primary end point.

RESULTS

Thirteen trials of SUs and 14 of oral non-SU antihyperglycaemic agents (16 260 patients) were included. All reported hypoglycaemia only as adverse events. Producing comparable reductions in HbA_1C of -0.66 to -0.84% (-7 to -9 mmol/mol), the risk of hypoglycaemia was lowest with gliclazide compared to glipizide (OR 0.22, CrI: 0.05 to 0.96), glimepiride (OR 0.40, CrI: 0.13 to 1.27), and glibenclamide (OR 0.21, CrI: 0.03 to 1.48). A major limitation is varying definitions of hypoglycaemia across studies.

CONCLUSIONS

When added to metformin, gliclazide was associated with the lowest risk of hypoglycaemia between the newer generation SUs. Clinicians should consider the risk of hypoglycaemia agent-specific when selecting an SU agent.

The effect of gliquidone on KATP channels in pancreatic β-cells, cardiomyocytes, and vascular smooth muscle cells

AIMS

Sulfonylurea drugs exert an insulinotropic effect through ATP-sensitive potassium (KATP) channel inhibition in pancreatic islet cells. These channels are also expressed in cardiomyocytes and vascular smooth muscle cells (VSMCs), suggesting potential for adverse cardiovascular effects. We evaluated the effects of Gliquidone (Glq) on sulfonylurea receptors in HIT-T15 cells (SUR1), cardiomyocytes (SUR2A), and VSMCs (SUR2B).

METHODS

The concentration-dependent effects of Glq (0.001-500 μM) on KATP channels were assessed using whole-cell patch clamp in HIT-T15 cells, rat cardiomyocytes, and VSMCs. Parallel studies using Glibenclamide (Glb) (0.001-10 μM) and Gliclazide (Glc) (0.01-500 μM)were conducted as controls.

RESULTS

In HIT-T15 cells, Glb exhibited the lowest IC50 (0.03 μM), as compared to Glq (0.45μM) and Glc (1.21μM). However, Glq had higher IC50 in cardiomyoctes and VSMCs, as compared to Glb (119.1 vs. 0.01 and 149.7 vs. 0.09 μM, respectively), suggesting that Glq is more selective to β-cells than Glb. Thus, Glq may have fewer side effects in cardiomyoctes and VSMCs.

CONCLUSIONS

Glq is a highly selective SUR secretagogue with moderate affinity to β-cells, but low affinity to cardiomyocytes and VSMCs. Our data also reveal the non-selective nature of Glb, as evidenced by high binding affinity to KATP channels in all the three cell types examined.

Effect of exenatide, sitagliptin, or glimepiride on β-cell secretory capacity in early type 2 diabetes

OBJECTIVE

Agents that augment GLP-1 effects enhance glucose-dependent β-cell insulin production and secretion and thus are hoped to prevent progressive impairment in insulin secretion characteristic of type 2 diabetes (T2D). The purpose of this study was to evaluate GLP-1 effects on β-cell secretory capacity, an in vivo measure of functional β-cell mass, early in the course of T2D.

RESEARCH DESIGN AND METHODS

We conducted a randomized controlled trial in 40 subjects with early T2D who received the GLP-1 analog exenatide (n = 14), the dipeptidyl peptidase IV inhibitor sitagliptin (n = 12), or the sulfonylurea glimepiride (n = 14) as an active comparator insulin secretagogue for 6 months. Acute insulin responses to arginine (AIRarg) were measured at baseline and after 6 months of treatment with 5 days of drug washout under fasting, 230 mg/dL (glucose potentiation of arginine-induced insulin release [AIRpot]), and 340 mg/dL (maximum arginine-induced insulin release [AIRmax]) hyperglycemic clamp conditions, in which AIRmax provides the β-cell secretory capacity.

RESULTS

The change in AIRpot was significantly greater with glimepiride versus exenatide treatment (P < 0.05), and a similar trend was notable for the change in AIRmax (P = 0.1). Within each group, the primary outcome measure, AIRmax, was unchanged after 6 months of treatment with exenatide or sitagliptin compared with baseline but was increased with glimepiride (P < 0.05). α-Cell glucagon secretion (AGRmin) was also increased with glimepiride treatment (P < 0.05), and the change in AGRmin trended higher with glimepiride than with exenatide (P = 0.06).

CONCLUSIONS

After 6 months of treatment, exenatide or sitagliptin had no significant effect on functional β-cell mass as measured by β-cell secretory capacity, whereas glimepiride appeared to enhance β- and α-cell secretion.

Factors influencing the durability of the glucose-lowering effect of sitagliptin combined with a sulfonylurea

We analyzed the changes of glycemic control over 12 months and the factors influencing blood glucose in 162 Japanese patients with type 2 diabetes having inadequate glycemic control despite sulfonylurea-based therapy who received add-on sitagliptin. Hemoglobin A1c (HbA1c) decreased significantly after 4 weeks of treatment, and this improvement was maintained for 1 year, although HbA1c was slightly higher in week 52 than in week 24. Comparison of the patients showing a ≥0.4% increase of HbA1c between weeks 24 and 52 (n = 57) with the others (n = 105) showed a significant difference in the change of bodyweight, as well as the dose of glibenclamide (both P < 0.01). Although combined therapy with sitagliptin and a sulfonylurea seems to be effective for at least 1 year, blood glucose levels are more likely to increase again in patients who show greater weight gain after 24 weeks of treatment and those receiving a higher dose of glibenclamide.

Tolbutamide controls glucagon release from mouse islets differently than glucose: involvement of K(ATP) channels from both α-cells and δ-cells

We evaluated the role of ATP-sensitive K⁺ (K(ATP)) channels, somatostatin, and Zn²⁺ in the control of glucagon secretion from mouse islets. Switching from 1 to 7 mmol/L glucose inhibited glucagon release. Diazoxide did not reverse the glucagonostatic effect of glucose. Tolbutamide decreased glucagon secretion at 1 mmol/L glucose (G1) but stimulated it at 7 mmol/L glucose (G7). The reduced glucagon secretion produced by high concentrations of tolbutamide or diazoxide, or disruption of K(ATP) channels (Sur1(-/-) mice) at G1 could be inhibited further by G7. Removal of the somatostatin paracrine influence (Sst(-/-) mice or pretreatement with pertussis toxin) strongly increased glucagon release, did not prevent the glucagonostatic effect of G7, and unmasked a marked glucagonotropic effect of tolbutamide. Glucose inhibited glucagon release in the absence of functional K(ATP) channels and somatostatin signaling. Knockout of the Zn²⁺ transporter ZnT8 (ZnT8(-/-) mice) did not prevent the glucagonostatic effect of glucose. In conclusion, glucose can inhibit glucagon release independently of Zn²⁺, K(ATP) channels, and somatostatin. Closure of K(ATP) channels controls glucagon secretion by two mechanisms, a direct stimulation of α-cells and an indirect inhibition via somatostatin released from δ-cells. The net effect on glucagon release results from a balance between both effects.

Glucose and pharmacological modulators of ATP-sensitive K+ channels control [Ca2+]c by different mechanisms in isolated mouse alpha-cells

OBJECTIVE

We studied how glucose and ATP-sensitive K(+) (K(ATP)) channel modulators affect alpha-cell [Ca(2+)](c).

RESEARCH DESIGN AND METHODS

GYY mice (expressing enhanced yellow fluorescent protein in alpha-cells) and NMRI mice were used. [Ca(2+)](c), the K(ATP) current (I(KATP), perforated mode) and cell metabolism [NAD(P)H fluorescence] were monitored in single alpha-cells and, for comparison, in single beta-cells.

RESULTS

In 0.5 mmol/l glucose, [Ca(2+)](c) oscillated in some alpha-cells and was basal in the others. Increasing glucose to 15 mmol/l decreased [Ca(2+)](c) by approximately 30% in oscillating cells and was ineffective in the others. alpha-Cell I(KATP) was inhibited by tolbutamide and activated by diazoxide or the mitochondrial poison azide, as in beta-cells. Tolbutamide increased alpha-cell [Ca(2+)](c), whereas diazoxide and azide abolished [Ca(2+)](c) oscillations. Increasing glucose from 0.5 to 15 mmol/l did not change I(KATP) and NAD(P)H fluorescence in alpha-cells in contrast to beta-cells. The use of nimodipine showed that L-type Ca(2+) channels are the main conduits for Ca(2+) influx in alpha-cells. gamma-Aminobutyric acid and zinc did not decrease alpha-cell [Ca(2+)](c), and insulin, although lowering [Ca(2+)](c) very modestly, did not affect glucagon secretion.

CONCLUSIONS

alpha-Cells display similarities with beta-cells: K(ATP) channels control Ca(2+) influx mainly through L-type Ca(2+) channels. However, alpha-cells have distinct features from beta-cells: Most K(ATP) channels are already closed at low glucose, glucose does not affect cell metabolism and I(KATP), and it slightly decreases [Ca(2+)](c). Hence, glucose and K(ATP) channel modulators exert distinct effects on alpha-cell [Ca(2+)](c). The direct small glucose-induced drop in alpha-cell [Ca(2+)](c) contributes likely only partly to the strong glucose-induced inhibition of glucagon secretion in islets.

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.

Gliclazide protects human islet beta-cells from apoptosis induced by intermittent high glucose

BACKGROUND

Decreased beta-cell mass, mainly due to apoptosis, is crucial for the development and progression of type 2 diabetes. Chronic exposure to high glucose levels is a probable underlying mechanism, whereas the role of oral anti-diabetic agents (sulphonylureas in particular) is still unsettled.

METHODS

To directly investigate more on such issues, we prepared isolated human islets, which were then cultured for 5 days in continuous normal glucose concentration (NG, 5.5 mmol/L) or normal and high (HG, 16.7 mmol/L) glucose levels (alternating every 24 h), with or without the addition of therapeutical concentration (10 micromol L) of gliclazide or glibenclamide.

RESULTS

Intermittent high glucose caused a significant decrease of glucose-stimulated insulin secretion, which was not further affected by either sulphonylurea. Apoptosis, as assessed by electron microscopy, was also significantly increased by alternating high glucose exposure, which was accompanied by altered mitochondria morphology and density volume, and increased concentrations of nitrotyrosine, a marker of oxidative stress. Gliclazide, but not glibenclamide, was able to significantly reduce high glucose induced apoptosis, mitochondrial alterations, and nitrotyrosine concentration increase.

CONCLUSION

Therefore, gliclazide protected human beta-cells from apoptosis induced by intermittent high glucose, and this effect was likely to be due, at least in part, to the anti-oxidant properties of the molecule.

Alpha-cells of the endocrine pancreas: 35 years of research but the enigma remains

Glucagon, a hormone secreted from the alpha-cells of the endocrine pancreas, is critical for blood glucose homeostasis. It is the major counterpart to insulin and is released during hypoglycemia to induce hepatic glucose output. The control of glucagon secretion is multifactorial and involves direct effects of nutrients on alpha-cell stimulus-secretion coupling as well as paracrine regulation by insulin and zinc and other factors secreted from neighboring beta- and delta-cells within the islet of Langerhans. Glucagon secretion is also regulated by circulating hormones and the autonomic nervous system. In this review, we describe the components of the alpha-cell stimulus secretion coupling and how nutrient metabolism in the alpha-cell leads to changes in glucagon secretion. The islet cell composition and organization are described in different species and serve as a basis for understanding how the numerous paracrine, hormonal, and nervous signals fine-tune glucagon secretion under different physiological conditions. We also highlight the pathophysiology of the alpha-cell and how hyperglucagonemia represents an important component of the metabolic abnormalities associated with diabetes mellitus. Therapeutic inhibition of glucagon action in patients with type 2 diabetes remains an exciting prospect.

Sulfonylurea compounds uncouple the glucose dependence of the insulinotropic effect of glucagon-like peptide 1

Glucagon-like peptide (GLP)-1 mimetics have been reported to cause hypoglycemia when combined with sulfonylureas. This study investigated the impact of tolbutamide on the glucose dependence of the GLP-1-mediated effects on insulin, glucagon, and somatostatin secretion in the in situ perfused rat pancreas. At 3 mmol/l glucose, GLP-1 alone did not augment insulin secretion, whereas tolbutamide alone caused a rapid increase in insulin secretion. However, when GLP-1 and tolbutamide were administered simultaneously, insulin secretion increased significantly to 43.7 +/- 6.2 pmol/min (means +/- SE), exceeding the sum of the responses to GLP-1 (2.0 +/- 0.6 pmol/min; P = 0.019) and tolbutamide (11.3 +/- 3.8; P = 0.005) alone by a factor of 3.3. At 11 mmol/l glucose, co-infusion of GLP-1 and tolbutamide augmented insulin secretion to 141.7 +/- 10.3 vs. 115.36 +/- 14.1 (GLP-1) and 42.5 +/- 7.3 pmol/min (tolbutamide). Interestingly, increases in somatostatin secretion, both by glucose and GLP-1, were consistently paralleled by suppression of glucagon release. In conclusion, we demonstrate uncoupling of GLP-1 from its glucose dependence by tolbutamide. This uncoupling probably explains the tendency of GLP-1 to provoke hypoglycemia in combination with sulfonylureas. The results suggest that closure of ATP-sensitive K(+) channels by glucose might be involved in the glucose dependence of GLP-1's insulinotropic effect and that somatostatin acts as a paracrine regulator of glucagon release.

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.

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.

Secondary sulfonylurea failure: comparison of period until insulin treatment between diabetic patients treated with gliclazide and glibenclamide

We retrospectively evaluated a possible difference in periods until start of insulin treatment between type 2 diabetic patients treated with gliclazide (GCZ) and glibenclamide (GBC), because GCZ might be protective for beta cells than GBC. Subjects were Japanese patients. GCZ group consisted of patients treated with GCZ alone or with GCZ and GBC in the separate treatment periods in combination with or without other oral hypoglycemic agents (OHAs), while GBC group consisted of patients with GBC alone or in combination with other OHAs except GCZ. The periods until the treatment of insulin commenced were calculated using the Kaplan-Meier method. Proportional hazards models were used to adjust the differing variables between GCZ and GBC groups. The periods until the start of insulin treatment from diabetes onset, diabetes treatment, or GCZ or GBC treatment were significantly longer in the GCZ group than those in GBC group (P<0.001 in each group). Independent variables affecting the period were average HbA1c levels during GCZ or GBC treatment (hazard ratio=2.5 per %), other OHAs combined (hazard ratio=1.9 on combination), and difference between GCZ and GBC groups (hazard ratio=0.5 on GCZ). These results imply that GCZ may be more protective against secondary beta cell failure than GBC.

Sulfonylurea treatment of type 2 diabetes mellitus: focus on glimepiride

Sulfonylureas, which have evolved through two generations since their introduction nearly 50 years ago, remain the most frequently prescribed oral agents for treatment of patients with type 2 diabetes mellitus. Glyburide, glipizide, and glimepiride, the newest sulfonylureas, are as effective at lowering plasma glucose concentrations as first-generation agents but are more potent, better tolerated, and associated with a lower risk of adverse effects. Differences in their binding affinity to the beta-cell sulfonylurea receptor have been described, with preservation of cardioprotective responses to ischemia with glimepiride. Clinical studies have shown glimepiride to be safe and effective in reducing fasting and postprandial glucose levels, as well as glycosylated hemoglobin concentrations, with dosages of 1-8 mg/day. In comparative trials, glimepiride was as effective in lowering glucose levels as glyburide and glipizide, but glimepiride was associated with a reduced likelihood of hypoglycemia and a smaller increase in fasting insulin and C-peptide levels than glyburide, and a more rapid lowering of fasting plasma glucose levels than glipizide. Glimepiride also improves first-phase insulin secretion, which plays an important role in reducing postprandial hyperglycemia. Insulin secretagogues, specifically glimepiride, merit consideration as first-line therapy for patients with type 2 diabetes.

GUIDE study: double-blind comparison of once-daily gliclazide MR and glimepiride in type 2 diabetic patients

BACKGROUND

Progressive beta-cell failure is a characteristic feature of type 2 diabetes; consequently, beta-cell secretagogues are useful for achieving sufficient glycaemic control. The European GUIDE study is the first large-scale head-to-head comparison of two sulphonylureas designed for once-daily administration used under conditions of everyday clinical practice.

DESIGN

Eight hundred and forty-five type 2 diabetic patients were randomized to either gliclazide modified release (MR) 30-120 mg daily or glimepiride 1-6 mg daily as monotherapy or in combination with their current treatment (metformin or an alpha-glucosidase inhibitor) according to a double-blind, 27-week, parallel-group design. Efficacy was evaluated by HbA1c and safety by hypoglycaemic episodes using the European Agency definition.

RESULTS

HbA1c decreased similarly in both groups from 8.4% to 7.2% on gliclazide MR and from 8.2% to 7.2% on glimepiride. Approximately 50% of the patients achieved HbA1c levels less than 7%, and 25% less than 6.5%. The mean difference between groups of the final HbA1c was -0.06% (noninferiority test P < 0.0001). No hypoglycaemia requiring external assistance occurred. Hypoglycaemia with blood glucose level < 3 mmol L(-1) occurred significantly less frequently (P = 0.003) with gliclazide MR (3.7% of patients) compared with glimepiride (8.9% of patients). The distribution of the sulphonylurea doses was similar in both groups.

CONCLUSIONS

This study provides new insights into therapeutic strategies using sulphonylureas. It shows that gliclazide MR is at least as effective as glimepiride, either as monotherapy or in combination. The safety of gliclazide MR was significantly better, demonstrating approximately 50% fewer confirmed hypoglycaemic episodes in comparison with glimepiride.

Effects of S 21403 on hormone secretion from isolated rat pancreas at different glucose concentrations

We investigated the in vitro effects of therapeutical concentrations of S 21403 (a succinic acid derivative also known as KAD 1229 and mitiglinide) on insulin and glucagon secretion during a metabolic stimulus (glucose rising from 5 to 8.33 mM) or at a stable 2.22 mM glucose using the isolated perfused rat pancreas model, and we compared them with the patterns of repaglinide and glibenclamide. Control perfusions were also performed. During 8.33 mM glucose, insulin release peaked to 339.12+/-22.87 microU/ml in controls. S 21403 enhanced insulin release (first peak 413.02+/-14.90 microU/ml; P<0.03 vs. controls, P=ns vs. repaglinide, P<0.005 vs. glibenclamide). Repaglinide increased glucose-induced first peak secretion to 409.33+/-20.05 microU/ml within the eighth minute (P<0.05 vs. controls, P<0.01 vs. glibenclamide). Glibenclamide did not affect the first phase of glucose-induced insulin release (peak of 338.41+/-29.79 microU/ml) but potentiated and delayed the second phase. No drug affected glucagon release. In conclusion, S 21403 induces a faster, more physiological pattern of insulin release than the other drugs we tested.

Gliclazide directly inhibits arginine-induced glucagon release

Arginine-stimulated insulin and somatostatin release is enhanced by the sulfonylurea gliclazide. In contrast, gliclazide inhibits the glucagon response. The aim of the present study was to investigate whether this inhibition of glucagon release was mediated by a direct suppressive effect of gliclazide or was secondary to the paracrine effect of released somatostatin. To eliminate the paracrine effects of somatostatin, we first perfused isolated rat pancreata with a medium supplemented with 23% of the standard calcium content. Second, we perifused isolated rat islets with a novel and highly specific antagonist of type 2 somatostatin receptor, DC-41-33 (2 micro mol/l), which fully antagonizes the suppressive somatostatin effect on rat A cells. Gliclazide (30 micro mol/l) inhibited glucagon release by 54% in the perfusion experiments, whereas the somatostatin response was nearly abolished. In islet perifusions with DC-41-33, arginine-induced glucagon release was inhibited by 66%. We therefore concluded that gliclazide inhibits glucagon release by a direct action on the pancreatic A cell.

Gliclazide modified release

Gliclazide modified release (MR) is a new formulation of the drug gliclazide and is given once daily. The hydrophilic matrix of hypromellose-based polymer in the new formulation effects a progressive release of the drug which parallels the 24-hour glycaemic profile in untreated patients with type 2 diabetes mellitus. The formulation shows high bioavailability and its absorption profile is unaffected by coadministration with food. Mean plasma glucose levels are significantly reduced over a 24-hour period in patients with type 2 diabetes mellitus treated with gliclazide MR once daily, in both fasting and postprandial states. No cardiovascular ATP-sensitive potassium channel interaction has been observed at therapeutic concentrations of gliclazide MR. Gliclazide MR has also demonstrated antioxidant properties that are independent of glycaemic control. In a randomised, double-blind, multicentre study, gliclazide MR 30 to 120 mg once daily showed similar efficacy to gliclazide immediate release (IR) 80 to 320 mg/day (in divided doses for doses >80 mg) in patients with type 2 diabetes mellitus over a 10-month period, reducing glycosylated haemoglobin (HbA(1c)) and fasting plasma glucose (FPG) to a similar extent. The drug appeared most efficacious in patients who had previously been treated by diet alone, where significant reductions in HbA(1c) from baseline of 0.9% and 0.95% were seen at 10 and 24 months. Similarly, a sustained effect of gliclazide MR was observed in a subgroup of elderly patients defined a priori; HbA(1c) was decreased to a similar degree to that observed in the general study population. Gliclazide MR showed similar tolerability to gliclazide IR after 10 months' treatment in the randomised trial. The most commonly observed adverse events were arthralgia, arthritis, back pain and bronchitis (each <5%). Bodyweight remained stable. In this study no episodes of nocturnal hypoglycaemia or hypoglycaemia requiring third party assistance were observed during treatment with gliclazide MR. Episodes of symptomatic hypoglycaemia were infrequent, occurring in approximately 5% of patients.

Postprandial Hyperglycemia in Patients with Type 2 Diabetes Mellitus

The role of postprandial hyperglycemia (PPHG) in diabetes mellitus is being increasingly recognized. It is known that PPHG contributes to the increased risk of both micro- and macrovascular complications in patients with diabetes mellitus. This review looks at the clinical significance of PPHG and the currently available therapeutic modalities. The causes of PPHG are influenced by many factors which include a rapid flux of glucose from the gut, impaired insulin release, endogenous glucose production by the liver and peripheral insulin resistance. Knowledge of the pathophysiology of PPHG is essential when adopting treatment options to tackle the problem. Although most oral antihyperglycemic agents and insulins lower both fasting and postprandial blood glucose levels, drugs are now available which specifically act to control PPHG. These drugs may be classified based on the site of their action. alpha-Glucosidase inhibitors like acarbose and miglitol attenuate the rate of absorption of sucrose by acting on the luminal enzymes. Adverse effects of these agents are predominantly gastrointestinal. Newer insulin secretagogues have been developed which attempt to mimic the physiological release of insulin and thus ameliorate PPHG. These include third generation sulfonylureas like glimepiride and nonsulfonylurea secretagogues like repaglinide and nateglinide. Rapid-acting insulin analogs, the amino acid sequences of which have been altered such that they have a faster onset of action, help to specifically target PPHG. Pre-mixed formulations of the analogs have also been developed. Finally, drugs under development which hold promise in the management of patients with PPHG include pramlintide, an amylin analog, and glucagon-like peptide-1 and its analogs.

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.

Acute and short-term administration of a sulfonylurea (gliclazide) increases pulsatile insulin secretion in type 2 diabetes

The high-frequency oscillatory pattern of insulin release is disturbed in type 2 diabetes. Although sulfonylurea drugs are widely used for the treatment of this disease, their effect on insulin release patterns is not well established. The aim of the present study was to assess the impact of acute treatment and 5 weeks of sulfonylurea (gliclazide) treatment on insulin secretory dynamics in type 2 diabetic patients. To this end, 10 patients with type 2 diabetes (age 53 +/- 2 years, BMI 27.5 +/- 1.1 kg/m(2), fasting plasma glucose 9.8 +/- 0.8 mmol/l, HbA(1c) 7.5 +/- 0.3%) were studied in a double-blind placebo-controlled prospective crossover design. Patients received 40-80 mg gliclazide/placebo twice daily for 5 weeks with a 6-week washout period intervening. Insulin pulsatility was assessed by 1-min interval blood sampling for 75 min 1) under baseline conditions (baseline), 2) 3 h after the first dose (80 mg) of gliclazide (acute) with the plasma glucose concentration clamped at the baseline value, 3) after 5 weeks of treatment (5 weeks), and 4) after 5 weeks of treatment with the plasma glucose concentration clamped during the sampling at the value of the baseline assessment (5 weeks-elevated). Serum insulin concentration time series were analyzed by deconvolution, approximate entropy (ApEn), and spectral and autocorrelation methods to quantitate pulsatility and regularity. The P values given are gliclazide versus placebo; results are means +/- SE. Fasting plasma glucose was reduced after gliclazide treatment (baseline vs. 5 weeks: gliclazide, 10.0 +/- 0.9 vs. 7.8 +/- 0.6 mmol/l; placebo, 10.0 +/- 0.8 vs. 11.0 +/- 0.9 mmol/l, P = 0.001). Insulin secretory burst mass was increased (baseline vs. acute: gliclazide, 43.0 +/- 12.0 vs. 61.0 +/- 17.0 pmol. l(-1). pulse(-1); placebo, 36.1 +/- 8.4 vs. 30.3 +/- 7.4 pmol. l(-1). pulse(-1), P = 0.047; 5 weeks-elevated: gliclazide vs. placebo, 49.7 +/- 13.3 vs. 37.1 +/- 9.5 pmol. l(-1). pulse(-1), P < 0.05) with a similar rise in burst amplitude. Basal (i.e., nonoscillatory) insulin secretion also increased (baseline vs. acute: gliclazide, 8.5 +/- 2.2 vs. 16.7 +/- 4.3 pmol. l(-1). pulse(-1); placebo, 5.9 +/- 0.9 vs. 7.2 +/- 0.9 pmol. l(-1). pulse(-1), P = 0.03; 5 weeks-elevated: gliclazide vs. placebo, 12.2 +/- 2.5 vs. 9.4 +/- 2.1 pmol. l(-1). pulse(-1), P = 0.016). The frequency and regularity of insulin pulses were not modified significantly by the antidiabetic therapy. There was, however, a correlation between individual values for the acute improvement of regularity, as measured by ApEn, and the decrease in fasting plasma glucose during short-term (5-week) gliclazide treatment (r = 0.74, P = 0.014, and r = 0.77, P = 0.009, for fine and coarse ApEn, respectively). In conclusion, the sulfonylurea agent gliclazide augments insulin secretion by concurrently increasing pulse mass and basal insulin secretion without changing secretory burst frequency or regularity. The data suggest a possible relationship between the improvement in short-term glycemic control and the acute improvement of regularity of the in vivo insulin release process.

Characteristics of pancreatic beta-cell secretion in Type 2 diabetic patients treated with gliclazide and glibenclamide

The aim of the present cross-over study was to compare the beta-cell response to gliclazide and glibenclamide administered orally during and following a hyperglycaemic clamp in sulphonylurea treated Type 2 diabetes. Nine patients (6 males), aged 61.4 (S.D. 6.9) years with a body mass index of 27.5 (3.1) kg m(-2) and HbA(1c) at baseline of 7.2 (0.9)% were included. Eight healthy control subjects underwent the same tests. Patients received 80-240 mg gliclazide or 5-15 mg glibenclamide for 6 weeks. Thirty minutes after administration of 160 mg of gliclazide or 10 mg of glibenclamide a 1-h hyperglycaemic clamp (11.0 mmol l(-1)) was begun, and followed by a 3.5-h observation period. Nadir blood glucose levels were 4.2 (1.0), 4.3 (1.2) and 3.4 (1.0) mmol l(-1) for glibenclamide gliclazide and controls, respectively (both P=0.07 vs. controls). Glucose levels decreased slowly and linearly in people with diabetes and reached nadirs after 204 (8) and 198 (18) min, respectively, after cessation of glucose infusion, while in controls, glucose levels declined steeply to a nadir at 98 (47) min (P<0.003 vs. both drugs). No first phase insulin secretion peak was observed in people with diabetes. Insulin levels remained elevated during the 3-h observation period in SU treated patients but, in control subjects decreased to baseline values within 2 h of the clamp. The proinsulin to C-peptide ratio increased during the observation period. In conclusion, the effects of glibenclamide and gliclazide on insulin secretion are very similar in patients with Type 2 diabetes who are in moderate glycaemic control, with a slow rise to lower amplitude, poor responsiveness to falling glucose levels, and raised proinsulin to C-peptide ratio.

Gliclazide modified release: its place in the therapeutic armamentarium

The constraints of intensive multifactorial management of type 2 diabetes dictate a need for effective, well-tolerated agents with simple administration regimens. Sulfonylureas remain the most frequently used agents, and represent a rational approach when consideration is given to the pathophysiology of this common condition. Trials of gliclazide modified release in varied populations have yielded very acceptable clinical results that support its first-line use in type 2 diabetes, including obese, elderly, and mild-to-moderate renal insufficient patients. The simplicity of its dose regimen and its efficacy and tolerance profile may significantly contribute to improving compliance.

Gliclazide modified release: from once-daily administration to 24-hour blood glucose control

Although sulfonylureas have been used for more than 40 years, it is only recently that their molecular mechanisms of action have been elucidated. Gliclazide modified release, whose introduction comes soon after the sequencing and cloning of the sulfonylurea receptor, is the first sulfonylurea for which it is possible to detail its action from the moment of oral administration through to its effects on long-term glycemic control. Piecing together these steps for this new agent underlines the rationality of its development and the important differences from other members of the sulfonylurea class. Employing an innovative pharmaceutical form based on a hydrophilic matrix to deliver this short-acting sulfonylurea, gliclazide modified release is associated with an unsurpassed efficacy:acceptability ratio, with the potential additional advantages inherent in reduced dosage and once-daily administration.

Comparative tolerability of sulphonylureas in diabetes mellitus

The sulphonylurea drugs have been the mainstay of oral treatment for patients with diabetes mellitus since they were introduced. In general, they are well tolerated, with a low incidence of adverse effects, although there are some differences between the drugs in the incidence of hypoglycaemia. Over the years, the drugs causing the most problems with hypoglycaemia have been chlorpropamide and glibenclamide (glyburide), although this is a potential problem with all sulphonylureas because of their action on the pancreatic beta cell, stimulating insulin release. Other specific problems have been reported with chlorpropamide that occur only rarely, if at all, with other sulphonylureas. Hyponatraemia secondary to inappropriate antidiuretic hormone activity, and increased flushing following the ingestion of alcohol, have been well described. The progressive beta cell failure with time results in eventual loss of efficacy, as these agents depend on a functioning beta cell and are ineffective in the absence of insulin-producing capacity. Differences in this secondary failure rate have been reported, with chlorpropamide and gliclazide having lower failure rates than glibenclamide or glipizide. The reasons for this are unclear, but the more abnormal pattern of insulin release produced by glibenclamide may be partly responsible and, indeed, may explain the increased risk of hypoglycaemia with this agent. Previously reported increased mortality associated with tolbutamide therapy has not been substantiated, and more recent data have shown no increased mortality from sulphonylurea treatment. Indeed, benefit from glycaemic control, regardless of the agent used--insulin or sulphonylurea--was reported by the United Kingdom Prospective Diabetes Study. Nevertheless, there is still ongoing controversy in view of the experimental evidence, mainly from animal studies, of potential adverse effects on the heart from sulphonylureas, but these are difficult to extrapolate into clinical situations. Most of these studies have been carried out with glibenclamide, which makes comparison of possible risk difficult. Other cardiovascular risk factors may be modified by gliclazide, which seems unique among the sulphonylureas in this respect. Its reported haemobiological and free radical scavenging activity probably resides in the azabicyclo-octyl ring structure in the side chain. Reduced progression or improvement in retinopathy has been reported in comparative trials with other sulphonylureas, and the effect is unrelated to improvements in glycaemia. There are differences between the sulphonylureas in some adverse effects, risk of hypoglycaemia, failure rates and actions on vascular risk factors. As a group of drugs, they are very well tolerated, but differences in overall tolerability can be identified.

Prolonged sulfonylurea-induced hypoglycemia in diabetic patients with end-stage renal disease

Renal impairment is a recognized risk factor for prolonged hypoglycemia, but predisposing characteristics in patients with advanced renal impairment have not been studied. We observed prolonged hypoglycemia in a number of patients with end-stage renal disease (ESRD) and conducted a case-control study at two Canadian centers to identify such risk factors. Through hospital, pharmacy, and dialysis program records, we retrospectively identified 7 case patients and 31 controls with ESRD and type 2 diabetes using oral hypoglycemic monotherapy. Control patients had no history of hospital admission for prolonged hypoglycemia. All case patients and 28 controls were receiving glyburide (glibenclamide in Europe); the remainder were treated with tolbutamide. Duration of intravenous treatment for hypoglycemia ranged from 28 to 256 hours, with 83 g to 2 kg of glucose administered per episode. Preceding treatment with glyburide varied from 2 days to 13 years. Univariate analyses showed a recent decline in oral intake (odds ratio [OR], 81; 95% confidence interval [CI], 3.6 to 1,840), previous hypoglycemic episodes (OR, 15; 95% CI, 0.77 to 297), longer duration of diabetes (22 versus 12 years; P = 0.008), and a history of cerebrovascular disease (OR, 7. 0; 95% CI, 1.0 to 47) to be associated with prolonged hypoglycemia. No association between prolonged hypoglycemia and age, sex, beta blockers, angiotensin-converting enzyme inhibitors, oral hypoglycemic dose, or duration of treatment was identified. This study describes the potentially devastating effect of sulfonylurea-based oral hypoglycemic therapy in ESRD. Patients at greatest risk appear to be those with reduced intake, previous hypoglycemic episodes, and longer duration of diabetes. We describe the mechanisms for observed hypoglycemia and suggest that alternative drugs may be considered in this patient group.

Evidence that insulin can directly inhibit hepatic glucose production

In order to evaluate the role of portal insulin in the modulation of hepatic glucose production (HGP), measurements of plasma glucose and insulin concentrations and both HGP and peripheral glucose disappearance rates were made following an infusion of a dose of tolbutamide (0.74 mg x m(-2) x min[-1]) in healthy volunteers that does not result in an increase in peripheral vein insulin concentrations or metabolic clearance rate of glucose. The results showed that the infusion of such a dose of tolbutamide was associated with a significant and rapid decline in both HGP (from 9.0 +/- 0.5 to 7.7 +/- 0.5 micromol x kg(-1) x min(-1) or delta = -13.8 +/- 4.5%; p < 0.001 compared to saline) and plasma glucose concentration (from 5.1 +/- 0.2 to 4.4 +/- 0.1 mmol/l or delta = -13.0 +/- 2.1%; p < 0.01 compared to saline). Since neither HGP nor fasting glucose fell when tolbutamide-stimulated insulin secretion was inhibited by the concurrent administration of somatostatin, it indicated that tolbutamide by itself, does not directly inhibit HGP. Finally, HGP fell by 26.3 +/- 6.0% at 10 min after a dose of tolbutamide that elevated both peripheral and portal insulin concentrations, at a time when HGP had barely increased (delta = +6.9 +/- 5.3%). The difference in the magnitude of the two responses was statistically significant (p < 0.03), providing further support for the view that insulin can directly inhibit HGP, independent of any change in flow of substrates from periphery to liver.

Effects of glimepiride on insulin and glucagon release from isolated rat pancreas at different glucose concentrations

The effects of glimepiride, the newest sulphonylureic compound, on pancreatic insulin and glucagon secretion were studied using the classical, isolated, perfused rat pancrease model. The influence of four different environmental glucose conditions (during a glycaemic stimulus with glucose increasing from 5 to 8.33 mM and at stable 0, 5 and 2.22 mM glucose levels) on the effects of glimepiride was also assessed. At a pharmacological concentration glimepiride strongly stimulated beta-cell activity, producing a characteristic biphasic insulin release with a sharp first-phase secretory peak, followed by a prolonged and sustained second phase. Environmental glucose concentrations markedly influenced the extent, but not the pattern of glimepiride-induced insulin secretion, as hormone release dropped significantly when the glucose level was reduced. Glimepiride failed to influence alpha-cell activity at any of the environmental glycaemic levels.

Comparison of efficacy, secondary failure rate, and complications of sulfonylureas

The data from three clinical trials are presented, comparing the efficacy of different sulfonylureas in the treatment of type II diabetes. In a multicenter study, gliclazide improved control in 49% of patients who had failed on other drugs. When five groups of type II diabetic patients were treated concurrently with five randomly allocated different sulfonylureas over 1 year, the percentage of patients achieving normal HbA1 levels was best with gliclazide (80%) and glibenclamide (74%), when compared with chlorpropamide (17%), glipizide (40%), and gliquidone (40%). Secondary failure rate over 5 years was assessed in 248 type II diabetic patients randomly allocated to three different sulfonylureas and found to be lowest with gliclazide (7%) compared with glibenclamide (17.9%): p < 0.1) and glipizide (25.6%: p < 0.005). The incidence of hypoglycemia was significantly higher with glibenclamide than with gliclazide (p < 0.05). The differences in efficacy and secondary failure rate between sulfonylureas may be related to the mechanism of insulin release from the beta-cell and the more physiological action of gliclazide could partly explain this. These trials suggest that gliclazide is a potent sulfonylurea with a low rate of secondary failure and a low incidence of side effects and may be a better choice in long-term sulfonylurea therapy.

Glucose modulates the amount, but not the kinetics, of insulin released by sulfonylureas

This study compares the insulin-secretory profiles induced by therapeutical concentrations of four different sulfonylureas--tolbutamide, gliquidone, gliclazide, and glibenclamide--and the amount of hormone released by each under different ambient glucose concentrations, using the isolated perfused rat pancreas model. All four sulfonylureas stimulated B-cell function, but the kinetics varied. Tolbutamide, gliquidone, and gliclazide produced a quick, biphasic release, whereas glibenclamide stimulated a delayed monophasic insulin secretion. Dramatic falls in insulin release were observed when ambient glucose concentrations were lowered. Glucagon release was not influenced by any of the sulfonylureas whatever the metabolic condition, neither directly nor indirectly, via an insulin-mediated paracrine inhibition of A-cell activity.

Gliclazide. An update of its pharmacological properties and therapeutic efficacy in non-insulin-dependent diabetes mellitus

Gliclazide is a second generation sulphonylurea oral hypoglycaemic agent used in the treatment of non-insulin-dependent diabetes mellitus (NIDDM). It improves defective insulin secretion and may reverse insulin resistance observed in patients with NIDDM. These actions are reflected in a reduction in blood glucose levels which is maintained during both short and long term administration, and is comparable with that achieved by other sulphonylurea agents. Gradually accumulating evidence suggests that gliclazide may be useful in patients with diabetic retinopathy, due to its haemobiological actions, and that addition of gliclazide to insulin therapy enables insulin dosage to be reduced. Thus, gliclazide is an effective agent for the treatment of the metabolic defects associated with NIDDM and may have the added advantage of potentially slowing the progression of diabetic retinopathy. These actions, together with its good general tolerability and low incidence of hypoglycaemia have allowed gliclazide to be well placed within the array of oral hypoglycaemic agents available for the control of NIDDM.