Efficacy and safety of once daily gliclazide (20 mg/day) compared with nateglinide

The Impact of Low-dose Gliclazide on the Incretin Effect and Indices of Beta-cell Function

AIMS/HYPOTHESIS

Studies in permanent neonatal diabetes suggest that sulphonylureas lower blood glucose without causing hypoglycemia, in part by augmenting the incretin effect. This mechanism has not previously been attributed to sulphonylureas in patients with type 2 diabetes (T2DM). We therefore aimed to evaluate the impact of low-dose gliclazide on beta-cell function and incretin action in patients with T2DM.

METHODS

Paired oral glucose tolerance tests and isoglycemic infusions were performed to evaluate the difference in the classical incretin effect in the presence and absence of low-dose gliclazide in 16 subjects with T2DM (hemoglobin A1c < 64 mmol/mol, 8.0%) treated with diet or metformin monotherapy. Beta-cell function modeling was undertaken to describe the relationship between insulin secretion and glucose concentration.

RESULTS

A single dose of 20 mg gliclazide reduced mean glucose during the oral glucose tolerance test from 12.01 ± 0.56 to 10.82 ± 0.5mmol/l [P = 0.0006; mean ± standard error of the mean (SEM)]. The classical incretin effect was augmented by 20 mg gliclazide, from 35.5% (lower quartile 27.3, upper quartile 61.2) to 54.99% (34.8, 72.8; P = 0.049). Gliclazide increased beta-cell glucose sensitivity by 46% [control 22.61 ± 3.94, gliclazide 33.11 ± 7.83 (P = 0.01)] as well as late-phase incretin potentiation [control 0.92 ± 0.05, gliclazide 1.285 ± 0.14 (P = 0.038)].

CONCLUSIONS/INTERPRETATION

Low-dose gliclazide reduces plasma glucose in response to oral glucose load, with concomitant augmentation of the classical incretin effect. Beta-cell modeling shows that low plasma concentrations of gliclazide potentiate late-phase insulin secretion and increase glucose sensitivity by 50%. Further studies are merited to explore whether low-dose gliclazide, by enhancing incretin action, could effectively lower blood glucose without risk of hypoglycemia.

Type 2 diabetes

415 million people live with diabetes worldwide, and an estimated 193 million people have undiagnosed diabetes. Type 2 diabetes accounts for more than 90% of patients with diabetes and leads to microvascular and macrovascular complications that cause profound psychological and physical distress to both patients and carers and put a huge burden on health-care systems. Despite increasing knowledge regarding risk factors for type 2 diabetes and evidence for successful prevention programmes, the incidence and prevalence of the disease continues to rise globally. Early detection through screening programmes and the availability of safe and effective therapies reduces morbidity and mortality by preventing or delaying complications. Increased understanding of specific diabetes phenotypes and genotypes might result in more specific and tailored management of patients with type 2 diabetes, as has been shown in patients with maturity onset diabetes of the young. In this Seminar, we describe recent developments in the diagnosis and management of type 2 diabetes, existing controversies, and future directions of care.

The role of nateglinide and repaglinide, derivatives of meglitinide, in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases worldwide, presenting a great challenge to the public health systems due to high morbidity and mortality, because of frequent micro-/macro-vascular complications. Many treatment options are now available, with different efficacy as well as mechanisms of action to improve deranged glucose metabolism. We review some of the available data on derivatives of meglitinide, namely nateglinide and repaglinide. These two compounds increase insulin secretion by a mechanism similar to the one of sulfonylureas, but with a shorter half-life. Nateglinide and repaglinide, derivatives of meglitinides, have characteristic pharmacodynamic and pharmacokinetic properties that, together with their proposed mechanism of action, make them useful for type 2 diabetes mellitus, especially when used in combination therapy.

Meglitinide analogues: a review of clinical data focused on recent trials

Glinides represent a chemically heterogeneous new class of insulin-secreting agents characterized by a rapid onset and short duration of action. They act by closure of the ATP-dependant K channel. Repaglinide, the only glinide available in France, has an equivalent HbA1c lowering effect to conventional sulfonylureas but reduces predominantly postprandial glucose levels. Several studies indicate a decreased risk of hypoglycaemias, particularly nocturnal or in case of a shift or omission of a meal. This drug appears particularly useful in early stage type 2 diabetes or in combination with metformin. The only significant drug-drug interaction concerns gemfibrozil. Due to its hepatic metabolism and biliary elimination, repaglinide can be used in patients with renal insufficiency. Nateglinide has a even shorter duration of action and has almost no effect on fasting plasma glucose levels. For this reason, this drug is only indicated in combination with metformin in the countries where it is licensed. Several experimental data suggest that glinides could preserve B cell function over time better than hypoglycaemic sulfonylureas, and that the improvement of post-prandial glucose levels could exert a long term protective cardiovascular effect.

Safety and efficacy of low-dose pioglitazone (7.5 mg/day) vs. standard-dose pioglitazone (15 mg/day) in Japanese women with type 2 diabetes mellitus

It is well known that pioglitazone, a potent thiazolidinedione, improves metabolic control. However, weight gain or peripheral edema may be of major clinical concern when using this agent. The purpose of our study was to prospectively evaluate the effects of low-dose pioglitazone (7.5 mg/day) on metabolic control, weight gain and the incidence of edema compared with a standard dose of pioglitazone (15.0 mg/day) in patients with type 2 diabetes mellitus (T2DM). Ninety-five Japanese female patients (mean age 58.4 +/- 10.4 years) with newly diagnosed T2DM were selected for this study. They were randomly divided into the following 2 groups according to therapy regimens, and examined every month for 6 months after diagnosis. Group A consisted of 54 patients treated with low-dose pioglitazone orally; Group B, the control-group, consisted of 41 patients treated with standard-dose pioglitazone orally. The incidence of peripheral edema was significantly much lower in group A (2/54) than in group B (11/41) (p = 0.0014). In addition, % change of body weight during the 6-month treatment in group A was significantly less than that in group B (p < 0.0001). On the other hand, the % change of biochemical parameters including HbA1c did not differ significantly between group A and group B, although glucose and lipid control significantly improved from baseline in both groups. Our results demonstrate the safety and efficacy of low-dose pioglitazone, suggesting that it could be another good choice of treatment for Japanese women with T2DM.

Efficacy and adverse effects of nateglinide in early type 2 diabetes. Comparison with voglibose in a cross-over study

An open-label prospective cross-over trial was performed to compare the efficacy and adverse effects of nateglinide with those of voglibose on Japanese early type 2 diabetes (who were oral hypoglycemic agent naïve and whose HbA(1C) levels were between 7.0 and 7.9% before treatment). Fourteen patients received 270 mg/day of nateglinide and 15 patients received 0.6 mg/day of voglibose. After 12 weeks of either therapy, the drugs were switched and treatment was continued for another 12 weeks. After 3-month treatment with each drug, HbA(1C) value decreased significantly (baseline HbA(1C) 7.24 +/- 0.42%, 6.70 +/- 0.47% with nateglinide: p<0.01, 6.93 +/- 0.62% with voglibose: p<0.05) but the difference in the effect between nateglinide and voglibose was not significant (p = 0.121). Symptoms related to hypoglycemia (e.g., increased appetite, palpitation, sweating, tremor) were scarcely observed with either voglibose or nateglinide treatments. Abdominal fullness/borborygmi was frequently reported, with variable severity, by patients on voglibose but this was absent or mild in those on nateglinide. After completion of both arms of the study, more patients favored nateglinide than voglibose. Our results suggest that nateglinide is an effective and safe drug in the treatment of early type 2 diabetes, similar to voglibose.

Therapeutic efficacy of mitiglinide combined with once daily insulin glargine after switching from multiple daily insulin regimen of aspart insulin and glargine in patients with type 2 diabetes mellitus

Mitiglinide is novel class of rapid-acting insulin secretagogues, which have been widely used alone or in combination with other oral hypoglycemic drugs to improve postprandial hyperglycemia in early type 2 diabetes. While mitiglinide enhances postprandial requirement of insulin, the efficacy of mitiglinide combined with insulin has yet to be established. We investigated the efficacy of mitiglinide combined with insulin glargine, the first soluble insulin analog that has a flat and prolonged effect. After control with the intensive regimen (daily aspart insulin and glargine), 30 inpatients with type 2 diabetes were switched to premeal mitiglinide combined with once daily insulin glargine (mitiglinide regimen), and daily profiles of blood glucose level were compared under each regimen. Fifteen patients showed similar control of hyperglycemia with mitiglinide regimen and intensive insulin regimen, assessed by M value (<32), while the remaining 15 showed worsening under the mitiglinide regimen. The patients who were well controlled with mitiglinide regimen were significantly younger (51.9 +/- 16.0 years, p<0.005) and heavier (body mass index: 25.7 +/- 3.3 kg/m(2), p<0.05) than those who were not (67.9 +/- 8.7 and 23.0 +/- 3.1, respectively). Moreover, insulin doses of aspart per body weight were significantly fewer in effective group than in ineffective group. Duration of diabetes was shorter in the effective group, albeit insignificantly. Previous treatment before starting intensive insulin regimen, such as insulin and sulfonylurea, was not different between the two groups. Our results suggest that mitiglinide plus insulin glargine combination therapy is useful for lowering both fasting and postprandial hyperglycemia in a subpopulation of type 2 diabetes. The long-term effects of such treatment need to be established in future studies.

Anti-oxidative effect of fluvastatin in hyperlipidemic type 2 diabetic patients

An open-label prospective cross-over trial was performed to evaluate the antioxidative effect of fluvastatin in Japanese type 2 diabetics with hyperlipidemia. The study subjects were 10 patients who were on pravastatin (10 mg/day) or simvastatin (5 mg/day). After at least 12 weeks of continuous pravastatin or simvastatin therapy, the drugs were washed out for 12 weeks and replaced with fluvastatin (30 mg/day), then the treatment was continued for another 12 weeks. Total cholesterol and LDL cholesterol were efficiently and comparably reduced by all three statin agents. There were no differences in serum parameters of oxidative stress such as malondialdehyde-modified low-density lipoprotein, thiobarbituric acid-reactive substances, and 8-iso-prostaglandin F2alpha between pravastatin/simvastatin and fluvastatin. However, fluvastatin, but not pravastatin/simvastatin, significantly reduced 3,5,7-cholestatriene in erythrocyte membrane, representing the extent of membrane cholesterol peroxidation. Our data demonstrated that fluvastatin has a unique anti-oxidative effect in patients with type 2 diabetes and hyperlipidemia, compared with other statins.