Nateglinide alone and in combination with metformin improves glycemic control by reducing mealtime glucose levels in type 2 diabetes

Importance of postprandial glucose levels as a target for glycemic control in type 2 diabetes

Increasing evidence supports the importance of postprandial glucose (PPG) in glycemic control with regard to the development of complications in patients with diabetes. PPG plays a critical role in determining overall glycemic control, particularly in patients who are close to their glycemic goals. Data also indicate that postprandial hyperglycemia may have a greater effect on the development of cardiovascular complications compared with elevated fasting plasma glucose. Several antidiabetic agents that specifically target PPG are currently available, including glinides, glucagon-like peptide-1 mimetics, dipeptidyl peptidase-4 inhibitors, and rapid-acting insulin analogs. A more intensive approach to managing PPG may improve the care of patients with diabetes and, ultimately, the outcome of these patients.

Cardiovascular outcomes in trials of oral diabetes medications: a systematic review

BACKGROUND

A wide variety of oral diabetes medications are currently available for the treatment of type 2 diabetes mellitus, but it is unclear how these agents compare with respect to long-term cardiovascular risk. Our objective was to systematically examine the peer-reviewed literature on the cardiovascular risk associated with oral agents (second-generation sulfonylureas, biguanides, thiazolidinediones, and meglitinides) for treating adults with type 2 diabetes.

METHODS

We searched MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials, from inception through January 19, 2006. Forty publications of controlled trials that reported information on cardiovascular events (primarily myocardial infarction and stroke) met our inclusion criteria. Using standardized protocols, 2 reviewers serially abstracted data from each article. Trials were first described qualitatively. For comparisons with 4 or more independent trials, results were pooled quantitatively using the Mantel-Haenszel method. Results are presented as odds ratios (ORs) and corresponding 95% confidence intervals (CIs).

RESULTS

Treatment with metformin hydrochloride was associated with a decreased risk of cardiovascular mortality (pooled OR, 0.74; 95% CI, 0.62-0.89) compared with any other oral diabetes agent or placebo; the results for cardiovascular morbidity and all-cause mortality were similar but not statistically significant. No other significant associations of oral diabetes agents with fatal or nonfatal cardiovascular disease or all-cause mortality were observed. When compared with any other agent or placebo, rosiglitazone was the only diabetes agent associated with an increased risk of cardiovascular morbidity or mortality, but this result was not statistically significant (OR, 1.68; 95% CI, 0.92-3.06).

CONCLUSIONS

Meta-analysis suggested that, compared with other oral diabetes agents and placebo, metformin was moderately protective and rosiglitazone possibly harmful, but lack of power prohibited firmer conclusions. Larger, long-term studies taken to hard end points and better reporting of cardiovascular events in short-term studies will be required to draw firm conclusions about major clinical benefits and risks related to oral diabetes agents.

New-onset diabetes mellitus after solid organ transplantation

New-onset diabetes mellitus is a common complication of solid organ transplantation and is likely to become even more common with the current epidemic of obesity in some countries. It has become clear that both new-onset diabetes and prediabetic states (impaired fasting glucose and impaired glucose tolerance) negatively influence graft and patient survival after transplantation. This observation forms the basis for recommending meticulous screening for glucose intolerance before and after transplantation. Although a number of clinical factors including age, weight, ethnicity, family history, and infection with hepatitis C are closely associated with the new-onset diabetes mellitus, immunosuppression with corticosteroids, calcineurin inhibitors and possibly sirolimus plays a dominant role in its pathogenesis. Management of new-onset diabetes after transplantation generally conforms to the guidelines for treatment of type 2 diabetes mellitus in the general population. However, further studies are needed to determine the optimal immunosuppressive regimens for patients with this disorder.

Insulin exocytosis in Goto-Kakizaki rat beta-cells subjected to long-term glinide or sulfonylurea treatment

Sulfonylurea and glinide drugs display different effects on insulin granule motion in single beta-cells in vitro. We therefore investigated the different effects that these drugs manifest towards insulin release in an in vivo long-term treatment model. Diabetic GK (Goto-Kakizaki) rats were treated with nateglinide, glibenclamide or insulin for 6 weeks. Insulin granule motion in single beta-cells and the expression of SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins were then analysed. Perifusion studies showed that decreased first-phase insulin release was partially recovered when GK rats were treated with nateglinide or insulin for 6 weeks, whereas no first-phase release occurred with glibenclamide treatment. In accord with the perifusion results, TIRF (total internal reflection fluorescence) imaging of insulin exocytosis showed restoration of the decreased number of docked insulin granules and the fusion events from them during first-phase release for nateglinide or insulin, but not glibenclamide, treatment; electron microscopy results confirmed the TIRF microscopy data. Relative to vehicle-treated GK beta-cells, an increased number of SNARE clusters were evident in nateglinide- or insulin-treated cells; a lesser increase was observed in glibenclamide-treated cells. Immunostaining for insulin showed that nateglinide treatment better preserved pancreatic islet morphology than did glibenclamide treatment. However, direct exposure of GK beta-cells to these drugs could not restore the decreased first-phase insulin release nor the reduced numbers of docked insulin granules. We conclude that treatment of GK rats with nateglinide and glibenclamide varies in long-term effects on beta-cell functions; nateglinide treatment appears overall to be more beneficial.

Impact of therapeutic advances on hypoglycaemia in type 2 diabetes

Patients with type 2 diabetes experience hypoglycaemia less frequently than those with type 1 diabetes. Some protection against hypoglycaemia is afforded by the relatively intact glucose counter-regulatory pathways that characterize the pathophysiology of early type 2 diabetes. To some extent, this protection explains why hypoglycaemic episodes in intensively treated individuals with type 2 diabetes, when they occur, are rarely severe. As diabetes progresses and therapy intensifies to achieve recommended glycaemic goals, hypoglycaemia frequency and severity increase. Thus, when it comes to instituting intensive therapy, fear of hypoglycaemia may contribute to health-care providers' 'clinical inertia'. Because maintaining glycaemic control is so important to both public and individual health, many new therapies and technologies have been developed. This manuscript reviews and considers whether these advancements in therapy make glycaemic goals easier to achieve by minimizing hypoglycaemia. Putting the hypoglycaemia experienced by type 2 diabetes patients into appropriate clinical perspective, the impact of recent progress made in pharmacotherapy, drug delivery systems, and BG monitoring on hypoglycaemia incidence is largely positive. The extent to which this progress can effect improvement over traditional therapies will, however, depend upon patient (and provider) education, motivation and behaviour change.

Nateglinide prevents fatty liver through up-regulation of lipid oxidation pathway in Goto-Kakizaki rats on a high-fat diet

Dyslipidemia and fatty liver are important components of the metabolic syndrome and are the factors most commonly associated with the development of nonalcoholic fatty liver disease. Delayed and excessive insulin secretion in response to food intake is a key element in the onset of these risk factors. Nateglinide (NAT) is known to restore early-phase insulin secretion. We assessed the effect of NAT on postprandial hypertriglyceridemia and fatty liver in type 2 diabetic Goto-Kakizaki (GK) rats. The GK rats fed a high-fat diet containing 30% beef tallow twice a day were administered either the vehicle alone or NAT (50 mg/kg) before each meal for 12 weeks. Delayed insulin secretion and an increase of total insulin release were caused by feeding 30% beef tallow to the rats. This diet also induced postprandial hypertriglyceridemia and increased the hepatic triglyceride content. Treatment with NAT restored early-phase insulin secretion without any increase of total insulin release and also reduced postprandial hypertriglyceridemia and the hepatic triglyceride content. There was up-regulation of the hepatic expression of peroxisome proliferators-activated receptor alpha and its downstream enzymes after 12 weeks of NAT treatment, as well as normalization of the plasma total ketone body level. Furthermore, NAT also up-regulated hepatic expression of the adiponectin receptor AdipoR2, although there was no effect on the plasma adiponectin level. These findings indicate that long-term treatment with NAT prevented the development of fatty liver through the up-regulation of hepatic lipid oxidation pathways. Restoration of early-phase insulin secretion and suppression of recurrent postprandial hypertriglyceridemia might be involved in these effects of NAT. The present results may support the use of NAT to prevent the onset and progression of the metabolic syndrome and chronic liver disease.

Safety of nateglinide as used in general practice in England: results of a prescription-event monitoring study

Nateglinide (Starlix((R))) is licensed for the treatment of Type 2 diabetes in patients inadequately controlled with metformin. The study objective was to monitor the safety and use of nateglinide prescribed by primary care physicians (GPs) in England, using the observational cohort technique, Prescription-Event Monitoring. Exposure data were derived from dispensed nateglinide prescriptions issued October 2001-June 2004; demographic and outcome data, from questionnaires sent to patients' GPs at least 6 months after patients' first prescription. Incidence densities (IDs; number of first reports of an event/1,000 patient-months exposure) were calculated for month 1 (ID(1)), months 2-6 (ID(2-6)); rate differences [ID(1)-ID(2-6) (+99% CI)] were examined. Cohort comprised 4,557 patients, median age 60 (IQR 51, 68 years); 2,439 (53.5%) male; 3,463 (76.0%) received nateglinide in combination with metformin. GPs reported 1,625 reasons for stopping in 1,474 (32.3%) patients and 80 events as adverse drug reactions in 66 (1.5%) patients. Events associated with starting treatment included nausea/vomiting [ID(1)-ID(2-6) 9.6 (99% CI 5.3, 13.9)], malaise/lassitude [ID(1)-ID(2-6) 6.03 (99% CI 2.2, 9.9)]. No serious hypersensitivity reactions were reported. Two pregnancies (< 0.1%) and 73 deaths (1.6%) were reported. Nateglinide appeared to be generally well tolerated when used in combination with metformin for the treatment of Type 2 diabetes.

Intensive diabetes therapy and body weight: focus on insulin detemir

Weight gain can be a significant barrier to the treatment of diabetes. Insulin detemir is a basal insulin analog that can help patients move safely toward glycemic targets with less weight gain. This review discusses the potential adverse effects of, and hypothesis for, weight gain resulting from intensive insulin management of diabetes. In addition, an assessment of all weight change data from clinical trials and observational studies involving insulin detemir are presented. Finally, we discuss how the ability of insulin detemir to closely mimic endogenous insulin secretion leads to more predictable glycemic control with reduced weight gain and provides patients with a more acceptable method of achieving glycemic control.

Multi-component plasma quantitation of anti-hyperglycemic pharmaceutical compounds using liquid chromatography-tandem mass spectrometry

Type-2 diabetes is a disorder characterized by disrupted insulin production leading to high blood glucose levels. To control this disease, combination therapy is often used. Hypoglycemic agents such as metformin, glipizide, glyburide, repaglinide, rosiglitazone, nateglinide, and pioglitazone are widely prescribed to control blood sugar levels. These drugs provide the basis for the development of a quantitative multianalyte bioanalytical method. As an example, a highly sensitive and selective multi-drug method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. This rapid, automated method consists of protein precipitation of 20 microL of plasma coupled with gradient HPLC elution of compounds using 10 mM ammonium formate buffer and 0.1% formic acid in acetonitrile as the mobile phases. MS/MS detection was performed using turbo ion spray in the positive ion multiple reaction monitoring (SRM) mode. A lower limit of quantitation (LLQ) in a range of 1.0-5.0 ng/mL was achieved for all analytes. The linearity of the method was observed over a 500-fold dynamic range. Drug recoveries ranged from 86.2 to 94.2% for all analytes of interest. Selectivity, sample dilution, intra-day and inter-day accuracy and precision, and stability assessment were evaluated for all compounds.

Improvement of insulin sensitivity and beta-cell function by nateglinide and repaglinide in type 2 diabetic patients - a randomized controlled double-blind and double-dummy multicentre clinical trial

AIM

To evaluate the efficacy of nateglinide vs. repaglinide in blood glucose (BG) control and the effect on insulin resistance and beta-Cell function in patients with type 2 diabetes.

METHODS

A randomized controlled double-blind and double-dummy multicentre clinical trial was conducted. A total of 230 Chinese patients with type 2 diabetes were enrolled in five clinical centres. The patients were divided randomly into group A [repaglinide 1.0 mg three times daily (t.i.d.), n = 115] or group B (nateglinide 90 mg t.i.d., n = 115). At baseline and end of the 12-week clinical trial, standard mixed meal tolerance tests were performed.

RESULTS

A total of 223 patients (96.9%) completed the trial. There was no significant difference between repaglinide and nateglinide groups in the effects of reducing fasting blood glucose (FBG), 30-, 60- and 120-min BG during 12 weeks (p > 0.05). At week 12, no significant difference was shown between the two groups in BG or haemoglobin A(1c) (HbA(1c)) (p > 0.05). However, the effect on HbA(1c) in repaglinide group was stronger than that in nateglinide group (p < 0.05). After 12-week treatment, area under the curve (AUC) of BG decreased (p < 0.05), and AUC of insulin and C-peptide (CP) increased in both groups (p < 0.05). The effects of nateglinide on AUC of BG, insulin and CP were similar to that of repaglinide (p > 0.05). There was no significant difference between the two groups in AUC of BG, insulin or CP in week 12 (p > 0.05). Furthermore, homeostasis model assessment of insulin resistance (HOMA-IR) and beta-cell function indexes measured by HOMA-beta, DeltaI(30)/DeltaG(30) and (DeltaI(30)/DeltaG(30))/HOMA-IR were improved significantly in both groups during 12 weeks (p < 0.05). The effects of improving HOMA-IR and beta-cell function indexes in nateglinide group were comparable with that of repaglinide group (p > 0.05).

CONCLUSIONS

The efficacy of repaglinide and nateglinide in FBG, postprandial glucose excursion and early-phase insulin secretion is similar. But the effect of repaglinide 1.0 mg t.i.d. on HbA(1c) is stronger than that of nateglinide 90 mg t.i.d.. This trial had shown that nateglinide and repaglinide could comparably improve insulin sensitivity and beta-cell function.

Meglitinide analogues for type 2 diabetes mellitus

BACKGROUND

In type 2 diabetes mellitus, impairment of insulin secretion is an important component of the disease. Meglitinide analogues are a class of oral hypoglycaemic agents that increase insulin secretion, in particular, during the early phase of insulin release.

OBJECTIVES

The aim of this review was to assess the effects of meglitinide analogues in patients with type 2 diabetes mellitus.

SEARCH STRATEGY

We searched several databases including The Cochrane Library, MEDLINE and EMBASE. We also contacted manufacturers and searched ongoing trials databases, and the American Diabetes Association (ADA) and European Association for the Study of Diabetes (EASD) websites.

SELECTION CRITERIA

We included randomised controlled, parallel or cross-over trials comparing at least 10 weeks of treatment with meglitinide analogues to placebo, head-to-head, metformin or in combination with insulin.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality.

MAIN RESULTS

Fifteen trials involving 3781 participants were included. No studies reported the effect of meglitinides on mortality or morbidity. In the eleven studies comparing meglitinides to placebo, both repaglinide and nateglinide resulted in a reductions in glycosylated haemoglobin (0.1% to 2.1% reduction in HbA1c for repaglinide; 0.2% to 0.6% for nateglinide). Only two trials compared repaglinide to nateglinide (342 participants), with greater reduction in glycosylated haemoglobin in those receiving repaglinide. Repaglinide (248 participants in three trials) had a similar degree of effect in reducing glycosylated haemoglobin as metformin. Nateglinide had a similar or slightly less marked effect on glycosylated haemoglobin than metformin (one study, 355 participants). Weight gain was generally greater in those treated with meglitinides compared with metformin (up to three kg in three months). Diarrhoea occurred less frequently and hypoglycaemia occurred more frequently but rarely severely enough as to require assistance.

AUTHORS' CONCLUSIONS

Meglitinides may offer an alternative oral hypoglycaemic agent of similar potency to metformin, and may be indicated where side effects of metformin are intolerable or where metformin is contraindicated. However, there is no evidence available to indicate what effect meglitinides will have on important long-term outcomes, particularly mortality.

Diabetes: the latest trends in glycemic control

The increasing pervasiveness of diabetes mellitus on a global stage has been well documented. Many groundbreaking studies have detailed the consequences of inadequate glycemic control, but only recently have data supported evidence that demonstrates benefits in the acute setting. Consensus is lacking with regard to how to achieve glycemic control in the hospital setting. This article discusses glycemic control, with special emphasis on the perioperative patient. Emerging therapeutic treatments and less frequently encountered protocols such as insulin pump management and insulin infusion are considered.

Long-term effect of combination therapy with mitiglinide and once daily insulin glargine in patients who were successfully switched from intensive insulin therapy in short-term study

We have previously reported the therapeutic efficacy of mitiglinide combined with once daily insulin glargine (mitiglinide regimen) after switching from multiple daily insulin regimen of aspart insulin and glargine (intensive insulin regimen) in inpatients with type 2 diabetes mellitus in two consecutive days. In the present study, we followed up 9 of the 15 responsive patients with these novel regimens for 6 months after discharge. The data collected from these patients were compared to those of 15 randomly chosen patients who had well matched background and received intensive insulin regimen during hospitalization which was continued after discharge. The average HbA1c level of these 9 patients with mitiglinide regimen at 6 months was 6.7 +/- 0.8% and was comparable to that of the patients with intensive insulin regimen (HbA1c = 7.0 +/- 1.0%). In conclusion, mitiglinide and insulin glargine combination therapy maintained fair glycemic control for as long as 6 months in subpopulation of Japanese patients with type 2 diabetes.

Factors associated with the effect-size of thiazolidinedione (TZD) therapy on HbA(1c): a meta-analysis of published randomized clinical trials

OBJECTIVE

To examine factors affecting the size of the HbA(1c) response to thiazolidinedione (TZD) therapy.

RESEARCH DESIGN AND METHODS

Meta-analysis of randomized TZD controlled trials which were identified using PubMed, EBSCO and Sci-lit databases and were published in English. Sociodemographic and clinical data were extracted from each trial. HbA(1c) effect size was defined as either a placebo-subtracted change in HbA(1c) or a change in HbA(1c) from baseline. Weighted multivariable regression was used to examine factors associated with changes in HbA(1c). Bootstrapped smearing estimates were computed to obtain reliable estimates of HbA(1c) effect size.

RESULTS

Forty-two trials yielded 60 trial arms which represented 8322 patients treated with thiazolidinediones. Weighted placebo-subtracted change in HbA(1c) was -0.99% +/- 0.02% with an average baseline HbA(1c) of 9.1% +/- 1.0%. Weighted bootstrapped smearing estimate of the placebo-subtracted change in HbA(1c) was -1.02% +/- 0.004%. After controlling for other variables, the baseline HbA(1c) level had a significant negative association with placebo-subtracted HbA(1c) change (p = 0.004) and also with change in HbA(1c) from baseline (p = 0.002). Longer trial duration was associated with greater placebo-subtracted HbA(1c) change (p = 0.01) but not with the change in HbA(1c) from baseline. The multivariable models explained 72% of the variation in placebo-subtracted HbA(1c) change. It was not possible to estimate effects of the run-in period and obesity on TZD effect size.

CONCLUSION

Baseline HbA(1c) and trial duration significantly impacted the effect size of TZD therapy on HbA(1c). Age, gender, duration of diabetes and prior use of anti-diabetic therapy were not associated with the TZD effect size.

Imaging docking and fusion of insulin granules induced by antidiabetes agents: sulfonylurea and glinide drugs preferentially mediate the fusion of newcomer, but not previously docked, insulin granules

Sulfonylurea and glinide drugs, commonly used for antidiabetes therapies, are known to stimulate insulin release from pancreatic beta-cells by closing ATP-sensitive K+ channels. However, the specific actions of these drugs on insulin granule motion are largely unknown. Here, we used total internal reflection fluorescence (TIRF) microscopy to analyze the docking and fusion of single insulin granules in live beta-cells exposed to either the sulfonylurea drug glibenclamide or the glinide drug mitiglinide. TIRF images showed that both agents caused rapid fusion of newcomer insulin granules with the cell membrane in both control and diabetic Goto-Kakizaki (GK) rat pancreatic beta-cells. However, in the context of beta-cells from sulfonylurea receptor 1 (SUR1) knockout mice, TIRF images showed that only mitiglinide, but not glibenclamide, caused fusion of newcomer insulin granules. Compositely, our data indicate that 1) the mechanism by which both sulfonylurea and glinide drugs promote insulin release entails the preferential fusion of newcomer, rather than previously docked, insulin granules, and that 2) mitiglinide can induce insulin release by a mechanism independent of mitiglinide binding to SUR1.

Targeting postprandial hyperglycemia

In healthy individuals, blood glucose levels in the fasting state are maintained by the continuous basal-level insulin secretion. After a meal, the rise in postprandial glucose (PPG) is controlled by the rapid pancreatic release of insulin, stimulated by both glucose and the intestinal production of the incretins glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1. In diabetic individuals, postprandial insulin secretion is insufficient to suppress an excessive rise in PPG. There is increasing evidence that elevated PPG exerts a more deleterious effect on the vascular system than elevation of fasting plasma glucose. In particular, individuals with normal fasting plasma glucose but impaired glucose tolerance have significantly increased risk of cardiovascular events. With the recognition of the importance of PPG and the availability of new pharmacologic options, management of diabetes will shift to greater attention to PPG levels. The prototype for such an approach is in the treatment of gestational diabetes and diabetic pregnancies where PPG is the primary target of efforts at glycemic control. These efforts have been extremely successful in improving the outlook for diabetic pregnant women. There are many approaches to reduction of PPG; dietary management and promotion of exercise are very effective. Sulfonylureas, meglitinides, metformin, thiazolidinediones, and disaccharidase inhibitors all counteract PPG elevation. The development of glucagon-like peptide 1 agonists such as exendin and dipeptidyl peptidase IV inhibitors such as vildagliptin offers a new approach to suppression of PPG elevation. New semisynthetic insulin analogues permit a more aggressive response to postprandial glucose elevation, with lower risk of hypoglycemia, than with regular insulin. Inhaled insulin also has a rapid onset of action and offers benefits in PPG control. It is proposed that an aggressive treatment approach focusing on PPG, similar to the current standards for diabetic pregancies, be directed at individuals with diabetes and impaired glucose tolerance.

Drug interactions of clinical importance with antihyperglycaemic agents: an update

Because management of type 2 diabetes mellitus usually involves combined pharmacological therapy to obtain adequate glucose control and treatment of concurrent pathologies (especially dyslipidaemia and arterial hypertension), drug-drug interactions must be carefully considered with antihyperglycaemic drugs. Additive glucose-lowering effects have been extensively reported when combining sulphonylureas (or the new insulin secretagogues, meglitinide derivatives, i.e. nateglinide and repaglinide) with metformin, sulphonylureas (or meglitinide derivatives) with thiazolidinediones (also called glitazones) and the biguanide compound metformin with thiazolidinediones. Interest in combining alpha-glucosidase inhibitors with either sulphonylureas (or meglitinide derivatives), metformin or thiazolidinediones has also been demonstrated. These combinations result in lower glycosylated haemoglobin (HbA(1c)), fasting glucose and postprandial glucose levels than with either monotherapy. Even if modest pharmacokinetic interferences have been reported with some combinations, they do not appear to have important clinical consequences. No significant adverse effects, except a higher risk of hypoglycaemic episodes that may be attributed to better glycaemic control, occur with any combination. Challenging the classical dual therapy with sulphonylurea plus metformin, there is a recent trend to use alternative dual combinations (sulphonylurea plus thiazolidinedione or metformin plus thiazolidinedione). In addition, triple therapy with the addition of a thiazolidinedione to the metformin-sulphonylurea combination has been recently evaluated and allows glucose targets to be reached before insulin therapy is considered. This triple therapy appears to be safe, with no deleterious drug-drug interactions being reported so far.Potential interferences may also occur between glucose-lowering agents and other drugs, and such drug-drug interactions may have important clinical implications. Relevant pharmacological agents are those that are widely coadministered in diabetic patients (e.g. lipid-lowering agents, antihypertensive agents); those that have a narrow efficacy/toxicity ratio (e.g. digoxin, warfarin); or those that are known to induce (rifampicin [rifampin]) or inhibit (fluconazole) the cytochrome P450 (CYP) system. Metformin is currently a key compound in the pharmacological management of type 2 diabetes, used either alone or in combination with other antihyperglycaemics. There are no clinically relevant metabolic interactions with metformin, because this compound is not metabolised and does not inhibit the metabolism of other drugs. In contrast, sulphonylureas, meglitinide derivatives and thiazolidinediones are extensively metabolised in the liver via the CYP system and thus, may be subject to drug-drug metabolic interactions. Many HMG-CoA reductase inhibitors (statins) are also metabolised via the CYP system. Even if modest pharmacokinetic interactions may occur, it is not clear whether drug-drug interactions between oral antihyperglycaemic agents and statins may have clinical consequences regarding both efficacy and safety. In contrast, a marked pharmacokinetic interference has been reported between gemfibrozil and repaglinide and, to a lesser extent, between gemfibrozil and rosiglitazone. This leads to a drastic increase in plasma concentrations of each antihyperglycaemic agent when they are coadministered with the fibric acid derivative, and an increased risk of adverse effects. Some antihypertensive agents may favour hypoglycaemic episodes when co-prescribed with sulphonylureas or meglitinide derivatives, especially ACE inhibitors, but this effect seems to result from a pharmacodynamic drug-drug interaction rather than from a pharmacokinetic drug-drug interaction. No, or only modest, interferences have been described with glucose-lowering agents and other pharmacological compounds such as digoxin or warfarin. The effects of inducers or inhibitors of CYP isoenzymes on the metabolism and pharmacokinetics of the glucose-lowering agents of each pharmacological class has been tested. Significantly increased (with CYP inhibitors) or decreased (with CYP inducers) plasma levels of sulphonylureas, meglitinide derivatives and thiazolidinediones have been reported in healthy volunteers, and these pharmacokinetic changes may lead to enhanced or reduced glucose-lowering action, and thus hypoglycaemia or worsening of metabolic control, respectively. In addition, some case reports have evidenced potential drug-drug interactions with various antihyperglycaemic agents that are usually associated with a higher risk of hypoglycaemia.

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.

Prevalence and correlates of post-prandial hyperglycaemia in a large sample of patients with type 2 diabetes mellitus

AIMS/HYPOTHESIS

Post-prandial glucose may be a risk factor for cardiovascular disease and chronic diabetic complications. We tested the hypothesis that post-prandial hyperglycaemia is common in type 2 diabetes, even among patients in apparently good glycaemic control, and that simple clinical characteristics identify subsets of diabetic patients with frequent post-prandial hyperglycaemia.

SUBJECTS AND METHODS

Three self-assessed daily blood glucose profiles over a 1-week period, including 18 glucose readings before and 2 h after meals, were obtained from 3,284 unselected outpatients (men 51%; age 63+/-10 years) with non-insulin-treated type 2 diabetes mellitus attending 500 different diabetes clinics operating throughout Italy.

RESULTS

A post-prandial blood glucose value >8.89 mmol/l (160 mg/dl) was recorded at least once in 84% of patients, and 81% of patients had at least one Delta glucose > or =2.22 mmol/l (40 mg/dl). Among patients with apparently good metabolic control, 38% had >40% of post-prandial blood glucose readings >8.89 mmol/l (> or =4 of 9 meals in total), and 36% had >40% Delta glucose > or =2.22 mmol/l. In multivariate analysis adjusted for pre-prandial glucose levels, older age, longer duration of diabetes, absence of obesity, hyperlipidaemia and hypertension, as well as treatment with sulfonylureas, were significantly associated with greater glucose excursions after meals.

CONCLUSIONS/INTERPRETATION

These results indicate that post-prandial hyperglycaemia is a very frequent phenomenon in patients with type 2 diabetes mellitus on active treatment; can occur even when metabolic control is apparently good; and can be predicted by simple clinical features.

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.

Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus

BACKGROUND

Metformin is an oral anti-hyperglycemic agent used in the treatment of type 2 diabetes mellitus. The results of the UK Prospective Diabetes Study indicate that metformin treatment is associated with a reduction in total mortality compared to other anti-hyperglycemic treatments. Metformin, however, is thought to increase the risk of lactic acidosis, and is considered to be contraindicated in many chronic hypoxemic conditions that may be associated with lactic acidosis, such as cardiovascular, renal, hepatic and pulmonary disease, and advancing age.

OBJECTIVES

To assess the incidence of fatal and nonfatal lactic acidosis with metformin use compared to placebo and other glucose-lowering treatments in patients with type 2 diabetes mellitus. A secondary objective was to evaluate the blood lactate levels for those on metformin treatment compared to placebo or non-metformin therapies.

SEARCH STRATEGY

A search was performed of The Cochrane Library (up to 8/2005), MEDLINE (up to 8/2005), EMBASE (up to 11/2000), OLD MEDLINE, and REACTIONS (up to 8/2005), in order to identify all studies of metformin treatment from 1966 to August 2005. The Cumulated Index Medicus was used to search relevant articles from 1959 to 1965. The search was augmented by scanning references of identified articles, and by contacting principal investigators. Date of latest search: August 2005.

SELECTION CRITERIA

Prospective trials in patients with type 2 diabetes that lasted longer than one month were included if they evaluated metformin, alone or in combination with other treatments, compared to placebo or any other glucose-lowering therapy. Observational cohort studies of metformin treatment lasting greater than one month were also included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials to be included, assessed study quality and extracted data. The incidence of fatal and nonfatal lactic acidosis was recorded as cases per patient-years, for metformin treatment and for placebo or other treatments. The upper limit for the true incidence of cases in the metformin and non-metformin groups were calculated using Poisson statistics. In a second analysis lactate levels were measured as a net change from baseline or as mean treatment values (basal and stimulated by food or exercise) for treatment and comparison groups. The pooled results were recorded as a weighted mean difference (WMD) in mmol/L, using the fixed effect model for continuous data.

MAIN RESULTS

Pooled data from 206 comparative trials and cohort studies revealed no cases of fatal or nonfatal lactic acidosis in 47,846 patient-years of metformin use or in 38,221 patients-years in the non-metformin group. Using Poisson statistics with 95% confidence intervals the upper limit for the true incidence of metformin-associated lactic acidosis was 6.3 cases per 100,000 patient-years, and the upper limit for the true incidence of lactic acidosis in the non-metformin group was 7.8 cases per 100,000 patient-years. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to placebo or other non-biguanide therapies. The mean lactate levels were slightly lower for metformin treatment compared to phenformin (WMD -0.75 mmol/L, 95% CI -0.86 to -0.15).

AUTHORS' CONCLUSIONS

There is no evidence from prospective comparative trials or from observational cohort studies that metformin is associated with an increased risk of lactic acidosis, or with increased levels of lactate, compared to other anti-hyperglycemic treatments if prescribed under the study conditions.

Nateglinide with glibenclamide examination using the respiratory quotient (RQ)

PURPOSE

The respiratory quotient (RQ) is useful for evaluating glucose and lipid metabolism in vivo. We previously reported that the RQ value, even after fasting, was high in diabetics being treated with sulphonylurea (SU), which might explain the accumulation of fat, leading to weight gain in such individuals. In the present study, we measured the RQ in type II diabetic patients who were being treated with a rapid-onset/short-duration insulinotropic agent, nateglinide, and compared it with those being treated with SU.

METHODS

A glucose tolerance test was performed in 20 patients with type II diabetes mellitus treated with nateglinide and in 14 patients treated with SU, and the RQ was simultaneously measured.

RESULTS

The RQ values in the patients treated with nateglinide, were similar to those in healthy adults, but was lower than in those treated with SU. No weight gain was observed in patients treated with nateglinide.

CONCLUSION

A significant weight gain was reported in subjects treated with SU, accompanied by an increase in RQ. However, weight gain was less frequent in diabetics treated with nateglinide.

Oral agents in managing diabetes mellitus in children and adolescents

Type 2 diabetes mellitus is a chronic disease with potentially devastating long-term complications. Despite the tremendous body of research and experience in the adult population, relatively little is established regarding this condition and its optimal management in children and adolescents. The pediatric community awaits results of ongoing trials as well as further study of optimal intervention in children, as they continue to extrapolate management practices from their adult counterparts.

Effect of N-benzoyl-d-phenylalanine on lipid profile in liver of neonatal streptozotocin diabetic rats

The effect of N-benzoyl-d-phenylalanine (NBDP) and metformin combination treatment on liver lipids and lipid peroxidation markers was studied in neonatal streptozotocin (nSTZ) diabetic rats. Oral administration of NBDP (50, 100 and 200 mg/kg body weight) and metformin (500 mg/kg body weight) for 6 weeks significantly reduced the elevated blood glucose, liver cholesterol, triglycerides, free fatty acids and phospholipids. The combination treatment also caused a significant decrease in hepatic hydroxymethyl glutaryl-coenzyme A reductase, Thiobarbituric Acid Reactive Substances (TBARS) and significant increase in reduced glutathione levels. The results show that NBDP and metformin improve the hepatic lipid profile and antioxidant status in nSTZ diabetic rats. Combination treatment was more effective than either drug alone.

Rapid and efficient chiral separation of nateglinide and its l-enantiomer on monolithic molecularly imprinted polymers

A monolithic molecularly imprinted polymer (monolithic MIP) was designed and prepared for chiral separation of nateglinide and its L-enantiomer. The enantiomers were rapidly separated on this novel monolithic MIP based chiral stationary phase (MIP-CSP), whereas the enantioseparation was not obtained on the non-imprinted polymer (NIP). Chiral recognition was found to be dependent on the stereo structures and the arrangement of functional groups of the imprinted molecule and the cavities on MIP. Thermodynamic data (deltadeltaH and deltadeltaS) obtained by Van't Hoff plots revealed an enthalpy-controlled enantioseparation. The binding capacity was evaluated by frontal analysis. Monolithic nateglinide-MIP had an effective number of binding sites Bt = 41.15 micromol g(-1) with a dissociation constant of Kd = 7.40 mM. The morphological characteristics of the monolithic MIP were investigated by pore analysis and scanning electron microscope (SEM). Results showed that both mesopores and macropores were formed in the monolith. Over all, this study presents a new and practical possibility for providing high rates of mass transfer, fast separations and high efficiencies without the pressure constraints of the traditional bulk molecularly imprinted polymers, through the monolithic MIPs.

[Metformin for type-2 diabetes mellitus. Systematic review and meta-analysis]

OBJECTIVE

To evaluate the efficacy of metformin against placebo, diet, oral anti-diabetics, or insulin in type 2 diabetes mellitus.

DESIGN

Systematic review.

DATA SOURCES

MEDLINE (1966-2003), EMBASE (1974-2003), LILACS (1986-2003), Cochrane library (Issue 3, 2003).

SELECTION OF STUDIES

29 randomized clinical trials of metformin in monotherapy, with results on mortality, morbidity, and biochemistry. EXTRACTION OF DATA: RevMan 4 computer program. Two reviewers extracted the data and evaluated the quality.

MAIN VARIABLES

any clinical event related to diabetes (mortality, coronary disease, stroke, arterial disease, and retinopathy). Secondary variables: weight and biochemistry.

RESULTS

29 clinical studies with 37 comparisons of metformin were analyzed (13 with sulphonylureas, 12 with placebo, 3 with diet, 3 with thiazolidinediones, 2 with alpha-glucosidase inhibitors, 2 with insulin, and 2 with meglitinides). Metformin was more beneficial than the sulphonylureas or insulin for any clinical event associated with diabetes (relative risk [RR]=0.78; 95% confidence interval [CI], 0.65-0.94) and than diet (RR=0.74; 95% CI, 0.60-0.90). Metformin decreased glycosylated hemoglobin A1 (weighted mean difference, -1.21%; 95% CI, -1.48 to -0.94), low density lipoprotein cholesterol (weighted mean difference, -0.24; 95% CI, -0.40 to -0.09), and weight (standardized mean difference, -0.11; 95% CI, -0.18 to -0.04). Metformin was more beneficial than the placebo, diet or the thiazolidinediones on glycosylated hemoglobin A1, and than the sulphonylureas or insulin on weight.

CONCLUSIONS

In the long term metformin reduces the risks of clinical events associated with diabetes. There are no long term clinical trials which compare alpha-glucosidase inhibitors, meglitinides, and thiazolidinediones with metformin, in primary results. The different treatments compared with metformin did not obtain more benefit for the secondary results evaluated.

Metformin monotherapy for type 2 diabetes mellitus

BACKGROUND

Metformin is an anti-hyperglycaemic agent used for the treatment of type 2 diabetes mellitus. Type 2 diabetes may present long-term complications: micro- (retinopathy, nephropathy and neuropathy) and macrovascular (stroke, myocardial infarction and peripheral vascular disease). Two meta-analyses have been published before, although only secondary outcomes were assessed.

OBJECTIVES

To assess the effects of metformin monotherapy on mortality, morbidity, quality of life, glycaemic control, body weight, lipid levels, blood pressure, insulinaemia, and albuminuria in patients with type 2 diabetes mellitus.

SEARCH STRATEGY

Studies were obtained from computerised searches of multiple electronic databases and hand searches of reference lists of relevant trials identified. Date of last search: September 2003.

SELECTION CRITERIA

Trials fulfilling the following inclusion criteria: Diabetes mellitus type 2, metformin versus any other oral intervention, assessment of relevant clinical outcome measures, use of random allocation.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data, using a standard data extraction form. Data were summarised under a random effects model. Dichotomous data were expressed as relative risk. We calculated the risk difference (RD), and the Number Needed to Treat, when it was possible. We collected data of mean and standard deviation from changes to baseline. However many trials reported end point data. This limitation lead to the expression of the results as standardised mean differences (SMD) and an overall SMD was calculated. Heterogeneity was tested for using the Z score and the I-squared statistic. Subgroup, sensitivity analysis and meta-regression were used to explore heterogeneity.

MAIN RESULTS

We included for analysis 29 trials with 37 arms (5259 participants), comparing metformin (37 arms and 2007 participants) with sulphonylureas (13 and 1167), placebo (12 and 702), diet (three and 493), thiazolidinediones (three and 132), insulin (two and 439), meglitinides (two and 208), and glucosidase inhibitors (two and 111). Nine studies reported data on primary outcomes. Obese patients allocated to intensive blood glucose control with metformin showed a greater benefit than chlorpropamide, glibenclamide, or insulin for any diabetes-related outcomes (P = 0.009), and for all-cause mortality (P = 0.03). Obese participants assigned to intensive blood glucose control with metformin showed a greater benefit than overweight patients on conventional treatment for any diabetes-related outcomes (P = 0.004), diabetes-related death (P = 0.03), all-cause mortality (P = 0.01), and myocardial infarction (P = 0.02). Patients assigned to metformin monotherapy showed a significant benefit for glycaemia control, weight, dyslipidaemia, and diastolic blood pressure. Metformin presents a strong benefit for HbA1c when compared with placebo and diet; and a moderated benefit for: glycaemia control, LDL cholesterol, and BMI or weight when compared with sulphonylureas.

AUTHORS' CONCLUSIONS

Metformin may be the first therapeutic option in the diabetes mellitus type 2 with overweight or obesity, as it may prevent some vascular complications, and mortality. Metformin produces beneficial changes in glycaemia control, and moderated in weight, lipids, insulinaemia and diastolic blood pressure. Sulphonylureas, alpha-glucosidase inhibitors, thiazolidinediones, meglitinides, insulin, and diet fail to show more benefit for glycaemia control, body weight, or lipids, than metformin.

Pharmacology of the meglitinide analogs: new treatment options for type 2 diabetes mellitus

The expression meglitinide analogs was introduced in 1995 to cover new molecules proposed as non-sulfonylurea insulinotropic agents and displaying structural analogy with meglitinide, such as repaglinide, nateglinide, and mitiglinide. Meglitinide analogs display, as judged by conformation analysis, a U-shaped configuration similar to that of antihyperglycemic sulfonylureas such as glibenclamide (glyburide) and glimepiride. In rat pancreatic islets incubated in the presence of 7.0 mmol/L D-glucose, repaglinide and mitiglinide demonstrate comparable concentration-response relationships for stimulation of insulin release, with a threshold value < 10 nmol/L and a maximal secretory response at about 10 nmol/L. Several findings indicate that meglitinide analogs provoke the closing of adenosine triphosphate-sensitive potassium channels, with subsequent gating of voltage-sensitive calcium channels. The effects of meglitinide analogs upon the binding of [3H]glibenclamide to islet cells membranes reinforces this concept. At variance, however, with other meglitinide analogs, the ionic and secretory response to repaglinide (10 micromol/L) is not rapidly reversible in perifused rat islets. In experiments conducted in vivo in control and diabetic rats, repaglinide provokes a greater and more rapid increase in plasma insulin concentration and an earlier fall in glycemia than glibenclamide or glimepiride. Onset of effect is also more rapid and duration of effect shorter with nateglinide versus glibenclamide. In clinical studies, single or repeated daily administration of repaglinide increased plasma insulin concentration in a dose-dependent manner, with an incremental peak reached about 2 hours after repaglinide intake. Plasma concentrations of repaglinide are about 5.0 microg/L 2-2.5 hours after oral intake of the drug. Despite the slow reversibility of repaglinide action in vitro, this drug offers advantages over glibenclamide in terms of the possible occurrence of hypoglycemia if a meal is missed. In volunteers receiving a single oral dose of nateglinide (120mg) 10 minutes before a standardized 800 Kcal breakfast, the plasma insulin concentration was higher 5, 10, and 20 minutes after meal intake than when they received a single dose of repaglinide (0.5 or 2.0mg) or placebo 10 minutes before breakfast. Peak plasma concentrations of nateglinide were reached within 2 hours in most volunteers. Peak plasma concentrations of mitiglinide were reached 30 minutes after a single oral dose in a representative volunteer. Mitiglinide significantly suppressed meal-induced elevations in blood glucose concentrations in a study of patients with type 2 diabetes. In conclusion, two obvious differences among these meglitinide analogs should be underlined. First, on a molar basis, nateglinide is somewhat less potent than repaglinide or mitiglinide, as an insulinotropic agent. The maximal secretory responses evoked by these three meglitinide analogs are, however, identical to one another. Secondly, and as already mentioned, the functional effects of nateglinide and mitiglinide are more rapidly reversible than those of repaglinide, for instance in perifused rat islets. The meglitinide analogs offer the advantage over the long-acting antihyperglycemic sulfonylurea glibenclamide of minimizing the risk of undesirable hypoglycemia.

Does metformin decrease blood pressure in patients with Type 2 diabetes intensively treated with insulin?

AIMS

We investigated in a double-blind study whether metformin reduces blood pressure (BP) in patients with Type 2 diabetes intensively treated with insulin.

METHODS

A total of 220 patients with Type 2 diabetes were asked to undergo 24-h ambulatory BP monitoring (24-h ABPM). One hundred and eighty-two gave informed consent. Eighty-nine were randomized to metformin and 93 to placebo. Thirty-five subjects dropped out (13 placebo, 22 metformin users); 147 patients underwent a second 24-h ABPM, 16 weeks after randomization.

RESULTS

Systolic BP (SBP), diastolic BP (DBP), pulse BP (PP), mean BP (MP) and heart rate (HR) were measured as office BP measurements and as 24-h ABPM for 24-h, day and night. Office BP measurements did not differ significantly between the placebo- and metformin-treated groups for any BP measure, but showed a non-significant trend for SBP reduction with metformin use (mean baseline-adjusted difference, metformin minus placebo: -4.2 mmHg, 95% CI, -9.9 to +1.5; P = 0.15). The baseline-adjusted differences of the ambulatory measurements were -0.2 mmHg (95% CI, -2.9 to +2.6) for the 24-h SBP, and +1.1 mmHg (95% CI, -0.7 to +2.8) for the 24-h DBP. On the whole, BP differences between metformin- and placebo-treated groups were not statistically significant. The only significant difference was for night-time PP (baseline-adjusted difference: -2.2 mmHg; 95% CI, -4.2 to -0.2). These results were not different after adjustment for age and diabetes duration, or for (changes in) body mass index, glycated haemoglobin, insulin dose or plasma homocysteine.

CONCLUSION

Metformin does not significantly affect BP in patients with Type 2 diabetes intensively treated with insulin.

Role of insulin secretagogues and insulin sensitizing agents in the prevention of cardiovascular disease in patients who have diabetes

In the absence of clinical trial evidence to compare the secretagogues with sensitizers, it is difficult to make recommendations about which class of drug is more important to prescribe for the prevention of cardiovascular disease in diabetes mellitus. Epidemiologic data supports insulin resistance as a major factor in cardiovascular disease through a variety of mechanisms. Because sensitizers improve insulin sensitivity and correct many of the vascular abnormalities that are associated with insulin resistance, it is tempting to suggest that they may be superior for this purpose. Conversely, meeting the goals that are recommended for glycemia also are important and achieving them may not be always possible with sensitizers, particularly in the later stages of the disease when insulin levels are not high,despite insulin resistance. In such situations,combination therapy may be needed with both types of drugs. No data are available on the cardiovascular effects of such combinations;some retrospective data suggest a possibility of increased events with the combination of sulfonylureas and metformin. Thus, further prospective studies in this area are necessary.

Treatment for childhood type 2 diabetes

Urine glucose screening at school implemented in Japan is useful for detecting childhood type 2 diabetes at the early stage of the disease. Most patients detected by the screening can improve hyperglycemia and reduce overweight within one to three months by changing lifestyle with diet and exercise. For patients who are unable to alter their lifestyle and for those who have hyperglycemia despite maintaining these changes, a variety of oral hypoglycemic agents, including α-glucosidase inhibitors, sulfonylureas, glitinides, metformin, thiazolidenediones, and insulin are available. Metformin is considered to be the most effective oral agent as monotherapy for Japanese young persons with type 2 diabetes, because most of them are obese with insulin resistance. The approach to insulin therapy in patients with type 2 diabetes often differs from that most frequently used in patients with type 1 diabetes. Adjustment of the dose of insulin at each injection using sliding scales or algorithms is not required in most cases. In some cases, combination therapy with metformin and sulfonylureas or use of insulin is more effective for stabilization of blood glucose values. Therapeutic means for childhood type 2 diabetes should be variable depending on each patient's characteristics.

Effects of nateglinide on myocardial microvascular reactivity in Type 2 diabetes mellitus--a randomized study using positron emission tomography

AIMS

To evaluate effects of the oral antidiabetic insulinotropic agent nateglinide on myocardial blood flow (MBF) and microvascular reactivity in Type 2 diabetic patients.

METHODS

Forty-seven Type 2 diabetic patients were randomly assigned 2 : 1 to nateglinide 120 mg (t.i.d., n = 33) or placebo (n = 14). At baseline and after 16 weeks of treatment, MBF was quantified using positron emission tomography with N-13 ammonia at rest, during endothelial-dependent stimulation by cold pressor test and during adenosine-mediated vasodilation. Additional blood samples were taken to assess glycaemic control and lipid profile.

RESULTS

MBF at rest and during adenosine did not change during the study. The percentage of flow increase from rest during cold pressor test did not improve significantly in the nateglinide group vs. placebo (from 26.1 +/- 37.2% to 29.1 +/- 27.8% between week 0 to week 16 for nateglinide vs. 14.9 +/- 37.1% to 18.1 +/- 28.4% for placebo; P = 0.07 for nateglinide when adjusted for higher baseline values). Nateglinide decreased HbA1c by 0.4% (from 7.6 +/- 0.9% to 7.2 +/- 1.3%) compared to an increase of 0.5% in the placebo group (from 7.9 +/- 0.8% to 8.4 +/- 1.7%; P = 0.02 for nateglinide). No differences between the two groups were observed in insulin levels and lipid status.

CONCLUSIONS

Nateglinide neither improved, nor impaired myocardial blood flow in Type 2 diabetic patients. Potential effects on endothelial-dependent myocardial blood flow remain to be investigated further. Positron emission tomography is a sensitive approach to assess the effects of therapeutic agents on myocardial blood flow in patients with diabetes.

Development and validation for high selective quantitative determination of metformin in human plasma by cation exchanging with normal-phase LC/MS/MS

An assay based on cation exchange solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed for the quantitative determination of metformin in human plasma. The analytical method consists of cation exchange solid-phase extraction (VersaPlate CBA) without any further evaporation/dissolution steps and cation exchange-based HPLC separation (Capcell Pak SCX column) with a normal-phase gradient system followed by semi-micro LC/MS/MS in positive ion selected reaction monitoring mode using electrospray ionization. The method exhibited excellent performance in terms of selectivity, robustness, short run time (7 min/sample) and simplicity of sample preparation. The calibration range was 10-1000 ng/ml with 0.2 ml of plasma. Intra- and inter-day mean accuracies were within the ranges of 100.3-105.0% and 101.2-105.3%, respectively. Intra- and inter-day precisions were within the ranges of 0.8-1.9% and 1.5-8.6%, respectively. Mean absolute recovery was 67.0% for metformin. No apparent loss of metformin after extraction was observed in an autosampler at 10 degrees C for 24 h. Dilution of metformin by blank human plasma up to 20-fold was tested and revealed no impact on the results of determination. Furthermore, the method exhibited high selectivity, since no effect on metformin analysis was observed on comparison of samples with or without nateglinide and other agents in plasma. Results obtained with the method were also comparable to a published LC-UV method on cross-validation. This method can be applied to various clinical pharmacokinetic studies of metformin.

Acute and long-term effects of nateglinide on insulin secretory pathways

Acute and chronic effects of the insulinotropic drug nateglinide upon insulin release were examined in the BRIN-BD11 cell line. Nateglinide (10-400 microm) stimulated a concentration-dependent increase (P<0.05-P<0.001) in insulin release at a non-stimulatory (1.1 mm) glucose concentration. The insulinotropic response to 200 microm nateglinide was increased at 30 mm (P<0.01), but not 5.6-16.7 mm glucose concentrations. In depolarized cells, nateglinide (50-200 microm) evoked K(ATP) channel-independent insulin secretion (P<0.05-P<0.001) in the absence and presence of 5.6-30.0 mm glucose (P<0.001). Exposure for 18 h to 100 microm nateglinide abolished the acute insulinotropic effects of 200 microm nateglinide, tolbutamide or glibenclamide, but had no effect upon the insulinotropic effect of 200 microm efaroxan. While 18 h exposure to 100 microm nateglinide did not affect basal insulin release or insulin release in the presence of 16.7 mm glucose, 25 microm forskolin or 10 nm PMA, significant inhibition of the insulinotropic effects of 20 mm leucine and 20 mm arginine were observed. These data show that nateglinide stimulates both K(ATP) channel-dependent and-independent insulin secretion. The maintained insulinotropic effects of this drug with increasing glucose concentrations support the antihyperglycaemic actions of nateglinide in Type II diabetes. Studies of the long-term effects of nateglinide indicate that nateglinide shares signalling pathways with sulphonylureas, but not the imidazoline efaroxan. This may be significant when considering a nateglinide treatment regimen, particularly in patients previously treated with sulphonylurea.

Treatment of the patient with diabetes: importance of maintaining target HbA(1c) levels

OBJECTIVE

To review clinical trial evidence supporting treatment of patients to a near-normal HbA(1c) target level and outline therapeutic strategies that optimize glycemic control.

RESEARCH DESIGN AND METHODS

The current MEDLINE database and bibliographies were searched for literature relevant to diabetic complications, glycemic control, and the intensive management of diabetes mellitus.

RESULTS

Two randomized trials, the Diabetes Control and Complications Trial and the UK Prospective Diabetes Study (UKPDS), provided evidence that intensive glycemic control obtained with either intensive insulin or oral therapy effectively slowed the onset and progression of diabetic retinopathy, nephropathy, and neuropathy in patients with type 1 and type 2 diabetes. An epidemiologic analysis of the UKPDS results showed a significant correlation between glycemic control and microvascular and cardiovascular disease risk and mortality rates.

CONCLUSIONS

The results of clinical trials confirm that stringent levels of glycemic control can be attained through the use of intensive multiple-injection insulin regimens (administration of insulin 3 or more times daily by injection or an external pump with dosage adjustments as needed), oral monotherapy or combination therapy, or a combination of insulin and oral therapy. The expanded choices for oral agents and the availability of insulin analogs now provide physicians with the tools to tailor therapy to prevent or delay the devastating complications of diabetes. Indeed, newer insulin analogs, both short-acting (insulin lispro, insulin aspart) and long-acting (insulin glargine), are an important part of a treatment strategy to circumvent diabetes complications and overcome the shortcomings of conventional insulin preparations.

The combination oral and nutritional treatment of late-onset diabetes mellitus (CONTROL DM) trial results

OBJECTIVE

To examine the effect of short-term improvements in glycaemic control on brachial artery endothelial function as a marker of cardiovascular health.

METHODS

Persons with Type 2 diabetes who were poorly controlled on oral therapy were randomly assigned to monotherapy with repaglinide or combination therapy with repaglinide plus metformin. Brachial artery flow-mediated vasodilation was assessed by ultrasonography at randomization and following 16 weeks of therapy. The primary outcome was change in brachial artery endothelial function from baseline. Comparison of randomized groups was a secondary aim.

RESULTS

Eighty-six participants were randomized, and 83 were followed to study completion. Post occlusion brachial artery vasodilation was 3.74% at baseline and 3.82% following 16 weeks of therapy (P = 0.77). The treatment effect was 0.08% (95% CI: -0.48%, 0.64%). No difference was seen between treatment groups (P = 0.69). Overall, A1C was reduced from 8.3% to 7.0%, with a greater reduction in the combination therapy group (from 8.4% to 6.7%) than in the monotherapy group (from 8.3% to 7.3%, p for difference between groups = 0.01). Statistically significant reductions were observed in fasting glucose, and plasminogen activator inhibitor-1. Statistically significant increases were observed for fasting insulin, uric acid, weight and BMI.

CONCLUSIONS

Brachial artery endothelial function was not influenced by short-term improvements in glycaemic control. The CONTROL DM group was successful in lowering A1C. Future research should explore more intensive and longer-lasting improvements in glycaemic control on endothelial function. Some data previously published in abstract form (Diabetes 2001; 50 (Suppl. 2): A217).

Hypoglycemic potential of nateglinide versus glyburide in patients with type 2 diabetes mellitus

Antidiabetic agents that augment insulin secretion can cause hypoglycemia. With the current trend toward early and aggressive treatment of patients with type 2 diabetes, the hypoglycemic potential of insulinotropic agents is of concern. This study aimed to compare the propensity of the "glinide," nateglinide, and the sulfonylurea (SU), glyburide, to elicit hypoglycemia in type 2 diabetic patients with moderately elevated fasting plasma glucose (FPG). Hyperglycemic clamps (target plasma glucose = 11.1 mmol/L) were initiated, and 30 minutes later patients received a single oral dose of nateglinide (120 mg, n = 15) or glyburide (10 mg, n = 12) in a double-blind fashion. At the end of the 2-hour clamp when the glucose infusion was terminated, plasma glucose and insulin levels were measured for 4 additional hours. The minimum plasma glucose level achieved after terminating the glucose infusion (glucose nadir) was used as an index of hypoglycemic potential. The mean (+/-SEM) glucose nadir was significantly lower in patients given glyburide (3.3 +/- 0.2 mmol/L) versus nateglinide (4.4 +/- 0.3 mmol/L, P = .025). Confirmed hypoglycemia (plasma glucose < or = 2.8 mmol/L) occurred in 2 of 12 patients given glyburide and in none of those given nateglinide. Plasma insulin levels were significantly higher from 100 to 240 minutes after clamp termination in patients given glyburide versus nateglinide. Nateglinide has less hypoglycemic potential than glyburide, suggesting that nateglinide may be a more appropriate insulinotropic agent for patients with moderate fasting hyperglycemia, such as elderly patients and those with comorbid cardiac ischemia.

Nateglinide alone or with metformin safely improves glycaemia to target in patients up to an age of 84

AIM

To assess the effect of nateglinide on efficacy [fasting plasma glucose (FPG), postprandial plasma glucose (PPG) plasma glucose and HbA1c], tolerability and safety in patients with type 2 diabetes mellitus (T2Dm) on diet alone or on metformin in subjects up to an age of 84.

METHODS

In an open-labelled 12-week, parallel study of 358 patients, aged 35-84 years with T2Dm, nateglinide was given as either monotherapy in patients previously on diet alone or low-dose sulfonylureas, which required washout before the study (group 1), or as an addition therapy in patients on steady dose of metformin (group 2). Nateglinide 120 mg was given before main meals. HbA1c, FPG and PPG values were taken at the time of breakfast at the beginning and the end of the study.

RESULTS

HbA1c fell by a mean of 0.83%, 95% confidence interval (CI) (-0.97, -0.69) (p < 0.001) in group 1, and 0.67%, 95% CI (-0.77, -0.58) (p < 0.001) in group 2. There was a significant improvement in PPG in group 1 by a mean reduction of -3.47 mmol/l, 95% CI (-4.08, -2.87) (p < 0.0001) and in group 2 of -2.41 mmol/l, 95% CI (-2.84, -1.99) (p < 0.0001). There was an improvement in FPG of -1.2 mmol/l, 95% CI (-1.49, -0.81) (p < 0.0001) and -0.8 mmol/l, 95% CI -(1.07, -0.53) (p < 0.0001) in group 1 and 2 respectively. 44% of patients in group 1 and 34% in group 2 achieved target of HbA1c < 7.0 and 66% in group 1 and 59% in group 2 achieved of HbA1c < 7.5%. Only one subject on nateglinide and metformin was withdrawn due to the side effect of hypoglycaemia. No patient required third-party assistance nor was admitted to hospital due to hypoglycaemia.

CONCLUSION

These data demonstrate that nateglinide is a safe and effective agent in treatment to target in patients with T2Dm up to an age of 84 years.

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.

Oral antidiabetic agents: 2004

The appropriate management of patients with type 2 diabetes presents many challenges to health care providers. The first several years of type 2 diabetes are likely to be unrecognized and untreated. The pathophysiology of type 2 diabetes dictates that treatment of insulin resistance should be an early and central focus for every therapeutic program. The pharmacologic tools currently available are capable of allowing most patients with type 2 diabetes to achieve good metabolic control. Implementation of early combination therapy is essential if glycemic targets are to be met.

Repaglinide versus nateglinide monotherapy: a randomized, multicenter study

OBJECTIVE

A randomized, parallel-group, open-label, multicenter 16-week clinical trial compared efficacy and safety of repaglinide monotherapy and nateglinide monotherapy in type 2 diabetic patients previously treated with diet and exercise.

RESEARCH DESIGN AND METHODS

Enrolled patients (n = 150) had received treatment with diet and exercise in the previous 3 months with HbA(1c) >7 and < or =12%. Patients were randomized to receive monotherapy with repaglinide (n = 76) (0.5 mg/meal, maximum dose 4 mg/meal) or nateglinide (n = 74) (60 mg/meal, maximum dose 120 mg/meal) for 16 weeks. Primary and secondary efficacy end points were changes in HbA(1c) and fasting plasma glucose (FPG) values from baseline, respectively. Postprandial glucose, insulin, and glucagon were assessed after a liquid test meal (baseline, week 16). Safety was assessed by incidence of adverse events or hypoglycemia.

RESULTS

Mean baseline HbA(1c) values were similar in both groups (8.9%). Final HbA(1c) values were lower for repaglinide monotherapy than nateglinide monotherapy (7.3 vs. 7.9%). Mean final reductions of HbA(1c) were significantly greater for repaglinide monotherapy than nateglinide monotherapy (-1.57 vs. -1.04%; P = 0.002). Mean changes in FPG also demonstrated significantly greater efficacy for repaglinide than nateglinide (-57 vs. -18 mg/dl; P < 0.001). HbA(1c) values <7% were achieved by 54% of repaglinide-treated patients versus 42% for nateglinide. Median final doses were 6.0 mg/day for repaglinide and 360 mg/day for nateglinide. There were 7% of subjects treated with repaglinide (five subjects with one episode each) who had minor hypoglycemic episodes (blood glucose <50 mg/dl) versus 0 patients for nateglinide. Mean weight gain at the end of the study was 1.8 kg in the repaglinide group as compared with 0.7 kg for the nateglinide group.

CONCLUSIONS

In patients previously treated with diet and exercise, repaglinide and nateglinide had similar postprandial glycemic effects, but repaglinide monotherapy was significantly more effective than nateglinide monotherapy in reducing HbA(1c) and FPG values after 16 weeks of therapy.

Efficacy and tolerability of initial combination therapy with nateglinide and metformin in treatment-naïve patients with type 2 diabetes

OBJECTIVE

To assess the efficacy and tolerability of the combination of nateglinide (120 mg, ac) and metformin (500 mg, tid) as initial treatment in drug-naïve patients with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

This study reports data from the treatment-naïve (TN) subgroup of patients in a previously published, randomized, multicenter, placebo-controlled, 24- week trial that compared nateglinide, metformin, and the combination therapy (CT) in 701 patients with T2DM with baseline HbA(1c) between 6.8% and 11.0%. Of the 401 TN patients, 104, 104, 89, and 104 patients received nateglinide (120 mg, ac), metformin (500 mg, tid), CT, and placebo, respectively. The baseline characteristics of each group were similar, with mean age, BMI, duration of diabetes, HbA(1c), and fasting plasma glucose (FPG) levels of approximately 58 years, 30 kg/m(2), 4 Gastrointestinal side effects occurred in 27% of years, 8.2%, and 10.2 mmol/L, respectively.

RESULTS

In patients receiving initial CT, HbA(1c) decreased substantially (Delta = -1.6 +/- 0.1%, p < 0.0001 vs. baseline or placebo) from a mean baseline of 8.2 +/- 0.1%, an effect significantly greater than the 0.8% reduction observed with both monotherapies (p < 0.001); whereas, in placebo-treated patients, HbA(1c) increased modestly (Delta = +0.3 +/- 0.1%, p < 0.05) from an identical baseline value. Seventy percent of CT-treated patients achieved a target HbA(1c) of < 7.0%. Both fasting plasma glucose (FPG) and the 2-hour postprandial glucose excursion (PPGE) after a liquid meal challenge decreased by 2.3 mmol/L in patients receiving CT, while the changes from baseline values in FPG and PPGE were +0.2 +/- 0.3 mmol/L and -0.5 +/- 0.2 mmol/L, respectively, in placebo-treated patients. The incremental 30-minute post-load insulin levels increased by 88 +/- 32 pmol/L (p = 0.006) in patients receiving CT and did not change significantly in placebo-treated patients. patients receiving CT (vs. 27.9% in the metformin monotherapy, and 14.4% in the placebo groups). Confirmed hypoglycemia (glucose <or= 2.8 mmol/L) occurred in 3.4% of patients receiving CT.

CONCLUSIONS

Initial CT with the rapid-acting insulinotropic agent, nateglinide, and metformin, an agent with insulin-sensitizing effects in the liver and periphery, is a safe and effective means of achieving glycemic targets in TN patients with T2DM.

Clinical pharmacokinetics of nateglinide: a rapidly-absorbed, short-acting insulinotropic agent

The prevalence and medical and economic impact of type 2 diabetes mellitus is increasing in Western societies. New agents have been developed that act primarily to reduce postprandial glucose excursions, which may be of particular significance now that postprandial glucose excursions are known to be correlated with cardiovascular morbidity and mortality. Nateglinide is a phenylalanine derivative that blocks K+ channels in pancreatic beta-cells, facilitating insulin secretion. Nateglinide sensitises beta-cells to ambient glucose, reducing the glucose concentration needed to stimulate insulin secretion. The pharmacokinetics of nateglinide are characterised by rapid absorption and elimination, with good (73%) bioavailability. Nateglinide is more rapidly absorbed when given 0-30 minutes prior to meal ingestion than if given during the meal. Nateglinide is extensively metabolised, primarily by cytochrome P450 2C9, and eliminated primarily by the kidney. Nateglinide pharmacokinetics are linear over the dose range 60-240 mg. No significant pharmacokinetic alterations occur in renally impaired patients, in the elderly, or in mildly hepatically impaired patients. Nateglinide administered prior to meals stimulates rapid, short-lived insulin secretion in a dose-dependent manner, thus decreasing mealtime plasma glucose excursions. Its effects on insulin secretion are synergistic with those of a meal. With increasing nateglinide doses, the risk of hypoglycaemia also increases, but its incidence is low. Even if a meal is missed, and the patient skips the dose of nateglinide (as recommended in the event of a missed meal), the incidence of subsequent hypoglycaemia remains low compared with long-acting agents. The postprandial insulinotropic effects of nateglinide are more rapid than those of repaglinide and more rapid and greater than those of glibenclamide (glyburide), while producing less prolonged insulin exposure and less risk of delayed hypoglycaemia. Further investigation is required to determine if nateglinide inhibition of postprandial glucose excursions will help to prevent diabetic complications or preserve pancreatic beta-cell function.