A risk-benefit assessment of metformin in type 2 diabetes mellitus

Herbal therapies for type 2 diabetes mellitus: chemistry, biology, and potential application of selected plants and compounds

Diabetes mellitus has been recognized since antiquity. It currently affects as many as 285 million people worldwide and results in heavy personal and national economic burdens. Considerable progress has been made in orthodox antidiabetic drugs. However, new remedies are still in great demand because of the limited efficacy and undesirable side effects of current orthodox drugs. Nature is an extraordinary source of antidiabetic medicines. To date, more than 1200 flowering plants have been claimed to have antidiabetic properties. Among them, one-third have been scientifically studied and documented in around 460 publications. In this review, we select and discuss blood glucose-lowering medicinal herbs that have the ability to modulate one or more of the pathways that regulate insulin resistance, β-cell function, GLP-1 homeostasis, and glucose (re)absorption. Emphasis is placed on phytochemistry, anti-diabetic bioactivities, and likely mechanism(s). Recent progress in the understanding of the biological actions, mechanisms, and therapeutic potential of compounds and extracts of plant origin in type 2 diabetes is summarized. This review provides a source of up-to-date information for further basic and clinical research into herbal therapy for type 2 diabetes. Emerging views on therapeutic strategies for type 2 diabetes are also discussed.

Herbal therapies for type 2 diabetes mellitus: chemistry, biology, and potential application of selected plants and compounds

Background:

Diabetes mellitus, becoming the third killer of mankind after cancer and cardiovascular diseases, is one of the most challenging diseases facing health care professionals today. That is why; there has been a growing interest in the therapeutic use of natural products for diabetes, especially those derived from plants.

Aim:

To evaluate the anti-diabetic activity together with the accompanying biological effects of the fractions and the new natural compounds of Hyphaene thebaica (HT) epicarp.

Materials and Methods:

500 g of coarsely powdered of (HT) fruits epicarp were extracted by acetone. The acetone crude extract was fractionated with methanol and ethyl acetate leaving a residual water-soluble fraction WF. The anti-diabetic effects of the WF and one of its compounds of the acetone extract of the (HT) epicarp were investigated in this study using 40 adult male rats.

Results:

Phytochemical investigation of active WF revealed the presence of ten different flavonoids, among which two new natural compounds luteolin 7-O-[6”-O-α-Lrhamnopyranosyl]-β-D-galactopyranoside 3 and chrysoeriol 7-O-β-D-galactopyranosyl(1→2)-α-L-arabinofuranoside 5 were isolated. Supplementation of the WF improved glucose and insulin tolerance and significantly lowered blood glycosylated hemoglobin levels. On the other hand, compound 5 significantly reduced AST and ALT levels of liver, respectively. Likewise, the kidney functions were improved for both WF and compound 5, whereby both urea and creatinine levels in serum were highly significant

Conclusion:

The results justify the use of WF and compound 5 of the (HT) epicarp as anti-diabetic agent, taking into consideration that the contents of WF were mainly flavonoids

Metformin revisited: a critical review of the benefit-risk balance in at-risk patients with type 2 diabetes

Metformin is unanimously considered a first-line glucose-lowering agent. Theoretically, however, it cannot be prescribed in a large proportion of patients with type 2 diabetes because of numerous contraindications that could lead to an increased risk of lactic acidosis. Various observational data from real-life have shown that many diabetic patients considered to be at risk still receive metformin and often without appropriate dose adjustment, yet apparently with no harm done and particularly no increased risk of lactic acidosis. More interestingly, recent data have suggested that type 2 diabetes patients considered at risk because of the presence of traditional contraindications may still derive benefit from metformin therapy with reductions in morbidity and mortality compared with other glucose-lowering agents, especially sulphonylureas. The present review analyzes the benefit-risk balance of metformin therapy in special populations, namely, patients with stable coronary artery disease, acute coronary syndrome or myocardial infarction, congestive heart failure, renal impairment or chronic kidney disease, hepatic dysfunction and chronic respiratory insufficiency, all conditions that could in theory increase the risk of lactic acidosis. Special attention is also paid to elderly patients with type 2 diabetes, a population that is growing rapidly, as older patients can accumulate several comorbidities classically considered contraindications to the use of metformin. A review of the recent scientific literature suggests that reassessment of the contraindications of metformin is now urgently needed to prevent physicians from prescribing the most popular glucose-lowering therapy in everyday clinical practice outside of the official recommendations.

Antidiabetic effect and mode of action of cytopiloyne

Cytopiloyne was identified as a novel polyacetylenic compound. However, its antidiabetic properties are poorly understood. The aim of the present study was to investigate the anti-diabetic effect and mode of action of cytopiloyne on type 2 diabetes (T2D). We first evaluated the therapeutic effect of cytopiloyne on T2D in db/db mice. We found that one dose of cytopiloyne reduced postprandial glucose levels while increasing blood insulin levels. Accordingly, long-term treatment with cytopiloyne reduced postprandial blood glucose levels, increased blood insulin, improved glucose tolerance, suppressed the level of glycosylated hemoglobin A_1c (HbA_1c), and protected pancreatic islets in db/db mice. Next, we studied the anti-diabetic mechanism of action of cytopiloyne. We showed that cytopiloyne failed to decrease blood glucose in streptozocin- (STZ-)treated mice whose β cells were already destroyed. Additionally, cytopiloyne dose dependently increased insulin secretion and expression in β cells. The increase of insulin secretion/expression of cytopiloyne was regulated by protein kinase Cα (PKCα) and its activators, calcium, and diacylglycerol (DAG). Overall, our data suggest that cytopiloyne treats T2D via regulation of insulin production involving the calcium/DAG/PKCα cascade in β cells. These data thus identify the molecular mechanism of action of cytopiloyne and prove its therapeutic potential in T2D.

Pharmacokinetic considerations for the treatment of diabetes in patients with chronic kidney disease

INTRODUCTION

People with chronic kidney disease (CKD) of stages 3 - 5 (creatinine clearance < 60 ml/min) represent ≈ 25% of patients with type 2 diabetes mellitus (T2DM), but the problem is underrecognized or neglected in clinical practice. However, most oral antidiabetic agents have limitations in case of renal impairment (RI), either because they require a dose adjustment or because they are contraindicated for safety reasons.

AREAS COVERED

The author performed an extensive literature search to analyze the influence of RI on the pharmacokinetics (PK) of glucose-lowering agents and the potential consequences for clinical practice.

EXPERT OPINION

As a result of PK interferences and for safety reasons, the daily dose should be reduced according to glomerular filtration rate (GFR) or even the drug is contraindicated in presence of severe CKD. This is the case for metformin (risk of lactic acidosis) and for many sulfonylureas (risk of hypoglycemia). At present, however, the exact GFR cutoff for metformin use is controversial. New antidiabetic agents are better tolerated in case of CKD, although clinical experience remains quite limited for most of them. The dose of DPP-4 inhibitors should be reduced (except for linagliptin), whereas both the efficacy and safety of SGLT2 inhibitors are questionable in presence of CKD.

Safety, tolerability, and efficacy of metformin extended-release oral antidiabetic therapy in patients with type 2 diabetes: an observational trial in Asia

BACKGROUND

The aim of the present prospective observational study was to assess the tolerability and antihyperglycemic efficacy of metformin extended-release (MXR) in the routine treatment of patients with type 2 diabetes mellitus (T2DM) from six Asian countries.

METHODS

Data from 3556 patients treated with once-daily MXR for 12 weeks, or until discontinuation, were analyzed.

RESULTS

Treatment with MXR was well tolerated, with 97.4% of patients completing 12 weeks of treatment. Only 3.3% of patients experienced one or more gastrointestinal (GI) side-effects and only 0.7% of patients discontinued for this reason (primary endpoint). The incidence of GI side-effects and related discontinuations appeared to be considerably lower during short-term MXR therapy than during previous treatment (mean 2.71 years' duration), most commonly with immediate-release metformin. A 12-week course of MXR therapy also reduced HbA1c and fasting glucose levels from baseline.

CONCLUSIONS

The present study provides new insights into the incidence of GI side-effects with MXR in Asian patients with T2DM and on the tolerability of MXR in non-Caucasian populations. Specifically, these data indicate that once-daily MXR not only improves measures of glycemic control in Asian patients with T2DM, but also has a favorable GI tolerability profile that may help promote enhanced adherence to oral antidiabetic therapy.

Combination of glibenclamide-metformin HCl for the treatment of type 2 diabetes mellitus

INTRODUCTION

Combination of glibenclamide (glyburide in the U.S.) and metformin hydrochloride simultaneously addresses two different but complimentary mechanisms to improve glycemic control in type 2 diabetes.

AREAS COVERED

The pharmacokinetics, efficacy, and side effect profile of the oral combination of glibenclamide-metformin are reviewed.

EXPERT OPINION

Those patients, uncontrolled with single oral agent sulfonylurea or metformin alone, benefit from combination glibenclamide-metformin. There is improvement in fasting plasma glucose, HbA(1C), and post-prandial glucose control, and patients are more likely to achieve a HbA(1C) < 7%. Initiation should be started at the lowest doses and titrated to get the desired effect. Combination therapy allows for reduced pill burden while treating a multifactorial disease by two different mechanisms. Practitioners should be cognizant of risks of hypoglycemia and the theoretical potential for lactic acidosis in the elderly and those with renal impairment. We caution the use of glibenclamide-metformin in patients at risk for cardiovascular disease. Therapy should be individualized, but overall, combination of glibenclamide-metformin should be considered in patients, without renal or cardiovascular impairment, who are not controlled on monotherapy alone. Alternatively, practitioners may want to weigh the efficacy and safety of available dipeptidyl-peptidase-4 inhibitor-metformin combinations to those of glibenclamide-metformin when considering combination therapy.

Toward the prediction of FBPase inhibitory activity using chemoinformatic methods

Currently, Chemoinformatic methods are used to perform the prediction for FBPase inhibitory activity. A genetic algorithm-random forest coupled method (GA-RF) was proposed to predict fructose 1,6-bisphosphatase (FBPase) inhibitors to treat type 2 diabetes mellitus using the Mold² molecular descriptors. A data set of 126 oxazole and thiazole analogs was used to derive the GA-RF model, yielding the significant non-cross-validated correlation coefficient r²_ncv and cross-validated r²_cv values of 0.96 and 0.67 for the training set, respectively. The statistically significant model was validated by a test set of 64 compounds, producing the prediction correlation coefficient r²_pred of 0.90. More importantly, the building GA-RF model also passed through various criteria suggested by Tropsha and Roy with r²_o and r²_m values of 0.90 and 0.83, respectively. In order to compare with the GA-RF model, a pure RF model developed based on the full descriptors was performed as well for the same data set. The resulting GA-RF model with significantly internal and external prediction capacities is beneficial to the prediction of potential oxazole and thiazole series of FBPase inhibitors prior to chemical synthesis in drug discovery programs.

Clinical pharmacokinetics of metformin

Metformin is widely used for the treatment of type 2 diabetes mellitus. It is a biguanide developed from galegine, a guanidine derivative found in Galega officinalis (French lilac). Chemically, it is a hydrophilic base which exists at physiological pH as the cationic species (>99.9%). Consequently, its passive diffusion through cell membranes should be very limited. The mean ± SD fractional oral bioavailability (F) of metformin is 55 ± 16%. It is absorbed predominately from the small intestine. Metformin is excreted unchanged in urine. The elimination half-life (t(&frac12;)) of metformin during multiple dosages in patients with good renal function is approximately 5 hours. From published data on the pharmacokinetics of metformin, the population mean of its clearances were calculated. The population mean renal clearance (CL(R)) and apparent total clearance after oral administration (CL/F) of metformin were estimated to be 510 ± 130 mL/min and 1140 ± 330 mL/min, respectively, in healthy subjects and diabetic patients with good renal function. Over a range of renal function, the population mean values of CL(R) and CL/F of metformin are 4.3 ± 1.5 and 10.7 ± 3.5 times as great, respectively, as the clearance of creatinine (CL(CR)). As the CL(R) and CL/F decrease approximately in proportion to CL(CR), the dosage of metformin should be reduced in patients with renal impairment in proportion to the reduced CL(CR). The oral absorption, hepatic uptake and renal excretion of metformin are mediated very largely by organic cation transporters (OCTs). An intron variant of OCT1 (single nucleotide polymorphism [SNP] rs622342) has been associated with a decreased effect on blood glucose in heterozygotes and a lack of effect of metformin on plasma glucose in homozygotes. An intron variant of multidrug and toxin extrusion transporter [MATE1] (G>A, SNP rs2289669) has also been associated with a small increase in antihyperglycaemic effect of metformin. Overall, the effect of structural variants of OCTs and other cation transporters on the pharmacokinetics of metformin appears small and the subsequent effects on clinical response are also limited. However, intersubject differences in the levels of expression of OCT1 and OCT3 in the liver are very large and may contribute more to the variations in the hepatic uptake and clinical effect of metformin. Lactic acidosis is the feared adverse effect of the biguanide drugs but its incidence is very low in patients treated with metformin. We suggest that the mean plasma concentrations of metformin over a dosage interval be maintained below 2.5 mg/L in order to minimize the development of this adverse effect.

Pharmacokinetic-Pharmacodynamic Modeling of Metformin for the Treatment of Type II Diabetes Mellitus

Metformin is an antihyperglycemic agent commonly used for the treatment of Type II diabetes mellitus. However, its effects on patients are derived usually from clinical experiments. In this study, a dynamic model of Type II diabetes mellitus with the treatment of metformin is proposed. The Type II diabetic model is a modification of an existing compartmental diabetic model. The dynamic simulation of the metformin effect for a Type II diabetic patient is based on the pharmacokinetic and pharmacodynamic relationship with a human body. The corresponding model parameters are estimated by optimization using clinical data from published reports. Then, the effect of metformin in both intravenous and oral administration on a Type II diabetes mellitus model are compared. The combination treatment of insulin infusion plus oral metformin is shown to be superior than the monotherapy with oral metformin only. These results are consistent with the clinical understanding of the use of metformin. For further work, the model can be analyzed for evaluating the treatment of diabetes mellitus with different pharmacological agents.

Pharmacological treatment of obesity in patients with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common disorder affecting women of reproductive age and it is associated with increased cardiovascular risk. Obesity plays an important role in the pathogenesis of PCOS, and the majority of patients with PCOS are obese. Over the last 20 years, the prevalence of obesity has dramatically increased, with probable associated increase in PCOS. Weight reduction plays an integral part in the management of women with PCOS. In this paper, current available weight reduction therapies in the management of PCOS are discussed.

Guideline-conformity of initiation with oral hypoglycemic treatment for patients with newly therapy-dependent type 2 diabetes mellitus in Austria

PURPOSE

To determine guideline conformity of initiation of oral hypoglycemic (OH) treatment for type 2 diabetes in Austria; to study patient and prescriber correlates of recommended initiation with metformin monotherapy.

METHODS

We used claims from 11 sickness funds that covered 7.5 million individuals, representing >90% of the Austrian population. First-time OH use was defined as a first filled prescription after one year without any OH drug or insulin. Among these incident users, we described the OH drug class used and defined correlates of initiation with metformin monotherapy.

RESULTS

From 1/2007 to 6/2008, we identified 42,882 incident users of an OH drug: 70.8% used metformin, 24.7% used a sulfonylurea, and 4.5% initiated treatment with another class. We estimated the incidence of OH-dependent type 2 diabetes at 3.8-4.4 per 1000 patient-years. We conducted multivariate analyses among 39 077 patients with available prescriber information. Independent correlates of initiation with metformin were younger age, female gender, waived co-payment, more recent initiation, fewer hospital days and more therapeutic classes received in the year prior to first OH therapy (all p < 0.001). Prescriber specialty and age (p < 0.001), but not gender, were also associated with metformin initiation. Approximately 20% of metformin initiators had a second OH drug added within <18 months. While we were unable to ascertain specific contraindications to metformin (renal insufficiency, hepatic failure), <10% of the general population are expected to have these conditions.

CONCLUSIONS

Seventy per cent of new initiators of OH treatment in Austria received metformin as recommended by international guidelines. At least 20% did not, taking into account possible contraindications, which provides an opportunity for intervention.

Anti-Hyperglycemic Properties of Crude Extract and Triterpenes from Poria cocos

Poria cocos, Bai Fu Ling in Chinese, is used in traditional Chinese medicine to treat diabetes. However, its claimed benefits and mechanism are not fully understood. This study aimed to investigate the effect and action of P. cocos on type 2 diabetes. We first performed phytochemical analysis on the crude extract and factions of P. cocos. P. cocos crude extract at 50 mg/kg body weight or more significantly decreased blood glucose levels in db/db mice. Based on a bioactivity-directed fractionation and isolation (BDFI) strategy, chloroform fraction and subfractions 4 and 6 of the P. cocos crude extract possessed a blood glucose-lowering effect. Dehydrotumulosic acid, dehydrotrametenolic acid, and pachymic acid were identified from the chloroform sub-fractions 4, 3, and 2, respectively. Dehydrotumulosic acid had anti-hyperglycemic effect to a greater extent than dehydrotrametenolic acid and pachymic acid. Mechanistic study on streptozocin- (STZ-) treated mice showed that the crude extract, dehydrotumulosic acid, dehydrotrametenolic acid, and pachymic acid of P. cocos exhibited different levels of insulin sensitizer activity. However, the P. cocos crude extract and triterpenes appeared not to activate PPAR-γ pathway. Overall, the data suggest that the P. cocos extract and its triterpenes reduce postprandial blood glucose levels in db/db mice via enhanced insulin sensitivity irrespective of PPAR-γ.

Anti-diabetic properties of three common Bidens pilosa variants in Taiwan

Bidens pilosa L. var. radiata (BPR), B. pilosa L. var. pilosa (BPP), and B. pilosa L. var. minor (BPM) are common variants of a plant often used as a folk remedy for diabetes in Taiwan. However, the three variants are often misidentified and little is known about their relative anti-diabetic efficacy and chemical composition. In this paper, we have first developed a method based on GC-MS and cluster analysis with visualization to assist in rapidly determining the taxonomy of these three Bidens variants. GC-MS was used to determine the chemical compositions of supercritical extracts, and differences and similarities in the variants were determined by hierarchical cluster analysis. Next, the HPLC profiles of the methanol crude extracts in the Bidens plants and evaluated anti-diabetic effects of methanol crude extracts were compared, as well as three polyacetylenic compounds of the Bidens plants using db/db mice. Single-dose and long-term experiments showed that the BPR extract had higher glucose-lowering and insulin-releasing activities than extracts from the other two variants, and that cytopiloyne was the most effective pure compound among the three polyacetylenic compounds. BPR extract and cytopiloyne also significantly reduced the percentage of the glycosylated hemoglobin A1c in db/db mice. Besides, both animal studies and HPLC analysis demonstrated a good correlation between anti-diabetic efficacy of the Bidens extracts and the particular polyacetylenes present.

Pharmacokinetics and bioavailability of metformin in horses

OBJECTIVE

To determine pharmacokinetics and oral bioavailability of metformin in healthy horses.

ANIMALS

4 adult horses.

PROCEDURES

6 g of metformin was administered 3 times IV and PO (fed and unfed) to each horse, by use of a crossover design, with a 1-week washout period between treatments. Plasma metformin concentration was determined via high-pressure liquid chromatography.

RESULTS

Mean +/- SD distribution half-life of metformin following IV administration was 24.9 +/- 0.4 minutes with a volume of distribution of 0.3 +/- 0.1 L/kg. Mean area under the curve was 20.9 +/- 2.0 h.microg/mL for IV administration; PO administration resulted in area under the curves of 1.6 +/- 0.4 h.microg/mL in unfed horses and 0.8 +/- 0.2 h.microg/mL in fed horses. Bioavailability was determined to be approximately 7.1 +/- 1.5% in unfed horses and 3.9 +/- 1.0% in fed horses. The maximal concentration following PO administration in unfed horses was 0.4 +/- 0.1 microg/mL with a time at maximal concentration of 0.9 +/- 0.1 hours. In fed horses, maximal concentration was reduced to 0.3 +/- 0.04 microg/mL with a time at maximal concentration at 1.3 +/- 0.3 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

The low bioavailability of metformin may explain the reported lack of clinical success in improving insulin sensitivity with metformin treatment in horses. Dosages and dose intervals previously used may have been insufficient to achieve plasma concentrations of drug comparable to the therapeutic range achieved in humans. Therefore, a larger and more frequently administered dose may be required to fully evaluate efficacy of metformin in horses.

Metformin treatment in diabetes and heart failure: when academic equipoise meets clinical reality

Objective

Metformin has had a 'black box' contraindication in diabetic patients with heart failure (HF), but many believe it to be the treatment of choice in this setting. Therefore, we attempted to conduct a pilot study to evaluate the feasibility of undertaking a large randomized controlled trial with clinical endpoints.

Study Design

The pilot study was a randomized double blinded placebo controlled trial. Patients with HF and type 2 diabetes were screened in hospitals and HF clinics in Edmonton, Alberta, Canada (population ~1 million). Major exclusion criteria included the current use of insulin or high dose metformin, decreased renal function, or a glycosylated hemoglobin <7%. Patients were to be randomized to 1500 mg of metformin daily or matching placebo and followed for 6 months for a variety of functional outcomes, as well as clinical events.

Results

Fifty-eight patients were screened over a six month period and all were excluded. Because of futility with respect to enrollment, the pilot study was abandoned. The mean age of screened patients was 77 (SD 9) years and 57% were male. The main reasons for exclusion were: use of insulin therapy (n = 23; 40%), glycosylated hemoglobin <7% (n = 17; 29%) and current use of high dose metformin (n = 12; 21%). Overall, contraindicated metformin therapy was the most commonly prescribed oral antihyperglycemic agent (n = 27; 51%). On average, patients were receiving 1,706 mg (SD 488 mg) of metformin daily and 12 (44%) used only metformin.

Conclusion

Despite uncertainty in the scientific literature, there does not appear to be clinical uncertainty with regards to the safety or effectiveness of metformin in HF making a definitive randomized trial virtually impossible.

Trial registration

ClinicalTrials.gov Identifier: NCT00325910

Treating type 2 diabetes: how safe are current therapeutic agents?

Sulphonylureas (SUs) and biguanides (metformin) are the current mainstays in the treatment of type 2 diabetes (T2DM) and represent the most commonly used oral hypoglycaemic agents (OHAs). In recent years, a variety of new OHAs have become available, including thiazolidinediones, glinides, alpha-glucosidase inhibitors, glucagon-like peptide-1 agonists, amylin analogues and dipeptidyl peptidase-IV inhibitors, providing physicians with a larger therapeutic catalogue than ever before. The traditional drugs metformin and SUs have an established safety profile through long-term use. However, long-term clinical trials and routine use are lacking for many of the new agents, and some potentially serious side effects have been reported with several of these compounds. Until adequate data is obtained, it is difficult to assess the risk-benefit ratio of these agents in relation to the traditional drugs. Until that becomes fully documented, it may be wise to start pharmacologic treatment of patients on an individual basis, weighing the benefits and costs of each medication. Thus, there remains a place for well-established drugs that have a proven safety record and are supported by years of clinical use for the treatment of T2DM.

Metformin added to insulin therapy for type 1 diabetes mellitus in adolescents

BACKGROUND

In adolescents with type 1 diabetes, insulin resistance likely plays a role in the deterioration of metabolic control. In type 1 diabetes, addition of metformin to insulin therapy, to improve insulin sensitivity, has been assessed in a few trials involving few patients or in uncontrolled studies of short duration. No systematic reviews are available up to date to summarize the evidence about metformin addition to insulin therapy in adolescents with type 1 diabetes.

OBJECTIVES

To assess the effects of metformin added to insulin therapy for type 1 diabetes mellitus in adolescents.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE and EMBASE. We also searched databases of ongoing trials, reference lists of relevant reviews, and we contacted experts, authors and manufacturers.

SELECTION CRITERIA

Any randomised controlled trial (RCT) of at least three months duration of treatment comparing metformin added to insulin therapy versus insulin therapy alone in adolescents with type 1 diabetes was included. Cross-over and quasi-randomised controlled trials were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers read all abstracts, assessed quality and extracted data independently. Authors were contacted for missing data.

MAIN RESULTS

Only two trials (60 participants) investigating the effect of metformin added to insulin therapy for three months in adolescents with poorly controlled type 1 diabetes could be included. Meta-analysis was not possible due to the clinical and methodological heterogeneity of data. Both studies suggested that metformin treatment lowered glycosylated haemoglobin A1c (HbA1c) in adolescents with type 1 diabetes and poor metabolic control. Improvements in insulin sensitivity, body composition or serum lipids were not documented in either study, however, one study showed a decrease in insulin dosage by 10%. Adverse effects were mainly gastrointestinal in both studies and hypoglycaemia in one study. No data on health-related quality of life, all-cause mortality or morbidity are currently available.

AUTHORS' CONCLUSIONS

There is some evidence suggesting improvement of metabolic control in poorly controlled adolescents with type 1 diabetes, on addition of metformin to insulin therapy. Stronger evidence is required from larger studies, carried out over longer time periods to document the long-term effects on metabolic control, health-related quality of life as well as morbidity and mortality in those patients.

Efficacy of benfluorex in combination with sulfonylurea in type 2 diabetic patients: an 18 to 34-week, open-label, extension period

AIM

The aim of this trial was to obtain further data on the efficacy and safety of benfluorex as an add-on therapy in type 2 diabetic patients insufficiently controlled by sulfonylurea monotherapy who had a limitation for the use of metformin during a 4-month extension period following a 4-month double-blind trial.

METHODS

Patients who completed the 18-week double-blind period entered the 16-week extension period. Patients in the benfluorex group during the double-blind period continued benfluorex 450 mg/day (B-B group), whilst patients in the placebo group switched to benfluorex 450 mg/day (P-B group). The main efficacy criterion was HbA(1c), analyzed as the change from week 18 (W18) to the end of treatment using a two-sided Student paired t-test. Secondary criteria were fasting plasma glucose (FPG), insulin resistance and lipids.

RESULTS

Between W18 and the end of treatment, HbA(1c) decreased in the P-B group from 8.53+/-1.37% to 7.49+/-1.04% (P<0.001) and remained stable in the B-B group from 7.52+/-1.07% to 7.53+/-1.14% (NS). In the P-B group, parameters of glycemic control showed improvements from W18 to week 34 (W34) which were similar to those observed from baseline to W18 in the B-B group. Overall, the target HbA(1c) (<or=7%) was achieved in 36% (103 of 289) of patients and a decrease in HbA(1c) of at least 1% was seen in 44% (128 of 289) of patients. Digestive disorders were the most common adverse events and the incidence of diarrhoea was 4.9% in patients receiving benfluorex for 34 weeks.

CONCLUSION

The beneficial effect of benfluorex as add-on therapy in lowering HbA(1c) at W18 was maintained at W34 without evidence for a loss of efficacy or an increased incidence of side effects over a 34-week follow-up.

Metformin therapy and clinical uses

Metformin is now established as a first-line antidiabetic therapy for the management of type 2 diabetes. Its early use in treatment algorithms is supported by lack of weight gain, low risk of hypoglycaemia and its mode of action to counter insulin resistance. The drug's anti-atherosclerotic and cardioprotective effects have recently been confirmed in prospective and retrospective studies, and appear to reflect a collection of glucose-independent effects on the vascular endothelium, suppressant effects on glycation, oxidative stress and formation of adhesion molecules, stimulation of fibrinolysis and favourable effects on the lipid profile. Although avoidance of troublesome gastrointestinal tolerability issues requires careful dose titration, the risk of serious adverse events is considered low provided that contra-indications (especially with respect to renal function) are observed. As many of its actions go beyond glucose lowering, emerging evidence indicates potential benefits in other insulin-resistant states and possibly tumour suppression.

A study of the pharmacokinetic interactions of the direct renin inhibitor aliskiren with metformin, pioglitazone and fenofibrate in healthy subjects

OBJECTIVE

Hypertension and type 2 diabetes are common comorbidities, thus many patients receiving antihypertensive medication require concomitant therapy with hypoglycemic or lipid-lowering drugs. The aim of these three studies was to investigate the pharmacokinetics, safety and tolerability of aliskiren, a direct renin inhibitor for the treatment of hypertension, co-administered with the glucose-lowering agents metformin or pioglitazone or the lipid-lowering agent fenofibrate in healthy volunteers.

METHODS

In three open-label, multiple-dose studies, healthy volunteers (ages 18 to 45 years) received once-daily treatment with either metformin 1000 mg (n = 22), pioglitazone 45 mg (n = 30) or fenofibrate 200 mg (n = 21) and aliskiren 300 mg, administered alone or co-administered in a two-period study design. Blood samples were taken frequently on the last day of each treatment period to determine plasma drug concentrations.

RESULTS

Co-administration of aliskiren with metformin decreased aliskiren area under the plasma concentration- time curve during the dose interval (AUC(tau)) by 27% (geometric mean ratio [GMR] 0.73; 90% confidence interval [CI] 0.64, 0.84) and maximum observed plasma concentration (C(max)) by 29% (GMR 0.71; 90% CI 0.56, 0.89) but these changes were not considered clinically relevant. Co-administration of aliskiren with fenofibrate had no effect on aliskiren AUC (GMR 1.05; 90% CI 0.96, 1.16) or C(max) (GMR 1.05; 90% CI 0.80, 1.38); similarly, co-administration of aliskiren with pioglitazone had no effect on aliskiren AUC(tau) (GMR 1.05; 90% CI 0.98, 1.13) or C(max) (GMR 1.01; 90% CI 0.84, 1.20). All other AUC and C(max) GMRs for aliskiren, metformin, pioglitazone, ketopioglitazone, hydroxypioglita-zone and fenofibrate were close to unity and the 90% CI were contained within the bioequivalence range of 0.80 to 1.25.

CONCLUSION

Co-administration of aliskiren with metformin, pioglitazone or fenofibrate had no significant effect on the pharmacokinetics of these drugs in healthy volunteers. These findings indicate that aliskiren can be co-administered with metformin, pioglitazone or fenofibrate without the need for dose adjustment.

Metformin: effects on micro and macrovascular complications in type 2 diabetes

INTRODUCTION

The antihyperglycaemic agent metformin is widely used in the treatment of type 2 diabetes. Data from the UK Prospective Diabetes Study and retrospective analyses of large healthcare databases concur that metformin reduces the incidence of myocardial infarction and increases survival in these patients. This apparently vasoprotective effect appears to be independent of the blood glucose-lowering efficacy.

EFFECTS OF METFORMIN

Metformin has long been known to reduce the development of atherosclerotic lesions in animal models, and clinical studies have shown the drug to reduce surrogate measures such as carotid intima-media thickness. The anti-atherogenic effects of metformin include reductions in insulin resistance, hyperinsulinaemia and obesity. There may be modest favourable effects against dyslipidaemia, reductions in pro-inflammatory cytokines and monocyte adhesion molecules, and improved glycation status, benefiting endothelial function in the macro- and micro-vasculature. Additionally metformin exerts anti-thrombotic effects, contributing to overall reductions in athero-thrombotic risk in type 2 diabetic patients.

Metformin prevents an adaptive increase in GSH and induces apoptosis under the conditions of GSH deficiency in H4IIE cells

The antidiabetic effect of metformin is mediated by activation of AMP-activated kinase (AMPK). This study investigated whether metformin at a high pharmacologic concentration alters the levels of cellular GSH in H4IIE hepatocytes and if so, whether the agent affects cell viability under GSH-deficient conditions. Treatment of cells with either metformin or 5-aminoimidazole-4-carboxamide riboside (AICAR) increased dichlorofluorescein oxidation, as did tert-butylhydroxyquinone (t-BHQ). Metformin or AICAR treatment blocked a rebound increase in GSH produced by t-BHQ and decreased GSH content below that of control. Exposure of cells to metformin or metformin + t-BHQ for 24 hr did not produce cell death. However, metformin treatment in combination with t-BHQ for a prolonged period of time (48 hr) at the concentrations, at which each agent was non-toxic, produced apoptosis. Treatment of AICAR with t-BHQ resulted in similar effects. Induction of apoptosis by the combination treatment was evidenced by changes in mitochondrial cytochrome c content, BCl(xl) expression, poly(ADP-ribose)polymerase (PARP) cleavage and caspase-3 activation. Compound C, an AMPK inhibitor, reversed apoptosis and changes in the apoptotic markers, suggesting a role of AMPK activation by metformin in the apoptotic process. Similarly, metformin treatment, when combined with buthionine sulfoximine or doxorubicin, induced apoptosis. Our data indicated that metformin prevents an adaptive increase in cellular GSH in H4IIE cells, and therefore induces apoptosis under the conditions of GSH deficiency.

Metformin-Associated Lactic Acidosis Precipitated by Diarrhea

Metformin-associated lactic acidosis (MALA) is a serious metabolic complication that occurs because of metformin accumulation in patients who become dehydrated or developed acute renal failure. Bicarbonate hemodialysis treatment should take place early in the course of management, especially in patients with severe metabolic acidosis who fail to respond to intravenous bicarbonate therapy or in whom renal failure is present. We report a case of MALA in which acute renal failure resulting from dehydration secondary to diarrhea and poor oral intake likely caused MALA. Early recognition of this condition and initiation of effective treatment can improve outcome.

Possible role of 5'AMP-activated protein kinase in the metformin-mediated arrest of bovine oocytes at the germinal vesicle stage during in vitro maturation

The 5'AMP-activated protein kinase (AMPK) activation is involved in the meiotic maturation of oocytes in the ovaries of mice and pigs. However, its effects on the oocyte appear to be species-specific. We investigated the patterns of AMPK and mitogen-activated protein kinases (MAPK3/1) phosphorylation during bovine in vitro maturation (IVM) and the effects of metformin, an AMPK activator, on oocyte maturation in cumulus-oocyte complexes (COCs) and denuded bovine oocytes (DOs). In bovine COCs, PRKAA Thr172 phosphorylation decreased, whereas MAPK3/1 phosphorylation increased in both oocytes and cumulus cells during IVM. Metformin (5 and 10 mM) arrested oocytes at the GV stage in COCs but not in DOs. In COCs, this arrest was associated with the inhibition of cumulus cell expansion, an increase in PRKAA Thr172 phosphorylation, and a decrease in MAPK3/1 phosphorylation in both oocytes and cumulus cells. However, the addition of compound C (10 muM), an inhibitor of AMPK, accelerated the initiation of the GV breakdown (GVBD) process without any alteration of MAPK3/1 phosphorylation in oocytes from bovine COCs. Metformin decreased AURKA and CCNB1 protein levels in oocytes. Moreover, after 1 h of IVM, metformin decreased RPS6 phosphorylation and increased EEF2 phosphorylation, suggesting that protein synthesis rates were lower in oocytes from metformin-treated COCs. Most oocytes were arrested after the GVBD stage following the treatment of COCs with the MEK inhibitor, U0126 (100 micromoles). Thus, in bovine COCs, metformin blocks meiotic progression at the GV stage, activates PRKAA, and inhibits MAPK3/1 phosphorylation in both the oocytes and cumulus cells during IVM. Moreover, cumulus cells were essential for the effects of metformin on bovine oocyte maturation, whereas MAPK3/1 phosphorylation was not.

Effects of metformin on bovine granulosa cells steroidogenesis: possible involvement of adenosine 5' monophosphate-activated protein kinase (AMPK)

In mammals, IGFs are important for the proliferation and steroidogenesis of ovarian cells. Metformin is an insulin sensitizer molecule used for the treatment of the infertility of women with polycystic ovary syndrome. It is, however, unclear whether metformin acts on ovarian cells. Adenosine 5' monophosphate-activated protein kinase (AMPK) is involved in metformin action in various cell types. We investigated the effects of metformin on bovine granulosa cell steroidogenesis in response to IGF1 and FSH, and studied AMPK in bovine ovaries. In granulosa cells from small follicles, metformin (10 mM) reduced production of both progesterone and estradiol and decreased the abundance of HSD3B, CYP11A1, and STAR proteins in presence or absence of FSH (10(-8) M) and IGF1 (10(-8) M). In cows, the different subunits of AMPK are expressed in various ovarian cells including granulosa and theca cells, corpus luteum, and oocytes. In bovine granulosa cells from small follicles, metformin, like AICAR (1 mM) a pharmaceutical activator of AMPK, increased phosphorylation of both Thr172 of AMPK alpha and Ser 79 of ACACA (Acetyl-CoA Carboxylase). Both metformin and AICAR treatment reduced progesterone and estradiol secretion in presence or absence of FSH and IGF1. Metformin decreased phosphorylation levels of MAPK3/MAPK1 and MAPK14 in a dose- and time-dependent manner. The adenovirus-mediated production of dominant negative AMPK abolished the effects of metformin on secretion of progesterone and estradiol and on MAPK3/MAPK1 phosphorylation but not on MAPK14 phosphorylation. Thus, in bovine granulosa cells, metformin decreases steroidogenesis and MAPK3/MAPK1 phosphorylation through AMPK activation.

Initial treatment with rosiglitazone/metformin fixed-dose combination therapy compared with monotherapy with either rosiglitazone or metformin in patients with uncontrolled type 2 diabetes

AIM

This study assessed the efficacy and safety of rosiglitazone and metformin (RSG/MET) fixed-dose combination (AVANDAMET) as initial therapy in patients with uncontrolled type 2 diabetes compared with monotherapy with either RSG or MET after 32 weeks of treatment.

METHODS

A total of 468 drug-naive patients with uncontrolled type 2 diabetes were recruited for this multicentre, double-blind trial if their glycated haemoglobin (A1c) was greater than 7.5%, but less than or equal to 11%, and their fasting plasma glucose (FPG) was less than or equal to 15 mmol/l. Patients were randomized to 32 weeks of blinded treatment with either RSG/MET fixed-dose combination (n = 155), MET (n = 154) or RSG (n = 159). The groups were comparable at baseline, with mean A1c of 8.8% and FPG of 11 mmol/l. RSG/MET was initiated with a total daily dose of 2 mg/500 mg and could be increased up to 8 mg/2000 mg; MET therapy began with a total daily dose of 500 mg and could be increased up to 2000 mg; and RSG treatment began with a total daily dose of 4 mg and could be increased up to 8 mg. Medication was uptitrated during on-therapy visits based on failure to attain glycaemic target of mean daily glucose less than or equal to 6.1 mmol/l (unless at maximum tolerated dose). Patients were assessed for efficacy and safety at nine visits over a 32-week treatment period. This was a trial designed to show greater efficacy of RSG/MET combination therapy compared with MET or RSG monotherapy. The primary end point was change in A1c from baseline to week 32. Secondary end points included the proportion of patients achieving recommended A1c and FPG targets for glycaemic control and change from baseline in FPG, free fatty acid, lipids, insulin, insulin sensitivity, C-reactive protein and adiponectin. Safety evaluations included adverse-event (AE) monitoring, changes in weight and clinical laboratory evaluations.

RESULTS

At week 32, RSG/MET showed significant improvements in A1c from a baseline of 8.9 +/- 1.1% to 6.6 +/- 1.0% at study end, and this 2.3% reduction was significantly greater than the reductions achieved individually with MET (-1.8%; p = 0.0008) and RSG (-1.6%; p < 0.0001). The greatest mean decrease in FPG was seen with RSG/MET (-4.1 mmol/l) and was significant compared with MET (-2.8 mmol/l; p < 0.0001) and RSG (-2.6 mmol/l; p < 0.0001). Target A1c of less than or equal to 6.5% and less than 7% were achieved in more patients in the RSG/MET group (60% and 77%) than with MET (39% and 57%) or RSG (35% and 58%) respectively. Treatment was well tolerated, with nausea, vomiting and diarrhoea as the most commonly reported AEs. Oedema was comparable between RSG/MET (6%) and RSG (7%) and lower in the MET group (3%). No new safety and tolerability issues were observed in the RSG/MET group.

CONCLUSIONS

As first-line therapy in patients with uncontrolled type 2 diabetes, RSG/MET fixed-dose combination therapy achieved significant reductions in A1c and FPG compared with either RSG or MET monotherapy. RSG/MET was generally well tolerated as initial therapy, with no new tolerability issues identified with the fixed-dose combination.

Acidose lactique et metformine

OBJECTIVE

The aims of this review are to precise the pathophysiological mechanisms leading to biguanide-associated lactic acidosis, to give elements of diagnosis, and to underline the precautionary conditions for prescribing these drugs by an improvement in physicians and patient's education.

DATA SOURCES

A PubMed database research in English and French language reports published until December 2005. The keywords were: lactic acidosis, metformin, biguanide, diabetes mellitus.

DATA EXTRACTION

Data in selected articles were reviewed, clinical and basic science research relevant informations were extracted.

DATA SYNTHESIS

Metformin, which is an oral antidiabetic agent, is the only one biguanide available in France. It acts by enhancing the sensitivity to insulin by a decrease in the hepatic glucose production and an increase in its peripheral use. In term of glycemic control, it has the same efficiency than the other hypoglycemic agents. It represents the treatment of choice for overweight type 2 diabetic patients because of its beneficial effects on the weight loss and on the cardiovascular complications. The incidence of metformin-associated lactic acidosis is very low when contra-indications and appropriate rules for prescribing this drug are respected. The relationship between metformin and lactic acidosis remains largely controversial. In practical, we can distinguish three situations which have different prognosis. In the first case, metformin seems to be responsible for lactic acidosis because of self-poisoning or accidental overdose, and prognosis is good. In the second case, the association between metformin and lactic acidosis is coincidental rather than causal, and may be induced by an underlying organ failure. In the last case there is a cause of lactic acidosis which is worsened by a precipitating factor leading to metformin accumulation. The 2 latter situations are very severe as mortality rate is about 50%. Symptomatic treatments and renal replacement therapy which allows metformin removal are the curative treatment. Prevention is essential. It requires the respect of metformin contraindications and a better education of physicians and patients for a safe prescription.

CONCLUSION

Due to its beneficial effects, metformin is the gold standard treatment for overweight type 2 diabetic patients. The essential precautionary conditions for prescribing metformin as well as the respect of its contra-indications permit largely to prevent lactic acidosis. This complication is serious when it is associated with intercurrent illnesses and metformin accumulation. The curative treatment is based on renal replacement therapy. Prevention only rests on the respect of the contra-indications. Education of physicians and patients concerning the rules of prescription remains essential.

Insulin sensitivity during oral glucose tolerance test and its relations to parameters of glucose metabolism and endothelial function in type 2 diabetic subjects under metformin and thiazolidinedione

AIM

This study was designed to assess the usefulness of a model-based index of insulin sensitivity during an oral glucose tolerance test (OGTT) in the identification of possible changes in this metabolic parameter produced by pharmacological agents known to be potent insulin sensitizers, that is metformin (M) and thiazolidinedione (T). The association of these agents with several other factors related to glucose metabolism was also investigated, as well as the relation of insulin sensitivity and secretion with markers of endothelial function such as different adhesion molecules (cAMs), that is vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and E-Selectin.

METHODS

Twenty type 2 diabetic patients treated with diet only underwent a 3-h OGTT for measurement of plasma glucose, insulin, proinsulin, C-peptide and cAMs before and after administration of randomly given M (n = 9; 1700 mg/day) or T (n = 11; 600 mg/day). After 16 weeks of treatment, a second OGTT was performed. Insulin sensitivity was calculated with homeostasis model assessment and with oral glucose insulin sensitivity (OGIS), which quantifies dynamic glucose clearance per unit change of insulin. Insulin secretion was assessed by modelling technique. Differences in these parameters before and after treatment, as well as possible relationships with cAMs, were assessed.

RESULTS

Basal and stimulated plasma glucose decreased after therapy in both the groups by approximately 20%. Basal insulin resistance also decreased. Insulin sensitivity in dynamic conditions (OGIS: ml/min/m(2)) increased with M (289.3 +/- 18.8 vs. 234.7 +/- 18.1, p < 0.02) and tended to improve with T (323.5 +/- 18.1 vs. 286.8 +/- 22.1, p = 0.09). Total insulin secretion over the OGTT [TIS: nmol/l(3 h)] tended to decrease with M (17.1 +/- 2.5 vs. 27.3 +/- 0.3, p = 0.08) but not with T (23.6 +/- 3.5 vs. 22.5 +/- 2.7). Plasma concentrations of E-Selectin decreased in T (38.0 +/- 2.3 vs. 51.2 +/- 6.1 ng/ml, p < 0.05). No correlation was found between insulin sensitivity and cAMs.

CONCLUSIONS

Model-based indices of insulin sensitivity and secretion during an OGTT can be able to detect changes observed in patients under treatment with pharmacological agents such as M or T. Both the drugs improved glucose control similarly. Decreased plasma E-Selectin concentrations were seen in patients on T therapy only.

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.

Metformin-induced stimulation of adenosine 5' monophosphate-activated protein kinase (PRKA) impairs progesterone secretion in rat granulosa cells

Metformin is an anti-diabetic drug commonly used to treat cycle disorders and anovulation in women with polycystic ovary syndrome. However, the effects and molecular mechanism of metformin in the ovary are not entirely understood. We investigated the effects of this drug on steroidogenesis and proliferation in rat granulosa cells. Metformin (10 mM) treatment for 48 h reduced progesterone and estradiol (E2) production in both basal conditions and under FSH stimulation. It also decreased the levels of the HSD3B, CYP11A1, STAR, and CYP19A1 proteins in response to FSH (10(-8) M) and of HSD3B in the basal state only. Metformin treatment (10 mM, 24 h) also reduced cell proliferation and the levels of CCND2 and CCNE proteins without affecting cell viability, both in the basal state and in response to FSH. Furthermore, metformin treatment for 1 h simultaneously increased the Thr172 phosphorylation of PRKAA (adenosine 5' monophosphate-activated protein kinase alpha) and the Ser79 phosphorylation of ACACA (acetyl-Coenzyme A carboxylase alpha). The adenovirus-mediated production of dominant-negative PRKAA totally abolished the effects of metformin on progesterone secretion, HSD3B and STAR protein production, and MAPK3/1 phosphorylation. Conversely, total inhibition of PRKAA Thr172 phosphorylation with the dominant-negative PRKAA adenovirus did not restore the decrease in E2 production and cell proliferation induced by metformin. Our results therefore strongly suggest that metformin reduces progesterone production via a PRKAA-dependent mechanism, whereas PRKAA activation is not essential for the decrease in E2 production and cell growth induced by metformin in rat granulosa cells.

Efficacy, tolerability, and safety of a novel once-daily extended-release metformin in patients with type 2 diabetes

OBJECTIVE

The purpose of this study was to determine the efficacy and safety of a novel extended-release metformin in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Adults with type 2 diabetes (newly diagnosed, treated with diet and exercise only, or previously treated with oral diabetic medications) were randomly assigned to receive one of three extended-release metformin treatment regimens (1,500 mg/day q.d., 1,500 mg/day twice daily, or 2,000 mg/day q.d.) or immediate-release metformin (1,500 mg/day twice daily) in a double-blind 24-week trial.

RESULTS

Significant decreases (P < 0.001) in mean HbA(1c) (A1C) levels were observed by week 12 in all treatment groups. The mean changes from baseline to end point in the two groups given 1,500 mg extended-release metformin (-0.73 and -0.74%) were not significantly different from the change in the immediate-release metformin group (-0.70%), whereas the 2,000-mg extended-release metformin group showed a greater decrease in A1C levels (-1.06%; mean difference [2,000 mg extended-release metformin - immediate-release metformin]: -0.36 [98.4% CI -0.65 to -0.06]). Rapid decreases in fasting plasma glucose levels were observed by week 1, which continued until week 8, and were maintained for the duration of the study. The overall incidence of adverse events was similar for all treatment groups, but fewer patients in the extended-release metformin groups discontinued treatment due to nausea during the initial dosing period than in the immediate-release metformin group.

CONCLUSIONS

Once- or twice-daily extended-release metformin was as safe and effective as twice-daily immediate-release metformin and provided continued glycemic control for up to 24 weeks of treatment.

Metformin extended release for the treatment of Type 2 diabetes mellitus

Metformin extended release (ER) (Glumetza, Depomed, Inc.) is a recently approved formulation that provides effective and well-tolerated glycaemic control with once-daily dosing. Metformin ER has similar bioavailability to conventional immediate-release (IR) formulations. In controlled clinical trials, metformin ER provided effective glycaemic control for 24 weeks when administered either as monotherapy or in combination with sulfonylurea. Good glycaemic control was maintained for an additional 24 weeks during an open-label extension study. Once-daily dosing with metformin ER 1500 mg/day was as effective as twice-daily dosing with metformin IR at the same total daily dose. Metformin ER was well tolerated at doses of 1500 or 2000 mg/day, with no increase in the frequency or severity of adverse events at the higher dose.

Efficacy of benfluorex in combination with sulfonylurea in type 2 diabetic patients: an 18-week, randomized, double-blind study

OBJECTIVE

The aim of this study was to demonstrate the superiority of benfluorex over placebo as an add-on therapy in type 2 diabetic patients in whom diabetes is insufficiently controlled by sulfonylurea monotherapy and who have a limitation for the use of metformin.

RESEARCH DESIGN AND METHODS

Type 2 diabetic patients with HbA(1c) (A1C) (7-10%) who were receiving the maximum tolerated sulfonylurea dose and had a contraindication to or poor tolerance of metformin were randomly assigned (double blind) to receive benfluorex 450 mg/day (n = 165) or placebo (n = 160) for 18 weeks. The main efficacy criterion was A1C, analyzed as the change from baseline to the end of treatment using ANCOVA with baseline and country as covariates. Secondary criteria were fasting plasma glucose (FPG), insulin resistance, and plasma lipid level.

RESULTS

Both groups were similar at baseline in the intention-to-treat population. A1C significantly decreased with benfluorex from 8.34 +/- 0.83 to 7.52 +/- 1.04% (P < 0.001) and tended to increase with placebo from 8.33 +/- 0.87 to 8.52 +/- 1.36% (NS), resulting in a mean adjusted difference between groups of -1.01% (95% CI -1.26 to -0.76; P < 0.001). The target A1C (< or =7%) was achieved in 34% of patients receiving benfluorex versus 12% of patients receiving placebo. Significant between-group differences in favor of benfluorex were observed for mean FPG (-1.65 mmol/l) (P < 0.001) and for homeostasis model assessment of insulin resistance. Overall tolerance was similar in both groups. Serious adverse events were more frequent in the benfluorex group, without evidence of causality relationship.

CONCLUSIONS

Benfluorex as an add-on therapy was superior to placebo in lowering A1C with a between-group difference of 1% in type 2 diabetic patients whose disease was insufficiently controlled with sulfonylurea alone and in whom metformin was contraindicated or not tolerated.

Contraindications can damage your health--is metformin a case in point?

Metformin is an effective anti-hyperglycaemic and cardioprotective agent, but a long list of contraindications precludes millions of patients with type 2 diabetes from using it. This is largely due to the historical experience of lactic acidosis with phenformin, despite the fact that metformin does not predispose to this when compared with other therapies. Contraindications such as old age, renal impairment and cardiac insufficiency are increasingly disregarded in clinical practice, yet there is no evidence that the incidence of lactic acidosis has changed. Metformin has been shown to improve metabolic control without causing lactic acidosis in elderly patients with multiple comorbidities, including explicit contraindications, and its use in patients with type 2 diabetes over the age of 70 with mild renal impairment did not produce a clinically relevant increase in plasma lactate. There is no correlation between levels of metformin and lactate in patients with lactic acidosis, and its prognosis is mainly related to the causal hypoxic underlying disease and comorbidities. These findings raise doubts about the pathogenetic significance of metformin in lactic acidosis. We propose that advanced age per se, mild renal impairment and compensated heart failure can no longer be upheld as contraindications for metformin. A clear re-definition of contraindications to metformin will enable more physicians to prescribe within guidelines.

Combination therapy using metformin or thiazolidinediones and insulin in the treatment of diabetes mellitus

The biguanide, metformin, sensitizes the liver to the effect of insulin, suppressing hepatic glucose output. Thiazolidinediones such as rosiglitazone and pioglitazone enhance insulin-mediated glucose disposal, leading to reduced plasma insulin concentrations. These classes of drugs may also have varying beneficial effects on features of insulin resistance such as lipid levels, blood pressure and body weight. Metformin in combination with insulin has been shown to significantly improve blood glucose levels while lowering total daily insulin dose and body weight. The thiazolidinediones in combination with insulin have also been effective in lowering blood glucose levels and total daily insulin dose. Triple combination therapy using insulin, metformin and a thiazolidinedione improves glycaemic control to a greater degree than dual therapy using insulin and metformin or insulin and a thiazolidinedione. There is insufficient evidence to recommend the use of metformin or thiazolidinediones in type 1 diabetic patients. Although these agents are largely well tolerated, some subjects experience significant gastrointestinal problems while using metformin. Metformin is associated with a low risk of lactic acidosis, but should not be used in patients with elevated serum creatinine or those being treated for congestive heart failure. The thiazolidinediones are associated with an increase in body weight, although this can be avoided with careful lifestyle management. Thiazolidinediones may also lead to oedema and are associated with a low incidence of hepatocellular injury. Thiazolidinediones are contraindicated in patients with underlying heart disease who are at risk of congestive heart failure and in patients who have abnormal hepatic function. The desired blood glucose-lowering effect and adverse event profiles of these agents should be considered when recommending these agents to diabetic patients. The potential for metformin or the thiazolidinediones to impact long-term cardiovascular outcomes remains under investigation.

Treating insulin resistance in type 2 diabetes with metformin and thiazolidinediones

Insulin resistance underlies the pathogenesis of hyperglycaemia and cardiovascular disease in most people with type 2 diabetes. Metformin and thiazolidinediones (pioglitazone and rosiglitazone) counter insulin resistance by different cellular mechanisms and with complementary effects, making them suited for use in combination. Metformin exerts a stronger suppression of hepatic glucose output, while thiazolidinediones produce a greater increase in peripheral glucose uptake, enabling metformin-thiazolidinedione combinations to improve glycaemic control in type 2 diabetes with additive efficacy. Basal insulin concentrations are not raised by metformin or thiazolidinediones, so there is minimal risk of hypoglycaemia, and metformin can reduce the weight gain associated with thiazolidinediones. There are overlapping effects of metformin and thiazolidinediones against a range of athero-thrombotic factors and markers. These include decreased plasminogen activator inhibitor-1, reduced platelet aggregation, reductions of several vascular adhesion molecules, and reduced markers of low-grade inflammation such as C-reactive protein. Additionally, thiazolidinediones increase adiponectin and slightly reduce blood pressure. Both metformin and thiazolidinediones can improve components of the lipid profile: thiazolidinediones consistently reduce free fatty acid concentrations and decrease the proportion of small dense low-density-lipoprotein, and pioglitazone also decreases triglycerides. During co-administration, metformin and thiazolidinediones do not interfere with each other's pharmacokinetics, and lower doses of the two agents together can achieve efficacy with fewer side effects. Metformin-thiazolidinedione combinations require attention to the precautions for both agents, especially renal, cardiac and hepatic status. Thus, metformin and thiazolidinediones can be used in combination to address the hyperglycaemia and vascular risk in type 2 diabetes.