Metformin treatment leads to an increase in basal, but not insulin-stimulated, glucose disposal in obese patients with impaired glucose tolerance

Metformin for prevention or delay of type 2 diabetes mellitus and its associated complications in persons at increased risk for the development of type 2 diabetes mellitus

BACKGROUND

The projected rise in the incidence of type 2 diabetes mellitus (T2DM) could develop into a substantial health problem worldwide. Whether metformin can prevent or delay T2DM and its complications in people with increased risk of developing T2DM is unknown.

OBJECTIVES

To assess the effects of metformin for the prevention or delay of T2DM and its associated complications in persons at increased risk for the T2DM.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Scopus, ClinicalTrials.gov, the World Health Organization (WHO) International Clinical Trials Registry Platform and the reference lists of systematic reviews, articles and health technology assessment reports. We asked investigators of the included trials for information about additional trials. The date of the last search of all databases was March 2019.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) with a duration of one year or more comparing metformin with any pharmacological glucose-lowering intervention, behaviour-changing intervention, placebo or standard care in people with impaired glucose tolerance, impaired fasting glucose, moderately elevated glycosylated haemoglobin A1c (HbA1c) or combinations of these.

DATA COLLECTION AND ANALYSIS

Two review authors read all abstracts and full-text articles and records, assessed risk of bias and extracted outcome data independently. We used a random-effects model to perform meta-analysis and calculated risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes, using 95% confidence intervals (CIs) for effect estimates. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included 20 RCTs randomising 6774 participants. One trial contributed 48% of all participants. The duration of intervention in the trials varied from one to five years. We judged none of the trials to be at low risk of bias in all 'Risk of bias' domains. Our main outcome measures were all-cause mortality, incidence of T2DM, serious adverse events (SAEs), cardiovascular mortality, non-fatal myocardial infarction or stroke, health-related quality of life and socioeconomic effects.The following comparisons mostly reported only a fraction of our main outcome set. Fifteen RCTs compared metformin with diet and exercise with or without placebo: all-cause mortality was 7/1353 versus 7/1480 (RR 1.11, 95% CI 0.41 to 3.01; P = 0.83; 2833 participants, 5 trials; very low-quality evidence); incidence of T2DM was 324/1751 versus 529/1881 participants (RR 0.50, 95% CI 0.38 to 0.65; P < 0.001; 3632 participants, 12 trials; moderate-quality evidence); the reporting of SAEs was insufficient and diverse and meta-analysis could not be performed (reported numbers were 4/118 versus 2/191; 309 participants; 4 trials; very low-quality evidence); cardiovascular mortality was 1/1073 versus 4/1082 (2416 participants; 2 trials; very low-quality evidence). One trial reported no clear difference in health-related quality of life after 3.2 years of follow-up (very low-quality evidence). Two trials estimated the direct medical costs (DMC) per participant for metformin varying from $220 to $1177 versus $61 to $184 in the comparator group (2416 participants; 2 trials; low-quality evidence). Eight RCTs compared metformin with intensive diet and exercise: all-cause mortality was 7/1278 versus 4/1272 (RR 1.61, 95% CI 0.50 to 5.23; P = 0.43; 2550 participants, 4 trials; very low-quality evidence); incidence of T2DM was 304/1455 versus 251/1505 (RR 0.80, 95% CI 0.47 to 1.37; P = 0.42; 2960 participants, 7 trials; moderate-quality evidence); the reporting of SAEs was sparse and meta-analysis could not be performed (one trial reported 1/44 in the metformin group versus 0/36 in the intensive exercise and diet group with SAEs). One trial reported that 1/1073 participants in the metformin group compared with 2/1079 participants in the comparator group died from cardiovascular causes. One trial reported that no participant died due to cardiovascular causes (very low-quality evidence). Two trials estimated the DMC per participant for metformin varying from $220 to $1177 versus $225 to $3628 in the comparator group (2400 participants; 2 trials; very low-quality evidence). Three RCTs compared metformin with acarbose: all-cause mortality was 1/44 versus 0/45 (89 participants; 1 trial; very low-quality evidence); incidence of T2DM was 12/147 versus 7/148 (RR 1.72, 95% CI 0.72 to 4.14; P = 0.22; 295 participants; 3 trials; low-quality evidence); SAEs were 1/51 versus 2/50 (101 participants; 1 trial; very low-quality evidence). Three RCTs compared metformin with thiazolidinediones: incidence of T2DM was 9/161 versus 9/159 (RR 0.99, 95% CI 0.41 to 2.40; P = 0.98; 320 participants; 3 trials; low-quality evidence). SAEs were 3/45 versus 0/41 (86 participants; 1 trial; very low-quality evidence). Three RCTs compared metformin plus intensive diet and exercise with identical intensive diet and exercise: all-cause mortality was 1/121 versus 1/120 participants (450 participants; 2 trials; very low-quality evidence); incidence of T2DM was 48/166 versus 53/166 (RR 0.55, 95% CI 0.10 to 2.92; P = 0.49; 332 participants; 2 trials; very low-quality evidence). One trial estimated the DMC of metformin plus intensive diet and exercise to be $270 per participant compared with $225 in the comparator group (94 participants; 1 trial; very-low quality evidence). One trial in 45 participants compared metformin with a sulphonylurea. The trial reported no patient-important outcomes. For all comparisons there were no data on non-fatal myocardial infarction, non-fatal stroke or microvascular complications. We identified 11 ongoing trials which potentially could provide data of interest for this review. These trials will add a total of 17,853 participants in future updates of this review.

AUTHORS' CONCLUSIONS

Metformin compared with placebo or diet and exercise reduced or delayed the risk of T2DM in people at increased risk for the development of T2DM (moderate-quality evidence). However, metformin compared to intensive diet and exercise did not reduce or delay the risk of T2DM (moderate-quality evidence). Likewise, the combination of metformin and intensive diet and exercise compared to intensive diet and exercise only neither showed an advantage or disadvantage regarding the development of T2DM (very low-quality evidence). Data on patient-important outcomes such as mortality, macrovascular and microvascular diabetic complications and health-related quality of life were sparse or missing.

Myths about Insulin Resistance: Tribute to Gerald Reaven

Gerald Reaven was often called the "father of insulin resistance." On the 1-year anniversary of his death in 2018, we challenge three myths associated with insulin resistance: metformin improves insulin resistance; measurement of waist circumference predicts insulin resistance better than body mass index; and insulin resistance causes weight gain. In this review, we highlight Reaven's relevant research that helped to dispel these myths associated with insulin resistance.

Protocol for a randomised controlled trial of the effect of dapagliflozin, metformin and exercise on glycaemic variability, body composition and cardiovascular risk in prediabetes (the PRE-D Trial)

INTRODUCTION

The primary aim of this study is to compare the efficacy of three short-term glucose-lowering interventions (exercise, metformin and dapagliflozin) on glycaemic variability in overweight or obese men and women with elevated diabetes risk (ie, prediabetes, defined as haemoglobin A1c (HbA1c)39-47 mmol/mol / 5.7%-6.4%). The secondary aims are to investigate the effects of the interventions on body composition and cardiometabolic risk factors.

METHODS AND ANALYSIS

The Pre-D Trial is an investigator-initiated, randomised, controlled, parallel, open-label, superiority trial. The study aims to assign 120 participants in a 1:1:1:1 ratio to receive one of four interventions for 13 weeks: (1) dapagliflozin (10 mg once daily); (2) metformin (850 mg twice daily); (3) exercise (interval training, 5 days a week, 30 min per session); or (4) control (lifestyle advice). After the 13 weeks of intervention, a follow-up period of 13 weeks will follow to study the long-term effects of the interventions. The primary endpoint is reduction from baseline to end-of treatment (13 weeks) in mean amplitude of glycaemic excursions measured by continuous glucose monitoring. The secondary endpoints include concomitant changes in various measures of glucose metabolism, body weight, cardiorespiratory fitness, blood pressure, plasma lipids, objectively measured physical activity and dietary intake.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Ethics Committee of the Capital Region and the Danish Medicines Agency. Approval of data and biobank storage has been obtained from the Danish Data Protection Board. The study will be carried out according to the Declaration of Helsinki and to the regulations for good clinical practice. The results from this trial will allow a number of research questions concerning the effect of exercise versus dapagliflozin or metformin in HbA1c-defined prediabetes to be addressed.

TRIAL REGISTRATION

NCT02695810.

Impaired glucose tolerance and metformin: clinical and mechanistic aspects

The Diabetes Prevention Program (DPP) showed that metformin reduced the incidence of diabetes in subjects with impaired glucose tolerance (IGT) who were at high risk of progression to type 2 diabetes. Metformin was not as efficient as intensive life style intervention, but had a clinically significant effect in obese individuals and in those with impaired fasting glucose (IFG). This review discusses the clinical implications and the mechanistic aspects of the effect of metformin in IGT and IFG. Acute actions of metformin on postprandial metabolism to improve hepatic glucose handling and improve the lipid profile could contribute to the lower incidence of diabetes. Longer term improvements in haemodynamic parameters and reduced oxidative stress are also implicated. Metformin offers a potential alternative or complement to lifestyle intervention for IGT, and deserves further evaluation in this respect.

Effect of Low Glycemic Index Diet Versus Metformin on Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) continues to be highly prevalent and contributes to a rapidly growing problem worldwide. The most important therapeutic intervention for metabolic syndrome is diet modification, an intervention whose efficacy has been proven for metabolic syndrome.

OBJECTIVES

The aim of the present study was to compare the effects of low glycemic index diet versus metformin on MetS components in adults with MetS.

PATIENTS AND METHODS

Fifty-one adults with MetS participated in this randomized controlled clinical trial. Patients were randomly allocated to two groups of metformin and low glycemic index diet. The intervention period was eight weeks. The studied participants were compared at baseline and the end of the trial, regarding the following factors: weight, blood pressure, waist circumference, fasting blood sugar, hemoglobin A1c and lipid profiles (Triglyceride (TG), Total Cholesterol (TC), Low-Density Lipoprotein (LDL) cholesterol, and High-Density Lipoprotein (HDL) cholesterol).

RESULTS

The anthropometric measurements, Fasting Blood Sugar (FBS), Hemoglobin A1c, serum lipid profiles (TG, TC, LDL-C, HDL-C) and lipoprotein ratio (LDL/HDL) showed a significant decrease after the intervention in both groups (P < 0.05). Comparison of the difference between the two groups was not significant, except for the mean reduction in FBS, which was more in the metformin group although this was not clinically significant.

CONCLUSIONS

This study supports the assumption that low glycemic index diet as well as metformin can positively affect metabolic syndrome components.

Prediabetes: to treat or not to treat?

The incidence of diabetes is continuously increasing worldwide. Pre-diabetes (defined as impaired glucose tolerance, impaired fasting glucose or both) represents an intermediate state, which often progresses to overt diabetes within a few years. In addition, pre-diabetes may be associated with increased risk of microvascular and macrovascular complications. Thus, reverting a pre-diabetic state as well as preventing the development of diabetes represents enormous challenge for the clinician. Lifestyle modification in pre-diabetic individuals was found particularly effective in the prevention of diabetes. However, compliance to lifestyle modification measures can be a crucial problem in the everyday clinical practice, especially in developing countries. During the last decade many studies support the use of anti-diabetic treatment schemes in pre-diabetic subjects to be advantageous. The American Diabetes Prevention Program (DPP) as well as other minor studies and meta-analyses has convincingly demonstrated the efficacy of metformin in this patient group. In addition, results of the 10 year DPP follow up have recently been published, demonstrating the long term safety and sustainability of metformin treatment benefits in this population. In contrast to metformin, the evidence from the use of other anti-diabetic agents (thiazolidinediones, a-glucosidase inhibitors, incretin mimetics) in pre-diabetic individuals is rather inadequate and prospective data is further needed. Furthermore, large scale studies with hard clinical endpoints are needed to delineate the effect of pre-diabetes treatment on macro- and microvascular complications. In conclusion, several strategies of patient management, mainly lifestyle modification and pharmacological interventions can prevent diabetes development in subjects diagnosed with pre-diabetes or even revert pre-diabetic state. However, whether this biochemical improvement can be translated into actual clinical benefit remains to be established.

Metformin does not improve the reproductive or metabolic profile in women with polycystic ovary syndrome (PCOS)

To determine whether metformin, when given to women with polycystic ovary syndrome (PCOS), promotes folliculogenesis by prompting a drop in free sex steroids resulting in a compensatory follicle stimulating hormone (FSH) rise, we conducted a randomized, double-blind, placebo-controlled crossover clinical trial. Eight mid-reproductive age PCOS participants with mean obese body mass index (BMI) and normal glucose tolerance received 8 weeks of metformin, given in a step-up fashion to a maximum dose of 2000 mg daily or placebo with daily urine sampling, 4-6 weeks washout, and crossover to the remaining arm for 8 weeks. To confirm the effects of metformin on glucose and other metabolic markers, a hyperinsulinemic, euglycemic 3-dose clamp (physiologic: 30 mU/m(2) per minute, high: 400 mU/m(2) per minute) followed each treatment. Urinary FSH, luteinizing hormone (LH), or pregnanediol glucuronide (Pdg) did not differ by treatment. Glucose disposal, endogenous glucose production, BMI, ovulation rates, serum sex steroids, free fatty acids, and lipids did not significantly differ by treatment, despite good evidence for compliance with the protocol. During the clamp, high-dose insulin administration was associated with an acute drop in serum LH. We conclude that short-term, high-dose metformin exerts minimal effects on both metabolic markers and reproductive hormones in a small sample of overall morbidly obese women.

Role of metformin for weight management in patients without type 2 diabetes

OBJECTIVE

To evaluate the efficacy and safety of metformin for weight management in overweight and obese patients without type 2 diabetes.

DATA SOURCES

Literature was obtained through MEDLINE Ovid (1950-February week 3, 2008), EMBASE (all years), and a bibliographic review of relevant articles. Key words included metformin, obesity, overweight, and weight loss.

STUDY SELECTION/DATA EXTRACTION

All studies published in the English language that evaluated the effects of metformin on weight in obese or overweight individuals were critically analyzed. Relevant articles were selected for inclusion in this review.

DATA SYNTHESIS

Metformin is first-line pharmacotherapy in the treatment of overweight or obese patients with type 2 diabetes, with beneficial effects on weight in this population. Multiple trials have evaluated the effect of metformin on weight and other metabolic parameters in adults and adolescents without diabetes. Five of 12 trials in adults evaluated weight loss as a primary endpoint. Significant weight reduction was found in 4 of these studies; however, the trials were small and of weak design. Weight reduction was significant in 5 of the 6 adolescent trials; similarly, these studies were limited by weak study design and small patient population. Metabolic parameters (blood pressure, waist circumference, cholesterol parameters, insulin/glucose levels) often showed varying results. Metformin was well tolerated; gastrointestinal effects were the most frequently reported adverse effects.

CONCLUSIONS

The weight loss effects of metformin in overweight or obese adults and adolescents without diabetes appear promising; however, trials have been limited by small patient populations and weak design. Metformin may also have a positive effect on metabolic parameters such as waist circumference, fasting insulin and glucose levels, and triglycerides. Further research involving large-scale trials that evaluate weight loss as a primary outcome is necessary to firmly establish the role of metformin in this population.

Meta-analysis: metformin treatment in persons at risk for diabetes mellitus

PURPOSE

We performed a meta-analysis of randomized controlled trials to assess the effect of metformin on metabolic parameters and the incidence of new-onset diabetes in persons at risk for diabetes.

METHODS

We performed comprehensive English- and non-English-language searches of EMBASE, MEDLINE, and CINAHL databases from 1966 to November of 2006 and scanned selected references. We included randomized trials of at least 8 weeks duration that compared metformin with placebo or no treatment in persons without diabetes and evaluated body mass index, fasting glucose, fasting insulin, calculated insulin resistance, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and the incidence of new-onset diabetes.

RESULTS

Pooled results of 31 trials with 4570 participants followed for 8267 patient-years showed that metformin reduced body mass index (-5.3%, 95% confidence interval [CI], -6.7--4.0), fasting glucose (-4.5%, CI, -6.0--3.0), fasting insulin (-14.4%, CI, -19.9--8.9), calculated insulin resistance (-22.6%, CI, -27.3--18.0), triglycerides (-5.3%, CI, -10.5--0.03), and low-density lipoprotein cholesterol (-5.6%, CI, -8.3--3.0%), and increased high-density lipoprotein cholesterol (5.0%, CI, 1.6-8.3) compared with placebo or no treatment. The incidence of new-onset diabetes was reduced by 40% (odds ratio 0.6; CI, 0.5-0.8), with an absolute risk reduction of 6% (CI, 4-8) during a mean trial duration of 1.8 years.

CONCLUSION

Metformin treatment in persons at risk for diabetes improves weight, lipid profiles, and insulin resistance, and reduces new-onset diabetes by 40%. The long-term effect on morbidity and mortality should be assessed in future trials.

Metformin as treatment for overweight and obese adults: a systematic review

PURPOSE

We wanted to determine whether metformin is an effective medication for treatment of overweight or obese adults who do not have diabetes mellitus or polycystic ovary syndrome (PCOS).

METHODS

We searched MEDLINE (1966-2003), EMBASE (1986-2003), Allied and Complementary Medicine Database (1985-2003), International Pharmaceutical Abstracts (1970-2003), the Cochrane Library, American College of Physicians Journal Club, Database of Abstracts of Reviews of Effects, Cochrane Controlled Trials Register, MEDLINE In-Process & Other Non-Indexed Citations, reference lists of retrieved articles, and articles by selected authors and pharmaceutical manufacturers. Inclusion criteria were being obese or overweight determined by a BMI of 25 kg/m2 or greater or waist-to-hip ratio (WHR) of more than 0.8, metformin use, and aged 18 years or older. Exclusion criteria were a diagnosis of diabetes mellitus, polycystic ovarian syndrome or descriptors of polycystic ovarian syndrome, human immunodeficiency virus infection, and concomitant antipsychotic medications. Trials were graded on an 11-point Jadad scale. Only randomized controlled and blinded trials were accepted. Two reviewers independently extracted data from each trial. Primary outcomes measured were changes in BMI, WHR, and weight.

RESULTS

Fifty-seven potentially relevant studies were initially identified; 48 were excluded because of lack of randomization, lack of blinding, failure to meet inclusion or exclusion criteria, inaccessible outcomes, or improper study design. Nine clinical trials met criteria for validity assessment. Four studies used the parameter of waist-to-hip ratio, 3 studies included BMI, and 8 used weight. Two of the 9 studies showed a small reduction in WHR.

CONCLUSION

Insufficient evidence exists for the use of metformin as treatment of overweight or obese adults who do not have diabetes mellitus or polycystic ovary syndrome. Further studies are needed to answer this clinical question.

Differential regulation of insulin action and tumor necrosis factor alpha system activity by metformin

BACKGROUND

Tumor necrosis factor alpha has a key role in insulin resistance. We study the effects of metformin on glucose tolerance, insulin resistance, beta cell function, and soluble tumor necrosis factor receptor (sTNFR) levels.

METHODS

We performed a double-blind, randomized metformin-placebo study. Twenty-three subjects with impaired glucose tolerance or impaired fasting glucose were studied. Oral glucose tolerance, homeostasis model assessment, and continuous infusion of glucose with model assessment tests were used to evaluate glucose tolerance, insulin sensitivity, and beta cell function, respectively. Soluble tumor necrosis factor receptor levels were measured before and after therapy. Repeated measures analysis of variance was used for statistical analysis.

RESULTS

After 12-week treatment, fasting glucose (110.1 +/- 9.9 to 98.9 +/- 15.7 mg/dl, P < .001), fasting insulin (11.6 +/- 5.4 to 8.8 +/- 3.5 mU/L, P = .05), fasting C-peptide (2.5 +/- 0.7 to 1.8 +/- 0.5 ng/mL, P < .05), and achieved C-peptide (5.2 +/- 1.2 to 4.2 +/- 1 ng/mL, P < .05) levels decreased in the metformin group. In addition, there was an improvement in insulin sensitivity (37.4% +/- 15.2% to 50.4% +/- 23.2%, P < .05) with unchanged sTNFR1 (2.0 +/- 0.8 to 2.3 +/- 1.2 microg/L, P = NS) and sTNFR2 (4.8 +/- 1.7 to 4.4 +/- 1.2 microg/L, P = NS) levels.

CONCLUSIONS

Metformin is able to reverse insulin resistance and hyperglycemia in high-risk subjects for type 2 diabetes mellitus independently of the effects on tumor necrosis factor alpha system activity.

Determinants of subclinical diabetic heart disease

AIMS/HYPOTHESIS

Subclinical left ventricular (LV) dysfunction has been shown by tissue Doppler and strain imaging in diabetic patients in the absence of coronary disease or LV hypertrophy, but the prevalence and aetiology of this finding remain unclear. This study sought to identify the prevalence and the determinants of subclinical diabetic heart disease.

METHODS

A group of 219 unselected patients with type 2 diabetes without known cardiac disease underwent resting and stress echocardiography. After exclusion of coronary artery disease or LV hypertrophy, the remaining 120 patients (age 57+/-10 years, 73 male) were studied with tissue Doppler imaging. Peak systolic strain of each wall and systolic (Sm) and diastolic (Em) velocity of each basal segment were measured from the three apical views and averaged for each patient. Significant subclinical LV dysfunction was identified according to Sm and Em normal ranges adjusted by age and sex. Strain and Em were correlated with clinical, therapeutic, echocardiographic and biochemical variables, and significant independent associations were sought using a multiple linear regression model.

RESULTS

Significant subclinical LV dysfunction was present in 27% diabetic patients. Myocardial systolic dysfunction by peak strain was independently associated with glycosylated haemoglobin level (p<0.001) and lack of angiotensin-converting enzyme inhibitor treatment (p=0.003). Myocardial diastolic function (Em) was independently predicted by age (p=0.013), hypertension (p=0.001), insulin (p=0.008) and metformin (p=0.01) treatment.

CONCLUSIONS/INTERPRETATION

In patients with diabetes mellitus, subclinical LV dysfunction is common and associated with poor diabetic control, advancing age, hypertension and metformin treatment; ACE inhibitor and insulin therapies appear to be protective.

Insulin resistance: from predisposing factor to therapeutic target in type 2 diabetes

BACKGROUND

Insulin resistance contributes to the pathogenesis of type 2 diabetes and is closely linked with cardiovascular risk factors and premature cardiovascular disease.

OBJECTIVE

The purpose of this paper was to review the importance of insulin resistance as a core defect in type 2 diabetes, a potential contributor to accelerated atherosclerosis, and a potential target for insulin-sensitizing agents.

METHODS

Articles considered for inclusion in this review were identified through a search of MEDLINE/PubMed for reports published from 1966 to April 2003. Search terms used were insulin resistance, diabetes, insulin sensitivity, obesity, cardiovascular disease, metformin, thiazolidinediones, pioglitazone, rosiglitazone, and troglitazone.

RESULTS

An overview of the epidemiology, natural history, and pathophysiology of type 2 diabetes is provided, with a focus on insulin resistance and a related discussion of the impact of current therapies used to treat insulin-resistant patients. In particular, information on insulin-sensitizing agents-metformin and the currently available thiazolidinediones (TZDs), pioglitazone and rosiglitazone-is presented. Although metformin has been shown to indirectly reduce insulin resistance, TZDs are the only available agents that have been shown to directly lower insulin resistance.

CONCLUSIONS

Recent evidence indicates that metformin, pioglitazone, and rosiglitazone may improve the dyslipidemic profile, reduce vascular inflammation, and improve endothelial dysfunction, all of which may be particularly important to physicians seeking treatment options to prevent or reduce cardiovascular complications in patients with type 2 diabetes.

Metformin blunts stress-induced hyperglycemia after thermal injury

BACKGROUND

Hyperglycemia is associated with detriments in immune function and impaired wound healing. The purpose of this study was to assess the effect of metformin, an oral antihyperglycemic agent approved for patients with diabetes mellitus, on glucose metabolism in severely burned patients.

METHODS

Metformin was given in a double-blind, placebo-controlled fashion to 10 patients, all with burns > 60% body surface area (age, 36 +/- 4 years; weight, 92 +/- 3 kg; mean +/- SEM). After 8 days of metformin or placebo, glucose kinetics were quantitated using isotopic dilution with 6,6-d glucose and indirect calorimetry. Measurements were made during fasting; during an intravenous glucose infusion (30 micromol/kg/min); and during a hyperinsulinemic (500 mIU/m2/h), euglycemic clamp (mean plasma glucose concentration, 6.5 +/- 0.3 mmol/L).

RESULTS

During fasting, metformin-treated subjects had a significantly lower rate of endogenous glucose production (met. 9.6) and glucose oxidation than placebo control subjects. With the administration of intravenous glucose, metformin treatment significantly accelerated glucose clearance, thereby attenuating hyperglycemia. During hyperinsulinemia, glucose uptake was significantly greater in metformin-treated patients. Patients receiving metformin also had a significantly higher plasma concentration of insulin.

CONCLUSION

These findings suggest a potential clinical efficacy of metformin to reduce stress-induced hyperglycemia by increasing glucose clearance. This effect may be mediated by either a metformin-induced augmentation of insulin sensitivity or by increasing insulin availability.

Pathophysiology and pharmacological treatment of insulin resistance

Diabetes mellitus type 2 is a world-wide growing health problem affecting more than 150 million people at the beginning of the new millennium. It is believed that this number will double in the next 25 yr. The pathophysiological hallmarks of type 2 diabetes mellitus consist of insulin resistance, pancreatic beta-cell dysfunction, and increased endogenous glucose production. To reduce the marked increase of cardiovascular mortality of type 2 diabetic subjects, optimal treatment aims at normalization of body weight, glycemia, blood pressure, and lipidemia. This review focuses on the pathophysiology and molecular pathogenesis of insulin resistance and on the capability of antihyperglycemic pharmacological agents to treat insulin resistance, i.e., a-glucosidase inhibitors, biguanides, thiazolidinediones, sulfonylureas, and insulin. Finally, a rational treatment approach is proposed based on the dynamic pathophysiological abnormalities of this highly heterogeneous and progressive disease.