Sulphonylurea treatment of NIDDM patients with cardiovascular disease: a mixed blessing?

Cardiovascular events and atherosclerosis in patients with type 2 diabetes and impaired glucose tolerance -What are the medical treatments to prevent cardiovascular events in such patients?

Type 2 diabetes mellitus (T2DM) and impaired glucose tolerance (IGT) significantly induce advanced coronary artery disease and systemic atherosclerosis. Thus, T2DM and IGT are traditional risk factors of cardiovascular disease (CVD). On the other hand, acute coronary syndrome is frequently caused by the rupture of coronary atherosclerotic plaques, which reduces patients' quality of life and may result in death. To date, many trials have sought to identify ways to determine the coronary plaque volume and its vulnerability, and many studies have demonstrated that some specific antihyperglycemic agents may prevent coronary or carotid plaque progression, decrease plaque volume, induce plaque stability, and improve clinical outcomes in patients with T2DM and IGT. This article reviews i) the association between coronary or carotid plaques and abnormal glucose tolerance, including T2DM; and ii) the effects of oral antihyperglycemic drugs to improve clinical outcomes and stabilize atherosclerotic plaques in patients with T2DM and IGT.

Sulphonylurea compared to DPP-4 inhibitors in combination with metformin carries increased risk of severe hypoglycemia, cardiovascular events, and all-cause mortality

AIMS

There are safety concerns related to sulphonylurea treatment. The objective of this nationwide study was to compare the risk of cardiovascular disease (CVD), all-cause mortality and severe hypoglycemia in patients with type 2 diabetes (T2D) starting second-line treatment with either metformin+sulphonylurea or metformin+dipeptidyl peptidase-4 inhibitor (DPP-4i).

METHODS

All patients with T2D in Sweden who initiated second-line treatment with metformin+sulphonylurea or metformin+DPP-4i during 2006-2013 (n=40,736 and 12,024, respectively) were identified in this nationwide study. The Swedish Prescribed Drug Register and the Cause of Death and National Patient Registers were used, and Cox survival models adjusted for age, sex, fragility, prior CVD, and CVD-preventing drugs were applied to estimate risks of events. Propensity score adjustments and matching methods were used to test the results.

RESULTS

Of 52,760 patients; 77% started metformin+SU and 23% metformin+DPP-4i. Crude incidences for severe hypoglycemia, CVD, and all-cause mortality in the SU cohort were 2.0, 19.6, and 24.6 per 1000 patient-years and in the DPP-4i cohort were 0.8, 7.6, and 14.9 per 1000 patient-years, respectively. Sulphonylurea compared with DPP4i was associated with higher risk of subsequent severe hypoglycemia, fatal and nonfatal CVD, and all-cause mortality; adjusted HR (95% CI): 2.07 (1.11-3.86); 1.17 (1.01-1.37); and 1.25 (1.02-1.54), respectively. Results were confirmed by additional propensity-adjusted and matched analyses. Among the SU drugs, glibenclamide had the highest risks.

CONCLUSIONS

Metformin+SU treatment was associated with an increased risk of subsequent severe hypoglycemia, cardiovascular events, and all-cause mortality compared with metformin+DPP4i. Results from randomized trials will be important to elucidate causal relationships.

Insulinotropic compounds decrease endothelial cell survival

OBJECTIVES

Hyperglycemia induces damage of vascular endothelial cells leading to diabetic complications. We investigated the effects of insulinotropic compounds and elevated glucose on endothelial cells in the absence or presence of vascular endothelial growth factor (VEGF).

RESULTS

Human umbilical vein endothelial cells (HUVECs) were treated with glibenclamide, repaglinide and insulinotropic imidazolines at high glucose concentration in the presence or absence of VEGF and viability, proliferation and nitric oxide production were measured. Hyperglycemia inhibited pro-survival effects of VEGF on endothelial cells. Glibenclamide and repaglinide decreased HUVEC viability at elevated glucose concentration in the absence but not in the presence of VEGF, without affecting HUVEC proliferation. Repaglinide also had some positive influence on HUVEC function elevating NO production in the presence of VEGF. Imidazolines showed different activities on endothelial cell survival. Efaroxan diminished HUVEC viability at elevated glucose concentration in the presence, however not in the absence of VEGF, while RX871024 decreased HUVEC survival regardless of the presence of VEGF.

SIGNIFICANCE OF THE STUDY

Our data demonstrate an important interplay between the actual insulinotropic compounds, VEGF and ambient glucose concentration affecting the survival of the vascular endothelial cells. Consequently, this interplay needs to be taken into consideration when designing novel oral antidiabetic compounds.

Durability and tolerability of dapagliflozin over 52 weeks as add-on to metformin and sulphonylurea in type 2 diabetes

AIMS

To evaluate the safety and efficacy of dapagliflozin as add-on therapy to metformin plus sulphonylurea over 52 weeks.

METHODS

Patients with type 2 diabetes mellitus (T2DM) using sulphonylurea and metformin received dapagliflozin 10 mg/day or placebo added to therapy for 52 weeks (24-week randomized, double-blind period plus 28-week double-blind extension).

RESULTS

A total of 219 patients were randomized 1 : 1 to dapagliflozin or placebo. Over 52 weeks, glycated haemoglobin (HbA1c) and fasting plasma glucose levels showed greater improvement from baseline with dapagliflozin (-0.8% and -1.5 mmol/l) than with placebo (-0.1% and 0.6 mmol/l). More patients achieved HbA1c <7.0% with dapagliflozin (27.3%) than with placebo (11.3%) at 52 weeks. Dapagliflozin was associated with greater reductions in body weight and systolic blood pressure (-2.9 kg and -1.0 mmHg) compared with placebo (-1.0 kg and 1.1 mmHg). Greater increases in total, LDL and HDL cholesterol and decreases in triglycerides were observed with dapagliflozin (3.4, 4.8, 6.9 and -8.0%, respectively) versus placebo (1.4, 0.9, 0.6 and 2.9%, respectively). Fewer patients were rescued for failing to reach glycaemic targets with dapagliflozin (9.3%) than with placebo (44.4%). Adverse events and serious adverse events were similar between groups (dapagliflozin: 69.7 and 6.4%; placebo: 73.4 and 7.3%). More hypoglycaemic events were observed with dapagliflozin (15.6%) than with placebo (8.3%). Genital infections were reported in more patients in the dapagliflozin (10.1%) than in the placebo group (0.9%) and urinary tract infection frequency was similar in the two groups (10.1 and 11.0%).

CONCLUSION

Dapagliflozin as add-on to metformin plus a sulphonylurea was well tolerated and improvement in glycaemic control was maintained over 52 weeks.

Current therapeutic agents and anesthetic considerations for diabetes mellitus

As the incidence of diabetes mellitus (DM) continues to increase worldwide, more diabetic patients will be presented for surgery and anesthesia. This increase of DM is a consequence of the rise in new patients of type 2 DM, and is likely attributable to rapid economic development, improved living standards, aging population, obesity, and lack of exercise. The primary goal of management in DM is to delay, or prevent the macro- and microvascular complications by achieving good glycemic control. More understanding of the pathophysiology of DM has contributed to the advance of new pharmacological approaches. In addition to the conventional therapy for DM, glucagon-like peptide-1 (GLP-1) mimetics, dipeptidyl peptidase-4 (DPP-4) inhibitors, thiazolidinediones (TZDs), and insulin analogues are currently available effective hypoglycemic agents for the management of the patients with DM in the perioperative period and also consider the adverse effects of newly introduced agents that need more clinical observations.

Comparison of antihyperglycemic effects of creatine and glibenclamide in type II diabetic patients

This study compares the effects of glibenclamide and creatine in type II diabetics. In a 14-day symmetrically randomized crossover trial recently detected type II diabetics received either creatine (3 g) or glibenclamide (3.5 mg) for five successive days, followed by two days of washout, and crossover to the opposite treatment. Glucose, insulin, c-peptide, and creatine were measured. Creatine and glibenclamide decreased glucose concentrations vs. basal glucose [-15, 60, 90, 120, 180, and 240 min; mol/l]: 12.6±0.83 vs. 12.2±0.56 vs. 12.1±0.57, 15.3±0.63 vs. 13.5± 0.70(a ) vs. 13.0±0.57(a), 14.8±0.57 vs. 13.8±0.59(a) vs. 13.4±0.46(a), 14.6±0.61 vs. 12.3±0.49(b) vs. 12.4±0.61(a), 12.8±0.76 vs. 10.0± 0.40(c) vs. 10.3±0.41(c), and 11.4±0.67 vs. 8.3±0.40(c) vs. 8.5±0.36(c); ((a) p<0.05; (b) p<0.01; (c) p<0.001 vs. basal glucose). Treatment with both creatine and glibenclamide increased insulin and c-peptide concentrations after 120 and 240 min (p<0.05 and p<0.01). At the doses applied short-term treatment with creatine and glibenclamide elicits similar glucose lowering effects.

Comparison of two sulfonylureas with high and low myocardial K(ATP) channel affinity on myocardial infarct size and metabolism in a rat model of type 2 diabetes

AIMS/HYPOTHESIS

Sulfonylureas (SUs) may impair outcome in patients with acute coronary syndrome. Most experimental studies of the myocardial effects of SU treatment are performed in non-diabetic models. We compared the effect of two widely used SUs, glibenclamide (gb) and gliclazide (gc), with high and low myocardial K(ATP) channel affinity, respectively, at therapeutic concentrations on infarct size, left ventricular (LV) function and myocardial glycogen, lactate and alanine content before and after ischaemia/reperfusion (I/R).

METHODS

Non-diabetic Wistar and diabetic Goto-Kakizaki rat hearts were investigated in a Langendorff preparation. Gb (0.1 μmol/l) and gc (1.0 μmol/l) were administrated throughout the study. Infarct size was evaluated after 120 min of reperfusion. Myocardial metabolite content was measured before and after ischaemia.

RESULTS

Infarct size was smaller in diabetic hearts than in non-diabetic hearts (0.33 ± 0.03 vs 0.51 ± 0.05, p < 0.05). Gb increased infarct size (0.54 ± 0.04 vs 0.33 ± 0.03, p < 0.05) and reduced post-ischaemic LV developed pressure (60 ± 3 vs 76 ± 3 mmHg, p < 0.05) and coronary flow (4.9 ± 0.5 vs 7.1 ± 0.4 ml min(-1) g(-1), p < 0.05) in gb-treated diabetic rats compared with untreated diabetic rats. On comparing gb-treated diabetic rats with untreated diabetic rats, glycogen content was reduced before (9.1 ± 0.6 vs 13.6 ± 1.0 nmol/mg wet weight, p < 0.01) and after ischaemia (0.9 ± 0.2 vs 1.8 ± 0.2 nmol/mg wet weight, p < 0.05), and lactate (4.8 ± 0.4 vs 3.2 ± 0.3 nmol/mg wet weight, p < 0.01) and alanine (1.38 ± 0.12 vs 0.96 ± 0.09 nmol/mg wet weight, p < 0.05) contents were increased during reperfusion. Gc-treatment of diabetic and non-diabetic rats did not affect any of the measured variables.

CONCLUSIONS/INTERPRETATIONS

Gb, but not gc, exacerbates I/R injury and deteriorates LV function in diabetic hearts. These effects of gb on diabetic hearts may be due to detrimental effects on myocardial carbohydrate metabolism.

Multiple outcomes associated with the use of metformin and sulphonylureas in type 2 diabetes: a population-based cohort study in Italy

OBJECTIVE

To compare the effect of metformin and sulphonylureas on the risks of switching to insulin therapy, hospitalisation for macrovascular disease and all-cause mortality.

METHODS

The 70,437 residents of the Italian Region of Lombardy aged 40 to 90 years who started diabetes treatment with metformin or sulphonylureas during 2001-2003 entered the study and were followed until July 2007. We estimated the effects of the first-line agent, early compliance, and persistence with first-line therapy on the risks of switching to insulin, hospitalisation for macrovascular disease and all-cause mortality, by fitting a multistate model and adjusting for age, gender and selected clinical factors.

RESULTS

Compared with patients who started on metformin, those who started on sulphonylureas were at a higher risk of switching to insulin (adjusted hazard ratio and 95% CI, 1.55; 1.43, 1.68), hospitalisation (1.15; 1.08, 1.21), and death (1.37; 1.26, 1.49). Compared with patients who stayed on sulphonylureas for 3 months or less, those on sulphonylureas for more than 9 months had an adjusted hazard ratio of 1.24 (1.13, 1.35) for switching to insulin and 1.14 (1.05, 1.23) for hospitalisation. The risks of switching to insulin and hospitalisation were both increased among patients who switched from metformin to another oral hypoglycaemic agent or combined initial monotherapy with another agent.

CONCLUSIONS

Our study provides evidence that the risks of switching to insulin, hospitalisation because of macrovascular events and death changes according to the first prescribed oral hypoglycaemic agent, as well as to the early compliance and persistence with such agent.

A novel insulin secretagogue based on a dinucleoside polyphosphate scaffold

Dinucleoside polyphosphates exert their physiological effects via P2 receptors (P2Rs). They are attractive drug candidates, as they offer better stability and specificity compared to nucleotides, the most common P2 receptor ligands. The activation of pancreatic P2Y receptors by nucleotides increases insulin secretion. Therefore, in the current study, dinucleoside polyphosphate analogues (di-(2-MeS)-adenosine-5',5''-P(1),P(4),alpha,beta-methylene-tetraphosphate), 8, (di-(2-MeS)-adenosine-5',5''-P(1),P(4),beta,gamma-methylene-tetraphosphate), 9, and di-(2-MeS)-adenosine-5',5''-P(1),P(3),alpha,beta-methylene triphosphate, 10, were developed as potential insulin secretagogues. Analogues 8 and 9 were found to be agonists of the P2Y(1)R with EC(50) values of 0.42 and 0.46 microM, respectively, whereas analogue 10 had no activity. Analogues 8-10 were found to be completely resistant to hydrolysis by alkaline phosphatase over 3 h at 37 degrees C. Analogue 8 also was found to be 2.5-fold more stable in human blood serum than ATP, with a half-life of 12.1 h. Analogue 8 administration in rats caused a decrease in a blood glucose load from 155 mg/dL to ca. 100 mg/dL and increased blood insulin levels 4-fold as compared to basal levels. In addition, analogue 8 reduced a blood glucose load to normal values (80-110 mg/dL), unlike the commonly prescribed glibenclamide, which reduced glucose levels below normal values (60 mg/dL). These findings suggest that analogue 8 may prove to be an effective and safe treatment for type 2 diabetes.

The influence of improved glycaemic control with chlorpropamide on microvascular reactivity and nitric oxide synthase activity in diabetic rats

Hyperglycaemia is a primary cause of vascular complications in diabetes. A hallmark of these vascular complications is endothelial cell dysfunction, which is partly due to reduced production of nitric oxide. The aim of this study was to verify the influence of improved glycaemic control with chlorpropamide on microvascular reactivity, endothelial nitric oxide synthase (e-NOS) expression, and NOS activity in neonatal streptozotocin-induced diabetic rats (n-STZ). Diabetes was induced by STZ injection into neonates Wistar rats. n-STZ diabetic rats were treated with chlorpropamide (200 mg kg−1, 15 days, by gavage). The changes in mesenteric arteriolar and venular diameters were determined in anaesthetized control and n-STZ diabetic rats, before and after topical application of acetylcholine, bradykinin and sodium nitroprusside (SNP). We also assessed e-NOS expression (using polymerase chain reaction after reverse transcription of mRNAs into cDNAs) and NOS activity (conversion of L-arginine to citrulline) in the mesenteric vascular bed of chlorpropamide-treated n-STZ, vehicle-treated n-STZ, and control rats. In n-STZ, chlorpropamide treatment reduced high glycaemic levels, improved glucose tolerance and homoeostatic model assessment (HOMA-beta), and restored NOS activity. Impaired vasodilator responses of arterioles and venules to acetylcholine, bradykinin and SNP were partially corrected by chlorpropamide treatment in n-STZ. We concluded that improved metabolic control and restored NOS activity might be collaborating with improved microvascular reactivity found in chlorpropamide-treated n-STZ.

The effect of sulphonylureas on the microvascular and macrovascular complications of diabetes

INTRODUCTION

Type 2 diabetes mellitus is a chronic progressive disease that is characterised by hyperglycaemia and is associated with an increased risk of the development of microvascular complications, such as retinopathy, nephropathy and neuropathy, and cardiovascular disease. With the introduction of newer oral hypoglycaemic agents, there is a need to re-evaluate critically the effectiveness and safety of the older agents, including sulphonylureas, to assess their place in the modern management of type 2 diabetes.

BACKGROUND

Though no clear benefit of sulphonylureas has been shown with respect to large vessel disease, long term studies have, however, shown benefits in patients with microvascular complications. Studies such as the University Group Diabetes Project raised concerns about the safety profile of sulphonylureas, but large prospective studies such as the UK Prospective Diabetes Study have helped to assuage such concerns to a large degree. Their utility in the peri-infarct period continues to be debatable because of the potential effect on cardiac pre-conditioning.

CONCLUSION

Though sulphonylureas continue to be a mainstay of treatment in type 2 diabetes, future clinical trials addressing clinically relevant outcomes are indicated with the newer generation of sulphonylureas that are more beta cell-specific to address the concerns raised about sulphonylureas and cardiac myocytes.

Human ether-a-go-go-related (HERG) gene and ATP-sensitive potassium channels as targets for adverse drug effects

Torsades de pointes (TdP) arrhythmia is a potentially fatal form of ventricular arrhythmia that occurs under conditions where cardiac repolarization is delayed (as indicated by prolonged QT intervals from electrocardiographic recordings). A likely mechanism for QT interval prolongation and TdP arrhythmias is blockade of the rapid component of the cardiac delayed rectifier K+ current (IKr), which is encoded by human ether-a-go-go-related gene (HERG). Over 100 non-cardiovascular drugs have the potential to induce QT interval prolongations in the electrocardiogram (ECG) or TdP arrhythmias. The binding site of most HERG channel blockers is located inside the central cavity of the channel. An evaluation of possible effects on HERG channels during the development of novel drugs is recommended by international guidelines. During cardiac ischaemia activation of ATP-sensitive K+ (KATP) channels contributes to action potential (AP) shortening which is either cardiotoxic by inducing re-entrant ventricular arrhythmias or cardioprotective by inducing energy-sparing effects or ischaemic preconditioning (IPC). KATP channels are formed by an inward-rectifier K+ channel (Kir6.0) and a sulfonylurea receptor (SUR) subunit: Kir6.2 and SUR2A in cardiac myocytes, Kir6.2 and SUR1 in pancreatic beta-cells. Sulfonylureas and glinides stimulate insulin secretion via blockade of the pancreatic beta-cell KATP channel. Clinical studies about cardiotoxic effects of sulfonylureas are contradictory. Sulfonylureas and glinides differ in their selectivity for pancreatic over cardiovascular KATP channels, being either selective (tolbutamide, glibenclamide) or non-selective (repaglinide). The possibility exists that non-selective KATP channel inhibitors might have cardiovascular side effects. Blockers of the pore-forming Kir6.2 subunit are insulin secretagogues and might have cardioprotective or cardiotoxic effects during cardiac ischaemia.

Risk of mortality and adverse cardiovascular outcomes in type 2 diabetes: a comparison of patients treated with sulfonylureas and metformin

AIMS/HYPOTHESIS

The aim of this study was to evaluate the risk of adverse cardiovascular outcomes in patients with type 2 diabetes newly treated with sulfonylureas and metformin.

SUBJECTS AND METHODS

The Diabetes Audit and Research in Tayside Scotland (DARTS) diabetes information system and the Medicines Monitoring Unit (MEMO) dispensed prescribing database for the population of Tayside, Scotland (400,000 people) were employed. Patients newly prescribed with oral hypoglycaemic agents between 1994 and 2001 were classified into five study cohorts according to the treatment received: metformin only, sulfonylureas only, sulfonylureas added to metformin, metformin added to sulfonylureas, and both drugs simultaneously. In Cox regression analyses, we estimated relative risks for all-cause mortality, cardiovascular mortality and cardiovascular hospital admission for patients in the five study cohorts, with metformin monotherapy as the reference group.

RESULTS

Of the 5,730 study patients, 1,000 died during a maximum of 8 years follow-up. Patients in the sulfonylureas only cohort had increased risks of mortality and cardiovascular mortality, with unadjusted relative risks of 3.12 (95% CI 2.54-3.84) and 3.71 (95% CI 2.64-5.22), respectively. After adjusting for differences between groups (age, sex, duration of diabetes, blood pressure, cholesterol, HbA(1c), smoking, previous hospital admission, treatment with cardiovascular medication), these relative risks were 1.43 (95% CI 1.15-1.77) and 1.70 (95% CI 1.18-2.45), respectively. Patients in the combination cohorts had significantly increased risks of cardiovascular hospital admission, as well as increased risks of mortality and cardiovascular mortality.

CONCLUSIONS/INTERPRETATION

In this cohort study of patients newly treated with oral hypoglycaemic agents, those treated with sulfonylureas only, or combinations of sulfonylureas and metformin, were at higher risk of adverse cardiovascular outcomes than those treated with metformin alone.

Dose-response relation between sulfonylurea drugs and mortality in type 2 diabetes mellitus: a population-based cohort study

BACKGROUND

Over the past 30 years, the relation between use of sulfonylureas to treat type 2 diabetes and the risk of cardiovascular events has been vigorously debated. The purpose of this study was to determine if the risk of death changes with level of exposure to sulfonylurea drugs.

METHODS

This was a retrospective, inception cohort study using administrative data from Saskatchewan Health (1991-1999). The 5795 subjects, identified by their first-ever dispensation for an oral antidiabetic agent, were grouped according to their use of such agents during follow-up. Potential subjects using insulin or combination therapy were excluded. Exposure level was defined by daily dose and degree of adherence. Separate multivariate Cox proportional-hazard models were constructed for each monotherapy group and used to calculate the risk of death associated with higher versus lower exposure category. Disease severity indicators were identified among the administrative data and entered as covariates in each model. The main outcomes were all-cause mortality and death from an acute ischemic event.

RESULTS

The mean age of the cohort members was 66.3 (standard deviation [SD] 13.4) years; 43.4% were female; and their mean duration of follow-up was 4.6 (SD 2.1) years. First-generation sulfonylureas were used exclusively by 120 subjects; glyburide, by 4138; and metformin, by 1537. A greater risk of death was associated with higher daily doses of the first-generation sulfonylureas (adjusted hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.0-4.7) and glyburide (HR 1.3, 95% CI 1.2-1.4), but not metformin (HR 0.8, 95% CI 0.7-1.1). Similar associations were observed for death caused by an acute ischemic event.

INTERPRETATION

Higher exposure to sulfonylureas was associated with increased mortality among patients newly treated for type 2 diabetes. The same relation was not observed with metformin. This implies that the manner in which blood glucose concentration is lowered may be as important as achieving recommended glucose targets.

Improved clinical outcomes associated with metformin in patients with diabetes and heart failure

OBJECTIVE

Metformin is considered contraindicated in patients with heart failure because of concerns over lactic acidosis, despite increasing evidence of potential benefit. The aim of this study was to evaluate the association between metformin and clinical outcomes in patients with heart failure and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Using the Saskatchewan Health databases, 12,272 new users of oral antidiabetic agents were identified between the years 1991 and 1996. Subjects with incident heart failure (n = 1,833) were identified through administrative records based on ICD-9 code 428 and grouped according to antidiabetic therapy: metformin monotherapy (n = 208), sulfonylurea monotherapy (n = 773), or combination therapy (n = 852). Multivariate Cox proportional hazards models were used to assess differences in all-cause mortality, all-cause hospitalization, and the combination (i.e., all-cause hospitalization or mortality).

RESULTS

Average age of subjects was 72 years, 57% were male, and average follow-up was 2.5 +/- 2.0 (SD) years. Compared with sulfonylurea therapy, fewer deaths occurred in subjects receiving metformin: 404 (52%) for sulfonylurea monotherapy versus 69 (33%) for metformin monotherapy (hazard ratio [HR] 0.70 [95% CI 0.54-0.91]) and 263 (31%) for combination therapy (0.61 [0.52-0.72]). A reduction in deaths or hospitalizations was also observed: 658 (85%) for sulfonylurea monotherapy versus 160 (77%) for metformin monotherapy (0.83 [0.70-0.99]) and 681 (80%) for combination therapy (0.86 [0.77-0.96]). There was no difference in time to first hospitalization between study groups.

CONCLUSIONS

Metformin, alone or in combination, in subjects with heart failure and type 2 diabetes was associated with lower morbidity and mortality compared with sulfonylurea monotherapy.

IRIS II study: intact proinsulin is confirmed as a highly specific indicator for insulin resistance in a large cross-sectional study design

BACKGROUND

The cross-sectional IRIS-II study tried to assess the prevalence of insulin resistance and macrovascular disease in orally treated patients with Type 2 diabetes.

METHODS

In total, 4,270 patients were enrolled into the study (2,146 male, 2,124 female; mean +/- SD age 63.9 +/- 11.1 years; body mass index 30.1 +/- 5.5 kg/m2; duration of disease 5.4 +/- 5.6 years; hemoglobin A1c 6.8 +/- 1.3%). The study consisted of a single morning visit with completion of a standardized questionnaire and collection of a fasting blood sample.

RESULTS

The mean intact proinsulin value was 11.4 +/- 12.4 pmol/L (normal range < 10 pmol/L). Homeostasis model assessment resulted in 1,147 insulin-sensitive patients (26.9%) and 3,123 patients (73.1%) with insulin resistance. Of the latter patients 1,465 (34.3% of all patients) had also elevated intact proinsulin values, while 1,658 (38.8%) had no proinsulin elevation. In contrast, 1,042 (24.4%) of the insulin-sensitive patients had normal intact proinsulin, and only 105 (2.4%) had elevated intact proinsulin concentrations (chi2 test P < 0.0001). A specificity of 93.2% (sensitivity 46.9%) was calculated for elevated intact proinsulin as an indirect marker for insulin resistance. Of the 1,451 patients treated with sulfonylurea 52% had elevated intact proinsulin values and increased prevalence of cardiovascular complications (odds ratio 1.45).

CONCLUSION

Type 2 patients with elevated fasting intact proinsulin values can be regarded as being insulin resistant. The results confirm that fasting intact proinsulin is a suitable measure for beta-cell dysfunction and insulin resistance in type 2 diabetes and may be used to support therapeutic decisions.

In vivo antidiabetic drug discovery

All of the glucose-lowering agents available today for the treatment of diabetes resulted from the in vivo antidiabetic drug discovery approach. This is not surprising given the limited understanding of the biochemical basis of diabetes. With new developments in the elucidation of the biochemistry and physiology of diabetes, along with the ever-increasing number of drug discovery technologies, screening tests have shifted from in vivo to in vitro and from a cellular to a molecular level. However, there are concerns with this shift because diabetes, especially type 2 diabetes, has multiple and independent molecular defects and most of the molecular targets currently used await clinical validation. One approach (employed by Shaman) has used focused in vivo screening and has been successful in avoiding or minimising the drawbacks of in vivo testing, while maintaining the benefits. It is hoped that the combined use of in vivo and in vitro approaches will generate new breakthroughs in diabetes.

Antihyperglycemic effects of stevioside in type 2 diabetic subjects

Stevioside is present in the plant Stevia rebaudiana Bertoni (SrB). Extracts of SrB have been used for the treatment of diabetes in, for example, Brazil, although a positive effect on glucose metabolism has not been unequivocally demonstrated. We studied the acute effects of stevioside in type 2 diabetic patients. We hypothesize that supplementation with stevioside to a test meal causes a reduction in postprandial blood glucose. Twelve type 2 diabetic patients were included in an acute, paired cross-over study. A standard test meal was supplemented with either 1 g of stevioside or 1 g of maize starch (control). Blood samples were drawn at 30 minutes before and for 240 minutes after ingestion of the test meal. Compared to control, stevioside reduced the incremental area under the glucose response curve by 18% (P =.013). The insulinogenic index (AUC(i,insulin)/AUC(i,glucose)) was increased by approximately 40% by stevioside compared to control (P <.001). Stevioside tended to decrease glucagon levels, while it did not significantly alter the area under the insulin, glucagon-like peptide 1, and glucose-dependent insulinotropic polypeptide curves. In conclusion, stevioside reduces postprandial blood glucose levels in type 2 diabetic patients, indicating beneficial effects on the glucose metabolism. Stevioside may be advantageous in the treatment of type 2 diabetes.

Diabetes mellitus and pharmacological therapy

Diabetes mellitus can be a devastating lifelong disease if not treated appropriately. The physician and the patient should be aware of both extremes involved with DM: hyperglycemia and hypoglycemia. Patient education and preventive care are perhaps more important in this disease than many others. A multidisciplinary approach involving the patient, physician, and diabetic educator is best to assure a better quality of life. Enormous advances in the treatment of diabetes have occurred over the past decade and even greater ones can be expected in the future. New drugs, insulin delivery devices, and noninvasive glucose monitoring machines have the potential to normalize blood sugar levels and return diabetics to a near normal lifespan without complications.

Antidiabetic effect of chronic administration of JTT-608, a new hypoglycemic agent, in diabetic Goto-Kakizaki rats

We investigated the chronic effect of a new antidiabetic agent, trans-4-(methylcyclohexyl)-4-oxobutyric acid (JTT-608), in Goto-Kakizaki rats, a genetic model of non-obese type II diabetes mellitus. The rats were fed a liquid meal, three times a day, for 12 weeks. The rats were treated orally with JTT-608 (10-100 mg/kg) 10 min before each meal. Fasting blood glucose, triglyceride and hemoglobin A1c levels were reduced by JTT-608 at all dose levels during the experimental period. Blood glucagon-like peptide-1 level with 100 mg/kg JTT-608 increased at the end of the treatment period. JTT-608 (30-100 mg/kg) reduced urinary protein levels after administration for 5-12 weeks. In Goto-Kakizaki rats showing slight diabetic renal lesions, pathological examination revealed that JTT-608 reduced the incidence of vacuolation in renal tubules. JTT-608 (30-100 mg/kg) ameliorated the reduced motor nerve conduction velocities observed in the Goto-Kakizaki rats after administration for 12 weeks. We conclude that chronic administration of JTT-608 produces good blood glucose control and gradually arrests the development of diabetic neuropathy and nephropathy.

Sulfonylureas and cardiovascular effects: from experimental data to clinical use. Available data in humans and clinical applications

OBJECTIVES

33 years after the UGDP study, the question of deleterious effects of the sulfoylurea (SU) is still raised. We have made a systematic review of the literature from experimental studies to clinical and epidemiological studies.

RESULTS

The main molecule studied is glibenclamide (GB). In vitro and in animal studies, GB is both deleterious for ischemic preconditionning (IPC) and protective for arrhythmia during acute ischemia. Glimepiride (GM) and gliclazide (GCZ) do not seem to have effect on IPC. These effects have been few studied in diabetic animals. In human, according to the investigations used, the GB seems nil or suppressing for IPC, it seems elsewhere decreases ventricular arrhythmias during periods of acute ischemia. It is possible that these two actions account for the non-appearance of concordant deleterious effects between short and long-term studies. With regards to other drugs, only the GM has been specifically studied in human and appears to be nil on IPC. The only prospective clinical study available, although not having for objective to answer to this question, is the UKPDS study. This trial demonstrates the absence of deleterious cardiac effects of GB compared to chlorpropamide and particularly compared to insulin.

CONCLUSION

In conclusion, in experimental studies the cardiac effects of SU differ: both deleterious and protective for GB, nil for GM and GCZ on IPC. In all cases the clinical consequences seems to be nil.

Decreased mortality associated with the use of metformin compared with sulfonylurea monotherapy in type 2 diabetes

OBJECTIVE

The aim of this study was to examine the relationship between use of metformin and sulfonylurea and mortality in new users of these agents.

RESEARCH DESIGN AND METHODS

Saskatchewan Health databases were used to examine population-based mortality rates for new users of oral antidiabetic agents. Individuals with prescriptions for sulfonylurea or metformin in 1991-1996 and no use in the year prior were identified as new users. Prescription records were prospectively followed for 1-9 years; subjects with any insulin use were excluded. Causes of death were identified based on ICD-9 codes in an electronic vital statistics database. Multivariate logistic regression and survival analyses were used to assess the differences in mortality between drug cohorts, after adjusting for potential confounding variables.

RESULTS

The total study sample comprised 12,272 new users of oral antidiabetic agents; the average length of follow-up was 5.1 (SD 2.2) years. In subjects with at least 1 year of drug exposure and no insulin use, mortality rates were 750/3,033 (24.7%) for those receiving sulfonylurea monotherapy, 159/1,150 (13.8%) for those receiving metformin monotherapy, and 635/4,683 (13.6%) for those receiving combination therapy over an average 5.1 (SD 2.2) years of follow-up. The adjusted odds ratio (OR) for all-cause mortality for metformin monotherapy was 0.60 (95% CI 0.49-0.74) compared with sulfonylurea monotherapy. Sulfonylurea plus metformin combination therapy was also associated with reduced all-cause mortality (OR 0.66, 95% CI 0.58-0.75). Reduced cardiovascular-related mortality rates were also observed in metformin users compared with sulfonylurea monotherapy users.

CONCLUSIONS

Metformin therapy, alone or in combination with sulfonylurea, was associated with reduced all-cause and cardiovascular mortality compared with sulfonylurea monotherapy among new users of these agents.

[Treatment of diabetes mellitus: general goals, and clinical practice management]

Diabetes mellitus is associated with a marked increased of cardiovascular events. The treatment strategy of diabetes has to be based on the knowledge of its pathophysiology. Thus, insulin is essential for treatment of type 1 diabetic patients because there is a defect in insulin secretion. However, treatment of type 2 diabetic patients is more complex because a defect in both insulin secretion and insulin action exists. Therefore, the treatment selection will depend on the stage of the disease and the individual characteristics of the patient. This article examines the general goals of the treatment and reviews the management of type 2 diabetes.

Type 2 diabetes therapy. A pathophysiologically based approach

The dramatic increase in the number of classes of oral antidiabetic agents has provided physicians with more tools to help patients manage type 2 diabetes. Of course, glycemic control must remain paramount when choosing an oral agent. However, the mechanism of action of an agent, its side effect profile, and the potential for various nonglycemic benefits may help determine which is the best drug for an individual patient.

Cardioselectivity of the sulphonylurea HMR 1098: studies on native and recombinant cardiac and pancreatic K(ATP) channels

In this study we investigated the effects of the putative cardioselective sulphonylurea derivative HMR 1098 on ATP-sensitive potassium (K(ATP)) channels from cardiac ventricular myocytes, the INS-1 beta-cell line and from recombinant K(ATP) channels composed of SUR2A/Kir6.2, SUR1/Kir6.2, SUR1/Kir6.1 an Kir6.2,DeltaC26. Recombinant channels were expressed in tsA201 or COS-1 cells. The effects of HMR 1098 on single channel and whole-cell currents were recorded using the patch-clamp technique. At the single channel level, using excised inside-out membrane patches, HMR 1098 inhibited K(ATP) channels from ventricular cells and INS-1 cells with IC(50)s of 0.88 and 720 microM respectively. Similar results to those in cardiac cells were obtained using recombinant SUR2A/Kir6.2 K(ATP) channels. HMR 1098 inhibition of SUR2A/Kir6.2 K(ATP) channels was unaffected by the presence of internal ADP. In whole-cell recordings, HMR 1098 inhibited SUR2A/Kir6.2 and SUR1/Kir6.2 currents with IC(50)s of 2.1 and 860 microM respectively. HMR 1098 was without effect on currents either from the Kir6.2,DeltaC26 truncation mutant or from Kir2.1. Our results demonstrate that HMR 1098 is a selective inhibitor of cardiac K(ATP) channels, showing a 400 - 800-fold selectivity over beta-cell K(ATP) channels. The non-aromatic substitutions in the sulphonylurea moiety greatly increase the cardioselectivity of this compound while reducing the overall blocking potency of this sulphonylurea derivative.

Absence of exacerbation of myocardial stunning in anesthetized dogs treated with KAD-1229, a novel hypoglycemic agent

The effect of (+)-momocalcium bis[(2S,3a,7a-cis)-alpha-benzylhexahydro-gamma-oxo-2-isoindolinebutyrate]dihydrate (KAD-1229), a novel hypoglycemic agent with a chemical structure different from that of the sulfonylureas, on myocardial stunning was assessed in anesthetized dogs by comparison with that of glibenclamide, a sulfonylurea. Even though their hypoglycemic effects were of similar magnitude, glibenclamide (1 mg/kg, i.v.), but not KAD-1229, exacerbated the myocardial stunning induced by occlusion/reperfusion of the descending coronary artery. In a receptor-binding experiment, unlabeled glibenclamide completely inhibited [(3)H]glibenclamide binding to the myocardium, but KAD-1229 did not. These results suggest that the difference in binding properties of KAD-1229 and glibenclamide toward cardiac sulfonylurea receptors is one of the causes of their different effects on myocardial stunning. It is likely that KAD-1229 is highly specific for pancreatic sulfonylurea receptors and is speculated to be a safer hypoglycemic agent than, at least, glibenclamide.

Sulfonylurea treatment of type 2 diabetic patients does not reduce the vasodilator response to ischemia

OBJECTIVE

Sulfonylureas block the activation of vascular potassium-dependent ATP channels and impair the vasodilating response to ischcmia in nondiabetic individuals, but it is not know whether this occurs in type 2 diabetic patients under chronic treatment with these drugs. Glimepiride, a new sulfonylurea, apparently has no cardiovascular interactions. The aim of our study was to compare the effect of the widely used compound glibenclamide, the pancreas-specific glimepiride, and diet treatment alone on brachial artery response to acute forearm ischemia.

RESEARCH DESIGN AND METHODS

Brachial artery examination was performed by a high-resolution ultrasound technique on 20 type 2 diabetic patients aged mean +/- SD) 67 +/- 2 years and on 18 nondiabetic patients matched for age, hypertension, and dislipidemia. Diabetic subjects underwent three separate evaluations at the end of each 8-week treatment period, during which they received glibenclamide, glimepiride, or diet alone according to crossover design. Scans were obtained before and after 4.5 min of forearm ischemia. Postischemic vasodilation and hyperemia were expressed as percent variations in vessel diameter and blood flow.

RESULTS

Postischemic vasodilation and hyperemia were, respectively, 5.42 +/- 0.90 and 331 +/- 38% during glibenclamide, 5.46 +/- 0.69 and 326 +/- 28% during glimepiride, and 5.17 +/- 0.64 and 357 +/- 35% during diet treatment (NS). These results were similar to those found in the nondiabetic patients (6.44 +/- 0.68 and 406 +/- 42%, NS).

CONCLUSIONS

In type 2 diabetic patients, the vasodilating response to forearm ischemia was the same whether patients were treated with diet treatment alone or with glibenclamide or glimepiride at blood glucose-lowering equipotent closes.

Diastolic dysfunction in normotensive men with well-controlled type 2 diabetes: importance of maneuvers in echocardiographic screening for preclinical diabetic cardiomyopathy

OBJECTIVE

Because a pseudonormal pattern of ventricular filling has never been considered in studies that reported a prevalence of left ventricular diastolic dysfunction (LVDD) between 20 and 40%, our aim was to more completely evaluate the prevalence of LVDD in subjects with diabetes.

RESEARCH DESIGN AND METHODS

We studied 46 men with type 2 diabetes who were aged 38-67 years; without evidence of diabetic complications, hypertension, coronary artery disease, congestive heart failure, or thyroid or overt renal disease; and with a maximal treadmill exercise test showing no ischemia. LVDD was evaluated by Doppler echocardiography, which included the use of the Valsalva maneuver and pulmonary venous recordings to unmask a pseudonormal pattern of left ventricular filling.

RESULTS

LVDD was found in 28 subjects (60%), of whom 13 (28%) had a pseudonormal pattern of ventricular filling and 15 (32%) had impaired relaxation. Systolic function was normal in all subjects, and there was no correlation between LVDD and indexes of metabolic control.

CONCLUSIONS

LVDD is much more common than previously reported in subjects with well-controlled type 2 diabetes who are free of clinically detectable heart disease. The high prevalence of this phenomenon in this high-risk population suggests that screening for LVDD in type 2 diabetes should include procedures such as the Valsalva maneuver and pulmonary venous recordings to unmask a pseudonormal pattern of ventricular filling.

Oxidative stress increases potassium efflux from pancreatic islets by depletion of intracellular calcium stores

Oxidative stress to B-cells is thought to be of relevance in declining B-cell function and in the process of B-cell destruction. In other tissues including heart, brain and liver, oxidative stress has been shown to elevate the intracellular free calcium concentration and to provoke potassium efflux. We studied the effect of oxidative stress on Ca2+ and K+ (Rb+) outflow from pancreatic islets using the thiol oxidants DIP and BuOOH. Both compounds reversibly increased 86Rb+ efflux in the presence of 3 and 16.7 mmol/l glucose. Stimulation of 86Rb+ efflux was also evident in the absence of calcium. DIP evoked release of 45Ca2+ from the pancreatic islets both in the presence or absence of extracellular calcium. Employing inhibitors of the calcium-activated potassium channel (KCa) and the high conductance K+-channel (BKCa), the effect of DIP on 86Rb+ efflux was slightly diminished. Tolbutamide had no effect on 86Rb+ efflux in the presence of DIP. On the other hand thapsigargin, a blocker of the Ca+-ATPase of the endoplasmic reticulum, completely suppressed the DIP-mediated 86Rb+ outflow. The data suggest that thiol oxidant-induced potassium efflux from pancreatic islets is mainly mediated through liberation of intracellular calcium and subsequent stimulation of calcium-activated potassium efflux.

Gliclazide modified release: its place in the therapeutic armamentarium

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

Pharmacotherapy of type 2 diabetes mellitus

OBJECTIVE

To review the drug treatments and some of the popular, nontraditional remedies now available for type 2 diabetes mellitus, as well as selected investigational agents; to describe each medication's place in the overall approach to treatment.

DATA SOURCES

English-language journals, abstracts, review articles, and newspaper accounts.

DATA SYNTHESIS

In the past five years, there has been tremendous progress in the pharmacotherapy of diabetes, particularly type 2 diabetes. Several new agents have entered the clinical arena, and many more are in the late stages of investigation leading to approval. Sulfonylureas stimulate the production and release of insulin; these drugs must be used in patients with an intact pancreas. The meglitinides are nonsulfonylurea agents that are also insulin secretagogues. Unlike the sulfonylureas, repaglinide appears to require the presence of glucose to close the adenosine triphosphate-sensitive potassium channels and induce calcium influx. Metformin reduces hepatic glucose production in some patients and increases peripheral glucose utilization, but its use is hampered by a high percentage of adverse reactions. Disaccharidase inhibitors effectively compensate for the defective early-phase insulin release by slowing the production of sugars from carbohydrates. Thiazolidinediones appear to activate peroxisome proliferator-activated receptor gamma, which is involved in the metabolism of lipids. Short-acting insulin and the role of weight-loss agents are also discussed.

CONCLUSIONS

The availability of new options for diabetes therapy provides a chance for successful therapy in a larger number of patients. However, it is important to consider how much true benefit these new forms of treatment will have on the diabetic community. The best choice for a patient remains controversial.

Comparative tolerability of sulphonylureas in diabetes mellitus

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

Chlorpropamide toxicity with survival despite 27-day hypoglycemia

CASE REPORT

In the past 5 years at our institution, 12 cases involving the ingestion of chlorpropamide 3-15 g were fatal. We report a 23-year-old woman with an estimated ingestion of chlorpropamide 5-10 g. Initial cardiovascular collapse, attributed to the blockade of potassium channel transport, responded to intensive support including 3 days of cardiac pacing. Urinary excretion of chlorpropamide and hypoglycemia persisted until day 27. The toxic mechanisms and high risk of chlorpropamide are summarized. A fatal therapeutic dose ratio as low as 4:1 has made this antidiabetic agent obsolete.

Lactic acidosis in metformin therapy

The biguanide drugs metformin and phenformin have been linked in the past to lactic acidosis, a metabolic condition associated with high rates of mortality. Although concern over the hyperlactataemic effect of phenformin led to the withdrawal of this drug from clinical practice in the 1970s, the situation with metformin has been less clear. Retrospective data indicate that, in metformin-treated patients with lactic acidosis, neither the degree of hyperlactataemia nor accumulation of metformin is of prognostic significance. Furthermore, the lowest rates of mortality were seen in patients with high plasma concentrations of metformin, which has led to the hypothesis that the drug may confer some benefit, linked to an increase in vasomotility, in such cases. Overall, it appears that mortality in patients receiving metformin who develop lactic acidosis is linked to underlying disease rather than to metformin accumulation, and that metformin can no longer be considered a toxic drug in this respect. These findings are likely to be of considerable relevance to the management of patients with type 2 (non-insulin-dependent) diabetes mellitus, especially where such patients are elderly.

The effects of tolbutamide on lipoproteins, lipoprotein lipase and hormone-sensitive lipase

Type 2 diabetic patients are at increased risk to develop atherosclerotic vascular disease. These patients are often treated with sulphonylurea derivatives, and it has been suggested that this treatment might contribute to the increased atherosclerotic process. The aim of the present study was therefore to investigate whether tolbutamide influences lipid metabolism in such a way that the atherosclerotic process may be promoted. Addition of tolbutamide (5-500 mg/l) to isolated rat fat adipocytes inhibited the lipoprotein lipase (LPL) activity in a dose-dependent manner to levels about 50% of those registered in the absence of tolbutamide. This effect was due to inhibition of the activation of the enzyme in the tissue and not to interference with the interaction of enzyme with its substrate. Addition of tolbutamide (500 mg/l) also inhibited noradrenaline (100 nM) and isoprenaline (40 nM)-induced lipolysis by 48.1 +/- 7.4% (mean +/- S.E.M.) and 47.3 +/- 5.5%, respectively. The decreased lipolysis in tolbutamide preincubated adipocytes was shown to be the result of an inhibition of the phosphorylation of hormone sensitive lipase (HSL). Three months of tolbutamide treatment (0.5 g t.i.d.) in diet treated type 2 diabetic patients did not influence the plasma concentrations of cholesterol, triglycerides, LDL cholesterol, HDL cholesterol as well as HDL triglycerides and HDL phospholipids, and there were no differences compared to placebo treated patients. There was a tendency towards a decrement in the elimination rate of exogenous triglycerides in the tolbutamide group (P = 0.0801). No differences between the groups and no treatment effects were seen on LPL and hepatic lipase activities. In conclusion, our in vitro data show that tolbutamide has dual effects on lipid transport, with impairment of the LPL system, which would tend to decrease plasma lipoproteins by reducing hepatic production of lipoproteins. In vivo, these two effects seem to balance each other and plasma lipoprotein levels remain unaffected.

Pharmacologic therapy for type 2 diabetes mellitus

Type 2 diabetes mellitus is a chronic metabolic disorder that results from defects in both insulin secretion and insulin action. An elevated rate of basal hepatic glucose production in the presence of hyperinsulinemia is the primary cause of fasting hyperglycemia; after a meal, impaired suppression of hepatic glucose production by insulin and decreased insulin-mediated glucose uptake by muscle contribute almost equally to postprandial hyperglycemia. In the United States, five classes of oral agents, each of which works through a different mechanism of action, are currently available to improve glycemic control in patients with type 2 diabetes. The recently completed United Kingdom Prospective Diabetes Study (UKPDS) has shown that type 2 diabetes mellitus is a progressive disorder that can be treated initially with oral agent monotherapy but will eventually require the addition of other oral agents, and that in many patients, insulin therapy will be needed to achieve targeted glycemic levels. In the UKPDS, improved glycemic control, irrespective of the agent used (sulfonylureas, metformin, or insulin), decreased the incidence of microvascular complications (retinopathy, neuropathy, and nephropathy). This review examines the goals of antihyperglycemic therapy and reviews the mechanism of action, efficacy, nonglycemic benefits, cost, and safety profile of each of the five approved classes of oral agents. A rationale for the use of these oral agents as monotherapy, in combination with each other, and in combination with insulin is provided.

[Present status in the treatment of type 2 diabetes mellitus. Insulin-secreting agents]

The functional defect of the pancreatic beta cell represents one of the main therapeutic targets in type 2 diabetes mellitus. Among the currently available oral antidiabetic drugs, only hypoglycaemic sulfonylureas exhibit beta cell stimulating properties. However, their use has some limits, particularly those related to the risk of hypoglycaemia and the frequent secondary therapeutic failure. These drugs have largely contributed to the knowledge of the mechanisms of insulin secretion. Besides some galenic modifications of existing sulfonylureas and the development of new drugs of this family with original properties, like glimepiride, the research is essentially focused on drugs derived from the non sulfonylurea moiety of some sulfonylureas, particularly the meglitinide family, which will probably be available for the clinician in the near future. These drugs act however grossly by the same mechanism than sulfonylureas, even if their binding site on a protein coupled with the ATP sensitive K channel appears different. Among the other possible approaches suggested by the theoretical data concerning the mechanisms of insulin secretion, GLP-1 derivatives probably represent good candidates, if stable analogues are developed.

Characterization of low-affinity binding sites for glibenclamide on the Kir6.2 subunit of the beta-cell KATP channel

The ATP-sensitive K+ channel, an octameric complex of two structurally unrelated types of subunits, SUR1 and Kir6.2, plays a central role in the physiological regulation of insulin secretion. The sulfonylurea glibenclamide, which trigger insulin secretion by blocking the ATP-sensitive K+ channel, interacts with both high and low affinity binding sites present on beta-cells. The high affinity binding site has been localized on SUR1 but the molecular nature of the low affinity site is still uncertain. In this study, we analyzed the pharmacology of glibenclamide in a transformed COS-7 cell line expressing the rat Kir6.2 cDNA and compared with that of the MIN6 beta cell line expressing natively both the Kir6.2 and the SUR1 subunits. Binding studies and Scatchard analysis revealed the presence of a single class of low affinity binding sites for glibenclamide on the COS/Kir6.2 cells with characteristics similar to that observed for the low affinity site of the MIN6 beta cells.

Adenosine triphosphate-sensitive potassium channels are involved in insulin-mediated glucose transport in humans

We investigated the influence of treatment with nicorandil, a K-channel opener currently used for angina, on glucose homeostasis in patients with non-insulin-dependent diabetes mellitus (NIDDM) and coronary artery disease (CAD). Adenosine triphosphate (ATP)-sensitive K (K-ATP) channels are present in various tissues, including pancreatic B cells and skeletal muscle, and are the putative targets of this agent. Nine NIDDM patients with CAD and five healthy subjects participated in the study. Fasting plasma levels (mean+/-SEM) of glucose (144+/-11 to 180+/-22 mg/dL, P<.05) and insulin (5.8+/-1.6 to 7.0+/-1.8 microU/mL, P<.05) and hemoglobin A1c (7.54+/-0.47 to 8.11+/-0.55%, P<.01) increased significantly in nine NIDDM patients after treatment with nicorandil at a dose of 5 mg three times daily for 2 to 8 months. Glucose tolerance as examined by an identical meal test deteriorated (P<.001), but the insulin response did not change significantly. A washout of nicorandil for 1 to 4 months restored glucose tolerance almost to pretreatment levels in four patients. A 5- to 7-day trial of nicorandil (5 mg three times daily) in five healthy subjects resulted in a marginal to twofold increase in fasting plasma insulin, reflecting the progression of insulin resistance. In addition, three healthy subjects showed a substantial reduction in the glucose infusion rate (GIR) required in the euglycemic-hyperinsulinemic clamp study. Since the therapeutic dose of nicorandil did not affect pancreatic B-cell function but caused insulin resistance in both healthy and NIDDM subjects, we conclude that K-ATP channels play a regulatory role in insulin-mediated glucose transport in humans.

Improving the adverse cardiovascular prognosis of type 2 diabetes

Approximately 80% of all patients with diabetes die of cardiovascular disease. The traditional management of type 2 diabetes has been ineffective in altering this dismal prognosis. Insulin resistance is the fundamental defect of type 2 diabetes. Insulin resistance often leads to hyperinsulinemia, which is associated with hypertension, atherogenic dyslipidemia, left ventricular hypertrophy, impaired fibrinolysis, visceral obesity, and sedentary lifestyle. Although all these conditions are associated with atherosclerosis and adverse cardiovascular events, the therapeutic efforts in patients with diabetes have focused predominantly on normalizing glucose levels. Improved insulin sensitivity through lifestyle modifications or pharmacologic therapy (troglitazone and metformin) will lower both insulin and glucose levels as well as diminish dyslipidemia and hypertension. In contrast, sulfonylurea agents lower glucose by increasing insulin levels and may increase the risk of cardiovascular events. Therapy including aspirin, lipid agents (for example, statins), angiotensin-converting enzyme inhibitors, beta-adrenergic blockers, postmenopausal estrogen replacement, and vitamin E should be considered for patients with type 2 diabetes. In most patients with diabetes who have multivessel coronary artery disease, coronary artery bypass grafting is superior to coronary angioplasty for improving long-term cardiovascular prognosis. This superiority is mediated in part by the use of a left internal mammary graft to the left anterior descending coronary artery. Urgent coronary angioplasty or thrombolytic therapy should be considered for all patients with diabetes who have acute myocardial infarction.

[Heart pathology of extracardiac origin. XI. Cardiac repercussions of diabetes mellitus]

Diabetes mellitus is one of the diseases with the greatest risk of developing coronary disease (CD), with the estimation of this risk in relation to the general population being from 2 to 4-fold greater. The existence of diabetes worsens the prognosis of CD and thus, postinfarction mortality in these patients is double that observed in non-diabetic patients. Together with the risk factors found in the general population, those of special interest are those derived from diabetes itself, such as hyperglycemia, dyslipemia, coagulation disorders and hyperinsulinemia or insulin resistance. Among these, the most important is probably the hyperglycemia which may contribute to the appearance of CD by different mechanisms such as proteic glycosylation, accumulation of sorbitol, increase in the synthesis of protein kinase C or oxidative stress. It must not be forgotten that an old controversy has recently been brought up suggesting that sulphonylureas may have a certain cardiotoxic effect, probably acting on the potassium channels dependent on ATP. Acute myocardial infarction in diabetic patients carries a greater risk of congestive heart failure, recurrent infarction, arrhythmia and cardiogenic shock, with one of its characteristics being the possibility of being silent when autonomic neuropathy is present. The prognosis of CD may be markedly improved by obtaining optimum glycemic control during the hours following infarction using intensified treatment. Diabetic myocardiopathy as a differentiated nosology responsible for alterations in myocardial contractile function and greater prevalence of heart failure in these patients seems to be clearly demonstrated although its etiology remains unknown.