The impact of pioglitazone on glycemic control and atherogenic dyslipidemia in patients with type 2 diabetes mellitus

Long-term efficacy and tolerability of add-on pioglitazone therapy to failing monotherapy compared with addition of gliclazide or metformin in patients with type 2 diabetes

AIMS/HYPOTHESIS

The aim of this analysis was to examine the long-term effects of pioglitazone or gliclazide addition to failing metformin monotherapy and pioglitazone or metformin addition to failing sulphonylurea monotherapy in patients with type 2 diabetes.

METHODS

Two 2-year, randomised, multicentre trials were performed in patients with inadequately controlled type 2 diabetes (HbA1c 7.5-11% inclusive), who were receiving either metformin or a sulphonylurea at > or = 50% of the maximum recommended dose or at the maximum tolerated dose. In the first study, patients on metformin received add-on therapy with pioglitazone (15-45 mg/day, n = 317) or gliclazide (80-320 mg/day, n = 313). In the second study, patients on sulphonylurea therapy were randomised to receive add-on therapy with either pioglitazone (15-45 mg/day, n = 319) or metformin (850-2,550 mg/day, n = 320). HbA(1)c, fasting plasma glucose, insulin and lipids were investigated.

RESULTS

At week 104, the mean reduction from baseline in HbA(1)c was 0.89% for pioglitazone and 0.77% for gliclazide addition to metformin (p = 0.200). There was a statistically significant between-group difference for the change in mean fasting plasma glucose at week 104 (-1.8 mmol/l for pioglitazone vs -1.1 mmol/l for gliclazide, p < 0.001). There were no significant differences in changes from baseline in glycaemic parameters for pioglitazone compared with metformin addition to sulphonylurea therapy. Whether added to metformin or sulphonylurea, pioglitazone caused significantly greater decreases in triglycerides and significantly greater increases in HDL cholesterol than the comparator regimens (p < or = 0.001). There were decreases in LDL cholesterol in the comparator groups and these were significantly different from the small changes observed with pioglitazone (p < 0.001). All treatment regimens were well tolerated. There were weight increases of 2.5 kg and 3.7 kg in the pioglitazone and 1.2 kg in the gliclazide add-on groups, and there was a mean decrease of 1.7 kg in the metformin add-on group.

CONCLUSIONS/INTERPRETATION

As add-on therapy to existing sulphonylurea or metformin therapy, pioglitazone improved glycaemic control and this improvement was sustained over 2 years. Furthermore, there were potential benefits in terms of improvements in specific lipid abnormalities. This could offer an advantage over the addition of other oral agents in the long-term treatment of diabetes.

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

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

Potential cardiovascular benefits of insulin sensitizers

A multiple risk factor approach is needed in patients who have type 2 diabetes. Because many risk factors are linked with IR, treatment with insulin sensitizers has the potential to modulate these risk factors favorably. TZDs 'have many important effects beyond lowering blood glucose. By targeting IR, they improve many cardiovascular risk factors that are associated with the IR syndrome. In particular, they increase HDL-C, have anti-inflammatory effects, improve endothelial function and fibrinolysis, and decrease carotid intimal thickness; however, no evidence-based studies on cardiovascular outcomes are available to substantiate the potential cardioprotective effects of TZDs. Several clinical trials that were designed to investigate the effect that these agents have on reducing cardiovascular events are well under way.

Peroxisome proliferator-activated receptor ligands in atherosclerosis

In this review, the effect of peroxisome proliferator-activated receptor (PPAR) ligands on atherosclerosis is examined. The PPAR-gamma agonist thiazolidinediones are currently indicated for the management of Type 2 diabetes mellitus, and the PPAR-alpha agonist fibrates are used in dyslipidaemia. Here their mechanism of action and the pre-clinical and clinical evidence for the use of these medications for the prevention and treatment of atherosclerotic disease is explored. In addition, the role of PPAR-delta and the possibilities for the role of dual-binding agonists are examined.

PPAR ligands: potential therapies for metabolic syndrome

Metabolic syndrome (MS), a condition characterized by multiple related clinical disorders including insulin resistance, central obesity, hyperlipidemia, hypertension, and heart disease, is an increasingly prevalent disease in industrialized societies. The intense research interest in the peroxisome proliferator-activated receptors (PPARs), by both the pharmaceutical industry and academia, stems largely from the well-documented therapeutic actions of their synthetic agonists in alleviating several of the maladies associated with MS. This report focuses on the current understanding of the mechanisms of action of PPAR agents and their clinical use in the context of MS.

Pharmacologic treatment of type 2 diabetic dyslipidemia

Patients with diabetes mellitus have a higher risk for cardiovascular heart disease (CHD) than does the general population, and once they develop CHD, mortality is higher. Good glycemic control will reduce CHD only modestly in patients with diabetes. Therefore, reduction in all cardiovascular risks such as dyslipidemia, hypertension, and smoking is warranted. The focus of this article is on therapy for dyslipidemia in patients with type 2 diabetes. Patients with the metabolic syndrome (insulin resistance) share similarities with patients with type 2 diabetes and may have a comparable cardiovascular risk profile. Diabetic patients tend to have higher triglyceride, lower high-density lipoprotein cholesterol (HDL), and similar low-density lipoprotein cholesterol (LDL) levels compared with those levels in nondiabetic patients. However, diabetic patients tend to have a higher concentration of small dense LDL particles, which are associated with higher CHD risk. Current recommendations are for an LDL goal of less than 100 mg/dl (an option of < 70 mg/dl in very high-risk patients), an HDL goal greater than 40 mg/dl for men and greater than 50 mg/dl for women, and a triglyceride goal less than 150 mg/dl. Nonpharmacologic interventions (diet and exercise) are first-line therapies and are used with pharmacologic therapy when necessary. Lowering LDL levels is the first priority in treating diabetic dyslipidemia. Statins are the first drug choice, followed by resins or ezetimibe, then fenofibrate or niacin. If a single agent is inadequate to achieve lipid goals, combinations of the preceding Drugs may be used. For elevated triglyceride levels, hyperglycemia must be controlled first. If triglyceride or HDL levels remain uncontrolled, pharmacologic agents should be considered. Fibrates are slightly more effective than niacin in lowering triglyceride levels, but niacin increases HDL levels appreciably more than do fibrates. Unlike gemfibrozil, niacin selectively increases subfraction Lp A-I, a cardioprotective HDL. Niacin is distinct in that it has a broad spectrum of beneficial effects on lipids and atherogenic lipoprotein subfraction levels. Niacin produces additive results when used in combination therapy. Recent data suggest that lower dosages and newer formulations of niacin can be used safely in diabetic patients with good glycemic control. Current evidence and guidelines mandate that diabetic dyslipidemia be treated aggressively, and lipid goals can be achieved in most patients with diabetes when all available products are considered and, if necessary, used in combination.

The impact of antidiabetic therapies on cardiovascular disease

Cardiovascular disease disproportionately affects people with diabetes and is a leading cause of death. Glycemic control has so far not been conclusively shown to decrease cardiovascular events. The therapeutic agents used in treating glycemia have different effects on cardiovascular risks and, therefore, may have different effects on outcome. Insulin sensitizers impact cardiovascular risk factors, including dyslipidemia and fibrinolysis. Metformin is the only oral antidiabetic medication shown to decrease cardiovascular events independent of glycemic control. Thiazolidinediones improve insulin resistance and lower insulin concentrations, which is beneficial because hyperinsulinemia is an independent predictor of cardiovascular disease. Insulin therapy acutely reduces cardiovascular mortality and morbidity in patients with diabetes and known coronary artery disease and also in patients with hyperglycemia when critically ill, but the long-term effects are unclear. In contrast, insulin secretagogues have very little effect on both cardiovascular risk factors and outcomes.

Thiazolidinediones and Insulin

The range of therapeutic modalities to treat type 2 diabetes mellitus has broadened in recent years. Biguanides and thiazolidinediones are the two currently available classes of anti-hyperglycemic agents with insulin-sensitizing properties. Thiazolidinediones, in particular, have received much attention, not only for the well documented hepatotoxicity of troglitazone that led to its removal from the market in 2000, but also for the emerging data that support the beneficial effects of the thiazolidinedione class of drugs on beta-cell rejuvenation and cardiovascular risk reduction. In the US, thiazolidinediones are indicated either as monotherapy or in combination with a sulfonylurea, metformin, or insulin in cases where diet, exercise, and a single drug fail. In contrast, the UK National Institute for Clinical Excellence included in its re-appraisal of 'glitazones' in August 2003 the continued exclusion from licensed use in the UK of combination therapy with thiazolidinediones and insulin. When added to insulin therapy, thiazolidinediones appear to effectively lower glucose levels and reduce insulin dosage in clinical trials involving individuals with poorly controlled type 2 diabetes. However, weight gain, hypoglycemia, and fluid retention pose problems in certain patients. The fluid retention may exacerbate or even precipitate congestive heart failure, which usually necessitates discontinuation of the drug. Risk stratification and careful management of patients at risk for heart failure, including those taking insulin concomitantly, allow healthcare providers to safely administer combination therapy with thiazolidinediones in patients with type 2 diabetes. Hepatic toxicity with currently available thiazolidinediones has been found to be minimal overall.

Mechanisms, Significance and Treatment of Vascular Dysfunction in Type 2 Diabetes Mellitus

Endothelial dysfunction and increased arterial stiffness occur early in the pathogenesis of diabetic vasculopathy. They are both powerful independent predictors of cardiovascular risk. Advances in non-invasive methodologies have led to widespread clinical investigation of these abnormalities in diabetes mellitus, generating a wealth of new knowledge concerning the mechanisms of vascular dysfunction, risk factor associations and potential treatment targets. Endothelial dysfunction primarily reflects decreased availability of nitric oxide (NO), a critical endothelium-derived vasoactive factor with vasodilatory and anti-atherosclerotic properties. Techniques for assessing endothelial dysfunction include ultrasonographic measurement of flow-mediated vasodilatation of the brachial artery and plethysmography measurement of forearm blood flow responses to vasoactive agents. Arterial stiffness may be assessed using pulse wave analysis to generate measures of pulse wave velocity, arterial compliance and wave reflection. The pathogenesis of endothelial dysfunction in type 2 diabetes is multifactorial, with principal contributors being oxidative stress, dyslipidaemia and hyperglycaemia. Elevated blood glucose levels drive production of reactive oxidant species (ROS) via multiple pathways, resulting in uncoupling of mitochondrial oxidative phosphorylation and endothelial NO synthase (eNOS) activity, reducing NO availability and generating further ROS. Hyperglycaemia also contributes to accelerated arterial stiffening by increasing formation of advanced glycation end-products (AGEs), which alter vessel wall structure and function. Diabetic dyslipidaemia is characterised by accumulation of triglyceride-rich lipoproteins, small dense low-density lipoprotein (LDL) particles, reduced high-density lipoprotein (HDL)-cholesterol and increased postprandial free fatty acid flux. These lipid abnormalities contribute to increasing oxidative stress and may directly inhibit eNOS activity. Although lipid-regulating agents such as HMG-CoA reductase inhibitors (statins), fibric acid derivatives (fibrates) and fish oils are used to treat diabetic dyslipidaemia, their impact on vascular function is less clear. Studies in type 2 diabetes have yielded inconsistent results, but this may reflect sampling variation and the potential over-riding influence of oxidative stress, dysglycaemia and insulin resistance on endothelial dysfunction. Results of positive intervention trials suggest that improvement in vascular function is mediated by both lipid and non-lipid mechanisms, including anti-inflammatory, anti-oxidative and direct effects on the arterial wall. Other treatments, such as renin-angiotensin-aldosterone system antagonists, insulin sensitisers and lifestyle-based interventions, have shown beneficial effects on vascular function in type 2 diabetes. Novel approaches, targeting eNOS and AGEs, are under development, as are new lipid-regulating therapies that more effectively lower LDL-cholesterol and raise HDL-cholesterol. Combination therapy may potentially increase therapeutic efficacy and permit use of lower doses, thereby reducing the risk of adverse drug effects and interactions. Concomitant treatments that specifically target oxidative stress may also improve endothelial dysfunction in diabetes. Vascular function studies can be used to explore the therapeutic potential and mechanisms of action of new and established interventions, and provide useful surrogate measures for cardiovascular endpoints in clinical trials.

Targeting insulin resistance and beta-cell dysfunction: the role of thiazolidinediones

Insulin resistance and beta-cell dysfunction are fundamental defects that contribute to the development of type 2 diabetes, and as such are targets for primary prevention of disease progression. The two parameters are linked by several factors, including glucotoxicity and lipotoxicity, and recent research has enlightened understanding of the molecular mechanisms underlying the development and progression of the disease. Historically, type 2 diabetes has been managed by controlling hyperglycemia, using agents that increase insulin levels or reduce hepatic glucose production, as exemplified by the United Kingdom Prospective Diabetes Study. The thiazolidinediones control hyperglycemia by targeting the fundamental defects of the disease, and have shown well-documented improvements in insulin sensitivity and beta-cell function, both in monotherapy and in combination with other oral antidiabetic agents. TRoglitazone In the Prevention Of Diabetes (TRIPOD) has demonstrated the potential for thiazolidinediones to delay progression to type 2 diabetes. Prospective studies such as Diabetes REduction Approaches with ramipril and rosiglitazone Medications (DREAM) are currently evaluating the long-term effects of thiazolidinediones on metabolic status and disease progression.

Comparison of the effects of pioglitazone and rosiglitazone on macrophage foam cell formation

In order to elucidate the antiatherogenic effects of pioglitazone (a peroxisome proliferator-activated receptor [PPAR]gamma agonist with PPARalpha agonistic activity) and rosiglitazone (a more selective PPARgamma agonist), we examined gene expression and cholesteryl ester accumulation in THP-1-derived macrophages. Pioglitazone enhanced the mRNA expression of the proatherogenic factors CD36 and adipophilin, but was approximately 10 times less potent than rosiglitazone. The potencies of the two agents appeared to correspond to their PPARgamma agonistic activities in this respect. However, both agents were similarly potent in enhancing the mRNA expression of the antiatherogenic factors liver X receptor alpha and ATP-binding cassette-transporter A1. Furthermore, both agents enhanced cholesteryl ester hydrolase mRNA expression and inhibited acyl-CoA cholesterol acyltransferase-1 mRNA expression and cholesteryl ester accumulation in macrophages. In this respect, their potencies appeared to correspond to their PPARalpha agonistic activities. These results suggest that pioglitazone has an equally beneficial effect on antiatherogenic events to rosiglitazone, despite being almost 10 times less potent than a PPARgamma agonist.

Glitazones and the management of insulin resistance: what they do and how might they be used

Thiazolidinediones (glitazones) are the only compounds currently available that specifically target tissue insulin resistance. The two currently available drugs in this class, pioglitazone and rosiglitazone,are approved by the Food and Drug Administration for the treatment of type 2 diabetes mellitus only. The therapeutic potential of the glitazones for other consequences of insulin resistance has stirred considerable interest, especially with regard to their potential beneficial impact on atherosclerotic cardiovascular disease and diabetes prevention. They also have been considered in the management of polycystic ovarian syndrome, nonalcoholic fatty liver disease, and other consequences of insulin resistance. The nonglycemic potential of glitazones is a clinical area in rapid evolution, wherein most data are on the impact of the glitazones onsurrogate markers that are associated with diseases, not on disease outcomes. This article provides insight and guidance to clinicians on the diverse nonglycemic potential of glitazones until conclusive outcome data become available.

Thiazolidinediones and congestive heart failure--exacerbation or new onset of left ventricular dysfunction?

BACKGROUND

Patients with diabetes mellitus have a high incidence of coronary heart disease and congestive heart failure (CHF). Thiazolidinediones (TZD) are a new class of pharmacological agents for the treatment of Type 2 diabetes mellitus, which have many beneficial cardiovascular effects. Peripheral oedema and weight gain have been reported in 4.8% of subjects on TZDs alone, with a higher incidence noted in those receiving combination insulin therapy (up to 15%), but there is limited data on the occurrence of CHF.

METHODS AND RESULTS

In this paper, we report on six cases of TZD-induced fluid retention with symptoms and signs of peripheral oedema and/or CHF that occurred in subjects attending our diabetic clinic. The predominant finding in all cases was of diastolic dysfunction. All subjects were obese and hypertensive, with 5/6 having the additional risk factor of LVH, 5/6 subjects had microvascular complications, whilst 3/6 were also on insulin therapy.

CONCLUSION

We suggest that obese, hypertensive diabetics may benefit from echocardiographic screening prior to commencement of TZDs, as these agents may exacerbate underlying undiagnosed left ventricular diastolic dysfunction.

Sustained effects of pioglitazone vs. glibenclamide on insulin sensitivity, glycaemic control, and lipid profiles in patients with Type 2 diabetes

AIMS

This study compared the effects of 52 weeks' treatment with pioglitazone, a thiazolidinedione that reduces insulin resistance, and glibenclamide, on insulin sensitivity, glycaemic control, and lipids in patients with Type 2 diabetes.

METHODS

Patients with Type 2 diabetes were randomized to receive either pioglitazone (initially 30 mg QD, n = 91) or micronized glibenclamide (initially 1.75 mg QD, n = 109) as monotherapy. Doses were titrated (to 45 mg for pioglitazone and 10.5 mg for glibenclamide) to achieve glycaemic targets during the next 12 weeks: fasting blood glucose of < or = 7 mmol/l and 1-h postprandial blood glucose of < or = 10 mmol/l. Patients were maintained on the titrated dose for 40 weeks.

RESULTS

Pioglitazone significantly increased insulin sensitivity compared with glibenclamide, as assessed by homeostasis model assessment (17.0% vs. -13.0%; P < 0.001), quantitative insulin sensitivity check index (0.011 vs. -0.007; P < 0.001) and fasting serum insulin (-1.3 pmol/l vs. 23.8 pmol/l; P = 0.007). The glibenclamide group had significantly lower HbA1c than the pioglitazone group after 12 weeks of therapy (7.8% vs. 8.3%, P = 0.015), but significantly higher HbA1c after 52 weeks of therapy (7.8% vs. 7.2%, P = 0.001). Pioglitazone significantly (vs. glibenclamide) increased mean HDL-C (P < 0.001), decreased mean triglycerides (P = 0.019), and decreased mean atherogenic index of plasma (AIP; P = 0.001) and mean total cholesterol/HDL-C (P = 0.004), without significantly elevating mean total cholesterol or mean LDL-C compared with glibenclamide. CONCLUSIONS These data suggest that the effects of pioglitazone are more sustained than those of glibenclamide for improving insulin sensitivity in patients with Type 2 diabetes, and that 52 weeks' treatment with pioglitazone has favourable effects on glycaemic control and lipoprotein profile.

Dyslipidemia in type 2 diabetes

Type 2 diabetes mellitus is associated with a cluster of lipid abnormalities:elevated plasma triglycerides, reduced high-density lipoprotein cholesterol, and smaller and denser low-density lipoproteins,which have been associated with an increased risk of cardiovascular disease. Insulin resistance may contribute to dyslipidemia associated with type 2 diabetes by increasing hepatic secretion of large,triglyceride-rich very low-density lipoprotein particles and by impairing the clearance of lipoprotein particles from plasma. Lifestyle interventions may be effective in improving the diabetic dyslipidemia syndrome. For patients who do not respond to lifestyle changes, pharmacologic therapies (lipid-lowering medications and anti-diabetic agents) are available. Clinical trials demonstrate that the use of such pharmaceutics to treat diabetic dyslipidemia concomitantly reduces the risk of coronary artery disease.

Lipids and lipoproteins in patients with type 2 diabetes

Insulin resistance and type 2 diabetes are associated with a clustering of interrelated plasma lipid and lipoprotein abnormalities, which include reduced HDL cholesterol, a predominance of small dense LDL particles, and elevated triglyceride levels. Each of these dyslipidemic features is associated with an increased risk of cardiovascular disease. Increased hepatic secretion of large triglyceride-rich VLDL and impaired clearance of VLDL appears to be of central importance in the pathophysiology of this dyslipidemia. Small dense LDL particles arise from the intravascular processing of specific larger VLDL precursors. Typically, reduced plasma HDL levels in type 2 diabetes are manifest as reductions in the HDL(2b) subspecies and relative or absolute increases in smaller denser HDL(3b) and HDL(3c). Although behavioral interventions such as diet and exercise can improve diabetic dyslipidemia, for most patients, pharmacological therapy is needed to reach treatment goals. There are several classes of medications that can be used to treat lipid and lipoprotein abnormalities associated with insulin resistance and type 2 diabetes, including statins, fibrates, niacin, and thiazolidinediones. Clinical trials have shown significant improvement in coronary artery disease after diabetic dyslipidemia treatment.

Use and abuse of HOMA modeling

Homeostatic model assessment (HOMA) is a method for assessing beta-cell function and insulin resistance (IR) from basal (fasting) glucose and insulin or C-peptide concentrations. It has been reported in >500 publications, 20 times more frequently for the estimation of IR than beta-cell function. This article summarizes the physiological basis of HOMA, a structural model of steady-state insulin and glucose domains, constructed from physiological dose responses of glucose uptake and insulin production. Hepatic and peripheral glucose efflux and uptake were modeled to be dependent on plasma glucose and insulin concentrations. Decreases in beta-cell function were modeled by changing the beta-cell response to plasma glucose concentrations. The original HOMA model was described in 1985 with a formula for approximate estimation. The computer model is available but has not been as widely used as the approximation formulae. HOMA has been validated against a variety of physiological methods. We review the use and reporting of HOMA in the literature and give guidance on its appropriate use (e.g., cohort and epidemiological studies) and inappropriate use (e.g., measuring beta-cell function in isolation). The HOMA model compares favorably with other models and has the advantage of requiring only a single plasma sample assayed for insulin and glucose. In conclusion, the HOMA model has become a widely used clinical and epidemiological tool and, when used appropriately, it can yield valuable data. However, as with all models, the primary input data need to be robust, and the data need to be interpreted carefully.

Differential Up-Regulation of Cytosolic and Membrane-Bound Heat Shock Protein 70 in Tumor Cells by Anti-Inflammatory Drugs

PURPOSE

Modulation of the heat shock protein (HSP) response affects sensitivity to therapeutic agents in cancer. Here, drugs with anti-inflammatory potential (cyclooxygenase 1/2 inhibitors) and peroxidase proliferator-activated receptor-gamma agonists were analyzed for their capacity to affect Hsp70 expression in human cancer cells with a divergent Hsp70 membrane expression pattern.

EXPERIMENTAL DESIGN

In dose kinetics, the nonlethal concentration of acetyl-salicyl acid, celecoxib, rofecoxib, and the insulin-sensitizer pioglitazone was identified for the human adenocarcinoma cell line CX-. With the exception of CLX, which was diluted in DMSO, all reagents were dissolved in water. After treatment with the different compounds at nontoxic concentrations for 6 h, followed by a 1-h recovery period, the cytosolic Hsp70 levels were measured in CX-2 and CX- tumor cells by Western blot analysis. Fold increase was calculated in relation to the housekeeping protein tubulin. Membrane-bound Hsp70 was analyzed by flow cytometry using a FITC-labeled Hsp70-specific monoclonal antibody. Untreated cells and cells incubated with equivalent amounts of the diluting agents served as controls. The immunological function was tested in granzyme B apoptosis assays, standard (51)Cr release assays, and antibody blocking studies.

RESULTS

Compared with aqua dest, the cytoplasmic amount of Hsp70 was equally enhanced in CX-2 and CX- cells by all compounds. An increase in membrane-bound Hsp70, detected selectively in CX- cells, corresponded to an enhanced sensitivity to granzyme B- and natural killer cell-mediated kill that was blockable by using a Hsp70-specific antibody.

CONCLUSIONS

Although increase in cytosolic Hsp70 levels conferred resistance to further stress, membrane-bound Hsp70 rendered tumor cells more sensitive to the immunological attack mediated by granzyme B and natural killer cells. Our data provide a biological rational for combining anti-inflammatory drugs with immunotherapy in cancer therapy.

HDL: a recipe for longevity

The concentration of high density lipoprotein cholesterol (HDL-C) has been found to be a powerful negative predictor of premature coronary heart disease (CHD) and stroke in human prospective population studies. Evidence of the protective properties of HDLs has also been documented in the elderly and their offspring. HDLs mediate several functions that provide an insight into their potential anti-atherogenic mechanisms. Intervention strategies to prevent CHD have generally focused on lowering low-density lipoprotein cholesterol (LDL-C). However, several lifestyle and pharmacological interventions have the capacity to raise the level of HDL-C. As data accumulate on the protective role of HDLs, there is growing support for interventions that act to raise HDL-C concentrations.

Effects of pioglitazone and glimepiride on glycemic control and insulin sensitivity in Mexican patients with type 2 diabetes mellitus: A multicenter, randomized, double-blind, parallel-group trial

BACKGROUND

Pioglitazone and glimepiride improve glycemic control in patients with type 2 diabetes mellitus by different mechanisms. Pioglitazone is a thiazolidinedione that reduces insulin resistance, and glimepiride is a sulfonylurea insulin secretagogue.

OBJECTIVE

The goals of this study were to compare changes in measures of glycemic control and insulin sensitivity in Mexican patients with type 2 diabetes who received pioglitazone or glimepiride for 1 year.

METHODS

This was a multicenter, 52-week, double-blind, parallel-group trial. Patients were randomized to receive monotherapy with either glimepiride (2 mg QD initially) or pioglitazone (15 mg QD initially). Doses were titrated (maximal doses: pioglitazone 45 mg, glimepiride 8 mg) to achieve glycemic targets (fasting blood glucose < or =7 mmol/L and 1-hour postprandial blood glucose < or =10 mmol/L). Insulin sensitivity (primary end point) was evaluated in terms of the Homeostasis Model Assessment for Insulin Sensitivity (HOMA-S), the Quantitative Insulin Sensitivity Check Index (QUICKI), and fasting serum insulin (FSI) concentrations. Glycemic control was evaluated in terms of glycosylated hemoglobin (HbA(1c)) values and fasting plasma glucose (FPG) concentrations. Patients were encouraged to maintain their individual diet and exercise regimens throughout the study.

RESULTS

Two hundred forty-four patients (125 women, 119 men; all but 1 Hispanic) were randomized to receive pioglitazone (n = 121) or glimepiride (n = 123). In the intent-to-treat sample, pioglitazone and glimepirede produced comparable reductions in HbA(1c) from baseline to the end of the study (-0.78% and -0.68%, respectively). The pioglitazone group had significantly higher HbA(1c) values compared with the glimepiride group after 12 weeks of therapy (8.66% vs 7.80%; P = 0.007) but had significantly lower values after 52 weeks (7.46% vs 7.77%; P = 0.027). Pioglitazone significantly reduced FPG compared with glimepiride (-0.6 vs 0.6 mmol/L; P = 0.01). Pioglitazone therapy was associated with significant increases in insulin sensitivity (reduced insulin resistance), whereas glimepiride had no effect. HOMA-S values changed 18.0% for pioglitazone and -7.9% for glimepiride (P < 0.001), QUICKI values changed a respective 0.013 and -0.007 (P < 0.001), and FSI values were -21.1 and 15.1 pmol/L (P< 0.001). Both drugs were well tolerated, with pioglitazone associated with more peripheral edema (number of treatment-emergent cases: 35/121[28.9%] vs 17/123 [13.8%]; P = 0.005) and fewer hypoglycemic episodes (19 [15.7%] vs 38 [30.9%]; P = 0.024). The incidence of weight gain was not significantly different between treatment groups.

CONCLUSIONS

These data suggest that long-term treatment with pioglitazone enhances insulin sensitivity relative to glimepiride in Mexican patients with type 2 diabetes and that pioglitazone may have a more sustained antihyperglycemic effect.

Pioglitazone, insulinosensibilité et diabète de type 2 : données récentes

Thiazolidinediones ("glitazones") were recently added to the oral treatment of type 2 diabetes. Two glitazones are available in France, pioglitazone and rosiglitazone, which progressively were granted broader therapeutic indications since their launch in 2002. This review presents the most recent pioglitazone pharmacological and clinical data, with a particular emphasis on the QUARTET clinical study program results. Available information generates perspectives and hopes: prevention of the progressive decline in beta-pancreatic cell function (and possibly, prevention of type 2 diabetes in at-risk subjects), cardiovascular prevention in type 2 diabetic patients depending on the results of the ongoing prospective morbi-mortality studies in high risk type 2 diabetic patients.

Economic benefits of pioglitazone for treating patients with Type 2 diabetes

Diabetes remains a significant economic burden to national healthcare systems. The traditional oral agents used to treat Type 2 diabetes do not address the underlying insulin resistance responsible for the development of diabetes. Newer medications, such as the thiazolidinediones, have been shown to reverse some of the metabolic processes believed to be responsible for the development of insulin resistance and ultimately, Type 2 diabetes. A comprehensive economic evaluation of pioglitazone using a modelling approach indicates that pioglitazone is a cost-effective therapy for patients with Type 2 diabetes when used in combination with either a sulfonylurea or metformin. This drug profile analyzes the clinical data on the use of piogltiazone for the treatment of Type 2 diabetes and the various economic evaluations of pioglitazone in the literature.

The effects of oral anti-hyperglycaemic medications on serum lipid profiles in patients with type 2 diabetes

AIM

Patients with type 2 diabetes often have dyslipidaemia, putting them at risk of cardiovascular disease, and are frequently treated with oral anti-hyperglycaemic medications (OAMs). This review compares the effects of OAMs on serum lipids [total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TGs) and free fatty acids (FFAs)] in patients with type 2 diabetes.

METHODS

medline was searched for entries indexed from January 1966 to November 2002; search terms included the names of OAMs and serum lipids, limited to English language and human subjects. We selected clinical studies in type 2 diabetes of OAM monotherapy that included serum lipid data, treated all patients in a treatment group with the same drug, used therapeutic OAM doses not higher than the maximum recommended in the USA, compared therapy with baseline or placebo and specified statistical tests used. One unblinded investigator selected studies for inclusion. Data reported include number of patients, study length, OAM dose, serum lipid data at baseline and endpoint, p-values and statistical tests.

RESULTS

Data on the serum lipid effects of sulphonylureas, repaglinide, nateglinide and miglitol were inconclusive. Acarbose increased HDL-C and decreased LDL-C and voglibose reduced TC. Metformin at higher doses reduced TC; data on its effects on other lipids were inconclusive. Rosiglitazone increased LDL-C, HDL-C and TC and reduced FFAs but had no effect on TGs. Pioglitazone increased HDL-C and reduced TGs and FFAs but did not affect LDL-C or TC.

CONCLUSIONS

Lipid changes as a result of improved glycaemic control are not uniform findings associated with anti-diabetic therapy. Only metformin, acarbose, voglibose, rosiglitazone and pioglitazone had significant effects on the lipid profile. These effects should be considered when selecting OAMs for patients with type 2 diabetes.

Progress with thiazolidinediones in the management of type 2 diabetes mellitus

BACKGROUND

Much progress has been made in the field of medicine within the past 20 years; however, cardiovascular outcomes in patients with diabetes mellitus have not improved to a corresponding degree. Although numerous treatments are available for the management of type 2 diabetes, current approaches appear to address the spectrum of the disease and its complications insufficiently.

OBJECTIVES

This article reviews evidence for the minimal effects of standard antidiabetic treatments on the macrovascular complications associated with type 2 diabetes, discusses the improvements in markers of cardiovascular risk seen with the thiazolidinediones (TZDs), and explores the rationale for their earlier use.

METHODS

Relevant articles and guidelines on the use of oral antidiabetic agents in the treatment of type 2 diabetes were identified through a search of MEDLINE for the past 15 years using the terms cardiovascular, insulin resistance, metabolic syndrome, metformin, sulfonylurea, type 2 diabetes, and thiazolidinediones. The reference lists of selected articles also were searched. Articles chosen for review were required to assess clinically important outcomes or surrogate markers that have been shown to have a direct link to clinically important outcomes.

RESULTS

The data reviewed suggest that the sulfonylureas and/or metformin are able to reduce microvascular complications associated with type 2 diabetes but do not substantially affect macrovascular complications. In contrast, the TZDs demonstrate insulin-sensitizing effects attributable to their novel mechanism of action on the peroxisome proliferator-activated receptor gamma. The resulting reduction in insulin resistance appears to improve many of the metabolic and cardiovascular pathways influenced by insulin activity. Blood pressure, vascular and coagulation defects, lipid abnormalities, and beta-cell function have been found to improve in patients receiving TZD treatment. For example, there are reports of significant reductions in levels of C-reactive protein (P < 0.01); small, dense low-density lipoprotein cholesterol particles (P < 0.05); and circulating free fatty acids (P < 0.003), in addition to improvements in the proinsulin-to-insulin ratio (P < 0.05).

CONCLUSIONS

In this review of the literature, use of TZDs as monotherapy or as part of combination therapy has been associated with effective glycemic control and reductions in markers of various macrovascular complications of type 2 diabetes. Although outcomes trials are ongoing, the preliminary effects of TZD therapy are promising and suggest that earlier use of TZDs in the pharmacologic management of type 2 diabetes has the potential to minimize severe disease sequelae.

Pioglitazone is Effective Therapy for Elderly Patients with Type 2 Diabetes Mellitus

BACKGROUND

Pioglitazone as monotherapy and in combination with sulfonylurea, metformin, or insulin has consistently demonstrated improved glycaemic and lipid parameters in patients with type 2 diabetes mellitus.

OBJECTIVE

We performed a subanalysis to examine the effect of pioglitazone on glycaemia and lipids in patients <65 and > or =65 years of age in two double-blind, placebo-controlled monotherapy studies and in three separate multi-centre trials.

METHOD

In Study 1, 197 patients were randomised to receive pioglitazone 30 mg/day or placebo for 16 weeks. Study 2 was a forced dose-titration trial in patients randomised to receive pioglitazone 7.5/15/30 mg/day, pioglitazone 15/30/45 mg/day, or placebo daily for 26 weeks. Each of the lower dosages was given for at least 4 weeks and the highest dosage for 16 weeks. The three combination studies evaluated efficacy of pioglitazone 30 or 45 mg/day over a 24-week period in combination with sulfonylureas, metformin, or insulin.

RESULTS

In both placebo-controlled monotherapy studies, at 16 weeks, and at maximum pioglitazone dosage, 0.53-0.55% and 0.57-1.27% mean reductions from baseline in glycosylated haemoglobin (HbA(1c)) were seen in patients aged <65 (n = 225) and > or =65 (n = 45) years, respectively. There were statistically significant differences between the placebo and pioglitazone groups in each age cohort. Similar effects were observed in fasting plasma glucose (FPG) levels, with 2.03-2.59 mmol/L and 3.20-4.44 mmol/L mean reductions from baseline, respectively, which were significantly different from the changes in the placebo group, but there was no difference between pioglitazone groups. At treatment endpoint in combination trials, pioglitazone added to sulfonylurea produced a mean decrease in HbA(1c) of 0.78-1.61%, and 1.64-1.96% in patients aged <65 (n = 557) and > or =65 (n = 115) years, respectively. Pioglitazone added to metformin produced a mean decrease in HbA(1c) of 0.78-1.03% and 0.78-0.98% in patients aged <65 (n = 686) and > or =65 (n = 112) years, respectively. Pioglitazone added to insulin produced a mean decrease in HbA(1c) of 1.13-1.37% and 1.39-1.66% in patients aged <65 (n = 500) and > or =65 (n = 156) years, respectively. In patients aged > or =65 years, hypoglycaemia was observed in 1 of 14 patients and in 0 of 13 patients in the two monotherapy studies. In the combination studies, the incidence of hypoglycaemia among patients aged > or =65 years was as follows: 26.7-28.8% combined with sulfonylurea; 0-4.4% combined with metformin; and 53.4-56.4% combined with insulin.

CONCLUSION

Pioglitazone monotherapy, or added to a sulfonylurea, metformin, or insulin demonstrated no significant differences in effectiveness while exhibiting similar adverse events in patients aged > or =65 years compared with patients aged <65 years. Well-controlled randomised clinical trials are recommended to confirm the impact of pioglitazone therapy on the glycaemic and lipid control in elderly patients with type 2 diabetes.

Pioglitazone preserves pancreatic islet structure and insulin secretory function in three murine models of type 2 diabetes

Thiazolidinediones may slow the progression of type 2 diabetes by preserving pancreatic beta-cells. The effects of pioglitazone (PIO) on structure and function of beta-cells in KKA(y), C57BL/6J ob/ob, and C57BL/KsJ db/db mice (genetic models of type 2 diabetes) were examined. ob/ob (n = 7) and db/db (n = 9) mice were randomly assigned to 50-125 mg.kg body wt-1.day-1 of PIO in chow beginning at 6-10 wk of age. Control ob/ob (n = 7) and db/db mice (n = 9) were fed chow without PIO. KKA(y) mice (n = 15) were fed PIO daily at doses of 62-144 mg.kg body wt-1.day-1. Control KKA(y) mice (n = 10) received chow without PIO. Treatment continued until euthanasia at 14-26 wk of age. Blood was collected at baseline (before treatment) and just before euthanasia and was analyzed for glucose, glycosylated hemoglobin, and plasma insulin. Some of the splenic pancreas of each animal was resected and partially sectioned for light or electron microscopy. The remainder of the pancreas was assayed for insulin content. Compared with baseline and control groups, PIO treatment significantly reduced blood glucose and glycosylated hemoglobin levels. Plasma insulin levels decreased significantly in ob/ob mice treated with PIO. All groups treated with PIO exhibited significantly greater beta-cell granulation, evidence of reduced beta-cell stress, and 1.5- to 15-fold higher levels of pancreatic insulin. The data from these studies suggest that comparable effects would be expected to slow the progression of type 2 diabetes, either delaying or possibly preventing progression to an insulin-dependent state.

Favorable effects of pioglitazone and metformin compared with gliclazide on lipoprotein subfractions in overweight patients with early type 2 diabetes

OBJECTIVE

To compare effects of different oral hypoglycemic drugs as first-line therapy on lipoprotein subfractions in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Sixty overweight type 2 diabetic patients not on lipid-lowering therapy were randomized to metformin, pioglitazone, or gliclazide after a 3-month dietary run-in. Drug doses were uptitrated for 3 months to optimize glycemia and were kept fixed for a further 3 months. LDL subfractions (LDL(1), LDL(2), and LDL(3)) were prepared by density gradient ultracentrifugation at randomization and study end. Triglycerides, cholesterol, total protein, and phospholipids were measured and mass of subfractions calculated. HDL subfractions were prepared by precipitation. The primary end point was change in proportion of LDL as LDL(3).

RESULTS

HbA(1c), triglycerides, glucose, and cholesterol were comparable across groups at baseline and over time. LDL(3) mass and the LDL(3)-to-LDL ratio fell with pioglitazone (LDL(3) mass 36.2 to 28.0 mg/dl, P < 0.01; LDL(3)-to-LDL 19.2:13.3%, P < 0.01) and metformin (42.7 to 31.5 mg/dl, P < 0.01; 21.3:16.2%, P < 0.01, respectively) with no change on gliclazide. LDL(3) reductions were associated with reciprocal LDL(1) increases. Changes were independent of BMI, glycemic control, and triglycerides. Total HDL cholesterol increased on pioglitazone (1.28 to 1.36 mmol/l, P = 0.02) but not gliclazide (1.39 to 1.37 mmol/l, P = NS) or metformin (1.26 to 1.18 mmol/l, P = NS), largely due to an HDL(2) increase (0.3 to 0.4 mmol/l, P < 0.05). HDL(3) cholesterol fell on metformin (0.9 to 0.85 mmol/l, P < 0.01). On pioglitazone and metformin, the HDL(2)-to-HDL(3) ratio increased compared with no change on gliclazide.

CONCLUSIONS

For the same improvement in glycemic control, pioglitazone and metformin produce favorable changes in HDL and LDL subfractions compared with gliclazide in overweight type 2 diabetic patients. Such changes may be associated with reduced atherosclerosis risk and may inform the choice of initial oral hypoglycemic agent.

Free fatty acids and type 2 diabetes mellitus

Acute elevation of plasma free fatty acids (FFAs) is necessary for insulin secretion. Sustained elevation, however, leads to apoptosis of pancreatic beta-cells and is a major risk factor for cardiovascular disease and sudden death in patients with insulin resistance or a family history of diabetes mellitus, as well as in individuals with normal glucose tolerance. Data suggest that reduction of FFA plasma levels may reduce the incidence of cardiovascular disease in these at-risk patients. Thiazolidinediones have been shown not only to improve insulin sensitivity but also to reduce FFA plasma levels. Consequently, endothelial function is maintained, vascular smooth muscle cell proliferation and migration are minimized, elevated blood pressure and microalbuminuria are reduced, and high-density lipoprotein and low-density lipoprotein cholesterol particle sizes are improved.

Improvement of insulin resistance by a new insulin secretagogue, nateglinide--analysis based on the homeostasis model

Type 2 diabetes is a heterogeneous disorder characterized by defects in the early phase of insulin secretion after meals and in insulin resistance at its early stage. A new insulin secretagogue, nateglinide, has been shown to elicit an acute insulin release and to reduce postprandial hyperglycemia. We have treated 30 patients with type 2 diabetes using nateglinide and performed a standard meal test at breakfast, both before and after the treatment. Insulin resistance and beta-cell function was assessed by the HOMA model. Nateglinide, at 1 and 2 h after the test meal, significantly stimulated postprandial insulin secretion by 62.0 and 41.0% and improved blood glucose values by 17.3 and 21.9%, respectively, after the treatment. Fasting blood glucose (FBG) and glycohemoglobin was significantly reduced by 9.8 and 10.3%, respectively. The reduction was significantly larger in postprandial glucose than in FBG (P<0.0005). A significant correlation was found in the HOMA-insulin resistant (IR) index and in the changes of fasting IRI. When the patients were divided into three groups, forming a markedly insulin resistant (MIR) group, an IR group and a non-insulin resistant (NIR) group, HOMA-IR levels improved significantly, from 7.0 +/- 4.3 to 4.5 +/- 2.8 (P=0.026) in the MIR group and showed a tendency toward improvement in the IR group, from 2.9 +/- 0.7 to 2.3 +/- 1.1 (P=0.062), but failed to exhibit such a positive response in the NIR group, changing from 1.2 +/- 0.2 to 1.9 +/- 0.9 (P=0.21). HOMA-beta, on the other hand, improved significantly in the NIR group only, from 16.4 +/- 7.8 to 26.9 +/- 9.9 (P=0.017), but not in the IR nor MIR groups (M +/- S.D.). In conclusion, nateglinide improved the excessive excursion of postprandial glucose by the augmentation of early insulin secretion after a meal and differentially affected fasting insulin levels and HOMA-IR indexes, depending on the degree of insulin resistance.

Thiazolidinediones in type 2 diabetes mellitus: current clinical evidence

Type 2 diabetes mellitus is characterised by insulin resistance as well as progressive pancreatic beta cell dysfunction. The cornerstone of current oral blood-glucose lowering therapy consists of metformin, which primarily lowers hepatic glucose production, and the sulphonylureas that act by stimulating pancreatic beta-cells to secrete insulin. Recently, a novel class of agents, the thiazolidinediones, has been introduced that favourably influence insulin sensitivity and possibly also pancreatic beta-cell function. The thiazolidinediones are synthetic ligands that bind to the nuclear peroxisome proliferator-activated receptor-gamma and exert their action by activating transcription of genes that, among others, regulate adipocyte differentiation and adipogenesis as well as glucose and lipid metabolism. To date, the precise mechanisms underlying the actions of thiazolidinediones are largely unknown. When given as monotherapy or in combination with sulphonylureas, metformin or insulin in patients with type 2 diabetes, the currently available thiazolidinediones (rosiglitazone and pioglitazone) ameliorate glycaemic control, by lowering fasting and postprandial blood glucose levels, and improve insulin sensitivity in placebo-controlled trials. They seem to have differential effects on dyslipidaemia in patients with type 2 diabetes; rosiglitazone increases total cholesterol as well as high-density lipoprotein (HDL) and low-density lipoprotein cholesterol levels and affects plasma triglyceride levels depending on the baseline values, whereas pioglitazone lowers triglycerides and increases HDL cholesterol levels. The adverse events of both agents that occur with greater frequency than in patients treated with placebo are fluid retention and oedema. As demonstrated, mainly in preclinical studies to date, rosiglitazone and pioglitazone possess beneficial effects on other cardiovascular risk factors associated with the insulin resistance syndrome. Thus, these agents were shown to decrease blood pressure, enhance myocardial function and fibrinolysis, as well as possess anti-inflammatory and other beneficial vascular effects. Long-term efficacy and surveillance of this promising class of drugs in patients, however, still need to be demonstrated in outcome trials.

Thiazolidinediones and blood lipids in type 2 diabetes

We evaluated study population characteristics and treatment effects on blood lipids between studies in which either rosiglitazone (RSG) or pioglitazone (PIO) was investigated in patients with type 2 diabetes. We performed a summary analysis of all published double-blind, placebo-controlled studies with RSG (4 and 8 mg/d) and PIO (15, 30, and 45 mg/d). Data were analyzed by the random-effects model. Nineteen trials met our inclusion criteria, yielding 5304 patients, 3236 in studies with RSG and 2068 in studies with PIO. Subjects treated with PIO were more obese and showed more pronounced hyperglycemia and dyslipidemia (increased triglycerides and decreased HDL cholesterol) at baseline than did subjects treated with RSG. By weighted linear-regression analysis, studies with PIO showed greater beneficial effects on triglycerides, total cholesterol, and LDL cholesterol, after adjustment for the respective lipid levels at baseline. RSG 8 mg/d showed greater increases in total cholesterol and LDL cholesterol than did RSG 4 mg/d. PIO 30 mg/d showed greater reductions in triglycerides than did PIO 15 mg/d. Studies conducted with PIO showed more beneficial effects on blood lipids, but also different study population characteristics in comparison with studies conducted with RSG. Differences in both pharmacologic properties between agents and study population characteristics are likely to have influenced the results.

The “Glitazones”: Rosiglitazone and Pioglitazone

Rosiglitazone and pioglitazone are two new additions to the therapeutic options for the treatment of type 2 diabetes mellitus. These agents differ from our current therapies in their mode of action. They have potential non-glucose lowering effects that may reduce cardiovascular risk and are effective both as monotherapy and in combination with sulfonylureas, metformin, and insulin. They are generally well tolerated, with the main side effects being weight gain and fluid retention. However, special precaution is warranted in patients with congestive heart failure or hepatic disease, and monitoring of liver enzymes is recommended for the first year of therapy. Despite their effectiveness, rosiglitazone and pioglitazone remain second-line agents to metformin and glyburide, agents that have demonstrated efficacy in decreasing the microvascular and macrovascular complications associated with type 2 diabetes mellitus.

Novel peroxisome proliferator-activated receptor ligands for Type 2 diabetes and the metabolic syndrome

As the incidence of Type 2 diabetes has reached near epidemic proportions, the quest for novel therapies to combat this disorder has intensified dramatically. In recent years, the peroxisome proliferator-activated receptor (PPAR) family has received tremendous attention as perhaps an ideal target class to address the multiple metabolic anomalies associated with the diabetic state. This review focuses on a variety of novel PPAR approaches currently being investigated for Type 2 diabetes or the metabolic syndrome, including the highly potent selective PPAR agonists, PPAR combination agonists and alternative PPAR ligands.

Management of diabetes mellitus and insulin resistance in patients with cardiovascular disease

Patients with diabetes have a greatly increased relative risk of developing cardiovascular disease when compared with patients without diabetes. Much of this risk is related to insulin resistance and is associated with both traditional and nontraditional cardiovascular risk factors. Therapy for diabetes must address these risk factors in an attempt to prevent and adequately treat cardiovascular disease. Pharmacologic therapy directed toward dyslipidemia and hypertension has a beneficial effect on risk factors and has been shown to decrease cardiovascular events. The effects of insulin and oral hypoglycemic agents on insulin resistance are variable, and their direct effect on cardiovascular disease is less clear. Metformin is the only oral hypoglycemic agent shown to decrease cardiovascular events independent of glycemia. The thiazolidinediones directly improve insulin resistance, decrease plasma insulin concentration, and have the potential to decrease the risk of cardiovascular disease in patients with diabetes. A number of studies have demonstrated that the thiazolidinediones produce changes in several cardiovascular risk factors associated with the insulin resistance syndrome, including lowering blood pressure, correcting diabetic dyslipidemia, improving fibrinolysis, and decreasing carotid artery intima-medial thickness. These agents bind a newly described class of receptors, peroxisome proliferator-activated receptors, which may have implications for atherosclerosis. Although these drugs increase low-density lipoprotein (LDL) cholesterol, they induce a favorable change in the LDL particle size and susceptibility to oxidation. Long-term clinical trials are being conducted to determine the effect that thiazolidinediones have on cardiovascular events in individuals with type 2 diabetes.

Effects of thiazolidinediones on cardiovascular risk factors

The thiazolidinediones are the insulin sensitizers used in the management of Type 2 diabetes mellitus. These drugs can potentially decrease the risk of cardiovascular disease by correcting the different components of the insulin resistance syndrome.

Effects of nonstatin lipid drug therapy on high-density lipoprotein metabolism

Low high-density lipoprotein (HDL) cholesterol is an important predictor of risk for coronary artery disease. Although current treatment guidelines for dyslipidemia do not include specific targets for HDL cholesterol, the categorical definition of low HDL cholesterol has been changed from <35 mg/dL to <40 mg/dL. 3-hydroxy-3-methylglutaryl reductase inhibitors (statins) increase HDL cholesterol to a moderate degree. Fibrates also increase HDL cholesterol to a moderate degree and have additive effects with statins. Niacin is the most potent currently available agent for increasing HDL cholesterol, and its effects are also additive to those of statins. Other agents that increase HDL cholesterol include thiazolidinediones, estrogen, and omega-3 fatty acids. The mechanisms by which nonstatin pharmacologic agents increase HDL cholesterol are not completely understood but probably involve multiple mechanisms for each class.

A randomized, double-blind, placebo-controlled, clinical trial of the effects of pioglitazone on glycemic control and dyslipidemia in oral antihyperglycemic medication-naive patients with type 2 diabetes mellitus

OBJECTIVE

The goal of this study was to compare the effects of 2 doses of pioglitazone hydrochloride (a thiazolidinedione insulin sensitizer) with placebo on glycated hemoglobin (HbA(1c)), insulin sensitivity, and lipid profiles in patients with type 2 diabetes mellitus who had suboptimal glycemic control and mild dyslipidemia.

METHODS

Patients with type 2 diabetes mellitus (HbA(1c) >/=6.5% and </=9.8%) who had not previously received insulin or oral antihyperglycemic medications (OAMs) were randomized to treatment with placebo, pioglitazone 30 mg QD, or pioglitazone 45 mg QD in double-blind fashion for 16 weeks at 41 centers in Canada and Spain.

RESULTS

A total of 297 patients were randomized (99 in each group). Overall, 286 (96.3%) were white. Mean (SD) age was 58.4 (10.9) years (range, 24-85 years), mean (SD) body mass index was 31.4 (4.8) kg/m(2), mean (SD) duration of type 2 diabetes mellitus was 20.0 (37.4) months, and 30.6% of patients were receiving medication for dyslipidemia. Treatment with pioglitazone 30 or 45 mg QD for 16 weeks reduced mean HbA(1c) by 0.8% and 0.9% from baseline, respectively (both P < 0.001 vs baseline and placebo). A reduction in HbA(1c) of 0.2% was observed in the placebo group (P = 0.025). In patients with medium (>/=7% to <8%) or high (>/=8% to </=9.8%) baseline HbA(1c), both doses of pioglitazone significantly reduced HbA(1c) (both P < 0.001 vs placebo). Pioglitazone 30 and 45 mg significantly reduced fasting serum insulin versus placebo (P = 0.008 and P = 0.006, respectively) and increased insulin sensitivity by Homeostasis Model Assessment versus placebo (P = 0.039 and P = 0.001, respectively). Relative to placebo, pioglitazone 30 and 45 mg significantly increased high-density lipoprotein cholesterol (HDL-C [P = 0.028 and P < 0.001, respectively]) and lowered the atherogenic index of plasma (P = 0.018 and P < 0.001, respectively). Pioglitazone 45 mg also significantly reduced serum triglycerides, apolipoprotein B, and total cholesterol:HDL-C ratio versus placebo (P = 0.007, P = 0.015, and P = 0.005, respectively). Pioglitazone 30 and 45 mg were associated with a significant reduction in serum alanine aminotransferase relative to placebo (P = 0.036 and P = 0.005, respectively). Pioglitazone appeared to be safe and was well tolerated.

CONCLUSIONS

In the present study, pioglitazone 30 and 45 mg produced significant improvements in HbA(1c), insulin sensitivity, and lipid profile in OAM-naive patients with type 2 diabetes mellitus with suboptimal glycemic control and mild dyslipidemia.

Analysis of the relationship between the Pro12Ala variant in the PPAR-gamma2 gene and the response rate to therapy with pioglitazone in patients with type 2 diabetes

OBJECTIVE

To investigate the influence of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) gene variants on the response rate to therapy with the thiazolidinedione (TZD) pioglitazone, because in vitro studies have suggested that genetic variants of the PPAR-gamma gene may influence the drug efficacy of TZD.

RESEARCH DESIGN AND METHODS

A total of 131 patients were treated in an open-label, randomized, multicenter study with pioglitazone (45 mg o.d.) during a course of >or=26 weeks. Response to the pioglitazone therapy was defined by either a >20% decrease in fasting plasma glucose or a >15% decrease in HbA(1c) values after 26 weeks of pioglitazone treatment. We evaluated the association between the PPAR-gamma genotype and the response rate to pioglitazone treatment.

RESULTS

The Pro12Ala and the Pro12Pro variants in the PPAR-gamma gene are not associated with the response rate to pioglitazone treatment in patients with type 2 diabetes. However, we identified initial fasting plasma glucose level >11.0 mmol/l, HbA(1c) value >9.0%, BMI >32 kg/m(2), and fasting C-peptide concentrations at baseline >2.5 pmol/l as predominant confounding factors for the responder frequency to pioglitazone treatment.

CONCLUSIONS

The Pro12Ala variant in the PPAR-gamma gene does not affect the therapy efficacy of pioglitazone, suggesting that the drug-treatment response is independent from pharmacogenetic effects between PPAR-gamma and its ligand pioglitazone. Whether the Ala12Ala genotype plays a role in the response rate to TZD therapy remains to be determined.

Thiazolidinedione therapy: the benefits of aggressive and early use in type 2 diabetes

Type 2 diabetes is now a global epidemic, with the number of people affected worldwide predicted to more than double to 300 million by the year 2025. While the importance of good glycemic control in countering the microvascular and macrovascular complications of diabetes is widely recognized, monotherapy with sulfonylureas or metformin achieves target blood glucose levels in only a minority of patients. Consequently, there is a pressing need for new treatment strategies that are more effective in providing sustained glycemic control and so reducing the burden of morbidity and mortality associated with diabetes and its complications. There is growing evidence of the benefits of early intervention with aggressive treatment strategies in improving glycemic control and reducing diabetic complications. To provide sustained control, such strategies need to address the combination of insulin resistance and beta-cell dysfunction that underlies most cases of type 2 diabetes. At the same time, treatment needs to address not only glycemic control but also the range of cardiovascular risk factors that are often found clustered together in patients with type 2 diabetes. This paper reviews the rationale and evidence for early combination therapy including a thiazolidinedione in improving glycemic control, and considers the potential for such aggressive therapy in reducing diabetic complications.

Type 2 diabetes, cardiovascular risk, and the link to insulin resistance

BACKGROUND

Patients with type 2 diabetes mellitus frequently have coexistent dyslipidemia, hypertension, and obesity, and are at risk for microvascular and macrovascular disease complications such as myocardial infarction, stroke, retinopathy, and microalbuminuria. To optimize cardiovascular health outcomes for patients with type 2 diabetes, strategies to reduce the risks of microvascular and macrovascular disease are needed in clinical practice.

OBJECTIVE

This article provides an overview of the cardiovascular risk profile of patients with type 2 diabetes and discusses the cardiovascular consequences of use of the thiazolidinediones (insulin-sensitizing agents) in the treatment of type 2 diabetes.

METHODS

A literature search of MEDLINE/PubMed was performed to identify relevant articles published from 1966 to April 2003. Search terms used were diabetes, cardiovascular disease, atherosclerosis, dyslipidemia, obesity, hypertension, blood pressure, hyperglycemia, inflammation, C-reactive protein, fibrinolysis, plasminogen activator inhibitor type-1, microalbuminuria, thiazolidinediones, safety, hepatotoxicity, and edema. Bibliographies within the identified articles were also evaluated for additional relevant articles and information.

RESULTS

Recommendations for cardiovascular risk reduction through preventive and therapeutic strategies that target the symptoms of insulin resistance may reduce the microvascular and macrovascular sequelae of diabetes and ameliorate the impact of other components of the metabolic syndrome, including hypertension, hyperglycemia, and obesity. In this regard, thiazolidinediones are promising therapies.

CONCLUSIONS

Early data suggest that, in addition to reducing hyperglycemia, pioglitazone and rosiglitazone effect changes in the dyslipidemic profile, hemodynamics, vascular inflammation, and endothelial functioning of patients with type 2 diabetes. Additional research is needed to further distinguish the cardiovascular benefits of these drugs.

Multicenter retrospective assessment of thiazolidinedione monotherapy and combination therapy in patients with type 2 diabetes: Comparative subgroup analyses of glycemic control and blood lipid levels

BACKGROUND

Thiazolidinediones (TZDs) have contributed to the management of patients with type 2 diabetes mellitus as unique insulin-sensitizing agents. When used as monotherapy or in combination therapy, these drugs not only reduce glycosylated hemoglobin (HbA(1c)) levels, but also effect changes in blood lipid concentrations and have the potential to ameliorate cardiovascular disease risk. Although drugs in the TZD class are perceived to be equivalent clinically, prospective and retrospective studies have demonstrated their ability to modify blood lipid levels.

OBJECTIVE

We evaluated and compared the effects of pioglitazone and rosiglitazone monotherapy and combination therapy on blood lipid levels and HbA(1c) in patients with type 2 diabetes.

METHODS

We conducted a multicenter retrospective chart review of 1115 records of patients with type 2 diabetes who received pioglitazone or rosiglitazone, alone or in combination with other antidiabetic agents, between August 1, 1999, and August 31, 2000. The review was conducted to evaluate pretreatment and posttreatment levels of triglyceride, total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and HbA(1c).

RESULTS

All observed demographic characteristics, comorbidities, and concomitant drug use were similar in both treatment cohorts. Of the patients who received pioglitazone, 83% also received >/=1 other antihyperglycemic agent and 59% received some form of antihyperlipidemic therapy. Among those who received rosiglitazone, 81% received concomitant antihyperglycemic medication and 60% received some form of antihyperlipidemic therapy. With pioglitazone, mean levels of serum triglyceride, total cholesterol, and LDL-C decreased and HDL-C increased in most patients, with or without concomitant antihyperglycemic medications; with rosiglitazone, with or without other antidiabetic agents, triglyceride and HDL-C levels decreased, whereas total cholesterol and LDL-C levels increased in most patients. Reductions in HbA(1c) levels and increases in body weight related to each study drug were comparable.

CONCLUSIONS

This comparative assessment of pioglitazone and rosiglitazone, based on observational data, reveals that use of these TZDs with other antidiabetic agents was similar in 605 primary care practices in the United States. In both monotherapy and combination treatment regimens, pioglitazone was associated with greater beneficial effects on lipids than was rosiglitazone. Additional studies are needed to determine the long-term outcomes of TZD therapy with concomitant antihyperglycemic medications.

Atherosclerosis in type 2 diabetes mellitus and insulin resistance: mechanistic links and therapeutic targets

The ongoing heavy burden of cardiovascular disease associated with diabetes mellitus highlights the failure of current treatment strategies to address effectively the cardiovascular risk profile in such patients. Insulin resistance is not only an underlying feature in most cases of type 2 diabetes, but is also associated, through the Insulin Resistance Syndrome, with cardiovascular risk factors that promote atherothrombosis through diverse mechanisms. Growing evidence suggests that treatment with anti-diabetic agents that improve insulin sensitivity, such as the thiazolidinediones, improve multiple components of the Insulin Resistance Syndrome, have beneficial effects on various atherothrombotic mechanisms, and reduce atherosclerosis in animal models and perhaps humans as well. Given data implicating chronic inflammation as a central feature of atherosclerosis, the anti-inflammatory activity of the thiazolidinediones may contribute to their potential anti-atherosclerotic effects. An improved understanding of the mechanisms linking diabetes, atherosclerosis, and cardiovascular disease is needed in order to understand how these and other current and emerging therapies might reduce diabetes-associated cardiovascular disease.

Role of inflammatory pathways in the development and cardiovascular complications of type 2 diabetes

Experimental and epidemiologic studies support the role of inflammation in the development of type 2 diabetes and atherosclerosis. Serum levels of inflammatory markers, in particular highly sensitive C-reactive protein, have been found to be strong predictors of increased risk for type 2 diabetes and cardiovascular disease independent of traditional risk factors. A beneficial effect of thiazolidinediones, angiotensin-converting enzyme inhibitors, and statins in the prevention of type 2 diabetes and cardiovascular events has recently been reported, and potential anti-inflammatory mechanisms of action for these compounds have been described. Prospective, randomized clinical trials are currently underway to confirm these initial findings and define indications for treatment of patients at risk.

Current concepts in insulin resistance, type 2 diabetes mellitus, and the metabolic syndrome

A clustering of risk factors, including elevated triglycerides, decreased high-density lipoprotein cholesterol, hyperinsulinemia, and hypertension often are observed in patients who are insulin resistant. Insulin resistance has been found to play a critical role in the development of cardiovascular disease, particularly in patients with type 2 diabetes. Patients with insulin resistance have an increase in small, dense low-density lipoprotein (LDL) cholesterol, which is more atherogenic than large, buoyant LDL cholesterol. In the context of insulin resistance, insulin has reduced effects on the phosphatidylinositol 3 kinase (PI3K) pathway, whereas mitogen-activated protein kinase activity is maintained. The result is an exaggeration of the mitogenic actions of insulin leading to vascular smooth muscle proliferation and elevated plasminogen activator inhibitor (PAI)-1. Notably, nitric oxide-mediated vasodilation also is impaired, further contributing to atherogenicity. In addition, hyperinsulinemia further contributes to cardiovascular risk by promoting thrombosis. Patients who are insulin resistant have decreased fibrinolysis, as indicated by increased levels of PAI-1. Studies have shown that enhancing insulin sensitivity with insulin sensitizers, such as thiazolidinediones, may improve insulin resistance and limit the development of adverse cardiovascular consequences.