Insulin-sensitizing agents: metformin and thiazolidinedione derivatives

Both metformin and thiazolidinedione derivatives(TZDs) improve insulin resistance, a major pathogenesis of type 2 diabetes, and decrease blood glucose levels without stimulating insulin secretion. Metformin inhibits glucose output from the liver, while TZDs increase glucose utilization in the peripheral tissues. In addition, there has been indicated that these agents ameliorate metabolic syndrome beyond glucose-level lowering. Molecular targets of these agents have recently been revealed; AMP-activated protein kinase (AMPK) for metformin and adiponectin, while PPAR gamma for TZDs which induce gene expression of adipocyte glycerol kinase and adiponectin. Insulin-sensitizing agents are clinically useful for obese diabetic patients with insulin resistance. However, periodical examinations are necessary to avoid serious adverse effects such as lactic acidosis, although rare, by metformin and liver injury by TZDs.     

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.     

Treatment of diabetes in patients with severe obesity.

Besides genetic predisposition, obesity is the most important risk factor for the development of diabetes mellitus, and weight reduction has been shown to markedly improve blood glucose control in obese subjects with type 2 diabetes. Therapeutic strategies for the obese diabetic patient include: 1) promoting weight loss through lifestyle modifications (hypocaloric diet and exercise) and anti-obesity drugs (orlistat, sibutramine, etc.); 2) improving blood glucose control, essentially through the reduction of insulin resistance (metformin, eventually thiazolidinediones) or insulin need (alpha-glucosidase inhibitors) and, at a later stage, the correction of defective insulin secretion (sulphonylureas, repaglinide) or low circulating insulin levels (exogenous insulin); and 3) treating common associated risk factors, such as arterial hypertension and dyslipidaemias, to improve cardiovascular prognosis. When morbid obesity is present, both restoring a good glycemic control and correcting associated risk factors can only be obtained through marked and sustained weight loss. This primary objective justifies more aggressive weight reduction programmes, including very low-calorie diets and bariatric surgery, but only within a multidisciplinary approach and in well-selected patients.     

Muscle-specific PPARgamma-deficient mice develop increased adiposity and insulin resistance but respond to thiazolidinediones

Activation of peroxisome proliferator-activated receptor gamma (PPARgamma) by thiazolidinediones (TZDs) improves insulin resistance by increasing insulin-stimulated glucose disposal in skeletal muscle. It remains debatable whether the effect of TZDs on muscle is direct or indirect via adipose tissue. We therefore generated mice with muscle-specific PPARgamma knockout (MuPPARgammaKO) using Cre/loxP recombination. Interestingly, MuPPARgammaKO mice developed excess adiposity despite reduced dietary intake. Although insulin-stimulated glucose uptake in muscle was not impaired, MuPPARgammaKO mice had whole-body insulin resistance with a 36% reduction (P < 0.05) in the glucose infusion rate required to maintain euglycemia during hyperinsulinemic clamp, primarily due to dramatic impairment in hepatic insulin action. When placed on a high-fat diet, MuPPARgammaKO mice developed hyperinsulinemia and impaired glucose homeostasis identical to controls. Simultaneous treatment with TZD ameliorated these high fat-induced defects in MuPPARgammaKO mice to a degree identical to controls. There was also altered expression of several lipid metabolism genes in the muscle of MuPPARgammaKO mice. Thus, muscle PPARgamma is not required for the antidiabetic effects of TZDs, but has a hitherto unsuspected role for maintenance of normal adiposity, whole-body insulin sensitivity, and hepatic insulin action. The tissue crosstalk mediating these effects is perhaps due to altered lipid metabolism in muscle.     

The backbone of oral glucose‐lowering therapy: time for a paradigm shift?

The complex array of metabolic abnormalities associated with type 2 diabetes provides a number of new targets for therapeutic intervention. Although the established oral glucose-lowering therapies, metformin and the sulfonylureas, continue to provide the backbone of therapeutic approaches, the thiazolidinediones (TZDs) also play an important role. Further, a new class of oral agents, the dipeptidyl peptidase-IV (DPP-IV) inhibitors, has recently become available with apparent utility in decreasing postprandial glucose excursions. This review examines how the TZDs and the DPP-IV inhibitors might integrate into current treatment strategies, considering not only glycemic goals, but also longer-term benefits such as durability of glycemic control, effect on metabolic parameters and cardiovascular outcomes. A practical approach is taken, reflecting potential clinical situations in which therapeutic intervention is required.     

Oral agents in the management of type 2 diabetes mellitus

Despite exhaustive efforts to better manage patients with type 2 diabetes mellitus (formerly known as non-insulin-dependent diabetes mellitus), attempts at maintaining near normal blood glucose levels in these patients remains unsatisfactory. This continues to pose a real challenge to physicians as the prevalence of this disease in the United States continues to rise. Type 2 diabetes is defined as a syndrome characterized by insulin deficiency, insulin resistance and increased hepatic glucose output. Medications used to treat type 2 diabetes are designed to correct one or more of these metabolic abnormalities. Currently, there are five distinct classes of hypoglycemic agents available, each class displaying unique pharmacologic properties. These classes are the sulfonylureas, meglitinides, biguanides, thiazolidinediones and alpha-glucosidase inhibitors. In patients for whom diet and exercise do not provide adequate glucose control, therapy with a single oral agent can be tried. When choosing an agent, it is prudent to consider both patient- and drug-specific characteristics. If adequate blood glucose control is not attained using a single oral agent, a combination of agents with different mechanisms of action may have additive therapeutic effects and result in better glycemic control.     

Combined metformin and insulin therapy for patients with type 2 diabetes mellitus

OBJECTIVE: This study was undertaken to assess the effects of combined treatment with insulin and metformin in patients with type 2 diabetes mellitus in whom dietary measures, weight control, and oral antihyperglycemic therapy had failed. BACKGROUND: Insulin resistance in peripheral tissues, increased hepatic gluconeogenesis, and impaired insulin secretion are the underlying factors in the development of type 2 diabetes. Metformin is a biguanide antihyperglycemic agent that increases peripheral insulin sensitivity, reduces hepatic gluconeogenesis, and decreases intestinal glucose absorption. METHODS: Thirty-one patients (24 women, 7 men; mean age, 61.8 years; mean body mass index [BMI], 28.0 kg/m2) were enrolled in this randomized, double-blind, 2-way, crossover, placebo-controlled study. Patients with type 2 diabetes who were treated previously with insulin or oral hypoglycemic agents and who had a glycosylated hemoglobin (HbA1c) level >9% or a fasting blood glucose level >8 mmol/L were included. Patients who were being treated with oral agents were switched to insulin therapy and required to maintain stable blood glucose control for 2 months prior to randomization. Patients received insulin plus either metformin 1,700 mg/d or placebo for 5 months, followed by a 2-month washout period, and were then crossed over to the other treatment arm for 5 months of additional treatment (total treatment period: 12 months). RESULTS: Thirty patients completed the study; 1 patient withdrew early because of hypoglycemia. Compared with placebo, metformin produced significant reductions from overall baseline in mean daily insulin dose requirement (-8.69 units (17.2%], P < 0.001), HbA1c level (-0.74 [9.9%], P = 0.005), serum fructosamine level (-44.40 micromol/L, P = 0.026), 24-hour blood glucose profile (P = 0.008), and total cholesterol level (-0.42 mmol/L, P = 0.005). No treatment effects were observed on body weight, blood pressure, serum high-density lipoprotein cholesterol levels, or serum triglyceride levels. There was no correlation between BMI and reduction in HbA1C. No major side effects were reported. CONCLUSIONS: Combination therapy with metformin and insulin improves glycemic control and reduces insulin requirements. with no major side effects, in patients with type 2 diabetes and may improve the risk profile in this patient population.     

Exploring an optimal approach to the use of oral hypoglycemic agents based on CGM results: implications for combination therapy with oral hypoglycemic agents

In the treatment of type 2 diabetes aimed at prevention of cardiovascular events impacting the prognosis of affected patients, it is critically important not only to lower HbAlc values but to find a way to improve postprandial hyperglycemia without causing hypoglycemia thus minimizing drastic glycemic variations or to maintain favorable glycemic control with daily glycemic variations in mind. In other words, it is no longer adequate to emphasize quantitative reductions in HbAlc as in conventional therapeutic approaches but qualitative glycemic control that takes daily glycemic variations into account is becoming of increasing importance to the management of type 2 diabetes. On the other hand, the 6 oral hypoglycemic agent (OHA) classes currently available for clinical use, i.e., biguanides (BGs), thiazolidinediones (TZDs), alpha-glucosidase inhibitors, sulfonylureas (SUs), fast-acting insulin secretagogues (glinides) and DPP-4 inhibitors, appear to vary from class to class or even from agent from agent within a class in regard to their impact on daily glycemic variations. In our CMG-based study of their impact on glycemic variations, it was demonstrated that BGs and TZDs improve hyperglycemia during nighttime and before breakfast more effectively than they do postprandial glycemic excursions; that, of the insulin secretagogues, glinides reduce daily glycemic variations as do alpha-glucosidase inhibitors, while SUs do not affect them very much; and that DPP-4 inhibitors lower not only mean glucose levels which are deemed equivalent to HbAlc values but also narrow the range of glycemic variations. Thus, OHAs can be broadly classified into those that primarily reduce 24-hour mean glucose levels as equivalent to HbAlc values and those that primarily narrow the range of glycemic variations. Therefore, with either of these agents as monotherapy, it is next to impossible to achieve reductions in HbAlc with a narrow range of glycemic variations, and combination therapy appears to be the only option available to fine-tune glycemic control. In other words, combining an agent that primarily reduces 24-hour mean glucose levels (HbAlc) with another that primarily narrows the range of daily glycemic variations appears to be an extremely useful option in achieving high-quality glycemic control (HbA1c reductions with a narrow range of glycemic variations).     

Macrophage PPAR gamma is required for normal skeletal muscle and hepatic insulin sensitivity and full antidiabetic effects of thiazolidinediones

PPAR gamma is required for fat cell development and is the molecular target of antidiabetic thiazolidinediones (TZDs), which exert insulin-sensitizing effects in adipose tissue, skeletal muscle, and liver. Unexpectedly, we found that inactivation of PPAR gamma in macrophages results in the development of significant glucose intolerance plus skeletal muscle and hepatic insulin resistance in lean mice fed a normal diet. This phenotype was associated with increased expression of inflammatory markers and impaired insulin signaling in adipose tissue, muscle, and liver. PPAR gamma-deficient macrophages secreted elevated levels of factors that impair insulin responsiveness in muscle cells in a manner that was enhanced by exposure to FFAs. Consistent with this, the relative degree of insulin resistance became more severe in mice lacking macrophage PPAR gamma following high-fat feeding, and these mice were only partially responsive to TZD treatment. These findings reveal an essential role of PPAR gamma in macrophages for the maintenance of whole-body insulin action and in mediating the antidiabetic actions of TZDs.     

Differential effects of metformin and troglitazone on cardiovascular risk factors in patients with type 2 diabetes

OBJECTIVE: Traditional cardiovascular risk factors (CVRF) only partly explain the excessive risk of cardiovascular disease in patients with type 2 diabetes. There is now an increasing appreciation for many novel CVRF that occur largely as a result of insulin resistance and hyperinsulinemia. Therefore, we investigated whether diabetes medications that vary in their mechanism of action and ability to reduce insulin resistance may differ in their effects on both traditional and novel CVRF. RESEARCH DESIGN AND METHODS: We compared the addition of metformin or troglitazone therapy on CVRF in 22 subjects with type 2 diabetes who remained in poor glycemic control (with HbA1c >8.5%) while taking glyburide 10 mg twice daily. Subjects were initially randomized to either metformin 850 mg once daily or troglitazone 200 mg once daily. Both medications were then titrated upward as needed to achieve fasting plasma glucose <120 mg/dl. Measures of glucose control, insulin resistance, and CVRF (blood pressure, lipids, plasminogen activator inhibitor-1, C-reactive protein, fibrinogen, and small dense LDL) were assessed both before and after therapy. RESULTS: After 4 months of treatment, both metformin and troglitazone led to similar decreases in fasting plasma glucose and HbA1c. The reduction in insulin resistance determined by hyperinsulinemic-euglycemic clamp was nearly twofold greater with troglitazone than metformin. Metformin did not induce significant changes in blood pressure, LDL cholesterol, LDL size, HDL cholesterol, triglycerides, or plasminogen activator inhibitor-1. However, C-reactive protein did decrease by 33% (6 +/- 1 to 4 +/- 1 mg/l; P < 0.01) [corrected]. Troglitazone therapy was associated with increases in LDL size (26.21 +/- 0.22 to 26.56 +/- 0.25 nm; P=0.04) and HDL cholesterol (33 +/- 3 to 36 +/- 3 mg/dl; P=0.05) and decreases in triglycerides (197 +/- 19 to 155 +/- 23 mg/dl; P=0.07) and C-reactive protein by 60% (8 +/- 3 to 3 +/- 1 mg/l, P < 0.01) [corrected]. CONCLUSIONS: For patients with type 2 diabetes in whom maximal sulfonylurea therapy failed, the addition of the insulin sensitizer troglitazone seemed to have greater benefits on several traditional and novel CVRF than metformin therapy. These differences were not related to glycemic improvement but reflected, in part, the greater reduction in insulin resistance obtained with addition of troglitazone. These data suggest that medications that more effectively address this underlying metabolic defect may be more beneficial in reducing cardiovascular risk in type 2 diabetes.     

Thiazolidinedione derivatives in diabetes and cardiovascular disease: an update

As the incidence and the public health impact of type 2 diabetes are constantly rising, treatment of hyperglycemia, prevention of diabetes-related complications are currently top medical priorities. Within the last decade several new classes of oral hypoglycemic agents were added to our armamentarium against diabetes. Among these new classes, the group of thiazolidinediones, which act through reduction of insulin resistance is perhaps the most widely used. For about 20 years, numerous background and clinical studies have evaluated the beneficial and adverse effects of these compounds. Current knowledge suggests that thiazolidinediones are as effective as metformin or sulfonylurea derivatives in improving glycemic control and exert several other beneficial metabolic and vascular effects, such as improvement in lipid profile, blood pressure lowering, redistribution of body fat away from the central compartment, microalbuminuria regression, reduction in subclinical vascular inflammation and others. On the other hand, currently used thiazolidinediones have well-established side effects, most important of which are fluid retention leading to weight gain and heart failure deterioration. Further, in the expectance of proper outcome studies to clarify the effects of these agents in cardiovascular morbidity and mortality, data from recent meta-analyses suggest that rosiglitazone may increase the risk for some cardiovascular outcomes. This article will discuss all the above issues attempting to provide an updated overview of this expanding field.     

Linagliptin/Metformin Fixed-Dose Combination Treatment: A Dual Attack to Type 2 Diabetes Pathophysiology

Combination therapies are a widely accepted approach to type 2 diabetes treatment, considering that monotherapies fail to provide adequate glycemic control in the majority of cases. The combination of oral antidiabetic agents into a single tablet would significantly simplify the therapeutic regimen and maximize patients’ adherence to treatment. Recently, a fixed-dose, single-tablet, combined formulation of linagliptin (a dipeptidyl peptidase-4 inhibitor) and metformin has been approved for use in type 2 diabetic patients, and is indicated as an adjunct to diet and exercise for those patients who remain inadequately controlled despite maximal tolerated doses of metformin, metformin and sulfonylurea, or linagliptin and metformin monotherapies. The combination tablet is administered twice daily and can be used either alone or combined with sulfonylureas. Clinical trials suggest that this fixed-dose combination provides significantly superior glycemic control compared to linagliptin and metformin monotherapy, in terms of improving key parameters of glucose homeostasis such as glycosylated hemoglobin, fasting and postprandial glucose levels. It also exhibits an excellent tolerability profile, without promoting weight gain and hypoglycemic episodes. The compounds of this formulation do not display clinically relevant pharmacokinetic interactions with each other, and exert synergistic (complementary) pharmacodynamic effects, including an enhanced incretin effect, suppressed hepatic glucose production, and improved peripheral insulin sensitivity. As a result, a linagliptin/metformin fixeddose combination offers the potential to address multiple defects of type 2 diabetes pathophysiology (pancreatic islet dysfunction, insulin resistance, increased hepatic glucose output), and most importantly, in the context of a safe, efficacious, flexible, and convenient therapeutic regimen.     

Metformin hydrochloride in the treatment of type 2 diabetes mellitus: a clinical review with a focus on dual therapy

BACKGROUND: Type 2 diabetes mellitus typically involves abnormal beta-cell function that results in relative insulin deficiency, insulin resistance accompanied by decreased glucose transport into muscle and fat cells, and increased hepatic glucose output, all of which contribute to hyperglycemia. OBJECTIVE: This review examines the pharmacology, pharmacokinetics, drug-interaction potential, adverse effects, and dosing guidelines for metformin hydrochloride, a biguanide agent for the treatment of type 2 diabetes. Clinical trial data are reviewed, including efficacy and tolerability information, with a focus on studies of dual metformin therapy (metformin plus another oral agent or insulin) published from 1998 to the present. Pharmacoeconomic considerations are also discussed. METHODS: Primary research and review articles were identified through a search of MEDLINE (1966-May 2003) and International Pharmaceutical Abstracts (1970-May 2003) using the terms metformin and/or Glucophage. Web of Science (1995-May 2003) was used to search for additional abstracts. The package inserts for metformin and metformin combination products were consulted. All identified articles and abstracts were assessed for relevance, and all relevant information was included. Priority was given to the primary medical literature and clinical trial reports. RESULTS: Metformin is the only currently available oral antidiabetic/hypoglycemic agent that acts predominantly by inhibiting hepatic glucose release. Because patients with type 2 diabetes often have excess hepatic glucose output, use of metformin is effective in lowering glycosylated hemoglobin (HbA1c) by 1 to 2 percentage points when used as monotherapy or in combination with other blood glucose-lowering agents or insulin. Other metabolic variables (eg, dyslipidemia, fibrinolysis) may be improved with the use of metformin. Body weight is often maintained or slightly reduced from baseline. Metformin is well tolerated and is associated with few clinically deleterious adverse events. The most important and potentially life-threatening adverse event associated with its use is lactic acidosis, which occurs very rarely. CONCLUSIONS: Metformin has multiple benefits in patients with type 2 diabetes. It can effectively lower HbA1c values, positively affect lipid profiles, and improve vascular and hemodynamic indices. Adverse effects are generally tolerable and self-limiting. The availability of products combining metformin with a sulfonylurea or rosiglitazone has expanded the array of therapies for the management of type 2 diabetes.     

Prevention and treatment for development and progression of diabetic macroangiopathy with pioglitazone and metformin

Prevention and treatment for diabetic macroangiopathy, causing the main etiology for mortality in patients with diabetes mellitus, is crucial target point, but is still controversial. Many clinical studies improving glycemic control by insulin and oral drugs were not demonstrating enough prevention for diabetic macroangiopathy to improve life prognosis. Insulin resistance is now considered to be major pathogenesis for diabetic macroangiopathy. The agents that improve insulin resistance, such as metformin and pioglitazone, have multiple effects to improve glucose and lipid metabolism by increasing sensitivity for insulin without increasing insulin secretion and exert anti-atherogenic properties resulting in preventing development of atherosclerosis. Some clinical studies such as UKPDS 34 and PROactive demonstrated preventive effects of these agents for diabetic macroangiopathy.     

Diabetes mellitus

The thiazolidinedione compound is known as an insulin-sensitizing agent and is considered a very promising drug, because insulin resistance is a major component of type 2 diabetes. Many reports have demonstrated that the thiazolidinedione has the good hypoglycemic effect in monotherapy and in combination therapy with sulfonylureas, metformin, alpha-glucosidase inhibitors, or insulin. Furthermore, the thiazolidinedione has additional beneficial effects on serum lipids, arterial blood pressure, coagulation-fibrinolysis system, arterial wall cell function. These favorable effects suggest the thiazolidinedione may have inhibitory actions on both macroangiopathy and microangiopathy in patients with diabetes mellitus. However, some patients treated with troglitazone, the first available thiazolidinedione, have suffered from liver dysfunction; in some cases, patients have progressed to hepatic failure and death unfortunately. As the thiazolidinediones are clearly excellent drugs to diabetics with insulin resistance, we should check hepatic function and monitor symptomes of hepatic damage.     

Nateglinide and mitiglinide

Patients with type 2 diabetes mellitus are associated with insulin resistance and/or impaired insulin secretion. Previous observations indicate that Japanese patients with type 2 diabetes tend to have impaired insulin response after glycemic load more often than Caucasian counterparts. Recently it has been reported that hyperglycemia after glucose load is itself a risk factor for the development of cardiovascular complications in the absence of elevated fasting plasma glucose. Recent observations on the association of post-challenge or post-prandial hyperglycemia with cardiovascular events suggest that lowering post-prandial plasma glucose may protect patients from developing cardiovascular diseases. Results of STOP-NIDDM trial suggest that nateglinide, which attenuates post-prandial glycemic surge in type 2 diabetes, may also be helpful for the protection against cardiovascular events. Nateglinide exerts its effects shortly after its administration and the effects continue for only about 3 hours. The patients receiving this agent rarely gain weight and develop hypoglycemia. This agent exerts hypoglycemic effects additively with alpha-gulucosidase inhibitors or metformin.     

Mechanisms of thiazolidinedione derivatives for hypoglycemic and insulin sensitizing effects

Ciglitazone was the first insulin sensitizer with a thiazolidinedione structure to reduce insulin resistance and hyperglycemia and many thiazolidinedione derivatives (TZDs) have since been reported as insulin sensitizers. Pioglitazone is reported to lower blood glucose through reductions in both hepatic and peripheral insulin resistance. Regarding the molecular mechanism, pioglitazone was first reported to increase the tyrosine kinase activity of the insulin receptor and then TZDs were reported to increase the insulin signal transduction. TNF-alpha causes insulin resistance through inhibition of the insulin signal transduction and TZDs have been shown to reduce insulin resistance by the suppression of the TNF-alpha gene expression. In addition, TZDs are specific agonists of PPAR gamma and the hypoglycemic effect of TZDs has been shown to involve PPAR gamma among the PPARs. Based on these observations, the molecular mechanisms of TZDs are discussed.     

Insulin sensitizers

Type 2 diabetes mellitus is an increasingly prevalent disorder associated with multiple metabolic derangements. Insulin resistance is the most prominent feature common in both type 2 diabetes and its associated metabolic abnormalities. Until 1995, the only therapeutic interventions available in the United States were the insulin secretagogues sulfonylureas and insulin. With the introduction of metformin in the United States in the mid-1990s and the subsequent advent of thiazolidinediones, an opportunity exists to address and directly reverse, at least in part, the defects in insulin action seen in individuals with type 2 diabetes. Evidence shows that insulin sensitizers not only have beneficial effects on glycemic control but also have multiple effects on lipid metabolism and atherosclerotic vascular processes that could prove to be beneficial. We discuss safety issues of these agents, their potential use in preventing onset and progression of diabetes, and their use in other related metabolic conditions such as polycystic ovary syndrome.