Effect of troglitazone in insulin-treated patients with type II diabetes mellitus. Troglitazone and Exogenous Insulin Study Group

c-Fos-driven transcriptional activation of transforming growth factor beta-1: inhibition of high glucose-induced promoter activity by thiazolidinediones

The peroxisome proliferator-activated receptor gamma activating compounds thiazolidinedione (TZD) have been shown to inhibit diabetes-induced glomerular transforming growth factor-beta1 (TGF-beta1) expression, thereby ameliorating diabetic nephropathy. Here we examined the hypothesis that TZDs block high glucose-induced TGF-beta1 gene activation by interaction with the activated protein kinase C-c-Fos-TGF-beta1 promoter cascade in mesangial cells. The TZD compounds troglitazone and rosiglitazone completely prevented the high glucose induction of both TGF-beta1 promoter activity and elevation in nuclear c-Fos protein levels. The scavenging properties of troglitazone were shown not to be responsible for this inhibitory action, because hydrogen peroxide-mediated stimulation of TGF-beta1 promoter activity was not blocked. TZD-treatment did not interfere with the transcriptional activity of c-Fos responsible for stimulation of the TGF-beta1 promoter. The findings suggest a molecular mechanism by which TZD-treatment reduces specifically high glucose-induced, c-Fos-mediated gene activation, since phorbol ester-induced c-Fos mRNA and protein expression and subsequent elevation of TGF-beta1 mRNA expression were not prevented by TZDs.

Combination therapy with PPARgamma and PPARalpha agonists increases glucose-stimulated insulin secretion in db/db mice

Although peroxisome proliferator-activated receptor (PPAR)gamma agonists ameliorate insulin resistance, they sometimes cause body weight gain, and the effect of PPAR agonists on insulin secretion is unclear. We evaluated the effects of combination therapy with a PPARgamma agonist, pioglitazone, and a PPARalpha agonist, bezafibrate, and a dual agonist, KRP-297, for 4 wk in male C57BL/6J mice and db/db mice, and we investigated glucose-stimulated insulin secretion (GSIS) by in situ pancreatic perfusion. Body weight gain in db/db mice was less with KRP-297 treatment than with pioglitazone or pioglitazone + bezafibrate treatment. Plasma glucose, insulin, triglyceride, and nonesterified fatty acid levels were elevated in untreated db/db mice compared with untreated C57BL/6J mice, and these parameters were significantly ameliorated in the PPARgamma agonist-treated groups. Also, PPARgamma agonists ameliorated the diminished GSIS and insulin content, and they preserved insulin and GLUT2 staining in db/db mice. GSIS was further increased by PPARgamma and -alpha agonists. We conclude that combination therapy with PPARgamma and PPARalpha agonists may be more useful with respect to body weight and pancreatic GSIS in type 2 diabetes with obesity.

Pharmacological management of type 2 diabetes mellitus: rationale for rational use of insulin

Type 2 diabetes mellitus is a chronic metabolic disorder associated with high morbidity and mortality from long-term microvascular and macrovascular complications. Evidence from randomized controlled trials indicates that aggressive treatment directed at improving glycemic control reduces the incidence of diabetes-related microvascular complications. Traditionally, oral monotherapy for type 2 diabetes is initiated when diet and exercise do not control hyperglycemia, followed by the sequential, stepwise addition of oral agents as glycemic control deteriorates. Insulin is the last therapeutic option used, generally reserved for advanced stages of the disease when multiple oral combination treatment fails. Despite a better understanding of the pathophysiologic disease mechanisms in the past decade, the expanded armamentarium of targeted oral antidiabetic drugs, and the conclusive evidence of the benefits of stringent glycemic control, actual treatment outcomes in clinical practice remain suboptimal relative to established treatment goals (glycosylated hemoglobin A1c level <7%). Earlier detection and aggressive treatment are critical to address the natural progression of diabetes because multiple defects (insulin resistance, insulin insufficiency, glucotoxicity, and lipotoxicity) and vascular complications may be present at the time of diagnosis. Acknowledging the inadequacy of traditional strategies and underscoring the importance of insulin as an integral part of the therapeutic armamentarium, clinical trends are moving toward earlier use of insulin combined with 1 or more oral agents. Such strategies can address the multiple abnormalities present early in the disease course and may restore optimal control. A new treatment paradigm for patients with type 2 diabetes to achieve and maintain near-normal glycemic control is warranted.

Modulation of hunger by plasma glucose and metformin

The plasma glucose concentration is a major short-term regulator of hunger and food intake. In patients with diabetes, therapies lowering plasma glucose are frequently associated with body weight gain, suggesting that lowered plasma glucose leads to increased feelings of hunger and food intake. However, as many physiological and symptomatic responses to low plasma glucose are attenuated after repeated episodes of hypoglycemia, this may also pertain to feelings of hunger. Here we tested whether the stimulatory effect of low plasma glucose on feelings of hunger is likewise reduced by repeated episodes of hypoglycemia. As metformin has been shown to reduce plasma glucose levels without increasing body weight and also to decrease food intake, we tested for possible interacting effects of this substance with hypoglycemia-induced hunger. Feelings of hunger were assessed by rating scales during 3 consecutive hypoglycemic clamps performed on 2 consecutive d in 15 normal weight men. Subjects were tested once while being treated with 850 mg metformin twice daily and once while receiving placebo. Treatment was started 14 d before the clamp experiments and was performed in a random order and double-blind fashion. Hypoglycemia markedly enhanced feelings of hunger (P < 0.001). However, rated feelings of hunger on the first and last hypoglycemic clamps were comparable (P = 0.304). Compared with placebo, metformin decreased feelings of hunger during hypoglycemia (P = 0.015). This reduction was not associated with a decrease in posthypoglycemic food intake as measured by the number of cookies consumed after the last clamp (P = 0.676). Data indicate that the stimulatory effect of low plasma glucose on hunger is not attenuated after repeated episodes of hypoglycemia, which implies that, in contrast to other symptoms, hunger is not subject to adaptive attenuation upon repeated hypoglycemia. Metformin attenuates hypoglycemia-induced hunger, but does not appear to influence posthypoglycemic food intake.

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.

Pharmacotherapy of diabetes mellitus: implications for the prevention and treatment of cardiovascular disease

Diabetes mellitus in adults is associated with an increased risk of premature vascular disease and a higher mortality rate. The presence of other risk factors, often seen in diabetic patients, such as systemic hypertension, augments the rate of vascular diseases. Evidence is growing that tight control of hyperglycemia using insulin and/or oral hypoglycemic agents will modify this risk. More aggressive control of concomitant hypertension and/or hyperlipidemia is also required. Diabetic patients who have myocardial infarctions do worse than nondiabetic patients. Various strategies to improve outcomes include the use of tight blood glucose control, and various coronary interventions are currently under clinical study.

PPAR(gamma) and glucose homeostasis

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor involved in the control of metabolism. Research on PPARgamma is oriented towards understanding its role in insulin sensitization, which was inspired by the discovery that antidiabetic agents, the thiazolidinediones, were agonists for PPARgamma. PPARgamma stimulation improves glucose tolerance and insulin sensitivity in type 2 diabetic patients and in animal models of insulin resistance through mechanisms that are incompletely understood. Upon activation, PPARgamma heterodimerizes with retinoid X receptor, recruits specific cofactors, and binds to responsive DNA elements, thereby stimulating the transcription of target genes. Because PPARgamma is highly enriched in adipose tissue and because of its major role in adipocyte differentiation, it is thought that the effects of PPARgamma in adipose tissue are crucial to explain its role in insulin sensitization, but recent studies have highlighted the contribution of other tissues as well. Although relatively potent for their insulin-sensitizing action, currently marketed PPARgamma activators have some important undesirable side effects. These concerns led to the discovery of new ligands with potent antidiabetic properties but devoid of certain of these side effects. Data from human genetic studies and from PPARgamma heterozygous knockout mice indicate that a reduction in PPARgamma activity could paradoxically improve insulin sensitivity. These findings suggest that modulation of PPARgamma activity by partial agonists or compounds that affect cofactor recruitment might hold promise for the treatment of insulin resistance.

Troglitazone: the discovery and development of a novel therapy for the treatment of Type 2 diabetes mellitus

Prior to the introduction of troglitazone, it had been more than 30 years since the last significant improvement in antidiabetic therapy. In view of the pressing need for more effective oral agents for the treatment of Type 2 diabetes mellitus, troglitazone was granted priority review by the FDA and was launched in the USA in 1997. The first of the thiazolidinedione insulin sensitizing agents, troglitazone was quickly followed by rosiglitazone and pioglitazone. The glitazones proved to be effective not only in lowering blood glucose, but also to have beneficial effects on cardiovascular risk. Troglitazone was subsequently withdrawn because of concerns about hepatotoxicity, which appears to be less of a problem with rosiglitazone and pioglitazone. Recent insights into the molecular mechanism of action of the glitazones, which are ligands for the peroxisome proliferator-activated receptors, open the prospect of designing more effective, selective and safer antidiabetic agents. This document will review the history of troglitazone from discovery through clinical development.

Comparison of insulin monotherapy and combination therapy with insulin and metformin or insulin and troglitazone in type 2 diabetes

OBJECTIVE

To evaluate the safety and efficacy of treatment with insulin alone, insulin plus metformin, or insulin plus troglitazone in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 88 type 2 diabetic subjects using insulin monotherapy (baseline HbA(lc) 8.7%) were randomly assigned to insulin alone (n = 31), insulin plus metformin (n = 27), or insulin plus troglitazone (n = 30) for 4 months. The insulin dose was increased only in the insulin group. Metformin was titrated to a maximum dose of 2,000 mg and troglitazone to 600 mg.

RESULTS

HbA(lc) levels decreased in all groups, the lowest level occurring in the insulin plus troglitazone group (insulin alone to 7.0%, insulin plus metformin to 7.1%, and insulin plus troglitazone to 6.4%, P < 0.0001). The dose of insulin increased by 55 units/day in the insulin alone group (P < 0.0001) and decreased by 1.4 units/day in the insulin plus metformin group and 12.8 units/day in the insulin plus troglitazone group (insulin plus metformin versus insulin plus troglitazone, P = 0.004). Body weight increased by 0.5 kg in the insulin plus metformin group, whereas the other two groups gained 4.4 kg (P < 0.0001 vs. baseline). Triglyceride and VLDL triglyceride levels significantly improved only in the insulin plus troglitazone group. Subjects taking metformin experienced significantly more gastrointestinal side effects and less hypoglycemia.

CONCLUSIONS

Aggressive insulin therapy significantly improved glycemic control in type 2 diabetic subjects to levels comparable with those achieved by adding metformin to insulin therapy. Troglitazone was the most effective in lowering HbA(lc), total daily insulin dose, and triglyceride levels. However, treatment with insulin plus metformin was advantageous in avoiding weight gain and hypoglycemia.

Increasing incidence of type 2 diabetes in children and adolescents: treatment considerations

The emerging public health problem of type 2 diabetes in youth reflects increasing rates of childhood obesity. As in adults, type 2 diabetes in children is part of the insulin resistance syndrome that includes hypertension, dyslipidemia and other atherosclerosis risk factors, and hyperandrogenism seen as premature adrenarche and polycystic ovary syndrome. Studies in children document risk factors for type 2 diabetes and associated cardiovascular risk factors, including obesity, family history, diabetic gestation, and underweight or overweight for gestational age. Genetically determined insulin resistance, or limited beta-cell reserve, has been demonstrated in high risk individuals. This genetic background, considered advantageous in a feast and famine existence (the thrifty genotype), is rendered detrimental with abundant food and physical inactivity, a lifestyle demonstrated to be typical of families of children with type 2 diabetes. Case finding in high risk individuals who are asymptomatic may be an appropriate response to the public health challenge of type 2 diabetes in children, because risk factors for cardiovascular disease are already present at the time of diagnosis. Treatment is dictated by the degree of metabolic derangement and symptoms. The only data on the use of oral hypoglycemic agents in children has been with metformin. Prevention efforts will require community and government involvement to reduce obesity and increase physical activity in the child, as well as adult, population.

Combination therapy with nateglinide and a thiazolidinedione improves glycemic control in type 2 diabetes

OBJECTIVE

To compare the effects of monotherapy using nateglinide and the thiazolidinedione troglitazone with initial combination of the two agents on glycated hemoglobin (HbA(1c)) in patients with type 2 diabetes inadequately controlled by diet alone.

RESEARCH DESIGN AND METHODS

This study consisted of a 28-week, double-blind, randomized, multicenter study that included a 4-week, single-blind, placebo, run-in period and a 24-week (shortened to 16 weeks), double-blind, active treatment period.

RESULTS

At the 16-week end point, nateglinide 120 mg, troglitazone 600 mg, and the combination of the agents achieved statistically significant decreases in HbA(1c) in comparison with placebo and a baseline HbA(1c) of 8.1-8.4% (P < 0.001). The reductions in HbA(1c) were similar in the nateglinide (0.6%) and troglitazone (0.8%) monotherapy groups. The reduction in HbA(1c) (1.7%) was greatest in the combination group; 79% of patients in the combination group achieved HbA(1c) levels of <7%. The combination group had a higher number of adverse events, primarily due to an increased incidence of mild hypoglycemia in this treatment group.

CONCLUSIONS

Nateglinide and troglitazone are equally effective in decreasing HbA(1c) levels. However, these reductions from baseline HbA(1c) values of >8% are not adequate to achieve HbA(1c) levels of <7%. In contrast, the combination of nateglinide and of a thiazolidinedione shows an additive effect that is highly effective in reducing HbA(1c) levels to the target of <7% in 66% of patients, from a baseline HbA(1c) that is just above 8%.

Genetically defined pancreatic beta cell failure

The major subtypes of diabetes mellitus (DM) are complex diseases in which the interactions between genetic susceptibility and metabolic, immunologic and environmental factors ultimately lead to the clinical phenotype. The unraveling of these factors and the study of their contribution to the pathogenesis of DM is a process of unimaginable complexity. As a result, despite the individual differences in DM phenotype, most patients with DM receive treatment according to generalized treatment protocols, only discriminating between Type 1 and Type 2 DM and not related to the individual genetic background of the patients. Nevertheless, in recent years, much progress has been made in the search for genetic factors in DM. As an example, the recognition of monogenetic defects in beta cell function has lead to the definition of novel DM subtypes, which have important implications for the individual therapeutic approach for these patients and the understanding of the etiology of DM.

Metabolic and additional vascular effects of thiazolidinediones

Several cardiovascular risk factors (dyslipidaemia, hypertension, glucose intolerance, hypercoagulability, obesity, hyperinsulinaemia and low-grade inflammation) cluster in the insulin resistance syndrome. Treatment of these individual risk factors reduces cardiovascular complications. However, targeting the underlying pathophysiological mechanisms of the insulin resistance syndrome is a more rational treatment strategy to further improve cardiovascular outcome. Our understanding of the so-called cardiovascular dysmetabolic syndrome has been improved by the discovery of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors belonging to the nuclear receptor superfamily. As transcription factors, PPARs regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, vascular tone and inflammation. Activation of the subtype PPAR-gamma improves insulin sensitivity. Expression of PPAR-gamma is present in several cell types involved in the process of atherosclerosis. Thus, modulation of PPAR-gamma activity is an interesting therapeutic approach to reduce cardiovascular events. Thiazolidinediones are PPAR-gamma agonists and constitute a new class of pharmacological agents for the treatment of type 2 (non-insulin-dependent) diabetes mellitus. Two such compounds are currently available for clinical use: rosiglitazone and pioglitazone. Thiazolidinediones improve insulin sensitivity and glycaemic control in patients with type 2 diabetes. In addition, improvement in endothelial function, a decrease in inflammatory conditions, a decrease in plasma levels of free fatty acids and lower blood pressure have been observed, which may have important beneficial effects on the vasculature. Several questions remain to be answered about PPAR-gamma agonists, particularly with respect to the role of PPAR-gamma in vascular pathophysiology. More needs to be known about the adverse effects of thiazolidinediones, such as hepatotoxicity, increased low-density lipoprotein cholesterol levels and increased oedema. The paradox of adipocyte differentiation with weight gain concurring with the insulin-sensitising effect of thiazolidinediones is not completely understood. The decrease in blood pressure induced by thiazolidinedione treatment seems incompatible with an increase in the plasma volume, and the discrepancy between the stimulation of the expression of CD36 and the antiatherogenic effects of the thiazolidinediones also needs further explanation. Long-term clinical trials of thiazolidinediones with cardiovascular endpoints are currently in progress. In conclusion, studying the effects of thiazolidinediones may shed more light on the mechanisms involved in the insulin resistance syndrome. Furthermore, thiazolidinediones could have specific, direct effects on processes involved in the development of vascular abnormalities.

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

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

Rosiglitazone amplifies the benefits of lifestyle intervention measures in long-standing type 2 diabetes mellitus

AIMS

To evaluate the efficacy of a lifestyle intervention programme including meal replacements and increased physical activity upon body weight, diabetes control and other cardiovascular risk factors in obese, poorly controlled, insulin-treated, type-2-diabetic individuals and to assess the impact of concomitant rosiglitazone (RSG) therapy.

METHODS

This 6-month intervention study included 21 patients with type 2 diabetes mellitus (DM) requiring insulin therapy with haemoglobin A1c (HbA1c) > 7% and with a body mass index (b.m.i.) > 27. All subjects were enrolled in a 6-month lifestyle intervention programme and randomized to placebo or RSG 4 mg/day. Participation in the lifestyle programme included meal replacements, increased intake of fruits and vegetables and increased daily physical activity. Measured end-points included body weight, waist circumference, blood pressure, HbA1c and serum lipids, before entry into the study.

RESULTS

The baseline mean b.m.i. was 36.4 and the mean HbA1c was 9.0%. The greatest weight losses occurred during the first 12 weeks (19 lbs for RSG, 13.4 lbs for placebo) with a greater weight loss at each point for the group receiving RSG. Waist circumference declined by 2.8 and 4.0 inches for the placebo and RSG groups. Systolic BP declined 16.2 mmHg in the placebo group and 14.3 mmHg in the RSG group. Diastolic blood pressure decreased by 12.8 mmHg in the placebo group. HbA1c was reduced significantly by 1.3% for the placebo group and 1.1% in the RSG group.

DISCUSSION

This study demonstrates the benefits of lifestyle intervention using meal replacements and increased physical activity with resultant modest weight loss in long-standing, poorly controlled type 2 diabetes. RSG did not impede weight loss and, in fact, amplified some of the positive benefits of lifestyle intervention.

Peroxisome proliferator-activated receptor agonists, hyperlipidaemia, and atherosclerosis

Dyslipidaemia is a major risk factor in the development of atherosclerosis, and lipid lowering is achieved clinically using fibrate drugs and statins. Fibrate drugs are ligands for the fatty acid receptor peroxisome proliferator-activated receptor (PPAR)alpha, and the lipid-lowering effects of this class of drugs are mediated by the control of lipid metabolism, as directed by PPARalpha. PPARalpha ligands also mediate potentially protective changes in the expression of several proteins that are not involved in lipid metabolism, but are implicated in the pathogenesis of heart disease. Clinical studies with bezafibrate and gemfibrozil support the hypothesis that these drugs may have a significant protective effect against cardiovascular disease. The thiazolidinedione group of insulin-sensitising drugs are PPARgamma ligands, and these have beneficial effects on serum lipids in diabetic patients and have also been shown to inhibit the progression of atherosclerosis in animal models. However, their efficacy in the prevention of cardiovascular-associated mortality has yet to be determined. Recent studies have found that PPARdelta is also a regulator of serum lipids. However, there are currently no drugs in clinical use that selectively activate this receptor. It is clear that all three forms of PPARs have mechanistically different modes of lipid lowering and that drugs currently available have not been optimised on the basis of PPAR biology. A new generation of rationally designed PPAR ligands may provide substantially improved drugs for the prevention of cardiovascular disease.

Troglitazone enhances the hepatotoxicity of acetaminophen by inducing CYP3A in rats

Troglitazone (TRZ) is the first of a new group of oral antidiabetic drugs, the thiazolidinediones, and is proven to lower plasma glucose levels in patients with type 2 diabetes mellitus. However, the concern has been raised because of several reports, in which severe hepatic dysfunction leading to hepatic failure was demonstrated in a few patients receiving the drug. We studied the effects of TRZ on the hepatotoxicity of carbon tetrachloride (CCl(4)) and acetaminophen (APAP) in rats, both of which exert their toxic effects through bioactivation associated with cytochrome P450 3A (CYP3A) and 2E1 (CYP2E1). Male standard (Wistar/ST) and type 2 diabetic model (GK/Jal) rats were kept on a powdered chow diet containing 0, 100, 500 mg/kg/rat of TRZ. Three weeks later, the rats were either sacrificed for an in vitro metabolism study or challenged with 0.50 g/kg CCl(4) p.o. or 0.75 g/kg APAP i.p.TRZ at 100 and 500 mg/kg/rat increased the CYP3A level as well as the testosterone 6beta-hydroxylation activities in liver microsomes, but did not affect CYP2E1. TRZ also enhanced APAP hepatotoxicity, as evidenced by significantly increased levels of alanine aminotransferase, aspartate aminotransferase and alpha-glutathione S-transferase in the plasma of rats, and by significantly low hepatic glutathione concentration. Our study demonstrated that high doses of TRZ can enhance hepatotoxicity of APAP in Wistar/ST and GK/Jal by inducing hepatic CYP3A.

Combination of insulin and thiazolidinedione therapy in massively obese patients with Type 2 diabetes

AIMS

To evaluate the influence of addition of rosiglitazone to insulin therapy over a 24-week period in massively obese patients with poorly controlled Type 2 diabetes taking large doses of insulin.

METHODS

Eight massively obese patients (median body mass index (BMI) 42 kg/m2) with Type 2 diabetes who were on large doses of insulin (median daily dose of 204 U) and/or had poor glycaemic control (median HbA1c of 8.1% (upper limit for normal 5.5%)) were treated over a 24-week period with the combination of insulin and maximum doses of rosiglitazone. Outcomes monitored were changes in weight, BMI, HbA1c, dose of insulin and development of side-effects.

RESULTS

At the end of 24 weeks there was a median weight gain of 3 kg (P < 0.01), a fall in median HbA1c from 8.1% to 6.7% (16% reduction from baseline) (P < 0.01) and a reduction in median insulin dose from 204 U/day to 159 U/day (P < 0.01) (23% reduction from baseline). Peripheral oedema was the only significant side-effect and was seen in five patients.

CONCLUSIONS

Combination of insulin and rosiglitazone is effective in massively obese patients with Type 2 diabetes, though there is a high incidence of peripheral oedema.

Antidiabetic thiazolidinediones inhibit collagen synthesis and hepatic stellate cell activation in vivo and in vitro

BACKGROUND & AIMS

The ligand-dependent transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is expressed in hepatic stellate cells (HSC), and its transcriptional activity is reduced during cell transdifferentiation in culture. PPARgamma transcriptional activation decreases platelet-derived growth factor-induced proliferation and inhibits alpha-smooth muscle actin expression in cultured HSC. The aim of our study was to evaluate whether oral administration of synthetic PPARgamma ligands, thiazolidinediones (TZD), might affect collagen deposition in animal models of liver fibrosis.

METHODS

The effect of 2 TZD (pioglitazone or rosiglitazone) was tested on liver fibrosis induced in rats by either toxin administration (dimethylnitrosamine or carbon tetrachloride) or bile duct ligation. In vivo PPARgamma activation was evaluated by gel shift assay using nuclear extracts from HSC isolated from control and treated rats.

RESULTS

Oral administration of TZD reduced extracellular matrix deposition and HSC activation in both toxic and cholestatic models of liver fibrosis. PPARgamma-specific DNA binding was significantly impaired in nuclear extracts of HSC isolated from fibrotic rats compared with HSC from control rats. TZD administration restored PPARgamma DNA binding in HSC nuclei. In vitro, TZD-induced PPARgamma activation inhibited collagen and fibronectin synthesis induced by transforming growth factor (TGF)-beta1 in human HSC, as measured by enzyme-linked immunosorbent assay and Northen blotting. TZD also reduced the TGF-beta1-induced activity of a 3.5-kilobase procollagen type I promoter transfected in human HSC.

CONCLUSIONS

These findings indicate that PPARgamma activation in HSC retards fibrosis in vivo and suggest the use of TZD for the treatment of liver fibrosis.

Peroxisome proliferator-activated receptor-gamma agonists inhibit experimental allergic encephalomyelitis by blocking IL-12 production, IL-12 signaling and Th1 differentiation

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor transcription factor that regulates adipocyte differentiation and glucose homeostasis. PPARgamma agonists are potent therapeutic agents for the treatment of type 2 diabetes and obesity. PPARgamma agonists also prevent inflammation in animal models, suggesting their use for the treatment of human inflammatory diseases. Experimental allergic encephalomyelitis (EAE) is a Th1 cell-mediated inflammatory demyelinating disease model of multiple sclerosis (MS) and IL-12 plays a crucial role in the pathogenesis of EAE and MS. In this study we have examined the effect of PPARgamma agonists on the pathogenesis of EAE. In vivo treatment of SJL/J mice with PPARgamma agonists, 15-deoxydelta(12,14) prostaglandin J2 or Ciglitazone, decreased the duration and clinical severity of active immunization and adoptive transfer models of EAE. PPARgamma agonists inhibited EAE in association with a decrease in IL-12 production and differentiation of neural antigen-specific Th1 cells. In vitro treatment of activated T cells with PPARgamma agonists inhibited IL-12-induced activation of JAK-STAT signaling pathway and Th1 differentiation. These findings highlight the fact that PPARgamma agonists regulate central nervous system inflammation and demyelination by inhibiting IL-12 production, IL-12 signaling and Th1 differentiation in EAE.

Differentiating members of the thiazolidinedione class: a focus on efficacy

The thiazolidinediones (TZDs) or 'glitazones' are a new class of drug used for the treatment of type 2 diabetes. Although their precise mechanism of action is not known, TZDs target insulin resistance directly and thus tackle an underlying cause of the disease. Two TZDs are indicated for use in type 2 diabetes in the USA, pioglitazone and rosiglitazone. A third, troglitazone, has been associated with significant hepatotoxicity and has been withdrawn from use. In clinical trials, all three TZDs effectively lower blood glucose levels as monotherapy and in combination therapy with sulfonylureas, metformin and insulin. To date, head-to-head comparative studies with these agents have not been performed. It is difficult, therefore, to make direct comparisons of their efficacy since other variables, including baseline glucose levels and study design, can have a significant impact on treatment outcome. Despite this and in light of unique safety issues characterized with certain TZDs, it is useful to look closely at the efficacy data for these agents. It is not sufficient to assume that 'all glitazones are the same' because the studies have not yet been done to support this statement. This article will review what is known about the relative efficacy of the TZDs.

Differentiating members of the thiazolidinedione class: a focus on safety

Troglitazone, rosiglitazone and pioglitazone are members of the thiazolidinedione (TZD) class - antidiabetic agents that have proven efficacy in the treatment of patients with type 2 diabetes. All three agents are believed to mediate their effects via activation of the gamma isoform of the peroxisome proliferator-activated receptor (PPAR gamma). Despite this common mechanism of action, they all have unique chemical structures and receptor-binding affinities, and consequently, in addition to the class effects (probably mediated through PPAR gamma), each TZD has a unique safety profile. Side effects have been categorized as unique to individual TZDs, or common to the class of drug. Of the unique effects, the best characterized is hepatotoxicity, which has been associated specifically with troglitazone to date. Studies with rosiglitazone and pioglitazone indicate that hepatotoxicity is not a class effect. Further differences in the safety profiles of these agents arise because the oxidative metabolism for each agent occurs by distinct cytochrome pathways: troglitazone and pioglitazone involve CYP 3A4 and CYP 2C8 whereas rosiglitazone is principally metabolized by CYP 2C8. CYP 3A4 is involved in the metabolism of over 150 drugs, hence the potential for drug interactions with troglitazone and pioglitazone is much greater than with rosiglitazone. Class effects include edema, slight reductions in hemoglobin and hematocrit (due to hemodilution), weight gain and alterations in plasma lipid profiles. This article considers safety data obtained from both clinical trials and clinical practice as a means of differentiating among troglitazone, rosiglitazone and pioglitazone.

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.

Increased lymphatic lipid transport in genetically diabetic obese rats

Otsuka Long-Evans Tokushima fatty (OLETF) rats are a model for noninsulin-dependent diabetes mellitus (NIDDM), which is first manifested at 18 wk of age. We assessed age-related changes in lymphatic lipid transport in the intestine of OLETF rats and compared them with those of control Long-Evans Tokushima Otsuka (LETO) rats. Olive oil was infused into the rats with a mesenteric lymph fistula, which was created under ethrane anesthesia. A significant increase in lymphatic triglyceride (TG) transport in OLETF rats was observed at 18-19 wk compared with under 17 wk, but no age-related change was observed in LETO rats. Food restriction, exercise training, or troglitazone treatment in OLETF rats prevented the age-related increase in lipid transport. Biliary phosphatidylcholine concentration was higher in OLETF rats than in LETO rats, but no difference was seen in bile acid concentrations or the activity of microsomal TG transfer protein between the two strains. This study shows that increased lipid transport in the intestine may occur in NIDDM.

Thiazolidinedione derivative improves fat distribution and multiple risk factors in subjects with visceral fat accumulation--double-blind placebo-controlled trial

BACKGROUND

It has been clarified that visceral fat accumulation leads to atherosclerosis through multiple risk factors such as insulin resistance, glucose intolerance, hyperlipidemia and hypertension. So far, it has been reported that a thaizolidinedione derivative, troglitazone, improves the insulin resistance in subjects with diabetes, glucose intolerance and obesity. However, it has not been reported yet that troglitazone affects fat distribution in subjects concomitant with visceral fat accumulation and multiple risk factors.

METHODS

Twenty-nine subjects with visceral fat accumulation who had at least two risk factors including glucose intolerance, hyperlipidemia and hypertension were investigated. They were randomly assigned to receive either 200 or 400 mg per day of troglitazone or placebo for 12 weeks. A 75 g oral glucose tolerance test (OGTT) was performed before and after the treatment for 12 weeks. Fasting plasma glucose, insulin, HbA(1c), total serum cholesterol (T-chol), triglyceride (TG), HDL-cholesterol (HDL-C), and blood pressure, as well as the number of risk factors were measured periodically during the treatment. The change of the abdominal fat distribution was evaluated using computed tomographic scanning (CT scan) at the umbilicus level.

RESULTS

After the treatment for 12 weeks, the area under the curve (AUC) of plasma glucose from a 75 g OGTT decreased dose-dependently. HbA(1c) and TG decreased significantly in the high-dose troglitazone group (400 mg per day) compared with the placebo group (P<0.05). Systolic blood pressure was significantly lower in subjects with hypertension in the pooled troglitazone group than in the placebo group (P<0.05). Therefore, the number of risk factors decreased with the troglitazone treatment. The ratio of visceral fat area (VFA) to subcutaneous fat area (SFA) (V/S ratio) decreased in the troglitazone groups due to decreased VFA and increased SFA.

CONCLUSION

These results suggest that thiazolidinedione derivative may be a useful drug to improve multiple risk factors by changing the fat distribution in subjects with visceral fat accumulation.

Combination oral agent and insulin therapy for type 2 diabetes mellitus

Type 2 diabetes is a chronic metabolic disorder that results from defects in both insulin secretion and insulin action. Over time, there is progressive beta-cell failure. Combination oral and insulin therapy aims at treating both the defects in underlying pathophysiology and replacing insulin once beta-cell failure has occurred. Combination therapy is routinely used in the management of diabetes to reduce hemoglobin A1c, weight gain, and the number of insulin injections a patient requires. This article examines the effects of combining various oral agents with insulin on glycemic control, hypoglycemia, weight gain, and nonglycemic benefits of these combinations.

Serum leptin level as an indicator to predict the clinical efficacy of troglitazone in patients with type 2 diabetes mellitus

Troglitazone is effective in approximately 50% in patients with type 2 diabetes (NIDDM). In this study, we investigated the relations between serum leptin levels and clinical efficacy of troglitazone. Forty-five type 2 diabetic patients (23 men and 22 women) from our outpatient clinic were treated with troglitazone 400 mg daily for 12 weeks. Fasting plasma glucose (FPG), HbA1c, body weight, serum insulin and leptin concentrations were measured before and after troglitazone treatment. After 12 weeks of troglitazone treatment, FPG (before versus after, 179+/-33 vs. 138+/-26 mg/dl, mean+/-SD), HbA1c (7.8+/-1.3 vs. 6.9+/-1.0%), IRI (8.3+/-4.3 vs. 6.3+/-3.4 microU/ml) and HOMA-R index (homeostasis model assessment of insulin resistance) (3.8+/-2.4 vs. 2.2+/-1.3) decreased significantly, while body mass index (BMI) slightly increased (26.3+/-3.5 vs. 26.6+/- 3.6 kg/m(2)), and serum leptin remained unchanged (8.5+/-7.2 vs. 9.1+/-8.7 ng/ml). Reduction in FPG (DeltaFPG) after troglitazone treatment were correlated with reduction in HOMA-R (DeltaHOMA-R) (r=0.721, P<0.0001). DeltaFPG was correlated with serum leptin (r=0.441, P<0.01), HOMA-R (r=0.460, P<0.01) and FPG (r=-0.781, P<0.0001) at baseline, but not with BMI and serum IRI at baseline. Furthermore, serum leptin at baseline was significantly correlated with DeltaHOMA-R (r=0.634, P<0.01). Leptin concentration before treatment therefore, can be used as an predictor for clinical efficacy of troglitazone in patients with type 2 diabetes.

Dermal neurovascular dysfunction in type 2 diabetes

OBJECTIVE

To review evidence for a relationship between dermal neurovascular dysfunction and other components of the metabolic syndrome of type 2 diabetes.

RESEARCH DESIGN AND METHODS

We review and present data supporting concepts relating dermal neurovascular function to prediabetes and the metabolic syndrome. Skin blood flow can be easily measured by laser Doppler techniques.

RESULTS

Heat and gravity have been shown to have specific neural, nitrergic, and independent mediators to regulate skin blood flow. We describe data showing that this new tool identifies dermal neurovascular dysfunction in the majority of type 2 diabetic patients. The defect in skin vasodilation is detectable before the development of diabetes and is partially correctable with insulin sensitizers. This defect is associated with C-fiber dysfunction (i.e., the dermal neurovascular unit) and coexists with variables of the insulin resistance syndrome. The defect most likely results from an imbalance among the endogenous vasodilator compound nitric oxide, the vasodilator neuropeptides substance P and calcitonin gene-related peptide, and the vasoconstrictors angiotensin II and endothelin. Hypertension per se increases skin vasodilation and does not impair the responses to gravity, which is opposite to that of diabetes, suggesting that the effects of diabetes override and counteract those of hypertension.

CONCLUSIONS

These observations suggest that dermal neurovascular function is largely regulated by peripheral C-fiber neurons and that dysregulation may be a component of the metabolic syndrome associated with type 2 diabetes.

Troglitazone quinone formation catalyzed by human and rat CYP3A: an atypical CYP oxidation reaction

Oxidative ring opening of troglitazone (TGZ)(1) a thiazolidine 2,4-dione derivative used for the treatment of type II diabetes mellitus, leads to the formation of a quinone metabolite. The formation of TGZ quinone was shown to be NADPH dependent and to require active microsomal enzymes. Quinone formation was not affected by co-incubation with catalase or sodium azide and was partially inhibited (25%) by superoxide dismutase (SOD). Kinetic analysis of TGZ quinone formation in human liver microsomes implied single enzyme involvement. CYP3A isoforms were characterized as the primary enzymes involved in quinone formation by several lines of evidence including: (a) troleandomycin and ketoconazole almost completely inhibited microsomal quinone formation when SOD was present, whereas other CYP inhibitors had minimal effects (<20%); (b) TGZ quinone formation was highly correlated with regard to both contents (r(2): 0.9374) and activities (r(2): 0.7951) of CYP3A4 in human liver microsomes (HLM); (c) baculovirus insect cell-expressed human CYP3A4 was able to catalyze TGZ quinone formation at a higher capacity (V(max)/K(m)) than other human CYPs with the relative contribution of CYP3A4 in HLM estimated to be 20-fold higher than that of other CYPs; (d) TGZ quinone formation was increased by 350% in liver microsomes from rats pretreated with dexamethasone (DEX); and (e) plasma concentrations of TGZ quinone were increased by 260-680% in rats pretreated with DEX. The chemical nature of the quinone metabolite suggests an atypical CYP reaction consistent with a one-electron oxidation mechanism where an intermediate phenoxy radical combines with ferryl oxygen to subsequently form the quinone metabolite.

A randomized trial of rosiglitazone therapy in patients with inadequately controlled insulin-treated type 2 diabetes

OBJECTIVE

To determine the efficacy and safety of rosiglitazone (RSG) when added to insulin in the treatment of type 2 diabetic patients who are inadequately controlled on insulin monotherapy.

RESEARCH DESIGN AND METHODS

After 8 weeks of insulin standardization and placebo (PBO) run-in, 319 type 2 diabetic patients with mean baseline HbA(1c) > or = 7.5% (8.9 +/- 1.1 to 9.1 +/- 1.3) on twice-daily insulin therapy (total daily dose > or = 30 U) were randomized to 26 weeks of additional treatment with RSG (4 or 8 mg daily) or PBO. Insulin dose could be down- titrated only for safety reasons. The primary end point was reduction of HbA(1c) from baseline.

RESULTS

RSG 4 and 8 mg daily significantly improved glycemic control, which was unchanged on PBO. By intent-to-treat analysis, treatment with RSG 8 mg plus insulin resulted in a mean reduction from baseline in HbA(1c) of 1.2% (P < 0.0001), despite a 12% mean reduction of insulin dosage. Over 50% of subjects treated daily with RSG 8 mg plus insulin had a reduction of HbA(1c) > or = 1.0%. Neither total:HDL cholesterol nor LDL:HDL cholesterol ratios significantly changed with RSG treatment. Serious adverse events did not differ among groups.

CONCLUSIONS

The addition of RSG to insulin treatment results in significant improvement in glycemic control and is generally well tolerated.

Treating dyslipidaemia in non-insulin-dependent diabetes mellitus -- a special reference to statins

Patients with non-insulin-dependent diabetes (NIDDM) have an increased incidence of ischaemic heart disease (IHD) when compared with nondiabetic subjects. In addition, they have a worse prognosis after their first myocardial infarction (MI). According to the recent USA recommendations, the threshold for initiation of dietary intervention in diabetic subjects is an LDL greater than 2.6 mmol/l, with the goal to achieve levels less than 2.6 mmol/l (100 mg/dl). This is also the threshold for initiation and treatment goal for pharmacological intervention in diabetic subjects, unless they are completely free of IHD, peripheral vascular disease or cerebrovascular disease and have no other IHD risk factors. In the latter circumstances, the threshold for treatment is an LDL greater than 3.38 mmol/l (130 mg/dl), with the goal to achieve levels less than 3.38 mmol/l. The HMG-CoA reductase inhibitors (statins) can improve the lipid profile effectively and safely in NIDDM. Results from post hoc analyses of diabetic subgroups in the large intervention trials suggest that some statins significantly reduce the risk for IHD-related mortality/morbidity. However, because these results are derived from secondary prevention trials, we cannot be sure if these benefits apply to all diabetic subjects or only to those who already have IHD. Nevertheless, it seems logical to assume that this benefit also applies to NIDDM patients who do not have IHD because they share a similar vascular risk as nondiabetic subjects who have IHD. Intervention trials using statins and fibrates, alone or in combination, in NIDDM are under way. In a few years these trials will provide definitive end-point-based evidence in this high-risk group of patients.

Effects of high-dose troglitaz one on insulin sensitivity and beta-cell function in Watanabe heritable hyperlipidemic rabbits

To clarify the dose-response effects of troglitazone on insulin sensitivity and beta-cell function, we examined the effects of high-dose troglitazone (100 mg/day per animal, administered as a food admixture) on glucose and insulin metabolism in hyperinsulinemic Watanabe heritable hyperlipidemic (WHHL) rabbits, and compared the results with our previous results with low-dose troglitazone (10 mg /day per animal).

MATERIALS AND METHODS

Glucose and insulin metabolism were quantitatively characterized by a minimal model technique as reported previously.

RESULTS

When troglitazone was administrated at a high dose for 6 months, it reduced hyperinsulinemia as reflected by a reduced basal (steady-state) insulin concentration lb and the insulin response to a glucose load, improved beta-cell function as reflected by decreased second-phase post-hepatic insulin delivery to glucose phi2, and reduced insulin resistance as reflected by increased insulin sensitivity to glucose disposal Si, without affecting glucose tolerance as reflected by an unchanged rate of glucose utilization Kg or insulin-independent glucose disposal Sg. The reductions in Ib and phi2 and the increases in Si in WHHL rabbits treated with a high dose of troglitazone were greater (p<0.05) than those observed in WHHL rabbits treated with a low dose of troglitazone, as assessed by a two-way repeated measures analysis of variance and the Wilcoxon-Mann-Whitney test.

CONCLUSION

In WHHL rabbits, troglitazone dose-dependently reduced hyperinsulinemia, improved beta-cell function, and increased insulin sensitivity.

Lessons from the glitazones: a story of drug development

Troglitazone, the first in the thiazolidinedione class of oral hypoglycaemic agents, was launched in the USA in March, 1997. It reached Europe later that year, only to be withdrawn within weeks on the grounds of liver toxicity. Meanwhile it went on to generate sales of over $2 billion in the USA, and caused at least 90 cases of liver failure (70 resulting in death or transplantation) before it was withdrawn in March, 2000. Rosiglitazone and pioglitazone reached the US market in 1999 as first-line agents to be used alone or in combination with other drugs, but in Europe the same dossiers were used one year later to apply for a limited licence as second-line agents restricted to oral combination therapy. How should we use the glitazones? And how did they achieve blockbuster status without any clear evidence of advantage over existing therapy?

Troglitazone treatment increases plasma vascular endothelial growth factor in diabetic patients and its mRNA in 3T3-L1 adipocytes

Troglitazone is one of the thiazolidinediones, a new class of oral antidiabetic compounds that are ligands of peroxisome proliferator-activated receptor-gamma. This study on vascular endothelial growth factor (VEGF), also known as vascular permeability factor, was prompted by our clinical observation that the characteristics of troglitazone-induced edema were very similar to those caused by vascular hyperpermeability. When Japanese diabetic patients were screened for plasma VEGF, we found levels to be significantly (P < 0.001) increased in troglitazone-treated subjects (120.1 +/- 135.0 pg/ml, n = 30) compared with those treated with diet alone (29.2 +/- 36.1 pg/ml, n = 10), sulfonylurea (25.8 +/- 22.2 pg/ml, n = 10), or insulin (24.6 +/- 19.0 pg/ml, n = 10). Involvement of troglitazone in increased VEGF levels was further supported by the plasma VEGF levels in five patients before treatment (20.2 +/- 7.0 pg/ml), after 3 months of troglitazone treatment (83.6 +/- 65.9 pg/ml), and 3 months after discontinuation (28.0 +/- 11.6 pg/ml). We further demonstrated that troglitazone, as well as rosiglitazone, at the plasma concentrations observed in patients, increased VEGF mRNA levels in 3T3-L1 adipocytes. VEGF is an angiogenic and mitogenic factor and is currently considered the most likely cause of neovascularization and hyperpermeability in diabetic proliferative retinopathy. Although increased VEGF may be beneficial for subjects with macroangiopathy and troglitazone is currently not available for clinical use, vascular complications, especially diabetic retinopathy, must be followed with great caution in subjects treated with thiazolidinediones.

New insights into insulin resistance pathophysiology: how it affects glucose and lipid metabolism

Insulin resistance is a metabolic state encountered in many physiological and physiopathological conditions. Its pivotal effect on glucose and lipid metabolism is increasingly recognised. Over the last few years, numerous molecular/intracellular pathways affected by this condition have been elucidated. The author reviews some recent findings underlying several major metabolic abnormalities. An overview of current and future therapeutics is also provided.

[Role and modalities of insulin treatment in type 2 diabetics]

INTRODUCTION

The natural history of type 2 diabetes mellitus is characterized by an inescapable and gradual worsening of a decrease in insulin secretion. Thus after several years of progress, less than half of type 2 diabetic patients have good glycemic control. This explains the increase in insulin prescription to type 2 diabetic patients in France in recent years. This work's objective is to take into account recent publication data to clarify the status of and adjustments in insulin therapy.

CURRENT KNOWLEDGE AND KEY POINTS

The benefit of insulin treatment-mediated glycemic control optimization on microvascular complications is now proven. However, there is still controversy concerning macrovascular complications. Hypoglycemic risk in type 2 diabetic patients is limited and the main problem with insulin treatment is weight gain. Following failure with treatment by tablets, the most suitable treatment in terms of metabolic improvement, weight gain limitation and treatment adhesion is to add an intermediate insulin injection at bedtime. The next step remains several injections a day, with metformine addition if possible.

FUTURE PROSPECTS AND PROJECTS

Therapeutic treatment in type 2 diabetes mellitus may become an earlier start of insulin therapy to preserve the remaining pancreatic insulin reserve. The role of brief and long-lasting insulin analogues, as well as inhaled insulin, which will soon be available, should be specified.

Troglitazone, an antidiabetic drug, improves left ventricular mass and diastolic function in normotensive diabetic patients

AIMS

Patients with NIDDM have excessive cardiovascular morbidity and mortality, even in the absence of hypertension. Left ventricular hypertrophy (LVH), which is an ominous prognostic sign and an independent risk factor for cardiac events, is often present in NIDDM patients.

METHODS AND RESULTS

NIDDM male patients with (n=10) and without (n=12) hypertension, all of whom had been diagnosed over 10 years ago, were examined in the present study. Normotensive NIDDM patients had not received any anti-hypertensive drugs. All patients were classified according to the left ventricular mass (LVM) index by using M-mode echocardiography and were assessed regarding their systolic (fractional shortening) and diastolic function, which included the maximal early flow velocity (MFV), the mitral valve deceleration time (DT), and the isovolumic relaxation time (IRT) as determined by Doppler indices. Troglitazone (TRO), an antidiabetic drug, was administered to both groups at a dose of 400 mg/day for 6 months. After TRO treatment, a reduction in the LVM index and an improvement in the diastolic function were observed in the normotensive but not in the hypertensive patients.

CONCLUSION

The TRO treatment was sensitive for cardiac regression in those normotensive patients. These results suggest that LVH and the diastolic function in NIDDM patients without hypertension may be associated with elevated insulin resistance because TRO has a pharmacological function to increase the insulin sensitivity and to decrease insulin resistance.

Pathophysiology and pharmacological treatment of insulin resistance

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

PPAR-gamma agonists: therapeutic role in diabetes, inflammation and cancer

The recent development of a novel class of insulin-sensitizing drugs, the thiazolidinediones (TZDs), represents a significant advance in antidiabetic therapy. One key mechanism by which these drugs exert their effects is by activation of the peroxisome proliferator activated receptor gamma (PPAR-gamma), a member of the nuclear receptor family. Evidence supporting this mechanism of action of the TZDs will be reviewed in this article. Recent data suggests that PPAR-gamma agonists might also have therapeutic potential in the treatment of inflammatory diseases and certain cancers.