Rosiglitazone reduces urinary albumin excretion in type II diabetes

Rosiglitazone reduces microalbuminuria and blood pressure independently of glycemia in type 2 diabetes patients with microalbuminuria

OBJECTIVE

To test the hypothesis that rosiglitazone combined with metformin provides a greater reduction in microalbuminuria and blood pressure than metformin and glyburide at comparable levels of glycemic control.

METHODS

In a double-blind, parallel-group design 389 participants with type 2 diabetes were followed for 32 weeks.

RESULTS

Urinary albumin: creatinine ratio was significantly reduced at 32 weeks compared with baseline in the rosiglitazone plus metformin group (-22.7%; P < 0.01) but not in the glyburide plus metformin comparator group (-7.1%; P = 0.32). Patients who completed the study (81.5%) demonstrated a treatment difference of -19.5% (P = 0.03), favoring the rosiglitazone group. Rosiglitazone plus metformin reduced both mean 24-h systolic (-3.4 mmHg; P = 0.01) and diastolic (-2.5 mmHg; P < 0.01) ambulatory blood pressure compared with glyburide plus metformin. Addition of rosiglitazone to metformin also reduced levels of plasminogen activator inhibitor-1 antigen and activity, C-reactive protein, von Willebrand factor and fibrinogen compared with addition of glyburide.

CONCLUSIONS

Rosiglitazone added to background therapy with metformin provides greater reductions in microalbuminuria and blood pressure as compared with glyburide. These additional improvements in microalbuminuria, blood pressure and cardiovascular biomarkers were observed despite comparable improvements in glycemic control in both groups and may be related to the anti-inflammatory properties of rosiglitazone.

Insulin resistance in diabetic nephropathy--cause or consequence?

Insulin resistance (IR) is associated with multiple risk factors for cardiovascular disease. Many studies have shown that IR is present in chronic renal failure (CRF), and recent evidence suggests that IR can also occur in the early stages of renal disease. Patients with diabetic nephropathy (DN) have an increase in cardiovascular mortality, and since IR may be a contributing factor, this emphasizes the importance of a detailed understanding of the mechanisms linking IR and renal dysfunction at different stages of DN. IR can be detected early on in DN, e.g. at the stage of microalbuminuria (MA) and this could indicate a common genetic trait for IR and DN. As DN progresses further, IR is aggravated and it may, in addition to other factors, possibly accelerate the decline in renal function toward end-stage renal disease (ESRD). Several potentially modifiable mechanisms including circulating hormones, neuroendocrine pathways and chronic inflammation, are said to contribute to the worsening of IR. In ESRD, uremic toxins are of major importance. In this review article, we address the association between different stages of DN and IR and attempt to summarize major findings on potential mechanisms linking DN and IR. We conclude that IR is a consequence, and potentially also a cause of DN. In addition, there are probably genetic and environmental background factors that predispose to both IR and DN.

The metabolic syndrome: evolving evidence that thiazolidinediones provide rational therapy

The metabolic syndrome, also known as the dysmetabolic syndrome, syndrome X or the insulin resistance syndrome, refers to the clustering of cardiovascular disease risk factors that are present in many individuals who are at increased risk for both cardiovascular events and type 2 diabetes. Prediabetic subjects typically exhibit an atherogenic pattern of cardiovascular risks that is associated with hyperinsulinaemia. Thus, identification of components of the metabolic syndrome is important if patients are to be treated early enough to prevent cardiovascular events and other complications related to diabetes. Therapies targeted to specific components of the metabolic syndrome such as improving glycaemic control, managing dyslipidaemia and reducing the prothrombotic state should help to minimize cardiovascular risk, particularly if initiated early. Traditional pharmacologic agents used to manage the individual components of the metabolic syndrome do not typically impact the other components. The thiazolidinediones, a new class of agents that improve insulin resistance, have the ability, in addition to their glucose-lowering effects, to exert several powerful anti-atherogenic properties, including anti-inflammatory effects in the vascular endothelium, redistribution of visceral fat and reduction of insulin resistance, hyperinsulinaemia and hyperproinsulinaemia. This makes the thiazolidinediones ideal candidates for the early treatment of many components associated with the metabolic syndrome.

Rationale, design, and methods for glycemic control in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) Trial

A major therapeutic question in considering accelerated atherogenesis in patients with type 2 diabetes mellitus is whether reducing insulin resistance, as a proximal defect of a host of proatherogenic abnormalities including hyperglycemia, will be superior for decreasing mortality and coronary artery disease (CAD) risk compared with treating hyperglycemia to overcome insulin resistance with insulin-providing agents. This question is highly relevant, since earlier targeted glycemic control trials utilizing conventional glucose-lowering strategies that increase insulin levels have generally failed to reduce CAD risk despite markedly reducing microvascular risk. The Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial seeks to determine whether primarily using an insulin-sensitizing strategy for treatment of type 2 diabetes is superior when compared with primarily using an insulin-providing strategy with regard to cardiovascular outcomes. This article presents the rationale, design, and methods being used to test the glycemic control hypothesis in BARI 2D.

Can PPARgamma agonists have a role in the management of obesity-related hypertension?

Peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. PPARgamma is the most extensively studied amongst the three subtypes (alpha, delta and gamma). This receptor is a key modulator of lipid and glucose homeostasis and is predominantly expressed in adipose tissue. Expression of PPARgamma is also found in non-adipose tissues including heart, kidney, spleen, and interestingly, in all relevant components of the vasculature: endothelial and smooth muscle cells. These receptors may therefore also play a role in the regulation of vascular tone and blood pressure. Genetic variants of PPARgamma have also been associated with features of the metabolic syndrome, including obesity and increased blood pressure. The discovery of synthetic ligands for PPARgamma, the Thiazolidinediones (TZDs) has greatly enhanced our understanding of their ligand dependent activation and more importantly their role in vascular pathobiology. Approximately 10 years ago, serendipitous animal experiments demonstrated that despite causing sodium retention, the TZDs actually lowered blood pressure. This review will highlight the role of TZDs in various models of hypertension and discuss their potential role in the management of obesity-related hypertension.

A meta-analysis of the effect of thiazolidinediones on blood pressure

In epidemiologic studies, insulin resistance is associated with hypertension. Thiazolidinediones (TZDs) are antidiabetic agents that decrease insulin resistance. Multiple clinical trials have evaluated the effect of TZDs on blood pressure (BP) with inconsistent results. The aim of this study was to estimate the effect of TZDs on BP. The authors searched PubMed for clinical trials published in English. A total of 37 clinical trials that reported a change in BP were included in the analysis. Trials with independent-group design and trials with pre-post design were evaluated separately. When compared with baseline, TZDs lowered systolic BP by 4.70 mm Hg (95% confidence interval, -6.13 to -3.27) and diastolic BP by 3.79 mm Hg (95% confidence interval, -5.82 to -1.77). When compared with placebo, TZDs lowered systolic BP by 3.47 mm Hg (95% confidence interval, -4.91 to -2.02) and diastolic BP by 1.84 mm Hg (95% confidence interval, -3.43 to -0.25). Thus, TZDs lower both systolic and diastolic BP, albeit the BP-lowering effect is small and may not be of clinical significance.

Emerging drugs for diabetic nephropathy

There is an increasing number of patients with diabetes mellitus in many countries. Diabetic kidney disease, one of its microvascular complications, is also increasing markedly and has become a major cause of end stage renal disease worldwide. Intervention for preventing and delaying the development and progression of diabetic kidney disease is not only a medical concern, but also a social issue. Despite extensive efforts, however, medical interventions thus far are not effective enough to prevent the progression of the disease and the development of end stage renal disease. This justifies attempts to develop novel therapeutic approaches for diabetic nephropathy. Recent insights on its pathogenesis and progression have suggested new targets for the specific treatment of this disease. They include aldosterone, aldose reductase, arachidonic acid metabolites, growth factors, advanced glycosylation end-products, peroxisome proliferator-activated receptors and endothelin. Several other biochemical mediators have been targeted in experimental animal models with the goal to prevent diabetic nephropathy progression, but translation to clinics of these experimental achievements are still limited or lacking.

Thiazolidinediones and progression of renal disease in patients with diabetes

OBJECTIVE

Thiazolidinediones (TZDs) are used in the treatment of type 2 diabetes mellitus (T2DM) and appear to have beneficial effects on markers of cardiovascular or renal risk that are independent of glycemic control. We examined the effects of TZDs on renal survival in a predominantly black population with T2DM.

METHODS

We performed a retrospective case-control study in patients with T2DM seen in our nephrology clinic in 2001 to 2002. Cases had T2DM and were on a TZD at presentation or for >or= 6 months over follow-up. Controls were matched for sex, age, duration of T2DM, and initial creatinine. Reaching end-stage renal disease (ESRD) was the primary end point.

RESULTS

From 387 records, 43 cases (34 blacks, 31 females) and 106 controls (96 blacks, 83 females) were identified. The baseline characteristics were similar for both groups. Both groups had moderate renal disease (estimated glomerular filtration rate approximately 40-45 mL/min). Cases had lower systolic blood pressure over follow-up (p=.02), but there was no difference in glycemic control or use of insulin. Renal survival was better among cases (age- and gender-adjusted odds ratio for reaching ESRD 0.17 [95% confidence interval 0.03-0.8]; p=.03). When adjusted for systolic blood pressure over follow-up, the tendency for improved renal survival in cases remained but was no longer significant.

CONCLUSION

We conclude that TZDs may protect against the progression of renal disease in T2DM. Prospective studies are required to determine the effects of TZDs on renal survival in T2DM.

Pioglitazone increases circulating adiponectin levels and subsequently reduces TNF-alpha levels in Type 2 diabetic patients: a randomized study

BACKGROUND

Adipocytokines are involved in the development of insulin resistance and endothelial dysfunction in diabetic patients. However, the relationship between these factors remains unclear. We observed a chronological change in circulating adipocytokines and blood pressure levels with administration of oral hypoglycaemic agents in Type 2 diabetic (T2DM) subjects.

METHODS

Thirty poorly controlled T2DM subjects (aged 60.1 +/- 1.5 years, 11 males and 19 females) were randomized into two groups: voglibose (initial dose 0.6 mg/day, increased to 0.9 mg/day) and pioglitazone (initial dose 15 mg/day, increased to 30 mg/day).

RESULTS

Both treatment groups showed a similar improvement in glycaemic control. In pioglitazone-treated patients, circulating adiponectin levels were significantly increased from 4 weeks after the start of treatment, and until the end of the study at 12 weeks. Plasma tumour necrosis factor-alpha (TNF-alpha) levels were significantly decreased only at 12 weeks. In contrast, no significant changes in plasma adiponectin or TNF-alpha levels were observed in voglibose-treated patients. Plasma PAI-1 and leptin levels were not significantly changed at 12 weeks in either treatment group. Pioglitazone significantly decreased systolic and diastolic blood pressure levels at 12 weeks, but voglibose had no effect.

CONCLUSION

In summary, pioglitazone caused an immediate increase in circulating adiponectin levels, followed by a reduction of TNF-alpha. The observed increase in circulating adiponectin could be related to decreases in both systolic and diastolic blood pressure.

Fluid retention and vascular effects of rosiglitazone in obese, insulin-resistant, nondiabetic subjects

OBJECTIVE

The use of thiazolidinedione (TZD) derivatives is associated with fluid retention, especially when combined with insulin. Because TZDs improve the metabolic effect of insulin, they may also reverse the blunted vascular response to insulin. We hypothesize that improvement of the action of insulin on vascular tone or permeability is the key mechanism of TZD-related fluid retention.

RESEARCH DESIGN AND METHODS

In a randomized, double-blind, placebo-controlled, cross-over study in 18 obese, nondiabetic subjects with features of the metabolic syndrome, we investigated the effects of a 12-week treatment with 4 mg rosiglitazone twice a day on glucose disposal, hemodynamics (including forearm vasoconstrictor response to nitric oxide [NO]), synthase inhibition by N-monomethyl-L-arginine-acetate (L-NMMA), vascular permeability (transcapillary escape rate of albumin), and plasma volume during a hyperinsulinemic-euglycemic clamp (120 min, 120 mU/m(2) per min).

RESULTS

As expected, rosiglitazone increased the glucose infusion rate during clamping. However, neither vascular permeability nor forearm blood flow response to hyperinsulinemia or L-NMMA was affected by rosiglitazone. Compared with placebo, rosiglitazone decreased diastolic blood pressure by 5 mmHg (95% CI 2.35-6.87, P = 0.0005) and increased plasma volume by 255 ml/1.73 m(2) (80-430, P = 0.007). Interestingly, the positive effect of rosiglitazone on glucose disposal correlated with change in foot volume (R(2) = 0.53, P = 0.001).

CONCLUSIONS

Rosiglitazone improved insulin sensitivity but had no effect on NO-dependent vasodilatation in the forearm or vascular permeability in obese, insulin-resistant, nondiabetic subjects. As such, TZD-related fluid retention was not caused by improvement of the vascular actions of insulin. Nonetheless, rosiglitazone-induced improvement in insulin sensitivity appears to be correlated to edema formation.

Implications of Rosiglitazone and Pioglitazone on Cardiovascular Risk in Patients with Type 2 Diabetes Mellitus

Clinical data suggest that thiazolidinediones--specifically, rosiglitazone and pioglitazone--may improve cardiovascular risk factors through multiple mechanisms. Low insulin sensitivity has been described as an independent risk factor for coronary artery disease and cerebrovascular disease. Patients with insulin resistance often have several known risk factors, such as obesity, dyslipidemia, and hypertension. Other emerging risk factors may be prevalent in patients with insulin resistance, such as hyperinsulinemia, elevated C-reactive protein, elevated plasminogen activator inhibitor levels, and small, dense, low-density lipoproteins. The only available drug class that primarily targets insulin resistance is the thiazolidinediones. These drugs have shown efficacy in affecting surrogate markers of cardiovascular risk in patients with diabetes mellitus. Alterations in these risk factors are likely due to their effects on improving insulin sensitivity and/or glycemic control. Trials to assess whether thiazolidinediones actually reduce cardiovascular outcomes are continuing.

Microalbuminuria as a marker of cardiovascular risk in patients with type 2 diabetes

Diabetes is a major risk factor for coronary artery disease and most patients with diabetes die of cardiovascular complications. Reduction of cardiovascular risk is therefore a high priority in the management of patients with diabetes. Microalbuminuria is an important predictor of cardiovascular events and forms one of the components of the insulin resistance/metabolic syndrome, which confers a particularly high risk of cardiovascular death. The currently available glucose-lowering agents vary considerably in their ability to reduce microalbuminuria. The sulfonylureas and metformin appear to have little effect on microalbuminuria expressed as urinary albumin/creatinine ratio, while the thiazolidinediones have unique effects on this risk factor, in parallel with their effects on insulin resistance. In two 1-year European multicenter, randomized, double-blind monotherapy trials (n=2444), pioglitazone produced similar reductions in urinary albumin/creatinine ratio to gliclazide and greater reductions than metformin (P<0.001). Similarly, two further 1-year European multicenter, randomized, double-blind trials assessed the effects of add-on therapy (n=1269) on urinary albumin/creatinine ratio. In the first study, urinary albumin/creatinine ratio was reduced by pioglitazone add-on to sulfonylurea (-15%), but was largely unaffected by metformin add-on to sulfonylurea (2%; P<0.05). In the second, urinary albumin/creatinine ratio was also reduced by pioglitazone add-on to metformin (-10%), but increased by gliclazide add-on to metformin (6%, P<0.05). The results of these studies indicated that compared with metformin or gliclazide, pioglitazone may provide therapeutic benefits, over and above those due to improved glycemic control. These include significant reductions in urinary albumin/creatinine ratio, a known cardiovascular risk marker.

Protective effect of peroxisome proliferator activated receptor gamma agonists on diabetic and non-diabetic renal diseases

Peroxisome proliferator activated receptor gamma (PPARgamma) agonist has not only antidiabetic effect but also a protective effect against various types of injury of the kidney. The protective effects of PPARgamma agonists are observed in diabetic nephropathy and non-diabetic renal diseases such as 5/6 ablation model of renal failure, experimental glomerulonephritis, ischemia-reperfusion injury, hypertensive nephropathy and cyclosporin-induced renal injury. The mechanism of renoprotection by PPARgamma agonist is multifactorial. Anti-fibrotic and anti-inflammatory effects, suppression of renin-angiotensin system, vascular protective effect and antiapoptotic effect were proposed.

PPAR-gamma agonists and diabetic nephropathy

Diabetic nephropathy is a clinical syndrome of albuminuria, declining glomerular filtration rate, and increased risk of cardiovascular disease. Multiple mechanisms have been implicated in its pathogenesis. Although current therapies appear to be effective, treatment of diabetic nephropathy remains suboptimal. This review summarizes the recently emerging evidence suggesting that peroxisome proliferator-activated receptor-gamma agonists may prove to be effective therapeutic agents in the treatment of diabetic renal complications.

Kidney Disease and the Metabolic Syndrome

The epidemic of metabolic syndrome contributes to the rapid growth of cardiovascular and renal diseases. Hyper-hemodynamics, impaired pressure natriuresis, excess excretory load, insulin resistance, endothelial dysfunction, chronic inflammation, and prothrombotic status individually and interdependently initiate renal injury in metabolic syndrome. The prevention and treatment of kidney disease require a multifactorial approach. Weight loss through diet control and exercise can reverse many pathophysiologic processes. Pharmacologic intervention includes insulin sensitizers, tight glycemic and lipid control, blockage of renin angiotensin aldosterone system, and anti-inflammatory and antithrombotic therapies. Each peroxisome proliferator-activated receptor isoform plays a distinct role in metabolic syndrome, and their agonists may prevent or reverse the early renal injuries.

Drug Insight: thiazolidinediones and diabetic nephropathy—relevance to renoprotection

Up to a third of people with diabetes mellitus suffer end-stage renal failure due to diabetic nephropathy. Strategies to delay progression of diabetic nephropathy-including glycemic and blood pressure control, modification of the renin-angiotensin system and management of lipid levels with statins-have been effective, but development of new strategies is essential if the ever-increasing burden of this disease is to be minimized. Thiazolidinediones (TZDs) are a family of compounds used as oral hypoglycemic agents in patients with type 2 diabetes mellitus. The therapeutic effects of TZDs are largely a function of their activity as ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), a transcription factor that has a central role in adipogenesis and insulin sensitization. In vitro animal and clinical studies have shown that TZDs ameliorate symptoms and pathogenic mechanisms of diabetic and nondiabetic nephropathy, including proteinuria, excessive deposition of glomerular matrix, cellular proliferation, inflammation and fibrosis. Many of these favorable effects occur under both normal and high-glucose conditions. The mechanisms responsible probably involve both PPARgamma-dependent and PPARgamma-independent pathways. So, TZDs and other agonists of PPARgamma offer promise for treatment of diabetic nephropathy; however, before their putative renoprotective effects can be translated into clinical practice, the complex mechanisms of PPARgamma activity and regulation will need to be investigated further.

Treating insulin resistance in type 2 diabetes with metformin and thiazolidinediones

Insulin resistance underlies the pathogenesis of hyperglycaemia and cardiovascular disease in most people with type 2 diabetes. Metformin and thiazolidinediones (pioglitazone and rosiglitazone) counter insulin resistance by different cellular mechanisms and with complementary effects, making them suited for use in combination. Metformin exerts a stronger suppression of hepatic glucose output, while thiazolidinediones produce a greater increase in peripheral glucose uptake, enabling metformin-thiazolidinedione combinations to improve glycaemic control in type 2 diabetes with additive efficacy. Basal insulin concentrations are not raised by metformin or thiazolidinediones, so there is minimal risk of hypoglycaemia, and metformin can reduce the weight gain associated with thiazolidinediones. There are overlapping effects of metformin and thiazolidinediones against a range of athero-thrombotic factors and markers. These include decreased plasminogen activator inhibitor-1, reduced platelet aggregation, reductions of several vascular adhesion molecules, and reduced markers of low-grade inflammation such as C-reactive protein. Additionally, thiazolidinediones increase adiponectin and slightly reduce blood pressure. Both metformin and thiazolidinediones can improve components of the lipid profile: thiazolidinediones consistently reduce free fatty acid concentrations and decrease the proportion of small dense low-density-lipoprotein, and pioglitazone also decreases triglycerides. During co-administration, metformin and thiazolidinediones do not interfere with each other's pharmacokinetics, and lower doses of the two agents together can achieve efficacy with fewer side effects. Metformin-thiazolidinedione combinations require attention to the precautions for both agents, especially renal, cardiac and hepatic status. Thus, metformin and thiazolidinediones can be used in combination to address the hyperglycaemia and vascular risk in type 2 diabetes.

A pilot randomized controlled trial of renal protection with pioglitazone in diabetic nephropathy

BACKGROUND

Diabetic nephropathy progresses relentlessly to end-stage renal disease (ESRD). Animal experiments have found that peroxisome proliferator activated receptor-gamma (PPAR-gamma)-based therapy can have a glucose independent effect on renal protection. We hypothesized that PPAR-gamma-based antidiabetic therapy would result in greater reduction in proteinuria compared to sulfonylurea-based therapy.

METHODS

In 44 patients with overt diabetic nephropathy, an open-label, blinded end point trial was conducted in which subjects were randomized to either pioglitazone or glipizide to achieve similar glucose control. Proteinuria was assessed by two collections of 24-hour urine samples each month for 4 months.

RESULTS

The glipizide group had an adjusted mean increase in proteinuria of 6.1% (95% CI -11.7%, 23.8%), whereas the pioglitazone group had a reduction of 7.2% (95% CI -24.9%, 10.6%). The adjusted reduction with pioglitazone of 13.2% (95% CI -38.4%, 11.9%) was not statistically significant (P= 0.294). Baseline proteinuria, diastolic ambulatory blood pressure, and serum albumin concentration were independent predictors of reduction in proteinuria. The frequency and patterns of adverse events were similar in the two groups.

CONCLUSION

In patients with advanced diabetic nephropathy, we found no reduction in proteinuria over 4 months. These data are useful to design larger studies with longer duration of follow-up to demonstrate renal protection of PPAR-gamma agonists.

Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD): study design and protocol

AIMS/HYPOTHESIS

Studies suggest that in addition to blood glucose concentrations, thiazolidinediones such as rosiglitazone improve some cardiovascular (CV) risk factors and surrogate markers, that are abnormal in type 2 diabetes. However, fluid retention might lead to cardiac failure in a minority of people. The aim of the Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD) study is to evaluate the long-term impact of these effects on CV outcomes, as well as on long-term glycaemic control, in people with type 2 diabetes.

MATERIALS AND METHODS

RECORD is a 6-year, randomised, open-label study in type 2 diabetic patients with inadequate blood glucose control (HbA1c 7.1-9.0%) on metformin or sulphonylurea alone. The study is being performed in 327 centres in Europe and Australasia. After a 4-week run-in, participants were randomised by current treatment stratum to add-on rosiglitazone, metformin or sulphonylurea, with dose titration to a target HbA1c of < or = 7.0%. If confirmed HbA1c rises to > or = 8.5%, either a third glucose-lowering drug is added (rosiglitazone-treated group) or insulin is started (non-rosiglitazone group). The same criterion for failure of triple oral drug therapy in the rosiglitazone-treated group is used for starting insulin in this group. The primary endpoint is the time to first CV hospitalisation or death, blindly adjudicated by a central endpoints committee. The study aim is to evaluate non-inferiority of the rosiglitazone group vs the non-rosiglitazone group with respect to CV outcomes. Safety, tolerability and study conduct are monitored by an independent board. All CV endpoint and safety data are held and analysed by a clinical trials organisation, and are not available to the study investigators while data collection is open.

RESULTS

Over a 2-year period a total of 7,428 people were screened in 25 countries. Of these, 4,458 were randomised; 2,228 on background metformin, 2,230 on background sulphonylurea. Approximately half of the participants are male (52%) and almost all are Caucasian (99%).

CONCLUSIONS/INTERPRETATION

The RECORD study should provide robust data on the extent to which rosiglitazone, in combination with metformin or sulphonylurea therapy, affects CV outcomes and progression of diabetes in the long term.

L2L: a simple tool for discovering the hidden significance in microarray expression data

L2L is a database consisting of lists of differentially expressed genes compiled from published mammalian microarray studies, along with an easy-to-use application for mining the database with the user's own microarray data. As illustrated by re-analysis of a recent study of diabetic nephropathy, L2L identifies novel biological patterns in microarray data, providing insights into the underlying nature of biological processes and disease. L2L is available online at the authors' website [http://depts.washington.edu/l2l/].

Metabolic syndrome therapy: prevention of vascular injury by antidiabetic agents

More than 65 million Americans are currently obese. Type 2 diabetes mellitus, frequently seen in obese subjects, affects 17 million adults in the United States, with a continuous and alarmingly increasing rate. To prevent development of diabetes in those who are at high risk, it is recommended to optimize meal planning and enhance physical activity to make sustained weight reduction possible. In addition to lifestyle changes, various oral antidiabetic agents are available, with diverse mechanisms of action. Some target defective insulin secretion (sulphonylureas, benzoic acid derivatives) or glucose absorption (glycosidase inhibitors), whereas others target insulin resistance (metformin, thiazolidinediones). Patients with metabolic syndrome and diabetes have an increased risk for cardiovascular disease linked to a higher prevalence of hypertension, dyslipidemia, microalbuminuria, and altered hemostasis--parameters that may be modified by antidiabetic agents. In this article, we review the oral agents used to treat type 2 diabetes and the metabolic syndrome, and their effects on vascular tissue.

Rosiglitazone improves glomerular hyperfiltration, renal endothelial dysfunction, and microalbuminuria of incipient diabetic nephropathy in patients

Microalbuminuria, an early feature of diabetic nephropathy, indicates intrarenal endothelial damage. In type 2 diabetes, microalbuminuria is strongly related to insulin resistance. We therefore investigated whether rosiglitazone, an insulin-sensitizing drug that is known to improve endothelial dysfunction, was able to improve intrarenal endothelial dysfunction and microalbuminuria. Nineteen type 2 diabetic patients participated in this double-blind cross-over trial. Nine patients with newly diagnosed disease without microalbuminuria were randomized to a treatment with rosiglitazone or nateglinide, each for 12 weeks. Ten patients with microalbuminuria were randomized to rosiglitazone or placebo, each for 12 weeks in addition to their previous antidiabetic medication. After each treatment, glomerular filtration rate (GFR), renal plasma flow, and filtration fraction were measured before and after blockade of nitric oxide (NO) by intravenous administration of N-monomethyl-L-arginine-acetate (L-NMMA). Ten healthy subjects served as control subjects. Type 2 diabetic patients at baseline showed glomerular hyperfiltration compared with healthy control subjects. Rosiglitazone reduced elevated GFR and filtration fraction toward control primarily in patients with microalbuminuria (GFR: 133.4 +/- 9.8 vs. 119.6 +/- 8.7 ml/min; filtration fraction: 23.2 +/- 1.7 vs. 20.5 +/- 1.6% before and after rosiglitazone, respectively; control subjects: GFR 111.7 +/- 8.6 ml/min, filtration fraction 20.4 +/- 1.5%). Rosiglitazone improved intrarenal NO bioavailability in type 2 diabetes toward control as shown by infusion of L-NMMA. Rosiglitazone reduced albumin excretion in type 2 diabetes with microalbuminuria from 116.5 +/- 31 to 40.4 +/- 12 mg/day. Rosiglitazone ameliorated glomerular hyperfiltration in early type 2 diabetes, improved NO bioavailability, and lessened renal end-organ damage in type 2 diabetes with microalbuminuria.

PPARgamma agonists exert antifibrotic effects in renal tubular cells exposed to high glucose

Peroxisome proliferator-activated receptor-gamma (PPARgamma) are ligand-activated transcription factors that regulate cell growth, inflammation, lipid metabolism, and insulin sensitivity. We recently demonstrated that PPARgamma agonists limit high glucose-induced inflammation in a model of proximal tubular cells (PTC; Panchapakesan U, Pollock CA, and Chen XM. Am J Physiol Renal Physiol 287: F528-F534, 2004). However, the role of PPARgamma in the excess extracellular matrix production is largely unknown. We evaluated the effect of 24- to 48-h 8 microM l-805645 or 10 microM pioglitazone on 25 mM D-glucose-induced markers of fibrosis in HK-2 cells. High D-glucose induced nuclear binding of activator protein-1 (AP-1) to 140.8 +/- 10.9% (P < 0.05), which was attenuated with L-805645 and pioglitazone to 82.3 +/- 14.4 (P < 0.01 vs. high D-glucose) and 99.3 +/- 12.2% (P < 0.05 vs. high D-glucose), respectively. High D-glucose increased total production of transforming growth factor (TGF)-beta(1) 139.6 +/- 6.5% (P < 0.05), which was reversed with L-805645 and pioglitazone to 68.73 +/- 5.7 (P < 0.01 vs. high D-glucose) and 112 +/- 13.6% (P < 0.05 vs. high D-glucose). L-805645 and pioglitazone reduced high d-glucose-induced fibronectin from 156.0 +/- 24.9 (P < 0.05) to 81.9 +/- 16.0 and 57.4 +/- 12.7%, respectively (both P < 0.01 vs. high D-glucose). Collagen IV was not induced by high d-glucose. L-805645 and pioglitazone suppressed collagen IV to 68.0 +/- 14.5 (P < 0.05) and 46.5 +/- 11.6% (P < 0.01) vs. high D-glucose, respectively. High D-glucose increased the nuclear binding of NF-kappaB to 167 +/- 22.4% (P < 0.05), which was not modified with PPARgamma agonists. In conclusion, PPARgamma agonists exert antifibrotic effects in human PTC in high glucose by attenuating the increase in AP-1, TGF-beta(1), and the downstream production of the extracellular matrix protein fibronectin.

Thiazolidinediones-benefits on microvascular complications of type 2 diabetes

Type 2 diabetes is associated with serious microvascular complications, such as nephropathy, retinopathy, and neuropathy, which have a significant impact on patients' quality of life, morbidity, and mortality. Type 2 diabetes management strategies to reduce the risk of microvascular complications include treatment of hyperglycaemia, hypertension, and other vascular risk factors. The importance of glycaemic control in reducing the risk of microvascular complications of diabetes is well established. However, many antihyperglycaemic therapies fail to provide adequate glycaemic control and do not prevent complications in the long term. The thiazolidinediones (TZDs) are a class of agents that provide sustained glycaemic control, mediated primarily by reductions in insulin resistance. Evidence reviewed suggests that the TZDs may have the potential to reduce microvascular complications through benefits that go beyond glycaemic control. Insulin resistance underlies a range of metabolic abnormalities, collectively known as the metabolic syndrome (MS), which are cardiovascular (CV) risk factors. Components include visceral obesity, hyperglycaemia, hypertension, dyslipidaemia, low-grade inflammation and microalbuminuria (an early manifestation of target organ damage). Reducing insulin resistance, therefore, has the potential to reduce both microvascular and macrovascular complications.

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.

Increased urinary albumin excretion, insulin resistance, and related cardiovascular risk factors in patients with type 2 diabetes: evidence of a sex-specific association

OBJECTIVE

While the relevant role of insulin resistance in the pathogenesis of increased urinary albumin excretion (UAE) is well established in type 1 diabetes, its contribution in type 2 diabetes is controversial. Our aim was to investigate whether insulin resistance was associated with increased UAE in a large cohort of patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 363 men and 349 women, aged 61 +/- 9 years, with a disease duration of 11 +/- 9 years and HbA(1c) levels of 8.6 +/- 2.0% were included. Insulin resistance was derived from the homeostasis model assessment of insulin resistance (HOMA(IR)), and UAE was derived from the albumin-to-creatinine ratio (ACR) defined as increased if the value was > or =2.5 mg/mmol in men and > or =3.5 mg/mmol in women. ACR was correlated with HOMA(IR) (r = 0.15, P = 0.0001), independently of age, disease duration, blood pressure, HbA(1c), triglycerides, waist circumference, and smoking.

RESULTS

When the two sexes were investigated separately, a significant correlation between ACR and HOMA(IR) was reached in men (n = 363; r = 0.21, P = 0.0001) but not women (n = 349; r = 0.08, P = 0.14), suggesting that insulin resistance and sex may interact (P for interaction = 0.04) in determining UAE. When men were subgrouped into quartiles of HOMA(IR), those of the third and fourth quartile (i.e., the most insulin resistant) were at higher risk to have increased ACR than patients of the first quartile (third quartile: odds ratio 2.2 [95% CI 1.2-4.2], P = 0.01) (fourth quartile: 4.1 [2.2-7.9], P = 0.00002). Finally, ACR was significantly higher in men with two or more insulin resistance-related cardiovascular risk factors (i.e., abdominal obesity, dyslipidemia, and arterial hypertension) than in men with fewer than two insulin resistance-related cardiovascular risk factors (0.90 [0.2-115.1] vs. 1.56 [0.1-1367.6], respectively, P = 0.005).

CONCLUSIONS

In type 2 diabetic patients, increased UAE is strongly associated with insulin resistance and related cardiovascular risk factors. This association seems to be stronger in men than in women.

A comparison of urinary albumin excretion rate and microalbuminuria in various glucose tolerance subjects

AIMS

To investigate the difference of urinary albumin excretion rate (UAER) and microalbuminuria (MAU) in various glucose tolerance subjects, especially between isolated-impaired glucose tolerance subjects and isolated-impaired fasting glycaemia subjects.

METHODS

A total of 2934 subjects were divided into five groups with various glucose tolerances, based on a 75-g oral glucose tolerance test. Microalbuminuria was defined when urinary albumin excretion rate was between 20 and 200 microg/min.

RESULTS

(i) The UAER in the newly diagnosed Type 2 diabetes mellitus group, impaired glucose tolerance/impaired fasting glycaemia group and isolated-impaired glucose tolerance group were all higher than that in the isolated-impaired fasting glycaemia group and normal glucose tolerance group, but it was comparable between isolated-impaired fasting glycemia group and normal glucose tolerance group. The prevalence of MAU and the odds ratio for MAU with adjustment for age and sex in various glucose tolerance groups showed the same trend as the UAER. (ii) After adjusting for age and sex, there is a significant association between logUAER and independent risk factors (partial correlation coefficients: r = 0.26 for 2-h post-challenge blood glucose, r = 0.26 for systolic blood pressure, r = 0.27 for diastolic blood pressure, r = 0.27 for body mass index and r = -0.13 for high density lipoprotein-cholesterol, all P < 0.001). The risks for MAU were 2-h post-challenge blood glucose, body mass index and diastolic blood pressure, while high density lipoprotein-cholesterol was protective.

CONCLUSIONS

The urinary albumin excretion rate and prevalence of microalbuminuria were higher in isolated-impaired glucose tolerance subjects than those in isolated-impaired fasting glycaemia subjects. At early abnormal glucose tolerance stage, the increasing post-challenge glycaemia might be a more important risk factor for urinary albumin excretion rate and microalbuminuria than increasing fasting glycaemia.

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.

Rosiglitazone plus metformin: combination therapy for Type 2 diabetes

Type 2 diabetes is a common disease associated with an increased risk of long-term complications, in particular cardiovascular disease. Intervention trials have provided evidence that strict metabolic control can substantially reduce the burden of the disease. However, in order to accomplish this, the pathogenetic defects must be tackled by appropriate therapy. Insulin resistance is a common defect in these patients and it is even more severe in those who are obese. Insulin resistance not only contributes to impaired glucose homeostasis, but also to the development of dyslipidaemia, hypertension, inflammatory response and endothelial dysfunction, thus exacerbating the cardiovascular risk. Improvement of insulin sensitivity can be obtained with metformin and thiazolidinediones. These drugs act through different mechanisms with metformin exerting a prevalent effect on the liver and glitazones improving insulin sensitivity in peripheral tissue. Because of different mechanisms, the association of the two compounds is likely to result in an additive effect. Clinical trials available indicate that the combination of the two drugs results in greater improvement in plasma glucose concentration and HbA(1c) as compared to single therapy, without increasing the occurrence of specific side effects. More recently, the two compounds have been associated in the same tablet, thus providing the opportunity for a more convenient treatment that may encourage patient compliance and, at the same time, provide a tool to assess whether a more aggressive intervention on insulin resistance may produce favourable effects on the cardiovascular risk.

Ambulatory blood pressure reduction after rosiglitazone treatment in patients with type 2 diabetes and hypertension correlates with insulin sensitivity increase

BACKGROUND

Within the metabolic syndrome, insulin resistance and compensatory hyperinsulinemia are associated with blood pressure (BP) elevation through various potential mechanisms. Thiazolidinediones are antihyperglycemic agents that decrease insulin resistance.

OBJECTIVE

To determine the effect of the thiazolidinedione rosiglitazone on BP and insulin resistance in patients with type 2 diabetes and hypertension.

METHODS

In 20 subjects (nine men and 11 women) with type 2 diabetes but with a poor glycemic control, and with poorly controlled or newly diagnosed hypertension, rosiglitazone 4 mg daily was added-on therapy for 26 weeks. At baseline and at the end of the treatment period patients underwent ambulatory blood pressure monitoring, a hyperinsulinemic euglycemic clamp, and blood tests for glucose, insulin, HbA1c, lipids, and routine laboratory parameters.

RESULTS

Insulin sensitivity estimated with the clamp significantly increased (Mbw/I index changed from 33.9 +/- 2.6 to 41.9 +/- 3.2 micromol/min per kg per nmol/l, P < 0.001) and the HOMA-IR index significantly decreased (6.34 +/- 0.39 versus 4.40 +/- 0.33, P < 0.001) during rosiglitazone treatment. Ambulatory BP presented small but significant reductions for the total 24-h period (135.3 +/- 1.8 versus 129.9 +/- 1.7 mmHg, P < 0.001 for systolic BP and 76.0 +/- 1.6 versus 71.9 +/- 1.6 mmHg, P < 0.001 for diastolic BP), daytime and night-time. The changes in systolic and diastolic BP correlated with the change in insulin sensitivity (r = -0.78, P < 0.01 and r = -0.68, P < 0.01, respectively). There were also significant reductions in fasting plasma glucose (9.39 +/- 0.41 versus 7.55 +/- 0.31 mmol/l, P < 0.001), insulin (94.0 +/- 0.41 versus 79.5 +/- 5.6 pmol/l, P < 0.01) and HbA1c (8.15 +/- 0.24 versus 7.24 +/- 0.19%, P < 0.001).

CONCLUSIONS

Treatment of type 2 diabetic hypertensive patients with rosiglitazone significantly increased insulin sensitivity and lowered ambulatory BP. These changes were strongly correlated. Thiazolidinediones may thus possess a BP-lowering effect beyond their antihyperglycemic properties.

Mechanical stretch induces monocyte chemoattractant activity via an NF-kappaB-dependent monocyte chemoattractant protein-1-mediated pathway in human mesangial cells: inhibition by rosiglitazone

Hemodynamic abnormalities are important in the pathogenesis of the glomerular damage in diabetes. Glomerular macrophage infiltration driven by the chemokine monocyte chemoattractant protein-1 (MCP-1) is an early event in diabetic nephropathy. The thiazolidinedione rosiglitazone ameliorates albumin excretion rate in diabetic patients with microalbuminuria and has anti-inflammatory properties, raising the possibility of a relationship between its renoprotective and anti-inflammatory activity. Investigated was whether mesangial cell stretching, mimicking in vitro glomerular capillary hypertension, enhances MCP-1 expression and monocyte chemoattractant activity. The effect of the combination of stretch with high glucose on MCP-1 production was studied and, finally, the effect of rosiglitazone on these processes was assessed. Stretching of human mesangial cells significantly enhanced their monocyte chemoattractant activity. This effect was mediated by MCP-1 as it was paralleled by a significant rise in both MCP-1 mRNA and protein levels and was completely abolished by MCP-1 blockade. Combined exposure to both stretch and high glucose further increased MCP-1 production. Stretch activated the IkappaB-NF-kappaB pathway, and NF-kappaB inhibition, with the use of the specific inhibitor SN50, completely abolished stretch-induced MCP-1, indicating that stretch-induced MCP-1 was NF-kappaB dependent. The addition of rosiglitazone significantly diminished stretch-induced NF-kappaB activation, MCP-1 production, and monocyte chemotaxis. In conclusion, stretching of mesangial cells stimulates their monocyte chemoattractant activity via an NF-kappaB-mediated, MCP-1-dependent pathway, and this effect is prevented by rosiglitazone.

Oral antihyperglycemic therapy for type 2 diabetes mellitus

Diabetes mellitus is a chronic disease that is growing in prevalence worldwide. Pharmacologic therapy is often necessary to achieve optimal glycemic control in the management of diabetes. Orally administered antihyperglycemic agents (OHAs) can be used either alone or in combination with other OHAs or insulin. The number of available OHAs has increased significantly in the last decade, which translates into more therapeutic options and complex decision-making for physicians. This review article is designed to help with these decisions. We review the mechanism of action, efficacy and side effects of the different classes of OHAs (alpha-glucosidase inhibitors, biguanides, insulin secretagogues, insulin sensitizers and intestinal lipase inhibitor) and discuss the current recommendations for their use.

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.

Diabetic nephropathy: diagnosis, prevention, and treatment

Diabetic nephropathy is the leading cause of kidney disease in patients starting renal replacement therapy and affects approximately 40% of type 1 and type 2 diabetic patients. It increases the risk of death, mainly from cardiovascular causes, and is defined by increased urinary albumin excretion (UAE) in the absence of other renal diseases. Diabetic nephropathy is categorized into stages: microalbuminuria (UAE >20 microg/min and < or =199 microg/min) and macroalbuminuria (UAE > or =200 microg/min). Hyperglycemia, increased blood pressure levels, and genetic predisposition are the main risk factors for the development of diabetic nephropathy. Elevated serum lipids, smoking habits, and the amount and origin of dietary protein also seem to play a role as risk factors. Screening for microalbuminuria should be performed yearly, starting 5 years after diagnosis in type 1 diabetes or earlier in the presence of puberty or poor metabolic control. In patients with type 2 diabetes, screening should be performed at diagnosis and yearly thereafter. Patients with micro- and macroalbuminuria should undergo an evaluation regarding the presence of comorbid associations, especially retinopathy and macrovascular disease. Achieving the best metabolic control (A1c <7%), treating hypertension (<130/80 mmHg or <125/75 mmHg if proteinuria >1.0 g/24 h and increased serum creatinine), using drugs with blockade effect on the renin-angiotensin-aldosterone system, and treating dyslipidemia (LDL cholesterol <100 mg/dl) are effective strategies for preventing the development of microalbuminuria, in delaying the progression to more advanced stages of nephropathy and in reducing cardiovascular mortality in patients with type 1 and type 2 diabetes.

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.

Diabetes and cardiovascular risk markers

BACKGROUND

People with type 2 diabetes generally carry an array of risk factors for cardiovascular disease (CVD), including hyperglycaemia, dyslipidaemia, alterations in inflammatory mediators and coagulation/thrombolytic parameters, as well as other 'non-traditional' risk factors, many of which may be closely associated with insulin resistance. Consequently, rates of CVD mortality and morbidity are particularly high in this population. Targeting hyperglycaemia alone does not reduce the excess risk in diabetes, highlighting the need for aggressive treatment of other risk factors.

SCOPE

This is a review of cardiovascular risk markers in diabetes, based on MEDLINE and EMBASE literature searches (1994-2004).

FINDINGS

Although, the current use of statin therapy is effective at reducing low-density lipoprotein (LDL)-cholesterol, residual risk remains from other independent lipid and non-lipid factors. The peroxisome proliferator-activated receptor-gamma(PPARgamma) appears to be intimately involved in regulating risk markers at multiple levels. Ligands that activate PPARgamma, which include the thiazolidinedione (TZD) insulin-sensitizing agents used to manage type 2 diabetes, display a number of potential anti-atherogenic properties, including effects on high-density lipoprotein (HDL) cholesterol and triglycerides, as well as other beneficial non-lipid effects, such as regulating levels of mediators involved in inflammation and endothelial dysfunction. Data from several sources suggest that simple strategies combining TZDs and statins could have complementary effects on CVD risk factors profiles in diabetes, alongside the ability to control glycaemia.

CONCLUSION

It is hoped that studies currently underway will provide insights into the value of such treatment approaches in terms of reducing the excess CVD risk, morbidity and mortality associated with type 2 diabetes.

Thiazolidinediones: a review of their mechanisms of insulin sensitization, therapeutic potential, clinical efficacy, and tolerability

The thiazolidinediones (TZDs) rosiglitazone and pioglitazone are newer additions to the antidiabetic armamentarium and are indicated for the treatment of type 2 diabetes mellitus (T2DM) in the United States. The TZDs are peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists that provide clinically effective glycemic control and unique pharmacologic effects on multiple risk factors for T2DM-related morbidity, including improvement of insulin sensitivity and endothelial dysfunction, reduction of blood pressure, and amelioration of dyslipidemia. Weight gain and fluid retention occur with TZD therapy, especially when they are administered in higher doses and in combination with insulin. Although fluid retention associated with the use of TZDs is generally mild and reversible, these agents should not be used in patients with New York Heart Association Class III or IV heart failure symptoms. The findings of ongoing, long-term, prospective studies will clarify the role of the TZDs in the treatment of T2DM, particularly in terms of the durability of improvements in glycemic control, insulin sensitivity, pancreatic beta- cell function, and cardiovascular health.

[The place of thiazolidinediones in the treatment of type 2 diabetes]

SUPPLEMENTARY ORAL ANTIDIABETICS: Thiazolidinediones or glitazones are a new class of oral antidiabetics, the effects on blood sugar control of which are mediated by the sensitivity of the peripheral tissue to the effect of insulin. Hence, their effect is complementary to that of the insulin secreting agents and that of metformin, which acts by blocking the hepatic production of glucose. OTHER BENEFICIAL EFFECTS: Other than their effect on blood glucose, thiazolidinediones have a favorable influence upon the cardiovascular risk factors or markers such as blood pressure, C-reactive protein and metalloproteinase-9. They also appear to induce long term preservation of the beta-cell capital. Principle side effects are salt-water retention with a risk of decompensation of a pre-existing heart failure and weight gain with regard to the subcutaneous adipose tissue, without deleterious effects on blood glucose control.

Pleiotropic effects of thiazolidinediones: taking a look beyond antidiabetic activity

Thiazolidinediones (TZD) [Troglitazone (TRO), Pioglitazone (PGZ), Rosiglitazone, (RGZ)] are a novel class of antidiabetic drugs for patients with Type-2 diabetes mellitus (T2DM) able to decrease blood glucose, working through a reduction of insulin resistance. The family of TZD exerts its effect specifically bound to peroxisome proliferator-activated receptor y (PPARy). This is a member of the nuclear hormone receptor superfamily of ligand-dependent transcription factors, together with PPARalpha and deltabeta. Although PPARgamma is essentially expressed in adipose tissue, it has also been found in endothelial cells, macrophages, vascular smooth muscle cells, glomerular mesangial cells, hepatic stellate cells and in several cancer cell lines. In these cells, the PPARgamma activation by TZD determines modulatory effects on growth factor release, production of cytokine, cell proliferation and migration, extracellular matrix remodeling and control on cell cycle progression and differentiation. In addition, TZD have been shown to have a potent antioxidant effect. This review, taking a quick look beyond the antidiabetic activity of PPARgamma, shows the dramatic ranging of medical implications that the use of TZD could have modulating the PPARgamma activity in several diseases with a strong social impact, such as insulin resistance syndrome, chronic inflammation, atherosclerosis and cancer.

Insulin resistance and cardiovascular disease: the role of PPARgamma activators beyond their anti-diabetic action

Over the past few years it has been recognised that insulin resistance (IR) is an independent risk factor for major cardiovascular events. In addition, IR is associated with other factors such as hypertension, dyslipidaemia and endothelial dysfunction, and this cluster of metabolic disorders contributes to the cardiovascular risk of patients with IR. Given the increasing number of patients with IR, the modulation of their cardiovascular risk is a major task in diabetology and vascular medicine. This review will focus on the role of IR as a cardiovascular risk factor and on the potential of activators of the nuclear transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) to modulate these risk factors associated with IR.

Effect of pioglitazone on carotid intima-media thickness and arterial stiffness in type 2 diabetic nephropathy patients

Atherosclerosis is the major cause of morbidity and mortality in patients with type 2 diabetes, and pioglitazone has been reported to have anti-inflammatory and potential antiatherogenic effects. The aim of the present study was to determine whether pioglitazone, glibenclamide, or voglibose affects carotid intima-media thickness (IMT), pulse wave velocity (PWV), and urinary albumin excretion (UAE) in normotensive type 2 diabetic nephropathy patients. Forty-five normotensive type 2 diabetes patients with microalbuminuria were randomized to 12-month treatment with pioglitazone (30 mg/d, n = 15), glibenclamide (5 mg/d, n = 15), or voglibose (0.6 mg/d, n = 15). Pre- and posttreatment UAE, PWV, and IMT values were compared between treatment groups and a group of age-matched healthy control subjects (n = 30). Pretreatment PWV, IMT, and UAE values differed little between the 3 groups, but UAE was greater in the 45 type 2 diabetes patients (132.5 +/- 36.4 microg/min) than in the control subjects (6.2 +/- 1.8 microg/min, P < .001). IMT (0.76 +/- 0.12 mm) was significantly greater in the diabetics than in the controls (0.60 +/- 0.08 mm, P < .01). PWV (1,840 +/- 320 cm/s) was also significantly greater in the diabetics than in the controls (1,350 +/- 225 cm/s, P < .01). After 6 and 12 months, UAE, IMT, and PWV in the pioglitazone treatment group were significantly lower than those in the glibenclamide treatment group and voglibose treatment group (UAE: 6 months, P < .05 and 12 months, P < .01; IMT and PWV: 6 months, P < .05 and 12 months, P < .05). Pioglitazone, but not glibenclamide or voglibose, appears to be effective in reducing UAE, IMT, and PWV in normotensive type 2 diabetes patients with microalbuminuria.

Avandamet: combined metformin-rosiglitazone treatment for insulin resistance in type 2 diabetes

Insulin resistance is a major endocrinopathy underlying the development of hyperglycaemia and cardiovascular disease in type 2 diabetes. Metformin (a biguanide) and rosiglitazone (a thiazolidinedione) counter insulin resistance, acting by different cellular mechanisms. The two agents can be used in combination to achieve additive glucose-lowering efficacy in the treatment of type 2 diabetes, without stimulating insulin secretion and without causing hypoglycaemia. Both agents also reduce a range of atherothrombotic factors and markers, indicating a lower cardiovascular risk. Early intervention with metformin is already known to reduce myocardial infarction and increase survival in overweight type 2 patients. Recently, a single-tablet combination of metformin and rosiglitazone, Avandamet, has become available. Avandamet is suitable for type 2 diabetic patients who are inadequately controlled by monotherapy with metformin or rosiglitazone. Patients already receiving separate tablets of metformin and rosiglitazone may switch to the single-tablet combination for convenience. Also, early introduction of the combination before maximal titration of one agent can reduce side effects. Use of Avandamet requires attention to the precautions for both metformin and rosiglitazone, especially renal, cardiac and hepatic competence. In summary, Avandamet is a single-tablet metformin-rosiglitazone combination that doubly targets insulin resistance as therapy for hyperglycaemia and vascular risk in type 2 diabetes.

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.