Impact of adjunctive thiazolidinedione therapy on blood lipid levels and glycemic control in patients with type 2 diabetes

GQ-11: A new PPAR agonist improves obesity-induced metabolic alterations in LDLr-/- mice

BACKGROUND

Obesity and insulin resistance/diabetes are important risk factors for cardiovascular diseases and demand safe and efficacious therapeutics.

OBJECTIVE

To assess the effects of a new thiazolidine compound-GQ-11-on obesity and insulin resistance induced by a diabetogenic diet in LDL receptor-deficient (LDLr^-/-) mice.

METHODS

Molecular docking simulations of GQ-11, PPARα and PPARγ structures were performed. Male C57BL/6J LDLr^-/- mice fed a diabetogenic diet for 24 weeks were treated with vehicle, GQ-11 or pioglitazone or (20 mg/kg/day) for 28 days by oral gavage. Glucose tolerance test, insulin, HOMA-IR, adipokines (leptin, adiponectin) and the lipid profile were assessed after treatment. Adipose tissue was analysed by X-ray analysis and morphometry; gene and protein expression were evaluated by real-time PCR and western blot, respectively.

RESULTS

GQ-11 showed partial agonism to PPARγ and PPARα. In vivo, treatment with GQ-11 ameliorated insulin sensitivity and did not modify subcutaneous adipose tissue and body weight gain. In addition, GQ-11 restored adipokine imbalance induced by a diabetogenic diet and enhanced Glut-4 expression in the adipose tissue. Improved insulin sensitivity was also associated with lower levels of MCP-1 and higher levels of IL-10. Furthermore, GQ-11 reduced triglycerides and VLDL cholesterol and increased HDL-cholesterol by upregulation of Apoa1 and Abca1 gene expression in the liver.

CONCLUSION

GQ-11 is a partial/dual PPARα/γ agonist that demonstrates anti-diabetic effects. Additionally, it improves the lipid profile and ameliorates chronic inflammation associated with obesity in atherosclerosis-prone mice.

Rosiglitazone Improves Insulin Resistance Mediated by 10,12 Conjugated Linoleic Acid in a Male Mouse Model of Metabolic Syndrome

Trans-10, cis-12 conjugated linoleic acid (10,12 CLA) is a dietary fatty acid that promotes weight loss and disproportionate fat loss. Obese mice fed a high-fat, high-sucrose (HFHS) diet containing 10,12 CLA are resistant to weight gain and contain markedly reduced subcutaneous fat and adiponectin, with a concurrent lack of improvement in insulin sensitivity despite significant weight loss. Taken together, 10,12 CLA promotes a phenotype resembling peroxisome proliferator-activated receptor (PPAR)γ antagonism. Because thiazolidinediones such as rosiglitazone (Rosi) are used clinically to improve insulin sensitivity by activating PPARγ, with particular efficacy in subcutaneous white adipose tissue, we hypothesized that Rosi would improve glucose metabolism in mice losing weight with 10,12 CLA. Obese low-density lipoprotein receptor-deficient mice were fed a HFHS control diet, or supplemented with 1% 10,12 CLA with or without Rosi (10 mg/kg) for 8 weeks. Body composition, glucose and insulin tolerance tests, tissue gene expression, and plasma lipid analyses were performed. Mice consuming 10,12 CLA with Rosi lost weight and body fat compared with control groups, but with a healthier redistribution of body fat toward more subcutaneous adipose tissue than with 10,12 CLA alone. Further, Rosi improved 10,12 CLA-mediated insulin resistance parameters and increased plasma and subcutaneous adipose tissue adiponectin levels without adverse effects on plasma or hepatic lipids. We conclude that cotreatment of mice with 10,12 CLA and Rosi promotes fat loss with a healthier fat distribution that leads to improved insulin sensitivity, suggesting that the combination treatment strategy of 10,12 CLA with Rosi could have therapeutic potential for obesity treatment.

Paradoxically Decreased HDL-Cholesterol Levels Associated with Rosiglitazone Therapy

Objective:

To report 2 cases of very low high-density lipoprotein cholesterol (HDL-C) levels associated with rosiglitazone therapy.

Case Summary:

Two patients with type 2 diabetes taking rosiglitazone for glycemic control developed paradoxically low HDL-C levels during rosiglitazone therapy. In the first patient, the HDL-C level decreased from 33 to 11.6 mg/dL after 8 months of therapy. The second patient's HDL-C level decreased from the baseline level of 44.8 mg/dL to 19.7 mg/dL after 4 months of rosiglitazone use. These abnormalities resolved on discontinuation of rosiglitazone and were not observed when the patients were treated with pioglitazone. The patients had no changes to other drug therapy or medical conditions known to affect lipid metabolism during treatment with rosiglitazone.

Discussion:

Thiazolidinediones, insulin sensitizers widely used in the treatment of type 2 diabetes, have been reported to have beneficial effects on lipids, such as triglyceride lowering and HDL-C elevation, in addition to their glucose-lowering effects. It has been suggested that rosiglitazone and pioglitazone, the 2 currently available thiazolidinediones, may differ in their effects on lipids. As of July 2006, a total of 8 cases of paradoxical lowering of plasma HDL-C associated with rosiglitazone have now been reported. Based on use of the Naranjo probability scale, the 2 cases presented here were probably associated with rosiglitazone. The duration of therapy may be important in this paradoxical effect.

Conclusions:

Rosiglitazone is associated with a paradoxical decrease in HDL-C levels in patients with type 2 diabetes. In patients receiving rosiglitazone, a baseline lipid panel should be performed and lipid values should be monitored during the course of therapy.

Differential Role of Adipose Tissues in Obesity and Related Metabolic and Vascular Complications

This review focuses on the contribution of white, brown, and perivascular adipose tissues to the pathophysiology of obesity and its associated metabolic and vascular complications. Weight gain in obesity generates excess of fat, usually visceral fat, and activates the inflammatory response in the adipocytes and then in other tissues such as liver. Therefore, low systemic inflammation responsible for insulin resistance contributes to atherosclerotic process. Furthermore, an inverse relationship between body mass index and brown adipose tissue activity has been described. For these reasons, in recent years, in order to combat obesity and its related complications, as a complement to conventional treatments, a new insight is focusing on the role of the thermogenic function of brown and perivascular adipose tissues as a promising therapy in humans. These lines of knowledge are focused on the design of new drugs, or other approaches, in order to increase the mass and/or activity of brown adipose tissue or the browning process of beige cells from white adipose tissue. These new treatments may contribute not only to reduce obesity but also to prevent highly prevalent complications such as type 2 diabetes and other vascular alterations, such as hypertension or atherosclerosis.

New PPARγ partial agonist improves obesity-induced metabolic alterations and atherosclerosis in LDLr(-/-) mice

Peroxisome proliferator-activated receptor gamma (PPARγ) regulates multiple pathways involved in the pathogenesis of obesity and atherosclerosis. Here, we evaluated the therapeutic potential of GQ-177, a new thiazolidinedione, on diet-induced obesity and atherosclerosis. The intermolecular interaction between PPARγ and GQ-177 was examined by virtual docking and PPAR activation was determined by reporter gene assay identifying GQ-177 as a partial and selective PPARγ agonist. For the evaluation of biological activity of GQ-177, low-density lipoprotein receptor-deficient (LDLr(-/-)) C57/BL6 mice were fed either a high fat diabetogenic diet (diet-induced obesity), or a high fat atherogenic diet, and treated with vehicle, GQ-177 (20mg/kg/day), pioglitazone (20mg/kg/day, diet-induced obesity model) or rosiglitazone (15mg/kg/day, atherosclerosis model) for 28 days. In diet-induced obesity mice, GQ-177 improved insulin sensitivity and lipid profile, increased plasma adiponectin and GLUT4 mRNA in adipose tissue, without affecting body weight, food consumption, fat accumulation and bone density. Moreover, GQ-177 enhanced hepatic mRNA levels of proteins involved in lipid metabolism. In the atherosclerosis mice, GQ-177 inhibited atherosclerotic lesion progression, increased plasma HDL and mRNA levels of PPARγ and ATP-binding cassette A1 in atherosclerotic lesions. GQ-177 acts as a partial PPARγ agonist that improves obesity-associated insulin resistance and dyslipidemia with atheroprotective effects in LDLr(-/-) mice.

Peroxisome Proliferator-Activated Receptors and the Heart: Lessons from the Past and Future Directions

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear family of ligand activated transcriptional factors and comprise three different isoforms, PPAR-α, PPAR-β/δ, and PPAR-γ. The main role of PPARs is to regulate the expression of genes involved in lipid and glucose metabolism. Several studies have demonstrated that PPAR agonists improve dyslipidemia and glucose control in animals, supporting their potential as a promising therapeutic option to treat diabetes and dyslipidemia. However, substantial differences exist in the therapeutic or adverse effects of specific drug candidates, and clinical studies have yielded inconsistent data on their cardioprotective effects. This review summarizes the current knowledge regarding the molecular function of PPARs and the mechanisms of the PPAR regulation by posttranslational modification in the heart. We also describe the results and lessons learned from important clinical trials on PPAR agonists and discuss the potential future directions for this class of drugs.

Peroxisome proliferator-activated receptors and their ligands: nutritional and clinical implications--a review

Peroxisome proliferator-activated receptors are expressed in many tissues, including adipocytes, hepatocytes, muscles and endothelial cells; however, the affinity depends on the isoform of PPAR, and different distribution and expression profiles, which ultimately lead to different clinical outcomes. Because they play an important role in lipid and glucose homeostasis, they are called lipid and insulin sensors. Their actions are limited to specific tissue types and thus, reveal a characteristic influence on target cells. PPARα mainly influences fatty acid metabolism and its activation lowers lipid levels, while PPARγ is mostly involved in the regulation of the adipogenesis, energy balance, and lipid biosynthesis. PPARβ/δ participates in fatty acid oxidation, mostly in skeletal and cardiac muscles, but it also regulates blood glucose and cholesterol levels. Many natural and synthetic ligands influence the expression of these receptors. Synthetic ligands are widely used in the treatment of dyslipidemia (e.g. fibrates--PPARα activators) or in diabetes mellitus (e.g. thiazolidinediones--PPARγ agonists). New generation drugs--PPARα/γ dual agonists--reveal hypolipemic, hypotensive, antiatherogenic, anti-inflammatory and anticoagulant action while the overexpression of PPARβ/δ prevents the development of obesity and reduces lipid accumulation in cardiac cells, even during a high-fat diet. Precise data on the expression and function of natural PPAR agonists on glucose and lipid metabolism are still missing, mostly because the same ligand influences several receptors and a number of reports have provided conflicting results. To date, we know that PPARs have the capability to accommodate and bind a variety of natural and synthetic lipophilic acids, such as essential fatty acids, eicosanoids, phytanic acid and palmitoylethanolamide. A current understanding of the effects of PPARs, their molecular mechanisms and the role of these receptors in nutrition and therapeutic treatment are delineated in this paper.

PPAR agonists for the treatment of cardiovascular disease in patients with diabetes

Diabetes is a complex disease defined by hyperglycaemia; however, strong associations with abdominal obesity, hypertension and dyslipidaemia contribute to the high risk of cardiovascular disease. Although aggressive glycaemic control reduces microvascular complications, the evidence for macrovascular complications is less certain. The theoretical benefits of the mode of action of peroxisome proliferator-activated receptor (PPAR) agonists are clear. In clinical practice, PPAR-α agonists such as fibrates improve dyslipidaemia, while PPAR-γ agonists such as thiazolidinediones improve insulin resistance and diabetes control. However, although these agents are traditionally classed according to their target, they have different and sometimes conflicting clinical benefit and adverse event profiles. It is speculated that this is because of differing properties and specificities for the PPAR receptors (each of which targets specific genes). This is most obvious in the impact on cardiovascular outcomes--in clinical trials pioglitazone appeared to reduce cardiovascular events, whereas rosiglitazone potentially increased the risk of myocardial infarction. The development of a dual PPAR-α/γ agonist may prove beneficial in effectively managing glycaemic control and improving dyslipidaemia in patients with type 2 diabetes. Yet, development of agents such as muraglitazar and tesaglitazar has been hindered by various serious adverse events. Aleglitazar, a balanced dual PPAR-α/γ agonist, is currently the most advanced in clinical development and has shown promising results in phase II clinical trials with beneficial effects on glucose and lipid variables. A phase III study, ALECARDIO, is ongoing and will establish whether improvements in laboratory test profiles translate into an improvement in cardiovascular outcomes.

Impact of rosiglitazone therapy on the lipid profile, glycemic control, and medication costs among type 2 diabetes patients

OBJECTIVE

To investigate the impact of rosiglitazone therapy on lipid profiles, glycemic control, and costs associated with cholesterol-lowering and diabetic medications among Type 2 diabetes mellitus (T2DM) patients in a standard practice setting.

METHOD

This retrospective cohort study was conducted using data from the General Practice Research Database during 1999-2006. T2DM patients were classified based on the addition of rosiglitazone versus either metformin or a sulfonylurea ('comparison group') to pre-existing glucose lowering agents. After propensity score matching to control for differences in baseline patient characteristics, 1450 matched pairs were identified. The mean changes in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), glycosylated hemoglobin A1C (A1C), and daily medication costs were calculated. To investigate the incremental costs for lipid-lowering medications, a two-part model was utilized.

RESULTS

The mean changes in TC and A1C for the rosiglitazone and metformin/sulfonylurea groups were 9 vs -10 mg/dL for TC, -2 vs -9 mg/dL for LDL-C, and -0.8% vs. -1.2% for A1C, respectively. The mean changes in daily medication costs of glucose- and lipid-lowering drugs were $3.95 for rosiglitazone patients and $0.27 for metformin/sulfonylurea patients. For patients with positive incremental lipid-lowering costs, rosiglitazone use was significantly associated with costs eight times greater than metformin/sulfonylureas. Generalizability of the study is limited due to cost estimates using the national formulary and potential selection bias.

CONCLUSIONS

Addition of rosiglitazone to an existing antidiabetic medication regimen improved glycemic control to a lesser extent than metformin/sulfonylurea, and also deteriorated patients' lipid profiles, leading to significantly greater daily costs. Economic evaluations of alternative therapies should consider such costs to estimate the full impact of different therapeutic approaches in diabetes.

A 26-week, placebo- and pioglitazone-controlled, dose-ranging study of rivoglitazone, a novel thiazolidinedione for the treatment of type 2 diabetes

OBJECTIVE

To examine the efficacy and general safety of rivoglitazone, a novel thiazolidinedione, as a treatment for type 2 diabetes in a dose-ranging study over a period of up to 6 months.

RESEARCH DESIGN AND METHODS

A 26-week, randomized, double-blind, double-dummy, placebo- and active comparator (pioglitazone 45 mg)-controlled study designed to evaluate the efficacy and safety of once-daily rivoglitazone 1, 2, or 3 mg in subjects with type 2 diabetes. The study was conducted in adults with type 2 diabetes (glycated hemoglobin [HbA(1c)] >or=7.0% and <10.5%) who were either naïve to prior antidiabetes drug treatment or discontinued pre-study antidiabetes medications and were switched to study medication. A total of 441 subjects were randomized, using an equal allocation schedule to one of five treatment arms, including placebo. The primary efficacy measurement was the change in HbA(1c) from baseline to week 26 in the intent-to-treat population (last observation carried forward), for drug treatments minus placebo (placebo-subtracted).

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT00143520.

RESULTS

The incidence of early discontinuations was >50%, with most cases being related to a lack of efficacy (highest on placebo) or adverse experiences (highest on rivoglitazone 3 mg). Rivoglitazone 1, 2, and 3 mg and pioglitazone 45 mg were more effective than placebo in reducing HbA(1c) from baseline to week 26 (placebo-subtracted change from baseline: -0.55% [p = 0.0034], -0.99% [p < 0.0001], -1.10% [p < 0.0001], and -0.59% [p = 0.0016], respectively). In general, all treatments were safe. The most common drug-related adverse events reported with rivoglitazone were peripheral edema and weight gain; incidences increased with dose and were higher with rivoglitazone 2 and 3 mg than with pioglitazone or rivoglitazone 1 mg.

CONCLUSIONS

Rivoglitazone is a potent thiazolidinedione agent with demonstrated glycemic benefits over a 6-month period in subjects with type 2 diabetes. Once-daily doses of 1, 2, and 3 mg rivoglitazone demonstrated HbA(1c) reduction similar or superior to those observed for pioglitazone 45 mg. Limitations in generalizing from this study include a modest sample size and a high rate of discontinuation prior to the last scheduled visit.

Exercise training ameliorates the effects of rosiglitazone on traditional and novel cardiovascular risk factors in patients with type 2 diabetes mellitus

The aim of the study was to investigate the effects of rosiglitazone and/or exercise training on novel cardiovascular risk factors in patients with type 2 diabetes mellitus. One hundred overweight/obese type 2 diabetes mellitus patients, with inadequate glycemic control (hemoglobin A(1c) >7%) despite combined treatment with gliclazide plus metformin, were randomized using a 2 x 2 factorial design to 4 equivalent (n = 25) groups, as follows: (1) CO: maintenance of habitual activities, (2) RSG: add-on therapy with rosiglitazone (8 mg/d), (3) EX: adjunctive exercise training, and (4) RSG + EX: supplementary administration of rosiglitazone (8 mg/d) plus exercise training. No participant had diabetic vascular complications or was receiving lipid-lowering therapy. Anthropometric parameters, cardiorespiratory capacity, glycemic and lipid profile, apolipoprotein (apo) A-I, apo B, interleukin (IL)-10, IL-18, insulin resistance, and blood pressure were measured before and after 12 months of intervention (P < .05). Both RSG and EX groups significantly reduced glycemic indexes, insulin resistance, blood pressure, and IL-18, whereas they significantly increased high-density lipoprotein, cardiorespiratory capacity, and IL-10, compared with CO group (P < .05). Besides this, exercise-treated patients conferred a remarkable down-regulation in the rest of lipid parameters (total cholesterol, low-density lipoprotein cholesterol, triglycerides, apo B) and body fat content (P < .05) in comparison with CO group. On the other hand, RSG group rather than CO group considerably increased apo A-I levels and body mass index (P < .05). Notably, the combined treatment group yielded pronounced beneficial changes in glycemic indexes, lipid profile, insulin resistance, blood pressure, IL-10, IL-18, apo A-I, and apo B (vs CO group, P < .05). Furthermore, the addition of exercise to rosiglitazone treatment counteracted the drug-related negative effects on body weight, low-density lipoprotein, and total cholesterol. Rosiglitazone plus exercise training elicited additive effects on body composition, glycemic control, and traditional and novel cardiovascular risk factors in type 2 diabetes mellitus patients, indicating complementary effects.

Effects of rosiglitazone and metformin treatment on apelin, visfatin, and ghrelin levels in patients with type 2 diabetes mellitus

Visfatin, ghrelin, and apelin are the most recently identified adipocytokines; but their response to insulin-sensitizing agents is poorly clarified. We aimed to assess the differential effects of either rosiglitazone or metformin monotherapy on the aforementioned adipocytokines in patients with type 2 diabetes mellitus (T2DM). One hundred T2DM patients (30 men, 70 women), with poor glycemic control (glycosylated hemoglobin >6.5%) while taking 850 mg of metformin daily, were enrolled. All participants were randomized to receive either adjunctive therapy with rosiglitazone (8 mg/d, n = 50) or the maximum dose (2550 mg/d) of metformin (MET group, n = 50). Anthropometric parameters, glycemic and lipid profile, high-sensitivity CRP (hs-CRP), insulin resistance (homeostasis model assessment of insulin resistance index [HOMA-IR]), visfatin, ghrelin, and apelin were assessed at baseline and after 14 weeks of therapy. Both rosiglitazone and metformin led to similar, significant improvement in glycemic profile and apelin levels, whereas lipid parameters, fat mass, and visfatin remained almost unaffected (P > .05). Insulin resistance was significantly attenuated in both groups, but to a lesser degree in the MET group (P = .045). Rosiglitazone-treated patients experienced a significant decrease in hs-CRP and systolic blood pressure compared with baseline values and those of the MET group (P < .05). Besides, rosiglitazone treatment considerably increased plasma ghrelin (3.74 +/- 1.52 ng/mL) in comparison with either baseline (P = .034) or metformin monotherapy values (-2.23 +/- 1.87 ng/mL, P = .008). On the other hand, the MET group, rather than the rosiglitazone group, had decreased body mass index (-0.79 +/- 0.47 vs 0.56 kg/m(2), P = .009). The aforementioned changes in apelin and ghrelin were independently associated with HOMA-IR changes. Both rosiglitazone and metformin favorably changed glycemic indexes and apelin levels. The addition of rosiglitazone seemed to confer greater benefits in ghrelin, hs-CRP, systolic blood pressure, and HOMA-IR regulation than metformin monotherapy. Although these results reflect improvement in cardiovascular risk profile, the overall clinical importance of insulin sensitizers must be further assessed.

Beneficial effects of rosiglitazone on novel cardiovascular risk factors in patients with Type 2 diabetes mellitus

AIM

Impaired exercise capacity, adiponectin, MMPs and TIMPs have all been implicated in the development of cardiovascular disease. The aim of our study was to determine the effects of rosiglitazone on these factors in diabetic patients.

METHODS

Seventy individuals with Type 2 diabetes were assigned randomly to either a rosiglitazone group (8 mg/day, RG) or a control group (CG) for 6 months. All participants took gliclazide 160 mg plus metformin 1700 mg in stable dose. None of the individuals had diabetic complications or had previously participated in an exercise programme. Anthropometric parameters, VO2 peak, oxygen pulse, glycaemic indices, lipid profile, adiponectin, insulin resistance, blood pressure and serum MMP-9, TIMP-1, TIMP-2 levels were assessed at baseline and at the end of the study. After Bonferroni adjustment, a P-value < 0.017 was assumed to be statistically significant.

RESULTS

Rosiglitazone treatment significantly increased VO2 peak (P < 0.0001), the duration of the exercise test (P < 0.0001), oxygen pulse (P = 0.010) and TIMP-2 levels (P = 0.008) in comparison with CG. Insulin resistance, hyperglycaemia, diastolic blood pressure and MMP-9 levels were also reduced (P < 0.017). Fat mass, lipid profile, TIMP-1 levels and MMP9 : TIMP-1 ratio were unaltered after rosiglitazone treatment. There were no significant changes in these parameters in control subjects. In univariate analysis, the rosiglitazone-induced increment of VO2 peak was associated with alterations in plasma adiponectin (r = 0.691), HOMA-IR (r = -0.782) and HbA(1c) (r = -0.676) (P < 0.017). These relationships retained significance after multiple regression analysis (P = 0.005).

CONCLUSIONS

Rosiglitazone treatment increases cardiorespiratory fitness and modulates favourably serum adiponectin, MMP-9 and TIMP-2 levels. Whether these effects produce cardiovascular benefits in the long term requires further investigation.

Pioglitazone and sulfonylureas: effectively treating type 2 diabetes

Type 2 diabetes is characterised by a gradual decline in glycaemic control and progression from oral glucose-lowering monotherapy to combination therapy and exogenous insulin therapy. Functional decline of the insulin-secreting beta-cells is largely responsible for the deterioration in glycaemic control. Preservation of beta-cell functionality, in addition to maintaining glycaemic control and reducing insulin resistance, is now regarded as a key target for long-term management strategies. Early, aggressive intervention with combination therapy is emerging as a valid approach to optimise long-term outcomes and combining agents with differing modes of action and secondary effect profiles should prove valuable. Sulfonylureas and thiazolidinediones exert their glucose-lowering effect through differing mechanisms of action - the sulfonylureas by stimulating insulin secretion, whereas the thiazolidinediones are insulin sensitisers. Both agents offer excellent improvements in glycaemic control when given as monotherapy or in combination. The thiazolidinediones protect beta-cell structural and functional integrity and functionality and complement the sulfonylureas by inducing and maintaining improvements in insulin resistance, the abnormal lipid profile associated with type 2 diabetes and other cardiovascular risk factors. Thus, there is a strong rationale to support the addition of thiazolidinediones to sulfonylureas as a treatment option for type 2 diabetes. This combination may be particularly effective in the early stages of the disease when beta-cell function is at its highest, allowing maximal benefit to be obtained from the insulin secretion-promoting abilities of the sulfonylureas and the beta-cell-protective effects of the thiazolidinediones.

Drug-induced metabolic syndrome

The metabolic syndrome is a cluster of risk factors associated with an increased risk for cardiovascular disease and type 2 diabetes. Based on data from 1988 to 1994, it is estimated that 24% of adults in the United States meet the criteria for diagnosis of the metabolic syndrome. The use of certain medications may increase the risk of the metabolic syndrome by either promoting weight gain or altering lipid or glucose metabolism. Health providers should recognize and understand the risk associated with certain medications and appropriately monitor for changes related to the metabolic syndrome. Careful attention to drug choices should be paid in patients who are overweight or have other risk factors for diabetes or cardiovascular disease.

Combined effects of rosiglitazone and conjugated linoleic acid on adiposity, insulin sensitivity, and hepatic steatosis in high-fat-fed mice

Dysfunctional cross talk between adipose tissue and liver tissue results in metabolic and inflammatory disorders. As an insulin sensitizer, rosiglitazone (Rosi) improves insulin resistance yet causes increased adipose mass and weight gain in mice and humans. Conjugated linoleic acid (CLA) reduces adipose mass and body weight gain but induces hepatic steatosis in mice. We examined the combined effects of Rosi and CLA on adiposity, insulin sensitivity, and hepatic steatosis in high-fat-fed male C57Bl/6 mice. CLA alone suppressed weight gain and adipose mass but caused hepatic steatosis. Addition of Rosi attenuated CLA-induced insulin resistance and dysregulation of adipocytokines. In adipose, CLA significantly suppressed lipoprotein lipase and fatty acid translocase (FAT/CD36) mRNA, suggesting inhibition of fatty acid uptake into adipose; addition of Rosi completely rescued this effect. In addition, CLA alone increased markers of macrophage infiltration, F4/80, and CD68 mRNA levels, without inducing TNF-alpha in epididymal adipose tissue. The ratio of Bax to Bcl2, a marker of apoptosis, was significantly increased in adipose of the CLA-alone group and was partially prevented by treatment of Rosi. Immunohistochemistry of F4/80 demonstrates a proinflammatory response induced by CLA in epididymal adipose. In the liver, CLA alone induced microsteatotic liver but surprisingly increased the rate of very-low-density lipoprotein-triglyceride production without inducing inflammatory mediator-TNF-alpha and markers of macrophage infiltration. These changes were accompanied by significantly increased mRNA levels of stearoyl-CoA desaturase, FAT/CD36, and fatty acid synthase. The combined administration of CLA and Rosi reduced hepatic liver triglyceride content as well as lipogenic gene expression compared with CLA alone. In summary, dietary CLA prevented weight gain in Rosi-treated mice without attenuating the beneficial effects of Rosi on insulin sensitivity. Rosi ameliorated CLA-induced lipodystrophic disorders that occurred in parallel with rescued expression of adipocytokine and adipocytes-abundant genes.

The effect of pioglitazone on recurrent myocardial infarction in 2,445 patients with type 2 diabetes and previous myocardial infarction: results from the PROactive (PROactive 05) Study

OBJECTIVES

This analysis from the PROactive (PROspective pioglitAzone Clinical Trial In macroVascular Events) study assesses the effects of pioglitazone on mortality and macrovascular morbidity in patients with type 2 diabetes and a previous myocardial infarction (MI).

BACKGROUND

People with type 2 diabetes have an increased incidence of MI compared with the general population. Those with diabetes and MI have a worse prognosis than nondiabetic patients with cardiovascular disease.

METHODS

The PROactive study was a prospective, multicenter, double-blind, placebo-controlled trial of 5,238 patients with type 2 diabetes and macrovascular disease. Patients were randomized to either pioglitazone or placebo in addition to their other glucose-lowering and cardiovascular medication. Treatment of diabetes, dyslipidemia, and hypertension was encouraged according to the International Diabetes Federation guidelines. Patients were followed for a mean of 2.85 years. The primary end point was the time to first occurrence of macrovascular events or death. Of the total cohort, the subgroup of patients who had a previous MI (n = 2,445 [46.7%]; n = 1,230 in the pioglitazone group and n = 1,215 in the placebo group) was evaluated using prespecified and post-hoc analyses.

RESULTS

Pioglitazone had a statistically significant beneficial effect on the prespecified end point of fatal and nonfatal MI (28% risk reduction [RR]; p = 0.045) and acute coronary syndrome (ACS) (37% RR; p = 0.035). There was a 19% RR in the cardiac composite end point of nonfatal MI (excluding silent MI), coronary revascularization, ACS, and cardiac death (p = 0.033). The difference in the primary end point defined in the main PROactive study did not reach significance in the MI population (12% RR; p = 0.135). The rates of heart failure requiring hospitalization were 7.5% (92 of 1,230) with pioglitazone and 5.2% (63 of 1,215) with placebo. Fatal heart failure rates were similar (1.4% [17 of the 92] with pioglitazone versus 0.9% [11 of the 63] with placebo).

CONCLUSIONS

In high-risk patients with type 2 diabetes and previous MI, pioglitazone significantly reduced the occurrence of fatal and nonfatal MI and ACS. (PROspective pioglitAzone Clinical Trial In macroVascular Events; http://www.clinicaltrials.gov/ct/show/NCT00174993?order = 1; ISRCTN NCT00174993).

Are thiazolidinediones good or bad for the heart?

Type 2 diabetes is a global epidemic contributing to significant cardiovascular morbidity and mortality. The high prevalence of cardiovascular disease can largely be attributed to the metabolic syndrome with its multiple cardiovascular risk factors, including central obesity, hypertension, glucose intolerance, chronic inflammation, and dyslipidemia. The peroxisome proliferator-activated receptor-gamma agonists, the thiazolidinediones, may potentially correct the inflammatory disarray, endothelial dysfunction, dyslipidemia, and plaque vulnerability associated with diabetic cardiovascular disease through their effects on insulin resistance and fat metabolism, yet they can also exacerbate congestive heart failure. This review summarizes basic science, animal, and human data on the effects of thiazolidinediones on cardiovascular disease.

Transcriptional suppression of human microsomal triglyceride transfer protein by hypolipidemic insulin sensitizers

Microsomal triglyceride transfer protein (MTP) catalyzes the assembly and secretion of liver triglyceride-rich lipoproteins. The human MTP (hMTP) promoter activity is reported here to be suppressed by HNF-4alpha ligand antagonists (e.g., Medica analogs) or by PPARgamma ligand agonists (e.g., thiazolidinediones), thus accounting for their hypolipidemic activity in humans. Suppression of liver hMTP by Medica analogs or by thiazolidinediones was mediated by the TAAA sequence that serves as non-canonical TATA box of the hMTP core promoter. MTP suppression was evident in the specific context of the wild type hMTP core promoter, but not in the context of the mutated rodent-conforming hMTP core promoter governed by a canonical TATA box conjoined with its proximal (-50/-38)DR-1 element. hMTP suppression by Medica analogs or thiazolidinediones mediated by hMTP TAAA was independent of HNF-4alpha or PPARgamma. hMTP suppression by Medica analogs, but not by thiazolidinediones, was further complemented by inhibition of HNF-4alpha transcriptional activity transduced by the distal (-83/-70)DR-1 element of hMTP promoter. hMTP promoter activity was unaffected by PPARalpha activation. Furthermore, in contrast to hMTP, the promoter activity of the rodent-conforming hMTP was robustly activated by Wy-14,643-activated PPARalpha or by thiazolidinedione-activated PPARgamma. Transcriptional activation by PPARalpha or PPARgamma of the rodent-conforming, but not the wild type hMTP gene promoter, resulted from the species-specific context of the respective proximal DR-1 elements. Hence, suppression of hMTP transcription by hypolipidemic insulin sensitizers requires the specific context of hMTP core promoter. In light of the species-specific context of MTP core promoters, the rodent MTP promoter may not substitute for the human promoter when searching for hypolipidemic MTP suppressors.

Metabolic effects of pioglitazone in combination with insulin in patients with type 2 diabetes mellitus whose disease is not adequately controlled with insulin therapy: results of a six-month, randomized, double-blind, prospective, multicenter, parallel-group study

BACKGROUND

Type 2 diabetes mellitus (DM) is a progressive disease. Initial therapy begins with dietary and lifestyle modifications. However, as the disease progresses, glycemic control becomes more difficult to attain, often requiring > or =1 oral antihyperglycemic medication (OAM), and finally the addition of insulin to the OAMs and insulin monotherapy.

OBJECTIVE

This study was designed to determine the effect of pioglitazone 30 mg plus insulin (PIO + INS) versus placebo plus insulin (PLB + INS) on glycemic control, the serum lipid profile, and selected cardiovascular risk factors in patients with type 2 DM whose disease was inadequately controlled with insulin therapy alone despite efforts to intensify such treatment.

METHODS

This was a 6-month, randomized, double-blind, prospective, multicenter, placebo-controlled, parallel-group study. Patients with type 2 DM and a glycosylated hemoglobin (HbA(1c)) value > or =7.5% who were using insulin (with or without OAMs) entered a 3-month insulin intensification phase to achieve blood glucose targets with insulin monotherapy. After insulin intensification, those patients with HbA(1c) values > or =7.0% were randomized to PIO + INS or PLB + INS. The primary end point was the change in HbA(1c) from baseline. Cardiovascular risk markers (highly sensitive C-reactive protein [hs CRP] and plasminogen activator inhibitor-1 [PAI-1]) were measured at baseline and end point.

RESULTS

Of the 289 patients randomized to treatment (mean [SD] age, 58.9 [7.1] years; 164 women, 125 men), 142 received PIO + INS and 147 received PLB + INS. A total of 263 patients completed the study. After 6 months, PIO + INS reduced mean HbA(1c) (-0.69%; P < 0.002) and mean fasting plasma glucose ([FPG] -1.45 mmol/L; P < 0.002) from baseline. PLB + INS produced no significant changes in HbA(1c) or FPG. The between-treatment differences for HbA(1c) (-0.55%; P < 0.002) and FPG (-1.80 mmol/L; P < 0.002) occurred despite a reduction of insulin dose in the PIO + INS group from baseline (-0.16 U/d . kg; P < 0.002). Significant between-group differences were observed for high-density lipoprotein cholesterol (0.13 mM; P < 0.002), triglycerides (ratio of geometric mean [PIO/PLB], 0.871; P < 0.01), atherogenic index of plasma (-0.11; P < 0.002), PAI-1 (-5.10 U/mL; P < 0.001), and hs CRP (-1.47 mg/L; P < 0.05). The rate of clinical and biochemical hypoglycemia (blood glucose <2.8 mmol/L) did not differ statistically between treatment groups, but reported incidences of subjective hypoglycemia occurred more often with PIO + INS than with PLB + INS (90 vs 75; P < 0.05). Edema was more common with PIO + INS than with PLB + INS (20 vs 5 instances, respectively), as was gain (mean [SEM]) in body weight (4.05 [4.03] vs 0.20 [2.92] kg, respectively).

CONCLUSION

Adding pioglitazone to insulin in these study patients with type 2 DM whose disease was inadequately controlled with insulin monotherapy further improved their glycemic control.

Acute myopathy in a type 2 diabetic patient on combination therapy with metformin, fenofibrate and rosiglitazone

AIMS/HYPOTHESIS

This report describes the case of a 75-year-old male type 2 diabetic Caucasian who was admitted to the clinical ward because of acute pain and cramps in both calf muscles.

MATERIALS AND METHODS

Neuromuscular function was assessed by electromyography and electroneurography of the right leg. An open biopsy was taken from the left vastus lateralis muscle for histological and histochemical analyses. Southern blotting was performed to detect defects in mitochondrial DNA and tRNA. Cytochrome P450 (CYP-P450) polymorphisms were analysed in blood cells.

RESULTS

Fifteen weeks before admission, the patient's lipid-lowering medication was switched from simvastatin to fenofibrate because of predominant hypertriglyceridaemia; this did not affect creatine kinase levels. Three weeks before admission, rosiglitazone was added to his existing metformin therapy because of worsening metabolic control. Upon admission, serum enzymes indicating myopathy were elevated (creatine kinase 6897 U/l, myoglobin 902 ng/ml) and kidney function was impaired (creatinine 0.116 mmol/l, blood urea nitrogen 2.3 mmol/l). Electrophysiology revealed myopathy and sensory polyneuropathy. Histology showed multiple damage of the myofibrillar architecture. There was no evidence of defects in mitochondrial DNA or tRNA. Furthermore, no functional limitations in CYP2C9, CYP2C19 and CYP2D6 were detected. Following withdrawal of the oral medication and intravenous hydration, clinical symptoms and laboratory parameters gradually decreased.

CONCLUSIONS/INTERPRETATION

Until more data from controlled trials are available, we recommend that combination therapy with fibrates and thiazolidinediones should be monitored frequently by measurements of serum creatine kinase and creatinine, specifically in patients with pre-existing nephropathy and polyneuropathy.

Therapeutic roles of peroxisome proliferator-activated receptor agonists

Peroxisome proliferator-activated receptors (PPARs) play key roles in the regulation of energy homeostasis and inflammation, and agonists of PPARalpha and -gamma are currently used therapeutically. Fibrates, first used in the 1970s for their lipid-modifying properties, were later shown to activate PPARalpha. These agents lower plasma triglycerides and VLDL particles and increase HDL cholesterol, effects that are associated with cardiovascular benefit. Thiazolidinediones, acting via PPARgamma, influence free fatty acid flux and thus reduce insulin resistance and blood glucose levels. PPARgamma agonists are therefore used to treat type 2 diabetes. PPARalpha and -gamma agonists also affect inflammation, vascular function, and vascular remodeling. As knowledge of the pleiotropic effects of these agents advances, further potential indications are being revealed, including roles in the management of cardiovascular disease (CVD) and the metabolic syndrome. Dual PPARalpha/gamma agonists (currently in development) look set to combine the properties of thiazolidinediones and fibrates, and they hold considerable promise for improving the management of type 2 diabetes and providing an effective therapeutic option for treating the multifactorial components of CVD and the metabolic syndrome. The functions of a third PPAR isoform, PPARdelta, and its potential as a therapeutic target are currently under investigation.

New therapeutic options for the metabolic syndrome: what's next?

The metabolic syndrome (MSX), characterized by obesity, insulin resistance, dyslipidemia and hypertension, increases the risk of cardiovascular morbidity and mortality. It has recently been hypothesized that MSX and type 2 diabetes are caused by triglyceride and long-chain fatty acid accumulation in liver, muscle, pancreatic islets and selected brain areas. This lipocentric approach is integrated with analysis of inflammation associated with end-organ damage, including the vascular wall. Genes and proteins contributing to insulin resistance, beta cell dysfunction and vascular wall damage have been identified. Transcription factors and coactivators, including peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator-1 are crucial in mediating insulin resistance and accelerating vascular wall inflammation, and represent promising therapeutic targets. New pharmacological strategies include dual PPARalpha/gamma agonists, drugs with pleiotropic effects or combination therapies.

A comparison of lipid and glycemic effects of pioglitazone and rosiglitazone in patients with type 2 diabetes and dyslipidemia

OBJECTIVE

Published reports suggest that pioglitazone and rosiglitazone have different effects on lipids in patients with type 2 diabetes. However, these previous studies were either retrospective chart reviews or clinical trials not rigorously controlled for concomitant glucose- and lipid-lowering therapies. This study examines the lipid and glycemic effects of pioglitazone and rosiglitazone.

RESEARCH DESIGN AND METHODS

We enrolled subjects with a diagnosis of type 2 diabetes (treated with diet alone or oral monotherapy) and dyslipidemia (not treated with any lipid-lowering agents). After a 4-week placebo washout period, subjects randomly assigned to the pioglitazone arm (n = 400) were treated with 30 mg once daily for 12 weeks followed by 45 mg once daily for an additional 12 weeks, whereas subjects randomly assigned to rosiglitazone (n = 402) were treated with 4 mg once daily followed by 4 mg twice daily for the same intervals.

RESULTS

Triglyceride levels were reduced by 51.9 +/- 7.8 mg/dl with pioglitazone, but were increased by 13.1 +/- 7.8 mg/dl with rosiglitazone (P < 0.001 between treatments). Additionally, the increase in HDL cholesterol was greater (5.2 +/- 0.5 vs. 2.4 +/- 0.5 mg/dl; P < 0.001) and the increase in LDL cholesterol was less (12.3 +/- 1.6 vs. 21.3 +/- 1.6 mg/dl; P < 0.001) for pioglitazone compared with rosiglitazone, respectively. LDL particle concentration was reduced with pioglitazone and increased with rosiglitazone (P < 0.001). LDL particle size increased more with pioglitazone (P = 0.005).

CONCLUSIONS

Pioglitazone and rosiglitazone have significantly different effects on plasma lipids independent of glycemic control or concomitant lipid-lowering or other antihyperglycemic therapy. Pioglitazone compared with rosiglitazone is associated with significant improvements in triglycerides, HDL cholesterol, LDL particle concentration, and LDL particle size.

Attenuation of accumulation of neointimal lipid by pioglitazone in mice genetically deficient in insulin receptor substrate-2 and apolipoprotein E

Rupture of vulnerable atherosclerotic plaques that are characterized by extensive neointimal accumulation of lipid is a cause of acute coronary syndromes. To identify whether insulin resistance alters atherogenesis, we characterized the composition of atherosclerotic lesions in the proximal aortas in mice deficient in apolipoprotein E (ApoE(-/-)) and in ApoE(-/-) mice in which insulin resistance was intensified by a concomitant heterozygous deficiency in insulin receptor substrate type 2 (IRS2(+/-) ApoE(-/-) mice). In addition, we characterized the effect of an insulin sensitizer, pioglitazone, on the atherogenesis in IRS2(+/-) ApoE(-/-) mice. The extent of the aortic intima occupied by lesion was increased in the IRS2(+/-) ApoE(-/-) compared with ApoE(-/-) mice (79 +/- 3% compared with 68 +/- 8%, p<0.05). Treatment with pioglitazone decreased the neointimal content of lipid in 20-week-old mice from 50 +/- 6% to 30 +/- 7%, p=0.005 and decreased the cellularity reflected by the multisection cross-sectional areas of lesions comprising cells in atheroma from 24 +/- 1% to 19 +/- 3%, p=0.018. Accordingly, genetically induced intensification of insulin resistance increases atheroma formation. Furthermore, attenuation of insulin resistance by treatment with pioglitazone decreases accumulation of lipid in the neointima.

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: comparison of long-term effects on glycemic control and cardiovascular risk factors

OBJECTIVE

To compare the long-term effects on HbA(1c), lipid parameters, body weight, and hepatotoxicity after switching type 2 diabetes patients from troglitazone to either pioglitazone or rosiglitazone.

METHODS

Of 125 study candidates from a previous prospective study, 100 patients (51 pioglitazone, 49 rosiglitazone) met criteria for comparing HbA(1c), lipids, body weight, and incidence of hepatotoxicity over 2 successive observation periods (3.1 and 12.6 months).

RESULTS

Mean absolute HbA(1c) decreased significantly, 0.53 and 0.27% in the pioglitazone and rosiglitazone groups, respectively, at the 12.6-month observation. Mean triglyceride (TG) decreased in the pioglitazone group at each interval with a cumulative decrease of 26.4% from baseline. In contrast, TG increased in the rosiglitazone patients by 43.3% at 3.1 months and then decreased (but remained above baseline) at 12.6 months. Mean high density lipoprotein (HDL) increased 22.1% with pioglitazone and 13.3% with rosiglitazone. In patients who had a baseline HDL < 35 mg/dL (0.91 mmol/L), pioglitazone treated patients experienced a significant increase at each interval resulting in a 52.6% increase in HDL compared to a 26.9% increase for rosiglitazone patients. Patients in both treatment groups had similar weight increases at each interval and no hepatotoxicity was noted.

CONCLUSION

With pioglitazone or rosiglitazone, changes in glycemic control, lipid effects, and body weight appear to continue over time. Pioglitazone treatment resulted in decreased triglyceride levels, while rosiglitazone was associated with an increase in triglyceride levels. HDL increased in both treatment groups, but in patients with a baseline HDL < 35 mg/dL (0.91 mmol/L), pioglitazone improved the HDL to a greater extent than rosiglitazone.