Lipid lowering explains the insulin sensitivity enhancing effects of a thiazolidinedione, 5-(4-(2-(2-phenyl-4-oxazolyl)ethoxy)benzyl)-2,4 thiazolidinedione

Rethinking pioglitazone as a cardioprotective agent: a new perspective on an overlooked drug

Since 1985, the thiazolidinedione pioglitazone has been widely used as an insulin sensitizer drug for type 2 diabetes mellitus (T2DM). Although fluid retention was early recognized as a safety concern, data from clinical trials have not provided conclusive evidence for a benefit or a harm on cardiac function, leaving the question unanswered. We reviewed the available evidence encompassing both in vitro and in vivo studies in tissues, isolated organs, animals and humans, including the evidence generated by major clinical trials. Despite the increased risk of hospitalization for heart failure due to fluid retention, pioglitazone is consistently associated with reduced risk of myocardial infarction and ischemic stroke both in primary and secondary prevention, without any proven direct harm on the myocardium. Moreover, it reduces atherosclerosis progression, in-stent restenosis after coronary stent implantation, progression rate from persistent to permanent atrial fibrillation, and reablation rate in diabetic patients with paroxysmal atrial fibrillation after catheter ablation. In fact, human and animal studies consistently report direct beneficial effects on cardiomyocytes electrophysiology, energetic metabolism, ischemia–reperfusion injury, cardiac remodeling, neurohormonal activation, pulmonary circulation and biventricular systo-diastolic functions. The mechanisms involved may rely either on anti-remodeling properties (endothelium protective, inflammation-modulating, anti-proliferative and anti-fibrotic properties) and/or on metabolic (adipose tissue metabolism, increased HDL cholesterol) and neurohormonal (renin–angiotensin–aldosterone system, sympathetic nervous system, and adiponectin) modulation of the cardiovascular system. With appropriate prescription and titration, pioglitazone remains a useful tool in the arsenal of the clinical diabetologist.

Association of thiazolidinedione with a lower risk of Parkinson's disease in a population with newly-diagnosed diabetes mellitus

OBJECTIVES

We investigated the association of thiazolidinedione and its dose effect with the risk of Parkinson's disease (PD) in patients with diabetes mellitus (DM).

METHODS

This study enrolled 38,521 patients with newly-diagnosed DM, between 2001 and 2013, and compared them to the matched subjects without DM. The hazard ratios (HRs) for PD were compared between the thiazolidinedione-treated and non-thiazolidinedione-treated groups of the study cohort, and between subgroups who received different cumulative dosages of thiazolidinedione.

RESULTS

We observed that 544 (1.4%) patients developed PD during the follow-up median duration of 6.2 years in patients with newly-diagnosed DM or had a higher risk for PD than patients without DM (HR = 1.150). In the study cohort, the risk of PD was significantly lower in the thiazolidinedione-treated group (HR = 0.399) compared to the non-thiazolidinedione-treated group. Thiazolidinedione reduced the risk of PD in a dose-dependent manner, with HRs ranging from 0.613 to 0.081 with defined daily doses of 0-90 to >720, respectively.

CONCLUSIONS

Thiazolidinedione use was associated with a significantly reduced risk of PD in patients with newly-diagnosed DM. Further studies to elucidate the common mechanism of PD and DM may provide novel therapies for these two diseases. Key messages Newly-diagnosed diabetes mellitus slightly increases the risk for Parkinson's disease. Thiazolidinedione is associated with a lower risk of Parkinson's disease in a dose-dependent manner in patients with newly-diagnosed diabetes mellitus.

Doxorubicin treatment inhibits PPARγ and may induce lipotoxicity by mimicking a type 2 diabetes-like condition in rodent models

Doxorubicin-treated animals show elevated serum triglyceride and blood glucose levels. Adipocytes play an important role in buffering blood glucose and lipids. A raise in serum lipid level triggers adipogenesis in order to increase the lipid absorption capacity of adipose tissue. Doxorubicin inhibits adipogenesis through the down-regulation of PPARγ, a crucial component of the lipid metabolic pathway which controls the expression of glucose and fatty acid transporters. Doxorubicin-mediated down-regulation of PPARγ inhibits blood glucose and lipid clearance thereby causing hyperglycemia and hyperlipidemia resulting in lipotoxicity, glucotoxicity, inflammation and insulin resistance. Therefore we hypothesize that doxorubicin treatment could mimic a type 2 diabetic condition.

The novel hypoglycemic agent YM440 improves hepatic insulin resistance in obese Zucker fatty rats

The novel hypoglycemic agent YM440 ((Z)-1,4-bis{4-[(3,5-dioxo-1,2,4-oxadiazolidin-2-yl)methyl] phenoxy}but-2-ene) is a ligand of the peroxisome proliferator-activated receptor (PPAR) gamma. YM440 has unique pharmacological profiles both in vitro and in vivo, but, it is not clear whether the compound has a significant effect on hepatic or peripheral insulin response throughout the body. The aim of this study is to examine the effects of YM440 on hepatic and peripheral insulin resistance in Zucker fatty (ZF) rats using the euglycemic-hyperinsulinaemic clamp technique. Treatment of ZF rats with YM440 (300 mg/kg per day) for 2 weeks significantly decreased plasma concentrations of glucose and insulin without inducing obesity. YM440 caused a 2-fold increase in the glucose infusion rate during euglycemic clamping compared with the vehicle control. YM440 also decreased the percent change in hepatic glucose production rate caused by intravenous insulin infusion in ZF rats. YM440 had no significant effect on the glucose disposal rate. These results indicate that YM440 ameliorates hepatic, but not peripheral insulin resistance in ZF rats. These findings strongly suggest that the main target organ of YM440 is the liver, unlike other PPARgamma agonist.

Rosiglitazone improves myocardial glucose uptake in patients with type 2 diabetes and coronary artery disease: a 16-week randomized, double-blind, placebo-controlled study

Rosiglitazone therapy improves insulin sensitivity and glucose uptake in patients with uncomplicated type 2 diabetes. In coronary artery disease (CAD), glucose is an important source of energy and preserved myocardial glucose uptake is essential for the viability of jeopardized myocardium. The aim was to test whether rosiglitazone changes myocardial metabolism in type 2 diabetic patients with CAD. We studied 54 patients (38 men and 16 women) with type 2 diabetes (HbA(1c) 7.2 + 0.9%) and CAD. Myocardial glucose uptake was measured with [(18)F]fluoro-2-deoxy-d-glucose positron emission tomography in ischemic (evaluated by single-photon emission tomography and coronary angiography) and nonischemic regions during euglycemic-hyperinsulinemic clamp before and after a 16-week intervention period with rosiglitazone (n = 27) or placebo (n = 27). Rosiglitazone significantly improved glycemic control (P < 0.0001) and whole-body insulin sensitivity (P < 0.0001). Rosiglitazone increased myocardial glucose uptake from 20.6 +/- 11.8 to 25.5 +/- 12.4 micromol . 100 g(-1) . min(-1) (P = 0.038 vs. baseline, P = 0.023 vs. placebo) in ischemic regions and from 21.7 +/- 12.1 to 28.0 +/- 12.7 micromol . 100 g(-1) . min(-1) (P = 0.014 vs. baseline, P = 0.003 vs. placebo) in nonischemic regions. The increase in myocardial glucose uptake was partly explained by the suppression of free fatty acid levels during clamp. Rosiglitazone therapy significantly increased insulin sensitivity and improved myocardial glucose uptake in type 2 diabetic patients with CAD. These results suggest that rosiglitazone therapy may facilitate myocardial glucose storage and utilization in these patients.

Enhancement of insulin-stimulated myocardial glucose uptake in patients with Type 2 diabetes treated with rosiglitazone

AIMS

Peroxisome proliferator-activated receptor gamma (PPARgamma) activators have recently been identified as regulators of cellular proliferation, inflammatory responses and lipid and glucose metabolism. These agents prevent coronary arteriosclerosis and improve left ventricular remodelling and function in heart failure after myocardial infarction. Improvement in myocardial metabolic state may be one of the mechanisms behind these findings. The aim of this study was to investigate the effects of rosiglitazone on myocardial glucose uptake in patients with Type 2 diabetes. Placebo and metformin were used as control treatments.

METHODS

Forty-four patients were randomized to treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.) or placebo in a 26-week double-blinded trial. Myocardial glucose uptake was measured using [(18)F]-2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) and positron emission tomography (PET) during euglycaemic hyperinsulinaemia before and after the treatment.

RESULTS

Rosiglitazone increased insulin-stimulated myocardial glucose uptake by 38% (from 38.7 +/- 3.4 to 53.3 +/- 3.6 micromol 100 g(-1) min(-1), P = 0.004) and whole body glucose uptake by 36% (P = 0.01), while metformin treatment had no significant effect on myocardial (40.5 +/- 3.5 vs. 36.6 +/- 5.2, NS) or whole body glucose uptake. Myocardial work as determined by the rate-pressure-product was similar between the groups. Neither treatment had any significant effect on fasting serum free fatty acids (FFA) but the FFA levels during hyperinsulinaemia were more suppressed in the rosiglitazone group (-47%, P = 0.02). Myocardial glucose uptake correlated inversely to FFA concentrations both before (r =-0.54, P = 0.002) and after (r = -0.43, P = 0.01) the treatment period in the pooled data. Furthermore, the increase in myocardial glucose uptake correlated inversely with interleukin-6 (IL-6) concentrations (r = -0.58, P = 0.03).

CONCLUSIONS

In addition to the improvement in whole body insulin sensitivity, rosiglitazone treatment enhances insulin stimulated myocardial glucose uptake in patients with Type 2 diabetes, most probably due to its suppression of the serum FFAs.

PPARgamma agonists in the treatment of type II diabetes: is increased fatness commensurate with long-term efficacy?

The nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the PPAR family. The endogenous activators of all members of the PPAR family are a variety of fatty acids, which suggests that the PPARs are highly involved in lipid metabolism. In the present paper, the current understanding of the involvement of PPARgamma in adipocyte proliferation and adipose tissue formation is extensively reviewed, and it is stressed that PPARgamma seems to be a major regulator in the differentiation of adipocytes. Thiazoledinediones (TZDs) are a group of PPARgamma-agonists used in the treatment of type 2 diabetes (T2D) since 1997. They are characterized by their ability to decrease insulin resistance, and have been suggested to slow down the progression of insulin resistance. Treatment with TZD requires several weeks of treatment to decrease plasma glucose levels, but in addition they markedly decrease plasma triglycerides and free fatty acids. A major drawback of treatment with TZD is body fat gain, but some evidence suggests that the fat is redistributed in a favourable direction, that is, from visceral to subcutaneous depots. However, the effect of long-term treatment on weight gain following TZD treatment is unknown, and it may be questioned whether the use of these 'adipogenic compounds' is appropriate, considering that excess body fat is almost a prerequisite for the development of type 2 diabetes.

Chlorogenic acid modifies plasma and liver concentrations of: cholesterol, triacylglycerol, and minerals in (fa/fa) Zucker rats

Chlorogenic acid, a phenolic compound found ubiquitously in plants, is an in vitro antioxidant and metal chelator. Some derivatives of chlorogenic acid are hypoglycemic agents and may affect lipid metabolism. Concentrations of cholesterol and triacylglycerols are of interest due to their association with diseases such as non-insulin-dependent-diabetes- mellitus and obese insulin resistance. As little is known about the effects of chlorogenic acid in vivo, studies using obese, hyperlipidemic, and insulin resistant (fa/fa) Zucker rats were conducted to test the effect of chlorogenic acid on fasting plasma glucose, plasma and liver triacylglycerols and cholesterol concentrations. Aditionally, the effects of chlorogenic acid on selected mineral concentrations in plasma, spleen, and liver were determined. Rats were implanted with jugular vein catheters. Chlorogenic acid was infused (5 mg/Kg body weight/day) for 3 weeks via intravenous infusion. Chlorogenic acid did not promote sustained hypoglycemia and significantly lowered the postprandial peak response to a glucose challenge when compared to the same group of rats before Chlorogenic acid treatment. In Chlorogenic acid-treated rats, fasting plasma cholesterol and triacylglycerols concentrations significantly decreased by 44% and 58% respectively, as did in liver triacylglycerols concentrations (24%). We did not find differences (p > 0.05) in adipose triacylglycerols concentration. Significant differences (p < 0.05) in the plasma, liver, and spleen concentration of selected minerals were found in chlorogenic acid-treated rats. In vivo, chlorogenic acid was found to improve glucose tolerance, decreased some plasma and liver lipids, and improve mineral pool distribution under the conditions of this study.

Rosiglitazone but not metformin enhances insulin- and exercise-stimulated skeletal muscle glucose uptake in patients with newly diagnosed type 2 diabetes

Rosiglitazone, a thiazolidinedione, enhances peripheral insulin sensitivity in patients with type 2 diabetes. Because the synergic action of insulin and exercise has been shown to be decreased in insulin resistance, the aim of this study was to compare the effects of rosiglitazone and metformin on muscle insulin responsiveness at rest and during exercise in patients with type 2 diabetes. Therefore, 45 patients with newly diagnosed or diet-treated type 2 diabetes were randomized for treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.), or placebo in a 26-week double-blind trial. Skeletal muscle glucose uptake was measured using fluorine-18-labeled fluoro-deoxy-glucose and positron emission tomography (PET) during euglycemic-hyperinsulinemic clamp and one-legged exercise before and after the treatment period. Rosiglitazone (P < 0.05) and metformin (P < 0.0001) treatment lowered the mean glycosylated hemoglobin. The skeletal muscle glucose uptake was increased by 38% (P < 0.01) and whole-body glucose uptake by 44% in the rosiglitazone group. Furthermore, the exercise-induced increment during insulin stimulation was enhanced by 99% (P < 0.0001). No changes were observed in skeletal muscle or whole-body insulin sensitivity in the metformin group. In conclusion, rosiglitazone but not metformin 1) improves insulin responsiveness in resting skeletal muscle and 2) doubles the insulin-stimulated glucose uptake rate during physical exercise in patients with type 2 diabetes. Our results suggest that rosiglitazone improves synergic action of insulin and exercise.

New pharmacologic agents for diabetes

New agents are being developed to address the underlying endocrinopathies and metabolic disturbances of type 2 diabetes. Stimulants of the nuclear peroxisome proliferator-activated receptor gamma (PPAR gamma) are being identified to selectively improve insulin actions, and dual agonists of PPAR gamma and PPAR alpha are being evaluated for enhanced control of hyperglycemia and dyslipidemia. Novel activators of insulin receptor phosphorylation and inhibitors of receptor dephosphorylation are offering encouraging leads for new agents. Analogues of glucagon-like peptide-1 that increase glucose-induced insulin secretion may additionally increase beta-cell neogenesis from progenitor duct cells. The amylin analogue pramlintide, which suppresses glucagon secretion and reduces weight, is advancing in clinical trial. Direct stimulants of glucose utilization and partial inhibitors of gluconeogenesis are providing useful new drug templates. Thus, new pharmacologic approaches are emerging to treat the multiple lesions of type 2 diabetes.