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PubMed2004

Structural and functional analysis of pancreatic islets preserved by pioglitazone in db/db mice.

To evaluate preventive effects of pioglitazone on pancreatic beta-cell damage in C57BL/KsJ db/db mice, an obese diabetic animal model, the pancreatic islets were compared morphologically between pioglitazone-treated (100 mg/kg daily po) and untreated db/db mice (n = 7 for each) after a 12-wk intervention (6-18 wk of age). The fasting blood glucose level was significantly improved by the treatment with pioglitazone (260 +/- 12 vs. 554 +/- 62 mg/dl, P < 0.05). The islet mass in the pancreas was significantly greater in pioglitazone-treated mice than in untreated mice (10.2 +/- 1.1 vs. 4.6 +/- 0.2 mg, P < 0.01). Subsequently, biochemical and physiological analyses of the beta-cell function were employed using pioglitazone-treated and untreated db/db mice (n = 6 for each) and pioglitazone-treated and untreated db/+ mice (n = 6 for each). After 2 wk of treatment (10-12 wk of age), the plasma levels of triglyceride and free fatty acid were significantly decreased, whereas the plasma adiponectin level increased significantly compared with the untreated group (65.2 +/- 18.0 vs. 18.3 +/- 1.3 microg/ml, P < 0.05). Pioglitazone significantly reduced the triglyceride content in the islets (43.3 +/- 3.6 vs. 65.6 +/- 7.6 ng/islet, P < 0.05) with improved glucose-stimulated insulin secretion. Pioglitazone showed no significant effects on the biochemical and physiological parameters in db/+ mice. The present study first demonstrated that pioglitazone prevents beta-cell damage in an early stage of the disease progression in db/db mice morphologically and physiologically. Our results suggest that pioglitazone improves glucolipotoxicity by increasing insulin sensitivity and reducing fat accumulation in the pancreatic islets.

Adiponectin↗
PubMed2006

Pioglitazone prevents acute and chronic cardiac allograft rejection.

BACKGROUND: Peroxisome proliferator-activated receptor-gamma plays an important role in regulating inflammation. Although cardiac transplantation is an established therapy for patients with end-stage heart disease, allograft rejection is a major concern for long-term survival. We investigated the role of pioglitazone in acute and chronic rejection in a murine cardiac transplantation model. METHODS AND RESULTS: We performed heterotopic murine cardiac transplantation in total allomismatch or major histocompatibility complex class II-mismatched combinations. Recipient mice were given standard chow or chow containing pioglitazone (3 mg.kg(-1).d(-1)) beginning 1 day before cardiac transplantation. In acute rejection, animals given pioglitazone showed significantly longer cardiac allograft survival than control mice (mean survival time, 34.6+/-7.8 versus 8.4+/-0.4 days; P<0.003). Treatment with pioglitazone significantly suppressed graft expression of interferon-gamma and monocyte chemoattractant protein-1. In chronic rejection, neointimal hyperplasia was significantly lower in allografts from mice treated with pioglitazone (luminal occlusion, 25.1+/-8.8%) than in those from control mice (65.8+/-7.3%, P<0.001). Pioglitazone-treated allografts showed significantly reduced expression of interferon-gamma, interleukin-10, and monocyte chemoattractant protein-1. We performed mixed lymphocyte reactions and in vitro proliferation assays of smooth muscle cells. Addition of pioglitazone to mixed lymphocyte reactions inhibited proliferation of T cells. Smooth muscle cells showed significant proliferation when cocultured with activated splenocytes. This proliferation was significantly inhibited by the addition of pioglitazone (1 micromol/L). CONCLUSIONS: Pioglitazone prolongs allograft survival and attenuates neointimal hyperplasia through the suppression of proliferation of smooth muscle cells. Pioglitazone may be a novel means to prevent acute and chronic allograft rejection.

Animals↗
PubMed2002

Effect of pioglitazone on abdominal fat distribution and insulin sensitivity in type 2 diabetic patients.

We examined the effect of pioglitazone on abdominal fat distribution to elucidate the mechanisms via which pioglitazone improves insulin resistance in patients with type 2 diabetes mellitus. Thirteen type 2 diabetic patients (nine men and four women; age, 52 +/- 3 yr; body mass index, 29.0 +/- 1.1 kg/m(2)), who were being treated with a stable dose of sulfonylurea (n = 7) or with diet alone (n = 6), received pioglitazone (45 mg/d) for 16 wk. Before and after pioglitazone treatment, subjects underwent a 75-g oral glucose tolerance test (OGTT) and two-step euglycemic insulin clamp (insulin infusion rates, 40 and 160 mU/m(2).min) with [(3)H]glucose. Abdominal fat distribution was evaluated using magnetic resonance imaging at L4-5. After 16 wk of pioglitazone treatment, fasting plasma glucose (179 +/- 10 to 140 +/- 10 mg/dl; P < 0.01), mean plasma glucose during OGTT (295 +/- 13 to 233 +/- 14 mg/dl; P < 0.01), and hemoglobin A(1c) (8.6 +/- 0.4% to 7.2 +/- 0.5%; P < 0.01) decreased without a change in fasting or post-OGTT insulin levels. Fasting plasma FFA (674 +/- 38 to 569 +/- 31 microEq/liter; P < 0.05) and mean plasma FFA (539 +/- 20 to 396 +/- 29 microEq/liter; P < 0.01) during OGTT decreased after pioglitazone. In the postabsorptive state, hepatic insulin resistance [basal endogenous glucose production (EGP) x basal plasma insulin concentration] decreased from 41 +/- 7 to 25 +/- 3 mg/kg fat-free mass (FFM).min x microU/ml; P < 0.05) and suppression of EGP during the first insulin clamp step (1.1 +/- 0.1 to 0.6 +/- 0.2 mg/kg FFM.min; P < 0.05) improved after pioglitazone treatment. The total body glucose MCR during the first and second insulin clamp steps increased after pioglitazone treatment [first MCR, 3.5 +/- 0.5 to 4.4 +/- 0.4 ml/kg FFM.min (P < 0.05); second MCR, 8.7 +/- 1.0 to 11.3 +/- 1.1 ml/kg FFM(.)min (P < 0.01)]. The improvement in hepatic and peripheral tissue insulin sensitivity occurred despite increases in body weight (82 +/- 4 to 85 +/- 4 kg; P < 0.05) and fat mass (27 +/- 2 to 30 +/- 3 kg; P < 0.05). After pioglitazone treatment, sc fat area at L4-5 (301 +/- 44 to 342 +/- 44 cm(2); P < 0.01) increased, whereas visceral fat area at L4-5 (144 +/- 13 to 131 +/- 16 cm(2); P < 0.05) and the ratio of visceral to sc fat (0.59 +/- 0.08 to 0.44 +/- 0.06; P < 0.01) decreased. In the postabsorptive state hepatic insulin resistance (basal EGP x basal immunoreactive insulin) correlated positively with visceral fat area (r = 0.55; P < 0.01). The glucose MCRs during the first (r = -0.45; P < 0.05) and second (r = -0.44; P < 0.05) insulin clamp steps were negatively correlated with the visceral fat area. These results demonstrate that a shift of fat distribution from visceral to sc adipose depots after pioglitazone treatment is associated with improvements in hepatic and peripheral tissue sensitivity to insulin.

Abdomen↗
PubMed2001

[Insulin resistance-reducing effect of a new thiazolidinedione derivative, pioglitazone].

Takeda has a relatively long history in diabetes research. Pioglitazone, a thiazolidinedione derivative, was developed from our basic research on diabetic animal models in the 1960s and our chemical research on lipid-lowering agents in the 1970s. Pioglitazone reduced plasma glucose, triglyceride and insulin levels in obese-diabetic animal models with insulin resistance in liver and/or peripheral tissues, but did not decrease normoglycemia in normal rats and aged dogs or hyperglycemia in insulin-deficient streptozocin-induced diabetic rats and impaired-insulin-secretory Goto-Kakizaki rats. The ED50 of plasma glucose-lowering action was 0.5 mg/kg/day in Wistar fatty rats. These findings clearly indicate that pioglitazone works in animals with insulin resistance and has a quite different mechanism from sulfonylureas and insulin itself. Although the exact mechanism of pioglitazone still remains obscure, pioglitazone normalized abnormalities in the cellular signal transduction of insulin. These effects seem to be due to the inhibitory action of pioglitazone on TNF-alpha production, which is one of the factors responsible for insulin resistance. Pioglitazone is a potent agonist for the peroxisome proliferator-activated receptor, (PPAR)-gamma, that is related to differentiation of adipocytes, and the relationship between TNF-alpha production and PPAR-gamma has been reported. Therefore, the agonistic activity of pioglitazone on PPAR-gamma may be involved in the mechanism of reduction of insulin resistance. The clinical data clearly demonstrated that pioglitazone, at clinical doses of 15-45 mg/day, decreased plasma glucose, HbA1c and triglyceride, increased plasma HDL-cholesterol, but did not alter total cholesterol and LDL-cholesterol levels. These findings suggest that pioglitazone has a benefit for prevention of cardiovascular diseases in addition to diabetic complications.

Animals↗
PubMed1997

The effect of pioglitazone on hepatic glucose uptake measured with indirect and direct methods in alloxan-induced diabetic dogs.

Pioglitazone, a thiazolidinedione derivative, ameliorates hyperglycemia by augmenting peripheral glucose disposal and suppressing hepatic glucose production in diabetic animals. However, the effect of this agent on hepatic glucose uptake has not been explored. To determine this, experiments were conducted in alloxan-induced diabetic dogs with (pioglitazone group, n = 7) or without (control group, n = 5) a 10-day oral treatment with pioglitazone (1 mg x kg(-1) x day(-1)). A euglycemic-hyperinsulinemic (insulin infusion rate 25.2 pmol x kg(-1) x min(-1)) clamp was maintained by adjusting the peripheral glucose infusion rate (GIR). After a 60-min basal period (period I), portal glucose infusion (Pinf, 33.3 micromol x kg(-1) x min(-1)) was administered for 120 min (period II). This was followed by a 60-min recovery period (period III). Arterial insulin levels were kept stable in the supraphysiological range throughout the experiment (1,623 +/- 52, pioglitazone group; 1,712 +/- 52 pmol/l, C group). There was no significant difference in whole-body glucose utilization determined by [3-3H]glucose between the pioglitazone and C groups in period I (68.4 +/- 2.8 vs. 70.1 +/- 2.8 micromol x kg(-1) x min(-1), respectively) and period III (81.2 +/- 5.0 vs. 74.5 +/- 3.3 micromol x kg(-1) x min(-1), respectively). Net hepatic glucose uptake (NHGU) determined by arteriovenous difference method was approximately zero in the basal period (-0.7 +/- 1.1, pioglitazone group; 0.1 +/- 1.2 micromol x kg(-1) x min(-1), C group). In period II, hepatic glucose uptake, determined by the changes in GIR, was significantly higher in the pioglitazone group (6.5 +/- 0.6 micromol x kg(-1) x min(-1)) than in the C group (-0.4 +/- 0.6 micromol x kg(-1) x min(-1), P < 0.001). This observation was also confirmed by NHGU during portal glucose infusion (6.9 +/- 1.4 vs. 2.1 +/- 1.8 micromol x kg(-1) x min(-1), pioglitazone vs. C, respectively; P < 0.025). We conclude that pioglitazone treatment enhances hepatic glucose uptake during portal glucose loading in alloxan-induced diabetic dogs. However, in hyperinsulinemic conditions, pioglitazone does not enhance the already high peripheral glucose uptake.

Animals↗
PubMed2002

Dose-response effect of pioglitazone on insulin sensitivity and insulin secretion in type 2 diabetes.

OBJECTIVE: To investigate the dose-response effects of pioglitazone on glycemic control, insulin sensitivity, and insulin secretion in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 58 diet-treated patients with type 2 diabetes (aged 54 +/- 1 years; 34 men and 24 women; BMI 31.5 +/- 0.6 kg/m(2)) were randomly assigned to receive placebo (n=11) or 7.5 mg (n=13), 15 mg (n=12), 30 mg (n=11), or 45 mg (n=11) of pioglitazone per day for 26 weeks. Before and after 26 weeks, subjects underwent a 75-g oral glucose tolerance test (OGTT). RESULTS: Patients treated with 7.5 or 15 mg/day of pioglitazone had no change in fasting plasma glucose (FPG) and fasting plasma insulin (FPI) concentrations or in plasma glucose (PG) and insulin concentrations during the OGTT. Patients treated with 30 and 45 mg/day of pioglitazone, respectively, had significant decreases from placebo in HbA1c (delta=-2.0 and -2.9%), FPG (delta=-66 and -97 mg/dl), and mean PG during OGTT (delta=-84 and -107 mg/dl). Fasting plasma insulin decreased significantly in the 45-mg/day pioglitazone group, but the mean plasma insulin during the OGTT did not change. The insulinogenic index (delta area under the curve [AUC] insulin/deltaAUC glucose) during the OGTT increased significantly in the 30- and 45-mg/day pioglitazone groups (0.13 +/- 0.03 to 0.27 +/- 0.05, P < 0.05). From the OGTT, we previously have derived a composite whole-body insulin sensitivity index (ISI) that correlates well with that measured directly with the insulin clamp technique. Whole-body ISI [ISI=10,000/(square-root (FPG x FPI) x (PG x PI)) where PG and PI equal mean plasma glucose and insulin concentrations during OGTT] increased significantly in patients treated with 30 mg (1.8 +/- 0.3 to 2.5 +/- 0.3, P < 0.05) or 45 mg (1.6 +/- 0.2 to 2.7 +/- 0.6, P < 0.05) per day of pioglitazone. In the basal state, the hepatic ISI [k/(FPG x FPI)[k/(FPG x FPI)], which agrees closely with that measured directly with tritiated glucose, increased in patients treated with 30 mg (0.13 +/- 0.02 to 0.21 +/- 0.03, P < 0.05) and 45 mg (0.11 +/- 0.02 to 0.24 +/- 0.06, P < 0.05) per day of pioglitazone. Significant correlations between the dose of pioglitazone and the changes in HbA1c (r=-0.58), FPG (r=-0.47), mean PG during the OGTT (r=-0.46), insulinogenic index (r=0.34), hepatic ISI (r=0.44), and whole-body ISI (r=0.36) were observed. CONCLUSIONS: Pioglitazone improves glycemic control through the dose-dependent enhancement of beta-cell function and improved whole-body and hepatic insulin sensitivity.

Adult↗
PubMed2001

The impact of pioglitazone on glycemic control and atherogenic dyslipidemia in patients with type 2 diabetes mellitus.

BACKGROUND: To evaluate the glycemic control, lipid effects, and safety of pioglitazone in patients with type 2 diabetes mellitus. DESIGN AND METHODS: Patients (n = 197) with type 2 diabetes mellitus, a hemoglobin A1c (HbA1c) > or = 8.0%, fasting plasma glucose (FPG) > 7.7 mmol/l (140 mg/dl), and C-peptide > 0.331 nmol/l (1 ng/ml) were enrolled in this 23-week multi-center (27 sites), double-blind clinical trial and randomized to receive either a placebo or pioglitazone HCl 30 mg (pioglitazone), administered once daily, as monotherapy. Patients were required to discontinue all anti-diabetic medications 6 weeks before receiving study treatment. Efficacy parameters included HbA1c fasting plasma glucose (FPG), serum C-peptide, insulin, triglycerides (Tg), and cholesterol (total cholesterol [TC], high-density lipoprotein-cholesterol [HDL-C], low-density lipoprotein-cholesterol [LDL-C]). Adverse event rates, serum chemistry, and physical examinations were recorded. RESULTS: Compared with placebo, pioglitazone significantly (P= 0.0001) reduced HbA1c (-1.37% points), FPG (-3.19 mmol/l; -57.5 mg/dl), fasting C-peptide (-0.076+/-0.022 nmol/l), and fasting insulin (-11.88+/-4.70 pmol/l). Pioglitazone significantly (P < 0.001) decreased insulin resistance (HOMA-IR; -12.4+/-7.46%) and improved beta-cell function (Homeostasis Model Assessment (HOMA-BCF); +47.7+/-11.58%). Compared with placebo, fasting serum Tg concentrations decreased (-16.6%; P = 0.0178) and HDL-C concentrations increased (+12.6%; P= 0.0065) with pioglitazone as monotherapy. Total cholesterol and LDL-C changes were not different from placebo. The overall adverse event profile of pioglitazone was similar to that of placebo, with no evidence of drug-induced elevations of serum alanine transaminase (ALT) concentrations or hepatotoxicity. CONCLUSIONS: Pioglitazone improved insulin resistance and glycemic control, as well as Tg and HDL-C - which suggests that pioglitazone may reduce cardiovascular risk for patients with type 2 diabetes.

Adult↗
PubMed2006

Comparison of glycaemic control over 1 year with pioglitazone or gliclazide in patients with Type 2 diabetes.

AIMS: To compare long-term (1 year) efficacy and safety of pioglitazone and gliclazide in patients with Type 2 diabetes. METHODS: This was a double-blind, multicentre, comparative, parallel group trial in 283 patients with Type 2 diabetes, who were randomized to receive 1-year treatment with pioglitazone 30-45 mg/day or gliclazide 80-320 mg/day. Drug dose was titrated on the basis of self-monitored blood glucose (SMBG) measurements and HbA1c values. The 1-year changes in HbA1c, fasting blood glucose (FBG), insulin, HOMA-S (HOmeostatic Model Assessment) and SMBG were compared. In a subgroup of patients (n = 10), systemic glucose production and utilization were determined by a combination of isotopic (deuterated glucose) and clamp techniques. RESULTS: In both groups, there were similar decreases in HbA1c (pioglitazone: -0.79%; gliclazide: -0.79%) and FBG (pioglitazone: -1.0 mmol/l; gliclazide: -0.7 mmol/l), whereas the slope of the reduction of fasting blood glucose was different between groups (P = 0.004). Insulin levels as well as insulin resistance assessed using HOMA-S decreased significantly only after pioglitazone treatment (-11.94 pmol/l and -1.03, respectively, both P = 0.002 vs. baseline). A significantly greater reduction in systemic glucose production was observed in the pioglitazone group (-2.48 micromol/kg/min, P = 0.042) than in the gliclazide group (-1.02 micromol/kg/min). A few, mild adverse events occurred in both groups. CONCLUSIONS: A comparable decrease in HbA1c and FBG was observed with pioglitazone and gliclazide. However, with pioglitazone there was a continuous decrease in FBG over 1 year, whereas gliclazide failed to maintain a similar trend. This favourable effect of pioglitazone was due to its insulin-sensitizing effect and ability to decrease systemic glucose production.

Blood Glucose↗
PubMed1995

Pioglitazone treatment for 7 days failed to correct the defect in glucose transport and glucose transporter translocation in obese Zucker rat (fa/fa) skeletal muscle plasma membranes.

Insulin resistance in the obese (fa/fa) Zucker rat is associated with decreased insulin stimulated glucose transport in skeletal muscle, due primarily to a failure of insulin to stimulate GLUT4 translocation to the plasma membrane from an intracellular pool (1). The thiazolidinedione analog Pioglitazone (PIO) has been shown to improve glucose tolerance in this and other animal models of insulin resistance. The current study was designed to determine whether 7 days of Pioglitazone treatment (20 mg/kg/day by gavage) would improve glucose transport and/or glucose transporter translocation and intrinsic activity in plasma membranes prepared from hindlimb skeletal muscle of obese Zucker (fa/fa) rats. Basal plasma glucose and insulin concentrations in these animals were unchanged by Pioglitazone, while basal plasma triglyceride and nonesterified fatty acid concentrations (NEFA) were reduced by Pioglitazone treatment (501 +/- 88 vs 161 +/- 13 mg/dl, P < 0.0001) and (678 +/- 95 vs 467 +/- 75 microM, P < 0.05) respectively. Pioglitazone had no effect on basal or insulin stimulated glucose influx (Vmax or Km) into plasma membrane vesicles determined under equilibrium exchange conditions compared to controls. Plasma membrane glucose transporter number (R0) (measured by cytochalasin B binding) under basal or insulin stimulated conditions was unchange by Pioglitazone and R0 failed to increase following insulin stimulation in either group. Glucose transporter turnover number (Vmax/R0) increased 2-fold with insulin stimulation compared to basal in both control and Pioglitazone groups, similar to turnover numbers observed in normal rats. These data confirm that impaired glucose transporter translocation in muscle of the Zucker rat is a major factor contributing to its insulin resistance. We conclude that the improved glucose tolerance observed in fa/fa rats following Pioglitazone treatment is not due to an improvement in basal or insulin stimulated skeletal muscle plasma membrane glucose transport or glucose transporter translocation and that Pioglitazone treatment does not affect transporter intrinsic activity.

Animals↗
PubMed2006

Montelukast and zafirlukast do not affect the pharmacokinetics of the CYP2C8 substrate pioglitazone.

OBJECTIVE: Pioglitazone, a thiazolidinedione antidiabetic drug, is metabolised mainly by the cytochrome P450 (CYP) 2C8 enzyme. The leukotriene receptor antagonists montelukast and zafirlukast have potently inhibited CYP2C8 activity and the metabolism of pioglitazone in vitro. Our objective was to determine whether montelukast and zafirlukast increase the plasma concentrations of pioglitazone in humans. METHODS: In a randomised, double-blind crossover study with three phases and a washout period of 3 weeks, 12 healthy volunteers took either 10 mg montelukast once daily and placebo once daily, or 20 mg zafirlukast twice daily, or placebo twice daily, for 6 days. On day 3, they received a single oral dose of 15 mg pioglitazone. The plasma concentrations of pioglitazone and its metabolites M-IV, M-III, M-V and M-XI were measured for 96 h. RESULTS: The total area under the plasma concentration-time curve of pioglitazone during the montelukast and zafirlukast phases was 101% (range 71-143%) and 103% (range 78-146%), respectively, of that during the placebo phase. Also, the peak plasma concentration and elimination half-life of pioglitazone remained unaffected by montelukast and zafirlukast. There were no statistically significant differences in the pharmacokinetics of any of the metabolites of pioglitazone between the phases. CONCLUSIONS: Montelukast and zafirlukast do not increase the plasma concentrations of pioglitazone, indicating that their inhibitory effect on CYP2C8 is negligible in vivo, despite their strong inhibitory effect on CYP2C8 in vitro. The results highlight the importance of in vivo interaction studies and of the incorporation of relevant pharmacokinetic properties of drugs, including plasma protein binding data, to in vitro-in vivo interaction predictions.

Acetates↗
PubMed2006

Pioglitazone increases the numbers and improves the functional capacity of endothelial progenitor cells in patients with diabetes mellitus.

BACKGROUND: Endothelial progenitor cells (EPCs) are present in peripheral blood and can promote postnatal angiogenesis. The number and function of circulating EPCs are altered in diabetics. This study sought to investigate whether the number and functional properties of EPCs from patients with type II diabetes could be improved by pioglitazone. METHODS: For this randomized controlled study, we recruited 36 type II diabetic patients on metformin monotherapy with a glycohemoglobin A1c of <7%. Patients were separated into pioglitazone (n = 24) and control (n = 12) groups. The number and functional activity of EPCs, and the brachial artery flow-mediated dilation were determined before and after pioglitazone treatment (8 weeks) as an add-on therapy to metformin. In addition, direct effects of pioglitazone on EPCs were also investigated. RESULTS: After pioglitazone treatment, the numbers of circulating EPCs significantly increased (from 0.44% +/- 0.14% to 0.89% +/- 0.29%, P = .01). The migratory response and the adhesive capacity to fibronectin and collagen were improved by 158%, 34%, and 83%, respectively (all P < .05). Treatment with pioglitazone significantly lowered triglyceride, very low density lipoprotein cholesterol, and high-sensitivity C-reactive protein (hsCRP) levels, and increased high-density lipoprotein levels and insulin sensitivity (all P < .05). The increase in the number of circulating EPCs and the improvement in the migratory response after pioglitazone treatment were independently correlated to the decrease in hsCRP levels (P < or = .01). The increase in the adhesive capacity was independently correlated to the decreases in very low density lipoprotein cholesterol (P = .01) and hsCRP levels (P = .03). In addition, pioglitazone was also demonstrated to have direct effects on increasing EPC proliferation and colony formation, and attenuating EPC apoptosis (all P < .05, versus the controls). There were no significant changes in flow-mediated dilation in either group. CONCLUSIONS: Pioglitazone significantly increased the number and improved the functional properties of EPCs in type II diabetic patients through direct effects and/or anti-inflammation and lipid modification effects.

Aged↗
PubMed2006

Effects of 1 year of treatment with pioglitazone or rosiglitazone added to glimepiride on lipoprotein (a) and homocysteine concentrations in patients with type 2 diabetes mellitus and metabolic syndrome: a multicenter, randomized, double-blind, controlled clinical trial.

BACKGROUND: Although the metabolic effects of the thiazolidinediones have been well studied, there is a lack of comparative data on their effects on certain cardiovascular risk factors, such as elevated plasma levels of lipoprotein (a) (Lp[a]) and homocysteine (Hcy). OBJECTIVE: This study compared the effects of pioglitazone or rosiglitazone added to glimepiride on a range of lipid parameters, focusing on Lp(a) and Hcy, in patients with type 2 diabetes mellitus and the metabolic syndrome. METHODS: This was a multicenter, randomized, controlled, double-blind study in patients with type 2 diabetes and the metabolic syndrome (hypertension [>or=130/85 mm Hg]) and triglyceridemia (>or=150 mg/dL). In addition to glimepiride 4 mg/d, patients received pioglitazone 15 mg QD or rosiglitazone 4 mg QD for 1 year. The primary efficacy variables were change from baseline in body mass index (BMI), glycosylated hemoglobin (HbA(1c)), Lp(a), and Hey. Secondary efficacy measures were changes in fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) concentrations, fasting and postprandial insulin concentrations (FPI and PPI, respectively), the Homeostasis Model Assessment index, and the lipid profile (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglycerides). All these parameters were measured after a 12-hour fast every 3 months for 1 year. Tolerability was assessed based on reported adverse events and laboratory abnormalities at each study visit. RESULTS: Ninety-one white patients with type 2 diabetes and the metabolic syndrome were enrolled, and 87 completed the study (43 men, 44 women; mean [SD] age, 53 [6] years; mean weight, 68.4 [3.3] kg). Mean baseline values for BMI and HbA(1c) were 24.3 (0.8) kg/m(2) and 8.1 % (0.8 %), respectively. At the end of 1 year, both treatment groups had significant increases from baseline in BMI (4.9% glimepiride + pio glitazone, 6.2% glimepiride + rosiglitazone; P < 0.05). Glimepiride + pioglitazone was associated with the following percent improvements from baseline in measures of glycemic control: -17.1% in HbA(1c), -19.3% in FPG, -17.8% in PPG, -40.1% in FPI, and -22.6% in PPI (all, P < 0.01). The corresponding percent improvements from baseline with glimepiride + rosiglitazone were -16.3%, -19.9%, -15.0%, -44.8%, and -22.1% (all, P < 0.01). There were no significant differences between treatment groups in any of these parameters. The pioglitazone group had significant improvements from baseline in TC (-11.1%), LDL-C (-12.0%), HDL-C (15.0%), and triglycerides (-22.4%) [corrected] (all, P < 0.05), whereas the rosiglitazone group had significant increases in TC (14.9%), LDL-C (16.5%), and triglycerides (17.9%) (all, P < 0.05); the difference between pioglitazone and rosiglitazone was statistically significant (P < 0.05). The change from baseline in Lp(a) was significant in the pioglitazone group, both relative to baseline and compared with the rosiglitazone group (-19.7% vs 0.5%, respectively; P < 0.05 vs baseline and vs rosiglitazone). Changes from baseline in Hey were significant in both the pioglitazone and rosiglitazone groups (-20.2% and -25.0%, respectively; P < 0.05), with no significant difference between groups. Both treatments were well tolerated, and no patients had significant changes in transaminases. CONCLUSIONS: In these patients with type 2 diabetes and the metabolic syndrome, the combinations of glimepiride with pioglitazone and glimepiride with rosiglitazone produced significant improvements in measures of glycemic control, plasma lipids, and homocysteinemia. One year of treatment with the pioglitazone combination was associated with significantly reduced plasma Lp(a) levels compared with the rosiglitazone combination.

Blood Glucose↗
PubMed2006

Pioglitazone limits cyclosporine nephrotoxicity in rats.

Chronic cyclosporine (CsA) nephrotoxicity is a relevant factor in the pathogenesis of chronic allograft nephropathy. Pioglitazone is an agonist of PPARgamma, capable of reducing chronic inflammation. We investigated the capacity of pioglitazone in preventing renal dysfunction. Adult male Wistar rats were assigned to: Vehicle (olive oil 1 ml/kg/day), CsA (10 mg/kg/day) alone and with pioglitazone (5 or 10 mg/kg/day). The animals were sacrificed at 28 days, where blood (serum creatinine ratio, CR) and kidney samples (arteriolopathy analyses) were collected. The mRNA transcripts of TGF-beta1, PAI-1, Smad3 and 7 were evaluated by real-time PCR. As expected, CsA treatment significantly decreased renal function that peaked at day 28, compared with vehicle (CR=1.29+/-0.03 vs. 0.95+/-0.14, p<0.05). In contrast, the administration of pioglitazone 5 or 10 mg/kg combined with CsA resulted in better renal function (CR=1.09+/-0.05 and 1.14+/-0.14, respectively, p<0.05). Animals treated with CSA showed relevant arteriolopathy (49.5+/-2.86%) and pioglitazone administration significantly limited it (37.0+/-3.59% and 36.6+/-1.72%, respectively, 5 or 10 mg/kg, p<0.05). In CsA-treated animals (alone and with pioglitazone), TGF-beta1 and Smad3 increased significantly. In animals treated with CsA and pioglitazone (5 mg/kg), PAI-1 was significantly lower than CsA alone (3.96+/-0.92 vs. 7.53+/-1.38, p<0.05). Interestingly, the administration of pioglitazone 5 or 10 mg/kg was associated with an increase in Smad7 (1.79+/-0.25 and 1.75+/-0.19, respectively), compared to vehicle and to CsA-treated groups (1.08+/-0.17 and 1.17+/-0.19, respectively, p<0.05). These data provide evidence that pioglitazone acts through down regulation of pro-fibrotic cytokine PAI-1 and overexpression of the regulatory Smad7.

Animals↗
PubMed2004

The effect of nitric oxide synthase inhibitor on improved insulin action by pioglitazone in high-fructose-fed rats.

The present study was performed to investigate whether nitric oxide synthase (NOS) inhibition influences the increased whole-body insulin action by pioglitazone in high-fructose-fed rats. Male Wistar rats aged 6 weeks were randomly divided into 3 groups and each group was fed one of the following diets for 3 weeks: standard chow diet (control group), high-fructose diet (fructose-fed group), and high-fructose diet plus pioglitazone (pioglitazone-treated group). The control and pioglitazone-treated groups were further divided into 2 subgroups respectively, and some rats of each subgroup were infused the NOS inhibitor, N(G)-monomethyl-l-arginine (L-NMMA), during the euglycemic clamp studies. In vivo insulin action was determined by the 2-step (3 and 30 mU/kg body weight [BW]/min low- and high-dose, respectively) hyperinsulinemic euglycemic clamp procedure in the awake condition. Glucose infusion rate (GIR) was considered as the index of insulin action. Endothelium-type NOS (eNOS) and inducible NOS (iNOS) in skeletal muscle were also measured. At the low-dose clamp, high-fructose feeding produced a marked decrease in GIR compared with the control group. Pioglitazone-treated animals showed a significant increase in GIR, reaching a similar level as the control group. However, the improved GIR was decreased to the level of the fructose-fed group by L-NMMA infusion. The GIR of the control group was not affected by L-NMMA infusion. The same tendency as the low-dose clamp was found at the high-dose clamp. In skeletal muscle, eNOS and iNOS protein content were not affected by high-fructose feeding and/or pioglitazone treatment. These results suggest that NOS inhibition can decrease the improved insulin resistance by pioglitazone in high-fructose-fed rats. Therefore, although NOS protein content is not changed by high-fructose feeding and/or pioglitazone treatment, it could be concluded that nitric oxide (NO) plays an important role in the improvement of insulin action by pioglitazone.

Animals↗
PubMed2005

Short-term pioglitazone treatment improves vascular function irrespective of metabolic changes in patients with type 2 diabetes.

To determine whether pioglitazone influences endothelial function directly, we examined in a randomized, crossover, placebo-controlled, double-blind trial the effects of 4 weeks of pioglitazone treatment in 20 male type 2 diabetic patients. We conclude that short-term pioglitazone treatment ameliorates endothelial dysfunction in conduit arteries irrespective of significant beneficial changes in plasma levels of insulin, FFA, adiponectin, or CRP in type 2 patients with diabetes. Pioglitazone, a PPARgamma agonist, not only improves insulin resistance and glycemic control but may also have additional beneficial vascular effects in patients with type 2 diabetes. Low-grade inflammation, free fatty acids, and adiponectin may play a role in modulation of vascular function. We studied the effect of 4 weeks of pioglitazone treatment on endothelial function, metabolic changes, and C-reactive protein in patients with type 2 diabetes. A randomized, crossover, placebo-controlled, double-blind trial was performed in which pioglitazone 30 mg once daily was administered to 20 patients with type 2 diabetes on oral antihyperglycemic agents for 4 weeks. Shear stress-induced flow-mediated dilation (FMD) of the brachial artery was used as outcome parameter for vascular function. Brachial artery endothelial function was significantly increased by pioglitazone treatment compared with placebo (FMD 5.4 +/- 0.5% versus 3.1 +/- 0.5%, P = 0.001). Endothelium-independent vasodilation was not different between the 2 study periods. Pioglitazone treatment reduced insulin, FFA, and C-reactive protein concentrations compared with placebo (18.3 +/- 2.4 versus 14.8 +/- 2.1 mU/L, P = 0.03; 641 +/- 46 versus 542 +/- 33 mumol/L, P = 0.04; and 3.5 +/- 0.6 mg/L versus 2.6 +/- 0.5 mg/L, P = 0.01; respectively). A significant increase in plasma adiponectin concentration (3.95 +/- 0.57 microg/mL versus 7.59 +/- 0.95 microg/mL, P = 0.002) was also observed. No correlations were found between these metabolic changes and the improvement of conduit artery endothelial function. Short-term pioglitazone treatment ameliorates endothelial dysfunction in conduit arteries irrespective of changes in insulin, FFA, adiponectin, or CRP in type 2 patients with diabetes.

Adiponectin↗
PubMed2003

Pioglitazone, a peroxisome proliferator-activated receptor-gamma agonist, attenuates myocardial ischemia/reperfusion injury in a rat model.

Thiazolidinediones are insulin-sensitizing drugs, ligands for peroxisome proliferator-activated receptor-gamma (PPAR-gamma), which play an important role in the modulation of inflammatory responses. Myocardial ischemia/reperfusion (MI/R) injury is associated with inflammation, in which various cells, particularly monocytes and macrophages, are involved. This study examined the effects of the thiazolidinedione peroxisome proliferator-activated receptor-gamma ligand, pioglitazone, in a rat model of MI/R injury. Pioglitazone at 3 mg/kg/day or the vehicle was administered for 7 days before rats were subjected to 30 minutes of coronary ligation followed by 24 hours of reperfusion. The mRNA expression [monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1] in the ischemic region, the number of infiltrating macrophages in the ischemic region, and the myocardial infarct size were examined. The inhibitory effects of pioglitazone on activated macrophages were studied in vitro. Phorbol 12-myristate 13-acetate-induced MCP-1 production, in the absence or presence of pioglitazone, were assayed in cultured macrophages. Compared with the control group, (1). mRNA levels of MCP-1 and intercellular adhesion molecule-1 and the number of infiltrating macrophages in the ischemic region were significantly lower in the pioglitazone-treated group; and (2). myocardial infarct size was significantly smaller in the pioglitazone-treated group. Phorbol 12-myristate 13-acetate-stimulated cultured macrophages in the presence of pioglitazone produced significantly lower levels of MCP-1 than the stimulated control in the absence of pioglitazone. These observations demonstrate that pioglitazone has anti-inflammatory effects in MI/R injury that are independent of its insulin-sensitizing effect.

Animals↗
PubMed2006

Effect of rifampicin on the pharmacokinetics of pioglitazone.

AIMS: The effect of enzyme induction on the pharmacokinetics of pioglitazone, a thiazolidinedione antidiabetic drug that is metabolized primarily by CYP2C8, is not known. Rifampicin is a potent inducer of several CYP enzymes and our objective was to study its effects on the pharmacokinetics of pioglitazone in humans. METHODS: In a randomized, two-phase crossover study, ten healthy subjects ingested either 600 mg rifampicin or placebo once daily for 6 days. On the last day, they received a single oral dose of 30 mg pioglitazone. The plasma concentrations and cumulative excretion of pioglitazone and its active metabolites M-IV and M-III into urine were measured up to 48 h. RESULTS: Rifampicin decreased the mean total area under the plasma concentration-time curve (AUC(0-infinity)) of pioglitazone by 54% (range 20-66%; P = 0.0007; 95% confidence interval -78 to -30%) and shortened its dominant elimination half-life (t(1/2)) from 4.9 to 2.3 h (P = 0.0002). No significant effect on peak concentration (C(max)) or time to peak (t(max)) was observed. Rifampicin increased the apparent formation rate of M-IV and shortened its t(max) (P < 0.01). It also decreased the AUC(0-infinity) of M-IV (by 34%; P = 0.0055) and M-III (by 39%; P = 0.0026), shortened their t1/2 (M-IV by 50%; P = 0.0008, and M-III by 55%; P = 0.0016) and increased the AUC(0-infinity) ratios of M-IV and M-III to pioglitazone by 44% (P = 0.0011) and 32% (P = 0.0027), respectively. Rifampicin increased the M-IV/pioglitazone and M-III/pioglitazone ratios in urine by 98% (P = 0.0015) and 95% (P = 0.0024). A previously unrecognized metabolite M-XI, tentatively identified as a dihydroxy metabolite, was detected in urine during both phases, and rifampicin increased the ratio of M-XI to pioglitazone by 240% (P = 0.0020). CONCLUSIONS: Rifampicin caused a substantial decrease in the plasma concentration of pioglitazone, probably by induction of CYP2C8. Concomitant use of rifampicin with pioglitazone may decrease the efficacy of the latter drug.

Administration, Oral↗
PubMed2005

Comparison of metabolic effects of pioglitazone, metformin, and glimepiride over 1 year in Japanese patients with newly diagnosed Type 2 diabetes.

AIMS: To compare the metabolic effects of pioglitazone, metformin, and glimepiride in the treatment of Japanese patients with newly diagnosed Type 2 diabetes. METHODS: A total of 114 patients with Type 2 diabetes who had never used oral hypoglycaemic drugs were studied for 12 months. Patients were randomly assigned to pioglitazone (30-45 mg/day, n = 38), metformin (750 mg/day, n = 39), or glimepiride (1.0-2.0 mg/day, n = 37). The effect of treatment on fasting plasma glucose (FPG), glycated haemoglobin (HbA(1c)), 1,5-anhydroglucitol (1,5AG), total cholesterol, high-density lipoprotein (HDL)-cholesterol, triglycerides, free fatty acids (FFA), and fasting plasma insulin levels was monitored monthly. Body weight and safety data were also collected. RESULTS: Eight patients withdrew from the study (three in the pioglitazone group, two in the metformin group, and three in the glimepiride group). The rate of reduction of HbA(1c) was fastest in patients receiving glimepiride and slowest in patients receiving pioglitazone. Although there were no significant differences among the three groups in HbA(1c) levels at the end of the study, patients taking pioglitazone had relatively lower FPG and 1,5AG levels than patients taking the other two drugs. These results suggest that pioglitazone acts predominantly on nocturnal metabolism rather than at mealtimes. FFA were reduced significantly in those taking pioglitazone (542.2 microEq/l vs. 237.3 microEq/l; P < 0.01) before a decrease in HbA(1c) was apparent. The change in FFA levels correlated with the change in HbA(1c) (r = 0.409, P < 0.01). There were no significant differences in other lipid parameters among the groups. CONCLUSIONS: Pioglitazone, metformin, and glimepiride are equally effective in reducing blood glucose in patients with newly diagnosed Type 2 diabetes. However, their specific characteristics, such as the rapid action on blood glucose levels of glimepiride and the favourable action on FPG and FFA of pioglitazone, should be considered when choosing an appropriate agent.

Aged↗