Effects of pioglitazone on metabolic control and blood pressure: a randomised study in patients with type 2 diabetes mellitus

In praise of pioglitazone: An economically efficacious therapy for type 2 diabetes and other manifestations of the metabolic syndrome

Pioglitazone improves glycaemic control, not only by lowering insulin resistance, but also by improving beta cell function. Because of the improved beta cell function the glycaemic control that occurs with pioglitazone is prolonged. Pioglitazone has positive effects not only on cardiac risk factors and surrogate measures of cardiovascular disease, it also lowers the incidence of cardiac events in patients with diabetes. The recurrence of transient ischaemic attack and ischaemic stroke is also reduced in non-diabetic, insulin-resistant subjects. Utilized at preclinical stages (but not later) of heart failure, pioglitazone improves diastolic function and avoids progression to heart failure. Pioglitazone, through suppression of atrial remodelling, also decreases the incidence of atrial fibrillation. The manifestations of diseases associated with insulin resistance (non-alcoholic steatohepatitis and polycystic ovary disease) are also improved with pioglitazone. Pioglitazone may possibly improve psoriasis and other dermopathies. Pioglitazone is therefore an inexpensive and efficacious drug for the insulin-resistant subject with diabetes that is underutilized because of biases that have evolved from the toxicities of other thiazolidinediones.

Hyperinsulinemia rather than insulin resistance itself induces blood pressure elevation in high fat diet-fed rats

OBJECTIVE

To investigate if insulin resistance per se or the accompanying hyperinsulinemia induced hypertension and its underlying mechanisms.

METHODS

Sprague-Dawley rats were randomized into normal diet-fed group (ND group) and high-fat diet-fed group (HFD group). Then, the HFD group was further randomly divided into the control group (HFD_C group), the PIO group (treated with pioglitazone), the STZ_DM group (to induce diabetes with streptozotocin) and the DM+Ins group (streptozotocin injection followed by insulin treatment). Insulin sensitivity, plasma insulin, endothelin-1, norepinephrine, aldosterone, angiotensinⅡ and 24-h urinary sodium excretion (USE) levels of the groups were measured and analyzed. A multiple stepwise regression analysis method was applied to exam our hypothesis.

RESULTS

Compared to HFD_C group, the groups with lower plasma insulin, the PIO group and STZ_DM group, showed higher USE and lower blood pressure. The groups with higher plasma insulin (but same level of insulin resistance), the HFD_C group and DM+Ins group, showed lower USE and higher blood pressure. The 24-h urinary sodium excretion was the most important contributor to the significant changes of blood pressure with an R² of 25.2% in this animal experiment.

CONCLUSIONS

It is the compensatory hyperinsulinemia rather than insulin resistance per se that causes blood pressure elevation. The urinary sodium excretion is the key mediator among the multiple mechanisms. Therapies targeting hyperinsulinemia and restricting salt intake may favor a better control of hypertension associated with insulin resistance.

Effects of pioglitazone therapy on blood parameters, weight and BMI: a meta-analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is one of the most common diseases worldwide and insulin insufficiency and insulin resistance are two main metabolic issues connected with it. The dyslipidemia associated with insulin resistance and T2DM is characterized by higher triglycerides (TGs), higher very-low-density lipoprotein cholesterol and lower apo A1. Pioglitazone, a member of the thiazolidinedione class, with a proven antihyperglycemic effect, is known to positively influence insulin sensitivity and β-cell function and to have the potential to alter the lipid profile.

METHODS

The aim of our meta-analysis is to summarize and determine the influence of pioglitazone on the glycemic profile and lipoprotein metabolism as well as on weight and BMI in order to highlight the benefit of pioglitazone therapy in patients with T2DM. A comprehensive literature search was conducted through the electronic databases PubMed, MEDLINE, Scopus, PsyInfo, eLIBRARY.ru (from 2000 until February 2016) to identify studies that investigate the effect of pioglitazone on the glycemic and lipid profile and on the weight and BMI. We chose the random-effects method as the primary analysis. Forest plots depict estimated results from the studies included in the analysis and funnel plots are used to evaluate publication bias. Sensitivity analyses were performed in order to evaluate the degree of influence of the consequent elimination of each individual study on the final result.

RESULTS

Of the 1536 identified sources only 15 randomised trials were included in the meta-analysis. Pioglitazone treatment was associated with improvement in the glycemic profile. It reduced FPG levels by a mean of 1.1-2 mmol/l and HbA1c by a mean of 0.9-1.3%. Our results reaffirmed the hypothesis that pioglitazone has a positive influence on the lipid profile of T2DM patients with increase in TC and HDL, no significant changes in LDL and notable decrease in TGs. Results also showed that pioglitazone therapy led to increase in both weight and BMI (WMD 1.755, 95% CI 0.674 to 2.837 and 1.145, 95% CI 0.389 to 1.901 respectively).

CONCLUSION

Our results prove that the PPAR γ agonist pioglitazone has the potential to be beneficial to patients with T2DM.

Pioglitazone — an oral antidiabetic agent and metabolic syndrome modulator. Can theory translate into practice?

The metabolic syndrome, associated with insulin resistance, is a cluster of cardiovascular risk factors which results in premature morbidity and mortality from atherosclerotic vascular disease. Pioglitazone, a peroxisome-proliferator-activated receptor gamma (PPARγ) agonist, is an insulin sensitiser with the ability to address key features of the metabolic syndrome: glucose intolerance including type 2 diabetes, hypertension, dyslipidaemia, the pro-coagulant state, endothelial dysfunction, inflammation and atherosclerosis. The greatest potential benefit of pioglitazone is to influence atherogenesis itself through its pleiotrophic effects on vascular risk factors. This has been tested by the PROactive study, results of which are published in September 2005.

Sildenafil does not enhance but rather attenuates vasorelaxant effects of antidiabetic agents

Type 2 diabetic men commonly experience erectile dysfunction for which phosphodiesterase-5 (PDE5) inhibitors like sildenafil (Viagra) are often recommended. By preventing degradation of cyclic guanosine monophosphate (cGMP) in vascular smooth muscle, these inhibitors also enhance arterial vasorelaxant effects of nitric oxide donors (which stimulate cGMP synthesis). In the present work, we confirmed this enhancing effect after co-administration of sildenafil with nitroprusside to freshly-isolated rat tail arterial tissues. However, in the same tissues we also observed that sildenafil does not enhance but rather attenuates vasorelaxant effects of three commonly-used antidiabetic drugs, i.e. the biguanide metformin and the thiazolidinediones pioglitazone and rosiglitazone. Indeed, sildenafil completely blocked vasorelaxant effects of low concentrations of these drugs. In addition, we found that this same novel anti-vasorelaxant interaction of sildenafil with these agents was abolished by either 1) omitting extracellular glucose or 2) inhibiting specific smooth muscle glycolytic pathways; pathways known to preferentially utilize extracellular glucose to fuel certain adenosine triphosphate (ATP)-dependent ion transporters: e.g. ATP-sensitive K channels, sarcoplasmic reticulum Ca-ATPase, plasma membrane Ca-ATPase and Na/K-ATPase. Accordingly, we suspect that altered activity of one or more of these ion transporters mediates the observed attenuating (anti-vasorelaxant) interaction of sildenafil with the antidiabetic drugs. The present results are relevant because hypertension is so common and difficult to control in Type 2 diabetes. The present data suggest that sildenafil might interfere with the known antihypertensive potential of metformin and the thiazolidinediones. However, they do not suggest that it will interact with them to cause life-threatening episodes of severe hypotension, as can occur when it is co-administered with nitrates.

PPAR-gamma, Microglial Cells, and Ocular Inflammation: New Venues for Potential Therapeutic Approaches

The last decade has witnessed an increasing interest for the role played by the peroxisome proliferator-activated receptor-γ (PPAR-γ) in controlling inflammation in peripheral organs as well as in the brain. Activation of PPAR-γ has been shown to control the response of microglial cells, the main macrophage population found in brain parenchyma, and limit the inflammation. The anti-inflammatory capacity of PPAR-γ agonists has led to the hypothesis that PPAR-γ might be targeted to modulate degenerative brain diseases in which inflammation has been increasingly recognized as a significant component. Recent experimental evidence suggests that PPAR-γ agonists could be exploited to treat ocular diseases such as diabetic retinopathy, age-related macular degeneration, autoimmune uveitis, and optic neuritis where inflammation has relevant role. Additional PPAR-γ agonist beneficial effects could involve amelioration of retinal microcirculation and inhibition of neovascularization. However, PPAR-γ activation could, in some instances, aggravate the ocular pathology, for example, by increasing the synthesis of vascular endothelial growth factor, a proangiogenic factor that could trigger a vicious circle and further deteriorate retinal perfusion. The development of new in vivo and in vitro models to study ocular inflammation and how to modulate for the eye benefit will be instrumental for the search of effective therapies.

Rosiglitazone prevents the progression of renal injury in DOCA-salt hypertensive rats

This study was designed to evaluate the possible renoprotective effects of rosiglitazone (RGT), a peroxisome proliferator-activated subtype gamma receptor agonist, in deoxycorticosterone acetate (DOCA)-salt hypertension and its role in endogenous endothelin-1 (ET-1) production and renal fibrosis associated with inflammation. Rats were implanted with DOCA strips (200 mg kg(-1)) at 1 week after unilateral nephrectomy. DOCA-salt rats received control diet with or without RGT (10 mg kg(-1) per day). Systolic blood pressure was measured by the tail-cuff method. Glomerulosclerosis and tubulointerstitial fibrosis were evaluated on kidney sections. The expression of ED-1, cyclooxygenase-2 (COX-2), heat shock protein-25 (HSP25) and transforming growth factor-beta1 (TGF-beta1) was determined in the kidney by semiquantitative immunoblotting. In DOCA-salt rats, systolic blood pressure was increased, whereas creatinine clearance decreased compared with controls, which were counteracted by RGT treatment. Tubular injury and glomerulosclerois in the histological study were prominent in DOCA-salt rats, which were counteracted by RGT treatment. ET-1 expression was increased in DOCA-salts rats, which was attenuated by RGT treatment. The expression of TGF-beta1, ED-1 and COX-2 was increased in DOCA-salt, which was attenuated by RGT treatment. In conclusion, RGT treatment decreases blood pressure and is effective in preventing the progression of renal injury in DOCA-salt hypertension, the mechanisms of which are associated with anti-inflammatory and anti-fibrotic effects through reducing the overexpression of ET-1, ED-1, COX-2 and TGF-beta1 in the kidney.

Risk of cardiovascular disease and all cause mortality among patients with type 2 diabetes prescribed oral antidiabetes drugs: retrospective cohort study using UK general practice research database

OBJECTIVE

To investigate the risk of incident myocardial infarction, congestive heart failure, and all cause mortality associated with prescription of oral antidiabetes drugs.

DESIGN

Retrospective cohort study.

SETTING

UK general practice research database, 1990-2005.

PARTICIPANTS

91,521 people with diabetes.

MAIN OUTCOME MEASURES

Incident myocardial infarction, congestive heart failure, and all cause mortality. Person time intervals for drug treatment were categorised by drug class, excluding non-drug intervals and intervals for insulin.

RESULTS

3588 incident cases of myocardial infarction, 6900 of congestive heart failure, and 18,548 deaths occurred. Compared with metformin, monotherapy with first or second generation sulphonylureas was associated with a significant 24% to 61% excess risk for all cause mortality (P<0.001) and second generation sulphonylureas with an 18% to 30% excess risk for congestive heart failure (P=0.01 and P<0.001). The thiazolidinediones were not associated with risk of myocardial infarction; pioglitazone was associated with a significant 31% to 39% lower risk of all cause mortality (P=0.02 to P<0.001) compared with metformin. Among the thiazolidinediones, rosiglitazone was associated with a 34% to 41% higher risk of all cause mortality (P=0.14 to P=0.01) compared with pioglitazone. A large number of potential confounders were accounted for in the study; however, the possibility of residual confounding or confounding by indication (differences in prognostic factors between drug groups) cannot be excluded.

CONCLUSIONS

Our findings suggest a relatively unfavourable risk profile of sulphonylureas compared with metformin for all outcomes examined. Pioglitazone was associated with reduced all cause mortality compared with metformin. Pioglitazone also had a favourable risk profile compared with rosiglitazone; although this requires replication in other studies, it may have implications for prescribing within this class of drugs.

The effects of thiazolidinediones on blood pressure levels – A systematic review

Insulin resistance has been proposed to be the underlying disorder of the so-called metabolic or insulin resistance syndrome, which represents the clustering in the same individual of several cardiovascular risk factors, such as type 2 diabetes mellitus, hypertension, abdominal obesity, elevated triglycerides and low high-density lipoprotein-cholesterol. As far as the connection of insulin resistance and compensatory hyperinsulinaemia with hypertension is concerned, a number of mechanisms possibly linking these disturbances have been described, such as activation of sympathetic nervous system, enhancement of renal sodium reabsorption, or impairment of endothelium-dependent vasodilatation. Thiazolidinediones (TZDs) constitute a class of oral antihyperglycaemic agents that act by decreasing insulin resistance, and apart from their action on glycaemic control, they have been also reported to exert beneficial effects on other parameters of the metabolic syndrome. In particular, during recent years a considerable number of animal and human studies have shown that the use of TZDs was associated with usually small but significant reductions of blood pressure (BP) levels. Since a possible beneficial action of these compounds on BP could be of particular value for patients with the metabolic syndrome, this review aimed to summarize and evaluate the literature data in the field, derived either from studies that just examined BP levels among other parameters or from studies that were specifically designed to determine the effect of a TZD on BP.

Effects of rosiglitazone on heat shock protein and the endothelin system in deoxycorticosterone acetate-salt hypertensive rats

The deoxycorticosterone acetate (DOCA)-salt rat is known as a model of volume dependent hypertension and characterized by increased cardiac endothelin-1 (ET-1) content. Recently, it has been reported that rosiglitazone (RGT), a peroxisome proliferator-activated subtype gamma receptor agonist, shows blood pressure lowering effect. We investigated whether DOCA-salt hypertension is associated with altered expression of heat shock proteins (HSP) and ET-1 in the heart, aorta, and kidney, and whether RGT changes HSP expression and ET-1 in association with its blood pressure lowering effect. Two weeks after the silastic DOCA (200 mg/kg) strips implantation, DOCA-salt rats were randomly divided to receive control diet with or without RGT (10 mg/kg/day) for another 2 weeks. The mRNA expression of ET-1 was determined by real time polymerase chain reaction. The expression of HSP was determined by semiquantitative immunoblotting. In DOCA-salt rats, systolic blood pressure was markedly increased, while creatinine clearance decreased. RGT treatment attenuated high blood pressure and decreased creatinine clearance in DOCA-salt rats. The mRNA expression of ET-1 was increased in DOCA-salt rats compared to controls, which was counteracted by RGT treatment. The protein expression of HSP70, HSP32, and HSP25 was increased in the kidney and heart in DOCA-salt rats, which was attenuated by RGT treatment in the kidney, but not in the heart. In conclusion, increased expression of ET-1 may play a role in the pathogenesis of hypertension in DOCA-salt rats, which was counteracted by the treatment of RGT. Up-regulation of HSP70, HSP32, and HSP25 in the kidney and heart may play a role in organ protection against a variety of stresses.

Thiazolidinediones-improving endothelial function and potential long-term benefits on cardiovascular disease in subjects with type 2 diabetes

Endothelial dysfunction, which leads to impaired vasodilation, is an early event in the development of atherosclerosis. A number of mechanisms involving, for example, cell adhesion molecules, chemokines, and cytokines, contribute to this inflammatory disease, and insulin resistance plays a cardinal role in accelerating these processes. Hyperglycemia and other metabolic abnormalities that are commonly associated with insulin resistance also contribute to impaired endothelial function. In addition, the important role of the endothelium in damage repair following a cardiovascular event is emerging. The combination of proatherogenic factors in patients with type 2 diabetes results in blunted endothelial function and an increased risk of cardiovascular disease. Insulin-sensitizing agents such as thiazolidinediones have demonstrated a number of clinical benefits, including anti-inflammatory and antithrombotic properties, which may impact on the course of atherosclerosis. Recent studies have demonstrated that thiazolidinediones improve endothelial function in subjects with and without type 2 diabetes.

Pioglitazone decreases ambulatory blood pressure in type 2 diabetics with difficult-to-control hypertension

Blood pressure (BP) control at recently established goals of <130/80 mm Hg is often difficult to achieve in diabetic patients. This work examines the effect of pioglitazone on 24-hour ambulatory BP monitoring in patients with type 2 diabetes and difficult-to-control hypertension. Twenty-seven participants with difficult-to-control hypertension (defined as ambulatory BP monitoring >or=125/75 mm Hg) taking antihypertensive medications (mean, 4.1+/-0.8 drugs) were enrolled in an open, prospective, blinded end point study of add-on therapy with pioglitazone 30 to 45 mg for 20 weeks. After 20 weeks of treatment, 24-hour ambulatory BP monitoring showed significant reductions (from 144+/-13 to 136+/-16 mm Hg systolic BP and from 79+/-9 to 76+/-10 mm Hg diastolic BP [P=.001]). Treatment was also associated with improvements in insulin sensitivity and glycemic and lipid profile. These findings suggest that pioglitazone could be a therapeutic option in diabetics who still have elevated BP values in spite of receiving treatment with at least 3 antihypertensive drugs.

Thiazolidinediones inhibit the progression of established hypertension in the Dahl salt-sensitive rat

We evaluated the effects of two thiazolidinediones (TZDs), the potent PPARgamma agonist rosiglitazone currently being used to treat diabetes, and a structurally similar experimental compound that is a poor PPARgamma agonist, in a non-diabetic, established hypertension model with continuous measurement of blood pressure by telemetry. Hypertension was induced in male Dahl salt-sensitive rats by a three-week pre-treatment with 4% salt before initiation of treatment. Fasting blood samples were taken for analysis of a biomarker panel to assess metabolic, anti-inflammatory and antioxidant activity of the treatments. Both TZDs significantly reduced both systolic and diastolic blood pressure. When used at the maximally effective doses established for metabolic improvement, both compounds produced equivalent reduction in lipids and elevation of adiponectin, yet the poorer PPARgamma agonist produced significantly greater reductions in blood pressure. Neither compound had a significant effect on circulating glucose or insulin in this animal model. The data demonstrate that these TZDs lower blood pressure significantly in Dahl rats and that this cardiovascular pharmacology is not directly correlated with the metabolic actions or with the magnitude of PPARgamma activation. These data suggest that it may be possible to find insulin-sensitising agents that have beneficial cardiovascular pharmacology with broad applications for disease prevention.

Inflammation in diabetes mellitus: role of peroxisome proliferator-activated receptor-alpha and peroxisome proliferator-activated receptor-gamma agonists

Patients with type 2 diabetes mellitus and/or the metabolic syndrome have considerable cardiovascular risk. Treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and with antihypertensive and some antihyperglycemic agents reduces this risk, but residual macrovascular morbidity and mortality persist, even in patients assigned to intensive multifactorial intervention programs. Therapeutic strategies that target inflammation and lipid abnormalities not well addressed by statins may offer additional opportunities for improving the prognosis of these patients. Inflammation, a key mechanism of atherogenesis, appears to have particular relevance to diabetic vascular complications, as well as in the development of diabetes itself. Oxidative stress and hyperglycemia also figure among the pathogenic factors that promote cardiovascular complications in patients with the metabolic syndrome and/or diabetes and may augment the ongoing inflammation. Peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma, members of the nuclear receptor family, form ligand-activated transcription factors that regulate key important metabolic pathways. PPARs have become therapeutic targets through the use of the fibrate class of antidyslipidemic drugs (PPAR-alpha) and the insulin-sensitizing thiazolidinediones (PPAR-gamma). The activation of these PPARs may also suppress inflammation and atherosclerosis. Recent clinical trials (Fenofibrate Intervention and Event Lowering in Diabetes [FIELD], Prospective Pioglitazone Clinical Trial in Macrovascular Events [PROactive]) have considered the impact of these PPAR agonists on cardiovascular disease, with mixed effects that require careful analysis, especially given ongoing trials and additional PPAR agonists in development.

Diabetes and Hypertension: Epidemiology of the Relationship and Pathophysiology of Factors Associated With These Comorbid Conditions

Diabetes and hypertension frequently coexist, leading to additive increases in the risk of life-threatening cardiovascular events. Hypertension is a common comorbid condition in patients with type 1 or type 2 diabetes when compared with the general population and occurs in 75% of patients with the more prevalent form of diabetes, type 2. Arterial blood pressure plays an important role in the development of renal damage and presents a complex relationship. It is well-known that hypertension accelerates the course of microvascular and macrovascular complications of diabetes and that hypertension often precedes type 2 diabetes and vice versa. Patients with type 1 and 2 diabetes and nephropathy frequently have circadian changes in blood pressure that correlate to nephropathy risk. Early detection of nocturnal hypertension and early intervention with angiotensin blockade may delay progression of diabetic nephropathy.

Thiazolidinediones and their Fluid-Related Adverse Effects

Thiazolidinediones (TZDs) or glitazones are agents that are widely used for the treatment of type 2 diabetes mellitus. These drugs have a multitude of therapeutic effects including reduction in insulin resistance and hyperglycaemia, anti-inflammatory effects and amelioration of hypertension, microalbuminuria and hepatic steatosis. The TZD molecular target, peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear transcription factor, is expressed diffusely in humans, including many tissues comprising the cardiovascular and renal systems. This suggests a potential for TZDs to elicit perturbing effects on these systems, which are independent of their effects on glucose and lipid metabolism. One of the most common adverse effects of TZDs is fluid retention, which can result in, or exacerbate, oedema and congestive heart failure (CHF). The frequency of peripheral oedema is approximately 5% when TZDs are used in mono- or combination oral therapy, and about 15% when used with insulin. Patients with type 2 diabetes are at high risk of myriad morbid complications, including CHF. The development of CHF, particularly in the elderly, is a harbinger of premature mortality. TZD-induced oedema is largely peripheral, may have its origins in changes in haemodynamics, with some contribution from molecules, which regulate cell and tissue permeability (e.g. vascular endothelial growth factor and protein kinase Cbeta), and remains the preponderant manifestation of TZD-induced fluid retention even in those with existing heart failure. Preclinical and pilot clinical data attest to the fact that at least part of the fluid retention derives from a direct effect of TZDs on sodium reabsorption via the renal medullary collecting duct, a mechanism that is sensitive to diuretic agents that have this nephron segment as their site of action, in whole or in part (spironolactone, amiloride and hydrochlorothiazide). Our review suggests various potential clinical strategies by which TZD-induced fluid retention might be effectively monitored and addressed.

Peroxisome proliferator-activated receptor gamma agonists: their role as vasoprotective agents in diabetes

Both type 1 and type 2 diabetes melitius are associated with increased cardiovascular morbidity, and now affect more than 170 million individuals worldwide. The incidence of type 2 diabetes is growing rapidly and now accounts for 90 to 95 percent of all diabetes cases. Thiazolidinediones (TZDs) a class of insulin sensitizing agents commonly used in the treatment of patients who have type 2 diabetes, improve endothelial dysfunction and exert beneficial effects on lipid profiles by activating the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-gamma). In addition, TZDs exhibit antiatherogenic effects, independent of their antidiabetic and lipid-lowering properties, by attenuating proinflammatory processes. The combination of increased insulin sensitivity, improved lipid profile, and reduced inflammation may explain the cardiovascular benefits of this class of drugs

Vascular effects of TZDs: New implications

The incidence of diabetes, now affecting more than 170 million individuals is growing rapidly. Type 2 diabetes, which accounts for 90% of all diabetes cases, is associated with increased cardiovascular morbidity and mortality. Thiazolidinediones (TZDs), used for the treatment of patients with type 2 diabetes improve insulin sensitivity and endothelial dysfunction and exert beneficial effects on the lipid profile by activating the peroxisome proliferator-activated receptor gamma (PPAR-gamma). Moreover, a large body of evidence indicates that TZDs exhibit antiatherogenic effects independent of their antidiabetic and lipid-lowering properties by modulating inflammatory processes. This review will focus on the role of PPAR-gamma agonists in the vessel wall and summarize their effects on C-reactive protein (CRP), plasminogen activator inhibitor type-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), adiponectin and ATP-binding cassette transporter A1 (ABCA1) and their implications for treatment of advanced stages of atherosclerosis, particularly in a setting of type 2 diabetes.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pioglitazone: a review of its use in type 2 diabetes mellitus

Pioglitazone is an antihyperglycaemic agent that, in the presence of insulin resistance, increases hepatic and peripheral insulin sensitivity, thereby inhibiting hepatic gluconeogenesis and increasing peripheral and splanchnic glucose uptake. Pioglitazone is generally well tolerated, weight gain and oedema are the most common emergent adverse events, and there are no known drug interactions between pioglitazone and other drugs. In clinical trials in patients with type 2 diabetes mellitus, pioglitazone as monotherapy, or in combination with metformin, repaglinide, insulin or a sulphonylurea, induced both long- and short-term improvements in glycaemic control and serum lipid profiles. Pioglitazone was also effective in reducing some measures of cardiovascular risk and arteriosclerosis. Pioglitazone thus offers an effective treatment option for the management of patients with type 2 diabetes.

Peroxisome proliferator-activated receptor-gamma and its agonists in hypertension and atherosclerosis : mechanisms and clinical implications

Cardiovascular diseases are the leading cause of morbidity and mortality in the US. Proper management and/or prevention of atherosclerosis and hypertension, two complex and chronic disorders, would significantly reduce the risk for cardiovascular events such as myocardial infarction and stroke, but this requires an understanding of the mechanisms underlying their development and progression. Whereas a great deal has been learned and applied toward the management of these disorders, especially hypertension, morbidity and mortality remains unacceptably high, most likely because there are disease-causing mechanisms that have yet to be fully recognized. Understanding these disease mechanisms is necessary so that novel management strategies can be developed. One of these novel mechanisms centers on peroxisome proliferator-activated receptor (PPAR)-gamma. PPAR-gamma is a member of the nuclear receptor superfamily of ligand-activated transcription factors known to play a role in glucose homeostasis and adipocyte differentiation and, more recently, has been shown to have anti-inflammatory, antiatherogenic, and antihypertensive effects. Thiazolidinediones, a class of drugs used in the treatment of type 2 diabetes mellitus, are high-affinity ligands for PPAR-gamma. In this review, the anti-inflammatory, anti-atherosclerotic, and anti-hypertensive mechanisms by which PPAR-gamma and its agonists are thought to exert protective effects on the cardiovascular system are discussed. Ongoing clinical trials using PPAR-gamma activators for the management of cardiovascular diseases, especially in patients with type 2 diabetes mellitus, are summarized.

Obesity, peroxisome proliferator-activated receptor, and atherosclerosis in type 2 diabetes

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. The 3 PPAR isotypes, PPAR-alpha, PPAR-gamma, and PPAR-delta, play a key role in the regulation of lipid and glucose metabolism. Obesity and the interrelated disorders of the metabolic syndrome have become a major worldwide health problem. In this review, we summarize the critical role of PPARs in regulating inflammation, lipoprotein metabolism, and glucose homeostasis and their potential implications for the treatment of obesity, diabetes, and atherosclerosis.

The effect of rosiglitazone on novel atherosclerotic risk factors in patients with type 2 diabetes mellitus and hypertension. An open-label observational study

Thiazolidinediones are antidiabetic agents that decrease insulin resistance. Emerging evidence indicates that they present beneficial effects for the vasculature beyond glycemic control. The aim of this open-label observational study was to determine the effect of the thiazolidinedione rosiglitazone on novel cardiovascular risk factors, namely, lipoprotein(a) [Lp(a)], C-reactive protein (CRP), homocysteine, and fibrinogen in patients with type 2 diabetes and hypertension. A total of 40 type 2 diabetic patients already on treatment with 15 mg of glibenclamide daily and with poorly controlled or newly diagnosed hypertension were included in the study. Twenty of them received 4 mg of rosiglitazone daily as added-on therapy, whereas the rest remained on the preexisting antidiabetic treatment for 26 weeks. At baseline and the end of the study, subjects gave blood tests for the determination of Lp(a), CRP, homocysteine, fibrinogen, serum lipids, apolipoprotein (apo) A-I, and apo B. At the end of the study, rosiglitazone treatment was associated with significant reductions in Lp(a) (10.5 [8.9-54.1] to 9.8 [8.0-42.0] mg/dL, P<.05) and CRP levels (0.33 [0.07-2.05] to 0.25 [0.05-1.84] mg/dL, P<.05) vs baseline. Homocysteine levels were not affected but plasma fibrinogen presented a significant increase (303.5+/-75.1 to 387.5+/-70.4 mg/dL, P<.01) with rosiglitazone. Although no significant changes were observed in the rosiglitazone group for triglycerides, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein (LDL) cholesterol, both apo A-I and apo B presented small significant reductions and the LDL-apo B ratio was significantly increased. None of the above parameters were changed in the control group. In conclusion, rosiglitazone treatment had a beneficial impact on Lp(a), CRP, and LDL particles' lipid content in type 2 diabetic hypertensive patients but not on homocysteine and fibrinogen. The overall effect of rosiglitazone on cardiovascular risk factors seems positive but must be further evaluated.

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.

Effect of a peroxisome proliferator-activated receptor-gamma agonist on myocardial blood flow in type 2 diabetes

OBJECTIVE

The relationship between coronary endothelial function and insulin resistance remains speculative. We sought to determine whether pioglitazone, an insulin-sensitizing peroxisome proliferator-activated receptor (PPAR)-gamma agonist, improves cardiac endothelial function in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Sixteen subjects with insulin-treated type 2 diabetes and without overt cardiovascular disease were randomly assigned to receive either 45 mg of pioglitazone or matching placebo for 3 months. Rest and adenosine-stimulated myocardial blood flow (MBF) were quantified with [(13)N]ammonia and positron emission tomography at baseline and study conclusion.

RESULTS

After 3 months, HbA(1c) levels dropped by 0.68% in the pioglitazone group and increased by 0.17% in the placebo group (P = 0.009 for difference between groups). Triglyceride (-93 vs. -39 mg/dl, P = 0.026) and HDL concentrations (+4.8 vs. -6.0 mg/dl, P = 0.014) improved significantly in the pioglitazone group compared with placebo. Despite these favorable changes, there was no demonstrable change in baseline MBF (-0.05 +/- 0.24 vs. -0.09 +/- 0.24 ml . min(-1) . g(-1), P = 0.45), adenosine-stimulated MBF (0.10 +/- 0.75 vs. 0.14 +/- 0.31 ml . min(-1) . g(-1), P = 0.25), or coronary flow reserve (0.45 +/- 1.22 vs. 0.35 +/- 0.72 ml . min(-1) . g(-1), P = 0.64) after 12 weeks of exposure to pioglitazone or placebo, respectively. Regression analysis revealed that lower glucose concentration at the time of the study was associated with higher coronary flow reserve (P = 0.012).

CONCLUSIONS

Pioglitazone treatment for 12 weeks in subjects with insulin-requiring type 2 diabetes had no demonstrable effect on coronary flow reserve despite metabolic improvements. Higher ambient glucose levels contribute to impaired vascular reactivity in individuals with diabetes.

Peroxisome proliferator-activated receptor ligands in atherosclerosis

In this review, the effect of peroxisome proliferator-activated receptor (PPAR) ligands on atherosclerosis is examined. The PPAR-gamma agonist thiazolidinediones are currently indicated for the management of Type 2 diabetes mellitus, and the PPAR-alpha agonist fibrates are used in dyslipidaemia. Here their mechanism of action and the pre-clinical and clinical evidence for the use of these medications for the prevention and treatment of atherosclerotic disease is explored. In addition, the role of PPAR-delta and the possibilities for the role of dual-binding agonists are examined.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Will the potential of peroxisome proliferator-activated receptor agonists be realized in the clinical setting?

Drugs targeting both peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists (the thiazolidinediones) and PPAR-alpha (the fibrates) have already been developed for clinical use. However, the thiazolidinediones, currently prescribed to treat hyperglycemia and improve peripheral insulin resistance, may also have cardiovascular benefits that have yet to be fully realized. Animal models of atherosclerosis have shown that the thiazolidinediones reduce the extent of atherosclerotic lesions and inhibit macrophage accumulation. Clinical studies have also shown that these drugs improve the lipid profile of patients at risk of developing atherosclerosis and reduce circulating levels of inflammatory markers. This combination of lower lipid concentrations and reduced inflammation may explain the cardiovascular benefits of this class of drugs. Early trials in patients with coronary stents have reported promising findings, with restenosis rates being greatly reduced with thiazolidinedione therapy. It is hoped that the results of future clinical trials will continue to be encouraging, so that the thiazolidinediones' cardiovascular benefits can be fully realized in the clinic.

Pathophysiology of diabetes mellitus

As we learn more about the pathophysiology of diabetes mellitus, we find that there is more yet to be learned. This may sound like a trite statement, but in reality it is true. The following article reviews the basic pathophysiology of both type 1 diabetes mellitus and type 2 diabetes mellitus as we understand it today. It continues on to reveal the "things that go wrong" when there is too much or too little glucose available to the body organs and especially to the brain. The article points out the signs and symptoms to be aware of when the person is in the acute state of diabetic ketoacidosis, hyperglycemic hyperosmolar nonketotic coma (or state), and severe hypoglycemia. It concludes with important considerations when the individual is in one of these acute states and contributes key points related to the control of diabetes when the person is in the state of compromise.

A comparison of the effects of thiazolidinediones and metformin on metabolic control in patients with type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus is a condition characterized by impaired insulin secretion and resistance to insulin-mediated glucose uptake and utilization. A number of oral antidiabetic medication are available for its treatment, including metformin and the thiazolidinediones (TZDs). The TZDs have been shown to improve insulin resistance, and it has been suggested that metformin has similar effects. Although both types of agents improve glycemic control, their mechanisms of action and effects on metabolic processes differ.

OBJECTIVE

The goal of this review was to compare the effects of TZDs and metformin on metabolic control in patients with type 2 diabetes.

METHODS

A search of MEDLINE to March 2004 using the terms metformin and biguanides, and thiazolidinediones and glitazones was conducted to identify preclinical and clinical studies focusing on the mechanisms of action and comparative effects of TZDs and metformin. Also searched were published abstracts from recent major diabetes and endocrinology conferences.

RESULTS

In the studies reviewed, both TZDs and metformin demonstrated the ability to improve glycemic control, although long-term monotherapy with TZDs appeared to be more effective than metformin. There continues to be debate about whether metformin is more effective than TZDs in terms of inhibition of hepatic glucose production. However, various studies have found TZDs to be more effective in promoting an increase in whole-body insulin sensitivity. With respect to lipid metabolism, patients who received TZDs had a greater reduction in concentrations of both plasma triglycerides and free fatty acids. Metformin was more effective in promoting weight loss in patients with type 2 diabetes, although TZDs may decrease visceral fat levels. Treatment with either metformin or TZDs was associated with a reduction in the risk of cardiovascular disease, although the mechanisms by which they accomplished this seem to differ.

CONCLUSIONS

The evidence suggests that the predominant effect of metformin is inhibition of hepatic glucose production, whereas the primary effects of TZDs is reduction of insulin resistance and promotion of peripheral glucose uptake. TZDs appear to have more positive effects on other metabolic processes and to be associated with greater improvements in cardiovascular risk factors compared with metformin.