Thiazolidinediones and congestive heart failure--exacerbation or new onset of left ventricular dysfunction?

Does Thiazolidinedione therapy exacerbate fluid retention in congestive heart failure?

The ever-growing global burden of congestive heart failure (CHF) and type 2 diabetes mellitus (T2DM) as well as their co-existence necessitate that anti-diabetic pharmacotherapy will modulate the cardiovascular risk inherent to T2DM while complying with the accompanying restrictions imposed by CHF. The thiazolidinedione (TZD) family of peroxisome proliferator-activated receptor γ (PPARγ) agonists initially provided a promising therapeutic option in T2DM owing to anti-diabetic efficacy combined with pleiotropic beneficial cardiovascular effects. However, the utility of TZDs in T2DM has declined in the past decade, largely due to concomitant adverse effects of fluid retention and edema formation attributed to salt-retaining effects of PPARγ activation on the nephron. Presumably, the latter effects are potentially deleterious in the context of pre-existing fluid retention in CHF. However, despite a considerable body of evidence on mechanisms responsible for TZD-induced fluid retention suggesting that this class of drugs is rightfully prohibited from use in CHF patients, there is a paucity of experimental and clinical studies that investigate the effects of TZDs on salt and water homeostasis in the CHF setting. In an attempt to elucidate whether TZDs actually exacerbate the pre-existing fluid retention in CHF, our review summarizes the pathophysiology of fluid retention in CHF. Moreover, we thoroughly review the available data on TZD-induced fluid retention and proposed mechanisms in animals and patients. Finally, we will present recent studies challenging the common notion that TZDs worsen renal salt and water retention in CHF.

Cardiovascular risk of rosiglitazone: another perspective

Rosiglitazone is an effective therapy for type 2 diabetes although concerns have grown about the incidence of oedema and cardiovascular adverse events in patients treated with the drug. The following review was conducted to evaluate further and complement the evidence linking rosiglitazone with an increased risk for cardiovascular adverse events by examining trials and case reports not included in recent meta-analyses. Rosiglitazone-related publications describing case reports and prospective and retrospective cohort analyses were identified using MEDLINE and EMBASE, from July 1999 to July 2007. Relevant reports cited in these publications were also obtained. A recently-published meta-analysis and a double-blind, randomized, placebo-controlled trial were also reviewed. This review of 20 case reports and 10 uncontrolled studies supports the need for added vigilance when prescribing rosiglitazone to patients for the treatment of type 2 diabetes who may be at risk for congestive heart failure. Clinical data from numerous case reports and uncontrolled studies suggested that patients receiving rosiglitazone should be monitored for the development of weight gain or oedema. Prudence should be observed in patients with a history or risk factors for congestive heart failure as they may be poor candidates for rosiglitazone therapy.

A decision analysis study of the value of a liver biopsy in nonalcoholic steatohepatitis

OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is an increasingly prevalent clinical syndrome reflecting a mixture of pathological liver histology with the potential to progress to cryptogenic cirrhosis. Liver biopsy (LB) is the only way to determine the severity of disease. However, LB is invasive, has complications and financial costs. The aim of this study is to determine the benefits of early LB for diagnosis and early treatment.

METHODS

A decision tree model tracked the potential outcomes of NAFLD between an LB-directed approach vs. no initial LB. Each specific biopsy category determined subsequent care actions. The baseline probabilities were determined by literature review and expert opinion.

RESULTS

An initial LB strategy was projected to have a lower mortality compared with the no initial LB group and fewer transplant eligible patients after 5 years. If the prevalence of NAFLD is increased, the mortality increases in both the study groups. With improved efficacy of medical and/or surgical intervention, the mortality rate was decreased.

CONCLUSION

This decision tree model provides a context for balancing the risk and benefit of LB in NAFLD. With early biopsy, and early intervention, the relative return of preventing advanced liver disease per LB was high.

Thiazolidinedione insulin sensitizers and the heart: a tale of two organs?

Thiazolidinediones (TZDs) are relatively new agents for the treatment of type 2 diabetes. They act as agonists at the PPAR-gamma nuclear receptor and their therapeutic effects include decreased insulin resistance and hyperglycaemia, an improved plasma lipid, inflammation and pro-coagulant profile, and amelioration of hypertension, microalbuminuria and hepatic steatosis. The most common side effects of TZDs include weight gain and oedema, with occasional reports of congestive heart failure (CHF). This review discusses the benefit-risk profile of TZDs in treating patients with type 2 diabetes, with particular reference to the heart. To provide context, we explore briefly the epidemiology and pathophysiology of heart failure in patients with type 2 diabetes, touch on the association of heart disease and cardiovascular mortality with antihyperglycaemic treatment modalities other than TZDs, and then focus on the effects of TZDs on the heart, cardiovascular risk factors and outcomes. We describe the cluster of host factors, which seems to predispose patients with type 2 diabetes to TZD-induced or TZD-exacerbated oedema and CHF and then provide an overview of the putative mechanisms of these TZD-related side effects. We also propose that certain diuretics (amiloride and spironolactone), by targeting the distal nephron that expresses PPARgamma in collecting duct cells, might be of benefit in ameliorating the fluid retention and oedema associated with TZDs.

Prevalence and predictors of cardiac hypertrophy and dysfunction in patients with Type 2 diabetes

The aim of the present study was to determine the prevalence and predictors of an abnormal echocardiogram in patients with Type 2 diabetes. Cardiac function and structure were rigorously assessed by comprehensive transthoracic echocardiographic techniques in 229 patients with Type 2 diabetes. Cardiovascular risk factors and diabetic complications were assessed, and predictors of an abnormal echocardiogram were identified using multivariate logistic regression analysis. An abnormal echocardiogram was present in 166 patients (72%). LVH (left ventricular hypertrophy) occurred in 116 patients (51%), and cardiac dysfunction was found in 146 patients (64%), of whom 109 had diastolic dysfunction alone and 37 had systolic±diastolic dysfunction. Independent predictors of an abnormal echocardiogram were obesity, age, the number of antihypertensive drugs used (all P<0.001) and creatinine clearance (P<0.05). The risk of an abnormal echocardiogram increased by 9% for each year over 50 years of age {OR (odds ratio), 1.09 [95% CI (confidence interval), 1.04–1.15]}, 3-fold if obesity was present [BMI (body mass index) >30; OR, 4.2 (95% CI, 1.9–9.0)] and by 80% for each antihypertensive agent used [OR, 1.8 (95% CI, 1.3–2.4) per agent]. In conclusion, an abnormal cardiac echocardiogram is common in patients with Type 2 diabetes. Importantly, although cardiac abnormalities can be predicted by traditional risk factors, such as age, obesity and renal function, the absence of micro- or macro-vascular complications does not predict a normal echocardiogram. We suggest that an echocardiogram identifies those with Type 2 diabetes at increased cardiovascular risk due to occult LVH and diastolic dysfunction, and this information may lead to more aggressive management of known risk factors in the clinic.

PPARgamma agonists: safety issues in heart failure

PPARgamma agonists (or thiazolidinediones, TZD) are popular oral drugs for glycaemic control in patients with diabetes mellitus. However, side-effects of fluid retention, oedema and congestive heart failure have been reported in the literature as well as observed in clinical registries and trials. Concerns regarding the safety of TZD use in patients with underlying heart failure have been implicated by its propensity to cause fluid retention. There is relatively good documentation in the literature that TZDs do not produce adverse haemodynamic consequences. TZD-induced fluid retention is often sub-acute in nature, developed over weeks to months following initiation, and primarily located in the periphery. Drug withdrawal may lead to complete resolution of fluid retention. Current approval of TZD use in patients with mild (NYHA class I - II) and stable heart failure is supported by existing literature and clinical experience. There have been few reports of severe adverse consequences following drug withdrawal, and emerging data are suggesting potential benefits of TZDs in the diabetic population with or without underlying heart failure. Future research should therefore be directed at better understanding PPARgamma-related mechanisms of renal sodium retention and endothelial vascular permeability of the periphery, as well as development of newer compounds without this side-effect.

A Randomized, Placebo-Controlled Trial Assessing the Effects of Rosiglitazone on Echocardiographic Function and Cardiac Status in Type 2 Diabetic Patients With New York Heart Association Functional Class I or II Heart Failure

OBJECTIVES

This study investigated the effects of rosiglitazone (RSG) on left ventricular ejection fraction (LVEF) in subjects with type 2 diabetes (T2DM) and pre-existing chronic heart failure (CHF) (New York Heart Association [NYHA] functional class I to II).

BACKGROUND

Fluid retention is an important consideration in the use of thiazolidinediones in T2DM patients because it could exacerbate symptoms or precipitate decompensation in those with previously stable CHF.

METHODS

A total of 224 patients with T2DM and NYHA functional class I to II CHF with LVEF < or =45% were randomized to a 52-week treatment with RSG (4 to 8 mg daily, n = 110) or placebo (PLB) (n = 114) in addition to background antidiabetes therapy. Treatment was uptitrated to achieve target fasting plasma glucose <126 mg/dl; CHF medications were adjusted as appropriate.

RESULTS

The LVEF was similar in both groups at baseline (RSG 35.3 +/- 6.2%, PLB 35.7 +/- 7.8%) and after 52 weeks of treatment (mean difference 1.49%, p = 0.1). Glycemic control was significantly better in the RSG group (mean difference in hemoglobin A1c -0.65%, p < 0.0001). There were significantly more adjudicated events in the RSG group of new or worsening edema (RSG n = 28 [25.5%]; PLB n = 10 [8.8%]; p = 0.005) and increased CHF medication (RSG n = 36 [32.7%], PLB n = 20 [17.5%]; p = 0.037), but no significant difference between groups for other adjudicated end points. A similar proportion of patients withdrew from each treatment group because of adverse events.

CONCLUSIONS

After 52 weeks of treatment, RSG improved glycemic control but did not adversely affect LVEF in patients with T2DM and NYHA functional class I to II CHF. More fluid-related events occurred with RSG, although these generally did not lead to withdrawal from the study.

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.

The complex role of PPARgamma in renal dysfunction in obesity: managing a Janus-faced receptor

Obesity is frequently accompanied by insulin resistance, type II diabetes, hypertension and atherosclerosis, a cluster of pathologies that are the major components of the metabolic syndrome. Obesity is a known cause for renal dysfunction that leads to two major renal pathologies: hypertension and glomerular and tubulointerstitial injury. Peroxizome proliferator activated receptors (PPARs) are transcription factors belonging to the nuclear hormone receptor superfamily with important functions in the regulation of metabolism. The role of PPARgamma isoforms in adipogenesis and vascular inflammation associated to obesity has been vastly studied and is well recognized, albeit not completely mechanistically understood. Also, the effect of various PPARgamma agonists on blood pressure reduction in different forms of hypertension, including obesity related hypertension has been reported, but the mechanisms involved are only beginning to be studied. Even less clear is the concurrent beneficial effect of PPARgamma agonists thiazolinendiones (TZD) on blood pressure reduction in different forms of hypertension and, at the same time, in some cases, the significant water retention leading to edema and heart failure. The occurrence of both these apparently opposite effects on the renal water and sodium handling suggests a complex role of PPARgamma in the kidney that is likely related to the metabolic state. Also, PPARgamma activation leads to a reduction in mesangial cell proliferation while stimulating apoptosis. TZD treatment reduces albuminuria in obese and diabetic humans and rodent models suggesting protective effects against renal tubuloglomerular injury. The focus of this review is to present and critically discuss the recent findings on the roles of PPARgamma in the kidney in direct relation to renal function and renal injury in obesity and obesity-initiated diabetes.

Thiazolidinediones in patients with diabetes mellitus and heart failure : implications of emerging data

Individuals with diabetes mellitus have an increased risk of developing heart failure, usually as a consequence of coronary artery disease, although a specific diabetic cardiomyopathy, secondary to a microangiopathy, may also exist. The thiazolidinediones, a relatively new class of insulin-sensitizing agents used in the management of type 2 diabetes mellitus, have a number of complex metabolic actions on surrogate markers of atherogenesis, supported by the results of the recently published PROACTIVE (PROspective pioglitAzone Clinical Trial In macroVascular Events) trial. Unfortunately, the use of thiazolidinediones in individuals with diabetes mellitus and heart failure is limited because of a propensity to cause fluid retention. The underlying mechanisms of fluid retention have yet to be fully elucidated, but appear to be a dose-related class effect, exacerbated by combination therapy with insulin, and in some cases may be localized to peripheral edema. In parallel, echocardiographic studies show no significant effect of thiazolidinediones on cardiac structure or function. The design of epidemiologic studies describing an increased risk of developing heart failure in individuals with type 2 diabetes mellitus prescribed thiazolidinediones has been questioned, and a study of 'new users' of antihyperglycemic treatments found no increased risk of hospitalization for heart failure with thiazolidinedione therapy. There is also increasing evidence for the potential benefits of insulin sensitization in patients with diabetes mellitus and known heart failure, and a large observational study of over 16 000 patients with a principal discharge diagnosis of heart failure found a reduced mortality (hazard ratio [HR] 0.87; 95% CI 0.80, 0.94) in those prescribed thiazolidinediones. This benefit was offset by an increased risk of readmission with heart failure (HR 1.06; 95% CI 1.00, 1.09). Despite an increase in fluid-related events, recent studies suggest that individuals with type 2 diabetes mellitus and heart failure (New York Heart Association grade I/II) can be treated with thiazolidinediones with appropriate monitoring and adjustment of heart failure therapies. These findings would suggest the need for large-scale, prospective trials to investigate the safety and potential benefits of thiazolidinedione use in patients with diabetes mellitus and heart failure.

Left ventricular diastolic dysfunction in diabetic patients: pathophysiology and therapeutic implications

Patients with signs and symptoms of heart failure and a preserved left ventricular (LV) systolic function may have significant abnormalities in diastolic function. This condition is called diastolic heart failure (DHF) and is observed in about 40% of patients with chronic heart failure (CHF). Diabetes mellitus is one of the major risk factors for DHF. Diastolic dysfunction is observed in about 40% of patients with diabetes mellitus and correlates with poor glycemic control. Suggested mechanisms for diastolic dysfunction in the diabetic heart are: (i) abnormalities in high-energy phosphate metabolism; (ii) impaired calcium transport; (iii) interstitial accumulation of advanced glycosylation end products; (iv) imbalance in collagen synthesis and degradation; (v) abnormal microvascular function, (vi) activated cardiac renin-angiotensin system; (vii) decreased adiponectin levels; and (viii) alteration in the metabolism of free fatty acids and glucose. Because most large, randomized clinical trials in CHF have enrolled only patients with systolic dysfunction, the specific management of diastolic dysfunction is largely unknown. The CHARM-Preserved (Candesartan in Heart Failure: Assessment of Reduction in Mortality and Morbidity-Preserved) trial, the only mega trial specific for DHF (LV ejection fraction >40%), showed that the angiotensin II type 1 receptor antagonist (angiotensin receptor blocker [ARB]) candesartan cilexetil reduced hospital admissions for CHF but not cardiovascular death. Currently, the pharmacologic treatment used in systolic heart failure is also recommended in DHF and includes administration of diuretics and nitrates for pulmonary congestion, and long-term management with ACE inhibitors, ARBs, aldosterone antagonists, and beta-adrenoceptor antagonists. Poor glycemic control is associated with a high incidence of heart failure in diabetic patients, but the preferable antihyperglycemic regimen for DHF in patients with diabetes mellitus needs to be determined in further studies.

Peroxisome proliferator-activated receptor gamma as a drug target in the pathogenesis of insulin resistance

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. The activation of PPAR-gamma, an isotype of PPARs, can either increase or decrease the transcription of target genes. The genes controlled by this form of PPAR have been shown to encode proteins or peptides that participate in the pathogenesis of insulin resistance. Insulin resistance is defined as a state of reduced responsiveness to normal circulating concentrations of insulin and it often co-exists with central obesity, hypertension, dyslipidemia, and atherosclerosis. There is substantial evidence that links obesity with insulin resistance and type-2 diabetes. The early phase of obesity-related insulin resistance has 2 components: (a) interruption of lipid homeostasis leading to the increased plasma concentration of fatty acids that is normally suppressed by the activation of PPAR-gamma, and (b) activation of factors such as cytokines depressed by PPAR-gamma that cause insulin resistance. Therefore, it is logical to suggest that activation of PPAR-gamma may partially reverse the state of insulin resistance. Evidently, activation of the nuclear receptor, PPAR-gamma, by thiazolidinediones has been reported to ameliorate insulin resistance. Although hepatotoxity and possibility to induce congestive heart failure (CHF) limit the widely use of thiazolodinediones, they are still powerful weapon to fight against insulin resistance and type-2 diabetes if use properly. This article reviews the physiology of PPAR-gamma and insulin-signaling transduction, the pathogenesis of insulin resistance in obesity-related type-2 diabetes, the pharmacological role of PPAR-gamma in insulin resistance, and additional effects of thiazolidinediones.