Cardiovascular risk of rosiglitazone: another perspective

Exploring Rosiglitazone's Potential to Treat Alzheimer's Disease through the Modulation of Brain-Derived Neurotrophic Factor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that debilitates over 55 million individuals worldwide. Currently, treatments manage and alleviate its symptoms; however, there is still a need to find a therapy that prevents or halts disease progression. Since AD has been labeled as "type 3 diabetes" due to its similarity in pathological hallmarks, molecular pathways, and comorbidity with type 2 diabetes mellitus (T2DM), there is growing interest in using anti-diabetic drugs for its treatment. Rosiglitazone (RSG) is a peroxisome proliferator-activated receptor-gamma agonist that reduces hyperglycemia and hyperinsulinemia and improves insulin signaling. In cellular and rodent models of T2DM-associated cognitive decline and AD, RSG has been reported to improve cognitive impairment and reverse AD-like pathology; however, results from human clinical trials remain consistently unsuccessful. RSG has also been reported to modulate the expression of brain-derived neurotrophic factor (BDNF), a protein that regulates neuroplasticity and energy homeostasis and is implicated in both AD and T2DM. The present review investigates RSG's limitations and potential therapeutic benefits in pre-clinical models of AD through its modulation of BDNF expression.

Increased pulmonary vascular expression of receptor for advanced glycation end products (RAGE) in experimental congenital diaphragmatic hernia

AIM OF THE STUDY

Persistent pulmonary hypertension (PH) continues to be a major cause of high mortality in congenital diaphragmatic hernia (CDH). The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin protein family. Recently, RAGE has been implicated in mediating pulmonary arterial smooth muscle cell proliferation and vascular remodeling in experimental PH. RAGE has been reported to be highly upregulated in lung tissue of patients with severe PH. We designed this study to investigate the hypothesis that RAGE expression is increased in nitrofen-induced CDH.

METHODS

Pregnant rats were exposed to nitrofen or vehicle on D9. Fetuses were sacrificed on D21 and divided into nitrofen (n=16) and control group (n=16). Quantitative real-time polymerase chain reaction, Western blotting, and confocal immunofluorescence were performed.

MAIN RESULTS

Pulmonary RAGE gene expression levels were significantly increased in nitrofen-induced CDH compared to controls (p<0.003). Western blotting and confocal microscopy revealed increased pulmonary RAGE protein expression in CDH compared to controls.

CONCLUSION

This study provides striking evidence of increased gene and protein expression of RAGE in the pulmonary vasculature of nitrofen-induced CDH, suggesting that increased expression of RAGE may play a role in the pathogenesis of PH in nitrofen-induced CDH.

Increased pulmonary vascular expression of Krüppel-like factor 5 and activated survivin in experimental congenital diaphragmatic hernia

AIM OF THE STUDY

The high morbidity and mortality in congenital diaphragmatic hernia (CDH) is attributed to pulmonary hypoplasia and persistent pulmonary hypertension (PH). PH is characterized by increased pulmonary artery smooth muscle cell (SMC) proliferation, suppressed apoptosis as well as endothelial dysfunction. Krüppel-like factor 5 (KLF5) belongs to a family of transcription factors that has diverse functions during cell differentiation and embryonic development. KLF5 is preferentially expressed in proliferating SMCs but reduced in differentiated cells. KLF5 induces the expression of Survivin, a 16.5 kDa protein overexpressed in almost all malignancies but hardly detected in normal differentiated tissues. Survivin has been shown to inhibit apoptosis, promote cell proliferation, and enhance angiogenesis. Recent studies have implicated activation of KLF5 and Survivin in the pathogenesis of human and experimental PH. We designed this study to investigate the hypothesis that KLF5 and Survivin expression are increased in nitrofen-induced CDH.

METHODS

Pregnant rats were exposed to nitrofen or vehicle on D9. Fetuses were sacrificed on D21 and divided into nitrofen (n = 16) and control group (n = 16). Quantitative real-time PCR, western blotting, and confocal immunofluorescence were performed to determine pulmonary gene expression levels and protein expression of KLF5, Survivin, and phosphorylated Survivin (p-Survivin).

MAIN RESULTS

Confocal microscopy revealed markedly increased pulmonary vascular KLF5 and p-Survivin expression in lungs of nitrofen-exposed fetuses compared to controls. These results were confirmed by western blotting, showing increased pulmonary expression of KLF5 and p-Survivin. Furthermore, the relative pulmonary gene expressions of KLF5 and Survivin were significantly increased in the CDH group compared to controls (p < 0.005 rsp. p < 0.01).

CONCLUSION

This study provides striking evidence of increased gene and protein expression of KLF5 and activated Survivin in the pulmonary vasculature of nitrofen-induced CDH, suggesting that increased expression of KLF5 may activate p-Survivin expression and play an important role in the pathogenesis of PH in nitrofen-induced CDH.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

Critical role for the advanced glycation end-products receptor in pulmonary arterial hypertension etiology

Background

Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This results in both increase in pulmonary arterial pressure and pulmonary vascular resistance. Recent studies have shown the implication of the signal transducer and activator of transcription 3 (STAT3)/bone morphogenetic protein receptor 2 (BMPR2)/peroxisome proliferator‐activated receptor gamma (PPARγ) in PAH. STAT3 activation induces BMPR2 downregulation, decreasing PPARγ, which both contribute to the proproliferative and antiapoptotic phenotype seen in PAH. In chondrocytes, activation of this axis has been attributed to the advanced glycation end‐products receptor (RAGE). As RAGE is one of the most upregulated proteins in PAH patients' lungs and a strong STAT3 activator, we hypothesized that by activating STAT3, RAGE induces BMPR2 and PPARγ downregulation, promoting PAH‐PASMC proliferation and resistance to apoptosis.

Methods and Results

In vitro, using PASMCs isolated from PAH and healthy patients, we demonstrated that RAGE is overexpressed in PAH‐PASMC (6‐fold increase), thus inducing STAT3 activation (from 10% to 40% positive cells) and decrease in BMPR2 and PPARγ levels (>50% decrease). Pharmacological activation of RAGE in control cells by S100A4 recapitulates the PAH phenotype (increasing RAGE by 6‐fold, thus activating STAT3 and decreasing BMPR2 and PPARγ). In both conditions, this phenotype is totally reversed on RAGE inhibition. In vivo, RAGE inhibition in monocrotaline‐ and Sugen‐induced PAH demonstrates therapeutic effects characterized by PA pressure and right ventricular hypertrophy decrease (control rats have an mPAP around 15 mm Hg, PAH rats have an mPAP >40 mm Hg, and with RAGE inhibition, mPAP decreases to 20 and 28 mm Hg, respectively, in MCT and Sugen models). This was associated with significant improvement in lung perfusion and vascular remodeling due to decrease in proliferation (>50% decrease) and BMPR2/PPARγ axis restoration (increased by ≥60%).

Conclusion

We have demonstrated the implications of RAGE in PAH etiology. Thus, RAGE constitutes a new attractive therapeutic target for PAH.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

Effects of Endogenous PPAR Agonist Nitro-Oleic Acid on Metabolic Syndrome in Obese Zucker Rats

Nitroalkene derivatives of nitro-oleic acid (OA-NO₂) are endogenous lipid products with novel signaling properties, particularly the activation of PPARs. The goal of this proposal was to examine the therapeutic potential of this OA-NO₂ in treatment of obesity and obesity-related conditions in obese Zucker rats. The animals were randomly divided to receive OA-NO₂, oleic acid (OA), both at 7.5 μg/kg/d, or vehicle ethanol via osmotic mini-pumps for 2 weeks. Following OA-NO₂ treatment, food intake was decreased as early as the first day and this effect appeared to persist throughout the experimental period. At day 14, body weight gain was significantly reduced by OA-NO₂ treatment. This treatment significantly reduced plasma triglyceride and almost normalized plasma free fatty acid and significantly increased plasma high-density lipid (HDL). The plasma TBARS and proteinuria were paralelly decreased. In contrast, none of these parameters were affected by OA treatment. After 14 days of OA-NO₂ treatment, hematocrit, a surrogate of fluid retention associated with PPARγ agonists, remained unchanged. Together, these data demonstrated that OA-NO₂ may offer an effective and safe therapeutic intervention for obesity and obesity-related conditions.

Diabetes mellitus: new challenges and innovative therapies

Diabetes mellitus is a widespread disease prevalence and incidence of which increases worldwide. The introduction of insulin therapy represented a major breakthrough in type 1 diabetes; however, frequent hyper- and hypoglycemia seriously affects the quality of life of these patients. New therapeutic approaches, such as whole pancreas transplant or pancreatic islet transplant, stem cell, gene therapy and islets encapsulation are discussed in this review. Regarding type 2 diabetes, therapy has been based on drugs that stimulate insulin secretion (sulphonylureas and rapid-acting secretagogues), reduce hepatic glucose production (biguanides), delay digestion and absorption of intestinal carbohydrate (alpha-glucosidase inhibitors) or improve insulin action (thiazolidinediones). This review is also focused on the newer therapeutically approaches such as incretin-based therapies, bariatric surgery, stem cells and other emerging therapies that promise to further extend the options available. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Some of these therapies rely on genetic modification of non-differentiated cells to express pancreatic endocrine developmental factors, promoting differentiation of non-endocrine cells into β-cells, enabling synthesis and secretion of insulin in a glucose-regulated manner. Alternative therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications. In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality-life and allow personalized therapy-planning in the near future.

Type 2 diabetes, mitochondrial biology and the heart

Diabetes is recognized as an independent risk factor for cardiovascular morbidity and mortality. This is due, in large part, to premature atherosclerosis, enhanced thrombogenicity and activation of systemic inflammatory programs with resultant vascular dysfunction. More enigmatic mechanisms underpinning diabetes-associated cardiac pathophysiology include the direct metabolic consequences of this disease on the myocardium. Nevertheless, a role for diabetes-associated disruption in cardiac contractile mechanics and in increasing cardiomyocyte susceptibility to ischemic-stress has been implicated independent of vascular pathology. This review will focus broadly on the direct effects of diabetes on the cardiac myocardium with more specific reference to the role of the modulation of cardiomyocyte mitochondrial function in these disease processes. This focus in part, stems from the growing recognition that in some instances mitochondrial dysfunction is central to the development of insulin resistance and diabetes, and in others, diabetes associated disruption in mitochondrial function exacerbates and accentuates the pathophysiology of diabetes.