Troglitazone treatment increases plasma vascular endothelial growth factor in diabetic patients and its mRNA in 3T3-L1 adipocytes

Thiazolidinedione use and retinal fluid in the comparison of age-related macular degeneration treatments trials

Background

Thiazolidinediones, commonly used antidiabetic medications, have been associated with an increased risk of development of diabetic macular oedema and increased vascular endothelial cell permeability. Macular neovascularisation in age-related macular degeneration (AMD) and associated fluid leakage may be influenced by thiazolidinediones. This study aims to determine the association between thiazolidinedione usage and retinal morphological outcomes or visual acuity (VA) in patients treated with bevacizumab or ranibizumab for neovascular AMD (nAMD).

Methods

Secondary analysis of data from the Comparison of Age-related Macular Degeneration Treatments Trials. Participant self-reported diabetes status and thiazolidinedione usage at baseline. VA, intraretinal, subretinal and subretinal pigment epithelium fluid, and foveal thickness of retinal layers were evaluated at baseline and during 2-year follow-up. Comparisons of outcomes between thiazolidinedione usage groups were adjusted by macular neovascularisation lesion type in multivariable regression models.

Results

Patients taking thiazolidinedione (n=30) had lower adjusted mean VA score at baseline (difference −6.2 letters; p=0.02), greater proportion with intraretinal fluid (IRF) at year 2 (75% vs 50%, adjusted OR 2.8; p=0.04), greater mean decrease in subretinal tissue complex thickness from baseline at year 1 (difference −75.1 um; p=0.02) and greater mean decrease in subretinal thickness at year 1 (difference −41.9 um; p=0.001) and year 2 (difference −43.3 um; p=0.001).

Conclusions

In this exploratory analysis, patients with diabetes taking thiazolidinediones and treated with bevacizumab or ranibizumab for nAMD had worse baseline mean VA, greater reductions in subretinal and subretinal tissue complex thickness from baseline, and greater proportions with IRF comparing to patients not taking thiazolidinediones.

Trial registration number

ClinicalTrials.gov NCT00593450.

Subclinical Hypothyroidism in TAFRO Syndrome

Objective TAFRO syndrome is rare, and its underlying mechanisms currently remain unknown. Furthermore, standard therapeutic strategies have yet to be established. One of the hallmarks of TAFRO is pathological hypercytokinemia, which involves vascular endothelial growth factor (VEGF). A correlation has been reported between elevated VEGF and TSH levels in patients with hypothyroidism. Although hypothyroidism is a common endocrine abnormality, its clinical significance in TAFRO syndrome remains unclear. Methods and Patients We investigated six patients diagnosed with TAFRO syndrome and examined their thyroid function in detail to obtain a deeper understanding of its relationship with cytokines and the manifestations of thyroid abnormalities as well as their clinical significance in TAFRO syndrome. Results Five patients had subclinical hypothyroidism, while one had clinical hypothyroidism. Plasma VEGF levels were elevated in all patients, with a mean level of 256 pg/mL. Treatment with thyroxine supplements and immunotherapy or chemotherapy improved the symptoms of TAFRO syndrome without recurrence as well as increased the VEGF levels in three patients. Conclusion The present results suggest that subclinical hypothyroidism may be a potential factor in the pathogenesis and symptomatology of TAFRO syndrome with VEGF elevation.

Diabetic macular edema: Evidence-based management

Diabetic macular edema (DME) is the most common cause of vision loss in patients with diabetic retinopathy with an increasing prevalence tied to the global epidemic in type 2 diabetes mellitus. Its pathophysiology starts with decreased retinal oxygen tension that manifests as retinal capillary hyperpermeability and increased intravascular pressure mediated by vascular endothelial growth factor (VEGF) upregulation and retinal vascular autoregulation, respectively. Spectral domain optical coherence tomography (SD-OCT) is the cornerstone of clinical assessment of DME. The foundation of treatment is metabolic control of hyperglycemia and blood pressure. Specific ophthalmic treatments include intravitreal anti-VEGF drug injections, intravitreal corticosteroid injections, focal laser photocoagulation, and vitrectomy, but a substantial fraction of eyes respond incompletely to all of these modalities resulting in visual loss and disordered retinal structure and vasculature visible on SD-OCT and OCT angiography. Efforts to close the gap between the results of interventions within randomized clinical trials and in real-world contexts, and to reduce the cost of care increasingly occupy innovation in the social organization of ophthalmic care of DME. Pharmacologic research is exploring other biochemical pathways involved in retinal vascular homeostasis that may provide new points of intervention effective in those cases unresponsive to current treatments.

Successful treatment of refractory TAFRO syndrome with elevated vascular endothelial growth factor using thyroxine supplements

Although the clinical significance of hypothyroidism in TAFRO syndrome is unknown, vascular endothelial growth factor (VEGF) levels decreased with improvements in the condition of our refractory TAFRO cases after thyroxine supplement therapy. Our results indicate that elevated VEGF levels are a potential factor in the pathogenesis and anasarca of TAFRO syndrome with hypothyroidism.

Risk factors for diabetic macular oedema in type 2 diabetes: A case-control study in a United Kingdom primary care setting

AIM

To identify risk factors associated with the development of DMO among patients diagnosed with type 2 diabetes managed in a primary care setting in the UK.

METHODS

A case-control study nested in a cohort of incident Type 2 diabetes identified in The Health Improvement Network database from 2000-2007. Cases were people with DMO (N=211) and controls were a DMO-free sample (N=2194). No age restrictions were applied. Adjusted odds ratios and 95%CIs were estimated (OR; 95%CI).

RESULTS

DMO increased with high alcohol use (2.88; 1.49-5.55), cataracts (4.10; 2.73-6.15), HbA1c ≥7% (1.58; 1.08-2.32), systolic blood pressure ≥160mm Hg (2.03; 1.17-3.53), total cholesterol ≥5mmol/L (1.66; 1.15-2.39), LDL ≥3mmol/L (1.73; 1.14-2.61), and microalbuminuria (1.78; 1.16-2.73). Diuretic drugs were associated with a reduced risk of DMO (0.68; 0.47-0.99), as did smoking (0.47; 0.28-0.77), overweight (0.53; 0.30-0.96) or obesity (0.52; 0.30-0.91) at diabetes diagnosis, and high triglyceride levels (0.51; 0.35-0.74). Patients treated with anti-diabetic drugs showed higher risk of DMO than non-treated patients, particularly those with sulphonylureas (3.40; 2.42-4.78), insulin (3.21; 1.92-5.36) or glitazones (1.88; 1.17-3.04).

CONCLUSION

In patients with type 2 diabetes managed in primary care, multiple factors associated with DMO were identified, such as cataracts, microalbuminuria and high levels of HbA1c, systolic BP, total cholesterol, and LDL. Diuretic drugs were associated with a reduced risk of DMO. Treated diabetes, particularly with sulphonylureas, insulin or glitazones showed highest risk of DMO. The inverse association between smoking, obesity, and triglycerides and DMO deserves further research.

Role of Peroxisome Proliferator-Activated Receptor γ in Ocular Diseases

Peroxisome proliferator-activated receptor γ (PPAR γ), a member of the nuclear receptor superfamily, is a ligand-activated transcription factor that plays an important role in the control of a variety of physiological processes. The last decade has witnessed an increasing interest for the role played by the agonists of PPAR γ in antiangiogenesis, antifibrosis, anti-inflammation effects and in controlling oxidative stress response in various organs. As the pathologic mechanisms of major blinding diseases, such as age-related macular degeneration (AMD), diabetic retinopathy (DR), keratitis, and optic neuropathy, often involve neoangiogenesis and inflammation- and oxidative stress-mediated cell death, evidences are accumulating on the potential benefits of PPAR γ to improve or prevent these vision threatening eye diseases. In this paper we describe what is known about the role of PPAR γ in the ocular pathophysiological processes and PPAR γ agonists as novel adjuvants in the treatment of eye diseases.

Eicosapentaenoic acid upregulates VEGF-A through both GPR120 and PPARγ mediated pathways in 3T3-L1 adipocytes

Vascular endothelial growth factor-A (VEGF-A) released from adipocytes promotes angiogenesis; and thereby ameliorates the local hypoxia-induced adipose inflammation and insulin resistance. Here, we newly found that eicosapentaenoic acid (EPA) upregulated both mRNA expression and release of VEGF-A in mature 3T3-L1 adipocytes. Silencing mRNA of G-protein coupled receptor 120 (GPR120) and specific inhibition of peroxisome proliferator-activated receptor γ (PPARγ) by GW9662 respectively attenuated the EPA-induced augmentation of VEGF-A release by adipocytes. Furthermore, transfection of GPR120 gene alone and PPARγ gene alone to HEK293 cells respectively increased the promoter activity of VEGF-A as assessed by luciferase reporter assay, which was further augmented when both genes were co-transfected. Promoter deletion analysis and chromatin immunoprecipitation assay revealed that co-transfection of GPR120 enhanced EPA-induced PPARγ binding to PPAR-response element in VEGF-A promoter region. Thus, by the synchronized activation of a membrane receptor GRP120 and a nuclear receptor PPARγ, EPA enhances VEGF-A production in adipocytes.

PPARγ agonist-induced fluid retention depends on αENaC expression in connecting tubules

BACKGROUND/AIMS

Thiazolidinediones (TZDs, like rosiglitazone (RGZ)) are peroxisome proliferator-activated receptor γ (PPARγ) agonists used to treat type 2 diabetes. Clinical limitations include TZD-induced fluid retention and body weight (BW) increase, which are inhibited by amiloride, an epithelial-sodium channel (ENaC) blocker. RGZ-induced fluid retention is maintained in mice with αENaC knockdown in the collecting duct (CD). Since ENaC in the connecting tubule (CNT) rather than in CD appears to be critical for normal NaCl retention, we aimed to further explore the role of ENaC in CNT in RGZ-induced fluid retention.

METHODS

Mice with conditional inactivation of αENaC in both CNT and CD were used (αENaC lox/lox AQP2-Cre; 'αENaC-CNT/CD-KO') and compared with littermate controls (αENaC lox/lox mice; 'WT'). BW was monitored and total body water (TBW) and extracellular fluid volume (ECF) were determined by bioelectrical impedance spectroscopy (BIS) before and after RGZ (320 mg/kg diet for 10 days).

RESULTS

On regular NaCl diet, αENaC-CNT/CD-KO had normal BW, TBW, ECF, hematocrit, and plasma Na(+), K(+), and creatinine, associated with an increase in plasma aldosterone compared with WT. Challenging αENaC-CNT/CD-KO with a low NaCl diet unmasked impaired NaCl and K homeostasis, consistent with effective knockdown of αENaC. In WT, RGZ increased BW (+6.1%), TBW (+8.4%) and ECF (+10%), consistent with fluid retention. These changes were significantly attenuated in αENaC-CNT/CD-KO (+3.4, 1.3, and 4.3%).

CONCLUSION

Together with the previous studies, the current results are consistent with a role of αENaC in CNT in RGZ-induced fluid retention, which dovetails with the physiological relevance of ENaC in this segment.

Activation of a retinoic acid receptor pathway by thiazolidinediones induces production of vascular endothelial growth factor/vascular permeability factor in OP9 adipocytes

Thiazolidinediones, ligands of peroxisome proliferator-activated receptorγ (PPARγ), are used in the management of type 2 diabetes mellitus. However, they can cause edema, which often leads to a discontinuation of treatment. The mechanism by which thiazolidinediones induce edema is poorly understood. We have confirmed that troglitazone (TGZ), a thiazolidinedione, induced the differentiation of a preadipocyte cell line, OP9, into adipocytes. The differentiated OP9 cells produced vascular permeability factors and the activity was completely neutralized by an antibody against vascular endothelial growth factor (VEGF). TGZ induced the expression of VEGF but not interleukin-6 and monocyte chemoattractant protein-1. 2-chloro-5-nitrobenzanilide (GW9662) blocked both the differentiation and the production of VEGF induced by TGZ. 15-deoxy-Δ(12,14)-Prostaglandin J2, a natural ligand of PPARγ, and another PPARγ agonist, ginkgolic acid, also induced an increase in the expression of VEGE as well as the differentiation of OP9 cells. Indomethacin, a nonsteroidal anti-inflammatory drug (NSAID) with PPARγ activity, up-regulated VEGF expression, but acetylsalicylic acid, a NSAID without PPARγ activity, did not. Although VEGF expression was enhanced under hypoxic conditions, the expression of hypoxia inducible factor and Ets-1 was down-regulated during the TGZ-induced differentiation. On the other hand, retinoic acid enhanced the expression of VEGF despite inhibiting the TGZ-induced differentiation. Moreover, retinoic acid receptor (RAR) β expression was increased by TGZ and retinoic acid. These findings suggested that the major adipocyte-derived vascular permeability factor produced in response to TGZ was VEGF, and a RAR pathway was involved in the production.

Molecular Implications of the PPARs in the Diabetic Eye

Diabetic retinopathy (DR) remains as the leading cause of blindness among working age individuals in developed countries. Current treatments for DR (laser photocoagulation, intravitreal corticosteroids, intravitreal anti-VEGF agents, and vitreoretinal surgery) are applicable only at advanced stages of the disease and are associated with significant adverse effects. Therefore, new pharmacological treatments for the early stages of the disease are needed. Emerging evidence indicates that peroxisome proliferator-activator receptors (PPARs) agonists (in particular PPARα) are useful for the treatment of DR. However, the underlying molecular mechanisms are far from being elucidated. This paper mainly focuses on PPARs expression in the diabetic eye, its molecular implications, and the effect of PPAR agonists as a new approach for the treatment of DR. The availability of this new strategy will not only be beneficial in treating DR but may also result in a shift towards treating earlier stages of diabetic retinopathy, thus easing the burden of this devastating disease (Cheung et al. (2010)).

The case for intraocular delivery of PPAR agonists in the treatment of diabetic retinopathy

Background

Systemic therapeutics targeting the peroxisome proliferator-activated receptors have been found to be beneficial in the treatment of diabetic retinopathy. In this paper, we provide a rationale for the use of these therapeutics as intraocular agents. In addition, we introduce the peroxisome proliferator-activated receptors and describe their functions in response to the drugs.

Discussion

Based on the evidence of large-scale clinical studies investigating the systemic administration of fenofibrate, this ligand for peroxisome proliferator-activated receptor-α is potentially a good candidate for intraocular delivery. Here, we describe the mechanisms by which it might be acting to improve diabetic retinopathy, its relative safety and we speculate on how it could be developed for intraocular delivery.

Summary

In this paper, we provide a rationale for the further investigation of peroxisome proliferator-activated receptor-α agonists as intraocular agents for the treatment of diabetic retinopathy.

Tesaglitazar, a dual PPAR-α/γ agonist, hamster carcinogenicity, investigative animal and clinical studies

Tesaglitazar was developed as a dual peroxisome proliferator-activated receptor (PPARα/γ). To support the clinical program, a hamster carcinogenicity study was performed. The only neoplastic findings possibly related to treatment with tesaglitazar were low incidences of hemangioma and hemangiosarcoma in the liver of male animals. A high-power, two-year investigative study with interim necropsies was performed to further elucidate these findings. Treatment with tesaglitazar resulted in changes typical for exaggerated PPARα pharmacology in rodents, such as hepatocellular hypertrophy and hepatocellular carcinoma, but not an increased frequency of hemangiosarcomas. At the highest dose level, there was an increased incidence of sinusoidal dilatation and hemangiomas. No increased endothelial cell (EC) proliferation was detected in vivo, which was confirmed by in vitro administration to ECs. Immunohistochemistry and gene expression analyses indicated increased cellular stress and vascular endothelial growth factor (VEGF) expression in the liver, which may have contributed to the sinusoidal dilatation. A two-fold increase in the level of circulating VEGF was detected in the hamster at all dose levels, whereas no effect on VEGF was observed in patients treated with tesaglitazar. In conclusion, investigations have demonstrated that tesaglitazar does not produce hemangiosarcomas in hamster despite a slight effect on vascular morphology in the liver.

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.

Regulation of HIF-1{alpha} activity in adipose tissue by obesity-associated factors: adipogenesis, insulin, and hypoxia

The transcription factor HIF-1α activity is increased in adipose tissue to contribute to chronic inflammation in obesity. However, its upstream and downstream events remain to be characterized in adipose tissue in obesity. We addressed this issue by investigating adipocyte HIF-1α activity in response to obesity-associated factors, such as adipogenesis, insulin, and hypoxia. In adipose tissue, both HIF-1α mRNA and protein were increased by obesity. The underlying mechanism was investigated in 3T3-L1 adipocytes. HIF-1α mRNA and protein were augmented by adipocyte differentiation. In differentiated adipocytes, insulin further enhanced HIF-1α in both levels. Hypoxia enhanced only HIF-1α protein, not mRNA. PI3K and mTOR activities are required for the HIF-1α expression. Function of HIF-1α protein was investigated in the regulation of VEGF gene transcription. ChIP assay shows that HIF-1α binds to the proximal hypoxia response element in the VEGF gene promoter, and its function is inhibited by a corepressor composed of HDAC3 and SMRT. These observations suggest that of the three obesity-associated factors, all of them are able to augment HIF-1α protein levels, but only two (adipogenesis and insulin) are able to enhance HIF-1α mRNA activity. Adipose tissue HIF-1α activity is influenced by multiple signals, including adipogenesis, insulin, and hypoxia in obesity. The transcriptional activity of HIF-1α is inhibited by HDAC3-SMRT corepressor in the VEGF gene promoter.

Rosiglitazone attenuates hypoxia-induced pulmonary arterial hypertension in rats

BACKGROUND AND OBJECTIVE

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) is decreased in the lungs of patients with pulmonary hypertension, and PPARgamma ligands have been associated with the release of vasoactive substances from vascular endothelial cells and prevention of vascular remodelling. We hypothesized that PPARgamma may play a critical role in the development of pulmonary hypertension induced by chronic hypoxia.

METHODS

Male adult Sprague-Dawley rats were exposed to normoxia, normoxia and rosiglitazone (8 mg/kg orally, 5 days/week), hypoxia (12% inspired O(2) fraction), or hypoxia and rosiglitazone for 4 weeks. On the last day of the fourth week, pulmonary arterial pressure was measured and morphological changes in pulmonary vessels were assessed. The expression of PPARgamma, endothelin (ET)-1 and vascular endothelial growth factor (VEGF) was also analysed.

RESULTS

Rosiglitazone inhibited the development of pulmonary hypertension, and pulmonary vascular remodelling induced by chronic hypoxia. PPARgamma expression was decreased and expression of ET-1 and VEGF was increased in lung tissues of the hypoxia group. Rosiglitazone treatment prevented the hypoxia-induced reduction in PPARgamma expression, and restored ET-1 and VEGF expression almost to the levels of the normoxia group.

CONCLUSIONS

Rosiglitazone inhibited the development of pulmonary hypertension induced by chronic hypoxia, perhaps by reversing the changes in PPARgamma, ET-1 and VEGF expression induced by hypoxia. These findings indicate that rosiglitazone may be beneficial in the treatment of chronic hypoxic pulmonary hypertension.

Cardiovascular sex differences influencing microvascular exchange

The vital role of the cardiovascular (CV) system is maintenance of body functions via the matching of exchange to tissue metabolic demand. Sex-specific differences in the regulatory mechanisms of CV function and the metabolic requirements of men and women, respectively, have been identified and appreciated. This review focuses on sex differences of parameters influencing exchange at the point of union between blood and tissue, the microvasculature. Microvascular architecture, blood pressure (hydrostatic and oncotic), and vascular permeability, therefore, are discussed in the specific context of sex in health and disorders. It is notable that when sex differences exist, they are generally subtle but significant. In the aggregate, though, they can give rise to profoundly different phenotypes. The postulated mechanisms responsible for sex differences are attributed to genomics, epigenetics, and sex hormones. Depending on specific circumstances, the effect of the combined factors can range from insignificant to lethal. Identifying and understanding key signalling mechanisms bridging genomics/sex hormones and microvascular exchange properties within the scope of this review holds significant promise for sex-specific prevention and treatment of vascular barrier dysfunction.

Concomitant therapy with pioglitazone and insulin for the treatment of type 2 diabetes

To prevent hyperinsulinemia, which may cause atherosclerosis, thiazolidinediones (TZDs), also known as insulin sensitizers, are often added to the therapeutic regimen of patients with type 2 diabetes who are receiving insulin. The combination of insulin with pioglitazone, a TZD, reduces glycoated hemoglobin (HbA(1c)) by 0.6%-2.1%. The higher the HbA(1c) baseline the larger the therapeutic reduction of HbA(1c). This combination therapy has been shown to be beneficial even in lean Japanese patients with diabetes. It should be noted that such combination therapy is much more useful when the main clinical aim is lowering not postprandial, but fasting and nocturnal glycemia. The glycemic-lowering effects of pioglitazone alone occur slowly, whereas the addition of insulin to pioglitazone often shows a dramatic glucose-lowering effect. Thus, such combination therapy increases the possibility of frequent hypoglycemia within 1 to 2 months of combining the drugs. Severe hypoglycemia in patients using this therapy is rare. Patients treated with combination therapy who show a predominant reduction of glycemia often have severe edema; in 10%-20% of patients, combination therapy leads to drug-related congestive heart failure (CHF). However, this phenomenon is usually weakened if low doses of pioglitazone which are added to insulin therapy (ie, 15 mg/day or even 7.5 mg/day for women). It is well known that pioglitazone has an anti-atherosclerotic effect, although it is unclear if hyperinsulinemia induces atherogenic changes, either directly or indirectly, by the promotion of obesity. Until now, we have not confirmed whether the anti-atherosclerotic effects of pioglitazone exceed the supposed disadvantageous action of insulin when used in combination therapy. The addition of pioglitazone tends to reduce daily insulin dosages, but study findings have not been consistent. Improvement of lipid profiles has also been weak with this combination therapy. Long-term trials are needed before any conclusions can be reached concerning atherogenic effects of treatment for type 2 diabetes. Combination therapy of even small doses of pioglitazone with insulin should be primarily used for patients who achieve insufficient reduction in glycemia with insulin monotherapy.

Thiazolidinediones enhance vascular endothelial growth factor expression and induce cell growth inhibition in non-small-cell lung cancer cells

Background

It is known that thiazolidinediones are involved in regulating the expression of various genes, including the vascular endothelial growth factor (VEGF) gene via peroxisome proliferator-activated receptor γ (PPARγ); VEGF is a prognostic biomarker for non-small-cell lung cancer (NSCLC).

Methods

In this study, we investigated the effects of troglitazone and ciglitazone on the mRNA expression of VEGF and its receptors in human NSCLC cell lines, RERF-LC-AI, SK-MES-1, PC-14, and A549. These mRNA expressions were evaluated by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. We also studied the effect of Je-11, a VEGF inhibitor, on the growth of these cells.

Results

In NSCLC cells, thiazolidinediones increased the mRNA expression of VEGF and neuropilin-1, but not that of other receptors such as fms-like tyrosine kinase and kinase insert domain receptor-1. Furthermore, the PPARγ antagonist GW9662 completely reversed this thiazolidinedione-induced increase in VEGF expression. Furthermore, the addition of VEGF inhibitors into the culture medium resulted in the reversal of thiazolidinedione-induced growth inhibition.

Conclusions

Our results indicated that thiazolidinediones enhance VEGF and neuropilin-1 expression and induce the inhibition of cell growth. We propose the existence of a pathway for arresting cell growth that involves the interaction of thiazolidinedione-induced VEGF and neuropilin-1 in NSCLC.

Effects of intensive insulin therapy alone and with added pioglitazone on renal salt/water balance and fluid compartment shifts in type 2 diabetes

OBJECTIVE

To evaluate the effects of intensive insulin therapy alone or with added pioglitazone on renal salt/water balance and body fluid compartment shifts in type 2 diabetes.

METHODS

A total of 25 insulin-treated, obese patients with type 2 diabetes were randomized to pioglitazone 45 mg (n = 12) or placebo (n = 13) and treated intensively for 12-16 weeks to achieve equivalent glycaemic control. We measured total body water (TBW) and extracellular/intracellular fluid by bioimpedance analysis; plasma/RBC volume with I(131)albumin; sodium handling by fractional excretion of sodium/lithium (FeNa/FeLi) and other renal/hormonal parameters.

RESULTS

Intensification of insulin therapy and the addition of pioglitazone significantly improved glycaemia (HbA1C 7.8-7.2% and 7.6-7.1%) and increased body weight (1.7 and 4.9 kg) respectively. TBW increased 1.7 l with insulin alone (65% intracellular) and 1.6 l with added pioglitazone (75% extracellular) (p = 0.06 and 0.09 respectively). Plasma volume increased 0.2 +/- 0.1 l with insulin alone (p = 0.05) and 0.4 +/- 0.1 l with added pioglitazone (p < 0.05). Extravascular, extracellular (interstitial) fluid increased significantly and more with added pioglitazone (0.8 +/- 0.2 l, p < 0.01) than with insulin alone (0.4 +/- 0.2 l, p = ns). At steady-state, FeLi (marker of proximal-tubular sodium delivery to the distal nephron) increased significantly with added pioglitazone (12.4 +/- 1.3 to 18.0 +/- 3.2%) vs. no significant change with insulin alone (15.4 +/- 1.2 to 14.5 +/- 2.3%). There were no significant changes in the other parameters.

CONCLUSION

In intensively insulin-treated obese type 2 diabetic patients, at equivalent glycaemic control, the addition of pioglitazone causes greater weight gain, but a similar increase in body water that is mainly extracellular and interstitial compared with intracellular increase with insulin therapy alone. Pioglitazone also increases the filtered load of sodium reabsorbed at the distal nephron with no net change in FeNa.

Differential healing after sirolimus, paclitaxel, and bare metal stent placement in combination with peroxisome proliferator-activator receptor gamma agonists: requirement for mTOR/Akt2 in PPARgamma activation

RATIONALE

Sirolimus-eluting coronary stents (SESs) and paclitaxel-eluting coronary stents (PESs) are used to reduce restenosis but have different sites of action. The molecular targets of sirolimus overlap with those of the peroxisome proliferator-activated receptor (PPAR)gamma agonist rosiglitazone (RSG) but the consequence of this interaction on endothelialization is unknown.

OBJECTIVE

Using the New Zealand white rabbit iliac model of stenting, we examined the effects of RSG on SESs, PESs, and bare metal stents endothelialization.

METHODS AND RESULTS

Animals receiving SESs, PESs, or bare metal stents and either RSG (3 mg/kg per day) or placebo were euthanized at 28 days, and arteries were evaluated by scanning electron microscopy. Fourteen-day organ culture and Western blotting of iliac arteries and tissue culture experiments were conducted. Endothelialization was significantly reduced by RSG in SESs but not in PESs or bare metal stents. Organ culture revealed reduced vascular endothelial growth factor in SESs receiving RSG compared to RSG animals receiving bare metal stent or PESs. Quantitative polymerase chain reaction in human aortic endothelial cells (HAECs) revealed that sirolimus (but not paclitaxel) inhibited RSG-induced vascular endothelial growth factor transcription. Western blotting demonstrated that inhibition of molecular signaling in SES+RSG-treated arteries was similar to findings in HAECs treated with RSG and small interfering RNA to PPARgamma, suggesting that sirolimus inhibits PPARgamma. Transfection of HAECs with mTOR (mammalian target of rapamycin) short hairpin RNA and with Akt2 small interfering RNA significantly inhibited RSG-mediated transcriptional upregulation of heme oxygenase-1, a PPARgamma target gene. Chromatin immunoprecipitation assay demonstrated sirolimus interferes with binding of PPARgamma to its response elements in heme oxygenase-1 promoter.

CONCLUSIONS

mTOR/Akt2 is required for optimal PPARgamma activation. Patients who receive SESs during concomitant RSG treatment may be at risk for delayed stent healing.

Diabetic cardiomyopathy

Diabetic cardiomyopathy is a distinct primary disease process, independent of coronary artery disease, which leads to heart failure in diabetic patients. Epidemiological and clinical trial data have confirmed the greater incidence and prevalence of heart failure in diabetes. Novel echocardiographic and MR (magnetic resonance) techniques have enabled a more accurate means of phenotyping diabetic cardiomyopathy. Experimental models of diabetes have provided a range of novel molecular targets for this condition, but none have been substantiated in humans. Similarly, although ultrastructural pathology of the microvessels and cardiomyocytes is well described in animal models, studies in humans are small and limited to light microscopy. With regard to treatment, recent data with thiazoledinediones has generated much controversy in terms of the cardiac safety of both these and other drugs currently in use and under development. Clinical trials are urgently required to establish the efficacy of currently available agents for heart failure, as well as novel therapies in patients specifically with diabetic cardiomyopathy.

Risk management in the treatment of type 2 diabetes with pioglitazone

INTRODUCTION

Type 2 diabetes mellitus is one of the most important cardiovascular risk factors. Insulin-resistance represents the common mechanism that leads to type 2 diabetes in obese subjects. Pioglitazone is an insulin-sensitizing agent available for treatment of type 2 diabetes. Large clinical trials have demonstrated the effectiveness of pioglitazone in achieving metabolic control and reducing cardiovascular morbidity and mortality.

AIM

The purpose of this article is to review the effectiveness and tolerability of pioglitazone in the prevention and management of atherosclerosis in patients with type 2 diabetes.

EVIDENCE REVIEW

We reviewed the main monotherapy and comparative studies of pioglitazone, and particularly the recent evidence in the field of atherosclerosis and cardiovascular prevention.

PLACE IN THERAPY

The current evidence shows that pioglitazone is an effective option in the treatment of type 2 diabetes. More studies are needed to establish a role for pioglitazone in atherosclerosis prevention beyond glycemic control.

Diabetic cardiomyopathy--a distinct disease?

Diabetic individuals have a significantly increased likelihood of developing cardiovascular disease. Whilst part of this association is explained by the presence of concomitant risk factors, large epidemiological studies have consistently reported diabetes as a strong risk factor for the development of heart failure after adjusting for such covariates. This has resulted in the notion that there is a distinct cardiomyopathy specific to diabetes, termed 'diabetic cardiomyopathy'. The natural history is characterized by a latent subclinical period, during which there is evidence of diastolic dysfunction and left ventricular hypertrophy, before overt clinical deterioration and systolic failure ensue. These clinical findings have been supported by a growing body of experimental data which support the notion that diabetes inflicts a direct insult to the myocardium, with cellular, structural and functional changes manifest as the diabetic myocardial phenotype. Several of these mechanisms appear to work in unison, forming complicated reciprocal pathways of disease. Reactive oxygen species and alterations in intracellular calcium homeostasis appear to play significant roles in many of these mechanisms. Determining the hierarchy of this cascade of disease will allow identification of the pathological trigger most responsible for disease. Translational research in this field is currently hindered by a lack of clinical studies and intervention trials specifically in patients with diabetic cardiomyopathy. Future clinical and experimental studies of accurate models of diabetic cardiomyopathy should help to define the true aetiology and lead to the development of specific pharmacotherapies for this condition, ultimately reducing the increased cardiovascular morbidity and mortality in diabetic patients.

Proangiogenic contribution of adiponectin toward mammary tumor growth in vivo

PURPOSE

Adipocytes represent one of the most abundant constituents of the mammary gland. They are essential for mammary tumor growth and survival. Metabolically, one of the more important fat-derived factors ("adipokines") is adiponectin (APN). Serum concentrations of APN negatively correlate with body mass index and insulin resistance. To explore the association of APN with breast cancer and tumor angiogenesis, we took an in vivo approach aiming to study its role in the mouse mammary tumor virus (MMTV)-polyoma middle T antigen (PyMT) mammary tumor model.

EXPERIMENTAL DESIGN

We compared the rates of tumor growth in MMTV-PyMT mice in wild-type and APN-null backgrounds.

RESULTS

Histology and micro-positron emission tomography imaging show that the rate of tumor growth is significantly reduced in the absence of APN at early stages. PyMT/APN knockout mice exhibit a reduction in their angiogenic profile resulting in nutrient deprivation of the tumors and tumor-associated cell death. Surprisingly, in more advanced malignant stages of the disease, tumor growth develops more aggressively in mice lacking APN, giving rise to a larger tumor burden, an increase in the mobilization of circulating endothelial progenitor cells, and a gene expression fingerprint indicative of more aggressive tumor cells.

CONCLUSIONS

These observations highlight a novel important contribution of APN in mammary tumor development and angiogenesis, indicating that APN has potent angio-mimetic properties in tumor vascularization. However, in tumors deprived of APN, this antiangiogenic stress results in an adaptive response that fuels tumor growth through mobilization of circulating endothelial progenitor cells and the development of mechanisms enabling massive cell proliferation despite a chronically hypoxic microenvironment.

Glitazone use associated with diabetic macular edema

PURPOSE

To determine the ocular safety of glitazones in patients with diabetes, we investigated the association of diabetic macular edema (DME) in a large population of glitazone users.

DESIGN

Prospective cohort study.

METHODS

The study was conducted at Kaiser Permanente Southern California. About 170,000 persons with diabetes were identified using the Diabetes Case Identification Database. Glitazone drug use was obtained from the pharmacy database. The main outcome measure was the development of macular edema (ME). The chi2 test was used to compare proportions and t tests were used for means. Logistic regression analysis was used to adjust for potential confounding variables.

RESULTS

In 2006, there were 996 new cases of ME. Glitazone users were more likely to develop ME in 2006 (odds ratio [OR], 2.6; 95% confidence interval [CI], 2.4 to 3.0). After excluding patients who did not have the drug benefit, did not have an eye exam, and had a HgA1c <7.0, glitazone use was still associated with an increased risk of developing ME (OR, 1.6; 95% CI, 1.4 to 1.8).

CONCLUSION

The current study appears to show that the glitazone class of drug is associated with DME. After adjusting for confounding factors of age, glycemic control, and insulin use, glitazones are still modestly associated with DME. A more in-depth study will need to be done to evaluate the role of other confounding factors. When treating patients with DME, ophthalmologists should consider the role of the glitazones.

Diabetic macular edema: pathogenesis and treatment

Diabetic macular edema is a major cause of visual impairment. The pathogenesis of macular edema appears to be multifactorial. Laser photocoagulation is the standard of care for macular edema. However, there are cases that are not responsive to laser therapy. Several therapeutic options have been proposed for the treatment of this condition. In this review we discuss several factors and mechanisms implicated in the etiology of macular edema (vasoactive factors, biochemical pathways, anatomical abnormalities). It seems that combined pharmacologic and surgical therapy may be the best approach for the management of macular edema in diabetic patients.

Effect of pioglitazone and rosiglitazone on mediators of endothelial dysfunction, markers of angiogenesis and inflammatory cytokines in type-2 diabetes

The purpose of this study was to assess the effects of PPAR-gamma agonists (pioglitazone and rosiglitazone) on mediators of endothelial dysfunction and markers of angiogenesis in patients with type-2 diabetes. Pioglitazone group showed favorable reductions in serum total cholesterol, triglycerides, LDL cholesterol, VLDL cholesterol and increase in HDL cholesterol as compared to rosiglitazone group, after 16 weeks of treatment and also with control group. There was significant reduction of CRP level in pioglitazone and rosiglitazone group. The level of serum TNF-alpha decreased significantly in pioglitazone and mildly decreased in rosiglitazone group. The level of VEGF, IL-8 and Angiogenin were increased in pioglitazone than rosiglitazone group. There were no significant changes observed in the serum angiogenin and IL-8 levels in the control group. Pioglitazone and rosiglitazone therapy in type-2 diabetes subjects have additional benefits of reducing mediators of endothelial dysfunction. Increase in angiogenesis markers in patients receiving pioglitazone could have variable effects in diabetic nephropathy and retinopathy as there may be increased vascular neogenesis. Pioglitazone has advantage over rosiglitazone in lowering lipid and proinflammatory cytokines.

Thiazolidinedione-induced fluid retention is independent of collecting duct alphaENaC activity

Thiazolidinediones are agonists of peroxisome proliferator-activated receptor gamma (PPARgamma) that can induce fluid retention and weight gain through unclear mechanisms. To test a proposed role for the epithelial sodium channel ENaC in thiazolidinedione-induced fluid retention, we used mice with conditionally inactivated alphaENaC in the collecting duct (Scnn1a(loxloxCre) mice). In control mice, rosiglitazone did not alter plasma aldosterone levels or protein expression of ENaC subunits in the kidney, but did increase body weight, plasma volume, and the fluid content of abdominal fat pads, and decreased hematocrit. Scnn1a(loxloxCre) mice provided functional evidence for blunted Na+ uptake in the collecting duct, but still exhibited rosiglitazone-induced fluid retention. Moreover, treatment with rosiglitazone or pioglitazone did not significantly alter the open probability or number of ENaC channels per patch in isolated, split-open cortical collecting ducts of wild-type mice. Finally, patch-clamp studies in primary mouse inner medullary collecting duct cells did not detect ENaC activity but did detect a nonselective cation channel upregulated by pioglitazone. These data argue against a primary and critical role of ENaC in thiazolidinedione-induced fluid retention.

The effect of rosiglitazone on integrated cardiovascular performance, cardiac structure, function and myocardial triglyceride: trial design and rationale

The thiazolidinedione (TZD) class of medications has been associated with increased risk for peripheral oedema, as well as incident and worsening heart failure (HF). The mechanism of these observed effects remains unclear. Here we present the rationale and study design for a randomised clinical trial designed to evaluate the cardiac effects of rosiglitazone on integrated cardiovascular performance, cardiac structure and function. The study is a randomised, single-centre, double-blind, placebo-controlled, parallel-group clinical trial to evaluate the effect of rosiglitazone on integrated cardiovascular performance in a cohort of patients with type 2 diabetes mellitus (T2DM) at increased risk for developing heart failure (HF). Participants will be randomised to receive rosiglitazone or matching placebo for six months. All subjects will undergo maximal treadmill cardiopulmonary exercise testing at baseline and after six months on study drug, with the primary trial end point of peak oxygen uptake indexed to fat-free mass (VO 2peak-FFM). Approximately two-thirds of the study cohort will undergo cardiac magnetic resonance imaging (MRI) and spectroscopy (MRS) at baseline and after six months of study therapy to assess cardiac structure, function and myocardial triglyceride content. While concerns for peripheral oedema and HF continue to confound clinical use of TZD medications, the direct cardiac effects of these drugs remain poorly understood and the clinical relevance of these clinical observations remains unclear. The present study will combine a series of state-of-the-art assessments to evaluate the cardiac effects of rosiglitazone treatment.

Effects of weight loss after bariatric surgery for morbid obesity on vascular endothelial growth factor-A, adipocytokines, and insulin

BACKGROUND

Adipocytes regulate blood vessel formation, and in turn endothelial cells promote preadipocyte differentiation through the expression of proangiogenic factors, such as vascular endothelial growth factor (VEGF)-A. Some adipocytokines and hormones also have an effect on vascular development.

OBJECTIVES

Our objectives were to analyze the relationship between weight and circulating VEGF-A in morbidly obese subjects before and after bariatric surgery, and investigate the relationship between circulating VEGF-A and certain adipocytokines and hormones regulating adipocytes.

METHODS

A total of 45 morbidly obese women and nine lean females were included in the study. Patients underwent bariatric surgery: vertical banded gastroplasty (n=17), gastric bypass (n=17), and biliopancreatic diversion (n=11). Serum samples for VEGF-A, adiponectin, leptin, ghrelin, and insulin were obtained preoperatively and 9-12 months after surgery.

RESULTS

Obese patients showed significantly higher VEGF-A levels than controls (306.3+/-170.3 vs. 187.6+/-91.9 pg/ml; P=0.04), decreasing to 246.1+/-160.4 after surgery (P<0.001), with no differences among surgical procedures. In controls there was an inverse correlation between VEGF-A and ghrelin (r=-0.85; P<.01), but not in obese patients. Leptin and insulin concentrations were increased in obese patients, with a significant decrease shown after weight loss with surgery. Conversely, adiponectin concentrations were lower in obese patients, with a significant increase shown after weight loss with surgery. Ghrelin was higher in controls than obese patients, decreasing after gastric bypass and biliopancreatic diversion, but not after vertical banded gastroplasty.

CONCLUSION

Serum VEGF-A levels are significantly higher in obese patients than in lean controls, decreasing after weight loss with bariatric surgery, behaving similarly to other hormones related to adipose mass like leptin and insulin.

Thiazolidinediones in type 2 diabetes: a cardiology perspective

OBJECTIVE

To examine the cardiovascular effects of thiazolidinediones (TZDs), discuss concerns regarding this drug class and its relation to heart failure (HF) and myocardial infarction (MI), and address the clinical implications of HF and MI.

DATA SOURCES

Literature was accessed through MEDLINE (1979-April 2008) using the search terms type 2 diabetes mellitus, thiazolidinediones, cardiovascular events, heart failure, myocardial infarction, and edema. Reviews, meta-analyses, clinical trials, observational studies (case-control, cohort), and descriptive studies (case reports, case series) were included.

STUDY SELECTION AND DATA EXTRACTION

All articles that were written in English and identified from the data sources were reviewed.

DATA SYNTHESIS

The American Diabetes Association recommends metformin as first-line therapy for type 2 diabetes, with the subsequent addition of a TZD, sulfonylurea, or insulin if the target is not met. Beyond glucose lowering, TZDs improve various factors associated with cardiovascular risk. Whether the effects translate into beneficial cardiovascular outcomes is controversial. In PROactive (Prospective Pioglitazone Clinical Trial in Macrovascular Events), pioglitazone did not produce a significant reduction in the primary endpoint that included a composite of coronary and vascular deaths, but the secondary composite endpoint of all-cause mortality, MI, or stroke was significantly reduced. Concerns related to HF have led to warnings in the labeling of TZDs. The drugs are contraindicated in patients with New York Heart Association Class III or IV HF. Rosiglitazone, but not pioglitazone, is associated with an increased risk of myocardial ischemic events, although the absolute magnitude is extremely small.

CONCLUSIONS

Although the glycemic efficacy of TZDs is comparable to that of metformin, adverse effects and higher costs make TZDs less appealing for initial therapy. Among the TZDs, pioglitazone should be considered based on cardiovascular safety data. In combination with metformin, pioglitazone may be particularly beneficial for patients with diabetes and metabolic syndrome. For patients on rosiglitazone who are achieving glycemic goals and tolerating the therapy without apparent complications, rosiglitazone may be continued.

Insulin increases tristetraprolin and decreases VEGF gene expression in mouse 3T3-L1 adipocytes

OBJECTIVES

Tristetraprolin (TTP) family proteins (TTP/ZFP36; ZFP36L1, ZFP36L2, ZFP36L3) destabilize adenylate uridylate-rich element-containing mRNAs encoding cytokines, such as tumor necrosis factor (TNF) and vascular endothelial growth factor (VEGF). Little is known about the expression and insulin regulation of TTP and related genes in adipocytes. We analyzed the relative abundance of TTP family mRNAs in 3T3-L1 adipocytes compared to RAW264.7 macrophages and investigated insulin effects on the expression of 43 genes in 3T3-L1 adipocytes.

METHODS AND PROCEDURES

Insulin was added to mouse 3T3-L1 adipocytes. Relative abundance of mRNA levels was determined by quantitative real-time PCR. TTP and ZFP36L1 proteins were detected by immunoblotting.

RESULTS

Zfp36l1 and Zfp36l2 genes were expressed at eight- to tenfold higher than Ttp in adipocytes. Zfp36l3 mRNA was detected at approximately 1% of Ttp mRNA levels in adipocytes and its low level expression was confirmed in RAW cells. Insulin at 10 and 100 nmol/l increased Ttp mRNA levels by five- to sevenfold, but decreased those of Zfp36l3 by 40% in adipocytes after a 30-min treatment. Immunoblotting showed that insulin induced TTP but did not affect ZFP36L1 protein levels in adipocytes. Insulin decreased mRNA levels of Vegf and a number of other genes in adipocytes.

DISCUSSION

Insulin induced Ttp mRNA and protein expression and decreased Vegf mRNA levels in adipocytes. Zfp36l3 mRNA was detected, for the first time, in cells other than mouse placenta and extraembryonic tissues. This study established a basis for the investigation of TTP and VEGF genes in the regulation of obesity and suggested that Vegf mRNA may be a target of TTP in fat cells.

Effects of the thiazolidinedione medications on micro- and macrovascular complications in patients with diabetes--update 2008

INTRODUCTION

The thiazolidinedione (TZD) drugs, including pioglitazone (Actos) and rosiglitazone (Avandia), are commonly prescribed in patients with type 2 diabetes mellitus (T2DM), largely due to their favorable effects on hyperglycemia, insulin sensitivity, and cardiometabolic profile. However, the data are sparse assessing the effects of TZDs on micro- and macrovascular disease risk.

DISCUSSION

Although no studies have been published on microvascular clinical outcomes, both TZDs significantly reduce the urine albumin-to-creatinine ratio. TZDs have consistently been associated with favorable effects on atherosclerosis and cardiovascular disease (CVD) risk. Only one study has been published to date specifically designed to assess the effects of a TZD (pioglitazone) on macrovascular outcomes, the PROactive trial. In this trial, pioglitazone versus placebo was associated with a non-significant 10% reduction in the combined primary endpoint of mortality, coronary and peripheral vascular events, and revascularizations. No individual trial has been published specifically assessing the CVD effects of rosiglitazone, but several meta-analyses and a published interim report from an ongoing trial (RECORD) point to safety concerns regarding rosiglitazone use and the risk of myocardial infarctions (MI), leading to amplified warnings in the product labeling for rosiglitazone to reflect these concerns.

CONCLUSION

All published trials and meta-analyses of TZDs have consistently shown increased risk of heart failure (HF) with both TZDs, though the actual placebo-subtracted incidence of HF is low (<0.5% per year). The initiation of either TZD is contraindicated in patients with NHYA class III or IV HF, and cautions exist for their use in any patient with heart failure. Much uncertainty remains regarding the aggregate CVD effects of the TZDs, and several trials are presently underway to further address these issues.

Peroxisome proliferator-activated receptor-gamma agonists and diabetes: current evidence and future perspectives

Since their initial availability in 1997, the thiazolidinediones (TZDs) have become one of the most commonly prescribed classes of medications for type 2 diabetes. In addition to glucose control, the TZDs have a number of pleiotropic effects on myriad traditional and non-traditional risk factors for diabetes. TZDs may benefit cardiovascular parameters, such as lipids, blood pressure, inflammatory biomarkers, endothelial function and fibrinolytic state. In this review, we summarise the experimental, preclinical and clinical data regarding the effects of the TZDs in conditions for which they are indicated and discuss their potential in the treatment of other conditions.

Pioglitazone ameliorates endothelial dysfunction and restores ischemia-induced angiogenesis in diabetic mice

Angiogenesis, the formation of new blood vessels, is a physiological response to tissue ischemia. Clinical evidence suggests that diabetic patients have endothelial dysfunction and impaired angiogenesis in response to ischemia. Here, we investigated the impact of diabetes on ischemia-induced collateral growth, and tested the hypothesis that peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist augments collateral flow to ischemic tissue. We conducted unilateral hindlimb ischemia surgery in KKAy mice. Blood flow recovery was markedly impaired in diabetic mice compared with that in wild-type mice as determined by laser Doppler imaging. Treatment of KKAy mice with pioglitazone partially restored the blood flow recovery. Anti-CD31 immunostaining revealed that pioglitazone also significantly improved the capillary density in ischemic limb muscle. Endothelial NO synthase (eNOS) activity was ameliorated in diabetic mice treated with pioglitazone as determined by vasorelaxation in response to acetylcholine. Pioglitazone normalized vascular endothelial growth factor (VEGF) protein levels, which was decreased in ischemic muscle of KKAy mice, and up-regulated eNOS phosphorylation at Ser-1177 and Akt phosphorylation at Ser-473 in ischemic muscle. Pioglitazone had no beneficial effects on blood flow recovery in diabetic mice treated with N(G)-nitro-l-arginine methyl ester (L-NAME). Our findings demonstrate that pioglitazone significantly ameliorates endothelial dysfunction and enhances blood flow recovery after tissue ischemia in diabetic mice. Activation of eNOS appears to be essential for pioglitazone to promote angiogenesis in ischemic tissue.

A case of subclinical hypothyroidism developing marked pleural effusions and peripheral edema with elevated vascular endothelial growth factor

A 69-year-old woman was admitted for the treatment of marked pleural effusions and peripheral edema. Analytical studies of the pleural effusion revealed exudates. Culture for bacterial organisms and tuberculosis were negative, and cytology was normal. She had a mediastinal tumor at the age of 61 and regular follow-up showed no evidence of malignancy. She underwent the mediastinal tumor resection, because we thought this was the cause of her symptoms. However, her clinical symptoms persisted after surgery. Next, we noticed subclinical hypothyroidism, in which serum TSH level was elevated with concomitant normal thyroid hormone levels. In addition, serum vascular endothelial growth factor (VEGF) levels, which have been reported to be related to the pathophysiology of the extravascular volume overload, were elevated. Although her TSH level was slightly elevated (15.4 microU/ml), we started thyroid hormone replacement therapy. This therapy gradually ameliorated her clinical manifestation and abnormal laboratory data, including elevated VEGF levels. These observations indicate that even subclinical hypothyroidism may cause severe clinical manifestations. Furthermore, elevated VEGF may be a contributing factor in the pathogenesis of extravascular volume overload in hypothyroid patients.

Thiazolidinediones in patients with type 2 diabetes mellitus and heart failure

PURPOSE

A review of the significant findings related to the use of the thiazolidinediones (TZDs) in the treatment of patients with type 2 diabetes mellitus and heart failure was conducted.

SUMMARY

TZDs are antihyperglycemic medications that increase insulin sensitivity and improve the underlying defect of insulin resistance and type 2 diabetes mellitus, and they have the potential to slow or decrease the cardiovascular damage that results from these conditions. TZDs are also implicated in weight gain; however, this is accompanied by an improvement in insulin sensitivity and, therefore, its clinical significance is unclear. Edema has been well characterized in patients treated with TZDs. Edema is more common in patients treated with a TZD in combination with insulin and higher doses of TZDs. Because of the potential for fluid retention and worsening edema, clinical studies have excluded patients with New York Heart Association (NYHA) functional class III or IV heart failure. In patients at risk for heart failure or those who have NYHA functional class I or II symptoms, initiation of therapy should be at the lower dose for TZDs with close monitoring of weight gain, edema, and other signs of worsening heart failure.

CONCLUSION

Current data suggest that TZDs may be used cautiously in patients with type 2 diabetes mellitus who are at risk for heart failure or who have NYHA functional class I or II heart failure. Patients with NYHA functional class III or IV heart failure should not receive TZDs.

Effect of thiazolidinedione on the proliferation of bovine retinal endothelial cells stimulated by vascular endothelial cell growth factor

PURPOSE

To investigate the effect of troglitazone, an antidiabetic drug, on the cytosolic Ca(2+) concentrations ([Ca(2+)]i) and the cell cycles of bovine retinal endothelial cells (RECs) stimulated with vascular endothelial growth factor (VEGF).

METHODS

The changes in [Ca(2+)]i were monitored using microfluorometry with Fura-2. The phase of the cell cycle was examined by an immunocytochemical analysis using monoclonal antibodies against cell cycle-specific nuclear antigens.

RESULTS

In the presence of extracellular Ca(2+), VEGF-induced transient [Ca(2+)]i elevation followed by continuous steady-state elevation resulted in cell cycle progression in RECs. The removal of extracellular Ca(2+) inhibited the continuous component, but transient [Ca(2+)]i elevation was still observed. These results are compatible with the hypothesis that a continuous steady-state elevation of [Ca(2+)]i may be mediated mainly through the influx of extracellular Ca(2+). Pretreatment with 10 microM troglitazone prevented the transient and continuous steady-state elevation of [Ca(2+)]i, resulting in an inhibition of the cell cycle in RECs stimulated with VEGF.

CONCLUSIONS

These data suggest that troglitazone inhibits VEGF-induced cell cycle progression through the inhibition of [Ca(2+)]i in RECs.

Vascular endothelial growth factor secretion from mesenteric adipose tissue and from creeping fat in Crohn's disease

BACKGROUND

Creeping fat represents a characteristic feature of Crohn's disease (CD), and adipose tissue secretes adipocytokines and chemokines/growth factors such as vascular endothelial growth factor (VEGF). Because VEGF serum levels and mucosal VEGF expression is elevated in CD patients, the aim of the present paper was to investigate creeping fat-derived VEGF secretion in CD.

MATERIAL AND METHODS

Adipose tissue was obtained from creeping fat of 10 patients with CD. Mesenteric adipose tissue was resected from 13 patients with colon cancer (CC) and from seven patients with diverticulitis (DIV). Three fat tissue specimens per well, and several wells (6-8) per patient were incubated ex vivo for 24 h. The release of VEGF into the supernatant was measured by ELISA.

RESULTS

There was stable VEGF secretion from mesenteric adipose tissue of patients with CC or DIV and from creeping fat of patients with CD. Whereas the VEGF secretion rate was not different between patients with CD (465 +/- 98 pg/g fat per 24 h) and CC (399 +/- 48 pg/g fat per 24 h), VEGF secretion was significantly reduced in patients suffering from DIV (115 +/- 41 pg/g fat per 24 h; P < 0.0001 and P = 0.001, respectively). The CD patients treated with steroids had significantly lower VEGF secretion rates (294 +/- 42 pg/g fat per 24 h) than CD patients not receiving steroids (607 +/- 105 pg/g fat per 24 h; P = 0.001).

CONCLUSIONS

Creeping fat is an important source of VEGF secretion. The characteristics of the inflammatory changes in CD might be due to the lack of VEGF downregulation that is seen in DIV.

Therapeutic implications of the gender-specific aspects of cardiovascular disease

The manifestations of cardiovascular diseases differ between men and women, as do outcomes after therapeutic interventions. It is important that those involved in drug discovery and development, as well as disease treatment, are aware of these differences because such variations are likely to have an increasing role in therapeutic decisions in the future. Here, I review gender differences in the most frequent cardiovascular diseases and their underlying sex-dependent molecular pathophysiology, and discuss gender-specific effects of current cardiovascular drugs and the implications for novel strategies for drug development.

Diabetic macular edema associated with glitazone use

PURPOSE

To describe diabetic macular edema (DME) in patients who developed fluid retention as a consequence of glitazone use.

METHODS

A chart review identified 30 patients who used pioglitazone or rosiglitazone and had both lower extremity edema and macular edema. Clinical reports, photographs, and fluorescein angiograms were reviewed. Patients followed for >3 months were analyzed separately.

RESULTS

Seventeen patients took oral pioglitazone, 11 took rosiglitazone, and 2 took both drugs at different times. Eleven patients were observed for >3 months after cessation of glitazones. Mean weight gain during drug administration in this group was 30 lb, and mean weight loss after drug discontinuation was 19 lb. Rapid reduction in macular edema off drug occurred in only 4 of 11 patients, but 8 of 11 had reduced edema over 2 years. Mean visual acuity in this group at the initial visit was 20/60, and at the final visit, it was 20/85. Four eyes of three patients had resolution of diffuse macular edema with improved vision after cessation of glitazones without laser treatment.

CONCLUSIONS

Fluid retention occurs in 5% to 15% of patients taking glitazones. In some of these patients, glitazone use appears to be a cause of macular edema, and drug cessation appears to result in rapid resolution of both peripheral and macular edema. Fluid retention associated with glitazone use should be considered when assessing treatment options for patients with DME, especially those with concomitant peripheral edema.

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.

Thiazolidinediones associated with recurrent pleural effusions post coronary artery bypass surgery

We report the case of a patient in which thiazolidinediones (TZDs) were associated with recurrent pleural effusions post coronary artery bypass surgery, in spite of a normal left ventricular function. The potential mechanisms are discussed, particularly in relation to the "vascular leak syndrome". This finding has important implications for the management of diabetic patients who are referred for coronary artery bypass surgery and who are on TZDs for glycemic control.