PPARγ agonists diminish serum VEGF elevation in diet-induced insulin resistant SD rats and ZDF rats

Repurposing drugs targeting metabolic diseases for cancer therapeutics

Hurdles in the identification of new drugs for cancer treatment have made drug repurposing an increasingly appealing alternative. The approach involves the use of old drugs for new therapeutic purposes. It is cost-effective and facilitates rapid clinical translation. Given that cancer is also considered a metabolic disease, drugs for metabolic disorders are being actively repurposed for cancer therapeutics. In this review, we discuss the repurposing of such drugs approved for two major metabolic diseases, diabetes and cardiovascular disease (CVD), which have shown potential as anti-cancer treatment. We also highlight the current understanding of the cancer signaling pathways that these drugs target.

Antidiabetic drugs and the risk of cancer: beneficial, neutral, or detrimental?

The prevalence of diabetes mellitus is rapidly rising, especially in low- and middle-income countries. Also, early-onset diabetes is on the rise, and millions of individuals have to be on antidiabetic medications for a prolonged period. Therefore, more people are getting exposed to the adverse effects of antidiabetic medications.

Cancer is among the top ranking causes of death worldwide. Researches are still ongoing to understand the etiologies, precipitants, risk factors, correlates, and predictors of cancers. Diabetes mellitus is associated with various cancers, as extensively documented in the literature. There are conflicting reports about the association between antidiabetic drugs and cancer. This is even of crucial importance, considering that the prevalence of diabetes is rising.

Insulin glargine is reported to be associated with cancers, but clinical trials have not confirmed this. Metformin is largely believed to be beneficial in oncologic practice. Glibenclamide is reported to reduce tumor growth. The association between pioglitazone and bladder cancer is still an area for further research. Meglitinides have also been associated with cancers. Incretin-based therapy and the α-glucosidase inhibitors appear to have beneficial effects on cancers.

There is still a need for randomized multicentric clinical trials to further substantiate and clarify reports from epidemiological studies. Further in vitro studies will also be necessary to characterize the interaction of these pharmacological agents with other molecules in the body.

An Insight into the Synthesis and SAR of 2,4-Thiazolidinediones (2,4-TZD) as Multifunctional Scaffold: A Review

2,4-Thiazolidinedione (2,4-TZD) is a versatile pharmacophore, a privileged scaffold, and a remarkable sulphur-containing heterocyclic compound with diverse pharmacological activities. The multifarious biological activities, due to different mechanisms of action, low cost, and easy availability of 2,4-TZD impressed medicinal chemists to integrate this moiety to develop various lead compounds with diverse therapeutic actions. This resulted in the swift development in the last decade for generating different new potential molecules bearing 2,4-TZD. In this review, the authors attempt to shape and present the latest investigations (2012 onwards) going on in generating promising 2,4-TZD containing lead compounds. The data has been collected and analyzed to develop the structure-activity relationship (SAR). The SAR and active pharmacophores of various leads accountable for antidiabetic, anticancer, antimicrobial, and antioxidant activities have also been illustrated. This review also highlighted some of the important chemical synthetic routes for the preparation of various 2,4-TZD derivatives. This review will definitely serve as a useful source of structural information to medicinal chemists and may be utilized for the strategic design of potent 2,4-TZD derivatives in the future.

Synthesis, Anticancer, and Antibacterial Studies of Benzylidene Bearing 5-substituted and 3,5-disubstituted-2,4-Thiazolidinedione Derivatives

AIM

To develop novel compounds having potent anticancer and antibacterial activities.

BACKGROUND

Several studies have proved that benzylidene analogues of clinical 2,4-TZDs, such as troglitazone and ciglitazone, have more potent antiproliferative activity than their parent compounds. Literature studies also revealed that the attachment of more heterocyclic rings, containing nitrogen on 5th position of 2,4-TZD, can enhance the antimicrobial activity. Hence, attachment of various moieties on the benzylidene ring may produce safe and effective compounds in the future.

OBJECTIVE

The objective of the present study was to synthesize a set of novel benzylidene ring containing 5- and 3-substituted-2,4-thiazolidinedione derivatives and evaluate them for their anticancer and antibacterial activity.

METHODS

The synthesized compounds were characterized by IR, NMR, mass, and elemental studies. The in vitro cytotoxicity studies were performed for human breast cancer (MCF-7) and human lung cancer (A549) cells and HepG2 cell-line and compared to standard drug doxorubicin by MTT assay. Antimicrobial activity of the synthesized 2,4-thiazolidinediones derivatives was carried out using the cup plate method with slight modification.

RESULTS

The results obtained showed that TZ-5 and TZ-13 exhibited good antiproliferative activity against A549 cancer cell-line, whereas TZ-10 exhibited moderate antiproliferative activity against HepG2 cell-line when compared to standard drug doxorubicin. TZ-5 also exhibited reasonable activity against the MCF-7 cell-line with doxorubicin as standard. TZ-4, TZ-5, TZ-6, TZ-7, and TZ- 16 exhibited remarkable antibacterial activity against Gram positive and moderate activity against Gram negative bacteria with the standard drug ciprofloxacin.

CONCLUSION

Attachment of heterocyclic rings containing nitrogen as the hetero atom improves the anticancer and antimicrobial potential. Attachment of electronegative elements like halogens can also enhance the antimicrobial activity. Further structure modifications may lead to the development of more potent 2,4-TZD leads that can be evaluated for further advanced studies.

Indole and 2,4-Thiazolidinedione conjugates as potential anticancer modulators

Background

Thiazolidinediones (TZDs), also called glitazones, are five-membered carbon ring molecules commonly used for the management of insulin resistance and type 2 diabetes. Recently, many prospective studies have also documented the impact of these compounds as anti-proliferative agents, though several negative side effects such as hepatotoxicity, water retention and cardiac issues have been reported. In this work, we synthesized twenty-six new TZD analogues where the thiazolidinone moiety is directly connected to an N-heterocyclic ring in order to lower their toxic effects.

Methods

By adopting a widely applicable synthetic method, twenty-six TZD derivatives were synthesized and tested for their antiproliferative activity in MTT and Wound healing assays with PC3 (prostate cancer) and MCF-7 (breast cancer) cells.

Results

Three compounds, out of twenty-six, significantly decreased cellular viability and migration, and these effects were even more pronounced when compared with rosiglitazone, a well-known member of the TZD class of antidiabetic agents. As revealed by Western blot analysis, part of this antiproliferative effect was supported by apoptosis studies evaluating BCL-xL and C-PARP protein expression.

Conclusion

Our data highlight the promising potential of these TZD derivatives as anti-proliferative agents for the treatment of prostate and breast cancer.

Potential Roles of Stevia rebaudiana Bertoni in Abrogating Insulin Resistance and Diabetes: A Review

Insulin resistance is a key factor in metabolic disorders like hyperglycemia and hyperinsulinemia, which are promoted by obesity and may later lead to Type II diabetes mellitus. In recent years, researchers have identified links between insulin resistance and many noncommunicable illnesses other than diabetes. Hence, studying insulin resistance is of particular importance in unravelling the pathways employed by such diseases. In this review, mechanisms involving free fatty acids, adipocytokines such as TNFα and PPARγ and serine kinases like JNK and IKKβ, asserted to be responsible in the development of insulin resistance, will be discussed. Suggested mechanisms for actions in normal and disrupted states were also visualised in several manually constructed diagrams to capture an overall view of the insulin-signalling pathway and its related components. The underlying constituents of medicinal significance found in the Stevia rebaudiana Bertoni plant (among other plants that potentiate antihyperglycemic activities) were explored in further depth. Understanding these factors and their mechanisms may be essential for comprehending the progression of insulin resistance towards the development of diabetes mellitus.

Expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ in the lung tissue of obese mice and the effect of rosiglitazone on proinflammatory cytokine expressions in the lung tissue

Purpose

We investigated the mRNA levels of peroxisome proliferator-activated receptor (PPAR)-α, PPAR-γ, adipokines, and cytokines in the lung tissue of lean and obese mice with and without ovalbumin (OVA) challenge, and the effect of rosiglitazone, a PPAR-γ agonist.

Methods

We developed 6 mice models: OVA-challenged lean mice with and without rosiglitazone; obese mice with and without rosiglitazone; and OVA-challenged obese mice with and without rosiglitazone. We performed real-time polymerase chain reaction for leptin, leptin receptor, adiponectin, vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, PPAR-α and PPAR-γ from the lung tissue and determined the cell counts and cytokine levels in the bronchoalveolar lavage fluid.

Results

Mice with OVA challenge showed airway hyperresponsiveness. The lung mRNA levels of PPARα and PPAR-γ increased significantly in obese mice with OVA challenge compared to that in other types of mice and decreased after rosiglitazone administeration. Leptin and leptin receptor expression increased in obese mice with and without OVA challenge and decreased following rosiglitazone treatment. Adiponectin mRNA level increased in lean mice with OVA challenge. Lung VEGF, TNF-α, and TGF-β mRNA levels increased in obese mice with and without OVA challenge compared to that in the control mice. However, rosiglitazone reduced only TGF-β expression in obese mice, and even augmented VEGF expression in all types of mice. Rosiglitazone treatment did not reduce airway responsiveness, but increased neutrophils and macrophages in the bronchoalveolar lavage fluid.

Conclusion

PPAR-α and PPAR-γ expressions were upregulated in the lung tissue of OVA-challenged obese mice however, rosiglitazone treatment did not downregulate airway inflammation in these mice.

Effects of PPARγ and RBP4 gene variants on metabolic syndrome in HIV-infected patients with anti-retroviral therapy

Background

PPARγ and RBP4 are known to regulate lipid and glucose metabolism and insulin resistance. The influences of PPARγ (C1431T and Pro12Ala) and RBP4 (−803GA) polymorphisms on metabolic syndrome in HIV-infected patients receiving anti-retroviral therapy were examined in this study.

Materials and Methods

A cross-sectional study of HIV-1 infected adults with antiretroviral therapy for more than one year in the National Cheng Kung University Hospital was conducted. The gene polymorphisms were determined by quantitative PCR.

Results

Ninety-one patients were included in the study. Eighty-two (90.1%) patients were males with a mean age of 44.4 years. For the C1431T polymorphism in PPARγ, while patients with the T allele (48.4%) had trends toward lower rate of hypertriglyceridemia, the borderline significance together with insignificant power did not support the protective effect of the T allele against development of hypertriglyceridemia. For the Pro12Ala polymorphism in PPARγ, although patients with the Pro/Ala genotype (8.8%) had a higher level of serum LDL (138.0 vs. 111.5 mg/dl, P = 0.04) and trends toward higher rates of hypercholesterolemia and serum LDL>110 mg/dl, these variables were found to be independent of the Pro/Ala genotype in the multivariate analysis. For the −803GA polymorphism in RBP4, patients with the A allele (23.1%) more often had insulin resistance (HOMA>3.8; 33.3 vs. 8.7%, P = 0.01) and more often received anti-hypoglycemic drugs (14.3 vs. 1.4%, P = 0.04). The detrimental effect of the A allele in RBP4 −803GA polymorphism on development of insulin resistance was supported by the multivariate analysis adjusting for covariates.

Conclusion

The impacts of PPARγ C1431T and Pro12Ala polymorphisms on metabolism in HIV-infected patients are not significant. RBP4 −803GA polymorphism has increased risk of insulin resistance in HIV-infected patients with anti-retroviral therapy.

Soy protein preserves basement membrane integrity through a synergistic effect on nephrin, matrix metalloproteinase and vascular endothelial growth factor

BACKGROUND/AIMS

Soy protein improves renal function and prevents albuminuria in diabetic rats. This study investigates whether the renoprotective effect of soy protein is related to sustenance of basement membrane integrity.

METHODS

Adult male albino rats were randomized into four groups and fed one of the following semi-synthetic diets consisting of corn starch (60%) and casein (20%; CCD), fructose (60%) and casein (20%; FCD), fructose (60%) and soy protein (20%; FSD), or corn starch (60%) and soy protein (20%; CSD). Plasma chemistry and renal changes were analyzed after 60 days.

RESULTS

FCD rats displayed metabolic derangements and renal ultrastructural changes. FSD rats showed reduction in type IV collagen, tissue inhibitor for matrix metallo-proteinase-2, vascular endothelial growth factor and tumor necrosis factor-α expression and improved matrix metallo-proteinase expression. Renal architecture was preserved in these rats.

CONCLUSION

Soy protein supplementation not only improved insulin sensitivity but also markedly attenuated renal basement membrane changes in fructose diet-fed rats. These findings provide evidence in support of the use of dietary soy protein in patients with diabetic kidney disease.

Identifying systemic safety signals following intravitreal bevacizumab: systematic review of the literature and the Canadian Adverse Drug Reaction Database

OBJECTIVE

As the off-label use of intravitreal bevacizumab continues for an increasing number of ocular conditions, a systematic review of the literature aimed at detecting temporally associated systemic adverse events was undertaken.

DESIGN

Systematic review of the literature and a health regulatory database.

PARTICIPANTS

A total of 22 different clinical studies representing 12,699 patients.

METHODS

A systematic review indexed by Ovid MEDLINE, EMBASE, ISI Web of Science, the Cochrane database (CENTRAL), and the Canadian Adverse Drug Reaction Information System Database was performed. All clinical studies with at least 100 eyes injected with bevacizumab and case reports documenting suspected events were included for review.

RESULTS

A total of 22 different clinical studies were reviewed, including an international internet survey, 6 retrospective studies assessing the safety of intravitreal bevacizumab, and 15 clinical trials. The most common adverse systemic event reported in these studies, representing 12,699 patients was an increase in blood pressure (0.46% of patients), followed by cerebrovascular accidents (0.21% of patients), and myocardial infarction (0.19% of patients). The 6 case reports documented suspected events not previously identified and only 1 systemic event from the Health Canada database was retrieved.

CONCLUSIONS

The systemic events temporally associated with intravitreal bevacizumab are mainly of cardiovascular and neurological origin and can be predicted from an exaggerated pharmacology, although a causal association cannot be established at this time. Health Canada's spontaneous drug reporting system is an underutilized resource and a more active surveillance system such as a patient registry may be better suited to establish the low rates of systemic adverse events following bevacizumab use in ophthalmology.

Pioglitazone improves lipid and insulin levels in overweight rats on a high cholesterol and fructose diet by decreasing hepatic inflammation

BACKGROUND AND PURPOSE

Nutrient overload leads to obesity and insulin resistance. Pioglitazone, a selective peroxisome proliferator-activated receptor (PPAR)gamma agonist, is currently used to manage insulin resistance, but the specific molecular mechanisms activated by PPARgamma are not yet fully understood. Recent studies suggest the involvement of suppressor of cytokine signalling (SOCS)-3 in the pathogenesis of insulin resistance. This study aimed to investigate the hepatic signalling pathway activated by PPARgamma activation in a non-genetic insulin-resistant animal model.

EXPERIMENTAL APPROACH

Male Wistar rats were maintained on a high-cholesterol fructose (HCF) diet for 15 weeks. Pioglitazone (3 mg x kg(-1)) was administered orally for the last 4 weeks of this diet. At the end of the treatment, serum was collected for biochemical analysis. Levels of PPARgamma, SOCS-3, pro-inflammatory markers, insulin receptor substrate-2 and Akt/glycogen synthase kinase-3beta phosphorylation were assessed in rat liver.

KEY RESULTS

Rats fed the HCF diet exhibited hyperlipidemia, hyperinsulinemia, impaired glucose tolerance and insulin resistance. Pioglitazone administration evoked a significant improvement in lipid metabolism and insulin responsiveness. This was accompanied by reduced hepatic expression of SOCS-3, interleukin-6, tumour necrosis factor-alpha and markers of neutrophil infiltration. Diet-induced PPARgamma expression was unaffected by the pioglitazone treatment.

CONCLUSION AND IMPLICATIONS

Chronic pioglitazone administration reduced hepatic inflammatory responses in rats fed a HCF diet. These effects were associated with changes in hepatic expression of SOCS-3, which may be a crucial link between the reduced local inflammation and the improved insulin signalling.

Rosiglitazone prevents high glucose-induced vascular endothelial growth factor and collagen IV expression in cultured mesangial cells

Peroxisome proliferator-activated receptor (PPARγ), a ligand-dependent transcription factor, negatively modulates high glucose effects. We postulated that rosiglitazone (RSG), an activator of PPARγ prevents the upregulation of vascular endothelial growth factor (VEGF) and collagen IV by mesangial cells exposed to high glucose. Primary cultured rat mesangial cells were growth-arrested in 5.6 mM (NG) or 25 mM D-glucose (HG) for up to 48 hours. In HG, PPARγ mRNA and protein were reduced within 3 h, and enhanced ROS generation, expression of p22^phox, VEGF and collagen IV, and PKC-ζ membrane association were prevented by RSG. In NG, inhibition of PPARγ caused ROS generation and VEGF expression that were unchanged by RSG. Reduced AMP-activated protein kinase (AMPK) phosphorylation in HG was unchanged with RSG, and VEGF expression was unaffected by AMPK inhibition. Hence, PPARγ is a negative modulator of HG-induced signaling that acts through PKC-ζ but not AMPK and regulates VEGF and collagen IV expression by mesangial cells.

Telmisartan-enhanced hypercholesterolaemic serum-induced vascular endothelial growth factor expression in immortalized human umbilical vascular endothelial cells

OBJECTIVE

To clarify whether hypercholesterolaemia can increase vascular endothelial growth factor (VEGF) expression in human umbilical vascular endothelial cells (HUVECs) through the phosphatidylinositol 3-kinase (PI3K) pathway, and whether a special angiotensin II receptor blocker, telmisartan, can attenuate VEGF expression induced by hypercholesterolaemia.

METHODS

Levels of VEGF expression, PI3K activity and angiogenesis in vitro were determined by various methods after HUVECs were incubated with hypercholesterolaemic serum or combined with telmisartan and/or wortmannin.

RESULTS

We found that hypercholesterolaemic serum (cholesterol > or = 0.08 mmol/L) can increase VEGF expression in HUVECs and that telmisartan cooperates with hypercholesterolaemic serum in promoting VEGF expression. The increased VEGF expression was associated with enhanced PI3K activity and could be significantly inhibited by wortmannin, a potent PI3K inhibitor. Likewise, hypercholesterolaemic serum significantly promoted angiogenesis in vitro, which could be inhibited when PI3K activity was suppressed.

CONCLUSIONS

Our study suggests that hypercholesterolaemic serum induces VEGF expression through PI3K in HUVECs and that telmisartan cooperates with hypercholesterolaemia in promoting VEGF expression.

2-Methoxyestradiol and 2-Ethoxyestradiol Retard the Progression of Renal Disease in Aged, Obese, Diabetic ZSF1 Rats

The metabolic syndrome is a main cause for cardiovascular disease and for the accelerating epidemic of chronic renal failure. Previous studies show that 2-hydroxyestradiol (2-HE), an estradiol metabolite with little estrogenic activity, decreases obesity and arterial blood pressure and attenuates the development of renal disease in young, obese, diabetic ZSF1 rats. In humans, however, diabetic renal disease is more frequent and severe in older patients. In vivo, 2-HE is readily converted to 2-methoxyestradiol (2-ME), an estradiol metabolite with no estrogenic activity. Accordingly, one purpose of this study was to determine whether 2-ME would provide benefit in aged rats with a very severe form of diabetic renal disease. Another objective was to determine whether synthetic analogs of estradiol metabolites might be beneficial in diabetic renal disease. To achieve these objectives we examined the effects of 2-ME and its analog 2-ethoxyestradiol (2-EE) in aged (35-week-old), obese ZSF1 rats. Animals were treated for 9 weeks with vehicle (PEG-400, 0.5 microL per hour), 2-ME or 2-EE (18 microg/kg per hour). Metabolic and renal function were measured at weeks 0, 3, 6, and 9, and renal hemodynamics and excretory function were assessed at week 9. Aged ZSF1 rats had elevated levels of glycosylated hemoglobin; increased renal cortical expression of proliferating cell nuclear antigen (PCNA), nuclear factor kappa B (NF-kappaB), and vascular endothelial growth factor (VEGF); glycosuria, hypertension; and proteinuria. 2-ME and 2-EE did not affect obesity or hypertension and had variable effects on glucose homeostasis, yet they attenuated proteinuria; increased renal blood flow and glomerular filtration; and reduced renal cortical expression of PCNA, NFkappaB, and VEGF. We conclude that 2ME and 2EE are strikingly renoprotective even in aged animals with severe diabetic renal disease. The present study warrants further investigation of 2-ME and analogs of estradiol metabolites for treatment of kidney disease associated with the metabolic syndrome.

Changes of skeletal muscle adiponectin content in diet-induced insulin resistant rats

The current study examined the relationship between skeletal muscle levels of adiponectin and parameters of insulin sensitivity. A high fat/sucrose diet (HFD) for 20 weeks resulted in significant increases in body weight, serum insulin, triglycerides (TG), and free fatty acids (FFA) (all p < 0.01). Interestingly, this diet leads to a slight increase in serum adiponectin, but significant decreases in gastrocnemius muscle and white adipose adiponectin (all p < 0.05). HFD for 4 weeks also resulted in a significant decrease in muscle adiponectin, which correlated with serum insulin, TG, and FFA (all p < 0.05). Treatment of the 4-week HFD rats with a PPARgamma agonist GI262570 ameliorated the diet-induced hyperinsulinemia and dyslipidemia, and effectively restored muscle adiponectin (all p < 0.05). This study demonstrated that HFD-induced hyperinsulinemia and dyslipidemia appeared without changes in serum adiponectin, but were associated with decreased tissue adiponectin. This provides the first evidence for a connection between tissue adiponectin and diet-induced hyperinsulinemia and dyslipidemia.