Therapeutic index for rosiglitazone in dietary obese rats: separation of efficacy and haemodilution

Rosiglitazone Mitigates Dexamethasone-Induced Depression in Mice via Modulating Brain Glucose Metabolism and AMPK/mTOR Signaling Pathway

Major depressive disorder (MDD) is a common, complex disease with poorly understood pathogenesis. Disruption of glucose metabolism is implicated in the pathogenesis of depression. AMP-activated protein kinase (AMPK) has been shown to regulate the activity of several kinases, including pAKT, p38MAPK, and mTOR, which are important signaling pathways in the treatment of depression. This study tested the hypothesis that rosiglitazone (RGZ) has an antidepressant impact on dexamethasone (DEXA)-induced depression by analyzing the function of the pAKT/p38MAPK/mTOR pathway and NGF through regulation of AMPK. MDD-like pathology was induced by subcutaneous administration of DEXA (20 mg/kg) for 21 days in all groups except in the normal control group, which received saline. To investigate the possible mechanism of RGZ, the protein expression of pAMPK, pAKT, p38MAPK, and 4EBP1 as well as the levels of hexokinase, pyruvate kinase, and NGF were assessed in prefrontal cortex and hippocampal samples. The activities of pAMPK and NGF increased after treatment with RGZ. The administration of RGZ also decreased the activity of mTOR as well as downregulating the downstream signaling pathways pAKT, p38MAPK, and 4EBP1. Here, we show that RGZ exerts a potent inhibitory effect on the pAKT/p38MAPK/mTOR/4EBP1 pathway and causes activation of NGF in brain cells. This study has provided sufficient evidence of the potential for RGZ to ameliorate DEXA-induced depression. A new insight has been introduced into the critical role of NGF activation in brain cells in depression. These results suggest that RGZ is a promising antidepressant for the treatment of MDD.

Pharmacological Studies on the Antidiabetic, Antioxidant, and Antimicrobial Efficacies of Commiphora myrrha Resin in Streptozotocin-Induced Diabetes in Rats: A Preclinical Study

RESULTS

The aqueous extracts of MAE were phytochemically analyzed, and the results revealed the presence of high concentrations of tannins, sterols, and isoprenoids (terpenoids), while steroids and flavonoids were found in moderate concentrations. The plant extract showed promising inhibition of the growth of gram-positive and gram-negative pathogens. It also showed that MAE has potential antihyperglycemic and antioxidant activities. Microscopic examination of the pancreas showed degenerative changes and atrophy associated with dilatation of the exocrine ducts in the STZ-induced diabetic rats, while the treatment revealed that the Langerhans islets were close to normal without any histopathological alteration.

CONCLUSION

The present results suggested that an aqueous extract of MAE could be considered an efficient antidiabetic, antioxidant, and antimicrobial treatment in the future.

In Combo Studies for the Optimization of 5-Aminoanthranilic Acid Derivatives as Potential Multitarget Drugs for the Management of Metabolic Syndrome

Metabolic syndrome is a set of risk factors that consist of abdominal obesity, arterial hypertension, alterations in the lipid profile, and hyperglycemia. The current therapeutic strategy includes polypharmacy, using three or more drugs to control each syndrome component. However, this approach has drawbacks that could lead to therapeutic failure. Multitarget drugs are molecules with the ability to act on different targets simultaneously and are an attractive alternative for treating complex diseases such as metabolic syndrome. Previously, we identified a triamide derivative of 5-aminoanthranilic acid that exhibited hypoglycemic, hypolipemic, and antihypertensive activities simultaneously. In the present study, we report the synthesis and in combo evaluation of new derivatives of anthranilic acid, intending to identify the primary structural factors that improve the activity over metabolic syndrome-related parameters. We found that substitution on position 5, incorporation of 3,4-dimethoxyphenyl substituents, and having a free carboxylic acid group lead to the in vitro inhibition of HMG-CoA reductase, and simultaneously the diminution of the serum levels of glucose, triglycerides, and cholesterol in a diet-induced in vivo model.

Characterization and Comparison of the Divergent Metabolic Consequences of High-Sugar and High-Fat Diets in Male Wistar Rats

Diet-induced obesity (DIO) in laboratory rodents can serve as a model with which to study the pathophysiology of obesity, but obesogenic diets (high-sugar and/or high-fat) are often poorly characterised and simplistically aimed at inducing metabolic derangements for the purpose of testing the therapeutic capacity of natural products and other bioactive compounds. Consequently, our understanding of the divergent metabolic responses to different obesogenic diet formulations is limited. The aim of the present study was to characterise and compare differences in the metabolic responses induced by low-fat, medium-fat/high-sugar and high-fat diets in rats through multivariate statistical modelling. Young male Wistar rats were randomly assigned to CON (laboratory chow, low-fat), OB1 (high-sugar, medium-fat) or OB2 (high-fat) dietary groups (n = 24 each) for 17 weeks, after which metabolic responses were characterised. Projection-based multivariate analyses (principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA)) were used to explore the associations between measures of body composition and metabolism. Furthermore, we conducted a systematic literature survey to examine reporting trends in rat dietary intervention studies, and to determine how the metabolic responses observed in the present study compared to other recently published studies. The OB1 and OB2 dietary regimens resulted in distinct metabolic profiles, with OB1 characterised by perturbations in insulin homeostasis and adipose tissue secretory function, while OB2 was characterised by altered lipid and liver metabolism. This work therefore confirms, by means of direct comparison, that differences in dietary composition have a profound impact on metabolic and pathophysiological outcomes in rodent models of DIO. However, through our literature survey we demonstrate that dietary composition is not reported in the majority of rat dietary intervention studies, suggesting that the impact of dietary composition is often not considered during study design or data interpretation. This hampers the usefulness of such studies to provide enhanced mechanistic insights into DIO, and also limits the translatability of such studies within the context of human obesity.

Conditioning the microenvironment for soft tissue regeneration in a cell free scaffold

The use of cell-free scaffolds for the regeneration of clinically relevant volumes of soft tissue has been challenged, particularly in the case of synthetic biomaterials, by the difficulty of reconciling the manufacturing and biological performance requirements. Here, we investigated in vivo the importance of biomechanical and biochemical cues for conditioning the 3D regenerative microenvironment towards soft tissue formation. In particular, we evaluated the adipogenesis changes related to 3D mechanical properties by creating a gradient of 3D microenvironments with different stiffnesses using 3D Poly(Urethane-Ester-ether) PUEt scaffolds. Our results showed a significant increase in adipose tissue proportions while decreasing the stiffness of the 3D mechanical microenvironment. This mechanical conditioning effect was also compared with biochemical manipulation by loading extracellular matrices (ECMs) with a PPAR-γ activating molecule. Notably, results showed mechanical and biochemical conditioning equivalency in promoting adipose tissue formation in the conditions tested, suggesting that adequate mechanical signaling could be sufficient to boost adipogenesis by influencing tissue remodeling. Overall, this work could open a new avenue in the design of synthetic 3D scaffolds for microenvironment conditioning towards the regeneration of large volumes of soft and adipose tissue, with practical and direct implications in reconstructive and cosmetic surgery.

Ethno-pharmacological insulin signaling induction of aqueous extract of Syzygium paniculatum fruits in a high-fat diet induced hepatic insulin resistance

ETHNOPHARMACOLOGICAL RELEVANCE

The ethnopharmacological significance of the fruits of Syzygium paniculatum Gaertn (Magenta Cherry) is widely recognized in the Indian traditional medicine system to treat various disorders, such as diabetes, hyperlipidaemia, hypertension, and cardiovascular problems.

AIM OF THE STUDY

This research work investigated the supplementation of the aqueous extract of S. paniculatum fruit (AESPF) on liver function; the molecular effects on the expression of the protein of insulin receptor (IR) and insulin receptor substrate 1 (IRS-1) in high-fat diet-induced hepatic insulin resistance in the rat model.

MATERIALS AND METHODS

High-fat diet was used to induce obesity in albino Wistar for 120 days. Biochemical, enzymatic, and histopathological analysis, as well as analysis of hepatic insulin resistance proteins and expression of IRS-1, were performed.

RESULTS

The supplementation of AESPF with a dose of 100 mg/kg bw significantly reduced bodyweight, blood sugar, insulin, lipid profiles, and liver enzymes. Hepatic insulin resistance was improved with a reduced level of IR and IRS-1 to protein levels. HFD alters the sensitivity of hepatocytes to insulin due to the down-regulation of insulin receptor proteins.

CONCLUSIONS

The fruits of S. paniculatum possess biological activities to alleviate all risky effects by regulating hepatic lipogenesis activity that can be used in the progress of medication for HFD-induced hepatic insulin resistance and metabolic disorders.

[Positive effect of a propolis supplement on lipid profile, glycemia, and hepatic antioxidant status in an experimental animal model]

Introduction

Introduction: the use of natural nutritional supplements can be used as a coadjuvant therapy since they have several phytochemicals with potential antioxidant effects that could influence lipid and glycemic metabolism. Objectives: to determine the effect of natural propolis supplementation on lipid metabolism and liver antioxidant activity. Material and methods: 20 male Wistar albino rats (8 weeks) were divided into two groups of 10 animals each. Subsequently, they were fed two different types of diet for 90 days: a standard diet for the control group (diet C) and a standard diet + 2 % propolis (diet P). Hematological and biochemical parameters were assessed. The livers were extracted and washed with saline solution, and the cytosolic fractions were prepared fresh for additional analysis of antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Results: after consuming the diet supplemented with propolis, we found a reduction in glucose (p < 0,01), total cholesterol (p < 0,001), GOT (p < 0,05) and GPT (p < 0,01), whereas the propolis supplement induced an increase in the hepatic activity of SOD (p < 0,001), CAT (p < 0,01) and GR (p < 0,05). Conclusion: the present study reveals that a dietary propolis supplement (2 %) can improve the lipid and glycemic profiles, also increasing antioxidant enzimes and reducing the release of liver transaminases.

Long-chain free fatty acids inhibit ischaemic preconditioning of the isolated rat heart

We recently reported that non-preconditioned hearts from diet-induced obese rats showed, compared to controls, a significant reduction in infarct size after ischaemia/reperfusion, whilst ischaemic preconditioning was without effect. In view of the high circulating FFA concentration in diet rats, the aims of the present study were to: (i) compare the effect of palmitate on the preconditioning potential of hearts from age-matched controls and diet rats (ii) elucidate the effects of substrate manipulation on ischaemic preconditioning. Substrate manipulation was done with dichloroacetate (DCA), which enhances glucose oxidation and decreases fatty acid oxidation. Isolated hearts from diet rats, age-matched controls or young rats, were perfused in the working mode using the following substrates: glucose (10 mM); palmitate (1.2 mM)/3% albumin) + glucose (10 mM) (HiFA + G); palmitate (1.2 mM/3% albumin) (HiFA); palmitate (0.4 mM/3% albumin) + glucose(10 mM) (LoFA + G); palmitate (0.4 mM/3% albumin) (LoFA). Hearts were preconditioned with 3 × 5 min ischaemia/reperfusion, followed by 35 min coronary ligation and 60 min reperfusion for infarct size determination (tetrazolium method) or 20 min global ischaemia/10 or 30 min reperfusion for Western blotting (ERKp44/42, PKB/Akt). Preconditioning of glucose-perfused hearts from age-matched control (but not diet) rats reduced infarct size, activated ERKp44/42 and PKB/Akt and improved functional recovery during reperfusion (ii) perfusion with HiFA + G abolished preconditioning and activation of ERKp44/42 (iii) DCA pretreatment largely reversed the harmful effects of HiFA. Hearts from non-preconditioned diet rats exhibited smaller infarcts, but could not be preconditioned, regardless of the substrate. Similar results were obtained upon substrate manipulation of hearts from young rats. Abolishment of preconditioning in diet rats may be due to altered myocardial metabolic patterns resulting from changes in circulating FA. The harmful effects of HiFA were attenuated by stimulation of glycolysis and inhibition of FA oxidation.

Molecular effects of Moringa leaf extract on insulin resistance and reproductive function in hyperinsulinemic male rats

BACKGROUND

Many studies have reported that insulin resistance impairs the antioxidant defense system and causes male infertility. Moringa oleifera is a medicinal plant that has been employed for the medicament of many disorders. It controls the levels of glucose and manages male sexual disorders. However, its extracts can reverse insulin resistance-linked metabolic alterations remains unknown. Therefore, the current study investigated the potential of the aqueous leaves extract from Moringa oleifera to reverse insulin resistance and testicular disorders in rats.

METHODS

Rats were fed either a chow (as a control group) or a high fructose diet (HFD, to persuade a state of insulin resistance), in addition to a group of rats fed HFD and treated with Moringa (300 mg/kg) for 4 weeks.

RESULTS

Moringa reversed hepatic insulin insensitivity and this was linked to up-regulation of genes involved in insulin receptors and glucose uptake in the liver. These results were associated with amended the insulin level in serum and standardization of insulin sensitivity. In addition, it improved the serum testosterone level and the gene expression of the testicular steridogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD).

CONCLUSION

Taken together, our findings demonstrate that Moringa reversed HFD diet-induced insulin resistance and improved the testicular function.

Novel Strategies to Treat Hepatic Steatosis and Steatohepatitis

Concordant with soaring obesity rates, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in the world. The obesity epidemic demands interventions to reverse obesity-associated hepatic steatosis, NAFLD, and nonalcoholic steatohepatitis, and several new pharmacologic approaches have been developed within the past several years. Steatosis develops when energy delivery to the liver, modulated by rates of hepatic lipogenesis, exceeds the capacity of the liver to utilize or export this energy. Therefore, pharmacologic approaches to reverse hepatic steatosis have focused largely, though not exclusively, on (1) reducing substrate availability to the liver, (2) reducing hepatic lipid synthesis, and (3) increasing hepatic mitochondrial fat oxidation (Figure 1). This Perspective will discuss these three classes of emerging pharmacologic therapies against hepatic steatosis, with the ultimate intent to ameliorate NAFLD and/or nonalcoholic steatohepatitis, and the advantages and pitfalls afforded by each strategy to treat these epidemics of obesity-associated liver disease.

Tributyltin exposure disturbs hepatic glucose metabolism in male mice

Some previous studies showed that organotin compounds induced diabetes in animal models. The underlying mechanisms should be further revealed. In this study, male KM mice were exposed to tributyltin (TBT) at 0.5, 5 and 50 μg/kg once every three days for 45 days. The TBT-treated mice exhibited an elevation of fasting blood glucose level and glucose intolerance. The fasting serum insulin levels were increased and reached a significant difference in the 50 μg/kg group; the glucagon levels were significantly decreased in all the treatments. Pancreatic β-cell mass was significantly decreased in all the treatments; α-cell mass showed a significant decrease in the 5 and 50 ug/kg groups. The transcription of pancreatic insulin gene (Ins2) showed an up-regulation and reached a significant difference in the 5 and 50 μg/kg groups, which would be responsible for the increased serum insulin levels. The transcription of glucagon gene (Gcg) in the pancreas was significantly down-regulated in the 5 and 50 ug/kg groups. The protein expression of hepatic glucagon receptor was down-regulated, while the expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase was up-regulated accompanied by increased hepatic glycogen content. These results indicated that hepatic gluconeogenesis was enhanced during insulin resistance stage caused by TBT exposure, which would exert a potential risk inducing the development of diabetes mellitus.

Antiretroviral drug-induced endothelial dysfunction is improved by dual PPARα/γ stimulation in obesity

Obesity rates are rising in HIV-infected populations; however, the putative role of highly active antiretroviral therapy (HAART) in the development of endothelial and cardiovascular derangements in the presence of pre-existing overweight/obesity is unclear. Although dual peroxisome proliferator-activated receptors-alpha/gamma (PPARα/γ) stimulation mitigates HAART-induced metabolic dysfunction, vascular effects are unresolved. To investigate whether HAART induces vascular dysfunction in obesity and to explore the underlying mechanisms of PPARα/γ stimulation, male Wistar rats were placed on a high-calorie diet for 16 weeks. After 10 weeks, HAART (lopinavir/ritonavir, azidothymidine/lamivudine) with/without PPARα/γ agonist, Saroglitazar, was administered daily for six weeks. Excised thoracic aorta rings were subjected to isometric tension studies and Western blot measurements. HAART+Saroglitazar-treated obese animals recorded lower adiposity indices (4.3 ± 0.5%) vs. HAART only-treated obese rats (5.6 ± 0.3%; p < .01). Maximum acetylcholine-induced vasorelaxation (R_max), was lower in obese+HAART group (76.10 ± 3.58%) vs. obese control (101.40 ± 4.75%; p < .01). However, R_max was improved in obese+ HAART+Saroglitazar (101.00 ± 3.12%) vs. obese+HAART rats (p < .001). The mean LogEC₅₀ was improved in obese+HAART+Saroglitazar vs. obese+HAART group; p = .003. Improved endothelial function in obese+ HAART+Saroglitazar group was associated with upregulation of eNOS, PKB/Akt and downregulated p22-phox expression vs. obese+HAART group. Therefore, PPARα/γ stimulation attenuated HAART-induced endothelial dysfunction by upregulating vasoprotective eNOS, PKB/Akt signaling and downregulating pro-oxidative p22-phox expression.

Rice bran oil ameliorates hepatic insulin resistance by improving insulin signaling in fructose fed-rats

Background

Insulin resistance is an inadequate metabolic response of the peripheral tissue to circulating insulin. It plays an important pathophysiological role in type 2 diabetes mellitus. The purpose of the study was to investigate the molecular effects of rice bran oil (RBO) on the gene expression of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), glucose transporters-4 and 5 (GLUT-4 and 5) in insulin-resistant rats induced by high fructose diet (HFD).

Methods

Rats were divided into six groups (10 rats each) as follows: Groups 1 and 2: rats received a standard diet with corn oil or RBO (as the sole source of fat), respectively. Group 3: animals fed on HFD, which was furtherly divided into 2 sub-groups: rats fed HFD either for one (HFD1) or for 2 months (HFD2). Group 4, rats fed HFD containing RBO for 1 month (HFD1 + RBO), while rats in group 5 fed HFD for 30 days then RBO was added to the diet for another 30 days (HFD2 + RBO). Serum levels of glucose and insulin, as well as hepatic gene expression of insulin receptors and glucose transporters were determined. Livers were isolated for histopathological study.

Results

HFD induced insulin resistance with a reduction in the hepatic level of insulin receptor and glucose transporters at both protein and molecular levels. Addition of RBO improved the insulin sensitivity and up-regulated the expression of the tested genes.

Conclusion

HFD impaired the insulin sensitivity of the hepatocytes by down-regulating the insulin receptor genes. Addition of RBO alleviated all the hazardous effects.

ENOblock inhibits the pathology of diet-induced obesity

Obesity is a medical condition that impacts on all levels of society and causes numerous comorbidities, such as diabetes, cardiovascular disease, and cancer. We assessed the suitability of targeting enolase, a glycolysis pathway enzyme with multiple, secondary functions in cells, to treat obesity. Treating adipocytes with ENOblock, a novel modulator of these secondary ‘moonlighting’ functions of enolase, suppressed the adipogenic program and induced mitochondrial uncoupling. Obese animals treated with ENOblock showed a reduction in body weight and increased core body temperature. Metabolic and inflammatory parameters were improved in the liver, adipose tissue and hippocampus. The mechanism of ENOblock was identified as transcriptional repression of master regulators of lipid homeostasis (Srebp-1a and Srebp-1c), gluconeogenesis (Pck-1) and inflammation (Tnf-α and Il-6). ENOblock treatment also reduced body weight gain, lowered cumulative food intake and increased fecal lipid content in mice fed a high fat diet. Our results support the further drug development of ENOblock as a therapeutic for obesity and suggest enolase as a new target for this disorder.

Highly Active Antiretroviral Therapy Alters Sperm Parameters and Testicular Antioxidant Status in Diet-Induced Obese Rats

The efficacy of highly active antiretroviral therapy (HAART) has led to an increase demand for therapeutic use, thereby necessitating investigation into drug toxicity. This study was designed to investigate the in vivo effects of HAART on sperm parameters and testicular oxidative stress in lean and obese rats. Wistar rats (males, n = 40, weighing 180~200 g) were assigned randomly into 4 groups and treated accordingly for 16 weeks as follows: Control (C): lean group fed with standard rat chow; Diet induced obesity (DIO): obese animals fed a high caloric diet; C + ART: lean animals treated with HAART; DIO + ART: obese animals treated with HAART. An antiretroviral drug combination of Tenofovir, Emtricitabine and Efavirenz at a dose of 17, 26 and 50 mg/kg/day was administered for the latter 6 weeks via jelly cube feeding. At the end of the experimental period, sperm analysis was performed on sperm collected from the caudal epididymis, while the testis was homogenized for antioxidant enzyme and lipid peroxidation assays. Results showed that HAART significantly decreased sperm motility (p < 0.05) in both lean and obese animals, and viability (p < 0.05) in the DIO group. Testicular glutathione, catalase and superoxide dismutase were significantly decreased (p < 0.05), while Thiobarbituric acid reactive substances (TBARS) levels were significantly increased (p < 0.05) when the DIO+ART group was compared to Control group. Thus, the decreased sperm qualities associated with HAART might be as a result of increased testicular oxidative stress prominent in obese animals.

Peroxisome proliferator-activated receptors as therapeutic targets for heart failure

Heart failure (HF) is a common clinical syndrome that affects more than 23 million individuals worldwide. Despite the marked advances in its management, the mortality rates in HF patients have remained unacceptably high. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription regulators, involved in the regulation of fatty acid and glucose metabolism. PPAR agonists are currently used for the treatment of type II diabetes mellitus and hyperlipidemia; however, their role as therapeutic agents for HF remains under investigation. Preclinical studies have shown that pharmacological modulation of PPARs can upregulate the expression of fatty acid oxidation genes in cardiomyocytes. Moreover, PPAR agonists were proven able to improve ventricular contractility and reduce cardiac remodelling in animal models through their anti-inflammatory, anti-oxidant, anti-fibrotic, and anti-apoptotic activities. Whether these effects can be replicated in humans is yet to be proven. This article reviews the interactions of PPARs with the pathophysiological mechanisms of HF and how the pharmacological modulation of these receptors can be of benefit for HF patients.

Rosiglitazone promotes cardiac hypertrophy and alters chromatin remodeling in isolated cardiomyocytes

Rosiglitazone is an anti-diabetic agent that raised a major controversy over its cardiovascular adverse effects. There is in vivo evidence that Rosiglitazone promotes cardiac hypertrophy by PPAR-γ-independent mechanisms. However, whether Rosiglitazone directly alters hypertrophic growth in cardiac cells is unknown. Chromatin remodeling by histone post-translational modifications has emerged as critical for many cardiomyopathies. Based on these observations, this study was initiated to investigate the cardiac hypertrophic effect of Rosiglitazone in a cellular model of primary neonatal rat cardiomyocytes (NRCM). We assessed whether the drug alters cardiac hypertrophy and its relationship with histone H3 phosphorylation. Our study showed that Rosiglitazone is a mild pro-hypertrophic agent. Rosiglitazone caused a significant increase in the release of brain natriuretic peptide (BNP) into the cell media and also increased cardiomyocytes surface area and atrial natriuretic peptide (ANP) protein expression significantly. These changes correlated with increased cardiac phosphorylation of p38 MAPK and enhanced phosphorylation of H3 at serine 10 globally and at one cardiac hypertrophic gene locus. These results demonstrate that Rosiglitazone causes direct cardiac hypertrophy in NRCM and alters H3 phosphorylation status. They suggest a new mechanism of Rosiglitazone cardiotoxicity implicating chromatin remodeling secondary to H3 phosphorylation, which activate the fetal cardiac gene program.

Does Weight Gain Associated with Thiazolidinedione Use Negatively Affect Cardiometabolic Health?

Thiazolidinediones (TZDs) are oral anti-diabetic drugs that are peroxisome proliferator-activated receptor gamma (PPARγ) agonists and act as insulin sensitizers. The clinical efficacy and durability of the currently available TZDs in improving glycemic control are well established. However, TZDs cause weight gain, which has been thought to be a class effect of TZDs. TZD-associated weight gain may result mainly from increased fat mass and fluid retention and may be in part congruent to the mechanism of action of TZD. Increases in fat mass are almost exclusively limited to subcutaneous fat, while there are no effects or even decreases in visceral fat. Insulin resistance and cardiovascular risk associated with fat accumulation (obesity) depend on body fat distribution, with visceral fat associated with insulin resistance and a greater degree of risk than subcutaneous fat. Therefore, despite TZD-associated weight gain, TZDs are less likely to confer an increased risk of insulin resistance and cardiovascular complications. As patients with diabetes are younger and/or more obese in Korea, TZDs may be a cost-effective treatment option, offering a unique insulin-sensitizing action and good durability for the long-term management of type 2 diabetes.

Beneficial Effects of Phyllanthus amarus Against High Fructose Diet Induced Insulin Resistance and Hepatic Oxidative Stress in Male Wistar Rats

Insulin resistance (IR) is a characteristic feature of obesity, type 2 diabetes mellitus, and cardiovascular diseases. Emerging evidence suggests that the high-fructose consumption is a potential and important factor responsible for the rising incidence of IR. The present study investigates the beneficial effects of aqueous extract of Phyllanthus amarus (PAAE) on IR and oxidative stress in high-fructose (HF) fed male Wistar rats. HF diet (66% of fructose) and PAAE (200 mg/kg body weight/day) were given concurrently to the rats for a period of 60 days. Fructose-fed rats showed weight gain, hyperglycemia, hyperinsulinemia, impaired glucose tolerance, impaired insulin sensitivity, dyslipidemia, hyperleptinemia, and hypoadiponectinemia (P < 0.05) after 60 days. Co-administration of PAAE along with HF diet significantly ameliorated all these alterations. Regarding hepatic antioxidant status, higher lipid peroxidation and protein oxidation, lower reduced glutathione levels and lower activities of enzymatic antioxidants, and the histopathological changes like mild to severe distortion of the normal architecture as well as the prominence and widening of the liver sinusoids observed in the HF diet-fed rats were significantly prevented by PAAE treatment. These findings indicate that PAAE is beneficial in improving insulin sensitivity and attenuating metabolic syndrome and hepatic oxidative stress in fructose-fed rats.

Myocardial susceptibility to ischaemia/reperfusion in obesity: a re-evaluation of the effects of age

Background

Reports on the effect of age and obesity on myocardial ischaemia/reperfusion (I/R) injury and ischaemic preconditioning are contradictory. The aim of this study was to re-evaluate the effects of age and diet-induced obesity (DIO) on myocardial I/R injury and preconditioning potential.

Methods

Four groups of Wistar male rats were used: age-matched controls (AMC) receiving standard rat chow for (i) 16 weeks and (ii) 16 months respectively; DIO rats receiving a sucrose-supplemented diet for (iii) 16 weeks and (iv) 16 months respectively. The ages of groups (i) and (iii) were 22 weeks (“young”) and groups (ii) and (iv) 17 months (“middle-aged”) at time of experimentation. Isolated perfused working hearts were subjected to 35 min regional ischaemia/1 h reperfusion. Endpoints were infarct size (tetrazolium staining) and functional recovery. Hearts were preconditioned by 3 × 5 min ischaemia/5 min reperfusion. Results were processed using GraphPad Prism statistical software.

Results

Age did not affect baseline heart function before induction of ischaemia and I/R damage as indicated by infarct size and similar values were obtained in hearts from both age groups. Age also had no effect on functional recovery of hearts during reperfusion after regional ischaemia in AMC rats, but cardiac output during reperfusion was better in hearts from middle-aged than young DIO rats.

The diet reduced infarct size in hearts from young rats (% of area at risk: AMC: 32.4 ± 3.6; DIO: 20.7 ± 2.9, p < 0.05), with no differences in hearts from middle-aged rats (AMC: 24.6 ± 4.6; DIO: 28.3 ± 13.5, p = NS). Compared to their respective AMC, diet-induced obesity had no significant effect on functional recovery of hearts from both age groups after exposure to regional ischaemia.

When exposed to the more severe stress of global ischaemia, the functional recovery potential of middle-aged DIO rats appeared to be impeded compared to hearts of young DIO rats, while age had no effect on the functional recovery of AMC hearts.

Preconditioning reduced infarct size in hearts from young control rats and both middle-aged groups, but not from young DIO rats. Age had a significant effect on functional recovery in preconditioning: it was improved in hearts from young control and DIO rats, but depressed in both middle-aged groups.

Conclusions

The data showed that middle-age and obesity had no effect on baseline myocardial function and did not increase susceptibility to I/R damage upon exposure to regional ischaemia. On the contrary, obesity reduced I/R damage in young rats. Preconditioned aging hearts showed a decreased infarct size, but a reduction in functional recovery.

Does Thiazolidinedione therapy exacerbate fluid retention in congestive heart failure?

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

Cardioprotective role of peroxisome proliferator-activated receptor-γ agonist, rosiglitazone in a unique murine model of diabetic cardiopathy

AIMS

Rosiglitazone (RSZ), a PPARγ agonist was potent efficacious insulin sensitizing blockbuster drug for treatment of Type 2 diabetes mellitus (T2DM) but the benefit of PPARγ activation in congestive heart failure (CHF) was controversial. The present work was planned to study the role of RSZ in diabetic cardiopathy.

MAIN METHODS

Zucker fa/fa rats, the genetic model of T2DM were subjected to constriction of suprarenal abdominal aorta so that they represent a combined model of diabetes and cardiopathy. The development cardiopathy was assessed biochemically (plasma BNP and aldosterone levels), using echocardiography and expression angiotensin II receptor type 1a gene in heart and Endothelin-1 gene in aorta. Rats were treated with RSZ and in combination with amiloride for four weeks and were assessed to evaluate the effect of RSZ or amiloride or its combination on antidiabetic activity, adverse or toxic effects and congestive heart failure status.

KEY FINDINGS

RSZ shows its anti-diabetic effect from 0.3mg/kg dose onwards and at 3mg/kg dose levels it caused beneficial effects (reduction of blood pressure) on cardiovascular system and at highest (30mg/kg) dose it starts showing adverse effects like body weight gain, edema, left ventricular hypertrophy. However, when highest dose of RSZ animals were treated with amiloride (ENaC inhibitor) at 2mg/kg the reversal of the adverse effects was evident, indicating the combination of RSZ and amiloride is beneficial in diabetic cardiopathy model.

SIGNIFICANCE

RSZ and amiloride combination appeared promising treatment in diabetic patients with cardiopathy without any side effect.

Serum Natriuretic Peptides as Differential Biomarkers Allowing for the Distinction between Physiologic and Pathologic Left Ventricular Hypertrophy

Given the proven utility of natriuretic peptides as serum biomarkers of cardiovascular maladaptation and dysfunction in humans and the high cross-species sequence conservation of atrial natriuretic peptides, natriuretic peptides have the potential to serve as translational biomarkers for the identification of cardiotoxic compounds during multiple phases of drug development. This work evaluated and compared the response of N-terminal proatrial natriuretic peptide (NT-proANP) and N-terminal probrain natriuretic peptide (NT-proBNP) in rats during exercise-induced and drug-induced increases in cardiac mass after chronic swimming or daily oral dosing with a peroxisome proliferator-activated receptor γ agonist. Male Sprague-Dawley rats aged 8 to 10 weeks were assigned to control, active control, swimming, or drug-induced cardiac hypertrophy groups. While the relative heart weights from both the swimming and drug-induced cardiac hypertrophy groups were increased 15% after 28 days of dosing, the serum NT-proANP and NT-proBNP values were only increased in association with cardiac hypertrophy caused by compound administration. Serum natriuretic peptide concentrations did not change in response to adaptive physiologic cardiac hypertrophy induced by a 28-day swimming protocol. These data support the use of natriuretic peptides as fluid biomarkers for the distinction between physiological and drug-induced cardiac hypertrophy.

Chronic stress and Rosiglitazone increase indices of vascular stiffness in male rats

Prolonged and/or frequent exposure to psychological stress responses may lead to deterioration of organs and tissues, predisposing to disease. In agreement with this, chronic psychosocial stress is linked to greater cardiovascular risk, including increased incidence of atherosclerosis, myocardial ischemia, coronary heart disease, and death. Thus the association between stress and cardiovascular dysfunction represents an important node for therapeutic intervention in cardiovascular disease. Here we report that 2weeks of chronic variable stress (CVS) increased indices of vascular stiffness, including increased collagen deposition in the aortic adventitia and increased resting pulse pressure, in male rats. Thus CVS may represent a useful rodent model for stress-associated CVD, especially for aging populations for which widening pulse pressure is a well-known risk factor. Additionally, we report that the thiazolidinedione Rosiglitazone (RSG) blunts chronic stress-associated increases in circulating corticosterone. Despite this, RSG was not protective against adverse cardiovascular outcomes associated with chronic stress. Rather RSG itself is associated with increased pulse pressure, and this is exacerbated by chronic stress-highlighting that chronic stress may represent an additional contributor to RSG-associated cardiovascular risk.

Peroxisome Proliferator-Activated Receptors and the Heart: Lessons from the Past and Future Directions

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear family of ligand activated transcriptional factors and comprise three different isoforms, PPAR-α, PPAR-β/δ, and PPAR-γ. The main role of PPARs is to regulate the expression of genes involved in lipid and glucose metabolism. Several studies have demonstrated that PPAR agonists improve dyslipidemia and glucose control in animals, supporting their potential as a promising therapeutic option to treat diabetes and dyslipidemia. However, substantial differences exist in the therapeutic or adverse effects of specific drug candidates, and clinical studies have yielded inconsistent data on their cardioprotective effects. This review summarizes the current knowledge regarding the molecular function of PPARs and the mechanisms of the PPAR regulation by posttranslational modification in the heart. We also describe the results and lessons learned from important clinical trials on PPAR agonists and discuss the potential future directions for this class of drugs.

Chronic Exposure to Aroclor 1254 Disrupts Glucose Homeostasis in Male Mice via Inhibition of the Insulin Receptor Signal Pathway

Epidemiological studies demonstrate that polychlorinated biphenyls (PCBs) induce diabetes and insulin resistance. However, the development of diabetes caused by PCBs and its underlying mechanisms are still unclear. In the present study, male C57BL/6 mice were orally administered with Aroclor 1254 (0.5, 5, 50, and 500 μg/kg) once every 3 days for 60 days. The body weight and the fasting blood glucose levels were significantly elevated; the levels of serum insulin, resistin, tumor necrosis factor α (TNFα), and interleukin-6 (IL-6) increased, while glucagon levels decreased in the animals treated with Aroclor 1254. Pancreatic β-cell mass significantly increased, while α-cell mass was reduced. Aroclor 1254 inhibited the expression of the insulin receptor signaling cascade, including insulin receptor, insulin receptor substrate, phosphatidylinositol 3-kinase-Akt, and protein kinase B and glucose transporter 4, both in the skeletal muscle and the liver. The results suggested that chronic exposure to Aroclor 1254 disrupted glucose homeostasis and induced hyperinsulinemia. The significant elevation of serum resistin, TNFα and IL-6 indicated that obesity caused by Aroclor 1254 is associated with insulin resistance. The elevation of blood glucose levels could have been mainly as a result of insulin receptor signals pathway suppression in skeletal muscle and liver, and a decrease in pancreatic α-cells, accompanied by a reduction of serum glucagon levels, may play an important role in the development of type 2 diabetes.

Rosiglitazone inhibits hepatic insulin resistance induced by chronic pancreatitis and IKK-β/NF-κB expression in liver

OBJECTIVES

This study aimed to investigate the influence of rosiglitazone on hepatic insulin resistance and the expressions of IκB kinase-β (IKK-β)/nuclear factor-κB (NF-κB) in chronic pancreatitis (CP).

METHODS

After CP was induced in rats, rosiglitazone and GW9662 were administered at the doses of 4 and 2 mg/kg per day for 4 weeks, respectively. Then, glucose and insulin tolerance tests were performed. Hepatocytes were isolated for the glucose release experiments. Determination of the IKK-β, NF-κB, and Ser307p-insulin receptor substrates-1 (Ser307p-IRS-1) expression in the liver was performed.

RESULTS

The increased plasma glucose, reduced insulin sensitivity, and the capacity of insulin to suppress glucose release in hepatocytes were observed in CP rats. The IKK-β, NF-κB, and Ser307p-IRS-1 expressions were significantly higher in the liver of CP rats than in sham-operated rats (P < 0.05). Rosiglitazone treatment significantly improved hepatic insulin sensitivity and inhibited the IKK-β, NF-κB, and Ser307p-IRS-1 expressions in the liver (P < 0.05). Counteraction with peroxisome proliferator-activated receptor-γ by GW9662 attenuated the aforementioned effects of rosiglitazone.

CONCLUSIONS

Rosiglitazone attenuates hepatic insulin resistance induced by CP. The inhibition of hepatic IKK-β and NF-κB expressions via peroxisome proliferator-activated receptor-γ may be involved in the therapeutic effect of rosiglitazone.

Minireview: Challenges and opportunities in development of PPAR agonists

The clinical impact of the fibrate and thiazolidinedione drugs on dyslipidemia and diabetes is driven mainly through activation of two transcription factors, peroxisome proliferator-activated receptors (PPAR)-α and PPAR-γ. However, substantial differences exist in the therapeutic and side-effect profiles of specific drugs. This has been attributed primarily to the complexity of drug-target complexes that involve many coregulatory proteins in the context of specific target gene promoters. Recent data have revealed that some PPAR ligands interact with other non-PPAR targets. Here we review concepts used to develop new agents that preferentially modulate transcriptional complex assembly, target more than one PPAR receptor simultaneously, or act as partial agonists. We highlight newly described on-target mechanisms of PPAR regulation including phosphorylation and nongenomic regulation. We briefly describe the recently discovered non-PPAR protein targets of thiazolidinediones, mitoNEET, and mTOT. Finally, we summarize the contributions of on- and off-target actions to select therapeutic and side effects of PPAR ligands including insulin sensitivity, cardiovascular actions, inflammation, and carcinogenicity.

High carbohydrate and high fat diets protect the heart against ischaemia/reperfusion injury

Background

Although obesity is still considered a risk factor in the development of cardiovascular disorders, recent studies suggested that it may also be associated with reduced morbidity and mortality, the so-called “obesity paradox”. Experimental data on the impact of diabetes, obesity and insulin resistance on myocardial ischaemia/reperfusion injury are controversial. Similar conflicting data have been reported regarding the effects of ischaemic preconditioning on ischaemia/reperfusion injury in hearts from such animals. The aim of the present study was to evaluate the susceptibility to myocardial ischaemia/reperfusion damage in two models of diet-induced obesity as well as the effect of ischaemic and pharmacological preconditioning on such hearts.

Methods

Three groups of rats were fed with: (i) normal rat chow (controls) (ii) a sucrose-supplemented diet (DIO) (iii) a high fat diet (HFD). After 16 weeks, rats were sacrificed and isolated hearts perfused in the working mode and subjected to 35 min regional ischaemia/60 min reperfusion. Endpoints were infarct size and functional recovery. Infarct size was determined, using tetrazolium staining. Activation of PKB/Akt and ERKp44/p42 (RISK pathway) during early reperfusion was determined using Western blot. Statistical evaluation was done using ANOVA and the Bonferroni correction.

Results

Infarct sizes of non-preconditioned hearts from the two obese groups were significantly smaller than those of the age-matched controls. Ischaemic as well as pharmacological (beta-adrenergic) preconditioning with a beta2-adrenergic receptor agonist, formoterol, caused a significant reduction in infarct size of the controls, but were without effect on infarct size of hearts from the obese groups. However, ischaemic as well as beta-preconditioning caused an improvement in functional performance during reperfusion in all three groups. A clear-cut correlation between the reduction in infarct size and activation of ERKp44/p42 and PKB/Akt was not observed: The reduction in infarct size observed in the non-preconditioned hearts from the obese groups was not associated with activation of the RISK pathway. However, beta-adrenergic preconditioning caused a significant activation of ERKp44/p42, but not PKB/Akt, in all three groups.

Conclusions

Relatively long-term administration of the two obesity-inducing diets resulted in cardioprotection against ischaemia/reperfusion damage. Further protection by preconditioning was, however, without effect on infarct size, while an improvement in functional recovery was observed.

Effects of rosiglitazone treatment on the pentose phosphate pathway and glutathione-dependent enzymes in liver and kidney of rats fed a high-fat diet

BACKGROUND

Animals fed high-fat diets have been shown to develop hyperglycemia, insulin resistance, hyperlipidemia, and moderate obesity, which resemble the human metabolic syndrome. Obesity, the metabolic syndrome, and some thiazolidinediones, which act as insulin sensitizers, may increase oxidative stress, and/or influence the levels of cellular reducing equivalents and homeostasis.

OBJECTIVE

This study investigated the effects of a high-fat diet, rosiglitazone, or a high-fat diet plus rosiglitazone on metabolic syndrome parameters and crucial liver and kidney enzyme activities in rats.

METHODS

Male Wistar rats were assigned to 4 groups (n = 6 per group): (1) the fat (F) group was fed a rodent diet comprising 45 kcal% fat, (2) the rosiglitazone (R) group was fed a standard rat chow comprising 4.97 kcal% fat plus rosiglitazone (3 mg/kg.d), (3) the fat + rosiglitazone (FR) group was fed a rodent diet comprising 45 kcal% fat (as lard, product D12451) plus rosiglitazone (3 mg/kg.d), and (4) the control (C) group was fed a standard rat chow comprising 4.97 kcal% fat. Animals were housed for 4 weeks, at which time the liver and kidney were isolated for spectrophotometric determination of enzyme activities. Body weight was measured before treatment (baseline) and then weekly throughout the study. Adiposity was measured at the end of the 4 weeks.

RESULTS

The activities of glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6-PGD), glutathione reductase (GR), and glutathione-S-transferase (GST) were significantly reduced in the livers of groups F, R, and FR compared with group C (all P < 0.05). Kidney G6PD, 6-PGD, and GR were found to be significantly lower in group R compared with the other groups (all P < 0.05). Kidney GST was similar in all groups. Plasma glucose, triglyceride, and insulin concentrations were significantly higher than in group F versus the other groups (all P < 0.05). Adiposity was increased in groups F and FR compared with groups C and R (all P < 0.05). Serum cholesterol concentrations were similar in all groups.

CONCLUSIONS

In this study, high-fat diet in rats decreased the enzyme activities responsible for pentose phosphate pathway and glutathione-dependent metabolism in liver but not in kidney. Similarly, these enzyme activities were inhibited with rosiglitazone treatment alone in both organs.

Cardioprotective and anti-hypertensive effects of Prosopis glandulosa in rat models of pre-diabetes

Aim

Obesity and type 2 diabetes present with two debilitating complications, namely, hypertension and heart disease. The dried and ground pods of Prosopis glandulosa (commonly known as the Honey mesquite tree) which is part of the Fabaceae (or legume) family are currently marketed in South Africa as a food supplement with blood glucose-stabilising and anti-hypertensive properties. We previously determined its hypoglycaemic effects, and in the current study we determined the efficacy of P glandulosa as anti-hypertensive agent and its myocardial protective ability.

Methods

Male Wistar rats were rendered either pre-diabetic (diet-induced obesity: DIO) or hypertensive (high-fat diet: HFD). DIO animals were treated with P glandulosa (100 mg/kg/day for the last eight weeks of a 16-week period) and compared to age-matched controls. Hearts were perfused ex vivo to determine infarct size. Biometric parameters were determined at the time of sacrifice. Cardiac-specific insulin receptor knock-out (CIRKO) mice were similarly treated with P glandulosa and infarct size was determined. HFD animals were treated with P glandulosa from the onset of the diet or from weeks 12–16, using captopril (50 mg/kg/day) as the positive control. Blood pressure was monitored weekly.

Results

DIO rats and CIRKO mice: P glandulosa ingestion significantly reduced infarct size after ischaemia–reperfusion. Proteins of the PI-3-kinase/PKB/Akt survival pathway were affected in a manner supporting cardioprotection. HFD model: P glandulosa treatment both prevented and corrected the development of hypertension, which was also reflected in alleviation of water retention.

Conclusion

P glandulosa was cardioprotective and infarct sparing as well as anti-hypertensive without affecting the body weight or the intra-peritoneal fat depots of the animals. Changes in the PI-3-kinase/PKB/Akt pathway may be causal to protection. Results indicated water retention, possibly coupled to vasoconstriction in the HFD animals, while ingestion of P glandulosa alleviated both. We concluded that treatment of pre-diabetes, type 2 diabetes or hypertension with P glandulosa poses possible beneficial health effects.

Increased susceptibility of db/db mice to rosiglitazone-induced plasma volume expansion: role of dysregulation of renal water transporters

Thiazolidinediones (TZDs), which are synthetic peroxisome proliferator-activated receptor subtype-γ (PPARγ), agonists are highly effective for treatment of type 2 diabetes. However, the side effect of fluid retention has significantly limited their application. Most of the previous studies addressing TZD-induced fluid retention employed healthy animals. The underlying mechanism of this phenomenon is still incompletely understood, particularly in the setting of disease state. The present study was undertaken to examine rosiglitazone (RGZ)-induced fluid retention in db/db mice and to further investigate the underlying mechanism. In response to RGZ treatment, db/db mice exhibited an accelerated plasma volume expansion as assessed by hematocrit (Hct) and fluorescent nanoparticles, in parallel with a greater increase in body weight, compared with lean controls. In response to RGZ-induced fluid retention, urinary Na(+) excretion and urine volume were significantly increased in lean mice. In contrast, the natriuretic and diuretic responses were significantly blunted in db/db mice. RGZ db/db mice exhibited a parallel decrease in plasma Na(+) concentration and plasma osmolality, contrasting to unchanged levels in lean controls. Imunoblotting analysis showed downregulation of renal aquaporin (AQP) 2 expression in response to RGZ treatment in lean mice but not in db/db mice. Renal AQP3 protein expression was unaffected by RGZ treatment in lean mice but was elevated in db/db mice. In contrast, the expression of Na(+)/H(+) exchanger-3 (NHE3) and NKCC2 was unchanged in either mouse strain. Together these results suggest that compared with the lean controls, db/db mice exhibited accelerated plasma volume expansion that was in part due to the inappropriate response of renal water transporters.

Effect of chronic CPT-1 inhibition on myocardial ischemia-reperfusion injury (I/R) in a model of diet-induced obesity

PURPOSE

By increasing circulating free fatty acids and the rate of fatty acid oxidation, obesity decreases glucose oxidation and myocardial tolerance to ischemia. Partial inhibition of fatty acid oxidation may improve myocardial tolerance to ischemia/reperfusion (I/R) in obesity. We assessed the effects of oxfenicine treatment on post ischemic cardiac function and myocardial infarct size in obese rats.

METHODS

Male Wistar rats were fed a control diet or a high calorie diet which resulted in diet induced obesity (DIO) for 16 weeks. Oxfenicine (200 mg/kg/day) was administered to control and DIO rats for the last 8 weeks. Isolated hearts were perfused and infarct size and post ischemic cardiac function was assessed after regional or global ischemia and reperfusion. Cardiac mitochondrial function was assessed and myocardial expression and activity of CPT-1 (carnitine palmitoyl transferase-1) and IRS-1 (insulin receptor substrate-1) was assessed using Western blot analysis.

RESULTS

In the DIO rats, chronic oxfenicine treatment improved post ischemic cardiac function and reduced myocardial infarct size after I/R but had no effect on the cardiac mitochondrial respiration. Chronic oxfenicine treatment worsened post ischemic cardiac function, myocardial infarct size and basal mitochondrial respiration in control rat hearts. Basal respiratory control index (RCI) values, state 2 and state 4 respiration rates and ADP phosphorylation rates were compromised by oxfenicine treatment.

CONCLUSION

Chronic oxfenicine treatment improved myocardial tolerance to I/R in the obese rat hearts but decreased myocardial tolerance to I/R in control rat hearts. This decreased tolerance to ischemia of oxfenicine treated controls was associated with adverse changes in basal and reoxygenation mitochondrial function. These changes were absent in oxfenicine treated hearts from obese rats.

Short-Term Therapy with Rosiglitazone, a PPAR-γ Agonist, Improves Metabolic Profile and Vascular Function in Nonobese Lean Wistar Rats

A number of preclinical and clinical studies have reported blood-pressure-lowering benefits of thiazolidinediones in diabetic subjects and animal models of diabetes. This study was designed to further elucidate vascular effects of rosiglitazone, on healthy nonobese, lean animals. Adult male Wistar rats were randomized and assigned to control and rosiglitazone-treated groups and were dosed daily with either vehicle or rosiglitazone (10 mg kg(-1) day(-1)) by oral gavage for 5 days. Compared with control group, rosiglitazone treatment significantly reduced plasma levels of triglycerides (>240%) and nonesterified free fatty acids (>268%) (both, P < 0.001). There were no changes in vascular contractility to KCl or noradrenaline between two groups. However, rosiglitazone therapy improved carbamylcholine-induced vasorelaxation (93 ± 3 % versus control 78 ± 2, P < 0.01) an effect which was abolished by L-NAME. There was no difference in sodium nitroprusside-induced vasorelaxation between the control and rosiglitazone-treated animals. These results indicate that short-term rosiglitazone therapy improves both metabolic profile and vascular function in lean rats. The vascular effect of rosiglitazone appears to be mediated by alteration in NO production possibly by activation of endothelial PPARγ. This increased NO production together with improved lipid profile may explain mechanism(s) of blood-pressure-lowering effects of thiazolidinediones on both human and experimental animals.

Protective effect of ethanolic extract of Commiphora mukul gum resin against oxidative stress in the brain of streptozotocin induced diabetic Wistar male rats

The objective of the study was to investigate the possible neuroprotective effect of ethanolic extract of Commiphora mukul gum resin (EtCMGR) against oxidative stress in the brain of streptozotocin (STZ) induced diabetic Wistar rats. The experimental animals were divided into four groups: control (C), control treated with EtCMGR (C+CM), diabetic (D) and diabetic treated with EtCMGR (D+CM). Diabetes was induced by a single intraperitoneal injection of STZ (55 mg/kg body weight). Plant extract treated groups (C+CM and D+CM) were administered EtCMGR at a dose of 200 mg/kg body weight/day by gavage for 60 days. Diabetic rats showed hyperglycemia, hypoinsulinemia with impaired insulin sensitivity. EtCMGR treatment to diabetic (D+CM group) rats prevented the rise in glucose level by 96.7 %, while enhancing insulin level (77.7 %) and improving insulin sensitivity (27.3 %) compared to D group. The brain antioxidant status of D group rats showed higher levels of lipid peroxidation (77.9 %), protein glycation (100 %), and increased activities of xanthine oxidase (47.1 %) and sorbitol dehydrogenase (101.9 %) and lowered concentration of reduced glutathione (38.2 %) and decreased activities of antioxidant enzymes i.e., glutathione reductase (24 %), glutathione peroxidase (24.4 %) and superoxide dismutase (42.1 %) and increased activities of catalase (87.4 %) and glutathione-S-transferase (45.3 %) compared to control group. While EtCMGR treatment for 60 days in D+CM group prevented the observed abnormalities of antioxidant status of D group. This study demonstrates that EtCMGR is a potent neuroprotective agent against oxidative damage induced under diabetes.

Idealized PPARγ-Based Therapies: Lessons from Bench and Bedside

The incidence of type 2 (T2D) diabetes and other chronic conditions associated with insulin resistance is increasing at an alarming rate, underscoring the need for effective and safe therapeutic strategies. Peroxisome-proliferator-activated receptor gamma (PPARγ) has emerged as a critical regulator of glucose homeostasis, lipid homeostasis, and vascular inflammation. Currently marketed drugs targeting this receptor, the thiazolidinediones (TZDs), have proven benefits on insulin resistance and hyperglycemia associated with T2D. Unfortunately, they have been associated with long-term unfavorable effects on health, such as weight gain, plasma volume expansion, bone loss, cardiovascular toxicity, and possibly cancer, and these safety concerns have led to reduced interest for many PPARγ ligands. However, over the last years, data from human genetic studies, animal models, and studies with ligands have increased our understanding of PPARγ's actions and provided important insights into how ligand development strategies could be optimized to increase effectiveness and safety of PPARγ-based therapies.

Antihyperglycemic, hypolipidemic and antioxidant activities of ethanolic extract of Commiphora mukul gum resin in fructose-fed male Wistar rats

High fructose feeding (66 % of fructose) induces type-2 diabetes in rats, which is associated with the insulin resistance, hyperinsulinemia, hypertriglyceridemia and oxidative stress. The present study was undertaken to evaluate the effect of ethanol extract of Commiphora mukul gum resin (CMEE) on blood glucose, plasma insulin, lipid profiles, reduced glutathione, lipid peroxidation, protein oxidation and enzymatic antioxidants like superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase in fructose-induced type-2 diabetic rats. A significant gain in body weight, hyperglycemia, hyperinsulinemia, increased lipid profiles, lipid peroxidation, protein oxidation and decreased reduced glutathione, activities of enzymatic antioxidants and insulin sensitivity (increased homeostasis assessment assay) were observed in high-fructose-induced diabetic rats. The administration of CMEE (200 mg/kg/day) daily for 60 days in high-fructose-induced diabetic rats reversed the above parameters significantly. CMEE has the ability to improve insulin sensitivity and delay the development of insulin resistance, aggravate antioxidant status in diabetic rats and may be used as an adjuvant therapy for patients with insulin resistance.

Physiological responses to acute psychological stress are reduced by the PPARγ agonist rosiglitazone

Physiological reactions to psychological stress are positively associated with several important chronic conditions including cardiovascular and neurodegenerative diseases and are linked to increased mortality. As such, the identification of cellular and molecular pathways that act to reduce stress responding may represent important targets for therapeutic intervention. Here we report that acute treatment with the peroxisome-proliferator activated receptor-γ (PPARγ) agonist rosiglitazone (RSG) blunts systemic responses to acute psychological stress in rats. Rats that had previously received oral RSG for 5 d exhibited a 40% reduction in the initial heart rate response to an acute restraint stress, compared with vehicle-treated controls, suggesting that increased PPARγ signaling blunts the acute autonomic response to stress. Rats previously treated with RSG likewise had a blunted hormonal response to this stressor, exhibiting a 30% reduction in peak corticosterone levels compared with controls. Moreover, stress-induced expression of c-Fos, a marker of early neuronal activation, was similarly reduced in the paraventricular hypothalamus, a key site for brain stress integration, facilitating both autonomic and hypothalamic-pituitary-adrenocortical responses to stress. Taken as a whole, these data suggest that PPARγ stimulation potently inhibits physiological responses to psychological stress, prescribing a novel role for PPARγ signaling in the regulation of brain stress integration.

Depot-specific and hypercaloric diet-induced effects on the osteoblast and adipocyte differentiation potential of adipose-derived stromal cells

Adipose-derived stromal cells (ADSCs) can be differentiated in vitro into several mesenchyme-derived cell types. We had previously described depot-specific differences in the adipocyte differentiation of ADSCs, and consequently we hypothesized that there may also be depot-specific differences in osteoblast differentiation of ADSCs. For this study, the osteoblast differentiation potential of rat subcutaneous ADSCs (scADSCs) and perirenal visceral ADSCs (pvADSCs) was compared. Osteoblast differentiation media (OM) induced markers of the osteoblastic phenotype in scADSCs, but not in pvADSCs. ADSCs harvested from rats with diet-induced visceral obesity (DIO) exhibited reduced osteoinduction, compared to lean controls, but adipocyte differentiation was not affected. Expression of the pro-osteogenic transcription factor Msx2 was significantly higher in naïve scADSCs from lean and DIO rats than in pvADSCs. Our findings indicate that ADSCs from different anatomical sites are uniquely pre-programmed in vivo in a depot-specific manner, and that diet-induced metabolic disturbances translate into reduced osteoblast differentiation of ADSCs.

Peroxisome proliferator-activated receptor-gamma agonists suppress tissue factor overexpression in rat balloon injury model with paclitaxel infusion

The role and underlying mechanisms of rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist, on myocardial infarction are poorly understood. We investigated the effects of this PPAR-γ agonist on the expression of tissue factor (TF), a primary molecule for thrombosis, and elucidated its underlying mechanisms. The PPAR-γ agonist inhibited TF expression in response to TNF-α in human umbilical vein endothelial cells, human monocytic leukemia cell line, and human umbilical arterial smooth muscle cells. The overexpression of TF was mediated by increased phosphorylation of mitogen-activated protein kinase (MAPK), which was blocked by the PPAR-γ agonist. The effective MAPK differed depending on each cell type. Luciferase and ChIP assays showed that transcription factor, activator protein-1 (AP-1), was a pivotal target of the PPAR-γ agonist to lower TF transcription. Intriguingly, two main drugs for drug-eluting stent, paclitaxel or rapamycin, significantly exaggerated thrombin-induced TF expression, which was also effectively blocked by the PPAR-γ agonist in all cell types. This PPAR-γ agonist did not impair TF pathway inhibitor (TFPI) in three cell types. In rat balloon injury model (Sprague-Dawley rats, n = 10/group) with continuous paclitaxel infusion, the PPAR-γ agonist attenuated TF expression by 70±5% (n = 4; P<0.0001) in injured vasculature. Taken together, rosiglitazone reduced TF expression in three critical cell types involved in vascular thrombus formation via MAPK and AP-1 inhibitions. Also, this PPAR-γ agonist reversed the paclitaxel-induced aggravation of TF expression, which suggests a possibility that the benefits might outweigh its risks in a group of patients with paclitaxel-eluting stent implanted.

The efficacy of Prosopis glandulosa as antidiabetic treatment in rat models of diabetes and insulin resistance

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus is rampantly increasing and the need for therapeutics is crucial. In recognition of this, untested antidiabetic agents are flooding the market. Diavite™ which is a product consisting solely of the dried and ground pods of Prosopis glandulosa (Torr.) [Fabaceae] is currently marketed as a food supplement with glucose stabilizing properties. However, these are anecdotal claims lacking scientific evidence. The aim of this study was to determine the efficacy of Prosopis glandulosa as an antidiabetic agent.

MATERIALS AND METHODS

Male Wistar rats were rendered (a) type 1 diabetic after an intraperitoneal injection of STZ (40 mg/kg) and (b) insulin resistant after a 16-week high caloric diet (DIO). Zucker fa/fa ZDF rats were used in a pilot study. Half of each group of animals was placed on Prosopis glandulosa treatment (100mg/kg/day) for 8 weeks and the remaining animals served as age-matched controls. At the time of sacrifice, blood was collected for glucose and insulin level determination, the pancreata of the STZ rats were harvested for histological analysis and cardiomyocytes prepared from the DIO and Zucker fa/fa hearts for determination of insulin sensitivity.

RESULTS

Type 1 diabetic model: Prosopis glandulosa treatment resulted in significant increased insulin levels (p<0.001), which was accompanied by a significant decrease in blood glucose levels (p<0.05). Additionally, Prosopis glandulosa treatment resulted in increased small β-cells (p<0.001) in the pancreata. The body weight of the STZ animals decreased significantly after STZ injection, with Prosopis glandulosa treatment partially preventing this. Zucker fa/fa rats: Prosopis glandulosa treatment significantly reduced fasting glucose levels (p<0.01) and improved IPGTT, when comparing treated to untreated animals. DIO insulin resistant model: Prosopis glandulosa treatment resulted in an increased basal (p<0.01) and insulin-stimulated (p<0.05) glucose uptake by cardiomyocytes prepared from this group.

CONCLUSIONS

The present study showed that Prosopis glandulosa treatment moderately lowers glucose levels in different animal models of diabetes, stimulates insulin secretion, leads to the formation of small β-cells and improves insulin sensitivity of isolated cardiomyocytes.

Pre-treatment with a DPP-4 inhibitor is infarct sparing in hearts from obese, pre-diabetic rats

Cardiovascular risk is closely associated with insulin resistance and type 2 diabetes. Therapy based on the actions of GLP-1 is currently seen as a novel approach to treat this disease. The aims of this study was therefore to use an animal model to determine whether (i) pre-treatment of obese, insulin resistant but pre-diabetic rats with a DPP4 inhibitor, PFK275-055, could protect the heart from ischaemia/reperfusion injury and (ii) the possible mechanisms involved in such protection. Obese, pre-diabetic rats (DIO) were treated for 4 weeks with 10 mg/kg/day of the DPP4 inhibitor PFK275-055. Ex vivo perfusion was used to subject hearts to ischaemia/reperfusion to determine infarct size, functional recovery and post-ischaemic activation of proteins associated with cardiac protection. Adult ventricular cardiomyocytes were isolated to determine insulin sensitivity. Other assessments included body weight, intra-peritoneal fat weight, insulin and GLP-1 levels as well as histological evaluation of the pancreata. Results showed that DIO animals had higher body mass and intra-peritoneal fat mass than chow-fed animals. They presented with elevated plasma insulin levels and lower GLP-1 levels. Treatment with the DPP4 inhibitor resulted in smaller infarct size development in hearts from DIO rats after ischaemia/reperfusion accompanied by activation of cardioprotective kinases. GLP-1 levels were elevated and plasma insulin levels lower after treatment. In addition, the beta-cell to alpha-cell ratio of the pancreas was improved. We conclude that treatment with PFK275-055 for 4 weeks protected the heart against ischaemia/reperfusion injury, elevated GLP-1 levels and improved metabolic control in obese, pre-diabetic rats.

PPAR-gamma in the Cardiovascular System

Peroxisome proliferator-activated receptor-γ (PPAR-γ), an essential transcriptional mediator of adipogenesis, lipid metabolism, insulin sensitivity, and glucose homeostasis, is increasingly recognized as a key player in inflammatory cells and in cardiovascular diseases (CVD) such as hypertension, cardiac hypertrophy, congestive heart failure, and atherosclerosis. PPAR-γ agonists, the thiazolidinediones (TZDs), increase insulin sensitivity, lower blood glucose, decrease circulating free fatty acids and triglycerides, lower blood pressure, reduce inflammatory markers, and reduce atherosclerosis in insulin-resistant patients and animal models. Human genetic studies on PPAR-γ have revealed that functional changes in this nuclear receptor are associated with CVD. Recent controversial clinical studies raise the question of deleterious action of PPAR-γ agonists on the cardiovascular system. These complex interactions of metabolic responsive factors and cardiovascular disease promise to be important areas of focus for the future.

Phenotypic and genotypic assessment of concomitant drug-induced toxic effects in liver, kidney and blood

Several studies have characterized drug-induced toxicity in liver and kidney. However, the majority of these studies have been performed with 'individual' organs in isolation. Separately, little is known about the role of whole blood as a surrogate tissue in drug-induced toxicity. Accordingly, we investigated the 'concurrent' response of liver, kidney and whole blood during a toxic assault. Rats were acutely treated with therapeutics (acetaminophen, rosiglitazone, fluconazole, isoniazid, cyclophosphamide, amphotericin B, gentamicin and cisplatin) reported for their liver and/or kidney toxicity. Changes in clinical chemistry parameters (e.g. AST, urea) and/or observed microscopic tissue damage confirmed induced hepatotoxicity and/or nephrotoxicity by all drugs. Drug-induced toxicity was not confined to an 'individual' organ. Not all drugs elicited significant alterations in phenotypic parameters of toxicity (e.g. ALT, creatinine). Accordingly, the transcriptional profile of the organs was studied using a toxicity panel of 30 genes derived from literature. Each of the test drugs generated specific gene expression patterns which were unique for all three organs. Hierarchical cluster analyses of purported hepatotoxicants and nephrotoxicants each led to characteristic 'fingerprints' (e.g. decrease in Cyp3a1 indicative of hepatotoxicity; increase in Spp1 and decrease in Gstp1 indicative of nephrotoxicity). In whole blood cells, a set of genes was derived which closely correlated with individual drug-induced concomitant changes in liver or kidney. Collectively, these data demonstrate drug-induced multi-organ toxicity. Furthermore, our findings underscore the importance of transcriptional profiling during inadequate phenotypic anchorage and suggest that whole blood may be judiciously used as a surrogate for drug-induced extra-hematological organ toxicity.

Glucose-lowering effect of DLBS3233 is mediated through phosphorylation of tyrosine and upregulation of PPARγ and GLUT4 expression

Background:

DLBS3233 is a standardized extract combination containing Lagerstroemia speciosa and Cinnamomum burmannii. The effect of DLBS3233 on glucose uptake, adiponectin secretion, and insulin signaling was examined in this study.

Methods:

3T3 Swiss albino preadipocytes and adipocytes were used to investigate gene expression detected using the reverse transcription polymerase chain reaction method. Immunoblotting assay and in vitro glucose uptake assay were also carried out in the experiment.

Results:

DLBS3233 was seen to increase phosphorylation at the tyrosine residue of the insulin receptor substrate. DLBS3233 was also found to enhance the expression of genes associated with increased insulin signaling and sensitivity, such as peroxisome proliferator-activated receptor gamma, phosphatidylinositol-3 kinase, Akt, and glucose transporter 4. In addition, glucose transporter 4 protein levels were seen to increase as a result of DLBS3233 administration. The combination of extracts also increased glucose uptake and adiponectin secretion, and decreased resistin secretion significantly relative to control cells. Moreover, DLBS3233 administered to insulin-resistant Wistar rats showed an ability to control blood sugar, insulin levels, and other lipoproteins, including high-density lipoprotein, low-density lipoprotein, triglycerides, and total cholesterol.

Conclusion:

DLBS3233, as a combination of herbal extracts, holds promise in the treatment of type 2 diabetes, and possibly also in prevention of the disease.