PPARγ agonists partially restores hyperglycemia induced aggravation of vascular dysfunction to angiotensin II in thoracic aorta isolated from rats with insulin resistance

[Molecular mechanisms of the effect of standardized placental hydrolysate peptides on mitochondria functioning]

BACKGROUND

Human placenta hydrolysates (HPH), the study of which was initiated by the scientific school of Vladimir P. Filatov, are currently being investigated using modern proteomic technologies. HPH is a promising tool for maintaining the function of mitochondria and regenerating tissues and organs with a high content of mitochondria (liver, heart muscle, skeletal muscles, etc.). The molecular mechanisms of action of HPH are practically not studied.

AIM

Identification of mitochondrial support mitochondrial function-supporting peptides in HPH (Laennec, produced by Japan Bioproducts).

MATERIALS AND METHODS

Data on the chemical structure of the peptides were collected through a mass spectrometric experiment. Then, to establish the amino acid sequences of the peptides, de novo peptide sequencing algorithms based on the mathematical theory of topological and metric analysis of chemographs were applied. Bioinformatic analysis of the peptide composition of HPH was carried out using the integral protein annotation method.

RESULTS

The biological functions of 41 peptides in the composition of HPH have been identified and described. Among the target proteins, the activity of which is regulated by the identified peptides and significantly affects the function of mitochondria, are caspases (CASP1, CASP3, CASP4) and other proteins regulating apoptosis (BCL2, CANPL1, PPARA), MAP kinases (MAPK1, MAPK3, MAPK4, MAPK8, MAPK9 , MAPK10, MAPK14), AKT1/GSK3B/MTOR cascade kinases, and a number of other target proteins (ADGRG6 receptor, inhibitor of NF-êB kinase IKKE, pyruvate dehydrogenase 2/3/4, SIRT1 sirtuin deacetylase, ULK1 kinase).

CONCLUSION

HPH peptides have been identified that promote inhibition of mitochondrial pore formation, apoptosis, and excessive mitochondrial autophagy under conditions of oxidative/toxic stress, chronic inflammation, and/or hyperinsulinemia.

AT2 Receptor Stimulation Inhibits Vascular Smooth Muscle Cell Senescence Induced by Angiotensin II and Hyperglycemia

BACKGROUND

Hyperglycemia has been widely reported to induce vascular senescence. We have previously demonstrated that angiotensin II (Ang II) could promote brain vascular smooth muscle cell (VSMC) senescence, and its type 2 (AT2) receptor deletion could enhance VSMC senescence. Therefore, we examined the possible cross-talk between Ang II and hyperglycemia on VSMC senescence, and the roles of AT2 receptor agonist, compound 21 (C21) on it.

METHODS

Aortic VSMCs were prepared from adult male mice and stimulated with Ang II and/or high glucose (Glu) and/or C21 and/or an autophagy inhibitor, 3-methyladenine (3-MA), and/or an autophagy agonist, rapamycin (RAP) for the indicated times. Cellular senescence, oxidative stress, and protein expressions were evaluated.

RESULTS

Combination treatment with Ang II and Glu synergistically increased the proportion of VSMC senescent area compared with control group and each treatment alone, which was almost completely attenuated by C21 treatment. Moreover, combination treatment induced significant changes in the levels of superoxide anion, the expressions of p21 and pRb, and the ratio of LC3B II/I expression, which were also significantly attenuated by C21 treatment. The proportion of VSMC senescent area and the levels of superoxide anion by combination treatment were increased after 3-MA treatment, and the proportion of senescent area and the expressions of p21 and pRb were decreased after RAP treatment, both of which were further attenuated by C21 treatment.

CONCLUSIONS

Ang II and hyperglycemia synergistically promoted VSMC senescence, at least partly through the participation by autophagy, oxidative stress, and p21-pRb pathway, which could be inhibited by C21.

Optimization of photo-biomodulation therapy for wound healing of diabetic foot ulcers in vitro and in vivo

Unclear optical parameters make photo-biomodulation (PBM) difficult to implement in diabetic foot ulcer (DFU) clinically. Here, 12 wavelengths (400-900 nm) were used to conduct PBM to heal DFU wounds in vitro and in vivo. PBM at 10 mW/cm² and 0.5-4 J/cm² with all 12 wavelengths promoted proliferation of diabetic wound cells. In a mimic DFU (mDFU) rat model, PBM (425, 630, 730, and 850 nm, and a combination light strategy) promoted mDFU healing. The positive cell proliferation, re-epithelialization, angiogenesis, collagen synthesis, and inflammation were possible mechanisms. The combination strategy had the best effect, which can be applied clinically.

Agave tequilana Counteracts Chronic Hypertension and Associated Vascular Damage

Systemic arterial hypertension (SAH) is a health problem of great importance worldwide, and endothelial dysfunction underlies SAH development. This condition's main characteristics include vasoconstriction, inflammation, oxidative stress, and procoagulant and proliferative states. This study's objective was to evaluate the antihypertensive, anti-inflammatory, and antioxidant effects of the whole extract and fractions of Agave tequilana in a murine model of SAH. SAH was induced in male ICR or CD-1 (Strain obtained from animals from Charles River Laboratories, Massachusetts) mice by intraperitoneal administration of angiotensin II (AGII) (0.1 μg/kg) for 4 weeks, and then A. tequilana treatments were co-administered with AGII. At the end of the experiment, systolic and diastolic blood pressure were measured and the kidneys were dissected to quantify interleukin (IL)-1β, IL-6, tumor necrosis factor-alpha, IL-10, and malondialdehyde (MDA). The whole extract and the fractions of A. tequilana were chemically characterized using gas chromatography-mass spectrometry. The results indicate that the whole extract (At-W) and At-AcOEt fraction treatment are the most efficient in lowering blood pressure, although all the treatments had an immunomodulatory effect on the cytokines evaluated and an antioxidant effect on lipid peroxidation. Finally, the chromatographic profile shows that the integral extract and fractions of A. tequilana contained phytol (M)3,7,11,15-Tetramethyl-2-hexadecen-1-ol; 9,12-octadecadienoic acid; hentriacontane; 9,19-cyclolanost-24-en-3-ol,(3b); t-sitosterol; and stigmasta-3,5-dien-7-one.

Aggravation of Cerebral Ischemia/Reperfusion Injury by Peroxisome Proliferator-Activated Receptor-Gamma Deficiency via Endoplasmic Reticulum Stress

BACKGROUND Ischemic stroke is a dominant contributor to disability and mortality worldwide and is recognized as an important health concern. As a transcription factor triggered via stress, peroxisome proliferator-activated receptor-gamma (PPAR-γ) has a crucial impact on differentiation, cell death, and cell growth. However, the role of PPAR-γ and its precise mechanism in cerebral ischemia injury (CII) remain unclear. MATERIAL AND METHODS The male C57Bl/6 mice (12 weeks old, n=52) were subjected to middle cerebral artery occlusion (MCAO). Infarct volume was evaluated by 2, 3, 5-Triphenyltetrazolium chloride staining. Cell apoptosis was measured by terminal dUTP nick-end labeling (TUNEL) staining. The expression of apoptotic-related protein was examined by Western blotting. Neuron2A cells were transfected with PPAR-γ-specific siRNA and then were subjected to oxygen-glucose exhaustion and reoxygenation. RESULTS It was observed that PPAR-γ-deficient mice displayed extended infarct trigon in the MCAO stroke model. Neuronal deficiency was more severe in PPAR-γ-deficient models. Additionally, expression of cell death-promoting Bcl-2 associated X and active caspase-3 was reinforced, while that of cell death-counteracting Bcl-2 was repressed in PPAR-γ-deficient mice. This was characterized by reinforced endoplasmic reticulum (ER) stress reactions in in vivo brain specimens as well as in vitro neurons in ischemia/reperfusion (I/R) injury. CONCLUSIONS This research proved that PPAR-γ protected the brain from cerebral I/R injury by repressing ER stress and indicated that PPAR-γ is a potential target in the treatment of ischemia.

The Antagonist Effect of Arachidonic Acid on GLUT4 Gene Expression by Nuclear Receptor Type II Regulation

OBJECTIVES

Obesity is a complex disease that has a strong association with diet and lifestyle. Dietary factors can influence the expression of key genes connected to insulin resistance, lipid metabolism, and adipose tissue composition. In this study, our objective was to determine gene expression and fatty acid (FA) profiles in visceral adipose tissue (VAT) from lean and morbidly obese individuals. We also aimed to study the agonist effect of dietary factors on glucose metabolism.

DESIGN AND METHODS

Lean and low and high insulin resistance morbidly obese subjects (LIR-MO and HIR-MO) were included in this study. The gene expression of liver X receptor type alpha (LXR-α) and glucose transporter type 4 (GLUT4) and the FA profiles in VAT were determined. Additionally, the in vivo and in vitro agonist effects of oleic acid (OA), linoleic acid (LA), and arachidonic acid (AA) by peroxisome proliferator-activated receptor type gamma 2 (PPAR-γ2) on the activity of GLUT4 were studied.

RESULTS

Our results showed a dysregulation of GLUT4 and LXR-α in VAT of morbidly obese subjects. In addition, a specific FA profile for morbidly obese individuals was found. Finally, AA was an PPAR-γ2 agonist that activates the expression of GLUT4.

CONCLUSIONS

Our study suggests a dysregulation of LXR-α and GLUT4 expression in VAT of morbidly obese individuals. FA profiles in VAT could elucidate their possible role in lipolysis and adipogenesis. Finally, AA binds to PPAR-γ2 to activate the expression of GLUT4 in the HepG2 cell line, showing an alternative insulin-independent activation of GLUT4.

Metformin ameliorates podocyte damage by restoring renal tissue nephrin expression in type 2 diabetic rats

BACKGROUND

Previous studies found that metformin provided some renoprotection for diabetic renal damage. In the present study, we evaluated the effects of different doses of metformin on the expression of renal tissue nephrin in type 2 diabetes mellitus (T2DM) model rats and the possible mechanism underlying its protective effect in kidney podocytes.

METHODS

A high-fat diet combined with a low dose of streptozotocin was used to induce T2DM model rats. Diabetic rats were treated with 150, 300, or 500 mg/kg metformin for 8 weeks. At the end of the study, urine and blood samples were collected for measurement of different indices. Light microscopy and transmission electron microscopy were used to identify morphological changes. Renal expression of nephrin protein was assayed by immunohistochemical staining, whereas real-time polymerase chain reaction was used to detect renal nephrin (Nphs1) mRNA expression.

RESULTS

Metformin treatment of T2DM rats produced dose-dependent significant reductions in urinary albumin and nephrin concentrations, glomerular basement membrane thickness (GBMT), and the foot process fusion rate (FPFR) compared with control T2DM model rats, whereas renal expression of nephrin protein and Nphs1 mRNA was dose-dependently increased by metformin treatment.

CONCLUSION

Metformin protects kidney podocytes in T2DM model rats by dose-dependently adjusting renal nephrin expression.

Tangzhiqing Granules Alleviate Podocyte Epithelial-Mesenchymal Transition in Kidney of Diabetic Rats

This study discussed the effect of Tangzhiqing granules on podocyte epithelial-mesenchymal transition in kidney of diabetic rats. The diabetic rats were divided randomly into five groups: DM group treated with vehicle, Tangzhiqing granules low-dose treatment group, Tangzhiqing granules middle-dose treatment group, and Tangzhiqing granules high-dose treatment group. Eight Wistar rats used as control group were given saline solution. The intervention was all intragastric administration for 8 weeks. At the end of the 8 weeks, biochemical parameters and kidney weight/body weight ratio were measured. The kidney tissues were observed under light microscope and transmission electron microscopy. To search for the underlying mechanism, we examined the epithelial-to-mesenchymal transition (EMT) related molecular markers and TGF-β/smad signaling pathway key proteins expression. The results showed that Tangzhiqing granules relieved the structural damage and functional changes of diabetic kidneys. Kidney podocyte EMT related molecular markers nephrin and CD2AP expression were increased, when desmin and α-SMA levels were decreased by Tangzhiqing granules in diabetic rats. Further TGF-β/smad signaling pathway key proteins TGF-β1 and p-smad2/3 levels were decreased in diabetic rats after treatment with Tangzhiqing granules. These findings suggest that Tangzhiqing granules may protect the podocytes of diabetic nephropathy rats via alleviating podocyte EMT and likely activating TGFβ/smad signaling pathway.

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.

Effects of a PPAR-gamma receptor agonist and an angiotensin receptor antagonist on aortic contractile responses to alpha receptor agonists in diabetic and/or hypertensive rats

Aim

The aim of this study was to investigate the effects of pioglitazone and losartan pre-treatment on the aortic contractile response to the alpha-1 agonist, phenylephrine, and the alpha-2 agonist, clonidine, in L-NAME-induced hypertensive, STZ-induced diabetic, and hypertensive diabetic rats.

Methods

Male Wistar rats were randomly allocated to four groups: control, diabetic (DM), hypertensive (HT) and hypertensive diabetic (HT + DM) groups. Three weeks after drug application, in vitro dose–response curves to phenylephrine (Phe) (10^-9–10^-5 M) and clonidine (Clo) (10^-9–10^-5 M) were recorded in aortic rings in the absence (control) and presence of pioglitazone (10 μM) and/or losartan (10 μM).

Results

Pioglitazone and losartan caused a shift to the right in contractile response to phenylephrine in all groups. The sensitivity of the aortic rings to phenylephrine was decreased in the presence of pioglitazone and/or losartan in all groups. The contractile response of clonidine decreased in the presence of pioglitazone and/or losartan in the control, HT and DM groups.

Conclusion

The sensitivity of aortic rings to alpha-1 and alpha-2 adrenoceptors was decreased in the presence of pioglitazone and/or losartan in diabetic and hypertensive rats. Concomitant use of PPAR-gamma agonists, thiazolidinediones, and angiotensin receptor blockers may be effective treatment for diabetes and hypertension.

Alternatives to the Streptozotocin-Diabetic Rodent

The study of diabetic neuropathy has relied primarily on the use of streptozotocin-treated rat and mouse models of type 1 diabetes. This chapter will review the creation and use of other rodent models that have been developed in order to investigate the contribution of factors besides insulin deficiency to the development and progression of diabetic neuropathy as it occurs in obesity, type 1 or type 2 diabetes. Diabetic peripheral neuropathy is a complex disorder with multiple mechanisms contributing to its development and progression. Even though many animal models have been developed and investigated, no single model can mimic diabetic peripheral neuropathy as it occurs in humans. Nonetheless, animal models can play an important role in improving our understanding of the etiology of diabetic peripheral neuropathy and in performing preclinical screening of potential new treatments. To date treatments found to be effective for diabetic peripheral neuropathy in rodent models have failed in clinical trials. However, with the identification of new endpoints for the early detection of diabetic peripheral neuropathy and the understanding that a successful treatment may require a combination therapeutic approach there is hope that an effective treatment will be found.

Differential regulation of angiotensin converting enzyme 2 and nuclear factor-κB by angiotensin II receptor subtypes in type 2 diabetic kidney

Angiotensin II (Ang II) acts through Angiotensin Converting Enzyme (ACE)/Ang II type 1 receptor (AT1R) axis to promote renal failure whereas the Ang II type 2 receptor (AT2R)/Angiotensin Converting Enzyme 2 (ACE2)/Ang1-7/Mas axis constitutes the protective arm of Renin Angiotensin System (RAS). Though Ang II has been known to activate the Nuclear Factor-κB (NF-κB) signalling pathway through different receptor subtype(s) in different tissues under various diseases, the subtype orchestrating this stimulation in type 2 diabetic kidney remains elusive. ACE2, a protective monocarboxypeptidase, responsible for conversion of Ang II to Ang1-7, opposes the deleterious effects of RAS pathway but how its expression is altered with blockade of AT1R and AT2R is not yet known. Hence, the present study was conceived to understand the regulation of NF-κB and ACE2 by using specific AT1 and AT2 receptor antagonists in non-genetic model of type 2 diabetic nephropathy. Our results show that the AT1R and AT2R antagonists lead to the repression and activation of NF-κB signalling pathway, respectively which suggests the role of AT1R in NF-κB activation. The blockade of AT2R led to an increase in ACE2 expression, which may be a compensatory response to the drastically increased inflammatory mediators and oxidative stress in the diabetic kidney. To the best of our knowledge, this is the first study showing the differential regulation of NF-κB and ACE2 by Ang II receptor subtypes and thus this study improves our understanding regarding regulation of inflammatory cascade and ACE2 by AT1R and AT2R in type 2 diabetic kidney, which may help in designing novel strategies to combat the disease in future.

In-vivo antioxidant and anti-inflammatory activity of rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonists in animal model of bronchial asthma

OBJECTIVES

Peroxisome proliferator activated receptor-gamma (PPAR-γ) has been shown to play an important role in the control of immunological and inflammatory responses. This study aims at investigating the potential role of rosiglitazone, a strong PPAR-γ agonist in a murine model of bronchial asthma.

METHODS

Adult male guinea pigs were administered ovalbumin 100 mg/kg subcutaneous (SC) and 100 mg/kg intraperitoneal (IP). Treatment with rosiglitazone [5 mg/kg/day, per oral (PO)] was assessed for 21 days. On day 21, the animals were challenged with the same dose of ovalbumin. The forced expiratory volume in 1 s (FEV1 ) to forced vital capacity (FVC), FEV1 /FVC, was measured using a spirometer to diagnosis lung obstruction. Serum levels of interleukin-5 (IL-5) and immunoglobulin E (IgE) were assessed. The activity of superoxide dismutase (SOD) and catalase and the level of reduced glutathione (GSH) were determined in lung tissue homogenates.

KEY FINDINGS

Our results demonstrated that treatment with rosiglitazone resulted in a statistically significant improvement in lung function and histopathological features. Significant decrease in the serum levels of IL-5 and IgE were observed. The activity of SOD and catalase as well as the GSH level were significantly increased in the lung tissues of treated animals compared with untreated asthmatic animals. Serum IgE concentrations and IL-5 levels were directly correlated to each other and inversely correlated to the SOD, GSH and catalase levels in the all studied guinea pigs.

CONCLUSIONS

Our results provide evidence that the PPAR-γ agonist rosiglitazone may have potential in the development of therapies for bronchial asthma.

Metformin Ameliorates Podocyte Damage by Restoring Renal Tissue Podocalyxin Expression in Type 2 Diabetic Rats

Podocalyxin (PCX) is a signature molecule of the glomerular podocyte and of maintaining integrity of filtration function of glomerulus. The aim of this study was to observe the effect of different doses of metformin on renal tissue PCX expression in type 2 diabetic rats and clarify its protection on glomerular podocytes. Type 2 diabetic Sprague-Dawley (SD) rats in which diabetes was induced by high-fat diet/streptozotocin (HFD-STZ) were treated with different doses of metformin (150, 300, and 500 mg/kg per day, resp.) for 8 weeks. Various biochemical parameters, kidney histopathology, and renal tissue PCX expression levels were examined. In type 2 diabetic rats, severe hyperglycemia and hyperlipidemia were developed. Urinary albumin and PCX were markedly increased. Diabetes induced significant alterations in renal glomerular structure. In addition, protein and mRNA expression of renal tissue PCX were highly decreased. However, treatment of rats with different doses of metformin restored all these changes to a varying degree. These results suggested that metformin can ameliorate glomerular podocyte damage in type 2 diabetic rats, which may be partly associated with its role in restoring PCX expression and inhibiting urinary excretion of PCX with dose dependence.

Analysis of RXR/THR and RXR/PPARG2 heterodimerization by bioluminescence resonance energy transfer (BRET)

Background

Nuclear receptors (NR) regulate transcription of genes involved in many biological processes such as development, cell proliferation, differentiation and cell death. Amongst them, PPARG2 and THR control tissue glucose and lipid homeostasis which are deregulated in severe pathophysiological conditions such as metabolic syndromes.

Methodology/Principal Findings

Here, we describe a real time BRET approach to monitor heterodimerization between RXR and PPARG2 or THR in vitro or in living cells. The presence of a specific DNA target was required to induce in vitro a BRET shift reflecting heterodimerization of RXR/PPARG2 or RXR/THR. As in electrophoretic mobility shift assay (EMSA), the stringency and specificity of the BRET shift assay depended upon assay condition optimization including MgCl₂ concentration. For the nuclear receptors, we found by mutagenesis analysis that each heterodimer partner must harbor an intact DNA binding domain to induce BRET and heterodimerization on a DNA target. Moreover the interaction between the PPARG2 ligand binding domain and the RXR DNA binding domain stabilized the heterodimer on its DNA target. BRET microscopy in living cells highlighted the heterodimerization of RXR/PPARG2 within the nucleus clustered in discrete foci that may represent active target gene transcription regulation regions. BRET imaging also suggested that heterodimerization between RXR and PPARG2 required the DNA binding of PPARG2.

Conclusions/Significance

The BRET approach described here allowed us to study the dynamic interactions which exist between NR in vitro or in living cells and can provide important information on heterodimerization modes, affinity with a given RE and subcellular localization of the heterodimers. This method could be used to study real time changes of NR heterodimers occurring on DNA depending upon cell activation, chromatin state and help to define the mechanisms of ligands or drug action designed to target NRs.

An increased circulating angiotensin II concentration is associated with hypoadiponectinemia and postprandial hyperglycemia in men with nonalcoholic fatty liver disease

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) is a condition associated with type 2 diabetes (T2D). Insulin resistance, a common pathogenesis of NAFLD and T2D, is partially caused by alterations in angiotensin II (Ang II) and is accompanied by hypoadiponectinemia. We aimed to investigate whether the circulating Ang II and adiponectin concentrations are related to hyperglycemia in male NAFLD patients.

METHODS

Thirty-five controls and 85 NAFLD patients without prior known T2D were enrolled. All participants were non-smoking men who performed 75-g oral glucose tolerance tests. According to the American Diabetes Association (ADA) criteria, the NAFLD patients were divided into the euglycemia and hyperglycemia groups. The NAFLD patients with hyperglycemia were further divided into the isolated impaired fasting glucose (I-IFG) and postprandial hyperglycemia subgroups. The fasting serum Ang II and adiponectin concentrations were measured.

RESULTS

Among the 85 NAFLD patients, 40 (47%) had hyperglycemia, including I-IFG (18%) and postprandial hyperglycemia (29%). The serum Ang II concentrations in the euglycemia and hyperglycemia groups were significantly higher than those observed in the control and euglycemia groups, respectively; whereas the serum adiponectin concentrations were significantly lower. The serum Ang II concentrations were significantly higher in the postprandial hyperglycemia subgroup than in the I-IFG subgroup. The serum Ang II and adiponectin concentrations were found to be independent predictors of hyperglycemia in the NAFLD patients. The serum Ang II concentration was significantly associated with the serum adiponectin and 2-hour postprandial glucose concentrations in the NAFLD patients.

CONCLUSION

An increased circulating Ang II concentration is associated with hypoadiponectinemia and postprandial hyperglycemia in male NAFLD patients and may be involved in the pathogenesis of T2D in NAFLD patients.

Effects of Combination of Thiazolidinediones with Melatonin in Dexamethasone-induced Insulin Resistance in Mice

In type 2 Diabetes, oxidative stress plays an important role in development and aggregation of insulin resistance. In the present study, long term administration of the dexamethasone led to the development of insulin resistance in mice. The effect of thiazolidinediones pioglitazone and rosiglitazone, with melatonin on dexamethasone-induced insulin resistance was evaluated in mice. Insulin resistant mice were treated with combination of pioglitazone (10 mg/kg/day, p.o.) or rosiglitazone (5 mg/kg/day, p.o.) with melatonin 10 mg/kg/day p.o. from day 7 to day 22. In the biochemical parameters, the serum glucose, triglyceride levels were significantly lowered (P<0.05) in the combination groups as compared to dexamethasone treated group as well as with individual groups of pioglitazone, rosiglitazone, and melatonin. There was also, significant increased (P<0.05) in the body weight gain in combination treated groups as compared to dexamethasone as well as individual groups. The combination groups proved to be effective in normalizing the levels of superoxide dismutase, catalase, glutathione reductase and lipid peroxidation in liver homogenates may be due to antioxidant effects of melatonin and decreased hyperglycemia induced insulin resistance by thiazolidinediones. The glucose uptake in the isolated hemidiaphragm of mice was significantly increased in combination treated groups (PM and RM) than dexamethasone alone treated mice as well as individual (pioglitazone, rosiglitazone, melatonin) treated groups probably via increased in expression of GLUT-4 by melatonin and thiazolidinediones as well as increased in insulin sensitivity by thiazolidinediones. Hence, it can be concluded that combination of pioglitazone and rosiglitazone, thiazolidinediones, with melatonin may reduces the insulin resistance via decreased in oxidative stress and control on hyperglycemia.

Influence of pioglitazone on experimental heart failure and hyperlipidemia in rats

Objectives:

To investigate the effect of pioglitazone on isoproterenol-induced heart failure and high-fructose diet-induced metabolic changes in rats.

Materials and Methods:

Three doses of pioglitazone (Pio – 3, 10, 30 mg/kg, po) were tested in male Wistar rats. In the Heart Failure (HF) group, treatment was followed by Isoproterenol (ISO) injection. The markers for HF, such as enzyme estimation, relative heart weight, and antioxidant status, were evaluated. In another group, metabolic disturbances were induced by High Fructose Diet (HFD). The influence of Pio treatment on Systolic Blood Pressure (SBP), serum glucose, Triglycerides (TG), Total Cholesterol (TC), and High-Density Lipoprotein (HDL)-cholesterol (HDL-c) were determined.

Results:

The results indicated that Pio at 10 mg increased significantly (P<0.05) the Lactate Dehydrogenase (LDH), Creatinine Kinase-MB (CK-MB), and antioxidant enzyme levels as compared to ISO. The high dose of Pio (30 mg) enhanced (P<0.05) Aspartate Transaminase (AST), Alanine Transaminase (ALT), Lipid Peroxidation (LPO),and relative heart weight in addition to increased LDH, CK-MB, and antioxidant enzyme activity. In the HFD group, a dose-dependent inhibitory effect was observed. Pio at 3 mg significantly reduced (P<0.05) elevated glycemia, TG, and SBP as compared to HFD rats. Further, the higher doses of Pio (10 and 30 mg) enhanced the inhibitory effect on glucose, TG, and SBP besides elevating the HDL-c levels. However, none of the tested doses of Pio significantly altered the TC level in HFD rats.

Conclusion:

The observations suggest that Pio exhibits anti-diabetic and anti-hypertensive effects and also partially corrected the hyperlipidemia, but the treatment augmented the cardiac damage associated with ISO. The antioxidant property of Pio appears to have a limited role in protecting the ISO-mediated heart damage.

Effect of treatment of high fat fed/low dose streptozotocin-diabetic rats with Ilepatril on vascular and neural complications

We have previously shown that treating streptozotocin-induced diabetic rats, an animal model of type 1 diabetes, with Ilepatril (an inhibitor of neutral endopeptidase and angiotensin converting enzyme (ACE)) improves vascular and neural functions. In this study we sought to determine the effect of Ilepatril treatment of high fat fed/low dose streptozotocin-diabetic rats, a model for type 2 diabetes, on vascular and neural complications. Following 8 weeks on a high fat diet rats were treated with 30 mg/kg streptozotocin (i.p.) and after 4 additional weeks a group of these rats was treated for 12 weeks with Ilepatril followed by analysis of neural and vascular functions. Included in these studies were age-matched control rats and rats fed a high fat diet and treated with or without Ilepatril. Diabetic and diet induced obese rats have characteristics of insulin resistance, slowing of nerve conduction velocity, thermal hypoalgesia, reduction in intraepidermal nerve fiber density in the hindpaw and impairment in vascular relaxation to acetylcholine and calcitonin gene-related peptide in epineurial arterioles of the sciatic nerve. Treatment with Ilepatril was efficacious in improving all of these endpoints although improvement of insulin resistance in diabetic rats was minimal. These studies suggest that dual inhibition of angiotensin converting enzyme and neutral endopeptidase activity of type 2 diabetic rats is an effective approach for treatment of diabetic neural and vascular complications.

Antiobesity and lipid lowering effects of Glycyrrhiza chalcones: experimental and computational studies

Twelve flavonoids (1-12), isolated from Glycyrrhiza glabra roots were evaluated for their pancreatic lipase (PL) inhibitory activity in vitro. The structures of the isolated compounds were elucidated by spectroscopic methods. Amongst all the compounds 7, 8, 10 and 11 showed strong inhibition against PL with IC(50) values of 7.3 μM, 35.5 μM, 14.9 μM and 37.6 μM, respectively. Molecular docking studies on the most active compound 7 revealed that it binds with the key amino acid residues of the PL active site. In silico absorption, distribution, metabolism and excretion (ADME) parameters were also computed on the active compounds to determine their preliminary pharmacokinetic properties. Further, investigations were carried out to determine the antiobesity and lipid lowering effects of 7 and 10 in high fat diet (HFD) fed male SD rats. In the rats supplemented with compound 7 the body weight increase was only 23.2±3.6 g as compared to 64.2±0.5 g in the HFD control group while in the rats treated with compound 10 showed 23.2±3.6 g weight gain only. Compound 7 decreased the levels of plasma total cholesterol (TC) to 84.6±1.4 mg/dl and plasma total triglycerides (TG) to 128.8±6.0 mg/dl. Compound 10 also lowered the plasma TC and TG levels considerably. The results indicate the potential of the chalcone scaffold as a source of PL inhibitors for preventing obesity.

Effect of pioglitazone on altered expression of Aβ metabolism-associated molecules in the brain of fructose-drinking rats, a rodent model of insulin resistance

Accumulation of β-amyloid (Aβ) peptide in the brain is a major hallmark of Alzheimer's disease. An optimal brain insulin level promotes Aβ clearance, which may play protective roles against Alzheimer's disease. In this study we examined the role of dietary conditions leading to insulin resistance on amyloidosis in fructose-drinking rats. Further investigations tested pioglitazone, an insulin sensitizer, intervention on the altered amyloidosis in this rodent model of insulin resistance. Six-week-old male Wistar rats were fed a standard commercial diet and water without (control) or with 10% fructose for 16 weeks. The animals were randomly divided into 4 groups (n=10): non-treated and water-drinking rats (control group); pioglitazone treated and water-drinking (control treatment group); non-treated and fructose-drinking rats (fructose group) and pioglitazone-treated and fructose-drinking rats (fructose treatment group). Pioglitazone was given at the dose of 10mg/kgd by gavage for the last 12 weeks of the 16-week period. We found that diet-induced insulin resistance induced Aβ overproduction with altered expression of Aβ metabolism-associated molecules, which corresponded with increased β-secretase-1 (BACE1), γ-secretase (PS-1) activities and decreased insulin degrading enzyme (IDE) activities, but not neprilysin in the cortex and hippocampus. Additionally, pioglitazone treatment prevented all these observed abnormalities. This study indicates that insulin resistance induced by fructose-drinking affects the expression of Aβ metabolism-associated molecules that are responsible for Aβ deposition and pioglitazone treatment negatively modulate amyloidogenesis.

Epigenetic changes and alteration of Fbn1 and Col3A1 gene expression under hyperglycaemic and hyperinsulinaemic conditions

Little is known regarding the role of hyperglycaemia on histone H3 modifications and, in turn, altering the expression of genes during the development of diabetes-associated complications. In the present study, we have investigated the hyperinsulinaemia/hyperglycaemia-induced epigenetic changes and alteration of Fbn1 (fibrillin 1) and Col3A1 (collagen type III α1) gene expression. Insulin resistance and Type 2 diabetes in male Sprague-Dawley rats was developed by feeding rats an HFD (high-fat diet) and administering a low dose of STZ (streptozotocin). Hyperglycaemia induced deacetylation and dephosphorylation of histone H3 in the heart and kidneys of diabetic rats. Furthermore, mRNA expression of Fbn1 and Col3A1 increased in the kidneys and decreased in the heart under hyperglycaemic/hyperinsulinaemic conditions. Similar to mRNA expression, chromatin immunoprecipitation also showed an increase in the level of histone H3 acetylation of the Fbn1 gene, but not of the Col3A1 gene. Our present findings suggests that the change in expression of the Fbn1 gene is epigenetically regulated, but the expression of the Col3A1 gene may either be independent of epigenetic regulation or may involve other histone modifications. We provide the first evidence regarding the role of hyperglycaemia/hyperinsulinaemia in altering histone H3 modifications, which may result in the alteration of extracellular matrix gene expression.

Mechanisms underlying the losartan treatment-induced improvement in the endothelial dysfunction seen in mesenteric arteries from type 2 diabetic rats

It is well known that type 2 diabetes mellitus is frequently associated with vascular dysfunction and an elevated systemic blood pressure, yet the underlying mechanisms are not completely understood. We previously reported that in mesenteric arteries from established type 2 diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats, which exhibit endothelial dysfunction, there is an imbalance between endothelium-derived vasodilators [namely, nitric oxide (NO) and hyperpolarizing factor (EDHF)] and vasoconstrictors [contracting factors (EDCFs) such as cyclooxygenase (COX)-derived prostanoids]. Here, we investigated whether the angiotensin II receptor antagonist losartan might improve endothelial dysfunction in OLETF rats at the established stage of diabetes. In mesenteric arteries isolated from OLETF rats [vs. those from age-matched control Long-Evans Tokushima Otsuka (LETO) rats]: (1) the acetylcholine (ACh)-induced relaxation was impaired, (2) the NO- and EDHF-mediated relaxations were reduced, (3) the ACh-induced EDCF-mediated contraction and the production of prostanoids were increased, and (4) superoxide generation was increased. After such OLETF rats had received losartan (25 mg/kg/day p.o. for 4 weeks), their isolated mesenteric arteries exhibited: (1) improvements in ACh-induced NO- and EDHF-mediated relaxations, (2) reduced EDCF- and arachidonic acid-induced contractions, (3) suppressed production of prostanoids, (4) reduced PGE(2)-mediated contraction, and (5) reduced superoxide generation. Within the timescale studied here, losartan did not change the protein expressions of endothelial NO synthase, COX1, or COX2 in mesenteric arteries from either OLETF or LETO rats. Losartan thus normalizes vascular dysfunction in this type 2 diabetic model, and the above effects may contribute to the reduction of adverse cardiovascular events seen in diabetic patients treated with angiotensin II receptor blockers.

Effect of thiazolidinediones on the erythropoeitic and germinal cells in the male wistar rats

Hyperglycemia is the main determinant of long term diabetic complications mainly through induction of oxidative stress responsible for secondary defects including cancer, infertility etc. Thiazolidinediones (TZDs) are known to posses the antioxidant potential against the reactive oxygen species. The ability of clinically used TZDs like Rosiglitazone (RSG) and Pioglitazone (PIO) in diabetic complications is still need to be studied extensively in the literature. In this study, the role of RSG and PIO on the frequency of nuclear and germinal cell damage was studied using bone marrow micronucleus (MN) test, sperm shape abnormality and sperm count in normal animals. The drugs were tested in the three doses (1, 10 and 100 mg/kg) after acute (48 hrs and 72 hrs) and chronic (4 weeks) treatment. The results indicated that RSG has produced significant (p < 0.01) decrease in P/N (polychromatic and normochromatic erythrocytes) ratio at 10 and 100 mg/kg without affecting the frequency of micronucleated erythrocytes, sperm shape morphology and sperm count. PIO in the tested doses did not induce any change in P/N ratio and sperm count but the higher dose (100 mg/kg) showed suppression of MN in normochromatic erythrocytes and % sperm shape abnormality compared to the control group.