Effects of pioglitazone on hyperglycemia-induced alterations in antioxidative system in tissues of alloxan-treated diabetic animals

Pioglitazone treatment increases the cellular acid-labile and protein-bound sulfane sulfur fractions

BACKGROUND

Iron-sulfur clusters play a central role in cellular function and are regulated by the ATM protein. Iron-sulfur clusters are part of the cellular sulfide pool, which functions to maintain cardiovascular health, and consists of free hydrogen sulfide, iron-sulfur clusters, protein bound sulfides, which constitute the total cellular sulfide fraction. ATM protein signaling and the drug pioglitazone share some cellular effects, which led us to examine the effects of this drug on cellular iron-sulfur cluster formation. Additionally, as ATM functions in the cardiovasculature and its signaling may be diminished in cardiovascular disease, we examined pioglitazone in the same cell type, with and without ATM protein expression.

METHODS

We examined the effects of pioglitazone treatment on the total cellular sulfide profile, the glutathione redox state, cystathionine gamma-lyase enzymatic activity, and on double-stranded DNA break formation in cells with and without ATM protein expression.

RESULTS

Pioglitazone increased the acid-labile (iron-sulfur cluster) and bound sulfur cellular fractions and reduced cystathionine gamma-lyase enzymatic activity in cells with and without ATM protein expression. Interestingly, pioglitazone also increased reduced glutathione and lowered DNA damage in cells without ATM protein expression, but not in ATM wild-type cells. These results are interesting as the acid-labile (iron-sulfur cluster), bound sulfur cellular fractions, and reduced glutathione are low in cardiovascular disease.

CONCLUSION

Here we found that pioglitazone increased the acid-labile (iron-sulfur cluster) and bound sulfur cellular fractions, impinges on hydrogen sulfide synthesis, and exerts beneficial effect on cells with deficient ATM protein signaling. Thus, we show a novel pharmacologic action for pioglitazone.

Pioglitazone improves porcine oocyte maturation and subsequent parthenogenetic embryo development in vitro by increasing lipid metabolism

Optimization of culture conditions is important to improve oocyte maturation and subsequent embryo development. In particular, this study analyzed the effects of increasing concentrations of PIO in the maturation medium on spindle formation and chromosome alignment, glutathione, and intracellular ROS levels and expression of selected genes related to maternal markers, apoptosis, and lipid metabolism. The percentage of oocytes displaying normal spindle formation and chromosome alignment was higher in the 1 µM PIO (1 PIO)-treated group than in the control group. The glutathione level was significantly higher in the 1 PIO-treated group than in the control group, while the reactive oxygen species level did not differ. Expression of maternal marker (MOS and GDF9), antiapoptotic (BIRC5), and lipid metabolism-related (ACADS, CPT2, SREBF1, and PPARG) genes was higher in the 1 PIO-treated group than in the control group, while expression of a proapoptotic gene (CASP3) was lower. The blastocyst formation rate and the percentage of blastocysts that reached at least the hatching stage on Days 6 and 7, and the percentage of blastocysts containing more than 128 cells were significantly higher in the 1 PIO-treated group than in the control group. These results indicate that PIO treatment during in vitro maturation improves porcine oocyte maturation and subsequent parthenogenetic embryo development mainly by enhancing lipid metabolism and antioxidant defense in oocytes.

Pioglitazone inhibits advanced glycation induced protein modifications and down-regulates expression of RAGE and NF-κB in renal cells

The present work aims to determine the effect of pioglitazone on in-vitro albumin glycation and AGE-RAGE induced oxidative stress and inflammation. Bovine serum albumin was glycated by methylglyoxal in absence or presence of pioglitazone. Glycation markers (fructosamine, carbonyl groups, β-amyloid aggregation, thiol groups, bilirubin binding capacity and AOPP); protein conformational changes (native-PAGE and HPLC analysis) were determined. Cellular study was done by estimating antioxidants, ROS levels, expression profile of membrane RAGE, NF-κB and levels of inflammatory cytokines (IL-6, TNF-α) using HEK-293 cell line. We observed that levels of glycation markers were reduced at higher concentration of pioglitazone as compared to glycated albumin. Structural analysis of glycated albumin showed inhibition of protein migration and structural changes when treated with pioglitazone. Pioglitazone has potentially restored cellular antioxidants and reduced levels of IL-6 and TNF-α by declining expression of membrane RAGE and NF-κB. In conclusion, pioglitazone preferentially binds to protein and alleviates protein structural changes by maintaining its integrity. Additionally, it suppresses RAGE and NF-κB levels hence alleviate cellular oxidative stress and inflammation.

Hydroxytyrosol: Bioavailability, toxicity, and clinical applications

Many beneficial properties have been attributed to the Mediterranean diet. Over the years, researchers have attempted to learn which foods and which food components are responsible for good health. One of these components is hydroxytyrosol, an important phenolic compound present in olive oil. Hydroxytyrosol is a molecule of high interest to the pharmaceutical industry due to its anti-inflammatory and antimicrobial qualities its role against cardiovascular diseases and metabolic syndrome and for its neuroprotection, antitumour, and chemo modulation effects. The interest in this molecule has led to wide research on its biological activities, its beneficial effects in humans and how to synthetize new molecules from hydroxytyrosol. This review describes the vast range of information about hydroxytyrosol, focusing on its involvement in biological mechanisms and modulation effects on different pathologies. This review also serves to highlight the role of hydroxytyrosol as a nutraceutical and as a potential therapeutic agent.

The effect of pioglitazone on antioxidant levels and renal histopathology in streptozotocin-induced diabetic rats

Objective. Diabetic nephropathy is the most commonly seen cause of chronic renal failure, and oxidative stress is important in etiology. In the present study, favorable effects (if any) of the treatment with a thiazolidinedione group drug, pioglitazone, on antioxidant enzyme levels in the renal tissue, renal histopathology, and inflammatory cytokine levels have been investigated. Method. Forty male Wistar rats were divided into 4 groups as the control, diabetic control, and 10 and 30 mg pioglitazone-administered diabetic groups. After 4 weeks, antioxidant enzyme levels in renal tissues and inflammatory markers were investigated. Results. Blood glucose levels did not differ between the diabetic control and drug-administered groups. In pioglitazone-administered rats, histopathological findings such as tubular dilation, necrotic tubular epithelium, glomerular focal necrosis, and vascular consolidation were observed at a lesser extent than the diabetic control group. Any difference was not detected between the diabetic groups with respect to the levels of malondialdehyde, superoxide dismutase, catalase, glutathione, nitric oxide, interleukin-6, and tumor necrosis factor-alpha. Conclusion. Pioglitazone regressed development of histopathological lesions such as glomerular focal necrosis, tubular epithelial necrosis, tubular dilation, and vascular wall consolidation. However, any favorable effect on antioxidant enzyme levels in renal tissues and inflammation markers was not detected.

The renoprotective actions of peroxisome proliferator-activated receptors agonists in diabetes

Pharmaceutical agonists of peroxisome proliferator-activated receptors (PPARs) are widely used in the management of type 2 diabetes, chiefly as lipid-lowering agents and oral hypoglycaemic agents. Although most of the focus has been placed on their cardiovascular effects, both positive and negative, these agents also have significant renoprotective actions in the diabetic kidney. Over and above action on metabolic control and effects on blood pressure, PPAR agonists also appear to have independent effects on a number of critical pathways that are implicated in the development and progression of diabetic kidney disease, including oxidative stress, inflammation, hypertrophy, and podocyte function. This review will examine these direct and indirect actions of PPAR agonists in the diabetic kidney and explore recent findings of clinical trials of PPAR agonists in patients with diabetes.

Ellagic acid attenuates oxidative stress on brain and sciatic nerve and improves histopathology of brain in streptozotocin-induced diabetic rats

The aim of this study was to investigate the possible effects of ellagic acid in brain and sciatic nerve tissues of diabetic rats. Also, the impact of ellagic acid on catalase and paraoxonase (PON-1) activities, total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), malondialdehyde (MDA) and nitric oxide (NO) were examined. The rats were randomly divided into four groups, with eight rats each: Normal controls (not diabetic), only ellagic acid treated (ellagic acid controls, not diabetic), Diabetic controls (streptozotocin, diabetic), ellagic acid-treated diabetic (streptozotocin + ellagic acid). After a 4 week experiment, rats were sacrificed, and biomarkers for oxidative stress in the brain and sciatic nerve tissues of the rats were measured. There was significant depletion in the PON-1, catalase, and TAS levels in the brain and sciatic nerve tissues compared to the control groups (for both parameters, p<0.05). The values of catalase, PON-1 and TAS reversed back to normal levels in ellagic acid-treated diabetic rats compared to untreated diabetic rats (for both parameters, p<0.05). The levels of MDA, TOS, NO and, OSI in the brain and sciatic nerve tissues were higher in untreated diabetic rats compared to control group (for both parameters p<0.05). However, MDA, TOS, OSI, and NO levels were found to be significantly reduced in the ellagic acid-treated diabetic group compared to the untreated diabetic group in these tissues (for both parameters, p<0.05). In conclusion, the results of the present study suggested that ellagic acid exhibits neuroprotective effects against oxidative damage in diabetic rats.

Inhibitory effect of rosiglitazone on the acid-induced intracellular generation of hydrogen peroxide in cultured feline esophageal epithelial cells

Peroxisome proliferator-activated receptor-gamma (PPARγ) agonists have been reported to enhance antioxidant defenses by increasing levels of catalase and copper-zinc superoxide dismutase (Cu/Zn SOD) in oligodendrocyte progenitor cells. In this study, we investigated the effects of the PPARγ agonist, rosiglitazone, on hydrogen peroxide (H(2)O(2)) generation by acidified medium at pH 5.5 (AM5.5), which is in the pH range of duodenogastric refluxates, in primary cultured feline esophageal epithelial cells (EEC). Successful isolation of EEC was identified by immunocytochemistry. AM5.5- and rosiglitazone-induced cell viabilities were determined using 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyltetrazolium bromide assays. The NAD(P)H oxidase activity was measured, and expression of catalase or SOD protein by AM5.5 in the absence and presence of rosiglitazone was assessed using western blotting analysis. PPARγ protein and mRNA were constitutively expressed in EEC. In the incubation with rosiglitazone alone, cell viability was shown more than 90% at 0-10 μM for 72 h. After exposure to AM5.5 for 8 h, intracellular H(2)O(2) was significantly generated. Treatment with rosiglitazone prior to and during exposure to AM5.5 inhibited the H(2)O(2) generation whereas the specific PPARγ antagonist GW9662 offsets the inhibitory action of rosiglitazone. H(2)O(2) generation was also prevented by a nonspecific ROS scavenger N-acetylcysteine or an inhibitor of NADPH oxidase diphenyleneiodonium. The enhanced AM5.5-induced NAD(P)H oxidase activity was not suppressed by rosiglitazone. Instead, the pretreatment of rosiglitazone enhanced the protein expression of catalase, Cu/Zn SOD, and Mn SOD, which are endogenous antioxidative enzymes. These findings indicate that rosiglitazone inhibits AM5.5-induced intracellular H(2)O(2) production, which occurs via NAD(P)H oxidase activation, by using a PPARγ-dependent pathway, and that the underlying mechanism involves an increase in the expression of catalase and SOD proteins.

Agonism of Peroxisome Proliferator Receptor-Gamma may have Therapeutic Potential for Neuroinflammation and Parkinson's Disease

Evidence suggests inflammation, mitochondria dysfunction, and oxidative stress play major roles in Parkinson's disease (PD), where the primary pathology is the significant loss of dopaminergic neurons in the substantia nigra (SN). Current methods used to treat PD focus mainly on replacing dopamine in the nigrostriatal system. However, with time these methods fail and worsen the symptoms of the disease. This implies there is more to the treatment of PD than just restoring dopamine or the dopaminergic neurons, and that a broader spectrum of factors must be changed in order to restore environmental homeostasis. Pharmacological agents that can protect against progressive neuronal degeneration, increase the level of dopamine in the nigrostriatal system, or restore the dopaminergic system offer various avenues for the treatment of PD. Drugs that reduce inflammation, restore mitochondrial function, or scavenge free radicals have also been shown to offer neuroprotection in various animal models of PD. The activation of peroxisome proliferator receptor- gamma (PPAR-gamma ) has been associated with altering insulin sensitivity, increasing dopamine, inhibiting inflammation, altering mitochondrial bioenergetics, and reducing oxidative stress - a variety of factors that are altered in PD. Therefore, PPAR-gamma activation may offer a new clinically relevant treatment approach to neuroinflammation and PD related neurodegeneration. This review will summarize the current understanding of the role of PPAR-gamma agonists in neuroinflammation and discuss their potential for the treatment of PD.

Peroxisome proliferator-activated receptors in diabetic nephropathy

Diabetic nephropathy is a leading cause of end-stage renal disease, which is increasing in incidence worldwide, despite intensive treatment approaches such as glycemic and blood pressure control in patients with diabetes mellitus. New therapeutic strategies are needed to prevent the onset of diabetic nephropathy. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear transcription factors that play important roles in lipid and glucose homeostases. These agents might prevent the progression of diabetic nephropathy, since PPAR agonists improve dyslipidemia and insulin resistance. Furthermore, data from murine models suggest that PPAR agonists also have independent renoprotective effects by suppressing inflammation, oxidative stress, lipotoxicity, and activation of the renin-angiotensin system. This review summarizes data from clinical and experimental studies regarding the relationship between PPARs and diabetic nephropathy. The therapeutic potential of PPAR agonists in the treatment of diabetic nephropathy is also discussed.

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.

Chronic administration of pioglitazone attenuates intracerebroventricular streptozotocin induced-memory impairment in rats

Memory impairment induced by intracerebroventricular (ICV) injection of streptozotocin (STZ) in rats is associated with impaired brain glucose and energy metabolism, oxidative stress and impaired cholinergic neurotransmission. Treatment with antioxidants and cholinergic agonists has been reported to produce beneficial effect in this model. However, no reports are available on drugs that improve glucose utilization and metabolism. In the present study, we evaluated the effects of pioglitazone on cognitive performance, oxidative stress and glucose utilization in ICV STZ injected rats (3 mg/kg, on day 1 and 3). Pioglitazone (10 and 30 mg/kg) was administered per oral (p.o.) for 14 days, starting 5 days prior to STZ injection. Cognitive performance was assessed using step-through passive avoidance and Morris water maze task. Malondialdehyde (MDA) and glutathione levels in brain were estimated as parameters of oxidative stress. Glucose utilization by brain was assessed as the amount of glucose consumed from the media by the brain. ICV STZ injected rats showed a severe deficit in learning and memory associated with increased MDA levels (+67.5%), decreased glutathione levels (-29.2%) and impaired cerebral glucose utilization (-44.4%). In contrast pioglitazone treatment improved cognitive performance, lowered oxidative stress and improved cerebral glucose utilization in ICV STZ rats. The present study demonstrates the beneficial effects of pioglitazone in the ICV STZ induced cognitive deficits, which can be exploited for the dementia associated with diabetes and age-related neurodegenerative disorder, where oxidative stress and impaired glucose and energy metabolism are involved.

Modification of oxidative stress by pioglitazone in the heart of alloxan-induced diabetic rabbits

The study was undertaken to analyze the effect of pioglitazone on superoxide dismutase (Cu, Zn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione (GSH), ascorbic acid (AA), lipid peroxidation products (LPO) and protein carbonyl groups (PCG) in the heart of alloxan-induced diabetic rabbits after 4 and 8 weeks of pioglitazone treatment. In diabetic animals, Cu, Zn-SOD and CAT were elevated by 60 and 55%, and 90 and 77% as compared to controls at 4 and 8 weeks, respectively. GSH-Px, GSSG-R and GSH were diminished by 11, 14 and 33% as compared to controls at 4 or 8 weeks. AA was diminished by 52 and 41%. At P <0.05, pioglitazone normalized the activities of Cu, Zn-SOD, GSH-Px and GSSG-R. The activity of CAT was modified as compared to diabetic non-treated rabbits. After pioglitazone treatment, GSH and AA were increased as compared to diabetic non-treated animals. In diabetic rabbits, LPO was elevated by 52 and 111% and normalized by pioglitazone treatment. PCG was elevated by 72 and 133% and diminished as compared to diabetic non-treated animals at 8 weeks. The study shows that pioglitazone reduces oxidative stress in the heart of diabetic rabbits. In therapy, similar action can improve the cardiovascular system of diabetic patients.