Insulinotropic and anti-inflammatory effects of rosiglitazone in experimental autoimmune diabetes

Depression mediates impaired glucose tolerance and cognitive dysfunction: A neuromodulatory role of rosiglitazone

Comorbidity of depression and diabetes is a serious risk factor worsening the complications such as cognitive function and locomotion. Treatment under this condition becomes extremely complicated. Insulin signaling and autophagy pathways are involved in modulation of learning and memory. Rosiglitazone (ROSI) ameliorate cognitive deficit associated with depression and insulin resistance. In the present study, we investigated the effect of ROSI against chronic unpredictable stress (CUS) induced depression as a risk factor for diabetes and behavioral dysfunctions. Adult male Swiss albino mice were exposed to CUS alongside ROSI (5mg/kg/day) treatment for 21days. Thereafter, animals were subjected to different behavioral studies to assess depressive like behavior, cognition and locomotion. The effect of ROSI on insulin signaling, autophagy and apoptosis were evaluated in the hippocampus. CUS resulted in depressive like behavior, cognitive impairment and hypolocomotion associated with oxidative stress, impaired glucose tolerance and hypercorticosteronemia. CUS significantly impaired hippocampal insulin signaling, membrane translocation of glucose transporter type 4 (GLUT4) as well as decreased the expression of autophagy5, autophagy7, B-cell lymphoma 2 and apoptosis inhibitory protein 2. ROSI significantly reduced depressive like behavior, postprandial blood glucose, hypercorticosteronemia, oxidative and inflammatory stress, and apoptosis in stressed mice. Moreover, ROSI treatment effectively improved hippocampal insulin signaling, GLUT4 membrane translocation and cognitive performance in depressed mice. ROSI administration might prove to be effective for neurological disorders associated with depressive like behavior and impaired glucose tolerance.

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.

PPARγ Agonists in Adaptive Immunity: What Do Immune Disorders and Their Models Have to Tell Us?

Adaptive immunity has evolved as a very powerful and highly specialized tool of host defense. Its classical protagonists are lymphocytes of the T- and B-cell lineage. Cytokines and chemokines play a key role as effector mechanisms of the adaptive immunity. Some autoimmune and inflammatory diseases are caused by disturbance of the adaptive immune system. Recent advances in understanding the pathogenesis of autoimmune diseases have led to research on new molecular and therapeutic targets. PPARγ are members of the nuclear receptor superfamily and are transcription factors involved in lipid metabolism as well as innate and adaptive immunity. PPARγ is activated by synthetic and endogenous ligands. Previous studies have shown that PPAR agonists regulate T-cell survival, activation and T helper cell differentiation into effector subsets: Th1, Th2, Th17, and Tregs. PPARγ has also been associated with B cells. The present review addresses these issues by placing PPARγ agonists in the context of adaptive immune responses and the relation of the activation of these receptors with the expression of cytokines involved in adaptive immunity.

Protective and anti-angiopathy effects of caffeic acid phenethyl ester against induced type 1 diabetes in vivo

OBJECTIVE

This study aims at investigating the anti-diabetic effects of caffeic acid phenethyl ester (CAPE) against induced immunoregulated diabetes in vivo.

METHODS

Swiss mice were administered cyclosporine (CsA) 20mg/kg/day, s.c. for 10 days and simultaneously received multiple low doses of streptozotocin (MLDSTZ) 40mg/kg/day, i.p. for 5 consecutive days.

RESULTS

Our results showed that administering CAPE (5μM/kg i.p./every 2 days) to diabetic mice led to a time-dependent decrease in blood glucose levels to 137.1±7.2 from 229.1±12.6mg/dl and induced a significant increase in serum insulin levels by 93.8% compared with untreated ones. An in vivo anti-inflammatory effect of CAPE treated diabetic mice was observed, based on a significant decrease in IL-1β and IFN-γ (P<0.01) levels and a highly significant reduction in NO (P<0.001). An anti-angiogenic effect of CAPE was observed, as determined by a significant serum matrix metalloproteinase (MMP-9) reduction, angiopoietin (Ang-2) reduction and activation of endostatin serum level in the CAPE treated diabetic mice. Furthermore, histopathological examination showed that destroyed pancreatic islets were regenerated and became free of cell infiltration after treatment.

CONCLUSION

CAPE has a significant anti-diabetic effect on mice in vivo. This anti-diabetic effect may be related to its anti-inflammatory and angiostatic effects. It also reduced angiogenic factors which may shift the equilibrium to the angiostatic effect of CAPE. These findings provide the validity of CAPE as anti-diabetic agent in the special model of CsA/STZ and could be relevant in the future for human diabetes.

Activation of PPARγ by restores mast cell numbers and reactivity in alloxan-diabetic rats by reducing the systemic glucocorticoid levels

Mast cell function and survival have been shown to be down-regulated under diabetic conditions. This study investigates the role of the peroxisome proliferator-activated receptor (PPAR)-γ in reducing mast cell number and reactivity in diabetic rats. The effect of rosiglitazone on mast cell apoptosis was also evaluated. Diabetes was induced by intravenous injection of alloxan into fasted rats and PPARγ agonist rosiglitazone and/or specific antagonist 2-chloro-5-nitrobenzanilide (GW9662) were administered 3 day after diabetes induction, once daily for 18 consecutive days. Mast cell apoptosis and plasma corticosterone levels were evaluated by TUNEL and radioimmunoassay, respectively. Treatment with rosiglitazone restored mast cell numbers in the pleural cavity and mesenteric tissue of diabetic rats. Rosiglitazone also significantly reversed the diabetes-induced reduction of histamine release by mast cells, as measured by fluorescence, following activation with the antigen in vitro. Increased apoptosis in mast cells from diabetic rats were inhibited by rosiglitazone. Moreover, we noted that the increase in plasma corticosterone levels in diabetic rats was inhibited by rosiglitazone. In addition, GW9662 blocked the ability of rosiglitazone to restore baseline numbers of mast cells and plasma corticosterone in diabetic rats. In conclusion, our findings showed that rosiglitazone restored the number and reactivity of mast cells in diabetic rats, accompanied with a suppression of apoptosis, in parallel with impairment of diabetes hypercorticolism, indicating that PPARγ has an important role in these phenomena.

Differential transcriptional expression of PPARalpha, PPARgamma1, and PPARgamma2 in the peritoneal macrophages and T-cell subsets of non-obese diabetic mice

BACKGROUND

The peroxisome proliferator-activated receptors (PPARs) have been implicated in immune regulation. We determined the transcriptional expression of the three isoforms, PPARalpha, PPARgamma1, and PPARgamma2 in the peritoneal macrophages, CD4- and CD8-positive lymphocytes in non-obese diabetic (NOD) mice at 5 and 10 weeks of age as well as at diabetic stage.

RESULTS

Compared to the non-obese diabetic resistant (NOR) mice, the peritoneal macrophages of NOD mice expressed increased levels of PPARalpha but reduced levels of PPARgamma2, while PPARgamma1 expression was unchanged in all age groups. CD4-positive lymphocytes expressed low levels of PPARalpha in diabetic NOD mice and greatly reduced expression of PPARgamma2 in all age groups. Unlike peritoneal macrophages and CD4-positive cells, the CD8-positive cells expressed low levels of PPARgamma1 in diabetic NOD mice but no difference in PPARalpha and PPARgamma2 expression was observed compared to NOR mice.

CONCLUSION

The current findings may suggest an important regulatory role of PPARs in the pathogenesis of autoimmune diabetes.

Rosiglitazone modulates insulin-induced plasma membrane area changes in single 3T3-L1 adipocytes

In this study we hypothesized that rosiglitazone, an antidiabetic high-affinity agonist for the peroxisome proliferator-activated receptor gamma, affects the plasma membrane (PM) turnover in single 3T3-L1 adipocytes. To study the PM turnover, the patch-clamp electrophysiological method was used to measure changes in membrane capacitance (Cm), a parameter linearly related to the PM area. Microscopy results show that the presence of rosiglitazone in the differentiating medium significantly increased the differentiation of 3T3-L1 adipocytes in cell culture, based on oil red O-stained area (11.4 +/- 1.2%) vs. controls (3.1 +/- 0.5%). Moreover, rosiglitazone treatment significantly reduced the size of single 3T3-L1 adipocytes; their average radius of 21.1 +/- 1.1 microm in controls was reduced to 17.5 +/- 0.5 microm in rosiglitazone-treated cells. Consistent with this, insulin application increased the rate of Cm increase to 2.34 +/- 0.10%/min, which was significantly different from controls (0.12 +/- 0.08%/min). However, pretreatment of cells with rosiglitazone prior to the treatment with insulin resulted in an attenuated rate of Cm increase. These data support the involvement of insulin in the modulation of membrane area and show that treatment by rosiglitazone reduced the insulin-mediated membrane area increase in 3T3-L1 adipocytes.

Modulatory effects of 6-carboxymethylthiopurine on activated murine macrophages

The immunological activity of macrophages against pathogens in hosts includes the phagocytosis and the production of nitric oxide. We report herein the investigation of the effect of 6-carboxymethylthiopurine on nitric oxide production by murine macrophages as well as its effect on the cell viability and proliferation after stimulus with Mycobacterium bovis bacille Calmette-Guérin, interferon-gamma or a combination of both. J774A.1 macrophages stimulated or not by bacille Calmette-Guérin (20 microg/mL), interferon-gamma or both, were cultured in the presence of 6-carboxymethylthiopurine (125, 250 and 500 microm). Nitric oxide production was measured by the Griess method and cell viability/proliferation by the diphenyltetrazolium assay [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide]. We observed an increase of J774A.1 cell proliferation after stimulus with bacille Calmette-Guérin at 125, 250 and 500 microm (69.1, 124.0 and 89.7%, respectively) and with interferon-gamma at 125 and 250 microm (64.8% and 61.7%, respectively) (p < 0.05). In all cultures treated with 6-carboxymethylthiopurine, interferon-gamma-activated nitric oxide production by J774A.1 cells decreased as well as when subjected to interferon-gamma plus bacille Calmette-Guérin stimuli at 500 microm (p < 0.05). Altogether these data point to an anti-inflammatory effect of 6-carboxymethylthiopurine on stimulated macrophages.