Modulation of glucose transporter proteins by polyphenolic extract of Ichnocarpus frutescens (L.) W. T. Aiton in experimental type 2 diabetic rats

172-180Traditionally, in India, the decoction of Black creeper, Ichnocarpus frutescens (L.) W. T. Aiton leaves is used to treatment diabetes mellitus. However, its molecular mechanisms of antihyperglycemic effects have not been completely studied. Due to the potential antidiabetic effect of I. frutescens, we hypothesized that the polyphonic extract might add to glucose uptake through improvement in the expression of genes of the glucose transporter (GLUT) family messenger RNA (mRNA) in the liver and adipose tissues. Experimentally, diabetes mellitus was induced in Wistar rats through i.p. injection of freshly prepared solution of streptozotocin (45 mg/kg). This was done 15 minutes after the administration of nicotinamide (120 mg/kg, ip). Serum level of insulin and C-peptide were analyzed using standard methods. Glucose metabolism by the hepatocytes and adipocytes were also analyzed by quantitative RT-PCR mRNA expression levels of phosphoenolpyruvate carboxykinase 1 (PCK1), GLUT2 in the hepatocytes, and GLUT4 in the adipocytes. The hemidiaphragm were also isolated and processed to study in-vitro peripheral glucose utilization. Results of the present investigation suggest that STZ-NA induced diabetes is associated with hyperglycemia, altered levels of PCK1 and glucose transporters gene expression as well as decreased levels of insulin and C-peptide. On the other hand, the outcome of the daily oral administration of PPE to STZ-NA induced diabetic rats at different doses (150 and 300 mg/kg bodywt.) for 30 days supports our hypothesis by showing significant improvement of insulin levels, C-peptide level, downregulation of PCK1 and upregulation of GLUT (2, 4) mRNA expression levels when compared to those of diabetic rats. The administration of PPE had also increased the uptake of glucose by rat hemidiaphragm significantly. Findings from this study demonstrate that PPE enhances peripheral glucose uptake through glycogenesis pathway, mediated by upregulation of GLUT2 and GLUT4, and downregulation of PCK1. Our study suggests that the leaf of I. frutescens is a rich source of polyphenolic compounds, including those with an insulin-sensitizing function that may have the potential for treating or managing diabetes or insulin resistance

Understanding the mode-of-action of Cassia auriculata via in silico and in vivo studies towards validating it as a long term therapy for type II diabetes

Ethnopharmacological relevance: Cassia auriculata (CA) is used as an antidiabetic therapy in Ayurvedic and Siddha practice. This study aimed to understand the mode-of-action of CA via combined cheminformatics and in vivo biological analysis. In particular, the effect of 10 polyphenolic constituents of CA in modulating insulin and immunoprotective pathways were studied. Materials and methods: In silico target prediction was first employed to predict the probability of the polyphenols interacting with key protein targets related to insulin signalling, based on a model trained on known bioactivity data and chemical similarity considerations. Next, CA was investigated in in vivo studies where induced type 2 diabetic rats were treated with CA for 28 days and the expression levels of genes regulating insulin signalling pathway, glucose transporters of hepatic (GLUT2) and muscular (GLUT4) tissue, insulin receptor substrate (IRS), phosphorylated insulin receptor (AKT), gluconeogenesis (G6PC and PCK-1), along with inflammatory mediators genes (NF-κB, IL-6, IFN-γ and TNF-α ) and peroxisome proliferators-activated receptor gamma (PPAR-γ) were determined by qPCR. Results: In silico analysis shows that most of the top 10 enriched targets predicted for the constituents of CA are involved in insulin signalling pathways e.g. PTPN1, PCK-α, AKT2, PI3K-γ. Some of the predictions were supported by scientific literature such as the prediction of MAPK4 and MAPK8 for epigallocatechin gallate. Based on the in silico and in vivo findings, we hypothesized that CA may enhance glucose uptake and glucose transporter expressions via the IRS signalling pathway. This is based on AKT2 and PI3K-γ being listed in the top 20 enriched targets. In vivo analysis shows significant increase in the expression of IRS, AKT, GLUT2 and GLUT4 CA may also affect the PPAR-γ signalling pathway. This is based on the CA-treated groups showing significant activation of PPAR-γ in the liver compared to control. PPAR-γ was predicted by the in silico target prediction with high normalisation rate although it was not in the top 20 most enriched targets. CA may also be involved in the gluconeogenesis and glycogenolysis in the liver based on the downregulation of G6PC and PCK-1 genes seen in CA-treated groups. In addition, CA-treated groups also showed decreased cholesterol, triglyceride, glucose, CRP and Hb1Ac levels, and increased insulin and C-peptide levels. These findings demonstrate the insulin secretagogue and sensitizer effect of CA. Conclusion: Based on both an in silico and in vivo analysis, we propose here that CA mediates glucose/lipid metabolism via the PI3K signalling pathway, and influence AKT thereby causing insulin secretion and insulin sensitivity in peripheral tissues. CA enhances glucose uptake and expression of glucose transporters in particular via the upregulation of GLUT2 and GLUT4. Thus, based on its ability to modulate immunometabolic pathways, CA appears as an attractive long term therapy for T2DM even at relatively low doses

Human mesenchymal stem cells inhibit the differentiation and effector functions of monocytes

Although monocytes represent an essential part of the host defence system, their accumulation and prolonged stimulation could be detrimental and may aggravate chronic inflammatory diseases. The present study has explored the less-understood immunomodulatory effects of mesenchymal stem cells on monocyte functions. Isolated purified human monocytes were co-cultured with human umbilical cord-derived mesenchymal stem cells under appropriate culture conditions to assess monocytes’ vital functions. Based on the surface marker analysis, mesenchymal stem cells halted monocyte differentiation into dendritic cells and macrophages and reduced their phagocytosis functions, which rendered an inability to stimulate T-cell proliferation. The present study confers that mesenchymal stem cells exerted potent immunosuppressive activity on monocyte functions such as differentiation, phagocytosis and Ag presentation; hence, they promise a potential therapeutic role in down-regulating the unwanted monocyte-mediated immune responses in the context of chronic inflammatory diseases

Generation and characterization of human osteoarthritis cartilage-derived mesenchymal stem cells by modified sample processing and culture method

Introduction: Mesenchymal stem cells (MSCs) can be isolated from different tissue sources, and show a high differentiation capacity towards osteogenic, adipogenic, chondrogenic, neurogenic and myogenic lineages upon a specific induction. Although the retrieval of MSCs from normal tissues is very straightforward, yet it could be challenging in degenerative conditions that limit the expansion of stem cells such as osteoarthritis. Thus, this study aimed to establish human MSCs culture from osteoarthritic cartilage (OA hC-MSCs) by optimising the sample processing and culture techniques. Methods: Human osteoarthritis knee cartilage samples were obtained (2-4 g) from 8 patients with a mean age of 62.75 years old during the joint replacement surgery. A conventional culture method carried along with the modified method where the period of enzyme digestion and serial plating culture procedure were incorporated. Results: The modified culture method has significantly increased the number of single cells twice after the sample processing. The time taken to form colonies and achieve confluence was also reduced when samples subjected to the modified method. The number of cell yields after passage 0 for the conventional and modified methods were 3.05±0.31 and 6.10±0.42 million cells, respectively. The adherent cells generated under these two conditions comply with criteria for MSCs in term of immunophenotyping and mesodermal differentiation. Conclusions: The current modified method enhances the production of MSCs and could be opted for samples that known to have reduced or defective stem cell pool which may impede the in vitro cell expansion

Evaluation of anti-diabetic and immunomodulatory activity of polyphenols derived from Cassia auriculata L. on induced diabetic rat

Diabetes mellitus (DM) is considered as an immuno-metabolic disease as the immune system impairment is leads to the progression of the disease. In this study we have examined the potential effect of Cassia auriculata flowers derived polyphenols (CAP) in modulating immune integrity and antidiabetic activity on experimentally induced (Streptazocin induced & Streptazocin+ Nicotinamide induced ) diabetic rats. Normal and diabetic induced Sprague Dawley male rats at age of ~12 weeks were orally administrated with various CAP doses (10, 25, 50 &100 mg/kg) and observed for 28 days. Upon sacrifice measurement of glucose, insulin and HbA1c levels were done to assess the responses to therapy that facilitate reaching antidiabetic effect. Splenocytes were consumed to measure the expression of total T, B and NK and regulatory Tcells through flow cytometer analysis. The functional assay for Tcells and neutrophils were conducted using tritiated thymidine assay and oxidative burst assay respectively. In addition, biochemical parameters (cholesterol, triglyceride & albumin) and haematological parameters (Leukocyte count, haemoglobin level, neutrophils& lymphocytes counts) were also analysed. Supplementation of CAP in all dosages had reduced the blood glucose and increased the insulin level towards the normal in both rat models. Despite gaining of body weight, CAP supplementation also significantly normalised the biochemical and haematological parameters of diabetic rats in comparison to normal control. Flow cytometer analysis revealed that the CAP supplementation reduced the percentages of pan splenic T and B cells; however a gradual increase in T helper cell sub-population along with reduction in T cytotoxic cells were noted. Although, the percentage of T cells was reduced yet, their ability of respond to mitogen (Lipopolysaccharide) and cellular expansion was enhanced when treated with CAP. Such expansion was not confined to T cells only, but also extends towards regulatory T cells, whose expression was escalated in the presence of CAP supplementation. In term of innate immune cell activity, CAP treatment reduced the oxidative burst activity of neutrophils indicating abridged oxidative stress in diabetes. The results collectively showed that CAP supplementation has normalised the diabetic indicators by reducing glycaemic level and inducing insulin secretion. This anti-diabetic activity of CAP also imposed an immunomodulatory function on adaptive and innate immune cells. The enhanced proliferation of T cells; specific expansion of T helper sub-population and reduced oxidative burst activity of neutrophils are important to prevent the macromolecular damages that related to diabetes. Thus CAP could serves as holistic treatment that exerts anti-diabetic and immunomodulatory activity and maintains a protective mechanism by minimising complications in long term treatment for diabetes

Preliminary study on overproduction of reactive oxygen species by neutrophils in diabetes mellitus

Aim: To assess the amount and pattern of reactive oxygen species (ROS) production in diabetic patient-derived neutrophils. Methods: Blood samples from type 2 diabetes mellitus (DM) patients and volunteers (controls) were subjected to neutrophil isolation and the assessment of neutrophil oxidative burst using chemiluminescence assay. Neutrophils were activated by using phorbol myristate acetate (PMA) and neutrophils without activation were kept as a negative control. The chemiluminescence readings were obtained by transferring cell suspension into a 1.5 mL Eppendorf tube, with PMA and luminol. Reaction mixtures were gently vortexed and placed inside luminometer for a duration of 5 min. Results: Our results showed that in the resting condition, the secretion of ROS in normal non-diabetic individuals was relatively low compared to diabetic patients. However, the time scale observation revealed that the secreted ROS declined accordingly with time in non-diabetic individuals, yet such a reduction was not detected in diabetic patients where at all the time points, the secretion of ROS was maintained at similar magnitudes. This preliminary study demonstrated that ROS production was significantly higher in patients with DM compared to non-diabetic subjects in both resting and activated conditions. Conclusion: The respiratory burst activity of neutrophils could be affected by DM and the elevation of ROS production might be an aggravating factor in diabetic-related complications

Effects of Pharmacological Inhibitors of NADPH Oxidase on Myogenic Contractility and Evoked Vasoactive Responses in Rat Resistance Arteries

Reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide, are reported to contribute to the dynamic regulation of contractility in various arterial preparations, however, the situation in pressurized, myogenically active resistance arteries is much less clear. In the present study, we have utilized established pharmacological inhibitors of NADPH oxidase activity to examine the potential contribution of ROS to intrinsic myogenic contractility in adult Sprague-Dawley rat resistance arteries and responses to vasoactive agents acting via the endothelium (i.e., acetylcholine, SKA-31) or smooth muscle (i.e., sodium nitroprusside, phenylephrine). In cannulated and pressurized cremaster skeletal muscle and middle cerebral arteries, the NOX inhibitors 2-acetylphenothiazine (2-APT) and VAS2870, selective for NOX1 and NOX2, respectively, evoked concentration-dependent inhibition of basal myogenic tone in a reversible and irreversible manner, respectively, whereas the non-selective inhibitor apocynin augmented myogenic contractility. The vasodilatory actions of 2-APT and VAS2870 occurred primarily via the vascular endothelium and smooth muscle, respectively. Functional responses to established endothelium-dependent and -independent vasoactive agents were largely unaltered in the presence of either 2-APT or apocynin. In cremaster arteries from Type 2 Diabetic (T2D) Goto-Kakizaki rats with endothelial dysfunction, treatment with either 2-APT or apocynin did not modify stimulus-evoked vasoactive responses, but did affect basal myogenic tone. These same NOX inhibitors produced robust inhibition of total NADPH oxidase activity in aortic tissue homogenates from control and T2D rats, and NOX isozymes 1, 2 and 4, along with superoxide dismutase 1, were detected by qPCR in cremaster arteries and aorta from both species. Based on the diverse effects that we observed for established, chemically distinct NOX inhibitors, the functional contribution of vascular NADPH oxidase activity to stimulus-evoked vasoactive signaling in myogenically active, small resistance arteries remains unclear.Canadian Institutes of Health Research (CIHR)Natural Sciences and Engineering Research Council (NSERC

Maternal Cognitive Impairment Associated with Gestational Diabetes Mellitus—A Review of Potential Contributing Mechanisms

Gestational diabetes mellitus (GDM) carries many risks, where high blood pressure, preeclampsia and future type II diabetes are widely acknowledged, but less focus has been placed on its effect on cognitive function. Although the multifactorial pathogenesis of maternal cognitive impairment is not completely understood, it shares several features with type 2 diabetes mellitus (T2DM). In this review, we discuss some key pathophysiologies of GDM that may lead to cognitive impairment, specifically hyperglycemia, insulin resistance, oxidative stress, and neuroinflammation. We explain how these incidents: (i) impair the insulin-signaling pathway and/or (ii) lead to cognitive impairment through hyperphosphorylation of τ protein, overexpression of amyloid-β and/or activation of microglia. The aforementioned pathologies impair the insulin-signaling pathway primarily through serine phosphorylation of insulin receptor substances (IRS). This then leads to the inactivation of the phosphatidylinositol 3-kinase/Protein kinase B (PI3K/AKT) signaling cascade, which is responsible for maintaining brain homeostasis and normal cognitive functioning. PI3K/AKT is crucial in maintaining normal cognitive function through the inactivation of glycogen synthase kinase 3β (GSκ3β), which hyperphosphorylates τ protein and releases pro-inflammatory cytokines that are neurotoxic. Several biomarkers were also highlighted as potential biomarkers of GDM-related cognitive impairment such as AGEs, serine-phosphorylated IRS-1 and inflammatory markers such as tumor necrosis factor α (TNF-α), high-sensitivity C-reactive protein (hs-CRP), leptin, interleukin 1β (IL-1β), and IL-6. Although GDM is a transient disease, its complications may be long-term, and hence increased mechanistic knowledge of the molecular changes contributing to cognitive impairment may provide important clues for interventional strategies

Pharmacological Targeting of KCa Channels to Improve Endothelial Function in the Spontaneously Hypertensive Rat

Systemic hypertension is a major risk factor for the development of cardiovascular disease and is often associated with endothelial dysfunction. KCa2.3 and KCa3.1 channels are expressed in the vascular endothelium and contribute to stimulus-evoked vasodilation. We hypothesized that acute treatment with SKA-31, a selective activator of KCa2.x and KCa3.1 channels, would improve endothelium-dependent vasodilation and transiently lower mean arterial pressure (MAP) in male, spontaneously hypertensive rats (SHRs). Isolated vascular preparations exhibited impaired vasodilation in response to bradykinin (i.e., endothelial dysfunction) compared with Wistar controls, which was associated with decreased bradykinin receptor expression in mesenteric arteries. In contrast, similar levels of endothelial KCa channel expression were observed, and SKA-31 evoked vasodilation was comparable in vascular preparations from both strains. Addition of a low concentration of SKA-31 (i.e., 0.2–0.3 μM) failed to augment bradykinin-induced vasodilation in arteries from SHRs. However, responses to acetylcholine were enhanced. Surprisingly, acute bolus administration of SKA-31 in vivo (30 mg/kg, i.p. injection) modestly elevated MAP compared with vehicle injection. In summary, pharmacological targeting of endothelial KCa channels in SHRs did not readily reverse endothelial dysfunction in situ, or lower MAP in vivo. SHRs thus appear to be less responsive to endothelial KCa channel activators, which may be related to their vascular pathology