Presence of pyrroloquinazoline alkaloid in Adhatoda vasica attenuates inflammatory response through the downregulation of pro-inflammatory mediators in LPS stimulated RAW 264.7 macrophages.

Introduction: Inflammation is the primary response caused due to harmful stimuli which are followed by the increased draining of plasma and immune cells from the body into the site of the injured tissue. A signaling cascade of growth factors and cytokines propagates and eventually matures in the inflammatory site involving the blood vessels and immune markers within the injured tissue in order to promote the renewal of the degenerated tissue. During a chronic disorder like diabetic foot ulcer, there is an obstinate inflammation which may act as a prime factor for limb amputation and upon persistent prevalence may even lead to death. Methods: This study focuses on the mode of action of ALK-F (alkaloid fraction) isolated from Adhatoda vasica in attenuating the nitric oxide production which was estimated by Griess assay, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) expression was analyzed by ELISA and expression of COX-2 and iNOS by RT-PCR and western blotting in LPS stimulated RAW 264.7 macrophages. Total intracellular ROS was analyzed by DCFH-DA probing and the presence of quinazoline alkaloid (vasicine) in the ALK-F was evidenced by high performance liquid chromatography (HPLC). Results: The ALK-F of A. vasica exhibited a significant inhibitory effect on LPS elicited nitrite production (13.2 ± 1.06 µM), iNOS, and COX-2 (2.6 and 3.3 fold) in a dose-dependent manner. There was a significant decrease in the generation of these pro-inflammatory cytokines TNF-α (1102 ± 1.02 pg/mL) and IL-6 (18 ± 0.87 ng/mL) and total intracellular ROS in the highest tested concentrations (1 µg and 10 µg) of ALK-F of A. vasica. HPLC analysis by the gradient elution method revealed the presence of 12% of quinazoline alkaloid vasicine in the crude alkaloid fraction. Conclusion: Thus this study communally suggests that attenuation of nitric oxide and the dysregulation of genes responsible for inflammation which deliberates A. vasica to conflict against inflammation and provide remedial benefits in diabetic wound care.

Current trends in small molecule discovery targeting key cellular signaling events towards the combined management of diabetes and obesity.

Non-insulin dependent diabetes mellitus, also known as Type 2 diabetes is a polygenic disorder leading to abnormalities in the carbohydrate and lipid metabolism. The major contributors in the pathophysiology of type 2 diabetes (T2D) include resistance to insulin action, ß cell dysfunction, an abnormality in glucose metabolism and storage, visceral obesity and to some extent inflammation and oxidative stress. Insulin resistance, along with a defect in insulin secretion by the pancreatic ß cells is instrumental towards progression to hyperglycemia. Increased incidence of obesity is also a major contributing factor in the escalating rates of type 2 diabetes. Drug discovery efforts are therefore crucially dependent on identifying individual molecular targets and validating their relevance to human disease. The current review discusses bioactive compounds from medicinal plants offering enhanced therapeutic potential for the combined patho-physiology of diabetes and obesity. We have demonstrated that 3ß-taraxerol a pentacyclic triterpenoid (14-taraxeren-3-ol) isolated from the ethyl acetate extract of Mangifera indica, chlorogenic acid isolated from the methanol extract of Cichorium intybus, methyl tetracosanoate from the methanol extract of Costus pictus and vitalboside A derived from methanolic extract of Syzygium cumini exhibited significant effects on insulin stimulated glucose uptake causing insulin sensitizing effects on 3T3L1 adipocytes (an in vitro model mimicking adipocytes). Whereas, (3ß)-stigmast-5-en-3-ol isolated from Adathoda vasica and Aloe emodin isolated from Cassia fistula showed significant insulin mimetic effects favoring glucose uptake in L6 myotubes (an in vitro model mimicking skeletal muscle cells). These extracts and molecules showed glucose uptake through activation of PI3K, an important insulin signaling intermediate. Interestingly, cinnamic acid isolated from the hydro-alcohol extract of Cinnamomum cassia was found to activate glucose transport in L6 myotubes through the involvement of GLUT4 via the PI3K-independent pathway. However, the activation of glucose storage was effective in the presence of 3ß-taraxerol and aloe emodin though inhibition of GSK3ß activity. Therefore, the mechanism of improvement of glucose and lipid metabolism exhibited by the small molecules isolated from our lab is discussed. However, Obesity is a major risk factor for type-2 diabetes leading to destruction of insulin receptors causing insulin resistance. Identification of compounds with dual activity (anti-diabetic and antiadipogenic activity) is of current interest. The protein tyrosine phosphatase 1B (PTP1B) is an important negative regulator of the insulin and leptin-signaling pathway is of significance in target definition and discovery.

3beta-taraxerol of Mangifera indica, a PI3K dependent dual activator of glucose transport and glycogen synthesis in 3T3-L1 adipocytes.

BACKGROUND: The present study focuses on identifying and developing an anti-diabetic molecule from plant sources that would effectively combat insulin resistance through proper channeling of glucose metabolism involving glucose transport and storage. METHODS: Insulin-stimulated glucose uptake formed the basis for isolation of a bioactive molecule through column chromatography followed by its characterization using NMR and mass spectroscopic analysis. Mechanism of glucose transport and storage was evaluated based on the expression profiling of signaling molecules involved in the process. RESULTS: The study reports (i) the isolation of a bioactive compound 3beta-taraxerol from the ethyl acetate extract (EAE) of the leaves of Mangifera indica (ii) the bioactive compound exhibited insulin-stimulated glucose uptake through translocation and activation of the glucose transporter (GLUT4) in an IRTK and PI3K dependent fashion. (iii) the fate of glucose following insulin-stimulated glucose uptake was ascertained through glycogen synthesis assay that involved the activation of PKB and suppression of GSK3beta. GENERAL SIGNIFICANCE: This study demonstrates the dual activity of 3beta-taraxerol and the ethyl acetate extract of Mangifera indica as a glucose transport activator and stimulator of glycogen synthesis. 3beta-taraxerol can be validated as a potent candidate for managing the hyperglycemic state.

Probing key targets in insulin signaling and adipogenesis using a methanolic extract of Costus pictus and its bioactive molecule, methyl tetracosanoate.

A methanolic extract of Costus pictus (CPME) showed optimum anti-diabetic activity at 100 ng/ml. Bioactivity-guided purification of CPME led to the isolation of methyl tetracosanoate (MT) which showed an optimum glucose uptake at 1 ng/ml. CPME at 10 mug/ml inhibited adipogenesis whereas fully differentiated adipocytes exhibited a 3-fold increase in lipid accumulation compared to pre-adipocytes. Gene and protein expression of key targets in insulin signaling and adipogenesis pathway revealed that CPME exhibited anti-diabetic activity along with anti-adipogenic activity whereas MT demonstrated only anti-diabetic activity.

Cinnamic acid, from the bark of Cinnamomum cassia, regulates glucose transport via activation of GLUT4 on L6 myotubes in a phosphatidylinositol 3-kinase-independent manner.

BACKGROUND: Cinnamomum cassia (Family: Lauraceae) is an Ayurvedic medicinal plant used traditionally for the treatment of a number of diseases, including diabetes. The hypoglycemic effect of this plant has been established in vivo. However, the effects of cinnamic acid, isolated from C. cassia, on the insulin signaling cascade in an in vitro model have not been elucidated. Hence, the aim of the present study was to evaluate the anti-diabetic effect of cinnamic acid on glucose transport by L6 myotubes. METHODS: The mechanism of action of cinnamic acid was determined using specific targets in the insulin signaling pathway, including protein tyrosine phosphatase (PTP) 1B, phosphatidylinositol 3-kinase (PI3-K) and the glucose transporter GLUT4. After differentiation of myoblast to myotubes, the cells were serum deprived for 5 h and then treated with 1 ng/mL cinnamic acid and 50 µmol/L rosiglitazone for 18 h and 100 nmol/L insulin for 20 min for gene expression studies. RESULTS: Expression of GLUT4 mRNA was increased following treatment of L6 myotubes with 1 ng/mL cinnamic acid. Furthermore, cinnamic acid inhibited PTP1B activity (by 96.5%), but had no significant effect on PI3-K activity. CONCLUSION: On the basis of the results of the present study, we postulate that cinnamic acid isolated from the hydro-alcoholic extract of Cinnamomum cassia activates glucose transport by a PI3-K-independent pathway. However, the detailed mechanism of action requires further analysis.