Inhibition of epidermal growth factor receptor by ferulic acid and 4-vinylguaiacol in human breast cancer cells.

OBJECTIVES: To examine the potential of ferulic acid and 4-vinylguaiacol for inhibiting epidermal growth factor receptor (EGFR) in human breast cancer cells in vitro. RESULTS: Ferulic acid and 4-vinylguaiacol limit the EGF (epidermal growth factor)-induced breast cancer proliferation and new DNA synthesis. Western blot analysis revealed both ferulic acid and 4-vinylguaiacol exhibit sustained inhibition of EGFR activation through down-regulation of Tyr 1068 autophosphorylation. Molecular docking analysis shows ferulic acid forming hydrogen bond interaction with Lys 745 and Met 793 whereas, 4-vinylguaiacol forms two hydrogen bonds with Phe 856 and exhibits stronger hydrophobic interactions with multiple amino acid residues at the EGFR kinase domain. CONCLUSIONS: Ferulic acid and 4-vinylguaiacol could serve as a potential structure for the development of new small molecule therapeutics against EGFR.

AKT-p53 axis protect cancer cells from autophagic cell death during nutrition deprivation.

An altered metabolism supports growth of tumor. AKT, a major signal integrator plays a key role in cell metabolism. We have shown that nutritional deprivation activates AKT as observed by increased phosphorylation of both Thr308 and Ser473. Pharmacological inhibition or silencing of AKT by siRNA affects cell viability during starvation. The tumor suppressor, p53 is also observed to be elevated during nutritional deprivation due to AKT. Silencing of AKT and p53 enhanced autophagy as evidenced by increased acidic vesicular organelles and LC3B II levels, suggesting AKT-p53 to play a significant role in cell survival through regulating autophagy during nutritional deprivation.

Dexamethasone promotes hypertrophy of H9C2 cardiomyocytes through calcineurin B pathway, independent of NFAT activation.

Metabolic syndrome-induced cardiac hypertrophy is a global concern leading to an increase in the morbidity and mortality of patients, with the signalling mechanism associated with them still unclear. The present study attempts to understand the metabolic syndrome-associated cardiac hypertrophy through an in vitro model using external stimuli well known for inducing metabolic disorders, i.e. dexamethasone (DEX), a synthetic glucocorticoid. DEX (0.1 and 1 µM) promoted cardiac hypertrophy in H9C2 cells at 4 days of treatment as evidenced through increased cell size and protein content. A significant induction in foetal gene reprogramming was observed, confirming the establishment of hypertrophy. Moreover, the hypertrophic response at 4 days was perceived to be physiological at 0.1 µM and pathological at 1 µM based on α-MHC and IGF1R expression, but complete inhibition in the PKB/AKT expression confirmed it to be pathological hypertrophy at both the concentrations (0.1 and 1 µM). The present study reports for the first time the mechanistic insights into DEX-mediated hypertrophy. It is hypothesized to be orchestrated through the activation of AT1R that is involved in the alteration of the cardiac isoform of SERCA2 expression perturbing the calcium homeostasis. This leads to the activation of calcineurin B, independent of NFAT involvement, which in coordination with ROS induces the activation of JNK of the MAPK signalling.

Increased circulatory levels of lipopolysaccharide (LPS) and zonulin signify novel biomarkers of proinflammation in patients with type 2 diabetes.

Emerging data indicate that gut-derived endotoxin (metabolic endotoxemia) may contribute to low-grade systemic inflammation in insulin-resistant states. Specific gut bacteria seem to serve as lipopolysaccharide (LPS) sources and several reports claim a role for increased intestinal permeability in the genesis of metabolic disorders. Therefore, we investigated the serum levels of LPS and zonulin (ZO-1, a marker of gut permeability) along with systemic levels of tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6) in patients with type 2 diabetes mellitus (T2DM) compared to control subjects. Study subjects were recruited from the Chennai Urban Rural Epidemiology Study [CURES], Chennai, India. Study group (n = 45 each) comprised of a) subjects with normal glucose tolerance (NGT) and (b) patients with T2DM. LPS, ZO-1, TNF-α, and IL-6 levels were measured by ELISA. Serum levels of LPS [p < 0.05], LPS activity [p < 0.001], ZO-1 [p < 0.001], TNFα [p < 0.001], and IL-6 [p < 0.001] were significantly increased in patients with T2DM compared to control subjects. Pearson correlation analysis revealed that LPS activity was significantly and positively correlated with ZO-1, fasting plasma glucose, 2 h post glucose, HbA1c, serum triglycerides, TNF-α, IL-6, and negatively correlated with HDL cholesterol. Regression analysis showed that increased LPS levels were significantly associated with type 2 diabetes [odds ratio (OR) 13.43, 95 % CI 1.998-18.9; p = 0.003]. In Asian Indians who are considered highly insulin resistant, the circulatory LPS levels, LPS activity, and ZO-1 were significantly increased in patients with type 2 diabetes and showed positive correlation with inflammatory markers and poor glycemic/lipid control.

p53 mediates impaired insulin signaling in 3T3-L1 adipocytes during hyperinsulinemia.

Hyperinsulinemia is being implicated in the development of insulin resistance but remains poorly understood. The present study focuses on p53-mediated impaired insulin signaling by hyperinsulinemia in 3T3-L1 adipocytes. Hyperinsulinemia impairs insulin-stimulated glucose uptake and its cellular signaling in a dose- and time-dependent manner. An increased level of reactive oxygen species (ROS) and stress response signals were observed, and quenching of the ROS by an antioxidant N-acetylcysteine (NAC) did not revert impaired insulin sensitivity. The tumor suppressor p53 has emerged as a crucial factor in the metabolic adaptation of cancer cells under nutritional starvation and is being studied in the development of insulin resistance in adipocytes at physiological level. Interestingly, we observed hyperinsulinemia-enhanced p53 level in a time-dependent manner without exhibiting cytotoxicity. Transient knockdown of p53 partially improved insulin sensitivity revealing a novel link between p53 and insulin signaling in adipocytes. The findings suggest that hyperinsulinemia-induced p53 impairs insulin sensitivity in 3T3-L1 adipocytes.

Rapid non-genomic signalling by 17ß-oestradiol through c-Src involves mTOR-dependent expression of HIF-1α in breast cancer cells.

BACKGROUND: Hypoxia-inducible factor 1 (HIF1) has been implicated in regulating many of the genes responsible for angiogenesis, erythropoiesis, glucose metabolism and cancer pathogenesis. In this study, we demonstrate that exposure of human breast cancer lines to 17ß-oestradiol (E2) rapidly induced the expression of HIF-1α, the regulated subunit of HIF1, in normoxic condition. Hypoxia-inducible factor-1α is normally degraded in normoxia through ubiquitination-mediated proteolysis, whereas hypoxia modulates HIF-1α level by inhibiting ubiquitination-mediated degradation. METHODS: Oestradiol-induced accumulation of HIF-1α in breast cancer lines was detected by western blot analysis and its promoter activity was measured by HIF1 reporter assay. Molecular signalling of oestradiol-mediated HIF-1α expression was studied using specific pharmacological inhibitors and small interference RNA by co-immunoprecipitation and western blotting analysis. RESULTS: Oestradiol has been observed to rapidly activate the nongenomic signalling cascade leading to HIF-1α protein synthesis. The results define a signalling pathway in breast cancer cells whereby oestradiol induces a rapid protein-protein interaction of ERα-c-Src-PI3K, resulting in the activation of PI3K/AKT pathway leading to mammalian target of rapamycin (mTOR) phosphorylation. The mTOR then stimulates translation by phosphorylating p70 S6 kinase and 4EB-P1, modulating HIF-1α protein synthesis. Oestradiol-stimulated HIF-1α activity was inhibited by either siRNA or pharmacological inhibitors to ERα, c-Src, PI3K and mTOR, providing a mechanism for the modulation of HIF-1α protein synthesis. CONCLUSION: These results show oestradiol-induced expression of HIF-1α, downstream of the ERα/c-Src/PI3K/AKT/mTOR pathway in human breast cancer cells.

Inhibition of protein tyrosine phosphatase 1B and regulation of insulin signalling markers by caffeoyl derivatives of chicory ( Cichorium intybus) salad leaves.

Evaluations of molecular mechanisms of dietary plants with their active molecules are essential for the complete exploration of their nutritive and therapeutic value. In the present study, we investigated the effect of chicory (Cichorium intybus) salad leaves in inhibiting protein tyrosine phosphatase 1B (PTP1B), and evaluated their role in modulating the key markers involved in insulin cell signalling and adipogenesis using 3T3-L1 adipocytes. Bioactivity-directed purification studies enlightened the additive effects of chlorogenic acid (CGA) along with other caffeic acid derivatives present in methanolic extract of C. intybus (CME). Incubation of CME and CGA with 3T3-L1 adipocytes significantly enhanced the 2-deoxy-d-3[H]-glucose uptake and inhibited adipogenesis through altering the expressions of insulin signalling and adipogenesis markers. Extending to an in vivo model, the effect of CME was also investigated on insulin sensitivity in high-fat diet with low streptozotocin-induced diabetic rats. Supplementation of CME for 2 weeks reinstated the insulin sensitivity along with plasma metabolic profile. The present results demonstrate that the caffeoyl derivatives of chicory salad leaves show promising pharmacological effect on energy homoeostasis via PTP1B inhibition both in vitro and in vivo.

Insulinomimetic activity of two new gallotannins from the fruits of Capparis moonii.

Bioassay guided fractionation of the hydro-alcoholic extract of the fruits of Capparis moonii, led to the isolation of two new chebulinic acid derivatives. The compounds 1 and 2 displayed significant glucose uptake effect of 223% and 219% over the control at the 10ng/ml and 100ng/ml concentration, respectively. The increased glucose uptake effects of the compounds were associated with significant IR and IRS-1 phosphorylation, GLUT4 and PI3-kinase mRNA expression in the L6 cells.

In silico prediction of a new lead compound targeting enolase of trypanosomatids through structure-based virtual screening and molecular dynamic studies.

Enolase is one of the key glycolytic metalloenzyme in many organisms, and it is a potential therapeutic target including trypanosomatids. Sequence and structural analysis of enolase of Trypanosoma bruzi (TbENO), Trypanosoma cruzi (TcENO) and Leishmania donovani (LdENO) revealed conserved sequence pattern and structural features. Hence identification of an inhibitor against enolase of one trypanosomatid organism may have similar effects on enolase of homologous organisms belonging to same family. In the process to identify potent inhibitor compounds against TbENO by in silico methods, compounds containing the substructures of substrate, i.e. phosphoenolpyruvate (PEP) and the well-known inhibitors, fluoro-2-phosphono-acetohydroxamate (FPAH) and phosphono-acetohydroxamate (PAH), were collected. Virtual screening and induced fit docking studies were carried out to explore compounds that have better binding affinity than PEP and FPAH. PPPi was found to be the top hit exhibiting significant binding affinity towards enolase. Glide energy values of two other compounds represented by PubChem ID: 511392 and 101803456 was in good agreement with PEP and PAH. TbENO-PPPi complex was subjected to molecular orbital analysis and molecular dynamic studies by considering its remarkable binding affinity as it could be a potent inhibitor of enolase. Despite being an endogenous compound, based on the results of this study, we highlight PPPi to be a lead compound, and its structure can be treated as a model for further chemical modifications to obtain more potent antagonists.

Tannins present in Cichorium intybus enhance glucose uptake and inhibit adipogenesis in 3T3-L1 adipocytes through PTP1B inhibition.

Insulin resistance is a fundamental aspect for the etiology of non-insulin dependent diabetes mellitus (NIDDM) and has links with a wide array of secondary disorders including weight gain and obesity. The present study analyzes the effect of Cichorium intybus methanolic (CME) extract on glucose transport and adipocyte differentiation in 3T3-L1 cells by studying the radiolabelled glucose uptake and lipid accumulation assays, respectively. By performing detannification (CME/DT), the role of tannins present in CME on both the activities was evaluated. CME and CME/DT exhibited significant glucose uptake in 3T3-L1 adipocytes with a dose-dependent response. Glucose uptake profile in the presence of PI3K and IRTK inhibitors (Wortmannin and Genistein) substantiates the mechanism used by both the extracts. CME inhibited the differentiation of 3T3-L1 preadipocytes but failed to show glucose uptake in inhibitor treated cells. The activity exhibited by CME/DT is exactly vice versa to CME. Furthermore, the findings from PTP1B inhibition assay, mRNA and protein expression analysis revealed the unique behavior of CME and CME/DT. The duality exhibited by C. intybus through adipogenesis inhibition and PPARgamma up regulation is of interest. Current observation concludes that the activities possessed by C. intybus are highly desirable for the treatment of NIDDM because it reduces blood glucose levels without inducing adipogenesis in 3T3-L1 adipocytes.

LamB-mediated adherence of enteropathogenic Escherichia coli to HEp-2 cells.

AIMS: To establish the role of maltoporin (LamB) in adherence of enteropathogenic Escherichia coli (EPEC) to epithelial cells in vitro. METHODS AND RESULTS: Three strains, wild type (WT) EPEC, a maltoporin (LamB) mutant DeltalamB, and DH5alpha were used to study adherence to cultured HEp-2 cells. Mutant DeltalamB was found to be deficient in adherence compared to WT EPEC. Adherence of DeltalamB was restored to wild type levels when complemented with the cloned lamB gene. The non-adherent strain DH5alpha also adhered to HEp-2 cells when it harboured the cloned lamB gene. The LamB protein was isolated from WT EPEC by electroelution and antibodies were raised in rabbits. The specificity of the antibodies was analysed by Western blotting. Anti-LamB antiserum reduced adherence of WT EPEC to HEp-2 cells. The LamB protein was coated on latex beads and the beads adhered to HEp-2 cells. Anti-LamB antiserum prevented bead adherence to HEp-2 cells. Multiple sequence alignment showed that the L9 loop of EPEC LamB had four amino acids different from the L9 loop of LamB from several other related pathogens. CONCLUSIONS: LamB serves as an alternative or additional adherence factor for EPEC. SIGNIFICANCE AND IMPACT OF THE STUDY: Adherence is an important component of the pathogenesis of noninvasive pathogens like EPEC. A putative adhesin such as LamB, which has already been found to be co-expressed with virulence factor EspB may be a potential vaccine candidate for control of EPEC and related pathogens.

Pure compound from Boswellia serrata extract exhibits anti-inflammatory property in human PBMCs and mouse macrophages through inhibition of TNFalpha, IL-1beta, NO and MAP kinases.

The aim of the present study is to probe the anti-inflammatory potential of the plant Boswellia serrata by studying the effect of the crude extract and the pure compound isolated from it on key inflammatory mediators like TNFalpha, IL-1beta, and NO thus enabling the understanding of the key signaling events involved. The crude methanolic extract and the pure compound were analysed for their inhibitory effect on TNFalpha, IL-1beta and IL-6. The results demonstrated that all three cytokines are down regulated when PBMCs are cultured in the presence of crude extract or the pure compound at various time points. Observations on Th1/Th2 cytokines revealed marked down regulation of Th1 cytokines IFNgamma and IL-12 while the Th2 cytokines IL-4 and IL-10 were up regulated upon treatment with crude extract and pure compound. The extract and the pure compound isolated also showed considerable inhibition of NO production in activated RAW 264.7 cells, possibly via suppression of inducible NO synthase mRNA expression. Further to elucidate the underlying mechanism of action the effect of 12-ursene 2-diketone on LPS-induced activation of MAPK has also been examined. Our results demonstrated that 12-ursene 2-diketone inhibits the expression of pro-inflammatory cytokines and mediators via inhibition of phosphorylation of the MAP kinases JNK and p38 while no inhibition was seen in ERK phosphorylation in LPS-stimulated PBMCs. The above study therefore indicates that the crude methanolic extract and the isolated pure compound are capable of carrying out a natural anti-inflammatory activity at sites where chronic inflammation is present by switching off the pro-inflammatory cytokines and mediators, which initiate the process.

Withanolide induces apoptosis in HL-60 leukemia cells via mitochondria mediated cytochrome c release and caspase activation.

The present study is on the growth inhibitory effect of Withania somnifera methanolic leaf extract and its active component, withanolide on HL-60 promyelocytic leukemia cells. The decrease in survival rate of HL-60 cells was noted to be associated with a time dependent decrease in the Bcl-2/Bax ratio, leading to up regulation of Bax. Both the crude leaf extract and the active component activated the apoptotic cascade through the cytochrome c release from mitochondria. The activation of caspase 9, caspase 8 and caspase 3 revealed that caspase was a key mediator in the apoptotic pathway. DNA fragmentation analysis revealed typical ladders as early as 12h indicative of caspase 3 role in the apoptotic pathway. Flow cytometry data demonstrated an increase of sub-G1 peak upon treatment by 51% at 24h, suggesting the induction of apoptotic cell death in HL-60 cells.

Employment Status of Patients Receiving Maintenance Dialysis - Peritoneal and Hemodialysis: A Cross-sectional Study.

The long-term dialysis therapy for end-stage renal disease takes a heavy toll of quality of life of the patient. Several factors such as fatigue and decreased physical capability, impaired social and mental functioning, contribute to this forlorn state. To meld maintenance dialysis treatment with a regular employment can be a serious test. A cross-sectional study of employment of patients on hemodialysis and peritoneal dialysis in a state government tertiary institute in South India was performed between June 2015 and December 2015. Patients who completed 3 months of regular dialysis were only included in the study. The number of patients on hemodialysis was 157 and on peritoneal dialysis was 69. The employment status before the initiation of dialysis was 60% (93 out of 155) and 63.7% (44 out of 69) in hemodialysis and peritoneal dialysis, respectively. After initiation, the loss of employment was observed in 44% (41 out of 93) in hemodialysis and 51.2% (26 out of 44) in peritoneal dialysis (P = 0.2604). Even though there was fall of absolute number of job holders in both the blue and white collar jobs, the proportion of jobholders in the white collar job holders improved. On univariate analysis, the factors which influenced the loss of employment were males, age between 50 and 60 years, number of comorbidities >2, illiteracy and blue collar versus white collar job before the initiation of dialysis. The majority of patients had the scores above 80 on Karnofsky performance scale and the majority belonged upper and middle classes than lower classes on modified Kuppuswamy's socioeconomic status scale; however, the loss of employment was also disproportionately high. There appeared a substantial difference in the attitude of the patients toward the employment. There was no difference between hemodialysis and peritoneal dialysis in the loss of employment of our patients.

Estrogen suppresses breast cancer proliferation through GPER / p38 MAPK axis during hypoxia.

Breast cancer cells frequently experience hypoxia which is associated with resistance to hormonal therapy and poor clinical prognosis, making it important to understand the function of estrogen under hypoxic condition. Here, we demonstrate that estrogen suppresses breast cancer cell growth under hypoxia, through inhibition at G1/S phase of cell cycle, by elevation of p21 expression. The involvement of GPER in estrogen mediated growth arrest was elucidated using specific ligands and siRNA. Although, estrogen was observed to activate both p44/42 and p38 MAPK signaling, pharmacological inhibition and silencing of p38 MAPK abrogated the induction of p21 expression and growth arrest, during hypoxia. The involvement of estrogen induced ROS in the p38 MAPK mediated p21 expression and cell growth arrest was established by observing that scavenging of ROS by NAC abrogated p38 MAPK activation and p21 expression during hypoxia. In conclusion, Estrogen suppresses breast cancer growth by inhibiting G1/S phase transition through GPER/ROS/p38 MAPK/p21 mediated signaling during hypoxic condition.

5-Methyl phenazine-1-carboxylic acid: a novel bioactive metabolite by a rhizosphere soil bacterium that exhibits potent antimicrobial and anticancer activities.

A new rhizosphere soil bacterium that exhibits antimicrobial potential against human pathogens was isolated. On the basis of 16S ribosomal RNA nucleotide sequence homology and subsequent phylogenetic tree analysis, the strain PUW5 was identified as Pseudomonas putida. A bioactive metabolite was extracted and purified using silica gel column chromatography and preparative HPLC. Characterization of metabolite was done by employing Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS). On the basis of spectroscopic data, the metabolite was structurally elucidated as 5-methyl phenazine-1-carboxylic acid betaine (MPCAB). The MPCAB exhibits selective cytotoxicity towards lung (A549) and breast (MDA MB-231) cancer cell lines in dose-dependent manner with IC50 value of 488.7±2.52 nM and 458.6±2.48 nM respectively. The MPCAB exhibited inhibition of cell viability, DNA synthesis, induced G1 cell cycle arrest and apoptosis in cancer cells. The docking and interaction studies confirmed the binding potential of MPCAB with Bcl-2 than Bcl-xL and Bcl-w proteins. These results strongly suggest that the MPCAB induces apoptosis in A549 and MDA MB-231 cancer cells through mitochondrial intrinsic pathway via activation of caspase-3 and down regulation of Bcl-2 protein.

Naturally derived biofunctional nanofibrous scaffold for skin tissue regeneration.

Significant wound healing activity of Aloe vera (AV) and higher elastic strength of Silk fibroin (SF) along with mammalian cell compatibility makes AV and SF an attractive material for tissue engineering. The purpose of the present work was to combine their unique properties, with the advantage of electrospinning to prepare a hybrid transdermal biomaterial for dermal substitutes. The physico-chemical characterization of the developed scaffold showed finer morphology expressing amino and esteric groups with improved hydrophilic properties and favorable tensile strain of 116% desirable for skin tissue engineering. Their biological response showed favorable fibroblast proliferation compared to control which almost increased linearly by (p<0.01) 34.68% on day 3, (p<0.01) 19.13% on day 6, and (p<0.001) 97.86% on day 9 with higher expression of CMFDA, collagen and F-actin proteins. The obtained results prove that the nanofibrous scaffold with synergistic property of AV and SF would be a potential biomaterial for skin tissue regeneration.

Precipitation of hydroxyapatite on electrospun polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds for bone tissue engineering.

Advances in electrospun nanofibres with bioactive materials have enhanced the scope of fabricating biomimetic scaffolds for tissue engineering. The present research focuses on fabrication of polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds by electrospinning followed by hydroxyapatite deposition by calcium-phosphate dipping method for bone tissue engineering. Morphology, composition, hydrophilicity and mechanical properties of polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds along with controls polycaprolactone and polycaprolactone/aloe vera/silk fibroin nanofibrous scaffolds were examined by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle and tensile tests, respectively. Adipose-derived stem cells cultured on polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds displayed highest cell proliferation, increased osteogenic markers expression (alkaline phosphatase and osteocalcin), osteogenic differentiation and increased mineralization in comparison with polycaprolactone control. The obtained results indicate that polycaprolactone/aloe vera/silk fibroin-hydroxyapatite nanofibrous scaffolds have appropriate physico-chemical and biological properties to be used as biomimetic scaffolds for bone tissue regeneration.

Reversal of dexamethasone induced insulin resistance in 3T3L1 adipocytes by 3ß-taraxerol of Mangifera indica.

AIM: The present study investigates the efficacy of Mangifera indica ethyl acetate extract (MIEE) and its bioactive compound, 3ß-taraxerol in the reversal of dexamethasone (DEX) induced insulin resistance in 3T3L1 adipocytes. MAIN METHODS: MIEE and 3ß-taraxerol were evaluated for their ability to restore impaired glucose uptake and, expression of molecular markers in the insulin signaling pathway induced by DEX in 3T3L1 adipocytes using 2-deoxy-D-[1-(3)H] glucose uptake assay and ELISA. KEY FINDINGS: An insulin resistant model has been developed using a glucocorticoid, DEX on 3T3L1 adipocytes. Insulin resistant condition was observed at 24h of DEX induction wherein a maximum degree of resistance of about 50% was measured based on inhibition of glucose uptake, which was confirmed using cytotoxicity analysis. The developed model of insulin resistance was studied in comparison to positive control rosiglitazone. DEX induced inhibition of glucose uptake and the expression of insulin signaling markers GLUT4 and PI3K were found to be restored by 3ß-taraxerol and MIEE, thus delineating its mechanism of action in the reversal of insulin resistance. SIGNIFICANCE: 3ß-Taraxerol effectively restored DEX induced desensitization via restoration of PI3K and GLUT4 expression. To conclude, since 3ß-taraxerol exhibits significant effect in reversing insulin resistance it can be further investigated as an insulin resistance reversal agent.

Antihyperglycemic effect of Annona squamosa hexane extract in type 2 diabetes animal model: PTP1B inhibition, a possible mechanism of action?

AIM: The mechanism of action of Annona squamosa hexane extract in mediating antihyperglycemic and antitriglyceridimic effect were investigated in this study. MATERIALS AND METHODS: The effects of extract on glucose uptake, insulin receptor-ß (IR-ß), insulin receptor substrate-1 (IRS-1) phosphorylation and glucose transporter type 4 (GLUT4) and phosphoinositide 3-kinase (PI3 kinase) mRNA expression were studied in L6 myotubes. The in vitro mechanism of action was tested in protein-tyrosine phosphatase 1B (PTP1B), G-protein-coupled receptor 40 (GPR40), silent mating type information regulation 2 homolog 1 (SIRT1) and dipeptidyl peptidase-IV (DPP-IV) assays. The in vivo efficacy was characterized in ob/ob mice after an oral administration of the extract for 21 days. RESULTS: The effect of extract promoted glucose uptake, IR-ß and IRS-1 phosphorylation and GLUT4 and PI3 kinase mRNA upregulation in L6 myotubes. The extract inhibited PTP1B with an IC(50) 17.4 µg/ml and did not modulate GPR40, SIRT1 or DPP-IV activities. An oral administration of extract in ob/ob mice for 21 days improved random blood glucose, triglyceride and oral glucose tolerance. Further, the extract did not result in body weight gain before and after treatment (29.3 vs. 33.6 g) compared to rosiglitazone where significant body weight gain was observed (28.4 vs. 44.5 g; *P<0.05 after treatment compared to before treatment). CONCLUSION: The results suggest that Annona squamosa hexane extract exerts its action by modulating insulin signaling through inhibition of PTP1B.