Investigation Potential Antidiabetic Activity of Angelica gigas Nakai Leaf Extract

The aim of the present study was to investigate effects of the ethyl acetate fraction of an ethanol extract of Coix lachryma-jobi (ECLJ) on glucose uptake and adipocyte differentiation in 3T3-L1 cells. ECLJ phosphorylated AMP-activated protein kinase (AMPK) and its downstream substrate acetyl-coenzymeA carboxylase in 3T3-L1 cells in a time- and dose-dependent manner. Moreover, we discovered that compound C inhibits ECLJ-stimulated ACC phosphorylation. In addition, ECLJ exhibited a dose-dependent stimulation of glucose uptake in 3T3-L1 cells, and this increase was obviously attenuated by compound C. ECLJ also caused a decrease in the expression levels of adipogenesis factors such as fatty acid synthase, sterol-regulatory-element-binding protein-1c, peroxisome proliferator-activated receptor γ, and CAATT/enhancer binding protein α in a dose-dependent manner. Differentiation was examined by Oil red O staining activity after ECLJ treatment for 6 days. ECLJ decreased mean droplet size. These results suggest a possible role for AMPK in the process of adipose differentiation and that ECLJ targeted for adipocyte functions could be effective in improving the symptoms of metabolic syndrome.

The sesquiterpene hydroquinones/quinones belong to one class of marine sponge metabolites, and they have received considerable attention due to their varied biological activities, including anti-tumor, anti-HIV, and anti-inflammatory action. In order to probe the potential anti-diabetic effect of the sesquiterpene hydroquinones/quinones, the effect of dysidine on the insulin pathway was studied. The promotion of glucose uptake by dysidine was studied in differentiated 3T3-L1 cells. The increase in membrane-located GLUT4 by dysidine was studied in CHO-K1/GLUT4 and 3T3-L1 cells by immuno-staining. The activation of the insulin signaling pathway by dysidine was probed by Western blotting. The inhibition of PTPases by dysidine was detected in vitro. Dysidine, found in the Hainan sponge Dysidea villosa in the Chinese South Sea, effectively activated the insulin signaling pathway, greatly promoted glucose uptake in 3T3-L1 cells, and showed strong insulin-sensitizing activities. The potential targets of action for dysidine were probed, and the results indicated that dysidine exhibited its cellular effects through activation of the insulin pathway, possibly through the inhibition of protein tyrosine phosphatases, with more specific inhibition against protein tyrosine phosphatase 1B (PTP1B). Our findings are expected to expand understanding of the biological activities of sesquiterpene hydroquinones/quinones, and they show that dysidine could be a potential lead compound in the development of an alternative adjuvant in insulin therapy.

Nano-assemblies enhance chaperone activity, stability, and delivery of alpha B-crystallin-D3 (αB-D3).

Metabolism, and especially glucose uptake, is a key quantitative cell trait that is closely linked to cancer initiation and progression. Therefore, developing high-throughput assays for measuring glucose uptake in cancer cells would be enviable for simultaneous comparisons of multiple cell lines and microenvironmental conditions. This study was designed with two specific aims in mind: the first was to develop and validate a high-throughput screening method for quantitative assessment of glucose uptake in "normal" and tumor cells using the fluorescent 2-deoxyglucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG), and the second was to develop an image-based, quantitative, single-cell assay for measuring glucose uptake using the same probe to dissect the full spectrum of metabolic variability within populations of tumor cells in vitro in higher resolution. The kinetics of population-based glucose uptake was evaluated for MCF10A mammary epithelial and CA1d breast cancer cell lines, using 2-NBDG and a fluorometric microplate reader. Glucose uptake for the same cell lines was also examined at the single-cell level using high-content automated microscopy coupled with semi-automated cell-cytometric image analysis approaches. Statistical treatments were also implemented to analyze intra-population variability. Our results demonstrate that the high-throughput fluorometric assay using 2-NBDG is a reliable method to assess population-level kinetics of glucose uptake in cell lines in vitro. Similarly, single-cell image-based assays and analyses of 2-NBDG fluorescence proved an effective and accurate means for assessing glucose uptake, which revealed that breast tumor cell lines display intra-population variability that is modulated by growth conditions. These studies indicate that 2-NBDG can be used to aid in the high-throughput analysis of the influence of chemotherapeutics on glucose uptake in cancer cells.

The semi-refined polysaccharide of Pseudostellaria heterophylla is a complex polysaccharide that exhibits significantly hypoglycemic activities. A novel homogeneous polysaccharide, named as H-1-2, was isolated from the semi-refined polysaccharide. The mean molecular weight of H-1-2 was 1.4 × 104 Da and it was only composed of d-glucose monosaccharide. Structure elucidation indicated that H-1-2 contains pyranride, and has the characteristics of the α-iso-head configuration, a non-reducing end (T-), 4-, 1,6-, and 1,4,6-connection, in all four ways to connect glucose. H-1-2 was a type of glucan, where chemical combination exists in the main chain between 1→4 linked glucose, and contains a small amount of 1,6-linked glucose, which was in the branched chain. In vitro HepG2, 3T3-L1, and L6 cells were used to assess cellular glucose consumption and cellular glucose uptake by glucose oxidase, and the transport of 2-NBDG fluorescence probe results showed that H-1-2 could clearly increase glucose uptake and utilization in muscle and adipose cells, which is beneficial to screen for in the discovery of anti-diabetes lead compounds. H-1-2 was labeled with radioisotopes (99mTc-pertechnetate). 99mTc-labeled-H-1-2 was performed by SPECT/CT analysis images after oral administration in rats. At 4 h post ingestion, about 50% of the radioactivity was observed in the intestine. No significant radioactivity was found in the heart, liver, and kidney, conjecturing that absorption of 99mTc-labeled H-1-2 might, via intestinal mucosa, be absorbed into systemic circulation. This problem, as to whether the polysaccharide is absorbed orally, will need further examination.

Objective: To investigate the in vivo and in vitro antidiabetic potential of Chrysophyllum albidum.Methods: The effects of oral treatment with hydro-ethanolic extract (125, 250 and 500 mg/kg) of the stem bark of Chrysophyllum albidum and glibenclamide for 21 d on glucose level, serum enzyme markers for liver function, lipid profile, total protein, serum urea, serum creatinine, and body weight were evaluated in experimental diabetic rats administered with 45 mg/kg of streptozotocin. In vitro assays including glucose uptake in C2C12 cells and 3T3-L1 adipose tissues, α-glucosidase and α-amylase inhibition were employed to evaluate the possible mechanism of hypoglycemic action of the extract. DPPH and nitric oxide radical antioxidant activity of the extract was also measured.Results: The increased levels of blood glucose, triglycerides, low- density lipoprotein, total cholesterol, serum aspartate, and alanine transaminases, creatinine, and urea in the diabetic animals were reduced significantly (P<0.01) after treatment with Chrysophyllum albidum extract. The decreased total protein and high-density lipoprotein concentrations were normalized after treatment. In addition, the extract significantly (P<0.01) increased the transport of glucose in 3T3-L1 cells and C2C12 myotubes and exhibited considerable potential to inhibit α-amylase and α-glucosidase. It also demonstrated potent antioxidant action by scavenging considerably DPPH and nitric oxide radicals.Conclusions: Chrysophyllum albidum stem bark extract exhibits considerable antidiabetic effect by stimulating glucose uptake and utilization in C2C12 myotubes and 3T3-L1 adipocytes as well as inhibiting the activities of α-amylase and α-glucosidase.

SummaryFenugreek microgreen and mint leaf displayed antidiabetic potential during in vitro assays including cell line‐based analysis. Aqueous fenugreek microgreen extract (FME) (2 mg mL−1) inhibited α‐amylase by 70%. It also enhanced glucose uptake in L6 cells by 25% at 10 mg mL−1 which further improved to 44% in the presence of insulin. On the other hand, fresh mint leaf extract (MLE) inhibited α‐glucosidase up to 90% and increased glucose uptake by 15% in HepG2 cells. Besides, both these extracts also inhibited nonenzymatic glycation of protein. FME and MLE were also found to have high levels of total phenolics, flavonoids and antioxidants which could play a possible role in the observed antidiabetic activity. As blood glucose levels in diabetes can be regulated by inhibition of enzymes regulating carbohydrate metabolism and improving glucose uptake in cells, the findings indicate a complimentary therapeutic role of these two dietary herbs in diabetes.

Selected Herbal Extracts Improve Diabetes Associated Factors in 3T3-L1 Adipocytes

Wheat (Triticum aestivum L.) is a primary source of nutrition worldwide, and the development of wheat varieties with enhanced functionality has gained considerable interest. This study investigated the antidiabetic activities of three purple wheat varieties and their correlations with their metabolite profiles. We evaluated the antioxidant and antidiabetic activities of the anthocyanin-rich fractions derived from these cultivars. Anthocyanins were extracted from wheat bran using acidified 80% methanol and purified using ion-exchange chromatography. The metabolites were analyzed using UHPLC-HESI-Orbitrap MS/MS. Antioxidant capacity was evaluated by measuring the total polyphenol content and analyzing DPPH, ABTS, ORAC, and ROS levels. Antidiabetic activity was determined through α-glucosidase inhibition and glucose uptake in insulin-resistant HepG2 cells. The effect on the PI3K/AKT signaling pathway was investigated using western blot analysis. The “Ari-heukchal” cultivar exhibited the highest total polyphenol content, antioxidant capacity, and α-glucosidase inhibitory activity. Treatment of insulin-resistant HepG2 cells with 200 µg/mL of the anthocyanin-rich fraction improved glucose uptake and significantly increased AKT phosphorylation at Ser473. This effect was attributed to the high anthocyanin content in the “Ari-heukchal” cultivar. The findings support the potential use of natural anthocyanin pigments from purple-wheat cultivars for the development of functional materials from colored grains.

The aim of this study was to investigate the mechanism of (S)-[6]-gingerol in promoting glucose uptake in L6 skeletal muscle cells. The effect of (S)-[6]-gingerol on glucose uptake in L6 myotubes was examined using 2-[1,2-3H]-deoxy-D-glucose. Intracellular Ca2+ concentration was measured using Fluo-4. Phosphorylation of AMPKα was determined by Western blotting analysis. (S)-[6]-Gingerol time-dependently enhanced glucose uptake in L6 myotubes. (S)-[6]-Gingerol elevated intracellular Ca2+ concentration and subsequently induced a dose- and time-dependent enhancement of threonine172 phosphorylated AMPKα in L6 myotubes via modulation by Ca2+/calmodulin-dependent protein kinase kinase. The results indicated that (S)-[6]-gingerol increased glucose uptake in L6 skeletal muscle cells by activating AMPK. (S)-[6]-gingerol, a major component of Zingiber officinale, may have potential for development as an antidiabetic agent.

Treatment of C2C12 muscle cells with metformin or the NR4A1 ligand 1,1-bis(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH) induced NR4A1 and Glut4 messenger RNA and protein expression. Similar results were observed with buttressed (3- or 3,5-substituted) analogs of DIM-C-pPhOH, including 1,1-bis(3'-indolyl)-1-(3-chloro-4-hydroxy-5-methoxyphenyl)methane (DIM-C-pPhOH-3-Cl-5-OCH3), and the buttressed analogs were more potent than DIM-C-pPhOH NR4A1 agonists. Metformin and the bis-indole substituted analogs also induced expression of several glycolytic genes and Rab4, which has previously been linked to enhancing cell membrane accumulation of Glut4 and overall glucose uptake in C2C12 cells, and these responses were also observed after treatment with metformin and the NR4A1 ligands. The role of NR4A1 in mediating the responses induced by the bis-indoles and metformin was determined by knockdown of NR4A1, and this resulted in attenuating the gene and protein expression and enhanced glucose uptake responses induced by these compounds. Our results demonstrate that the bis-indole-derived NR4A1 ligands represent a class of drugs that enhance glucose uptake in C2C12 muscle cells, and we also show that the effects of metformin in this cell line are NR4A1-dependent.

The hypothesis of the study was that inhibition of PPARβ/δ increases glucose uptake and lactose synthesis in bovine mammary epithelial cells by reducing the expression of the glucose transporter mRNA destabiliser calreticulin. Three experiments were conducted to test the hypothesis using immortalised bovine mammary alveolar (MACT) and primary bovine mammary (PBMC) cells. In Experiment 1, the most effective dose to inhibit PPARβ/δ activity among two synthetic antagonists (GSK-3787 and PT-s58) was assessed using a gene reporter assay. In Experiment 2, the effect on glucose uptake and lactose synthesis was evaluated by measuring glucose and lactose in the media and expression of related key genes upon modulation of PPARβ/δ using GSK-3787, the synthetic PPARβ/δ agonist GW-501516, or a combination of the two in cells cultivated in plastic. In Experiment 3, the same treatments were applied to cells cultivated in Matrigel and glucose and lactose in media were measured. In Experiment 1 it was determined that a significant inhibition of PPARβ/δ in the presence or absence of fetal bovine serum was achieved with ≥ 1000 nm GSK-3787 but no significant inhibition was observed with PT-s58. In Experiment 2, inhibition of PPARβ/δ had no effect on glucose uptake and lactose synthesis but they were both increased by GW-501516 in PBMC. The mRNA abundance of PPARβ/δ target gene pyruvate dehydrogenase kinase 4 was increased but transcription of calreticulin was decreased (only in MACT cells) by GW-501516. Treatment with GSK-3787 did not affect the transcription of measured genes. No effects on glucose uptake or lactose synthesis were detected by modulation of PPARβ/δ activity on cells cultivated in Matrigel. The above data do not provide support for the original hypothesis and suggest that PPARβ/δ does not play a major role in glucose uptake and lactose synthesis in bovine mammary epithelial cells.

Characterization of Green and Yellow Papaya for Antioxidation and Glucose Uptake Stimulatory Activity in HepG2 Liver Cells

Aquilaria sinensis (Lour.) Spreng is known for its resinous secretion (agarwood), often secreted in defense against injuries. We investigated the effects of A. sinensis flower extract (AF) on peroxisome proliferator-activated receptors alpha and gamma (PPARα and PPARγ), liver X receptor (LXR), glucose uptake, and lipid accumulation (adipogenesis). Activation of PPARα, PPARγ and LXR was determined in hepatic (HepG2) cells by reporter gene assays. Glucose uptake was determined in differentiated muscle (C2C12) cells using 2-NBDG (2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose). Adipogenesis was determined in adipocytes (3T3-L1 cells) by Oil red O staining. At a concentration of 50 µg/mL, AF caused 12.2-fold activation of PPARα and 5.7-fold activation of PPARγ, while the activation of LXR was only 1.7-fold. AF inhibited (28%) the adipogenic effect induced by rosiglitazone in adipocytes and increased glucose uptake (32.8%) in muscle cells at 50 μg/mL. It was concluded that AF acted as a PPARα/γ dual agonist without the undesired effect of adipogenesis and exhibited the property of enhancing glucose uptake. This is the first report to reveal the PPARα/γ dual agonistic action and glucose uptake enhancing property of AF along with its antiadipogenic effect, indicating its potential in ameliorating the symptoms of metabolic syndrome.

The fruits of Terminalia bellerica Roxb. (Combretaceae) and T. chebula Retz. (Combretaceae) are important components of triphala, a popular Ayurvedic formulation which is used for the treatment of diabetes in Indian traditional medicine. This study was aimed to evaluate the effects of T. bellerica and T. chebula extracts and their constituents on PPARα/γ-activation and glucose uptake in HepG2 cells and adipogenesis in 3T3-L1 cells. Out of the twenty constituents, two ellagitannins, chebulagic acid (1) and corilagin (2), and three gallotannins, 2,3,6-tri-O-galloyl-β-D-glucose (3), 1,2,3,6-tetra-O-galloyl-β-D-glucose (4), and 1,2,3,4,6-penta-O-galloyl-β-D-glucose (5), increased PPARα and/or PPARγ activities to a considerable extent. The gallotannins (3-5) enhanced insulin-stimulated glucose uptake into HepG2 cells out of which 4 was the most active with a 9.92-fold increase in cellular glucose uptake. In the test for adipogenesis, lipid content was increased by 1 and 2 in differentiated adipocytes while no effect was observed with 3-5. Additional experiment showed that 3-5 exhibited antagonistic effect on the adipogenic activity of PPARγ agonist rosiglitazone. Evaluation of the PPARα and PPARγ protein expression in HepG2 cells in response to treatment with these compounds is in progress. Acknowledgements: The United States Department of Agriculture, Agricultural Research Service, Specific Cooperative Agreement No. 58 – 6408 – 02 – 1-612 is acknowledged for partial support of this work.