Two triterpeniods from Cyclocarya paliurus (Batal) Iljinsk (Juglandaceae) promote glucose uptake in 3T3-L1 adipocytes: The relationship to AMPK activation

PurposeThe current study investigated the efficacy of Cyclocarya paliurus chloroform extract (CPEC) and its two specific triterpenoids (cyclocaric acid B and cyclocarioside H) on the regulation of glucose disposal and the underlying mechanisms in 3T3-L1 adipocytes.MethodsMice and adipocytes were stimulated by macrophages-derived conditioned medium (Mac-CM) to induce insulin resistance. CPEC was evaluated in mice for its ability by oral glucose tolerance test (OGTT) and insulin tolerance test (ITT). To investigate the hypoglycemic mechanisms of CPEC and its two triterpenoids, glucose uptake, AMP-activated protein kinase (AMPK) activation, inhibitor of NF-κB kinase β (IKKβ) phosphorylation and insulin signaling transduction were detected in 3T3-L1 adipocytes using 2-NBDG uptake assay and Western blot analysis.ResultsMac-CM, an inflammatory stimulus which induced the glucose and insulin intolerance, increased phosphorylation of IKKβ, reduced glucose uptake and impaired insulin sensitivity. CPEC and two triterpenoids improved glucose consumption and increased AMPK phosphorylation under basal and inflammatory conditions. Moreover, CPEC and its two triterpenoids not only enhanced glucose uptake in an insulin-independent manner, but also restored insulin-mediated protein kinase B (Akt) phosphorylation by reducing the activation of IKKβ and regulating insulin receptor substrate-1 (IRS-1) serine/tyrosine phosphorylation. These beneficial effects were attenuated by AMPK inhibitor compound C, implying that the effects may be associated with AMPK activation.ConclusionsCPEC and its two triterpenoids promoted glucose uptake in the absence of insulin, as well as ameliorated IRS-1/PI3K/Akt pathway by inhibiting inflammation. These effects were related to the regulation of AMPK activity.     

In vitro investigation of hypoglycemic and oxidative stress properties of fava bean (Vicia faba L.) seed extract in Saccharomyces cerevisiae 2376

Abstract

Imbalance of free radicals over antioxidants in human body may result in oxidative damage to biomolecules (lipids, proteins, DNA) that causes severe chronic diseases. The aim of this proposed research was to examine the hypoglycemic and oxidative stress potential of fava bean (Vicia faba L.) seed extract. Acetone extract showed a significant effect on glucose uptake rate (77.28?±?2.42%) in yeast cells at 25?mM glucose concentration. Minimum glucose uptake rate was found to be 52.36?±?2.06% % by chloroform seed extract. Atomic force microscopy revealed that 3% hydrogen peroxide concentration results in roughness was found to be maximum (441?±?6.7?nm) and along with extract treatment showed a significant reduction in roughness (251?±?6.2?nm). Propidium iodide and DAPI staining showed apoptotic ratio as 0.40 (40?±?1.18%,) and 0.42 (42?±?1.16%) in hydrogen peroxide treated cell only as compared to other treatments. MTT assay showed that acetone extract had maximum survival rate (82.067%) and least survival rate was found in chloroform extract (70.48%). Hypoglycaemic potential and oxidative stress might be polyphenols (phenolics, flavonoids) present in seed extract or synergistic effect.     

3β-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 3β-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 GSK3β.

General significance

This study demonstrates the dual activity of 3β-taraxerol and the ethyl acetate extract of Mangifera indica as a glucose transport activator and stimulator of glycogen synthesis. 3β-taraxerol can be validated as a potent candidate for managing the hyperglycemic state.     

Effect of a brewer's yeast extract on growth and glucose metabolism of cells in culture.

Brewer's yeast preparations influence glucose metabolism in vivo and in isolated tissues. We have studied the effect of a brewer's yeast extract on glucose metabolism and grwoth of rat hepatoma and human embryonic cells. Growth of the rat hepatoma cells was very much stimulated by the extract in a concentration-dependent manner. Glucose uptake was, on the other hand, appreciably inhibited, and lactate uptake completely abolished by the extract. Insulin stimulated cell growth and inhibited lactate uptake but did not affect the glucose level. Insulin and the extract had additive effects on growth and lactate uptake of the hepatoma cells. The inhibition by the brewer's yeast extract of glucose uptake was, however, antagonized by insulin. Niacin or Cr³⁺, which are suggested to be components of a “glucose tolerance factor” of brewer's yeast, did not affect growth or glucose and lactate uptake. The glucose uptake of the human embryonic cells was strongly inhibited by the brewer's yeast extract. Cell growth and lactate production were not influenced by the extract or by insulin; however, when both insulin and extract were present simultaneously, a slight stimulation of growth and inhibition of lactate production was observed. The results indicate that brewer's yeast can have appreciable direct effects on cells and that not all of these effects are “insulin-like”.     

Antidiabetic activities of extract from Malva verticillata seed via the activation of AMP-activated protein kinase

Stimulation of AMP-activated protein kinase (AMPK) signaling followed by increase of glucose uptake in L6 myotubes were studied with organic solvent extract of Malva verticillata (MV) seeds. Ethanol extract of M. verticillata seeds (MVE) significantly increased the phosphorylation level of AMPK, acetyl-CoA carboxylase (ACC), and glucose uptake in L6 myotube cells. The MVE was fractionated with n-hexane (MVE-H), chloroform (MVE-C), ethylacetate (MVE-E), n-butanol (MVE-B), and water (MVE-W). MVE-H (150 microgram/ml) showed the highest phosphorylating activity and increased glucose uptake by 2.3-fold. Oral administration of MVE-H (40 mg/kg) for 4 weeks to type 2 diabetic (db/db) mice reduced non-fasting and fasting blood glucose levels by 17.1% and 23.3%, respectively. Phosphorylation levels of AMPK and ACC in the soleus muscle and liver tissue of db/db mice were significantly increased by the administration of MVE-H. MVE-H was further fractionated using preparative HPLC to identify the AMPK-activating compounds. The NMR and GC-MS analyses revealed that β-sitosterol was a major effective compound in MVE-H. Phosphorylation levels of AMPK and ACC, and glucose uptake were significantly increased by the treatment of MVE-S (β-sitosterol) isolated from M. verticillata to L6 cells, and these effects were attenuated by an AMPK inhibitor (Compound C) pretreatment. These results, taken together, demonstrate that increased glucose uptake in L6 myotubes by MVE-H treatment is mainly accomplished through the activation of AMPK. Our finding suggests that the extract isolated from M. verticillata seed would be beneficial for the treatment of metabolic disease including type 2 diabetes and hyperlipidemia.     

Ganoderma lucidum extract stimulates glucose uptake in L6 rat skeletal muscle cells

The effect of Ganoderma lucidum extract on glucose uptake was studied in L6 rat skeletal muscle cells. G. lucidum extract increased glucose uptake about 2-fold compared to control. The extract stimulated the activity of phosphatidylinositol (PI) 3-kinase which is a major regulatory molecule in the glucose uptake pathway. About 7-fold increased activity of a PI 3-kinase was observed after treatment with G. lucidum extract, whereas PI 3-kinase inhibitor, LY294002, blocked the G. lucidum extract-stimulated PI 3-kinase activity in L6 skeletal muscle cells. Protein kinase B, a downstream mediator of PI 3-kinase, was also activated by G. lucidum extract. We then assessed the activity of AMP-activated protein kinase (AMPK), another regulatory molecule in the glucose uptake pathway. G. lucidum extract increased the phosphorylation level of both AMPK alpha1 and alpha2. Activity of p38 MAPK, a downstream mediator of AMPK, was also increased by G. lucidum extract. Taken together, these results suggest that G. lucidum extract may stimulate glucose uptake, through both PI 3-kinase and AMPK in L6 skeletal muscle cells thereby contributing to glucose homeostasis.     

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 10 ng/ml and 100 ng/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.     

Petalonia improves glucose homeostasis in streptozotocin-induced diabetic mice

The anti-diabetic potential of Petalonia binghamiae extract (PBE) was evaluated in vivo. Dietary administration of PBE to streptozotocin (STZ)-induced diabetic mice significantly lowered blood glucose levels and improved glucose tolerance. The mode of action by which PBE attenuated diabetes was investigated in vitro using 3T3-L1 cells. PBE treatment stimulated 3T3-L1 adipocyte differentiation as evidenced by increased triglyceride accumulation. At the molecular level, peroxisome proliferator-activated receptor γ (PPARγ) and terminal marker protein aP2, as well as the mRNA of GLUT4 were up-regulated by PBE. In mature adipocytes, PBE significantly stimulated the uptake of glucose and the expression of insulin receptor substrate-1 (IRS-1). Furthermore, PBE increased PPARγ luciferase reporter gene activity in COS-1 cells. Taken together, these results suggest that the in vivo anti-diabetic effect of PBE is mediated by both insulin-like and insulin-sensitizing actions in adipocytes.     

Effects of mebendazole on the absorption of low molecular weight nutrients by Ascaris suum

Van Den Bossche H. and De Nollin S. 1973. Effects of mebendazole on the absorption of low molecular weight nutrients by Ascaris suum. International Journal for Parasitology3: 401–407. The effect of the anthelmintic drug, mebendazole, on the uptake and/or transport of glucose, fructose, 3-O-methylglucose, glycine, proline, methionine and palmitic acid was studied on in vitro incubated Ascaris suum. The experiments presented indicate that mebendazole inhibits the uptake and/or transport of glucose by A. suum. This inhibition is followed by a marked decrease in the glycogen content of the ascaris muscle. The addition of glucose to the incubation medium significantly enhanced the rate of uptake and/or transport of 3-O-methylglueose, glycine, methionine, proline and palmitic acid indicating that the absorption mechanisms depend on energy.Therefore, the inhibitory effect of mebendazole on the glucose uptake also results in a decreased uptake of 3-O-methylglucose and of the amino acids and fatty acid studied. The fructose uptake was not affected by the addition of glucose.Although mebendazole decreased the uptake of the hexoses and of the amino acids whether or not glucose was added, the uptake of palmitic acid was not affected when glucose was omitted from the medium. Mebendazole failed to exhibit an effect on the uptake, transport and/or utilization of glucose in rat.     

Magnolia dealbata Zucc and its active principles honokiol and magnolol stimulate glucose uptake in murine and human adipocytes using the insulin-signaling pathway

Some Magnolia (Magnoliaceae) species are used for the empirical treatment of diabetes mellitus, but the antidiabetic properties of Magnolia dealbata have not yet been experimentally validated. Here we report that an ethanolic extract of Magnolia dealbata seeds (MDE) and its active principles honokiol (HK) and magnolol (MG) induced the concentration-dependent 2-NBDG uptake in murine 3T3-F442A and human subcutaneous adipocytes. In insulin-sensitive adipocytes, MDE 50 μg/ml induced the 2-NBDG uptake by 30% respect to insulin, while HK and MG, 30 μM each, did it by 50% (murine) and 40% (human). The simultaneous application of HK and MG stimulated 2-NBDG uptake by 70% in hormone-sensitive cells, on which Magnolia preparations exerted synergic effects with insulin. In insulin-resistant adipocytes, MDE, HK and MG induced 2-NBDG uptake by 57%, 80% and 96% respect to Rosiglitazone (RGZ), whereas HK and MG simultaneously applied stimulated 2-NBDG uptake more efficiently than RGZ (120%) in both murine and human adipocytes. Inhibitors of the insulin-signaling pathway abolished the glucose uptake induced by Magnolia dealbata preparations, suggesting that their antidiabetic effects are mediated by this signaling pathway. In addition, MDE, HK and MG exerted only mild to moderate proadipogenic effects on 3T3-F442A and human preadipocytes, although the combined application of HK and MG markedly increased the lipid accumulation in both cell types. In summary, Magnolia dealbata and its active principles HK and MG stimulate glucose uptake in insulin-sensitive and insulin-resistant murine and human adipocytes using the insulin signaling pathway.     

Anthraquinones from Morinda longissima and their insulin mimetic activities via AMP-activated protein kinase (AMPK) activation

AMP-activated protein kinase (AMPK) activators are known to increase energy metabolism and to reduce body weight, as well as to improve glucose uptake. During for searching AMPK activators, a new anthraquinone, modasima A (10), along with eighteen known analogues (1–9 and 11–19) were isolated from an ethanol extract of the roots of Morinda longissima Y. Z. Ruan (Rubiaceae). Using the fluorescent tagged glucose analogues, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxy-D-glucose (2-NBDG), insulin mimetics were screened with compounds 1–19 in 3T3-L1 adipocytes. Among them, compounds 2, 8 and 10 enhanced significantly glucose uptake into adipocytes and up-regulated the phosphorylated AMPK (Thr¹⁷²) whereas the glucose uptake enhancing activities of compounds 2, 8 and 10 were abrogated by treatment of compound C, an AMPK inhibitor. Taken together, these anthraquinones showed the potential action as insulin mimetic to improve glucose uptake via activation of AMPK.     

An in vitro assessment of the effect of Athrixia phylicoides DC. aqueous extract on glucose metabolism

Athrixia phylicoides DC. is an aromatic shrub indigenous to the eastern parts of Southern Africa. Indigenous communities brew "bush tea" from dried twigs and leaves of A. phylicoides, which is consumed as a beverage and used for its medicinal properties. Plant polyphenols have been shown to be beneficial to Type 2 diabetes mellitus (T2D) and obesity. Aqueous extracts of the plant have been shown to be rich in polyphenols, in particular phenolic acids, which may enhance glucose uptake and metabolism. The aim of this study was to determine the phenolic composition of a hot water A. phylicoides extract and assess its in vitro effect on cellular glucose utilisation. The most abundant phenolic compounds in the extract were 6-hydroxyluteolin-7-O-glucoside, chlorogenic acid, protocatechuic acid, a di-caffeoylquinic acid and a methoxy-flavonol derivative. The extract increased glucose uptake in C2C12, Chang and 3T3-L1 cells, respectively. Intracellular glucose was utilised by both oxidation (C2C12 myocytes and Chang cells; p < 0.01 and p < 0.05, respectively) and by increased glycogen storage (Chang cells; p < 0.05). No cytotoxicity was observed in Chang cells at the concentrations tested. The effects of the extract were not dose-dependent. A. phylicoides aqueous extract stimulated in vitro glucose uptake and metabolism, suggesting that consumption of this phenolic-rich extract could potentially ameliorate metabolic disorders related to obesity and T2D.     

Products of rat liver mitochondrial protein synthesis: electrophoretic analysis of the number and size of these proteins and their solubility in chloroform: methanol

Rat liver mitochondria were incubated in vitro with radioactive leucine, and submitochondrial particles prepared by several methods. Analysis of the labeled mitochondrial membrane fractions by sodium dodecylsulfate gel electrophoresis revealed three labeled bands of molecular weights corresponding to 40,000; 27,000; and 20,000 daltons. Electrophoresis for longer times at higher concentrations of acrylamide revealed eight labeled bands, ranging in molecular weights from 48,000 to 12,000.Mitochondria were incubated for 5 min with [³H]leucine followed by a chase of unlabeled leucine. Gel electrophoresis of the membranes obtained after labeling for 5 min indicated significant synthesis of polypeptides in the 40,000 M_r, range and very little labeling of low molecular-weight polypeptides. After addition of the chase, increased synthesis of the high molecular-weight polypeptides was observed; however, no significant increase or decrease of radioactivity in the bands of low molecular-weight was observed, suggesting that rat liver mitochondria have the ability to synthesize complete proteins in the M_r 27,000–40,000 range.Approximately 16% of the total leucine incorporated into protein by isolated rat liver mitochondria in vitro could be extracted by chloroform: methanol. Gel electrophoresis of the chloroform: methanol extract revealed several bands containing radioactivity with the majority of counts in a band of 40,000 molecular weight. Gel electrophoresis of the chloroform: methanol extract of lyophilized submitochondrial particles indicated label in two broad bands in the low molecular-weight region of 14,000-10,000 with insignificant counts in the higher molecular-weight regions of the gel.Yeast cells were pulse labeled in vivo with [³H]leucine in the presence of cycloheximide and the submitochondrial particles extracted with chloroform:methanol. The extract separated after gel electrophoresis into four labeled bands ranging in molecular weight from 52,000 to 10,000. Preincubation of the yeast cells with chloramphenicol prior to the pulse labeling caused a 6-fold stimulation of labeling into the band of lowest molecular weight of the chloroform: methanol extract. These results suggest that the accumulation of mitochondrial proteins synthesized in the cytoplasm, when chloramphenicol is present in the medium, may stimulate the synthesis of certain specific mitochondrial proteins which are soluble in chloroform: methanol.     

Effects of ketamine on glucose uptake by glucose transporter type 3 expressed in Xenopus oocytes: The role of protein kinase C

We investigated the effects of ketamine on the type 3 facilitative glucose transporter (GLUT3), which plays a major role in glucose transport across the plasma membrane of neurons. Human-cloned GLUT3 was expressed in Xenopus oocytes by injection of GLUT3 mRNA. GLUT3-mediated glucose uptake was examined by measuring oocyte radioactivity following incubation with 2-deoxy-d-[1,2-³H]glucose. While ketamine and S(+)-ketamine significantly increased GLUT3-mediated glucose uptake, this effect was biphasic such that higher concentrations of ketamine inhibited glucose uptake. Ketamine (10 μM) significantly increased V_max but not K_m of GLUT3 for 2-deoxy-d-glucose. Although staurosporine (a protein kinase C inhibitor) increased glucose uptake, no additive or synergistic interactions were observed between staurosporine and racemic ketamine or S(+)-ketamine. Treatment with ketamine or S(+)-ketamine partially prevented GLUT3 inhibition by the protein kinase C activator phorbol-12-myrisate-13-acetate. Our results indicate that ketamine increases GLUT3 activity at clinically relevant doses through a mechanism involving PKC inhibition.     

The insulin sensitizing effect of homoisoflavone-enriched fraction in Liriope platyphylla Wang et Tang via PI3-kinase pathway

In the present study, we screened candidates for enhancing insulin action, using glucose uptake as an indicator, from Liriope platyphylla Wang et Tang (LPWT) extract, Liliaceae, in 3T3-L1 adipocytes. The mechanism of insulin sensitizing action in the fractions was also investigated. LPWT extract with 70% MeOH was sequentially separated with Diaion HP-20 and silica gel column chromatography. The 9:1 fraction from silica gel column chromatography increased glucose uptake with 1 ng/mL up to glucose uptake with 50 ng/mL insulin. The 9:1 fraction, determined as homoisoflavone-enriched fraction, worked as an insulin sensitizer. It increased insulin stimulated glucose uptake in 3T3-L1 adipocytes, insulin responsive cells, through increased glucose transporter 4 (GLUT4) contents in the plasma membrane. GLUT4 translocation was increased through insulin receptor substrate 1 (IRS1)-PI3 kinase-Akt signaling mechanism. Thus, homoisoflavone-enriched fraction in LPWT extract played an important role as an insulin sensitizer in adipocytes.     

Biological effects of THC and a lipophilic cannabis extract on normal and insulin resistant 3T3-L1 adipocytes

Type 2 diabetes, a chronic disease, affects about 150 million people world wide. It is characterized by insulin resistance of peripheral tissues such as liver, skeletal muscle, and fat. Insulin resistance is associated with elevated levels of tumor necrosis factor alpha (TNF-α), which in turn inhibits insulin receptor tyrosine kinase autophosphorylation. It has been reported that cannabis is used in the treatment of diabetes. A few reports indicate that smoking cannabis can lower blood glucose in diabetics. Δ⁹-tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis. This study aimed to determine the effect of a lipophilic cannabis extract on adipogenesis, using 3T3-L1 cells, and to measure its effect on insulin sensitivity in insulin resistant adipocytes. Cells were cultured in Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) and differentiated over a 3 day period for all studies. In the adipogenesis studies, differentiated cells were exposed to the extract in the presence and absence of insulin. Lipid content and glucose uptake was subsequently measured. Insulin-induced glucose uptake increased, while the rate of adipogenesis decreased with increasing THC concentration. Insulin-resistance was induced using TNF-α, exposed to the extract and insulin-induced glucose uptake measured. Insulin-induced glucose was increased in these cells after exposure to the extract. Semiquantitative real time polymerase chain reaction (RT-PCR) was performed after ribonucleic acid (RNA) extraction to evaluate the effects of the extract on glucose transporter isotype 4 (GLUT-4), insulin receptor substrate-1 (IRS-1) and IRS-2 gene expression.     

In Vitro Sugar Transport in Zea mays L. Kernels : II. Characteristics of Sugar Absorption and Metabolism by Isolated Developing Embryos

In vitro sugar transport into developing isolated maize embryos was studied. Embryo fresh and dry weight increased concomitantly with endogenous sucrose concentration and glucose uptake throughout development. However, endogenous glucose and fructose concentration and sucrose uptake remained constant. The uptake kinetics of radiolabeled sucrose, glucose, and fructose showed a biphasic dependence on exogenous substrate concentration. Hexose uptake was four to six times greater than sucrose uptake throughout development. Carbonylcyanide-m-chlorophenylhydrazone and dinitrophenol inhibited sucrose and glucose uptake significantly, but 3-O-methyl glucose uptake was less affected. The uptake of 1 millimolar sucrose was strongly pH dependent while glucose was not. Glucose and fructose were readily converted to sucrose and insoluble products soon after absorption into the embryo. Thus, sucrose accumulated, while glucose pools remained low. Based on the findings of this and other studies a model for sugar transport in the developing maize kernel is presented.     

Hypoglycemic activity of leaf organic extracts from Smallanthus sonchifolius: Constituents of the most active fractions

The aim of the present study was to determine the in vivo hypoglycemic activity of five organic extracts and enhydrin obtained from yacon leaves. The main constituents of the most active fraction were identified. Five organic extracts and pure crystalline enhydrin were administered to normoglycemic, transiently hyperglycemic and streptozotocin (STZ)-diabetic rats. The fasting and post-prandial blood glucose, and serum insulin levels were estimated and an oral glucose tolerance test (OGTT) was performed for the evaluation of hypoglycemic activity and dose optimization of each extract.We found that the methanol, butanol and chloroform extracts showed effective hypoglycemic activity at minimum doses of 50, 10 and 20 mg/kg body weight, respectively, and were selected for further experiments. Oral administration of a single-dose of each extract produced a slight lowering effect in the fasting blood glucose level of normal healthy rats, whereas each extract tempered significantly the hyperglycemic peak after food ingestion. Daily administration of each extract for 8 weeks produced an effective glycemic control in diabetic animals with an increase in the plasma insulin level. Phytochemical analysis of the most active fraction, the butanol extract, showed that caffeic, chlorogenic and three dicaffeoilquinic acids were significant components. Additionally, enhydrin, the major sesquiterpene lactone of yacon leaves, was also effective to reduce post-prandial glucose and useful in the treatment of diabetic animals (minimum dose: 0.8 mg/kg body weight).The results presented here strongly support the notion that the phenolic compounds above as well as enhydrin are important hypoglycemic principles of yacon leaves that could ameliorate the diabetic state.     

A Mutant of Synechococcus PCC7942 Incapable of Adapting to Low CO(2) Concentration

In isolated phloem segments of celery (Apium graveolens L.), a tissue highly specific for sucrose and mannitol uptake, glucose uptake occurs at very low rates and exhibits biphasic kinetics. Nonpenetrating inhibitors such as parachloromercuribenzene sulfonic acid did not inhibit glucose uptake. However, uptake was greatly inhibited by penetrating inhibitors such as N-ethylmaleimide and carbonylcyanide-m-chlorophenyl hydrazone. Carbonylcyanide-m-chlorophenyl hydrazone inhibition of uptake was reversed by washing and addition of thiol reagents to uptake solutions. Phlorizin, a competitive inhibitor of glucose caused moderate inhibition of uptake only after 3 hours of tissue exposure. Low pH, fusicoccin, and low turgor which enhance H⁺-sugar cotransport did not alter uptake rates. Furthermore, glucose did not induce alkalinization of the uptake media. Efflux analysis indicated that the presence of 50 millimolar unlabeled glucose in the wash media enhanced exchange of the labeled glucose across the tonoplast. Results indicate that the glucose carrier is not located at the plasmalemma but appears to be present at the membrane of an intracellular compartment, most likely the tonoplast. Carrier-mediated glucose transport in this tissue is proposed to be a facilitated diffusion.     

In vitro alpha-amylase and alpha-glucosidase inhibitory activity and in vivo antidiabetic activity of Quercus coccifera (Oak tree) leaves extracts

Quercus species are group of plants known as oak which represent important genus of Fagaceae family. These species are widely distributed in Mediterranean countries. Many of those species used in traditional medicine to treat and prevent various human disorders such as diabetes. Exhausted extraction for Quercus coccifera leaves were carried out using n-hexane, chloroform, methanol, boiled water and microwaved water. Extracts were subjected to phytochemical screening, acute toxicity study, and in vitro and in vivo animal model to evaluate antidiabetic activity of the produced extracts. The highest in vitro activity against α-amylase and α-glucosidase activity was obtained from methanolic extract with an IC₅₀ of 0.17 and 0.38 µg/ml respectively and better than the positive control acarbose. While the rest of the extract was either with moderate or low activity. Similarly, in the in vivo study, methanolic extract with a concentration of 200 mg/kg/day was able to reduce the blood glucose level for the diabetic mice to 146.8 mg/dL with normal bodyweight and biochemical signs when compared to the normal mice group. While the rest of the extracts were either with moderate or low ability to maintain blood glucose level for diabetic mice with few signs of hepatic and renal toxicity and weight loss. All data were statistically significantly different with p-value of less than 0.001 at confidence interval of 95% with high variance homogeneity. In conclusion, methanolic plant leaves extract of Q. coccifera can possibly be used alone to control the elevation of blood glucose level with a renal and hepatic protective property.