RESUMEN
BACKGROUND: Perturbation of energy homeostasis in skeletal muscle and liver resulting from a transient inhibition of mitochondrial energy transduction can produce effects of relevance for the control of hyperglycemia through activation of the AMP-activated protein kinase, as exemplified by the antidiabetic drug metformin. The present study focuses on uncoupling of oxidative phosphorylation rather than its inhibition as a trigger for such effects. METHODS: The reference weak uncoupler 2,4-dinitrophenol, fourteen naturally-occurring phenolic compounds identified as uncouplers in isolated rat liver mitochondria, and fourteen related compounds with little or no uncoupling activity were tested for enhancement of glucose uptake in differentiated C2C12 skeletal muscle cells following 18 h of treatment at 25-100 µM. A subset of compounds were tested for suppression of glucose-6-phosphatase (G6Pase) activity in H4IIE hepatocytes following 16 h at 12.5-25 µM. Metformin (400 µM) was used as a standard in both assays. RESULTS: Dinitrophenol and nine of eleven compounds that induced 50% or more uncoupling at 100 µM in isolated mitochondria enhanced basal glucose uptake by 53 to 269%; the effect of the 4'-hydroxychalcone butein was more than 6-fold that of metformin; negative control compounds increased uptake by no more than 25%. Dinitrophenol and four 4'-hydroxychalconoids also suppressed hepatocyte G6Pase as well as, or more effectively than metformin, whereas the unsubstituted parent compound chalcone, devoid of uncoupling activity, had no effect. CONCLUSIONS: Activities key to glycemic control can be induced by a wide range of weak uncouplers, including compounds free of difficult-to-metabolize groups typically associated with uncouplers. GENERAL SIGNIFICANCE: Uncoupling represents a valid and possibly more efficient alternative to inhibition for triggering cytoprotective effects of therapeutic relevance to insulin resistance in both muscle and liver. Identification of actives of natural origin and the insights into their structure-activity relationship reported herein may lead to alternatives to metformin.
Asunto(s)
Glucosa-6-Fosfatasa/metabolismo , Glucosa/metabolismo , Hepatocitos/enzimología , Células Musculares/metabolismo , Músculo Esquelético/citología , Fosforilación Oxidativa/efectos de los fármacos , Desacopladores/farmacología , 2,4-Dinitrofenol/química , 2,4-Dinitrofenol/farmacología , Animales , Línea Celular , Chalconas/química , Chalconas/farmacología , Hepatocitos/efectos de los fármacos , Insulina/farmacología , Masculino , Metformina/farmacología , Ratones , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Células Musculares/efectos de los fármacos , Fibras Musculares Esqueléticas/efectos de los fármacos , Fibras Musculares Esqueléticas/metabolismo , Consumo de Oxígeno/efectos de los fármacos , Ratas , Ratas Wistar , Relación Estructura-Actividad , Desacopladores/química , Regulación hacia Arriba/efectos de los fármacosRESUMEN
A mechanistic model of uncoupling of oxidative phosphorylation by lipophilic weak acids (i.e. proton shuttles) was developed for the purposes of predicting the relative activity of xenobiotics of widely varying structure and of guiding the design of optimized derivatives. The model is based on thermodynamic premises not formulated elsewhere that allow for the calculation of steady-state conditions and of rate of energy dissipation on the basis of acid-dissociation and permeability behavior, the later estimated from partitioning behavior and geometric considerations. Moreover, permeability of either the neutral or of the ionized species is proposed to be effectively enhanced under conditions of asymmetrical molecular distribution. Finally, special considerations were developed to accommodate multi-protic compounds. The comparison of predicted to measured activity for a diverse testset of 48 compounds of natural origin spanning a wide range of activity yielded a Spearman's rho of 0.90. The model was used to tentatively identify several novel proton shuttles, as well as to elucidate core structures particularly conducive to proton shuttle activity from which optimized derivatives can be designed. Principles of design were formulated and examples of derivatives projected to be active at concentrations on the order of 10(-7)M are proposed. Among these are di-protic compounds predicted to shuttle two protons per cycle iteration and proposed to maximally exploit the proton shuttle mechanism. This work promotes the design of highly active, yet easily-metabolized uncouplers for therapeutic applications, namely the indirect activation of AMP-kinase, as well as for various industrial applications where low persistence is desirable.
Asunto(s)
Modelos Químicos , Desacopladores/química , Permeabilidad de la Membrana Celular/fisiología , Difusión , Diseño de Fármacos , Fosforilación Oxidativa , Protones , Relación Estructura-Actividad , TermodinámicaRESUMEN
Through ethnobotanical surveys, the CIHR Team in Aboriginal Antidiabetic Medicines identified 17 boreal forest plants stemming from the pharmacopeia of the Cree First Nations of Eeyou Istchee (James Bay region of Northern Quebec) that were used traditionally against diabetes symptoms. The leaves of Sarracenia purpurea (pitcher plant), one of the identified Cree plants, exhibited marked antidiabetic activity in vitro by stimulating glucose uptake in C2C12 mouse muscle cells and by reducing glucose production in H4IIE rat liver cells. Fractionation guided by glucose uptake in C2C12 cells resulted in the isolation of 11 compounds from this plant extract, including a new phenolic glycoside, flavonoid glycosides, and iridoids. Compounds 6 (isorhamnetin-3-O-glucoside), 8 [kaempferol-3-O-(6â³-caffeoylglucoside], and 11 (quercetin-3-O-galactoside) potentiated glucose uptake in vitro, which suggests they represent active principles of S. purpurea (EC(50) values of 18.5, 13.8, and 60.5 µM, respectively). This is the first report of potentiation of glucose uptake by compounds 6 and 8, while compound 11 (isolated from Vaccinium vitis) was previously shown to enhance glucose uptake. Treatment of H4IIE liver cells with the new compound 1, 6'-O-caffeoylgoodyeroside, decreased hepatic glucose production by reducing glucose-6-phosphatase enzymatic activity (IC(50) = 13.6 µM), which would contribute to lowering glycemia and to the antidiabetic potential of S. purpurea.
Asunto(s)
Flavonoides/aislamiento & purificación , Flavonoides/farmacología , Glucosa-6-Fosfatasa/metabolismo , Glucosa/metabolismo , Glicósidos/aislamiento & purificación , Glicósidos/farmacología , Hipoglucemiantes/aislamiento & purificación , Hipoglucemiantes/farmacología , Sarraceniaceae/química , Animales , Flavonoides/química , Glicósidos/química , Humanos , Hipoglucemiantes/química , Indígenas Norteamericanos , Medicina Tradicional , Ratones , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Hojas de la Planta/química , RatasRESUMEN
Canadian Aboriginals, like others globally, suffer from disproportionately high rates of diabetes. A comprehensive evidence-based approach was therefore developed to study potential antidiabetic medicinal plants stemming from Canadian Aboriginal Traditional Medicine to provide culturally adapted complementary and alternative treatment options. Key elements of pathophysiology of diabetes and of related contemporary drug therapy are presented to highlight relevant cellular and molecular targets for medicinal plants. Potential antidiabetic plants were identified using a novel ethnobotanical method based on a set of diabetes symptoms. The most promising species were screened for primary (glucose-lowering) and secondary (toxicity, drug interactions, complications) antidiabetic activity by using a comprehensive platform of in vitro cell-based and cell-free bioassays. The most active species were studied further for their mechanism of action and their active principles identified though bioassay-guided fractionation. Biological activity of key species was confirmed in animal models of diabetes. These in vitro and in vivo findings are the basis for evidence-based prioritization of antidiabetic plants. In parallel, plants were also prioritized by Cree Elders and healers according to their Traditional Medicine paradigm. This case study highlights the convergence of modern science and Traditional Medicine while providing a model that can be adapted to other Aboriginal realities worldwide.
RESUMEN
Nonenzymatic formation of advanced glycation end products (AGEs) is accelerated under hyperglycemic conditions characteristic of type 2 diabetes mellitus and contributes to the development of vascular complications. As such, inhibition of AGE formation represents a potential therapeutic target for the prevention and treatment of diabetic complications. In the present study, ethanolic extracts of 17 medicinal plants were assessed for inhibitory effects on in vitro AGE formation through fluorometric and immunochemical detection of fluorescent AGEs and N(ε)-(carboxymethyl)lysine adducts of albumin (CML-BSA), respectively. Most extracts inhibited fluorescent AGE formation with IC (50) values ranging from 0.4 to 38.6 µg/mL and all extracts reduced CML-BSA formation but to differing degrees. Results obtained through both methods were highly correlated. Antiglycation activities were positively correlated with total phenolic content, free radical scavenging activity and reduction in malonyldiadehyde levels following oxidation of low-density lipoprotein, but negatively correlated with lag time to formation of conjugated dienes. Together, these results provide evidence that antioxidant phenolic metabolites mediate the antiglycation activity of our medicinal plant collection, a relationship that likely extends to other medicinal and food plants.
Asunto(s)
Antioxidantes/farmacología , Productos Finales de Glicación Avanzada/antagonistas & inhibidores , Fenoles/farmacología , Extractos Vegetales/farmacología , Plantas Medicinales/química , Canadá , Depuradores de Radicales Libres/química , Productos Finales de Glicación Avanzada/química , Productos Finales de Glicación Avanzada/metabolismo , Lisina/análogos & derivados , Lisina/antagonistas & inhibidores , Lisina/química , Malondialdehído/química , Oxidación-Reducción , Extractos Vegetales/química , Factores de TiempoRESUMEN
A number of potential anti-diabetic plants were identified through an ethnobotanical survey of the traditional pharmacopeia of the Cree of Eeyou Istchee (CEI-Northeastern Canada) used against symptoms of diabetes and their biological activity assessed by in vitro bioassays. Among these, Sorbus decora C.K.Schneid. (Rosacea) ranked highly and increased the transport of glucose in skeletal muscle cells in culture. The present study thus aimed at confirming the antidiabetic potential of S. decora in in vivo models of insulin resistance and diabetes, notably the streptozotocin Type 1 diabetic rat (STZ), the genetic KK-A(y) Type 2 diabetic mouse and the rat rendered insulin resistant with 10% glucose water consumption for 6 weeks. Sorbus decora ethanolic crude extract (SDEE) was administered orally (200 mg kg(-1)) and compared to metformin (150 or 500 mg kg(-1)). The intragastric (i.g.) gavage of SDEE transiently decreased glycemia in STZ rats in a bi-phasic manner but the effect was cumulative over several days. In KK-A(y) mice, SDEE incorporated in food (0.12%) decreased glycemia by 15% within 1 week as compared to vehicle controls. In pre-diabetic insulin-resistant rats, SDEE fed daily by i.g. gavage for 2 weeks significantly decreased the slight hyperglycemia and hyperinsulinemia, without affecting sugar water intake. Using the HOMA insulin resistance parameter, the effect of SDEE was equivalent to that of metformin. In conclusion, the ethanolic crude extract of S. decora demonstrates both anti-hyperglycemic and insulin-sensitizing activity in vivo, thereby confirming anti-diabetic potential and validating CEI traditional medicine.
RESUMEN
Obesity is an epidemic in most developed countries and novel therapeutic approaches are needed. In the course of a screening project of medicinal plants used by the Eastern James Bay Cree of Canada and having potential for the treatment of diabetes, we have identified several products that inhibit adipogenesis, suggesting potential antiobesity activities. The inhibitory activity of two of these, the extract of the inner bark of the deciduous trees Alnus incana ssp. rugosa (Speckled Alder) and Populus balsamifera L. (Balsam Poplar), was analyzed using the 3T3-L1 cell model of adipogenesis. Intracellular triglyceride accumulation, pre-adipocyte proliferation, and PPAR- γ activity were measured. Alnus incana extracts acted early in the differentiation process but did not affect clonal expansion of pre-adipocytes nor the morphological transformation from fibroblast-like to rounded fat-laden cells. Alnus incana extracts were found to act as partial agonists toward PPAR- γ activity. In contrast, Populus balsamifera extracts completely abrogated adipogenesis, severely limited clonal expansion of pre-adipocytes and generally maintained cells in an undifferentiated fibroblast-like morphology. Populus balsamifera extracts exerted antagonistic action against PPAR- γ activity. It is concluded that, through their actions on the adipocyte, these plant products may be useful for the treatment of obesity and related metabolic diseases.
Asunto(s)
Adipocitos/efectos de los fármacos , Adipogénesis/efectos de los fármacos , Alnus , Fármacos Antiobesidad/farmacología , Obesidad/prevención & control , Extractos Vegetales/farmacología , Populus , Células 3T3-L1 , Adipocitos/metabolismo , Animales , Fármacos Antiobesidad/uso terapéutico , Proliferación Celular/efectos de los fármacos , Fibroblastos , Ratones , Obesidad/metabolismo , PPAR gamma/metabolismo , Corteza de la Planta , Extractos Vegetales/uso terapéutico , Triglicéridos/metabolismoRESUMEN
Among modern day metabolic diseases, obesity has reached epidemic proportions worldwide and novel therapeutic support strategies are urgently needed. Adipocytes are interesting targets in this context. Using ethnobotanical and bioassay screening techniques, we have identified two Boreal Forest plants used by the James Bay Cree that potently inhibit adipogenesis, namely ALNUS INCANA ssp. RUGOSA (Speckled Alder) and POPULUS BALSAMIFERA (Balsam Poplar). The mode of action of this inhibitory activity was reported in a companion paper. The current study report the results of a classical bioassay-guided fractionation approach aimed at identifying the active principles responsible for the inhibition of adipogenesis, as measured using triglyceride accumulation in the 3T3-L1 adipocyte model cell line. The glycosides oregonin and salicortin were isolated and identified as the respective active principles for ALNUS INCANA and POPULUS BALSAMIFERA. These compounds thus offer promise as novel agents to mitigate the incidence or the progression of obesity.
Asunto(s)
Adipogénesis/efectos de los fármacos , Alnus/química , Diarilheptanoides/farmacología , Glucósidos/farmacología , Corteza de la Planta/química , Populus/química , Células 3T3 , Animales , Bioensayo , Fraccionamiento Químico , Diarilheptanoides/química , Diarilheptanoides/aislamiento & purificación , Glucósidos/química , Glucósidos/aislamiento & purificación , Ratones , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Extractos Vegetales/farmacologíaRESUMEN
Like many aboriginal populations, First Nations communities such as the Cree of Eeyou Istchee are facing continuously increasing rates of diabetes and related complications. Advanced glycation endproducts (AGEs), which readily form and accumulate with sustained hyperglycemia, contribute to the development of diabetic complications and, as such, are considered a potential therapeutic target. In the present study, the inhibition of AGE formation by ethanolic extracts of the Cree medicinal plant Vaccinium vitis-idaea L. was assessed by fluorometric detection of fluorescent AGEs and immunodetection of N(epsilon)-(carboxymethyl)lysine adducts of albumin. Extracts from V. vitis-idaea berries demonstrated a concentration-dependent inhibition of AGE formation in both measures. High performance liquid chromatography mass spectrometry (HPLC/MS) identified nine main phenolic constituents. Four were selected for further testing, of which catechin, quercetin-3-O-galactoside and cyanidin-3-O-glucoside but not para-coumaric acid displayed antiglycation activities. These results demonstrate that the flavonoid components of the berry extract are potent antiglycation agents and provide pharmacological validation for the traditional use of V. vitis-idaea as an antidiabetic remedy.
Asunto(s)
Flavonoides/química , Productos Finales de Glicación Avanzada/química , Fenoles/química , Extractos Vegetales/química , Vaccinium vitis-Idaea/química , Cromatografía Líquida de Alta Presión , Flavonoides/aislamiento & purificación , Frutas/química , Lisina/análogos & derivados , Medicina Tradicional , Fenoles/aislamiento & purificaciónRESUMEN
Among the Cree of northern Quebec, the disproportionately high rate of diabetic complications is largely due to the cultural inadequacy of modern therapies for type 2 diabetes. To establish culturally adapted antidiabetic treatments, our team identified several candidate plant species used by the Cree to treat symptoms of diabetes. An initial study focused on 8 species and revealed that most possess significant in vitro antidiabetic activity. The purpose of the present study was to assess a further 9 species identified through the ethnobotanical survey. Crude plant extracts were screened for (i) potentiation of basal and insulin-stimulated glucose uptake by skeletal muscle cells (C2C12) and adipocytes (3T3-L1); (ii) potentiation of glucose-stimulated insulin secretion by pancreatic beta cells (betaTC); (iii) potentiation of adipogenesis in 3T3-L1 cells; (iv) protection against glucose toxicity and glucose deprivation in PC12-AC neuronal precursor cells; and (v) diphenylpicrylhydrazyl (DPPH) oxygen free radical scavenging. Four species potentiated basal glucose uptake in muscle cells or adipocytes, one species being as potent as metformin. Adipogenesis was accelerated by 4 species with a potency roughly half that of rosiglitazone. Five species protected PC12-AC cells against glucose toxicity and 4 protected against glucose deprivation. Five species exhibited antioxidant activity comparable to ascorbic acid. However, no species increased insulin secretion. The present study revealed that Gaultheria hispidula, Rhododendron tomentosum, and Vaccinium vitis-idaea exhibit a promising profile of antidiabetic potential and are good candidates for more in-depth evaluation.
Asunto(s)
Diabetes Mellitus Tipo 2/tratamiento farmacológico , Hipoglucemiantes/uso terapéutico , Indígenas Norteamericanos , Extractos Vegetales/uso terapéutico , Plantas Medicinales , Árboles , Células 3T3-L1 , Adipocitos/efectos de los fármacos , Adipocitos/metabolismo , Animales , Diferenciación Celular/efectos de los fármacos , Citoprotección/efectos de los fármacos , Diabetes Mellitus Tipo 2/etnología , Relación Dosis-Respuesta a Droga , Radicales Libres/metabolismo , Glucosa/metabolismo , Humanos , Hipoglucemiantes/efectos adversos , Hipoglucemiantes/farmacología , Insulina/metabolismo , Secreción de Insulina , Células Secretoras de Insulina/efectos de los fármacos , Células Secretoras de Insulina/metabolismo , Ratones , Células PC12 , Extractos Vegetales/efectos adversos , Extractos Vegetales/farmacología , Plantas Medicinales/clasificación , Quebec/epidemiología , RatasRESUMEN
ETHNOPHARMACOLOGICAL RELEVANCE: Rhododendron groenlandicum (Oeder) Kron & Judd (Labrador tea) was identified as an antidiabetic plant through an ethnobotanical study carried out with the close collaboration of Cree nations of northern Quebec in Canada. OBJECTIVES: In a previous study the plant showed glitazone-like activity in a 3T3-L1 adipogenesis bioassay. The current study sought to identify the active compounds responsible for this potential antidiabetic activity using bioassay guided fractionation based upon an in vitro assay that measures the increase of triglycerides content in 3T3-L1 adipocyte. MATERIALS AND METHODS: Isolation and identification of the crude extract's active constituents was carried out. The 80% ethanol extract was fractionated using silica gel column chromatography. Preparative HPLC was then used to isolate the constituents. The identity of the isolated compounds was confirmed by UV and mass spectrometry. RESULTS: Nine chemically distinct fractions were obtained and the adipogenic activity was found in fraction 5 (RGE-5). Quercetins, (+)-catechin and (-)-epicatechin were detected and isolated from this fraction. While (+)-catechin and (-)-epicatechin stimulated adipogenesis (238±26% and 187±21% relative to vehicle control respectively) at concentrations equivalent to their concentrations in the active fraction RGE-5, none afforded biological activity similar to RGE-5 or the plant's crude extract when used alone. When cells were incubated with a mixture of the two compounds, the adipogenic activity was close to that of the crude extract (280.7±27.8 vs 311± 30%). CONCLUSION: Results demonstrate that the mixture of (+)-catechin and (-)-epicatechin is responsible for the adipogenic activity of Labrador tea. This brings further evidence for the antidiabetic potential of R. groenlandicum and provides new opportunities to profile active principles in biological fluids or in traditional preparations.
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Adipogénesis/efectos de los fármacos , Catequina/farmacología , Hipoglucemiantes/farmacología , Ledum/química , Extractos Vegetales/farmacología , Rhododendron/química , Células 3T3 , Animales , Bahías , Línea Celular , Medicina Tradicional/métodos , Ratones , Plantas Medicinales/química , QuebecRESUMEN
Mechanical forces regulate many cellular processes. Mechanotransduction, however, is poorly understood. In skeletal muscle, mechanical forces have a major impact on the regulation of cellular volume, yet the nature of the mechanical stimulation to which muscle is most sensitive is unknown. It was recently demonstrated that activation of the mechanically-sensitive kinase p54 jun-N-terminal-kinase (JNK), is a quantitative marker of mechanical stimulation in skeletal muscle. This marker was shown to be more sensitive to peak tension than to other tension-related parameters such as the tension-time integral (TTI) and the rate of change of tension (dT/dt). The purpose of the present study was to parcel out the contribution of TTI and dT/dt to mechanical stimulation of muscle under conditions of constant peak tension. The rat medial gastrocnemius in situ was subjected to one of four 5-min passive stretch protocols consisting of equal length excursions, but differing in displacement-time integral (4%, 40%, or 100%) and/or rate of stretch (0, 3, or 30 mm/s), and the resulting p54-JNK phosphorylation was assessed. A linear relationship between TTI and p54-JNK signaling was observed. However, no effect of dT/dt was observed. It is concluded that peak tension and TTI are necessary parameters for modeling the mechanical stimulus-response of muscle. Additionally, the mechanism of mechanotransduction is sensitive to peak tension and TTI, but not to dT/dt, and thus exhibits spring-like behavior. These findings may contribute to the refinement of disuse atrophy countermeasures.
Asunto(s)
Sistema de Señalización de MAP Quinasas/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Animales , Fenómenos Biomecánicos , Femenino , Proteínas Quinasas JNK Activadas por Mitógenos , Cinética , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/fisiología , Músculo Esquelético/citología , Músculo Esquelético/metabolismo , Fosforilación , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/fisiología , Ratas , Ratas Sprague-Dawley , Factores de TiempoRESUMEN
ETHNOBOTANICAL RELEVANCE: : In previous in vitro bioassay studies, Populus balsamifera L. (Salicaceae), a medicinal plant ethnobotanically identified from the traditional pharmacopoeia of the Cree of Eeyou Istchee (Eastern James Bay area of Canada), exhibited a strong anti-obesity potential by potently inhibiting adipogenesis in 3T3-L1 adipocytes. The aim of the study is to evaluate the effectiveness of this plant extract in mitigating the development of obesity and the metabolic syndrome in diet-induced obese (DIO) C57BL/6 mice. MATERIALS AND METHODS: Mice were subjected for eight weeks to a standard diet (CHOW), a high fat diet (HFD; DIO group), or HFD to which Populus balsamifera was incorporated at 125 and 250 mg/kg. RESULTS: The results showed that Populus balsamifera decreased in a dose-dependent manner the weight gain of whole body, retroperitoneal fat pad and liver as compared to DIO controls and reduced the severity of hepatic macrovesicular steatosis and triglyceride accumulation. This plant extract also decreased glycemia in the second half of the feeding period and improved insulin sensitivity by diminishing insulin levels and the leptin/adiponectin ratio, as well as augmenting adiponectin levels. These effects were associated with slightly but significantly reduced food intake with 250 mg/kg Populus balsamifera as well as with an increase in energy expenditure (increase in skin temperature and increased expression of uncoupling protein-1; UCP-1). Data also suggest other mechanisms, such as inhibition of adipocyte differentiation, decrease of hepatic inflammatory state and potential increase in hepatic fatty acid oxidation. CONCLUSION: Taken together, these results confirm the potential of Populus balsamifera as a culturally adapted therapeutic approach for the care and treatment of obesity and diabetes among the Cree.
Asunto(s)
Fármacos Antiobesidad/uso terapéutico , Hipoglucemiantes/uso terapéutico , Resistencia a la Insulina , Obesidad/tratamiento farmacológico , Extractos Vegetales/uso terapéutico , Populus , Tejido Adiposo/efectos de los fármacos , Tejido Adiposo/metabolismo , Animales , Fármacos Antiobesidad/farmacología , Dieta Alta en Grasa , Modelos Animales de Enfermedad , Hipoglucemiantes/farmacología , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Obesidad/metabolismo , Extractos Vegetales/farmacología , Temperatura Cutánea , Triglicéridos/metabolismoRESUMEN
Caffeic acid phenethyl ester (CAPE) has recently been shown to potently stimulate glucose uptake in cultured skeletal muscle cells through the AMPK pathway and therefore to have anti-diabetic potential. We report here that CAPE increases glucose uptake in C2C12 muscle cells by 225+/-21% at 50 microM, and that activation of AMPK is a consequence of the metabolic stress resulting from an uncoupling-type disruption of mitochondrial function (complete uncoupling at 50 microM). We also observe that the therapeutic potential of CAPE is offset by its high potential for toxicity. The purpose of this study was therefore to identify other active caffeic acid derivatives, evaluate their ratio of activity to toxicity, and elucidate their structure-activity relationship. Twenty naturally occurring derivatives were tested for glucose-uptake stimulating activity in C2C12 cells following 18 h of treatment and for uncoupling activity in isolated rat liver mitochondria. Cytotoxicity was assessed in C2C12 cells by the release of lactate dehydrogenase over 18 h. In addition to CAPE, four compounds were identified to be active, both stimulating glucose uptake and uncoupling isolated mitochondria. Activity required that the caffeic acid moiety be intact and that the compound not contain a strongly ionized group. Both activity and toxicity were found to be well-correlated to predicted lipophilicity. However, two compounds exhibited little to no toxicity while still stimulating glucose uptake by 65-72%. These results support a therapeutic potential for this family of compounds and provide the framework for the design of alternatives to Metformin with an optimized balance of safety and activity.
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Ácidos Cafeicos/metabolismo , Resistencia a la Insulina/fisiología , Lípidos de la Membrana/metabolismo , Mitocondrias Hepáticas/metabolismo , Desacopladores/metabolismo , Animales , Ácidos Cafeicos/química , Células Cultivadas , Ésteres , Masculino , Ratones , Ratas , Ratas Wistar , Relación Estructura-Actividad , Desacopladores/químicaRESUMEN
AIM: The purpose of the present study was to elucidate the mechanisms of action mediating enhancement of basal glucose uptake in skeletal muscle cells by seven medicinal plant products recently identified from the pharmacopeia of native Canadian populations (Spoor et al., 2006). METHODS: Activity of the major signaling pathways that regulate glucose uptake was assessed by western immunoblot in C2C12 muscle cells treated with extracts from these plant species. Effects of extracts on mitochondrial function were assessed by respirometry in isolated rat liver mitochondria. Metabolic stress induced by extracts was assessed by measuring ATP concentration and rate of cell medium acidification in C2C12 myotubes and H4IIE hepatocytes. Extracts were applied at a dose of 15-100 microg/ml. RESULTS: The effect of all seven products was achieved through a common mechanism mediated not by the insulin signaling pathway but rather by the AMP-activated protein kinase (AMPK) pathway in response to the disruption of mitochondrial function and ensuing metabolic stress. Disruption of mitochondrial function occurred in the form of uncoupling of oxidative phosphorylation and/or inhibition of ATPsynthase. Activity of the AMPK pathway, in some instances comparable to that stimulated by 4mM of the AMP-mimetic AICAR, was in several cases sustained for at least 18h post-treatment. Duration of metabolic stress, however, was in most cases in the order of 1h. CONCLUSIONS: The mechanism common to the seven products studied here is analogous to that of the antidiabetic drug Metformin. Of interest is the observation that metabolic stress need not be sustained in order to induce important adaptive responses. The results support the use of these products as culturally adapted treatments for insulin resistance and hyperglycemia in susceptible aboriginal populations where adherence to modern diabetes pharmaceuticals is an issue. The mechanism reported here may be widespread and mediate the antidiabetic activity of traditional remedies from various other cultures.
Asunto(s)
Glucosa/metabolismo , Metformina/farmacología , Fibras Musculares Esqueléticas/efectos de los fármacos , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/citología , Plantas Medicinales , Animales , Canadá , Células Cultivadas , Metabolismo Energético/efectos de los fármacos , Metabolismo Energético/fisiología , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Masculino , Metformina/análogos & derivados , Metformina/química , Ratones , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Corteza de la Planta , Ratas , Ratas Wistar , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiologíaRESUMEN
BACKGROUND: Type II diabetes and obesity are major health problems worldwide and aboriginal peoples are particularly at risk. To address this problem in Canadian native populations who find modern pharmaceuticals culturally inappropriate, our team is testing the traditional pharmacopeia of the James Bay Cree for anti-diabetic and anti-obesity activities. More specifically, the aim of the present study was to define the effects of traditional plants on intestinal glucose absorption, an under-appreciated anti-hyperglycaemic and anti-obesity activity. METHODS: Crude ethanol extracts of 17 Boreal forest medicinal plants were tested in vitro using the Caco-2 human enterocytic cell line and in vivo using an oral glucose tolerance test. RESULTS: Thirteen of seventeen extracts were observed to significantly inhibit uptake when administered simultaneously with (3)H-deoxyglucose. Inhibition was dose-dependent and, in a few cases, even surpassed that induced by a combination of the positive controls. To validate these effects in vivo, four plant extracts were administered by intragastric gavage at 250 mg/kg to normal rats simultaneously with a 3g/kg bolus of glucose. This resulted in a decrease in peak glycaemia by approximately 40% for two of them. Similarly, only 2 extracts reduced glucose transport after long term incubation and this could be related to reductions in the expression of SGLT-1 or GLUT-2 proteins. CONCLUSIONS: These findings indicate that competitive inhibition of intestinal glucose uptake can be achieved by crude extracts of medicinal plants. Such extracts could be taken with meals to control postprandial glycaemia and reduce caloric intake in high risk populations that are positively inclined towards traditional medicine.
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Diabetes Mellitus Tipo 2/tratamiento farmacológico , Glucosa/metabolismo , Hipoglucemiantes/farmacología , Absorción Intestinal/efectos de los fármacos , Fitoterapia , Extractos Vegetales/farmacología , Plantas Medicinales , Animales , Células CACO-2 , Canadá , Prueba de Tolerancia a la Glucosa , Transportador de Glucosa de Tipo 2/metabolismo , Humanos , Hiperglucemia/tratamiento farmacológico , Hipoglucemiantes/toxicidad , Indígenas Norteamericanos , Masculino , Farmacopeas como Asunto , Extractos Vegetales/administración & dosificación , Extractos Vegetales/toxicidad , Ratas , Ratas Wistar , Transportador 1 de Sodio-Glucosa/metabolismoRESUMEN
Several medicinal plants that stimulate glucose uptake in skeletal muscle cells were identified from among species used by the Cree of Eeyou Istchee of northern Quebec to treat symptoms of diabetes. This study aimed to elucidate the mechanism of action of one of these products, the berries of Vaccinium vitis idaea, as well as to isolate and identify its active constituents using a classical bioassay-guided fractionation approach. Western immunoblot analysis in C2C12 muscle cells revealed that the ethanol extract of the berries stimulated the insulin-independent AMP-activated protein kinase (AMPK) pathway. The extract mildly inhibited ADP-stimulated oxygen consumption in isolated mitochondria, an effect consistent with metabolic stress and the ensuing stimulation of AMPK. This mechanism is highly analogous to that of Metformin. Fractionation guided by glucose uptake activity resulted in the isolation of ten compounds. The two most active, quercetin-3-O-glycosides, enhanced glucose uptake by 38-59% (50 muM; 18 h treatment) in the absence of insulin. Quercetin aglycone, a minor constituent, stimulated uptake by 37%. The quercetin glycosides and the aglycone stimulated the AMPK pathway at concentrations of 25-100 muM, but only the aglycone inhibited ATP synthase in isolated mitochondria (by 34 and 79% at 25 and 100 muM, respectively). This discrepancy suggests that the activity of the glycosides may require hydrolysis to the aglycone form. These findings indicate that quercetin and quercetin 3-O-glycosides are responsible for the antidiabetic activity of V. vitis crude berry extract mediated by AMPK. These common plant products may thus have potential applications for the prevention and treatment of insulin resistance and other metabolic diseases.
Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo , Glucosa/metabolismo , Glicósidos/farmacología , Hipoglucemiantes/farmacología , Mioblastos Esqueléticos/efectos de los fármacos , Quercetina/farmacología , Vaccinium vitis-Idaea/química , Adenosina Trifosfato/metabolismo , Animales , Línea Celular , Diabetes Mellitus/dietoterapia , Diabetes Mellitus/prevención & control , Frutas/química , Glicósidos/química , Glicósidos/aislamiento & purificación , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Concentración de Iones de Hidrógeno , Hipoglucemiantes/química , Hipoglucemiantes/aislamiento & purificación , Cinética , Masculino , Ratones , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Mioblastos Esqueléticos/metabolismo , Concentración Osmolar , Extractos Vegetales/química , Extractos Vegetales/farmacología , Plantas Medicinales/química , Quebec , Quercetina/análogos & derivados , Quercetina/química , Quercetina/aislamiento & purificación , Ratas , Ratas WistarRESUMEN
SCOPE: Products of cashew tree (Anacardium occidentale) are used in traditional medicine for various ailments, including diabetes. METHODS AND RESULTS: The anti-diabetic properties of cashew plant parts were studied using differentiated C2C12 myoblasts (myotubes) and rat liver mitochondria. Hydroethanolic extract of cashew seed (CSE) and its active component, anacardic acid (AA), stimulated glucose transport into C2C12 myotubes in a concentration-dependent manner. Extracts of other parts (leaves, bark and apple) of cashew plant were inactive. Significant synergistic effect on glucose uptake with insulin was noticed at 100 µg/mL CSE. CSE and AA caused activation of adenosine monophosphate-activated protein kinase in C2C12 myotubes after 6 h of incubation. No significant effect was noticed on Akt and insulin receptor phosphorylation. Both CSE and AA exerted significant uncoupling of succinate-stimulated respiration in rat liver mitochondria. CONCLUSION: Activation of adenosine monophosphate-activated protein kinase by CSE and AA likely increases plasma membrane glucose transporters, resulting in elevated glucose uptake. In addition, the dysfunction of mitochondrial oxidative phosphorylation may enhance glycolysis and contribute to increased glucose uptake. These results collectively suggest that CSE may be a potential anti-diabetic nutraceutical.
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Ácidos Anacárdicos/farmacología , Anacardium/química , Glucosa/metabolismo , Hipoglucemiantes/farmacología , Fibras Musculares Esqueléticas/citología , Semillas/química , Análisis de Varianza , Animales , Western Blotting , Línea Celular , Insulina/metabolismo , Masculino , Ratones , Mitocondrias Hepáticas/efectos de los fármacos , Células Musculares/citología , Células Musculares/metabolismo , Nueces/química , Fosforilación Oxidativa , Extractos Vegetales/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Ratas Wistar , Receptor de Insulina/metabolismoRESUMEN
Rapid increase in the incidence of type 2 diabetes (DM2) in Papua New Guinea, coupled with compelling epidemiological evidence supporting a diabetogenic association with betel quid (BQ) chewing has lead us to investigate dietary strategies that might offer protection from developing DM2. We investigated the dietary habits of Kalo residents from coastal Central Province who are avid BQ chewers yet have a relatively low incidence of DM2 compared to the ethnically similar and adjacent Wanigelans who abstain from BQ yet have an unusually high incidence of DM2. In Kalo, guava bud (Psidium guajava L) and noni (Morinda citrifolia L) were consumed much more frequently than in Wanigela, whereas the inverse was observed for mangrove bean (Bruguiera gymnorrhiza (L) Lam.). These plants, along with BQ and its component ingredients areca nut (Areca catechu L) and Piper betle L inflorescence, were assessed for their ability to mediate insulin-dependent and insulin-independent glucose transport in cultured 3T3-L1 adipocytes. A dose-dependent inhibition of glucose uptake from methanolic extracts of BQ, areca nut and P. betle inflorescence supports previous reports of prodiabetic activity. Conversely, guava bud extract displayed significant insulin-mimetic and potentiating activity. Noni fruit, noni leaf, commercial noni juice and mangrove bean all displayed insulin-like activity but had little or no effect on insulin action. Habitual intake of guava and noni is proposed to offer better protection against DM2 development and/or betel quid diabetogenicity than cooked mangrove bean. These findings provide empirical support that DM2 risk reduction can be accomplished using traditional foods and medicines.
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Areca , Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/prevención & control , Morinda/química , Extractos Vegetales/farmacología , Psidium/química , Células 3T3 , Adulto , Animales , Areca/efectos adversos , Glucemia/metabolismo , Diabetes Mellitus Tipo 2/etnología , Relación Dosis-Respuesta a Droga , Humanos , Insulina/metabolismo , Ratones , Papúa Nueva Guinea/epidemiología , Extractos Vegetales/uso terapéuticoRESUMEN
Non-enzymatic glycation and the accumulation of advanced glycation end products (AGEs) are associated with various disease states, including complications of diabetes and aging. Secondary metabolites from several plant species are known to inhibit non-enzymatic glycation and the formation of AGEs, including flavonoids found in the style (silk) of Zea mays (maize). Thirteen modern maize inbreds and one land race were tested for in vitro inhibition of non-enzymatic glycation of bovine serum albumin. Many of the tested extracts exhibited inhibitory activity, in particular the newest inbreds, which were bred for resistance to gibberella ear rot (Fusarium graminearum) and common smut (Ustilago maydis). The most active maize genotype (CO441), displaying an IC50 of 9.5 microg/mL, was more effective than aminoguanidine, a known inhibitor of glycation. Zapalote chico, a land race with high maysin content, showed only moderate inhibitory activity compared with the modern maize genotypes. Antiglycation activity was highly correlated with the total phenolic content of silk extracts and mildly correlated with resistance to certain fungal infections. The results identify modern resistant and high phenolic maize inbreds as promising candidates for the development of natural AGE inhibitors for the prevention and treatment of diabetic complications and the degenerative effects of aging.