Effet allèlopathique des extraits de la luzerne (Medicago sativa L.) sur le souchet (Cyperus rotundus L.) et le chiendent (Cynodon dactylon (L.) Pers.

Le souchet (Cyperus rotundus L.) et le chiendent (Cynodon dactylon (L.) Pers.) sont les mauvaises herbes vivaces les plus nocives des vergers d'agrumes dans la région de Gharb au Maroc. L'objectif de cette étude était de purifier et d'identifier les composés allelopathiques issus de l'extrait de luzerne (Medicago sativa L.) qui ont la capacité d'inhiber la croissance de ces espèces de mauvaises herbes. Les substances allelopathiques provenant d'extraits aqueux de luzerne ont été isolées et caractérisées par Chromatographie en Couche Mince (CCM), Cromatographie Liquide à haute Performance (HPLC) et Chromatographie Gazeuse-Spectrométrie de Masse (GC-MS). Plusieurs acides phénoliques dans la partie aérienne et racinaire de la luzerne ont été identifiés. Lorsque les standards de ces acides phénoliques ont été testées séparément sur le souchet et le chiendent à une concentration de 10 mM, une excellente inhibition de la croissance des pousses de souchet a été obtenue avec les acides p-hydroxybenzoïques, génétiques et syringiques. Les acides gallique, salicylique et p-coumarique ont produit un effet d'inhibition élevé sur la croissance des pousses de souchet alors que les acides malique, ferulique et succinique présentaient un effet d'inhibition faible à médiocre. Sur la croissance de la racine du souchet, les acides p-hydroxybenzoïque, gallique, salicylique, ferulique, p-coumarique et syringique étaient des inhibiteurs très efficaces. Les acides gentisiques et maliques ont un effet d'inhibition modéré tandis que l'acide succinique n'a produit aucun effet inhibiteur. Malgré l'effet faible à médiocre de l'extrait aqueux de luzerne sur la croissance du chiendent, certains acides phénoliques, lorsqu'ils ont été testés séparément à une concentration de 10 mM, ont montré des effets d'inhibition variables sur la croissance de cette espèce. Par conséquent, les acides géntisique, salicylique, ferulique et p-coumarique ont montré un effet modéré à élevé sur la croissance des racines de chiendent de plus de 70% d'inhibition. Même si les acides p-hydroxybenzoïque et gallique ont un effet médiocre sur la croissance aérienne, ils ont un effet très élevé sur les racines du chien

Glucose-Induced O2 Consumption Activates Hypoxia Inducible Factors 1 and 2 in Rat Insulin-Secreting Pancreatic Beta-Cells

Glucose increases the expression of glycolytic enzymes and other hypoxia-response genes in pancreatic beta-cells. Here, we tested whether this effect results from the activation of Hypoxia-Inducible-factors (HIF) 1 and 2 in a hypoxia-dependent manner

Effet allélopathique de quelques plantes médicinales sur la germination des graines de Phalaris canariensis L. et Lactuca sativa L.

L’utilisation d’un herbicide naturel peut réduire les impacts préjudiciables à l’environnement. Dans ce sens l’allélopathie est considérée comme une technique prometteuse pour la lutte biologique. Cependant, les effets des substances allelopathiques restent peu expérimentés dans les conditions du laboratoire et du champ. Dans cette étude, les extraits aqueux des feuilles de 15 espèces de différentes régions du Maroc ont été testés sur la germination de l’alpiste des canaries (Phalaris canariensis L.) comme plante représentative de la classe des monocotylédones et la laitue (Lactuca sativa L.) représentative des dicotylédones. Il s’est avéré que seules trois espèces sur 15 répondent aux critères d’un herbicide biologique efficace, il s’agit d’Ammi visnaga (L.) Lam., d’Atractylis gummifera L. et de Ruta montana L.. Ainsi, le taux de réduction de la germination de l’alpiste des canaries par ces trois plantes variait entre 96 et 100%, alors que la germination de la laitue n’a pas été affectée et dont le pourcentage d’inhibition était compris entre -8 et 4%. En effet, les extraits aqueux de ces trois plantes ont montré une très bonne efficacité herbicide sur l’alpiste des canaries et peut être la même efficacité sur les monocotylédones et une sélectivité vis-à-vis de la laitue qui serait la même pour les dicotylédones

SGLT2 is not expressed in pancreatic α- and β-cells, and its inhibition does not directly affect glucagon and insulin secretion in rodents and humans.

OBJECTIVE: Sodium-glucose cotransporter 2 (SGLT2) inhibitors (SGLT2i), or gliflozins, are anti-diabetic drugs that lower glycemia by promoting glucosuria, but they also stimulate endogenous glucose and ketone body production. The likely causes of these metabolic responses are increased blood glucagon levels, and decreased blood insulin levels, but the mechanisms involved are hotly debated. This study verified whether or not SGLT2i affect glucagon and insulin secretion by a direct action on islet cells in three species, using multiple approaches. METHODS: We tested the in vivo effects of two selective SGLT2i (dapagliflozin, empagliflozin) and a SGLT1/2i (sotagliflozin) on various biological parameters (glucosuria, glycemia, glucagonemia, insulinemia) in mice. mRNA expression of SGLT2 and other glucose transporters was assessed in rat, mouse, and human FACS-purified α- and β-cells, and by analysis of two human islet cell transcriptomic datasets. Immunodetection of SGLT2 in pancreatic tissues was performed with a validated antibody. The effects of dapagliflozin, empagliflozin, and sotagliflozin on glucagon and insulin secretion were assessed using isolated rat, mouse and human islets and the in situ perfused mouse pancreas. Finally, we tested the long-term effect of SGLT2i on glucagon gene expression. RESULTS: SGLT2 inhibition in mice increased the plasma glucagon/insulin ratio in the fasted state, an effect correlated with a decline in glycemia. Gene expression analyses and immunodetections showed no SGLT2 mRNA or protein expression in rodent and human islet cells, but moderate SGLT1 mRNA expression in human α-cells. However, functional experiments on rat, mouse, and human (29 donors) islets and the in situ perfused mouse pancreas did not identify any direct effect of dapagliflozin, empagliflozin or sotagliflozin on glucagon and insulin secretion. SGLT2i did not affect glucagon gene expression in rat and human islets. CONCLUSIONS: The data indicate that the SGLT2i-induced increase of the plasma glucagon/insulin ratio in vivo does not result from a direct action of the gliflozins on islet cells

Glucose Induces Pancreatic Islet Cell Apoptosis That Requires the BH3-Only Proteins Bim and Puma and Multi-BH Domain Protein Bax

OBJECTIVE: High concentrations of circulating glucose are believed to contribute to defective insulin secretion and beta-cell function in diabetes and at least some of this effect appears to be caused by glucose-induced beta-cell apoptosis. In mammalian cells, apoptotic cell death is controlled by the interplay of proapoptotic and antiapoptotic members of the Bcl-2 family. We investigated the apoptotic pathway induced in mouse pancreatic islet cells after exposure to high concentrations of the reducing sugars ribose and glucose as a model of beta-cell death due to long-term metabolic stress. RESEARCH DESIGN AND METHODS: Islets isolated from mice lacking molecules implicated in cell death pathways were exposed to high concentrations of glucose or ribose. Apoptosis was measured by analysis of DNA fragmentation and release of mitochondrial cytochrome c. RESULTS: Deficiency of interleukin-1 receptors or Fas did not diminish apoptosis, making involvement of inflammatory cytokine receptor or death receptor signaling in glucose-induced apoptosis unlikely. In contrast, overexpression of the prosurvival protein Bcl-2 or deficiency of the apoptosis initiating BH3-only proteins Bim or Puma, or the downstream apoptosis effector Bax, markedly reduced glucose- or ribose-induced killing of islets. Loss of other BH3-only proteins Bid or Noxa, or the Bax-related effector Bak, had no impact on glucose-induced apoptosis. CONCLUSIONS: These results implicate the Bcl-2 regulated apoptotic pathway in glucose-induced islet cell killing and indicate points in the pathway at which interventional strategies can be designed

Differential Glucose-Regulation of MicroRNAs in Pancreatic Islets of Non-Obese Type 2 Diabetes Model Goto-Kakizaki Rat

The Goto-Kakizaki (GK) rat is a well-studied non-obese spontaneous type 2 diabetes (T2D) animal model characterized by impaired glucose-stimulated insulin secretion (GSIS) in the pancreatic beta cells. MicroRNAs (miRNAs) are short regulatory RNAs involved in many fundamental biological processes. We aim to identify miRNAs that are differentially-expressed in the pancreatic islets of the GK rats and investigate both their short- and long term glucose-dependence during glucose-stimulatory conditions

Nano-Sampling and Reporter Tools to Study Metabolic Regulation in Zebrafish

In the past years, evidence has emerged that hallmarks of human metabolic disorders can be recapitulated in zebrafish using genetic, pharmacological or dietary interventions. An advantage of modeling metabolic diseases in zebrafish compared to other “lower organisms” is the presence of a vertebrate body plan providing the possibility to study the tissue-intrinsic processes preceding the loss of metabolic homeostasis. While the small size of zebrafish is advantageous in many aspects, it also has shortcomings such as the difficulty to obtain sufficient amounts for biochemical analyses in response to metabolic challenges. A workshop at the European Zebrafish Principal Investigator meeting in Trento, Italy, was dedicated to discuss the advantages and disadvantages of zebrafish to study metabolic disorders. This perspective article by the participants highlights strategies to achieve improved tissue-resolution for read-outs using “nano-sampling” approaches for metabolomics as well as live imaging of zebrafish expressing fluorescent reporter tools that inform on cellular or subcellular metabolic processes. We provide several examples, including the use of reporter tools to study the heterogeneity of pancreatic beta-cells within their tissue environment. While limitations exist, we believe that with the advent of new technologies and more labs developing methods that can be applied to minimal amounts of tissue or single cells, zebrafish will further increase their utility to study energy metabolism