京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第19806号 / 人博第777号 / 新制||人||187(附属図書館) / 27||人博||777(吉田南総合図書館) / 32842 / 京都大学大学院人間・環境学研究科共生人間学専攻 / (主査)教授 林 達也, 教授 森谷 敏夫, 教授 石原 昭彦 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

The intestinal epithelium is able to adapt to varying blood flow and, thus, oxygen availability. Still, the adaptation fails under pathologic situations. A better understanding of the mechanisms underlying the epithelial adaptation to hypoxia could help to improve the therapeutic approach. We hypothesized that the short-term adaptation to hypoxia is mediated via AMP-activated protein kinase (AMPK) and that it is coupled to the long-term adaptation by a common regulation mechanism, the HIF-hydroxylase enzymes. Further, we hypothesized the transepithelial transport of glucose to be part of this short-term adaptation. We conducted Ussing chamber studies using isolated lagomorph jejunum epithelium and cell culture experiments with CaCo-2 cells. The epithelia and cells were incubated under 100% and 21% O2, respectively, with the panhydroxylase inhibitor dimethyloxalylglycine (DMOG) or under 1% O2. We showed an activation of AMPK under hypoxia and after incubation with DMOG by Western blot. This could be related to functional effects like an impairment of Na+-coupled glucose transport. Inhibitor studies revealed a recruitment of glucose transporter 1 under hypoxia, but not after incubation with DMOG. Summing up, we showed an influence of hydroxylase enzymes on AMPK activity and similarities between hypoxia and the effects of hydroxylase inhibition on functional changes.

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This research developed methods for culturing self-assembling capillaries in an injectable gel as a potential method for vascularizing tissue-on-a-chip models to mimic physiological drug delivery. Additionally, a mathematical model was developed as a tool for understanding nutrient delivery and comparison of potential delivery systems. Organs-on-a-chip provide novel platforms for studying biology and physiology in 3D, allow exploration of tissue engineering on a manageable scale, and serve as models for drug screening and drug-delivery testing. Methods were first developed for co-culture of endothelial cells and fibroblasts (3T3s or HDFs) in 2D, evaluating culture time, seeding density and ratio of HUVECs and fibroblasts, and immunostaining with a HUVEC-specific marker. Cells formed large sheets with no signs of vessel formation in 2D; therefore, the setup was translated to 3D culture to further induce stress and release of angiogenetic factors, using fibrin gel to suspend cells in 3D. After 9 days of culture, HUVECs had extensive network formation with a high degree of complexity in the experimental cell ratios (especially with 5:1 HUVECs:HDFs). Therefore, these parameters can be used as a starting point for further development of vascularized tissue constructs. A mathematical model was also successfully developed to assess the impact of cell concentration, consumption, and mode of nutrient delivery on 3D cellular constructs which can be used to predict the spatial distribution of glucose over time. Although the model shows flow introduced through a device is sufficient to maintain nutrient levels for cell growth, developing perfusable capillaries is still a critical part of creating physiologically representative tissues.

Par l'entremise d'un modèle de souris transgénique exprimant une forme mutée et inactive d'AMPKa2 (KD), cette étude avait comme principal objectif de tester le rôle de l'AMPK dans le transport de glucose stimulé par la contraction musculaire. Un protocole de stimulation électrique a été défini pour assurer une génération de force égale entre l'extenseur digitorum longus (EDL) de souris KD et son contrôle sauvage (SA). Nous avons observé que le transport de glucose est réduit de 70% dans l'EDL de souris KD. Une cible protéique a aussi été identifiée comme étant modulée par l'AMPK lors de la contraction musculaire, soit la p38 MAPK. L'activité de p38 MAPK n'est pas modulée lors de la contraction musculaire chez la souris KD, contrairement à la souris SA. Le niveau d'ARNm de l'hexokinase II (HKII) est diminué chez la souris KD. Il est donc postulé qu'AMPK est un activateur essentiel de la p38 MAPK, ce qui pourrait contribuer à l'augmentation du transport de glucose par la contraction et à la modulation du niveau d'ARNm d'HKII cellulaire. On suggère que p38 MAPK pourrait induire l'ARNm d'HKII par l'entremise de CREB, un facteur reconnu pour être impliqué dans la transcription d'HKII.

The glucose transport protein, GLUT1, is highly expressed in rapidly proliferating cells, including cancer cells, while decreased GLUT1 levels are found in diseases such as GLUT1 deficiency syndrome and Alzheimer’s. There is increased interest in developing GLUT1 inhibitors as novel anticancer therapeutics, and the discovery of compounds that directly stimulate GLUT1 function. This work investigates how small molecules stimulate and/or inhibit GLUT1-mediated glucose transport, either directly or through the AMPK pathway. Using sugar transport assays and docking analyses to explore Ligand–GLUT1 interactions and specificity of binding, we show that: 1) Ligands inhibit GLUT1 by competing with glucose for binding to the exofacial or endofacial sugar binding sites; 2) Subsaturating inhibitor concentrations stimulate sugar uptake; 3) Ligands inhibit GLUT1–, GLUT3– and GLUT4–mediated sugar uptake in HEK293 cells; and 4) Inclusion of a benzonitrile head group on endofacial GLUT1 inhibitors confers greater inhibitory potency. Furthermore, we investigated AMPK-regulated GLUT1 trafficking in cultured blood-brain barrier endothelial cells, and show that inhibition of GLUT1 internalization is not responsible for increased cell surface levels of GLUT1 observed with AMPK activation in these cells. This study provides a framework for screening candidate GLUT1 inhibitors for specificity, and for optimizing drug design and delivery. Our data on transport stimulation at low inhibitor concentrations support the idea that GLUT1 functions as a cooperative oligomer of allosteric alternating access subunits.

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Le DT2 est caractérise par un défaut combiné de la sécrétion et de l’action de l’insuline. Depuis près d’un demi siècle la chirurgie bariatrique et notamment le Roux-en-Y Gastric Bypass (RYGB) ont montré des effets spectaculaires sur le contrôle glycémique remettant en question le paradigme de la prise en charge médicale du DT2. L’exclusion gastro duodénale induite par le RYGB améliore le métabolisme glucidique indépendemment de la perte de poids. Ainsi les modifications du flux biliaire semblent jouer un rôle, cependant les mécanismes sous-jacents ne sont pas clairs. Nous avons réalisés des RYGB chez le miniporc et nous avons montré que l'absorption intestinale du glucose est diminuée dans l’anse alimentaire (AL) dépourvue de bile. L'absorption du glucose dans l’AL était restaurée par l'ajout de la bile, et cet effet était inhibé lorsque le co transport actif sodium glucose 1 (SGLT1) était bloquée par la phlorizine. SGLT1 restait exprimée dans la AL, cependant la teneur dans la lumière de l’intestin en sodium était nettement diminuée. L’ajout de sodium dans l'AL provoquait le même effet que la bile sur l'absorption du glucose et augmentait également l’excursion glycémique post prandiale chez le miniporc au cours d’un repas test vigil. La diminution de l'absorption intestinale du glucose après RYGB a ensuite été confirmée chez l'homme. Nos résultats démontrent que la l’exclusion biliaire affecte le métabolisme post prandiale du glucose par modulation des co transporteurs intestinaux sodium-glucose. / Type 2 diabetes (T2D) is characterized primarily as a combined defect of insulin secretion and insulin action. For nearly a decade, the somewhat mysterious but spectacular benefit of metabolic surgery, and more specifically of Roux-en-Y gastric bypass (RYGB), on glucose control has been caused a questioning the current paradigm of T2D management. Gastro-intestinal exclusion by RYGB improves glucose metabolism, independent of weight loss. Although changes in intestinal bile trafficking have been shown to play a role, the underlying mechanisms are unclear. We performed RYGB in minipigs and showed that the intestinal uptake of ingested glucose is blunted in the bile deprived alimentary limb (AL). Glucose uptake in the AL was restored by the addition of bile, and this effect was abolished when active glucose intestinal transport was blocked with phlorizin. Sodium-glucose cotransporter 1 remained expressed in the AL, while intraluminal sodium content was markedly decreased. Adding sodium to the AL had the same effect as bile on glucose uptake. It also increased postprandial blood glucose response in conscious minipigs following RYGB. The decrease in intestinal uptake of glucose after RYGB was confirmed in humans. Our results demonstrate that bile diversion affects postprandial glucose metabolism by modulating sodium-glucose intestinal cotransport.

Le diabète de type 2 et l'obésité sont des problèmes de santé majeurs et les peuples autochtones sont particulièrement à risque. Pour remédier à ce problème largement répandu dans les populations autochtones canadiennes pour qui la médication moderne n’est pas culturellement adaptée, notre équipe s’est donné comme objectif d’étudier les activités potentielles antidiabétique et anti-obésité de la pharmacopée traditionnelle des Cris de la Baie James. Le but de cette étude est de tester l’hypothèse selon laquelle certaines plantes médicinales pourraient inhiber l'absorption intestinale du glucose, une activité anti-hyperglycémique qui, par la même occasion, contribuerait à combattre l’obésité. Les extraits éthanoliques de dix-sept plantes médicinales de la forêt boréale ont été testés dans des cellules intestinales Caco-2 et comparés à l’effet d’inhibiteurs compétitifs connus, tels que la phlorizine et la phlorétine. Ces inhibiteurs sont des composés polyphénoliques qui partagent de nombreuses caractéristiques structurelles avec des constituants moléculaires de plusieurs plantes Cri. Les résultats démontrent que treize des dix-sept extraits de plantes ont inhibé de façon significative l'absorption intestinale du 3H-D-glucose. Pour valider ces effets in vivo, quatre extraits ont été administrés à des rats Wistar par gavage intragastrique (250 mg/kg) en même temps qu’un bolus de glucose (3 g/kg). Suite à ce gavage, deux de ces extraits ont restreint l’augmentation de la glycémie d'environ 40% par rapport à un contrôle sans extrait. Ces résultats indiquent qu’une inhibition compétitive de l'absorption intestinale du glucose peut être atteinte par des extraits bruts de plantes médicinales. La prise de ces plantes durant les repas aiderait à un meilleur contrôle post-prandial de la glycémie, particulièrement chez les personnes à risque. / 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 for whom modern pharmaceuticals are culturally misadapted, 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. Crude ethanol extracts of seventeen Boreal forest medicinal plants were examined in the Caco-2 human enterocytic cell line and compared to the competitive classical inhibitors phlorizin and phloretin. It is worth noting that the latter compounds are polyphenols that share many structural characteristics with components of several Cree plants. Thirteen of seventeen extracts were observed to significantly inhibit uptake when administered simultaneously with 3H-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 3 g/kg bolus of glucose. This resulted in a decrease in peak glycaemia by approximately 40% for two of them. These findings indicate that competitive inhibition of facilitative intestinal glucose uptake can be achieved by crude extracts of medicinal plants. Intake of the latter with meals may help control post-prandial glycaemia and reduce caloric intake in high risk populations.