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Autophagy induced by hypothalamic AMPK increases food intake via inhibiting POMC expression

Title
Autophagy induced by hypothalamic AMPK increases food intake via inhibiting POMC expression
Authors
Han Chae Cho
DGIST Authors
Cho, Han Chae; Yoo, Joo-Yeon; Kim, Eun-Kyoung
Advisor(s)
김은경
Co-Advisor(s)
Joo-Yeon Yoo
Issue Date
2019
Available Date
2020-02-28
Degree Date
2019-08
Type
Thesis
Description
AMPK, Appetite, Autophagy, Hypothalamus, POMC
Abstract
AMP-activated protein kinase (AMPK) has a major role in the modulation of energy balance. Current evidence has implicated the importance of hypothalamic AMPK regu-lating appetite through the modulation of neuropeptide expression. However, the underlying mechanisMaster of this regulation are largely unknown. Here, I report a nov-el mechanism of AMPK-mediated regulation of neuropeptide expression and feeding behavior. In hypothalamic cell line expressing anorexigenic neuropeptide POMC, low glucose availability such as glucoprivation or glucose deprivation increased autophagy. Low glucose availability activated AMPK, which regulates ULK1 and mTOR complex 1, fol-lowed by decreased Pomc expression. Inhibition of autophagy by its inhibitors or siRNA diminished the effect of AMPK on Pomc expression in hypothalamic cell line. In accordance with in vitro data, ARC-specific AMPK knockdown suppressed autophagy, leading to a reduction in food intake and body weight in both normal diet- and high fat diet-fed mice. Moreover, hypothalamic AMPK knockdown attenuated Pomc expres-sion, and suppressed hyperphagia, which was induced by intraperitoneal (ip) injec-tion of the 2DG, Taken together, these results demonstrate a novel role of AMPK-mediated hypotha-lamic autophagy in the regulation of feeding behavior by decreasing Pomc expression in response to low glucose availability. These findings suggest that hypothalamic autophagy may be a potential prognostic marker and therapeutic target in metabolic diseases.|시상하부의 AMPK 효소는 식욕 조절 신경펩티드의 발현을 변화시킴으로써 식욕 조절에 중요한 역할을 하는 것으로 알려져 있지만 아직 자세한 기전은 밝혀져 있지 않다. 본 연구에서는 시상하부 AMPK가 자가 포식 작용을 활성화시켜 식욕 억제 신경펩티드인 POMC의 발현을 억제하는 것을 in vitro, in vivo 모델에서 밝혔다. 마우스 시상하부 세포에서 당 결핍 시, AMPK는 ULK1, mTORC1을 통해 자가 포식 작용은 촉진하여 POMC 발현이 억제됨을 증명했다. 또한 AMPK의 발현을 억제할 경우 자가 포식 작용 감소 및 POMC 발현 증가와 더불어 마우스의 식욕 및 체중 감소를 관찰했다. 본 연구는 활성화된 자가 포식 작용이 식욕 조절 기전 중 하나라는 것을 확인 함으로써, 이러한 연구 결과를 토대로 시상하부 AMPK가 매개된 자가 포식 작용의 역할에 대한 폭넓은 이해로 비만 예방과 치료에 새로운 실마리 제시할 것으로 기대된다.
Table Of Contents
Abstract i List of Contents ii List of Tables iv List of Figures v List of Abbreviations vii Ⅰ. INTRODUCTION 1.1. Hypothalamic circuits regulating appetite and energy homeostasis 1 1.1.1. Regulation of appetite and body metabolism in the hypothalamus 1.1.2. POMC: Anorexigenic neuropeptide 1.2. AMPK in controlling energy balance 10 1.2.1. Structure and regulation of AMPK 1.2.2. Regulation of energy metabolism by hypothalamic AMPK 1.3. Brain autophagy involving appetite and body metabolism 15 1.3.1. Overview of the autophagy process 1.3.2. Role of brain autophagy involved in appetite and body metabolism Ⅱ. Materials and Methods 2.1 Materials 19 2.1.1. Drugs and Reagents 2.1.2. Antibodies 2.2 Methods 21 2.2.1. Animals 2.2.2. Stereotaxic surgery of lentivirus delivering into the ARC 2.2.3. Administration of 2DG in mice and analysis 2.2.4. Preparation of brain tissue 2.2.5. Immunohistochemistry (IHC) 2.2.6. Cell culture 2.2.7. siRNA and plasmid transfection 2.2.8. Lentivirus production 2.2.9. Generation of stable cell lines by virus infection 2.2.10. mRFP-GFP-LC3 system 2.2.11. Immunocytochemistry (ICC) 2.2.12. Immunoblot analysis 2.2.13. RNA extraction 2.2.14. Quantitative Real-Time PCR 2.2.15. Statistical analysis Ⅲ. Results 3.1. Glucose deprivation induces autophagy through the AMPK signaling pathway 26 3.2. Hypothalamic AMPK inhibits Pomc expression in response to low glucose availability 37 3.3. Inhibition of autophagy impedes AMPK-dependent downregulation of Pomc expression 40 3.4. Mice with AMPK knockdown in the ARC show decreased autophagy, food intake, and body weight 46 3.5. Knockdown of AMPK in the hypothalamic ARC prevents 2DG-induced hyperphagia 50 Ⅳ. Discussion 55 Ⅴ. References 59 Ⅵ. 국문 요약문 71
URI
http://dgist.dcollection.net/common/orgView/200000218126
http://hdl.handle.net/20.500.11750/10454
DOI
10.22677/thesis.200000218126
Degree
Doctor
Department
Department of Brain and Cognitive Sciences
University
DGIST
Related Researcher
  • Author Kim, Eun-Kyoung Lab of Neuro-Metabolism & Neurometabolomic Research Center
  • Research Interests Neural functions in metabolic diseases; 뇌신경세포와 비만; 당뇨 등의 대사 질환 관련 연구
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Collection:
Department of Brain and Cognitive SciencesThesesPh.D.


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