2021 Fiscal Year Annual Research Report
A New Role for Glucose-sensing Neurons during Torpor
| Project/Area Number |
21F21406
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| Allocation Type | Single-year Grants |
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| Research Institution | Center for Novel Science Initatives, National Institutes of Natural Sciences |
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Principal Investigator |
根本 知己 大学共同利用機関法人自然科学研究機構(新分野創成センター、アストロバイオロジーセンター、生命創成探究, 生命創成探究センター, 教授 (50291084)
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| Co-Investigator(Kenkyū-buntansha) |
LEE MING-LIANG 大学共同利用機関法人自然科学研究機構(新分野創成センター、アストロバイオロジーセンター、生命創成探究, 生命創成探究センター, 外国人特別研究員
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| Project Period (FY) |
2021-11-18 – 2024-03-31
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| Keywords | glucose metabolism / Q-neuron / glucose sensing / torpor / hypothermia / hypometabolism |
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| Outline of Annual Research Achievements |
We first determined the procedure to artificially induce Q-neuron-induced hypothermia and hypometabolism (QIH) such as viral injection and chemogenetics. We successfully induced QIH by activating Qrfp neurons in APV (QrfpAPV). As previous reports, the QIH mice have very lower body temperature than normal mice. We found the basal blood glucose was significantly lowered by QIH which implies that QIH disturbs glucose metabolism. Results of the glucose tolerance test (GTT) and insulin tolerance test (ITT) support this thought. Agree with this, QIH animals did not lose body weight as much as control mice after overnight fasting, which suggests QIH animals preserve more energy during fasting.
We then tried to define regions which regulate glucose metabolism during QIH. We traced the axon projection of QrfpAPV and found its downstream regions. Some of these regions have been reported to control glucose metabolism and are filled with glucose sensing neurons. The cfos expression was clearly decreased in one of these regions, suggesting this region may be involved in QIH-disturbed glucose metabolism.
Moreover, we have successfully set up the in vivo calcium imaging system by using miniscope and GRIN lens for the future research in this project.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
To execute this project, a new strain of the transgenic mice was transported to our institute. It would take months to stably generate pups. At the same time, because there is no experimental system for physiologic research in the host lab, we set up several key systems for physiological experiments, such as a space for GTT or ITT, thermal imaging system, and in vivo calcium imaging system on free moving mice. Even though we spent months to breed new transgenic animals and developed many new experimental system, several key preliminary results were still be made:
1) QIH was successfully induced and our hypothesis that glucose metabolism is changed by QIH was validated. This result makes sure the project is realistic.
2) A candidate region which may be involved in the QIH-affected glucose metabolism was found.
These achievements show us a clear way how we go for the project and we also have already set up the techniques we will need.
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| Strategy for Future Research Activity |
Our next step is to understand the glucose sensing function of glucose sensing neurons during QIH. Although we found some candidate regions receiving projections from QrfpAPV , this result is not as same as the previous paper. It may be because the labeling we use (mcherry) is too weak to detect axon terminals in every down region. We will continue to investigate the downstream regions by another marker (ex. eGFP). Glucose responsiveness of downstream regions of QrfpAPV will be profiled in QIH mice by cfos-immunohistochemistry. Once a region whose glucose responsiveness is found affected by QIH, this region will be a candidate region. To investigate neuronal glucose sensing in the candidate region, a virus delivering GCaMP8 will be injected, and a GRIN lens will be implanted into the region. In vivo calcium imaging will be performed with UCLA miniscopeV4. The neuronal activity will be recorded on normal and QIH mice before and after glucose or saline i.p. injection to assess the neuronal glucose sensing between the two groups of mice. GTT and ITT show glucose metabolism can be affected by QIH. Along this line, we will set up hyperinsulinemia-euglycemia clamp technique to further understand the details of glucose metabolism during QIH.
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