1. Orexin and Thermogenesis
Yufeng Zhang

2. Background Physiological Function Counter-productive nature
Non-shivering thermogenesis (BAT)
Sleep/awake cycles
Physicial activity
Cognition
Counter-productive nature
Increase feeding
Elevating energy expenditure
Diet-induced thermogenesis
Arousal from hibernation

3. Background Autonomic function, both central and peripheral
Blood pressure, heart rate
HPA axis, GNHR/soma-tostatin-GH axis
Influences psychological, behavioral, and physiological characteristics
Hibernation
Thermogenesis (holding and raising)
Arousal from hibernation

4. Orexin and feeding Negative feedback system
Glucose
Coordinate various elements of appetite regulation system
Leptin, NPY, Galanin, Gherlin
Interdependent functions between NPY and orexin

5. Orexin and sleep/awake cycle
Orexin neurons project to
Locus coeruleus (LC)
Dorsal raphe (DR)
Tuberomammilary nucleus (TMN)
GABA → laterpdorsal tegmental nucleus (LDT)

6. Orexin and BAT
BAT
Multiple lipid droplets, numerous mitochondria, dense capillary network
UCP 1
Sympathetic nervous system → noradrenalin → β-3 adrenergic receptors → lipolysis
Orexin-knockout mice, orexin receptor 1- deficient mice
Hypersensitivity to cold
Developmental differentiation
defect

7. Orexin and Hibernation
During hibernation, thermogensis depend on BAT
Paradoxical actions: feeding and energy expenditure
BAT in human
BAT increase in size during hibernation

8. Conclusion

9. Stress-induced hyperthermia
Core body temperature rise under stress
measure antistress or anxiolytic-like effects
Orexin neurons with stress-induced thermogenesis
Located in dorsol-medial hypothalamus (DMH)
Project to medullary raphe
ORX-KO and ORX-AB
ORX-AB more REM than ORX-AB

16. Conclusion/introduction
Orexins do not regulate resting body temperature.
Orexin neurons in stress-induced thermogenesis
Function as DMH-raphe neurons
Receive stress then activate DMH-raphe neurons
FGE2 injection and cold exposure
Dynorphin, Galanin, Glutamate

28. Conclusion
Orexin neurons can be sources of glutamate transmission for cold-evoke thermogenesis
Orexin may be involve with PGE2 shivering
Orexin neuron participate in thermogenic output pathways
Glutamate from orexin neuron could be responsible for thermogenic response