Elevated sleep quality and orexin receptor mRNA in obesity-resistant rats.
OBJECTIVE
To determine if resistance to weight gain is associated with alterations in sleep-wake states and orexin receptor gene expression.


METHODS
Three-month-old obesity-susceptible Sprague-Dawley (SD) and obesity-resistant (OR) rats were fed standard rodent chow. Sleep-wake cycle was measured by radiotelemetry and orexin receptor profiles in sleep-wake regulatory areas of the brain were quantified by quantitative reverse transcriptase-PCR.


METHODS
Adult male obesity-susceptible SD and selectively bred OR rats.


METHODS
Body weight, food intake, energy efficiency, percent time spent in active wake (AW), quiet wake (QW), slow-wave sleep (SWS), rapid eye movement (REM) sleep, number and mean duration of sleep-wake episodes, number of stage transitions, SWS sleep delta power and orexin receptor mRNA levels were measured.


RESULTS
OR rats weighed significantly less and had lower energy efficiency than SD rats. Food intake was not different between SD and OR rats. Time spent in QW was similar between groups, and therefore AW and QW were combined and are referred to as 'wakefulness'. OR rats spent significantly more time in wakefulness and less time in SWS compared with SD rats during the 24-h recording period. Relative to SD rats, OR rats had significantly fewer sleep-wake episodes and the duration of the episodes were prolonged, indicating less fragmented sleep. Furthermore, OR rats had fewer transitions between sleep stages, which indicates that OR rats were behaviorally more stable and had more consolidated sleep than obesity-susceptible SD rats. OR rats showed lower delta power during SWS, indicating a lower sleep drive. Our results showed greater orexin receptor gene expression in sleep regulatory brain areas in OR rats.


CONCLUSIONS
These results show that prolonged wakefulness, better sleep quality, lower sleep drive and greater orexin signaling may confer protection against obesity.
Mavanji
V
V
Department of Food Science and Nutrition, University of Minnesota St Paul, MN, USA. mavan001@umn.edu
Teske
J A
JA
Billington
C J
CJ
Kotz
C M
CM
D000818:Animals; D015870:Gene Expression; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009765:Obesity / Q000188:drug therapy / Q000503:physiopathology*; D064446:Orexin Receptors; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D018013:Receptors, Neuropeptide / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012894:Sleep Stages / Q000187:drug effects / Q000502:physiology*
D064446:Orexin Receptors; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide