Rethinking the Role of Orexin in the Regulation of REM Sleep and Appetite

Abstract

Orexin plays a significant role in the modulation of REM sleep, as well as in the regulation of appetite and feeding. This review explores, first, the current evidence on the role of orexin in the modulation of sleep and wakefulness and highlights that orexin should be considered essentially as a neurotransmitter inhibiting REM sleep and, to a much lesser extent, a wake promoting agent. Subsequently, the relationship between orexin, REM sleep, and appetite regulation is examined in detail, shedding light on their interconnected nature in both physiological conditions and diseases (such as narcolepsy, sleep-related eating disorder, idiopathic hypersomnia, and night eating syndrome). Understanding the intricate relationship between orexin, REM sleep, and appetite regulation is vital for unraveling the complex mechanisms underlying sleep-wake patterns and metabolic control. Further research in this field is encouraged in order to pave the way for novel therapeutic approaches to sleep disorders and metabolic conditions associated with orexin dysregulation.

GABALAGEN Alleviates Stress-Induced Sleep Disorder in Rats

“…The LH coordinates sleep-promoting activities, and disruptions in orexin function may upset the delicate balance between sleep and wakefulness, thereby contributing to a spectrum of sleep-related problems [36][37][38]. This emphasizes the importance of investigating the role of the LH and orexin in comprehending and addressing sleep-related disturbances [33,38]. We found that GBL decreased expression of Orexin positive cells in the LH region.…”

“…Orexin neurons are characterized by wakefulness-promoting activity, reaching peak firing rates during wakefulness [32][33][34], and exhibiting the highest extracellular levels of orexin during wakefulness [35]. The LH coordinates sleep-promoting activities, and disruptions in orexin function may upset the delicate balance between sleep and wakefulness, thereby contributing to a spectrum of sleep-related problems [36][37][38].…”

Association between Low Energy Availability (LEA) and Impaired Sleep Quality in Young Rugby Players

“…In contrast, leptin is an anorexigenic adipose hormone. Therefore, a plausible explanation for the increases in WASO and cortical arousal is that, in LEA states, orexigenic signals could be activated in the brain, promoting wakefulness and inducing fragmented sleep and early awakening [ 49 ]. A previous study by Falkenberg et al [ 50 ] observed an inverse association between the length of the last meal to bedtime window and sleep duration in professional rugby players during intensive training, suggesting that early awakening could result from low energy flux and higher hunger sensations.…”

Is Sleep-Related Eating Disorder (SRED) a NREM Parasomnia or a Heterogenous Disease?

“…They are lacking in patients with narcolepsy type 1 (NT1). The fact that SRED is frequent in NT1 [31] indicates that orexin may also play a role in SRED. It needs to be emphasized that most previous studies were carried out in NES but not in patients with SRED, because of the lack of clear distinction between the two disorders [2].…”