Abstract
Orexin is a neuropeptide produced in the hypothalamus that plays a key role in regulating slee-wake cycles, energy metabolism, feeding behavior, and physical activity. It exists in two forms, orexin-A and orexin-B, which bind to G protein-coupled receptors OX(1)R and OX(2)R with differing affinities. Orexin signaling is widespread in the brain and extends to peripheral tissues, including adipose tissue. Its involvement in hypothalamic and extrahypothalamic circuits suggests a broad role in homeostatic regulation. Dysfunctions in the orexinergic system are implicated in neurodegenerative diseases such as Alzheimer's, Parkinson's, and multiple sclerosis, particularly through mechanisms involving sleep disturbances and neuroinflammation. This study examines how orexin influences neural circuits related to arousal, motivation, and motor control. It also explores how physical activity stimulates orexin release, enhancing neuroplasticity and cognitive resilience. In addition, orexin's role in reward-related feeding, genetic susceptibility to obesity, and brown adipose tissue thermogenesis is discussed. Overall, the orexinergic system represents a vital neurochemical link between physical activity, metabolism, and cognitive health. Although many of its mechanisms remain to be clarified, its central role in integrating energy balance and behavioral responses makes it a promising target for future therapeutic strategies.