Avian Orexin: Feed Intake Regulator or Something Else?

Area of Science:

• Neuroendocrinology
• Metabolic Research
• Comparative Physiology

Background:

• Orexin (hypocretin) is a neuropeptide originally identified in the hypothalamus, known for regulating feeding behavior, energy homeostasis, and sleep.
• Its roles in central and peripheral neuroendocrine functions, energy balance, and metabolism are well-established in mammals, including livestock like cattle, pigs, and sheep.
• Orexin is also implicated in human neurological disorders such as narcolepsy, depression, and Alzheimer's disease.

Purpose of the Study:

• To review current knowledge on the physiological roles of orexin in livestock.
• To highlight the limited research on orexin in non-mammalian species, specifically avian species.
• To identify knowledge gaps and suggest future research directions for orexin's function in avian metabolism.

Main Methods:

• Literature review of existing studies on orexin.
• Synthesis of findings regarding orexin's effects in mammalian and avian species.
• Analysis of research gaps in non-mammalian orexin physiology.

Main Results:

• Orexin influences feeding behavior, energy homeostasis, and metabolism in mammals, including food production animals.
• In avian species, orexin does not appear to centrally affect feed intake.
• Orexin is involved in muscle energy metabolism and hepatic lipogenesis in birds.

Conclusions:

• Orexin plays diverse roles in metabolism across species.
• Further research is needed to fully elucidate orexin's physiological functions in avian species.
• Understanding orexin in livestock and birds can inform agricultural and metabolic research.