Brain accessibility delineates the central effects of circulating ghrelin

Area of Science:

• Neuroendocrinology
• Gastroenterology
• Metabolic research

Background:

• Ghrelin is a gastrointestinal hormone that binds to the growth hormone secretagogue receptor.
• Ghrelin signaling in the central nervous system influences behavior, neuroendocrine function, metabolism, and autonomic processes.
• Previous studies indicate restricted access of circulating ghrelin to specific brain regions in mice.

Purpose of the Study:

• To review evidence on the limited accessibility of circulating ghrelin to the brain.
• To discuss potential pathways for plasma ghrelin entry into the brain and their physiological significance.
• To explore potential differences in ghrelin brain accessibility between mice and humans.

Main Methods:

• Review of existing literature on ghrelin's central effects and brain penetration.
• Analysis of studies using radiolabeled or fluorescent ghrelin variants.
• Examination of studies involving systemic ghrelin administration in mice.
• Consideration of human studies on ghrelin administration.

Main Results:

• Evidence suggests strikingly low and localized accessibility of circulating ghrelin into the mouse brain.
• Indirect evidence from systemic ghrelin injections in mice supports limited brain penetration.
• Human studies provide observations on the consequences of ghrelin administration.

Conclusions:

• The brain penetration of ghrelin is a critical factor in its central effects.
• Understanding ghrelin's access pathways is crucial for elucidating its physiological roles.
• Further research is needed to fully characterize ghrelin's brain accessibility in humans.