Melatonin in the Digestive System of Vertebrates: Daily Rhythms and Body Functions

Melatonin levels in the gut of carp show significant daily variations, peaking at midday across all seasons.

• Arylalkylamine N-acetyltransferase (AANAT) is identified as the main regulator of melatonin production.
• Unlike the pineal gland, gut melatonin does not respond directly to light-dark cycles.
• The temporal pattern of melatonin in the gut may be influenced by environmental non-photic cues.
• Gut-derived melatonin may have unique physiological roles, acting locally through paracrine and/or autocrine functions.
• Evidence suggests a relationship between gut-derived melatonin and melatonin produced in the pineal gland across vertebrates.

Simplified