Motilin Comparative Study: Structure, Distribution, Receptors, and Gastrointestinal Motility

Area of Science:

• Comparative physiology
• Gastroenterology
• Endocrinology

Background:

• Motilin is a key regulator of gastrointestinal (GI) motility, controlling the migrating motor complex (MMC) and hunger signaling.
• Its role in mammals is established, but less understood across diverse species due to experimental variations.
• Motilin and its receptor (MLN-R) are found in vertebrates, with distinct sequences in non-mammalian groups.

Purpose of the Study:

• To review the structure, distribution, receptor, and GI motility regulatory functions of motilin.
• To synthesize current knowledge on motilin's role in vertebrates, from fish to mammals.
• To highlight evolutionary conservation and divergence of motilin signaling.

Main Methods:

• Literature review and synthesis of existing research on motilin and MLN-R.
• Comparative analysis of motilin and MLN-R sequences across vertebrate classes.
• Examination of physiological studies on GI motility regulation by motilin.

Main Results:

• Motilin and MLN-R exhibit conserved functions in GI motility regulation across vertebrates.
• Sequence analysis reveals distinct evolutionary paths for motilin and MLN-R in fish compared to other vertebrates.
• MLN-R can be classified into two major clades: mammal/bird/reptile/amphibian and fish.

Conclusions:

• Motilin plays a significant, albeit varied, role in GI motility and hunger signaling throughout vertebrate evolution.
• Understanding motilin's diverse roles across species is crucial for comprehending its overall physiological significance.
• Further research is needed to fully elucidate species-specific functions and the evolutionary trajectory of motilin signaling.