Cholecystokinin: how many functions? Observations in seabreams

Area of Science:

• Comparative physiology
• Gastrointestinal endocrinology
• Fish biology

Background:

• Cholecystokinin (CCK) is a key gastrointestinal peptide hormone.
• Its distribution and function in fish, particularly in the hindgut, are not fully understood.
• Previous studies have focused on CCK in the anterior digestive tract.

Purpose of the Study:

• To investigate the regional distribution of CCK in fish, specifically in seabreams (Diplodus puntazzo and Diplodus sargus).
• To explore the potential role of hindgut CCK in regulating digestive processes.
• To differentiate the functions of various CCK isoforms in Diplodus sargus.

Main Methods:

• Molecular studies to analyze CCK gene expression.
• Immunological studies to detect CCK protein presence.
• Comparative analysis of CCK expression in fed versus fasted fish.

Main Results:

• CCK was detected in the hindgut of Diplodus puntazzo and Diplodus sargus.
• CCK gene and protein expression levels varied between fed and fasted fish.
• Evidence suggests two distinct CCK isoforms in D. sargus with potentially different roles.

Conclusions:

• The presence of CCK in the hindgut indicates a novel regulatory function in this region.
• One CCK isoform in D. sargus may be involved in digestive regulation from pyloric caeca through the hindgut.
• A second CCK isoform might have a function independent of digestive process regulation.