Fish physiology and biochemistryMar 25, 2018

Changes in gut melatonin, antioxidants, and digestive enzymes with different feeding in carp (Catla catla)

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Apr 3, 2026

Abstract

Gut levels of melatonin, antioxidants, and digestive enzymes in sub-tropical carp (Catla catla) were monitored under varying feeding conditions.

Melatonin, SOD, CAT, GPx, and GST levels increased gradually during food deprivation, then decreased sharply after re-feeding on day 4, before rising again.
All digestive enzyme activities significantly decreased following food deprivation and began to increase with the restoration of food supply.
Gut melatonin concentrations showed a positive correlation with antioxidant levels in both food-deprived and re-fed fish groups.
In food-deprived fish, gut melatonin had a negative correlation with digestive enzyme activity, whereas a positive correlation was observed in re-fed fish.
Findings suggest a potential physiological interplay between gut melatonin, oxidative status, and digestive functions in response to feeding conditions.

Simplified

The purpose of present study was to ascertain whether the response of gastrointestinal (gut) melatonin to altered feeding conditions was related to the levels of different antioxidants and digestive enzymes in the same gut tissues of a sub-tropical carp (Catla catla). Accordingly, the fish were subjected to food deprivation for 4 or 8 days and separately to re-feeding for 4 or 8 or 12 days after deprivation of food for 8 days, and their gut tissue homogenates were used to measure the levels of melatonin, both enzymatic [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST)] and non-enzymatic [reduced glutathione (GSH)] antioxidants, as well as different digestive enzymes (α-amylase, cellulase, protease, and lipase). Notably, the gut levels of melatonin, SOD, CAT, GPx, and GST underwent gradual increase with the progress of food deprivation, but a sudden fall after restoration of food supply for 4 days and a rise thereafter. Conversely, the activity of all the digestive enzymes significantly decreased after deprivation of food, but started increasing when food supply was reinforced. Gut melatonin concentrations by showing a positive correlation with the titers of different antioxidants (in both food-deprived and re-fed fish groups) and a negative (in food-deprived fish) or a positive (in re-fed fish) correlation with the activity of each digestive enzyme underlined possible physiological interplay between them. Collectively, our findings lend support to the hypothesis that gut melatonin response to altered feeding conditions in carp might be associated with the oxidative status as well as the digestive functions of the gastrointestinal tissues itself.

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Changes in gut melatonin, antioxidants, and digestive enzymes with different feeding in carp (Catla catla)

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