Effects of feeding with corn gluten meal on trypsin activity and mRNA expression in Fugu obscurus

The molecular regulation of the trypsin activity and the effects of corn gluten meal (CGM) on the trypsin activity and gene expression in Fugu obscurus were examined. The fish were fed with diets containing 0, 50, 100, 150, and 200 g kg⁻¹ CGM for 60 days. The trypsin activity and mRNA levels in the intestine, stomach, and hepatopancreas were measured before and after the experimental feeding. Enzyme activity was highest in the intestine, and mRNA expression was highest in the hepatopancreas prior to feeding the experimental diets. The effect of dietary CGM on the trypsin activity was dependent on the concentration. Enzyme activity was significantly lower in the hepatopancreas and stomach of the 200 g kg⁻¹ treatment group than in control group. In contrast, activity was enhanced in the stomach of the 100 g kg⁻¹ treatment group. Different amounts of CGM in the diets also resulted in significant changes in the trypsin mRNA levels in all three tissues. The trypsin mRNA expression in stomach, hepatopancreas, and intestine increased with increasing CGM from 0 to 10% and decreased with increasing CGM from 10 to 20%. The trypsin mRNA expression was highest in the 100 g kg⁻¹ treatment group, which was significantly higher than that of in the control. In addition, the changes in the trypsin mRNA expression levels were not reflected by changes in the trypsin activity. Our results suggest that the trypsin activity is regulated not only at the transcription level but also during translation and posttranslational modification.