Gene expression analysis is a biomolecular tool that helps to understand the relationship between nutrient intake and physiological responses. As an important fishery resource in Mexican cuisine, freshwater prawn Macrobrachium acanthurus contributes to the overall economic growth of the region. However, knowledge of culture conditions of this species is lacking; hence, the aim of this study is to evaluate the effect of different macronutrients intake on the expression of genes related to metabolism and antioxidant function.
Figure 1 summarizes the methodology; briefly, six diets were formulated with 2 protein levels (35% = P35; 40% = P40) and 3 lipid – carbohydrate ratios (2:1, 1:2 and 1:6) and fed to 180 juvenile prawns for 60 days. Figure 2 shows the relative gene expression. Genes related to fatty acid synthesis (FAS) were upregulated with high levels of carbohydrates (L:C ratio 1:6) and with higher protein intake in diet (P40), which suggests that excessive energy is stored as lipid deposits. In contrast, CPT1 which is related to b-oxidation of lipids was downregulated in all treatments. These, combined with the upregulation of hexoquinase (HK) in treatment P35 L:C ratio 1:2 indicates that glycolysis may be the chosen source of energy in these organisms. Gluconeogenesis genes (PEPCK) were downregulated in all treatments; thus, it is believed that carbohydrates are being utilized to fuel the metabolism of prawns instead of lipids or proteins. Gene expression of the antioxidant system revealed that SOD was significantly upregulated in treatment P35 L:C ratio 1:2 which may suggest a favorable effect of this diet, while CAT was upregulated at an L:C ratio 1:2 and in P40 L:C 1:6, suggesting that excess of lipids and high protein and carbohydrate intake could induce oxidative stress caused by reactive oxygen and nitrogen species (ROS and RNS) derived from a macronutrient imbalance in diet.
In conclusion, results suggest that prawns fed the diet with 35% protein and a L:C ratio 1:2 (10% lipids and 20% carbohydrates) favors carbohydrate utilization and show improved antioxidant capacity.