Mechanisms of hepatic dysfunction in Nile tilapia (Oreochromis n iloticus) fed a high-fava bean (Vicia faba L.) diet

Abstract

Fava bean is currently utilized as a specialized feed ingredient to enhance the muscle texture of fish. When incorporated at appropriate levels, fava beans can improve fish muscle crispy texture. However, high dietary levels of fava beans may lead to liver damage in fish, although the specific mechanisms behind this effect remain unclear. In this study, 600 genetic improvement of farmed tilapia (GIFT; Oreochromis niloticus) of uniform size (initial body weight 552.3 ± 10.12 g) and healthy appearance were randomly divided into four groups, each with three replicates of 50 fish. The fish diets contained different levels of fava beans (0, 50%, 60%, and 70%), designated as D0, D50, D60, and D70, respectively, over a ten-week feeding experiment. A comprehensive analysis of the impact of fava beans on muscle texture and liver health in GIFT was performed. The results showed that 50%, 60%, and 70% dietary fava beans had no significant effect on the growth performance of GIFT (P > 0.05), but 70% dietary fava beans increased feed conversion ratio (FCR) (P = 0.022). Consumption of fava beans at levels of 50%, 60%, and 70% in the diet altered GIFT muscle texture (P < 0.05), and adversely effected serum biochemistry and liver health (P < 0.05). Non-targeted metabolome analysis of the liver revealed that dietary fava beans may cause irreversible damage to liver cells by disrupting the DNA methylation process (P < 0.05). This finding enhances the understanding of the mechanisms behind the negative impact of fava bean consumption on liver function. It is crucial to investigate potential strategies to mitigate these adverse effects while maintaining the desired muscle quality when fava beans are used in aquatic feed.

Keywords: Fava bean; Liver health; Metabolomics; Muscle texture; Tilapia.

Fig. 1

The effect of dietary fava bean on the morphological changes of GIFT muscle tissue (A) and liver (B). D0, D50, D60, and D70 represent 0, 50%, 60%, and 70% fava beans supplemental group, respectively. Magnification, 200×. GIFT = genetic improvement of farmed tilapia; MF = muscle fiber; MFD = muscle fiber diameter; CN = cell nucleus; HC = hepatocyte cell; CV = cellular vacuoles; NM = nuclear migration; HS = hepatocyte swelling.

Fig. 2

Orthogonal partial least squares-discriminant analysis (OPLS-DA) analysis (A) and differentially expressed metabolites (DEMs) count statistics (B) of each comparison group in positive and negative ion mode. D0, D50, D60, and D70 represent 0, 50%, 60%, and 70% fava beans supplemental group, respectively. In graph A, t1 represents principal component 1; t2 represents principal component 2; R²X represents the explanatory power of the model on variable X; R²Y represents the explanatory power of the model on the Y variable; Q² represents the predictive ability of the model, and Q² ≥ 0.5 indicates that the model is stable and reliable. The ellipse represents the 95% confidence interval. In graph B, red represents up-regulated DEMs, while blue represents down-regulated DEMs.

Fig. 3

Comparison and functional enrichment of differentially expressed metabolites (DEMs). Venn diagram of common DEMs in D50 vs. D0, D60 vs. D0, and D70 vs. D0 (A). Enrichment classification of DEMs in KEGG for each comparison group (B). D0, D50, D60, and D70 represent 0, 50%, 60%, and 70% fava beans supplemental group, respectively. × represents that the number of KEGG pathways in this classification is 0. Top-10 KEGG signaling pathways enriched by DEMs in each comparison group (C). The size of the dots indicates the number of DEMs, and the color scale represents the -log₁₀ (P-value). KEGG = Kyoto Encyclopedia of Genes and Genomes. Blue boxes represent the KEGG pathway that is significantly enriched in differential metabolites (P < 0.05).