Effects of Replacing Fish Meal by Plant Protein Sources in Fish Feed on Serum and Muscle Cholesterol Levels, Cholesterol Metabolism-Related Enzyme Activity and Gene Expression of Fish – A Review

This review examines the effects of replacing fish meal with plant protein sources on cholesterol metabolism and physiological responses in fish, driven by sustainable aquaculture needs. Plant-based diets significantly alter lipid metabolism, particularly cholesterol homeostasis, due to lower dietary cholesterol intake. Fish like Atlantic salmon, European sea bass, and rainbow trout compensate by upregulating the low-density lipoprotein receptor (LDLR) to enhance cholesterol uptake from circulation. Plant proteins also modulate enzymes such as cholesterol acyltransferase (ACAT) and HMG-CoA reductase (HMGCR), with ACAT esterifying cholesterol for storage and HMGCR boosting endogenous synthesis. Phytosterols in plant feeds further reduce intestinal cholesterol absorption, amplifying LDLR activity. Short-term adaptations maintain cholesterol balance, but long-term plant-based diets may disrupt lipid metabolism, increasing hepatic fat deposition and altering lipid profiles. Such changes can impair growth and liver health, suggesting fish meal’s essential fatty acids and nutrients remain critical. The review underscores the need for balanced plant-based formulations, including supplemental lipids and cholesterol, to ensure fish health and performance. Sustainable aquaculture must tailor diets to species-specific nutritional requirements.