Dietary Protein Level Alters Appetite Hormones and Digestive Enzymes in Tilapia
Increasing dietary protein from 30% to 42% in red tilapia reduced growth performance, decreased ghrelin and insulin expression, and increased satiety hormones CCK and peptide YY.
Quick Facts
What This Study Found
The 30% CP diet optimized growth, while 42% CP decreased ghrelin and insulin expression, increased CCK and peptide YY expression, and reduced growth performance compared to moderate protein levels.
Key Numbers
240 fish; 4 diets (24-42% CP); 42 days; 30% optimal; 42% decreased ghrelin/insulin, increased CCK/PYY
How They Did This
240 red tilapia juveniles across 20 tanks fed four isoenergetic diets (24%, 30%, 36%, 42% crude protein) for 42 days. Measured growth performance, protein retention, body composition, protease activity, and gene expression for digestive enzymes and appetite-regulating hormones.
Why This Research Matters
Understanding how dietary protein affects appetite hormones in fish has dual value: optimizing aquaculture feeding and demonstrating conserved peptide hormone mechanisms across vertebrates.
The Bigger Picture
The appetite-regulating peptides (ghrelin, CCK, PYY) respond to dietary protein in fish just as they do in mammals, highlighting the ancient evolutionary conservation of these satiety systems.
What This Study Doesn't Tell Us
Fish study — appetite regulation mechanisms may not directly apply to human protein intake recommendations. Only one fish species tested. Gene expression measured but not circulating hormone levels.
Questions This Raises
- ?Is there a similar U-shaped protein response curve for growth in other aquaculture species?
- ?Do these appetite peptide changes in fish inform our understanding of protein-satiety interactions in humans?
- ?What protein digestion products specifically trigger CCK and PYY in the fish gut?
Trust & Context
- Key Stat:
- 30% protein optimal Moderate protein diet (30%) produced the best growth while very high protein (42%) reduced growth and altered appetite hormones
- Evidence Grade:
- Moderate — well-designed aquaculture experiment with adequate sample size (240 fish) and multiple endpoints, though limited to one species.
- Study Age:
- Published in 2020; aquaculture nutrition optimization continues to incorporate molecular-level appetite regulation studies.
- Original Title:
- Dietary protein modulates digestive enzyme activities and gene expression in red tilapia juveniles.
- Published In:
- Animal : an international journal of animal bioscience, 14(9), 1802-1810 (2020)
- Authors:
- Santos, W M, Costa, L S, López-Olmeda, J F, Costa, N C S, Santos, F A C, Oliveira, C G, Guilherme, H O, Bahiense, R N, Luz, R K, Ribeiro, P A P
- Database ID:
- RPEP-05109
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
Why would too much protein reduce growth in fish?
Excess protein must be metabolized and excreted, which costs energy. The fish also produced more satiety hormones (CCK, PYY) and less appetite-stimulating ghrelin, likely eating less and diverting energy from growth to protein metabolism.
Are fish appetite hormones the same as human ones?
Very similar. Ghrelin stimulates appetite in both fish and humans, while CCK and peptide YY promote satiety. This evolutionary conservation means fish studies can inform our understanding of appetite regulation across species.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-05109APA
Santos, W M; Costa, L S; López-Olmeda, J F; Costa, N C S; Santos, F A C; Oliveira, C G; Guilherme, H O; Bahiense, R N; Luz, R K; Ribeiro, P A P. (2020). Dietary protein modulates digestive enzyme activities and gene expression in red tilapia juveniles.. Animal : an international journal of animal bioscience, 14(9), 1802-1810. https://doi.org/10.1017/S1751731120000543
MLA
Santos, W M, et al. "Dietary protein modulates digestive enzyme activities and gene expression in red tilapia juveniles.." Animal : an international journal of animal bioscience, 2020. https://doi.org/10.1017/S1751731120000543
RethinkPeptides
RethinkPeptides Research Database. "Dietary protein modulates digestive enzyme activities and ge..." RPEP-05109. Retrieved from https://rethinkpeptides.com/research/santos-2020-dietary-protein-modulates-digestive
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.