Intramuscular fat deposition in rabbits: insights into host-microbiome biological mechanisms
- Autores: Agostina Zubiri Gaitán
- Directores de la Tesis: María del Pilar Hernández Pérez (dir. tes.), Agustín Blasco (dir. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2024
- Idioma: inglés
- Tribunal Calificador de la Tesis: Andrés Moya Simarro (presid.), Luca Fontanesi (secret.), Amélia Camarinha Silva (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología de la Producción Animal por la Universitat Politècnica de València
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
The Thesis aimed to study the genetically determined mechanisms involved in intramuscular fat (IMF) deposition, using two lines divergently selected for IMF in Longissimus thoracis et Lumborum (LTL) muscle of rabbits (H and L lines). It comprises five studies focused on studying the host and microbiome roles using metabolomics and metagenomics approaches.
The response to selection in the 10th generation was 0.49g IMF/100g LTL, equivalent to 3.8 standard deviations (SD). Selection led to a positive correlated response in carcass adiposity, and to changes in the fatty acids (FA) of LTL, showing greater saturated (H-L= 5.05g/100g IMF) and monounsaturated FA (H-L= 5.04g/100g IMF) in the H line. No differences were found in liver fat, but they were found in its FA profile, being the most notorious the lower C15:0 (H-L= -0.04g/100g lipids) and C17:0 (H-L= -0.09g/100g lipids) in the H line, which could be due to different microbial digestion.
The plasma metabolomics analysis identified 393 differential metabolites with 95% classification accuracy, and 383 metabolites with linear adjustment to IMF and 65% prediction ability, from which 322 overlapped with differences ranging from -6.04 to +1.97 SD. Lipids were greater in the L line (e.g., triglycerides, secondary bile acids, FA) while carnitine was lower, suggesting greater intestinal lipids absorption in the L line, followed by their lower uptake and storage, possibly related to lower FA ß oxidation. Among amino acids, branched-chain (BCAA) and aromatic (AAA) stood out, indicating lower BCAA gut degradation in the H line followed by greater host catabolism, and a complex host-microbiome AAA metabolism.
The caecum metagenomics analysis confirmed the microbial relevance in IMF development, identifying changes in its composition and functionality. The microbial composition analysis defined two enterotypes with 51 microbial genera and 91% classification accuracy. The H-enterotype was enriched in Hungateiclostridium, Limosilactobacillus, Legionella, Lysinibacillus, Phorphyromonas, Methanosphaera and Desulfovibrio, and the L-enterotype in Escherichia, Fonticella, Candidatus Amulumruptor, Methanobrevicater, Exiguobacterium, Flintibacter and Coprococcus. A compositional balance was proposed as biomarker to predict the genetic predisposition to IMF deposition, composed of 26 microbial genera, with 93% classification accuracy and 69% prediction ability.
The microbial functionality analysis identified 240 differential microbial genes (MG) with 95% classification accuracy, and 230 MG with linear adjustment to IMF and 79% prediction ability, from which 122 overlapped with differences ranging from -0.75 to +0.73 SD and related to numerous metabolisms. In the H line, greater lipopolysaccharides and peptidoglycans biosynthesis, related to fat-mass development, AAA biosynthesis, related to associated disorders of increased fat deposition, and propionate to acetate conversion, related to greater liver lipogenesis and lower C15:0 and C17:0 synthesis, were found. Additionally, greater BCAA degradation was found in the L line, related to lower triglycerides synthesis in the liver.
The caecum metabolomics analysis identified 142 differential metabolites with 99% classification accuracy and differences ranging from -1.03 to +1.19 SD; 156 related to IMF in the H line with 61% prediction ability; and 107 related to IMF in the L line with 57% prediction ability. Differences found in purine metabolism could suggest greater energy and nitrogen utilization efficiencies in the L line, while those in secondary bile acids, AAA and BCAA were consistent with the previous results. A compositional balance composed of two secondary bile acids and two proteins by-products with 88% classification accuracy was proposed as biomarker, suggesting that the interaction between lipids absorption and dietary proteins metabolism influences IMF. If validated, it could be used to predict the genetic predisposition to IMF deposition.
