Unraveling the Molecular Mechanism of Fat Deposition Through Dietary Manipulation and Feed Restriction

This study was conducted to test the hypothesis that enriching developing adipose tissue in long chain omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) reduces adiposity compared to enrichment in n-6 LCUFA. Sixty Cobb 500 broiler breeders were fed a diet containing either 5% fish oil (FO) or corn oil (CO). After four weeks, fertilized eggs were collected and hatched, and all chicks were fed the same corn oil-based broiler starter diet. At days 7 and 14 post-hatch, chicks in each group were weighed, euthanized and blood, liver, breast, and subcutaneous and abdominal fat samples harvested. Gas or liquid chromatography and mass spectrometry were used to determine the effects of diet on fatty acid profiles of tissue triglyceride, free fatty acid, phospholipid pools and protein expression. RNA sequencing and PCR was used to determine the effect on gene expression. Mixed model ANOVA and least square means were used to identify effects of maternal diet and age*diet interactions on chick phenotypes (SAS v9.4, Cary NC). Differentially expressed genes were determined using the DESeq2 R package. Hen dietary fat source did not significantly affect performance. Phospholipids and total lipids in muscle and adipose tissue of FO-chicks were significantly enriched in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) species relative to CO-chicks, with corresponding reductions in n-6 LCPUFA (p<0.05). FO-chicks had significantly lower abdominal and subcutaneous fat deposition (p<0.05). Proteomics identified 95 known proteins that differed in abundance between FO and CO adipose tissue. KEGG pathway enrichment analysis of differentially abundant proteins indicated that hen FO feeding significantly suppressed glycolysis (n=5 proteins) and altered the cytoskeletal architecture of adipocytes and lipid droplet proteins (n=11 proteins). Hen FO resulted in 190 upregulated and 46 downregulated genes 7 days and 13 upregulated and 32 down regulated genes at 14 days Combined, these results suggest that hen FO programs reduced adiposity by promoting differentiation of adipocytes with reduced capacity for fatty acid uptake and storage. Future studies are needed to identify long term effects of this method of programming and additional strategies that may be necessary to sustain its effect.