Effect of source and duration of feeding omega-3 and omega-9 protected fatty acids on the expression of some genes involved in fat metabolism in fattening lambs

Introduction: Based on current knowledge, it has been proven that many edible ingredients in addition to meeting the needs of creatures, in terms of energy and protein, contain compounds that affect cellular actions and intracellular signaling pathways and can temporarily or permanently change the function of the cell. The use of molecular biology tools and genetic research defines the mechanisms through which gene expression is affected by food, and conversely, these genes also affect the absorption of food, metabolism, and excretion. From the point of view of nutrigenomics, dietary nutrients are signals that are received by sensitive cell systems and can affect the expression of genes and proteins and the production of metabolites. Nutritional manipulations and strategies are key tools to influence ruminant production. Fatty acids act on the nucleus by binding to and regulating the activity of specific nuclear receptors or transcription factors, thus playing a central role in regulating the expression of genes involved in fatty acid uptake by muscle cells. Interactions between diet nutrients and the expression of genes involved in lipid metabolism have many possibilities regarding the deposition of fatty acids in the tissue. The study of gene expression has enabled clarification of the mode of fatty acid metabolism in muscle and the accumulation of intramuscular fat or marbling and the role of the genes that promote fatty acid oxidation and mitochondrial respiration in the liver muscle and adipose tissue. Polyunsaturated fatty acids with multiple double bonds (PUFA) and monounsaturated fatty acids with one double bond (MUFA) have received much attention in the last decade, and their health benefits are increasingly evident. Therefore, this study investigated the effect of using calcium salts of fish oil, olive oil, and saturated fat on the expression of some genes related to fat metabolism in Lori Bakhtiari×Romanov fattening lambs. Materials and methods: This study was carried out at the educational research station of the Department of Animal Science of the College of Agriculture and Natural Resources, University of Tehran. 49 male lambs aged four to five months with an average initial weight of 29.97 ± 0.88 kg were divided into seven groups of seven lambs in a completely randomized design. The experiment consisted of seven treatments with a basic diet as follows: 1) Basic diet without fat powder (control), 2 and 3) Basic diet with calcium salt of fish oil (rich in omega-3 fatty acids) in the amount of 2% dry matter of the diet for 90 and 45 days, respectively, 4 and 5) Basic diet with calcium salt of olive oil (rich in omega-9 fatty acids) at the rate of 2% dry matter of the diet for 90 and 45 days, respectively, 6 and 7) Basic diet with saturated fat powder in the amount of 2% dry matter of the diet for 90 and 45 days, respectively. Rations were adjusted based on the NRC Sheep and Goat and using the fifth version of CNCPS (The Cornell Net Carbohydrate and Protein System) software so that they are the same in terms of energy and protein. Twenty-eight lambs were slaughtered and a liver sample was taken for nutrigenomics studies. Total RNA was extracted from liver tissue samples using the RNA extraction kit produced by Dena Bio Asia Company (Mashhad) and according to the protocol provided with the kit. The expression of four main genes involved in lipid metabolism in liver tissue was investigated to provide comprehensive information on the effects of omega-3, omega-9 fatty acids, and saturated fat at the molecular level. Results and discussion: The results showed that feeding with calcium salts of fish oil, olive oil, and saturated fat, both in the whole 90 days or the last 45 days of the fattening period, had no significant effect on the expression of FADS1 and FADS2 genes in liver tissue compared to the control group. However, the use of calcium salts of fish and olive oils in periods of 90 and 45 days significantly increased the hepatic mRNA expression of the CPT1 gene (P=0.001) and ACOX1 gene mRNA expression in liver tissue compared to control and saturated fat treatments (P=0.002). The CPT1 enzyme is responsible for a mitochondrial transport system and plays a key role in controlling the oxidation of long-chain fatty acids and stimulating mitochondrial β-oxidation. Conclusions: The results of this study showed that diet supplementation with calcium salts of fish and olive unsaturated fatty acids, regardless of the period of consumption, increased the expression of genes involved in the lipolysis of liver tissue fats of lambs.