Abstract
An experiment was conducted on broiler chickens to study the effects of different dietary fats (Conjugated linoleic acid (CLA), fish oil, soybean oil, or their mixtures, as well as palm oil, as a more saturated fat), with a as fed dose of 7% for single fat and 3.5 + 3.5% for the mixtures, on Peroxisome Proliferator-Activated Receptors (PPARs) gene expression and its relation with body fat deposits. The CLA used in this experiment was CLA LUTA60 which contained 60% CLA, so 7% and 3.5% dietary inclusions of CLA LUTA60 were equal to 4.2% and 2.1% CLA, respectively. Higher abdominal fat pad was found in broiler chickens fed with a diet containing palm oil compared to chickens in the other experimental groups (P ≤ 0.05). The diets containing CLA resulted in an increased fat deposition in the liver of broiler chickens (P ≤ 0.05). The only exception was related to the birds fed with diets containing palm oil or fish oil + soybean oil, where contents of liver fat were compared to the CLA + fish oil treatment. PPARγ gene in adipose tissue of chickens fed with palm oil diet was up-regulated compared to other treatments (P ≤ 0.001), whereas no significant differences were found in adipose PPARγ gene expression between chickens fed with diets containing CLA, fish oil, soybean oil or the mixture of these fats. On the other hand, the PPARα gene expression in liver tissue was up-regulated in response to the dietary fish oil inclusion and the differences were also significant for both fish oil and CLA + fish oil diets compared to the diets with palm oil, soybean oil or CLA as the only oil source (P ≤ 0.001). In conclusion, the results of present study showed that there was a relationship between the adipose PPARγ gene up-regulation and abdominal fat pad deposition for birds fed with palm oil diet, while no deference was detected in n-3 and n-6 fatty acids, as well as CLA on PPARγ down regulation in comparison to a more saturated fat. When used on its own, fish oil was found to be a more effective fat in up-regulating hepatic PPARα gene expression and this effect was related to a less fat deposition in liver tissue. A negative correlation coefficient (−0.3) between PPARα relative gene expression and liver tissue fat content confirm the anti-lipogenic effect of PPARα, however, the change in these parameters was not completely parallel.
Highlights
Broiler chickens have a high ability for lipid biosynthesis
Dietary palm oil significantly increased abdominal fat pad deposition (P ≤ 0.05), but no differences were found in this respect between other experimental groups
The only exceptions were related to the birds fed Palm oil (PO) or Fish oil (FO) + Soybean oil (SO) diets; their liver fat content was comparable to the Conjugated linoleic acid (CLA) + FO treatment
Summary
Broiler chickens have a high ability for lipid biosynthesis. It is reported that total body lipids of growing chickens doubles every 5.5 days, and they reach to the maximum rate of hepatic fatty acid synthesis at 7 weeks of age [1,2].Liver is the main site of lipogenesis in birds and based on equal weight, this is 20 times more than adipose tissue lipogenesis capacity [3]. It is reported that total body lipids of growing chickens doubles every 5.5 days, and they reach to the maximum rate of hepatic fatty acid synthesis at 7 weeks of age [1,2]. Adipose tissue is the major site of lipid synthesis in pigs, ruminants and laboratory rodents [4]. Previous reports suggest that in both birds and mammals, PUFAs reduce lipid synthesis [6,7,8,9,10] and increase fatty acid oxidation [10,11,12] and diet-mediated thermogenesis [13], while saturated and monounsaturated fatty acids have no inhibitory effects on body fat deposition [8]
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