The effect of docosahexaenoic acid on the expression of hepatic genes in pigs
Date Issued
2005
Date
2005
Author(s)
Chang, Wei-Chun
DOI
zh-TW
Abstract
Docosahexaenoic acid (DHA) is one of the polyunsaturated fatty acids that can decrease gene expression of a transcription factor, sterol regulatory element-binding protein-1 (SREBP-1). In mammals, SREBP1 regulates the function of a group of lipogenic genes. Through the reduction of lipogenic genes, DHA may reduce lipid accumulation in animals. Besides the regulation on lipogenic genes, DHA may have other effects on animal physiology.
Therefore, the first purpose of this study was to determine whether DHA influenced the expression of liver fatty-acid binding protein (L-FABP) and albumin to affect fatty acid transportation. FABP is a cytosolic protein which has low molecular weight (12 to 15 kD) and high affinity in binding fatty acids. Albumin is produced in the liver and functions as a carrier for free fatty acids in the blood stream. In the first experiment, pigs were fed with either 2% DHA oil (n-3 fatty acid) or 2% tallow (saturated fatty acid) containing diet for 18d. In the second experiment, pigs were fed with 10% DHA oil , 10% tallow or 10% soybean oil (n-6 fatty acid) containing diet for 2d.We found that neither 2% dietary DHA for 18d nor 10% dietary DHA for 2d had a significant effect on the expression of L-FABP and albumin genes. These data demonstrated that different dietary fatty acid composition did not differentially affect the expression of L-FABP and albumin in the livers of the pigs.
In order to study which hepatic genes were affected by dietary DHA in pigs, we extracted mRNA from pig livers either fed with diets containing 2% DHA oil or 2% tallow for 18d. Suppression subtractive hybridization was used to explore genes that were specifically regulated by DHA. After subtraction, we got 288 cDNA fragments differentially expressed between livers from pigs either fed with 2% DHA oil or 2% tallow for 18d. The sequences of these specific cDNA fragments were compared with sequences from GenBank database of NCBI (http://www.ncbi.nlm.nih.gov/). After colony array screening, we found that 7 genes were differentially expressed. Northern analysis data showed that hepatic serum amyloid A protein (SAA) was upregulated by dietary DHA. We have confirmed that both treatments with 2% DHA oil for 18d and 10% DHA oil for 2d significantly increased the expression of SAA when compared with the control group （P<0.05）. The data showed that dietary DHA upregulated the expression of SAA in porcine liver. Whether elevated SAA has other physiological effect requires further demonstration.
Therefore, the first purpose of this study was to determine whether DHA influenced the expression of liver fatty-acid binding protein (L-FABP) and albumin to affect fatty acid transportation. FABP is a cytosolic protein which has low molecular weight (12 to 15 kD) and high affinity in binding fatty acids. Albumin is produced in the liver and functions as a carrier for free fatty acids in the blood stream. In the first experiment, pigs were fed with either 2% DHA oil (n-3 fatty acid) or 2% tallow (saturated fatty acid) containing diet for 18d. In the second experiment, pigs were fed with 10% DHA oil , 10% tallow or 10% soybean oil (n-6 fatty acid) containing diet for 2d.We found that neither 2% dietary DHA for 18d nor 10% dietary DHA for 2d had a significant effect on the expression of L-FABP and albumin genes. These data demonstrated that different dietary fatty acid composition did not differentially affect the expression of L-FABP and albumin in the livers of the pigs.
In order to study which hepatic genes were affected by dietary DHA in pigs, we extracted mRNA from pig livers either fed with diets containing 2% DHA oil or 2% tallow for 18d. Suppression subtractive hybridization was used to explore genes that were specifically regulated by DHA. After subtraction, we got 288 cDNA fragments differentially expressed between livers from pigs either fed with 2% DHA oil or 2% tallow for 18d. The sequences of these specific cDNA fragments were compared with sequences from GenBank database of NCBI (http://www.ncbi.nlm.nih.gov/). After colony array screening, we found that 7 genes were differentially expressed. Northern analysis data showed that hepatic serum amyloid A protein (SAA) was upregulated by dietary DHA. We have confirmed that both treatments with 2% DHA oil for 18d and 10% DHA oil for 2d significantly increased the expression of SAA when compared with the control group （P<0.05）. The data showed that dietary DHA upregulated the expression of SAA in porcine liver. Whether elevated SAA has other physiological effect requires further demonstration.
Subjects
二十二碳六烯酸
docosahexaenoic acid
Type
thesis