Abstract
To study the acute effect of dietary docosahexaenoic acid (DHA, C22:6) on the expression of adipocyte determination and differentiation-dependent factor 1 (ADD1) mRNA in pig tissues, weaned, crossbred pigs (28 d of age) were fed with either 10% (on as-fed basis) tallow (high stearic acid), soybean oil (high linoleic acid), or high DHA algal oil for 2 d. The plasma and liver DHA reflected the composition of the diet. The adipose tissue and skeletal muscle DHA did not reflect the diet in the short term feeding. The results also showed that the diet containing 10% algal DHA oil significantly decreased the total plasma cholesterol (39%) and triacylglycerol (TG; 46%) in the pigs. Soybean oil significantly decreased plasma TG (13.7%; p<0.05), but did not have an effect on plasma cholesterol. The data indicate that different dietary fatty acid compositions have different effects on plasma lipids. The ADD1 mRNA was decreased (p<0.05) in the liver of DHA oil-treated pigs compared with the tallow-treated pigs. The diets did not have significant effect on the ADD1 mRNA in adipose tissue. Addition of algal DHA oil in the diet increased acyl CoA oxidase (ACO) mRNA concentration in the liver, suggesting that dietary DHA treatment increases peroxisomal fatty acid oxidation in the liver. However, dietary soybean oil supplementation did not affect mRNA concentrations of ADD1 or ACO in the tissues of pigs. Because ADD1 increases the expression of genes associated with lipogenesis, and ACO is able to promote fatty acid oxidation, feeding DHA oil may change the utilization of fatty acids through changing the expression of ADD1 and ACO. Therefore, feeding pigs with high DHA may lead to lower body fat deposition. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 10 : 1451-1456)
Highlights
Dietary fatty acids can be incorporated to a large extent into tissues (Sink et al, 1964; Mason and Sewell, 1967; Eder et al, 2001) and plasma lipids in pigs (Smith et al, 1996; Ding et al, 2003a)
Plasma triacylglycerol and cholesterol Triacylglycerol and cholesterol content in the plasma were affected by the dietary docosahexaenoic acid (DHA) oil supplementation in pigs (Table 2)
The current study showed that while the hepatic ADD1 mRNA concentration was sensitive to short term dietary DHA oil treatment, it was not affected by the linoleic acid enrichment, suggesting that DHA has greater potential in inhibiting the gene expression of lipogenic genes in the porcine liver than linoleic acid
Summary
Dietary fatty acids can be incorporated to a large extent into tissues (Sink et al, 1964; Mason and Sewell, 1967; Eder et al, 2001) and plasma lipids in pigs (Smith et al, 1996; Ding et al, 2003a). Docosahexaenoic acid (DHA; C22:6) has no effect on adipocyte differentiation but reduces the lipogenic transcription factor adipocyte determination and differentiation-dependent factor 1 (ADD1) mRNA (Ding et al, 2002). This transcription factor is known as sterol regulatory element-binding protein 1c (SREBP-1c; Kim and Spiegelman, 1996). High DHA algal oil was added to the pig diet to test the hypothesis that dietary DHA has the effect on inhibiting ADD1 mRNA in both adipose tissue and liver. Transcripts for acyl CoA oxidase (ACO), the enzyme associated with peroxisomal fatty acid oxidation was measured in adipose tissue, liver, and skeletal muscle
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