|Name:||Geetha C. Jayan|
|Title:||Activity and mRNA abundance of enzymes for fatty acid synthesis and desaturation in mammary cell cultures|
|Degree:||Doctor of Philosophy|
|Department:||Animal Science (Dairy)|
|Committee Chair:||Dr. J. H. Herbein|
|Committee Members:||Dr. T. W. Keenan|
|Dr. E. A. Wong|
|Dr. R. E. Pearson|
|Dr. S. E. Duncan|
|Keywords:||milk fat, acetyl-CoA carboxylase, fatty acid synthetase, stearoyl-CoA desaturase, conjugated linoleic acid, trans-vaccenic acid|
|Date of defense:||August 14. 1998|
|Availability:||Release the entire work for Virginia Tech access only.
After one year release worldwide only with written permission of the student and the advisory committee chair.
Activity and mRNA abundance of enzymes for fatty acid synthesis and desaturation in mammary cell cultures
Geetha C. Jayan, firstname.lastname@example.org
Department of Dairy Science Virginia Tech, Blacksburg, VA 24061, USA
Dr. Joseph H. Herbein, email@example.com
The effect of exogenous unsaturated fatty acids on cellular fatty acid biosynthesis in mammary cells was examined. Under normal situations, even though the diet of a dairy cow contains considerable amounts of unsaturated fatty acids, viz. oleic acid (18:1) and linoleic acid (18:2), the major 18-carbon fatty acid that enters the circulation post-ruminally for delivery to the mammary gland is saturated fatty acid, viz. stearic acid (18:0). This is due to extensive ruminal biohydrogenation of unsaturated fatty acids. Studies have indicated that saturated fatty acids such as 18:0 are enhancers and that certain unsaturated fatty acids are inhibitors of de novo fatty acid synthesis in tissues such as the liver and adipose tissue. The present study investigated the effect of cis and trans isomers of 18:1 and 18:2 on de novo fatty acid synthesis and desaturation in mouse and bovine mammary epithelial cell cultures, and compared it with the effect caused by 18:0. In the first experiment 12.5, 25, 50 or 100 micromoles stearic acid (SA), oleic acid (OA), elaidic acid (EA), trans-vaccenic acid (TVA), linoleic acid (LA) or conjugated linoleic acid (CLA) were supplemented in the media of mouse mammary epithelial (MME) cells that were grown to confluence in Dulbecco's modified Eagle's medium (DMEM). As indicated by cellular palmitic acid (16:0) content and fatty acid synthetase (FAS) activity, when compared with SA all unsaturated fatty acid treatments inhibited de novo fatty acid synthesis in MME cells. In addition, OA at all concentrations and LA and CLA at 50 and 100 micromoles inhibited cellular stearoyl-CoA desaturase (SCD) activity and mRNA abundance. However, EA and TVA, when compared with SA, enhanced SCD activity and mRNA abundance at 12.5 and 25 micromoles. In the second experiment 25, 50 or 100 micromoles SA, OA, TVA, LA or CLA were supplemented in the media of bovine mammary epithelial cells that were grown to confluence in DMEM. As indicated by cellular 16:0 content, acetyl-CoA carboxylase (ACC) activity and FAS activity, treatment with the unsaturated fatty acids inhibited de novo fatty acid synthesis at all concentrations, when compared with SA. Unsaturated fatty acid treatments also reduced the abundance of ACC and FAS mRNA in the cells. When compared with SA at all treatment-concentrations, OA and LA inhibited whereas TVA and CLA enhanced cellular SCD activity and mRNA abundance in the bovine cells. In both cell types, CLA and TVA appeared to be the most potent inhibitors of saturated fatty acid biosynthesis.
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