title: Expression of enzymes and key regulators of lipid synthesis is upregulated in adipose tissue during CLA-induced milk fat depression in dairy cows.
abstract: Milk fat depression (MFD) is a naturally occurring condition in dairy cows where milk fat synthesis is inhibited by intermediates of ruminal biohydrogenation. One of these bioactive fatty acids (FA), trans-10, cis-12 conjugated linoleic acid (CLA), decreases milk fat synthesis through transcriptional downregulation of genes involved in mammary lipid synthesis. Energy partitioning during MFD is not well characterized because of the complexity of observing energy metabolism in ruminant animals. To investigate energy partitioning during MFD, adipose tissue biopsies were taken from 4 cows arranged in a switchback design. Treatments were control and 4-d abomasal infusion of trans-10, cis-12 CLA (7.5 g/d). CLA decreased milk fat yield by 38% and milk fat content by 34%, but yields of milk and other milk components were unchanged. In contrast to reported changes in mammary tissue, adipose tissue expression of lipid synthesis enzymes, including lipoprotein lipase, FA synthase, stearoyl-CoA desaturase, and FA binding protein 4, was increased. Expression of regulators of lipid synthesis, including sterol-response element binding protein 1, thyroid hormone responsive spot 14, and PPARgamma, also increased in adipose tissue. Thus, a CLA dose resulting in near maximal inhibition of mammary lipid synthesis resulted in increased expression of lipid synthesis-related genes in adipose tissue. A meta-analysis of intake response during CLA infusion was conducted to extend the investigation of energy metabolism during MFD. Voluntary intake decreased (P < 0.001) by 1.5 kg/d during CLA-induced MFD in the 14 studies analyzed, but the reduction in intake only partially accounts for the energy spared from reduced milk fat synthesis. Results are consistent with energy spared from the reduction in milk fat synthesis being partitioned toward adipose tissue fat stores during short-term MFD.
authors.affiliation: Department of Animal Science, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Harvatine
authors.forename: James W
authors.initials: JW
authors.lastname: Perfield
authors.forename: Dale E
authors.initials: DE
authors.lastname: Bauman
mesh_terms: D000018:Abomasum / Q000187:drug effects; D000273:Adipose Tissue / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D005223:Fats / Q000032:analysis*; D064429:Fatty Acid Synthases / Q000235:genetics; D050556:Fatty Acid-Binding Proteins / Q000235:genetics; D005260:Female; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage*; D008055:Lipids / Q000096:biosynthesis / Q000235:genetics*; D008071:Lipoprotein Lipase / Q000235:genetics; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism; D008892:Milk / Q000737:chemistry* / Q000187:drug effects; D013230:Stearoyl-CoA Desaturase / Q000235:genetics
chemical_list: D005223:Fats; D050556:Fatty Acid-Binding Proteins; D044243:Linoleic Acids, Conjugated; D008055:Lipids; C496197:trans-10,cis-12-conjugated linoleic acid; D013230:Stearoyl-CoA Desaturase; D064429:Fatty Acid Synthases; D008071:Lipoprotein Lipase