title: The effect of ractopamine hydrochloride on gene expression in adipose tissues of finishing pigs.
abstract: The long-term effect of feeding the catecholamine analog ractopamine (RAC; ractopamine hydrochloride, Elanco Animal Health, Indianapolis, IN) on the expression of genes involved in energy and lipid metabolism in subcutaneous adipose tissue was studied. Large White pigs (84 kg) were fed corn- and soybean meal-based diets supplemented with 0, 20, or 60 mg/kg of RAC for 14, 28, or 42 d. Expression (mRNA abundance) in adipose tissue of sterol regulatory binding protein-1 (SREBP-1), PPARα, PPARγ2, fatty acid synthase (FAS), glucose transporter 4 (GLUT4), and stearoyl-CoA desaturase was determined by Northern blotting. Feed intakes did not differ, and RAC (20 and 60 mg/kg) improved BW gain at d 14, 28, and 42 (P < 0.05) and increased loin eye area (measured on d 42 only; P < 0.05). Expression of SREBP-1 and PPARγ2 declined (P < 0.05) with RAC by d 28 and 42, whereas expression of PPARα was increased (P < 0.05) on d 14, 28, and 42. After 14 d, expression of FAS and GLUT4 was decreased (P < 0.05) with 60 mg/kg of RAC, whereas both RAC concentrations attenuated FAS expression on d 28 and 42. Overall, adipose tissue stearoyl-CoA desaturase expression was not affected by RAC but showed somewhat less expression (P < 0.15) on d 28 at 60 mg/kg of RAC. Although prolonged, chronic RAC feeding most likely downregulates adipose tissue membrane β-adrenergic receptors, mRNA abundances of anabolic lipid metabolism transcription factors, glucose transporters, and enzymes (SREBP-1, PPARγ2, FAS, GLUT4) were still attenuated up to d 42. Conversely, a transcription factor related to oxidative metabolism expression (PPARα) was enhanced. We conclude that even after 42 d, RAC still decreased expression of lipogenic genes in adipose tissue by yet undefined cyclic adenosine monophosphate-directed mechanisms, but in contemporary lean pigs, this effect is likely of limited practical significance.
authors.affiliation: Department of Animal Sciences, Auburn University, Auburn, AL 36849-5415, USA.
authors.forename: C H C
authors.initials: CH
authors.lastname: Halsey
authors.forename: P S
authors.initials: PS
authors.lastname: Weber
authors.forename: S S
authors.initials: SS
authors.lastname: Reiter
authors.forename: B N
authors.initials: BN
authors.lastname: Stronach
authors.forename: J L
authors.initials: JL
authors.lastname: Bartosh
authors.forename: W G
authors.initials: WG
authors.lastname: Bergen
mesh_terms: D000818:Animals; D004734:Energy Metabolism; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D006133:Growth Substances / Q000494:pharmacology*; D050356:Lipid Metabolism; D008297:Male; D010627:Phenethylamines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects; D013230:Stearoyl-CoA Desaturase / Q000235:genetics / Q000378:metabolism; D050151:Subcutaneous Fat / Q000187:drug effects* / Q000378:metabolism; D034421:Sus scrofa / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D051275:Glucose Transporter Type 4; D006133:Growth Substances; D010627:Phenethylamines; D012333:RNA, Messenger; D014157:Transcription Factors; C060897:ractopamine; D013230:Stearoyl-CoA Desaturase; D064429:Fatty Acid Synthases