title: Glycogenic induction of thyroid hormone conversion and leptin system activation in the liver of postpartum dairy cows.
abstract: In the regulation of energy metabolism, the liver plays an important role in the reinforcement of energy production. In periparturient cows the energy homeostasis turns into a negative energy balance that may shift the physiological regulation of energy balance towards pathological processes. Propylene glycol (PG), as a complementary source of energy used in the nutrition of dairy cows, alters systemic thyroid hormone economy; however, the exact mechanism through which highly glycogenic feed supplements impact liver metabolism is little known. Previous studies showed that only leptin receptors are expressed in the liver of cows, and now we report that leptin mRNA is expressed in the liver of cows as well. The present results show that the mRNA of leptin and its receptors are differentially modulated by the increased energy content of the feed consumed. Simultaneous changes in hepatic type I deiodinase activity suggest that hepatic modulation of the leptin system by PG supplementation may be mediated by an increased local thyroxine-triiodothyronine conversion. Since PG supplementation with simultaneous T4-T3 turnover and increased hepatic leptin- and short-form leptin receptor mRNA were not associated with a significant change in hepatic total lipid levels, it is suggested that the leptin system, directly or indirectly modulated by thyroid hormones, may represent a local defence mechanism to prevent fatty liver formation.
authors.affiliation: Department of Physiology and Biochemistry, Faculty of Veterinary Science, Szent István University, István u. 2, H-1078 Budapest, Hungary. gyorffy.andrea@aotk.szie.hu
authors.forename: Andrea
authors.initials: A
authors.lastname: Gyorffy
authors.forename: Mónika
authors.initials: M
authors.lastname: Keresztes
authors.forename: Vera
authors.initials: V
authors.lastname: Faigl
authors.forename: Vilmos László
authors.initials: VL
authors.lastname: Frenyó
authors.forename: Margit
authors.initials: M
authors.lastname: Kulcsár
authors.forename: Tibor
authors.initials: T
authors.lastname: Gaál
authors.forename: Miklós
authors.initials: M
authors.lastname: Mézes
authors.forename: Attila
authors.initials: A
authors.lastname: Zsarnovszky
authors.forename: Gyula
authors.initials: G
authors.lastname: Huszenicza
authors.forename: Tibor
authors.initials: T
authors.lastname: Bartha
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism*; D005260:Female; D020738:Leptin / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D049590:Postpartum Period / Q000187:drug effects* / Q000378:metabolism; D019946:Propylene Glycol / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013963:Thyroid Hormones / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D020738:Leptin; D012333:RNA, Messenger; D013963:Thyroid Hormones; D019946:Propylene Glycol