title: Effects of heat stress on carbohydrate and lipid metabolism in growing pigs.
abstract: Heat stress (HS) jeopardizes human and animal health and reduces animal agriculture productivity; however, its pathophysiology is not well understood. Study objectives were to evaluate the direct effects of HS on carbohydrate and lipid metabolism. Female pigs (57 ± 5 kg body weight) were subjected to two experimental periods. During period 1, all pigs remained in thermoneutral conditions (TN; 20°C) and were ad libitum fed. During period 2, pigs were exposed to: (1) constant HS conditions (32°C) and fed ad libitum (n = 7), or (2) TN conditions and pair-fed (PFTN; n = 10) to minimize the confounding effects of dissimilar feed intake. All pigs received an intravenous glucose tolerance test (GTT) and an epinephrine challenge (EC) in period 1, and during the early and late phases of period 2. After 8 days of environmental exposure, all pigs were killed and tissue samples were collected. Despite a similar reduction in feed intake (39%), HS pigs tended to have decreased circulating nonesterified fatty acids (NEFA; 20%) and a blunted NEFA response (71%) to the EC compared to PFTN pigs. During early exposure, HS increased basal circulating C-peptide (55%) and decreased the insulinogenic index (45%) in response to the GTT. Heat-stressed pigs had a reduced T3 to T4 ratio (56%) and hepatic 5'-deiodinase activity (58%). After 8 days, HS decreased or tended to decrease the expression of genes involved in oxidative phosphorylation in liver and skeletal muscle, and ATGL in adipose tissue. In summary, HS markedly alters both lipid and carbohydrate metabolism independently of nutrient intake.
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: M
authors.initials: M
authors.lastname: Victoria Sanz Fernandez
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Jay S
authors.initials: JS
authors.lastname: Johnson
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Mohannad
authors.initials: M
authors.lastname: Abuajamieh
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Sara K
authors.initials: SK
authors.lastname: Stoakes
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Jacob T
authors.initials: JT
authors.lastname: Seibert
authors.affiliation: Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, Utah, USA.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Cox
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, USA.
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Kahl
authors.affiliation: Animal Biosciences and Biotechnology Laboratory, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland, USA.
authors.forename: Theodore H
authors.initials: TH
authors.lastname: Elsasser
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Jason W
authors.initials: JW
authors.lastname: Ross
authors.affiliation: Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, Utah, USA.
authors.forename: S Clay
authors.initials: SC
authors.lastname: Isom
authors.affiliation: Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Rhoads
authors.affiliation: Department of Animal Science, Iowa State University, Ames, Iowa, USA.
authors.forename: Lance H
authors.initials: LH
authors.lastname: Baumgard
keywords: Epinephrine challenge; glucose tolerance test; heat stress; metabolism; thyroid hormones