title: Insulin Signaling in Liver and Adipose Tissues in Periparturient Dairy Cows Supplemented with Dietary Nicotinic Acid.
abstract: The glucose homeostasis in dairy cattle is very well controlled, in line with the metabolic adaptation during the periparturient period. Former studies showed that nicotinic acid (NA) lowered plasma non-esterified fatty acids (NEFA) concentrations and increased insulin sensitivity in dairy cows. Thus, the purpose of this study was to investigate whether the expression of proteins involved in hepatic and adipose insulin signaling and protein expression of hepatic glucose transporter 2 (GLUT2) were affected by dietary NA and dietary concentrate intake in periparturient dairy cows. Twenty pluriparous German Holstein cows were fed with the same diet from about 21 days before the expected calving date (d-21) to calving. After calving, cows were randomly assigned in 4 groups and fed with diets different in concentrate proportion ("HC" with 60:40% or "LC" with 30:70% concentrate-to-roughage ratio) and supplemented with NA (24 g/day) (NA) or without (CON) until d21. Biopsy samples were taken from the liver, subcutaneous (SCAT) and retroperitoneal (RPAT) adipose tissues at d-21 and d21. Protein expression of insulin signaling molecules (insulin receptor (INSR), phosphatidylinositol-3-kinase (PI3K), protein kinase Cζ (PKCζ)) and hepatic GLUT2 was measured by Western Blotting. The ratio of protein expression at d21/at d-21 was calculated and statistically evaluated for the effects of time and diet. Cows in HC had significantly higher dietary energy intake than cows in LC. In RPAT a decrease in PI3K and PKCζ expression was found in all groups, irrespectively of diet. In the liver, the GLUT2 expression was significantly lower in cows in NA compared with cows in CON. In conclusion, insulin signaling might be decreased in RPAT over time without any effect of diet. NA was able to modulate hepatic GLUT2 expression, but its physiological role is unclear.
authors.affiliation: Department of Physiology, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Asako
authors.initials: A
authors.lastname: Kinoshita
authors.affiliation: Institute of Animal Science, University of Hohenheim, Stuttgart, Germany.
authors.forename: Ákos
authors.initials: Á
authors.lastname: Kenéz
authors.affiliation: Clinic for Ruminants with Ambulatory and Herd Health Services at the Center of Veterinary Clinical Medicine, Ludwig-Maximilians-University Munich, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Locher
authors.affiliation: Institute of Animal Nutrition, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute, Braunschweig, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Meyer
authors.affiliation: Institute of Animal Nutrition, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute, Braunschweig, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Dänicke
authors.affiliation: Clinic for Cattle, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Rehage
authors.affiliation: Institute of Animal Science, University of Hohenheim, Stuttgart, Germany.
authors.forename: Korinna
authors.initials: K
authors.lastname: Huber
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose; D002417:Cattle; D019587:Dietary Supplements; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D015870:Gene Expression; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D009525:Niacin / Q000008:administration & dosage*; D009536:Niacinamide / Q000097:blood; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D049590:Postpartum Period; D011247:Pregnancy; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000099221:Protein Kinase C zeta
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D051273:Glucose Transporter Type 2; D007328:Insulin; D009525:Niacin; D009536:Niacinamide; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D011972:Receptor, Insulin; D000099221:Protein Kinase C zeta