title: Intravenous infusions of glucose stimulate key lipogenic enzymes in adipose tissue of dairy cows in a dose-dependent manner.
abstract: The present study was investigated whether increasing amounts of glucose supply have a stimulatory effect on the mRNA abundance and activity of key lipogenic enzymes in adipose tissue of midlactation dairy cows. Twelve Holstein-Friesian dairy cows in midlactation were cannulated in the jugular vein and infused with either a 40% glucose solution (n=6) or saline (n=6). For glucose infusion cows, the infusion dose increased by 1.25%/d relative to the initial net energy for lactation (NEL) requirement until a maximum dose equating to a surplus of 30% NEL was reached on d 24. This maximum dose was maintained until d 28 and stopped thereafter (between d 29-32). Cows in the saline infusion group received an equivalent volume of 0.9% saline solution. Samples of subcutaneous adipose tissue were taken on d 0, 8, 16, 24, and 32 when surplus glucose reached 0, 10, 20, and 30% of the NEL requirement, respectively. The mRNA abundance of fatty acid synthase, cytoplasmic acetyl-coenzyme A synthetase, cytoplasmic glycerol 3-phosphate dehydrogenase-1, and glucose 6-phosphate dehydrogenase showed linear treatment × dose interactions with increasing mRNA abundance with increasing glucose dose. The increased mRNA abundance was paralleled by a linear treatment × dose interaction for fatty acid synthase and acetyl-coenzyme A synthetase enzymatic activities. The mRNA abundance of ATP-citrate lyase showed a tendency for linear treatment × dose interaction with increasing mRNA abundance with increasing glucose dose. The mRNA abundance of all tested enzymes, as well as the activities of fatty acid synthase and acetyl-coenzyme A synthetase, correlated with plasma glucose and serum insulin levels. In a multiple regression model, the predictive value of insulin was dominant over that of glucose. In conclusion, gradual increases in glucose supply upregulate key lipogenic enzymes in adipose tissue of midlactating dairy cows with linear dose dependency. Insulin appears to be critically involved in this regulation.
authors: Institute of Physiology, Pathophysiology and Biophysics, University of Veterinary Medicine Vienna, 1210 Vienna, Austria.
authors: Mirja
authors: M
authors: Carra
authors: Bahaa
authors: B
authors: Al-Trad
authors: Gregory B
authors: GB
authors: Penner
authors: Thomas
authors: T
authors: Wittek
authors: Gotthold
authors: G
authors: Gäbel
authors: Manfred
authors: M
authors: Für
authors: Jörg R
authors: JR
authors: Aschenbach
mesh_terms: D000106:Acetate-CoA Ligase / Q000235:genetics / Q000378:metabolism; D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle / Q000378:metabolism*; D003612:Dairying; D004305:Dose-Response Relationship, Drug; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000008:administration & dosage*; D007262:Infusions, Intravenous / Q000662:veterinary; D007328:Insulin / Q000097:blood; D007774:Lactation; D050155:Lipogenesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000032:analysis; D050151:Subcutaneous Fat / Q000187:drug effects / Q000201:enzymology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D012333:RNA, Messenger; D064429:Fatty Acid Synthases; D000106:Acetate-CoA Ligase; D005947:Glucose