2 research outputs found
Intravenous infusions of glucose stimulate key lipogenic enzymes in adipose tissue of dairy cows in a dose-dependent manner
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. Copyright © 2013 American Dairy
Science Association. Published by Elsevier Inc. All rights reserved