Bovine tissue mRNA abundance related to acute cold exposure and acute feeding restriction

Thirty-six steers were used to determine the effects of acute cold (-20°C) and acute feed restriction (0.4× maintenance) on mRNA abundance of five candidate genes. To investigate adaptational physiology in cattle we evaluated gene expression patterns for uncoupling protein 2 (UCP-2), uncoupling protein 3 (UCP-3), leptin, leptin receptor and neuropeptide Y receptor (NPY receptor) in specific tissues. We measured relative mRNA abundance using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) on mRNA extracted from duodenum, iver, skeletal muscle, mesenteric adipose tissue, subcutaneous adipose tissue, and peri-renal adipose tissue. We obtained carcass grades for comparison to mRNA abundance profiles. Leptin receptor mRNA abundance was increased by acute feed restriction in the liver (P = 0.02) and trended to increase in the duodenum (P = 0.06) of acute feed-restricted steers. NPY receptor RNA abundance decreased (P = 0.02) in the liver of feed-restricted steers, and acute cold-stress-treated steers (P = 0.03), but increased (P = 0.03) in mesenteric adipose tissue of acute-cold-treated steers. Leptin mRNA abundance was decreased in subcutaneous adipose tissue (P = 0.04) by acute cold, but trended to increase in the peri-renal adipose tissue (P = 0.09). UCP-3 mRNA abundance was not significantly altered by our acute treatments. UCP-2 mRNA abundance increased in subcutaneous adipose tissue of both acute cold (P = 0.004) and acute feed-restricted steers (P = 0.03) and in biceps femoris, after acute cold (P = 0.003) and acute feed restriction (P = 0.002). There was an inverse relationship between the leptin mRNA abundance in subcutaneous adipose and the carcass grade, where the AAA , AA and A grade carcasses had mean values of 501.6 ± 30.0, 535.5 ± 14.0 and 653.4 ± 61.0. Our results show that tissue-specific mRNA abundance of these candidate genes may be altered by acute stressors, and that may relate to tissue-specific adaptational strategies in cattle. Furthermore, leptin mRNA abundance in subcutaneous adipose tissue may inversely reflect the maturity or finishing characteristics of beef cattle such that it is inversely related to the final carcass grade. Key words: Acute cold, acute feed restriction, UCP-2, UCP-3, leptin, leptin receptor, NPY receptor, cattle