Abstract #T145

# T145
Influence of adipocyte size and adipose depot on the expression of adipokines in dairy cows at the end of pregnancy.
J. De Koster*1, M. Van Poucke3, M. Hostens2, K. Hermans2, W. Van den Broeck4, L. Peelman3, G. Opsomer2, 1Large Animal Clinical Sciences, Michigan State University, East Lansing, MI, 2Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Gent, Belgium, 3Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Gent, Belgium, 4Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Gent, Belgium.

The aim of this study was to determine the mRNA expression of adiponectin (ADIPOQ), leptin (LEP), interleukin 6 (IL6) and tumor necrosis factor (TNF) in adipose depots from cows with a variable body condition score (BCS 2.75–5) at the end of the dry period. Ten pregnant dairy cows were euthanized 10 to 13 d before the expected parturition date. Immediately after euthanasia, samples of subcutaneous, omental, mesenteric, perirenal and intrapelvic adipose depot were taken and snap frozen in liquid nitrogen or fixed in 4% formaldehyde. Expression of the different genes was determined by RT-qPCR according to the MIQE guidelines. Expression is represented as relative mRNA abundance after normalization with 3 reference genes (MARVELD1, EIF3K, LRP10) determined using geNorm. Size of the adipocytes was determined by measuring the area of 100 adipocytes on histological sections after HE staining. Statistical analyses were performed using SAS version 9.4. A generalized linear mixed model was built with expression of the individual genes as dependent variable, depot, adipocyte area and the interaction between depot and adipocyte area were included as independent variables and cow was included as random factor. Pairwise comparisons between depots were checked using the Tukey post-hoc test. Adipocyte size (10,243 ± 1,347µm2) was positively related to the expression of LEPT (0.38 ± 0.05; β = 102.87; P < 0.05), IL6 (0.23 ± 0.04; β = 78.44; 0.05 < P < 0.1) and TNF (1.03 ± 0.13; β = 66.50; P < 0.05), while no association could be detected between ADIPOQ (0.43 ± 0.04; β = −22.79; not significant) and the size of the adipocytes. The expression of the different adipokines was clearly different between the different adipose depots. In general, the expression of pro-inflammatory adipokines (LEPT and IL6) was greater in the internal compared with the subcutaneous adipose depots. In conclusion, the results of the present study indicate a pro-inflammatory state of adipose depots with large adipocytes in cows at the end of pregnancy, which might induce a dysregulation of inflammatory processes and contribute to metabolic and infectious disorders in overconditioned cows in the periparturient period.

Key Words: adipose tissue, adiopkine, transition period