Abstract #M194

# M194
Adipose tissue remodeling in transition dairy cows is affected by body condition score and lipolysis intensity.
G. A. Contreras*1, C. S. Barboza1, K. Thelen1, J. de Souza2, J. De Koster1, A. L. Lock2, 1Department of Large Animal Clinical Sciences, East Lansing, MI, 2Department of Animal Science, East Lansing, MI.

Lipolysis induces a remodeling process in adipose tissue (AT) that is characterized by an inflammatory response with immune cell migration, proliferation of cellular components of the stromal vascular fraction (SVF), and changes in the extracellular matrix. This study evaluated the effect of body condition score (BCS) and lipolysis intensity on markers of AT remodeling in transition dairy cows. Blood and subcutaneous AT samples were collected from multiparous Holstein cows with high (HB; n = 12; BCS > 3.75) or moderate (MB; n = 9; BCS < 3.5) BCS at 27 ± 7 (FO) and 10 ± 5 (CU) d prepartum and at 8 ± 3 (PP) d postpartum. Expression of genes related to AT remodeling was analyzed by RT-PCR, and immune cell trafficking in AT SVF was evaluated by flow cytometry. Lipolysis increased at CU and reached its peak at PP compared with FO as reflected in circulating free fatty acid (FFA) concentrations (FO: 0.27 ± 0.05, CU: 0.39 ± 0.05, PP:0.99 ± 0.05 mEq/L, P < 0.05). FFA were higher in HB (0.63 ± 0.02 mEq/L) compared with MB (0.47 ± 0.02 mEq/L) cows reflecting an effect of BCS on lipolysis rate during gestation and after parturition. Gene expression indicated that osteopontin (SPP1), an inflammatory cytokine that triggers macrophage infiltration during AT remodeling, its receptor CD44, and signal regulatory protein α (SIRPA), a marker of mononuclear immune cells, were higher at PP compared with FO and CU. Serum FFA concentrations were positively associated with AT expression of SIRPA (r = 0.59; P < 0.001), and negatively associated with expression of IL10 (r = −0.54; P < 0.001), an anti-inflammatory cytokine. Immune cell trafficking showed that BCS had no effect on the expression of macrophage markers CD14, CD16, and CD163. However, compared with MB, HB had fewer SVF cells expressing T cell markers CD8, CD4, and CD3, and B cells (all P < 0.01). These data indicate that during the transition period, lipolysis is associated with macrophage infiltration into AT as suggested by the enhanced expression of chemoattractant adipokines that was independent of prepartum BCS. Future studies will evaluate the effect of AT remodeling and lipolysis intensity on macrophage phenotype and its effect on adipocyte insulin sensitivity during the transition period.

Key Words: lipolysis, adipose tissue macrophage, remodeling