Short communication: localization and expression of monocyte chemoattractant protein-1 in different subcutaneous and visceral adipose tissues of early-lactating dairy cows.

The present study aimed to examine the mRNA abundance of the monocyte chemoattractant protein-1 (MCP-1) and to localize the MCP-1 protein in different subcutaneous (s.c.) and visceral (v.c.) fat depots in high-yielding dairy cows. Early-lactating German Holstein cows (n=25) were divided into a control (CON) and a conjugated linoleic acids (CLA)-supplemented group to investigate potential effects of dietary CLA treatment on MCP-1. The MCP-1 was localized in different s.c. and v.c. adipose tissue (AT) by immunohistochemistry, whereas the mRNA abundance was investigated using quantitative PCR. Albeit the infiltration of immune cells into bovine AT has been demonstrated to be only marginal, both MCP-1 protein and mRNA could be detected in bovine AT depots. The MCP-1 protein was localized both in the cytoplasm of adipocytes and in the cytoplasm of cells from the stromal vascular fraction; however, the number of MCP-1-positive cells was low. The mRNA abundances of MCP-1 were higher in v.c. compared with s.c. AT. Moreover, neither mRNA abundance nor protein expression of MCP-1 was seriously influenced by CLA supplementation of early-lactating dairy cows.

Detection of 11 beta-hydroxysteroid dehydrogenase type 1, the glucocorticoid and mineralocorticoid receptor in various adipose tissue depots of dairy cows supplemented with conjugated linoleic acids.

Early lactating cows mobilize adipose tissue (AT) to provide energy for milk yield and maintenance and are susceptible to metabolic disorders and impaired immune response. Conjugated linoleic acids (CLA), mainly the trans-10, cis-12 isomer, reduce milk fat synthesis and may attenuate negative energy balance. Circulating glucocorticoids (GC) are increased during parturition in dairy cows and mediate differentiating and anti-inflammatory effects via glucocorticoid (GR) and mineralocorticoid receptors (MR) in the presence of the enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ßHSD1). Activated GC are the main ligands for both receptors in AT; therefore, we hypothesized that tissue-specific GC metabolism is effected by varying amounts of GR, MR and 11ßHSD1 and/or their localization within AT depots. Furthermore, the lipolytic and antilipogenic effects of CLA might influence the GC/GR/MR system in AT. Therefore, we aimed to localize GR and MR as well as the expression pattern and activity of 11ßHSD1 in different AT depots during early lactation in dairy cows and to identify potential effects of CLA. Primiparous German Holstein cows were divided into a control (CON) and a CLA group. From day 1 post-partum (p.p.) until sample collection, the CLA group was fed with 100 g/d CLA (contains 10 g each of the cis-9, trans-11 and the trans-10, cis-12-CLA isomers). CON cows (n = 5 each) were slaughtered on day 1, 42 and 105 p.p., while CLA cows (n = 5 each) were slaughtered on day 42 and 105 p.p. Subcutaneous fat from tailhead, withers and sternum, and visceral fat from omental, mesenteric and retroperitoneal depots were sampled. The localization of GR and 11ßHSD1 in mature adipocytes - being already differentiated - indicates that GC promote other effects via GR than differentiation. Moreover, MR were observed in the stromal vascular cell fraction and positively related to the pre-adipocyte marker Pref-1. However, only marginal CLA effects were observed in this study.

Characterization of the dynamics of fat cell turnover in different bovine adipose tissue depots.

In many but not all high producing cows, the energy requirements for milk yield and maintenance exceed energy intake by voluntary feed intake during early lactation. Prioritizing milk secretion, body reserves mainly from adipose tissue are mobilized and imply an increased risk for metabolic diseases. Reducing the energy output via milk by decreasing the milk fat content through feed supplements containing conjugated linoleic acids (CLAs) may attenuate the negative energy balance during this period. In two separate trials, variables characterizing fat cell turnover were investigated in different subcutaneous and visceral fat depots from primiparous heifers (n = 25) during early lactation, and subcutaneous fat from non-lactating, over-conditioned heifers (n = 12) by immunohistochemistry. The portion of apoptotic adipocytes was consistently greater than that of proliferating cells and preadipocytes; the sporadically observed effects of CLA were limited to visceral fat. Lactating heifers had more apoptosis and less preadipocytes than non-lactating heifers.