Chirivi_2024_J.Dairy.Sci__

Dairy cows with clinical ketosis (CK) exhibit excessive adipose tissue (AT) lipolysis and systemic inflammation. Lipolysis in cows can be induced by the canonical (hormonally induced) and inflammatory lipolytic pathways. Currently, the most common treatment for CK is oral propylene glycol (PG); however, PG does not reduce lipolysis or inflammation. Niacin (NIA) can reduce the activation of canonical lipolysis, whereas cyclooxygenase inhibitors such as flunixin meglumine (FM) can limit inflammation and inhibit the inflammatory lipolytic pathway. The objective of this study was to determine the effects of including NIA and FM in the standard PG treatment for postpartum CK on AT function. Multiparous Jersey cows [n = 18; 7.1 (SD = 3.8) DIM] were selected from a commercial dairy. Inclusion criteria were CK symptoms (lethargy, depressed appetite, and drop in milk yield) and high blood levels of beta-hydroxybutyrate (BHB <= 1.2 mmol/L). Cows with CK were randomly assigned to one of 3 treatments: 1) PG: 310 g administered orally once per d for 5 d, 2) PG+NIA: 24 g administered orally oral once per d for 3 d, 3) PG+NIA+FM: 1.1 mg/kg administered IV once per day for 3 d. Healthy cows (HC; n = 6) matched by lactation and DIM (+/-2 d) were sampled. Subcutaneous AT explants were collected at d 0 (d0) and 7 (d7) relative to enrollment. To assess AT insulin sensitivity, explants were treated with insulin (INS = 1 microL/L) during lipolysis stimulation with a beta-adrenergic receptor agonist (isoproterenol, ISO = 1 microM). Lipolysis was quantified by glycerol release in the media. Lipid mobilization and inflammatory gene networks were evaluated using real-time qPCR. Protein biomarkers of lipolysis, insulin signaling, and AT inflammation, including HSL, AKT, and ERK1/2, were quantified by capillary immunoassays. Flow cytometry of AT cellular components was used to characterize macrophage inflammatory phenotypes. Statistical significance was determined by a non-parametric t-test when 2 groups (HC vs CK) were analyzed and an ANOVA test with Tukey adjustment when 3 treatment groups (PG vs PGNIA vs PGNIAFM) were evaluated. At d0, AT from CK cows showed higher mRNA expression of lipolytic enzymes ABHD5, LIPE, and LPL, as well as increased phosphorylation of the lipase HSL (pHSL) compared with HC. At d0, INS reduced lipolysis by 41 +/- 8% in AT from HC, while CK cows were unresponsive (-2.9 +/- 4%). AT from CK cows exhibited reduced Akt phosphorylation compared with HC. CK had increased AT expression of inflammatory gene markers, including CCL2, IL8, IL10, TLR4, and TNF, along with ERK1/2 phosphorylation. AT from CK cows showed increased macrophage infiltration compared with HC. By d7, AT from PGNIAFM cows had a more robust response to INS, as evidenced by reduced glycerol release (36.5 +/- 8% compared with PG, 26.9 +/- 7%, and PGNIA, 7.4 +/- 8%) and enhanced phosphorylation of Akt. By d7, PGNIAFM cows presented lower inflammatory markers, including ERK1/2 phosphorylation and reduced macrophage infiltration, compared with PG and PGNIA. These data suggest that including NIA and FM in CK treatment improves AT insulin sensitivity and reduces AT inflammation and macrophage infiltration.