Adipokines as biomarkers of postpartum subclinical endometritis in dairy cows

Abstract

Adipokines emerged as regulators of metabolism and inflammation in several scenarios. This study evaluated the relationship between adipokines (adiponectin, chemerin and visfatin) and cytological (subclinical) endometritis, by comparing healthy (without), transient (recovered by 45 days postpartum (DPP)) and persistent (until 45 DPP) endometritis cows (n = 49). Cows with persistent endometritis had higher adiponectin concentrations in plasma (at 21 DPP, P < 0.05 and at 45 DPP, P < 0.01) and in uterine fluid (at 45 DPP, P < 0.001), and higher chemerin concentrations in plasma (P < 0.05) and uterine fluid (P < 0.01) at 45 DPP than healthy cows. Cows with persistent endometritis had higher gene transcription in the cellular pellet of uterine fluid and protein expression in the endometrium of these adipokines and their receptors than healthy cows. Adiponectin plasma concentrations allowed to discriminate healthy from persistent endometritis cows, in 87% (21 DPP) and 98% (45 DPP) of cases, and adiponectin and chemerin uterine fluid concentrations at 45 DPP allowed for this discrimination in 100% of cases. Cows with concentrations above the cutoff were a minimum of 3.5 (plasma 21 DPP), 20.4 (plasma 45 DPP), and 33.3 (uterine fluid 45 DPP) times more at risk of evidencing persistent endometritis at 45 DPP than cows with concentrations below the cutoff. Overall, results indicate a relationship between adipokine signalling and the inflammatory status of the postpartum uterus of dairy cows, evidencing that adipokines represent suitable biomarkers of subclinical endometritis, able to predict the risk of persistence of inflammation.

Figure 1

Plasma and uterine fluid concentrations of adiponectin (A, B and C), chemerin (D, E and F) and visfatin (G, H and I) in healthy cows (group HH), cows with cytological endometritis at 21 DPP but recovered by 45 DPP (group EH), and cows with persistent cytological endometritis until 45 DPP (group EE). Different letters indicate a significant difference at P < 0.05. Horizontal black lines indicate median, boxes extend from the 25th to the 75th percentile and vertical lines indicate values within 1.5 interquartile range of the 25th and 75th percentile. Asterisks indicate outliers.

Figure 2

Receiver operating characteristic curve analysis of adiponectin (A) and chemerin (B) to discriminate cows with cytological endometritis at 45 days postpartum. Concentrations were measured in plasma at 21 and 45 days postpartum and in uterine fluid (UF) at 45 days postpartum.

Figure 3

Representative photomicrographs of endometrial sections from biopsies recovered at 45 days postpartum from a subset of healthy cows pregnant at first AI (group HHP), cows with cytological endometritis at day 21 postpartum but that recovered by day 45 postpartum (group EH), and cows with persistent cytological endometritis until day 45 postpartum (group EE). Immunostaining for ADIPOQ (A, B, C, D, E and F), for ADIPOR1 (G, H and I) and for ADIPOR2 (J, K and L). In D, arrow pointing to stained endothelial cell; in E, arrows pointing to non-stained PMN; in F, arrow pointing to stained macrophage. Scale bar 10 µm (D, E, F and all the insets) and 100 µm (A, B, C, G, H, I, J, K and L).

Figure 4

Representative photomicrographs of endometrial sections from biopsies recovered at 45 days postpartum from a subset of healthy cows pregnant at first AI (group HHP), cows with cytological endometritis at day 21 postpartum but that recovered by day 45 postpartum (group EH), and cows with persistent cytological endometritis until day 45 postpartum (group EE). Immunostaining for RARRES2 (A, B, C), CMKLR1 (D, E, F) and negative control (G, H, I). Scale bar 10 µm (insets) and 100 µm (A, B, C, D, E, F, G, H and I).

Figure 5

Transcript abundance of ADIPOQ (A), ADIPOR1 (B) and ADIPOR2 (C) standardized to the geometric mean of GAPDH, ACTB and PPIA in uterine cell pellets collected at 45 days postpartum. Data analysed using Kruskal–Wallis test with Dunns post-test. Different letters indicate a significant difference at P < 0.05. Groups HHP, healthy cows pregnant at first AI; EH, cows with cytological endometritis at 21 days postpartum but that recovered by 45 days postpartum; EE, cows with persistent cytological endometritis until 45 days postpartum. Horizontal black lines indicate median, boxes extend from the 25th to the 75th percentile and vertical lines indicate values within 1.5 interquartile range of the 25th and 75th percentile. Asterisks indicate outliers.

Figure 6

Transcript abundance of RARRES2 (A), CMKLR1 (B) and GPR1 (C) standardized to the geometric mean of GAPDH, ACTB and PPIA in uterine cell pellets collected at 45 days postpartum. Data analysed using Kruskal–Wallis test with Dunns post-test. Different letters indicate a significant difference at P < 0.05. Groups HHP, healthy cows pregnant at first AI; EH, cows with cytological endometritis at 21 days postpartum but that recovered by 45 days postpartum; EE, cows with persistent cytological endometritis until 45 days postpartum. Horizontal black lines indicate median, boxes extend from the 25th to the 75th percentile and vertical lines indicate values within 1.5 interquartile range of the 25th and 75th percentile. Asterisks indicate outliers.