Associations of cytological endometritis with insulin resistance and gene expression in adipose tissue in transition dairy cows

Cytological endometritis (CYTO), characterized by an elevated number of polymorphonuclear neutrophils in the endometrium, negatively affects reproductive outcomes in dairy cows. In this study, we investigated the associations between insulin resistance (IR) during the transition period and the occurrence of CYTO. We measured insulin sensitivity and adipose tissue gene expression on d -21 and d 21 and a selection of blood metabolites weekly from d -21 to d 42 relative to calving of 39 Holstein dairy cows. Study groups were formed based on the CYTO status on d 42. Our findings indicate that cows with CYTO had a greater insulin response to a glucose infusion prepartum, suggesting a link between prepartum IR and the development of CYTO. Postpartum, CYTO cows showed lower insulin and higher nonesterified fatty acids concentrations in plasma. Additionally, CYTO cows showed altered gene expression in subcutaneous adipose tissue, with increased mRNA levels of hormone-sensitive lipase (LIPE) and insulin receptor (INSR), and a tendency for higher glucose transporter 4 (GLUT4) protein levels. These results suggest that metabolic stress and IR are interconnected, contributing to the development of CYTO. The study underscores the importance of managing metabolic health before calving to prevent CYTO and improve reproductive performance in dairy cows.