Interaction effect of insulin infusion and induced mastitis by lipopolysaccharide on glucose metabolism and glucagon hormone secretion in dairy cows

Insulin and glucagon are glucoregulatory hormones which their secretions are critical for glucose hemostasis during inflammations. Intra-mammary LPS (lipopolysaccharide) challenge causes an immune reaction which is accompanied by metabolic and endocrine changes. The objective of the present study was to investigate the effects of intra-mammary LPS challenge concomitantly with elevated insulin concentrations on glucagon concentration during simultaneous hypoglycemia or euglycemia in dairy cows. Nineteen Holstein dairy cows with body weight of 3.0 ± 0.1 (mean ± SD) were randomly assigned to three treatment groups: an intravenous insulin infusion (Hypoglycemia; HypoG, n=5), insulin and glucose infusion (EuG, n=6), and a 0.9 % saline solution infusion (Control, n=8). At 48 h of metabolites infusions, LPS injected to two quarters of mammary glands. In response to LPS challenge, plasma insulin and glucose concentration increased. Intra-mammary LPS challenge caused an increase in plasma glucagon concentrations in HypoG and control compared to EuG group, pre infusion level, and pre LPS challenge. In conclusion, intra-mammary LPS challenge induced increases of glucose, insulin, and glucagon concentrations. The results showed that glucagon concentrations increased during immune system stimulation despite the increase of insulin concentrations, and its role is important in glucose metabolism hemostasis during inflammation.