Growth hormone (GH) deficiency is associated with increased sensitivity to insulin, but the molecular mechanisms involved in this association are poorly understood. In the current work, we have examined the consequences of the absence of the biological effects of GH on the first steps of the insulin signaling system in vivo in liver of mice with targeted disruption of the GH receptor/GH binding protein gene (GHR-KO mice). In these animals, circulating insulin concentrations are less than 4 µIU/ml, and glucose concentrations are low, concordant with a state of insulin hypersensitivity. The abundance and tyrosine phosphorylation state of the insulin receptor (IR), the IR substrate-1 (IRS-1), and Shc, the association between IRS-1 and the p85 subunit of phosphatidylinositol (PI) 3-kinase, the IRS-1-and the phosphotyrosine-associated PI 3-kinase in liver were examined. We found that, in liver of GHR-KO mice, the lack of GHR and GH effects is associated with: (1) increased IR abundance, (2) increased insulin-stimulated IR tyrosine phosphorylation, (3) normal efficiency of IRS-1 and Shc tyrosine phosphorylation and (4) normal activation of PI 3-kinase by insulin. These alterations could represent an adaptation to the low insulin concentrations displayed by these animals, and may account for their increased insulin sensitivity.

Non-esterified fatty acids (NEFAs) such as oleic acid (OA) and linoleic acid (LA) are associated with a higher incidence of infectious diseases such as metritis and mastitis during the bovine peripartum. Fatty acids can induce an increase in the release of ATP, and changes in the expression levels of purinergic receptors in bovine polymorphonuclears (PMN) during peripartum have also been reported. PMN respond to inflammatory processes with production of ROS, release of proteolytic and bactericidal proteins, and formation of neutrophil extracellular traps (NETs). NETs formation is known to require ATP production through glycolysis. Studies have shown that the above-mentioned metabolic changes alter innate immune responses, particularly in PMN. We hypothesized that NEFAs induce the formation of NETs through ATP release by Pannexin 1 and activation of purinergic receptors. In this study, we found that OA and LA induce NET formation and extracellular ATP release. Carbenoxolone, a pannexin-1 (PANX1) inhibitor, reduced OA-and LA-induced ATP release. We also found that P2X1, P2X4, P2X5, P2X7, and PANX1 were expressed at the mRNA level in bovine PMN.Additionally, NEFA-induced NET formation was completely abolished with exposure to NF449, a P2X1 antagonist, and partially inhibited by treatment with etomoxir, an inhibitor of fatty acid oxidation (FAO). Our results suggest that OA and LA induce NET formation and ATP release via PANX1 and activation of P2X1. These new data contribute to explaining the effects of NEFA high concentrations during the transition period of dairy cattle and further understanding of pro-inflammatory effects and outcome of postpartum diseases.