Lipocalin-2 Deficiency Reduces Hepatic and Hippocampal Triggering Receptor Expressed on Myeloid Cells-2 Expressions in High-Fat Diet/Streptozotocin-Induced Diabetic Mice

Abstract

Background: Lipocalin-2 (LCN2) is an acute-phase protein that has been linked to insulin resistance, diabetes, and neuroinflammatory diseases. Triggering receptor expressed on myeloid cells-2 (TREM2) has been also implicated in microglia-mediated neuroinflammation. However, the potential role of LCN2 on TREM2 in diabetic mouse models is not fully understood. Methods: We investigated hepatic and hippocampal TREM2 expressions in high-fat diet (HFD) and streptozotocin (STZ)-induced diabetic LCN2 knockout (KO) mice. Results: In addition to increased serum LCN2 level, diabetic wild-type (WT) mice had insulin resistance and hepatic steatosis. However, LCN2 deletion attenuated these metabolic parameters in diabetic mice. We also found that LCN2 deletion reduced hepatic inflammation and microglial activation in diabetic mice. In particular, diabetic LCN2 KO mice had a reduction in hepatic and hippocampal TREM2 expressions compared with diabetic WT mice. Furthermore, we found that many TREM2-positive Kupffer cells and microglia in diabetic WT mice were reduced through LCN2 deletion. Conclusions: These findings indicate that LCN2 may promote hepatic inflammation and microglial activation via upregulation of TREM2 in diabetic mice.