Objective: To determine whether and by what mechanism systemic delivery of curcumin-containing liposomes improves insulin resistance in the leptin deficient (ob/ob) mouse model of insulin resistance.
Research design and methods: Insulin resistant ob/ob mice with steatosis were injected intraperitoneally with liposome nanoparticles, entrapping the nuclear factor-κB (NF-κB) inhibitor curcumin (curcusomes), and uptake in liver and adipose tissue was determined by flow cytometry. The effects of curcusomes on macrophage NF-κB activation and cytokine production were assessed. Transfer experiments determined the role of hepatic tumor necrosis factor (TNF)/inducible nitric oxide synthase-producing dendritic cells (Tip-DCs) and adipose tissue macrophages (ATMs) in inflammation-induced insulin resistance, determined by homeostatic assessment of insulin resistance.
Results: Phagocytic myeloid cells infiltrating the liver in ob/ob mice had the phenotypic characteristics of Tip-DCs that arise from monocyte precursors in the liver and spleen after infection. Targeting Tip-DCs and ATMs with curcusomes in ob/ob mice reduced NF-κB/RelA DNA binding activity, reduced TNF, and enhanced interleukin-4 production. Curcusomes improved peripheral insulin resistance.
Conclusions: Both hepatic Tip-DCs and ATMs contribute to insulin resistance in ob/ob mice. Curcusome nanoparticles inhibit proinflammatory pathways in hepatic Tip-DCs and ATMs and reverse insulin resistance. Targeting inflammatory DCs is a novel approach for type 2 diabetes treatment.