Abstract 179: Resistin Regulates ATP-citrate lyase Expression a Key Metabolic Enzyme of Lipogenesis and Histone acetylation in Human Macrophage

Abstract

BACKGROUND: Human resistin synthesized by macrophages is associated with insulin resistance, type 2 diabetes, atherosclerosis, and chronic inflammation. We used a comparative global protein expression profiling of human macrophage treated with resistin to identify downstream targets and intracellular signaling pathways involving hyper-resistinemia-associated metabolic disorders by HPLC-ESI-MS/MS. ATP-citrate lyase (ACLY), is an essential cytosolic enzyme for generating acetyl-CoA, a key metabolite for glycolysis, de novo lipogenesis, cholesterol synthesis, and histone acetylation. Its dysregulation is associated with diabetes, hypercholesterolemia, and oncogenesis and is a potent therapeutic target . In this study, we explored the regulation of ACLY and its phosphorylation by resistin. METHODS: Mϕ derived from THP1 cells were treated with human resistin for 24-72 hrs. Samples of total protein tryptic digest of untreated control and resistin-treated Mϕ were analyzed by HPLC-ESI-MS/MS. Total protein were also analyzed by western blot for ACLY and its phosphorylation . Gene expression was measured by Quantitative Real-time PCR. RESULTS: ACLY showed a significant (ρ < 0.05) differences in expression between control and resistin treated groups by quantitative mass spectrometry. ACLY formed protein-protein interaction (PPI) with 23 out of 162 significantly differentially regulated proteins. Level of ACLY protein decreased 2 fold after 48 hours of resistin treatment. However, after 72 hours of resistin treatment ACLY proteins increase with a 4-5 fold increase in its serine 455 phosphorylation (Figure 1). In human macrophage, ACLY mRNA also increased ~2 fold after 24 hours of resistin treatment (Figure 2). CONCLUSION: Resistin significantly changed the gene expression of ACLY in humanMϕ. Although there was an initial decrease in ACLY protein with no change in its phosphorylation. However, a longer 72 hours treatment of resistin induce ACLY protein in human macrophages and a very significant increase in its phosphorylation. ACLY plays a pivotal role in many metabolic and epigenetic processes, this late ACLY activation may mediate the effect of resistin on chronic diseases like diabetes, atherosclerosis, and chronic inflammation.