Fatty acid amide metabolism in systemic lupus erythematosus: Evidence, mechanisms, and translational potential

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease in which loss of immune tolerance, chronic inflammation, and metabolic reprogramming are closely interconnected. Fatty acid amides (FAAs) are endogenous lipid mediators that include N-acylethanolamines (NAEs), such as anandamide (AEA), palmitoylethanolamide (PEA), oleoylethanolamide (OEA), palmitoleoylethanolamide, and linoleoylethanolamide, as well as primary fatty acid amides such as palmitamide, octadecanamide, and oleamide. The evidence base for FAA metabolism in SLE should be interpreted at two levels. First, direct human multi-omics evidence now supports disease-associated alteration of several FAA-class serum metabolites: a serum proteome-metabolome study identified palmitoleoylethanolamide, linoleoylethanolamide, palmitamide, and octadecanamide among candidate metabolite biomarkers for SLE classification. Second, a targeted endocannabinoid study found increased 2-arachidonoylglycerol (2-AG) and enhanced diacylglycerol lipase (DAGL) activity in peripheral blood mononuclear cells, whereas AEA, PEA, and OEA were not significantly different from healthy controls. Because 2-AG is an endocannabinoid but not an FAA, these data support broader endocannabinoidome dysregulation rather than universal NAE dysregulation. Mechanistic evidence is primarily derived from lupus mouse models: PEA is reduced in serum and spleen of MRL/lpr mice and suppresses TLR9-induced IL-6 production, dendritic-cell and B-cell activation, IgM production, and B-cell proliferation; FAAH is upregulated in B cells from a lupus-prone Sle2z model and FAAH inhibition reduces receptor revision, RAG expression, and polyreactive autoantibody production; nano-encapsulated AEA reduces inflammatory cytokines and lesion severity in a murine model of cutaneous lupus erythematosus. Collectively, these findings indicate that FAA-related pathways are relevant to SLE, although current evidence remains heterogeneous, species-specific, and insufficient to establish causality in patients. Future work should combine targeted lipidomics, cell-type-resolved enzyme profiling, immune perturbation assays, and organ-specific phenotyping to determine whether FAA metabolism contributes to disease pathogenesis, biomarker development, or adjunctive therapy in defined SLE subsets.