LY6D promotes hepatic steatosis via the GRB2-AMPK-SREBP1 signaling axis

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent chronic liver disease globally and can progress to metabolic dysfunction-associated steatohepatitis, a more severe and fibrotic form. Although the recent FDA approval of Resmetirom and Semaglutide, represents a major therapeutic milestone, its efficacy is limited to a subset of patients. Thus, identifying additional molecular targets is essential. This study aimed to investigate the role of lymphocyte antigen 6 complex locus D (LY6D) in hepatic lipid accumulation and MASLD pathogenesis.

LY6D expression was assessed in liver tissue samples from patients with MASLD and validated in leptin or leptin receptor knockout mice (ob/ob and db/db) and high-fat diet-fed mouse models. Transcriptomic profiling was performed using RNA sequencing to identify LY6D-associated metabolic pathways. Functional analyses were conducted using LY6D-overexpressing mice to evaluate hepatic lipid content, gene expression, and protein signaling. Protein-protein interactions were assessed via co-immunoprecipitation, and downstream effects on AMP-activated protein kinase (AMPK) phosphorylation and sterol regulatory element-binding protein 1(SREBP1) activation were evaluated by Western blotting.

LY6D expression was significantly elevated in liver samples from patients with MASLD and in mouse models of hepatic steatosis. Transcriptomic analysis revealed enrichment of fatty acid synthesis pathways in LY6D-high livers. In LY6D-overexpressing mice, de novo lipogenesis was increased, with upregulation of lipogenic genes including Srebf1, Fasn, Acaca, and Scd1. Mechanistically, LY6D associated with growth factor receptor-bound protein 2 (GRB2) and was accompanied by reduced AMPK phosphorylation at Thr172. Modulation of AMPK activity altered LY6D-dependent SREBP1c abundance and nuclear accumulation, supporting an LY6D-associated GRB2-AMPK-SREBP1c regulatory node that promotes lipogenic transcription.

LY6D is an upstream regulator of hepatic de novo lipogenesis in MASLD. Our data support a model in which LY6D promotes lipogenic signaling via an LY6D-associated GRB2-AMPK-SREBP1c pathway, and suggest that LY6D may represent a therapeutic entry point to complement current MASLD/MASH treatments. LY6D was found to bind GRB2, leading to suppression of AMPK phosphorylation at Thr172. This inhibition promoted transcription and nuclear translocation of SREBP1, thereby enhancing transcription of key lipogenic genes (Acaca, Fasn, and Scd1) and consequently increasing hepatic de novo lipogenesis.