Background
Heart failure with preserved ejection fraction (HFpEF) is a multisystemic syndrome, accounting for the majority of heart failure cases. Up to 50% of HFpEF patients also suffer from “metabolic dysfunction-associated fatty liver disease” (MAFLD). The shared metabolic dysfunction in HFpEF and MAFLD triggered growing research interest in the liver-heart crosstalk, however, a cell type–specific understanding of the liver secretome has remained elusive.
Purpose
We aimed to uncover the hepatocyte-derived secretome in HFpEF using an innovative in vivo proximity labeling strategy. Our goal was to identify liver-secreted proteins with potential roles in interorgan communication, particularly focusing on mechanisms contributing to cardiac inflammation and fibrosis.
Methods
We employed a hepatocyte-specific proximity labeling system using adeno-associated viruses encoding the biotin ligase TurboID under the control of the hepatocyte-selective thyroxine-binding globulin (Tbg) promoter in male C57BL/6N mice. HFpEF was induced via high-fat/L-NAME diet. Following biotin injections, biotinylated proteins were isolated from plasma and tissues using streptavidin affinity purification and analyzed via high-resolution mass spectrometry. Tissue localization of biotinylated proteins and protein expression of candidates were confirmed by Western blotting and single-cell transcriptomic data and validated in human patient cohorts.
Results
Our approach successfully labeled the hepatocyte-specific secretome, identifying 244 significantly enriched plasma proteins under baseline conditions. Notably, in HFpEF mice, we observed substantial disturbance of the hepatic secretome, with 17 proteins up- and 20 downregulated compared to controls. Gene ontology analysis revealed enrichment of „immune response“ and „cytokine-mediated signaling“ pathways, highlighting the liver’s role in systemic inflammation in HFpEF.
A striking finding was the upregulation of soluble leukemia inhibitory factor receptor (LIFR), a component of IL-6 family cytokine receptor complexes. LIFR was exclusively detected in biotinylated plasma of TurboID mice, confirming hepatocyte origin. Elevated LIFR levels were validated in both HFpEF mice and human patients with HFpEF and MAFLD. Epidemiological proteome-wide association studies further linked plasma LIFR levels to key HFpEF traits, including type 2 diabetes, hypertension, and liver disease.
Functionally, recombinant soluble LIFR enhanced fibroblast migration and, in combination with TGF-β1, synergistically induced collagen-gel contraction and profibrotic gene expression. Mechanistic assays demonstrated LIFR-mediated amplification of TGF-β1–induced Smad3 phosphorylation, suggesting a pivotal role for soluble LIFR in promoting cardiac fibrosis.
Conclusions
This study pioneers a translationally relevant, cell type–specific secretome profiling approach in vivo, revealing the hepatocyte-secreted factor LIFR as a novel mediator of liver-to-heart communication in HFpEF. By demonstrating the profibrotic effects of LIFR on fibroblasts and its clinical associations in human cohorts, we provide compelling evidence for LIFR’s role in interorgan fibrotic signaling. This innovative methodology not only deepens mechanistic insight into HFpEF pathophysiology but also establishes a versatile platform for mapping dynamic secretome landscapes in other cell types and disease contexts, advancing the frontier of systems-level, organ crosstalk research.
