Type I interferon sensing unlocks dormant adipocyte inflammatory potential

Obesity is an ongoing public health crisis. Pathological expansion of adipocytes in obesity creates a dynamic inflammatory milieu within white adipose tissue (WAT), driving low-grade chronic inflammation linked to type 2 diabetes mellitus and non-alcoholic fatty liver disease. While myeloid cell regulation of inflammation is well studied, regulation of adipocyte inflammatory potential and its contribution to obesity-associated inflammation is poorly understood. Adipocytes share some immune-like features with myeloid cells, including production of proinflammatory cytokines, expression of innate immune receptors, and antigen presentation, raising the question of whether adipocytes possess intrinsic potential to behave like myeloid cells and what mechanisms regulate this potential. Type I interferons (IFNα/IFNβ) orchestrate innate and adaptive immunity and tune myeloid inflammatory vigor. Obesity-associated metabolic endotoxemia and other TLR ligands robustly induce type I IFN production, which signals through IFNAR. Existing literature on IFNAR in obesity suggests both detrimental and beneficial effects, but the role of type I IFN/IFNAR in regulating adipocyte inflammatory potential had not been investigated. The authors hypothesized that activating type I IFN/IFNAR in adipocytes would reveal immune-like inflammatory signatures and exacerbate adipocyte-intrinsic inflammatory vigor.

Prior studies indicate adipocytes can produce cytokines, express TLRs, and present antigen, suggesting partial overlap with myeloid cell functions. Type I IFNs modulate myeloid cell inflammatory responses, with IFNβ induced by TLR stimulation. In metabolic disease, type I IFN/IFNAR signaling has been reported as either detrimental (e.g., promoting hepatic/metabolic dysfunction and insulin resistance) or beneficial (e.g., protection against metabolic dysfunction with certain overexpression or cell-type–specific contexts). Unresolved issues include how IFNAR signaling integrates within adipocytes, whether it uncovers immune-like programs, and how such signaling impacts whole-body metabolic sequelae during obesity.

• Mouse models: Male C57BL/6 WT, total-body IFNAR−/−, AdipoqCre-IFNARfl/fl, and controls were housed SPF. Obesity induced by high-fat diet (60% kcal fat) beginning at 6–8 weeks; chow diet as control. Body composition assessed by EchoMRI; glucose and insulin tolerance tests performed after overnight fasting; energy expenditure quantified by indirect calorimetry.
• Primary mouse adipocytes: Inguinal WAT stromal vascular fraction (SVF) isolated by collagenase/dispase digestion; preadipocytes expanded and differentiated with rosiglitazone/insulin/dexamethasone/IBMX protocols to mature adipocytes. Mature eWAT adipocytes also isolated from obese mice. Stimulation regimens included saline, IFNβ (250 U/ml, 3 h), then LPS (100 ng/ml, 4 h); additional TLR ligands Pam2Cys (TLR2) and Poly I:C (TLR3) were used. Cytokines (IL-6, TNF) quantified by ELISA; type I IFN activity measured using IFN-sensitive luciferase reporter in L-929 cells. Gene expression was measured by qRT-PCR for type I IFN signature genes (e.g., Irf9, Oas1a, Isg15), Ifnb1, Ifnar1, and glycolytic enzymes (Pfk1, Pgk1, Pkm2). Jak1 inhibition assays performed to probe signaling requirements.
• RNA-seq: Primary adipocytes and bone-marrow–derived macrophages treated with NS, IFNβ, LPS, or IFNβ+LPS, followed by RNA-seq (50 bp single-end, ~20M reads/sample). Reads aligned to mm10, expression quantified as RPKM, normalized (DESeq), and differentially expressed genes identified (two-way ANOVA, FDR<0.05, fold change >1.5). Principal component analysis, heatmaps, and ontology enrichment (ToppGene) performed. Transcription factor motif enrichment and overlap with ChIP-seq/DNase-seq datasets (510 mouse datasets) conducted; HOMER used for motif analysis.
• Cellular bioenergetics: Seahorse XF96 analysis measured extracellular acidification rate (ECAR) and oxygen consumption rate (OCR). Glycolysis stress test with sequential injections of glucose, oligomycin, and 2-deoxy-D-glucose (2-DG). Mitochondrial stress test with oligomycin and FCCP. Pharmacologic inhibitors included 2-DG (2 mM or 10 mM in specific assays) and etomoxir (fatty acid oxidation inhibitor). Lactate quantified colorimetrically.
• In vivo obesity studies: WT and IFNAR−/− mice on HFD for up to 22 weeks. Tissue weights (eWAT, iWAT, pWAT), BAT Ucp1 expression, and serum lipids measured. Immune cell infiltration in eWAT and liver analyzed by flow cytometry after PMA/ionomycin stimulation; populations included CD45+, CD3+CD4+, CD3+CD8+, B220+, and F4/80+CD11b+ macrophages producing IL-6 or TNF. Serum ALT measured as hepatocellular injury marker.
• Bone marrow chimera: Reciprocal BMT between WT (CD45.2) and IFNAR−/− (CD45.1) recipients, reconstitution confirmed by flow cytometry at day 74; mice then fed HFD for 18 weeks. Metabolic tests and immune profiling performed to parse hematopoietic vs non-hematopoietic IFNAR contributions.
• Adipocyte-specific IFNAR deletion: AdipoqCre-IFNARfl/fl and littermate Cre− controls fed HFD for 18 weeks. Ex vivo adipocyte cytokine responses to IFNβ±LPS measured; WAT depot masses, immune infiltration, glucose tolerance, liver triglycerides, and ALT assessed.
• Human studies: Pediatric bariatric surgery cohort recruited under IRB approval. Liver histology scored with pediatric NASH-CRN NAS. Subjects stratified as metabolically healthy (Met-H) or metabolically challenged (Met-C) by clinical parameters (e.g., steatosis, inflammation, ballooning). Omental SVF isolated, differentiated to adipocytes; stimulated with NS, human IFNβ (250 U/ml), and/or LPS (100 ng/ml). IL-6 and IFNβ quantified by ELISA. Plasma cytokines/chemokines (IFNβ, TNFα, IL-6, CXCL9, CCL3, CXCL10) measured by Luminex. Correlations between systemic IFNβ and AST, fasting glucose, and HOMA-IR evaluated by linear regression. Statistical analyses used unpaired two-tailed Student’s t tests for normally distributed data; significance thresholds standard; outlier tests (ROUT, Grubbs).

• Activation of type I IFN axis in adipocytes: LPS stimulated mouse primary adipocytes to produce IFNβ and induced IFNAR-dependent expression of Irf9, Oas1a, and Isg15. IFNβ priming enhanced IFNAR-dependent LPS-driven IL-6 and TNF production, similar to myeloid cells. TLR2 and TLR3 ligands (Pam2Cys, Poly I:C) also induced IL-6 and IFNβ in adipocytes, indicating multiple TLRs can activate the IFN axis.
• Convergence with macrophage programs: RNA-seq showed that IFNβ+LPS drove adipocyte transcriptomes to converge toward macrophage profiles. Overlap among the 2500 most highly expressed genes: baseline 0.7% shared; IFNβ alone 25.1%; LPS alone 20.2%; IFNβ+LPS 30.4%. Upregulated genes included antigen presentation and broad inflammatory pathways. Transcription factor motif/ChIP-seq overlap analyses indicated enrichment of STATs, IRFs, and NF-κB programs and increased chromatin accessibility. Jak1 inhibition abrogated IFNβ augmentation of adipocyte inflammatory vigor.
• Glycolysis linkage: IFNβ increased expression of glycolytic enzymes (Pfk1, Pgk1, Pkm2) and elevated basal ECAR and OCR, suggesting altered aerobic glycolysis. Glycolysis inhibition with 2-DG reversed IFNβ-mediated OCR increases, reduced expression of IFN signature genes (Oas1a, Isg15), and diminished IFNβ-driven augmentation of IL-6, whereas etomoxir (fatty acid oxidation inhibitor) did not. Thus, IFNβ-modified glycolysis is tied to enhanced adipocyte inflammatory potential.
• Obesity induces IFN axis in adipocytes: Adipocytes from HFD mice showed elevated Ifnb1, Ifnar1, Oas1a, and Isg15 versus chow. IFNβ priming amplified LPS-induced IL-6 more strongly in adipocytes from HFD mice.
• Whole-body IFNAR deletion: IFNAR−/− and WT mice on HFD gained similar weight, energy expenditure, adiposity, and serum cholesterol, but IFNAR deficiency altered WAT depot distribution (increased eWAT, decreased iWAT and pWAT). eWAT of IFNAR−/− mice had reduced total CD45+ infiltration, fewer CD4+, CD8+, and B cells, and fewer macrophages producing IL-6 and TNF. Improved systemic metabolic readouts (glucose and insulin tolerance) and reduced liver injury (lower ALT) were observed, along with decreased hepatic immune cell inflammatory cytokine production.
• Hematopoietic and non-hematopoietic contributions: Reciprocal bone marrow chimera experiments demonstrated that both compartments’ IFNAR expression contribute to obesity-associated immune infiltration, glucose intolerance, and liver injury phenotypes under HFD.
• Adipocyte-intrinsic IFNAR: AdipoqCre-IFNARfl/fl mice had attenuated ex vivo adipocyte IL-6 responses to IFNβ+LPS, alterations in WAT depot masses, improved glucose tolerance, and minimal impact on hepatocellular damage (ALT, liver immune cell infiltration), indicating adipocyte IFNAR primarily modulates glucose dysmetabolism severity.
• Human conservation and clinical correlations: Human primary adipocytes (from omental WAT) produced IFNβ upon LPS, upregulated IRF1, OAS1, ISG15, and showed IFNβ-mediated augmentation of LPS-induced IL-6; glycolysis modulation impacted IL-6 output. In a pediatric severe obesity cohort stratified as Met-H vs Met-C: Met-C exhibited higher fasting glucose, NAFLD activity scores, ALT and AST, and elevated systemic inflammatory chemokines/cytokines. Systemic IFNβ levels correlated positively with AST and were associated with obesity-linked metabolic derangements. Sample sizes included Met-H n=18 and Met-C n=30 (clinical metrics), Luminex n=11 Met-H and n=12 Met-C; regression analyses n=19.

The study addresses whether type I IFN/IFNAR signaling regulates adipocyte inflammatory potential and whether such signaling contributes to obesity-associated pathogenesis. Findings show that adipocytes are competent to sense and produce type I IFNs, and that IFNβ engagement of IFNAR unlocks a dormant, immune-like transcriptional program that converges with macrophage inflammatory signatures. Mechanistically, IFNβ enhances adipocyte glycolytic pathways, and glycolysis is required for IFNβ-driven augmentation of inflammatory gene expression and cytokine production. In vivo, obesity induces a type I IFN signature in adipocytes, and IFNAR signaling exacerbates adipose and hepatic inflammatory milieus and glucose dysmetabolism. Genetic dissection through whole-body knockout, reciprocal bone marrow chimeras, and adipocyte-specific deletion indicates both hematopoietic and non-hematopoietic IFNAR expression contribute to disease severity, with adipocyte-intrinsic IFNAR specifically modulating glucose intolerance. Human adipocytes display conserved IFNβ effects, and systemic type I IFN signatures correlate with markers of metabolic and hepatic dysfunction, supporting translational relevance. Together, these results position adipocyte IFNAR signaling as an important regulator of WAT inflammation and systemic metabolic outcomes, suggesting crosstalk between adipocytes and immune cells that is coordinated by type I IFN pathways and cellular metabolism.

This work reveals that type I IFN/IFNAR signaling in adipocytes uncovers a dormant immune-like inflammatory program, converging with myeloid gene expression, and that this program is coupled to glycolytic metabolism. Obesity activates the type I IFN axis in adipocytes, and IFNAR signaling amplifies adipose inflammation and contributes to metabolic derangements in mice. Adipocyte-specific IFNAR expression exacerbates glucose dysmetabolism, while its deletion ameliorates it with limited effects on liver injury, and both hematopoietic and non-hematopoietic IFNAR contribute to disease severity. Human data support conservation of these mechanisms and associations with clinical metabolic dysfunction. Future research should define the precise metabolic rewiring downstream of IFNAR in adipocytes, clarify epigenetic mechanisms, identify cellular sources and subtypes of type I IFNs in adipose tissue, assess potential compensation by type III IFNs, and determine how IFN signaling affects WAT architecture. Therapeutically, targeting IFN/IFNAR signaling or its glycolytic coupling in adipocytes and immune cells may mitigate obesity-associated metabolic disease.

• Human cohort size was limited and predominantly comprised severely obese pediatric patients without established type 2 diabetes, constraining generalizability and the ability to detect associations (e.g., with fasting glucose/HOMA-IR) and timing effects of transient type I IFN signals.
• AdipoqCre-driven deletion, while widely used, may carry potential for off-target Cre effects or toxicity not fully excluded.
• The study did not comprehensively dissect maximal and spare metabolic capacities in adipocytes or fully map the metabolome/flux changes induced by IFNβ.
• Possible compensatory roles of type III IFNs and contributions of other IFNAR-expressing cell types were not exhaustively tested.
• Effects of IFN/IFNAR signaling on WAT architecture (ECM deposition, fibrosis, angiogenesis) were not assessed.
• Most mechanistic data derive from murine models; although human adipocyte experiments and clinical correlations support conservation, causal relationships in humans remain to be established.