The prevailing model posits that adipose tissue dysfunction drives systemic inflammation via soluble factors like IL-6 and TNFα (1, 2). This 'source' model is supported but incomplete. We propose that adipose tissue—particularly visceral depots—actively packages its inflammatory signal into extracellular vesicles (EVs), which act as targeted, stable vectors for metabolic disruption in distant organs. This reframes the pathology from passive leakage to active, directed communication.

Mechanistic Reasoning:

1. Signal Amplification & Specificity: Soluble cytokines are promiscuous and rapidly degraded. Adipose-derived EVs, however, can carry a concentrated cargo of SASP factors (IL-1β, TNFα), miRNAs, and damaged mitochondria, delivering them directly to recipient hepatocytes, myocytes, or endothelial cells. This explains the targeted organ damage (e.g., hepatic steatosis) (3) that systemic dilution alone cannot account for. The cargo could include specific miRNAs that reprogram recipient cell metabolism toward a senescent or insulin-resistant state.
2. Cellular Crosstalk Amplifier: The reported age-associated reprogramming of γδ T cells (1) and M1 macrophage polarization (4) within fat likely alters the EV secretion profile. Inflammatory immune cells are prolific EV producers. Thus, the 'immune war' is encoded not just in soluble signals, but in a barrage of EVs that can perpetuate inflammation and even transfer senescence (via 'bystander senescence') to healthy cells in other tissues.
3. Therapeutic Implications & Falsifiability: Current interventions (senolytics, rapamycin, RAGE deficiency) (3, 5, 6) may work partly by normalizing the EV cargo. This hypothesis predicts that:
   • Test 1: Isolating EVs from aged/obese adipose tissue (or conditioned media from senescent adipocytes) and administering them to young, lean mice will recapitulate hepatic inflammation and insulin resistance, while EVs from young/adipose-senescent-depleted mice will not.
   • Test 2: Pharmacological inhibition of EV biogenesis or release (e.g., via GW4869, an nSMase2 inhibitor) specifically in adipose tissue should mitigate systemic inflammation and organ damage in aged or obese models, even if local adipose inflammation persists.
   • Test 3: Cargo analysis of adipose-derived EVs will reveal age-dependent enrichment of specific miRNAs (e.g., miR-34a, miR-146a) and mitochondrial DNA known to activate TLR9/NF-κB pathways in recipient cells.

Conclusion: Adipose tissue may not just be a battlefield but a broadcast station. Targeting the EV-mediated 'signal' could offer a more precise therapeutic strategy than broadly dampening the adipose 'source' or its soluble factors, potentially avoiding the metabolic trade-offs of systemic immunosuppression.