Obesity Reprogrammes Adipose Extracellular Vesicles to Induce Muscle Atrophy via miR-150-5p-Mediated Transcriptional Silencing.

BACKGROUND: Sarcopenic obesity, where excess body fat coexists with reduced muscle mass and function, is becoming increasingly common in ageing populations and contributes to poor physical and metabolic health. Although adipose tissue-secreted factors are implicated in muscle decline, the specific mechanisms remain unclear. Extracellular vesicles (EVs), which carry regulatory cargo such as microRNAs (miRNAs) between cells, may play a key role in this adipose-muscle communication. METHODS: EVs were isolated from adipose-conditioned media (ACM) collected from lean and non-lean human donors using ultracentrifugation. Donors were grouped by BMI (lean: 20.7-24.4; non-lean: 25.3-39.3) and age (younger: 31-56 years; older: 60-84 years). EVs were characterised using nanoparticle tracking analysis (NTA), ExoView, nanoscale flow cytometry (CytoFLEX Nano) and transmission electron microscopy (TEM). Primary human myoblasts were differentiated into myotubes and treated for 24 h with lean or non-lean EVs (1.3 × 10(9) particles/mL) or left untreated. Myotube thickness was measured by immunofluorescence microscopy. Transcriptomic changes were assessed by bulk RNA sequencing. EV miRNA cargo was profiled by small RNA-seq and validated by qPCR. The role of miR-150-5p was tested using antagomir inhibition. RESULTS: Non-lean EVs significantly reduced myotube thickness in older adult-derived myotubes compared to both untreated controls (8.7 ± 1.66 μm vs. 12.4 ± 1.72 μm, p < 0.01) and lean EV-treated myotubes (8.7 ± 1.66 μm vs. 13.2 ± 3.84 μm, p < 0.05), indicating a donor BMI-specific effect. This atrophy was restricted to myotubes derived from older donors. The same experimental approach was applied to younger adult-derived myotubes; no reduction in myotube thickness was observed. MAFbx expression was significantly increased in response to non-lean EVs (p < 0.05). RNA-seq revealed 471 differentially expressed genes (DEGs) in EV-treated versus untreated cells and 293 DEGs between lean and non-lean EV conditions, with enrichment in inflammatory (TNF and IL1B), oxidative stress, mitochondrial and chromatin pathways. Small RNA-seq identified seven differentially expressed miRNAs (annotated using miRBase release 22.1), including miR-150-5p and miR-193b-5p, both significantly upregulated in non-lean EVs and validated by qPCR. Inhibiting miR-150-5p partially rescued myotube thickness (10.5 ± 1.37 μm vs. 8.7 ± 1.66 μm, p < 0.05) and reduced MAFbx expression. CONCLUSIONS: EVs from non-lean adipose tissue drive muscle atrophy and transcriptional changes in an age-dependent manner. These effects are partially mediated by miR-150-5p, highlighting a mechanistic role for EV cargo in adipose-muscle signalling. Targeting EV-derived miRNAs may offer a novel strategy to combat muscle loss in obesity and ageing.