Islet-derived exosomal miR-204 accelerates insulin resistance in skeletal muscle by suppressing sirtuin 1: An in vivo study in a mouse model of high-fat diet-induced obesity.

Aims: The interaction between pancreatic islets and skeletal muscle plays a pivotal role in the development of insulin resistance. The present study aimed to elucidate the impact of non-hormonal molecules from islets on the insulin sensitivity of skeletal muscle cells.

Materials And Methods: We developed a mouse model of obesity through a high-fat diet, assessing glucose tolerance and conducting miRNA sequencing on skeletal muscle samples. An in vitro model was established by treating cells with palmitic acid, and exosomes in the supernatant were characterized using scanning electron microscopy and CD63 expression analysis. Intracellular miR-204-5p levels were quantified by RT-PCR.

Results: Our in vivo model demonstrated a robust correlation between miR-204-5p level alterations and obesity-induced insulin resistance. Elevated fatty acid levels were observed to increase miR-204-5p in both skeletal muscle and islets. In cellular studies, palmitic acid increased miR-204-5p in MIN-6 islet β-cells but not in C2C12 skeletal muscle cells. Exosomes containing miR-204-5p, secreted by palmitic acid-treated MIN6 cells, were identified through morphological examination, immunoblotting for the exosomal marker CD63, and intraexosomal miR-204-5p level measurement. C2C12 cells were shown to uptake islet-derived miR-204-5p exosomes, as evidenced by the uptake of Exo-Red labeled exosomes. TargetScan analysis identified a highly conserved binding site for miR-204-5p in the 3' UTR of Sirt mRNA. Functional studies indicated that miR-204-5p overexpression reduced glucose consumption and uptake in C2C12 cells, decreased Sirt expression, and impaired insulin signaling, as evidenced by reduced Akt phosphorylation and membrane Glut4 levels.

Conclusions: Our findings reveal that miR-204-5p contributes to the development of insulin resistance in obesity and acts as a signaling molecule in the crosstalk between pancreatic islets and skeletal muscle.