Exercise is well known to enhance insulin sensitivity in skeletal muscle, yet the underlying mechanisms remain incompletely understood. We have previously shown that neutrophil recruitment contributes to contraction-induced GLUT4 translocation and local myokine induction, but whether these immune cells also participate in the post-exercise increase in insulin sensitivity has been unclear. Here using GLUT4-EGFP transgenic mice and sciatic nerve-mediated in situ contraction of the hindlimb, with analyses focused on extensor digitorum longus (EDL) muscle, we demonstrate that neutrophil recruitment and subsequent formation of neutrophil extracellular traps (NETs) are crucial for the well-known post-exercise increase in insulin sensitivity. Two-photon imaging revealed that NET-like cell-free DNA (cfDNA) structures persisted for hours after contraction, forming spatially confined perivascular immunometabolic niches along the capillary meshwork. Strikingly insulin-stimulated GLUT4 translocation was preferentially enriched at these NET-rich sites, whereas DNase-mediated NET degradation eliminated cfDNA signals and abolished the contraction-induced enhancement of GLUT4 translocation, glucose uptake and attenuated AS160 (T642) phosphorylation under low-dose insulin. Our findings demonstrate that neutrophils are essential components of the mechanism underlying enhanced post-exercise insulin sensitivity involving, at least in part, the local formation of NETs. These NET-governed immunometabolic niches constitute a structural and spatial framework underlying the exercise-induced acute improvement of insulin-responsive metabolic efficiency in skeletal muscle. KEY POINTS: Neutrophil extracellular traps (NETs) establish spatially confined immunometabolic niches that are indispensable for the post-exercise increase in insulin sensitivity. High-resolution imaging revealed that insulin-stimulated GLUT4 translocation is markedly enhanced predominantly in NET-rich perivascular regions, indicating a spatially restricted mechanism of post-exercise insulin sensitization. DNase-mediated degradation of NETs abolished this enhancement, establishing their essential role in local insulin-responsive GLUT4 translocation. These NETs are formed by neutrophils rapidly recruited to skeletal muscle after contraction and deposited along the capillary network.
Chen et al. (Tue,) studied this question.