Exercise modulates postreceptor insulin signaling and glucose transport in muscle-specific insulin receptor knockout mice
Summary
This summary is machine-generated.Muscle insulin receptors are not essential for exercise to increase glucose uptake or glycogen synthesis. Exercise-stimulated glucose uptake and insulin sensitivity in muscle remain normal even without muscle insulin receptors.
Area Of Science
- Exercise Physiology
- Metabolic Signaling
- Skeletal Muscle Biology
Background
- Physical exercise enhances skeletal muscle glucose uptake and insulin sensitivity.
- Insulin receptor (IR) signaling is crucial for mediating insulin's effects on glucose metabolism.
- The specific role of muscle IR in exercise-induced metabolic adaptations requires further elucidation.
Purpose Of The Study
- To investigate the necessity of muscle-specific insulin receptors for exercise-stimulated glucose uptake and insulin sensitivity.
- To determine the impact of muscle IR deletion on glucose metabolism and insulin signaling pathways during exercise and insulin stimulation.
- To explore the mechanisms underlying the synergistic effects of exercise and insulin on glucose transport in the absence of muscle IR.
Main Methods
- Utilized muscle-specific insulin receptor knockout (MIRKO) mice.
- Assessed 2-deoxy-glucose (2DG) uptake in soleus muscles under resting, insulin-stimulated, exercise-stimulated, and combined exercise-plus-insulin conditions.
- Measured glycogen content, glycogen synthase activity, IR tyrosine phosphorylation, and phosphatidylinositol 3-kinase (PI3K) and Akt/GSK3 signaling pathway activation.
Main Results
- MIRKO mice exhibited normal resting and exercise-stimulated 2DG uptake, and preserved synergistic activation with combined exercise and insulin.
- Exercise, but not insulin, increased glycogen synthase activity in MIRKO mice.
- Insulin-induced IR phosphorylation and PI3K activity were absent in MIRKO muscle, yet exercise markedly enhanced a small insulin-mediated activation of Akt and GSK3.
Conclusions
- Normal muscle insulin receptor expression is not required for exercise-induced glucose uptake and glycogen synthase activation in vivo.
- The synergistic potentiation of glucose transport by exercise and insulin is retained in MIRKO mice, suggesting roles for non-muscle factors or downstream signaling.
- These findings highlight the complex interplay between exercise and insulin signaling in skeletal muscle glucose homeostasis.
View abstract on PubMed