Context: Given the promising effects of prolonged treatment with beta2-agonist on insulin sensitivity in animals and nondiabetic individuals, the beta2-adrenergic receptor has been proposed as a target to counter peripheral insulin resistance. On the other hand, rodent studies also reveal that beta2-agonists acutely impair insulin action, posing a potential caveat for their use in treating insulin resistance.
Objective: To assess the impact of beta2-agonist on muscle insulin action and glucose metabolism and identify the underlying mechanism(s) in 10 insulin-resistant subjects.
Methods and participants: In a crossover design, we assessed the effect of beta2-agonist on insulin-stimulated muscle glucose uptake during a 3-hour hyperinsulinemic isoglycemic clamp with and without intralipid infusion in 10 insulin-resistant, overweight subjects. Two hours into the clamp, we infused beta2-agonist. We collected muscle biopsies before, 2 hours into, and by the end of the clamp and analyzed them using metabolomic and lipidomic techniques.
Results: We establish that beta2-agonist, independently from and additively to intralipid, impairs insulin-stimulated muscle glucose uptake via different mechanisms. In combination, beta2-agonist and intralipid nearly eliminates insulin-dependent muscle glucose uptake. Although both beta2-agonist and intralipid elevated muscle glucose-6-phosphate, only intralipid caused accumulation of downstream muscle glycolytic intermediates, whereas beta2-agonist attenuated incorporation of glucose into glycogen.
Conclusion: Our findings suggest that beta2-agonist inhibits glycogenesis, whereas intralipid inhibits glycolysis in skeletal muscle of insulin-resistant individuals. These results should be addressed in future treatment of insulin resistance with beta2-agonist.
Keywords: beta2-adrenergic agonists; glucose-6-phosphate; glycogenesis; insulin resistance; intralipid; muscle glucose uptake.
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