A comparison of chronic AICAR treatment-induced metabolic adaptations in red and white muscles of rats.

The signaling molecule 5'-AMP-activated protein kinase plays a pivotal role in metabolic adaptations. Treatment with 5-aminoimidazole-4-carboxamide-1-β-D-ribofranoside (AICAR) promotes the expression of metabolic regulators and components involved in glucose uptake, mitochondrial biogenesis, and fatty acid oxidation in skeletal muscle cells. Our aim was to determine whether AICAR-induced changes in metabolic regulators and components were more prominent in white or red muscle. Rats were treated with AICAR (1 mg/g body weight/day) for 14 days, resulting in increased expression levels of nicotinamide phosphoribosyltransferase (NAMPT), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), glucose transporter 4 proteins, and enhanced mitochondrial biogenesis. These changes were more prominent in white rather than red gastrocnemius muscle or were only observed in the white gastrocnemius. Our results suggest that AICAR induces the expression of metabolic regulators and components, especially in type II (B) fibers.