AMPK and PPARdelta agonists are exercise mimetics

Published in the prestigious journal Cell, this study led by Ronald Evans at the Salk Institute was a landmark in exercise biology. The research investigated whether pharmacological activation of the molecular pathways activated by exercise — specifically AMPK (AMP-activated protein kinase) and PPARδ (peroxisome proliferator-activated receptor delta) — could reproduce the metabolic benefits of physical activity in sedentary animals.

Sedentary mice received AICAR (an AMPK activator) orally for 4 weeks without any exercise protocol. The results revealed that treatment induced the expression of oxidative metabolic genes in skeletal muscle, increased fatty acid oxidation capacity, and promoted a reprogramming of muscle fibers toward a more oxidative phenotype. The most impressive finding was the 44% increase in exercise endurance (measured by treadmill running time) in AICAR-treated animals compared to controls.

Interestingly, the combination of GW1516 (a PPARδ agonist) with exercise produced even greater synergistic effects, with a 77% increase in endurance. This suggested that simultaneous activation of both pathways potentiates the benefits. The researchers also demonstrated that PPARδ acts as a "genomic switch" for the reprogramming of type I (oxidative) muscle fibers.

This work had enormous repercussions: the World Anti-Doping Agency (WADA) added AICAR to the list of prohibited substances in sport before there was even documented use by athletes. The study opened a new frontier in exercise mimetics research, with potential implications for patients with reduced mobility, muscular dystrophies, and metabolic diseases.