Allosteric Modulation of AMPK Enzymatic Activity: In Vitro Characterization

Design, synthesis, and biological evaluation of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinones as a new series of AMPKɑ1β1γ1 activators

Adenosine monophosphate-activated protein kinase (AMPK) plays a key role in maintaining whole-body homeostasis and has been regarded as a therapeutic target for the treatment of diabetic nephropathy (DN). Herein, a series of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinone derivatives is reported as AMPKɑ1β1γ1 activators. The in vitro biological assay demonstrated that compounds 12k (EC₅₀ [AMPKα1γ1β1] = 180 nM) and 13q (EC₅₀ [AMPKα1γ1β1] = 2 nM) displayed significant enzyme activation. Mechanism studies indicated that both compounds reduced the levels of reactive oxygen species in a rat kidney fibroblast cell line (NRK-49F) stimulated by transforming growth factor-β and induced early apoptosis of NRK-49F cells at 10 μM. Molecular docking studies suggested that 13q exhibited critical hydrogen-bond interactions with the critical amino acid residues Lys29, Lys31, Asn111, and Asp88 at the binding site of the AMPK protein. These results enrich the structure pool of AMPK activators and provide novel lead compounds for the subsequent development of compounds with a promising therapeutic potential against DN.

Promise and challenges for direct small molecule AMPK activators

AMP-activated protein kinase (AMPK) is an evolutionary conserved and ubiquitously expressed serine/threonine kinase playing a central role in the coordination of energy homeostasis. Based on the beneficial outcomes of its activation on metabolism, AMPK has emerged as an attractive target for the treatment of metabolic diseases. Identification of novel downstream targets of AMPK beyond the regulation of energy metabolism has renewed considerable attention in exploiting AMPK signaling for novel therapeutic targeting strategies including treatment of cancer and inflammatory diseases. The complexity of AMPK system with tissue- and species-specific expression of multiple isoform combination regulated by various inputs, post-traductional modifications and subcellular locations presents unique challenges for drug discovery. Here, we review the most recent advances in the understanding of the mechanism(s) of action of direct small molecule AMPK activators and the potential therapeutic opportunities.