AMP-activated protein kinase (AMPK) is a central energy sensor at the cellular and organismal level and a promising target in the therapy of metabolic disorders. Studies show that methotrexate, a dihydrofolate reductase inhibitor, and the sulphanilamide sulfasalazine can affect AMPK activity in skeletal muscle. The mechanism of action is inhibition of the ATIC (5-amino-4-imidazolecarboxamide ribonucleotide formyltransferase/IMP cyclohydrolase) enzyme, which suppresses the metabolism of ZMP, a phosphorylated (active) form of pharmacological AMPK activator AICAR. In this way, the threshold for AICAR-stimulated AMPK activation is decreased. Consequently, cellular glucose uptake and lipid oxidation are increased, thus reducing hyperglycaemia and insulin resistance in persons with type 2 diabetes. Our aim was to investigate whether, in addition to methotrexate and sulfasalazine, AMPK function in skeletal muscle is modulated by some other clinically useful inhibitors of dihydrofolate reductase (trimetrexate and trimethoprim) or by sulphanilamides, such as sulfamethoxazole, which is used in combination with trimethoprim.
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