Analyses of Off-Target Effects on Cardiac and Skeletal Muscles by Berberine, a Drug Used to Treat Cancers and Induce Weight Loss.

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Previous reports from our laboratory describing the formation of myofibrils in cultured embryonic cardiac and skeletal muscle cells have proposed that myofibrillogenesis occurs in three steps of increasing protein organization: beginning with premyofibrils, followed by nascent myofibrils, and ending in mature myofibrils. Inhibitors of the ubiquitin proteasome system (UPS) prevented nascent myofibrils from progressing directly to mature myofibrils in cultured cardiac and skeletal muscle cells, supporting a three-step model of assembly in which some of the proteins in nascent myofibrils are proteolyzed to allow the assembly of mature myofibrils. Application of UPS inhibitors on cultured muscle cells suggests possible explanations for the off-target cardiac and skeletal muscle adverse effects of UPS drugs, which are used on cancer patients. Berberine, a plant derivative, has been used to treat various cancers, including multiple myelomas. In contrast to the use of UPS drugs, success was reported with Berberine in multiple myeloma patients with no off-target effects on their hearts. We have exposed cultured cardiac and skeletal muscle cells to Berberine, a ligase inhibitor of UHRF1 (ubiquitin-like with PHD and RING finger domains). Berberine inhibited myofibril assembly at the nascent myofibril stage in embryonic skeletal muscle cells but had no effect in the assembly of mature myofibrils in embryonic heart cells. RT-PCR experiments demonstrated Berberine inhibition of mRNA for muscle myosin II heavy chains but not for muscle actin mRNA in skeletal muscle cells. Berberine is also being used as a popular weight losing compound, because it is much cheaper and available without a prescription than the semaglutide containing weight losing drugs (Wegovy and Ozempic). In contrast to Berberine, semaglutide had no effects on myofibril assembly in culture assays for both cardiac and skeletal muscle cells. We postulate that analyses of cultured embryonic cardiac and skeletal muscle cells will provide a preclinical assay for the testing of novel cancer drugs with improved outcomes for patients, an important goal for cancer therapeutics.