3,3'-Diindolylmethane ameliorates muscle atrophy by modulating mitochondrial function and calcium homeostasis

Background: Sarcopenia is a chronic degenerative condition characterized by the progressive loss of muscle mass and function. Current therapeutic strategies exhibit limited therapeutic efficacy and present substantial challenges in ensuring sustained patient compliance. Although mitochondrial dysfunction is a confirmed biomarker of skeletal muscle atrophy, the exact molecular mechanisms governing this process have yet to be fully elucidated. Notably, store-operated calcium entry (SOCE) not only serves as a pivotal mechanism in mitochondrial calcium signaling but has also been recently identified as a key contributor to sarcopenia. Novel formulations of 3,3'-Diindolylmethane (DIM) shows improved pharmacokinetics with minimal side effects and high bioavailability, thereby enhancing therapeutic adherence. However, previous studies have not fully unraveled the therapeutic potential of DIM for managing sarcopenia or its precise molecular mechanisms.

Purpose: This research was conducted to systematically explore the therapeutic efficacy of DIM in sarcopenia through three research models and hierarchically clarify the underlying molecular mechanisms.

Methods: We used three distinct models: a murine model of muscle atrophy induced by long-term injection of dexamethasone (DEX), a worm model of natural aging in Caenorhabditis elegans (C. elegans), and a cell model of C2C12 myotube atrophy intervened by dexamethasone. The primary evaluation measures encompassed histopathological examination, immunofluorescence, fluorescent probes, western blot and flow cytometry.

Results: DIM demonstrated therapeutic promise by enhancing grip strength and myofiber quality in mice, extending lifespan of C. elegans. DIM attenuated DEX-induced myotube atrophy while promoting myotube differentiation. Mechanistically, DIM mitigated mitochondrial dysfunction by inhibiting excessive Reactive Oxygen Species generation and decline of mitochondrial membrane potential caused by muscle atrophy. Concurrently, DIM enhanced the expression of stromal interaction molecule 1 to activate SOCE, thereby modulating calcium homeostasis and promoting muscle cell differentiation, effectively preventing further muscle atrophy.

Conclusions: Importantly, this study constitutes the inaugural demonstration across three distinct experimental models (murine muscle atrophy, Caenorhabditis elegans and cellular systems) that DIM activates and enhances the SOCE mechanism by improving mitochondrial function, thereby restoring disrupted calcium homeostasis and alleviating muscle atrophy. These findings offer novel mechanistic insights and promising intervention targets regarding how natural phytochemicals counteract sarcopenia, while concurrently underscoring the therapeutic potential of DIM in alleviating muscle atrophy.