Hee Kyu Kim’s scientific contributions

This study investigates the effects of pilot scale Alnus japonica hot water extract (AJHW) on muscle loss and muscle atrophy. Building on previous in vitro studies, in vivo experiments were conducted to evaluate muscle strength, mass, fiber size, protein synthesis, and antioxidant activity. The results showed that AJHW significantly restored muscle strength, increased muscle mass, enhanced the expression of muscle synthesis markers, such as Akt and mTOR, and apoptosis inhibition markers, such as Bcl-2, compared to the muscle atrophy control. Muscle degradation markers, such as Atrogin1, MuRF1, FoxO3α, and the apoptosis activation marker Bax, were decreased compared to the muscle atrophy control. Additionally, AJHW significantly boosted the activity of antioxidant factors like SOD, catalase, and Gpx, suggesting its protective role against oxidative stress-induced muscle damage. The enhanced effects were attributed to the high content of hirsutanonol and hirsutenone, which synergized with oregonin, compounds, identified through phytochemical analysis. While these findings support the potential of AJHW as a candidate for preventing muscle loss, further studies are needed to confirm its efficacy across diverse atrophy models and to elucidate its exact mechanisms.

Background/Objectives: Sarcopenia is characterized by the loss of muscle mass and function, increases in mortality rate, and risk of comorbidities in the elderly. This study evaluated the effects of Alnus japonica hot water extract (AJHW) and its active compound, oregonin, on muscle atrophy and apoptosis in vitro. Methods: AJHW underwent phytochemical analysis. C2C12 cells were subjected to H2O2 and dexamethasone to induce oxidative stress and muscle loss, after which AJHW and oregonin were administered to assess their impacts on cell viability, apoptosis, muscle protein synthesis stimulation, and muscle protein degradation inhibition. Cell viability was assessed via an MTT assay, and apoptosis was analyzed by measuring Bcl-2, Bax, cleaved caspase-3, and cleaved PARP through Western blotting. Western blotting and RT-PCR were utilized to analyze MyoD, Myogenin, Atrogin-1, and MuRF1 protein and gene expression in a muscle atrophy model, as well as the Akt/mTOR and FoxO3α pathways. Results: AJHW was confirmed to contain oregonin, an active compound. AJHW and oregonin significantly increased cell viability and reduced apoptosis by upregulating Bcl-2 and downregulating Bax, cleaved caspase-3, and cleaved PARP. They significantly enhanced muscle protein synthesis through the upregulation of MyoD and Myogenin, while diminishing muscle degradation by downregulating Atrogin-1 and MuRF1. The activation of the Akt/mTOR pathway and inhibition of the FoxO3α pathway were also observed. Conclusions: AJHW and oregonin effectively prevented muscle cell apoptosis, promoted muscle protein synthesis, and inhibited muscle protein degradation in vitro. These results suggest that AJHW and oregonin could serve as therapeutic agents to prevent and treat sarcopenia.