# Propionibacterium freudenreichii MJ2 Improves Dexamethasone-Induced Muscle Atrophy in Rats by Increasing Muscle Mass and Muscle Fiber Area **Authors:** Sang-Hun Kim, Hee-Eun Woo, Mirae An, Young- Hee Lim PMC · DOI: 10.4014/jmb.2510.10050 · 2026-01-18 ## TL;DR This study shows that Propionibacterium freudenreichii MJ2 can help reduce muscle atrophy caused by dexamethasone in rats. ## Contribution The novel finding is that both live and heat-killed MJ2 improve muscle atrophy by increasing muscle mass and fiber area. ## Key findings - Heat-killed MJ2 inhibits the decrease in C2C12 myotube diameter caused by dexamethasone. - MJ2 treatment increases grip strength, muscle mass, and muscle fiber area in rats with DEX-induced atrophy. - MJ2 downregulates atrophy-related genes and activates muscle protein synthesis pathways. ## Abstract Muscle atrophy refers to the loss or wasting of muscle tissue caused by medication, aging, disease, and injury. Propionibacterium freudenreichii MJ2 (MJ2) shows anti-inflammatory and anti-obesity properties. This study aimed to determine the effects of MJ2 on dexamethasone (DEX)-induced muscle atrophy in C2C12 myoblast cell line and rats. Heat-killed P. freudenreichii MJ2 (HK-MJ2) inhibited a decrease in the diameter of DEX-treated C2C12 myotubes. Additionally, it downregulated the expression of muscle atrophy- and apoptosis-related genes (MuRF-1, Atrogin-1, and Bax/Bcl-2) in DEX-treated C2C12 cells while activating proteins (p-Akt/Akt and p-mTOR/mTOR) associated with muscle protein synthesis. Live- and HK-MJ2 treatment increased grip strength, muscle mass, and muscle fiber area in rats with DEX-induced muscle atrophy. In conclusion, both live- and HK-MJ2 increase muscle mass and muscle fiber area, resulting in the improvement of DEX-induced muscle atrophy. ## Linked entities - **Genes:** TRIM63 (tripartite motif containing 63) [NCBI Gene 84676], Fbxo32 (F-box protein 32) [NCBI Gene 67731], BAX (BCL2 associated X, apoptosis regulator) [NCBI Gene 581], BCL2 (BCL2 apoptosis regulator) [NCBI Gene 596] - **Chemicals:** dexamethasone (PubChem CID 5743) - **Species:** Mus musculus (taxon 10090) ## Full-text entities - **Genes:** glyceraldehyde-3-phosphate dehydrogenase [NCBI Gene 108351137], Trim63 (tripartite motif containing 63) [NCBI Gene 140939] {aka Murf, Murf1, Rnf28}, Bcl2 (BCL2, apoptosis regulator) [NCBI Gene 24224] {aka Bcl-2}, Fbxo32 (F-box protein 32) [NCBI Gene 171043] {aka Atrogin1, MAFbx}, Bcl2 (B cell leukemia/lymphoma 2) [NCBI Gene 12043] {aka Bcl-2, C430015F12Rik, D630044D05Rik, D830018M01Rik}, Got2 (glutamic-oxaloacetic transaminase 2) [NCBI Gene 25721] {aka ASPATA, mAAT}, Nr3c1 (nuclear receptor subfamily 3, group C, member 1) [NCBI Gene 14815] {aka GR, Grl-1, Grl1}, MTOR (mechanistic target of rapamycin kinase) [NCBI Gene 2475] {aka FRAP, FRAP1, FRAP2, RAFT1, RAPT1, SKS}, PTK2B (protein tyrosine kinase 2 beta) [NCBI Gene 2185] {aka CADTK, CAKB, FADK2, FAK2, PKB, PTK}, Akt1 (Akt serine/threonine kinase 1) [NCBI Gene 11651] {aka Akt, LTR-akt, PKB, PKB/Akt, PKBalpha, Rac}, Myog (myogenin) [NCBI Gene 29148], Foxo3 (forkhead box O3) [NCBI Gene 56484] {aka 1110048B16Rik, 2010203A17Rik, FKHRL1, Fkhr2, Foxo3a}, Mtor (mechanistic target of rapamycin kinase) [NCBI Gene 56717] {aka 2610315D21Rik, FRAP, FRAP2, Frap1, RAFT1, RAPT1}, Akt1 (AKT serine/threonine kinase 1) [NCBI Gene 24185] {aka Akt}, Fbxo32 (F-box protein 32) [NCBI Gene 67731] {aka 4833442G10Rik, ATROGIN1, Gm20361, MAFbx}, Trim63 (tripartite motif-containing 63) [NCBI Gene 433766] {aka MuRF1, RF1, Rnf28}, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) [NCBI Gene 2597] {aka G3PD, GAPD, HEL-S-162eP}, Bax (BCL2-associated X protein) [NCBI Gene 12028], AKT1 (AKT serine/threonine kinase 1) [NCBI Gene 207] {aka AKT, PKB, PKB-ALPHA, PRKBA, RAC, RAC-ALPHA}, Mtor (mechanistic target of rapamycin kinase) [NCBI Gene 56718] {aka Frap1, RAFT1} - **Diseases:** inflammation (MESH:D007249), arthritis (MESH:D001168), brain disorders (MESH:D001927), allergies (MESH:D004342), wasting of muscle tissue (MESH:D009379), Liver toxicity (MESH:D056486), COPD (MESH:D029424), intestinal disorders (MESH:D007410), bone loss (MESH:D001847), muscle (MESH:D019042), diabetes (MESH:D003920), Muscle Atrophy (MESH:D009133), Muscle loss (MESH:D009135), asthma (MESH:D001249), atrophy (MESH:D001284), Osteoporosis (MESH:D010024), Cytotoxicity (MESH:D064420), cancer (MESH:D009369), infectious diseases (MESH:D003141), loss of skeletal muscle (MESH:D005207), wasting (MESH:D019282), sarcopenia (MESH:D055948), spinal diseases (MESH:D013122), musculoskeletal diseases (MESH:D009140), atrophic (MESH:D020966), loss of body weight (MESH:D001835), infection (MESH:D007239), obesity (MESH:D009765), loss of muscle mass (MESH:C536030) - **Chemicals:** HS (MESH:D006859), isoflurane (MESH:D007530), saline (MESH:D012965), water (MESH:D014867), paraffin (MESH:D010232), CO2 (MESH:D002245), MTT (MESH:C070243), resveratrol (MESH:D000077185), hematoxylin (MESH:D006416), polyacrylamide (MESH:C016679), teichoic acids (MESH:D013682), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MESH:C022616), Ser (MESH:D012694), eosin (MESH:D004801), H&E (MESH:D006371), PVDF (MESH:C024865), penicillin (MESH:D010406), Tween 20 (MESH:D011136), streptomycin (MESH:D013307), DEX (MESH:D003907), Branched-chain amino acids (MESH:D000597), HDDMJ (-), CRE (MESH:D003404), thalidomide (MESH:D013792), LEU (MESH:D007930), matrine (MESH:D000093842), salidroside (MESH:C009172), propionic acid (MESH:C029658), vitamin B12 (MESH:D014805), nitrogen (MESH:D009584), formaldehyde (MESH:D005557), SDS (MESH:D012967) - **Species:** Rattus norvegicus (brown rat, species) [taxon 10116], Mycolicibacterium sp. J2 (species) [taxon 2993511], Propionibacterium freudenreichii (species) [taxon 1744] - **Cell lines:** C2C12 — Mus musculus (Mouse), Spontaneously immortalized cell line (CVCL_0188), HK-MJ2 — Homo sapiens (Human), Primary cutaneous T-cell non-Hodgkin lymphoma, Cancer cell line (CVCL_1414) ## Figures 8 figures with captions in the complete paper: https://tomesphere.com/paper/PMC12828323/full.md --- Source: https://tomesphere.com/paper/PMC12828323