Exogenous Delta-Like 1 Homolog (DLK1)-Fc Treatment Attenuates Muscle Atrophy in Both Dexamethasone and High-Fat Diet–Induced Obesity Mice Models

Abstract

Skeletal muscle degeneration is accelerated in elderly patients with diabetes and the imbalance between muscle growth and wasting can lead to metabolic dysfunction. DLK1 is a member of the EGF-like family and essential for skeletal muscle development and regeneration. To identify whether exogenous DLK1 treatment can prevent muscle wasting, we assessed muscle mass as well as muscle differentiation and atrophy markers in two different models: dexamethasone and high fat diet (HFD)-induced obesity mice models (n=7-8 per each group). In the dexamethasone model, mice were divided into (1) control, (2) dexamethasone treatment (1mg/Kg, 2 weeks), and (3) DLK1 (0.8mg/Kg, 2 weeks) and dexamethasone treatment groups. In the HFD model, mice were divided into (1) control, (2) HFD (60% calories from fat, 8 weeks), and (3) HFD with DLK1 treatment (0.8mg/Kg, 8 weeks) groups. The expressions of genes related to muscle differentiation and atrophy were determined using RT-PCR. We observed that dexamethasone reduced muscle mass and markedly increased atrophy makers including atrogin-1 and murf-1. DLK1 treatment attenuated these degenerative changes. Furthermore, the level of myostatin, which inhibits muscle cell growth, was reduced in DLK1 treatment group compared to dexamethasone group. Additionally, compared to HFD group, DLK1 inhibited muscle atrophy by increasing the differentiation marker: myoD, and decreasing the atrophy markers: mysotatin, atrogin-1, and murf-1. Taken together, these results suggest that DLK1 attenuates both dexamethasone and HFD-induced muscle atrophy in mice by suppressing the downstream signaling of myostatin/atrogin-1/murf-1 pathway. The increased expression of myoD indicates that DLK1 treatment can also improve the quality of muscle formation. Our study implies that DLK1 could be a promising candidate in the treatment of aging or diabetes-related sarcopenia, characterized by muscle atrophy and dysfunction. Disclosure J. Lee: None. M. Lee: None. H. Jung: None. J. Lee: None. Y. Cho: None. J. Bae: None. Y. Lee: None. B. Lee: None. E. Kang: None. B. Cha: None.