Meeting Abstract

92.3  Wednesday, Jan. 7  Does myostatin play a regulatory role outside of muscle growth and metabolism? BIGA, P. R. *; BRASCHAYKO, E.; GALT, N; PAKALA, K. P.; JENSEN, J.; North Dakota State Univeristy, Fargo; North Dakota State Univeristy, Fargo; North Dakota State Univeristy, Fargo; North Dakota State Univeristy, Fargo; North Dakota State Univeristy, Fargo peggy.biga@ndsu.edu

Myostatin (MSTN) is known to function as a negative regulator of muscle growth and has been shown to play a role in energy homeostasis in mammals. MSTN has been identified in many fish species and recent evidence supports similar functions in fish as seen in mammals. It appears that MSTNs actions are antagonistic to that of growth hormone (GH), as earlier work demonstrated decreased MSTN expression in GH-treated trout. Also, in trout and giant danio primary myoblast cells, MSTN gene expression is lowest during rapid cellular proliferation and increases as cells differentiate into myofibers. In determinate and indeterminate growing species that are closely related, MSTN is differentially expressed in response to GH. These results suggest that MSTN plays a role in muscle growth regulation and might be important in satellite cell fate in indeterminate growing fish. In addition to growth regulation, new evidence is emerging that MSTN might play a pivotal role outside of growth and metabolism. In mice, high-fat diet induced obesity induces an initial pro-inflammatory response, with an accompanying increase in muscle and spleen MSTN gene expression. In mice resistant to high-fat diet induced obesity, MSTN gene expression is significantly elevated in muscle and initially down-regulated in spleen tissue. In addition, a novel down-stream target of MSTN, mighty, plays an important role in innate immunity through NF-kappaB-dependent IL-6 production. Mighty also appears to be a positive growth-regulating factor, as gene expression is down-regulated during fasting, while MSTN is up-regulated. Circumstantial evidence supports a potential role of MSTN in regulating growth, metabolism, and immune responses in a possible combinatorial fashion.