Endocrine Abstracts

Type II diabetes is a clinical disorder of glucose and fat metabolism, caused by an inability of insulin to promote sufficient glucose uptake into adipose tissue and striated muscle and to prevent glucose output from the liver. Skeletal muscle is an important element for the maintenance of glucose homeostasis because it can increase, after stimulation, glucose uptake from the blood. In previous experiments we found that acylated ghrelin (AG), unacylated ghrelin (UAG), obestatin (Ob) exert antiapoptotic and protective effects on β-cells and human pancreatic islets; moreover they enhance insulin secretion and stimulate glucose uptake in β-cells and human pancreatic islets. The aim of this study is to gain further insight on the metabolic role of AG, UAG and Ob in peripheral tissues, in particular on a muscle cell line (C2C12). Cells were grown in DMEM containing 10% FCS. At 80% confluence, cells were switched to a 2% heat-inactivated horse serum in DMEM, for differentiation of myoblast into myotubes. During this time, medium was changed every 24 h, and treatments began on day 5. All the experiments were conducted on myotubes. Gene expression was evaluated by RT-PCR or real time PCR, while the activation of specific signaling pathways by western blotting. To assess the effects of the peptides, we performed metabolical studies: free fatty acid (FFA) and glucose uptake, respectively using QBT Fatty acid uptake kit and [³H]-2-deoxyglucose (with liquid scintillation counting). In C2C12 AG, UAG and Ob increased expression of GLUT-4 and CD36, which binds long-chain fatty acids and facilitates their transport into cells. These effects involved PI3K/Akt and AMPK phosphorylation. These findings indicate that AG, UAG and Ob promote glucose and FFA uptake in C2C12 muscle cells and suggest that they may exert beneficial effects in vivo in disorders such as insulin resistance and type II diabetes.