Fat Cell Culture Supernatant Increased Liver Glycogen Synthesis Mechanism

Objective: To determine the effects of supernatant from pre-adipocytes or differentiated adipocytes of 3T3L1 cells on insulin sensitivity and glycometabolism of hepatocytes.Methods: (1) pre-adipocytes of 3T3L1 cells had been differentiated to mature adipocytes and the supernatant had been extracted from fat cells during 3T3L1 differentiation. (2) Glycogen staining were used to detect glycogen synthesis. (3) Western blotting evaluate the phosphorylation of IRS-2 and Akt in primary mice hepatocytes and HepG2 cells which treated with the supernatant, respectively. Meanwhile, the lever of phosphorylated Akt were assayed after treatment with TNF-α.Results: After treatment with the supernatant from pre-adipocytes and differentiated adipocytes of 3T3L1 cells, the synthesis of glycogen in mice primary hepatocytes and HepG2 cells increased. Furthermore, the level of phosphorylated Akt increased obviously after treated with the supernatant for 15 min and reached maximum at 30 min, then, decreased after treatment for 1 hour. Addition of exogenous TNF-αcan block the activation of Akt induced by the supernatant. Conclusion: Insulin resistance in obesity might caused primarily by adipose dysfunctions include secretions of abnormal levels of cytokines. Some substance in the supernatant from pre-adipocytes and differentiated adipocytes promoted the synthesis of glycogen and increased insulin sensitivity of hepatocytes, but these substance remained unknown and TNF-αcan diminished these effects.