title: Co-culture with fat cells induces cellular insulin resistance in primary hepatocytes.
abstract: Obesity is highly correlated with systemic insulin resistance. To assess the effect of fat cell on the development of hepatic insulin resistance, an in vitro system was developed in which primary hepatocytes were kept in co-culture with 3T3-L1 cells, then insulin signaling and glycogen production were subsequently analyzed in hepatocytes. The results showed that insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-2 was significantly blocked. Insulin-regulated activation of Akt kinase and glucose production in the hepatocytes were also reduced after co-culture. On the other hand, addition of TNF-alpha or IL-6 neutralizing antibodies to the supernatant of co-culture recovered both IRS-2 phosphorylation and Akt activation. In conclusion, fat cells may induce insulin resistance in liver cells, and this process appears to be mediated by TNF-alpha and IL-6. Our data present first the direct evidence of interaction for insulin signaling event between the adipocytes and hepatocytes.
authors.affiliation: Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, China.
authors.forename: Zhencheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Jinghuan
authors.initials: J
authors.lastname: Lv
authors.forename: Rihua
authors.initials: R
authors.lastname: Zhang
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Zhu
authors.forename: Dongya
authors.initials: D
authors.lastname: Zhu
authors.forename: Yujie
authors.initials: Y
authors.lastname: Sun
authors.forename: Jian
authors.initials: J
authors.lastname: Zhu
authors.forename: Xiao
authors.initials: X
authors.lastname: Han
mesh_terms: D041721:3T3-L1 Cells; D021581:Active Transport, Cell Nucleus; D017667:Adipocytes / Q000166:cytology*; D000818:Animals; D018920:Coculture Techniques; D022781:Hepatocytes / Q000166:cytology*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D015850:Interleukin-6 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010750:Phosphoproteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; C526298:Irs2 protein, mouse; D010750:Phosphoproteins; D014409:Tumor Necrosis Factor-alpha; D051057:Proto-Oncogene Proteins c-akt