Resistin induces insulin resistance by both AMPK-dependent and AMPK-independent mechanisms in HepG2 cells.
Resistin is a 12.5-KDa cysteine-rich peptide that has been implicated in the impairment of glucose homeostasis via the AMP-activated protein kinase (AMPK) pathway in a rodent model. However, the role resistin plays in humans is controversial. This study investigated the effect of resistin on glucose metabolism and insulin signaling using human recombinant resistin and small interfering RNA (siRNA) against AMPKalpha2 to treat the human liver HepG2 cells. The mRNA of key genes involved in glucose metabolism and the insulin-signaling pathway were detected by real-time RT-PCR. Phosphorylation levels of Akt and AMPK were measured by western blot. The incorporation of D-[U-(14)C] glucose into glycogen was quantitated by liquid scintillation counting. The results demonstrate that resistin stimulated expressions of glucose-6-phosphatase (G6Pase), phosphoenolypyruvate carboxykinase (PEPCK), and suppressor of cytokine signaling 3 (SOCS-3), repressed the expressions of insulin receptor substrate 2(IRS-2) and glucose transporter 2(GLUT2). In addition, resistin inhibited the insulin-induced phosphorylation of Akt independent of AMPK. In conclusion, our findings suggest that resistin induces insulin resistance in HepG2 cells at least partly via induction of SOCS-3 expression and reduction of Akt phosphorylation through an AMPK-independent mechanism. Resistin also increases glucose production via AMPK-mediated upregulated expression of the genes encoding hepatic gluconeogenic enzymes, G6Pase, and PEPCK.
Luo
Zhaofan
Z
Department of Endocrinology, The Second Affiliated Hospital, Sun Yat-Sen University, 510120, Guangzhou, People's Republic of China.
Zhang
Ying
Y
Li
Fangping
F
He
Juan
J
Ding
Helin
H
Yan
Li
L
Cheng
Hua
H
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D005937:Glucaric Acid / Q000378:metabolism; D051273:Glucose Transporter Type 2 / Q000235:genetics; D005952:Glucose-6-Phosphatase / Q000235:genetics; D006003:Glycogen / Q000096:biosynthesis; D006801:Humans; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins / Q000235:genetics; D007333:Insulin Resistance / Q000502:physiology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering; D052243:Resistin / Q000378:metabolism* / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics
D051273:Glucose Transporter Type 2; D007004:Hypoglycemic Agents; C526297:IRS2 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C499624:RETN protein, human; D034741:RNA, Small Interfering; D052243:Resistin; C495680:SLC2A2 protein, human; C106644:SOCS3 protein, human; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D006003:Glycogen; C526181:PRKAA2 protein, human; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases; D005952:Glucose-6-Phosphatase; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D005937:Glucaric Acid