TITLE:
Effect of Iron-Mediated Oxidative Stress on Insulin Resistance Through the Forkhead Box-Containing Protein O Subfamily-1 (FOXO-1) Pathway in Chronic Hepatitis C
AUTHORS:
Yoshinao Kobayashi, Motoh Iwasa, Hirohide Miyachi, Ryosuke Sugimoto, Hideaki Tanaka, Rumi Mifuji-Moroka, Naoki Fujita, Yasuhiro Sumida, Yoshiyuki Takei
KEYWORDS:
Chronic Hepatitis C; Gluconeogenesis; Insulin Resistance; Iron Metabolism; Oxidative Stress
JOURNAL NAME:
International Journal of Clinical Medicine,
Vol.4 No.1,
January
18,
2013
ABSTRACT:
Aims: Chronic hepatitis C virus (HCV) infection is often associated with glucose metabolic disorders and iron overload. It has recently been shown that reactive oxygen species (ROS) increase gluconeogenesis in hepatocytes through the forkhead box-containing protein O subfamily-1 (FOXO1)-dependent pathway. The aim of this study is proving a cause-and-effect relationship between iron-mediated ROS production and insulin resistance (IR) in chronic hepatitis C (CH-C) patients. Methods: The study included 42 patients with CH-C (22 males and 20 females, median age 53 years). Homeostasis model assessment of insulin resistance (HOMA-IR) value was assessed for each patient at entry. Gene expression levels in the biopsied liver tissues were determined by quantitative reverse transcription-polymerase chain reaction (RT- PCR). In addition, the effect of ROS on gluconeogenesis was assessed using HepG2 cells treated with a well-known ROS generator, diethylmaleate (DEM). Results: The serum ferritin levels were significantly correlated with the serum aspartate aminotransferase level, alanine aminotransferase level, HOMA-IR value, grade of fatty accumulation, total hepatic iron score, and 8-OH-deoxy-2’-guanosine (8-OHdG)-positive cell count. FOXO1 expression was correlated with 8-OHdG-positive cell count, phosphoenolpyruvate carboxykinase (PEPCK) expression, and HOMA-IR. In HepG2 cells, the gene transcription of FOXO1 and PEPCK was increased by DEM treatment, which was associated with an increase in non-phosphorylated FOXO1 protein in the nuclear fraction. Conclusions: Iron-mediated ROS production enhances gluconeogenesis through the FOXO1-mediated pathway and is an affecting factor to IR in patients with CH-C.