Insulin decreases inflammatory signal transcription factor expression in primary human liver cells after LPS challenge

Abstract

Hepatic homeostasis is essential for survival in critically ill and burned patients. Insulin administration improves survival and decreases infections in these patients. To determine the molecular mechanisms, the aim of the present study was to establish a stress model using primary human hepatocytes (PHHs) and to study the effects of insulin on the hepatic inflammatory signaling cascade. Liver tissue was obtained from general surgical patients, and PHHs were isolated and maintained in culture. Primary hepatocyte cultures were challenged with various doses of lipopolysaccharide (LPS), and the inflammatory signal transcription cascade was determined by real-time PCR. In subsequent experiments, primary hepatocyte cultures were challenged with LPS and insulin was added in various doses. Glucose was determined by colorimetric assays. PHHs treated with 100 μg/mL LPS showed a profound inflammatory reaction with increased expression of interleukin (IL)-6, IL-10, IL-1β, tumor necrosis factor (TNF), and signal transducer and activator of transcription 5 (STAT-5). Insulin at 10 IU/mL significantly decreased IL-6, TNF, and IL-1β at pretranslational levels, an effect associated with decreased STAT-5 mRNA expression (P < 0.05). Glucose concentration and cellular metabolic activity were not different between controls and insulin-treated cells. Based on our results, we suggest that primary hepatocyte cultures can be used to study the effect of LPS on the inflammatory cascade. Insulin decreases hepatic cytokine expression, which is associated with decreased STAT-5 expression.