Palmitate induces insulin resistance without significant intracellular triglyceride accumulation in HepG2 cells

• Published in: Metabolism, clinical and experimental clinical and experimental, 2010-07, Vol.59 (7), p.927-934
• Main Authors: Lee, Jin-young, Cho, Hyang-Ki, Kwon, Young Hye
• Format: Article
• Language: English
• Subjects: Azo Compounds; Biological and medical sciences; Blotting, Western; Cell Line; Chromatography, Thin Layer; Endocrinology & Metabolism; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - metabolism; Fatty Acids, Nonesterified - pharmacology; Fatty Liver - chemically induced; Fatty Liver - pathology; Feeding. Feeding behavior; Fluorometry; Fundamental and applied biological sciences. Psychology; Histocytochemistry; Humans; Insulin Resistance; Lipids - chemistry; Lipids - isolation & purification; Liver - drug effects; Liver - metabolism; Molecular Chaperones; Oleic Acid - pharmacology; Oxazines; Palmitates - pharmacology; Triglycerides - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0026-0495; 1532-8600
• DOI: 10.1016/j.metabol.2009.10.012

Abstract Previous studies showed that increased release of free fatty acids from adipocytes leads to insulin resistance and triglyceride (TG) accumulation in the liver, which may progress into hepatic steatohepatitis. We and other investigators have previously reported that palmitate induces endoplasmic reticulum stress-mediated toxicity in several tissues. This work investigated whether palmitate could induce insulin resistance and steatosis in HepG2 cells. We treated cells with either saturated fatty acid (palmitate) or unsaturated fatty acid (oleate), and observed that palmitate significantly activated c-jun N-terminal kinase and inactivated protein kinase B. Both 4-phenylbutyric acid and glycerol significantly activated protein kinase B, confirming the involvement of endoplasmic reticulum stress in palmitate-mediated insulin resistance. Oleate, but not palmitate, significantly induced intracellular TG deposition and activated sterol regulatory element binding protein–1. Instead, diacylglycerol level and protein kinase C ɛ activity were significantly increased by palmitate, suggesting the possible role of diacylglycerol in palmitate-mediated lipotoxicity. Therefore, the present study clearly showed that palmitate impairs insulin resistance, but does not induce significant TG accumulation in HepG2 cells.