Pterostilbene reverses palmitic acid mediated insulin resistance in HepG2 cells by reducing oxidative stress and triglyceride accumulation

Abstract

Insulin resistance (IR) is known to precede onset of type 2 diabetes and increased oxidative stress appears to be a deleterious factor leading to IR. In this study, we evaluated ability of Pterostilbene (PTS), a methoxylated analog of Resveratrol and a known antioxidant, to reverse palmitic acid (PA)-mediated IR in HepG2 cells. PTS prevented ROS formation and subsequent oxidative lipid damage by reducing the expression of NADPH Oxidase 3 (NOX3) in PA treated HepG2 cells. Hepatic glucose production was used as a measure of IR and PTS reversed PA-mediated increase in hepatic glucose production by reducing expression of genes coding for gluconeogenic enzymes namely glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC); and their transcription factors cAMP response element binding protein (CREB) and fork head class box O (FOXO1) along with its co-activator peroxisome proliferator-activated receptor gamma co-activator-1 α (PGC1α). PTS reversed PA-mediated activation of c-jun N-terminal kinase (JNK), which in turn altered insulin signaling pathway by phosphorylating IRS-1 at Ser 307, leading to inhibition of phosphorylation of Akt and GSK3β. PTS also reduced PA-mediated lipid accumulation by reducing expression of transcription factors SREBP1c and PPARα. SREBP1c activates genes involved in fatty acid and triglyceride synthesis while PPARα activates CPT1, a rate limiting enzyme for controlling entry and oxidation of fatty acids into mitochondria. PTS, however, did not influence PA uptake confirmed by using BODIPY-labeled fluorescent C16 fatty acid analog. Thus, our data provides a possible mechanistic explanation for reversal of PA-mediated IR in HepG2 cells.

Four sesquiterpene glycosides from loquat (Eriobotrya japonica) leaf ameliorates palmitic acid-induced insulin resistance and lipid accumulation in HepG2 Cells via AMPK signaling pathway

“…Liver is a critical metabolic organ in maintenance of glucose and lipid homeostasis (Birkenfeld & Shulman, 2014). It has been shown that excessive nutrients induce a greater increase in liver fat and insulin resistance and long-term treatment with PA can cause IR (Malik et al, 2019). PA-induced cells have been widely used as an IR model in vitro.…”

Skimmin Improves Insulin Resistance via Regulating the Metabolism of Glucose: In Vitro and In Vivo Models

“…The activity of the NADPH oxidase (NOX) is critical to the production of ROS in the organism. Previous studies showed that the ROS production increased by up-regulating the expression of NADPH oxidase 3 (NOX3), activating p38MAPK and JNK signaling pathway, and inducing insulin resistance in palmitate-induced HepG2 cells (Gao et al, 2010;Malik et al, 2019). Our studies found that skimmin can inhibit palmitic acid-induced the production of ROS, and 40 mmol/L skimmin was more obvious using flow cytometry assay (P < 0.05), which was better than metformin, a drug used to treat diabetes ( Figure 3A).…”

Apigenin Ameliorates Insulin Resistance and Lipid Accumulation by Endoplasmic Reticulum Stress and SREBP-1c/SREBP-2 Pathway in Palmitate-Induced HepG2 Cells and High-Fat Diet–Fed Mice

“…HepG2 cells are currently widely applied to study fatty liver (Chen et al, 2018). Palmitic acid (PA) is one of the most common saturated fats in the diet (Malik et al, 2019). The culture medium containing PA can induce the HepG2 cells to produce IR and can also better simulate the nutritional obesity status of the human liver (Mo et al, 2019).…”