Suppression of Grb2 expression improved hepatic steatosis, oxidative stress, and apoptosis induced by palmitic acid in vitro partly through insulin signaling alteration

Abstract

In this study, we aimed to study the role of growth factor receptor-bound protein 2 (Grb2) in palmitic acid-induced steatosis and other "fatty liver" symptoms in vitro. HepG2 cells, with or without stably suppressed Grb2 expression, were incubated with palmitic acid for 24 h to induce typical clinical "fatty liver" features, including steatosis, impaired glucose metabolism, oxidative stress, and apoptosis. MTT and Oil Red O assays were applied to test cell viability and fat deposition, respectively. Glucose uptake assay was used to evaluate the glucose utilization of cells. Quantitative polymerase chain reaction and Western blot were used to measure expressional changes of key markers of insulin signaling, lipid/glucose metabolism, oxidative stress, and apoptosis. After 24-h palmitic acid induction, increased fat accumulation, reduced glucose uptake, impaired insulin signaling, enhanced oxidative stress, and increased apoptosis were observed in HepG2 cells. Suppression of Grb2 in HepG2 significantly reduced fat accumulation, improved glucose metabolism, ameliorated oxidative stress, and restored the activity of insulin receptor substrate-1/Akt and MEK/ERK pathways. In addition, Grb2 deficiency attenuated hepatic apoptosis shown by reduced activation of caspase-3 and fluorescent staining. Modulation of Bcl-2 and Bak1 also contributed to reduced apoptosis. In conclusion, suppression of Grb2 expression in HepG2 cells improved hepatic steatosis, glucose metabolism, oxidative stress, and apoptosis induced by palmitic acid incubation partly though modulating the insulin signaling pathway.

Genome‐Wide Transcriptional Analysis Reveals the Protection against Hypoxia‐Induced Oxidative Injury in the Intestine of Tibetans via the Inhibition of GRB2/EGFR/PTPN11 Pathways

“…As reported in previous studies, GRB2 was related with formation of reactive and oxidative products [55, 56]. ROS are directly involved in gastrointestinal injury.…”

“…The inhibition of GRB2 can significantly reduce fat accumulation, improve glucose metabolism, ameliorate oxidative stress [55], and activate mitogen-activated protein kinase pathways [59]. Additionally, GRB2 deficiency reduces cell apoptosis by inactivating caspase-3.…”

SWELL1 is a regulator of adipocyte size, insulin signalling and glucose homeostasis

“…It is noteworthy that GRB2 loss of function enhances insulin-PI3K-AKT and MAP kinase signaling in cultured hepatocytes 47 and in C2C12 myoblasts 48 ; and also augments insulin signaling and glucose tolerance in vivo 48 , suggesting that GRB2 is a negative regulator of insulin signaling. We find that insulin-stimulation reduces both SWELL1-GRB2 and Cav1-GRB2, but not SWELL1-Cav1 interactions in WT adipocytes (Fig.…”

MiR-329 restricts tumor growth by targeting GRB2 in pancreatic cancer

“…pERK) to attenuate cell growth [24,25]. It has been illustrated that suppression of GRB2 is able to induce apoptosis in hepatic cancer [28]. Additionally, inhibition of GRB2/pERK pathway limited tumor development by promoting cell apoptosis [29,30].…”