The Effect And Mechanism Of Sleeve Gastrectomy Inhibiting NF-κB Signaling Pathway To Improve Non-Alcoholic Fatty Liver Disease

ObjectivesNonalcoholic fatty liver disease(NAFLD)is a clinicopathological syndrome characterized by diffuse hepatocyte steatosis in addition to alcohol and other defined liver injury factors.Metabolic syndrome(MS)is a group of clinical syndromes characterized by multiple metabolic disorders including obesity,insulin resistance,hypertension and dyslipidemia.With the steep increase in the number of obese individuals worldwide,NAFLD,a hepatic manifestation of MS,has become the most common chronic liver condition and imposed a heavy burden on human health and social medical expenditures.Currently,the primary treatment for NAFLD is weight loss.More and more studies have confirmed that sleeve gastrectomy(SG)can achieve weight loss and significantly improve NAFLD,but the specific mechanism remains to be further elucidated.Nuclear transcription factor-κB(NF-κB)pathway is a classic inflammatory pathway closely related to the occurrence and development of NAFLD.This study aims to determine the effects of SG on lipid metabolism indicators and hepatic histomorphology through a NAFLD animal model,and to detect the expression levels of hepatic NF-κB pathway related proteins and inflammatory cytokines in the liver and serum after SG.To investigate intermedium of SG affecting the expression of hepatic NF-κB pathway through NAFLD cell model,and to further explore the mechanism of SG improving NAFLD.The NAFLD cell model is used to investigate the intermedium that may mediate the effect of SG on hepatic lipid accumulation and inflammation,and further explore the role and mechanism of SG in improving NAFLD.Materials and MethodsIn the animal experiment,NAFLD mouse models were induced by high fat diet(HFD)and randomly divided into sham operation group(Sham)and SG group.Within 8 weeks after surgery,the body weight of the mice was measured once a week,and the food intake was measured at the 1st,4th,and 8th weeks after surgery respectively.The mice were sacrificed to collect serum and liver samples at the 8th week after surgery.The differences in liver weight,liver function,and serum lipids between groups were detected.Hematoxylin eosin(HE)staining,oil red O staining,and Sirius red staining were used to evaluate the histological and morphological changes of the liver.Real-time quantitative polymerase chain reaction(RT-qPCR)was used to detect the mRNA levels of hepatic lipid metabolism genes and inflammatory cytokines genes.Western blot(WB)was used to detect the expression levels of proteins related to the hepatic NF-κB pathway and its negative regulatory signal AMP-activated protein kinase(AMPK)pathway.Enzyme linked immunosorbent assay(ELISA)was used to detect the levels of serum inflammatory cytokines and glucagon-like peptide-1(GLP-1)in mice.In the cell experiment,a mixture of 0.5mM palmitic acid(PA)and 1mM oleic acid(OA)was used to intervene HepG2 cells to establish models mimicking NAFLD in vitro.The established models were used to explore the effects of different concentrations of GLP-1(10nM,20nM,50nM,100nM,and 200nM)on NF-κB pathway related proteins at the cellular and molecular level,to determine the optimal GLP-1 intervention concentration,and to further investigate the effects of GLP-1 on lipid accumulation,AMPK pathway related proteins,and inflammatory related cytokines mRNA levels.ResultsCompared with Sham group,metabolic indicators such as body weight,food intake,liver weight,liver function,and blood lipids of mice in SG group were significantly improved.Histomorphological staining of the liver showed that the hepatic structure,hepatic steatosis,and degree of fibrosis were significantly improved after SG.In addition,the expression levels of hepatic lipogenesis and lipid uptake related genes,hepatic NF-κB pathway related proteins,hepatic and systemic pro-inflammatory cytokines(Interleukin(IL)-1β,IL-6,tumor necrosis factor-α(TNF-α),C-X-C motif chemokine ligand2(CXCL2))were significantly downregulated,and the expression levels of hepatic fatty acids β oxidative genes,hepatic and systemic anti-inflammatory cytokines(IL-4 and IL-10),and serum GLP-1 were significantly upregulated.In vitro experiments have shown that GLP-1 could inhibit NF-κB pathway activity in a concentration dependent manner,significantly alleviate lipid accumulation in HepG2 cells under metabolic stress,downregulate the expression levels of pro-inflammatory cytokines,and upregulate the expression levels of anti-inflammatory cytokines.In vivo and in vitro experiments have confirmed that both SG and GLP-1 can activate AMPK pathway which is the negative regulatory signal of NF-κB pathway.ConclusionSG can significantly reduce body weight and improve metabolic indicators such as liver function,serum lipids,and hepatic steatosis.SG can also activate AMPK signaling pathways and inhibit NF-κB activity through GLP-1,regulate the expression level of inflammatory related cytokines,thereby relieve hepatic and systemic inflammation levels,and ultimately alleviate the progression of NAFLD.