Establishment Of NAFLD Mice Model And Exploration Of Endoplasmic Reticulum Stress PERK-eIF2?-ATF4 Pathway Under GLP-1 Intervention

Objective:The specific mechanism of GLP-1 in the treatment of NAFLD is not completely clear.In this study,we established mice model of NAFLD to observe the expression of GRP78,PERK,eIF2? and ATF4,CHOP,Caspase12 in endoplasmic reticulum stress under GLP-1 intervention,and explore the regulation of GLP-1 on PERK-eIF2?-ATF4 pathway in non-alcoholic fatty liver disease.Methods:Five-week-old male C57BL/6 mice of SPF grade were randomly divided into two groups: high fat diet group(n = 17)and normal chow group(n = 9).After 12 weeks of feeding,each one was executed and the effect of modeling was evaluated.The high-fat diet group was further randomly divided into the experimental group(8)and the model group(8),and the normal diet group was classified into the normal group(8).The normal group was given normal chow + intraperitoneal injection of normal saline(0.6mg/kg.d),the model group was given high-fat feed + intraperitoneal injection of normal saline(0.6mg/kg.d),and the experimental group was given high-fat feed + intraperitoneal injection of Liraglutide(0.6mg/kg.d).During the intervention,drinking water was free,the duration of intervention was 4 weeks,and the specimens were collected 12 hours after fasting.Liver tissue was collected after 4 weeks of intervention and 12 hours of fasting.one part of tissue for pathological sections,other tissue for measuring GRP78?PERK?eIF2??ATF4?CHOP and Caspase12 expression levels by Western-blot and IHC.Rerults: 1.Body weight: Compared with normal group,body weight of the model group significantly increased,and the difference was statistically significant(37.00± 2.20vs27.50±1.69,p=0.000);compared with the model group,body weight of the experimental group significantly decreased,and the difference was statistically significant(27.63±1.50vs37..00±2.20,p=0.000).2.Liver histological score:Compared with normal group,the score of steatosis,ballooning,lobular inflammation,activity(ballooning and lobular inflammation),fibrosis in the model group significantly increased,and the difference was statistically significant(1.63±0.91vs0.00±0.00,P=0.002;1.38±0.52vs0.13±0.35,P=0.000;1.50±0.76vs0.00±0.00,P=0.001;2.88±0.99vs0.13±0.35,P=0.000;1.13±0.64vs0.00±0.00,P=0.002).Compared with model group,score of steatosis,ballooning,lobular inflammation,activity(ballooning and lobular inflammation)in the experimental group significantly decreased and the difference was statistically significant(0.00±0.00vs1.63±0.91,P=0.002;0.75±0.46vs1.38±0.52,P=0.023;0.75±0.46vs1.50±0.76,P=0.031;1.50±0.76vs2.88±0.99,P=0.008).The fibrosis score of the experimental group was slightly lower than that of the model group,but the difference was not statistically significant(1.00 0.93vs1.13 0.64,P = 0.758).3.Western blot:Compared with normal group,the expression level of GRP78?P ERK?eIF2??ATF4?Caspase12 and CHOP in the model group significantly in creased,and the difference was statistically significant(0.2800±0.0993vs0.1775±0.0287,P=0.014;0.6675±0.1835vs0.4987±0.1103,P=0.047;0.5000±0.1453 v s0.2336±0.1219,P=0.001;0.4250±0.1007vs0.2550±0.1392,P=0.014;0.7825±0.3109vs0.2688±0.1110,P=0.002;0.3288±0.1168vs0.1338±0.0534,P=0.001).Compared with model group,the expression level of GRP78?PERK?eIF2??A TF4?Caspase12 and CHOP in the experimental group significantly decreased,a nd the difference was statistically significant(0.1775±0.0255vs0.2800±0.0993,P=0.013;0.3288±0.2116vs0.6675±0.1835,P=0.004;0.3313±0.0783vs0.5000±0.1453,P=0.012;0.2875±0.1193vs0.4250±0.1007,P=0.026;0.2925±0.0911vs0.7825±0.3109,P=0.003;0.2288±0.0295vs0.3288±0.1168,P=0.047).4.Immunohistochemistry: Compared with normal group,the integrated option density of GRP78?PERK?eIF2??ATF4?Caspase12 and CHOP in the model group significantly increased,and the difference was statistically significant(5231.5±2210.0vs2104.3±2528.0,P=0.02;2869.3±749.9vs1710.9±661.3,P=0.006;3347.4±1594.2vs1330.0±285.3,P=0.009;3714.0±1302.3vs2307.9±706.1,P=0.018;5591.9±1295.9vs2185.7±503.9,P=0.000;4011.9±2288.9vs1256.2±332.6,P=0.011).Compared with model group,integrated option density of GRP78?PERK?eIF2??ATF4?Caspase12 and CHOP in the experimental group significantly decreased,and the difference was statistically significant(1344.1±673.7vs5231.5± 2210.0,P = 0.001;1060.4 ± 247.0vs2869.3 ± 749.9,P = 0.000;1339.4 ±394.5vs3347.4 ± 1594.2,P = 0.009;1982.2 ± 409.7vs3714.0 ± 1302.3,P = 0.007;1755.1±198.8vs5591.9±1295.9,P=0.000;1226.3±163.9vs4011.9±2288.9,P=0.011).Conclusions: 1.High fat diet can induce hepatocyte steatosis,balloonlike degeneration,lobular inflammation and fibrosis.2.Endoplasmic reticulum stress and apoptosis were found in NAFLD.3.GLP-1 may improve hepatocyte steatosis,balloon like degeneration and lobular inflammation in NAFLD by regulating endoplasmic reticulum stress PERK-eIF2?-ATF4 pathway and its induced CHOP and Caspase12 apoptosis pathways,but the improvement of fibrosis was not significant.4.GLP-1 may improve NAFLD by weight loss.