Objective:To investigate the effects of early enteral nutrition intervention on systemic inflammation and intestinal injury in rats with acute pancreatitis and its mechanism.Method:Rat acute pancreatitis model was established. The rats were divided into sham surgery groups, model group, 12 h nutrition support group, 24 h nutrition support group, 48 h nutrition support group, and 48 h nutrition support group +PMA group according to the random number chart method, with 10 rats in each group. After laparotomy, the rats in sham operation group were closed after gently turning the pancreas. The sham operation group and model group were injected with the same amount of physiological salt. Nutritional support group for 12 h, nutritional support group for 24 h and nutritional support group for 48 h were given enteral nutrition support for 12, 24 and 48 h, respectively. Nutritional support group for 48 h +PMA group, intraperitoneal injection of 5 mg/kg NF-κB signaling pathway activator PMA was given after modeling, and nutritional support was given for 48 h. The contents of lipase, amylase and creatinine in serum of each group were detected by automatic biochemical analyzer. The serum levels of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10) and D-lactic acid were detected by enzyme-linked immunosorbent assay (ELISA). The content of diamine oxidase (DAO) was detected by colorimetry. Hematoxylin-eosin (HE) staining was used to detect the pathological changes of intestinal mucosa. Western blot was used to detect the expression of NF-κB pathway-related proteins in pancreatic tissue of rats in each group.Results:(1) Lipase, amylase and creatinine in sham operation group, model group, 12 h nutrition support group, 24 h nutrition support group and 48 h nutrition support group were (4.37±0.61) vs (12.021±1.00) vs (8.77±0.62) vs (6.88±0.63) vs (5.20±0.41) U/ml, (1674.03±172.24) vs (4356.30±229.38) vs (3676.11±382.43) vs (2990.06±251.93) vs (1919.75±179.40) U/L, (32.12±3.37) vs (91.73±9.76) vs (72.38±6.83) vs (53.72±5.98) vs (41.82±4.00) U/L. Compared with sham operation group, the contents of serum lipase, amylase and creatinine in model group were significantly increased. Compared with model group, the contents of lipase, amylase and creatinine were significantly decreased after 12, 24 and 48 h of nutritional support, and were time-dependent ( P<0.05). (2) The levels of IL-6, IL-1β, TNF-α and IL-10 were (40.26±3.93) vs (123.34±13.19) pg/ml in sham operation group, model group, 12 h nutritional support group, 24 h nutritional support group and 48 h nutritional support group, respectively vs (108.97±12.70) vs (77.36±6.75) vs (49.18±4.97) pg/ml, (77.53±9.95) vs (316.36±23.76) vs (254.79±13.96) vs (177.92±17.20) vs (119.19±13.17) pg/ml, (62.94±5.39) vs (353.16±28.03) vs (275.87±22.11) vs (198.78±24.33) vs (94.60±9.41) pg/ml, (41.21±4.29) vs (6.92±1.01) vs (10.76±0.66) vs (21.24±1.64) vs (35.33±1.69) pg/ml. Compared with sham operation group, the contents of serum inflammatory cytokines IL-6, IL-1β and TNF-α in model group were significantly increased, while the content of IL-10 was significantly decreased. Compared with model group, the contents of IL-6, IL-1β and TNF-α were significantly decreased after 12, 24 and 48 h of nutritional support, while the contents of IL-10 were significantly increased in a time-dependent manner ( P<0.05). (3) The intestinal histopathological scores, DAO and D-lactic acid of sham operation group, model group, 12 h nutritional support group, 24 h nutritional support group and 48 h nutritional support group were (0.00±0.00) vs (4.20±0.60) vs (3.00±0.45) points, respectively vs (1.90±0.54) vs (1.30±0.64) points, (4.92±0.42) vs (14.95±1.20) vs (11.87±1.13) vs (9.02±0.53) vs (6.30±0.59) U/L, (2.39±0.22) vs (6.92±0.46) vs (5.21±0.28) vs (3.64±0.39) vs (2.95±0.15) nmol/ml. Compared with sham operation group, intestinal histopathological scores, DAO and D-lactic acid levels were significantly increased in model group. Compared with model group, intestinal histopathological scores, DAO and D-lactic acid levels were significantly decreased after 12, 24 and 48 h of nutritional support ( P<0.05). (4) The protein expressions of NF-κB p65 and p-IκBα were (0.23±0.03) vs (0.94±0.10) vs (0.75±0.06) vs (0.62±0.06) in sham operation group, model group, 12 h nutrition support group, 24 h nutrition support group and 48 h nutrition support group, respectively. vs (0.41±0.06), (1.06±0.12) vs (0.25±0.04) vs (0.47±0.03) vs (0.62±0.08) vs (0.85±0.08). Compared with sham operation group, NF-κB p65 protein level in model group was significantly increased, while p-IκBα protein level was significantly decreased. Compared with model group, the NF-κB p65 protein level was significantly decreased after 12, 24 and 48 h of nutritional support, while the P-iκBα protein was significantly increased ( P<0.05). (5) NF-κB p65, p-IκBα, IκBα, IL-6, IL-1β, TNF-α, IL-10, lipase, amylase and creatinine were (0.41±0.06) vs (0.82±0.06) in the 48 h group and the 48 h +PMA group, respectively. (0.85±0.08) vs (0.37±0.02), (1.05±0.11) vs (1.10±0.14), (49.18±4.97) vs (105.68±10.69) pg/ml, (119.19±13.17) vs (247.16±23.41) pg/ml, (94.60±9.41) vs (328.24±30.86) pg/ml, (5.20±0.41) vs (10.33±1.01) U/ml, (1919.75±179.40) vs (4023.40±334.56) U/L, (5.20±0.41) vs (10.33±1.01) U/ml, (41.82±4.00) U/L vs (81.33±7.96) U/L. Compared with the 48 h group, the expression level of NF-κB p65 protein, IL-6, IL-1β, TNF-α, lipase, amylase and creatinine in the 48 h +PMA group were significantly increased, while the expression level of P-iκBα protein and the content of IL-10 were significantly decreased ( P<0.05) . Conclusion:Early nutritional intervention can inhibit inflammatory response, reduce intestinal injury and control the development of acute pancreatitis by regulating NF-κB signaling pathway.