The Effect And Mechanism Of Palmitic Acid On Colorectal Tumor-like Lesions

Part 1Objective:To analyze the epidemiological and clinical characteristics of asymptomatic physical examinations to reveal the risk factors of colorectal adenomas.Methods:Asymptomatic physical examination subjects who underwent colonoscopy in Peking Union Medical College Hospital from January 2020 to July 2021 were included.According to the results of colonoscopy,all subjects were divided into patients with no polyps,non-advanced adenomas,or advanced adenoma.The epidemiological information and clinical parameters of patients were collected,the differences between groups were compared by parametric or nonparametric test,and the risk factors of colorectal adenoma were identified by univariate and multivariate logistic regression analysis.Results:Patients without polyps,non-advanced adenomas,and advanced adenomas were significantly different in gender,age≥50 years,BMI≥25 kg/m2,diabetes,elevated ApoB/ApoA1,metabolic syndrome,smoking,GGT,AST,FBG,UA,TG,ApoA1,ApoB,and CEA.There were no significant differences in the location of the adenoma and whether it was multiple adenomas between patients with non-advanced and advanced adenomas.Male(OR=3.00,95%CI 1.66-5.41,P<0.001),age≥50 years(OR=1.91,95%CI 1.12-3.28,P=0.018),elevated ApoB/ApoA1 levels(OR=4.27,95%CI 1.71-10.68,P=0.002),smoking(OR=1.88,95%CI 1.02-3.50,P=0.045)were independent risk factors for non-advanced adenoma;age>50 years(OR=3.18,95%)CI 1.04-9.79,P=0.043),diabetes(OR=4.32,95%CI 1.59-11.72,P=0.004),family history of cancer(OR=3.28,95%CI 1.12-9.50,P=0.029),smoking(OR=3.74,95%CI 1.48-9.46,P=0.005)was an independent risk factor for advanced adenoma.Conclusion:Male,age≥50 years,elevated ApoB/ApoA1,and smoking can identify high-risk groups for non-advanced adenoma;age≥50 years,with diabetes,family history of tumor,and smoking can be used to identify high-risk groups for advanced adenoma.Part 2Objective:To explore the effect of palmitic acid on the proliferation and migration of colorectal cancer cells and the role of OLR1 gene in it.Methods:Four different colorectal cancer cell lines,DLD-1,HCT 116,HT-29,and SW620,were selected,and the colorectal cancer cell lines most sensitive to sodium palmitate stimulation and the most suitable time and concentration were determined through preliminary experiments.Then,colorectal cancer cells were stimulated with sodium palmitate,the cell proliferation ability was detected by CCK-8,and the cell migration ability was detected by scratch assay.After stimulation with sodium palmitate,OLR1 gene expression was detected by qPCR and western blot at the mRNA and protein levels,respectively.After transfection of siRNA,the knockdown effect of OLR1 gene was evaluated by qPCR and western blot either.The most effective siRNA was selected to knock down OLR1 gene expression in colorectal cancer cells,and the cells were stimulated with sodium palmitate,and the proliferation experiments and cell scratch experiments were repeated to explore the role of OLR1 in the stimulation effect of sodium palmitate.Results:(1)Sodium palmitate stimulation can promote the proliferation of DLD-1,HCT 116 and HT-29 cells,among which DLD-1 cells are the most sensitive.After sodium treatment of DLD-1 cells for 12 h,the proliferation ability of DLD-1 cells was 1.96±0.14 times(P<0.001)and 2.05±0.51 times(P=0.015)of the control group,respectively;(2)After DLD-1 cells were treated with 50 μmol/L sodium palmitate for 24h,the scratch width was 0.37±0.05 times of the original width,significantly lower than control group,which was 0.47±0.02 times that of the original width(P=0.008);(3)12.5,25,50,100 μmol/L sodium palmitate can significantly up-regulate the mRNA expression of OLR1 gene at 12h,but only 100 μmol/L palmitic acid can promote OLR1 protein expression;(4)After transfection of siRNA3,the relative fold of OD450 was significantly decreased at 12h,48h and 72h(the relative fold of OD450 was 0.50±0.02,P=0.001;0.39±0.01,P<0.001;0.29±0.01,P<0.01,respectively);(5)After transfection of siRNA3,the relative width of scratch was higher than that of the control group(the relative scratch width was 0.65±0.03 vs 0.59±0.03,P=0.038),while the sodium palmitate treatment could accelerate the scratch healing(the relative scratch width was 0.65±0.03 vs 0.53±0.07,P=0.04).Conclusion:Palmitic acid can promote the proliferation and migration of colorectal cancer cells by up-regulating the expression of OLR1 in vitro.Part 3Objective:To explore the effect of palmitic acid-rich diet on tumorigenesis in colitisassociated colorectal cancer mouse model.Methods:AOM/DSS was used to build a mouse model of colitis-associated colorectal cancer,and the mice were fed a palmitic acid-rich diet or a control diet for 12 weeks.At the end of the experiment,the differences in body weight,survival,number of intestinal tumors,and tumor size were compared.Results:All mice in the AOM/DSS model group developed colorectal tumors,and the weight of the mice fed palmitic acid-rich diet increased compared with the control diet group(35.53±0.90 g vs 27.32±2.85 g,P=0.006).However,the survival rate was lower(50.0%vs 83.3%),but there was no significant difference in survival analysis between the two groups.In the AOM/DSS model,both groups developed high-grade intraepithelial neoplasia or adenocarcinoma in the intestine,but there were no significant differences in tumor number and tumor size.Conclusion:Animal experiments show that high palmitic acid diet can increase the body weight of colitis-associated colorectal cancer model mice,but does not affect mouse survival,tumor number and size.