| Background:The incidence rate of colorectal cancer increased year by year.The colorectal cancer’s development is a multi-stage and multi-step pathological process,ACF and adenoma are regarded as the precancerous lesions.Recent there are more and more studies of preventive drugs of ACF and adenoma,especially the chemopreventive effect of COX-2 inhibitors,but the researches of preventive effect of metformin are few and mostly retrospective studies.We devised a prospective randomized controlled trial to evaluate the chemopreventive effect of metformin against ACF and adenoma through animal experiments.PartⅠChemopreventive Effects of Metformin or Celecoxib onChemically induced Colorectal Aberrant Crypt Foci in MiceObjective: To investigate chemopreventive effects of metformin or celecoxib on chemically induced colorectal aberrant crypt foci in mice.Methods: Sixty six-week old female BALB / c mice were randomly assigned to control group,metformin group and celecoxib group 3 group.after 1 week adaptation,and mice were given intraperitoneal injection of AOM(10mg / kg),once a week for 2 weeks.The mice in control group,metformin group and celecoxib group were treated with saline,metformin(250mg/kg/d)and celecoxib(20mg/kg/d)by gavage,respectively.The changes of body weight were monitored weekly in mice.After 6 weeks,mice were sacrificed and the colorectal tissues were separated.The ACF and aberrant crypt(AC)of the colorectal mucosa were assessed after stained with methylene bule.Proliferation of lesions of tissue was detected by proliferating cell nuclear antigen(PCNA)labeling indices,and apoptosis was detected by transferase deoxynucleotidyl uridine end labeling(TUNEL)staining.Moreover,to assess the state of mice insulin resistance,the fasting plasma glucose and insulin in mice were detected.Results: There was no significant difference between the average weight in the 3 groups of mice after the drug intervention(P>0.05).The average numbers of colorectal ACF and AC in control group mice were 9.25±0.78、27.45±2.56 respectively.The average numbers of ACF and AC in metformin group were 3.75±0.46、8.54±0.68 respectively.The average numbers of ACF and AC in celecoxib group were 5.46±0.78 、 14.23±1.52 respectively.Compared with the control group,the numbers of ACF and AC in the metformin group and celecoxib group were significantly less(P<0.05).There was significant difference between metformin group and celecoxib group(P<0.05).The proliferation index(PI)of control group was 55.20±2.15,which was higher than that of the metformin group(26.20±1.38,P<0.05)and celecoxib group(36.40±2.24,P<0.05),and that of metformin group was significantly lower,Compared with celecoxib group(P<0.05).The apoptosis index(AI)in control group was 5.30±1.45,which was lower than that in the metformin group(7.80±1.14,P<0.05)and celecoxib group(7.20±1.25,P<0.05).No significant difference in fasting plasma glucose and insulin resistance index of mice was found between control group,metformin group and celecoxib group(P>0.05).Conclusions: We confirm the effect of metformin and celecoxib on ACF suppression,that may play a preventive role for colorectal cancer(CRC).The mechanism may be related to the inhibition of cell proliferation and promoting of apoptosis.Moreover,the effect of metformin is better than celecoxib.PartⅡ Comparison of Chemopreventive Effects of Metforminor Celecoxib on Mice Colorectal PolypsObjective: To examine the chemoprophylactic effects of metformin on mice colorectal polyps model induced by azoxymethane(AOM),and compared with celecoxib.Methods: 75 only six-week old female BALB / c mice were randomly divided to control group,metformin group and celecoxib group.after 1 week adaptation,and mice were given intraperitoneal injection of AOM(10mg / kg),once a week,for 6 weeks.At the same time,the control group were treated with normal saline(0.5ml)by gavage treatment,and the other two groups were treated with metformin(250mg/kg/d)and celecoxib(20mg/kg/d)by gavage,respectively.After 30 weeks,the number and size of mice colorectal polyps were recorded.Proliferation and apoptosis of polyps tissue were detected by proliferating cell nuclear antigen(PCNA)labeling indices and transferase deoxynucleotidyl uridine end labeling(TUNEL)staining,respectively.In addition,the insulin resistance status was detected to assess indirect effects of metformin.Results: The numbers of polyps in metformin group mice(1.82±0.86)and the celecoxib group(3.00±0.93)were lower than in the control group(4.43±1.02,P<0.05).And the size of polyp in metformin group mice was 1.72±0.53 mm,the celecoxib group was 2.08±0.84 mm,and both were smaller than that in the control group(2.48±0.76 mm,P<0.05).Compared with celecoxib group,metformin significantly reduced the number of polyps induced by AOM(P<0.05),but there was no significant difference of the polyp size in 2 groups.The proliferation index(PI)in control group was 68.35±5.23,which was more than that in the metformin group(36.89±3.76,P<0.05)and celecoxib group(45.78±5.12,P<0.05).The apoptosis index(AI)in control group was 3.75±1.17,which was lower than that in the metformin group(6.45±1.35,P<0.05)and celecoxib group(5.95±1.43,P<0.05).Compared with the control group,no significant difference in insulin resistance index was observed(P>0.05)after mice treated with metformin and celecoxib.Conclusions: Metformin and celecoxib may have chemopreventive effect on colorectal polyps induced by AOM in mice,and the chemoprevention of metformin was more notable and stable compared with that of celecoxib.Part III The Inhibitory Effect of Metformin on AberrantCrypt Foci in Nondiabetic PatientsObjective: To investigate the inhibitory effects and possible mechanism of metformin on aberrant crypt foci.Methods :105 cases with aberrant crypt foci in non diabetes pateints were taked in from April to November of 2015.They were randomly divided into three groups,metformin group(metformin 500 mg bid,n=35),celecoxib group(celecoxib 200 mg bid,n=35)and the control group(no treatment,n=35).Before and after treatment for 3 months respectively in the endoscopic detection number were rectal aberrant crypt foci,and to detect the normal rectal mucosa amp activated protein kinase(Adenosine monnophophate activated protein kinase,AMPK)and rapamycin(Mammalian target of rapamycin protein,mTOR)and the expression of proliferating cell nuclear application RNA(Proliferating cell nuclear antigen,antigen,PCNA)immunohistochemistry;in addition,before and after treatment,body weight,body mass index monitoring patients(Body Mass,Index,BMI),blood fasting glucose,fasting insulin,glycosylated hemoglobin,total cholesterol and triglyceride levels.Results: ACF of metformin group were 7.43±5.31 before treatment versus 4.72 ±4.09 at 3 monthes,P<0.05;ACF of celexobi group were 7.94 ±5.85 before treatment versus 5.46±4.02 at 3 monthes,P<0.05.And there was no significant difference in the number of ACF in the control group before and after treatment(P>0.05).The difference of metformin group and celexobi group is statistically significant(P < 0.05).In the control group,the proliferation index(PI)in before and after treatment showed no obvious change,and metformin group and celecoxib group proliferation index were decreased before and after the treatment,the difference is statistically significant(P < 0.05).Metformin group compared with the control group,celecoxib group,can improve the AMPK RNA expression levels and reduce mTOR RNA expression level(P < 0.05).In addition,there were no significant differences in BMI,fasting insulin,blood glucose,body weight,glycosylated hemoglobin,total cholesterol and triglyceride levels between the three groups(P>0.05).Conclusions Metformin can suppress the nondiabetic patient’s ACF and colonic epithelial proliferation via the inhibition of the mTOR pathway through the activation of AMPK.Moreover,the effect of metformin is better than celecoxib. |
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