The Effect Of Cigarettes And Alcohol On Intestinal Flora In Healthy Humans

Background and aimsCigarettes and alcohol are two major global risk factors contributing to burden of disease and mortality.Cigarette smoking has an objective association with lung cancer and several other diseases,while chronic alcohol consumption has been linked to the deaths caused by alcohol-attributable cancer,liver cirrhosis and injury.Recently,more attention has been paid to the effects caused by joint use of cigarettes and alcohol.The paired use of these two substances may produce a multiplicative or synergistic increase in cancer rates.Animal and human studies have found that smoking and alcohol can reduce the diversity of intestinal flora and alter the distribution of flora.Interestingly,some intestinal microbiome changes caused by smoking are similar to those shown in diseases such as inflammatory bowel disease and obesity.And changes in the composition and metabolic function of the gastrointestinal microbiota caused by alcohol can promote oxidative stress induced by alcohol,intestinal hyperpermeability to bacterial products in the cavity,and alcoholic liver disease(ALD).In addition,clinical and preclinical data indicate that diseases related to smoking and alcohol are related to quantitative and qualitative adverse biological changes in the intestinal flora,and may be caused by increased gastrointestinal inflammation,endotoxemia caused by intestinal permeability,systemic inflammation and tissue damage/organ diseaseAnd few is known about the co-effects of cigarette smoking and alcohol drinking on the intestinal flora and their metabolism.As such,we aimed to comprehensively investigate the co-effect of cigarette smoking plus alcohol drinking on the host,intestinal microbial homeostasis and metabolic products(short chain fatty acids)in a population-based cross-sectional studyMethodsHealth subjects aged between 22 and 75 years were recruited and signed an informed consent form prior to sample collection at Sir Run Run Shaw Hospital,College of Medicine,Zhejiang University from December 2016 to March 2019.A questionnaire was given to all subjects to evaluate general characteristics including age,weight,gender,marital status,diseases history,and cigarette and alcohol consumption The total bacterial DNA from collected stool samples was extracted and sequenced by 16S rRNA to analyze microbial composition and functional pathways predicted by KEGG.Short-chain fatty acid(SCFA)levels in stool were determined by gas chromatographyResults170 healthy subjects were included and divided into four groups:non-smoking and non-drinking group(group A),only smoking group(group B),only drinking group(group C),and smoking and drinking group(group D).There were no significant differences in body weight,age and marital status among groups,but only male subjects were in groups B and DThe results shown that smoking and drinking can reduce the diversity and uniformity of the intestinal flora,causing significant changes in the distribution of the flora community(PCoA R=0.0852,p=0.001;NMDS R=0.0290,p=0.013)Compared with group A,the abundance of Bacteroides significantly increased in group B(p<0.001),and the Firmicutes decreased in group B(p<0.001)and in group C(p<0.05),while there was no significant difference in group D.In addition,the Bacteroidetes:Firmicutes ratio increased by nearly 3-,1.5-and 2-fold change,respectively,compared with the group A(p<0.05).LEfSe analysis revealed that group A was dominated by Firmicutes,Ruminococcaceae,Bacillus,and group B was dominated by Bacteroidetes and Pseudomonas,group C is dominated by Lachnospiraceae and Romboutsia,and group D is dominated by Proteobacteria and LachnoclostridiumCorrelation analysis of environmental factors found that Bacteroides was positively correlated with carcinoembryonic antigen(p<0.01),and negatively correlated with high-density lipoprotein(p<0.05);Fusobacterium were positively related with blood glucose and triglyceride index(p<0.05);Dialister was negatively correlated with triglyceride,C-reactive protein and carcinoembryonic antigen index(p<0.5)In addition,the smoker or drinker population was more abundant in the prediction pathways related to bacterial toxicity,inflammation and disease,and the B:F ratio of the flora was positively correlated with the prediction pathway of lipopolysaccharide synthesis.There was no significant difference in SCFA among groupsConclusionsSmoking and drinking have a negative impact on the intestinal flora of healthy people,cause a decline in intestinal flora biodiversity and affect the overall microbial community composition.Disturbances of the intestinal flora may cause disorders in the energy metabolism and other potential functional pathways.In addition,smoking has a greater effect on the intestinal flora than drinking or a combination of smoking and drinking.