Smoking and Nonalcoholic Fatty Liver Disease

A comprehensive analysis of the impact of smoking on adverse clinical outcomes of steatotic liver diseases

Background

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is an increasingly prevalent liver disorder.

Objectives

This study investigated the effect of smoking status on various clinical outcomes in MASLD and metabolic dysfunction and alcohol-associated liver disease (MetALD).

Design

This study is a retrospective cohort analysis utilizing data from the UK Biobank (Application ID: 117214). Participants were categorized as current, previous, or never smokers, and outcomes were analyzed using inverse probability of treatment weighting to adjust for confounders.

Methods

The primary outcomes were all-cause mortality and liver-related mortality. Secondary outcomes included incidence of liver cirrhosis, hepatic decompensation, cardio-cerebrovascular diseases (CVD), and hepatocellular carcinoma (HCC). Multivariate Cox proportional hazards models were employed to evaluate associations.

Results

Previous and never smokers had significantly lower hazard ratios (HRs) for mortality compared to current smokers in all cohorts (HR: 0.33, 95% confidence interval (CI): 0.31-0.35, p < 0.001 for never smokers in No SLD cohort, HR: 0.43, 95% CI: 0.41-0.44, p < 0.001 for never smokers in MASLD cohort, and HR: 0.41, 95% CI: 0.38-0.45, p < 0.001 for never smokers in MetALD cohort). Previous and never smokers showed significantly lower incidences of liver cirrhosis compared to current smokers across all cohorts, except for MetALD. Previous and never smokers showed lower incidences of CVD compared to current smokers. In the MASLD cohort, never smokers had the lowest incidence of hepatic decompensation and HCC. In the MetALD cohort, no significant differences were observed in the risk of hepatic decompensation and HCC between different smoking statuses.

Conclusion

Smoking is related to worse survival outcomes and higher incidences of liver cirrhosis and CVD in MASLD and MetALD cohorts. Therefore, smoking cessation and prevention are crucial strategies for reducing the burden of liver disease and improving patient prognosis.

The relationship between nutrient intake, lifestyle, and non-alcoholic fatty liver disease in patients with type 2 diabetes mellitus: Results from the National Health and Nutrition Examination Surveys 2007-2018

OBJECTIVE

More than half of the individuals with type 2 diabetes mellitus (T2DM) are accompanied by Non-alcoholic fatty liver disease (NAFLD). This study aimed to explore the relationship between nutrient intake, lifestyle, and the risk NAFLD in patients with T2DM.

METHODS

This study comprised 2110 adult patients with diabetes from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018. We employed weighted logistic regression to assess the associations between nutrient intake, lifestyle and NAFLD, while exploring potential non-linear relationships using restrictive cubic spline analysis. Additionally, we validated our findings through subgroup analyses and sensitivity analyses to ensure the robustness and reliability of our results.

RESULT

Out of 2110 diabetes patients, 1743 were diagnosed with NAFLD, and 53.43 % of them were male. After adjusting for potential confounders, we found a negative correlation between Vitamin K intake and the occurrence of NAFLD in patients with T2DM (OR = 0.885 [0.829, 0.959]). This dose-response relationship was further validated through stratification analysis by tertiles of vitamin K intake. Lycopene intake is identified as a risk factor for NAFLD in patients with T2DM. Specifically, for every 100 μg of lycopene ingested, there was a 0.2 % higher likelihood of NAFLD (OR = 1.002 [1.0001, 1.005], p < 0.05). Conversely, a 0.5 % reduction in NAFLD risk was observed with the same amount of lutein intake (OR = 0.995 [0.992, 0.999], p < 0.05). Furthermore, we also found that a high-quality diet can reduce the risk of NAFLD in patients with T2DM, with an odds ratio of 0.208 (0.101, 0.430).

CONCLUSION

Increasing intake of Vitamin K and lutein, reducing intake of lycopene, and improving dietary quality may lower the risk of NAFLD in patients with T2DM.

Health outcomes of electronic cigarettes

ABSTRACT

The usage of electronic cigarettes (e-cigarettes) sparked an outbreak of unidentified vaping-related lung disease in the US during late 2019. With e-cigarettes becoming more and more popular, smokers have more options other than conventional cigarettes. Under these circumstances, a comprehensive evaluation of the general safety of new tobacco and tobacco-related products, represented by e-cigarettes, to human health is necessary. In this review, we summarize the current research on potential negative impacts of e-cigarette exposure on human health. In particular, studies detailing the relationship between e-cigarettes and the digestive system are summarized, with mechanisms mainly including hepatic metabolic dysfunction, impaired gut barrier, and worsened outcomes of inflammatory bowel disease (IBD). Although believed to be safer than traditional cigarettes, e-cigarettes exert adverse effects on systemic health and induce the development of multiple diseases including asthma, cardiovascular disease, and IBD. Moreover, nicotine-containing e-cigarettes have a negative impact on the childhood development and increase the risk of arterial stiffness compared to the non-nicotine e-cigarettes. However, non-nicotine e-cigarette components have detrimental effects including promoting liver damage and metabolic disorders.

Preventive effects of caffeine on nicotine plus high-fat diet-induced hepatic steatosis and gain weight: a possible explanation for why obese smokers with high coffee consumption tend to be leaner

Non-alcoholic fatty liver disease (NAFLD) is a prevalent liver disorder, affecting approximately 25 % of the population. Coffee-drinking obese smokers exhibit lower body weights and decreased NAFLD rates, but the reasons behind this remain unclear. Additionally, the effect of nicotine, the main component of tobacco, on the development of NAFLD is still controversial. Our study aimed to explore the possible reasons that drinking coffee could alleviate NAFLD and gain weight and identify the real role of nicotine in NAFLD of obese smokers. A NAFLD model in mice was induced by administering nicotine and a high-fat diet (HFD). We recorded changes in body weight and daily food intake, measured the weights of the liver and visceral fat, and observed liver and adipose tissue histopathology. Lipid levels, liver function, liver malondialdehyde (MDA), superoxide dismutase (SOD), serum inflammatory cytokine levels and the expression of hepatic genes involved in lipid metabolism were determined. Our results demonstrated that nicotine exacerbated the development of NAFLD and caffeine had a hepatoprotective effect on NAFLD. The administration of caffeine could ameliorate nicotine-plus-HFD-induced NAFLD by reducing lipid accumulation, regulating hepatic lipid metabolism, alleviating oxidative stress, attenuating inflammatory response and restoring hepatic functions. These results might explain why obese smokers with high coffee consumption exhibit the lower incidence rate of NAFLD and tend to be leaner. It is essential to emphasise that the detrimental impact of smoking on health is multifaceted. Smoking cessation remains the sole practical and effective strategy for averting the tobacco-related complications and reducing the risk of mortality.

Associations between Healthy Lifestyle and All-Cause Mortality in Individuals with Metabolic Associated Fatty Liver Disease

Background and Aims: There is limited evidence about the association of healthy lifestyle and all-cause mortality in individuals with metabolic associated fatty liver disease (MAFLD). We aimed to examine this association and compare it with the association in those without MAFLD. Methods: A prospective cohort study was performed and linked mortality data through 2019 in the National Health Nutrition Examination Survey (NHANES 1999–2010). A healthy lifestyle score was constructed from cigarette smoking, alcohol drinking, healthy eating score, and leisure-time physical activity. Risk stratification was conducted in participants with MAFLD by fibrosis biomarkers and liver enzymes. Survey-weight adjusted Cox regression was used to estimate adjusted hazard ratios (HRs) and confidence intervals (CIs) for all-cause mortality associated with healthy lifestyle. Results: There was a protective association between healthy lifestyle and all-cause mortality in participants with MAFLD (HR per 1-unit increase of healthy lifestyle score 0.77 [95% CI 0.69–0.85]), with no difference from the association in participants without MAFLD (HR 0.77 [0.72–0.82]). In participants with MAFLD, the associations tended to be stronger in those with lower risk of advanced fibrosis (HR per 1-unit increase of healthy lifestyle score 0.64 [0.50–0.79] for low NAFLD fibrosis score [NFS] and 0.84 [0.75–0.93] for high NFS, p-value for interaction 0.02), but did not differ by liver enzymes. The results for non-alcoholic fatty liver disease (NAFLD) mirrored those for MAFLD. Conclusions: Healthy lifestyle showed protective associations with all-cause mortality regardless of MAFLD status, and the associations tended to be stronger in those with lower risk of advanced fibrosis. Timely lifestyle modification matters for individuals with MAFLD.

Cigarette smoking and liver diseases

Cigarette smoking is a preventable risk factor for premature morbidity and mortality. A history of smoking is observed in approximately 40% of patients with liver disease, while a growing number of studies are investigating the potential impact of smoking in chronic liver diseases. This review discusses the effects of smoking on liver diseases, at multiple levels, with a focus on its potential causal role. Clinical evidence indicates that cigarette smoking negatively impacts the incidence and severity of fatty liver disease, fibrosis progression, hepatocellular carcinoma development, and the outcomes of patients with advanced liver disease. The underlying mechanisms are complex and involve different pathophysiological pathways including oxidative stress and oncogenic signals. Importantly, smoking promotes cardiovascular disease and extrahepatic cancers in patients with steatohepatitis and in transplant recipients. We discuss how promoting smoking cessation could improve the rates of treatment response (in clinical trials) and fibrosis regression, while reducing the risk of hepatocellular carcinoma and improving liver transplant outcomes. Finally, we discuss current challenges such as the referral of smokers to specialised units for smoking cessation.

Association between TFEB gene polymorphism, gene-environment interaction, and fatty liver disease: A case-control study in China

BACKGROUND

Fatty liver disease (FLD) is a serious public health problem that is rapidly increasing. Evidence indicates that the transcription factor EB (TFEB) gene may be involved in the pathophysiology of FLD; however, whether TEFB polymorphism has an association with FLD remains unclear.

OBJECTIVES

To explore the association among TFEB polymorphism, gene-environment interaction, and FLD and provide epidemiological evidence for clarifying the genetic factors of FLD.

METHODS

This study is a case-control study. Sequenom MassARRAY was applied in genotyping. Logical regression was used to analyze the association between TFEB polymorphism and FLD, and the gene-environment interaction in FLD was evaluated by multiplication and additive interaction models.

RESULTS

(1) The alleles and genotypes of each single nucleotide polymorphism and haplotypes of TFEB in the case and control groups were evenly distributed; no statistically substantial difference was observed. (2) Logistic regression analysis indicated that TFEB polymorphism is not remarkably associated with FLD. (3) In the multiplicative interaction model, rs1015149, rs1062966, rs11754668 and rs2273068 had remarkable interaction with the amount of cigarette smoking. Rs1062966 and rs11754668 also had a considerable interaction body mass index and alcohol intake, respectively. However, no remarkable additive interaction was observed.

CONCLUSION

TFEB polymorphism is not directly associated with FLD susceptibility, but the risk can be changed through gene-environment interaction.

The association between smoking and both types of microscopic colitis: A systematic review and meta-analysis

BACKGROUND AND STUDY AIMS

It has been suggested that smoking may be associated with microscopic colitis (MC) in some studies; however, there are conflicting results in the current literature with many of these studies having significant limitations. Our study aims to offer a meta-analysis evaluating the association between MC, including both its subtypes, and smoking.

PATIENTS AND METHODS

A systemic review was conducted in PUBMED, Embase, PubMed Central, and ScienceDirect databases from inception through December 2019. Effect estimates from the individual studies were extracted and combined using the random effect, generic inverse variance method of DerSimonian and Laird and a pooled odds ratio (OR) was calculated. Forest plots were generated, and publication bias was assessed for using conventional techniques.

RESULTS

Eight observation studies with a total of 1461 patients with MC were included in this study, 383 of whom were active smokers (26.2%). Current smoking was significantly associated with MC (OR 3.58, 95% CI, 2.51-5.11), lymphocytic colitis (LC) (OR 3.64, 95% CI, 2.46-5.38), and collagenous colitis (CC) (OR 4.43, 95% CI, 2.68-7.32). Gender-specific subgroup analysis showed a significant association with smoking was found for CC in men (OR 4.53, 95% CI, 1.59-12.85), CC in women (OR 3.27, 95% CI, 2.35-4.54), LC in women (OR 2.27, 95% CI, 1.27-4.06) and MC in women (OR 2.93, 95% CI, 2.09-4.10). We found no publication bias as assessed by the funnel plots and Egger's regression asymmetry test.

CONCLUSION

Our meta-analysis found a statistically significant association between smoking and both subtypes of MC.