Environmental exposure as a risk-modifying factor in liver diseases: Knowns and unknowns

Global, regional, and national total burden related to hepatitis B in children and adolescents from 1990 to 2021

BACKGROUND

Hepatitis B remains a significant global health concern with widespread communicability. Nevertheless, data on its burden and trends in children and adolescents were limited. We aim to evaluate the global, regional, and national trends of total burden related to hepatitis B in children and adolescents aged 0-19 years from 1990 to 2021.

METHODS

The age-standardized incidence, prevalence, mortality, and disability-adjusted life years (DALYs) were calculated by the Global Burden of Disease (GBD) study from 1990 to 2021. These indicators were stratified by sex, age, socio-demographic index (SDI), and disease stage. We calculated the correlation between them and SDI. The temporal trends were examined using the annual average percentage change (AAPC) and joinpoint regression.

RESULTS

The global age-standardized incidence of hepatitis B in children and adolescents decreased from 1385.20 per 100,000 population in 1990 to 418.68 per 100,000 population in 2021, with an AAPC of -3.76%. Similarly, age-standardized DALYs decreased from 70.78 per 100,000 population to 36.31 per 100,000 population, with an AAPC of -2.13%. The age-standardized prevalence (AAPC - 3.53%) and mortality (AAPC - 2.09%) of hepatitis B also decreased significantly. From 1990 to 2021, the age-standardized incidence and prevalence among males exhibited a higher trend compared to females, although both declined over time. These two indicators also decreased across all age subgroups, with consistently higher rates observed in the 15-19 age group compared to other age groups. The burden of hepatitis B demonstrated a notable reduction in countries with high-middle SDI, while it was highest in countries with low SDI. In 2021, Central sub-Saharan Africa and West sub-Saharan Africa reported the highest age-standardized incidence. For age-standardized DALYs, South Asia was the only region to experience an increase (AAPC 1.09%), while East Asia showed the largest decline (AAPC - 7.58%). Alcohol and drug use remained important risk factors for DALYs among people aged 15-19 years. Furthermore, the impact of drug use on disease burden was increasing, particularly in high-SDI countries.

CONCLUSIONS

The global burden and trends of hepatitis B decreased significantly in children and adolescents, exhibiting regional and national variations. Management of alcohol and drug use remains a major challenge for people aged 15-19 years.

RISING STARS: Sex differences in toxicant-associated fatty liver disease

Based on biological sex, the consequential health outcomes from exposures to environmental chemicals or toxicants can differ in disease pathophysiology, progression, and severity. Due to basal differences in cellular and molecular processes resulting from sexual dimorphism of organs including the liver and additional factors influencing 'gene-environment' interactions, males and females can exhibit different responses to toxicant exposures. Associations between environmental/occupational chemical exposures and fatty liver disease (FLD) have been well-acknowledged in human epidemiologic studies and their causal relationships demonstrated in experimental models. However, studies related to sex differences in liver toxicology are still limited to draw any inferences on sex-dependent chemical toxicity. The purpose of this review is to highlight the present state of knowledge on the existence of sex differences in toxicant-associated FLD (TAFLD), discuss potential underlying mechanisms driving these differences, implications of said differences on disease susceptibility, and emerging concepts. Chemicals of interest include various categories of pollutants that have been investigated in TAFLD, namely persistent organic pollutants, volatile organic compounds, and metals. Insight into research areas requiring further development is also discussed, with the objective of narrowing the knowledge gap on sex differences in environmental liver diseases. Major conclusions from this review exercise are that biological sex influences TAFLD risks, in part due to (i) toxicant disruption of growth hormone and estrogen receptor signaling, (ii) basal sex differences in energy mobilization and storage, and (iii) differences in chemical metabolism and subsequent body burden. Finally, further sex-dependent toxicological assessments are warranted for the development of sex-specific intervention strategies.

Protection of Liver Functions and Improvement of Kidney Functions by Twelve Weeks Consumption of Cuban Policosanol (Raydel®) with a Decrease of Glycated Hemoglobin and Blood Pressure from a Randomized, Placebo-Controlled, and Double-Blinded Study with Healthy and Middle-Aged Japanese Participants

Policosanol consumption has been associated with treating blood pressure and dyslipidemia by increasing the level of high-density lipoproteins-cholesterol (HDL-C) and HDL functionality. Although policosanol supplementation also ameliorated liver function in animal models, it has not been reported in a human clinical study, particularly with a 20 mg doage of policosanol. In the current study, twelve-week consumption of Cuban policosanol (Raydel^®) significantly enhanced the hepatic functions, showing remarkable decreases in hepatic enzymes, blood urea nitrogen, and glycated hemoglobin. From the human trial with Japanese participants, the policosanol group (n = 26, male 13/female 13) showed a remarkable decrease in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from baseline up to 21% (p = 0.041) and 8.7% (p = 0.017), respectively. In contrast, the placebo group (n = 26, male 13/female 13) showed almost no change or slight elevation. The policosanol group showed a 16% decrease in γ-glutamyl transferase (γ-GTP) at week 12 from the baseline (p = 0.015), while the placebo group showed a 1.2% increase. The policosanol group exhibited significantly lower serum alkaline phosphatase (ALP) levels at week 8 (p = 0.012), week 12 (p = 0.012), and after 4-weeks (p = 0.006) compared to those of the placebo group. After 12 weeks of policosanol consumption, the ferric ion reduction ability and paraoxonase of serum were elevated by 37% (p < 0.001) and 29% (p = 0.004) higher than week 0, while placebo consumption showed no notable changes. Interestingly, glycated hemoglobin (HbA_1c) in serum was lowered significantly in the policosanol group 4 weeks after consumption, which was approximately 2.1% (p = 0.004) lower than the placebo group. In addition, blood urea nitrogen (BUN) and uric acid levels were significantly lower in the policosanol group after 4 weeks: 14% lower (p = 0.002) and 4% lower (p = 0.048) than those of the placebo group, respectively. Repeated measures of ANOVA showed that the policosanol group had remarkable decreases in AST (p = 0.041), ALT (p = 0.008), γ-GTP (p = 0.016), ALP (p = 0.003), HbA_1c (p = 0.010), BUN (p = 0.030), and SBP (p = 0.011) from the changes in the placebo group in point of time and group interaction. In conclusion, 12 weeks of 20 mg consumption of policosanol significantly enhanced hepatic protection by lowering the serum AST, ALT, ALP, and γ-GTP via a decrease in glycated hemoglobin, uric acid, and BUN with an elevation of serum antioxidant abilities. These results suggest that improvements in blood pressure by consumption of 20 mg of policosanol (Raydel^®) were accompanied by protection of liver function and enhanced kidney function.

Western diet unmasks transient low-level vinyl chloride-induced tumorigenesis; potential role of the (epi-)transcriptome

BACKGROUND & AIMS

Vinyl chloride (VC) monomer is a volatile organic compound commonly used in industry. At high exposure levels, VC causes liver cancer and toxicant-associated steatohepatitis. However, lower exposure levels (i.e., sub-regulatory exposure limits) that do not directly damage the liver, enhance injury caused by Western diet (WD). It is still unknown if the long-term impact of transient low-concentration VC enhances the risk of liver cancer development. This is especially a concern given that fatty liver disease is in and of itself a risk factor for the development of liver cancer.

METHODS

C57Bl/6 J mice were fed WD or control diet (CD) for 1 year. During the first 12 weeks of feeding only, mice were also exposed to VC via inhalation at sub-regulatory limit concentrations (<1 ppm) or air for 6 h/day, 5 days/week.

RESULTS

Feeding WD for 1 year caused significant hepatic injury, which was exacerbated by VC. Additionally, VC increased the number of tumors which ranged from moderately to poorly differentiated hepatocellular carcinoma (HCC). Transcriptomic analysis demonstrated VC-induced changes in metabolic but also ribosomal processes. Epitranscriptomic analysis showed a VC-induced shift of the modification pattern that has been associated with metabolic disease, mitochondrial dysfunction, and cancer.

CONCLUSIONS

These data indicate that VC sensitizes the liver to other stressors (e.g., WD), resulting in enhanced tumorigenesis. These data raise concerns about potential interactions between VC exposure and WD. It also emphasizes that current safety restrictions may be insufficient to account for other factors that can influence hepatotoxicity.

Associations between residential volatile organic compound exposures and liver injury markers: The role of biological sex and race

While occupational exposures to volatile organic compounds (VOCs) have been linked to steatohepatitis and liver cancer in industrial workers, recent findings have also positively correlated low-dose, residential VOC exposures with liver injury markers. VOC sources are numerous; factors including biological make up (sex), socio-cultural constructs (gender, race) and lifestyle (smoking) can influence both VOC exposure levels and disease outcomes. Therefore, the current study's objective is to investigate how sex and race influence associations between residential VOC exposures and liver injury markers particularly in smokers vs. nonsmokers. Subjects (n = 663) were recruited from residential neighborhoods; informed consent was obtained. Exposure biomarkers included 16 urinary VOC metabolites. Serological disease biomarkers included liver enzymes, direct bilirubin, and hepatocyte death markers (cytokeratin K18). Pearson correlations and generalized linear models were conducted. Models were adjusted for common liver-related confounders and interaction terms. The study population constituted approximately 60% females (n = 401) and 40% males (n = 262), and a higher percent of males were smokers and/or frequent drinkers. Both sexes had a higher percent of White (75% females, 82% males) vs. Black individuals. Positive associations were identified for metabolites of acrolein, acrylamide, acrylonitrile, butadiene, crotonaldehyde, and styrene with alkaline phosphatase (ALP), a biomarker for cholestatic injury; and for the benzene metabolite with bilirubin; only in females. These associations were retained in female smokers. Similar associations were also observed between these metabolites and ALP only in White individuals (n = 514). In Black individuals (n = 114), the styrene metabolite was positively associated with aspartate transaminase. Interaction models indicated that positive associations for acrylamide/crotonaldehyde metabolites with ALP in females were dose-dependent. Most VOC associations with K18 markers were negative in this residential population. Overall, the findings demonstrated that biological sex, race, and smoking status influence VOC effects on liver injury and underscored the role of biological-social-lifestyle factor(s) interactions when addressing air pollution-related health disparities.

Endocrine disrupting chemicals: A promoter of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent liver disorder. With the improvement in human living standards, the prevalence of NAFLD has been increasing in recent years. Endocrine-disrupting chemicals (EDCs) are a class of exogenous chemicals that simulate the effects of hormones in the body. There has been growing evidence regarding the potential effects of EDCs on liver health, especially in NAFLD. This paper aims to summarize the major EDCs that contribute to the growing burden of NAFLD and to raise public awareness regarding the hazards posed by EDCs with the objective of reducing the incidence of NAFLD.