Higher flavonoid intake is associated with a lower progression risk of non-alcoholic fatty liver disease in adults: a prospective study

Flavonoids for gastrointestinal tract local and associated systemic effects: A review of clinical trials and future perspectives

BACKGROUND

Flavonoids are naturally occurring dietary phytochemicals with significant antioxidant effects aside from several health benefits. People often consume them in combination with other food components. Compiling data establishes a link between bioactive flavonoids and prevention of several diseases in animal models, including cardiovascular diseases, diabetes, gut dysbiosis, and metabolic dysfunction-associated steatotic liver disease (MASLD). However, numerous clinical studies have demonstrated the ineffectiveness of flavonoids contradicting rodent models, thereby challenging the validity of using flavonoids as dietary supplements.

AIM OF REVIEW

This review provides a clinical perspective to emphasize the effective roles of dietary flavonoids as well as to summarize their specific mechanisms in animals briefly.

KEY SCIENTIFIC CONCEPTS OF REVIEW

First, this review offers an in-depth elucidation of the metabolic processes of flavonoids within human, encompassing the small, large intestine, and the liver. Furthermore, the review provides a comprehensive overview of the various functions of flavonoids in the gastrointestinal tract, including hindering the breakdown and assimilation of macronutrients, such as polysaccharides and lipids, regulating gut hormone secretion as well as inhibition of mineral iron absorption. In the large intestine, an unabsorbed major portion of flavonoids interact with the gut flora leading to their biotransformation. Once absorbed and circulated in the bloodstream, bioactive flavonoids or their metabolites exert numerous beneficial systemic effects. Lastly, we examine the protective effects of flavonoids in several metabolic disorders, including endothelial dysfunction, MASLD, cardiovascular disease, obesity, hyperlipidemia, and insulin resistance. In conclusion, this review outlines the safety and future prospects of flavonoids in the field of health, especially in the prevention of metabolic syndrome (MetS).

Associations of the Intake of Individual and Multiple Flavonoids with Metabolic Dysfunction Associated Steatotic Liver Disease in the United States

BACKGROUND

Evidence regarding the individual and combined impact of dietary flavonoids on the risk of metabolic dysfunction associated with steatotic liver disease (MASLD) remains scarce. Our objective is to evaluate the association between individual and multiple dietary flavonoids with MASLD in adults.

METHODS

Data sets were obtained from the National Health and Nutrition Examination Survey (NHANES), 2017-2018. In total, 2581 participants aged over 18 years, with complete information on dietary flavonoid intake, MASLD, and covariates, were included. Flavonoid intake was energy-adjusted using the residual method. Logistic regression analysis was employed to examine the impact of total flavonoid intake on MASLD. Weighted quantile sum (WQS) analyses were used to evaluate the combined and individual effects of flavonoids on MASLD and to identify the predominant types with the most significant contribution to MASLD prevention.

RESULTS

The highest tertile of total flavonoid intake was associated with a 29% reduction in the risk of MASLD compared to the lowest tertile after multivariable adjustments (OR: 0.71, 95% CI: 0.51-0.97). The WQS analysis revealed that anthocyanidins, flavones, and flavanones were the most critical contributors among six subclasses (weights = 0.317, 0.279, and 0.227, respectively) and naringenin, apigenin, and delphinidin were the most critical contributors among 29 monomers. (weights = 0.240, 0.231, and 0.114, respectively). Also, a higher intake of anthocyanidins, flavones, naringenin, apigenin, and delphinidin was linked to a reduced risk of MASLD (p < 0.05).

CONCLUSIONS

Our findings suggested that a higher flavonoid intake is associated with a lower risk of MASLD, with anthocyanidins, flavones, flavanones, naringenin, apigenin, delphinidin, and myricetin contributing most to the protective effects of flavonoids.

Therapeutic potential of the flavonoid compound Licochalcone D in metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent chronic liver disease associated with type 2 diabetes, which doubles the risk of developing this condition. Various flavonoid compounds have a positive effect on lipid metabolism, inflammation, and insulin resistance and can contribute to slowing down the progression of MASLD. In the current study, we investigated the biological effects of Licochalcone D (Lico D), a flavonoid, in a metabolic disease model. Oil Red O staining, quantitative real-time polymerase chain reaction, and western blotting were performed. For in vivo experiments, we used high-fat diet (60 %) plus low-dose streptozotocin (30 mg/kg; 5 days; intraperitoneal)-induced metabolic disease mouse model and evaluated lipid metabolism. We observed that Lico D reduced lipid accumulation and increased lipid metabolism both in vitro and in vivo. Additionally, we identified that the AMP-activated protein kinase and Sirtuin 1 pathways were activated in the mouse liver and hepatic steatosis cell model. In silico analysis revealed that Lico D passes the "Lipinski Rule of Five," which indicates drug-likeness properties. In conclusion, our findings highlight the role of Lico D in improving metabolic dysfunction-associated steatotic liver disease.

A flavonoid-rich diet is associated with lower risk and improved imaging biomarkers of nonalcoholic fatty liver disease: a prospective cohort study

BACKGROUND

Mechanistic studies and short-term randomized trials suggest higher intakes of dietary flavonoids may protect against nonalcoholic fatty liver disease (NAFLD).

OBJECTIVES

We aimed to perform the first population-based study with long-term follow-up on flavonoid consumption, incident NAFLD, and validated NAFLD biomarkers.

METHODS

In a prospective study, we assessed the associations between flavonoid intake based on ≥2 24-h dietary assessments and NAFLD risk among 121,064 adults aged 40-69 y by multivariable Cox regression analyses. We further assessed the associations between flavonoid intake and magnetic resonance imaging-derived liver fat (a subset of n = 11,435) and liver-corrected T1 values (cT1; a subset of n = 9570), a marker of steatosis, more sensitive to inflammatory pathology.

RESULTS

Over 10 y of follow-up, 1081 cases of NAFLD were identified. Participants in the highest quartile (Q4) of the flavodiet score reflecting the consumption of foods high in flavonoids, had a 19% lower risk of NAFLD compared to the lowest quartile (Q1) [hazard ratio (HR) (95% confidence interval (CI): 0.81 (0.67, 0.97), P-trend = 0.02)]. Moreover, participants in the Q4 of the flavodiet score had lower liver fat and cT1 values than those in Q1 (liver fat: relative difference Q1 compared with Q4: -5.28%, P-trend = <0.001; cT1: relative difference Q1 compared with Q4: -1.73%, P-trend = <0.001). When compared to low intakes, high intakes of apples and tea were associated with lower NAFLD risk [apples: HR (95% CI): 0.78 (0.67, 0.92), P-trend = <0.01; tea: HR (95% CI): 0.86 (0.72, 1.02), P-trend = 0.03)]. Additionally, when compared to low intakes, high apple, tea, and dark chocolate intakes were significantly associated with lower liver fat values, whereas high tea and red pepper intakes were significantly associated with lower cT1 values.

CONCLUSIONS

The consumption of flavonoid-rich foods was associated with a reduced risk of NAFLD among middle-aged adults.

The Reduced Gut Lachnospira Species Is Linked to Liver Enzyme Elevation and Insulin Resistance in Pediatric Fatty Liver Disease

The objective of this study was to investigate gut dysbiosis and its metabolic and inflammatory implications in pediatric metabolic dysfunction-associated fatty liver disease (MAFLD). This study included 105 children and utilized anthropometric measurements, blood tests, the Ultrasound Fatty Liver Index, and fecal DNA sequencing to assess the relationship between gut microbiota and pediatric MAFLD. Notable decreases in Lachnospira spp., Faecalibacterium spp., Oscillospira spp., and Akkermansia spp. were found in the MAFLD group. Lachnospira spp. was particularly reduced in children with MAFLD and hepatitis compared to controls. Both MAFLD groups showed a reduction in flavone and flavonol biosynthesis sequences. Lachnospira spp. correlated positively with flavone and flavonol biosynthesis and negatively with insulin levels and insulin resistance. Body weight, body mass index (BMI), and total cholesterol levels were inversely correlated with flavone and flavonol biosynthesis. Reduced Lachnospira spp. in children with MAFLD may exacerbate insulin resistance and inflammation through reduced flavone and flavonol biosynthesis, offering potential therapeutic targets.

Polyphenol consumption and Nonalcoholic fatty liver disease risk in adults

In this cross-sectional investigation, the primary objective was to explore the correlation between the consumption of polyphenols and the likelihood of non-alcoholic fatty liver disease (NAFLD) in the adult population participating in the Hoveyzeh cohort. Data from the Hoveyzeh cohort study, part of the Persian Cohort Study, involving 10,009 adults aged 35-70, were analyzed. Exclusions were made for missing data, extreme energy intake, and liver cancer patients. Dietary habits were assessed using a food frequency questionnaire, and polyphenol intake was calculated using the Phenol Explorer database. Logistic regression analyses, adjusted for confounders, were performed to assess the relationship between polyphenol subclasses (total polyphenols, total flavonoids, phenolic acid, and lignin) and NAFLD. Among 9894 participants, those in the highest quintile of total polyphenol (OR 0.65, CI 0.5-0.84; P = 0.007), phenolic acid (OR 0.67, CI 0.52-0.86; P < 0.001), and lignin intake (OR 0.69, CI 0.52-0.87; P = 0.001) demonstrated lower odds of NAFLD compared to the lowest quintile, even after adjusting for confounding factors. However, no significant association was found between total flavonoid intake and NAFLD (OR 1.26, CI 0.96-1.67; P = 0.47). Subgroup analysis indicated a significant inverse association between total polyphenols and NAFLD in women (OR 0.64, CI 0.42-0.93; P = 0.001). Higher intake of total polyphenols, phenolic acid, and lignin was associated with reduced odds of NAFLD among adults in the Hoveyzeh cohort. This suggests that dietary patterns rich in these polyphenols may play a role in mitigating the risk of NAFLD. Further interventional and longitudinal studies are needed to validate these findings and explore potential preventive strategies involving polyphenol-rich diets.

Interaction between dietary flavonoid intake and trouble sleeping on non-alcoholic fatty liver disease risk: a cross-sectional study

OBJECTIVE

The possible interaction of dietary flavonoid intake and sleep on non-alcoholic fatty liver disease (NAFLD) has not been well studied. This study investigated the interaction between dietary flavonoid intake and trouble sleeping on the risk of NAFLD.

METHODS

Three discrete National Health and Nutrition Examination Survey data cycles from 2007 to 2010 and 2017 to 2018 were used. NAFLD was diagnosed by a US Fatty Liver Index ≥30. A sleep questionnaire diagnosed trouble sleeping. Univariate and multivariate logistic regression, restricted cubic spline (RCS) and subgroup analyses were used to evaluate the association between dietary flavonoids, trouble sleeping and NAFLD. We employed the relative excess risk due to interaction, attributable proportion of interaction and synergy index to evaluate additive interactions.

RESULTS

Ultimately, 5056 participants were enrolled, and higher anthocyanidins and flavanones intake was negatively correlated with NAFLD. Conversely, trouble sleeping was positively associated with NAFLD. These correlations remained stable after adjusting for confounders, and there was a sex difference in this relationship. In the RCS model, anthocyanins were negatively non-linearly related to NAFLD, while flavanones showed a negative linear relationship. Moreover, there was a synergistic interplay between low dietary anthocyanin intake and trouble sleeping on the risk of NAFLD. A similar relationship existed for flavanone intake.

CONCLUSION

Anthocyanin and flavanone intake were negatively associated, whereas trouble sleeping was positively associated with NAFLD risk. There was a synergistic effect of low anthocyanin intake and trouble sleeping. The same relationship existed for low flavanone intake.

Does Flavonoid Supplementation Alleviate Non-Alcoholic Fatty Liver Disease? A Systematic Review and Meta-Analysis of Randomized Controlled Trials

SCOPE

Higher flavonoid intake is associated with reduced risk of non-alcoholic fatty liver disease (NAFLD). However, there is a large discrepancy in the effects of flavonoid supplementation on NAFLD. To fill such knowledge gap, we systematically reviewed randomized clinical trials (RCTs) to critically assess flavonoid supplementation effect on liver function, lipid profile, inflammation, and insulin resistance in adults with NAFLD.

METHODS AND RESULTS

A systematic search was conducted from 4 databases from inception until May 2023. Twelve RCTs were included in the final analysis demonstrating beneficial effects of flavonoids on ALT (SMD = -3.59, p = 0.034), AST (SMD = -4.47, p = 0.001), GGT (SMD = -8.70, p = 0.000), CK-18M30 (SMD = -0.35, p = 0.042), TG (SMD = -0.37, p = 0.001), LDL-C (SMD = -0.38, p = 0.039), TC (MD = -0.25 mmol/l, p = 0.017), steatosis score (MD = -18.97, p = 0.30), TNF-α (MD = -0.88, p = 0.000), and NF-κB (MD = -1.62, p = 0.001).

CONCLUSION

This meta-analysis suggests that flavonoid alleviates NAFLD through exerting favourable effects on liver function, lipid profile, and inflammation, indicating flavonoid supplementation presents a promising drug regimen for the management of NAFLD and its associated complications.

Preventive and therapeutic effects of natural products and herbal extracts on nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a common condition that is prevalent in patients who consume little or no alcohol, and is characterized by excessive fat accumulation in the liver. The disease is becoming increasingly common with the rapid economic development of countries. Long-term accumulation of excess fat can lead to NAFLD, which represents a global health problem with no effective therapeutic approach. NAFLD is a complex, multifaceted pathological process that has been the subject of extensive research over the past few decades. Herbal medicines have gained attention as potential therapeutic agents to prevent and treat NAFLD due to their high efficacy and low risk of side effects. Our overview is based on a PubMed and Web of Science database search as of Dec 22 with the keywords: NAFLD/NASH Natural products and NAFLD/NASH Herbal extract. In this review, we evaluate the use of herbal medicines in the treatment of NAFLD. These natural resources have the potential to inform innovative drug research and the development of treatments for NAFLD in the future.

The effects of medicinal and food homologous substances on blood lipid and blood glucose levels and liver function in patients with nonalcoholic fatty liver disease: a systematic review of randomized controlled trials

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a prevalent chronic liver disorder worldwide. According to several previous studies, the treatment of patients with NAFLD using medicinal and food-homologous substances has consistent effects on the levels of blood lipids and blood glucose and liver function.

OBJECTIVE

This systematic review was conducted to investigate the impact of medicinal and food homologous substances on blood lipid and glucose levels as well as liver function in patients with NAFLD.

METHODS

A thorough search was conducted in eight databases, including China Science and Technology Journal Database (VIP), Chinese National Knowledge Infrastructure(CNKI), China Biomedical Literature Database (SinoMed), Wanfang Database, PubMed, Cochrane Library, Web of Science and Embase, for articles published from database inception until June 24, 2023. The methodological quality of the included studies was evaluated utilizing Cochrane Randomized Trial Risk Bias Tool, Edition 2 and GRADE methodology for assessment.

RESULTS

A total of 13 randomized controlled trials, involving 829 patients with NAFLD, were included in the analysis, these studies included a total of 9 medicinal and food homologous substances. In the 13 studies, hawthorn (2), sea buckthorn (1), ginger (2), turmeric (4) (1 with chicory seeds), cinnamon (1), cardamom (1), purslane (1) and saffron (1) were included. The results of the included studies showed that medicinal and food homologous substances could improve high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglycerides (TGs), fasting blood glucose (FBG) and liver enzyme levels in patients with NAFLD to a certain extent, but the effect of turmeric on TC, liver enzyme levels is controversial.

CONCLUSION

In patients with NAFLD, dietary intervention using medicinal and food homologous substances can ameliorate blood lipid and blood glucose levels and liver enzymes to some extent. In clinical work, medicinal and food homologous substances can be used to provide patients with NAFLD with a safe and effective dietary plan to help prevent and treat disease onset and progression.

Associations between dietary flavonoid intake with hepatic steatosis and fibrosis quantified by VCTE: Evidence from NHANES and FNDDS

BACKGROUND AND AIM

Flavonoids are natural products of plant origin and have been shown to be beneficial for nonalcoholic fatty liver disease (NAFLD) in animal studies. However, relevant epidemiological evidence is still lacking, and the relationship between flavonoid and subclass intake with quantified hepatic steatosis and fibrosis has not been investigated.

METHODS AND RESULTS

This study was based on the Food and Nutrient Database for Dietary Studies (FNDDS) expanded flavonoid intake database and the National Health and Nutrition Examination Survey (NHANES) 2017-2018 and included a total of 4113 participants with vibration-controlled transient elastography (VCTE) data. Multiple logistic regression was used to assess linear relationships between flavonoids and hepatic steatosis and fibrosis. Smoothed curve fit and a generalized additive model were used to investigate the non-linear relationship, and a two-tailed linear regression model was used to find potential inflection points. Of the 4113 participants, 1045 (25.41%) were diagnosed with NAFLD. After adjusting for energy and major non-dietary covariates, significant linear negative correlations were observed between total flavonoids and CAP [-1.53 (-2.59, -0.47)] and LSM [-0.17 (-0.27, -0.07)]. After adjusting for all covariates, flavones had the strongest and most significant negative association with hepatic steatosis [-1.98 (-3.79, -0.17)]. The results of smooth curve fitting and subgroup analysis demonstrated gender differences, and threshold effect analysis further identified a U-shaped relationship and inflection point between flavonoid intake and hepatic steatosis (infection point: 287.25 mg/d).

CONCLUSIONS

Our findings suggest negative associations between flavonoid and subclass intake with hepatic steatosis and fibrosis.

Association between daidzein intake and metabolic associated fatty liver disease: A cross-sectional study from NHANES 2017-2018

Background

Metabolic associated fatty liver disease (MAFLD) has become the most common liver disease globally, yet no new drugs have been approved for clinical treatment. Therefore, we investigated the relationship between dietary intake of soy-derived daidzein and MAFLD, to find potentially effective treatments.

Methods

We conducted a cross-sectional study using data from 1,476 participants in National Health and Nutrition Examination Survey (NHANES) from 2017 to 2018 and their associated daidzein intake from the flavonoid database in the USDA Food and Nutrient Database for Dietary Studies (FNDDS). We investigated the relationship between MAFLD status, controlled attenuation parameter (CAP), AST/Platelet Ratio Index (APRI), Fibrosis-4 Index (FIB-4), liver stiffness measurement (LSM), nonalcoholic fatty liver disease (NAFLD) fibrosis score (NFS), hepatic steatosis index (HSI), fatty liver index (FLI), and daidzein intake by adjusting for confounding variables using binary logistic regression models and linear regression models.

Results

In the multivariable-adjusted model II, there was a negative association between daidzein intake and the incidence of MAFLD (OR for Q4 versus Q1 was 0.65, 95% confidence interval [CI] = 0.46-0.91, p = 0.0114, p for trend was 0.0190). CAP was also negatively associated with daidzein intake, β = -0.37, 95% CI: -0.63 to -0.12, p = 0.0046 in model II after adjusting for age, sex, race, marital status, education level, family income-to-poverty ratio (PIR), smoking, and alcohol consumption. Stratified by quartiles of daidzein intake, trend analysis of the relationship between daidzein intake and CAP remained significant (p for trend = 0.0054). In addition, we also found that HSI, FLI, and NFS were negatively correlated with daidzein intake. LSM was negatively related to daidzein intake but had no statistical significance. The correlation between APRI, FIB-4, and daidzein intake was not strong (although p < 0.05, β values were all 0).

Conclusion

We found that MAFLD prevalence, CAP, HSI, and FLI, all decreased with increased daidzein intake, suggesting that daidzein intake may improve hepatic steatosis. Therefore, dietary patterns of soy food or supplement consumption may be a valuable strategy to reduce the disease burden and the prevalence of MAFLD.

Association between flavonoid and subclasses intake and metabolic associated fatty liver disease in U.S. adults: Results from National Health and Nutrition Examination Survey 2017-2018

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) formerly known as non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. Flavonoid is considered a promising candidate for metabolic disease prevention although few studies have explored the relationship between flavonoid intake and MAFLD.

PURPOSE

To assess the relationship between flavonoid intake and MAFLD prevalence in the U.S. adult population.

MATERIALS AND METHODS

The data of this cross-sectional study was obtained from National Health and Nutrition Examination Survey (NHANES) and Food and Nutrient Database for Dietary Studies (FNDDS) 2017-2018. Flavonoid and subclasses intake was assessed by two 24h recalls. MAFLD was diagnosed according to the consensus definitions. Multivariate logistic regression model was performed to examine the association between flavonoid intake and MAFLD with adjustments for confounders.

RESULTS

A total of 4,431 participants were included in this cross-sectional analysis. MAFLD had a weighted prevalence of 41.93% and was not associated with total flavonoid intake. A higher anthocyanin and isoflavone intake, on the other hand, was associated with a lower prevalence of MAFLD. The protective effect of higher anthocyanin intake was significant among male, Non-Hispanic White, and Non-Hispanic Asia participants. Higher isoflavone intake was associated with a lower risk of MAFLD in participants of younger (age < 50), Non-Hispanic Black, Non-Hispanic Asia, and higher HEI-2015 scores compared with the lowest quartile of isoflavone intake. Stratified analysis showed that compared with the lowest quartile of anthocyanin intake, the effect of anthocyanin intake on MAFLD varied by racial groups (P _interaction = 0.02). A positive correlation existed between HDL and anthocyanidin intake (P = 0.03), whereas a negative correlation existed between FPG and isoflavone intake (P = 0.02).

CONCLUSION

MAFLD was adversely linked with flavonoid subclasses, anthocyanin and isoflavone. This modifiable lifestyle provides a potential opportunity to prevent MAFLD. These findings promote future research into the links and mechanisms between anthocyanin and isoflavone intake and MAFLD.

Structural Insights into Amelioration Effects of Quercetin and Its Glycoside Derivatives on NAFLD in Mice by Modulating the Gut Microbiota and Host Metabolism

The sugar moieties of natural flavonoids determine their absorption, bioavailability, and bioactivity in humans. To explore structure-dependent bioactivities of quercetin, isoquercetin, and rutin, which have the same basic skeleton linking different sugar moieties, we systemically investigated the ameliorative effects of dietary these flavonoids on high-fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) of mice. Our results revealed that isoquercetin exhibits the strongest capability in improving NAFLD phenotypes of mice, including body and liver weight gain, glucose intolerance, and systemic inflammation in comparison with quercetin and rutin. At the molecular level, dietary isoquercetin markedly ameliorated liver dysfunction and host metabolic disorders in mice with NAFLD. At the microbial level, the three flavonoids compounds, especially isoquercetin, can effectively regulate the gut microbiota composition, such as genera Akkermansia, Bifidobacterium, and Lactobacillus, which were significantly disrupted in NAFLD mice. These comparative findings offer new insights into the structure-dependent activities of natural flavonoids for NAFLD treatment.

Flavonoid 4,4'-dimethoxychalcone suppresses cell proliferation via dehydrogenase inhibition and oxidative stress aggravation

Flavonoids are natural polyphenolic compounds with a diverse array of biological activities and health-promoting effects. Recent studies have found that 4,4'-dimethoxychalcone (DMC) promoted longevity via autophagy; however, its targets are currently unknown. Herein, we employed an unbiased thermal proteome profiling (TPP) method and identified multiple targets of DMC, including ALDH1A3, ALDH2, and PTGES2. We further determined the dissociation constant (Kd) of DMC and ALDH1A3 to be 2.8 μM using microscale thermophoresis (MST) analysis, which indicated that DMC inhibited ALDH1A3 activity and aggravated cellular oxidative stress. DMC treatment significantly increased cellular reactive oxygen species (ROS) production and inhibited cancer cell growth. Quantitative proteomic analysis showed that DMC upregulated proteins associated with stress-responses and downregulated proteins associated with cell cycle progression, and this was confirmed using cell cycle analysis. Taken together, we showed that TPP is an effective tool with which to identify flavonoid targets and set a precedent for deciphering flavonoid function in the future. We have demonstrated that DMC inhibited cell proliferation via ROS-induced cell cycle arrest and is an anti-proliferative agent in cancer treatment.

A double-edged sword: The Kelch-like ECH-associated protein 1-nuclear factor erythroid-derived 2-related factor 2-antioxidant response element pathway targeted pharmacological modulation in nonalcoholic fatty liver disease

Nutraceuticals activating the Kelch-like epichlorohydrin (ECH)-associated protein 1 (Keap1)-nuclear factor erythroid-derived 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway are widely used for nonalcoholic fatty liver disease (NAFLD) because no specific drugs are approved yet. The pathology of NAFLD is summarized as the 'two-hit' hypothesis. The 'first hit' includes insulin resistance and lipid accumulation. Oxidative stress, lipid peroxidation, and inflammation are regarded as the 'second hit'. Now there is controversial evidence about the roles of the Keap1-Nrf2-ARE pathway and its activators in NAFLD. When the 'first hit' occurs, the hepatocyte-specific Nrf2 deficiency reduces insulin resistance and significantly attenuates lipid accumulation. However, when the 'second hit' occurs, Nrf2 activation reduces oxidative stress and combats inflammation. We reviewed the roles of the Keap1-Nrf2-ARE pathway as a double-edged sword in the development of NAFLD, its inhibitors as a novel therapeutic approach for early NAFLD, and the nutraceutical character of its activators.

Similarities and Differences: A Comparative Review of the Molecular Mechanisms and Effectors of NAFLD and AFLD

Non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) are the most prevalent metabolic liver diseases globally. Due to the complex pathogenic mechanisms of NAFLD and AFLD, no specific drugs were approved at present. Lipid accumulation, oxidative stress, insulin resistance, inflammation, and dietary habits are all closely related to the pathogenesis of NAFLD and AFLD. However, the mechanism that promotes disease progression has not been fully elucidated. Meanwhile, the gut microbiota and their metabolites also play an important role in the pathogenesis and development of NAFLD and AFLD. This article comparatively reviewed the shared and specific signaling pathways, clinical trials, and potential intervention effectors of NAFLD and AFLD, revealing their similarities and differences. By comparing the shared and specific molecular regulatory mechanisms, this paper provides mutual reference strategies for preventing and treating NAFLD, AFLD, and related metabolic diseases. Furthermore, it provides enlightenment for discovering novel therapies of safe and effective drugs targeting the metabolic liver disease.