Non-alcoholic fatty liver disease: when to intervene and with what

Mapping global research trends: Nutrition associations with nonalcoholic fatty liver disease - a Scopus bibliometric analysis

BACKGROUND

Several bibliometric analyses have been carried out to identify research hotspots and trends in nonalcoholic fatty liver disease (NAFLD) research. Nonetheless, there are still significant knowledge gaps that must be filled to advance our understanding of and ability to treat NAFLD.

AIM

To evaluate, through bibliometric and visual analysis, the current status of related research, related research frontiers, and the developmental trends in the field of diet and NAFLD.

METHODS

We retrieved publications about diet and NAFLD published between 1987 and 2022 from Scopus. Next, we used VOSviewer 1.6.20 to perform bibliometric analysis and visualization.

RESULTS

We found a total of 1905 studies, including 1637 (85.93%) original articles and 195 (10.24%) reviews, focused on the examination of NAFLD and its correlation with diet that were published between 1987 and 2022. Among the remaining five types of documents, 38 were letters, notes, editorials, meeting minutes, or brief surveys, representing 1.99% of the total documents. The countries with the most publications on this topic were China (n = 539; 28.29%), followed by the United States (n = 379; 19.90%), Japan (n = 133; 6.98%), and South Korea (n = 127; 6.6%). According to the citation analysis, the retrieved papers were cited an average of 32.3 times and had an h-index of 106, with 61014 total citations. The two main clusters on the map included those related to: (1) Inflammation and oxidative stress; and (2) Dietary interventions for NAFLD.

CONCLUSION

This was the first study to use data taken from Scopus to visualize network mapping in a novel bibliometric analysis of studies focused on diet and NAFLD. After 2017, the two domains that received the most attention were "dietary interventions for NAFL"' and "'inflammation and oxidative stress implicated in NAFLD and its correlation with diet." We believe that this study provides important information for academics, dietitians, and doctors, and that additional research on dietary interventions and NAFLD is warranted.

Identifying a distinct fibrosis subset of NAFLD via molecular profiling and the involvement of profibrotic macrophages

BACKGROUND

There are emerging studies suggesting that non-alcoholic fatty liver disease (NAFLD) is a heterogeneous disease with multiple etiologies and molecular phenotypes. Fibrosis is the key process in NAFLD progression. In this study, we aimed to explore molecular phenotypes of NAFLD with a particular focus on the fibrosis phenotype and also aimed to explore the changes of macrophage subsets in the fibrosis subset of NAFLD.

METHODS

To assess the transcriptomic alterations of key factors in NAFLD and fibrosis progression, we included 14 different transcriptomic datasets of liver tissues. In addition, two single-cell RNA sequencing (scRNA-seq) datasets were included to construct transcriptomic signatures that could represent specific cells. To explore the molecular subsets of fibrosis in NAFLD based on the transcriptomic features, we used a high-quality RNA-sequencing (RNA-seq) dataset of liver tissues from patients with NAFLD. Non-negative matrix factorization (NMF) was used to analyze the molecular subsets of NAFLD based on the gene set variation analysis (GSVA) enrichment scores of key molecule features in liver tissues.

RESULTS

The key transcriptomic signatures on NAFLD including non-alcoholic steatohepatitis (NASH) signature, fibrosis signature, non-alcoholic fatty liver (NAFL) signature, liver aging signature and TGF-β signature were constructed by liver transcriptome datasets. We analyzed two liver scRNA-seq datasets and constructed cell type-specific transcriptomic signatures based on the genes that were highly expressed in each cell subset. We analyzed the molecular subsets of NAFLD by NMF and categorized four main subsets of NAFLD. Cluster 4 subset is mainly characterized by liver fibrosis. Patients with Cluster 4 subset have more advanced liver fibrosis than patients with other subsets, or may have a high risk of liver fibrosis progression. Furthermore, we identified two key monocyte-macrophage subsets which were both significantly correlated with the progression of liver fibrosis in NAFLD patients.

CONCLUSION

Our study revealed the molecular subtypes of NAFLD by integrating key information from transcriptomic expression profiling and liver microenvironment, and identified a novel and distinct fibrosis subset of NAFLD. The fibrosis subset is significantly correlated with the profibrotic macrophages and M2 macrophage subset. These two liver macrophage subsets may be important players in the progression of liver fibrosis of NAFLD patients.

Probiotics as Potential Therapy in the Management of Non-Alcoholic Fatty Liver Disease (NAFLD)

Background: Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease, the prevalence of which has increased over the years. The management of this pathology is not clear, and a specific pharmacological drug that can treat NAFLD is not available. In this sense, efforts are focused on the potential use of compounds with a natural origin that can contribute to reversing hepatic steatosis. Supplementation with probiotics, live microorganisms, is a potential strategy for the management of NAFLD. Methods: In the present review, the available information on the potential therapeutic effects of probiotics in NAFLD, mainly in animal models and in some clinical trials, is summarized. Results: Studies carried out using animal models of NAFLD induced by a high-fat diet have shown the beneficial effects of probiotic supplementation in reducing liver steatosis and normalizing the blood lipid profile and liver enzyme activities. In addition, a decrease in lipogenesis and an increase in lipolysis have been observed, together with a reduction in the pro-oxidative and pro-inflammatory state and a normalization of intestinal dysbiosis. Clinical trials have reported a decrease in the serum transaminases and an improved lipid profile, as well as a reduction in inflammatory markers. Conclusions: In conclusion, probiotic supplementation can be used as a potential therapy for the management of NAFLD.

Polyunsaturated and Saturated Oxylipin Plasma Levels Allow Monitoring the Non-Alcoholic Fatty Liver Disease Progression to Severe Stages

Hepatic fat accumulation is the hallmark of non-alcoholic fatty liver disease (NAFLD). Our aim was to determine the plasma levels of oxylipins, free polyunsaturated fatty acids (PUFA) and markers of lipid peroxidation in patients with NAFLD in progressive stages of the pathology. Ninety 40–60-year-old adults diagnosed with metabolic syndrome were distributed in without, mild, moderate or severe NAFLD stages. The free PUFA and oxylipin plasma levels were determined by the UHPLC–MS/MS system. The plasma levels of oxylipins produced by cyclooxygenases, lipoxygenases and cytochrome P450, such as prostaglandin 2α (PGF2α), lipoxinB4 and maresin-1, were higher in severe NAFLD patients, pointing to the coexistence of both inflammation and resolution processes. The plasma levels of the saturated oxylipins 16-hydroxyl-palmitate and 3-hydroxyl-myristate were also higher in the severe NAFLD patients, suggesting a dysregulation of oxidation of fatty acids. The plasma 12-hydroxyl-estearate (12HEST) levels in severe NAFLD were higher than in the other stages, indicating that the hydroxylation of saturated fatty acid produced by reactive oxygen species is more present in this severe stage of NAFLD. The plasma levels of 12HEST and PGF2α are potential candidate biomarkers for diagnosing NAFLD vs. non-NAFLD. In conclusion, the NAFLD progression can be monitored by measuring the plasma levels of free PUFA and oxylipins characterizing the different NAFLD stages or the absence of this disease in metabolic syndrome patients.

A Greater Improvement of Intrahepatic Fat Contents after 6 Months of Lifestyle Intervention Is Related to a Better Oxidative Stress and Inflammatory Status in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a disorder characterized by the excessive accumulation of lipids in the liver parenchyma. To date, there is no effective pharmacological treatment against NAFLD. Objective: To assess the relationship between the improvement of the intrahepatic fat content (IFC) in patients with NAFLD and metabolic syndrome and biomarkers of oxidative stress and inflammation after 6 months of lifestyle intervention. Patients diagnosed with NAFLD (n = 60 adults; 40-60 years old) residing in the Balearic Islands, Spain, were distributed in tertiles attending the improvement of IFC calculated by magnetic resonance imaging (MRI). Anthropometrics, blood pressure, maximal oxygen uptake, and pro/antioxidant and inflammatory biomarkers were determined in plasma before and after the lifestyle intervention. The improvement in IFC levels was higher in tertile 3 with respect to tertiles 2 and 1. The greatest improvement in IFC is related to cardiorespiratory fitness and adherence to the Mediterranean diet (ADM). Higher reductions in weight, body mass index (BMI), and alanine aminotransferase (ALT) were observed in tertile 3 with respect to tertile 1 after 6 months of intervention. The improvement in catalase, irisin, and cytokeratin 18 plasma levels were higher in tertile 3, whereas no differences were observed in superoxide dismutase activity. Malondialdehyde and protein carbonyl levels, as biomarkers of oxidative damage, remained unchanged in all groups. The present data show that the reduction of IFC is associated with an improvement in pro/antioxidant and pro-inflammatory status and a better cardiorespiratory fitness in NAFLD patients.

Impact of Physical Activity Differences Due to COVID-19 Pandemic Lockdown on Non-Alcoholic Fatty Liver Parameters in Adults with Metabolic Syndrome

BACKGROUND

A Mediterranean lifestyle with a Mediterranean diet and regular physical activity (PA) improves metabolic syndrome (MetS) characteristics and non-alcoholic fatty liver disease (NAFLD). The COVID-19 pandemic stopped healthy habits and increased NAFLD progression.

OBJECTIVES

To assess how PA differences due to COVID-19 lockdown affected NAFLD parameters in adults with MetS.

DESIGN

Longitudinal 2-year analysis of data obtained between COVID-19 pre- and post-lockdown in a parallel-group randomized trial (n = 57, aged 40-60 years old, with MetS and NAFLD).

METHODS

NAFLD status and related parameters were assessed by magnetic resonance imaging (MRI), blood collection analysis and related indexes. PA and fitness status were assessed by an Alpha-Fit test battery, accelerometers, validated Minnesota questionnaire and functional fitness score. During lockdown, study personnel telephoned patients to motivate them. Participants were grouped according to PA levels.

RESULTS

The low PA group improved its fitness score tests (0.2) after lockdown more than the medium PA group, and it decreased its sedentary activity (-48.7 min/day), increased light (20.9 min/day) and moderate (32.3 min/day) PA intensities and improved sleep efficiency (0.6%) in comparison with the medium and high PA groups. The high PA group increased its steps per day more than the other groups. The low PA group was the only group that decreased its gamma glutamyl transferase (GGT) levels (-17.0 U/L). All groups increased their fatty liver index (FLI) after lockdown, but the medium PA group increased its FLI more than the low PA group. Participants in the high PA group decreased their HDL-cholesterol levels more than participants in the medium PA group (-0.4 mg/dL).

CONCLUSIONS

Stopping regular PA together with an unhealthy lifestyle leads to a worsening of MetS and NAFLD. COVID-19 lockdown induced a decrease in PA in more active people, but inactive people increased their PA levels. Motivation seemed to be very important during lockdown.

Effect of a Six-Month Lifestyle Intervention on the Physical Activity and Fitness Status of Adults with NAFLD and Metabolic Syndrome

(1) Background: Physical inactivity has been linked to NAFLD, and exercise has been reported as useful to reduce intrahepatic fat content in NAFLD. (2) Objectives: To assess the physical activity (PA) and fitness status after a six-month lifestyle intervention (diet and PA) in adults with NAFLD and metabolic syndrome (MetS). (3) Design: Prospective cohort analysis of data obtained between baseline and six-year parallel-group randomized trial (n = 155, aged 40-60 years old, with MetS and NAFLD). Participants were randomized into three nutritional and PA intervention groups: Conventional diet (CD); MedDiet-high meal frequency (MD-HMF); MedDiet-physical activity (MD-PA). (4) Methods: PA and fitness status were assessed using a validated Minnesota questionnaire, ALPHA-FIT test battery, accelerometers, and functional fitness score. Information related to age, gender, education level, marital status, socioeconomic status, smoking habit, and alcohol consumption were also obtained. (5) Results: The CD group had higher improvement in standing handgrip than the MD-HMF group. The MD-PA group did more modified push-up repetitions than the CD group. The MD-PA and CD groups showed higher sitting handgrip than the MD-HMF group. The MD-HMF group showed the highest decrease in aerobic capacity. The MD-PA group showed lower light intensity PA/day than the CD and MD-HMF groups. The MD-PA group showed higher moderate intensity PA than the CD and MD-HMF groups. The CD group reported more METs per day than the MD-HMF group. (6) Conclusions: Lifestyle six-month intervention with diet and regular PA improved functional fitness in middle-aged patients with NAFLD and MetS. Aerobic capacity improved in patients who followed a Mediterranean diet and regular training sessions at six months.

Association between Non-Alcoholic Fatty Liver Disease and Mediterranean Lifestyle: A Systematic Review

Background and Aims: Non-alcoholic fatty liver disease (NAFLD) is an excessive accumulation of fat in the liver without alcohol abuse. It is linked to metabolic syndrome (MetS) and no pharmacological treatment exists. This systematic review aims to assess evidence about the effect of Mediterranean lifestyle on the prevention and reversion of NAFLD. Methods: A systematic literature search was performed in MEDLINE via Pubmed. MeSH terms used were: non-alcoholic fatty liver disease [MeSH Major Topic] AND metabolic syndrome [MeSH Term] AND (Diet, Mediterranean [MeSH Term]) OR (Exercise [MeSH Term]). (PROSPERO ID: 2021 CRD42021289495). Results: Thirteen articles were selected and divided into two categories (four focused on Mediterranean diet and NAFLD and nine focused on Mediterranean diet, physical activity, and NAFLD). Information of clinical endpoints was based on NAFLD, as well as MetS, body mass index, fasting glycemia, obesity, cholesterol, triglycerides, transaminases, albuminuria, and hepatic steatosis, among others. All studies found beneficial associations between the clinical parameters of NAFLD/MetS and following a Mediterranean diet and regular physical activity. Conclusions: An effective treatment that prevents, and even reverses, NAFLD is to adapt lifestyle to the Mediterranean one, based on a Mediterranean diet and regular physical activity.

Oxidative Stress and Pro-Inflammatory Status in Patients with Non-Alcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive fat accumulation, especially triglycerides, in hepatocytes. If the pathology is not properly treated, it can progress to nonalcoholic steatohepatitis (NASH) and continue to fibrosis, cirrhosis or hepatocarcinoma.

OBJECTIVE

The aim of the current research was to identify the plasma biomarkers of liver damage, oxidative stress and inflammation that facilitate the early diagnosis of the disease and control its progression.

METHODS

Antioxidant and inflammatory biomarkers were measured in the plasma of patients diagnosed with NAFLD (n = 100 adults; 40-60 years old) living in the Balearic Islands, Spain. Patients were classified according to the intrahepatic fat content (IFC) measured by magnetic resonance imaging (MRI).

RESULTS

Circulating glucose, glycosylated haemoglobin, triglycerides, low-density lipoprotein-cholesterol, aspartate aminotransferase and alanine aminotransferase were higher in patients with an IFC ≥ 2 of NAFLD in comparison to patients with an IFC of 0 and 1. The plasma levels of catalase, irisin, interleukin-6, malondialdehyde, and cytokeratin 18 were higher in stage ≥2 subjects, whereas the resolvin D1 levels were lower. No differences were observed in xanthine oxidase, myeloperoxidase, protein carbonyl and fibroblast growth factor 21 depending on liver status.

CONCLUSION

The current available data show that the severity of NAFLD is associated with an increase in oxidative stress and proinflammatory status. It may be also useful as diagnostic purpose in clinical practice.

Increased liver echogenicity and liver enzymes are associated with extreme obesity, adolescent age and male gender: analysis from the German/Austrian/Swiss obesity registry APV

Background

Childhood obesity is often associated with non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease in pediatrics.

Methods

This multi-center study analyzed liver echogenicity and liver enzymes in relation to obesity, age, gender and comorbidities. Data were collected using a standardized documentation software (APV) from 1.033 pediatric patients (age: 4–18 years, body mass index = BMI: 28–36 kg/m², 50% boys) with overweight (BMI >90th percentile), obesity (BMI >97th percentile) or extreme obesity (BMI > 99.5th percentile) and obesity related comorbidities, especially NAFLD from 26 centers of Germany, Austria and Switzerland. Liver enzymes aspartate aminotransferase (AST), alanine-aminotransferase (ALT) and gamma glutamyltransferase (gammaGT) were evaluated using 2 cut-off values a) > 25 U/L and b) > 50 U/L. Multiple logistic regression models were used for statistical analysis.

Results

In total, 44% of the patients showed increased liver echogenicity. Liver enzymes > 25 U/L were present in 64% and > 50 U/L in 17%. Increased liver echogenicity was associated with elevated liver enzymes (> 25 U/L: odds ratio (OR) = 1.4, 95% CI: 1.1–1.9, P < 0.02; > 50 U/L: OR = 3.5, 95% CI: 2.4–5.1, P < 0.0001). Extreme obesity, adolescence and male gender were associated with increased liver echogenicity (extreme obesity vs overweight OR = 3.5, 95% CI: 1.9–6.1, P < 0.0001; age > 14 years vs age < 9 years OR = 2.2, 95% CI: 1.4–3.5, P < 0.001; boys vs girls OR = 1.6, 95% CI: 1.2–2.0, P < 0.001) and elevated liver enzymes (extreme obesity vs overweight > 25 U/L: OR = 4.1, 95% CI: 2.4–6.9, P < 0.0001; > 50 U/L: OR = 18.5, 95% CI: 2.5–135, P < 0.0001; age > 14 years vs age < 9 years > 50 U/L: OR = 1.9, 95% CI: 1.0–3.7, P > 0.05; boys vs girls > 25 U/L: OR = 3.1, 95% CI: 2.4–4.1, P < 0.0001; > 50 U/L: OR = 2.1, 95% CI: 1.5–2.9, P < 0.0001). Impaired glucose metabolism showed a significant correlation with elevated liver enzymes > 50 U/L (OR = 4.4, 95% CI: 1.6–11.8, P < 0.005). Arterial hypertension seemed to occur in patients with elevated liver enzymes > 25 U/L (OR 1.6, 95% CI: 1.2–2.0, P < 0.005).

Conclusions

NAFLD is strongly related to extreme obesity in male adolescents. Moreover impaired glucose tolerance was observed in patients with elevated liver enzymes > 50 U/L, but arterial hypertension was only present in patients with moderately elevated liver enzymes > 25 U/L.

AGTR1 rs3772622 gene polymorphism increase the risk of nonalcoholic fatty liver disease patients suffer coronary artery disease in Northern Chinese Han population

Background

Cardiovascular disease (CAD) responsible and nonalcoholic fatty liver disease (NAFLD) are both metabolic diseases, and they are mostly influenced by genetic factors. The aim of our study is to evaluate the relationship between angiotensin II type-1 receptor (AGTR1) gene rs3772622 polymorphisms and the risk of developing coronary artery disease (CAD) in Chinese patients with NAFLD.

Methods

Genotype for AGTR1 rs3772622 in 574 NAFLD patients with CAD or 589 NAFLD patients without CAD, 332 CAD patients exclude NAFLD and 338 health control subjects were determined by sequencing and polymerase chain reaction analysis. Relevant statistical methods were employed to analyze the genotypes, alleles and the clinical date. Inter-group differences and associations were assessed statistically using t-tests and Chi square and logistic analyses. The relative risk of AGTR1 rs3772622 for NAFLD was estimated by logistic regression analysis.

Results

No significant difference in genotype and allele frequency of AGTR1 rs3772622 was found between the NAFLD without CAD population and the controls (P > 0.05). However, makeable difference was found when compared the CAD in patients with NAFLD and CAD free NAFLD patients (P < 0.001 OR = 2.09). Similarly, significant difference was found in AGTR1 rs3772622 genotype distribution between the groups of CAD patients and control (P = 0.046 OR = 1.71).

Conclusions

AGTR1 rs3772622 gene polymorphism was not associated with the risk of NAFLD, but could increase the risk of NAFLD patients suffering from CAD in the Chinese Han population. Deeply mechanisms underlying the association between AGTR1 rs3772622 gene polymorphism and the risk of CAD in NAFLD patients need more research.

Gut microbiota manipulation with prebiotics in patients with non-alcoholic fatty liver disease: a randomized controlled trial protocol

Background

Evidence for the role of the gut microbiome in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) is emerging. Strategies to manipulate the gut microbiota towards a healthier community structure are actively being investigated. Based on their ability to favorably modulate the gut microbiota, prebiotics may provide an inexpensive yet effective dietary treatment for NAFLD. Additionally, prebiotics have established benefits for glucose control and potentially weight control, both advantageous in managing fatty liver disease. Our objective is to evaluate the effects of prebiotic supplementation, adjunct to those achieved with diet-induced weight loss, on heptic injury and liver fat, the gut microbiota, inflammation, glucose tolerance, and satiety in patients with NAFLD.

Methods/design

In a double blind, placebo controlled, parallel group study, adults (BMI ≥25) with confirmed NAFLD will be randomized to either a 16 g/d prebiotic supplemented group or isocaloric placebo group for 24 weeks (n = 30/group). All participants will receive individualized dietary counseling sessions with a registered dietitian to achieve 10 % weight loss. Primary outcome measures include change in hepatic injury (fibrosis and inflammation) and liver fat. Secondary outcomes include change in body composition, appetite and dietary adherence, glycemic and insulinemic responses and inflammatory cytokines. Mechanisms related to prebiotic-induced changes in gut microbiota (shot-gun sequencing) and their metabolic by-products (volatile organic compounds) and de novo lipogenesis (using deuterium incorporation) will also be investigated.

Discussion

There are currently no medications or surgical procedures approved for the treatment of NAFLD and weight loss via lifestyle modification remains the cornerstone of current care recommendations. Given that prebiotics target multiple metabolic impairments associated with NAFLD, investigating their ability to modulate the gut microbiota and hepatic health in patients with NAFLD is warranted.

Trial registration

ClinicalTrials.gov (NCT02568605) Registered 30 September 2015

The Emerging Role of Disturbed CoQ Metabolism in Nonalcoholic Fatty Liver Disease Development and Progression

Although non-alcoholic fatty liver disease (NAFLD), characterised by the accumulation of triacylglycerol in the liver, is the most common liver disorder, the causes of its development and progression to the more serious non-alcoholic steatohepatitis (NASH) remain incompletely understood. Oxidative stress has been implicated as a key factor in both these processes, and mitochondrial dysfunction and inflammation are also believed to play a part. Coenzyme Q (CoQ) is a powerful antioxidant found in all cell membranes which has an essential role in mitochondrial respiration and also has anti-inflammatory properties. NAFLD has been shown to be associated with disturbances in plasma and liver CoQ concentrations, but the relationship between these changes and disease development and progression is not yet clear. Dietary supplementation with CoQ has been found to be hepatoprotective and to reduce oxidative stress and inflammation as well as improving mitochondrial dysfunction, suggesting that it may be beneficial in NAFLD. However, studies using animal models or patients with NAFLD have given inconclusive results. Overall, evidence is now emerging to indicate that disturbances in CoQ metabolism are involved in NAFLD development and progression to NASH, and this highlights the need for further studies with human subjects to fully clarify its role.