Dietary Treatment for NAFLD: New Clinical and Epidemiological Evidence and Updated Recommendations

Navigating nonalcoholic fatty liver disease (NAFLD): Exploring the roles of estrogens, pharmacological and medical interventions, and life style

The pursuit of studying this subject is driven by the urgency to address the increasing global prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) and its profound health implications. NAFLD represents a significant public health concern due to its association with metabolic disorders, cardiovascular complications, and the potential progression to more severe conditions like non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Liver estrogen signaling is important for maintaining liver function, and loss of estrogens increases the likelihood of NAFLD in postmenopausal women. Understanding the multifaceted mechanisms underlying NAFLD pathogenesis, its varied treatment strategies, and their effectiveness is crucial for devising comprehensive and targeted interventions. By unraveling the intricate interplay between genetics, lifestyle, hormonal regulation, and gut microbiota, we can unlock insights into risk stratification, early detection, and personalized therapeutic approaches. Furthermore, investigating the emerging pharmaceutical interventions and dietary modifications offers the potential to revolutionize disease management. This review reinforces the role of collaboration in refining NAFLD comprehension, unveiling novel therapeutic pathways, and ultimately improving patient outcomes for this intricate hepatic condition.

Heterogeneity in intrahepatic macrophage populations and druggable target expression in patients with steatotic liver disease-related fibrosis

Background & Aims

Clinical trials for reducing fibrosis in steatotic liver disease (SLD) have targeted macrophages with variable results. We evaluated intrahepatic macrophages in patients with SLD to determine if activity scores or fibrosis stages influenced phenotypes and expression of druggable targets, such as CCR2 and galectin-3.

Methods

Liver biopsies from controls or patients with minimal or advanced fibrosis were subject to gene expression analysis using nCounter to determine differences in macrophage-related genes (n = 30). To investigate variability among individual patients, we compared additional biopsies by staining them with multiplex antibody panels (CD68/CD14/CD16/CD163/Mac387 or CD163/CCR2/galectin-3/Mac387) followed by spectral imaging and spatial analysis. Algorithms that utilize deep learning/artificial intelligence were applied to create cell cluster plots, phenotype profile maps, and to determine levels of protein expression (n = 34).

Results

Several genes known to be pro-fibrotic (e.g. CD206, TREM2, CD163, and ARG1) showed either no significant differences or significantly decreased with advanced fibrosis. Although marked variability in gene expression was observed in individual patients with cirrhosis, several druggable targets and their ligands (e.g. CCR2, CCR5, CCL2, CCL5, and LGALS3) were significantly increased when compared to patients with minimal fibrosis. Antibody panels identified populations that were significantly increased (e.g. Mac387+), decreased (e.g. CD14+), or enriched (e.g. interactions of Mac387) in patients that had progression of disease or advanced fibrosis. Despite heterogeneity in patients with SLD, several macrophage phenotypes and druggable targets showed a positive correlation with increasing NAFLD activity scores and fibrosis stages.

Conclusions

Patients with SLD have markedly varied macrophage- and druggable target-related gene and protein expression in their livers. Several patients had relatively high expression, while others were like controls. Overall, patients with more advanced disease had significantly higher expression of CCR2 and galectin-3 at both the gene and protein levels.

Impact and implications

Appreciating individual differences within the hepatic microenvironment of patients with SLD may be paramount to developing effective treatments. These results may explain why such a small percentage of patients have responded to macrophage-targeting therapies and provide additional support for precision medicine-guided treatment of chronic liver diseases.

Non-Alcoholic Fatty Liver Disease and Vitamin D in the UK Biobank: A Two-Sample Bidirectional Mendelian Randomisation Study

Evidence for a role for vitamin D in non-alcoholic fatty liver disease (NAFLD) pathogenesis is conflicting. As Mendelian randomisation (MR) avoids many limitations of conventional observational studies, this two-sample bidirectional MR analysis was conducted to determine the following: (i) whether genetically predicted 25-hydroxyvitamin D [25(OH)D] levels are a risk factor for NAFLD, and (ii) whether genetic risk for NAFLD influences 25(OH)D levels. Single-nucleotide polymorphisms (SNPs) associated with serum 25(OH)D levels were obtained from the European ancestry-derived SUNLIGHT consortium. SNPs associated with NAFLD or NASH (p-value < 1 × 10−5) were extracted from previous studies and supplemented by genome-wide association studies (GWASs) performed in the UK Biobank. These GWASs were done both without (primary analysis) and with (sensitivity analysis) the population-level exclusion of other liver diseases (e.g., alcoholic liver diseases, toxic liver diseases, viral hepatitis, etc.). Subsequently, MR analyses were performed to obtain effect estimates using inverse variance weighted (IVW) random effect models. Cochran’s Q statistic, MR-Egger regression intercept, MR pleiotropy residual sum and outlier (MR-PRESSO) analyses were used to assess pleiotropy. No causal association of genetically predicted serum 25(OH)D (per standard deviation increase) with risk of NAFLD was identified in either the primary analysis: n = 2757 cases, n = 460,161 controls, odds ratio (95% confidence interval): 0.95 (0.76, −1.18), p = 0.614; or the sensitivity analysis. Reciprocally, no causal association was identified between the genetic risk of NAFLD and serum 25(OH)D levels, OR = 1.00 (0.99, 1.02, p = 0.665). In conclusion, this MR analysis found no evidence of an association between serum 25(OH)D levels and NAFLD in a large European cohort.

Patients with fibrosis from non-alcoholic steatohepatitis have heterogeneous intrahepatic macrophages and therapeutic targets

Background and Aims

In clinical trials for reducing fibrosis in NASH patients, therapeutics that target macrophages have had variable results. We evaluated intrahepatic macrophages in patients with non-alcoholic steatohepatitis to determine if fibrosis influenced phenotypes and expression of CCR2 and Galectin-3.

Approach & Results

We used nCounter to analyze liver biopsies from well-matched patients with minimal (n=12) or advanced (n=12) fibrosis to determine which macrophage-related genes would be significantly different. Known therapy targets (e.g., CCR2 and Galectin-3) were significantly increased in patients with cirrhosis.However, several genes (e.g., CD68, CD16, and CD14) did not show significant differences, and CD163, a marker of pro-fibrotic macrophages was significantly decreased with cirrhosis. Next, we analyzed patients with minimal (n=6) or advanced fibrosis (n=5) using approaches that preserved hepatic architecture by multiplex-staining with anti-CD68, Mac387, CD163, CD14, and CD16. Spectral data were analyzed using deep learning/artificial intelligence to determine percentages and spatial relationships. This approach showed patients with advanced fibrosis had increased CD68+, CD16+, Mac387+, CD163+, and CD16+CD163+ populations. Interaction of CD68+ and Mac387+ populations was significantly increased in patients with cirrhosis and enrichment of these same phenotypes in individuals with minimal fibrosis correlated with poor outcomes. Evaluation of a final set of patients (n=4) also showed heterogenous expression of CD163, CCR2, Galectin-3, and Mac387, and significant differences were not dependent on fibrosis stage or NAFLD activity.

Conclusions

Approaches that leave hepatic architecture intact, like multispectral imaging, may be paramount to developing effective treatments for NASH. In addition, understanding individual differences in patients may be required for optimal responses to macrophage-targeting therapies.

PNPLA3 GENE POLYMORPHISM AND RED MEAT CONSUMPTION INCREASED FIBROSIS RISK IN NASH BIOPSY-PROVEN PATIENTS UNDER MEDICAL FOLLOW-UP IN A TERTIARY CENTER IN SOUTHWEST BRAZIL

BACKGROUND

Recent studies show an increase in nonalcoholic fatty liver disease (NAFLD) in populations with higher consumption of red meat, processed and cooked at high temperatures. On the other hand, the single nucleotide polymorphism rs738409 in the Patatin-like phospholipase domain containing 3 (PNPLA3) gene has been implicated in susceptibility to NAFLD and liver fibrosis. However, the synergistic effect between red meat consumption and the PNPLA3 gene polymorphism in NAFLD has not yet been evaluated.

OBJECTIVE

To evaluate the association between the presence of the polymorphism in the PNPLA3 gene and the consumption of macronutrients, including meat consumption and its cooking method among NAFLD patients.

METHODS

This was a cross-sectional study with 91 patients diagnosed with NAFLD by liver biopsy with genotyping for the polymorphism in the PNPLA3 gene were included. The consumption of calories and macronutrients was verified using the semi-quantitative food frequency questionnaire and the specific questionnaire on meat consumption. PNPLA3 gene polymorphism was analyzed by real-time polymerase chain reaction (RT-PCR) and anthropometric evaluation was realized.

RESULTS

The mean BMI was 32.38±4.58 kg/m² and the waist circumference was 107±10 cm. On liver biopsy, 42% of patients had significant fibrosis (F≥2). The odds ratio of F≥2 was 2.12 for the GG group and 1.54 for the CG group, compared to the CC group. The mean caloric intake was 1170±463.20 kcal/d. The odds ratio in the CC group concerning high red meat consumption in comparison to low consumption was 1.33. For white meat, the odds ratio was 0.8 when comparing high and low intake, also in the CC group.

CONCLUSION

High red meat intake and PNPLA3 gene polymorphism seem to synergistically affect NAFLD and liver fibrosis, requiring confirmation in a larger number of patients and in different populations.

Fatty Liver Disease-Alcoholic and Non-Alcoholic: Similar but Different

In alcohol-induced liver disease (ALD) and in non-alcoholic fatty liver disease (NAFLD), there are abnormal accumulations of fat in the liver. This phenomenon may be related to excessive alcohol consumption, as well as the combination of alcohol consumption and medications. There is an evolution from simple steatosis to steatohepatitis, fibrosis and cirrhosis leading to hepatocellular carcinoma (HCC). Hepatic pathology is very similar regarding non-alcoholic fatty liver disease (NAFLD) and ALD. Initially, there is lipid accumulation in parenchyma and progression to lobular inflammation. The morphological changes in the liver mitochondria, perivenular and perisinusoidal fibrosis, and hepatocellular ballooning, apoptosis and necrosis and accumulation of fibrosis may lead to the development of cirrhosis and HCC. Medical history of ethanol consumption, laboratory markers of chronic ethanol intake, AST/ALT ratio on the one hand and features of the metabolic syndrome on the other hand, may help in estimating the contribution of alcohol intake and the metabolic syndrome, respectively, to liver steatosis.

Dietary Recommendations for the Management of Non-alcoholic Fatty Liver Disease (NAFLD): A Nutritional Geometry Perspective

Diet could be both culprit and solution of NAFLD. Dietary modifications have been associated with histological features improvement in NAFLD. The Western diet was related to a greater risk of disease progression while the Mediterranean diet (MD) could promote regression of histological lesions. Modifications in the nutrient composition seems to have lesser impact on NAFLD than dietary modifications. An intrinsic interaction between nutrients in the diet support a specific effect not seen when added separately. Dietary modifications should focus on promoting weight loss but also look for patterns that are able to promote histological improvement. Although several micronutrients' deficit has been related to NAFLD progression, prescribing these micronutrients' supplementation did not reach a positive impact. However, an enriching diet with specific nutrients could be useful, like olive oil supplemented in MD. Geometry of nutrition defines a framework to better understand the interaction between nutrients, foods, and dietetic pattern in the model of diseases and how we could approach taking into consideration the interaction between meals and disease features. After analyzing baseline diet and histological lesions, we could calculate the distance to optimal diet and to promote changes in lifestyle to reach all these goals. A standard MD menu would be recommended.

Current Evidence Concerning Effects of Ketogenic Diet and Intermittent Fasting in Patients with Nonalcoholic Fatty Liver

Nonalcoholic fatty liver disease (NAFLD) is emerging globally, while no therapeutic medication has been approved as an effective treatment to date, lifestyle intervention through dietary modification and physical exercise plays a critical role in NAFLD management. In terms of dietary modification, Mediterranean diet is the most studied dietary pattern and is recommended in many guidelines, however, it may not be feasible and affordable for many patients. Recently, a ketogenic diet and intermittent fasting have gained public attention and have been studied in the role of weight management. This article reviews specifically whether these trendy dietary patterns have an effect on NAFLD outcomes regarding intrahepatic fat content, fibrosis, and liver enzymes, the scientific rationales behind these particular dietary patterns, as well as the safety concerns in some certain patient groups.