MAFLD progression contributes to altered thalamus metabolism and brain structure

MAFLD as part of systemic metabolic dysregulation

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. In recent years, a new terminology and definition of metabolic dysfunction-associated fatty liver disease (MAFLD) has been proposed. Compared to the NAFLD definition, MAFLD better emphasizes the pathogenic role of metabolic dysfunction in the development and progression of this highly prevalent condition. Metabolic disorders, including overweight/obesity, type 2 diabetes mellitus (T2DM), atherogenic dyslipidemia and hypertension, are often associated with systemic organ dysfunctions, thereby suggesting that multiple organ damage can occur in MAFLD. Substantial epidemiological evidence indicates that MAFLD is not only associated with an increased risk of liver-related complications, but also increases the risk of developing several extra-hepatic diseases, including new-onset T2DM, adverse cardiovascular and renal outcomes, and some common endocrine diseases. We have summarized the current literature on the adverse effect of MAFLD on the development of multiple extrahepatic (cardiometabolic and endocrine) complications and examined the role of different metabolic pathways and organ systems in the progression of MAFLD, thus providing new insights into the role of MAFLD as a multisystem metabolic disorder. Our narrative review aimed to provide insights into potential mechanisms underlying the known associations between MAFLD and extrahepatic diseases, as part of MAFLD as a multisystem disease, in order to help focus areas for future drug development targeting not only liver disease but also the risk of extrahepatic complications.

Targeting leptin/CCL3-CCL4 axes in NAFLD/MAFLD: A novel role for BPF in counteracting thalamic inflammation and white matter degeneration

Non-alcoholic fatty liver disease (NAFLD), redefined as Metabolic Associated Fatty Liver Disease (MAFLD), is characterized by an extensive multi-organ involvement. MAFLD-induced systemic inflammatory status and peripheral metabolic alteration lead to an impairment of cerebral function. Herein, we investigated a panel of leptin-related inflammatory mediators as predictive biomarkers of neuroinflammation and evaluated the possible role of Bergamot Polyphenolic Fraction (BPF) in counteracting this MAFLD-induced inflammatory cascade. Male DIAMOND mice were randomly assigned to fed chow diet and tap water or high fat diet with sugar water. Starting from week 16, mice were further divided and treated with vehicle or BPF (50 mg/kg/day), via gavage, until week 30. Magnetic resonance imaging was performed at the baseline and at week 30. Correlation and regression analyses were performed to discriminate the altered lipid metabolism in the onset of cerebral alterations. Steatohepatitis led to an increase in leptin levels, resulting in a higher expression of proinflammatory mediators. The inflammatory biomarkers involved in leptin/CCL3-CCL4 axes were correlated with the altered thalamus energetic metabolism and the white matter degeneration. BPF administration restored leptin level, improved glucose and lipid metabolism, and reduced chronic low-grade inflammatory mediators, resulting in a prevention of white matter degeneration, alterations of thalamus metabolism and brain atrophy. The highlighted positive effect of BPF, mediated by the downregulation of the inflammatory biomarkers involved in leptin/CCL3-CCL4 axes, affording novel elements to candidate BPF for the development of a therapeutic strategy aimed at counteracting MAFLD-related brain inflammation.

Dramatic Suppression of Lipogenesis and No Increase in Beta-Oxidation Gene Expression Are among the Key Effects of Bergamot Flavonoids in Fatty Liver Disease

Bergamot flavonoids have been shown to prevent metabolic syndrome, non-alcoholic fatty liver disease (NAFLD) and stimulate autophagy in animal models and patients. To investigate further the mechanism of polyphenol-dependent effects, we performed a RT2-PCR array analysis on 168 metabolism, transport and autophagy-related genes expressed in rat livers exposed for 14 weeks to different diets: standard, cafeteria (CAF) and CAF diet supplemented with 50 mg/kg of bergamot polyphenol fraction (BPF). CAF diet caused a strong upregulation of gluconeogenesis pathway (Gck, Pck2) and a moderate (>1.7 fold) induction of genes regulating lipogenesis (Srebf1, Pparg, Xbp1), lipid and cholesterol transport or lipolysis (Fabp3, Apoa1, Lpl) and inflammation (Il6, Il10, Tnf). However, only one β-oxidation gene (Cpt1a) and a few autophagy genes were differentially expressed in CAF rats compared to controls. While most of these transcripts were significantly modulated by BPF, we observed a particularly potent effect on lipogenesis genes, like Acly, Acaca and Fasn, which were suppressed far below the mRNA levels of control livers as confirmed by alternative primers-based RT2-PCR analysis and western blotting. These effects were accompanied by downregulation of pro-inflammatory cytokines (Il6, Tnfa, and Il10) and diabetes-related genes. Few autophagy (Map1Lc3a, Dapk) and no β-oxidation gene expression changes were observed compared to CAF group. In conclusion, chronic BPF supplementation efficiently prevents NAFLD by modulating hepatic energy metabolism and inflammation gene expression programs, with no effect on β-oxidation, but profound suppression of de novo lipogenesis.

Underlying Mechanisms behind the Brain-Gut-Liver Axis and Metabolic-Associated Fatty Liver Disease (MAFLD): An Update

Metabolic-associated fatty liver disease (MAFLD) includes several metabolic dysfunctions caused by dysregulation in the brain-gut-liver axis and, consequently, increases cardiovascular risks and fatty liver dysfunction. In MAFLD, type 2 diabetes mellitus, obesity, and metabolic syndrome are frequently present; these conditions are related to liver lipogenesis and systemic inflammation. This study aimed to review the connection between the brain-gut-liver axis and MAFLD. The inflammatory process, cellular alterations in hepatocytes and stellate cells, hypercaloric diet, and sedentarism aggravate the prognosis of patients with MAFLD. Thus, to understand the modulation of the physiopathology of MAFLD, it is necessary to include the organokines involved in this process (adipokines, myokines, osteokines, and hepatokines) and their clinical relevance to project future perspectives of this condition and bring to light new possibilities in therapeutic approaches. Adipokines are responsible for the activation of distinct cellular signaling in different tissues, such as insulin and pro-inflammatory cytokines, which is important for balancing substances to avoid MAFLD and its progression. Myokines improve the quantity and quality of adipose tissues, contributing to avoiding the development of MAFLD. Finally, hepatokines are decisive in improving or not improving the progression of this disease through the regulation of pro-inflammatory and anti-inflammatory organokines.

The dangerous "West Coast Swing" by hyperglycaemia and chronic stress in the mouse hippocampus: Role of kynurenine catabolism

Growing epidemiological studies highlight a bi-directional relationship between depressive symptoms and diabetes mellitus. However, the detrimental impact of their co-existence on mental health suggests the need to treat this comorbidity as a separate entity rather than the two different pathologies. Herein, we characterized the peculiar mechanisms activated in mouse hippocampus from the concurrent development of hyperglycaemia, characterizing the different diabetes subtypes, and chronic stress, recognized as a possible factor predisposing to major depression. Our work demonstrates that kynurenine overproduction, leading to apoptosis in the hippocampus, is triggered in a different way depending on hyperglycaemia or chronic stress. Indeed, in the former, kynurenine appears produced by infiltered macrophages whereas, in the latter, peripheral kynurenine preferentially promotes resident microglia activation. In this scenario, QA, derived from kynurenine catabolism, appears a key mediator causing glutamatergic synapse dysfunction and apoptosis, thus contributing to brain atrophy. We demonstrated that the coexistence of hyperglycaemia and chronic stress worsened hippocampal damage through alternative mechanisms, such as GLUT-4 and BDNF down-expression, denoting mitochondrial dysfunction and apoptosis on one hand and evoking the compromission of neurogenesis on the other. Overall, in the degeneration of neurovascular unit, hyperglycaemia and chronic stress interacted each other as the partners of a "West Coast Swing" in which the leading role can be assumed alternatively by each partner of the dance. The comprehension of these mechanisms can open novel perspectives in the management of diabetic/depressed patients, but also in the understanding the pathogenesis of other neurodegenerative disease characterized by the compromission of hippocampal function.

Bidirectional two-sample mendelian randomization analysis identifies causal associations of MRI-based cortical thickness and surface area relation to NAFLD

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) patients have exhibited extra-hepatic neurological changes, but the causes and mechanisms remain unclear. This study investigates the causal effect of NAFLD on cortical structure through bidirectional two-sample Mendelian randomization analysis.

METHODS

Genetic data from 778,614 European individuals across four NAFLD studies were used to determine genetically predicted NAFLD. Abdominal MRI scans from 32,860 UK Biobank participants were utilized to evaluate genetically predicted liver fat and volume. Data from the ENIGMA Consortium, comprising 51,665 patients, were used to evaluate the associations between genetic susceptibility, NAFLD risk, liver fat, liver volume, and alterations in cortical thickness (TH) and surface area (SA). Inverse-variance weighted (IVW) estimation, Cochran Q, and MR-Egger were employed to assess heterogeneity and pleiotropy.

RESULTS

Overall, NAFLD did not significantly affect cortical SA or TH. However, potential associations were noted under global weighting, relating heightened NAFLD risk to reduced parahippocampal SA and decreased cortical TH in the caudal middle frontal, cuneus, lingual, and parstriangularis regions. Liver fat and volume also influenced the cortical structure of certain regions, although no Bonferroni-adjusted p-values reached significance. Two-step MR analysis revealed that liver fat, AST, and LDL levels mediated the impact of NAFLD on cortical structure. Multivariable MR analysis suggested that the impact of NAFLD on the cortical TH of lingual and parstriangularis was independent of BMI, obesity, hyperlipidemia, and diabetes.

CONCLUSION

This study provides evidence that NAFLD causally influences the cortical structure of the brain, suggesting the existence of a liver-brain axis in the development of NAFLD.

A New Non-Obese Steatohepatitis Mouse Model with Cardiac Dysfunction Induced by Addition of Ethanol to a High-Fat/High-Cholesterol Diet

Non-obese metabolic dysfunction-associated steatotic liver disease (MASLD) has been associated with cardiovascular-related mortality, leading to a higher mortality rate compared to the general population. However, few reports have examined cardiovascular events in non-obese MASLD mouse models. In this study we created a mouse model to mimic this condition. In this study involving seven-week-old C57BL/6J male mice, two dietary conditions were tested: a standard high-fat/high-cholesterol diet (STHD-01) and a combined diet of STHD-01 and ethanol. Over periods of 6 and 12 weeks, we analyzed the effects on liver and cardiac tissues using various staining techniques and PCR. Echocardiography and blood tests were also performed to assess cardiac function and liver damage. The results showed that mice on the ethanol-supplemented STHD-01 diet developed signs of steatohepatitis and cardiac dysfunction, along with increased sympathetic activity, as early as 6 weeks. At 12 weeks, more pronounced exacerbations accompanied with cardiac dilation, advanced liver fibrosis, and activated myocardial fibrosis with sympathetic activation were observed. This mouse model effectively replicated non-obese MASLD and cardiac dysfunction over a 12-week period using a combined diet of STHD-01 and ethanol. This dietary approach highlighted that both liver inflammation and fibrosis, as well as cardiac dysfunction, could be significantly worsened due to the activation of the sympathetic nervous system. Our results indicate that alcohol, even when completely metabolized on the day of drinking, exacerbates the progression of non-obese MASLD and cardiac dysfunction.

Nonalcoholic fatty liver disease, liver fibrosis, and structural brain imaging: The Cross-Cohort Collaboration

BACKGROUND AND PURPOSE

Prior studies reported conflicting findings regarding the association of nonalcoholic fatty liver disease (NAFLD) and liver fibrosis with measures of brain health. We examined whether NAFLD and liver fibrosis are associated with structural brain imaging measures in middle- and old-age adults.

METHODS

In this cross-sectional study among dementia- and stroke-free individuals, data were pooled from the Offspring and Third Generation cohorts of the Framingham Heart Study (FHS), the Rotterdam Study (RS), and the Study of Health in Pomerania. NAFLD was assessed through abdominal imaging. Transient hepatic elastography (FibroScan) was used to assess liver fibrosis in FHS and RS. Linear regression models were used to explore the relation of NAFLD and liver fibrosis with brain volumes, including total brain, gray matter, hippocampus, and white matter hyperintensities, adjusting for potential confounders. Results were combined using fixed effects meta-analysis.

RESULTS

In total, 5660 and 3022 individuals were included for NAFLD and liver fibrosis analyses, respectively. NAFLD was associated with smaller volumes of total brain (β = -3.5, 95% confidence interval [CI] = -5.4 to -1.7), total gray matter (β = -1.9, 95% CI = -3.4 to -0.3), and total cortical gray matter (β = -1.9, 95% CI = -3.7 to -0.01). In addition, liver fibrosis (defined as liver stiffness measure ≥8.2 kPa) was related to smaller total brain volumes (β = -7.3, 95% CI = -11.1 to -3.5). Heterogeneity between studies was low.

CONCLUSIONS

NAFLD and liver fibrosis may be directly related to brain aging. Larger and prospective studies are warranted to validate these findings and identify liver-related preventive strategies for neurodegeneration.

Reducing gut microbiome-driven adipose tissue inflammation alleviates metabolic syndrome

BACKGROUND

The gut microbiota contributes to macrophage-mediated inflammation in adipose tissue with consumption of an obesogenic diet, thus driving the development of metabolic syndrome. There is a need to identify and develop interventions that abrogate this condition. The hops-derived prenylated flavonoid xanthohumol (XN) and its semi-synthetic derivative tetrahydroxanthohumol (TXN) attenuate high-fat diet-induced obesity, hepatosteatosis, and metabolic syndrome in C57Bl/6J mice. This coincides with a decrease in pro-inflammatory gene expression in the gut and adipose tissue, together with alterations in the gut microbiota and bile acid composition.

RESULTS

In this study, we integrated and interrogated multi-omics data from different organs with fecal 16S rRNA sequences and systemic metabolic phenotypic data using a Transkingdom Network Analysis. By incorporating cell type information from single-cell RNA-seq data, we discovered TXN attenuates macrophage inflammatory processes in adipose tissue. TXN treatment also reduced levels of inflammation-inducing microbes, such as Oscillibacter valericigenes, that lead to adverse metabolic phenotypes. Furthermore, in vitro validation in macrophage cell lines and in vivo mouse supplementation showed addition of O. valericigenes supernatant induced the expression of metabolic macrophage signature genes that are downregulated by TXN in vivo.

CONCLUSIONS

Our findings establish an important mechanism by which TXN mitigates adverse phenotypic outcomes of diet-induced obesity and metabolic syndrome. TXN primarily reduces the abundance of pro-inflammatory gut microbes that can otherwise promote macrophage-associated inflammation in white adipose tissue. Video Abstract.

Salvia rosmarinus Spenn. (Lamiaceae) Hydroalcoholic Extract: Phytochemical Analysis, Antioxidant Activity and In Vitro Evaluation of Fatty Acid Accumulation

Salvia rosmarinus Spenn. is a native Mediterranean shrub belonging to the Lamiaceae family and is well-known as a flavoring and spicing agent. In addition to its classical use, it has drawn attention because its biological activities, due particularly to the presence of polyphenols, including carnosic acid and rosmarinic acid, and phenolic diterpenes as carnosol. In this study, the aerial part of rosemary was extracted with a hydroalcoholic solution through maceration, followed by ultrasound sonication, to obtain a terpenoids-rich Salvia rosmarinus extract (TRSrE) and a polyphenols-rich Salvia rosmarinus extract (PRSrE). After phytochemical characterization, both extracts were investigated for their antioxidant activity through a classical assay and with electron paramagnetic resonance (EPR) for their DPPH and hydroxyl radicals scavenging. Finally, their potential beneficial effects to reduce lipid accumulation in an in vitro model of NAFLD were evaluated.

Imbalance of thalamic metabolites in an experimental model of hypertension: role of bergamot polyphenols

Cerebral metabolites are associated with different physiological and pathological processes in brain tissue. Among them, the concentrations of N-acetylaspartate (NAA) and choline-containing compounds (Cho) in the thalamic region are recognized and analyzed as important predictive markers of brain impairment. The relationship among hypertension, modulation of brain metabolite levels and cerebral diseases is of recent investigation, leaving many unanswered questions regarding the origin and consequences of the metabolic damage caused in grey and white matter during hypertension. Here we provide evidence for the influence of hypertension on NAA and Cho ratios in hypertensive rat thalamus and how the use of natural occurring compounds ameliorates the balance of thalamic metabolites.

Avenues within the gut-liver-brain axis linking chronic liver disease and symptoms

Symptoms of fatigue, social withdrawal and mood disturbances are commonly encountered in patients with chronic liver disease and have a detrimental effect on patient quality of life. Treatment options for these symptoms are limited and a current area of unmet medical need. In this review, we will evaluate the potential mechanistic avenues within the gut-liver-brain axis that may be altered in the setting of chronic liver disease that drive the development of these symptoms. Both clinical and pre-clinical studies will be highlighted as we discuss how perturbations in host immune response, microbiome, neural responses, and metabolites composition can affect the central nervous system.

Machine learning for detecting Wilson's disease by amplitude of low-frequency fluctuation

Wilson's disease (WD) is a genetic disorder with the A7P7B gene mutations. It is difficult to diagnose in clinic. The purpose of this study was to confirm whether amplitude of low-frequency fluctuations (ALFF) is one of the potential biomarkers for the diagnosis of WD. The study enrolled 30 healthy controls (HCs) and 37 WD patients (WDs) to obtain their resting-state functional magnetic resonance imaging (rs-fMRI) data. ALFF was obtained through preprocessing of the rs-fMRI data. To distinguish between patients with WDs and HCs, four clusters with abnormal ALFF-z values were identified through between-group comparisons. Based on these clusters, three machine learning models were developed, including Random Forest (RF), Support Vector Machine (SVM), and Logistic Regression (LR). Abnormal ALFF z-values were also combined with volume information, clinical variables, and imaging features to develop machine learning models. There were 4 clusters where the ALFF z-values of the WDs were significantly higher than that of the HCs. Cluster1 was in the cerebellar region, Cluster2 was in the left caudate nucleus, Cluster3 was in the bilateral thalamus, and Cluster4 was in the right caudate nucleus. In the training set and test set, the models trained with Cluster2, Cluster3, and Cluster4 achieved area of curve (AUC) greater than 0.80. In the Delong test, only the AUC values of models trained with Cluster4 exhibited statistical significance. The AUC values of the Logit model (P = 0.04) and RF model (P = 0.04) were significantly higher than those of the SVM model. In the test set, the LR model and RF model trained with Cluster3 had high specificity, sensitivity, and accuracy. By conducting the Delong test, we discovered that there was no statistically significant inter-group difference in AUC values between the model that integrates multi-modal information and the model before fusion. The LR models trained with multimodal information and Cluster 4, as well as the LR and RF models trained with multimodal information and Cluster 3, have demonstrated high accuracy, specificity, and sensitivity. Overall, these findings suggest that using ALFF based on the thalamus or caudate nucleus as markers can effectively differentiate between WDs and HCs. The fusion of multimodal information did not significantly improve the classification performance of the models before fusion.

Nocellara Del Belice (Olea europaea L. Cultivar): Leaf Extract Concentrated in Phenolic Compounds and Its Anti-Inflammatory and Radical Scavenging Activity

Olea europaea L. is a plant belonging to the Oleaceae family, widely grown around the Mediterranean Basin and its leaves are a source of phenolic compounds with antioxidant and anti-inflammatory capacity. Among these, oleuropein and luteolin-7-O-glucoside represent two major polyphenolic compounds in olive-leaf extract. Herein, a polystyrene resin was used to recover the polyphenolic fraction from the acetone-water leaf extract from Nocellara del Belice cultivar, which showed the higher level of analysed bioactive compounds, compared to Carolea cultivar. The antioxidant activity of the extract concentrated in phenolic compounds (OLECp) was evaluated through a classical assay and electron paramagnetic resonance (EPR) for DPPH and hydroxyl radicals scavenging. Thus, the anti-inflammatory activity and the potential beneficial effects in reducing lipid accumulation in an in vitro model of NAFLD using McA-RH7777 cells exposed to oleic acid (OA) were evaluated. Nile Red and Oil Red O have been used to stain the lipid accumulation, while the inflammatory status was assessed by Cytokines Bioplex Assay. OLECp (TPC: 92.93 ± 9.35 mg GAE/g, TFC: 728.12 ± 16.04 mg RE/g; 1 g of extract contains 315.250 mg of oleuropein and 17.44 mg of luteolin-7-O-glucoside) exerted a good radical scavenging capability (IC₅₀: 2.30 ± 0.18 mg/mL) with a neutralizing power against DPPH and hydroxyl radicals, as confirmed by the decreased signal area of the EPR spectra. Moreover, OLECp at concentration of 25, 50 and 100 μg/mL counteracted the intracellular inflammatory status, as result of decreased intracellular lipid content. Our results highlighted the multiple properties and applications of an O. europaea extract concentrated in polyphenols, and the possibility to formulate novel nutraceuticals with antioxidant properties, destined to ameliorate human health.