A Distinctive NAFLD Signature in Adipose Tissue from Women with Severe Obesity

The role of novel adipokines and adipose-derived extracellular vesicles (ADEVs): Connections and interactions in liver diseases

Adipose tissues (AT) are an important endocrine organ that secretes various functional adipokines, peptides, non-coding RNAs, and acts on AT themselves or other distant tissues or organs through autocrine, paracrine, or endocrine manners. An accumulating body of evidence has suggested that many adipokines play an important role in liver metabolism. Besides the traditional adipokines such as adiponectin and leptin, many novel adipokines have recently been identified to have regulatory effects on the liver. Additionally, AT can produce extracellular vesicles (EVs) that act on peripheral tissues. However, under pathological conditions, such as obesity and diabetes, dysregulation of adipokines is associated with functional changes in AT, which may cause liver diseases. In this review, we focus on the newly discovered adipokines and EVs secreted by AT and highlight their actions on the liver under the context of obesity, nonalcoholic fatty liver diseases (NAFLD), and some other liver diseases. Clarifying the action of adipokines and adipose tissue-derived EVs on the liver would help to identify novel therapeutic targets or biomarkers for metabolic diseases.

Markers of adipose tissue fibrogenesis associate with clinically significant liver fibrosis and are unchanged by synbiotic treatment in patients with NAFLD

BACKGROUND AND AIMS

Subcutaneous adipose tissue (SAT) dysfunction contributes to NAFLD pathogenesis and may be influenced by the gut microbiota. Whether transcript profiles of SAT are associated with liver fibrosis and are influenced by synbiotic treatment (that changes the gut microbiome) is unknown. We investigated: (a) whether the presence of clinically significant, ≥F2 liver fibrosis associated with adipose tissue (AT) dysfunction, differential gene expression in SAT, and/or a marker of tissue fibrosis (Composite collagen gene expression (CCGE)); and (b) whether synbiotic treatment modified markers of AT dysfunction and the SAT transcriptome.

METHODS

Sixty-two patients with NAFLD (60 % men) were studied before and after 12 months of treatment with synbiotic or placebo and provided SAT samples. Vibration-controlled transient elastography (VCTE)-validated thresholds were used to assess liver fibrosis. RNA-sequencing and histological analysis of SAT were performed to determine differential gene expression, CCGE and the presence of collagen fibres. Regression modelling and receiver operator characteristic curve analysis were used to test associations with, and risk prediction for, ≥F2 liver fibrosis.

RESULTS

Patients with ≥F2 liver fibrosis (n = 24) had altered markers of AT dysfunction and a SAT gene expression signature characterised by enrichment of inflammatory and extracellular matrix-associated genes, compared to those with

CONCLUSION

A differential gene expression signature in SAT associates with ≥F2 liver fibrosis is explained by a measure of systemic insulin resistance and is not changed by synbiotic treatment. SAT CCGE values are a good predictor of ≥F2 liver fibrosis in NAFLD.

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Key Words

• Adipose tissue
• Gut microbiome
• Liver fibrosis
• NAFLD
• Synbiotic
• Transcriptome

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MESH Headings

• Male
• Humans
• Female
• Non-alcoholic Fatty Liver Disease/genetics
• Non-alcoholic Fatty Liver Disease/therapy
• Non-alcoholic Fatty Liver Disease/complications
• Synbiotics
• Biomarkers
• Liver Cirrhosis/genetics
• Liver Cirrhosis/therapy
• Liver Cirrhosis/complications
• Fibrosis
• Adipose Tissue/pathology
• Collagen/genetics
• Liver/pathology

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Affiliation(s)

Josh Bilson School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK
Carolina J Oquendo School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
James Read School of Chemistry, Faculty of Engineering and Physical sciences, University of Southampton, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Eleonora Scorletti School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Division of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
Paul R Afolabi School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK
Jenny Lord School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
Laure B Bindels Metabolism and Nutrition Research Group, Louvain Drug Research Institute, UC Louvain, Université Catholique de Louvain, Brussels, Belgium; Welbio department, WEL Research Institute, Wavre, Belgium
Giovanni Targher Department of Medicine, University of Verona, Italy; Metabolic Diseases Unit, IRCCS Sacro Cuore - Don Calabria Hospital, Negrar di Valpolicella, Italy
Sumeet Mahajan School of Chemistry, Faculty of Engineering and Physical sciences, University of Southampton, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Diana Baralle School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
Philip C Calder School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK
Christopher D Byrne School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK.
Jaswinder K Sethi School of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK; National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton National Health Service Foundation Trust, Southampton, UK; Institute for Life Sciences, University of Southampton, Southampton, UK.

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Type 2 Diabetes Mellitus, Non-Alcoholic Fatty Liver Disease, and Metabolic Repercussions: The Vicious Cycle and Its Interplay with Inflammation

The prevalence of metabolic-related disorders, such as non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (DM2), has been increasing. Therefore, developing improved methods for the prevention, treatment, and detection of these two conditions is also necessary. In this study, our primary focus was on examining the role of chronic inflammation as a potential link in the pathogenesis of these diseases and their interconnections. A comprehensive search of the PubMed database using keywords such as "non-alcoholic fatty liver disease", "type 2 diabetes mellitus", "chronic inflammation", "pathogenesis", and "progression" yielded 177 relevant papers for our analysis. The findings of our study revealed intricate relationships between the pathogenesis of NAFLD and DM2, emphasizing the crucial role of inflammatory processes. These connections involve various molecular functions, including altered signaling pathways, patterns of gene methylation, the expression of related peptides, and up- and downregulation of several genes. Our study is a foundational platform for future research into the intricate relationship between NAFLD and DM2, allowing for a better understanding of the underlying mechanisms and the potential for introducing new treatment standards.

Cross-tissue omics analysis discovers ten adipose genes encoding secreted proteins in obesity-related non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a fast-growing, underdiagnosed, epidemic. We hypothesise that obesity-related inflammation compromises adipose tissue functions, preventing efficient fat storage, and thus driving ectopic fat accumulation into the liver.

METHODS

To identify adipose-based mechanisms and potential serum biomarker candidates (SBCs) for NAFLD, we utilise dual-tissue RNA-sequencing (RNA-seq) data in adipose tissue and liver, paired with histology-based NAFLD diagnosis, from the same individuals in a cohort of obese individuals. We first scan for genes that are differentially expressed (DE) for NAFLD in obese individuals' subcutaneous adipose tissue but not in their liver; encode proteins secreted to serum; and show preferential adipose expression. Then the identified genes are filtered to key adipose-origin NAFLD genes by best subset analysis, knockdown experiments during human preadipocyte differentiation, recombinant protein treatment experiments in human liver HepG2 cells, and genetic analysis.

FINDINGS

We discover a set of genes, including 10 SBCs, that may modulate NAFLD pathogenesis by impacting adipose tissue function. Based on best subset analysis, we further follow-up on two SBCs CCDC80 and SOD3 by knockdown in human preadipocytes and subsequent differentiation experiments, which show that they modulate crucial adipogenesis genes, LPL, SREBPF1, and LEP. We also show that treatment of the liver HepG2 cells with the CCDC80 and SOD3 recombinant proteins impacts genes related to steatosis and lipid processing, including PPARA, NFE2L2, and RNF128. Finally, utilizing the adipose NAFLD DE gene cis-regulatory variants associated with serum triglycerides (TGs) in extensive genome-wide association studies (GWASs), we demonstrate a unidirectional effect of serum TGs on NAFLD with Mendelian Randomization (MR) analysis. We also demonstrate that a single SNP regulating one of the SBC genes, rs2845885, produces a significant MR result by itself. This supports the conclusion that genetically regulated adipose expression of the NAFLD DE genes may contribute to NAFLD through changes in serum TG levels.

INTERPRETATION

Our results from the dual-tissue transcriptomics screening improve the understanding of obesity-related NAFLD by providing a targeted set of 10 adipose tissue-active genes as new serum biomarker candidates for the currently grossly underdiagnosed fatty liver disease.

FUNDING

The work was supported by NIH grants R01HG010505 and R01DK132775. The Genotype-Tissue Expression (GTEx) Project was supported by the Common Fund of the Office of the Director of the National Institutes of Health, and by NCI, NHGRI, NHLBI, NIDA, NIMH, and NINDS. The KOBS study (J. P.) was supported by the Finnish Diabetes Research Foundation, Kuopio University Hospital Project grant (EVO/VTR grants 2005-2019), and the Academy of Finland grant (Contract no. 138006). This study was funded by the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant No. 802825 to M. U. K.). K. H. P. was funded by the Academy of Finland (grant numbers 272376, 266286, 314383, and 335443), the Finnish Medical Foundation, Gyllenberg Foundation, Novo Nordisk Foundation (grant numbers NNF10OC1013354, NNF17OC0027232, and NNF20OC0060547), Finnish Diabetes Research Foundation, Finnish Foundation for Cardiovascular Research, University of Helsinki, and Helsinki University Hospital and Government Research Funds. I. S. was funded by the Instrumentarium Science Foundation. Personal grants to U. T. A. were received from the Matti and Vappu Maukonen Foundation, Ella och Georg Ehrnrooths Stiftelse and the Finnish Foundation for Cardiovascular Research.

Recent evaluation about inflammatory mechanisms in nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is common chronic metabolic liver disorder which is associated with fat accumulation in the liver. It causes a wide range of pathological effects such as insulin resistance, obesity, hypertension, diabetes, non-alcoholic steatohepatitis (NASH) and cirrhosis, cardiovascular diseases. The molecular mechanisms that cause the initiation and progression of NAFLD remain fully unclear. Inflammation is regarded as a significant mechanism which could result in cell death and tissue injury. Accumulation of leukocytes and hepatic inflammation are important contributors in NAFLD. Excessive inflammatory response can deteriorate the tissue injury in NAFLD. Thus, inhibition of inflammation improves NAFLD by reducing intrahepatic fat content, increasing β-oxidation of fatty acids, inducing hepato-protective autophagy, overexpressing peroxisome proliferator-activated receptor- γ (PPAR-γ), as well as attenuating hepatocyte apoptosis and increasing insulin sensitivity. Therefore, understanding the molecules and signaling pathways suggests us valuable information about NAFLD progression. This review aimed to evaluate the inflammation in NAFLD and the molecular mechanism on NAFLD.

What's New in the Treatment of Non-Alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a serious health problem due to its high incidence and consequences. In view of the existing controversies, new therapeutic options for NAFLD are still being sought. Therefore, the aim of our review was to evaluate the recently published studies on the treatment of NAFLD patients. We searched for articles in the PubMed database using appropriate terms, including "non-alcoholic fatty liver disease", "nonalcoholic fatty liver disease", "NAFLD", "diet", "treatment", "physical activity", "supplementation", "surgery", "overture" and "guidelines". One hundred forty-eight randomized clinical trials published from January 2020 to November 2022 were used for the final analysis. The results show significant benefits of NAFLD therapy associated with the use of not only the Mediterranean but also other types of diet (including low-calorie ketogenic, high-protein, anti-inflammatory and whole-grain diets), as well as enrichment with selected food products or supplements. Significant benefits in this group of patients are also associated with moderate aerobic physical training. The available therapeutic options indicate, above all, the usefulness of drugs related to weight reduction, as well as the reduction in insulin resistance or lipids level and drugs with anti-inflammatory or antioxidant properties. The usefulness of therapy with dulaglutide and the combination of tofogliflozin with pioglitazone should be emphasized. Based on the results of the latest research, the authors of this article suggest a revision of the therapeutic recommendations for NAFLD patients.

Visceral Adipose Tissue Molecular Networks and Regulatory microRNA in Pediatric Obesity: An In Silico Approach

Childhood obesity carries an increased risk of metabolic complications, sleep disturbances, and cancer. Visceral adiposity is independently associated with inflammation and insulin resistance in obese children. However, the underlying pathogenic mechanisms are still unclear. We aimed to detect the gene expression pattern and its regulatory network in the visceral adipose tissue of obese pediatric individuals. Using differentially-expressed genes (DEGs) identified from two publicly available datasets, GSE9624 and GSE88837, we performed functional enrichment, protein–protein interaction, and network analyses to identify pathways, targeting transcription factors (TFs), microRNA (miRNA), and regulatory networks. There were 184 overlapping DEGs with six significant clusters and 19 candidate hub genes. Furthermore, 24 TFs targeted these hub genes. The genes were regulated by miR-16-5p, miR-124-3p, miR-103a-3p, and miR-107, the top miRNA, according to a maximum number of miRNA–mRNA interaction pairs. The miRNA were significantly enriched in several pathways, including lipid metabolism, immune response, vascular inflammation, and brain development, and were associated with prediabetes, diabetic nephropathy, depression, solid tumors, and multiple sclerosis. The genes and miRNA detected in this study involve pathways and diseases related to obesity and obesity-associated complications. The results emphasize the importance of the TGF-β signaling pathway and its regulatory molecules, the immune system, and the adipocytic apoptotic pathway in pediatric obesity. The networks associated with this condition and the molecular mechanisms through which the potential regulators contribute to pathogenesis are open to investigation.

Increased Secreted Frizzled-Related Protein 5 mRNA Expression in the Adipose Tissue of Women with Nonalcoholic Fatty Liver Disease Associated with Obesity

Secreted frizzled-related protein 5 (SFRP5) is an anti-inflammatory adipocytokine secreted by adipocytes that seems to be linked with nonalcoholic fatty liver disease (NAFLD). We aimed to evaluate the role of the SFRP5-wingless-MMTV integration site family member 5a (WNT5A) pathway, closely related to adipogenesis, in subcutaneous (SAT) and visceral adipose tissues (VAT) and its relationship with obesity-related NAFLD. Our cohort was composed of 60 women with morbid obesity (MO), who underwent hypocaloric diet, subclassified according to their hepatic histopathology and 15 women with normal weight. We observed increased SFRP5 mRNA expression in VAT and lower WNT5A expression in SAT in MO compared to normal weight. We found elevated SFRP5 expression in nonalcoholic steatohepatitis (NASH) in SAT and in mild simple steatosis (SS) and NASH in VAT. We observed higher WNT5A expression in SS compared to normal liver in SAT, and a peak of WNT5A expression in mild SS. To conclude, we reported increased SFRP5 mRNA expression in SAT and VAT of NAFLD-related to obesity subjects, suggesting an implication of the SFRP5-WNT5A pathway in NAFLD pathogenesis, probably due to the adipose tissue-liver axis. Since the mechanisms by which this potential interaction takes place remain elusive, more research in this field is needed.

Biological Determinants of Metabolic Syndrome in Visceral and Subcutaneous Adipose Tissue from Severely Obese Women

The metabolic syndrome (MetS) is a cluster of the most dangerous heart attack risk factors: diabetes or raised fasting plasma glucose, abdominal obesity, high cholesterol and high blood pressure. The goal of this study is to compare the state of the main features of obesity-associated white adipose tissue (WAT) dysfunction in 66 women with severe obesity without (MetS-) or with MetS (MetS+). Fat cell area, adipocyte size distribution and histological fibrosis were analysed in visceral (VAT) and abdominal subcutaneous WAT (SAT) in 33 age- and BMI-matched pairs of MetS- and MetS+ subjects. The mRNA expression of 93 genes implicated in obesity-associated WAT dysfunction was analysed by RT-qPCR in both fat depots. MetS+ females showed higher adipocyte hypertrophy in both fat depots and increased fibrosis and expression of macrophage and hypoxia markers in SAT. Transcriptional data suggest increased fatty acid oxidation in SAT and impaired thermogenesis and extracellular matrix remodelling in VAT from MetS+ subjects. A sPLS-DA model, including SAT expression of PPARA and LEPR genes identified MetS with an AUC = 0.87. Despite equal age, BMI and body composition, MetS+ females display morphological and transcriptional differences in both WAT depots, especially in SAT. These factors may contribute to the transition to MetS.