Microbial Signature in Adipose Tissue of Crohn's Disease Patients

Interplay between creeping fat and gut microbiota: A brand-new perspective on fecal microbiota transplantation in Crohn's disease

Inflammatory bowel disease, particularly Crohn's disease (CD), has been linked to modifications in mesenteric adipose tissue (MAT) and the phenomenon known as "creeping fat" (CrF). The presence of CrF is believed to serve as a predictor for early clinical recurrence following surgical intervention in patients with CD. Notably, the incorporation of the mesentery during ileocolic resection for CD has been correlated with a decrease in surgical recurrence, indicating the significant role of MAT in the pathogenesis of CD. While numerous studies have indicated that dysbiosis of the gut microbiota is a critical factor in the development of CD, the functional implications of translocated microbiota within the MAT of CD patients remain ambiguous. This manuscript commentary discusses a recent basic research conducted by Wu et al. In their study, intestinal bacteria from individuals were transplanted into CD model mice, revealing that fecal microbiota transplantation (FMT) from healthy donors alleviated CD symptoms, whereas FMT from CD patients exacerbated these symptoms. Importantly, FMT was found to affect intestinal permeability, barrier function, and the levels of proinflammatory factors and adipokines. Collectively, these findings suggest that targeting MAT and CrF may hold therapeutic potential for patients with CD. However, the study did not evaluate the composition of the intestinal microbiota of the donors or the subsequent alterations in the gut microbiota. Overall, the gut microbiota plays a crucial role in the histopathology of CD, and thus, targeting MAT and CrF may represent a promising avenue for treatment in this patient population.

Creeping fat and gut microbiota in Crohn's disease

In this article, we explored the role of adipose tissue, especially mesenteric adipose tissue and creeping fat, and its association with the gut microbiota in the pathophysiology and progression of Crohn's disease (CD). CD is a form of inflammatory bowel disease characterized by chronic inflammation of the gastrointestinal tract, influenced by genetic predisposition, gut microbiota dysbiosis, and environmental factors. Gut microbiota plays a crucial role in modulating immune response and intestinal inflammation and is associated with the onset and progression of CD. Further, visceral adipose tissue, particularly creeping fat, a mesenteric adipose tissue characterized by hypertrophy and fibrosis, has been implicated in CD pathogenesis, inflammation, and fibrosis. The bacteria from the gut microbiota may translocate into mesenteric adipose tissue, contributing to the formation of creeping fat and influencing CD progression. Although creeping fat may be a protective barrier against bacterial invasion, its expansion can damage adjacent tissues, leading to complications. Modulating gut microbiota through interventions such as fecal microbiota transplantation, probiotics, and prebiotics has shown potential in managing CD. However, more research is needed to clarify the mechanisms linking gut dysbiosis, creeping fat, and CD progression and develop targeted therapies for microbiota modulation and fat-related complications in patients with CD.

The Hydrophobic Amino Acid-Rich Fish Collagen Peptide Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Mice via Repairing the Intestinal Barrier, Regulating Intestinal Flora and AA Metabolism

The incidence of ulcerative colitis (UC) is increasing annually, but treatment option is limited. Fish collagen peptide (FCP) is a food source collagen peptide that has shown promise in alleviating UC symptoms. However, its impact on the intestinal barrier and intestinal metabolic homeostasis in UC remains unclear. This study aimed to analyze the peptide sequences and absolute amino acid (AA) content of FCP, assessing its effects on UC in mice induced by dextran sulfate sodium (DSS). FCP was examined by liquid chromatography and tandem mass spectrometry (LC-MS/MS) analysis. The 3% DSS was utilized to induce UC in murine models, followed by the assessment of the therapeutic efficacy of FCP. Clinical manifestations of UC mice were meticulously evaluated and scored. Subsequently, samples were procured for histological examination and intestinal epithelial barrier integrity analysis as well as macrogenomic and metabolomic profiling. Here, it shows that abundant peptide sequences and AAs were in FCP, particularly enriched in hydrophobic AAs (HAAs). Furthermore, it was observed that FCP effectively reversed colon shortening and reduced the extent of histological damage. Additionally, FCP suppressed the abnormal expression of inflammatory factors and intestinal barrier proteins and modulated the dysbiosis of gut microbiota toward a balanced state. These alterations led to the activation of intestinal alkaline AA and various AA metabolisms, ultimately contributing to the mitigation of UC symptoms. In summary, the diverse peptide sequences and high AAs in FCP, particularly rich in HAAs, can alleviate DSS-induced UC via preserving intestinal barrier integrity, regulating gut microbiota, and modulating AA metabolism.

Genome-wide DNA Methylome and Transcriptome Profiling Reveals Key Genes Involved in the Dysregulation of Adipose Stem Cells in Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease [CD] is characterised by the expansion of mesenteric adipose tissue [MAT], named creeping fat [CF], which seems to be directly related to disease activity. Adipose-stem cells [ASCs] isolated from the CF of patients with CD are extremely pro-inflammatory, which persists during disease remission. We hypothesised that the dysfunctional ASCs in CD accumulate epigenetic modifications triggered by the inflammatory environment, that could serve as molecular markers.

METHODS

Genome-wide DNA methylome and transcriptome profiling were performed in ASCs isolated from MAT biopsies of patients with active and inactive disease and from non-Crohn's disease patients [non-CD]. A validation cohort was used to test the main candidate genes via quantitative polymerase chain reaction in other fat depots and immune cells.

RESULTS

We found differences in DNA methylation and gene expression between ASCs isolated from patients with CD and from non-CD subjects, but we found no differences related to disease activity. Pathway enrichment analysis revealed that oxidative stress and immune response were significantly enriched in active CD, and integration analysis identified MAB21L2, a cell fate-determining gene, as the most affected gene in CD. Validation analysis confirmed the elevated gene expression of MAB21L2 in MAT and in adipose tissue macrophages in active CD. We also found a strong association between expression of the calcium channel subunit gene CACNA1H and disease remission, as CACNA1H expression was higher in ASCs and MAT from patients with inactive CD, and correlates negatively with C-reactive protein in peripheral blood mononuclear cells.

CONCLUSION

We identified a potential gene signature of CD in ASCs obtained from MAT. Integration analysis highlighted two novel genes demonstrating a negative correlation between promoter DNA methylation and transcription: one linked to ASCs in CD [MAB21L2] and the other [CACNA1H] related to disease remission.

Preventing fibrosis in IBD: update on immune pathways and clinical strategies

INTRODUCTION

Intestinal fibrosis is a common and serious complication of inflammatory bowel diseases (IBD) driving stricture formation in Crohn's disease patients and leading to submucosal damage in ulcerative colitis. Recent studies provided novel insights into the role of immune and nonimmune components in the pathogenesis of intestinal fibrosis. Those new findings may accelerate the development of anti-fibrotic treatment in IBD patients.

AREAS COVERED

This review is designed to cover the recent progress in mechanistic research and therapeutic developments on intestinal fibrosis in IBD patients, including new cell clusters, cytokines, proteins, microbiota, creeping fat, and anti-fibrotic therapies.

EXPERT OPINION

Due to the previously existing major obstacle of missing consensus on stricture definitions and the absence of clinical trial endpoints, testing of drugs with an anti-fibrotic mechanism is just starting in stricturing Crohn's disease (CD). A biomarker to stratify CD patients at diagnosis without any complications into at-risk populations for future strictures would be highly desirable. Further investigations are needed to identify novel mechanisms of fibrogenesis in the intestine that are targetable and ideally gut specific.

Intestinal mRNA expression profiles associated with mucosal healing in ustekinumab-treated Crohn's disease patients: bioinformatics analysis and prospective cohort validation

BACKGROUND

Variations exist in the response of patients with Crohn's disease (CD) to ustekinumab (UST) treatment, but the underlying cause remains unknown. Our objective was to investigate the involvement of immune cells and identify potential biomarkers that could predict the response to interleukin (IL) 12/23 inhibitors in patients with CD.

METHODS

The GSE207022 dataset, which consisted of 54 non-responders and 9 responders to UST in a CD cohort, was analyzed. Differentially expressed genes (DEGs) were identified and subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Least absolute shrinkage and selection operator (LASSO) regression was used to screen the most powerful hub genes. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive performances of these genes. Single-sample Gene Set Enrichment Analysis (ssGSEA) was used to estimate the proportions of immune cell types. These significantly altered genes were subjected to cluster analysis into immune cell-related infiltration. To validate the reliability of the candidates, patients prescribed UST as a first-line biologic in a prospective cohort were included as an independent validation dataset.

RESULTS

A total of 99 DEGs were identified in the integrated dataset. GO and KEGG analyses revealed significant enrichment of immune response pathways in patients with CD. Thirteen genes (SOCS3, CD55, KDM5D, IGFBP5, LCN2, SLC15A1, XPNPEP2, HLA-DQA2, HMGCS2, DDX3Y, ITGB2, CDKN2B and HLA-DQA1), which were primarily associated with the response versus nonresponse patients, were identified and included in the LASSO analysis. These genes accurately predicted treatment response, with an area under the curve (AUC) of 0.938. T helper cell type 1 (Th1) cell polarization was comparatively strong in nonresponse individuals. Positive connections were observed between Th1 cells and the LCN2 and KDM5D genes. Furthermore, we employed an independent validation dataset and early experimental verification to validate the LCN2 and KDM5D genes as effective predictive markers.

CONCLUSIONS

Th1 cell polarization is an important cause of nonresponse to UST therapy in patients with CD. LCN2 and KDM5D can be used as predictive markers to effectively identify nonresponse patients.

TRIAL REGISTRATION

Trial registration number: NCT05542459; Date of registration: 2022-09-14; URL: https://www.

CLINICALTRIALS

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Visceral adipose microbial and inflammatory signatures in metabolically healthy and unhealthy nonhuman primates

OBJECTIVE

Obesity is a key risk factor for metabolic syndrome (MetS); however, >10% of lean individuals meet MetS criteria. Visceral adipose tissue (VAT) disproportionately contributes to inflammation and insulin resistance compared with subcutaneous fat depots. The primary aim of this study was to profile tissue microbiome components in VAT over a wide range of metabolic statuses in a highly clinically relevant model.

METHODS

VAT was profiled from nonhuman primates that naturally demonstrate four distinct health phenotypes despite consuming a healthy diet, namely metabolically healthy lean and obese and metabolically unhealthy lean and obese.

RESULTS

VAT biopsied from unhealthy lean and obese nonhuman primates demonstrated upregulation of immune signaling pathways, a tissue microbiome enriched in gram-negative bacteria including Pseudomonas, and deficiencies in anti-inflammatory adipose tissue M2 macrophages. VAT microbiomes were distinct from fecal microbiomes, and fecal microbiomes did not differ by metabolic health group, which was in contrast to the VAT bacterial communities.

CONCLUSIONS

Immune activation with gram-negative VAT microbial communities is a consistent feature in elevated MetS risk in both lean and obesity states.

Creeping fat formation and interaction with intestinal disease in Crohn's disease

Creeping fat (CrF), also known as fat wrapping, is a significant disease characteristic of Crohn's disease (CD). The transmural inflammation impairs intestinal integrity and facilitates bacteria translocation, aggravating immune response. CrF is a rich source of pro-inflammatory and pro-fibrotic cytokines with complex immune microenvironment. The inflamed and stricturing intestine is often wrapped by CrF, and CrF is associated with greater severity of CD. The large amount of innate and adaptive immune cells as well as adipocytes in CrF promote fibrosis in the affected intestine by secreting large amount of pro-fibrotic cytokines, adipokines, growth factors and fatty acids. CrF is a potential therapeutic target for CD treatment and a promising bio-marker for predicting response to drug therapy. This review aims to summarize and update the clinical manifestation and application of CrF and the underlying molecular mechanism involved in the pathogenesis of intestinal inflammation and fibrosis in CD.

Huangqin decoction ameliorates DSS-induced ulcerative colitis: Role of gut microbiota and amino acid metabolism, mTOR pathway and intestinal epithelial barrier

BACKGROUND

The clinical treatment of ulcerative colitis (UC) is limited. A traditional Chinese medicinal formula, Huangqin decoction (HQD), is chronicled in Shang Han Lun and is widely used to ameliorate gastrointestinal disorders, such as UC; however, its mechanism is yet to be clarified.

PURPOSE

The present study aimed to investigate the effect of HQD on 7-day colitis induced by 3% dextran sulfate sodium (DSS) in mice and further explore the inhibitory effect of metabolites on DSS-damaged FHC cells.

METHODS

The therapeutic efficacy of HQD was evaluated in a well-established DSS-induced colitis mice model. The clinical symptoms were analyzed, and biological samples were collected for microscopic examination, metabolomics, metagenomics, and the evaluation of the epithelial barrier function. The mechanism of metabolites regulated by HQD was evaluated in the DSS-induced FHC cell damage model. The samples were collected to detect the physiological functions of the cells.

RESULTS

HQD suppressed the inflammation of DSS-induced colitis in vivo, attenuated DSS-induced clinical manifestations, reversed colon length reduction, and reduced histological injury. After HQD treatment, the DSS-induced gut dysbiosis was modulated, and the gut microbiota achieved a new equilibrium state. In addition, HQD activated the mTOR signaling pathway by upregulating amino acid metabolism. Significant phosphorylation of S6 and 4E-BP1 ameliorated intestinal epithelial barrier dysfunction. Moreover, HQD-regulated metabolites protected the epithelial barrier integrity by inhibiting DSS-induced apoptosis of FHC cells and regulating the proteins affecting apoptosis and cell-cell junction.

CONCLUSIONS

These findings indicated that the mechanism of HQD was related to regulating the gut microbiota and amino acid metabolism, activating the mTOR signaling pathway, and protecting the intestinal mucosal barrier integrity.

The Gut Microbiota Metabolite Succinate Promotes Adipose Tissue Browning in Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease [CD] is associated with complex microbe-host interactions, involving changes in microbial communities, and gut barrier defects, leading to the translocation of microorganisms to surrounding adipose tissue [AT]. We evaluated the presence of beige AT depots in CD and questioned whether succinate and/or bacterial translocation promotes white-to-beige transition in adipocytes.

METHODS

Visceral [VAT] and subcutaneous [SAT] AT biopsies, serum and plasma were obtained from patients with active [n = 21] or inactive [n = 12] CD, and from healthy controls [n = 15]. Adipose-derived stem cells [ASCs] and AT macrophages [ATMs] were isolated from VAT biopsies.

RESULTS

Plasma succinate levels were significantly higher in patients with active CD than in controls and were intermediate in those with inactive disease. Plasma succinate correlated with the inflammatory marker high-sensitivity C-reactive protein. Expression of the succinate receptor SUCNR1 was higher in VAT, ASCs and ATMs from the active CD group than from the inactive or control groups. Succinate treatment of ASCs elevated the expression of several beige AT markers from controls and from patients with inactive disease, including uncoupling protein-1 [UCP1]. Notably, beige AT markers were prominent in ASCs from patients with active CD. Secretome profiling revealed that ASCs from patients with active disease secrete beige AT-related proteins, and co-culture assays showed that bacteria also trigger the white-to-beige switch of ASCs from patients with CD. Finally, AT depots from patients with CD exhibited a conversion from white to beige AT together with high UCP1 expression, which was corroborated by in situ thermal imaging analysis.

CONCLUSIONS

Succinate and bacteria trigger white-to-beige AT transition in CD. Understanding the role of beige AT in CD might aid in the development of therapeutic or diagnostic interventions.

Chewing the Fat with Microbes: Lipid Crosstalk in the Gut

It is becoming increasingly important for any project aimed at understanding the effects of diet on human health, to also consider the combined effect of the trillions of microbes within the gut which modify and are modified by dietary nutrients. A healthy microbiome is diverse and contributes to host health, partly via the production and subsequent host absorption of secondary metabolites. Many of the beneficial bacteria in the gut rely on specific nutrients, such as dietary fiber, to survive and thrive. In the absence of those nutrients, the relative proportion of good commensal bacteria dwindles while communities of opportunistic, and potentially pathogenic, bacteria expand. Therefore, it is unsurprising that both diet and the gut microbiome have been associated with numerous human diseases. Inflammatory bowel diseases and colorectal cancer are associated with the presence of certain pathogenic bacteria and risk increases with consumption of a Western diet, which is typically high in fat, protein, and refined carbohydrates, but low in plant-based fibers. Indeed, despite increased screening and better care, colorectal cancer is still the 2nd leading cause of cancer death in the US and is the 3rd most diagnosed cancer among US men and women. Rates are rising worldwide as diets are becoming more westernized, alongside rising rates of metabolic diseases like obesity and diabetes. Understanding how a modern diet influences the microbiota and how subsequent microbial alterations effect human health will become essential in guiding personalized nutrition and healthcare in the future. Herein, we will summarize some of the latest advances in understanding of the three-way interaction between the human host, the gut microbiome, and the specific class of dietary nutrients, lipids.

Role of mesenteric component in Crohn’s disease: A friend or foe?

Crohn’s disease (CD) is a complex and relapsing gastrointestinal disease with mesenteric alterations. The mesenteric neural, vascular, and endocrine systems actively take part in the gut dysbiosis-adaptive immunity-mesentery-body axis, and this axis has been proven to be bidirectional. The abnormalities of morphology and function of the mesenteric component are associated with intestinal inflammation and disease progress of CD via responses to afferent signals, neuropeptides, lymphatic drainage, adipokines, and functional cytokines. The hypertrophy of mesenteric adipose tissue plays important roles in the pathogenesis of CD by secreting large amounts of adipokines and representing a rich source of proinflammatory or profibrotic cytokines. The vascular alteration, including angiogenesis and lymphangiogenesis, is concomitant in the disease course of CD. Of note, the enlarged and obstructed lymphatic vessels, which have been described in CD patients, are likely related to the early onset submucosa edema and being a cause of CD. The function of mesenteric lymphatics is influenced by endocrine of mesenteric nerves and adipocytes. Meanwhile, the structure of the mesenteric lymphatic vessels in hypertrophic mesenteric adipose tissue is mispatterned and ruptured, which can lead to lymph leakage. Leaky lymph factors can in turn stimulate adipose tissue to proliferate and effectively elicit an immune response. The identification of the role of mesentery and the crosstalk between mesenteric tissues in intestinal inflammation may shed light on understanding the underlying mechanism of CD and help explore new therapeutic targets.

Dysbiotic microbiota interactions in Crohn's disease

Crohn's disease (CD) is a major form of inflammatory bowel disease characterized by transmural inflammation along the alimentary tract. Changes in the microbial composition and reduction in species diversity are recognized as pivotal hallmarks in disease dynamics, challenging the gut barrier function and shaping a pathological immune response in genetically influenced subjects. The purpose of this review is to delve into the modification of the gut microbiota cluster network during CD progression and to discuss how this shift compromises the gut barrier integrity, granting the translocation of microbes and their products. We then complete the scope of the review by retracing gut microbiota dysbiosis interactions with the main pathophysiologic factors of CD, starting from the host's genetic background to the immune inflammatory and fibrotic processes, providing a standpoint on the lifestyle/exogenous factors and the potential benefits of targeting a specific gut microbiota.

Bacterial Characteristics of Intestinal Tissues From Patients With Crohn's Disease

Background and Aims

It is believed that intestinal bacteria play an indispensable role in promoting intestinal inflammation. However, the characteristics of these tissue-associated bacteria remain elusive. The aim of this study is to explore the bacterial loads, compositions, and structures in the noninflamed mucosa, inflamed mucosa, and creeping fat taken from patients with Crohn’s disease (CD).

Methods

Noninflamed mucosa, inflamed mucosa, and creeping fat samples were obtained from 10 surgical patients suffering from CD. Total bacterial DNA was extracted in a sterile environment using aseptic techniques. The V3–V4 regions of bacterial 16S rDNA were amplified and analysed using standard microbiological methods. qPCR was used to confirm the change in abundance of specific species in additional 30 independent samples.

Results

Inflamed mucosa exhibited the highest bacterial load (3.8 and 12 times more than that of non-inflamed mucosa and creeping fat) and species diversity. The relative abundance of Proteobacteria was dominant in most samples and was negatively associated with Firmicutes. Moreover, the relative abundances of Methylobacterium and Leifsonia in creeping fat significantly increased more than twice as much as other tissue types. The bacterial community structure analysis showed that the bacterial samples from the same individual clustered more closely.

Conclusion

This study reveals the significant differences in bacterial load, species diversity, and composition among different intestinal tissue types of CD patients and confirms that the bacterial samples from the same individual are highly correlated. Our findings will shed light on fully revealing the characteristics of tissue-associated bacteria and their roles in CD pathogenesis.

Microbiota in mesenteric adipose tissue from Crohn's disease promote colitis in mice

BACKGROUND

Mesenteric adipose tissue (mAT) hyperplasia, known as creeping fat is a pathologic characteristic of Crohn's disease (CD). The reserve of creeping fat in surgery is associated with poor prognosis of CD patients, but the mechanism remains unknown.

METHODS

Mesenteric microbiome, metabolome, and host transcriptome were characterized using a cohort of 48 patients with CD and 16 non-CD controls. Multidimensional data including 16S ribosomal RNA gene sequencing (16S rRNA), host RNA sequencing, and metabolome were integrated to reveal network interaction. Mesenteric resident bacteria were isolated from mAT and functionally investigated both in the dextran sulfate sodium (DSS) model and in the Il10 gene-deficient (Il10^-/-) mouse colitis model to validate their pro-inflammatory roles.

RESULTS

Mesenteric microbiota contributed to aberrant metabolites production and transcripts in mATs from patients with CD. The presence of mAT resident microbiota was associated with the development of CD. Achromobacter pulmonis (A. pulmonis) isolated from CD mAT could translocate to mAT and exacerbate both DSS-induced and Il10 gene-deficient (Il10^-/-) spontaneous colitis in mice. The levels of A. pulmonis in both mAT and mucous layer from CD patients were higher compared to those from the non-CD group.

CONCLUSIONS

This study suggests that the mesenteric microbiota from patients with CD sculpt a detrimental microenvironment and promote intestinal inflammation. Video abstract.

Novel mechanisms and clinical trial endpoints in intestinal fibrosis

The incidence of inflammatory bowel diseases (IBD) worldwide has resulted in a global public health challenge. Intestinal fibrosis leading to stricture formation and bowel obstruction is a frequent complication in Crohn's disease (CD), and the lack of anti-fibrotic therapies makes elucidation of fibrosis mechanisms a priority. Progress has shown that mesenchymal cells, cytokines, microbial products, and mesenteric adipocytes are jointly implicated in the pathogenesis of intestinal fibrosis. This recent information puts prevention or reversal of intestinal strictures within reach through innovative therapies validated by reliable clinical trial endpoints. Here, we review the role of immune and non-immune components of the pathogenesis of intestinal fibrosis, including new cell clusters, cytokine networks, host-microbiome interactions, creeping fat, and their translation for endpoint development in anti-fibrotic clinical trials.

Role of Adipose Tissue in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs), chronic inflammatory disorders affecting the gastrointestinal tract, include Crohn's disease and ulcerative colitis. There are increasing clinical and experimental data showing that obesity, especially visceral adiposity, plays a substantial role in the pathogenesis of IBD. Obesity seems to be an important risk factor also for IBD disease severity and clinical outcomes. Visceral adipose tissue is an active multifunctional metabolic organ involved in lipid storage and immunological and endocrine activity. Bowel inflammation penetrates the surrounding adipose tissue along the mesentery. Mesenteric fat serves as a barrier to inflammation and controls immune responses to the translocation of gut bacteria. At the same time, mesenteric adipose tissue may be the principal source of cytokines and adipokines responsible for inflammatory processes associated with IBD. This review is particularly focusing on the potential role of adipokines in IBD pathogenesis and their possible use as promising therapeutic targets.