Screening for rheumatoid arthritis-associated interstitial lung disease-a Delphi-based consensus statement.

OBJECTIVE: Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a major driver of premature mortality in patients with rheumatoid arthritis (RA). Detection of RA-ILD is crucial but requires awareness among the treating physicians. To date, however, there is no international recommendation concerning screening for ILD in RA patients. METHODS: After a systematic literature review, the modified Delphi technique in combination with the nominal group technique was used to provide a Delphi consensus statement elaborated by an expert panel of pneumonologists, rheumatologists, and a radiologist. Based on the available evidence, several clusters of questions were defined and discussed until consent was reached. RESULTS: A screening algorithm for ILD in patients with RA based on clinical signs, respiratory symptoms, and risk factors has been developed. Further, the recommendations address diagnostic tools for RA-ILD and the follow-up of RA patients qualifying for ILD screening.

[National consensus statement by the Austrian Societies for Rheumatology, Pulmonology, Infectiology, Dermatology and Gastroenterology regarding the management of latent tuberculosis and the associated utilization of biologic and targeted synthetic DMARDS (disease modifying antirheumatic drugs)]. / Consensus Statement der Österreichischen Gesellschaften für Rheumatologie und Rehabilitation, Pneumologie, Infektiologie, Dermatologie und Gastroenterologie zum Umgang mit latenter Tuberkulose bei Therapien mit biologischen oder "targeted synthetic" DMARDs ("disease modifying antirheumatic drugs").

This nationwide Austrian consensus statement summarizes the recommendations on the management of latent tuberculosis by treatment with biologic and targeted synthetic DMARDs. The essential questions with respect to screening and preventive treatment were discussed by experts from the disciplines of rheumatology, pneumology, infectious diseases, dermatology and gastroenterology, based on the available data, and then a joint consensus was formed by agreement. This involved a differentiated discussion on the various forms of treatment, and clear recommendations were formulated.

Mitochondrial impairment drives intestinal stem cell transition into dysfunctional Paneth cells predicting Crohn's disease recurrence.

OBJECTIVE: Reduced Paneth cell (PC) numbers are observed in inflammatory bowel diseases and impaired PC function contributes to the ileal pathogenesis of Crohn's disease (CD). PCs reside in proximity to Lgr5+ intestinal stem cells (ISC) and mitochondria are critical for ISC-renewal and differentiation. Here, we characterise ISC and PC appearance under inflammatory conditions and describe the role of mitochondrial function for ISC niche-maintenance. DESIGN: Ileal tissue samples from patients with CD, mouse models for mitochondrial dysfunction (Hsp60Δ/ΔISC) and CD-like ileitis (TNFΔARE), and intestinal organoids were used to characterise PCs and ISCs in relation to mitochondrial function. RESULTS: In patients with CD and TNFΔARE mice, inflammation correlated with reduced numbers of Lysozyme-positive granules in PCs and decreased Lgr5 expression in crypt regions. Disease-associated changes in PC and ISC appearance persisted in non-inflamed tissue regions of patients with CD and predicted the risk of disease recurrence after surgical resection. ISC-specific deletion of Hsp60 and inhibition of mitochondrial respiration linked mitochondrial function to the aberrant PC phenotype. Consistent with reduced stemness in vivo, crypts from inflamed TNFΔARE mice fail to grow into organoids ex vivo. Dichloroacetate-mediated inhibition of glycolysis, forcing cells to shift to mitochondrial respiration, improved ISC niche function and rescued the ability of TNFΔARE mice-derived crypts to form organoids. CONCLUSION: We provide evidence that inflammation-associated mitochondrial dysfunction in the intestinal epithelium triggers a metabolic imbalance, causing reduced stemness and acquisition of a dysfunctional PC phenotype. Blocking glycolysis might be a novel drug target to antagonise PC dysfunction in the pathogenesis of CD.

Activated ATF6 Induces Intestinal Dysbiosis and Innate Immune Response to Promote Colorectal Tumorigenesis.

BACKGROUND & AIMS: Activating transcription factor 6 (ATF6) regulates endoplasmic reticulum stress. We studied whether ATF6 contributes to the development of colorectal cancer (CRC) using tissue from patients and transgenic mice. METHODS: We analyzed data from 541 patients with CRC in The Cancer Genome Atlas database for genetic variants and aberrant expression levels of unfolded protein response genes. Findings were validated in a cohort of 83 patients with CRC in Germany. We generated mice with intestinal epithelial cell-specific expression of the active form of Atf6 (nATF6IEC) from 2 alleles (homozygous), mice with expression of nATF6IEC from 1 allele (heterozygous), and nATF6IECfl/fl mice (controls). All nATF6IEC mice were housed under either specific-pathogen-free or germ-free conditions. Cecal microbiota from homozygous nATF6IEC mice or control mice was transferred into homozygous nATF6IEC mice or control mice. nATF6IEC mice were crossed with mice with disruptions in the myeloid differentiation primary response gene 88 and toll-like receptor adaptor molecule 1 gene (Myd88/Trif-knockout mice). Intestinal tissues were collected from mice and analyzed by histology, immunohistochemistry, immunoblots, gene expression profiling of unfolded protein response and inflammatory genes, array-based comparative genome hybridization, and 16S ribosomal RNA gene sequencing. RESULTS: Increased expression of ATF6 was associated with reduced disease-free survival times of patients with CRC. Homozygous nATF6IEC mice developed spontaneous colon adenomas at 12 weeks of age. Compared with controls, homozygous nATF6IEC mice had changes in the profile of their cecal microbiota, increased proliferation of intestinal epithelial cells, and loss of the mucus barrier-all preceding tumor formation. These mice had increased penetration of bacteria into the inner mucus layer and activation of signal transducer and activator of transcription 3, yet inflammation was not observed at the pretumor or tumor stages. Administration of antibiotics to homozygous nATF6IEC mice greatly reduced tumor incidence, and germ-free housing completely prevented tumorigenesis. Analysis of nATF6IEC MyD88/TRIF-knockout mice showed that tumor initiation and growth required MyD88/TRIF-dependent activation of signal transducer and activator of transcription 3. Transplantation of cecal microbiota from nATF6IEC mice and control mice, collected before tumor formation, caused tumor formation in ex-germ-free nATF6IEC mice. CONCLUSIONS: In patients with CRC, ATF6 was associated with reduced time of disease-free survival. In studies of nATF6IEC mice, we found sustained intestinal activation of ATF6 in the colon to promote dysbiosis and microbiota-dependent tumorigenesis.

Helicobacter pylori γ-glutamyltranspeptidase impairs T-lymphocyte function by compromising metabolic adaption through inhibition of cMyc and IRF4 expression.

Helicobacter pylori (H. pylori) is a human-specific pathogen that has evolved to cope with the immune response elicited against the infection. We previously reported that H. pylori γ-glutamyltranspeptidase (gGT) impairs T-lymphocyte proliferation and thus might act as immune regulatory factor. In this study, we analysed the underlying mechanism and its implications for H. pylori persistence. We found that H. pylori gGT compromised T-cell proliferation, activation and effector cytokine expression by specifically depriving the extracellular space of glutamine. When assessing signalling cascades and transcription factors affected by H. pylori gGT, we found that expression of cMyc and IRF4, both required for metabolic adaptation of T-lymphocytes, was highly sensitive to extracellular glutamine levels and downregulated upon gGT treatment. Moreover, we could confirm decreased IRF4 expression in T-lymphocytes infiltrating the stomach of infected individuals. Thus, our results suggest that H. pylori gGT-mediated glutamine deprivation in the gastric mucosa may suppress T-cell function thereby contributing to bacterial persistence.

Efficacy and safety of rituximab in rheumatic diseases.

B-cell depleting therapy is now in clinical use for more than 10 years in rheumatology. In 2001, a first report was published on five rheumatoid arthritis patients responding to the chimeric anti-CD20 antibody rituximab. Since then, numerous clinical trials, prospective and retrospective studies, registry data as well as case reports on the use of rituximab in autoimmune rheumatic diseases have been published. This review gives a short overview on clinical data of rituximab in rheumatic diseases currently available.

Dual-energy computed tomography compared with ultrasound in the diagnosis of gout.

OBJECTIVES: The aim of our study was to compare dual-energy CT (DECT) with US for the diagnosis of gouty arthritis and to correlate the imaging findings with results from synovial fluid aspiration whenever possible. METHODS: We recruited 21 patients (17 male and 4 female) who presented with a clinical suspicion of acute or chronic gout in 37 joints. DECT scans of the hands, wrists, feet, ankles, knees and elbows were performed. For post-processing, a colour-coding gout software protocol was used. US examinations of the same joints were performed. In addition, joint fluid aspiration was performed in a total of 14 joints. RESULTS: DECT images were positive for urate crystal deposits in 25 of 37 joints. US findings were positive in 24 of 37 examined joints. In 12 of 14 joints the synovial fluid aspiration was positive. CT and US findings correlated in 32 of 37 joints (86.5%; κ = 0.698, P < 0.001). CT and synovial fluid results correlated in 12 of 14 joints (85.7%; κ = 0.417, P = 0.119). US and cytology findings correlated in 14 of 14 joints (100%; κ = 1, P < 0.001). CONCLUSION: DECT and US have comparable sensitivity for the detection of gouty arthritis in a clinical setting. However, DECT results should be interpreted carefully, as there could be some false-negative findings.

Mitochondrial perturbation in the intestine causes microbiota-dependent injury and gene signatures discriminative of inflammatory disease.

Mitochondrial dysfunction is associated with inflammatory bowel diseases (IBDs). To understand how microbial-metabolic circuits contribute to intestinal injury, we disrupt mitochondrial function in the epithelium by deleting the mitochondrial chaperone, heat shock protein 60 (Hsp60Δ/ΔIEC). This metabolic perturbation causes self-resolving tissue injury. Regeneration is disrupted in the absence of the aryl hydrocarbon receptor (Hsp60Δ/ΔIEC;AhR-/-) involved in intestinal homeostasis or inflammatory regulator interleukin (IL)-10 (Hsp60Δ/ΔIEC;Il10-/-), causing IBD-like pathology. Injury is absent in the distal colon of germ-free (GF) Hsp60Δ/ΔIEC mice, highlighting bacterial control of metabolic injury. Colonizing GF Hsp60Δ/ΔIEC mice with the synthetic community OMM12 reveals expansion of metabolically flexible Bacteroides, and B. caecimuris mono-colonization recapitulates the injury. Transcriptional profiling of the metabolically impaired epithelium reveals gene signatures involved in oxidative stress (Ido1, Nos2, Duox2). These signatures are observed in samples from Crohn's disease patients, distinguishing active from inactive inflammation. Thus, mitochondrial perturbation of the epithelium causes microbiota-dependent injury with discriminative inflammatory gene profiles relevant for IBD.

Induction of dsRNA-activated protein kinase links mitochondrial unfolded protein response to the pathogenesis of intestinal inflammation.

OBJECTIVE: Inflammatory bowel diseases (IBDs) feature multiple cellular stress responses, including endoplasmic reticulum (ER) unfolded protein responses (UPRs). UPRs represent autoregulatory pathways that adjust organelle capacity to cellular demand. A similar mechanism, mitochondrial UPR (mtUPR), has been described for mitochondria. ER UPR in intestinal epithelial cells (IECs) contributes to the development of intestinal inflammation, and since mitochondrial alterations and dysfunction are implicated in the pathogenesis of IBDs, the authors characterised mtUPR in the context of intestinal inflammation. METHODS: Truncated ornithine transcarbamylase was used to selectively induce mtUPR in a murine IEC line. Dextran sodium sulphate (DSS) was administered to PKR (double-stranded-RNA-activated protein kinase) knockout mice to induce IEC stress in vivo and to test for their susceptibility to DSS-induced colitis. Expression levels of the mitochondrial chaperone chaperonin 60 (CPN60) and PKR were quantified in IECs from patients with IBDs and from murine models of colitis using immunohistochemistry and Western blot analysis. RESULTS: Selective mtUPR induction by truncated ornithine transcarbamylase transfection triggered the phosphorylation of eukaryotic translation initiation factor (eIF) 2α and cJun through the recruitment of PKR. Using pharmacological inhibitors and small inhibitory RNA, the authors identified mtUPR-induced eIF2α phosphorylation and transcription factor activation (cJun/AP1) as being dependent on the activities of the mitochondrial protease ClpP and the cytoplasmic kinase PKR. Pkr(-/-) mice failed to induce CPN60 in IECs upon DSS treatment at early time points and subsequently showed an almost complete resistance to DSS-induced colitis. Under inflammatory conditions, primary IECs from patients with IBDs and two murine models of colitis exhibited a strong induction of the mtUPR marker protein CPN60 associated with enhanced expression of PKR. CONCLUSION: PKR integrates mtUPR into the disease-relevant ER UPR via eIF2α phosphorylation and AP1 activation. Induction of mtUPR and PKR was observed in IECs from murine models and patients with IBDs. The authors' results indicate that PKR might link mitochondrial stress to intestinal inflammation.

Unfolded protein responses in the intestinal epithelium: sensors for the microbial and metabolic environment.

In inflammatory bowel disease, the intestinal microbiota is a key driver of inflammation. Hence, efficient sensing of luminal antigens and subsequent initiation of adequate immune responses is crucial for maintaining homeostasis, particularly in intestinal epithelial cells. Pathways such as Toll-like receptor-mediated signaling and autophagy sense microbial products to activate inflammatory processes and, concomitantly, interact with cellular stress responses such as the unfolded protein response (UPR). Proteostasis is particularly sensitive toward environmental challenges and triggers, such as oxidative stress and metabolic alterations, and impact protein folding in different cellular compartments. In contrast, disturbances in energy supply including impaired mitochondrial function and epithelial ß-oxidation have been suspected to contribute toward intestinal inflammation. Interestingly, the 2 main organelles linking metabolic pathways, inflammatory signaling and pathogen-sensing, endoplasmic reticulum (ER) and mitochondria (mt), can trigger distinct UPRs, and both ER UPR and mt UPR have been shown to be disease-relevant in inflammatory bowel disease. The ER is essential for the coordination of metabolic responses through controlling the synthetic and catabolic pathways of various nutrients and furthermore, ER UPR signaling directly intersects with inflammation-associated NF-κB and Toll-like receptor pathways. Consistently, next to their function in cellular energy supply, mitochondria are increasingly recognized as integrators of immune responses. For instance, mitochondria participate in innate immunity to viral infection through the pattern recognition receptor retinoic acid inducible gene-I and are involved in inflammasome activation. Thus, we hypothesize that a concerted UPR activation might represent an innate mechanism to sense potentially threatening changes of the mucosal metabolic environment and impacts host cellular functions and immune responses.

Nutrigenomics and nutrigenetics in inflammatory bowel diseases.

Inflammatory bowel diseases (IBD) including ulcerative colitis and Crohn's disease are chronically relapsing, immune-mediated disorders of the gastrointestinal tract. A major challenge in the treatment of IBD is the heterogenous nature of these pathologies. Both, ulcerative colitis and Crohn's disease are of multifactorial etiology and feature a complex interaction of host genetic susceptibility and environmental factors such as diet and gut microbiota. Genome-wide association studies identified disease-relevant single-nucleotide polymorphisms in approximately 100 genes, but at the same time twin studies also clearly indicated a strong environmental impact in disease development. However, attempts to link dietary factors to the risk of developing IBD, based on epidemiological observations showed controversial outcomes. Yet, emerging high-throughput technologies implying complete biological systems might allow taking nutrient-gene interactions into account for a better classification of patient subsets in the future. In this context, 2 new scientific fields, "nutrigenetics" and "nutrigenomics" have been established. "Nutrigenetics," studying the effect of genetic variations on nutrient-gene interactions and "Nutrigenomics," describing the impact of nutrition on physiology and health status on the level of gene transcription, protein expression, and metabolism. It is hoped that the integration of both research areas will promote the understanding of the complex gene-environment interaction in IBD etiology and in the long-term will lead to personalized nutrition for disease prevention and treatment. This review briefly summarizes data on the impact of nutrients on intestinal inflammation, highlights nutrient-gene interactions, and addresses the potential of applying "omic" technologies in the context of IBD.

Intestinal epithelial cell metabolism at the interface of microbial dysbiosis and tissue injury.

The intestinal epithelium represents the most regenerative tissue in the human body, located in proximity to the dense and functionally diverse microbial milieu of the microbiome. Episodes of tissue injury and incomplete healing of the intestinal epithelium are a prerequisite for immune reactivation and account for recurrent, chronically progressing phenotypes of inflammatory bowel diseases (IBD). Mitochondrial dysfunction and associated changes in intestinal epithelial functions are emerging concepts in the pathogenesis of IBD, suggesting impaired metabolic flexibility of epithelial cells affects the regenerative capacity of the intestinal tissue. Next to rendering the intestinal mucosa susceptible to inflammatory triggers, metabolic reprogramming of the epithelium is implicated in shaping adverse microbial environments. In this review, we introduce the concept of "metabolic injury" as a cell autonomous mechanism of tissue wounding in response to mitochondrial perturbation. Furthermore, we highlight epithelial metabolism as intersection of microbiome, immune cells and epithelial regeneration.

A mitochondrial unfolded protein response inhibitor suppresses prostate cancer growth in mice via HSP60.

Mitochondrial proteostasis, regulated by the mitochondrial unfolded protein response (UPRmt), is crucial for maintenance of cellular functions and survival. Elevated oxidative and proteotoxic stress in mitochondria must be attenuated by the activation of a ubiquitous UPRmt to promote prostate cancer (PCa) growth. Here we show that the 2 key components of the UPRmt, heat shock protein 60 (HSP60, a mitochondrial chaperonin) and caseinolytic protease P (ClpP, a mitochondrial protease), were required for the development of advanced PCa. HSP60 regulated ClpP expression via c-Myc and physically interacted with ClpP to restore mitochondrial functions that promote cancer cell survival. HSP60 maintained the ATP-producing functions of mitochondria, which activated the ß-catenin pathway and led to the upregulation of c-Myc. We identified a UPRmt inhibitor that blocked HSP60's interaction with ClpP and abrogated survival signaling without altering HSP60's chaperonin function. Disruption of HSP60-ClpP interaction with the UPRmt inhibitor triggered metabolic stress and impeded PCa-promoting signaling. Treatment with the UPRmt inhibitor or genetic ablation of Hsp60 inhibited PCa growth and progression. Together, our findings demonstrate that the HSP60-ClpP-mediated UPRmt is essential for prostate tumorigenesis and the HSP60-ClpP interaction represents a therapeutic vulnerability in PCa.

National consensus statement by the Austrian Societies for Rheumatology, Pulmonology, Infectiology, Dermatology and Gastroenterology regarding the management of latent tuberculosis and the associated utilization of biologic and targeted synthetic disease modifying antirheumatic drugs (DMARDs).

This publication provides a thorough analysis of the most relevant topics concerning the management of latent tuberculosis when using biologic and targeted synthetic Disease Modifying Antirheumatic Drugs (DMARDs) by a multidisciplinary, select committee of Austrian physicians. The committee includes members of the Austrian Societies for Rheumatology and Rehabilitation, Pulmonology, Infectiology, Dermatology and Gastroenterology. Consensus was reached on issues regarding screening and treatment of latent tuberculosis and includes separate recommendations for each biologic and targeted synthetic DMARD.

Phenotypic and functional analysis of CD4+ CD25- Foxp3+ T cells in patients with systemic lupus erythematosus.

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) that specialize in the suppression of immune responses might be critically involved in the pathogenesis of autoimmune diseases. Recent studies have described increased proportions of CD4(+)Foxp3(+) T cells that lacked expression of CD25 in systemic lupus erythematosus (SLE) patients but the suppressive capacity of these cells has not been analyzed so far. We therefore performed combined phenotypic and functional analyses of CD4(+)CD25(-)Foxp3(+) T cells in patients with autoimmune diseases and healthy controls (HC). Phenotypic analysis revealed increased proportions of CD4(+)CD25(-)Foxp3(+) T cells in SLE patients as compared with patients with systemic sclerosis, rheumatoid arthritis, (RA), or HC. In addition, increased proportions of CD4(+)CD25(-)Foxp3(+) T cells correlated with the clinical disease activity and the daily cortisone dose. According to phenotypic analysis, CD4(+)CD25(-)Foxp3(+) T cells resembled regulatory T cells rather than activated T cells. For functional analysis, a surrogate surface marker combination to substitute for intracellular Foxp3 was defined: CD4(+)CD25(-)CD127(-) T cells from SLE patients were isolated by FACS sorting and analyzed for their suppressive capacity in vitro. CD4(+)CD25(-)CD127(-) T cells, that contained up to 53% Foxp3(+) T cells, were found to suppress T cell proliferation but not IFN-gamma production in vitro. In summary, CD4(+)CD25(-)Foxp3(+) T cells phenotypically and to a certain extent also functionally resemble conventional Treg. Despite increased proportions, however, their selective functional defects might contribute to the failure of Treg to control autoimmune dysregulation in SLE patients.

Inflammation and cellular stress: a mechanistic link between immune-mediated and metabolically driven pathologies.

BACKGROUND: Multiple cellular stress responses have been implicated in chronic diseases such as obesity, diabetes, cardiovascular, and inflammatory bowel diseases. Even though phenotypically different, chronic diseases share cellular stress signaling pathways, in particular endoplasmic reticulum (ER) unfolded protein response (UPR). RESULTS AND METHODS: The purpose of the ER UPR is to restore ER homeostasis after challenges of the ER function. Among the triggers of ER UPR are changes in the redox status, elevated protein synthesis, accumulation of unfolded or misfolded proteins, energy deficiency and glucose deprivation, cholesterol depletion, and microbial signals. Numerous mouse models have been used to characterize the contribution of ER UPR to several pathologies, and ER UPR-associated signaling has also been demonstrated to be relevant in humans. Additionally, recent evidence suggests that the ER UPR is interrelated with metabolic and inflammatory pathways, autophagy, apoptosis, and mitochondrial stress signaling. Furthermore, microbial as well as nutrient sensing is integrated into the ER-associated signaling network. CONCLUSION: The data discussed in the present review highlight the interaction of ER UPR with inflammatory pathways, metabolic processes and mitochondrial function, and their interrelation in the context of chronic diseases.

Drug Screening, Oral Bioavailability and Regulatory Aspects: A Need for Human Organoids.

The intestinal epithelium critically contributes to oral bioavailability of drugs by constituting an important site for drug absorption and metabolism. In particular, intestinal epithelial cells (IEC) actively serve as gatekeepers of drug and nutrient availability. IECs' transport processes and metabolism are interrelated to the whole-body metabolic state and represent potential points of origin as well as therapeutic targets for a variety of diseases. Human intestinal organoids represent a superior model of the intestinal epithelium, overcoming limitations of currently used in vitro models. Caco-2 cells or rodent explant models face drawbacks such as their cancer and non-human origin, respectively, but are commonly used to study intestinal nutrient absorption, enterocyte metabolism and oral drug bioavailability, despite poorly correlative data. In contrast, intestinal organoids allow investigating distinct aspects of bioavailability including spatial resolution of transport, inter-individual differences and high-throughput screenings. As several countries have already developed strategic roadmaps to phase out animal experiments for regulatory purposes, intestinal organoid culture and organ-on-a-chip technology in combination with in silico approaches are roads to go in the preclinical and regulatory setup and will aid implementing the 3Rs (reduction, refinement and replacement) principle in basic science.

Intestinal sodium/glucose cotransporter 3 expression is epithelial and downregulated in obesity.

AIM: We aimed to determine whether the sodium/glucose cotransporter family member SGLT3, a proposed glucose sensor, is expressed in the intestine and/or kidney, and if its expression is altered in mouse models of obesity and in humans before and after weight-loss surgery. MAIN METHODS: We used in-situ hybridization and quantitative PCR to determine whether the Sglt3 isoforms 3a and 3b were expressed in the intestine and kidney of C57, leptin-deficient ob/ob, and diabetic BTBR ob/ob mice. Western blotting and immunohistochemistry were also used to assess SGLT3 protein levels in jejunal biopsies from obese patients before and after weight-loss Roux-en-Y gastric bypass surgery (RYGB), and in lean healthy controls. KEY FINDINGS: Sglt3a/3b mRNA was detected in the small intestine (duodenum, jejunum and ileum), but not in the large intestine or kidneys of mice. Both isoforms were detected in epithelial cells (confirmed using intestinal organoids). Expression of Sglt3a/3b mRNA in duodenum and jejunum was significantly lower in ob/ob and BTBR ob/ob mice than in normal-weight littermates. Jejunal SGLT3 protein levels in aged obese patients before RYGB were lower than in lean individuals, but substantially upregulated 6 months post-RYGB. SIGNIFICANCE: Our study shows that Sglt3a/3b is expressed primarily in epithelial cells of the small intestine in mice. Furthermore, we observed an association between intestinal mRNA Sglt3a/3b expression and obesity in mice, and between jejunal SGLT3 protein levels and obesity in humans. Further studies are required to determine the possible role of SGLT3 in obesity.

Mitochondrial Metabolism in the Intestinal Stem Cell Niche-Sensing and Signaling in Health and Disease.

Mitochondrial metabolism, dynamics, and stress responses in the intestinal stem cell niche play a pivotal role in regulating intestinal epithelial cell homeostasis, including self-renewal and differentiation. In addition, mitochondria are increasingly recognized for their involvement in sensing the metabolic environment and their capability of integrating host and microbial-derived signals. Gastrointestinal diseases such as inflammatory bowel diseases and colorectal cancer are characterized by alterations of intestinal stemness, the microbial milieu, and mitochondrial metabolism. Thus, mitochondrial function emerges at the interface of determining health and disease, and failure to adapt mitochondrial function to environmental cues potentially results in aberrant tissue responses. A mechanistic understanding of the underlying role of mitochondrial fitness in intestinal pathologies is still in its infancy, and therapies targeting mitochondrial (dys)function are currently lacking. This review discusses mitochondrial signaling and metabolism in intestinal stem cells and Paneth cells as critical junction translating host- and microbe-derived signals into epithelial responses. Consequently, we propose mitochondrial fitness as a hallmark for intestinal epithelial cell plasticity, determining the regenerative capacity of the epithelium.

Organoids to Study Intestinal Nutrient Transport, Drug Uptake and Metabolism - Update to the Human Model and Expansion of Applications.

Intestinal transport and sensing processes and their interconnection to metabolism are relevant to pathologies such as malabsorption syndromes, inflammatory diseases, obesity and type 2 diabetes. Constituting a highly selective barrier, intestinal epithelial cells absorb, metabolize, and release nutrients into the circulation, hence serving as gatekeeper of nutrient availability and metabolic health for the whole organism. Next to nutrient transport and sensing functions, intestinal transporters including peptide transporter 1 (PEPT1) are involved in the absorption of drugs and prodrugs, including certain inhibitors of angiotensin-converting enzyme, protease inhibitors, antivirals, and peptidomimetics like ß-lactam antibiotics. Here, we verify the applicability of 3D organoids for in vitro investigation of intestinal biochemical processes related to transport and metabolism of nutrients and drugs. Establishing a variety of methodologies including illustration of transporter-mediated nutrient and drug uptake and metabolomics approaches, we highlight intestinal organoids as robust and reliable tool in this field of research. Currently used in vitro models to study intestinal nutrient absorption, drug transport and enterocyte metabolism, such as Caco-2 cells or rodent explant models are of limited value due to their cancer and non-human origin, respectively. Particularly species differences result in poorly correlative data and findings obtained in these models cannot be extrapolated reliably to humans, as indicated by high failure rates in drug development pipelines. In contrast, human intestinal organoids represent a superior model of the intestinal epithelium and might help to implement the 3Rs (Reduction, Refinement and Replacement) principle in basic science as well as the preclinical and regulatory setup.