In vivo imaging of cathepsin B in activated glia in the brain after orofacial formalin test.

PURPOSE Cathepsin B (Cat B) is a cysteine lysosomal protease that is upregulated in many inflammatory diseases and widely expressed in the brain. Here, we used a Cat B activatable near-infrared (NIR) imaging probe to measure glial activation in vivo in the formalin test, a standard orofacial inflammatory pain model. The probe's efficacy was quantified with immunohistochemical analysis of the somatosensory cortex. PROCEDURES Three different concentrations of Cat B imaging probe (30, 50, 100 pmol/200 g bodyweight) were injected intracisternally into the foramen magnum of rats under anesthesia. Four hours later formalin (1.5%, 50 µl) was injected into the upper lip and the animal's behaviors recorded for 45 min. Subsequently, animals were repeatedly scanned using the IVIS Spectrum (8, 10, and 28 h post imaging probe injection) to measure extracellular Cat B activity. Aldehyde fixed brain sections were immunostained with antibodies against microglial marker Iba1 or astrocytic GFAP and detected with fluorescently labeled secondary antibodies to quantify co-localization with the fluorescent probe. RESULTS The Cat B imaging probe only slightly altered the formalin test results. Nocifensive behavior was only reduced in phase 1 in the 100 pmol group. In vivo measured fluorescence efficiency was highest in the 100 pmol group 28 h post imaging probe injection. Post-mortem immunohistochemical analysis of the somatosensory cortex detected the greatest amount of NIR fluorescence localized on microglia and astrocytes in the 100 pmol imaging probe group. Sensory neuron neuropeptide and cell injury marker expression in ipsilateral trigeminal ganglia was not altered by the presence of fluorescent probe. CONCLUSIONS These data demonstrate a concentration- and time-dependent visualization of extracellular Cat B in activated glia in the formalin test using a NIR imaging probe. Intracisternal injections are well suited for extracellular CNS proteinase detection in conditions when the blood-brain barrier is intact.

Event-free survival of maralixibat-treated patients with Alagille syndrome compared to a real-world cohort from GALA.

BACKGROUND AND AIMS: Alagille syndrome (ALGS) is characterized by chronic cholestasis with associated pruritus and extrahepatic anomalies. Maralixibat, an ileal bile acid transporter inhibitor, is an approved pharmacologic therapy for cholestatic pruritus in ALGS. Since long-term placebo-controlled studies are not feasible or ethical in children with rare diseases, a novel approach was taken comparing 6-year outcomes from maralixibat trials with an aligned and harmonized natural history cohort from the G lobal AL agille A lliance (GALA) study. APPROACH AND RESULTS: Maralixibat trials comprise 84 patients with ALGS with up to 6 years of treatment. GALA contains retrospective data from 1438 participants. GALA was filtered to align with key maralixibat eligibility criteria, yielding 469 participants. Serum bile acids could not be included in the GALA filtering criteria as these are not routinely performed in clinical practice. Index time was determined through maximum likelihood estimation in an effort to align the disease severity between the two cohorts with the initiation of maralixibat. Event-free survival, defined as the time to first event of manifestations of portal hypertension (variceal bleeding, ascites requiring therapy), surgical biliary diversion, liver transplant, or death, was analyzed by Cox proportional hazards methods. Sensitivity analyses and adjustments for covariates were applied. Age, total bilirubin, gamma-glutamyl transferase, and alanine aminotransferase were balanced between groups with no statistical differences. Event-free survival in the maralixibat cohort was significantly better than the GALA cohort (HR, 0.305; 95% CI, 0.189-0.491; p <0.0001). Multiple sensitivity and subgroup analyses (including serum bile acid availability) showed similar findings. CONCLUSIONS: This study demonstrates a novel application of a robust statistical method to evaluate outcomes in long-term intervention studies where placebo comparisons are not feasible, providing wide application for rare diseases. This comparison with real-world natural history data suggests that maralixibat improves event-free survival in patients with ALGS.

Alagille syndrome: understanding the genotype-phenotype relationship and its potential therapeutic impact.

INTRODUCTION: Alagille syndrome (ALGS) is an autosomal dominant, multisystem genetic disorder with wide phenotypic variability caused by mutations in the Notch signaling pathway, specifically from mutations in either the Jagged1 (JAG1) or NOTCH2 gene. The range of clinical features in ALGS can involve various organ systems including the liver, heart, eyes, skeleton, kidney, and vasculature. Despite the genetic mutations being well-defined, there is variable expressivity and individuals with the same mutation may have different clinical phenotypes. AREAS COVERED: While no clear genotype-phenotype correlation has been identified in ALGS, this review will summarize what is currently known about the genotype-phenotype relationship and how this relationship influences the treatment of the multisystemic disorder. This review includes discussion of numerous studies which have focused on describing the genotype-phenotype relationship of different organ systems in ALGS as well as relevant basic science and population studies of ALGS. A thorough literature search was completed via the PubMed and National Library of Medicine GeneReviews databases including dates from 1969, when ALGS was first identified, to February 2023. EXPERT OPINION: The genetics of ALGS are well defined; however, ongoing investigation to identify genotype-phenotype relationships as well as genetic modifiers as potential therapeutic targets is needed. Clinicians and patients alike would benefit from identification of a correlation to aid in diagnostic evaluation and management.

Iron promotes glycolysis to drive colon tumorigenesis.

Colorectal cancer (CRC) is the third most common cancer and is also the third leading cause of cancer-related death in the USA. Understanding the mechanisms of growth and progression of CRC is essential to improve treatment. Macronutrients such as glucose are energy source for a cell. Many tumor cells exhibit increased aerobic glycolysis. Increased tissue micronutrient iron levels in both mice and humans are also associated with increased colon tumorigenesis. However, if iron drives colon carcinogenesis via affecting glucose metabolism is still not clear. Here we found the intracellular glucose levels in tumor colonoids were significantly increased after iron treatment. 13C-labeled glucose flux analysis indicated that the levels of several labeled glycolytic products were significantly increased, whereas several tricarboxylic acid cycle intermediates were significantly decreased in colonoids after iron treatment. Mechanistic studies showed that iron upregulated the expression of glucose transporter 1 (GLUT1) and mediated an inhibition of the pyruvate dehydrogenase (PDH) complex function via directly binding with tankyrase and/or pyruvate dehydrogenase kinase (PDHK) 3. Pharmacological inhibition of GLUT1 or PDHK reactivated PDH complex function and reduced high iron diet-enhanced tumor formation. In conclusion, excess iron promotes glycolysis and colon tumor growth at least partly through the inhibition of the PDH complex function.

A rare case of primary gastric Hodgkin lymphoma in an adolescent with Nijmegen breakage syndrome.

BACKGROUND: Nijmegen Breakage Syndrome (NBS) is a rare autosomal recessive DNA repair disorder that increases risk of hematological malignancy. Primary gastric malignancies are exceedingly rare in pediatric patients and not typically high on the differential of abdominal pain. CASE PRESENTATION: A 14-year-old male with NBS presented with persistent abdominal pain and was diagnosed with primary Hodgkin disease of the stomach. CONCLUSIONS: In pediatric patients with predisposition to malignancies, such as those with underlying chromosome instability disorders, all symptoms must be carefully considered.

Transferrin Receptor-Mediated Iron Uptake Promotes Colon Tumorigenesis.

Transferrin receptor (TFRC) is the major mediator for iron entry into a cell. Under excessive iron conditions, TFRC is expected to be reduced to lower iron uptake and toxicity. However, the mechanism whereby TFRC expression is maintained at high levels in iron-enriched cancer cells and the contribution of TFRC to cancer development are enigmatic. Here the work shows TFRC is induced by adenomatous polyposis coli (APC) gene loss-driven ß-catenin activation in colorectal cancer, whereas TFRC-mediated intratumoral iron accumulation potentiates ß-catenin signaling by directly enhancing the activity of tankyrase. Disruption of TFRC leads to a reduction of colonic iron levels and iron-dependent tankyrase activity, which caused stabilization of axis inhibition protein 2 (AXIN2) and subsequent repression of the ß-catenin/c-Myc/E2F Transcription Factor 1/DNA polymerase delta1 (POLD1) axis. POLD1 knockdown, iron chelation, and TFRC disruption increase DNA replication stress, DNA damage response, apoptosis, and reduce colon tumor growth. Importantly, a combination of iron chelators and DNA damaging agents increases DNA damage response and reduces colon tumor cell growth. TFRC-mediated iron import is at the center of a novel feed-forward loop that facilitates colonic epithelial cell survival. This discovery may provide novel strategies for colorectal cancer therapy.

Norepinephrine induces growth of Desulfovibrio vulgaris in an iron dependent manner.

Desulfovibrio spp. is a commensal sulfate reducing bacterium that is present in small numbers in the gastrointestinal tract. Increased concentrations of Desulfovibrio spp. (blooms) have been reported in patients with inflammatory bowel disease and irritable bowel syndrome. Since stress has been reported to exacerbate symptoms of these chronic diseases, this study examined whether the stress catecholamine norepinephrine (NE) promotes Desulfovibrio growth. Norepinephrine-stimulated growth has been reported in other bacterial taxa, and this effect may depend on the availability of the micronutrient iron. OBJECTIVES: This study tested whether norepinephrine exposure affects the in vitro growth of Desulfovibrio vulgaris in an iron dependent manner. METHODS: DSV was incubated in a growth medium with and without 1 µm of norepinephrine. An additional growth assay added the iron chelator deferoxamine in NE exposed DSV. Iron regulatory genes were assessed with and without the treatment of NE and Deferoxamine. RESULTS: We found that norepinephrine significantly increased growth of D. vulgaris. Norepinephrine also increased bacterial production of hydrogen sulfide. Additionally, norepinephrine significantly increased bacterial expression in three of the four tested iron regulatory genes. The iron chelator deferoxamine inhibited growth of D. vulgaris in a dose-dependent manner and reversed the effect of norepinephrine on proliferation of D. vulgaris and on bacterial expression of iron regulatory genes. CONCLUSION: The data presented in this work suggests that promotion of D. vulgaris growth by norepinephrine is iron dependent.

Effect of real-time virtual reality-based teaching cues on learning needle passing for robot-assisted minimally invasive surgery: a randomized controlled trial.

PURPOSE: Current virtual reality-based (VR) simulators for robot-assisted minimally invasive surgery (RAMIS) training lack effective teaching and coaching. Our objective was to develop an automated teaching framework for VR training in RAMIS. Second, we wanted to study the effect of such real-time teaching cues on surgical technical skill acquisition. Third, we wanted to assess skill in terms of surgical technique in addition to traditional time and motion efficiency metrics. METHODS: We implemented six teaching cues within a needle passing task on the da Vinci Skills Simulator platform (noncommercial research version). These teaching cues are graphical overlays designed to demonstrate ideal surgical technique, e.g., what path to follow while passing needle through tissue. We created three coaching modes: TEACH (continuous demonstration), METRICS (demonstration triggered by performance metrics), and USER (demonstration upon user request). We conducted a randomized controlled trial where the experimental group practiced using automated teaching and the control group practiced in a self-learning manner without automated teaching. RESULTS: We analyzed data from 30 participants (14 in experimental and 16 in control group). After three practice repetitions, control group showed higher improvement in time and motion efficiency, while experimental group showed higher improvement in surgical technique compared to their baseline measurements. The experimental group showed more improvement than the control group on a surgical technique metric (at what angle is needle grasped by an instrument), and the difference between groups was statistically significant. CONCLUSION: In a pilot randomized controlled trial, we observed that automated teaching cues can improve the performance of surgical technique in a VR simulator for RAMIS needle passing. Our study was limited by its recruitment of nonsurgeons and evaluation of a single configuration of coaching modes.

Intestinal Alkaline Phosphatase Exerts Anti-Inflammatory Effects Against Lipopolysaccharide by Inducing Autophagy.

Intestinal alkaline phosphatase (IAP) regulates bicarbonate secretion, detoxifies lipopolysaccharide (LPS), regulates gut microbes, and dephosphorylates proinflammatory nucleotides. IAP also exhibits anti-inflammatory effects in a Toll-like Receptor-4 (TLR-4) dependent manner. However, it is not known whether IAP induces autophagy. We tested the hypothesis that IAP may induce autophagy which may mediate the anti-inflammatory effects of IAP. We found that exogenous IAP induced autophagy in intestinal epithelial cells and in macrophages. TLR4INC34 (C34), a TLR4 signaling inhibitor, suppressed IAP-induced autophagy. IAP also inhibited LPS-induced IL-1ß mRNA expression and activation of NF-κB. When autophagy was blocked by 3-methyladenine (3MA) or by Atg5 siRNA, IAP failed to block LPS-mediated effects. IAP also upregulated autophagy-related gene expression in small intestine in mice. We administered either vehicle or IAP (100 U/ml) in drinking water for 14 days in C57BL/6 mice. Mice were sacrificed and ileal tissues collected. Increased expression of Atg5, Atg16, Irgm1, Tlr4, and Lyz genes was observed in the IAP treated group compared to the vehicle treated group. Increase in Atg16 protein expression and fluorescence intensity of LC3 was also observed in IAP-treated tissues compared to the vehicle-treated tissues. Thus, our study lays the framework for investigating how IAP and autophagy may act together to control inflammatory conditions.

Bismuth(III) interactions with Desulfovibrio desulfuricans: inhibition of cell energetics and nanocrystal formation of Bi2S3 and Bi0.

Sulfate-reducing bacteria have been suggested to have an etiological role in the development of inflammatory bowel diseases and ulcerative colitis in humans. Traditionally. bismuth compounds have been administered to alleviate gastrointestinal discomfort and disease symptoms. One mechanism by which this treatment occurs is through binding bacterial derived hydrogen sulfide in the intestines. With the addition of bismuth-deferiprone, bismuth-citrate and bismuth subsalicylate to reactions containing cells of D. desulfuricans ATCC 27774, the oxidation of H2 with sulfate as the electron acceptor was inhibited but H2 oxidation with nitrate, nitrite and sulfite was not reduced. Our research suggests that a target for bismuth inhibition of D. desulfuricans is the F1 subunit of the ATP synthase and, thus, dissimilatory sulfate reduction does not occur. At sublethal concentrations, bismuth as Bi(III) is precipitated by hydrogen sulfide produced from respiratory sulfate reduction by D. desulfuricans. Nanocrystals of bismuth sulfide were determined to be Bi2S3 through the use of high resolution transmission electron microscopy imaging with X-ray energy-dispersive spectroscopy analysis. In the absence of sulfate, D. desulfuricans oxidizes H2 with the reduction of Bi(III) to Bi0 and this was also established by X-ray energy-dispersive spectroscopy analysis.

A theoretical model of temperate phages as mediators of gut microbiome dysbiosis.

Bacteriophages are the most prominent members of the gut microbiome, outnumbering their bacterial hosts by a factor of 10. Phages are bacteria-specific viruses that are gaining attention as highly influential regulators of the gut bacterial community. Dysregulation of the gut bacterial community contributes to dysbiosis, a microbiome disorder characterized by compositional and functional changes that contribute to disease. A role for phages in gut microbiome dysbiosis is emerging with evidence that the gut phage community is altered in dysbiosis-associated disorders such as colorectal cancer and inflammatory bowel disease. Several recent studies have linked successful fecal microbiota transplantation to uptake of the donor's gut phage community, offering some insight into why some recipients respond to treatment whereas others do not. Here, we review the literature supporting a role for phages in mediating the gut bacterial community, giving special attention to Western diet dysbiosis as a case study to demonstrate a theoretical phage-based mechanism for the establishment and maintenance of dysbiosis.

A case report of a challenging diagnosis of biliary atresia in a patient receiving total parenteral nutrition.

BACKGROUND: Total parenteral nutrition (TPN) and biliary atresia (BA) are common causes of cholestasis in infancy. The diagnosis of BA is time sensitive due to an inverse correlation between age at intervention (hepatic portoenterostomy - HPE) and survival without liver transplantation. Clinical, laboratory, and histologic features of BA and parenteral nutrition associated cholestasis (PNAC) are similar, creating a diagnostic dilemma for cholestatic infants on parenteral nutrition. There is limited published information about the natural history of PNAC including time to resolution, or diagnostic tests that distinguish BA from other etiologies of cholestasis. CASE PRESENTATION: We present a case of a child diagnosed with BA whose cholestasis began while receiving TPN. His clinical course was notable for transient resolution of his cholestasis after stopping parenteral nutrition and ultimate intraoperative diagnosis. CONCLUSIONS: Clinicians who care for patients who frequently receive TPN should be aware that clinical, laboratory, imaging, and biopsy findings can be similar between BA and PNAC.

Autophagy counters LPS-mediated suppression of lysozyme.

Impaired Paneth cell expression of antimicrobial protein (AMP) lysozyme is found in patients with Crohn's disease with the autophagy gene ATG16L1 risk allele, in mice with mutations in autophagy genes Atg16L1, Atg5 and Atg7, and in Irgm1 knockout mice. Defective autophagy is also associated with expansion of resident Gram-negative bacteria in the intestinal lumen. These findings suggest that autophagy may control extracellular resident microbes by governing expression of lysozyme. To test the hypothesis that autophagy may have a defensive role in host response to resident extracellular microbes, we investigated the relationship between gut microbes, autophagy, and lysozyme. RAW 264.7 macrophages were treated with fecal slurry (FS), representing the resident microbial community; lipopolysaccharide (LPS); or butyrate, representing microbial products; or a representative resident Gram-negative bacterium Desulfovibrio vulgaris (DSV). FS, LPS, and DSV inhibited lysozyme expression, whereas butyrate had no effect. Induction of autophagy by rapamycin countered this inhibition, whereas silencing of the autophagy gene Irgm1 exacerbated the inhibitory effects of LPS on lysozyme expression. LPS also inhibited lysozyme activity against DSV and autophagy reversed this effect. Our results provide a novel insight into an interaction between gut bacteria, autophagy and AMP whereby autophagy may defend the host by countering the suppression of antimicrobial protein by Gram-negative bacteria.

Sulfur Cycling and the Intestinal Microbiome.

In this review, we focus on the activities transpiring in the anaerobic segment of the sulfur cycle occurring in the gut environment where hydrogen sulfide is produced. While sulfate-reducing bacteria are considered as the principal agents for hydrogen sulfide production, the enzymatic desulfhydration of cysteine by heterotrophic bacteria also contributes to production of hydrogen sulfide. For sulfate-reducing bacteria respiration, molecular hydrogen and lactate are suitable as electron donors while sulfate functions as the terminal electron acceptor. Dietary components provide fiber and macromolecules that are degraded by bacterial enzymes to monomers, and these are fermented by intestinal bacteria with the production to molecular hydrogen which promotes the metabolic dominance by sulfate-reducing bacteria. Sulfate is also required by the sulfate-reducing bacteria, and this can be supplied by sulfate- and sulfonate-containing compounds that are hydrolyzed by intestinal bacterial with the release of sulfate. While hydrogen sulfide in the intestinal biosystem may be beneficial to bacteria by increasing resistance to antibiotics, and protecting them from reactive oxygen species, hydrogen sulfide at elevated concentrations may become toxic to the host.

Autophagy Genes of Host Responds to Disruption of Gut Microbial Community by Antibiotics.

BACKGROUND: Defective autophagic machinery, such as that in Crohn's disease patients homozygous for ATG16L1 risk allele, is associated with alteration of resident gut bacterial communities. However, whether or not host autophagy responds to changes in the resident gut microbial community is not known. Here, we investigated the effect of antibiotic-induced disruption of the gut microbiome (dysbiosis) on autophagy gene expression and the expression of antimicrobial peptides/protein (AMP) over time. AIM: To test the hypothesis that antibiotic treatment may cause time-dependent changes in gut bacterial density, autophagy genes, and antimicrobial protein/peptide gene expression. METHODS: Mice (n = 8 per group) were treated with antibiotic cocktail and sacrificed at different intervals of recovery (days 3, 7, 10, 14, 21, 28, 35, and 42) post-antibiotics. DNA and RNA were extracted from small intestinal tissues. Bacterial density, expression of host autophagy genes, and AMP genes were analyzed by relative quantitative PCR. Fold change difference in comparison with untreated control group was calculated using 2-ΔΔCt method. Statistical analysis was performed using nonparametric Mann-Whitney test. RESULTS: Gut bacterial density changed in a time-dependent fashion in response to antibiotic treatment. These changes were concurrent with upregulation of autophagy genes and antimicrobial peptide/protein gene expression. We further showed that an oral gavage of a resident microbe Desulfovibrio, which bloomed in antibiotic-treated animals, induced Atg5 and lysozyme (Lyz) gene expression. CONCLUSION: Autophagy genes respond to dysbiosis induced by antibiotics. This response may be a host mechanism to detect and possibly correct dysbiosis by activating antimicrobial peptides/proteins that control the microbial load in the gut.

Hepatic Fibrosis Is Universal Following Fontan Operation, and Severity is Associated With Time From Surgery: A Liver Biopsy and Hemodynamic Study.

BACKGROUND: Congestive hepatopathy is a recognized complication of Fontan physiology. Data regarding the incidence of hepatopathy and risk factors are lacking. METHODS AND RESULTS: Liver biopsies and cardiac catherizations were performed as part of an evaluation offered to all patients ≥10 years after Fontan. Quantitative determination of hepatic fibrosis was performed using Sirius red staining with automated calculation of collagen deposition per slide (%CD). Biopsies from included subjects were compared to stained specimens from controls without known fibrotic liver disease. Patient characteristics, echocardiographic findings, and hemodynamic measures were evaluated as potential risk factors. The cohort consisted of 67 patients (31 female) at mean age of 17.3±4.5 years and mean time from Fontan of 14.9±4.5 years. Right ventricular morphology was present in 37 subjects. Median %CD by Sirius red staining was 21.6% (range 8.7% to 49.4%) compared to 2.6% (range 2.2% to 3.0%) in controls. There was a significant correlation between time from Fontan and degree of Sirius red staining (r=0.33, P<0.01). Serum liver enzymes and platelet count did not correlate with %CD. The median inferior vena cava pressure was 13 mm Hg (range 6-24 mm Hg) and did not correlate with %CD. There was no difference in %CD based on ventricular morphology or severity of atrioventricular valve insufficiency. CONCLUSIONS: In this cohort of predominantly asymptomatic children and adolescents electively evaluated after a Fontan operation, all exhibited evidence for hepatic fibrosis as measured by collagen deposition in the liver. Time from Fontan was the only factor significantly associated with collagen deposition. These findings demonstrate that liver fibrosis is an inherent feature of Fontan physiology and that the degree of fibrosis increases over time.

Prevalence and characterization of fibrosis in surveillance liver biopsies of patients with Fontan circulation.

The Fontan operation is a widely used palliative procedure in patients with single-ventricle anatomy that results in liver injury. As timely identification of liver fibrosis may result in management changes to Fontan patients, the aim of our study was to identify clinically meaningful semi quantitative/quantitative pathologic parameters for biopsy assessment. We performed a retrospective review of 74 liver needle biopsies from Fontan patients. Fibrosis was assessed using quantitative % collagen deposition by Sirius red image analysis, METAVIR, congestive hepatic fibrosis score, sinusoidal fibrosis score, and sinusoidal dilation score. Contemporaneous laboratory, hemodynamic, and ultrasound data were collected. Centrilobular and peri sinusoidal fibrosis was observed in all cases, with 39.2% high grade. Portal fibrosis was observed in 93.2%, with 36.2% high-grade (METAVIR F3-F4). Cirrhosis was observed in 5.4%. % Collagen deposition was increased over control tissue (P < .001) and correlated with time from Fontan (r = 0.3, P = .009) and prothrombin time (r = 0.25, P = .034). Mildly elevated prothrombin time/international normalized ratio was the only measure of liver function consistently associated with multiple high-grade fibrosis scores (METAVIR P = .046, sinusoidal fibrosis P = .018). Abnormal liver echotexture on ultrasound was associated with high-grade congestive hepatic fibrosis score (P = .03). Pathologic gradings and %CD correlated with each other (r = 0.48-0.8, P < .001). Hepatic fibrosis in Fontan patients in our study is universally present, appears to be time dependent, and correlates with few laboratory measurements of liver function. Careful assessment of needle liver biopsies lends a more meaningful measure of liver fibrosis in the Fontan patient than clinical and laboratory data, allowing for appropriate changes to patient management.

Hydrogen Sulfide in Physiology and Diseases of the Digestive Tract.

Hydrogen sulfide (H2S) is a Janus-faced molecule. On one hand, several toxic functions have been attributed to H2S and exposure to high levels of this gas is extremely hazardous to health. On the other hand, H2S delivery based clinical therapies are being developed to combat inflammation, visceral pain, oxidative stress related tissue injury, thrombosis and cancer. Since its discovery, H2S has been found to have pleiotropic effects on physiology and health. H2S is a gasotransmitter that exerts its effect on different systems, such as gastrointestinal, neuronal, cardiovascular, respiratory, renal, and hepatic systems. In the gastrointestinal tract, in addition to H2S production by mammalian cystathionine-ß-synthase (CBS), cystathionine-γ-lyase (CSE), H2S is also generated by the metabolic activity of resident gut microbes, mainly by colonic Sulfate-Reducing Bacteria (SRB) via a dissimilatory sulfate reduction (DSR) pathway. In the gut, H2S regulates functions such as inflammation, ischemia/ reperfusion injury and motility. H2S derived from gut microbes has been found to be associated with gastrointestinal disorders such as ulcerative colitis, Crohn's disease and irritable bowel syndrome. This underscores the importance of gut microbes and their production of H2S on host physiology and pathophysiology.

A rare presentation and diagnosis of juvenile polyposis syndrome and hereditary hemorrhagic telangiectasia overlap syndrome.

We present a unique case of juvenile polyposis and hereditary hemorrhagic telangiectasia overlap syndrome. The patient was found to have polyps on colonoscopy leading to genetic testing revealing an SMAD4 mutation. In children with SMAD4 mutation and juvenile polyposis, this overlap syndrome needs to be considered in the differential diagnosis and prompt the clinician to look for telangiectasias on examination and consider surveillance imaging to look for arteriovenous malformations. Our case highlights this clinical relationship and shows how nontraditional imaging using computed tomography colonography (CTC) can provide complimentary information along with colonoscopy. Despite low-dose techniques, CTC does add a radiation burden in the evaluation of these children who are at high risk for malignancy and should be used cautiously.