Small Intestinal Enterocytes Research Articles

Cellular Iron Imbalance Alters Metabolite Profile in Gut Epithelial Cells

ObjectiveThe study aims to investigate the metabolic profile and proliferative activity of small intestinal enterocytes in response to dietary iron deficiency and excess. We hypothesize that iron imbalance affects cellular iron, energy and fatty acid metabolism and alters cell proliferation.MethodsA porcine jejunal epithelial cell line (IPEC‐J2) was used as an in vitro model and cultured in DMEM/F12 containing 10% fetal bovine serum and 1% antibiotics. Cells were treated with the complete growth media for as control (CON), or the growth media supplemented with 500 µM Deferiprone (DFP) to induce iron deficiency (ID), 10 µM ferric ammonium citrate (FAC) to induce iron overload, or 500 µM DFP followed by 10 µM FAC in treatment for iron deficiency and replenishment (IDIR). An XTT assay determined doses of 500 µM of DFP and 10 µM of FAC as non‐cytotoxic. The relative expression of genes encoding iron regulatory proteins and zinc transporters were determined at 24, 48, 72, and 96 hours of treatment using RT‐qPCR. A BrdU assay was used to assess the proliferative activity of cells cultured after 48 hours of IE, ID or control treatments. Cell lysate was extracted after 48 hours of treatment media and analyzed for untargeted metabolomics using GC coupled to time‐of‐flight MS. Data were subjected to two‐way ANOVA mixed‐effect analysis with Geisser‐Greenhouse correction and statistical significance was determined at p<0.05.ResultsThe relative expression of transferrin receptor 1 was significantly higher in IE compared to ID (P < 0.05) regardless of the time of exposure. Iron treatment did not affect the expression of cytochrome B reductase (CYBRD1), divalent metal transporter 1 (DMT1), Solute Carrier Family 39 (ZIP14), or ferritin light chain (FTL). FPN expression increased significantly at 96 hour post DFP treatment compared to 24 hours. (P <0.05). Iron deficiency gradually increased the expression of CYBRD1, DMT1 and FTL with the increase of exposure time (Ptime < 0.05). The results suggested a compensatory induction of genes associated with iron uptake in IPEC‐J2 cells in response to extended exposure to iron deficiency. BrdU assay revealed that ID significantly reduced the rate of DNA replication compared to IE (P < 0.05), which did not alter cell proliferation rate in comparison with IR. Metabolome analysis revealed that iron treatment altered 71 metabolites (FDR < 0.1), among which 19 were mapped in the user database. In comparison with CON, the most drastic changes in metabolite profile were observed in ID‐treated cells and 33 altered metabolites changed to an opposite direction in IE‐ and ID‐treated cells. Iron replenishment dampened or reversed changes of metabolites affected by ID. The profile of altered metabolites highlighted reduction of cytidine‐5‐monophosphate and changes in glucose metabolism (e.g. glucuronic acid and glucose‐1‐phosphate), the Kreb’s cycle (e.g. citric acid and aconitic acid) suggesting a significant impact of ID on cellular energy metabolism.ConclusionIntracellular iron status can have a significant impact on the cellular metabolism in enterocytes. Given the absorptive function of the enterocyte, whether and how ID and IE affect nutrient absorption in the intestinal epithelium and proliferative activity of crypt‐based intestinal stem cells warrants future study.

The developmental changes in intestinal epithelial cell proliferation, differentiation, and shedding in weaning piglets.

Intestinal epithelial homeostasis plays an important role in intestinal morphology and function. However, the developmental changes in intestinal epithelial cell turnover in piglets during early weaning are unknown so far. Thus, the aim of this work was to detect changes in piglet gut development from weaning to post-weaning d 14. Accordingly, 40 piglets were used in the present study, and 8 piglets were randomly selected for sampling at d 0, 1, 3, 7 and 14 post-weaning, respectively. The results showed that weaning stress significantly affected small intestinal morphological architecture, and this impact was the worst on d 3, and then returned to normal on d 14. Furthermore, the number of the marker of proliferation Ki-67 (Ki67) positive cells was decreased on d 1 and 3, and then recovered on d 14 (P < 0.001). Also, weaning strikingly increased jejunal epithelial cell shedding on d 1 to 7 compared on d 0 (P < 0.05). Moreover, weaning remarkably affected the number of small intestinal enterocytes, goblets and endocrine cells (P < 0.05), and there were also significant differences in genes expression related to proliferation and differentiation (P < 0.05). Additionally, the mechanistic target of rapamycin (mTOR) phosphorylation level was higher on d 3 (P < 0.05). However, the Wingless/Int1 (WNT)/β-catenin pathway was not influenced by post-weaning days. Taken together, weaning induced noteworthy changes in intestinal epithelial cell proliferation, differentiation and shedding, and the mTOR signaling pathway was involved in this process. Our findings provide a cellular mechanism for intestinal developmental changes during weaning periods. This may provide nutritionists with better insight into designing efficient in-feed alternatives for preventing the unfavorable gut development in weaning piglets.

Molecular Insights into SARS-CoV2-Induced Alterations of the Gut/Brain Axis.

For a yet unknown reason, a substantial share of patients suffering from COVID-19 develop long-lasting neuropsychiatric symptoms ranging from cognitive deficits to mood disorders and/or an extreme fatigue. We previously reported that in non-neural cells, angiotensin-1 converting enzyme 2 (ACE2), the gene coding for the SARS-CoV2 host receptor, harbors tight co-expression links with dopa-decarboxylase (DDC), an enzyme involved in the metabolism of dopamine. Here, we mined and integrated data from distinct human expression atlases and found that, among a wide range of tissues and cells, enterocytes of the small intestine express the highest expression levels of ACE2, DDC and several key genes supporting the metabolism of neurotransmitters. Based on these results, we performed co-expression analyses on a recently published set of RNA-seq data obtained from SARS-CoV2-infected human intestinal organoids. We observed that in SARS-CoV2-infected enterocytes, ACE2 co-regulates not only with DDC but also with a specific group of genes involved in (i) the dopamine/trace amines metabolic pathway, (ii) the absorption of microbiota-derived L-DOPA and (iii) the absorption of neutral amino acids serving as precursors to neurotransmitters. We conclude that in patients with long COVID, a chronic infection and inflammation of small intestine enterocytes might be indirectly responsible for prolonged brain alterations.

S-layer protein 2 of vaginal Lactobacillus crispatus 2029 enhances growth, differentiation, VEGF production and barrier functions in intestinal epithelial cell line Caco-2

We have previously demonstrated the ability of the human vaginal strain Lactobacillus crispatus 2029 (LC2029) for strong adhesion to cervicovaginal epithelial cells, expression of the surface layer protein 2 (Slp2), and antagonistic activity against urogenital pathogens. Slp2 forms regular two-dimensional structure around the LC2029 cells,which is secreted into the medium and inhibits intestinal pathogen-induced activation of caspase-9 and caspase-3 in the human intestinal Caco-2 cells. Here, we elucidated the effects of soluble Slp2 on adhesion of proteobacteria pathogens inducing necrotizing enterocolitis (NEC), such as Escherichia coli ATCC E 2348/69, E. coli ATCC 31705, Salmonella Enteritidis ATCC 13076, Campylobacter jejuni ATCC 29428, and Pseudomonas aeruginosa ATCC 27853 to Caco-2 cells, as well as on growth promotion, differentiation, vascular endothelial growth factor (VEGF) production, and intestinal barrier function of Caco-2 cell monolayers. Slp2 acts as anti-adhesion agent for NEC-inducing proteobacteria, promotes growth of immature Caco-2 cells and their differentiation, and enhances expression and functional activity of sucrase, lactase, and alkaline phosphatase. Slp2 stimulates VEGF production, decreases paracellular permeability, and increases transepithelial electrical resistance, strengthening barrier function of Caco-2 cell monolayers. These data support the important role of Slp2 in the early postnatal development of the human small intestine enterocytes.

The Roles of Cytoplasmic Lipid Droplets in Modulating Intestinal Uptake of Dietary Fat.

Dietary fat absorption is required for health but also contributes to hyperlipidemia and metabolic disease when dysregulated. One step in the process of dietary fat absorption is the formation of cytoplasmic lipid droplets (CLDs) in small intestinal enterocytes; these CLDs serve as dynamic triacylglycerol storage organelles that influence the rate at which dietary fat is absorbed. Recent studies have uncovered novel factors regulating enterocyte CLD metabolism that in turn influence the absorption of dietary fat. These include peroxisome proliferator-activated receptor α activation, compartmentalization of different lipid pools, the gut microbiome, liver X receptor and farnesoid X receptor activation, obesity, and physiological factors stimulating CLD mobilization. Understanding how enterocyte CLD metabolism is regulated is key in modulating the absorption of dietary fat in the prevention of hyperlipidemia and its associated metabolic disorders.

Loss of Myosin Vb Results in Decreased Apical P‐Glycoprotein in vivo and in vitro

Background & Aims P-glycoprotein (p-gp), also known as multidrug resistance protein 1, is a xenobiotic efflux pump. In the small intestine, p-gp is localized to the apical membrane of enterocytes. Changes in p-gp expression is linked to inflammatory bowel diseases (IBD) and impairment of drug response in cancer. Regulating the trafficking of p-gp to the plasma membrane represents a plausible approach to improve therapy for cancer treatment. At present, the trafficking mechanism responsible for delivery of p-gp to the apical membrane of epithelial cells is unclear. Myosin Vb (Myo5b) is a molecular motor that is crucial for the proper transport of vesicles and proteins to the apical membrane of epithelial cells. Loss of functional Myo5b results in a congenital diarrheal disorder termed Microvillus Inclusion Disease (MVID). Individuals with MVID present with severe, unremitting diarrhea requiring parenteral nutrition and eventual small bowel transplantation. Studies using animal models of MVID and MVID patient tissue have revealed that loss of Myo5b results in a dramatic decrease in key transporters on the apical membrane of enterocytes. Therefore, we investigated whether proper localization of p-glycoprotein was impeded by loss of Myo5b. Methods Intestinal tissue was analyzed from neonatal control and germline Myo5b knockout (Myo5b KO) mice. Additionally, a tamoxifen inducible, intestinal specific mouse model of loss of Myo5b was also used (VillinCreERT2;Myo5bflox/flox). Adult Myo5bflox/flox mice treated with tamoxifen were used as controls for VillinCreERT2;Myo5bflox/flox mice. Intestinal organoids were generated from VillinCreERT2;Myo5bflox/flox mice and treated with either ethanol as a control or 4 hydroxy tamoxifen to induce loss of Myo5b. Results Immunostaining of gamma actin staining was performed to delineate the actin rich microvilli and identify the apical membrane. In control mice, p-gp was restricted to the apical membrane and co-localized with gamma actin as expected. In germline Myo5b KO mice, p-gp had increased immunofluorescence intensity and was observed below the apical membrane of small intestinal enterocytes. Lamp1 immunostaining also revealed that subapical p-gp was surrounded by lamp1 positive lysosomes in Myo5b KO mice. The association of lysosomes with p-gp suggests that improper localization of p-gp resulting from loss of Myo5b may promote lysosomal degradation of p-gp. Adult Myo5bflox/flox control mice treated with tamoxifen showed normal distribution of p-gp on the apical membrane of small intestinal enterocytes demonstrating co-localization with gamma actin. In contrast, tamoxifen induced VillinCreERT2;Myo5bflox/flox mice showed no p-gp at the apical brush border and no overlap with gamma actin immunostaining. Tamoxifen induced VillinCreERT2;Myo5bflox/flox mice displayed a large accumulation of p-gp below the apical membrane. Complementing our in vivo data, in vitro induction of Myo5b loss using 4 hydroxy tamoxifen resulted in a similar subapical localization of p-gp in induced VillinCreERT2;Myo5bflox/flox intestinal organoids compared to ethanol treated organoids. Conclusions Loss of Myo5b results in improper localization of p-gp. Collectively, these data suggest that Myo5b is necessary for the proper trafficking of p-gp to the apical membrane of intestinal cells.

Changes in the structural components of the mucous membrane and plasma proteins of small intestine enterocytes in fetuses of cattle

The interrelationships of morphological changes of the mucosa of the large intestine with the dynamics of enzyme activity at different poles of enterocytes of cattle during the fetal period of ontogenesis are shown and analyzed. The work was performed on Holstein cattle aged two to nine months. The activity of hydrolytic and transport enzymatic systems in the basolateral membrane of cattle enterocytes depends less on the morphometric parameters of the large intestine than in the apical membrane. It is proved that during the fruitful period of ontogenesis there are dynamic transformations of enzyme systems of enterocytes of the large intestine of cattle which are connected with morphological changes of the mucous membrane of the large intestine. The activity of hydrolytic and transport enzymes in different domains of the plasma enterocytes of fetal cattle is interrelated with the morphometric parameters of the colon, in particular. the activity of alkaline phosphatase, γ-glutamyltransferase, Na+, K+-ATPase, Ca2 +, Mg2 +-ATPase and Mg-ATPase in the apical membrane of enterocytes is inversely related to the thickness of the intestinal wall with villi and the mucous membrane of the cavity (P ≤ 0.01–0.001). A significant correlation was found between the activity of alkaline phosphatase, γ-glutamyltransferase, Na+, K+-ATPase, Ca2 +, Mg2 +-ATPase and Mg-ATPase in the apical membrane of enterocytes with villi height (P ≤ 0.05). The activity of hydrolytic and transport enzymatic systems in the basolateral membrane of bovine fetal enterocytes depends to a lesser extent on the morphometric parameters of the large intestine than in the apical membrane. In particular, only the activity of alkaline phosphatase and γ-glutamyltransferase is inversely related to the thickness of the intestinal wall with villi and the mucous membrane of the jejunum with villi (P ≤ 0.01–0.001). The activity of transport enzymes is directly related to the morphometric parameters of the colon (P ≤ 0.01). The activity of these enzymes in the basolateral membrane does not significantly depend on the width of the villi, but is dependent on their height.

COVID‑19 and SARS‑CoV‑2 host cell entry mediators: Expression profiling of TMRSS4 in health and disease.

Severe acute respiratory syndrome (SARS) coronavirus-2 (SARS-CoV-2), the causative viral agent for the ongoing COVID-19 pandemic, enters its host cells primarily via the binding of the SARS-CoV-2 spike (S) proteins to the angiotensin-converting enzyme 2 (ACE2). A number of other cell entry mediators have also been identified, including neuropilin-1 (NRP1) and transmembrane protease serine 2 (TMPRSS2). More recently, it has been demonstrated that transmembrane protease serine 4 (TMPRSS4) along with TMPRSS2 activate the SARS-CoV-2 S proteins, and enhance the viral infection of human small intestinal enterocytes. To date, a systematic analysis of TMPRSS4 in health and disease is lacking. In the present study, using in silico tools, the gene expression and genetic alteration of TMPRSS4 were analysed across numerous tumours and compared to controls. The observations were also expanded to the level of the central nervous system (CNS). The findings revealed that TMPRSS4 was overexpressed in 11 types of cancer, including lung adenocarcinoma, lung squamous cell carcinoma, cervical squamous cell carcinoma, thyroid carcinoma, ovarian cancer, cancer of the rectum, pancreatic cancer, colon and stomach adenocarcinoma, uterine carcinosarcoma and uterine corpus endometrial carcinoma, whilst it was significantly downregulated in kidney carcinomas, acute myeloid leukaemia, skin cutaneous melanoma and testicular germ cell tumours. Finally, a high TMPRSS4 expression was documented in the olfactory tubercle, paraolfactory gyrus and frontal operculum, all brain regions which are associated with the sense of smell and taste. Collectively, these data suggest that TMPRSS4 may play a role in COVID-19 symptomatology as another SARS-CoV-2 host cell entry mediator responsible for the tropism of this coronavirus both in the periphery and the CNS.

GASTROINTESTINAL COMPLICATIONS OF CORONAVIRUS DISEASE (COVID-19).

ABSTRACT Background: It is currently understood that severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) directly enters target cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. Accordingly, tissues with high expression levels of ACE2 are more susceptible to infection, including pulmonary alveolar epithelial cells, small intestine enterocytes, cholangiocytes, and vascular endothelial cells. Considering the atypical manifestations of COVID-19 and the challenges of early diagnosis, this review addresses the possible gastrointestinal complications of the disease. Method: The phrase “Gastrointestinal complication of COVID” was searched in the PubMed, Medline, and SciELO databases. Due to the heterogeneity of the studies included in the present review, a narrative synthesis of the available qualitative data was performed. Result: The literature search retrieved 28 articles, primarily case reports and case series, for the qualitative analysis of gastrointestinal complications of COVID-19, in addition to two retrospective cohort and one case-control. The studies focused on hemorrhagic, thrombotic, ischemic, and perforation complications, in addition to acute pancreatitis and pneumatosis intestinalis. Conclusion: There is a straight relationship between high expression levels of ACE2 in the gastrointestinal tract and its greater susceptibility to direct infection by SARS-CoV-2. So, it is important to consider the gastrointestinal infection manifestations for early diagnosis and treatment trying to avoid more serious complications and death.

Serum glucose excretion after Roux-en-Y gastric bypass: a potential target for diabetes treatment

ObjectiveThe mechanisms underlying type 2 diabetes resolution after Roux-en-Y gastric bypass (RYGB) are unclear. We suspected that glucose excretion may occur in the small bowel based on observations in humans....

ACE2 and gut amino acid transport.

ACE2 is a type I membrane protein with extracellular carboxypeptidase activity displaying a broad tissue distribution with highest expression levels at the brush border membrane (BBM) of small intestine enterocytes and a lower expression in stomach and colon. In small intestinal mucosa, ACE2 mRNA expression appears to increase with age and to display higher levels in patients taking ACE-inhibitors (ACE-I). There, ACE2 protein heterodimerizes with the neutral amino acid transporter Broad neutral Amino acid Transporter 1 (B0AT1) (SLC6A19) or the imino acid transporter Sodium-dependent Imino Transporter 1 (SIT1) (SLC6A20), associations that are required for the surface expression of these transport proteins. These heterodimers can form quaternary structures able to function as binding sites for SARS-CoV-2 spike glycoproteins. The heterodimerization of the carboxypeptidase ACE2 with B0AT1 is suggested to favor the direct supply of substrate amino acids to the transporter, but whether this association impacts the ability of ACE2 to mediate viral infection is not known. B0AT1 mutations cause Hartnup disorder, a condition characterized by neutral aminoaciduria and, in some cases, pellagra-like symptoms, such as photosensitive rash, diarrhea, and cerebellar ataxia. Correspondingly, the lack of ACE2 and the concurrent absence of B0AT1 expression in small intestine causes a decrease in l-tryptophan absorption, niacin deficiency, decreased intestinal antimicrobial peptide production, and increased susceptibility to inflammatory bowel disease (IBD) in mice. Thus, the abundant expression of ACE2 in small intestine and its association with amino acid transporters appears to play a crucial role for the digestion of peptides and the absorption of amino acids and, thereby, for the maintenance of structural and functional gut integrity.

Short communication: Effect of delaying the first colostrum feeding on small intestinal histomorphology and serum insulin-like growth factor-1 concentrations in neonatal male Holstein calves

The primary objective of this study was to determine the effect of delaying the first colostrum feeding on small intestinal histomorphology and serum insulin-like growth factor-1 (IGF-1) concentrations, and the secondary objective was to characterize the ultrastructure of the small intestine of neonatal calves at 51 h of life. Twenty-seven male Holstein calves were fed pooled, pasteurized colostrum (7.5% of birth body weight; 62 g of IgG/L) at 45 min (0H, n = 9), 6 h (6H, n = 9), or 12 h (12H, n = 9) after birth. At 12 h after their respective colostrum feeding, calves were fed milk replacer at 2.5% of birth body weight per meal and every 6 h thereafter. Blood samples were collected every 6 h using a jugular catheter and analyzed for serum IGF-1 concentrations using an automated solid-phase chemiluminescent immunoassay. At 51 h of life, calves were euthanized to facilitate collection of the duodenum, proximal and distal jejunum, and ileum. All segments of the small intestine were assessed for histomorphology, whereas scanning electron and transmission electron microscopy analyses were conducted only for the proximal jejunum and ileum. The results revealed that there was no overall effect of colostrum feeding time on serum IGF-1 concentrations; however, serum IGF-1 concentrations were influenced by time. Specifically, concentrations of serum IGF-1 at 48 h were 29% greater than concentrations at 0 h of life (312.8 ± 14.85 vs. 241.9 ± 14.06 ng/mL). Although there was no overall effect of colostrum feeding time on all histomorphological measures assessed, treatment × segment interactions were observed. Villi height was 1.4 times greater in the distal jejunum of 0H calves than in 6H and 12H calves, and 0H calves tended to have 1.2 times greater ileal villus height than 12H calves. In addition, 0H calves had 1.2 and 1.3 times greater ileal crypt depth than 6H and 12H calves, respectively, and 1.3 times greater surface area index than 12H calves in the distal jejunum. Qualitative ultrastructural evaluation of small intestinal enterocytes conducted irrespective of colostrum treatment revealed the presence of large vacuoles of electron-dense material, apical mitochondria, and apical canalicular systems in the jejunum and ileum. These results indicate that the calf intestine at 51 h of life contains unique enterocyte characteristics similar to fetal enterocytes and that delaying colostrum feeding may negatively influence intestinal growth and development.

Plasma citrulline correlates with basolateral amino acid transporter LAT4 expression in human small intestine

Background & aimsPlasma citrulline, a non-protein amino acid, is a biochemical marker of small intestine enterocyte mass in humans. Indeed, citrulline is highly correlated with residual bowel length in patients with short bowel syndrome. It is known to be synthesised in epithelial cells of the small intestine from other amino acids (precursors). Citrulline is then released into systemic circulation and interconverted into arginine in kidneys. If plasma citrulline concentration depends on abundance of intestinal amino acid transporters is not known. The aim of the present study was to explore whether plasma citrulline concentration correlates with the expression of intestinal amino acid transporters. Furthermore, we assessed if arginine in urine correlates with plasma citrulline.MethodsDuodenal samples, blood plasma and urine were collected from 43 subjects undergoing routine gastroduodenoscopy. mRNA expression of seven basolateral membrane amino acid transporters/transporter subunits were assessed by real-time PCR. Plasma and urine amino acid concentrations of citrulline, its precursors and other amino acids were analysed using High Performance Liquid Chromatography measurements. Amino acid transporter mRNA expression was correlated with blood plasma and urine levels of citrulline and its precursors using Spearman's rank correlation. Likewise, urine arginine was correlated with plasma citrulline.ResultsPlasma citrulline correlated with the mRNA expression of basolateral amino acid transporter LAT4 (Spearman's r = 0.467, p = 0.028) in small intestine. None of the other basolateral membrane transporters/transporter subunits assessed correlated with plasma citrulline. Plasma citrulline correlated with urinary arginine, (Spearman's r = 0.419, p = 0.017), but not with urinary citrulline or other proteinogenic amino acids in the urine.ConclusionsIn this study, we showed for the first time that small intestinal basolateral LAT4 expression correlates with plasma citrulline concentration. This finding indicates that LAT4 has an important function in mediating citrulline efflux from enterocytes. Furthermore, urine arginine correlated with plasma citrulline, indicating arginine in the urine as possible additional marker for small intestine enterocyte mass. Finally, basolateral LAT4 expression along the human small intestine was shown for the first time.

Gastrointestinal and kidney manifestations in SARS-CoV and SARS-CoV-2 infections: role of angiotensin-converting enzyme 2

The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in 2020, which has a substantial structural similarity to severe acute respiratory syndrome coronavirus (SARS-CoV) that caused the outbreak in 2003, is currently a threat to global health. Lung involvement is the principal clinical feature in infected patients but extra-pulmonary clinical presentations are also common. The reasons for the extensive involvement of other organs are not yet clear. Angiotensin-converting enzyme 2 (ACE2), the key peptide of renin–angiotensin system (RAS), has recently identified as a major receptor for the both SARS-CoV and SARS-CoV-2 that might be a main target of coronavirus infection. ACE2 is mainly expressed in the pulmonary pneumocytes, the small intestine enterocytes as well as the proximal tubule epithelial cells of the kidneys. In addition to the respiratory tract infection symptoms, the noticeable prevalence of gastrointestinal symptoms as well as kidney impairment in hospitalized infected patients highlights other routes of infection/transmission. In present review, we discussed the role of RAS with emphasis on ACE2 in the pathogenesis of SARS-CoV and SARS-CoV-2, particularly in gastrointestinal and kidney manifestations of the diseases.

Fallacies and Facts Around COVID-19: The Multifaceted Infection.

It has been 5 months since the identification of first cases of coronavirus disease 2019 (COVID-19), however, unveiling clinical characteristics and modes of transmission of the disease is not complete yet. The initially identified clinical sign of COVID-19 was respiratory in nature in the form of pneumonia with possible fatal consequences due to severe acute lung fibrosis. Extrapulmonary symptoms of the disease are now well recognized with involvement of the liver, kidney, and even multisystem organ failure and acute cardiac arrest. Symptoms related to the gastrointestinal tract are particularly interesting and these could represent a mode of transmission requiring more attention from researchers and clinicians. Prevalence of diarrhea, nausea, vomiting, or abdominal discomfort is estimated to be approximately 5%.1 The possible multiple routes of transmission could be explained by the fact that angiotensin converting enzyme 2 protein presents in abundance on lung alveolar epithelial cells and enterocytes of small intestine remarkably.2 During the first days of the disease, a fallacy was distributed mainly through social media. Drinking hot drinks was promoted as a means to eradicate the virus before it goes beyond the pharynx; however, as more studies were conducted, it was revealed that SARS-CoV-2 can withstand temperatures up to 56°C.3 On the contrary to this fallacy, an important fact is related to the possibility of the fecal-oral route of transmission which has been identified in multiple case studies and clinical settings. The nucleic acid of the virus has been detected in the feces and anal swabs of some COVID-19 patients, and live virions were shown to exist in fecal specimens in patients with negative oropharyngeal specimen, which indicates that viral infection of the gastrointestinal tract and the potential fecal-oral transmission can outlast the viral clearance in the respiratory tract.4 An observation that needs further investigation was actually reported from clinicians caring for infected patients, whereby expulsion of excess colonic gas which has an unpleasant odor with or without diarrhea has been noticed (unpublished data). Although this observation is not yet documented, it should be further analyzed and investigated. Whether abdominal gases in COVID-19 patients with gastrointestinal manifestations can be a potential mode of transmission of the virus needs to be ascertained. Other fallacies that relate to the size of the virus claimed that airborne spread is not possible due to the large size of the virus which makes it drop onto surfaces after 3 hours. It was also claimed that COVID-19 primarily spreads through the respiratory tract, by droplets, respiratory secretions, and direct contact and is not transmitted by aerosol, therefore, only infection control precautions and social distancing for at least 1 m would suffice to prevent the spread of the infection. However, the most recent studies reported that it could be transmitted as an airborne infection for distances exceeding 4 m.5 Within this context, there has been some confusion about the types of masks that should be used among healthcare teams caring for COVID-19 patients. Several developing countries have adopted the use of regular surgical masks among healthcare workers caring for COVID-19 patients early in the course of the disease. Medical health workers who primarily use this type of masks are susceptible to infection. Although this is not documented yet, but many healthcare workers in developing countries like Egypt and other countries like Italy and Saudi Arabia have been infected and unfortunately were deceased due to COVID-19. These types of masks alone without complete face shield are not adequate for protection against COVID-19.6 Within the context of cross-infection control, we would like to stress that donning and doffing of personal protective equipment (PPE) should be conducted in a particular order to prevent infection. The recommended sequence involves removal of the high level maximum protective masks as the last step in doffing of PPE. Handling the contaminated mask itself may transmit the virus and hence cause infection.7 A suggestion to prevent transmission while doffing involves that PPE undergoes disinfection in a special room or to utilize a specific equipment for disposal of used PPE before doffing. In conclusion, more facts about COVID-19 transmission and effective preventive measures should be revealed and disseminated among the medical community to preserve the precious lives of healthcare team members. The aim of this correspondence is to draw attention of healthcare workers caring for COVID-19 patients especially those working in developing countries to the possibility of transmission of infection through the gastrointestinal route with particular reference to colonic gases. We further warn them against the use of conventional surgical masks because it is useless in the clinical setting, and also warn them against handling of the contaminated masks during doffing of PPE. Here we suggest the use of disinfection of PPE before removal and the proper way of disposal.

Knowledge synthesis of 100 million biomedical documents augments the deep expression profiling of coronavirus receptors

The COVID-19 pandemic demands assimilation of all biomedical knowledge to decode mechanisms of pathogenesis. Despite the recent renaissance in neural networks, a platform for the real-time synthesis of the exponentially growing biomedical literature and deep omics insights is unavailable. Here, we present the nferX platform for dynamic inference from over 45 quadrillion possible conceptual associations from unstructured text, and triangulation with insights from single-cell RNA-sequencing, bulk RNA-seq and proteomics from diverse tissue types. A hypothesis-free profiling of ACE2 suggests tongue keratinocytes, olfactory epithelial cells, airway club cells and respiratory ciliated cells as potential reservoirs of the SARS-CoV-2 receptor. We find the gut as the putative hotspot of COVID-19, where a maturation correlated transcriptional signature is shared in small intestine enterocytes among coronavirus receptors (ACE2, DPP4, ANPEP). A holistic data science platform triangulating insights from structured and unstructured data holds potential for accelerating the generation of impactful biological insights and hypotheses.

Specific ACE2 expression in small intestinal enterocytes may cause gastrointestinal symptoms and injury after 2019-nCoV infection

The coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China and rapidly spread in other countries in December 2019. The infected patients presented with fever, respiratory symptoms, sometimes with digestive and other systemic manifestations, and some progressed with a severe acute respiratory syndrome or even death. Associated digestive symptoms were frequently observed in the patients, with an unknown significance and mechanism. ACE2, as the major known functional receptor of the 2019 novel coronavirus (2019-nCoV) attracted our attention. We collected the clinical data of the 2019-nCoV-infected patients from published studies and extracted the data about the incidence of gastrointestinal symptoms. Furthermore, we used online datasets to analyze ACE2 expression in different human organs, especially in the small intestine, to explore the relationship between ACE2 expression patterns and clinical symptoms. We found that diarrhea accounted for a notable proportion of COVID-19 patients, ranging from 8.0% to 12.9%. The results reveal that ACE2 mRNA and protein are highly expressed in the small intestinal enterocytes but not in the goblet cells or intestinal immune cells. High expression of ACE2 on the surface cells in the digestive tract may lead to gastrointestinal symptoms and inflammation susceptibility. Overall, digestive symptoms were common in the COVID-19 patients. ACE2 expression on surface cells of the small intestine may mediate the invasion and amplification of the virus and activation of gastrointestinal inflammation. It is a possible mechanism of digestive symptoms in the COVID-19 patients and explains the presence of the virus in patients’ stool samples. The study also highlights the necessity of taking stool samples for suspected patients to help in early diagnosis and assessment of disease status.

Propionate enhances the expression of key genes involved in the gluconeogenic pathway in bovine intestinal epithelial cells

Approximately 15 to 50% of short-chain fatty acids (SCFA) reach the ruminant small intestine. Previous research suggests that activation of small intestinal gluconeogenesis induced by propionate has beneficial effects on energy homeostasis. However, the regulatory effect of propionate on key gluconeogenic genes in enterocytes of the bovine small intestine remains less known. Therefore, the purpose of this study was to establish the long-term cultures of bovine intestinal epithelial cells (BIEC) from bovine jejunum tissue using SV40T (1:200; Santa Cruz, Shanghai, China) and investigate the regulatory effect of propionate on the key gluconeogenic genes in BIEC. Our study showed that long-term BIEC cultures were established by SV40T-induced immortalization. Immortal BIEC were distinguished by the expression of cytokeratin 18, villin, fatty acid binding protein 2, and small intestine peptidase. The mRNA expression of genes involved in the SCFA transporters, monocarboxylate transporter 4, and Na+/H+ exchanger isoforms 1 were significantly elevated with 20 mM SCFA compared with untreated controls. In addition, BIEC exhibited significant uptake of propionate and butyrate from the culture medium. Remarkably, 3 mM propionate induced profound changes in mRNA level of key genes involved in gluconeogenesis, including phosphoenolpyruvate carboxykinase 2, pyruvate carboxylase, fructose-1,6-bisphosphatase 1, and peroxisome proliferator-activated receptor-γ coactivator 1α. Additionally, 3 mM propionate enhanced the expression of PGC1A mRNA at 3, 6, 12, and 24 h of incubation. These findings suggest that propionate controls the mRNA expression of genes involved in key enzymes for gluconeogenesis in the enterocytes of bovines.

New insights into the molecular basis of lactase non-persistence/persistence: a brief review.

Lactose, a disaccharide and main carbohydrate in milk, requires hydrolysis in the intestinal tract to release its monosaccharides galactose and glucose for use as energy source by enterocytes. This hydrolysis is catalyzed by the enzyme lactase, a β-galactosidase located in the brush border membrane of small intestinal enterocytes. In most mammals, lactase activity declines after the weaning, a condition known as lactase non-persistence (LNP). Lactase persistence (LP) is an autosomal dominant trait enabling the continued production of the enzyme lactase throughout adult life. Non-persistence or persistence of lactase expression into adult life being a polymorphic trait has been attributed to various single nucleotide polymorphisms in the enhancer region surrounding lactase gene (LCT). However, latest research has pointed to 'genetic-epigenetic interactions' as key to regulation of lactase expression. LNP and LP DNA haplotypes have demonstrated markedly different epigenetic aging as genetic factors contribute to gradual accumulation of epigenetic changes with age to affect lactase expression. This review will attempt to present an overview of latest insights into molecular basis of LNP/LP including the crucial role of 'genetic-epigenetic interactions' in regulating lactase expression.

Mechanisms underlying reduced weight gain in intestinal fatty acid-binding protein (IFABP) null mice.

Intestinal-fatty acid binding protein (IFABP; FABP2) is a 15-kDa intracellular protein abundantly present in the cytosol of the small intestinal (SI) enterocyte. High-fat (HF) feeding of IFABP-/- mice resulted in reduced weight gain and fat mass relative to wild-type (WT) mice. Here, we examined intestinal properties that may underlie the observed lean phenotype of high fat-fed IFABP-/- mice. No alterations in fecal lipid content were found, suggesting that the IFABP-/- mice are not malabsorbing dietary fat. However, the total excreted fecal mass, normalized to food intake, was increased for the IFABP-/- mice relative to WT mice. Moreover, intestinal transit time was more rapid in the IFABP-/- mice. IFABP-/- mice displayed a shortened average villus length, a thinner muscularis layer, reduced goblet cell density, and reduced Paneth cell abundance. The number of proliferating cells in the crypts of IFABP-/- mice did not differ from that of WT mice, suggesting that the blunt villi phenotype is not due to alterations in proliferation. IFABP-/- mice were observed to have altered expression of genes and proteins related to intestinal structure, while immunohistochemical analyses revealed increased staining for markers of inflammation. Taken together, these studies indicate that the ablation of IFABP, coupled with high-fat feeding, leads to changes in gut motility and morphology, which likely contribute to the relatively leaner phenotype occurring at the whole-body level. Thus, IFABP is likely involved in dietary lipid sensing and signaling, influencing intestinal motility, intestinal structure, and nutrient absorption, thereby impacting systemic energy metabolism.NEW & NOTEWORTHY Intestinal fatty acid binding protein (IFABP) is thought to be essential for the efficient uptake and trafficking of dietary fatty acids. In this study, we demonstrate that high-fat-fed IFABP-/- mice have an increased fecal output and are likely malabsorbing other nutrients in addition to lipid. Furthermore, we observe that the ablation of IFABP leads to marked alterations in intestinal morphology and secretory cell abundance.