Enterocyte fatty acid-binding proteins (FABPs): different functions of liver and intestinal FABPs in the intestine

ScRNA-seq identified the metabolic reprogramming of human colonic immune cells in different locations and disease states

Different regions and states of the human colon are likely to have a distinct influence on immune cell functions. Here we studied the immunometabolic mechanisms for spatial immune specialization and dysregulated immune response during ulcerative colitis at single-cell resolution. We revealed that the macrophages and CD8⁺ T cells in the lamina propria of the human colon possessed an effector phenotype and were more activated, while their lipid metabolism was suppressed compared with those in the epithelial. Also, IgA⁺ plasma cells accumulated in lamina propria of the sigmoid colon were identified to be more metabolically activated versus those in the cecum and transverse colon, and the improved metabolic activity was correlated with the expression of CD27. In addition to the immunometabolic reprogramming caused by spatial localization colon, we found dysregulated cellular metabolism was related to the impaired immune functions of macrophages and dendritic cells in patients with ulcerative colitis. The cluster of OSM⁺ inflammatory monocytes was also identified to play its role in resistance to anti-TNF treatment, and we explored targeted metabolic reactions that could reprogram them to a normal state. Altogether, this study revealed a landscape of metabolic reprogramming of human colonic immune cells in different locations and disease states, and offered new insights into treating ulcerative colitis by immunometabolic modulation.

BMP gradient along the intestinal villus axis controls zonated enterocyte and goblet cell states

Intestinal epithelial cells derive from stem cells at the crypt base and travel along the crypt-villus axis to die at the villus tip. The two dominant villus epithelial cell types, absorptive enterocytes and mucous-secreting goblet cells, are mature when they exit crypts. Murine enterocytes switch functional cell states during migration along the villus. Here, we ask whether this zonation is driven by the bone morphogenetic protein (BMP) gradient, which increases toward the villus. Using human intestinal organoids, we show that BMP signaling controls the expression of zonated genes in enterocytes. We find that goblet cells display similar zonation involving antimicrobial genes. Using an inducible Bmpr1a knockout mouse model, we confirm that BMP controls these zonated genes in vivo. Our findings imply that local manipulation of BMP signal strength may be used to reset the enterocyte "rheostat" of carbohydrate versus lipid uptake and to control the antimicrobial response through goblet cells.

Biomarkers of Necrotizing Enterocolitis: The Search Continues

Necrotizing enterocolitis (NEC) is the most common gastrointestinal (GI) emergency in the neonatal intensive care unit. Despite advances in medical care, mortality and morbidity from NEC have not changed. This is likely due to the lack of a clear understanding of this multifactorial disease, and reliable biomarkers for accurate diagnosis of NEC. Currently, the diagnosis of NEC is made by a combination of nonspecific clinical signs, symptoms, and radiological findings. Though biomarkers have been studied extensively, none offer an acceptable sensitivity or specificity to be used. This review will focus on the available literature on biomarkers for preterm NEC, acknowledging the limitations in studies including the variability of inclusion criteria, and most importantly, the lack of gold standard case definition for NEC.

Porcine Intestinal Apical-Out Organoid Model for Gut Function Study

Simple Summary

Pigs have been used in various animal model studies on the gastrointestinal tract (GIT) across both animal science and biomedical science fields. Recently, intestinal organoids have been used as a research tool for the GIT, and they have also been applied to farm animals, including pigs. However, to our knowledge, no functional studies of the porcine intestine using intestinal organoids have been conducted to date. In the present study, we developed two porcine intestinal organoid models (basal-out and apical-out organoids) and compared their characteristics. We also confirmed the possibility of conducting research related to intestinal functions, such as nutrient uptake and gut barrier function. The present study suggests that porcine intestinal organoids can be used as potential models for future GIT mechanism studies, such as host–microbe interactions, harmful ingredient tests, and nutritional research.

Abstract

Pig models provide valuable research information on farm animals, veterinary, and biomedical sciences. Experimental pig gut models are used in studies on physiology, nutrition, and diseases. Intestinal organoids are powerful tools for investigating intestinal functions such as nutrient uptake and gut barrier function. However, organoids have a basal-out structure and need to grow in the extracellular matrix, which causes difficulties in research on the intestinal apical membrane. We established porcine intestinal organoids from jejunum tissues and developed basal-out and apical-out organoids using different sub-culture methods. Staining and quantitative real-time PCR showed the difference in axis change of the membrane and gene expression of epithelial cell marker genes. To consider the possibility of using apical-out organoids for intestinal function, studies involving fatty acid uptake and disruption of the epithelial barrier were undertaken. Fluorescence fatty acid was more readily absorbed in apical-out organoids than in basal-out organoids within the same time. To determine whether apical-out organoids form a functional barrier, a fluorescent dextran diffusion assay was performed. Hence, we successfully developed porcine intestinal organoid culture systems and showed that the porcine apical-out organoid model is ideal for the investigation of the intestinal environment. It can be used in future studies related to the intestine across various research fields.

A Lard and Soybean Oil Mixture Alleviates Low-Fat-High-Carbohydrate Diet-Induced Nonalcoholic Fatty Liver Disease in Mice

Dietary habit is highly related to nonalcoholic fatty liver disease (NAFLD). Low-fat-high-carbohydrate (LFHC) diets could induce lean NAFLD in Asians. Previously, we found that a lard and soybean oil mixture reduced fat accumulation with a medium-fat diet; therefore, in this study, we evaluated the effect of a lard and soybean oil mixture (LFHC diet) on NAFLD and its underlying mechanisms. Mice in groups were fed with lard, soybean oil, or a lard and soybean oil mixture-an LFHC diet-separately. Our results showed that mixed oil significantly inhibited serum triglyceride, liver triglyceride, serum free fatty acids (FFAs), and liver FFAs compared with soybean oil or lard, and we found fewer inflammatory cells in mice fed with mixed oil. RNA-seq results indicate that mixed oil reduced FFAs transportation into the liver via decreasing liver fatty acid-binding protein 2 expression, inhibited oxidative phosphorylation via tumor necrosis factor receptor superfamily member 6 downregulation, and alleviated inflammation via downregulating inflammatory cytokine. The liquid chromatography-mass spectrometry results showed that the mixed oil promoted bile acid conjugated with taurine and glycine, thus activating G-protein-coupled bile acid receptor 1 for improved lipids metabolism. In conclusion, the lard and soybean oil mixture alleviated NAFLD.

Association between liver-type fatty acid-binding protein and hyperuricemia before and after laparoscopic sleeve gastrectomy

BACKGROUND

Liver-type fatty acid-binding protein (FABP1) contributes to metabolic disorders. However, the relationship between FABP1 and hyperuricemia remains unknown. We aimed to evaluate the correlation between serum FABP1 and hyperuricemia in patients with obesity before and after laparoscopic sleeve gastrectomy (LSG).

METHODS

We enrolled 105 patients (47 men and 58 women) with obesity who underwent LSG. They were divided into two groups: normal levels of uric acid (UA) (NUA, n = 44) and high levels of UA (HUA, n = 61) with matching sexes. FABP1 levels and other biochemical parameters were measured at baseline and 3, 6, and 12 months after LSG.

RESULTS

Serum FABP1 levels were significantly higher in the HUA group than in the NUA group (34.76 ± 22.69 ng/mL vs. 25.21 ± 21.68 ng/mL, P=0.024). FABP1 was positively correlated with UA (r=0.390, P=0.002) in the HUA group. The correlation still existed after adjusting for confounding factors. Preoperative FABP1 levels were risk factors for hyperuricemia at baseline. UA and FABP1 levels decreased at 3, 6, and 12 months postoperatively. FABP1 showed a more significant decrease in the HUA group than in the NUA group at 12 months (27.06 ± 10.98 ng/mL vs. 9.54 ± 6.52 ng/mL, P=0.003). Additionally, the change in FABP1 levels positively correlated with changes in UA levels in the HUA group 12 months postoperatively (r=0.512, P=0.011).

CONCLUSIONS

FABP1 was positively associated with UA and may be a risk factor for hyperuricemia in obesity. FABP1 levels were higher but decreased more after LSG in obese patients with hyperuricemia than in those without hyperuricemia.

The Protective Effects of Lactoferrin on Aflatoxin M1-Induced Compromised Intestinal Integrity

Aflatoxin M1 (AFM1), the only toxin with maximum residue levels in milk, has adverse effects on the intestinal barrier, resulting in intestinal inflammatory disease. Lactoferrin (LF), one of the important bioactive proteins in milk, performs multiple biological functions, but knowledge of the protective effects of LF on the compromised intestinal barrier induced by AFM1 has not been investigated. In the present study, results using Balb/C mice and differentiated Caco-2 cells showed that LF intervention decreased AFM1-induced increased intestinal permeability, improved the protein expression of claudin-3, occludin and ZO-1, and repaired the injured intestinal barrier. The transcriptome and proteome were used to clarify the underlying mechanisms. It was found that LF reduced the intestinal barrier dysfunction caused by AFM1 and was associated with intestinal cell survival related pathways, such as cell cycle, apoptosis and MAPK signaling pathway and intestinal integrity related pathways including endocytosis, tight junction, adherens junction and gap junction. The cross-omics analysis suggested that insulin receptor (INSR), cytoplasmic FMR1 interacting protein 2 (CYFIP2), dedicator of cytokinesis 1 (DOCK1) and ribonucleotide reductase regulatory subunit M2 (RRM2) were the potential key regulators as LF repaired the compromised intestinal barrier. These findings indicated that LF may be an alternative treatment for the compromised intestinal barrier induced by AFM1.

Dietary fatty acids in gut health: Absorption, metabolism and function

In biological responses, fatty acids (FA) are absorbed and metabolized in the form of substrates for energy production. The molecular structures (number of double bonds and chain length) and composition of dietary FA impact digestion, absorption and metabolism, and the biological roles of FA. Recently, increasing evidence indicates that FA are essentially utilized as an energy source and are signaling molecules that exert physiological activity of gut microbiota and immune responses. In addition, FA could serve as natural ligands for orphan G protein-coupled receptors (GPCR), also called free fatty acid receptors (FFAR), which intertwine metabolic and immune systems via multiple mechanisms. The present review explores the recent findings on FA absorption and its impact on gut health, particularly addressing the mechanism by which dietary FA potentially influences intestinal microbiota and epithelial functions. Also, this work attempts to uncover research ideas for devising future strategies for manipulating the composition of dietary FA to regulate gut health and support a normal immune system for metabolic and immune disorders.

A review on interplay between obesity, lipoprotein profile and nutrigenetics with selected candidate marker genes of type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus, a rapidly growing epidemic, and its frequently related complications demand global attention. The two factors commonly attributed to the epidemic are genetic factors and environmental factors. Studies indicate that the genetic makeup at an individual level and the environmental aspects influence the occurrence of the disease. However, there is insufficiency in understanding the mechanisms through which the gene mutations and environmental components individually lead to T2DM. Also, discrepancies have often been noted in the association of gene variants and type 2 diabetes when the gene factor is examined as a sole attribute to the disease.

STUDY

In this review initially, we have focused on the proposed ways through which CAPN10, FABP2, GLUT2, TCF7L2, and ENPP1 variants lead to T2DM along with the inconsistencies observed in the gene-disease association. The article also emphasizes on obesity, lipoprotein profile, and nutrition as environmental factors and how they lead to T2DM. Finally, the main objective is explored, the environment-gene-disease association i.e. the influence of each environmental factor on the aforementioned specific gene-T2DM relationship to understand if the disease-causing capability of the gene variants is exacerbated by environmental influences.

CONCLUSION

We found that environmental factors may influence the gene-disease relationship. Reciprocally, the genetic factors may alter the environment-disease relationship. To precisely conclude that the two factors act synergistically to lead to T2DM, more attention has to be paid to the combined influence of the genetic variants and environmental factors on T2DM occurrence instead of studying the influence of the factors separately.

Abomasal infusion of oleic acid increases fatty acid digestibility and plasma insulin of lactating dairy cows

Our objective was to determine whether abomasal infusions of increasing doses of oleic acid (cis-9 C18:1; OA) improved fatty acid (FA) digestibility and milk production of lactating dairy cows. Eight rumen-cannulated multiparous Holstein cows (138 d in milk ± 52) were randomly assigned to treatment sequence in a replicated 4 × 4 Latin square design with 18-d periods consisting of 7 d of washout and 11 d of infusion. Production and digestibility data were collected during the last 4 d of each infusion period. Treatments were 0, 20, 40, or 60 g/d of OA. We dissolved OA in ethanol before infusions. The infusate solution was divided into 4 equal infusions per day, occurring every 6 h, delivering the daily cis-9 C18:1 for each treatment. Animals received the same diet throughout the study, which contained (percent diet dry matter) 28% neutral detergent fiber, 17% crude protein, 27% starch, and 3.3% FA (including 1.8% FA from a saturated FA supplement containing 32% C16:0 and 52% C18:0). Infusion of OA did not affect intake or digestibility of dry matter and neutral detergent fiber. Increasing OA from 0 to 60 g/d linearly increased the digestibility of total FA (8.40 percentage units), 16-carbon FA (8.30 percentage units), and 18-carbon FA (8.60 percentage units). Therefore, increasing OA linearly increased absorbed total FA (162 g/d), 16-carbon FA (26.0 g/d), and 18-carbon FA (127 g/d). Increasing OA linearly increased milk yield (4.30 kg/d), milk fat yield (0.10 kg/d), milk lactose yield (0.22 kg/d), 3.5% fat-corrected milk (3.90 kg/d), and energy-corrected milk (3.70 kg/d) and tended to increase milk protein yield. Increasing OA did not affect the yield of mixed milk FA but increased yield of preformed milk FA (65.0 g/d) and tended to increase the yield of de novo milk FA. Increasing OA quadratically increased plasma insulin concentration with an increase of 0.18 μg/L at 40 g/d OA, and linearly increased the content of cis-9 C18:1 in plasma triglycerides by 2.82 g/100 g. In conclusion, OA infusion increased FA digestibility and absorption, milk fat yield, and circulating insulin without negatively affecting dry matter intake. In our short-term infusion study, most of the digestion and production measurements responded linearly, indicating that 60 g/d OA was the best dose. Because a quadratic response was not observed, improvements in FA digestibility and production might continue with higher doses of OA, which deserves further attention.

Mitochondrial transcription factor A in RORγt+ lymphocytes regulate small intestine homeostasis and metabolism

RORγt+ lymphocytes, including interleukin 17 (IL-17)-producing gamma delta T (γδT17) cells, T helper 17 (Th17) cells, and group 3 innate lymphoid cells (ILC3s), are important immune regulators. Compared to Th17 cells and ILC3s, γδT17 cell metabolism and its role in tissue homeostasis remains poorly understood. Here, we report that the tissue milieu shapes splenic and intestinal γδT17 cell gene signatures. Conditional deletion of mitochondrial transcription factor A (Tfam) in RORγt+ lymphocytes significantly affects systemic γδT17 cell maintenance and reduces ILC3s without affecting Th17 cells in the gut. In vivo deletion of Tfam in RORγt+ lymphocytes, especially in γδT17 cells, results in small intestine tissue remodeling and increases small intestine length by enhancing the type 2 immune responses in mice. Moreover, these mice show dysregulation of the small intestine transcriptome and metabolism with less body weight but enhanced anti-helminth immunity. IL-22, a cytokine produced by RORγt+ lymphocytes inhibits IL-13-induced tuft cell differentiation in vitro, and suppresses the tuft cell-type 2 immune circuit and small intestine lengthening in vivo, highlighting its key role in gut tissue remodeling.

Persistent Systemic Microbial Translocation and Intestinal Damage During Coronavirus Disease-19

Microbial translocation (MT) and intestinal damage (ID) are poorly explored in COVID-19. Aims were to assess whether alteration of gut permeability and cell integrity characterize COVID-19 patients, whether it is more pronounced in severe infections and whether it influences the development of subsequent bloodstream infection (BSI). Furthermore, we looked at the potential predictive role of TM and ID markers on Intensive Care Unit (ICU) admission and in-hospital mortality. Over March–July 2020, 45 COVID-19 patients were enrolled. Markers of MT [LPB (Lipopolysacharide Binding Protein) and EndoCab IgM] and ID [I-FABP (Intestinal Fatty Acid Binding Protein)] were evaluated at COVID-19 diagnosis and after 7 days. As a control group, age- and gender-matched healthy donors (HDs) enrolled during the same study period were included. Median age was 66 (56-71) years. Twenty-one (46.6%) were admitted to ICU and mortality was 22% (10/45). Compared to HD, a high degree of MT and ID was observed. ICU patients had higher levels of MT, but not of ID, than non-ICU ones. Likewise, patients with BSI had lower EndoCab IgM than non-BSI. Interestingly, patients with high degree of MT and low ID were likely to be admitted to ICU (AUC 0.822). Patients with COVID-19 exhibited high level of MT, especially subjects admitted to ICU. COVID-19 is associated with gut permeability.

Aflatoxin B1 and Aflatoxin M1 Induce Compromised Intestinal Integrity through Clathrin-Mediated Endocytosis

With the growing diversity and complexity of diet, humans are at risk of simultaneous exposure to aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1), which are well-known contaminants in dairy and other agricultural products worldwide. The intestine represents the first barrier against external contaminants; however, evidence about the combined effect of AFB1 and AFM1 on intestinal integrity is lacking. In vivo, the serum biochemical parameters related to intestinal barrier function, ratio of villus height/crypt depth, and distribution pattern of claudin-1 and zonula occluden-1 were significantly affected in mice exposed to 0.3 mg/kg b.w. AFB1 and 3.0 mg/kg b.w. AFM1. In vitro results on differentiated Caco-2 cells showed that individual and combined AFB1 (0.5 and 4 μg/mL) and AFM1 (0.5 and 4 μg/mL) decreased cell viability and trans-epithelial electrical resistance values as well as increased paracellular permeability of fluorescein isothiocyanate-dextran in a dose-dependent manner. Furthermore, AFM1 aggravated AFB1-induced compromised intestinal barrier, as demonstrated by the down-regulation of tight junction proteins and their redistribution, particularly internalization. Adding the inhibitor chlorpromazine illustrated that clathrin-mediated endocytosis partially contributed to the compromised intestinal integrity. Synergistic and additive effects were the predominant interactions, suggesting that these toxins are likely to have negative effects on human health.

Molecular basis for the interaction of cellular retinol binding protein 2 (CRBP2) with nonretinoid ligands

Present in the small intestine, cellular retinol binding protein 2 (CRBP2) plays an important role in the uptake, transport, and metabolism of dietary retinoids. However, the recent discovery of the interactions of CRBP2 with 2-arachidonoylglycerol and other monoacylglycerols (MAGs) suggests the broader involvement of this protein in lipid metabolism and signaling. To better understand the physiological role of CRBP2, we determined its protein-lipid interactome using a fluorescence-based retinol replacement assay adapted for a high-throughput screening format. By examining chemical libraries of bioactive lipids, we provided evidence for the selective interaction of CRBP2 with a subset of nonretinoid ligands with the highest affinity for sn-1 and sn-2 MAGs that contain polyunsaturated C18-C20 acyl chains. We also elucidated the structure-affinity relationship for nonretinoid ligands of this protein. We further dissect the molecular basis for this ligand's specificity by analyzing high-resolution crystal structures of CRBP2 in complex with selected derivatives of MAGs. Finally, we identify T51 and V62 as key amino acids that enable the broadening of ligand selectivity to MAGs in CRBP2 as compared with retinoid-specific CRBP1. Thus, our study provides the molecular framework for understanding the lipid selectivity and diverse functions of CRBPs in controlling lipid homeostasis.

Anterior gradient 2 increases long-chain fatty acid uptake via stabilizing FABP1 and facilitates lipid accumulation

Anterior gradient 2 (AGR2), a protein disulfide isomerase (PDI), is a well-established oncogene. Here, we found that Agr2-/- mice had a decreased fat mass and hepatic and serum lipid levels compared with their wild-type littermates after fasting, and exhibited reduced high-fat diet (HFD)-induced fat accumulation. Transgenic mice overexpressing AGR2 (Agr2/Tg) readily gained fat weight on a HFD but not a normal diet. Proteomic analysis of hepatic samples from Agr2-/- mice revealed that depletion of AGR2 impaired long-chain fatty acid uptake and activation but did not affect de novo hepatic lipogenesis. Further investigations led to the identification of several effector substrates, particularly fatty acid binding protein-1 (FABP1) as essential for the AGR2-mediated effects. AGR2 was coexpressed with FABP1, and knockdown of AGR2 resulted in a reduction in FABP1 stability. Physical interactions of AGR2 and FABP1 depended on the PDI motif in AGR2 and the formation of a disulfide bond between these two proteins. Overexpression of AGR2 but not a mutant AGR2 protein lacking PDI activity suppressed lipid accumulation in cells lacking FABP1. Moreover, AGR2 deficiency significantly reduced fatty acid absorption in the intestine, which might be resulted from decreased fatty acid transporter CD36 in mice. These findings demonstrated a novel role of AGR2 in fatty-acid uptake and activation in both the liver and intestine, which contributed to the AGR2-mediated lipid accumulation, suggesting that AGR2 is an important regulator of whole-body lipid metabolism and down-regulation of AGR2 may antagonize the development of obesity.

Elevated Intestinal Inflammation in Preterm Infants With Signs and Symptoms of Gastroesophageal Reflux Disease

OBJECTIVES

Reflux is common in infancy; however, persistent signs and symptoms of gastrointestinal distress are often attributed to gastroesophageal reflux disease (GERD). In this pilot study, we aimed to characterize associations between signs and symptoms of suspected GERD and noninvasive markers of intestinal inflammation in preterm infants.

METHODS

We reviewed Electronic Medical Record (EMR) data to identify clinical signs and symptoms among case patients (n = 16). Controls (n = 16) were matched on gestational age. Univariate and multivariate regression analyses were used to compare fecal calprotectin and urinary intestinal fatty acid binding protein (I-FABP) levels between cases and controls.

RESULTS

We found no differences in baseline characteristics between cases and controls. In the multivariate regression analysis controlling for the proportion of mother's milk, cases had higher fecal calprotectin levels than controls, with no differences in I-FABP levels between cases and controls.

CONCLUSION

Our findings suggest that preterm infants with signs and symptoms of GERD have higher levels of intestinal inflammation as indicated by fecal calprotectin compared to their controls. Further studies are needed to evaluate the role of intestinal inflammation in signs and symptoms of gastrointestinal distress and whether fecal calprotectin might have predictive value in diagnosing GERD.

D-Lactate and intestinal fatty acid-binding protein are elevated in serum in patients with acute ischemic stroke

Experimental studies suggest that the intestinal barrier is affected in ischemic stroke. D-Lactate and intestinal fatty acid-binding protein (IFABP) are markers of intestinal mucosa integrity and barrier function. Our purpose was to evaluate the serum concentrations of these markers in patients with acute ischemic stroke (AIS). We included patients with AIS and used healthy subjects as controls. Clinical, demographic and outcome measures were recorded. Blood was drawn within 24 h of symptom onset. Serum concentrations of D-Lactate and IFABP were determined using commercially available colorimetric and ELISA kits, respectively. We included a total of 61 patients (median age of 64 years). The majority of patients were male (57.4%). The most common cause of stroke was atherosclerosis (34.4%), followed by small-vessel disease and cardioembolic (32.7% each). Mean admission NIHSS score was 8. Median IFABP and D-Lactate concentrations were significantly higher in patients than in controls. Concentrations were not associated with stroke severity or 3-month outcome. Patients with large-artery atherosclerosis and cardioembolic etiology had higher D-Lactate values than patients with small-vessel disease. D-Lactate and IFABP were significantly elevated in patients with AIS. This suggests that there is disruption of the intestinal barrier in patients with AIS.

Intestinal fatty acid-binding protein, a biomarker of intestinal barrier dysfunction, increases with the progression of type 2 diabetes

OBJECTIVE

To investigate serum intestinal fatty acid-binding protein (I-FABP) in two groups of patients with different duration of hyperglycemia in a cross-sectional study.

MATERIALS AND METHODS

In the present study, a total of 280 individuals (158 outpatients and 122 inpatients) suffering from hyperglycemia were recruited between May and September 2019. The clinical information of all participants was collected from the hospital information system, including the duration of hyperglycemia, age, gender, hemoglobin A1c (HbA1c), 75-g oral glucose tolerance test including fasting plasma glucose (FPG), 2-hour plasma glucose (2hPG), fasting C-peptide (FC-pep), 2-hour C-peptide (2hC-pep), fasting insulin (FIns), and 2-hour insulin (2hIns). In addition, the morbidity of diabetic complications (retinopathy, neuropathy, and nephropathy) in the inpatient group was determined. Furthermore, the difference between 2hPG and FPG (ΔPG), the difference between 2hC-pep and FC-pep (ΔC-pep), and the difference between 2hIns and FIns (ΔIns) were calculated. The level of serum I-FABP, a biomarker of intestinal barrier (IB) dysfunction, was estimated by an enzyme-linked immunosorbent assay.

RESULTS

For the outpatient group, the median duration of hyperglycemia was less than a year; the serum I-FABP level was positively correlated with age (R = 0.299, P < 0.001). For the inpatient group, the median duration of hyperglycemia was ten years; correlation analysis showed that the serum I-FABP level was positively associated with age and ΔPG (R = 0.286, P = 0.001; R = 0.250, P = 0.006, respectively) while negatively associated with FC-pep and 2hC-pep (R =  - 0.304, P = 0.001; R =  - 0.241, P = 0.008, respectively); multiple linear regression analysis showed that the serum I-FABP level was positively associated with the duration of hyperglycemia (β = 0.362, P < 0.001); moreover, patients with retinopathy had a significantly higher I-FABP level than those without retinopathy (P = 0.001).

CONCLUSIONS

In the outpatients whose duration of hyperglycemia was less than a year, the serum I-FABP level was positively associated with age. In the inpatients with different courses of diabetes, the serum I-FABP level was positively associated with the duration of hyperglycemia and glycemic variability but negatively associated with islet beta-cell function; moreover, the serum I-FABP level was higher in patients with retinopathy than in those without retinopathy, suggesting that the IB dysfunction got worse with the progression of diabetes.

Transcriptome profiling reveal Acanthopanax senticosus improves growth performance, immunity and antioxidant capacity by regulating lipid metabolism in GIFT (Oreochromis niloticus)

Acanthopanax senticosus (APS) is a natural and officinal herb with an impressive range of health benefits for animal. An 8-week feeding trail with different APS levels (0, 0.5, 1, 2, 4, and 8‰) was conducted to evaluate the promotive effects of APS in GIFT. Results indicate that APS improved the growth performance, improved specific growth ratio (SGR) and feed efficiency ratio (FER), the optimum APS supplementation was estimated to 1.97‰ based on the regression analysis of SGR. Meanwhile, 2‰ and 4‰ APS improved the immune and antioxidant capacity in some extent evidenced by the plasma and hepatic biomarkers. With the analysis of transcriptome sequencing, 293 differentially expressed genes (DEGs) were identified, including 106 up-regulated and 187 down-regulated. According to the GO and KEGG enrichments, DEGs were mainly involved in lipid metabolism regulation, followed by amino acid metabolism, carbohydrate metabolism, immunity, and antioxidant response. Transcriptional expression of PPARs signaling and key genes retrieved from transcriptome database confirmed that lipid metabolism was the main active biological process in response to dietary APS administration. These results indicate optimum APS (2‰) could be used as a feed additive that improve the growth performance by regulating lipid metabolism. This may provide insights for Chinese herb additive application in aquaculture production.

Faecal cytokine profiling as a marker of intestinal inflammation in acutely decompensated cirrhosis

BACKGROUND & AIMS

Gut dysbiosis and inflammation perpetuate loss of gut barrier integrity (GBI) and pathological bacterial translocation (BT) in cirrhosis, contributing to infection risk. Little is known about gut inflammation in cirrhosis and how this differs in acute decompensation (AD). We developed a novel approach to characterise intestinal immunopathology by quantifying faecal cytokines (FCs) and GBI markers.

METHODS

Faeces and plasma were obtained from patients with stable cirrhosis (SC; n = 16), AD (n = 47), and healthy controls (HCs; n = 31). A panel of 15 cytokines and GBI markers, including intestinal fatty-acid-binding protein-2 (FABP2), d-lactate, and faecal calprotectin (FCAL), were quantified by electrochemiluminescence/ELISA. Correlations between analytes and clinical metadata with univariate and multivariate analyses were performed.

RESULTS

Faecal (F) IL-1β, interferon gamma, tumour necrosis factor alpha, IL-21, IL-17A/F, and IL-22 were significantly elevated in AD vs. SC (q <0.01). F-IL-23 was significantly elevated in AD vs. HC (p = 0.0007). FABP2/d-lactate were significantly increased in faeces in AD vs. SC and AD vs. HC (p <0.0001) and in plasma (p = 0.0004; p = 0.011). F-FABP2 correlated most strongly with disease severity (Spearman's rho: Child-Pugh 0.466; p <0.0001; model for end-stage liver disease 0.488; p <0.0001). FCAL correlated with plasma IL-21, IL-1β, and IL-17F only and none of the faecal analytes. F-cytokines and F-GBI markers were more accurate than plasma in discriminating AD from SC.

CONCLUSIONS

FC profiling represents an innovative approach to investigating the localised intestinal cytokine micro-environment in cirrhosis. These data reveal that AD is associated with a highly inflamed and permeable gut barrier. FC profiles are very different from the classical innate-like features of systemic inflammation. There is non-specific upregulation of TH1/TH17 effector cytokines and those known to mediate intestinal barrier damage. This prevents mucosal healing in AD and further propagates BT and systemic inflammation.

LAY SUMMARY

The gut barrier is crucial in cirrhosis in preventing infection-causing bacteria that normally live in the gut from accessing the liver and other organs via the bloodstream. Herein, we characterised gut inflammation by measuring different markers in stool samples from patients at different stages of cirrhosis and comparing this to healthy people. These markers, when compared with equivalent markers usually measured in blood, were found to be very different in pattern and absolute levels, suggesting that there is significant gut inflammation in cirrhosis related to different immune system pathways to that seen outside of the gut. This provides new insights into gut-specific immune disturbances that predispose to complications of cirrhosis, and emphasises that a better understanding of the gut-liver axis is necessary to develop better targeted therapies.

Advances in fatty acids nutrition in dairy cows: from gut to cells and effects on performance

High producing dairy cows generally receive in the diet up to 5-6% of fat. This is a relatively low amount of fat in the diet compared to diets in monogastrics; however, dietary fat is important for dairy cows as demonstrated by the benefits of supplementing cows with various fatty acids (FA). Several FA are highly bioactive, especially by affecting the transcriptome; thus, they have nutrigenomic effects. In the present review, we provide an up-to-date understanding of the utilization of FA by dairy cows including the main processes affecting FA in the rumen, molecular aspects of the absorption of FA by the gut, synthesis, secretion, and utilization of chylomicrons; uptake and metabolism of FA by peripheral tissues, with a main emphasis on the liver, and main transcription factors regulated by FA. Most of the advances in FA utilization by rumen microorganisms and intestinal absorption of FA in dairy cows were made before the end of the last century with little information generated afterwards. However, large advances on the molecular aspects of intestinal absorption and cellular uptake of FA were made on monogastric species in the last 20 years. We provide a model of FA utilization in dairy cows by using information generated in monogastrics and enriching it with data produced in dairy cows. We also reviewed the latest studies on the effects of dietary FA on milk yield, milk fatty acid composition, reproduction, and health in dairy cows. The reviewed data revealed a complex picture with the FA being active in each step of the way, starting from influencing rumen microbiota, regulating intestinal absorption, and affecting cellular uptake and utilization by peripheral tissues, making prediction on in vivo nutrigenomic effects of FA challenging.

Short communication: Molecular markers for epithelial cells across gastrointestinal tissues and fecal RNA in preweaning dairy calves

The objective of this study was to compare the transcription of gene markers for gastrointestinal (GI) epithelial cells, including fatty acid binding protein 2 (FABP2) and cytokeratin 8 (KRT8), and tight junction complex genes (TJP1, CLDN1, CLDN4) in fecal RNA against several GI tract tissue sections in dairy calves. Eight healthy Jersey calves were euthanized at 5 wk of age, and postmortem samples were collected from rumen, duodenum, jejunum, ileum, large intestine, cecum, and feces for total RNA isolation. Tissues and fecal samples were immediately frozen in liquid nitrogen until RNA isolation. A real-time quantitative PCR analysis was performed using a single standard curve composited of equal amounts of all samples, including cDNA from fecal and GI tract tissues. The mRNA expression of the tight junctions TJP1, CLDN1, and CLDN4 was greater in fecal RNA compared with lower GI tract tissues (i.e., duodenum, jejunum, ileum, large intestine, and cecum). Similar to fecal RNA, rumen tissue had greater expression of tight junctions CLDN1 and CLDN4 than lower GI tract tissues. Similarly, rumen tissue had greater expression of TPJ1 than all lower GI tract tissues except duodenum. The expression of TJP1 and CLDN4 was greater in fecal RNA than in rumen tissue; in contrast, CLDN1 mRNA expression was greater in rumen tissue than in the fecal RNA. The expression of FABP2 was greater in duodenum in comparison to all tissue except ileum. The mRNA expression of FABP2 in fecal samples was similar to jejunum and ileum. The expression of KRT8 in fecal samples was similar to duodenum, large intestine, and cecum. The fecal RNA had a greater expression of KRT8 in comparison to jejunum and ileum. The rumen tissue had the lowest mRNA expression of KRT8. The expression levels of FABP2, KRT8, and tight junction genes observed in fecal transcripts suggest that a considerable amount of RNA derived from GI tract epithelial cells can be detected in fecal RNA, which is in agreement with previous data in neonatal dairy calves and other biological models including humans, rodents, and primates. The greater expression of tight junctions in fecal RNA in comparison to sections of the low GI remains to be understood, and due to the importance of tight junctions in GI physiology, further clarification of this effect is warranted. The similarities in mRNA expression of FABP2 and KRT8 between fecal RNA and intestinal sections add up to the accumulating evidence that fecal RNA can be used to investigate molecular alterations in the GI tract of neonatal dairy calves. Further research in this area should include high-throughput transcriptomic analysis via RNA-seq to uncover novel molecular markers for specific sections of the GI tract of neonates.

DDX5 promotes oncogene C3 and FABP1 expressions and drives intestinal inflammation and tumorigenesis

Tumorigenesis in different segments of the intestinal tract involves tissue-specific oncogenic drivers. In the colon, complement component 3 (C3) activation is a major contributor to inflammation and malignancies. By contrast, tumorigenesis in the small intestine involves fatty acid-binding protein 1 (FABP1). However, little is known of the upstream mechanisms driving their expressions in different segments of the intestinal tract. Here, we report that the RNA-binding protein DDX5 binds to the mRNA transcripts of C3 and Fabp1 to augment their expressions posttranscriptionally. Knocking out DDX5 in epithelial cells protected mice from intestinal tumorigenesis and dextran sodium sulfate (DSS)-induced colitis. Identification of DDX5 as a common upstream regulator of tissue-specific oncogenic molecules provides an excellent therapeutic target for intestinal diseases.

The Intestinal Barrier and Current Techniques for the Assessment of Gut Permeability

The intestinal barrier is essential in human health and constitutes the interface between the outside and the internal milieu of the body. A functional intestinal barrier allows absorption of nutrients and fluids but simultaneously prevents harmful substances like toxins and bacteria from crossing the intestinal epithelium and reaching the body. An altered intestinal permeability, a sign of a perturbed barrier function, has during the last decade been associated with several chronic conditions, including diseases originating in the gastrointestinal tract but also diseases such as Alzheimer and Parkinson disease. This has led to an intensified interest from researchers with diverse backgrounds to perform functional studies of the intestinal barrier in different conditions. Intestinal permeability is defined as the passage of a solute through a simple membrane and can be measured by recording the passage of permeability markers over the epithelium via the paracellular or the transcellular route. The methodological tools to investigate the gut barrier function are rapidly expanding and new methodological approaches are being developed. Here we outline and discuss, in vivo, in vitro and ex vivo techniques and how these methods can be utilized for thorough investigation of the intestinal barrier.

Molecular cloning, tissue expression, and transcriptional regulation of fabp1 and fabp2 in javelin goby (Synechogobius hasta) in response to starvation stress

Fatty acid binding proteins (FABPs) are intracellular lipid chaperones with low molecular weight, which are widely distributed in a variety of tissues, participating in fatty acid transport, cell proliferation, and angiogenesis. In this study, full-length sequences of two fabp genes (fabp1 and fabp2) from javelin goby (Synechogobius hasta) were cloned via RACE PCR, followed by bioinformatic analyses and gene expression evaluation. The fabp1 and fabp2 cDNA sequences were 493 and 626 bp in length, encoding 126 and 132 amino acids, respectively. Phylogenetic analysis revealed that both genes from S. hasta were clustered with those of other fish species in accordance with their known taxonomic relationships. fabp1 and fabp2 mRNA showed distinct expression patterns in different tissues, with fabp1 being most expressed in the liver and fabp2 in the intestine. Furthermore, the expression of fabp1 in the liver was significantly up-regulated during starvation, whereas fabp2 mRNA level in the intestine initially increased and then decreased, indicating that the transcriptional responses of the two genes could be influenced by malnourishment/starvation. Changes in the transcriptional levels of fabp1 and fabp2 also suggested that glycogen was catabolized in the liver of S. hasta at the beginning of starvation prior to lipid depletion, whereas lipids served as fuel reserves in the intestine during short-term starvation. In conclusion, this study provides fundamental insights into the role of Fabps in S. hasta lipid metabolism.

The stem-like Stat3-responsive cells of zebrafish intestine are Wnt/β-catenin dependent

The transcription factor Stat3 is required for proliferation and pluripotency of embryonic stem cells; we have prepared and characterized fluorescent Stat3-reporter zebrafish based on repeats of minimal responsive elements. These transgenic lines mimic in vivo Stat3 expression patterns and are responsive to exogenous Stat3; notably, fluorescence is inhibited by both stat3 knockout and IL6/Jak/STAT inhibitors. At larval stages, Stat3 reporter activity correlates with proliferating regions of the brain, haematopoietic tissue and intestine. In the adult gut, the reporter is active in sparse proliferating cells, located at the base of intestinal folds, expressing the stemness marker sox9b and having the morphology of mammalian crypt base columnar cells; noteworthy, zebrafish stat3 mutants show defects in intestinal folding. Stat3 reporter activity in the gut is abolished with mutation of T cell factor 4 (Tcf7l2), the intestinal mediator of Wnt/β-catenin-dependent transcription. The Wnt/β-catenin dependence of Stat3 activity in the gut is confirmed by abrupt expansion of Stat3-positive cells in intestinal adenomas of apc heterozygotes. Our findings indicate that Jak/Stat3 signalling is needed for intestinal stem cell maintenance and possibly crucial in controlling Wnt/β-catenin-dependent colorectal cancer cell proliferation.

Summary: Using a fluorescent reporter for Stat3 activity, we have identified the stem cells of zebrafish intestine and characterized their Wnt requirements and responsiveness.

Adaptation of extracellular matrix to massive small bowel resection in mice

BACKGROUND

Extracellular matrix (ECM) affects cell behavior, and vice versa. How ECM changes after small bowel resection (SBR) to support adaptive cellular processes has not been described. Here we characterize changes in ECM following SBR and integrate this with concomitant transcriptional perturbations.

METHODS

A 50% proximal SBR or sham surgery was performed on mice. On postoperative day 7, ileal tissue was sequentially depleted of protein components to generate an ECM-enriched fraction. ECM was analyzed for protein composition using mass spectrometry with subsequent Ingenuity Pathway Analysis (IPA) to identify predicted pathways and upstream regulators. qPCR and RNA-sequencing (RNA-Seq) were performed to corroborate these predicted pathways.

RESULTS

3034 proteins were differentially regulated between sham and SBR, of which 95 were significant (P < 0.05). IPA analysis predicted PPARα agonism to be an upstream regulator of the observed proteomic changes (P < 0.001). qPCR and RNA-Seq with KEGG analysis confirmed significant engagement of the PPAR pathway (P < 0.05).

CONCLUSION

Transcriptional signatures of adapting bowel predict subsequent ECM changes after SBR. How ECM communicates with surrounding cells to drive adaptation and vice versa merits further investigation. Our findings thus far suggest ECM supports tissue hyperplasia and altered metabolic demand following SBR.

Retinol-binding protein 2 (RBP2): biology and pathobiology

Retinol-binding protein 2 (RBP2; originally cellular retinol-binding protein, type II (CRBPII)) is a 16 kDa cytosolic protein that in the adult is localized predominantly to absorptive cells of the proximal small intestine. It is well established that RBP2 plays a central role in facilitating uptake of dietary retinoid, retinoid metabolism in enterocytes, and retinoid actions locally within the intestine. Studies of mice lacking Rbp2 establish that Rbp2 is not required in times of dietary retinoid-sufficiency. However, in times of dietary retinoid-insufficiency, the complete lack of Rbp2 gives rise to perinatal lethality owing to RBP2 absence in both placental (maternal) and neonatal tissues. Moreover, when maintained on a high-fat diet, Rbp2-knockout mice develop obesity, glucose intolerance and a fatty liver. Unexpectedly, recent investigations have demonstrated that RBP2 binds long-chain 2-monoacylglycerols (2-MAGs), including the canonical endocannabinoid 2-arachidonoylglycerol, with very high affinity, equivalent to that of retinol binding. Crystallographic studies establish that 2-MAGs bind to a site within RBP2 that fully overlaps with the retinol binding site. When challenged orally with fat, mucosal levels of 2-MAGs in Rbp2 null mice are significantly greater than those of matched controls establishing that RBP2 is a physiologically relevant MAG-binding protein. The rise in MAG levels is accompanied by elevations in circulating levels of the hormone glucose-dependent insulinotropic polypeptide (GIP). It is not understood how retinoid and/or MAG binding to RBP2 affects the functions of this protein, nor is it presently understood how these contribute to the metabolic and hormonal phenotypes observed for Rbp2-deficient mice.

Pharmacokinetic functions of human induced pluripotent stem cell-derived small intestinal epithelial cells

To develop a novel intestinal drug absorption system using intestinal epithelial cells derived from human induced pluripotent stem (iPS) cells, the cells must possess sufficient pharmacokinetic functions. However, the CYP3A4/5 activities of human iPS cell-derived small intestinal epithelial cells prepared using conventional differentiation methods is low. Further, studies of the CYP3A4/5 activities of human iPS-derived and primary small intestinal cells are not available. To fill this gap in our knowledge, here we used forskolin to develop a new differentiation protocol that activates adenosine monophosphate signaling. mRNA expressions of human iPS cell-derived small intestinal epithelial cells, such as small intestine markers, drug-metabolizing enzymes, and drug transporters, were comparable to or greater than those of the adult small intestine. The activities of CYP3A4/5 in the differentiated cells were equal to those of human primary small intestinal cells. The differentiated cells had P-glycoprotein and PEPT1 activities equivalent to those of Caco-2 cells. Differentiated cells were superior to Caco-2 cells for predicting the membrane permeability of drugs that were absorbed through a paracellular pathway and via drug transporters. In summary, here we produced human iPS cell-derived small intestinal epithelial cells with CYP3A4/5 activities equivalent to those of human primary small intestinal cells.

Two fatty acid-binding proteins expressed in the intestine interact differently with endocannabinoids

Two different members of the fatty acid-binding protein (FABP) family are found in enterocyte cells of the gastrointestinal system, namely liver-type and intestinal fatty acid-binding proteins (LFABP and IFABP, also called FABP1 and FABP2, respectively). Striking phenotypic differences have been observed in knockout mice for either protein, for example, high fat-fed IFABP-null mice remained lean, whereas LFABP-null mice were obese, correlating with differences in food intake. This finding prompted us to investigate the role each protein plays in directing the specificity of binding to ligands involved in appetite regulation, such as fatty acid ethanolamides and related endocannabinoids. We determined the binding affinities for nine structurally related ligands using a fluorescence competition assay, revealing tighter binding to IFABP than LFABP for all ligands tested. We found that the head group of the ligand had more impact on binding affinity than the alkyl chain, with the strongest binding observed for the carboxyl group, followed by the amide, and then the glycerol ester. These trends were confirmed using two-dimensional ¹ H-¹⁵ N nuclear magnetic resonance (NMR) to monitor chemical shift perturbation of the protein backbone resonances upon titration with ligand. Interestingly, the NMR data revealed that different residues of IFABP were involved in the coordination of endocannabinoids than those implicated for fatty acids, whereas the same residues of LFABP were involved for both classes of ligand. In addition, we identified residues that are uniquely affected by binding of all types of ligand to IFABP, suggesting a rationale for its tighter binding affinity compared with LFABP.

Rapid Gut Adaptation to Preterm Birth Involves Feeding-Related DNA Methylation Reprogramming of Intestinal Genes in Pigs

Following preterm birth, the immature gut function and immunology must rapidly adapt to cope with bacterial colonization and enteral milk feeding. We hypothesized that intestinal epigenetic changes are involved in the gut response to preterm birth and the first feeding. Using piglets as models for infants, preterm, and term pigs were fed total parenteral nutrition (TPN) or partial enteral feeding for 5 days, followed by exclusive enteral feeding with bovine milk until day 26 (weaning age). Intestinal structure, function, microbiome, DNA methylome, and gene expressions were compared between preterm and term pigs on days 0, 5, and 26 (n = 8 in each group). At birth, the intestine of preterm pigs showed villus atrophy and global hypermethylation, affecting genes related to the Wnt signaling pathway. Hypermethylation-associated lowered expression of lipopolysaccharide-binding protein and genes related to the Toll-like receptor 4 pathway were evident during the first 5 days of life, but most early methylation differences disappeared by day 26. Regardless, sucrase and maltase activities (adult-type brush border enzymes) remained reduced, and the gut microbiota altered (fewer Akkermansia, more Lachnoclostridia and Lactobacilli) until day 26 in preterm pigs. During the 0- to 5-day period, many new preterm–term methylation differences appeared, but mainly when no enteral feed was provided (TPN feeding). These methylation differences affected intestinal genes related to cell metabolism, including increased GCK (glucokinase) expression via promoter hypomethylation. In conclusion, the immature intestine has a remarkable capacity to adapt its gene methylation and expression after preterm birth, and only few preterm-related defects persisted until weaning. Early enteral feeding may be important to stimulate the methylation reprogramming of intestinal genes, allowing rapid intestinal adaptation to preterm birth.

Retinol-binding protein 2 (RBP2) binds monoacylglycerols and modulates gut endocrine signaling and body weight

Expressed in the small intestine, retinol-binding protein 2 (RBP2) facilitates dietary retinoid absorption. Rbp2-deficient (Rbp2-/- ) mice fed a chow diet exhibit by 6-7 months-of-age higher body weights, impaired glucose metabolism, and greater hepatic triglyceride levels compared to controls. These phenotypes are also observed when young Rbp2-/- mice are fed a high fat diet. Retinoids do not account for the phenotypes. Rather, RBP2 is a previously unidentified monoacylglycerol (MAG)-binding protein, interacting with the endocannabinoid 2-arachidonoylglycerol (2-AG) and other MAGs with affinities comparable to retinol. X-ray crystallographic studies show that MAGs bind in the retinol binding pocket. When challenged with an oil gavage, Rbp2-/- mice show elevated mucosal levels of 2-MAGs. This is accompanied by significantly elevated blood levels of the gut hormone GIP (glucose-dependent insulinotropic polypeptide). Thus, RBP2, in addition to facilitating dietary retinoid absorption, modulates MAG metabolism and likely signaling, playing a heretofore unknown role in systemic energy balance.

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.

The Role of Microbial Translocation and Immune Activation in AIDS-Associated Non-Hodgkin Lymphoma Pathogenesis: What Have We Learned?

Human immunodeficiency virus (HIV) infection is associated with greatly increased risk for development of non-Hodgkin lymphoma (NHL). Nearly all acquired immunodeficiency syndrome (AIDS)-associated NHL (AIDS-NHL) is of B-cell origin. Two major mechanisms are believed to contribute to the genesis of AIDS-NHL: (1) loss of immunoregulation of Epstein-Barr virus (EBV)+ B cells, resulting from impaired T-cell function late in the course of HIV disease and (2) chronic B-cell activation, leading to DNA-modifying events that contribute to oncogene mutations/ translocations. HIV infection has long been known to be associated with chronic inflammation and polyclonal B-cell activation, and more recently, microbial translocation. Microbial translocation is bacterial product leakage from gut lumen into the peripheral circulation, resulting in high levels of lipopolysaccharide (LPS) in the peripheral circulation, leading to chronic immune activation and inflammation. We review recent literature linking microbial translocation to lymphom-agenesis. This includes epidemiological studies of biomarkers of microbial translocation with risk of AIDS-NHL and emerging data on the mechanisms by which microbial translocation may lead to AIDS-NHL development.

Persistent Systemic Microbial Translocation, Inflammation, and Intestinal Damage During Clostridioides difficile Infection

BACKGROUND

Clostridioides difficile infection (CDI) might be complicated by the development of nosocomial bloodstream infection (n-BSI). Based on the hypothesis that alteration of the normal gut integrity is present during CDI, we evaluated markers of microbial translocation, inflammation, and intestinal damage in patients with CDI.

METHODS

Patients with documented CDI were enrolled in the study. For each subject, plasma samples were collected at T0 and T1 (before and after CDI therapy, respectively), and the following markers were evaluated: lipopolysaccharide-binding protein (LPB), EndoCab IgM, interleukin-6, intestinal fatty acid binding protein (I-FABP). Samples from nonhospitalized healthy controls were also included. The study population was divided into BSI+/BSI- and fecal microbiota transplantation (FMT) +/FMT- groups, according to the development of n-BSI and the receipt of FMT, respectively.

RESULTS

Overall, 45 subjects were included; 8 (17.7%) developed primary n-BSI. Markers of microbial translocation and intestinal damage significantly decreased between T0 and T1, however, without reaching values similar to controls (P < .0001). Compared with BSI-, a persistent high level of microbial translocation in the BSI+ group was observed. In the FMT+ group, markers of microbial translocation and inflammation at T1 tended to reach control values.

CONCLUSIONS

CDI is associated with high levels of microbial translocation, inflammation, and intestinal damage, which are still present at clinical resolution of CDI. The role of residual mucosal perturbation and persistence of intestinal cell damage in the development of n-BSI following CDI, as well as the possible effect of FMT in the restoration of mucosal integrity, should be further investigated.

Effects of phytogenic inclusion level on broiler carcass yield, meat antioxidant capacity, availability of dietary energy, and expression of intestinal genes relevant for nutrient absorptive and cell growth–protein synthesis metabolic functions

Context Phytogenic applications in animal nutrition currently attract worldwide scientific attention for their potential to contribute positively to sustainable and high-quality animal production. However, further understanding and substantiation of dietary phytogenic functions is required. Aims The inclusion level of a phytogenic premix (PP) comprising functional flavouring substances from ginger, lemon balm, oregano and thyme was studied for its effects on broiler growth performance, carcass traits, nutrient digestibility, liver and meat total antioxidant capacity (TAC), and lipid oxidation. The expression of genes for nutrient transporter proteins (SGLT1, GLUT2, PEPT1, BOAT and LAT1), for FABP2 involved in cellular fatty acid uptake and metabolism, and for the mTORC1 complex relevant for protein synthesis were profiled along the intestine. Methods One-day-old Cobb broiler chickens (n = 500) were assigned to four treatments with five replicates of 25 chickens each. Starter (1–10 days), grower (11–22 days) and finisher (23–42 days) basal diets were supplemented with four levels of PP inclusion as treatments: 0, 750, 1000 and 2000 mg/kg diet, termed control, PP750, PP1000 and PP2000. Feed and water were available ad libitum. Data were analysed by ANOVA, taking the treatment as fixed effect. Statistically significant (P ≤ 0.05) effects were further analysed and means were compared using Tukey’s HSD test. Polynomial contrasts tested the linear and quadratic effect of PP inclusion levels. Key results Growth performance responses were not improved significantly (P &gt; 0.05) by PP inclusion level. However, carcass (P = 0.030) and breast meat yield (P = 0.023) were higher in PP1000 than in the control. In addition, PP1000 had higher (P = 0.049) apparent metabolisable energy than PP2000 and the control. Increasing PP inclusion level increased breast (P = 0.005), thigh (P = 0.002) and liver (P = 0.040) TAC. Breast and thigh meat TAC reached a plateau at PP1000, whereas liver TAC continued to increase linearly. Lipid oxidation in breast meat and liver was delayed linearly (P ≤ 0.05) with increasing PP inclusion level. Expression of genes SGLT1, GLUT2, PEPT1, BOAT and FABP2 were not affected by PP inclusion. However, PP inclusion affected the expression of LAT1 (P &lt; 0.001) in jejunum and of mTORC1 in duodenum (P = 0.010) and ceca (P = 0.025). In particular, expression increased with increasing PP inclusion level in a linear and quadratic pattern depending on the intestinal segment. Conclusions Overall, PP inclusion at 1000 mg/kg diet improved carcass and breast yield, dietary available energy, and overall meat and liver TAC. Preliminary evidence was highlighted for effects of PP in promoting expression of genes relevant for muscle protein synthesis. Implications This study has contributed new information on effects of a phytogenic premix on broiler meat yield and antioxidant capacity, digestibility, absorption and metabolic functions, further supporting phytogenic benefits for broiler production.

Transcriptome analysis reveals mechanism underlying the differential intestinal functionality of laying hens in the late phase and peak phase of production

Background

The compromised performance of laying hens in the late phase of production relative to the peak production was thought to be associated with the impairment of intestinal functionality, which plays essential roles in contributing to their overall health and production performance. In the present study, RNA sequencing was used to investigate differences in the expression profile of intestinal functionality-related genes and associated pathways between laying hens in the late phase and peak phase of production.

Results

A total of 104 upregulated genes with 190 downregulated genes were identified in the ileum (the distal small intestine) of laying hens in the late phase of production compared to those at peak production. These upregulated genes were found to be enriched in little KEGG pathway, however, the downregulated genes were enriched in the pathways of PPAR signaling pathway, oxidative phosphorylation and glutathione metabolism. Besides, these downregulated genes were mapped to several GO clusters in relation to lipid metabolism, electron transport of respiratory chain, and oxidation resistance. Similarly, there were lower activities of total superoxide dismutase, glutathione S-transferase and Na⁺/K⁺-ATPase, and reductions of total antioxidant capacity and ATP level, along with an elevation in malondialdehyde content in the ileum of laying hens in the late phase of production as compared with those at peak production.

Conclusions

The intestine of laying hens in the late phase of production were predominantly characterized by a disorder of lipid metabolism, concurrent with impairments of energy production and antioxidant property. This study uncovers the mechanism underlying differences between the intestinal functionality of laying hens in the late phase and peak phase of production, thereby providing potential targets for the genetic control or dietary modulation of intestinal hypofunction of laying hens in the late phase of production.

SWATH Differential Abundance Proteomics and Cellular Assays Show In Vitro Anticancer Activity of Arachidonic Acid- and Docosahexaenoic Acid-Based Monoacylglycerols in HT-29 Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most common and mortal types of cancer. There is increasing evidence that some polyunsaturated fatty acids (PUFAs) exercise specific inhibitory actions on cancer cells through different mechanisms, as a previous study on CRC cells demonstrated for two very long-chain PUFA. These were docosahexaenoic acid (DHA, 22:6n3) and arachidonic acid (ARA, 20:4n6) in the free fatty acid (FFA) form. In this work, similar design and technology have been used to investigate the actions of both DHA and ARA as monoacylglycerol (MAG) molecules, and results have been compared with those obtained using the corresponding FFA. Cell assays revealed that ARA- and DHA-MAG exercised dose- and time-dependent antiproliferative actions, with DHA-MAG acting on cancer cells more efficiently than ARA-MAG. Sequential window acquisition of all theoretical mass spectra (SWATH) - mass spectrometry massive quantitative proteomics, validated by parallel reaction monitoring and followed by pathway analysis, revealed that DHA-MAG had a massive effect in the proteasome complex, while the ARA-MAG main effect was related to DNA replication. Prostaglandin synthesis also resulted as inhibited by DHA-MAG. Results clearly demonstrated the ability of both ARA- and DHA-MAG to induce cell death in colon cancer cells, which suggests a direct relationship between chemical structure and antitumoral actions.

The Effect of Increasing Inclusion Levels of a Fucoidan-Rich Extract Derived from Ascophyllum nodosum on Growth Performance and Aspects of Intestinal Health of Pigs Post-Weaning

This study examines the effects of increasing dietary inclusion levels of fucoidan, from a 44% fucoidan extract on the growth performance and intestinal health of pigs post-weaning (PW). Seventy-two newly weaned pigs (8.4 kg (SD 1.06)) were assigned to: (T1) basal diet (BD); (T2) BD + 125 ppm fucoidan; (T3) BD + 250 ppm fucoidan (8 pens/treatment). The appropriate quantity of a 44% fucoidan extract was included to achieve these inclusion levels. Faecal scores were recorded daily. On d15 PW, samples were collected from the intestinal tract from 1 pig/pen from the BD and BD + 250 ppm fucoidan groups. Pigs supplemented with 250 ppm fucoidan had improved faecal scores and increased concentrations of total volatile fatty acids and propionate in the colon (p < 0.05). The fucoidan-rich extract reduced the expression of CLDN5 (duodenum), SCL5A1/SGLT1 and SI (jejunum) and TJP1, FABP2, and SLC5A1 (ileum) (p < 0.05). The extract reduced the relative abundance of Prevotella and Lachnospiraceae (p < 0.05) and increased the abundance of Helicobacter (p < 0.01) in the caecum. However, no negative impact on growth performance or small intestinal morphology was observed. Thus, the inclusion of 250 ppm fucoidan improves faecal consistency without affecting growth performance and therefore warrants further investigation as a supplement for the prevention of PW diarrhoea under more challenging commercial conditions.

GutSelf: Interindividual Variability in the Processing of Dietary Compounds by the Human Gastrointestinal Tract

Nutritional research is currently entering the field of personalized nutrition, to a large extent driven by major technological breakthroughs in analytical sciences and biocomputing. An efficient launching of the personalized approach depends on the ability of researchers to comprehensively monitor and characterize interindividual variability in the activity of the human gastrointestinal tract. This information is currently not available in such a form. This review therefore aims at identifying and discussing published data, providing evidence on interindividual variability in the processing of the major nutrients, i.e., protein, fat, carbohydrates, vitamins, and minerals, along the gastrointestinal tract, including oral processing, intestinal digestion, and absorption. Although interindividual variability is not a primary endpoint of most studies identified, a significant number of publications provides a wealth of information on this topic for each category of nutrients. This knowledge remains fragmented, however, and understanding the clinical relevance of most of the interindividual responses to food ingestion described in this review remains unclear. In that regard, this review has identified a gap and sets the base for future research addressing the issue of the interindividual variability in the response of the human organism to the ingestion of foods.

Fatty acid-binding proteins: functional understanding and diagnostic implications

PURPOSE OF REVIEW

Fatty acid-binding proteins (FABPs) are a family of small, abundant proteins with highly tissue-specific expression patterns whose different functions remain incompletely understood. The purpose of this review is to summarize recent findings regarding FABP functions and mechanisms of action, including their potential utilization as serum markers of tissue-specific metabolic diseases.

RECENT FINDINGS

FABPs are important not only in their tissues of origin but also appear to influence the metabolism and function of tissues distal to their sites of expression. This may be secondary to metabolic changes in their primary tissues, and/or a result of FABP secretion from these tissues leading to effects on distal sites. Their levels in the circulation are increasingly explored as potential biomarkers for tissue-specific disease prognosis and progression.

SUMMARY

The nine fatty acid-binding members of the FABP family have unique tissue-specific functions and important secondary effects on tissues in which they are not expressed. For many of the FABPs, circulating levels may be indicative of disease processes related to their primary tissues, and may influence physiological function in distal tissues.

Osteopontin and Fatty Acid Binding Protein in Ifosfamide-treated Rats

Introduction

Ifosfamide (IF) is a cytostatic that exhibits adverse nephrotoxic properties. Clinically, IF-induced nephrotoxicity takes various forms, depending on applied dose and length of treatment.

Objectives

The aim of the study was to evaluate the two proteins: osteopontin (OP) and fatty acid binding protein (FABP), as markers of kidney function in rats treated with ifosfamide.

Material and Methods

Rats receiving a single IF dose (250 mg/kg b.w.; group 1) or treated with five consecutive IF doses administrated on following days (50mg/kg b.w.; group 3), compared with control groups 2 and 4, respectively, were studied. Kidney function was assessed using classical (urea, creatinine) and novel (FABP, OP) laboratory parameters and by histopathology.

Results

Single IF dose administration resulted in significant total proteinuria with urinary concentrations and 24-hour excretions of both FABP and OP comparable to the appropriate control. In rats treated with five consecutive IF doses, the urinary concentrations and 24-hour excretion of both FABP and OP were significantly higher compared to the appropriate control. The development of cystitis was revealed in groups 1 and 3, which was not accompanied by significant histopathological kidney damage.

Conclusions

Both OP and FABP may be useful laboratory markers of tubulopathy in the early stage of chronic nephrotoxicity of ifosfamide.

Intestinal Fatty Acid Binding Protein, a Biomarker of Intestinal Barrier, is Associated with Severity of Psoriasis

Alterations of intestinal microbiota play a significant role in the pathogenesis of psoriasis. Dysbiosis may cause disruption of the intestinal barrier, which contributes to immune activation by translocation of microbial antigens and metabolites. Intestinal fatty acid binding protein (I-FABP) serves as a biomarker of enterocyte damage. The aim of this study was to investigate clinical and metabolic factors affecting plasma concentration of I-FABP in patients with psoriasis. Eighty patients with psoriasis and 40 control subjects were enrolled in the study. Serum I-FABP (243.00 (108.88–787.10) vs. 114.38 (51.60–241.60) pg/ml, p < 0.001) and neutrophil to lymphocyte ratio (NLR; 2.59 (1.96–3.09) vs. 1.72 (1.36–47 2.11), p < 0.01) were significantly increased in patients with psoriasis compared to controls. A significant positive correlation was found between I-FABP and body mass index (BMI) (r = 0.82, p < 0.001), Psoriasis Area Severity Index (PASI) (r = 0.78, p < 0.001) and neutrophil to lymphocyte ratio (NLR) (r = 0.24, p < 0.001). Rising quartiles of I-FABP were associated with increasing values of BMI, PASI and NLR. The results of the logistic regression model confirmed an increased risk of higher disease severity with I-FABP concentration – odds ratio 3.34 per 100 pg/mL I-FABP increase. In conclusion, intestinal integrity in patients with psoriasis is affected by obesity, severity of the disease and systemic inflammation. The modulation of gut barrier may represent a new therapeutic approach for psoriasis.

Lysine Enhances the Stimulation of Fatty Acids on Milk Fat Synthesis via the GPRC6A-PI3K-FABP5 Signaling in Bovine Mammary Epithelial Cells

Amino acids can enhance milk fat synthesis in bovine mammary epithelial cells (BMECs), but the molecular mechanism is not well-known. In this study, we explored the regulatory role and molecular mechanism of lysine (Lys) on milk fat synthesis induced by fatty acids (FAs). We show that Lys dose-dependently affects number of cells and milk fat synthesis, and has more stimulatory effects in the presence of FAs. Lys enhances FA-induced sterol regulatory element binding protein 1c (SREBP-1c) expression and maturation in a fatty-acid-binding protein 5 (FABP5)-dependent manner. We further show that the Lys stimulates FABP5 expression via the GPRC6A (GPCR, class C, group 6, subtype A)-PI3K (phosphatidylinositol 3-kinase) signaling. Lys dose-dependently affects GPRC6A expression and localization at the plasma membrane. In summary, our data reveals that Lys enhances FAs-stimulated SREBP-1c expression and maturation leading to milk fat synthesis via the GPRC6A-PI3K-FABP5 signaling in BMECs.

Toxicokinetic patterns, metabolites formation and distribution in various tissues of the Chinese rare minnow (Gobiocypris rarus) exposed to tri(2‑butoxyethyl) phosphate (TBOEP) and tri-n-butyl phosphate (TNBP)

Alkylated organophosphate esters (alkyl-OPEs) are widely used and extensively detected in aquatic organisms. This work investigated the tissue-specific toxicokinetics of two common alkyl-OPEs, tri(2‑butoxyethyl) phosphate (TBOEP) and tri‑n‑butyl phosphate (TNBP) in Chinese rare minnow (Gobiocypris rarus) through a 50 day uptake and depuration experiment. The tissue-specific bioconcentration factor (BCF) values for the two alkyl-OPEs ranged from 1 to 30 L/kg wet weight (ww), with the kidney and ovary as the tissues with the highest accumulation. The tissue BCFs only exhibited a significant correlation with lipid contents only in storage tissues (i.e., muscle, brain, ovary and testis), indicating that lipids might not be the major contributor to tissue distribution of TBOEP and TNBP. However, the contribution of blood perfusion and active transport to tissue-specific OPE accumulation needs to be further investigated. Lower accumulation of metabolites than parent chemicals was observed, with metabolite parent concentration factors (MPCFs) <1. Di-alkyl phosphate (DAP), bis(2‑butoxyethyl) phosphate (BBOEP) and di(n-butyl) phosphate (DNBP) were the most abundantly formed metabolites of TBOEP and TNBP in various tissues, followed by the monohydroxylated OPEs (OH-OPEs). However, bis(2‑butoxyethyl) hydroxyethyl phosphate (BBOEHEP), was detected at much lower levels in the tissues. All the investigated metabolites showed high production rates (k_{prod,metabolites}) in the fish liver, followed by the GI tract and the kidney, indicating the importance of the hepatobiliary and urinary systems in eliminating the metabolites. Our study suggested that metabolism plays an important role in eliminating these two alkyl-OPEs in rare minnow and results in different tissue distribution mechanisms for metabolites and their compounds.

Single-Cell Analysis Reveals Regional Reprogramming During Adaptation to Massive Small Bowel Resection in Mice

BACKGROUND & AIMS

The small intestine (SI) displays regionality in nutrient and immunological function. Following SI tissue loss (as occurs in short gut syndrome, or SGS), remaining SI must compensate, or "adapt"; the capacity of SI epithelium to reprogram its regional identity has not been described. Here, we apply single-cell resolution analyses to characterize molecular changes underpinning adaptation to SGS.

METHODS

Single-cell RNA sequencing was performed on epithelial cells isolated from distal SI of mice following 50% proximal small bowel resection (SBR) vs sham surgery. Single-cell profiles were clustered based on transcriptional similarity, reconstructing differentiation events from intestinal stem cells (ISCs) through to mature enterocytes. An unsupervised computational approach to score cell identity was used to quantify changes in regional (proximal vs distal) SI identity, validated using immunofluorescence, immunohistochemistry, qPCR, western blotting, and RNA-FISH.

RESULTS

Uniform Manifold Approximation and Projection-based clustering and visualization revealed differentiation trajectories from ISCs to mature enterocytes in sham and SBR. Cell identity scoring demonstrated segregation of enterocytes by regional SI identity: SBR enterocytes assumed more mature proximal identities. This was associated with significant upregulation of lipid metabolism and oxidative stress gene expression, which was validated via orthogonal analyses. Observed upstream transcriptional changes suggest retinoid metabolism and proximal transcription factor Creb3l3 drive proximalization of cell identity in response to SBR.

CONCLUSIONS

Adaptation to proximal SBR involves regional reprogramming of ileal enterocytes toward a proximal identity. Interventions bolstering the endogenous reprogramming capacity of SI enterocytes-conceivably by engaging the retinoid metabolism pathway-merit further investigation, as they may increase enteral feeding tolerance, and obviate intestinal failure, in SGS.

Phorbol 12-Myristate 13-Acetate-Induced Changes in Chicken Enterocytes

Increased intestinal epithelial permeability has been linked to many enteric diseases because it allows easy access of microbial pathogens and toxins into the system. In poultry production, the restrictions in the use of antibiotic growth promoters have increased the chances of birds being susceptible to different enteric diseases. Thus, understanding the mechanisms which compromise intestinal function is pertinent. Based on our previous observation which showed the primary chicken enterocytes in culture undergoing dystrophic changes on treatment with phorbol myristate acetate (PMA), we surmised that this model, which appeared to mimic increased intestinal permeability, may help to understand the mechanisms of this problem. As genomic and proteomic changes are associated with many physiological and pathological problems, we were interested to find whether certain proteomic changes underlie the morphological alterations in the enterocytes induced by PMA. We exposed primary enterocyte cultures to a sub-lethal concentration of PMA, extracted the proteins, and analyzed by mass spectrometry for differentially regulated proteins. Our results showed that PMA affected several biological processes which negatively affected their energy metabolism, nuclear activities, and differentially regulated the levels of several stress proteins, chaperon, cytoskeletal, and signal transduction proteins that appear to be relevant in the cause of enterocyte dystrophy. Phorbol myristate acetate-affected signal transduction activities also raise the possibilities of their increased susceptibility to pathogens. The changes in enterocyte integrity can make intestine vulnerable to invasion by microbial pathogens and disrupt gut homeostasis.

Diet Induced Obesity Alters Intestinal Cytoplasmic Lipid Droplet Morphology and Proteome in the Postprandial Response to Dietary Fat

Dietary fat absorption by the small intestine is an efficient, multistep process that regulates the uptake and delivery of essential nutrients and energy. Fatty acids taken up by enterocytes, the absorptive cells of the small intestine, are resynthesized into triacylglycerol (TAG) and either secreted in chylomicrons or temporarily stored in cytoplasmic lipid droplets (CLDs). Proteins that associate with CLDs are thought to regulate the dynamics of TAG storage and mobilization. It is currently unclear what effect diet induced obesity (DIO) has on the balance between dietary fat storage and secretion. Specifically, there is limited knowledge of how DIO affects the level and diversity of proteins that associate with CLDs and regulate CLD dynamics. In the current study, we characterize CLDs from lean and DIO mice through histological and proteomic analyses. We demonstrate that DIO mice have larger intestinal CLDs compared to lean mice in response to dietary fat. Additionally, we identified 375 proteins in the CLD fraction isolated from enterocytes of lean and DIO mice. We identified a subgroup of lipid related proteins that are either increased or unique to the DIO CLD proteome. These proteins are involved in steroid synthesis, TAG synthesis, and lipolysis. This analysis expands our knowledge of the effect of DIO on the process of dietary fat absorption in the small intestine (D’Aquila, 2016).