Systemic and luminal influences on the perinatal development of the gut

Hypothyroidism impairs development of the gastrointestinal tract in the ovine fetus

Growth and maturation of the fetal gastrointestinal tract near term prepares the offspring for the onset of enteral nutrition at birth. Structural and functional changes are regulated by the prepartum rise in cortisol in the fetal circulation, although the role of the coincident rise in plasma tri-iodothyronine (T3) is unknown. This study examined the effect of hypothyroidism on the structural development of the gastrointestinal tract and the activity of brush-border digestive enzymes in the ovine fetus near term. In intact fetuses studied between 100 and 144 days of gestation (dGA; term ∼145 days), plasma concentrations of T3, cortisol and gastrin; the mucosal thickness in the abomasum, duodenum, jejunum and ileum; and intestinal villus height and crypt depth increased with gestational age. Removal of the fetal thyroid gland at 105-110 dGA suppressed plasma thyroxine (T4) and T3 concentrations to the limit of assay detection in fetuses studied at 130 and 144 dGA, and decreased plasma cortisol and gastrin near term, compared to age-matched intact fetuses. Hypothyroidism was associated with reductions in the relative weights of the stomach compartments and small intestines, the outer perimeter of the intestines, the thickness of the gastric and intestinal mucosa, villus height and width, and crypt depth. The thickness of the mucosal epithelial cell layer and muscularis propria in the small intestines were not affected by gestational age or treatment. Activities of the brush border enzymes varied with gestational age in a manner that depended on the enzyme and region of the small intestines studied. In the ileum, maltase and dipeptidyl peptidase IV (DPPIV) activities were lower, and aminopeptidase N (ApN) were higher, in the hypothyroid compared to intact fetuses near term. These findings highlight the importance of thyroid hormones in the structural and functional development of the gastrointestinal tract near term, and indicate how hypothyroidism in utero may impair the transition to enteral nutrition and increase the risk of gastrointestinal disorders in the neonate.

Heat Stress Modulates a Placental Immune Response Associated With Alterations in the Development of the Fetal Intestine and Its Innate Immune System in Late Pregnant Mouse

The placenta is critical for the regulation of fetal innate immune function. Maternal heat stress (HS) impairs the immune function and the intestinal barrier in the offspring. However, the effects of maternal HS on the placental immune response and the development of the fetal intestine and its innate immune system remain unclear. Fetal mice were divided into the utero control (IUTN) and heat stress (IUHS) groups according to the maternal ambient temperature. Transcriptome analysis revealed that the expressions of placental immune response–related genes such as macrophage antigen CD68 and Fc gamma receptors 1 and 3 (fcgγ1 and fcgγ3) were increased, but the mRNA expression and protein levels of colony-stimulating factor-1 (Csf1) were decreased in the HS group compared with the TN group (p < 0.05). Furthermore, there was no significant difference in the intestinal length normalized to pup weight between the IUTN and IUHS groups. The expression of genes (such as alpi and ttr) involved in fetal duodenum and jejunum development was downregulated by maternal HS, whereas the expression of genes enriched in the cell cycle was increased. The mRNA expression and protein levels of cell division cycle 6 (Cdc6) in the fetal duodenum and jejunum were much higher in the IUHS group than in the IUTN group (p < 0.05). Maternal HS also down-regulated the expression of genes enriched in the innate immune system in the fetal duodenum and jejunum. The mRNA expression and protein levels of interleukin 1 alpha (IL1a) were reduced in the IUHS group compared with the IUTN group (p < 0.05). Taken together, these data demonstrated that maternal HS modulated the expression of genes in the placenta related to the immune response and inhibited the development of the fetal intestine and its innate immune system.

Interdependence of Thyroid and Corticosteroid Signaling in Vertebrate Developmental Transitions

Post-embryonic acute developmental processes mainly allow the transition from one life stage in a specific ecological niche to the next life stage in a different ecological niche. Metamorphosis, an emblematic type of these post-embryonic developmental processes, has occurred repeatedly and independently in various phylogenetic groups throughout metazoan evolution, such as in cnidarian, insects, molluscs, tunicates, or vertebrates. This review will focus on metamorphoses and developmental transitions in vertebrates, including typical larval metamorphosis in anuran amphibians, larval and secondary metamorphoses in teleost fishes, egg hatching in sauropsids and birth in mammals. Two neuroendocrine axes, the hypothalamic-pituitary-thyroid and the hypothalamic-pituitary-adrenal/interrenal axes, are central players in the regulation of these life transitions. The review will address the molecular and functional evolution of these axes and their interactions. Mechanisms of integration of internal and environmental cues, and activation of these neuroendocrine axes represent key questions in an “eco-evo-devo” perspective of metamorphosis. The roles played by developmental transitions in the innovation, adaptation, and plasticity of life cycles throughout vertebrates will be discussed. In the current context of global climate change and habitat destruction, the review will also address the impact of environmental factors, such as global warming and endocrine disruptors on hypothalamic-pituitary-thyroid and hypothalamic-pituitary-adrenal/interrenal axes, and regulation of developmental transitions.

Cortisol advantage of neighbouring the opposite sex in utero

Population sex ratios naturally fluctuate around equality. It is argued that the production of an equal number of male and female offspring by individual parents should be favoured by selection, if all costs and benefits are equal. Theoretically, an even sex ratio should yield the highest probability for a fetus to be adjacent to a fetus of the opposite sex in utero. This may cause developmental costs or benefits that have been overlooked. We examined the physiological and developmental parameters associated with in utero sex ratios in the nutria (Myocastor coypus), an invasive wildlife species with a strong reproductive output. Using hair testing, we found that litters with even sex ratios had the highest average cortisol levels. Fetuses neighbouring the opposite sex exhibited longer trunks than those neighbouring the same sex, which might imply better lung development. Our results are the first, to our knowledge, to link intra-utero sex ratios and fetal cortisol and suggest that fetal cortisol might be a mechanism by which even sex ratios are maintained via developmental advantages.

Gastrointestinal mucosal development and injury in premature lambs supported by the artificial placenta

BACKGROUND

An Artificial Placenta (AP) utilizing extracorporeal life support (ECLS) could revolutionize care of extremely premature newborns, but its effects on gastrointestinal morphology and injury need investigation.

METHODS

Lambs (116-121days GA, term=145; n=5) were delivered by C-section, cannulated for ECLS, had total parenteral nutrition (TPN) provided, and were supported for 7days before euthanasia. Early and Late Tissue Controls (ETC, n=5 and LTC, n=5) delivered at 115-121days and 125-131days, respectively, were immediately sacrificed. Standardized jejunal samples were formalin-fixed for histology. Crypt depth (CD), villus height (VH), and VH:CD ratios were measured. Measurements also included enterocyte proliferation (Ki-67), Paneth cell count (Lysozyme), and injury scores (H&E). ANOVA and Chi Square were used with p<0.05 considered significant.

RESULTS

CD, VH, and VH:CD were similar between groups (p>0.05). AP demonstrated more enterocyte proliferation (95.7±21.8) than ETC (49.4±23.4; p=0.003) and LTC (66.1+11.8; p=0.04), and more Paneth cells (81.7±17.5) than ETC (41.6±7.0; p=0.0005) and LTC (40.7±8.2, p=0.0004). Presence of epithelial injury and congestion in the bowel of all groups were not statistically different. No villus atrophy or inflammation was present in any group.

CONCLUSIONS

This suggests preserved small bowel mucosal architecture, high cellular turnover, and minimal evidence of injury.

STUDY TYPE

Research paper/therapeutic potential.

LEVEL OF EVIDENCE

N/A.

Psychological Stress, Immunity, and the Effects on Indigenous Microflora

Psychological stress is an intrinsic part of life that affects all organs of the body through direct nervous system innervation and the release of neuroendocrine hormones. The field of PsychoNeuroImmunology (PNI) has clearly demonstrated that the physiological response to psychological stressors can dramatically impact the functioning of the immune system, thus identifying one way in which susceptibility to or severity of diseases are exacerbated during stressful periods. This chapter describes research at the interface between the fields of PNI and Microbial Endocrinology to demonstrate that natural barrier defenses, such as those provided by the commensal microflora, can be disrupted by exposure to psychological stressors. These stress effects are evident in the development of the intestinal microflora in animals born from stressful pregnancy conditions, and in older animals with fully developed microbial populations. Moreover, data are presented demonstrating that exposure to different types of stressors results in the translocation of microflora from cutaneous and mucosal surfaces into regional lymph nodes. When considered together, a scenario emerges in which psychological stressors induce a neuroendocrine response that has the potential to directly or indirectly affect commensal microflora populations, the integrity of barrier defenses, and the internalization of microbes. Finally, a hypothesis is put forth in which stressor-induced alterations of the microflora contribute to the observed stressor-induced increases in inflammatory markers in the absence of overt infection.

Fetal Sex Modulates Developmental Response to Maternal Malnutrition

The incidence of obesity and metabolic diseases is dramatically high in rapidly developing countries. Causes have been related to intrinsic ethnic features with development of a thrifty genotype for adapting to food scarcity, prenatal programming by undernutrition, and postnatal exposure to obesogenic lifestyle. Observational studies in humans and experimental studies in animal models evidence that the adaptive responses of the offspring may be modulated by their sex. In the contemporary context of world globalization, the new question arising is the existence and extent of sex-related differences in developmental and metabolic traits in case of mixed-race. Hence, in the current study, using a swine model, we compared male and female fetuses that were crossbred from mothers with thrifty genotype and fathers without thrifty genotype. Female conceptuses evidence stronger protective strategies for their adequate growth and postnatal survival. In brief, both male and female fetuses developed a brain-sparing effect but female fetuses were still able to maintain the development of other viscerae than the brain (mainly liver, intestine and kidneys) at the expense of carcass development. Furthermore, these morphometric differences were reinforced by differences in nutrient availability (glucose and cholesterol) favoring female fetuses with severe developmental predicament. These findings set the basis for further studies aiming to increase the knowledge on the interaction between genetic and environmental factors in the determination of adult phenotype

Sex and breed-dependent organ development and metabolic responses in foetuses from lean and obese/leptin resistant swine

The present study aimed to determine the effects of breed and sex on growth patterns and metabolic features of advanced-pregnancy foetuses exposed to the same environmental conditions. Thus, at Day 62 of pregnancy, swine foetuses from an obese breed with leptin resistance (Iberian breed) were compared to lean crossbred foetuses (25% Large White ×25% Landrace ×50% Pietrain). There were differential developmental patterns in foetuses with leptin resistance, mainly a higher relative weight of the brain resembling “brain-sparing effect”. Prioritization of brain growth may be protective for the adequate growth and postnatal survival of the Iberian individuals, an ancient breed reared in extensive semi-feral conditions for centuries. There were also clear sex-related differences in foetal development and metabolism in the Iberian breed. Female Iberian foetuses were similar in size and weight to male littermates but had a significantly higher relative liver to body weight ratio resembling “liver-sparing effect” and a trend for a higher relative intestine to body ratio. Moreover, the availability of triglycerides, cholesterol and IL-6 in female Iberian foetuses was similar to that of lean crossbred foetuses. Overall, these features may favour a better postnatal survival and development of females, the sex more critical for the species survival. These findings set the basis for future translational studies aimed at increasing the knowledge on the interaction between genetic and environmental factors in the early programming of the adult phenotype.

Beta-catenin/TCF4 transactivates miR-30e during intestinal cell differentiation

The Wnt/beta-catenin/TCF4 pathway plays critical roles in the maintenance of small intestinal epithelium; however, downstream targets of the beta-catenin/TCF4 complex are not extensively characterized. We identified miR-30e as an immediate target activated by the beta-catenin/TCF4 complex. miR-30e was detected in the peri-nuclear region of the intestinal crypt IEC-6 cells. Bioinformatics analysis revealed clustered beta-catenin/TCF4 binding sites within the miR-30e promoter region. This promoter region was cloned into pGL3-control luciferase reporter vector, with the enhancer region removed. Transfection of pCMV-SPORT6-beta-catenin expression vector dose-dependently increased luciferase activity, and co-transfection of pCMV-SPORT6-TCF4 expression vector further enhanced the promoter activity. Dexamethasone-induced IEC-6 cells differentiation caused a 2.5-fold increase in miR-30e expression, and upon beta-catenin siRNA transfection, miR-30e increased 1.3-fold. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed the binding between beta-catenin/TCF4 complexes from IEC-6 nuclear extracts and the putative sequences in the miR-30e promoter. These results demonstrate that beta-catenin/TCF4 transactivates miR-30e during intestinal cell differentiation.

Cortisol increases the activities of intestinal apical membrane hydrolases and nutrient transporters before weaning in mink (Mustela vison)

Glucocorticoids from endogenous and exogenous sources accelerate maturation of brush-border membrane (BBM) hydrolases in omnivorous laboratory rodents and pigs. Less is known for carnivores, and whether the route of administration (oral or systemic) has an influence. The present study examined the influence of administering cortisol (hydrocortisone succinate, 5 mg/kg-day) to mink during postnatal week 4, just prior to weaning, on small intestine glucose and amino acid (aspartate, leucine, lysine, methionine, proline) absorption and on the activities of BBM disaccharidases and peptidases. Kits treated with cortisol were smaller (P<0.05), but had small intestines that were proportionally larger (P<0.05 for length and mass per kg body weight, but not for mucosal mass) than control kits with higher rates of absorption for most nutrients, except leucine, and increased activities of most BBM hydrolases, except lactase. As a consequence, cortisol increased hydrolytic and absorptive capacities of the entire small intestine, with the responses more pronounced when the cortisol was given orally. These findings indicate administration of cortisol stimulates growth of the developing mink small intestine, but does not accelerate the postnatal declines in nutrient transport, and may be a dam-to-kit signal that prepares suckling mink to digest and absorb the adult diet.