Randal K. Buddington

Dietary prebiotics: current status and new definition

In November 2008, a group of scientists met at the 6th Meeting of the International Scientific Association of Probiotics and Prebiotics (ISAPP) in London, Ontario, Canada, to discuss the functionality of prebiotics. As a result of this, it was concluded that the prebiotic field is currently dominated by gastrointestinal events. However, in the future, it may be the case that other mixed microbial ecosystems may be modulated by a prebiotic approach, such as the oral cavity, skin and the urogenital tract. Therefore, a decision was taken to build upon the current prebiotic status and define a niche for ‘dietary prebiotics’. This review is co-authored by the working group of ISAPP scientists and sets the background for defining a dietary prebiotic as ‘‘a selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health’’.

Preterm Birth Affects the Intestinal Response to Parenteral and Enteral Nutrition in Newborn Pigs

Maturation of gastrointestinal (GI) function in neonates is stimulated by enteral nutrition, whereas parenteral nutrition induces GI atrophy and malfunction. We investigated whether preterm birth alters the GI responses to parenteral and enteral nutrition. Pigs were delivered either preterm (107 d gestation) or at term (115 d gestation) and fed total parenteral nutrition (TPN) or enteral sows milk (ENT) for 6 d after birth. Immaturity of the preterm pigs was documented by reduced blood pH, oxygen saturation and neutrophil granulocyte function, impaired intestinal immunoglobulin G uptake from colostrum, and altered relative weights of visceral organs (small intestine, liver, spleen, pancreas, and adrenals). For both ages at delivery, increases occurred in pancreatic weight (30-75%) and amylase activity (0.5- to 13-fold) after birth, but much more in ENT than in TPN pigs (P < 0.05). Six days of TPN feeding was associated with reduced intestinal weight for both delivery groups (60% of values in ENT, P < 0.001), but only in term TPN pigs was the weight lower than at birth (-20%, P < 0.05). Likewise, it was only in term TPN pigs that intestinal maltase activity increased, compared with ENT, and the absorption of glucose and proline decreased. Only in preterm pigs did TPN feeding increase lactase activity (+50% compared with ENT, P < 0.05). For both delivery ages, the mRNA of lactase-phloridzin hydrolase and sodium-coupled glucose transporter 1 (SGLT-1) were increased in TPN, compared with ENT. In conclusion, the trophic effect of enteral vs. parenteral nutrition on the GI tract is also present after preterm birth, but the postnatal maturation of many GI functions is modified, compared with term birth. The effects of nutritional regimen on the maturation of the gut epithelium in neonates depend on gestational age at birth.

Invited review: the preterm pig as a model in pediatric gastroenterology.

At birth, the newborn mammal undergoes a transition from a sterile uterine environment with a constant nutrient supply, to a microbe-rich environment with intermittent oral intake of complex milk nutrients via the gastrointestinal tract (GIT). These functional challenges partly explain the relatively high morbidity and mortality of neonates. Preterm birth interrupts prenatal organ maturation, including that of the GIT, and increases disease risk. Exemplary is necrotizing enterocolitis (NEC), which is associated closely with GIT immaturity, enteral feeding, and bacterial colonization. Infants with NEC may require resection of the necrotic parts of the intestine, leading to short bowel syndrome (SBS), characterized by reduced digestive capacity, fluid loss, and dependency on parenteral nutrition. This review presents the preterm pig as a translational model in pediatric gastroenterology that has provided new insights into important pediatric diseases such as NEC and SBS. We describe protocols for delivery, care, and handling of preterm pigs, and show how the immature GIT responds to delivery method and different nutritional and therapeutic interventions. The preterm pig may also provide a sensitive model for postnatal adaptation of weak term piglets showing high mortality. Attributes of the preterm pig model include close similarities with preterm infants in body size, organ development, and many clinical features, thereby providing a translational advantage relative to rodent models of GIT immaturity. On the other hand, the need for a sow surgical facility, a piglet intensive care unit, and clinically trained personnel may limit widespread use of preterm pigs. Studies on organ adaptation in preterm pigs help to identify the physiological basis of neonatal survival for hypersensitive newborns and aid in defining the optimal diet and rearing conditions during the critical neonatal period.

Digestive and feeding characteristics of the chondrosteans

SynopsisStructure and function of the digestive system and feeding characteristics of the chondrosteans are reviewed. Although the group exhibits a wide diversity of feeding habits including piscivory, benthophagy, and planktivory, they are principally carnivores throughout their life history. Examination of digestive system structure reveals the basic structure to be similar among the species with some modification to accomodate the different food types. For the species studied, composition of the adult digestive enzyme complement is consistent with the carnivorous habits with proteases dominating and only low levels of carbohydrase activity. There are three secretory phases during development of the digestive system. Each corresponds with different food habits of the different life-history intervals. Vision is apparently not utilized for feeding in any interval. Instead food is recognized and located primarily by gustation, olfaction, textural qualities, and, possibly, electroreception.

Evaluation of Fructooligosaccharide Supplementation of Oral Electrolyte Solutions for Treatment of Diarrhea Recovery of the Intestinal Bacteria

Although oral electrolyte solutions (OES)replenish salts and water lost during diarrhea, presentformulations do not address disturbances of the normalintestinal microbiota. Therefore, we evaluated the efficacy of an OES with and withoutfructooligosaccharide (FOS) for treatment of pigs withacute secretory diarrhea induced by cholera toxin.Before, during, and after diarrhea, bacteriologicevaluation was made of contents collected from the midsmall intestine, cecum, and distal colon and mucosascraped from the mid small intestine. Diarrhea causedsignificant declines in total bacterial counts ofcontents from all three regions, with less of an impacton bacteria associated with the mucosa. Although totalbacterial counts recovered within 24 hr, regardless oftreatment, densities of Enterobacteriaceae were higher in pigs treated with OES whereas thosereceiving FOS had more lactobacilli. Our results showthat secretory diarrhea disturbs the normal densitiesand relative species abundance of the microbiota, with the influences more pronounced forcontents relative to the mucosa, and that adding FOS toOES accelerates the recovery of bacteria perceived asbeneficial while potentially slowing the recovery of pathogenic forms.

Carbohydrate maldigestion induces necrotizing enterocolitis in preterm pigs

Necrotizing enterocolitis (NEC) remains the most severe gastrointestinal disorder in preterm infants. It is associated with the initiation of enteral nutrition and may be related to immature carbohydrate digestive capacity. We tested the hypothesis that a formula containing maltodextrin vs. a formula containing lactose as the principal source of carbohydrate would predispose preterm pigs to a higher NEC incidence. Cesarean-derived preterm pigs were given total parenteral nutrition for 48 h followed by total enteral nutrition with a lactose-based (n = 11) or maltodextrin-based (n = 11) formula for 36 h. A higher incidence (91% vs. 27%) and severity (score of 3.3 vs. 1.8) of NEC were observed in the maltodextrin than in the lactose group. This higher incidence of NEC in the maltodextrin group was associated with significantly lower activities of lactase, maltase, and aminopeptidase; reduced villus height; transiently reduced in vivo aldohexose uptake; and reduced ex vivo aldohexose uptake capacity in the middle region of the small intestine. Bacterial diversity was low for both diets, but alterations in bacterial composition and luminal concentrations of short-chain fatty acids were observed in the maltodextrin group. In a second study, we quantified net portal absorption of aldohexoses (glucose and galactose) during acute jejunal infusion of a maltodextrin- or a lactose-based formula (n = 8) into preterm pigs. We found lower net portal aldohexose absorption (4% vs. 42%) and greater intestinal recovery of undigested carbohydrate (68% vs. 27%) in pigs acutely perfused with the maltodextrin-based formula than those perfused with the lactose-based formula. The higher digestibility of the lactose than the maltodextrin in the formulas can be attributed to a 5- to 20-fold higher hydrolytic activity of tissue-specific lactase than maltases. We conclude that carbohydrate maldigestion is sufficient to increase the incidence and severity of NEC in preterm pigs.

Dietary oligofructose and inulin modulate immune functions in mice

Host defense functions are responsive to diet composition. Since inulin and oligofructose increase resistance to health challenges, selected systemic immune variables were measured in B6C3F1 mice fed diets containing 10g/100g cellulose (C) or with cellulose replaced entirely with oligofructose (OF) or inulin (I), or partially (2.5 g) with oligofructose (C-OF). White blood cell counts for all groups were within normal ranges, but were 100% higher (P < 0.05) in C mice compared to mice fed fructan-containing diets, which had similar counts. Spleen mass, CD4/CD8 and T/B ratios from suspensions of spleen and thymus, and fecal IgA concentrations did not differ among groups. OF and I mice had higher natural killer cell activity of splenocytes and greater phagocytic activity of peritoneal macrophages. Apparently oligofructose and inulin do not elicit an increase or redistribution of the examined lymphocyte populations (CD4/CD8 and T/B), but up-regulate macrophage-dependent (T-helper 1 type) immune responses in a dose-dependent manner.

Compartmentalized Cyclic Adenosine 3,5-Monophosphate at the Plasma Membrane Clusters PDE3A and Cystic Fibrosis Transmembrane Conductance Regulator into Microdomains

PDE3A functionally and physically interacts with CFTR. Inhibition of PDE3A generates compartmentalized cAMP, which further clusters PDE3A and CFTR into microdomains at the plasma membrane of epithelial cells and potentiates CFTR channel function. Our findings provide insights into the important role of PDE3A in compartmentalized cAMP signaling.

Postnatal Changes in Selected Bacterial Groups of the Pig Colonic Microflora

The importance of the colonic microflora in health and nutrition is well known, but how they colonize and become established in the colon is not well understood. We therefore characterized the quantitative and qualitative changes of the colonic microflora during the first 120 days of postnatal development. Unlike previous studies, changes were defined for individual pigs using in situ samples collected anaerobically and aseptically from the distal colon. Although the colons were sterile at birth, they were rapidly colonized, and within 12 h bacterial densities had stabilized at 10(-9)-10(10) bacteria/g colonic content. Facultative anaerobes, notably coliforms, initially dominated the microflora, but were supplanted within 48 h after birth by obligate anaerobes, which constituted greater than 90% of the microflora thereafter. Bacteroides spp., the predominant anaerobes in the adult colon, did not markedly increase in abundance until after weaning and were still increasing by postnatal day 120. Shifts in the relative abundances of different bacterial populations throughout the first 120 days after birth confirm previous reports that the establishment of the adult colonic microflora is a gradual, sequential process, and highlight the need to focus research on anaerobic groups.

A successful microbound diet for the larval culture of freshwater prawn Macrobrachium rosenbergii

A high moisture (63–71%), semi-purified microbound diet containing alginate was compared to newly hatched live Artemia nauplii as an exclusive diet for the culture of larval freshwater prawn Macrobrachium rosenbergii from 5th stage (weighted mean) through metamorphosis to postlarva. Two separate trials, representing larvae from different hatches, were conducted. Larvae were stocked at 50/l into cone-shaped vessels that contained 2 l of 12‰ seawater and were part of a temperature-controlled (28 °C) recirculating culture system. Larvae were manually fed either the live Artemia diet or the microbound diet exclusively, several times daily. After 14 days (23 days post-hatch (dph)), growth of larvae fed the microbound diet was 90% of that achieved for larvae fed newly hatched nauplii of Artemia. Survival of larvae fed the microbound diet was 77.3% and 73.3%, and was not significantly different from that of Artemia-fed larvae. Composed of readily available ingredients, the diet contains 46.2% crude protein and 37.4% lipid, is easy to prepare, and has good water stability. The diet is an economically practical alternative to the fluctuating cost, nutrient uncertainty, and labor associated with the use of Artemia nauplii hatched from cysts. The characteristics of the diet suggest good potential for successful use in the larviculture of other fish and crustacean species, in either the existing or a modified state.