Route and type of nutrition influence mucosal immunity to bacterial pneumonia.
(1/1225)
OBJECTIVE: To develop a model of established respiratory immunity against Pseudomonas aeruginosa pneumonia and to investigate the effects of route and type of nutrition on this immunity. SUMMARY BACKGROUND DATA: Diet influences the ability of gut-associated lymphoid tissue (GALT) to maintain mucosal immunity. Complex enteral diets and chow maintain normal GALT populations against established IgA-mediated antiviral respiratory immunity. Both intravenous and intragastric total parenteral nutrition (TPN) produce GALT atrophy, but only intragastric TPN preserves established antiviral immunity. The authors hypothesized that both GALT-depleting diets (intragastric and intravenous TPN) would impair immunity against bacterial pneumonia. METHODS: P. aeruginosa was administered intratracheally to determine the mortality rate at increasing doses, and liposomes containing P. aeruginosa antigens were used to generate effective respiratory immunization. In the final experiment, mice received liposomes containing P. aeruginosa antigens to establish immunity and then were randomized to chow, complex enteral diets, intragastric TPN, or intravenous TPN. After 5 days of diet, mice received live intratracheal P. aeruginosa, and the death rate was recorded at 24 and 48 hours. RESULTS: The LD50 and LD100 were 9 x 10(7) and 12 x 10(7), respectively. Immunization reduced the mortality rate from 66% to 12%. This immunization was maintained in mice fed chow or a complex enteral diet and was lost in animals receiving intravenous TPN. Intragastric TPN partially preserved this respiratory immunity. CONCLUSIONS: Protection against bacterial pneumonia can be induced by prior antigenic immunization. This protection is lost with intravenous TPN, partially preserved with a chemically defined enteral diet, and completely preserved with chow or complex enteral diets. Both route and type of nutrition influence antibacterial respiratory tract immunity. (+info)
The sodium concentration of enteral diets does not influence absorption of nutrients but induces intestinal secretion of water in miniature pigs.
(2/1225)
Contradictory opinions exist as to whether the sodium concentration of enteral diets influences absorption of macronutrients and transepithelial movement of sodium and water. Therefore, we investigated the effects of various sodium concentrations of enteral diets on absorption of macronutrients and on net fluxes of sodium and water. In unanesthetized miniature pigs, a 150-cm jejunal segment was perfused with an oligopeptide (Peptisorb), an oligomeric and a polymeric diet. The polymeric diet was supplemented with pancreatic enzymes. The sodium concentrations varied between 30 and 150 mmol/L. The energy density was 3.4 MJ/L. The sodium concentration of the diets did not influence absorption of macronutrients and of total energy. However, increasing sodium concentrations of the diets were associated with increasing osmolality of the solutions, resulting in a linear increase in net secretion of water and flow rate of chyme. With all diets and sodium concentrations net secretion of sodium occurred. The sodium secretion was independent of the initial sodium concentration of the diets. It was linearly correlated with net flux of water and was largest in miniature pigs infused with the oligomeric diet. The sodium concentration of the jejunal effluent did not correspond to the initial sodium concentration of the diets. The present results indicate that enteral feeding of diets with high energy density inevitably increases net secretion of water and sodium as sodium concentration increases. Therefore, the sodium concentration of diets should be as low as possible to meet only the minimal daily requirement of sodium. Low sodium concentrations of diets have no negative effects on absorption of macronutrients. (+info)
Endotoxin-induced changes in IGF-I differ in rats provided enteral vs. parenteral nutrition.
(3/1225)
The purpose of the present study was to determine whether acute changes in the insulin-like growth factor (IGF) system induced by mild surgical trauma/fasting or endotoxin [lipopolysaccharide (LPS)] are differentially modulated by total enteral nutrition (TEN) or total parenteral nutrition (TPN). Rats had vascular catheters and a gastrostomy tube surgically placed and were fasted overnight. The next morning animals randomly received an isocaloric, isonitrogenous (250 kcal. kg-1. day-1, 1.6 g N. kg-1. day-1) infusion of either TEN or TPN for 48 h. Then rats were injected intravenously with Escherichia coli LPS (1 mg/kg) while nutritional support was continued. Time-matched control animals were injected with saline. After mild surgical trauma and an 18-h fast, TEN was more effective at increasing plasma IGF-I levels than TPN. Subsequent injection of LPS decreased IGF-I in blood, liver, and muscle in both TEN- and TPN-fed rats compared with saline-injected control animals. However, this decrease was approximately 30% greater in rats fed TPN compared with those fed TEN. LPS-induced downregulation of IGF-I mRNA expression in liver and muscle was also more prominent in TPN-fed rats. The LPS-induced increase in plasma corticosterone and tumor necrosis factor-alpha was greater (2- and 1.6-fold, respectively) in TPN-fed rats, and these changes were consistent with the greater reduction in IGF-I seen in these animals. In similarly treated rats allowed to survive for 24 h after LPS injection, the LPS-induced increase in the urinary 3-methylhistidine-to-creatinine ratio was smaller in TEN-fed rats. In summary, LPS reduced systemic levels of IGF-I as well as IGF-I protein and mRNA in critical target organs. Enteral feeding greatly attenuated this response. Maintenance of higher IGF-I levels in TEN-fed rats was associated with a reduction in inflammatory cytokine levels and lower rates of myofibrillar degradation. (+info)
Composition of enteral diets and meals providing optimal absorption rates of nutrients in mini pigs.
(4/1225)
BACKGROUND: Commercial enteral diets differ widely in nutrient composition. It is unknown whether the nutrient composition of the diets influences intestinal absorption. OBJECTIVE: The objective of this study was to investigate the effects of different enteral diets providing 60% of energy as carbohydrate, protein, or fat or 33.3% of energy from each nutrient on intestinal absorption in mini pigs. DESIGN: Kinetics of nutrient absorption were determined by perfusing a 150-cm jejunal segment. The kinetics of absorption were used to determine optimal relations between the absorption and recovery of each nutrient. From these data, the optimal nutrient composition of the diets providing complete absorption of the macronutrients in the shortest intestinal length was evaluated. Absorption of nutrients was further determined after oral administration of 4 corresponding meals. RESULTS: With all enteral diets, the absorption of nutrients displayed saturation kinetics. Absorption rates of carbohydrate were significantly larger than those of fat and protein. Consequently, the amounts of nutrients remaining unabsorbed per unit length of jejunum differed among the macronutrients. After administration of various test meals, the length of the small intestine required for complete absorption of the nutrients depended on the composition of the meals. The shortest intestinal length for complete absorption was needed for a diet providing 48% of energy as carbohydrate, 23% as protein, and 29% as fat. This composition closely matched the nutritional requirements. CONCLUSION: The nutrient composition of diets can optimize intestinal absorption. This may be especially important in patients with malabsorption or short-bowel syndrome. (+info)
Is blood glucose predictable from previous values? A solicitation for data.
(5/1225)
An important question about blood glucose control in diabetes is, Can present and future blood glucose values be predicted from recent blood glucose history? If this is possible, new continuous blood glucose monitoring technologies under development may lead to qualitatively better therapeutic capabilities. Not only could continuous monitoring technologies alert a user when a hypoglycemic episode or other blood glucose excursion is underway, but measurements may also provide sufficient information to predict near-future blood glucose values. A predictive capability based only on recent blood glucose history would be advantageous because there would be no need to involve models of glucose and insulin distribution, with their inherent requirement for detailed accounting of vascular glucose loads and insulin availability. Published data analyzed here indicate that blood glucose dynamics are not random, and that blood glucose values can be predicted, at least for the near future, from frequently sampled previous values. Data useful in further exploring this concept are limited, however, and an appeal is made for collection of more. (+info)
Gastric emptying after elective abdominal aortic aneurysm surgery: the case for early postoperative enteral feeding.
(6/1225)
OBJECTIVE: To assess gastric emptying with a view to early postoperative enteral nutrition after elective abdominal aortic aneurysm (AAA) surgery. METHODS: The paracetamol absorption test was used to assess gastric emptying in 13 consecutive patients at 6, 18 and 32 h following elective AAA surgery. All patients received postoperative analgesia with marcaine given via an epidural catheter during the first 48 postoperative hours. Normal emptying was defined as an area under the plasma paracetamol concentration curve at 60 min (AUC-60) of > 600 mg/min/l. RESULTS: The median time to normal gastric emptying was 18 +/- 7.7 h. One patient (7.6%) had normal emptying at 6 h, nine (69%) at 18 h and 12 (92%) at 32 h. The nasogastric tubes were removed at a median of 3.2 days after surgery, and enteral feeding was commenced on day 4. CONCLUSIONS: Gastric emptying was normal 18 h post-AAA surgery as assessed by the paracetamol absorption test. In view of the importance of maintaining an intact gastrointestinal mucosa, enteral nutrition may be commenced on the second postoperative day. (+info)
Nutrient-specific preferences by lambs conditioned with intraruminal infusions of starch, casein, and water.
(7/1225)
We hypothesized that lambs discriminate between postingestive effects of energy and protein and associate those effects with a food's flavor to modify food choices. Based on this hypothesis, we predicted that 1) lambs would acquire a preference for a poorly nutritious food (grape pomace) eaten during intraruminal infusions of energy (starch) or protein (casein) and that 2) shortly after an intraruminal infusion of energy or protein (preload), lambs would decrease their preferences for foods previously conditioned with starch or casein, respectively. Thirty lambs were allotted to three groups and conditioned as follows. On d 1, lambs in each group received grape pomace containing a different flavor and water was infused into their rumens as they ate the pomace. On d 2, the flavors were switched so each group received a new flavor and a suspension of starch (10% of the DE required per day) replaced the water infusion. On d 3, the flavors were switched again, and a suspension of casein (2.7 to 5.4% of the CP required per day) replaced the starch infusion. Conditioning was repeated during four consecutive trials. Lambs in Trial 1 had a basal diet of alfalfa pellets (e.g., free access from 1200 to 1700) and 400 g of rolled barley. Lambs in Trials 2, 3, and 4 received a restricted amount of alfalfa pellets (990 g/d) as their basal diet. After conditioning, all animals received an infusion of water, and, 30 min later, they were offered a choice of the three flavors previously paired with water, starch, or casein. On the ensuing days, the choice was repeated, but starch, casein, and barley replaced the water preload. The nutrient density of the infused preloads was increased during consecutive trials. Lambs preferred the flavors paired with starch > water > casein during Trial 1 (P < .05) and the flavors paired with starch > casein > water during Trials 2 (P < .05), 3 (P < .001), and 4 (P < .001). Preloads of casein decreased preferences for flavors previously paired with casein (P < .10 [Trial 2]; P < .001 [Trial 3], and increased preferences for flavors paired with starch (P < .05 [Trial 2]; P < .001 [Trial 3]). Preloads of energy (barley) had the opposite effect (P < .05 [Trial 3]). These results indicate that lambs discriminated between the postingestive effects of starch and casein and associated the effects with specific external cues (i.e., added flavors) to regulate macronutrient ingestion. (+info)
Influence of erythromycin on establishment of feeding in preterm infants: observations from a randomised controlled trial.
(8/1225)
AIM: To determine the effect of erythromycin on the establishment of enteral feeding in ventilated infants < 31 weeks gestation. METHODS: Erythromycin was randomly allocated as an antimicrobial treatment for the first 7 days of life in 76 infants: 35 received erythromycin and 41 acted as controls. Feed toleration, time taken to establish full enteral feeding, vomiting, prescription of glycerine suppositories and occurrence of necrotising enterocolitis were recorded. RESULTS: There were no significant differences between the groups for any of the outcomes. The infants treated with erythromycin reached full feeding at a median (quartile) age of 8 (5-12) days compared with 9 (6-14) days for controls. CONCLUSIONS: Intravenous erythromycin in antimicrobial doses is unlikely to benefit the introduction of feeding in preterm infants. (+info)