Ricardo A Caicedo

The developing intestinal ecosystem: implications for the neonate.

Interactions of resident intestinal microbes with the luminal contents and the mucosal surface play important roles in normal intestinal development, nutrition, and innate and adaptive immunity. The neonate, especially the premature, who possesses a highly immunoreactive intestinal submucosa underlying a single layer of epithelial cells that are continuously exposed to the luminal environment, is highly susceptible to perturbations of the luminal environment. Understanding the interactions of the intestinal ecosystem with the host and luminal nutritional environment, especially in regard to human milk and pre- and probiotics, has major implications for the pathogenesis of diseases that affect not only the intestine but distal organs such as the lung and brain.

Metabolic effects of different protein intakes after short term undernutrition in artificially reared infant rats.

BACKGROUND Early postnatal nutrition is involved in metabolic programming. Small for gestational age and premature babies commonly receive insufficient dietary protein during the neonatal period due to nutrition intolerance, whereas high protein formulas are used to achieve catch up growth. Neither the short term, nor the long term effects of such manipulation of protein intake are known. AIM We hypothesized that high or low protein intake during infancy would induce metabolic alterations both during early-life and in adulthood. METHODS Gastrostomized neonatal rat pups received either 50% (P50%), 100% (P100%), or 130% (P130%) of the normal protein content in rat milk from the 7th to the 15th day of life (D7 to D15), when they were either sacrificed or placed with mothers for the long term study. Glucose tolerance tests (GTT) were performed at D230. Long term rats were sacrificed at D250. RESULTS At D15, weight of P50% pups was lower than P100% and P130% pups. Neither liver and kidney mass, nor islet beta-cell areas were altered. Brain weight (adjusted to body weight) was higher in P50% vs. P130% (p<0.05). Insulin/glucose ratio was lower in P50% vs. P130%. Expression of GLUT4 on adipocyte cell membrane and GLUT2 in liver cytosol was significantly enhanced in P50% vs. P130%. Long term, neither GTT results nor body nor organ weights differed between groups. CONCLUSION In neonatal rats, higher protein intakes via the enteral route led to enhanced short term weight gain, insulin resistance, and modified expression of glucose transporters. However, these differences were not sustained.

Neonatal Formula Feeding Leads to Immunological Alterations in an Animal Model of Type 1 Diabetes

Neonatal diet may influence the development of type 1 diabetes (T1D) in susceptible individuals through an intestinal mucosal inflammatory response, resulting in loss of self-tolerance. We tested the hypothesis that formula feeding during the neonatal period accelerates the development of T1D in diabetes-prone BioBreeding (BBDP) rats through regulation of CD4+CD25+ regulatory T lymphocytes (Treg) and anti-inflammatory cytokines. BBDP rat pups fed rat milk substitute (RMS) via a “pup-in-the cup” system were compared with mother-fed (MF) rats. The spleen and thymus were analyzed for Foxp3-expressing CD4+/CD25+ T cells. Multiplex enzyme-linked immunosorbent assays (ELISAs) were performed to measure cytokine-induced neutrophil chemoattractant (CINC), tumor necrosis factor α (TNF-α), interferon-gamma (IFN-γ), interleukin (IL)-4, IL-10, and IL-18. Diabetes-free survival, time of disease onset, and Treg/total T lymphocyte ratios were not different. MF pups had higher ileal CINC (p < 0.001) and IL-18 (p = 0.002), but no differences in the liver. There were no differences in ileal cytokine concentrations of 75-d-old rats, but the formula-fed rats had greater liver TNF-α (p < 0.001), IFN-γ, and IL-4 (p < 0.01) and lower IL-10 (p = 0.002) compared with MF animals. Formula versus maternal milk altered the hepatic cytokine profile at 75 d toward an inflammatory pattern but did not result in altered Treg cell frequencies or the development of T1D.

90 Protein Intake Affects Glucose Metabolism Prior to Weaning in Rat Pups.

Background: Fetal malnutrition can lead to a metabolic syndrome in adulthood. Early postnatal nutrition is probably also involved in metabolic programming. Epigenetic mechanisms could be responsible. Protein intake is frequently increased for small babies in order to attain catch-up growth. Short and long term effects of this practice at this critical period of life are not known.Hypothesis: Protein overfeeding during the neonatal period could lead to modifications of glucose metabolism and epigenetic changes.Methods: Rat pups were randomized in 3 experimental groups receiving different diets via gastrostomy with 50% (G50%), 100% (G100%) and 130% (G130%) of usual mother fed amount of protein from D7 to D15. The control group consisted of mother-fed pups (MF). At D15, the pups were sacrificed. Tissues were harvested for morphometry, epigenetic and biochemical analysis. Plasma insulin/glucose ratio was calculated. Epigenetic markers were studied in the brain: quantification of histone H3 acetylation and methylation, and of mRNA levels of the glucocorticoid receptors (GR).Results: There was a trend toward higher insulin/glucose ratio in the G130%, and lower in the G50%.In G130% compared to G100% as control, H3/K14 acetylation increased (p<0.05). In contrast, H3/K9 acetylation decreased (p<0.01) and H3/K9 di- and trimethylation increased (p<0.01). mRNA levels of GR exon 1 isoforms 1.5 and 1.6 were decreased (p<0.01). Total body weight, liver and kidney weights did not differ among the groups, whereas brain weight per total body weight was greatest in the group fed 50% protein (p<0.005). There was no correlation between the pancreatic islet area and the insulin/glucose ratio.Conclusion: These data suggest a trend toward glucose intolerance in infant rats receiving high protein diets, associated with epigenetic changes.Background: Fetal malnutrition can lead to a metabolic syndrome in adulthood. Early postnatal nutrition is probably also involved in metabolic programming. Epigenetic mechanisms could be responsible. Protein intake is frequently increased for small babies in order to attain catch-up growth. Short and long term effects of this practice at this critical period of life are not known.Hypothesis: Protein overfeeding during the neonatal period could lead to modifications of glucose metabolism and epigenetic changes.Methods: Rat pups were randomized in 3 experimental groups receiving different diets via gastrostomy with 50% (G50%), 100% (G100%) and 130% (G130%) of usual mother fed amount of protein from D7 to D15. The control group consisted of mother-fed pups (MF). At D15, the pups were sacrificed. Tissues were harvested for morphometry, epigenetic and biochemical analysis. Plasma insulin/glucose ratio was calculated. Epigenetic markers were studied in the brain: quantification of histone H3 acetylation and methylation, and of mRNA levels of the glucocorticoid receptors (GR).Results: There was a trend toward higher insulin/glucose ratio in the G130%, and lower in the G50%.In G130% compared to G100% as control, H3/K14 acetylation increased (p<0.05). In contrast, H3/K9 acetylation decreased (p<0.01) and H3/K9 di- and trimethylation increased (p<0.01). mRNA levels of GR exon 1 isoforms 1.5 and 1.6 were decreased (p<0.01). Total body weight, liver and kidney weights did not differ among the groups, whereas brain weight per total body weight was greatest in the group fed 50% protein (p<0.005). There was no correlation between the pancreatic islet area and the insulin/glucose ratio.Conclusion: These data suggest a trend toward glucose intolerance in infant rats receiving high protein diets, associated with epigenetic changes.