The mutagenic potential of duodenoesophageal reflux

SUMMARY BACKGROUND DATA: Duodenogastric-esophageal reflux disease is directly linked to Barrett's esophagus and to the development of esophageal adenocarcinoma. Despite this link, little is known about the mutagenic potential of refluxed material on the esophageal mucosa. We hypothesize that the reflux of gastric and duodenal content causes mutations in esophageal mucosa in vivo. METHODS: Seven Sprague Dawley/Big Blue F1 lacI transgenic rats underwent esophagoduodenostomy (ED) to surgically create duodeno-gastric-esophageal reflux. Fourteen nonoperated rats served as negative (n = 7) and as positive (n = 7/methyl-N-amyl-nitrosamine [MNAN] intraperitoneally) controls. The animals were killed 16 weeks after operation or injection, the entire esophageal mucosa was harvested, and mutation frequency was determined through standard Big Blue Mutagenesis Assay. RESULTS: Gross esophagitis was evident in all operated animals. The frequency of lacI mutations in esophageal mucosal cells of animals with ED was significantly higher, nearly 1.5-fold, than that of nonoperated animals. Nitrosamine administration resulted in a nearly 20-fold increase of lacI mutation frequency. Thirteen mutations were successfully sequenced, 46% occurred at CpG dinucleotide sites and 61% were either C to T or G to A transitions. CONCLUSIONS: The data provide preliminary evidence of the mutagenic potential of bile reflux on esophageal epithelium. The specific mutations are markedly higher than would be expected by chance and are similar to that found in p53 mutations of human esophageal adenocarcinoma, providing a link to human esophageal cancer.     

Assessment of cysteine synthesis in very low-birth weight neonates using a [13C6]glucose tracer

Background/Purpose

Cysteine is an amino acid necessary for the synthesis of all proteins, the antioxidant glutathione, and the neuromodulator taurine. Whether cysteine is an essential amino acid for premature neonates remains controversial. Using a [¹³C₆]glucose precursor in very-low-birth weight (VLBW) premature neonates, we measured the ¹³C content of cysteine in hepatically derived apolipoprotein (apo) B-100 and in the plasma to determine whether cysteine synthesis occurs and to relate minimum synthetic capacity to neonatal maturity.

Methods

Twelve VLBW premature neonates (birth weight, 907 ± 274 [SD] g; gestational age, 26.8 ± 2.4 weeks) were studied on day of life 7.8 ± 4.2 while on total parenteral nutrition (TPN) for 5.6 ± 4.5 days. A 4-hour intravenous infusion of [¹³C₆]glucose was administered. Blood samples were obtained immediately before and at the end of the infusion. Isotopic enrichment of cysteine was determined by gas chromatography/mass spectrometry. Analysis of variance, Student's t test, and linear regression were used for comparisons.

Results

The ¹³C isotope ratio of apo B-100-derived cysteine after the [¹³C₆]glucose infusion was significantly higher than baseline (18.57 ± 0.38 [SEM] vs 17.54 ± 0.25 mol%, P < .05). The ¹³C isotope ratio of plasma cysteine was also significantly higher than baseline (17.36 ± 0.25 vs 16.91 ± 0.16 mol%, P < .05). When expressed as a product/precursor ratio, the mole percent above baseline of [¹³C]apo B-100 cysteine/[¹³C₆]glucose correlated with birth weight (r = 0.74, P < .01).

Conclusions

Very low-birth weight neonates are capable of cysteine synthesis as evidenced by incorporation of ¹³C label into hepatically derived apo B-100 cysteine and plasma cysteine from a glucose precursor. The minimum capacity for intrahepatic cysteine synthesis appears to be directly proportional to the maturity of the neonate and may impact the capabilities of VLBW neonates to counteract oxidative stresses such as bronchopulmonary dysplasia and necrotizing enterocolitis.     

The role of enteral nutrition in the reversal of parenteral nutrition-associated liver dysfunction in infants

Background

Liver dysfunction in children dependent on parenteral nutrition (PN) is well established, and the extent of hyperbilirubinemia has been shown to correlate with morbidity and mortality. The aim of this study was to assess whether increasing provisions of enteral nutrition can improve PN-associated hyperbilirubinemia over time.

Methods

A retrospective review was conducted on infants in our institution's Short Bowel Syndrome Clinic from 1999 to 2004. Inclusion criteria included PN duration more than 1 month, serum direct bilirubin more than 3 mg/dL while on PN, and tolerance of full enteral nutrition with eventual discontinuation of PN. Paired t tests were used for statistical analyses.

Results

Twelve infants were identified with a PN duration of 5 ± 1 months. Five patients underwent liver biopsy while on PN, and histological evidence of cholestasis was found on all specimens. Peak total and direct bilirubin levels were 10.5 ± 1.9 and 7.0 ± 1.6 mg/dL, respectively, and occurred at time of PN discontinuation. Only 2 patients had improvement in serum bilirubin levels before initiation of full enteral nutrition. After initiation of full enteral nutrition and discontinuation of PN, all patients achieved permanent normalization of bilirubin levels by 4 months (P < .05) after a 1-month plateau phase. Alkaline phosphatase levels approached reference range within this time but were not significant.

Conclusion

These data demonstrate for the first time that although PN-dependent infants can achieve normalization of marked hyperbilirubinemia with enteral nutrition, the improvement in liver function usually begins only after full enteral nutrition is tolerated and PN is withdrawn. These findings support the aggressive weaning of PN to enteral nutrition in infants with short bowel syndrome.     

Perinatal management of gastroschisis: analysis of a newly established clinical pathway

Purpose

The authors developed a clinical pathway for optimal management after antenatal diagnosis of gastroschisis. This is the outcomes analysis of our first 30 consecutive patients.

Method

Antenatal counseling was provided for all families with in-utero diagnosis of gastroschisis. Bowel dilatation, thickness, motility, amniotic fluid volume, and fetal development were followed by ultrasonography every 4 weeks. Babies were delivered by cesarean section between 36 and 38 weeks gestation if the lungs were mature or earlier for bowel complications. Gastroschisis repair was scheduled 90 minutes after birth. Primary repair was attempted in all through the abdominal wall defect without an additional incision, resulting in an umbilicus with no abdominal scar.

Results

Primary repair was achieved in 83%. Babies needed assisted ventilation for 3 days, reached full feeds by 19 days, and were discharged by 24 days (all medians). There were 3 (10%) deaths, all after staged repair.

Conclusions

Our new protocol of both scheduled elective cesarean section and early gastroschisis repair resulted in a higher proportion of primary repair, shorter duration of mechanical ventilation, earlier full feeds, and shorter length of stay. There was no increase in mortality or morbidity. The primary-repair babies had no mortality and had excellent cosmesis.