T. J. Sinclair1, D. Zhang1,2, B. X. Ling1, H. J. Cohen4, K. G. Sylvester1,3 1Stanford University School Of Medicine,Department Of Surgery,Stanford, CA, USA 2University Of Science And Technology Beijing,School Of Computer And Communication Engineering,Beijing, HAIDIAN, China 3Lucile Packard Children’s Hospital Stanford,Center For Fetal And Maternal Health,Stanford, CA, USA 4Stanford University School Of Medicine,Department Of Pediatrics,Stanford, CA, USA
Introduction:
We hypothesize that prematurity predisposes to metabolic vulnerability, and in combination with clinical exposures such as nutrition, leads to the development of acquired diseases of prematurity including necrotizing enterocolitis (NEC). Routine newborn screening (NBS), that includes measurements of amino acids (AA) and fatty acid metabolism associated acylcarnitines (AC) can be re-purposed to elucidate the metabolic impact of prematurity and clinical care on disease development.
Methods:
We performed a retrospective longitudinal cohort study by querying a multicenter, longitudinal database that included 995 preterm infants (<32 weeks gestation) and 72 cases of NEC. Patient samples were obtained on day of life 1, 7, 28, and 42. Metabolite data from each time point included 72 AA and AC measures. Nutritional data (total calories, enteral feed, and total parenteral nutrition) were collected and average at each of the same time points. Cases of NEC were separated into sub-cohorts based on age of diagnosis: day of life 8-28, 29-42, and > 42. Control subjects were alive at the end of the study and had no history of bowel disease. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for all the NEC cases using the Day 1 analyte level, as well as for each sub-cohort using the analyte levels at each time point prior to the age of NEC diagnosis. Corrections were made for birth weight, gestational age, and multiple hypothesis testing with a false discovery rate of 5%. Loess curves were plotted over time for the significant analytes in each analysis and for the nutritional data.
Results:
Day 1 analyte levels of phenylalanine (OR 1.6, CI 1.4-2.2), citrulline/arginine ratio (OR 0.4, CI 0.2-0.8), and arginine (OR 1.4, CI 1.1-1.9) were significantly associated with NEC and these differences persisted over time. In the sub-cohort analyses, the number of metabolites that were significantly associated with NEC increased with proximity to the day of diagnosis and included a combination glycine, citrulline, essential amino acids methionine and phenylalanine, and predominantly short chain AC’s. Subjects with NEC were administered significant less enteral feeds and more TPN components over time, but also received significantly lower weight-adjusted total calories (p=2.9×10-4).
Conclusion:
Premature infants that develop NEC demonstrate progressive metabolic dysfunction both at birth and over time compared to controls on serial laboratory sampling obtained prior to diagnosis. The significant analytes involved specific biochemical pathways including homocysteine metabolism, nitric oxide synthesis, the urea cycle, and short chain fatty acid metabolism. The progressive metabolite abnormalities observed in infants that acquire NEC may reflect differences in metabolic function, nutritional content, and caloric deficiencies.