Integrating genetics with newborn metabolomics in infantile hypertrophic pyloric stenosis.

INTRODUCTION: Infantile hypertrophic pyloric stenosis (IHPS) is caused by hypertrophy of the pyloric sphincter muscle. OBJECTIVES: Since previous reports have implicated lipid metabolism, we aimed to (1) investigate associations between IHPS and a wide array of lipid-related metabolites in newborns, and (2) address whether detected differences in metabolite levels were likely to be driven by genetic differences between IHPS cases and controls or by differences in early life feeding patterns. METHODS: We used population-based random selection of IHPS cases and controls born in Denmark between 1997 and 2014. We randomly took dried blood spots of newborns from 267 pairs of IHPS cases and controls matched by sex and day of birth. We used a mixed-effects linear regression model to evaluate associations between 148 metabolites and IHPS in a matched case-control design. RESULTS: The phosphatidylcholine PC(38:4) showed significantly lower levels in IHPS cases (P = 4.68 × 10-8) as did six other correlated metabolites (four phosphatidylcholines, acylcarnitine AC(2:0), and histidine). Associations were driven by 98 case-control pairs born before 2009, when median age at sampling was 6 days. No association was seen in 169 pairs born in 2009 or later, when median age at sampling was 2 days. More IHPS cases than controls had a diagnosis for neonatal difficulty in feeding at breast (P = 6.15 × 10-3). Genetic variants known to be associated with PC(38:4) levels did not associate with IHPS. CONCLUSIONS: We detected lower levels of certain metabolites in IHPS, possibly reflecting different feeding patterns in the first days of life.

A novel missense mutation in the transcription factor FOXF1 cosegregating with infantile hypertrophic pyloric stenosis in the extended pedigree linked to IHPS5 on chromosome 16q24.

BACKGROUND: The aim was to identify susceptibility alleles for infantile hypertrophic pyloric stenosis (IHPS) in a pedigree previously linked to IHPS5 on chromosome 16q24. METHODS: We screened the positional and functional candidate gene FOXF1 by Sanger sequencing in a single affected individual. All family members for whom DNA was available were genotyped to determine cosegregation status of the putative causal variant. Immunofluorescence studies were performed to compare the cellular localization of wildtype and mutant form of the protein. Transcriptional activity was compared using a luciferase assay. RESULTS: A single novel substitution in FOXF1 (c.416G>A) predicted to result in a missense mutation (R139Q) was shown to cosegregate with disease trait. It was not seen in 560 control chromosomes nor has it been reported in ExAC or ESP. The R139Q substitution affects a conserved arginine residue within the DNA-binding domain of FOXF1. The transcriptional activity of the mutant FOXF1 protein is significantly reduced in comparison to wild-type. CONCLUSION: These results provide strong evidence that the R139Q substitution in FOXF1 causes IHPS in this family and imply a novel pathological pathway for the condition. They further support a role for FOXF1 in the regulation of embryonic and neonatal development of the gastro-intestinal tract.

Infantile hypertrophic pyloric stenosis (IHPS): a study of its pathophysiology utilizing the newborn hph-1 mouse model of the disease.

Infantile hypertrophic pyloric stenosis (IHPS) is a common disease of unknown etiology. The tetrahydrobiopterin (BH4)-deficient hyperphenylalaninemia-1 (hph-1) newborn mouse has a similar phenotype to the human condition. For hph-1 and wild-type control animals, pyloric tissue agonist-induced contractile properties, reactive oxygen species (ROS) generation, cGMP, neuronal nitric oxide synthase (nNOS) content, and Rho-associated protein kinase 2 (ROCK-2) expression and activity were evaluated. Primary pyloric smooth muscle cells from wild-type newborn animals were utilized to evaluate the effect of BH4 deficiency. One-week-old hph-1 mice exhibited a fourfold increase (P < 0.01) in the pyloric sphincter muscle contraction magnitude but similar relaxation values when compared with wild-type animals. The pyloric tissue nNOS expression and cGMP content were decreased, whereas the rate of nNOS uncoupling increased (P < 0.01) in 1-wk-old hph-1 mice when compared with wild-type animals. These changes were associated with increased pyloric tissue ROS generation and elevated ROCK-2 expression/activity (P < 0.05). At 1-3 days of age and during adulthood, the gastric emptying rate of the hph-1 mice was not altered, and there were no genotype differences in pyloric tissue ROS generation, nNOS expression, or ROCK-2 activity. BH4 inhibition in pyloric smooth muscle cells resulted in increased ROS generation (P < 0.01) and ROCK-2 activity (P < 0.05). Oxidative stress upregulated ROCK-2 activity in pyloric tissue, but no changes were observed in newborn fundal tissue in vitro. We conclude that ROS-induced upregulation of ROCK-2 expression accounts for the increased pyloric sphincter tone and nNOS downregulation in the newborn hph-1 mice. The role of ROCK-2 activation in the pathogenesis of IHPS warrants further study.

The association of molybdenum cofactor deficiency and pyloric stenosis.

Molybdenum cofactor deficiency (MoCD) is a rare autosomal recessive disorder that may present during the neonatal period with intractable seizures. Co-existence of MoCD and pyloric stenosis is previously reported as a coincidence or common etiology. The etiology of the two conditions is unclear; however, reports demonstrate neuronal deficiency in both. We report a neonate who was diagnosed with MoCD and hypertrophic pyloric stenosis.

Hypertrophic pyloric stenosis: predicting the resolution of biochemical abnormalities.

PURPOSE: Hypertrophic pyloric stenosis (HPS) is a common condition of infancy, often presenting with marked biochemical derangement, requiring correction. Previous studies have looked at the relationship between serum electrolytes and acid-base balance in HPS but not at the relationship between the degree of biochemical derangement and time taken to resolve the biochemical abnormality. METHODS: Retrospective analysis was performed on all 151 infants undergoing pyloromyotomy over a 3 year period. Of these, 105 met the inclusion criteria of: compliance with the unit HPS fluid protocol, and the documentation of at least three serial biochemical investigations. The rate of correction for each biochemical marker (sodium, potassium, chloride, urea, pCO2, hydrogen ion concentration, bicarbonate and the base excess) was plotted against the degree of disturbance and then against time. RESULTS: A significant relationship (P < 0.01) was found between the rate of correction of an abnormal chloride, urea or base excess and the degree of initial derangement. This enables the prediction of the time taken for the required correction of biochemical abnormalities prior to theatre. CONCLUSION: This method of analysis may be of value in comparing the effectiveness of different fluid regimes in use for the correction of biochemical abnormalities in infants with IHPS.

New insights into the pathogenesis of infantile pyloric stenosis.

Infantile hypertrophic pyloric stenosis (IHPS) is the most common surgical cause of vomiting in infants. Despite numerous hypotheses, the aetiopathogenesis of IHPS is not fully understood. Genetic, extrinsic and hormonal factors have been implicated in the pathogenesis of the disease. Furthermore, abnormalities of various components of the pyloric muscle such as smooth muscle cells, growth factors, extracellular matrix elements, nerve and ganglion cells, synapses, nerve supporting cells, neurotransmitters and interstitial cells of Cajal have been reported. Recently, genetic studies have identified susceptibility loci for IHPS and molecular studies have concluded that smooth muscle cells are not properly innervated in IHPS.

Sarcoglycan immunoreactivity is lacking in infantile hypertrophic pyloric stenosis. A confocal laser scanning microscopic study.

OBJECTIVES: The Dystrophin-Glycoprotein Complex (DGC) is a large multisubunit complex that plays a crucial role in maintaining the structural integrity and physiology of muscle fibers. Dystrophin has been reported to be absent in the pyloric muscle of infantile hypertrophic pyloric stenosis (IHPS) patients. The present study was designed to investigate the other two patterns of DGC (dystroglycan and sarcoglycan complexes) in normal pyloric muscle and their possible modifications in IHPS patients. METHODS: Ten pyloric muscle biopsies were obtained from babies operated for IHPS and five control pylorus biopsy taken at autopsy from cases without gastrointestinal disease. The DGC sub-complexes (beta-dystroglican and beta, delta- sarcoglycans) were localized immunohistochemically using specific monoclonal antibodies. The results were evaluated using a confocal laser scanning microscope. RESULTS: Positive immunolocalization of the two DGC sub complexes was demonstrated in the smooth muscle cells (SMCs) of the pyloric region of control patients. Similarly, a positive immune expression of beta-dystroglican was observed in the pyloric SMCs of IHPS patients. On the other hand a negative immunoreaction for sarcoglycans was recorded within the full thickness of the pyloric SMCs of these patients. CONCLUSIONS: The absence of sarcoglycans within the hypertrophied pyloric muscle may be a predisposing factor in the pathogenesis of IHPS since it could alter the normal physiology of SMCs through the modifications of structural integrity of sarcolemma and signaling between the extracellular and intracellular compartment.

Study of insulin-like growth factor-1 (IGF-1) and platelet-derived endothelial cell growth factor (PDEGF) expression in children with infantile hypertrophic pyloric stenosis.

BACKGROUND: The pathogenesis of infantile hypertrophic pyloric stenosis (IHPS) is not fully understood. Hypertrophy of the pyloric muscle is probably regulated by growth factors. Recent studies reported an increase in the local synthesis of insulin-like growth factor-1 (IGF-1). There are no reports concerning platelet-derived endothelial cell growth factor (PDEGF) playing an important role in the pathological angiogenesis. The aim of this study was to analyze the expressions of IGF-1 and PDEGF by immunohistochemistry (IHC) in the muscularis propria of the pyloric muscle in children with IHPS. MATERIAL/METHODS: Twenty-two muscle biopsies were obtained at the time of pyloromyotomy. The control group consisted of seven children. Specimens were evaluated by routine histopathological methods and by immunohistochemistry using monoclonal mouse anti-PDEGF or -IGF-1 antibodies. Cells showing positive reaction were counted in five random 200x high-power fields. Values were expressed as the mean +/-SD of the real expression area of the analyzed marker to the total analyzed area. RESULTS: In children with IHPS the average area of PDEGF expression was 62+/-52.5, whereas in the control group it was 15+/-12.1. The average area of IGF-1 expression was 1037+/-491.9) in study group and 259+/-221.44 in the controls. Statistically significant differences were found. CONCLUSIONS: These results show a local increase in the expressions of IGF-1 and PDEGF in the muscularis propria of the pyloric muscle in children with IHPS, which may have implications to the pathogenesis of the disease.