Bryan E. Hainline

Class selection of amino acid metabolites in body fluids using chemical derivatization and their enhanced 13C NMR

We report a chemical derivatization method that selects a class of metabolites from a complex mixture and enhances their detection by 13C NMR. Acetylation of amines directly in aqueous medium with 1,1′-13C2 acetic anhydride is a simple method that creates a high sensitivity and quantitative label in complex biofluids with minimal sample pretreatment. Detection using either 1D or 2D 13C NMR experiments produces highly resolved spectra with improved sensitivity. Experiments to identify and compare amino acids and related metabolites in normal human urine and serum samples as well as in urine from patients with the inborn errors of metabolism tyrosinemia type II, argininosuccinic aciduria, homocystinuria, and phenylketonuria demonstrate the method. The use of metabolite derivatization and 13C NMR spectroscopy produces data suitable for metabolite profiling analysis of biofluids on a time scale that allows routine use. Extension of this approach to enhance the NMR detection of other classes of metabolites has also been accomplished. The improved detection of low-concentration metabolites shown here creates opportunities to improve the understanding of the biological processes and develop improved disease detection methodologies.

Citrin deficiency, a perplexing global disorder

Citrin deficiency, caused by mutations in SLC25A13, can present with neonatal intrahepatic cholestasis or with adult onset neuropsychiatric, hepatic and pancreatic disease. Until recently, it had been thought to be found mostly in individuals of East Asian ancestry. A key diagnostic feature has been the deficient argininosuccinate synthetase (ASS) activity (E.C. 6.3.4.5) in liver, with normal activity in skin fibroblasts. In this series we describe the clinical presentation of 10 patients referred to our laboratories for sequence analysis of the SCL25A13 gene, including several patients who presented with elevated citrulline on newborn screening. In addition to sequence analysis performed on all patients, ASS enzyme activity, citrulline incorporation and Western blot analysis for ASS and citrin were performed on skin fibroblasts if available. We have found 5 unreported mutations including two apparent founder mutations in three unrelated French-Canadian patients. In marked contrast to previous cases, these patients have a markedly reduced ASS activity in skin fibroblasts. The presence of citrin protein on Western blot in three of our cases reduces the sensitivity of a screening test based on protein immunoblotting. The finding of citrin mutations in patients of Arabic, Pakistani, French Canadian and Northern European origins supports the concept that citrin deficiency is a panethnic disease.

1H NMR metabolomics study of age profiling in children

Metabolic profiling of urine provides a fingerprint of personalized endogenous metabolite markers that correlate to a number of factors such as gender, disease, diet, toxicity, medication, and age. It is important to study these factors individually, if possible to unravel their unique contributions. In this study, age‐related metabolic changes in children of age 12 years and below were analyzed by 1H NMR spectroscopy of urine. The effect of age on the urinary metabolite profile was observed as a distinct age‐dependent clustering even from the unsupervised principal component analysis. Further analysis, using partial least squares with orthogonal signal correction regression with respect to age, resulted in the identification of an age‐related metabolic profile. Metabolites that correlated with age included creatinine, creatine, glycine, betaine/TMAO, citrate, succinate, and acetone. Although creatinine increased with age, all the other metabolites decreased. These results may be potentially useful in assessing the biological age (as opposed to chronological) of young humans as well as in providing a deeper understanding of the confounding factors in the application of metabolomics. Copyright

Growth Failure in Prader-Willi Syndrome Is Secondary to Growth Hormone Deficiency

Growth failure is a recognized feature of the Prader-Willi syndrome (PWS). Despite evidence that hypothalamic dysfunction accompanies the syndrome, the etiology of this growth failure remains controversial because most patients with PWS are obese. In order to contribute to resolution of this controversy, we performed a retrospective analysis of 16 obese and non-obese PWS children. GH deficiency was diagnosed in 12 of the 16 subjects and occurred independently of weight status. All of the non-obese subjects were GH deficient. Of the 4 GH-sufficient children, 2 were moderately obese and 2 were morbidly obese. One of these children had clinical evidence of GH deficiency including a low IGF-1 level. Only one of the children had evidence of GH deficiency and a normal IGF-1 level, a pattern that could be attributable to obesity. We conclude that most short children with PWS have growth hormone deficiency and that this deficiency probably results from hypothalamic dysfunction.

Tissue specific and developmental expression of rat long-and medium-chain acyl-CoA dehydrogenases

Utilization of fatty acids for energy varies among mammalian tissues and during development due to changes in expression of enzymes of mitochondrial beta oxidation. To discern whether two related nuclear genes are expressed similarly, the tissue distribution and developmental profile of the rat long- and medium-chain acyl-CoA dehydrogenase (LCAD and MCAD) mRNAs were compared. A 1451 base full-length LCAD cDNA from neonatal rat aorta was used to study mRNA accumulation in adult and fetal rat tissues. LCAD and MCAD mRNAs were expressed in aorta, heart, and brown fat at levels 8-40 fold greater than in liver, kidney, and duodenum. Brain, placenta, ovary, testes, and skeletal muscle showed the least mRNA. Western blots of adult tissues with anti-rat LCAD antiserum showed corresponding amounts of LCAD protein subunits. LCAD mRNA was detectable in heart, liver, kidney, and brain of fetal rats and increased with age. LCAD and MCAD mRNAs were present in brown fat in 2-10 fold greater amounts compared to other tissues from the newborn period to the end of the weaning period. The high level of expression of LCAD and MCAD mRNA in aorta, heart, and brown fat likely reflects the high energy requirements of those tissues. Differential expression of LCAD and MCAD mRNAs reflects not only inherent gene prescribed programs, but also external influences such as hormones and diet.

Pyruvate carboxylase deficiency--insights from liver transplantation.

Pyruvate carboxylase deficiency, complex form, presents in early infancy with lethal metabolic acidosis, resulting from ketoacidosis and lactic acidemia. Renal tubular acidosis, hyperammonemia, and citrullinemia complete the picture. In an infant with this disease, large amounts of glucose ameliorated the ketoacidosis, but worsened the lactic acidosis. Orthotopic hepatic transplantation completely reversed the ketoacidosis and the renal tubular abnormality and ameliorated the lactic acidemia. Concentrations of glutamine in cerebrospinal fluid were low and did not improve with liver transplantation.

Fetal Tissue Derived From Spontaneous Pregnancy Losses Is Insufficient for Human Transplantation

Objective To determine if sufficient fetal tissue with desirable transplant characteristics can be obtained from spontaneous abortions. Methods A survey of fetal tissues collected from newly diagnosed spontaneous pregnancy losses from three Indianapolis hospitals was conducted from December 1992 to September 1993. Forty-nine of 356 mothers (13.8%) with spontaneous abortions or ectopic pregnancies consented to the evaluation of their products of conception by gross and microscopic pathologic examination, bacterial culture, cytogenetic analysis, cell culture, and maternal serologic tests. Results Forty-nine pregnancies (gestational age range 5–30 weeks) provided four identifiable embryos, 12 second-trimester fetuses, and one third-trimester fetus. Nine samples (18.4%) were of excellent or good quality on pathologic grading. Twenty-five of 38 samples tested (66%) grew pathogenic bacteria. Maternal serologic tests were negative for antibodies to human immunodeficiency virus, human T-cell lymphotropic virus, syphilis, and hepatitis B in all cases. One of 43 sera was reactive for hepatitis C, and 33 (77%) were positive for cytomegalovirus. Cytogenetic abnormalities were found in 25% of cultured samples. Five fetal brain samples had cell viabilities of 50% or more. Few viable fetal hepatocytes were found. Only two fetal brain samples (4.1%) were potential candidates for human transplantation. Conclusion Spontaneous pregnancy losses yield minimal usable tissue for human transplantation because of a lack of embryonic or fetal tissues, delayed collection, decomposition, genetic abnormality, and bacterial contamination.

An atypical case of Canavan disease with stroke-like presentation.

BACKGROUND Canavan disease is an autosomal recessive leukodystrophy caused by a deficiency of aspartoacylase. The disease has a severe course, with death occurring in the first few years of life. Atypical patients with mild courses have been reported, but acute presentations similar to stroke have not been well described. PATIENT DESCRIPTION We present a boy who presented at 4 months of age with seizures after an episode of cardiopulmonary arrest is discussed. RESULTS He was initially thought to have an ischemic watershed stroke based on his initial clinical presentation and magnetic resonance imaging. However, biochemical and follow-up radiologic evaluation were consistent with mild Canavan disease. DNA sequencing of the ASPA gene indicated one known mutation (A305E) and a novel mutation, L30V. Follow-up magnetic resonance imaging did not reveal the atrophy which would have been expected with watershed ischemia. Magnetic resonance spectroscopy demonstrated elevated N-acetyl aspartate to creatinine and N-acetyl aspartate to choline ratios. At 4 years of age, he was normocephalic, with mild clumsiness, speech delay, and seizures. CONCLUSIONS This childs unusual acute presentation, along with his prolonged mild course, raises questions about the relationship between biochemical signs of abnormal aspartoacylase function and clinical findings. This patient highlights the need for long-term clinical follow-up of children with mild Canavan disease to clarify the significance of these biochemical abnormalities.