The presence of ?-m-Hydroxyphenylhydracrylic acid in the urine of patients with ADHD and other neurodegenerative metabolic disorders
β-m-Hydroxyphenylhydracrylic acid (BHHA) is an aromatic organic acid frequently detected in the urine of patients. The diagnostic value of this acid is as yet unknown. Previous reports indicated that BHHA may be of bacterial origin. With the aim to establish the diagnostic value of BHHA organic acid GC-MS analyses were conducted on more than a thousand patients. The creatinine value for each urine sample was determined and the volumes of acid and derivatization reagent adjusted accordingly to facilitate the analysis of constant amounts of creatinine. The concentration of BHHA was determined using an internal standard, 3-phenylbutyrig acid. The urine of nineteen patients that showed elevated BHHA were further analysed to determine the presence of other abnormal metabolites. Phenylalanine (Phe) loading was also done on one of these samples and Phe and tyrosine (Tyr) were measured. The effect of aspartame on the concentration of Phe in this patient was also tested. A mercury test was also done on one of the patients, to determine the role that mercury plays in the transport of amino acids. The concentrations of BHHA ranged from trace amounts to more than a 1000 mmol/mol creatinine. Other metabolites with elevated levels in the urine of the nineteen patients included: phydroxyphenylacetic acid, m-hydroxyhippuric acid, p-hydroxyhippuric acid and p-hydroxyphenyllactic acid. These patients also excreted a few unique metabolites: benzoylsuccinic acid, phenylacrylylglycine, phenylacetylglycine and β -m-hydroxyphenylhydracrylglycine. Two of the patients also displayed elevated levels of phenylacetic acid and phenyllactate in their urine. One patient had undergone a pancreasectomy for reasons unknown to us. Clinical symptoms in most cases were not acute. ADHD and hyperactivity were the most common symptoms present in the clinical profile of these patients. Because phenylacetic acid and phenyllactic acid (that were, besides BHHA, present in two of the patients) may be indicative of a phenylalanine metabolic defect, a phenylalanine loading was carried out on two of the patients. The Phe loading caused a decreased absorption of Phe. Subsequently this was followed up with a tryptophan loading. Tyrosine absorption, analogous with the phenylalanine, was reduced but tryptophan absorption was normal, excluding Hartnup's Disease (HD). Aspartame loading did however; effect higher Phe levels, indicating that peptide absorption was normal. The metabolites found in the urine of the patients suggest that they may be of a bacterial origin. Compounds such as benzoylsuccinic acid are produced only by anaerobic microorganisms. Most of the other metabolites excreted at abnormal concentrations can also be characterised as bacterial metabolites excreted in the urine as a result of maldigestion or malabsorption. One patient in this study had undergone a pancreasectomy in which case malabsorption would be expected. This investigation should be seen as a pilot study and quite extensive research is still required before a final conclusion will be reached. Currently it seems that BHHA is excreted as a result of malabsorption or maldigestion, as was expected, but it does appear however, that BHHA may be an important indicator of defects that may cause these abnormalities.
- Health Sciences