Sulphation Deficit in “Low-Functioning” Autistic Children: A Pilot Study Antonino Alberti, Patrizia Pirrone, Maurizio Elia, Rosemary H. Waring, and Corrado Romano Background: Parents of autistic children and autism support groups often report that autistic episodes are exacerbated when the children eat certain foodstuffs such as dairy products, chocolates, wheat, corn sugar, apples, and bananas. The hypothesis that autistic behavior might be related to metabolic dysfunctions has led us to inves- tigate in a group of “low functioning” autistic children and in an age-matched control group each made up of 20 subjects, the sulphation capacity available. Methods: Utilizing the biochemical characteristics of paracetamol we evaluated by high performance liquid chromatography, the urine paracetamol–sulfate/paraceta- mol-glucuronide (PS/PG) ratio in all subjects following administration of this drug. Results: The PS/PG ratio in the group of autistic subjects gave a significantly lower result than the control group with p  .00002. Conclusions: The inability to effectively metabolize cer- tain compounds particularly phenolic amines, toxic for the CNS, could exacerbate the wide spectrum of autistic behavior. Biol Psychiatry 1999;46:420 – 424 © 1999 Society of Biological Psychiatry Key Words: Sulphation, autism, HPLC, paracetamol, urine, PS/PG ratio Introduction I t has been hypothesized that autistic children might have metabolic dysfunctions, and that some substances con- tained in the food they ingest make them behave in an autistic manner. Parents and autism support groups often report that the autistic episodes are exacerbated when the children eat certain foodstuffs such as dairy products, wheat, corn, sugar, apples, bananas, and chocolate. This has led to the belief that autism could be allergy induced (Rapp 1978; Rapp 1980; O’Bannion et al 1978; Knivsberg et al 1990). Preliminary studies have demonstrated that these chil- dren have a compromised capacity for sulphoconjugation and therefore, are unable to effectively metabolize numer- ous compounds particularly phenolic amines such as dopamine, tyramine, and serotonin (present in many food- stuffs), which function as neurotransmitters (Ngong 1994). These substances are normally metabolized into nontoxic, water soluble, readily excreted metabolites through a detoxification process of conjugation with sulphate in the gastrointestinal tract and in the liver after absorption, or by monoamine oxidase activity. Other detoxification pro- cesses include conjugation with glucuronic acid. Paracetamol (4-acetylaminophenol, acetaminophen) is a well known, widely used analgesic and antipyretic drug. It contains a phenolic grouping that is normally conjugated with glucuronic acid or sulphate before excretion in the urine. The glucuronic acid residue is transferred via UDPGA (uridine diphosphate glucuronic acid) and the microsomal glucuronyl transferase enzymes, while sul- phoconjugation (addition of sulphonate, SO 3 2- , residue) occurs via PAPS (3'-phosphoadenosine-5'-phosphosul- phate) as an active carrier of sulphate and the cytosolic sulphotransferase enzymes. Both these pathways give metabolites that are more water soluble, more readily excreted, and less toxic than the parent, paracetamol. Because pure reference metabolites are not readily avail- able, paracetamol glucuronide and paracetamol sulphate are measured by following the increase in paracetamol when the conjugates are hydrolysed by -glucuronidase or sulphatase (both hydrolytic enzymes), respectively. In any individual, although absolute amounts of the metabolites may vary over time, the ratio of the paracetamol sulphate excreted to paracetamol glucuronide is constant and the use of the PS/PG ratio enables metabolism to be compared over a population (Bonham Carter et al 1983; Rona et al 1994). Paracetamol has been used as a “probe” drug to estimate the relative contributions of glucuronide and sulphate pathways in a number of clinical dysfunctional states (Bradley et al 1991; Steventon et al 1990; Al- From the Departments of Pediatrics (AA, PP, CR) and Neurology (ME), Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy; and the School of Biochemistry (RHW), University of Birmingham, Birmingham, UK. Address reprint requests to Antonino Alberti, MD, Dept. of Pediatrics, Oasi Institute, Via Conte Ruggero, 73, 94018 Troina, Italy. Received August 25, 1997; revised March 2, 1998; revised September 8, 1998; accepted September 28, 1998. © 1999 Society of Biological Psychiatry 0006-3223/99/$20.00 PII S0006-3223(98)00337-0