Survey of the human acetylator polymorphism in spontaneous disorders

The role of arylamine N-acetyltransferases in chronic degenerative diseases: Their possible function in the immune system

Since their discovery, arylamine N-acetyltransferases 1 and 2 (NAT1 and NAT2, respectively) have been associated with the metabolism of xenobiotics. NAT2 is the main factor in the therapeutic success of tuberculosis treatment due to its role in the biotransformation of isoniazid. However, researchers have started to investigate the possible participation of NAT1 and NAT2 (NATs) in carcinogenesis, although the mechanisms have not been elucidated fully. NATs enzymatic activity is essential in some types of cancer, such as breast cancer and acute lymphoblastic leukemia. Whether NAT1 and/or NAT2 participate in insulin resistance level in diabetes mellitus or in the immune system remains to be explored. Therefore, it is clear that its role in cell physiology has more implications than just metabolizing compounds.

Assessment of UGT polymorphisms and neonatal jaundice

Elevation of the serum bilirubin level is a common, if not universal, finding during the first week of life. This can be a transient phenomenon that resolves spontaneously or can signify a serious or even life-threatening condition. There are many causes of hyperbilirubinemia and related therapeutic and prognostic implications. The diseases in which there is a primary disorder of the metabolism of bilirubin will be reviewed regarding their clinical presentation, pathophysiology, diagnosis, and treatment. These disorders-Gilbert's syndrome and Crigler-Najjar Syndrome-both involve abnormalities in bilirubin conjugation secondary to deficiency of bilirubin uridine diphosphate glucuronosyltransferase. The purpose of this article is to review the current understanding of the genetic polymorphisms that result in these diseases and discuss recent advances in diagnosis and treatment.

Stevens-Johnson syndrome caused by combined use of lamotrigine and fluoxetine and review of the literature

Stevens-Johnson syndrome (SJS) is a rare, life-threatening acute allergic drug reaction presenting with target lesions and blebs of epidermis. Although a variety of etiologies such as infections and underlying malignancies have been implicated as potential causes of SJS, drugs remain the predominant inciting agent. This report presents a SJS case due to combined use of lamotrigine and fluoxetine. A 41-year-old man was admitted to our clinic with fever, skin eruptions (especially on the face and trunk) and lesions around the mouth. The patient’s history revealed lamotrigine and fluoxetine use during the previous three weeks for major depression. Dermatological examination revealed a typical clinical picture of SJS; his psychotropic medications were all stopped. While topical and ocular prednisolone (1mg/kg/day) cares were initiated, steroid dosage was reduced within 15 days. The condition of patient rapidly improved through this treatment. Effective management of SJS begins with prompt recognition of the entity, combined with attention to each of the major organs that may be affected, potential comorbidities and withdrawal of all potentially causative drugs. Clinicians should bear in mind the possibility that drugs with potential risk in developing SJS must be used carefully.

Pharmacology and pharmacogenetics of chemotherapeutic agents

The last decade the field of oncology has seen the introduction of several efficacious chemotherapeutic agents. However the benefits achieved have been modest at best. The choice of chemotherapeutic agent is often empirical and geared to fit the average patient with the result that approximately 40% of patients may be receiving the wrong drug. With greater understanding of the mechanisms behind the heterogeneity observed across patient populations, both in terms of efficacy and toxicity of a variety of therapeutic agents, research has now focused on individualizing treatment strategies by incorporating a combination of physiological variables, genetic characteristics and environmental factors together with the traditional tumor characteristics that currently drives clinical decision making. This review focuses on defining some of the principle components of personalized medicine. In addition we will review the pharmacological and pharmacogenetic predictors of toxic effects of chemotherapeutic agents drawing on examples of commonly used agents in oncology.

Stevens-Johnson syndrome: pathogenesis, diagnosis, and management

Cutaneous drug reactions are the most common type of adverse drug reaction. These reactions, ranging from simple pruritic eruptions to potentially life-threatening events, are a significant cause of iatrogenic morbidity and mortality. Stevens-Johnson syndrome (SJS) is a serious and potentially life-threatening cutaneous drug reaction. Although progress has been made in the management of SJS through early detection, prompt hospitalization, and immediate cessation of offending agents, the prevalence of permanent disabilities associated with SJS remains unchanged. Nevertheless, despite being a problem that is global in scope, government and health care agencies worldwide have yet to find a consensus on either diagnostic criteria or therapy for this disorder. Here, we provide the internist and emergency room physician with a brief review the SJS literature and summarize the latest recommended interventions with the hope of improving early recognition of this disease and prevention of permanent sequelae and mortality that frequently complicate SJS.

Pharmacogenetics of the arylamine N-acetyltransferases

The arylamine N-acetyltransferases (NATs) are involved in the metabolism of a variety of different compounds that we are exposed to on a daily basis. Many drugs and chemicals found in the environment, such as those in cigarette smoke, car exhaust fumes and in foodstuffs, can be either detoxified by NATs and eliminated from the body or bioactivated to metabolites that have the potential to cause toxicity and/or cancer. NATs have been implicated in some adverse drug reactions and as risk factors for several different types of cancers. As a result, the levels of NATs in the body have important consequences with regard to an individual's susceptibility to certain drug-induced toxicities and cancers. This review focuses on recent advances in the molecular genetics of the human NATs.

Biomonitoring of urinary aromatic amines and arylamine hemoglobin adducts in exposed workers and nonexposed control persons

The renal excretion of arylamines in occupationally exposed and nonexposed subjects was measured by a gas chromatography-electron capture detector method. Additionally, in the occupationally exposed persons hemoglobin adduct levels of arylamines were determined by a liquid chromatography-electrochemical detector method, together with the individual acetylator status. The aromatic amines aniline, p-toluidine, 2-naphthylamine, and 4-chloro-o-toluidine were detected in the urine of nonsmoking subjects who were not occupationally exposed to arylamines. Significantly higher concentrations of aniline, o-toluidine, m-toluidine, 2-naphthylamine, and 4-methyl-1,3-phenylenediamine could be observed in the urine of smoking control persons in comparison to nonsmokers. Comparison of smokers and nonsmokers in a group of workers primarily exposed to aniline and 4-chloroaniline revealed significant differences (P < 0.05) in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 2-naphthylamine. The slow acetylators in this group produced significantly more hemoglobin adducts of aniline and 4-chloroaniline than did the fast acetylators. In slow acetylators among the smoking workers there was a significant increase in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 4-chloroaniline and m-toluidine. The results indicate that there are influences of smoking habits and acetylator status on the levels of arylamine hemoglobin adducts as well as urinary arylamine concentrations. Hemoglobin adducts seem to be good parameters for monitoring aniline and 4-chloroaniline exposure at the workplace, especially if the acetylator polymorphism can be taken into account. 4-Aminodiphenyl hemoglobin adducts might be good parameters for monitoring individual smoking habits. The determination of urinary arylamine concentrations provides additional information concerning acute exposures to aromatic amines.

Low N-acetylating capacity in patients with Stevens-Johnson syndrome and toxic epidermal necrolysis

Low constitutive N-acetylating capacity has been implicated as a predisposing factor for the development of adverse reactions to certain drugs. This prompted us to investigate whether the N-acetylating capacity of patients with serious cutaneous adverse reactions, i.e., Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) differed from that of healthy control subjects. N-acetylating activity was measured in hair root cells by preparing a homogenate from freshly extracted hair roots and assessing acetyl-CoA-dependent N-acetylation by RP-HPLC using 2-aminofluorene as a substrate. Samples were obtained from hospitalized patients suffering from acute SJS and TEN or from healthy controls. All patients with SJS and TEN were found to have a low N-acetylating capacity (0.85 nmol/mg/min compared to 2.21 nmol/mg/min in controls, p < 0.05). Based on these findings, a low constitutive N-acetylating capacity may be one of the predisposing factors for the development of serious cutaneous adverse reactions to drugs that require N-acetylation in these patients.

The influence of pyruvic acid on the pharmacokinetics of sulphadiazine in rabbits

During the past few years, acetylation polymorphism has been shown to be a proven, established fact, and N-acetyltransferase, an enzyme that transfers an acetyl group to the substrate, has been recognized as the main factor in acetylation polymorphism. In a recent study, a significant difference between the acetylation phenotype and plasma pyruvic acid (PA) concentration in rabbits was found. In this report, the influence of PA on the pharmacokinetics of sulphadiazine (SDZ), a drug that has been used in pharmacogenetic studies of acetylation, was studied. By using a loading dose of 300 mg kg-1, and an infusion rate of 7.5 mg min-1 kg-1 of PA, the concentration of PA reached a steady state (Css approximately equal to 100 micrograms mL-1) in 30 min. During PA infusion in rapid-acetylation rabbits, no significant changes were found in any of the pharmacokinetic parameters for SDZ. However, differences were found in the beta half-life, AUC, clearance, and k10 of SDZ in slow acetylators: the beta half-life decreased from 115.74 +/- 12.47 min to 62.96 +/- 4.36 min (p < 0.001); AUC decreased from 10,617.38 +/- 1179.81 micrograms min mL-1 to 6217.14 +/- 391.32 micrograms min mL-1 (p < 0.001); clearance increased from 0.0044 +/- 0.0008 L min-1 kg-1 to 0.0068 +/- 0.0007 L min-1 kg-1 (p < 0.001); and k10 increased from 0.0090 +/- 0.0009 min-1 to 0.0193 +/- 0.0028 min-1 (p < 0.005). The reason for this may be that PA influences the elimination of SDZ in slow-acetylation rabbits.

The N-acetyltransferase (NAT) gene: an early risk marker for diabetic nephropathy in Japanese type 2 diabetic patients?

A point mutation in the N-acetyltransferase gene (NAT2) leads to the recessive trait for the slow acetylator phenotype, which is suggested to be associated with microalbuminuria in Type 1 diabetic patients. Our study was designed to elucidate whether the NAT2 gene polymorphism would be a marker for diabetic nephropathy. The genotype distribution was studied in Japanese Type 2 diabetic patients with established nephropathy (n = 43), with microalbuminuria (n = 24), with normoalbuminuria (n = 18), non-diabetic patients with kidney disease (n = 62), and healthy control subjects (n = 51). The different alleles of the NAT2 gene were identified by restriction fragment length polymorphism analysis: the gene was amplified from genomic DNA (obtained from blood) and digested with restriction enzymes. The genotype was classified by the specific pattern of each allele (M1, M2, M3) in the agarose electrophoresis and ethdium bromide fluorescence. Alleles M1, M2, and M3 of NAT2 gene were found in 42.4% of all subjects (40.0% in all diabetic patients and 44.2% in all non-diabetic controls). The prevalence of the genotype, encoding the slow acetylator phenotype, was 7.0% in diabetic patients with established diabetic nephropathy, 20.8% in microalbuminuric diabetic patients, 0% in normoalbuminuric diabetic patients, 6.5% in non-diabetic patients with kidney disease, and 7.8% in healthy control subjects. The differences in the prevalence were non-significant. The results suggest that the N-acetyltransferase gene polymorphism may not be a genetic risk marker for diabetic nephropathy in Japanese Type 2 diabetic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylator polymorphism in multiple sclerosis

To elucidate whether any relationship exists between genetic polymorphic acetylation and the risk for multiple sclerosis (MS), we determined this polymorphism, using sulphamethazine, in 71 patients with definite MS and in 268 age-matched controls. Thirty-seven patients (52.1%) and 151 controls (56.3%) were classified as slow acetylators (not significant difference). No relation was found between acetylator polymorphism and age at onset of disease in MS patient's group. Our results do not support the existence of any relationship between acetylator polymorphism and the risk for MS.

Future Directions for Pharmacogenetics

The discipline of pharmacogenetics will continue to expand as scientific and clinical investigations increase our understanding of genetic variabilities in drug metabolism and response. These research efforts will include determination of molecular mechanisms for the different polymorphisms and evaluation of their clinical significance. The availability of molecular methodologies such as restriction fragment length polymorphisms analysis, polymerase chain reaction, and expression of cDNAs in cell cultures will further the investigative work in detection of normal and mutant alleles, identification of new substrates for different polymorphic metabolizing enzymes, and evaluation of mechanisms of individual susceptibility to biological disorders. Other areas such as the role of pharmacogenetics in drug development and regulatory control, in evaluation of potential drug-drug interactions, ethnic variation in polymorphic metabolism, and response, also need to be evaluated.

Genetically Determined Polymorphisms in Drug Metabolism

Many factors can influence the metabolism and disposition of drugs. Genetically determined differences in an individual's capacity to metabolize drugs are known causes of interindividual and interethnic variabilities in drug disposition and response. In general, a poor metabolizer for a specific metabolic pathway would likely develop adverse effects, and an extensive metabolizer for the same metabolic pathway might have less than optimal response. Although there are different types of polymorphism in drug metabolism, polymorphisms in debrisoquine-type oxidation, S-mephenytoin oxidation, and N-acetylation have been the most extensively studied. This article will present the basic concepts of pharmacogenetics, review the major types of metabolic polymorphisms, outline ways to determine phenotyping and genotyping differences in metabolizing enzyme activities, and discuss how these differences relate to drug metabolism, response, and toxicity. When evaluating drug response and adverse reactions in individual patients, an awareness of genetic differences in metabolic capacities would help contribute to optimization in drug therapy.

Structure and restriction fragment length polymorphism of genes for human liver arylamine N-acetyltransferases

Genomic DNA clones coding for polymorphic and monomorphic arylamine N-acetyltransferases (NAT) of human liver were isolated from a genomic DNA library, and their restriction maps and partial nucleotide sequences were determined. Messenger RNA for monomorphic NAT was coded in one exon, while mRNA for polymorphic NAT was coded in two exons; the 5'-noncoding region was located in one exon 8 kb upstream from another exon containing the coding and 3'-noncoding regions. Recently, we have shown that there are three types of polymorphic NAT gene; one of the genes corresponds to a high NAT activity, while the other two genes give rise to a low NAT activity. The restriction fragment length polymorphism (RFLP) was analyzed by Southern blot hybridization of genomic DNAs from homozygotes of the three polymorphic NAT genes using various fragments of the cloned NAT gene. RFLPs of polymorphic NAT gene were observed in coding and 3'-flanking region upon digestion with BamHI and KpnI.

The effect of diabetes on the in vivo acetylation capacity of the spontaneously diabetic, insulin-dependent BB/Edinburgh Wistar rat

In contrast to previous studies using chemically-induced diabetic rats, the in vivo acetylation of sulphamethazine is increased in spontaneously diabetic, insulin-dependent BB/Edinburgh (BB/E) Wistar rats compared to non-diabetic control animals from the same colony. In both diabetic and non-diabetic rats, male animals had a significantly higher acetylation capacity than female animals. The percentage recovery of the administered dose was significantly higher in urine samples from female rats.

Pharmacogenetics and drug metabolism: an Irish perspective

Genetic factors, particularly in relation to control of liver drug metabolism, are a major cause of variability in the response to drugs. In 145 Irish subjects 48% were fast acetylators of sulphadimidine in contrast to 80% in Chinese subjects. Eleven (7.6%) of our Irish population showed an improved ability to oxidise delrisoquine. The therapeutic implications of these findings are discussed.

Genetic polymorphisms of drug metabolism

The molecular mechanisms of 3 genetic polymorphisms of drug metabolism have been studied at the level of enzyme activity, enzyme protein and RNA/DNA. As regards debrisoquine/sparteine polymorphism, cytochrome P-450IID6 was absent in livers of poor metabolizers; aberrant splicing of premRNA of P-450IID6 may be responsible for this. Moreover, 3 mutant alleles of the P-450IID6 locus on chromosome 22 associated with the poor metabolizer phenotype were identified by Southern analysis of leucocyte DNA. The presence of 2 identified mutant alleles allowed the prediction of the phenotype in approximately 25% of poor metabolizers. The additional gene-inactivating mutations which are operative in the remainder of poor metabolizers are now being studied. Regarding mephenytoin polymorphism, although the deficient reaction, S-mephenytoin 4'-hydroxylation, has been well defined in human liver microsomes, the mechanism of this polymorphism remains unclear. All antibodies prepared to date against cytochrome P-450 fractions with this activity recognize several structurally similar enzymes and several cDNAs related to these enzymes have been isolated and expressed in heterologous systems. However, which isozyme is affected by this polymorphism is not known. As regards N-acetylation polymorphism, N-acetyltransferases have been purified from human liver, specific antibodies prepared; it was observed that immunoreactive N-acetyltransferase is decreased or undetectable in liver of "slow acetylators". Two genes that encode functional N-acetyltransferase were characterized. The product of one of these genes has identical activity and characteristics as the polymorphic liver enzyme. Cloned DNA from rapid and slow acetylator individuals has been analyzed to identify the structural or regulatory defect that causes deficient N-acetyltransferase.

The effect of streptozotocin-induced diabetes on the in vivo acetylation capacity and the in vitro blood N-acetyltransferase activity of the adult male Sprague-Dawley rat

Induction of experimental diabetes using streptozotocin significantly reduced the extent of sulphamethazine acetylation by Sprague-Dawley rats. This treatment did not significantly change the total amount of sulphonomide excreted in the urine. The in vitro blood N-acetyltransferase activity of rats treated with streptozotocin was significantly higher than that of untreated animals. Increasing the in vitro glucose concentration of blood samples from both groups significantly increased the amount of acetylsulphamethazine produced.

Human arylamine N-acetyltransferase genes: isolation, chromosomal localization, and functional expression

N-Acetylation by hepatic arylamine N-acetyltransferase (NAT, EC 2.3.1.5) is a major route in the metabolism and detoxification of numerous drugs and foreign chemicals. NAT is the target of a common genetic polymorphism of clinical relevance in human populations. We have used our recently isolated rabbit cDNA rnat to clone three human NAT genes from human leukocyte DNA. None of the three genomic coding sequences was interrupted by introns. Two genes, designated NAT1 and NAT2, each possessed open reading frames of 870 bp. Both genes have been assigned to human chromosome 8, pter-q11. Following transfection they were transiently expressed in monkey kidney COS-1 cells. NAT1 and NAT2 gave rise to functional NAT proteins, as judged by their NAT enzyme activity with the arylamine substrate sulfamethazine. Western blots with NAT-specific antisera detected proteins of apparent molecular weight of 33 and 31 kD in NAT1- and NAT2-transfected cultures, respectively. The product of NAT2 had an identical apparent molecular weight as that of NAT detected in human liver cytosol. The deduced amino acid sequence of NAT2 also contained 6 peptide sequences which had previously been determined from tryptic peptides of the polymorphic NAT purified from human liver. These data suggest that NAT2 encodes the polymorphic NAT protein. The third gene, NATP, had multiple deleterious mutations and did not encode a functional NAT protein; it most likely represents a pseudogene.

N-acetylation pharmacogenetics: a gene deletion causes absence of arylamine N-acetyltransferase in liver of slow acetylator rabbits

The New Zealand White rabbit provides a widely used animal model for the human acetylation polymorphism, which confers marked interindividual variation in the effect and toxicity of numerous drugs, chemicals, and potential carcinogens. The relationship of a recently isolated cDNA clone, designated rnat, to genetically polymorphic arylamine N-acetyltransferase (NAT; acetyl-CoA:arylamine N-acetyltransferase, EC 2.3.1.5) of rabbit liver was established by its expression in monkey kidney COS-1 cells: (i) cytosols from transfected cultures contained high levels of an Ac-CoA-dependent NAT activity, which was kinetically indistinguishable from that observed in cytosols from livers of genetically rapid-acetylator rabbits; (ii) transfected cells also contained an immunoreactive protein, recognized by NAT-specific antibodies, with identical electrophoretic mobility to NAT from rabbit liver. The rnat clone and anti-NAT antibodies were then used to study the relationship between NAT activity, liver enzyme protein, and the level of mRNA in livers from in vivo phenotyped rapid- and slow-acetylator rabbits. Livers from slow acetylators were devoid of both immunodetectable NAT protein and its corresponding mRNA. Analysis of genomic DNA with a panel of restriction enzymes revealed the loss of specific hybridizing bands in the DNA of slow-acetylator rabbits. These data strongly suggest that defective arylamine N-acetylation in the rabbit model is caused by a gene deletion resulting in an absence of specific mRNA and NAT enzyme protein.

Genetically determined N-acetylation and oxidation capacities in Japanese patients with non-occupational urinary bladder cancer

Genetically determined polymorphisms of N-acetylation and oxidative capacity have been studied using dapsone and metoprolol in 51 Japanese patients with spontaneous bladder cancer and 203 healthy control subjects. The results for N-acetylation pharmacogenetics were against the initial expectation that there would be a preponderance of slow acetylators in the cancer group, as 3 such patients (5.9%) were found as compared to 13 (6.4%) in the healthy group. There was no poor metabolizer (PM) of metoprolol in the cancer group, whereas in the healthy group one (0.5%) was a PM. There were no significant differences between the groups in the frequency of slow acetylator and poor oxidiser phenotypes, or in the frequency distribution profiles of acetylation (monoacetyldapsone/dapsone) and oxidative metabolic ratio (log metoprolol/alpha-hydroxymetoprolol). The results indicate that neither N-acetylation nor the debrisoquine/sparteine-type oxidative phenotype and/or capacity represent a genetic predisposition to spontaneous bladder carcinogenesis in Japanese patients. In the normal Japanese population there is a great predominance of rapid acetylators and extensive oxidisers.

Acetylator phenotype and congenital malformations

The hypothesis has been tested that an unusual maternal acetylator phenotype can predispose to congenital malformations in the fetus. The acetylator phenotype of normal caucasian control women and of mothers of malformed children was established by measuring urinary sulphadimidine and its acetylated metabolite. A further control group was the fathers of the malformed newborn. The malformations studied were facial-cleft, spina-bifida and congenital heart disease. The acetylator phenotype was shown not be modified by pregnancy. 49 of 100 (49%) control women were rapid acetylators. Amongst the 108 mothers of malformed babies, 56 (52.8%) were slow acetylators and 52 (47.2%) were fast acetylators, 42 out of 83 (50.5%) of the fathers of malformed were slow acetylators and 41 (49.5%) were fast acetylators. Thus, the acetylator phenotype of the mothers of malformed children is no different from the acetylator phenotype of controls.

Acetylator polymorphism in Parkinson's disease

Acetylator phenotype has been determined using sulphamethazine in 100 patients with Parkinson's disease and in 93 age-matched normal control subjects. Sixty-nine patients and 54 control subjects were classified as slow acetylators (NS). No relation was found among acetylator polymorphism and age at onset or clinical stage of disease. Amongst slow acetylators, the percentage of acetylated sulphamethazine in plasma was significantly lower in patients than in controls. Despite this finding, the results do not support any relationship between acetylator polymorphism and the risk of developing Parkinson's disease.

N-acetylation and serotonergic measures in a group of psychiatric patients

Serotonin is N-acetylated to melatonin. The purpose of this study was to explore the possibility of N-acetylation of dapsone reflecting serotonergic activity. The ratio of monoacetyldapsone/dapsone (MAD/DDS) in plasma, 5-HIAA in CSF, and imipramine-binding to platelets were investigated in a group of psychiatric patients, diagnosed according to the DSM-III as affective disorders, schizophrenia, and personality disorders. There was no significant correlation between either of the serotonergic estimates and N-acetylation in the whole patient group or in diagnostic subgroups of patients. Sixty-four percent of the patients were slow N-acetylators (MAD/DDS less than 0.4), which is a ratio in line with several other studies of psychiatric patients. Among patients with affective disorders, all unipolar patients were slow N-acetylators, while five out of six bipolar patients were fast N-acetylators. The N-acetylation of patients with a history of suicide attempt did not differ from those without. The discrepancy in N-acetylation between uni- and bipolar patients might again address the issue of them representing two different biochemical and genetic disorders.

N-acetylation polymorphism of dapsone in a Japanese population

1. The N-acetylation of dapsone (DDS) was studied in 182 unrelated healthy Japanese subjects. The frequency of slow acetylators determined using the plasma monoacetyldapsone (MADDS) to DDS ratio (MADDS/DDS, slow acetylators less than 0.30 and rapid acetylators greater than 0.35) at 3 h after an oral dose of DDS (100 mg) was 6.6% (12 of the 182 subjects) with a 95% confidence interval of 3.8 to 11.2%. 2. The frequency distribution histogram of the plasma MADDS/DDS ratio showed an apparent trimodal pattern. However, the numbers of heterozygous (n = 105) and homozygous rapid acetylators (n = 65) derived from the observed data did not agree with those predicted for the respective rapid acetylators (n = 70, and n = 100) by applying the Hardy-Weinberg Law, when the suggested antimode of 0.85 discriminating these two rapid acetylators was employed. 3. The incidence of slow acetylators was unexpectedly lower in the males (1.4%, 1 of the 69 subjects, with a 95% confidence interval of 0.2 to 7.7%) compared with the incidence in the females (9.7%, 11 of the 113 subjects, with a 95% confidence interval of 5.5 to 16.6%). The difference reached a marginally significant level (Fisher's exact probability test, P = 0.02). 4. The mean plasma concentration of MADDS was significantly (P less than 0.001) lower in the slow compared to the rapid acetylators and there was a highly significant correlation (rs = 0.757, P less than 0.001) between plasma MADDS levels and MADDS/DDS ratios. 5. Slow acetylators showed a significantly (P less than 0.001) lower urinary MADDS/DDS ratio and excreted less (P less than 0.001) MADDS than rapid acetylators.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylator polymorphism in discoid lupus erythematosus

Acetylator phenotype was determined, using sulphamethazine, in 37 patients with histologically confirmed discoid lupus erythematosus, who were free from visceral damage, and in 157 normal control subjects. Twenty patients (54%) and 90 control subjects (57.4%) were slow acetylators (p not significant). Acetylator polymorphism appears not to be related to the risk of developing pure cutaneous discoid lupus erythematosus.

An epidemiologic approach to ecogenetics

Although "ecogenetics" seeks to examine genetically mediated differences in susceptibility to environmental agents, researchers often examine the relation between genetic markers and disease without regard to environmental determinants. By using epidemiologic definitions of genotype-environment interaction, it can be shown that the relative risk of disease for the genetic marker is a function of the frequency of exposure to the environmental agent, the strength of interaction between the genotype and the agent, and the specificity of the environmental effect vis-à-vis the genotype. Using examples from the literature, we illustrate under six patterns of genotype-environment interaction that the relative risk associated with the marker can fluctuate markedly. However, with infrequent exposures, the relative risk is close to unity (implying no genetic effect) even in the face of strong genotype-environment interaction. Alternatively, elevated relative risks imply a frequent environmental exposure or a strong pattern of interaction. We suggest that genetic marker-disease associations be evaluated within the context of an epidemiologic study design that considers specific environmental determinants of risk.

Influence of age, sex and body weight on the dapsone acetylation phenotype

The acetylation of dapsone (DDS) was determined by estimation of the ratio of monoacetyldapsone (MADDS) to DDS concentrations in plasma following a single dose of DDS in 337 white British subjects (193 female; 144 male). The percentage of slow DDS acetylators in the whole group was 60.3%. There was no statistically significant difference in this proportion between 191 elderly subjects (age greater than 65 years) and 143 young subjects (age less than 30 years). Although there was a small (66.3%) but significant (P = 0.033) preponderance of slow acetylators in the young male group there was no difference in the distribution of acetylator phenotypes between the sexes among either the elderly group or in the whole population studied. No correlation was found between absolute body weight and MADDS/DDS ratios.

The effect of glucose on acetylation status

Forty-nine healthy volunteers (47 male, 2 female) had their sulphadimidine acetylator status determined on a control day and on a second occasion when they were given an oral glucose load. They were classified as fast and slow acetylators using the standard urine method and as fast, slow and intermediate acetylators using calculated metabolic and total body clearances. Twenty-seven (55%) were slow acetylators and this proportion was not altered by glucose loading either with or before sulphadimidine ingestion. On the control day, five (10%) were fast and 17 (35%) were intermediate acetylators but these sub-groups were not clearly distinguishable from each other when glucose was given. The glucose load did not cause any individual to change from slow to fast categories. Two type 2 (insulin independent) diabetics also showed no difference in acetylator status when studied with widely different blood glucose concentrations. We conclude that glucose can induce minor increases in sulphadimidine clearance but is unlikely to alter phenotypic acetylation status. Previous observations of an increased incidence of fast acetylators in diabetics may therefore indicate a genetic marker.

Further evidence for the lack of association between acetylator phenotype and systemic lupus erythematosus

An association between host acetylator phenotype and idiopathic systemic lupus erythematosus (SLE) has been sought for over a decade, without a definitive result. We have observed that the frequency of the slow acetylator phenotype was similar in 64 patients with idiopathic SLE (38%), 60 healthy volunteers (50%), and 52 non-SLE medical service patients (44%). The slow acetylator phenotype was not more frequent among subgroups of the SLE patients defined by demographic features or specific manifestations of disease. Our results, as well as a majority of previously published results, do not provide evidence for an association between acetylator phenotype and idiopathic SLE.

The acetylator phenotypes of Saudi Arabian diabetics

There is a significant association between the rapid acetylator phenotype and diabetes in European populations. Diabetes is a common problem in Saudi Arabians with some clinical features differentiating it from the disorder in Europeans. A series of 100 Saudi diabetics and 100 Saudi controls has been acetylator phenotyped. The controls showed 33 rapid acetylators (R) and 67 slow acetylators (S), a result closely similar to that previously published for the Saudi population. Overall the diabetics showed 27 R and 73 S which is not significantly different from the controls. The type I diabetics, however, showed two R and 22 S which is not only significantly different from the controls and the type II diabetics, but also the reverse of the association found in European populations.