Polymorphic acetylation of sulphamethazine in rural bedouin and urban-dwellers in Saudi Arabia

Isoniazid acetylation phenotyping in Saudi Arabs

AIMS

The present study is designed to investigate the acetylator status in Saudi Arabs.

METHODS

Isoniazid (INH) acetylation phenotyping was studied in 136 Saudi Arabs in Riyadh, Saudi Arabia, using a single plasma sample taken 3 h post-INH oral dose of 200 mg. Metabolic ratio (MR) of plasma acetyl-INH (Ac-INH) to INH was used to determine the acetylation phenotype.

RESULTS

The MR had a bimodal distribution with an antimode of 1.0. The frequency distribution of slow acetylators (MR < 1.0) was 94.9% (n = 129). Using Hardy-Weinberg Law, the gene frequency (q) of the recessive allele determining slow acetylator phenotype was found to be 0.97.

CONCLUSION

INH phenotyping suggests a high frequency of slow acetylators among Saudi Arabs. There was no association between the MR of plasma Ac-INH/INH and age or gender.

Potential chemoprotective effects of the coffee components kahweol and cafestol palmitates via modification of hepatic N-acetyltransferase and glutathione S-transferase activities

Coffee drinking has been associated with reduced incidence of colorectal cancer, possibly via chemoprotection/modification of the metabolism of dietary heterocyclic amine carcinogens such as 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) by kahweol and cafestol palmitates (K/C), two components of unfiltered coffee. Using the PhIP-exposed male Fisher F344 rat as a model, K/C have been shown to reduce colonic PhIP-DNA adducts by > 50%. We have used the male F344 rat to investigate the effects of dietary K/C (0.02-0.2% as a 1:1 mixture) on the metabolism of PhIP by N-acetyltransferase- (NAT), sulfotransferase- (SULT), and glutathione-dependent pathways. K/C decreased hepatic NAT-dependent PhIP activation by up to 80% in a dose-dependent manner. Conversely, hepatic glutathione S-transferase (GST) activity/expression increased, e.g., 3-4 fold toward 1-chloro-2,4-dinitrobenzene (total activity), up to 23-fold toward 4-vinylpyridine (rGSTP1), and approximately 7-fold for rGSTA2 protein. These effects had fully developed after 5 days of the test diet and persisted for at least 5 days after withdrawal of K/C. Hepatic glutathione increased two- to threefold and this increase was more short-lived than other changes. K/C did not modify hepatic SULT activity or colon NAT and GST activities. Benzylisothiocyanate and black tea, which have also been shown to reduce the formation of PhIP-DNA adducts in this model, had little effect on hepatic NAT, SULT, GST, or GSH. In primary culture of rat hepatocytes, both kahweol and cafestol palmitates reduced NAT activity by 80%. In summary, the unique potential of K/C to convert rapid acetylators to a slow acetylator phenotype, accompanied by GST induction, might contribute to chemoprevention against cancers associated with heterocyclic amines.

Acetylator phenotype in Behçet's disease

The purpose of this study was to determine the acetylator status in Behçet's disease (BD) patients and compare it to a matched group of normal individuals. Thirty-seven healthy volunteers and forty-one BD patients were included. Detailed history was taken from the patients. HLA-B51 was determined in the BD patients. In addition, the Clinical Manifestation Index (C.M.I.) was determined for each patient. Pathergy test was also done. After an overnight fast, each control subject and patient received a single oral dose of 100 mg of DDS. A blood sample was collected after 3 hours and the plasma was separated for determination of dapsone/monoacetyldapsone by HPLC. The frequency of slow acetylators in healthy individuals was 70.2%, while the frequency of rapid acetylators was 29.8%. The frequency of slow acetylators in BD patients was 53.7%, while the frequency of non-acetylators (undetected monoacetyldapsone MADDS in plasma) was 46.3%. There were no rapid acetylators among the BD patients. There was a strong negative association between the acetylator status and the severity of BD. In addition, acetylator status correlated with HLA-B51, in that BD patients with positive HLA-B51 were characterized by a very slow or non-acetylator status. Slow or non-acetylators had more severe BD. We conclude that BD patients have a unique acetylator status. This finding may have implications for the theories for the pathogenesis of the disease as well as for therapeutic aspects.

N-acetylation phenotyping using dapsone in a Jordanian population

1. The N-acetylation of dapsone (DDS) was studied in 160 unrelated healthy Jordanian volunteers. 2. The frequency of slow acetylators determined using the plasma monoacetyldapsone (MADDS) to DDS ratio (MADDS/DDS), was 67.5% with a 95% confidence interval of 59 to 76%. Slow acetylators had an acetylation ratio of less than 0.42. 3. Applying the Hardy-Weinberg Law, the frequency of the recessive allele controlling slow acetylation was found to be 0.82 +/- 0.02. 4. The frequency distribution histogram of the plasma MADDS/DDS ratio showed an apparent trimodal pattern. The number of homozygous (n = 16) and heterozygous (n = 36) rapid acetylators derived from the observed data did not agree with those predicted for the respective rapid acetylators (n = 5 and n = 47) according to the Hardy-Weinberg Law. The suggested antimode used to discriminate the two groups was 0.82. 5. The mean plasma concentration of MADDS and the mean plasma acetylation ratio were about three times lower in slow than in rapid acetylators. However, there was no difference in mean plasma DDS concentration between slow and rapid acetylators. 6. There was a significant correlation (r = 0.853, P less than 0.001) between plasma MADDS concentration and the acetylation ratio. For DDS such a correlation was absent (r = 0.059, P = 0.23).

The acetylator phenotypes of Saudi Arabians with coronary arterial atheroma

The acetylator phenotypes were determined by means of a sulfamethazine test in 101 Saudi Arabian patients with authenticated coronary atheroma; 65 were found to be slow acetylators. This distribution of phenotypes is not significantly different from that in 220 controls, 148 of whom were slow acetylators. This finding makes it unlikely that compounds containing a primary aromatic amino or a hydrazino group are involved in the aetiology or pathogenesis of coronary atheroma.

Acetylation phenotyping of isoniazid using a simple and accurate high-performance liquid chromatography

A simple, specific, accurate and reproducible method for the analysis of isoniazid and its major metabolite, N-acetylisoniazid in urine using high-performance liquid chromatography (HPLC) is described. The assay is performed after extraction of isoniazid, N-acetylisoniazid and 5-(4-methylphenyl)-5-phenylhydantoin (internal standard) from urine using a mixture of chloroform:isopropanol (70:30, v/v) and eluted from a 5 microns C-18 reversed phase column at ambient temperature with a mobile phase consisting of 10 mM sodium acetate:methanol:acetonitrile (40:40:20, v/v) containing 10 mM dioctylsulphosuccinate sodium and adjusted to pH 2.9 with sulphuric acid (less than 1 ml), at a flow rate of 1 ml/min with u.v. detection at 266 nm. Quantification was achieved by the measurement of the peak height ratio, and the absolute recoveries ranged from 94 to 99%. Within-day coefficients of variation ranged from 2.81 to 4.54% for isoniazid and from 2.37 to 3.75% for N-acetylisoniazid. Between-day CVs varied from 3.27 to 5.62% and from 2.5 to 4.91% for isoniazid and N-acetylisoniazid, respectively. Preliminary stability tests using a urine sample from a subject showed an increase in mean isoniazid concentration of about 25% after 1 month storage at -20 degrees C. The method was used for acetylation phenotyping of five individuals.

Acetylator phenotypes of Saudi Arabians by a simplified caffeine metabolites test

The authors examined acetylator phenotypes of 296 Saudi subjects of Arabic origin by measuring the molar concentration ratio of two caffeine metabolites, 5-acetylamino-6-formylamino-3-methyluracil (AFMU) and 1-methylxanthine (1MX), using a simplified version of a previously reported high-performance liquid chromatographic method. Spot urine samples were collected from the subjects who regularly drink coffee, tea, or other caffeinated beverages. The subjects were originally from different regions of Saudi Arabia but currently live primarily in the capital city of Riyadh. The day-to-day reproducibility of the molar concentration ratio of AFMU/1MX was established in 14 randomly selected subjects. These metabolites were stable in urine at 4 degrees and -20 degrees, but AFMU was unstable at room temperature (23 degrees). The frequency distribution data indicate that 72.3% of the subjects are of slow acetylator phenotype.

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.