The incidence of severe neonatal hyperbilirubinemia is higher in Asians than in whites. A case-control study was designed to investigate the effects of eight known risk factors [breast feeding, ABO incompatibility, premature birth, infection, cephalohematoma, asphyxia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and variant UDP-glucuronosyltransferase 1A1 (UGT1A1) gene] and a suspicious analog [organic anion transporter 2 (OATP 2) gene] on severe hyperbilirubinemia in Taiwanese neonates. The 72 study subjects and 100 hospital control subjects consisted of neonates with peak serum bilirubin levels Ն342 M and Ͻ256.5 M, respectively. The PCR-restriction fragment length polymorphism method was applied to detect the UGT1A1, OATP 2, and G6PD genes. Bilirubin is mainly produced in its unconjugated form by the turnover of erythrocytes. It may be transported by the organic anion transporter 2 (OATP 2) (1), and it is then conjugated with glucuronic acid through reaction with UDP-glucuronosyltransferase 1A1 (UGT1A1) in the liver before being excreted into the bile (2). The bilirubin level in neonates is much higher than in adults because the life span of the erythrocytes is relatively short and the capacity for bilirubin elimination is lower than in adults (3). The peak serum levels of unconjugated bilirubin in full-term Asian and American-Indian neonates are double those in white and black populations (4). The incidence of severe hyperbilirubinemia and kernicterus is also higher among newborn Asian infants (3). These findings suggest that genetic factors may be involved in the development of severe neonatal hyperbilirubinemia.Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common genetic defect, affecting Ͼ400 million individuals worldwide (5). Furthermore, G6PD deficiency was the main risk factor for development of severe hyperbilirubinemia in Taiwanese neonates in the past (6). The situation has improved, however, since neonatal G6PD screening tests and health education were instituted at the Cathay General Hospital (CGH) in Taipei and nationwide in Taiwan in 1981 (7) and 1987 (6), respectively. Recently, another genetic defect, a variation in the promoter area or within the coding region of the UGT1A1 gene, was associated with neonatal hyperbilirubinemia in whites and in Japanese and Taiwanese, respectively (8 -12). It has been determined that the A(TA) 7 TAA promoter variant or homozygous G to A variation at nucleotide 211 in

The activity of uridine-diphosphoglucuronosyl transferase 1 (UGT1) may influence the concentration of serum bilirubin. Because UGT1 is too labile to be measured with classical biochemical methods, we analysed the whole UGT1A1 gene in 290 healthy Taiwanese adults by using the polymerase chain reaction method, and investigated the relationship between UGT1A1 genotypes and serum bilirubin levels. The results showed that slightly more than 50% of the subjects had one or more variant sites in UGT1A1 gene. The most common variant was A(TA)6TAA/A(TA)7TAA (6/7) in the promoter area, followed by heterozygous variation within the coding region, compound heterozygous and homozygous variations. Among the four variant sites within the coding region, 211 G to A was the predominate one, 1091 C to T was a novel variation, and 686 C to A was associated with 6/7. Subjects with 6/7 or heterozygous variation within the coding region or compound heterozygous (plus one homozygous) variation had significantly higher bilirubin levels than those with wild UGT1A1 gene. When the 290 subjects were stratified into six groups according to their serum bilirubin concentrations, the bilirubin levels were correlated well to the frequencies of variant UGT1A1 gene. Our results show that there is a strong association between UGT1A1 gene and bilirubin levels in healthy Taiwanese adults. The occurrence of A(TA)7TAA allele was relatively rare and the variation rate within the coding region was much higher in Taiwanese compared to that in Caucasians.

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Molecular mutations of the glucose-6-phosphate dehydrogenase (G6PD) gene and clinical manifestations of neonatal jaundice in 112 male and 50 female Chinese neonates with G6PD deficiency were studied. In the 112 males, the nucleotide (nt) 1376 (G-->T) mutation was the dominant type (50.0%), followed by nt 1388 (G-->A) (16.1%), nt 493 (A-->G) (8.0%), nt 1024 (C-->T) (6.2%), nt 95 (A-->G) (5.4%), nt 392 (G-->T) (1.8%), nt 487 (G-->A) (1.8%), nt 871 (G-->A) (0.9%), and nt 1360 (C-->T) (0.9%). The nt 871 variant has not been reported in Taiwan before. The occurrence rates for nt 1376, nt 1388, nt 493, nt 95, and nt 1024 mutations in the 50 females were 44.0%, 18.0%, 12.0%, 6.0%, and 6.0%, respectively. The type of G6PD mutation in 10 male and 7 female neonates has not been identified yet. Although G6PD deficient neonates had higher frequency of phototherapy than G6PD normal neonates in both sexes, a significant difference in the prevalence of hyperbilirubinemia (peak bilirubin > or = 15.0 mg/dl) between G6PD deficient and normal neonates was found only in males. Further analysis showed that duration of phototherapy was longer in G6PD deficient male neonates than in the control group, while the outcome of phototherapy was better in subjects with non-nt 1376 mutations than subjects with the nt 1376 mutation. Most (78.3%) of the 23 G6PD deficient neonates who subsequently suffered from neonatal hyperbilirubinemia carried the nt 1376 mutation. The results of this study indicate that the nucleotide substitution at 1376 is the most common and important mutation for G6PD deficiency in Chinese neonates in Taiwan.

Some variations in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene are involved in the development of unconjugated hyperbilirubinemia. We hypothesize that other genetic factors may also be associated with this disease. A total of 227 adults with normal routine haematology and liver function (apart from bilirubin testing for which they revealed bilirubin > or = 25.7 micromol/l and unconjugated bilirubin/total bilirubin > or = 80%), and 235 sex- and age-matched controls, were recruited. All subjects were analysed for UGT1A1, glucose-6-phosphate dehydrogenase (G6PD) and organic anion transporter polypeptide 2 (OATP2) genotypes using polymerase chain reaction-restriction fragment length polymorphism. The results indicated that G6PD deficiency, variant UGT1A1 gene and variant OATP2 gene were risk factors for hyperbilirubinemia. The odds ratios (OR) (with 95% confidence interval) were 220.83 (34.68-1406.30), 73.61 (17.01-318.63), 45.15 (11.19-182.22), 15.46 (4.35-54.99) and 6.51 (1.83-23.09), respectively, for individuals featuring the common UGT1A1/OATP2 haplotypes homozygous/heterozygous, compound heterozygous/heterozygous, compound heterozygous/wild-type, heterozygous/heterozygous and heterozygous/wild-type variations amongst subjects with normal G6PD activity. Amongst the subjects with G6PD deficiency, the OR was 159.00 (24.57-1028.94) for individuals carrying variations in both UGT1A1 and OATP2 genes. The UGT1A1/OATP2 haplotypes homozygous/wild-type, homozygous/compound heterozygous and homozygous/homozygous for G6PD normal and variant/wild-type for G6PD deficient individuals were only observed in the case group, and not in the control group. Amongst hyperbilirubinemic adults, bilirubin values tended to parallel variation status of their haplotypes. Adults featuring certain haplotypes in UGT1A1, OATP2 and G6PD genes face a high risk of developing unconjugated hyperbilirubinemia.