Inhibition of heme oxygenase activity using a microparticle formulation of zinc protoporphyrin in an acute hemolytic newborn mouse model.

BACKGROUND: Increased bilirubin production due to hemolysis can lead to neonatal hyperbilirubinemia. Inhibition of heme oxygenase (HO), the rate-limiting enzyme in heme catabolism, by metalloporphyrins (Mps) may be an ideal preventive strategy for neonatal hemolytic disease. Zinc protoporphyrin (ZnPP) is a naturally occurring Mp, potent, not phototoxic, with minimal HO-1 upregulation, but is not orally absorbed. Recently, we designed a lipid-based ZnPP formulation (ZnPP-Lipid), which is orally absorbed by newborn mice. Here, we evaluated the efficacy of ZnPP-Lipid in heme-loaded newborn mice, a model analogous to hemolytic infants. METHODS: After 24 h of heme administration (30 µmol/kg s.c.), 4-d-old mice were given 30 µmol ZnPP-Lipid/kg via intragastric injections. After 3 h, liver and brain HO activity were measured. HO-1 upregulation was assessed by determinations of HO-1 protein, promoter activity, and mRNA by Western blot, in vivo bioluminescence imaging, and RT-PCR, respectively. RESULTS: After heme loading, liver HO activity significantly increased ~1.6-fold, which was inhibited in a dose-dependent manner by ZnPP-Lipid. A dose of 30 µmol/kg returned activity to control levels. Brain HO activity was not inhibited. No significant increases in liver and brain HO-1 protein, promoter activity, and mRNA were observed. CONCLUSION: ZnPP-Lipid is effective and thus has potential for treating neonatal hyperbilirubinemia due to hemolysis.

UGT1A1 gene mutations and neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations.

BACKGROUND: Uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene mutation was shown to be responsible for neonatal hyperbilirubinemia. This study aimed to investigate whether UGT1A1 gene mutation is associated with neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations. METHODS: Two hundred and eighteen infants with hyperbilirubinemia (118 Heiyi Zhuang, 100 Han) and 190 control subjects (110 Heiyi Zhuang, 80 Han) were enrolled. Polymerase chain reaction and gene sequencing were used to detect the TATA-box and exon 1 of UGT1A1. RESULTS: (TA)7 insertion mutation, 211G>A (G71R), 686C>A (P229Q), and 189C>T (D63D) were detected. Logistic regression analysis showed odds ratios (OR) of 2.64 (95% confidence interval (CI) 1.64-4.24; P < 0.001) and 0.69 (95%CI 0.43-1.10; P = 0.115) for neonates who carried UGT1A1 G71R and (TA)7 insertion mutation, respectively. G71R homozygosity increased the odds of dangerous bilirubin levels by a factor 34.23, and G71R heterozygosity only by 2.10. CONCLUSION: We found that UGT1A1 G71R mutation is a risk factor for neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations. Meanwhile, the UGT1A1 (TA)7 insertion mutation is not associated with neonatal hyperbilirubinemia in the two ethnic groups.

Association of HMOX1 gene promoter polymorphisms with hyperbilirubinemia in the early neonatal period.

BACKGROUND: Heme oxygenase (HO) is the rate-limiting enzyme in the heme degradation pathway that produces bilirubin. The promoter region of human heme oxygenase-1 (HMOX1) contains a polymorphic (GT)n repeat that can regulate gene expression. Here, we investigated the association of (GT)n repeat length in the HMOX1 promoter region with neonatal hyperbilirubinemia in a population of Japanese term neonates. METHODS: Using polymerase chain reaction and fragment analysis, we determined the number of (GT)n repeats in 149 Japanese neonates. To omit the effects of the G71R mutation in uridine diphosphoglucuronosyltransferase on hyperbilirubinemia, we excluded 41 neonates with the G71R mutation. As a result, 25 neonates with hyperbilirubinemia and 83 non-hyperbilirubinemic controls were included in this prospective case-control study. Allele and genotype frequencies of (GT)n repeats in the HMOX1 gene were compared between hyperbilirubinemic and non-hyperbilirubinemic control neonates. RESULTS: The prevalence of short alleles (< 22 (GT)n repeats) was significantly higher in hyperbilirubinemic than in control neonates (18% vs 7%, P = 0.015). Hyperbilirubinemia was more frequent in homozygous or heterozygous short allele carriers than control neonates (28% vs 11%, respectively, P = 0.03). Possession of short alleles was significantly associated with the development of neonatal hyperbilirubinemia (OR, 3.1; 95%CI: 1.03-9.53). CONCLUSIONS: Infants carrying short alleles (< 22 (GT)n repeats) in the HMOX1 gene promoter region appear to be at a higher risk for developing neonatal hyperbilirubinemia.

Impact of fatty acids on human UDP-glucuronosyltransferase 1A1 activity and its expression in neonatal hyperbilirubinemia.

While breast milk has been known as a cause of neonatal hyperbilirubinemia, the underlying mechanism of breast milk-induced jaundice has not been clarified. Here, the impact of fatty acids on human UDP-glucuronosyltransferase (UGT) 1A1--the sole enzyme that can metabolize bilirubin--were examined. Oleic acid, linoleic acid, and docosahexaenoic acid (DHA) strongly inhibited UGT1A1 activity. Forty-eight hours after a treatment with a lower concentration of DHA (10 mg/kg), total bilirubin significantly increased in neonatal hUGT1 mice, which are human neonatal jaundice models. In contrast, treatments with higher concentrations of fatty acids (0.1-10 g/kg) resulted in a decrease in serum bilirubin in hUGT1 mice. It was further demonstrated that the treatment with higher concentrations of fatty acids induced UGT1A1, possibly by activation of peroxisome proliferator-activated receptors. Our data indicates that activation of peroxisome proliferator-activated receptors would increase UGT1A1 expression, resulting in reduction of serum bilirubin levels in human infants.

Importance of UDP-glucuronosyltransferase 1A1 expression in skin and its induction by UVB in neonatal hyperbilirubinemia.

UDP-glucuronosyltransferase (UGT) 1A1 is the sole enzyme that can metabolize bilirubin. Human infants physiologically develop hyperbilirubinemia as the result of inadequate expression of UGT1A1 in the liver. Although phototherapy using blue light is effective in preventing jaundice, sunlight has also been suggested, but without conclusive evidence, to reduce serum bilirubin levels. We investigated the mRNA expression pattern of human UGT1A1 in human skin, human skin keratinocyte (HaCaT) cells, and skin of humanized UGT1 mice. The effects of UVB irradiation on the expression of UGT1A1 in the HaCaT cells were also examined. Multiple UGT1A isoforms, including UGT1A1, were expressed in human skin and HaCaT cells. When HaCaT cells were treated with UVB-exposed tryptophan, UGT1A1 mRNA and activity were significantly induced. Treatment of the HaCaT cells with 6-formylindolo[3,2-b]carbazole, which is one of the tryptophan derivatives formed by UVB, resulted in an induction of UGT1A1 mRNA and activity. In neonates, the expression of UGT1A1 was greater in the skin; in adults, UGT1A1 was expressed mainly in the liver. Treatment of humanized UGT1 mice with UVB resulted in a reduction of serum bilirubin levels, along with increased UGT1A1 expression and activity in the skin. Our data revealed a protective role of UGT1A1 expressed in the skin against neonatal hyperbilirubinemia. Sunlight, a natural and free source of light, makes it possible to treat neonatal jaundice while allowing mothers to breast-feed neonates.

Neonatal hyperbilirubinemia in infants with G6PD c.563C > T Variant.

BACKGROUND: There is a strong correlation between glucose-6-phosphate dehydrogenase (G6PD) deficiency and neonatal hyperbilirubinemia with a rare but potential threat of devastating acute bilirubin encephalopathy. G6PD deficiency was observed in 4-14% of hospitalized icteric neonates in Pakistan. G6PD c.563C > T is the most frequently reported variant in this population. The present study was aimed at evaluating the time to onset of hyperbilirubinemia and the postnatal bilirubin trajectory in infants having G6PD c.563C > T. METHODS: This was a case-control study conducted at The Aga Khan University, Pakistan during the year 2008. We studied 216 icteric male neonates who were re-admitted for phototherapy during the study period. No selection was exercised. Medical records showed that 32 were G6PD deficient while 184 were G6PD normal. Each infant was studied for birth weight, gestational age, age at the time of presentation, presence of cephalhematoma, sepsis and neurological signs, peak bilirubin level, age at peak bilirubin level, days of hospitalization, whether phototherapy or exchange blood transfusion was initiated, and the outcome. During hospital stay, each baby was tested for complete blood count, reticulocyte count, ABO and Rh blood type, direct antiglobulin test and quantitative G6PD estimation [by kinetic determination of G6PDH]. G6PDgenotype was analyzed in 32 deficient infants through PCR-RFLP analysis and gene sequencing. RESULTS: G6PD variants c.563C > T and c.131 C > G were observed in 21 (65%) and three (9%) of the 32 G6PD deficient infants, respectively. DNA of eight (25%) newborns remained uncharacterized. In contrast to G6PD normal neonates, infants with c.563C > T variant had significantly lower enzyme activity (mean ± 1SD; 0.3 ± 0.2 U/gHb vs. 14.0 ± 4.5 U/gHb, p < 0.001) experienced higher peak levels of total serum bilirubin (mean ± 1SD; 16.8 ± 5.4 mg/dl vs. 13.8 ± 4.6 mg/dl, p = 0.008) which peaked earlier after birth (mean ± 1SD 2.9 ± 1.6 vs. 4.3 ± 2.3 days, p = 0.007). No statistically significant difference was observed in mean weight, age at presentation, hemoglobin, reticulocyte count, TSH level, hospital stay or in the frequency of initiation of phototherapy or blood exchange between the two groups. CONCLUSIONS: We concluded that infants with G6PD c.563C > T variant developed jaundice earlier than infants with normal G6PD enzyme levels. Compared to G6PD normal infants, G6PD c.563C > T carrying infants had significantly low G6PD activity.

Reduced expression of UGT1A1 in intestines of humanized UGT1 mice via inactivation of NF-κB leads to hyperbilirubinemia.

BACKGROUND & AIMS: Bilirubin is a natural and potent antioxidant that accumulates in the blood of newborn children and leads to physiological jaundice. Breastfed infants have higher serum levels of bilirubin than formula-fed infants and are at risk for bilirubin-induced neurological dysfunction (BIND). Clearance of bilirubin requires the expression of uridine diphosphate glucuronosyltransferase (UGT) 1A1; we investigated its role in the association between breast feeding with jaundice in mice. METHODS: We studied mice in which the original Ugt1 locus was disrupted and replaced with the human UGT1 locus (hUGT1 mice); these mice spontaneously develop neonatal hyperbilirubinemia and BIND. We fed human breast milk or formula to neonatal hUGT1 mice and examined activation of the intestinal xenobiotic receptors pregnane X receptor and constitutive androstane receptor. We also examined inflammatory signaling pathways in mice with disruptions in IκB-kinase-α and IκB kinase-ß in the intestinal epithelium. RESULTS: hUGT1 mice that were fed breast milk developed severe hyperbilirubinemia because of suppression of UGT1A1 in the gastrointestinal tract. Formula-fed hUGT1 mice had lower serum levels of bilirubin, which resulted from induction of UGT1A1 in the gastrointestinal tract. hUGT1/Pxr-null mice did not develop severe hyperbilirubinemia, whereas hUGT1/Car-null mice were susceptible to BIND when they were fed breast milk. Breast milk appeared to suppress intestinal IκB kinase α and ß, resulting in inactivation of nuclear factor-κB and loss of expression of UGT1A1, leading to hyperbilirubinemia. CONCLUSIONS: Breast milk reduces expression of intestinal UGT1A1, which leads to hyperbilirubinemia and BIND; suppression of this gene appears to involve inactivation of nuclear factor-κB. Hyperbilirubinemia can be reduced by activation of pregnane X receptor, constitutive androstane receptor, or nuclear factor-κB.

Glutathione S-transferase gene polymorphisms in neonatal hyperbilirubinemia.

BACKGROUND: Glutathione S-transferases (GSTs) are a polymorphic superfamily of multifunctional enzymes known to play an important role in the detoxification of several substances. GSTM1 and GSTT1 are present in the liver in relatively high levels. Polymorphisms of the GSTM1 and GSTT1 genes may affect ligandin functions that are important in bilirubin transportation. OBJECTIVE: The aim of this study was to investigate the role of GSTM1 and GSTT1 gene polymorphisms as risk factors for neonatal jaundice. METHODS: This study was conducted on 72 neonates with pathologic hyperbilirubinemia (bilirubin >15 mg/dL) and 112 neonates with bilirubin level less than 15 mg/dL as a control group. GSTM1 and GSTT1 genotypes were assessed by multiplex polymerase chain reaction. RESULTS: GSTM1 null genotype was significantly higher in the patient compared with control groups (P = 0.005; odds ratio = 2.43; 95% confidence interval, 1.29-4.55) and was significantly associated with higher bilirubin levels compared with the wild genotype (P < 0.001). There was no statistically significant difference in the GSTT1 genotypes between the patient and the control groups. In the patient group, total bilirubin levels did not vary significantly among the null and wild GSTT1 genotypes (P = 0.108). CONCLUSIONS: Neonates with the GSTM1 null genotype are at high risk to develop pathologic hyperbilirubinemia and may have higher bilirubin levels.

Alkaline phosphatase as an early marker of hemolysis in newborns.

BACKGROUND: Early diagnosis and appropriate management of neonatal hyperbilirubinemia are very important in order to prevent bilirubin encephalopathy and kernicterus. Several diagnostic tests may be used for this purpose, including bilirubin level itself. The aim of the present study was to investigate whether serum alkaline phosphatase (ALP), which is an intracellular enzyme found abundantly in red blood cells, could be used for the early diagnosis and prediction of hyperbilirubinemia in newborns. METHODS: A total of 100 babies were evaluated, starting from the sixth hour after birth, and serum ALP and bilirubin levels were analyzed. RESULTS: ALP levels were significantly higher in babies requiring therapy such as phototherapy or exchange transfusion (247.01 ± 67.44 IU/L vs 154.25 ± 56.07 IU/L). ALP levels rose significantly with rising total bilirubin level. CONCLUSION: ALP levels at the sixth hour of life may be a significant predictor of developing hemolysis and hyperbilirubinemia requiring treatment.

Glucose-6-phosphate dehydrogenase activity, structure, molecular characteristics and role in neonatal hyperbilirubinemia in cord blood in Cukurova region.

The most common causes of neonatal indirect hyperbilirubinemia are blood incompatibility and erythrocyte enzyme defects. Glucose-6-phosphate dehydrogenase (G6PD) is a guarantee of erythrocyte stability and capability of existence of red cells. We present here the results of a study on the effect of enzyme kinetics and different mutations on neonatal hyperbilirubinemia in the Cukurova region. Two hundred healthy term male neonates born in Cukurova University Balcall Hospital, Adana Maternity Hospital and Cukurova Maternal and Children's Hospital between 1 November 2004 and 30 November 2007 were consecutively studied. Nanogen DNA microarray was used to determine Gd Union, Gd San, Gd Mediterranean, and Gd San Antonio mutations. Quantitative G6PD enzyme assays were performed. Glucose-6-phosphate dehydrogenase deficiency was detected in six out of 200 male neonates (3%). The other 194 neonates had normal G6PD activity, with a mean of 8.3 +/- 2.1 IU/g hemoglobin (Hb) (5.2-12.7 IU/g Hb). Clinical follow-up, enzyme kinetics and genetic studies were performed in the G6PD-deficient neonates. Differences were observed in clinical outcomes, rates of bilirubin decline and maximum total bilirubin levels in the neonates having the same mutation. These differences might be caused by the effects of kinetic variant on the hyperbilirubinemia without the direct effect of the mutation. In future studies, mutation analyses of further G6PD-deficient cases may address the genotype differences and their clinical effects in G6PD-deficient patients.

Neonatal hyperbilirubinemia and organic anion transporting polypeptide-2 gene mutations.

The aim of this study was to investigate the genotypic distribution of organic anion transporting polypeptide 2 (OATP-2) gene mutations and the relationship with hyperbilirubinemia of unknown etiology. Polymerase chain reaction, restriction fragment length polymorphism, and agarose gel electrophoresis techniques were used for detection of OATP-2 gene mutations in 155 newborn infants: 37 with unexplained hyperbilirubinemia, 65 with explained hyperbilirubinemia, and 53 without hyperbilirubinemia. In the OATP-2 gene, we identified A→G transitions at nucleotide positions 388 and 411 and observed six polymorphic forms. The 388/411-411 mutation was the most common form (43%) in subjects with hyperbilirubinemia of unknown etiology. Male sex [odds ratio (OR): 3.08] and two polymorphic forms of the OATP-2 gene [the 388/411-411 A→G mutation (OR: 3.6) and the 388-411 mutation (OR: 2.4)] increased the risk of neonatal hyperbilirubinemia. In male infants with the 388 A→G mutation of the OATP-2 gene, the levels of unconjugated bilirubin in plasma were significantly increased compared with those observed in females. The polymorphic forms of 388 nucleotide of the OATP-2 gene were identified as risk factors for hyperbilirubinemia of unknown etiology.

Cooperating G6PD mutations associated with severe neonatal hyperbilirubinemia and cholestasis.

We report a novel glucose-6-phosphate dehydrogenase (G6PD) mutation, which we propose to name G6PD Cincinnati (c.1037A > T, p.N346I), found in combination with G6PD Gastonia (c.637G > T, p.V213L) in an infant who presented with neonatal cholestasis. The G6PD Cincinnati mutation results in a non-conservative amino acid substitution at the tetramer interface disturbing its formation, as seen by native gel electrophoresis and immunoblotting. G6PD Gastonia disrupts dimerization of the enzyme and by itself causes chronic non-spherocytic hemolytic anemia. The G6PD Cincinnati mutation may have aggravated the clinical picture of G6PD Gastonia with the result of severe perinatal hemolysis causing cholestasis and associated liver injury.

211 G to a variation of UDP-glucuronosyl transferase 1A1 gene and neonatal breastfeeding jaundice.

Breastfeeding jaundice is a common problem in neonates who were exclusively breastfed, but its pathogenesis is still unclear. The uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) gene polymorphism was shown to contribute to the development of neonatal hyperbilirubinemia. We hypothesize that the variation of UGT1A1 gene may contribute to neonatal breastfeeding jaundice. We prospectively enrolled 688 near-term and term infants who were exclusively breastfed (BF group) or were supplemented by infant formula partially (SF group) before onset of hyperbilirubinemia. Genotyping of the promoter and exon1 of UGT1A1 was performed in all neonates. Neonates in BF group had a significantly higher maximal body weight loss ratio, peak bilirubin level, and a greater incidence of hyperbilirubinemia than those in SF group. Neonates with nucleotide 211 GA or AA variation in UGT1A1 genotypes had higher peak serum bilirubin levels and higher incidence of hyperbilirubinemia than WTs (GG). This phenomenon was only seen in BF group but not in SF group when subset analysis was performed. This suggests that neonates who carry the nucleotide 211 GA or AA variation within coding region in UGT1A1 gene are more susceptible to develop early-onset neonatal breastfeeding jaundice.

Glucose-6-phosphate dehydrogenase deficiency and severe neonatal hyperbilirubinemia: a complexity of interactions between genes and environment.

Glucose-6-phosphate dehydrogenase deficiency is a commonly occurring genetic condition, likely to be encountered today in virtually any corner of the globe. Sudden episodes of hemolysis associated with the condition may result in exponential increases in serum total bilirubin concentrations to levels at which bilirubin-induced neurologic damage may occur. The hyperbilirubinemia is the result of complex interactions between genes and environment. Neonatal screening programs coupled with parental and medical caretaker education may be successful in limiting the severity of disease.

Hyperbilirubinemia in African American neonates: clinical issues and current challenges.

African American neonates evidence a low incidence of hyperbilirubinemia yet account for more than 25% of the reported kernicterus cases in the USA. Glucose-6-phosphate dehydrogenase (G6PD) deficiency accounts for approximately 60%, and late preterm gestation and ABO hemolytic disease approximately 40% of these cases. Females heterozygous for G6PD A- harbor a population of G6PD-deficient red blood cells and are at risk for hyperbilirubinemia. Pre-discharge bilirubin measurement coupled with gestational age enhances the identification of neonates at hyperbilirubinemia risk. Parental education at the time of birth hospitalization discharge combined with timely follow-up may help to reduce the risk of developing hazardous hyperbilirubinemia.

Metalloporphyrins in the management of neonatal hyperbilirubinemia.

Neonatal jaundice in the first week of life is a common problem in newborns. It is due to an imbalance of bilirubin production and its elimination, which can lead to significantly elevated levels of circulating bilirubin or hyperbilirubinemia. Use of phototherapy and/or exchange transfusion are the current modes for treating neonatal hyperbilirubinemia and preventing any neurologic damage. These strategies, however, only remove bilirubin that has already been formed. Preventing the production of excess bilirubin may be a more logical approach. Synthetic heme analogs, metalloporphyrins, are competitive inhibitors of heme oxygenase, the rate-limiting enzyme in bilirubin production, and their use has been proposed as an attractive alternative strategy for preventing or treating severe hyperbilirubinemia.

Exploring the genetic architecture of neonatal hyperbilirubinemia.

The potential for genetic variation to modulate neonatal hyperbilirubinemia risk is increasingly being recognized. In particular, polymorphisms across three genes involved in bilirubin production and metabolism [glucose-6-phosphate dehydrogenase (G6PD), uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1), and solute carrier organic anion transporter polypeptide 1B1 (SLCO1B1)] may interact with each other and/or environmental contributors to produce significant hyperbilirubinemia. Variant gene co-expression including compound and synergistic heterozygosity enhances hyperbilirubinemia risk, contributing to the etiologic heterogeneity and complex nature of neonatal jaundice.

Comparison of detection of glucose-6-phosphate dehydrogenase deficiency using fluorescent spot test, enzyme assay and molecular method for prediction of severe neonatal hyperbilirubinaemia.

INTRODUCTION: This study aimed to compare the detection rates of glucose-6-phosphate dehydrogenase (G6PD) deficiency in neonates by fluorescent spot test (FST), enzyme assay and molecular methods, and to identify which method was a significant predictor of severe hyperbilirubinaemia. METHODS: 74 term infants of Chinese descent admitted with severe hyperbilirubinaemia (total serum bilirubin equal or greater than 300 micromol/L) and 125 healthy term infants born in the hospital without severe hyperbilirubinaemia were recruited into the study. Specimens of blood were collected from each infant for FST, G6PD enzyme assay and TaqMan minor groove binder single nucleotide polymorphism genotyping assay. RESULTS: 26 (13.1 percent) infants were diagnosed to have G6PD deficiency by FST. They had significantly lower median enzyme levels (0.8 IU/g Hb, interquartile range [IQR] 0.4-4.3) than those diagnosed to be normal (12.0 IU/g Hb, IQR 10.3-15.8) (p-value is less than 0.0001). Based on the enzyme assay, 39 (19.6 percent) infants had G6PD deficiency at an enzyme cut-off level of less than 8.5 IU/g Hb. G6PD mutation was detected in 27 (13.6 percent) infants. Logistic regression analysis showed that the only significant predictors of severe hyperbilirubinaemia were G6PD deficiency based on a cut-off level of less than 8.5 IU/g Hb (adjusted odds ratio [OR] 5.3, 95 percent confidence interval [CI] 2.4-11.4; p-value is less than 0.0001) and exclusive breast-feeding (adjusted OR 11.4, 95 percent CI 3.1-42.4; p-value is less than 0.0001). The gender and birth weight of infants, FST results, G6PD mutation and the actual G6PD enzyme levels were not significant predictors. CONCLUSION: A G6PD enzyme level of less than 8.5 IU/g Hb is a significant predictor of severe hyperbilirubinaemia.

ADA genetic polymorphism and the effect of smoking on neonatal bilirubinemia and developmental parameters.

BACKGROUND: Genetic variability of metabolic enzymes may influence the effect of cigarette smoking on intrauterine development and on early neonatal events. AIMS: To investigate the role of adenosine deaminase genetic polymorphism on the effect of smoking on neonatal bilirubinemia and developmental parameters. STUDY DESIGN: Analysis of association between adenosine deaminase phenotypes and neonatal developmental parameters. Prospective study of serum bilirubin level in relation to adenosine deaminase phenotype. METHODS: We have studied 360 consecutive newborn infants from the Caucasian population of Rome. Serum bilirubin concentration was determined at birth and every 24 h for the first five days. RESULTS: Overall maternal smoking is associated with a slight decrease in the incidence of phototherapy (13.4% in non smoking vs 11.7% in smoking mothers) and with a reduction of birth weight (3374 g in non smoking mothers vs 3133 g in smoking mothers). There is a significant interaction between smoke and adenosine deaminase. While in non smoking mothers the incidence of phototherapy in carriers of ADA 2 allele is higher than in ADA 1 phenotype, in infants from smoking mothers the pattern is reversed and the incidence of phototherapy in carriers of ADA 2 allele is lower than in infants with ADA 1 phenotype. Other neonatal bilirubin parameters follow a similar pattern of interaction between smoking and ADA. The negative effect of smoke on birth weight is much more evident in infant with ADA 1 phenotype than in those carrying the ADA 2 allele. CONCLUSIONS: The data suggest that ADA phenotype modifies the effect of smoking on developmental and bilirubin parameters.

(TA)n UDP-glucuronosyltransferase 1A1 promoter polymorphism in Nigerian neonates.

Nigerian neonates have a high incidence of bilirubin encephalopathy. Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is prevalent in this population. (TA)7 promoter polymorphism in the gene encoding the bilirubin conjugating enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1) potentiates hyperbilirubinemia in G-6-PD deficient neonates. We studied (TA)n allele frequency to determine, at least in part, its contribution to the frequency and severity of hyperbilirubinemia. DNA was extracted from umbilical cord blood of sequentially born Nigerian neonates and the (TA)n UGT1A1 promoter sequence determined. The (TA)n allele distribution was compared with reported adults of varying African ancestry and Sephardic Jewish neonates. Among 88 Nigerian neonates, (TA)6 and (TA)7 alleles were almost equally distributed (0.46 and 0.43, respectively). Some individuals with (TA)5 and (TA)8 sequences were encountered. Allele distribution was similar to that of the African ancestry population but differed from the Sephardic Jewish newborns, in whom the (TA)6/(TA)7 distribution was 0.65/0.35. Whereas 45% of Nigerian alleles and 50% of African ancestry alleles, respectively, included a (TA)7 or (TA)8 sequence, only 35% of Jewish alleles were (TA)7 (p < 0.001), and no (TA)8 alleles were encountered. The high frequency of (TA)n promoter polymorphism, coupled with G-6-PD deficiency, may contribute to the pathogenesis of extreme neonatal hyperbilirubinemia in Nigeria.