Multiple Genetic Modifiers of Bilirubin Metabolism Involvement in Significant Neonatal Hyperbilirubinemia in Patients of Chinese Descent

<div><p>The potential for genetic variation to modulate neonatal hyperbilirubinemia risk is increasingly being recognized. A case-control study was designed to assess comprehensive contributions of the multiple genetic modifiers of bilirubin metabolism on significant neonatal hyperbilirubinemia in Chinese descendents. Eleven common mutations and polymorphisms across five bilirubin metabolism genes, namely those encoding UGT1A1, HMOX1, BLVRA, SLCO1B1 and SLCO1B3, were determined using the high resolution melt (HRM) assay or PCR-capillary electrophoresis analysis. A total of 129 hyperbilirubinemic infants and 108 control subjects were evaluated. Breastfeeding and the presence of the minor A allele of rs4148323 (UGTA*6) were correlated with an increased risk of hyperbilirubinemia (OR=2.17, P=0.02 for breastfeeding; OR=9.776, P=0.000 for UGTA*6 homozygote; OR=3.151, P=0.000 for UGTA*6 heterozygote); whereas, increasing gestational age and the presence of –TA₇ repeat variant of UGT1A1 decreased the risk (OR=0.721, P=0.003 for gestational age; OR=0.313, P=0.002 for heterozygote TA₆/TA₇). In addition, the SLCO1B1 and SLCO1B3 polymorphisms also contributed to an increased risk of hyperbilirubinemia. This detailed analysis revealed the impact of multiple genetic modifiers on neonatal hyperbilirubinemia. This may support the use of genetic tests for clinical risk assessment. Furthermore, the established HRM assay can serve as an effective method for large-scale investigation.</p></div

Demographic and clinical features of the neonates in the case and control groups.

<p>^a Mean±SD.</p><p>^b Median (95% CI).</p><p>Demographic and clinical features of the neonates in the case and control groups.</p

Ordinal logistic model: association of genetic and clinical risk factors with the severity of hyperbilirubinemia according to the TSB level.

<p>*Abbreviation: GW: Gestational week; F: Model fitting statistic; P: Pearson χ² statistic; D: Deviance χ² statistic; L: Parallel line test statistic. C: Cox and Snell; N: Nagelkerke; M: McFadden. The parallel line test was tested using the χ² statistic. A non-significant P value indicated that the odds ratio could be interpreted as constant across all possible cut-off points of the outcome (Null hypothesis). This Null hypothesis was applied for only the evaluation of the location model. Pearson χ² and Deviance χ² were used to test the Goodness of fitting. If the P value of the χ² statistic was less than 0.05, we rejected the null hypothesis and concluded that there was a significant difference between the observed and expected values. The larger the R², the better the model fit.</p><p>^a The feeding (1) group was comprised of breast or mixed breast and formula fed infants; the feeding (2) group was comprised of exclusively formula fed infants.</p><p>Ordinal logistic model: association of genetic and clinical risk factors with the severity of hyperbilirubinemia according to the TSB level.</p

HRM analysis of 9 single base polymorphisms across the UGT1A1, SLCO1B1, SLCO1B3 and BLVRA genes.

<p>(a): rs4148323 G>A; (b): rs6742078 T>G; (c):rs35390940 C>A; (d): rs108124 A>G; (e): rs2306283 G>A; (f): rs4149056 T>C; (g): rs2117032 T>C; (h): rs2417940 T>C; (i): rs699512 A>G.</p

Association analysis of the 10 polymorphisms in bilirubin metabolism genes and the risk of hyperbilirubinemia under different inheritance models: binary logistic regression.

<p>^a Adjusted for age, gender, and feeding practice.</p><p>^b polymorphisms are in order of: rs4148323-rs6742078-rs108124-(TA)_n.</p><p>^c other haplotypes had frequencies of less than 1%.</p><p>Association analysis of the 10 polymorphisms in bilirubin metabolism genes and the risk of hyperbilirubinemia under different inheritance models: binary logistic regression.</p

Molecular Epidemiological Characterization and Health Burden of Thalassemias in the Chaoshan Region, People’s Republic of China

<p>Thalassemia is one of the most prevalent inherited disease in southern China. However, there have been only a few epidemiological studies of thalassemia in the Chaoshan region of Guangdong Province, People’s Republic of China (PRC). A total of 6231 unrelated subjects in two main geographical cities of the Chaoshan region was analyzed for thalassemia. Seven hundred and thirty-six cases of suspected thalassemia carriers with microcytosis [mean corpuscular volume (MCV) <82.0 fL] were found by complete blood cell (CBC) count, and were tested by reverse dot-blot gene chip to reveal a total of 331 mutant chromosomes, including 278 α-thalassemia (α-thal) alleles and 53 β-thalassemia (β-thal) alleles. The most common α-thal mutations were the Southeast Asian (– –^SEA), followed by the –α^3.7 (rightward) and –α^4.2 (leftward) deletions. The two most common β-thal mutations were <i>HBB</i>: c.316-197C>T and <i>HBB</i>: c.126_129delCTTT, accounting for 69.81% of the β-thal defects in the studied individuals. In addition, a rare mutation, Cap +1 (A>C) (<i>HBB</i>: c.-50A>C) was described for the first time in the Chaoshan region. Our results gave a heterozygote frequency of 5.31% for common α- and β-thal in the Chaoshan region, and also indicated a higher prevalence of thalassemia with a heterozygote frequency of 6.29% in Chaozhou, followed by Shantou (3.37%). This study provided a detailed prevalence and molecular characterization of thalassemia in the Chaoshan region, and will be valuable for developing a strategy for prevention of thalassemia and reducing excessive health care costs in this area.</p

Geographic location of the Jiangxi province and three regional centers of our study.

<p>Geographic location of the Jiangxi province and three regional centers of our study.</p

Interactive effect between the <i>H63D</i> genotype and blood lead levels on transferrin.

<p><i>H63D</i> genotype: HD or DD: open dots, dashed line; HH: close dots, full line. The data are analyzed using multivariate analysis.</p

Demographic Characteristics of Subjects by Exposure [M(P₂₅, P₇₅)or N(%)].

<p>*(**) <i>p<0.05</i> (<i>0.01</i>) (Chi-square test or nonparametric test) compared with the unexposed group of the same sex.</p><p>Results were expressed as the mean ± SD when the continuous variables followed a normal distribution.</p><p>Results were expressed as M (P25, P75) when the continuous variables did not follow a normal distribution.</p

Linear regression models evaluating effect of <i>HFE</i> genotypes on the association between lead exposure and iron metabolism.

<p>Abbreviations: BPb, blood lead; Tf, transferrin; BIC, body iron content; HH, wild-type; HD, <i>H63D</i> heterozygous variant; DD, <i>H63D</i> homozygous variant.</p><p>Linear models were adjusted stepwise for age (year), gender (male vs. female), education (lower than high school vs. higher than high school), marriage (yes vs. no), tobacco use (yes vs. no), alcohol consumption (yes vs. no), occupational lead exposure (unexposed, dissolved lead operations or electrolytic lead operations) and work years. <i>H63D</i> genotype (HH vs. HD or DD), iron metabolic index/BPb and the cross-product with the genotype and each iron metabolic index/BPb. While BPb was independent factor, each iron metabolic index and the cross-product with the genotype were put separately into the model.</p>1<p><i>P</i> value for each statistic;</p>2<p><i>P</i> value for each regression model.</p