Analysis of uridine diphosphate glucuronosyl transferase 1A1 gene mutations in neonates with unconjugated hyperbilirubinemia

Developing and evaluating a predictive model for neonatal hyperbilirubinemia based on UGT1A1 gene polymorphism and clinical risk factors

Background

Neonatal hyperbilirubinemia (NHB) is one of the most common diseases in the neonatal period. Without timely diagnosis and treatment, it can lead to long-term complications. In severe cases, it may even result in fatality. The UGT1A1 gene and clinical risk factors play important roles in the development and progression of NHB.

Methods

In this study, we conducted a cohort study and analyzed 3258 newborns from the Jilin Women And Children Health Hospital in northern China, including 372 children with hyperbilirubinemia. We established a predictive model using a logistic regression model based on clinical risk factors and the polymorphism of the G211A locus in the UGT1A1 gene of newborns. Furthermore, the performance of the prediction model was evaluated using the ROC curve.

Results

The logistic regression model indicates that the following factors are associated with an increased risk of NHB: the time when stool turns yellow [P ≤ 0.001, OR 1.266 (95% CI: 1.125-1.425)]; neonatal cephalohematoma [P ≤ 0.001, OR 33.642 (95% CI: 21.823-51.861)]; hemolytic disease of newborn [P ≤ 0.001, OR 33.849 (95% CI: 18.589-61.636)]; neonatal weight loss [P ≤ 0.001, OR 11.275 (95% CI: 7.842-16.209)]; neonatal premature rupture of membranes (PROM) history [P = 0.021, OR 1.422 (95% CI: 1.056-1.917)]; genetic polymorphism at the UGT1A1 gene G211A locus. Gestational age is a protective factor [P ≤ 0.001, OR 0.766 (95% CI: 0.686-0.855)]. Compared to natural labor, cesarean section is a protective factor [P = 0.011, OR 0.711 (95% CI: 0.546-0.926)], while assisted delivery is a risk factor [P = 0.022, OR 2.207 (95% CI: 1.121-4.346)]. The area under the curve (AUC) of this prediction model is 0.804 (95% CI: 0.777-0.831), indicating good discrimination ability and value for predicting the risk of NHB after birth.

Conclusion

We have developed and evaluated a predictive model that combines UGT1A1 gene polymorphism and clinical risk factors for the first time. By using this nomogram and taking into account the results of serum total bilirubin measurement or transcutaneous bilirubin measurement, early prediction of the risk of neonatal hyperbilirubinemia can be achieved.

Association of UGT1A1 gene variants, expression levels, and enzyme concentrations with 2,3,7,8-TCDD exposure in individuals exposed to Agent Orange/Dioxin

Among the congener of dioxin, 2,3,7,8-TCDD is the most toxic, having a serious long-term impact on the environment and human health. UDP-glucuronosyltransferase 1A1 (UGT1A1) plays a crucial role in the detoxification and excretion of endogenous and exogenous lipophilic compounds, primarily in the liver and gastrointestinal tract. This study aimed to investigate the association of UGT1A1 gene polymorphisms, expression levels, and enzyme concentration with Agent Orange/Dioxin exposure. The study included 100 individuals exposed to Agent Orange/Dioxin nearby Da Nang and Bien Hoa airports in Vietnam and 100 healthy controls. UGT1A1 SNP rs10929303, rs1042640 and rs8330 were determined by Sanger sequencing, mRNA expression was quantified by RT-qPCR and plasma UGT1A1 concentrations were measured by ELISA. The results showed that UGT1A1 polymorphisms at SNPs rs10929303, rs1042640 and rs8330 were associated with Agent Orange/Dioxin exposure (OR = 0.55, P = 0.018; OR = 0.55, P = 0.018 and OR = 0.57, P = 0.026, respectively). UGT1A1 mRNA expression levels and enzyme concentration were significantly elevated in individuals exposed to Agent Orange/Dioxin compared to controls (P < 0.0001). Benchmark dose (BMD) analyses showed that chronic exposure to 2,3,7,8-TCDD contamination affects the UGT1A1 mRNA and protein levels. Furthermore, UGT1A1 polymorphisms affected gene expression and enzyme concentrations in individuals exposed to Agent Orange/Dioxin. In conclusion, UGT1A1 gene polymorphisms, UGT1A gene expression levels and UGT1A1 enzyme concentrations were associated with Agent Orange/Dioxin exposure. The metabolism of 2,3,7,8-TCDD may influence UGT1A gene expression and enzyme concentrations.

Bilirubin metabolism and UDP-glucuronosyltransferase 1A1 variants in Asians: Pathogenic implications and therapeutic response

In the Asian general population, at least six single-nucleotide variants (SNVs) in the UDP-glucuronosyltransferase (UGT) 1A1 gene have been identified: -3279T>G, -53A(TA)₆ TAA>A(TA)₇ TAA, 211G>A, 686C>A, 1091C>T, and 1456T>G. Each of these six SNVs was observed in at least four ethnic groups of the 12 Asian populations studied. In East Asian populations, the descending frequency of these six SNVs was as follows: -3279G>[-53A(TA)₇ TAA, 211A]>(686A, 1091T)>1456G. Because of the presence of linkage disequilibrium and the expulsion phenomenon, when the SNVs -3279G, -53A(TA)₇ TAA, 211A, and 686A were simultaneously involved, 15 instead of the estimated 81 genotypes were observed. Those carrying 686AA or 1456GG developed Gilbert's syndrome or Crigler-Najjar syndrome type 2. Both -53A(TA)₇ TAA/A(TA)₇ TAA and 211AA are the main causes of Gilbert's syndrome in East Asian populations. In East Asian populations, the 211AA genotype is the main cause of neonatal hyperbilirubinemia, whereas -53A(TA)₇ TAA/A(TA)₇ TAA exerts a protective effect on hyperbilirubinemia development in neonates fed with breast milk. Both 211A and -53A(TA)₇ TAA are significantly associated with adverse drug reactions induced by irinotecan (one of the most widely used anticancer agents) in Asians. However, at least three common SNVs (-3279G, -53A(TA)₇ TAA, and 211A) should be comprehensively analyzed. This study investigated the clinical significance of these six SNVs and demonstrated that examining UGT1A1 variants in Asian populations is considerably challenging.

[Research advances in neonatal hyperbilirubinemia and gene polymorphisms]

Hyperbilirubinemia is a prevalent disease in neonates and is also a main reason for hospitalization within the first week after birth, and this disease is mainly caused by the imbalance between production and elimination of bilirubin. Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1), organic anion transporter polypeptide 2 (OATP2), heme oxygenase 1 (HO-1), and biliverdin reductase A (BLVRA) play crucial roles in the metabolism of bilirubin. More and more studies have revealed the association between the variation of the encoding genes for these enzymes and hyperbilirubinemia. This article reviews the research advances in the association between the gene polymorphisms of bilirubin metabolic enzymes and hyperbilirubinemia.