Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. ...Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.
The objective of this study was to assess the prevalence and trends for neonatal hyperbilirubinemia, and the development of bilirubin neurotoxicity in the USA.
We used a de-identified national ...dataset for the years 2002-2017. The study included all newborn inpatients with postnatal age ≤28 days. Cochran-Armitage trend test was used for trend analyses. Regression analyses were performed and adjusted odds ratios (aOR) were reported.
The study included 57,989,476 infants; of them 53,259,758 (91.8%) were term infants and 4,725,178 (8.2%) were preterm infants. Bilirubin neurotoxicity decreased over the years in term infants (Z = 0.36, p = 0.03) without change in preterm infants (Z = 42.5, p = 0.12). Black neonates were less likely to be diagnosed with hyperbilirubinemia than White neonates (aOR = 0.77, 95% confidence interval (CI): 0.77-0.78, p < 0.001) and more likely to develop bilirubin neurotoxicity than White neonates (aOR = 3.0.5, 95% CI: 2.13-4.36, p < 0.001). Bilirubin neurotoxicity rate in the overall population was 2.4 per 100,000 live births.
Bilirubin neurotoxicity has significantly decreased in term infants and did not change in preterm infants. Despite the less diagnosis of hyperbilirubinemia in Black newborns, they are disproportionately at increased risk of developing bilirubin neurotoxicity when compared to White newborns.
In this article, we analyzed the National Inpatient Database. This is the largest study of its kind using data on 57,989,476 neonates. The article has multiple novel findings: (1) it demonstrated that utilization of phototherapy has increased significantly over the years, (2) the rate of kernicterus for neonates decreased in term infants and did not change in preterm babies, (3) kernicterus was mostly encountered in infants without isoimmunization jaundice, and (4) there is a clear racial disparity in neonatal jaundice; although Black newborns have less neonatal jaundice, they are at increased risk of developing kernicterus.
Bilirubin: The yellow hormone? Vítek, Libor; Tiribelli, Claudio
Journal of hepatology,
December 2021, 2021-12-00, 20211201, Volume:
75, Issue:
6
Journal Article
Peer reviewed
Open access
Bilirubin is a tetrapyrrolic compound originating from heme catabolism. Although originally considered only a potentially dangerous waste product, it has become increasingly evident that this ...molecule represents an important modulator of various biological functions in the human body. Bilirubin appears to have versatile functions, from cell signaling (behaving almost like a “real” hormonal substance), modulation of metabolism, to immune regulation, affecting biological activities with apparent clinical and even therapeutic consequences. These activities may be the reason for the lower incidence of diseases of civilisation (cardiovascular diseases, arterial hypertension, diabetes, obesity, metabolic syndrome, certain cancers, autoimmune, and neurodegenerative diseases) observed in individuals with a chronic mild unconjugated hyperbilirubinemia, a typical sign of Gilbert’s syndrome. While higher serum concentrations of unconjugated bilirubin may serve as an important protective factor against these diseases, low levels of bilirubin are associated with the opposite effect.
Inherited disorders of hyperbilirubinemia may be caused by increased bilirubin production or decreased bilirubin clearance. Reduced hepatic bilirubin clearance can be due to defective (i) ...unconjugated bilirubin uptake and intrahepatic storage, (ii) conjugation of glucuronic acid to bilirubin (e.g., Gilbert syndrome, Crigler-Najjar syndrome, Lucey-Driscoll syndrome, breast milk jaundice), (iii) bilirubin excretion into bile (Dubin-Johnson syndrome), or (iv) conjugated bilirubin re-uptake (Rotor syndrome). In this review, the molecular mechanisms and clinical manifestations of these conditions are described, as well as current approaches to diagnosis and therapy.
Cholestatic jaundice in infancy affects approximately 1 in every 2500 term infants and is infrequently recognized by primary providers in the setting of physiologic jaundice. Cholestatic jaundice is ...always pathologic and indicates hepatobiliary dysfunction. Early detection by the primary care physician and timely referrals to the pediatric gastroenterologist/hepatologist are important contributors to optimal treatment and prognosis. The most common causes of cholestatic jaundice in the first months of life are biliary atresia (25%-40%) followed by an expanding list of monogenic disorders (25%), along with many unknown or multifactorial (eg, parenteral nutrition-related) causes, each of which may have time-sensitive and distinct treatment plans. Thus, these guidelines can have an essential role for the evaluation of neonatal cholestasis to optimize care. The recommendations from this clinical practice guideline are based upon review and analysis of published literature and the combined experience of the authors. The committee recommends that any infant noted to be jaundiced after 2 weeks of age be evaluated for cholestasis with measurement of total and direct serum bilirubin, and that an elevated serum direct bilirubin level (direct bilirubin levels >1.0 mg/dL or >17 μmol/L) warrants timely consideration for evaluation and referral to a pediatric gastroenterologist or hepatologist. Of note, current differential diagnostic plans now incorporate consideration of modern broad-based next-generation DNA sequencing technologies in the proper clinical context. These recommendations are a general guideline and are not intended as a substitute for clinical judgment or as a protocol for the care of all infants with cholestasis. Broad implementation of these recommendations is expected to reduce the time to the diagnosis of pediatric liver diseases, including biliary atresia, leading to improved outcomes.
Hyperbilirubinemia is a serious hazard to human health due to its neurotoxicity and lethality. So far, successful therapy for hyperbilirubinemia with fewer side effects is still lacking. In this ...study, we aimed to clarify the effects of oridonin (Ori), an active diterpenoid extracted from Rabdosia rubescens, on hyperbilirubinemia and revealed the underlying molecular mechanism in vivo and in vitro. Here, we showed that liver X receptor alpha (LXRα) deletion eliminated the protective effect of Ori on phenylhydrazine hydrochloride-induced hyperbilirubinemia mice, indicating that LXRα acted as a key target for Ori treatment of hyperbilirubinemia. Ori significantly increased the expression of LXRα and UDP-glucuronosyltransferase 1A1 (UGT1A1) in the liver of wild-type (WT) mice, which were lost in LXRα-/- mice. Ori or LXR agonist GW3965 also reduced lipopolysaccharide/D-galactosamine-induced hyperbilirubinemia via activating LXRα/UGT1A1 in WT mice. Liver UGT1A1 enzyme activity was elevated by Ori or GW3965 in WT mice. Further, Ori up-regulated LXRα gene expression, increased its nuclear translocation and stimulated UGT1A1 promoter activity in HepG2 cells. After silencing LXRα by siRNA, Ori-induced UGT1A1 expression was markedly reduced in HepG2 cells and primary mouse hepatocytes. Taken together, Ori stimulated the transcriptional activity of LXRα, resulting in the up-regulation of UGT1A1. Therefore, Ori or its analogs might have the potential to treat hyperbilirubinemia-related diseases through modulating LXRα-UGT1A1 signaling.
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•Two animal models of hyperbilirubinemia confirmed the medicative effect of Oridonin.•Oridonin is a UGT1A1 inducer both in vivo and in vitro.•Oridonin attenuated hyperbilirubinemia through LXRα-dependent mechanisms.•Oridonin increased UGT1A1 promoter activity by promoting LXRα nuclear translocation.
Total serum bilirubin (TSB) levels ≥ 30 mg/dL are rare but potentially hazardous. A better understanding of their incidence, causes, and outcomes could help inform preventive efforts.
We identified ...infants born ≥ 35 weeks' gestational age from 1995-2011 in Kaiser Permanente Northern California (n = 525409) and examined the medical records of infants with a TSB ≥ 30 mg/dL to determine etiology and the occurrence of acute bilirubin encephalopathy. We reviewed inpatient and outpatient encounters through 2013 for evidence of sensorineural hearing loss (SNHL) or cerebral palsy (CP).
We identified 47 infants with TSB ≥ 30 mg/dL (8.6 per 100000 births). In 44 infants (94%), the hyperbilirubinemia occurred after the initial birth hospitalization. The etiology was not identified in 33 (70%). Glucose-6-phosphate dehydrogenase (G6PD) activity was measured in only 25 (53%) of whom 10 (40%) were deficient. Four children had acute bilirubin encephalopathy of whom 2 developed both CP and SNHL, and 1 developed isolated SNHL. These 3 infants all had G6PD deficiency and TSB >40 mg/dL. One additional 35-week infant with TSB 38.2 mg/dL had SNHL.
Hazardous (≥ 30 mg/dL) hyperbilirubinemia is a rare event. No etiology could be identified from the clinical record in most cases. G6PD deficiency was the leading cause of hazardous hyperbilirubinemia when an etiology was identified, but many were not tested. Chronic, bilirubin-induced neurotoxicity was uncommon and occurred only in the setting of additional risk factors and TSB values well over (>15 mg/dL) the American Academy of Pediatrics exchange transfusion thresholds.
Hyperbilirubinemia, caused by the accumulation of unconjugated bilirubin, is one of the most common clinical diagnoses in both premature and term newborns. Owing to the fact that bilirubin is ...metabolized solely through glucuronidation by UDP-glucuronosyltransferase (UGT) 1A1, it is now known that immaturity of UGT1A1, in combination with the overproduction of bilirubin during the developmental stage, acts as a bottleneck to bilirubin elimination and predisposes the infant to high total serum bilirubin levels. Although neonatal jaundice is mostly benign, excessively high levels of serum bilirubin in a small percentage of newborns can cause bilirubin-induced neurologic dysfunction, potentially leading to permanent brain damage, a condition known as
Although a large portion of hyperbilirubinemia cases in newborns are associated with hemolytic diseases, we emphasize here the impaired ability of UGT1A1 to eliminate bilirubin that contributes to hyperbilirubinemia-induced neurotoxicity in the developmental stage. As a series of hereditary UGT1A1 mutations have been identified that are associated with UGT1A1 deficiency, new evidence has verified that delayed expression of UGT1A1 during the early stages of neonatal development is a tightly controlled event involving coordinated intrahepatic and extrahepatic regulation. This review recapitulates the progress that has been made in recent years in understanding the causes and physiopathology of severe hyperbilirubinemia, investigating molecular mechanisms underlying bilirubin-induced encephalopathy, and searching for potential therapies for treating pathologic hyperbilirubinemia. Several animal models have been developed to make it possible to examine bilirubin-induced neurotoxicity from multiple directions. Moreover, environmental factors that may alleviate or worsen the condition of hyperbilirubinemia are discussed.
The antiretroviral protease inhibitor atazanavir inhibits hepatic uridine diphosphate glucuronosyltransferase (UGT) 1A1, thereby preventing the glucuronidation and elimination of bilirubin. Resultant ...indirect hyperbilirubinemia with jaundice can cause premature discontinuation of atazanavir. Risk for bilirubin‐related discontinuation is highest among individuals who carry two UGT1A1 decreased function alleles (UGT1A1*28 or *37). We summarize published literature that supports this association and provide recommendations for atazanavir prescribing when UGT1A1 genotype is known (updates at www.pharmgkb.org).
Neonatal hyperbilirubinemia (NNH) is a common disease in newborns. This research study aimed to assess the associations between uridine diphospho-glucuronate-glucuronosyltransferase 1A1 (UGT1A1, ...c.-3279 T > G) polymorphisms and NNH risk.
We searched PubMed, the Cochrane Library, and the Embase electronic databases. All published eligible studies before July 1, 2019, were searched for this meta-analysis.
We identified 7 independent studies including 1560 cases. The data showed that in the general population, compared with the GT + GG vs TT and GG vs TT, c.-3279 T > G (rs4124874) was significantly related to a higher NNH risk (GG vs TT: OR = 1.865, 95% CI: 1.031-3.373, P = 0.039; GT + GG vs TT: OR = 1.331, 95% CI: 1.055-1.679, P = 0.016). Although not statistically significant, the data showed that c.3279 T > G had a tendency to be associated with NNH under the allele model and GG vs GT + TT in the overall population (G vs T: OR = 1.288, 95% CI: 0.982-1.689, P = 0.067; GG vs TT + GT: OR = 1.583, 95% CI: 0.947-2.647, P = 0.080).
The UGT1A1 gene c.-3279 T > G (rs4124874) polymorphism increased susceptibility to NNH, especially for the comparison of GT + GG vs TT and GG vs TT. In the future, we can use homozygous state of the UGT1A1 gene c.-3279 T > G (rs4124874) polymorphism for the diagnosis and screening of molecular biomarkers in NNH patients.
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