beta-Glucuronidase and hyperbilirubinaemia in breast-fed and formula-fed babies

Challenges Related to Acquisition of Physiological Data for Physiologically Based Pharmacokinetic (PBPK) Models in Postpartum, Lactating Women and Breastfed Infants-A Contribution from the ConcePTION Project

Physiologically based pharmacokinetic (PBPK) modelling is a bottom-up approach to predict pharmacokinetics in specific populations based on population-specific and medicine-specific data. Using an illustrative approach, this review aims to highlight the challenges of incorporating physiological data to develop postpartum, lactating women and breastfed infant PBPK models. For instance, most women retain pregnancy weight during the postpartum period, especially after excessive gestational weight gain, while breastfeeding might be associated with lower postpartum weight retention and long-term weight control. Based on a structured search, an equation for human milk intake reported the maximum intake of 153 mL/kg/day in exclusively breastfed infants at 20 days, which correlates with a high risk for medicine reactions at 2-4 weeks in breastfed infants. Furthermore, the changing composition of human milk and its enzymatic activities could affect pharmacokinetics in breastfed infants. Growth in breastfed infants is slower and gastric emptying faster than in formula-fed infants, while a slower maturation of specific metabolizing enzymes in breastfed infants has been described. The currently available PBPK models for these populations lack structured systematic acquisition of population-specific data. Future directions include systematic searches to fully identify physiological data. Following data integration as mathematical equations, this holds the promise to improve postpartum, lactation and infant PBPK models.

175 Years of Bilirubin Testing: Ready for Point-of-Care?

Bilirubin was first detected in blood in 1847 and since then has become one of the most widely used biomarkers for liver disease. Clinical routine bilirubin testing is performed at the hospital laboratory, and the gold standard colorimetric test is prone to interferences. The absence of a bedside test for bilirubin delays critical clinical decisions for patients with liver disease. This clinical care gap has motivated the development of a new generation of bioengineered point-of-care bilirubin assays. In this Perspective, recently developed bilirubin assays are critically discussed, and their translational potential evaluated.

Impact of Saccharomyces boulardii on jaundice in premature infants undergoing phototherapy

OBJECTIVES

To evaluate the therapeutic effect of Saccharomyces boulardii supplementation on jaundice in premature infants undergoing phototherapy.

METHODS

In this article, the authors reviewed 100 hospitalized jaundiced premature infants under 35 weeks of gestational age. All infants were assigned to a control group (n = 45) and a treatment group (n = 55) randomly. The infants in the treatment group received S. boulardii supplementation by undergoing phototherapy and the infants in the control group were only treated by phototherapy. The total serum bilirubin levels were detected before and at the end of phototherapy, and transcutaneous bilirubin levels were measured on the 1st, 4th, 8th and 15th day of treatment. The duration of jaundice resolution and phototherapy, stool frequency, and characteristics were compared after phototherapy.

RESULTS

The duration of jaundice resolution and phototherapy were shortened. Total serum bilirubin level was lower than the control group at the end of phototherapy (p < 0.05). Transcutaneous bilirubin levels decreased more significantly on the 8th and 15th day of treatment (p < 0.05), while there were no significant differences on the post-treatment 1st and 4th day (p > 0.05). In addition, bowel movements including stool frequency and Bristol Stool Form Scale ratings of stools also improved after treatment.

CONCLUSIONS

S. boulardii in combination with phototherapy is effective and safe in reducing bilirubin levels and duration of phototherapy, accelerating jaundice resolution in premature infants with jaundice. The procedure also provided an ideal therapeutic effect of diarrhea induced by phototherapy to promote compliance and maternal-infant bonding.

Fetal and neonatal bilirubin metabolism

Human fetal and neonatal bilirubin metabolism is centered on 4Z,15Z-bilirubin IXα (BR) due to the extremely low BR conjugating capacity of the liver. BR is a unique, highly lipophilic substance with physiological and toxic effects in the cell membranes of organs and body tissues. The fetus excretes BR through the placenta to the maternal circulation. After birth, BR is thought to act as an antioxidant against the increase in reactive oxygen species caused by the rapid increase in oxygen concentration during the adaptation process from in amniotic fluid to in air. However, bilirubin encephalopathy is a toxic effect of bilirubin. Due to the lipophilic nature of BR, it must be bound to a carrier to be distributed to various parts of the body by hydrophilic blood. This carrier of BR is human serum albumin (HSA). In humans, BR can be excreted efficiently after undergoing photochemical reactions upon high affinity binding to HSA. HSA also plays an important role in the prevention of bilirubin encephalopathy. This review focuses on the developmental and physiological role of bilirubin metabolism during the fetal and neonatal periods.

Inherited disorders of bilirubin clearance

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.

Role of extrahepatic UDP-glucuronosyltransferase 1A1: Advances in understanding breast milk-induced neonatal hyperbilirubinemia

Newborns commonly develop physiological hyperbilirubinemia (also known as jaundice). With increased bilirubin levels being observed in breast-fed infants, breast-feeding has been recognized as a contributing factor for the development of neonatal hyperbilirubinemia. Bilirubin undergoes selective metabolism by UDP-glucuronosyltransferase (UGT) 1A1 and becomes a water soluble glucuronide. Although several factors such as gestational age, dehydration and weight loss, and increased enterohepatic circulation have been associated with breast milk-induced jaundice (BMJ), deficiency in UGT1A1 expression is a known cause of BMJ. It is currently believed that unconjugated bilirubin is metabolized mainly in the liver. However, recent findings support the concept that extrahepatic tissues, such as small intestine and skin, contribute to bilirubin glucuronidation during the neonatal period. We will review the recent advances made towards understanding biological and molecular events impacting BMJ, especially regarding the role of extrahepatic UGT1A1 expression.

Quantitative assessment of the multiple processes responsible for bilirubin homeostasis in health and disease

Serum bilirubin measurements are commonly obtained for the evaluation of ill patients and to screen for liver disease in routine physical exams. An enormous research effort has identified the multiple mechanisms involved in the production and metabolism of conjugated (CB) and unconjugated bilirubin (UB). While the qualitative effects of these mechanisms are well understood, their expected quantitative influence on serum bilirubin homeostasis has received less attention. In this review, each of the steps involved in bilirubin production, metabolism, hepatic cell uptake, and excretion is quantitatively examined. We then attempt to predict the expected effect of normal and defective function on serum UB and CB levels in health and disease states including hemolysis, extra- and intrahepatic cholestasis, hepatocellular diseases (eg, cirrhosis, hepatitis), and various congenital defects in bilirubin conjugation and secretion (eg, Gilbert's, Dubin-Johnson, Crigler-Najjar, Rotor syndromes). Novel aspects of this review include: 1) quantitative estimates of the free and total UB and CB in the plasma, hepatocyte, and bile; 2) detailed discussion of the important implications of the recently recognized role of the hepatic OATP transporters in the maintenance of CB homeostasis; 3) discussion of the differences between the standard diazo assay versus chromatographic measurement of CB and UB; 4) pharmacokinetic implications of the extremely high-affinity albumin binding of UB; 5) role of the enterohepatic circulation in physiologic jaundice of newborn and fasting hyperbilirubinemia; and 6) insights concerning the clinical interpretation of bilirubin measurements.

Bilirubin uridine diphosphate-glucuronosyltransferase variation is a genetic basis of breast milk jaundice

OBJECTIVE

To evaluate the role of bilirubin UDP-glucuronosyltransferase family 1, polypeptide A1 (UGT1A1) gene variations on prolonged unconjugated hyperbilirubinemia associated with breast milk feeding (breast milk jaundice [BMJ]).

STUDY DESIGN

UGT1A1 gene allelic variation was analyzed in 170 Japanese infants with BMJ with polymerase chain reaction-direct sequencing, and their genotypes compared with serum bilirubin concentrations. In 62 of 170 infants, serum bilirubin concentration was followed after 4 months of life. Genotypes were examined in 55 infants without BMJ.

RESULTS

Of 170 infants with BMJ, 88 (51.8%) were homozygous UGT1A1*6. Serum bilirubin concentrations (21.8 ± 3.65 mg/dL) were significantly greater than in infants with other genotypes (P < .0001). The Gilbert UGT1A1*28 allele was not detected in infants with BMJ, except in an infant who was compound heterozygous with UGT1A1*6. At 4 months of age, serum bilirubin concentration improved to >1 mg/dL, except in 2 infants who were homozygous UGT1A1*7. Homozygous UGT1A1*6 was not detected in the control group.

CONCLUSION

One-half of the infants with BMJ were homozygous UGT1A1*6 and exhibited a serum bilirubin concentration significantly greater than other genotypes. This finding indicates that UGT1A1*6 is a major cause of BMJ in infants in East Asia. Previous finding have demonstrated that 5β-pregnane-3α,20β-diol present in breast milk inhibits p.G71R-UGT1A1 bilirubin glucuronidation activity. Thus, prolonged unconjugated hyperbilirubinemia may develop in infants with UGT1A1*6 who are fed breast milk.

Correlation of UGT1A1 TATA-box polymorphism and jaundice in breastfed newborns-early presentation of Gilbert's syndrome

OBJECTIVE

The etiology of jaundice in otherwise healthy breastfed newborns that can present as early-onset exaggerated physiologic jaundice, or late breast milk jaundice (BMJ), is not yet entirely understood. This study tested the hypothesis that molecular marker for Gilbert's syndrome (GS), UGT1A1 TATA-box polymorphism, is associated with this disorders.

METHODS

We have investigated the UGT1A1 polymorphism frequency and its relation to severity of hyperbilirubinemia and jaundice duration among 220 exclusively breastfed term newborns; 57 of them with non-physiologic hyperbilirubinemia (NH), and 163 with BMJ, and in 187 healthy controls.

RESULTS

Significant differences in TA7/7 genotype frequency were established. The highest frequency was observed among the newborns with BMJ (42.0%), intermediate in the NH group (24.6%), while the controls had the lowest TA7/7 frequency (12.8%). Linear increase in TA7/7 frequency was observed depending on the duration of jaundice, peaking at 42.4% in newborns with the longest jaundice duration. Positive correlation between the serum bilirubin levels and the TATA-box length was established in all groups.

CONCLUSION

This study provides evidence that UGT1A1 TATA-box polymorphism is an important risk factor for developing jaundice in term breastfed newborns, presented as either early non-physiologic hyperbilirubinemia or breast milk jaundice. These results further support the original Odell's idea of neonatal jaundice as an early presentation of GS.

Cytokines in human milk and late-onset breast milk jaundice

BACKGROUND

Maternal milk plays an important role in the development of late-onset breast milk jaundice (BMJ), possibly due to the unique characteristics of breast milk. The aim of this study was to investigate whether there is a relation between cytokine concentrations in the milk of nursing mothers and BMJ.

METHODS

Breast milk samples were collected from breast-feeding mothers of healthy full-term neonates, 40 with BMJ and 40 without jaundice. Milk samples were taken between the second and the fourth postpartum week. The concentrations of interleukin (IL)-1 β, IL-6, IL-8, IL-10, and tumor necrosis factor-α were measured by flow cytometric bead array.

RESULTS

There were significant differences between the study groups in terms of IL-1 β concentrations (P= 0.013). Not statistically significant but similar trends were also seen for IL-10 (P= 0.067) and tumor necrosis factor-α (P= 0.053) concentrations. However, no significant differences were noted in IL-6 (P= 0.174) and IL-8 (P= 0.285) concentrations.

CONCLUSIONS

IL-1 β concentration seems to be increased in milk of mothers whose infants had BMJ. Although the effect of these cytokines on BMJ is unknown, it may cause prolonged jaundice via hepatic uptake, hepatic excretion, conjugation and intestinal absorption.

Risk factors for hyperbilirubinemia in breastfed term neonates

Increased breastfeeding was suggested as a contributing factor to significant hyperbilirubinemia. The aim of this study was to identify the risk factors associated with jaundice in exclusively breastfed term neonates. We retrospectively reviewed all consecutively live-born neonates from August 2009 to July 2010 who had complete outpatient department (OPD) follow-up at ≤14 days old. Hyperbilirubinemia was defined as a transcutaneous bilirubin (TcB) value of ≥15 mg/dl. During the study period, there were 718 deliveries, of which 152 neonates were transferred to the special care nursery or neonatal intensive care unit; 566 neonates were discharged from the nursery, and 243 neonates were excluded: 83 did not return to the OPD, 46 were older than 14 days at OPD follow-up, 44 were <37 weeks of gestational age, and 70 had been fed formula. In total, 323 neonates were enrolled and classified into the hyperbilirubinemic (114 neonates) and non-hyperbilirubinemic groups (209 neonates). The gender, gestational age, Apgar score, age at nursery discharge, birth weight, and body weight at nursery discharge and at OPD were comparable between the two groups. TcB values at nursery discharge were positively correlated with TcB values in the OPD. Infants with hyperbilirubinemia exhibited significantly greater body weight loss from birth to the OPD follow-up and significantly less body weight gain from nursery discharge to OPD follow-up.

CONCLUSION

High TcB values at nursery discharge and a smaller body weight gain are associated with hyperbilirubinemia in term neonates who are exclusively breastfed.

Screening and early postnatal management strategies to prevent hazardous hyperbilirubinemia in newborns of 35 or more weeks of gestation

Although kernicterus is a rare condition, it is still being reported in North America and Western Europe in addition to less developed parts of the world. The majority of affected infants are term and late-preterm newborns who have been discharged from the nursery as 'healthy newborns' yet have subsequently developed extreme hyperbilirubinemia and the classic neurodevelopmental findings associated with kernicterus. Published guidelines provide the basic tools for preventing hazardous hyperbilirubinemia and the two most important of these are a systematic assessment, prior to discharge, of each infant, for the risk of severe hyperbilirubinemia, and appropriate follow-up based on the time of discharge and the risk assessment. The most recent recommendations call for a predischarge measurement of the serum or transcutaneous bilirubin in all infants. When combined with the gestational age and other risk factors for hyperbilirubinemia, this provides the best estimate of the risk, or lack of risk, for subsequent hyperbilirubinemia, and determines the timing of follow-up and the need for further evaluation and treatment. The application of these principles to the management of the jaundiced newborn might not eliminate every case of kernicterus, but should contribute to a reduction in its occurrence.

A polymorphic mutation, c.-3279T>G, in the UGT1A1 promoter is a risk factor for neonatal jaundice in the Malay population

The uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene encodes the enzyme responsible for bilirubin glucuronidation. To evaluate the contribution of UGT1A1 promoter mutations to neonatal jaundice, we determined the genotypes of c.-3279T>G, c.-3156G>A, and A(TA)7TAA in Malay infants with neonatal jaundice (patients) and in infants without neonatal jaundice (controls). In our population study, only c.-3279T>G was associated with neonatal jaundice. The genotype distributions between both groups were significantly different (p = 0.003): the frequency of homozygosity for c.-3279G was much higher in patients than those in controls. Allele frequency of c.-3279G was significantly higher in patients than those in controls (p = 0.006). We then investigated changes in transcriptional activity because of c.-3279T>G. Luciferase reporter assay in HepG2 cells demonstrated that transcriptional activity of the c.-3279G allele was significantly lower than that of the c.-3279T allele in both the absence and presence of bilirubin. Luciferase reporter assay in COS-7 cells elucidated that c.-3279T>G modified the synergistic effects of the nuclear factors associated with transcriptional machinery. In conclusion, the c.-3279T>G mutation in the UGT1A1 promoter is a genetic risk factor for neonatal jaundice.

Homozygous variant of UGT1A1 gene mutation and severe neonatal hyperbilirubinemia

BACKGROUND

The aim of the present study was to compare, in a case-control study, the prevalence of nucleotide 211 guanine to adenine (G-->A) mutation of uridine diphosphoglucuronosyl transferase (UGT1A1) gene in Malaysian Chinese newborns with and without severe hyperbilirubinemia (total serum bilirubin >250 micromol/L during first 48 h of life or > or =300 micromol/L thereafter), and to determine whether this mutation was a significant risk factor associated with severe hyperbilirubinemia.

METHODS

Seventy-four term infants of Chinese descent admitted with severe hyperbilirubinemia were recruited. Infants without severe hyperbilirubinemia (n = 125) were randomly selected from among healthy Chinese term infants. UGT1A1 nucleotide 211 polymorphism was assayed using the Taqman single nucleotide polymorphism genotyping method. Using gestational age, types of feeds, G6PD mutation, G6PD enzyme levels, and UGT1A1 gene mutation status as independent variables, logistic regression analysis was carried out to determine the significant risk factors associated with severe hyperbilirubinemia.

RESULTS

UGT1A1 gene mutation was significantly more common among hyperbilirubinemic infants (39.2%) than controls (25.6%; P = 0.04). Gestational age (adjusted odds ratio [OR], 0.7; 95% confidence intervals [CI]: 0.5-0.9; P = 0.01), G6PD mutation (adjusted OR, 7.2; 95%CI: 2.7-19.0; P < 0.0001), exclusive breast-feeding (adjusted OR, 11.7; 95%CI: 2.7-49.9; P = 0.001), and homozygous variant of UGT1A1 gene mutation (adjusted OR, 32.2; 95%CI: 3.8-273.2; P = 0.001) were significant risk factors. Heterozygous variant of UGT1A1 gene mutation, actual levels of G6PD enzyme, and mixed feeding were not.

CONCLUSION

Homozygous variant of nucleotide 211 G-->A mutation of UGT1A1 gene is a significant risk factor associated with severe hyperbilirubinemia among Malaysian Chinese newborns.

Neonatal jaundice and stool production in breast- or formula-fed term infants

It has remained unclear whether the amount of fecal fat excreted in the stool and stool production influences the severity of neonatal jaundice. We determined the relationship between stool production, fecal fat excretion and jaundice in healthy breast-fed (BF) or formula-fed (FF) (near-)term neonates. From postnatal day 1-4, we quantitatively collected stools from 27 FF and 33 BF infants in daily fractions. Stool production and fecal fat contents were related to unconjugated bilirubin (UCB) levels, as determined by transcutaneous bilirubinometry (TcB). Bilirubin concentrations and stool production did not differ between FF and BF neonates during the study period. Neonatal bilirubin levels were not inversely correlated with stool production. FF and BF infants had similar fecal fat excretion rates. The stool production of FF infants was profoundly lower in the present study than in a 1985 study by De Carvalho et al. [J Pediatr (1985) 107:786-790]. We conclude that increased jaundice during the first postnatal days in healthy term neonates can no longer be attributed to breast-feeding and speculate that improved absorbability of formulas since 1985 has contributed to similar fat excretion and stool production in FF and BF neonates in 2007.

Cytokines in human colostrum and neonatal jaundice

Breast-fed infants have higher bilirubin levels than formula-fed infants, possibly because of variations in the composition of the breast milk. The aim of this study was to investigate whether there is a relationship between cytokine levels in the colostrum of nursing mothers and neonatal jaundice (NJ). Breast milk samples were collected from breast-feeding mothers of healthy full-term neonates, 32 with NJ and 29 without jaundice. The concentrations of IL-1beta, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-alpha were measured by chemiluminescence enzyme immunometric assays. Mothers of infants with NJ had a higher concentration of IL-1beta in colostrum, compared with those feeding neonates without NJ, and similar trends were seen for IL-6, IL-8, IL-10, and for TNF-alpha. The concentrations of IL-1beta significantly correlated with IL-6, IL-8, IL-10, and TNF-alpha concentrations, but not with serum bilirubin levels of infants with NJ. In conclusion, the concentrations of IL-1beta were increased in colostrum from breast-feeding mothers whose infants had NJ. The correlation between the concentrations of cytokines involved in the function of hepatic uptake and excretory systems and in the enterohepatic circulation of bilirubin provides additional data to the delineation of the cascade of pathophysiological events that can lead to NJ.

Immunizations, neonatal jaundice and animal-induced injuries

PURPOSE OF REVIEW

To review the literature published within the last year on three topics essential to clinical pediatrics: immunizations, neonatal jaundice, and animal-induced injuries.

RECENT FINDINGS

New vaccines that protect against meningococcus, pertussis and rotavirus are safe, effective and recommended for routine immunization. Young children remain a high priority for influenza vaccination while the world awaits further developments of avian influenza. Pneumococcal and varicella vaccinations have benefited many. Debate exists on how to screen for hyperbilirubinemia in neonates and new strategies are emerging to prevent it. There seems to be no link between hyperbilirubinemia and autism spectrum disorders. We have learned that rabies can be transmitted by transplantation; it remains a global public health problem and its incidence is frequently underestimated in developing nations. Lastly, brown recluse spider bites are often misdiagnosed.

SUMMARY

The face of pediatric infectious disease is changing as we incorporate new vaccines into our routine practice. Rotavirus vaccine has significant implications for the health of children across the globe. The management strategy for neonatal jaundice continues to focus on screening and prevention. We need to devote more energy to combating rabies in countries where it is endemic.

A controlled, randomized, double-blind trial of prophylaxis against jaundice among breastfed newborns

OBJECTIVES

Neonatal jaundice is a greater problem for infants fed breast milk, compared with formula. This study tested the hypotheses that feeding breastfed newborns beta-glucuronidase inhibitors during the first week after birth would increase fecal bilirubin excretion and would reduce jaundice without affecting breastfeeding deleteriously.

METHODS

Sixty-four breastfed newborns were randomized to 4 groups, ie, control or receiving 6 doses per day (5 mL per dose) of L-aspartic acid, enzymatically hydrolyzed casein (EHC), or whey/casein (W/C) for the first week. L-aspartic acid and EHC inhibit beta-glucuronidase. Transcutaneous bilirubin levels (primary outcome) were measured daily (Jaundice Meter [Minolta/Air Shields, Hatboro, PA] and Bilicheck [Respironics, Pittsburgh, PA]). All stools were collected, and fecal bile pigments, including bilirubin diglucuronide, bilirubin monoglucuronides, and bilirubin, were analyzed with high-performance liquid chromatography. Follow-up assessments included day 7 body weight, day 6/7 prebreastfeeding/postbreastfeeding weights, maternal ratings, and ages at formula introduction and breastfeeding cessation.

RESULTS

The groups were comparable at entry. Overall, the L-aspartic acid, EHC, and W/C groups had significantly lower transcutaneous bilirubin levels than did the control group (75.8%, 69.6%, and 69.2%, respectively, of the control mean, 8.53 mg/dL, at the bilirubin peak on day 4). The L-aspartic acid, EHC, and W/C groups had significantly lower transcutaneous bilirubin levels on days 3 to 7. Fecal bile pigment excretion was greatest in the L-aspartic acid group, significantly greater than control values. There were no significant differences in dosages, follow-up measurements, and maternal ratings.

CONCLUSIONS

Use of minimal aliquots of L-aspartic acid and EHC for beta-glucuronidase inhibition results in increased fecal bilirubin excretion and less jaundice, without disruption of the breastfeeding experience. Decreased jaundice in the W/C group, which lacked a beta-glucuronidase inhibitor, suggests a different mechanism.

Enterohepatic cycling of bilirubin as a cause of 'black' pigment gallstones in adult life

In contrast to bile salts, which undergo a highly efficient enterohepatic circulation with multiple regulatory and physiologic functions, glucuronic acid conjugates of bilirubin are biliary excretory molecules that in health do not have a continuing biologic life. Intestinal absorptive cells are devoid of recapture transporters for bilirubin conjugates, and their large size and polarity prevent absorption by passive diffusion. However, unconjugated bilirubin, the beta-glucuronidase hydrolysis product of bilirubin glucuronides can be absorbed passively from any part of the small and large intestines. This can occur only if unconjugated bilirubin is kept in solution and does not undergo rapid bacterial reduction to form urobilinoids. Here we collect, and in some cases reinterpret, experimental and clinical evidence to show that in addition to the well-known occurrence in newborns, enterohepatic cycling of unconjugated bilirubin can reappear in adult life. This happens as a result of several common conditions, particularly associated with bile salt leakage from the small intestine, the most notable ileal dysfunction resulting from any medical or surgical cause. We propose that when present in excess, colonic bile salts solubilize unconjugated bilirubin, delay urobilinoid formation, prevent calcium complexing of unconjugated bilirubin and promote passive absorption of unconjugated bilirubin from the large intestine. Following uptake, reconjugation, and resecretion into bile, this source of 'hyperbilirubinbilia' may be the important pathophysiological risk factor for 'black' pigment gallstone formation in predisposed adult humans.

Breast-feeding, neonatal jaundice and kernicterus

Despite the many advantages of breast-feeding, there is ample documentation of the strong association between breast-feeding and an increase in the risk of neonatal hyperbilirubinaemia. Breast-fed infants have higher bilirubin levels than formula-fed infants. Suggested mechanisms for these findings include poor fluid and caloric intake, inhibition of hepatic excretion of bilirubin, and intestinal absorption of bilirubin (enterohepatic circulation). On rare occasions, breast-fed infants without evidence of haemolysis have developed extreme hyperbilirubinaemia and kernicterus. Because almost all of the cases of kernicterus reported in the last 15 years have occurred in fully or partially breast-fed newborns, it is important that these infants be followed closely. Appropriate support and advice must be provided to the lactating mother so that successful breast-feeding can be established and the risk of severe hyperbilirubinaemia reduced.

Breastfeeding and jaundice

In the breastfed infant, prolongation of unconjugated hyperbilirubinemia into the third and later weeks of life in the healthy newborn is a normal and regularly occurring extension of physiologic jaundice. This is known as breastmilk jaundice. A factor in human milk increases the enterohepatic circulation of bilirubin. Insufficient caloric intake resulting from maternal and/or infant breastfeeding difficulties may also increase serum unconjugated bilirubin concentrations. This is the infantile equivalent of adult starvation jaundice. It is known as breastfeeding jaundice or "breast-nonfeeding jaundice." This increase in severity of physiologic jaundice of the newborn also results from increased enterohepatic circulation of bilirubin, but not because of a factor in human milk. In extreme cases, it may place the infant at risk for development of bilirubin encephalopathy. Optimal breastfeeding practices, which result in minimal initial weight loss and early onset of weight gain, are associated with both reduced breastfeeding jaundice and minimization of the intensity of breastmilk jaundice.

A novel inhibitor of beta-glucuronidase: L-aspartic acid

Infants who consume casein hydrolysate formula have been shown to have lower neonatal jaundice levels than infants who consume routine formula or breast milk. Because casein hydrolysate has been shown to contain a beta-glucuronidase inhibitor, one possible mechanism to explain this finding is blockage of the enterohepatic circulation of bilirubin by a component of the formula. The aim of this research was to identify the source of the beta-glucuronidase inhibition in hydrolyzed casein. A beta-glucuronidase inhibition assay and measurements of physical and kinetic parameters were used to analyze the components of hydrolyzed casein and infant formulas. Kinetic studies used purified beta-glucuronidase. The L-aspartic acid in hydrolyzed casein accounts for the majority of the beta-glucuronidase inhibition present. Kinetic studies indicate a competitive inhibition mechanism. L-aspartic acid is a newly identified competitive inhibitor of beta-glucuronidase.

Jaundice and breastfeeding

Optimal management of breastfeeding does not eliminate neonatal jaundice and elevated serum bilirubin concentrations. Rather, it leads to a pattern of hyperbilirubinemia that is normal and, possibly, beneficial to infants. Excessive frequency of exaggerated jaundice in a hospital or community population of breastfed infants may be a warning that breastfeeding policies and support are not ideal for the establishment of good breastfeeding practices. The challenge to clinicians is to differentiate normal patterns of jaundice and hyperbilirubinemia from those that indicate an abnormality or place an infant at risk.

Differences in transcutaneous bilirubin readings in Japanese term infants according to feeding method

BACKGROUND

Controversy has existed for many years over whether infant feeding methods are related to serum bilirubin concentrations during the first few days of life. Differences in initial jaundice patterns according to the feeding method until 72 h after birth have not been elucidated hitherto. The difference may become clear in Japanese neonates because jaundice shows a much higher peak bilirubin concentration and a later peak in Japanese neonates than in Caucasian neonates.

METHODS

In the present study, we investigated variations in the transcutaneous bilirubin reading (TcB) obtained within 72 h after birth among 177 breast-fed and 494 formula-fed healthy Japanese term neonates.

RESULTS

There was no difference between TcB in formula-fed and breast-fed infants until the first 30 h, after which time the rate of increase in TcB was lower in formula-fed infants. Among breast-fed neonates, a good linear regression between time after birth and TcB was maintained. Similarly, weight losses in breast-fed infants at 24-48 h and 48-72 h after birth were greater than those in formula-fed infants.

CONCLUSIONS

The jaundice pattern in Japanese neonates from 30 to 72 h after birth according to the feeding method was different from that in Caucasian neonates.

Prolonged unconjugated hyperbilirubinemia associated with breast milk and mutations of the bilirubin uridine diphosphate- glucuronosyltransferase gene

OBJECTIVE

Breast milk jaundice is a common problem in nursing infants. It has been ascribed to various breast milk substances, but the component or combination of components that is responsible remains unknown. During our study of defects of the bilirubin uridine diphosphate-glucuronosyltransferase gene (UGT1A1) in patients with hereditary unconjugated hyperbilirubinemia (Crigler-Najjar syndrome and Gilbert's syndrome) and neonatal hyperbilirubinemia, we encountered a prolonged case associated with breastfeeding; after cessation of breastfeeding, the infant's bilirubin level became normal. Genetic analysis revealed a missense mutation identical to that found in patients with Gilbert's syndrome, which usually causes jaundice after puberty. We analyzed the bilirubin UGT1A1 of infants with prolonged unconjugated hyperbilirubinemia associated with breast milk to ascertain whether genetic factors are involved.

PATIENTS AND METHODS

We analyzed 17 breastfed Japanese infants with apparent prolonged jaundice (total serum bilirubin concentrations above 171 micromol/L [10 mg/dL]) 3 weeks to 1 month after their birth. Except for jaundice, the infants were healthy and did not show evidence of hemolytic anemia, liver dysfunction, or hypothyroidism. After cessation of breastfeeding, the serum bilirubin concentration began to decrease in all cases. When breastfeeding was resumed, serum bilirubin concentration again became elevated in some infants, but the concentration fell to within normal by 4 months of age. We analyzed the polymerase chain reaction-amplified exon, promoter, and enhancer regions of UGT1A1 by direct sequencing.

RESULTS

Sixteen infants had at least one mutation of the UGT1A1. Seven were homozygous for 211G-->A (G71R), which is the most common mutation detected in the East Asian population, and the mutant enzyme had one third of the normal activity. G71R is the most common missense mutation we found in our analyses in Japanese patients with Gilbert's syndrome, and it corresponds to a UGT1A1 polymorphism in the Japanese population (the allele frequency is.16). One was heterozygous for 1456T-->G (Y486D) and homozygous for 211G-->A. Six were heterozygous for 211G-->A. One was heterozygous for both 211G-->A and a TATA box mutation (A(TA)7TAA). One had a heterozygous mutation in an enhancer region (C-->A at -1353). We did not detect a homozygous A(TA)7TAA mutation, which was the most common cause of Gilbert's syndrome in European population, in this study of Japanese infants with prolonged hyperbilirubinemia triggered by breast milk.

CONCLUSIONS

The results indicate that defects of UGT1A1 are an underlying cause of the prolonged unconjugated hyperbilirubinemia associated with breast milk. One or more components in the milk may trigger the jaundice in infants who have such mutations. The mutations we found were identical to those detected in patients with Gilbert's syndrome, a risk factor of neonatal nonphysiologic hyperbilirubinemia and a genetic factor in fasting hyperbilirubinemia.

Anticonvulsant use during lactation

The issue of prescribing anticonvulsant drugs during lactation is clinically important, but also complex. Data for some drugs are completely lacking and for other drugs information is only available from single dose or short term studies or case reports. Moreover, limited knowledge exists about the practical impact of the drug concentrations found in breast milk and there are great methodological problems in the assessment of possible adverse drug reactions in infants. Nevertheless, based on current knowledge, some recommendations can be suggested. Treatment with carbamazepine, valproic acid (sodium valproate) and phenytoin is considered compatible with breastfeeding. Treatment with ethosuximide or phenobarbital (phenobarbitone)/primidone should most probably be regarded as potentially unsafe and close clinical monitoring of the infant is recommended if it is decided to continue breastfeeding. Occasional or short term treatment with benzodiazepines could be considered as compatible with breastfeeding, although maternal diazepam treatment has caused sedation in suckling infants after short term use. During long term use of benzodiazepines, infants should be observed for signs of sedation and poor suckling. Only very limited clinical data are available for the new generation anticonvulsant drugs and no clearcut recommendations can be made until further data are present. If it is decided to continue breast feeding during treatment with these drugs, the infant should be monitored for possible adverse effects. In general, the drug should be given in the lowest effective dose, guided by maternal serum or plasma drug concentration monitoring. If breast feeding is avoided at times of peak drug levels in milk, the exposure of the infant can be reduced to some extent. As breast milk has considerable advantages over formula milk, the benefits of continuing breast feeding should always be taken into consideration in the risk-benefit analysis.

Inhibition of beta-glucuronidase by casein hydrolysate formula

BACKGROUND

A casein hydrolysate infant formula has been shown to be associated with lower levels of neonatal jaundice than are standard infant formulas. Because beta-glucuronidase is related to neonatal jaundice, this study examined the effect of a casein hydrolysate formula on beta-glucuronidase.

METHODS

Beta-glucuronidase activity was measured with or without added dietary components. The beta-glucuronidase sources used were meconium, breast milk, and the purified bovine liver enzyme. The dietary components assayed for their effect on beta-glucuronidase activity included casein hydrolysate formula (Nutramigen), whey-predominant formula (Enfamil), breast milk; enzymatically hydrolyzed casein, and other constituents of the casein hydrolysate formula. Stool samples of 6-day-old infants, who were exclusively fed one of the two formulas or breast milk, were also assayed for inhibition of beta-glucuronidase.

RESULTS

Only Nutramigen, enzymatically hydrolyzed casein, and stool from Nutramigen-fed infants consistently demonstrated significant inhibition of beta-glucuronidase activity, ranging from 45% to 85% of that in controls. The inhibition of beta-glucuronidase in purified bovine liver demonstrates a dose response in a pH range from 4 to 7.3.

CONCLUSIONS

Hydrolyzed casein contains a beta-glucuronidase inhibitor that, in casein hydrolysate-fed infants, persists after passage through the digestive tract. These data are consistent with the possibility that inhibition of beta-glucuronidase is a mechanism by which infants fed casein hydrolysate have lower jaundice levels than infants fed routine formulas or breast milk. Further study of this mechanism is needed.

Breast milk beta-glucuronidase and prolonged jaundice in the neonate

Breast milk samples from mothers of breast-fed, healthy, term newborns with unexplained prolonged jaundice were analyzed for beta-glucuronidase activity. Mean enzyme activity was 75.7 +/- 34.5 modified Sigma units/ml in the breast milk samples ingested by the study group of jaundiced babies (n = 25) and 82.2 +/- 40.1 modified Sigma units/ml in the samples ingested by the control group of non-jaundiced babies (n = 20) (p > 0.05). Enzyme activities at 2, 3 and 4 postnatal weeks were 101.0 +/- 39.9, 66.0 +/- 20.7 and 57.0 +/- 22.4 modified Sigma units/ml in the study group and 87.9 +/- 36.1, 58.5 +/- 15.0 and 88.3 +/- 49.1 modified Sigma units/ml in the controls. The differences were not statistically significant (p > 0.05). We conclude that breast milk beta-glucuronidase activity may be a contributory factor, in the presence of other variables, in hyperbilirubinemia but it is neither the main nor the only cause of prolonged jaundice in neonates.

The effects of benzodiazepine use during pregnancy and lactation

Although there are a number of studies and individual case reports concerning the use of benzodiazepines in human pregnancy, the data concerning teratogenicity and effects on postnatal development and behaviour are inconsistent. There is evidence from studies in the 1970s that first trimester exposure to benzodiazepines in utero has resulted in the birth of some infants with facial clefts, cardiac malformations, and other multiple malformations, but no syndrome of defects. Diazepam and chlordiazepoxide are amongst the drugs most frequently implicated in the earlier studies. However, data from later studies provide no clear evidence of significant increase in either the overall incidence of malformations or of any particular type of defect. Many of the women included in these studies has psychiatric illnesses, epilepsy, or diabetes all of which have an intrinsic risk in pregnancy, and some were on multidrug therapy. Medical-obstetric histories and family history of malformations were not always presented in the publications, which makes assessment of risk associated with benzodiazepine use per se difficult. Nevertheless, in most of the studies involving first trimester use of benzodiazepines, the majority of infants were normal at birth and had normal postnatal development. Late third trimester use and exposure during labour seems to be associated with much greater risks to the fetus/neonate. Some, but by no means all infants exposed at this time, exhibit either the floppy infant syndrome, or marked neonatal withdrawal symptoms. Symptoms vary from mild sedation, hypotonia, and reluctance to suck, to apnoeic spells, cyanosis, and impaired metabolic responses to cold stress. These symptoms have been reported to persist for periods from hours to months after birth. This correlates well with the pharmacokinetic and placental transfer of the benzodiazepines and their disposition in the neonate. However, there has been no significant increase in the incidence of neonatal jaundice and kernicterus in term infants. The prolonged use of benzodiazepines throughout pregnancy raised the concern that there may be altered transmitter synthesis and function, leading to neurobehavioural problems in the children. In approximately 550 children who were followed up for various times up to four years of age, there is no increase in either the malformation rate or adverse effects on neurobehavioural development and IQ. Although some of the data indicate that a small number of children were slower to develop during the first year or so, they did exhibit catch up growth and most had developed normally by four years of age. Where developmental deficits persisted, it was not possible to prove a cause-effect relationship with benzodiazepine exposure. These children were often from families where there was maternal illness requiring prolonged drug therapy or where there were social problems. It is important to consider poor environmental and social factors when assessing the possible prenatal influence of the benzodiazepines on the postnatal health and development of the child. There is evidence that clonazepam, clorazepate, diazepam, lorazepam, midazolam, nitrazepam, and oxazepam are excreted into breast milk. The published data indicate that the levels detected in breast milk are low; therefore, the suckling infant is unlikely to ingest significant amounts of the drug in this way. Problems may arise if the infant is premature or has been exposed to high concentrations of drug either during pregnancy or at delivery.

The development of a neonatal stool colour comparator

The policies which exist to monitor the passage of neonatal stool vary between and within hospitals. When stool colour is required, the recorded observations are invariably subjective opinions and as such are largely unreliable. The development of a stool colour comparator allowed an objective test to be used by professional staff and mothers. This facilitated data collection for a study which sought to determine, among other factors, the transition time of meconium through to the yellow stool of the milk-fed baby, during the early neonatal period. The transition time of the meconium is indicative of gastrointestinal activity in the newborn and midwives are able to correlate accurately documented changes in stool colour with the baby's daily weight loss to assess the quality and/or adequacy of early infant feeding particularly breast feeding. The stool colour comparator is used in postnatal wards at Ninewells Hospital, Dundee by mothers and midwives and the numerical coding has replaced the previously used subjective abbreviations Mec (Meconium), Ch (Changing) and Y (Yellow).

The effect of diet on feces and jaundice during the first 3 weeks of life

This study examined the relationship between fecal output and neonatal jaundice in infants exclusively fed either human milk or one of three infant formulas (whey predominant, Enfamil; casein predominant, 3305H; and casein hydrolysate, Nutramigen; all from Mead Johnson, Evansville, IN). Stool output was quantitated during the first 3 weeks of life. Jaundice was assessed by measuring serum bilirubin level and transcutaneous jaundice index. In general, after the fourth day, breast-fed infants produced lower-weight individual wet and dry stools than formula-fed infants. Cumulative wet and dry stool output was also lowest in the breast-fed infants during this time. After the first week, breast-fed infants had a higher stooling frequency than formula-fed infants. The jaundice indexes of the four groups differed significantly on all days after day 3, with highest levels in breast-fed infants and lowest levels, for unknown reasons, in those fed casein hydrolysate. The jaundice index of those fed casein hydrolysate was significantly lower than that of the other formula-fed infants on days 10-18. In the breast-fed group the decrease from day 3 to day 21 in both serum bilirubin level and the jaundice index was positively correlated with both the 21-day total wet and total dry cumulative stool weights. It is concluded that the quantity of stool excreted is related to decreases in serum bilirubin levels in infants fed human milk.

Beta glucuronidase and hyperbilirubinaemia in breast fed infants of diabetic mothers

A prospective study was performed comparing bilirubin concentrations in 10 breast fed term infants of diabetic mothers (IDM) to those of 10 breast fed normal term infants. The beta-glucuronidase concentrations in serum and breast milk were assayed in the respective mothers. Significantly higher bilirubin concentrations were noted in the IDM group. Serum and breast milk beta-glucuronidase concentrations were significantly higher in diabetic mothers as compared with those of non-diabetic mothers. We suggest that the high concentration of beta-glucuronidase in breast milk of diabetic mothers is an additional important cause leading to hyperbilirubinaemia in their breast fed infants.

Abnormal results of biochemical liver function tests in breast-fed infants with prolonged indirect hyperbilirubinaemia

To clarify the relationship between hyperbilirubinaemia and abnormal results of biochemical liver function tests in infants with breast milk jaundice (BMJ), 58 breast-fed infants with indirect hyperbilirubinaemia were enrolled in this study. Sera obtained from the above infants were subjected to routine liver function tests. Although serum transaminases were within normal limits in all 58 patients, serum alkaline phosphatase levels were abnormally increased in 13, gamma-glutamyltranspeptidase in 8 and total bile acids in 11 out of all patients examined. A total of 18 (31%) patients had abnormal results in at least one item of the liver function tests. The intrinsic bile acid loading test showed postprandial increases in bile acids in 5 of 16 (31%) patients examined at either 60 or 120 min, while all 13 breast-fed, age-matched controls had no abnormal results. The decrease in rate of serum bilirubin levels after the 3-day discontinuation of breast-feeding was significantly less in patients with increased fasting bile acids than in patients with normal fasting levels of serum bile acids. These results may suggest that mild hepatic dysfunction or cholestasis is associated with indirect hyperbilirubinaemia in some infants with BMJ.

Enterohepatic circulation of nonconjugated bilirubin in rats fed with human milk

To test the hypothesis that enhanced intestinal absorption of bilirubin may contribute to prolonged nonconjugated hyperbilirubinemia in human milk-fed infants, we studied a cross-section of 36 healthy infants and mothers. Milk from mothers and serum from infants were collected at 16.3 +/- 2.4 days. Milk was studied for its effect on the absorption of bilirubin labeled with carbon 14 in rats and compared with buffer and iron-fortified infant formula (Similac With Iron). The percentage of a 1 mg bilirubin dose absorbed by the rat was 25.29 +/- 4.0% when it was administered into the duodenum with buffer, 4.67 +/- 2.4% with Similac formula, and 7.7 +/- 2.9% with human milk. Linear regression analysis, using the infant's serum nonconjugated bilirubin level as the dependent variable and the percentage of (14C)bilirubin absorbed by the rat with the corresponding mother's milk as the independent variable, revealed a significant correlation (r = 0.40; p = 0.016). Inspection of the data suggested that absorptive permissiveness correlated closely with infant serum bilirubin values greater than 24 mumol/L (1.4 mg/dl) (r = 0.55; p = 0.007), whereas in those with bilirubin values less than or equal to 24 mumol/L, there was no apparent correlation. Milk was also analyzed for beta-glucuronidase, nonesterified fatty acids, and the ability to inhibit glucuronosyltransferase activity of rat liver microsomes in vitro, none of which correlated with the infant's serum bilirubin. These data support the theory that enhanced intestinal absorption of bilirubin contributes to the jaundice associated with breast-feeding.

Breastfeeding and breast milk jaundice

Two Types of jaundice associated with breast-feeding are recognized. The first type is early onset breastfeeding jaundice which may result from caloric deprivation and/or insufficient frequency of feeding. This type of jaundice can be prevented or treated by encouraging mothers to nurse as frequently as possible, particularly if the bilirubin level is rising. The second type is later onset, prolonged jaundice, known as the breast milk jaundice syndrome which is associated with one or more abnormalities in the maternal milk itself. Breast milk jaundice syndrome generally needs no therapy if serum bilirubin concentrations remain below 270 mumol/l in healthy full-term infants. When the serum bilirubin concentration is above 270 mumol/l and rising, temporary interruption of breastfeeding may be indicated.

Breast milk jaundice in preterm infants

A retrospective study was performed comparing bilirubin levels in 40 preterm newborns with uncomplicated courses fed a combination of premature breast milk and formula to those of 60 comparable preterm newborns fed formula only. A significantly higher bilirubin level was noted in the group fed the combined diet on the 6th day of life and on the day of discharge. Seventy-six and seven tenths percent of the preterm infants fed breast milk and formula met the criteria for phototherapy, whereas only 45 percent were treated in the group fed formula alone. Our findings indicate that premature breast milk might cause early and late increase in bilirubin levels in healthy preterm newborns.

Piroxicam in breast milk after long-term treatment

The presence of piroxicam in breast milk was determined by HPTLC during initial and long term dosing in 4 women treated for arthritis. Piroxicam appeared in breast milk at about 1-3% of the maternal plasma concentration. No accumulation of piroxicam occurred in milk relative to that in plasma up to 52 days of treatment. Neither piroxicam nor its conjugates were detectable in the urine of one breast-fed infant. The daily dose ingested by the infant was calculated to average 3.5% (maximum 6.3%) of the weight-related maternal dose of piroxicam. It is concluded that a breast-fed infant will be exposed to a very small amount of piroxicam.