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Biomedical subjects

Eve A Roberts

Publications and source records attributed to Eve A Roberts.

At least 19 recordsLinked to original sources
PubMed2006

Effect of orthotopic liver transplantation (OLT) on branched-chain amino acid requirement.

Little is known regarding the impact of liver transplantation on amino acid requirements in children. Since plasma levels of the branched-chain amino acids (BCAA) are decreased in the presence of normal levels of the aromatic amino acids after liver transplantation, normalization of hepatic function may not fully correct changes in BCAA metabolism that occur in the pretransplant period. The goal of the present study was to determine total BCAA requirements of children following liver transplantation. The requirement of total BCAA was determined using indicator amino acid oxidation (IAAO) in five clinically stable children (5.7 +/- 3.5 y, mean +/- SD) 1-8 y post liver transplantation. Children received in random order 6 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. Total BCAA requirement was determined by measuring the oxidation of L-[1-13C] phenylalanine to 13CO2 [F13CO2 in micromol/kg/h], after a primed, continuous infusion of the tracer and using a two-phase linear regression crossover regression analysis. The estimated average requirement and the upper limit of the 95% CI for total BCAA in children who have undergone liver transplantation were 172 and 206 mg/kg/d), respectively. Total BCAA requirement in children who have undergone orthotopic liver transplantation (OLT) remain increased in the post-liver transplant period when compared with healthy school aged children, but is decreased when compared with children with mild-moderate chronic cholestatic (MCC) liver disease.

Amino Acids, Branched-Chain↗
PubMed2006

Proteomics of metal transport and metal-associated diseases.

Proteomics technology has the potential to identify groups of proteins that have similar biological function. However, few attempts have been made to identify and characterize metal-binding proteins by using proteomics strategies. Many transition metals are essential to sustain life. Copper, iron, and zinc are the most abundant transition metals relevant to biological systems. In addition to their important biological functions, metals can also catalyze the formation of damaging free radical species. Hence, their intracellular transport is tightly regulated. Despite recent insights into the intracellular transport of copper and other metals, our overall understanding of intracellular metal metabolism remains incomplete and it is likely that many metal-binding proteins remain undiscovered. Furthermore, the protein targets for metals during metal-associated disease states or during exposure to toxic levels of environmental metals are yet to be unravelled. A proteomics strategy for the analysis of metal-transporting or metal-binding proteins has the potential to uncover how a large number of proteins function in normal or metal-associated diseased states. Here we discuss the principal aspects of metal metabolism, and the recent developments in the area of the proteomics of metal transport.

Biological Transport↗
PubMed2006

Nonalcoholic Fatty Liver Disease (NAFLD): Approach in the Adolescent Patient.

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of liver disease whose hallmark is the accumulation of large-droplet fat in hepatocytes. This metabolic disorder occurs mainly in overweight or obese individuals. The disease mechanism involves hyperinsulinemia and hepatic insulin resistance, not ethanol abuse. NAFLD may be the hepatic manifestation of the "metabolic syndrome" classically associated with type 2 diabetes mellitus and cardiovascular disease. NAFLD ranges from simple steatosis, which is the least rapidly progressing disorder, to nonalcoholic steatohepatitis to cirrhosis, which can evolve to chronic liver failure. The high prevalence of NAFLD in children has been recognized only in the past 5 to 10 years, as rates of childhood obesity have soared. Accordingly, the best strategies for diagnosis and treatment of childhood NAFLD are a work in progress and remain controversial. Weight reduction through a healthy diet and regular medium-intensity exercise is the mainstay of current treatment. Few research data are available to guide pharmacologic therapy. Certain points regarding management of childhood NAFLD require emphasis: It is a serious liver disease that requires detailed clinical investigation. Other liver diseases causing fatty liver and/or abnormal liver tests, notably Wilson disease and chronic viral hepatitis, need to be excluded. Liver biopsy can provide critical diagnostic and staging information. Associated genetic or endocrine disorders need to be identified. Treatment should begin with a low-glycemic index diet that provides adequate nutrients but is low in harmful fats and eliminates foods causing postprandial hyperglycemia. Initially, this can target two to three problem foods so that it is easy for the adolescent to follow. Regular exercise suited to the capabilities and interests of the teenager should be added to the daily routine. Where possible, a team approach, including a dietician and psychologist, should be utilized, as adolescents do better in a supportive atmosphere. Optimal drug treatment requires further research: current front-runners are vitamin E and metformin. The roles of drugs that alter appetite and bariatric surgery for adolescents with NAFLD have not been determined.

Journal Article↗
PubMed2006

Nonalcoholic fatty liver disease in children.

Nonalcoholic fatty liver disease (NAFLD) is likely to reach epidemic proportions in children worldwide in the next decade. NAFLD may be the hepatic aspect of the metabolic syndrome in adults and children. The entire range of liver involvement characterizing NAFLD can occur in children: hepatic macrovesicular steatosis without inflammation, steatosis with inflammation or fibrosis, and cirrhosis. NAFLD may be more severe in children from certain ethnic groups or in association with metabolic disorders characterized by abnormalities in insulin receptor structure and function. Treatment strategies focus on modifying risk factors because specific drug treatments are lacking. Overweight/obesity should be identified as early as possible. Comprehensive clinical management to normalize weight should be instituted immediately to avoid hepatic and nonhepatic complications.

Child↗
PubMed2006

Branched-chain amino acid needs in children with mild-to-moderate chronic cholestatic liver disease.

Protein-energy malnutrition is prevalent in children with chronic cholestatic liver disease. Supplementation of branched-chain amino acids (BCAA) in infants and children with chronic liver disease has been associated with significant improvement in growth and nitrogen balance, suggesting that BCAA requirements are increased in chronic liver disease. The goal of the present study was to determine the total BCAA requirement in children with mild-to-moderate chronic cholestatic (MCC) liver disease using indicator amino acid oxidation (IAAO). Total BCAA requirements were determined in 6 children (6.3 +/- 3.7 y, mean +/- SD) with MCC liver disease. Children were randomly assigned to receive 7 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as those present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. The total BCAA requirement was determined by measuring the oxidation of l-[1-13C] Phe to 13CO2 [F13CO2 in micromol/(kg x h)], after a primed, continuous oral administration of the tracer and using a 2-phase linear regression crossover regression analysis. The estimated mean requirement and the upper limit of the 95% CI for total BCAA establishing using the IAAO in children with MCC liver disease were 209 and 272 mg/(kg x d), respectively. Total BCAA estimated average requirements using the IAAO were significantly higher than mean requirements established previously for healthy children (P < 0.05).

Amino Acids, Branched-Chain↗
PubMed2006

Mild-to-moderate chronic cholestatic liver disease increases leucine oxidation in children.

Malnutrition is prevalent in children with chronic cholestatic liver disease. Using the noninvasive indicator amino acid oxidation (IAAO) technique, we recently determined that mild-to-moderate chronic cholestatic (MCC) liver disease increases the need for branched-chain amino acids (BCAA) in children. To examine the underlying mechanisms responsible for this increased need for BCAA in liver disease, we measured L-[1-(13C)]-leucine oxidation in the postabsorptive and fed states in 10 children with MCC liver disease (8.8 +/- 3.5 y) and in 11 healthy children (9.4 +/- 2.2 y). The oxidation of L-[1-(13C)]-leucine to 13CO2 [F13CO2 in micromol/(kg.h)] was determined after a primed, continuous oral administration of the tracer. Total BCAA in diet was provided at 300 mg/(kg.d) to ensure that leucine oxidation was measured when leucine intake was in excess of requirements. In the postabsorptive state, the rate of release of 13CO2 from 13C-leucine oxidation (F13CO2) and whole-body leucine oxidation were significantly higher in children with MCC liver disease (P < 0.05). However, F13CO2 and whole-body leucine oxidation did not differ in the fed state. We conclude that the increased need for dietary BCAA in MCC liver disease is mediated in part by increased leucine oxidation in the postabsorptive state.

Amino Acids, Branched-Chain↗
PubMed2006

Prevalence of vitamin K deficiency in children with mild to moderate chronic liver disease.

OBJECTIVES: Children with chronic liver disease are at risk for vitamin K deficiency because of fat malabsorption and inadequate dietary intake. The objective of this study was to determine the prevalence of vitamin K deficiency in children with mild to moderate chronic cholestatic and noncholestatic liver disease. METHODS: Vitamin K status was examined in 43 children (0.25-15.9 years) with mild to moderate chronic cholestatic liver disease, 29 children (0.9-16.9 years) with chronic mild to moderate noncholestatic liver disease, and in 44 healthy children (1-18 years). Vitamin K status was assessed by the plasma PIVKA-II (protein induced in vitamin K absence) assay (enzyme-linked immunosorbent assay). Plasma PIVKA-II values greater than 3 ng/mL are indicative of vitamin K deficiency. RESULTS: The mean plasma PIVKA-II (+/-SD) in cholestatic, noncholestatic, and healthy children was 61.9 +/-144, 1.2 +/- 3, and 2.1 +/- ng/mL, respectively (P < 0.002). Fifty-four percent of the children supplemented with vitamin K had plasma PIVKA-II greater than 3 ng/mL. Plasma conjugated bilirubin, total bile acids, and severity of liver disease were positively correlated with plasma PIVKA-II levels (P < 0.05). CONCLUSIONS: Vitamin K deficiency is prevalent in children with mild to moderate chronic cholestatic liver disease, even with vitamin K supplementation. Elevated PIVKA-II levels occurred in children with a normal prothrombin, indicating that more sensitive markers of vitamin K status should be used in children with chronic liver disease. Vitamin K deficiency was related to degree of cholestasis and severity of liver disease in children. Children without cholestasis did not exhibit vitamin K deficiency.

Adolescent↗
PubMed2005

Non-alcoholic fatty liver disease (NAFLD) in children.

Childhood NAFLD has become an important childhood liver disease, and it is probably highly prevalent. The full of spectrum of NAFLD has been identified in children. It is not currently known whether or not simple hepatic steatosis in children is benign or whether it evolves to NASH over time. In contrast, childhood NASH certainly can have serious consequences. Cirrhosis is apparently rare in children with NAFLD, but it definitely occurs. Childhood NAFLD may occur in very young children, and there is no female predominance in the pediatric age bracket. Children present with vague abdominal pain, if they have any symptoms at all, but frequently hepatic steatosis is found incidentally on abdominal imaging. Laboratory studies show that serum aminotransferase abnormalities are rather moderate, with serum alanine aminotransferase (ALT) more elevated than serum aspartate aminotransferase (AST). Hypertriglyceridemia is the typical blood lipid abnormality, although hypercholesterolemia may occur. NASH may be more severe in children from certain ethnic groups, including Hispanics and Asians, or in association with certain metabolic disorders characterized by abnormalities in insulin receptor structure or signaling, such as lipodystrophy syndromes. Weight loss through dietary redesign and a regimen of regular exercise remains the mainstay for treatment for childhood NAFLD. A dietary strategy to minimize postprandial hyperinsulinemia and overall fat intake, such as a low glycemic index diet, may be the best dietary strategy. The real efficacy of drug treatments in children requires further investigation. The overriding message is that childhood obesity poses important health problems, including but not limited to potentially severe chronic liver disease. Early diagnosis of children who are only overweight is a worthy goal so that strategies to limit obesity can be instituted as early as possible. Identification of genetic risks is important, but management will invariably require changes in environmental factors. In addition to individual treatment, a multifaceted, societal initiative is required for solving the childhood obesity epidemic.

Child↗
PubMed2003

Identification of metal-binding proteins in human hepatoma lines by immobilized metal affinity chromatography and mass spectrometry.

The metalloproteome is defined as the set of proteins that have metal-binding capacity by being metalloproteins or having metal-binding sites. A different metalloproteome may exist for each metal. Mass spectrometric characterization of metalloproteomes provides valuable information relating to cellular disposition of metals physiologically and in metal-associated diseases. We examined the Cu and Zn metalloproteomes in three human hepatoma lines: Hep G2 and Mz-Hep-1, which retain many functional characteristics of normal human hepatocytes, and SK-Hep-1, which is poorly differentiated. Additionally we studied a single specimen of normal human liver and Hep G2 cells depleted in vitro of cellular copper. We used matrix-assisted laser desorption ionization and electrospray ionization quadrupole time-of-flight mass spectrometry to analyze peptide sequences of tryptic digests obtained by either in-gel digestion of metal-binding proteins or peptides on an immobilized metal affinity chromatography column loaded with either Cu or Zn. Mainly high abundance proteins were identified. Cu-binding proteins identified included enolase, albumin, transferrin, and alcohol dehydrogenase as well as certain intracellular chaperone proteins. The Cu metalloproteome was not identical to the Zn metalloproteome. Peptide binding experiments demonstrated that Cu coordination prefers the order of residues histidine > methionine > cysteine. Although the Cu metalloproteome was similar from line to line, subtle differences were apparent. Gel profiling showed more extensive variation in expression of annexin II in SK-Hep-1 and Mz-Hep-1 than in Hep G2 and normal liver tissue. Glycerylphosphorylethanolamine was identified as a post-translational modification at residue Glu-301 of elongation factor 1-alpha in Hep G2. Intracellular copper depletion was associated with loss of the glycerylphosphoryl side group. These findings suggest that post-translational modification could be affected by intracellular actions of copper. Comparison of the Cu and Zn metalloproteomes in Hep G2 with a published general proteome of Hep G2 disclosed little overlap (Seow, T. K., et al. (2001) Proteomics 1, 1249-1263). Proteins in the metalloproteomes of human hepatocytes can be identified by these methods. Variations in these metalloproteomes may have important physiological relevance.

Amino Acid Sequence↗
PubMed2003

Abnormalities in villin gene expression and canalicular microvillus structure in progressive cholestatic liver disease of childhood.

BACKGROUND: The molecular basis of clinical cholestasis is a subject of intense investigation. Villin is an actin binding, bundling, and severing protein needed for maintenance of structural integrity of canalicular microvilli, in which membrane transporters required for bile secretion are located. We aimed to investigate the role of canalicular cytoskeletal proteins in three genetically unrelated children with a biliary atresia-like clinical disorder, each of whom developed liver failure requiring liver transplantation. METHODS: Explanted livers from the three patients were examined by standard pathological methods followed by transmission and cryoimmunoelectron microscopy. With archival tissue samples, a panel of cytoskeletal proteins was investigated by immunohistochemistry and western blotting, with purified canalicular membrane preparations. Villin mRNA analyses were undertaken on liver homogenates, with primers from coding regions of the human villin gene. Classic biliary atresia, other types of cholestasis, and normal livers served as controls. FINDINGS: In patients, pronounced ultrastructural deformities of canaliculi and especially of their microvilli were noted, which correlated with absence of villin protein by immunostaining of liver tissue sections and by western blot analysis. Additionally, villin mRNA was strikingly reduced or absent. These results differed greatly from those in controls. INTERPRETATION: These results suggest that the disorder described mimics biliary atresia, but structural and molecular pathological findings differ. We propose that a functional abnormality in villin gene expression is key to the mechanism of cholestasis in patients with progressive cholestasis and hepatic failure.

Biliary Atresia↗
PubMed2003

Nonalcoholic steatohepatitis in children.

Nonalcoholic steatohepatitis (NASH) is one entity in a spectrum of chronic liver disease related to obesity, hyperinsulinemia, insulin resistance, and liver cell injury from free fatty acid toxicity or other oxidant stress. The more inclusive term "nonalcoholic fatty liver disease" (NAFLD) is increasingly being used to encompass the entire spectrum, which includes simple hepatic steatosis without inflammation (which may not lead to progressive liver injury), NASH itself, and the resulting cirrhosis (which may be devoid of steatosis). Children get NAFLD, and the incidence of this pediatric liver disease is rising as childhood obesity becomes increasingly prevalent. Although much remains to be learned about pediatric NAFLD, it is already evident that children with NASH risk progressive liver damage, including cirrhosis. Liver biopsy is required for definitive diagnosis, and other causes of fatty liver in childhood must be excluded. Gradual weight loss through increased regular exercise and a low-fat, low-refined carbohydrate diet appears to be effective. Drug treatments are being developed. Pediatric NASH is a serious complication of childhood obesity.

Adolescent↗
PubMed2003

Neonatal hepatitis syndrome.

Conjugated hyperbilirubinaemia in an infant indicates neonatal liver disease. This neonatal hepatitis syndrome has numerous possible causes, classified as infective, anatomic/structural, metabolic, genetic, neoplastic, vascular, toxic, immune and idiopathic. Any infant who is jaundiced at 2-4 weeks old needs to have the serum conjugated bilirubin measured, even if he/she looks otherwise well. If conjugated hyperbilirubinaemia is present, a methodical and comprehensive diagnostic investigation should be performed. Early diagnosis is critical for the best outcome. In particular, palliative surgery for extrahepatic biliary atresia has the best chance of success if performed before the infant is 8 weeks old. Definitive treatments available for many causes of neonatal hepatitis syndrome should be started as soon as possible. Alternatively, liver transplantation may be life saving. Supportive care, especially with attention to nutritional needs, is important for all infants with neonatal hepatitis syndrome.

Genetic Predisposition to Disease↗
PubMed2002

Modeling of human hepatic CYP3A4 enzyme kinetics, protein, and mRNA indicates deviation from log-normal distribution in CYP3A4 gene expression.

AIMS: To determine whether the variability in cytochrome P(450) (CYP)3A4 metabolic function is exhibited at both transcription and translation levels and to examine the population distribution of CYP3A4 enzyme kinetics, protein, and mRNA. METHODS: Enzyme kinetics of testosterone 6beta-hydroxylation, immunoblot CYP3A4 protein, and CYP3A4 mRNA were determined in a microsomal bank of human livers. The distribution of these determinations was analyzed using cumulative distribution (probit) plots and normality test variable (NTV) to detect deviation from normality. RESULTS: Mean hepatic CYP3A4 protein and relative CYP3A4 mRNA were 35+/-23 pmol/mg and 79+/-59 (CYP3A4/beta-actin), respectively. Kinetic parameter estimates of testosterone 6beta-hydroxylation were 611+/-684 pmol/mg/min for maximum rate of the reaction (V(max)) and 206+/-48 micro M for the Michaelis constant (K(m)). The CYP3A4 gene expression and its activity exhibited a relatively high degree of interindividual variability. Furthermore, significant correlation between CYP3A4 protein and V(max) of testosterone 6beta-hydroxylation (r=0.82, P<0.001) as well as CYP3A4 protein and its mRNA (r=0.52, P<0.01) was observed. Cumulative distribution plots and histograms for the CYP3A4 protein, its mRNA, and maximum testosterone 6beta-hydroxylation exhibited evidences of deviation from log-normal distribution. The minimum NTV value for the distribution of CYP3A4 protein corresponding to the inflection point in the probit occurred at approximately 10% cumulative frequency. The percentage of low CYP3A4 protein phenotype was consistent for CYP3A4 activity and its mRNA. In contrast, the distribution of K(m) of testosterone 6beta-hydroxylation does not show evidence of bimodality. CONCLUSIONS: The distribution of CYP3A4 metabolic function, protein, and mRNA is non-normal and may represent a regulatory polymorphism in hepatic CYP3A4 gene expression. In contrast, assessment of the possibility of a structural variant of CYP3A4 through evaluation of the standard deviation relative to the mean kinetic constant value suggests that structural mutation of CYP3A4 may not be a major factor affecting interindividual variation in CYP3A4 metabolic function.

Adolescent↗
PubMed2002

Steatohepatitis in children.

Steatohepatitis in children occurs in the childhood version of non-alcoholic fatty liver disease (NAFLD), as a result of hepatotoxicity and with certain genetic/metabolic diseases. Until recently, NAFLD was considered to be rare in children. It is now recognized as an important childhood liver disease, especially because childhood obesity is much more common. Children with NAFLD may present as young as 4 years old; males tend to predominate; fibrosis is often found on liver biopsy and cirrhosis has been reported. Treatment for childhood NAFLD currently consists of weight reduction plus regular aerobic exercise; vitamin E may be an effective adjunctive therapy. Drug hepatotoxicity and genetic/metabolic diseases that can cause fatty liver, such as Wilson's disease and cystic fibrosis, must be excluded since treatment is radically different. Other causes of chronic hepatitis, such as chronic viral hepatitis, must also be excluded. Multisystemic inherited diseases with hyperinsulinaemia plus insulin resistance may have NAFLD as hepatic involvement and should be identified.

Child↗