Paediatric screening for hypercholesterolaemia in Europe

Different screening strategies are currently recommended to identify children with (familial) hypercholesterolaemia in order to initiate early lipid management. However, these strategies are characterised to date by low adherence by the medical community and limited compliance by parents and children. In a literature review, the authors assess which children should undergo screening and which children are in effect identified through the currently recommended strategies. Furthermore, the authors discuss the different screening tools and strategies currently used in Europe and what is known about the negative aspects of screening. The authors conclude that currently recommended selective screening strategies, which are mainly based on family history, lack precision and that a large percentage of affected children who are at increased risk of future coronary artery disease are not being identified. The authors propose universal screening of children between 1 and 9 years of age, a strategy likely to be most effective in terms of sensitivity and specificity for the identification of children with familial hypercholesterolaemia. However, this concept has yet to be proven in clinical practice.

The treatment of hypercholesterolemic children: efficacy and safety of a combination of red yeast rice extract and policosanols

BACKGROUND AND AIMS

The prevention of cardiovascular risk, as occurs in lipoprotein disorders, is required since childhood. Aim of the study was to evaluate, in a group of children affected by primary dyslipidemia, the efficacy, tolerability and safety of a short-term treatment with a dietary supplement containing red yeast rice extract and policosanols.

METHODS AND RESULTS

40 children affected by heterozygous Familial Hypercholesterolemia (FH) (n=24) and Familial Combined Hyperlipidemia (FCH) (n=16), aged 8-16 years, were enrolled in a double-blind, randomized, placebo-controlled, cross-over trial. After a 4-week run-in period with only dietary advice, children received a dietary supplement containing 200mg red yeast rice extract, corresponding to 3mg of monacolins, and 10mg policosanols once-daily and placebo for 8 weeks, separated by a 4-week washout period. Lipid profile was assessed after each treatment period. The dietary supplement, compared with the placebo, significantly reduced total cholesterol by 18.5% (p<0.001), LDL-C levels by 25.1% (p<0.001), and apolipoprotein B by 25.3% (p<0.001) when patients were considered as a whole group. Similar results were obtained when FH and FCH were considered separately and no significant difference between groups was detected. No significant differences were observed in HDL-C and apolipoprotein A-I levels. No adverse effects were detected when liver and muscular enzymes (AST, ALT, and CK) were determined.

CONCLUSIONS

The treatment with a dietary supplement containing red yeast rice extract and policosanols has been for the first time successfully employed in hypercholesterolemic children. Results indicate this strategy as an effective, safe and well tolerated in a short-term trial.

Primary hyperlipidemias in children: effect of plant sterol supplementation on plasma lipids and markers of cholesterol synthesis and absorption

Plant sterols lower serum cholesterol concentration. Available data have confirmed the lipid-lowering efficacy in adults, while there is a relative dearth of data in children and almost exclusively restricted to subjects with familial hypercholesterolemia (FH). Aim of the present study was to evaluate the efficacy, tolerability and safety of plant sterol supplementation in children with different forms of primary hyperlipidemias. The effect of plant sterol consumption on plasma lipids was evaluated in 32 children with heterozygous FH, 13 children with Familial Combined Hyperlipidemia (FCH) and 13 children with Undefined Hypercholesterolemia (UH) in a 12-week open-label intervention study using plant sterol-enriched yoghurt. Plasma lipids and apolipoproteins were measured by routine methods. Markers of cholesterol synthesis (lathosterol) and absorption (campesterol and sitosterol) were measured by GC-MS. Tolerability and adherence to recommended regimen was very high. A significant reduction was observed in LDL-cholesterol in the three groups (10.7, 14.2 and 16.0% in FH, FCH and UH, respectively). Lathosterol concentrations were unchanged, reflecting a lack of increased synthesis of cholesterol. Of the two absorption markers, only sitosterol showed a slight but significant increase. Daily consumption of plant sterol dairy products favorably changes lipid profile by reducing LDL-cholesterol. To our knowledge, this is the first report of the use of plant sterols-enriched foods in treating children with primary hyperlipidemia such as FCH and UH, likely to be the most frequent form also in the young age in the western populations.

Identification and management of dyslipidemic children

Atherosclerotic cardiovascular disease is a leading cause of morbidity and premature mortality in Western countries and dyslipidemia is a recognized major cardiovascular risk factor. Evidences demonstrate that the atherosclerotic process begins early in childhood. Children showing dyslipidemia, as well as other cardiovascular risk factors, including hypertension, overweight/obesity and diabetes mellitus, are defined at high risk. To identify these children a selective screening between 2 to 10 years of age is necessary. This program must be performed to those children showing a familiarity for primary dyslipidemia and/or precocious cardiovascular events. These subjects need to undergo lipid biochemical analysis and assessment of other emergent risk factors (as ApoB, ApoA-I and their ratio). Given that total cholesterol and low-density lipoprotein cholesterol (LDL-C) concentrations vary by age and sex, the use of percentile values according to these parameters is now recommended. In these high-risk subjects the first step to lower LDL-C under the value of 130 mg/dL is represented by an appropriate physical activities and Step II diet. This entails further reduction of saturated fatty acid intake to less than 7% of daily calories and of cholesterol to less than 200 mg/day (since two years of age). When diet therapy is insufficient to lower LDL-C to the acceptable concentration, the use of non-pharmacologic agents (soluble fibers, plant stanols, sterols) is suggested. The third approach, for children showing persistent elevated LDL-C >95(th) percentile, is represented by drugs, that are allowed only in children older than eight years.

Beta-sitosterolaemia: a new nonsense mutation in the ABCG5 gene

BACKGROUND

Sitosterolaemia is a rare autosomal recessive disorder characterised by elevated plasma levels of plant sterols and cholesterol. Sitosterolaemia is caused by gene mutations in either of two ATP-binding cassette (ABC) half transporters, ABCG5 and ABCG8. The plasma sterol profile and genetic analysis of a 10-year-old girl who had tuberous xanthomas is the subject of this report.

MATERIALS AND METHODS

Genomic DNA was isolated from white blood cells from the proband, her family and a control group of healthy people. All exons of ABCG5 and ABCG8 were sequenced. Plasma cholesterol and triglycerides were measured by routine methods. All other plasma sterols were measured by Gas Chromatography coupled to Mass Spectrometry.

RESULTS

The proband was found to be homozygous for a single nucleotide mutation in exon 10 of the ABCG5 gene, consisting of a C to T transition at nucleotide 1336 of the coding sequence, which results in the premature termination of the ABCG5 protein at amino acid 446 (Arg446X). Her mother and brother were also homozygous for the same mutation and all had elevated plasma beta-sitosterol levels. The father was heterozygous and showed normal beta-sitosterol levels. This mutation was not found in healthy normolipidaemic subjects.

CONCLUSIONS

We describe a novel nonsense mutation in exon 10 of the ABCG5 gene in a 10-year-old girl showing clinical and biochemical features of sitosterolaemia. This family study broadens the spectrum of the ABCG5/ABCG8 mutations causing sitosterolaemia and helps highlight the correlations between such gene mutations, biochemical phenotype and the development of cardiovascular disease.

[Influence of diet on lipoprotein profile in familial combined hyperlipidemia affected children]

BACKGROUND

Familial Combined Hyperlipidemia is an inherited disorder affecting cholesterol and triglycerides metabolism, well known myocardial infarction risk factors. The FCHL clinical presentation is usually silent until the third decade although children can be affected, and the more recent opinion is that precocious diagnosis is mandatory in preventing complications. Aim of this study is to examine the effectiveness of the diet therapy (Step-One-Diet) in a group of 13 children affected by Familial Combined Hyperlipidemia.

METHODS

The patients have been submitted to a normocaloric diet, 30% fat of the total caloric daily intake according with the Dietary Intervention Study in Children (Step-One-Diet). The patients then have been submitted to a two year-follow-up and lipoprotein levels (total cholesterol, LDL-cholesterol, triglycerides and apolipoprotein B), nutritional status (macro- and micro-nutrients) as well as anthropometric data (height, weight, BMI) have been monitored.

RESULTS

Results showed a 10% total cholesterol and 30% triglycerides decrease, Iron and Calcium intake show increased levels approaching to the normal ones after controlled diet, while cholesterol intake was correct on both regimen. The growth parameters show a decrease in weight only in two obese and two overweight patients.

CONCLUSIONS

The present study confirmed the effectiveness and safety of the Step-One-Diet in children patients, allowing triglycerides normalization in 60% of the patients, and a 10% cholesterol decrease, in agreement with the complex genetic inheritance of the disease.

A novel missense mutation in the C-terminal domain of lipoprotein lipase (Glu410-->Val) leads to enzyme inactivation and familial chylomicronemia

Lipoprotein lipase (LPL) is a complex enzyme consisting of multiple functional domains essential for the initial hydrolysis of triglycerides present in plasma lipoproteins. Previous studies have localized the catalytic domain of LPL, responsible for the hydrolytic function of the enzyme, to the N-terminus whereas the C-terminal end may play a role in lipid and heparin binding. To date, most described missense mutations resulting in a nonfunctional LPL have been located in the N-terminal region of the enzyme. In this manuscript we describe the defect in the LPL gene of a patient with triglycerides ranging from normal to 12,000 mg/dl, low LPL mass, and no LPL activity in post-heparin plasma. Sequencing of patient PCR-amplified DNA identified two separate mutations in the C-terminal domain of LPL: an A-->T transversion at nucleotide 1484 resulting in a Glu410-->Val substitution and a C-->G mutation at position 1595 that introduces a premature stop codon at position 447. Digestion with MaeIII and MnII established that the patient is a true homozygote for both mutations. In order to investigate the functional significance of these defects, mutant enzymes containing either the Val410 or the Ter447 mutations as well as both Val410 and Ter447, were expressed in vitro. Compared to the wild-type enzyme, LPL447 demonstrated a moderate reduction of specific activity using triolein (70% of normal) and tributyrin (74% of normal) substrates, while LPL410 had a significant (11% and 23% of normal) reduction of the normal lipase and esterase specific activities, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent episodes of bizarre behavior in a boy with ornithine transcarbamylase deficiency: diagnostic failure of protein loading and allopurinol challenge tests

Recurrent episodes of bizarre behavior were the only clinical symptoms that finally led to the diagnosis of ornithine transcarbamylase deficiency in an 8-year-old boy. The suspected diagnosis could not be confirmed with the use of current challenge tests. The response to a high-protein diet for 24 hours appeared to be a helpful diagnostic aid.

Rapid detection of medium chain acyl-CoA dehydrogenase gene mutations by non-radioactive, single strand conformation polymorphism minigels

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is a common inherited metabolic disorder affecting fatty acid beta oxidation. Identification of carriers is important since the disease can be fatal and is readily treatable once diagnosed. Twelve molecular defects have been identified in the MCAD gene; however, a single highly prevalent mutation, A985G, accounts for > 90% of mutant alleles in the white population. In order to facilitate the molecular diagnosis of MCAD deficiency, oligonucleotide primers were designed to amplify the exon regions encompassing the 12 mutations enzymatically, and PCR products were then screened with a single strand conformation polymorphism (SSCP) based method. Minigels were used allowing much faster run times, and silver staining was used after gel electrophoresis to eliminate the need for radioisotopic labelling strategies. Our non-radioactive, minigel SSCP approach showed that normals can be readily distinguished from heterozygotes and homozygotes for all three of the 12 known MCAD mutations which were detected in our sampling of 48 persons. In addition, each band pattern is characteristic for a specific mutation, including those mapping in the same PCR product like A985G and T1124C. When necessary, the molecular defect was confirmed using either restriction enzyme digestion of PCR products or by direct DNA sequence analysis or both. This rapid, non-radioactive approach can become routine for molecular diagnosis of MCAD deficiency and other genetic disorders.

Antenatal diagnosis of tetrahydrobiopterin deficiency by quantification of pterins in amniotic fluid and enzyme activity in fetal and extrafetal tissue

Prenatal diagnosis of tetrahydrobiopterin (BH4) deficiency was undertaken by evaluating the pterin patterns in amniotic fluid and the specific enzyme activities in fetal or extrafetal tissues. This allowed the prenatal diagnosis in 19 pregnancies at risk. In 8 families with a child already affected by dihydropteridine reductase deficiency 4 fetuses were diagnosed as homozygotes and 4 as heterozygotes for the defect. In 11 families with a child affected by 6-pyruvoyl tetrahydropterin synthase deficiency 4 fetuses were homozygous, 4 heterozygous and 3 normal. This study also advanced our knowledge of tetrahydrobiopterin metabolism during fetal development. The key enzymes involved in the biosynthesis of BH4 are expressed early and allow the fetus to be autotrophous for its cofactor requirement. In a twin pregnancy, both fetuses were diagnosed to be heterozygotes for dihydropteridine reductase deficiency and primapterin (7-biopterin) in amniotic fluid was increased. This indicates that pterin-4 alpha-carbinolamine dehydratase activity seems to be differently expressed during fetal life. As a consequence, pterins detected in amniotic fluid are of fetal origin and 6- and 7-substituted pterins can be present in amniotic fluid in higher proportions when compared with other body fluids.

Maple syrup urine disease (MSUD): screening for known mutations in Italian patients

Maple syrup urine disease (MSUD) is an autosomal recessive disease due to deficiency of the branched-chain alpha-ketoacid dehydrogenase (BCKDH) caused by a large number of mutations. In the present study, DNA from Italian patients and their relatives was examined for three point mutations (Y393N in the E1 alpha gene, T841G and G1031A in the E2 gene) and two deletions (-G at the intron/exon border of exon 8 in the E2 gene and an 11 bp deletion in exon 1 of the E1 beta gene) using the polymerase chain reaction (PCR) followed by allele-specific oligonucleotide (ASO) hybridization, gene-scanning size analysis of fluorescent-tagged PCR products and/or automated DNA sequence analysis. Our results show that two different mutations account for 7 of the 20 mutant MSUD alleles. Two unrelated affected children, two of their parents and one sibling were carriers for the 11 bp deletion in the E1 beta gene, one patient and her mother were heterozygous for Y393N in E1 alpha, while T841G, G1031A and the -G deletion in E2 were not detected. This study is the first attempt to characterize at a nucleic acid level MSUD mutations in Italy. Our results indicate that additional defects are present in the Italian population and that, unlike the Mennonites, a number of different MSUD mutations exist in Italians.

Differential diagnosis of hyperphenylalaninaemia by a combined phenylalanine-tetrahydrobiopterin loading test

We describe a new fully reliable method for the differential diagnosis of tetrahydrobiopterin-dependent hyperphenylalaninaemia (HPA). The method comprises the combined phenylalanine (Phe) plus tetrahydrobiopterin (BH4) oral loading test and enables the selective screening of BH4 deficiency when pterin analysis is not available or when a clear diagnosis has not been previously made. It should be performed together with the measurement of dihydropteridine reductase (DHPR) activity in blood. The new combined loading test was performed in nine patients with primary HPA, three with classical phenylketonuria (PKU), three with DHPR deficiency, and three with 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency. Three hours after oral Phe loading (100 mg/kg body weight), synthetic BH4 was administered orally at doses of either 7.5 or 20 mg/kg body weight. Amino acid (Phe and tyrosine) and pterin (neopterin and biopterin) metabolism and kinetics were analysed. By exploiting the decrease in serum Phe 4 and 8 h after administration, a clear response was obtained with the higher BH4 dose (20 mg/kg body weight), allowing detection of all cases of BH4 deficiency, as well as differentiation of BH4 synthesis from regeneration defects. Since DHPR deficient patients who were previously shown to be non-responsive to the simple BH4 loading test gave a positive response, the combined Phe plus BH4 loading test can be used as a more reliable tool for the differential diagnosis of HPA in these patients. Moreover, it takes advantage of being performed while patients are on a Phe-restricted diet.

Hyperphenylalaninemia and pterin metabolism in serum and erythrocytes

The relationship between blood phenylalanine concentrations and serum and erythrocyte biopterin and neopterin concentrations was investigated in 20 phenylketonuric patients with different dietary compliance. At serum phenylalanine concentrations ranging from 43 to 1004 mumol/l, a good correlation was found with serum biopterin (r = 0.76, P < 0.001) and with red blood cell biopterin (r = 0.62, P < 0.001). A similar correlation was found between serum neopterin and phenylalanine (r = 0.60, P < 0.001). The correlation between red blood cell neopterin and serum phenylalanine was less evident, however (r = 0.47, P < 0.005). After oral loading with phenylalanine (100 mg/kg body weight), serum and red blood cell biopterin concentrations increased in patients with classical phenylketonuria as well as in one patient with dihydropteridine reductase deficiency in response to the induced acute hyperphenylalaninemia. One patient suffering from 6-pyruvoyl tetrahydropterin synthase deficiency was loaded orally with tetrahydrobiopterin (20 mg/kg body weight). The kinetics of administered cofactor confirmed its rapid absorption, with early increase of serum concentrations followed by its transport into the red blood cells. The half-life of biopterin was approximately 7 h in serum and 15 h in red blood cells. Because both values are less than the half-life of phenylalanine (20-30 h) in serum, biopterin measurement offers no advantage in monitoring dietary control in hyperphenylalaninemic patients.

Catalytic activity of tetrahydrobiopterin in dihydropteridine reductase deficiency and indications for treatment

It is now widely accepted that tetrahydrobiopterin (BH4), the natural cofactor of aromatic amino acid hydroxylases, in the absence of its regenerating enzyme dihydropteridine reductase (DHPR), will function only stoichiometrically in the phenylalanine (Phe) hydroxylating system. This has limited the use of pterin cofactor in diagnosis and treatment of patients suffering from inherited DHPR deficiency, one of the most common forms of hyperphenylalaninemia caused by BH4 deficiency. This is despite the observation of a dramatic fall in serum Phe concentration after BH4 loading in such patients. In this study, quantitation of this phenomenon was obtained by comparing the kinetics of serum Phe after either a simple Phe or a combined Phe plus BH4 oral loading in patients with Phe hydroxylase or with DHPR deficiency. Only in the latter was the total body clearance of Phe enhanced up to 5 times by the cofactor administration, resulting in the molar equivalent of Phe hydroxylated/mol of BH4 ranging from at least 6 to 10, against the postulated 1. As a consequence, BH4 administration should be attempted therapeutically in DHPR-deficient patients, thus avoiding a lifelong Phe-restricted diet. Preliminary experience with such treatment is given with two cases.

Tetrahydrobiopterin loading test in hyperphenylalaninemia

Some cases of primary hyperphenylalaninemia are not caused by the lack of phenylalanine hydroxylase, but by the lack of its cofactor tetrahydrobiopterin. These patients are not clinically responsive to a phenylalanine-restricted diet, but need specific substitution therapy. Thus, it became necessary to examine all newborns screened as positive with the Guthrie test for tetrahydrobiopterin deficiency. Methods based on urinary pterin or on specific enzyme activity measurements are limited in their availability, and the simplest method, based on the lowering of serum phenylalanine after loading with cofactor, was discouraged by the finding that some dihydropteridine reductase-deficient patients were unresponsive. The preliminary observation that this limitation could be overcome by increasing the dose of the administered cofactor prompted us to reevaluate the potential of the tetrahydrobiopterin loading test in hyperphenylalaninemia. Fifteen patients, eight with ultimate diagnosis of phenylketonuria, three with 6-pyruvoyl tetrahydropterin synthase-, and four with dihydropteridine reductase-deficiency, have been examined by administering synthetic tetrahydrobiopterin both orally, at doses of 7.5 and 20 mg/kg, and i.v., at a dose of 2 mg/kg. All the tetrahydrobiopterin-deficient patients, unlike those with phenylketonuria, responded to the oral dose of 20 mg/kg cofactor by lowering their serum phenylalanine concentration markedly below baseline to an extent easily detectable by Guthrie cards. This method allows for a simple screening method when enzyme or pterin studies are not available.

Two mutations of dihydropteridine reductase deficiency

Two patients with dihydropteridine reductase (DHPR) deficiency, in one case due to the absence of any enzyme protein (DHPR- cross reactive material (CRM)-) and in the other case due to the production of a mutant type devoid of catalytic activity (DHPR- CRM+) were examined. This latter form of malignant phenylketonuria, whose relative frequency seems to be higher in the Italian population, possibly has a worse prognosis. The earlier onset and the greater severity of clinical symptoms are associated with a more pronounced hydroxylation defect, as shown by higher degree of neonatal hyperphenylalaninaemia, unresponsiveness to an oral tetrahydrobiopterin load, lower concentrations of neurotransmitter metabolites, and reduced tyrosine production after an oral phenylalanine load.

[Trial of indirect screening of tetrahydrobiopterin deficiency]

The possibility of an early diagnosis of tetrahydrobiopterin deficiency among hyperphenylalaninemic infants, when specific screening tests cannot be performed, was evaluated. Three tetrahydrobiopterin deficient patients, two with dihydropteridine reductase deficiency and one with dihydrobiopterin synthetase deficiency were examined together with their parents and compared with twelve phenylketonuric patients, their parents and sixteen normal subjects. The parameters considered in the hyperphenylalaninemic patients (degree of neonatal hyperphenylalaninemia, phenylalanine lowering speed in response to a restricted diet, dietary tolerance to phenylalanine, oral phenylalanine load) were found to be insufficiently or lately indicative. By contrast, heterozygosity tests (molar ratio (Phe)2/Tyr and sigma discriminant function) performed on the parents allowed a suspicion of tetrahydrobiopterin deficiency, the definite diagnosis being of course based upon specific investigations.

Prenatal diagnosis of "dihydrobiopterin synthetase" deficiency, a variant form of phenylketonuria

Amniocentesis was performed at 19 weeks gestation in a mother who had previously delivered a boy with "dihydrobiopterin synthetase" (DHBS) deficiency. The amniotic fluid contained neopterin in high (136 nmol/l) and biopterin in very low concentrations (1.8 nmol/l). The activity of the phosphate-eliminating enzyme (PEE, also called 6-pyruvoyl tetrahydropterin synthase, substrate: 7,8-dihydroneopterin triphosphate) which is present in liver and erythrocytes and defective in DHBS deficiency, was measured in the erythrocytes of the family members. The fetal sample showed only 2% of the activity of healthy adult controls and was comparable with that of the affected sibling. Obligate heterozygotes had activities around 20% of the controls. Two fetal control samples showed even higher activities than adult erythrocytes, Sepiapterin reductase activities wer normal in all cases. At autopsy, PEE deficiency was confirmed in the liver of the fetus. We concluded that DHBS deficiency (and most probably also GTP cyclohydrolase I deficiency) can be diagnosed by metabolite measurements in amniotic fluid. PEE activity is measurable in erythrocytes, although the assay needs to be improved. Since maternal tetrahydrobiopterin does not cross the placenta, treatment of a tetrahydrobiopterin-deficient fetus with tetrahydrobiopterin in utero is not possible.

Tetrahydrobiopterin non-responsiveness in dihydropteridine reductase deficiency is associated with the presence of mutant protein

Correlation of the response to a load of tetrahydrobiopterin (BH4) in dihydropterin reductase (DHPR) deficient patients to the type of mutation in these patients has led to the conclusion that 4 patients without mutant DHPR molecules in their cells respond to the BH4 load, whereas 3 patients with mutant DHPR in their cells do not respond. Intravenous injection of BH4 in 1 of the cases not responding to BH4 again showed no response.

Bethanechol versus antiacids in the treatment of gastroesophageal reflux

To compare the efficacy of bethanechol in the treatment of gastroesophageal reflux with that of antiacids, a prospective, cross-over study was undertaken, in which 20 affected infants and children were randomized into two groups on 6-week alternate bethanechol and antiacids oral medication. Patients were evaluated clinically and by esophageal pH-metry before and after each treatment. Clinical score amelioration was achieved earlier than reflux number reduction and with similar incidence in both groups of patients, irrespectively to the initial medication; moreover, the differences in the degree of improvement between the two groups after either treatment were not found to be significant. These results fail to show that bethanechol is more effective than antiacids in controlling gastroesophageal reflux; moreover, bethanechol is more difficult to administer and offers a higher rate of undesired side effects.