Disorders of branched chain amino acid metabolism.

The three essential branched-chain amino acids (BCAAs), leucine, isoleucine and valine, share the first enzymatic steps in their metabolic pathways, including a reversible transamination followed by an irreversible oxidative decarboxylation to coenzyme-A derivatives. The respective oxidative pathways subsequently diverge and at the final steps yield acetyl- and/or propionyl-CoA that enter the Krebs cycle. Many disorders in these pathways are diagnosed through expanded newborn screening by tandem mass spectrometry. Maple syrup urine disease (MSUD) is the only disorder of the group that is associated with elevated body fluid levels of the BCAAs. Due to the irreversible oxidative decarboxylation step distal enzymatic blocks in the pathways do not result in the accumulation of amino acids, but rather to CoA-activated small carboxylic acids identified by gas chromatography mass spectrometry analysis of urine and are therefore classified as organic acidurias. Disorders in these pathways can present with a neonatal onset severe-, or chronic intermittent- or progressive forms. Metabolic instability and increased morbidity and mortality are shared between inborn errors in the BCAA pathways, while treatment options remain limited, comprised mainly of dietary management and in some cases solid organ transplantation.

MRI characteristics of globus pallidus infarcts in isolated methylmalonic acidemia.

BACKGROUND: Bilateral infarcts confined to the globus pallidus are unusual and occur in conjunction with only a few disorders, including isolated methylmalonic acidemia, a heterogeneous inborn error of metabolism. On the basis of neuroradiographic features of metabolic strokes observed in a large cohort of patients with methylmalonic acidemia, we have devised a staging system for methylmalonic acidemia-related globus pallidus infarcts. MATERIALS AND METHODS: Forty patients with isolated methylmalonic acidemia and neurologic symptoms underwent clinical brain MR imaging studies, which included 3D-T1WI. Infarcted globus pallidus segments were neuroanatomically characterized, and infarct volumes were measured. RESULTS: Globus pallidus infarcts were present in 19 patients; all were bilateral, and most were left-dominant. A neuroanatomic scoring system based on the infarct patterns was devised; this revealed a 5-stage hierarchical susceptibility to metabolic infarct, with the posterior portion of the globus pallidus externa being the most vulnerable. Globus pallidus infarct prevalence by methylmalonic acidemia class was the following: cblA (5/7, 71%), cblB (3/7, 43%), mut(o) (10/22, 45%), and mut- (1/4, 25%). Tiny lacunar infarcts in the pars reticulata of the substantia nigra, previously unrecognized in methylmalonic acidemia, were found in 17 patients, 13 of whom also had a globus pallidus infarct. CONCLUSIONS: The staged pattern of globus pallidus infarcts in isolated methylmalonic acidemia suggests a nonuniform, regionally specific cellular susceptibility to metabolic injury, even for patients having milder biochemical phenotypes. In support of this hypothesis, the delineation of lacunar infarcts in the pars reticulata of the substantia nigra, a tissue functionally and histologically identical to the globus pallidus interna, supports the concept of cell-specific pathology.

Update on transcobalamin deficiency: clinical presentation, treatment and outcome.

Transcobalamin (TC) transports cobalamin from blood into cells. TC deficiency is a rare autosomal recessive disorder usually presenting in early infancy with failure to thrive, weakness, diarrhoea, pallor, anemia, and pancytopenia or agammaglobulinemia. It can sometimes resemble neonatal leukemia or severe combined immunodeficiency disease. Diagnosis of TC deficiency is suspected based on megaloblastic anemia, elevation of total plasma homocysteine, and blood or urine methylmalonic acid. It is confirmed by studying the synthesis of TC in cultured fibroblasts, or by molecular analysis of the TCN2 gene. TC deficiency is treatable with supplemental cobalamin, but the optimal type, route and frequency of cobalamin administration and long term patient outcomes are unknown. Here we present a series of 30 patients with TC deficiency, including an update on multiple previously published patients, in order to evaluate the different treatment strategies and provide information about long term outcome. Based on the data presented, current practice appears to favour treatment of individuals with TC deficiency by intramuscular injections of hydroxy- or cyanocobalamin. In most cases presented, at least weekly injections (1 mg IM) were necessary to ensure optimal treatment. Most centres adjusted the treatment regimen based on monitoring CBC, total plasma homocysteine, plasma and urine methylmalonic acid, as well as, clinical status. Finally, continuing IM treatment into adulthood appears to be beneficial.

Development of a human mitochondria-focused cDNA microarray (hMitChip) and validation in skeletal muscle cells: implications for pharmaco- and mitogenomics.

Mitochondrial research has influenced our understanding of human evolution, physiology and pathophysiology. Mitochondria, intracellular organelles widely known as 'energy factories' of the cell, also play fundamental roles in intermediary metabolism, steroid hormone and heme biosyntheses, calcium signaling, generation of radical oxygen species, and apoptosis. Mitochondria possess a distinct DNA (mitochondrial DNA); yet, the vast majority of mitochondrial proteins are encoded by the nuclear DNA. Mitochondria-related genetic defects have been described in a variety of mostly rare, often fatal, primary mitochondrial disorders; furthermore, they are increasingly reported in association with many common morbid conditions, such as cancer, obesity, diabetes and neurodegenerative disorders, although their role remains unclear. This study describes the creation of a human mitochondria-focused cDNA microarray (hMitChip) and its validation in human skeletal muscle cells treated with glucocorticoids. We suggest that hMitChip is a reliable and novel tool that will prove useful for systematically studying the contribution of mitochondrial genomics to human health and disease.

Early growth, pubertal development, body mass index and final height of patients with congenital adrenal hyperplasia: factors influencing the outcome.

OBJECTIVE: The management of children with congenital adrenal hyperplasia (CAH) remains a challenge, especially with regard to growth potentials. The objective of our analysis was to uncover the factors that influence the growth and final height of patients with CAH. DESIGN: The linear growth pattern and body mass index (BMI) at different developmental stages (birth to 2 years, 2 years to puberty initiation and puberty initiation to final height) and the final height achieved were analysed retrospectively in 48 patients with 21-hydroxylase deficiency; 17 with the salt-wasting (SW) form, 25 with the simple virilizing (SV) and six with the nonclassical (NC) form. RESULTS: Mean final height (FH) and FH-SDS were, respectively, 170.8 +/- 5.6 m and -0.57 +/- 0.8 in males and 156.7 +/- 6 cm and -0.61 +/- 1 in females with the SW form, 166.1 +/- 6.1 cm and -1.05 +/- 1 in males and 151.6 +/- 5.4 cm and -1.4 +/- 1 in females with the SV form and 159.7 +/- 6.9 cm and 0.3 +/- 1.4 in females with the NC form. In subjects with the SW form, height SDS at 2 years, at puberty initiation and at FH were -0.18 +/- 0.9, 0.11 +/- 1.28 and -0.6 +/- 1.0, respectively. FH achieved was not different from target height (TH) in the SW group, but it was significantly lower than TH in the SV group (P = 0.003). FH in the SW group showed a positive correlation to the height achieved at 2 years of age (r = 0.68, P = 0.019), and height at 2 years was negatively related to the hydrocortisone dose in the birth to 2-year period (r = -0.79, P = 0.011). FH showed no correlation to hydrocortisone dose at any of the three developmental periods studied. BMI-SDS were not different in the various forms of CAH and showed no correlation to FH or hydrocortisone dose. Age at menarche was comparable to that in our general population. CONCLUSIONS: Under our conditions of management, the final height of patients with the salt-wasting form was comparable to the target height and to the most favourable literature data. The patients with the simple virilizing form fare less well, mainly due to delayed diagnosis and consequent advancement of bone age and early puberty. In salt-wasting patients, height at 2 years is comparable to normals, it is influenced by the hydrocortisone dose and is related to the final height. Some height is lost during puberty. Hence, monitoring treatment over the first 2 years and during puberty is critical for the outcome in these patients.

"White coat hypertension" in adolescents: increased values of urinary cortisol and endothelin.

OBJECTIVE: To investigate whether "white coat hypertension" (WCH) in adolescents is an innocent phenomenon or is associated with early changes of the vascular system and/or increased stress response, reflected in the urinary endothelin and cortisol values, respectively. STUDY DESIGN: The study group included 36 subjects, 14 with WCH (8 males and 6 females) aged 12.9 +/- 3 years and 22 normotensive control subjects (12 males and 10 females) aged 13 +/- 3.5 years. WCH was defined as systolic and/or diastolic blood pressure (BP) > or =95th percentile for age, sex, and height and with reported normal BP measurements at home. Urinary endothelin (UET1), urinary free cortisol (UFC), and plasma renin levels were determined by radioimmunoassay; and urinary albumin levels were determined by nephelometry. For statistical analysis, the Mann Whitney U test, Spearman correlation coefficient, and multivariate analysis of variance/multivariate analysis of covariance were used, as applicable. RESULTS: The 24-hour values of UET1 and UFC were greater in male subjects with WCH than in male control subjects (P =.02), whereas no such difference was found in female subjects. The difference in UFC values in male subjects was accounted for by the day values. In subjects with WCH, and not in control subjects, a positive correlation of UET1 to UFC (r = 0.59, P =.027), diastolic BP (r = 0.55, P =.04), and mean BP (r = 0.65, P =.012) was detected. CONCLUSIONS: Our data indicate that WCH in adolescence may not be an innocent phenomenon and may represent a prelude to permanent idiopathic hypertension of adulthood.