1 • The former term: Inborn errors of metabolism • Definition: heterogeneous group of diseases, genetically conditioned change of protein • In the early 20th century – the conception of IMD was formulated by British physician sir Archibald Garrod • He is known for his work that prefigured the „one gene-one enzyme“ hypothesis • He also described the first four IMD: alkaptonuria, albinismus, pentosuria, cystinuria 2 • IMDs are diseases based on molecular level • IMDs are caused by a change in the genetic information • Mutation in DNA → fault transcription to mRNA → fault syntesis protein → protein with a modified structure • Mutation → defective transcription → defective translation • 1 gene encodes synthesis of 1 molecule of protein 3 • Enzyme • Transport protein • Structural protein • Regulatory protein 4 ENYZME SUBSTRATE PRODUCT NUCLEAR DNA • Autosomal recessive inheritance • Autosomal dominant inheritance • Gonosomal dominant inheritance • Gonosomal recessive inheritance MITOCHONDRIAL (extranuclear) DNA • Maternal type inheritance 5 • Most IMDs are inherited autosomal recessive • Disease only affects individuals with two defective copies of the gene – one from each parent (recessive homozygotes) • Heterozygot is healthy individual, he is only „carrier“ of the defect gene 6 7 • Individual incidence is quite rare (1:15 000 – 200 000) • Collective – all together is frequent (1:1000 or higher) 8 1. According to the speed of the onset of clinical symptoms 2. According to the metabolic systems 3. According to the subcellular localization of modified protein 4. According to the analytical method used for the detection of IMD 9 • Acute metabolic • With intermittent course • Chronically progressive 10 Disorders of: • amino acid metabolism • carbohydrate metabolism • organic acid metabolism • storage diseases 11 • cytosolic • mitochondrial • lysosomal • peroxisomal • Golgi apparatus • ion channels etc. 12 • Symptoms may appear at any age – from birth to adulthood • They may be brought on by foods, medications, dehydratation, minor illnesses, or other factors • Symptoms may come on suddenly or progress slowly • Severity of the disease depends on the degree of disability 13 • Non specific symptoms – lethargy, coma, muscular hypo or hypertonia, convulsions, poor appetite, vomiting, abdominal pain, weight loss, jaundice, developmental delay… • Specific symptoms – abnormal odor of urine, sweat or saliva…,ectopia of lens,trombembolic events 14 • Acidosis (for example accumulation of lactic acid – disorders of pyruvate dehydrogenase) • Alkalosis • Hypoglycaemia • Hyperammonaemia (disorders of urea cycle enzymes) • Hypoketosis (mitochondrial fatty acid oxidation disorders) • Hyperketosis (some types of organic aciduria) • Hypouricemia/hyperuricemia (disorders of purine metabolism) • Hypocholesterolemia/hypercholesterolemia (7dehydrocholesterol reductase deficiency - Smith-LemliOpitz syndrom) 15 16 1. At the level of metabolites 2. At the level of enzymes 3. At the molecular level (mutations) 17 • Characteristic: quantitative measurement of metabolites such as amino acids, carbohydrates, mucopolysaccharides, purine, pyrimidine, lipids, steroids…or various abnormal metabolites • Material: serum or plasma, urine, cerebrospinal fluid, whole blood as dry blood spot on the filter paper… 18 chromatography - paper - thin layer - liquid (ion - exchange, high performance - HPLC) - gas (with mass spectrometry GC/MS) electromigration techniques - classical electroforesis - capillary electroforesis tandem mass spectrometry MS/MS 19 Pozitive result of fructose and galactose in urine Pozitive result of galactose in serum and urine 20 High peak of plasma phenylalanine 21 • Characteristic: measurement of decreased activity of the enzyme • Material: leukocytes, erytrocytes or plateles isolated from peripheral blood, serum or plasma, culture of skin fibroblasts, tissue from muscle or liver biopsy 22 • Characteristic: specific DNA tests show defect of gene • Material: leukocytes of periferal blood, amniotic fluid cells obtained by amniocentesis, chorionic villus cells obtained by biopsy of placenta 23 1. At the level of metabolites 2. At the level of enzyme 3. At the molecular level (experimental) • The only causal treatment – at the molecular level • The symptomatic treatment – reduces symptoms but does not remove the cause. 24 • Reducing or eliminating of any food that can´t be metabolized properly (special diets) • Removing toxic products of metabolism that accumulate due to the metabolic disorder (for example by dialysis) • Replacing the enzyme that is missing or inactive, where it is possible (ERT) • Replacing other supplements that support metabolism (for example vitamin cofactors) 25 • Organ transplantation (liver, kidneys, bone marrow) • Treatment of symptoms and complictions • Gene transfer – treatment of the future 26 • Disorders of AMINO ACID METABOLISM (phenylketonuria, maple syrup urine disease…) • UREA CYCLE defects • Disorders of CARBOHYDRATE METABOLISM (galactosemia, glycogen storage diseases…) • Disorders of ORGANIC ACID METABOLISM (metylmalonic and propionic acidemia) • Disorders of FATTY ACID OXIDATION and MITOCHONDRIAL METABOLISM (Medium-change acyl-coenzyme A dehydrogenase deficiency…) 27 28 Phenylanine hydroxylase • Phenylalanin – aromatic amino acid • PKU is an IMD due to a deficiency of hepatic phenylalanin hydroxylase. • Deficiency of this enzyme results in high levels of phenylalanine in the blood. • Accumulation of phenylalanin and its metabolites leads to mental retardation, if this condition is not recognized and the strict diet isn´t observed. 29 High peak of plasma phenylalanine 30 1. Case report - phenylketonuria 31 1. Case report - PKU 32 2. Case report – argininosuccinic aciduria 33 Urea cycle 34 Aminogram of serum– report from AAA CITRULLINE ARGININOSUCCCINATE ARGININEORNITINE 35 3. Case report – SLOS - characteristic physical features Mandibular hypoplasia Genital malformations 36 3. Case report – SLOS - characteristic physical features Polydactyly and syndactyly 37 SLOS - syntesis of cholesterol 38 3. Case report - SLOS 39 3. Case report - SLOS 40 7-dehydrocholesterol – record (graph from HPLC) 41 Standard Patient sample 7 dehydrocholesterol – absorption spectrum 42 Literature: • Hoffmann, G.F., Nyhan, W.L. et al., Inherited Metabolic Diseases • Fernandes,J., Saudubray,J.M., et al., Inborn Metabolic Diseases: Diagnosis and Treatment (2006) • Scriver Ch.R., Beaudet A.L. et al., The metabolic and molecular bases of inherited disease Website: www.omim.org 43