METABOLISM = summary of all chemical (and physical) processes included in: 1. Production of energy from internal and external sources 2. Synthesis and degradation of structural and functional tissue components 3. Excretion of waste products and toxins from body METABOLISM •Proteins •Saccharides •Lipids METABOLIC DISORDERS 1. Inherited metabolic disorders (enzymopathies) 2. Combined metabolic disorders (DM, gout, degenerative disorder of joints and bones) 3. Metabolic disorders from external reasons http://www.derangedphysiology.com/main/required-reading/endocrinology-metabolism-and-nutrition/Chapter%203.1.8/physiological-adaptation-prolonged-starvation Ballanced diet should contain: – sugars – saccharides (50 –55 %) – fats (30 %) – proteins (15 –20 %) – vitamines, innorganic compounds – water – daily requirements correspond to 2,4 l: The daily energy requirement is: – an adult man ~12600 kJ – an adult woman ~9200 kJ – real consumption depends on: • body weight • the extent of physical activity • other physiological and pathophysiological factors DIET Insulin versus glucagon SHORT-TERM VERSUS LONG TERM FASTING 24 h. Rate of lipolysis Prolonged starvation • Decrease energy requirements • BMR (- 20 to 25 kcal / kg / day) • A majority of effects is given by hypoinsulinemia, effect on the liver is determined by glucagon • The gradual increase in the ratio of gluconeogenesis • Initially increase the rate of proteolysis • Increasing the rate of lipolysis activation of hormone-sensitive lipase = mobilization of glycerol and FAs • Glycerol = an additional substrate for gluconeogenesis; excess of FAs = substrate for muscles (insulin resistance, interference with "activation" of GLUT4) and peripheral tissues = enough glucose to nervous tissue • Further starvation: – Reduction of proteolysis (= reduced production of urea = reduced excretion of water), increasing use of fat for ketogenesis – Use of ketones nervous tissue (b-hydroxybutyrate and acetoacetate) – Reduction of hepatic gluconeogenesis X increased gluconeogenesis in the kidney (40% of production) – Further mobilization of lipids = lipolysis = increase in hepatic ketogenesis (100 g d) – Further lipolysis = loss of adipose tissue, hormonal changes (leptin, FSH, LH - anovulation) 20 % of body weight Other changes as a result of starvation: • Loss of K+ in the initial stage, a stable concentration of 3 mmol/L • Mg2+ - unchanged or only slight hypomagnesemia • Ca2+ - unchanged • Phosphates – unchanged • Uric acid – increase (protein catabolism) • Next changes:  Decreased heart rate (35 t/min, from 4. week slight increase)  Drop of blood pressure  ECG changes - flattening of the T wave, decrease of amplitude of QRS  In cases of extreme starvation - prolongation of the QT interval, T wave inversion, ST segment depression  Why? o The decrease of protein synthesis - myofibrils, myofilaments o Changes in the composition of the ECT/ICT o Losses of trace elements (Cu - ischemia) o Sympathetic (catecholamines) - Arrhythmia METABOLIC DISORDERS EXAMINATION LABORATORY METHODS (biochemistry) • Lack or absence of metabolite (blood, urine, tissue, cells) • Overproduction of metabolite • Pathological storing of metabolite in tissues (histochemistry) • Pathological metabolite FINDINGS OF CAUSE OF METABOLIC DISORDER • Disorder in resorption or excretion (functional load tests) • Measurement of activity of certain enzymes or enzyme systems GENEALOGIC EXAMINATION SCREENING TESTS (fenylketonuria, hyperlipoproteinemia, aminoaciduria, thyroid gland hormones…) METABOLISM OF SACCHARIDES 1.Source of energy 2.Part of glycoproteins, glycopeptides, glycolipids– structural or functional (collagen in basal membranes, mucopolysaccharides, myelin, hormones, receptors…) Dietary carbohydrates– hexoses (glucose, fructose, galactose) Key substrate – glucose. Postprandial plasmatic levels of glucose: 3,5 – 6,5mmol/l Glycaemia. Hypoglycaemia, hyperglycaemia. Hypoglycaemia: decreased oxygen supply of CNS Glycolysis, gluconeogenesis. Humoral control of glycaemia. Glycolysis: main products – lactate and pyruvate – mean plasmatic concentrations 0,7 and 0,07mmol/l (ratio 10:1 remains even at various turnover); during hypoxia – 30:1 (metabolic acidosis) •Glucose turnover: 2mg/kg/min (11mmol/kg/min)~9g/hr~225g/day •55% of glucose utilisation – terminal oxidation (CNS) •20% - glycolysis, lactate back to liver, gluconeogenesis (Cori cycle) •20% - absorption by liver and splanchnic tissues •70% consumption of glucose at rest is insulin-independent •Circulating glucose pool (pool) – only a little bigger than expenditure by liver per 1 hour •Brain oxidation is kept by pool only for approx. 3 hrs •NECESSITY OF CONTINUOUS GLUCOSE PRODUCTION FROM LIVER during starving •80% - glycogenolysis, 20% - gluconeogenesis (more than 50% from lactate trapped by liver for gluconeogenesis, rest – AA, esp. alanine; lactate from glycolysis in muscles, ery, leu, etc.; AA – from proteolysis of muscles) •Morning glucose intake – 70% is needed by peripheral tissues (muscles), 30% - splanchnic organs (liver) •20-30% of consumed glucose – oxidised during 3-5 hrs to cover needs of GIT, 70-80% stored as glycogen (muscle, liver) •Muscle glycogen – later transported to liver (lactate from glycolysis in muscles, re-uptake, gluconeogenesis in liver, glycogenolysis) •During maximal absorption of exogenous glucose – release of glucose from liver is suppressed (insulin and glucagon facilitate this process) LIVER GLUCOSTAT - Maintaining the constant blood glucose - Endocrine control: • glycogenolysis (glucagon, adrenaline, noradrenaline = activation of glycogen phosphorylase) • why only liver and not muscles? (glucose-6phosphatase in liver) • gluconeogenesis (glucagon, adrenaline, noradrenaline, glucocorticoids, thyroid hormones) GLYCOSURIA •Renal glycosuria (congenital deficiency of glucose transport in the kidneys, blood glucose is normal) •Alimentary glycosuria (renal threshold for glucose = 10 mmol/l) •Inhibitors of SGLT2 METABOLISM OF LIPIDS •Fat – approx. 50% of daily amount of substrates for oxidation (100gr, 900kcal) •Main and most profitable form of energy store •Daily intake: approx. 100gr (40% of daily diet) •Main component of dietary sources and stores in body: triglycerides •No strict dietary recommendation (part of FA synthetised in liver and adipose tissue) •BUT: 3-5% of FA are polyunsaturated!!! – ESSENTIAL FA •Precursors of membrane phospholipids, glycolipids, prostaglandins •Cholesterol – part of membranes, precursor of bile acids, steroid hormones; daily intake – 300-600mg/day, synthesised too •Lipoproteins: transport of lipids by blood plasma •Apoproteins (from liver or intestine), catalytic function, receptors •Chylomicrons – from diet, lowest density, lipoprotein lipase (endothelium of capillaries), activation by apoprotein C-II, transport of HDL •Free FA absorbed by adipocytes (resynthesis of triglycerides, store) and other tissues (oxidation) •Rest of lipoprotein particles (more cholesterol) – chylomicron rests – degradation in liver •VLDL – endogenous synthesis in liver (less in intestine), in postabsorption phase •Dense, more cholesterol, longer plasmatic half-time •Speed of production: 15-90g/day •Beginning of metabolism – see chylomicrons •Products of lipoprotein lipase effect – IDL (intermediate-density lipoprotein) •50% IDL – back to liver (as chylomicron rests) •50% IDL – enriched by cholesterol – LDL •Circulating LDL – transport of cholesterol into cells •Absorption of LDL, IDL, rests of ch. – apoproteins, receptors, endocytosis Uptake of LDL-cholesterol into cells – down regulation of LDL receptors (slowed resorption) and slowed synthesis de novo •HDL – long plasmatic half-time, synthesis in liver and intestine •Facilitation of other particles movement •Exchange of key apoproteins •They accept molecules of free cholesterol, estherify them (lecithincholesterol-acetyltransferase) and incorporate back to particles •Main effect: acceleration of clearance of triglycerides from plasma and regulation of ration free:estherified cholesterol •Free FA •Average concentration: 400mM/l •Bound to molecules of albumins •Fast turnover (approx. 8g/hr): 50% - oxidation, 50% reestherification to triglycerides •Total cholesterol: 185mg/l •LDL cholesterol: 120mg/l •HDL cholesterol •Arteriosclerosis, genetic predisposition (LDL apo or receptor) Převzato. Silverthorn, D. U. Human Physiology – an Integrated Approach. 6th. edition. Pearson Education, Inc. 2012.x METABOLIC DISORDERS - SACCHARIDES 1. Diabetes mellitus 2. McArdle syndrom: glycogenesis from deficiency of myophosphorylase Accumulation of glycogen in muscles Muscle stiffness, rigor during exercise, lower tolerance of load 3. Galactosemia (inherited deficiency of phosphogalactosauridyltransferase; disorders of growths and development) 1. HYPERLIPIDEMIA, HYPERLIPOPROTEINEMIA 2. INFREQUENT DISORDERS OF LIPID METABOLIS METABOLIC DISORDERS - LIPIDS Ad 1) 5% of population Primary and secondary forms Arteriosclerosis •Hyperlipoproteinemia induced by lipids •Familiar hypercholesterolemia (xantomatosis) •Mixed hyperlipoproteinemia •Familiar hypercholesterolemia with hyperlipemia •Saccharides-induced triglyceridemia •Secondary hyperlipoproteinemia (dependent; alimentary) Ad 2) •Lipidoses •Abetalipoproteinemia (LDL, VLDL) •Analfalipoproteinemia (HDL) •Inherited defect acetyltranspherase LCAT (accumulation of lecithin) Adipose tissue • = the long-term repository for excess energy • = reflection of the imbalance between energy intake and energy expenditure, integrated over a long period Lipogenesis • TAGs in adipocytes (approx. 80 - 90% of the cell volume) • Sources of FAs (free circulating, enzymatic hydrolysis of TAGs – chylomicrons, VLDLs, LDLs) • De novo lipogenesis from non-lipid substrates (carbohydrates) • Production of glycerol 3-phosphate (glycolysis, gluconeogenesis, glycerol kinase activity) • TAG synthesis (G3P acyltransferases) Regulation of lipogenesis • Nutritional – feeding, fasting, and diet composition – Excessive carbohydrate consumption stimulates lipogenesis in both the liver and AT, increasing the availability of TAG in the postabsorptive state – Blood Glu! (lipogenic capability – substrate for lipogenesis) • Hormonal – Insulin (+) – GH (dramatically reduces lipogenesis in AT; mechanism - decrease in insulin sensitivity and a reduction in the number of insulin receptors) – Leptin (limits lipid storage not only by inhibiting food intake, but also by affecting specific metabolic pathways in AT) Lipolysis • Lipolysis of TAG reserves • Release of FFAs and glycerol • Insulin • Natriuretic peptides (especially during exercise-stimulated lipolysis) • Catecholamines Adipogenesis • = transformation of undifferentiated preadipocytes in AT to adipocytes • balance between adipogenesis, triglyceride synthesis, and lipolysis is responsible for the quantity of AT in an organism • Three distinct phases - growth arrest, clonal expansion, and terminal differentiation – three CCAAT-binding proteins (C/EBPs) b, d, and a and PPAR-g, expressed in a defined sequence and thus coordinating the series of adipogenic stages Endocrine role of AT Cytokines (IL-6, TNF-a) Chemokines (MCP-1) Complement factors (adipsin) Factors of angiogenesis, blood vessels and coagulation (PAI-1, VEGF) Glucose homeostasis (adiponectin, visfatin, apelin, omentin) Leptin Lipid metabolism (resistin, RBP, CETP, ) Blood pressure factors (angiotensinogen) Adipose tissue secreted products regulated by energy balance Crosstalk between AT and other tissues • an effect on AT: – Endocrine function, regulating adipokine secretion – cell number in the fat pad, regulating cell turnover (adipogenesis and apoptosis – metabolic regulation of lipogenesis, lipolysis, and oxidation • Muscle tissue – Myokines – IL-6 – lipolysis in AT – Irisin BROWN ADIPOSE TISSUE LIPIDS: structural, neutral and brown Specific localisation Sympathetic innervations of vessels and also adipocytes Several drops of fat in adipocyte More mitochondria Production of heat Adaptation to cold After meal – increased production of heat http://www.nature.com/nm/journal/v19/n10/fig_tab/nm.3361_F4.html • Irisin = ??? (transformation of white fat to brown...), production increased during physical exertion? • FGF21 = increased intake of Glu by peripheral tissues, increased oxidation of FAs • Natriuretic peptides, ANP - increased lipolysis; protection against low temperatures? • Bmp8b = produced by brown adipocytes and some hypothalamic nuclei - regulation of sympathetic activity • T4/T3 - increasing the expression of thermogenic genes Chechi K, Carpentier AC, Richard D: Understanding the brown adipocyte as a contributor to energy homeostasis. Trends Endocrinol Metab 2013, 24(8):408-420. Exercise-induced adipose tissue browning through PGC-1α and irisin. Exercise increases the expression levels of PGC-1α in the muscle. This, in turn, upregulates the expression of FNDC5, a type I membrane protein, which is Cterminally cleaved and secreted as irisin into the circulation. Binding of irisin to an unknown receptor on the surface of adipocytes in WAT changes their genetic profile. In particular, irisin induces the expression of PPAR-α, which is thought to be an intermediate downstream effector that increases the expression of UCP1 (highly expressed in BAT and a marker of browning). The browning of WAT is associated with augmented mitochondrial density and oxygen consumption. Browning is accompanied by an increase in the energy expenditure profile, leading to favourable effects on metabolism. Peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1a Castillo-Quan JI: From white to brown fat through the PGC-1 alpha-dependent myokine irisin: implications for diabetes and obesity. Disease Models & Mechanisms 2012, 5(3):293-295. http://www.e- dmj.org/ViewImage.php?Type=F&aid =284781&id=F1&afn=2004_DMJ_37_1 _22&fn=dmj-37-22-g001_2004DMJ METABOLISM OF PROTEINS •Proteins = AA bound by peptide bonds (above 100 AA) •Peptides (2-10 AA), polypeptides (10-100 AA) •Primary, secondary, tertiary a quarterly structure of protein Proteins, lipoproteins, glycoproteins Structure of proteins Primary Secondary Tertiary Quaternary Assembly Folding Packing Interaction Structure Proces Total proteins in body: 10 kg Metabolically active: 6 kg (e.g.60%) Proteolysis of muscles: 50 g of proteins / day Minimal daily intake: 50 g Protein minimum: 0,5 g / kg of body mass Protein optimum: 0,7 g / kg of body mass Increased supply (growth, convalescence, pregnancy, lactation): 1,5 – 2,0 AMINOACIDES •Essential (not synthesised) •Non-essential (from glucose metabolism – citrate cycle) •Aminoacid pool •Need of essential AA: 0,5 – 1,5 g / day •Disorders of proteosynthesis •Optimal source of E-AA:NE-AA milk, eggs •During growth: 40% E-AA, in adults: 20% •Precursors: purines, pyrimidines, polyamines, phospholipids, creatin, carnitin, donors of methyl group, catecholamines, thyroid gland hormones, neurotransmitters Amino acids - the surplus in food Degradation, used as an energy source AMK as other substrates: - Glucogenic AMK – synthesis of carbohydrates - Ketogenic AMK – lipids and ketones Isoelectric point = pI Ionization states of amino acids as a function of pH: pH 2 12 4 6 8 10 0 0,5 1,0 1,5 2,0 Disociované H+ ionty/ molekula pK1 pI pK2 HNH3 + CH CH3 COO + H +-NH3 + CH CH3 COO + H +-NH3 + CH CH3 COO-NH3 + CH CH3 COO Determination of pK1, pK2 and pI of alanine pI =(pK1 + pK2) / 2 (isoelectric point, pI = 6) Derivatives of AMK with physiological functions g-Aminomáselná kyselina CH2 CH2 NH3 + OOC CH2 g ba (GABA) Histamin CH2 CH2 NH3 + N N H Dopamin CH2 CH2 NH3 + OH OH Thyroxin CH CH2 NH3 + O COO I I OH I I - DEGRADATION OF PROTEINS Binding to ubiquitin (74 AA). Oxidation to CO2 and H2O after removing the amino-group (deamination). Gluconeogenesis (except of leucin), ketogenesis (5AA, acetoacetate or CoA precursors), ureagenesis (all AA, ammonium bound to glutamin or alanine, liver, Krebs-Henseleit cycle). Regulated speed of degradation (muscle hypertrophy, atrophy of denerved or non-stimulated muscle). AMINOACIDS AMMONIUMCO2 + ATP + CARBAMOYLPHOSPHATE CITRULIN ASPARTATE ARGININOSUKCINATE FUMARATE ARGININ ORNITIN UREA URINE Degradation of proteins •lysozomes • Extracellular proteins • Membrane proteins • Proteins with long half-time • Process does not require ATP •cytosol • Metabolic proteins • Proteins with short half-time • Process requires ATP and ubiquitin http://ebm.sagepub.com/content/231 /7/1197.full.pdf+html URIC ACID Excreted in urine. 4mg/100ml of blood plasma Kidney: filtration, resorption (98% filtration), tubular secretion (80%) Daily: approx. 1g excreted in urine Disorder in uric acid metabolism – gout. Hyperuricemia – primary (overproduction) or secondary (reduced excretion, increased intake of purines in diet, blood disorders). METABOLISM OF PURINES AND PYRIMIDINES Purines and pyrimidines – physiological meaning of nucleosides (reactants with ribose); from diet or synthesis de novo from AA in liver; RNA is in balance with AA pool, DNA is stabile. Recirculation or catabolism, eventually excretion in urine. Pyrimidines – CO2 and NH3, purines – uric acid. Synthesis of purines/pyrimidines • de novo (new synthesis of purine/pyrimidine ring) • „saving“ reactions (synthesis from nucleotides and bases) is more energy saving than de novo synthesis They decrease the synthesis de novo substrates: a) bases (adenine, guanine, hypoxanthine) PRDP b) ribonucleosides ATP Harper´s Illustrated Biochemistry 26th ed./ R.K.Murray; McGraw-Hill Companies, 2003, ISBN 0-07-138901-6. Analogs of bases and nucleotides are used as cytostatics GOUT (arthritis urica) •Primary and secondary gout •Acute (gouty attack) and chronic (chalkstones, urolithiasis) form •General metabolic disorder - disease of purine metabolism •Local cumulating of uric acid salts (urate) in tissues, urine (joints, kidneys), primary hyperuricemia •Gouty attacks – repeated attacks of arthritis, typical localisation – metatarsophalangeal joint (podagra; omagra, cheiragra…) •Hurtfulness during attack – phagocytosis of urates grains •Therapy: NSA, colchicin – inhibition of fagocytosis, allopurinol – inhibition of xantinoxidase, phenylbutazon and probenecid – inhibition of resorption NITROGEN BALANCE Necessity to keep AA pool. AA mixtures. Amount of N in urine – indicator of intensity of irreversible disintegration of proteins and AA. Nitrogen balance: amount of N in urine = amount of N in dietary proteins •Negative nitrogen balance: loss exceeds intake (starvation, immobilisation, catabolism, lack of E-AA!!!…) •Positive nitrogen balance: intake exceeds loss (anabolic drugs, growth, convalescence…) Synthesis and degradation of body proteins: 3–4g/kg of body mass (balanced diet) From this amount: 5% - synthesis of albumins and proteins with fast-exchange in liver In deficient diet (energetically, amount of proteins or E-AA) – proteosynthesis deceleration, compensatory –degradation deceleration (BUT of lower extent loss of body proteins) CREATIN AND CREATININ CREATIN Synthesis in liver (methionin, glycin, arginin). Phosphorylation in skeletal muscle – phosphocreatin. CREATININ From phosphocreatin, in urine. Speed of excretion is relatively constant. CREATINURIE Physiological – in children, in pregnancy, after pregnancy, occasionally in non-pregnant. During muscle catabolism – in enormous amounts (starving, DM, myopathy, thyreotoxicosis…) Wyss M, Kaddurah-Daouk R: Creatine and creatinine metabolism. Physiol Rev 2000, 80(3):1107-1213. Wyss M, Kaddurah-Daouk R: Creatine and creatinine metabolism. Physiol Rev 2000, 80(3):1107-1213. METABOLIC DISORDERS – PROTEINS QUANTITATIVE CHANGES Proteinemia = plasmatic level of proteins. Controlled: 1. Supply with full-value proteins and their use 2. Synthesis of proteins 3. Protein catabolism and loss from organism Ad 1) nutrition disorders, special dietary trends Ad 2) liver disorders, endocrine diseases Ad 3) liver and muscles release E-AA when proteins are reduced in diet METABOLIC DISORDERS – PROTEINS QUALITATIVE CHANGES 1. Dysproteinemia = change in representation of particular proteins (fractions shift) – nephrotic syndrome, cirrhosis, acute inflammatory reactions, chronic inflammatory reactions, tumours 2. Paraproteinemia = presence of pathological imunoglobulines (with no antibodies specificity) – monoclonal immunopathy 3. Defect proteinemia = some components of plasma proteins are missing or lowered (1/10 – 1/1000 normal values) – syndromes of immunodeficiency, symptomatic hypo- and dysgamaglobulinemia (familiar lack of IgA), polyclonal hypergamaglobulinemia METABOLIC DISORDERS – AMINOACIDES 1. Disorders of AA metabolism during hypovitaminoses and avitaminoses – vit.C (colagen synthesis– proline hydroxylation; metabolic osteopathy, haemorrhage, poor healing), vit.B6 (tryptophan metabolism – lack of nicotinic acid) 2. Disorders of AA metabolism during liver diseases – regulation of plasmatic level of AA (transamination, oxidation, decarboxylation, deamination, ammonia, urea, kidneys); badly soluble AA (cystine, tyrosine) may form crystals in urine; liver encephalopathy, liver coma, glutamine in coeliolymph AMYLOIDOSIS = infiltration of organs by amyloid (complex of protein with polysaccharide) Mechanism of disease is alteration of immune system. Primary and secondary amyloidosis Primary – idiopathic; infliction of heart, muscles, GIT; elderly patients; no gender differences Secondary – complication of chronic inflammatory diseases, tumours; more frequent; infliction of kidney (most often), lien, liver, adrenal glands A protein during and after its synthesis at the ribosome folds through different intermediates to its native, three-dimensional structure. Proteotoxic stresses, mutations in the synthesized protein or translational errors can cause protein misfolding. Once present, misfolded intermediates can be refolded to the native state or be degraded by different cellular proteolysis systems that prevent the accumulation of misfolded proteins. Once the quality-control network is overwhelmed — for example, through persisting harsh stress conditions, increased amounts of aberrant proteins or in aged cells — aggregates can form. Their formation can be guided by molecular chaperones. Forming aggregates can have varying degrees of structure, ranging from mostly unstructured, disordered aggregates to prefibrillar species and highly ordered β-sheet-rich amyloid fibrils. Disordered aggregates and intermediates during amyloid formation may be degraded. Arrows indicate a process that can include several single steps; dashed arrows indicate a process of minor significance.