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A Seminar on Taurine Deficiency in Cats Group 10 1 March 3, 2014 Biochemistry of Taurine Figure 1. Chemical structure of taurine IUPAC name : 2-aminoethanesulfonic acid Taurine is an sulfonic acid containing an amino group, yet it is not an amino acid as it is often called one, because it lacks a carboxyl group. 2 Biosynthesis of Taurine Methionine Vit Transulfuration Cystein Phosphopantothenate Cysteine dioxygenase (CDO) Cysteine sulfunic acid Cysteine sulfinic acid dehydrogenase Cysteamine Cysteamine dioxygenase Hypotaurine Hypotaurine decarboxylase Taurine Cysteic acid 3 A dietary deficiency of vitamin B6 shows a depressing effect on taurine biosynthesis. Taurine Transport in the Body Taurine transport across cell membrane • Na+ - dependent taurine transporter Taurine release from the cell via three mechanisms - Exocytosis occurs at basal membrane - Energy-dependent transporter - Ca2+ - dependent transport 4 Physiological Function of Taurine Bile acid conjugation Nervous Cardiovascular system system Taurine Renal system Visual system Immune system 5 Roles of Taurine in Nervous System • Taurine acts as a neurotransmitter. - Its ability to elicit neuronal hyperpolarization. - The presence of specific taurine synthesizing enzymes (CSAD), taurine-specific receptor, and a taurine transporter system. CSAD = Cysteine sulfinic acid decarboxylase 6 Taurine as a neuroprotective agent. 7 Roles of Taurine in Cardiovascular System Taurine acts as positive inotropes by promoting calcium-ion release from sarcoplasmic reticulum in cardiac myocytes by modulates calcium transportation during the excitationcontraction coupling. 8 Roles of Taurine in Cardiovascular System Excitation-contraction coupling 9 of cardiac myocyte. Roles of Taurine in Visual System • Taurine is found in high concentration at the retina, particularly in photoreceptor cell bodies of outer nuclear layer. • Kittens are more prone to taurine depletion in photoreceptor cells compared to adult cats. 10 Synaptic terminal Inner segment outer segment Outer segment Na+/Ca2+ exchanger disks CNG channelNa+ Ca2+ Ca2+ Na+ Ca2+ Na+ reopening depolarization Intracellular Ca2+ taurine Roles of Taurine in Immune System Myeloperoxidase Taurine can eradicate free radicals generated from specific myeloperoxidase reaction, i.e. hypochlorous acid (HOCl) and hypobromous acid (HOBr), thus it can reduce oxidative stress. 13 Roles of Taurine in Renal System Renal vascular resistance • Taurine aids in renal blood flow regulation. Glomerulus • Elimination of reactive oxygen species (ROS) Proximal tubule Medullary collecting duct • Taurine affects sodium transportation. • Regulation of taurine body pool size. • Taurine acts as osmoregulator, thus it can control the cell volume. Taurine may prevent glomerulonephritis, diabetic nephopathy, chronic renal failure, and acute kidney injury (AKI) 14 Roles of Taurine in Renal System Taurine transport in renal tubular cell 15 Taurine Deficiency in Cats Why are cats more likely to develop taurine deficiency? -CSAD -Bile conjugation How does taurine deficiency affects cats health? 16 Bile acid conjugation Cholesterol 7αHydroxylase 7αHydroxyCholesterol Cholic acid (primary bile acid) Glycine Glyconolic acid Taurine Taurocholic acid Chenodeoxy (primary bile acid) Taurine Taurochenodeoxycholic acid Linthocolic acid 17 (secondary bile acid) Taurine Deficiency on Cats Health Immune System Visual System Reproductive System & Development Cardiac Function 18 Cardiac Function Impaired sensitivity of contractile protein to Ca2+ Decrease Ca2+ influx Cell Apoptosis Impaired systole and diastole Feline Dilated Cardiomyopathy (DCM) Heart failure 19 Immune system 1. Leucopenia 2. Decrease respiratory burst of neutrophils 3. Decrease phagocytic activity of phagocytes 23 Reproductive System & Development Taurine-deficient pregnant queen 1. More incidences of fetal death (resorption), abortion, or stillbirth. 2. Reduction of taurine concentration in feline maternal milk. Kittens born from taurinedeficient female cats 1. 2. 3. 4. 5. Low survival rate Low birth weight Growth retardation Bone malformation Impaired nervous and visual system development. 24 Kittens born from taurine-deficient female cats. a. A premature kitten with congenital hydrocephalus. b. A stillbirth kitten with anencephaly. c. Severe congenital hydrocephalus, a brain from 1-year old kitten. 25 Nutritional Aspects Recommended amount Commercial diets Bioavailability Ingredients Processing Effects on digestive physiology 26 Taurine Requirement for Cats The Association of American Feed Control Officials (AAFCO) Growth and Reproduction Adult Maintenance Nutrient Minimum Minimum Taurine (extrude,%) Taurine (canned,%) 0.10 0.10 0.20 0.20 Maximum 27 Nutritional Aspects How to prevent taurine deficiency in cats? Commercial diets Homemade meal 28 Taurine amount labelled on Hill’s commercial cats diets Dry diets (DM) Dry diet Canned diet Dry diets (Fed) Canned diets (DM) Canned diets (Fed) 29 0 0.1 0.2 0.3 0.4 0.5 Taurine amount in food (mg/kg, wet weight) 3000 2500 Raw 2000 Baked Boiled 1500 1000 500 30 0 Beef Lamb Pork Chicken Cod fish Oyster Clam Case study Feline Dilated Cardiomyopathy History taking Domestic male cat, 4 years old, 3.8 kg. body weight • Signs of depression, poor appetite, cough, and dyspnea since 3 weeks ago. • The cat has muffled cardiac sound. • The owner had fed the cat with commercial dog food for 1 year and 6 months. 31 Examination • Thoracic radiograph shows severe fluid accumulation in • • • • pleural space. Electrocardiography shows decrease in 'R' wave amplitude Echocardiography shows incress in EDV = End diastolic volume or LVIDd ↓ , ESV = End systolic volume or LVIDs ↓ and shortening fraction ↑ Hematology and Serum biochemical parameter are normal Direct opthalmoscopic is normal 32 Shortening fraction Measurement Normal LVIDd (cm) 2.45 1.59 ± 0.19 LVISd (cm) 2.27 0.80 ± 0.14 ∆ D (%) 8.5 49.8 ± 5.3 33 Thank you for your attention 34