1. A Seminar on Taurine Deficiency in Cats Group 10
March 3, 2014

2. 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.

3. Biosynthesis of Taurine
Methionine
Vit
Transulfuration
Cysteamine
Phosphopantothenate
Cystein
Cysteamine
dioxygenase
Cysteine
dioxygenase (CDO)
Hypotaurine
Cysteine sulfunic acid
Cysteine sulfinate decarboxylase
Cysteine sulfinic acid pathway
Hypotaurine
decarboxylase
Cysteine sulfinic acid
dehydrogenase
Taurine
Cysteine sulfinate decarboxylase
Cysteic acid
A dietary deficiency of vitamin B6 shows a depressing effect on taurine biosynthesis.

4. 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

5. Physiological Function of Taurine
system
Visual system
Immune system
Renal system
Bile acid
conjugation
Nervous
system
Cardiovascular

6. 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.
Taurine is essential for normal function of central nervous system. Its accumulation varies in location, depends on species and age.
Its amount gradually decreases after development.
Taurine can be found in majority of brain cells, more concentrated in glial cells than neurons. Astrocytes can accumulate taurine up to 20 mM.
CSAD = Cysteine sulfinic acid decarboxylase

7. Taurine as a neuroprotective agent.
- Cellular injury prevention
- Intracellular calcium-ion modulation
- Change of anti-apoptotic protein (Bcl-2) and pro-apoptotic protein (Bax) ratio
- Autolysis inhibition
Taurine as a neuroprotective agent.

8. 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 excitation- contraction coupling.

9. Roles of Taurine in Cardiovascular System
Excitation-contraction coupling
of cardiac myocyte.

10. 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.

11. Photoreceptor cell Phototransduction system outer segment
Inner segment
Synaptic terminal
Photoreceptor cell
Phototransduction
system

12. taurine depolarization Intracellular Ca2+ Outer segment Na+ Ca2+ Ca2+
exchanger
CNG channel
disks
Na+
Ca2+
Ca2+
Ca2+
Na+
Na+
reopening
depolarization
taurine
Intracellular Ca2+

13. 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.
Myeloperoxidase enzyme presents in leucocytes as a defense against microbes can generate free radicals which are potentially toxic to host cells.

14. 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
Taurine affects sodium transportation.
Regulation of taurine body pool size.
Medullary collecting duct
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)

15. Taurine transport in renal tubular cell
Roles of Taurine in Renal System
Taurine transport in renal tubular cell

16. Taurine Deficiency in Cats
-Bile conjugation
-CSAD
Why are cats more likely to develop taurine deficiency?
How does taurine deficiency affects cats health?
Cats have low activity of cysteine sulfinic acid decarboxylase (CSAD) in the liver, which is essential for taurine biosynthesis.
It is obligatory that cats conjugate bile acid solely with taurine, even in the status of taurine depletion.

17. Taurochenodeoxycholic acid
Bile acid conjugation
Cholesterol
7αHydroxylase
7αHydroxyCholesterol
Cholic acid
(primary bile acid)
Chenodeoxy
(primary bile acid)
Glycine
Taurine
Taurine
Cats have low activity of cysteine sulfinic acid decarboxylase (CSAD) in the liver, which is essential for taurine biosynthesis.
It is obligatory that cats conjugate bile acid solely with taurine, even in the status of taurine depletion.
Taurochenodeoxycholic acid
Glyconolic acid
Taurocholic acid
Linthocolic acid
(secondary bile acid)

18. Taurine Deficiency on Cats Health
Cardiac Function
Visual System
Immune System
Reproductive System & Development

19. Impaired sensitivity of contractile protein to Ca2+
Cardiac Function
Impaired sensitivity of contractile protein to Ca2+
Decrease
Ca2+ influx
Cell
Apoptosis
Impaired systole and diastole
Feline Dilated Cardiomyopathy (DCM)
Decrease in calcium influx to cardiac myocytes.
Impaired sensitivity of contractile protein to calcium ion.
Decrease in number of cardiac myocytes due to apoptosis.
Heart failure

20. Retina Visual system Lens Tapetum Lucidum Feline central retinal
degeneration
(FCRD)
Retina
Tapetum Lucidum
Visual system
Lateral geniculate body
Superior colliculus
Lens

21. Feline central retinal degeneration (FCRD)

22. Tapetum lucidum
normal
Taurine deficiency

23. Immune system Leucopenia Decrease respiratory burst of neutrophils
Decrease phagocytic activity of phagocytes

24. Reproductive System & Development
Taurine-deficient pregnant queen
Kittens born from taurine- deficient female cats
More incidences of fetal death (resorption), abortion, or stillbirth.
Reduction of taurine concentration in feline maternal milk.
Low survival rate
Low birth weight
Growth retardation
Bone malformation
Impaired nervous and visual system development.
Kitten obtain taurine from the queen
In other species, the placenta provides the fetus with essential nutrients. The mechanism by which the queen supplied taurine to the kittens in utero was not known. This work was conducted in collaboration with scientists at the University of Manchester (Champion et al. 2004; Champion et al.2005). Taurine uptake was characterised in placental fragments obtained from queens during normal parturition. For the first time, it was shown that the cat placenta possesses amino acid transport systems that are functionally similar to the system β and system A transporters of the human placenta (Champion et al. 2004).

25. Kittens born from taurine-deficient female cats.
A premature kitten with congenital hydrocephalus.
A stillbirth kitten with anencephaly.
Severe congenital hydrocephalus, a brain from 1-year old kitten.
Kitten obtain taurine from the queen
In other species, the placenta provides the fetus with essential nutrients. The mechanism by which the queen supplied taurine to the kittens in utero was not known. This work was conducted in collaboration with scientists at the University of Manchester (Champion et al. 2004; Champion et al.2005). Taurine uptake was characterised in placental fragments obtained from queens during normal parturition. For the first time, it was shown that the cat placenta possesses amino acid transport systems that are functionally similar to the system β and system A transporters of the human placenta (Champion et al. 2004).

26. Effects on digestive physiology
Nutritional Aspects
Recommended amount
Commercial diets
Bioavailability
Ingredients
Processing
Dry diet
Effects on digestive physiology
Canned diet
Processing

27. Taurine Requirement for Cats
The Association of American Feed Control Officials (AAFCO) 
Growth and Reproduction
Adult Maintenance
Nutrient
Minimum
Maximum
Taurine (extrude,%)
0.10
Taurine (canned,%)
0.20
AAFCO
Nutrient requirements are indicated on a dry-matter basis. These AAFCO nutrient profiles for cat foods presume an energy density of 4.0 kcal ME/g dry matter.
By comparison, the average mature body weight of domestic cats is 3.2 kg (7 lb) for toms and 2.8 kg (6 lb) for queens. Normal birth weight of kittens is 90–100 g. The growth rate is exceptionally rapid for the first 3–4 mo, and kittens gain 50–100 g/wk. The growth rate begins to plateau at 150–160 days of age, and growth is usually completed within 200–220 days.

28. How to prevent taurine deficiency in cats?
Nutritional Aspects
How to prevent taurine deficiency in cats?
Commercial diets
Homemade meal
Processing

29. Taurine amount labelled on Hill’s commercial cats diets

30. Taurine amount in food
(mg/kg, wet weight)

31. 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.

32. 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

33. 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

34. Thank you for your attention