Introduction

• Taurine is a sulfur-containing β-amino acid, with a role in retinal, platelet, immune, neurologic, reproductive and myocardial function.
• Taurine is not an essential amino acid in dogs as adequate amounts can normally be endogenously synthesized.
• Cause: predisposed breeds, diet deficient in taurine precursors, cystinuria.
• Signs: see dilated cardiomyopathy Heart: dilated cardiomyopathy (DCM).
• Diagnosis: serology or whole blood levels.
• Treatment: oral supplementation, pimobendan, treatment for heart failure if present.

Pathogenesis

Etiology

• Breed: predisposed breeds include American Cocker Spaniels, Golden Retrievers, Portuguese Water Dogs and some Newfoundlands. A relationship between DCM and taurine Taurine has not been found in English Cocker Spaniels but measurement of taurine levels and supplementation is still currently recommended if DCM is identified.
• Diet: vegetarian, restricted protein, high-fiber, lamb and rice. DCM has more recently been reported in dogs receiving grain-free diets and diets high in peas, lentils and potatoes. These diets generally had methionine and cysteine values above the minimum requirements. Investigations are ongoing as to the underlying cause of DCM in these cases, but it is currently unknown if it is related to taurine deficiency.
• Cystinuria Urolithiasis: failure of absorption of cysteine from the urine. Low plasma taurine has been demonstrated in some dogs with this disease and some have developed DCM that responded to taurine and carnitine L-carnitine supplementation.

Pathophysiology

• Dogs can endogenously synthesize adequate amounts of taurine from cystine and methionine.
• Predisposed breeds may have altered taurine metabolism or requirements.
• Exact role of taurine in tissue metabolism unclear:
  • Regulates flux of potassium and calcium ions across photoreceptor and myocardial cell membranes.
  • Directly affects contractile proteins in the heart.
  • Acts as a natural antagonist of angiotensin II. 
  • Inactivates free radicals.
  • Osmoregulation.
• Deficiency   →   disruption of cell membranes   →   cell degeneration and death   →
  • DCM  Heart: dilated cardiomyopathy (DCM) Heart: occult dilated cardiomyopathy. 
  • Reproductive failure.

Diagnosis

Treatment

Outcomes