Assessment of the neurologic effects of dietary deficiencies of phenylalanine and tyrosine in cats

Peter J. Dickinson Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Peter J. Dickinson in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD
,
Peter J. B. Anderson Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Peter J. B. Anderson in
Current site
Google Scholar
PubMed
Close
 PhD
,
Diane C. Williams Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Diane C. Williams in
Current site
Google Scholar
PubMed
Close
 BS
,
Henry C. Powell Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, CA 92093.

Search for other papers by Henry C. Powell in
Current site
Google Scholar
PubMed
Close
 MD, DSc
,
G. Diane Shelton Department of Pathology, School of Medicine, University of California, San Diego, La Jolla, CA 92093.

Search for other papers by G. Diane Shelton in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
James G. Morris Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by James G. Morris in
Current site
Google Scholar
PubMed
Close
 MAgr Sc, PhD
, and
Richard A. LeCouteur Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616.

Search for other papers by Richard A. LeCouteur in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD

Abstract

Objective—To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats.

Animals—53 specific pathogen-free black domestic shorthair cats.

Procedure—Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for ≤ 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats.

Results—After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet.

Conclusions and Clinical Relevance—Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function. ( Am J Vet Res 2004;65:671–680)

Abstract

Objective—To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats.

Animals—53 specific pathogen-free black domestic shorthair cats.

Procedure—Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for ≤ 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats.

Results—After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet.

Conclusions and Clinical Relevance—Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function. ( Am J Vet Res 2004;65:671–680)

All Time Past Year Past 30 Days
Abstract Views 56 0 0
Full Text Views 1445 1246 294
PDF Downloads 265 144 11
Advertisement