Metabolism of amino acids in cats with severe cobalamin deficiency.
OBJECTIVE
To validate an automated chemiluminescent immunoassay for measuring serum cobalamin concentration in cats, to establish and validate gas chromatography-mass spectrometry techniques for use in quantification of methylmalonic acid, homocysteine, cysteine, cystathionine, and methionine in sera from cats, and to investigate serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine as indicators of biochemical abnormalities accompanying severe cobalamin (vitamin B12) deficiency in cats.


METHODS
Serum samples of 40 cats with severe cobalamin deficiency (serum cobalamin concentration < 100 ng/L) and 24 control cats with serum cobalamin concentration within the reference range.


METHODS
Serum concentrations of cobalamin were measured, using a commercial automated chemiluminescent immunoassay. Serum concentrations of methylmalonic acid, methionine, homocysteine, cystathionine, and cysteine were measured, using gas chromatography-mass spectrometry, selected ion monitoring, stable-isotope dilution assays.


RESULTS
Cats with cobalamin deficiency had significant increases in mean serum concentrations bf methylmalonic acid (9,607 nmol/L), compared with healthy cats (448 nmol/L). Affected cats also had substantial disturbances in amino acid metabolism, compared with healthy cats, with significantly increased serum concentrations of methionine (133.8 vs 101.1 micromol/L) and significantly decreased serum concentrations of cystathionine (449.6 vs 573.2 nmol/L) and cysteine (142.3 vs 163.9 micromol/L). There was not a significant difference in serum concentrations of homocysteine between the 2 groups.


CONCLUSIONS
Cats with gastrointestinal tract disease may have abnormalities in amino acid metabolism consistent with cobalamin deficiency. Parenteral administration of cobalamin may be necessary to correct these biochemical abnormalities.
Ruaux
C G
CG
Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station 77843-4474, USA.
Steiner
J M
JM
Williams
D A
DA
D000596:Amino Acids / Q000097:blood* / Q000378:metabolism; D000818:Animals; D002371:Cat Diseases / Q000097:blood* / Q000201:enzymology; D002415:Cats; D003540:Cystathionine / Q000097:blood / Q000378:metabolism*; D003545:Cysteine / Q000097:blood / Q000378:metabolism; D005260:Female; D005767:Gastrointestinal Diseases / Q000097:blood / Q000378:metabolism / Q000662:veterinary; D006710:Homocysteine / Q000097:blood / Q000378:metabolism; D007118:Immunoassay / Q000662:veterinary; D008297:Male; D008715:Methionine / Q000097:blood / Q000378:metabolism; D008764:Methylmalonic Acid / Q000097:blood; D018709:Statistics, Nonparametric; D014805:Vitamin B 12 / Q000097:blood; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000378:metabolism / Q000662:veterinary*
D000596:Amino Acids; D006710:Homocysteine; D003540:Cystathionine; D008764:Methylmalonic Acid; D008715:Methionine; D003545:Cysteine; D014805:Vitamin B 12