The resultant relative area values but not the absolute contents were further normalized by the content of methylhistidine
(MH; sum of 1 MH and 3 MH, 3 MH is a skeletal muscle-specific metabolite ) which is not affected by postmortem aging time in pork (unpublished data).
While generally recognised as useful markers, superiority of surrogate markers such as serum concentrations of methylhistidine
, ceruloplasmin, copper, and sex hormone binding globulin (SHBG) over TSH and thyroid hormone concentrations has so far been shown in athyreotic patients and other rare disorders of thyroid homeostasis [38,58].
Classes of compounds detected by the NMR method included amino acids (alanine, asparagine, arginine, cysteine, glycine, glutamate, glutamine, homoserine, isoleucine, leucine, lysine, methionine, phenylalanine, sarcosine, serine, threonine, tyrosine, taurine, valine); alcohols (methanol and glycerol); ketones and fatty acid by-products (acetoacetate, acetate, 3-hydroxybutyrate, acetone, pyruvate, isobutyrate); sugar (glucose); other small molecule intermediates (o-phosphocholine, choline, n,n-dimethylglycine, citrate, creatine, lactate, methylhistidine
, succinate, myo-inositol, dimethylamine, methylsuccinate, and 2-hydroxyisobutyrate).
[down arrow] valine, alanine, 2014  pyroacemic acid, inose, p- hydroxyphenylalanine, methylhistidine
in hypertension patients [up arrow] ornithine, TMAO Vaarhorst et al.
Plasma levels of 3- methylhistidine
after ingestion of the pure amino acid or of muscular proteins measured by radioimmunoassay.
Effect of glucocorticoid administration on the rate muscle protein breakdown in vivo in rats, as measured by urinary excretion of N7 methylhistidine
. Biochem J., 178: 139-146.
Once histidine is used to synthesize muscle, it turns into another form, namely, methylhistidine
Metabolites: (1) LDL/VLDL, (2) isoleucine, (3) leucine, (4) valine, (5) 3-hydroxybutyrate, (6) lactate, (7) alanine, (8) lysine, (9) acetate, (10) acetone, (11) acetoacetate, (12) glutamate, (13) pyruvate, (14) succinate, (15) glutamine, (16) citrate, (17) N,N- dimethylglycine, (18) creatine, (19) choline, (20) O- phosphocholine, (21) betaine, (22) glycine, (23) glucose, (24) serine, (25) fumarate, (26) tyrosine, (27) T- methylhistidine
, (28) phenylalanine, and (29) format.
Methylation of the imidazole ring of histidine appeared to substantially decrease its reactivity; this is relevant to biuret reactivity of urine in that methylhistidines
are relatively abundant urinary components.