Hepatocyte transplantation (HTx) corrects selected neurometabolic abnormalities in murine intermediate maple syrup urine disease (iMSUD).
Skvorak et al. [1] demonstrated the therapeutic efficacy of HTx in a murine model of iMSUD, confirming significant metabolic improvement and survival. To determine the effect of HTx on extrahepatic organs, we examined the metabolic effects of HTx in brain from iMSUD animals. Amino acid analysis revealed that HTx corrected increased ornithine, partially corrected depleted glutamine, and revealed a trend toward alloisoleucine correction. For amino acid and monoamine neurotransmitters, decreased GABA was partially corrected with HTx, while the l-histidine dipeptide of GABA, homocarnosine, was decreased in iMSUD mice and hypercorrected following HTx. Elevated branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in MSUD can deplete brain tyrosine and tryptophan (the precursors of monoamine neurotransmitters, dopamine (DA) and serotonin (5-hydroxytryptamine; 5-HT)) through competition via the large neutral amino acid transporter. HTx corrected decreased DA levels and the DA metabolite, 3-methoxytyramine, and partially corrected the DA intermediate 3,4-dihydroxyphenylacetate (DOPAC) and 5-HT levels, despite normal tyrosine and tryptophan levels in iMSUD mouse brain. We further observed enhanced intracellular turnover of both DA and 5-HT in iMSUD mouse brain, both of which partially corrected with HTx. Our results suggest new pathomechanisms of neurotransmitter metabolism in this disorder and support the therapeutic relevance of HTx in iMSUD mice, while providing proof-of-principle that HTx has corrective potential in extrahepatic organs.
Skvorak
Kristen J
KJ
Department of Pediatrics, University of Pittsburgh School of Medicine, USA; Children's Hospital of Pittsburgh of UPMC, USA.
Hager
Elizabeth J
EJ
Arning
Erland
E
Bottiglieri
Teodoro
T
Paul
Harbhajan S
HS
Strom
Stephen C
SC
Homanics
Gregg E
GE
Sun
Qin
Q
Jansen
Erwin E W
EE
Jakobs
Cornelis
C
Zinnanti
William J
WJ
Gibson
K Michael
KM
D000818:Animals; D001921:Brain / Q000002:abnormalities* / Q000378:metabolism* / Q000473:pathology; D002336:Carnosine / Q000031:analogs & derivatives / Q000378:metabolism; D022781:Hepatocytes / Q000637:transplantation*; D006801:Humans; D008099:Liver / Q000473:pathology; D008375:Maple Syrup Urine Disease / Q000473:pathology* / Q000628:therapy*; D051379:Mice; D008954:Models, Biological; D018377:Neurotransmitter Agents / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D018377:Neurotransmitter Agents; C005038:homocarnosine; D005680:gamma-Aminobutyric Acid; D002336:Carnosine
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