Huntington’s disease and selenoproteins

L-selenomethionine is metabolized by cystathionine gamma-lysase. Dysregulation of cystathionine gamma-lyase would dysregulate selenoprotein synthesis from L-selenomethionine, which is the food form of selenium. In the N171-82Q Huntington’s disease mouse model various selenoprotein levels are changed compared to controls. Changed levels of selenoproteins in the N171-82Q Huntington’s disease mouse model compared to controls could be due to dysregulation of cystathionine gamma-lyase.

Supplemental Se-methylselenocysteine could be useful in the treatment of Huntington’s disease as metabolism of Se-methylselenocysteine does not depend on cystathionine gamma-lyase. Se-methylselenocysteine is metabolized by kynurenine aminotransferase 1. Supplementation of Se-methylselenocysteine taken alone would be far from a completely effective treatment for Huntington’s disease as decreases in cystathionine gamma-lyase would dysregulate various pathways downstream from the transsulfuration pathway. Se-methylselenocysteine could be of assistance in the treatment of cognitive symptoms of Huntington’s disease. Se-methylselenocysteine taken daily in two divided dosages is more effective than Se-methylselenocysteine taken once daily.

Huntington’s disease and pathways downstream from the transsulfuration pathway

Huntington’s disease is associated with dysregulation of the transsulfuration pathway. Research points to cystathionine gamma-lyase, the second enzyme in the transsulfuration pathway, as being profoundly depleted in Huntington’s disease. L-cysteine is synthesized via the transsulfuration pathway.

Huntington’s disease develops in later decades. By the time Huntington disease manifests dysregulations of the transsulfuration pathway could have resulted in epigenetic changes. See Treatment-resistant schizophrenia: focus on the transsulfuration pathway and A disease-modifying treatment for Alzheimer’s disease: focus on the trans-sulfuration pathway as to how dysregulation of the transsulfuration pathway could result in epigenetic changes. Pathways downstream of the transsulfuration pathway, for example, iron-sulfur cluster formation where sulfur for iron-sulfur cluster formation is derived from cysteine, seleonprotein synthesis where the transsulfuration pathway is required to metabolize selenomethionine which is the food form selenium, glutathione synthesis where cysteine is the rate limiting amino acid in glutathione synthesis and taurine synthesis where taurine is synthesized from L-cysteine could all be dysregulated due to the transsulfuration pathway being dysregulated.

Since mutation in genes that confer Huntington’s disease are present from birth but Huntington’s disease only develops in later decades manifestations of Huntington’s disease must be due to accumulated changes where such accumulated changes could be epigenetic changes attendant on dysregulations of cystathionine gamma-lyase. Supplementation of sulfur containing free form amino acids, except L-taurine, would not be of assistance in the treatment of Huntington’s disease both due to the toxicities of such supplements and due to pathways downstream of the transsulfuration pathway being dysregulated due to epigenetic changes attendant on dysregulations of the transsulfuration pathway.