Provided is use of thiamine pyrophosphokinase TPK as a target in the treatment of Alzheimer's disease; and AD symptoms due to the inhibited TPK can be prevented by promoting the kinase activity and/or expression level of TPK protein in brain with TPK as a target.

The present disclosure relates to a genetically modified host cell having improved production of thiamine, wherein the host cell expresses one or more heterologous ThiO enzymes converting glycine into dehydroglycine (DHG) in the host cell and/or one or more heterologous ThiI enzymes catalyzing the transfer of sulfur from IscS to the sulfur carrier protein ThiS in the host cell, whereby the production of the thiamine in the genetically modified host cell is improved compared to an unmodified parent host cell.