Reduced Taurine Transporter Expression in Lymphoblastoid Cell Lines From Alzheimer's Disease Patients Compared With Age-Matched Controls: Therapeutic Implications?

Abstract

Taurine is an atypical amino acid that cannot form peptide bonds and thus does not take place in building proteins. Yet, taurine takes part in regulating many cell functions, including cell osmolarity and volume, mitochondrial function, membrane ion channels and neuronal activity, and cell survival. Taurine is synthesized by the liver, and available from consumption of meat and fish, but not plants. It has millimolar concentrations in the brain, skeletal muscle, blood, heart, retina, and other tissues. Taurine is transported from the liver (following synthesis) or the intestine (following consumption) to blood by the taurine transporter, encoded in humans by SLC6A6. A recent study reported that blood taurine declines dramatically in aged individuals. Several studies indicated that dietary taurine slows cognitive decline in Alzheimer's disease (AD) model mice. We therefore measured SLC6A6 mRNA expression in human lymphoblastoid cell lines (LCLs) from AD patients and age-matched controls and observed 2.8-fold lower expression in AD LCLs (p = 0.0005). Additionally, glutathione peroxidase 1 (GPX1), a key free-radical scavenging selenoenzyme, had reduced mRNA expression in LCLs from AD patients compared with controls. Our observations suggest that reduced taurine transporter expression may contribute to AD pathogenesis and that dietary taurine might be beneficial for slowing disease progression in early-stage AD. Clinical trials with dietary taurine supplementation of individuals with mild cognitive impairment (MCI) or early-stage AD are required to assess its tentative therapeutic potential.