Taurine Partially Improves Abnormal Anxiety in Taurine-Deficient Mice

Taurine is abundant in various tissues including the brain, muscle, heart, spleen, liver and kidney with various physiological functions. Since taurine is produced by cysteine sulfinic acid decarboxylase (CSAD) in the liver and kidney, taurine-deficient mice without CSAD have been investigated for abnormal physiological functions such as retinal development, immune, pancreatic and liver function. In this study, the behavioral effects and abnormal brain development caused by low taurine in the developing brain were examined. In neonatal brains of homozygous CSAD knockout mice (HO), taurine was reduced by 85%, compared to wild-type mice (WT). Taurine was reduced by 35% in the brains of 2 month-old HO, compared to WT. Anxiety, motor coordination and autistic-like behaviors were evaluated at 2 months of age using five behavioral tests: elevated plus maze, open field, social approach, marble burying and accelerating rotarod. Mice were tested from 3 groups including WT, HO and HO with oral treatment of 0.2% taurine in the drinking water (HOT). HOT were born from HO dams treated with taurine from before pregnancy and were continuously treated with taurine in the drinking water after weaning. The taurine levels in the brain and plasma of HOT were restored to WT at 2 months of age. Taurine-deficiency did not lead to changes in autistic-like behaviors as the HO were not significantly different from WT in marble burying and social approach. However, taurine-deficiency increased anxiety-like behavior in HO in the elevated plus maze and open field, compared to WT. Taurine treatment significantly restored the HOT to WT levels of anxiety-like behavior in the elevated plus maze. However, changes in exploratory activity in the open field were not improved with taurine treatment. There was a slight difference in motor ability as the WT mice stayed on the accelerating rotarod longer that the HO and HOT, but the difference was significant in the HOT during the first trial only, compared to WT.These data support hypothesis that taurine is essential for the emotional development of the brain. First, taurine is remarkably low in the neonatal brain of HO, compared to the adult brain of HO. Second, taurine treatment in HO partially improves anxiety-like behavior to WT.