Effects of Taurine Depletion on Body Weight and Mouse Behavior during Development

Abstract

Taurine (2-aminoethanesulfonic acid) plays an important role in various physiological functions and is abundant in the brain and skeletal muscle. Extracellular taurine is an endogenous agonist of gamma-aminobutyric acid type A and glycine receptors. Taurine actively accumulates in cells via the taurine transporter (TauT). Adult taurine-knockout (TauT^-/-) mice exhibit lower body weights and exercise intolerance. To further examine the physiological role of taurine, we examined the effect of its depletion on mouse behavior, startle responses, muscular endurance, and body weight during development from postnatal day 0 (P0) until P60. In the elevated plus maze test, TauT^-/- mice showed decreased anxiety-like behavior. In addition, TauT^-/- mice did not show a startle response to startle stimuli, suggesting they have difficulty hearing. Wire-hang test revealed that muscular endurance was reduced in TauT^-/- mice. Although a reduction of body weight was observed in TauT^-/- mice during the developmental period, changes in body weight during 60% food restriction were similar to wild-type mice. Collectively, these results suggest that taurine has important roles in anxiety-like behavior, hearing, muscular endurance, and maintenance of body weight.

Keywords: behavior; body weight; brain; knockout mice; skeletal muscle; taurine; taurine transporter.

Figure 1

(A–C) In the open field test, mice were placed in the center of the open field apparatus and their movement was tracked for 10 min. The percentage of time spent in the center (A), percentage of time spent in the corner (B), and total distance moved in an open field (C) were measured for WT, TauT^+/−, and TauT^−/− mice. (D,E) In the elevated plus maze test, mice were placed in the center of the elevated plus maze and allowed to explore for 5 min. The percentage of time spent in the open arms, closed arms, and center (* p < 0.05, n.s. = not significant by Kruskal–Wallis test) (D) and total distance moved (E) in the elevated plus maze were measured. Error bars represent S.E.M.

Figure 2

Muscular endurance was reduced in TauT^−/− mice. Wire-hang test was performed. Average latency to fall from the wire mesh of two trials in WT and TauT^−/− mice. * p < 0.05 by Mann-Whitney test. Error bars represent S.E.M. Closed circles represent animals.

Figure 3

TauT^−/− mice exhibited lower body weights during development. (A) Body weights of male WT, TauT^+/−, and TauT^−/− pups at P0. Closed circles represent animals. (B) Body weights of female WT, TauT^+/−, and TauT^−/− pups at P0. (C) Changes in body weights of male WT, TauT^+/−, and TauT^−/− mice during development. (D) Changes in body weights of female WT, TauT^+/−, and TauT^−/− mice during development. Error bars represent S.E.M. * p < 0.05 TauT^−/− vs. WT, ** p < 0.01 TauT^−/− vs. WT, † p < 0.05 TauT^−/− vs. WT and TauT^+/−, ‡ p < 0.01 TauT^−/− vs. WT and TauT^+/−, †† p < 0.05 TauT^−/− vs. TauT^+/−, ‡‡ p < 0.01 TauT^−/− vs. TauT^+/−, and ^a p < 0.05 TauT^+/− vs. WT by Kruskal-Wallis test.

Figure 4

Changes in body weights following 60% food restriction in WT and TauT^−/− mice. (A) Changes in body weight after 60% food restriction and recovery (food ad libitum) in WT mice and TauT^−/− mice. (B) Body weight changes are shown as a percentage of the initial body weight before 60% food restriction. (C) Body weight loss or gain after 60% food restriction and recovery (food ad libitum) in WT mice and TauT^−/− mice. Error bars represent S.E.M. * p < 0.05, ** p < 0.01 by Kruskal-Wallis test.