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Image 1: Bought in bulk, taurine is one of
the cheapest amino acids on the market. |
If you listened to the third installment of the
Amino Acids for Super Humans Series on
Carl Lenore's Super Human Radio, you will know that I
am a firm a believer in the power of the
non-essential sulfur-amino
acid taurine. You would have heard me talk about it's
beneficial effects
on diabetes, hepatic health, weight management and more.... a recent
study (
Solon. 2011) published in the influential journal
Amino Acids does not
only confirm all the beneficial effects, we already knew about, it
also expands our current knowledge about taurine to its effects on the
hypothalamic
Akt/FOXO1, JAK2/STAT3 and mTOR/AMPK/ACC signaling cascades and the
satiety signal
neuropeptide Y (NPY).
Carina S. Solon and her colleagues from the
University of Campinas in
Brazil hypothesized that "some of the activity of taurine in the
control of body fat would be exerted through direct action in the
hypothalamus". To verify their hypothesis, the scientists injected an
acute dose of taurine (1.0, 3.0 and 5.0mM) and/or insulin
intracerebroventricularly into a cannula that had been placed in the
lateral ventricle of the animals more than a week before. What they found was
that the intracerebroventricular injection of an acute dose of taurine reduces food intake and locomotor activity, and activates signal transduction through the Akt/FOXO1, JAK2/STAT3 and mTOR/AMPK/ACC signaling pathways. These effects are accompanied by the modulation of expression of NPY. In addition, taurine can enhance the anorexigenic action of insulin.
Even administered on its own (without insulin) the
anorexic effect of
taurine had a "similar magnitude to the effect produced by either
insulin or leptin" that cannot be ascribed to the reduction in locomotor
activity alone. Rather, the scientists argue that the latter is
probably a direct result of the "increased primary satiety produced by
taurine", which suppresses the well-known food-seeking behavior
food-deprived rodents (and interestingly also anorexic human beings)
display.
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| Figure 1: Changes in Akt, mTOR & AMPK expression after intracerebroventricular injection of insulin, taurine or a combination of both (calculated based on Solon. 2011) |
At the hypthalamic level, taurine did in fact act similarly to insulin
and activated the "Akt/FOXO1 and JAK2/STAT3 signaling pathways, while
inhibiting the AMPK signaling pathway" without modulating systemic
glucose or insulin levels. By selective inhibition of the JAK2 pathway
and upregulation of the AMPK signaling cascade by AICAR infusion, the
scientists were able to show that the upregulation of JAK2 and not the
downregulation of AMPK were responsible for the appetite-suppressant
effects of taurine.
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| Figure 2: Relative changes in food intake in rats vs. control after
intracerebroventricular injection of taurine, AICAR or a combination of both (calculated based on Solon. 2011) |
Taken together, these results suggest that the effects of taurine go
well beyond its insulin-sensitizing effects on peripheral tissues (
Wu. 2010). And while the
exact mechanism by which taurine acts
on the complex signaling cascade in the hypothalamus, as well as the
respective downstream effects at the tissue level (eg. muscle, liver, pancreas, etc.) still have to be
elucidated, it becomes increasingly evident that an amino acid, of which
many people still believe that it was a somewhat esoteric,
horse-sperm
derived ingredient of energy drinks, could become a cornerstone in the
ongoing battle against obesity.
