The results showed that l-Theanine intake resulted in a reduction
in the heart rate (HR) and salivary immunoglobulin
A (s-IgA) responses to an acute stress task relative to
the placebo control condition.
Moreover,
analyses of heart rate variability indicated that the
reductions in HR and s-IgA were likely attributable to
an attenuation of
sympathetic nervous activation. Thus,
it was suggested that the oral intake of l-Theanine could
cause anti-stress effects via the inhibition
of cortical
neuron excitation.
L
Theanine research
Theanine might be useful for preventing ischemic neuronal
damage.
Theanine increases the idarubicin-induced antitumor activity
and ameliorates its toxicities.
Theanine Research Update
Anti-obesity effects of three major components of green
tea, catechins, caffeine and theanine, in mice.
In Vivo. 2004 Jan-Feb;18(1):55-62.
To elucidate the anti-obesity effects of three major components
of green tea, catechins, caffeine and theanine, female
mice were fed on diets containing 2% green tea powder
and diets containing 0.3% catechins, 0.05% caffeine and
0.03% theanine, which correspond, respectively, to their
concentrations in a 2% green tea powder diet, singly and
in combination for 16 weeks. Body weight and food intake
were determined monthly during this period, kidneys, adrenals,
liver, spleen, brain, pituitary and intraperitoneal adipose
tissues (IPAT) were weighed and lipid levels in the serum
and liver were measured at the end of this period. The
body weight increase and weight of IPAT were significantly
reduced by the diets containing green tea, caffeine, theanine,
caffeine + catechins, caffeine + theanine and caffeine
+ catechins + theanine. Noticeably, the IPAT weight decreased
by 76.8% in the caffeine + catechins compared to the control
group. Serum concentrations of triglycerides and non-esterified
fatty acids (NEFA) were decreased by green tea, catechins
and theanine. Moreover, caffeine + catechins, caffeine
+ theanine and caffeine + catechins + theanine also decreased
NEFA in the serum. The triglyceride level in the liver
was significantly reduced by catechins and catechins +
theanine in comparison with the control. These results
indicated that at least caffeine and theanine were responsible
for the suppressive effect of green tea powder on body
weight increase and fat accumulation. Moreover, it was
shown that catechins and caffeine were synergistic in
anti-obesity activities. I theanine side effects
Neuroprotective effect of gamma-glutamylethylamide ( theanine
) on cerebral infarction in mice.
Neurosci Lett. 2004 Jun 3;363(1):58-61.
In the present study, we examined the neuroprotective
effect of gamma-glutamylethylamide (theanine) on the ischemic
brain damage in a middle cerebral artery occlusion model
in mice. L-Theanine was injected i.p. 3 h after the occlusion
or immediately before and 3 h after the occlusion. Theanine
(1 mg/kg) significantly decreased the size of the cerebral
infarcts 1 day after the occlusion. In contrast, theanine
did not affect the cerebral blood flow, brain temperature
and physiological variables (pH, pCO(2), pO(2) and hematocrit)
in this model. These results suggest that theanine directly
provides neuroprotection against focal cerebral ischemia
and may be clinically useful for preventing cerebral infarction.
Arch Med Res. 2004 Jul-Aug;35(4):271-4.
The aim of this study was to
evaluate effects of pyridoxine and butylated hydroxytoluene
(BHT) on lipid peroxidation and on levels of 5-hydroxytryptophan
and serotonin. METHODS: Thirty rats (30 days of age)
were used in the survey, measuring levels of lipid peroxidation
(TBARS), hemoglobin, 5-hydroxytryptophan (5-HTP or l
5-htp), and serotonin (5-HT) after intraperitoneal (i.p.)
injections of 4 and 10 mg/kg/day of pyridoxine HCl during
20 days and a single dose of 2 microM/kg (440 microg)
of BHT. RESULTS: Levels of TBARS and 5-HTP increased
considerably (p <0.05) in all vitamin- and/or BHT-treated
groups, and 5-HT increased partially (p <0.05) only
in B(6) with or without BHT-treated groups compared
with control group. CONCLUSIONS: Results suggest that
pyridoxine plays a role in tryptophan metabolism, increasing
production of 5-HTP.
5-HTP is a more potent in vitro hydroxyl radical scavenger
than melatonin or vitamin C.
J Pineal Res. 2005 Jan;38(1):62-6.
Hydroxyl radicals are involved in direct damage of important
biomolecules. Potent radical scavengers such as vitamin
C and indoles of the tryptophan family can avert the
potential damage. Melatonin and its precursor 5-hydroxytryptophan
( 5-HTP ) were compared with water-soluble vitamin C.
5-HTP showed highest hydroxyl radical scavenging effects,
more than vitamin C, which was more than melatonin.
5-HTP Prevents Panic Attacks
-- A panic attack involves
the sudden appearance of several symptoms including
shortness of breath, sweating or shaking, palpitations,
and the fear of dying or losing control. Women are more
likely than men to have this condition. Doctors often
prescribe anti-anxiety medicines such as Xanax or Valium.
However, a nutrient known as 5-HTP may play an important
role. 5-HTP stands for 5-Hydroxytryptophan, a supplement
available over the counter that, when ingested, goes
to the brain and converts into the brain chemical serotonin.
Serotonin is known to induce relaxation and balance
mood. Researchers at the Department of Neuropsychology
at Maastricht University in The Netherlands were able
to induce a panic attack in volunteers who suffer from
panic disorder by having them breathe a high concentration
of carbon dioxide. They repeated the study, this time
giving half of the volunteers 200-mg of 5-HTP while
the others received a placebo. Those who took 5-HTP
had a significantly diminished panic response compared
to those on placebo.
The effect of 5-hydroxytryptophan
on cholecystokinin-4-induced panic attacks in healthy
volunteers.
Department of Psychiatry,
University of Tartu, Raja, Estonia.
J Psychopharmacol. 2004 Jun;18(2):194-9.
Previous studies suggest a modulatory role of serotonin
in experimentally-induced panic attacks. In the current
study, we investigated the acute effects of 5-HT precursor
l-5-hydroxytryptophan (5-HTP) on the response to panicogenic
challenge with cholecystokinin-tetrapeptide (CCK-4)
in healthy volunteers. Thirty-two subjects were randomized
to receive either 200 mg of 5-HTP or placebo with the
CCK-4 challenge following in 90 min in a double-blind,
parallel-group design. The results showed a nonsignificant
difference between the groups in panic rate (19% after
5-HTP and 44% after placebo, p = 0.13) with a trend
for lower intensity of symptoms after 5-HTP (p = 0.08).
Further analysis by gender revealed that females in
the 5-HTP group had a significantly lower panic rate
and intensity of cognitive symptoms whereas, in males,
the effect of 5-HTP was limited to lowering the intensity
of somatic panic symptoms. Thus, an increased availability
of 5-HT may have a gender-dependent protective effect
in CCK-4-induced panic.
Single-dose administration of 5-hydroxytryptophan (5-HTP)
is regularly used as a challenge test of the serotonergic
system. The use of 5-HTP has been limited by an apparent
small window between the occurrence of neuroendocrine
endpoints and the occurrence of side effects. Therefore,
many dosing strategies have been tried with and without
concurrent administration of carbidopa, a peripheral
inhibitor of the decarboxylation from 5-HTP to serotonin.
The aim of the current study was to assess the relation
between pharmacokinetics and pharmacodynamics of 5-HTP.
Twelve healthy male volunteers were included in a placebo-controlled,
randomized, four-way crossover, double-blind, single-dose
investigation of oral 5-HTP with or without coadministration
of carbidopa. The four dose regimens were placebo, 5-HTP
100 mg, 5-HTP 200 mg, and 5-HTP 100 mg with coadministration
of carbidopa 100 mg and 50 mg at 3 hours before and
3 hours after the administration of 5-HTP, respectively.
The last regimen resulted in a doubling of the elimination
half-life, an apparent clearance at least 14 times smaller,
and a 15.4 times greater area under the curve compared
with 5-HTP 100 mg without carbidopa. Furthermore, it
was the only regimen to induce a significant change
in cortisol and prolactin. It did not induce any change
in subjective psychologic symptoms or cardiovascular
parameters, but it was the only regimen to induce some
nausea in three participants. The authors conclude that
this regimen of 5-HTP 100 mg plus carbidopa is a relatively
simple, effective, and tolerable challenge of the presynaptic
serotonergic system.
Sugiyama T. Sadzuka Y. Tanaka K.
Sonobe T.
Inhibition of glutamate transporter by theanine
enhances the therapeutic efficacy of doxorubicin.
Toxicol Lett 2001 Apr 30;121(2):89-96
Yokogoshi H, et al.
Effect of Theanine, r-glutamylethylamide, on
Brain Monoamines, striatal dopamine release and some
kinds of behavior in rats. Nutrition 2000,
Sep; 16(9):776-777
Juneja L, et al.
L-theanine - A unique amino acid of green tea
and its relaxation effect in humans.
Trends in food science technology June/July 1999. v.
10(6/7) p. 199-204
Yokogoshi H, et al.
Theanine-induced reduction of brain serotonin
concentration in rats.
Biosci Biotechnol Biochem. 1998 Apr;62(4):816-7.
Kobayashi A, et al.
Effects of L-theanine on the release of a-waves
in human volunteers.
Nippon Nogeikagaku Kaishi. 1998 Vol. 72, 153-157.
Yokogoshi H, et al.
Reduction effect of theanine on blood pressure
and brain 5-hydroxyindoles in spontaneoulsy hypertensive
rats. Biosci Biotechnol Biochem. 1995 Apr;59(4):615-8
Sagesaka Y, et al.
Pharmacological effect of theanine.
Proceedings of the International Symposium on Tea Science,
August 26-29, 1991, 362-364.
Feldheim, W. et al.
Investigation of the presence and significance
of theanine in the tea plant.
Journal of the Science of Food and Agriculture. 1986,
Vol. 37, No 6, p. 527-534
Kimura R, et al.
Effect of theanine on norepinephrine and serotonin
levels in rat brain.
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