USE OF L-CARNITINE, SALTS AND DERIVATIVES THEREOF FOR REDUCING
OR PREVENTING FATIGUE AND IMPROVING COGNITIVE FUNCTION
The invention relates to uses of L-carnitine, a salt of L-carnitine, a derivative of Lcarnitine
and/or salt of a derivative of L-carnitine, and respective methods and
compositions for reducing or preventing fatigue and/or for improving cognitive function
in an animal.
Background of the invention
Carnitine (vitamin Bt; 3-hydroxy-4-trimethylammonio-butanoate) is a quaternary
ammonium compound biosynthesized from the amino acids lysine and methionine.
Carnitine exists in two stereoisomers. The biologically active form is L-carnitine, whilst
its enantiomer, D-carnitine, is biologically inactive. L-carnitine (LC) is an endogenous
compound, which plays a key metabolic role, transporting long chain fatty acids into
the mitochondria for energetic oxidation. Supplementation with acetyl-L-carnitine
(ALC) has been shown to increase overall regional cerebral metabolism in rodents.
Carnitine and its esters also have non-metabolic roles in brain function as
neuroprotectants, antioxidants and modulators of neurotransmission.
Carnitine deficiencies and chronic fatigue co-exist across a number of patient groups.
Early evidence suggests that supplementation may improve indices of chronic fatigue
associated with cancer (Cruciani et al. 2006). Evidence also suggests beneficial roles
for supplementation with carnitine and its esters in attenuating the symptoms and
cognitive deficits associated with Alzheimer's disease (Montgomery et al. 2003) and in
reducing fatigue and improving cognitive function in centenarians (Malaguarnera et al.,
2007, 2008).
Karlic and Lohninger suggest that carnitine supplementation may foster exercise
performance of athletes. They conclude that there is evidence for a beneficial effect of
L-carnitine supplementation in training, competition and recovery from strenuous
exercise and in regenerative athletics.
JP 20050971 6 1-A discloses an anti-fatigue composition for preventing physical and
mental fatigue, which comprises coenzyme Q, carnitine and an inorganic acid as
active ingredients.
Another fatigue improver based on biotin, carnitine and pantothenic acid as active
ingredients is described in JP 07-233070-A.
A food supplement based on vitamin C, vitamin E, L-carnitine and alpha-lipoic acid for
inhibiting the deterioration of cognitive function is disclosed in WO 02/43666 A2.
Therefore, L-carnitine is generally used in the art for the treatment of individuals
suffering from diseases, such as cancer or Alzheimer's disease, or having an impaired
metabolism as a result of high age or extreme physical exercise. Further,
combinations of multiple active agents, comprising L-carnitine, have been suggested
for other uses. Compositions for treating fatigue or improving cognitive function
described in the art are mixed compositions comprising multiple active ingredients,
such as vitamins and antioxidants.
Problem underlying the invention
The problem underlying the invention is to provide a composition, or use or method,
for reducing or preventing fatigue or for improving cognitive function in an animal,
preferably a human animal. The composition shall overcome the above-mentioned
problems and shall be applicable for healthy and young, or at least non-elderly,
individuals. In other words, the fatigue or cognitive function shall not be the result of a
disease, or associated with a disease, or with impaired metabolic function, for
example due to high age. The composition shall be easily available, efficient and
applicable without side effects in a simple manner.
Disclosure of the invention
Surprisingly, the problem underlying the invention is solved by the process according
to the claims. Further inventive embodiments are disclosed throughout the description.
Subject of the invention is the use of L-carnitine, a salt of L-carnitine, a derivative of Lcarnitine
and/or a salt of a derivative of L-carnitine for reducing or preventing fatigue
and/or for improving cognitive function in an animal.
L-carnitine is the physiologically active form of carnitine. In the following, the term
"carnitine" refers to the active L-carnitine.
According to the invention, L-carnitine can be administered in the form of L-carnitine
as such, a salt of L-carnitine, a derivative of L-carnitine and/or a salt of a derivative of
L-carnitine, or mixtures thereof. In the following, when referring to administration
modes and uses, the terms "L-carnitine" or "L-carnitine, a salt or derivative thereof"
refer to "L-carnitine as such, a salt of L-carnitine, a derivative of L-carnitine and/or a
salt of a derivative of L-carnitine".
Preferably, the inventive use is a non-therapeutic use. Preferably, the animal is a
healthy animal. As used herein, "healthy" refers to the absence of illness or injury.
Preferably, the animal is human.
In a preferred embodiment of the invention, the use of L-carnitine is for improving
cognitive function. Cognitive functions refer to higher brain functions that encompass
sense, perception, recognition, judgment and action or suppression. Information on
the surrounding circumstances is continuously transmitted via sense organs (visual
sense, auditory sense, tactile sense, taste sense, and smell sense) to the brain, which
selects the necessary information. At that time, the ability of a person to pay attention
to a plurality of pieces of information (divided attention or allocated attention) is
important. Selected pieces of information are integrated to form one piece of
information having a particular meaning, that is, a perception. Next, perceived
information is remembered for a short period of time, a current perception and a
previous memory are checked against each other (recognition), and judgment is
performed.
Cognitive performance can be evaluated by various measuring methods, for example,
neuropsychologic tests and neurophysiological tests. Examples of such a
neuropsychological test include a computerized Cognitive Demand Battery (CDB),
CogHealth, Wechsler Adult Intelligence Scale, Stanford Binet Intelligence test, Visual
Perception Test for Agnosia (VPTA), Standard Performance Test for Apraxia (SPTA),
Wechsler Memory Scale-Revised, Clinical Assessment for Attention-Clinical
Assessment for Spontaneity (CAT-CAS), Digit Cancellation Test for attention (D-CAT),
Hamamatsu higher brain function scale, new Stroop test, Hasegawa dementia scale,
Nishimura dementia scale, COGNISTAT, multiphasic early dementia examination
(MEDE), NS dementia test, TAIS, MMSE, and the like. Examples of such a
neurophysiological test include event-related potentials, and the event-related
potentials include contingent negative variation (CNV), P 1-N1 -P2, NA, Nd, N2b, P300,
MMN, N400, and the like. In a more medical sense, evaluation is possible also by
measuring the activity of high-level functions of the brain using functional magnetic
resonance imaging (fMRI), single photon emission computed tomography (SPECT),
optical topography, or the like. Furthermore, as a popular method, evaluation is
possible also with so called "brain training (Nou-Tore)", which is a series of television
game software. Moreover, such cognitive performance can be evaluated with, for
example, measurements of physical fitness for checking the time taken to react to
light.
In a preferred embodiment of the invention, the use of L-carnitine is for reducing or
preventing physical fatigue. Physical fatigue or muscle weakness (or "lack of
strength") is a direct term for the inability to exert force with one's muscles to the
degree that would be expected given the individual's general physical fitness.
In another preferred embodiment of the invention, the use of L-carnitine is for reducing
or preventing mental fatigue. Mental fatigue can manifest itself as somnolence
(decreased wakefulness), or just as a general decrease of attention, not necessarily
including sleepiness. It may also be described as a more or less decreased level of
consciousness. In any case, this can be dangerous when performing tasks that
require constant concentration, such as driving a vehicle. For instance, a person who
is somnolent may experience microsleeps.
There are different ways to measure mental fatigue, e.g. by means of an EEG-based
mental-fatigue monitoring system, self-rating fatigue scales, different standardized
questionnaires, blink rate, or the Multidimensional Fatigue Inventory (MFI) which is a
20-item self-report instrument designed to measure fatigue. It covers the following
dimensions: General Fatigue, Physical Fatigue, Mental Fatigue, Reduced Motivation
and Reduced Activity. Preferably, the Cognitive Demand Battery test is used (CDB;
Kennedy et al. 2008; Kennedy and Scholey 2004; Reay et al. 2005; 2006; Kennedy et
al., 201 0). The CDB-test is well established in the art.
Preferably, the animal is a healthy and/or young animal. So far, L-carnitine has not
been associated with the improvement of mental and physical fatigue or cognitive
function in healthy or young animals.
In a preferred embodiment of the invention, the animal, especially human individual, is
not an elderly animal or individual. Preferably, the individual's age is below 60 or
below 50. The individual may be an adult, or older than 8 , 12, 16 or 18 years.
Preferably, the age range is from 8 to 60 or from 16 to 50.
Preferably, the animal is a healthy animal. More preferably, the animal does not have
decreased L-carnitine levels and/or impaired metabolic function as a result of a
disease, or associated with a disease.
Preferably, the individual does not suffer from chronic fatigue and/or chronic Lcarnitine
depletion, dementia, cancer, neurodegenerative diseases, Alzheimer 's
disease, depression, age-related memory decline, bacterial or virus infections.
Preferably, the impairment of cognitive function or fatigue is not due to the
consumption of alcohol or other drugs known to impair such physical functions.
The fatigue, especially the physical fatigue, is preferably a result of working, such as
mental work or light or medium physical work, or a result of mental stress,
overstimulation, understimulation, jet lag, active recreation or lack of sleep. Preferably,
the fatigue, especially the physical fatigue, is not a result of extreme physical exercise
and/or the L-carnitine is not used in association with training, competition and recovery
from extreme physical exercise of athletes.
In a preferred embodiment of the invention, the individual has a plasma level of Lcarnitine,
which is considered normal. L-Carnitine plasma levels are considered
normal if they are > 20 pmol/L. More importantly though is the ratio of esterified to free
L-carnitine in plasma, as only the free L-Carnitine is active. Ratios of acyl-carnitine to
free L-carnitine of > 0.4 are considered to be related to L-Carnitine deficiency.
According to the invention, it is preferred that the plasma ratio of acyl-carnitine to free
L-carnitine of the individual is below 0.4.
In a preferred embodiment of the invention, before administration of the L-carnitine,
salt or derivative thereof, the animal is experiencing a temporary fatigue and/or
temporary impairment of cognitive function.
Preferably, the fatigue and/or impairment of cognitive function are a result of a
prolonged time of mental exercise and/or lack of sleep. For example, a temporary
fatigue and/or temporary impairment of cognitive function is experienced by students
who study for a long time or by drivers, especially truck drivers, or by other individuals
working on monotonous tasks for a long time without breaks.
In a preferred embodiment of the invention, the inventive use is for improving cognitive
function of an animal, preferably a human, which is experiencing fatigue. In this
embodiment, the animal may have impaired cognitive function associated with or
resulting from fatigue. Thus the inventive use improves cognitive function of an animal
experiencing fatigue.
In another preferred embodiment of the invention, the inventive use is for improving
cognitive function of an animal, preferably human, which is not experiencing fatigue. In
this embodiment, the use is preferably for improving short-time cognitive function,
especially within 3 hours or within 2.5 hours after administration. Especially, cognitive
function could be improved within a time span of 1 to 3 hours, more preferably within
1.5 to 2.5 hours after administration. It was found that especially executive function in
the absence of fatigue can be improved.
In another embodiment of the invention, the inventive use is for decreasing
psychomotor function of an animal, preferably a human, which is not experiencing
fatigue. In this embodiment, the use is preferably for decreasing long-time
psychomotor function, especially after more than 3 hours after administration.
Preferably, psychomotor function is decreased within a time span of 3 to 8 hours,
preferably within 3.5 to 6.5 hours, after administration. It was found that at the same
time, higher cognitive processes, such as memory and executive function, are not
impaired. This effect of carnitine may be advantageous for calming down or relaxing
an individual. For example, this may be advantageous for individuals, who are
nervous, irritable, hyperactive and/or suffering from attention deficit hyperactivity
disorder (ADHD).
According to the invention, it is highly preferred to use L-carnitine or a salt of Lcarnitine.
Preferably, the salt of L-carnitine or salt of a derivative of L-carnitine is a salt of a
carboxylic acid, such as a tartrate, citrate, succinate, fumarate or hydrochloride. In a
preferred embodiment of the invention, L-carnitine tartrate or L-carnitine citrate is
used.
According to the invention, a salt of L-carnitine, a derivative of L-carnitine and/or a salt
of a derivative of L-carnitine can be used. Under physiological conditions, the
derivative should be converted into L-carnitine. Preferably, the derivative is a
derivative of L-carnitine, in which the hydroxyl group is substituted with a substituent
which is cleaved of under physiological conditions. The derivative of L-carnitine may
be acetyl-L-carnitine, which is known to be converted into L-carnitine under
physiological conditions. However, according to the invention, it was found that the
beneficial effect of L-carnitine is pronounced, whereas preliminary findings suggest
that the effect of acetyl-L-carnitine is at best moderate.
In another embodiment of the invention, the salt of a derivative of carnitine is an amino
carnitine. Amino carnitines are inner salts of L-carnitinyl esters, especially inner salts
of acetyl-L-carnitine or propionyl-L-carnitine. Preferably, the amino carnitine is an inner
salt of an L-carnitine ester, an amino acid and at least one anion or acid, preferably
chloride or hydrochloric acid. Preferably, the amino carnitine is selected from glycine
propionyl L-carnitine hydrochloride, acetyl-L-carnitine arginate dihydrochloride or
taurine acetyl-L-carnitine hydrochloride.
The dosage is selected depending on the purpose of administration, the animal to
whom it is administered (sex, age, body weight, etc.) and similar factors. In a preferred
embodiment of the invention, the L-carnitine, salt or derivative thereof is administered
in an amount between 10 and 3000 mg, more preferably 100 to 1500 mg, most
preferably between 250 to 1000 mg.
Preferably, the L-carnitine, salt of L-carnitine, derivative of L-carnitine and/or salt of a
derivative of L-carnitine is administered in an amount corresponding to an equivalent
amount of L-carnitine between 10 and 3000 mg, preferably between 50 and 1900 mg,
more preferably between 100 and 1500 mg or between 250 and 750 mg. The
equivalent amount of L-carnitine in an L-carnitine salt is the total amount of L-carnitine
in the salt. The equivalent amount if L-carnitine in a derivative or salt thereof is the
total amount of L-carnitine after cleaving of the substituent or substituents. It was
found that an amount or equivalent amount of 500 mg L-carnitine is especially
beneficial.
In a preferred embodiment of the invention, the L-carnitine, salt or derivative thereof is
administered in a single dose. This is advantageous, because complicated dosage
instructions are not necessary. However, the carnitine, salt or derivative thereof could
also be administered in multiple doses.
Preferably, the use is not a long-term use. The use should rather be in response to a
temporary event of fatigue and/or decreased cognitive function. Preferably, the use is
not a long-term treatment over a time period of for more than one day, or even weeks
or months. Nonetheless, the L-carnitine may be administered in response to multiple
outbreaks of fatigue or cognitive problems within a relatively short time period.
In a preferred embodiment of the invention, the L-carnitine, salt or derivative thereof is
administered in pure form. In another preferred embodiment, it is used as part of a
composition comprising more than 50%, more than 80% or more than 95% (w/w) Lcarnitine,
based on the total weight of the composition.
Preferably, the L-carnitine, salt or derivative thereof is the main active ingredient in the
composition. In this embodiment, it is preferred that the composition comprises more
than 50%, more than 80% or more than 95% (w/w) L-carnitine, based on the total
amount of all active ingredients. Active ingredients are usually vitamins, antioxidants
etc. Non-active ingredients are solvents, carriers and the like.
In a preferred embodiment of the invention, the L-carnitine, salt or derivative thereof is
not administered in combination with another agent which is effective in reducing or
preventing fatigue or for improving cognitive functions in an animal.
Preferably, the carnitine, derivative or salt is not administered in combination with
vitamins, especially vitamin E, or coenzyme Q 10 , and/or with organic acids, such as
maleic acid, biotin or pantothenic acid.
In a preferred embodiment of the invention, the L-carnitine, salt or derivative is
administered orally, preferably in the form of a liquid or a solid preparation, such as a
tablet, capsule, powder, or a gel or a paste. The dosage form is selected in view of the
route of administration. Examples of oral preparations include powders, granules,
tablets, capsules, pills, inhalers, enteric coated preparations, liquids for internal use,
suspensions, emulsions and syrups. To prepare these dosage forms, auxiliary
substances commonly used in the field of pharmaceutical manufacturing technology,
such as excipients, binders, antiseptics, antioxidants, disintegrators, lubricants, and
flavoring agents, can be used as necessary. From the above, a tablet, powder or
solution is preferred. The L-carnitine, salt or derivative may also be provided as an
effervescent tablet or powder or the like for preparing a liquid preparation.
In another embodiment of the invention, the L-carnitine, salt or derivative is
administered as part of a food and drink. Preferably, the food or drink is a functional
food or drink. Preferred drinks are energy drinks or shots. The use may also be as a
nutritional supplement. It may be used in conjunction with common additives for food
products, such as sweeteners, seasonings, antiseptics, preservatives, germicides and
antioxidants. In a preferred embodiment, the drink or food comprises the desired dose
for a single administration.
Preferably, the composition comprises at least one carrier. The L-carnitine, salt or
derivative may also be used in a combination, consisting essentially of the L-carnitine,
salt or derivative and at least one carrier. Preferably, the carrier is selected from
cellulose or microcrystalline cellulose and cellulose derivatives like HPMC, HPC and
ethylcellulose, starch and modified starch, Ca-carbonates and Ca-silicates, lactose,
sugars or sugar alcohols and derivatives and edible wax.
It is preferred that the animal is human. However, the animal may also be a nonhuman
mammal. The animal may be any animal known to have relatively highly
developed cognitive abilities. In a preferred embodiment, the animal is a horse or a
pet, preferably a dog or cat. Dogs have highly developed cognitive abilities, especially
dogs assisting humans, for example as police dogs, guide dogs, rescue dogs, herd
dogs or hunting dogs.
Another subject of the invention is a non-therapeutic method for reducing or
preventing fatigue and/or for improving cognitive function in an animal, comprising
administering L-carnitine, salt of L-carnitine, a derivative of L-carnitine and/or salt of a
derivative of L-carnitine to that animal.
Another subject of the invention is also a non-therapeutic composition for reducing or
preventing fatigue and/or for improving cognitive function in an animal, the
composition comprising L-carnitine, a salt of L-carnitine, a derivative of L-carnitine
and/or salt of a derivative of L-carnitine.
The method of the invention is carried out, and the composition of the invention is
prepared fully in accordance with the above described use of the invention. In other
words, all the specific embodiments of the use of the invention disclosed herein are
also specific embodiments of the method and composition of the invention.
The inventive use, method and composition solve the problem underlying the
invention. Surprisingly, it was found that L-carnitine is an efficient agent for reducing or
preventing fatigue and improving cognitive functions in an animal, especially in
humans, especially in young and healthy individuals. In the prior art, similar functions
of L-carnitine were only attributed to the treatment of individuals suffering from
diseases associated with disturbed metabolism, or elderly subjects with impaired
carnitine metabolism or athletes recovering from extreme exercise. Further
compositions, such as energy drinks or functional foods or specific mixtures of Lcarnitine
with other vitamins are known in the art. However, an impact of L-carnitine
against fatigue or for improving cognitive function has never been attributed
specifically to L-carnitine itself. It was not known previously that L-carnitine would be
useful by itself, if not being part of a multi-component composition. The inventive use,
method and composition are easily applicable and available, especially when using a
single dose. According to the invention, individuals experiencing temporary fatigue or
impairment of cognitive function, such as students or truck drivers, can overcome this
impairment rapidly and in a simple way without risks or side effects.
Figures:
Figure 1 shows a timeline and running order for each assessment. Participants arrived
at 8.30am on each occasion and consumed a standard breakfast. Following the
baseline completion of the attention tasks and two 10 minute repetitions of the CDB
battery tasks they received the day's treatment (placebo, 500 mg LC, 2000 mg LC,
1000 mg ALC). Two hours later they completed the attention tasks, the CDB (6
repetitions) and the executive tasks with mood assessments as shown.
Figure 2 shows the mean 'change from baseline' scores for each treatment on
outcomes from the CDB. Significant treatment effects on the planned comparisons
comparing each treatment with placebo on data from each repetition of the battery are
indicated (t=trend; * p<0.05; * * p<0.01 ) . Graphs are plotted with up indicating benefits.
Figure 3 shows the mean change from baseline ratings for each treatment of mental
fatigue across the 6 repetition of the CDB and alert, content and calm ratings
assessed pre and post-task performance. Significant treatment effects compared with
placebo are indicated (t=trend; * p<0.05; * * p<0.01 ) . Graphs are plotted with up
indicating benefits.
Figure 4 : The table shows mean (plus Standard Errors of Means) pre-dose baseline
scores and post-dose 'change from baseline' scores, plus F and P statistics from the
ANOVAs, for the cognitive tasks that were completed once pre-dose and once postdose.
Figures 5a, 5b: The tables show mean (plus Standard Errors of Means) pre-dose
baseline scores and post-dose 'change from baseline' scores, plus F and P statistics
from the ANOVAs (T = treatment main effect, TxR = treatment x repetition interaction),
for the baseline and six post-dose repetitions of the CDB tasks.
Figure 6 : The table shows mean (plus Standard Errors of Means) pre-dose baseline
scores and post-dose 'change from baseline' scores, plus F and P statistics from the
ANOVAs (T = treatment main effect, TxR = treatment x repetition interaction), for the
baseline and two post-dose Bond-Lader assessments.
EXAMPLES
A. Cognitive Demand Battery (CDB)
The study described in the following utilized a computerized Cognitive Demand
Battery (CDB) that has been shown to be sensitive to cognitive enhancement
inculcated by a number of natural food components and supplements (Kennedy et al.
2008; Kennedy and Scholey 2004; Reay et al. 2005; 2006). The working hypothesis
underlying this approach is that neural activity is costly in terms of local neural
resources (e.g. metabolic substrates) and that the brain is therefore liable to suffer
deficiencies in the short term. Any psychoactive properties of a test substance are
therefore liable to be more readily apparent during this period of intense cognitive
demand and the 'mental fatigue' state elicited by prolonged task performance. This
paradigm may therefore be more sensitive than the use of less demanding cognitive
tasks, particularly if an intervention has an impact on the delivery or utilisation of
metabolic substrates.
Additionally, the methodology took advantage of the intrinsic relationship between
fatigue and aspects of cognitive function. As an example, the speed of performing
tasks assessing attention is related to both sleep deprivation and sleep duration.
Similarly, mental fatigue has been shown to impact negatively on a wide variety of
cognitive tasks, with the effects most pronounced for those tasks that require high
levels of executive control of cognitive processes, i.e. the brain function that controls
and manages other cognitive processes, and which is intrinsic to processes such as
planning, cognitive flexibility, rule acquisition, abstract thinking, and inhibiting irrelevant
sensory information and inappropriate actions (Kato et al. 2009; Lorist et al. 2009).
Previous research has established that fatigue related deficits in both cerebroelectrical
activity and tasks requiring executive control processes can be inculcated by
extended 'difficult' task performance in the laboratory (Boksem et al. 2005, van der
Linden 2003). The proposed methodology will take advantage of the potential
performance decrements related to the mental fatigue associated with task
performance by interposing two executive function tasks after the 60 minutes of the
CDB.
In the current double-blind, placebo-controlled, balanced cross-over experiment we
assessed the effects of single doses of LC (500mg and 2000mg) and ALC ( 1000mg),
administered on separate occasions, on mental fatigue and cognitive function during
extended performance of mentally demanding tasks in healthy, young male and
female adults.
MATERIALS AND METHODS
DESIGN
This study employed a randomized, double-blind, placebo-controlled, balanced cross
over design.
PARTICIPANTS
20 healthy adults ( 10 male, 10 female, 18 to 25 years) who had not taken prescription
or illicit drugs or any food supplements within the preceding 4 weeks were recruited.
Smokers and excessive consumers of caffeine were excluded, as were those who had
consumed alcohol or caffeine within the 12 hours prior to a testing session.
TREATMENTS
Each participant received each treatment in an order counterbalanced by random
allocation to a Latin square. Depending on the condition to which the participant was
allocated on each day they received 4 capsules containing either 500 mg LC or 500
mg ALC or a placebo which were combined to give a total dose of either:
1) Placebo
2) 500 mg L-carnitine (LC; as 750 mg Carnipure™ tartrate, Lonza AG)
3) 2000 mg L-carnitine (LC; as 3000 mg Carnipure™ tartrate, Lonza AG)
4) 1000 mg acetyl-L-carnitine (ALC; as Carnipure™ ALC, Lonza AG)
COGNITIVE AND MOOD MEASURES
Prior to the Cognitive Demand Battery (CDB) three tasks assessed simple
psychomotor function and attention.
Simple Reaction Time
The participant pressed the response button as quickly as possible every time an
upwards pointing arrow appeared on screen. Fifty stimuli were presented with an interstimulus
duration that varied randomly between 1 and 3.5 seconds. The outcome was
speed of response (msecs).
Choice Reaction Time
Arrows pointing to the left or to the right were presented on the screen, one at a time.
Participants respond by pressing a left or right key press corresponding to the
direction of the arrow. Fifty stimuli were presented with an inter-stimulus duration that
varied randomly between 1 and 3.5 seconds. The outcomes were speed of response
(msecs) and accuracy (% correct).
Four Choice Reaction Time
A visual representation of arrows, pointing up, down, left and right was presented on
screen. The arrows 'lit up' at random with participants responding with the
corresponding response button. A total of 48 stimuli were presented with an interstimulus
duration that varied randomly between 1 and 3.5 seconds. The outcomes
were speed of response (msecs) and accuracy (% correct).
Cognitive Demand Battery (CDB)
The objective of this battery is to assess the impact of a treatment on speed/accuracy
and mental fatigue during continuous performance of cognitively demanding tasks.
Application of this battery in its 60 minute form (i.e. 6 repetitions of the 10-minute
battery) has been shown to reliably increase self-ratings of 'mental fatigue' and to be
sensitive to a number of herbal and natural interventions (Kennedy et al. 2008;
Kennedy and Scholey 2004; Reay et al. 2005; 2006). The 10 minute battery
comprises:
Serial Subtractions (3s and 7s - two minutes each)
Modified, two minute, computerised versions of the Serial Threes and Serial Sevens
tests were utilised. For both tasks a standard instruction screen informed the
participant to count backwards in threes or sevens from the given randomly generated
number, as quickly and accurately as possible, using the linear number keys to enter
each response. Participants were also instructed verbally that if they made a mistake
they should continue subtracting from the new, incorrect number. Each three-digit
response was entered using the linear number keys on the keyboard with each digit
being represented on screen by an asterisk. Pressing the enter key signals the end of
each response and clears the three asterisks from the screen. The task was scored
for total number of subtractions and number of errors. In the case of incorrect
responses, subsequent responses were scored as positive if they were correct in
relation to the new number.
Rapid Visual Information Processing Task (5 minutes)
The participants monitored a continuous series of digits for targets of three
consecutive odd or three consecutive even digits. The digits were presented at the
rate of 100 per minute and the participants responded to the detection of a target
string by pressing a response key as quickly as possible. The task is continuous and
lasts for 5 minutes, with 8 correct target strings being presented in each minute. The
task was scored for percentage of target strings correctly detected, average reaction
time for correct detections, and number of false alarms.
Subjective 'mental fatigue' scale
At the end of each set of tasks participants were asked to indicate how mentally
fatigued they felt by marking a 100 mm line with the end-points labelled "not at all" and
"extremely".
Executive function tasks
It has been hypothesised (see above) that cognitive deficits due to mental fatigue
reflect decrements in executive functioning. The following classic 'executive' tasks
have been shown to be sensitive to fatigue (van der Linden et al. 2003).
Logical Reasoning task
Participants were required to decide whether a series of statement correctly described
the order of 2 letters. They were shown a number of short sentences each followed by
a pair of letters. The sentences claimed to describe the order of the two letters, i.e., to
say which came first. They could do this in several different ways. For example, the
order AB can be correctly described by saying either ( 1 ) A precedes B or (2) B follows
A, or (3) B does not precede A, or (4) A does not follow B. All these are correct
descriptions of the pair AB but are incorrect when applied to the other pair BA.
Participants were required to decide whether each sentence was a true or false
description of the letter pair which followed it. The task was scored for accuracy and
response times.
Stroop Task
This is a computerised version of a commonly used classic task which requires
attentional and central executive resources. In this case the task ran for 10 minutes,
with the data collapsed into 2 minute epochs. Words describing one of four colours
('RED', 'YELLOW, 'GREEN', 'BLUE') were presented in different coloured fonts in the
centre of a computer screen. The participants pressed one of four coloured response
buttons in order to identify the font colour (e.g. if the word 'GREEN' was presented in a
blue font, the correct response would be to respond with the blue button). The
presented words were either 'congruent' (word and font are the same colour) or
'incongruent' (word and font are different colours) and were presented in a random
order. The task was scored for reaction times and accuracy of responses to
'congruent' and 'incongruent' words.
Mood
Bond-Lader Mood Scales (Bond and Lader 974)
Prior to and following the tasks mood was assessed with Bond and Lader scales. This
measure has been utilised in numerous pharmacological, psychopharmacological and
medical trials. The scales comprise a total of sixteen lines (approximately 100 mm on
screen) anchored at either end by antonyms (e.g. alert-drowsy, calm-excited).
Subjects indicate their current subjective position between the antonyms on the line.
Individual item scores were calculated as % distance along the line. Outcomes
comprised three factor analysis derived scores: 'Alertness', 'Calmness' and
'Contentment'.
PROCEDURE
Participants attended the laboratory on five separate occasions. Testing took place in
a suite of testing facilities with participants visually isolated from each other.
The first, introductory visit to the laboratory comprised: obtaining of informed consent;
training on the cognitive and mood measures; health screening; and collection of
demographic data.
Following the introductory visit participants attended the laboratory at 8.30 am on four
further occasions, one week apart, receiving a different treatment on each occasion.
They fasted (no food or drink except for water) and consumed no caffeine or alcohol
for at least 12 hours prior to each session. On their first study day participants were
randomly allocated to a treatment regime on the Latin square. On arrival on each
occasion participants consumed a standard breakfast (40 g Kellogg's All-bran with 150
ml skimmed milk and a glass of water) following which they undertook an initial
cognitive/mood assessment comprising completion of the attention tasks
('Simple'/'Choice'/'Four choice' reaction time) followed by 2 completions of the 10
minute CDB tasks (the first completion was a practice and the second was used for
baseline assessment of performance) and the Stroop and Logical Reasoning tasks.
They then consumed their treatment for that day. At 120 minutes post-dose they
completed the attention tasks then commenced the full 60 minute (i.e. 6 completions
of the 10 minutes of tasks) CDB. Following completion of the CDB participants
completed the 'Logical Reasoning' and the 'Stroop' executive function tasks. Mood
was assessed with Bond-Lader mood scales pre-treatment and before and after the
post-treatment cognitive assessment. The set-up is shown schematically in figure 1.
STATISTICAL APPROACH
Primary Analysis
Statistical analysis for all of the cognitive/fatigue and mood measures derived from the
battery were analysed by repeated measures Analysis of Variance (ANOVA) of
baseline adjusted data (calculated against pre-dose). Measures with a single postdose
repetition (attention tasks, executive tasks) were analysed by one way ANOVA
(condition). Measures with multiple post-dose repetitions (Mood, CDB) were analysed
with two way ANOVA (condition x repetition). Planned comparisons (placebo versus
each active treatment) were then undertaken on baseline adjusted data from the
single completion, or each of the multiple completions, as appropriate, utilising t-tests
with Mean Squares Error from the ANOVA (Keppel 1991 ) .
RESULTS
The statistics from the ANOVAs are shown in figures 4 , 5 and 6 .
Cognitive tasks
Reaction Time Tasks
Neither the initial ANOVAs nor planned comparisons revealed any significant effects
on the Simple Reaction Time, Choice Reaction Time or 4-Choice Reaction Time
tasks.
Executive Tasks
Neither the initial ANOVAs nor planned comparisons revealed any significant effects
on the Stroop task or Logical reasoning task.
Cognitive Demand Battery (CDB)
Figure 2 shows the outcomes from the CDB that evinced significant effects on the
planned comparisons of data from each active treatment to placebo during each
repetition of the tasks.
Serial subtractions
Serial 3s: The initial ANOVA showed no significant main effect of condition or
interaction involving condition on performance of the Serial 3s task. However, the
planned comparisons showed that participants carried out more subtractions following
500mg LC compared to placebo during the 4th [t [270] =2.74, p=0.006] and 6th [t
[270] =2.41 , p=0.016] repetitions, with statistical trends towards the same effect during
the 2nd [t [270] = 1.74, p=0.08] and 3rd [t [270] = 1 .67, p=0.09] repetitions. In addition,
more subtractions were made during the 5th repetition following 2000mg of LC
compared to placebo [t [270] =2.06, p=0.04]. This latter effect is not replicated at other
repetitions so may be attributable to a type 1 error. There was no significant effect on
the accuracy (number of errors) of performance.
Serial 7s: The initial ANOVA showed no significant main effects or interactions
involving treatment on the serial 7s task. However, the planned comparisons showed
that participants completed more subtractions following 500mg compared to placebo
during the 2nd [t [255] =2.02, p=0.044] and 4th [t [255] =2.38, p=0.01 8] repetitions.
There was also a trend towards more subtractions following 2000mg LC compared to
placebo during the 4th repetition [t [255] = 1.94, p=0.053]. There was no significant
effect on the accuracy (number of errors) of performance.
RVIP
ANOVA revealed a main effect of condition on speed of responses on the RVIP task
[F(3,57)=2.78, p<0.05]. However, post-hoc comparisons of the treatment means
showed that this effect was due to differences between active treatments, rather than
with placebo. The planned comparisons also revealed that, whilst participants
performed faster at each repetition following 500 mg LC, this effect only reached
significance during the 3rd repetition of the task [t [285] = 2.51 , p=0.01 3]. There was
also a trend towards slower responding following 2000mg LC during the 4th repetition
[t [255] = 1.71 , p=0.089].
Whilst the initial ANOVA showed no significant main effect of condition or interaction
involving condition on the accuracy of performing the RVIP task, the planned
comparisons showed that 500 mg LC outperformed placebo during the 2nd [t [285] =
2.44, p=0.015] and 3rd [t [285] = 2.1 1, p=0.036] repetitions of the task, with a trend
towards the same effect during the 4th [t [285] = 1.83, p=0.07] repetition.
Subjective fatigue
As expected the ANOVA revealed a main effect of repetition [F(5,95)=42.32, p<0.001 ]
with increasing fatigue throughout the repetitions of the tasks. However, there was no
main effect of condition or a condition by repetition interaction. The planned
comparisons did reveal that ratings of fatigue were lower following 500mg LC
compared to placebo during the 6th repetition [t [285] = 2.14, p=0.033]with a trend
towards the same effect during the 4th repetition [t [285] = 1.85, p=0.065]. In contrast
fatigue ratings were higher than placebo following 2000mg LC following the 5th
repetition [t [285] = 2.32, p=0.02].
Bond-Lader mood scales
The results are shown in figure 3 . The initial ANOVA showed no significant treatment
related effects on the Bond-Lader mood scales. However, following 500 mg LC
participants rated themselves as less calm [t [57] = 2.12, p=0.037] and less content [t
[57] = 3 , p=0.004] at the first (pre-task) assessment, with this effect dissipating by the
post task assessment, at which point this group rated themselves as more calm [t [57]
= 2.47, p=0.016]. Following 1000 mg ALC participants rated themselves as less alert
before undertaking the tasks [t [57] = 2.7, p=0.009] and less content both before [t [57]
= 3.6, p=0.001 ] and after [t [57] = 2.5, p=0.015] the post-dose tasks.
SUMMARY OF FINDINGS
The study employed two statistical analyses that were carried out independently of
each other; focussed planned comparisons (t tests utilising Mean Squares Error from
the ANOVA) that assessed any differences between placebo and each of the three
active treatment at each assessment, and a more general ANOVA that assessed main
effects and interaction effects (where appropriate) across treatments and
assessments. There were no significant differences in the second of these analysis
(ANOVA), but there was a pattern of effects evident within the planned comparisons.
The following summarizes the effects evident for each of the treatments in comparison
to placebo.
500 mg LC (as 750mg Carnipure tartrate)
Significant benefits on the planned comparison analyses were seen in performance of
each of the CDB tasks. Participants completed more Serial 3 subtractions during two
repetitions, with trends towards improvements at a further two time-points. They also
completed more Serial 7 subtractions at two time points, and responded more quickly
on the RVIP task during one repetition of the task. This latter effect was accompanied
by improved accuracy on the RVIP at two time-points, with a trend towards an
improvement during one further repetition. Participants in this condition also reported
themselves as numerically less 'mentally fatigued' after each repetition of the tasks,
but this effect only reached significance after the last set of tasks, with a trend towards
the same effect at one other time-point.
Results in terms of mood on the Bond-Lader scales were mixed, with 500 mg LC
associated with reduced 'calmness' and 'contentment' before starting the posttreatment
tasks, but increased 'calmness' following completion of the assessment.
2000mg LC (as 3000mg Carnipure tartrate)
The pattern with regards 2000 mg LC was composed of several isolated differences.
Participants completed more Serial 3s at one time point, with a trend towards
increased Serial 7s subtractions at one time-point. In contrast there was a trend
towards slower responses on the RVIP and significantly increased ratings of mental
fatigue at one repetition. Given that the pattern of results is composed of single,
contradictory findings it seems likely that the results pertaining to this treatment are
due to chance.
000 mg ALC (as Carnipure ALC)
ALC was associated with negative effects on mood with lower levels of alertness at
the second post-dose time-point and reduced levels of 'contentment' at both post-dose
time points.
Conclusion
Despite a lack of any significant treatment related effects on the ANOVAs there was
consistent evidence of significant improvements in performance of the CDB following
500 mg LC in comparison to placebo on the planned comparisons. However, there
was no evidence of benefits following the 2000 mg LC and 1000 mg ALC treatments.
DISCUSSION
The findings from the current study demonstrate that 500 mg LC enhance the
cognitive performance of healthy, young adults. Improvements were seen during more
than one (of six) task repetition on all three of the Cognitive Demand Battery tasks,
with some evidence of a treatment related attenuation of task related mental fatigue.
Presently, there was no consistent evidence that the higher dose (2000 mg) of LC or
1000 mg ALC had beneficial effects.
B. Early Phase Cognitive Test Battery
Effects of carnitine on cognitive function were studied with a CogState™ 12 minute
Early Phase cognitive test battery. The test was developed by CogState, US, and is
described in US 716351 3 B2. The test uses playing cards and computer mazes for
measuring the cognitive domains of executive function, psychomotor function, visual
attention and visual learning. Tasks correspond to cognitive domains as follows:
Maze learning task. Executive function/spatial problem solving
Detection task: Psychomotor function/speed of processing
Identification task: Visual attention/vigilance
One card learning task: Visual learning
The test is designed such that the individuals do not experience fatigue when
performing the tests. It was carried out with 20 healthy male and female individuals
aged between 20 and 40 years. The test was double-blind and placebo-controlled and
studied effects of 500 mg L-carnitine, administered as 736 mg L-carnitine L-tartrate
(Carnipure™ tartrate, Lonza AG) in water in a single dose. A single test battery of
about 10 min comprised maze learning task, a detection task with playing cards, an
identification task with playing cards and a one card learning task. Consecutive
accomplishing of the test battery took place twice prior to and hourly after intake of the
study preparation over a period of 6 hours.
Comparison and evaluation of the results showed, that there is some evidence for a
short-acting benefit of L-carnitine on executive function two hours after sample intake.
However, there was no significant effect on visual attentional function or visual
learning. Interestingly, a decrease of psychomotor function was observed after four,
five and six hours. It was found that at the same time, higher cognitive processes,
such as memory and executive function, are not impaired.
The results suggest that healthy individuals without fatigue may benefit from Lcarnitine
intake within a short interval of approximately two hours, whereas a long time
improvement of cognitive function was not observed. The result complements the
Cognitive Demand Battery (CDB) described above by suggesting an effect of carnitine
administration on cognitive functions of individuals, who do not experience fatigue.
References
Boksem MAS, Meijman TF, Lorist MM (2005) Effects of mental fatigue on attention:
An ERP study. Cognitive Brain Research 25: 107-1 16
Cruciani RA, Dvorkin E, Homel P, Malamud S, Culliney B, Lapin J , Portenoy RK,
Esteban-Cruciani N (2006) Safety, Tolerability and Symptom Outcomes Associated
with l-Carnitine Supplementation in Patients with Cancer, Fatigue, and Carnitine
Deficiency: A Phase l/ll Study. Journal of Pain and Symptom Management 32: 551 -
559
Karlic, H., Lohninger, A., (2004) Supplementation of L-carnitine in athletes: does it
make sense? Nutrition 20:709-71 5
Kato Y, Endo H, Kizuka T (2009) Mental fatigue and impaired response processes:
Event-related brain potentials in a Go/NoGo task. International Journal of
Psychophysiology 72: 204-21 1
Kennedy DO, Haskell CF, Robertson B, Reay J , Brewster-Maund C, Luedemann J ,
Maggini S, Ruf M, Zangara A , Scholey AB (2008) Improved cognitive performance
and mental fatigue following a multi-vitamin and mineral supplement with added
guarana (Paullinia cupana). Appetite 50: 506-51 3
Kennedy DO, Scholey AB (2004) A glucose-caffeine 'energy drink' ameliorates
subjective and performance deficits during prolonged cognitive demand. Appetite 42:
331 -333
Kennedy DO, Dodd FL, Okello EJ, Reay JL, Scholey AB, Haskell CF (201 0)
Monoterpenoid extract of sage with cholinesterase inhibiting properties improves
cognitive performance and mood in healthy adults. J . Psychopharmacol. Oct. 201 1
(Epub. ahead of print).
Lorist MM, Bezdan E, ten Caat M, Span MM, Roerdink JBTM, Maurits NM (2009) The
influence of mental fatigue and motivation on neural network dynamics; an EEG
coherence study. Brain Research 1270: 95-1 06
Malaguarnera M, Cammalleri L , Gargante MP, Vacante M, Colonna V, Motta M (2007)
L-Carnitine treatment reduces severity of physical and mental fatigue and increases
cognitive functions in centenarians: a randomized and controlled clinical trial.
American Journal of Clinical Nutrition 86: 1738-1 744
Malaguarnera M, Gargante MP, Cristaldi E, Colonna V, Messano M, Koverech A, Neri
S, Vacante M, Cammalleri L , Motta M (2008) Acetyl L-carnitine (ALC) treatment in
elderly patients with fatigue. Archives of Gerontology and Geriatrics 46: 18 1-190
Montgomery SA, Thai LJ, Amrein R (2003) Meta-analysis of double blind randomized
controlled clinical trials of acetyl-L-carnitine versus placebo in the treatment of mild
cognitive impairment and mild Alzheimer's disease. International Clinical
Psychopharmacology 18 : 6 1-71
Reay JL, Kennedy DO, Scholey AB (2005) Single doses of Panax ginseng (G1 5)
reduce blood glucose levels and improve cognitive performance during sustained
mental activity. Journal of Psychopharmacology 19 : 357-365
Reay JL, Kennedy DO, Scholey AB (2006) Effects of Panax ginseng, consumed with
and without glucose, on blood glucose levels and cognitive performance during
sustained mentally demanding tasks. J . Psychopharmacol. 20, 771 -81 .
van der Linden D, Frese M, Meijman TF (2003) Mental fatigue and the control of
cognitive processes: effects on perseveration and planning. Acta Psychologica 113 :
45-65
CLAIMS
1. The use of L-carnitine, a salt of L-carnitine, a derivative of L-carnitine and/or a salt
of a derivative of L-carnitine for reducing or preventing fatigue and/or for improving
cognitive function in an animal.
2 . The use of claim 1, wherein the use is a non-therapeutic use.
3 . The use of at least one of the preceding claims, wherein the animal is a healthy
animal.
4 . The use of at least one of the preceding claims, wherein the animal is human.
5 . The use of claim 4 , wherein the individual 's age is below 60.
6 . The use of at least one of the preceding claims, wherein the fatigue is mental
fatigue.
7 . The use of at least one of the preceding claims, wherein the animal does not suffer
from chronic fatigue and/or chronic L-carnitine deficiency.
8 . The use of at least one of the preceding claims, wherein before administration of
the L-carnitine, salt of L-carnitine, derivative of L-carnitine and/or salt of a
derivative of L-carnitine, the animal is experiencing a temporary fatigue and/or
temporary impairment of cognitive function.
9 . The use of at least one of the preceding claims, wherein the salt is a tartrate,
citrate, succinate, fumarate or hydrochloride.
10 .The use of at least one of the preceding claims, wherein the L-carnitine, salt of Lcarnitine,
derivative of L-carnitine and/or salt of a derivative of L-carnitine is
administered in an amount corresponding to an equivalent amount of L-carnitine
between 10 and 3000 mg, preferably between 50 and 1900 mg.
11.The use of at least one of the preceding claims, wherein the L-carnitine, salt of Lcarnitine,
derivative of L-carnitine and/or salt of a derivative of L-carnitine is
administered in a single dose.
12. The use of at least one of the preceding claims, wherein the L-carnitine, salt of Lcarnitine,
derivative of L-carnitine and/or salt of a derivative of L-carnitine is
administered as part of a solid composition comprising more than 50% (w/w) Lcarnitine.
13 .The use of at least one of the preceding claims, wherein the L-carnitine, salt of Lcarnitine,
derivative of L-carnitine and/or salt of a derivative of L-carnitine is not
administered in combination with another agent, which is effective in reducing or
preventing fatigue or for improving cognitive functions in an animal.
14. The use of at least one of the preceding claims, wherein the L-carnitine, salt of Lcarnitine,
derivative of L-carnitine and/or salt of a derivative of L-carnitine is
administered orally, preferably in the form of a liquid, or a solid preparation, such
as a tablet, capsule, powder, or a gel or a paste.
15 .The use of at least one of the preceding claims, wherein the animal is a horse or a
pet, preferably a dog or cat.
16. A method for reducing or preventing fatigue and/or for improving cognitive function
in an animal, comprising administering L-carnitine, a salt of L-carnitine, a derivative
of L-carnitine and/or salt of a derivative of L-carnitine to that animal, wherein the
method is preferably non-therapeutic.
17 .A composition for reducing or preventing fatigue and/or for improving cognitive
function in an animal, the composition comprising L-carnitine, a salt of L-carnitine,
a derivative of L-carnitine and/or salt of a derivative of L-carnitine, wherein the
composition is preferably non-therapeutic.