Dr Pierre-Marie Lledo from the Pasteur Institute in
Paris reported on his studies of the sensory neurones in the human
olfactory (smell) system. (Neurones are
electrically excitable cells in the nervous system that process and
Sensory neurones are replaced every two months. The brain, whose neurones are
also regularly replaced, is the first relay of
‘New-born’ neurones come from stem cells, after which they have to ‘migrate’ to
the site in which they are needed and then ‘integrate’ themselves
with the existing network. This process takes around four weeks during which
time the neurone is not able to ‘speak’ or transmit information but
is able to ‘listen’ or receive it. The information which the neurone
receives may alter it or allow it to be ‘epigenetically regulated’.
means that although the neurone is genetically programmed, it can be altered
by its ‘experiences’ on
its way to being integrated into the network.)
Moreover, this regulation can be controlled. For example, olfaction has a strong
link to memory. The more the sense of smell is used the more new and more complex ‘smell
cells’ will be created. Mice introduced to new smells every day for 40
days doubled the number of cells created every day and improved their short-term
memory from 30 minutes to four hours.
Is it possible to adapt and use new born neurones? We don’t know whether
using stem cells or stem cell neurones devised for olfaction for some other purpose
might throw the whole system.
Dr Tom Brenna from Cornell University, Ithaca looked in more
detail at DHA (docosahexaenoic acid) the highly unsaturated fatty acid that is
vital for efficient brain function.
The human brain continues to accumulate DHA for up to two years although it accumulates
most rapidly in the last three months of pregnancy. The brain continues to grow
and refine its synapses
(connection or signalling points) throughout early childhood.
Supplementation of breast-fed babies with DHA resulted in significant improvement
in visual acuity. It also appears that regular fish eaters (who absorb high levels
of DHA from the fish) are 50% less likely to suffer from Alzheimer's.
Dr Stephen Cunnane from the Université de Sherbrooke,
Canada looked at brain function in the aging. In Europe 10% of over
olds suffer from cognitive brain decline, as do 50% over over 85 year
Genetic factors may be relevant in this decline but they are uncontrollable.
However it seems clear that insulin resistance/type 2 diabetes, low fish intake
and a reduced uptake of glucose (brain fuel) all affect the incidence of decline.
To keep all neurones and synapses in the brain fully operational requires a high
input of fuel (glucose and metabolites - amino acids, glycerol and glycogen):
it takes 74% of the total energy consumed by a new born baby, 23% of total energy
consumed by an adult.
In omega 3 deficient animals the brain uptake of glucose is poor; there is 20%
less glucose uptake in the brains of Alzheimer's patients than in normal brains.
Is there a connection?
Insulin must play a role in glucose supply so insulin resistance impairs the
ability to get glucose into
the tissues, thus starving the brain of fuel.
It is possible that ketones (the substances made when the body, in search of
energy/fuel/glucose, breaks downs fats to access it) may help to supply the brain
with fuel but there is little evidence of this.
It is not clear whether the inability of the brain to access sufficient fuel
is a vascular problem (not enough glucose is getting through) or neurone problem
(they are unable to capture the glucose when it arrives). Nor is it known how
fatty acids are actually transported into the brain.
Humans are not good at making DHA out of omega 3 fatty acids - we are most efficient
as neo-nates but get worse as we get older. But if there is a sufficient dietary
supply (fish) there is no need for us to convert it anyhow.
Dr Fernando Gomez-Pinilla of the University of California, LA
discussed the studies he had undertaken with rats on fitness training and cognitive
Increased exercise in rat models was shown to increase their hippocampal levels
of BDNF - brain-derived neurotrophic factor. BDNF is a protein that supports
existing neurones, and encourages the growth of new neurones and synapses in
the hippocampus, cortex, and basal forebrain - areas vital to learning, memory,
and higher thinking. Increased exercise enabled the rats to learn faster and
more quickly from a traumatic brain injury.
It was also found that a diet high in saturated fats reduced
hippocampal levels of BDNF while supplementing with fish oils increased levels
of BDNF. Like the exercise, the fish oil supplements speeded up recovery from
traumatic brain injury. Combining exercise and good diet had a positive synergistic
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Firist Published in 2006
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