Genetic aging of brain at 40, many genes linked to aging play a role in the functioning of the synapse

Main Category: Public Health
Article Date: 10 Jun 2004 - 12:00 PDT


According to scientists at Harvard, USA, hundreds of genes that are linked to aging, especially of the brain, start to change (ripen) when we reach the age of 40.

Professor Ann Grfaybiel, Brain Science Professor, MIT, said 'This finding gives new meaning to reaching 40' (she was not part of this research team).

The scientists also found that people's brains age at significantly different rates. Some 50-year olds had brains of young people while other 50-year-olds had genetic patterns of very old people. The age-related genes in people aged 40-70 varied tremendously.

You can read about this study in the journal Nature.

The scientists, led by Professor Yankner, collected brain tissue from 30 dead people (unidentified). Their ages at death varied from 26 to 106, they were also from all over the USA.

Yankner, and his team found that around 4% of 11,000 genes they identified changed significantly during a person's life span - these genes were closely linked to aging (the aging process).

The scientists wanted to identify the genes in the fontal lobe area of the brain. The frontal lobe regulates our ability to perform tasks, to organise and plan, make judgements and analyse data (information). They cut small pieces of the frontal lobe, placed then in lab dishes. The lab dishes were filled with thousands of gene markers. They could then identify the genes which were active at a given moment.

Many of the genes that are linked to aging (they play a role in the aging process) also play a role in the functioning of the synapse. Between two neurons there is a gap, this gap is called a synapse, communication between neurons takes place along these synapses. You have billions of synapses in your brain. The number of synapses made by brain cells and the strength of the synapses affects your learning and memory.

As we get older, the genes that govern what goes on in these synapses, the neurotransmitters, become less active, the team found. They also found that genes that repair brain proteins, genes that repair damaged genes, and genes that protect against free radicals work much harder as we get older (over 40).

Yankner said that it is how these genes work, their levels of performance and activity, which decides whether a person seems young for his/her age or old.

WHAT IS A SYNAPSE?

From Southampton University, UK

A synapse (S) is a specialised junction between two nerves. The function of a S is to STOP transmission.

If the nerves were functionally connected all the time, we would always be writhing and having convulsions, fits and twitches. The S allows different circuits to become active at different times so that we can make coordinated movements and reactions. (Strychnine blocks inhibition and makes many S active all the time hence the convulsions and poisoning of the system).

Different S have different degrees of connectivity. In some cases it may require 20 stimuli in nerve 1 for nerve 2 to become active. In other more used circuits one stimulus in nerve 1 will make nerve 2 active. This ratio is constantly changing with experience.

The S connections are not static. The way that they change determines what we can do and learn. There will be many hundred of S connections on to a nerve and they are physically altering with use and disuse making the connection better or worse.

There is a main chemical that is released at the S and this makes the second nerve active. There are many such chemicals S transmitters, eg acetylcholine, glutamate, serotonin, dopamine, noradrenalin, histamine. But there are many other chemicals released at the synapses and these are responsible for the dynamic changes in the S connections.

So far I have only considered excitatory S. There are an equal number of INHIBITORY S which stop transmission. The transmitters at these S are usually either glycine or GABA (gamma amino butyric acid).

It is just as important that you can stop doing something (inhibition) as start doing something (See article on "Are we race horses or a donkeys ?")

There is a fashion for trying to encourage the formation of many S in the brains of young children by exposing them to flash cards of information from the age of two onwards. Such detailed exposure does not seem to work.

It is better if babies have a rich and varied environment; their parents talk to them, they have young friends for social interaction, and possibly a pet cat, dog or hamster. Babies like playing and their toys can have an instructional basis, such as bricks, letters, a music keyboard and puzzles.

These will all increase the S connections in their brains.

• Additional
• References
• Citations