Table of Contents Table of Contents
Previous Page  16 / 42 Next Page
Information
Show Menu
Previous Page 16 / 42 Next Page
Page Background

certain well known risk factors for common chronic diseases linked to unhealthy behavior and

also consider socio-economic factors influencing health and health promotion. One scientist

detected that his life would increase by 3 years when driving a large SUV instead of his

existing small sedan (reported by John Sedivey and cited by Emily Underwood

(11)

).

Geroscience is using more sophisticated tools, and one of those even gained

Blackburn, Greider and Szotak the Nobel Prize for Physiology in Medicine in 200

9 5

. The

prize winning research showed that the ends of chromosomes, known as telomeres, need to be

a certain length so that the cell can divide. They also found that the enzyme telomerase can

repair and add to the length of telomeres. Each time a cell divides the telomeres get shorter.

Further research linked the telomeres to human aging and risk of cancer. Genetic factors and

non-genetic stimuli interact with each other throughout life and determine the length or

shortness of the telomeres

(12)

. Initially it was thought that the length of the telomere might

signal the biological age. The two Nobel Prize winning ladies, Blackburne and Greiner (Mr.

Szotak stepped into another research field) somehow assisted in the development of the

telomere into a biomarker thought to indicate biological age. A number of confounding

factors and results from further research cast doubt on the validity of the marker, and both

scientists finally dissociated themselves from attempts to use a commercial telomere-based

test

(11)

. The test is still available and is considered by some as a way of encouraging testees

to adopt a healthier life style in case the test result is not

as good as expecte

d 6

.

Other methods under study are worthwhile to

know about and to follow up in terms of their

development. An attractive combination of biomarker and

statistics for estimating the biological age of tissue has

been proposed by Horvath

(13)

. His idea is based on an

epigenetic mechanism and the important part which methyl groups have in its functio

n 7 .

Since

gene expression is influenced by methylation occurring throughout the entire life, it is

suggested by Horvath that methylation levels in numerous sites of the genome indicate the

biological age of tissues. For instance, he measured DNA methylation levels using 8.000

samples from 82 DNA methylation array datasets, encompassing 51 healthy tissues and cell

types and thousands of cancer samples from 32 datasets. One of his findings was that cancer

tissues have a high biological age and that the cerebellum of postmortem surveyed

centenarians has a low biological age.

The changes during aging of ‘long-lived proteins’ have recently raised the interest of

geroscientists as a potential indicator of biological age. Long-lived proteins are those which

don’t regenerate over a life time. Such proteins are found, for instance, in the brain. Like the

system proposed by Horvath mentioned above, the determination of changes in long-lived

proteins, which involve changes in transcription and translation of such proteins in young and

old rats

(14)

, cannot be expected to be of practical use for public health research, since

specimens must be obtained by biopsy or from postmortem samples.

5 http://www.nobelprize.org/nobel_prizes/medicine/laureates/2009/press.html

(accessed June 6, 2016)

6 http://biotech-spain.com/en/directory/life+length+/

(accessed June 6, 2016)

7

An introduction into what epigenetic is all about is given in the first issue of the KhonKaen Public Health Forum