Almost all organisms age and ageing is considered to be a normal biological process. Ageing occurs because damage to molecules, cells and tissues throughout life leads to loss of function and increased risk of death. Research can increase understanding of the human ageing process and lead to interventions that can improve health and quality of life in older people.

Processes in the suggested journal articles include:

  • Insulin/insulin like growth factor signalling (ISS)
  • Lipid metabolism (cholesterol profiles)
  • Genetic variation
  • Environmental factors
  • Glucose tolerance and insulin sensitivity
  • Preserved cognitive and motor functions - but the reasons why are unknown
  • Delayed bone loss
  • Delayed visual impairment
  • Improved cardiac function
  • Protection against cancer
  • Preserved immune system

This activity is focused on ageing at a cellular/molecular level however there are many theories about ageing at an organism level and beyond.

Some other theories of ageing/longevity are associated with:

  • Large body size
  • Predator-free environments (eg animals that can fly)
  • Slower metabolic rate - One theory is that metabolism produces by-products (eg reactive oxygen species) which can damage cells over time.

However there are some long-lived organisms that do not seem to conform to these patterns, for example the cave salamander - read the press release here.

 

Curriculum links

Biology

1.3 Biodiversity a) The variety of life, both past and present, is extensive, but the biochemical basis of life is similar for all living things.
1.6 Biological molecules d) Enzymes catalyse a wide range of intracellular reactions as well as extracellular ones.
1.9 Cellular control b) Enzymes catalyse the reactions that determine structures and functions from cellular to whole-organism level.
f) Gene technologies allow study and alteration of gene function in order to better understand organism function and to design new industrial and medical processes.


Scottish Curriculum

Biology Higher Potentially relevant to modules: DNA and the Genome (study of DNA and the genome. molecular basis of evolution and biodiversity, understanding of gene expression, at the cellular level) Metabolism and Survival (control of metabolic pathways is essential to cell survival. whole organism adaptations for the maintenance of metabolism for survival)

Human Biology Higher

Potentially relevant to modules: Physiology and Health (the cardiovascular system, relevant tissues and circulation and the pathology of cardiovascular disease, including their impact on society and on personal lifestyle) Neurobiology and Communication (neural communication and the links between neurotransmitters and behaviour, while considering personal and social citizenship)

Environmental Science Higher


Potentially relevant to modules: Sustainability (Global environmental issues will focus on problems, solutions and conflicts, such as population)

 

Theories of ageing

There are many different theories associated with ageing. At a cellular level, one factor that can influence the lifespan of a cell is telomere length. Telomeres are found at the ends of chromosomes. They consist of a repeating sequence of DNA - TTAGGG - that is the same in all vertebrates. Each time a cell divides, the telomeres get slightly shorter as the very ends of the chromosomes cannot be replicated efficiently. The enzyme telomerase can add new TTAGGG units to the ends of chromosomes to compensate for this. Telomerase is very active in stem cells and embryonic tissues, however in adult tissues it is much less active. Telomere length therefore reduces as individuals get older, and this is thought to be a factor involved in the ageing process.

However, when there are high levels of telomerase in cells where it is not normally expected, this can lead to cancer, because these cells lose the ability to die and continue to replicate excessively.

The diagram below summarises these processes:telomerase activity

Taken from " Telomeres in cancer and ageing" by L.E. Donate et al,  Phil Trans R Soc B (2011) 366, 76-84.

Activity: Your task is to find out about one other factor associated with ageing/longevity (living a long life) and draw a diagram to explain it.

The following articles contain some examples of processes that are associated with an extended lifespan and could be used as a starting point. Find out more about using scientific journals here, and use the information below to help you.

Both of these articles are reviews so give a summary of several different studies. Don't try to read the whole article as it will take a long time! Start by reading the abstract as this tells you what the article is about. Then skim through the titles of the different sections to see if any might be useful. For the purpose of this task you might want to look at the following sections.

 

" Genetics of human longevity"

A lot of the information in this paper comes from a study on a large number of people who come from families that live for a long time (over 90 years). This was called the LLS (Leiden Longevity Study). The families in the study are called "longevity families" and "offspring" refers to their children. The children's partners (who were not part of the LLS) were used as the control group.

Section 4. IIS signalling parameters in longevity families

IIS stands for "insulin/insulin-like growth factor signalling" The middle part of this section lists some of the differences seen in offspring of longevity families (the children of people who have lived to be over 90) compared to their partners whose parents did not live to be over 90.

Section 5. Lipid and thyroid metabolism in longevity families

This section tells us about differences in the types of fats (lipids) found in the blood that are linked with heart (cardiovascular) disease.

Section 8. The influence of environmental factors and early development on human ageing and longevity

This section gives some examples of environmental factors that have been shown to have an effect on ageing. The third paragraph discusses the effects of famine on ageing.

 

" Mammalian models of extended healthy lifespan"

This paper examines the effects of ageing in long-lived mice to get clues about what factors affect ageing in humans. In animal models the effects of mutating or removing individual genes can be studied by comparing animals that are identical apart from that single gene. When referring to mice (or other animals) the letters in italics (eg Irs1-/-) refer to the name of the gene (eg Insulin receptor substrate 1). The two minus signs (-/-) show both copies of the gene have been removed. The letters KO or the words "knock out" also means the gene has been removed (knocked out) from the animal's genome. WT = wild type (animals that have a two normal copies of the gene being studied).

Section 2. (a) Maintenance of a youthful metabolic profile in long-lived mice

This section talks about genes relating to glucose and insulin. This is related to the IIS pathway in humans that was described in the first paper.

Adiposity = fat content.

Insulin sensitivity = ability to respond to the effect of insulin.

The first paragraph explains how different levels of adiposity and insulin sensitivity are linked to various age-related diseases. The remaining paragraphs in Section 2 (a) talk about the differences in these processes in long-lived KO mice compared with WT control mice.

Section 2. (b) to (g)

The following sections look at long lived mice and how differences in their genes protect them (or not) from some of the effects of ageing. The language used in these sections is very difficult so don't worry if you don't understand a lot of it. Just try and pick out some of the key points that you can use.

(b) Preserved cognitive and motor functions in long-lived mice

(c) Delayed bone loss in long-lived mice

(d) Attenuated visual deterioration in long-lived mice

(e) Improved cardiac function in long-lived mice

(f) Protection against cancer in long-lived mice

(g) Youthful immune profile and reduced inflammation in long-lived mice

 

Scientific journals

Trans B coverA big part of science is making results available to everyone. This is usually done by publishing articles in scientific journals (magazines) that are produced on a regular basis (eg monthly). There are lots of different journals, and most of them focus on different topics within science. The articles are printed and made available online (although a lot of them need to be paid for by subscription before you can read them).

By publishing outcomes of scientific experiments, or new scientific theories, other scientists (and also members of the public, including journalists, policy-makers, or even school students!) can look at new results, repeat experiments and agree or disagree with previous work that has been done. The articles usually have a similar layout. They start with an abstract (summary) - this is the most useful place to start as it tells you what is going to be in the article. There is then an introduction, information about how they carried out their experiments (methods), results and a discussion or conclusions. Some articles are reviews of lots of other articles which give an up-to-date summary of that topic, and therefore don't have methods or results sections. At the end of the articles there is a list of references. These are the other journal articles that the author has used (cited) to support their article or work.

The Royal Society publishes eight different journals covering different areas of science, mathematics and engineering.