The idea of ageing ranges from wrinkled skin to declining performance and hair loss to forgetfulness. It is therefore a very broadly defined term. This is hardly surprising when you consider how differently the process manifests itself in people. However, all the processes described are merely the end state of a series of reactions and conditions in our bodies. Ordinary people may be content with this superficial view, in contrast to science. Researchers around the globe are trying to decipher the processes behind our wrinkles and our increasingly poor performance at an older age.
In this respect, science is a kind of construct that is not satisfied with the status quo, but constantly strives to gain new knowledge. In many cases, this very approach leads to the following view:
"If you understand how something works, then you can try to change it."
This is no different in the anti-ageing field. A group around the researcher Carlos López-Otín has described nine hallmarks of ageing in a highly regarded article. Below is a brief introductory explanation of each hallmark. In a subsequent series of articles, each Hallmark will be examined in detail.
1. genomic instability
DNA is similar to a blueprint for the body - if certain pages are missing, the whole book or blueprint sometimes doesn't make sense. Such changes can be better repaired by the body in younger years than in later phases of life. In addition, there is an increased susceptibility to errors in old age.
2. telomere attrition
DNA per se is not a single large book, but the genetic information is divided into 23 smaller booklets (chromosomes). Each individual cell is equipped with this small library (genome). The last chapter of these "little books" is special and is called the telomere. Here, no more information is encoded, but the telomeres function as degradation protection for the DNA. The telomeres naturally become shorter with each cell division. As soon as a certain threshold (Hayflick limit) is reached, the cell function then succumbs.
3. epigenetic changes
Epigenetics attempts to explain which factors temporarily determine the activity of a gene and subsequently the development of the cell. However, these factors are not based on possible changes in the genetic information (example: mutations), but on different small proteins that can bind to the DNA. As a result, the binding can influence the activity of one or even several genes (more or less). In addition, epigenetics is involved in the development or differentiation of cells.
4. loss of proteostasis
Proteostasis is composed of the two terms proteome (totality of proteins that can be produced in the body) and homeostasis (balance). If something goes wrong in the regulation of proteins, individual proteins may not appear at all or may even increase in number. This in turn influences the functionality of the cells. This process plays a role in known diseases such as Alzheimer's or Parkinson's.
5. deregulated nutrient measurement & fasting
In this indicator, the body's reaction to food intake is relevant. Its regulation takes place in interaction with growth hormone and other hormones. Among other things, calorie restriction and fasting are important here. We also deal with autophagy and special longevity genes: the sirtuins.
6. mitochondrial dysfunction & mitohormesis
As cells and organisms age, the efficiency of the respiratory chain (energy supply in the mitochondrion) tends to decrease. This finding is based on two mechanisms. Firstly, electrons are lost and secondly, ATP production decreases. ATP is the most important energy carrier in our body. In this context, we also learn about the term mitohormesis.
7. cellular senescence
Cellular senescence describes the state of a stopped cell cycle. This means that the cell shuts down its functionality and can no longer divide. This standstill is often triggered by DNA changes. In a way, it is a protective mechanism. This protective mechanism is well-intentioned, but sometimes poorly executed, especially in old age.
8. stem cell exhaustion
With age, the stem cells ' ability to divide decreases - they become "exhausted". As a result, broken or damaged cells can no longer be renewed. This ultimately leads to a wide variety of tissues no longer being able to regenerate or recover adequately.
9. altered intercellular communication
This characteristic looks beyond the cell-autonomous level. Ageing also involves changes in the way cells communicate with each other. Increasing inflammatory response and decreasing immune surveillance are exemplary consequences of this factor with sometimes drastic effects on physiological ageing.
At first glance, this all sounds very scientific, obscure and not very understandable - but don't let that put you off. We will now take a closer look at each of the Hallmarks of Aging individually in a series of articles with the aim of understanding the basics of growing older.
I can promise you one thing: The insight into the basis of bodily functions is absolutely fulfilling.
From the series: Hallmarks of Aging
What invisible changes happen in the body as we grow older? What are the reasons for wrinkles, cataracts or high blood pressure? In the series "Hallmarks of Aging" we take a look at the hallmarks of ageing: molecularly, profoundly, understandably.
López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G. (2013). The hallmarks of aging. Cell, 153(6), 1194-1217. https://doi.org/10.1016/j.cell.2013.05.039