Podcast: Episode 14, skin aging

Audio episode, skin aging


Comment effacer are you laughing at us? How to erase wrinkles? These questions often come up in our society. So let's look at why and how our skin ages.

Intrinsic aging

These are the chronological and genetic factors that occur naturally in our skin. They are linked to our genome.


  • chemical reaction between a sugar and a protein such as collagen and elastin
  • produces AGEs (Advanced Glycation end-products) which are entangled, rigid proteins that lose their functions
  • degradation of collagen, which gives resistance to the skin + degradation of elastin, which gives elasticity to the skin
  • result: loose, flabby, thin, wrinkled skin

Extrinsic Aging

These are the environmental factors, related to our lifestyle. It is our exposome (everything we are exposed to).

Photoaging and oxidative stress

UVA (315-400 nm)

  • penetrate deeper into the skin
  • induce ROS (reactive oxygen species) which interfere with collagen synthesis in the dermis, and recruit inflammation cells
  • activates MMPs (matrix metalloproteases) which degrade the ECM (extracellular matrix) including the elastic fibers of the dermis
  • result: loose, flabby, thin, wrinkled skin

UVB (280-315 nm)

  • penetrate less deeply into the skin but with more energy
  • induce ROS (reactive oxygen species) which interfere with the DNA of skin cells
  • potential outcome: cancer


  • induction of MMPs which would decrease the collagen content of the extracellular matrix
  • result: less flabby skin

A diet low in Vitamin E and Selenium

  • Vitamin E = tocopherol is found in almonds and hazelnuts
  • selenium is found a lot in fish and shellfish
  • result: no reduction in skin aging


  • ozone induces deleterious free radicals for the ECM (extracellular matrix)

Episode Notes


Hello, you are listening to episode 14 of The Sous de la Cosmétique, the Podcast which reveals and explains to you with clarity and sincerity the world of cosmetics. I am Julie Magand Castel, chemical biologist and cosmetologist specialized in natural cosmetics and today we are going to talk about skin aging. We will see what happens to our skin over time.

This episode is going to be slightly more technical so I advise you to listen and re-listen to episode 9 on the skin in which we describe the different layers of the skin: the epidermis, the dermis and the hypodermis. And in the dermis, the extracellular matrix theory is going to be particularly important in this episode.

The extra cellular matrix, which is abbreviated with the acronym MEC, is the set of macromolecules, large molecules such as collagen and elastin which surround the cells of the skin. Depending on the tissue, the location in the body of the ECM is more or less important. In the dermis, the second layer of skin, it represents a considerable ratio. And this dermal MEC will play a considerable role in skin aging, which is the subject of our episode. Besides, we are going to address different causes of skin aging but we cannot talk about everything so I limited myself to glycation, photoaging and oxidative stress. We will quickly discuss other environmental causes related to our lifestyle.

One of the mechanisms that induces skin aging is glycation. Glycation is a process that occurs naturally with age, ie it is part of intrinsic aging, therefore due to chronological and genetic factors. Glycation is a chemical reaction between a sugar and a protein, for chemists it will form a schiff base (a carbon/nitrogen double bond) which then rearranges.

I return quickly to the term chemical reaction, which is generally demonized in the various media. But chemistry is just the study of matter, of everything around us. It is the observation of our environment at the molecular or even atomic scale. We are talking about the same thing with different words. You can talk to me about "the acid taste of lemon" or "citric acid" and well, you will have described the same thing. Lemon is natural, we can talk about chemistry in the natural. Ok, I close the parenthesis.

We were just talking about skin aging induced by glycation, therefore the chemical reaction between a sugar and a protein. And this reaction will give what are called advanced glycation end products, the acronym of which is AGE for advanced glycation end product.

It's easy to remember because it is the AGEs that cause aging and therefore the age of the skin. These AGEs are roughly a protein, therefore potentially collagen or elastin, which has reacted with a sugar and which has made links with itself. And suddenly it is all tangled up, all rigid and it will lose its initial functions which, let us remember, are the elasticity of the skin for elastin and the maintenance of tissues, therefore the resistance of the skin for collagen.

And glycation is an irreversible modification of their structures, of their activities, which therefore cause dysfunctions of several mechanisms. It will directly or indirectly affect certain cells and therefore the organization of the extracellular matrix, because collagen and elastin are ECM proteins. So to put it simply, glycation is a reaction between a sugar and a protein thus producing AGEs which results in less elastic, less supple, looser, yellowing skin and the appearance of wrinkles. It's a completely normal reaction that happens with the sugars in your body (we all have them!)

So that was glycation, which is intrinsic aging. Other mechanisms that induce skin aging are photo aging and oxidative stress, they are part of extrinsic aging, ie due to factors outside our body, our environment, our exposome. UV rays, therefore ultra-violet rays directly impact the MEC of the dermis. Where do you distinguish UVA from UVB?

  • The UVA it is radiation of longer wavelength (315-400nm) which penetrates deeper into the skin. To give a figure, more than half of UVA rays reach the dermis, therefore the second layer of the skin. They will therefore impact the epidermis with its keratinocytes and the dermis with its fibroblasts. On the other hand, UVA rays have a lower energy than UVB rays. They induce indirect damage via reactive oxygen species, which are often abbreviated by ROS, for English reactive oxygen species. I don't know if you've ever heard of free radicals, it's a term that is more popular I believe. Well, free radicals are part of ROS. So, these ROS are extremely reactive and can therefore react with molecules in our body and cause harmful effects in our skin and in particular at the level of the extracellular matrix, the ECM. Indeed, they interfere with the synthesis of collagen in the dermis, which leads to photoaging and therefore to more flabby skin, wrinkles, etc. In addition, these ROS recruit inflammatory cells to the attacked area, and cause redness. UV rays activate metalloproteins which are often abbreviated as MMP for matrix metalloproteinases in English. These metalloproteinases are enzymes which degrade the extracellular matrix including the elastic fibers of the dermis. Thus the dermis becomes less elastic and looser.
  • The UVB, meanwhile, have a shorter wavelength (280 - 315 nm) ie they penetrate less far into the skin. They are 90% absorbed by the epidermis, therefore by the first layer of the skin. They will therefore interact mainly with keratinocytes. You should also know that UVB rays have a higher energy which risks damaging the DNA of certain cells and causing cancer. Generally melanin, which is the skin pigment we talked about in episode 9 about the skin, acts as a natural protection against the sun. It protects keratinocytes and their DNA.

Just a quick bio reminder, our DNA is in the nucleus of our skin cells, so whenever I say skin cells, they still contain our DNA.

  • (UVB continued): In fact, UV rays initiate photooxidation reactions via the ROS which we have just mentioned, therefore the reactive oxygen species. And when their quantity is too great, the skin is no longer able to protect itself from them and our DNA will be damaged.

That was photo aging which induces oxidative stress for the skin. And these harmful effects of the sun vary from one individual to another and cause, among other things, the appearance of wrinkles and sun spots on the skin, of more flabby, looser skin. We have just seen that it goes through two intermediaries in particular: MMPs and ROS. MMP for metaloproteinase and ROS for reactive oxygen species. I found it important to tell you a little about the details of these aggressions because when we talk about active ingredients in the next episodes we can directly say whether their effects are on the reduction of ROS for example or MMPs, etc.

I will not describe all the causes of aging but other extrinsic factors can be smoking, poor nutrition, pollution.

Tobacco would aggravate the effects of UV radiation by inducing MMP which would decrease the collagen content of the extracellular matrix, has tissue sagging, wrinkles.

A diet rich in antioxidants such as vitamin E, which is found in almonds and hazelnuts, or selenium, which is found a lot in fish and shellfish, could help slow down the aging process.

Pollution also accelerates skin aging and ozone, for example, induces free radicals which are harmful to the extracellular matrix.

So to recap skin aging is due to:

  • Intrinsic factors therefore linked to chronological and genetic factors to our genome and
  • To extrinsic factors therefore linked to our environment therefore to our exposome.

Intrinsic factors include the phenomenon of glycation which is a reaction between a sugar and a protein such as collagen and elastin. It produces AGE, advanced glycation end product which alters the functions of these proteins and therefore the resistance and elasticity of the skin.

In the extrinsic factors, there are UV rays which cause oxidative stress. This oxidative stress results in the presence of reactive oxygen species, therefore the ROS, which slow down the production of collagen. UV rays activate metalloproteinases and therefore MMP. These metalloproteinases are enzymes which degrade the extracellular matrix including the elastic fibers of the dermis.

Smoking, a diet low in antioxidants and pollution can also worsen skin aging. And all this results in less elastic, less plump, looser skin, the formation of wrinkles, a less uniform complexion, thinner and drier skin.

I hope you enjoyed this episode and sparked your curiosity about skin aging. This was obviously not an exhaustive list as there are other factors. But don't worry, it's only off for a next episode.

Besides, stay tuned because a new episode will be released next Saturday, in the meantime you can find the notes of these episodes on mastelcosmetics.com in the underside of cosmetics section. Mastel is written MASTEL and is the contraction of my two surnames Magand Castel. You can subscribe to the Podcast Les sous de la beauté today on various Podcast platforms including Spotify, Apple Podcast and Google Podcast. And by the way, if you appreciate this content, I would be very grateful if you take the time to leave me a 5-star review on Apple Podcast, it would help other people find Les Souss de la Cosmétique.

I wish you a great week and see you next Saturday for a special ingredients episode in which we will highlight coenzyme Q10, and guess what it does? She is anti-aging. Bye

Leave a comment

Please note, comments must be approved before they are published

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


A chemist in the cosmetics industry for more than 5 years and a graduate of the Natural Raw Materials in Cosmetics Master's degree from ISIPCA, Julie is an expert in the development of natural cosmetic products.