Sebum
Updated January 14, 2023
what is the biochemical connection between sebum and yeast?
Sebum, an oily substance produced by the sebaceous glands, can provide a nutrient-rich environment for the growth of yeast, such as Malassezia. Yeast, specifically Malassezia, is known to feed on sebum and can cause skin conditions such as dandruff and seborrheic dermatitis when overproduced. The overgrowth of yeast can also lead to an increase in inflammation and irritation in the skin.
what is the composition of sebum?
Sebum is an oily substance produced by the sebaceous glands. The exact composition of sebum can vary depending on factors such as age, gender, and hormonal levels. However, in general, sebum is composed of:
triglycerides (about 40-50%)
free fatty acids (about 20-30%)
wax esters (about 15-20%)
squalene (about 12-15%)
cholesterol (about 3-4%)
cholesteryl esters (about 1-2%)
other lipids such as phospholipids and glycolipids (about 1-2%)
Sebum also contains small amounts of other substances such as carotenoids, steroids and pro-inflammatory mediators.
what are the pro-inflammatory medicators in sebum?
Sebum contains small amounts of pro-inflammatory mediators, which are molecules that promote inflammation in the body. Some examples of pro-inflammatory mediators that have been identified in sebum include:
Prostaglandins: These are hormone-like molecules that play a role in the inflammatory response. They are derived from fatty acids and are involved in the regulation of pain, fever, and inflammation.
Leukotrienes: These are molecules that are also derived from fatty acids and play a role in the inflammatory response. They are involved in the recruitment of immune cells to the site of inflammation.
Cytokines: These are small proteins that are produced by cells of the immune system and play a role in the inflammatory response. Examples of cytokines that have been identified in sebum include interleukin-1 (IL-1) and tumor necrosis factor (TNF).
Lipoxygenase: This is an enzyme that catalyzes the formation of leukotrienes, which are inflammatory mediators.
Lipid peroxidation products: These are molecules that are formed when lipids, such as those found in sebum, are damaged by reactive oxygen species. They can contribute to inflammation by promoting the formation of inflammatory mediators and by causing tissue damage.
It’s worth noting that these pro-inflammatory mediators in sebum can act as a double-edged sword, as they can also play a role in the regulation of the immune response and have beneficial effects, such as fighting off bacteria and other pathogens.
how are the pro-inflammatory mediators in sebum generated? which cells?
Pro-inflammatory mediators in sebum are generated by a variety of cells within the sebaceous gland and surrounding skin. These include:
Sebocytes: These are the cells that produce sebum. They contain enzymes such as cyclooxygenase and lipoxygenase, which convert fatty acids into pro-inflammatory mediators such as prostaglandins and leukotrienes.
Immune cells: Inflammation can occur in the sebaceous gland, and immune cells such as macrophages, neutrophils, and lymphocytes infiltrate the area and release pro-inflammatory mediators such as cytokines (IL-1, TNF) and chemokines.
Keratinocytes: These are the cells that make up the majority of the epidermis. They have been known to produce cytokines such as IL-1 and TNF in response to inflammation or infection in the surrounding skin, which can contribute to the pro-inflammatory environment in the sebaceous gland.
Microorganisms: The presence of certain microorganisms in the sebaceous gland, such as Malassezia yeast, can promote inflammation by releasing enzymes, lipases, and other molecules that can cause tissue damage and generate pro-inflammatory mediators.
It’s worth noting that the presence of these pro-inflammatory mediators in sebum is not necessarily a negative thing, as they can also play a role in the regulation of the immune response and have beneficial effects such as fighting off bacteria and other pathogens. An overproduction or an imbalance of these mediators can lead to skin conditions like acne and seborrheic dermatitis.
how does maassezia metabolize sebum
Malassezia is a type of yeast that is naturally present on the skin and feeds on sebum, an oily substance produced by the sebaceous glands. The specific metabolic pathways used by Malassezia to metabolize sebum are not well understood, but it is known that the yeast converts the triglycerides and fatty acids found in sebum into various by-products.
Malassezia has been found to produce lipases, which are enzymes that break down triglycerides into fatty acids and glycerol. These fatty acids can then be further metabolized by the yeast into a variety of compounds, including fatty alcohols, aldehydes, and dicarboxylic acids.
Malassezia also has the ability to convert the fatty acids into short-chain fatty acids (SCFA) and free fatty acids (FFA). These molecules can act as pro-inflammatory mediators and contribute to the development of skin conditions such as dandruff and seborrheic dermatitis.
It’s worth noting that these metabolic pathways of Malassezia are not fully understood, and more research is needed to fully understand how the yeast metabolize sebum and how these by-products contribute to skin conditions.
