High consumption of omega-3s oil caused baldness… in mice

sarahjay1 (69)memberin Popular STEM • 2 years ago

Researchers from the University of Iowa accidentally noticed that mice whose diet is rich in fish oil lose hair.

The in-depth study showed that the culprit is a protein that binds fatty acids and is expressed in skin macrophages.

The protein sets off a cascade of reactions that causes other macrophages to accumulate around the hair follicles, causing inflammation and hair loss.

Fats that we consume with food are saturated and unsaturated.

It depends on what fatty acids they contain: omega-3 and omega-6 fatty acids are unsaturated, and palmitic acid, which is rich in meat and dairy products, is saturated.

Saturated fats are thought to promote inflammation and are often advised to cut down on people with obesity and heart disease.

Omega-3 fatty acids, on the other hand, are considered beneficial and should prevent inflammation.

Fish oil containing omega-3s is often advised to drink for healthy skin, hair and nails, although there is no serious scientific justification for this.

The FDA approves no more than 5% of total daily fat intake for omega-3s.

However, other studies do not support the benefits of omega-3 fatty acids, and a meta-analysis casts doubt on the harms of saturated fats.

Understanding how the metabolism of various fats influences cellular function and inflammatory responses in vivo may help resolve this controversy.

THE STUDY
An international team led by professor Bing Li has previously studied how high-fat diets (45%) affect obesity-related breast tumor growth.

The first diet was high in fish oil, the second diet was rich in cocoa butter (high in saturated fat), and the third was the control diet, which contained only 5% fat.

The scientists did not plan to study the effect of dietary fats on skin and hair.

However, they noticed that mice on a diet rich in omega-3 fatty acids lost more than 20% of hair.

Now the team set out to find out exactly how high-fat diets affect skin health.

Since only female mice participated in previous studies, the scientists put male mice on the same diets, and they also lost hair, although not to the same extent as females.

After treating mice with antibiotics, the authors were convinced that it was not the intestinal bacteria - the therapy did not affect weight gain and hair loss.

(Jiaqing Hao et al. / Cell Reports, 2022 https://bit.ly/3Wt3xaW)

THE REASON
The scientists performed skin histology and mass cytometry.

They found that a diet high in omega-3 promotes the accumulation of atypical infiltrates of langerin-negative myeloid macrophages around hair follicles in the dermis.

At the same time, such macrophages did not accumulate in the epidermis, spleen, lymph nodes, and blood.

These macrophages that surrounded the follicles expressed the pro-inflammatory protein TNF-α.

When the scientists gave the mice anti-TNF-α antibodies, the shedding stopped and within a month the hair grew back.

The researchers then sequenced the RNA of cells from mouse skin samples and found that 27 genes were upregulated in the cells of mice fed an omega-3 diet.

Several of these genes code for the interleukin-36 (IL-36) family of immune proteins that may play a role in inflammation and dermatological diseases.

When scientists exposed IL-36 to macrophages in vitro, they began to produce more TNF-α.

Thus, the authors concluded that the omega-3/IL-36 axis triggers increased expression of TNF-α and leads to hair loss in mice.

The last key player was a protein that binds fatty acids.

Fats do not dissolve in water, and in order to facilitate the transfer of fatty acids throughout the body, proteins that bind fatty acids - FABP are expressed in different tissues.

Skin, for example, expresses E-FABP, while adipose tissue expresses A-FABP.

Previously, the same team of scientists showed that E-FABP is also expressed in immune cells.

The new work found that E-FABP, expressed in skin macrophages, induces the production of ROS and the entire chain of reactions.

This eventually leads to hair loss.

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