It’s widely known that being overweight is associated with the development of a variety of illnesses in people. Diabetes, heart disease, and other diseases are prevalent in obese people. However, it’s still not evident how the body’s organs get especially specially deteriorated and lose function due to lifelong obesity. In a new article published in Nature, a team comprising researchers of Tokyo Medical and Dental University (TMDU) employed mouse models studies to evaluate how a high-fat diet and genetically-induced obesity could cause hair loss and thinning. The researchers found that obesity may result in the depletion of hair follicles stem cells (HFSCs) by the induction of particular inflammatory signals that can block hair follicles from regeneration and result in the loss of hair follicles.

In normal circumstances, HFSCs self-renew at every cycle of the hair follicle. This is a process that allows hair to regrow continuously. As we age, HFSCs cease to replenish themselves, resulting in less number of HFSCs, which leads to thinning of hair. While overweight individuals have a higher chance of suffering from androgenic alopecia but whether obesity will accelerate thinning of hair, how and what are the molecular mechanisms are still mostly unknown. This TMDU group aims to tackle those questions and identifies a few possible mechanisms.

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As explained by Hironobu Morinaga, the lead author, high-fat diets will accelerate thinning of hair by depleting hair follicles stem cells (HFSCs) which replenish mature cells for hair growth, particularly in older mice. Their study compares the expression of genes in HFSCs between mice that were fed a high fat diet and mice that were fed on a standard diet, and examined the fate of the HFSCs following their activation. They observed that HFSCs in obese mice fed with HFD alter their fate to sebocytes or skin surface corneocytes which secrete sebum after their activation. The mice exhibit smaller hair follicles and quicker hair loss, as well as depletion of the HFSCs.In only four days, researchers could observe changes in the skin and the hair in mice that were fed with the high-fat diet as well as evidence of an increase in levels of oxidative stress. While overweight individuals have higher risks of hair loss, whether obesity can result in hair thinning acceleration and what the molecular mechanisms are mostly not understood. Researchers have identified a few of the possible mechanisms.

According to Emi K. Nishimura who is the senior author, the gene expression levels in HFSCs from mice fed with high fat revealed the activation of inflammatory cytokine responses and signals within the HFSCs. The inflammation signals that are present in HFSCs remarkably repress Sonic hedgehog signaling which plays an important role in hair follicle regeneration within HFSCs.

Researchers have confirmed that the activated Sonic hedgehog’s pathway of signalling during this process could help in rescuing the HFSCs depletion. This can help prevent hair loss that is caused through the consumption of a high-fat diet.

This research provides fascinating new insight into the changes in cellular fate and the tissue dysfunction that may occur in the aftermath of a high-fat diet, or genetically-induced obesity. This may provide a path for the future prevention and treatment of hair loss and also for the understanding of the causes of obesity-related illnesses.

Nutritionists have suggested that fast weight loss and stress could be the main causes of hair loss, however, researchers now indicate that it’s due to the high fat levels.

These results collectively show that the inflammatory signalling of stem cells caused by obesity effectively suppress organ regeneration signals, which accelerates the miniaturization process of mini-organs and also suggests the importance of regular prevention of dysfunction of organs.