Obesity is a worldwide epidemic that predisposes individuals to many age-associated diseases, but its exact effects on organ dysfunction are largely unknown. Hair follicles—mini-epithelial organs that grow hair—are miniaturized by aging to cause hair loss through the depletion of hair follicle stem cells (HFSCs). 

Normally, HFSCs self-renew every hair follicle cycle. This is part of the process that allows our hair to continuously grow back. As humans age, HFSCs fail to replenish themselves leading to fewer HFSCs and therefore hair thinning. Although overweight people has higher risk of androgenic alopecia, whether obesity accelerates hair thinning, how and the molecular mechanisms have been largely unknown.

Researchers have uncovered a molecular mechanism behind why obesity can lead to hair thinning

Researchers from Tokyo Medical and Dental University (TMDU) used mouse model experiments to examine how a high-fat diet or genetically induced obesity can affect hair thinning and loss. 

They compared the gene expression in HFSCs between HFD-fed mice and standard diet-fed mice and traced the fate of those HFSCs after their activation. 

They found that those HFSCs in HFD-fed obese mice change their fate into the skin surface corneocytes or sebocytes that secrete sebum upon their activation. Those mice show faster hair loss and smaller hair follicles along with depletion of HFSCs. “Even with HFD feeding in four consecutive days, HFSCs show increased oxidative stress and the signs of epidermal differentiation.

The inflammatory signals in HFSCs strikingly repress Sonic hedgehog signaling that plays a crucial role in hair follicle regeneration in HFSCs.

The researchers confirmed the activation of the Sonic hedgehog signaling pathway in this process can rescue the depletion of HFSCs. This could prevent the hair loss brought on by the high-fat diet.

SOURCE:

Hironobu Morinaga, Yasuaki Mohri, Marina Grachtchouk, Kyosuke Asakawa, Hiroyuki Matsumura, Motohiko Oshima, Naoya Takayama, Tomoki Kato, Yuriko Nishimori, Yuriko Sorimachi, Keiyo Takubo, Takayoshi Suganami, Atsushi Iwama, Yoichiro Iwakura, Andrzej A. Dlugosz, Emi K. Nishimura (June 21, 2022). Obesity accelerates hair thinning by stem cell-centric converging mechanisms. Nature. Retrieved from : https://www.nature.com/articles/s41586-021-03624-x 

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https://www.telegraph.co.uk/content/dam/health-fitness/2018/07/10/TELEMMGLPICT000139727507_trans_NvBQzQNjv4Bq8Asj1eHb3tSpQqwok7bWew_2zTAw3jNyFsrmT3RDi-w.jpeg