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Titre du document / Document title

Administration of capsaicin and isoflavone promotes hair growth by increasing insulin-like growth factor-I production in mice and in humans with alopecia

Auteur(s) / Author(s)

HARADA Naoaki ; OKAJIMA Kenji ; ARAI Masatoku ; KURIHARA Hiroki ; NAKAGATA Naomi ;

Résumé / Abstract

Objective: Insulin-like growth factor-I (IGF-I) plays an important role in hair growth. Capsaicin activates vanilloid receptor-1, thereby increasing the release of calcitonin gene-related peptide (CGRP) from sensory neurons, and CGRP has been shown to increase IGF-I production. We recently reported that isoflavone, a phytoestrogen, increases production of CGRP by increasing its transcription in sensory neurons. These observations raise the possibility that administration of capsaicin and isoflavone might promote hair growth by increasing IGF-I production. In the present study, we examined this possibility in mice and humans with alopecia. Design: Dermal IGF-I levels, immunohistochemical expression of IGF-I in the skin and hair regrowth were examined after capsaicin and isoflavone administration to wild-type (WT) mice and CGRP-knockout mice. Plasma levels of IGF-I and promotion of hair growth were evaluated in 48 volunteers with alopecia after administration of capsaicin and isoflavone for 5 months. Results: Subcutaneous administration of capsaicin significantly increased dermal IGF-I levels at 30 min after administration in WT mice (p < 0.01), but not in CGRP-knockout mice. Dermal levels of IGF-I were significantly higher in WT mice administered capsaicin and isoflavone for 4 wks than in those administered capsaicin alone for 4 wks (p < 0.01) and in those administered neither of them (p < 0.01). Immunohistochemical expression of IGF-I at dermal papillae in hair follicles was increased in WT mice administered capsaicin and isoflavone and in those administered capsaicin alone at 4 wks. Hair regrowth was clearly more accelerated in WT mice administered capsaicin and isoflavone for 4 wks than in those administered capsaicin alone for 4 wks and in those administered neither of them. Plasma levels of IGF-I were significantly increased from baseline levels in 31 volunteers with alopecia at 5 months after oral administration of capsaicin (6 mg/day) and isoflavone (75 mg/day) (p< 0.01), while they were not increased in 17 volunteers with alopecia administered placebo. The number of volunteers with alopecia who showed promotion of hair growth at 5 months after administration was significantly higher among volunteers administered capsaicin and isoflavone (20/31: 64.5%) than among those administered placebo (2/17: 11.8%) (p < 0.01). Conclusions: These observations strongly suggested that combined administration of capsaicin and isoflavone might increase IGF-I production in hair follicles in the skin, thereby promoting hair growth. Such effects of capsaicin and isoflavone might be mediated by sensory neuron activation in the skin.

Revue / Journal Title

Growth hormone & IGF research    ISSN  1096-6374 

Source / Source

2007, vol. 17, no5, pp. 408-415 [8 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Kidlington, ROYAUME-UNI  (1998) (Revue)

Mots-clés d'auteur / Author Keywords

Sensory neurons

;

Calcitonin gene-related peptide

;

Capsaicin

;

Isoflavone

;

Hair growth

;

Insulin-like growth factor-I

;

Localisation / Location

INIST-CNRS, Cote INIST : 27274, 35400016245509.0060

Nº notice refdoc (ud4) : 19062253



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