Vitamins as Hormones

Abstract

Vitamins A and D are the first group of substances that have been reported to exhibit properties of skin hormones, such as organized metabolism, activation, inactivation, and elimination in specialized cells of the tissue, exertion of biological activity, and release in the circulation. Vitamin A and its two important metabolites, retinaldehyde and retinoic acids, are fat-soluble unsaturated isoprenoids necessary for growth, differentiation and maintenance of epithelial tissues, and also for reproduction. In a reversible process, vitamin A is oxidized IN VIVO to give retinaldehyde, which is important for vision. The dramatic effects of vitamin A analogues on embryogenesis have been studied by animal experiments; the clinical malformation pattern in humans is known. Retinoic acids are major oxidative metabolites of vitamin A and can substitute for it in vitamin A-deficient animals in growth promotion and epithelial differentiation. Natural vitamin A metabolites are vitamins, because vitamin A is not synthesized in the body and must be derived from carotenoids in the diet. On the other hand, retinoids are also hormones - with intracrine activity - because retinol is transformed in the cells into molecules that bind to and activate specific nuclear receptors, exhibit their function, and are subsequently inactivated. The mechanisms of action of natural vitamin A metabolites on human skin are based on the time- and dose-dependent influence of morphogenesis, epithelial cell proliferation and differentiation, epithelial and mesenchymal synthetic performance, immune modulation, stimulation of angiogenesis and inhibition of carcinogenesis. As drugs, vitamin A and its natural metabolites have been approved for the topical and systemic treatment of mild to moderate and severe, recalcitrant acne, photoaging and biologic skin aging, acute promyelocytic leukaemia and Kaposi's sarcoma. On the other hand, the critical importance of the skin for the human body's vitamin D endocrine system is documented by the fact that the skin is both the site of vitamin D (3)- and 1,25-dihydroxyvitamin D (3) [1, 25(OH) (2)D (3)]-synthesis and a target organ for 1,25(OH) (2)D (3). 1,25(OH) (2)D (3) is not only essential for mineral homeostasis and bone integrity, but also for numerous further physiologic functions including regulation of growth and differentiation in a broad variety of normal and malignant tissues, including cells derived from prostate, breast and bone. In keratinocytes and other cell types, 1,25(OH) (2)D (3) regulates growth and differentiation. Consequently, vitamin D analogues have been introduced for the treatment of the hyperproliferative skin disease psoriasis. Other newly detected functions of vitamin D analogues include profound effects on the immune system as well as protection against cancer and other diseases, including autoimmune and infectious diseases, in various tissues. Current investigation of the biological effects of vitamin D analogues are likely to lead to new therapeutic applications that, besides cancer pr...

Folate receptor overexpression is associated with poor outcome in breast cancer

“…It would not be surprising to learn that folate could modulate gene expression also via association with a nuclear form of the folate receptor. [20][21][22][23] Several lines of evidence suggest that the high-affinity folate receptor may contribute to the malignant phenotype. 24 First, the known biologic function of the folate receptor is to supply folates for the biosynthesis of nucleotide bases and the methylation of isoprenylated proteins such as ras.…”

Psoriasis and Nutrition Interactions

“…Retinoid reseptörler aracılığıyla retinoidler keratinositlerin hiperproliferasyonunu baskılarken, termal farklılaşmayı uyarabilmektedir (19). Psoriasisli hastaların serum A vitamini düzeylerini irdeleyen çalışmaların sonuçları ise çelişkilidir.…”

“…Ancak psoriatik derideki A vitamini metabolizması anormal olduğu saptanmıştır. Topikal ve sistemik A vitamini analoglarının etkinlikleri çok iyi bilinmesine rağmen saçlarının dökülmesi, hipertriglisedimi, hiperostozis, doku kalsifikasyonu, kserosiz ve teratojenik yan etkileri geniş çapta kullanılmasını engellemektedir (19). Psoriasiste oksidatif stresin oluşması ve serbest radikallerin artışı inflamatuvar mekanizmaların harekete geçirmektedir.…”

“…İn vitro çalışmalarda 1,25 (OH)2 D3 vitamininin gereksinimden yüksek dozlarda kullanılması, keratinositlerin proliferasyonunu inhibe ettiği tespit edilmiştir (19). Orta ve şiddetli düzeyde 17 psoriasisli hastaya başlangıç dozu olarak 0,25 µg/gün D vitamini verilmiş ve üriner kalsiyum düzeylerinin normal kaldığı sürece günlük doz arttırılmıştır.…”

The relationship of diet and acne

“…29 Vitamins A and D are the first group of nutrients that has been reported to exhibit properties of skin hormones. 30 In that property they control metabolism, activation, inactivation, and elimination of specialized skin cell. Many retinoids are also hormones since they bind to and activate specific nuclear receptors, affect their function, and are subsequently inactivated.…”