Abstract

The role of Vitamin D related to sunlight, has always been recognized in the past fundamental for the reduction of rickets in children. The 1,25-dihydroxy-vitamin D (1,25-OH2)D is the steroid hormone, involved in the regulation of mineral homeostasis and bone metabolism. Vitamin D is synthesized in the skin, due to the effect of ultraviolet radiation (cholecalciferol) and is also introduced with the diet (ergocalciferol), but minimally. The biological effects of 1,25 (OH2) D are manifested thanks to the binding with the Vitamin D receptor (VDR) which belongs to the family of nuclear super-receptors and are expressed in numerous cell types and tissues. The 1,25(OH2)D, like parathyroid hormone (PTH), represents the mechanism which induces bone resorption. In recent years the beneficial effects of Vitamin D it also known in cancer prevention and treatment in several epidemiological studies. In laboratory studies, Vitamin D demonstrate a potential and important role in the tumorigenesis process as the cells regulation and proliferation or apoptosis. Also, in the immunomodulation process seem that the Vitamin D can be involved, both for innate and adaptive immune system. A possible association between Vitamin D deficiency and autoimmune disease (i.e. psoriasis, type I diabetes, multiple sclerosis, etc) has been published. The recent pandemic COVID-19 infection around the world seems that could be influenced by multiple factors (as age, comorbidity, obesity, diabetes, etc.), one of that, seems related to the deficiency of Vitamin D. Vitamin D deficiency is associate with an increasing susceptibility of infection diseases as upper respiratory tract producing antimicrobial peptides that might help to reduce the inflammatory response to COVID-19 infection. This review critically examines the current information on the role of Vitamin D in humans.

Keywords: Vitamin D; Vitamin D Receptors (VDR); 1-25-Dihidroxyvitamin D; Cholecalciferol; Rickets; Parathyroid Hormone (PTH); Bone Metabolism; Inflammation; Immune System; Autoimmune Disorders; COVID-19

References

1. Holick MF., et al. “Evolution, treatment and prevention of vitamin D deficiency: an endocrine society clinical practice guideline”. The Journal of Clinical Endocrinology and Metabolism 7 (2011): 1911-1930.
2. Nipith Charonngam and Michael F Holick. “Immunologic effects of vitamin D on human health and diseases”. Nutrients 12 (2020): 2097.
3. Holick MF. “Vitamin D deficiency”. The New England Journal of Medicine 357 (2007): 266-281.
4. Haussler MR., et al. “The vitamin D hormone and its nuclear receptors: Molecular action and disease state”. Journal of Endocrinology 154 (1997): 557-573.
5. Holick M and Gordon CM. “Patients Guide to Vitamin D deficiency”. The Journal of Clinical Endocrinology and Metabolism 7 (2011): 1911-1930.
6. Heanej RP. “Functional indices of vitamin D status and ramifications of vitamin D deficiency”. The American Journal of Clinical Nutrition 6 (2004): 1706-1709.
7. Lips P., et al. “The prevalence of Vitamin D inadequacy among women with osteoporosis: an international epidemiological investigation”. Journal of Internal Medicine 260 (2006): 245-254.
8. Maeda SS., et al. “The effects of sun exposure on 25- hydroxyvitamin D concentrations in young healthy subjects living in the city of San Paulo, Brazil”. Brazilian Journal of Medical and Biological Research 40 (2007): 1653-1659.
9. Loeker AC., et al. “Serum 25-hydroxyvitamin D status of the US population: 1988-1994 compared to 2000-2004”. The American Journal of Clinical Nutrition 88 (2008): 1519-1527.
10. Matsouka LY., et al. “Sunscreens suppress cutaneous vitamin D3 synthesis”. The Journal of Clinical Endocrinology and Metabolism 64 (1987): 1165-1168.
11. Clemens TL., et al. “Increased skin pigment reduces the capacity of skin to synthesis of vitamin D3”. Lancet 1 (1982): 74-76.
12. Wortsman J., et al. “Decreased bioavailability of vitamina D in obesity”. The American Journal of Clinical Nutrition 72 (2000): 690-963.
13. Holick MF., et al. “Prevalence of vitamin D inadequacy among post menopausal north American women receiving osteoporosis therapy”. The Journal of Clinical Endocrinology and Metabolism 90 (2005): 321-322.
14. Holick M-F., et al. “High prevalence of vitamin D inadequacy and implications for health”. Mayo Clinic Proceedings 81 (2006): 357-373.
15. Sizar O., et al. “In: Stat Pearls [Internet]. Treasure Island (FL): Stat Pearls Publishing (2021): 30335299.
16. Kivtj S., et al. “Vitamin D and autoimmune thyroid diseases”. Cellular and Molecular Immunology 8 (2011): 2-43.
17. Metvalley KA., et al. “Vitamin D status in children and adolescents with autoimmune thyroiditis”. Journal of Endocrinological Investigation 39 (2016): 793-797.
18. Chung C., et al. “Vitamin D-Cathelicidin Axis: at the Crossroads between Protective Immunity and Pathological Inflammation during Infection”. Immune New 2 (2020).
19. Piemonti L., et al. “Vitamina D3 affects differentiation, maturation, and function of human monocytes-derived dendritic cells”. Journal of Immunology 164 (2000): 4443-4451.
20. Jeffery LE., et al. “1,25-dihidroxyvitaminD3 and IL-2 combine to inhibit T-cells production of inflammatory cytokines and promote development of regulatory T-cells expressing CTLA-4 and FoxP”. Journal of Immunology 153 (2009): 5458-5467.
21. Mitchell Fiona Lancet Diabetes Endocrinol. “Vitamin D and COVID-19: do deficient risk a poorer outcome?” The Lancet Diabetes and Endocrinology 7 (2020): 570.