Vitamin D, calcium homeostasis and aging

Abstract

Osteoporosis is characterized by low bone mass and microarchitecture deterioration of bone tissue, leading to enhanced bone fragility and consequent increase in fracture risk. Evidence is accumulating for an important role of calcium deficiency as the process of aging is associated with disturbed calcium balance. Vitamin D is the principal factor that maintains calcium homeostasis. Increasing evidence indicates that the reason for disturbed calcium balance with age is inadequate vitamin D levels in the elderly. In this article, an overview of our current understanding of vitamin D, its metabolism, and mechanisms involved in vitamin D-mediated maintenance of calcium homeostasis is presented. In addition, mechanisms involved in age-related dysregulation of 1,25(OH)₂D₃ action, recommended daily doses of vitamin D and calcium, and the use of vitamin D analogs for the treatment of osteoporosis (which remains controversial) are reviewed. Elucidation of the molecular pathways of vitamin D action and modifications that occur with aging will be an active area of future research that has the potential to reveal new therapeutic strategies to maintain calcium balance.

Osteoporosis: Vitamin D and calcium balance

A greater understanding of how vitamin D regulates calcium would help the development of drugs to maintain bone health during aging. Age-related deterioration of bones leads to osteoporosis, and vitamin D deficiency in elderly people contributes to this process by reducing absorption of calcium. Sylvia Christakos and colleagues from the Rutgers, The State University of New Jersey, New Jersey Medical School, USA, have reviewed the role of vitamin D in maintaining calcium levels, and consider the potential of correcting vitamin D deficiency to treat osteoporosis. Treatment with vitamin D reduces the risk of fractures, and analogues of vitamin D are beneficial in osteoporosis, although this treatment is controversial. The authors conclude that further insight into the genetic and molecular mechanisms of vitamin D-mediated calcium regulation will enable the development of drugs that selectively target these mechanisms.

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