Disorders of biological rhythms resulting from light pollution - selected physiological aspects of melatonin and vitamin D deficiency

Abstract

The increase in time of exposure to artificial lighting affects physiological processes in animals and humans. Changes in physiological rhythms result mainly from malfunction of the master clock, located in humans in the nucleus suprachiasmaticus of the anterior hypothalamus, and in consequence – from reduction of melatonin amount produced in the pineal gland and secreted into the circulation only in the dark. That hormone regulates a number of body functions, and its deficiency in the conditions of increased exposure to light is associated, among others, with various forms of cancer, including breast cancer. Anticarcinogenic effects of melatonin are due to its antioxidant, immunomodulatory and antiestrogen properties. Reducing the level of melatonin also interferes with the normal rhythm of sleep and wakefulness, making sleep lighter and increasing the risk of depression. Increased exposure to artificial light, with limited time spent under natural, solar light also causes deficit of calcitriol - vitamin D, whose initial synthesis takes place in the skin due to UV radiation. Vitamin D deficiency may lead to cardiovascular disease and atherosclerosis, increased insulin resistance and diabetes, as well as obesity. In the paper, selected aspects of the physiological mechanisms leading to the development of the above disorders.