The role of Vitamin D deficiency in the onset of AF was suggested because of several potential mechanisms described previously.16 Vitamin D regulates inflammatory responses and up-regulates the expression of anti-inflammatory cytokines, such as IL-10, according to in vitro experiments.17 Also, Vitamin D regulates activity of the renin–angiotensin–aldosterone system (RAAS). The gene discussed is REN; the disease is vitamin D deficiency.