Role of Fat-Soluble Vitamins A and D in the Pathogenesis of Influenza: A New Perspective

Abstract

Reduced exposure to solar radiation, leading to a de�ciency of vitamin D and hence impaired innate immunity, has been suggested as a trigger for in�uen�a viral replication and as an explanation of seasonal in�uen�a. Although this hypothesis accounts for many unexplained facts about the epidemiology of in�uen�a, gaps remain in understanding the pathogenesis and manifestations of the disease. Several observations suggest a role for vitamin A compounds (retinoids) in the disease. is paper presents a new model of the etiopathogenesis of in�uen�a, suggesting that host resistance and susceptibility depend importantly on the ratio of vitamin D to vitamin A activity. Retinoid concentrations within normal physiological limits appear to inhibit in�uen�a pathogenesis whereas higher background concentrations (i.e., very low vitamin D : A ratios) increase the risk of severe complications of the disease. ere is also evidence that in�uen�a-induced or preexisting liver disease, diabetes, and obesity worsen the severity of infection, possibly via liver dysfunction and alterations in retinoid metabolism. e model could be tested by determining the presence of retinoids in the secretions of patients with in�uen�a and by studies of retinoid pro�les in patients and controls. Potential strategies for prevention and treatment are discussed.

Role of vitamin D in pathogenesis and severity of COVID-19 infection

“…The active form of vitamin D, also known as calcitriol (1,25-dihydroxycholecalciferol) is a steroid hormone that acts as an immune system modulator by down-regulating the expression of inflammatory cytokines and enhancing macrophage function [6]. Furthermore, it induces the expression of potent antimicrobial peptides (AMPs), which are present in natural killer cells, monocytes, neutrophils, as well as the epithelial cells lining the respiratory tract 13 . Vitamin D triggers development of suppressive regulatory T cells and inhibits development of pro-inflammatory Th17 cells 14 .…”

“…Moreover, the pro-inflammatory peptides of the adaptive immune system are modulated by vitamin D, particularly those involved in acute inflammation cytokine storms 9,11,13,15 . It has also been found that metabolites of vitamin D induce other innate antimicrobial effector mechanisms, including autophagy and synthesis of reactive oxygen and nitrogen intermediates 11 .…”

Therapeutic Potential of Nutraceuticals and Dietary Supplements in the Prevention of Viral Diseases: A Review

“…Vitamin D is a steroid hormone and an immune system modulator, which lowers the expression of inflammatory cytokines in addition to increasing the macrophage activity. It also promotes the expression of antimicrobial peptides (AMPs) that are present in natural killer cells, monocytes, neutrophils, and epithelial cells lining the respiratory tract (23). Vitamin D acts both by suppressing and defending against infection by increasing anti-pathogen peptides.…”

Role of ACE 2 and Vitamin D: The Two Players in Global Fight against COVID-19 Pandemic

“…73 It further blocks the production of T-helper 17 cells (proinflammatory) and induces the production of suppressive regulatory T cells. 74 Furthermore, the proinflammatory peptides associated with the adaptive immune system, especially the ones involved in acute inflammatory cytokine storm, are regulated by vitamin D. 70,73,75 Numerous epidemiological studies have demonstrated the potential link between deficiency of vitamin D in the body and enhanced risks of respiratory tract infections. 76,77 Also, many studies reveal the protective role of vitamin D supplementation against virus mediated infections.…”