The Effect of Vitamin A Supplementation on CD4+ T-cell Secretion in Obese Individuals

Obesity is a chronic disease consisting of the increase in body fat stores. Obesity is an important health concern because of its well known relationships with metabolic and endocrine disorders such as cardiovascular disease, type 2 diabetes, hypertension and immune dysfunction. Low-grade systemic inflammation, confirmed by the increase of inflammatory markers such as C-reactive protein and interleukin-6 has been observed in obesity. CD4+ T-helpers are the most important regulators of immune system. Epidemiological evidence has linked obesity to several (but not all) autoimmune disorders, including inflammatory bowel disease (IBD) and psoriasis .Some sublineages of T- helpers plays core roles in immune dysfunction, and recent evidence demonstrates that an imbalance of T-cell subgroups including Th1, Th2, Th17 and Treg has occurred in obesity. This imbalance is the redirection of the immune response from most often Th2 and Treg like responses to Th1 and Th17 like responses respectively, however the opposite is desired. Vitamin A (VA) or VA-like analogs known as retinoids, are potent hormonal modifiers of type 1 or type 2 responses but a definitive description of their mechanism(s) of action is lacking. High level dietary vitamin A enhances Th2 cytokine production and IgA responses, and is likely to decrease Th1 cytokine production. Retinoic acid inhibits IL-12 production in activated macrophages, and RA pretreatment of macrophages reduces IFNγ and TNF α production and increases IL4 production in antigen primed CD4 T cells. Supplemental treatment with vitamin A or retinoic acid (RA) decreases IFNγ and increases IL5, IL10, and IL4 production.