Ricerc@Sapienza

Much has been published in scientific literature about the positive effects of adeguate levels of vitamin D and its lower levels have been linked to a number of chronic diseases, such as osteoporosis, diabetes and cardiovascular disease. Much is known about factors influencing vitamin D concentration, such as skin type, BMI, season (sunlight exposure) and vitamin D ingested from foods or supplements, but for others like smoking, knowledge is just emerging. Indeed, recently studies investigated the effect of vitamin D and smoking on healthy people, lung function, CODP, children with asthma, bone health and dermatological diseases. Thus, vitamin D deficiency was found to be associated with lower lung function and with more rapid lung function decline in smokers over 20 years in a longitudinal cohort of elderly men. In patients with COPD and Metabolic Syndrome, a negative association was found between smoking and vitamin D and a novel mechanism was proposed via a direct effect of smoking for both insulin resistance and COPD development.
Surprisingly, the knowledge on the effects of smoking on vitamin D levels in patients with colorectal polyps and CRC is very scarce, nevertheless smoking is a risk factor for both. To our knowledge, only one article has been published on this topic, but it refers only to Hispanic people.
Generally, most of the recent studies report lower serum vitamin D in current smokers than in never smokers. However, since smokers tend to smoke outside, due to indoor smoking ban, they could be more exposed to sunlight. Evaluating the interplay among vitamin D, smoking and colorectal polyps is of great importance due to the high prevalence both of ipovitaminosis, smoking and CRC worldwide. If smoking results to be an effect modifier of the association between vitamin D level and colorectal polyps, its implications would be serious because usually people who undergo colonoscopy are middle aged or elderly whose vitamin D concentrations are lower, who often have comorbidities such as diabetes and who are not physically active.
IDO has been shown to act as immune checkpoint involved in peripheral immune tolerance since it is able to inhibit T-cells proliferation by starving them from tryptophan to sensitize T-cells to apoptosis. IDO expression has been associated with a worse outcome in several cancer types, but few studies also reported a positive prognostic effect. For CRC, a higher kynurenine/tryptophan ratio was reported to be associated with a higher presence of metastasis and a shorter survival. IDO expression by tumor cells can be part of genetic changes involved in malignant transformation and due to the large number of carcinogens that may bind to DNA and form adducts, tobacco may play a role, but nothing is known about its effect on IDO. Investigating IDO activity and its interaction with smoking, if any, might shed some light into its possible implication as a biomarker of peripheral immune tolerance or prognosis.
Clarifing the effects of smoking and on vitamin D, especially in patients with polyps, can be very important for prevention. Screening for CRC and colonoscopy constitutes a great goal which could further give the opportunity to prevent severe vitamin D ipovitaminosis and promote the quitting of smoking, both of which could have repercussions also on many other diseases. Patients with vitamin D insufficiency could be recommended to increase their values (either by sun exposure, diet or supplements), patients who smoke could be recommend to quit and patients with both conditions could be informed about their risk factors and their interaction, if any.
Motivation is essential to quit smoking and medical examinations, like CRC screening, colonoscopy, vitamin D and IDO activity assessment, may greatly contribute not only to quit smoking but also to avoid malignant evolution of colic lesions.