Vitamin D status and its relation with insulin resistance and VDR-FokI polymorphism in Iranian non-melanoma skin cancer (NMSC) patients: a case-control study

Abstract

Background: Sunlight exposure, the main source of endogenous vitamin D synthesis, may increase the risk of non-melanoma skin cancer (NMSC) development. Vitamin D receptor (VDR) polymorphisms are associated with 25(OH)D levels, cancer development and insulin resistance. This study was aimed to examine the associations among vitamin D status, VDR FokI polymorphism, insulin resistance and NMSC. Methods: This case-control study included 73 diagnosed cases of NMSC and 72 healthy controls from dermatology clinics at Razi Hospital, Tehran, Iran. A questionnaire was used to assess sunlight exposure. The extracted DNA from whole blood samples were genotyped. Fasting serum 25-hydroxyvitaminD (25(OH)D)), lipid profile, glucose, and insulin were measured. To evaluate insulin resistance, HOMA-IR formula was used. Results: We found a significant higher duration of cumulative sunlight exposure in cases compared with controls (p<0.001). However, 25(OH)D concentrations were not significantly different between cases and controls (30±15 vs. 29±15 ng/mL, p=0.78). Higher levels of insulin (p = 0.004) and HOMA-IR score (p= 0.019) were observed in Ff and ff genotype of FokI. We did not observe any significant increased risk of NMSC due to f allele, as compared with FF (OR =2.33, 95% CI 0.81-6.75, p=0.12). The components of lipid profile, fasting serum glucose, iPTH and anthropometric measures did not differ significantly across VDR genotypes. Conclusion: In conclusion, sunlight exposure was associated with NMSC risk. VDR FokI polymorphisms appears to influence insulin resistance in the NMSC patients. Keywords: sun exposure; non-melanoma skin cancer; polymorphisms; insulin resistance