Vitamin D and Metabolic Syndrome

Vitamin DVitamin D is a steroid whose primary function is maintaining serum calcium and phosphorus levels to ensure bone homeostasis. Overall, there are very high levels of inadequate vitamin DVitamin D intake worldwide. Risk groups, including older people, pregnant and lactating women, individuals with osteoporosis, chronic renal failure, malabsorption syndromes, and obesity should be prioritized for screening vitamin DVitamin D status. Vitamin DVitamin D deficiency has been observed in individuals with metabolic syndromeMetabolic syndrome (MetS). The pathophysiological changes caused by MetS can interfere with the metabolic pathway of activation or the bioavailability of vitamin DVitamin D, thus triggering vitamin DVitamin D deficiency. Different pathophysiologic mechanisms are proposed to underlie the effect of vitamin DVitamin D on MetS components. Serum 25(OH)D concentration has been negatively associated with MetS components, such as fasting blood glucose, blood pressure, and triglycerides. Among the genetic factors underlying the hereditary risk of MetS, some involve polymorphisms (SNPs) in genes associated with vitamin DVitamin D pathways. Studies have evidenced the association between VDR SNPs with MetS risk and MetS-related components, especially the lipidLipid profile. Also, a few studies have explored the relationship between the main GC gene variants that encode Vitamin DVitamin D binding protein (VDBP) and MetS, revealing heterogeneity in results among populations. Mendelian randomization studies based on a large-scale genome-wide association study (GWAS)Genome-wide association studies (GWAS) did not reveal any causal association between genetically decreased vitamin DVitamin D and increased risk of MetS or its metabolic traits. Several studies have also already demonstrated associations between circulating microRNAMicro RNA and aspects related to MetS, mainly glucose homeostasis and insulin resistanceInsulin resistance. Vitamin DVitamin D can regulate the transcription of miRNA genes through its active form—1,25(OH)2D—binding the VDR transcription factor, and miRNA maturation through regulating genes involved in miRNA processing or miRNA stability. Taken together, the findings on the interrelationship between vitamin DVitamin D and metabolic disordersMetabolic disorder that occur in MetS components may be related to vitamin DVitamin D deficiency and also partly to genetic and epigeneticEpigenetic factors which may act on the pathophysiological mechanisms of MetS related to the interaction with the environment and lifestyle factors.