Interaction Of VDR Gene Polymorphisms And Dietary Lipid Intakes On Metabolic Syndrome

Background: The prevalence of metabolic syndrome(MS) is rapidly increasing worldwidely, which bring a heavy burden to global health and economy. MS is a typical complex disease that is caused by interactions between many genes and a variety of environmental factors. However, few researches focusing on the interactions were conducted.Objective: This study was designed to explore the relationship between MS and some potential factors like VDR gene and dietary lipids in rural Ningxia, and the possible effect of the interaction between VDR gene and dietary lipids on MS.Methods: This study was a case-control study based on a cross-sectional study, which included 177 patients and 237 controls according to definition of IDF(2005)on MS and exclusion criteria. The study content mainly included questionnaire interview, anthropometric measurements, blood pressure measurement, blood biochemistry analyses, plasma phospholipid fatty acid determination, dietary survey and genotyping of VDR gene. The interaction of the VDR gene and dietary lipids was analyzed by using Generalized Multifactor Dimensionality Reduction(GMDR).Results: The distribution of general demographic characteristics is at the equilibrium in cases and controls, except for the age. The anthropometric measurements and blood biochemistry analyses were significantly different between cases and controls(P≤0.05), indicating that the grouping is reasonable.Hardy-Weinberg equilibrium test show that the inherited conditions of VDR gene in the target population were stable. Bsm I BB genotype frequency and B allele frequency in patients with MS were higher than those in controls.The mainly food intake of the study population was plant food, and the dietary structure was mainly composed of grains and vegetables. The dietary structure, food intake, dietary nutrition intake, fat and fatty acids intakes between cases and controls had no significant difference(P>0.05). However, these variables in Han ethnic group were significant higher than those in Hui ethnic group both in cases and controls. The concentration of plasma phospholipid acids including SFA、n3/n6/n9 unsaturated fatty acids in patients with MS were higher than those in controls(P≤0.05). Specifically, the cases got the higher concentration of plasma tetradecanoic acid, palmitic acid, stearic acid, elaidic acid, linoleic acid andα-linolenic acid, and got lower concentration of plasma γ-linolenic acid.Multivariable logistic regression analysis found that Bsm I Bb genotype for VDR gene was a protective factor of MS, while SFA and n3 unsaturated fatty acid were risk factors of MS.Logistic regression was used to analyze the interactions by combining different levels of the risk factors. It was showed that Bsm I BB genotype interacted with SFA(>Q75) to affect MS by increasing risk for 3.317 times(P≤0.05). There was an interaction between Bsm I Bb genotype and n3 unsaturated fatty acid as well(P≤0.05), and it increased the risk to become MS for 6.31 times. After merging genotype Bb and bb, it was showed that Bsm I BB genotype still interacted with SFA(>Q75) by increasing the risk of MS for 3.317 times(P≤0.05).After adjusting age, sex and ethic group, GMDR analysis found that VDR Bsm I, SFA and n3 unsaturated fatty acid interacted with each other. With the merging of genotype Bb and bb, two interactions were found. One showed that VDR Bsm I was interacted with n3 unsaturated fatty acid, and the other showed that the three factors interacted with each other.Conclusion: MS was likely to be influenced by VDR gene Bsm I(BB genotype and B allele) in rural Ningxia.The dietary situation between cases and controls had no significant difference. However, it was quite different between Han and Hui ethic groups. The Han ethic group got higher intakes than those in Hui ethic group. The concentration of plasma phospholipid acids including SFA, n3/n6/n9 unsaturated fatty acids in patients with MS were higher than those in controls.The risk factors of MS were Bsm I BB genotype, SFA and n3 unsaturated fatty acid. There were interactions between Bsm I BB genotype and SFA,and also between Bsm I BB genotype and n3 unsaturated fatty acid in Logistic Regression analysis. GMDR analysis also showed Bsm I BB genotype, SFA and n3 unsaturated fatty acid interacted with each other after adjusting age, sex and ethic group.These results suggested VDR gene Bsm I polymorphism might predict the susceptibility of MS. If one got VDR gene Bsm I BB genotype, he or she should avoid the excessive intake of SFA and n3 unsaturated fatty acid for preventing the occurrence of MS.