A common polymorphism near the interleukin-6 gene modifies the association between dietary fat intake and insulin sensitivity

Cristina Cuda¹, Bibiana Garcia-Bailo^1,2, Mohamed Karmali^1,2, Ahmed El-Sohemy¹, Alaa Badawi^2
1Department of Nutritional Sciences, University of Toronto, ²Office of Biotechnology, Genomics and Population Health, Public Health Agency of Canada, Toronto, Ontario, Canada

Background: Increasing evidence suggests a role for inflammation in the development of type 2 diabetes. Elevated levels of inflammatory cytokines, including interleukin-6, have been associated with insulin resistance, and dietary lipids can increase cytokine production. The objective of this study was to determine whether a single nucleotide polymorphism near the IL6 gene (rs7801406) modifies the relationship between dietary fat and markers of insulin sensitivity.
Methods: Subjects were healthy men and women aged 20–29 years from the Toronto Nutrigenomics and Health Study. Dietary intake was estimated using a one-month semiquantitative food frequency questionnaire. Fasting blood samples were taken for genotyping and biomarker measurement.
Results: The single nucleotide polymorphism was not associated with any of the measures of insulin sensitivity. However, it modified the relationship between total dietary fat and the homeostasis model assessment of insulin resistance (P = 0.053 for interaction). Total fat intake was positively related to HOMA-IR in individuals homozygous for the G allele (ß = 0.005 ± 0.002, P = 0.03), but not among heterozygotes. There was an inverse relationship between total fat intake and HOMA-IR in individuals who were homozygous for the A allele (β= –0.012 ± 0.006, P = 0.047).
Conclusion: These findings suggest that dietary fat influences insulin sensitivity differently depending on genotype.

Keywords: interleukin-6, insulin sensitivity, nutrigenomics, dietary fat