HFE Genetic Variability, Body Iron Stores, and the Risk of Type 2 Diabetes in U.S. Women

To determine whether the HFE gene variants H63D and C282Y are associated with body iron stores and the risk of type 2 diabetes, we conducted a nested case-control study of 714 incident cases of type 2 diabetes and 1,120 matching control subjects in a prospective cohort, the Nurses’ Health Study. In both healthy control and diabetic case subjects, H63D homozygosity, C282Y, and the compound heterozygotes were associated with significantly higher levels of plasma ferritin and significantly lower ratios of transferrin receptors to ferritin. Such effects were independent of age, BMI, and lifestyle factors. Overall, there were no significant differences in genotypes of H63D and C282Y between the case and control subjects. A meta-analysis of 4,245 case and 5,982 control subjects indicated a null association of C282Y with diabetes risk, whereas carriers of H63D or the compound heterozygotes had marginally increased risk (odds ratio [OR] 1.11 [95% CI 1.00–1.25] and 1.60 [0.99–2.60], respectively). In addition, we found a significant interaction between HFE variants and heme iron intake (P for interaction = 0.029). The ORs of type 2 diabetes across increasing quartiles of heme iron were 1.00, 1.21 (0.72–2.01), 1.72 (1.03–2.88), and 1.49 (0.91–2.46) among the participants with either the H63D or C282Y variant, whereas the ORs were 1.00, 0.71 (0.49–1.05), 1.12 (0.76–1.66), and 0.96 (0.65–1.42) among those with wild-type genotypes. Our data indicate significant effects of H63D and C282Y on body iron stores and suggest a potential interaction between HFE genotypes and heme iron intake in relation to the risk of type 2 diabetes.