Adapted dietary inflammatory index and its association with a summary score for low-grade inflammation and markers of glucose metabolism: the Cohort study on Diabetes and Atherosclerosis Maastricht (CODAM) and the Hoorn study

Background: Diet may be associated with the development of type 2 diabetes through its effects on low-grade inflammation. Objectives: We investigated whether an adapted dietary inflammatory index (ADII) is associated with a summary score for low-grade inflammation and markers of glucose metabolism. In addition, we investigated the mediating role of inflammation in the association between ADII and markers of glucose metabolism. Design: We performed cross-sectional analyses of 2 Dutch cohort studies (n= 1024). An ADII was obtained by multiplying standardized energy-adjusted intakes of dietary components by literature-based dietary inflammatory weights that reflected the inflammatory potential of components. Subsequently, these multiplications were summed. Six biomarkers of inflammation were compiled in a summary score. Associations of the ADII (expressed per SD) with the summary score for inflammation and markers of glucose metabolism were investigated by using multiple linear regression models. Inflammation was considered a potential mediator in the analysis with markers of glucose metabolism. Results: A higher ADII was associated with a higher summary score for inflammation [beta-adjusted = 0.04 per SD (95% CI: 0.01, 0.07 per SD)]. The ADII was, also adversely associated with insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR): beta-adjusted = 3.5% per SD (95% CI: 0.6%, 6.-3% per SD)]. This association was attenuated after the inclusion of the summary score for inflammation [beta-adjusted+inflammation = 2.2% (95% CI: -0.6%, 5.0%)]. The ADII was also adversely associated with fasting glucose and postload glucose but not with glycated hemoglobin. Conclusion: The significant mediating role of low-grade inflammation in the association between the ADII and HOMA-IR suggests that inflammation might be one of the pathways through which diet affects insulin resistance