Protective Effect of Dietary Vitamin C on the Association between PM2.5 and Insulin Resistance

Abstract

Objectives: To investigate influence of dietary vitamin C on the relationship between ambient fine particulate matter and insulin resistance in a panel study of elderly population from a metropolitan residence. Methods: Panel study on 560 subjects over 60 years old in Seoul, Korea, was conducted from 2008 to 2010. Serum glucose and insulin levels were repeatedly measured, and monitored data on PM2.5 were collected. Mixed model analyses were used to evaluate the association between PM2.5 mass or elements and markers for insulin resistance, represented by homeostatic model assessment (HOMA-IR). We compared the relationship in groups of low or high dietary vitamin C, according to median value of vitamin C intake calculated from food frequency questionnaire. Results: Effect of PM2.5 mass or trace metals such as lead and zinc on insulin resistance was significant over lag days of 0 to 2 in both exponential (EMA) and simple (SMA) moving averages. When stratified by dietary vitamin C group, we observed positive association between PM2.5 mass, lead, zinc and HOMA-IR in low vitamin C group (ßmass = 0.013, P = 0.003; ßlead = 8.646, P = 0.005; ßzinc = 5.949, P = 0.001; at lag day 1, EMA). However, all significance disappeared in high vitamin C group (ßmass = -0.005, P = 0.231; ßlead = -3.584, P = 0.250; ßzinc = -1.450, P = 0.501). Conclusions: From a panel study of elderly population, we found protective effect of dietary vitamin C on the relationship between ambient fine particulate matter exposure and insulin resistance, especially with trace metals from anthropogenic sources. Acknowledgement: This study was supported by the Susceptible Population Research Program (2008-2010) of the Ministry of Environment, Republic of Korea Government.