Introduction: T-helper type 1 (Th1) cells provide important stimulatory and regulatory signals to immune cells and are positively associated with subclinical atherosclerosis in the Multi-Ethnic Study of Atherosclerosis (MESA). Fish and fish oils are a major source of n-3 polyunsaturated fatty acids (PUFAs), and several studies in Japanese populations with high fish consumption reported inverse associations with subclinical atherosclerosis. Animal studies have suggested an inverse relationship of n-3 PUFAs with Th1 cells; however, this has not been investigated in humans. We hypothesized that n-3 PUFAs would have an inverse association with Th1 cells in MESA.
Methods: We included 895 MESA participants with data on n-3 PUFAs at exam 1 (2000-02) and Th1 cells at exam 4 (2005-07) (age 61±10 years, 467 women, 396 Caucasians, 219 Hispanics, 185 African-Americans, 95 Chinese-Americans). Th1 cells were measured by flow cytometry as a percentage of CD4+ lymphocytes that were interferon-γ+ (%Th1). Phospholipid n-3 PUFAs (% of total fatty acids), defined as the sum of eicosapentaenoic and docosahexaenoic acids, were measured by gas chromatography. Dietary intake of n-3 PUFAs was evaluated by food frequency questionnaire (n=847). General linear models were used to analyze cross-sectional associations of n-3 PUFA quartiles with %Th1 adjusting for covariates.
Results: Mean n-3 PUFA and %Th1 levels were 4.8±2.1% and 15.9±8.3%. n-3 PUFAs were not significantly associated with %Th1 (P for trend=.58). The association remained non-significant after adjusting for covariates. Dietary intake of n-3 PUFAs also showed no significant association with %Th1 (Table).
Conclusion: Circulating levels and dietary intake of n-3 PUFAs were not significantly associated with %Th1 in this multi-ethnic U.S. population. n-3 PUFA levels in this cohort may be too low to have an effect on Th1 levels. Further research is needed to assess potential benefits of n-3 PUFA supplementation and dietary consumption of fish on T helper cell profiles and atherogenesis.