Traditional Ethnic Diets, Genetic Pre-Susceptibility and Gene-Diet Interaction Associations with Type 2 Diabetes and Risk Factors
Mercado, Carla Isabel
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The prevalence of obesity and type 2 diabetes in the US is reaching epidemic levels particularly among ethnic minorities. It is believed that this discrepancy is due to a shift from traditionally ethnic to westernized lifestyles. This shift may affect distinct ethnicities differently due to some unknown genetic factor. A recent study found that genetic differences in the proglucagon gene exist among various ethnic backgrounds. This gene is responsible for the production of the gut derived peptide hormone GLP-1 that delays gastric emptying, triggers satiety signals in the brains, and acts as an incretin. The need to replicate these findings as well as consider diet in the association between the proglucagon gene and type 2 diabetes are addressed here. This dissertation identified traditional ethnic dietary patterns and investigated whether diet acculturation is associated with presence, development and risk factors of type 2 diabetes. The genetic association between the proglucagon gene and diabetes prevalence and incidence, fasting glucose, fasting insulin, A1c, and body mass index were examined. The testing of the proglucagon gene-diet acculturation interaction in the risk factors as well as prevalence and incidence of type 2 diabetes were then evaluated. The MESA Study was ideal for examining these relationships as it is a prospective multi-site study of adults from various ethnic backgrounds who were periodically evaluated for dietary, anthropometric and phlebotomy measures over 10 years of follow-up. Statistical approaches included confirmatory factor analysis (CFA) to calculate dietary adherence, Cox proportional hazards regression to test diet and genetic associations with incidence of type 2 diabetes, and multiple linear regressions of the data to test diet and genetic associations with risk factors for type 2 diabetes. We found that adherence to a Western diet was positively associated with BMI in Mexican Americans (β = 0.84, 95% CI = 0.15-1.53), African Americans (β = 0.89, 95% CI = 0.18-1.60), and European Americans (β = 0.67, 95% CI = 0.13-1.21). No significant associations were found between the proglucagon SNPs and A1c, fasting glucose, and risk or incidence of type 2 diabetes. There was gene-diet interaction associated with incident type 2 diabetes (interaction p-values ranged from 0.03 - 0.08) among Chinese, Mexican, and African Americans. These findings provide new knowledge that can be used to develop effective intervention strategies for obesity as well as prevention of type 2 diabetes.
- Epidemiology