Abstract P127: Adverse Endothelial Cell Protein Expression is Associated With Type 1 Diabetes

Abstract

Cardiovascular risk is increased in adults with type 1 diabetes (T1D), although the mechanism is poorly understood. Endothelial dysfunction may contribute to increased coronary artery calcium (CAC) in T1D, and CAC severity may be associated with reduced nitric oxide (NO) synthesis and/or increased inflammation. We tested the hypotheses that high CAC and T1D are associated with expression of endothelial NO synthase (eNOS, enzyme that produces NO), phosphorylated eNOS (p-eNOS), and NFκB (pro-inflammatory transcription factor). Participants were categorized as having high (>80 Agatston units [AU]) or low CAC (<15 AU), measured by CT scan. Protein expression was measured using quantitative immunofluorescence in endothelial cells harvested from 14 women with T1D (mean age 52±8 years; 7 high CAC); 13 men with T1D (mean age 58±7 years; 5 high CAC); 10 women without diabetes (mean age 61±4 years; 3 high CAC); and 10 men without diabetes (mean age 59±6 years; 4 high CAC). All analyses used ratios of endothelial cell protein expression to control human umbilical vein endothelial cell protein expression. Independent t-tests compared protein expression by sex and T1D. Linear regression tested the associations of high vs. low CAC and T1D with the 3 proteins of interest after adjustment for age and sex. In men, eNOS expression differed by T1D: men with T1D had reduced cytoplasmic (0.34 vs.0.52, p=0.03) and nuclear (0.44 vs. 0.60, p=0.02) eNOS expression compared with men without T1D, suggesting reduced NO synthesis. There were no differences in p-eNOS expression, indicating that eNOS levels were likely not due to differential activation. In women, NFκB expression similarly differed by T1D: women with T1D had higher cytoplasmic (0.81 vs. 0.63, p=0.01) and nuclear (0.99 vs. 0.75, p=0.01) NFκB expression compared with women without T1D, suggesting greater inflammation. After adjustment for age and sex, there was no significant association between high vs. low CAC in endothelial expression of any proteins. The data trend suggested that high vs. low CAC is associated with reduced cytoplasmic (0.36 vs. 0.47, p=0.06) and nuclear (0.48 vs. 0.55, p=0.12) eNOS expression. T1D trended in the same direction for both cytoplasmic (0.36 vs. 0.47, p=0.06) and nuclear (0.47 vs. 0.55, p=0.13) eNOS expression. High vs. low CAC also trended towards an association with greater cytoplasmic (0.72 vs. 0.66, p=0.21) and nuclear (0.85 vs. 0.80, p=0.40) NFκB expression, while T1D was significantly associated with greater cytoplasmic (0.76 vs. 0.63, p=0.006) and nuclear (0.92 vs. 0.73, p=0.003) NFκB expression. Neither CAC nor T1D was associated with p-eNOS expression in linear regression. In conclusion, eNOS and NFκB expression are potential mechanisms for increased CAC given their roles in reduced NO synthesis and increased inflammation, and may differ by sex in people with T1D. Regardless of high CAC, inflammation in T1D is increased.