Serum Carotenoids and Risks of Diabetes and Diabetic Retinopathy in a Chinese Population Sample

Objective: Diabetes mellitus (DM) and diabetic retinopathy (DR) are associated with oxidative stress and carotenoids have antioxidant properties. This study aimed to test the relationship between serum carotenoid concentrations and the risk for DM and DR. Methods: This is a cross-sectional study of the Chinese urban population. A total of 747 subjects, consisting of 272 DR patients, 190 diabetic patients without retinopathy, and 285 non-diabetes mellitus healthy controls, were recruited to this study. Demographic and lifestyle characteristics were ascertained by questionnaire. General physical and ophthalmic examinations were completed for all participants. Serum carotenoids were measured by high-performance liquid chromatography (HPLC). The associations of serum carotenoids with DM and DR were assessed by logistic regression with adjustment of known risk factors. The correlation analyses of serum carotenoids with the candidate influence factors were assessed using the single variable linear regression. Results: Both pro-vitamin A (PVA) carotenoids and non-PVA carotenoids in the serum were measured and compared between different groups. Levels of α-carotene were significantly lower in DR patients and β-carotene were significantly lower in DM patients as compared to non DM healthy control group. In contrast, levels of β-cryptoxanthin, lycopene, lutein and zeaxanthin were comparable among different groups. After adjusting for confounding factors, β-carotene concentration was associated with reduced risk for DM (OR (95%CI): 0.56 (0.34, 0.91), P=0.02) and α-carotene was associated with reduced risk for DR in non-smokers (OR (95%CI): 0.41 (0.17, 0.99), P=0.048). No significant association was found between hemoglobin A1c and any carotenoids (P>0.05). Significantly associations with serum carotenoids were found in age, sex, BMI, smoking, and exercise (P<0.05). Conclusion: Serum β-carotene may have a protective effect on DM and α-carotene may be a protective factor for DR in non-smokers.