Identification of Surrogate Biomarkers for the Prediction of Patients at Risk of Low Macular Pigment in Type 2 Diabetes

ABSTRACT

Purpose: This cross-sectional study compared macular pigment (MP) levels among persons with Type 2 diabetes relative to healthy controls. Additionally, a range of behavioral, anthropometric, clinical and serum measures were explored as possible predictors of low MP optical density (MPOD) in diabetes.

Methods: Two health status groups; Group 1: Type 2 diabetes (n = 188), and Group 2: Healthy controls (n = 2,594) completed a full MP assessment using customized heterochromatic flicker photometry, as part of The Irish Longitudinal Study on Aging (TILDA). Clinical [blood pressure; cataract status; MPOD] and anthropometric [waist (cm); weight (kg); hip (cm)] measurements were taken, and a blood sample drawn for analysis of serum biomarkers [lipoproteins; inflammatory markers (C reactive protein and vitamin-D)].

Results: One-way ANOVA revealed lower MPOD in subjects with Type 2 diabetes relative to controls (p = .047). Amongst participants with diabetes, those with low serum vitamin D (≤50 nmol/L) had significantly lower mean MPOD compared to those with sufficient serum vitamin D levels >50 nmol/L (0.173(0.148) vs. 0.226(0.145); p = .006). Concomitantly, MP was significantly lower in diabetes participants with raised serum triglyceride (TG) to high density lipoprotein (HDL) ratio (TG/HDL); values >1.74 mmol/L (0.172 (0.140) vs 0.215 (0.152); p = .039). Body mass index, waist-to-height ratio and waist circumference, were all significantly negatively correlated with MPOD (Pearson’s correlation, p < .05 for all). Significant correlates of MPOD in the multivariate regression model included smoking, cataract, and vitamin D, which collectively contributed 18.5% of the overall variability in MPOD status amongst participants with Type 2 diabetes.

Conclusions: This study provides additional evidence that low MP may indeed be a feature of Type 2 diabetes, and further identifies smoking, cataract and vitamin D status as plausible predictors of low MPOD amongst persons with Type 2 diabetes.

KEYWORDS:

• Macular pigment
• high density lipoprotein
• triglycerides
• vitamin D
• oxidative stress

Acknowledgments

The authors would like to thank The Irish Longitudinal Study on Aging (TILDA) for the support received and are grateful to all of the TILDA respondents for participating in the study.

Declaration of interest

No potential conflict of interest was reported by the authors.