Fingertip-Measured Skin Carotenoids and Advanced Glycation End Product Levels in Glaucoma

Abstract

Carotenoids have antioxidant properties, and the accumulation of advanced glycation end products (AGEs) is associated with reactive oxygen species production; they have attracted attention as factors predictive of the onset and progression in glaucoma. Fingertip measurement is applicable for carotenoids and AGEs due to its noninvasiveness and simplicity. The study included 663 eyes of 663 Japanese subjects (357 males, 306 females). The mean age was 69.9 years with a standard deviation of 11.0. The study population comprised participants with primary open-angle glaucoma (PG) (n = 358), exfoliation glaucoma (EG) (n = 168), and controls (n = 137). Multivariate models suggested that lower skin carotenoid (SC) levels were associated with male gender (standard β = −0.14), AGE scores (−0.24), and a history of intraocular surgery (−0.22). Higher SC levels were associated with higher vegetable intake scores (0.21 for score 3) and diabetes (0.10). However, no association was seen between SCs and glaucoma type. AGEs levels were negatively associated with carotenoid scores (−0.25), PG (−0.15), and smoking habits (−0.26) and positively correlated with EG (0.14). SCs and AGEs were negatively correlated in the single regression analysis (r = −0.20, p < 0.0001). In conclusion, higher levels of AGEs may be candidates for systemic biomarkers of glaucoma associated with the exfoliation syndrome. SC levels can reflect self-reported daily vegetable intake.

Carotenoids in Human Skin In Vivo: Antioxidant and Photo-Protectant Role against External and Internal Stressors

“…In vivo studies on humans show that the controlled consumption of dietary carotenoid-containing supplements leads to a significant dose-dependent increase in the carotenoid concentration in the blood plasma (on average by 200%) and in the SC (on average by 25%) [ 115 , 245 , 248 , 249 ]. The same effect is observed with the consumption of carotenoid-containing food, in particular fruit and vegetables [ 250 , 251 , 252 , 253 , 254 , 255 ]. At the same time, the carotenoid concentrations in the blood plasma and in the SC are strictly correlated [ 116 , 124 , 256 , 257 , 258 ].…”

Relevance of Diabetic Retinopathy with AGEs and Carotenoid Levels Assessed by Skin Sensors

“…Elevated blood glucose levels were associated with the accumulation of AGEs [ 5 ], suggesting the involvement of AGEs in DM and diabetes complications [ 6 ]. In DM, AGEs can alter the function of intracellular proteins such as antioxidant enzymes, increase vascular stiffness by inducing collagen crosslinking, and activate inflammatory signaling pathways by interacting with receptors for AGEs [ 7 , 8 , 9 ]. On the other hand, higher levels of carotenoids in the blood were associated with a lower risk of developing DM [ 10 ]; especially, higher levels of provitamin A (e.g., α-, β-, and γ-carotenes) and β-cryptoxanthin among carotenoids were reported to be correlated with a lower risk of developing DM [ 11 ].…”

“…However, few studies have simultaneously estimated AGEs and carotenoid levels in patients with DM. The AGEs score estimated by skin autofluorescence (sAF) was correlated positively with the levels of nonfluorescent and fluorescent AGEs in serum [ 9 , 12 , 13 ]. Because the distributions of fluorescent and nonfluorescent AGEs were similar, sAF reflected the total amount of AGEs accumulation in vivo [ 8 , 9 ].…”

“…The AGEs score estimated by skin autofluorescence (sAF) was correlated positively with the levels of nonfluorescent and fluorescent AGEs in serum [ 9 , 12 , 13 ]. Because the distributions of fluorescent and nonfluorescent AGEs were similar, sAF reflected the total amount of AGEs accumulation in vivo [ 8 , 9 ]. In addition, the score obtained by the pressure-mediated reflection spectroscopy (RS) method, referred to as the Veggie score, correlated positively with the serum carotenoid levels [ 14 ].…”

“…In addition, the score obtained by the pressure-mediated reflection spectroscopy (RS) method, referred to as the Veggie score, correlated positively with the serum carotenoid levels [ 14 ]. The RS method is performed in the 350 to 850 nm wavelength range to include the carotenoid absorption wavelength peak at 480 nm [ 9 ]. Thus, these skin sensor-based measurements enable us to determine the in vivo levels of AGEs and carotenoids easily and noninvasively.…”