Nutrition et dégénérescence maculaire liée à l’âge

Genetic risk factors and age-related macular degeneration (AMD)

Age related macular degeneration (AMD) is the leading cause of blindness in individuals older than 65 years of age. It is a multifactorial disorder and identification of risk factors enables individuals to make lifestyle choices that may reduce the risk of disease. Collaboration between geneticists, ophthalmologists, and optometrists suggests that genetic risk factors play a more significant role in AMD than previously thought. The most important genes are associated with immune system modulation and the complement system, e.g., complement factor H (CFH), factor B (CFB), factor C3, and serpin peptidase inhibitor (SERPING1). Genes associated with membrane transport, e.g., ATP-binding cassette protein (ABCR) and voltage-dependent calcium channel gamma 3 (CACNG3), the vascular system, e.g., fibroblast growth factor 2 (FGF2), fibulin-5, lysyl oxidase-like gene (LOXL1) and selectin-P (SELP), and with lipid metabolism, e.g., apolipoprotein E (APOE) and hepatic lipase (LIPC) have also been implicated. In addition, several other genes exhibit some statistical association with AMD, e.g., age-related maculopathy susceptibility protein 2 (ARMS2) and DNA excision repair protein gene (ERCC6) but more research is needed to establish their significance. Modifiable risk factors for AMD should be discussed with patients whose lifestyle and/or family history place them in an increased risk category. Furthermore, calculation of AMD risk using current models should be recommended as a tool for patient education. It is likely that AMD management in future will be increasingly influenced by assessment of genetic risk as such screening methods become more widely available.

Decreased serum paraoxonase 1 activity and increased serum homocysteine and malondialdehyde levels in age-related macular degeneration

Age-related macular degeneration (AMD) is one of the most common causes of vision loss. AMD has been classified into two forms: atrophic and exudative forms. The exudative form is associated with choroidal neovascularization of the subretinal macular region, resulting in a sudden loss of central vision. However, the exact cause of AMD remains unknown. Several risk factors have been postulated, including smoking, atherosclerosis, and low levels of antioxidant enzymes. Malondialdehyde (MDA), a lipid peroxidation product, is used as a marker of oxidative stress. Paraoxonase 1 (PON1) metabolizes lipid peroxides and prevents oxidation of low-density lipoprotein. Increased levels of homocysteine may cause vascular endothelial injury by releasing free radicals. The purpose of this study is to investigate the relationships between serum PON1 activity and the serum levels of homocysteine and MDA in AMD. Forty patients with exudative-type AMD (63.3 +/- 5 years) and 40 controls (61+/- 4 years) were assessed in a cross-sectional study. The serum PON1 activity was significantly lower in the patients with AMD than that in the controls (p < 0.001). In contrast, the serum levels of MDA and homocysteine were significantly higher in the patients than those in the controls (p < 0.001, for both). In AMD patients, significant negative correlation was found between PON1 activity and MDA level (r = -0.493, p < 0.05) and between PON1 activity and homocysteine level (r = -0.557, p < 0.05). Increased serum homocysteine and MDA levels may be responsible for the decreased PON1 activity in patients with AMD.