"These data suggest that dietary SOD supplementation is efficient to limit retinal oxidative stress by increasing plasma antioxidant capacity," wrote the researchers from the Eye and Nutrition Research Group, National Institute for Research on Agronomy (Dijon).
SOD has a different mode of action to vitamins. Dubbed 'the enzyme of life' when first discovered in 1968, it is the first antioxidant mobilized by the cell for defence. It is thought to be more powerful than antioxidant vitamins as it activates the body's productions of its own antioxidants, including catalase and glutathione peroxidase.
GliSODin is patented and trademarked by Paris-based Isocell. In North America PL Thomas distributes the ingredient. Neither company was involved in the new research.
The researchers used two types of mouse models, a senescence-accelerated mouse prone 8 (SAM P8) and a SAM resistant 1 (SAM R1, controls). The mice were exposed to light (1900 lux for 7 hours) at one, two and three months of age to induce oxidative stress in the pigment cell layer that nourishes the retinal cells and promoting age-related macular degeneration (AMD).
AMD affects the central part of the retina called the macula, which controls fine vision, leaving sufferers with only limited sight. AMD affects over 30m people worldwide, and is the leading cause of blindness in people over 50.
At three months of age and before the last light exposure, the mice were given a dose of SOD (GliSODin: 10.8 mg/kg/day) or water (placebo) for one week.
The research has been presented at the Association for Research in Vision and Ophthalmology (ARVO) Eye Research Conference and is also published online in the peer-reviewed journal Investigative Ophthalmology & Vision Science (Vol. 47, pp. 2089).
The researchers report that exposure to light did not result in significantly different retinal degeneration between the groups, but the blood antioxidant capacity is reported to have increased by 30 per cent in the SOD supplemented group.
Furthermore, the cell oxidant levels, measured by the oxidant superoxide anion, were found to have risen by about 50 per cent in the retinal cell layer and by a whopping 300 per cent in the outer nuclear layer in all the light exposed animals, compared to control animals.
"These results demonstrate that our light-exposure conditions promote retinal oxidative stress without inducing retinal degeneration," wrote the researchers.
However, supplementation with SOD was found to significantly decrease superoxide anion levels significantly, compared to the non-supplemented group, said the researchers.
The Dijon-based researchers concluded that light-exposure promotes retinal oxidative stress while GliSODin supplementation efficiently limits retinal oxidative stress by increasing plasma antioxidant capacity.
The mechanism behind the apparent effects is reported to be due to the SOD supplement boosting the body's antioxidant defences. Previous studies in the laboratory and in humans have reported that the body's defences include production of its own SOD, catalase and glutathione peroxidase.
Significant further research is needed to elaborate further on the potential role of SOD supplements as a potential player in the eye-health market, which has seen a slight decline in eye health supplement launches since 2003, when 30 new products were launched, according to Mintel's Global New Product Database.
The majority of the products launched in the last three years have contained the carotenoid lutein, while some have also contained zeaxanthin.