Starving eye cells contribute to blindness in elders
Age-related macular degeneration (AMD) is the leading cause of visual impairment in people over 50 in developed countries. Although this condition affects up to 20% of people between the ages of 65 and 75, what drives abnormal blood vessels to invade the retina is unknown. Researchers from Montreal and Boston now provide a new mechanism for that blinding retinal disease in a study just published in the prestigious scientific journal Nature Medicine.
“In a murine model of AMD, we found that the inability of photoreceptors – nerve cells that capture light and generate vision – to produce energy may drive abnormal blood vessels to invade the retina” said Jean-Sébastien Joyal, an intensive care pediatrician at mother-child research hospital CHU Sainte-Justine and professor in the Department of Pediatrics at the University of Montreal. “We also discovered that photoreceptors do not rely exclusively on glucose to produce energy as previously thought, but also use lipids as a fuel substrate (like the heart, for example)” he said. These findings debunk the scientific beliefs surrounding the cause of abnormal proliferation of blood vessels leading to blindness, and thus open new therapeutic avenues for retinal diseases such as AMD.
Compensating for energy deficiency
The retina is covered with photoreceptors, which thrive on oxygen and nutrients carried by the blood. The abnormal growth of blood vessels causes blindness in some retinal diseases. “In general, the scientific community agrees that proliferation of blood vessels occurs when the body attempts to compensate for oxygen deficiency. We now show that abnormal vessels may also grow to compensate for a lack of fuel or energy production, in a model of AMD,” said Dr. Joyal.
Fat as energy substrate — a possible evolutionary advantage
The type of energy used also surprised the scientists in their study. “To our surprise, we found that photoreceptors also feed on fatty acids. It was previously believed that these specialized nerve cells, which are energy-intensive, rely primarily on glucose,” said Dr. Joyal. The ability of photoreceptors to use different fuel sources to produce energy may provide an evolutionary advantage during feast and famines.……..
Source: Science Codex