A new research at the Harvard University has found out a mechanism through which caloric restriction and exercise may delay some of the debilitating effects of aging by rejuvenating connections between nerves and the muscles that they control.
The research further explains earlier findings that exercise and restricted-calorie diets help to stave off the mental and physical degeneration of aging.
"Caloric restriction and exercise have numerous, dramatic effects on our mental acuity and motor ability," said Joshua Sanes, a professor of molecular and cellular biology and director of the Center for Brain Science at Harvard University.
"This research gives us a hint that the way these extremely powerful lifestyle factors act is by attenuating or reversing the decline in our synapses," he added.
Sanes said that the study was conducted on genetically engineered so that their nerve cells glow in fluorescent colors.
It shows that some of the debilitation of aging is caused by deterioration of connections that nerves make with the muscles they control, structures called neuromuscular junctions.
These microscopic links are remarkably similar to the synapses that connect neurons to form information-processing circuits in the brain.
In a healthy neuromuscular synapse, nerve endings and their receptors on muscle fibers are almost a perfect match, like two hands placed together, finger to finger, palm to palm.
This lineup ensures maximum efficiency in transmitting the nerve's signal from the brain to the muscle, which is what makes it contract during movement.
As people age, however, the neuromuscular synapses can deteriorate in several ways. Nerves can shrink, failing to cover the muscle's receptors completely.
The resulting interference with transmission of nerve impulses to the muscles can result in wasting and eventually even death of muscle fibers.
This muscle wasting, called sarcopenia, is a common and significant clinical problem in the elderly.
The new work showed that mice on a restricted-calorie diet largely avoid that age-related deterioration of their neuromuscular junctions, while those on a one-month exercise regimen when already elderly partially reverse the damage.
"With calorie restriction, we saw reversal of all aspects of the synapse disassembly. With exercise, we saw a reversal of most, but not all," Sanes said.
The study was published in the journal Proceedings of the National Academy of Sciences.