Calorie Restriction and the Ribosome

Ribosomes are structures within which protein assembly takes place in cells. Many interventions that modestly slow aging, such as calorie restriction, are associated with both a slower rate of protein production and a slower turnover of ribosomes - which, like near all structures in the cell, are periodically replaced as they become damaged or dysfunctional. The direction of causation in this and associated effects is still up for debate, though a consensus is emerging. In this context it is interesting to note that there is some evidence for selective ribosomal dsyfunction to mimic some of the effects of calorie restriction. Further, naked mole-rats, those paragons of mammalian longevity, have been found to have highly efficient ribosomes. Determining how this all fits together into a coherent picture of the effects of calorie restriction on aging, as well as the differences in aging between short-lived versus long-lived species, is still a work in progress.

Recent research offers one glimpse into how cutting calories impacts aging inside a cell. The researchers found that when ribosomes - the cell's protein makers - slow down, the aging process slows too. The decreased speed lowers production but gives ribosomes extra time to repair themselves. "The ribosome is a very complex machine, sort of like your car, and it periodically needs maintenance to replace the parts that wear out the fastest. When tires wear out, you don't throw the whole car away and buy new ones. It's cheaper to replace the tires." So what causes ribosome production to slow down in the first place? At least for mice: reduced calorie consumption.

Researchers observed two groups of mice. One group had unlimited access to food while the other was restricted to consume 35 percent fewer calories, though still receiving all the necessary nutrients for survival. "When you restrict calorie consumption, there's almost a linear increase in lifespan. We inferred that the restriction caused real biochemical changes that slowed down the rate of aging." The team isn't the first to make the connection between cut calories and lifespan, but they were the first to show that general protein synthesis slows down and to recognize the ribosome's role in facilitating those youth-extending biochemical changes. "The calorie-restricted mice are more energetic and suffered fewer diseases. And it's not just that they're living longer, but because they're better at maintaining their bodies, they're younger for longer as well."

Ribosomes, like cars, are expensive and important - they use 10-20 percent of the cell's total energy to build all the proteins necessary for the cell to operate. Because of this, it's impractical to destroy an entire ribosome when it starts to malfunction. But repairing individual parts of the ribosome on a regular basis enables ribosomes to continue producing high-quality proteins for longer than they would otherwise. This top-quality production in turn keeps cells and the entire body functioning well.


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