Identifying the missing link between growth size and lifespan

Many scientists believe that in mammals there is a trade-off between growth and lifespan. Pugs, for example, live longer than their larger counterpart in the canine world, the Great Dane.

But a new study led by Chen Hou, associate professor of biological sciences at Missouri University of Science and Technology, shows that when more energy is allocated to creating better cellular materials, longevity is improved.

Energy cost of biosynthesis

Hou argued that the “take-home message” of this research is that if you put more energy into making improved cellular materials, you'll live longer — a concept he said engineers may be more familiar with than biologists.

“Existing life cycle theories suggested a trade-off between growth and somatic maintenance, meaning that more energy spent on growth would translate into less energy spent on maintaining health,” Hou explained.

“But this study reveals that the energetic cost of biosynthesis is a hidden physiological mechanism underlying the well-established negative correlation between growth and lifespan in mammalian species.”

Linking growth and lifespan

Hou's study uses a new research model based on energy conservation to explain the physiological effect of varying energy costs on the aging process. It also illustrates its role in the link between growth and lifespan.

“Previously, the energetic cost of biosynthesis was considered a constant across species and therefore was not considered a contributing factor to variation in life history traits, such as growth and lifespan,” Hou said.

“This study uses a recently proposed model based on energy conservation to explain the physiological effect of variation in this energy cost on the aging process and illustrates its role in the link between growth and lifespan.”

Negative correlation between growth and lifespan

The study shows that after controlling for two energy components – mass-specific metabolic rate and the energetic cost of biosynthesis – there is still a negative correlation between the growth constant and lifespan, revealing that the energetic cost of biosynthesis is a link between growth and longevity in mammals.

According to Hou, since the energetic cost of biosynthesis links growth to aging processes, allocating more energy to growth may improve somatic maintenance.

Thus, the conventional understanding of the trade-off between growth and maintenance needs to be more carefully analyzed, and the potential combined effect of metabolic rate and energetic cost of biosynthesis needs to be considered in similar studies of aging.

The study is published in the journal Proceedings of the National Academy of Sciences.

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