Missing link between growth size and lifespan identified

Many scientists believe that in mammals, there’s a tradeoff between growth and lifespan. Pugs, for example, are known to live longer than their larger counterpart in the dog world, the Great Dane. 

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

Energetic cost of biosynthesis 

Hou argued that his “take-home message” from this research is that if you allocate more energy to making improved cellular materials, you will live longer – a concept that he says engineers may be more familiar with than biologists.

“The existing life history theories suggested a tradeoff between growth and somatic maintenance, meaning more energy spent on growth would result in less for maintaining health,” Hou explained. 

“But this study reveals that the energy cost for 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 the variation in the energetic cost on the aging process. It also illustrates its role in linking growth and lifespan.

“Previously, the energetic cost of biosynthesis has been thought to be a constant across species and therefore was not considered a contributor to the variation in any life history traits, such as growth and lifespan,” Hou said.

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

Negative correlation between growth and lifespan

The study shows that after controlling two energy components – mass-specific metabolic rate and the energetic cost of biosynthesis – there is still a negative correlation between 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 energy cost of biosynthesis links growth to aging processes, allocating more energy to growth may enhance somatic maintenance.

Thus, the conventional understanding of the tradeoff between growth and maintenance needs to be more carefully analyzed, and the potential combined effect of metabolic rate and energetic cost of biosynthesis should 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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