Searching for the missing link between growth and longevity

Many scientists believe that in mammals, there is a trade-off between growth and better health. Pugs, for example, live longer than their larger counterpart in the canine world, the Great Dane. But a new study shows that when more energy is allocated to creating better cellular materials, longevity is improved.

Dr. Chen Hou, associate professor of biological sciences at Missouri University of Science and Technology, published a paper titled “Energy Cost of Biosynthesis Is a Missing Link Between Growth and Longevity in Mammals” in the Proceedings of the National Academy of Sciences.

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

“Existing life history theories suggested a trade-off between growth and somatic maintenance, meaning that greater energy expenditure for growth would translate into less expenditure for maintaining health,” Hou says. “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.”

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 says.

“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.”

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.

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

He believes that the conventional understanding of the trade-off between growth and maintenance needs to be more carefully analyzed, and that the potential combined effect of metabolic rate and the energetic cost of biosynthesis should be taken into account in similar studies of aging.