Flashy, high-end items like Rolex watches and Red Wing boots are typically more expensive to make but last longer. This is a principle that manufacturers and customers are familiar with. But although this also applies to biology, scientists rarely discuss it.

Researchers have known for decades that The faster an animal grows, the shorter its lifespanat least among mammals. This is true for species of different sizes. Ecophysiologists like me They examine the trade-offs between the allocation of energy for growth or maintenance and how these trade-offs affect aging and lifespan.

One explanation is that because animals have a limited amount of energy, investing more energy into growth would reduce the energy available to maintain their health, thus leading to faster aging.

Another explanation is based on the following observation: metabolism All physical and chemical processes that transform or use energy fuel growth. Some researchers have suggested that Fast growth is associated with high metabolismThis causes stress, which accelerates aging.

However, these two explanations may not capture the whole picture balance between growth and longevity. For example, some species devote a greater portion of their energy to maintenance, but they do not have better resistance to stress than species that devote less energy to these processes. This finding suggests that the amount of energy devoted to care may not be the only thing that determines the quality of care.

Meanwhile, this negative relationship still standing strong Even after taking metabolic rate into account. This means that higher metabolism associated with faster growth cannot fully explain faster aging. There had to be other missing links to consider.

What did scientists miss? My recently published research shows that the energy cost required to make biological materials, or biosynthetic costIt also affects lifespan.

Cost of making biomass

IT energy cost making biological materials or biomass, such as combining individual amino acids into complete proteins. It also costs energy to check newly synthesized materials for errors, to break down and regenerate faulty materials, and to move finished materials to where they need to be.

To quantify the energy investment in building biomass across species, I derived a mathematical relationship between biosynthetic cost and growth and metabolism rates. I based my equation on: The first principle of energy savingData on the growth and metabolic rates of different mammals, indicating that energy is neither created nor destroyed, are routinely measured by other researchers in the field.

While researchers previously believed that the cost of synthesizing new biomass was the same across species, my analysis of data from 139 different animals found that big difference in biosynthetic cost between species. For example, the biosynthetic cost of the naked mole rat is three times that of a mouse of the same body mass. The naked mole rat has a lifespan of 30 years, while the lifespan of a mouse is only two to three years.

My findings show that some species expend more energy than others to obtain one unit of biomass. This is perhaps partly due to living in a more dangerous environment. Faster growing animals are more likely to reach reproductive maturity than slower growing animals, but at the cost of lower quality biomaterials.

Biosynthetic cost and aging

All things being equal, the more expensive growth is, the lower the growth rate. So how does this energy cost contribute to the aging process?

I used what I said cost-quality hypothesis To answer this question. At the cellular level, biosynthetic cost is determined in part by the cell’s tolerance for errors in material construction. Let’s take proteins as an example. Research has repeatedly suggested that: protein homeostasis Collective processes that maintain protein level, structure and function play an important role in the aging process. Simply put, faulty accumulation of proteins causes aging.

Protein synthesis and folding are defective. Researchers predicted that 20 to 30 percent of new proteins break down rapidly after it was made due to errors. Different species have different degrees of error tolerance and protein quality control. For example, the mouse proteome two to ten times higher Levels of proteins with incorrect amino acids relative to the proteome of naked mole rats.

Consider two species, one selective about protein errors and the other not so selective. Selective strains will break down a protein and regenerate it when they find a mistake; It constantly uses protein quality control mechanisms to fix, rapidly unfold and refold, degrade or resynthesize proteins. These processes not only cost energy but also slow down the animal’s overall biomass growth rate. A more selective species will expend more energy per unit of net new biomass synthesized than a generally slower growing, more tolerant species.

On the other hand, a species with a higher tolerance for errors will have a lower biosynthetic cost because it will incorporate the defective protein into its new biomass. Because this type carries more faulty proteins less resistant to stress therefore lives shorter.

Making things permanent

An animal’s ability to maintain homeostasis depends not only on the amount of energy it devotes to maintenance, but also on the quality of the tissue it produces. And the quality of this tissue depends at least in part on the energy expended in making biomass.

In other words, fancy things are more expensive to make but last longer.

My hope is that these results can be used as a framework for investigating how differences in a person’s rate of development and growth affect their health, risk of aging-related diseases, and lifespan. It also opens the door to a new area of ​​research: Can we manipulate the mechanisms that determine the energetic cost of biosynthesis and slow aging?

The article has been updated to clarify that species with more defective proteins have shorter lifespans.

This article was first published on The Conversation. Chen Ho -most Missouri University of Science and Technology. Read original article here.