The Sixth Hallmark of Aging: Deregulated Nutrient-Sensing

The sixth hallmark of aging is deregulated nutrient-sensing: the gradual loss of balance in the molecular systems that detect nutrients and coordinate growth, repair, energy use, and survival. These systems help cells decide when to build, when to conserve, and when to repair. With age, their signals can become chronically misaligned.

What nutrient-sensing means

Nutrient-sensing is not simply about how much food a person eats. It refers to interconnected cellular pathways that respond to energy, amino acids, glucose, and other metabolic signals. Among the best studied are insulin and IGF-1 signalling, mTOR, AMPK, and sirtuins. Together, they influence protein production, mitochondrial activity, autophagy, inflammation, and cellular stress resistance.

In a younger organism, these pathways are flexible. After nutrients are available, cells can support growth and rebuilding. During periods of lower energy availability, they can shift toward maintenance, recycling, and stress protection. Ageing may weaken this flexibility, leaving some signals persistently activated while others become less responsive.

From growth signals to maintenance signals

One important example is mTOR, a pathway that promotes growth and protein synthesis when nutrients are abundant. mTOR is essential, but chronic or poorly timed activation may reduce autophagy—the process by which cells remove damaged proteins and organelles. At the same time, impaired insulin and IGF-1 signalling can disturb glucose regulation and alter how tissues respond to energy demands.

AMPK and sirtuins provide a complementary perspective. They help cells respond to low energy and metabolic stress, supporting mitochondrial adaptation and repair. If these pathways become less responsive with age, cells may struggle to adjust when energy conditions change. The result is not one single defect, but a less coordinated metabolic system.

Why this matters across the body

Deregulated nutrient-sensing can affect many tissues at once. In muscle, it may contribute to reduced protein maintenance and loss of metabolic flexibility. In the liver, it can influence glucose and lipid handling. In the brain, altered nutrient signals may interact with inflammation, mitochondrial stress, and the systems that maintain neuronal function. These relationships are complex, and they differ between individuals.

Research in model organisms has shown that modifying nutrient-sensing pathways can influence healthy lifespan. However, findings from laboratory models cannot be translated directly into a universal diet, supplement, or treatment for people. Human ageing is shaped by genetics, activity, sleep, disease, medications, and many other factors.

A practical interpretation

The most useful interpretation is not that one nutrient pathway should be switched off. Rather, healthy ageing may depend on preserving the ability to respond appropriately: to use nutrients for growth and recovery when needed, and to support repair and cellular housekeeping when conditions call for it. Regular movement, adequate sleep, a varied diet, and appropriate medical care all influence metabolic regulation, but individual needs differ.

Deregulated nutrient-sensing therefore describes a loss of coordination rather than a single cause of ageing. It connects metabolism with cellular maintenance and helps explain why the same biological signals that support growth early in life may become less well balanced over time. Understanding this hallmark may eventually help researchers develop more precise strategies for extending healthspan—not simply lifespan.