Menin levels dropped sharply in the hypothalamus of lab mice as they grew older. It’s a protein that helps suppress inflammation.Scientists may have uncovered a hidden biological switch that helps control how quickly the body ages. Research published in PLOS Biology suggests that declining levels of a brain protein called Menin can trigger inflammation, memory decline and other age-related changes throughout the body. In experiments with mice, restoring the protein reversed several signs of ageing, while a simple amino acid supplement improved cognitive function.The findings add to growing evidence that ageing may be strongly influenced by the hypothalamus, a small but powerful brain region that regulates metabolism, hormones, body temperature, sleep and stress responses. Researchers increasingly view the hypothalamus as a central command centre for aging itself.The study, led by Lige Leng and colleagues at Xiamen University in China, focused on Menin, a protein that helps suppress inflammation in the brain. Earlier work had already shown that Menin plays an important role in controlling neuroinflammatory activity. The team wanted to know whether losing this protective protein might contribute to ageing. Their experiments revealed that Menin levels dropped sharply in the hypothalamus as mice grew older. The decline occurred specifically in neurons within the ventromedial hypothalamus (VMH), a region linked to metabolism and systemic ageing. Interestingly, Menin levels did not significantly decrease in nearby support cells such as astrocytes or microglia.To investigate what this loss might mean, the researchers engineered mice in which Menin activity could be selectively reduced. The effects were striking. Younger mice with lower Menin levels developed increased brain inflammation, thinning skin, lower bone mass, impaired balance, memory problems and a shorter lifespan compared to normal mice. The results suggest that Menin may act as a protective “anti-ageing” factor inside the brain. One of the most surprising discoveries involved D-serine, an amino acid that also functions as a neurotransmitter in the brain. D-serine helps regulate communication between neurons and is important for learning and memory. When Menin levels fell, D-serine production also dropped. The researchers traced this effect to reduced activity of an enzyme required for D-serine synthesis, which itself appears to be regulated by Menin. D-serine naturally occurs in foods including soybeans, eggs, fish and nuts, and is also sold as a dietary supplement.The connection caught the attention of researchers because other studies have linked declining D-serine levels with ageing-related cognitive impairment and reduced synaptic plasticity, which means the brain’s ability to strengthen neural connections involved in memory and learning.