Dihexa

Dihexa is a laboratory-developed peptide-like compound derived from the naturally occurring molecule angiotensin IV. It was initially created as an improved angiotensin analogue, but researchers later became interested in a different proposed mechanism. Today, Dihexa is studied mainly for possible effects on brain plasticity, memory and the formation or preservation of connections between nerve cells.

Unlike many experimental nootropic compounds that temporarily alter neurotransmitter activity, Dihexa research focuses on structural changes in neural networks. The aim has been to identify a compound that could promote new connections between neurons and help preserve existing ones. This is why Dihexa has attracted attention in experimental models related to Alzheimer’s disease, cognitive impairment and other neurodegenerative conditions.

The human brain contains roughly 86 billion neurons. Our ability to learn, remember information and make decisions, however, depends not only on the number of neurons but also on how effectively they communicate. Neurons exchange information through small contact points called synapses. A greater number of functional synapses can support more efficient information processing.

The brain can form new synapses throughout life. This process is known as synaptogenesis: the formation of new connections between nerve cells. It contributes to learning, adaptation and partial recovery after some forms of injury. During ageing and in neurodegenerative disease, synaptic density may decline. Many researchers consider synapse loss an important contributor to deterioration in memory and cognitive function.

How is Dihexa proposed to work?

Much of the Dihexa literature focuses on the HGF/c-Met system. HGF, or hepatocyte growth factor, is a naturally occurring protein involved in tissue growth, regeneration and cell survival. Despite its name, it also has important functions in the brain. When HGF binds to its c-Met receptor, it activates processes associated with neuronal survival, dendritic growth and formation of new synapses. Dendrites are the branching extensions through which neurons receive signals from other nerve cells. Experimental studies suggest that Dihexa can bind to HGF and enhance its biological activity, thereby activating c-Met-related pathways associated with neural plasticity and synaptogenesis. When researchers blocked HGF or c-Met signalling, the observed effects of Dihexa were largely lost, supporting the view that this pathway is central to its proposed mechanism.

Most Dihexa studies have been conducted in cell cultures and animal models. A frequently cited study reported increased synaptogenesis and dendritic-spine formation in hippocampal neurons. The hippocampus is a brain region central to learning and formation of new memories. The number of synapses formed was reported to be comparable with the response to HGF itself. In the Morris water maze, a standard animal test of spatial memory, treated animals performed better than controls, but the improvement disappeared when HGF signalling was blocked. This again linked the observed cognitive changes to the HGF/c-Met system.

A 2021 study in a mouse model of Alzheimer’s disease reported improved spatial learning and memory, increased levels of the synaptic protein synaptophysin, reduced neuronal loss and lower concentrations of inflammatory cytokines such as TNF-α and IL-1β in the brain. Researchers also observed greater activity in the PI3K/AKT pathway, which is involved in cell survival and repair. A systematic review of experimental research evaluated 32 studies; in models with induced cognitive impairment, 8 of 9 studies of angiotensin IV analogues, including Dihexa, reported improvements in learning or memory measures.

Alzheimer’s disease receives particular attention because synapse loss is one of its early biological features. Researchers are also examining broader questions. The HGF/c-Met system participates in neuronal regeneration, stem-cell differentiation, neural-tissue recovery and protection of neurons from various injuries. Dihexa and related compounds are therefore being considered in experimental research on other neurodegenerative diseases, traumatic brain injury and additional neurological models.

Dihexa research raises important questions about HGF/c-Met signalling, synapse formation and neural-network plasticity, but the available evidence comes from cells and animals. There are not enough controlled human studies to establish clinical effectiveness, safety or benefit in Alzheimer’s disease or other neurological disorders.