Elevated Ghrelin Levels Drive Ghrelin Receptor Dysfunction in the Hippocampus of an Alzheimer's Disease Mouse Model | Research

The takeaway

In a mouse model of late-onset Alzheimer's disease, rising blood ghrelin levels paradoxically desensitize brain ghrelin receptors, contributing to hippocampal damage.

Ghrelin elevation drives receptor shutdown
Rather than being compensatory, rising ghrelin overstimulates and desensitizes hippocampal GHSR, creating a vicious cycle of synaptic injury

What the researchers found

The study found that humanized amyloid-beta knockin mice develop concurrent plasma ghrelin elevation and hippocampal ghrelin receptor (GHSR) desensitization as disease progresses. Crucially, the researchers demonstrated that the ghrelin elevation is not a compensatory response to receptor dysfunction. Instead, chronic overstimulation by elevated ghrelin drives enhanced receptor internalization, causing the receptors to become desensitized. This creates a vicious cycle: rising ghrelin leads to receptor shutdown, resulting in hippocampal ghrelin resistance and synaptic injury.

Why it matters

Ghrelin-based therapies have been proposed as potential Alzheimer's treatments because ghrelin supports memory and synaptic function. However, this study reveals that in Alzheimer's-like conditions, the ghrelin system itself becomes dysfunctional — elevated ghrelin actually worsens the problem by shutting down its own receptors. This fundamentally changes how researchers should think about ghrelin-targeted interventions for Alzheimer's disease.

How the study worked

Researchers used humanized amyloid-beta knockin (hAβ KI) mice — a model of late-onset Alzheimer's disease — and measured plasma ghrelin levels alongside hippocampal GHSR function over time. They combined in vivo mouse studies with in vitro primary neuron cultures to dissect the mechanism. Multidisciplinary techniques were used to assess receptor desensitization, internalization, and the functional consequences of chronic ghrelin overstimulation.

What this study cannot tell us

This study was conducted in a mouse model and primary neuron cultures, so the findings may not directly translate to human Alzheimer's disease. The hAβ KI model represents one aspect of AD pathology (amyloid-beta) and may not capture the full complexity of the human disease. Specific quantitative data on ghrelin levels and receptor changes were not detailed in the abstract, making it difficult to assess effect sizes.

How to read the evidence

This is a preclinical study using a mouse model and cell cultures. While it provides mechanistic insight into ghrelin receptor dysfunction in Alzheimer's-like conditions, the findings are preliminary and have not been confirmed in human patients.

When this study was published

Published in 2023, this is recent research using a relatively new mouse model (hAβ KI) that was specifically designed to study late-onset Alzheimer's disease.

The bigger picture

Alzheimer's disease research increasingly recognizes that metabolic and hormonal dysregulation plays a significant role in neurodegeneration. Ghrelin, a peptide hormone that crosses the blood-brain barrier, is one of several hormonal systems being investigated for neuroprotective potential. This study adds an important nuance: simply boosting ghrelin signaling may backfire in Alzheimer's contexts because chronic elevation drives receptor desensitization. Future therapies may need to target receptor sensitivity rather than hormone levels.

Questions still open

Could drugs that prevent ghrelin receptor internalization protect the hippocampus in Alzheimer's disease?
Do Alzheimer's patients with higher circulating ghrelin levels show faster cognitive decline?
Would intermittent rather than chronic ghrelin receptor activation avoid the desensitization problem?

Common questions

What is ghrelin and what does it do in the brain?

Ghrelin is a peptide hormone primarily produced in the stomach, commonly known as the 'hunger hormone.' Beyond appetite regulation, ghrelin crosses the blood-brain barrier and supports memory, learning, and synaptic plasticity in the hippocampus by activating its receptor, GHSR. When this system malfunctions, it can contribute to cognitive decline.

Why is it bad that ghrelin levels are elevated in this Alzheimer's model?

Counterintuitively, more ghrelin isn't better. This study showed that chronically elevated ghrelin overstimulates its receptors in the hippocampus, causing them to internalize and become unresponsive — a process called desensitization. The result is that despite high ghrelin levels, the brain can't use the hormone's protective effects, leading to 'ghrelin resistance' and worsening synaptic damage.

Read the original research

Elevated Ghrelin Promotes Hippocampal Ghrelin Receptor Defects in Humanized Amyloid-β Knockin Mice During Aging.

Journal of Alzheimer's disease : JAD, 96(4), 1579-1592

View on PubMed ↗Publisher’s paper ↗

Citation

Tian, Jing; Du, Eric; Jia, Kun; Wang, Tienju; Guo, Lan; Zigman, Jeffrey M; Du, Heng. (2023). Elevated Ghrelin Promotes Hippocampal Ghrelin Receptor Defects in Humanized Amyloid-β Knockin Mice During Aging.. Journal of Alzheimer's disease : JAD, 96(4), 1579-1592. https://doi.org/10.3233/JAD-231002