Do weight loss drugs have a neuroprotective effect?

What is semaglutide?

You might know what semaglutide is, even if you have not heard of it! Semaglutide is the active ingredient in the weight loss medications Ozempic and Wegovy (these are just brand names). In the UK, Ozempic is officially licensed for managing type 2 diabetes. Using it for weight loss is considered off-label. Conversely, Wegovy is specifically licensed for chronic weight management in adults living with obesity or overweight accompanied by weight-related comorbidities. 

Semaglutide functions as a Glucagon-Like Peptide-1 (GLP-1) receptor agonist, mimicking the endogenous incretin gut hormone GLP-1. Incretins are a group of gut-derived peptide hormones released into the blood after eating. They lower blood sugar by signalling the pancreas to release insulin in a glucose-dependent way. Under physiological conditions, postprandial (post-meal) GLP-1 secretion stimulates glucose-dependent insulin release from pancreatic beta cells, inhibits glucagon secretion, delays gastric emptying, and promotes satiety.

Table 1: Table showing common ‘weight-loss drugs’ and their differences

Beyond metabolic regulation: mechanistic pathways in the CNS

While initially developed for metabolic control, GLP-1 receptors are also widely expressed across key areas of the central nervous system, including the hypothalamus, hippocampus, and brainstem (see Figure 2 below). This localisation has sparked significant scientific interest in semaglutide’s neuroprotective potential against neurodegenerative disorders like Alzheimer’s disease and Parkinson’s disease.

The underlying neuroprotective mechanisms operate across multiple interconnected cellular pathways:

Suppression of Neuroinflammation: Semaglutide activates intracellular cAMP/PKA and PI3K/Akt signalling cascades. This inhibits microglial and astrocytic overactivation, significantly reducing pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) and lowering neuroinflammatory markers like CD68. This is particularly relevant in Alzheimer’s Disease (AD), Parkinson’s Disease (PD), and ischemic stroke, where chronic neuroinflammation accelerates neuronal degeneration and blood-brain barrier disruption.

Mitigation of Oxidative Stress & Apoptosis: By upregulating CREB expression and downregulating reactive oxygen species (ROS) production, semaglutide protects neurons from oxidative damage and preserves mitochondrial integrity. This is useful in Parkinson’s disease (protecting vulnerable dopaminergic neurons in the substantia nigra from ROS-induced death) and traumatic brain injury or stroke (limiting secondary apoptotic cell death following ischemic insult).

Attenuation of Pathological Protein Aggregation: In preclinical rodent models, semaglutide interference reduces the accumulation of neurotoxic aggregates, notably amyloid-beta (Aβ) plaques and tau hyperphosphorylation in AD models, as well as -synuclein accumulation in the substantia nigra in PD models. This targets AD by reducing amyloid-beta (Aβ) plaque deposition and tau hyperphosphorylation, as well as PD by preventing -synuclein aggregation in the substantia nigra.

Restoration of Brain Insulin Signalling: GLP-1 receptor activation enhances central insulin sensitivity, restoring cerebral glucose metabolism and supporting synaptic plasticity. Often termed "Type 3 diabetes," AD involves localised brain insulin resistance. GLP-1 receptor activation enhances central insulin sensitivity, restoring cerebral glucose metabolism and supporting synaptic plasticity. This directly addresses AD (often referred to as "Type 3 diabetes" due to severe localized brain insulin resistance) and vascular dementia, where metabolic dysfunction impairs cognitive networks.

Has this been tested on humans?

Large-scale observational and epidemiological studies, such as Wang et al., 2024 and Tang el al., 2025, have repeatedly linked GLP-1 RA treatment with a lower incidence of cognitive decline and dementia amongst patients with type 2 diabetes. Furthermore, preclinical trials by Tipa et al., 2024 consistently demonstrate preserved motor function and enhanced memory in animal models.

However, translating these findings into clinical therapies for established neurodegenerative disease can be complex. Recent phase 3 clinical trials by Novo Nordisk (2025) testing oral semaglutide in patients with symptomatic early Alzheimer’s disease failed to achieve their primary clinical cognitive. While biomarker modulation was observed, clinical functional decline progressed largely unaltered.

This gap between lab results and human trials likely stems from a few key challenges: getting enough of the drug past the blood-brain barrier (low bioavailability due to low permeability of the blood-brain barrier), timing of intervention, and the fact that fixing metabolic pathways cannot undo advanced structural brain damage as structural damage in late-stage neurodegeneration that metabolic modulation alone cannot reverse. As a result, researchers are now focusing on using semaglutide to prevent disease in high-risk patients early on, rather than trying to cure advanced neurodegeneration.

Written by Chloe Kam

Related articles: A common diabetes drug / Innovations in the biosciences

REFERENCES

Novo Nordisk. (2025). Evoke phase 3 trials did not demonstrate a statistically significant reduction in Alzheimer's disease progression [Press release]. https://www.novonordisk.com/content/nncorp/global/en/news-and-media/news-and-ir-materials/news-details.html?id=916462 

Tang, H., Donahoo, W. T., DeKosky, S. T., & Wang, W. (2025). GLP-1RA and SGLT2i medications for type 2 diabetes and Alzheimer disease and related dementias. JAMA Neurology. https://doi.org/10.1001/jamaneurol.2025.0353

Tipa, R. O., Balan, D. G., Georgescu, M. T., Ignat, L. A., Vacaroiu, I. A., Georgescu, D. E., Raducu, L., Mihai, D. A., Chiperi, L. V., & Balcangiu-Stroescu, A. E. (2024). A systematic review of semaglutide’s influence on cognitive function in preclinical animal models and cell-line studies. International Journal of Molecular Sciences, 25(9), 4972. https://doi.org/10.3390/ijms25094972

Wang, W., Wang, Q., Qi, X., & Xu, R. (2024). Associations of semaglutide with first-time diagnosis of Alzheimer's disease in patients with type 2 diabetes: Target trial emulation using nationwide real-world data in the US. Alzheimer's & Dementia, 20(12), 8661–8672. https://doi.org/10.1002/alz.14313