Medical Bulletin 22/ April/ 2024

Here are the top medical news for the day:

Is western diet linked to lasting memory issues?

In a recent study published in the journal Brain, Behavior, and Immunity, researchers developed an initial-life Western diet (WD) murine model associated with long-term hippocampal (HPC) dysfunction to examine the neurobiological processes underlying these effects.

The Western diet, rich in processed foods, saturated fats, and simple carbs, harms memory, especially hippocampus-dependent functions. Its impact on brain development and long-term hippocampal damage is unclear. However, it alters synaptic plasticity, lowers BDNF levels, and increases neuro-inflammation markers. Additionally, disruptions in acetylcholine signaling may worsen Western diet-related memory issues.

In this study, researchers looked at how a diet similar to the Western diet during early life affects memory in rats. They used a cafeteria-style diet, like junk food, to mimic the Western diet in humans. Some rats ate this diet during their youth, while others ate regular rat food. They then measured their weight and food intake regularly. The rats on the cafeteria diet had memory problems even after switching to healthier food later in life. The researchers also studied the levels of certain proteins related to memory in the rats' brains. They used memory tests to see how well the rats remembered things.

The study found that rats who ate a Western-style diet early in life had lasting memory problems, even after switching to healthier food later on. Specifically, they had trouble remembering spatial information. However, their ability to recognize new items wasn't affected as much if it didn't involve using a specific part of the brain called the hippocampus.

The findings highlighted that early exposure to a Western diet (WD) was associated with long-term episodic memory deficits mediated by altered hippocampal acetylcholine (ACh) transmission.

Reference:Anna M.R. Hayes et al., Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling, Brain, Behavior, and Immunity, 2024, DOI: 10.1016/j.bbi.2024.03.015, https://www.sciencedirect.com/science/article/pii/S0889159124002952

Liver could potentially help in treatment of cancer, finds study

In a study, published in Nature Immunology,researchers discovered that cancer-induced liver inflammation causes liver cells to secrete proteins called serum amyloid A proteins, which circulate through the body and hinder the ability of T cells—major anticancer weapons of the immune system—to infiltrate and attack tumors elsewhere.

Liver inflammation, a common side-effect of cancers elsewhere in the body, has long been associated with worse cancer outcomes and more recently associated with poor response to immunotherapy.

“We want to better understand what causes cancer to resist or respond to immunotherapy to help design more effective strategies for patients. Our findings show that liver cells—with their release of SAA proteins—effectively serve as an immune checkpoint regulating anti-cancer immunity, making them a promising therapeutic target,” said senior author Gregory Beatty.

In the study, researchers at the University of Pennsylvania studied mice with pancreatic cancer to see how immune cells called T cells affect tumor growth. They found that mice with fewer T cells in their tumors had more inflammation in their livers. These mice also showed increased activity in a signaling pathway related to inflammation, which the researchers previously linked to liver metastasis in another study.

To see if the results from the mouse study applied to humans, the researchers analyzed tissue samples from patients who had surgery to remove pancreatic tumors. They discovered that patients with low levels of SAA in their tissue samples during surgery tended to live significantly longer after the procedure.

“The translational findings in human patients highlight the likely clinical relevance of our discoveries in the mice. Now that we’ve shown how liver inflammation puts up a roadblock to immunotherapy, our next step is to see if the same pathway can be targeted to reverse inflammation in patients who already have liver metastasis,” said Betty.

Reference: Stone, M.L., Lee, J., Lee, J.W. et al. Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins. Nat Immunol (2024). https://doi.org/10.1038/s41590-024-01820-1

Can retinal thickness predict cognitive progression in Parkinson's patients?

In a study published in the journal NPJ Parkinson’s Disease, researchers investigated whether the retinal thickness could predict cognitive progression in parkinson patients.

In Parkinson's disease, changes in the retina, including thinning and alterations in blood vessels, may occur and could serve as a biomarker for the disease. These changes reflect underlying brain degeneration and may be detected using non-invasive imaging techniques like optical coherence tomography. Understanding retinal progression could improve diagnosis and management of Parkinson's.

In the study, researchers used optical coherence tomography to measure the thickness of the innermost layer of the retina in Parkinson's patients. This tool is commonly used in eye tests because it provides detailed and accurate measurements. They looked at how this retinal layer changed over six years, comparing people with and without Parkinson's disease.

The results showed that the innermost retinal layer is thinner in Parkinson's patients. They noticed that during the early stages of the disease, the most significant nerve damage is seen in the retina. As the disease progresses, the nerve damage stabilizes even though the retinal layer remains thin. Interestingly, retinal thinning and cognitive decline don't happen at the same time. First, changes in the retina are noticeable, then over time, patients experience worsening cognitive and motor symptoms.

The findings concluded the slower retinal layer thickness loss is associated with faster cognitive decline; this slowness is linked to greater severity of the disease.

Reference: Murueta-Goyena, A., Romero-Bascones, D., Teijeira-Portas, S. et al. Association of retinal neurodegeneration with the progression of cognitive decline in Parkinson’s disease. npj Parkinson’s Dis. 10, 26 (2024). https://doi.org/10.1038/s41531-024-00637-x