“The Disturbing Connection Between Sugar Consumption, Obesity, and Brain Degeneration”

A recent study has uncovered a concerning link between a high-sugar diet and insulin resistance within the brain, which may hinder the clearance of neuronal waste and potentially elevate the risk of neurodegenerative conditions like Alzheimer’s disease.

Researchers, led by Mroj Alassaf at the Fred Hutchinson Cancer Research Center in the United States, have shed light on the association between obesity and neurodegenerative disorders, such as Alzheimer’s disease. Their investigation utilized the common fruit fly as a model organism and demonstrated that a high-sugar diet, a defining feature of obesity, induces insulin resistance in the brain. This insulin resistance, in turn, diminishes the brain’s capacity to eliminate neuronal waste, thereby increasing the vulnerability to neurodegeneration. These findings, published on November 7th in the open-access journal PLOS Biology, have significant implications for therapies aimed at reducing the risk of neurodegenerative diseases.

Understanding Insulin Resistance and Neuronal Waste Accumulation

While obesity is recognized as a risk factor for neurodegenerative ailments like Alzheimer’s and Parkinson’s diseases, the precise mechanisms linking the two have remained elusive. This recent study sought to unravel this mystery by capitalizing on the similarities between humans and fruit flies. Having previously established that a high-sugar diet induces insulin resistance in the peripheral organs of fruit flies, the researchers directed their focus toward the brain. Specifically, they examined glial cells because dysfunction in microglia, a type of glial cell, is known to lead to neural degeneration.

The Role of Sugar in Brain Function

The researchers assessed the levels of the protein PI3k, which reflects a cell’s ability to respond to insulin. Their findings revealed that the high-sugar diet resulted in reduced PI3k levels within glial cells, signifying the onset of insulin resistance. Furthermore, they examined the equivalent of microglia in fruit flies, known as ensheathing glia, which are responsible for clearing neural waste, including degenerating axons. Remarkably, these ensheathing glia exhibited low levels of the protein Draper, indicating impaired functionality.

Further experiments demonstrated that artificially lowering PI3k levels led to both insulin resistance and reduced Draper levels in ensheathing glia. The researchers also observed that, in fruit flies on the high-sugar diet, ensheathing glia were incapable of removing degenerating axons after actual damage to olfactory neurons because their Draper levels failed to increase.

In summary, the study’s authors state, “By utilizing fruit flies, we have established that high-sugar diets trigger insulin resistance in glial cells, disrupting their ability to clear neuronal waste. This research provides valuable insights into how diets promoting obesity may contribute to the heightened risk of neurodegenerative disorders.”

Reference: “Diet-induced glial insulin resistance impairs the clearance of neuronal debris in Drosophila brain” by Mroj Alassaf and Akhila Rajan, published on November 7, 2023, in PLOS Biology. DOI: 10.1371/journal.pbio.3002359.

Funding: This research was made possible through grants awarded to AR from the National Institute of General Medical Sciences (R35GM124593), the Brain Research Foundation (BRFSG-2022-09), and the 2023 McKnight Foundation Neurobiology Disorders Award. MA’s postdoctoral fellowship is supported by the Helen Hay Whitney Foundation. It is important to note that the funders had no involvement in the design of the study, data collection and analysis, the decision to publish, or the preparation of the manuscript.

Frequently Asked Questions (FAQs) about Neurodegenerative risk

More about Neurodegenerative risk

• Link to the research paper in PLOS Biology
• Fred Hutchinson Cancer Research Center
• National Institute of General Medical Sciences
• Brain Research Foundation
• Helen Hay Whitney Foundation
• 2023 McKnight Foundation Neurobiology Disorders Award