Michael Gwarisa
More than one in three American adults lives with obesity, and scientists have long known it fuels chronic inflammation linked to diabetes, heart disease, and fatty liver. Now, an NIH-funded study has uncovered the biological chain reaction behind this process, opening the door to new treatments beyond weight loss.
New research funded by the National Institutes of Health has uncovered a chain reaction inside immune cells that helps explain why obesity leads to widespread inflammation. The findings could pave the way for new treatments that reduce disease risk even without significant weight loss.
At the center of the discovery is a structure inside immune cells called the NLRP3 inflammasome, which plays a key role in triggering inflammation. Researchers found that this inflammasome becomes unusually overactive in people with obesity.
To understand why, scientists examined immune cells known as macrophages from people with obesity and from lean individuals. When the inflammasome was activated, macrophages from people with obesity produced a much stronger inflammatory response. The same effect was seen in mice fed a high-fat diet, suggesting obesity fundamentally alters immune behavior.
The researchers traced this heightened response to an enzyme called SAMHD1, which normally helps regulate inflammation by breaking down DNA building blocks inside cells. In immune cells from people with obesity, SAMHD1 was found in an inactive state, limiting its protective role.
Without functional SAMHD1, DNA components begin to accumulate and fuel the production of new mitochondrial DNA. This newly formed DNA is especially vulnerable to damage, leading to oxidative stress. Once damaged, this mitochondrial DNA acts as a danger signal, activating the inflammasome and amplifying inflammation throughout the body.
Animal studies confirmed the impact of this process. Mice lacking SAMHD1 in their macrophages developed greater insulin resistance, increased liver inflammation, and more severe fat buildup when fed a high-fat diet, compared to normal mice.
The findings suggest obesity promotes inflammation by disrupting the body’s ability to control DNA-related processes within immune cells. By targeting one or more steps in this chain reaction, future therapies may be able to reduce inflammation and lower the risk of obesity-related diseases.
Why this matters in the U.S.
Obesity-related inflammation is a major driver of diabetes, fatty liver disease, and heart disease — conditions that cost the U.S. healthcare system billions each year. Understanding the biology behind inflammation could lead to treatments that reduce disease risk even without weight loss.
Researchers say this discovery fills a critical gap in understanding how obesity damages health at the cellular level and offers hope for treatments that focus on inflammation itself — not just weight loss.
This research highlights how obesity affects immune function at a molecular level, offering insight into future treatments for chronic inflammatory diseases.
