In response to the early stages of prediabetes, the body may develop a type of fat called “brown fat” that helps protect the body from the effects of elevated blood glucose, according to new research published in the Journal of Nuclear Medicine.
Prediabetes is defined by elevated blood glucose levels that don’t meet the threshold needed for a diabetes diagnosis. Whether or not it is recognized and diagnosed, prediabetes occurs at first in nearly everyone who eventually develops type 2 diabetes. Body fat (also known as adipose tissue) is known to play an important role in prediabetes and type 2 diabetes, since a major contributor to these conditions is insulin resistance — tissues in the body becoming less responsive to insulin. Since insulin allows cells in the body to take in glucose to use as energy — or to convert the glucose into body fat for storage — insulin resistance can eventually lead to elevated blood glucose levels. The causes of insulin resistance are complex, but at least some types of fat tissue are known to be more resistant to insulin than other tissues in the body — meaning that greater body fat may play a role in insulin resistance.
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But not all body fat acts in the same way, and for the latest study, researchers focused on a type of body fat that may be protective against harmful metabolic changes — brown adipose tissue, or brown fat. Brown fat is typically activated when someone gets cold, and produces heat that warms the body, as noted in a news release on the study. The most common method for measuring brown fat activity in humans is PET or CT imaging scans, which have shown that brown fat consumes glucose and fatty acids in the bloodstream — meaning that it may play a helpful role in prediabetes, type 2 diabetes, and other metabolic disorders such as hyperlipidemia (elevated blood cholesterol or triglyceride levels).
The study participants were 34 lean and healthy adults between the ages of 18 and 35, who had blood samples taken and answered questions about their lifestyle habits. For the main part of the study participants wore cooling suits to help activate their brown fat — which cooled their bodies to just above the point of shivering. After two hours of wearing these suits, participants had them removed and underwent imaging scans to look at brown fat activity. The researchers compared this activity with participants’ blood levels of glucose, insulin, lipids (cholesterol and triglycerides), and other indicators of metabolic health. Based on the median level among all participants, each participant was classified as having a high or low level of activated brown fat.
Higher levels of brown fat linked to early metabolic dysfunction
The researchers found that a higher level of activated brown fat was linked to early signs of metabolic dysfunction — this group of participants tended to have higher blood levels of glucose, insulin, thyroid stimulating hormone (TSH) and triglycerides before they put on their cooling suits. And even though all participants in the study were lean — with a body-mass index (BMI, a measure of body weight that takes height into account) between 18 and 25 — participants with higher levels of activated brown fat tended to have a higher BMI than the other participants. Participants with lower levels of activate brown fat also tended to report following a healthy diet and engaging in regular physical activity.
“Our findings show that molecular imaging potentially may be useful for identifying patients who are at risk of developing metabolic disorders and suggests activation of brown fat is a metabolic coping mechanism in ‘pre-pre-diabetes,’” said Richard L. Wahl, MD, director of the Mallinckrodt Institute of Radiology at Washington University School of Medicine in St. Louis, in the news release. “Further studies in larger populations are warranted to confirm and expand upon our findings.”
Want to learn more about prediabetes? Read “What Is Prediabetes? Symptoms, Treatment, and More,” “Prediabetes Treatment” and “Diabetes Prevention: Eat to Beat Diabetes.”
