A blood pressure medication activated the body’s calorie-burning fat, according to a study by Paul Cohen’s team at Rockefeller University in the United States, published in the journal Nature. The clue came from an AI model that analyzed CT scans from 101,000 patients at Memorial Sloan Kettering Cancer Center. People with active tissue that converts calories into heat, known as brown fat, were less likely to have diabetes, heart disease, anxiety, and depression.
Brown fat is a remnant of human evolution that persists into adulthood and can be detected on PET/CT scans performed to investigate tumors. Of the 101,000 patients, 8,900 had detectable brown fat. The researchers compared this group with the others, adjusting for age, sex, body weight, and even the weather on the day of the scan. Brown fat was more commonly found in women, while its prevalence decreased with age and excess weight. People with brown fat were about half as likely to have type 2 diabetes and chronic ischemic heart disease. They were also significantly less likely to have hypertension, one-third less likely to experience depressive episodes, and less likely to report anxiety and insomnia.
The AI model also measured the activity of brown fat and each of its six deposits in 8,700 people. The more active the tissue, the less common diabetes, atrial fibrillation, coronary artery disease, and heart failure were. Fat in the armpit area showed the strongest association with health: its activity was linked to a more favorable distribution of harmful visceral fat, which accumulates around internal organs. Blood tests from people with brown fat also showed healthier profiles, from glucose levels to “good” cholesterol.
Until now, brown fat could be activated only through cold exposure or adrenergic stimulants, whose side effects prevented these approaches from becoming viable treatments. Researchers have therefore been developing drugs to stimulate it. An analysis of 125 medications found that beta-blockers and selective serotonin reuptake inhibitors (SSRIs), a class of antidepressants, were associated with reduced brown fat activity, while the presence of adrenal cortex hormones was associated with the opposite effect. A new potential candidate emerged in the form of angiotensin receptor blockers, which are used to treat hypertension.
For example, a drug that relaxes blood vessels increased levels of thermogenin UCP1, the key protein responsible for heat production. Mice given the drug expended more energy in both warm and cold conditions, without changes in body weight or appetite.
However, treatments are still a long way off. Further studies in humans will be needed, and existing observations already point to a potential downside of brown fat: slightly reduced bone density.
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