Healthcare (Commonwealth Union) – A recent study that was published in Nature Metabolism has discovered a surprising metabolic flaw that converts fat storage into fat utilization.
As anticipated, mice in the study gained weight after eating high-fat foods. However, the obese mice regained a healthy weight and decreased inflammation when Yale researchers eliminated an amino acid called cysteine from their diets and prevented the animals from producing it internally. This was done although the mice continued to eat the same quantity of high-fat chow.
The researchers discovered that this impact was caused by a significant change in the mice’s fat tissue: almost all of the white fat, which stores energy, was changed to brown fat, which releases energy as heat, a process known as “browning,” once the cysteine was eliminated from the diet. As they were eaten, the mice were effectively burning off the excess calories.
The results provide hints as to how this may be used to enhance human health and longevity, showing that the loss of a single amino acid in a diet that is otherwise normal activates a switch that burns fat without destroying muscle mass.
Vishwa Deep Dixit, DVM, PhD, lead author of the study, Waldemar Von Zedtwitz Professor at Yale School of Medicine, where he specializes in Pathology, Immunobiology, and Comparative Medicine, and serves as director of the Yale Center for Research on Aging indicated that these results were totally unanticipated—and in science, that kind of surprise is incredibly thrilling.
Cysteine gained attention as a potential key to longevity thanks to findings from the CALERIE-II trial (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), the first rigorously controlled study of calorie restriction in healthy adults. In this study, some participants reduced their daily food intake by about 15% over two years, allowing scientists to track the long-term health outcomes.
The results showed that even modest calorie reduction led to noticeable improvements in several cardiovascular and metabolic risk factors. Since then, researchers have been working to uncover the biological mechanisms behind those benefits. One major clue: in participants who cut their calories, the metabolic pathway that manages cysteine levels in the body started behaving in an entirely new way.
Dixit and his colleagues investigated this discovery further in the new study by assessing the amounts of amino acids and thousands of metabolites in the fat tissue of CALERIE-II participants. They discovered a reprogrammed metabolic pathway and decreased cysteine levels in those who cut calories.
“So then we wanted to understand whether cysteine was driving some of the beneficial effects calorie restriction had on the immune system, inflammation, and metabolism,” explained Dixit.
They did it by using an animal model, which allowed them to see that this basic change in fat tissue is brought on by cysteine deficiency.
“What we found in the mice was that cysteine deprivation converted white fat into brown fat,” added Dixit. “It wasn’t just a little bit here and there. It was a dramatic transformation.”
Since most of our lives are spent in climates that are mainly controlled by temperature, brown fat produces heat, which is unnecessary in the modern world. However, this is an essential evolutionary defense system since it can be lethal if our core body temperature drops even three or four degrees below normal.
Brown fat, which generates heat by burning fat, is made for human survival because this is true for all warm-blooded species.
The researchers found that eliminating cysteine from the body entirely sped up the burning of fat, thereby taking the brakes off metabolism. According to the researchers, this discovery makes controlled cysteine restriction a viable dietary strategy to improve health and longevity by lowering excess body fat.
