Fat Talks to the Brain

The received wisdom for years has been that the only biofeedback from fat to brain and back was via chemicals, hormones. The body’s adipose tissue, a technical term for fat, produces hormones and these chemical messages move passively in the blood through the body and to the brain which then makes any adjustments to the way the body works accordingly. Now scientists at Scripps Research have discovered that the adipose tissue and the brain are actually connected by sensory neurons and messages are actively sent back and forth between the body’s fat and the brain. Yes, in effect your fat talks to your brain!

In a press release Li Ye, PhD, the Abide-Vividion Chair in Chemistry and Chemical Biology and an associate professor of neuroscience at Scripps Research says:

“The discovery of these neurons suggests for the first time that your brain is actively surveying your fat, rather than just passively receiving messages about it,”

Li Ye continues “The implications of these findings are profound”

But just what might this discovery have a profound effect on? Scientists know that there is a relationship between body fat and several debilitating and life threatening diseases such as diabetes, certain liver diseases, circulatory problems, heart disease and more. If scientists could now build on this initial research and discover more about how the stream of electrical messages between the body’s fat tissue and the brain work in relation to the sympathetic nervous system then they might be able devise interventions to treat fat related illnesses.

The Scripps Research team used a novel imaging system to investigate the neural pathways between brain and fat tissue. This new imaging system is called HYBRiD and turns tissues surveyed, in this case mouse tissue, transparent. This allows the scientists to actually see the paths of neurons from the brain directly into the fat tissue. They were able to see for the first time that the neurons didn’t connect to the sympathetic nervous system but into the brain itself. They connect the body’s fat tissue to the dorsal root ganglia of the brain. This allows for a two way conversation between the fat and the brain.

Nobel laureate, Professor Ardem Patapoutian, PhD, an investigator at the Howard Hughes Medical Institute says in the Scripps Research press release:

“This is yet another example of how important sensory neurons are to health and disease in the human body,”

The adipose tissue is important as it is involved with the storage and release of energy in and from the fat cells of the body. When this system goes awry it can lead to obesity and disease. The adipose tissue not only directly stores and releases energy but also is involved in the control and production of various hormones that make us feel hungry or not and can alter the body’s metabolism. The HYBRiD imaging system has for the first time, along with another new technique developed by the Scripps Research teams in Patapoutian and Ye’s labs called ROOT, enabled them to see and explore in detail the nature and action of neurons within the adipose tissue.

The ROOT (retrograde vector optimized for organ tracing) system involves injecting a virus into specific neural clusters that destroys them allowing for an even clearer view of the neurons being studied in action.

The scientists found that the the sensory and sympathetic nervous systems might, in relation to the control of fat, work in opposition to each other. For the first time they were able to show that if active messaging between the fat cells, the adipose tissue and the brain is turned off or damaged then the sympathetic nervous system goes off kilter and larger than usual fat pads are created. These fat pads have greater levels of brown fat. The brown fat releases energy from sugar and other fat molecules. This produces heat and in fact in the mammals studied (mice) this resulted in an increase in body temperature.

The scientists at this stage don’t know exactly what the messages between the body fat tissues and the brain say but believe that the new findings could lead to advances in treating obesity, diabetes, heart disease and other illnesses.

Some of the above diseases could also be treated by lifestyle changes for instance in diet and physical activity but the research now shows clearly that when some obese people say ‘it’s my metabolism’ they could be right and suffering from a poor neural communication system between their adipose tissue and their brain. It is these individuals that might in future benefit from this groundbreaking research.

The research authors of “The role of somatosensory innervation of adipose tissue,” were Yu Wang, Verina Leung, Yunxiao Zhang, Victoria S. Nudell, Meaghan Loud, M. Rocio Servin-Vences, Dong Yang and Kristina Wang of Scripps Research; and Maria Dolores Moya-Garzon, Veronica L. Li, and Jonathan Z. Long of Stanford University.