"A surprising but welcome side effect of a therapy for obsessivecompulsive disorder may pave the way for a new approach to treating type  diabetes  and offer new insights into the links between obesity and the metabolic disease that afflicts close to  in  American adults. The therapy in question is deep brain stimulation of the nucleus accumbens https a structure best known for its role in motivation reward and addiction. It now appears that deep brain stimulation also increases the livers and muscles ability to take up and use insulin researchers reported this week. Thats important because the ability to use insulin effectively is compromised in most people with obesity and seriously impaired in those with type  diabetes. This curious side effect of deep brain stimulation became clear after an obese man with diabetes who had suffered the repetitive thoughts and behaviors of OCD was treated for the psychiatric condition with a device that delivers electrical impulses into the brain. Once the device was implanted and turned on it prompted the release of the neurotransmitter dopamine https throughout the ventral striatum in which the nucleus accumbens sits. In short order the patient noticed that his blood sugar control improved and his daily need for insulin injections decreased by roughly . The new study httpstm.sciencemag.org appeared this week in the journal Science Translational Medicine. The research is likely to generate renewed interest in understanding the addictive powers of food for some people and whether the brain processes behind that addiction also make people with obesity more vulnerable to diabetes depression heart disease and even some cancers. The connection between brain and metabolism is only partially understood said Dr. Miguel AlonsoAlonso httpsmbb.harvard.edupeoplemiguelalonsoalonsomdphd who directs Harvard Universitys Mind Brain Behavior Interfaculty Initiative. httpsmbb.harvard.edu Most research to date has focused on the hormonal influence of the hypothalamus a structure adjoining the ventral striatum on basic bodily functions he added. This is a new and exciting direction with the involvement of the striatum a key reward center AlonsoAlonso said. At the same time he cautioned that we first need to establish the nature of this association understand its magnitude and its clinical relevance before these early findings could be considered the basis for treatment. That a single patients metabolic function improved after he got a pacemaker in the brain might have met with a shrug anywhere else. But to the Dutch authors of the new research it was a clue that warranted further investigation. To explore the brains role in metabolism more rigorously the researchers led by Kasper W. ter Horst of the University of Amsterdams Academic Medical Center recruited  patients who also had had a brain stimulator implanted at the edge of the nucleus accumbens as treatment for OCD. None of the  subjects recruited had type  diabetes. But even healthy people vary daily and hourly in the ability of fat liver and muscles to take up insulin from the bloodstream and use it to convert food to energy. This measure of metabolic health is called insulin sensitivity and it is one of many metabolic functions that goes awry in people with obesity. In those who develop type  diabetes sensitivity to insulin becomes so impaired that the body is tricked into believing less insulin is needed and it pares back its production. The insulinproducing cells in the pancreas will often atrophy and die in response. As a persons insulin production declines an external supply of insulin is needed to control blood sugar and deliver fuel to muscles and organs. As the researchers turned the  subjects brain stimulators on and off they could see the subjects insulin sensitivity rise and fall. Metabolic function was better when their brain stimulators were turned on than when the devices were silenced. The Dutch team ruled out that the performance improvement came from changes in other hormones that can affect metabolism such as cortisol https epinephrine https and norepinephrine. https The action of dopamine in the nucleus accumbens appeared to be effecting the changes. The researchers also gleaned a potentially important insight about how obesity may lead to worsening metabolic function The effect of the deep brain stimulation appeared to be greater in the seven research subjects who were lean than it was in the seven who were either overweight or obese. Since longterm obesity is linked to changes in the striatal dopamine system the differing responses of lean and overweight subjects suggest that those changes may start the ball rolling toward development of type  diabetes.. In a further experimental group of  healthy humans the researchers found that using drugs to reduce dopamine levels across the body generated the opposite response decreasing insulin sensitivity. In mice too the researchers explored the role of the dopaminefueled neurons of the nucleus accumbens. Using a technique called optogenetics they bred mice with certain brain cells that could be activated when light of a particular frequency is shined on them. Light stimulation of the dopamineexpressing neurons in the brains of mice was sufficient to improve glucose tolerance and improve insulin sensitivity the authors reported. That suggests a key role for striatal neuronal activity in the central regulation of metabolism they added. The emerging data suggest that the brain may play a much more active and complex role in the regulation of metabolism than we usually believe said AlonsoAlonso who has explored the brains role in metabolism by using a less invasive means of activation called transcranial magnetic stimulation. https This makes sense because at the end metabolic needs should align well with the overall state of the individual he said. It stands to reason that theres crosstalk among key physiological functions an individuals cognitive mental and social states and situational circumstances he added. I think there are real good opportunities here for this integrative research we need to learn more about this connection AlonsoAlonso said."