MSGID: 1:317/3 63dc8de0   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Sugar is processed differently in the brains of obesity-prone vs.   
   obesity-resistant rats    
    Molecular insights point to neuronal underpinnings of obesity    
      
     Date:   
         February 2, 2023   
     Source:   
         Michigan Medicine - University of Michigan   
     Summary:   
         A new study tracked what happens in the brains of rats in real   
         time in the brain when presented with glucose, a type of sugar,   
         labeled with a tracer. The tracer allowed the researchers to   
         measure this new sugar in the brain.   
      
      
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   FULL STORY   
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   On a diet? Perhaps you're avoiding sweets or carbs altogether or curbing   
   late- night munchies. These are examples of behavior modifications and   
   when it comes to food, avoiding those diet triggers can be pretty hard   
   to do.   
      
      
   ==========================================================================   
   To understand what drives people to overeat, scientists are looking   
   more closely at a brain structure involved in motivation, called the   
   nucleus accumbens. This small region drives reward-seeking behaviors   
   underlying the pursuit of sex, recreational drugs like nicotine and   
   alcohol, and food.   
      
   "These brain motivation centers evolved to help us survive; finding   
   food and having sex are essential to the survival of an individual and   
   of a species," said Carrie Ferrario, Ph.D., associate professor in the   
   Department of Pharmacology at U-M Medical School.   
      
   "What was advantageous when food was hard to find has become a   
   disadvantage and unhealthy in the current food dense environment. This is   
   compounded by the over-abundance of over-processed, low nutrition foods   
   that may satisfy our taste but leave our bodies unnourished. People don't   
   tend to find it difficult to turn down an extra serving of broccoli,   
   but just one more french-fry or making room for a bit of chocolate   
   dessert...that's a different story. The real challenge is overcoming these   
   urges and changing our behavior when it comes to food," Ferrario added.   
      
   Given the immense toll obesity takes on virtually all body systems,   
   Ferrario, Peter Vollbrecht, Ph.D., of Western Michigan University, and   
   their colleagues are using rat models to understand potential brain   
   differences between animals who are prone to over-eating and obesity   
   and those who are not.   
      
   Previous research from Ferrario's lab pinpointed differences in the   
   nucleus accumbens in obesity-prone and obesity-resistant rats. Their   
   latest study, published in the Journal of Neurochemistry, tracked what   
   was happening in real time in the brain when these animals were presented   
   with glucose, a type of sugar, labeled with a tracer. The tracer allowed   
   the researchers to measure this new sugar in the brain.   
      
   Sugar is the brain's main fuel source and once there, the molecule is   
   broken down and used to create new molecules such as glutamine, glutamate,   
   and GABA, each with an important role in influencing the activation of   
   neurons in the brain and nervous system.   
      
   "Glucose that is consumed gets broken down and then its carbons get   
   incorporated into neurotransmitters. We see those labelled carbons showing   
   up in those molecules -- glutamate, glutamine, and GABA -- over time,"   
   explained Vollbrecht.   
      
   They found that glucose was taking longer to get into the nucleus   
   accumbens of obesity-prone animals.   
      
   Furthermore, when measuring the concentration of the glutamate,   
   glutamine, and GABA, they discovered excess levels of glutamate, an   
   excitatory neurotransmitter. This, said the team, implied a defect in a   
   neurotransmitter recycling process, typically maintained in the nervous   
   system by star-shaped cells called astrocytes.   
      
   Normally, astrocytes will pull glutamate out of the space between neurons,   
   called the synapse, convert it into glutamine, and then shuttle it back to   
   cells that produce GABA or glutamate. This sequence is crucial for turning   
   neurons off and on. "The findings suggest that we're getting too much   
   glutamate and it's not being taken out of the synapse," said Vollbrecht.   
      
   Ferrario added, "The balance between glutamate and GABA (the main   
   inhibitory transmitter) is really important for brain function and   
   will influence activity of the neurons in the nucleus accumbens."  This   
   balance, and therefore brain activity, is different in obesity-prone vs.   
      
   obesity-resistant rats.   
      
   The fact that these rats are either prone to obesity or not is important   
   for disentangling cause and effect, says Vollbrecht. "It allows us to   
   remove diet as one of the variables."  The team hopes to next study the   
   role of inflammation in the development of obesity, and how differences   
   in brain function contribute to susceptibility and resistance to obesity.   
      
       * RELATED_TOPICS   
             o Health_&_Medicine   
                   # Diet_and_Weight_Loss # Obesity # Nervous_System #   
                   Nutrition   
             o Mind_&_Brain   
                   # Dieting_and_Weight_Control # Nutrition_Research #   
                   Neuroscience # Brain_Injury   
       * RELATED_TERMS   
             o Blood_sugar o Sugar o Positron_emission_tomography o   
             Sugar_substitute o Brain o Diabetes o Honey o Brain_damage   
      
   ==========================================================================   
   Story Source: Materials provided by   
   Michigan_Medicine_-_University_of_Michigan. Original written by Kelly   
   Malcom. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Peter J. Vollbrecht, Kathryn M. Nesbitt, Victoria M. Addis,   
      Keenan M.   
      
         Boulnemour, Daniel A. Micheli, Kendall B. Smith, Darleen   
         A. Sandoval, Robert T. Kennedy, Carrie R. Ferrario. Differential   
         regulation of nucleus accumbens glutamate and GABA in   
         obesity‐prone and obesity‐resistant rats. Journal of   
         Neurochemistry, 2022; DOI: 10.1111/jnc.15720   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230202153602.htm   
      
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