Selective Deletion of Bdnf in the Ventromedial and Dorsomedial Hypothalamus
of Adult Mice Results in Hyperphagic Behavior and Obesity
By: Mayim Chaya Bialik, Ph.D.
Obesity and problems with overeating can be influenced by a number of factors
in the brain. One such factor is brain-derived neurotrophic factor (BDNF), which
is involved in eating and energy regulation. BDNF is found in the brain in the
cortex, the hippocampus, and the basal forebrain and it helps brain cells
survive and grow. Low levels of BDNF have been linked to depression, dementia,
schizophrenia, Obsessive-Compulsive Disorder, Alzheimerís Disease and
Unger and colleagues have recently explored the role of BDNF in energy
regulation and eating behaviors by giving normal mice injections of glucose
(sugar) and measuring the amount of BDNF in a brain region that is know to be
important for these processes, the Ventromedial Hypothalamus (VMH). They found
that glucose leads to an increase in BDNF, indicating that when the body gets
enough sugar and is full, it signals the brain to make BDNF.
Next, they wanted to see if taking BDNF out of an adult animalís brain could
affect eating behaviors and obesity as it has been shown to do in fetal and very
young mice. Removing BDNF from the VMH and another important brain region, the
Dorsomedial Hypothalamus (DMH), caused them to eat more and become obese. Thus,
BDNF normally signals when to stop eating.
This study showed for the first time that BDNF in the adult brain is
important for energy balance. If further studies can continue to confirm the
role of BDNF in obesity and overeating problems, this factor may be added to the
list of factors important for understanding and managing the weight and
hyperphagia problems in individuals with PWS. The mechanisms of overeating
involve (to name a few) leptin, insulin, melanocortins, noradrenaline, dopamine,
serotonin, and the gut hormone ghrelin. There is likely not one singular factor
or protein in the brain that causes the complex eating behaviors and subsequent
complications seen in those with PWS, but the study of BDNF may be the next step
in better understanding the complexity of energy regulation in PWS.
Abstracted from an article in The Journal of Neuroscience, 26 December 2007,
Bialik serves on the PWSA (USA) Research Advisory Board.