A fault in the blood vessels of the brain may be one cause of obesity, say researchers in Germany.
Heike Nave from Hannover Medical School and her colleagues found that a small number of obese rats had a damaged blood-brain barrier.
Normally the barrier tightly controls what passes from the blood into the brain, but in obese rats the barrier was breached in two specific brain regions. This may interfere with the brain鈥檚 uptake of an appetite-suppressing hormone, the researchers believe.
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Nave and her colleagues initially thought that the damage might alter the way the appetite-control hormone leptin passes into the brain. But they found equivalent leptin levels in the brains of obese and lean animals.
Instead, they believe that the damaged membranes of the capillary walls result in a loss or masking of the leptin receptors, the receiving sites for the hormone.
Leptin is released by fat cells and normally travels in the blood to the brain, where it acts mainly in the cortex and hypothalamus. These are precisely the brain regions where the blood-brain barrier is breached, says Nave.
The obese mice had no genetic defect that could have caused the damage to the barrier directly. They had simply been fed a high-fat diet.
The researchers can鈥檛 yet say how a high-calorie diet could cause membrane damage. But once the process is started, the resulting lack of appetite suppression could plausibly lead to a cycle of overeating and further damage.
鈥淚t鈥檚 just four rats so far,鈥� says Nave. 鈥淏ut this is just the first part of our study.鈥�
This research was presented at a conference in New Orleans, organised by the US-based Society for Neuroscience. 快猫短视频鈥檚 full coverage of the conference is here: www.newscientist.com/conferences/