Taste stimulation and its anticipation activates muscle glucose metabolism via ‘orexin’ neurons in the brain and thereby reduces blood glucose level in mice
Japanese research group led by Professor Yasuhiko Minokoshi and Dr. Tetsuya Shiuchi, scientists at the National Institute for Physiological Sciences, NIPS, Japan, found that meals stimulated with sweet taste and motivated with its anticipation regularly activates “orexin” in the brain and it stimulates muscle glucose metabolism via the sympathetic nervous system, thereby reducing blood glucose level in mice. They report their finding in Cell Metabolism published on Dec 2, 2009.
The research group focused on the function of “orexin” neurons in brain. Orexin is a kind of brain hormone … related to sleep/wakefulness and food intake. They found that orexin released in the brain from “orexin” neurons activates glucose metabolism in muscle but not adipose tissue in mice through the preferential activation of the sympathetic nervous system. Furthermore, they found that a pleasant meal with sweet taste stimulation and its anticipation activates orexin neurons and curbs the rise of blood glucose level by activating muscle metabolism via the sympathetic nervous system.
It is known that orexin plays an important role in the regulation of sleep/wakefulness and autonomic nervous system in human as well as experimental animals. Therefore, this finding implies the strong relationship between habits of diet and our health. Pleasant meal with tasty foods (of course, not high calorie) and with family and friends may prevent hyperglycemia by activating orexin neurons. In contrast, irregular dietary habits, especially eating fast food just before sleeping, may cause hyperglycemia and possibly obesity. “Orexin neurons have been shown to decrease the activity at night. Thus, eating just before sleeping may not be able to activate orexin neurons effectively, then resulting in hyperglycemia”, said Prof Minokoshi.
Orexin is interesting in that there are claims it may eliminate the need for sleep.
Background: the terms orexin and hypocretin both refer to the same entities. Â They refer to a pair of related small peptides that are found in the brains of vertebrates. Â Two labs discovered them simultaneously; each lab came up with a different name. Â The two terms are synonymous. Â I use the term orexin because I think it sounds better.
This is the link to the Wikipedia entry for orexin, for what it is worth.Â Â Orexin is produced in the hypothalamus and is distributed widely in the brain. Â It tends to excite the neurons that it interacts with, leading to wakefulness. – scienceblogs
An article in the December 2007 Wired gives more details:
A nasal spray of a key brain hormone cures sleepiness in sleep-deprived monkeys. With no apparent side effects, the hormone might be a promising sleep-replacement drug.
In what sounds like a dream for millions of tired coffee drinkers, Darpa-funded scientists might have found a drug that will eliminate sleepiness.
A nasal spray containing a naturally occurring brain hormone called orexin A reversed the effects of sleep deprivation in monkeys, allowing them to perform like well-rested monkeys on cognitive tests. The discovery’s first application will probably be in treatment of the severe sleep disorder narcolepsy.
The treatment is “a totally new route for increasing arousal, and the new study shows it to be relatively benign,” said Jerome Siegel, a professor of psychiatry at UCLA and a co-author of the paper. “It reduces sleepiness without causing edginess.”
Orexin A is a promising candidate to become a “sleep replacement” drug. For decades, stimulants have been used to combat sleepiness, but they can be addictive and often have side effects, including raising blood pressure or causing mood swings. The military, for example, administers amphetamines to pilots flying long distances, and has funded research into new drugs like the stimulant modafinil (.pdf) and orexin A in an effort to help troops stay awake with the fewest side effects.
The monkeys were deprived of sleep for 30 to 36 hours and then given either orexin A or a saline placebo before taking standard cognitive tests. The monkeys given orexin A in a nasal spray scored about the same as alert monkeys, while the saline-control group was severely impaired.
The study, published in the Dec. 26 edition of The Journal of Neuroscience, found orexin A not only restored monkeys’ cognitive abilities but made their brains look “awake” in PET scans.
Siegel said that orexin A is unique in that it only had an impact on sleepy monkeys, not alert ones, and that it is “specific in reversing the effects of sleepiness” without other impacts on the brain.
Such a product could be widely desired by the more than 70 percent of Americans who the National Sleep Foundation estimates get less than the generally recommended eight hours of sleep per night (.pdf).
The research follows the discovery by Siegel that the absence of orexin A appears to cause narcolepsy. That finding pointed to a major role for the peptide’s absence in causing sleepiness. It stood to reason that if the deficit of orexin A makes people sleepy, adding it back into the brain would reduce the effects, said Siegel.Â …