Research study on the function of orexin neurons in brain

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 hormones 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.