London, Nov 19: In a finding that could have bearing on obesity and sleep disorders, researchers say it's protein, not sugar, that stimulates cells keeping us awake and thin by burning calories.
 According to researchers from University of Cambridge, wakefulness and energy expenditure rely on "orexin cells," which secrete a stimulant called orexin/hypocretin in the brain.
 Reduced activity in these unique cells results in narcolepsy, uncontrollable desire for sleep or its sudden onset and has been linked to weight gain, the journal Neuron reports, citing a varsity statement.
 Cambridge scientists compared actions of different nutrients on orexin cells and found out that amino acids, nutrients found in proteins such as egg whites - stimulate orexin neurons much more than other nutrients.
 "Sleep patterns, health, and body weight are intertwined. Shift work, as well as poor diet, can lead to obesity," said Denis Burdakov, pharmacology researcher at the Cambridge Institute of Metabolic Science.
 "Electrical impulses emitted by orexin cells stimulate wakefulness and tell the body to burn calories. We wondered whether dietary nutrients alter those impulses," he added.
 Scientists highlighted the orexin cells (which are scarce and difficult to find) with genetically targeted fluorescence in mouse brains. They then introduced different nutrients, such as amino acid mixtures similar to egg whites, while tracking orexin cell impulses.
 They discovered that amino acids stimulate orexin cells. Previous work by the group found that glucose (a sugar) blocks orexin cells (which was cited as a reason for after-meal sleepiness).
 So researchers also looked at interactions between sugar and protein. They found that amino acids stop glucose from blocking orexin cells, or in other words, protein negates the effects of sugar on the cells.
 "What is exciting is to have a rational way to 'tune' select brain cells to be more or less active by deciding what food to eat," Burdakov said. "Not all brain cells are simply turned on by all nutrients, dietary composition is critical.
 These findings may shed light on previously unexplained observations showing that protein meals can make people feel less calm and more alert than carbohydrate meals. IANS

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