London: 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
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
"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
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.