fast before surgery. It is a common recommendation doctors give to patients to ensure a safe procedure. Now a new study in mice suggests that boards may have benefits beyond the operation itself: the extensive preoperative fasting seems to protect the organs of postoperative damage. Although preliminary, the conclusion is based on evidence that short-term starvation helps the bodyguard against stress and can be a useful medical tool.
Researchers have known for decades that drastically cutting calories may help pets live longer, but exactly why is unclear. One popular idea is that when calories are braked, the body must adapt to nutrient deficiency and thereby, it becomes more resistant to stress in general. The type of long-term calorie restriction in the test animal is too extreme to widely apply to people, but some scientists have wondered what very short-term restrictions, only a few days, could have.
James Mitchell, who studies stress resistance at the Harvard School of Public Health in Boston, was particularly interested in the ischemic reperfusion injury, a problem that often occurs with heart attacks and strokes and sometimes even cardiac and vascular surgery. When someone has a heart attack due to a blocked artery, the heart is deprived of oxygen (a condition called ischemia) and the cells die. Against all intuitive expectation, when blood flow is restored (reperfusion called) can also do damage by triggering inflammation. This kind of double whammy can be induced experimentally in other organs, too.
Mitchell focused on the kidney and liver in part because it is relatively easy to measure their function. There are two years, he and his colleagues reported in Aging Cell which cuts the calories ingested by mice by 30% for up to 4 weeks protected rodent kidneys when their blood was cycled. Others have found that short-term caloric restriction does the same for the heart in mice.
But was it just a component of the restricted diet that mattered, like slashing sugar, or have done all calories should be pruned? Some studies have suggested that sugars and fats has not cut all that matters, so Mitchell turned to the protein. In a series of experiments, mice dozens he divvied into two main groups: some offered as much food as they wanted to eat, and some who consumed the same number of calories as the first group, but by through a protein-free diet. The animals were fed in this manner for 6 to 14 days. Then the researchers briefly tight blood flow to the kidneys before allowing the blood to flow back into them and then tested renal function. In a separate study, the researchers did the same for livers of animals after feeding them a diet devoid of tryptophan, a constituent of proteins.
Mice that were on diets without protein were about 50% better organ function, based on common markers in the blood than those who eat as much as they liked, the Mitchell Group reported today in Science Translational Medicine . This organ protection was higher than what researchers have seen with caloric restriction, suggesting that simply cutting the protein is even better or to do both at once perhaps the best of all.
Mitchell can not say for sure, but he suspects that deprivation of protein, such as calorie restriction generally activates some internal programs in cells which in turn improves the body's ability to handle stress . "These animals could be better conditioned to face a depletion of energy" who just cut oxygen to an organ "because they are under stress" when they do not eat protein, said -he. Mice on special diets also had less inflammation, suggesting that the restriction of the protein somehow dampens the body's inflammatory response.
This remains a hypothesis for now. "What we do not understand is what is the exact mechanism of this, what actually happens in the body," says Mark Talan, cardiovascular researcher at the National Institute on Aging in Baltimore, Maryland. (Institute funded the work of Mitchell, but Talan was not involved.)
One of the next steps of Mitchell is to explore whether the diet improves surgical outcomes in humans. He is currently in discussion with the vascular surgeons at Brigham and Women's Hospital to see if some sort of short-term fasting or diet protein-free before cardiovascular surgery is still feasible in people. "You might think that the best way to be resistant to surgery to come is to be well rested and well fed, but in fact that may not be the case," said Mitchell. Yet he warns that person about to undergo surgery should experiment with radical regimes on their own until the approach received further consideration.
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