Calorie restriction boosts blood vessel health, study finds
The study has linked calorie intake with the chances of developing an enlargement of the main artery in the abdomen caused by a weakening of the blood vessel wall.
This condition, also known as abdominal aortic aneurysm (AAA) is greatly exacerbated by a number of risk factors, including abdominal obesity.
As part of a healthy diet, calorie restriction (CR) studies have implied efficacy in preventing obesity and insulin resistance.
“We think that calorie restriction mimics the natural living conditions with food shortage we get used to thousands years ago,” said Dr De-Pei Liu, the study’s lead author and professor at the Chinese Academy of Medical Sciences and Peking Union Medical College.
“Hence, in response to calorie restriction, a low dose of stress, the inherent adaptive reactions, are induced for the maintenance of cellular and systemic homeostasis of the organism.”
In this study, mice were subjected to 12 weeks of CR. These mice, selected for their susceptibility in developing AAA were compared to control mice fed a normal diet.
The calorie-restricted mice showed lower rates of AAA rupture and death.
“Our findings implicate that reducing calorie intake holds promise as an effective yet simple way for early prevention and intervention of AAA in humans, especially in patients who are obese and at an advanced age,” said Liu.
Despite, these findings, Liu did believe that calorie restriction should be practiced in a moderate and gradual manner and that the intensity and timing of calorie restriction were closely monitored to minimise the potential side effects.
“Evidence in mice and lower organisms suggested that physiological functions, such as fertility, were compromised by severe calorie restriction as a trade-off,” he said.
Additional studies in mice have suggested that obese mice are more susceptible to AAA than lean mice and that weight loss suppresses the expansion of established AAAs.
Although the development of AAA is related to metabolic disorders, this study goes someway in demonstrating that controlled metabolism through CR may prevent the formation of AAA.
What is the mechanism?
The explanation for this observation centres on a reduction in the levels of an enzyme called MMP2. This protein is thought to degrade the protein matrix surrounding blood vessels.
Following the 12 weeks of reduced calorie intake, vascular smooth muscle cells in the wall of the aorta increased levels of another protein called SIRT1. This protein plays a role in suppressing the actions of MMP2.
The experimental mice that did not have the SIRT1 protein in its vascular smooth muscle cells could not reduce MMP2 expression and the incidence of AAA under calorie-restricted conditions.
"Our findings support the benefit of a calorie-restricted lifestyle for AAA prevention in humans, and suggest that SIRT1 could be a promising molecular target for the treatment of AAA," said Liu.
“Although it is relatively well accepted that a calorie-restricted life style is effective in reducing the risks of metabolic disorders and, as we observed here, the risks of some vascular diseases caution should still be born in mind when a calorie-restricted diet is adopted.
He commented that a diet should contain adequate and balanced amounts of essential nutrients in order to avoid malnutrition that might be caused.
When carried out correctly, calorie restriction or dietary restriction is considered an effective non-genetic and non-pharmacological intervention that can delay the aging process.
Long-term calorie restriction was also reported to reduce the risk factors of atherosclerosis in humans.
Source: The Journal of Experimental Medicine
Published online ahead of print, DOI: 10.1084/jem.20151794
“Calorie restriction protects against experimental abdominal aortic aneurysms in mice.”
Authors: De-Pei Liu et al.