Diets high in saturated fat increase levels of endothelial lipase (EL), an enzyme linked to atherosclerosis, while diets rich in omega-3 polyunsaturated fats reduce levels of the same enzyme, according to a recent study conducted on mice which was published in Arteriosclerosis, Thrombosis, and Vascular Biology.
This study coincides with research from 2005, which claimed that high fat diets, as well as pollution, can cause atherosclerosis.
According to the report, these findings could also make it known why rosiglitazone (Avandia), a medication for type 2 diabetes, has been associated with heart problems.
EL, like other lipases, has a key function in blood lipoprotein metabolism. Lipoproteins are complex fats (lipids) and proteins. EL is secreted by a type of white blood cell called a “macrophage”, as well as some other cells located in the arteries. EL was discovered in 1999.
Previous research has demonstrated that raised EL is linked to inflammation, as well as atherosclerosis. However, according to the lead author of this study, Richard Deckelbaum, MD, from Columbia University Medical Center, until now, there was not much known about the effects of dietary fats on EL.
During the new trial, a type of mice prone to developing atherosclerosis was given a diet enhanced with either eicosapentaenoic acid (an omega03 fatty acid present in fish oils and other foods) or palmitic acid (a common saturated fat).
They examined the mice’s aortas after 12 weeks to see whether EL expression and inflammatory factors had changed. The mice that were fed the diet high in saturated fat demonstrated an increase in EL and harmful changes to inflammatory factors.
On the other hand, mice that were given the diets with polyunsaturated fat were seen to have a large decrease in EL, and their inflammatory factors benefitted from the diet as well. Cultured macrophages studies revealed related findings.
Dr. Deckelbaum said,
“Our study identifies a new way in which the high-saturated-fat Western diet could lead to the development of atherosclerosis, though, of course, these results need to be confirmed in human studies. The findings might also explain some of the cardiovascular benefits that have been attributed to omega-3 fatty acids.”
In addition, the authors discovered through cell culture investigations that when saturated fat was fed to macrophages, expression of PPAR-gama was increased. PPAR-gama is a cell-signaling molecule which is involved in the management of inflammatory responses and lipid metabolism.
“These findings are intriguing because we know that the diabetes drug rosiglitazone (sold under the brand name Avandia) is a strong PPAR-gamma activator and that it has been associated with an increased risk of heart disease. So we hypothesized that if rosiglitazone activated PPAR-gamma, it might also activate EL, which would explain its effects on the heart,” said Dr. Deckelbaum.
As soon as the marcophages received rosiglitazone, EL expression went up considerably. However, when omega-3 fatty acids were added, the increase was blocked.
Dr. Deckelbaum explained:
“This would suggest that besides raising LDL cholesterol levels, rosiglitazone can raise the risk of cardiovascular disease by increasing arterial inflammatory responses, EL increases the anchoring of LDL to cell surfaces, which could be associated with increased LDL accumulation in coronary arteries.”
In 2010, use of Avandia was prohibited, after experts found an association between the medication and heart disease.
Written by Christine Kearney