Good cholesterol (HDL) reduces inflammation in some parts of the body
But a new study shows HDL increases inflammation in some immune cells
Researchers warn this inflammation could counteract any other benefits
We are hounded with advice to embrace ‘healthy fats’ that will boost our ‘good’ cholesterol levels to protect our hearts.
But according to new research, the benefits may not be as strong as we have been led to believe.
Recent clinical trials looking at the relationship between high-density lipoprotein (HDL) levels and heart function have produced disappointing results.
In fact, the researchers found HDL – widely known as ‘good cholesterol’ – increases the inflammatory response of certain immune cells called macrophages.
And while HDL seems to be good for other parts of the body, the scientists warn this inflammation could counteract the benefits.
Avocados have been touted as a savior for your heart since they drive up your levels of good cholesterol. But a new study warns ‘good cholesterol’ (HDL) could also do some damage
‘A main take-home message of our study is that HDL’s functions are not as simple as initially thought, and appear to critically depend on the target tissue and cell type,’ study author Marjo Donners, of Maastricht University, said.
‘In the end, it is the balance between its pro- and anti-inflammatory effects that determines clinical outcome.’
HDL’s reputation as the ‘good cholesterol’ was earned over decades of research in humans and animals.
High HDL levels have shown to lower one’s risk of atherosclerosis – an inflammatory disease that causes plaque to build up inside of arteries.
It does this by blocking inflammation in two important vascular wall cells: endothelial cells and smooth muscle cells.
Low-density lipoprotein (LDL) deposits cholesterol in vessel walls, and is thus known as ‘bad cholesterol’.
Conversely, HDL removes cholesterol and transports it toward the liver for degradation.
However, in macrophages, HDL can have a damaging effect.
Macrophages are key immune cells contributing to the inflammation that characterizes atherosclerosis.
Surprisingly, this is one of the first studies to comprehensively study the effect of HDL on the inflammatory response in macrophages.
In the paper, published in Cell Metabolism on Thursday, Donners and Emiel van der Vorst tackled the murky issue.
To their surprise, they found that HDL boosted inflammation in macrophages.
Macrophages taken from mice with elevated HDL levels showed clear signs of inflammation.
However, there was some good news: this inflammation process helped lungs’ resistance against pathogens.
Donners says these findings show patients with low immune systems could still benefit from boosting their HDL levels.
However, several study limitations complicate clinical interpretations.
For one, the study focused on acute inflammatory responses rather than the chronic inflammatory conditions that characterize cardiovascular diseases.
The inflammation HDL causes in immune cells could counteract other benefits
Moreover, the researchers did not examine macrophages specifically in atherosclerotic tissue.
‘Whether HDL exerts beneficial or detrimental effects on the macrophage in a complex micro-environment, such as the atherosclerotic plaque, remains to be determined,’ Donners said.
The answer to this question may depend on disease stage and the net effect on all vascular wall cells.
‘For instance, in early atherosclerosis, a proper macrophage response could result in more effective scavenging and elimination of lipids and cellular debris, which may alleviate disease, whereas at later stages, such exaggerated responses may be detrimental because they destabilize the plaque,’ Donners said.
‘Moreover, the overt anti-inflammatory effects in other cell types should be taken into account, and it is the balance between these opposite effects of HDL that will determine clinical outcome for cardiovascular disease patients.’
This research could lead to the development of cell-specific therapies that exploit the benefits of HDL-targeted therapies while avoiding the side effects.
‘Future studies will have to evaluate the delicate balance of HDL’s cell-specific effects in humans and in various pathologies to get more insights and to develop and improve therapeutic strategies,’ Donners said.
Source: Daily Mail
