MS is a chronic disease that is caused by a complex set of interactions between genes and the environment. These interactions set off the immune system, causing it to degrade myelin, the protective coating around the nerve fibres. While there has been a strong focus on the genetic and environmental factors that result in a person getting MS in the first place, there has been far less research into what drives MS progression – the accumulation of disability over a person’s lifetime. One of the reasons for this is that the majority of genetic studies tend to focus on a single time point and cannot make comparisons over a person’s lifetime, as their disease changes. Longitudinal studies overcome this issue by looking at the same factors over a long period of time.
Some studies have looked at environmental factors contributing to MS progression. One such environmental factor that has been looked at is levels of fats in the blood. Fats in the blood include triglycerides, total cholesterol (TC), low density lipoprotein (LDL), and high density lipoprotein (HDL). Previous research has shown that high levels of triglycerides, high levels of TC, high levels of LDL, and/or low levels of HDL, are associated with increased disability progression. However, not much is known as to how these changes in fats might lead to disability progression. To help with this, a group of Australian researchers investigated whether genetic changes that related to fats are associated with disability progression in people with MS over time.
Published in the Journal of Neurology, Neurosurgery and Psychology, the researchers used a subset of the MS Research Australia-supported Ausimmune/AusLong longitudinal study, and followed 184 people with one suspected MS attack over five years. They discovered five genetic changes related to fats in the blood that were associated with disability progression as measured by the change in the expanded disability status scale or EDSS. The researchers generated a “risk score” for disability progression based on the combination of these genetic changes a person may have. They found that those with a lower risk score had lower rates of disability progression compared with those that carried a higher risk score. The researchers also predicted that those participants with higher risk scores in combination with a lower level of HDL or a higher TC:HDL ratio, experienced an even higher rate of disability progression.
The findings suggest that it is a combination of genetic changes and the level of fats in the blood that drive some disability progression. This interesting finding means that potentially there may be a way to modify MS disability progression through the treatment of abnormal fat levels in the blood – especially in those that have increased risk due to their genes. Determining the biological factors that underpin disability progression in MS is important as it will identify new ways to tackle and hopefully halt disability accumulation in people with MS.