Perilipins and the bigger picture

On Friday we posted a summary on the website of one of our latest publications. The paper was on perilipins – a type of protein that surrounds lipid droplets, and is important in the regulation of fat storage – and looked at how their expression is influenced by diet, exercise and energy balance. We found that endurance training and fat consumption affected perilipin expression, while strength training and insulin sensitivity did not.

Why should I care? you ask. What are perilipins to me? And that’s the challenge.

Here at CERG, the scope of our research in cardiovascular disease and exercise ranges from public health and fitness to underlying molecular mechanisms, with everything in between. We use a variety of grand epidemiological studies, comparative models and clinical studies.

From an academic perspective this is really important. Not only do we want to create successful treatment options for cardiovascular disease by means of exercise – we also want to know how they work. Conducting both top-down and bottom-up research is essential in order to achieve this. But when you want to explain your work to the public, the bare facts can seem dull if you don’t explain the context sufficiently.

Research that makes you go wow!
To be fair, a lot of our research has that immediate appeal, with an exciting conclusion at first glance. For example, aerobic interval training is more effective in increasing the peak oxygen uptake in myocardial infarction patients than usual care. That’s cool because peak oxygen uptake has been shown to be an accurate predictor of future health, so changing usual care could improve the prognosis for cardiovascular patients. Or; that even low levels of physical activity reduce mortality in people with metabolic syndrome. Lesson: even if you’re unable to exercise every day, every little bit counts! And there are plenty of other good examples…

Not-so-sexy, but still really cool research
But if the conclusion is that there’s a clear correlation between perilipins 2-5 and muscle fiber type 1; and aerobic interval training increased the expression of perilipin 2 and 3 by 101% and 105% respectively? It just doesn’t have that same ring to the uninitiated… So here’s a little more context, which hopefully will lead you to recognize that perilipins are cool, and you should care that we found a correlation between exercise (endurance only) and perilipin expression.

The body stores excess energy as triglycerides. Since these are hydrophobic, they aggregate as lipid droplets in the hydrophilic cytosol inside of cells. Perilipins (also known as PAT-proteins or PLINs) are a family of proteins coating these lipid droplets, and they have an interesting, but not fully understood role in regulating fat metabolism. As summarized in a 2007 review, under normal conditions, perilipin prevents cytosolic lipases from reaching lipid droplets, thus preventing them from being broken down to be used in metabolism. However, when there is an energy deficit, perilipin is altered through phosphorylation, and facilitates maximal lipolysis which generate lots of energy by metabolizing the triglycerides.

Small changes have big consequences
Both animal models and genetic studies have shown that perilipins matter, since small changes in them can have drastic consequences. For instance, a 2001 study showed that mice genetically engineered to lack perilipin 1 ate as much as their normal peers, but had 30% less adipose tissue. They found that the basal fat metabolism was elevated, yet interestingly these mice were unable to reach as high a level of fat metabolism when stimulated (as during energy deficiency). This indicates that not only is perilipin 1 necessary to protect the lipid droplets when extra energy isn’t needed, but it is also required for maximal lipolytic activity. The mice were protected from diet-induced obesity when fed a high-fat diet, but had an increased tendency to develop glucose intolerance and insulin resistance, meaning they were predisposed to type 2 diabetes.

Another fascinating study looked at the change of just two nucleotides in the gene encoding perilipin in humans, and found a connection to obesity and response to exercise. It had earlier been shown that individuals with the abnormal gene had an increased risk of obesity. Jenkins and colleagues then showed that those with the abnormal gene retained more fat after a 6-month endurance training program, and this blunted their maximal oxygen uptake (VO2max) adaptation to training. They concluded that perilipin variation could explain some of the differences between people with respect to training response and cardiovascular disease risk.

Are you convinced yet? There are lots of other interesting papers out there on perilipins, but this gives you an idea of the potential involved. Perilipin is a cool molecule, and understanding it better is very exciting! And now that you have a little more context, you can consider giving the paper summary another shot if you skimmed right past it in the first place.

Written by Hanna Sofie Ellingsen at CERG.

This entry was posted in About the blog, Cardiovascular disease, Fitness, In English, Obesity, Public health, Research, Science by CERG. Bookmark the permalink.

About CERG

The Cardiac Exercise Research Group (CERG) at the Norwegian University of Science and Technology (NTNU) seeks to identify the key mechanisms underlying the beneficial effects of physical on cardiac health in the context of disease prevention and treatment. Named the K.G. Jebsen Center for Exercise in Medicine under Professor Ulrik Wisløff's leadership in 2011, CERG uses both top-down and bottom-up approaches to combat lifestyle-related disease.

2 thoughts on “Perilipins and the bigger picture

  1. I am a lay person trying to understand the significance of this. If the perilipins “expression is increased” for interval training, does this mean fat metabolism is inhibited by aerobic interval training and we should concentrate on strength training if we want to metabolize fat?

  2. First of all, the role of perilipins is not completely understood, and the various perilipin types seem to have different effects, so it’s too soon to implicate them in an exact mechanism. Their role also isn’t black or white – for instance perilipin 1 is both need to store fat well, but also if you want to metabolize lipids at the greatest possible rate.

    But generally speaking, high-intensity exercise shifts your metabolism, reducing the percentage of your energy which comes from fat, and increasing the percentage from carbohydrates. Nevertheless, if your goal is to metabolize more total fat, you also need to bear in mind that high-intensity exercise (like aerobic interval training) burns more calories overall, so even if your energy percentage coming from fats is lowered, you still overall burn more fat than moderate-intensity activities since you use more energy overall. So if you want to metabolize fat, high-intensity exercise is absolutely a good idea!

    That’s not to say that strength training isn’t important, quite the contrary. Building muscle increases your basal metabolism, so if you’re looking to metabolize the most possible fat, a combination of strength and endurance training is best.

    Hope that answers your question!

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