Barbara Fielding: Metabolism of Fatty Acids
Obesity puts a huge strain on health care services in the UK, with 61% of people in England being overweight. By tracing fats containing heavy atoms from meals into the blood, her aim is to learn more about fat metabolism and target treatments for the complications associated with obesity and diabetes.
Q: What happens to the fats that we eat?
BF: When we eat fat it is first digested in the gut and then it is absorbed by cells that line the small intestine; they package the fat into particles which contain protein and other compounds which make it soluble for travelling in the blood, otherwise it would separate out a bit like oil and water. In fact, if you take a blood sample from someone who has eaten a fatty meal you can see the fat - it will look a bit cloudy in the plasma (the plasma is the part of the blood when you separate out the cells) and if you take another sample a few hours later it's cleared. One of the important tissues for clearing fat from the blood is muscle. This is a high requirement for energy and fat is energy dense; that helps to clear a lot of the fat and then what is left over is taken up by adipose tissue by our fat depots, and it is stored there for later.
Q: What techniques do you use to trace fat metabolism?
BF: We have a very special technique in Oxford; we use fats that are enriched with heavy atoms, typically we use carbon or hydrogen, and these are perfectly safe to give in humans. We give them as part of a test meal or we can give them intravenously, that is into a vein either as a dose or a continuous infusion. We can then trace it into the blood and follow it as it is cleared, and we can even measure the uptake into specific tissues.
Q: How can it affect people with obesity or diabetes?
BF: People with obesity who have an increased risk of getting type-2 diabetes generally have a slower metabolism of fatty acids. For example, we did a study in lean and obese people and we looked at how they metabolised fat from three sequential meals - typical of what you would have in 24 hours. We found that whereas the lean people stored about 40% of the fat that they had eaten in adipose tissue, only less than 20% was stored by people who have obesity. This means that the fat is not safely stored where it should be in adipose tissue and could then go on to lodge in other tissues such as the liver which could ultimately lead to increased risk of cardiovascular disease.
Q: What are the most important lines of research that have occurred over the past five or ten years?
BF: What I think is particularly interesting is the knowledge that different body shapes are important with regard to fat metabolism. We all know that it is important not to have too much fat, but it is also important where the fat is stored. A study in the Lancet recently showed that whereas people who have more fat around their stomachs have an increased risk of heart disease, people who store it more around their hips are actually protected. This is very interesting and we have done a study to start to investigate this and we, along with other people, have found that fat metabolism is different in the different depots and this could account for the differences in health risk.
Q: So why does your line of research matter, why should we put money into it?
BF: Obesity is a really big problem. About 61% of people in England at the moment are either obese or overweight, and this puts a tremendous burden on our health care services, so it is really important that we try to find ways of targeting treatment for the complications that result from diabetes and obesity.
Q: How does your research fit into translational medicine within the department?
BF: Translational medicine is all about moving from the bench side to the bed side and in a way we are already at the bed side because we carry out our research in whole people. This is possible because we have clinical research in it, at OCDEM, and this has really good services and is staffed by research nurses and they help to recruit and carry out the studies with us and even when we have a study that is happening we can take the samples up to the lab and start processing them.