Our weight is governed by our lifestyle and our genes. But new research at Linköping University has shown that the lifestyle of parents – before children are conceived – appears to impact their offspring’s weight.

“This is alarming from a public health viewpoint. It increases the risk of overweight for each generation,” says Öst, who researches at the Department of Clinical and Experimental Medicine, and is a Wallenberg Academy Fellow.

She has demonstrated a correlation between parents’ diet and obesity among offspring. In fruit flies.

“Whichever animal you choose to study – roundworms, mice or humans – their genes governing metabolism are actually very similar. We all need to do the same thing: save energy when food is plentiful, and draw on energy reserves when food is scarce,” Öst explains.

Genetic impact of eating sugar

She gave a group of male fruit flies an extra sugary diet for a period, and then allowed them to breed. Their offspring received exactly the same food as the control group. After a time she examined them to see whether they had become fatter. Examining fruit flies is a challenge in itself. Öst has devised a method whereby flies are crushed and mixed into a solution whose fat content can then be measured. The more fat in the solution, the fatter the flies. There was a clear difference: the offspring of the high-sugar-diet flies were much fatter.

But how has the effect of eating sugar been passed down? Genes are not changed by eating sugar. But diet may impact the way that genes are used.

Every cell in the body contains a complete set of all our genes. But not all genes are active in every cell. In each cell some genes are active and others silent, unused. This is controlled by what are known as “epigenetic factors”. These may be the way the DNA chain itself is coiled together, or small molecules attached to the chain and acting as signal flags. Epigenetic factors are affected by the way we live, and they can be inherited.

“Now we want to find out exactly which mechanism connects the sugar to obesity in the next generation. In purely physical terms, it must be molecules found in the sperm,” Öst says.

Researchers generous with their flies

High up on the list of suspects is a group of small RNA molecules. RNA performs many functions in the body. The type Öst is studying are most active in sex cells, and in early fetal development. She and her team are now looking to see what happens if the sugar experiment is repeated with flies that produce less of these RNA molecules. It is possible to “switch off” production of the molecules in the fly, but there are also fruit flies that already bear genetic changes affecting production. To date Öst’s team has studied some 40 or so fly variants of this kind that have purchased from, or donated by, other laboratories.

“One of the great advantages of using fruit flies is that they have been used in research for about a hundred years, and myriad variants have been bred and are generously made available by other research teams.”

Studying male sugar consumers

Öst is also about to begin a study on human subjects. A small number of men will eat a normal diet for a week, and then providing a sperm sample. They will then increase their calorie intake by 50 percent in the form of pure sugar. This represents about two liters of soda a day. After a week they will provide a fresh sperm sample so the researchers can compare the samples.

A week’s change in diet may not seem much, particularly given that it takes two or three months to form new sperm. But Öst believes changes in RNA occur in other cells, and that the changed molecules are then absorbed by the sperm.

If epigenetics is such a key factor in obesity, does diet play any part?

“Oh yes. Air alone will not make you fat. But a person may find it hard to lose weight if they have inherited a tendency to put it on. Those of us researching in this field hope one that it will one day be possible to influence epigenetics in some way. But it is also worth reflecting over the present-day unrestricted availability of sugar. I wouldn’t be surprised if we eventually see health warnings on packets of candy, as happened with cigarettes.”

“Being admitted as a Wallenberg Academy Fellow is a big deal. Of course, there is the money, but it’s also an acknowledgement – an imprimatur making everything run more smoothly. The university is also making a contribution – they are providing a new fly lab. They wouldn’t have done that if I had not received this grant.”

Work is like a hobby

Öst did not take a direct route to the world of research. She worked for Ericsson for ten years, first as a chemist then, having completed a course in market economics, in marketing and pricing. But when she had children she became increasingly interested in heredity and environment. She decide to return to the academic world.

“Now my work is like a hobby. I’m driven by the enormous pleasure I derive from research. The best thing of all is to perform experiments. When the lab work is done, I can sit at home in the evenings and follow new data coming in on my computer in real time, just because it’s fun.”

There is no mistaking her enthusiasm. We talk about the experiments she wants to do in the future, and the conversation turns to an entirely different topic: how metabolism might be affected by bacteria in the intestines. Öst leans forward eagerly:

“Yes – It’s so exciting! It’s just such a pity that I’ve already chosen my field…”

Text: Lisa Kirsebom
Translation: Maxwell Arding
Photo: Magnus Bergström