Study: Cloned Pigs on a Human Diet

DENMARK - It is not humans eating like pigs, but rather, pigs eating like humans that form the basis for a research project on obesity at the Faculty of Agricultural Sciences, Aarhus University.
calendar icon 30 October 2009
clock icon 4 minute read

Even pigs that have been bred for their leanness for generations can acquire double chins and spare tyres when they are allowed to eat as much as they like.
Photo: Janne Hansen

The voracious pigs taking part in a study at the Faculty of Agricultural Sciences, Aarhus University, are all pretty well bolstered. The pigs’ ad-lib feeding regime, which has resulted in double chins and blubbery potbellies, is part of a project that aims to study the mechanisms behind obesity in humans.

It is not possible to clone and use humans for an experiment that requires genetically identical twins eating as much as they can to get as fat as possible, so the first step of the project involved finding suitable test animals. The Faculty of Agricultural Sciences at Aarhus University is the perfect place for such studies, as the faculty has spent years refining the technique on pig cloning.

Cloned pigs are genetically exact copies of each other. They should therefore be particularly suited for experiments, since natural genetic variation can be ruled out as a confounding factor and effects of particular diets should become more obvious

Although the scientists at the Faculty of Agricultural Sciences are getting better at cloning pigs, the technique is, however, not always successful. Pig cloning is still in its infancy and the cloning procedure does not always produce viable offspring. Thus, while the project on obesity runs from 2007 to 2012, it did not start in earnest until this year because of a shortage of suitable, cloned pigs.

"We were too optimistic. We had hoped to produce 120 pigs for the experiment, but we will probably end up with about 30," says senior scientist Jan Stagsted from the Department of Food Science, who leads the project.

Cloned pigs are not 100 per cent identical

While the number of pigs produced was disappointing, there has nevertheless been an exciting discovery. Despite the cloned pigs being “photocopies” of each other and having precisely the same genetic make-up, it turns out that they are not completely identical after all.

"The variations between the cloned pigs are probably due to so-called epigenetic mechanisms, that determine whether a gene is expressed or not," explains Dr Stagsted.

The project has hitherto had fewer and more variable pigs than expected, but the pigs are nevertheless good models for research into human nutrition, as their digestive and hormonal systems closely resemble those of humans.

The next step in the project is to determine what happens in the body, genes and proteins in the cloned and normal pigs when they are fed different diets. The experiment uses nutriomics – that is to say techniques where you study the interaction between nutrition, metabolism and genetics, seen from a holistic viewpoint.

Some of the pigs in the experiment are genetically disposed for leanness (traditional Danish crossings between Landrace and Yorkshire), while some of the pigs are disposed for excessive body fat deposition (dark brown pigs from Yucatan in Mexico).

The test pigs have been given free access to feed with a high sugar and fat content and different beneficial microorganisms so that the scientists can investigate the physiological mechanisms behind fat deposition.

Obesity affects the body

Scientists are also interested in studying the effect of feeding on nutrition-related problems associated with obesity, such as atherosclerosis, high blood pressure, and inflammation to see if the different physiological mechanisms are linked.

"Earlier experiments on mice have, for example, shown that there are links between the intestinal microflora and the development of obesity. With extreme obesity there is an increased inflammatory reaction in the body, which implies communication between the immune systems and the mechanisms behind lifestyle diseases," Dr Stagsted explains.

The five-year nutriomics project is carried out in collaboration with several departments at DJF in addition to KU Life, the Danish Institute for Food and Veterinary Research at DTU and Arla Foods. The project is financed by the Programme Commission for Health, Food and Welfare under the Research Council for Strategic Research.

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