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Monday, December 23, 2013

Painted mice don't accumulate liver fat

Researchers from the University of Southern Denmark have been painting mice for science.

No, not this:

Fall Mouse
By ACEO, 2007


Why? To solve the mystery of why mice that are genetically lacking acyl CoA binding protein (ACBP) tend to accumulate fat in their livers. 

Organisms that have been bred without a specific gene (the gene might be removed or simply rendered non-functional) are referred to as ‘knock-outs’. Obviously, you can’t knock-out every gene, some are essential for life. However, where you can breed a knock-out, you have a tremendously useful model for seeing what that gene usually does. In this case, the ACBP knock-out seemed to be responsible for the changes in fat deposition.

The researchers noticed that in addition to fatty livers, the mice had greasy, tousled fur and leaky skin. That is, the animals lost excessive amounts of water through their skin. This in turn means that the mice also lose more heat than normal mice. The authors speculated that it was this extra heat loss that was causing them to store more fat than usual.

The scientists did two things to test this hypothesis. 

First, they bred some mice that were only lacking ACBP in their skin, but not in the rest of their bodies. Specifically, the animals’ livers had normal amounts of ACBP. Nonetheless, these specimens showed the same accumulation of fat in their livers as the total ACBP knock-outs.

Second, they painted the mice with a waterproof coating to prevent heat loss. At first, they used clear Vaseline, but grew concerned that the mice were absorbing fat from the Vaseline and that this might skew their results. So, the scientists switched to latex body paint. 

Regardless of body varnish, preventing heat loss through the skin reversed the liver fat accumulation in the ACBP-negative mice. 

Normally, ACBP knock-outs don’t live very long after weaning. If you choose to keep these animals as pets, make sure you refresh their body paint at regular intervals. 

Ditte Neess, Signe Bek, Maria Bloksgaard, Ann-Britt Marcher, Nils J. Færgeman, & Susanne Mandrup (2013). Delayed Hepatic Adaptation to Weaning in ACBP−/− Mice Is Caused by Disruption of the Epidermal Barrier Cell Reports DOI: 10.1016/j.celrep.2013.11.010.

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