Single-cell studies Slim survive better than fat cells

Amoeba: Slimming has a dramatic effect on cell health
Larger fat reserves are considered to be an effective means of surviving periods in which there is less food. Or it serves as an insulating layer, as with whales or bears, to protect the body from the cold. In amoeba, however, fat seems to bring health disadvantages, as a research team from the Institute of Biology at the University of Kassel found out.

Body fat fulfills many useful functions for living organisms. Biologists at the University of Kassel have now discovered surprising effects of storage fat on a primitive protozoan. The results of the experiments show that lean cells master starvation better than fat cells.

Presentation: fat cells. Picture: fotoliaxrender-fotolia

The single-celled Dictyostelium discoideum normally lives as an amoeba in the forest floor and feeds on bacteria. In lack of food, several hundred thousand cells rot together and form a tiny mushroom-shaped fruiting body, in which they can survive as spores. Whether fat reserves for the survival are beneficial, was previously unknown.

For warm-blooded marine mammals such as whales, body fat forms an insulating layer under the skin to protect the animal from heat loss. Bears serve as energy storage for the time of hibernation. Since fat does not bind water, it weighs little and has a small footprint, which is an advantage for migratory birds in the Alps crossing. Even plants provide their seeds with fat, because it provides more energy. Overall, fat storage under natural conditions appears to be a beneficial property.

"Because crossing the Alps, hibernation and increased body temperature are not suitable for unicellulars" says Prof. Dr. med. Markus Maniak, cell biologist from the Institute of Biology at the University of Kassel, "the experimental approach was quite obvious". In one experiment, his PhD student Jessica Kornke mixed amoebae with fat reserves with those that were lean. The mixture was then starved until fruiting bodies formed. The cells were labeled in different colors, making it easy to see which cells coped more easily with the direct competition. To the great surprise of the scientists, the slender amoebas broke through against the fat cells. In fact, within the 24 hours required for fruiting, about 80% of the fat cells died prematurely.

The researchers were spurred on by the conclusion that slimming has a drastic effect on cell health, to conduct further experiments. Kornke and Maniak investigated a number of Dictyostelium mutants in which genes are defective, which also lead in humans to disturbed metabolism and lack of adipose tissue. The amoebae, in spite of an overabundance of food, were just as unable to create fat reserves as people with a genetic defect. In keeping with previous findings, these "genetically lean" cells did not harm the Lenten pathway and contributed to normal fruiting.

"We are very surprised" explains Prof. Dr. med. Maniak "that these primitive unicellular organisms have problems common to over-nourished civilizations, and they now urgently need to find out what molecular causes are behind the drastically shortened life expectancy of fat cells."