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Fatty Acid Molecules: A Role in Cell Signaling

https://www.nature.com/scitable/topicpage/fatty-acid-molecules-a-role-in-cell-14231940/

Plenty of news articles and advertisements all promote the beneficial effects of omega-3 and omega-6 fatty acids. We know that fats provide caloric energy in our diet, but why should the particular kind of fat we eat make any difference? Specific fatty acids are the starting material for many vital signal molecules in plants and animals. Mammals cannot synthesize these fatty acid precursor molecules on their own, so a failure to obtain these fats from the diet can have major negative consequences. How were these molecules discovered and what specific features of their chemistry make them necessary? A fat-free diet for rats, hormonal secretions from the prostate gland, aspirin, and innovative chemical syntheses, are all parts of this developing story that help us explain the biological importance of these molecules.

What Happens When Fat is Removed from the Diet?

By the early twentieth century, scientists and doctors widely agreed on the basic set of vitamins needed for human health. But what about other nutrients? Working at the University of Minnesota, Burr & Burr (1929) examined the effect of fat-free diets on rats. They fed rats a diet containing sufficient calories, with protein and all of the known vitamins, but without fat. The control group of rats was fed the same diet, but containing fat. They carefully observed the health of the rats over several months. Over that time, the rats on the fat-free diet failed to thrive, developed severe skin and kidney problems, and often died within weeks. Interestingly, they could return the sickly animals to good health by adding some dietary fats, or small amounts of liver, back to their food, but many other fats had no beneficial effect. Why were these animals sick? Burr & Burr proposed several hypotheses. Perhaps the strain on the animals caused by synthesizing all of their own fats was the cause. Could there be a new fat-soluble vitamin (vitamin F), which was needed for animal health? Or were there specific features of the fat itself that were necessary? They knew that there are several kinds of fatty acids in the human diet, so they decided to answer some of these questions by systematically feeding the sick animals a selection of known fats to see if any of them had an effect (Figure 1). They eventually discovered that adding back two particular purified fatty acids, linolenic and linoleic acids, restored the sick animals to health, while the other fatty acids were unable to do so (Burr & Burr 1932). This led to the recognitions of linolenic and linoleic acids as essential fatty acids.