While the adverse health effects of saturated fats are commonly accepted, the biological mechanism for this has remained elusive. Using a newly developed microscopy technique, Columbia University scientists report that they have observed the process of saturated fatty acid build up in cell membranes. Their findings were published last week in the Proceedings of the National Academy of Sciences.
To make the discovery, the researchers developed a microscopy technique that allows for the direct tracking of fatty acids after they’ve been absorbed in living cells. The technique involves replacing hydrogen atoms on fatty acids with deuterium. This allows the molecules made from fatty acids to be observed inside living cells with Raman scattering (SRS) microscopy without changing their properties and behavior.
What the team found was that the cellular process of building a cell membrane from saturated fatty acids results in patches of hardened membrane in which molecules are “frozen” rather than flexible and fluidic as they should be. The fatty acids accumulate in clusters in the membrane, increasing its inelasticity and eventually damaging the entire cell.
"For a long time, we believed that all cell membrane is liquid-like, allowing embedded proteins to change their shape and perform reactions," said Principal Investigator Wei Min, a professor of chemistry. "Solid-like membrane was hardly observed in living mammalian cells before. What we saw was quite different and surprising."
Since unsaturated fatty acids have a kink in their chain, the lipids can’t align closely with each other as saturated fats do. Adding unsaturated fatty acids to a frozen membrane was found to ‘melt’ the membrane, which may partially explain the beneficial effects of unsaturated fats.
These findings could have significant impact for the understanding and treatment of obesity, diabetes and cardiovascular disease. Now that they have seen how the damage occurs, the researchers are hopeful that future treatments may someday be developed to reverse it.
Image: Saturated fatty acids build lipids that form 'frozen islands' (blue) in cell membrane (green). Image courtesy of Nicoletta Barolini, Columbia University.