University of Iowa scientists have discovered a new wrinkle in the remarkable ability of model organisms to extend lifespan when their caloric intake is restricted. When researchers restrict food to organisms as simple as yeast or as complicated as vertebrates, their lifespan is extended. In a new study, scientists uncovered evidence that baker’s yeast cells not only extend their own lifespan in response to caloric restriction but also communicate with other cells to share the benefit of caloric restriction.

In the study, “Calorie Restriction-Mediated Replicative Lifespan Extension in Yeast is Non-Cell Autonomous,” published today (Jan. 29, 2015) in PLOS Biology, University of Iowa researchers Szu-Chieh Mei, postdoctoral research scholar, and Charles Brenner, the Roy J. Carver Chair of Biochemistry and professor of internal medicine, document a cellular behavior that could be termed communitarian or altruistic.

“What our study shows is that even though yeast cells are considered simple, these cells communicate with each other and transmit the benefit of calorie restriction from cell to cell,” Brenner says.

A cell-autonomous behavior is one in which a single cell senses its environment and determines its response without the input of other cells. Non-cell-autonomous behaviors involve inputs or signaling from other cells.

“Much of evolutionary theory is based on the individual: every man for himself or every cell for itself,” Brenner says. “Surprisingly, when you calorie-restrict yeast, the cells respond by conditioning the environment in a way that spreads the longevity benefit to the local community.”

Brenner and Mei first grew yeast cells in a low-glucose environment, which restricted their calories and extended their lifespan. However, when they moved glucose-restricted cells to a new petri dish also containing low glucose, the move negated the longevity benefit of having been calorie restricted. The Iowa researchers hypothesized that the cells had left behind a communicable factor that is needed to extend their lifespan. A series of elegant experiments allowed them to show that calorie-restricted cells produce such a factor, which was not anticipated in the yeast system.

Ongoing experiments aim to identify the chemical nature of the yeast longevity factor and to dissect precisely how calorie restriction extends the lifespan of simple life forms such as yeast. While the health benefits of this research are not yet clear, the yeast system has served as a powerful model for understanding fundamental plant and animal functions and continues to surprise researchers with its complexity and sophistication.

“The National Science Foundation and the Roy J. Carver Trust supported our work to uncover regulation of yeast lifespan by glucose at a time when everyone’s thoughts were ‘inside the box’ of how a single cell changes its metabolism to extend its viability," Brenner says. "By looking ‘outside the box,’ we hope to stimulate new thinking about cellular regulation and aging, and to inspire people to appreciate the remarkable complexity of life on earth.”