glucose shortens the life span

During the study, Cynthia Kenyon of the University of California, San Francisco, found that by adding just a small amount of glucose to C. elegans usual fare of straight bacteria, worms lose about 20 percent of their usual life span.

They trace the effect to insulin signals, which can block other life-extending molecular players. Although the findings are in worms, Kenyon says there are known to be many similarities between worms and people in the insulin signaling pathways.

"In the early 90s, we discovered mutations that could double the normal life span of worms," Kenyon said. Those mutations effected insulin signals. Specifically, a mutation in a gene known as daf-2 slowed aging and doubled life span. That longer life depended on another "FOXO transcription factor" called DAF-16 and the heat shock factor HSF-1.

Now, the researchers have shown that those same players are also involved in numbering the days of worms that are fed on glucose. In fact, glucose makes no difference to the life span of worms that lack DAF-16 or HSF-1, they showed.

Glucose also completely prevents the life-extending benefits that would otherwise come with mutations in the daf-2 gene.

Ultimately, worms fed a steady diet containing glucose show a reduction in aquaporin channels that transport glycerol, one of the ingredients in the process by which the body produces its own glucose. "If there is not enough glucose, the body makes it with glycerol," Kenyon said.

That glycerol has to first get where it needs to go, which it does via the aquaporin channels.
Further studies are needed to see if these same effects of sugar can be seen in mice, or even people. But there is reason to think they may.

"Although we do not fully understand the mechanism by which glucose shortens the life span of C. elegans, the fact that the two mammalian aquaporin glycerol-transporting channels are downregulated by insulin raises the possibility that glucose may have a life-span-shortening effect in humans, and, conversely, that a diet with a low glycemic index may extend human life span," the researchers said.