Researchers have found that the insulin signaling pathways in worms have a direct bearing on their lifespan. This research is particularly interesting because humans and worms share very similar insulin signaling pathways.
Over a decade ago, the first part of this research led to some positive news as researchers found that certain mutations involved in the insulin pathways can greatly extend lifespan in worms.
“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.
Unfortunately, the recent results show that adding sugar to the worm diet has the opposite effect.
By adding just a small amount of glucose to C. elegans usual fare of straight bacteria, they found the 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.
Here is the technical aspect of the results:
In fact, glucose makes no difference to the life span of worms that lack DAF-16 or HSF-1, they show. 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 explained. That glycerol has to first get where it needs to go, which it does via the aquaporin channels.
There are a few ways in which the result from studying worms affects us as humans.
A diet with a low glycemic index seems like a safe bet for now. One of the scientists was alarmed enough with the data to make serious changes to her diet:
As an aside, Kenyon says she read up on low-carb diets and changed her eating habits immediately — cutting out essentially all starches and desserts — after making the initial discovery in worms. The discovery was made several years ago, but had not been reported in a peer-reviewed journal until now.
Another area of concern is medicine. Current drugs may be offering treatment which carry as of yet unknown long term side effects. Fortunately, as is the case with anti-depressant medication, science is continually advancing to make our lives better and this research will undoubtedly result in better life saving medicines.
She says the findings may also have implications for drugs now in development for the treatment of diabetes, which are meant to block glucose production by inhibiting glycerol channels. The new findings “raise a flag” that glycerol channels might be doing something else, she says, and that drugs designed to block them might have a downside.
A long term study recently found a connection between consuming two servings of diet soda daily and a significant decline in kidney function. How do different types of artificial sugars factor into these results? Is there any connection between these two studies?
Aging in humans is far more complex than in worms.
“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 write. Kenyon also points to recent studies that have linked particular FOXO variants to longevity in several human populations, making the pathway the first with clear effects on human aging.
Glucose and the insulin signaling pathways are probably just one piece in a complex puzzle explaining the aging process. With every piece of the puzzle that gets illuminated and understood we come one step closer to allowing science an opportunity to stop aging.