A recent review in The FEBS Journal gathers up what scientists understand so far about how our cells handle mannose, what it does in normal, healthy biology, and why cancer researchers have started to take a closer look. It isn’t new experiments. Think of it more like a stock-take: someone gathering all the research to date, mostly from laboratory and animal studies, and laying it out in one place.
So what is mannose?
Mannose is a simple, natural sugar. We find small amounts in certain fruits (such as cranberries, oranges, and apples), vegetables and legumes, and our own bodies quietly make some too. Here’s where it splits off from glucose. Glucose is fuel, the petrol in the tank. Mannose isn’t really about energy at all. Its main job is more like construction work. Our bodies are constantly building proteins, and many of them need a finishing touch to work properly, a bit like a piece of flat-pack furniture that only becomes useful once the right fittings are attached. Mannose helps add those fittings, in a process scientists call glycosylation. Without it, a lot of proteins wouldn’t fold into the right shape, stay stable, or communicate with the cells around them. It’s behind-the-scenes work that keeps the whole body ticking over.
Why has mannose caught researchers' attention?
It comes down to the way cancer cells feed themselves. Healthy cells are fairly economical with fuel. Many cancer cells are not. They gulp down glucose at a furious rate, far more than they strictly need, even when there’s plenty of oxygen around. Scientists call this the Warburg effect, but we can picture it as an engine left revving in the driveway, burning through fuel just to keep growing fast. Because cancer cells run their metabolism so differently, researchers started wondering: if researchers change which sugars are on offer, or how the cell processes them, could that throw a spanner in that engine? Mannose is one of the sugars in that conversation.
One little tool inside the cell makes a big difference
The review keeps coming back to one enzyme with a mouthful of a name: mannose phosphate isomerase, or MPI for short. Think of MPI as a tool the cell uses to process mannose, like a can opener. If the cell has plenty of them, mannose gets opened up, dealt with, and put to use with no fuss. But some cells carry hardly any. And when there’s no can opener, the mannose just piles up on the counter with nowhere to go. Inside the cell, that pile-up (a form called mannose-6-phosphate) seems to gum up the works, clogging the very production lines that fast-growing cells depend on to keep dividing. In some laboratory experiments, that traffic jam slowed certain cancer cells down, or left them more exposed to particular chemotherapy drugs. But here’s the honest bit: it didn’t happen everywhere. Whether it works seems to depend on how many of those “can openers” a cell has, and how it deals with mannose to begin with. And it’s worth being straight about where this comes from. These are results from cells grown in a dish and studies in animals. They give us a fascinating glimpse of what mannose might be doing, but whether the same thing happens inside a human being is a question scientists still have to answer.
Mannose has an everyday job too
A field still finding its feet
Where this connects with Dr Coy's work
Much of his research centres on a pathway inside the cell driven by an enzyme called transketolase, and in particular a related form known as TKTL1, which Dr Coy himself discovered. His reasoning is that this transketolase machinery is one of the engines cancer cells lean on to keep their fast, fermentation-style metabolism running, the same revving engine we described earlier. It’s a pathway he has spent years studying, ever since first identifying the gene behind it.
Mannose interests him because it acts on that very machinery. By dampening the pathway that transketolase and TKTL1 help power, mannose is one of the naturally occurring sugars that, Dr Coy postulates, behaves in a fundamentally different way to glucose.
That is why it sits within his wider thinking about sugars, and why he has worked with it alongside the others in his Sugar Family. You can read more about the TKTL1 pathway and his reasoning here.
The Intelligent Sugar perspective
At Intelligent Sugar, we start from a simple idea: to really understand sugar, we have to understand its biology.
Mannose belongs to Dr Coy’s Sugar Family, a group of natural sugars that each look a little different and each do a different job. Glucose is the famous one, the energy sugar everybody knows. Mannose is a reminder that others are quietly working away on something else entirely, out of the spotlight.
And that’s the heart of it. Sugars aren’t all the same, and they aren’t interchangeable. The more we learn about mannose, the clearer it becomes that every sugar deserves to be understood on its own terms.
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