Insulin grown in lettuce can be taken orally

Researchers at the University of Pennsylvania have found a way to harvest insulin grown in lettuce — and unlike today’s synthetic insulin, this kind wouldn’t require any painful injections.

The challenge: Our bodies use the hormone insulin to convert sugar in our blood into energy. People with type 1 diabetes make little to no insulin naturally, so they have to inject synthetic insulin, and some people with type 2 need insulin shots, as well.

If not well calibrated, injections can get too much insulin into the bloodstream too fast.

Typically, this insulin is grown in bacteria or yeast cells, and it’s a complicated process that deters many would-be manufacturers from getting into the market. Partly as a result, only a few companies produce most of the world’s insulin, and that lack of competition has led to higher costs for users.

Today’s synthetic insulin must also be stored and transported at low temperatures, which adds another hurdle in places where reliable electricity and refrigerated trucks aren’t available.

Cost aside, injections are painful, and if they’re not well calibrated, they can get too much insulin into the bloodstream too fast, causing blood sugar levels to drop below the healthy range, a condition called “hypoglycemia.”

Plant-based insulin: Using a device called a “gene gun,” University of Pennsylvania researchers blasted human insulin genes into lettuce cells, past the tough plant cell walls. The genes then integrated with the lettuce genome, and the plants ended up producing insulin using human genes.

The researchers then freeze-dried the lettuce, ground it up, and made the powder into a pill that can be stored and transported at room temperature.

When fed to diabetic mice, the plant-based insulin regulated the rodents’ blood sugar levels within 15 minutes, without causing them to fall too low. Mice treated with insulin injections, meanwhile, often saw their blood sugar levels quickly drop, leading to temporary hypoglycemia.

The tough plant cell walls protect the insulin hormone in the stomach.

Down the hatch: This is far from the first attempt to create insulin that can be taken orally, but many past efforts have been stymied by the fact that stomach acids tend to break down the insulin before enough of it can reach the bloodstream. 

The Penn team found that the same tough plant cell walls that necessitated the use of the gene gun also protect the insulin hormone in the stomach, allowing it to travel to the gut and eventually reach the liver. 

Unlike currently available synthetic insulin, which is missing one of the three peptides found in natural insulin, the Penn team’s plant-based insulin contains the missing C-peptide, too, making it a better substitute for the real kind.

Looking ahead: The next steps for the Penn researchers will be trialing their plant-based insulin in dogs and then people. If it works as hoped, lead researcher Henry Daniell believes it could be a game-changer for the half a billion people with diabetes worldwide.

“I grew up in a developing country and saw people die because they couldn’t afford drugs or vaccines,” he said. “For me, affordability and global access to health care are the foundation for my work.”

“In this case,” Daniell continued, “we are making insulin more affordable while significantly improving it. Patients can get a superior drug at a lower cost.”

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