A cow produces insulin –

NEW YORK (HealthDay News)—There may be an unexpected solution to the current insulin shortage: A brown bovine in Brazil recently made history as the first transgenic cow capable of producing human insulin in its milk.

“Mother Nature designed the mammary gland as a factory to make proteins very, very efficiently,” explained study leader Matt Wheeler, a professor of animal sciences at the University of Illinois at Urbana-Champaign. “We can harness that system to produce a protein that can help hundreds of millions of people around the world.”

His team, which included scientists from the University of Sao Paulo, described how they developed the insulin-producing cow.

More testing, a purification system, and approval from the U.S. Food and Drug Administration would be needed to put the strategy into practice. But insulin produced by genetically modified cows might alleviate shortages that often make the hormone difficult to obtain for the 8.4 million Americans with diabetes who depend on it to survive.

“Our goal was to produce proinsulin, purify it into insulin, and go from there,” Wheeler said in a university news release. “But the cow basically processed it herself… The mammary gland is something magical.”

To produce the transgenic cow, a segment of human DNA was inserted into the cell nuclei of 10 cow embryos. It contained the code for proinsulin, a precursor to the active form of insulin. Through genetic engineering, human DNA was selected for expression only in breast tissue.

The altered embryos were implanted into the uteruses of normal cows in Brazil, and a transgenic calf was born. Once she matured, researchers used artificial insemination to try to get her pregnant. When that failed, they used hormones to stimulate her to produce milk for the first time.

Although it had less than a successful pregnancy would have produced, the milk not only had detectable levels of human proinsulin, but also insulin itself. The researchers didn’t expect that.

Still, insulin and proinsulin would have to be extracted and purified for use, and each liter of milk contained only a few grams. Researchers don’t know how much insulin would be typical.

But Wheeler did a quick calculation: If a cow can produce 1 gram of insulin per liter of milk, and a typical Holstein produces 40 to 50 liters a day, that’s a lot of insulin.

A typical unit of insulin is equal to 0.0347 milligrams.

“That means each gram is equivalent to 28,818 units of insulin,” Wheeler said. “And that’s just one liter: Holsteins can produce 50 liters a day. “You can do the math.”

The next step is to clone the cow once more. Researchers are hoping to achieve greater success with gestation and full lactation cycles in the next generation of animals.

Eventually, the goal is to create transgenic bulls, mate them with the transgenic females and create a “purpose-built” herd. Even a small herd might quickly surpass existing methods for insulin production, without requiring highly technical facilities or infrastructure, Wheeler said.

“I might see a future in which a herd of 100 head, equivalent to a small dairy in Illinois or Wisconsin, might produce all the insulin needed for the country,” he said. —And a larger flock? “You might supply the entire world in a year.”