Cow modified to produce human insulin in her milk

BY ANTHONY KING | 10 APRIL 2024

A brown Jersey cow has been genetically modified to produce human insulin in her milk.

The Brazilian heifer became the first transgenic cow to make this important protein, needed by patients with diabetes.

The technique relied on a virus to transfer the DNA recipe for insulin into an ordinary adult cell from a cow, a process resembling how Dolly the sheep was famously cloned in 1996.

The DNA contained the proinsulin gene but also a special genetic switch – called a promoter – that turned the gene on only in mammary glands and when the cow is lactating (Biotechnology Journal, doi: 10.1002/biot.202300307).

Out of ten transgenic embryos implanted, one resulted in a pregnancy. The milk from the cow was later shown to contain the protein precursor proinsulin and – unexpectedly – insulin itself. The researchers in Brazil and the US say that such transgenic cattle could be used to produce insulin protein on a large scale.

‘The next step would be to breed a small herd, then make the protein so we could do some biochemical characterisation and tests on efficacy, potency and stability, as you would with any pharmaceutical,’ says Matthew B. Wheeler, livestock geneticist at the University of Illinois Urbana-Champaign, US.

He collaborated with a Brazilian group on the research. ‘It’s been six years’ worth of effort to get where we are today,’ says Wheeler. The group are now looking for funding to move the project forward.

This is not the first time that milk has been tapped as a potential source of active pharmaceutical ingredients. Two other proteins have been produced in the milk of transgenic animals – one in a goat and the other in a rabbit.

‘Insulin is currently made using recombinant DNA technology and microbes,’ says Alison Van Eenennaam, animal geneticist at the University of California, Davis, US. ‘Whether this new approach [with cows] would be less expensive than bacteria, I don’t know. You’d have to do the cost of goods calculations.’

an Eenennaam regards Brazil as superior to Europe or the US in terms of its regulatory authorities for genetically modified animals.

‘The regulatory approach in Brazil, I would argue, is a lot more science-based than in other countries,’ she says.