Good news! I am not sure cow milk is the best route!
"... The animal is transgenic – meaning DNA from another species, in this case human, was introduced into it through genetic engineering.
... it takes advantage of the special factors of the mammary gland. ...
The insulin-producing cow is a ‘proof-of-concept’ that could one day be scaled up to produce enough insulin to supply the world’s diabetics, eliminating scarcity and high costs associated with it. ...
Wheeler’s colleagues at the University of São Paulo in Brazil inserted a segment of human DNA coding for proinsulin – the precursor of the active form of insulin – into the cell nuclei of 10 cow embryos. These were implanted in the uteruses of normal cows, which resulted in the birth of one transgenic cow. ...
The insulin and proinsulin were expressed at a few grams per litre of milk. But because the milk volume was smaller than expected due to the hormone-induced lactation, the researchers can’t say exactly how much insulin would be made in a typical lactation.
... typical unit of insulin equals 0.0347 milligrams and, conservatively, if a cow could make 1 gram of insulin per litre “that means each gram is equivalent to 28,818 units of insulin.”
“And that’s just one litre; Holsteins can produce 50 litres per day. You can do the math,” ..."
From the abstract:
"Background
The worldwide growing demand for human insulin for treating diabetes could be supplied by transgenic animals producing insulin in their milk.
Methods and Results
Pseudo-lentivirus containing the bovine β-casein promoter and human insulin sequences was used to produce modified adult fibroblasts, and the cells were used for nuclear transfer. Transgenic embryos were transferred to recipient cows, and one pregnancy was produced. Recombinant protein in milk was evaluated using western blotting and mass spectrometry. One transgenic cow was generated, and in milk analysis, two bands were observed in western blotting with a molecular mass corresponding to the proinsulin and insulin. The mass spectrometry analysis showed the presence of human insulin more than proinsulin in the milk, and it identified proteases in the transgenic milk that could convert proinsulin into insulin and insulin-degrading enzyme that could degrade the recombinant protein.
Conclusion
The methodologies used for generating the transgenic cow allowed the detection of the production of recombinant protein in the milk at low relative expression compared to milk proteins, using mass spectrometry, which was efficient for detecting recombinant protein with low expression in milk. Milk proteases could act on protein processing converting recombinant protein to functional protein. On the other hand, some milk proteases could act in degrading the recombinant protein."
Figure 1 Schematic of the lentiviral vector constructed for mammary gland-specific human insulin expression and restriction map analysis.
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