20 million daily doses of insulin per year [28]. C-peptide
of proinsulin, which is not present in current commercially
available insulin and insulin analogues derived from
E. coli and S. cereviciae, would be a great advantage in
long-term treatment of diabetic complications such as
stimulation of nerve and renal functions. Very high level
of expression of biologically active proinsulin in tobacco
and lettuce leaves and long-term stability in dried leaves
offers a reliable low-cost technology for both injectable
as well as oral delivery of proinsulin.