Insulin, a hormone produced by the pancreas, regulates blood glucose levels. Its function involves facilitating glucose uptake into cells, where it provides energy or is stored. Without sufficient insulin, glucose accumulates in the blood, leading to high blood sugar, a hallmark of diabetes. Individuals with type 1 diabetes, whose bodies produce little to no insulin, require external insulin to survive, and some with type 2 diabetes also need it to manage blood sugar effectively. This external supply prevents severe health complications.
Historical Journey of Insulin Production
Insulin’s discovery marked a turning point in diabetes treatment. In July 1921, Frederick Banting and Charles Best isolated insulin from animal pancreases at the University of Toronto. This breakthrough led to the first human treatment in 1922, transforming diabetes from a rapidly fatal disease into a manageable condition.
Initially, insulin was extracted and purified from the pancreases of pigs and cattle. However, this method had challenges. Animal-derived insulin differed slightly in chemical structure from human insulin, sometimes causing allergic or immune responses. Meeting global demand was difficult, requiring vast animal organs. These limitations highlighted the need for a sustainable, human-compatible source.
The Revolution of Recombinant DNA Technology
Recombinant DNA technology revolutionized insulin production. This approach combines genetic material from different sources to create new DNA sequences. For insulin, this meant isolating the human insulin gene and inserting it into a host organism.
This technology enabled mass production of human insulin, chemically identical to the natural hormone. This eliminated allergic and immune responses seen with animal-derived insulin, offering a safer, purer product. It also provided a virtually limitless supply, addressing scarcity and high cost.
Steps in Modern Insulin Manufacturing
Modern insulin production uses recombinant DNA technology, a multi-step process. Scientists first isolate the human gene that codes for insulin. This gene is typically obtained as complementary DNA (cDNA) from pancreatic beta cells.
Once isolated, the human insulin gene is inserted into a plasmid, a small, circular piece of bacterial DNA. Restriction enzymes cut the plasmid and insulin gene at specific sites, creating “sticky ends” for precise insertion. DNA ligase then joins the gene into the plasmid, forming a recombinant plasmid. These plasmids often carry an antibiotic resistance gene, serving as a marker to identify bacteria that have taken up the recombinant DNA.
The next step, transformation, involves introducing these recombinant plasmids into host microorganisms. Escherichia coli (E. coli) or certain yeasts, like Saccharomyces cerevisiae, are commonly used due to their rapid growth and well-understood genetics. These engineered microorganisms are then cultivated in large, sterile bioreactors in a process known as fermentation.
Inside bioreactors, under controlled conditions of temperature, pH, and nutrient supply, host cells multiply rapidly. As they grow, their cellular machinery reads the inserted gene and produces proinsulin, a precursor to active insulin. After fermentation, proinsulin is harvested from host cells, often requiring cell disruption, especially with E. coli.
The harvested proinsulin then undergoes purification steps to separate it from other cellular components and impurities. Chromatography techniques are employed to achieve high purity. Finally, purified proinsulin is converted into active insulin through enzymatic cleavage, where an enzyme removes a connecting peptide (C-peptide) to yield the two-chain insulin molecule. Active insulin is then formulated into various types, such as rapid-acting or long-acting, to meet diverse patient needs.
Quality Control and Insulin Variations
Pharmaceutical insulin manufacturing involves stringent quality control to ensure safety, purity, and effectiveness. Throughout production, from raw materials to the final product, rigorous testing detects contaminants, verifies potency, and confirms stability. These controls ensure each batch meets high medical standards.
Recombinant DNA technology also creates various insulin analogs. These are modified versions of human insulin with different onset and duration profiles. For instance, some analogs act quickly for mealtime delivery, while others provide prolonged, steady basal coverage. These analogs are produced using similar genetic engineering principles to alter the protein’s characteristics, offering flexible, personalized treatment options.