What produces insulin
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Insulin Production: Key Sources and Mechanisms
Pancreatic Beta Cells: Primary Insulin Producers
The primary source of insulin in the human body is the pancreatic beta cells located in the islets of Langerhans. These cells synthesize insulin from its precursor, proinsulin, through specific proteolytic processing . The mature insulin molecule consists of two polypeptide chains, A and B, linked by disulfide bonds, and is stored in secretory granules within the beta cells. Upon release, insulin plays a crucial role in regulating blood glucose levels by promoting glucose uptake and storage in tissues such as the liver, muscles, and adipose tissue.
Choroid Plexus: A Novel Insulin Source
Recent research has identified the choroid plexus (ChP) in the brain as an additional site of insulin production. The epithelial cells of the choroid plexus (EChP) synthesize and release insulin, which is regulated by serotonergic signaling rather than glucose levels. This discovery highlights the brain's role in insulin production and suggests a complex regulatory mechanism involving serotonin.
Bacterial Production of Human Insulin
Advancements in biotechnology have enabled the production of human insulin using recombinant DNA technology. Bacteria, specifically Escherichia coli, are engineered to produce the A and B chains of human insulin, which are then combined to form active insulin. This method has revolutionized insulin availability, making it possible to meet the growing demand for insulin therapy in diabetic patients .
Insulin Production in Yeast and Plants
In addition to bacterial systems, yeast (Saccharomyces cerevisiae) and transgenic plants are also employed for insulin production. These systems offer efficient posttranslational modifications and protein refolding capabilities, essential for producing biologically active insulin. Plant-based expression systems, in particular, hold promise for large-scale, cost-effective insulin production, potentially facilitating new delivery methods such as oral or inhalable insulin.
Insulin in the Cerebral Cortex and Hippocampus
Emerging evidence suggests that insulin is also synthesized by neurons in the cerebral cortex and neural progenitor cells in the hippocampus. This locally produced insulin may play a role in regulating synaptic transmission and energy homeostasis within neural networks. The modulation of insulin production in the brain could have therapeutic implications for conditions like diabetes, obesity, and neurodegenerative diseases.
Conclusion
Insulin production is a multifaceted process involving various sources and mechanisms. While pancreatic beta cells remain the primary producers of insulin, novel sites such as the choroid plexus and neurons in the brain have been identified. Additionally, recombinant DNA technology has enabled the production of human insulin in bacterial, yeast, and plant systems, significantly enhancing the availability and affordability of insulin therapy. Understanding these diverse sources and mechanisms is crucial for advancing diabetes treatment and exploring new therapeutic avenues.
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