Insulin and related peptides formulation

• Insulin structure

  The MW of insulin is 6000 with three amino acids on the end of the B chain: proline, lysine, and threonine at the COOH end of the B chain
• Insulin 3D structure

  The tertiary structure includes alpha helices and beta sheets, each chain is in a U shape and perpendicular to each other
• Hexamers formation

  Dimer groups form hexamers retaining alternating orientation, B-helices point upwards and downwards, hexamers can have a set of each T or R state
• Interaction with phenolics

  The R-form monomer in dimer allows phenol in, while the T-form monomer in dimer does not allow phenol in, phenol increases solubility and prevents bacterial growth
• Insulin


  The protein for treating diabetes
• Insulin dimerisation

  Two structures form a dimer where one is inverted vertically and displaced so the B chains are in contact, the dimer exists with the wedges in opposite directions
• In the hexamer model, the B chains are all in the R state and there is phenol in all of them, each section comprises two mutually inverted monomers
• Pancreas release insulin pulsatile every 3-4 minutes in response to glucose, preventing down-regulation of receptors in peripheral cells
• Phenol affects solubility, promotes R and T configuration, and the bacterial status
• After injection, the onset of insulin effect is delayed by about half an hour due to the time taken to reach tissue receptors and undertake biochemistry within the cell
• Hexamer


  • Molecular weight = 36,000
  • B chains are all in the R state with phenol in all of them
  • Each section comprises two mutually inverted monomers, each consisting of an A and B chain
  • The hole down the centre should normally hold two zincs, but more zincs can compromise solubility
• Degradation reactions

  1. Acid pH: Deamidation at A21, covalent dimerisation

  2. Neutral pH: Deamidation at B3, covalent dimerisation

  3. Alkaline pH: Disulphide bond loss (liberates A and B chains)
• Most of the insulin in the plasma is degraded by the liver with a half-life of only 12 minutes
• Action at the receptor


  Insulin finds receptors in peripheral fatty tissue, muscle, and liver, linked to tyrosine kinases enabling glucose import
• Insulin therapy is mostly given subcutaneously, with slower diffusion from subcutaneous tissue to plasma due to the large molecule
• Monomers


  • Some are "coloured" and one set of three are white
• Trimer state


  • Each set is a trimer state that some papers refer to
• Insulin degrades steadily in solution but the rate is quite low
• Internalised receptors

  Recycled to the surface and destroyed by enzymes, taking about an hour from when insulin reaches the blood
• In a non-diabetic person, plasma insulin concentration is closely controlled by fast release from pancreas beta-cells and fast metabolism in plasma to shadow the glucose concentration in the blood
• Injection of insulin

  1. Into the dermis and fat, so that cell membranes are not involved

  2. Insulin fluid formulation leaches through cell-free tissues

  3. Some may be carried away by capillaries but most may travel through the lymph system

  4. Eventually reaches plasma and from there reaches the extracellular fluid (ECF)
• Insulin aspart and insulin glulisine are fast-acting synthetic analogues
• Regular soluble insulin acts only as quickly as the production and transfer to plasma of the monomer will allow if injected subcutaneously
• Present therapy for diabetic people is "open loop" with slow release of subcutaneous insulin giving blanket but abnormally flat profiles for background control
• Lispro insulin operates as a monomer only, avoiding dissociation delay and diffuses much more quickly into plasma
• All subcutaneous insulin is abnormal (soluble or insoluble)
• Actrapid peaks in activity at about 2 hours instead of 1 hour like normal pancreatic insulin because it is injected subcutaneously
• Plasma level reaches a peak long after the subcutaneous injection of insulin solution
• Closed loop systems are biological microprocessor controlled pumps linked to electronic glucose sensors
• Wifi feedback to pump can be trusted to reduce the dose but not to increase it
• Dual hormone version is designed to reduce hypos
• Tight control


  1. More measurements and injections are needed

  2. Aim is normal blood glucose (5.4mmol/L) and HbA1c (<42mmol/mol)

  3. “Tight control” involves many tests with coupled injections or variable rate pumped dose rate

  4. Tight control is the best approach but hard to impose on people, especially children

  5. Many UK children are misguided to an HbA1c of approaching 70mmol/mol
• Closed loop systems chemical

  Implantable design, one of the four carbohydrate receptors in concanavalin A
• Many diabetic people have deviations in diabetes control more than 50% of the time
• Improved injection

  1. Lispro, insulin aspart, and glulisine are faster acting and can be injected shortly before a meal

  2. Newer injection “pen” devices make injections easy and dignified

  3. Pens are available for regular soluble and insulin suspensions

  4. Other novel injection devices like needleless types have helped people to be in better control of their condition
• Healthy transplanted pancreas beta cells gene therapy advantage is that no insulin reservoir is needed
• Never refer to “diabetics” people with diabetes are really offended by it
• Therapy


  1. Open loop slow release of subcutaneous insulin gives blanket but abnormally flat profiles for background control

  2. Patients have to decide how much insulin they need to cover meals

  3. They titrate insulin to measured and predicted glucose levels but this is often unsuccessful
• Glucose, mannose, galactose are depictions of concanavalin A and its four receptors
• Closed loop systems electronic needs immunosuppression