Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton and Kim Jackson  

Introduction[edit | edit source]


Insulin is the predominant mediator of metabolic homeostasis [1] that is essential especially for the metabolism of carbohydrates and the regulation of glucose levels in the blood and that when insufficiently produced results in diabetes mellitus[2]

  • It is an anabolic hormone that elicits metabolic effects throughout the body. 
  • It is a protein-based hormone that is made by the beta cells of the pancreas.
  • By monitoring glucose levels, amino acids, keto acids, and fatty acids circulating within the plasma, beta cells regulate the production of insulin accordingly[3].
  • Without insulin, life-threatening complications can occur due to high blood sugar levels.

Secretion[edit | edit source]

Blood Glucose.png

Several factors stimulate insulin secretion, but by far the most important is the concentration of glucose in the arterial (oxygenated) blood that perfuses the islets.

  • When blood glucose concentrations increase (after eating) a large amounts of glucose are taken up and metabolized by the beta cells, and the secretion of insulin increases.
  • Conversely, as blood glucose concentrations decrease, the secretion of insulin decreases; however, even during fasting, small amounts of insulin are secreted.

The pancreas of a normal adult contains approximately 200 units of insulin, and the average daily secretion of insulin into the circulation in healthy individuals ranges from 30 to 50 units.[4]

Site of Action[edit | edit source]

Glycogen structure.jpeg

Insulin acts primarily to stimulate glucose uptake by three tissues:

  1. Adipose tissue: stimulates lipogenesis and conversely inhibits lipolysis. Insulin helps synthesize fatty acids in the liver cells.  If the glycogen levels make up at least 5 percent of the mass of the liver, the glycogen synthesis is suppressed and fatty acids are instead made by the liver to be used to make the lipid layer of the cells of the body.  The fatty acids are then taken out of the liver and are transferred to lipoproteins, which allow for the transportation of the fatty acids to make cells or to be stored inside fat cells as fat[5].
  2. Muscle: Promotes glycogenesis and protein synthesis. Inhibits protein catabolism. Insulin prevents proteins from being broken down in muscle and maybe even in tissue, which helps stabilize muscle strength and ensures the body uses carbohydrates instead of protein for energy.[6]
  3. Liver: affects glycogen metabolism by stimulation of glycogen synthesis.

Insulin also:

  • Is one of the few hormones that cross the blood-brain barrier. Insulin widely affects the brain as it controls the amount of glucose that is sent to the brain. Proper insulin levels are needed to enhance memory and learning.[6]
  • Has a role in appetite regulation[7]
  • It aids in the synthesis of proteins and DNA replication, which also helps the body heal after injury or illness.Promotes cellular growth and differentiation[8].
  • After any damage or illness, insulin helps restore the area by transporting amino acids to the affected muscle tissue. Amino acids are needed to help rebuild and repair tissue damage. Insulin is also required for the uptake of amino acids on a regular basis[6].
  • Insulin is also needed for proper usage of the different electrolytes, especially potassium[5] Insulin increases the permeability of many cells to potassium, allowing potassium to cross over the cellular membrane into cells where it is needed for many functions. Insulin is also needed to balance the excretion of sodium and the volume of fluid in urine.
  • When amino acid levels are low, such as in a state of fasting, insulin helps stimulate the uptake of amino acids by pushing the balance toward intracellular protein degradation, or the breakdown of protein into amino acids[6].

Role in Inflammation[edit | edit source]

Insulin plays an important role in the inflammatory response

  • Insulin’s actions within endothelial cells and macrophages have an anti-inflammatory effect on the body. Within endothelial cells, insulin stimulates the release of nitric oxide (NO), which leads to vasodilation.
  • Insulin suppresses nuclear factor-kappa-B (NF-kB) found intracellularly in endothelial cells. Ultimately this suppression leads to a decrease in cell adhesion molecules in circulation, lowering the risk of atherosclerotic arterial plaques.
  • Insulin suppresses the generation of O2 radicals and reactive oxygen species (ROS)[1].

Physiotherapy Implications[edit | edit source]

Risk of diabetes and exercise.png

Diabetes is a metabolic disorder in which the body is unable to appropriately regulate the level of sugar, specifically glucose, in the blood, either by poor sensitivity to the protein insulin, or due to inadequate production of insulin by the pancreas.

The adoption and maintenance of physical activity are critical foci for blood glucose management and overall health in individuals with diabetes and prediabetes. See Physical Activity in Diabetes.

References[edit | edit source]

  1. 1.0 1.1 Felix-Soriano E, Moreno-Aliaga MJ, Ramirez MJ, Solas M. Interactions Between Age, Diet, and Insulin and Their Effect on Cognition: Implications for Alzheimer’s Disease. Role of the Mediterranean Diet in the Brain and Neurodegenerative Diseases. 2018 Jan 1:223-38.Available: 11.12.2021)
  2. Merriam Webster Insulin Available: (accessed 12.12.2021)
  3. Vargas E, Joy NV, Sepulveda MA. Biochemistry, insulin metabolic effects. StatPearls [Internet]. 2021 Feb 1.Available: (accessed 11.12.2021)
  4. Britannica Insulin Available: (accessed 11.12.2021)
  5. 5.0 5.1 Diabetes Library Functions of insulin Available: (accessed 12.12.2021)
  6. 6.0 6.1 6.2 6.3 Healthprep Diabetes Available: (accessed 12.12.2021)
  7. Thota S, Akbar A. Insulin. StatPearls [Internet]. 2021 Jul 16.Available: (accessed 11.12.2021)
  8. Dave HD, Preuss CV. Human Insulin. StatPearls [Internet]. 2020 Apr 13.Available: (accessed 11.12.2021)