Before we dive into insulin resistance, let us ensure you understand insulin’s actions and where it’s produced. The pancreas produces insulin, and the pancreas is a long, narrow organ that lies behind the stomach in the left upper quadrant of our abdomen. There are four pancreatic endocrine cell types, known as islet cells: beta, alpha, delta, and gamma. #Beta cells produce two hormones, insulin, and amylin; #alpha cells secrete glucagon; #delta cells secrete somatostatin; and #gamma cells produce an unknown protein.
The function of insulin in our bodies is to direct our cells to take in and use glucose. Glucose is formed in our bodies mainly from the carbohydrates we eat, with a small amount formed from ingested proteins. Insulin has several actions in the body, all designed to help the body store energy and prevent cells from metabolically burning, meaning blood sugar and blood fats are drawn into body cells when insulin is secreted. Insulin stimulates cholesterol production and elevates serum triglycerides, also known as fatty acids.
Actions of Insulin
- Stimulates muscle fibers to take up glucose and store it as glycogen (a type of starch)
- Stimulates muscle fibers to take up amino acids and store them as proteins
- Stimulates liver cells to take up glucose and store it as glycogen
- Inhibits the liver from breaking down glycogen stores
- Inhibits the liver from undergoing gluconeogenesis—that is, prevents the liver from converting amino acids and glycerol into glucose
- Stimulates the liver to produce cholesterol and fatty acids
- Stimulates fat cells to take up glucose and store it as fat
- Acts on the hypothalamus to reduce appetite
Enter Insulin resistance
We secrete insulin when our blood glucose and amino acid levels rise, which we break down from carbohydrates and proteins. Insulin travels to various cells, particularly our fat, liver, and muscle cells, and lands on a receptor. The receptor, which acts like a switch, signals a molecule called glucose transporter 4 (GLUT4) to move to the cell wall and take glucose from the bloodstream into the cell. The glucose is then transformed into fat or starch and is stored.
When people with type two diabetes become overweight, and their abdominal fat cells are already packed full of fat, their fat cells can prevent glucose from entering the cells, as they do not need to turn more glucose into more fat. As a result, their insulin receptors lose their responsiveness. When insulin lands on a receptor, the cell does not automatically absorb glucose from the blood.
Ironically, folks with Type one diabetes or those with Type two who use insulin can also become insulin resistant. The average non-diabetic, non-insulin-resistant person makes around 30 to 40 units of insulin a day to process the entirety of their food. However, if a T1 person injects more than 40 units daily to correct their glucose numbers, they are essentially self-inducing a form of insulin resistance. This is usually from eating a high-carbohydrate diet. These people can also become insulin resistant when their glucose numbers elevate (higher than 9.5 Mmol/L or they require more than 40 units daily).
In our next update, we will discuss factors involved in insulin resistance and practical ways to handle it and adopt a healthy lifestyle where you feel energetic and require less drugs or insulin for T1.