Insulin Resistance: Part One

Diabetes: The Not So Sweet Reality

Diabetes is a leading cause of death globally, and its prevalence in Australia is estimated to have more than doubled in the last thirty years (1). Diabetes increases the risk of many diseases, including pathologies of the eyes, heart, kidneys, and nerves (2). Insulin resistance is an issue for all diabetes sufferers, and is something that can be addressed to improve diabetic management, and in some cases, even reverse the disease all together. There are, however, two main types of diabetes and they differ substantially. Let’s break them down.

Type 1 diabetes is an autoimmune condition, which usually appears in childhood or adolescence, although people can also be diagnosed in their twenties. The beta cells of the pancreas produce insulin, and in Type 1, the body’s immune system destroys these cells. Ultimately, the body cannot produce its own insulin and people must rely on an exogenous source (coming from outside of the body). Unfortunately, there is no cure for Type 1.

Type 2 diabetes is a metabolic condition where the body makes its own insulin, but it can’t make enough for the body’s demands. This can be due to poor output of insulin release, but also because the insulin cannot work effectively.

When untreated, both diseases end up with the same result: high blood sugar, otherwise known as hyperglycaemia.

To understand what is happening when the body is not functioning properly, it helps to first understand what is happening when the body is functioning well. Let’s take a closer look!

Insulin: Sugar’s Key to Your Cells

Insulin’s primary role is to allow glucose - your body’s main and preferred fuel - to enter your cells and provide you with energy. Insulin release is triggered after you eat and your blood sugar rises. Glucose cannot enter your cells without a key – and that key is insulin. Two of the most important tissues insulin acts upon are your liver and your muscle. These cells have insulin receptors. If insulin is the key, then an insulin receptor is the locked door. In a healthy insulin sensitive person, insulin enters the lock easily and is able to open the door.

Diagram One: Depiction of insulin’s action (key) on the cell’s insulin receptor (door) to bring glucose (sugar) into the cell.

Within the cell, glucose can be used in several ways:

-       Burned for energy (glycolysis)

-       Stored as glycogen (glycogenesis)

-       Stored as fat (lipogenesis)

Your metabolic demands and your energy stores determine how your glucose is used. If you are undertaking activity it will be used for energy. If you have space to store carbohydrate you will store glycogen. And if your glycogen stores are full you will store fat. After glucose has left the blood and entered the cells, blood glucose returns to normal, and insulin ceases to be released. This is called a negative feedback loop – bringing you back to baseline and restoring homeostasis. 

Insulin is known as an “anabolic” hormone – it is involved in processes of growth. It even triggers muscle protein synthesis (2). The opposite of anabolic is “catabolic” – a process of breaking down – and glucagon is the hormone of this mechanism. Glucagon is also released from the pancreas, but from alpha cells. Opposite to insulin, it is triggered when there are LOW glucose levels. The processes of glucagon are contrary to insulin. They are:

-       Production of new glucose in the liver (gluconeogenesis)

-       Break down and release of glycogen (glycogenolysis)

-       Burning of fat (lipolysis)

Diagram Two: Pancreatic hormonal regulation of high and low blood sugar - releasing insulin to lower blood glucose, and releasing glucagon to raise blood glucose.

These anabolic and catabolic processes are mutually exclusive. Insulin’s actions and glucagon’s actions cannot occur together. It is an all or nothing approach. Insulin also suppresses the actions of glucagon – including the creation of new and release of stored glucose into the blood (gluconeogenesis and glycogenolysis) (2).

Therefore, if insulin is not present, the liver will release sugar into the blood and cause blood sugar levels to rise. This is because no insulin means no blood sugar. In fact, when you have fasting blood glucose measured, the glucose in your blood is what your liver has produced while you were sleeping and in a fasted state.

Now that we have a better understanding of normal insulin and metabolic functioning, we will discuss insulin resistance in the next blog.

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Written By Jessica Zabow
Accredited Practicing Nutritionist (BHSc) & Yoga Teacher (RYT500)

References:

1.     Zhang, H., Rogers, K., Sukkar, L., Jun, M., Kang, A., Young, T., Campain, A., … Hockman, C. (2020). Prevalence, incidence and risk factors of diabetes in Australian adults aged ³ 45 years: A cohort study using linked routinely-collected data. Journal of Clinical & Translational Endocrinology, 22(1), 1-9. https://doi.org/10.1016/j.jcte.2020.100240

2.     Rahman, S., Hossain, K.S., Das, S., Kundu, S., Adegoke, E.O., Rahman, A., … Pang, M.G. (2021). Role of insulin in health and disease: An update. International Journal of Molecular Sciences, 22(12), https://doi.org/1-19. https://doi.org/10.3390/ijms22126403