Type 2 Diabetes (Non-Insulin Dependent)

Jennifer Kong

Diabetes Mellitus

Type 2 Diabetes (Non-Insulin Dependent)

Jennifer Kong

Learning Objectives

By the end of this section, you will be able to:

Identify some risk factors of developing type 2 diabetes mellitus
Identify the manifestations of type 2 diabetes mellitus
Briefly describe the management of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) accounts for approximately >90% of all diagnoses of diabetes. About 80 to 90 percent of people with T2DM are overweight or obese; however, there are also genetic and other lifestyle factors that cause T2DM.

In T2DM, cells become resistant to the effects of insulin: thus, tissues will not allow glucose to enter the cell and the glucose remains in the blood. In response, the pancreas will increase insulin production. Eventually your pancreas can’t keep up with insulin production, resulting in blood sugar rising. This is considered to be the pre-diabetic stage: rising blood sugars with normal or decreased insulin production. However, over time, the beta cells will ‘burn out’ and insulin production drops as blood sugars dramatically rise.

^{T2DM causes hyperglycemia – Although insulin (purple triangles) can be made and there are insulin receptors on tissues (blue), the receptors do not recognize and/or refuse to be stimulated by insulin. Thus there is nothing to stimulate glucose receptors (green) to allow glucose (gold hexagons) to enter the tissues. As a result, the cells are deprived of glucose and glucose stays in the blood causing hyperglycemia. Images created by Sarah Perkins under a CC BY ND license}

Because of the gradual, yet continuous, rise of blood sugars, prediabetes and diabetes have a insidious onset. Prediabetes, although a serious health condition, will have higher than normal blood sugar levels, but not high enough yet to be officially diagnosed as T2DM. Similarly, the signs and symptoms are easily ignored or explained away since it can take years to develop blood sugars high enough to be considered T2DM. In the developed world, it is estimated that approximately 1 in 3 adults have prediabetes: and of those with prediabetes, less than 20% of them know they are pre-diabetic.

What makes tissue insensitive to insulin? It depends on whether it is an inheritable (genetic) cause or acquired during lifetime:

Genetic causes:

insulin receptors are present in all tissues but are made less effective to respond to insulin. As a result, glucose can’t enter the tissues even though insulin is made in appropriate amounts. In this situation, blood glucose levels will still be high, despite being active regularly and eating a healthy diet. This genetic cause will have a family history of T2DM in close relatives.
like all organs, the pancreas will lose function as we age. The risk for pancreatic insufficiency (ie can’t make enough insulin) increases at middle age (>45 yo)
Similarly, some ethnicities are more at risk for T2DM – regardless of the the aformentioned lifestyle causes. First Nation peoples, Asians, and African Americans are at higher risk for T2DM.

Acquired insulin resistance:

an overabundance of circulating nutrients (e.g. overweight, physical inactivity, poor diet, exposed to gestational diabetes in utero) are constantly available to tissues causing continuous release of insulin. As a result, tissues will tend to ‘ignore’ insulin and don’t take up any more nutrients. Hence the tissues have become insulin resistant.
medications which affect glucose homeostasis (e.g. steroid treatment for inflammation ), body metabolism (e.g. lipid lowering drugs), hurt beta cells (e.g. certain antipsychotics, chemotherapy) or alter potassium level that affects insulin secretion (e.g. diuretics) might produce an overabundance of circulating nutrients/decr insulin release that lead to tissues being less responsive to insulin.

Clinical Manifestations of Type 2 Diabetes

As blood sugars rise due to insulin resistance, the signs and symptoms are more insidious. T2DM can occur at any age, but more likely in adulthood. Like with T1DM, the commons signs of diabetes (hunger, thirst, & frequent urination) develop gradually – such that patient might not notice as abnormal

As you will see in a later chapter, T2DM might not know they have diabetes until a diabetic complication (most often in the eye, kidney, or nerve) brings them in for health care and diagnosis.

Management of Type 2 Diabetes

In many cases, T2DM can be reversed by weight loss, physical activity, and a healthy diet. However, if blood glucose levels still can not be managed, medications can be used to encourage tissue sensitivity to insulin or promote insulin release. However if the diabetic has exhausted their beta cells, insulin will be required to help manage their T2DM.

^{Muscle contraction promotes glucose uptake – The action of muscle contraction and movement promotes the uptake of glucose (gold hexagons) through the glucose receptors (green) of tissues. This occurs with insulin present (purple triangles). As a result, blood sugar levels lower and the tissues get glucose. Images created by Sarah Perkins under a CC BY ND license}

Section Summary

T2DM is the most common form of diabetes. The pancreas can make insulin but the tissues do not respond to it. As a result, the tissues do not take in sugar from the blood, causing chronic high blood sugar levels. Common signs are excessive thirst, hunger, and urination. T2DM is most commonly caused by lifestyle factors leading to an overabundance of nutrients (e.g. overweight, medications); however, there are some genetic factors that may make T2DM more likely (e.g. ethnicity, family history). T2DM can be managed with a combination of exercise, diet modifications, and possibly medications to improve tissue sensitivity to insulin.

Review Questions

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