When Insulin Resistance and Type 1 Diabetes Lead to Double Diabetes

Type 1 diabetes (T1D) is characterized by the presence of antibodies that destroy the pancreas’s insulin-producing beta cells. Without this vital hormone, people with T1D must either take multiple injections of insulin every day or use an insulin pump to regulate their blood sugar levels. 

In type 2 diabetes (T2D), the pancreas still produces insulin, but often in a lesser amount combined with delayed secretion and insulin resistance (i.e., the insulin is less effective). Excess body fat, especially around the abdomen, lack of physical activity and certain drugs, among other factors, can lead to insulin resistance where the body does not use sugar properly, resulting in high blood sugar levels. 

The pancreas is then required to work harder to produce more insulin in order to stabilize blood sugar levels. Treatment for T2D sometimes includes a combination of active lifestyle and oral or injectable medication that increases the body’s sensitivity to its own insulin. But once the pancreas gets tired, insulin injections might become necessary. Some people with T2D require four daily injections or an insulin pump, just like people with T1D.

There are cases of people with T1D who present with characteristics that are usually specific to T2D; this is referred to as double diabetes. These patients both have antibodies that destroy the pancreas’s beta cells and excess weight and/or insulin resistance.

What about treatment?

Managing your blood sugar levels when you have insulin resistance and double diabetes is more difficult than when you only have T1D or T2D. 

Not only do you have to determine the proper insulin doses, but you also have to make some lifestyle changes, such as doing physical activity or losing weight in order to reduce insulin resistance.

Metformin is an oral medication that can be prescribed as a treatment for both T1D and T2D to increase insulin sensitivity. 

But sometimes, metformin is no longer enough, and in those cases, treatment options are limited. A few studies have been conducted with patients with T1D on the use of GLP-1 receptor agonists (Victoza, Ozempic, etc.), an injectable drug that promotes weight loss, and SGLT2 inhibitors (Invokana, Forxiga, etc.), an oral medication that eliminates some sugar through urine. 

However, these drugs are not yet approved as a treatment for T1D due to insufficient data (GLP-1 receptor agonists) and certain major, but rare, risks associated with SGLT2 inhibitors (ketoacidosis). 

Higher risk of complications

Several studies have found that double diabetes leads to a higher risk of complications. 

One study, for instance, estimated that risks of heart disease were 8% for people with double diabetes, compared to 3% for people with T1D.

The study also estimated that risks of retinopathy (a condition affecting small blood vessels in the eyes) were 32% for people with double diabetes versus 22% for people with T1D.

Decreasing insulin resistance with lifestyle changes

There are many ways to reduce the risks of developing insulin resistance that can lead to T2D or double diabetes: reducing hypoglycemia to avoid ingesting additional carbs (sugar), doing regular physical activity, losing weight, eating healthier (e.g., limiting the intake of processed foods and foods high in carbs and fat), and limiting tobacco use and alcohol consumption.

It’s important to know that in spite of a healthy lifestyle, some risk factors such as genetic factors can cause insulin resistance. Double diabetes is more prevalent among people who have a family history of type 2 diabetes.

Don’t hesitate to talk to your healthcare team about assessing your risk of developing double diabetes.

References

• Cleland, S. J., Fisher, B. M., Colhoun, H. M., Sattar, N., & Petrie, J. R. (2013). Insulin resistance in type 1 diabetes: what is ‘double diabetes’ and what are the risks? Diabetologia, 56(7), 1462–1470. https://doi.org/10.1007/s00125-013-2904-2
• Merger, S. R., Kerner, W., Stadler, M., Zeyfang, A., Jehle, P., Müller-Korbsch, M., & Holl, R. W. (2016). Prevalence and comorbidities of double diabetes. Diabetes Research and Clinical Practice, 119, 48–56.
• Priya, G., & Kalra, S. (2017). A Review of Insulin Resistance in Type 1 Diabetes: Is There a Place for Adjunctive Metformin? Diabetes Therapy, 9(1), 349–361. https://doi.org/10.1007/s13300-017-0333-9
• Schauer, I. E., Snell-Bergeon, J. K., Bergman, B. C., Maahs, D. M., Kretowski, A., Eckel, R. H., & Rewers, M. (2010). Insulin Resistance, Defective Insulin-Mediated Fatty Acid Suppression, and Coronary Artery Calcification in Subjects With and Without Type 1 Diabetes. Diabetes, 60(1), 306–314. https://doi.org/10.2337/db10-0328 

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