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What is Type 1 diabetes?

Diabetes is not a single disease, but a group of chronic metabolic diseases characterized by high levels of blood glucose. There are two main types of diabetes, type 1 diabetes (T1D) and type 2 diabetes (T2D). Type 1 diabetes is generally caused by an autoimmune condition that destroys insulin-producing cells in the pancreas, resulting in low insulin levels in the bloodstream. In contrast, T2D is characterized by an insensitivity of the body to insulin and is often associated with obesity.

After the body has broken down food into usable compounds, like glucose, it absorbs those molecules into the blood. The hormone, insulin, allows glucose that is circulating in the bloodstream to enter cells, where it can be used for energy.

In T1D, the immune system mistakenly destroys pancreatic beta cells, which are located in the pancreatic islets and are responsible for producing insulin. This causes insulin levels to be very low. Without insulin, cells cannot absorb the glucose that is circulating in the blood. As a result, glucose concentration in the blood rises, and cells do not get the glucose they need as an energy source. Patients with T1D must administer synthetic insulin for the rest of their lives to keep their blood glucose balanced.1,2

Type 1 diabetes accounts for only 5-10% of all diabetes cases.3 It was previously called insulin-dependent,4 juvenile, and childhood-onset diabetes. Although T1D is usually diagnosed during childhood, it can appear at any age.

What are the symptoms?

Symptoms of poorly controlled T1D are serious and may occur suddenly. They can include2:

  • Constant hunger
  • Fatigue
  • Polydipsia (abnormal thirst)
  • Polyuria (excessive excretion of urine)
  • Vision changes
  • Weight loss

If untreated, high blood sugar can lead to a more serious condition known as diabetic ketoacidosis. Symptoms of diabetic ketoacidosis include4:

  • Breath that smells fruity
  • Confusion
  • Difficulty breathing
  • Difficulty paying attention
  • Dry or flushed skin
  • Nausea or vomiting
  • Stomach pain
Diabetic ketoacidosis is a metabolic complication of diabetes, occurring when blood levels of ketones (byproducts of fat metabolism produced in response to uncontrolled blood sugar) are high enough to affect bodily functions.

 What are the causes?

Although the cause of T1D is still unknown, we do know that genetic, epigenetic, and environmental factors contribute to the risk of developing the disease.

Certain genes increase the risk of developing T1D. More than 50 genes associated with T1D have been identified, and most of these genes affect immune tolerance regulation. The gene responsible for up to 50% of the risk is part of the major histocompatibility complex (MHC), an important protein complex responsible for detecting foreign molecules. In T1D, the MHC falsely identifies the pancreatic beta cells as foreign and launches an immune response against them.

Epigenetic modifications may contribute to the risk of developing T1D when they malfunction. The modifications at risk include DNA methylation, histone modifications, and miRNA dysregulation.5

Additionally, influential environmental factors include drugs, pollutants, foods, stress, infectious agents, and the gut microbiota.

Immune intolerance occurs when the immune system fails to respond to substances or tissues that would usually elicit an immune response.
DNA methylation occurs when methyl (-CH3) binds to DNA. This changes how the gene is expressed without actually changing gene sequence. This modification is commonly used as a regulatory mechanism.
Histones are proteins that compact DNA in the chromosome. Chemical modifications to their composition can cause changes to DNA structure (how the DNA is packaged) and regulation (how the expression of that particular gene is activated or repressed).
miRNA, or microRNA, is a type of small, non-coding RNA molecule which often executes regulatory functions over other genes.

How does this topic relate to my microbiome?

Studies show that certain changes in the intestinal microbiome are associated with an increased susceptibility to T1D.6 Such changes can be caused by antibiotic treatments, diet, and drugs (such as proton pump inhibitors). Further studies are needed to determine the impact of these factors on the microbiome.7

Studies in laboratory animals have identified gut microorganisms that could impact T1D. When the microorganism Bacillus cereus is present in the gut, it could delay the onset of the disease. Another study shows that Akkermansia muciniphila can protect against T1D, especially during childhood.8 On the other hand, Citrobacter rodentium may encourage the development of T1D.7

In humans, research shows that gut microbial diversity decreases as T1D progresses.9 Compared with healthy subjects, the gut microbiota in T1D patients show increased Bacteroides; decreased butyrate-producing bacteria; and decreased abundance of microbes such as Roseburia faecis, Faecalibacterium prausnitzii, Akkermansia, Prevotella, and Bifidobacterium.8,10

Which diseases/topics are related to T1D?

Poorly controlled T1D can generate serious complications due to high blood glucose, leading to problems such as:

  • Depression
  • Eye problems
  • Foot problems
  • Heart disease
  • Kidney disease
  • Nerve damage
  • Sleep apnea
  • Stroke

How can I take action?

First, consult your healthcare provider. Type 1 diabetes is a serious disease that develops gradually, but its symptoms may appear suddenly, within a few days or weeks. Type 1 diabetes cannot be prevented.

Healthcare professionals usually base their diagnosis on a series of tests, including:

  • Random plasma glucose, which measures the level of sugar/glucose you have in your blood at a single point in time.
  • Fasting Glucose test, which measures the amount of glucose in your blood after an overnight fast.
  • Glucose Tolerance test, which measures your blood sugar before and after (60 and 120 minutes) you drink a liquid that contains glucose; this test requires previous overnight fasting.
  • A1C blood test, which measures the average glucose/sugar levels in your blood over the last three months. This test is also known as the hemoglobin A1C, HbA1C, glycated hemoglobin, or glycosylated hemoglobin test.
  • Autoantibody test, which looks for certain autoantibodies in your blood to diagnose T1D and rule out T2D.

Type 1 diabetes management consists of insulin administration, a tailored diet plan, physical activity, and blood sugar monitoring. Following the treatments recommended by your healthcare professional can prevent or delay complications of the disease.4


1. Kent, S. C., Mannering, S. I., Michels, A. W., & Babon, J. A. B. (2017). Deciphering the Pathogenesis of Human Type 1 Diabetes (T1D) by Interrogating T Cells from the “Scene of the Crime.” Current Diabetes Reports, 17(10), 95.

2. World Health Organization (2016). Global Report on Diabetes.

3. Daneman, D. (2006). Type 1 diabetes. The Lancet, 367(9513), 847–858.

4. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). National Institutes of Health. Type 1 Diabetes.

5. Wang, Z., Xie, Z., Lu, Q., Chang, C., & Zhou, Z. (2017). Beyond Genetics: What Causes Type 1 Diabetes. Clinical Reviews in Allergy & Immunology, 52(2), 273–286.

6. Alkanani, A. K., Hara, N., Gottlieb, P. A., Ir, D., Robertson, C. E., Wagner, B. D., … Zipris, D. (2015). Alterations in Intestinal Microbiota Correlate With Susceptibility to Type 1 Diabetes. Diabetes, 64(10), 3510–3520.

7. Zheng, P., Li, Z., & Zhou, Z. (2018). Gut microbiome in type 1 diabetes: A comprehensive review. Diabetes/Metabolism Research and Reviews, e3043.

8. Vaarala, O. (2013). Human Intestinal Microbiota and Type 1 Diabetes. Current Diabetes Reports, 13(5), 601–607.

9. Kostic, A. D., Gevers, D., Siljander, H., Vatanen, T., Hyötyläinen, T., Hämäläinen, A.-M., … Xavier, R. J. (2015). The Dynamics of the Human Infant Gut Microbiome in Development and in Progression toward Type 1 Diabetes. Cell Host & Microbe, 17(2), 260–273.

10. de Goffau, M. C., Fuentes, S., van den Bogert, B., Honkanen, H., de Vos, W. M., Welling, G. W., … Harmsen, H. J. M. (2014). Aberrant gut microbiota composition at the onset of type 1 diabetes in young children. Diabetologia, 57(8), 1569–1577.