For Diabetes Awareness Month, the following article explores some interesting connections between diabetes and Lyme disease — an infection that can also trigger autoimmune processes. In humans, neither a causal relationship nor a clear correlation has been proven so far, but there are several intriguing, documented links.

Type 1 diabetes mellitus is an autoimmune disease that affects the insulin-producing cells of the pancreas after an inflammatory process leads to chronic insulin deficiency in genetically susceptible individuals. Only a small proportion of type 2 diabetes cases can be attributed to autoimmune mechanisms.

Since the exact cause that triggers autoimmune processes has not yet been clarified in either type of diabetes, it may be worthwhile to examine more broadly other potential factors that could initiate autoimmune reactions — such as certain infections, including Lyme disease.

So far, there is limited concrete experience regarding the coexistence of Lyme disease and diabetes. Most available case studies focus on distinguishing the symptoms of the two conditions, or on the possibility of excluding one while treating the other. There are few confirmed cases in which both conditions have been proven — partly because the treating physician often does not request laboratory testing for potential infections. Even when Lyme disease is suspected, the commonly used Lyme tests detect less than half of all infections.

There are symptom clusters in which both diseases may be considered, such as facial nerve paralysis (Bell’s palsy), disturbances in vitamin D metabolism, restricted movement of small and large joints, scleroderma, inflammation of capillaries, and various eye and vision problems.

Unfortunately, in diabetes the damage to the pancreas is often so extensive that even if the autoimmune process were to cease, full function is unlikely to return: in many cases, only 10–20% of the insulin-producing cells retain their function. Thus, even if the autoimmune reaction were to resolve after treating a possible infection, insulin production would most likely not be restored. This is why, especially when type 1 diabetes is suspected, it is crucial for the patient to receive immediate and thorough diagnostic evaluation — and to consider even the less likely underlying causes.

Although Lyme disease as an underlying cause of diabetes cannot currently be proven, there is increasing evidence that diabetes — and the resulting elevated blood glucose levels — may worsen the course of Lyme borreliosis.

A recent study conducted laboratory experiments on mice to investigate how hyperglycemia — the high blood glucose level seen in type 1 diabetes — affects the clearance of the bacteria that cause Lyme disease and the associated immune responses. The elimination of these bacteria in the immune system is carried out by a type of white blood cell called the neutrophil granulocyte, which is also responsible for the inflammatory processes triggered during infection. In diabetes — specifically type 1 diabetes (insulin deficiency) — neutrophil granulocytes are known to be less effective at locating and destroying pathogens; in other words, their function is impaired. This also means that a larger proportion of pathogens survive within the body. These pathogens tend to persist in certain tissues, typically in the brain, heart, lungs, liver, and knee joints. All of this suggests that it would be essential to examine how other coexisting conditions — such as the aforementioned diabetes — influence the outcome of Borrelia infection.

Hyperglycemia can be caused by factors other than diabetes, including those seen in the example above. Lyme disease presents with numerous symptoms and can affect multiple organ systems — including the adrenal glands. The adrenal glands produce hormones that regulate metabolism, immune function, blood pressure, and the body's response to stress. Lyme disease can impair the regulatory function of the adrenal glands, leading to blood sugar fluctuations, high blood glucose levels (hyperglycemia), high blood pressure, weakness, mood swings, depression, and autoimmune symptoms. Autoimmune manifestations can also appear in diabetes. Because hyperglycemia resulting from adrenal impairment makes symptom control and recovery more difficult, it is not surprising that many Lyme patients find strict dietary measures — such as gluten-free or reduced-sugar diets — essential parts of their treatment plan. Interestingly, hyperglycemia is also among the symptoms of Babesia infection, one of the common co-infections associated with Lyme disease.

Chronic inflammation caused by long-standing Lyme disease can lead to significant weight loss or weight gain, both of which can adversely affect blood glucose levels.

A study supported by the Canadian Institutes of Health Research and conducted by a researcher at the University of Toronto in 2013 examined a topic similar to the first study, but from a slightly different perspective. This project investigated whether the elevated blood glucose levels triggered by Borrelia infection worsen the symptoms of Lyme arthritis, and whether controlling blood glucose with insulin reduces the severity of Lyme arthritis.

Lyme disease — that is, Borrelia infection — can on its own produce a wide range of symptoms, which are further complicated by symptoms arising from other coexisting conditions. It is important to examine the cross-reactions and the impact these illnesses may have on Lyme disease, because the better we understand the pathology of a disease, the more effectively we can treat it.