Study reveals link between diabetes, urinary tract infections

Diabetes is linked to weakened immunity and repeated illnesses. According to researchers at Sweden’s Karolinska Institutet, patients with diabetes have reduced amounts of the antimicrobial peptide psoriasin, which impairs the urinary bladder’s cell barrier, increasing the risk of urinary tract infection.

The study’s findings were reported in Nature Communications. Diabetes is caused by a shortage of insulin and/or a reduction in insulin activity. Insulin is a hormone that controls glucose (sugar) and consequently the delivery of energy to cells. Type 1 diabetes occurs when the body stops generating insulin, but type 2 diabetes occurs when the cells become less responsive to insulin, contributing to high blood glucose levels. Diabetes is a prevalent condition that has a wide range of health consequences.

One impact is that it weakens the innate immune system, making many individuals more susceptible to common diseases such urinary tract infections (UTIs) caused by E. coli bacteria. These are more prone to cause general blood poisoning, sepsis, and urinary tract infection in diabetics.

An endogenous antibiotic

Karolinska Institutet researchers have recently explored whether glucose levels in persons with diabetes (type 1, type 2, or prediabetes) are associated with psoriasin, an endogenous antibiotic that is part of the innate immune system.

The researchers examined psoriasin and other peptide levels in urine, urinary bladder cells, and blood serum samples from patients to ensure that the bladder mucosa stays intact and protects against infection. The findings were subsequently confirmed in mice and urinary bladder cells infected and uninfected.

“We found that high glucose concentrations reduce the levels of the antimicrobial peptide psoriasin, while insulin has no effect,” says Annelie Brauner, professor at the Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet who led the study. “People with diabetes have lower levels of psoriasin, which weakens the cells’ protective barrier function and increases the risk of bladder infection.”

Oestrogen therapy reduced bacterial population

Professor Brauner’s research group has previously shown that treatment with oestrogen restores the protective function of bladder cells in humans and mice and thereby help to regulate the immune response to a UTI. The researchers therefore tested how oestrogen treatment affects infected cells exposed to high glucose concentrations. They found that the treatment boosted levels of psoriasin and reduced bacterial populations, indicating that the treatment may have an effect also among patients with diabetes.

“We now plan to probe deeper into the underlying mechanisms of infections in individuals with diabetes,” says the study’s lead author Soumitra Mohanty, researcher at the same department at Karolinska Institutet. “The ultimate goal is to reduce the risk of infection in this growing patient group.”

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