"Patients with type-2 diabetes and females with gestational diabetes are at higher risk for acquiring urinary tract infections as compared to non-diabetic patients and even individuals with type-1 diabetes. Although all these groups have high levels of glucose [in the blood] that can spill into the urine, type-2 diabetics and pregnant women with gestational diabetes can also have high levels of insulin which can also spill into the urine," says Karolina Klosowka, a researcher on the study.
Klosowka and her colleagues investigated the effects of insulin on Escherichia coli, a bacterium that commonly causes UTIs. An essential part of E. coli's ability to cause UTIs is its ability to adhere in the bladder. The researchers found that insulin along with glucose in concentrations similar to what are found in the urine of type-2 and gestational diabetics increases E. coli's adherence. This enhanced binding may begin to explain why these types of diabetics have a greater risk for UTIs. They also found that insulin affected the cell surface of the bacteria in ways that may provide some protection against antibiotics.
"Based on our observations, it appears that insulin with glucose affects the growth and some of the surface characteristic of E. coli that correlate with its ability to cause urinary tract infections," says Klosowka. "These findings bring a new perspective in helping to understand why patients with type-2 diabetes and females with gestational diabetes have a higher incidence of urinary tract infections."