Dysbiosis of Urinary Microbiota Positively Correlated with Diabetes

Type 2 diabetes mellitus (T2DM) accounts for 90% of diabetes, and T2DM is not due to insufficient use of insulin but due to insufficient insulin secretion and insufficient insulin action. Hospitalization rate for urinary tract infection (UTI) caused by diabetes is over twice as much as those caused by other factors.

Damage to the genitourinary system caused by diabetic neuropathy results in bladder dysfunction, and increases the probability of UTI. High levels of urine glucose (UGLU) can favor a proper microenvironment for UTI due to increased bacterial overgrowth and female patients are known to have higher prevalence of UTI than males, which may be associated with the anatomical and structural differences in the urethra between genders.

Scientists at Zhejiang University investigated alterations of urinary microbiota in Chinese female T2DM patients, and explored the associations between urinary microbiota and a patient’s fasting blood glucose (FBG), urine glucose (UGLU), age, menstrual status, and body mass index (BMI). They collected the modified mid-stream urine (MMSU) and asymptomatic bacteriuria is defined as the presence of two consecutive MMSU specimens with isolations of the same bacterial strain at more than 105 CFU/mL. The matched case-control study enrolled 70 patients with T2DM patients and 70 healthy controls (HCs) from June 2015 to January 2016.

Total DNA was extracted from the pellet of urine from Tubes 2 and 3, and 40 mL of urine was aspirated from each tube, separated into three sections, and injected into three 15 mL sterile centrifuge tubes. Magnetic bead isolation of genomic DNA from bacteria was performed and the concentration of extracted DNA was determined by using a Nanodrop ND-1000 spectrophotometer. Microbial diversity and composition were analyzed using the MiSeq sequencing platform by targeting the hypervariable V3-V4 regions of the 16S rRNA gene.

The investigators found that found that bacterial diversity was decreased in T2DM patients. Increased Actinobacteria phylum was positively correlated with FBG, UGLU, and BMI; Lactobacillus abundance decreased with age and menopause; and increased Lactobacillus correlated positively with FBG and UGLU. Decreased Akkermansia muciniphila was associated with FBG and UGLU. Escherichia coli abundance did not differ between the two cohorts. Carbohydrate and amino acid metabolism was reduced in T2DM patients, which were associated with bacterial richness indices.

The authors concluded that microbiota dysbiosis may be associated with T2DM. Secondly, the relative abundance of some key bacteria in T2DM patients was different than in the HCs, and the relative abundancies were affected by the patients’ characteristics. Lastly, there was interdependency between urine microbiota and the patients’ metabolism. Future studies should focus on how the urinary microbiota affects patient’s characteristics such as FBG and UGLU. The study was published on December 19, 2016, in the journal Oncotarget.