Functional and morphological alterations of the urinary bladder in type 2 diabetic FVBdb/db mice

Aims Diabetic bladder dysfunction (DBD) has been extensively studied in animal models of type 1 diabetes. We aimed to examine the functional and morphological alterations of the urinary bladder in a type 2 diabetes model, FVBdb/db mice. Methods FVBdb/db mice and age-matched FVB/NJ control mice were tested at either 12, 24 or 52weeks of age. Body weight, blood glucose and glycated hemoglobin (HbA1c) levels were measured. Bladder function was assessed by measurement of 24-h urination behavior and conscious cystometry. Bladder was harvested for Masson's Trichrome staining and morphometric analysis. Results The body weights of FVBdb/db mice were twice as those of FVB/NJ control mice. The blood glucose and HbA1c levels were higher in FVBdb/db mice at 12 and 24weeks, but not at 52weeks. A significant increase in the mean volume per void, but decrease in the voiding frequency, in FVBdb/db mice was observed. Cystometry evaluation showed increased bladder capacity, voided volume, and peak micturition pressure in FVBdb/db mice compared with FVB/NJ mice. Morphometric analysis revealed a significant increase in the areas of detrusor muscle and urothelium in FVBdb/db mice. In addition, some FVBdb/db mice, especially males at 12 and 24weeks, showed small-volume voiding during 24-h urination behavior measurement, and detrusor overactivity in the cystometry measurement. Conclusions The FVBdb/db mouse, displaying DBD characterized by not only increased bladder capacity, void volume, and micturition pressure, but also bladder overactivity, is a useful model to further investigate the mechanisms of type 2 diabetes-related bladder dysfunction.