Insulin is Not Driving Urinary Bladder Enlargement in Rodent Models of Diabetes

Abstract

The urinary bladder is enlarged in all models of type 1 and several of type 2 diabetes (doi 10.1002/nau.23786). We have previously reported that such enlargement is correlated to insulin, but not glucose levels in fructose‐fed rats (doi 10.1096/fasebj.2020.34.s1.00542). Because this was surprising, we have now repeated that study and expanded our analysis to other models of diabetes and obesity.Five studies were performed in models of type 2 diabetes and obesity, one in fructose‐fed rats (n = 16), one each in ZSF1 rats at age 20 and 28 weeks (a cross between a female Zucker Diabetic Fatty and a male spontaneously hypertensive SHHF rat; n = 30 and 45, respectively), and two in mice on a high‐fat diet (n = 23 and 24, respectively). Bladder weight at study end and blood insulin concentrations were subjected to linear correlation analysis based on individual animal data, and data expressed a squared Pearsson correlation coefficient (r2).Animals in the diabetic/obese groups were hyperinsulinemic, whereas bladder enlargement was observed in both studies with ZSF1 rats, the old but not the new in fructose‐fed rats, and in neither study with mice on a high‐fat diet. Bladder weight and insulin levels were not correlated in the new study in fructose‐fed rats or any of the other four studies; the numerical correlation coefficient was negative in two of these studies. When data from all six studies were pooled, a very weak inverse correlation was observed (r2 0.0682, descriptive p‐value 0.0094; Figure 1).We conclude that, contrary to our previous observation, bladder weight is not positively correlated with insulin levels in rodent models of type 2 diabetes and obesity.