Diabetic bladder dysfunction is a frequent complication of diabetes. Although many mouse models of diabetes now exist, there has been little systematic effort to characterize them for the timing of onset and severity of bladder dysfunction. We monitored metabolic status and tested bladder function by void spot assay and limited anesthetized cystometry in both male and female mice of three models of obesity and diabetes: a type 1 diabetes model (the Akita mouse) and two type 2 diabetes models [the diet-induced obese (DIO) model and the ob/ob mouse]. Akita mice had insulin pellets implanted subcutaneously every 3 mo to mimic poorly controlled type 1 diabetes in humans. Mice were hyperglycemic by 48 days after implants. Female mice exhibited no bladder dysfunction at any age up to 20 mo and gained weight normally. In contrast, by 7 mo, male Akita mice developed a profound polyuria and failed to show normal weight gain. There were no observable signs of bladder dysfunction in either sex. DIO mice on high/low-fat diets for 16 mo exhibited mild hyperglycemia in female mice (not in male mice), mild weight gain, and no evidence of bladder dysfunction. Ob/ob mice were followed for 8 mo and became extremely obese. Male and female mice were glucose intolerant, insulin intolerant, and hyperinsulinemic at 4 mo. By 8 mo, their metabolic status had improved but was still abnormal. Urine volume increased in male mice but not in female mice. Bladder dysfunction was observed in the spotting patterns of female mice at 4 and 6 mo of age, resolving by 8 mo. We conclude there are dramatic sex-related differences in lower urinary tract function in these models. Male Akita mice may be a good model for polyuria-related bladder remodeling, whereas female ob/ob mice may better mimic storage problems related to loss of outlet control in a setting of type 2 diabetes complicated by obesity.
Publications by Year: 2020
2020
BACKGROUND: Our understanding of the neural circuits controlling micturition and continence is constrained by a paucity of techniques for measuring voiding in awake, behaving mice.
NEW METHOD: To facilitate progress in this area, we developed a new, non-invasive assay, micturition video thermography (MVT), using a down-facing thermal camera above mice on a filter paper floor.
RESULTS: Most C57B6/J mice void infrequently, with a stereotyped behavioral sequence, and usually in a corner. The timing of each void is indicated by the warm thermal contrast of freshly voided urine. Over the following 10-15 min, urine cools to ∼3 °C below the ambient temperature and spreads radially in the filter paper. By measuring the area of cool contrast comprising this "thermal void spot," we can derive the initially voided volume. Thermal videos also reveal mouse behaviors including a home-corner preference apart from void spots, and a stereotyped, seconds-long pause while voiding.
COMPARISON WITH EXISTING METHODS AND CONCLUSIONS: MVT is a robust, non-invasive method for measuring the timing, volume, and location of voiding. It improves on an existing technique, the void spot assay, by adding timing information, and unlike the cystometrogram preparation, MVT does not require surgical catheterization. Combining MVT with current neuroscience techniques will improve our understanding of the neural circuits that control continence, which is important for addressing the growing number of patients with urinary incontinence as the population ages.
The general anesthetic ketamine has been repurposed by physicians as an anti-depressant and by the public as a recreational drug. However, ketamine use can cause extensive pathological changes, including ketamine cystitis. The mechanisms of ketamine's anti-depressant and adverse effects remain poorly understood. Here we present evidence that ketamine is an effective L-type Ca2+ channel (Cav1.2) antagonist that directly inhibits calcium influx and smooth muscle contractility, leading to voiding dysfunction. Ketamine prevents Cav1.2-mediated induction of immediate early genes and transcription factors, and inactivation of Cav1.2 in smooth muscle mimics the ketamine cystitis phenotype. Our results demonstrate that ketamine inhibition of Cav1.2 signaling is an important pathway mediating ketamine cystitis. In contrast, Cav1.2 agonist Bay k8644 abrogates ketamine-induced smooth muscle dysfunction. Indeed, Cav1.2 activation by Bay k8644 decreases voiding frequency while increasing void volume, indicating Cav1.2 agonists might be effective drugs for treatment of bladder dysfunction.