Role of PKC and CaV1.2 in Detrusor Overactivity in a Model of Obesity Associated with Insulin Resistance in Mice

Abstract

Obesity/metabolic syndrome are common risk factors for overactive bladder. This study aimed to investigate the functional and molecular changes of detrusor smooth muscle (DSM) in high-fat insulin resistant obese mice, focusing on the role of protein kinase C (PKC) and Cav1.2 in causing bladder dysfunction. Male C57BL/6 mice were fed with high-fat diet for 10 weeks. In vitro functional responses and cystometry, as well as PKC and Cav1.2 expression in bladder were evaluated. Obese mice exhibited higher body weight, epididymal fat mass, fasting glucose and insulin resistance. Carbachol (0.001–100 µM), α,β-methylene ATP (1–10 µM), KCl (1–300 mM), extracellular Ca2+ (0.01–100 mM) and phorbol-12,13-dibutyrate (PDBu; 0.001–3 µM) all produced greater DSM contractions in obese mice, which were fully reversed by the Cav1.2 blocker amlodipine. Cystometry evidenced augmented frequency, non-void contractions and post-void pressure in obese mice that were also prevented by amlodipine. Metformin treatment improved the insulin sensitivity, and normalized the in vitro bladder hypercontractility and cystometric dysfunction in obese mice. The PKC inhibitor GF109203X (1 µM) also reduced the carbachol induced contractions. PKC protein expression was markedly higher in bladder tissues from obese mice, which was normalized by metformin treatment. The Cav1.2 channel protein expression was not modified in any experimental group. Our findings show that Cav1.2 blockade and improvement of insulin sensitization restores the enhanced PKC protein expression in bladder tissues and normalizes the overactive detrusor. It is likely that insulin resistance importantly contributes for the pathophysiology of this urological disorder in obese mice.

Effect of type II diabetes on male rat bladder contractility

“…This supports our conclusion that the hypertrophy was generalized over the entire bladder wall. Similar results were found in the STZ-induced type I diabetes rat model (11,27). However, multiple studies suggest that this hypertrophy may be mostly due to diuresis as opposed to diabetes per se (17,27).…”

“…This neurogenic residual component could be due to activation of P2X receptors not affected by ␣,␤-methylene ATP or PPADS. Other studies have also shown residual components of EFS-induced contractions in diabetic animal models (4,24,27). There was also an increased TTX-resistant component to EFS-induced contraction in diabetic animals.…”

“…Mice fed a high-fat diet resulted in overactive bladder and enhanced contractility to both agonist-and membrane depolarization-induced bladder contractions; obesity and diabetes, however, were not individually studied (27). In contrast, Fan et al (20) demonstrated that mice fed a high-fat diet exhibited reduced bladder smooth muscle contractile responses to agonist and membrane depolarization stimulation.…”

Soluble Guanylyl Cyclase (sGC) Degradation and Impairment of Nitric Oxide-Mediated Responses in Urethra from Obese Mice: Reversal by the sGC Activator BAY 60-2770

“…Fourweek-old male C57BL6/J mice were provided by the Central Animal House Services of State University of Campinas (CEUA-UNICAMP). The animals were housed two per cage on a 12-hour light/dark cycle, and fed for 12 weeks with either a standard chow diet (carbohydrate: 70%; protein: 20%; fat: 10%) or a high-fat diet that induces obesity (carbohydrate: 29%; protein: 16%; fat: 55%) (Leiria et al, 2012).…”

“…Animal models have provided evidence to confirm a relationship between metabolic syndrome/hyperlipidemia and OAB symptoms (Rahman et al, 2007;Nobe et al, 2008;Lee et al, 2011;Gasbarro et al, 2010). Obesity-associated insulin resistance has been shown to play an important role in OAB pathophysiology in mice (Leiria et al, 2012).…”