Changes of urinary bladder contractility in high-fat diet-fed mice: the role of tumor necrosis factor-α.

Objectives: To study the role of tumor necrosis factor-α in bladder dysfunction associated with obesity.

Methods: Male 8-week-old C57BL/6J mice were divided into three groups: (i) control mice; (ii) vehicle-treated high-fat diet-fed mice; and (iii) etanercept-treated high-fat diet-fed mice. High-fat diet feeding lasted for 12 weeks, vehicle or etanercept (0.8 mg/kg/day, a tumor necrosis factor-α antagonist) treatment was given during the last 4 weeks. At the end of the treatment period, serum tumor necrosis factor-α, total cholesterol, triglyceride and blood glucose were measured. Bladder strip contractile responses to 1 μmol/L acetylcholine or 50 mmol/L KCl were studied in an organ bath. Bladder protein kinase Cζ, nuclear factor-κB and intercellular adhesion molecule-1 expressions were analyzed using western blots.

Results: Serum levels of tumor necrosis factor-α total cholesterol, triglyceride and glucose were significantly elevated in high-fat diet-fed mice; and the levels were not ameliorated by etanercept treatment. High-fat diet-fed mouse bladder showed reduced contractile responses to acetylcholine and KCl stimulation accompanied by high expression levels of phospho-protein kinase Cζ, nuclear nuclear factor-κB and intercellular adhesion molecule-1. Etanercept restored normal bladder contractile responses, as well as protein kinase Cζ nuclear factor-κB and intercellular adhesion molecule-1 expressions.

Conclusions: A high-fat diet induces bodyweight gain, hyperlipidemia and hyperglycemia in mice. Elevated serum tumor necrosis factor-α level associated with increased protein kinase Cζ phosphorylation, nuclear factor-κB nuclear migration, intercellular adhesion molecule-1 expression and impaired muscle contractility are shown in the high-fat diet-fed mouse bladder. Tumor necrosis factor-α antagonist treatment restores normal bladder contractility, and protein kinase Cζ nuclear factor-κB and intercellular adhesion molecule-1 levels.