Oxidative Stress Alterations in the Bladder of a Short-period Type 2 Diabetes Rat Model: Antioxidant Treatment Can Be Beneficial for the Bladder

Methylglyoxal and Advanced Glycation End Products (AGEs): Targets for the Prevention and Treatment of Diabetes-Associated Bladder Dysfunction?

Methylglyoxal (MGO) is a highly reactive α-dicarbonyl compound formed endogenously from 3-carbon glycolytic intermediates. Methylglyoxal accumulated in plasma and urine of hyperglycemic and diabetic individuals acts as a potent peptide glycation molecule, giving rise to advanced glycation end products (AGEs) like arginine-derived hydroimidazolone (MG-H1) and carboxyethyl-lysine (CEL). Methylglyoxal-derived AGEs exert their effects mostly via activation of RAGE, a cell surface receptor that initiates multiple intracellular signaling pathways, favoring a pro-oxidant environment through NADPH oxidase activation and generation of high levels of reactive oxygen species (ROS). Diabetic bladder dysfunction is a bothersome urological complication in patients with poorly controlled diabetes mellitus and may comprise overactive bladder, urge incontinence, poor emptying, dribbling, incomplete emptying of the bladder, and urinary retention. Preclinical models of type 1 and type 2 diabetes have further confirmed the relationship between diabetes and voiding dysfunction. Interestingly, healthy mice supplemented with MGO for prolonged periods exhibit in vivo and in vitro bladder dysfunction, which is accompanied by increased AGE formation and RAGE expression, as well as by ROS overproduction in bladder tissues. Drugs reported to scavenge MGO and to inactivate AGEs like metformin, polyphenols, and alagebrium (ALT-711) have shown favorable outcomes on bladder dysfunction in diabetic obese leptin-deficient and MGO-exposed mice. Therefore, MGO, AGEs, and RAGE levels may be critically involved in the pathogenesis of bladder dysfunction in diabetic individuals. However, there are no clinical trials designed to test drugs that selectively inhibit the MGO-AGEs-RAGE signaling, aiming to reduce the manifestations of diabetes-associated bladder dysfunction. This review summarizes the current literature on the role of MGO-AGEs-RAGE-ROS axis in diabetes-associated bladder dysfunction. Drugs that directly inactivate MGO and ameliorate bladder dysfunction are also reviewed here.

Potential role of oxidative stress in the pathogenesis of diabetic bladder dysfunction

Diabetes mellitus is a chronic metabolic disease, posing a considerable threat to global public health. Treating systemic comorbidities has been one of the greatest clinical challenges in the management of diabetes. Diabetic bladder dysfunction, characterized by detrusor overactivity during the early stage of the disease and detrusor underactivity during the late stage, is a common urological complication of diabetes. Oxidative stress is thought to trigger hyperglycaemia-dependent tissue damage in multiple organs; thus, a growing body of literature has suggested a possible link between functional changes in urothelium, muscle and the corresponding innervations. Improved understanding of the mechanisms of oxidative stress could lead to the development of novel therapeutics to restore the redox equilibrium and scavenge excessive free radicals to normalize bladder function in patients with diabetes.

Established and emerging treatments for diabetes-associated lower urinary tract dysfunction

Dysfunction of the lower urinary tract (LUT) including urinary bladder and urethra (and prostate in men) is one of the most frequent complications of diabetes and can manifest as overactive bladder, underactive bladder, urinary incontinence, and as aggravated symptoms of benign prostate hyperplasia. We have performed a selective literature search to review existing evidence on efficacy of classic medications for the treatment of LUT dysfunction in diabetic patients and animals, i.e., α1-adrenoceptor and muscarinic receptor antagonists, β3-adrenoceptor agonists, and phosphodiesterase type 5 inhibitors. Generally, these agents appear to have comparable efficacy in patients and/or animals with and without diabetes. We also review effects of antidiabetic medications on LUT function. Such studies have largely been performed in animal models. In the streptozotocin-induced models of type 1 diabetes, insulin can prevent and reverse alterations of morphology, function, and gene expression patterns in bladder and prostate. Typical medications for the treatment of type 2 diabetes have been studied less often, and the reported findings are not yet sufficient to derive robust conclusions. Thereafter, we review animal studies with emerging medications perhaps targeting diabetes-associated LUT dysfunction. Data with myoinositol, daidzein, and with compounds that target oxidative stress, inflammation, Rac1, nerve growth factor, angiotensin II receptor, serotonin receptor, adenosine receptor, and soluble guanylyl cyclase are not conclusive yet, but some hold promise as potential treatments. Finally, we review nonpharmacological interventions in diabetic bladder dysfunction. These approaches are relatively new and give promising results in preclinical studies. In conclusion, the insulin data in rodent models of type 1 diabetes suggest that diabetes-associated LUT function can be mostly or partially reversed. However, we propose that considerable additional experimental and clinical studies are needed to target diabetes itself or pathophysiological changes induced by chronic hyperglycemia for the treatment of diabetic uropathy.

Plasma Concentration of the Lipid Peroxidation (LP) Biomarker 4-Ηydroxynonenal (4-HNE) in Benign and Cancer Patients

BACKGROUND/AIM

The present study investigated the plasma concentration of the lipid peroxidation (LP) biomarker 4-hydroxynonenal (4-HNE) in benign and cancer patients having the rectus sheath block (RSB) analgesia after midline laparotomy. Plasma concentrations of catalase (CAT) and malondialdehyde (MDA) were used as a reference.

PATIENTS AND METHODS

This study assessed three LP biomarkers; CAT, MDA and 4-HNE and compared the plasma levels to the patient satisfaction 24 h postoperatively (SFS₂₄; 0=fully unsatisfied; 10=fully satisfied); the overall pain at rest (NRS_r) and when pressing the wound at 20 Newton force (NRS_p) were surveyed and filed on a 11-point numeric rating scale at 24 h following surgery (NRS; 0=no pain; 10=worst pain). There were 56 patients in the study, of whom 12 were excluded due to missing plasma samples. The final study cohort consisted of 15 patients with benign disease and 29 patients with cancer.

RESULTS

The RSB analgesia enhanced significantly the SFS₂₄ scores in the study groups (p=0.001). The plasma 4-HNE decreased immediately after operation (POP1) and the postoperative decrease between the preoperative and the POP1 values in the 4-HNE marker were statistically significant (p<0.001). The individual plasma 4-HNE and MDA concentration correlated significantly in benign and cancer patients (r=0.413, p<0.001).

CONCLUSION

The present study confirms the applicability of the plasma biomarker 4-HNE to cast further light on the postoperative pain in midline laparotomy patients.

The effect of amino acids on the bladder cycle: a concise review

The human bladder maintains a cycle of filling, storing, and micturating throughout an individual's lifespan. The cycle relies on the ability of the bladder to expand without increasing the intravesical pressure, which is only possible with the controlled relaxation of well-complaint muscles and the congruously organized construction of the bladder wall. A competent bladder outlet, which functions in a synchronous fashion with the bladder, is also necessary for this cycle to be completed successfully without deterioration. In this paper, we aimed to review the contemporary physiological findings on bladder physiology and examine the effects of amino acids on clinical conditions affecting the bladder, with special emphasis on the available therapeutic evidence and possible future roles of the amino acids in the treatment of the bladder-related disorders.

Efficacy of resveratrol in male urogenital tract dysfunctions: an evaluation of pre-clinical data

Resveratrol is a polyphenol found naturally in fruits and plants. Recently, studies in humans and animal models have suggested beneficial properties of this polyphenol, such as improvements to metabolic and lipid profiles, along with antioxidant, anti-inflammatory and anti-proliferative effects. In the urogenital tract (UGT), resveratrol has also been tested clinically and experimentally as a therapeutic drug in several diseases; however, the translational efficacy of resveratrol, especially in UGT, is still a matter of debate. In the present review, we address the pre-clinical efficacy of resveratrol in UGT-related dysfunctions, focusing on lower urinary tract symptoms, non-cancerous prostatic disease (benign prostatic hyperplasia and prostatitis) and erectile dysfunction. In vitro studies indicate that resveratrol reduces inflammatory markers and oxidative stress, and improves endothelial function in UGT organs and cells isolated from humans and animals. Despite displaying low oral bioavailability, in vivo administration of resveratrol largely improves erectile dysfunction, benign prostatic hyperplasia, prostatitis and voiding impairments, as evidenced in different animal models. Resveratrol also acts as a microbiota modulator, which may explain some of its beneficial effects in vivo. In contrast to the large amount of pre-clinical data, there are insufficient clinical trials to establish resveratrol treatment efficacy in human UGT-related diseases. In summary, we provide an overview of the in vivo and in vitro efficacy of resveratrol in animal and human UGT dysfunctions, which may support future clinical trials.

Effect of Electroacupuncture on Bladder Dysfunction via Regulation of MLC and MLCK Phosphorylation in a Rat Model of Type 2 Diabetes Mellitus

Previous studies observed have reported that electroacupuncture (EA) is effective in relieving diabetic bladder dysfunction (DBD); however, little is known about the mechanism. Therefore, we explored the effects and mechanisms of EA on DBD in streptozotocin–high-fat diet- (STZ–HFD-) induced diabetic rats. The Sprague-Dawley male rats were divided randomly into four groups: normal group, diabetes mellitus group (DM group), DM with EA treatment group (EA group), and DM with sham EA treatment group (sham EA group). After 8 weeks of EA treatment, the body weight, serum glucose, bladder weight, and cystometrogram were evaluated. The bladder wall thickness was examined by abdominal ultrasound imaging. After the transabdominal ultrasound measurements, hematoxylin-eosin (HE) staining was used to observe the bladder mucosa layer. The bladder detrusor smooth muscle cells (SMCs) and fibroblasts were observed under transmission electron microscopy (TEM). The phospho-myosin light chain (p-MLC), phospho-myosin light chain kinase (p-MLCK), and phospho-myosin phosphatase target subunit 1 (p-MYPT1) levels in the bladder were examined using Western blot. The bladder weight, serum glucose, bladder wall thickness, volume threshold for micturition, and postvoid residual (PVR) volume in the diabetic rats were significantly higher than those in the control animals. EA treatment significantly reduced the bladder weight, bladder wall thickness, volume threshold for micturition, and PVR volume in diabetic rats. EA caused a significant increase in the MLC dephosphorylation and MLCK phosphorylation levels in the group compared to the sham EA and model groups. EA reduced the infiltration of inflammatory cells in the bladder mucosa layer of diabetic rats. In addition, EA repaired the damaged bladder detrusor muscle of diabetic rats by reducing mitochondrial damage of the SMCs and fibroblasts. Therefore, EA could reduce the bladder hypertrophy to ameliorate DBD by reversing the impairment in the mucosa layer and detrusor SMCs, which might be mainly mediated by the regulation of p-MLC and p-MLCK levels.

CGRP protects bladder smooth muscle cells stimulated by high glucose through inhibiting p38 MAPK pathway in vitro

This study aimed to explore the effect of calcitonin gene-related peptide (CGRP) on bladder smooth muscle cells (BSMCs) under high glucose (HG) treatment in vitro. BSMCs from Sprague-Dawley rat bladders were cultured and passaged in vitro. The third-generation cells were cultured and divided into control group, HG group, HG + CGRP group, HG + CGRP + asiatic acid (AA, p-p38 activator) group, CGRP group, AA group, HG + CGRP + CGRP-8-37 (CGRP receptor antagonist) group and HG + LY2228820 (p38 MAPK inhibitor) group. The cell viability, apoptosis, malondialdehyde (MDA) and superoxide dismutase (SOD) levels of BSMCs were observed by the relevant detection kits. The expressions of α-SM-actin, p38 and p-p38 were detected by qRT-PCR or Western blot analysis. Compared with the control group, the cell viability, SOD and α-SM-actin levels of BSMCs were decreased and apoptotic cells, MDA and p-p38 levels were increased after HG treatment, while these changes could be partly reversed when BSMCs were treated with HG and CGRP or LY2228820 together. Moreover, AA or CGRP-8-37 could suppress the effect of CGRP on BSMCs under HG condition. Our data indicate that CGRP protects BSMCs from oxidative stress induced by HG in vitro, and inhibit the α-SM-actin expression decrease through inhibiting the intracellular p38 MAPK signaling pathway.

EP2 and EP3 receptors as therapeutic targets for underactive bladder/detrusor underactivity due to diabetic cystopathy in a type 1 diabetic rat model

OBJECTIVES

Diabetic cystopathy (DC) is recognized as one of the major etiologies of underactive bladder (UAB)/detrusor underactivity (DU). Although DC was first reported about three decades ago, there is a distinct lack of effective pharmacological management methods for UAB/DU due to DC with a robust certainty of evidence. In this study, we investigated whether EP2 and EP3 receptors are promising targets of pharmacological management of UAB/DU due to DC.

METHODS

We used streptozotocin (STZ)-induced diabetic Sprague-Dawley rats with postvoid residual urine (PVR) greater than 0.1 mL. Sixteen weeks after induction of diabetes, we performed awake single cystometry after oral administration of the vehicle, an α-blocker (tamsulosin [TAM], 0.1 and 0.3 mg/kg), a cholinesterase inhibitor (distigmine [DIS], 0.3 and 1.0 mg/kg), or an EP2/3 dual agonist (ONO-8055, 0.01 and 0.03 mg/kg). We compared cystometric parameters after administration of the vehicle and drugs using a paired t test. P < .05 was considered to be statistically significant.

RESULTS

Compared with the vehicle, TAM significantly decreased maximum intravesical pressure during voiding (Pmax), while DIS significantly increased it. However, neither drug significantly affected PVR or the residual urine rate (RUR). On the other hand, ONO-8055 significantly decreased PVR and tended to decrease RUR, although it did not significantly affect Pmax.

CONCLUSION

The present study was unable to demonstrate that stimulation of EP2 and EP3 receptors caused major improvements in UAB/DU due to DC. However, this equivocal result could arise from inherent limitations of the STZ-induced diabetic rat as a UAB/DU model.