Temporal Changes in Micturition and Bladder Contractility after Sucrose Diuresis and Streptozotocin-induced Diabetes Mellitus in Rats

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.

Analysis of 16 studies in nine rodent models does not support the hypothesis that diabetic polyuria is a main reason of urinary bladder enlargement

The urinary bladder is markedly enlarged in the type 1 diabetes mellitus model of streptozotocin-injected rats, which may contribute to the frequent diabetic uropathy. Much less data exists for models of type 2 diabetes. Diabetic polyuria has been proposed as the pathophysiological mechanism behind bladder enlargement. Therefore, we explored such a relationship across nine distinct rodent models of diabetes including seven models of type 2 diabetes/obesity by collecting data on bladder weight and blood glucose from 16 studies with 2–8 arms each; some studies included arms with various diets and/or pharmacological treatments. Data were analysed for bladder enlargement and for correlations between bladder weight on the one and glucose levels on the other hand. Our data confirm major bladder enlargement in streptozotocin rats and minor if any enlargement in fructose-fed rats, db/db mice and mice on a high-fat diet; enlargement was present in some of five not reported previously models. Bladder weight was correlated with blood glucose as a proxy for diabetic polyuria within some but not other models, but correlations were moderate to weak except for RIP-LCMV mice (r² of pooled data from all studies 0.0621). Insulin levels also failed to correlate to a meaningful extent. Various diets and medications (elafibranor, empagliflozin, linagliptin, semaglutide) had heterogeneous effects on bladder weight that often did not match their effects on glucose levels. We conclude that the presence and extent of bladder enlargement vary markedly across diabetes models, particularly type 2 diabetes models; our data do not support the idea that bladder enlargement is primarily driven by glucose levels/glucosuria.

Improvement in bladder dysfunction after bladder transplantation of amniotic fluid stem cells in diabetic rats

To examine the effects of human amniotic fluid stem cells (hAFSCs) transplantation on bladder function and molecular changes in diabetic rats, 60 female Sprague-Dawley rats were used for study. Three groups were assigned including sham control rats, streptozotocin (STZ, 60 mg/kg)-induced diabetic rats and STZ-induced diabetic rats plus bladder hAFSCs transplantation. Compared to controls, diabetic rats had decreased body weight but increased bladder weight. Cystometries showed non-voiding contraction, residual volume, voided volume and intercontraction interval increased significantly in diabetic rats at week 4 and 12 after DM induction, but improved after hAFSCs transplantation. The immunoreactivities and mRNAs of nerve growth factor (NGF) decreased significantly in diabetic bladder at week 4 and 12 after DM induction, but recovered after hAFSCs transplantation. The immunoreactivities and mRNAs of M2 and M3 muscarinic receptor increased significantly in diabetic bladder at week 4 after DM induction but recovered after hAFSCs transplantation. The immunoreactivity of 8-hydroxy-20-deoxyguanosine increased significantly in diabetic bladder at week 4 and 12 after DM induction but reduced after hAFSCs transplantation. The present study showed bladder dysfunction in STZ-induced diabetic rats could be improved by hAFSCs transplantation into bladder, which may be related to the recovery of bladder NGF and muscarinic receptors.

Effects of Moderate Alcohol Intake in the Bladder of the Otsuka Long Evans Tokushima Fatty Diabetic Rats

Diabetes is related with a number of cystopathic complications. However, there have been no studies about the influence of alcohol consumption in the bladder of type 2 diabetes. Thus, we investigated the effect of moderate alcohol intake in the bladder of the Otsuka Long Evans Tokushima Fatty (OLETF) diabetic rat. The non-diabetic Long-Evans Tokushima Otsuka (LETO, n=14) and the OLETF control group (n=14) were fed an isocaloric diet; the LETO (n=14) and the OLETF ethanol group (n=14) were fed 36% ethanol 7 g/kg/day. After ten weeks, muscarinic receptors, RhoGEFs, myogenic change, and the level of oxidative stress were evaluated. Moderate alcohol intake significantly decreased excessive muscarinic receptor and Rho kinase expressions in the OLETF rats compared with the LETO rats. In addition, iNOS and collagen expression were not changed in the OLETF rats in spite of alcohol consumption. Superoxide dismutase levels, which is involved in antioxidant defense, in the LETO rats were significantly decreased after alcohol consumption, however those in the OLETF rats were similar. Moderate alcohol consumption reduces the oxidative stress, and may prevent molecular and pathologic changes of the bladder of rats with type 2 diabetes.

Diabetic plasticity of non-adrenergic non-cholinergic and P2X-mediated rat bladder contractions

We investigated the plasticity effects of diabetes mellitus and diuresis on the non-adrenergic non-cholinergic (NANC) and purinergic (P2X-type) contractile responses in longitudinal rat bladder strips. Female Sprague-Dawley rats received streptozotocin to induce diabetes, or sucrose in water to induce diuresis as a control condition for polyuria. Experiments were carried out at four weeks after treatments, using bladders from non-treated rats as control. Urinary bladder strips were electrically stimulated throughout the experiments to generate neurally evoked contractions (NEC). In all cases, P2X-mediated purinergic contractions were evaluated at the beginning and end of the stimulations with α,β-methylene-adenosine triphosphate (α,βMeATP). The NANC responses were assessed by using two independent protocols. First, cholinergic receptors were activated with carbachol (CCh), followed by inhibition of the muscarinic component with atropine. In the second protocol, the application order for CCh and atropine was reversed. The NANC response, unmasked with the application of atropine, and the P2X purinergic contractions were analyzed. NANC contractions in diabetic bladder strips are more resistant to the desensitizing effects caused by activation of cholinergic receptors. In early stages of experimental diabetes, NANC responses in diabetic strips are less sensitive to functional inhibition mediated by the cholinergic activation. However, P2X-mediated purinergic contractions are more sensitive to desensitization in diabetic or diuretic bladders. For instance preventing muscarinic receptor activation with atropine does not counteract the desensitization of purinergic contractions in either diabetic or diuretic strips. We suggest that diabetes may induce a plasticity of the NANC and P2X-mediated bladder contractile responses. The first one may be associated with diabetic neuropathic damage to bladder nerves, while impaired P2X purinergic contractions might be associated with detrusor hypertrophy observed in diabetic and diuretic strips.

Calcineurin and Akt expression in hypertrophied bladder in STZ-induced diabetic rat

Diabetes causes significant increases in bladder weight but the natural history and underlying mechanisms are not known. In this study, we observed the temporal changes of detrusor muscle cells (DMC) and the calcineurin (Cn) and Akt expressions in detrusor muscle in the diabetic rat. Male Sprague-Dawley rats were divided into 3 groups: streptozotocin-induced diabetics, 5% sucrose-induced diuretics, and age-matched controls. The bladders were removed 1, 2, or 9weeks after disease induction and the extent of hypertrophy was examined by bladder weights and cross sectional area of DMC. Cn and Akt expression were evaluated by immunoblotting. Both diabetes and diuresis caused significant increases in bladder weight. The mean cross sectional areas of DMC were increased in both diabetic and diuretic animals 1, 2, or 9weeks after disease induction. The expression levels of both the catalytic A (CnA) and regulatory B (CnB) subunits of Cn were increased at 1 and 2weeks, but not at 9weeks. Expression of Akt was similar among control, diabetic, and diuretic rat bladder at all time points. In conclusion, diabetes and diuresis induce similar hypertrophy of detrusor muscle during the first 9weeks, indicating that bladder hypertrophy in the early stage of diabetes is in response to the presence of increased urine output in diabetes. Our results suggest that the Cn, but not the Akt signaling pathway may be involved in the development of bladder hypertrophy.

Functional, morphological and molecular characterization of bladder dysfunction in streptozotocin-induced diabetic mice: evidence of a role for L-type voltage-operated Ca2+ channels

BACKGROUND AND PURPOSE

Diabetic cystopathy is one of the most common and incapacitating complications of diabetes mellitus. This study aimed to evaluate the functional, structural and molecular alterations of detrusor smooth muscle (DSM) in streptozotocin-induced diabetic mice, focusing on the contribution of Ca(2+) influx through L-type voltage-operated Ca(2+) channels (L-VOCC).

EXPERIMENTAL APPROACH

Male C57BL/6 mice were injected with streptozotocin (125 mg·kg(-1) ). Four weeks later, contractile responses to carbachol, α,β-methylene ATP, KCl, extracellular Ca(2+) and electrical-field stimulation were measured in urothelium-intact DSM strips. Cystometry and histomorphometry were performed, and mRNA expression for muscarinic M(2) /M(3) receptors, purine P2X1 receptors and L-VOCC in the bladder was determined.

KEY RESULTS

Diabetic mice exhibited higher bladder capacity, frequency, non-void contractions and post-void pressure. Increased bladder weight, wall thickness, bladder volume and neural tissue were observed in diabetic bladders. Carbachol, α,β-methylene ATP, KCl, extracellular Ca(2+) and electrical-field stimulation all produced greater DSM contractions in diabetic mice. The L-VOCC blocker nifedipine almost completely reversed the enhanced DSM contractions in bladders from diabetic animals. The Rho-kinase inhibitor Y27632 had no effect on the enhanced carbachol contractions in the diabetic group. Expression of mRNA for muscarinic M(3) receptors and L-VOCC were greater in the bladders of diabetic mice, whereas levels of M(2) and P2X1 receptors remained unchanged.

CONCLUSIONS AND IMPLICATIONS

Diabetic mice exhibit features of urinary bladder dysfunction, as characterized by overactive DSM and decreased voiding efficiency. Functional and molecular data suggest that overactive DSM in diabetes is the result of enhanced extracellular Ca(2+) influx through L-VOCC.

Pudendal nerve injury reduces urethral outlet resistance in diabetic rats

Diabetics have voiding and continence dysfunction to which elevated levels of advanced glycation end products (AGE) may contribute. In addition, pudendal nerve injury is correlated with voiding dysfunction and stress incontinence in rats. The aim of this study was to investigate whether pudendal nerve crush (PNC) in diabetic rats alters urinary function. Female virgin Sprague-Dawley rats (144) were divided equally into diabetic, diuretic, and control groups. Half of the animals in each group were subjected to PNC, and the other half to sham PNC. Diabetes was induced 8 wk before PNC or sham PNC by streptozotocin injection (35 mg/kg). Animals underwent conscious cystometry and leak point pressure (LPP) testing 4 or 13 days after PNC or sham PNC. Tissues of half the animals were tested for levels of AGEs. Qualitative histological assessment was performed in the remaining animals. Diabetic rats 4 days after PNC voided significantly greater volume in a shorter time and with significantly less pressure than after sham PNC, suggesting that diabetic rats have a functional outlet obstruction that is relieved by PNC. LPP was significantly reduced 4 days after PNC in diabetic and diuretic animals and returned to normal 13 days after PNC. Diabetic rats with PNC demonstrated increased muscle fiber disruption and atrophy of the external urethral sphincter. AGEs were significantly elevated in diabetic rats. PNC relieves a functional outlet obstruction in diabetic rats. AGEs are elevated in diabetic rats and could play a role in urinary dysfunction and recovery from PNC.

Exercise improves bladder function in diabetic mice

AIMS

We determined the effect of exercise on bladder dysfunction and voiding frequency in db/db mice.

MATERIALS AND METHODS

Diabetic db/db female mice (BKS.Cg-Dock7m +/+ Leprdb/J strain) and their age-matched wild-type controls (WT) were equally divided into sedentary and exercise groups. Mice were exercised for 1 hr everyday for 8 weeks (speed of 5.2 m/min). We performed a voiding pattern test, cystometric analysis and reactivity of isolated bladder strips in WT and db/db mice, both sedentary and exercised.

RESULTS

Diabetes increased the frequency of voiding, bladder capacity, and residual volume. Exercise decreased voiding frequency in db/db mice; voiding frequency was 5.8 ± 0.5 (db/db exercise) versus 10.8 ± 1.1 (db/db control, P < 0.001). In cystometric analysis, the bladder capacity of db/db sedentary mice was 0.27 ± 0.05 ml and was 0.14 ± 0.02 ml in the db/db exercise group (P < 0.05), whereas the residual volume was 0.2 ± 0.03 ml in db/db sedentary mice and 0.06 ± 0.02 ml in db/db Ex mice. Isolated strips of bladder muscle from sedentary db/db mice were more responsive to carbachol than strips from db/db exercise mice. Exercise did not improve the urodynamic properties of WT mice, both sedentary and exercised.

CONCLUSIONS

Exercise improves bladder function in diabetic mice by reducing voiding frequency and improving urodynamic parameters.

Role of angiogenesis in bladder response to partial outlet obstruction

Benign prostatic hyperplasia (BPH) is a disease that has its etiology in the abnormal growth of the adult human prostate gland that accompanies the aging process in men. The symptomatic presentation of this disease, however, is related largely to degenerative changes in the bladder that occur as a result of the increasing urethral resistance and partial bladder outlet obstruction (PBOO) caused by the growing prostate gland. BPH is characterized by bladder hypertrophy, significant decreases in urinary flow and compliance, presence of residual urine after voiding, voiding urgency and incontinence (). Obstructed bladder dysfunction secondary to BPH is a slow, progressive disease that is so strongly associated with human aging that it is an expected occurrence of the male aging process. Although the symptoms of BPH are usually not life threatening, they effect an extremely negative quality of life for men who suffer from them. However, many men delay seeking medical treatment for early BPH since bladder function can remain relatively normal as the hypertrophying bladder initially compensates for the progressive increase in urethral resistance caused by prostatic obstruction. The limited changes in micturition pressure and flow characteristics that occur during compensated function are not usually disabling enough to motivate seeking medical attention, which, often, is not sought until the symptoms become typical of advanced disease. Recent advances in detection methods enable identification of patients with significant BPH during compensation before the bladder becomes dysfunctional (decompensated). A more complete understanding of the disease processes that underlie the loss of bladder function associated with BPH might enable the development of treatments that better protect these early-stage BPH patients from the more debilitating aspects of the disease. This review updates the understanding of obstructive bladder dysfunction via the use of animal models.

Diabetes-induced alternations in biomechanical properties of urinary bladder wall in rats

OBJECTIVES

To determine whether diabetes mellitus and the associated changes in bladder function will trigger bladder wall tissue remodeling and concomitant alterations in the mechanical properties. We investigated the time course of changes in function and mechanical properties of diabetic and diuretic rat bladders using both in vivo and in vitro techniques

METHODS

Cystometry was performed at 2, 4, and 8 weeks on female Sprague-Dawley rats that had received either a single injection of streptozotocin (65 mg/kg intraperitoneally) or 5% sucrose in drinking water for the duration of the experiments. At each point, the biaxial mechanical properties of 10 x 10-mm tissue specimens obtained from the posterior part of bladder wall were quantified. The changes in overall tissue compliance and mechanical anisotropy as a function of time were examined

RESULTS

Both diabetic and diuretic conditions led to increases in bladder weight, bladder capacity, and in vivo compliance compared with the controls at all points tested. Under biaxial loading, all bladder wall tissues exhibited a nonlinear stress-strain relationship and mechanical anisotropy, with greater tissue compliance in the circumferential direction than in the longitudinal direction. Although the compliance of the bladder wall increased progressively and synchronously in both diabetic and diuretic bladders for < or = 4 weeks, only the diabetic bladders continued to increase the compliance for < or = 8 weeks (diabetic 0.64 +/- 0.04 vs diuretic 0.48 +/- 0.05, P = .03)

CONCLUSIONS

The results of our study have shown that diuresis mainly contributes to the "early" changes of mechanical properties of the bladder, with diabetes inducing additional "late" changes of mechanical properties of the rat bladders after 4 weeks.

External urethral sphincter activity in diabetic rats

AIM

To examine the temporal effects of diabetes on the bladder and the external urethral sphincter (EUS) activity in rats.

METHODS

Female Sprague-Dawley rats (n = 24) were divided into two groups: streptozotocin-induced diabetic rats and age-matched controls. Cystometrograms (CMGs) were taken under urethane anesthesia and electromyograms (EMG) of the EUS were evaluated in all rats at 6 and 20 weeks after diabetes induction. After EMG assessment, the tissues of the urethra were harvested for morphological examination.

RESULTS

Diabetes caused reduction of body weight, but an increase in bladder weight. CMG measurements showed diabetes increased threshold volume, contraction duration, high-frequency oscillations (HFO), and residual volume. Peak contraction amplitude increased in 6-week but not 20-week diabetic rats. EUS-EMG measurements showed increased frequency of EUS-EMG bursting discharge during voiding in 6-week diabetic rats (8.1 +/- 0.2 vs. 6.9 +/- 0.6/sec) but not in 20-week (5.8 +/- 0.3 vs. 6.0 +/- 0.2/sec) diabetic rats compared with controls. EUS-EMG bursting periods were also increased in both 6-week and 20-week diabetic rats compared with controls. EUS-EMG silent periods were reduced in 6-week diabetic rats, but were not changed in 20-week diabetic rats compared with controls. Active periods did not change in 20-week diabetic rats, but increased in 6-week diabetic rats compared with controls. Morphometric analysis showed atrophy of the EUS after 20 week but not 6 weeks of DM induction.

CONCLUSIONS

Our data indicates diabetes causes functional and anatomical abnormalities of the EUS. These abnormalities may contribute to the time-dependent bladder dysfunction in diabetic rats.

Time-dependent alterations of select genes in streptozotocin-induced diabetic rat bladder

OBJECTIVES

To investigate time-course changes in the expression of select genes and extracellular matrix proteins in the bladder of rats with streptozotocin-induced diabetes, so as to examine the mechanisms underlying changes in mechanical properties of the bladder due to diabetic cystopathy.

METHODS

Female Sprague-Dawley rats were injected with streptozotocin (65 mg/kg). Rats that were fed with 5% sucrose in drinking water served as diuretic controls, in addition to normal control rats. At the end of 2, 4, and 8 weeks, total ribonucleic acid (RNA) isolated from the detrusor layer of the bladders was reverse transcribed, and then complementary deoxyribonucleic acid was amplified with polymerase chain reaction primer sets for type I collagen, type III collagen, tropoelastin, and transforming growth factor beta 1 (TGF-beta-1). Collagen and elastin contents of the bladders were quantified with commercially available assays.

RESULTS

Both diabetic and diuretic rat bladders exhibited significantly (P <0.05) lower expression of type I collagen and TGF-beta-1 messenger RNA (mRNA) compared with normal controls at all time points tested. In contrast, downregulation of type III collagen mRNA expression in both diabetic and diuretic groups was seen at 4 and 8 weeks. Furthermore, tropoelastin mRNA expression in the diabetic rat bladders was, compared with normal and diuretic rats, significantly (P <0.05) greater at 2 weeks. Both diabetic and diuretic rat bladders exhibited significantly (P <0.05) decreased collagen and increased elastin protein content at 2 and 8 weeks.

CONCLUSIONS

The results of the present study suggest that increases in compliance of the bladders in diabetic cystopathy result not only from diuresis-driven reduction of collagen synthesis but also from increased elastin synthesis.

Changes of M3-muscarinic receptor protein and mRNA expressions in the bladder urothelium and muscle layer of streptozotocin-induced diabetic rats

Diabetes induced alterations of M3-muscarinic receptors (M3-mAChR) in the urothelium and muscle layer of the urinary bladder were studied using streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were divided into two groups; group I: normal control rats; group II: STZ-induced diabetic rats, 2 weeks after induction. The bladder was divided into urothelium and muscle layer by microdissection. Tissue M3-mAChR protein levels were measured by Western blotting. Expression of the mRNA that encoded M3-mAChR was estimated using the method of reverse transcription combined with polymerase chain reaction (RT-PCR). M3-mAChR protein and mRNA expressions were found in both the urothelium and muscle layer of the rat urinary bladder. In control rats, the M3-mAChR protein expression ratio in the urothelium and muscle layer was 1:1.87; that for mRNA was 1:0.74. Two weeks after induction of diabetes, the M3-mAChR mRNA expression in the urothelium and muscle layer were significantly increased by 45.7% (P<0.01, n=8) and 80.8% (P<0.001, n=8), respectively. Correspondingly, the bladder M3-mAChR protein levels were significantly increased by 50.0% (P<0.01, n=8) in the urothelium and 147.1% (P<0.001, n=8) in the muscle layer of the diabetic rats. In conclusion, M3-mAChR mRNA and protein are expressed in both the urothelium and muscle layer of the rat urinary bladder. STZ-induced diabetes increases mRNA and protein expression of the M3-mAChR in the urothelium as well as the muscle layer.

Alterations of M2-muscarinic receptor protein and mRNA expression in the urothelium and muscle layer of the streptozotocin-induced diabetic rat urinary bladder

Diabetes associated alterations of M2-muscarinic receptors (M2-mAChR) in the urothelium and muscle layer of the urinary bladder were studied using streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were divided into two groups; group I: normal control rats; group II: STZ-induced diabetic rats, 2 weeks after induction. The bladder was divided into urothelium and muscle layer by microdissection. Tissue M2-mAChR protein levels were measured by Western blotting. Expression of the mRNA that encoded M2-mAChR was estimated using the method of reverse transcription combined with polymerase chain reaction (RT-PCR). M2-mAChR protein and mRNA expressions were found in both the urothelium and muscle layer of the rat urinary bladder. In control rats, the M2-mAChR protein expression ratio in the urothelium and muscle layer was 1:1.66; that for mRNA was 1:0.97. Two weeks after induction of diabetes, the M2-mAChR mRNA expression in the urothelium and muscle layer were significantly increased by 44.4% (P<0.01, n=8) and 28.6% (P<0.01, n=8), respectively. Correspondently, the bladder M2-mAChR protein levels were significantly increased by 33.3% (P<0.001, n=8) in the urothelium and 25.3% (P<0.01, n=8) in the muscle layer of the diabetic rats. In conclusion, M2-mAChR mRNA and protein are expressed in both the urothelium and muscle layer of the rat urinary bladder. STZ-induced diabetes increases mRNA and protein expression of the M2-mAChR in the urothelium as well as the muscle layer.

Time dependent changes in diabetic cystopathy in rats include compensated and decompensated bladder function

PURPOSE

Diabetic bladder dysfunction is among the most common and bothersome complications of diabetes mellitus. While bladder filling and voiding problems have been reported, the precise functional changes in diabetic bladders remain unclear. We investigated time dependent changes in bladder function in streptozotocin induced diabetic rats.

MATERIALS AND METHODS

Cystometrograms and detrusor muscle contractility were examined in male age matched control and diabetic Sprague-Dawley rats (Harlan, Indianapolis, Indiana) 3, 6, 9, 12 and 20 weeks after diabetes induction with streptozotocin.

RESULTS

Diabetes decreased average body weight and increased bladder weight, capacity and compliance. Peak detrusor leak pressure increased gradually from weeks 3 to 6 to 9 in diabetic rats (mean +/- SEM 47.3 +/- 2.5, 50.8 +/- 3.0 and 56.0 +/- 3.6 cm H(2)O) and in controls (36.9 +/- 1.4, 37.7 +/- 1.5 and 41.6 +/- 1.81 cm H(2)O, respectively). However, at 12 and 20 weeks diabetic rats deviated strongly from this trend with peak detrusor leak pressure decreasing vs controls (41.6 +/- 2.8 and 37.3 +/- 0.9 vs 45.2 +/- 1.7 and 49.6 +/- 1.4 cm H(2)O, respectively) and post-void resting pressures increasing from 9-week levels vs controls (interactions p <0.0001). In contractility studies increased contractile force responses of diabetic animals to carbamylcholine chloride, potassium chloride, adenosine 5'-triphosphate and electric field stimulation peaked at 6 or 9 weeks but at 12 to 20 weeks they generally reverted toward those of controls (carbamylcholine chloride and electrical field stimulation interactions p = 0.0022 and 0.01, respectively).

CONCLUSIONS

Diabetic bladders may undergo a transition from a compensated to a decompensated state and transition in the streptozotocin rat model may begin 9 to 12 weeks after induction.

Temporal diabetes- and diuresis-induced remodeling of the urinary bladder in the rat

The natural history of diabetes mellitus-induced remodeling of the urinary bladder is poorly understood. In this study, we examined temporal remodeling of the bladder in diabetic and diuretic rats. Male Sprague-Dawley rats were divided into three groups: streptozotocin-induced diabetic, 5% sucrose-induced diuretic, and age-matched control. Micturition and morphometric characteristics were evaluated using metabolic cages and light-microscopic examination of the bladder 4 days and 1, 2, 3, and 9 wk after induction. Digital image analysis was used to quantify equatorial cross-sectional areas of bladder tissue and lumen, as well as relative content of the three primary tissue components: smooth muscle, urothelium, and collagen. Diabetes and diuresis caused significant increases in fluid intake, urine output, and bladder weight. In both groups, progressive increases were observed in lumen area from 4 days to 3 wk after induction and in wall area from 2 to 3 wk after induction. Wall thickness decreased within the first 2 wk in the diabetic and diuretic rats but returned to control at 3 and 9 wk. As a percentage of total cross-sectional area, smooth muscle area increased, urothelium area was unchanged, and collagen area decreased in diabetic and diuretic rats after 2-3 wk compared with control rats. In conclusion, diabetes and diuresis induced similar bladder remodeling. Diabetes-induced diuresis caused adaptive physical changes in rat bladder by 4 days after induction; remodeling was observed by 2-3 wk after induction and remained stable from 3 to 9 wk.

Alterations in neurogenically mediated contractile responses of urinary bladder in rats with diabetes

Diabetic bladder dysfunction (DBD) is among the most common and bothersome complications of diabetes mellitus. Autonomic neuropathy has been counted as the cause of DBD. In the present study, we compared the alterations in the neurogenically mediated contractile responses of urinary bladder in rats with streptozocin-induced diabetes, 5% sucrose-induced diuresis, and age-matched controls. Male Sprague-Dawley rats were divided into three groups: 9-wk diabetic rats, diuretic rats, and age-matched controls. Micturition and morphometric characteristics were evaluated using metabolic cage and gross examination of the bladder. Bladder detrusor muscle strips were exposed to either periodic electrical field stimulation (EFS) or to EFS in the presence of atropine, alpha,beta-methylene adrenasine 5'-triphosphate, or tetrodotoxin. The proportions of cholinergic, purinergic, and residual nonadrenergic-noncholinergic (NANC) components of contractile response were compared among the three groups of animals. Diabetes caused a significant reduction of body weight compared with diuresis and controls, although the bladders of diabetic and diuretic rats weighed more than the controls. Both diabetes and diuresis caused significant increase in fluid intake, urine output, and bladder size. Diabetes and diuresis caused similarly increased response to EFS and reduced response to cholinergic component compared with controls. However, the purinergic response was significantly smaller in diuretic bladder strips compared with controls but not in diabetic rats. A residual NANC of unknown origin increased significantly but differently in diabetics and diuretics compared with controls. In conclusion, neurogenically mediated bladder contraction is altered in the diabetic rat. Diabetic-related changes do not parallel diuretic-induced changes, indicating that the pathogenesis of DBD needs further exploration.

Experimental study of excitability and autorhthmicity in urinary bladder detrusor of diabetes rats

The changes in excitability and autorhthmicity of bladder detrusor in experimental non-insulin dependent diabetes mellitus (NIDDM) rats were observed. Sixty-nine NIDDM rats as NIDDM group and 69 normal rats as control group were enrolled into this experimental study. At 6th, 10th, 14th, 18th, 22nd and 26th week after the rats were injected last time, the changes in the excitability and autorhthmicity of detrusor strips in vitro were observed. The results showed that the threshold of the tension which made the detrusor strips contract was significantly higher in NIDDM group (0.716 +/- 0.325 g) than in control group (0.323 +/- 0.177 g) (F = 59.63, P < 0.001). At different stages, the threshold of the tension resulting the contract of the detrusor strips in NIDDM group was also higher than in control group. At 18th week after STZ injection, the frequency of spontaneous contract of the detrusor strips in NIDDM was significantly higher than in control group (P < 0.05), whereas at 22nd week, that in NIDDM group was significantly lower than in control group (P < 0.05). It was concluded that the decreased excitability of the bladder detrusor was the earliest and most obvious changes in bladder function in diabetes rats and the autorhthmicity had also changed at the early stage of diabetic bladder.

Effect of timing of diuresis on response of rat bladder to outlet obstruction

OBJECTIVES

To determine whether results similar to a previous study, in which sucrose-induced diuresis started before creating partial outlet obstruction resulted in protection of bladder contractile function in obstructed animals, would be obtained if diuresis were begun after creation of partial outlet obstruction.

METHODS

Thirty-six rats were separated into six groups of 6 rats each: group 1, control; group 2, diuresis; group 3, obstructed; group 4, obstructed immediately after diuresis; group 5, obstructed with diuresis beginning 10 days after obstruction; and group 6, obstructed before diuresis. Diuresis was induced by feeding 5% sucrose instead of water. After 3 weeks of obstruction, all bladders were excised, cut into longitudinal strips, and mounted in isolated muscle baths for physiologic study.

RESULTS

Sucrose-induced diuresis resulted in a statistically significant increase in bladder mass and a mild increase in smooth muscle contractility compared with the control water-fed group. Obstruction resulted in a fourfold increase in bladder weight and substantial decreases in the responses to all forms of stimulation. The bladder weights of the obstruction plus diuresed groups were all similar to the diuresis-alone group and significantly lower than those of the obstructed group. All diuresed groups showed protection of the contractile responses compared with the obstruction-alone group. Unexpectedly, the group that began diuresis 1 day after obstruction showed the strongest protection.

CONCLUSIONS

Diuresis significantly reduced the increase in bladder mass induced by obstruction and also reduced the level of contractile dysfunction. Diuresis begun 1 day after obstruction resulted in the greatest level of protection.

Diabetes decreases rabbit bladder smooth muscle contraction while increasing levels of myosin light chain phosphorylation

The effect of diabetes mellitus on the regulation of urinary bladder smooth muscle contraction was studied. Diabetes was induced in the rabbit by alloxan injection followed by 16 wk of housing. The bladder was harvested and strips of wall devoid of both mucosa and serosa were examined. Intact strips of bladder smooth muscle from diabetic animals produced less stress in response to membrane depolarization than muscle from control animals; sensitivity to KCl was not changed. Carbachol responses were similar in muscle strips from the two animal groups. Basal myosin light chain (MLC) phosphorylation levels were significantly elevated in response to most stimuli in muscle strips from diabetic animals, although levels of stress were either unchanged or lower. alpha-Toxin-permeabilized strips that allow for control of the intracellular environment while maintaining excitation-contraction coupling showed increased levels of MLC phosphorylation but decreased sensitivity to activator Ca2+ in smooth muscle from diabetic animals. MLC phosphatase contents were similar in smooth muscle from the two animal groups; however, MLC phosphatase activity was greater in muscle from control compared with diabetic animals. These results suggest that diabetes mellitus uncouples basal MLC phosphorylation from force in the bladder smooth muscle cell.

Diabetes Mellitus Increases the Rate of Development of Decompensation in Rats With Outlet Obstruction

PURPOSE

We investigated the effects of the combination of bladder outlet obstruction and diabetes mellitus on in vitro rat bladder body strip function.

MATERIALS AND METHODS

Longitudinal strips were removed from ventral and dorsal detrusor of age matched control, 2-week diabetic, 2-week obstructed and 2-week obstructed diabetic rats. Contractile responses to electrical field stimulation, carbachol, adenosine triphosphate, KCl and phenylephrine, and relaxations in response to norepinephrine and isoproterenol were measured.

RESULTS

Bladders from diabetic, obstructed and obstructed diabetic rats were 1.6-fold, 2.6-fold and 3.6-fold heavier than those from controls. Responses of bladder strips from diabetics to all stimuli were similar to those of controls. Strips from obstructed rats were significantly less responsive to norepinephrine than those from controls or diabetics and strips from obstructed diabetics were significantly less responsive to norepinephrine and isoproterenol than those from all other groups. Strips from obstructed diabetics had significantly decreased responses to field stimulation, while responses to carbachol were decreased to a lesser extent. Responses of strips from obstructed rats to field stimulation were also decreased compared with controls but were significantly greater than those of the obstructed diabetic group. Responses to adenosine triphosphate, KCl and phenylephrine were similar in all groups.

CONCLUSIONS

The combination of outlet obstruction and diabetes mellitus causes significant increases in bladder mass compared with either diabetes or obstruction alone. Bladder strips from obstructed diabetics show characteristics of denervation accompanied by alterations in beta-adrenergic function, suggesting that the coexistence of outlet obstruction and diabetes increases the rate of development of bladder decompensation.

Functional response of bladder strips from streptozotocin diabetic rats depends on bladder mass

PURPOSE

We investigated the relationship of bladder mass to responses to electrical field stimulation and adrenergic agonists in diabetic rat bladders.

MATERIALS AND METHODS

Longitudinal strips were removed from the ventral and dorsal detrusor of age matched control, 2-month diabetic and sucrose drinking rats. Contractile responses to electrical field stimulation, KCl and phenylephrine, and relaxation in response to norepinephrine and isoproterenol were measured.

RESULTS

Bladders from sucrose drinking and diabetic rats weighed significantly more than those of controls. Diabetic rats were divided into 2 groups with the bladder weighing less than or greater than 265 mg. Strips from small diabetic bladders were generally more responsive to field stimulation and norepinephrine than those from control or sucrose drinking rats. Conversely decreased function was especially apparent in dorsal strips from large diabetic bladders. Ventral strips were significantly more sensitive to the relaxant actions of norepinephrine and isoproterenol than dorsal strips.

CONCLUSIONS

Our results suggest that the responsiveness of diabetic rat bladder to electrical field stimulation and adrenergic agonists is related to bladder mass, analogous to observations after partial outlet obstruction. Decreased function was particularly apparent in dorsal strips from diabetic rats with a large bladder.

Proceedings of the National Institute of Diabetes and Digestive and Kidney Diseases International Symposium on Epidemiologic Issues in Urinary Incontinence in Women

The Epidemiologic Issues in Urinary Incontinence: Current Databases and Future Collaborations Symposium included an international group of 29 investigators from 10 countries. The purpose of the symposium was to discuss the current understanding and knowledge gaps of prevalence, incidence, associated risk factors, and treatment outcomes for incontinence in women. During the symposium, investigators identified existing large databases and ongoing studies that provide substantive information on specific incontinence research questions. The investigators were able to form an international collaborative research working group and identify potential collaborative projects to further research on the epidemiology of urinary incontinence and bladder dysfunction.

Effects of Ba-Wei-Die-Huang-Wan on the cholinergic function and protein expression of M2 muscarinic receptor of the urinary bladder in diabetic rats

The study investigated the effect of a traditional Chinese herbal preparation 'Ba-Wei-Die-Huang-Wan' on the cholinergic function of the urinary bladder in diabetic rats, as well as its influence on the protein expression of muscarinic M(2) receptors. Wistar rats were divided into three groups: (1) control rats; (2) 2-week streptozotocin-induced diabetic rats; and (3) diabetic rats treated with Ba-Wei-Die-Huang-Wan 26 mg/kg thrice daily for 3 days. A dose-response study was performed for bladder muscle strip contractile response to a muscarinic agonist, arecaidine propargyl ester (APE). The amount of M(2) receptor protein in the bladder was measured by Western immunoblotting using monoclonal antibodies. The bladder contractile response to APE was significantly increased in the diabetic rats compared to the control. The M(2) receptor protein density was also significantly higher by 106% (P < 0.01, n = 8) in diabetes. Ba-Wei-Die-Huang-Wan treatment significantly lowered the plasma glucose level of the diabetic rats. The increases in contractile response to APE as well as the M(2) receptor protein density were partially reversed by the treatment. In conclusion, there was an over-expression of M(2) receptor resulting in hyper-contractility in the bladder of diabetic rats. Ba-Wei-Die-Huang-Wan significantly alleviated the alterations.

Influence of gender on the diurnal variation of urine production and micturition characteristics of the rat

The diurnal variation in the frequency/volume characteristics of male and female conscious rats was evaluated with reference to fluid consumption and urine production. Baseline values of the micturition volume and frequency of nine male and 10 female SD adult rats were measured over a 24-hour time period. The level of initial hydration conditions was standardized with 5 ml of water administered orally. With animals in a metabolism chamber having free access to water, the total volume of water consumed, the frequency/volume characteristics during micturition and the urine production rate were derived from the measurements of voided volume as detected by a digital balance. To establish reliability of measurements two separate micturition studies were done per rat at an interval of 1 week. Mean frequency of micturition and mean volume voided per micturition and urine production rate were computed in 3-hour time bins and represented over the 24-hour period. In addition the mean values of the number of micturitions and mean micturated volumes during the day/dark cycle were evaluated. The results show significant gender specificity in water consumption, urine production, and diurnal variations in micturition frequency/volume characteristics. Females consistently consume significantly larger amounts of water (83%) than males while urine production rate was correspondingly higher in females. It is concluded that water consumption and urine production are gender-specific. Because higher volumes of water are imbibed by females than males, the frequency/volume characteristic of micturition in the rat is also gender-specific. Data suggest that the volume voided per micturition depends on the urine production rate.

Automated noninvasive measurement of cyclophosphamide-induced changes in murine voiding frequency and volume

PURPOSE

We developed an automated noninvasive method for studying bladder function in mice. Changes in voided volume and frequency accompanying cyclophosphamide-induced cystitis were measured using computerized digital balances.

MATERIALS AND METHODS

Eight CRL CD-1 mice were given a solution of glucose and saccharin to increase urine output and studied during the dark cycle, when most voiding occurs. Urine fell directly onto electronic balance pans. The time and weight of each void was recorded. Computer programs adjusted for evaporative loss analyzed voiding data within and across sessions. After establishing stable voiding patterns 300 mg./kg. cyclophosphamide were administered intraperitoneally. The Wilcoxon signed rank test was done to compare median voided volumes, frequency and gm. per hour of urine produced before and after cyclophosphamide.

RESULTS

We implemented an automated method for voiding studies in mice. After cyclophosphamide administration the number of voids per hour increased and voided volume decreased. Some mice had as much as a 70% decrease in bladder volume and a tripling of urinary frequency. Mice responded by a sustained elevation in frequency and decreased voided volume as early as 24 hours after cyclophosphamide administration or by a pattern of delayed toxicity.

CONCLUSIONS

This noninvasive technique measures changes in mouse voiding patterns with great sensitivity and minimal effort. The method is applicable to murine models of interstitial cystitis, detrusor instability and other abnormal voiding states. It may be used for evaluating potential therapies for such conditions.

Influence of 5-hydroxytryptamine and the effect of a new serotonin receptor antagonist (sarpogrelate) on detrusor smooth muscle of streptozotocin-induced diabetes mellitus in the rat

BACKGROUND

We evaluated the changes in the response of detrusor muscle to 5-hydroxytryptamine (5-HT; serotonin) and its receptor mechanisms in pathologic bladder of diabetes mellitus rats.

METHODS

Eight-week-old male Wistar rats were given an intraperitoneal injection of streptozotocin (STZ, 60 mg/kg) in order to induce diabetes mellitus (4 weeks' duration). The bladder strips (10 x 2 mm) were subjected to a tension of 1.0 g in organ baths for the measurements of isotonic contractile responses to 5-HT or relaxation responses to 5-HT antagonists.

RESULTS

Bladder strips from STZ-diabetic rats responded to 5-HT with greater contractions than did those of control rats, given vehicle alone. However, bladder strip weights gradually increased in the STZ-diabetic rats as compared with control rats and when the contractile response to 5-HT was expressed as a percentage of the response to 10(-1) mol/L KCl there was no statistically significant difference between the groups. In both control and diabetic rats, the 5-HT3 selective antagonist did not markedly inhibit the contractile response to 5-HT. In contrast, the 5-HT2A selective antagonist inhibited the contractile response to 5-HT in a dose-dependent manner.

CONCLUSIONS

These results suggest that the increased contractile response to 5-HT in diabetic rats' bladder is related to smooth muscle hypertrophy and/or hyperplasia and indicate that this effect is mediated by activation of 5-HT2A receptors.

Sucrose diuresis protects rat bladder from outlet partial obstruction-induced contractile dysfunction

OBJECTIVES

Evidence is accumulating that bladder dysfunction caused by experimental partial obstruction of the bladder outlet can be reduced or reversed by treatment that results in upregulation of bladder function, even in the presence of obstruction. Inducing diuresis in rats or rabbits results in a significant increase in bladder mass and increased contractility in response to stimulation. The objective of the present study was to determine whether diuresis-induced amplification of bladder function in the rat could protect the bladder from contractile dysfunctions caused by partial outlet obstruction.

METHODS

Thirty-two rats were separated into four groups of 8 rats each. Groups 2 and 4 were fed 5% sucrose instead of water; groups 1 and 3 were fed only water. Three weeks later, partial outlet obstructions were created in groups 3 and 4. After 4 weeks of obstruction, all bladders were rapidly excised and cut into longitudinal strips; each strip was mounted in an isolated muscle bath for contractile studies.

RESULTS

Sucrose-induced diuresis caused a moderate but significant increase in bladder mass. Partial outlet obstruction stimulated significant increases in bladder mass in both water-drinking and sucrose-drinking groups; the bladder mass of sucrose-drinking rats, however, increased less than that of water-drinking rats. In water-drinking rats, partial outlet obstruction resulted in significantly decreased bladder strip contractility in vitro in response to field stimulation (1 to 32 Hz), carbachol (0.1 to 22 microM), and KCl (120 mM). After 3 weeks of sucrose-induced diuresis, partial obstruction of the rat bladder outlet did not result in decreased in vitro contractile responses to any form of stimulation applied.

CONCLUSIONS

Sucrose-induced diuresis caused an increase in bladder mass and an increase in contractile strength, consequently protecting the rat bladder from the contractile dysfunctions that usually follow partial outlet obstruction.

Smooth muscle of the bladder in the normal and the diseased state: pathophysiology, diagnosis and treatment

The smooth muscle of the normal bladder wall must have some specific properties. It must be very compliant and able to reorganise itself during filling and emptying to accommodate the change in volume without generating any intravesical pressure, but whilst maintaining the normal shape of the bladder. It must be capable of synchronous activation to generate intravesical pressure at any length to allow voiding. The cells achieve this through spontaneous electrical activity combined with poor electrical coupling between cells, and a dense excitatory innervation. In the diseased state, alterations of the smooth muscle may lead to failure to store or failure to empty properly. The diseased states discussed are bladder instability and diabetic neuropathy. Bladder instability is characterised urodynamically by uninhibitable rises in pressure during filling, and is seen idiopathically and in association with bladder outflow obstruction and neuropathy. In diabetic neuropathy, many of the smooth muscle changes are a consequence of diuresis, but there is evidence for alterations in the sensory arm of the micturition reflex. In the unstable bladder, additional alterations of the smooth muscle are seen, which are probably caused by the patchy denervation that occurs. The causes of this denervation are not fully established. Nonsurgical treatment of instability is not yet satisfactory; neuromodulation has some promise, but is expensive, and the mechanisms poorly understood. Pharmacological treatment is largely through muscarinic receptor blockade. Drugs to reduce the excitability of the smooth muscle are being sought, since they may represent a better pharmacological option.

Diabetic cystopathy: relationship to autonomic neuropathy detected by sympathetic skin response

PURPOSE

The possible relationship between bladder dysfunction and autonomic neuropathy was investigated in unselected diabetic patients.

MATERIALS AND METHODS

Bladder function was examined by cystometry in 53 unselected diabetic patients and 10 healthy controls. Sympathetic skin response was recorded in 23 of 53 patients and all control subjects to evaluate autonomic neuropathy associated with diabetes, and the results were compared to cystometric findings.

RESULTS

Cystometrograms exhibited significant increases in bladder volume at first desire to void and maximal bladder capacity, and a decrease in detrusor contractility in diabetic patients compared to those in controls. In addition, mean residual urine was significantly larger in diabetic patients than in controls. Among the 53 diabetic patients these bladder dysfunctions were also found in each subset of patients with no sign of retinopathy (33), no subjective urinary symptoms (32) or duration of diabetes less than 1 year (12). In 23 patients in whom sympathetic skin response was measured 12 without sympathetic skin responses had increased residual urine and decreased detrusor contraction pressure. The remaining 11 patients with a lower amplitude of sympathetic skin response and more prolonged latency than controls had a significant decrease in detrusor contraction pressure.

CONCLUSIONS

Bladder dysfunction, characterized by loss of sensation, increased capacity and decreased contractility, was the main observation of diabetic cystopathy regardless of the duration or severity of the disease. The association of bladder dysfunction and autonomic neuropathy detected by the sympathetic skin response might indicate that diabetic cystopathy is a manifestation of peripheral neuropathy induced by diabetes.

Diabetic sexual dysfunction

Although the overall incidence of erectile dysfunction in the general population between the ages of 40 and 70 years is 52%, men with diabetes mellitus have impotence at an earlier age and with a significantly higher prevalence, ranging as high as 75%. Numerous advances have been made in understanding the physiologic and biochemical mechanisms controlling penile erection. Improved clinical techniques for the diagnosis and treatment of impotence, including dynamic vascular testing, intracavernosal pharmacotherapy, and microsurgical revascularization, have allowed us to enter a new and exciting era in the quest for a more complete understanding of erectile dysfunction.

Alterations in urinary bladder synaptosomal neurotransmitter concentrations in two-week streptozotocin-induced diabetic rats

Three-month-old male Wistar rats were rendered diabetic with a single intravenous injection of streptozotocin (60 mg/kg body weight). Two weeks after induction of diabetes, synaptosome-rich fractions were prepared from urinary bladder tissue homogenate of the diabetic rats and control rats by differential centrifugation (1000 x g, 17,000 x g and 100,000 x g) with discontinuous sucrose gradient. Synaptosomal acetylcholine, norepinephrine, epinephrine and dopamine were measured by the method of high-performance liquid chromatography. The respective neurotransmitter concentrations for the diabetic rats were 1537.8 +/- 65.3, 4757.7 +/- 361.9, 3720.7 +/- 276.1, and 2447.8 +/- 196.8 pmol/mg synaptosomal protein, respectively; those for the control rats were 338.1 +/- 25.0, 1009.0 +/- 54.6, 645.3 +/- 52.2, and 1426.1 +/- 123.9 pmol/mg protein, respectively. Thus, the synaptosomal concentrations for all the measured neurotransmitters were significantly higher in the diabetic rats (P < 0.05 for each comparison). In conclusion, it has been demonstrated that the vesicle-bound acetylcholine and catecholamines in the synaptosome-rich fraction of the urinary bladder were significantly increased in 2-week diabetic rats. This finding would suggest impaired neurotransmitter release from both the bladder sympathetic and parasympathetic efferent nerve endings in early streptozotocin-induced diabetes.