Diabetes slows the recovery from urinary incontinence due to simulated childbirth in female rats

The influence of hyperglycemia on the remodeling of urethral connective tissue in pregnant rats

OBJECTIVE

To analyze the distribution and quantification of the key structural extracellular matrix components of the urethral tissue in a rat model of hyperglycemia and pregnancy.

STUDY DESIGN

A total of 120 female Wistar rats were distributed into the following four experimental groups: virgin, pregnant, hyperglycemic and hyperglycemic + pregnant groups. The urethra was harvested for histochemical, morphometric, immunohistochemical, Western blot and glycosaminoglycan analyses. All protocols were approved by the Institutional Animal Care and Use Committee of Botucatu Medical School (process number 828-2010).

RESULTS

The hyperglycemic + pregnant group showed significantly increased stiffness in urethral tissue. The total striated muscle was decreased, with increased deposition of collagen fibers around the muscle fibers and a change in the organization of the collagen fibrils. An increase in the relative collagen type I/III ratio and a decrease in total glycosaminoglycans were also observed.

CONCLUSIONS

This study provides the first line of experimental evidence supporting a metabolic relationship between hyperglycemia and urethral remodeling of connective tissue in pregnant rats. The different organization of the collagen fibrils and the profile of glycosaminoglycans found in urethral samples suggest that the pathology of the urethral fibromuscular system could be related to hyperglycemia-induced pelvic floor dysfunction in women, which has direct clinical implications with the possibility to develop new multidisciplinary treatments for improving the health care of these women.

Evaluation of the relationship between the pelvic floor muscles and insulin resistance

PURPOSE

The aim of this study was to evaluate the pelvic floor muscles (PFMs) in women with insulin resistance (IR) using surface electromyography and to associate the results with insulin levels.

PATIENTS AND METHODS

Through an analytical, cross-sectional study, 86 women were evaluated and divided into two groups: a control group (n=35) and an IR group (n=51). Data were collected through detailed history-taking, physical examination, and biochemical analysis. Fasting insulin levels were used for diagnosing IR. Electromyography of the PFMs was used for analyzing the tone and maximal voluntary contraction (MVC). The measures of central tendency and linear regression models were used.

RESULTS

The average age was 25.3±4.5 years in the IR group and 27.2±4.4 years in the control group. The mean weight was 75.6±17.6 kg and 51.8±4.9 kg in the IR and control groups, respectively. Fasting insulin levels were 19.7±6.6 µIU/mL in the IR group and 5.4±1.8 µIU/mL in the control group (P<0.010). There were significant differences between the groups with regard to PFM tone (IR: 13.4±3.4 µV; control: 25.1±3.3 µV; P<0.001) and MVC (IR: 47.6±4.5 µV; control: 64.3±5.0 µV; P<0.001). Multiple linear regression analysis using the insulin levels as dependent variable showed a significant association for MVC (P=0.047), weight (P=0.017), and waist circumference (P=0.000).

CONCLUSION

Compared with the control group, the IR group showed lower electromyographic activity of the PFMs, and there was an association between insulin levels and electromyographic activity.

[Translational research in gestational diabetes mellitus and mild gestational hyperglycemia: current knowledge and our experience]

Maternal diabetes constitutes an unfavorable environment for fetal-placental and embryonic development. It is has important repercussion in modern obstetrics, since it is associated to an increased risk of neonatal and maternal morbidity, and it still is a significant medical challenge. The increased occurrence of diabetes worldwide, the increase in diabetes type 2 in women at reproductive age and the crossed generation of intrauterine programming for diabetes type 2 are the bases for the growing interest in utilization of diabetic experimental samples, with the aim to acquire knowledge about the mechanisms that induce development alterations in gestational diabetes. Several studies have shown the benefits of diabetes prevention, with interventions in lifestyle, metabolic improvement and control of cardiovascular risk factors to substantially prevent the complications of this devastating disease. Despite these findings, the recent revolution in the scientific knowledge, and the infinite number of new therapies for diabetes, there is still a large gap between what was learned through research and what is really done in public, clinical and community health. The negative economic impact of this complacency in people, families, and national economies is alarming. It is expected that translational research in the binomial diabetes and pregnancy are implemented in centers of excellence, in both basic and applied research, and complemented by multicenter clinical studies, conducted in a pragmatic way to increase the level of scientific evidence with more reliable diagnostic and propaedeutic resources.

Urethral striated muscle and extracellular matrix morphological characteristics among mildly diabetic pregnant rats: translational approach

INTRODUCTION AND HYPOTHESIS

Diabetes mellitus (DM) during pregnancy is associated with high levels of urinary incontinence (UI) and pelvic floor muscle dysfunction. Mild DM can lead to changes in urethral striated muscle and extracellular matrix (ECM) in pregnant rats considering both structures as an entire system responsible for urinary continence.

METHODS

Ninety-two female Wistar rats were distributed in four experimental groups: virgin, pregnant, diabetic, and diabetic pregnant. In adult life, parental nondiabetic female rats were mated with nondiabetic male rats to obtain newborns. At the first day of birth, newborns received citrate buffer (nondiabetic group) or streptozotocin 100 mg/kg body weight, subcutaneous route (mild DM group). At day 21 of the pregnancy, the rats were lethally anesthetized and the urethra and vagina were extracted as a unit. Urethral and vaginal sections were cut and analyzed by: (a) cytochemical staining for ECM and muscle structural components, (b) immunohistochemistry to identify fast- and slow-muscle fibers, and (c) transmission electron microscopy for ultrastructural analysis of urethral striated muscle.

RESULTS

In comparison with the three control groups, variations in the urethral striated muscle and ECM from diabetic pregnant rats were observed including thinning, atrophy, fibrosis, increased area of blood vessels, mitochondria accumulation, increased lipid droplets, glycogen granules associated with colocalization of fast and slow fibers, and a steady decrease in the proportion of fast to slow fibers.

CONCLUSIONS

Mild DM and pregnancy can lead to a time-dependent disorder and tissue remodeling in which the urethral striated muscle and ECM has a fundamental function.

Animal models of stress urinary incontinence

Stress urinary incontinence (SUI) is a common health problem significantly affecting the quality of life of women worldwide. Animal models that simulate SUI enable the assessment of the mechanism of risk factors for SUI in a controlled fashion, including childbirth injuries, and enable preclinical testing of new treatments and therapies for SUI. Animal models that simulate childbirth are presently being utilized to determine the mechanisms of the maternal injuries of childbirth that lead to SUI with the goal of developing prophylactic treatments. Methods of assessing SUI in animals that mimic diagnostic methods used clinically have been developed to evaluate the animal models. Use of these animal models to test innovative treatment strategies has the potential to improve clinical management of SUI. This chapter provides a review of the available animal models of SUI, as well as a review of the methods of assessing SUI in animal models, and potential treatments that have been tested on these models.

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.

Temporal morphological and functional impact of complete urinary diversion on the bladder: a model of bladder disuse in rats

PURPOSE

Urinary diversion has been used as a surgical option for some bladder diseases. We developed a urinary diversion model in the rat and examined the effects of urinary diversion on the bladder.

MATERIALS AND METHODS

We distributed female Sprague-Dawley® rats into age matched control, sham urinary diversion and urinary diversion groups. Each group was subsequently evaluated 1 or 8 weeks after urinary diversion or sham operation. Diversion was done by surgical disconnection of the ureters from the bladder and implantation to the uterine cervix. Conscious cystometry was examined. Bladders were harvested for histological examination and quantification of smooth muscle, urothelium and collagen. Vaginal histology was assessed. Bladder muscarinic and purinergic receptor expression was examined.

RESULTS

All rats survived the urinary diversion procedure. Bladder weight decreased in the diversion group. Cystometry showed decreased intercontractile interval and voided volume in the urinary diversion group compared to those in the control and sham operated groups. Compliance was decreased in diverted rats. Smooth muscle and urothelium were decreased as a percent of total bladder cross-sectional area. Collagen increased in 1 and 8-week diverted rats vs controls. Histological examination of the vaginal wall revealed mild swelling in 2 rats. Urinary diversion caused decreased muscarinic 3 and ligand gated purinergic 1 receptor expression but no change in muscarinic 2 or ligand gated purinergic 2 receptors.

CONCLUSIONS

Creating a urinary diversion model by ureterovaginostomy in the rat is feasible. Urinary diversion causes distinct functional and morphometric bladder alterations.

Postpartum stress urinary incontinence: lessons from animal models

Postpartum stress urinary incontinence (SUI) is associated with chronic SUI in later life, which is 240% more likely to occur in women who deliver vaginally than those who did not. The etiology of SUI is multifactoral and has been associated with defects in both neuromuscular and structural components of continence. Specifically, clinical studies have demonstrated that pudendal nerve damage occurs during vaginal delivery, supporting the concept that neuromuscular damage to the continence mechanism can result in postpartum SUI. Urethral hypermobility and the loss of pelvic floor support, such as that involved in pelvic organ prolapse, have also been associated with SUI. Animal models provide an opportunity to investigate these injuries, individually and in combination, enabling researchers to gain further insight into their relative contributions to the development of SUI and the effectiveness of potential therapies for it. This article discusses the use of animal models of postpartum SUI in addition to the broad insights into treatment efficacy they provide.

Animal models of female stress urinary incontinence

PURPOSE

Urinary incontinence affects 40% of women in the United States and stress urinary incontinence accounts for a large portion of affected patients. As defined by the International Continence Society, stress urinary incontinence is the involuntary leakage of urine upon effort, exertion, sneezing or coughing. Since the ultimate success of long-term management for any condition is based on an understanding of its pathophysiology, and because the pathophysiology of stress urinary incontinence is incompletely defined, animal models have recently been developed to better understand stress urinary incontinence and develop novel treatment alternatives.

MATERIALS AND METHODS

Several animal models for urethral dysfunction have emerged in the last few years, including those based on pathophysiological theories of urethral sphincter dysfunction that were designed to simulate maternal birth trauma. Other models have focused on the creation of a durable model of dysfunction for investigating novel treatments.

RESULTS

Since animals cannot express intent, these animal models have focused on measuring decreased urethral resistance. The most widely used methods are the sneeze test, the tilt table technique and the leak point pressure test. Newer techniques include abdominal leak point pressure, urethral pressure measurement and retrograde urethral perfusion pressure. In addition to the advantages and disadvantages of each technique, all methods measure the composite contribution to urethral resistance from smooth and striated muscle, urethral closure and connective tissue, although none measures intent.

CONCLUSIONS

We critically reviewed the different models of stress urinary incontinence and urethral dysfunction as well as the different methods of measuring urethral resistance.