Morphometric studies of pituitary glands and testes in rats with streptozotocin-induced diabetes

Knockout of insulin-degrading enzyme leads to mice testicular morphological changes and impaired sperm quality

Insulin-degrading enzyme (IDE) is a zinc metalloprotease responsible for degrading and inactivating several bioactive peptides, including insulin. Individuals without this enzyme or with a loss-of-function mutation in the gene that codifies it, present hyperinsulinemia. In addition, impairment of IDE-mediated insulin clearance is associated with the development of metabolic diseases, namely prediabetes. Although insulin regulates male fertility, the role of IDE on male reproductive function remains unknown. We proposed to study the influence of IDE in the reproductive potential of males. As insulin mediates key events for the normal occurrence of spermatogenesis, we hypothesized that IDE functioning might be linked with sperm quality. We used C57BL/6N mice that were divided in three groups according to its genotype: wild type (WT), heterozygous and knockout (KO) male mice for Ide. Spermatozoa were collected from the cauda of epididymis and sperm parameters were evaluated. Testicular tissue morphology was assessed through hematoxylin and eosin stain. Mitochondrial complex protein levels and lipid peroxidation were also evaluated in the testicular tissue. Our results show that KO mice present a 50% decrease in testes weight compared to WT mice as well as a decrease in seminiferous tubules diameter. Moreover, KO mice present impaired sperm quality, namely a decrease in both sperm viability and morphology. These results provide evidence that IDE plays an important role in determining the reproductive potential of males.

Taurine Recovers Testicular Steroidogenesis and Spermatogenesis in Streptozotocin-Induced Diabetic Rats

A great deal of investigations have verified that diabetic male reproductive impairment is associated with the dysfunction of testicular steroidogenesis and spermatogenesis resulted from insulin deficiency and hyperglycaemia-induced oxidative stress. It has been identified taurine is profitable for diabetes mellitus and diabetic implications through its insulin-like and islet cells protective activity. Furthermore, our previous studies found that taurine could increase testicular antioxidative ability, stimulate the endocrine activity of hypothalamic-pituitary-testicular axis, elevate testosterone level, raise sperm quality, suppress the deterioration of testicular function. Accordingly, we hypothesized that taurine may have beneficial effects on testicular dysfunction under diabetic mellitus status. Here, we investigated the effects of taurine on testicular steroidogenesis and spermatogenesis in streptozotocin (STZ)-induced type I diabetic rats. We observed that taurine treatment can markedly increase the body and testis weights, testicular SDH and G6PDH activities, decrease the serum fasting glucose concentration of diabetic rats. Serum contents of GnRH, LH, FSH, T, and testicular StAR, 3β-HSD, 17β-HSD mRNA expression levels were also obviously raised by taurine administration, indicating that taurine can improve testicular steroidogenesis in diabetic animals. Finally, we found taurine supplementation effectively elevated the sperm count and motility, reduced sperm abnormality, suggesting that taurine can increase the testicular spermatogenesis function of diabetic rat. In summary, the present data indicated that taurine can rescue the function of testicular steroidogenesis and spermatogenesis in STZ-induced type I diabetic rats possibly by increasing the endocrine activity of hypothalamic-pituitary-testicular axis.

Insulin-dependent diabetes affects testicular function by FSH- and LH-linked mechanisms

A study was conducted to form a unified hypothesis regarding the gonadotropin-related mechanisms that underlie alterations in the male reproductive system in individuals with diabetes. Streptozotocin-induced diabetes resulted in reduced fertility, prolificacy, and libido. Testes showed a marked decrease in the number and function of Leydig cells, the latter manifested as changes in the expression of biochemical markers, including the GLUT-3 hexose transporter, c-kit, insulin-like growth factor I (IGF-I), androgen receptors, and overall tyrosine phosphorylation, as assessed by Western blot and immunocytochemical analyses. The expression of c-kit, IGF-I, insulin, and follicle-stimulating hormone (FSH) receptors in the seminiferous tubules was also affected. Serum levels of luteinizing hormone (LH), FSH, and testosterone significantly decreased. There was a significant (P <.05) correlation between the serum levels of insulin and FSH. No significant correlation was found between the serum levels of insulin or glucose and LH. On the basis of our results, we conclude that, in insulin-dependent diabetes, 1) Leydig cell function and testosterone production decrease because of the absence of the stimulatory effect of insulin on these cells and an insulin-dependent decrease in FSH, which, in turn, reduces LH levels; and 2) sperm output and fertility are reduced because of a decrease in FSH caused by a reduction in insulin.

LHRH receptors and LHRH receptor-bearing cells in pituitaries of streptozocin diabetic male rats

Streptozocin (STZ)-diabetic rats have low hypothalamic luteotropic hormone-releasing hormone (LHRH) secretion and various alterations of gonadotrope cells, among which low luteotropic hormone (LH) secretion. Possible causes for the gonadotrope disorders may be low hypothalamic LHRH secretion alone or combined with reduced (a) number of LHRH receptor sites, or (b) receptor to ligand affinity, or (c) of LHRH receptor-bearing cells. To clarify this question we determined by saturation and competition binding Bmax, KD and KA of the LHRH receptor sites and counted the receptor-bearing cells in pituitary glands of control and STZ-diabetic adult male rats. We found a single receptor class, the Bmax was strongly reduced in diabetic animals whereas both KD and KA were similar in the two groups. The number of LHRH receptor-bearing cells in diabetic animals was increased. Therefore a reduced number of receptor sites per gonadotrope cell occurs in our model. Since in the STZ-diabetic male rats the number of gonadotropes is increased, a higher number of receptor-bearing cells was observed. We conclude that the reduced LH secretion from the diabetic pituitary gland might be due to a reduced number of LHRH receptor sites in the pituitary gland. The increased number of receptor-bearing cells might partially compensate for this change.

Histological and endocrinological investigations of cyclosporine effects on the rat testis

To investigate the effects of cyclosporine on spermatogenesis and endocrinological function of the testis, cyclosporine was administered subcutaneously to mature male Sprague-Dawley rats. Four and 6 weeks after the termination of cyclosporine administration (40 or 60 mg kg-1), the diameter of seminiferous tubules was diminished. The percentage of tubules with spermatozoa was decreased 6 weeks after the termination of cyclosporine treatment (20-60 mg kg-1). However, tubular wall thickness did not change throughout the experiment. Serum follicular stimulating hormone level increased significantly immediately after termination of cyclosporine administration dose-dependently, while the serum levels' luteinizing hormone and testosterone did not alter throughout the experiment. It is strongly suggested that cyclosporine impairs spermatogenesis and Sertoli cell function, although Leydig cell function is not injured.

Ultrastructural changes in mouse Leydig cells after streptozotocin administration

Male ICR mice were intraperitoneally injected with a single dose (100 mg/kg BW) of streptozotocin (STZ). The pancreas and testis were excised at 1, 2 or 4 weeks after STZ administration and observed by light and electron microscopy. At 2 weeks after injection (p.i.), the islets of Langerhans in the pancreas showed severe atrophy, indicating a diabetic state. In the testis, although no conspicuous morphological changes were detected at 2 weeks p.i., noticeable changes had occurred in the Leydig cells at 4 weeks p.i. In the cells, lipid droplets increased in number, whereas smooth endoplasmic reticulum (sER) decreased. Giant whorl-like sER appeared frequently at this time. These findings indicate the declined secretory activity of Leydig cells in STZ diabetic mice.

Sustained hyperglycemia results in testicular dysfunction and reduced fertility potential in BBWOR diabetic rats

Rats with short-term diabetes show a greater than 50% reduction of serum testosterone and increased lipid in Leydig cells but normal testicular structure. The purpose of this study was to determine the extent of testicular pathology (morphology index), integrity of the blood-testis barrier, daily sperm production (DSP), number of Leydig cells per testis (LC/T), and total trunk testosterone (TTT) in diabetic rats (BBWORdp) with long-term hyperglycemia (300-350 mg/dl for greater than 180 days) and to evaluate its effects on fertility potential. Results were compared with similarly aged normoglycemic rats (BBWORdr) and normal control Wistar rats. After 6 mo of diabetes, testis weights, DSPs, TTTs, and the morphology index were significantly reduced. The LC/T was not different from BBWORdr rats. The blood-testis barrier appeared intact, although structural abnormalities were noted in Sertoli-Sertoli junction complexes. There was a significant reduction in the number of pregnancies per rat and implantations per pregnancy in matings utilizing the diabetic BBWORdp rat and control Wistar female rats. Results indicate that long-term diabetes with sustained hyperglycemia leads to significant testicular dysfunction associated with decreased fertility potential.

Histometric investigations of the effect of cyclosporin A on the testicular tissue of rats

The effect of cyclosporin A (CsA) on rat testes was assessed in Lewis rats which were given 10 mg/kg of CsA im per day. The rats were divided into 13 subgroups, and 1 subgroup was sacrificed each month. The rat testes were measured and examined for histometrical and morphological changes in comparison to controls. Histometrical analysis included testicular cross-sectional surface area, tubular density, tubular diameter, and the amounts of testicular germinal epithelium, lumen, and interstitial tissue. In the parameters examined, there were no overall differences between CsA-treated animals and controls. CsA does not affect rat testicular tissue.

Thyroid and pituitary secretory disorders in streptozotocin-diabetic rats are associated with severe structural changes of these glands

Streptozotocin diabetes in rats is associated with reduced function of the hypothalamo-pituitary-thyroid axis. The structure and hormone secretion of the thyroid and pituitary glands were studied in adult male rats 1 month after streptozotocin injection. The thyroid of diabetic rats was characterized by decreased follicle area and epithelial thickness. By electron microscopy, thyroid epithelial cells were characterized by flattened and almost empty rough endoplasmic reticulum cisternae, scanty exocytotic apical and endocytotic vesicles as well as degenerate mitochondria and rough endoplasmic reticulum. By immunohistochemistry, intracolloidal thyroglobulin and T3 as well as intraepithelial thyroglobulin were reduced. Electron microscopic and immunohistochemical analysis of pituitary glands showed that in diabetic rats thyrotrophs were mostly of type II, and the number of thyrotrophs (type I + type II) was greater than in controls. By radioimmunoassay (RIA), plasma T3, T4, and TSH levels were markedly reduced, and the TSH response to TRH was deficient in diabetic animals. The pituitary TSH concentration was increased, as expected from the morphological data. This study demonstrates severe structural changes in the thyroid and pituitary glands of diabetic rats which are accompanied by marked alterations of their secretory activity.

Morphometry and cytochemistry of Leydig cells in experimental diabetes

Leydig cell ultrastructure and function in diabetic rats were studied by concurrent cytochemistry, morphometry, and testosterone assay. The streptozotocin (Stz) model was modified to include nondiabetic Stz-injected rats, an insulin-treated diabetic group, and semistarved animals in addition to controls and untreated diabetic rats. The separation of the effects of diabetes, Stz, semistarvation, and insulin treatments was achieved by application of orthogonal contrast statistics. After 3 months of treatments, testes were perfusion-fixed, incubated for delta 5,3 beta-hydroxysteroid dehydrogenase (HSD) activity, and processed for electron microscopy. Diabetes increased Leydig cell smooth endoplasmic reticulum (SER), increased mitochondrial and lipid content, decreased HSD staining, and decreased serum testosterone levels. Insulin treatment reduced SER and increased testosterone concentrations. Semistarvation also increased SER and reduced testosterone levels but did not alter HSD staining. Stz had no significant effect on these variables. The results suggested that the hypoandrogen state was due to a primary Leydig cell compromise and not solely to malnutrition and that it was correctable by insulin treatment.

Testicular histology in streptozotocin-induced diabetes

The use of the streptozotocin rat model for diabetes has been questioned by the appearance of extrapancreatic cytotoxicity, notably renal and hepatic. In this study the model was made specific to diabetic, drug-induced, and starvation effects on parameters of testicular histology. Formulation of orthogonal contrast expressions permitted the statistical separation of these influences. Tubules from moderately diabetic animals showed frequent thinning, and premature desquamation of pachytene spermatocytes and early spermatids from the germinal epithelium. Results showed that only diabetes significantly decreased seminiferous tubule diameter and increased testicular blood vessel numbers. In addition, significant alteration from the control pattern of tubule stage distribution was noted, particularly at stages IX-XI. Due to the inclusion of a drug-treated but nondiabetic group, streptozotocin itself was shown to have no significant effect on these parameters.

Interstitial compartment pathology and spermatogenic disruption in testes from impotent diabetic men

Studies utilizing animal models of diabetes suggest that diabetic complications of impotence involve structural lesions in the testis as part of an overall defect in the pituitary-testicular axis. In the present study testicular biopsies from ten oligospermic and/or impotent men with diabetes were evaluated by light and electron microscopy. One biopsy was judged normal. The remaining tissue showed variable testicular pathology ranging from minimally to grossly affected. Seminiferous tubules had decreased tubule diameters, hyalinized tubule walls, and occluded lumina owing either to epithelial encroachment or cellular debris and exfoliated round germ cells. Sertoli cells were vacuolated and showed a high degree of apical cell membrane redundancy and degeneration. Although Sertoli-Sertoli cell junctional complexes appeared normal, Sertoli junctional specializations associated with spermatids were structurally abnormal or absent. All tubules were variably depleted of adluminal compartment germ cell types. The interstitial compartment was filled with a collagen-rich extracellular matrix concentrated around small blood vessels and seminiferous tubule walls. Capillaries and lymphatic endothelia appeared structurally abnormal and compromised by the interstitial "matrix expansion." Some Leydig cells contained a variable number of small to large lipid droplets, vacuoles, and secondary lysosomes. Results indicate the presence of tissue pathology in testes of impotent diabetic men. Discrete ultrastructural lesions in apical Sertoli cell cytoplasm are associated with spermatogenic disruption and morphological changes in the interstitial compartment suggest microvascular complications.

Effect of streptozotocin-induced hyperglycaemia on androgen-binding protein in rat testis and epididymis

In adult male rats treated with streptozotocin 6 weeks before the experiments, androgen-binding protein concentration was increased in testicular tissue by 33% (p less than 0.01) and reduced in epididymal tissue by 25% (p less than 0.005) in animals exhibiting severe hyperglycaemia as compared with animals remaining in normoglycaemia or moderate hyperglycaemia. Androgen-binding protein content was diminished in epididymal tissue by 40% (p less than 0.0005) but not changed in testicular tissue. If related to constant body weight, the sum of testicular and epididymal androgen-binding protein was identical in both normo- and hyperglycaemic animals. This disturbance in androgen-binding protein distribution may be the consequence of altered testicular secretion or impaired transport of androgen-binding protein from testes to epididymides.