Vitamin D supplementation alleviates diabetic complications by increasing the amount of irisin in testicular tissues and blood of rats with experimental diabetes.

OBJECTIVE: Diabetes is an important endocrinological disease that has an increasing incidence in the world and affects all biological tissues including testicles. Therefore, this study aimed to reveal the histological and biochemical effects of vitamin D on irisin, apoptosis, total antioxidant status (TAS), and total oxidant status (TOS) in testicular tissues of rats with experimental diabetes. MATERIALS AND METHODS: 41 male Wistar rats, 8-10 weeks old, weighing between 200-220 g, were included in the study as the following groups: control group (n=7; no treatment), sham group [only sodium citrate buffer (SCB)] [n=7; single dose 0.1 Molar (M) SCB given intraperitoneally (i.p)], vitamin D group (n=7; 50 IU/day given orally), diabetes group [n=10; single dose 50 mg/kg Streptozotocin (STZ) dissolved in 0.1 M SCB and given i.p (tail vein blood glucose level above 250 mg/dl after 72 hours)] and diabetes+vitamin D group [n=10, single dose 50 mg/kg STZ, dissolved in 0.1 M SCB and given i.p (tail vein blood glucose level above 250 mg/dl after 72 hours) and when diabetes occurs, oral vitamin D administration of 50 IU/day)]. At the end of the 8 weeks experiment, blood was drawn from the tail vein of all rats, they were sacrificed and testicular tissues were taken. While the amount of irisin in the blood and testicular tissue supernatants was analyzed with the Enzyme-Linked Immunosorbent Assay (ELISA) method, TAS and TOS measurements were analyzed with the REL method, testicular tissues were analyzed histopathologically, immunohistochemically, and with the TUNEL method. RESULTS: When the diabetes group was compared with the control and sham groups, it was reported that the amounts of blood and tissue supernatant irisin and TAS significantly decreased and the TOS was significantly increased; a statistically significant increase in irisin and TAS of blood and tissue supernatants and a significant decrease in TOS were detected when diabetes+vitamin D and diabetes groups were compared among themselves. Similar results were obtained in the immunohistochemical studies. Tissue expressions of irisin decreased in the diabetes group compared to the control and sham groups, while the application of vitamin D increased the tissue expressions of irisin. Additionally, when the numbers of apoptotic cells were compared, it was reported that apoptotic cells in the diabetes group increased significantly compared to the control and sham groups, and vitamin D administration significantly decreased the number of apoptotic cells. CONCLUSIONS: Taken together, vitamin D administration to diabetic rats decreased the number of apoptotic cells and increased the amount of irisin. Vitamin D had an effective role in maintaining the physiological integrity of rat testicular tissues, so vitamin D may be a potent agent to be used in the treatment of diabetes in the future.

Immunohistochemical localization of irisin in mole rats (Spalax leucodon).

Irisin was first identified in skeletal muscle cells. It is an exercise protein that is secreted into the circulation; it causes conversion of white adipose tissue to brown adipose tissue. We investigated irisin immunoreactivity in mole rat (Spalax leucodon) tissues. We examined cerebellum, pituitary, heart, liver, pancreas, spleen, uterus, kidney and striated muscle in female adult mole rats. Tissues were processed, embedded in paraffin, sectioned at 5 µm and stained immunohistochemically for irisin. Irisin immunostaining was detected in the cytoplasm of stained cells; the cytoplasm of Purkinje cells was unstained. We found that irisin may be synthesized in many tissues. The function of locally synthesized irisin currently is unknown.

Immunohistochemical localization of irisin in skin, eye, and thyroid and pineal glands of the crested porcupine (Hystrix cristata).

Irisin was first identified in muscle cells. We detected irisin immunoreactivity in various organs of the crested porcupine (Hystrix cristata). In the epidermis, irisin immunoreactivity was localized mainly in stratum basale, stratum spinosum and stratum granulosum layers; immunoreactivity was not observed in the stratum corneum. In the dermis, irisin was found in the external and internal root sheath, cortex and medulla of hair follicles, and in sebaceous glands. Irisin immunoreactivity was found in the neural retina and skeletal muscle fibers associated with the eye. The pineal and thyroid glands also exhibited irisin immunoreactivity.