Abstract: BACKGROUND: As a common complication of diabetes mellitus, male reproductive disorders have received increasing attention in recent years. Ganoderma spore have hypoglycemic, antioxidant and anti-inflammatory effects, but the regulatory mechanism for diabetic testicular tissue has not been fully elucidated. 
OBJECTIVE: To investigate the effect of ganoderma spore on the PTEN-induced kinase 1/E3 ubiquitin ligase pathway and cell apoptosis in testicular tissue of diabetic rats.
METHODS: Forty male Sprague-Dawley rats were randomly divided into normal group, high fat and high sugar group, diabetic group and ganoderma spore group, with 10 rats in each group. The latter three groups were given high fat/high sugar diet until the end of the experiment. After 1 month of high fat/high sugar diet, the diabetic and ganoderma spore groups were given intraperitoneal injection of streptozotocin (30 mg/kg per day) to establish type 2 diabetic rat models. After successful modeling, the ganoderma spore group was intragastrically given ganoderma spore (300 mg/kg per day), and the other groups were given the same amount of normal saline for continuous 12 weeks. The sperm number and morphology were detected. The histopathological changes of the testicle were observed. Serum testosterone and oxidative stress levels in testicular tissue were measured. The levels of PTEN-induced kinase 1, E3 ubiquitin ligase, and anti-nucleoporin p62 were analyzed by immunohistochemistry and the expression of PTEN-induced kinase 1, E3 ubiquitin ligase, anti-nucleoporin p62, programmed cell death-1, microtubule-associated protein light chain 3 II/I, caspase 3, cleaved-caspase 3 were detected by western blot assay.
RESULTS AND CONCLUSION: Compared with the normal group and the high fat and high sugar group, the diabetic group had decreased sperm number (P < 0.01), increased sperm malformation rate (P < 0.01), and decreased serum testosterone level (P < 0.01). Compared with the diabetic group, ganoderma spore intervention could increase the sperm number (P < 0.05), decrease the malformation rate (P < 0.01), and increase the serum testosterone level (P < 0.01). Compared with the normal group and the high fat and high sugar group, the malondialdehyde level in testis tissue was increased in the diabetic group (P < 0.01), while the levels of glutathione deoxidase and superoxide dismutase decreased (P < 0.01). Compared with the diabetic group, the malondialdehyde level in testis tissue was decreased in the ganoderma spore group (P < 0.01), and the levels of glutathione deoxidase and superoxide dismutase increased (P < 0.01). Immunohistochemical staining showed that compared with the normal group and the high fat and high sugar group, the positive expressions of PTEN-induced kinase 1 and E3 ubiquitin ligase in testicular tissue were decreased in the diabetic group, while the positive expressions of anti-nucleoporin p62 were increased. Compared with the diabetic group, the positive expressions of PTEN-induced kinase 1 and E3 ubiquitin ligase in testicular tissue e were increased in the ganoderma spore group, while the positive expression of anti-nucleoporin p62 was decreased. Western blot assay results indicated that compared to the normal group and the high fat and high sugar group, the expression of PTEN-induced kinase 1 and E3 ubiquitin ligase, programmed cell death-1 and the ratio of microtubule-associated protein light chain 3 II/I protein were decreased in the diabetic group (P < 0.05 or P < 0.01), while the expressions of anti-nucleoporin p62, caspase3 and cleaved-caspase3 were increased (P < 0.01). Compared with the diabetic group, ganoderma spore intervention could elevate the expression of PTEN-induced kinase 1 and E3 ubiquitin ligase, programmed cell death-1 and the ratio of microtubule-associated protein light chain 3 II/I protein (P < 0.05 or P < 0.01) as well as reduce the expressions of anti-nucleoporin p62, caspase3 and cleaved-caspase3 (P < 0.05 or P < 0.01). Overall, ganoderma spores may activate the PTEN-induced kinase 1/E3 ubiquitin ligase pathway to enhance autophagy in testicular tissue and reduce apoptosis in tissue cells, so as to protect testicular tissue.

Key words: diabetes mellitus, testis, PTEN-induced kinase 1, E3 ubiquitin ligase, autophagy, ganoderma spore