Insulin treatment to type 1 male diabetic rats protects fertility by avoiding testicular apoptosis and cell cycle arrest

• Published in: Gene 2021-10, Vol.799, p.145847, Article 145847
• Main Authors: Minas, Aram, Talebi, Hatef, Taravat Ray, Morteza, Yari Eisalou, Mohammad, Alves, Marco G., Razi, Mazdak
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Cell cycle; Cell Cycle Checkpoints - drug effects; Cell Proliferation - drug effects; Diabetes; Diabetes Mellitus, Experimental - drug therapy; Diabetes Mellitus, Experimental - physiopathology; Diabetes Mellitus, Type 1 - drug therapy; Diabetes Mellitus, Type 1 - physiopathology; Fertility; Gene Expression - drug effects; Insulin - physiology; Male; Protective Agents - pharmacology; Rats; Rats, Wistar; Sperm Count; Sperm Motility - drug effects; Spermatogenesis; Streptozotocin; Testis - drug effects; Testis - pathology; Testosterone - blood
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2021.145847

Interaction between cell cycle machinery and apoptosis-related genes: (1) Diabetes results in a significant reduction in Bcl-2 expression which in turn up-regulates the Bax oligomerization. The Bax oligomerization, triggers the pro-apoptotic caspase-3 expression that ultimately ends with DNA fragmentation and apoptosis. However, the insulin, by maintaining Bcl-2 expression inhibits Bax oligomerization and maintains mitochondrial membrane integrity; (2) Increased DNA fragmentation in the diabetes condition triggers the p53 overexpression which in turn blocks cell cycle process at G2 stage. In contrast, treatment with insulin (Ins T1D) is able to potentially inhibit p53 expression and consequently promotes the cell cycle process by maintaining the DNA integrity; (3) The overexpressed p53 (high amount of p53) is able to trigger p21 expression. The overexpressed p21 interacts with cdk-4 resulting in Cyclin D1/cdk complex impairment. In contrast to diabetes, due to low p53 expression, this cascade of interactions is controlled in insulin-treated group; (4) The interaction between Cyclin D1 and cdk-4 is necessary to cell transition from G1 to S stages. However, insulin promotes cell cycle process, by up-regulating Cyclin D1 and cdk-4 expression and inhibiting p21 expression. [Display omitted] Uncontrolled type 1 diabetes mellitus (T1D) impairs reproductive potential of males. Insulin treatment restores metabolic parameters but it is unclear how it protects male reproductive health. Herein, we hypothesized that insulin treatment to T1D rats protects testicular physiology by mediating mechanisms associated with apoptosis and cell cycle. Mature male Wistar rats (n = 24) were divided into 3 groups: control, T1D-induced (received 40 mg kg−1 streptozotocin) and insulin-treated T1D (Ins T1D; received 40 mg kg−1 streptozotocin and then treated 0.9 IU/100 gr of insulin for 56 days) (N = 8/group). Expression levels of intrinsic apoptosis pathways regulators (Bcl-2, Bax, Caspase-3 and p53) and core regulators of cell cycle machinery (Cyclin D1, Cdk-4 and p21) were determined in testicular tissue by immunohistochemistry (IHC) and RT-PCR techniques. The percentage of testicular apoptotic cells was evaluated by TUNEL staining. Our data shows that insulin treatment to T1D rats restored (P