Protective mechanisms of the brown alga Cystoseira myrica supplementation against testicular alterations in streptozotocin-induced diabetic rats

Diabetes (DM) is a significant public health issue associated with the increased risk of male infertility. Brown seaweeds are excellent sources of bioactive compounds with multiple biological activities. This study investigates the protective mechanisms of brown alga Cystoseira myrica against the testicular lesion of diabetic animals. DM was induced in male rats using a single intraperitoneal injection of streptozotocin (STZ). Animals were fed a diet supplemented with 2% Cystosira for 60 days, concurrently with STZ administration. Blood and testis tissues were sampled for biochemical, histopathological and immunohistochemical investigations. STZ treated animals showed significant decrease in serum testosterone, superoxide dismutase (SOD) and catalase (CAT) activities along with a significant elevation in malondialdehyde (MDA) level, indicating oxidative stress. However, Cystoseira supplementation to STZ diabetic animals significantly increased the above mentioned data and significantly reduced MDA level with respect to STZ treated group. Histological and ultrastructural evaluations revealed that Cystoseira ameliorated STZ-induced degenerative changes in seminiferous tubules and preserved spermatogenic cell integrity. Immunohistochemically, Cystoseira supplementation to STZ treated animals markedly upregulated PCNA and Bcl-2 expression while down regulating Bax, reflecting enhanced cell proliferation and reduced apoptosis, further supporting its potent antiapoptotic and cytoprotective efficacy. Consistently, AO/EB dual staining confirmed a decrease in apoptotic spermatogenic cells. This study provides the first evidence that Cystoseira myrica protects against diabetes-induced testicular damage by enhancing antioxidant capacity, restoring hormonal balance, and regulating apoptotic signaling. These findings suggest that Cystoseira myrica represents a promising bioactive nutritional supplement for preserving spermatogenic function and mitigating male reproductive complications associated with diabetes.